Morris Parisa M, Francois Annie G, Marcus Randall E, Farrow Lutul D
Canyon Orthopaedic Surgeons, Avondale, Arizona, USA.
Department of Orthopaedic Surgery, University of Arizona College of Medicine, Tucson, Arizona, USA.
Foot Ankle Int. 2015 May;36(5):579-84. doi: 10.1177/1071100714565177. Epub 2014 Dec 30.
Nonunion of classic Jones fractures has typically been attributed to the precarious vascular anatomy of the proximal fifth metatarsal. Despite this theory, the operative treatment of these fractures utilizes biomechanical solutions. The purpose of the present study was to evaluate the influence of the peroneus brevis (PB) tendon on the stability of fractures of the proximal fifth metatarsal.
We utilized 5 matched pairs (10 specimens) of fresh-frozen cadaveric specimens. We used 2 loading conditions: (1) a simulated fracture distal to the PB insertion (Jones equivalent) and (2) a simulated fracture within the footprint of the PB insertion (avulsion equivalent). Following the creation of the fracture, each lower extremity was statically loaded through the Achilles and PB tendons. Our primary outcome measure was the degree of fracture diastasis with loading of the PB. Anteroposterior images with and without loading were obtained to evaluate fracture separation. We utilized a paired Student t test and the intraclass correlation coefficient (ICC) for all statistical analyses.
The average length of the PB footprint was 15.2 mm. The simulated Jones fractures demonstrated greater fracture widening following loading of the PB tendon compared to the simulated avulsion fractures. The simulated avulsion fractures widened 0.4 mm on loading compared to 1.1 mm of widening in the simulated Jones fractures (P = .02). Intraobserver reliability for all radiographic measurements showed substantial agreement (ICC = 0.91).
The PB exerted a deforming force on the proximal fragment of simulated Jones fractures. This deforming force was less pronounced in the simulated avulsion fractures. The principal findings of this study were that proximal fifth metatarsal fractures distal to the PB insertion were significantly more unstable than more proximal fractures.
Our findings help support the notion that a mechanical component may contribute to the poor healing potential of Jones fractures secondary to deformation exerted by the PB tendon.
经典琼斯骨折不愈合通常归因于第五跖骨近端不稳定的血管解剖结构。尽管有此理论，但这些骨折的手术治疗采用的是生物力学解决方案。本研究的目的是评估腓骨短肌（PB）肌腱对第五跖骨近端骨折稳定性的影响。
我们使用了5对匹配的（10个标本）新鲜冷冻尸体标本。我们采用2种加载条件：（1）模拟PB肌腱止点远端的骨折（类琼斯骨折）和（2）模拟PB肌腱止点范围内的骨折（撕脱类骨折）。骨折形成后，通过跟腱和PB肌腱对每个下肢进行静态加载。我们的主要观察指标是加载PB时骨折断端分离的程度。获取加载和未加载时的前后位影像以评估骨折分离情况。我们对所有统计分析采用配对学生t检验和组内相关系数（ICC）。
PB肌腱止点的平均长度为15.2毫米。与模拟撕脱骨折相比，模拟琼斯骨折在加载PB肌腱后显示出更大的骨折增宽。模拟撕脱骨折加载时增宽0.4毫米，而模拟琼斯骨折增宽1.1毫米（P = 0.02）。所有影像学测量的观察者内可靠性显示出高度一致性（ICC = 0.91）。
PB对模拟琼斯骨折的近端骨折块施加了变形力。这种变形力在模拟撕脱骨折中不太明显。本研究的主要发现是，PB肌腱止点远端的第五跖骨近端骨折比更靠近近端处的骨折明显更不稳定。
我们的研究结果有助于支持这样一种观点，即机械因素可能导致PB肌腱施加变形力继发的琼斯骨折愈合潜力不佳。
