The influence of different pelvic technical marker sets upon hip kinematics during gait.

BACKGROUND The pelvis is commonly tracked during three-dimensional motion analysis using markers located on the anterior and posterior superior iliac spines. However, these markers are prone to soft tissue artefact and marker occlusion, highlighting the need for alternative technical marker sets. RESEARCH QUESTION How comparable are hip joint kinematics calculated using two alternative pelvic technical marker sets and a conventionally modelled pelvis? METHODS Fourteen participants undertook 3D gait analysis, walking overground at a self-selected pace (1.38 ± 0.14 m·s-1), barefoot. Hip joint kinematics were compared using root mean square error (RMSE) between a conventionally tracked pelvis and two alternative technical marker sets; (1) posterior cluster and (2) additional iliac crest markers. RESULTS The average RMSE in the sagittal, frontal and transverse planes was 2.5° ± 2.8°, 1.6° ± 0.4° and 0.8° ± 0.4°, respectively for the posterior cluster, and 1.3° ± 0.7°, 0.8° ± 0.3° and 1.4° ± 0.5° for the iliac crest marker set. The RMSE was significantly larger for the posterior cluster compared to the iliac crest model in the sagittal (p =  .05, d = .28) and frontal planes (p <  .001, d = 7.65). In contrast, the RMSE was significantly lower for the posterior cluster in the transverse plane (p =  .01, d = -2.85). SIGNIFICANCE The findings of this study suggest that either a posterior cluster or additional iliac crest markers offer means of accurately calculating hip joint kinematics within 3° of the conventional pelvic model. Therefore, either technical marker set offers a viable alternative to the conventional pelvic model for calculating hip joint kinematics.