Defining Critical Humeral Bone Loss: Inferior Craniocaudal Hill-Sachs Extension as Predictor of Recurrent Instability After Primary Arthroscopic Bankart Repair.

BACKGROUND: The glenoid track concept for shoulder instability primarily describes the medial-lateral relationship between a Hill-Sachs lesion and the glenoid. However, the Hill-Sachs position in the craniocaudal dimension has not been thoroughly studied. HYPOTHESIS: Hill-Sachs lesions with greater inferior extension are associated with increased risk of recurrent instability after primary arthroscopic Bankart repair. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The authors performed a retrospective analysis of patients with on-track Hill-Sachs lesions who underwent primary arthroscopic Bankart repair (without remplissage) between 2007 and 2019 and had a minimum 2-year follow-up. Recurrent instability was defined as recurrent dislocation or subluxation after the index procedure. The craniocaudal position of the Hill-Sachs lesion was measured against the midhumeral axis on sagittal magnetic resonance imaging (MRI) using either a Hill-Sachs bisecting line through the humeral head center (sagittal midpoint angle [SMA], a measure of Hill-Sachs craniocaudal position) or a line tangent to the inferior Hill-Sachs edge (lower-edge angle [LEA], a measure of Hill-Sachs caudal extension). Univariate and multivariate regression were used to determine the predictive value of both SMA and LEA for recurrent instability. RESULTS: In total, 176 patients were included with a mean age of 20.6 years, mean follow-up of 5.9 years, and contact sport participation of 69.3%. Of these patients, 42 (23.9%) experienced recurrent instability (30 dislocations, 12 subluxations) at a mean time of 1.7 years after surgery. Recurrent instability was found to be significantly associated with LEA >90° (ie, Hill-Sachs lesions extending below the humeral head equator), with an OR of 3.29 (P = .022). SMA predicted recurrent instability to a lesser degree (OR, 2.22; P = .052). Post hoc evaluation demonstrated that LEA >90° predicted recurrent dislocations (subset of recurrent instability) with an OR of 4.80 (P = .003). LEA and SMA were found to be collinear with Hill-Sachs interval and distance to dislocation, suggesting that greater LEA and SMA proportionally reflect lesion severity in both the craniocaudal and medial-lateral dimensions. CONCLUSION: Inferior extension of an otherwise on-track Hill-Sachs lesion is a highly predictive risk factor for recurrent instability after primary arthroscopic Bankart repair. Evaluation of Hill-Sachs extension below the humeral equator (inferior equatorial extension) on sagittal MRI is a clinically facile screening tool for higher-risk lesions with subcritical glenoid bone loss. This threshold for critical humeral bone loss may inform surgical stratification for procedures such as remplissage or other approaches for at-risk on-track lesions.

Myotendinous junction tears of the pectoralis major are occurring more frequently and discrepancies exist between intraoperative and radiographic assessments.

Background: Pectoralis major (PM) tears have been shown to occur most frequently at the tendinous humeral insertion. However, no substantial updates on tear location have been published in 20 years or are based on relatively small sample sizes. The primary purpose of this study was to evaluate PM tear location based on magnetic resonance imaging (MRI). A secondary purpose was to evaluate agreement between MRI and intraoperative assessments of tear characteristics. We hypothesized that PM tears at the myotendinous junction (MTJ) occur at a higher rate than previously reported and that intraoperative and MRI assessments would demonstrate agreement in at least 80% of cases. Materials and methods: An observational study of consecutive patients evaluated for a PM tear at a single institution between 2010 and 2022 was conducted. Patient demographics as well as MRI and intraoperative assessments of tear location, extent of tear, and muscle head involvement were collected from the electronic medical record. Agreement was calculated by comparing radiographic and intraoperative assessments per variable and reported as percentages. Data and statistical analysis were performed with SPSS software with a significance level set to P < .05. Results: A total of 102 patients were included for analysis. Mean age was 35.8 ± 10.5 years and mean body mass index was 29.4 ± 4.8 kg/m2. 60.4% of the study population had tears of the MTJ, 34.9% of the tendinous humeral insertion, and 4.7% within the muscle belly, as determined intraoperatively. Complete tears had significantly higher agreement between MRI and intraoperative assessments relative to partial tears (83.9% and 62.5%, respectively; P ≤ .01). Discussion: The majority of PM tears occurred at the MTJ. Preoperative MRI and intraoperative assessments agreed in 80% of cases, a value that was significantly higher for complete over partial tears. These findings demonstrate that tears of the MTJ are increasingly more common and support the use of MRI in preoperative planning for complete PM tears.

Increased Failure Rates After Arthroscopic Bankart Repair After Second Dislocation Compared to Primary Dislocation With Comparable Clinical Outcomes.

PURPOSE: The purpose of this study was to compare rates of recurrent dislocation and postsurgical outcomes in patients undergoing arthroscopic Bankart repair for anterior shoulder instability immediately after a first-time traumatic anterior dislocation versus patients who sustained a second dislocation event after initial nonoperative management. METHODS: A retrospective chart review was performed of patients undergoing primary arthroscopic stabilization for anterior shoulder instability without concomitant procedures and minimum 2-year clinical follow-up. Primary outcome was documentation of a recurrent shoulder dislocation. Secondary clinical outcomes included range of motion, Visual Analog Scale (VAS), American Shoulder and Elbow Surgeons Shoulder Score (ASES), and Shoulder Activity Scale (SAS). RESULTS: Seventy-seven patients (mean age 21.3 years ± 7.3 years) met inclusion criteria. Sixty-three shoulders underwent surgical stabilization after a single shoulder dislocation, and 14 underwent surgery after 2 dislocations. Average follow-up was 35.9 months. The rate of recurrent dislocation was significantly higher in the 2-dislocation group compared to single dislocations (42.8% vs 14.2%, P = .03). No significant difference was present in range of motion, VAS, ASES, and SAS scores. The minimal clinically important difference (MCID) was 1.4 for VAS and 1.8 for SAS scores. The MCID was met or exceeded in the primary dislocation group in 31/38 (81.6%) patients for VAS, 23/31 (74.1%) for ASES, and 24/31 for SES (77.4%) scores. For the second dislocation cohort, MCID was met or exceeded in 7/9 (77.8%) for VAS, 4/7 (57.1%) for ASES, and 5/7 for SES (71.4%) scores. CONCLUSION: Immediate arthroscopic surgical stabilization after a first-time anterior shoulder dislocation significantly decreases the risk of recurrent dislocation in comparison to those who undergo surgery after 2 dislocation events, with comparable clinical outcome scores. These findings suggest that patients who return to activities after a primary anterior shoulder dislocation and sustain just 1 additional dislocation event are at increased risk of a failing arthroscopic repair. STUDY DESIGN: Retrospective comparative study; Level of evidence, 3.

Distance to Dislocation and Recurrent Shoulder Dislocation After Arthroscopic Bankart Repair: Rethinking the Glenoid Track Concept.

BACKGROUND: The "distance to dislocation" (DTD) calculation has been proposed as 1 method to predict the risk of recurrent dislocation after arthroscopic Bankart repair for an "on-track" shoulder. Rates of recurrent dislocation at specific DTD values are unknown. HYPOTHESIS: Among patients with "on-track" shoulder lesions who underwent primary arthroscopic Bankart repair, the rate of recurrent dislocation would increase as DTD values decrease. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: We performed a retrospective analysis of 188 patients with "on-track" shoulder lesions who underwent primary arthroscopic anterior labral repair between 2007 and 2019, with a minimum 2-year follow-up. Glenoid bone loss, Hill-Sachs interval, glenoid track, and DTD were determined from preoperative magnetic resonance imaging scans. The rate of recurrent dislocation was determined at 2-mm DTD intervals. Univariate and multivariate regression analyses were used to evaluate the relationship between recurrent dislocation, patient characteristics, and bone loss variables. A multivariate regression model was created to predict the probability of failure at continuous DTD values. A subgroup analysis of failure rate based on collision sports participation was also performed. RESULTS: A total of 29 patients (15.4%) sustained recurrent dislocations. Patient age (P = .046), multiple dislocations (P = .03), glenoid bone loss (P < .001), Hill-Sachs interval length (P < .001), and DTD (P < .001) were all independent predictors of failure. As the DTD decreased, the rate of recurrent dislocation increased. Below a DTD threshold of 10 mm, the recurrent dislocation rate increased exponentially. Up to a threshold of 24 mm, the failure rate for collision athletes remained >12.3%, independent of the DTD. Conversely, the failure rate among noncollision athletes decreased steadily as the DTD increased. CONCLUSION: For "on-track" shoulder lesions, as the DTD approached 0 mm ("off-track" threshold), the risk of recurrent dislocation after arthroscopic Bankart repair increased significantly. Below a DTD threshold of 10 mm, the risk of failure increased exponentially. The risk of recurrent dislocation for collision sports athletes remained elevated at higher DTD values than for noncollision athletes.

Liposomal bupivacaine infiltration in the surgical site for analgesia after rotator cuff repair: a randomized, double-blinded, placebo-controlled trial.

INTRODUCTION: Arthroscopic rotator cuff repair is among the most painful of orthopedic surgeries. Liposomal bupivacaine is Food and Drug Administration approved for administration into surgical sites to provide postsurgical analgesia and has been used to address postoperative pain after many types of surgery, including total shoulder arthroplasty. However, its efficacy for pain control after rotator cuff repair is unclear. METHODS: In this randomized, double-blind, placebo-controlled trial, we compared liposomal bupivacaine with an equivalent volume of saline injected into the subacromial space and arthroscopy portal sites in patients undergoing rotator cuff repair under the interscalene block with sedation. The primary outcome measure was numeric rating pain score at the time of block resolution, as reported during the follow-up phone call on postoperative day 1. Secondary outcomes included mean pain scores at rest as well as oral morphine equivalent requirements on postoperative days 1, 2, and 3. This study provides Level 1 evidence. RESULTS: There were no statistically significant differences in the primary outcome of numeric rating pain scores on resolution of the interscalene nerve block, nor in those reported on postoperative day 1 or 2. There was a minor but statistically significant difference in mean resting pain scores on day 3, though opioid consumption and patient satisfaction score did not differ between groups. In those instructed to perform passive range-of-motion exercises, there was no difference in reported mean pain scores among the groups. DISCUSSION: In this study of patients undergoing arthroscopic rotator cuff repair, we found no statistically significant difference in mean pain scores on interscalene block resolution, a result consistent with a number of studies investigating liposomal bupivacaine for total shoulder arthroplasty. A modest reduction in pain was evident only on day 3, and there was no impact on perioperative opioid requirements, opioid-related side effects, or pain with motion. Liposomal bupivacaine, when injected into the subacromial space and the tissues around the arthroscopy port sites, provided minimal improvement in pain control in this patient population.

Humeral head resurfacing is associated with less pain and clinically equivalent functional outcomes compared with stemmed hemiarthroplasty at mid-term follow-up.

PURPOSE: Humeral head resurfacing (HHR) is a less invasive, anatomic alternative to the conventional stemmed hemiarthroplasty in patients in whom isolated humeral head replacement is preferred. It was hypothesized that, in a mid-term cross-sectional subjective outcome analysis, HHR would have equivalent patient-reported and functional outcomes to stemmed hemiarthroplasty (HA). METHODS: A total of 213 HHR and 153 HA procedures were performed at a single academic institution from 2000 to 2014. Of these, 106 HHR and 47 HA patients corresponding with 120 HHR and 55 HA shoulders responded to a survey that collected patient demographics, surgical outcomes, patient satisfaction, and self-reported range of motion scores using both bespoke and validated metrics. RESULTS: Follow-up was longer in the HA group (9.4 ± 3.4 vs. 5.2 ± 1.8 years, p < 0.0001). Self-reported range of motion was equivalent between groups. Surgery was perceived as helpful following 76.7% of HHRs and 78.2% of HAs (p > 0.99). The ASES pain subscore was significantly worse in the HA group (25.2 ± 29.5 vs. 38.5 ± 12.7 after HHR, p < 0.0001), which translated into worse ASES total scores (45.1 ± 14.8 HA vs. 52.2 ± 23.7 HHR, p < 0.05). These findings were equivocal in responses received 2-8 years vs. ≥ 8 years after surgery. CONCLUSIONS: Indications should be equivocal; humeral head resurfacing is a viable alternative to hemiarthroplasty, with equivalent patient satisfaction and reduced pain in the mid-term post-operative period. LEVEL OF EVIDENCE: III.

The Rotator Cuff Organ: Integrating Developmental Biology, Tissue Engineering, and Surgical Considerations to Treat Chronic Massive Rotator Cuff Tears.

The torn rotator cuff remains a persistent orthopedic challenge, with poor outcomes disproportionately associated with chronic, massive tears. Degenerative changes in the tissues that comprise the rotator cuff organ, including muscle, tendon, and bone, contribute to the poor healing capacity of chronic tears, resulting in poor function and an increased risk for repair failure. Tissue engineering strategies to augment rotator cuff repair have been developed in an effort to improve rotator cuff healing and have focused on three principal aims: (1) immediate mechanical augmentation of the surgical repair, (2) restoration of muscle quality and contractility, and (3) regeneration of native enthesis structure. Work in these areas will be reviewed in sequence, highlighting the relevant pathophysiology, developmental biology, and biomechanics, which must be considered when designing therapeutic applications. While the independent use of these strategies has shown promise, synergistic benefits may emerge from their combined application given the interdependence of the tissues that constitute the rotator cuff organ. Furthermore, controlled mobilization of augmented rotator cuff repairs during postoperative rehabilitation may provide mechanotransductive cues capable of guiding tissue regeneration and restoration of rotator cuff function. Present challenges and future possibilities will be identified, which if realized, may provide solutions to the vexing condition of chronic massive rotator cuff tears.

The ability of preoperative factors to predict patient-reported disability following surgery for rotator cuff pathology.

PURPOSE: Minimal research has examined the prognostic ability of shoulder examination data or psychosocial factors in predicting patient-reported disability following surgery for rotator cuff pathology. The purpose of this study was to examine these factors for prognostic value in order to help clinicians and patients understand preoperative factors that impact disability following surgery. METHODS: Sixty-two patients scheduled for subacromial decompression with or without supraspinatus repair were recruited. Six-month follow-up data were available for 46 patients. Patient characteristics, history of the condition, shoulder impairments, psychosocial factors, and patient-reported disability questionnaires were collected preoperatively. Six months following surgery, the Western Ontario Rotator Cuff Index (WORC) and global rating of change dichotomized subjects into responders versus nonresponders. Logistic regression quantified prognostic ability and created the most parsimonious model to predict outcome. RESULTS: Being on modified job duty (OR = .17, 95%CI: 0.03-0.94), and having a worker's compensation claim (OR = 0.08, 95%CI: 0.01-0.74) decreased probability of a positive outcome, while surgery on the dominant shoulder (OR = 11.96, 95%CI: 2.91-49.18) increased probability. From the examination, only impaired internal rotation strength was a significant univariate predictor. The Fear-avoidance Beliefs Questionnaire (FABQ) score (OR = 0.95, 95%CI: 0.91-0.98) and the FABQ_work subscale (OR = 0.92, 95%CI: 0.87-0.97) were univariate predictors. In the final model, surgery on the dominant shoulder (OR = 8.9, 95%CI 1.75-45.7) and FABQ_work subscale score ≤25 (OR = 15.3, 95%CI 2.3-101.9) remained significant. DISCUSSION: Surgery on the dominant arm resulted in greater improvement in patient-reported disability, thereby increasing the odds of a successful surgery. The predictive ability of the FABQ_work subscale highlights the potential impact of psychosocial factors on patient-reported disability. Implications for Rehabilitation Impairment-based shoulder measurements were not strong predictors of patient-reported outcome. Having high fear-avoidance behavior scores on the FABQ, especially the work subscale, resulted in a much lower chance of responding well to rotator cuff surgery as measured by self-reported disability. Having surgery on the dominant shoulder, as compared to the nondominant side, resulted in larger improvements in disability levels.

A biomechanical analysis of the native coracoclavicular ligaments and their influence on a new reconstruction using a coracoid tunnel and free tendon graft.

PURPOSE: To understand and characterize the kinematic properties of the 2 coracoclavicular ligaments and to evaluate the biomechanical performance of a new 3-tunnel reconstruction of the coracoclavicular ligaments by use of a free tendon graft. METHODS: Ten fresh-frozen cadaveric shoulders were tested. The kinematics and in situ forces of the coracoclavicular ligaments were tested with a robotic testing system. Kinematics of the shoulder in the intact state, in the sectioned state, and finally, after a coracoclavicular reconstruction and a coracoclavicular sling reconstruction were evaluated. RESULTS: The conoid had higher in situ forces during anterior and superior loading of the clavicle when compared with the trapezoid ligament, whereas the trapezoid ligament had higher in situ forces during posterior loading. Sectioning the trapezoid ligament significantly increased translation of the clavicle in the posterior direction, whereas sectioning the conoid ligament significantly increased superior translation. When we compared the 2 reconstruction techniques, the coracoid tunnel reconstruction was superior in controlling anterior translation whereas the coracoclavicular sling reconstruction was inferior because of anterior displacement of the graft. There was no significant difference in posterior or superior translation between either reconstruction technique. CONCLUSIONS: The trapezoid and conoid ligaments have unique functions in normal shoulder kinematics because of their anatomic attachments. By more faithfully restoring these insertion sites on the clavicle and controlling motion of the graft on the coracoid, the 3-tunnel reconstruction technique more closely restores native shoulder kinematics than the coracoclavicular sling technique. CLINICAL RELEVANCE: Understanding the unique roles of the conoid and trapezoid bundles of the coracoclavicular ligament may improve surgical techniques in the management of acromioclavicular joint injuries. The reconstructive technique presented more faithfully restores normal kinematics and forces across the acromioclavicular joint than the coracoclavicular sling technique.

Biomechanical evaluation of 2 arthroscopic biceps tenodeses: double-anchor versus percutaneous intra-articular transtendon (PITT) techniques.

BACKGROUND: Recently, there is increasing interest in different arthroscopic biceps tenodesis techniques. However, little data have been published about the biomechanical properties of soft tissue tenodesis. PURPOSE: This study was undertaken to evaluate the biomechanical properties of 2 different arthroscopic biceps tenodeses: the percutaneous intra-articular transtendon (PITT) technique and the suture-anchor technique. STUDY DESIGN: Controlled laboratory study. METHODS: Fifteen fresh-frozen cadaveric specimens were randomly allocated to the 2 different biceps tenodesis techniques. The humerus with biceps tenodesis was mounted on a materials testing machine to perform a load to failure test. The structural properties including ultimate load (N) and stiffness (N/mm) were derived from the load-displacement curve. The mode of failure was also recorded. Ultimate load and stiffness were compared with the parametric Student t test. RESULTS: Both repairs showed typical load-displacement curves followed by a constant increase in load and displacement until failure occurred. Suture-anchor and PITT techniques had ultimate loads of 175.4 +/- 40.4 N and 142.7 +/- 30.9 N (P = .10) and stiffness of 15.9 +/- 8.4 N/mm and 13.3 +/- 3 N/mm (P = .36), respectively, with no significant differences between them. All of the surgical constructs failed in the tendon site by pulling out with the sutures through the substance of the tendon. CONCLUSION: The suture-anchor and PITT techniques exhibited satisfactory initial strength with no statistical difference between the 2 groups. These findings, along with the consistent pullout of the suture through the tendon during failure, suggest that the most important factor for initial strength is not the attachment site but the quality of the biceps tendon. CLINICAL RELEVANCE: The quality of the tendon should be taken into account when deciding the surgical technique and the rehabilitation program. The PITT technique has the benefit of avoiding hardware complications and cost.

Symptomatic os acromiale.

Os acromiale, the joining of the acromion to the scapular spine by fibrocartilaginous tissue rather than bone, is an anatomic variant that has been reported in approximately 8% of the population worldwide. It is more common in blacks and males than in whites and females. Although it is often an incidental finding, os acromiale has been identified as a contributor to shoulder impingement symptoms and rotator cuff tears. When nonsurgical management of a symptomatic os acromiale fails to relieve symptoms, surgical intervention is considered. Options include os acromiale excision, open reduction and internal fixation, and arthroscopic decompression. Excision usually is reserved for small to midsized fragments (preacromion) or after failed open reduction and internal fixation. Persistent deltoid dysfunction may result from excision of a large os acromiale. Open reduction and internal fixation preserves large fragments while maintaining deltoid function. Cannulated screw fixation has been shown to result in good union rates. Arthroscopic techniques have shown mixed results when used for treating impingement secondary to an unstable os acromiale. Associated rotator cuff tears may be addressed arthroscopically or through an open transacromial approach, followed by open reduction and internal fixation of the os acromiale.

Arthroscopic biceps tenodesis using the percutaneous, intra-articular trans-tendon technique: preliminary results.

The percutaneous intra-articular trans-tendon procedure relieved pain, increased or maintained strength and function, and did not cause a cosmetic deformity in this small consecutive series of patients.

Biomechanical rationale for development of anatomical reconstructions of coracoclavicular ligaments after complete acromioclavicular joint dislocations.

BACKGROUND: Surgical treatments of complete acromioclavicular joint dislocations replace or reconstruct the coracoclavicular ligaments with a single structure and do not account for the anatomical variance of each ligament in the design. PURPOSE: To evaluate the cyclic behavior and structural properties of an anatomic tendon reconstruction of the coracoclavicular ligament complex after a simulated acromioclavicular joint dislocation. STUDY DESIGN: Controlled laboratory study. METHODS: Cyclic loading followed by a load-to-failure protocol (simulated dislocation) of the normal coracoclavicular ligament complex was performed and repeated after an anatomic reconstruction on the same specimen (n = 9). The anatomical reconstruction consisted of a semitendinosus tendon that replicated the direction and orientation of both the trapezoid and conoid ligaments. RESULTS: The coracoclavicular ligament and anatomical reconstruction complexes had clinically insignificant (<3 mm) permanent elongation after cyclic loading. The stiffness and ultimate load of the coracoclavicular ligament complex (60.8 +/- 12.2 N/mm and 560 +/- 206 N) were significantly greater than for the anatomical reconstruction complex (23.4 +/- 5.2 N/mm and 406 +/- 60 N), respectively (P < .05). Further analysis of the complexes revealed a 40% decrease in the bending stiffness of the clavicle after the simulated dislocation and failure of the normal coracoclavicular ligament complex (P < .05), which contributed to the diminished properties of the anatomic reconstruction. CONCLUSIONS: The low level of permanent elongation after cyclic loading suggests that the anatomic reconstruction complex could withstand early rehabilitation; however, the decrease in the structural properties and stiffness of the clavicle should be considered in optimizing the anatomic reconstruction technique. CLINICAL RELEVANCE: Despite the differences compared to the normal coracoclavicular ligament complex, the anatomical reconstruction complex more closely approximates the stiffness of the coracoclavicular ligament complex than current surgical constructs, and the incorporation of biological tissue could improve the overall structural properties with healing.

Internal impingement: findings on magnetic resonance imaging and arthroscopic evaluation.

PURPOSE: The purpose of this study was to examine preoperative shoulder magnetic resonance imaging (MRI) and intraoperative arthroscopic findings in throwing athletes with a clinical diagnosis of internal impingement. TYPE OF STUDY: Retrospective review. METHODS: A retrospective review of the surgical indications for 769 shoulder arthroscopic procedures performed from 1997 to 2000 revealed 9 throwing athletes with a diagnosis of severe internal impingement. Each had failed treatment that included a minimum of 3 months of rehabilitation. Preoperative MRIs in all 9 were read by a fellowship-trained musculoskeletal radiologist blinded to the operative findings. Findings at arthroscopy were culled from the operative reports. RESULTS: On both MRI and at arthroscopy, all 9 athletes had posterosuperior labral lesions, 1 had a humeral head articular cartilage lesion, and 1 had a SLAP lesion. Additional findings on MRI included humeral head edema, subchondral cystic changes, posterosuperior glenoid sclerosis, and rotator cuff tendonopathy predominantly in the infraspinatus. At arthroscopy, there were additional findings of articular-sided partial rotator cuff tears not shown on MRI. CONCLUSIONS: Both MRI and arthroscopic findings described labral and humeral head articular cartilage lesions. These findings may be indicative of internal impingement in throwing athletes. LEVEL OF EVIDENCE: Level III, diagnostic.

Reflexive muscle activation alterations in shoulders with anterior glenohumeral instability.

BACKGROUND: Patients with glenohumeral instability have proprioceptive deficits that are suggested to contribute to muscle activation alterations. HYPOTHESIS: Muscle activation alterations will be present in shoulders with anterior glenohumeral instability. STUDY DESIGN: Posttest-only control group design. METHODS: Eleven patients diagnosed with anterior glenohumeral instability were matched with 11 control subjects. Each subject received an external humeral rotation apprehension perturbation while reflexive muscle activation characteristics were measured with indwelling electromyography and surface electromyography. RESULTS: Patients with instability demonstrated suppressed pectoralis major and biceps brachii mean activation; increased peak activation of the subscapularis, supraspinatus, and infraspinatus; and a significantly slower biceps brachii reflex latency. Supraspinatus-subscapularis coactivation was significantly suppressed in the patients with instability as well. CONCLUSIONS AND CLINICAL RELEVANCE: In addition to the capsuloligamentous deficiency and proprioceptive deficits present in anterior glenohumeral instability, muscle activation alterations are also present. The suppressed rotator cuff coactivation, slower biceps brachii activation, and decreased pectoralis major and biceps brachii mean activation may contribute to the recurrent instability episodes seen in this patient group. Clinicians can implement therapeutic exercises that address the suppressed muscles in patients opting for conservative management or rehabilitation before and after capsulorraphy procedures.

Biomechanical function of surgical procedures for acromioclavicular joint dislocations.

PURPOSE: Surgical procedures for treatment of acromioclavicular (AC) joint dislocation replace the coracoclavicular (CC) ligaments to minimize motion, allow scarring, and increase the subsequent stability of the joint. The purpose of this study was to evaluate the biomechanical function of the surgically repaired or reconstructed (CC Sling, Rockwood Screw [DePuy Orthopaedics, Warsaw, IN], and Coracoacromial [CA] Ligament Transfer Construct) AC joint after AC joint dislocation. TYPE OF STUDY: A cadaver study using a convenience sample. METHODS: Twelve cadaveric shoulders were tested using a robotic/UFS testing system. Three external loading conditions (anterior, posterior, or superior load of 70 N) were applied to intact and surgically repaired or reconstructed AC joint. The resulting kinematics of the AC joint and in situ forces in the CC ligaments or surgical constructs was determined. RESULTS: For the CC Sling, anterior and posterior translation significantly increased by 110% and 330% in response to an anterior and posterior load, respectively. However, the posterior translation for the Rockwood Screw significantly decreased by 60%. Anterior, posterior, and superior translation for the CA Ligament Transfer Construct significantly increased by 110%, 360%, and 100%, respectively. The coupled translations also significantly increased for the CC Sling and CA Ligament Transfer Construct in response to all loading conditions. In contrast, the coupled translations for the Rockwood Screw tended to decrease. Furthermore, the in situ forces increased significantly for all 3 surgical constructs compared with the intact CC Ligaments in response to an anterior and posterior load. CONCLUSIONS: At time zero, increases in the primary and coupled motion for the CC Sling and CA Ligament Transfer Construct could comprise the initial healing period prescribed for AC joint dislocation. Our findings also suggest that the Rockwood Screw provides a highly rigid fixation and may explain the complications frequently seen in clinical practice. CLINICAL RELEVANCE: Current surgical procedures do not have the appropriate stiffness to restore the stability of the intact joint before healing. Therefore, our results may lead to the design and development of new repairs, reconstructions, and rehabilitation protocols for AC joint dislocation.

Arthroscopic biceps tenodesis using the percutaneous intra-articular transtendon technique.

Traditional management of end-stage pain and degeneration of the proximal biceps tendon has included open tenodesis of the biceps tendon. Several methods have been described. More recently, however, arthroscopic techniques have been developed. This article introduces a novel method of arthroscopic biceps tenodesis that does not require any specialized hardware.

Viscoelastic behavior and structural properties of the coracoclavicular ligaments.

During contact sports such as football, hockey or rugby, the coracoclavicular ligaments are commonly ruptured. Currently, the limited biomechanical data on the properties and function of these ligaments have led to debate on the "gold standard" treatment for these injuries. Therefore, the objective of this study was to characterize the geometry, viscoelastic behavior and structural properties of the coracoclavicular ligaments (n=11). The trapezoid and conoid were found to have similar length (9.6+/-4.4 vs. 11.2+/-4.1 mm) and cross-sectional area (103+/-43 vs. 69+/-51 mm2), respectively (P>0.05). Static and cyclic stress relaxation tests were then performed, followed by uniaxial tensile testing with the insertions of each ligament aligned to ensure a uniform distribution of load across the fibers. No significant differences were observed for the trapezoid and conoid during the static (36+/-8% vs. 31+/-7%) and cyclic (23+/-12% vs. 16+/-6%) stress relaxation tests, respectively (P>0.05). Similarly, no statistically significant differences were found between the trapezoid and conoid for linear stiffness (83+/-40 vs. 70+/-23 N mm(-1)), ultimate load (312+/-133 vs. 266+/- 108 N), energy absorbed at failure (820+/-576 vs. 752+/- 410 N mm), percent elongation (74+/-47% vs. 62+/-22%) and elongation at failure (5.8+/-2.2 vs. 6.1+/-1.6 mm), respectively (P>0.05). A comparison of our data to previous studies suggests that the complex fiber orientation of these ligaments has a significant role in determining the maximum load that can be transferred between the clavicle and scapula by each bone-ligament-bone complex. Our findings also further confirm the functional role of the coracoclavicular ligaments in supporting the upper extremity, and provide data for reconstruction and rehabilitation protocols as well as computational models.

Joint compression alters the kinematics and loading patterns of the intact and capsule-transected AC joint.

High compressive loads are transmitted through the shoulder across the acromioclavicular (AC) joint to the axial skeleton during activities of daily living and can lead to early joint degeneration or instability. The objective of this study was to quantify the effect of joint compression on the biomechanics of the intact and capsule-transected AC joint during application of three loading conditions. A robotic/universal force-moment sensor testing system was utilized to apply an anterior, posterior or superior load of 70 N in combination with 10 or 70 N of joint compression to fresh-frozen cadaveric shoulders (n=12). The application of joint compression to the intact AC joint decreased the posterior translation in response to a posterior load (-6.6+/-2.5 vs -3.7+/-1.0 mm, p<0.05). Joint compression also decreased the in situ force in the superior AC capsule by 10 N while increasing the joint contact force by 20 N for all loading conditions (p<0.05). The application of joint compression to the capsule-transected AC joint significantly decreased the amount of posterior and superior translation during posterior (-12.7+/-6.1 vs -5.5+/-3.2 mm, p<0.05) and superior (5.3+/-2.9 vs 4.2+/-2.3 mm, p<0.05) loading, respectively, while significantly increasing the coupled translations (anterior-posterior, superior-inferior or proximal-distal) in all loading conditions (p<0.05). The joint contact force also significantly increased by 20 N for all loading conditions (p<0.05). This quantitative data suggests: (1) common surgical techniques such as distal clavicle resection, which initially reduce painful joint contact, may cause unusually high loads to be supported by the soft tissue structures at the AC joint; and (2) compressive loads transmitted across a capsule-transected AC joint could be concentrated over a smaller area due to the increased coupled motion and joint contact force.

Effect of arthroscopic procedures on the acromioclavicular joint.

The objective of the current study was to determine the effect of arthroscopic acromioplasty, and combined acromioplasty and distal clavicle resection on joint kinematics and in situ forces in response to an anterior, posterior, and superior load of 70 N. The loading conditions were applied to 10 fresh-frozen cadaveric shoulders using a robotic and universal force and moment sensor testing system. Translations in response to a posterior load increased by approximately 30% after combined acromioplasty and distal clavicle resection when compared with the intact and acromioplasty conditions. The in situ force in the trapezoid and conoid ligaments increased significantly from 13 +/- 15 N to 40 +/- 25 N and 13 +/- 13 N to 38 +/- 28 N, respectively, between the intact and combined acromioplasty and distal clavicle resection conditions during anterior loading. The results suggest that an arthroscopic acromioplasty alone does not significantly affect the mechanics of the acromioclavicular joint with these loading conditions. However, an acromioplasty combined with a distal clavicular resection does result in significant increases in joint motion and ligament forces. In some circumstances, such as after a previous joint separation, the increased forces in the coracoclavicular ligaments could result in additional damage to weak ligaments.