Publications by authors named "Michelle H McGarry"

154 Publications

Posterior Cruciate Ligament Reconstruction With Internal Brace Augmentation Reduces Posterior Tibial Translation Under Cyclic Loading.

Orthopedics 2021 Jul-Aug;44(4):235-240. Epub 2021 Jul 1.

The goal of this study was to evaluate the stiffness and resistance to elongation of an internal bracing (IB) construct in posterior cruciate ligament reconstruction (PCLR). The authors hypothesized that augmentation with an internal brace would increase construct stiffness and decrease posterior tibial translation during cyclic loading in a fresh frozen cadaveric model. Ten cadaver knees underwent PCL reconstruction with (PCLR+IB) and without (PCLR) augmentation with an internal brace and were compared with an intact PCL state. Knees were subjected to cyclic posterior drawer loading at 45 N, 90 N, and 134 N. The PCLR+IB showed significantly less tibial translation with posterior drawer loading compared with the PCLR. Posterior tibial translation measured 8.83 mm for the PCLR vs 6.59 mm for the PCLR+IB (=.05) at 45 N posterior load. This difference remained significant at higher loads, with posterior translation of 10.84 mm and 8.44 mm for PCLR and PCLR+IB, respectively, at 90 N (=.035) and posterior translation of 12.80 mm and 10.23 mm for PCLR and PCLR+IB, respectively, at 134 N (=.023). No significant differences were found in overall construct stiffness between groups. These data suggest a checkrein mechanism of action for the internal brace in this construct, rather than a load-sharing mechanism. Importantly, the PCLR+IB technique did not constrain posterior translation more than the intact, physiologic state. Clinical studies are warranted to determine whether these ex vivo biomechanical benefits will translate to improved outcomes. [. 2021;44(4):235-240.].
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http://dx.doi.org/10.3928/01477447-20210621-03DOI Listing
July 2021

What's the best surgical repair technique of an ulnar styloid fracture? A biomechanical comparison of different techniques.

Injury 2021 Jul 2. Epub 2021 Jul 2.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundatiom, Pasadena, CA, USA. Electronic address:

Introduction: 8-10% of all Ulnar styloid fractures (USF) accompanying distal radius fractures are addressed surgically. The surgical fixation has to counteract forces of translation and rotation acting on the distal radioulnar joint (DRUJ). The different technics used were never compared biomechanically. Our study aims to compare the effects of different techniques of USF fixation on the forearm rotation and the dorsal-palmar (DP)-translation of the DRUJ.

Material And Methods: 9 forearm specimens were mounted on a custom testing system. Load was applied for Pronosupination and DP-translation with the forearm placed in neutral position, pronation and supination. The positional change of the DRUJ was measured using a MicroScribe. Six different, sequential conditions were tested in the same specimen: intact, USF and 4 repair techniques (2 K-wire, tension band wiring (TBW), headless compression screw, suture anchor).

Results: The USF significantly increased DP-translation and pronosupination compared to the intact condition. The DP-translation in neutral was reduced significantly with all four techniques compared to the USF condition. TBW and suture anchor also showed a significant difference to the K-wire fixation. In supination only the TBW and suture anchor significantly decreased DP-Translation. The rotational stability of the DRUJ was only restored by the K-wire fixation and the TBW.

Conclusions: All four USF repair techniques partially restored translational stability; however, only K-wire fixation and TBW techniques restored rotational stability. TBW was biomechanically superior to the other techniques as it restored translational stability and rotational stability.
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http://dx.doi.org/10.1016/j.injury.2021.06.026DOI Listing
July 2021

Load-to-failure characteristics of patellar tendon allograft superior capsule reconstruction compared with the native superior capsule.

JSES Int 2021 Jul 11;5(4):623-629. Epub 2021 May 11.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Background: The potential use of a patellar tendon allograft for superior capsular reconstruction has been demonstrated biomechanically; however, there are concerns regarding compromised fixation strength owing to the longitudinal orientation of the fibers in the patellar tendon. Therefore, the purpose of this study was to compare the fixation strength of superior capsule reconstruction using a patellar tendon allograft to the intact superior capsule.

Methods: The structural properties of the intact native superior capsule (NSC) followed by superior capsular reconstruction using a patellar tendon allograft (PT-SCR) were tested in eight cadaveric specimens. The scapula and humerus were potted and mounted onto an Instron testing machine in 20 degrees of glenohumeral abduction. Humeral rotation was set to achieve uniform loading across the reconstruction. Specimens were preloaded to 10 N followed by cyclic loading from 10 N to 50 N for 30 cycles, then load to failure at a rate of 60 mm/min. Video digitizing software was used to quantify the regional deformation characteristics.

Results: During cyclic loading, there was no difference found in stiffness between PT-SCR and NSC (cycle 1 - PT-SCR: 12.9 ± 3.6 N/mm vs. NSC: 22.5 ± 1.6 N/mm;  = .055 and cycle 30 - PT-SCR: 27.3 ± 1.4 N/mm vs. NSC: 25.4 ± 1.7 N/mm;  = .510). Displacement at the yield load was not significantly different between the two groups (PT-SCR: 7.0 ± 1.0 mm vs. NSC: 6.5 ± 0.3 mm;  = .636); however, at the ultimate load, there was a difference in displacement (PT-SCR: 20.7 ± 1.1 mm vs. NSC: 8.1 ± 0.5 mm;  < .001). There was a significant difference at both the yield load (PT-SCR: 71.4 ± 2.2 N vs. NSC: 331.6 ± 56.6 N;  = .004) and the ultimate load (PT-SCR: 217.1 ± 26.9 N vs. NSC: 397.7 ± 62.4 N;  = .019). At the yield load, there was a difference found in the energy absorbed (PT-SCR: 84.4 ± 8.9 N-mm vs. NSC: 722.6 ± 156.8 N-mm;  = .005), but no difference in energy absorbed was found at the ultimate load.

Conclusions: PT-SCR resulted in similar stiffness to NSC at lower loads, yield displacement, and energy absorbed to ultimate load. The ultimate load of the PT-SCR was approximately 54% of the NSC, which is comparable with the percent of the ultimate load in rotator cuff repair and the intact supraspinatus at time zero.
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http://dx.doi.org/10.1016/j.jseint.2021.04.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8245992PMC
July 2021

Kinematic analysis of two scapholunate ligament reconstruction techniques.

J Orthop Surg (Hong Kong) 2021 May-Aug;29(2):23094990211025830

Orthopedic Biomechanic Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Purpose: This study compares the kinematic changes after the procedures for scapholunate interosseous ligament (SLIL) reconstruction-the modified Brunelli technique (MBT) and Mark Henry's technique (MHT).

Methods: Ten cadaveric wrists were used. The scapholunate (SL) interval and angle and radiolunate (RL) angle were recorded using the MicroScribe system. The SL interval was measured by dividing the volar and dorsal portions. Four motions of the wrist were performed-neutral, flexion, extension, and clenched fist (CF) positions-and compared among five conditions: (1) intact wrist, (2) volar SLIL resection, (3) whole SLIL resection, (4) MBT reconstruction, and (5) MHT reconstruction.

Results: Under the whole SLIL resection condition, the dorsal SL intervals were widened in all positions. In all positions, the dorsal SL intervals were restored after MBT and MHT. The volar SL interval widened in the extension position after volar SLIL resection. The volar SL interval was not restored in the extension position after MBT and MHT. The SL angle increased in the neutral and CF positions under the whole SLIL resection condition. The SL angle was not restored in the neutral and CF positions after MBT and MHT. The RL angle increased in the neutral and CF positions under the whole SLIL resection condition. The RL angle was not restored in the neutral and CF positions after MBT and MHT.

Conclusion: The MBT and MHT may restore the dorsal SL interval. No significant differences in restoration of the SL interval between MBT and MHT were found in the cadaveric models.

Clinical Relevance: No significant differences between MBT and MHT were found in the cadaveric models for SLIL reconstruction. When considering the complications due to volar incision and additional procedures in MHT, MBT may be a more efficient technique in terms of operative time and injury of the anterior structures during surgery, but further research is needed.
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http://dx.doi.org/10.1177/23094990211025830DOI Listing
June 2021

Biceps Box Configuration for Superior Capsule Reconstruction of the Glenohumeral Joint Decreases Superior Translation but Not to Native Levels in a Biomechanical Study.

Arthrosc Sports Med Rehabil 2021 Apr 30;3(2):e343-e350. Epub 2021 Jan 30.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, California, U.S.A.

Purpose: To quantitatively biomechanically assess superior stability, subacromial contact pressures, and glenohumeral kinematics of an in situ biceps tenodesis and a box-shaped long head of the biceps tendon (LHBT) superior capsule reconstruction (SCR) in a superior massive rotator cuff tear (MCT) model.

Methods: Eight cadaveric shoulders (mean age, 62 years; range, 46-70 years) were tested with a custom testing system used to evaluate range of motion, superior translation, and subacromial contact pressure at 0°, 20°, and 40° of abduction. Conditions tested included native state, MCT (complete supraspinatus and one-half of the infraspinatus), a box-shaped LHBT SCR, and an in situ biceps tenodesis. The box-shaped SCR was performed by maintaining the biceps origin, securing 2 corners to the greater tuberosity, and one corner to the posterior glenoid. The in situ tenodesis was performed anatomically at the top of the articular margin in the same shoulder after take-down of the box SCR.

Results: Range of motion was not impaired with either repair construct ( > .05). The box SCR decreased superior translation by approximately 2 mm compared with the MCT at 0°, but translation remained greater compared with the intact state in nearly every testing position. The in situ tenodesis had no effect on superior translation. Peak subacromial contact pressure was increased in the MCT at 0° and 20° abduction compared with the native state but not different between the native and box SCR at the same positions.

Conclusions: A box-shaped SCR using the native biceps tendon partially restores increased superior translation and peak subacromial contact pressure due to MCT. The technique may have a role in augmentation of an irreparable MCT.

Clinical Relevance: The box-shaped LHBT SCR technique may have a role in augmentation of an irreparable MCT.
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http://dx.doi.org/10.1016/j.asmr.2020.09.024DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8129057PMC
April 2021

Biomechanical Evaluation of a Cadaveric Flatfoot Model and Lateral Column Lengthening Technique.

J Foot Ankle Surg 2021 Apr 11. Epub 2021 Apr 11.

Department of Orthopaedic Surgery, University of California, Irvine, CA; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA.

Patients with adult acquired flatfoot have progressive worsening of bony alignment with many being unable to perform a heel rise. Following reconstruction, pathologic skeletal alignment is corrected and the ability to perform a heel rise is often restored. The purpose of this study was to evaluate the relationship between forefoot liftoff forces and skeletal alignment in a cadaveric flatfoot model by assessing the effect of sequential lengthening of the lateral column using an Evans-type calcaneal osteotomy. Bony alignment was measured in 8 cadaveric specimens with the use of a 3-dimensional digitizing system. Transection of the spring ligament, pie-crusting of the plantar fascia, and cyclic axial loading of the foot was performed to create an anatomic and functional flatfoot model. An Evans-type calcaneal osteotomy using 6, 8, 10, and 12 mm wedges was performed. Specimens were mounted to a custom jig that applies tensile loads to the Achilles, peroneus brevis, peroneus longus, and tibialis posterior tendons. Creation of a flatfoot reduced the lateral talo-first metatarsal angle (Meary's angle) by 13° (23.6° ± 2.8° vs 10.6° ± 3.8°, p < .05) and forefoot force by 7% (199.3 N ± 7.3 N vs 185.4 N ± 9 N, p < .05). Sequential lengthening of the lateral column restored skeletal alignment and force transfer to the forefoot (12 mm wedge: Meary's angle 22.7° ± 3.9°, liftoff force 206.8 N ± 7.5 N). The cadaveric flatfoot model demonstrated decreased forefoot forces that were restored with an Evans-type calcaneal osteotomy wedge. This highlights the importance of restoring skeletal alignment when correcting advanced adult acquired flatfoot.
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http://dx.doi.org/10.1053/j.jfas.2021.04.003DOI Listing
April 2021

Comparison of Three Different Internal Brace Augmentation Techniques for Scapholunate Dissociation: A Cadaveric Biomechanical Study.

J Clin Med 2021 Apr 2;10(7). Epub 2021 Apr 2.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA 91105, USA.

Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. However, there is no detailed information about the direction, location, or number of IBs required for scapholunate interosseous ligament (SLIL) injury repair. Thus, this study compared the biomechanical characteristics of short-transverse IB, long-oblique IB, and the combination of short-transverse and long-oblique (Combo) IB for SLIL injury in a biomechanical cadaveric model. We prepared nine fresh-frozen full upper extremity cadaveric specimens for this study. The scapholunate distance, scapholunate angle, and radioscaphoid angle were measured using the MicroScribe digitizing system with the SLIL intact, after scapholunate dissociation and the three different reconstructions. Three-dimensional digital records were obtained in six wrist positions in each experimental condition. Short-transverse IB had a similar effect compared with long-oblique IB in addressing the widening of the scapholunate distance. However, both were less effective than Combo IB. For scaphoid flexion deformity, short-transverse IB had minimal effect, while long-oblique IB had a similar effect compared to Combo IB. Combo IB was the most effective for improving distraction intensity and rotational strength. This study provides important information about the biomechanical characteristics of three different IB methods for SLIL injury and may be useful to clinicians in treating scapholunate dissociation.
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http://dx.doi.org/10.3390/jcm10071482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8038308PMC
April 2021

Biomechanical analysis of progressive rotator cuff tendon tears on superior stability of the shoulder.

J Shoulder Elbow Surg 2021 Apr 22. Epub 2021 Apr 22.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Background: The biomechanical relationship between irreparable rotator cuff tear size and glenohumeral joint stability in the setting of superiorly directed forces has not been characterized. The purpose of this study was to quantify kinematic alterations of the glenohumeral joint in response to superiorly directed forces in a progressive posterosuperior rotator cuff tear model.

Methods: Nine fresh-frozen cadaveric shoulders (mean age; 58 years) were tested with a custom shoulder testing system. Three conditions were tested: intact, stage II (supraspinatus) tear, stage III (supraspinatus + anterior half of infraspinatus) tear. At each condition, range of motion and humeral head positions were measured with a "balanced" loading condition, and with a superiorly directed force ("unbalanced loading condition"). At each of the 0°, 20°, and 40° of glenohumeral abduction positions, all measurements were made at 0°, 30°, 60°, and 90° of external rotation (ER). Two-way repeated measures analysis of variance with Tukey post hoc tests were performed for statistical analyses.

Results: With the balanced load, no significant change in superior humeral head position was observed in stage II tears. Stage III tears significantly changed the humeral head position superiorly at 30° and 60° ER at each abduction angle compared with the intact condition (P ≤ .028). With superiorly directed load, stage II and stage III tears both showed statistically significant increases in superior translation at all degrees of ER for all degrees of abduction (P ≤ .035), except stage II tears at 0° ER and 40° abduction (P = .185) compared with the intact condition. Stage II tears showed posterior translations with 30° and 60° ER, both at 20° and 40° of abduction. Stage III tears also showed posterior translations with 90° ER for all abduction angles (P ≤ .039).

Conclusion: With superiorly directed loads, complete supraspinatus tendon tears created superior translations at all abduction angles, and posterior instability in the middle ranges of rotation for 20° and 40° of abduction. Larger tears involving the anterior half of the infraspinatus tendon caused significant superior and posterior translations within the middle ranges of ER for all abduction angles. In addition to superior instability, posterior translation should be considered when selecting or developing surgical techniques for large posterosuperior rotator cuff tears.
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http://dx.doi.org/10.1016/j.jse.2021.04.012DOI Listing
April 2021

Double-Bundle Anterior Cruciate Ligament Reconstruction With Lateral Extra-Articular Tenodesis Is Effective in Restoring Knee Stability in a Chronic, Complex Anterior Cruciate Ligament-Injured Knee Model: A Cadaveric Biomechanical Study.

Arthroscopy 2021 07 9;37(7):2220-2234. Epub 2021 Mar 9.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, California, U.S.A.

Purpose: To compare knee stability after intra-articular isolated double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) and single-bundle (SB) and DB ACLR combined with lateral extra-articular tenodesis (LET) in a chronic, complex anterior cruciate ligament (ACL)-injured knee model.

Methods: In 10 fresh-frozen cadaveric knees, we measured knee laxity in the following order: (1) intact knee; (2) ACL-sectioned knee; (3) complex ACL-injured knee model with additional sectioning of the anterolateral complex and the posterior horns of the medial and lateral menisci; (4) SB ACLR plus LET; (5) DB ACLR; and (6) DB ACLR plus LET.

Results: In comparison with the intact knee, significantly increased internal rotation (IR) laxity persisted at 60° and 90° after DB ACLR (P = .002 and P = .003, respectively). SB ACLR plus LET and DB ACLR plus LET resulted in significant reductions in IR laxity at 90° (P = .003 and P = .037, respectively), representing overconstraint in IR. SB ACLR plus LET resulted in persistently increased external rotation (ER) laxity at 30°, 60°, and 90° (P = .001, P < .001, and P < .001, respectively). The DB ACLR condition persistently showed significant increases in anterior tibial translation laxity at 60° and 90° (P = .037 and P = .024, respectively). A greater increase in ER laxity was seen after SB ACLR plus LET versus DB ACLR plus LET at 30°, 60°, and 90° (P < .001, P < .001, and P < .001, respectively).

Conclusions: DB ACLR plus LET restored intact knee stability in IR, ER, and anterior tibial translation laxity at 0°, 30°, 60°, and 90° of knee flexion except for overconstraint in IR at 90° in a chronic, complex ACL-injured knee model.

Clinical Relevance: This cadaveric study provides some biomechanical evidence to support performing DB ACLR combined with LET to restore knee stability after a complex, chronic knee injury involving an ACL tear combined with anterolateral complex injury and irreparable tears of the posterior horns of the medial and lateral menisci.
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http://dx.doi.org/10.1016/j.arthro.2021.02.041DOI Listing
July 2021

Anterior Cable Reconstruction of the Superior Capsule Using Semitendinosus Allograft for Large Rotator Cuff Defects Limits Superior Migration and Subacromial Contact Without Inhibiting Range of Motion: A Biomechanical Analysis.

Arthroscopy 2021 05 23;37(5):1400-1410. Epub 2020 Dec 23.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, California, U.S.A.

Purpose: To biomechanically assess translation, contact pressures, and range of motion for anterior cable reconstruction (ACR) using hamstring allograft for large to massive rotator cuff tears.

Methods: Eight cadaveric shoulders (mean age, 68 years) were tested with a custom testing system. Range of motion (ROM), superior translation of the humeral head, and subacromial contact pressure were measured at 0°, 30°, 60°, and 90° of external rotation (ER) with 0°, 20°, and 40° of glenohumeral abduction. Three conditions were tested: intact, stage III tear (supraspinatus + anterior half of infraspinatus), and stage III tear + allograft ACR (involving 2 supraglenoid anchors for semitendinosus tendon allograft fixation. Allograft ACR included loop-around fixation using 3 side-to-side sutures and an anchor at the articular margin to restore capsular anatomy along the anterior edge of the cuff defect.

Results: ACR with allograft for stage III tears showed significantly higher total ROM compared with intact at all angles (P ≤ .028). Augmentation significantly decreased superior translation for stage III tears at 0°, 30°, and 60° ER for both 0° and 20° abduction, and at 0° and 30° ER for 40° abduction (P ≤ .043). Augmentation for stage III tears significantly reduced overall subacromial contact pressure at 30° ER with 0° and 40° abduction, and at 60° ER with 0° and 20° abduction (P ≤ .016).

Conclusion: Anterior cable reconstruction using cord-like allograft semitendinosus tendon can biomechanically improve superior migration and subacromial contact pressure (primarily in the lower combined abduction and rotation positions), without limiting range of motion for large rotator cuff tendon defects or tears.

Clinical Relevance: In patients with superior glenohumeral instability, using hamstring allograft for ACR may improve rotator cuff tendon defect longevity by providing basic static ligamentous support to the dynamic tendon while helping to limit superior migration, without restricting glenohumeral kinematics.
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http://dx.doi.org/10.1016/j.arthro.2020.12.183DOI Listing
May 2021

Superior Capsule Reconstruction Using Fascia Lata Allograft Compared With Double- and Single-Layer Dermal Allograft: A Biomechanical Study.

Arthroscopy 2021 04 8;37(4):1117-1125. Epub 2020 Dec 8.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, California, U.S.A.. Electronic address:

Purpose: To biomechanically characterize superior capsule reconstruction (SCR) using fascia lata allograft, double-layer dermal allograft, and single-layer dermal allograft for a clinically relevant massive irreparable rotator cuff tear involving the entire supraspinatus and 50% of the infraspinatus tendons.

Methods: Eight cadaveric specimens were tested in 0°, 30°, and 60° abduction for (1) intact, (2) massive rotator cuff tear, (3) SCR using fascia lata, (4) SCR using double-layer dermis, and (5) SCR using single-layer dermis. Superior translation and subacromial contact pressure were measured. Statistical analysis was conducted using repeated measures ANOVA or paired t test with P < .05.

Results: Massive rotator cuff tear significantly increased superior translation of the humeral head at all abduction angles (P < .05). At 0° abduction, all SCR conditions significantly decreased superior translation compared with the massive tear but did not restore translation (P < .05) to intact. Fascia lata and double-layer dermis SCR restored superior translation to intact at 30° and 60° of abduction, but single-layer dermis did not. Subacromial contact pressure at 0° of abduction significantly decreased with SCR with fascia lata and double-layer dermis compared with tear. At 30°, all SCR conditions significantly decreased subacromial contact pressure. Single-layer dermis graft thickness significantly decreased more than fascia lata during testing (P = .02).

Conclusion: For SCR tensioned at 20° glenohumeral abduction, all 3 graft types may restore superior translation and subacromial contact pressure depending on the glenohumeral abduction angle; fascia lata and double-layer dermis may be more effective than single-layer dermis.

Clinical Relevance: If a dermal graft is to be used for SCR, consideration should be given to doubling the graft for increased thickness and better restorative biomechanical properties, which may improve clinical outcomes following SCR.
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http://dx.doi.org/10.1016/j.arthro.2020.11.054DOI Listing
April 2021

Biomechanical assessment of docking ulnar collateral ligament reconstruction after failed ulnar collateral ligament repair with suture augmentation.

J Shoulder Elbow Surg 2021 Jul 2;30(7):1477-1486. Epub 2020 Dec 2.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA; Department of Orthopaedic Surgery, University of California, Irvine, Orange, CA, USA.

Background: Ulnar collateral ligament (UCL) repair with single-strand suture augmentation has been introduced as a viable surgical option for throwers with acute UCL tears. For the original single-strand suture augmentation construct, revision UCL reconstructions can be challenging owing to the bone loss at the site of anchor insertion in the center of the sublime tubercle. This biomechanical study assessed a small-diameter (1.5-mm) ulnar bone tunnel technique for double-strand suture-augmented UCL repair that may be more easily converted to salvage UCL reconstruction if necessary, as well as a salvage UCL reconstruction with a docking technique after a failed primary suture-augmented UCL repair.

Methods: In 7 fresh-frozen cadaveric upper extremities (mean age, 66.3 years), a custom shoulder testing system was used to simulate the late cocking phase of throwing. The elbow valgus opening angle was evaluated using a MicroScribe 3DLX device for sequentially increasing valgus torque (from 0.75 to 7.5 Nm in 0.75-Nm increments) at 90° of flexion. Valgus angular stiffness (in newton-meters per degree) was defined as the correlation of sequentially increasing valgus torque with the valgus opening angle through simple linear regression (slope of valgus torque - valgus opening angle curve). Four conditions were tested: intact elbow, distal UCL avulsion, primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels, and subsequent docking UCL reconstruction in the same specimen. Load-to-failure tests were performed for primary UCL repair with double-strand suture augmentation and subsequent docking UCL reconstruction.

Results: With increasing elbow valgus torque, the valgus opening angle increased linearly in each condition (R ≥ 0.98, P < .001). Distal UCL avulsion resulted in significantly decreased angular stiffness compared with the intact UCL (P < .001). Both UCL repair with double-strand suture augmentation and subsequent UCL reconstruction showed significantly increased angular stiffness values compared with distal UCL avulsion (P < .001 and P < .001, respectively). On load-to-failure testing, there was no significant difference in stiffness, yield torque, and ultimate torque between the primary suture-augmented UCL repair and the subsequent UCL reconstruction (P = .11, P = .77, and P = .38, respectively). In all specimens undergoing the small-diameter ulnar bone tunnel technique for double-strand suture-augmented UCL repair, failure occurred by retear of the repaired ligament without causing an ulnar bone bridge fracture.

Conclusion: Primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels was able to restore valgus stability. When failure occurs, this technique retains enough cortical bone to permit subsequent docking UCL reconstruction.
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http://dx.doi.org/10.1016/j.jse.2020.10.034DOI Listing
July 2021

Optimal Fixation of the Capitellar Fragment in Distal Humerus Fractures.

J Orthop Trauma 2021 07;35(7):e228-e233

Department of Orthopedic Surgery, University of California Irvine, Orange, CA; and.

Objectives: To determine if orthogonal or parallel plate position provides superior fixation of the separate capitellar fragment often present in intra-articular distal humerus fractures. We hypothesized that orthogonal plating would provide stiffer fixation given a greater number of opportunities for capitellar fixation and screw trajectories perpendicular to the fracture plane offered by a posterolateral plate compared with a parallel plate construct.

Methods: Ten matched pairs of cadaveric distal humeri were used to compare parallel and orthogonal plating in a fracture gap model with an isolated capitellar fragment. The capitellum was loaded in 20 degrees of flexion using a cyclic, ramp-loading protocol. Fracture displacement was measured using video tracking software. The primary outcome was axial stiffness for each construct. Secondary outcomes included maximum axial and angular fracture displacement.

Results: The parallel plate construct was more than twice as stiff as the orthogonal plate construct averaged across all loads (1464.8 ± 224.0 N/mm vs. 526.3 ± 90.8 N/mm, P < 0.001). Average axial fracture displacement was 0.15 ± 0.03 mm versus 0.53 ± 0.10 mm for parallel versus orthogonal plating, respectively (P = 0.003). Angular fracture displacement was minimal for both constructs (0.009 ± 0.001 degrees vs. 0.028 ± 0.006 degrees for parallel vs. orthogonal constructs).

Conclusions: Despite fewer points of fixation, a parallel plate construct provided stiffer fixation with less displacement of the simulated capitellar fracture fragment than an orthogonal plate construct in this biomechanical study. In the setting of an articular fracture, in which absolute stability and primary bone healing are desirable, parallel fixation should be considered even in fractures with a separate capitellar fragment if the size of fragment and fracture orientation allows.
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http://dx.doi.org/10.1097/BOT.0000000000002012DOI Listing
July 2021

Posterior stabilized total knee arthroplasty reproduces natural joint laxity compared to normal in kinematically aligned total knee arthroplasty: a matched pair cadaveric study.

Arch Orthop Trauma Surg 2021 Jan 10;141(1):119-127. Epub 2020 Oct 10.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, 800 South Raymond Avenue, Pasadena, CA, 91105, USA.

Purpose: As the goal of kinematic aligned (KA) total knee arthroplasty (TKA) is to preserve soft tissue tension to the native knee, many KA surgeons recommend cruciate-retaining (CR) prosthesis. However, how a posterior-stabilizing (PS) prosthesis affects the biomechanics of a KA TKA remains unclear. This cadaveric study tested the hypothesis that a PS prosthesis in KA TKA would produce biomechanics similar to CR prosthesis and KA TKA with a PS prosthesis would produce more native knee biomechanics than mechanical aligned (MA) TKA with PA prosthesis.

Methods: Fourteen cadaver knees (7 pairs) were mounted on a knee-testing system to measure knee motion during flexion. For each pair, 1 knee was assigned to KA TKA and the other to MA TKA. In the KA TKA group, the native knee, CR TKA, and PS TKA were tested sequentially. MA TKA was performed using conventional measured resection techniques with a PS prosthesis. All kinematics were measured and compared with the native knee before and after surgery.

Results: A PS prosthesis restored femoral rollback similar to a CR prosthesis. CR TKA showed less lateral rollback at knee flexion ≤ 60° than the native knee. There were no differences in soft tissue tensions among the native knee, CR, and PS prosthesis, except in varus tension at 30° of flexion. Varus tension of CR TKA was larger than those of PS TKA and the native knee after KA TKA with < 1 degree difference. Meanwhile, KA TKA achieved knee motion that was closer to the native knee than did MA TKA at ≥ 60° of flexion when using a PS prosthesis. There were no differences in soft tissue tension between KA-PS and MA-PS TKA.

Conclusions: After KA TKA, a PS prosthesis affords similar femoral rollback and soft tissue tension when compared with a CR prosthesis. A PS TKA may be a feasible strategy for patients requiring a PS prosthesis when performing KA TKA.

Level Of Evidence: Therapeutic Laboratory study, I.
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http://dx.doi.org/10.1007/s00402-020-03624-yDOI Listing
January 2021

Biomechanics of tensor fascia lata allograft for superior capsular reconstruction.

J Shoulder Elbow Surg 2021 Jan 9;30(1):178-187. Epub 2020 Jun 9.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA. Electronic address:

Background: We hypothesized that in a cadaveric massive rotator cuff tear (MCT) model, a fascia lata (FL) allograft superior capsular reconstruction (SCR) would restore subacromial contact pressure and humeral head superior translation without limiting range of motion (ROM). Therefore, the objective of this study was to compare these parameters between an intact rotator cuff, MCT, and allograft FL SCR.

Methods: Eight fresh cadavers were studied using a custom shoulder testing system. ROM, superior translation, and subacromial contact pressure were measured in each of 3 states: (1) intact rotator cuff, (2) MCT, and (3) MCT with SCR.

Results: Total ROM was increased in the MCT state at 60° of abduction (P = .037). FL SCR did not restrict internal or external rotational ROM. Increased superior translation was observed in the MCT state at 0° and 30° of humeral abduction, with no significant difference between the intact cuff and FL SCR states. The MCT state significantly increased mean subacromial contact pressure at 0° of abduction with 30° and 60° of external rotation, and FL SCR restored this to intact levels. Peak subacromial contact pressure was increased for the MCT state at 0° of abduction with 30° and 60° of external rotation, as well as 30° of abduction with 30° of external rotation.

Conclusion: This study demonstrates a tensor FL allograft preparation technique for use in SCR. After MCT, FL SCR restores ROM, superior translation, and subacromial contact pressure to the intact state.
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http://dx.doi.org/10.1016/j.jse.2020.04.025DOI Listing
January 2021

Knee laxity in anterolateral complex injuries versus medial meniscus posterior horn injuries in anterior cruciate ligament injured knees: A cadaveric study.

Orthop Traumatol Surg Res 2020 09 1;106(5):945-955. Epub 2020 Aug 1.

Department of Orthopaedic Surgery, Dongguk University Ilsan Hospital, Goyangsi, Gyeonggido, South Korea.

Introduction: There is considerable debate regarding the function of anterolateral knee structures, including the anterolateral ligament (ALL) and anterolateral capsule, as knee stabilizers in anterior cruciate ligament (ACL) injured knees. Medial meniscus posterior horn (MMPH) injuries have also been associated with increased knee laxity in ACL injured knees. The purpose of this cadaveric biomechanical study was to compare the effects of the anterolateral complex (ALC) injury and meniscectomy of MMPH on knee laxity in ACL injured knees.

Hypothesis: ALC injury would have a greater effect on internal rotational laxity in ACL-injured knee than meniscectomy of MMPH.

Material And Methods: Matched-pair 10 fresh-frozen cadaveric knees underwent biomechanical evaluation of knee laxity. After testing the intact knee and ACL sectioned knee (ACL-) in matched-pair 10 fresh-frozen cadaveric knees, two groups were established: an ALC sectioning (ACL-/ALC-) group (n=5) and a MMPH meniscectomy (ACL-/MMPH-) group (n=5). Knee laxity was measured in terms of internal-external rotation, anterior-posterior translation, and varus-valgus angulation for each condition at knee flexion angles of 0°, 30°, 60° and 90°.

Results: After the additional sectioning of the ALC (ACL-/ALC-), the mean internal rotation at 0°, 30°, 60° and 90° of knee flexion showed the greater internal rotation laxity compared than intact knee (p=0.020, 0.011, 0.005 and<0.001). It also significantly increased anterior translation from ACL- at 30° and 60° (p=0.011 and 0.005). In contrast, additional meniscectomy of the MMPH (ACL-/MMPH-) significantly increased external rotation laxity compared to intact knee (p=0.021, 0.018 and 0.024) and ACL- (p=0.037, 0.011 and 0.025) at 30°, 60° and 90°. ACL-/MMPH- also resulted in significantly increased anterior translation from ACL- at 30°, 60° and 90° (p=0.004, 0.008 and 0.002).

Discussion: In conclusion, the anterolateral complex, which include the ALL and anterolateral capsule, may play an important role in stabilizing the knee against internal rotation and anterior translation, while the MMPH may contribute to resisting external rotation and anterior translation stability in ACL-injured knee.

Level Of Evidence: II, controlled laboratory study.
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http://dx.doi.org/10.1016/j.otsr.2020.03.025DOI Listing
September 2020

Ulnar footprints of the distal radioulnar ligaments: a detailed topographical study in 21 cadaveric wrists.

J Hand Surg Eur Vol 2020 Nov 27;45(9):931-938. Epub 2020 Jul 27.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Understanding of the exact topography of the distal radioulnar ligaments insertions remains limited. An anatomical study was performed in 21 fresh frozen cadaveric wrists, where the superficial and deep ligaments were sequentially transected sharply at their ulnar insertions. The relationships between the distal radioulnar ligament footprints relative to the bony landmarks of the ulnar styloid were digitized. Our study demonstrated that in the coronal plane, the superficial distal radioulnar ligaments inserted at an average of 87% of the styloid height proximally to the styloid tip distally. The deep distal radioulnar ligaments inserted at an average of 81% of the styloid height distally to the fovea proximally. The superficial footprint had an area of 10.6 mm on the ulnar styloid. The deep distal radioulnar ligaments attachment was asymmetric and generally had two separate footprints. This study adds important topographical knowledge about the footprint of the distal radioulnar ligaments and may contribute to understanding the consequences of ulnar styloid fractures and distal radioulnar ligaments lesions.
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http://dx.doi.org/10.1177/1753193420944705DOI Listing
November 2020

Posterior Inferior Comminution Significantly Influences Torque to Failure in Vertically Oriented Femoral Neck Fractures: A Biomechanical Study.

J Orthop Trauma 2020 12;34(12):644-649

University of California Irvine Department of Orthopedic Surgery, Orange, CA.

Objectives: To evaluate axial fracture obliquity and posterior inferior comminution in vertically oriented femoral neck fractures (FNFs) in the physiologically young patient. A biomechanical investigation was designed to evaluate the impact of these fracture elements on torque to failure using cannulated screw (CS) and sliding hip screw fixation.

Methods: Four Pauwels III FNF models were established in synthetic femurs: (1) vertically oriented in the coronal plane (COR), (2) coronal plane with axial obliquity (AX), (3) coronal plane with posterior inferior comminution (CCOM), and (4) coronal plane with axial obliquity and posterior inferior comminution (ACOM). In each group (n = 10), specimens were fixed using either 3 CSs or a sliding hip screw with supplemental antirotation screw (SHS). Quasistatic cyclic ramp-loading to failure was performed using a custom testing jig combining axial preloading and torsional ramp-loading. The primary outcome was torque to failure, defined as angular displacement ≥5 degrees.

Results: In the CS group, torque to failure was 40.2 ± 2.6 Nm, 35.0 ± 1.4 Nm, 29.8 ± 1.5 Nm, and 31.8 ± 2.2 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In the SHS group, torque to failure was 28.6 ± 1.3 Nm, 24.2 ± 1.4 Nm, 21.4 ± 1.2 Nm, and 21.0 ± 0.9 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In both constructs, groups with posterior inferior comminution demonstrated significantly lower torque to failure compared to the COR group (P < 0.05). The CS construct demonstrated higher torque to failure in all groups when compared to the SHS construct (P < 0.01).

Conclusions: Posterior inferior comminution significantly affects torque to failure in vertically oriented FNFs. Three peripherally placed CSs may resist combined axial and torsional loading better than a sliding hip screw construct.
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http://dx.doi.org/10.1097/BOT.0000000000001846DOI Listing
December 2020

Internal Bracing Augmentation for Scapholunate Interosseous Ligament Repair: A Cadaveric Biomechanical Study.

J Hand Surg Am 2020 Oct 17;45(10):985.e1-985.e9. Epub 2020 May 17.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA.

Purpose: Internal bracing (IB) is an augmentation method using high-strength nonabsorbable tape. This study compared scapholunate interosseous ligament (SLIL) repair alone, SLIL repair with IB augmentation (RIBA), and native intact SLIL (NIS) in a biomechanical cadaveric model.

Methods: We used 21 specimens of fresh-frozen wrists in this study (7 matched pairs, SLIL repair-only and SLIL RIBA groups; and 7 independent fresh-frozen wrists, NIS group). In the SLIL RIBA group, augmentation using IB was performed after the repair. The specimens were preloaded and cyclically loaded in tension. Maximum extension and hysteresis were measured in all specimens. The specimens were subsequently tested for load to failure. Failure load (yield point load, mean ultimate load, and load at clinical failure) and linear stiffness were calculated.

Results: In cyclic tensile testing, RIBA showed lower maximum extension and lower hysteresis than repair alone. In load to failure testing, the yield point load was statistically higher in the RIBA (59.3 N) group than in the repair-only (30.4 N) group but showed no significant difference compared with the NIS (90.7 N) groups. Moreover, the RIBA (98.5 N) group showed higher and lower mean ultimate loads than the repair-only (37.7 N) and NIS (211.8 N) groups, respectively. Load at clinical failure was higher with RIBA than with repair alone (3-mm extension: 70.0 vs 26.4 N; 4-mm extension: 84.1 vs 33.4 N). Repair alone and RIBA had comparable linear stiffness (38.2 vs 44.1 N/mm).

Conclusions: Although SLIL RIBA did not recreate biomechanical properties equivalent to those of NIS, it demonstrated a significantly higher strength than repair alone.

Clinical Relevance: Repair with IB augmentation could serve as a novel surgical technique that enhances SLIL direct repair through biomechanical support.
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http://dx.doi.org/10.1016/j.jhsa.2020.03.017DOI Listing
October 2020

Effect of biceps rerouting technique to restore glenohumeral joint stability for large irreparable rotator cuff tears: a cadaveric biomechanical study.

J Shoulder Elbow Surg 2020 Jul 17;29(7):1425-1434. Epub 2020 Feb 17.

Department of Orthopedic Surgery, Seoul St. Mary's Hospital, The Catholic University of Korea, Seoul, Republic of Korea. Electronic address:

Background: The concept of stabilizing the humerus has taken on an important role in the treatment of irreparable cuff tears, and the biceps rerouting (BR) method is considered one of the most effective treatments in this field. The study aimed to evaluate the biomechanical effects of BR for large irreparable rotator cuff tears (LICTs).

Methods: A total of 8 cadaveric shoulders were used for testing under 5 conditions: intact shoulder, LICT, partial repair (PR), BR, and biceps rerouting with side-to-side repair (BRSS). Total rotational range of motion was measured at 40°, then 20°, and finally 0° of glenohumeral (GH) abduction. Superior humeral translation and subacromial contact pressure were measured at 0°, 30°, 60°, and 90° of external rotation at each abduction angle. Repeated-measures analyses of variance with Tukey post hoc tests were used for statistical comparisons.

Results: Superior humeral translation was significantly decreased in the BR and BRSS conditions compared with the LICT and PR conditions at 0° and 20° of GH abduction (P < .001). BR and BRSS significantly reduced subacromial contact pressure compared with LICT and PR at 0° of GH abduction (P < .001). There was no significant decrease in total rotational range of motion after BR at any abduction angle.

Conclusion: BR biomechanically restored shoulder stability without overconstraining range of motion in an LICT model.
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http://dx.doi.org/10.1016/j.jse.2019.11.015DOI Listing
July 2020

Supplemental Fixation of Supracondylar Distal Femur Fractures: A Biomechanical Comparison of Dual-Plate and Plate-Nail Constructs.

J Orthop Trauma 2020 Aug;34(8):434-440

University of California, Irvine, Department of Orthopaedic Surgery, Orange, CA; and.

Objectives: This biomechanical study compares the effectiveness of dual-plate (DP) and plate-nail (PN) constructs for fixation of supracondylar distal femur fractures in synthetic and cadaveric specimens.

Methods: Twenty-four synthetic osteoporotic femurs were used to compare 4 constructs in an extra-articular, supracondylar fracture gap model (OTA/AO type 33-A3). Constructs included: (1) distal lateral femoral locking plate (DLFLP), (2) retrograde intramedullary nail (rIMN), (3) DLFLP + medial locking compression plate (DP construct), and (4) DLFLP + rIMN (PN construct). DP and PN constructs were then directly compared using 7 matched pairs of cadaveric femurs. Specimens underwent cyclic loading in torsion and compression. Biomechanical effectiveness was measured by quantifying the load-dependent stiffness of each construct.

Results: In synthetic osteoporotic femurs, the DP construct had the greatest torsional stiffness (1.76 ± 0.33 Nm/deg) followed by the rIMN (1.67 ± 0.14 Nm/deg), PN construct (1.44 ± 0.17 Nm/deg), and DLFLP (0.68 ± 0.10 Nm/deg) (P < 0.01). The DP construct also had the greatest axial stiffness (507.9 ± 83.1 N/mm) followed by the PN construct (371.4 ± 41.9 N/mm), DLFLP (255.0 ± 45.3 N/mm), and rIMN (109.2 ± 47.6 N/mm) (P < 0.05). In cadaveric specimens, the DP construct was nearly twice as stiff as the PN construct in torsion (8.41 ± 0.58 Nm/deg vs. 4.24 ± 0.41 Nm/deg, P < 0.001), and over one-and-a-half times stiffer in compression (2148.1 ± 820.4 vs. 1387.7 ± 467.9 N/mm, P = 0.02).

Conclusions: DP constructs provided stiffer fixation than PN constructs in this biomechanical study of extra-articular distal femur fractures. In the clinical setting, fracture morphology, desired healing mode, surgical approach, and implant cost should be considered when implementing these fixation strategies.
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http://dx.doi.org/10.1097/BOT.0000000000001749DOI Listing
August 2020

Knee laxity in anterolateral complex injuries versus lateral meniscus posterior horn injuries in anterior cruciate ligament deficient knees: A cadaveric study.

Knee 2020 Mar 23;27(2):363-374. Epub 2019 Dec 23.

Department of Orthopaedic Surgery, Dongguk University Ilsan Hospital, Goyangsi, Gyeonggido, South Korea.

Background: In the anterior cruciate ligament (ACL) injured knee, additional injury of the anterolateral ligament (ALL) and capsule may increase the pathologic laxity. The purpose of this study was to compare the effects of the anterolateral complex (ALC) injury in ACL injured knee with the effects of lateral meniscus posterior horn (LMPH) meniscectomy.

Methods: Ten fresh-frozen cadaveric knees were used. After testing the (1) intact knees and (2) ACL sectioned knees (ACL-), two groups were established: an (3) ALC sectioning group (n = 5), which underwent additional ALC sectioning (ACL-/ALC-) after ACL sectioning, and a separate (3) LMPH meniscectomy group (n = 5) that underwent LMPH meniscectomy (ACL-/LMPH-) after ACL sectioning. Knee laxity was measured in terms of internal-external rotation, anterior-posterior translation, and varus-valgus angulation for each condition at knee flexion angles of 0°, 30°, 60° and 90°.

Results: After additional sectioning of the ALC (ACL-/ALC-), the mean internal rotation at 0, 30, 60 and 90° of knee flexion was 11.9 ± 1.3°, 18.1 ± 1.6°, 18.3 ± 1.8°, and 17.8 ± 2.4°, respectively, showing significant internal rotation laxity when compared to the intact knee (P = .031, .020, .001 and .033). Anterior translation also significantly increased compared to the ACL- knee at 30° (12.7 ± 1.4 to 16.8 ± 1.7 mm: P = .039). In contrast, additional meniscectomy of the LMPH (ACL-/LMPH-) significantly increased valgus laxity compared to the intact knee at 30, 60 and 90° (P = .021, .018 and .024).

Conclusion: These findings suggest that the anterolateral complex, which include the ALL and anterolateral capsule, may play an important role in stabilizing the knee against internal rotation and anterior translation.
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http://dx.doi.org/10.1016/j.knee.2019.11.018DOI Listing
March 2020

Improved Rotator Cuff Footprint Contact Characteristics With an Augmented Repair Construct Using Lateral Edge Fixation.

Am J Sports Med 2020 02 4;48(2):444-449. Epub 2019 Dec 4.

Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Medical Center, Long Beach, California, USA.

Background: The transosseous-equivalent (TOE) rotator cuff repair construct has become the gold standard for the repair of medium and large rotator cuff tears. Repair failure, however, continues to be a problem. One contributing factor may be the inability of the TOE repair to replicate the native footprint contact characteristics during shoulder movement, especially in rotation. This results in higher strain across the repair, which leads to gapping and predisposes the construct to failure. In an effort to better reproduce the native compression forces throughout the footprint, an augmented TOE construct supplemented with lateral edge fixation is proposed, and the contact characteristics were compared with those of the gold standard TOE construct.

Hypothesis: The augmented TOE repair will demonstrate improved footprint contact characteristics when compared with the classic TOE repair.

Study Design: Controlled laboratory study.

Methods: Ten fresh-frozen cadaveric shoulders underwent supraspinatus repair using both the classic TOE double-row construct and the augmented TOE repair. For the augmented repair, 2 luggage tag sutures were used to secure the lateral edge and incorporated into the lateral row anchors. A Tekscan pressure sensor (Tekscan Inc) placed under the repaired tendon was used to collect footprint contact area, force, peak pressure, and contact pressure data for each construct.

Results: The augmented construct demonstrated significantly greater contact forces (average difference, 4.9 N) and significantly greater contact pressures (average difference, 23.1 kPa) at all degrees of abduction and all degrees of rotation. At 30° of internal and 30° of external rotation at both 0° and 30° of shoulder abduction, the augmented construct demonstrated significantly greater peak contact pressures.

Conclusion: The augmented construct showed superior contact characteristics when compared with the classic TOE technique. The addition of lateral edge fixation to the classic TOE repair significantly improves bone-tendon contact characteristics with minimal additional surgical effort.

Clinical Relevance: The results of this study indicate that lateral augmentation of the classic TOE repair produces a biomechanically superior construct that may optimize tendon healing.
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http://dx.doi.org/10.1177/0363546519888182DOI Listing
February 2020

Kinematics of Thumb Ulnar Collateral Ligament Repair With Suture Tape Augmentation.

J Hand Surg Am 2020 Feb 11;45(2):117-122. Epub 2019 Nov 11.

Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Long Beach Healthcare System and University of California Irvine, Long Beach, CA; Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA.

Purpose: Acute thumb ulnar collateral ligament (UCL) tears are common injuries of the thumb in athletes. Thumb UCL repair with suture tape augmentation is a novel procedure that may allow earlier return to play. The purpose of this study was to evaluate the biomechanical characteristics of the thumb after UCL repair with and without suture tape augmentation.

Methods: Eight cadaveric thumbs were tested in a custom hand testing system. Varus-valgus kinematics were measured at -10°, 0°, 15°, and 30° of thumb metacarpophalangeal flexion under the following conditions: (1) intact thumb UCL, (2) complete UCL tear (proper and accessory ligaments), (3) UCL repair, and (4) UCL repair with suture tape augmentation. Angular stiffness was also quantified after application of sequentially increasing valgus torque in the intact UCL repair and the UCL repair with suture tape augmentation conditions.

Results: Complete UCL tear increased total varus-valgus angulation at all degrees of thumb metacarpophalangeal flexion. Thumb UCL repair alone and repair with suture tape augmentation decreased total varus-valgus angulation relative to complete UCL tear at all flexion angles. Total varus-valgus angulation was not significantly different from intact results for either the repair alone or the repair with suture tape augmentation at all flexion angles. Repair with suture tape augmentation had significantly higher valgus angular stiffness compared with repair alone but not compared with intact.

Conclusions: Thumb UCL repair with suture tape augmentation is able to restore varus-valgus kinematics after complete UCL tear without over-constraining the joint. In addition, the higher angular stiffness afforded by the suture tape augmentation may allow for earlier rehabilitation after surgery.

Clinical Relevance: Thumb UCL repair with suture tape augmentation may allow earlier return to sport in athletes than with repair alone.
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http://dx.doi.org/10.1016/j.jhsa.2019.09.005DOI Listing
February 2020

Anterior Capsule Reconstruction Versus Pectoralis Major Transfer for Irreparable Subscapularis Tears Involving the Anterior Capsule: A Comparative Biomechanical Cadaveric Study.

Arthroscopy 2019 11 16;35(11):3002-3008. Epub 2019 Oct 16.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, California, U.S.A.; Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Medical, Long Beach, California, U.S.A.; Department of Orthopaedic Surgery, University of California, Irvine, Irvine, California, U.S.A.

Purpose: To compare the biomechanical effectiveness of human dermal allograft (HDA) anterior capsular reconstruction (ACR) and pectoralis major tendon transfer (PMTT) for treating irreparable subscapularis tears with capsular insufficiency in human cadaver shoulders.

Methods: Glenohumeral rotational range of motion and translation were measured in 6 cadaveric shoulders under the following 5 conditions: intact, deficient subscapularis/anterior capsule, ACR using HDA, HDA ACR with concomitant PMTT, and PMTT alone.

Results: The deficient subscapularis/anterior capsule condition significantly increased external and total rotational range of motion at 0° (P < .001, P < .001) and 30° (P = .005, P = .002) abduction as well as anterior-inferior translation (P ≤ .001 to .03). HDA ACR, both with and without PMTT, restored anterior-inferior stability to that of the intact condition; however, PMTT alone did not restore anterior-inferior translation or rotational range of motion.

Conclusions: HDA ACR for treating irreparable subscapularis tears with capsular insufficiency restored anterior-inferior glenohumeral translation and rotational range of motion at time 0 in human cadaver shoulders.

Clinical Relevance: Anterior capsule reconstruction may be a viable option for treating massive irreparable subscapularis tears with capsular insufficiency.
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http://dx.doi.org/10.1016/j.arthro.2019.05.046DOI Listing
November 2019

Biomechanical Evaluation of a Modified Internal Brace Construct for the Treatment of Ulnar Collateral Ligament Injuries.

Orthop J Sports Med 2019 Oct 2;7(10):2325967119874135. Epub 2019 Oct 2.

Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Medical Center, Long Beach, California, USA.

Background: Ulnar collateral ligament (UCL) repair augmented with the "internal brace" construct for the management of acute UCL injuries has recently garnered increasing interest from the sports medicine community. One concern with this technique is excessive bone loss at the sublime tubercle, should revision UCL reconstruction be required. In an effort to preserve the bony architecture of the sublime tubercle, an alternative internal brace construct is proposed and biomechanically compared with the gold standard UCL reconstruction.

Hypothesis: The internal brace repair construct will restore valgus laxity and rotation to its native state and demonstrate comparable load-to-failure characteristics with the 3-strand reconstruction technique.

Study Design: Controlled laboratory study.

Methods: For this study, 8 matched pairs of fresh-frozen cadaveric elbows were randomized to undergo either UCL reconstruction with the 3-ply docking technique or UCL repair with a novel internal brace construct focused on augmenting the posterior band of the anterior bundle of the ligament (modified repair-IB technique). Valgus laxity and rotation measurements were quantified through use of a MicroScribe 3DLX digitizer at various flexion angles of the native ligament, transected ligament, and repaired or reconstructed ligament. Laxity testing was performed from maximum extension to 120° of flexion. Each specimen was then loaded to failure, and the method of failure was recorded.

Results: Valgus laxity was restored to the intact state at all degrees of elbow flexion with the modified repair-IB technique, and rotation was restored to the intact state at both full extension and 30°. In the reconstruction group, valgus laxity was not restored to the intact state at either full extension or 30° of flexion ( < .001 and = .004, respectively). Laxity was restored at 60° of flexion, but the elbow was overconstrained at 90° and 120° of flexion ( = .027 and = .003, respectively). In load-to-failure testing, the reconstruction group demonstrated significantly greater yield torque (19.1 vs 9.0 N·m; < .005), yield angle (10.2° vs 5.4°; = .007), and ultimate torque (23.9 vs 17.6 N·m; = .039).

Conclusion: UCL repair with posterior band internal bracing was able to restore valgus laxity and rotation to the native state. The construct exhibited lower load-to-failure characteristics when compared with the reconstruction technique.

Clinical Relevance: In selected patients with acute, avulsion-type UCL injuries, ligament repair with posterior band internal bracing is a viable alternative surgical option that, by preserving bone at the sublime tubercle, may decrease the complexity of future revision procedures.
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http://dx.doi.org/10.1177/2325967119874135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6775552PMC
October 2019

Biomechanical analysis of anterior capsule reconstruction and latissimus dorsi transfer for irreparable subscapularis tears.

J Shoulder Elbow Surg 2020 Feb 6;29(2):374-380. Epub 2019 Oct 6.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Background: Anterior capsule reconstruction (ACR) and latissimus dorsi transfers (LTs) have been proposed as solutions for irreparable subscapularis tears. The purpose of this study was to biomechanically assess the effects of ACR and LT separately and together for treatment of irreparable subscapularis tears.

Materials And Method: Eight cadaveric shoulders underwent 5 testing conditions: (1) intact, (2) irreparable subscapularis tear, (3) ACR, (4) ACR+LT, and (5) LT alone. Anteroinferior translation loads of 20, 30, and 40 N were applied. Range of motion and magnitudes of glenohumeral anterior and inferior translation at 0°, 30°, and 60° of abduction and at 30° and 60° of external rotation were measured for each testing condition.

Results: At 30° of abduction and 60° of external rotation, ACR and ACR+LT restored anterior and inferior translation to intact (P > .702) for 30 and 40 N of anteroinferiorly directed force. LT alone did not restore anteroinferior stability at 30 N of distraction force at 30° of glenohumeral abduction and 60° of external rotation (P < .001). However, ACR and ACR+LT led to significant decreases in total range of motion compared to intact at 0° and 30° of abduction (P < .007).

Conclusions: ACR with dermal allograft was able to restore anteroinferior stability in the setting of irreparable subscapularis tears but resulted in decreased total range of motion. LT alone was less effective than ACR in restoring glenohumeral stability. The addition of LT as a dynamic restraint did not increase the efficacy of ACR.
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http://dx.doi.org/10.1016/j.jse.2019.07.033DOI Listing
February 2020

Biomechanical Analysis of Thumb Ulnar Collateral Ligament Tear Kinematics.

Hand (N Y) 2021 Jul 20;16(4):467-473. Epub 2019 Aug 20.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Thumb ulnar collateral ligament (UCL) injuries are common, but the kinematics of these injuries have not been comprehensively described, especially regarding kinematic changes with progressive UCL injury. Eleven cadaveric thumbs underwent kinematic testing under 4 conditions: intact, partial tear (50%) of the proper UCL, full tear of the proper UCL, and complete tear of both the proper and accessory UCL. Kinematic testing parameters included varus/valgus stress, pronation/supination, and volar/dorsal translation at -10 degree, 0 degree, 15 degree, and 30 degree of metacarpophalangeal flexion. Partial tear of the proper UCL did not result in significant increases in laxity in any direction compared with intact ( ≥ .132). Full tear of the proper UCL resulted in a significant increase in valgus angulation (18.8° ± 1.7° vs 11.5° ± 1.5°; = .024) and pronation (15.4° ± 2.5° vs 12.6° ± 2.3°; = .034) at 30 degree of flexion relative to intact. Complete tear of both the proper and accessory collateral ligaments resulted in increased valgus angulation at all degrees of flexion ( < .001). Complete tear also resulted in a significant volar translation at 0 degree, 15 degree, and 30 degree of flexion ( ≤ .016). Partial tear of the proper UCL does not significantly affect the stability of the joint, but full tear of the proper UCL increases valgus instability at 30 degree of flexion. Complete tear of the UCL is necessary for increased varus/valgus instability at all degrees of flexion and results in significant increases in pronation/supination and volar translation.
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http://dx.doi.org/10.1177/1558944719868518DOI Listing
July 2021

Posterior shoulder tightness can be a risk factor of scapular malposition: a cadaveric biomechanical study.

J Shoulder Elbow Surg 2020 Jan 14;29(1):175-184. Epub 2019 Aug 14.

Orthopaedic Biomechanics Laboratory, Congress Medical Foundation, Pasadena, CA, USA.

Background: Scapular malposition and posterior shoulder tightness are key pathologic processes in the shoulder of throwing athletes. The objective of this study was to investigate the effects of posterior capsule tightness, posterior rotator cuff muscle tightness, or both on scapular position.

Methods: Ten shoulders from 5 fresh frozen cadaveric male torsos were tested in maximum internal, neutral, and maximum external shoulder rotations at 0°, 45°, and 90° of shoulder abduction. Scapular rotation-namely, upward and downward rotation, internal and external rotation, and anterior and posterior tilt-and the scapula-spine distance were measured by using a MicroScribe digitizer (Revware, Raleigh, NC, USA). Each shoulder underwent 4 experimental stages: intact; isolated posterior rotator cuff muscle (infraspinatus and teres minor) tightness; both posterior rotator cuff muscle and capsule tightness; and isolated posterior capsule tightness.

Results: Posterior muscle tightness significantly decreased upward rotation (P< .05) only in maximum shoulder internal rotation at 45° or 90° of shoulder abduction, whereas posterior capsule tightness did not affect upward rotation (P= .09 to .96). Posterior capsule tightness significantly increased scapular internal rotation (P< .01), but posterior muscle tightness did not change scapular internal rotation (P= .62 to .89). Posterior capsule tightness significantly increased both the superior and inferior scapula-spine distance (ie, caused scapular protraction) in maximum shoulder external rotation at 90° of abduction (P< .01).

Conclusion: Posterior shoulder tightness resulted in scapular malposition. However, the muscular and capsular components of that tightness affected the scapular position differently. For the treatment of scapula malposition, stretching of the posterior shoulder capsule and muscles is recommended.
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http://dx.doi.org/10.1016/j.jse.2019.05.040DOI Listing
January 2020

Elongation Patterns of the Anterior and Posterior Borders of the Anterolateral Ligament of the Knee.

Arthroscopy 2019 07;35(7):2152-2159

Orthopaedic Biomechanics Laboratory, Tibor Rubin VA Medical Center, Long Beach, California, U.S.A.; Department of Orthopaedic Surgery, University of California, Irvine, Irvine, California, U.S.A.

Purpose: To compare the elongation patterns of the anterior and posterior borders of the anterolateral ligament (ALL) at varying knee flexion angles with the knee in a neutral position without any external forces and with external forces applied, including anterior-posterior translation, internal-external rotation, and varus-valgus angulation.

Methods: Eight cadaveric knees were tested in a custom knee testing system. Elongation of the anterior and posterior borders of the ALL was measured using a MicroScribe 3DLX system at knee flexion angles of 0°, 30°, 60°, and 90° and after the application of internal-external rotation, anterior-posterior translation, and varus-valgus angulation.

Results: The anterior border showed a slight noncontinuous increase in percentage elongation (0.8% ± 2.2%) whereas the posterior border showed a continuous decrease in percentage elongation (-12.0% ± 2.8%) as knee flexion increased (P < .001). Apart from the elongation of the posterior border at 90° of knee flexion, internal rotation, varus angulation, and anterior translation resulted in a significant increase in the percentage elongation of the anterior and posterior borders at each flexion angle compared with external rotation, valgus angulation, and posterior translation, respectively.

Conclusions: The ALL shows different elongation patterns between the anterior and posterior borders, with a continuous decrease in the percentage elongation of the posterior border as knee flexion increases.

Clinical Relevance: This study presents useful evidence to resolve the uncertainty regarding the change in length of the ALL at various degrees of knee flexion. This information may be helpful for deciding the optimal knee flexion angle during ALL graft fixation. The findings from this study suggest that graft fixation during ALL reconstructions should be performed at close to full extension of the knee.
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http://dx.doi.org/10.1016/j.arthro.2019.02.042DOI Listing
July 2019
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