RESUMEN
Recently, biodegradable implants made from magnesium (Mg) alloys have been developed to obviate the need for later implant removal. Mg-based cannulated compression screws (CCS) are ideal for intramedullary screw (IMS) fixation of metacarpal fractures. The present study aimed at investigating the torque acting on Mg-based CCS at failure and at intramedullary metacarpal insertion. The devices were CE certified Magnezix 2.7 and 3.2 mm CCSs (Syntellix®, Hannover, Germany). Torque at failure was measured in a synthetic bone model using a standardized polyurethane foam block. In a second assessment, insertional torque was measured in ten cadaveric metacarpal bones. Mean torque at failure for the 2.7 mm and 3.2 mm CCSs was 42.8 Ncm (±1.9 Ncm) and 63.0 Ncm (±2.2 Ncm), respectively. In the human cadaver model, the torque distribution curve at metacarpal insertion showed three peaks. The highest reached 53.6% of the lowest torque at failure measured in the synthetic bone model for the 3.2 CCS (31.4 vs. 58.6 Ncm). The mean difference between peak torque at metacarpal insertion and torque at failure was 38.3 Ncm (99% CI [33.6, 43.0 Ncm], p < 0.0001). In terms of torque load, Mg-based CCSs are suitable for IMS fixation of metacarpal fractures. Biodegradable implants may represent an important improvement of this treatment method; confirmation by in-vivo studies is needed.
Asunto(s)
Fracturas Óseas , Huesos del Metacarpo , Fenómenos Biomecánicos , Tornillos Óseos , Fijación Interna de Fracturas/métodos , Fracturas Óseas/cirugía , Humanos , Magnesio , Huesos del Metacarpo/cirugía , TorqueRESUMEN
Traditionally, the angle between the intersecting central axes (lateral projection intersecting central axes - LCA) of the proximal and distal fragments of metacarpal fractures is measured on radiographs. We recommend using the angle between the intersecting dorsal tangent lines instead (lateral projection intersecting dorsal tangent lines - LDT). We analyzed radiographs of 25 fractures of the fifth metacarpal bone shaft in three planes. Intraclass correlation coefficients (ICC) were used to estimate inter-rater and intra-rater reliability. Mean palmar tilt was 35.6° ± 12.5° according to LCA and 27.6° ± 12.0° according to LDT. There were no differences during repeated measurements. Intra-rater reliability was high: ICC (95% CI) for LDT was 0.82 (0.74-0.88) and for LCA it was 0.71 (0.51-0.83). Mean values of palmar tilt using LCA exceeded those using LDT by 8.0° ± 7.7° (p < 0.001). Only LDT measurements provided comparable results between all raters. In conclusion, we demonstrated the feasibility and reliability of intersecting dorsal tangent lines for measuring palmar tilt in fifth metacarpal fractures as an alternative to the commonly used angle between the intersecting central axes.