The use of pedobarographic analysis to evaluate movement patterns in unstable total knee arthroplasty: A proof of concept study.

ABSTRACT

BACKGROUND: Definition and clinical diagnosis of instability in TKA is challenging. Sensitive and objective biomechanical tools to aid diagnosis are currently lacking. This proof-of-concept study evaluates the use of pressure mat analyses to identify abnormal biomechanical loading patterns associated with TKA instability within an outpatient clinical setting. METHODS: Twenty participants were examined 10 patients with suspected unilateral TKA instability and 10 healthy controls. Participants underwent bilateral stance and gait tests measuring time and limb loading pressure parameters. Gait was divided into three phases heel strike, mid-foot and toe off. Pressure recordings are expressed relative to bodyweight. Between-limb loading discrepancies were calculated in TKA patients and controls, and these differences were then compared between groups. Statistical significance was accepted at p < 0.05. RESULTS: TKA patients consistentlyoffloadedpressure away from the operated limb, whereas healthy controls exhibited more even limb loading throughout bilateral stance (p < 0.05). TKA patients exhibited greater discrepancy in overall step contact time between limbs (-0.09 s ± 0.16 s; p = 0.016) compared to controls (0.06 s ± 0.08 s; p = 0.04). Post-hoc tests showed significant between-group differences during midfoot (-0.04 s ± 0.07 s; p = 0.03) and toe-off (0.05 s ± 0.14 s; p = 0.013). Between-group differences in limb loading discrepancy were evident at heel strike (-9.24% ± 2.11%; p = 0.0166) and toe-off (-10.34% ± 5.51%; p = 0.0496). DISCUSSION: Pedobarographic measurements demonstrated differences in mechanical loading patterns in patients with TKA instability compared to healthy controls during functional tasks and warrants further investigation. This may prove to be a useful clinical diagnostic tool in identifying patients that would benefit from revision surgery or physical therapy.