Quantification of Articular Surface Involvement During Intramedullary Fixation of the Phalanges.

Purpose: Phalangeal fractures of the hand are the second most common upper-extremity fracture in the United States. Numerous studies have reported on the biomechanical efficacy of intramedullary (IM) hand nail fixation of the phalanges and increased utilization of IM hand nails. During IM fixation, the nail often penetrates the articular cartilage during insertion. This study seeks to quantify the percentage of cartilage involvement created by anterograde and retrograde intramedullary fixation of proximal and middle phalangeal fractures with 3.0 mm and 3.5 mm IM threaded hand nails. Methods: Thirty-two frozen fingers were studied from eight cadaveric hands. Four different techniques for nail placement were used: (1) retrograde across an unflexed distal interphalangeal joint, (2) retrograde across a flexed distal interphalangeal joint into the middle phalanx, (3) retrograde through a flexed proximal interphalangeal joint into the proximal phalanx, and 4) antegrade through the metacarpal phalangeal joint into the proximal phalanx. Clinical photographs and fluoroscopy images were taken for each specimen, and the articular cartilage damage was quantified using Image J software. Results: The average articular involvement using intramedullary hand nails for phalangeal fixation was less than 10% of the articular surface regardless of nail placement technique and nail size (mean range 3.56% to 9.73%). The damaged area was always greater with the 3.5 mm than the 3.0 mm nails. Conclusions: Our results are consistent with the literature. Our study is unique in that we compare the different methods of hand nail insertion and the different diameter hand nails and evaluate the degree of articular surface involvement in an approach that has not been tested on cadaveric models. Phalanx fracture fixation with intramedullary hand nails may be beneficial, as it has acceptable joint cartilage damage based on our study data. Type of study/level of evidence: Bench research/laboratory study V.