Mechanical properties of the long‐head of the biceps tendon are altered in the presence of rotator cuff tears in a rat model

Rotator cuff tears are disabling conditions that result in changes in joint loading and functional deficiencies. Clinically, damage to the long‐head of the biceps tendon has been found in conjunction with rotator cuff tears, and this damage is thought to increase with increasing tear size. Despite its importance, controversy exists regarding the optimal treatment for the biceps. An animal model of this condition would allow for controlled studies to investigate the etiology of this problem and potential treatment strategies. We created rotator cuff tears in the rat model by detaching single (supraspinatus) and multiple (supraspinatus + infraspinatus or supraspinatus + subscapularis) rotator cuff tendons and measured the mechanical properties along the length of the long‐head of the biceps tendon 4 and 8 weeks following injury. Cross‐sectional area of the biceps was increased in the presence of a single rotator cuff tendon tear (by ～150%), with a greater increase in the presence of a multiple rotator cuff tendon tear (by up to 220%). Modulus values decreased as much as 43 and 56% with one and two tendon tears, respectively. Also, multiple tendon tear conditions involving the infraspinatus in addition to the supraspinatus affected the biceps tendon more than those involving the subscapularis and supraspinatus. Finally, biceps tendon mechanical properties worsened over time in multiple rotator cuff tendon tears. Therefore, the rat model correlates well with clinical findings of biceps tendon pathology in the presence of rotator cuff tears, and can be used to evaluate etiology and treatment modalities. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:416–420, 2009     

Effect of glenohumeral abduction angle on the mechanical interaction between the supraspinatus and infraspinatus tendons for the intact,partial‐thickness torn,and repaired supraspinatus tendon conditions

Rotator cuff tears are difficult to manage because of the structural and mechanical inhomogeneity of the supraspinatus tendon. Previously, we showed that with the arm at the side, the supraspinatus and infraspinatus tendons mechanically interact such that conditions that increase supraspinatus tendon strain, such as load or full‐thickness tears, also increase infraspinatus tendon strain. This suggests that the infraspinatus tendon may shield the supraspinatus tendon from further injury while becoming at increased risk of injury itself. In this study, the effect of glenohumeral abduction angle on the interaction between the two tendons was evaluated for supraspinatus tendon partial‐thickness tears and two repair techniques. Principal strains were quantified in both tendons for 0°, 30°, and 60° of glenohumeral abduction. Results showed that interaction between the two tendons is interrupted by an increase in abduction angle for all supraspinatus tendon conditions evaluated. Infraspinatus tendon strain was lower at 30° and 60° than at 0° abduction angle. In conclusion, interaction between the supraspinatus and infraspinatus tendons is interrupted with increase in abduction angle. Additionally, 30° abduction should be further evaluated for management of rotator cuff tears and repairs as it is the angle at which both supraspinatus and infraspinatus tendon strain is decreased. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:846–851, 2010     

Supraspinatus tears: propagation and strain alteration

It was hypothesized that there would be an alteration in strain when macroscopically normal supraspinatus tendons were subjected to three patterns of surgically created tear. The propagation of joint-side partial-thickness tears was also examined. Cadaveric shoulders were tested on a purpose-built rig with static loading from 20 to 200 N and during glenohumeral abduction from 0 degrees to 120 degrees with a 100-N tensile load. Differential variable reluctance transducers were used to calculate strain. Six-millimeter-wide midsubstance full-thickness tears (n = 2) caused an increase in bursal-side strain both with abduction 1.93% (90 degrees ) and with loading 0.33% (150 N). Intratendinous delamination (n = 2) increased joint-side strain during abduction and bursal-side strain with loading. A 2-mm-deep tear across the tendon insertion (n = 5) increased the bursal-side strain in abduction by 3.54% (120 degrees ) and with load by 2.53% (200 N). Tear propagation was observed from joint to bursal sides during abduction. Tendon failure occurred at the insertion.     

The Correlation between Various Shoulder Anatomical Indices on X-Ray and Subacromial Impingement and Morphology of Rotator Cuff Tears

Objectives

Rotator cuff injury caused by subacromial impingement presents different morphologies. This study aims to investigate the correlation between various shoulder anatomical indexes on X-ray with subacromial impingement and morphology of rotator cuff tears to facilitate surgical management.

Method

This retrospective study was carried out between January 2020 and May 2022. Patients who were diagnosed as sub-acromial impingement associated with rotator cuff tears (without tendon retraction) and received arthroscopic surgery were enrolled in this study. The radiographic indexes of acromial slope (AS), acromial tilt (AT), lateral acromial angle (LAA), acromial Index (AI), and sub-acromial distance (SAD) were measured on preoperative true AP view and outlet view. The location of rotator cuff tear (anterior, middle, posterior, medial, and lateral) and morphology of tear (horizontal, longitudinal, L-shaped, and irregular shaped) were evaluated by arthroscopy. Groups were set up due to different tear location and tear morphologies, by comparing the various radiographic indices between each group (one-way analysis of variance and t-test), the correlation between radiographic indices and tear characteristics was investigated.

Results

We analyzed 92 shoulders from 92 patients with a mean age of 57.23 ± 8.45 years. The AS in anterior tear group (29.32 ± 6.91°) was significantly larger than that in middle tear group (18.41 ± 6.13°) (p = 0.000) and posterior tear group (24.01 ± 7.69°) (p = 0.041). The AS in posterior tear group (24.01 ± 7.69°) was significantly larger than that in middle tear group (18.41 ± 6.13°) (p = 0.029). The LAA in middle tear group (67.41 ± 6.54°) was significantly smaller than that in posterior group (72.74 ± 8.78°) (p = 0.046). The AS in longitudinal tear group (26.86 ± 8.41°) was significantly larger than that in horizontal tear group (22.05 ± 9.47°) (p = 0.035) and L-shaped group (21.56 ± 6.62°) (p = 0.032). The LAA in horizontal group (70.60 ± 6.50°) was significantly larger than that in L-shaped group (66.39 ± 7.31°) (p = 0.033). The AI in L-shaped tear group (0.832 ± 0.074) was significantly larger than that in horizontal tear group (0.780 ± 0.084) (p = 0.019) and irregular tear group (0.781 ± 0.068) (p = 0.047).

Conclusion

Acromion with a larger AS and a smaller LAA tend to cause anterior or posterior rotator cuff tears rather than middle tears in sub-acromial impingement. Meanwhile acromion with a larger AS tends to cause a longitudinal tear, a larger LAA tends to cause horizontal tears and a larger AI tends to cause L-shaped tears.     

The accuracy of “subacromial grind test” in diagnosis of supraspinatus rotator cuff tears

Purpose:The aim of this study is to assess the accuracy of a simple clinical test (subacromial grind test) in diagnosing supraspinatus tendon tears.Results:During arthroscopy, 17 patients had full thickness (FT) tears of supraspinatus tendon and 10 had partial thickness tears. For any supraspinatus tear, the sensitivity of the test was 63%, specificity 95%, positive predictive value 94%, negative predictive value 66% and overall accuracy 79%. For FT tears, the sensitivity was 82%, specificity 87%, positive predictive value 78%, negative predictive value 90% and overall accuracy 85%.Conclusion:We found that this is a useful single test for diagnosing FT supraspinatus tears.

Level of Evidence:

Level IV diagnostic study.     

Dynamic ultrasonography to evaluate coracoacromial ligament displacement during motion in shoulders with supraspinatus tendon tears

We evaluated coracoacromial ligament (CAL) displacement during motion in shoulders with supraspinatus tendon tears by dynamic ultrasonography (US). Twenty subjects with unilateral, full‐thickness supraspinatus tendon tears (SST group) and 20 subjects with intact supraspinatus tendons (control group) underwent dynamic US. The CAL displacement in their bilateral shoulders was measured in the transverse US view during passive and active shoulder abduction and internal rotation (SAIR). In the SST group, the CAL displacement was significantly greater in the affected shoulders than in the intact ones (1.9 mm ± 0.8 mm vs. 1.5 mm ± 0.5 mm, p = 0.01) during passive SAIR, but was not significantly different between the shoulders (1.7 mm ± 0.7 mm vs. 1.7 mm ± 0.4 mm, p = 0.81) during active SAIR. In the control group, no difference in the CAL displacement between the shoulders was noted during passive and active SAIR. Thus, dynamic US revealed greater CAL displacement in shoulders with supraspinatus tendon tears than in intact ones during passive SAIR. Dynamic US may help to detect abnormal kinematics in shoulders with such injury. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1430–1434, 2012     

Arthroscopic repair of partial articular supraspinatus tendon avulsion lesions by conversion to full-thickness tears through a small incision

Purpose: To assess the clinical efficacy of converting partial articular supraspinatus tendon avulsion (PASTA) lesions to full-thickness tears through a small local incision of the bursal-side supraspinatus tendon followed by repair. Methods: We retrospectively analyzed 41 patients with Ellman grade 3 PASTA lesions and an average age of (54.7 ± 11.4) years from March 2013 to July 2017. Patients without regular conservative treatment and concomitant with other shoulder pathologies or previous shoulder surgery were excluded from the study. The tears were confirmed via arthroscopy, and a polydioxanone suture was placed to indicate the position of each tear. A small incision of approximately 6 mm was made using a plasma scalpel on the bursal-side supraspinatus tendon around the positioned suture to convert the partial tear into a fullthickness tear. The torn rotator cuff was sutured through the full thickness using a suture passer after inserting a 4.5-mm double-loaded suture anchor. Data were analyzed using a paired Student’s t-test with statistical significance defined as p <0.05. Results: At the final follow-up of 2 years, the pain-free shoulder joint range of motion and visual analog scale score were significantly improved compared to those before surgery (p < 0.001). The postoperative American Shoulder and Elbow Surgeons shoulder score was (90.6 ± 6.2), which was significantly higher than the preoperative score of (47.9 ± 8.3) (p < 0.001). The University of California at Los Angeles shoulder rating scale score increased from (14.7 ± 4.1) prior to surgery to (32.6 ± 3.4) points after surgery (p < 0.001). No patient had joint stiffness. Conclusion: This modified tear completion repair, by conversion to full-thickness tears through a small incision, has less damage to the supraspinatus tendon on the side of the bursa compared to traditional tear completion repair in the treatment of PASTA lesions. This surgical method is a simple and effective treatment that can effectively alleviate pain and improve shoulder joint function.     

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. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:638–644, 2014.     

Biceps tendon properties worsen initially but improve over time following rotator cuff tears in a rat model

Damage to the biceps tendon is often seen in conjunction with rotator cuff tears. However, controversy exists regarding its role in the shoulder and its optimal treatment. A previous study determined that biceps tendons were detrimentally affected in the presence of rotator cuff tears in the rat model and this damage worsened over time. However, whether this damage progresses at later time points to provide a chronic model is unknown. The objective of this study was to determine the changes in the biceps tendon in the presence of a cuff tear over time. Our hypothesis was that histological, compositional, organizational, and mechanical properties would worsen with time. We detached the supraspinatus and infraspinatus tendons of 48 rats and evaluated these properties at 1, 4, 8, and 16 weeks postdetachment. Properties worsened through 8 weeks, but improved between 8 and 16 weeks. We therefore conclude that biceps tendon changes in this model are not truly chronic. Additionally, it has been shown that infraspinatus properties in this model return to normal by 16 weeks, when biceps properties improve, indicating that earlier repair of one or more of the rotator cuff tendons may lead to resolved pathology of the long head of the biceps tendon. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:874–879     

Concomitant injuries affect prognosis in patients with central slip tear

Central slip tears often occur with concomitant hand injuries. However, the outcome of a central slip tear and the effect of concomitant injuries are rarely reported. We evaluated 67 fingers in 63 patients with central slip tears who underwent primary surgery in our hospital between April 2009 and June 2017. We performed multivariate analyses, with proximal interphalangeal (PIP) joint active range of motion (AROM) and existing extension lag greater than 10° as dependent variables and age, existence of concomitant fractures, skin defects, collateral ligament injuries, ruptured lateral bands, ruptured flexor tendons or vascular injury in the injured finger as independent variables. Concomitant injuries of tendons in the adjacent fingers were also independent variables. The average AROM of the PIP joint was 62°, and extension lag occurred in 34 fingers (51%). Patients aged?>?40 years with fractures of the injured finger or flexor tendon injuries in an adjacent finger had low decreases in AROM (partial regression coefficient [95% confidence interval, CI]: ?13.7 [43–66], ?31.6 [30–57], ?34.5 [32–60] and ?33.5 [10–43]). Extensor tendon injuries in an adjacent finger caused significantly more extension lag in the PIP joint (odds ratio [95% CI]: 3.2 [1.0–9.6]). The present study indicated the negative impact of a tendon injury on adjacent fingers, a circumstance widely known as the quadriga phenomenon. Ultimately, we can use these prognostic factors in surgical repair planning, particularly when comparing treatments such as central slip reconstruction and primary arthrodesis.     

Supraspinatus tendon load during abduction is dependent on the size of the critical shoulder angle: A biomechanical analysis

Shoulders with supraspinatus (SSP) tears are associated with significantly larger critical shoulder angles (CSA) compared to disease‐free shoulders. We hypothesized that larger CSAs increase the ratio of joint shear to joint compression forces (defined as “instability ratio”), requiring substantially increased compensatory supraspinatus loads. A shoulder simulator with simulated deltoid, supraspinatus, infraspinatus/teres minor, and subscapularis musculotendinous units was constructed. The model was configured to represent either a normal CSA of 33° or a CSA characteristic of shoulders with rotator cuff tears (38°), and the components of the joint forces were measured. The instability ratio increased for the 38° CSA compared with the control CSA (33°) for a range of motion between 6° to 61° of thoracohumeral abduction with the largest differences in instability observed between 33° and 37° of elevation. In this range, SSP force had to be increased by 13–33% (15–23 N) to stabilize the arm in space. Our results support the concept that a high CSA can induce SSP overload particularly at low degrees of active abduction. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:952–957, 2014.     

Effects of biceps tension on the torn superior glenoid labrum

The purpose of this study was to evaluate the role of the tension on the long head of the biceps tendon in the propagation of SLAP tears by studying the mechanical behavior of the torn superior glenoid labrum. A previously validated finite element model was extended to include a glenoid labrum with type II SLAP tears of three different sizes. The strain distribution within the torn labral tissue with loading applied to the biceps tendon was investigated and compared to the inact and unloaded conditions. The anterior and posterior edges of each SLAP tear experienced the highest strain in the labrum. Labral strain increased with increasing biceps tension. This effect was stronger in the labrum when the size of the tear exceeded the width of the biceps anchor on the superior labrum. Thus, this study indicates that biceps tension influences the propagation of a SLAP tear more than it does the initiation of a tear. Additionally, it also suggests that the tear size greater than the biceps anchor site as a criterion in determining optimal treatment of a type II SLAP tear. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1545–1551, 2015.     

Restoration of anterior–posterior rotator cuff force balance improves shoulder function in a rat model of chronic massive tears

The rotator cuff musculature imparts dynamic stability to the glenohumeral joint. In particular, the balance between the subscapularis anteriorly and the infraspinatus posteriorly, often referred to as the rotator cuff “force couple,” is critical for concavity compression and concentric rotation of the humeral head. Restoration of this anterior–posterior force balance after chronic, massive rotator cuff tears may allow for deltoid compensation, but no in vivo studies have quantitatively demonstrated an improvement in shoulder function. Our goal was to determine if restoring this balance of forces improves shoulder function after two‐tendon rotator cuff tears in a rat model. Forty‐eight rats underwent detachment of the supraspinatus and infraspinatus. After four weeks, rats were randomly assigned to three groups: no repair, infraspinatus repair, and two‐tendon repair. Quantitative ambulatory measures including medial/lateral forces, braking, propulsion, and step width were significantly different between the infraspinatus and no repair group and similar between the infraspinatus and two‐tendon repair groups at almost all time points. These results suggest that repairing the infraspinatus back to its insertion site without repair of the supraspinatus can improve shoulder function to a level similar to repairing both the infraspinatus and supraspinatus tendons. Clinically, a partial repair of the posterior cuff after a two‐tendon tear may be sufficient to restore adequate function. An in vivo model system for two‐tendon repair of massive rotator cuff tears is presented. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29: 1028–1033, 2011     

Influence of distinct anatomic subregions of the supraspinatus on humeral rotation

The supraspinatus, having distinct anterior and posterior subregions, is most commonly considered an abductor of the humerus, but it has also been shown to induce humeral rotation. The objective of this study was to quantify the magnitude and direction of humeral rotation that results from loading the distinct anterior and posterior subregions of the supraspinatus. Fourteen cadaver specimens were tested under four loading conditions based on physiological cross section area of the supraspinatus: (1) anterior only; (2) posterior only; (3) physiologic (each subregion loaded simultaneously); and (4) nonphysiologic (the tendon loaded as a whole). Each specimen was tested at 0, 15, 30, 45, and 60° of glenohumeral abduction in the scapular plane and from 60° of internal to 45° of external rotation in 15° increments. The humeral rotation that occurred with loading from the initial starting rotation position was measured using a rotary variable inductance transducer. In the scapular plane, the anterior subregion of the supraspinatus acts as both an internal and external rotator depending on the initial position of the humerus. The posterior subregion either acted as an external rotator or did not induce rotation. This study demonstrated a distinct functional difference between the anatomic subregions of the supraspinatus. This understanding will help to improve testing methods and the development of repair strategies of the supraspinatus. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:12–17, 2010     

A Cross-Sectional Study on Novel-Risk Factors Associated with Supraspinatus Tendon Tear

Background and AimSeveral patient-related factors have been identified which are responsible for the development of rotator cuff tears. The purpose of the study was to assess various parameters which can be risk factors for the development of supraspinatus tendon tear.MethodsA total of 100 patients with symptomatic rotator cuff tear, aged > 18 years, of either gender, presenting to the outpatient department were included in this cross-sectional study. Magnetic resonance imaging was done and based on its results; patients were identified for the type of tear. Demographic, clinical, and biochemical factors affecting the tears were assessed using logistic regression analysis.ResultsFactors such as age, gender, pain radiation, night pain, and analgesic intake had significant association with supraspinatus tendon tears.Conclusion“Pain radiation” and “Analgesic intake” were two new parameters found associated with the supraspinatus tendon tears. New parameters that have been assessed as risk factors will help in better understanding of supraspinatus tendon tears.     

Inhomogeneous mechanical behavior of the human supraspinatus tendon under uniaxial loading.

Disorders of the rotator cuff, particularly tears of the rotator cuff tendons, cause significant shoulder disability. Among numerous factors thought to be responsible for the initiation and progression of supraspinatus tears are those related to the tendon's biomechanical properties. We hypothesized that in supraspinatus tendons subjected to tensile loading a strain gradient (difference) exists between the articular and bursal tendon surfaces, that regional strain differences exist on each of these two tendon surfaces, and that tendon surface strains vary with glenohumeral abduction. To test these hypotheses, the intrinsic inhomogeneous deformational characteristics of the articular and bursal surfaces of eight intact human cadaveric supraspinatus tendons were studied at three glenohumeral abduction angles using a novel multiple strain measuring system which simultaneously recorded surface marker displacements on two opposing soft tissue surfaces. Under applied tensile loads, the articular surface exhibited greater strain at 22 degrees (7.4+/-2.6% vs. 1.3+/-0.7%, p=0.0002) and 63 degrees (6.4+/-1.6% vs. 2.7+/-1.2%, p=0.0001) whereas the bursal surface exhibited greater strain at 90 degrees (7.6+/-2.8% vs. 4.9+/-0.4%, p=0.013). At all abduction angles, insertion strains were higher than those of the mid-tendon and tendon-muscle junction regions. The existence of inhomogeneous surface strains in the intact supraspinatus tendon demonstrates that intratendinous shear occurs within the tendon. The higher strain on the articular side of the tendon, especially at the insertion region, suggests a propensity for tears to initiate in the articular tendinous zone.     

Glenoid version and rotator cuff tears.

The purpose of this study was to determine the relationship between rotator cuff (RC) tear and the orientation of the glenoid. Ninety-six shoulders (94 patients) that underwent open RC repair were grouped according to the type of tear. We measured on MRI the acromio-glenoid angle (AG) and the supraspinatus fossa glenoid angle on the anterior-posterior (SGAP) and axial (SGAX) views. RC patients had a smaller AG angle (76+/-7 degrees vs. 86+/-10 degrees ) and a larger SGAP angle (112+/-6 degrees vs. 102+/-7 degrees ) compared to controls (p<0.001). We also found a highly significant difference (p<0.001) in glenoid version measured by SGAX between anterior cuff tears (-5+/-4 degrees ) and posterior cuff tears (3+/-3 degrees ). Furthermore, we identified an association between RC tear and the orientation of the glenoid relative to the axis of the supraspinatus fossa. Greater retroversion is predictive of an anterior cuff injury and greater anteversion is predictive of a posterior cuff injury.     

Atrophy of the rotator cuff muscles and site of cuff tears

We determined the relationship between the site of rotator cuff tears and atrophy of the cuff muscles. 28 shoulders (28 patients) had rotator cuff tears: 19 isolated tears of the supraspinatus tendon (isolatedtear group) and 9 combined tears of the supraspinatus and infraspinatus tendons (combined-tear group). The cross-sectional area of the subscapularis, supraspinatus, the infraspinatus and teres minor muscles in the coronal oblique MR images were measured before and after surgery. Although we found no difference in tear size, the cross-sectional areas of the muscles were smaller in the combined-tear group than in the isolated-tear group. We conclude that atrophy of the supraspinatus and infraspinatus muscles also depends on the site of the tear.     

Latissimus dorsi transfer for primary treatment of irreparable rotator cuff tears

Transfer of the musculotendinous unit of the latissimus dorsi was performed in seven patients (5 men and 2 women, with a mean age of 57 years) with irreparable rotator cuff tear who had had no previous surgery for cuff repair. Preoperatively, the mean active shoulder motion was 86° in flexion, 74° in abduction and 22° in external rotation. One patient had a positive lift-off test. The average preoperative Constant and Murley score was 44%. Diagnosis of irreparability of the cuff leasion was made preoperatively only in one case. In the remaining patients, the preoperative data only led to suspect that the tear was irreparable. At surgery, all patients had an irreparable tear of the superoinferior portion of the cuff and one patient also had a tear of the subscapularis tendon. In all cases the latissimus dorsi tendon was inserted to the greater tuberosity and, in four cases, to the subscapularis tendon; in three patients it was sutured to the bicipital tendon. Postoperatively all patients had relief of shoulder pain. The mean improvement in active flexion, abduction and external rotation was, respectively, 39°, 29° and 10°: At the latest follow-up, the average Constant and Murley score was 64%. The results of surgery were rated as excellent in three cases, good in two, fair in one and poor in one. All patients but one returned to preoperative work. Transfer of the latissimus dorsi muscle is an effective procedure for patients in middle or early elderly age who have an irreparable tear of the supraspinatus and infraspinatus tendons. Received: 18 December 2001/Accepted: 4 January 2002     

A Proximal Fibularis Brevis Muscle Is Associated with Longitudinal Split Tendons: A Cadaveric Study

The anomalous distal musculotendinous junction of the fibularis brevis muscle has been hypothesized to contribute to the development of longitudinal fibularis brevis tendon tears. Specifically, the mass effect of the low-lying fibularis brevis muscle belly was thought to increase the pressure on the superior peroneal retinaculum and increase the probability of fibularis brevis tendon subluxation. A more recent examination of the fibularis brevis tendon junction found, contrary to this hypothesis, a statistically significant association between an anomalous proximal musculotendinous junction and the prevalence of longitudinal split tears. However, no rationale was offered. The present study examined the relationship between the musculotendinous junction and the prevalence of longitudinal fibularis brevis tendon tears. A total of 24 fibularis brevis tendon lengths were measured bilaterally in 12 human cadaveric specimens. The tendon lengths were assessed as the vertical distance from the most inferior aspect of the lateral malleolus to the most distal fibularis brevis musculotendinous extension. Only full-thickness tears were identified and included. The lengths of tendons with and without longitudinal tears were compared. Of the 24 tendons examined, 7 (29%) presented with full-thickness longitudinal tears from 4 cadavers (33%). The mean length for the tendons with tears was significantly longer (p < .001) than the mean length of those without tears (28.86 ± 3.02 mm versus 16.29 ± 7.30 mm). Our research concurs with the most recent findings, identifying a statistically significant association between an anomalous proximal muscle belly extension and longitudinal fibularis brevis tendon tears. Furthermore, we propose the hypothesis that a more proximal musculotendinous junction might predispose individuals to a lesser stabilizing effect of the muscle against the posterior lateral surface of the fibula, increasing the probability of anterolateral subluxation, attrition, and longitudinal tear development.