Excessive hypercorrection after an open wedge high tibial osteotomy: a clinical case

Background: Currently, there is a tendency to increasing the proportion of knee joint organ-preserving surgeries. High tibial osteotomy (HTO) has proven itself a good method for the treatment of the knee joint varus deformity in extra-articular deformity cases. The question of the perfect angle of correction, which will not significantly impair the biomechanics of the knee and adjacent joints, remains controversial, as well as the issue of preventing excessive hypercorrection as an osteotomy complication. Clinical case description: A clinical case of a 59-year-old patient who underwent primary and revision HTOs is analyzed in this article. The patient had a varus deformity of the left lower limb with isolated medial knee osteoarthritis. The patient’s body mass index (BMI) was 28 kg/m2. The patient complained only of pain and a limited range of motion in the knee joint. According to the arthroscopy and magnetic resonance imaging (MRI) data, there was a cartilage damage classified as Outerbridge 4 stage of the medial compartment. There were no signs of a lateral compartment cartilage damage and patellofemoral joint arthritis. The varus deformity of the knee joint was 10°. The patient underwent a medial high tibial open wedge osteotomy. During the preoperative planning, topograms of the lower limb with weight bearing were used. The clinical status before the operation, according to the used scales, was as follows: Knee injury and Osteoarthritis Outcome Score (KOOS) - 46 points, Visual Analogue Scale (VAS) - 7 cm, American Orthopaedic Foot and Ankle Society (AOFAS) - 92 points. 6 months after the initial surgery, the clinical status was as follows: knee joint VAS - 1 cm, ankle joint VAS - 5 cm, KOOS - 88 points, AOFAS - 63 points. During the clinical examination and according to the instrumental studies, excessive valgus hypercorrection of 11.2° was noted. Also, the tibial plafond inclination (TPI) and the talar inclination (TI) were significantly increased. 1.5 years after the primary osteotomy, a revision closed wedge osteotomy was performed. The valgus deformity of the knee joint became 3°, the axis of the ankle joint changed to the normal values. The clinical and functional results 6 months after the revision osteotomy were the following: KOOS - 92 points, AOFAS - 99 points, pain in the knee and ankle joint - 1 cm by the VAS scale. Conclusions: The case showed that the careful preoperative planning and the use of additional methods for monitoring the intraoperative correction were important. Excessive valgus hypercorrection promotes good regeneration of the medial compartment cartilage; however, it overloads a lateral compartment and adversely affects the ankle joint and foot.