Removal Rate of the Tomofix ^® System after High Tibial Osteotomy is Higher Than Reported

Objective  Medial open wedge high tibial osteotomy (MOWHTO) significantly relieves pain in the medial joint line in medial compartment osteoarthritis of the knee. But some patients complain of pain over the pes anserinus even 1 year after the osteotomy, which may require implant removal for relief. This study aims to define the implant removal rate after MOWHTO due to pain over the pes anserinus. Methods  One hundred and three knees of 72 patients who underwent MOWHTO for medial compartment osteoarthritis between 2010 and 2018 were enrolled in the study. Knee injury and osteoarthritis outcome score (KOOS), Oxford knee score (OKS), and visual analogue score (VAS) were assessed for pain in the medial knee joint line (VAS-MJ) preoperatively, 12 months postoperatively, and yearly thereafter; adding VAS for pain over the pes anserinus (VAS-PA). Patients with VAS-PA ≥ 40 and adequate bony consolidation after 12 months were recommended implant removal. Results  Thirty-three (45.8%) of the patients were male and 39 (54.2%) were female. The mean age was 49.4 ± 8.0 and the mean body mass index was 27.0 ± 2.9. The Tomofix medial tibial plate-screw system (DePuy Synthes, Raynham, MA, USA) was used in all cases. Three (2.8%) cases with delayed union requiring revision were excluded. The KOOS, OKS, and VAS-MJ significantly improved 12 months after MOWHTO. The mean VAS-PA was 38.3 ± 23.9. Implant removal for pain relief was needed in 65 (63.1%) of the103 knees. The mean VAS-PA decreased to 4.5 ± 5.6 3 months after implant removal ( p  < 0.0001). Conclusion  Over 60% of the patients may need implant removal to relieve pain over the pes anserinus after MOWHTO. Candidates for MOWHTO should be informed about this complication and its solution.