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Resende R.1, Kirkwood R.2, Rudan J.3, Deluzio K.4
1Universidade Federal de Minas Gerais, Physical Therapy, Belo Horizonte, Brazil, 2Universidade Federal de Minas Gerais, Belo Horizonte, Brazil, 3Queen's University, Department of Surgery, Kingston, Canada, 4Queen's University, Department of Mechanical and Materials Engineering, Kingston, Canada
Background: Metal-on-metal hip resurfacing patients demonstrate hip biomechanics closer to normal in comparison to total hip arthroplasty during gait. However, it is not clear how symmetric is the gait of patients submitted to hip resurfacing.
Purpose: To compare the biomechanics of the operated side of individuals with unilateral hip resurfacing with the biomechanics of the healthy side during walking.
Methods: Biomechanical data of 12 unilateral metal-on-metal hip resurfacing participants (10 males) were collected during walking at a mean time of 44 months (SD 20) after surgery. The senior author was responsible for the hip resurfacing surgery in all participants using a direct lateral approach to the hip joint. All implants were the Depuy Orthopaedic ASR (Warsaw, Ind). Ankle, knee, hip, pelvis and trunk kinematics and kinetics of both sides on the three planes of motion were measured with a Qualysis motion capture system synchronized with 6 force platforms (AMTI). Principal component analysis was performed to reduce the gait variables and then mean hypothesis tests were used to compare the healthy and operated sides with the level of significance set at 0.05. In addition, the participants answered the Hip disability and osteoarthritis outcome score (HOOS) (20) and the Lower Extremity Activity Scale (LEAS).
Results: The participants had an average age, mass and height of 60 years (SD 5.2), 88.3 kg (SD 15) and 178 cm (SD 0.08), respectively. The participants total HOOS´ score was 87.4 (SD 16.8). For the LEAS, the participants presented a mean score of 14.2 (SD 2.8). The score 14 in the LEAS means: I am up and about at my will in my house and outside. I also work participate in relaxed physical activity such as jogging, dancing, cycling and swimming 2-3 times per week.
The operated side had prolonged ankle eversion angle during late stance and delayed increased ankle inversion angle during early swing (p=0.008; effect size=0.70), increased ankle inversion moment during late stance (p=0.001; effect size=0.78), increased knee adduction angle during swing (p=0.044; effect size=0.57), reduced knee adduction moment during stance (p=0.05; effect size=0.40), reduced hip range of motion in the sagittal plane (p=0.046; effect size=0.56), reduced range of hip abduction moment during stance (p=0.02; effect size=0.63), increased hip range of motion in the transverse plane (p=0.02; effect size=0.62), reduced hip internal rotation moment during the transition from loading response to midstance (p=0.001; effect size=0.81) and increased trunk ipsilateral lean (p=0.03; effect size=0.60).
Conclusion(s): These findings may be related to hip weakness and reduced range of motion, to foot misalignments and to strategies implemented to reduce loading on the operated hip. It is possible that interventions such as muscle strengthening and stretching, use of foot insoles and gait feedback training help improving symmetry following hip resurfacing.
Implications: Some of these findings, such as the reduced hip sagittal plane range of motion, reduced hip abduction moment and increased hip transverse plane of motion, suggest that these individuals may benefit from hip extensors, external rotators and abductors strengthening and hip flexors stretching and strengthening in the lengthened position exercises.
Funding acknowledgements: We would like to acknowledge the Brazilian Funding Agencies, CAPES, FAPEMIG and CNPQ for supporting this work.
Topic: Musculoskeletal: peripheral
Ethics approval: This work was approved by the Queen´s University Ethics Board under the number 6007570.
All authors, affiliations and abstracts have been published as submitted.
