Aiona Michael, Do K Patrick, Emara Khaled, Dorociak Robin, Pierce Rosemary
*Shriners Hospitals for Children ‡Northwest Biomechanics LLC, Portland, OR †Orthopaedic Surgery, Ain Shams University, Cairo, Egypt.
J Pediatr Orthop. 2015 Apr-May;35(3):280-4. doi: 10.1097/BPO.0000000000000262.
Very few articles describe the compensations in gait caused by limb-length discrepancy (LLD). Song and colleagues explored kinematic and kinetic variables utilizing work equalization as a marker of successful compensation for LLD. They found no difference in strategies based on the location of pathology. The purpose of this study was to define the various gait patterns in patients with LLD and the impact of these compensations on gait kinetics.
Forty-three children (mean age 12.9±3.7 y) with LLD >2 cm were evaluated in the motion lab using a VICON motion system with 2 AMTI force plates. Etiologies included Legg-Calve-Perthes, developmental hip dysplasia, growth plate damage due to infection or trauma, congenital shortening of the femur or tibia, and syndromes creating shortening of the limb. Evaluation included physical examination and 3-dimensional motion data generated using the model described by Vicon Clinical Manager (VCM). For data analysis, 3 representative trials were processed with the Plug-in Gait lower-body model using the "VCM spline" filter. Walking strategies were identified by visual review. A kinematic threshold of 2 SD away from normal values was used for inclusion in each group. Strategies included: (1) pelvic obliquity with the short side lower (<-1.5 degrees); (2) flexion of the knee of the longer leg in stance (>5.2 degrees); (3) plantar flexion of the ankle on the shorter leg through the gait cycle (<0 degrees); and (4) early plantarflexion crossover of the shorter limb (plantarflexion crossover occurred before 35% of the gait cycle). Variables were extracted into Excel using PECS (Vicon Motion Systems). The mean of the 3 trials was used for analysis. Scanograms were used to establish lengths of the femur and the lower leg including the foot. The percentage difference for the subject (%LLD) was calculated as the leg length between the 2 sides divided by the length of the long side. The total mechanical work over the stride was the sum of the positive work and the absolute value of the negative work in all planes. Paired t tests were used to analyze the work differences between the short limb versus the long limb. Unpaired t tests were used to compare between the different groups (short tibias, short femurs, and controls).
Distribution of single strategies for the group included: pelvis (11), equinis (5), vaulting (7), knee flexion (3); 17 subjects used multiple strategies. If the discrepancy was in the femur, patients chose a more distal compensation strategy, utilizing ankle movements, which resulted in more work at the ankle joint on the short limb compared with normal (P<0.0001). All subjects with tibia shortening showed pelvic obliquity (3 combined with knee flexion), which caused more work at the hip joint on the short limb compared with normal (P<0.01). Total mechanical work on the uninvolved limb was above normal for all groups (P<0.0001).
Our study contradicts previous literature that found no difference in strategy on the basis of location of the shortening and also a higher number of children with pelvic obliquity than previously described. It appears that different compensation schemes are used by patients with LLD. The increase in work may have long-term implications for management. Future studies will include changes in kinematics and work, after intervention. Better understanding of postoperative changes from different surgical methods may provide more insight for preoperative planning and may lead to a more satisfactory outcome for specific patients.
Level II.
极少有文章描述肢体长度差异（LLD）导致的步态代偿情况。宋及其同事利用功均衡作为LLD成功代偿的标志，探讨了运动学和动力学变量。他们发现基于病变位置的策略并无差异。本研究的目的是确定LLD患者的各种步态模式以及这些代偿对步态动力学的影响。
使用配备2块AMTI测力台的VICON运动系统，在运动实验室对43例LLD>2 cm的儿童（平均年龄12.9±3.7岁）进行评估。病因包括Legg-Calve-Perthes病、发育性髋关节发育不良、感染或创伤导致的生长板损伤、先天性股骨或胫骨缩短以及导致肢体缩短的综合征。评估包括体格检查和使用Vicon临床管理器（VCM）描述的模型生成的三维运动数据。为进行数据分析，使用“VCM样条”滤波器，通过插入式步态下肢模型处理3次代表性试验。通过视觉检查确定步行策略。每组纳入的运动学阈值为偏离正常值2个标准差。策略包括：（1）短侧较低的骨盆倾斜（<-1.5度）；（2）站立时较长腿的膝关节屈曲（>5.2度）；（3）短腿在整个步态周期中的踝关节跖屈（<0度）；以及（4）短肢体的早期跖屈交叉（跖屈交叉发生在步态周期的35%之前）。使用PECS（Vicon运动系统）将变量提取到Excel中。使用3次试验的平均值进行分析。使用扫描图确定股骨和包括足部在内的小腿长度。计算受试者的百分比差异（%LLD），即两侧腿长之差除以长腿长度。步幅上的总机械功是所有平面上正功与负功绝对值之和。使用配对t检验分析短肢体与长肢体之间的功差异。使用非配对t检验比较不同组（短胫骨组、短股骨组和对照组）。
该组单一策略的分布包括：骨盆（11例）、马蹄足（5例）、跳跃（7例）、膝关节屈曲（3例）；17名受试者使用多种策略。如果差异在股骨，患者会选择更靠远端的代偿策略，利用踝关节运动，这导致短肢体踝关节的功比正常情况更多（P<0.0001）。所有胫骨缩短的受试者均表现出骨盆倾斜（3例合并膝关节屈曲），这导致短肢体髋关节的功比正常情况更多（P<0.01）。所有组未受累肢体的总机械功均高于正常水平（P<0.0001）。
我们的研究与之前的文献相矛盾，之前的文献发现基于缩短位置的策略无差异，且骨盆倾斜的儿童数量比之前描述的更多。似乎LLD患者使用了不同的代偿方案。功的增加可能对治疗有长期影响。未来的研究将包括干预后运动学和功的变化。更好地理解不同手术方法术后的变化可能为术前规划提供更多见解，并可能为特定患者带来更满意的结果。
二级。
