DYNAMIC BAROPODOMETRY TO MEASURE LATEROMEDIAL FORCE IN SEVERE PES PLANOVALGUS BEFORE AND AFTER SURGERY

Abstract

Purpose of the study: Gait in patients with severe pes planovalgus is generally compromised by the excessive medial force. The altered gait pattern affects the overall static and the opposite lower limb. Dynamic baropodometry can be used to measure the lateromedial force in pes planovalgus before and after corrective surgery.

Material and methods: This series included 26 patients (28 feet), mean age 54.4 years (range 15–75 years), ten males and 16 females. All of the patients had stage 2 pes planovalgus due to posterior tibial tendinopathy without lower limb misalignment. The emed-SF gait platform (Novel) was used to make three consecutive measurements with recording of the second step while walking on the platform. Measurements were made before and after conservative surgery for pes planoval-gus which combined lengthening of the calcaneum (Evans), systematic percutaneous lengthening of the Achilles tendon, lengthening of the peroneal tendons, and reconstruction of the medial arch by lowering the first metatarsal in most cases. The force index (lateral over medial force) was calculated by the Novel-ortho software which also displayed the curve of the force index during the step movement.

Results: The force index (lateral over medial) was 0.87 in this series of pes planovalgus (normal = 1.07). This index remained below 1 throughout the step movement for 13 of 28 feet. For the others, medial force increased uniquely during weight bearing phases: taligrade, plantigrade or digitigrade. After surgery, the index increased to 1.25 with normalization of the force index curve in 15 of 28 feet. A comparative study on the first ray was not very significant: scarf lowering (9 cases from 0.81 to 1.16), basal lowering by dorsal addition (8 cases from 0.87 to 1.14), arthrodesis of the first cuneometatarsal (5 cass from 0.89 to 1.15); three cases did not have lowering procedures with less favorable clinical results but with an index which changed from 0.75 to 1.05.

Discussion: This study enabled an assessment of the lat-eromedial balance of the planovalgus foot without misalignment of the lower limbs. We were able to show that realigning the foot lessens the stress on the posterior tibial tendon which did not always have to be repaired to achieve a good clinical result. This re-balancing of the muscle stabilizing the rear foot occurs progressively, as was noted on the successive baropodometric examinations. This points out the importance of not starting proprioceptive rehabilitation exercises before four months postop. On the other hand, active reinforcement of the toe flexors should be started early. This study was conducted with a very small sample but did show that a postoperative force index below 0.9 is a sign of under correction and that an index above 1.8 corresponds to overcorrection.

Conclusion: Functional management requires good knowledge of the pathological processes and the therapeutic implications. This study shows that baropodometry, even without footprint analysis or pressure distribution measurements, enables definition of functional parameters which can be helpful in achieving more precise management for foot and ankle surgery.