Effect of capitate morphology on contact biomechanics after proximal row carpectomy

Purpose: Proximal row carpectomy (PRC) is used as a treatment for a variety of wrist pathologies to maintain motion and to improve strength and decrease pain. Several studies have looked at how PRC alters wrist characteristics, although they did not provide an explanation for the variability observed in outcomes. Studies have classified the capitate into 3 unique types: round, V-shaped, or flat. We hypothesized that these differences in morphology could affect the contact biomechanics between the radius and the capitate after PRC. Methods: A total of 14 cadaveric wrists underwent PRC. They were classified by capitate morphology and then loaded to 200 N in a neutral position, flexion, and extension. We measured contact area, contact pressure, and location using pressure-sensitive film in all 3 positions and compared their morphology types. Results: Nine wrists had a round-type capitate, 4 had a V-shaped capitate, and 1 had a flat capitate, which we excluded from statistical analysis. Comparing round and V-shaped types, we found no differences in contact area, pressure, or location in any wrist position For the V-shaped capitates, there was increased contact pressure in flexion and extension compared with the wrist in neutral. Center of pressure translated dorsal and radial in flexion to volar and ulnar in extension for all types. Conclusions: When we compared V-shaped and round-type capitates, we found no significant differences in contact characteristics of the wrist after PRC. There were some differences in contact pressure for V-shaped capitates in various wrist positions. Clinical relevance: Differences between round and V-shaped capitates do not appear to affect contact biomechanics after PRC. Thus, these 2 capitate shapes may not necessarily be a factor in the decision-making process to perform PRC.