Introduction: Preoperative planning is an important issue for total hip arthroplasty (THA). We normally use a traditional handwritten method with X-ray and two-dimensional (2-D) template. This method is simple and easy to plan the THA. However the 2-D planning is not accurately analyzed for especially DDH or severe deformity. New three-dimensional (3-D) preoperative planning software (ATHENA, Soft Cube) was developed for total knee replacement. The method of this software is based on roentogen stereophotogrammetoric analysis (RSA). The software can superimpose the 3-D CT and the prosthetic CAD model onto 2 X-rays. We hypothesized that this software would improve the accuracy of preoperative THA planning compared to the 2-D planning.

Materials and Methods: Fifty patients (male/female = 2/48) underwent THA using cementless stem and cementless acetabular component. Preoperatively, two different planning Methods: were done for all hips. The conventional 2-D handwritten planning was done with a template of the total hip system based on a standard AP X-ray of the hip (Group 1). Each patient had 2 directions X-ray with a particular marker and CT around only hip. The software calculated the source position of X-ray in each view by the marker and the angle between 2 X-rays based on RSA. The software superimposed the 3-D CT hip model and the proper size prosthetic CAD model onto 2 X-rays (Group 2).

Results: The acetabular component implanted was the same as that planned in 78% (Group 1) and 90% (Group2). The stem implanted was the same as that planned in 38% (Group 1) and 68% (Group2). The stem planning with the software improved significantly compared to the 2-D templating (P< 0.05, Chi-square for independence test).

Discussion and Conclusions: CT based computer preoperative planning was introduced to improve the accuracy of THA planning and reported good results in recent years. However the CT based method depends on high quality CT and cannot use effectively X-ray. This 3-D preoperative planning software can synchronize both digital X-ray and CT and define proper 3-D space. The software corrects the CAD model’s angles such as ante-version and torsional abnormalities accurately and easily in the same space. We can confirm those data simultaneously and get a lot of accurate information before the surgery. This method improves the accuracy of THA.

Introduction: This study prospectively measured fifty consecutive patients who had the preoperative diagnosis of osteoarthritis undergoing total knee arthroplasty (TKA) to evaluate the change of the bone mineral density (BMD) of the calcaneus.

Materials & Methods: Broadband ultrasound attenuation through the calcaneus was measured to assess the BMD of patients. The BMD was measured preoperatively and 1 month (M), 3M, 6M, 1 year, and 2 years after TKA.

Results: The mean BUA at each stage was 47.1, 45.8, 46.7, 46.7, 47.8 and 53.1, respectively. During the first 6 months, the BUA declined inconsistently in most patients, but by 1 year, the BUA recovered to the initial BUA before surgery and by 2 years, the BUA increased than the initial BUA, although there ware not satisfactory different. Despite a predicted age-related loss of 4% during 2 years, 78% of the calcaneus on the operative side had BMD higher than preoperative levels and 85% had BMD that was within the expected 4% age-related loss.

Discussion: These results indicated that TKA might contribute to decrease the age-related BMD loss. The increase with TKA in patient mobility and the increased heel loading may be a mechanism whereby the calcaneus BMD increases.

Conclusion: It is very important for surgeons to recognize the objection beneficial effects of TKA in addition to pain relief.

Introduction: The purpose of this study is to determine in vivo femorotibial axial rotation magnitudes and patterns in mobile-bearing posterior stabilized total knee arthroplasty (PS-TKA) and unicondylar knee arthroplasty (UKA) in deep flexion.

Material and Methods: Using video fluoroscopy, 12 subjects having a mobile-bearing PS-TKA (NexGen LPS Flex) and 12 subjects having a mobile-bearing UKA (Oxford UNI) were analyzed to determine their in vivo kinematic patterns under both weight bearing and non weight bearing. All implants were implanted by the same surgeon and were judged successful clinically with no pain and ligament laxity. The femoral and tibial components were overlaid onto the fluoroscopic images using a three-dimensional automated model-fitting technique to determine joint mobility.

Results: The average range of motion was 124 degrees of flexion for the PS-TKA and 137 degrees of flexion for the UKA. Although subjects in this study exhibited variable motion pattern, the common is anterior movement in extension to 45 degrees of flexion and posterior movement in 60 degrees of flexion to full flexion. The average internal rotation of the tibia was 18 degrees in UKA and 6 degrees in PS-TKA at 100 degrees of flexion to full. Incidence of lateral condylar lift off greater than 2mm was 5 in the PS-TKA and 1 in the UKA.

Discussion: A medial pivot kinematic pattern was observed in deep flexion in UKA. However in extension to 45 or 60 degrees of flexion, anterior condylar movement was observed in both groups. The motion pattern of UKA in 60 degree of flexion to full was close to the natural knee motion.

Suggestions for improved wear performance of total knee replacements have included replacement of standard CoCr femoral components with ceramic. Yttria-stabilized zirconia (y-TZP) was introduced as high-strength and high toughness ceramic as an alternative to alumina ceramic. Since the introduction of zirconia in 1985, the clinical outcomes and successes for hip joint have been controversial. Y-TZP ceramics have been studied both experimentally and clinically. Magnesia-stabilized zirconia (Mg-PSZ) also appears promising for total knee replacements (TKR).

Mg-ZrO2 and CoCr femoral condyles were compared in the VanguardTM knee configuration (Biomet Inc, IN). Molded tibial inserts (GUR1050) were gamma-irradiation sterilization to 3.2-Mrad under argon. Knee simulation was conducted on a 6 station simulator (Shore Western Manufacturing, Monrovia, CA). Motion included 20 degrees of flexion/extension, 5 degrees of internal/external rotation and 5 mm of AP-translation. All knee components were subjected to 6 million cycles of normal walking (2.9 kN max, freq 1.4 Hz). Lubricant was 50% alfa-calf serum diluted to 20 mg/ml protein and using EDTA additive. Test duration was 6 million cycles (6-Mc), and wear was measured by weight-loss techniques.

For wear trending of CoCr/PE and MGZ/PE, linear wear trends were apparent from 1 to 6 Mc test duration. The control implants (CoCr/PE) showed excellent linear trending (regression coeff r> 0.99) with wears rate averaging 6.3 mm3/Mc. These data showed good control of experimental variance (< 10%). The ZrO2/PE combination showed good linear trending (r > 0.86) with wear rate averaging only 0.8 mm3/Mc. This set also showed good control of experimental variance (< 15%. The MGZ/PE wear was 8-fold reduced from that of CoCr/PE.

The laboratory knee wear simulation appeared very supportive of femoral condyles of Mg-stabilized zirconia. Such implants may provide excellent performance for active patients who may risk high wear rates over many years of use.

Introduction: The excellent character of cross-linked polyethylene on wear has been reported from basic researches. However, few clinical results were seen about irradiated polyethylene sockets. This presentation reports a long-term clinical result of irradiated polyethylene sockets.

Material and method: Two 100M-rad gamma irradiated polyethylene sockets were retrieved, each 25 and 27 years after implantation. Socket joint surface were scanned by 3-D scanner and analyzed. On the other hand, ten patients had total hip replacements with 6.5M-rad irradiated polyethylene sockets. Anterior-posterior and lateral radiograph were taken and the movement of the head to the socket was analyzed by 3-D wear measurement software GAWDI. The results were compared to conventional polyethylene sockets of matched patients.

Results: Wear of the 100M-rad sockets were 0.23mm/ 25yrs and 0.46mm/27yrs respectively. The direction of wear was observed over the whole surface. Wear of the conventional polyethylene socket retrieved 15yrs after implantation were 2.54mm/15yes and 1.76mm/12yrs. The wear were toward weight bearing directions.

The average movement of heads in 6.5M-rad irradiated polyethylene sockets was 0.22mm one year post operation and its direction was toward backside of patients’ body. The average movement of conventional polyethylene sockets was 0.24mm one year post operation and its direction was just the same as irradiated polyethylene sockets.

Discussion: The difference of long term results between 100M-rad irradiated polyethylene and conventional one was obvious. A definite wear path way was observed on conventional polyethylene sockets. However, it was ambiguous on 100M-rad irradiated polyethylene because it was small or it did not exist. No remarkable difference was observed in short term after operation between 6.5M-rad irradiated and conventional sockets. The present analysis suggests that a high dose irradiated polyethylene socket may benefit a good long-term clinical result.

The new 3-Dimensional (3D) polyethylene wear measurement software GAWDI (Genetic Algorithm for Wear Detect Instrument) was developed to evaluate in vivo movement of the femoral head into the polyethylene liner. It enabled to detect 3D position of femoral head against polyethylene socket from two radiographs. Inter observer error of this system was 0.09 mm, intra observer error was 0.08 mm. Fifteen patients after THA was taken anterior-posterior (AP) and semi-lateral radiographs in both standing and supine position one year post operation. The difference of the 3D position of the femoral head was not observed between standing and supine position. However 8.1 degrees (mean) and 0.2 to 16.5 degrees (range) pelvic tilt was observed between these positions. 0.8 mm (mean) difference was observed by 2-Dimensional measurement system although no difference was observed by 3D system. Small separation between head and socket was observed in a few patients. However the influence of pelvic tilt was main origin of the difference between 2D and 3D measurement methods.