Abstract
Introduction
Improvements in function after THA can be evaluated using validated health outcome surveys but studies have shown that PROMs are unreliable in following the progress of individuals. Formal gait lab analysis is expensive, time consuming and fixed in terms of location. Inertial Measurement Units (IMUs) containing accelerometers and gyroscopes can determine aspects of gait kinematics in a portable package and can be used in the outpatient setting (Figure 1). In this study multiple metrics describing gait were evaluated pre- and post THA and comparisons made with the normal population
Methods
The gait of 55 patients with monarthrodial hip arthrosis was measured pre-operatively and at one year post-surgery. Patients with medical co-morbidity or other condition affecting their gait were excluded. Six IMUs aligned in the sagittal plane were attached at the level of the anterior superior iliac spines, mid-thigh and mid-shank. Data was analysed using proprietary software (Figure 2). Each patient underwent a conventional THA using a posterolateral approach. An identical test was performed one year after surgery. 92 healthy individuals with a normal observed gait were used as controls.
Results
In the pre-operative test the range of movement in the sagittal plane of both the ipsilateral hip (mean range 20.4) and the contra-lateral non-diseased hip (35.3 degrees) was reduced compared to the control group (40.5 degrees), (P<0.001). The pre-operative range of motion of both knees was also reduced compared with normal (P<0.001). Pelvic movement on the ipsilateral side was increased.
After one year the range of movement of the ipsilateral hip significantly improved (Mean range 28.9 deg SD 6.6) but did not attain normal values (P<0.001). Movement measured in the contralateral hip reduced further from its pre-operative value with a mean difference of −5.25 degrees (95% CI −8.06 to −2.43). Measurements of the symmetry of movement were increased. Knee movement on both sides increased but not to normal values (p<0.001). In contradistinction, there was bilateral increased coronal movement at the thigh and calf a year after surgery.
Discussion and Conclusion
Gait after routine THA does not return to normal on the ipsilateral or contralateral side. Pathology in one hip causes bilateral gait abnormality that can be quantified by movement at the pelvis, hip, thigh and knee. The ability of a patient to walk normally after surgery will depend on many factors including details of the hip operation such as accurate recreation of the biomechanics of the joint and physical therapy regimens. Advances in technology now allow assessment of gait in large number of patients in the clinic setting and will better allow us to establish the important factors to improve patients gait and thereby potentially improve further satisfaction and PROMS scores.
For any figures or tables, please contact authors directly (see Info & Metrics tab above).
