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The Bone & Joint Journal
Vol. 104-B, Issue 5 | Pages 640 - 644
1 May 2022
Gaston MS Wordie SJ Wagner P Hägglund G Robb JE

Aims

The Uppföljningsprogram för cerebral pares (CPUP) Hip Score distinguishes between children with cerebral palsy (CP) at different levels of risk for displacement of the hip. The score was constructed using data from Swedish children with CP, but has not been confirmed in any other population. The aim of this study was to determine the calibration and discriminatory accuracy of this score in children with CP in Scotland.

Methods

This was a total population-based study of children registered with the Cerebral Palsy Integrated Pathway Scotland. Displacement of the hip was defined as a migration percentage (MP) of > 40%. Inclusion criteria were children in Gross Motor Function Classification System (GMFCS) levels III to V. The calibration slope was estimated and Kaplan-Meier curves produced for five strata of CPUP scores to compare the observed with the predicted risk of displacement of the hip at five years. For discriminatory accuracy, the time-dependent area under the receiver operating characteristic curve (AUC) was estimated. In order to analyze differences in the performance of the score between cohorts, score weights, and subsequently the AUC, were re-estimated using the variables of the original score: the child’s age at the first examination, GMFCS level, head shaft angle, and MP of the worst hip in a logistic regression with imputation of outcomes for those with incomplete follow-up.


The Bone & Joint Journal
Vol. 97-B, Issue 10 | Pages 1441 - 1444
1 Oct 2015
Hermanson M Hägglund G Riad J Rodby-Bousquet E Wagner P

Hip displacement, defined in this study as a migration percentage (MP) of more than 40%, is a common, debilitating complication of cerebral palsy (CP). In this prospective study we analysed the risk of developing hip displacement within five years of the first pelvic radiograph.

All children with CP in southern and western Sweden are invited to register in the hip surveillance programme CPUP. Inclusion criteria for the two groups in this study were children from the CPUP database born between 1994 and 2009 with Gross Motor Function Classification System (GMFCS) III to V. Group 1 included children who developed hip displacement, group 2 included children who did not develop hip displacement over a minimum follow-up of five years. A total of 145 children were included with a mean age at their initial pelvic radiograph of 3.5 years (0.6 to 9.7).

The odds ratio for hip displacement was calculated for GMFCS-level, age and initial MP and head-shaft angle. A risk score was constructed with these variables using multiple logistic regression analysis. The predictive ability of the risk score was evaluated using the area under the receiver operating characteristics curve (AUC).

All variables had a significant effect on the risk of a MP > 40%. The discriminatory accuracy of the CPUP hip score is high (AUC = 0.87), indicating a high ability to differentiate between high- and low-risk individuals for hip displacement. The CPUP hip score may be useful in deciding on further follow-up and treatment in children with CP.

Cite this article: Bone Joint J 2015;97-B:1441–4.


The Bone & Joint Journal
Vol. 96-B, Issue 11 | Pages 1546 - 1552
1 Nov 2014
Hägglund G Alriksson-Schmidt A Lauge-Pedersen H Rodby-Bousquet E Wagner P Westbom L

In 1994 a cerebral palsy (CP) register and healthcare programme was established in southern Sweden with the primary aim of preventing dislocation of the hip in these children.

The results from the first ten years were published in 2005 and showed a decrease in the incidence of dislocation of the hip, from 8% in a historical control group of 103 children born between 1990 and 1991 to 0.5% in a group of 258 children born between 1992 and 1997. These two cohorts have now been re-evaluated and an additional group of 431 children born between 1998 and 2007 has been added.

By 1 January 2014, nine children in the control group, two in the first study group and none in the second study group had developed a dislocated hip (p < 0.001). The two children in the first study group who developed a dislocated hip were too unwell to undergo preventive surgery. Every child with a dislocated hip reported severe pain, at least periodically, and four underwent salvage surgery. Of the 689 children in the study groups, 91 (13%) underwent preventive surgery.

A population-based hip surveillance programme enables the early identification and preventive treatment, which can result in a significantly lower incidence of dislocation of the hip in children with CP.

Cite this article: Bone Joint J 2014; 96-B:1546–52.


The Bone & Joint Journal
Vol. 95-B, Issue 1 | Pages 23 - 30
1 Jan 2013
Kiernan S Hermann KL Wagner P Ryd L Flivik G

Progressive retroversion of a cemented stem is predictive of early loosening and failure. We assessed the relationship between direct post-operative stem anteversion, measured with CT, and the resulting rotational stability, measured with repeated radiostereometric analysis over ten years. The study comprised 60 cemented total hip replacements using one of two types of matt collared stem with a rounded cross-section. The patients were divided into three groups depending on their measured post-operative anteversion (< 10°, 10° to 25°, >  25°). There was a strong correlation between direct post-operative anteversion and later posterior rotation. At one year the < 10° group showed significantly more progressive retroversion together with distal migration, and this persisted to the ten-year follow-up. In the < 10° group four of ten stems (40%) had been revised at ten years, and an additional two stems (20%) were radiologically loose. In the ‘normal’ (10° to 25°) anteversion group there was one revised (3%) and one loose stem (3%) of a total of 30 stems, and in the > 25° group one stem (5%) was revised and another loose (5%) out of 20 stems. This poor outcome is partly dependent on the design of this prosthesis, but the results strongly suggest that the initial rotational position of cemented stems during surgery affects the subsequent progressive retroversion, subsidence and eventual loosening. The degree of retroversion may be sensitive to prosthetic design and stem size, but < 10° of anteversion appears deleterious to the long-term outcome for cemented hip prosthetic stems.

Cite this article: Bone Joint J 2013;95-B:23–30.


Orthopaedic Proceedings
Vol. 93-B, Issue SUPP_II | Pages 168 - 168
1 May 2011
Brogren E Hofer M Petranek M Wagner P Dahlin L Atroshi I
Full Access

Purpose: The purpose was to investigate the relationship between distal radius fracture malunion and arm-related disability.

Methods: This prospective population-based cohort study included 143 patients above 18 years with acute distal radius fracture treated at one emergency hospital with either closed reduction and cast (55 patients) or with closed reduction and external and/or percutaneous pin fixation (88 patients). The patients were evaluated with the disabilities of the arm, shoulder and hand (DASH) questionnaire at baseline (inquiring about disabilities before fracture) and at 6, 12 and 24 months after the fracture. The 12-month follow-up also included the SF-12 health status questionnaire as well as clinical and radiographic examination. The patients were classified according to the degree of malunion (defined as dorsal tilt > 10 degrees or ulnar variance > 0 mm) into three groups; no malunion, malunion involving either dorsal tilt or ulnar variance, and malunion involving both dorsal tilt and ulnar variance. A Cox regression analysis was performed to determine the relationship between the 1-year DASH score (≥ 15 or < 15) and malunion adjusting for age, sex, fracture AO type, and treatment method and the relative risk (RR) of obtaining the higher DASH score was calculated. The number needed to harm (NNH) associated with malunion was calculated.

Results: The mean DASH score at 1 year after fracture was about 10 points worse with each degree of increased malunion. The degree of malunion also correlated with SF-12 score, grip strength and supination. The regression analysis showed significantly higher disability with each degree of malunion compared to no malunion; for malunion involving either dorsal tilt or ulnar variance the RR was 2.4 (95% CI 1.0–5.7; p=0.038), and for malunion involving both dorsal tilt and ulnar variance the RR was 3.2 (95% CI 1.4–7.5; p=0.007). The NNH was 2.5 (95% CI 1.8–5.4).

Conclusion: Malunion after distal radius fracture was associated with higher arm-related disability.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 444 - 444
1 Sep 2009
Aspenberg P Wagner P Nilsson KG Ranstam J
Full Access

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.


Orthopaedic Proceedings
Vol. 91-B, Issue SUPP_III | Pages 456 - 456
1 Sep 2009
Aspenberg P Wagner P Hilding M Ranstam J
Full Access

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.


The Journal of Bone & Joint Surgery British Volume
Vol. 90-B, Issue 12 | Pages 1558 - 1561
1 Dec 2008
Ranstam J Wagner P Robertsson O Lidgren L

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.