Total knee arthroplasty for a valgus deformity angle of >90°: A case report.

Rationale: Valgus knees are relatively rare in the clinic. Treatments for valgus deviations >90° represent a surgical challenge to achieve a balance between the soft tissue and bone and prevent nerve damage.

Patient Concerns: A 63-year-old woman with valgus deviations >90° in both knees complained that she had been unable to walk for 50 years.

Diagnoses: Congenital malformation valgus deformity.

Interventions: Bilateral total knee arthroplasty (TKA) was performed using a rotating hinge knee instrument from Endo-Model for axial correction and stabilization of the joint.

Outcomes: The patient fully recovered 3 months after surgery. At the follow-up 6 years after the operation, the function of the knee joint clearly improved. The knee society score (KSS) increased from 35 to 90.

Lessons: Constrained implants are commonly used to stabilize the joint and correct the bone axis in patients with severe ligamental instability, gross deformity, bone loss, and extreme deviation of the straight leg axis. Intraoperative exploration of the common peroneal nerve and the postoperative flexed position of the knee joints could help prevent nerve injuries.