Design Parameters of Hand Surgery Screws: Measurement Discrepancies and Clinical Implications

Purpose The use of self-tapping cortical screws is indicated in patients with metacarpal and phalangeal fractures requiring formal stabilization. The aim of this study was to systematically compare and evaluate the design parameters of 4 commercially available self-tapping screw systems. Methods We measured various design parameters of self-tapping cortical screws of different lengths from several manufactures using scanning electron microscopy. Screws were obtained in 8, 12, 16, and 20 mm lengths. The measured parameters included screw length, head height, pitch, outer diameter, inner diameter, terminal thread diameter, terminal thread-to-tip distance, thread-to-tip distance of 1 full revolution, and crest width. Data were assessed statistically using 1- and 2-way analysis of variance (ANOVA) tests, and the significance level was set at a P value Results There was variability in advertised screw lengths compared with measured screw lengths with 2 manufacturers. There was a statistically significant difference between the thread-to-tip distance and head height between screws while controlling for diameter. Conclusions Screw sizes and dimensions are critical in order to avoid complications such as prominent hardware and postoperative stiffness. Knowledge of the design parameters presented for each of the different manufacturers may prove useful to hand surgeons when selecting screws for fixation of metacarpal and phalangeal fractures. Clinical relevance Specific design characteristics of commonly used screws in hand surgery vary slightly by manufacturer and may have clinically relevant implications in fixation of metacarpal and phalangeal fractures.