Dale Kevin M, Burns Geoffrey T, Li Ying
Department of Orthopaedic Surgery, C.S. Mott Children's Hospital.
Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI.
J Pediatr Orthop. 2019 Jul;39(6):275-281. doi: 10.1097/BPO.0000000000000956.
Femoroacetabular impingement as a result of slipped capital femoral epiphysis (SCFE) has been treated traditionally with a proximal femoral osteotomy, but open and arthroscopic femoral osteoplasty is becoming increasingly popular. Cam lesions result from excess bone primarily at the anterolateral femoral head-neck junction. SCFEs result from posterior and inferior slippage of the femoral epiphysis, causing the metaphysis to move anteriorly. This study's purpose was to compare fourth-generation sawbones standard femurs with SCFE femurs to determine whether bone resection from the anterior metaphysis results in similar biomechanical properties.
A custom fourth-generation composite SCFE sawbone was created with a 30-degree slip angle. Control group consisted of fourth-generation composite standard nondeformed medium femurs. The femoral neck at the head-neck junction was divided into 4 quadrants. All resections were done in the anterolateral quadrant. Twenty SCFE sawbones and 20 standard sawbones were divided into 4 subgroups based on resection depths of 0%, 10%, 30%, and 50% of the metaphysis at the head-neck junction. After resection, all proximal femurs were loaded to failure in an Instron testing machine to determine the ultimate load to failure, stiffness, and energy to failure.
The standard femurs were significantly stronger than the SCFE femurs (P<0.001) and the strength of the femurs decreased significantly as the resection amount increased (P<0.001). Similarly, the standard femurs withstood significantly more energy before failing than the SCFE femurs (P<0.001) and the energy to failure decreased significantly with varying resection amounts (P<0.001).
SCFE femurs demonstrate a significant reduction in strength and energy to failure after osteoplasty compared with nondeformed femurs in a sawbone model. Strength and energy to failure are inversely proportional to the depth of bone resection.
Aggressive femoral neck osteoplasty for treatment of a SCFE deformity may lead to increased risk of fracture. Further studies are necessary to determine the safe depth of resection in a clinical setting.
股骨头骨骺滑脱（SCFE）导致的股骨髋臼撞击症传统上采用股骨近端截骨术治疗，但开放和关节镜下股骨成形术正变得越来越流行。凸轮病变主要是由于股骨头-颈交界处前外侧的骨质过多所致。SCFE是由股骨骨骺向后下方移位引起的，导致干骺端向前移动。本研究的目的是比较第四代人工合成标准股骨与SCFE股骨，以确定从前侧干骺端切除骨质是否会导致相似的生物力学特性。
制作了一个定制的第四代复合SCFE人工合成股骨，其滑移角度为30度。对照组由第四代复合标准未变形中型股骨组成。股骨头-颈交界处的股骨颈被分为4个象限。所有切除均在前外侧象限进行。20个SCFE人工合成股骨和20个标准人工合成股骨根据在股骨头-颈交界处干骺端切除深度的0%、10%、30%和50%分为4个亚组。切除后，所有股骨近端在Instron试验机上加载至失效，以确定失效的极限载荷、刚度和失效能量。
标准股骨明显比SCFE股骨更强（P<0.001），并且随着切除量的增加，股骨强度显著降低（P<0.001）。同样，标准股骨在失效前承受的能量明显比SCFE股骨更多（P<0.001），并且失效能量随着切除量的变化而显著降低（P<0.001）。
在人工合成股骨模型中，与未变形股骨相比，SCFE股骨在成形术后的强度和失效能量显著降低。强度和失效能量与骨质切除深度成反比。
积极的股骨颈成形术治疗SCFE畸形可能会导致骨折风险增加。需要进一步研究以确定临床环境中的安全切除深度。
