Detrimental effects of overstuffing or understuffing with a radial head replacement in the medial collater-alligament deficient elbow
Faculty of Medicine and Health Sciences
The journal of bone and joint surgery : American volume. - London, 1948, currens
, p. 2629-2635
University of Antwerp
Background: Comminuted radial head fractures associated with an injury of the medial collateral ligament can be treated with a radial head implant. We hypothesized that lengthening and shortening of the radial neck would alter the kinematics and the pressure through the radiocapitellar joint in the medial collateral ligament-deficient elbow. Methods: The effects of lengthening (2.5 and 5 mm) and shortening (2.5 and 5 mm) of the radial neck were assessed in six human cadaveric upper extremities in which the medial collateral ligament had been surgically released. The three-dimensional spatial orientation of the ulna was recorded during simulated active motion from extension to flexion. Total varus-valgus laxity and ulnar rotation were measured, Radiocapitellar joint pressure was assessed with use of pressure-sensitive film. Results: Radial neck lengthening or shortening of greater than or equal to2.5 mm significantly changed the kinematics in the medial collateral ligament-deficient elbow. Lengthening caused a significant decrease (p < 0.05) in varus-valgus laxity and ulnar rotation (p < 0.05), with the ulna tracking in varus and external rotation. Shortening caused a significant increase in varus-vaigus laxity (p < 0.05) and ulnar rotation (p < 0.05), with the ulna tracking in valgus and internal rotation. The pressure on the radiocapitellar joint was significantly increased after 2.5 mm of lengthening. Conclusions: This study suggests that accurate restoration of radial length is important and that axial understuffing or overstuffing of the radiolhurneral joint by greater than or equal to2.5 mm alters both elbow kinematics and radiocapitellar pressure. Clinical Relevance: This in vitro cadaver study indicates that a radial head replacement should be performed with the same level of concern for accuracy and reproducibility of component position and orientation as is appropriate with any other prosthesis.