Publications by authors named "Thay Q Lee"

244 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

Muscular forces responsible for proximal humeral deformity following fracture.

J Orthop Trauma 2021 May 14. Epub 2021 May 14.

University of California Irvine School of Medicine University of California Irvine, Department of Orthopedic Surgery Cornell University Orthopaedic Biomechanics Laboratory, Congress Medical Foundation.

Objectives: To evaluate the contribution of each of the rotator cuff muscles and deltoid to fracture deformity in a two-part proximal humerus fracture model. Our hypothesis was that superior cuff muscles would have the greatest contribution to coronal plane deformity while muscles with anterior and posterior attachments would have the greatest contribution to axial and sagittal plane deformity.

Methods: A medial wedge osteotomy was created in eight cadaveric shoulder specimens. A custom shoulder testing system was used load to each rotator cuff muscle and deltoid under increasing loading conditions. Fracture displacement was measured using a Microscribe digitizing system. The primary outcome was the contribution of each muscle to varus collapse. Secondary outcomes included contributions of each muscle to apex anterior/posterior deformity and humeral head anteversion/retroversion.

Results: Unbalanced loading of the supraspinatus resulted in the greatest varus deformity (34.5±2.3°) followed by the infraspinatus (22.3±3.6°) and subscapularis (21.7±3.1°) (p<0.05). Unbalanced loading of the subscapularis induced the greatest apex posterior (27.5±4.8°, p<0.05) and retroversion (39.0±5.6°, p<0.05) deformity while the infraspinatus induced the greatest apex anterior (8.7±3.4°, p>0.05) and anteversion (17.7±5.7°, p>0.05) deformity.

Conclusions: In this proximal humerus fracture model, the supraspinatus was the primary driver of varus deformity while the subscapularis and infraspinatus contributed to apex posterior/retroversion and apex anterior/anteversion, respectively. The subscapularis and infraspinatus are also important secondary drivers of varus deformity. This study establishes a physiologically relevant fracture model that mimics in vivo conditions for future biomechanical testing.
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http://dx.doi.org/10.1097/BOT.0000000000002142DOI Listing
May 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

Anterior Cable Reconstruction Using the Proximal Biceps Tendon for Large Rotator Cuff Defects.

Arthrosc Tech 2021 Mar 10;10(3):e807-e813. Epub 2021 Mar 10.

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

Tears of the rotator cuff tendons can occur that do not allow anatomic footprint restoration yet may not be large enough to require a superior capsular reconstruction technique. Typically, these intermediate-sized tears are addressed with a medialized repair or partial repair technique. A partially repaired rotator cuff tendon, however, can lead to a high retear rate, as the repaired tendon is required to serve as both a dynamic tendon and a static ligamentous stabilizer. One potential static support, as a nearby autologous graft donor, is the proximal long head biceps tendon. The purpose of this Technical Note is to describe a surgical technique for an anterior cable reconstruction using the proximal biceps tendon for large rotator cuff defects.
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http://dx.doi.org/10.1016/j.eats.2020.10.070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7953232PMC
March 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

Arthroscopic Superior Capsule Reconstruction for Irreparable Rotator Cuff Tears: Comparison of Clinical Outcomes With and Without Subscapularis Tear.

Am J Sports Med 2020 12 26;48(14):3429-3438. Epub 2020 Oct 26.

Department of Orthopedic Surgery, Osaka Medical College, Takatsuki, Japan.

Background: Arthroscopic superior capsule reconstruction (SCR) was developed to restore shoulder superior stability, muscle balance, and function in patients with irreparable posterior-superior rotator cuff tears.

Purpose: To assess the effects of concomitant subscapularis tendon tear, which may reduce glenohumeral stability and force coupling, on clinical outcomes of SCR for irreparable posterior-superior rotator cuff tears.

Study Design: Cohort study; Level of evidence, 3.

Methods: In total, 193 patients with irreparable posterior-superior rotator cuff tears underwent arthroscopic SCR using fascia lata autograft between 2007 and 2015. They were allocated to 3 groups: group 1, no subscapularis tear (160 patients); group 2, reparable subscapularis tear, which underwent arthroscopic repair (26 patients); and group 3, irreparable subscapularis tear (7 patients). American Shoulder and Elbow Surgeons (ASES) and Japanese Orthopaedic Association (JOA) scores, visual analog scale (VAS) score for pain, active shoulder range of motion (ROM), muscle strength (manual muscle test), and acromiohumeral distance were evaluated before surgery and at final follow-up (mean, 3 years, 7 months; range, 2-11 years). Postoperative complications were assessed.

Results: In groups 1 and 2, ASES, JOA, and VAS scores and shoulder ROM and muscle strength improved significantly after SCR with subscapularis repair ( < .001). SCR in group 3 significantly improved ASES, JOA, and VAS scores ( < .001), whereas shoulder ROM and muscle strength did not increase significantly. Postoperative acromiohumeral distance was significantly smaller in group 3 (5.7 ± 2.9 mm [mean ± SD]) than group 2 (9.1 ± 2.3 mm) ( = .002). Group 3 had a significantly higher rate of graft tear ( < .001) and postoperative infection ( < .001) than group 1.

Conclusion: The presence of subscapularis tendon tear affects clinical outcomes and complication rates after SCR. The reparability of the subscapularis affects superior glenohumeral stability; therefore, an intact subscapularis or reparable subscapularis tendon tear is the best indication for arthroscopic SCR in patients with irreparable posterior-superior rotator cuff tendon tears.
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http://dx.doi.org/10.1177/0363546520965993DOI Listing
December 2020

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

Human motor endplate remodeling after traumatic nerve injury.

J Neurosurg 2020 Sep 18:1-8. Epub 2020 Sep 18.

4Reeve-Irvine Research Center, University of California, Irvine, California.

Objective: Current management of traumatic peripheral nerve injuries is variable with operative decisions based on assumptions that irreversible degeneration of the human motor endplate (MEP) follows prolonged denervation and precludes reinnervation. However, the mechanism and time course of MEP changes after human peripheral nerve injury have not been investigated. Consequently, there are no objective measures by which to determine the probability of spontaneous recovery and the optimal timing of surgical intervention. To improve guidance for such decisions, the aim of this study was to characterize morphological changes at the human MEP following traumatic nerve injury.

Methods: A prospective cohort (here analyzed retrospectively) of 18 patients with traumatic brachial plexus and axillary nerve injuries underwent biopsy of denervated muscles from the upper extremity from 3 days to 6 years after injury. Muscle specimens were processed for H & E staining and immunohistochemistry, with visualization via confocal and two-photon excitation microscopy.

Results: Immunohistochemical analysis demonstrated varying degrees of fragmentation and acetylcholine receptor dispersion in denervated muscles. Comparison of denervated muscles at different times postinjury revealed progressively increasing degeneration. Linear regression analysis of 3D reconstructions revealed significant linear decreases in MEP volume (R = -0.92, R2 = 0.85, p = 0.001) and surface area (R = -0.75, R2 = 0.56, p = 0.032) as deltoid muscle denervation time increased. Surprisingly, innervated and structurally intact MEPs persisted in denervated muscle specimens from multiple patients 6 or more months after nerve injury, including 2 patients who had presented > 3 years after nerve injury.

Conclusions: This study details novel and critically important data about the morphology and temporal sequence of events involved in human MEP degradation after traumatic nerve injuries. Surprisingly, human MEPs not only persisted, but also retained their structures beyond the assumed 6-month window for therapeutic surgical intervention based on previous clinical studies. Preoperative muscle biopsy in patients being considered for nerve transfer may be a useful prognostic tool to determine MEP viability in denervated muscle, with surviving MEPs also being targets for adjuvant therapy.
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http://dx.doi.org/10.3171/2020.8.JNS201461DOI Listing
September 2020

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

The anterolateral ligament of the knee joint: a review of the anatomy, biomechanics, and anterolateral ligament surgery.

Knee Surg Relat Res 2019 Nov 28;31(1):12. Epub 2019 Nov 28.

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

Residual knee instability and low rates of return to previous sport are major concerns after anterior cruciate ligament (ACL) reconstruction. To improve outcomes, surgical methods, such as the anatomical single-bundle technique or the double-bundle technique, were developed. However, these reconstruction techniques failed to adequately overcome these problems, and, therefore, new potential answers continue to be of great interest. Based on recent anatomical and biomechanical studies emphasizing the role of the anterolateral ligament (ALL) in rotational stability, novel surgical methods including ALL reconstruction and anterolateral tenodesis have been introduced with the possibility of resolving residual instability after ACL reconstruction. However, there is still little consensus on many aspects of the ALL, including: several anatomical issues, appropriate indications for ALL surgery, and the optimal surgical method and graft choice for reconstruction surgery. Therefore, further studies are necessary to advance our knowledge of the ALL and its contribution to knee stability.
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http://dx.doi.org/10.1186/s43019-019-0012-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7219606PMC
November 2019

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

Editorial Commentary: Biomechanical Investigation of Superior Capsule Reconstruction Requires Meticulous Methods.

Authors:
Thay Q Lee

Arthroscopy 2020 02;36(2):365-366

Pasadena, California.

One of the treatment options for a massive irreparable rotator cuff tear is superior capsule reconstruction (SCR). Biomechanically, SCR depresses and centers the humeral head on the glenoid so that the remaining rotator cuff muscles and the deltoid can provide function. Therefore, in SCR, graft characteristics such as graft type, graft thickness, and graft tension are the critical parameters contributing to the biomechanical effectiveness. SCR was originally developed with fascia lata autografts, but in the United States, the most popular graft used is acellular human dermal allograft. Both have been clinically successful with their own advantages and disadvantages. The effects of graft thickness on SCR are fairly well understood, and using a thicker graft provides 2 distinct advantages. The first is stiffness; the thicker the graft, the stiffer the graft. The second is the spacer effect, which helps to maintain the acromiohumeral distance. A key caveat is that a double-layer graft is fundamentally different from a single-layer graft, and the number and location of stitches strongly influence the biomechanical characteristics. SCR biomechanical studies may be applied in concept, but clinical application will require detailed information on the graft preparation strategy to control graft thickness and tension.
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http://dx.doi.org/10.1016/j.arthro.2019.10.037DOI Listing
February 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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Source
http://dx.doi.org/10.1016/j.jhsa.2019.09.005DOI Listing
February 2020
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