Wear of Retrieved UHMWPE Hip Liners

After the gamma-irradiation sterilization, the most widely used orthopaedic grade polymer bearing liner material for the total joint replacement, ultra-high molecular weight polyethylene (UHMWPE), degrades through the progressive in vivo oxidation. The oxidative degradation makes UHMWPE brittle and leads to reduction of its mechanical properties. In this study, the effect of the in vivo post-irradiation ageing time on the wear of UHMWPE was investigated. Twelve retrieved polyethylene hip liners implanted for 3-16 years and then stored in the air for 1.5-8 years were used. Two types of the pin-on-disk wear testing were conducted. The uni-directional repeat pass rotating and the linear reciprocating wear testing were done with stainless steel disks against stationary polyethylene pins under 4MPa at 1Hz with bovine serum lubrication. Wear of the retrieved polyethylene hip liners does not have significant correlation with the in vivo or total ageing time. The linear reciprocal sliding motion generated a more pronounced wear than the uni-directional repeat pass sliding motion. This indicates that the kinematic motion significantly affects the wear of aged UHMWPE, having a brittle, white band region.

Long-Term Results of Total Hip Arthroplasty using a Cemented Muller Prosthesis / 대한정형외과학회잡지

PURPOSE: The purpose of this study was to evaluate the long-term results of cemented Muller prostheses using a 32 mm metal femoralhead. MATERIALS AND METHODS: We reviewed 43 (31 patients) of 76 (55 patients) consecutive THAs, which were performed between April 1978and September 1985. The average duration of follow-up was 148 months (range, 65-279 months). The average age at the time of indexoperation was 44.4 years. Preoperative diagnosis was osteonecrosis in 31 hips, posttraumatic osteonecrosis in 8 hips, osteoarthritis in 2hips, and rheumatoid arthritis in 2 hips. We assessed cases clinically by Harris hip scores and radiographically by loosening and osteolysis, and measured polyethylene wear by the Livermore method. Kaplan-Meier analysis was used to evaluate survivability. We analyzedthe relationship and the statistical difference between wear and age, weight, height, body mass index, diagnosis, polyethylenethickness, and cup inclination (Pearson correlation's analysis, Student t-test, ANOVA test). The p-value was set p50 degrees) (p<0.05). CONCLUSION: Cemented Muller THAs using a 32 mm metal head showed poor survivability after an average follow-up of 12 years, due to the high incidence of loosening, the high rate of polyethylene wear and osteolysis. These results seem to be due to the relatively largenumber of operation for osteonecrosis of the femoral head in young patients and shortcomings of curved femoral stem design and the first generation cementing technique.

Early Failure of Total Hip Arthroplasty with Hydroxyapatite-Coated Smooth Surface Acetabular Component / 대한정형외과학회잡지

PURPOSE: To evaluate the early intermediate outcomes of total hip arthroplasty using hydroxyapatite (HA)-coated smooth surface hemispherical acetabular component. MATERIALS AND METHODS: Seventy total hip arthroplasties were performed, in 63 patients, using a HA-coated smooth surface hemispherical acetabular component consecutively between June 1993 and August 1996. Fifty-four cases were followed at an average of 71 months. The mean age at the time of arthroplasty was 49 years old. Clinical results were evaluated using the modified Harris hip score, and the radiologic results were evaluated in terms of stability, polyethylene wear rate, and osteolysis around the acetabular component. RESULTS: The mean preoperative Harris hip score of 50.9 was improved to 82.2 points at the most recent follow-up. Pelvic osteolysis was found at 18 cases (33%) and the mean polyethylene wear rate was 0.15 mm/year. Eight acetabular components (15%) were unstable radiologically and 7 acetabular components (13%) were revised. CONCLUSION: Total hip arthroplasty using HA-coated smooth surface hemispherical acetabular component showed accelerated polyethylene wear rate, which was accompanied by a high incidence of osteolysis, and a high loosening rate due to failure of bony ongrowth at early midterm.

Development of chewing simulator / 대한치과보존학회지

Chewing simulator, which can partly mimic the motion of chewing motion of human, has been successfully developed. The purpose of its development was to make a new machine which can anticipate the clinical results of restoration in the human teeth more accurately in vitro condition It is composed of 4 major parts; chewing part, motor part, water bath, controlling part. The controlling part control the chewing force, frequency, the temperature and running time of water. Additionally, the actual chewing force and remaining time is shown in the monitor of controlling part. At present, the chewing cycle is composed depending on the pre-published data of foreign people. Long term clinical data should be additionally collected for the simulator to mimic the clinical results more accurately.