Primary Open Latarjet Procedure Versus Revision to Open Latarjet Procedure for Anterior Shoulder Instability.

BACKGROUND: Although the Latarjet operation may be performed as a revision surgery for anterior shoulder instability, the high recurrence rate of anterior shoulder instability after arthroscopic Bankart repair (ABR) has led some to advocate for performing the Latarjet procedure as a primary stabilization surgery. The purpose of this study was to compare the intermediate-term outcomes after primary open Latarjet (PLJ) and revision to open Latarjet (RLJ). MATERIALS AND METHODS: This was a single-institution retrospective analysis of patients who underwent either PLJ or RLJ procedures for anterior shoulder instability between 2014 and 2023. Patients with less than 1 year of follow-up, seizure history, multidirectional instability, concurrent rotator cuff repair, or the absence of preoperative imaging were excluded. Glenoid bone loss (GBL), the width of Hill-Sachs lesions, recurrent dislocations, and reoperations were assessed. RESULTS: The study included 29 patients, with 12 undergoing PLJ procedures and 17 undergoing RLJ procedures. The mean duration of follow-up was similar for the two groups (4.7 vs 4.6 years, P=.854). Patients undergoing PLJ procedures demonstrated a higher mean GBL (18.4%) compared with patients undergoing revision (10.5%; P=.035); however, there was no significant difference in Hill-Sachs lesion size (14.2 vs 10.4 mm, P=.374). After stratifying according to GBL, the groups undergoing PLJ and RLJ procedures had similar recurrent dislocation rates (8.3% and 11.8%, respectively; P=1.0) and reoperation frequency (25.0% and 23.5%, respectively; P=1.0). CONCLUSION: The PLJ and RLJ groups had comparable rates of recurrent dislocations, complications, and reoperations, emphasizing the value of considering Latarjet procedures as revision surgery after unsuccessful primary arthroscopic stabilization. [Orthopedics. 202x;4x(X):xx-xx.].

Risk factors associated with atraumatic posterolateral rotatory instability.

BACKGROUND: Traumatic posterolateral rotatory instability after elbow dislocation or fracture dislocation has been well described. However, few reports cover atraumatic posterolateral rotatory instability as a cause of lateral-sided elbow pain. We assessed the risk factors and epidemiology of atraumatic posterolateral rotatory instability in a case-control study. METHODS: A retrospective review of all patients treated operatively for atraumatic posterolateral rotatory instability during a 6-year period was compared with a group of patients with extensor carpi radialis brevis tendinopathy without instability treated during the same time period. Bivariate and multiple logistic regression statistical analyses were used to investigate the following risk factors: gender, age, hand dominance, diabetes, smoking, body mass index, corticosteroid injection history, and duration of symptoms. Disabilities of the Arm, Shoulder, and Hand and pain scores were obtained preoperatively and postoperatively. RESULTS: Thirteen patients with atraumatic posterolateral rotatory instability were compared with 12 patients with extensor carpi radialis brevis tendinopathy. Multivariate analysis revealed patients with atraumatic posterolateral rotatory instability were more likely to have multiple corticosteroid injections (P = .05) and present with a longer duration of symptoms (P = .03). Postoperative pain scores improved in both groups. CONCLUSIONS: Atraumatic posterolateral rotatory instability should be considered in the differential diagnosis of lateral elbow when patients present with a protracted clinical course. Statistically, posterolateral rotatory instability patients more often present with a history of multiple corticosteroid injections.

Preoperative tendon retraction, not smoking, is a risk factor for failure with continuity after rotator cuff repair.

BACKGROUND: Smoking is a poor prognostic factor for healing after rotator cuff repair and is associated with inferior results. We hypothesized that smokers would have higher recurrent tear rates and more postoperative myotendinous junction (MTJ) retraction in healed repairs than nonsmokers three months postoperatively. METHODS: Rotator cuff repairs (RCRs) were retrospectively reviewed over a 2-year period. Patients underwent magnetic resonance imaging (MRI) within 6 months prior to surgery and again at 3 months postoperatively. Seventy-nine patients were included and stratified by smokers versus nonsmokers. Baseline patient demographics, tear characteristics, and surgical factors were collected. Preoperative and postoperative MRIs were assessed to quantify the MTJ position and to establish the recurrent tear rate. RESULTS: For the total cohort (nonsmokers, n = 56; smokers, n = 23), significant differences in age, race, and traumatic onset of injury existed between groups. There were no significant differences in recurrent tear between smokers (26%) and nonsmokers (27%), but nonsmokers were more satisfied. For patients with healed RCRs (nonsmokers, n = 41; smokers, n = 17), there were significant differences in race. On univariate analysis, nonsmokers had a significantly more lateral MTJ postoperatively (P = 0.05). On multivariable regression analysis, medialized postoperative MTJ position in healed cuffs was driven only by greater preoperative rotator cuff retraction preoperatively. There were no significant differences in MTJ position based on smoking status for patients with healed RCRs. CONCLUSION: Smoking does not appear to be an independent risk factor for postoperative MTJ retraction in healed RCRs, also known as failure in continuity. Preoperative tear size and retraction play the biggest roles in predicting postoperative MTJ position, regardless of smoking status. There are no significant differences in patient-reported outcomes for patients with healed RCRs, but nonsmokers had more satisfaction following RCR in the total cohort. LEVEL OF EVIDENCE: Level III; Retrospective cohort study; Diagnostic study.

Risk Factors for Cerebral Desaturation Events During Shoulder Surgery in the Beach Chair Position.

PURPOSE: The goals of this study were 2-fold: (1) to determine the risk factors for cerebral desaturation events (CDEs) after implementation of a comprehensive surgical and anesthetic protocol consisting of patient risk stratification, maintenance of normotensive anesthesia, and patient positioning in a staged fashion, and (2) to assess for subclinical neurologic decline associated with intraoperative ischemic events through cognitive testing. METHODS: One hundred patients undergoing shoulder surgery in the beach chair position were stratified for risk of CDE based on Framingham stroke criteria, body mass index (BMI), and history of cerebrovascular accidents. Cerebral oxygen saturation was monitored with near-infrared spectroscopy. As per a standardized protocol, mean arterial pressure was maintained between 70 and 90 mm Hg. The head was raised in 2 stages separated by 3 minutes. CDE were defined as >20% drop from baseline or <55% O2 absolute threshold. Patients completed a Mini-Mental State Examination during preoperative examination and at the first postoperative visit. RESULTS: The CDE rate was 4% overall and 4.3% in patients undergoing general anesthesia. Forty-five patients were in the higher risk category, and all CDEs occurred in that group. Patients with a Framingham score ≥ 10 or BMI ≥ 35 who underwent general anesthesia had an increased risk of CDE (P = .04). No significant change was noted in Mini-Mental State Examination scores between pre- and postoperative visits. No correlation was shown between CDE and history of diabetes, smoking, cardiovascular disease, or left ventricular hypertrophy. CONCLUSIONS: Our observed CDE rate was lower than previously reported rates, likely because of risk stratification, staged positioning, and normotensive anesthesia. Framingham score ≥ 10 and BMI ≥ 35 are risk factors for CDE in the beach chair position. LEVEL OF EVIDENCE: Level II, prospective observational study with >80% follow-up.

Prevalence and risk factors for kidney stones in fibrodysplasia ossificans progressiva.

The worldwide prevalence and risk factors for kidney stones in patients with fibrodysplasia ossificans progressiva (FOP) are unknown. We conducted a survey of 383 patient-members of the International Fibrodysplasia Ossificans Progressiva Association, comprising the entire global membership of the international FOP community. Two hundred seven patients from 31 nations and 6 continents (54%) responded. Nineteen of 207 respondents had kidney stones, revealing a worldwide prevalence of 9.2%. In a confirmatory follow-up study of subjects participating in a longitudinal FOP natural history study, 9 of 114 individuals reported a history of kidney stones (7.9%). In both study populations patients with kidney stones were found to be more functionally impaired compared to those without nephrolithiasis. The prevalence of kidney stones in the adult FOP population of the Unites States was 15.8% (9/57 individuals) compared to a sex- and age-weighted prevalence of 4.5% (p=4×10-5) in the general population. Although geographical variation exists, patients with FOP have an approximately three-fold greater prevalence of kidney stones than the general population. This unusually high prevalence may be due to high bone turnover from chronic immobilization, or to unknown mechanistic effects of the activating FOP mutation in activin A receptor, type I/activin-like kinase-2 (ACVR1/ALK2), increasing the disease burden and morbidity in this already disabling condition.

Arthroscopic Cortical Button Stabilization of Isolated Acute Neer Type II Fractures of the Distal Clavicle.

Neer type II distal clavicle fractures are inherently unstable. The purpose of this study was to review the outcome of Neer type II distal clavicle fractures arthroscopically treated using a suspensory cortical button technique. Between 2008 and 2012, a total of 17 Neer type IIB fractures were managed operatively at the authors' institution. Functional outcomes were assessed using the pain score, the Disabilities of the Arm, Shoulder and Hand score, the Penn Shoulder Score, and the American Shoulder and Elbow Surgeons score. Radiographic union was also assessed. At a mean of 1 year, the mean pain score was 0.9±1.1, the mean Disabilities of the Arm, Shoulder and Hand score was 10.9±11.1, the mean Penn Shoulder Score was 90.3±7.9, and the mean American Shoulder and Elbow Surgeons score was 90.1±10.1. Radiographic union occurred in 14 patients. An all-arthroscopic surgical fixation of Neer type II distal clavicle fractures using a suspensory cortical button technique can result in a predictable outcome with a low complication rate. [Orthopedics. 2017; 40(6):e1050-e1054.].

Biceps tenotomy in the presence of a supraspinatus tear alters the adjacent intact tendons and glenoid cartilage.

A rotator cuff tear is a common injury in athletes and workers who repeatedly perform overhead movements, and it is not uncommon for this demographic to return to activity shortly after treatment. A biceps tenotomy is often performed in the presence of a rotator cuff tear to help reduce pain and improve joint function. However, the effect of this procedure on the surrounding tissues in the glenohumeral joint is unknown. Therefore, the purpose of this study was to investigate the effect of a biceps tenotomy in the presence of a supraspinatus rotator cuff tear followed by overuse activity on ambulatory function and mechanical and histologic properties of the remaining rotator cuff tendons and glenoid cartilage. 46 rats underwent 4weeks of overuse activity to create a tendinopathic condition, then were randomized into two groups: unilateral detachment of the supraspinatus tendon or detachment of the supraspinatus and long head of the biceps tendons. Ambulatory measurements were performed throughout the 8weeks prior to euthanasia, followed by analysis of the properties of the remaining intact tendons and glenoid cartilage. Results demonstrate that shoulder function was not effected in the biceps tenotomy group. However, the intact tendons and glenoid cartilage showed altered mechanical and histologic properties. This study provides evidence from an animal model that does not support the use of tenotomy in the presence of a supraspinatus tendon rotator cuff tear, and provides a framework for physicians to better prescribe long-term treatment strategies for patients.

The timing of retears after arthroscopic rotator cuff repair.

BACKGROUND: Little is known about the time dependence of the failure rate of surgically repaired rotator cuffs. Retears are significant, as they are common and may lead to less satisfactory outcomes and additional operations. Their timing is critical foundational information for understanding failure mechanisms. However, this remains unclear. Currently, there exist a number of studies that have reported retear rates at specific time points. Combining data from these publications can reveal when cuffs retear, which will help inform expectations and guidelines for progression of activity after surgery. METHODS: PubMed, Medline, and Embase were searched for studies relating to rotator cuff repair. Abstracts and articles were evaluated on the basis of predefined inclusion and exclusion criteria. Data were extracted from those publications that satisfied all requirements, and regression analysis was performed. RESULTS: Thirteen articles were included in the final meta-analysis. Retear rates for medium tears increased for approximately 15 months and leveled off at approximately 20%. Retear rates for large tears progressed steadily for about 12 months and approached an upper limit of approximately 40%. Retear rates for massive tears ranged from 20% to 60%, but the distribution of retear rate over time for these cuff tears is not clear from these data. CONCLUSION: Retear rates for medium and large tears generally increase until at least 10-15 months after surgery, after which they are likely to level off. Retear rates for massive tears are variable and may follow a time course different from that of other tear sizes. Retear rates depend on size of the original tear.

The development and application of a risk stratification index system for outpatient shoulder arthroscopy patient management-a single academic center's experience.

BACKGROUND: Our goal was to develop a risk stratification index (RSI) that could guide management of our patients. We hypothesized that the risks of unexpected overstay admission (OS) and emergency department (ED) transfer are predictable on the basis of patient factors for elective outpatient shoulder arthroscopic surgery. METHODS: We first identified 124,860 subjects who received shoulder arthroscopic surgery in the Healthcare Cost and Utilization Project database. We next conducted multivariable regression analysis to identify risk factors associated with unanticipated OS or ED transfer. The risk factors were then adopted to construct the RSI. We last applied the RSI into our practice and prospectively collected outcome data between August 2014 and June 2015. RESULTS: The significant risk factors included arrhythmia, chronic obstructive pulmonary disease, diabetes, obesity, neurologic disease with function impairment, and general anesthesia. All significant risk factors were then adopted to calculate the RSI with equal weight assignment. Simulated analysis concluded that a patient with 2 or fewer risk factors would carry a theoretical rate for OS or ED events of 0.73%. A total of 583 shoulder arthroscopy procedures were performed, among which 472 (81.0%) patients passed the RSI and were successfully managed in the outpatient surgical center without any admission. There were 111 (19.0%) subjects with procedures performed in the main hospital, with 2 unexpected admissions (1.8%). CONCLUSION: We developed an RSI tool for shoulder arthroscopic surgery with an existing national database. It is our conclusion that the RSI system is an effective tool to optimize clinical practice. However, over time, a longer follow-up period might provide more convincing evidence.

Is there a dose response of dexamethasone as adjuvant for supraclavicular brachial plexus nerve block? A prospective randomized double-blinded clinical study.

STUDY OBJECTIVE: The study objective is to examine the analgesic effect of 3 doses of dexamethasone in combination with low concentration local anesthetics to determine the lowest effective dose of dexamethasone for use as an adjuvant in supraclavicular brachial plexus nerve block. DESIGN: The design is a prospective randomized double-blinded clinical study. SETTING: The setting is an academic medical center. PATIENTS: The patients are 89 adult patients scheduled for shoulder arthroscopy. INTERVENTIONS: All patients were randomly assigned into 1 of 4 treatment groups: (i) bupivacaine, 0.25% 30 mL; (ii) bupivacaine, 0.25% 30 mL with 1-mg preservative-free dexamethasone; (iii) bupivacaine, 0.25% 30 mL with 2-mg preservative-free dexamethasone; and (iv) bupivacaine, 0.25% 30 mL with 4-mg preservative-free dexamethasone. All patients received ultrasound-guided supraclavicular brachial plexus nerve blocks and general anesthesia. MEASUREMENTS: The measurements are the duration of analgesia and motor block. MAIN RESULTS: The median analgesia duration of supraclavicular brachial plexus nerve block with 0.25% bupivacaine was 12.1 hours; and 1-, 2-, or 4-mg dexamethasone significantly prolonged the analgesia duration to 22.3, 23.3, and 21.2 hours, respectively (P = .0105). Dexamethasone also significantly extended the duration of motor nerve block in a similar trend (P = .0247). CONCLUSION: Low-dose dexamethasone (1-2 mg) prolongs analgesia duration and motor blockade to the similar extent as 4-mg dexamethasone when added to 0.25% bupivacaine for supraclavicular brachial plexus nerve block.

Glenoid perforation with pegged components during total shoulder arthroplasty.

A subset of patients undergoing primary total shoulder arthroplasty (TSA) have a medialized joint line secondary to glenoid wear. In some cases, the central pegs or peripheral pegs of a peg design glenoid component may violate the medial cortex of the glenoid vault. It is unknown whether this leads to early failure. The objectives of this study were to determine (1) whether glenoid components with uncontained pegs would be associated with a high rate of failure and (2) whether peg perforation would be associated with inferior clinical outcomes. The authors performed a case-control retrospective review comparing 25 TSAs in which one or multiple pegs perforated the medial glenoid vault (uncontained group) with 25 TSAs without peg perforation (contained group). Implant survival was calculated with revision for glenoid component loosening as the primary outcome variable. Clinical outcomes were determined using American Shoulder and Elbow Surgeons (ASES) and Penn Shoulder Scores. Average follow-up was more than 5 years. No patient in either group had symptomatic glenoid loosening. Two (8%) patients in the uncontained group required revision for rotator cuff tears. Penn and ASES scores were significantly lower in the uncontained group (Penn, P=.002; ASES, P=.004). Pain and satisfaction subscores were similar between the groups, but function subscores were significantly lower in the uncontained group (Penn, P=.002; ASES, P=.005). Uncontained pegs of an anchor peg glenoid component are not associated with early glenoid loosening. Similar pain relief is obtained when compared with contained glenoid components, but shoulder function is significantly lower in patients with uncontained pegs.

Disruption of the anterior-posterior rotator cuff force balance alters joint function and leads to joint damage in a rat model.

The rotator cuff assists in shoulder movement and provides dynamic stability to the glenohumeral joint. Specifically, the anterior-posterior (AP) force balance, provided by the subscapularis anteriorly and the infraspinatus and teres minor posteriorly, is critical for joint stability and concentric rotation of the humeral head on the glenoid. However, limited understanding exists of the consequences associated with disruption of the AP force balance (due to tears of both the supraspinatus and infraspinatus tendons) on joint function and joint damage. We investigated the effect of disrupting the APforce balance on joint function and joint damage in an overuse rat model. Twenty-eight rats underwent 4 weeks of overuse to produce a tendinopathic condition and were then randomized into two surgical groups: Detachment of the supraspinatus only or detachment of the supraspinatus and infraspinatus tendons. Rats were then gradually returned to their overuse protocol. Quantitative ambulatory measures including medial/lateral, propulsion, braking, and vertical forces were significantly different between groups. Additionally, cartilage and adjacent tendon properties were significantly altered. These results identify joint imbalance as a mechanical mechanism for joint damage and demonstrate the importance of preserving rotator cuff balance when treating active cuff tear patients.

Biceps detachment decreases joint damage in a rotator cuff tear rat model.

BACKGROUND: Pathology in the long head of the biceps tendon often occurs in patients with rotator cuff tears. Arthroscopic tenotomy is the most common treatment. However, the role of the long head of the biceps at the shoulder and the consequences of surgical detachment on the remaining shoulder structures remain unknown. QUESTIONS/PURPOSES: We hypothesized that detachment of the long head of the biceps, in the presence of supraspinatus and infraspinatus tears, would decrease shoulder function and decrease mechanical and histologic properties of both the subscapularis tendon and the glenoid articular cartilage. METHODS: We detached the supraspinatus and infraspinatus or the supraspinatus, infraspinatus, and long head of the biceps after 4 weeks of overuse in a rat model. Animals were gradually returned to overuse activity after detachment. At 8 weeks, the subscapularis and glenoid cartilage biomechanical and histologic properties were evaluated and compared. RESULTS: The supraspinatus, infraspinatus, and long head of the biceps group had a decreased change in braking and vertical force. [corrected]. This group also had an increased upper and lower subscapularis modulus but without any differences in glenoid cartilage modulus. Finally, this group had a significantly lower cell density in both the upper and lower subscapularis tendons, although cartilage histology was not different. CONCLUSIONS: Detachment of the long head of the biceps tendon in the presence of a posterior-superior cuff tear resulted in improved shoulder function and less joint damage in this animal model. CLINICAL RELEVANCE: This study provides evidence in an animal model that supports the use of tenotomy for the management of long head of the biceps pathology in the presence of a two-tendon cuff tear. However, long-term clinical trials are required.

Addressing glenoid bone deficiency and asymmetric posterior erosion in shoulder arthroplasty.

Glenoid bone deficiency and eccentric posterior wear are difficult problems faced by shoulder arthroplasty surgeons. Numerous options and techniques exist for addressing these issues. Hemiarthroplasty with concentric glenoid reaming may be a viable alternative in motivated patients in whom glenoid component failure is a concern. Total shoulder arthroplasty has been shown to provide durable pain relief and excellent function in patients, and numerous methods and techniques can assist in addressing bone loss and eccentric wear. However, the ideal amount of version correction in cases of severe retroversion has not yet been established. Asymmetric reaming is a commonly used technique to address glenoid version, but correction of severe retroversion may compromise bone stock and component fixation. Bone grafting is a technically demanding alternative for uncontained defects and has mixed clinical results. Specialized glenoid implants with posterior augmentation have been created to assist the surgeon in correcting glenoid version without compromising bone stock, but clinical data on these implants are still pending. Custom implants or instruments based on each patient's unique glenoid anatomy may hold promise. In elderly, sedentary patients in whom bone stock and soft-tissue balance are concerns, reverse total shoulder arthroplasty may be less technically demanding while still providing satisfactory pain relief and functional improvements.

Returning to overuse activity following a supraspinatus and infraspinatus tear leads to joint damage in a rat model.

Large rotator cuff tears (supraspinatus and infraspinatus) are common in patients who perform overhead activities (laborers, athletes). In addition, following large cuff tears, these patients commonly attempt to return to pre-injury activity levels. However, there is a limited understanding of the damaging effects on the uninjured joint tissues when doing so. Therefore, the objective of this study was to investigate the effect of returning to overuse activity following a supraspinatus and infraspinatus tear on shoulder function and the structural and biological properties of the intact tendons and glenoid cartilage. Forty rats underwent 4 weeks of overuse followed by detachment of the supraspinatus and infraspinatus tendons and were then randomized into two groups: return to overuse or cage activity. Ambulatory measurements were performed over time and structural and biological properties of the adjacent tendons and cartilage were evaluated. Results demonstrated that animals returning to overuse activity did not have altered shoulder function but despite this, did have altered cartilage and tendon properties. These mechanical changes corresponded to altered transcriptional regulation of chondrogenic genes within cartilage and tendon. This study helps define the mechanical and biological mechanisms leading to joint damage and provides a framework for treating active cuff tear patients.

Effect of return to overuse activity following an isolated supraspinatus tendon tear on adjacent intact tendons and glenoid cartilage in a rat model.

Rotator cuff tears are common conditions that can alter shoulder mechanics and may lead to damage of intact joint tissues. These injuries are of particular concern in populations who perform tasks requiring repetitive overhead activity (e.g., athletes and laborers) and who are likely to return to aggressive pre-injury activity levels despite limited understanding of the potentially damaging effects on the remaining tissues. Therefore, we investigated the effect of returning to overuse activity following a supraspinatus tear on shoulder function and the mechanical properties of the remaining intact tendons and glenoid cartilage. Forty rats underwent 4 weeks of overuse activity to create a tendinopathic condition followed by detachment of the supraspinatus tendon and were then randomized into two groups: continued overuse or cage activity. Ambulatory measurements were performed throughout the 8 weeks prior to euthaniasia, and properties of the adjacent tendons and cartilage were evaluated. Results demonstrated that shoulder function was not compromised in the return to overuse group. However, alterations of the glenoid cartilage and biceps tendon properties occurred. Our results help define the contributory roles of common mechanical injury mechanisms and provide a framework by which physicians could better prescribe long-term treatment strategies for patients.

Glenoid cartilage mechanical properties decrease after rotator cuff tears in a rat model.

Rotator cuff repairs are commonly performed to reduce pain and restore function. Tears are also treated successfully without surgical intervention; however, the effect that a torn tendon has on the glenohumeral cartilage remains unknown. Clinically, a correlation between massive rotator cuff tears and glenohumeral arthritis has often been observed. This may be due to a disruption in the balance of forces at the shoulder, resulting in migration of the humeral head and subsequently, abnormal loading of the glenoid. Our lab previously demonstrated changes in ambulation and intact tendon mechanical properties following supraspinatus and infraspinatus rotator cuff tendon tears in a rat model. Therefore, the purpose of this study was to investigate the effects of supraspinatus and infraspinatus rotator cuff tears on the glenoid cartilage. Nine rats underwent unilateral detachment of the supraspinatus and infraspinatus tendons and were sacrificed after 4 weeks. Cartilage thickness significantly decreased in the antero-inferior region of injured shoulders. In addition, equilibrium elastic modulus significantly decreased in the center, antero-superior, antero-inferior, and superior regions. These results suggest that altered loading after rotator cuff injury may lead to damage to the joint with significant pain and dysfunction. Clinically, understanding the mechanical processes involved with joint damage will allow physicians to better advise patients.

Intra-articular changes precede extra-articular changes in the biceps tendon after rotator cuff tears in a rat model.

HYPOTHESIS: Biceps tendon pathology is common with rotator cuff tears. The mechanisms for biceps changes, and therefore its optimal treatment, are unknown. Our objective was to determine the effect of rotator cuff tears on regional biceps tendon pathology. We hypothesized that histologic and compositional changes would appear before organizational changes, both would appear before mechanical changes, and changes would begin at the tendon's insertion site. MATERIALS AND METHODS: Detachment of supraspinatus and infraspinatus tendons or sham surgery was done in 65 Sprague-Dawley rats. Rats were euthanized at 1, 4, or 8 weeks for regional measurements of histologic, compositional, organizational (1, 4 and 8 weeks), or mechanical properties (4 and 8 weeks only). RESULTS: One week after tendon detachments, decreased organization and more rounded cell shape were found in the intra-articular space of the biceps tendon. Aggrecan expression was increased along the entire length of the tendon, whereas all other compositional changes were only at the tendon's proximal insertion into bone. With time, this disorganization and more rounded cell shape extended the length of the tendon. Organizational and cell shape changes also preceded detrimental mechanical changes: decreased modulus in the intra-articular space was found after 8 weeks. CONCLUSIONS: Results support a degenerative component to pathology in the biceps tendon. In addition, changes resembling a tendon exposed to compressive loading occurring first in the intra-articular space indicate that the biceps tendon plays an increased role as a load-bearing structure against the humeral head in the presence of rotator cuff tears.

Decreased loading after rotator cuff tears leads to improved biceps tendon properties in a rat model.

BACKGROUND: The purpose of this study was to elucidate the mechanism of biceps tendon changes after rotator cuff tears. We hypothesized that increased loading on the biceps tendon after rotator cuff tears will result in further detrimental changes whereas decreased loading will result in increased organization and more normal tendon composition. In addition, we hypothesized that changes with altered loading will begin at the proximal insertion into bone and progress along the tendon length at later time points. MATERIALS AND METHODS: Supraspinatus and infraspinatus tendon detachments in rats were followed by various loading protocols at various time points. Regional changes in cellularity, cell shape, collagen organization, and matrix proteins of the long head of the biceps tendon were determined by histologic measures and immunohistochemistry. RESULTS: Increased loading after detachments resulted in more disorganized collagen after only 1 week and compositional changes by 4 weeks. By 8 weeks, decreased loading resulted in increased organization, decreased cellularity, a more elongated cell shape, and more normal tendon composition. Organizational changes with increased loading began in the intra-articular space and progressed along the tendon length with time. CONCLUSIONS: Combined with previous findings of decreased mechanics with increased loading, these results show that increased compressive loading away from the proximal insertion into bone is a mechanism for biceps tendon pathology in the presence of rotator cuff tears. The striking improvements with decreased loading further support increased loading as a mechanism for biceps tendon pathology because removal of this load led to improvements in tendon histology, organization, and composition.