Publications by authors named "Wolfgang Lehmann"

102 Publications

Cage or Pelvic Graft-Study on Bony Fusion of the Ventral Thoracic and Lumbar Spine in Traumatic Vertebral Fractures.

Medicina (Kaunas) 2021 Jul 31;57(8). Epub 2021 Jul 31.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Robert-Koch Str. 40, 37075 Göttingen, Germany.

Stabilization of the spine by cage implantation or autologous pelvic bone graft are surgical methods for the treatment of traumatic spine fractures. These methods serve to stably re-adjust the spine and to prevent late detrimental effects such as pain or increasing kyphosis. They both involve ventral interventions using interbody fusion to replace the intervertebral disc space between the vertebral bodies either by cages or autologous pelvic bone grafts. We examined which of these methods serves the patients better in terms of bone fusion and the long-term clinical outcome. Forty-six patients with traumatic fractures (12 cages; mean age: 54.08/34 pelvic bone grafts; mean age: 42.18) who received an anterior fusion in the thoracic or lumbar spine were included in the study. Postoperative X-ray images were evaluated, and fusion of the stabilized segment was inspected by two experienced spine surgeons. The time to discharge from hospital and gender differences were evaluated. There was a significant difference of the bone fusion rate of patients with autologous pelvic bone grafts in favor of cage implantation ( = 0.0216). Also, the stationary phase of patients who received cage implantations was clearly shorter (17.50 days vs. 23.85 days; = 0.0089). In addition, we observed a significant gender difference with respect to the bony fusion rate in favor of females treated with cage implantations ( < 0.0001). Cage implantations after spinal fractures result in better bony fusion rates as compared to autologous pelvic bone grafts and a shorter stay of the patients in the hospital. Thus, we conclude that cage implantations rather than autologous pelvic bone grafts should be the preferred surgical treatment for stabilizing the spine after fracture.
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http://dx.doi.org/10.3390/medicina57080786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8398686PMC
July 2021

The impact of bilateral facetectomy on the instantaneous helical axis of the functional thoracic spinal unit T4-5 during axial rotation.

Int Biomech 2021 12;8(1):42-53

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University of Göttingen, Göttingen, Germany.

The location of the instantaneous helical axis (IHA) and the impact of the facet joints (FJ) on the kinematics in the thoracic spine remain inconclusive. This study aimed to examine the IHA in the functional spinal unit (FSU) T4-5 during axial rotation in intact conditions and after bilateral facetectomy. Four human T4-5 FSUs were examined with an established 6D measuring apparatus in intact conditions and after bilateral facetectomy. The IHA's parameters migration, location, and direction in the horizontal plane were calculated. Defined preloads in different positions were applied. Under the intact conditions, the IHA migrated about 4 mm and from one to the contralateral side according to the applied preload. The location of the IHA was observed in the anterior part of the spinal canal. After bilateral facetectomy, the location of the IHA shifted ventrally about 10 mm compared to the intact conditions. Under intact conditions, the direction of the IHA was minimally dorsally reclined. After bilateral facetectomy, the IHA was significantly more ventrally inclined. The study determined the location of the IHA under intact conditions at the anterior part of the spinal canal. The IHA of the FSU T4-5 is substantially influenced by the guidance of the FJs.
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http://dx.doi.org/10.1080/23335432.2021.1958059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8344236PMC
December 2021

Perioperative and posttraumatic anti-edematous decongestive device-based negative pressure treatment for anti-edematous swelling treatment of the lower extremity - a prospective quality study.

Int J Burns Trauma 2021 15;11(3):145-155. Epub 2021 Jun 15.

Department of Trauma Surgery, Orthopedics and Plastic Surgery of The University Medical Centre of Goettingen Lower Saxony, Germany.

Background: The perioperative management of trauma cases and orthopedic procedures is negatively influenced by tissue swelling and edema. They delay surgical treatment, extend stay in hospital and prolong the overall time of convalescence. In case of traumatic or postoperative edema the limited transport capacity (missing muscle pump and destruction of lymphatic channels) is casual. Edema mostly results in pain, limited function of the extremity, change in shape, higher infection rate and wound disorders. Manual lymph drainage (MLD) is a treatment option with respect to the complex physical decongestion (CPD).

Objective: To evaluate whether a device-based negative pressure lymph drainage (NPLD) is capable of reducing posttraumatic and perioperative swelling of the lower extremity effectively and sustainably.

Methods: Prospective quality study submitted to the Ethics Committee. The patients only received the procedures after signing the informed consent. The negative pressure was applied locally by using LymphaTouch® device (LT) (FDA approved) with a silicone-coated applicator. The lymphatic drainage had been either applied by a local stationary manner or by using the "Lift + Twist" technique. A negative pressure has been adjusted between 50-250 mm Hg depending on the skin and tissue texture. The frequency was chosen between 90-70 Hz. Type of application: pulsed or continuous negative pressure treatment. The procedure always began in the supraclavicular fossa and continued until reaching the area of surgery in the lower extremity. Duration approx. 30 min. The patient was encouraged to drink fluids after the LymphaTouch treatment (LTT). The results were documented by measurement of the girth and movement according to neutral-zero-method (NZM) and photographs.

Statistics: Multi-variance, Wilcoxon test non-parametric.

Inclusion Criteria: Patients with injury to the lower extremity (LE), elective patients, age > 18 years, signed informed consent.

Results: 101 patients with injuries/surgical interventions to the lower extremity, age: 64.9 ± 13.17 years. The swelling was more pronounced at the knee. After 4 treatments, there was a measurable decrease in swelling of 11.6% at the lower extremity. In patients with trauma to the hip joint or hip interventions, the swelling at the femur was reduced by 8.6% between LTT 0 vs. 4. In patients with trauma to the knee joint and surgical interventions, significantly more female patients showed a positive effect to LTT. The mobility improved substantially, while the level of pain decreased. The patients reported immediate pain relief. No complications occurred.

Conclusion: The perioperative and posttraumatic swelling at the lower extremity can be positively affected by the LT-NPLD within the first days. The preoperative duration until surgical intervention was decreased. The postoperative stage of wound and soft tissue swelling was reduced.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8310870PMC
June 2021

Analysis of trans-sacral corridors in stabilization of fractures of the pelvic ring.

J Orthop Res 2021 Jul 22. Epub 2021 Jul 22.

Department for Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

Percutaneous screw fixation combined with pelvic reduction is a surgical technique used to stabilize fractures of the posterior pelvic ring. This is the standard surgical treatment of unstable posterior pelvic ring injuries. The primary goal of this treatment is an anatomic reduction and stable fixation. This has been shown to reduce pain and improve the patients' long-term well-being. The aim of this analysis was to determine the possible screw lengths and the positioning of the screws in the S1 and S2 sacral segments. A population of 697 pelvises from the Stryker Orthopaedic Modeling and Analytics database were analyzed. The dimensions of the S1 and S2 screw corridors were determined and after assessing for sacral dysmorphism, the correct screw placement was chosen to determine the necessary screw length for surgical treatment. The measurements of the screw lengths show a Gaussian distribution for the analyzed population. The percentage of dysmorphic pelvises for the S1 screw corridor was 31.3% and for the S2 corridor 8%. Average screw length for S1 was 163.8 ± 16.2 mm and for the S2 137.3 ± 9.5 mm. The results show that the S1/S2 axis cannot be used for a trans-sacral screw placement in every patient. The study shows that intraosseous screw corridors are present in 68.7% of the patients in the S1 position and in 92% at the S2 level where an intended implant can be placed fully intraosseous.
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http://dx.doi.org/10.1002/jor.25144DOI Listing
July 2021

Biomechanical Effects of a Cross Connector in Sacral Fractures - A Finite Element Analysis.

Front Bioeng Biotechnol 2021 26;9:669321. Epub 2021 May 26.

Department of Trauma, Orthopedics and Reconstructive Surgery, Georg-August-University of Göttingen, Göttingen, Germany.

Spinopelvic fractures and approaches of operative stabilization have been a source of controversial discussion. Biomechanical data support the benefit of a spinopelvic stabilization and minimally invasive procedures help to reduce the dissatisfying complication rate. The role of a cross connector within spinopelvic devices remains inconclusive. We aimed to analyze the effect of a cross connector in a finite element model (FE model). A FE model of the L1-L5 spine segment with pelvis and a spinopelvic stabilization was reconstructed from patient-specific CT images. The biomechanical relevance of a cross connector in a Denis zone I (AO: 61-B2) sacrum fracture was assessed in the FE model by applying bending and twisting forces with and without a cross connector. Biomechanical outcomes from the numerical model were investigated also considering uncertainties in material properties and levels of osseointegration. The designed FE model showed comparable values in range-of-motion (ROM) and stresses with reference to the literature. The superiority of the spinopelvic stabilization (L5/Os ilium) ± cross connector compared to a non-operative procedure was confirmed in all analyzed loading conditions by reduced ROM and principal stresses in the disk L5/S1, vertebral body L5 and the fracture area. By considering the combination of all loading cases, the presence of a cross connector reduced the maximum stresses in the fracture area of around 10%. This difference has been statistically validated ( < 0.0001). The implementation of a spinopelvic stabilization (L5/Os ilium) in sacrum fractures sustained the fracture and led to enhanced biomechanical properties compared to a non-reductive procedure. While the additional cross connector did not alter the resulting ROM in L4/L5 or L5/sacrum, the reduction of the maximum stresses in the fracture area was significant.
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http://dx.doi.org/10.3389/fbioe.2021.669321DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8188498PMC
May 2021

Correction to: Anatomic reduction of the sacroiliac joint in unstable pelvic ring injuries and its correlation with functional outcome.

Eur J Trauma Emerg Surg 2021 Jun 10. Epub 2021 Jun 10.

Department for Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Robert-Koch Str. 40, 37075, Göttingen, Germany.

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http://dx.doi.org/10.1007/s00068-021-01698-wDOI Listing
June 2021

Impact of Screw Diameter on Pedicle Screw Fatigue Strength-A Biomechanical Evaluation.

World Neurosurg 2021 Aug 1;152:e369-e376. Epub 2021 Jun 1.

Department of Trauma Surgery, Orthopaedic Surgery and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany. Electronic address:

Objective: Loosening of pedicle screws is a frequently observed complication in spinal surgery. Because additional stabilization procedures such as cement augmentation or lengthening of the instrumentation involve relevant risks, optimal stability of the primarily implanted pedicle screw is of essential importance. The aim of the present study was to investigate the effect of increasing the screw diameter on pedicle screw stability.

Methods: A total of 10 human cadaveric vertebral bodies (L4) were included in the present study. The bone mineral density was evaluated using quantitative computed tomography and the pedicle diameter using computed tomography. The vertebrae underwent instrumentation using 6.0-mm × 45-mm pedicle screws on 1 side and screws with the largest possible diameter (8-10-mm × 45-mm) on the other side. Fatigue testing was performed by applying a cyclic loading (craniocaudal sinusoidal 0.5 Hz) with increasing peak force (100 N + 0.1 N/cycle) until screw head displacement of 5.4 mm was reached.

Results: The mean fatigue load was 334 N for the 6-mm diameter screws and was increased significantly to 454 N (+36%) for the largest possible diameter screws (P < 0.001). With an increase in the fatigue load by 52%, this effect was even more pronounced in vertebrae with reduced bone density (bone mineral density <120 mg/cm; n = 7; P < 0.001). The stiffness of the construct was significantly greater in the largest diameter screw group compared with the standard screw group during the entire testing period (start, P < 0.001; middle, P < 0.001; end, P = 0.009).

Conclusions: Increasing the pedicle screw diameter from a standard 6-mm screw to the largest possible diameter (8-10 mm) led to a significantly greater fatigue load.
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http://dx.doi.org/10.1016/j.wneu.2021.05.108DOI Listing
August 2021

Investigating the Microchannel Architectures Inside the Subchondral Bone in Relation to Estimated Hip Reaction Forces on the Human Femoral Head.

Calcif Tissue Int 2021 May 22. Epub 2021 May 22.

Department of Trauma Surgery, Orthopaedic Surgery and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

The interplay between articular cartilage (AC) and subchondral bone (SB) plays a pivotal role in cartilage homeostasis and functionality. As direct connective pathways between the two are poorly understood, we examined the location-dependent characteristics of the 3D microchannel network within the SB that connects the basal cartilage layer to the bone marrow (i.e. cartilage-bone marrow microchannel connectors; CMMC). 43 measuring points were defined on five human cadaveric femoral heads with no signs of osteoarthritis (OA) (age ≤ 60), and cartilage-bone cylinders with diameters of 2.00 mm were extracted for high-resolution scanning (n = 215). The micro-CT data were categorized into three groups (load-bearing region: LBR, n = 60; non-load-bearing region: NLBR, n = 60; and the peripheral rim: PR, n = 95) based on a gait analysis estimation of the joint reaction force (young, healthy cohort with no signs of OA). At the AC-SB interface, the number of CMMC in the LBR was 1.8 times and 2.2 times higher compared to the NLBR, and the PR, respectively. On the other hand, the median Feret size of the CMMC were smallest in the LBR (55.2 µm) and increased in the NLBR (73.5 µm; p = 0.043) and the PR (89.1 µm; p = 0.043). AC thickness was positively associated with SB thickness (Pearson's r = 0.48; p < 1e-13), CMMC number. (r = 0.46; p < 1e-11), and circularity index (r = 0.61; p < 1e-38). In conclusion, our data suggest that regional differences in the microchannel architecture of SB might reflect regional differences in loading.
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http://dx.doi.org/10.1007/s00223-021-00864-xDOI Listing
May 2021

Osseointegration of a novel 3D porous Ti-6Al-4V implant material - Histomorphometric analysis in rabbits.

Histol Histopathol 2021 May 11:18342. Epub 2021 May 11.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

Porous structure properties are known to conduct initial and long-term stability of titanium alloy implants. This study aims to assess the histomorphometric effect of a 3-D porosity in Ti-6Al-4V implants (PI) on osseointegration in comparison to solid Ti-6Al-4V implants (SI). The PI was produced in a spaceholder method and sintering and has a pore size of mean 400 µm (50 µm to 500 µm) and mimics human trabecular bone. Pairs of PI and equal sized SI as reference were bilaterally implanted at random in the lateral femoral condyle of 16 Chinchilla-Bastard rabbits. The animals were sacrificed after 4 and 12 weeks for histomorphometric analysis. The histomorphometric evaluation confirmed a successful short-term osseohealing (4 weeks) and mid-term osseoremodeling (12 weeks) for both types of implants. The total newly formed bone area was larger for PI than for SI after 4 and 12 weeks, with the intraporous bone area being accountable for the significant difference (p<0.05). A more detailed observation of bone area distribution revealed a bony accumulation in a radius of +/- 500 µm around the implant surface after remodeling. The bone-to-implant contact (BIC) increased significantly (p<0.05) from 4 to 12 weeks (PI 26.23 % to 42.68 %; SI 28.44 % to 47.47 %) for both types of implants. Due to different surface properties, however, PI had a significant (p<0.05) larger absolute osseous contact (mm) to the implant circumference compared to the SI (4 weeks: 7.46 mm vs 5.72 mm; 12 weeks: 11.57 mm vs 9.52 mm [PI vs. SI]). The regional influences (trabecular vs. cortical) on bone formation and the intraporous distribution were also presented. Conclusively, the porous structure and surface properties of PI enable a successful and regular osseointegration and enhance the bony fixation compared to solid implants under experimental conditions.
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http://dx.doi.org/10.14670/HH-18-342DOI Listing
May 2021

Risk Analysis of Perioperative Injections in Arthroscopic Reconstruction of the Rotator Cuff of the Shoulder - A Systematic Review.

Z Orthop Unfall 2021 Mar 29. Epub 2021 Mar 29.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, Georg-August-University Göttingen Medical Centre, Göttingen, Germany.

Background: The present study used a systematic review to analyse the risk of perioperative injections during arthroscopic reconstruction of the rotator cuff of the shoulder. The questions of interest were whether perioperative local injection increases the infection risk and whether the number of postoperative revisions is increased.

Material And Methods: A systematic review of the U. S. National Library of Medicine/National Institutes of Health (PubMed) database and the Cochrane Library was performed using the PRISMA checklist. The keywords used were "shoulder" and "arthroscopy" and "injection" and "risk". In the course of the study, work that was not also primarily concerned with the reconstruction of the rotator cuff was excluded. English original articles and case series were included that contained at least some arthroscopic reconstructions of the rotator cuff. The risk of bias was determined using the Newcastle-Ottawa Scale. The content of the articles relevant to the research questions was analysed.

Results: 48 hits were primarily generated. 9 articles corresponded to the inclusion criteria and were analysed. In the 6 studies with details on the injected substances, cortisone was used in 98 - 100% of the cases. The reported infection and revision rates based on insurance data were higher with injection than without. The risk of bias in the studies analysed here was rather low based on the Newcastle-Ottawa Score. The risk of infection after a cortisone injection before, during or after surgery was increased. Injection was associated with infection in up to 8% of cases with injections within two weeks of surgery. The risk of infection was increased by up to 11 times with injections within 4 weeks after the operation. Likewise, the risk of revision surgery after injection was increased, with the time intervals between injection and surgery sometimes differing between studies.

Discussion: Local infections and to a lesser extent revision surgery are associated with perioperative injections (with cortisone) within 3 months preoperatively and 4 weeks postoperatively. However, there were only database studies of insurance data with several studies from a few centres. Thus, no causal relationships could be proven. Currently, however, the following can be recommended using a cautious approach: The interval between injection with cortisone before surgery should be at least 2 weeks, better 3 months. No cortisone injections should be applied intraoperatively. Postoperatively, cortisone should not be injected for at least 4 weeks. If, in exceptional cases, deviations from these time limits are required, patients should be informed about an increased risk of complications.
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http://dx.doi.org/10.1055/a-1394-6469DOI Listing
March 2021

Sequential osseointegration from osseohealing to osseoremodeling - Histomorphological comparison of novel 3D porous and solid Ti-6Al-4V titanium implants.

Histol Histopathol 2021 Mar 29:18333. Epub 2021 Mar 29.

Department of Trauma Surgery, Orthopedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

In the present study, we analyzed the histological characteristics of osseointegration of an open-porous Ti-6Al-4V material that was produced in a space holder method creating a 3-D through-pores trabecular design that mimics the inhomogeneity and size relationships of trabecular bone in macro- as well as microstructure. Pairs of cylindrical implants with a porosity of 49 % and an average pore diameter of 400 µm or equal sized solid, corundum blasted devices as reference were bilaterally implanted press fit in the lateral condyles of 16 rabbits. Histological examination was performed after 4 weeks of short-term osseohealing and 12 weeks of mid-term osseoremodeling and we summarized the criteria for sequential osseointegration. After 4 weeks, osteoid had already been largely replaced by mineralized woven bone in both types of implants but was only represented to a greater extent in the deeper pores of PI. The cortical as well as trabecular region showed regular osseohealing with excessive and spatially undirected formation of immature woven bone. A dense bone mass was found in the cortical area, while in the trabecular region the bone mass was reduced distinctly, presenting large lacuna-like recesses and a demarcating trabecular structure. The pores near the implant surface contained more mineralized woven bone than the deeper pores. After 12 weeks, the osseoremodeling was largely completed with a physiological maturation to lamellar bone. The newly formed bone mass increased for PI and SI compared to the 4-week group and osteoid was only detectable in the deeper pores. The inhomogeneous trabecular design of the pores enables an excellent ingrowth of mineralized lamellar bones after remodeling to a pore depth of 1800 µm, which proves a functional load transfer from the surrounding bone into the implant. According to the concept of osseointegration by Branemark and Albrektsson, the histological evaluation confirms a successful, superior osseointegration of the presented porous properties improving long-term implant stability. The presented study protocol allows an excellent evaluation and comparison of the sequential osseointegration from short-term osseohealing to mid-term osseoremodeling.
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http://dx.doi.org/10.14670/HH-18-333DOI Listing
March 2021

The influence of bone quality on radiological outcome in 50 consecutive acetabular fractures treated with a pre-contoured anatomic suprapectineal plate.

Arch Orthop Trauma Surg 2021 Mar 24. Epub 2021 Mar 24.

Department of Trauma and Orthopaedic Surgery, University Medical Center Hamburg-Eppendorf, Martinistraße 52, 20246, Hamburg, Germany.

Purpose: To investigate the range of indications of an anatomical-preshaped three-dimensional suprapectineal plate and to assess the impact of the bone mass density on radiologic outcomes in different types of acetabular fractures.

Patients And Methods: A consecutive case series of 50 acetabular fractures (patient age 69 ± 23 years) treated with suprapectineal anatomic plates were analyzed in a retrospective study. The analysis included: Mechanism of injury, fracture pattern, surgical approach, need for additional total hip arthroplasty, intra- or postoperative complications, as well as bone mass density and radiological outcome on postoperative computed tomography.

Results: Most frequently, anterior column fracture patterns with and without hemitransverse components as well as associated two column fractures were encountered. The anterior intrapelvic approach (AIP) was used in 98% (49/50) of the cases as primary approach with additional utilization of the first window of the ilioinguinal approach in 13/50 cases (26%). Determination of bone density revealed impaired bone quality in 70% (31/44). Postoperative steps and gaps were significantly greater in this subgroup (p < 0.05). Fracture reduction quality for postoperative steps revealed anatomic results in 92% if the bone quality was normal and in 46% if impaired (p < 0.05). In seven cases (14%), the plate was utilized in combination with acute primary arthroplasty.

Conclusion: A preshaped suprapectineal plate provides good radiological outcomes in a variety of indications in a predominantly geriatric cohort. Impaired bone quality has a significantly higher risk of poor reduction results. In cases with extensive joint destruction, the combination with total hip arthroplasty was a valuable option.
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http://dx.doi.org/10.1007/s00402-021-03867-3DOI Listing
March 2021

Biomechanical evaluation of self-cinching stitch techniques in rotator cuff repair: The single-loop and double-loop knot stitches.

Open Med (Wars) 2021 12;16(1):293-298. Epub 2021 Feb 12.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Robert-Koch-Strasse 40, 37075, Goettingen, Germany.

In rotator cuff repair, strong and reliable suturing is necessary to decrease failure rates. The biomechanics of two self-cinching stitches - the single-loop knot stitch (SLKS) and the double-loop knot stitch (DLKS) - and the modified Mason-Allen stitch (mMAS) were compared. Twenty-seven porcine infraspinatus tendons were randomized among the three stitches. Each was cyclically loaded (10-80-200 N for 50 cycles each) while the gap formation was measured. Next, ultimate load to failure was tested. The gap widths after cyclic loading were 8.72 ± 0.93 mm for the DLKS, 8.65 ± 1.33 mm for the mMAS, and 9.14 ± 0.89 mm for the SLKS, without significant differences. The DLKS showed the highest ultimate load (350.52 ± 38.54 N) compared with the mMAS (320.88 ± 53.29 N; = 0.304) and the SLKS (290.54 ± 60.51 N; < 0.05). The DLKS showed similar reliability and better strength compared with the mMAS, while the SLKS showed a slight but not significant decrease in performance. In our experience, the DLKS and SLKS have clinical advantages, as they are easy to perform and the self-cinching loop knot allows the surgeon to grasp degenerative tendon tissue. Initial intraoperative tightening of the suture complex (preloading) before locking is important in order to decrease postoperative elongation.
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http://dx.doi.org/10.1515/med-2021-0211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7892937PMC
February 2021

Osseointegration of 3D porous and solid Ti-6Al-4V implants - Narrow gap push-out testing and experimental setup considerations.

J Mech Behav Biomed Mater 2021 03 14;115:104282. Epub 2020 Dec 14.

Department of Trauma Surgery, Orthopedics and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

Porosity in titanium alloy materials improves the bony integration and mechanical properties of implants. In certain areas of application such as vertebral spacers or trabecular bone replacement (e.g. wedge augmentation in prosthetics), surface structures are desirable that promote bone integration and have biomechanical properties that are resistant to intraosseous load transfers and at the same time resemble the stiffness of bone to possible reduce the risk of stress shielding. In the present study, we investigated the biomechanical push-out behavior of an open-porous Ti-6Al-4V material that was produced in a space-holder and sintering method creating a 3-D through-pores trabecular design that corresponds with the inhomogeneity and size relationships of trabecular bone. The short-term and mid-term effects of the material properties on osseointegration in a biomechanical push-out study were compared to those of to a conventional solid Ti-6Al-4V material. In order to raise the measurement accuracy we implemented a strict study protocol. Pairs of cylindrical implants with a porosity of 49% and an average pore diameter of 400 μm and equal sized solid, corundum blasted devices as reference were bilaterally implanted press fit in the lateral femoral condyles of 14 rabbits. After sacrifice at 4 and 12 weeks, a push-out test was performed while the test set-up was designed to ensure conformity of implant axes and direction of applied force. Maximum holding force, Young's modulus, and mode of failure were recorded. Results of maximum push-out force (F-max) revealed a significant material effect (p < 0.05) in favor of porous implants after 4 weeks of osseohealing (6.39 vs. 3.36 N/mm) as well as after 12 weeks of osseoremodeling (7.58 vs. 4.99 N/mm). Evaluation of the failure mode resulted in three different types of displacement characteristics, which revealed a different mechanism of osseous anchoring between the two types of implants and substantiate the F-max and Young's modulus results. Conclusively, the porous implant offers surface properties that significantly improve its osseous stability compared to solid material under experimental conditions. In addition, we have optimized our study protocol for biomechanical push-out tests to produce precise and comparable results.
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http://dx.doi.org/10.1016/j.jmbbm.2020.104282DOI Listing
March 2021

[Osteosynthesis of the unstable thoracic wall].

Oper Orthop Traumatol 2021 Jun 8;33(3):262-284. Epub 2020 Dec 8.

Klink für Unfallchirurgie, Orthopädie und Plastische Chirurgie, Universitätsmedizin Göttingen, Robert-Koch-Str. 40, 37075, Göttingen, Deutschland.

Objective: Surgical stabilization of patients with flail chest, dislocated serial rib and sternal fractures, posttraumatic deformities of the thorax, symptomatic non-unions of the ribs and/or sternum, and weaning failure to biomechanically stabilize the thorax and avoid respirator-dependent complications.

Indications: Combination of clinically and radiologically observed parameters, such as pattern of thoracic injuries, grade of fracture dislocation, pathological changes to breathing biomechanics, and failure of nonsurgical treatment.

Contraindications: Acute hemodynamical instability and signs of systemic infection.

Surgical Technique: Detailed preoperative planning. Open, minimally invasive reduction and osteosynthesis using precontoured, low-profile locking plates and/or intramedullary splints. Careful reduction drilling/implantation of screws due to proximity of the pleura, lungs and pericardium.

Postoperative Management: Weaning from respirator as early as possible and early therapy of pneumothorax perioperatively. Removal of implants usually not necessary.

Results: In a retrospective study, 15 polytraumatized patients with flail chest benefitted from an early interdisciplinary surgical treatment strategy within 24-48 h. Early osteosynthesis after severe thoracic trauma significantly reduced ventilator dependency and lowered the risk of pneumonia compared to patients who underwent surgery at a later time point. Patients with severe thoracic injury and life-threatening polytrauma, who meet the indication criteria for open reduction and surgical stabilization of the thorax, are in need of a throughly planned and interdisciplinary synchronized priorization and strategy. Longer intensive care unit stay, overall prolonged duration of admission in hospital, and higher level of respirator-associated complication should be expected in patients with life-threatening severe thoracic trauma (Abbreviated Injury Score (AIS) ≥ 3) compared to patients without thoracic trauma.
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http://dx.doi.org/10.1007/s00064-020-00688-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7722258PMC
June 2021

Comparison of the double loop knot stitch and Kessler stitch for Achilles tendon repair: A biomechanical cadaver study.

PLoS One 2020 3;15(12):e0243306. Epub 2020 Dec 3.

Department of Orthopaedics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Tendon elongation after Achilles tendon (AT) repair is associated with the clinical outcome. Reliable suture techniques are essential to reduce gap formations and to allow early mobilization. Cyclic loading conditions represent the repetitive loading in rehabilitation. The aim of this study was to compare the Kessler stitch and double loop knot stitch (DLKS) in a cyclic loading program focussing on gap formation. Sixteen human cadaveric ATs were transected and sutured using either the Kessler stitch or DLKS (eight matched pairs). The suture-tendon configurations were subjected to cyclic loading and additional ultimate load to failure testing using the Zwick 1446 universal testing machine. Each AT survived cyclic loading, with a mean gap formation less than 5 mm after 1000 cycles. The mechanical properties of the Kessler stitch and DLKS were not significantly different after cyclic loading with a mean displacement of 4.57 mm (± 1.16) for the Kessler stitch and 4.85 mm (± 1.14) for the DLKS (P = .76). There were no significant differences in the ultimate load testing (P = .85). Both bioprotective techniques prevent excessive gaping in cyclic testing when tendon loading is moderate. Our data and those from literature of gap formation in cyclic and ultimate loading allow the conclusion, that early aggressive AT loading after repair (e.g. full weightbearing) overstrain simple as well as complex suture configurations. Initial intraoperative tightening of the knots (preloading) before locking is important to decrease postoperative elongation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0243306PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7714161PMC
January 2021

Solutions for failed osteosynthesis of the acetabulum.

J Clin Orthop Trauma 2020 Nov-Dec;11(6):1039-1044. Epub 2020 Sep 28.

Pelvic and Acetabular Reconstruction Unit. Department of Trauma & Orthopaedics, North Bristol NHS Trust, Southmead Hospital, Southmead Rd, Bristol, BS10 5NB, UK.

Osteosynthesis of the acetabulum is complex and requires very careful planning and preoperative preparation. The goal is to achieve anatomical reduction without steps or gaps in the articular surface. If it has not been possible to achieve an optimal reconstruction, one has to consider whether it makes sense to carry out reosteosynthesis or revise the fixation. The risk of infection, heterotopic ossification, avascular necrosis of the femur and cartilage damage is much higher than with the primary procedure. Often, especially in older patients, it may make more sense to achieve fracture union and to implant a total hip prosthesis in due course. In younger patients, every attempt should be made to achieve optimum anatomical reduction and this may mean consideration of reosteosynthesis after careful planning and counselling of the patient. If reosteosynthesis is considered adequate imaging including a postoperative CT is essential as part of the planning. This article looks at the possible solutions for failed osteosynthesis of the acetabulum.
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http://dx.doi.org/10.1016/j.jcot.2020.09.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7656531PMC
September 2020

Minimally invasive posterior locked compression plate osteosynthesis shows excellent results in elderly patients with fragility fractures of the pelvis.

Eur J Trauma Emerg Surg 2021 Feb 26;47(1):37-45. Epub 2020 Oct 26.

Department of Orthopedic Surgery, Sports Traumatology and Trauma Surgery, Staedtisches Klinikum Wolfenbuettel, Alter Weg 80, 38302, Wolfenbuettel, Germany.

Purpose: Fragility fractures of the pelvis (FFP) are common in older patients. We evaluated the clinical outcome of using a minimally invasive posterior locked compression plate (MIPLCP) as therapeutic alternative.

Methods: 53 Patients with insufficiency fractures of the posterior pelvic ring were treated with MIPLCP when suffering from persistent pain and immobility under conservative treatment. After initial X-ray, CT-scans of the pelvis were performed. In some cases an MRI was also performed to detect occult fractures. Postoperatively patients underwent conventional X-ray controls. Data were retrospectively analyzed for surgical and radiation time, complication rate, clinical outcome and compared to the literature.

Results: Patients (average age 79.1 years) underwent surgery with operation time of 52.3 min (SD 13.9), intra-operative X-ray time of 9.42 s (SD 9.6), mean dose length product of 70.1 mGycm (SD 57.9) and a mean hospital stay of 21.2 days (SD 7.7). 13% patients (n = 7) showed surgery-related complications, such as wound infection, prolonged wound secretion, irritation of the sacral root or clinically inapparent screw malpositioning. 17% (n = 9) showed postoperative complications (one patient died due to pneumonia 24 days after surgery, eight patients developed urinal tract infections). 42 patients managed to return to previous living situation. 34 were followed-up after a mean period of 31.5 (6-90) months and pain level at post-hospital examination of 2.4 (VAS) with an IOWA Pelvic Score of 85.6 (55-99).

Conclusion: We showed that MIPLCP osteosynthesis is a safe surgical alternative in patients with FFP 3 and FFP 4. This treatment is another way of maintaining a high level of stability in the osteoporotic pelvic ring with a relatively low complication rate, low radiation and moderate operation time and a good functional outcome.
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http://dx.doi.org/10.1007/s00068-020-01498-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851100PMC
February 2021

Ostarine and Ligandrol Improve Muscle Tissue in an Ovariectomized Rat Model.

Front Endocrinol (Lausanne) 2020 17;11:556581. Epub 2020 Sep 17.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University of Göttingen, Göttingen, Germany.

In postmenopausal women, hormonal decline changes muscle function and structure. The non-steroidal selective androgen receptor modulators (SARMs) Ostarine (OS) and Ligandrol (LG) have been shown to increase muscle mass and physical function while showing a relative low risk profile. Information about their effects on muscle structure and metabolism is lacking. To analyze this, two experiments were performed using ovariectomized rats as a standard model for postmenopausal conditions. In each experiment, 3-month old Sprague-Dawley rats were divided into five groups ( = 12 to 15). One group remained intact (Non-OVX), the other four groups were ovariectomized (OVX) and remained untreated for eight (OS Experiment) or nine (LG Experiment) weeks. Thereafter, rats of three of the four OVX groups were treated with OS or LG (with doses of 0.04, 0.4, or 4 mg/kg body weight/day) for 5 weeks. Then, uterus, gastrocnemius, and soleus muscles were weighed, fiber size, capillary density, and enzyme activity (lactate dehydrogenase [LDH], citrate synthase [CS], and complex I) were analyzed. In the LG experiment, intramuscular fat content was determined in the quadriceps femoris muscle. All OS treatments resulted in a higher capillary density in the gastrocnemius and longissimus muscles compared with the Non-OVX and the OVX rats, whereas all LG treatments showed a higher capillary density compared with the Non-OVX group. Muscle fiber size and distribution patterns were not changed under either SARM. The CS activity was higher in the longissimus muscle under OS treatment. LG resulted in a higher activity of CS in the gastrocnemius and of LDH in the longissimus muscle. Both SARMs showed an uterotrophic effect, OS at 4 and 0,4 mg dosages, LG at 4 mg dosage. In sum, beneficial effect on muscle vascularization was observed for both SARMs with a stronger impact for OS. LG showed more effect on muscle metabolism. However, a higher muscle weight and intramuscular fat content observed after LG treatment (4 mg) as well as an uterotrophic effect of both SARMs at higher dosages could be considered as an unfavorable side effects and might be a limitation for their application at these dosages.
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http://dx.doi.org/10.3389/fendo.2020.556581DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7528560PMC
May 2021

Anatomic reduction of the sacroiliac joint in unstable pelvic ring injuries and its correlation with functional outcome.

Eur J Trauma Emerg Surg 2020 Sep 30. Epub 2020 Sep 30.

Department for Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Göttingen, Robert-Koch Str. 40, 37075, Göttingen, Germany.

Purpose: Reduction and percutaneous screw fixation of sacroiliac joint disruptions and sacral fractures are surgical procedures for stabilizing the posterior pelvic ring. It is unknown, however, whether smaller irregularities or the inability to achieve an anatomic reduction of the joint and the posterior pelvic ring affects the functional outcome. Here, the long-term well-being of patients with and without anatomic reduction of the posterior pelvis after sacroiliac joint disruptions is described.

Methods: Between 2011 and 2017, 155 patients with pelvic injuries underwent surgical treatment. Of these, 39 patients with sacroiliac joint disruption were examined by radiological images and computer tomography (CT) diagnostics and classified according to Tile. The functional outcome of the different surgical treatments was assessed using the short form health survey-36 (SF-36) and the Majeed pelvic score.

Results: Complete data sets were available for 31 patients, including 14 Tile type C and 17 type B injuries. Of those, 26 patients received an anatomic reduction, 5 patients obtained a shift up to 10 mm (range 5-10 mm). The SF-36 survey showed that the anatomic reduction was significantly better in restoring the patient's well being (vitality, bodily pain, general mental health and emotional well-being). Patients without this treatment reported a decrease in their general health status.

Conclusions: Anatomic reduction was achieved in over 80% of patients in this study. When comparing the long-term well-being of patients with and without anatomic reduction of the posterior pelvis after sacroiliac joint disruptions, the results suggest that anatomical restoration of the joint is beneficial for the patients.
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http://dx.doi.org/10.1007/s00068-020-01504-zDOI Listing
September 2020

Cortical threaded pedicle screw improves fatigue strength in decreased bone quality.

Eur Spine J 2021 01 17;30(1):128-135. Epub 2020 Sep 17.

Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.

Purpose: Inadequate anchoring of pedicle screws in vertebrae with poor bone quality is a major problem in spine surgery. The aim was to evaluate whether a modified thread in the area of the pedicle could significantly improve the pedicle screw fatigue strength.

Methods: Fourteen human cadaveric vertebral bodies (L2 and L3) were used for in vitro testing. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by standard pedicle screws with a constant double thread on the right pedicle and a partial doubling of the threads-quad thread-(cortical thread) in the area of the pedicle on the left pedicle. Pulsating sinusoidal, cyclic load (0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied orthogonal to the screw axis. The baseline force remained constant (50 N). Fatigue test was terminated after exceeding 5.4-mm head displacement (~ 20° screw tilting).

Results: The mean fatigue load at failure was 264.9 N (1682 cycles) for the standard screws and was increased significantly to 324.7 N (2285 cycles) by the use of cortical threaded screws (p = 0.014). This effect is particularly evident in reduced BMD (standard thread 241.2 N vs. cortical thread 328.4 N; p = 0.016), whereas in the group of vertebrae with normal BMD no significant difference could be detected (standard thread 296.5 N vs. cortical thread 319.8 N; p = 0.463).

Conclusions: Compared to a conventional pedicle screw, the use of a cortical threaded pedicle screw promises superior fatigue load in vertebrae with reduced bone quality.
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http://dx.doi.org/10.1007/s00586-020-06593-3DOI Listing
January 2021

Effect of Selective Androgen Receptor Modulator Enobosarm on Bone Healing in a Rat Model for Aged Male Osteoporosis.

Calcif Tissue Int 2020 12 2;107(6):593-602. Epub 2020 Sep 2.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Goettingen, Robert-Koch Str. 40, 37075, Goettingen, Germany.

Enobosarm (ostarine, MK-2866, or GTx-024) is a non-steroidal selective androgen receptor modulator. This study evaluated the effect of various regimens of enobosarm (EN) on bone healing in an orchiectomized rat model for aged male osteoporosis and compared it to testosterone (T) treatment. Ninety eight-month-old male Sprague Dawley rats were either orchiectomized (Orx) or left intact (Non-Orx) and divided into groups (n = 15/group): (1) Non-Orx; (2) Orx; (3) Orx+T-th; (4) Orx+EN-th; (5) Orx+T-pr; and (6) Orx+EN-pr. Prophylaxis (Pr) treatments were applied immediately after Orx for up to 18 weeks. Therapy (Th) treatments were applied 12 weeks after Orx for up to 6 weeks. Bilateral tibia osteotomy with plate osteosynthesis was performed 12 weeks after Orx in all groups. EN and T were mixed with the diet; the daily dosage was 0.35 ± 0.06 and 41 ± 8 mg/kg BW, respectively. Both T treatments improved bone healing by increasing callus volume and area, bone volume and density, and cortical width; they had no effect on prostate or levator ani weight. EN-pr increased the callus area and callus density and decreased cortical density, but increased prostate weight. The effect of T-pr and T-th on bone was stronger than EN-pr. EN-th affected bone healing negatively by reducing callus density and area and delaying osteotomy bridging. Levator ani weight was increased in both EN groups. EN treatment after fracture is not advisable in aged males. EN-pr treatment as a therapy for bone healing in men could be further investigated; endocrinological side effects must be closely monitored.
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http://dx.doi.org/10.1007/s00223-020-00751-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593387PMC
December 2020

Rescue Augmentation: Increased Stability in Augmentation After Initial Loosening of Pedicle Screws.

Global Spine J 2021 Jun 21;11(5):679-685. Epub 2020 Apr 21.

Department of Trauma Surgery, Orthopaedic Surgery and Plastic Surgery, University Medical Center Göttingen, Göttingen, Germany.

Study Design: Biomechanical study.

Objectives: Failure of pedicle screws is a major problem in spinal surgery not only postoperatively, but also intraoperatively. The aim of this study was to evaluate whether cement augmentation may restore mounting of initially loosened pedicle screws.

Methods: A total of 14 osteoporotic or osteopenic human cadaveric vertebral bodies (L2)-according to quantitative computed tomography (QCT)-were instrumented on both sides by conventional pedicle screws and cement augmented on 1 side. In vitro fatigue loading (cranial-caudal sinusoidal, 0.5 Hz) with increasing peak force (100 N + 0.1 N/cycles) was applied until a screw head displacement of 5.4 mm (∼20°) was reached. After loosening, the nonaugmented screw was rescue augmented, and fatigue testing was repeated.

Results: The fatigue load reached 207.3 N for the nonaugmented screws and was significantly ( = .009) exceeded because of initial cement augmentation (300.6 N). The rescue augmentation after screw loosening showed a fatigue load of 370.1 N which was significantly higher ( < .001) compared with the nonaugmented screws. The impact of bone density on fatigue strength decreased from the nonaugmented to the augmented to the rescue-augmented screws and shows the greatest effect of cement augmentation on fatigue strength at low bone density.

Conclusions: Rescue augmentation leads to similar or higher fatigue strengths compared with those of the initially augmented screws. Therefore, the cement augmentation of initially loosened pedicle screws is a promising option to restore adequate screw stability.
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http://dx.doi.org/10.1177/2192568220919123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8165920PMC
June 2021

Laser Ablated Periodic Nanostructures on Titanium and Steel Implants Influence Adhesion and Osteogenic Differentiation of Mesenchymal Stem Cells.

Materials (Basel) 2020 Aug 10;13(16). Epub 2020 Aug 10.

Department for Trauma Surgery, Orthopaedics and Plastic Surgery, University Medical Center Goettingen, Robert Koch Straße 40, 37075 Göttingen, Germany.

Metal implants used in trauma surgeries are sometimes difficult to remove after the completion of the healing process due to the strong integration with the bone tissue. Periodic surface micro- and nanostructures can directly influence cell adhesion and differentiation on metallic implant materials. However, the fabrication of such structures with classical lithographic methods is too slow and cost-intensive to be of practical relevance. Therefore, we used laser beam interference ablation structuring to systematically generate periodic nanostructures on titanium and steel plates. The newly developed laser process uses a special grating interferometer in combination with an industrial laser scanner and ultrashort pulse laser source, allowing for fast, precise, and cost-effective modification of metal surfaces in a single step process. A total of 30 different periodic topologies reaching from linear over crossed to complex crossed nanostructures with varying depths were generated on steel and titanium plates and tested in bone cell culture. Reduced cell adhesion was found for four different structure types, while cell morphology was influenced by two different structures. Furthermore, we observed impaired osteogenic differentiation for three structures, indicating reduced bone formation around the implant. This efficient way of surface structuring in combination with new insights about its influence on bone cells could lead to newly designed implant surfaces for trauma surgeries with reduced adhesion, resulting in faster removal times, reduced operation times, and reduced complication rates.
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http://dx.doi.org/10.3390/ma13163526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7475978PMC
August 2020

Reduction of postoperative swelling with a negative pressure treatment-A prospective study.

J Orthop Surg (Hong Kong) 2020 Jan-Apr;28(2):2309499020929166

Department of Trauma, Orthopedics and Plastic Surgery, Georg-August-University of Goettingen, Goettingen, Germany.

Purpose: Perioperative swelling and edema are the main factors that influence the time to definitive operative care, healing rate, as well as postoperative infection rate. Device-based negative pressure treatment is a new method to reduce post-traumatic and postoperative swelling of the upper extremities. The objective of this study was to evaluate a new negative pressure treatment with LymphaTouch (Helsinki, Finland) to reduce perioperative swelling in upper extremity injuries.

Methods: We analyzed 45 patients (26 female and 19 male) after operative treatment of upper extremity injuries. A predefined treatment algorithm of 30 min using LymphaTouch was performed on the patients every day for five consecutive days. Swelling was measured according to the neutral-zero method with six points of measurement.

Results: A total of 16 patients underwent an operation on their upper arm. An average of 3.5 measurements was performed per patient, with the start of therapy at a mean of 5.13 days after the operation. All of the measured circumferences except the elbow and 10 cm below the elbow were reduced from day 0 to 3. The percent reduction of swelling (relative to day 0) was 10.36%, 11.35%, 17.34%, and 3.25% for days 1-4, respectively. The greatest reduction of circumference was obtained in the metacarpus (-51.6%) and wrist (-33.1%).

Conclusion: The LymphaTouch system and a 30-min treatment program can reduce postoperative swelling of the upper arm, wrist, and hand on the first 5 days after surgery. The ease of learning and self-applicability of LymphaTouch makes it interesting for further controlled randomized trials.
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http://dx.doi.org/10.1177/2309499020929166DOI Listing
February 2021

Motor Recovery of the Suprascapular Nerve after Arthroscopic Decompression in the Scapular Notch - a Systematic Review.

Z Orthop Unfall 2020 May 11. Epub 2020 May 11.

Klinik für Unfallchirurgie, Orthopädie und Plastische Chirurgie, Universitätsmedizin Göttingen.

Background: The suprascapular nerve can be compromised as a result of a compression syndrome in different locations. A (proximal) compression within the scapular notch can lead to dorsal shoulder pain and simultaneous weakness of the infraspinatus and supraspinatus muscles. By transection of the lig. transversum this compression syndrome can be treated. By means of a systematic review, the present work analyzes the motor recovery potential after arthroscopic decompression.

Material And Methods: A systematic review of the U. S. National Library of Medicine/National Institutes of Health (PubMed) database and the Cochrane Library was performed using the PRISMA checklist. The search words used were "suprascapular" and "arthroscopic"; "suprascapular" and "arthroscopy". Based on the evaluated literature, articles in English with at least a partial arthroscopic case series from 4 cases on and a compression syndrome of the suprascapular nerve treated with arthroscopic decompression in the scapular notch were identified. Motor recovery was described by means of EMG, clinical strength and MRI.

Results: Primarily 408 hits were generated. Six articles met the inclusion criteria and were further analyzed. The number of arthroscopic cases was between 4 and a maximum of 27. The level of evidence was between III and IV. The majority of the reported clinical results were good. Motor recovery as measured by EMG was observed, recovery of full strength was not achieved in the majority of reported cases (60%), neither was regression of structural (fatty) degeneration of the muscle bellies.

Conclusion: Arthroscopic decompression of the suprascapular nerve in the scapular notch provides good clinical results and considerable pain relief. However, in the majority of cases it does not lead to a complete recovery of the strength of the supra- and infraspinatus muscles. Patients should be informed about this. An early decompression after diagnosis in the event of proximal compression within the suprascapular notch combined with beginning EMG or MRI changes appears reasonable. These beginning changes should be further defined. Future studies should develop prognostic criteria for motor recovery. Awareness regarding the diagnosis needs to be improved due to the probably time-dependent irreversibility of resulting muscular weakness.
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http://dx.doi.org/10.1055/a-1128-0557DOI Listing
May 2020

Reduced cement volume does not affect screw stability in augmented pedicle screws.

Eur Spine J 2020 06 23;29(6):1297-1303. Epub 2020 Mar 23.

Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.

Purpose: Cement augmentation of pedicle screws is able to improve screw anchorage in osteoporotic vertebrae but is associated with a high complication rate. The goal of this study was to evaluate the impact of different cement volumes on pedicle screw fatigue strength.

Methods: Twenty-five human vertebral bodies (T12-L4) were collected from donors between 73 and 97 years of age. Bone density (BMD) was determined by quantitative computed tomography. Vertebral bodies were instrumented by conventional pedicle screws, and unilateral cement augmentation was performed. Thirteen vertebrae were augmented with a volume of 1 ml and twelve with a volume of 3 ml bone cement. A fatigue test was performed using a cranial-caudal sinusoidal, cyclic load (0.5 Hz) with increasing compression force (100 N + 0.1 N/cycles).

Results: The load to failure was 183.8 N for the non-augmented screws and was increased significantly to 268.1 N (p < 0.001) by cement augmentation. Augmentation with 1 ml bone cement increased the fatigue load by 41% while augmentation with 3 ml increased the failure load by 51% compared to the non-augmented screws, but there was no significant difference in fatigue loads between the specimens with screws augmented with 1 ml and screws augmented with 3 ml of bone cement (p = 0.504).

Conclusion: Cement augmentation significantly increases pedicle screw stability. The benefit of augmentation on screw anchorage was not significantly affected by reducing the applied volume of cement from 3 ml to 1 ml. Considering the high risk of cement leakage during augmentation, we recommend the usage of a reduced volume of 1 ml bone cement for each pedicle screw. These slides can be retrieved under Electronic Supplementary Material .
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http://dx.doi.org/10.1007/s00586-020-06376-wDOI Listing
June 2020

Total disc arthroplasties change the kinematics of functional spinal units during lateral bending.

Clin Biomech (Bristol, Avon) 2020 03 16;73:130-139. Epub 2020 Jan 16.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany; DUO - Duderstadt Trauma Surgery and Orthopaedics, Westertorstr. 7, 37115 Duderstadt, Germany.

Background: Information about kinematics in different functional spinal units before and after total disc arthroplasties is necessary to improve prostheses and determine indications. There is little information about the nonstationary instantaneous helical axis of rotation under lateral bending in the cervical spine before and after total disc arthroplasty.

Methods: Kinematic analyses were performed with an established measuring apparatus on 8 human functional spinal units (C3/C4, C5/C6) under intact conditions and after total disc arthroplasty with two different types of prostheses: Bryan and Prestige. The instantaneous helical axis, migration, and stiffness of the segments were calculated.

Findings: The instantaneous helical axis direction was always inclined ventrally. Ventral inclination was significantly higher in segment C3/C4 than in segment C5/C6 under all conditions (p < 0.001). Both types of arthroplasties significantly increased ventral inclination compared to intact conditions. In both segments, the path length of the instantaneous helical axis' migration was significantly longer after total disc arthroplasty with Bryan (p = 0.001) and shorter after Prestige (p < 0.001) prostheses than under intact conditions. After both types of arthroplasties, the migration path length was significantly longer and the stiffness was significantly lower in segment C3/C4 than in segment C5/C6.

Interpretation: Both types of arthroplasties changed the kinematics of both segments during lateral bending. Altered instantaneous helical axis migration, greater ventral inclination and less stiffness after both arthroplasties indicate unphysiological motion. Both arthroplasties had greater impact on segment C3/C4 than on segment C5/C6 in terms of hypermobility. Increased translational motion after total disc arthroplasty with a Bryan prosthesis might be caused by the prosthetic design.
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http://dx.doi.org/10.1016/j.clinbiomech.2020.01.007DOI Listing
March 2020

Total disc arthroplasties alter the characteristics of the instantaneous helical axis of the cervical functional spinal units C3/C4 and C5/C6 during flexion and extension in in vitro conditions.

J Biomech 2020 02 7;100:109608. Epub 2020 Jan 7.

Department of Trauma Surgery, Orthopaedics and Plastic Surgery, University of Göttingen, Robert-Koch-Str. 40, 37075 Göttingen, Germany; DUO - Duderstadt Trauma Surgery and Orthopaedics, Westertorstr. 7, 37115 Duderstadt, Germany. Electronic address:

Total disc arthroplasty (TDA) increases the risk of adjacent segment disease (ASD). Kinematic analyses are necessary to compare the intact condition (IC) with alterations after TDA to develop better prostheses. A well-established 6D measuring apparatus (resolution < 2.4 μm; 400 positions/cycle) was used. Kinematics of the flexion and extension of 8 human cervical spine segments (cFSU) C3/C4 and C5/C6 (67.9 ± 13.2 y) were analyzed in the IC and after TDA (Bryan® Cervical Disc [B-TDA], Prestige LP® Cervical Disc [P-TDA]). The migration of the instantaneous helical axis (IHA) and the stiffness of the segments were calculated. Analyses demonstrated a stretched U-curved IHA migration in the sagittal plane. The IHA positions were significantly more cranial in cFSU C5/C6 than in C3/C4 in IC and after either TDA (IC: p < 0.001; B-TDA: p = 0.001; P-TDA: p = 0.045). In cFSU C3/C4 IHA positions shifted anteriocranially after either TDA (p < 0.001). In cFSU C5/C6, the IHA positions were significantly more anterocranial after B-TDA than in IC and after P-TDA (anterior: p < 0.001; cranial: p = 0.005). After B-TDA, the IHA migration path length was significantly longer in cFSU C3/C4 than in C5/C6 (p = 0.007) and longer than in IC in both cFSU (C3/C4: p = 0.047; C5/C6: p < 0.001). Stiffness was increased after both TDA. Various kinematic alterations were observed after both TDA. Increased translation and IHA position shifting after both TDA might indicate abnormal strain and a derogated benefit of TDA. These results imply the most abnormal strain after B-TDA. The lower cFSU might be more susceptible to alterations after TDA than the upper cFSU.
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http://dx.doi.org/10.1016/j.jbiomech.2020.109608DOI Listing
February 2020

Chronic hyponatremia in patients with proximal femoral fractures after low energy trauma: A retrospective study in a level-1 trauma center.

Bone Rep 2020 Jun 6;12:100234. Epub 2019 Dec 6.

Department of Trauma-, Orthopaedic- and Plastic Surgery, University Medical Center Goettingen, Goettingen, Germany.

Introduction: We evaluated the prevalence and influence of chronic hyponatremia in patients with low energy trauma. We also investigated the influence of medication and diseases on hyponatremia.

Material And Methods: This retrospective study included 314 cases of proximal femoral fracture due to low energy trauma. Patients were treated in the University Medical Center Goettingen within 3 years. Hyponatremia was defined as serum sodium <135 mmol/L at admission.

Results: Overall, 15.6% of patients in the low energy trauma group had hyponatremia. Among patients older than 80 years, women showed distinctly higher rates of hyponatremia (female: 16.4%; male: 5.9%). In contrast only 4.7% of patients who underwent elective hip arthroplasty showed hyponatremia. Patients on sartanes and aldosterone antagonists showed significantly higher rates of hyponatremia. Alcoholism was significantly associated with hyponatremia.

Conclusions: We confirmed a high prevalence of chronic hyponatremia in patients with fractures due to low energy trauma. Our data underscore chronic hyponatremia as a contributing factor to hip fractures. Women older than 80 have a higher risk of developing hyponatremia. Sartanes, aldosterone antagonists, and alcohol disease are associated with hyponatremia. Treating hyponatremia may decrease the risk of fracture after low energy trauma. Therefore, physicians of different specialties should focus on treatment of chronic hyponatremia to reduce the fracture rate associated with low energy trauma.
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http://dx.doi.org/10.1016/j.bonr.2019.100234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6940722PMC
June 2020
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