Subscapularis release in shoulder replacement determines structural muscular changes

Lesser Tuberosity Osteotomy for the Management of the Subscapularis During Total Shoulder Arthroplasty

Subscapularis integrity is critical after anatomic total shoulder arthroplasty, with failure leading to potential instability, loss of function, and revision surgery. The three well-described subscapularis mobilization techniques during total shoulder arthroplasty include tenotomy, peel, and lesser tuberosity osteotomy (LTO). While several comparative studies exist, the optimal approach remains controversial. LTO has been associated with the highest healing rates, but techniques and repair constructs are highly variable. The purpose of this article was to provide an overview of LTO with attention on radiographic assessment, repair options, and clinical outcomes.

Subscapularis management in anatomic total shoulder arthroplasty: A systematic review and network meta-analysis

Background

This systematic review and network meta-analysis compare clinical outcomes of three different subscapularis management techniques in anatomic total shoulder arthroplasty: lesser tuberosity osteotomy, subscapularis peel, and subscapularis tenotomy.

Methods

PubMed, Web of Science, Embase, and Cochrane's trial registry were searched in July 2021. Comparative studies and case series evaluating the outcomes of these three techniques were included. The network meta-analysis was performed only on comparative studies.

Results

Twenty-three studies were included. Both lesser tuberosity osteotomy and subscapularis peel had significantly higher Western Ontario Osteoarthritis Scores compared to subscapularis tenotomy, but no difference in American Shoulder and Elbow Society Scores. Subscapularis peel had superior external rotation compared to lesser tuberosity osteotomy. However, no difference was found in external rotation between subscapularis peel and subscapularis tenotomy or between subscapularis tenotomy and lesser tuberosity osteotomy. The overall weighted average for lesser tuberosity osteotomy bony union was 93.6%, whereas the overall weighted average for subscapularis tendon healing was 79.4% and 87% for subscapularis tenotomy and subscapularis peel, respectively.

Discussion

This network meta-analysis demonstrated that lesser tuberosity osteotomy and subscapularis peel were associated with the high union and subscapularis healing rates and may be associated with improved shoulder function and quality of life, compared to subscapularis tenotomy. Lesser tuberosity osteotomy and subscapularis peel demonstrate a trend of superior outcomes compared to subscapularis tenotomy during anatomic total shoulder arthroplasty.

Limited value of current shoulder arthroplasty registries in evidence-based shoulder surgery: a review of 7 national registries

National shoulder arthroplasty registries are currently used to assess incidence, indication, type of prosthesis and revision, but they seem to lack sufficient information to lead to evidence based decision-making in shoulder surgery. There appears to be a large difference in registered parameters and outcome measurement per country. First we investigated whether existing registries have sufficient common datasets to enable pooling of data. Second, we determined whether known risk factors for prosthetic failure are being recorded. Through a non-systematic literature review studies on registries were analyzed for included parameters. Seven national registries were scrutinized for the data collected and these were classified according to categories of risk factors for failure: patient-, implant and surgeon related, and other parameters. This shows a large heterogeneity of registered parameters between countries. The majority of parameters shown to be relevant to outcome and failure of shoulder prostheses are not included in the studied registries. International agreement on parameters and outcome measurement for registries is paramount to enable pooling and comparison of data. If we intend to use the registries to provide us with evidence to improve prosthetic shoulder surgery, we need adjustment of the different parameters to be included.

Biomechanics of anatomic and reverse shoulder arthroplasty

The biomechanics of the shoulder relies on careful balancing between stability and mobility. A thorough understanding of normal and degenerative shoulder anatomy is necessary, as the goal of anatomic total shoulder arthroplasty is to reproduce premorbid shoulder kinematics.With reported joint reaction forces up to 2.4 times bodyweight, failure to restore anatomy and therefore provide a stable fulcrum will result in early implant failure secondary to glenoid loosening.The high variability of proximal humeral anatomy can be addressed with modular stems or stemless humeral components. The development of three-dimensional planning has led to a better understanding of the complex nature of glenoid bone deformity in eccentric osteoarthritis.The treatment of cuff tear arthropathy patients was revolutionized by the arrival of Grammont's reverse shoulder arthroplasty. The initial design medialized the centre of rotation and distalized the humerus, allowing up to a 42% increase in the deltoid moment arm.More modern reverse designs have maintained the element of restored stability but sought a more anatomic postoperative position to minimize complications and maximize rotational range of motion. Cite this article: EFORT Open Rev 2021;6:918-931. DOI: 10.1302/2058-5241.6.210014.

Clinical and radiographic outcomes of an all-polyethylene fluted central peg glenoid component, implanted utilizing an off-label, uncemented technique, at a minimum 5-year follow-up

BACKGROUND

Glenoid component loosening remains an important concern in anatomic total shoulder arthroplasty. The aim of this study was to evaluate the clinical and radiographic results of a fully uncemented all-polyethylene fluted central peg bone-ingrowth glenoid component at a minimum 5-year follow-up.

METHODS

Thirty-five shoulders in 31 patients (mean age, 73 years) with a mean follow-up of 100 months were retrospectively evaluated at an early and mid-term time point for Constant score (CS). Computed tomography visualized glenoid component fixation at both time points.

RESULTS

Mean CS improved from 40 preoperatively to 66 postoperatively at latest follow-up (P < .001). A mean CS of 74 at early follow-up remained consistent with a mean CS of 66 at latest follow-up (P = .158), with only strength demonstrating a decrease over time (P < .001). An initial osseointegration rate of 81% at early follow-up decreased to 71% at latest follow-up with 74% of the shoulders demonstrating progressive radiolucent lines, resulting in a radiographic loosening rate of 31%. Of the 35 shoulders, 4 were revised (survival rate of 88%), of which 2 due to symptomatic aseptic loosening.

CONCLUSIONS

Uncemented fixation of an all-polyethylene central peg bone-ingrowth glenoid was associated with satisfactory clinical and radiographic scores, and an acceptable revision rate at mid- to long-term follow-up. Despite initial bony osseointegration in the majority of cases, radiographic loosening over time remains a concern, potentially jeopardizing long-lasting fixation of this type of glenoid component when implanted in an off-label uncemented fashion.

Subscapularis integrity, function and EMG/nerve conduction study findings following reverse total shoulder arthroplasty

Background

During reverse total shoulder arthroplasty, the functionality of the subscapularis remains unknown. The purpose of this study was to determine the integrity and function of the repaired subscapularis after reverse total shoulder arthroplasty using ultrasound, electromyography (EMG), and nerve conduction studies (NCS) to assess postoperative tendon healing, muscle, and nerve function.

Materials and methods

Patients who underwent reverse total shoulder arthroplasty and repair with minimum 6-month follow-up were included in the study. Patient-reported outcome, physical examination, ultrasound examination of the subscapularis tendon, subscapularis EMG, and lower subscapular NCS were performed. In addition, contralateral subscapularis ultrasound, EMG, and lower subscapular nerve nerve NCS were performed to establish normative values (abnormal defined at >20% increased latency or >50% decreased amplitude). Phi coefficients of association and point biserial coefficients were used to correlate the ultrasound examination, EMG, and NCS results with the functional outcomes.

Results

A total of 20 patients were included. Four patients had abnormal but intact subscapularis tendons on ultrasound. Nine patients had abnormal lower subscapular NCS compared with the contralateral shoulder. All patients had normal subscapularis EMGs. No significant correlation was found between the ultrasound and NCS results. No significant correlations were found between the ultrasound or the NCS results and any of the independent outcome variables.

Conclusion

This study demonstrates that the subscapularis remains neurologically functional after reverse total shoulder arthroplasty, based on EMG and NCS findings. Although side-to-side differences in lower subscapular NCS were identified in 45% of the postoperative shoulders, these abnormalities did not correlate with functional outcomes.

Glenoid exposure in shoulder arthroplasty: the role of soft tissue releases

Background

The deltopectoral approach is commonly used in shoulder arthroplasty. Various soft tissue releases can be performed to obtain adequate glenoid exposure, but their effectiveness is not known. The purpose of this study was to (1) quantify the effects of various releases on the amount of glenoid surface area exposure and (2) determine if common soft tissue releases performed about the shoulder significantly improve exposure of the glenoid.

Methods

A standard deltopectoral approach was used on cadaveric shoulders (n=8) in the beach chair position. The releases performed were as follows: long head of biceps, pectoralis major tendon, inferior capsule, and posterior capsule. Following each release, a custom-designed jig was used to mark the exposed glenoid surface. The glenoid was then digitized using a 3D surface scanner to quantify the exposed surface area with each release.

Results

The mean glenoid surface area exposure prior to any releases was 57% (SD 8%). Following release of the long head of biceps, exposure increased to 69% (SD 10%). The exposed area was increased to 83% (SD 6%) with release of the pectoralis major, and 93% (SD 2%) with inferior capsule. The entire glenoid was exposed following posterior capsule release.

Conclusions

Release of the long head of biceps, pectoralis major, and inferior and posterior capsule all independently led to significant increases in glenoid surface exposure in the deltopectoral approach. Mean surface area exposed with all 3 releases was 93%. Although posterior capsular release improved exposure, the results of this study suggest that this is rarely necessary.

Innervation of the subscapularis: an anatomic study

Background

Successful healing of the subscapularis during anatomic total shoulder arthroplasty surgery is critical to optimize functional outcomes and avoid complications. The purpose of this study was to examine the upper and lower subscapularis nerve insertion in relation to the musculotendinous junction to estimate the risk of nerve injury. Our hypothesis was that arm position changes the risks to these nerves when exposing the anterior glenoid.

Methods

Twenty cadaveric shoulders were dissected, and the subscapular nerves were identified from the posterior cord of the brachial plexus to the muscle insertion. The nerve length from the origin to the muscle insertion and the distance to the myotendinous junction were measured in various shoulder positions including neutral, external, and internal rotation.

Results

The mean length of the upper subscapular nerve was 51.4 ± 12.8 mm; that of the lower subscapular nerve was 50.5 ± 14 mm. The mean distance from the insertion of the upper subscapular nerve to the myotendinous junction 53.0 ± 14.7 mm with external rotation, 38.5 ± 9.7 mm with neutral rotation, and 30.0 ± 9.2 mm with internal rotation. The mean distance from the lower subscapular nerve to the myotendinous junction was 44.5 ± 13.8 mm with external rotation, 31.9 ± 9.3 mm with neutral rotation, and 25.4 ± 8.8 mm with internal rotation. The internally rotated position placed these nerves closest to the glenohumeral joint.

Conclusion

The upper and lower subscapular nerves insert in the muscle belly close to the myotendinous junction, putting them at risk of iatrogenic injury. Care must be taken to avoid damage with retractor placement in the anterior glenoid neck as these nerves are at risk of compression or torsional injury.

Subscapularis Management in Total Shoulder Arthroplasty: Current Evidence Comparing Peel, Osteotomy, and Tenotomy

The optimal approach to management of the subscapularis in total shoulder arthroplasty (TSA) is controversial. Options include the subscapularis tenotomy, lesser tuberosity osteotomy (LTO), and peel. This review provides a summary of subscapularis anatomy and function, outcomes associated with subscapularis management options in TSA, and postoperative subscapularis deficiency. Based on the available literature, LTO appears to result in improved function and subscapularis integrity relative to tenotomy, while peel and LTO have generally led to equivalent outcomes. The highest level of evidence to date is derived from a randomized controlled trial that demonstrated that outcomes following peel and LTO were not significantly different. There is currently a paucity of high-quality evidence as most studies have consisted of small retrospective series with varying outcome measures. Furthermore, the optimal approach to establishing the diagnosis of subscapularis deficiency following TSA is unclear.

Outcomes of lesser tuberosity osteotomy in revision anatomic shoulder arthroplasty

BACKGROUND

Lesser tuberosity osteotomy (LTO) is a common surgical approach during anatomic shoulder arthroplasty. Outcomes of LTO have been shown to be similar to subscapularis tenotomy and peel techniques, but little is known about the outcomes of LTO during revision arthroplasty.

METHODS

This retrospective case series included 10 consecutive patients who underwent LTO during revision shoulder arthroplasty at a single institution from 2012 to 2016. Patients underwent a preoperative computed tomography scan to evaluate the lesser tuberosity bone stock. Demographic information, radiographic evidence of LTO healing, outcomes of range of motion, subscapularis strength, and visual analog scale pain scores were analyzed.

RESULTS

Revision total shoulder arthroplasty with LTO was performed for glenoid arthritis after hemiarthroplasty in 10 patients. Average age at surgery was 59.8 years, and no humeral stems were revised. Eight of 10 patients had prior subscapularis tenotomy. Average follow-up after revision surgery was 9.2 months. LTO union was documented in 80% and nondisplaced nonunion in 20%. At follow-up, 50% reported mild pain. Subscapularis strength testing was graded normal in 80% and weak in 20%. Average visual analog scale pain improved from 9.4 prerevision to 4.8 postrevision (P < .05). On average, range of motion improved in active forward elevation from 123° to 141° and remained unchanged in active external rotation from 42° to 42°.

CONCLUSION

Patients undergoing LTO during revision anatomic shoulder arthroplasty demonstrate successful LTO bony healing, improvement in pain, and improved forward elevation. In select patients not requiring humeral stem revision, LTO is a safe and effective surgical approach to subscapularis management during revision anatomic shoulder arthroplasty.

Lesser Tuberosity Osteotomy Outcomes After Anatomic Shoulder Arthroplasty in Patients With Atraumatic Avascular Necrosis

Introduction

Lesser tuberosity osteotomy (LTO) is an attractive option for subscapularis management during anatomic shoulder arthroplasty due to the biomechanical strength and reliable bone-to-bone healing. Patients with humeral head avascular necrosis (AVN) may have compromised bone healing, and the outcomes of LTO during AVN are unknown.

Methods

A retrospective consecutive case series of 6 patients with Cruess grade 4 or 5 humeral head AVN who underwent anatomic shoulder arthroplasty with LTO from 2010 to 2016 was performed. Postoperative radiographic evaluation for LTO healing at 6 months was analyzed, and clinical outcomes at latest follow-up, including range of motion (ROM), strength, and pain were studied.>

Results

Average age was 50.3 years. AVN was secondary to sickle cell in 1 patient, steroid use for systemic lupus erythematosus in 4, and chronic alcoholism in 1. By 6 months after arthroplasty, 100% had radiographically united and healed LTO. Patients averaged 140 ± 21° of active forward elevation and 42 ± 7° of active external rotation. Patients reported an improvement in visual analogue scale pain from 8.3 preoperatively to 3.8 postoperatively. All patients had a normal abdominal compression test. No patients required revision surgery.

Conclusion

The use of LTO during anatomic shoulder arthroplasty for AVN has an excellent bony healing rate with improvements in pain, ROM, and strength. The diseases that cause humeral head AVN do not negatively influence LTO healing outcomes during anatomic shoulder replacement.

Level of Evidence

IV Case Series

Outcomes for subscapularis management techniques in shoulder arthroplasty: a systematic review

BACKGROUND

This systematic review aims to synthesize published data for the most common subscapularis takedown and repair to compare outcomes in the setting of shoulder arthroplasty.

METHODS

Searches of MEDLINE and Cochrane Library databases identified studies that reported clinical or radiologic outcomes for subscapularis management in the setting of shoulder arthroplasty. Comparisons included musculotendinous integrity, subscapularis testing and strength, shoulder range of motion, and functional outcome scores.

RESULTS

The 14 included studies reported considerable variability in techniques, outcomes, and musculotendinous integrity. Lesser tuberosity osteotomy (LTO) demonstrated better healing rates (93.1%) than subscapularis peel (SP; 84.1%) and midsubstance tenotomy (ST; 75.7%), although not significantly different. A statistically significant increase in fatty infiltration was found after surgery across techniques, and range of motion and strength were similar. Mean rates of normal results for belly-press and lift-off tests were uniformly better for LTO (79.1% and 80.7%) over ST (66.7% and 65.6%), although multiple studies showed poor correlation between subscapularis functional testing and musculotendinous integrity. Mean total Constant and Western Ontario Osteoarthritis of the Shoulder Index outcome scores were slightly better for LTO (77.6, 84.2) than for SP (71.8 and 82.7). Mean American Shoulder and Elbow Surgeons scores favored the ST group (80.8) over the SP (79.1) and LTO (73) groups.

CONCLUSIONS

The data suggest no significant differences exist for postoperative musculotendinous integrity or clinical outcomes among the subscapularis management techniques in shoulder arthroplasty. Subscapularis healing and integrity appear to favor the lesser tuberosity takedown method. Additional randomized controlled comparisons with long-term follow-up are needed to more effectively compare these surgical approaches.

Glenoid exposure in total shoulder arthroplasty

Glenoid exposure is agreed to be a difficult step, but is also a key step in total shoulder arthroplasty, both anatomic and reverse. It conditions unhindered use of the ancillary instrumentation and thus correct glenoid component positioning. The main stages comprise arthrotomy, by opening the rotator cuff, humeral head cut, and inferior glenohumeral release, enabling shifting of the humerus and good exposure of the glenoid cavity. The two main approaches are deltopectoral and anterosuperior transdeltoid. Using the deltopectoral approach, arthrotomy is performed through the subscapularis muscle, by various techniques. This approach enables extensive inferior glenohumeral release and thus an approach to the inferior apex of the glenoid cavity, which is a key area for glenoid implant positioning. The main drawbacks are postoperative shoulder instability and limited access to the posterior part of the glenoid in case of significant retroversion. Moreover, subscapularis healing is uncertain, which can impair the clinical outcomes, with risk of glenoid component loosening. Advantages, on the other hand, include the fact that it can be implemented in all cases, even the most difficult ones, and that the deltoid muscle is respected. The transdeltoid approach has the advantage of being simple, providing direct exposure of the glenoid cavity through a rotator cuff tear after passing through the deltoid. It is therefore especially indicated for reverse prosthesis in case of rotator cuff tear, and in traumatology. However, the approach to the inferior part of the glenoid cavity can be restricted, with insufficient exposure and a risk of glenoid component malpositioning (superior tilt). The preoperative assessment is essential, to detect at-risk situations such as severe stiffness and anticipate difficulties in glenoid exposure.

Management of the subscapularis tendon during total shoulder arthroplasty

Use of total shoulder arthroplasty has significantly increased during the past decade. For anatomic total shoulder arthroplasty, controversy exists regarding the best technique for detachment and repair of the subscapularis tendon. Options include tendon tenotomy, peel, lesser tuberosity osteotomy, and even subscapularis-sparing techniques. Inadequate healing of the subscapularis tendon can lead to postoperative pain, weakness, and instability. This review discusses the subscapularis pathoanatomy, different techniques for releasing and repairing the tendon, and reports biomechanical and clinical outcomes for each technique after total shoulder arthroplasty.

Evaluation of the muscle volumes of the transverse rotator cuff force couple in nonpathologic shoulders

BACKGROUND

The balance between the subscapularis muscle and the infraspinatus/teres minor muscles, often referred to as the rotator cuff transverse force couple (TFC), has been proposed to be a critical component for normal shoulder function. The relationship between the muscle volume and the power means that TFC can be evaluated with the measurement of the muscle volume of the subscapularis muscle and the infraspinatus/teres minor. The aim of this study is to evaluate an innovative computed tomography (CT)-based technique to measure the muscle volume and to evaluate if there is a significant difference between muscle volumes of both the subscapularis muscle and the infraspinatus/teres minor in nonpathologic shoulders.

MATERIALS AND METHODS

CT images of 27 shoulders (21 patients) with a full scapula and a proximal humeral head were evaluated. Two volume masks (subscapularis and infraspinatus/teres minor) were calculated on the basis of the assigned muscle contours on the transverse slices. The intraobserver and interobserver correlation coefficient was calculated.

RESULTS

The intraobserver and interobserver correlation coefficient was excellent. The correlation between the anterior and posterior part of the TFC was strong. There was no significant difference between the volume masks.

CONCLUSIONS

Muscle volume of the TCF can be quantified using CT images. In nonpathologic shoulders, there is no significant difference between the muscle volume of the anterior (subscapularis) and posterior part (teres minor/infraspinatus) of the TFC.

Soft tissue balancing in total shoulder replacement

Total shoulder arthroplasty is now capable of recreating near anatomic reproduction of native bony shoulder anatomy, but the function and longevity of anatomic shoulder replacement is dependent on a competent soft tissue envelope and adequate motoring of all musculo-tendinous units about the shoulder. Balancing the soft tissues requires understanding of the anatomy and pathology, as well as technical skills. The advent of reverse shoulder biomechanics has brought with it special requirements of understanding of the soft tissue elements still left in the shoulder despite major rotator cuff deficiency.

Fully uncemented glenoid component in total shoulder arthroplasty

BACKGROUND

Loosening of the glenoid component remains the most common problem in total shoulder arthroplasty. It has been described that the round-backed, all-polyethylene components with cemented peg fixation perform better biomechanically and clinically than flat-backed, metal-backed, or keeled components. However, side effects of cementing have been described. We hypothesized that cementing of a specific type of all-polyethylene glenoid component with 3 peripheral pegs and 1 central anchor peg is not necessary to obtain good clinical and radiologic results.

MATERIALS AND METHODS

Thirty-four shoulders (34 patients), with a mean follow-up of 28.3 months, were evaluated clinically with the Constant-Murley score and the SF-12 Health Survey score. The fixation of the glenoid component was evaluated with computed tomography scan.

RESULTS

The Constant-Murley score increased from 40.2 points (range, 13-73 points) preoperatively to 72 points (range, 54-93 points) postoperatively. The SF-12 Physical Component Summary score was 45, and the SF-12 Mental Component Summary score was 50. No signs of loosening were seen around the pegs or glenoid in 30 shoulders. Signs of loosening were seen around the central anchor peg and the peripheral pegs in 4 shoulders. There was no statistical difference between the clinical outcome of patients with and without signs of loosening.

CONCLUSION

The clinical and radiologic evaluation of an uncemented all-polyethylene glenoid is promising, with good clinical results and with no signs of loosening in 88% of the patients on computed tomography scans.

Importance of the subscapularis muscle after total shoulder arthroplasty

BACKGROUND

The rotator cuff muscles are the main stabilizer of the glenohumeral joint. After total shoulder arthroplasty using anterior approaches, a dysfunction of the subscapularis muscle has been reported. In the present paper we tested the hypothesis that a deficient subscapularis following total shoulder arthroplasty can induce joint instability.

METHODS

To test this hypothesis we have developed an EMG-driven musculoskeletal model of the glenohumeral joint. The model was based on an algorithm that minimizes the difference between measured and predicted muscular activities, while satisfying the mechanical equilibrium of the glenohumeral joint. A movement of abduction in the scapular plane was simulated. We compared a normal and deficient subscapularis. Muscle forces, joint force, contact pattern and humeral head translation were evaluated.

FINDINGS

To satisfy the mechanical equilibrium, a deficient subscapularis induced a decrease of the force of the infraspinatus muscle. This force decrease was balanced by an increase of the supraspinatus and middle deltoid. As a consequence, the deficient subscapularis induced an upward migration of the humeral head, an eccentric contact pattern and higher stress within the cement.

INTERPRETATION

These results confirm the importance of the suscapularis for the long-term stability of total shoulder arthroplasty.