Introduction

Corrosion at the modular junction of the femoral component in total hip arthroplasty (THA) was considered as a cause of adverse local tissue reaction in recent years. We reported three adverse local tissue reaction cases after total hip arthroplasty using the same modular neck stem in this study.

Introduction

It is important to measure 2-dimensional (2D) polyethylene wear in total hip arthroplasty (THA) accurately in order to estimate value of wear performance. However, wear vector direction is usually defined in a coordinate system specific manner, which sometimes leads to confusion and makes it difficult to compare measures between techniques. We systematically evaluated the influence of four different coordinate system definitions for the measurement of 2D wear in acetabular cups form radiographs.

Introduction:

Highly cross-linked polyethylene (XLPE) was introduced into clinical practice to decrease acetabular cup wear in total hip arthroplasty (THA) based upon extremely low wear rates in vitro. Numerous short-term clinical studies using XLPE cups have shown promising improvements in wear performance. In this study we evaluated in vivo wear performance of XLPE cups compared to conventional PE (CPE) cups in primary THA at a minimum five years follow-up.

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.

Purpose

To determine the effect of early recovery with 2 different MIS THA for patients with dysplastic hip because of relatively severe muscle weakness before surgery.

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: 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.