Publications by authors named "Lukas Willinger"

34 Publications

Knee Joint Line Obliquity Causes Tibiofemoral Subluxation That Alters Contact Areas and Meniscal Loading.

Am J Sports Med 2021 Jul 14;49(9):2351-2360. Epub 2021 Jun 14.

The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, London, UK.

Background: Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO) before and after coronal realignment osteotomy.

Hypotheses: Higher JLO would lead to abnormal relative position of the femur on the tibia, a shift of the joint contact areas, and elevated joint contact pressures.

Study Design: Descriptive laboratory study.

Methods: 10 fresh-frozen human cadaveric knees (age, 59 ± 5 years) were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0°, 4°, 8°, and 12° varus ("downhill" medially) and valgus, at 0° and 20° of knee flexion. The mechanical compression axis was aligned to the center of the tibial plateau. Contact pressure and contact area were recorded by pressure sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system.

Results: Both medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to subluxate medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes ( < .01), giving a 6-mm range of subluxation. The areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the downhill meniscus and the "uphill" tibial spine. Changes in JLO had only small effects on maximum contact pressures.

Conclusion: A 4° change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. This caused large movements of the tibiofemoral contact pressures across each compartment.

Clinical Relevance: These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO. This information provides guidance regarding the choice of single- or double-level osteotomy. Excessive JLO alteration may cause abnormal tibiofemoral joint articulation and chondral or meniscal loading.
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http://dx.doi.org/10.1177/03635465211020478DOI Listing
July 2021

An Anterior Cruciate Ligament In Vitro Rupture Model Based on Clinical Imaging.

Am J Sports Med 2021 Jul 11;49(9):2387-2395. Epub 2021 Jun 11.

Biomechanics Group, Mechanical Engineering Department, Imperial College London, London, UK.

Background: Biomechanical studies on anterior cruciate ligament (ACL) injuries and reconstructions are based on ACL transection instead of realistic injury trauma.

Purpose: To replicate an ACL injury in vitro and compare the laxity that occurs with that after an isolated ACL transection injury before and after ACL reconstruction.

Study Design: Controlled laboratory study.

Methods: Nine paired knees were ACL injured or ACL transected. For ACL injury, knees were mounted in a rig that imposed tibial anterior translation at 1000 mm/min to rupture the ACL at 22.5° of flexion, 5° of internal rotation, and 710 N of joint compressive force, replicating data published on clinical bone bruise locations. In contralateral knees, the ACL was transected arthroscopically at midsubstance. Both groups had ACL reconstruction with bone-patellar tendon-bone graft. Native, ACL-deficient, and reconstructed knee laxities were measured in a kinematics rig from 0° to 100° of flexion with optical tracking: anterior tibial translation (ATT), internal rotation (IR), anterolateral (ATT + IR), and pivot shift (IR + valgus).

Results: The ACL ruptured at 26 ± 5 mm of ATT and 1550 ± 620 N of force (mean ± SD) with an audible spring-back tibiofemoral impact with 5 of valgus. ACL injury and transection increased ATT ( < .001). ACL injury caused greater ATT than ACL transection by 1.4 mm (range, 0.4-2.2 mm; = .033). IR increased significantly in ACL-injured knees between 0° and 30° of flexion and in ACL transection knees from 0° to 20° of flexion. ATT during the ATT + IR maneuver was increased by ACL injury between 0° and 80° and after ACL transection between 0° and 60°. Residual laxity persisted after ACL reconstruction from 0° to 40° after ACL injury and from 0° to 20° in the ACL transection knees. ACL deficiency increased ATT and IR in the pivot-shift test ( < .001). The ATT in the pivot-shift increased significantly at 0° to 20° after ACL transection and 0° to 50° after ACL injury, and this persisted across 0° to 20° and 0° to 40° after ACL reconstruction.

Conclusion: This study developed an ACL injury model in vitro that replicated clinical ACL injury as evidenced by bone bruise patterns. ACL injury caused larger increases of laxity than ACL transection, likely because of damage to adjacent tissues; these differences often persisted after ACL reconstruction.

Clinical Relevance: This in vitro model created more realistic ACL injuries than surgical transection, facilitating future evaluation of ACL reconstruction techniques.
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http://dx.doi.org/10.1177/03635465211017145DOI Listing
July 2021

High Rate of Initially Overlooked Kaplan Fiber Complex Injuries in Patients With Isolated Anterior Cruciate Ligament Injury.

Am J Sports Med 2021 Jul 4;49(8):2117-2124. Epub 2021 Jun 4.

Department of Orthopaedic Surgery, University of Connecticut, Farmington, Connecticut, USA.

Background: Injuries to the Kaplan fiber complex (KFC) are not routinely assessed for in the anterior cruciate ligament (ACL)-deficient knee during preoperative magnetic resonance imaging (MRI). As injuries to the KFC lead to anterolateral rotatory instability (ALRI) in the ACL-deficient knee, preoperative detection of these injuries on MRI scans may help surgeons to individualize treatment and improve outcomes, as well as to reduce failure rates.

Purpose: To retrospectively determine the rate of initially overlooked KFC injuries on routine MRI in knees with isolated primary ACL deficiency.

Study Design: Case series; Level of evidence, 4.

Methods: Patients who underwent isolated ACL reconstruction between August 2013 and December 2019 were identified. No patient had had Kaplan fiber (KF) injury identified on the initial reading of the MRI scan or at the time of surgery. Preoperative knee MRI scans (minimum 1.5 T) were reviewed and injuries to the proximal and distal KFs were recorded by 3 independent reviewers. KF length and distance to nearby anatomic landmarks (the lateral joint line and the lateral femoral epicondyle) were measured. Additional radiological findings, including bleeding, lateral femoral notch sign, and bone marrow edema (BME), were identified to detect correlations with KFC injury.

Results: The intact KFC could reliably be identified by all 3 reviewers (85.9% agreement; Kappa, 0.716). Also, 53% to 56% of the patients with initially diagnosed isolated ACL ruptures showed initially overlooked injuries to the KFC. Injuries to the distal KFs were more frequent (48.1%, 53.8%, and 43.3% by the first, second, and third reviewers, respectively) than injuries to the proximal KFs (35.6%, 47.1%, and 45.2% by the first, second, and third reviewers, respectively). Bleeding in the lateral supracondylar region was associated with KFC injuries ( = .023). Additionally, there was a positive correlation between distal KF injuries and lateral tibial plateau BME ( = .035), but no associations were found with the lateral femoral notch sign or other patterns of BME, including pivot-shift BME.

Conclusion: KF integrity and injury can be reliably detected on routine knee MRI scans. Also, 53% to 56% of the patients presenting with initially diagnosed isolated ACL ruptures had concomitant injuries to the KFC. This is of clinical relevance, as ACL injuries diagnosed by current routine MRI examination protocols may come with a high number of occult or hidden KFC injuries. As injuries to the KFC contribute to persistent ALRI, which may influence ACL graft failure or reoperation rates, significant improvements in preoperative diagnostic imaging are required to determine the exact injury pattern and to assist in surgical decision making.
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http://dx.doi.org/10.1177/03635465211015682DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8246408PMC
July 2021

Anterolateral complex injuries occur in the majority of 'isolated' anterior cruciate ligament ruptures.

Knee Surg Sports Traumatol Arthrosc 2021 Apr 1. Epub 2021 Apr 1.

Fortius Clinic, 17 Fitzhardinge St, London, W1H 6EQ, UK.

Purpose: The anterolateral soft tissue envelope of the knee is frequently injured at the time of ACL rupture. This study aims to investigate the MRI injury patterns to the Anterolateral complex and their associations in patients with acute 'isolated ligament' ACL ruptures.

Methods: Professional athletes who underwent ACL reconstruction for complete ACL rupture between 2015 and 2019 were included in this study. Patients' characteristics and intraoperative findings were retrieved from clinical and surgical documentation. Preoperative MRIs were evaluated and the injuries to respective structures of the Anterolateral complex and their associations were recorded.

Results: Anterolateral complex injuries were noted in 63% of cases. The majority of injuries were to Kaplan Fibre (39% isolated injury and 19% combined with Anterolateral ligament injury). There was a very low incidence of isolated Anterolateral ligament injuries (2%). Kaplan Fibre injuries are associated with the presence of lateral femoral condyle bone oedema, and injuries to the superficial MCL, deep MCL, and ramp lesions. High grade pivot shift test was not associated with the presence of Kaplan Fibre or Anterolateral ligament injuries. Patients with an intact Anterolateral complex sustained injury to other knee structures (13% to medial ligament complex, 14% to medial meniscus, and 16% to lateral meniscus).

Conclusion: There is a high incidence of concomitant Anterolateral complex injuries in combination with ACL ruptures, with Kaplan Fibre (and therefore the deep capsulo-osseous layer of the iliotibial band) being the most commonly injured structure. Anterolateral ligament injuries occur much less frequently. These findings reinforce the importance of considering the presence of, and if necessary, treating injuries to structures other than the ACL, as a truly isolated ACL injury is rare.
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http://dx.doi.org/10.1007/s00167-021-06543-6DOI Listing
April 2021

High incidence of superficial and deep medial collateral ligament injuries in 'isolated' anterior cruciate ligament ruptures: a long overlooked injury.

Knee Surg Sports Traumatol Arthrosc 2021 Mar 4. Epub 2021 Mar 4.

Fortius Clinic, 17 Fitzhardinge St, London, W1H 6EQ, UK.

Purpose: In anterior cruciate ligament (ACL) injuries, concomitant damage to peripheral soft tissues is associated with increased rotatory instability of the knee. The purpose of this study was to investigate the incidence and patterns of medial collateral ligament complex injuries in patients with clinically 'isolated' ACL ruptures.

Methods: Patients who underwent ACL reconstruction for complete 'presumed isolated' ACL rupture between 2015 and 2019 were retrospectively included in this study. Patient's characteristics and intraoperative findings were retrieved from clinical and surgical documentation. Preoperative MRIs were evaluated and the grade and location of injuries to the superficial MCL (sMCL), dMCL and the posterior oblique ligament (POL) recorded. All patients were clinically assessed under anaesthesia with standard ligament laxity tests.

Results: Hundred patients with a mean age of 22.3 ± 4.9 years were included. The incidence of concomitant MCL complex injuries was 67%. sMCL injuries occurred in 62%, dMCL in 31% and POL in 11% with various injury patterns. A dMCL injury was significantly associated with MRI grade II sMCL injuries, medial meniscus 'ramp' lesions seen at surgery and bone oedema at the medial femoral condyle (MFC) adjacent to the dMCL attachment site (p < 0.01). Logistic regression analysis identified younger age (OR 1.2, p < 0.05), simultaneous sMCL injury (OR 6.75, p < 0.01) and the presence of bone oedema at the MFC adjacent to the dMCL attachment site (OR 5.54, p < 0.01) as predictive factors for a dMCL injury.

Conclusion: The incidence of combined ACL and medial ligament complex injuries is high. Lesions of the dMCL were associated with ramp lesions, MFC bone oedema close to the dMCL attachment, and sMCL injury. Missed AMRI is a risk factor for ACL graft failure from overload and, hence, oedema in the MCL (especially dMCL) demands careful assessment for AMRI, even in the knee lacking excess valgus laxity. This study provides information about specific MCL injury patterns including the dMCL in ACL ruptures and will allow surgeons to initiate individualised treatment.

Level Of Evidence: III.
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http://dx.doi.org/10.1007/s00167-021-06514-xDOI Listing
March 2021

Unique myological changes associated with ossified fabellae: a femorofabellar ligament and systematic review of the double-headed popliteus.

PeerJ 2020 16;8:e10028. Epub 2020 Oct 16.

Department of Mechanical Engineering, Imperial College London, London, UK.

Introduction: The fabella is a sesamoid bone embedded in the tendon of the lateral head of the gastrocnemius. It is the only bone in the human body to increase in prevalence in the last 100 years. As the fabella can serve as an origin/insertion for muscles, tendons, and/or ligaments (e.g., the oblique popliteal and fabellofibular ligaments), temporal changes in fabella prevalence could lead to temporal changes in "standard" knee anatomy. The aim of this study was to investigate unique myological changes to the posterolateral corner knee associated with ossified fabella presence and perform a systematic review to contextualize our results.

Methods: Thirty-three fresh frozen cadaveric knees were considered. As the knees were all used for previous experimentation, the knees were in variable levels of preservation. Those with adequate preservation were used to determine ossified fabella presence/absence. When ossified fabellae were present, unique myologies associated with the fabella were recorded. A systematic review was performed on the double-headed popliteus to investigate possible correlations between this anatomical variant and the fabella.

Results: Of the 33 knees, 30 preserved enough soft tissue to determine fabella presence/absence: 16/30 knees had fabellae (five cartilaginous and 11 ossified). Eight of the eleven knees with ossified fabellae retained enough soft tissue to investigate the posterolateral knee anatomy. Of these, 4/8 exhibited unique myological changes. One knee had a double-headed popliteus muscle where one head originated from the medial side of a large, bulbous fabella. A systematic review revealed double-headed popliteus muscles are rare, but individuals are 3.7 times more likely to have a fabella if they have a double-headed popliteus. Another knee had a large, thick ligament stretching from the lateral edge of the fabella to the inferoposterior edge of the lateral femoral epicondyle, deep to the lateral collateral ligament (LCL) and near the popliteal sulcus. We found no mention of such a ligament in the literature and refer to it here as the "femorofabellar ligament". In all four knees, the plantaris and lateral gastrocnemius appeared to share a common tendinous origin, and the fabella was located at/near the junction of these muscles. In the case of the double-headed popliteus, the fabella clearly served as an origin for the plantaris.

Conclusions: Despite being found in an average of 36.80% of human knees, most standard anatomical models fail to account for the fabella and/or the unique myological changes associated with fabella presence. Although our sample is small, these data highlight aspects of human biological variability generally not considered when creating generalized anatomical models. Further work is needed to identify additional changes associated with ossified fabellae and the functional consequences of omitting these changes from models.
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http://dx.doi.org/10.7717/peerj.10028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7571414PMC
October 2020

Length-change patterns of the medial collateral ligament and posterior oblique ligament in relation to their function and surgery.

Knee Surg Sports Traumatol Arthrosc 2020 Dec 1;28(12):3720-3732. Epub 2020 Jun 1.

The Biomechanics Group, Department of Mechanical Engineering, Imperial College London, London, SW7 2AZ, UK.

Purpose: To define the length-change patterns of the superficial medial collateral ligament (sMCL), deep MCL (dMCL), and posterior oblique ligament (POL) across knee flexion and with applied anterior and rotational loads, and to relate these findings to their functions in knee stability and to surgical repair or reconstruction.

Methods: Ten cadaveric knees were mounted in a kinematics rig with loaded quadriceps, ITB, and hamstrings. Length changes of the anterior and posterior fibres of the sMCL, dMCL, and POL were recorded from 0° to 100° flexion by use of a linear displacement transducer and normalised to lengths at 0° flexion. Measurements were repeated with no external load, 90 N anterior draw force, and 5 Nm internal and 5 Nm external rotation torque applied.

Results: The anterior sMCL lengthened with flexion (p < 0.01) and further lengthened by external rotation (p < 0.001). The posterior sMCL slackened with flexion (p < 0.001), but was lengthened by internal rotation (p < 0.05). External rotation lengthened the anterior dMCL fibres by 10% throughout flexion (p < 0.001). sMCL release allowed the dMCL to become taut with valgus rotation (p < 0.001). The anterior and posterior POL fibres slackened with flexion (p < 0.001), but were elongated by internal rotation (p < 0.001).

Conclusion: The structures of the medial ligament complex react differently to knee flexion and applied loads. Structures attaching posterior to the medial epicondyle are taut in extension, whereas the anterior sMCL, attaching anterior to the epicondyle, is tensioned during flexion. The anterior dMCL is elongated by external rotation. These data offer the basis for MCL repair and reconstruction techniques regarding graft positioning and tensioning.
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http://dx.doi.org/10.1007/s00167-020-06050-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7669796PMC
December 2020

Visualization of Proximal and Distal Kaplan Fibers Using 3-Dimensional Magnetic Resonance Imaging and Anatomic Dissection.

Am J Sports Med 2020 07 14;48(8):1929-1936. Epub 2020 May 14.

Department of Trauma, Hand and Reconstructive Surgery, University Hospital Münster, Münster, Germany.

Background: In current magnetic resonance imaging (MRI) of the knee, injuries to the anterolateral ligament complex (ALC) and the Kaplan fibers (KFs) are not routinely assessed. As ruptures of the KFs contribute to anterolateral rotatory instability in the anterior cruciate ligament-deficient knee, detecting these injuries on MRI may help surgeons to individualize treatment.

Purpose: To visualize the KFs on 3-T MRI and to conduct a layer-by-layer dissection of the ALC.

Study Design: Descriptive laboratory study.

Methods: Ten fresh-frozen human cadaveric knees (mean ± SD age, 72 ± 8.5 years) without history of ligament injury were used in this study. Before layer-by-layer dissection of the ALC, MRI was performed to define the radiologic anatomy of the KFs. A coronal T1-weighted 3-dimensional turbo spin echo sequence and a transverse T2-weighted turbo spin echo sequence were obtained. Three-dimensional data sets were used for multiplanar reconstructions.

Results: KFs were identified in 100% of cases on MRI and in anatomic dissection. The mean length of the proximal and distal KFs was 17.9 ± 3.6 mm and 12.4 ± 6.5 mm, respectively. On MRI, the distance from the lateral femoral epicondyle to the proximal KFs was 35.9 ± 6.9 mm and to the distal KFs, 16.6 ± 4.1 mm; in anatomic dissection, the distances were 41.4 ± 8.1 mm for proximal KFs and 28.2 ± 8.1 mm for distal KFs. The distance from the lateral joint line to the proximal KFs was 63.5 ± 7.6 mm and to the distal KFs, 45.3 ± 3.7 mm. Interobserver reliability for image analysis was excellent for all measurements.

Conclusion: KFs can be consistently identified on MRI with use of 3-dimensional sequences. Subsequent anatomic dissection confirmed their close topography to the superior lateral genicular artery. For clinical implications, the integrity of the KFs should be routinely reviewed on MRI scans.

Clinical Relevance: As ruptures of the KFs contribute to anterolateral rotatory instability, accurate visualization of the KFs on MRI may facilitate surgical decision making for additional anterolateral procedures in the anterior cruciate ligament-deficient knee.
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http://dx.doi.org/10.1177/0363546520919986DOI Listing
July 2020

A constrained-condylar fixed-bearing total knee arthroplasty is stabilised by the medial soft tissues.

Knee Surg Sports Traumatol Arthrosc 2021 Feb 22;29(2):659-667. Epub 2020 Apr 22.

Department of Mechanical Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ, UK.

Purpose: Revision constrained-condylar total knee arthroplasty (CCK-TKA) is often used to provide additional mechanical constraint after failure of a primary TKA. However, it is unknown how much this translates to a reliance on soft-tissue support. The aim of this study was therefore to compare the laxity of a native knee to the CCK-TKA implanted state and quantify how medial soft-tissues stabilise the knee following CCK-TKA.

Methods: Ten intact cadaveric knees were tested in a robotic system at 0°, 30°, 60° and 90° flexion with ± 90  N anterior-posterior force, ± 8 Nm varus-valgus and ± 5 Nm internal-external torques. A fixed-bearing CCK-TKA was implanted and the laxity tests were repeated with the soft tissues intact and after sequential cutting. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were sequentially transected and the percentage contributions of each structure to restraining the applied loads were calculated.

Results: Implanting a CCK-TKA did not alter anterior-posterior laxity from that of the original native knee, but it significantly decreased internal-external and varus-valgus rotational laxity (p < 0.05). Post CCK-TKA, the sMCL restrained 34% of the tibial displacing load in anterior drawer, 16% in internal rotation, 17% in external rotation and 53% in valgus, across the flexion angles tested. The dMCL restrained 11% of the valgus rotation moment.

Conclusions: With a fully-competent sMCL in-vitro, a fixed-bearing CCK-TKA knee provided more rotational constraint than the native knee. The robotic test data showed that both the soft-tissues and the semi-constrained implant restrained rotational knee laxity. Therefore, in clinical practice, a fixed-bearing CCK-TKA knee could be indicated for use in a knee with lax, less-competent medial soft tissues.

Level Of Evidence: Controlled laboratory study.
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http://dx.doi.org/10.1007/s00167-020-05995-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7892729PMC
February 2021

Excellent clinical outcome and low complication rate after proximal hamstring tendon repair at mid-term follow up.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 24;28(4):1230-1235. Epub 2019 Oct 24.

Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: Proximal hamstring tendon avulsions lead to a significant loss of strength and a functional deficit of the respective lower limb and surgery is the recommended treatment. Only little is known about the clinical outcomes and complications when comparing acute and chronic management as well as partial and complete tears. Therefore, the purpose of this study was to investigate the clinical results and the complication rate of patients after surgical treatment of proximal hamstring tendon injuries. It was hypothesized that surgical treatment of an acute proximal hamstring avulsion would lead to a superior clinical outcome with a low complication rate and high return to sports rate compared to chronic cases and partial avulsions.

Methods: Patients who underwent proximal hamstring tendon repair between 2008 and 2015 were retrospectively evaluated with a minimum follow up of 2 years. Outcome measurements were obtained by means of Lysholm score, Harris Hip Score, Visual Analog Scale, and Tegner Activity Scale. Return to sports (RTS) rate was determined. Postoperative adverse events were recorded and complications reported. Patients' outcomes were compared between acute/chronic repair and partial/complete injury patterns.

Results: Ninety-four of 120 (78.3%) were available for final assessment at a mean follow-up of 56.2 ± 27.2 months. Clinical outcome measures were excellent and did not differ between the treatment groups or between the different injury patterns. RTS was achieved by 86.2% of the patients and was significantly superior after acute treatment (p < 0.05). The overall complication rate was 8.5% and significantly higher in complete tears compared to partial tears and in delay compared to acute surgery (p < 0.05).

Conclusion: Surgical treatment of proximal hamstring tendon avulsions results in excellent clinical outcome scores and a high RTS rate. Open surgical treatment has shown to be a safe procedure with a low complication rate. Surgical timing is important, as early surgical intervention provides a higher RTS rate and a lower complication rate than delayed surgery and should therefore be preferred in clinical practice. Repair of partial and complete tears lead to similar clinical outcome, but a higher complication rate in complete avulsions.

Level Of Evidence: Level IV.
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http://dx.doi.org/10.1007/s00167-019-05748-0DOI Listing
April 2020

Modified suture-bridge technique for tibial avulsion fractures of the posterior cruciate ligament: a biomechanical comparison.

Arch Orthop Trauma Surg 2020 Jan 26;140(1):59-65. Epub 2019 Sep 26.

Department of Orthopaedic Sports Medicine, Klinikum Rechts Der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Displaced tibial posterior cruciate ligament (PCL) avulsion fractures require surgical fixation in order to provide an adequate bone healing and to avoid a loss of posterior stability. The purpose of this study was to compare the biomechanical properties of a recently established modified suture bridge technique to a well-established transtibial pullout technique. It was hypothesized that the suture bridge technique shows lower elongation and higher load to failure force compared to a transtibial pullout fixation.

Methods: Twelve fresh-frozen human cadaveric knees were biomechanically tested using an uniaxial hydrodynamic material testing system. A standardized bony avulsion fracture of the tibial PCL insertion was generated. Two different techniques were used for fixation: (A) suture bridge configuration and (B) transtibial pullout fixation. In 90° of flexion elongation, initial stiffness and failure load were determined.

Results: The suture-bridge technique resulted in a significant lower elongation (4.5 ± 2.1 mm) than transtibial pullout technique (12.4 ± 3.0 mm, p < 0.001). The initial stiffness at the beginning of cyclic loading was 46.9 ± 3.9 N/mm in group A und 40.8 ± 9.0 N/mm in group B (p = 0.194). Load to failure testing exhibited 286.8 ± 88.3 N in group A and 234.3 ± 96.8 N in group B (p = 0.377).

Conclusion: The suture bridge technique provides a significant lower construct elongation during cyclic loading. But postoperative rehabilitation must respect the low construct strength of both techniques because both fixation techniques did not show a sufficient fixation strength to allow for a more aggressive rehabilitation.
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http://dx.doi.org/10.1007/s00402-019-03278-5DOI Listing
January 2020

Proximal hamstring tendon avulsion injuries occur predominately in middle-aged patients with distinct gender differences: epidemiologic analysis of 263 surgically treated cases.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 20;28(4):1221-1229. Epub 2019 Sep 20.

Department for Orthopedic Sports Medicine, Technical University Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: Epidemiologic data of proximal hamstring avulsions have mainly been reported in relatively small patient cohorts. Detailed information on patient demographics, injury mechanism, and injury patterns is lacking in the literature. Since these injuries are rare and frequently misdiagnosed, a better understanding may help to increase awareness and to improve diagnosis of proximal hamstring avulsions.

Methods: A chart review was performed to identify all patients who had undergone surgical repair for complete proximal hamstring avulsions between 01/2006 and 02/2019 at the authors' institution. The following demographic and injury-specific data were obtained: Sex, age, body mass index (BMI), cause of injury (sports, activities of daily living, and others), presence of neurologic symptoms referable to the sciatic nerve, time to surgery, injury pattern (affected tendons), tendon retraction, and type of injury according to Wood et al.`s classification (Type 1: osseous avulsions, Type 2: tear at the musculotendinous junction, Type 3: incomplete avulsion from bone, Type 4: complete avulsion with only minimal retraction, and Type 5: complete avulsion with retraction > 2 cm). Data were analyzed for the entire study population and group comparison was performed with regard to sex, cause of injury, and the type of injury.

Results: A total of 263 patients were included (53% male). The mean age was 49 ± 13 years with most patients (56%) aged between 45-59 years. Most injuries occurred while participating in sports (52%) and injury type 5 was most commonly diagnosed (66%). Five percent of patients had sensory deficits referable to the sciatic nerve. Gender comparison showed that female patients were significantly older, predominantly represented in the age group 45-59 years, and most commonly injured during activities of daily living, whereas male patients were significantly more often represented in younger age groups, and the most common cause of injury was sports. Compared to Type 4 and 5 injuries, patients with a Type 1 injury were significantly younger and had a significantly longer time to surgery.

Conclusion: Proximal hamstring avulsion occurs predominately in the middle-aged patient and only rarely in patients under the age of 30 years. No gender dominance exists. Female patients are typically older and get injured during activities of daily living, whereas male patients are younger and get injured more often during sports. These epidemiologic data may help physicians to make an accurate and early diagnosis.

Level Of Evidence: IV.
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http://dx.doi.org/10.1007/s00167-019-05717-7DOI Listing
April 2020

[All-arthroscopic fixation of tibial posterior cruciate ligament avulsion fractures with a suture-button technique].

Oper Orthop Traumatol 2020 Jun 6;32(3):236-247. Epub 2019 Sep 6.

Abteilung für Sportorthopädie, Klinikum rechts der Isar, TU München, Ismaninger Str. 22, 81675, München, Deutschland.

Objective: To restore the posterior stability of the knee after a tibial posterior cruciate ligament (PCL) avulsion with a suture-button construct.

Indications: Acute solid and monofragment bony avulsion of the tibial PCL insertion.

Contraindications: Chronic condition of avulsion fractures or posterior instability, multifragment avulsions, thin bone pieces, advanced knee osteoarthritis, high-grade soft tissue injury, infection.

Surgical Technique: Supine position, all-arthroscopic treatment via posteromedial and posterolateral portal, arthroscopic visualization and fracture reduction, transtibial drilling with a cannulated 2.4 mm drill, reduction of the fragment via FiberTape™ and Dog Bone. Knotting of the tapes against an additional Dog Bone at the anterior aspect of the tibia. Intraoperative x‑ray.

Postoperative Management: Knee extension brace with posterior tibial support for 6 weeks, 20 kg partial weight-bearing and restricted flexion up to 90° for 6 weeks, physiotherapy in prone position from the first postoperative day. Full weight bearing after x‑ray and clinical control after 6 weeks.

Results: Since 2016 eight tibial PCL avulsions were treated. In 6 patients a suture-bridge technique via a mini-open approach was performed due to a small or comminuted fracture fragment. In 2 patients an all-arthroscopic technique was performed. No complications. The all-arthroscopic technique requires a solid fragment and enables the surgeon to treat additional pathologies. In general, the arthroscopic technique makes the open posterior approach unnecessary. The arthroscopic techniques achieve slightly higher objective and subjective values compared to the open procedure, despite a higher rate of arthrofibrosis.
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http://dx.doi.org/10.1007/s00064-019-00626-xDOI Listing
June 2020

Varus alignment increases medial meniscus extrusion and peak contact pressure: a biomechanical study.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 5;28(4):1092-1098. Epub 2019 Sep 5.

Department of Orthopaedic Sports Medicine, Hospital Rechts Der Isar, Technical University of Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Assessment of medial meniscus extrusion (MME) has become increasingly popular in clinical practice to evaluate the dynamic meniscus function and diagnose meniscus pathologies. The purpose of this biomechanical study was to investigate the correlation between MME and the changes in joint contact pressure in varus and valgus alignment. It was hypothesized that varus alignment would result in significantly higher MME along with a higher joint contact pressure in the medial compartment.

Methods: Eight fresh-frozen human cadaveric knees were axially loaded, with a 750 N compressive load, in full extension with the mechanical axis shifted to intersect the tibial plateau at 30% and 40% (varus), 50% (neutral), 60% and 70% (valgus) of its width (TPW). Tibiofemoral peak contact pressure (PCP), mean contact pressure (MCP) and contact area (CA) were determined using pressure-sensitive films. MME was obtained via ultrasound at maximum load.

Results: MME was significantly increased from valgus (1.32 ± 0.22 mm) to varus alignment (3.16 ± 0.24 mm; p < 0.001). Peak contact pressure at 30% TPW varus alignment was significantly higher compared to 60% TPW valgus (p = 0.018) and 70% TPW valgus (p < 0.01). MME significantly correlated with PCP (r = 0.56; p < 0.001) and MCP (r = 0.47, p < 0.01) but not with CA (r = 0.23; n.s.).

Conclusion: MME was significantly increased in varus alignment, compared to neutral or valgus alignment, with an intact medial meniscus. It was also significantly correlated with PCP and MCP within the medial compartment. However, valgus malalignment and neutral axis resulted in reduced MME and contact pressure. Lower limb alignment must be taken into account while assessing MME in clinical practice.

Level Of Evidence: Controlled laboratory study.
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http://dx.doi.org/10.1007/s00167-019-05701-1DOI Listing
April 2020

Neither lateral patellar facet nor patellar size are altered in patellofemoral unstable patients: a comparative magnetic resonance imaging analysis.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 27;28(4):1064-1071. Epub 2019 Aug 27.

OrthoPlus München, Munich, Germany.

Purpose: It remains unclear if morphologic patterns of the patella itself predispose to patellar instability. This study examined established patellar landmarks in relation to the femoral condyle width to clarify differences of patellar morphologies in patellofemoral stable and unstable patients.

Methods: Magnetic Resonance Imaging of 50 subjects (20.7 ± 4.4 years; 17 males, 33 females) with patellofemoral instability (study group, SG) and 50 subjects (25.3 ± 5.8 years; 31 males, 19 females) with anterior cruciate ligament rupture (control group, CG) were analyzed. Corresponding patellar value indices (PW-I; LPF-I 1; LPF-I 2) in relation to the femoral condyle width (FCW) were evaluated after the measurement of absolute patellar dimension [patellar width (PW); direct length of the lateral patellar facet (LPF-1); projected length of the lateral patellar facet (LPF-2)]. The patellar shape according to Wiberg, trochlear dysplasia, patellar height, and tibial tubercle-trochlear groove (TT-TG) distance were determined.

Results: The SG showed a significantly longer absolute (LPF 2) (P = 0.041) and relative (LPF-I 1, LPF-I 2) (P < 0.001) lateral facet of the patella. No significant differences were evaluable for the relative patellar width (PW-I) (ns). A patellar shape type 3 (P = 0.001) as well as a higher position of the patella and TT-TG-distance (P < 0.001) were significantly more often present in the SG.

Conclusion: There are several bony alterations associated with patellofemoral instability, but our data did not show a significantly smaller lateral patellar facet or relative patellar width that could facilitate a patellar dislocation. This helps surgeons, that are considering to surgically address the patella in cases of patellofemoral instability, to better understand its morphologic pattern.

Level Of Evidence: III.
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http://dx.doi.org/10.1007/s00167-019-05660-7DOI Listing
April 2020

Varus alignment aggravates tibiofemoral contact pressure rise after sequential medial meniscus resection.

Knee Surg Sports Traumatol Arthrosc 2020 Apr 3;28(4):1055-1063. Epub 2019 Aug 3.

Department of Orthopedics and Sports Orthopedics, Technical University of Munich, Hospital Rechts der Isar, Munich, Germany.

Purpose: Arthroscopic partial meniscectomy of medial meniscus tears and varus alignment are considered independent risk factors for increased medial compartment load, thus contributing to the development of medial osteoarthritis. The purpose of this biomechanical study was to investigate the effect of lower limb alignment on contact pressure and contact area in the knee joint following sequential medial meniscus resection. It was hypothesized that a meniscal resection of 50% would lead to a significant overload of the medial compartment in varus alignment.

Methods: Eight fresh-frozen human cadaveric knees were axially loaded with a 750 N compressive force in full extension with the mechanical axis rotated to intersect the tibia plateau at 30%, 40%, 50%, 60% and 70% of its width. Tibiofemoral mean contact pressure (MCP), peak contact pressure (PCP), and contact area (CA) of the medial and lateral compartment were measured separately using pressure-sensitive films (K-Scan 4000, Tekscan) in four different meniscal conditions, respectively, intact, 50% resection, 75% resection, and total meniscectomy.

Results: Medial MCP was significantly increased when comparing the intact meniscus to each meniscal resection in all tested alignments (p < 0.05). Following meniscal resection of 50%, MCP was significantly higher with greater varus alignment compared to valgus alignment (p < 0.05). Similarly, medial PCP was higher at varus alignment compared to valgus alignment (p < 0.05). Further resection to 75% and 100% of the meniscus resulted in a significantly higher medial PCP at 30% of tibia plateau width compared to all other alignments (p < 0.05). Medial CA of the intact meniscus decreased significantly after 50%, 75% and 100% meniscal resection in all alignments (p < 0.05). Lateral joint pressure was not significantly increased by greater valgus alignment.

Conclusion: Lower limb alignment and the extent of medial meniscal resection significantly affect tibiofemoral contact pressure. Combined varus alignment and medial meniscal resection increased MCP and PCP within the medial compartment, whereas valgus alignment prevented medial overload. As a clinical consequence, lower limb alignment should be considered in the treatment of patients undergoing arthroscopic partial meniscectomy with concomitant varus alignment. In patients presenting with ongoing medial joint tenderness and effusion, realignment osteotomy can be a surgical technique to unload the medial compartment.
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http://dx.doi.org/10.1007/s00167-019-05654-5DOI Listing
April 2020

Proximal radius fracture morphology following axial force impact: a biomechanical evaluation of fracture patterns.

BMC Musculoskelet Disord 2019 Apr 6;20(1):147. Epub 2019 Apr 6.

Department of Orthopaedic and Trauma Surgery, Helios Hospital Munich West, Steinerweg 5, 81241, Munich, Germany.

Background: The most common location for articular fractures of the radial head is often reported to be the anterior lateral aspect of the radial head with the arm in neutral position. However, these findings mainly base on clinical observations rather than precise biomechanical measurements. The purpose of this study was to evaluate the formation of proximal radius fractures, the association between axial forces and fracture morphology, energy to failure and bone stiffness in a biomechanical in-vitro setup.

Methods: 18 fresh-frozen cadaveric radii performed axial load compression with 10 mm/min loading until bone failure. Energy to failure and bone stiffness were recorded. Proximal radial head fracture morphology and affection of the anterolateral quadrant were optically analyzed.

Results: All radii survived a compression load of 500 N. The mean compressive forces that lead to failure were 2,56 kN (range 1,30 - 7,32). The mean stiffness was 3,5 kN/mm (range 2,0 - 4,9). 11 radial neck fractures and 7 radial neck and radial head multifragment fractures were documented. The anterolateral quadrant was involved in 78% of tested radii.

Conclusion: The anterolateral quadrant of the radial head (in neutral position of the forearm) is confirmed to be the most common location for articular radial head fractures in a biomechanical setting. In case of a fall on the outstretched arm radial neck fractures should be securely ruled out due to prior occurrence to radial neck and head fractures.
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http://dx.doi.org/10.1186/s12891-019-2529-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451781PMC
April 2019

Effect of Lower Limb Alignment in Medial Meniscus-Deficient Knees on Tibiofemoral Contact Pressure.

Orthop J Sports Med 2019 Feb 6;7(2):2325967118824611. Epub 2019 Feb 6.

Department of Orthopedics and Sports Orthopedics, Rechts der Isar Hospital, Technical University of Munich, Munich, Germany.

Background: Degenerative medial meniscal tears and subsequent partial meniscal resection compromise meniscal function and lead to an overload of the medial compartment. In addition, lower limb alignment plays a key role in load distribution between the medial and lateral knee compartments, and varus alignment is a potential risk factor for medial osteoarthritis.

Purpose/hypothesis: The purpose of this biomechanical study was to investigate the effect of valgus and varus alignment on peak pressure and contact area in knees with concomitant horizontal medial meniscal tears and subsequent leaflet resection. It was hypothesized that varus alignment in combination with meniscal loss leads to the highest peak pressure within the medial compartment.

Study Design: Controlled laboratory study.

Methods: Six fresh-frozen human cadaveric knees were axially loaded using a 1000-N compressive load in full extension with the mechanical axis rotated to intersect the tibial plateau at 40%, 45%, 50%, 55%, and 60% of its width (TPW) to simulate varus and valgus alignment. Tibiofemoral peak contact pressure and contact area of the medial and lateral compartments were determined using pressure-sensitive foils in each of 4 different meniscal conditions: intact, 15-mm horizontal tear of the posterior horn, inferior leaflet resection, and resection of both leaflets.

Results: The effect of alignment on peak pressure (normalized to the neutral axis) within the medial compartment in cases of an intact meniscus was measured as follows: varus shift resulted in a mean increase in peak pressure of 18.5% at 45% of the TPW and 37.4% at 40% of the TPW, whereas valgus shift led to a mean decrease in peak pressure of 8.7% at 55% of the TPW and 23.1% at 60% of the TPW. Peak pressure changes between the intact meniscus and resection within the medial compartment was less in valgus-aligned knees (0.21 MPa at 60% TPW, 0.59 MPa at 50% TPW, and 0.76 MPa at 40% TPW). Contact area was significantly reduced after partial meniscal resection in the neutral axis (intact, 553.5 ± 87.6 mm; resection of both leaflets, 323.3 ± 84.2 mm; < .001). This finding was consistent in any alignment.

Conclusion: Both partial medial meniscal resection and varus alignment led to an increase in medial compartment peak pressure. Valgus alignment prevented medial overloading by decreasing contact pressure even after partial meniscal resection. A horizontal meniscal tear did not influence peak pressure and contact area even in varus alignment.

Clinical Relevance: As a clinical consequence, partial meniscal resection should be avoided to maintain the original biomechanical behavior, and the mechanical axis should be taken into account if partial meniscectomy is necessary.
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http://dx.doi.org/10.1177/2325967118824611DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6378645PMC
February 2019

No dynamic extrusion of the medial meniscus in ultrasound examination in patients with confirmed root tear lesion.

Knee Surg Sports Traumatol Arthrosc 2019 Oct 3;27(10):3311-3317. Epub 2019 Jan 3.

Klinik für Orthopädie und Unfallchirurgie, Martin Luther Krankenhaus, Berlin, Germany.

Purpose: Extrusion of the medial meniscus evaluated on magnetic resonance imaging (MRI) has been described as indirect radiological sign for meniscus root tears. However, ultrasound detectable dynamic extrusion is observed in normal physiological settings. The aim of the present study was to analyze the dynamic meniscal extrusion using ultrasound (US) examination in patients with MRI-confirmed meniscal root tears. The hypothesis was that dynamic meniscus extrusion is reduced in patients with medial root tear but not in the healthy meniscus.

Methods: Twenty-five patients with a medial root lesion of the meniscus (group I) and 25 healthy controls (group II) were enrolled in this study. The medial meniscus extrusion (MME) of the index knee was determined using ultrasound (US) in supine position and under full weight bearing. Standard knee MRI was used for determining whether the patients were eligible for this study according to the inclusion and exclusion criteria, respectively.

Results: In group I, the mean MME was 3.6 mm (± 1.0 mm) in supine position and 3.7 mm (± 0.9 mm) under full weight bearing according to US measurements. The mean Δ-extrusion was 0.1 mm (± 0.2 mm) and the ratio was 1.0 (± 0.1). Mean medial meniscus extrusion on MRI was 3.9 mm (± 0.9 mm). In group II, mean MME was 1.3 mm (± 0.3 mm) in supine position (US) and 2.3 mm (± 0.4 mm) under full weight bearing (US). The mean Δ-extrusion was 1.0 mm (± 0.4 mm) and the extrusion ratio was 1.8 (± 0.4). In this group, mean extrusion in MRI was 1.4 mm (± 0.7 mm). The difference in mean ultrasound Δ-extrusion, ratio, and MRI extrusion between both groups was statistically significant (p < 0.001).

Conclusions: Based on the results of dynamic ultrasound examination of the medial meniscus, medial root tear leads to significantly decreased dynamic medial displacement of the meniscus compared to healthy meniscus status. The absence of dynamic meniscus extrusion may be an indicator for medial meniscus root injury and could be detected using ultrasound ("dead meniscus sign").

Level Of Evidence: III.
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http://dx.doi.org/10.1007/s00167-018-5341-4DOI Listing
October 2019

High short-term return to sports rate despite an ongoing healing process after acute meniscus repair in young athletes.

Knee Surg Sports Traumatol Arthrosc 2019 Jan 11;27(1):215-222. Epub 2018 Dec 11.

Department of Orthopaedic Sports Medicine, Klinikum Rechts der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Acute meniscus repair in young athletes is always a challenge due to the long rehabilitation process and time to return to sport (RTS). The purpose was to investigate signal alterations in short-term follow-up after acute meniscus repair on specific magnetic resonance imaging (MRI) scan sequences. It was hypothesized that (1) MRI signal changes over the first postoperative healing phase and represent a continuous healing process and (2) meniscus healing properties correlates with clinical outcomes and RTS.

Methods: Young athletes with traumatic meniscus lesion and arthroscopic meniscus repair within 6 weeks and available preoperative MRI were enrolled. Clinical examination, outcome scores (IKDC, KOOS, Lysholm Score, Tegner activity score) and RTS were surveyed preoperatively and 6 and 12 weeks and 6 months after surgery. Radiological follow-up examinations were performed 2, 4, 6, 12 weeks and 6 months after operation using a 3T-MRI. Evaluation was based on ISAKOS meniscus classification system, meniscus healing were classified according to Henning's criteria.

Results: At final follow-up (FU) 30 patients (28 month, 2 week) with a total of 35 meniscus tears (19 medial, 16 lateral) were included. Clinical scores improved significantly after surgery: IKDC Score (preOP: 39.4 ± 18.5, final FU: 78.8 ± 15.3) KOOS (preOP: 45.7 ± 22.1, final FU: 82.7 ± 12.5) and Lysholm Score (preOP: 42.8 ± 23.7, final FU: 84.4 ± 13.8) (p < 0.01). Tegner activity score showed a steadily increase to 4 (range 3-9) at 6 months but did not reached the pre-injury level of 6 (range 3-9). RTS rate was 100% whereof 44.8% reached their pre-injury level. MRI examination revealed a continuous healing process and menisci were classified as 55.9% healed, 35.3% partially healed and 8.8% non-healed at final FU.

Conclusion: This study showed that MRI signal alterations of the meniscus steadily occur within the first 6 months postoperatively. MRI reveals an ongoing healing process at final FU that have to be carefully considered when RTS is discussed with high demanding patients. However, young athletes provide good clinical results and RTS rate even though MRI alterations are still present.

Level Of Evidence: Therapeutic study, prospective case series, Level IV.
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http://dx.doi.org/10.1007/s00167-018-5335-2DOI Listing
January 2019

Distal femoral torsional osteotomy increases the contact pressure of the medial patellofemoral joint in biomechanical analysis.

Knee Surg Sports Traumatol Arthrosc 2019 Jul 29;27(7):2328-2333. Epub 2018 Sep 29.

Department of Orthopaedic Sports Medicine, Hospital Rechts der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Torsional osteotomy of the distal femur allows anatomic treatment of patellofemoral instability and patellofemoral pain syndrome in cases of increased femoral antetorsion. The purpose of this study was to investigate the effects of distal femoral torsional osteotomy on pressure distribution of the medial and lateral patellar facet.

Methods: Nine fresh frozen human knee specimens were embedded in custom-made 3D-printed casts and tested with a robotic arm. Torsional osteotomy could be simulated ranging from increased femoral antetorsion of 25° with a corresponding lateralization of the patella to an overcorrected value of 5° of femoral antetorsion. The peak and mean lateral and medial compartment pressure was measured in 0°, 15°, 30°, 45°, 60° and 90° flexion beginning with neutral anatomic muscle rotation.

Results: The medial aspect of the patella showed a significant influence of femoral torsion with an increase of mean and peak pressure in all flexion angles with progressive derotation from 15° external rotation to 5° internal rotation (p = 0.004). The overall pressure difference was highest in near extension and stayed on a constant level with further flexion. On the lateral facet, the derotation resulted in decrease of pressure in near extension; however, it had no significant influence on the mean and peak pressure through the different torsion angles (n.s.). Unlike on the medial facet, a significant consistent increase of peak pressure from 0° to 90° flexion could be shown (p = 0.022) on the lateral patella aspect.

Conclusion: Distal femoral torsional osteotomy to correct pathological femoral antetorsion leads to a redistribution of retropatellar pressure. External derotation leads to an increased peak pressure on the medial patellar facet and can impair simultaneous cartilage repair. However, as the lateral patellofemoral load decreases, it has a potential in preventing patellofemoral osteoarthritis.
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http://dx.doi.org/10.1007/s00167-018-5165-2DOI Listing
July 2019

Clinical Outcomes, Tendon Integrity, and Shoulder Strength After Revision Rotator Cuff Reconstruction: A Minimum 2 Years' Follow-up.

Am J Sports Med 2018 09 7;46(11):2700-2706. Epub 2018 Aug 7.

Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany.

Background: The retear rate after primary rotator cuff (RC) reconstruction is high and commonly leads to poorer clinical outcomes and shoulder function. In the case of primary failure, revision RC reconstruction (RCR) has become increasingly important to re-create RC integrity and improve outcomes. To date, clinical and structural outcomes after RCR have not been sufficiently investigated and described at midterm follow-up. Hypothesis/Purpose: The purpose was to evaluate the clinical and radiological outcomes after revision RCR. It was hypothesized that revision RCR significantly improves clinical outcomes and that the outcomes positively correlate with tendon integrity on magnetic resonance imaging (MRI).

Study Design: Case series; Level of evidence, 4.

Methods: Patients who underwent revision RCR between 2008 and 2014 were retrospectively evaluated with a minimum follow-up of 2 years. Outcomes were assessed by a clinical examination, a visual analog scale for pain (VAS), the Constant Score (CS), the American Shoulder and Elbow Surgeons (ASES) score, and the Disabilities of the Arm, Shoulder and Hand (DASH) score. Tendon integrity was determined using 3-T MRI and graded according to the Sugaya classification.

Results: Thirty-one of 40 patients (77.5%) were available for the final assessment at a mean follow-up of 50.3 ± 20.4 months. Clinical outcome scores significantly improved from preoperatively to postoperatively for the CS (39.7 ± 16.7 to 65.1 ± 19.7; P < .001), ASES (44.2 ± 17.7 to 75.2 ± 24.8; P < .001), and DASH (68.6 ± 15.1 to 21.5 ± 19.1; P < .001). The VAS score decreased from 6.1 ± 1.8 preoperatively to 1.3 ± 1.8 at final follow-up ( P < .001). MRI demonstrated a retear rate of 55.5%. No differences in CS, ASES, and DASH scores were detected between patients with an intact repair and failure. Abduction strength was not significantly different in patients with an intact repair and retears (55.5 N vs 44.0 N, respectively, P = .52).

Conclusion: Revision RCR improves clinical outcomes and shoulder function at midterm follow-up. The clinical outcome scores were comparable in patients with an intact repair and those with failed RC healing. Therefore, tendon integrity was not correlated with better clinical outcomes after revision RCR at final follow-up.
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http://dx.doi.org/10.1177/0363546518786006DOI Listing
September 2018

[Rupture of the proximal hamstring tendon].

MMW Fortschr Med 2018 Jun;160(12):39-41

Abteilung für Sportorthopädie, Klinikum rechts der Isar, Technische Universität München, München, Deutschland.

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http://dx.doi.org/10.1007/s15006-018-0704-9DOI Listing
June 2018

[Shoulder pain in athletes - 5 steps from diagnosis to successful treatment].

MMW Fortschr Med 2018 Jun;160(12):44-47

Abteilung und Poliklinik für Sportorthopädie, Klinikum rechts der Isar, Technische Universität München, München, Deutschland.

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http://dx.doi.org/10.1007/s15006-018-0706-7DOI Listing
June 2018

Repair of the lateral posterior meniscal root improves stability in an ACL-deficient knee.

Knee Surg Sports Traumatol Arthrosc 2018 Aug 27;26(8):2302-2309. Epub 2018 Apr 27.

Department of Orthopaedics and Sportsorthopaedics, Technical, University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: To investigate the stabilizing effect of a lateral meniscus posterior root repair in an ACL and root deficient knee.

Methods: The hypothesis of the current study was that a sequential transection of the posterior root and the meniscofemoral ligaments in an ACL-deficient knee increases rotational instability, and conversely, a repair of the meniscus root reduces the internal tibial rotation. Therefore, eight human knee joints were tested in a robotic setup (5 N m internal torque, 50 N m anterior translation load). Five conditions were tested: intact, ACL cut, ACL cut + lateral meniscus posterior root tear (LMRT), ACL cut + LMRT + transection of the MFL and ACL cut + lateral meniscus root repair. The angles of internal tibial rotation as well as anterior tibial translation were recorded.

Results: Transection of the lateral meniscus posterior root increased the internal tibial instability as compared to the ACL-insufficient state. A significant increase was detected in 60° and 90° of flextion. Sectioning of the meniscofemoral ligament further destabilized the knees significantly at all flexion angles as compared to the ACL-deficient state. Even in 30°, 60° and 90° a significant difference was detected as compared to the isolated root tear. A tibial fixation of the lateral meniscus root reduced the internal tibial rotation in all flexion angles and led to a significant decrease of internal tibial rotation in 30° and 90° as compared to the transection of the root and the MFL. The anterior tibial translation was increased in all conditions as compared to the native state.

Conclusion: A lateral meniscus root repair can reduce internal tibial rotation in the ACL-deficient knee. To check the condition of the lateral posterior meniscus root attachment is clinical relevant as a lateral meniscus root repair might improve rotational stability.
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http://dx.doi.org/10.1007/s00167-018-4949-8DOI Listing
August 2018

Medial meniscus extrusion increases with age and BMI and is depending on different loading conditions.

Knee Surg Sports Traumatol Arthrosc 2018 Aug 6;26(8):2282-2288. Epub 2018 Mar 6.

Department for Orthopaedic Sports Medicine, Klinikum rechts der Isar, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: Meniscus extrusion has always been described as an indirect sign of meniscus pathology and is associated with a loss of function of the affected meniscus. The current cut-off value of 3 mm displacement is indicated as abnormal and has been determined on magnetic resonance images (MRI) and ultrasound (US). However, it has to be considered that there is no description of the physiological meniscus extrusion in healthy knees depending on age or different weight-bearing conditions. It was hypothesized that in healthy knees there is a physiological age and BMI dependent meniscal extrusion, and meniscus extrusion depends on different loading conditions.

Methods: Healthy volunteers with non-symptomatic knee, and no history of knee injuries or operations were included in this prospective cross-sectional study. Exclusion criteria were age < 18years, subjective or objective instability, malalignment and positive medial meniscus test. Secondary exclusion criteria were osteoarthritis ICRS grade 3-4 or signs of meniscus tear on MRI. Every patient underwent standard knee examination following measurement of medial meniscus extrusion (MME) using US. In US extrusion was determined in supine position (unloaded) and in standing position with full weight-bearing and 20° of flexion (loaded). MRI was performed in a neutral knee position to compare ultrasound measurements with the current gold standard. Based on the power calculation of preliminary results a minimum of 70 volunteers was needed.

Results: 75 patients were enrolled to this study. The mean US MME was 1.1 mm ± 0.5 mm in supine position and 1.9 mm ± 0.9 mm under full weight-bearing. The mean US Δ-extrusion was 0.8 mm ± 0.6 mm. With rising age, a significant increased MME in US and MRI could be demonstrated (p < 0.001). Furthermore, elevated BMI was significantly correlated to increased US MME under full weight-bearing (p = 0.002) and to US Δ-extrusion (p = 0.003).

Conclusion: Based on the results of this study, medial meniscus extrusion is an age-depending phenomenon in healthy knees and depends on various load-bearing conditions. Ultrasound examination of the MME might be favorable compared to MRI due to the ability of dynamic evaluation. As a consequence, the current cut-off value of 3 mm for meniscus pathologies should be reconsidered.

Level Of Evidence: III.
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http://dx.doi.org/10.1007/s00167-018-4885-7DOI Listing
August 2018

Smoking and obesity influence the risk of nonunion in lateral opening wedge, closing wedge and torsional distal femoral osteotomies.

Knee Surg Sports Traumatol Arthrosc 2018 Sep 8;26(9):2551-2557. Epub 2017 Nov 8.

Department of Orthopaedic Sports Medicine, Klinikum rechts der Isar, Technical University of Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose: Lateral distal femoral osteotomies (DFO) have recently been performed more frequently. In addition to realignment for varus and valgus deformity, the indication was extended with the introduction of torsional osteotomies in patellofemoral instability. The purpose of this study was to assess the general and technical risk factors for nonunion in lateral opening, closing and torsional DFO.

Methods: A total of 150 lateral DFO [98 opening wedge (LOWDFO) and 52 closing wedge (LCWDFO)] were analyzed in regard to potential risk factors for nonunion until plate removal. Nonunion was defined as failure of osseous consolidation according to clinical and radiological evaluation.

Results: In LOWDFO, the nonunion rate was 2%, in LCWDFO the rate was higher with 9.6%. Nicotine abuse (p = 0.009) and a higher body mass index (p = 0.003) were significant risk factors. Patient's age and gender, the wedge height, hinge fractures, monoplanar versus biplanar osteotomy as well as additional torsional osteotomies were not significant in regard of nonunion.

Conclusions: Lateral DFO have a low rate of complications and nonunion. Smoking and obesity were significantly associated with the risk of nonunion. Hinge fractures, monoplanar technique or complete bone cuts of the opposite hinge in torsional osteotomies did not negatively influence the nonunion rate in DFO.

Level Of Evidence: Level IV.
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http://dx.doi.org/10.1007/s00167-017-4754-9DOI Listing
September 2018

Arthroscopic arthrolysis provides good clinical outcome in post-traumatic and degenerative elbow stiffness.

Knee Surg Sports Traumatol Arthrosc 2018 Jan 1;26(1):312-317. Epub 2017 Jul 1.

Department of Orthopaedic Sports Medicine, Klinikum Rechts der Isar, Technical University Munich, Ismaningerstr. 22, 81675, Munich, Germany.

Purpose And Hypothesis: The purpose of this retrospective study was to report on the functional outcome after arthroscopic arthrolysis in patients with post-traumatic or degenerative elbow stiffness. It was hypothesized that this operative procedure leads to improved range of motion (ROM) and improved functional outcome in both groups.

Methods: Patients who underwent arthroscopic arthrolysis of the elbow between 2010 and 2015 were included in this study. Forty-two patients with an average age of 41.0 ± 13.5 years were available for evaluation. The mean follow-up was 28.3 ± 14.9 months. With regard to aetiology of elbow contractures, patients were divided into post-traumatic (group A) and degenerative (group B) cohort. General patients' data, previous surgical treatment and ROM were recorded. At follow-up evaluation, the clinical outcome was assessed by the ROM, visual analogue scale (VAS) for pain assessment and the Elbow Self-Assessment Score (ESAS).

Results: The mean arc of motion of group A (n = 20) increased from preoperatively 74.3° to 120.5° postoperatively (p < 0.001); group B (n = 22) showed an improvement of 104.6° preoperatively to 123.4° after surgery (p = 0.002). Mean improvement was 46.3° ± 27.5° in group A and 16.4° ± 19.4° in group B. Mean post-operative VAS was 0.9 ± 1.5 in group A and 1.3 ± 2.2 in group B. 92.9% of patients achieved a functional arc of elbow motion >100°. The ESAS indicated good to excellent clinical outcome showing 88.8 ± 10.0 points in group A and 84.1 ± 21.4 points in group B. Thirty-six patients (85.7%) returned to their previous work level after surgery.

Conclusions: Arthroscopic arthrolysis is an effective treatment option for patients with restriction in elbow motion reasoned by post-traumatic or degenerative changes. Both groups showed a significant improvement of ROM and comparable outcome scores.

Level Of Evidence: Therapeutic study, Level IV.
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http://dx.doi.org/10.1007/s00167-017-4630-7DOI Listing
January 2018

Critical shoulder angle combined with age predict five shoulder pathologies: a retrospective analysis of 1000 cases.

BMC Musculoskelet Disord 2017 Jun 15;18(1):259. Epub 2017 Jun 15.

St. Vincent Shoulder and Sports Clinic Vienna, Baumgasse 20A, 1030, Vienna, Austria.

Background: Acromial morphology has previously been defined as a risk factor for some shoulder pathologies. Yet, study results are inconclusive and not all major shoulder diseases have been sufficiently investigated. Thus, the aim of the present study was to analyze predictive value of three radiological parameters including the critical shoulder angle, acromion index, and lateral acromion angle in relationship to symptomatic patients with either cuff tear arthropathy, glenohumeral osteoarthritis, rotator cuff tear, impingement, and tendinitis calcarea.

Methods: A total of 1000 patients' standardized true-anteroposterior radiographs were retrospectively assessed. Receiver-operating curve analyses and multinomial logistic regression were used to examine the association between shoulder pathologies and acromion morphology. The prediction model was derived from a development cohort and applied to a validation cohort. Prediction model's performance was statistically evaluated.

Results: The majority of radiological measurements were significantly different between shoulder pathologies, but the critical shoulder angle was an overall better parameter to predict and distinguish between the different pathologies than the acromion index or lateral acromion angle. Typical critical shoulder angle-age patterns for the different shoulder pathologies could be detected. Patients diagnosed with rotator cuff tears had the highest, whereas patients with osteoarthritis had the lowest critical shoulder angle. The youngest patients were in the tendinitis calcarea and the oldest in the cuff tear arthropathy group.

Conclusions: The present study showed that critical shoulder angle and age, two easily assessable variables, adequately predict different shoulder pathologies in patients with shoulder complaints.
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http://dx.doi.org/10.1186/s12891-017-1559-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5472957PMC
June 2017

Nonunion and delayed union in lateral open wedge distal femoral osteotomies-a legitimate concern?

Int Orthop 2018 01 23;42(1):9-15. Epub 2017 May 23.

Department of Sport Orthopaedics, Technische Universität München, Klinikum Rechts der Isar, Ismaninger Str. 22, D-81675, Munich, Germany.

Introduction: Due to a supposed high rate of nonunions in lateral open wedge distal femur osteotomy (LOWDFO), the medial closing wedge technique has been favoured for a long time. The aim of this study was to report the occurrence of delayed- and nonunions following LOWDFO. We hypothesized that the occurrence of nonunions needing revision surgery is comparable to medial closing osteotomies.

Methods: Forty-one patients were treated with LOWDFO with a minimum follow-up of 12 months. Parameters such as age, gender, body mass index, valgus angle, the heights of the opening wedge, as well as the type of osteotomy (biplane vs single plane) were collected. Delayed union and nonunion were evaluated on radiographs along with clinical symptoms.

Results: The study group consisted of 21 females and 20 males, with a median age of 37 years at the time of surgery. Removal of hardware was performed in 63% after 1.3 years (0.6-2.1 years). The median preoperative valgus angle was 6.1° valgus (range 2-15.5°). The heights of the opening wedge ranged from 2 to 12 mm (mean 5.3 mm). Hinge fracture of the medial cortex was seen in 39%. Three patients had a delayed union, and one patient had a nonunion requiring revision surgery.

Conclusion: LOWDFO is a safe alternative to MCWDFO. Although radiolucency of the osteotomy gap can be evident on radiographs even after 12 months, this does not reflect the clinical finding. The nonunion rate is proven to be low and comparable with the nonunion rates of MCWDFOs as well as open wedge HTOs.
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http://dx.doi.org/10.1007/s00264-017-3504-4DOI Listing
January 2018
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