Differences in knee joint degeneration between primary hip osteoarthritis and hip osteoarthritis secondary to hip developmental dysplasia: A propensity score-based analysis

Abstract

Objectives

This study aimed to investigate differences in lower limb alignment and the prevalence of knee osteoarthritis (OA) among patients with primary hip osteoarthritis (PHOA) versus those with hip osteoarthritis secondary to developmental dysplasia of the hip (DDH-OA).

Methods

We compared 83 patients who underwent primary total hip arthroplasty for unilateral PHOA or DDH-OA after performing propensity score matching. The prevalence of knee OA and lower limb alignment were evaluated on preoperative plain radiographs.

Results

The prevalence of knee OA on the ipsilateral side was significantly higher in the PHOA group than in the DDH-OA group (p =.019), whereas there was no difference between the groups on the contralateral side (p = .631). Lower-limb alignment was more valgus on the ipsilateral side in the DDH-OA group than the PHOA group, whereas it was not significantly different on the contralateral side between groups.

Conclusion

The prevalence of knee OA and lower-limb malalignment on the ipsilateral side of hip OA were different for PHOA and DDH-OA patients. Shifting the mechanical axis of lower limbs might be associated with the prevalence of knee OA and lower limb malalignment in the presence of unilateral hip OA.

Keywords:

• Osteoarthritis
• knee alignment
• hip morphology
• propensity score matching

Acknowledgments

The authors thank Prof. Hideki Yoshikawa from Osaka University for his advice and criticism.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Informed consent

Formal consent is not required for this type of retrospective cohort study.

Conflict of interest

NS reports a grant (paid to Osaka University Graduate School of Medicine) from Kyocera Medical not related to this study.

Authors' Contribution

Study design: R.S., W.A., N.S. Data acquisition: R.S. and W.A. Data analysis and interpretation: All authors. Writing of the manuscript: R.S., W.A., N.S. Editing the manuscript: All authors. All authors have read and approved the final manuscript.