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. 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.Aims
Methods
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:
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:
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:
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.