Introduction

Alignment and positioning of implants is important in total knee arthroplasty (TKA). Identifying the femoral hip center (FHC) without fluoroscopy or computer navigation is considered difficult. The Complete Compass system (CoCo) is a femoral extramedullary guidance system designed to identify the FHC. This apparatus provides an accurate representation of the femoral functional axis in the coronal plane without a computer navigation system. We compared postoperative implant alignment of patients undergoing total knee arthroplasty between CoCo and intraoperative computer navigation.

Introduction

Total hip arthroplasty (THA) using the direct anterior approach (DAA) in a supine position is a minimally invasive surgery that reduces postoperative dislocation. Excellent exposure of both the acetabulum and proximal femoral part is important to reduce intraoperative complications. Generally, two surgical assistants need to hold four retractors to maintain excellent exposure of the acetabulum. We examined intra- and postoperative complications as indicators of the efficiency of using the “Magic Tower” (MT) device compared with a non-MT group.

Kneeling is one of important motion in Asians culture, also there were teachers of tea or flower ceremony who sit seiza routinely. But also, people in the Middle East need deep flexion keeling when they pray. At the symposium with the title of “A Challenge of deep flexion after TKA”, held at the 33rd Annual Meeting of Japanese Society of Reconstructive Arthroplasty in 2003, it was agreed that the definition of post-operative deep flexion to be more than 130 degrees of flexion. Four hundred and seventy two patients treated with a total of 598 consecutive primary total knee arthroplasties were performed and 480 knees were followed for 4.1 to 10.6 years(mean, 7.2 years). Preoperatively, the mean Hospital for Special Surgery knee score was 45.8 points. At the time of latest follow-up, the mean knee score was 88.5 points. The mean preoperative and postoperative ranges of flexion were 116 and 134 degrees, respectively. No knee developed osteolysis, aseptic loosening. A revision operation was performed in 3 knees because of infection. Achieving deep flexion is multi-factorial, such as preoperative planning, surgical procedure, prosthesis design, and postoperative rehabilitation. About surgical tips for deep flexion, posterior positioning of femoral component will increase the femoral posterior offset and decrease the anterior patello-femoral pressure. Through osteophyte removal will increase the posterior clearance and avoid the bone-polyethylene impingement. The flexion gap should be balanced after creating a balanced extension gap, since preparation of the flexion gap affects the extension gap in TKA. Based upon studies of the healthy knee in deep flexion, it was hypothesized that deep flexion would require tibial internal rotation greater than 20 degrees, greater posterior translation of the lateral femoral condyle than the medial condyle, and subluxation of the articular surfaces in terminal flexion. However, as the results of our fluoroscopic analysis of kinematics during deep flexion kneeling after fixed bearing PS TKA, tibial internal rotation increased with greater knee flexion, but there was high variability about the trend line. Patients with deeply flexing fixed bearing PS knee arthroplasty showed two phases of condylar translation with deep flexion. Interestingly, these two-phase translations are dictated by the design of the cam/post mechanism and serve to maintain the condyles within the posterior articular surfaces of the tibia plateau. Surface separation of both medial and lateral condyles was observed in terminal flexion. At least direct edge wear by the femoral condyle in maximum flexion is denied from this phenomenon. However, potential problems of TKA that allows for deep flexion are considerable such as dislocation, polyethylene wear, and anterior knee pain. In TKA using PS type of implant, the risk of insert damage also exists in factors other than deep flexion motion, such as cam/post or notch/post. Surgeons must confirm carefully not to set implants loose, or not to leave remnants of osteophytes during surgery and to pay attention not to raise the activity level of patients too high after surgery.