Impact of marker placement on angular kinematics in transfemoral osseointegrated prosthesis users - A longitudinal case-series study.

BACKGROUND

The accuracy of biomechanical data using a Helen Hayes model in instrumented gait analysis can be significantly affected by soft tissue artifacts (STA).

RESEARCH QUESTION

How can STA be quantified and the accuracy of angular kinematics be improved in transfemoral osseointegrated prosthesis gait analysis?

METHODS

To quantify STA associated with the thigh marker, we examined 12 data sets for which an implant marker was added to the Helen Hayes marker set, placed on the thigh segment of four transfemoral osseointegrated prosthesis users. This marker was located on the implant connection extending from the femur. We aimed to identify differences in the calculated range of motion (ROM) during gait when using implant, medial knee, or thigh markers.

RESULTS

The results indicate significant differences in ROM for hip rotation and knee varus/valgus between markers for all but one participant (p < .05). Hip rotation differences between the thigh and implant markers exceeded 10˚ for one participant and were about 5˚ for two others. Knee varus/valgus ROM differences between markers ranged from 3˚ to 9˚ for three participants. No significant differences were found for hip flexion/extension, hip abduction/adduction, or knee flexion/extension for most participants.

SIGNIFICANCE

Using an implant marker in transfemoral osseointegrated prosthesis users results in more accurate femoral tracking than using the thigh marker. Due to the similarity in angular kinematics observed between the medial knee and implant markers, the medial knee or the implant marker should be used as an alternative to the thigh marker for osseointegrated transfemoral prosthesis users.