Cavovarus With a Twist: Midfoot Coronal and Axial Plane Rotational Deformity in Charcot-Marie-Tooth Disease

Abstract

Background: The cavovarus deformity of Charcot-Marie-Tooth (CMT) disease is often characterized by a paradoxical relationship of hindfoot varus and forefoot valgus. The configuration of the midfoot, which links these deformities, is poorly understood. Accurate assessment of 3-dimensional alignment under physiologic loadbearing conditions is possible using weightbearing computed tomography (WBCT). This is the first study to examine the rotational deformity in the midfoot of CMT patients and, thus, provide key insights to successful correction of CMT cavovarus foot. Methods: A total of 27 WBCT scans from 21 CMT patients were compared to control WBCTs from 20 healthy unmatched adults. CMT patients with a history of bony surgery, severe degenerative joint disease, or open physes in the foot were excluded. Scans were analyzed using 3-dimensional software. Anatomic alignment of the tarsal bones was calculated relative to the anterior-posterior axis of the tibial plafond in the axial plane, and weightbearing surface in the coronal plane. Results: Maximal rotational deformity in CMT patients occurred at the transverse tarsal joints, averaging 61 degrees of external rotation (supination), compared to 34 degrees among controls ( P < .01). The talonavicular joint was also the site of peak adduction deformity in the midfoot, with an average talonavicular coverage angle measuring 12 degrees compared with −11 degrees in controls ( P < .01). Conclusion: This 3-dimensional WBCT analysis is the first to isolate and quantify the multiplanar rotational deformity in the midfoot of CMT patients. Compared with healthy unmatched control cases, CMT patients demonstrated increased axial plane adduction and coronal plane rotation at the talonavicular (TN) joint. These findings support performing soft tissue release at the TN joint to abduct and derotate the midfoot as a first step for targeted deformity correction. Level of Evidence: Level III, retrospective case-control study.

3D Analysis of Joint-Sparing Charcot-Marie-Tooth Surgery Effect on Initial Standing Foot Alignment

“…The method was previously validated in the foot and ankle literature. 1,6,9,17,18 As far as we know, this is the first study investigating perioperative WBCT findings in CMT feet using automated 3D measurements. Another major strength of this study is the relatively large number of CMT patients that were included.…”

“…The importance of the talonavicular joint in the axial correction of CMT deformity is well established in the literature. An et al 1 reported that CMT patients demonstrated increased axial plane adduction and coronal plane supination at the talonavicular joint, compared with healthy control cases. This may be attributable to chronic overpull of the posterior tibial tendon on the navicular, with inadequate, weakened abduction force by the peroneus brevis.…”

“…For this reason, semiautomated measurements are often used to assess complex 3-dimensional (3D) anatomy. 1,5,9 The 3D software can automatically measure the angle between bone axes after the manual registration of the bones. Sangoi et al 18 assessed differences in measurements done manually on 2D slices of WBCT vs 3D computer models in cavus feet.…”

The Surgical Correction of Cavovarus Deformity in Charcot-Marie-Tooth Disease

“…This axial plane imbalance is a major contributor to the characteristic twisting, supination deformity of the midfoot. 14 The first step of surgical treatment is to address PT contracture by releasing the tendon from its insertion, even if it has inadequate strength for transfer. It is invariably contracted and a deforming force.…”

Evaluation and Management of Cavus Foot in Adults: A Narrative Review

“…The radiological evaluation of cavus foot should also include the Coleman block test in order to assess the flexibility of the foot. In the recent literature, Dr. Michalski [36] and Dr. Tonya An [37] have conducted high quality research about bone morphology changes in cavus foot. Their research results indicate that the TN coverage angle (Figure 7) plays an important role in evaluating the effect of cavus foot correction.…”