Friday, November 23, 2012

Subscapularis Release in Shoulder Replacement Determines Structural Muscular Changes CORR

Subscapularis Release in Shoulder Replacement Determines Structural Muscular Changes CORR

This is an interesting paper in that it considers the effect of detachment and reattachment of the subscapularis via bone block on the structure and function of the muscle in 37 shoulders having total shoulder arthroplasty by a highly experienced surgeon. The authors remarked that the bone block detachment method allowed excellent access to the glenoid for reaming and all lesser osteotomies healed. One patient had a greater tuberosity fracture and one a large hematoma - these did not appear to affect the outcome.

Preoperatively, 60% of the shoulders had fatty atrophy (47% grade 1 fatty atrophy and 13% grade 2). At a minimum of 13 months (mean 18 mo) after shoulder arthroplasty 56% of the muscles showed fatty degeneration (39% grade 1, 14% grade 2 and 3% grade 3).  The cross sectional area of the muscle was reduced by 13%. These findings appeared to be of clinical significance: the post operative Constant-Murley score correlated with the fatty degeneration of the subscapularis muscle (r = -0.496; p = 0.002)  and the ratio of the anterior (subscapularis) to posterior (intraspinatus-teres minor) cross sectional area (r = -0.600; p<0.001).

Many approaches have been described for the takedown and repair of the subscapularis for shoulder arthroplasty, including tendon detachment from bone, tenotomy and lesser tuberosity osteotomy. Each method requires attention to the technique of the procedure; each has its own set of risks; and each has an effect on access to the glenoid. These authors report favorable results with what they refer to as a "C-block osteotomy" of the lesser tuberosity. They have provided some benchmarks against which other methods can be compared with respect to complications, technical difficulty, healing rates, muscle structure, and clinical function.

Perhaps the most important message from this paper is that the health of the subscapularis does matter in terms of the quality of the result. In our efforts to optimize the post-surgical health of this muscle-tendon-bone construct, we must consider its preoperative status, the technique of detachment and reattachment, the degree and method of soft tissue release, early protection/mobilization and the subsequent rehabilitation.


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