Contribution of Monoblock and Bipolar Radial Head Prostheses to Valgus Stability of the Elbow

Author(s): Pomianowski S, Morrey BF, Neale PG, Park MJ, O’Driscoll SW, An KN

Source: J Bone Joint Surg 83A: 1829-1834, 2001

Summary:

This study evaluates the ability of three different radial head prosthesis to restore valgus stability to a medial collateral ligament deficient elbow.  The Wright Medical Technology monoblock titanium radial head was compared with the Tornier Judet bipolar Vitallium-polyethylene-Vitallium implant and the KPS bipolar Vitallium-polyethylene implant.  9 fresh frozen cadaveric upper extremities were used for the study.  Valgus laxity was assessed at 20 degrees, 60 degrees and 100 degrees of elbow flexion in neutral, 80 degrees of supination, and 80 degrees of pronation.  As expected, the greatest laxity was noted after release of the MCL and resection of the radial head.  In addition, valgus laxity was always greatest in pronation compared to supination and neutral rotation.  Radial head replacement did diminish mean valgus laxity in supination and neutral rotation compared to values obtained for an intact native radial head.  Valgus laxity was not diminished significantly with radial head replacement in pronation.  Although there was no significant difference in stability provided by the three different radial head implants, in neutral forearm rotation there was a trend toward increased valgus laxity with the Judet implant than with the Wright or KPS implants.

Because of concerns of capitellar wear and implant loosening, newer radial head implants are being designed to minimize these risks.  This study did not show a significant difference with respect to valgus stability of a monoblock as compared to a bipolar radial head prosthesis.  However, only 9 specimens were used and there were large standard deviations, as high as 80 percent. There did appear to be a trend towards improved stability with the monoblock Wright prosthesis compared to the two bipolar designs.   In addition, these prosthesis were all secured with cement which departs from the standard treatment protocols.  In short, this study serves to provide some baseline data but overall is inconclusive due to the low sample numbers, high standard deviations, and uncertain clinical benefit.  It is clear, however, that a metallic implant can help transfer load and stabilize the medial collateral deficient elbow following trauma.

 

Related Links
Journal of Bone and Joint Surgery