Total knee replacement in severe genu recurvatum. High prosthetic survival rate without deformity recurrence, using rotating hinge prosthesis.

Introduction

Genu recurvatum can originate from neurological and non-neurological causes. Its presence associated with knee osteoarthritis represents 1% of the causes of total knee replacement (TKR). The aim of this retrospective study was to show the functional outcomes, recurrence rate and prosthetic survival in patients with genu recurvatum treated with articulated rotating hinge prostheses.

Methods

between January of 2008 and December of 2021, we performed 3224 primary TKR, of which 34 (1%) had recurvatum. This was defined as hyperextension ≥10º. Inclusion crirteria were patients with primary TKR and recurvatum that were treated with a rotating hinge prosthesis (Endo Model, Walderman Link, Ham, Germany), and completed a minimum follow-up of 24 months. Final series consisted in 23 patients with 25 TKR with 15 (65.22%) females and a mean age of 66.8 ± 14.2 years old. The median follow-up was 5.0 (range 2.11 – 11.5). Clinical analysis was performed with the use of Knee Society Score (KSS) and Western Ontario & McMaster Universities Osteoarthritis Index (WOMAC). Prosthetic survival rate was calculated with a Kaplan-Meier curve considering as the endpoint of the analysis revision due to any reason. Recurrence was defined as the presence of hyperextension ≥ 5º after surgery.

Results

of the 23 patients, 9 (39.13%) had history of neurological disorders. Median recurvatum observed was 20.12º (range 13.0º - 30.2º). A median of 19.6º (range 10.1º - 55.4º) valgus misalignment was observed in 19 patients and 10.7º (range 2.0 – 23.5º) of varus was observed in 6 (24%) patients. Clinical and functional KSS improved significantly after 12 months (from 34.2 ± 9.8 and 40.1 ± 12.6 to 82.1 ± 7.5 and 89.2 ± 6.8 respectively; p<0.01) and at the end of the study (84.3 ± 7.5 and 90.0 ± 11.3; p<0.01). Final mean WOMAC value was 24.1 ± 9.6. One (4.0%) complication was registered after surgery (superficial infection). Four (16.0%) patients had demarcation. Prosthetic survival rate was 100% at the end of the study.

Conclusion

The rotating hinge prosthesis restores joint function in patients with severe knee osteoarthritis with and without neurological disorders, without recurrence of misalignment and with excellent survival rates.