Precision of Pacient-specific Instrumented Open Wedge High Tibial Osteotomy vs Conventional Technicque

This study is a randomized clinical trial that will compare two surgical techniques for patients with knee osteoarthritis and varus deformity who are candidates for medial opening wedge high tibial osteotomy. The goal is to evaluate whether using patient-specific 3D-printed surgical guides improves the accuracy of the bone cut compared with the conventional technique performed with anatomical landmarks and fluoroscopy. A total of 50 adult patients will be randomly assigned to one of two groups: conventional osteotomy or osteotomy assisted by patient-specific instrumentation (PSI). The main outcome is the accuracy of the osteotomy cut, measured by comparing preoperative planning with the postoperative CT scan. Secondary outcomes include leg alignment, surgical time, radiation exposure, complications, and functional recovery assessed with validated questionnaires (KOOS, WOMAC, IKDC, EQ-5D) and gait analysis using depth cameras. Patients will be followed for up to 12 months after surgery to evaluate clinical and radiological outcomes.

Inclusion Criteria: * Informed consent: able to sign informed consent * Clinical: predominantly medial pain/limitation refractory ≥3-6 months * Mobility: flexion ≥90º and flexion contracture ≤10º Stability: varus/valgus and pivot-shift ≤ grade 1. * Radiology: * Medial gonarthrosis Ahlbäck I-III with preserved lateral compartment. * Patellofemoral Iwano 0-2 without disabling patellofemoral pain. * Varus alignment: HKA 4-10°. * Predominantly tibial deformity (decreased MPTA; LDFA close to normal) according to planning. * Anatomy/technical feasibility: proximal tibial morphology suitable for medial opening osteotomy and PSI guide placement. Exclusion criteria: * Comorbidity/clinical situations: * Inflammatory arthritis (e.g., RA, spondyloarthropathies), unresolved previous joint infection or osteomyelitis. * Severe peripheral vasculopathy (ABI \8.5%), advanced renal/hepatic failure (eGFR \20 cigarettes/day without commitment to cessation; active IV drug use or uncontrolled alcoholism. * BMI \>35 kg/m². * Disorder affecting gait (e.g., neurological disease). * Inability to walk at a speed of at least 0.8m/s * Anatomy/radiology * Multiplanar deformities not correctable with isolated medial opening tibial valgus osteotomy (e.g., dominant femoral deformity). * Severe medial subchondral bone defect or extensive necrosis. * Sequelae of proximal tibia fracture or previous ipsilateral HTO that prevent correction or guide use. * Treatments/medication and logistics * Anticoagulation/antiplatelet therapy that cannot be suspended or bridged. * Systemic corticosteroids \>10 mg/day or high-risk immunosuppressants without possibility of adjustment. * Intra-articular infiltration (HA/CS/PRP) within the previous 60 days (respect defined wash-out). * Pregnancy. * Participation in another interfering trial. * Inability to undergo CT (e.g., uncontrollable claustrophobia). * Inability to complete ≥12 months of follow-up.