Lower limb alignment in patients with primary valgus ankle arthritis: A comparative analysis with patients with varus ankle arthritis and healthy controls

Abstract

Background

While it is commonly acknowledged that the combined effect of lower limb orientation and ankle and hindfoot alignment play a fundamental role in ankle arthritis, supramalleolar/lower limb alignment has received less attention in valgus ankle arthritis. The purpose of this study was to analyze the lower limb alignment of patients with valgus ankle arthritis with primary origin, compared to that of varus ankle arthritis and normal controls. We hypothesized that patients with valgus ankle arthritis would have the opposite pattern of lower limb alignment as those with varus ankle arthritis.

Methods

A retrospective radiographic analysis was performed on 61 patients (62 ankles, mean age, 59.3 ± 12 years) with primary valgus ankle arthritis. On preoperative radiographs, seven parameters, including talar tilt angle, medial distal tibial angle (MDTA), talar center migration, anterior distal tibial angle, talo-first metatarsal (Meary's) angle, hindfoot moment arm (HMA), and mechanical axis deviation (MAD), were measured and compared to those of primary varus ankle arthritis (n = 55; mean age, 59.7 ± 8.1 years) and control patients (n = 59; mean age, 29.3 ± 7.3 years).

Results

The valgus group had a significantly lower mean MDTA than the control group (p < 0.0001), indicating a varus distal tibial plafond in comparison to the control group. Meary's angle and HMA were significantly lower in the valgus group compared to the varus group (p < 0.05 and p < 0.0001, respectively), indicating a lower medial longitudinal arch and valgus hindfoot alignment. On whole limb radiographs, the valgus group showed a greater MAD than the control group, indicating varus lower limb alignment (p < 0.05). However, the MAD did not differ significantly between the valgus and varus groups (p = 0.7031).

Conclusion

Our findings indicate that a significant proportion of ankles with primary valgus arthritis have a varus tibial plafond and a varus lower limb mechanical axis. This study contributes to our understanding of primary valgus ankle arthritis and suggests that lower limb alignment should be analyzed and considered throughout valgus ankle arthritis realignment procedures.

Introduction

A comprehensive analysis of the lower limb alignment may be a critical component of successful realignment procedures in ankle joint preservation surgery. For a long period of time, realignment procedures concentrated on realigning local geometry, particularly around the ankle and hindfoot. Recent studies, however, have found an interaction between overall lower limb alignment and the ankle and hindfoot in the development and progression of ankle arthritis [1], [2]. As a consequence, strategies for optimizing the mechanical axis of the whole lower limb are being documented in joint preservation surgeries in ankle arthritis [3].

While it is commonly acknowledged that the combined effect of lower limb orientation and ankle and hindfoot alignment is the fundamental cause of primary ankle arthritis [4], [5], supramalleolar alignment has received less attention in valgus ankle arthritis of primary origin. In cases of valgus ankle arthritis caused by deltoid ligament insufficiency secondary to advanced progressive collapsing foot deformity (PCFD), distal tibia orientation and lower limb alignment have not been incorporated into surgical planning, while inframalleolar causes have been extensively studied and treated [6], [7]. Therefore, unlike in varus ankle arthritis where supramalleolar osteotomies (SMOs) are frequently used in realignment surgery, use of supramalleolar correction has been limited to cases of posttraumatic distal tibial plafond deformity in valgus ankle arthritis [8], [9].

A recent study indicated that some valgus ankle arthritis with primary origin had no evidence of deltoid ligament insufficiency and can be successfully treated with SMOs that address both lower limb alignment and local geometry [10]. This implies that lower limb malalignment may be a contributing factor in valgus ankle arthritis, as it is in varus ankle arthritis. Thus, evaluating lower limb alignment in patients with valgus arthritis may be critical for elucidating the eccentric load vector on the tibiotalar joint, elucidating the etiology of arthritis development, and developing a treatment strategy for realignment surgery.

The purpose of this study was to analyze the lower limb alignment of patients with valgus ankle arthritis with primary origin, compared to that of varus ankle arthritis and controls. The authors hypothesized that patients with valgus ankle arthritis would have the opposite pattern of lower limb alignment as those with varus ankle arthritis: valgus mechanical axis, valgus distal tibial plafond, and valgus hindfoot alignment.