Superior Humeral Translation Research Articles

Acellular Human Dermal Allograft Tuberoplasty Improved the Biomechanics in Mid-Range and Higher Abduction Angles in a Cadaveric Model of Massive Irreparable Rotator Cuff Tears

PurposeTo evaluate the biomechanical effects of Acellular Human Dermal Allograft Tuberoplasty (AHDAT) in a cadaveric model of an irreparable supraspinatus + anterior ½ infraspinatus (Stage III) rotator cuff tear . MethodsEight cadaveric shoulders were tested at 20°, 40°, and 60° glenohumeral abduction (AB) and 0°, 30°, 60°, and 90° external rotation (ER). Superior humeral translation, acromiohumeral distance, and subacromial contact were quantified for four conditions: 1) intact, 2) stage III tear (entire supraspinatus and anterior one-half infraspinatus), 3) single-layer AHDAT, and 4) double-layer AHDAT. ResultsStage III tear significantly increased superior translation at 20° and 40°AB and all ER angles and at 60° AB/60° ER (P ≤ 0.045 vs. intact). Compared to the stage III tear, the single-layer AHDAT significantly decreased superior translation at 60° AB/60° ER (P = 0.003); whereas, the double-layer AHDAT significantly decreased superior translation at 40° and 60° AB at all ER angles except 60° AB/0° ER (P ≤ 0.028). The stage III tear significantly decreased acromiohumeral distance at 20° AB (P ≤ 0.003); both grafts increased acromiohumeral distance to intact levels(P ≥ 0.055 vs. intact). Stage III tear increased subacromial contact pressure at 20° and 40° AB/ 0° and 30° ER and at 60° AB/30° and 60° ER (P ≤ 0.034). Both AHDAT groups decreased contact pressure at 40° AB/30° and 60° ER back to intact; whereas the double-layer AHDAT also decreased contact pressure at 20° AB/0° and 60° ER and 60° AB/30° ER (P ≥ 0.051 vs. intact). ConclusionBoth single- and double- layer grafts for AHDAT, improved superior translation, subacromial contact characteristics and acromiohumeral distance after a stage III rotator cuff tear, with varying effectiveness due to the position-dependent nature of greater tuberosity-to-acromial contact with abduction.

Biomechanical Role of the Superior Capsule in a Rotator Cuff Sectioned and Repaired State: A Sequential Sectioning Study

Background: Individual contributions of the rotator cuff (RC) and superior capsule (SC) to prevent superior translation of the humerus are not well understood. Purpose: To evaluate the relative contributions of the SC and RC to normal and pathologic shoulder biomechanics by determining their independent effects on superior humeral translation. Study Design: Controlled laboratory study. Methods: Twelve cadaveric shoulders were tested at 0º, 45º, and 90º of abduction under 5 conditions: intact RC/SC, RC sectioned first, SC sectioned first, both structures sectioned, and RC repair. Matched pairs were randomly assigned to the second or third testing condition (RC or SC sectioned first). Specimens were tested under 2 static conditions (40-N deltoid load [balanced load], 80-N deltoid load [superiorly directed load]) and 1 dynamic condition during active abduction. A mixed-design 2-way repeated-measures analysis of variance with Bonferroni adjustments was performed to compare testing conditions. Paired t tests were used to compare specimens in the intact state versus the repaired state. Significance was set at P < .05. Results: During balanced deltoid loading at 0° and 45º, there was significantly greater humeral translation when both structures were sectioned as compared with the intact state and with both isolated sectioned states (P < .05 for all). No significant differences were observed between or within groups at 90º of abduction. These effects remained consistent with superiorly directed loading. Dynamic testing of both groups showed a significant increase in superior translation for specimens in which the RC was deficient versus the intact state (P = .027), with no difference when the SC was sectioned. The RC repair state returned translation to values similar to the intact state at all abduction angles and loading conditions (P > .05). Conclusion: In this cadaveric study, the SC and RC played an important role in preventing superior humeral translation; however, dynamic testing suggested preferential contribution of the RC. RC repair was effective in preventing superior humeral translation, even with a sectioned SC at the level of the glenohumeral joint. Clinical Relevance: RC repair was effective in preventing superior humeral translation, even in the presence of a sectioned SC at the level of the glenohumeral joint in this cadaveric model. Our data lay the groundwork for future studies investigating the clinical effect of RC repair in an SC sectioned state.

Reconstruction of the Coracoacromial Ligament during a Modified Latarjet Procedure for the Treatment of Shoulder Instability: Clinical Outcome at Minimum 5 Years Follow-Up.

The function of the coracoacromial ligament (CAL) in superior shoulder stability has been well established, and the release of the CAL with the Latarjet procedure leads to increased superior humeral translation. A surgical technique was developed recently to reconstruct the CAL during a modified Latarjet procedure, and the clinical outcome of this technique at medium-term follow-up is yet to be determined. Twenty-six patients with chronic post-traumatic anterior shoulder instability were included in this retrospective case-control study. Patients in group 1 (n = 12) were surgically treated with the classic congruent-arc Latarjet, where the CAL is sacrificed. In group 2 (n = 14), the CAL was reconstructed using a pectoralis minor fascia flap (PMFF). Primary outcomes were the return to sports activity and functional assessment based on the Western Ontario Shoulder Instability Index (WOSI) and the Constant Score (CS) at minimum 5 years follow-up. Patient's demographics, sport activities, duration of surgery, the rate of recurrent dislocations, and specific complications related to the surgical technique were recorded as secondary variables. There was a decrease of the WOSI in both groups, indicating a decrease of symptoms at follow-up compared to the preoperative level. There was no statistically significant difference between groups 1 and 2 for the total WOSI as well as for all subscales. There was an increase of the CS in both groups in all four items at follow-up compared to preoperatively, indicating an increase in shoulder function at follow-up. There was a statistically significant difference between groups 1 and 2 for the total CS, as well as for the items power, mobility, and activity, but not for pain. Most patients (n = 20) returned to their preoperative sports activity, 13 at the same level. However, seven patients who used to perform their sports competitively chose to perform their activity at a noncompetitive level after the Latarjet procedure. All were younger than 35 years of age. Six patients did not return to their preoperative sports activity. All except one were over 35 years of age. The duration of surgery ranged from 75 to 125 minutes with a mean ± SD of 94.23 ± 15.06 minutes for both groups with no significant difference between the groups (p = 0.117). None of the patients had intra- or postoperative complications related to the surgical procedure. Especially, no patient had recurrent dislocations of the affected shoulder following the Latarjet procedure. The use of a PMFF is a safe technique for reconstruction of the CAL, which does not result in a longer surgery time or higher rate of complications. The reconstruction of the CAL during the modified Latarjet procedure may lead to better functional results in medium-term follow-up.

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

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). 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. 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. BR biomechanically restored shoulder stability without overconstraining range of motion in an LICT model.

Multivariate analyses of rotator cuff pathologies in shoulder disability.

BackgroundDisability of the shoulder joint is often caused by a tear in the rotator cuff (RC) muscles. Four RC muscles coordinate shoulder movement and stability, among them the supraspinatus and infraspinatus muscle which are predominantly torn. The contribution of each RC muscle to tear pathology is not fully understood. We hypothesized that muscle atrophy and fatty infiltration, features of RC muscle degeneration, are predictive of superior humeral head translation and shoulder functional disability.MethodsShoulder features, including RC muscle surface area and fatty infiltration, superior humeral translation and RC tear size were obtained from a consecutive series of Magnetic Resonance Imaging with arthrography (MRA). We investigated patients with superior (supraspinatus, n = 39) and posterosuperior (supraspinatus and infraspinatus, n = 30) RC tears, and patients with an intact RC (n = 52) as controls. The individual or combinatorial contribution of RC measures to superior humeral translation, as a sign of RC dysfunction, was investigated with univariate or multivariate models, respectively.ResultsUsing the univariate model the infraspinatus surface area and fatty infiltration in both the supraspinatus and infraspinatus had a significant contribution to RC dysfunction. With the multivariate model, however, the infraspinatus surface area only affected superior humeral translation (p<0.001) and discriminated between superior and posterosuperior tears. In contrast neither tear size nor fatty infiltration of the supraspinatus or infraspinatus contributed to superior humeral translation.ConclusionOur study reveals that infraspinatus atrophy has the strongest contribution to RC tear pathologies. This suggests a pivotal role for the infraspinatus in preventing shoulder disability.

A biomechanical assessment of superior shoulder translation after reconstruction of anterior glenoid bone defects: The Latarjet procedure versus allograft reconstruction

Background:The coracoacromial ligament (CAL) is an important restraint to superior shoulder translation. The effect of CAL release on superior stability following the Latarjet is unknown; therefore, our purpose was to compare the effect of two Latarjet techniques and allograft reconstruction on superior instability.Materials and Methods:Eight cadaveric specimens were tested on a simulator. Superior translation was monitored following an axial force in various glenohumeral rotations (neutral, internal, and external) with and without muscle loading. Three intact CAL states were tested (intact specimen, 30% glenoid bone defect, and allograft reconstruction) and two CAL deficient states (classic Latarjet (classicLAT) and congruent-arc Latarjet (congruentLAT)).Results:In neutral without muscle loading, a significant increase in superior translation occurred with the classicLAT as compared to 30% defect (P = 0.046) and allograft conditions (P = 0.041). With muscle loading, the classicLAT (P = 0.005, 0.002) and the congruentLAT (P = 0.018, 0.021) had significantly greater superior translation compared to intact and allograft, respectively. In internal rotation, only loaded tests produced significant results; specifically, classicLAT increased translation compared to all intact CAL states (P < 0.05). In external rotation, only unloaded tests produced significant results with classicLAT and congruentLAT allowing greater translations than intact (P ≤ 0.028). For all simulations, the allograft was not significantly different than intact (P > 0.05) and no differences (P = 1.0) were found between classicLAT and congruentLAT.Discussion:In most simulations, CAL release with the Latarjet lead to increased superior humeral translation.Conclusion:The choice of technique for glenoid bone loss reconstruction has implications on the magnitude of superior humeral translation. This previously unknown effect requires further study to determine its clinical and kinematic outcomes.

The Effect of Coracoacromial Ligament Excision and Acromioplasty on Superior and Anterosuperior Glenohumeral Stability

To determine the effect of coracoacromial ligament (CAL) resection and subacromial decompression (SAD)/acromioplasty on humeral head translation under anterosuperior and superior loading in a cadaveric model with an intact rotator cuff. Six cadaveric shoulders were tested in the intact state, following CAL resection and following SAD. Excision of the CAL led to a significant increase in anterosuperior humeral translation of 2.1 mm (17%). SAD led to a significant increase in superior humeral translation of 2.5 mm (28%). The results of this cadaveric study showed that resection of the CAL led to a 2.1-mm increase in anterosuperior translation and that SAD led to a 2.5-mm increase in superior translation. CAL resection and SAD are common surgical procedures, which may lead to increases in anterosuperior and superior glenohumeral instability.

Glenoid inclination: In vivo measures in rotator cuff tear patients and associations with superior glenohumeral joint translation

Glenoid inclination has been associated with rotator cuff tears and superior humeral translation, but the relationship between glenoid inclination and superior humeral translation has not been assessed in vivo. This study compared glenoid inclination between repaired and contralateral shoulders in 21 unilateral rotator cuff repair patients. As a secondary analysis, we assessed the relationship between glenoid inclination and in vivo superior humeral translation. Glenoid inclination was measured from patient-specific, computed tomography-based bone models. Glenohumeral joint motion was measured from biplane radiographs collected during coronal-plane abductions. Glenoid inclination was significantly lower for the rotator cuff tear shoulders (90.7 degrees ) than the asymptomatic, contralateral shoulders (92.3 degrees , P = .04). No significant correlation existed between increased glenoid inclination and superior-inferior translation of the uninjured shoulder (P > .30). This study failed to support the theory that glenoid inclination is responsible for superior humeral translation and the development of subacromial impingement.

Total shoulder arthroplasty using the superior approach: Influence on glenoid loosening and superior migration in the long-term follow-up after Neer II prosthesis installation

Glenoid component loosening and superior humeral translation are common after Neer II total shoulder arthroplasty using the anterior approach. To determine whether the superior approach reduced these complications, we retrospectively reviewed 20 shoulders in 16 patients. Both components were cemented. Patient satisfaction, unweighted Constant score, and imaging studies were evaluated at a mean of 3.5 years and at a mean of 11.1 years. Fourteen patients were satisfied or very satisfied. The mean unweighted Constant score improved from 25/100 preoperatively to 57/100 after 3.5 years and to 51/100 after 11.1 years. Pain relief contrasted with low strength. Radiolucent lines appeared around 95% of glenoid components and 20% of humeral stems. Computed tomography showed severe glenoid osteolysis in 3 of 13 shoulders. Humeral superior translation did not occur. This study confirms the glenoid component fixation issue. The superior approach may reduce the risk of humeral superior translation and radiologic glenoid component loosening.

The effect of glenoid inclination on superior humeral head migration

Superior humeral head migration may contribute to the development of rotator cuff disease. The purpose of this study was to test the hypothesis that superior inclination of the glenoid facilitates superior humeral head migration. Eight cadaveric shoulders were tested by use of a custom test fixture, and rotator cuff forces were applied. Glenoid inclination was varied (intact, +5°, +10°, and +15°), and the force required to produce superior humeral head migration was measured. Each increase in glenoid inclination (more superiorly facing glenoid) produced significant reduction in the force required for superior humeral head migration (5°, 14.2% reduction; 10°, 29.9% reduction; and 15°, 37.5% reduction; P < .001). These findings demonstrate that glenoid inclination is an important factor in determining the force required for superior humeral head migration. This suggests that a more upward-facing glenoid increases the risk for superior humeral translation and, in turn, may play a role in the development of rotator cuff disease.

Active and passive restraints against superior humeral translation: The contributions of the rotator cuff, the biceps tendon, and the coracoacromial arch

Active and passive restraints against superior humeral translation: The contributions of the rotator cuff, the biceps tendon, and the coracoacromial arch