A 26-year-old male (height: 1.93 m; weight: 95 kg) presented with neutral limb alignment, painful tibiofemoral kissing lesions, and severe knee OA-related activity limitations due to pain in the left knee of one-year duration (Kellgren-Lawrence grade 2) (Figure 1). The knee OA was contained to the medial compartment, and the patient had failed lifestyle/activity modifications, physical therapy, quadriceps strengthening, and analgesics. Preoperative passive range of motion was measured to 140 , and no hyperextension or flexion deformity was recorded. During the orthopedic examination, isolated medial tibiofemoral tenderness was observed. The following symptoms were all absent: patellar tap (no joint effusion), lateral tibiofemoral tenderness, anserine bursa, patellofemoral crepitus, and patellar grind. The ligaments and meniscus were stable. The patient reported mild, continual pain during walking but distance was not limited by the knee pain.
As a former professional league basketball player, the patient indicated a strong desire to return to an active lifestyle including more strenuous activities such as jogging, racquet sports, and basketball, which he was unable to take part in due to pain. After providing written informed consent, he participated in a clinical study that received ethics committee approval and was conducted in compliance with the Ministry of Health and Declaration of Helsinki. The left knee of the patient was treated with the Atlas System, and the patient was followed for a period of six months after surgery.
The Atlas System consists of a cylindrical, polycarbonate urethane (PCU) load absorber located between femoral and tibial bases (Figure 2). The device, located within the subcutaneous tissue on the medial side of the knee, is designed to reduce loading on the affected medial compartment of the knee joint, without transfer of loading to other areas of the joint. The device was inserted through a single incision, guided by direct visualization and palpation of the patient's anatomy. Following identification of the femoral medial epicondyle, adductor magnus tubercle, tibial plateau, joint space, and anterior border of the superficial medial collateral ligament through visualization and palpation, the tibial and femoral fixation points were located, and an absorber length was selected based on the patient's anatomy. A trial device was introduced via two K-wires, and implant function was confirmed through direct visualization checks. Following confirmation of function of the trial device, the final implant was introduced with the femoral base placed deep to the vastus medialis obliquus muscle and the tibial base placed distal of the deep medial collateral ligament and proximal to the insertion of the pes anserine. After installation of the final device, visual confirmation of functional unloading from full extension through deep flexion was performed prior to wound closure. No concomitant intra-articular surgery was performed to ensure that any benefit was due solely to the implant. Postoperatively, the patient was given crutches and told to bear weight as tolerated and to keep the wound protected for an initial 2-week period. Following stitch removal at 2 weeks, the 2-month rehabilitation protocol focused initially on range of motion and daily living activities, followed by muscle strengthening and endurance.