Comparison of the native ulnar head and a partial ulnar head resurfacing implant.

PURPOSE: To assess the match in size and shape between the native ulnar head and a partial ulnar head implant in cadaver specimens.

METHODS

Ten fresh-frozen cadaver arms (6 male, 4 female, age range 79-91 years) with no history of previous distal radioulnar joint surgery were used. Radiographic measurements before and after implantation were used to compare ulnar head articular height, width, offset, and ulnar variance. Head diameter was measured using photographs of the resected ulnar heads.

RESULTS

The partial ulnar head implant consistently reproduced the natural anatomic size and shape for all variables except ulnar head height and ulnar variance. Head height was greater with the implant, but the additional height extended proximally into the distal radioulnar joint synovial recess, which is unlikely to have adverse affects. Ulnar variance match was technique dependent, with a tendency to place the implant in more neutral variance when positive variance was present before surgery.

CONCLUSIONS

Our study demonstrated that a partial ulnar head implant, which replaces the articular surfaces, can closely re-create the ulnar head anatomy. By virtue of restoring the anatomy without an extensive dissection, the clinical results should be expected to at least match the functional results of total head replacement, reduce the rehabilitation, and possibly reduce the risk of joint instability.