Operating room ventilation and the risk of revision due to infection after total hip arthroplasty: assessment of validated data in the Norwegian Arthroplasty Register.

BACKGROUND: The air in the operating room is considered a risk factor for surgical site infection (SSI) due to airborne bacteria shed from the surgical staff or from patients themselves. AIM: To assess the influence of validated operating room (OR) ventilation data on the risk of revision surgery due to deep infection after primary total hip arthroplasty (THA) reported to the Norwegian Arthroplasty Register (NAR). METHODS: Forty orthopaedic units reporting THAs to the NAR during the period 2005-2015 were included. The true type of OR ventilation in all hospitals at the time of primary THA was confirmed in a previous study. Unidirectional airflow (UDF) systems were subdivided into: small, low-volume, unidirectional vertical flow (lvUDVF) systems; large, high-volume, unidirectional vertical flow (hvUDVF) systems; and unidirectional horizontal flow (UDHF) systems. These three ventilation groups were compared with conventional, turbulent, mixing ventilation (CV). The association between the end-point, time to revision due to infection, and OR ventilation was estimated by calculating relative risks (RRs) in a multivariate Cox regression model, with adjustments for several patient- and surgery-related covariates. FINDINGS: A total of 51,292 primary THAs were eligible for assessment. Of these, 575 had been revised due to infection. A similar risk of revision due to infection after THA performed was found in ORs with lvUDVF and UDHF compared to CV. THAs performed in ORs with hvUDVF had lower risk of revision due to infection compared to CV (RR = 0.8; 95% CI: 0.6-0.9; P = 0.01). CONCLUSION: THAs performed in ORs with hvUDVF systems had lower risk of revision due to infection compared to THAs performed in ORs with CV systems. The perception that all UDF systems are similar and possibly harmful seems erroneous.

More reoperations for periprosthetic fracture after cemented hemiarthroplasty with polished taper-slip stems than after anatomical and straight stems in the treatment of hip fractures: a study from the Norwegian Hip Fracture Register 2005 to 2016.

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. PATIENTS AND METHODS: From the Norwegian Hip Fracture Register (NHFR), 20 532 primary cemented bipolar hemiarthroplasties, which were undertaken in patients aged > 70 years with a femoral neck fracture between 2005 and 2016, were included. Polished tapered stems (n = 12 065) (Exeter and CPT), straight stems (n = 5545) (Charnley, Charnley Modular, and Spectron EF), and anatomical stems (n = 2922) (Lubinus SP2) were included. The survival of the implant with any reoperation as the endpoint was calculated using the Kaplan-Meier method and hazard ratios (HRs), and the different indications for reoperation were calculated using Cox regression analysis. RESULTS: The one-year survival was 96.0% (95% confidence interval (CI) 95.6 to 96.4) for the Exeter stem, 97.0% (95% CI 96.4 to 97.6) for the Lubinus SP2 stem, 97.6% (95% CI 97.0 to 98.2) for the Charnley stem, 98.1% (95% CI 97.3 to 98.9) for the Spectron EF stem, and 96.4% (95% CI 95.6 to 97.2) for the Charnley Modular stem, respectively. The hazard ratio for reoperation after one year was lower for Lubinus SP2 (HR 0.77, 95% CI 0.60 to 0.97), Charnley (HR 0.64, 95% CI 0.48 to 0.86), and Spectron EF stems (HR 0.44, 95% CI 0.29 to 0.67) compared with the Exeter stem. Reoperation for periprosthetic fracture occurred almost exclusively after the use of polished tapered stems. CONCLUSION: We were able to confirm that implant survival after cemented hemiarthroplasty for a hip fracture is high. Differences in rates of reoperation seem to favour anatomical and straight stems compared with polished tapered stems, which had a higher risk of periprosthetic fracture.

Inferior results with unilateral compared with bilateral brace in Ponseti-treated clubfeet.

PURPOSE: The Ponseti method for treating clubfoot was introduced in Norway in 2003, and a cohort of children has been followed for 8 to 11 years. In a previous study, we found good results after follow-up of two to five years, with 3% rate of extensive surgery (posterior release or posteromedial release). During 8 to 11 years of follow-up, the rate of extensive surgery increased to 11%. The children had been treated with a bilateral brace or a unilateral brace. In this multicentre study we aimed to compare these two post-corrective treatment methods. METHODS: In all, 94 children (133 feet) were initially treated according to the Ponseti method, and had post-corrective treatment with either a bilateral foot abduction brace or a unilateral above-the-knee brace. The children were examined at a mean age of 9.3 years (8 to 11) regarding flexibility and deformity of the foot and ankle. Information including type of brace, brace compliance and surgical procedures was -obtained from the patient records. The parents answered questionnaires and radiographs were taken of the feet. RESULTS: Feet treated with a bilateral brace had better dorsal flexion (p = 0.008), plantar flexion (p = 0.02), external rotation (p = 0.001) and less forefoot adduction (p = 0.04) than feet treated with a unilateral brace. Children using a bilateral brace had a better Functional Rating System score (p = 0.005) and Disease Specific Instrument score (p = 0.02). CONCLUSION: Children treated with a bilateral brace had better parent-reported outcomes and more flexible feet than children treated with a unilateral brace. Our results do not support the use of a unilateral foot abduction brace in clubfoot treatment.

The alpha angle in cam-type femoroacetabular impingement: new reference intervals based on 2038 healthy young adults.

We report on gender-specific reference intervals of the alpha angle and its association with other qualitative cam-type findings in femoroacetabular impingement at the hip, according to a population-based cohort of 2038 19-year-olds, 1186 of which were women (58%). The alpha angle was measured on standardised frog-leg lateral and anteroposterior (AP) views using digital measurement software, and qualitative cam-type findings were assessed subjectively on both views by independent observers. In all, 2005 participants (837 men, 1168 women, mean age 18.6 years (17.2 to 20.1) were included in the analysis. For the frog-leg view, the mean alpha angle (right hip) was 47° (26 to 79) in men and 42° (29 to 76) in women, with 97.5 percentiles of 68° and 56°, respectively. For the AP view, the mean values were 62° (40 to 105) and 52° (36 to 103) for men and women, respectively, with 97.5 percentiles of 93° and 94°. Associations between higher alpha angles and all qualitative cam-type findings were seen for both genders on both views. The reference intervals presented for the alpha angle in this cross-sectional study are wide, especially for the AP view, with higher mean values for men than women on both views.

Authors' reply Cobb correspondence re: J-E. Gjertsen, S. A. Lie, T. Vinje, et al. More re-operations after uncemented than cemented hemiarthroplasty used in the treatment of displaced fractures of the femoral neck: An observational study of 11 116 hemiarthroplasties from a national register. J Bone Joint Surg [Br] 2012;94-B:1113-1119.

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.

Radiological findings that may indicate a prior silent slipped capital femoral epiphysis in a cohort of 2072 young adults.

The reported prevalence of an asymptomatic slip of the contralateral hip in patients operated on for unilateral slipped capital femoral epiphysis (SCFE) is as high as 40%. Based on a population-based cohort of 2072 healthy adolescents (58% women) we report on radiological and clinical findings suggestive of a possible previous SCFE. Common threshold values for Southwick's lateral head-shaft angle (≥ 13°) and Murray's tilt index (≥ 1.35) were used. New reference intervals for these measurements at skeletal maturity are also presented. At follow-up the mean age of the patients was 18.6 years (17.2 to 20.1). All answered two questionnaires, had a clinical examination and two hip radiographs. There was an association between a high head-shaft angle and clinical findings associated with SCFE, such as reduced internal rotation and increased external rotation. Also, 6.6% of the cohort had Southwick's lateral head-shaft angle ≥ 13°, suggestive of a possible slip. Murray's tilt index ≥ 1.35 was demonstrated in 13.1% of the cohort, predominantly in men, in whom this finding was associated with other radiological findings such as pistol-grip deformity or focal prominence of the femoral neck, but no clinical findings suggestive of SCFE. This study indicates that 6.6% of young adults have radiological findings consistent with a prior SCFE, which seems to be more common than previously reported.

Prevalence of radiographic findings associated with hip dysplasia in a population-based cohort of 2081 19-year-old Norwegians.

In Norway total joint replacement after hip dysplasia is reported more commonly than in neighbouring countries, implying a higher prevalence of the condition. We report on the prevalence of radiological features associated with hip dysplasia in a population of 2081 19-year-old Norwegians. The radiological measurements used to define hip dysplasia were Wiberg's centre-edge (CE) angle at thresholds of < 20° and < 25°, femoral head extrusion index < 75%, Sharp's angle > 45°, an acetabular depth to width ratio < 250 and the sourcil shape assessed subjectively. The whole cohort underwent clinical examination of their range of hip movement, body mass index (BMI), and Beighton hypermobility score, and were asked to complete the EuroQol (EQ-5D) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The prevalence of hip dysplasia in the cohort varied from 1.7% to 20% depending on the radiological marker used. A Wiberg's CE angle < 20° was seen in 3.3% of the cohort: 4.3% in women and 2.4% in men. We found no association between subjects with multiple radiological signs indicative of dysplasia and BMI, Beighton score, EQ-5D or WOMAC. Although there appears to be a high prevalence of hip dysplasia among 19-year-old Norwegians, this is dependent on the radiological parameters applied.

More re-operations after uncemented than cemented hemiarthroplasty used in the treatment of displaced fractures of the femoral neck: an observational study of 11,116 hemiarthroplasties from a national register.

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.

Bacterial findings in infected hip joint replacements in patients with rheumatoid arthritis and osteoarthritis: a study of 318 revisions for infection reported to the norwegian arthroplasty register.

High rates of Staphylococcus aureus are reported in prosthetic joint infection (PJI) in rheumatoid arthritis (RA). RA patients are considered to have a high risk of infection with bacteria of potentially oral or dental origin. One thousand four hundred forty-three revisions for infection were reported to the Norwegian Arthroplasty Register (NAR) from 1987 to 2007. For this study 269 infection episodes in 255 OA patients served as control group. In the NAR we identified 49 infection episodes in 37 RA patients from 1987 to 2009. The RA patients were, on average, 10 years younger than the OA patients and there were more females (70% versus 54%). We found no differences in the bacterial findings in RA and OA. A tendency towards a higher frequency of Staphylococcus aureus (18% versus 11%) causing PJI was found in the RA patients compared to OA. There were no bacteria of potential odontogenic origin found in the RA patients, while we found 4% in OA. The bacteria identified in revisions for infection in THRs in patients with RA did not significantly differ from those in OA. Bacteria of oral or dental origin were not found in infected hip joint replacements in RA.

Internal screw fixation compared with bipolar hemiarthroplasty for treatment of displaced femoral neck fractures in elderly patients.

BACKGROUND: Internal fixation and arthroplasty are the two main options for the treatment of displaced femoral neck fractures in the elderly. The optimal treatment remains controversial. Using data from the Norwegian Hip Fracture Register, we compared the results of hemiarthroplasty and internal screw fixation in displaced femoral neck fractures. METHODS: Data from 4335 patients over seventy years of age who had internal fixation (1823 patients) or hemiarthroplasty (2512 patients) to treat a displaced femoral neck fracture were compared at a minimum follow-up interval of twelve months. One-year mortality, the number of reoperations, and patient self-assessment of pain, satisfaction, and quality of life at four and twelve months were analyzed. Subanalyses of patients with cognitive impairment and reduced walking ability were done. RESULTS: In the arthroplasty group, only contemporary bipolar prostheses were used and uncemented prostheses with modern stems and hydroxyapatite coating accounted for 20.8% (522) of the implants. There were no differences in one-year mortality (27% in the osteosynthesis group and 25% in the arthroplasty group; p = 0.76). There were 412 reoperations (22.6%) performed in the osteosynthesis group and seventy-two (2.9%) in the hemiarthroplasty group during the follow-up period. After twelve months, the osteosynthesis group reported more pain (mean score, 29.9 compared with 19.2), higher dissatisfaction with the operation result (mean score, 38.9 compared with 25.7), and a lower quality of life (mean score, 0.51 compared with 0.60) than the arthroplasty group. All differences were significant (p < 0.001). For patients with cognitive impairment, hemiarthroplasty provided a better functional outcome (less pain, higher satisfaction with the result of the operation, and higher quality of life as measured on the EuroQol visual analog scale) at twelve months (p < 0.05). CONCLUSIONS: Displaced femoral neck fractures in the elderly should be treated with hemiarthroplasty.

Medium- and long-term performance of 11,516 uncemented primary femoral stems from the Norwegian arthroplasty register.

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 x 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.

Isolated acetabular liner exchange compared with complete acetabular component revision in revision of primary uncemented acetabular components: a study of 1649 revisions from the Norwegian Arthroplasty Register.

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.

Failure mechanisms after unicompartmental and tricompartmental primary knee replacement with cement.

BACKGROUND: Concern exists regarding the durability of unicompartmental knee replacements. The purpose of the present study was to compare the early failure rates and failure mechanisms of primary cemented unicompartmental knee replacements with those of primary cemented tricompartmental total knee replacements. METHODS: The rates of failure of primary cemented unicompartmental knee replacements (n = 2288) and tricompartmental total knee replacements (n = 3032) as reported to the Norwegian Arthroplasty Register from January 1994 through December 2004 were compared with use of Kaplan-Meier estimated survival rates and Cox multiple regression. RESULTS: The ten-year survival probability was 80.1% (95% confidence interval, 76.0% to 84.2%) for unicompartmental knee replacements, compared with 92.0% (95% confidence interval, 90.4 to 93.6%) for total knee replacements, with a relative risk of revision of 2.0 (95% confidence interval, 1.6 to 2.5) (p < 0.001). This increased risk of revision following unicompartmental knee replacement was seen in all age-categories. Unicompartmental knee replacement was associated with an increased risk of revision due to pain (relative risk, 11.3 [95% confidence interval, 4.8 to 26.8]; p < 0.001), aseptic loosening of the tibial component (relative risk, 1.9 [95% confidence interval, 1.2 to 3.0]; p = 0.01) and of the femoral component (relative risk, 4.8 [95% confidence interval, 2.3 to 10.3]; p < 0.001), and periprosthetic fracture (relative risk, 3.2 [95% confidence interval, 1.2 to 8.9]; p = 0.02) as compared with total knee replacement. Unicompartmental knee replacement was associated with a lower risk of infection compared with total knee replacement (relative risk, 0.28 [95% confidence interval, 0.10 to 0.74]; p = 0.01). CONCLUSIONS: The survival of cemented unicompartmental knee replacements is inferior to that of cemented tricompartmental total knee replacements in all age-categories.

Epidemiology of severely and fatally injured patients in western part of Norway.

BACKGROUND AND AIMS: Analysis of the injury mechanism and characteristics of severely and fatally injured patients in the western part of Norway. MATERIAL AND METHODS: We did a prospective registration of all severely injured patients hospitalized during a three-year period. The files of severely injured patients that died at scene or during transport were retrospectively retrieved from the Forensic Department. A total of 558 patients with an Injury Severity Score > 15 were included. RESULTS: Four-hundred-forty-four men (79.6 %) and 114 women (20.4 %) with a median age of 36 and 51.5 years respectively were included. The proportion of female patients older than 80 years were 19.3 % compared to 5.6 % for men. A total of 215 (38.5 %) patients died and 149 (69.3 %) of these patients died on scene or during transport. The incidence of severely injured patients in Hordaland County was 30 per 100,000 inhabitants per year. The incidence was lowest among children below 5 years (7/100,000/year) and highest among persons older than 80 years (95/100,000/year). Men had a 3.8 times greater risk of getting seriously injured compared to women. Road traffic accidents were the cause of the injuries in 235 (42.1 %) patients and 35.8 % of these patients died. A total of 215 (38.5 %) patients were injured due to falls and 30.2 % of these patients died. Patients who had sustained falls were significantly older than patents with other injury mechanisms (p < 0.001, CI = 13.0-20.2). The proportion of patients with penetrating injuries was 7.3 %. CONCLUSION: The incidence of severely injured patients was 30/100000/year. Men and elderly people had a higher risk of getting severely injured. Falls were the dominating injury mechanism among elderly.

Failure rates for 4762 revision total hip arthroplasties in the Norwegian Arthroplasty Register.

We present the results for 4762 revision total hip arthroplasties with no previous infection in the hip, which were reported to the Norwegian Arthroplasty Register between 1987 and 2003. The ten-year failure rate for revised prostheses was 26% (95% CI 25 to 26). Cox regression analyses were undertaken separately for acetabular and femoral revision components. Cemented revision components without allograft was the reference category. For acetabular components, we found a significantly reduced risk of failure for uncemented revisions both with (relative risk (RR) = 0.66; 95% CI 0.43 to 0.99) and without (RR = 0.37; 95% CI 0.22 to 0.61) allograft. For femoral components, we found a significantly reduced risk of failure for uncemented revisions, both with (RR = 0.27; 95% CI 0.16 to 0.46) and without (RR = 0.22; 95% CI 0.11 to 0.46) unimpacted allograft. This reduced risk of failure also applied to cemented revision components with allograft (RR = 0.53; 95% CI 0.33 to 0.84) and with impaction bone grafting (RR = 0.34; 95% CI 0.19 to 0.62). Revision prostheses have generally inferior results when compared with primary prostheses. Recementation without allograft, and uncemented revision with bone impaction, were associated with worse results than the other revision techniques which we studied.

The type of cement and failure of total hip replacements.

Using data from the Norwegian Arthroplasty egister, we have assessed the 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.

The performance of two hydroxyapatite-coated acetabular cups compared with Charnley cups. From the Norwegian Arthroplasty Register.

We have compared the survival of two hydroxyapatite (HA)-coated cups, 1208 Atoll hemispheric and 2641 Tropic threaded, with cemented Charnley all-polyethylene cups (16 021) using the Cox regression model. The Tropic cup used in combination with an alumina ceramic femoral head, had good results, similar to those of the Charnley cup. When used in combination with a stainless-steel head, however, the risk of revision beyond four years was increased 3.4 times for the Tropic cup compared with the Charnley cup (p < 0.001). Over the same period, the Atoll cup had an increased risk of revision of 3.8 times when used with the alumina heads (p < 0.001) and an increased risk of 6.1 times when used with stainless-steel heads (p < 0.001). Revision because of wear and osteolysis was more common with both types of HA-coated cup than with the Charnley cup. The rate of revision of the Atoll cup because of aseptic loosening was also increased. We found that HA-coated cups did not perform better than the Charnley cup.

Hip disease and the prognosis of total hip replacements. A review of 53,698 primary total hip replacements reported to the Norwegian Arthroplasty Register 1987-99.

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.