Pietropaoli M P, Wnorowski D C, Werner F W, Fortino M D
Orthopedic Service Group of Auburn, New York 13021, USA.
Foot Ankle Int. 1999 Sep;20(9):560-3. doi: 10.1177/107110079902000904.
The management of proximal fifth metatarsal ("Jones") fractures in athletes has become increasingly more aggressive, despite a lack of biomechanical data in the literature. A cadaver biomechanical study was conducted to evaluate the strength of intramedullary fixation of simulated Jones fractures loaded to failure via three-point bending on a Materials Testing System machine. In a series of eight intact fifth metatarsal control specimens, the force to failure (fracture) was measured for comparison with repaired specimens. Acute fractures were simulated in 10 pairs of feet via osteotomy at the typical fracture location and were fixed with either a 4.5-mm malleolar screw or a 4.5-mm partially threaded, cancellous, cannulated screw, both placed using conventional intramedullary techniques. Force at initial displacement averaged 73.9 N (SD, 64.7 N) for the malleolar screws and 72.5 N (SD, 42.3 N) for the cannulated screws. Force at complete displacement averaged 519.3 N (SD, 226.2 N) for the malleolar screws and 608.4 N (SD, 179.7 N) for the cannulated screws. The force to failure of the intact specimens was significantly greater than the initial and complete forces to failure for the fixed specimens (P < 0.05, independent measures analysis of variance). There was no statistical difference between the average forces at initial displacement or at complete displacement in the fixed metatarsal specimens for the two different types of screws, but the forces at complete displacement for each screw type were significantly greater than the forces at initial displacement (P < 0.05). On the basis of literature review and data generated from this study, it is apparent that the forces necessary to cause displacement of the stabilized Jones fracture are above what would be transmitted within the lateral midfoot during normal weightbearing. The choice of screw and intramedullary technique of fixation is a matter of surgeon preference, because the choice of screw makes no biomechanical difference.
尽管文献中缺乏生物力学数据，但运动员近端第五跖骨（“琼斯”）骨折的治疗已变得越来越积极。进行了一项尸体生物力学研究，以评估在材料测试系统机器上通过三点弯曲加载至破坏的模拟琼斯骨折的髓内固定强度。在一系列八个完整的第五跖骨对照标本中，测量破坏（骨折）力以与修复后的标本进行比较。通过在典型骨折部位进行截骨术，在10对足部模拟急性骨折，并用4.5毫米内踝螺钉或4.5毫米部分螺纹的松质骨空心螺钉固定，两者均采用传统的髓内技术放置。内踝螺钉初始位移时的平均力为73.9 N（标准差为64.7 N），空心螺钉为72.5 N（标准差为42.3 N）。完全位移时的平均力，内踝螺钉为519.3 N（标准差为226.2 N），空心螺钉为608.4 N（标准差为179.7 N）。完整标本的破坏力明显大于固定标本的初始和完全破坏力（P < 0.05，独立样本方差分析）。两种不同类型螺钉固定的跖骨标本在初始位移或完全位移时的平均力之间无统计学差异，但每种螺钉类型在完全位移时的力明显大于初始位移时的力（P < 0.05）。基于文献综述和本研究产生的数据，显然导致稳定的琼斯骨折移位所需的力高于正常负重时中足外侧所传递的力。螺钉的选择和髓内固定技术是外科医生的偏好问题，因为螺钉的选择在生物力学上没有差异。
