Extensor Mechanism Damage With Proximal Phalanx Antegrade Intramedullary Screws: A Cadaveric Study

Antegrade intramedullary screw instrumentation for treatment of proximal phalangeal fractures has become increasingly common. To date, there has been little investigation describing and quantifying extensor mechanism damage incurred with this treatment option.

Thirty-two fresh cadaveric proximal phalanges (thumbs excluded) underwent percutaneous antegrade screw insertion. Radial-based and ulnar-based intramedullary screws were inserted per phalange, and the sagittal band and/or extensor tendon defect were evaluated. The mean sagittal band violation was measured and calculated as a percentage violation of the whole structure. Measurements were then stratified by finger.

The mean radial-sided defect of the sagittal band by length was 11.6% (SD = 8.5%), compared with ulnar-sided defect (12.9%, SD = 7.4%). Across all digits, the mean percentage of total sagittal band disruption was 13.0%. There was a trend toward more sagittal band disruption in the ring finger relative to other fingers. While 3 of the 32 phalange defects were observed in the extensor tendon rather than the sagittal band, no extensor tendon defects exceeded 25% the width of the tendon after screw insertion. There was also no induced subluxation or dislocation of the extensor tendon through passive manipulation of all of the cadaveric specimens.

Our study found less than 50% sagittal band disruption with antegrade intramedullary screw insertion into all 32 cadaveric proximal phalanges. Antegrade intramedullary screw fixation of proximal phalangeal fractures can be performed using percutaneous approaches without significant disruption to the extensor mechanism.