Distal interphalangeal joint bony dimensions related to headless compression screw sizes.

Abstract

To determine the radiographic dimensions of the distal interphalangeal (DIP) joint and to compare these measurements with commonly used headless compression screws. Using standard posteroanterior and lateral radiographs of the hand, we measured the dimensions of the distal and middle phalanges in 60 index, middle, ring, and little fingers. We then compared these measurements with the diameters and lengths of 16 commercially available headless compression screws commonly used to perform DIP joint arthrodesis. Percent compatibility and risk factors for incompatibility were determined. In general, commercially available screw diameters were too large given the anatomic dimensions of the DIP joint. The distal phalanx shaft as measured on the lateral view was the narrowest determinant of fit. When the dimensions of all fixation devices were combined, screws were oversized relative to the bony anatomy in 66% of index fingers, 53% of middle fingers, 49% of ring fingers, and 72% of little fingers. This mismatch was greater in women than in men. Only 1 of the compression screw types demonstrated a compatibility rate greater than 90% for the index and little fingers, respectively. A multivariate analysis of independent risk factors showed the likelihood of a compatible fit to vary directly with patient height and to be less likely in the little and index fingers. Interobserver reliability analysis revealed excellent x-ray measurement correlation between observers. A size mismatch existed between the anatomic dimensions of the DIP joint and commercially available headless compression screws. Caution must be used when considering these screws for DIP joint arthrodesis, to avoid problems related to screw prominence in the narrow aspects of the distal and middle phalanges. Headless compression screws are frequently oversized for use in DIP arthrodesis.