Pathophysiology of abnormal compensation ability of the subtalar joint in the varus knee

Kotaro Miyazaki; Akira Maeyama; Taiki Matsunaga; Tetsuro Ishimatsu; Takuaki Yamamoto

doi:10.1016/j.jos.2023.09.009

Pathophysiology of abnormal compensation ability of the subtalar joint in the varus knee

J Orthop Sci. 2023 Oct 16:S0949-2658(23)00268-3. doi: 10.1016/j.jos.2023.09.009. Online ahead of print.

Authors

Kotaro Miyazaki¹, Akira Maeyama², Taiki Matsunaga³, Tetsuro Ishimatsu⁴, Takuaki Yamamoto⁵

Affiliations

¹ Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University 7-45-1 Nanakuma, Jonan-ku, Fukuoka 810-0180, Japan. Electronic address: miyataro_k@yahoo.co.jp.
² Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University 7-45-1 Nanakuma, Jonan-ku, Fukuoka 810-0180, Japan. Electronic address: akira.maeyama0713@joy.ocn.ne.jp.
³ Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University 7-45-1 Nanakuma, Jonan-ku, Fukuoka 810-0180, Japan. Electronic address: taiki.matsu.0730@gmail.com.
⁴ Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University 7-45-1 Nanakuma, Jonan-ku, Fukuoka 810-0180, Japan. Electronic address: md140002@yahoo.co.jp.
⁵ Department of Orthopaedic Surgery, Faculty of Medicine, Fukuoka University 7-45-1 Nanakuma, Jonan-ku, Fukuoka 810-0180, Japan. Electronic address: yamamotot@fukuoka-u.ac.jp.

PMID: 37852899
DOI: 10.1016/j.jos.2023.09.009

Abstract

Background: In recent years, the involvement of the compensation ability of the subtalar joint in lower extremity alignment has been reported. We previously showed that hindfoot alignment angle (HAA) is an indicator of compensation ability of the subtalar joint. The abnormal compensation ability of the subtalar joint was defined by the mobility of the subtalar joint, and evaluation of the mobility of the subtalar joint may help to further clarify the pathophysiology of abnormal compensation ability of the subtalar joint. This study was performed to evaluate the mobility of the subtalar joint and clarify the pathophysiology of abnormal compensation ability of the subtalar joint in the varus knee.

Methods: Seventy-two knees of 72 patients aged ≥40 years with varus knee were included in this study. Preoperative radiographs were used for measurement of this study parameters. Based on our previous study, we defined HAA of ≥15.9°as abnormal compensation ability of the subtalar joint. The patients were divided into an abnormal group (A-group) and normal group (N-group). All measurement parameters were compared between the groups, and correlations between the HAA and each measurement parameter were analyzed.

Results: The weight-bearing hindfoot angle (WBHA) (p < 0.001) and non-weight-bearing hindfoot angle (non-WBHA) (p = 0.003), were significantly greater in the A-group than in the N-group. Conversely, the ratio of change in hindfoot alignment (p = 0.006), were significantly smaller in the A-group than in the N-group. The HAA was positively correlated with WBHA (r = 0.66) and non-WBHA (r = 0.43) and negatively correlated with the ratio of change in hindfoot alignment (r = -0.32).

Conclusions: The pathophysiology of abnormal compensation ability of the subtalar joint in the varus knee is thought to involve a state of increased valgus of hindfoot alignment and an inability to move into normal hindfoot alignment.

Level of evidence: Level Ⅲ, retrospective study.

Keywords: Alignment; Compensation of subtalar joint; Hindfoot; Hindfoot alignment angle.