Dave Hudson, PT.
James Richards, PhD.
University of Delaware
Sports Science Center
Newark, Delaware 19176
INTRODUCTION: Excessive foot pronation is one of the most prevalent foot dysfunctions treated by health care practitioners. Hyperpronation is pronatory motion that occurs beyond the normal range, or motion that occurs at an inappropriate time. Clinicians from across several medical disciplines have indicated hyperpronation in the etiology of numerous maladies including hallux abducto-valgus, bunions, tarsal tunnel syndrome, "shin splints", patellar malalignment syndrome, hip and low back pain.
Researchers have found both plantar orthotics and strengthening exercises to be effective as independent treatments in managing hyperpronation. However, findings have been inconsistent . Clinicians estimate their success rate to be in the 70-80% range when treating hyperpronation with orthotics, and no data is available on the efficacy of strengthening exercises alone. The purpose of this study was to determine the effect of plantar orthotics and therapeutic procedures on controlling hyperpronation in the subtalar joint (STJ) during the stance phase of gait. For the purpose of this experiment, therapeutic procedures included strengthening, stretching, and proprioception exercises, and manual therapy techniques for the release of restricted tissues.
MATERIALS AND METHODS: Five males and two females with excessive pronation of the foot began this study, and three males and one female completed the experiment. Two subjects were dismissed due to non-compliance, and one sustained an injury unrelated to these experimental procedures. On the first day, each subject received custom prescribed plantar orthotics, and underwent a three dimensional gait analysis while walking shod with and without their orthotics at 2.8 mph on a level treadmill (Pacer). Six high-speed CCD video cameras captured data at 120 Hz during three full gait cycles from six retro-reflective markers placed on the right lower extremity. The markers were placed as follows: a) lateral femoral condyle b) on a post projecting lateral from mid-tibial shaft c) lateral malleolus d) proximal calcaneus e) distal calcaneus f) second metatarsal shaft. Data was processed using Motion Analysis software. Plantar pressures were recorded by an F-Scan sensor interfaced to a 486 PC. Following a one month accommodation period, all subjects underwent a second gait analysis. Within the next 72 hours, each subject was tested for maximal isokinetic strength of their hip abductors, knee extensors, and ankle inverters at 30_ and 180_/second on a Cybex II. Over the following four weeks, the subjects were treated three times a week. The subjects performed six therapeutic exercises, and received mobilizations and/or deep tissue releases of restricted structures as needed. The therapeutic exercises included: a) lateral step-ups with the subtalar joint in supination b) heel squeezes in supine with the hips extended and knees flexed c) calf raises with the subtalar joint in supination d) Biomechanical Ankle Platform System (BAPS) board exercise for eccentric strengthening of the posterior tibialis and anterior tibialis muscles e) gastrocnemius stretching with the STJ in supination f) soleus stretching with the STJ in supination. Upon completion of the exercise phase, all subjects underwent a third gait analysis and a second set of strength tests following the same protocol as previous sessions.
In this experimental design each subject will serve as their own control. A 2-way ANOVA with repeated measures will compare the 3-D kinematics in the right STJ of each subject for all conditions, as well as force data and maximal strength measurements. Movement in the STJ predominantly occurs on the frontal and transverse planes, therefore, calcaneal eversion and abduction will be of primary interest. F-scan data will be collected from 5 zones on the sole of the foot: a) rearfoot b) medial midfoot c) lateral midfoot d) medial forefoot e) lateral forefoot . Mean pressures from each zone will be compared to all conditions for each subject.
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