Kinematic, Kinetic and Electromyographic Response to Customized Foot Orthoses in Patients with Tibialis, Posterior Tenosynovitis, Pes Plano Valgus and Rheumatoid Arthritis

SLR- March 2014- Todd Peabody

Reference: Barn; R. Brandon; M. Rafferty; D. Sturrock; RD., Steultjens; M. Turner; DE. Woodburn; J. Kinematic, Kinetic and Electromyographic Response to Customized Foot Orthoses in Patients with Tibialis Posterior Tenosynovitis, Pes Plano Valgus and Rheumatoid Arthritis. Rheumatology 2014;53: 123-130.

 

Scientific Literature Review

Reviewed by: Todd Peabody, DPM
Residency Program: Botsford Hospital
 

Podiatric Relevance: Patients with rheumatoid arthritis (RA) are often encountered in the podiatric clinic. As the disease progresses, pathology involving the tibialis posterior tendon and an associated pes plano valgus (PPV) deformity is often encountered. In the treatment of these patients the use of functional custom orthoses is commonplace. While there is evidence to suggest that custom orthotics reduce foot pain and plantar pressures in the RA patient, this is one of the first studies to suggest that orthotics provide not only symptomatic relief but also improved foot function in the RA patient population.

Methods: Ten test subjects (four males, six females) with confirmed diagnosis of RA, passively correctable PPV deformity, and ultrasound-confirmed tibialis posterior tenosynovitis who had not worn or received custom foot orthoses in the past 12 months were included in the study. All participants were given custom orthotics from a subtalar joint neutral cast. After a 10-15 minute acclimatization period, biomechanical analysis was performed using both a 12-camera,120Hz 3-D motion analysis system to track motion during gait as well as a force plate to record ground reaction forces. Data was collected for five walking trials for each subject under both barefoot conditions and shod with orthoses. EMG activity was also recorded on all subjects during walking trials. Surface electrodes were used to gather readings on the flexor digitorum longus, tibialis anterior, soleus, peroneus longus, and medial gastrocnemius and intramuscular EMG was restricted to the tibialis posterior.
 

Results: For the variables recorded, there was significantly reduced peak rearfoot eversion, increased peak rearfoot plantar flexion and reduced peak forefoot abduction and dorsiflexion in the shod with orthotic construct compared to barefoot. There were minimal insignificant differences seen for ankle joint moment and ankle joint power between the two groups. EMG data was not normally distributed, however significant differences were seen in the shod with orthotic group witha later peak of contraction of the gastrocnemius and soleus, and increasedmagnitude of tibialis anterior when compared to the barefoot group. There was atrend toward reduced activity of tibialis posterior in the shoe with orthoticgroup, but these results did not reach significant levels.

Conclusions: The aim of the study was to investigate the effect of customized orthoses on tibialis posterior muscle activation and kinematic/kinetic features in patients with RA. Additionally, the study was the first to look at the effect of orthoses on EMG activity of tibialis posterior muscle in patients with RA and PPV. Although the response of the tibialis posterior and other lower leg muscles to the orthotics was variable, there was a trend toward reduced activity of tibialis posterior during the contact phase of gait. Despite a lack of significant results for alterations to EMG activity, there were significant findings for key discrete kinematic variables. Prior to this study a majority of the literature on the effect of orthotics on kinematics/kinetics are from control populations with normal foot posture, and therefore, can be difficult to translate to patient population with foot deformity. The kinematic changes in this study were not only significant with the use of orthotics, but the detected changes bring the values closer to the values reported in the previously mentioned control population studies. This study was subject to some limitations. First, the small sample size (10 patients) makes it difficult to draw strong conclusions from the data. Next, there is no accepted period of acclimatization for foot orthoses. This study allowed each test subject only 10-15 minutes of wear before initiating testing, while previous studies on orthotics have allowed periods ranging from six days up to four weeks for acclimatization. Finally, the study compared only barefoot and shod with orthotics walking trials and does not separate the effect of the footwear from the orthotics.