The purpose of this study was to examine the relationship between medial tibial joint line elevation and the improvement of range of motion (ROM) in unicompartmental knee arthroplasty (UKA). The hypothesis was that limited elevation of tibial joint line will improve knee range of motion in UKA.
Forty-six consecutive medial UKAs were enrolled in this study. Medial tibial joint line elevation was defined as the polyethylene insert and tibial tray thickness minus the tibial osteotomy and sawblade thickness. Positive values indicated an elevation of the tibial joint line. A component gap between the femoral trial prosthesis and the medial tibial osteotomy surface was also examined. Joint loosening was also calculated based on the joint component gap minus insert and tibial tray thickness. The correlation of the medial tibial joint line elevation with joint looseness and postoperative range of motion were analyzed.
The mean medial tibial joint line elevation was 4.9 ± 1.1 mm. The medial tibial joint line elevation reduced the improvement of knee extension (R = − 0.43, p < 0.01). The medial tibial joint line elevation was also correlated with reduced loosening of the joint knee extension (R = − 0.42, p < 0.01). This, in turn, resulted in limited improvement of the knee extension angle. Moreover, joint line elevation under 5 mm significantly improved knee extension angle compared to joint line elevation over 5 mm.
The medial joint line elevation of the tibia in UKA reduced the improvement of knee extension angle, due to a reduced joint looseness at knee extension. A tibial joint line elevation greater than 5 mm in UKA should be avoided to prevent postoperative flexion contracture. For the clinical relevance, this study clarified that the medial joint line of the tibia is an important factor to prevent postoperative flexion contracture in UKA.
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Unicompartmental knee arthroplasty
Total knee arthroplasty
Range of motion
Knee Society Knee Score
Knee Society Function Score
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Conflict of interest
The authors declare that they have no conflict of interest.
There was no external source of funding for this study.
Approval was obtained from the Ethics Committee at Kobe University Graduate School of Medicine. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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Takayama, K., Ishida, K., Muratsu, H. et al. The medial tibial joint line elevation over 5 mm restrained the improvement of knee extension angle in unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 26, 1737–1742 (2018). https://doi.org/10.1007/s00167-017-4763-8
- Unicompartmental knee arthroplasty
- Joint line
- Range of motion