SLR - November 2014 - Abby Smith

Evertor Muscle Activity as a Predictor of the Mid-Term Outcome Following Treatment of the Idiopathic and Non-Idiopathic Clubfoot

Reference: Y. Gelfer, M. Dunkley, D. Jackson, J Armstrong, C. Rafter, E. Parnell, D.M. Eastwood. Evertor Muscle Activity as a Predictor of the Mid-Term Outcome Following Treatment of the Idiopathic and Non-Idiopathic Clubfoot. Bone Joint J. 2014; 96-B: 1264-8.

Scientific Literature Review

Reviewed By: Abby Smith, DPM
Residency Program: North Colorado Podiatric Medicine and Surgery Residency, Greeley, CO

Podiatric Relevance: It is well established that serial casting utilizing the Ponseti method is a successful treatment for idiopathic and non-idiopathic clubfoot cases, with success rates greater than 90 percent in idiopathic cases. Recurrence of deformity is possible, and is most commonly attributed to noncompliance with post-cast bracing. However, recurrence has still been reported even with strict compliance to bracing. The authors suggest a deficiency in evertor strength as a possible contributing factor to both idiopathic and non-idiopathic clubfoot recurrence. Evertor activity is reportedly variable in idiopathic clubfeet and weak or absent in most non-idiopathic clubfeet, often depending on underlying pathology. The authors investigated multiple factors that could potentially cause a recurrent clubfoot deformity in both idiopathic and non-idiopathic cases.  Even if a podiatric physician does not practice Ponseti casting method, one should be aware of the factors that can potentially contribute to recurrence.

Methods: Between July 2005 and July 2011, 103 consecutive patients with clubfeet were treated, accounting for 116 total clubfeet. Fifty-nine feet (38 children) had idiopathic deformity, and 57 feet (29 children) had non-idiopathic deformity (neuromuscular, arthrogryposis, complex non-specific deformities.) Inclusion criteria included no previous surgery to the foot, less than six months old. Parental or guardian consent was obtained prior to collecting and clinical and photographic data.

Severity was determined by Pirani classification at initial presentation and at each subsequent visit. Once initial correction was obtained, evertor muscle activity was assessed and documented by trained physiotherapists. Evertor activity was graded similar to Pirani score: 0 for normal muscle activity, 0.5 for evertor flicker under skin, one for no activity. Bracing was also initiated at the time of initial evertor evaluation. Ankle and STJ range of motion was also assessed at these times. Number of plaster casts required for correction, whether or not percutaneous Achilles tenotomy was performed, and bracing compliance was also documented for each case.

Following complete correction, feet were screened regularly for signs of recurrence. If recurrence occurred, it was then classified according to Pirani classification. Feet that were not completely corrected were documented as such, along with the explanation as to why complete correction was not obtained. Compliance was stratified into full, partial, or poor. Gait was also captured by video camera, and documented as normal or not normal.

Statistical analysis involving two-tailed t-test compared data between the idiopathic clubfoot to the non-idiopathic groups with respect to predictive factors for recurrence, further surgical intervention, and static and dynamic gait parameters. .

Results: Primary correction was obtained in all idiopathic and 90 percent of non-idiopathic cases, with similar bracing compliance, 95 percent vs. 90 percent, respectively. Recurrence occurred in 16 percent of children with idiopathic deformity and 48 percent of children with non-idiopathic deformity.  All but one of these children had an absence or weakness of peroneal activity. Overall, 32 percent of children with idiopathic clubfoot had poor evertor muscle activity (0.5 or 1), compared to 70 percent of the non-idiopathic clubfoot children. Evertor activity did not change once the brace was applied. No statistically significant association was found between initial severity of deformity, age at treatment onset, number of casts, or brace compliance and recurrence in either group. Poor or absent evertor muscle activity displayed a statistically significant relationship with recurrence and further surgical correction. Poor evertor activity was associated with abnormal gait and forefoot adductus and heel varus in the idiopathic group.

Conclusions: The results of this study show that idiopathic and non-idiopathic clubfoot recurrence can occur despite strict brace compliance. Evertor muscle activity and function can be assessed to predict possible cases of recurrence in both groups. This may become helpful in counselling parents on potential need for future tibialis anterior tendon transfers to address the dynamic supination seen in many recurrent cases of clubfoot. Poor evertor muscle activity was found to be the only factor that was associated with recurrence, further surgery and abnormal gait. No change in evertor activity was noted once the foot was corrected and subjected to the abduction bracing. However, progressive deforming forces found in some non-idiopathic clubfoot cases could alter this finding. The authors concluded that recognizing risk factors, such as evertor weakness, for recurrent clubfoot deformity may help to identify children that may require more frequent monitoring for earlier intervention.

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