TYPE II SLAP LESIONS: A STUDY OF THE BIOMECHANICAL PROPERTIES OF THE SUPERIOR LABRAL COMPLEX AND ASSESSMENT OF SUTURE REPAIR

Abstract

We present a biomechanical cadaveric study investigating the effect of type II Superior Labrum Anterior Posterior (SLAP) lesions on the load-deformation properties of the Long Head of Biceps (LHB) and labral complex. We also report our assessment of whether repair of the type II SLAP lesion restored normal biomechanical properties to the superior labral complex.

Using a servo-controlled hydraulic material testing system (Bionix MTS 858, Minneapolis, MA), we compared the load-deformation properties of the LHB tendon with:

1. the LHB anchor intact;

2. a type II SLAP lesion present;

3. following repair with two different suture techniques (mattress versus ‘over-the-top’ sutures).

Seven fresh-frozen, cadaveric, human scapulae were tested. We found that the introduction of a type II SLAP lesion significantly increased the toe region of the load deformation curve compared to the labral complex with an intact LHB anchor. The repair techniques restored the stiffness of the intact LHB but failed to reproduce the normal load versus displacement profile of the labral complex with an intact LHB anchor.

Of the two suture techniques, the mattress suture best restored the normal biomechanics of the labral complex.

We conclude that a type II SLAP lesion significantly alters the biomechanical properties of the LHB tendon. Repair of the SLAP lesion only partially restores the biomechanical properties. We hypothesise that repairs of type II SLAP lesions may fail at loads as low as 150N, hence the LHB should be protected following surgery.