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26.  Good results after Ponseti treatment for neglected congenital clubfoot in Ethiopia 
Acta Orthopaedica  2014;85(6):641-645.
Background and purpose —
Neglected clubfoot deformity is a major cause of disability in low-income countries. Most children with clubfoot have little access to treatment in these countries, and they are often inadequately treated. We evaluated the effectiveness of Ponseti’s technique in neglected clubfoot in children in a rural setting in Ethiopia.
Patients and methods —
A prospective study was conducted from June 2007 through July 2010. 22 consecutive children aged 2–10 years (32 feet) with neglected clubfoot were treated by the Ponseti method. The deformity was assessed using the Pirani scoring system. The average follow-up time was 3 years.
Results —
A plantigrade functional foot was obtained in all patients by Ponseti casting and limited surgical intervention. 2 patients (4 feet) had recurrent deformity. They required re-manipulation and re-tenotomy of the Achilles tendon and 1 other patient required tibialis anterior transfer for dynamic supination deformity of the foot.
Interpretation —
This study shows that the Ponseti method with some additional surgery can be used successfully as the primary treatment in neglected clubfoot, and that it minimizes the need for extensive corrective surgery.
PMCID: PMC4259042  PMID: 25175659
27.  Adherence of hip and knee arthroplasty studies to RSA standardization guidelines 
Acta Orthopaedica  2014;85(5):447-455.
Background and purpose
Guidelines for standardization of radiostereometry (RSA) of implants were published in 2005 to facilitate comparison of outcomes between various research groups. In this systematic review, we determined how well studies have adhered to these guidelines.
We carried out a literature search to identify all articles published between January 2000 and December 2011 that used RSA in the evaluation of hip or knee prosthesis migration. 2 investigators independently evaluated each of the studies for adherence to the 13 individual guideline items. Since some of the 13 points included more than 1 criterion, studies were assessed on whether each point was fully met, partially met, or not met.
153 studies that met our inclusion criteria were identified. 61 of these were published before the guidelines were introduced (2000–2005) and 92 after the guidelines were introduced (2006–2011). The methodological quality of RSA studies clearly improved from 2000 to 2011. None of the studies fully met all 13 guidelines. Nearly half (43) of the studies published after the guidelines demonstrated a high methodological quality and adhered at least partially to 10 of the 13 guidelines, whereas less than one-fifth (11) of the studies published before the guidelines had the same methodological quality. Commonly unaddressed guideline items were related to imaging methodology, determination of precision from double examinations, and also mean error of rigid-body fitting and condition number cutoff levels.
The guidelines have improved methodological reporting in RSA studies, but adherence to these guidelines is still relatively low. There is a need to update and clarify the guidelines for clinical hip and knee arthroplasty RSA studies.
PMCID: PMC4164860  PMID: 24954489
28.  Body mass index and risk of perioperative cardiovascular adverse events and mortality in 34,744 Danish patients undergoing hip or knee replacement 
Acta Orthopaedica  2014;85(5):456-462.
Background and purpose
Obesity is a risk factor for osteoarthritis in the lower limb, yet the cardiovascular risks associated with obesity in hip or knee replacement surgery are unknown. We examined associations between body mass index (BMI) and the risk of a major adverse cardiovascular event (MACE: ischemic stroke, acute myocardial infarction, or cardiovascular death) or the risk of all-cause mortality in a nationwide Danish cohort of patients who underwent primary hip or knee replacement surgery.
Using Danish nationwide registries, we identified 34,744 patients aged ≥ 20 years who underwent elective primary hip or knee replacement surgery between 2005 and 2011. We used multivariable Cox regression models to calculate the 30-day risks of MACE and mortality associated with 5 BMI groups (underweight (BMI < 18.5 kg/m2), normal weight (18.5–24 kg/m2), overweight (25–29 kg/m2), obese 1 (30–34 kg/m2), and obese 2 (≥ 35 kg/m2)).
In total, 232 patients (0.7%) had a MACE and 111 (0.3%) died. Compared with overweight, adjusted hazard ratios (HRs) were 1.2 (95% CI: 0.4–3.3), 1.3 (0.95–1.8), 1.6 (1.1–2.2), and 1.0 (0.6–1.9) for underweight, normal weight, obese 1, and obese 2 regarding MACE. Regarding mortality, the corresponding HRs were 7.0 (2.8–15), 2.0 (1.2–3.2), 1.5 (0.9–2.7), and 1.9 (0.9–4.2). Cubic splines suggested a significant U-shaped relationship between BMI and risks with nadir around 27–28.
In an unselected cohort of patients undergoing elective primary hip or knee replacement surgery, U-shaped risks of perioperative MACE and mortality were found in relation to BMI. Patients within the extreme ranges of BMI may warrant further attention.
PMCID: PMC4164861  PMID: 24954493
29.  Worse patient-reported outcome after lateral approach than after anterior and posterolateral approach in primary hip arthroplasty 
Acta Orthopaedica  2014;85(5):463-469.
The surgical approach in total hip arthroplasty (THA) is often based on surgeon preference and local traditions. The anterior muscle-sparing approach has recently gained popularity in Europe. We tested the hypothesis that patient satisfaction, pain, function, and health-related quality of life (HRQoL) after THA is not related to the surgical approach.
1,476 patients identified through the Norwegian Arthroplasty Register were sent questionnaires 1–3 years after undergoing THA in the period from January 2008 to June 2010. Patient-reported outcome measures (PROMs) included the hip disability osteoarthritis outcome score (HOOS), the Western Ontario and McMaster Universities osteoarthritis index (WOMAC), health-related quality of life (EQ-5D-3L), visual analog scales (VAS) addressing pain and satisfaction, and questions about complications. 1,273 patients completed the questionnaires and were included in the analysis.
Adjusted HOOS scores for pain, other symptoms, activities of daily living (ADL), sport/recreation, and quality of life were significantly worse (p < 0.001 to p = 0.03) for the lateral approach than for the anterior approach and the posterolateral approach (mean differences: 3.2–5.0). These results were related to more patient-reported limping with the lateral approach than with the anterior and posterolateral approaches (25% vs. 12% and 13%, respectively; p < 0.001).
Patients operated with the lateral approach reported worse outcomes 1–3 years after THA surgery. Self-reported limping occurred twice as often in patients who underwent THA with a lateral approach than in those who underwent THA with an anterior or posterolateral approach. There were no significant differences in patient-reported outcomes after THA between those who underwent THA with a posterolateral approach and those who underwent THA with an anterior approach.
PMCID: PMC4164862  PMID: 24954494
30.  Wear of a sequentially annealed polyethylene acetabular liner 
Acta Orthopaedica  2014;85(5):470-473.
Background and purpose
We previously reported on a randomized controlled trial (RCT) that examined the effect of adding tobramycin to bone cement after femoral stem migration. The present study examined femoral head penetration into both conventional and highly crosslinked polyethylene acetabular liners in the same group of RCT patients, with a minimum of 5 years of postoperative follow-up.
Patients and methods
Linear penetration of the femoral head into an X3 (Stryker) crosslinked polyethylene (XLPE) liner was measured in 18 patients (19 hips) using radiostereometric analysis (RSA). Femoral head penetration was also measured in 6 patients (6 hips) with a conventional polyethylene liner (CPE), which served as a control group.
The median proximal femoral head penetration in the XLPE group after 5.5 years was 0.025 mm with a steady-state penetration rate of 0.001 mm/year between year 1 and year 5. The CPE liner showed a median proximal head penetration of 0.274 mm after 7.2 years, at a rate of 0.037 mm/year.
The Trident X3 sequentially annealed XLPE liner shows excellent in vivo wear resistance compared to non-crosslinked CPE liners at medium-term implantation. The rate of linear head penetration in the XLPE liners after > 5 years of follow-up was 0.001 mm/year, which is in close agreement with the results of previous studies.
PMCID: PMC4164863  PMID: 25140986
31.  Comparison of extracapsular pseudotumors seen in magnetic resonance imaging and in revision surgery of 167 failed metal-on-metal hip replacements 
Acta Orthopaedica  2014;85(5):474-479.
Background and purpose
Magnetic resonance imaging (MRI) is important for detecting extracapsular pseudotumors, but there is little information on the accuracy of MRI and appropriate intervals for repeated imaging. We evaluated the sensitivity and specificity of MRI for detecting pseudotumors in 155 patients (167 hips) with metal-on-metal (MoM) hip arthroplasties that failed due to adverse reactions to metal debris (ARMD).
Preoperative MRIs were performed with two 1.5 T MRI scanners and graded by a senior musculoskeletal radiologist using a previously described MRI pseudotumor grading system. Revision findings were retrieved from surgical notes, and pseudotumors were retrospectively graded as fluid-filled, mixed-type, or solid.
The sensitivity of MRI was 71% and the specificity was 87% for detecting extracapsular pseudotumors. The sensitivity was 88% (95% CI: 70–96) when MRI was performed less than 3 months before the revision surgery. Interestingly, when the time that elapsed between MRI and revision was more than 1 year, the sensitivity calculated was only 29% (95% CI: 14–56). Comparison between MRI and revision classifications gave moderate agreement (Cohen’s kappa = 0.4).
A recent MRI predicts the presence of a pseudotumor well, but there is more discrepancy when the MRI examination is over a year old, most likely due to the formation of new pseudotumors. 1 year could be a justifiable limit for considering a new MRI if development of ARMD is suspected. MRI images over a year old should not be used in decision making or in planning of revision surgery for MoM hips.
PMCID: PMC4164864  PMID: 24954485
32.  What is the optimal alignment of the tibial and femoral components in knee arthroplasty? 
Acta Orthopaedica  2014;85(5):480-487.
Surgeon-dependent factors such as optimal implant alignment are thought to play a significant role in outcome following primary total knee arthroplasty (TKA). Exact definitions and references for optimal alignment are, however, still being debated. This overview of the literature describes different definitions of component alignment following primary TKA for (1) tibiofemoral alignment in the AP plane, (2) tibial and femoral component placement in the AP plane, (3) tibial and femoral component placement in the sagittal plane, and (4) rotational alignment of tibial and femoral components and their role in outcome and implant survival.
We performed a literature search for original and review articles on implant positioning following primary TKA. Definitions for coronal, sagittal, and rotational placement of femoral and tibial components were summarized and the influence of positioning on survival and functional outcome was considered.
Many definitions exist when evaluating placement of femoral and tibial components. Implant alignment plays a role in both survival and functional outcome following primary TKA, as component malalignment can lead to increased failure rates, maltracking, and knee pain.
Based on currently available evidence, surgeons should aim for optimal alignment of tibial and femoral components when performing TKA.
PMCID: PMC4164865  PMID: 25036719
33.  Risk of re-admission, reoperation, and mortality within 90 days of total hip and knee arthroplasty in fast-track departments in Denmark from 2005 to 2011 
Acta Orthopaedica  2014;85(5):493-500.
To compare the risks of re-admission, reoperation, and mortality within 90 days of surgery in orthopedic departments with well-documented fast-track arthroplasty programs with those in all other orthopedic departments in Denmark from 2005 to 2011.
We used the Danish hip and knee arthroplasty registers to identify patients with primary total hip arthroplasty or total knee arthroplasty. Information about re-admission, reoperation, and mortality within 90 days of surgery was obtained from administrative databases. The fast-track cohort consisted of 6 departments. The national comparison cohort consisted of all other orthopedic departments. Regression methods were used to calculate relative risk (RR) of adverse events, adjusting for age, sex, type of fixation, and comorbidity. Cohorts were divided into 3 time periods: 2005–2007, 2008–2009, and 2010–2011.
79,098 arthroplasties were included: 17,284 in the fast-track cohort and 61,814 in the national cohort. Median length of stay (LOS) was less for the fast-track cohort in all 3 time periods (4, 3, and 3 days as opposed to 6, 4, and 3 days). RR of re-admission due to infection was higher in the fast-track cohort in 2005–2007 (1.3, 95% CI: 1.1–1.6) than in the national cohort in the same time period. This was mainly due to urinary tract infections. RR of re-admission due to a thromboembolic event was lower in the fast-track cohort in 2010–2011 (0.7, CI: 0.6–0.9) than in the national cohort in the same time period. No differences were seen in the risk of reoperation and mortality between the 2 cohorts during any time period.
The general reduction in LOS indicates that fast-track arthroplasty programs have been widely implemented in Denmark. At the same time, it appears that dedicated fast-track departments have been able to optimize the fast-track program further without any rise in re-admission, reoperation, and mortality rates.
PMCID: PMC4164867  PMID: 25036718
34.  Legg-Calvé-Perthes disease and the risk of ADHD, depression, and mortality 
Acta Orthopaedica  2014;85(5):501-505.
Background and purpose
Hyperactive behavior pattern (such as attention deficit hyperactivity disorder (ADHD)) is proposed to be present in individuals with Legg-Calvé-Perthes disease (LCPD). We investigated whether individuals with LCPD have a higher risk of ADHD, depression, and mortality.
Subjects and methods
We identified 4,057 individuals with LCPD in Sweden during the period 1964–2011. 40,570 individuals without LCPD were randomly selected from the Swedish general population and matched by year of birth, sex, and region (control group). We used Cox proportional hazard regression to estimate the relative risks.
Compared to the control group, individuals with LCPD had a raised hazard ratio (HR) of 1.5 (95% CI: 1.2–1.9) for ADHD. The risks were higher for female individuals (HR = 2.1, CI: 1.3–3.5) than for male individuals (HR = 1.4, CI: 1.1–1.8). Individuals with LCPD had a modestly higher hazard ratio for depression (HR = 1.3, CI: 1.1–1.5) than the control group. Furthermore, individuals with LCPD had a slightly higher mortality risk than the control group (HR = 1.2, CI: 1.0–1.4)
Individuals with LCPD have a higher risk of ADHD. Hyperactivity could expose the femoral head to higher mechanical stress and contribute to the etiology of LCPD. The higher risk of depression may be due to the burden of LCPD itself or could reflect neurobehavioral aspects of ADHD changing into depression later in life. Individuals with LCPD have a higher mortality risk, with higher risk of suicide and cardiovascular diseases.
PMCID: PMC4164868  PMID: 25036717
35.  The acetabulum in Perthes’ disease: Inter-observer agreement and reliability of radiographic measurements 
Acta Orthopaedica  2014;85(5):506-512.
Background and purpose
Perthes’ disease leads to radiographic changes in both the femoral head and the acetabulum. We investigated the inter-observer agreement and reliability of 4 radiographic measurements assessing the acetabular changes.
Patients and methods
We included 123 children with unilateral involvement, femoral head necrosis of more than 50%, and age at diagnosis of 6 years or older. Radiographs were taken at onset, and 1 year and 5 years after diagnosis. Sharp’s angle, acetabular depth-width ratio (ADR), lateral acetabular inclination (LAI), and acetabular retroversion (ischial spine sign, ISS) were measured by 3 observers. Before measuring, 2 of the observers had a consensus meeting.
We found good agreement and moderate to excellent reliability for Sharp’s angle for all observers (intra-class correlation coefficient (ICC) > 0.80 with consensus, ICC = 0.46–0.57 without consensus). There was good agreement and substantial reliability for ADR between the observers who had had a consensus meeting (ICC = 0.62–0.89). Low levels of agreement and poor reliability were found for observers who had not had a consensus meeting. LAI showed fair agreement throughout the course of the disease (kappa = 0.28–0.52). The agreement between observations for ISS ranged from fair to good (kappa = 0.20–0.76).
Sharp’s angle showed the highest reliability and agreement throughout the course of the disease. ADR was only reliable and showed good agreement between the observers when landmarks were clarified before measuring the radiographs. Thus, we recommend both parameters in clinical practice, provided a consensus is established for ADR. The observations for LAI had only fair agreement and ISS showed inconclusive agreement in our study. Thus, LAI and ISS can hardly be recommended in clinical practice.
PMCID: PMC4164869  PMID: 24954486
36.  Tibial fractures in children 
Acta Orthopaedica  2014;85(5):513-517.
Tibial fracture is the third most common long-bone fracture in children. Traditionally, most tibial fractures in children have been treated non-operatively, but there are no long-term results.
94 children (64 boys) were treated for a tibial fracture in Aurora City Hospital during the period 1980–89 but 20 could not be included in the study. 58 of the remaining 74 patients returned a written questionnaire and 45 attended a follow-up examination at mean 27 (23–32) years after the fracture.
89 children had been treated by manipulation under anesthesia and cast-immobilization, 4 by skeletal traction, and 1 with pin fixation. 41 fractures had been re-manipulated. The mean length of hospital stay was 5 (1–26) days. Primary complications were recorded in 5 children. The childrens’ memories of treatment were positive in two-thirds of cases. The mean subjective VAS score (range 0–10) for function appearance was 9. Leg-length discrepancy (5–10 mm) was found clinically in 10 of 45 subjects and rotational deformities exceeding 20° in 4. None of the subjects walked with a limp. None had axial malalignment exceeding 10°. Osteoarthritis of the hip and/or knee was seen in radiographs from 2 subjects.
The long-term outcome of tibial fractures in children treated non-operatively is generally good.
PMCID: PMC4164870  PMID: 24786903
37.  Prevalence and clinical significance of occult fractures in children with radiograph-negative acute ankle injury 
Acta Orthopaedica  2014;85(5):518-524.
Background and purpose
Plain radiographs may fail to reveal an ankle fracture in children because of developmental and anatomical characteristics. In this systematic review and meta- analysis, we estimated the prevalence of occult fractures in children with acute ankle injuries and clinical suspicion of fracture, and assessed the diagnostic accuracy of ultrasound (US) in the detection of occult fractures.
We searched the literature and included studies reporting the prevalence of occult fractures in children with acute ankle injuries and clinical suspicion of fracture. Proportion meta-analysis was performed to calculate the pooled prevalence of occult fractures. For each individual study exploring the US diagnostic accuracy, we calculated US operating characteristics.
9 studies (involving 187 patients) using magnetic resonance imaging (MRI) (n = 5) or late radiographs (n = 4) as reference standard were included, 2 of which also assessed the diagnostic accuracy of US. Out of the 187 children, 41 were found to have an occult fracture. The pooled prevalence of occult fractures was 24% (95% CI: 18–31). The operating characteristics for detection of occult ankle fractures by US ranged in positive likelihood ratio (LR) from 9 to 20, and in negative LR from 0.04 to 0.08.
A substantial proportion of fractures may be overlooked on plain radiographs in children with acute ankle injuries and clinical suspicion of fracture. US appears to be a promising method for detection of ankle fractures in such children when plain radiographs are negative.
PMCID: PMC4164871  PMID: 24875057
38.  Incidence of fractures requiring inpatient care 
Acta Orthopaedica  2014;85(5):525-530.
The overall incidence of fractures has been addressed in several studies, but there are few data on different types of fractures that require inpatient care, even though they account for considerable healthcare costs. We determined the incidence of limb and spine fractures that required hospitalization in people aged ≥ 16 years.
Patients and methods
We collected data on the diagnosis (ICD10 code), procedure code (NOMESCO), and 9 additional characteristics of patients admitted to the trauma ward of Central Finland Hospital between 2002 and 2008. Incidence rates were calculated for all fractures using data on the population at risk.
Results and interpretation
During the study period, 3,277 women and 2,708 men sustained 3,750 and 3,030 fractures, respectively. The incidence of all fractures was 4.9 per 103 person years (95% CI: 4.8–5.0). The corresponding numbers for women and men were 5.3 (5.1–5.4) and 4.5 (4.3–4.6). Fractures of the hip, ankle, wrist, spine, and proximal humerus comprised two-thirds of all fractures requiring hospitalization. The proportion of ankle fractures (17%) and wrist fractures (9%) was equal to that of hip fractures (27%). Four-fifths of the hospitalized fracture patients were operated. In individuals aged < 60 years, fractures requiring hospitalization were twice as common in men as in women. In individuals ≥ 60 years of age, the opposite was true.
PMCID: PMC4164872  PMID: 24694275
39.  Mechanical properties of a cemented porous implant interface 
Acta Orthopaedica  2014;85(5):531-537.
Revision arthroplasty often requires anchoring of prostheses to poor-quality or deficient bone stock. Recently, newer porous materials have been introduced onto the market as additional, and perhaps better, treatment options for revision arthroplasty. To date, there is no information on how these porous metals interface with bone cement. This is of clinical importance, since these components may require cementing to other prosthesis components and occasionally to bone.
We created porous metal and bone cylinders of the same size and geometry and cemented them in a well-established standardized setting. These were then placed under tensile loading and torsional loading until failure was achieved. This permitted comparison of the porous metal/cement interface (group A) with the well-studied bone/cement interface (group B).
The group A interface was statistically significantly stronger than the group B interface, despite having significantly reduced depth of cement penetration: it showed a larger maximum tensile force (effect size 2.7), superior maximum tensile strength (effect size 2.6), greater maximum torsional force (effect size 2.2), and higher rotational stiffness (effect size 1.5).
The newer porous implants showed good interface properties when cemented using medium-viscosity bone cement. The axial and rotational mechanical strength of a porous metal/cement interface appeared to be greater than the strength of the standard bone/cement interface. These results indicate that cementing of porous implants can provide great stability in situations where it is needed.
PMCID: PMC4164873  PMID: 24798109
40.  Thermal epiphysiodesis performed with radio frequency in a porcine model 
Acta Orthopaedica  2014;85(5):538-542.
Background and purpose
Current techniques for epiphysiodesis involve opening of cortical windows; use of staples, screws, and tension devices; and fusion with curettes or drills. Complications may have serious consequences. There is a need for a more reliable, precise, and less traumatic procedure that overcomes the known complications from existing techniques. We analyzed a new epiphysiodesis technique using radio-frequency ablation (RFA) in a porcine model.
Six 35-kg and two 25-kg immature pigs were used. 1 hind leg of each animal was randomly selected and the proximal tibia growth plate was ablated laterally and medially. The contralateral leg was used as a control. MR images were obtained immediately after the ablation and 12 weeks later for 6 animals, and 24 weeks later for the other 2 animals. CT was done for the 2 animals that were followed for 24 weeks for proof of bone bridges.
Both tibias were equal in length initially. At the 12-week follow-up, there was an average leg length discrepancy of 3.9 mm (95% CI: 3.0–4.8), and at 24 weeks the difference was 8.4 mm and 7.5 mm. No damage to the adjacent tissue was found. Bone bridges and physeal closure were found after 24 weeks. The pigs showed no discomfort after the intervention.
We found RFA to be feasible for epiphysiodesis in a pig model. The method is minimally invasive and recovery may be quick compared to conventional methods. We recommend that the method should be tested in larger-scale safety studies before clinical application.
PMCID: PMC4164874  PMID: 25036720
42.  Sequence of the Essex-Lopresti lesion–a high-speed video documentation and kinematic analysis 
Acta Orthopaedica  2014;85(5):545-546.
PMCID: PMC4164876  PMID: 25140987
43.  Role of preoperative pain, muscle function, and activity level in discharge readiness after fast-track hip and knee arthroplasty 
Acta Orthopaedica  2014;85(5):488-492.
Background and purpose
The concept of fast-track surgery has led to a decline in length of stay after total hip arthroplasty (THA) and total knee arthroplasty (TKA) to about 2–4 days. However, it has been questioned whether this is only achievable in selected patients—or in all patients. We therefore investigated the role of preoperative pain and functional characteristics in discharge readiness and actual LOS in fast-track THA and TKA.
Before surgery, hip pain (THA) or knee pain (TKA), lower-extremity muscle power, functional performance, and physical activity were assessed in a sample of 150 patients and used as independent variables to predict the outcome (dependent variable)—readiness for hospital discharge —for each type of surgery. Discharge readiness was assessed twice daily by blinded assessors.
Median discharge readiness and actual length of stay until discharge were both 2 days. Univariate linear regression followed by multiple linear regression revealed that age was the only independent predictor of discharge readiness in THA and TKA, but the standardized coefficients were small (≤ 0.03).
These results support the idea that fast-track THA and TKA with a length of stay of about 2–4 days can be achieved for most patients independently of preoperative functional characteristics.
PMCID: PMC4164866  PMID: 24954491
44.  Women in Charnley class C fail to improve in mobility to a higher degree after total hip replacement 
Acta Orthopaedica  2014;85(4):335-341.
The Charnley comorbidity classification organizes patients into 3 classes: (A) 1 hip involved, (B) 2 hips involved, and (C) other severe comorbidities. Although this simple classification is a known predictor of health-related quality of life (HRQoL) after total hip replacement (THR), interactions between Charnley class, sex, and age have not been investigated and there is uncertainty regarding whether A and B should be grouped together.
We selected a nationwide cohort of patients from the Swedish Hip Arthroplasty Register operated with THR due to primary osteoarthritis between 2008 and 2010. For estimation of HRQoL, we used the generic health outcome questionnaire EQ-5D of the EuroQol group. This consists of 2 parts: the EQ-5D index and the EQ VAS estimates. We modeled the EQ-5D index and the EQ VAS against the self-administered Charnley classification. Confounding was controlled for using preoperative HRQoL values, pain, and previous contralateral hip surgery.
We found that women in class C had a poorer EQ-5D outcome than men. This effect was mostly due to the fact that women failed to improve in the mobility dimension; only 40% improved, while about 50% of men improved. Age did not interact with Charnley class. We also found that the classification performed best without splitting or aggregating classes.
Our results suggests that the self-administered Charnley classification should be used in its full capacity and that it may be interesting to devote special attention to women in Charnley class C.
PMCID: PMC4105762  PMID: 24954483
45.  Higher revision risk for unicompartmental knee arthroplasty in low-volume hospitals 
Acta Orthopaedica  2014;85(4):342-347.
Background and purpose
Some studies have found high complication rates and others have found low complication rates after unicompartmental knee arthroplasty (UKA). We evaluated whether hospital procedure volume influences the risk of revision using data from the Norwegian Arthroplasty Register (NAR).
Materials and methods
5,791 UKAs have been registered in the Norwegian Arthroplasty Register. We analyzed the 4,460 cemented medial Oxford III implants that were used from 1999 to 2012; this is the most commonly used UKA implant in Norway. Cox regression (adjusted for age, sex, and diagnosis) was used to estimate risk ratios (RRs) for revision. 4 different volume groups were compared: 1–10, 11–20, 21–40, and > 40 UKA procedures annually per hospital. We also analyzed the reasons for revision.
Results and interpretation
We found a lower risk of revision in hospitals performing more than 40 procedures a year than in those with less than 10 UKAs a year, with an unadjusted RR of 0.53 (95% CI: 0.35–0.81) and adjusted RR of 0.59 (95% CI: 0.39–0.90). Low-volume hospitals appeared to have a higher risk of revision due to dislocation, instability, malalignment, and fracture than high-volume hospitals.
PMCID: PMC4105763  PMID: 24847789
46.  Metal release and metal allergy after total hip replacement with resurfacing versus conventional hybrid prosthesis 
Acta Orthopaedica  2014;85(4):348-354.
Metal-on-metal (MOM) total hip arthroplasties were reintroduced because of the problems with osteolysis and aseptic loosening related to polyethylene wear of early metal-on-polyethylene (MOP) arthroplasties. The volumetric wear rate has been greatly reduced with MOM arthroplasties; however, because of nano-size wear particles, the absolute number has been greatly increased. Thus, a source of metal ion exposure with the potential to sensitize patients is present. We hypothesized that higher amounts of wear particles result in increased release of metal ions and ultimately lead to an increased incidence of metal allergy.
52 hips in 52 patients (median age 60 (51–64) years, 30 women) were randomized to either a MOM hip resurfacing system (ReCap) or a standard MOP total hip arthoplasty (Mallory Head/Exeter). Spot urine samples were collected preoperatively, postoperatively, after 3 months, and after 1, 2, and 5 years and tested with inductively coupled plasma-sector field mass spectrometry. After 5 years, hypersensitivity to metals was evaluated by patch testing and lymphocyte transformation assay. In addition, the patients answered a questionnaire about hypersensitivity.
A statistically significant 10- to 20-fold increase in urinary levels of cobalt and chromium was observed throughout the entire follow-up in the MOM group. The prevalence of metal allergy was similar between groups.
While we observed significantly increased levels of metal ions in the urine during the entire follow-up period, no difference in prevalence of metal allergy was observed in the MOM group. However, the effect of long-term metal exposure remains uncertain.
PMCID: PMC4105764  PMID: 24930546
47.  No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty 
Acta Orthopaedica  2014;85(4):355-362.
The mechanism of failure of metal-on-metal (MoM) total hip arthroplasty (THA) has been related to a high rate of metal wear debris, which is partly generated from the head-trunnion interface. However, it is not known whether implant fixation is affected by metal wear debris.
Patients and methods
49 cases of MoM THA in 41 patients (10 women) with a mean age of 52 (28–68) years were followed with stereoradiographs after surgery and at 1, 2, and 5 years to analyze implant migration by radiostereometric analysis (RSA). Patients also participated in a 5- to 7-year follow-up with measurement of serum metal ions, questionnaires (Oxford hip score (OHS) and Harris hip score (HHS)), and measurement of cup and stem positions and systemic bone mineral density.
At 1–2 years, mean total translation (TT) was 0.04 mm (95% CI: –0.07 to 0.14; p = 0.5) for the stems; at 2–5 years, mean TT was 0.13 mm (95% CI: –0.25 to –0.01; p = 0.03), but within the precision limit of the method. For the cups, there was no statistically significant TT or total rotation (TR) at 1–2 and 2–5 years. At 2–5 years, we found 4 cups and 5 stems with TT migrations exceeding the precision limit of the method. There was an association between cup migration and total OHS < 40 (4 patients, 4 hips; p = 0.04), but there were no statistically significant associations between cup or stem migration and T-scores < –1 (n = 10), cup and stem positions, or elevated serum metal ion levels (> 7µg/L (4 patients, 6 hips)).
Most cups and stems were well-fixed at 1–5 years. However, at 2–5 years, 4 cups and 5 stems had TT migrations above the precision limits, but these patients had serum metal ion levels similar to those of patients without measurable migrations, and they were pain-free. Patients with serum metal ion levels > 7 µg/L had migrations similar to those in patients with serum metal ion levels < 7 µg/L. Metal wear debris does not appear to influence the fixation of hip components in large-head MoM articulations at medium-term follow-up.
PMCID: PMC4105765  PMID: 24847790
48.  Poor intermediate-term survival of the uncemented Optan anatomically adapted femoral component 
Acta Orthopaedica  2014;85(4):363-367.
We evaluated the 5-year survival of the uncemented Optan anatomically adapted femoral stem, with revision for aseptic loosening as the endpoint.
Between January 2004 and March 2007, 432 total hip arthroplasties (THAs) were performed in 432 patients. After follow-up for a mean time of 5 years, the patients were evaluated using the WOMAC questionnaire and plain radiography. Patients who were unable to attend the follow-up visit were contacted by telephone to determine whether they had had any revision surgery of their THA
Within 5 years, 39 patients (9%) had died of unrelated causes and 63 patients (15%) had been lost to follow-up. Of the remaining cohort, 224 patients (68%) had full follow-up while 88 patients (27%) were evaluated with WOMAC only and 18 patients (5%) were evaluated with radiography only. The mean WOMAC score of all evaluated patients was 21 (10–100). At 5-year follow-up, there were 26 stem revisions reported (6%), 14 hips (3%) showed aseptic loosening, and 12 hips (3%) had had a periprosthetic femoral fracture. The 5-year survival to revision for any reason was 94%. Worst-case analysis yielded a 5-year survival of 79%.
The 5-year survival for aseptic loosening of the Optan anatomically adapted femoral component was disappointing. Radiographic evaluation showed evidence of proximal radiolucencies and distal cortical bone hypertrophy, which we attribute to insufficient proximal bone in-growth and increased load transfer at the tip of the stem. We do not recommend the use of the Optan femoral stem.
PMCID: PMC4105766  PMID: 24954492
49.  10-year results of the uncemented Allofit press-fit cup in young patients 
Acta Orthopaedica  2014;85(4):368-374.
Background and purpose
Uncemented acetabular components in primary total hip arthroplasty (THA) are commonly used today, but few studies have evaluated their survival into the second decade in young and active patients. We report on a minimum 10-year follow-up of an uncemented press-fit acetabular component that is still in clinical use.
We examined the clinical and radiographic results of our first 121 consecutive cementless THAs using a cementless, grit-blasted, non-porous, titanium alloy press-fit cup (Allofit; Zimmer Inc., Warsaw, IN) without additional screw fixation in 116 patients. Mean age at surgery was 51 (21–60) years. Mean time of follow-up evaluation was 11 (10–12) years.
At final follow-up, 8 patients had died (8 hips), and 1 patient (1 hip) was lost to follow-up. 3 hips in 3 patients had undergone acetabular revision, 2 for deep infection and 1 for aseptic acetabular loosening. There were no impending revisions at the most recent follow-up. We did not detect periacetabular osteolysis or loosening on plain radiographs in those hips that were evaluated radiographically (n = 90; 83% of the hips available at a minimum of 10 years). Kaplan-Meier survival analysis using revision of the acetabular component for any reason (including isolated inlay revisions) as endpoint estimated the 11-year survival rate at 98% (95% CI: 92–99).
Uncemented acetabular fixation using the Allofit press-fit cup without additional screws was excellent into early in the second decade in this young and active patient cohort. The rate of complications related to the liner and to osteolysis was low.
PMCID: PMC4105767  PMID: 24875058
50.  A comparison of the diagnostic accuracy of MARS MRI and ultrasound of the painful metal-on-metal hip arthroplasty 
Acta Orthopaedica  2014;85(4):375-382.
Background and purpose
Metal artifact reduction sequence (MARS) MRI and ultrasound scanning (USS) can both be used to detect pseudotumors, abductor muscle atrophy, and tendinous pathology in patients with painful metal-on-metal (MOM) hip arthroplasty. We wanted to determine the diagnostic test characteristics of USS using MARS MRI as a reference for detection of pseudotumors and muscle atrophy.
Patients and methods
We performed a prospective cohort study to compare MARS MRI and USS findings in 19 consecutive patients with unilateral MOM hips. Protocolized USS was performed by consultant musculoskeletal radiologists who were blinded regarding clinical details. Reports were independently compared with MARS MRI, the imaging gold standard, to calculate predictive values.
The prevalence of pseudotumors on MARS MRI was 68% (95% CI: 43–87) and on USS it was 53% (CI: 29–76). The sensitivity of USS in detecting pseudotumors was 69% (CI 39–91) and the specificity was 83% (CI: 36–97). The sensitivity of detection of abductor muscle atrophy was 47% (CI: 24–71). In addition, joint effusion was detected in 10 cases by USS and none were seen by MARS MRI.
We found a poor agreement between USS and MARS MRI. USS was inferior to MARS MRI for detection of pseudotumors and muscle atrophy, but it was superior for detection of joint effusion and tendinous pathologies. MARS MRI is more advantageous than USS for practical reasons, including preoperative planning and longitudinal comparison.
PMCID: PMC4105768  PMID: 24694273

Results 26-50 (744)