Coronal plane stability of cruciate-retaining total knee arthroplasty in valgus gonarthrosis patients: A mid-term evaluation using stress radiographs

Abstract

BACKGROUND

Total knee arthroplasty (TKA) using implants with a high level of constraint has generally been recommended for patients with osteoarthritis (OA) who have valgus alignment. However, studies have reported favorable outcomes even with cruciate-retaining (CR) implants.

AIM

To evaluate the coronal plane stability of CR-TKA in patients with valgus OA at the mid-term follow-up.

METHODS

Patients with primary valgus OA of the knee who underwent TKA from January 2014 to January 2021 were evaluated through stress radiography using a digital stress device with 100 N of force on both the medial and lateral side. Gap openings and degrees of angulation change were determined. Descriptive statistical analysis was performed for both continuous and categorical variables. Inter-rater reliability of the radiographic measurements was evaluated using Cronbach’s alpha.

RESULTS

This study included 25 patients (28 knees) with a mean preoperative mechanical valgus axis of 11.3 (3.6-27.3) degrees. The mean follow-up duration was 3.4 (1.04-7.4) years. Stress radiographs showed a median varus and valgus gap opening of 1.6 (IQR 0.6-3.0) mm and 1.7 (IQR 1.3-2.3) mm and varus and valgus angulation changes of 2.5 (IQR 1.3-4.8) degrees and 2.3 (IQR 2.0-3.6) degrees, respectively. No clinical signs of instability, implant loosening, or revision due to instability were observed throughout this case series.

CONCLUSION

The present study demonstrated that using CR-TKA for patients with valgus OA of the knee promoted excellent coronal plane stability.

Keywords: Valgus osteoarthritis knee; Cruciate-retaining; Knee arthroplasty; Stress radiograph; Coronal stability

Core Tip: Cruciate-retaining total knee arthroplasty (CR-TKA) for knee valgus osteoarthritis (OA) has been associated with high rates of postoperative tibiofemoral instability. Our study utilized a digital ligament stress device to objectively measure the coronal stability of CR-TKA in patients with knee valgus OA at a mean follow of 3 years and found no significant instability, with a median varus and valgus gap change of < 2 mm. All patients were satisfied with their knee without revision due to instability, loosening, or patellar-related complication. We also describe the step-by-step details of the surgical technique used to ensure good exposure and soft tissue balance.