Axial Plane Rotation of the Talus in Progressive Collapsing Foot Deformity: A Weightbearing Computed Tomography Analysis

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Abstract

Background:

Progressive collapsing foot deformity (PCFD) is recognized as a 3-dimensional deformity centered around the talus. Previous studies have described some features of talar motion in the ankle mortise in PCFD, such as sagging in the sagittal plane or valgus tilt in the coronal plane. However, axial plane alignment of the talus in the ankle mortise in PCFD has not been investigated extensively. The purpose of this study was to examine this axial plane alignment of PCFD vs controls using weightbearing computed tomography (WBCT) images and to determine if talar rotation in the axial plane is associated with increased abduction deformity, as well as to assess the medial ankle joint space narrowing in PCFD that may be associated with axial plane talar rotation.

Methods:

Multiplanar reconstructed WBCT images of 79 patients with PCFD and 35 control patients (39 scans) were retrospectively analyzed. The PCFD group was divided into 2 subgroups depending on preoperative talonavicular coverage angle (TNC): moderate abduction (TNC 20-40 degrees, n=57) and severe abduction (TNC >40 degrees, n=22). Using the transmalleolar (TM) axis as a reference, the axial alignment of the talus (TM-Tal), calcaneus (TM-Calc), and second metatarsal (TM-2MT) were calculated. Difference between TM-Tal and TM-Calc was calculated to examine talocalcaneal subluxation. A second method to assess talar rotation within the mortise utilized an angle between the lateral malleolus and the talus (LM-Tal) in the axial slices of WBCT. In addition, the prevalence of medial tibiotalar joint space narrowing was assessed. These parameters were compared between the control and PCFD groups, and between moderate and severe abduction groups.

Results:

The talus was significantly more internally rotated with respect to the ankle TM axis and the lateral malleolus in PCFD patients compared to controls, and in the severe abduction group compared with the moderate abduction group, using both measurement methods. Axial calcaneal orientation did not differ between groups. There was significantly greater axial talocalcaneal subluxation in the PCFD group, and this was also greater in the severe abduction group. The prevalence of medial joint space narrowing was higher in PCFD patients.

Conclusion:

Our findings suggest that talar malrotation in the axial plane should be considered an underlying feature of abduction deformity in PCFD. The malrotation occurs in both the talonavicular and ankle joints. This rotational deformity should be corrected at the time of reconstructive surgery, especially in cases of severe abduction deformity. In addition, medial ankle joint narrowing was observed in PCFD patients, with a higher prevalence of medial ankle joint narrowing in those with severe abduction.

Level of Evidence:

Level III, case-control study.

Related collections

Most cited references 33

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The hindfoot alignment view.

Charles Saltzman, G Khoury (1995)

A modification of Cobey's method for radiographically imaging the coronal plane alignment of the hindfoot is described. Using this view, we estimated the moment arm between the weightbearing axis of the leg and the contact point of the heel. Normative data on 57 asymptomatic adult subjects are presented. The weightbearing line of the tibia falls within 8 mm of the lowest calcaneal point in 80% of subjects and within 15 mm of the lowest calcaneal point in 95% of subjects. The technique for measuring coronal plane hindfoot alignment is reliable, with an interobserver correlation coefficient of 0.97. This radiographic technique should help in the evaluation of complex hindfoot malalignments.

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Classification and Nomenclature: Progressive Collapsing Foot Deformity.

Mark S Myerson, David B Thordarson, Jeffrey Johnson … (2020)

The historical nomenclature for the adult acquired flatfoot deformity (AAFD) is confusing, at times called posterior tibial tendon dysfunction (PTTD), the adult flexible flatfoot deformity, posterior tibial tendon rupture, peritalar instability and peritalar subluxation (PTS), and progressive talipes equinovalgus. Many but not all of these deformities are associated with a rupture of the posterior tibial tendon (PTT), and some of these are associated with deformities either primarily or secondarily in the midfoot or ankle. There is similar inconsistency with the use of classification schemata for these deformities, and from the first introduced by Johnson and Strom (1989), and then modified by Myerson (1997), there have been many attempts to provide a more comprehensive classification system. However, although these newer more complete classification systems have addressed some of the anatomic variations of deformities encountered, none of the above have ever been validated. The proposed system better incorporates the most recent data and understanding of the condition and better allows for standardization of reporting. In light of this information, the consensus group proposes the adoption of the nomenclature "Progressive Collapsing Foot Deformity" (PCFD) and a new classification system aiming at summarizing recent data published on the subject and to standardize data reporting regarding this complex 3-dimensional deformity.

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Adult-acquired flatfoot deformity.

J T Deland (2008)

Originally known as posterior tibial tendon dysfunction or insufficiency, adult-acquired flatfoot deformity encompasses a wide range of deformities. These deformities vary in location, severity, and rate of progression. Establishing a diagnosis as early as possible is one of the most important factors in treatment. Prompt early, aggressive nonsurgical management is important. A patient in whom such treatment fails should strongly consider surgical correction to avoid worsening of the deformity. In all four stages of deformity, the goal of surgery is to achieve proper alignment and maintain as much flexibility as possible in the foot and ankle complex. However, controversy remains as to how to manage flexible deformities, especially those that are severe.