Evaluation of "neocollateral" ligament formation by magnetic resonance imaging after total excision of the proximal interphalangeal collateral ligaments.

The presence of palpable thickening and maintenance of stability within weeks of total excision of the proximal interphalangeal (PIP) joint collateral ligaments is an established, although somewhat mysterious, phenomenon. To further investigate this postoperative thickening, magnetic resonance imaging (MRI) scans were obtained on 10 joints in 9 patients who had undergone total ligament excision for posttraumatic stiff PIP joints 3 months to 14 years earlier. Although the ultrastructure of these newly formed structures is yet unknown, their palpable consistency, MRI contour, distribution, and signal intensity suggest the formation of a new soft tissue structure, albeit scar, which has all the attributes of a collateral ligament. This MRI of a "neocollateral ligament" would help explain the consistent observation of complete joint stability within weeks following total excision of both PIP joint collateral ligaments. All patients from the 14-year span sampled were found to have a similar, consistent, linear low signal density structure crossing the joint margins and essentially identical to that of a normal collateral ligament.