Purpose

Crowe IV complete dislocated hips were thought to be difficult for primary THA. Correction for leg length discrepancy associated with nerve palsy or tough to reduction during surgery. Purpose of this study was to evaluate 3.5cm total leg length correction for any type of Crowe IV patients setting in anatomical positioning of acetabular cup with femoral shortening osteotomy.

Purpose

Dysplastic acetabulum (DDH) have some difficulty even if with conventional approach of THA. Indication or contraindication is not clear with MIS THA. The purpose of this study was to evaluate complications with mini antero-lateral approach for DDH patients.

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.

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.