Current perspectives on rotator cuff anatomy

Optimizing Tissue Engineering for Clinical Relevance in Rotator Cuff Repair

Rotator cuff tear (RCT) is the most common cause of disability in the upper extremity. It results in 4.5 million physician visits in the United States every year and is the most common etiology of shoulder conditions evaluated by orthopedic surgeons. Over 460,000 RCT repair surgeries are performed in the United States annually. Rotator cuff (RC) retear and failure to heal remain significant postoperative complications. Literature suggests that the retear rates can range from 29.5% to as high as 94%. Weakened and irregular enthesis regeneration is a crucial factor in postsurgical failure. Although commercially available RC repair grafts have been introduced to augment RC enthesis repair, they have been associated with mixed clinical outcomes. These grafts lack appropriate biological cues such as stem cells and signaling molecules at the bone-tendon interface. In addition, they do little to prevent fibrovascular scar tissue formation, which causes the RC to be susceptible to retear. Advances in tissue engineering have demonstrated that mesenchymal stem cells (MSCs) and growth factors (GFs) enhance RC enthesis regeneration in animal models. These models show that delivering MSCs and GFs to the site of RCT enhances native enthesis repair and leads to greater mechanical strength. In addition, these models demonstrate that MSCs and GFs may be delivered through a variety of methods including direct injection, saturation of repair materials, and loaded microspheres. Grafts that incorporate MSCs and GFs enhance anti-inflammation, osteogenesis, angiogenesis, and chondrogenesis in the RC repair process. It is crucial that the techniques that have shown success in animal models are incorporated into the clinical setting. A gap currently exists between the promising biological factors that have been investigated in animal models and the RC repair grafts that can be used in the clinical setting. Future RC repair grafts must allow for stable implantation and fixation, be compatible with current arthroscopic techniques, and have the capability to deliver MSCs and/or GFs.

The Biological Effect of Platelet-Rich Plasma on Rotator Cuff Tears: A Prospective Randomized In Vivo Study

The positive effect of platelet-rich plasma (PRP) on tendon metabolism has been extensively investigated and proven in vitro. Additionally, in vivo animal studies have correlated the application of PRP with the enhancement of tenocyte anabolic activity in the setting of tendon degeneration. However, less is known about its in vivo effect on human tendon biology. The purpose of the current prospective randomized comparative study was to evaluate the effect of PRP on torn human supraspinatus tendon. Twenty consecutive eligible patients with painful and magnetic resonance imaging (MRI)-confirmed degenerative supraspinatus tendon tears were randomized in a one-to-one ratio into two groups. The patients in the experimental group (n = 10) underwent an ultrasound-guided autologous PRP injection in the subacromial space 6 weeks before the scheduled operation. In the control group (n = 10), no injection was made prior to surgery. Supraspinatus tendon specimens were harvested from the lateral end of the torn tendon during shoulder arthroscopy and were evaluated under optical and electron microscopy. In the control group, a mixed cell population of oval and rounded tenocytes within disorganized collagen and sites of accumulated inflammatory cells was detected. In contrast, the experimental group yielded abundant oval-shaped cells with multiple cytoplasmic processes within mainly parallel collagen fibers and less marked inflammation, simulating the intact tendon structure. These findings indicate that PRP can induce microscopic changes in the ruptured tendon by stimulating the healing process and can facilitate a more effective recovery.

The association between a rotator cuff tendon tear and a tear of the long head of the biceps tendon: Chart review study

Rotator cuff (RC) and long head of the biceps tendon (LHBT) tears are common shoulder problems presented to the orthopedic clinic. The aim of this study was to assess the association between RC and LHBT tears among a Saudi population sample. A total of 243 patients who were diagnosed with shoulder pain due to RC or LHBT tear between 2016 and 2018 using a magnetic resonance imaging scan were included in this study. Females comprised 66% of the sample, and 59% (n = 143) of the shoulders were on the right side. The mean age of the patients was 58 ± 11 years, ranging from 23 to 88 years. A significant association was detected between the LHBT and RC tears (P < 0.001). Out of 26 cases showing RC and LHBT tears, 81% had a full thickness tear, whereas 19% had a partial tear. The LHBT tears were presented significantly in 48% of cases with at least two completely torn RC compared to 10% in cases with one completely torn RC (P < 0.001). The LHBT tear was significantly observed in shoulders with RC tears including the tendons of subscapularis, supraspinatus, and infraspinatus, but not the teres minor (P < 0.001). Both types of tears were presented significantly in senior patients aged more than 65 years compared to younger patients (P < 0.01). Thus, the LHBT should be assessed carefully in shoulders with more than one RC tear or in chronic cases.

Construction of a Decellularized Multicomponent Extracellular Matrix Interpenetrating Network Scaffold by Gelatin Microporous Hydrogel 3D Cell Culture System

Interface tissue repair requires the construction of biomaterials with integrated structures of multiple protein types. Hydrogels that modulate internal porous structures provide a 3D microenvironment for encapsulated cells, making them promise for interface tissue repair. Currently, reduction of intrinsic immunogenicity and increase of bioactive extracellular matrix (ECM) secretion are issues to be considered in these materials. In this study, gelatin methacrylate (GelMA) hydrogel is used to encapsulate chondrocytes and construct a phase transition 3D cell culture system (PTCC) by utilizing the thermosensitivity of gelatin microspheres to create micropores within the hydrogel. The types of bioactive extracellular matrix protein formation by chondrocytes encapsulated in hydrogels are investigated in vitro. After 28 days of culture, GelMA PTCC forms an extracellular matrix predominantly composed of collagen type II, collagen type I, and fibronectin. After decellularization, the protein types and mechanical properties are well preserved, fabricating a decellularized tissue-engineered extracellular matrix and GelMA hydrogel interpenetrating network hydrogel (dECM-GelMA IPN) consisting of GelMA hydrogel as the first-level network and the ECM secreted by chondrocytes as the second-level network. This material has the potential to mediate the repair and regeneration of tendon-bone interface tissues with multiple protein types.

The subscapularis muscle: A meta-analysis of its variations, prevalence, and anatomy

BACKGROUND

The subscapularis (SSC) is the largest rotator cuff muscle and is involved in the medial rotation, abduction, adduction, and anterior stabilization of the shoulder. It is anatomically variable, as is the morphology and prevalence of the accessory SSC (aSSC), a rare muscle slip attached to the SSC. There is no current review investigating the prevalence and morphometrics of the SSC and aSSC.

PURPOSE

To investigate the prevalence of the morphological variants of the SSC and aSSC via meta-analysis and review the relevant literature involving cadaveric, magnetic resonance imaging, and ultrasonographic studies.

STUDY DESIGN

Meta-analysis.

MATERIALS AND METHODS

Literature data reporting the prevalence rates and morphometrics of the SSC and aSSC and their variants were pooled. Literature searches and data analyses were performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Anatomical Quality Assurance guidelines.

RESULTS

Forty-six studies, totaling 2166 shoulders, were assessed. The SSC showed an overall length, thickness, cross-sectional area, and volume of 152.2 mm (95% confidence interval, CI, 103.8-200.5 mm), 5.6 mm (95% CI, 4.6-6.6 mm), 18.1 cm² (95% CI, 14.2-22.0 cm² ), and 126.9 cm³ (95% CI, 87.2-166.5 cm³ ), respectively. The SSC displayed substantial variations in its origin and insertion points and in the composition of its tendon. The aSSC had an overall pooled prevalence of 24.6% (95% CI, 0.0%-76.9%).

CONCLUSIONS

The SSC and aSSC have been implicated in multiple shoulder pathologies, including muscle and tendon ruptures and neurovascular compromise. A better understanding of SSC and aSSC variants when diagnosing and treating their related pathologies will reduce patient morbidity and improve treatment regimens.

Is Bony Morphology and Morphometry Associated With Degenerative Full-Thickness Rotator Cuff Tears? A Systematic Review and Meta-analysis

PURPOSE

To scope the scientific literature and analyze the influence of bony risk factors for degenerative full-thickness primary rotator cuff tear.

METHODS

A systematic review of databases PubMed, Scopus, EMBASE, and Cochrane Library was performed up to June 30, 2018. Meta-analysis was performed with mean difference (MD) or risk ratio for degenerative full-thickness rotator cuff injury, and when there were ≥3 studies for the considered potential risk factor. Methodologic quality was assessed using the Newcastle-Ottawa scale.

RESULTS

We analyzed 34 studies comprising 5,916 shoulders (3,369 shoulders with rotator cuff tear and 2,546 controls) and identified 19 potential risk factors for degenerative full-thickness rotator cuff tears. There was moderate evidence that a higher critical shoulder angle (MD = 4.41, 95% confidence interval [CI] 3.43 to 5.39), higher acromion index (MD = 0.06, 95% CI 0.04 to 0.09), and lower lateral acromion angles (MD = -7.11, 95% CI -8.32 to -5.90) were associated with degenerative full-thickness rotator cuff tears compared with controls. Moderate evidence showed that a type III acromion significantly increases the risk for full-thickness degenerative rotator cuff tear (risk ratio = 2.26, 95% CI 1.38 to 3.70).

CONCLUSION

There is moderate evidence that larger critical shoulder angle, higher acromion index, lower lateral acromion angles, and a type III acromion are significantly associated with degenerative full-thickness rotator cuff tears. Other potential risk factors identified showed insufficient evidence.

LEVEL OF EVIDENCE

Level IV, systematic review of level II to IV studies.

The effect of subscapularis muscle contraction on coaptation of anteroinferior glenohumeral ligament-labrum complex after Bankart repair

Facilitation of healing is important for the anteroinferior glenohumeral ligament-labrum complex (AIGHL-LC) after Bankart repair in shoulder dislocation. The purpose of this study was to investigate the effect of subscapularis muscle loading on contact area and contact pressure between the subscapularis and AIGHL-LC and between the glenoid bone and the AIGHL-LC following Bankart repair. Twenty-two fresh-frozen cadaveric shoulders were used. They were attached to a shoulder-positioning device to which a compression force was applied. Loads applied to the supraspinatus, infraspinatus, and teres minor tendons were held constant. The loads applied to the subscapularis tendon were set at 0, 10, 20, and 30 Newton (N). Contact pressure and area between the subscapularis and the AIGHL-LC were measured with the arm at 4 rotational positions: 60° and 30° internal, neutral, and 30° external. After the Bankart lesion was created, the contact area and pressure between the AIGHL-LC and glenoid bone were measured while Bankart repair was performed with or without loading of the subscapularis. The contact area and pressures with 10, 20, and 30 N of subscapularis loadings were significantly greater than with 0 N of subscapularis loading at 60° internal rotation and 30° external rotation (P < .05). After Bankart repair, contact area and pressure with subscapularis loading between the AIGHL-LC and glenoid bone were significantly greater than without subscapularis loading (P < .01). We conclude that isometric contraction exercises of the subscapularis might facilitate healing of the AIGHL-LC after Bankart repair.

Subscapularis tendon tears: Management and arthroscopic repair

Tears of the subscapularis tendon have been under-recognised until recently. Therefore, a high index of suspicion is essential for diagnosis.A directed physical examination, including the lift-off, belly-press and increased passive external rotation can help identify tears of the subscapularis.All planes on MR imaging should be carefully evaluated to identify tears of the subscapularis, retraction, atrophy and biceps pathology.Due to the tendency of the tendon to retract medially, acute and traumatic full-thickness tears should be repaired. Chronic tears without significant degeneration should be considered for repair if no contraindication exists.Arthroscopic repair can be performed using a 30-degree arthroscope and a laterally-based single row repair; one anchor for full thickness tears ⩽ 50% of tendon length and two anchors for those ⩾ 50% of tendon length.Biceps pathology, which is invariably present, should be addressed by tenotomy or tenodesis.Timing of post-operative rehabilitation is dictated by the size of the repair and the security of the repair construct. The stages of rehabilitation typically involve a period of immobilisation followed by range of movement exercises, with a delay in active internal rotation (IR) and strengthening in IR. Cite this article: EFORT Open Rev 2017;2:484-495. DOI: 10.1302/2058-5241.2.170015.

Magnetic resonance arthrography results that indicate surgical treatment for partial articular-sided supraspinatus tendon avulsion: a retrospective study in a tertiary center

Background Specific findings on magnetic resonance arthrography (MRA) that indicate the need for surgery in patients with partial articular-sided supraspinatus tendon avulsion (PASTA) are not well understood. Purpose To determine which MRA findings are characteristic of patients who undergo surgery for PASTA. Material and Methods From July 2011 to February 2014, MRA findings for patients treated for PASTA were retrospectively reviewed. The patients were divided into two groups: conservative treatment and surgical repair. MRA findings were compared between the groups. The following MRA results were assessed: length grade, width grade, co-existing superior labrum anterior posterior (SLAP) lesions, degenerative changes in the glenohumeral joint, presence of subacromial-subdeltoid bursitis, acromion type, presence of adhesive capsulitis, and tears of the subscapularis or infraspinatus tendon within the rotator cuff. Logistic regression analyses were conducted to identify which MRA findings were significantly associated with surgical treatment. Results Forty-five surgically treated patients and 203 conservatively treated ones were evaluated. The MRA findings showed significant differences between the groups with respect to length grade, width grade, degenerative changes in glenohumeral joint, bursitis, and co-existing rotator cuff tears ( P < 0.05). Multivariate logistic regression showed correlations between surgical repair and both grade 3 length tears (odds ratio, 30.8) and co-existing tears of the subscapularis or infraspinatus tendon (odds ratio, 2.9). Conclusion Surgical treatment is commonly performed in PASTA patients whose lesion lengths are grade 3 or who have co-existing tears in the subscapularis or infraspinatus tendon. Radiologists should pay attention to these MRA signs when evaluating PASTA patients.

Biomechanical Performance of Medial Row Suture Placement Relative to the Musculotendinous Junction in Transosseous Equivalent Suture Bridge Double-Row Rotator Cuff Repair

PURPOSE

To compare the biomechanical performance of medial row suture placement relative to the musculotendinous junction (MTJ) in a cadaveric transosseous equivalent suture bridge (TOE-SB) double-row (DR) rotator cuff repair (RCR) model.

METHODS

A TOE-SB DR technique was used to reattach experimentally created supraspinatus tendon tears in 9 pairs of human cadaveric shoulders. The medial row sutures were passed either near the MTJ (MTJ group) or 10 mm lateral to the MTJ (rotator cuff tendon [RCT] group). After the supraspinatus repair, the specimens underwent cyclic loading and load to failure tests. The localized displacement of the markers affixed to the tendon surface was measured with an optical tracking system.

RESULTS

The MTJ group showed a significantly higher (P = .03) medial row failure (5/9; 3 during cyclic testing and 2 during load to failure testing) compared with the RCT group (0/9). The mean number of cycles completed during cyclic testing was lower in the MTJ group (77) compared with the RCT group (100; P = .07) because 3 specimens failed in the MTJ group during cyclic loading. There were no significant differences between the 2 study groups with respect to biomechanical properties during the load to failure testing.

CONCLUSIONS

In a cadaveric TOE-SB DR RCR model, medial row sutures through the MTJ results in a significantly higher rate of medial row failure.

CLINICAL RELEVANCE

In rotator cuff tears with tendon tissue loss, passage of medial row sutures through the MTJ should be avoided in a TOE-SB RCR technique because of the risk of medial row failure.

The role of tendon and subacromial bursa in rotator cuff tear pain: a clinical and histopathological study

PURPOSE

To evaluate a possible association of shoulder pain with the clinical features and the histopathological changes occurring in the ruptured tendon and subacromial bursa of patients with rotator cuff tear.

METHODS

One hundred and eighty patients were clinically evaluated with the constant score and the visual analogue pain scale. Radiographs and MRI were performed. The chronology of the rupture, the muscle fatty degeneration according to Goutallier's scale and the tear size were evaluated. For each patient, a biopsy of the supraspinatus tendon and subacromial bursa was performed during arthroscopic rotator cuff tear repair and the specimens were histopathologically analysed.

RESULTS

Clinically, the shoulder was more painful in females, in the presence of a chronic cuff lesion and a low Goutallier's grade (P < 0.05). No association was found between pain and age of the patient and between pain and tear size. Histologically, hypertrophy and inflammation of the tendon and hypertrophy, inflammation, oedema and necrosis of the subacromial bursa were directly associated with pain (P < 0.05). Pain decreased significantly in the presence of fatty metaplasia and necrosis of the tendon (P < 0.05).

CONCLUSIONS

This study defines the main clinical and histopathological features of painful rotator cuff tear. In particular, a greater association of pain was observed with the histopathological changes in the bursa compared with those in the rotator cuff. Considering that the bursa plays also an essential role during the healing process, this "new" role of the subacromial bursa as pain generator has important repercussions in both pharmacological and surgical treatments of rotator cuff tears.

LEVEL OF EVIDENCE

IV.

Rotator cuff tears: An evidence based approach

Lesions of the rotator cuff (RC) are a common occurrence affecting millions of people across all parts of the globe. RC tears are also rampantly prevalent with an age-dependent increase in numbers. Other associated factors include a history of trauma, limb dominance, contralateral shoulder, smoking-status, hypercholesterolemia, posture and occupational dispositions. The challenge lies in early diagnosis since a high proportion of patients are asymptomatic. Pain and decreasing shoulder power and function should alert the heedful practitioner in recognizing promptly the onset or aggravation of existing RC tears. Partial-thickness tears (PTT) can be bursal-sided or articular-sided tears. Over the course of time, PTT enlarge and propagate into full-thickness tears (FTT) and develop distinct chronic pathological changes due to muscle retraction, fatty infiltration and muscle atrophy. These lead to a reduction in tendon elasticity and viability. Eventually, the glenohumeral joint experiences a series of degenerative alterations - cuff tear arthropathy. To avert this, a vigilant clinician must utilize and corroborate clinical skill and radiological findings to identify tear progression. Modern radio-diagnostic means of ultrasonography and magnetic resonance imaging provide excellent visualization of structural details and are crucial in determining further course of action for these patients. Physical therapy along with activity modifications, anti-inflammatory and analgesic medications form the pillars of nonoperative treatment. Elderly patients with minimal functional demands can be managed conservatively and reassessed at frequent intervals. Regular monitoring helps in isolating patients who require surgical interventions. Early surgery should be considered in younger, active and symptomatic, healthy patients. In addition to being cost-effective, this helps in providing a functional shoulder with a stable cuff. An easily reproducible technique of maximal strength and sturdiness should by chosen among the armamentarium of the shoulder surgeon. Grade 1 PTTs do well with debridement while more severe lesions mandate repair either by trans-tendon technique or repair following conversion into FTT. Early repair of repairable FTT can avoid appearance and progression of disability and weakness. The choice of surgery varies from surgeon-to-surgeon with arthroscopy taking the lead in the current scenario. The double-row repairs have an edge over the single-row technique in some patients especially those with massive tears. Stronger, cost-effective and improved functional scores can be obtained by the former. Both early and delayed postoperative rehabilitation programmes have led to comparable outcomes. Guarded results may be anticipated in patients in extremes of age, presence of comorbidities and severe tear patters. Overall, satisfactory results are obtained with timely diagnosis and execution of the appropriate treatment modality.

Three-dimensional analysis of elbow soft tissue footprints and anatomy

BACKGROUND

Tendinous and ligamentous injuries commonly occur in the elbow. This study characterized the location, surface areas, and origin and insertional footprints of major elbow capsuloligamentous and tendinous structures in relation to bony landmarks with the use of a precision 3-dimensional modeling system.

METHODS

Nine unpaired cadaveric elbow specimens were dissected and mounted on a custom jig. Mapping of the medial collateral ligament (MCL), lateral ulnar collateral ligament (LUCL), triceps, biceps, brachialis, and capsular reflections was then performed with 3-dimensional digitizing technology. The location, surface areas, and footprints of the soft tissues were calculated.

RESULTS

The MCL had a mean origin (humeral) footprint of 216 mm(2), insertional footprint of 154 mm(2), and surface area of 421 mm(2). The LUCL had a mean origin footprint of 136 mm(2), an insertional footprint of 142 mm(2), and a surface area of 532 mm(2). Of the tendons, the triceps maintained the largest insertional footprint, followed by the brachialis and the biceps (P < .001-.03). The MCL, LUCL, and biceps footprint locations were consistent, with little variability. The surface areas of the anterior (1251 mm(2)) and posterior (1147 mm(2)) capsular reflections were similar (P = .82), and the anterior capsule extended farther proximally.

CONCLUSION

Restoring the normal anatomy of key elbow capsuloligamentous and tendinous structures is crucial for effective reconstruction after bony or soft tissue trauma. This study provides the upper extremity surgeon with information that may aid in restoring elbow biomechanics and preserving range of motion in these patients.

Lesions of the rotator cuff footprint: diagnostic performance of MR arthrography compared with arthroscopy

BACKGROUND

To evaluate the diagnostic performance of magnetic resonance arthrography (MR-A) of the shoulder in the diagnosis of rotator cuff tears involving the humeral insertion of the supraspinatus and infraspinatus tendon (footprint), using arthroscopy as the reference standard.

MATERIALS AND METHODS

The study population included 90 consecutive patients with history and clinical diagnosis of instability of the shoulder, rotator cuff tear or posterosuperior glenoid impingement. A total of 108 MR arthrograms were performed, since 18 patients had undergone a bilateral procedure. Arthroscopy, which was performed within 45 days after MR-A, was used as the reference standard. Sensitivity, specificity, accuracy, positive and negative predictive values were then calculated.

RESULTS

Magnetic resonance arthrography showed a sensitivity of 92 % and a specificity of 78 % for the overall detection of tears involving the rotator cuff footprint. The diagnostic accuracy was 90 %, and the positive and negative predictive values were 95 and 64 %, respectively. Ten lesions were non-classifiable on surgery, of which eight were non-classifiable on MR-A also.

CONCLUSIONS

Magnetic resonance arthrography is extremely accurate for the detection and classification of rotator cuff footprint tears. Most of these lesions are articular-sided (partial articular-sided supraspinatus tendon avulsion lesions) with predominance in younger patients and concealed type of tear (concealed interstitial delamination lesions).

Clinical and structural results of arthroscopic repair of isolated subscapularis tear

BACKGROUND

Even though the frequency of arthroscopic repair of isolated lesions of the subscapularis tendon has increased, few studies have presented clinical and anatomical outcomes of this treatment. We hypothesized that, after an arthroscopic repair, structural outcomes in the muscle have an influence on functional results.

METHODS

A retrospective study was performed on twenty-two patients who had undergone arthroscopic repair of an isolated tear of the subscapularis tendon and had a mean follow-up of thirty-six months. Patients were evaluated preoperatively and postoperatively with use of the Constant-Murley score, a subjective shoulder value, the lift-off test, the belly-press test, and magnetic resonance imaging or computed tomography arthrography. The results were compared with those of a cohort of thirteen patients who underwent open repair of the subscapularis tendon tear.

RESULTS

In the arthroscopic group, the Constant-Murley score improved from a mean of 66 points preoperatively to a mean of 85 points postoperatively (p < 0.05). The subscapularis tendon was healed in 86% of the patients. Three patients (14%) had a partial rupture limited to the superior tendon. Postoperatively, progression of fatty infiltration of the subscapularis muscle was observed in 55% of the patients. Ten patients (45%) had a severe but localized fatty infiltration area of the subscapularis muscle related to the larger tears. Subjective and functional outcomes were not influenced by tendon-healing or postoperative fatty infiltration (p > 0.05). Clinical testing was significantly improved, but incomplete corrections remained frequent. Although open repair resulted in higher subjective shoulder scores and better strength scores, most other clinical parameters, postoperative subscapularis testing results, and structural outcomes were comparable between the arthroscopic repair and the open repair group.

CONCLUSIONS

Arthroscopic repair of isolated subscapularis tears was associated with improved shoulder function and improved results on clinical testing. The tendon-healing rate was high but resulted in incomplete correction of the results of clinical testing. Progression of fatty infiltration in the subscapularis muscle was observed on magnetic resonance imaging but did not influence the clinical outcomes.

Arthroscopic anatomy, variants, and pathologic findings in shoulder instability

Shoulder instability is a common diagnosis that often requires surgical treatment. A detailed knowledge of the shoulder anatomy and its stabilizing structures is of utmost importance for successful treatment of shoulder instabilities. Identifying anatomic variants (e.g., sublabral hole, meniscoid labrum, cordlike middle glenohumeral ligament, and Buford complex) and distinguishing them from pathologic findings may be especially difficult, as shown by the high interobserver variability. Over the last decade, basic research and arthroscopic surgery have improved our understanding of the shoulder anatomy and pathology. In the context of shoulder instability, injuries of the glenoid (bony Bankart), injuries of the glenoid labrum superiorly (SLAP) or anteroinferiorly (e.g., Bankart, anterior labroligamentous periosteal sleeve avulsion, and Perthes), capsular lesions (humeral avulsion of the glenohumeral ligament), accompanying cartilage lesions (Hill-Sachs, glenolabral articular disruption), and rotator interval and pulley lesions, as well as signs of dynamic instability impingement (posterior-superior impingement, anterior-superior impingement) can be exactly diagnosed (magnetic resonance imaging with intra-articular gadolinium, arthroscopy) and treated (arthroscopy). Therefore the purpose of this article is to review the current literature concerning shoulder anatomy/pathology related to shoulder stability/instability to improve clinical diagnosis and surgical treatment of our patients.

Subacromial morphometric assessment of the clavicle hook plate

BACKGROUND

Clavicle hook plates are an effective plate fixation alternative for distal clavicle fractures and severe acromioclavicular joint dislocations. However, post-operative complications associated with the subacromial portion of the hook include acromial osteolysis and subacromial impingement. We examine and quantify the three-dimensional position of the subacromial portion of the hook plate relative to surrounding acromial and subacromial structures in a series of cadaveric shoulders to determine if hook positioning predisposes the shoulder to these noted post-operative complications.

MATERIALS AND METHODS

Fifteen cadaveric shoulders (seven males, eight females) were implanted with 15- or 18-mm hook plates. Dimensions of the acromion and hook plate were digitised and reconstructed into a three-dimensional model to measure acromion dimensions and distances of the subacromial hook relative to surrounding acromial and subacromial structures.

RESULTS

Inter-specimen dimensions of the acromion were highly variable. Mean acromion width and thickness were greater in males than in females (p=0.01). The posterior orientation of the subacromial hook varied widely (mean posterior implantation angle=32.5+/-20 degrees, range 0-67 degrees). The hook pierced the subacromial bursa in 13/15 specimens, made contact with the belly of the supraspinatus muscle in 9/15 specimens, and had focal contact at the hook tip with the undersurface of the acromion in 9/15 specimens.

CONCLUSIONS

The wide range of acromial dimensions leads to a high degree of variability in the positioning of the subacromial hook. The observed frequency of hook contact with surrounding subacromial structures in a static shoulder confirms that the position of the hook portion of the implant can predispose anatomic structures to the post-operative complications of subacromial impingement and bony erosion.