Is Socket Flexion Alignment Associated With Changes in Gait Parameters in Individuals With an Above-knee Amputation and a Hip Flexion Contracture?

Background: A hip flexion contracture (HFC) results in an inability to extend the hip by reducing the ROM of the affected hip. The condition affects one in four patients with above-knee amputations on the amputation side. While HFC in other disorders is known to decrease hip ROM and increase pelvic tilt during gait, its impact on the gait of patients with above-knee amputations remains unexplored. Typically, prosthetists design the socket with a flexion angle matching the HFC, potentially leading to compensations during the posterior stance phase of the gait cycle. To our knowledge, little is known about how or whether these compensations relate to the socket's flexion alignment.

Questions/purposes: (1) Is the presence of HFC associated with modifications of spatiotemporal and kinematic parameters during gait in patients with an above-knee amputation? (2) Is there a correlation between the socket flexion angle and the spatiotemporal and kinematic parameters during gait in patients with an above-knee amputation with and without HFC?

Methods: A comparative observational study was conducted between February 2022 and June 2023. Thirty-two participants with unilateral above-knee amputations who had undergone amputation at least 1 year prior and had a minimum of 1 month of experience with their current prostheses were eligible for consideration and included in the study. After the trial, 1 of 32 participants was excluded due to other impairments affecting gait, and 9% (3 of 32) were excluded because of pain or discomfort during data acquisition on their gait, leaving 88% (28 of 32) of participants included in the analysis. The median (IQR) age of participants in the HFC group (n = 13) was 50 years (26 to 56); 85% (11) were male and 15% (2) were female. The median (IQR) age of participants in the noHFC group (n = 15) was 41 years (32 to 56), and 100% were male. Time since amputation was similar between groups (HFC median 8 years [IQR 3 to 21], noHFC median 6 years [IQR 1 to 9], difference of medians 2; p = 0.31). Thirty-two percent (9 of 28) of patients were classified according to the Medicare Functional Classification Level system as K4 (exceeding basic ambulation skills) and 68% (19 of 28) were classified as K3 (ability to walk with variable cadence and traverse most environmental barriers). Clinical and prosthetic measurements were made, which comprised measurement of the HFC using a hand-held goniometer with the patient in the modified Thomas test position, the socket flexion alignment, and the difference (δ) between the HFC and socket flexion alignment. A gait analysis was performed with an optoelectronic system equipped with six infrared cameras and two force plates to analyze the time-distance and kinematic parameters of gait. To answer our first question, we quantitively compared the gait spatiotemporal and kinematic parameters between groups, and for the second question, we evaluated the correlations between the same parameters and prosthesis alignment for both groups.

Results: During gait, the HFC group exhibited reduced mean ± SD residual hip ROM in comparison with the noHFC group (35° ± 6° versus 44° ± 6°, mean difference -9° [95% CI -13° to -6°]; p < 0.001), increased pelvic tilt (11° ± 6° versus 7° ± 3°, mean difference 4° [95% CI 1° to 8°]; p = 0.02), increased pelvic rotation (12° ± 3° versus 9° ± 2°, mean difference 3° [95% CI 2° to 6°]; p < 0.001), and increased trunk rotation (15° ± 5° and 12° ± 2°, mean difference 3° [95% CI 0° to 6°]; p = 0.04). Greater δ correlated with decreased ROM in the contralateral hip (r = -0.71; p = 0.006), pelvis (r = -0.77; p = 0.002), and trunk (r = -0.58; p = 0.04) in the sagittal plane and with increased residual hip ROM (r = 0.62; p = 0.02). In terms of spatiotemporal gait parameters, in the HFC group, the δ correlated with an increase in contralateral step width (r = 0.58; p = 0.04) and a decrease in prosthetic step length (r = -0.65; p = 0.02).

Conclusion: Our findings further suggest that physiotherapists should consider the pelvic and trunk compensations associated with HFC in their rehabilitation because of potential long-term effects, such as low back pain or osteoarthritis. In addition, the correlation between the socket flexion angle and the parameters involved may support prosthetists in their choices of prosthetic settings. For now, we cannot consider these compensations as an impaired gait syndrome, and future studies are needed to evaluate their impact on patients' quality of life.

Level of evidence: Level III, therapeutic study.