Elsevier

The Knee

Volume 24, Issue 1, January 2017, Pages 107-115
The Knee

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

https://doi.org/10.1016/j.knee.2016.09.023Get rights and content

Abstract

Background

There are unanswered questions about knee–ankle alignment after total knee arthroplasty (TKA) for varus and valgus osteoarthritis (OA) of the knee. The aim of this retrospective study was to assess knee–ankle alignment after TKA.

Methods

The study consisted of 149 patients who had undergone TKA due to varus and valgus knee OA. The alignment and angles in the selected knees and ankles were measured on full-length standing anteroposterior radiographs, both pre-operatively and post-operatively. The paired t-test and Pearson's correlation tests were used for statistical analysis.

Results

The results showed that ankle alignment correlated with knee alignment both pre-operatively and postoperatively (P < 0.05). The pre-operative malalignment of the knee was corrected (P < 0.05), and the ankle tilt angle was accordingly improved in the operative side after TKA (P < 0.05). In addition, TKA had little effect on knee–ankle alignment on the non-operative side (P > 0.05).

Conclusion

These findings indicated that routine TKA could correct the varus or valgus deformity of a knee, and improve the tilt of the ankle. Ankle alignment correlated with knee alignment both pre-operatively and postoperatively. Both pre-operative knee and ankle malalignment can be simultaneously corrected following TKA.

Level of evidence

Level III.

Introduction

Total knee arthroplasty (TKA) is a very successful surgical procedure used to treat end-stage osteoarthritis (OA) of the knee so that pain can be relieved and joint function can be restored due to the correction of lower extremity malalignment [1], [2]. It is also known that TKA surgery can achieve normal Saxial alignment of the lower extremity in the coronal, sagittal and rotational planes by implanting the prosthesis precisely, contributing to improve long-term survival of the prosthesis [3]. Postoperative lower extremity alignment, measured on anteroposterior radiographs, is an important determinant of long-term outcomes following TKA [4], [5]. Several factors such as soft tissue laxity, tibial bone loss, inappropriate bone resection, improper cementation, pre-operative varus deformity of > 20°, and femoral bowing of > 5° could contribute to malalignment after TKA [6]. Malalignment after TKA could cause overloading of the implant bearing and the bone itself, leading to osteolysis, instability and early loosening [7], [8], which is one of the major mechanisms leading to early clinical failure and may result in revision surgery [4], [9], [10], [11], [12]. Moreland pointed out that prosthetic alignment is the most crucial factor affecting the survival of the implant [9]. Other studies have also thought that prosthesis survival following TKA depends on restoration of the mechanical alignment of the operated leg [11], [13], [14].

Patients with OA knee and requiring TKA commonly present with ankle OA and abnormal ankle alignment; [15] however, whether ankle malalignment is affected after TKA, and/or correlates with knee malalignment pre-operatively and postoperatively, remains uncertain. Few reports are available that assess the association of the abnormal alignment and degenerative changes in the ankle joint with the varus or valgus deformity in the knee. Two studies from different institutions reported inconsistent findings regarding the relationship between ankle and knee malalignment in TKA [15], [16]. Indeed, Chandler and Moskal did not find a relationship between knee and hindfoot malalignment before or after TKA [16]. Meanwhile, Tallroth et al. demonstrated that the ankle tilt is pre-operatively associated with deviation in the tibiofemoral angle and mechanical axis [15]. However, few studies have actually used full-length standing anteroposterior radiographs of both lower extremities to assess this issue, and there is no consensus concerning the change of knee–ankle alignment after TKA for varus or valgus OA knee.

The aim of this study was to compare pre-operative and postoperative knee–ankle alignment and angles, using both hip-to-ankle radiographs in the standing position, and assess knee–ankle alignment after primary TKA.

Section snippets

Patient information

A retrospective study was conducted of patients with symptomatic varus or valgus OA knee who had undergone primary TKA between January and October 2013 in China–Japan Friendship Hospital. During this period, all patients were submitted to routine pre-operative and postoperative full-length standing anteroposterior radiographs of both lower extremities. Exclusion criteria were patients that: lacked full-length pre-operative or postoperative standing anteroposterior radiographs; had unclear

Correlation between the knee and ankle alignment

Abnormal knee alignment significantly correlated with ankle malalignment in unilateral varus or valgus gonarthrosis pre-operatively and postoperatively. The HKA had a significant positive correlation with the TAA angle on the unilateral operative side before (P < 0.001) (Figure 2A, Table 2) and after TKA (P = 0.032) (Figure 2B, Table 2). There was also a significant positive correlation between the HKA and the TAA angle on the unilateral non-operative side before (P < 0.001) (Figure 2C, Table 2) and

Discussion

The present findings indicated that ankle alignment correlates with knee alignment both pre-operatively and postoperatively. The pre-operative malalignment of the knee was corrected, and the ankle tilt angle was accordingly improved on the operative side after TKA. In addition, both pre-operative knee and ankle malalignment could be simultaneously corrected following TKA.

Osteoarthritis is the most common form of arthritis; it often occurs in the knee, and can induce pain and physical disability

Source of funding

No disclosures of funding were received for this work.

Conflict of interest

This study was supported by the National Natural Science Foundation of China (81372013) and the Research Fund of China–Japan Friendship Hospital (2013-MS-27, 2014-4-QN-29). China–Japan Friendship Hospital Youth Science and Technology Excellence Project (2014-QNYC-A-06). The authors declare that they have no conflict of interest.

Acknowledgments

We are grateful to all the participating patients of this study. We thank the staff members of this trial, our colleagues, and all the study staff for their enormous efforts in collecting and ensuring the accuracy and completeness of all the data.

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