[Lateral unicompartmental knee arthroplasty - a challenge]

Objective: Joint surface replacement in the lateral compartment by unicondylar knee arthroplasty.

Indications: Lateral unicompartmental osteoarthritis of the knee joint, avascular necrosis of the lateral femoral condyle.

Contraindications: Full thickness cartilage defect in the central part of the medial compartment or in the medial aspect of the patellofemoral joint. Instability/contracture of cruciate and collateral ligaments, valgus deformity >15°, valgus deformity not passively correctable, flexion deformity >15°, an intraoperative flexion <100°, failed upper tibial osteotomy, rheumatoid arthritis.

Surgical technique: Leg positioning in leg holder. Minimally invasive parapatellar lateral arthrotomy. Exposure of the lateral compartment and removal of osteophytes. Attachment of the tibial saw guide. Horizontal cut 7-8 mm below the original tibial plateau with protection of the lateral collateral ligament. Vertical saw cut via an incision in the central aspect of the patellar ligament with an internal rotation of 20°. Femoral preparation. Insertion of the intramedullary rod, positioning of the femoral drill guide directing to the anterior superior iliac spine and drilling the holes. Insertion of the posterior resection guide. Saw cut with protection of the lateral collateral ligament. Insertion of the 0 mm spigot and first milling. Measurement of the extension gap. Insertion of the corresponding spigot (never use a spigot >5 mm). Milling and insertion of the trial components. Application of the anti-impingement guide and anterior and posterior resection of bone. Final preparation of the tibial plateau. Cementing of the components.

Postoperative management: Mobilization under full weight-bearing with two crutches.

Results: With a mean follow-up of 1.7-4 years, the dislocation rate is about 0-6.6%. Revision-free survival is 90-98%.