Monday, March 6, 2017

How should the subscapularis be managed in total shoulder arthroplasty?

Lift-off Test Results After Lesser Tuberosity Osteotomy Versus Subscapularis Peel in Primary Total Shoulder Arthroplasty

These authors conducted a retrospective cohort study of 90 primary anatomic total shoulder (TSA) procedures performed with either a subscapularis peel (SP) or a lesser tuberosity osteotomy (LTO) from 2002 to 2010. Procedures performed after 2007 had a LTO (44) whereas those before 2007 had a SP (46).

The authors used the 'lift off test' as their primary outcome measure, recognizing that while this assessment can be a highly specific and sensitive test of subscapularis function, "it is difficult to perform correctly."

Their lift-off test results plotted against the ordinal sequence of patients. Abnormal results are noted with a vertical line. Procedures 1 to 46 were performed with subscapularis peel. Procedures 47 to 90 were performed with lesser tuberosity osteotomy.

The results of their multivariate analysis is shown below, showing that in their patients, workers' compensation insurance, subscapularis peel, and smoking had the highest odds ratios of an abnormal lift off test.

The authors point out the limitations of this study:  different surgical techniques were employed between the two groups, different implants were used in the two groups, the two groups of procedures were not performed during the same time period, and the followup interval was twice as long for the SP group (5.6 vs 2.7 years).

They include a summary of some of the prior articles on the subject:

Comment: We avoid lesser tuberosity osteotomy because it can compromise the fixation of the humeral component in the metaphysis and obligates sacrifice of the long head tendon of the biceps (we are not routine 'biceps killers').

Our surgical approach involves a careful peel of the subscapularis tendon from the lesser tuberosity with attention to preserving the integrity of the biceps tendon and a 360 degree release of the capsule from the glenoid to resolve limitation of external rotation. By retaining the capsule on the deep surface of the tendon, the strength of the repair is enhanced.

At the conclusion of the case, drill holes are placed through good bone at the margin of the neck cut and six sutures of #2 non-absorbable suture are passed through these holes.

 These sutures are then passed through the tendon edge and tied securely.

A principal cause of post operative subscapularis failure is the overzealous and premature stretching of external rotation or premature initiation of internal rotation strengthening as explained in this post:
Rehabilitation after shoulder arthroplasty - cautions!

Our approach is to limit external rotation stretching to zero degrees (the hand shake position) and avoid internal rotation strengthening exercises for at least 3 months after surgery. We also caution patients about the risk of events that may suddenly externally rotate the shoulder such as a fall or a sudden pull on the arm from a leashed dog.

Other related posts are listed below:

Subscapularis failure after arthroplasty - evaluation and management

The biomechanics of subscapularis repair - all sutures are not equal!

Subscapularis in shoulder arthroplasty

Shoulder joint replacement arthroplasty - spare the subscapularis, spoil the arthroplasty?

How well does the subscapularis work after total shoulder arthroplasty? ?Hazards of inter scalene block?

Failure of lesser tuberosity osteotomy in total shoulder joint replacement - a cautionary tale