We identified a group of patients from the Swedish Arthroplasty Register who reported no relief of pain or worse pain one year after a total knee replacement (TKR). A total of two different patient-reported pain scores were used during this process. We then evaluated how the instruments used to measure pain affected the number of patients who reported no relief of pain or worse pain, and the relative effect of potential risk factors.

Between 2008 and 2010, 2883 TKRs were performed for osteoarthritis in two Swedish arthroplasty units. After applying exclusion criteria, 2123 primary TKRs (2123 patients) were included in the study. The Knee injury and Osteoarthritis Outcome Score (KOOS) and a Visual Analogue Scale (VAS) for knee pain were used to assess patients pre-operatively and one year post-operatively.

Only 50 of the 220 patients (23%) who reported no pain relief on either the KOOS pain subscale or the VAS for knee pain did so with both of these instruments. Patients who reported no pain relief on either measure tended to have less pain pre-operatively but a higher degree of anxiety. Charnley category C was a predictor for not gaining pain relief as measured on a VAS for knee pain.

The number of patients who are not relieved of pain after a TKR differs considerably depending on the instrument used to measure pain.

Cite this article: Bone Joint J 2014;96-B:1222–6.

We are entering a new era with governmental bodies taking an increasingly guiding role, gaining control of registries, demanding direct access with release of open public information for quality comparisons between hospitals. This review is written by physicians and scientists who have worked with the Swedish Knee Arthroplasty Register (SKAR) periodically since it began. It reviews the history of the register and describes the methods used and lessons learned.

Cite this article: Bone Joint Res 2014;3:217–22.

Purpose

To compare the efficacy and safety of balloon kyphoplasty (BKP) to non-surgical management (NSM) over 24 months in patients with acute painful fractures by clinical outcomes and vertebral body kyphosis correction and surgical parameters.

Purpose: Balloon kyphoplasty (BKP) is a minimally invasive treatment for acute vertebral compression fractures (VCF) that aims both to correct associated vertebral deformity (reduce) and stabilize the fracture by injecting bone cement. We performed the first multicenter randomized trial to assess the effect of BKP.

Method: Patients with 1–3 non-traumatic vertebral compression fractures diagnosed within 3 months were randomly assigned to receive either BKP (N=149) or usual nonsurgical care (NSC) (N=151). Measurements of quality of life, back pain and function, days of disability and bed rest were assessed at baseline, 1, 3, 6 and 12 months.

Results: The primary outcome measure, the difference between groups in change from baseline scores in the physical component summary of the SF-36 questionnaire, improved 3.5 points (95% CI, 1.6 to 5.4; p=0.0004) more in the BKP group when averaged across 12 months of follow-up. Compared with the NSC group, those assigned to BKP also had greater improvement in quality of life and back function throughout 12 months of follow-up as measured by the EuroQol and Roland-Morris scales; a difference of 0.14 points (95% CI, 0.05 to 0.23; p=0.0023) more and 3.2 points (95% CI, 1.7 to 3.8; p< 0.0001) and reported fewer days of limited activity in the previous 2 weeks due to back pain (2.5 fewer days; 95% CI, 1.2 to 3.8; p=0.0001). New radiographically detected vertebral fractures occurred in 41.8% of subjects in the kyphoplasty and 37.8% in the nonsurgical group (4% difference; 95% CI −7.5 to 15.6; p=0.5).

Conclusion: Compared to nonsurgical treatment, balloon kyphoplasty improved multiple measurements of quality of life, back pain and disability that last at least one year after the procedure. No difference is seen between groups in radiographically detected VCF’s (Clinicaltrials.gov number, NCT00211211).

Background: RSA cannot discern whether a single prosthesis is fixed or migrating below the detection level. Samples of patients usually show migration values that appear to be continuously distributed. Is there a dichotomy between stable and migrating prostheses?

Methods: We analysed the migration of 147 cemented acetabular cups of 7 different designs, by use of a new set of algoritms for frequency distribution analysis called Rmix. The migration vector lengths were assumed to be a compound of log-normal distributions. The algoritm then calculated if the observed frequency distribution is best explained by one or more log-normal distributions.

Results: After 2 years there was a significant dichotomy (p=0.006) between 2 lognormal subgroups within the sample. Neither cup design, sex or operating department could explain the dichotomy into two groups, which appears to reflect the existence of two different types of behaviour. The migration along the 3 axes in space, showed a similar dichotomy. During the second year, around 80 % of the patients belonged to a distinct, normally distributed subgroup with a mean not different from 0 mm and a small variation, corresponding to the measuring error. The remainder differed significantly from this subgroup and showed migration.

Interpretation: The majority of the cups belonged to a subpopulation that appeared completely stableduring the second year. For a single type of prosthesis, the relative size of the stable subgroup might be a good index of the expected performance.

Background: Balloon kyphoplasty is a minimally invasive treatment for acute vertebral fractures that aims to reduce and correct vertebral deformity by inserting expandable balloon tamps and then stabilize the body by filling it with bone cement. The effect of balloon kyphoplasty on quality of life has not been tested in a randomized trial.

Methods: Patients with up to 3 non-traumatic acute vertebral compression fractures were enrolled within 3 months of diagnosis and randomly assigned to receive either balloon kyphoplasty (N=149) or usual nonsurgical care (N=151). Measurements of quality of life, back pain and function, and days of disability and bed rest and spine radiographs were assessed through 12 months of follow-up.

Results: Compared with those assigned to nonsurgical care, participants assigned to balloon kyphoplasty had 5.2 points (95% CI, 2.9 to 7.4; p< 0.0001) greater improvement in the physical component of the SF-36 quality of life questionnaire at one month and 1.5 points (95% CI, − 0.8 to 3.8; p=0.2) at twelve months. Those in the balloon kyphoplasty group also had greater improvement in quality of life by the EuroQol questionnaire at one (0.18 points; 95% CI, 0.08 to 0.28; p=0.0003) and twelve months (0.12 points; 95% CI, 0.01 to 0.22; p=0.025) and improved disability by the Roland-Morris scale at one month (4.0 points; 95% CI, 2.6 to 5.5; p< 0.0001) and twelve months (2.6 points; 95% CI, 1.0 to 4.1; p=0.0012). Balloon kyphoplasty patients had less back pain on a 0 to 10-point numeric rating scale at seven days (2.2 points; 95% CI, 1.6 to 2.8; p< 0.0001) and twelve months (0.9 points; 95% CI, 0.3 to 1.5; p=0.0034) and reported fewer days of limited activity at one month (2.9 days per 2 weeks; 95% CI, 1.3 to 4.6; p=0.0004) and twelve months (1.6; 95% CI, − 0.1 to 3.3; p=0.068). Fewer patients assigned to balloon kyphoplasty took pain medications or used walking aids during follow-up. There was no significant difference in the number of patients with adverse events or serious adverse events in the kyphoplasty and nonsurgical groups. New radiographically detected vertebral fractures occurred in 41.8% of subjects in the balloon kyphoplasty and 37.8% in the nonsurgical group (4% difference; 95% CI − 7.5 to 15.6; p=0.5) and were not statistically different.

Conclusion: Compared to nonsurgical treatment, balloon kyphoplasty safely improved quality of life and reduced back pain, disability and the use of pain medications and walking aids. Significant improvements in multiple measurements of quality of life, pain and disability continue for at least 1 year. Balloon kyphoplasty did not increase adverse events including the risk of vertebral fractures (Clinicaltrials.gov number, NCT00211211).

Background: In a previous randomized studiy using Röntgen Stereometric Analysis (RSA), we showed that oral bisphosphonates reduce the mean migration distance during the first 6 months. In a similar randomized study, bisphosphonates applied locally at the operation had a similar effect. These studies showed a 0.1 mm difference in mean value between groups. Does such a small difference matter? We addressed this question by use of frequency analysis.

Methods: The 2 previous studies were combined for analysis, and designated as bisphosphonate (n=44) or control treated (n=49). We analysed the migration vector (for the center of the rigid body) by use of a set of algoritms for frequency distribution analysis called Rmix. The migration vector lengths were assumed to be a compound of log-normal distributions. The frequency analysis determined if the observed frequency distributions were best described as a single, or a sum of 2 or more lognormally distributed subgroups.

Results: After 6 months, the control patients had formed 2 subgroups, one comprising 85% of the patients. The dichotomy was significant (p=0.016).

After 2 years, the dichotomy persisted (p=0.027). In the bisphosphonate-treated patients, no dichotomies could be found. The distribution of the migration vector length appeared similar to the larger and less migrating subgroup among the controls.

Discussion: The risk of aseptic loosening for cemented knees is extremely small. However, the migrating subgroup among our control patients may be at risk of loosening, and would have run a high risk if they were young and active. This subgroup did not appear with bisphosphonate treatment

Summary: In previous comparisons we found a slight decrease in mean value with bisphosphonates. The present analysis shows that this reflects the disappearance of a small subgroup with large migration.

We identified 1305 femoral impaction bone grafting revisions using the Exeter stem performed between 1989 and 2002 in 30 hospitals throughout Sweden. There were 1188 patients with a mean age of 71 years (29 to 94) followed up for between five and 18 years.

The participating departments reported 70 further revisions in total, of which 57 could also be identified on the Swedish National Arthroplasty Registry.

Kaplan-Meier survivorship for all causes of failure was 94.0% (95% confidence interval (CI) 92 to 96) for women and 94.7% (95% CI, 92 to 96) for men at 15 years. Survivorship at 15 years for aseptic loosening was 99.1% (95% CI 98.4 to 99.5), for infection 98.6% (95% CI 97.6 to 99.2), for subsidence 99.0% (95% CI 98.2 to 99.4) and for fracture 98.7% (95% CI 97.9 to 99.2)

Statistically significant predictors of failure were the year in which revision was conducted (p < 0.001). The number of previous revisions was slightly above the level of signifance (p = 0.056). Age, gender, the length of the stem and previous septic loosening were not predictors of failure (p = 0.213, p = 0.399, p = 0.337, p = 0.687, respectively). The difference in survivorship between high- and low-volume departments was only 3% at ten years.

We conclude that impaction bone grafting with the Exeter stem has an excellent long-term survivorship following revision arthroplasty. The technique of impaction grafting appears to be reliable, can be learned rapidly and produces a predictably low incidence of aseptic loosening.

Public disclosure of outcome-orientated ranking of hospitals is becoming increasingly popular and is routinely used by Swedish health-care authorities. Whereas uncertainty about an outcome is usually presented with 95% confidence intervals, ranking’s based on the same outcome are typically presented without any concern for bias or statistical precision. In order to study the effect of incomplete registration of re-operation on hospital ranking we performed a simulation study using published data on the two-year risk of re-operation after total hip replacement.

This showed that whereas minor registration incompleteness has little effect on the observed risk of revision, it can lead to major errors in the ranking of hospitals. We doubt whether a level of data entry sufficient to generate a correct ranking can be achieved, and recommend that when ranking hospitals, the uncertainties about data quality and random events should be clearly described as an integral part of the results.

Patients with osteoarthritis undergoing knee replacement have been reported to have an overall reduced mortality compared with that of the general population. This has been attributed to the selection of healthier patients for surgery. However, previous studies have had a maximum follow-up time of ten years. We have used information from the Swedish Knee Arthroplasty Register to study the mortality of a large national series of patients with total knee replacement for up to 28 years after surgery and compared their mortality with that of the normal population. In addition, for a subgroup of patients operated on between 1980 and 2002 we analysed their registered causes of death to determine if they differed from those expected.

We found a reduced overall mortality during the first 12 post-operative years after which it increased and became significantly higher than that of the general population. Age-specific analysis indicated an inverse correlation between age and mortality, where the younger the patients were, the higher their mortality. The shift at 12 years was caused by a relative over-representation of younger patients with a longer follow-up. Analysis of specific causes of death showed a higher mortality for cardiovascular, gastrointestinal and urogenital diseases. The observation that early onset of osteoarthritis of the knee which has been treated by total knee replacement is linked to an increased mortality should be a reason for increased general awareness of health problems in these patients.

We report 60 synovectomies of the knee in 51 children with juvenile chronic arthritis. Synovitis had been present for an average of 5 years and the average age at operation was 13 years. Results were evaluated in terms of pain, knee movement, relapse of synovitis and radiological change during a follow-up averaging 7.5 years. The relief of pain was rewarding and there was a slight postoperative gain in range of knee movement in most cases. The older the patient at onset of disease, the greater the risk of pain during follow-up. Progressive joint destruction was more common in younger patients, those with systemic or polyarticular disease, and those with highly active disease at the time of operation. Recurrence of synovitis was more frequent in patients who had their operation in a phase of high disease activity; this occurred most often in patients with polyarticular disease.