Hybrid Oxford unicompartmental knee arthroplasty has lower residual cement extrusion than cemented arthroplasty in treating end-stage unicompartmental knee osteoarthritis

Abstract

Background: Hybrid Oxford unicompartmental knee arthroplasty (OUKA) consists of cementless femoral prostheses and cemented tibial prostheses. Although a hybrid OUKA has been used in clinical practice, the clinical outcome has not been reported. The purpose of this study was to compare the short-term clinical outcomes and rate of residual bone cement extrusion between hybrid and cemented prostheses and analyse the possible reasons for differences between outcomes.

Methods: A total of 128 knees (118 patients) with end-stage osteoarthritis were included in this study, of which underwent consecutive operations using unicondylar Oxford phase 3 implants from July 2017 and September 2019 in our centre. Follow-up was performed at 6 weeks, 3 and 6 months, 1 year and every year after operation, and complications and changes in the Oxford knee score (OKS) were recorded. The OKS of the two groups was analysed by the generalized estimating equation approach. Prosthesis-based standard fluoroscopy was performed in a timely manner after each operation, and the rate of residual cement extrusion of the two groups was estimated using T-tests and a multivariate regression analysis.

Results: Excluding the cases that lost follow-up, a total of 120 knees (65 in hybrid group and 55 in cemented group) were included in the analysis. There was no statistically significant difference in patient characteristics between the two groups (p > 0.05). The average follow-up time was 23.4 months (and ranged from 12 to 38 months). As of the last follow-up, there were no complications, such as dislocation, fracture, prosthesis loosening and subsidence, but one patient in the cemented group experienced symptoms caused by residual loose cement. Postoperative OKS in both groups improved significantly (p < 0.001). There was no significant difference in the OKS at any point during the follow-up or in the improvement of the OKS between the two groups (p > 0.05). Residual cement was mainly extruded behind the tibial prosthesis. The rate of hybrid periprosthetic residual cement extrusion was significantly lower in the hybrid group than in the cemented group, and the difference was statistically significant (OR = 3.38; p = 0.014).

Conclusions: Hybrid OUKA is as effective as cemented OUKA in the short term after operation and can significantly reduce the residual cement extrusion rate around the tibial prosthesis.

Keywords: Cement extrusion; Hybrid; OUKA outcome; Unicompartmental knee arthroplasty.

Fig. 1

A. The surgeon manipulated X-ray beam and operative limb under fluoroscopic control until the X-ray beam was parallel to the side wall and base plate of the tibial component. B. The patient was positioned in a supine position with the knee flexed 30-40°.The fluoroscope was rotated through 90°so that the X-ray beam was centered on the femoral component. This meant that the X-ray was perpendicular to the side of the femoral component, so as to evaluate the residual cement around the prosthesis. C. One case of fixed excess cement of the posterior tibial component (arrow)

Fig. 2

OKS score-time change trend of hybrid OUKA (A) and cemented OUKA (B)

Fig. 3

A.B. Postoperative standard unicompartmental fluoroscopy and CT showed residual cement (arrow) in the medial tibial prosthesis. C. D. When the patient developed symptoms 2 years after surgery, radiology revealed that the foreign body in the lateral compartment (arrow) was the same as the previous medial cement residue

Fig. 4

Arthroscopic removal of free cement body in the lateral compartment