Computerized gait analysis in Legg Calvé Perthes disease--analysis of the frontal plane.

OBJECTIVE: Current follow-up and outcome studies of Legg Calvé Perthes disease (LCPD) are based on subjective measures of function, clinical parameters and radiological changes [Herring JA, Kim HT, Browne RH. Legg-Calvé-Perthes disease. Part II: prospective multicenter study of the effect of treatment on outcome. J Bone Joint Surg 2004;86A:2121-34; Aksoy MC, Cankus MC, Alanay A, Yazici M, Caglar O, Alpaslan AM. Radiological outcome of proximal femoral varus osteotomy for the treatment of lateral pillar group-C. J Pediatr Orthop 2005;14 B:88-91; Kitakoji T, Hattori T, Kitoh H, Katho M, Ishiguro N. Which is a better method for Perthes' disease: femoral varus or Salter osteotomy? Clin Orthop 2005;430:163-170; Joseph B, Rao N, Mulpuri K, Varghese G, Nair S. How does femoral varus osteotomy alter the natural evolution of Perthes' disease. J Pediatr Orthop 2005;14B:10-5; Ishida A, Kuwajima SS, Laredo FJ, Milani C. Salter innominate osteotomy in the treatment of severe Legg-Calvé-Perthes disease: clinical and radiographic results in 32 patients (37 hips) at skeletal maturity. J Pediatr Orthop 2004;24:257-64.]. The objective of this study was to evaluate the frontal plane kinematics and the effect on hip joint loading on the affected side in children with a radiographic diagnosis of LCPD.

MATERIAL AND METHOD: Computerized, three-dimensional gait analysis was performed in 33 individuals aged > or =5 years (mean 8.0+/-2 years) with unilateral LCPD and no history of previous surgery to the hip or any disorder leading to gait abnormality. Frontal plane kinematics and kinetics were compared to a group of healthy children (n=30, mean age 8.1+/-1.2 years). Hip joint loading was estimated as a function of the hip abductor moment.

RESULTS: Subjects with LCPD demonstrated two distinct frontal plane gait patterns, both deviating from normal. Type 1 (n=3) was characterized by a pelvic drop of the swinging limb, a trunk lean in relation to the pelvis towards the stance limb and hip adduction during stance phase and corresponded well to the description of Trendelenburg gait caused by abductor insufficiency. Type 2 (n=12) is characterized by a trunk lean toward the affected stance limb with the pelvis stable or elevated on the swinging limb during single stance phase. The abductor moment of the involved side during single stance was significantly reduced in type 2 compared to the controls (p=0.004) indicating a hip-unloading mechanism. These results may influence the physiotherapy regimen, which may require to work towards a hip-unloading gait pattern.