■在确定掌骨骨折后可接受的掌骨缩短时,先前的生物力学研究和临床研究之间存在差异。这项研究旨在确定在手指运动和力量受损之前,掌骨骨折后可接受的缩短量。
■我们解冻了十只新鲜冷冻的尸体手。放置了一个螺钉驱动的外部固定器来稳定掌骨,然后切除了15.0毫米的索引掌骨部分,并用三维打印代替,定制设计的聚乙烯插入。然后将手安装在定制的测试台上,食指使用屈指前肌腱弯曲。当手指弯曲时记录关节角度和指尖力。放置的刀片逐渐变小,并重复测试。
■掌指骨完整状态的平均关节角度,近端指间,远端指间关节为(54[SD=13],79[SD=21],和73[SD=10]),分别。在任何缩短量的情况下,任何关节角度都没有统计学上的显着变化。最大指尖接触压力为41N(17),31N(12),24N(14),19N,(11),和14N(8)的15毫米,12.5mm,10mm,7.5mm,和5毫米刀片,分别。指尖力随插入尺寸的所有变化均具有统计学意义。
■无论缩短量如何,掌骨缩短都不会影响屈曲运动范围,但它明显影响手指的力量。对于骨折的掌骨,缩短后的强度损失约为每毫米缩短6.5%。
■当在手作为一个整体的背景下观察时,食指对抓握的贡献仅为23.5%,任何缩短都不可能显著影响普通患者的握力。然而,对于一个需要精细运动力量的病人来说,任何程度的缩短都可能影响他们的手指功能,需要解决。
UNASSIGNED: Discrepancies exist between previous biomechanical and clinical studies when determining acceptable metacarpal shortening after metacarpal fractures. This study aimed to determine the amount of acceptable
shortening after a metacarpal fracture before finger motion and strength is compromised.
UNASSIGNED: We defrosted ten fresh-frozen cadaveric hands. A screw-driven external fixator was placed to stabilize the metacarpal, then a 15.0-mm section of the index metacarpal was excised and replaced with a three dimensional-printed, custom-designed polyethylene insert. The hand was then mounted on a custom testing rig, and the index finger was flexed using the flexor digitorum profundus tendon. Joint angles and fingertip force were recorded as the finger was flexed. Incrementally smaller inserts were placed, and testing was repeated.
UNASSIGNED: The average joint angles of the intact condition for the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were (54 [SD = 13], 79 [SD = 21], and 73 [SD = 10]), respectively. There were no statistically significant changes to any joint angle with any amount of
shortening. The maximal fingertip contact pressures were 41 N (17), 31 N (12), 24 N (14), 19 N, (11), and 14 N (8) for the 15 mm, 12.5 mm, 10 mm, 7.5 mm, and 5 mm inserts, respectively. All changes in fingertip force by insert size were statistically significant.
UNASSIGNED: Metacarpal
shortening does not affect flexion range of motion regardless of the amount of
shortening, but it significantly affects finger strength. The loss of strength after
shortening was approximately 6.5% per mm of
shortening for the fractured metacarpal.
UNASSIGNED: When viewed in the context of the hand as a whole and the contribution of the index finger to grip being only 23.5%, it is unlikely that any shortening will significantly affect the average patient regarding grip strength. However, for a patient who requires fine motor strength, any amount of shortening may affect their finger function and needs to be addressed.