Sunday, June 14, 2015

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

Total shoulder arthroplasty using a subscapularis-sparing approach: a radiographic analysis.

These authors conducted a randomized trial to compare the incidence of humeral head malpositioning, incorrect sizing, and residual osteophytes on postoperative radiographs after a subscapularis-sparing total shoulder compared with the traditional approach. The study included 96 patients of which 50 had a subscapularis tenotomy 7 mm medial to the insertion and 46 had a subscapularis-sparing approach in which a small window was used to resect the inferior capsule and excise the inferior osteophytes and a rotator interval window used to perform the arthroplasty. In seven patients (15%) the subscapularis-sparing approach was abandoned because of inadequate exposure.

While many of the postoperative radiographic parameters regarding the humerus were similar among the two groups, significantly more postoperative osteophytes (29%) were noted in the subscapularis-sparing TSA group. The authors concluded "Although anatomic restoration of the shoulder can be accomplished using subscapularis-sparing TSA, retained osteophytes and significant mismatch of the humeral head diameter raise concerns regarding long-term outcomes."

The concern about the subscapularis-sparing approach is that exposure may be limited so that an optimal arthroplasty cannot be performed. This paper evaluates the humeral side of the arthroplasty, finding that even with the addition of an inferior 'window', inferior humeral osteophytes remained at "Pooh Corner" in 30% of the cases. They did not access the adequacy of the glenoid side of arthroplasty, but the radiograph of a case with subscapularis-sparing (Figure 4) shows not only retained humeral osteophytes, but also radiolucent lines around a keeled glenoid component.

In that glenoid component failure is an important cause of failed total shoulder arthroplasty and in that glenoid exposure is the key to an optimal prosthetic glenoid arthroplasty, compromise in exposure should be avoided.

The risk of subscapularis failure can be minimized as explained in this link.

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