Biomechanical Effect of Thickness and Tension of Fascia Lata Graft on Glenohumeral Stability for Superior Capsule Reconstruction in Irreparable Supraspinatus Tears.
PURPOSE To investigate the effects of graft length and thickness on shoulder biomechanics after superior capsule reconstruction. METHODS Subacromial peak contact pressure and glenohumeral superior translation were measured at 0deg, 30deg, and 60deg of glenohumeral abduction in 8 fresh frozen cadaveric shoulders under 5 conditions: (1) intact shoulder; (2) irreparable supraspinatus tendon tear, (3) superior capsule reconstruction with a fascia lata allograft 4 mm thick and 15 mm longer than the distance from the superior glenoid to the lateral edge of the greater tuberosity, as determined during placement at 30deg of glenohumeral abduction; (4) superior capsule reconstruction with a fascia lata allograft 8 mm thick and with the same 15 mm relative length determined at 10deg of glenohumeral abduction, and (5) superior capsule reconstruction with a fascia lata allograft 8 mm thick and with the 15 mm relative length determined at 30deg of glenohumeral abduction. To investigate the effect of graft thickness, we compared the data from conditions 1, 2, 3, and 5. To assess the effect of graft length, we compared conditions 1, 2, 4, and 5. RESULTS With superior capsule reconstruction using a 4 mm graft, subacromial peak contact pressure (but not superior translation) was significantly lower than with irreparable supraspinatus tears (at 0deg abduction: 259% decrease; P .0002; at 30deg abduction: 113% decrease; P .01) The superior capsule reconstruction using an 8 mm graft significantly decreased both subacromial peak contact pressure (at 0deg abduction: 246% decrease, P .0002; at 30deg abduction: 158% decrease; P .0008; at 60deg abduction: 57% decrease; P .04) and superior translation (at 0deg abduction: 135% decrease; P .02; at 30deg abduction; 130% decrease; P .004) Graft length with placement at 10deg glenohumeral abduction was 5 mm greater than that at 30deg abduction. The 8 mm superior capsule reconstruction performed at 10deg or 30deg of glenohumeral abduction significantly decreased subacromial peak contact pressure (placement at 10deg and 30deg: 0deg abduction, P .0002 and .0002, respectively; 30deg abduction, P .0004 and .0005, respectively; 60deg abduction, P .04 and .04, respectively) and superior translation (placement at 10deg and 30deg; 0deg abduction, P .04 and .02, respectively; 30deg abduction, P .02 and .004, respectively) compared with irreparable supraspinatus tears. CONCLUSIONS Superior capsule reconstruction normalized the superior stability of the shoulder joint when the graft was attached at 10deg or 30deg of glenohumeral abduction. An 8 mm thick graft of fascia lata had greater stability than did a 4 mm thick graft. CLINICAL RELEVANCE Grafts 8 mm thick and attached at 15deg to 45deg of shoulder abduction (equal to 10deg to 30deg of glenohumeral abduction) biomechanically restore shoulder stability during superior capsule reconstruction using fascia lata.
Arthroscopy the journal of arthroscopic related surgery official publication of the Arthroscopy Association of North America and the International Arthroscopy Association