Biomechanical Characterization of a New Locking Loop Stitch for Graft Fixation versus Krackow Stitch.

Background: The purpose of this study was to quantify and compare the biomechanical characteristics of a new locking loop stitch (LLS), developed utilizing the concepts of both running locking stitch and needleless stitch, to the traditional Krackow stitch. Methods: The Krackow stitch with No.2 braided suture and the LLS with 1.3-mm augmented polyblend suture tape were compared biomechanically. The LLS was performed with single strand locking loops and wrapping suture around the tendon, resulting in half the needle penetrations through the graft compared to the Krackow stitch. Twenty bovine extensor tendons were divided randomly into two groups. The tendons were prepared to match equal thickness and cross-sectional area. Each suture-tendon was stitched and preloaded to 5 N for 60 seconds, cyclically loaded to 20 N, 40 N, and 60 N for 10 cycles each, and then loaded to failure. The deformation of the suture-tendon construct, stiffness, yield load, and ultimate load were measured. Results: The LLS had significantly less deformation of the suture-tendon construct at 100 N, 200 N, 300 N, and at ultimate load compared to the Krackow stitch (Krackow stitch and LLS at 100 N: 1.3 ± 0.1 mm and 1.0 ± 0.2 mm, p < 0.001; 200 N: 3.0 ± 0.3 mm and 1.9 ± 0.2 mm, p < 0.001; 300 N: 5.1 ± 0.6 mm and 2.9 ± 0.4 mm, p < 0.001; ultimate load: 12.8 ± 2.8 mm and 5.0 ± 1.2 mm, p < 0.001). The LLS had significantly greater stiffness (Krackow stitch and LLS: 97.5 ± 6.9 N/mm and 117.2 ± 13.9 N/mm, p < 0.001) and yield load (Krackow stitch and LLS: 66.2 ± 15.9 N and 237.9 ± 93.6 N, p < 0.001) compared to the Krackow stitch. There was no significant difference in ultimate load (Krackow stitch: 450.2 ± 49.4 N; LLS: 472.6 ± 59.8 N; p = 0.290). Conclusions: The LLS had significantly smaller deformation of the suture-tendon construct compared to the Krackow stitch. The LLS may be a viable surgical alternative to the Krackow stitch for graft fixation when secure fixation is necessary.

Structural and clinical outcomes after superior capsule reconstruction using an at least 6-mm-thick fascia lata autograft including the intermuscular septum.

BACKGROUND: Superior capsule reconstruction (SCR) is a viable treatment option for irreparable rotator cuff tears. However, graft tear rate is highly variable in the previous studies, and the impact of graft tears on clinical outcomes after arthroscopic SCR remains controversial. We aimed to investigate the graft tear rate, timing of graft tear, and the impact of graft tears on clinical outcomes after arthroscopic SCR using an at least 6-mm-thick fascia lata autograft including the intermuscular septum. METHODS: This retrospective multi-institutional study included 154 patients (79 women and 75 men; mean age, 69.9 yr; age range, 49-87 yr) with irreparable rotator cuff tears who underwent arthroscopic SCR using an at least 6-mm-thick fascia lata autograft including the intermuscular septum and completed a minimum 2-year follow-up. Postoperative graft integrity was evaluated by magnetic resonance imaging examinations performed at 3, 6, 12, and 24 mo after surgery. The presence of a full-thickness defect within the graft was diagnosed as a graft tear. In contrast, a graft without a full-thickness defect was diagnosed as a healed graft. We compared the following data between patients with and without graft tears: (1) baseline characteristics, (2) visual analog scale pain score, (3) Japanese Orthopaedic Association score, (4) American Shoulder and Elbow Surgeons shoulder score, and (5) active range of motion. RESULTS: The overall graft tear rate was 11.7% (18 of 154 patients). Of 18 graft tears, 14 (77.8%) occurred within 6 mo after SCR. Two additional graft tears were diagnosed at 12 mo postoperatively and another 2 at 24 mo after SCR. The visual analog scale, American Shoulder and Elbow Surgeons, and Japanese Orthopaedic Association scores improved significantly after SCR in both patients with and without graft tears (all P < .0001). However, patients with graft tears showed significantly inferior postoperative visual analog scale, American Shoulder and Elbow Surgeons, and Japanese Orthopaedic Association scores (1.9, 75.2, and 77.4, respectively) than those without graft tears (0.5, 93.1, and 92.3, respectively; all P < .01). CONCLUSIONS: The overall graft tear rate after arthroscopic SCR using an at least 6-mm-thick fascia lata autograft including the intermuscular septum was low (11.7%), relatively to that reported in previous studies. The majority of graft tears (77.8%) occurred within 6 mo after SCR. Graft healing was associated with more favorable clinical outcomes after SCR.

Human Dermal Allograft Superior Capsule Reconstruction With Graft Length Determined at Glenohumeral Abduction Angles of 20° and 40° Decreases Joint Translation and Subacromial Pressure Without Compromising Range of Motion: A Cadaveric Biomechanical Study.

PURPOSE: To compare the biomechanical effects of superior capsule reconstruction (SCR) graft fixation length determined at 20° and 40° of glenohumeral (GH) abduction. METHODS: Humeral translation, rotational range of motion (ROM), and subacromial contact pressure were quantified at 0°, 30°, and 60° of GH abduction in the scapular plane in 6 cadaveric shoulders for the following states: intact, massive rotator cuff tear, SCR with dermal allograft fixed at 20° of GH abduction (SCR 20), and SCR with dermal allograft fixed at 40° of GH abduction (SCR 40). Statistical analysis was conducted using a repeated-measures analysis of variance and a paired t test (P < .05). RESULTS: A massive cuff tear significantly increased total ROM compared with the intact state at 0° and 60° of abduction. SCR 20 or SCR 40 did not affect ROM. Compared with the intact state, the massive cuff tear model significantly increased superior translation by an average of 4.6 ± 0.5 mm in 9 of 12 positions (P ≤ .002). Both SCR 20 and SCR 40 reduced superior translation compared with the massive cuff tear model (P < .05); however, SCR 40 significantly decreased superior translation compared with SCR 20 at 0° of abduction (P ≤ .046). Peak subacromial pressure for the massive cuff tear model increased by an average of 486.8 ± 233.9 kPa relative to the intact state in 5 of 12 positions (P ≤ .037). SCR 20 reduced peak subacromial pressure in 2 of 12 positions (P ≤ .012), whereas SCR 40 achieved this in 6 of 12 positions (P ≤ .024). CONCLUSIONS: SCR with dermal allograft fixed at 20° or 40° of GH abduction decreases GH translation and subacromial pressure without decreasing ROM. CLINICAL RELEVANCE: With an increasing abduction angle for graft fixation, the medial-to-lateral graft length is decreased and the graft tension is effectively increased. Surgeons may increase shoulder stability without restricting ROM by fixing the graft at higher abduction angles. However, surgeons should remain cognizant of potential graft failure due to increased tension.

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

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.

Histologic changes during healing with autologous fascia lata graft after superior capsule reconstruction in rabbit model.

BACKGROUND: Superior capsule reconstruction (SCR) has been developed to improve shoulder function and relieve pain in the treatment of irreparable rotator cuff tears. Previous studies have reported that graft healing can enhance favorable outcomes after SCR. On the other hand, graft tears often lead to less desirable outcomes and sometimes require additional surgical procedures. However, the healing process underlying this remains unclear. In this study, we aimed to investigate histologic changes occurring during the healing process associated with autologous fascia lata graft after SCR in vivo. We hypothesized that (1) autologous fascia lata graft can regenerate the fibrocartilaginous insertion into both the greater tuberosity and superior glenoid and (2) the midsubstance of the grafted fascia gradually remodels into tendon- and/or ligament-like tissue after SCR. METHODS: Irreparable supraspinatus tendon defects were created in 24 mature Japanese white rabbits (age, 6 months; mean weight, 3.2 kg). Four weeks after creation of the defects, the right shoulders were subjected to SCR using autologous fascia lata grafts. The left shoulders were left untreated. Samples from the shoulders were harvested at 4, 8, 12, and 16 weeks after surgery to undergo histologic and immunohistochemical examinations. RESULTS: Macroscopically, we did not observe graft tears after SCR in our experiments. Histologically, the number of chondrocyte-like cells gradually increased, and the extracellular matrices around those cells contained glycosaminoglycan at the fascia-bone junction after SCR. The unmineralized fibrocartilage, mineralized fibrocartilage, and tidemark were observed 16 weeks after SCR. The distribution of type II collagen presented a pattern similar to that of a normal tendon and ligament insertion. The cells and collagen fiber gradually oriented parallelly to the long axis in the midsubstance of the grafted fascia lata. Additionally, type III collagen was replaced with type I collagen in the midsubstance of the grafted fascia lata after SCR. CONCLUSIONS: SCR using fascia lata autograft regenerated the fibrocartilaginous insertion at both the greater tuberosity and superior glenoid. The midsubstance of the grafted fascia gradually remodeled into tendon- and/or ligament-like tissue. These results suggest that the fascia lata autograft has the capacity for graft-to-bone healing and remodeling after SCR.

Biomechanical Analysis of Thumb Ulnar Collateral Ligament Tear Kinematics.

Background: 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. Methods: 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. Results: Partial tear of the proper UCL did not result in significant increases in laxity in any direction compared with intact (P ≥ .132). Full tear of the proper UCL resulted in a significant increase in valgus angulation (18.8° ± 1.7° vs 11.5° ± 1.5°; P = .024) and pronation (15.4° ± 2.5° vs 12.6° ± 2.3°; P = .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 (P < .001). Complete tear also resulted in a significant volar translation at 0 degree, 15 degree, and 30 degree of flexion (P ≤ .016). Conclusion: 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.

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

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 (R2 ≥ 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.

Relationship between humeral retroversion and baseball positions during elementary and junior-high school.

BACKGROUND: Humeral retroversion is greater in the dominant shoulder than in the nondominant shoulder in baseball players. However, the effect of different baseball positions during childhood on humeral retroversion remains unknown. The purpose of this study was to investigate the following: (1) the relationship between humeral retroversion and baseball positions played during elementary and junior-high schools; (2) the association between humeral retroversion and the prevalence of pain during the medical checkup and self-reported history of injuries in the dominant shoulder or elbow. METHODS: We enrolled 149 male high-school baseball players who started playing baseball in elementary school. The subjects were classified into 3 groups according to their baseball positions in elementary and junior-high schools. All participants completed questionnaires regarding their current and past positions, current incidence and history of injuries in their shoulder or elbow joints, and the age they started playing baseball. Shoulder range of motion, humeral retroversion on ultrasonographic-assisted measurement, and the association between humeral retroversion and shoulder and elbow pain were evaluated. RESULTS: Humeral retroversion was significantly greater in the dominant shoulder than in the nondominant shoulder in all groups (P < .001). In addition, humeral retroversion in the dominant shoulder was significantly greater in players who were pitchers in both elementary and junior-high schools than in those who were fielders during both periods (96.2° and 89.4°, respectively; P = .02). Humeral retroversion in the dominant shoulder was positively correlated (P = .005, r = 0.23) with the length of career as a pitcher during elementary and junior-high schools. Humeral retroversion was not correlated with the prevalence of pain during the medical checkup or self-reported history of injuries in the dominant shoulder or elbow (P values ranging from 0.09-0.99). CONCLUSION: These results suggest that playing baseball as a pitcher during elementary school and junior-high school affects the increase in humeral retroversion in the dominant shoulder. Increased humeral retroversion in the dominant shoulder by repetitive throwing motion is an adaptive change, rather than a pathologic change.

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

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.

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

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.

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

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.

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

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 (P < .001 and P = .004, respectively). Laxity was restored at 60° of flexion, but the elbow was overconstrained at 90° and 120° of flexion (P = .027 and P = .003, respectively). In load-to-failure testing, the reconstruction group demonstrated significantly greater yield torque (19.1 vs 9.0 N·m; P < .005), yield angle (10.2° vs 5.4°; P = .007), and ultimate torque (23.9 vs 17.6 N·m; P = .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.

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

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.

Biomechanical analysis of latissimus dorsi tendon transfer with and without superior capsule reconstruction using dermal allograft.

BACKGROUND: Irreparable rotator cuff tears (ICTs) remain a challenging treatment dilemma. Superior capsule reconstruction (SCR) acts as a static stabilizer to decrease superior humeral head migration. Latissimus dorsi tendon transfers (LDTs) dynamically decrease superior humeral head migration and improve external rotation. We hypothesized that the dynamic stabilizing effect of the latissimus transfer plus the static stabilizing effect of SCR would improve shoulder kinematics in shoulders with ICTs. MATERIALS AND METHODS: Eight fresh-frozen cadaveric shoulders were tested in 5 conditions: (1) intact, (2) ICT (supraspinatus plus anterior half of infraspinatus), (3) SCR with dermal allograft, (4) SCR plus LDT, and (5) LDT alone. Rotational range of motion, superior translation, anteroposterior translation, and peak subacromial contact pressure were measured at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane. Statistical analysis was performed using a repeated-measures analysis of variance test, followed by a Tukey post hoc test for pair-wise comparisons. RESULTS: ICTs increased total shoulder rotation, superior translation, posterior translation, and peak subacromial contact pressure. SCR plus LDT significantly decreased internal rotation only at 60° of abduction. The effect of SCR plus LDT was most evident at lower levels of abduction. At the mid range of abduction (30°), the static stabilizing effect diminished but the dynamic stabilizing effect remained, allowing SCR plus LDT to reduce superior translation more effectively than SCR with dermal allograft alone. CONCLUSIONS: Adding SCR to LDT adds static stabilization to a dynamic stabilizer. Therefore, SCR plus LDT may provide additional stability at the low to mid ranges of abduction.

A biomechanical cadaveric study of patellar tendon allograft as an alternative graft material for superior capsule reconstruction.

HYPOTHESIS: In a cadaveric irreparable rotator cuff tear model, patellar tendon allograft-superior capsule reconstruction (PT-SCR) will restore glenohumeral stability and reduce subacromial contact pressures without significant graft deformation during testing. METHODS: Eight cadaveric shoulders were tested in a custom shoulder testing system. Rotational range of motion (ROM), superior translation, and subacromial contact pressure were measured in the following experimental conditions: intact rotator cuff, irreparable supraspinatus tear (massive cuff tear [MCT]), and PT-SCR. RESULTS: MCT and PT-SCR resulted in significantly increased total ROM at all degrees of abduction compared with the intact state (P < .001). In both 0° and 30° of glenohumeral abduction, MCT showed a significant increase in superior translation compared with the intact state (P < .001). Application of the PT-SCR resulted in a decrease of superior translation compared with MCT (P < .001). At 0° abduction/60° external rotation and 0° abduction/90° external rotation, MCT showed significantly greater peak subacromial contact pressure compared with the intact state (P < .006). At both of these positions, PT-SCR was able to reduce peak pressure to lower than or no significant difference from the intact state. There was no statistically significant change in graft thickness, length, or width after testing. CONCLUSION: PT-SCR was able to reduce superior translation of the humeral head and peak subacromial contact pressure without restricting ROM. Furthermore, there was no significant graft deformation during testing. PT-SCR in this validated cadaveric model demonstrates favorable biomechanical properties and is a viable source of graft material for SCR.

Bicruciate lesion biomechanics, Part 1-Diagnosis: translations over 15 mm at 90° of knee flexion are indicative of a complete tear.

PURPOSE: Understanding the pathomechanics of a bicruciate injury (BI) is critical for its correct diagnosis and treatment. The purpose of this biomechanical study aims to quantify the effects of sequential sectioning of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) bundles on knee laxity. METHODS: Twelve cadaveric knees (six matched pairs) were used. Knee laxity measurements consisted of neutral tibial position, anterior-posterior translation, internal-external rotation, and varus-valgus angulation in different conditions: intact, ACL cut, incomplete BI (divided into two groups: anterolateral (AL) bundle intact or posteromedial (PM) bundle intact) and complete bicruciate tear. Data were collected using a Microscribe system at 0°, 30°, 60°, and 90° of knee flexion. RESULTS: In comparison to the intact knees, incomplete BI and complete BI showed a significant increase of total antero-posterior tibial translation. The largest significant increase was observed at 90° of flexion after a complete bicruciate resection (p < 0.001). A threshold difference greater than 15 mm from the intact could be used to identify a complete BI from an incomplete BI evaluating the total antero-posterior translation at 90°. All sectioned states had significant increases compared with the intact condition in internal-external rotation and varus-valgus stability at all tested flexion angles. CONCLUSION: Both incomplete and complete BI led to an important AP translation instability at all angles; however, full extension was the most stable position at all injured models. Total antero-posterior translation at 90° of knee flexion over 15 mm, in comparison to the intact condition, was indicative of a complete BI. Since the appropriate assessment of a combined ACL and PCL lesion remains a challenge, this study intends to assist its diagnosis. As BI's main antero-posterior instability occurred at 90°, a total antero-posterior drawer test is proposed to evaluate BI in the clinical setting. Total antero-posterior translation at 90° > 15 mm, in comparison to the intact condition or the contra-lateral non-injured knee, can be used to identify a complete from an incomplete BI.

Bicruciate lesion biomechanics, Part 2-treatment using a simultaneous tensioning protocol: ACL fixation first is better than PCL fixation first to restore tibiofemoral orientation.

PURPOSE: An uncommon technique for bicruciate ligament reconstruction involving simultaneous tensioning of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) grafts with ACL graft fixation first has been pointed out as superior to the "gold-standard" PCL graft fixation first. The purpose of this study was to compare tibiofemoral biomechanics between ACL fixation first and PCL fixation first in a simultaneous tensioning protocol for bicruciate ligament reconstruction. METHODS: 12 fresh-frozen cadaveric knees (six matched pairs) were tested using a custom testing system. Neutral tibial position representing tibiofemoral orientation, anterior-posterior (AP) tibial translation, varus-valgus laxity, and internal-external rotation were measured using a Microscribe 3DLX at 0°, 30°, 60°, and 90° of knee flexion. The following knee conditions were evaluated: intact, bicruciate deficient and following bicruciate reconstruction. A simultaneous tensioning protocol was used for bicruciate reconstruction and PCL fixation first was compared to ACL fixation first. PCL graft fixation was always performed at 90° of flexion and ACL graft fixation was always performed at full extension. RESULTS: ACL fixation first achieved a tibiofemoral orientation closer to the intact knee than PCL fixation first at 90° flexion (1.8 ± 1.6 mm versus 6.1 ± 3.2 mm, p = 0.016). PCL fixation first had a larger decrease in AP translation than ACL fixation first at 30° flexion (64.6 ± 3.5% vs. 58.3 ± 2.4%, p = 0.01). No significant differences were found for varus/valgus, external-internal rotation decrements after bicruciate reconstruction nor for AP translation, varus/valgus and internal/external rotation increase after bicruciate lesion comparing ACL fixation first to PCL fixation first. CONCLUSION: Bicruciate ligament reconstruction using a simultaneous tensioning protocol with ACL fixation first resulted in a closer to normal tibiofemoral orientation. This study will help guide surgeons in decision making for the graft tensioning protocol and fixation sequence in a bicruciate ligament reconstruction. LEVEL OF EVIDENCE: V therapeutic study.

Biomechanical effects of position and angle of insertion for all-suture anchors in arthroscopic Bankart repair.

BACKGROUND: The biomechanical properties of all-suture anchor for labral repair depending on the insertion angle and location are lacking. The purpose of this study was to quantify the biomechanical fixation characteristics of the anchor position and insertion angle of all-suture anchors for arthroscopic Bankart repair. METHODS: Twenty-four fresh frozen cadaveric glenoid were used. All-suture anchors with 1.5-mm diameter were randomly inserted at 2:30, 4:00, and 5:30 o'clock positions on the glenoid edge, with either 30°, 45° or 60° insertion angles to the mediolateral axis of the glenoid. Anchors were preloaded to 5 N and cyclically loaded from 5 N to 20 N for 10 cycles, followed by a load to failure test at 60 mm/min. Permanent, non-recoverable displacement was quantified at the end of the cyclic loading test to yield load. FINDINGS: All-suture anchors implanted at the 2:30 o'clock position of the glenoid provided greater stiffness, yield load, and ultimate load than those inserted at the 4:00 and 5:30 o'clock positions, regardless of the insertion angle. Displacement at yield and ultimate load were similar among the positions and insertion angles (yield load, vs. 4:00, p = 0.01; vs. 5:30, p = 0.045; ultimate load, vs. 4:00, p < 0.01; vs. 5:30, p < 0.01). The insertion angles of 30°, 45° and 60° did not influence mechanical stability between the 4:00 and 5:30 o'clock positions. INTERPRETATION: The insertion angle of all-suture anchors does not significantly affect the stability at antero-inferior quadrant of the glenoid.

Biomechanical Analysis of Single-, Double-, and Triple-Bundle Configurations for Coracoclavicular Ligament Reconstruction Using Cortical Fixation Buttons With Suture Tapes: A Cadaveric Study.

PURPOSE: To compare the acromioclavicular (AC) joint stability of single-bundle (SB), double-bundle with an anterolateral limb (DBa), double-bundle with a posterolateral limb (DBp), and triple-bundle (TB) coracoclavicular (CC) ligament reconstructions using cortical fixation buttons with suture tapes. METHODS: Eight cadaveric shoulders were used. AC joint translation and rotational stability were tested for intact and following 4 different CC reconstruction techniques: SB, DBa, DBp, and TB configurations using cortical fixation buttons with suture tapes. For each reconstruction and native AC joint as control, anteroposterior (AP) and superoinferior translations were quantified using 10- and 15-N translational loads and anterior and posterior rotations were measured using 0.16- and 0.32-Nm rotational torque. RESULTS: DBp reconstruction showed significantly better AP stability compared with SB and DBa reconstruction at 10 and 15 N (DBp: 4.1 ± 0.6 mm, SB: 7.8 ± 1.1 mm, P < .001; DBa: 6.5 ± 0.7 mm, P = .02 at 10 N; DBp: 5.5 ± 0.8 mm, SB: 10.1 ± 1.0 mm, P = .003; DBa: 9.1 ± 0.7 mm, P = .02 at 15 N). The degree of total rotation showed tendency to decrease according to increasing number of bundles; however, there were no significant differences (SB: 43.1 ± 9.2°, DBa: 37.9 ± 7.3°, DBp: 33.9 ± 6.8°, TB: 32.2 ± 6.6°, P = .37 at 0.32 Nm). CONCLUSIONS: An additional posterolateral clavicular hole for CC ligament reconstruction using cortical fixation buttons with suture tapes resulted in better AP stability compared with SB reconstruction, whereas use of additional anterolateral clavicular hole did not show any improvement compared with SB reconstruction. Reconstruction using both anterolateral and posterolateral clavicular holes did not guarantee better stability compared with SB reconstruction. There was an increasing tendency of rotational stability with number of bundle increases, although they did not reach statistical difference. CLINICAL RELEVANCE: When surgeons consider double-bundle CC ligament reconstruction using cortical fixation buttons with suture tapes, it is better to position the lateral clavicular hole posteriorly to restore AP stability.

Effect of Increased Scapular Internal Rotation on Glenohumeral External Rotation and Elbow Valgus Load in the Late Cocking Phase of Throwing Motion.

BACKGROUND: Scapular dyskinesis among throwers is thought to affect kinetic chain function and increase the load demands on the shoulder and/or elbow. However, the biomechanical relationship between scapular orientation and elbow valgus load, which is associated with ulnar collateral ligament (UCL) injury, has not been determined. PURPOSE: To evaluate the effect of increased scapular internal rotation (IR) and glenohumeral external rotation (GHER) on elbow valgus load in a static simulation of the late cocking phase of throwing. STUDY DESIGN: Controlled laboratory study. METHODS: Seven fresh-frozen male cadaveric upper extremities were used with a custom testing system to simulate the late cocking phase. First, the authors evaluated the effect of increasing scapular IR on maximum GHER and forearm angle (forearm axis relative to the ground). Each parameter was evaluated at 20° to 40° (5° increments) of scapular IR by applying 2.2-N·m external rotation torque to the humerus and 0.75-N·m valgus torque to the forearm. Next, to evaluate elbow valgus stability, the humerus was locked in maximal GHER at 40° of scapular IR, and sequentially increasing torque (0.75-7.5 N·m by 0.75-N·m increments) was applied to the forearm. Valgus angle and joint gap were evaluated at each torque. RESULTS: Increases in scapular IR ≥5° significantly decreased GHER ( P < .01). With increasing valgus torque, forearm angle also increased linearly ( R2 = 0.85, P < .001). To compensate for the GHER deficit at 40° of scapular IR, a linear regression model showed that 25.3 N·m of valgus torque would be necessary to reach the original forearm position. In the intact condition, applying elbow valgus torque ≥5.25 N·m significantly increased valgus angle and the joint gap ( P < .01). CONCLUSION: Increased scapular IR significantly decreased GHER. Compensation for the GHER deficit significantly increased the elbow valgus load required to reach the same forearm position. CLINICAL RELEVANCE: Increased scapular IR may increase the risk of elbow UCL injury among throwing athletes.