Aims: Crosslinked acetabular inserts have been introduced as a solution to the wear related periacetabular osteolysis, caused by the polyethylene wear debris. Laboratory tests and simulators have demonstrated that crosslinked-polyethylene has a higher resistance to wear than conventional polyethylene. However, studies have shown early crack or degeneration of crosslinked inserts. Concerns still remain about the clinical performances of crosslinked inserts. Although questionable, the roentgenographic measurement of the wear of the cup represents an indicator of the performance of the implant. Early catastrophic failures of other inserts taught us that for new materials it is mandatory to conduct an accurate clinical surveillance. In this work the radiographic-evaluated linear wear of a group of cross-linked inserts is compared to that of a non-crosslinked inserts for the same socket at 5 years.

Methods: From 2000 to 2002 we implanted a series of cups in which crosslinked and conventional acetabular inserts were placed randomly. Patients from each group underwent radiographic assessment after implantation, at 3 and 6 months and then yearly. Radiographs were obtained using a digitalized image system, which allowed a computerized bi-dimensional measurement by a specially developed Auto-CAD program. 12 healthy and active patients (6 crosslinke – 6 conevtional UHMWPE) have been selected for measurement.

Results: No macroscopic signs of loosening, mobilization and osteolysis were detected. Despite an increased wear rate for the conventional insert, no statistically sig-nificant differences of the linear wear were detected at five years for the two groups.

Conclusions: Longer follow-up and larger case studies are needed for more definitive conclusions. Nevertheless, this preliminary study shows that crosslinked polyethylene in vivo at 5 years does not give early failures and that its linear wear in the short term does not differ from that of a conventional polyethylene. Several other factors, such as the number and dimension of the debris, which are not detected by roentgenographic measurements, might be taken into consideration. Moreover it has been hypothesized for the crosslinked polyethylene an early plastic deformation, with consequent penetration of the head without wearing, which could affect the measurement on plan radiographs. Despite these limitations, roentgenographic measurements are quick and easy to perform, and therefore might be useful for the clinical practice of the periodical evaluation of the implants.

Introduction and Objectives: The goal of this study is to document radiographic changes occurring in patients with hydroxyapatite(HA)-coated total hip prostheses (THP).

Materials and Methods: From May 1990 to May 1993, 60 THP with complete (femoral and acetabular) HA-coating were implanted in 59 patients. Of these 59 patients, 36 were male and 23 female. Average age was 69.26 years. A retrospective study of these patients was done, with an average follow-up time of 11 years. Radiological follow-up was done at 1 month, 3 months, 6 months, 1 year, and annually thereafter. Available imaging methods included conventional radiography, direct digital radiography, digital processing, CT scan, bone scintigra-phy, and tomodensitometry. We used the first 3 of these techniques. The acetabular cup and femoral stem have been divided based on DeLee-Charnley zones (cup) and Gruen zones (femur). The following variables were tracked for the acetabular component: subchondral sclerosis, radiolucent lines, resorption, remodeling, and the appearance of osteolyic lesions. For the femoral component, the following were tracked: radiolucent lines, calcar resorption, periprosthetic cortical thickness, appearance and progression of the pedestal, appearance of osteo-lytic lesions, new intramedullary bone formation, and state of cancellous bone, with particular emphasis on periprosthetic trabeculation. We also assessed prosthetic positioning (normal, varus, valgus), angle of the acetabular component, changes in the polyethylene, and heterotopic ossification (Brooker’s classification). Radiographic studies were performed by 2 independent observers, blinded as to the clinical situation.

Results: Of the 60 THP with HA coating in our study, 5 could not be reviewed due to incorrect personal data on their clinical records, and 6 were deceased. With the cups, DeLee-Charnley zone 1 showed bone remodeling with frequent sclerotic changes, and zone 3 showed radiolucent lines of less than 1 mm. Femoral stems had a typical pattern of poor endosteal apposition around Gruen’s zone 6. Calcar remodeling was slowly progressive, with thinning of the cortex. Minimal resorption of the femoral neck was also observed. A periosteal reaction was noted in eccentrically loaded stems. Pedestals were common and did not seem to reflect loosening of the prosthesis in our data. Image digitalisation permitted the examination of newly-formed trabeculae, particularly in Gruen’s zones 2–3 and 5–6, which appeared at 3 months.

Discussion and Conclusions: Radiographic progression in most of the patients with THP with HA coating was satisfactory. Digitalisation of radiographic images permitted better visualization of changes occurring at the bone-prosthesis interface.