Background and aim

A significant reduction in wear using Durasul highly cross-linked polyethylene (PE) versus Sulene polyethylene (sterilized with nitrogen) at 5 and 10 years have been reported previously. We ask if the improvement observed at the earlier follow-up continues at 15 years.

Acetabular bone structure is not the same in all patients and can be defined by the radiolucent triangle superior to the acetabulum. We ask if the acetabular anatomy determines the initial cup fixation and screws use.

We have assessed 205 hips in which a Cerafit cementless cup was implanted. According to Dorr et al., acetabulae were classified as type A, in which the radiolucent triangle had an isosceles shape (86 hips), type B, in which the triangle extended into the teardrop (90 hips), and type C which had a right-angle triangle (29 hips). The use of screws was decided at the time of surgery and according to cup stability, not acetabular anatomy.

Avascular necrosis and inflammatory arthritis were the most frequent diagnoses in type A hips, osteoarthritis in type B, and dysplasia in type C. Women were more frequent in types A and C (p< 0.001). The use of screws was more frequent in women (p< 0.001) and in type A (34.9%) and type C hips (62.1%) than in type B hips (20.0%) (p< 0.001). The multivariate logistic regression model showed the acetabular type (p=0.11) and gender (p=0.003) as independent factors. Acetabular types A (OR=1.98, 95% CI: 0.922–4.208, p=0.075) and C (OR=5.09, 95% CI: 1.74–14.9, p=0.003) increase the risk for screw use. Men have a lower risk for screw use (OR=0.329, 95% CI: 0.16–0.68, p=0.003).

Acetabular anatomy and gender determine the use of screws in cementless cups. Continued follow-up is necessary to determine if screws results in less loosening and osteolysis.

Introduction: Severe stress shielding and radiographic cortical changes in the proximal femur are frequent after extensively porous-coated stem in revision surgery. We have analyzed the evolution of the femoral cortex at different levels and related factors.

Material and Methods: We assessed 95 extensively porous-coated stems in revision surgery with a minimum 5-year follow-up (Mean 10.2 years). 77 hips were revised due to aseptic loosening and 18 due to periprosthetic fractures. Extended osteotomy was used in 29 hips. No cortical struts were used. Preoperative and postoperative osteoporosis was graded according to Moreland and bone defect according to Paprosky. Femoral cortex width was measured at different levels in the immediate postoperative radiograph, at 3, 6 and 12 months and at the last follow-up.

Results: There were 2 re-revisions for aseptic loosening. Radiographic ingrowth fixation was more frequent in minor intraoperative bone defects (p=0.011). Preoperative osteoporosis was related to the width of the medial and lateral cortex. Medial cortical thickness increased at different levels with a mean increase of 13.4% (p< 0.001) and the lateral cortical thickness showed a mean decrease of 2.7% at the proximal level. The femoral medial cortex tended to show a higher slope trend in periprosthetic fractures (p=0.015). The outside femoral diameter increased more rapidaly with an extended trochanteric osteotomy (p=0.007). The slope trend of the lateral and medial cortex was significantly higher at proximal levels in hips with a 10-inch stem (p=0.015).

Conclusions: Although without clinical relevance at the end of follow-up, femoral medial cortical thickness increased while frequently lateral cortical thickness decreased over time after an extensively porous -coated stem in revision hip surgery.

Introdution. Gamma sterilisation in air produces free radicals in the polyethylene (PE) with the result of degrading its mechanical properties, increasing wear and debris, and producing osteolysis and loosening. PE sterilized in the absence of air and high cross-linked polyethylene (HXLPE) have been used to avoid osteolysis and loosening. This prospective randomized study has assessed results in a series using two different poly-ethylenes associated with the same prosthetic design.

Methods: We assessed 45 Allofit cups with Sulene-PE liner (sterilized with nitrogen) and 45 Allofit cups with Durasul-PE liner (HXLPE), both associated with an Alloclassic stem (28-mm femoral head) (Zimmer). The minimum follow-up is 5 years and the mean follow-up 66.3 months. The linear femoral head penetration was estimated at 6 weeks, at 6 and 12 months and annually thereafter, using a software package employing the Dorr method, given the nonspherical cup shape.

Results All assessed hips had good clinical and radiographic results. There was no loosening of any prosthetic component. There were no radiolucent lines or osteolysis. Femoral head penetration in the early postoperative radiographs was 47.4% less in the Durasul group (0.09+0.03 mm) than the Selene-PE group (0.19+0.06 mm)(p< 0.0001). The mean yearly linear femoral head penetration was 20% lower in the Durasul group (0.008+0.008) than the Sulene-PE group (0.04+0.02)(p< 0.0001). Differences increase after the third year. Mean linear femoral head penetration at 5 years was 39.1% less in the Durasul group (p< 0.0001).

Conclusions: Although the digitized method used is not totally accurate and is used only for a general estimate, there is a significant reduction in yearly linear femoral head penetration with Durasul-PE. Longer-term results are needed to confirm that this polyethylene generates less osteolysis.

Aim: We assessed prospectively clinical and radiographic results of two different polyethylenes (PE) associated with the same prosthetic design (Zimmer-Centerpulse).

Material and Methods: We assessed 56 Allofit cups with Sulene-PE liner (sterilized in nitrogen) and 45 with Durasul-PE liner (highly cross-linked) associated with an Alloclassic stem (28-mm femoral head) implanted between 1999–2002. The mean follow-up was 29.4 months for the Sulene-PE and 25.3 for Durasul-PE. The radiologic study according to Johnston et al. and the PE wear estimated according to a software package (AutoCAD R14), were analysed at 6 weeks (zero position), at 6 and 12 months and annually thereafter.

Results: There were 3 dislocations which were excluded from the follow-up study. There were no infections. All assessed hips had good clinical and radiographic results. There was no loosening of any prosthetic component. There were no radiolucent lines, osteolysis, cortical hypertrophy, or femoral osteopenia. The distances between the acetabular shell and the femoral head centres taken in the early postoperative radiographs (zero position or bedding-in) were 0.30+0.094 mm for the Sulene-PE group and 0.20+0.074 for the Durasul-PE (p=0.029). The mean wear related with the zero position was 0.1035+0.0686 and 0.0819+0.078 (p=0.108) respectively.

Conclusions: Despite the measurement error of PE wear being higher in the Allofit cup, a higher zero position (bedding-in) was found in the Sulene-PE group than in the Durasul-PE. Although the mean wear was higher in the Sulene-PE than in the Durasul-PE, with the number of hips available, differences were not significant after 3 years

Introduction and purpose: This is a prospective analysis of the clinical and radiographical results of two different types of PE, both associated to the same kind of prosthesis (Zimmer-Centerpulse).

Materials and methods: A total of 101 Allofit shells were analyzed; 56 had Sulene-PE (nitrogen sterilized) and 45 had Durasul highly cross-linked PE, associated to an Alloclassic stem (femoral head: 28 mm). They were all implanted between 1999 and 2002. Mean follow-up was 29.4 months for Sulene-PE and 25.3 for Durasul-PE. PE wear was assessed by means of image digitalization with special software (AutoCAD 14R) after six weeks (initial settling or position zero), after 6 and 12 months and on a yearly basis.

Results: Three cases dislocated and were thus excluded from the study. There were no infections. All cases assessed had good clinical and radiological results. There were no instances of implant loosening. There were no radiolucent lines, osteolysis, cortical hyperthrophy or proximal osteopenia. On the initial radiograph (position zero), the distance between the axes of the femoral head and those of the shell was 0.30+0.094 mm for the Sulene-PE group and 0.20+0.074 for the Durasul-PE one (p=0.029). Mean wear, taking position zero as a reference point, was 0.1035+0.0686 and 0.0819+0.078 (p=0.108) respectively.

Conclusions: In spite of the higher error rates found in the wear measurements of the Allofit cup, a greater position zero was found in Sulene-PE than in Durasul-PE. Although mean wear was higher in Sulene-PE than in Duarsul-PE, the differences found were not significant 3 years postop.

Aim: To assess the long-term results of a series of porous-coated anatomic cementless total hip prostheses. Material and Methods: A total of 91 PCA (How-medica) total hip arthroplasties performed between 1984–1988 were analyzed with a mean follow-up of 13.5 years. Clinical results were assessed according to Merle DñAubignŽ-Postel score. Radiographic þxation was assessed according to Engh et al. Results:Thigh pain (17 hips) was correlated with unstable þxation (p=0.0096). Thirty-one cups and six stems were revised. Radiographic loosening ocurred in 21 cups and 12 stems. Mean polyethylene wear was 0.16 mm/year. Cup loosening was related with an acetabular wear equal to or more than 2 mm (p=0.0018) and an small cup size (p=0.015). Stem loosening was related with poor femoral canal þlling (p=0.046). Fifty (54.9%) hips had femoral osteolysis and were related with polyethylene wear of more than 2 mm (p=0.0015) and with hips with poor femoral þlling (p=0.0285) and unstable þxation (p=0.00005). Conclusions:The PCA cup has had worse results than the stem. Cup loosening is related with the acetabular wear and cup size. The frequent proximal femoral osteolysis is associated with unstable þxation and poor femoral þlling