A polycentric hydraulic hip joint increases prosthetic gait biomechanics and functional capabilities for hip disarticulation amputees

Clinical Question

In patients with a hip disarticulation amputation, does a polycentric hydraulic hip joint improve gait biomechanics and functional capabilities compared to a single axis, constant friction hip joint?

Background

People with hip disarticulation amputations often have limitations in activities of daily living associated with walking, climbing stairs, and sitting down.¹ In addition, published literature shows that the higher the amputation level, the lower the acceptance rate of using a prosthesis.² Less than 50% of people with a hip disarticulation amputation use a prosthesis in everyday life.³ Lower user acceptance rates are caused by prosthetic limitations like poor gait pattern, socket discomfort, high energy consumption, and more walking aids required.^2-4 For the last several decades, hip disarticulation prostheses have been made with a forward tilted monocentric hip joint, which moves in one plane, allowing only flexion and extension. This motion limitation often leads to body compensations such as increased lumbar involvement or posterior pelvic tilt during prosthetic swing phase.^5-6 Polycentric hydraulic hip joints have a four-bar linkage hip joint with a hydraulic unit that provides controlled resistance to motion during both stance and swing phase.⁴ Due to the added motion of this style of hip joint, it has the potential to reduce some of the gait abnormalities commonly associated with hip disarticulation prostheses.

Search Strategy

Search Terms: (hip disarticulation OR hemipelvectomy) AND (gait) AND (outcome OR rehabilitation) AND (helix OR hip joint) AND (comparison OR evaluation OR analysis OR efficiency OR case report) NOT (infection OR cancer). The included articles are a representative sample.
Inclusion/Exclusion Criteria: English, peer-reviewed and published, 2010 to present

Synthesis of Results

Literature shows that gait using a hip disarticulation prosthesis with a monocentric hip joint has significant asymmetry compared to the intact side.⁴ However, significant enhancements with regards to the gait patterns of hip disarticulation amputees are shown when walking with a polycentric hydraulic hip joint compared to the monocentric joint.^3,4 Enhancements included improved hip extension control, more moderate hip flexion velocity during swing phase, and increased stance flexion in the prosthetic knee, which leads to improved gait kinematics and increased stability.³ Using a polycentric hydraulic hip joint “provided a gait pattern more similar to that of able-bodied persons.”³ In addition to biomechanical gait analysis, outcome measures showed reduced TUG times and increased walking velocity using a polycentric hydraulic hip joint.² For qualitative data, patient scores from the Locomotor Capabilities Index (LCI) showed increased advanced ambulation skills and activities considered difficult for hip disarticulation amputees when fit with a polycentric hydraulic hip joint, resulting in increased independence. Overall outcomes of participants fit with a polycentric hydraulic hip were statistically improved.² However, for some patients, the continued discomfort of wearing a prosthesis or the increased motion of a polycentric hydraulic hip joint ultimately led to rejection.⁴ Due to the low incidence of hip disarticulation amputations and complexity of their prostheses, there has not been considerable research done on this patient population. Some limitations to these studies include the small subject populations, the lack of comparative polycentric hip designs, and inconsistencies in prosthetic adjustment periods that can greatly effect outcome measure results as well as overall component selection and socket fit.

Clinical Message

Use of a polycentric hydraulic hip joint is likely to improve the gait biomechanics of hip disarticulation prosthetic wearers. Existing evidence has low subject populations with varying results, but qualitative and quantitative outcome measures with a polycentric hydraulic hip joint show higher patient-reported functional level of activities of daily living and self-selected walking speeds compared to the monocentric constant friction standard of care. The patient still must overcome the obstacles associated with prosthetic use at the hip disarticulation level, but the use of a polycentric hydraulic hip joint may prove to provide a more biomechanically effective alternative compared to monocentric options for these prosthetic users.

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