Aims

The aim of this study was to investigate mortality and risk of intraoperative medical complications depending on delay to hip fracture surgery by using data from the Norwegian Hip Fracture Register (NHFR) and the Norwegian Patient Registry (NPR).

Aims

The aim of this large registry-based study was to compare mid-term survival rates of cemented femoral stems of different designs used in hemiarthroplasty for a fracture of the femoral neck.

Aims

The aim of this consensus was to develop a definition of post-operative fibrosis of the knee.

We report the five-year outcome of a randomised controlled trial which used radiostereometric analysis (RSA) to assess the influence of surface oxidised zirconium (OxZr, Oxinium) on polyethylene wear in vivo.

A total of 120 patients, 85 women and 35 men with a mean age of 70 years (59 to 80) who were scheduled for primary cemented total hip arthroplasty were randomly allocated to four study groups. Patients were blinded to their group assignment and received either a conventional polyethylene (CPE) or a highly cross-linked (HXL) acetabular component of identical design. On the femoral side patients received a 28 mm head made of either cobalt-chromium (CoCr) or OxZr.

The proximal head penetration (wear) was measured with repeated RSA examinations over five years. Clinical outcome was measured using the Harris hip score.

There was no difference in polyethylene wear between the two head materials when used with either of the two types of acetabular component (p = 0.3 to 0.6). When comparing the two types of polyethylene there was a significant difference in favour of HXLPE, regardless of the head material used (p < 0.001).

In conclusion, we found no advantage of OxZr over CoCr in terms of polyethylene wear after five years of follow-up. Our findings do not support laboratory results which have shown a reduced rate of wear with OxZr. They do however add to the evidence on the better resistance to wear of HXLPE over CPE.

Cite this article: Bone Joint J 2015;97-B:1463–9.

We performed a randomised controlled trial comparing computer-assisted surgery (CAS) with conventional surgery (CONV) in total knee replacement (TKR). Between 2009 and 2011 a total of 192 patients with a mean age of 68 years (55 to 85) with osteoarthritis or arthritic disease of the knee were recruited from four Norwegian hospitals. At three months follow-up, functional results were marginally better for the CAS group. Mean differences (MD) in favour of CAS were found for the Knee Society function score (MD: 5.9, 95% confidence interval (CI) 0.3 to 11.4, p = 0.039), the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales for ‘pain’ (MD: 7.7, 95% CI 1.7 to 13.6, p = 0.012), ‘sports’ (MD: 13.5, 95% CI 5.6 to 21.4, p = 0.001) and ‘quality of life’ (MD: 7.2, 95% CI 0.1 to 14.3, p = 0.046). At one-year follow-up, differences favouring CAS were found for KOOS ‘sports’ (MD: 11.0, 95% CI 3.0 to 19.0, p = 0.007) and KOOS ‘symptoms’ (MD: 6.7, 95% CI 0.5 to 13.0, p = 0.035). The use of CAS resulted in fewer outliers in frontal alignment (> 3° malalignment), both for the entire TKR (37.9% vs 17.9%, p = 0.042) and for the tibial component separately (28.4% vs 6.3%, p = 0.002). Tibial slope was better achieved with CAS (58.9% vs 26.3%, p < 0.001). Operation time was 20 minutes longer with CAS. In conclusion, functional results were, statistically, marginally in favour of CAS. Also, CAS was more predictable than CONV for mechanical alignment and positioning of the prosthesis. However, the long-term outcomes must be further investigated.

Cite this article: Bone Joint J 2014; 96-B:609–18.

We welcome letters to the Editor concerning articles that have recently been published. Such letters will be subject to the usual stages of selection and editing; where appropriate the authors of the original article will be offered the opportunity to reply.

We evaluated the rates of survival and cause of revision of seven different brands of cemented primary total knee replacement (TKR) in the Norwegian Arthroplasty Register during the years 1994 to 2009. Revision for any cause, including resurfacing of the patella, was the primary endpoint. Specific causes of revision were secondary outcomes.

Three posterior cruciate-retaining (PCR) fixed modular-bearing TKRs, two fixed non-modular bearing PCR TKRs and two mobile-bearing posterior cruciate-sacrificing TKRs were investigated in a total of 17 782 primary TKRs. The median follow-up for the implants ranged from 1.8 to 6.9 years. Kaplan-Meier 10-year survival ranged from 89.5% to 95.3%. Cox’s relative risk (RR) was calculated relative to the fixed modular-bearing Profix knee (the most frequently used TKR in Norway), and ranged from 1.1 to 2.6. The risk of revision for aseptic tibial loosening was higher in the mobile-bearing LCS Classic (RR 6.8 (95% confidence interval (CI) 3.8 to 12.1)), the LCS Complete (RR 7.7 (95% CI 4.1 to 14.4)), the fixed modular-bearing Duracon (RR 4.5 (95% CI 1.8 to 11.1)) and the fixed non-modular bearing AGC Universal TKR (RR 2.5 (95% CI 1.3 to 5.1)), compared with the Profix. These implants (except AGC Universal) also had an increased risk of revision for femoral loosening (RR 2.3 (95% CI 1.1 to 4.8), RR 3.7 (95% CI 1.6 to 8.9), and RR 3.4 (95% CI 1.1 to 11.0), respectively). These results suggest that aseptic loosening is related to design in TKR.

Cite this article: Bone Joint J 2013;95-B:636–42.

Using data from the Norwegian Hip Fracture Register, 8639 cemented and 2477 uncemented primary hemiarthroplasties for displaced fractures of the femoral neck in patients aged > 70 years were included in a prospective observational study. A total of 218 re-operations were performed after cemented and 128 after uncemented procedures. Survival of the hemiarthroplasties was calculated using the Kaplan-Meier method and hazard rate ratios (HRR) for revision were calculated using Cox regression analyses. At five years the implant survival was 97% (95% confidence interval (CI) 97 to 97) for cemented and 91% (95% CI 87 to 94) for uncemented hemiarthroplasties. Uncemented hemiarthroplasties had a 2.1 times increased risk of revision compared with cemented prostheses (95% confidence interval 1.7 to 2.6, p < 0.001). The increased risk was mainly caused by revisions for peri-prosthetic fracture (HRR = 17), aseptic loosening (HRR = 17), haematoma formation (HRR = 5.3), superficial infection (HRR = 4.6) and dislocation (HRR = 1.8). More intra-operative complications, including intra-operative death, were reported for the cemented hemiarthroplasties. However, in a time-dependent analysis, the HRR for re-operation in both groups increased as follow-up increased.

This study showed that the risk for revision was higher for uncemented than for cemented hemiarthroplasties.

In this prospective study we studied the effect of the inclination angle of the acetabular component on polyethylene wear and component migration in cemented acetabular sockets using radiostereometric analysis.

A total of 120 patients received either a cemented Reflection All-Poly ultra-high-molecular-weight polyethylene or a cemented Reflection All-Poly highly cross-linked polyethylene acetabular component, combined with either cobalt–chrome or Oxinium femoral heads. Femoral head penetration and migration of the acetabular component were assessed with repeated radiostereometric analysis for two years. The inclination angle was measured on a standard post-operative anteroposterior pelvic radiograph. Linear regression analysis was used to determine the relationship between the inclination angle and femoral head penetration and migration of the acetabular component.

We found no relationship between the inclination angle and penetration of the femoral head at two years’ follow-up (p = 0.9). Similarly, our data failed to reveal any statistically significant correlation between inclination angle and migration of these cemented acetabular components (p = 0.07 to p = 0.9).

The Norwegian Arthroplasty Register has shown that several designs of uncemented femoral stems give good or excellent survivorship. The overall findings for uncemented total hip replacement however, have been disappointing because of poor results with the use of metal-backed acetabular components. In this study, we exclusively investigated the medium-to long-term performance of primary uncemented metal-backed acetabular components.

A total of 9113 primary uncemented acetabular components were implanted in 7937 patients between 1987 and 2007. These were included in a prospective, population-based observational study. All the implants were modular and metal-backed with ultra-high-molecular-weight polyethylene liners. The femoral heads were made of stainless steel, cobalt-chrome (CoCr) alloy or alumina ceramic. In all, seven different designs of acetabular component were evaluated by the Kaplan-Meier survivorship method and Cox regression analysis.

Most acetabular components performed well up to seven years. When the endpoint was revision of the acetabular component because of aseptic loosening, the survival ranged between 87% and 100% at ten years. However, when the endpoint was revision for any reason, the survival estimates were 81% to 92% for the same implants at ten years. Aseptic loosening, wear, osteolysis and dislocation were the main reasons for the relatively poor overall performance of the acetabular components. Prostheses with alumina heads performed slightly better than those with stainless steel or CoCr alloy in subgroups.

Whereas most acetabular components performed well at seven years, the survivorship declined with longer follow-up. Fixation was generally good. None of the metal-backed uncemented acetabular components with ultra-high-molecular-weight polyethylene liners in our study had satisfactory long-term results because of high rates of wear, osteolysis, aseptic loosening and dislocation.

Primary uncemented femoral stems reported to the Norwegian arthroplasty register between 1987 and 2005 were included in this prospective observational study. There were 11 516 hips (9679 patients) and 14 different designs of stem. Kaplan-Meier survival probabilities and Cox regression were used to analyse the data.

With aseptic loosening as the end-point, all currently used designs performed excellently with survival of 96% to 100% at ten years. With the end-point as stem revision for any cause, the long-term results of the different designs varied from poor to excellent, with survival at 15 years ranging between 29% and 97%. Follow-up for longer than seven years was needed to identify some of the poorly-performing designs. There were differences between the stems; the Corail, used in 5456 hips, was the most frequently used stem with a survival of 97% at 15 years. Male gender was associated with an increased risk of revision of × 1.3 (95% confidence interval 1.05 to 1.52), but age and diagnosis had no influence on the results. Overall, modern uncemented femoral stems performed well.

Moderate differences in survival between well-performing stems should be interpreted with caution since the differences may be caused by factors other than the stem itself.

We analysed the results of different strategies in the revision of primary uncemented acetabular components reported to the Norwegian Arthroplasty Register. The aim was to compare the risk of further acetabular revision after isolated liner exchange and complete component revision. The results of exchanging well-fixed components were also compared with those of exchanging loose acetabular components. The period studied was between September 1987 and April 2005. The following groups were compared: group 1, exchange of liner only in 318 hips; group 2, exchange of well-fixed components in 398; and group 3, exchange of loose components in 933. We found that the risk of a further cup revision was lower after revision of well-fixed components (relative risk from a Cox model (RR) = 0.56, 95% confidence interval 0.37% to 0.87%) and loose components (RR = 0.56, 95% confidence interval 0.39% to 0.80%), compared with exchange of the liner in isolation. The most frequent reason for a further acetabular revision was dislocation, accounting for 61 (28%) of the re-revisions. Other reasons for further revision included pain in 27 (12%), loosening in 24 (11%) and infection in 20 (9%). Re-revisions because of pain were less frequent when complete component (fixed or loose) revision was undertaken compared with isolated exchange of the liner (RR = 0.20 (95% confidence interval 0.06% to 0.65%) and RR = 0.10 (95% confidence interval 0.03% to 0.30%), respectively). The risk of further acetabular revision for infection, however, did not differ between the groups.

In this study, exchange of the liner only had a higher risk of further cup revision than revision of the complete acetabular component. Our results suggest that the threshold for revising well-fixed components in the case of liner wear and osteolysis should be lowered.

We performed a randomised, radiostereometric study comparing two different bone cements, one of which has been sparsely clinically documented. Randomisation of 60 total hip replacements (57 patients) into two groups of 30 was undertaken. All the patients were operated on using a cemented Charnley total hip replacement, the only difference between groups being the bone cement used to secure the femoral component. The two cements used were Palamed G and Palacos R with gentamicin. The patients were followed up with repeated clinical and radiostereometric examinations for two years to assess the micromovement of the femoral component and the clinical outcome.

The mean subsidence was 0.18 mm and 0.21 mm, and the mean internal rotation was 1.7° and 2.0° at two years for the Palamed G and Palacos R with gentamicin bone cements, respectively. We found no statistically significant differences between the groups. Micromovement occurred between the femoral component and the cement, while the cement mantle was stable inside the bone. The Harris hip score improved from a mean of 38 points (14 to 54) and 36 (10 to 57) pre-operatively to a mean of 92 (77 to 100) and 91 (63 to 100) at two years in the Palamed G and Palacos R groups, respectively. No differences were found between the groups.

Both bone cements provided good initial fixation of the femoral component and good clinical results at two years.

Using data from the Norwegian Arthroplasty Register, we have the assessed survival of 17 323 primary Charnley hip prostheses in patients with osteoarthritis based upon the type of cement used for the fixation of the implant.

Overall, 9.2% had been revised after follow-up for ten years; 71% of the failures involved aseptic loosening of the femoral component. We observed significantly increased rates of failure for prostheses inserted with CMW1 and CMW3 cements. Using implants fixed with gentamicin-containing Palacos cement as the reference, the adjusted Cox regression failure rate ratios were 1.1 (95% CI 0.9 to 1.4) for implants cemented with plain Palacos, 1.1 (95% CI 0.7 to 1.6) for Simplex, 2.1 (95% 1.5 to 2.9) for gentamicin-containing CMW1, 2.0 (95% CI 1.6 to 2.4) for plain CMW1 and 3.0 (95% CI 2.3 to 3.9) for implants fixed with CMW3 cement. The adjusted failure rate at ten years varied from 5.9% for implants fixed with gentamicin-containing Palacos to 17% for those fixed with CMW3.

We studied the rates of revision for 53 698 primary total hip replacements (THRs) in nine different groups of disease. Factors which have previously been shown to be associated with increased risk of revision, such as male gender, young age, or certain types of uncemented prosthesis, showed important differences between the diagnostic groups. Without adjustment for these factors we observed an increased risk of revision in patients with paediatric hip diseases and in a small heterogeneous ‘other’ group, compared with patients with primary osteoarthritis. Most differences were reduced or disappeared when an adjustment for the prognostic factors was made. After adjustment, an increased relative risk (RR) of revision compared with primary osteoarthritis was seen in hips with complications after fracture of the femoral neck (RR = 1.3, p = 0.0005), in hips with congenital dislocation (RR = 1.3, p = 0.03), and in the heterogenous ‘other’ group. The analyses were also undertaken in a more homogenous subgroup of 16 217 patients which had a Charnley prosthesis implanted with high-viscosity cement. The only difference in this group was an increased risk for revision in patients who had undergone THR for complications after fracture of the femoral neck (RR = 1.5, p = 0.0005).

THR for diagnoses seen mainly among young patients had a good prognosis, but they had more often received inferior uncemented implants. If a cemented Charnley prosthesis is used, the type of disease leading to THR seems in most cases to have only a minor influence on the survival of the prosthesis.