Abstract
INTRODUCTION: Patients with Paget's disease develop abnormal bony anatomy which can result in significantly altered lower limb alignment predisposing them to early secondary osteoarthritis. Due to the severe extra-articular deformity, total knee arthroplasty (TKA) in these patients is challenging. Conventional knee arthroplasty using intramedullary guides is not an option and can lead to erroneous limb alignment postoperatively. Patient-specific instrumentation (PSI) is a simple solution in such complex primary knee arthroplasty. CASE REPORT: A 70-year-old male patient presented with a severe left femur deformity and left knee pain. He was diagnosed to have monostotic Paget's disease of the left femur with tricompartmental osteoarthritis of the left knee. After reduction in pathological bone turnover, the patient was planned for a total knee replacement. As a standard intramedullary femoral jig was not applicable due to the femoral deformity, a computed topography-based 3D-printed patient-specific instrument was used. This custom jig was used to define and perform the distal femur cut at 90 degrees to the mechanical axis of the femur in the coronal and sagittal plane. Postoperatively, the patient did well and achieved good function and pain relief. CONCLUSION: The use of a 3D-printed PSI for complex primary knee arthroplasty is an excellent option with no additional operative time than a conventional knee arthroplasty. Although a robotic or computer-navigated TKA would be an excellent option in this case, we restored the limb alignment using a cost-effective patient-specific femoral jig. This could be a viable option in centers without navigation or robotic arthroplasty.