Foot loading pattern and hind foot alignment are corrected in varus knees following total knee arthroplasty: a pedobarographic analysis.

PURPOSE

Osteoarthritis of knees with varus deformity is associated with a compensatory valgus deformity of the hindfoot and a lateral loading foot pressure pattern. However, whether this abnormal loading pattern is corrected in total knee arthroplasty (TKA) is unclear.

METHODS

The alignment and loading pattern of 91 consecutive patients (121 knees) undergoing TKA with pre-operative varus more than 10° were evaluated prospectively with functional outcome scores, static conventional radiography and dynamic pedobarogaphy pre-operatively and 1-year post-operatively. Outcomes assessed were Oxford Knee Scores, American Orthopaedic Foot and Ankle Scores, femorotibial mechanical angle, tibia-hindfoot angle, hindfoot valgus/varus index (VVI), foot line of pressure (LOP) laterality and peak pressure (PP) at both time points.

RESULTS

Of 121 knees, 98 (81%) regained normal alignment of the knee and 114 (92%) of the hindfoot. Similarly, PP (p < 0.001), VVI (pre-operative: - 0.29 ± 0.22, post-operative: - 0.04 ± 0.23, p < 0.001) and LOP laterality (pre-operative: 7% medial, post-operative: 96% medial, p < 0.001) all medialised post-operatively. All patients had improved functional outcomes at the knee (pre-operative: 20 ± 2, post-operative: 40 ± 2, p < 0.001) and ankle (pre-operative: 59 ± 10, post-operative: 89 ± 6, p < 0.001).

CONCLUSION

The present study shows, following the correction of knee varus with TKA, hindfoot alignment and foot loading pattern are both restored in the majority of patients. TKA offers both static and dynamic correction as seen in the hindfoot and loading pattern, respectively.

LEVEL OF EVIDENCE

Level III: prospective case-control study.