categorical data. Biometrics 1977;33:159-74. 20. Porter AMW. Misuse of correlation and regression in three medical journals. J Roy Soc Med 1999;92:123-8. 21.
Valgus extension osteotomy for ‘hinge abduction’ in Perthes’ disease RESULTS AT MATURITY AND FACTORS INFLUENCING THE RADIOLOGICAL OUTCOME M. J. K. Bankes, A. Catterall, A. Hashemi-Nejad From the Royal National Orthopaedic Hospital NHS Trust, Stanmore, England
algus extension osteotomy (VGEO) is a salvage procedure for ‘hinge abduction’ in Perthes’ disease. The indications for its use are pain and fixed deformity. Our study shows the clinical results at maturity of VGEO carried out in 48 children (51 hips) and the factors which influence subsequent remodelling of the hip. After a mean follow-up of ten years, total hip replacement has been carried out in four patients and arthrodesis in one. The average Iowa Hip Score in the remainder was 86 (54 to 100). Favourable remodelling of the femoral head was seen in 12 hips. This was associated with three factors at surgery; younger age (p = 0.009), the phase of reossification (p = 0.05) and an open triradiate cartilage (p = 0.0007). Our study has shown that, in the short term, VGEO relieves pain and corrects deformity; as growth proceeds it may produce useful remodelling in this worst affected subgroup of children with Perthes’ disease.
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J Bone Joint Surg [Br] 2000;82-B:548-54. Received 2 July 1999; Accepted after revision 14 October 1999
‘Hinge abduction’ is a term used to describe the abnormal movement of the hip which occurs when the superolateral portion of a deformed femoral head impinges on the lateral 1,2 lip of the acetabulum. Its presence in Perthes’ disease indicates a femoral head which is uncontainable and suitable only for a salvage procedure. Various procedures have been advocated for the management of the prominent lat3-6 7 eral mass and hinge abduction. Quain and Catterall showed that valgus extension osteotomy (VGEO) of the proximal femur produced satisfactory results in the short term. Our study extends and enlarges their original series
M. J. K. Bankes, FRCS Orth, Specialist Orthopaedic Registrar A. Catterall, MChir, FRCS, Consultant Orthopaedic Surgeon A. Hashemi-Nejad, FRCS Orth, Consultant Orthopaedic Surgeon Royal National Orthopaedic Hospital NHS Trust, Brockley Hill, Stanmore, Middlesex HA7 4LP, UK. Correspondence should be sent to Mr M. J. K. Bankes at 18 Howard Walk, London N2 0HB, UK. ©2000 British Editorial Society of Bone and Joint Surgery 0301-620X/00/410339 $2.00 548
by reviewing the clinical and radiological outcome of this procedure at skeletal maturity and examines the factors associated with favourable remodelling of the femoral head after operation.
Patients and Methods The patients assessed were adults who had undergone VGEO for hinge abduction in Perthes’ disease, confirmed by arthrography, before skeletal maturity for pain and limp. Fixed flexion and/or adduction deformities were usually present. The operation had been carried out in a standard 8 manner. The amount of valgus and extension required to correct the fixed deformities and to allow a minimum of 10° of abduction without producing unstable movement had been determined by preoperative arthrography. Weightbearing was restricted until union had been confirmed radiologically. We collected data from the case notes and evaluated the mature patients in person or by a semistructured telephone interview in order to obtain an Iowa 9 Hip Score (IHS) which was modified so that the 20 points available for absence of fixed deformity and range of movement were substituted by five points for the subjective 10 range of movement based on daily activities. The total out of 85 was then converted to a percentage. In the 22 hips for which both the IHS and the modified IHS were available, the latter gave values on average 2.6 points higher. Although this difference was small it was highly significant (paired Student t-test, p = 0.003). Hence the two versions of the IHS could not be used interchangeably and the modified score was chosen. Radiographs were examined to determine the stage of the 11,12 disease and the Catterall group at the time of operation. Patients were regarded as skeletally immature when the contralateral capital femoral physis was open and as mature when there was bilateral closure of both these physes and the iliac apophyses. It was also noted whether the triradiate cartilage was open or closed. Quantitative and qualitative measurements of the morphology of the hip were made from preoperative arthrograms and from radiographs taken before operation and at maturity. These included the acet13 abular depth-to-height ratio, the size of the femoral head, 14 the percentage of acetabular cover, the acetabular angle 15 of Sharp and the arthrographic index of Shigeno and THE JOURNAL OF BONE AND JOINT SURGERY
VALGUS EXTENSION OSTEOTOMY FOR ‘HINGE ABDUCTION’ IN PERTHES’ DISEASE
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Fig. 1 Radiograph of the hip. The arthrographic index is calculated from the formula S/D/2. For comparison, 16 the caput index of H/D/2 is also shown.
Flat femoral heads shown by a) arthrography and b) plain radiography at maturity.
Fig. 2a
Fig. 2b
Ovoid femoral heads shown by a) arthrography and b) by plain radiography at maturity.
Fig. 3a
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Fig. 3b
Evans. The last was measured by identifying the maximum transverse diameter of the deformed femoral head and its midpoint; the index is the ratio of the smallest distance between the articulating surface and the midpoint, and half the maximum diameter (Fig. 1). The shape of the articulating surface of the femoral head was classified as flat, ovoid or spherical (Figs 2 and 3). A spherical head was defined as one in which the diameters measured on anteroposterior and frog lateral views were within 2 mm of each 17 other. This allowed each case to be assigned a Stulberg 14 class, which can be related to the long-term prognosis VOL. 82-B, NO. 4, MAY 2000
(Table I). These subjective assessments were carried out independently by two of the authors (MJKB and AH-N) on two occasions. If there was disagreement the least favourable outcome was used for the final analysis. The presence of a lateral ridge was also noted and its size expressed as a percentage of the maximum horizontal diameter. Favourable remodelling was defined as an improvement in the shape of the femoral head from flat to ovoid or spherical, from ovoid to spherical, or by loss of the lateral ridge. Statistical analysis. We compared radiological measurements before operation and at maturity using paired Student
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M. J. K. BANKES, A. CATTERALL, A. HASHEMI-NEJAD 14
Table I. The Stulberg classification of maturity radiographs in Perthes’ disease Class I
Definition Completely normal hip
Prognosis Spherically congruent. No risk of arthritis
II
Spherical femoral head, with abnormalities of head, neck and/or acetabulum
As class I
III
Ovoid femoral head (non-spherical, non-flat) with abnormalities of head, neck and/or acetabulum
Aspherically congruent. Mild to moderate arthritis in late adulthood
IV
Flat femoral head, with abnormalities of head, neck and/or acetabulum
As class III
V
Flat femoral head with normal femoral neck and normal acetabulum
Aspherically incongruent Severe arthritis
