Aims

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome.

Background

Polymethylmethacrylate (PMMA) has been used for total knee arthroplasty (TKA) as a method of fixation; however, its durability has been questionable for the long-term use because of the loosening after the cement deterioration, its vulnerability toward infectious resistance, and a smaller amount of healthy bone left for the knee revision surgery. Especially, a decrease of bone density on the proximal tibia has been believed to be triggered as a result of stress shielding. When compared with a cemented TKA, a cementless TKA reduces the amount of bone loss after surgery. In 1999, the Trabecular Metal (TM), with its main composition being the porous tantalum metal, became available as a choice of the porous cementless knee joint prosthesis. The characteristics of porous tantalum metal are its great affinity to the bone as well as its similarity to cancellous bone. The porous tantalum metal starts to bond with osteoblasts, and fills up 80% of porous structure in one year; therefore, it has been characterized by its higher initial fixation strength. However, it is questionable if strong fixation strength due to bone ingrowth between the tibial tray mainly made up with the porous tantalum metal and a cancellous bone will continually be kept. Bobyn, JD, Dunbar et al. have acknowledged the existence of bone ingrowth based on the radiographic evaluation; however, their data had not been quantified in their report. In this study, the bone ingrowth density have periodically quantified using 3D bone morphometric software (TRI/3D-BON64.RATOC) after taking CT of the knee joint prosthesis.

A 51 years old female who experienced difficulty in gait ambulation due to secondary osteoarthritis of knee showed knee instability caused by paralysis associated with poliomyelitis and scoliosis. At the first medical examination, right knee range of motion was 0° to 90°, and spino malleolar distance (SMD) showed 72cm for the right leg, 78cm for the left leg, and the bilateral comparison of SMD indicated the leg length discrepancy of 6cm. The patient has a history of surgeries with an anterior – posterior instrument for the treatment of scoliosis, and with Langenskiöld method for the paralyzed right knee at the age of seventeen. The patient also experienced varus degeneration at the age of twenty seven, which was surgically treated with high tibial osteotomy. In this case, a reoperation of her right knee was performed due to the reoccurrence of the knee pain. Preoperative planning was performed using Patient-matched instrument (Signature; Biomet) which was created based on computed tomography data. Each part of osteotomy followed the resection guide by Signature, and a total knee arthroplasty was carried out using the Rotating Hinge Knee System (Zimmer, warsaw. Inc). Two week after the operation, the patient showed the ability to walk without any assistance, and has been in a good condition.