Pressure distribution in carpometacarpal joint, due to step-off in operatively treated Bennett's fractures

The purpose of the current study was to investigate the effects of residual articular incongruity after Bennett's fracture on load distribution of the joint surface. Our aim was to investigate whether a residual joint step and the altered load distribution led to negative clinical outcomes or symptomatic degenerative osteoarthritis of the trapeziometacarpal joint.

Twenty-four patients were available for long-term follow-up examination and were contacted by phone, and they returned for follow-up examination. Computed tomography (CT) scans of both carpometacarpal (CMC) joints were performed. CT scans were taken in the sagittal plane of the forearms with a slice thickness of 0.625 mm for three-dimensional reconstruction. The CMC joints were analysed due to a residual step in the joint. Only patients with a residual step-off were included in this study. To determine the areas of maximum density in the joint, CT-osteoabsorptiometry was performed.

Ten patients had the maximum loading area radial and two patients central. The second major position of mineralization was detected central in four patients, volar-ulnar in two patients, radial in one patient, dorso-radial in one patient, volar in one patient and volar-radial in two patients.

Finally, no higher loading in the area of the beak fragment could be found. The Wagner technique, even if it results in a persistent 1-2-mm intra-articular step-off of the beak fragment, is still the favourable method for the treatment of Bennett's luxation fractures.