Analysis of plantar loading parameters pre and post surgical intervention for hallux vargus

Abstract

INTRODUCTION:: The purpose of the study was to compare range of motion (ROM) and plantar loading parameters pre and post surgical intervention for hallux valgus (HV). Fifteen female patients volunteered for the study, providing 27 feet with a diagnosis of moderate or severe HV deformity (greater than 26 degrees HV angle). All participants were screened by the same orthopaedic surgeon to ensure that no other foot deformities or neuromuscular diseases were present that would alter lower extremity biomechanics. Prior to surgery, each patient filled out a five-part questionnaire on previous medical history, description and location of symptoms, perceived pain and current functional status. Radiographs were taken from the dorsoplantar and oblique aspects with the patient weight bearing. HV and intermeditarsal angle (IM) were measured from the radiographs. Seated talocrural and first metatarsophalangeal (MP) joint active and passive (ROM) were measured with a hand-held goniometer as described by Norkin and White (1985). Plantar loading patterns were assessed using barefoot for the involved limb using the two step method as described by Meyers-Rice et al. (1992). Data was collected using a capacitive pressure measurement platform (EMED SD Pedography Analyzer, Novel GmbH, Munich) and stored for further analysis. The pressure platform consisted of a 32 x 62 sensor matrix with a resolution of 2 sensor/cm(2). The sampling rate of the platform was fixed at 70 Hz and auto triggered upon first contact. Five acceptable trials were collected for each subject. All of the following were conducted again eight weeks after a Chevron-Aikin Osteotomy surgical correction for HV. Each step was analysed by dividing the foot into seven plantar regions: heel (HL), midfoot (MF), medial forefoot (MFF), central forefoot (CFF), lateral forefoot (LFF), medial toe (MT) and lateral toe (LT). The following variables for each region were generated via the Novel-win software: peak force (%BW), peak pressure (Kpa), length of contact (ms), pressure time integral (Kpa(*)s), force time integral (%BW(*)s), instant of peak pressure (ms) and instant of peak force (ms). A repeated measures multivariate analysis of variance was used to detect differences in each loading and ROM measure before and after surgery. Post surgically, patients indicated that they had less pain and a higher rating of functional status (p<0.05). Differences were found in active dorsiflexion, active plantar flexion, and passive plantar flexion of the MP joint (p<0.05). No differences were found in talocrural ROM or MP neutral position. Radiographic measures indicated that HV and IM angles were changed following surgery (p<0.05). The average correction for HV angle was 14.0 degrees and 4.6 degrees for IM angle. No differences in loading were found for the HL, MF, MFF regions post surgically. Force time integrals increased from 15.7 BW(*)s to 18.8 BW(*)s post surgically in the CFF region (p<0.05). The LFF region exhibited a greater peak force (22.12 %BW vs. 27.12 %BW), force time integral (7.14 %BW(*)s vs. 9.04 %BW(*)s), pressure time integral (9.24 N/cm2(*)s vs. 12.10 N/cm2(*)s), instant to peak force (520.73 ms vs. 592.03 ms) and instant to peak pressure (548.40 ms vs. 607.97 ms) post surgically (p<0.05). Peak force and peak pressure decreased from 15.11 %BW to 6.92 %BW and 423.24 Kpa to 158.00 Kpa, respectively post surgically (p<0.05). Force time integrals decreased from 3.90 %BW(*)s to 1.72 %BW(*)s and pressure time integrals decreased from 10.41 Kpa(*)s to 4.40 Kpa(*)s post surgically (p<0.05). Contact time in the LT region increased from 627.57 ms to 575.33 ms post surgically (p<0.05). All pain scale and functional status measures improved eight weeks post surgically. Dorsiflexion ROM for the MP joint were decreased post surgically but were still adequate for gait (Hetherington et al., 1990). Loading variables indicated that, post surgically, the foot was loaded more laterally with less load on the hallux. Further research is needed to assess if the lateral loading pattern continues long term after Chevron-Aikin Osteotomy surgical correction for HV.