[Reconstruction of tibial metaphyseal defects with artificial components in revision arthroplasty (GenuX MK System)].

Objective: Restoration of knee function by using tibial metaphyseal components in advanced metaphyseal bone defects after multiple bone-damaging revision surgery on the knee joint.

Indications: Advanced tibial metaphyseal bone defects (Anderson Orthopaedic Research Institute [AORI] IIb and III defects) in revision arthroplasty of the knee joint.

Contraindications: Persistent or current joint infection, general infection (e.g., pneumonia), nonreconstructable insufficient extensor apparatus.

Surgical Technique: Standard access including existing skin scars, arthrotomy, removal of cement spacer if necessary and removal of multiple tissue samples; preparation of femur first, followed by preparation of the tibia. Referencing the tibial rotation and joint line height. Tibial osteotomy referenced intramedullarily. Determination of the metaphyseal defect size and choice of component size. Positioning of the rasp guide for the preparation of the metaphyseal component (sleeve); gradual preparation of the bed for the metaphyseal component. Afterwards the prepared component at the desired depth (when using augments +5 or +10 mm accordingly 5 or 10 mm above the tibial plateau) is left and the tibial plateau is fixed on the embedded sleeve. Test coupling, control of the implant position and the height of the joint line radiologically. If satisfactory the definitive implants accordingly to the components of used implants before can be implanted.

Postoperative Management: Full weight bearing. Regular wound control; limitation of the degree of flexion only with weakened or reconstructed extensor apparatus.

Results: Between May 2018 and August 2019, 14 metaphyseal tibial components were implanted in 14 patients. The mean follow-up was 10.4 months. The follow-up included clinical examination, KSS (Knee Society Score) and an X‑ray and failure analysis. A significant improvement in range of movement from 75 ± 16° to 100 ± 14° (p < 0.01) was achieved. The KSS improved significantly from 78 ± 12 points preoperatively to 137 ± 23 points postoperatively. Two patients complained of persistent pain after exercise (walking distance >200 m) after 6 months; tibial shaft pain was negated by all patients. The group examined afterwards showed an implant survival rate of 100% in the observation interval.