Aims

A significant reduction in wear at five and ten years was previously reported when comparing Durasul highly cross-linked polyethylene with nitrogen-sterilized Sulene polyethylene in total hip arthroplasty (THA). We investigated whether the improvement observed at the earlier follow-up continued, resulting in decreased osteolysis and revision surgery rates over the second decade.

Aims

To determine the effect of a change in design of a cementless ceramic acetabular component in fixation and clinical outcome after total hip arthroplasty

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.

A total of 31 patients, (20 women, 11 men; mean age 62.5 years old; 23 to 81), who underwent conversion of a Girdlestone resection-arthroplasty (RA) to a total hip replacement (THR) were compared with 93 patients, (60 women, 33 men; mean age 63.4 years old; 20 to 89), who had revision THR surgery for aseptic loosening in a retrospective matched case-control study. Age, gender and the extent of the pre-operative bone defect were similar in all patients. Mean follow-up was 9.3 years (5 to 18).

Pre-operative function and range of movement were better in the control group (p = 0.01 and 0.003, respectively) and pre-operative leg length discrepancy (LLD) was greater in the RA group (p < 0.001). The post-operative clinical outcome was similar in both groups except for mean post-operative LLD, which was greater in the study group (p = 0.003). There was a significant interaction effect for LLD in the study group (p < 0.001). A two-way analysis of variance showed that clinical outcome depended on patient age (patients older than 70 years old had worse pre-operative pain, p = 0.017) or bone defect (patients with a large acetabular bone defect had higher LLD, p = 0.006, worse post-operative function p = 0.009 and range of movement, p = 0.005), irrespective of the group.

Despite major acetabular and femoral bone defects requiring complex surgical reconstruction techniques, THR after RA shows a clinical outcome similar to those obtained in aseptic revision surgery for hips with similar sized bone defects.

Cite this article: Bone Joint J 2014;96-B:1478–84.

Between 1999 and 2001, 90 patients underwent total hip replacement using the same uncemented acetabular and femoral components with a 28 mm metallic femoral head but with prospective randomisation of the acetabular liner to either Durasul highly cross-linked polyethylene or nitrogen-sterilised Sulene polyethylene. We assessed 83 patients at a minimum follow-up of ten years. Linear penetration of the femoral head was estimated at six weeks, six and 12 months and annually thereafter, using the Dorr method, given the non-spherical shape of the acetabular component.

There was no loosening of any component; only one hip in the Sulene group showed proximal femoral osteolysis. The mean penetration of the femoral head at six weeks was 0.08 mm (0.02 to 0.15) for the Durasul group and 0.16 mm (0.05 to 0.28) for the Sulene group (p = 0.001). The mean yearly linear penetration was 64.8% lower for the Durasul group at 0.05 mm/year (sd 0.035) for the Sulene group and 0.02 mm/year (sd 0.016) for the Durasul (p < 0.001). Mean linear femoral head penetration at ten years was 61% less in the Durasul than Sulene group. Highly cross-linked polyethylene gives excellent results at ten years.

Cite this article: Bone Joint J 2013;95-B:326–32.

We report the results of 79 patients (81 hips) who underwent impaction grafting at revision hip replacement using the Exeter femoral stem. Their mean age was 64 years (31 to 83). According to the Endoklinik classification, 20 hips had a type 2 bone defect, 40 had type 3, and 21 had type 4. The mean follow-up for unrevised stems was 10.4 years (5 to 17).

There were 12 re-operations due to intra- and post-operative fractures, infection (one hip) and aseptic loosening (one hip). All re-operations affected type 3 (6 hips) and 4 (6 hips) bone defects. The survival rate for re-operation for any cause was 100% for type 2, 81.2% (95% confidence interval (CI) 67.1 to 95.3) for type 3, and 70.8% (95% CI 51.1 to 90.5) for type 4 defects at 14 years. The survival rate with further revision for aseptic loosening as the end point was 98.6% (95% CI 95.8 to 100). The final clinical score was higher for patients with type 2 bone defects than type 4 regarding pain, function and range of movement. Limp was most frequent in the type 4 group (p < 0.001). The mean subsidence of the stem was 2.3 mm (sd 3.7) for hips with a type 2 defect, 4.3 mm (sd 7.2) for type 3 and 9.6 mm (sd 10.8) for type 4 (p = 0.022).

The impacted bone grafting technique has good clinical results in femoral revision. However, major bone defects affect clinical outcome and also result in more operative complications.

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.

Revision surgery of the hip was performed on 114 hips using an extensively porous-coated femoral component. Of these, 95 hips (94 patients) had a mean follow-up of 10.2 years (5 to 17). No cortical struts were used and the cortical index and the femoral cortical width were measured at different levels.

There were two revisions for aseptic loosening. Survivorship at 12 years for all causes of failure was 96.9% (95% confidence interval 93.5 to 100) in the best-case scenario. Fibrous or unstable fixation was associated with major bone defects. The cortical index (p = 0.045) and the lateral cortical thickness (p = 0.008) decreased at the proximal level over time while the medial cortex increased (p = 0.001) at the proximal and distal levels. An increase in the proximal medial cortex was found in patients with an extended transtrochanteric osteotomy (p = 0.026) and in those with components shorter than 25 cm (p = 0.008).

The use of the extensively porous-coated femoral component can provide a solution for difficult cases in revision surgery. Radiological bony ingrowth is common. Although without clinical relevance at the end of follow-up, the thickness of the medial femoral cortex often increased while that of the lateral cortex decreased. In cases in which a shorter component was used and in those undertaken using an extended trochanteric osteotomy, there was a greater increase in thickness of the femoral cortex over time.

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.

Ultra-high-molecular-weight polyethylene sterilised in the absence of air and highly cross-linked polyethylene have been used to avoid osteolysis and loosening in total hip replacement. Our prospective randomised study has assessed the results using two different polyethylenes associated with the same prosthetic design. We assessed 45 Allofit acetabular components with a Sulene-polyethylene liner of conventional polyethylene gamma sterilised with nitrogen and 45 Allofit acetabular components with a Durasul-polyethylene liner sterilised in ethylene oxide, both matched with an Alloclassic stem with a 28 mm modular femoral head. The prostheses were implanted between May 1999 and December 2001. The mean follow-up was for 66.3 months (60 to 92). The linear penetration of the femoral head was estimated at 6 weeks, at 6 and 12 months and annually thereafter from standardised digitised radiographs using image-analysis software.

There was no loosening of any prosthetic component. There were no radiolucent lines or osteolysis. The mean rate of penetration calculated from regression analysis during the first five years was 38 μm/year (sd 2) for the Sulene group and 6 μm/year (sd 1) for the Durasul group (p = 0.00002). The rate of penetration of the Durasul group was 15.7% of that of the Sulene group.

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