Effects of proximal row carpectomy on wrist biomechanics: a cadaveric study.

BACKGROUND: Many studies show good clinical results after proximal row carpectomy. Some biomechanical consequences are documented, but to our knowledge muscle moment arm variations have not previously been quantified.

METHODS: In five fresh-frozen wrist, kinematics and tendon excursions were measured using a 3D electrogoniometer and Linear Variable Differential Transformers (SOLARTRON Inc., AMETEK Advanced Measurement Technology, Inc, 801 South Illinois Avenue, Oak Ridge, TN 37831-2011, USA), respectively, in three conditions: intact wrist, after posterior capsulotomy and after proximal row carpectomy. Mean pivot point, defined as the point whose sum of the squared distances to the helical axes is minimum, wrist range of motion and mean moment arms were measured during dorso-palmar flexion, radioulnar deviation and circumduction movements.

FINDINGS: No alteration of the range of motion was observed. On the other hand, the mean pivot point shifted proximally (6.8-9.1mm) after proximal row carpectomy (p<0.05) for all motions tested and most muscle moment arms decreased significantly after proximal row carpectomy.

INTERPRETATION: The results of this study allow a better understanding of the biomechanical effects of this procedure. The important moment arm reduction and pivot point displacement suggest modifications of joint biomechanical parameters which could influence the functional outcome of PRC.