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    The Over-the-Top Subscapularis Repair Technique for Reverse TSA

    With this novel surgical technique for subscapularis repair during RSA, the superior two thirds of the subscapularis tendon is repaired to the anterior aspect of the greater tuberosity, which is lateral to the bicipital groove and above the glenosphere center of rotation compared with the standard subscapularis repair.

    Authors

    Jorge Gil, MD; Clay Townsend, BS; Alexander T. Greene, BS; Thomas W. Wright, MD; Bradley S. Schoch, MD; Matthew A. Hamilton, PhD; Joseph J. King, MD

    Introduction

    The frequency of reverse total shoulder arthroplasty (RSA) has increased significantly following the 2003 approval of the first RSA implant by the US Food and Drug Administration. Since then, various studies have been done to assess optimal techniques for increasing stability, refining biomechanics, and improving patient-reported outcomes. 

    Subscapularis management in RSA is commonly debated. [1-3] One of the more controversial issues is whether to reattach the subscapularis tendon to its anatomic insertion on the lesser tuberosity or to leave the subscapularis as a tenotomy. Vourazeris et al [3] compared subscapularis tenotomy with repair after RSA and reported similar results with respect to clinical outcome scores, range of motion, strength, and complications at mean 3-year follow-up. The subscapularis is recommended to be repaired when using the traditional medialized Grammont-style prosthesis to avoid instability. [4,5]

    In this article, we present a novel surgical technique for subscapularis repair during RSA, called the over-the-top subscapularis repair. With this technique, the superior two thirds of the subscapularis tendon is repaired to the anterior aspect of the greater tuberosity, which is lateral to the bicipital groove and above the glenosphere center of rotation compared with the standard subscapularis repair (Figure 1).

     

    Figure 1. The over-the-top subscapularis repair (left) versus the standard subscapularis repair (right) in a medial glenoid lateral humerus reverse total shoulder arthroplasty design.

    This innovative technique provides a biomechanical abduction advantage compared with standard subscapularis repair techniques. [2] The advantage of the over-the-top subscapularis repair technique is based on the following principles:

    • Converting the subscapularis from a shoulder adductor to an abductor
    • Decreasing the subacromial dead space following RSA
    • Increasing anterior shoulder stability

    Operative Technique

    • A standard deltopectoral approach is used with a subscapularis peel, followed by an inferior capsular release.
    • Routine glenohumeral dislocation, humeral osteotomy, and preparation of the glenoid and humeral components are performed.
    • During glenoid exposure, release of all soft tissue from the base of the coracoid laterally and distally is performed with electrocautery to remove any subscapularis and rotator interval adhesions, as well as to completely release the coracohumeral ligament.
    • After reduction of the final prosthesis (Figure 2), completion of the 270° subscapularis release is performed using blunt dissection (typically digital dissection) along the posterior, superior, and anterior borders of the subscapularis tendon extending medial to the coracoid base. Inferior dissection is not performed to avoid axillary nerve injury.
    • The superior release of all soft tissue connecting the subscapularis tendon to the glenoid and the coracoid is important in adequately releasing the superior glenohumeral ligament and the coracohumeral ligament, [6] allowing for appropriate subscapularis excursion.

    Figure 2. Final reverse total shoulder arthroplasty after reduction but prior to subscapularis repair.

    • Any remaining coracohumeral ligament or subscapularis coracoid adhesion is carefully released using blunt dissection or a periosteal elevator.
    • A Kocher or Alice clamp is attached to the upper and lower aspects of the subscapularis tendon (Figure 3).

    Figure 3. Kocher attached to the upper and lower aspects of the subscapularis tendon.

    • A blunt retractor (ie, Army-Navy retractor) is used to protect the conjoint tendon and the structures anterior to the subscapularis tendon during the subscapularis split.
    • The delineation of the upper two thirds and lower one third of the tendon is identified for the tendinous portion of the subscapularis tendon only (evaluated with a combination of direct visualization and palpation). This generally leaves about 1.5 cm of the upper subscapularis tendon remaining for repair. For smaller patients, the split can be made slightly more distally, with the goal of leaving a minimum of 1 cm of the upper subscapularis tendon to repair.
    • Using electrocautery, the subscapularis tendon is split horizontally at the junction of the upper two thirds and the lower one third of the tendon (Figure 4).

    Figure 4. Subscapularis tendon split horizontally at the junction of the upper two thirds and lower one third of the tendon.

    • The tenotomy is extended as medially as possible into the subscapularis muscle belly under direct visualization (Figure 5).

    Figure 5. Tenotomy extended as medially as possible into the subscapularis muscle belly under direct visualization.

    • The lateral aspect of the lower one third of the subscapularis tendon is then excised as medially as the soft tissue will allow under direct visualization.
    • This lower one third tenotomy is performed to improve the biomechanical abduction advantage of the remaining subscapularis tendon, as well as to allow improved excursion so that it can be repaired to the over-the-top position.
    • An assessment of subscapularis mobility is performed following the previously mentioned soft tissue release and lower subscapularis split and excision.
    • The remaining upper two thirds of the subscapularis tendon is considered repairable if it can be reduced with mild force to the anterior greater tuberosity with the humerus at 0° of abduction and 20° of external rotation.
    • The subscapularis tendon is then repaired with interrupted non-absorbable sutures in a figure 8 fashion to either an intact anterior supraspinatus tendon, or to a remnant of the supraspinatus tendon on the anterior greater tuberosity (Figure 6).

    Figure 6. Subscapularis tendon repaired with interrupted nonabsorbable sutures to an intact anterior supraspinatus tendon or remnant of the supraspinatus tendon on the anterior greater tuberosity.

    • If no soft tissue remains on the anterior greater tuberosity, the subscapularis can be repaired through small drill holes on the anterior-most aspect of the greater tuberosity just lateral to the bicipital groove.
    • The repair is performed with minimal tendon-tendon or tendon-bone overlap to avoid excessive tension on the subscapularis tendon repair.

    Discussion

    As the number of RSAs increases and the indications for the procedure expand, patient are likely to have higher expectations for the outcome in terms of return to function and relief of pain, therefore placing higher and higher demands on RSA implants. Techniques to improve the biomechanics of the procedure will continue to evolve to keep pace, driven by the goal of achieving better patient outcomes.

    Subscapularis management is a modifiable factor that has the potential to change patient function after RSA, given that the subscapularis is the largest and strongest of the rotator cuff muscles. [7] Ignoring subscapularis repair during RSA could lead to: [8]

    • Increased risk of infection due to the joint space not being closed
    • Decreased glenohumeral stability
    • Imbalance in the force couple of posterior and anterior rotator cuff muscles

    Biomechanical studies have shown that subscapularis repair to its anatomic location after RSA causes an adduction moment, which counteracts the deltoid abduction forces. [9-13] One biomechanical study using a lateral glenoid medial humerus (LGMH) implant showed that only the upper subscapularis tendon was an abductor after 35° of abduction, with the middle and lower subscapularis tendons being adductors after RSA. [9]

    Another biomechanical study showed that subscapularis repair to the lesser tuberosity increased the force required by the deltoid and posterior cuff during shoulder range of motion in RSA. [13] Eno et al [10] similarly demonstrated that when the subscapularis is repaired to its native position, it acts as an antagonist to the deltoid.

    The over-the-top subscapularis repair has been shown to impart a biomechanical abduction advantage over the standard repair in all 3 RSA designs tested in a computer model study. [2] This concept is supported by Eno et al [10] in which, using a medial glenoid lateral humerus (MGLH) RSA virtual shoulder model, they showed that repairing the subscapularis on the superior aspect of the lesser tuberosity decreased the subscapularis adduction moment when compared with the standard repair or repair on the inferior aspect of the lesser tuberosity. The biomechanical advantages of the over-the-top subscapularis repair are the possibility of improving abduction strength and range of motion and decreasing complications related to deltoid muscle strain.

    Some surgeons are concerned that the standard subscapularis repair to the lesser tuberosity in RSA may lead to weak external rotation, especially in the setting of deficient external rotators. However, this has not been validated in the literature. Vourazeris et al [3] showed no difference in internal and external rotation when evaluating 202 patients with and without subscapularis repair using an MGLH design. Friedman et al [1] evaluated the largest RSA group, comparing subscapularis repair versus no repair with an MGLH design. They found that internal and external rotation were better in the subscapularis repair group, but internal rotation did not exceed the minimally clinical important difference.

    Collectively, these studies call into question the concern for weakness or limited external rotation when the subscapularis tendon is repaired following primary RSA.

    The functional outcome benefit of subscapularis repair after RSA is not clear in the current literature. One study showed greater improvements in forward elevation when the subscapularis was repaired, but no difference in ASES or Penn Shoulder scores. [14] Another study using an LGMH design found that RSAs with subscapularis repairs had smaller improvements in ASES scores compared with RSAs without subscapularis repair. [5] In addition, 2 large studies using an MGLH RSA design showed no difference in range of motion or outcome scores with and without subscapularis repair. [1,3]

    Because these studies are evaluating outcomes of the standard subscapularis repair on the lesser tuberosity, it is possible that changing the subscapularis repair location may add a biomechanical benefit, leading to better functional and patient-reported outcomes.

    Instability rates have been reported between 0.5% and 5% after primary RSA. [1,3,5,14-19] Subscapularis repair is a potentially modifiable risk factor that may decrease the risk of instability after RSA. One study that included multiple designs reported that lack of subscapularis repair was an independent risk factor for instability in 119 RSAs. [20] Some studies have shown that a lack of a subscapularis repair is associated with an increased risk of instability after RSA, [15,17,19] while others have not shown significantly increased rates of shoulder instability in patients with subscapularis repair compared with those who did not have subscapularis repair. [3,11,16]

    A recent meta-analysis that included several of the aforementioned studies showed decreased dislocation rates with subscapularis repair (0.7%, 5/723) compared with no subscapularis repair (4.1%, 24/583). [4] In addition, the pooled comparison found no difference in dislocation rates with subscapularis repair status when using a lateralized center of rotation design, but a significant difference in medialized designs. [4]Several authors have suggested that subscapularis repair does not affect the dislocation rates in RSA designs that lateralize the humerus or glenoid components. [3,21,22]

    If the over-the-top subscapularis repair adds a biomechanical benefit in abduction, as well as a stability benefit as seen in some subscapularis studies, then it is likely beneficial in RSA.

    The biomechanical benefits of the over-the-top subscapularis repair may impart a similar clinical benefit. In one author’s experience (JJK), the subscapularis can be repaired to the over-the-top position in approximately 75% of cases (the majority using an onlay medial glenoid lateral humeral RSA design), including cases in which there is a partial subscapularis tendon tear. This includes all indications for primary RSA, excluding acute proximal humerus fractures. In addition, there has not been a problem with limited or weak external rotation or any known complications after the over-the-top subscapularis repair.

    Clinical research on this technique is ongoing, with the intent of publishing the clinical results.

    Conclusion

    The over-the-top subscapularis repair is a feasible option for subscapularis management during RSA and imparts a biomechanical abduction advantage compared with the standard subscapularis repair.

    Author Information

    Jorge Gil, MD; Thomas W. Wright, MD; and Joseph J. King, MD, are from the Department of Orthopaedics and Rehabilitation at the University of Florida in Gainesville. Clay Townsend, BS, is from the University of Central Florida in Orlando. Alexander T. Greene, BS, and Matthew A. Hamilton, PhD, are from Exactech, Inc., Gainesville, Florida. Bradley S. Schoch, MD, is from Mayo Clinic, Jacksonville, Florida.

    Disclosures: Dr. Gil and Mr. Townsend have no disclosures relevant to this article. Mr. Green and Dr. Hamilton have disclosed that they are employees of Exactech, Inc. Dr. Wright has disclosed that he is a paid consultant for and receives royalties from Exactech, Inc. Dr. Schoch has disclosed that he is a paid speaker for DJO and that he receives royalties from and has a consultancy agreement with Exactech, Inc. Dr. King has disclosed that he is a consultant for Exactech, Inc.

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