Biomechanical effects of rotator interval closure in shoulder arthroplasty

The Lesser Tuberosity Osteotomy Exposure for Total Shoulder Arthroplasty

Background

The lesser tuberosity osteotomy (LTO) is a commonly employed technique for mobilizing the subscapularis tendon during anatomic total shoulder arthroplasty that is performed through a deltopectoral approach. During this procedure, the lesser tuberosity is osteotomized from the proximal aspect of the humerus while maintaining the strong tendon-to-bone attachment of the subscapularis tendon insertion. After the shoulder arthroplasty is performed, the lesser tuberosity osseous fragment is then resecured to the proximal aspect of the humerus with heavy nonabsorbable suture, which allows for direct bone-to-bone compression and healing of the fragment to the proximal aspect of the humerus. This technique may be utilized for subscapularis tendon mobilization in any primary and some revision anatomic total shoulder arthroplasty procedures.

Description

The procedure is performed as follows. (1) Preoperative planning is performed. (2) The patient is positioned in the semi-upright beach-chair position, and the shoulder girdle and the upper arm are prepared and draped. (3) A standard deltopectoral approach is utilized. (4) A tenotomy of the long head of the biceps tendon is performed, exposing the bicipital groove. (5) An LTO is made from lateral to medial with an oscillating saw and is completed with use of an osteotome. (6) The remaining inferior portion of the subscapularis and capsule are released off of the humerus. (7) The total shoulder arthroplasty is completed up to the point of implantation of the final humeral component. (8) Four drill-holes are made lateral to the bicipital groove and osteotomy site. (9) Heavy nonabsorbable sutures, with or without cerclage wires, are passed from lateral to medial around the humeral stem and passed medial to the osteotomy fragment through the insertion of the subscapularis tendon. (10) The sutures are then tensioned and tied with the arm in 30° of external rotation. (11) The wound is irrigated, dried, and closed in layered fashion.

Alternatives

The most commonly accepted alternative approaches include the subscapularis tenotomy and subscapularis peel techniques.

Rationale

The LTO approach technique was developed to take advantage of bone-to-bone healing and to address concerns regarding poor tendon-to-tendon or tendon-to-bone healing in the subscapularis tenotomy and subscapularis peel exposure techniques, respectively.

Expected Outcomes

Based on numerous published studies, excellent clinical results are achieved with anatomic total shoulder arthroplasty. When comparing surgical techniques involving the subscapularis in Level-I, randomized controlled trials, no significant differences exist among clinical outcomes, range of motion, or strength between the different techniques.

Important Tips

Three-dimensional preoperative templating software allows for the anticipation of potential operative challenges, the prediction of implant limitations, and more accurate assessment of abnormal glenoid morphology and wear patterns.An articulating arm positioner can be helpful in controlling the arm position without the need for an extra surgical assistant.The goal thickness of the LTO is 10 mm. If the osteotomy is made too thin, there is a risk that the repair sutures cut through the lesser tuberosity fragment, leading to subscapularis repair failure.Releasing the capsule from the subscapularis is a critical step to ensure adequate tendon excursion for later repair and restoration of external rotation in arthritic shoulders. However, careful attention must be directed to the position and orientation of the axillary nerve in order to avoid iatrogenic injury during this critical step.Creating the drill-holes lateral to the bicipital groove takes advantage of the very strong and dense bone in that area of the proximal aspect of the humerus, enhancing the integrity of the repair.The tension band suture is critical to aid in further compression of the LTO fragment when the arm is brought into external rotation.Closing the rotator interval substantially increases the strength of the subscapularis repair; however, the closure of the interval must be made with the arm in at least 30° of external rotation in order to avoid iatrogenic motion restriction.Using interrupted nonabsorbable sutures to close the deltopectoral interval at the conclusion of the procedure is helpful in the event that any revision procedure is needed because these sutures will guide the revision surgeon toward making the deltopectoral approach in the correct interval.

Acronyms and Abbreviations

LTO = lesser tuberosity osteotomyROM = range of motionASES = American Shoulder and Elbow SurgeonsWOOS = Western Ontario Osteoarthritis of the Shoulder indexVAS = visual analog scaleSF-36 = 36-Item Short Form Health SurveySST = Simple Shoulder TestDVT = deep-vein thrombosis.

Rotator cable and rotator interval: anatomy, biomechanics and clinical importance

The rotator cable and rotator interval are among the most recent topics of interest in current shoulder literature. Most of the research has been published in the last two decades and our understanding about the importance of these anatomical structures has improved with biomechanical studies, which changed the pre- and intra-operative approaches of shoulder surgeons to rotator cuff tears in symptomatic patients.

The rotator cable is a thick fibrous bundle that carries the applied forces to the rotator cuff like a ‘suspension bridge’. Tears including this weight-bearing bridge result in more symptoms. On the other hand, the rotator interval is more like a protective cover consisting of multiple layers of ligaments and the capsule rather than a single anatomical formation like the rotator cable.

Advances in our knowledge about the rotator interval demonstrate that even basic anatomical structures often have greater importance than we may have understood. Misdiagnosis of these two important structures may lead to persistent symptoms.

Furthermore, some distinct rotator cuff tear patterns can be associated with concomitant rotator interval injuries because of the anatomical proximity of these two anatomical regions. We summarize these two important structures from the aspect of anatomy, biomechanics, radiology and clinical importance in a review of the literature.

Cite this article: EFORT Open Rev 2019;4:56-62. DOI: 10.1302/2058-5241.4.170071.

Lesser Tuberosity Osteotomy in Anatomic Total Shoulder Arthroplasty

The deltopectoral exposure has earned the reputation as the “workhorse” approach to the shoulder. Due to the reproducible anatomy and its extensile nature, there is little debate when considering exposure in total shoulder arthroplasty (TSA). Despite this consensus, there is still significant variability in management of the subscapularis. Several repair techniques including a subscapularis tenotomy, peel, and lesser tuberosity osteotomy (LTO) have been developed to ensure healing and optimize function. This article focuses on performing a LTO in anatomic TSA. We will review the surgical technique and advantages in exposure in addition to biomechanical and clinical outcomes.

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.