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The painful subluxed or dislocated hip in adults with cerebral palsy presents a challenging problem. Prosthetic dislocation and heterotopic ossification are particular concerns. We present the first reported series of 19 such patients (20 hips) treated with hip resurfacing and proximal femoral osteotomy. The pre-operative Gross Motor Function Classification System (GMFCS) was level V in 13 (68%) patients, level IV in three (16%), level III in one (5%) and level II in two (11%). The mean age at operation was 37 years (13 to 57). The mean follow-up was 8.0 years (2.7 to 11.6), and 16 of the 18 (89%) contactable patients or their carers felt that the surgery had been worthwhile. Pain was relieved in 16 of the 18 surviving hips (89%) at the last follow-up, and the GMFCS level had improved in seven (37%) patients. There were two (10%) early dislocations; three hips (15%) required revision of femoral fixation, and two hips (10%) required revision, for late traumatic fracture of the femoral neck and extra-articular impingement, respectively. Hence there were significant surgical complications in a total of seven hips (35%). No hips required revision for instability, and there were no cases of heterotopic ossification. We recommend hip resurfacing with proximal femoral osteotomy for the treatment of the painful subluxed or dislocated hip in patients with cerebral palsy.

When performing total hip replacement (THR) in high dislocated hips, the presence of soft-tissue contractures means that most surgeons prefer to use a femoral shortening osteotomy in order to avoid the risk of neurovascular damage. However, this technique will sacrifice femoral length and reduce the extent of any leg-length equalisation. We report our experience of 74 THRs performed between 2000 and 2008 in 65 patients with a high dislocated hip without a femoral shortening osteotomy. The mean age of the patients was 55 years (46 to 72) and the mean follow-up was 42 months (12 to 78). All implants were cementless except for one resurfacing hip implant. We attempted to place the acetabular component in the anatomical position in each hip. The mean Harris hip score improved from 53 points (34 to 74) pre-operatively to 86 points (78 to 95) at final follow-up. The mean radiologically determined leg lengthening was 42 mm (30 to 66), and the mean leg-length discrepancy decreased from 36 mm (5 to 56) pre-operatively to 8.5 mm (0 to 18) postoperatively. Although there were four (5%) post-operative femoral nerve palsies, three had fully resolved by six months after the operation. No loosening of the implant was observed, and no dislocations or infections were encountered. Total hip replacement without a femoral shortening osteotomy proved to be a safe and effective surgical treatment for high dislocated hips.

We present the case of a young male patient with inferior dislocation of the hip and postulate a possible mechanism for this extremely rare injury.

Traumatic posterior dislocation of the hip associated with a fracture of the posterior acetabular wall and of the neck of the femur is a rare injury. A 29-year-old man presented at a level 1 trauma centre with a locked posterior dislocation of the right hip, with fractures of the femoral neck and the posterior wall of the acetabulum after a bicycle accident. An attempted closed reduction had failed. This case report describes in detail the surgical management and the clinical and radiological outcome. Open reduction and fixation with preservation of the intact retinaculum was undertaken within five hours of injury with surgical dislocation of the hip and a trochanteric osteotomy. Two years after operation the function of the injured hip was good. Plain radiographs and MR scans showed early signs of osteoarthritis with some loss of joint space but no evidence of avascular necrosis. The patient had begun skiing and hiking again. The combination of fractures of the neck of the femur and of the posterior wall of the acetabulum hampers closed reduction of a posterior dislocation of the hip. Surgical dislocation of the hip with trochanteric flip osteotomy allows controlled open reduction of the fractures, with inspection of the hip joint and preservation of the vascular supply.

The radiological evaluation of the anterolateral femoral head is an essential tool for the assessment of the cam type of femoroacetabular impingement. CT, MRI and frog lateral plain radiographs have all been suggested as imaging options for this type of lesion. The alpha angle is accepted as a reliable indicator of the cam type of impingement and may also be used as an assessment for the successful operative correction of the cam lesion. We studied the alpha angles of 32 consecutive patients with femoroacetabular impingement. The angle measured on frog lateral radiographs using templating tools was compared with that measured on CT scans in order to assess the reliability of the frog lateral view in analysing the alpha angle in cam impingement. A high interobserver reliability was noted for the assessment of the alpha angle on the frog lateral view with an intraclass correlation coefficient of 0.83. The mean alpha angle measured on the frog lateral view was 58.71 degrees (32 degrees to 83.3 degrees ) and that by CT was 65.11 degrees (30 degrees to 102 degrees ). A poor intraclass correlation coefficient (0.08) was noted between the measurements using the two systems. The frog lateral plain radiograph is not reliable for measuring the alpha angle. Various factors may be responsible for this such as the projection of the radiograph, the positioning of the patient and the quality of the image. CT may be necessary for accurate measurement of the alpha angle.

We present a new CT-based method which measures cover of the femoral head in both normal and dysplastic hips and allows assessment of acetabular inclination and anteversion. A clear topographical image of the head with its covered area is generated. We studied 36 normal and 39 dysplastic hips. In the normal hips the mean cover was 73% (66% to 81%), whereas in the dysplastic group it was 51% (38% to 64%). The significant advantage of this technique is that it allows the measurements to be standardised with reference to a specific anatomical plane. When this is applied to assessing cover in surgery for dysplasia of the hip it gives a clearer understanding of where the corrected hip stands in relation to normal and allows accurate assessment of inclination and anteversion.

There is much debate about the nature and extent of deformities in the proximal femur in children with cerebral palsy. Most authorities accept that increased femoral anteversion is common, but its incidence, severity and clinical significance are less clear. Coxa valga is more controversial and many authorities state that it is a radiological artefact rather than a true deformity. We measured femoral anteversion clinically and the neck-shaft angle radiologically in 292 children with cerebral palsy. This represented 78% of a large, population-based cohort of children with cerebral palsy which included all motor types, topographical distributions and functional levels as determined by the gross motor function classification system. The mean femoral neck anteversion was 36.5 degrees (11 degrees to 67.5 degrees) and the mean neck-shaft angle 147.5 degrees (130 degrees to 178 degrees). These were both increased compared with values in normally developing children. The mean femoral neck anteversion was 30.4 degrees (11 degrees to 50 degrees) at gross motor function classification system level I, 35.5 degrees (8 degrees to 65 degrees ) at level II and then plateaued at approximately 40.0 degrees (25 degrees to 67.5 degrees) at levels III, IV and V. The mean neck-shaft angle increased in a step-wise manner from 135.9 degrees (130 degrees to 145 degrees) at gross motor function classification system level I to 163.0 degrees (151 degrees to 178 degrees) at level V. The migration percentage increased in a similar pattern and was closely related to femoral deformity. Based on these findings we believe that displacement of the hip in patients with cerebral palsy can be explained mainly by the abnormal shape of the proximal femur, as a result of delayed walking, limited walking or inability to walk. This has clinical implications for the management of hip displacement in children with cerebral palsy.

In order to treat painful subluxation or dislocation secondary to cerebral palsy, 11 patients (12 hips) underwent combined femoral and Chiari pelvic osteotomies with additional soft-tissue releases at a mean age of 14.1 years (9.1 to 17.8). Relief of pain, improvement in movement of the hip, and in sitting posture, and ease of perineal care were recorded in all, and were maintained at a mean follow-up of 13.1 years (8 to 17.5). The improvement in general mobility was marginal, but those who were able to walk benefited the most. The radiological measurements made before operation were modified afterwards to use the lateral margin of the neoacetabulum produced by the pelvic osteotomy. The radiological migration index improved from a mean of 80.6% (61% to 100%) to 13.7% (0% to 33%) (p < 0.0001). The mean changes in centre edge angle and Sharp's angle were 72 degrees (56 degrees to 87 degrees; p < 0.0001) and 12.3 degrees (9 degrees to 15.6 degrees; p < 0.0001), respectively. Radiological evidence of progressive arthritic change was seen in one hip, in which only a partial reduction had been achieved, and there was early narrowing of the joint space in another. Painless heterotopic ossification was observed in one patient with athetoid quadriplegia. In seven hips the lateral Kawamura approach, elevating the greater trochanter, provided exposure for both osteotomies and allowed the construction of a dome-shaped iliac osteotomy, while protecting the sciatic nerve.

We treated 34 patients with recurrent dislocation of the hip with a constrained acetabular component. Roentgen stereophotogrammetric analysis was performed to assess migration of the prosthesis. The mean clinical follow-up was 3.0 years (2.2 to 4.8) and the radiological follow-up was 2.7 years (2.0 to 4.8). At the latest review six patients had died and none was lost to follow-up. There were four acetabular revisions, three for aseptic loosening and one for deep infection. Another acetabular component was radiologically loose with progressive radiolucent lines in all Gruen zones and was awaiting revision. The overall rate of aseptic loosening was 11.8% (4 of 34). Roentgen stereophotogrammetric analysis in the non-revised components confirmed migration of up to 1.06 mm of translation and 2.32 degrees of rotation at 24 months. There was one case of dislocation and dissociation of the component in the same patient. Of the 34 patients, 33 (97.1%) had no further episodes of dislocation. The constrained acetabular component reported in our study was effective in all but one patient with instability of the hip, but the rate of aseptic loosening was higher than has been reported previously and requires further investigation.

We describe a patient with cerebral palsy, of normal intelligence, who could not walk but who by the age of 16 had been successfully managed with a staged bilateral total hip arthroplasty using a constrained liner.

We carried out a morphometric analysis of acetabular dysplasia in patients with cerebral palsy requiring hip surgery using three-dimensional CT. We evaluated 54 hips in 27 patients. The contralateral normal hips of ten patients with unilateral Perthes' disease were used as a control group. The acetabular defects were assessed qualitatively as anterior, posterior or global. Quantitative assessments were made using three-directional acetabular indices (anterosuperior, superolateral and posterosuperior) and measured by multiplanar reformation, from which we calculated the acetabular volume. In the qualitative study, posterior defects were most common in the subluxation group whereas global defects predominated in the dislocation group. In the quantitative study, all acetabular indices in both the subluxation and dislocation groups were higher than those in the control group and the superolateral indices showed a tendency to elevation in the dislocation group. The acetabular volume was largest in the control group, smallest in the dislocation group, and intermediate between the two in the subluxation group.

Acetabular dysplasia was produced in 24 immature white rabbits. A rotational acetabular osteotomy was then carried out and radiological and histological studies of the articular cartilage were made. In the hips which did not undergo osteotomy, radiographs at 26 weeks showed that residual subluxation remained and arthritic changes such as narrowing of the joint space or dislocation were still seen. However, in the operated group there was a remarkable increase in cover, but arthritic changes were not observed. After 24 weeks, the Mankin grading score in the operated group was significantly lower than that in the non-operated group. The latter hips showed an irregular surface of the cartilage, exfoliation and proliferation of synovial tissue. In those undergoing osteotomy, primary cloning of chondrocytes or hypercellularity was seen and at 24 weeks after operation and metaplasia of the cartilage in the fibrous tissue was observed in the boundary between the medial area of the acetabulum and the acetabular fossa.

We describe a technique of 'cross-hip distraction' to reduce a dislocated hip with subsequent reconstruction of the joint for septic arthritis with extensive femoral osteomyelitis. A 27-year-old woman presented with a dislocated, collapsed femoral head and chronic osteomyelitis of the femur. Examination revealed a leg-length discrepancy of 7 cm and an irritable hip. A staged technique was used with primary clearance of osteomyelitis and secondary reconstruction of the hip. A cross-hip monolateral external fixator was used to establish normal anatomy followed by an arthroplasty. A good functional outcome was achieved. The use of cross-hip distraction avoids soft-tissue and nerve damage and achieved improved abductor function before arthroplasty.

We treated eight dysplastic acetabula in six skeletally mature patients with Down's syndrome by a modified Bernese periacetabular osteotomy. The mean age at the time of surgery was 16.5 years (12.8 to 28.5). Mean length of follow-up was five years (2 to 10.4).Pre-operatively the mean (Tonnis) acetabular angle was 28 degrees, the centre-edge angle was -9 degrees, and the extrusion index was 60%; post-operatively they were 3 degrees, 37 degrees, and 17%, respectively. Two patients with post-operative (Tonnis) acetabular angles > 10 degrees developed subluxation post-operatively and required secondary varus derotation femoral osteotomies. Another patient developed a late labral tear which was treated arthroscopically. All eight hips remain clinically stable, and are either asymptomatic or symptomatically improved. These results suggest that the modified Bernese periacetabular osteotomy can be used successfully in the treatment of acetabular dysplasia in patients with Down's syndrome.

In 1994, a register for cerebral palsy and a health-care programme were started in southern Sweden with the aim of preventing dislocation of the hip in children with cerebral palsy. It involved all children with cerebral palsy born in 1992 or later. None of the 206 affected children born between 1992 and 1997 has developed a dislocation following the introduction of the prevention programme. Another 48 children moved into the area and none developed any further dislocation. Of the 251 children with cerebral palsy, aged between five and 11 years, living in the area on January 1, 2003, only two had a dislocated hip. One boy had moved into the area at age of nine with a dislocation and a girl whose parents chose not to participate in the programme developed bilateral dislocation. One boy, whose condition was considered to be too poor for preventative surgery, developed a painful dislocation of the hip at the age of five years and died three years later. Eight of 103 children in a control group, consisting of all children with cerebral palsy living in the area between 1994 and 2002, and born between 1990 and 1991, developed a dislocation of the hip before the age of six years. The decreased incidence of dislocation after the introduction of the prevention programme was significant (p < 0.001). Dislocation of the hip in cerebral palsy remains a serious problem, and prevention is important. Our screening programme and early intervention when lateral displacement of the femoral head was detected appear to be successful.

Reimers' hip migration percentage is commonly used to document the extent of subluxation of the hip in children with spasticity. In this study, two measurers, with six months paediatric orthopaedic experience, measured the migration percentage on 44 pelvic radiographs of children with cerebral palsy, aged between two and eight years. Unknown to the measurers, each radiograph was duplicated, giving 22 non-identical radiographs (44 hips) which were measured twice at time 0 and twice six weeks later. The intra-measurer, intra-sessional absolute differences between the first and second measurements ranged from 0% to 23%, with median values of 2.5% to 3.6%. The intra-sessional median absolute differences were not statistically different between the two measurers and measuring sessions (p = 0.42, Kruskal-Wallis test). The inter-sessional absolute differences for measurements made by the same measurers ranged from 0% to 18% with a median absolute difference of 1.7% to 3.2%. Overall, only 5% of the intra-measurer measurement differences, within and between sessions, were above 13%. Repeated measurements by one measurer over time must, therefore, vary by more than 13% in order to be 95% confident of a true change. The inter-measurer error was higher with median absolute differences between the two measurers' measurements of the same hip of 3.25% to 5% (0% to 26%) and a 95th upper confidence interval of 21% to 23%. Averaging the four separate measurements over the two sessions reduced the inter-measurer error to a median absolute difference of 2.8%, but did not improve the 95th upper confidence interval, which measured 22.4%. Such inter-measurer errors may be clinically unacceptable.

We studied the reproducibility of ultrasonographic screening examination of the hip when read by diagnostic radiographers. In order to determine interobserver variability, 200 ultrasonograms were classified according to Graf's method by five observers (four radiographers and one radiologist). The kappa values for interobserver variability indicated moderate agreement (kappa 0.47) for the exact Graf classification and substantial agreement (kappa 0.65) for the classification of normal (type I) versus abnormal (type IIa-IV). Agreement was significantly different for normal, immature and abnormal hips. Comparison of the findings in our interobserver study with existing information based on other examinations and treatment revealed that only a small number of infants with mildly dysplastic hips would have been typed as normal by some observers as a result of observer variability. In conclusion, the interobserver agreement on the ultrasound assessment of the hip was good enough for screening purposes. Observer variability did not result in any severe cases being missed.

We describe a 15-year-old boy with a posterior dislocation of the hip, fracture of the posterior column of the acetabulum and separation of the femoral capital epiphysis. To our knowledge no previous case in a child has been reported. Such high-energy injuries are extremely rare, and a poor outcome is expected. We advocate early referral to a specialised tertiary centre, and the use of a modification of Delbet's classification to reflect the complexity and displacement which may occur with this injury.

We describe two patients with obturator dislocation of the hip which was irreducible by described techniques of closed reduction. The first required open reduction using the iliofemoral approach with release of rectus femoris. The second was treated on a traction table which allowed disengagement of the head and, when combined with simultaneous lateral traction, adduction and gradual release of the longitudinal traction, facilitated a smooth reduction. Since the hip is stable in flexion, early mobilisation in an extension-limiting brace avoids the prolonged bed rest traditionally recommended for this injury.

We have previously described a simple and reproducible three-dimensional technique of CT for the measurement of the cover of the femoral head in acetabular dysplasia in adults. We now describe the application of this technique in ten patients with symptomatic dysplasia to assess the degree and direction of dysplasia and to measure the cover obtained at acetabular osteotomy. The indices obtained gave a useful indication of the degree and direction of the dysplasia and confirmed which components had been used most efficiently to achieve cover. The information is easily presented in graphical form and gives a clearer indication of the cover obtained than the indices derived from plain radiographs.

We carried out the Bernese periacetabular osteotomy for the treatment of 13 dysplastic hips in 11 skeletally mature patients with an underlying neurological diagnosis. Seven hips had flaccid paralysis and six were spastic. The mean age at the time of surgery was 23 years and the mean length of follow-up was 6.4 years. Preoperatively, 11 hips had pain and two had progressive subluxation. Before operation the mean Tönnis angle was 33 degrees, the mean centre-edge angle was -10 degrees, and the mean extrusion index was 53%. Postoperatively, they were 8 degrees, 25 degrees and 15%, respectively. Pain was eliminated in 7 patients and reduced in four in those who had preoperative pain. One patient developed pain secondary to anterior impingement from excessive retroversion of the acetabulum. Four required a varus proximal femoral osteotomy at the time of the pelvic procedure and one a late varus proximal femoral osteotomy for progressive subluxation. Before operation no patient had arthritis. At the most recent follow-up one had early arthritis of the hip (Tönnis grade I) and one had advanced arthritis (Tönnis grade III). Our results suggest that the Bernese periacetabular osteotomy can be used successfully to treat neurogenic acetabular dysplasia in skeletally mature patients.

A six-year-old girl with congenital sensory neuropathy with anhidrosis (CSNA) presented with bilateral hip dysplasia and subluxation on the right side. Conservative treatment of the hips by closed reduction and a plaster cast was unsuccessful. When aged seven years the patient had an intertrochanteric varus rotation osteotomy on the right side, but subluxation was again evident after five months. A Salter-type pelvic osteotomy was carried out followed by immobilisation, but one year later subluxation was present in the right hip and dislocation in the left. At the age of nine years, the right femoral head resembled a Charcot joint, although walking ability was preserved. In patients with CSNA, surgery may not always be advisable.

We compared the prognostic value of the Catterall grouping, the Salter-Thompson grading, the arthrographic shape of the femoral head, and the Herring lateral pillar grouping during the fragmentation stage of Perthes' disease in 73 patients with 81 affected hips. Radiographs were available for study from the onset of the disease until skeletal maturity. We used the Stulberg classification to assess outcome. The Herring grade and arthrographic sphericity proved to be the best predictors of final outcome. Combining these two values further increased the predictive value. All but one patient in Herring group A achieved an excellent outcome. In Herring group B, the age of the child and the sphericity of the femoral head influenced the end result. If the child was less than seven years old at the onset of symptoms the prognosis was invariably good and all spherical hips in group B had a good outcome with Stulberg grades 1 or 2. Moderately and severely deformed hips on arthrography resulted in Stulberg 3 and 4 hips. None of the hips in Herring group C had a normal appearance at maturity and the outcome was not significantly influenced by the age at onset or the arthrographic appearance.

Over a 20-year period we treated 29 patients (31 dislocated hips) by non-operative reduction after nine months of age, using horizontal traction. They were followed up for a mean of 11.7 years, and 12 hips required secondary extra-articular surgery. The clinical result was excellent in 25 hips, good in four and fair in two. Of the 29 hips for which detailed radiographs were available, 18 achieved Severin grade I, nine grade II and two grade III. There were no major complications and, in particular, no cases of avascular necrosis. The non-operative reduction of late-presenting developmental dysplasia of the hip is still a viable option. It has a potential for excellent results and a very low complication rate.

We have evaluated the reliability of the measurement of radiological indicators in developmental dysplasia of the hip. Three observers each independently assessed 60 pelvic radiographs from infants aged from 3 to 36 months. Errors from the true value of a single measurement made by a single observer (E1), of the average of two measurements by a single observer (E2), and of the average of two single measurements by two different observers (E3) were established for the acetabular index of Hilgenreiner, for the assessment of superior and lateral femoral displacement and for indicators of pelvic alignment. The errors for the assessment of the acetabular index were E1 +/- 5 degrees, E2 +/- 5 degrees, and E3 +/- 3.5 degrees. There was a significant correlation between the presence of an acetabular notch on the radiograph and an increased error in measurement (p = 0.01). Yamamuro's measurement of lateral femoral displacement was more reliable than the Hilgenreiner distance. The errors of indicators of pelvic alignment showed a correlation with the age of the infant; the quotient of pelvic rotation was more reliable after seven months of age (p < 0.0001). The errors of the measurement of the symphysis os-ischium angle tended to increase with age and those of the measurement of the index of pelvic tilt decreased with skeletal maturation (p = 0.002).

Simultaneous bilateral posterior dislocation of the hip is very uncommon and most cases are caused by road accidents. Simultaneous bilateral posterior dislocation of the hip due to convulsions is extremely rare. We report the case of a man who was diagnosed late and operated on 15 weeks after the injury. We discuss the treatment of chronic dislocation of the hip and review the literature.

Between 1980 and 1988, displacement bone-marrow transplantation was performed on 25 children with Hurler's syndrome (type-1 mucopolysaccharidosis). We describe the musculoskeletal development of 11 of the 12 surviving children and the orthopaedic procedures undertaken to treat progressive thoracolumbar kyphosis, hip subluxation and carpal tunnel syndrome. We found abnormal bone modelling, focal failures of ossification and an avascular disorder of the femoral head in every patient and offer an explanation for these phenomena. Increasing valgus deformity of the knees and progressive generalised myopathy caused loss of mobility as the children entered adolescence. The benefit of bone-marrow transplantation as a treatment for the skeletal disorders of Hurler's syndrome is limited by the poor penetration of the musculoskeletal tissues by the enzyme derived from the leucocytes.

We report the results of 24 acetabular reconstructions in which cemented polyethylene cups and tamped corticocancellous allografts were used for severe acetabular bone deficiency. Eleven hips had type-II (cavitary) bone deficiency and 13 had type-III (combined) defects. At a mean follow-up of 5.8 years, two components had migrated more than 5 mm and had accompanying radiolucent zones of more than 2 mm width. A radiolucency 5 mm wide was also seen in zone III of an acetabular implant which had not migrated. None of the patients had required revision because of loosening or infection.

Dysplastic acetabula were augmented during total hip replacement by superolateral autografts. In cases of primary arthroplasty these were taken from the excised femoral head and in revision surgery from the iliac crest. Two or (usually) three small grafts were used to facilitate revascularisation; they were fixed with lag screws to the roughened iliac bone above the acetabulum. We reviewed 84 hips (63 primary arthroplasties and 21 revisions) more than five years (mean 10.1) after operation. All but one of the grafts showed consolidation within three months and they had become structurally integrated with the iliac bone, as evidenced by the trabecular reorientation. Resorption, which has caused early socket failure when large bone grafts have been used, did not occur.

We reviewed radiographs and CT scans of 38 total hip arthroplasties which had dislocated (36 posteriorly; 2 anteriorly) and compared the alignment of the prosthetic components with those of 14 uncomplicated arthroplasties. No difference was found between the alignment of the prosthetic components in the two groups. In the seven patients who had reoperations, the cause of dislocation diagnosed by CT was confirmed in only two cases (one retroversion of the cup and one protruding osteophyte). Muscular imbalance rather than malposition of the components was the major factor determining dislocation. CT allows accurate measurement of cup and neck anteversion but contributes little to preoperative planning.

We studied 1061 children with myelomeningocele, reviewing 3184 pelvic radiographs from 802 patients. Hip dislocation had occurred by the age of 11 years in 28% of children with a thoracic neurosegmental level, 30% of those with an L1/2 level, 36% of L3, 22% of L4, 7% of L5 and only 1% of those with sacral levels. Hip dislocation was not inevitable even when there was maximal muscle imbalance about the hip. The average hip flexion contracture in children aged 9 to 11 years was significantly greater in those with thoracic (22 degrees) and L1/2 (33 degrees) levels than in those with L4 (9 degrees), L5 (5 degrees) or sacral (4 degrees) levels. Our findings indicate that muscle imbalance is not a significant factor in the production of flexion deformity or dislocation of the hip; both are commonly seen in the absence of imbalance. The restoration of muscle balance should no longer be considered to be the principal aim of the management of the hip in children with myelomeningocele.

The Chiari osteotomy and various shelf procedures are used to augment the weight-bearing area in dysplastic acetabula. The new articular surface derives by metaplasia from the acetabular rim and joint capsule, and is therefore of poorer quality than congruous hyaline cartilage. We reviewed 32 patients after augmentation procedures, using conventional radiographs and three-dimensional reconstruction from CT scans. We showed that Chiari osteotomy and shelf procedures generally achieve less than complete cover, especially over the posterolateral quadrant of the femoral head. Our results suggest that alternative methods which reorientate the whole of the acetabulum are the treatment of choice. Augmentation procedures remain as a salvage option when reorientation is inappropriate or the original hyaline cartilage surface is absent, as in subluxed joints with a secondary acetabulum. Computerised assessment is recommended before operation to assess existing cover and the possible extent of provision of new cover.

After late reduction of the hip in children with developmental dysplasia the acetabular contour slowly improves and it is difficult to know if and when acetabular reconstruction is required. We studied the radiographs of 19 patients with unilateral dislocated or subluxated hips which had been reduced between the ages of one and two years. Preoperatively, all the affected hips showed acetabular dysplasia. After reduction they steadily improved for three years by which time none was dysplastic as measured by the acetabular index. After the age of ten years, when assessed by the more sensitive centre-edge angle, two were found to be dysplastic. It was not possible to predict these from early radiographs. We conclude that the decision to reconstruct an acetabulum should not be taken until three years after reduction, and that a few hips which appear to be developing satisfactorily at that time will, nevertheless, become dysplastic.

Total hip arthroplasty was performed in 45 hips of 44 patients who had pyogenic arthritis of the hip during childhood. The average age of the patients was 36.4 years (range 19 to 50). The interval between active infection and arthroplasty ranged from 11 to 40 years, and average follow-up was 65.4 months (range 58 to 80). Specimens of tissue taken before and during operation gave negative cultures in all hips, and no patient had reactivation of infection. The mean functional rating of the hips was 58 points before operation and 90 at the final review. Complications were seen in 11 cases (24%), loosening of components occurred in six (13%) and one hip had to be revised for acetabular component migration. Acetabular allografts were required in 27 hips (60%). All allografts united but there was partial resorption of the graft in the non-weight-bearing area in all.

The acetabular rim syndrome is a pathological entity which we illustrate by reference to 29 cases. The syndrome is a precursor of osteoarthritis of the hip secondary to acetabular dysplasia. The symptoms are pain and impaired function. All our cases were treated by operation which consisted in most instances of re-orientation of the acetabulum by peri-acetabular osteotomy and arthrotomy of the hip. In all cases, the limbus was found to be detached from the bony rim of the acetabulum. In several instances there was a separated bone fragment, or 'os acetabuli' as well. In acetabular dysplasia, the acetabular rim is subject to abnormal stress which may cause the limbus to rupture, and a fragment of bone to separate from the adjacent bone margin. Dysplastic acetabuli may be classified into two radiological types. In type I there is an incongruent shallow acetabulum. In type II the acetabulum is congruent but the coverage of the femoral head is deficient.

We report seven children in whom traumatic haemarthrosis of the hip had produced lateral subluxation of the femoral head, which is different from the apparent displacement seen in Perthes' disease. In all seven cases, aspiration of the haemarthrosis allowed reduction of the femoral head, and follow-up for a mean of 14 months revealed no evidence of avascular necrosis of the proximal femoral epiphysis. Traumatic haemarthrosis of the hip in children appears to be a clinical entity which can produce femoral head subluxation. Aspiration and traction is the treatment of choice and can cure the condition.

We report the short-term results of 100 cementless total hip replacements in 52 severely dysplastic and 48 totally dislocated hips, with some new technical solutions to the problems involved. In cases with a very narrow iliac bone, the acetabular screw ring is seated below the true cotyloid area. In hips with tight flexor and abductor muscles or with deformities of the proximal femur, various osteotomies were performed. Special attention was paid to careful pre-operative planning and precise operative technique. In spite of a high complication rate the results were generally good and even patients who required reoperation were satisfied with the final result.

The work capacity of 26 women after a Chiari pelvic osteotomy for symptomatic unilateral subluxation of the hip was assessed using two simple exercise tests: the maximal walking speed during a 12-minute test and the time taken to climb stairs. A significant linear decline in walking speed occurred with increasing age, despite the operation, and only one patient over the age of 25 years was able to walk at a normal rate. Compared to the results in a control group of women of similar age the stair climbing time was increased in 54 per cent of the patients and showed a significant negative correlation with the maximal walking speed. Age-adjusted walking speed was closely associated with the degree of pain experienced but there was no relationship between observed function and conventional clinical assessment based on the range of movement and the radiographic appearances of the hip.

Twenty-one cases of the Charnley low-friction arthroplasty were revised because of recurrent or irreducible dislocation. Three main reasons for this revision, usually in combination, were identified: loss of the abductor mechanism due to trochanteric detachment; shortening of the limb due to high placement of the socket or low section of the femoral neck; and malorientation of the components. Sixteen patients had no further problems after revision. One patient had a single dislocation, four had more than one dislocation although they managed to cope with them and did not require a further revision.

A retrospective study was made of the results of surgical treatment of subluxation or dislocation of the hip in patients who had suffered from poliomyelitis. Good results were achieved in 46% and satisfactory results in 24%. The key factors for success are muscle balance, the femoral neck-shaft and anteversion angles, and the acetabular geometry. Iliopsoas transfer can augment the hip abductor power by an average of one MRC grade. Varus derotation femoral osteotomy is important to re-establish a normal neck-shaft angle and anteversion. The results of pelvic osteotomy are variable and the importance of a posterior acetabular defect is emphasised.

We have studied the natural history of spontaneous dislocation of the hip in cerebral palsy, with particular reference to the pattern of neurological involvement. In patients with bilateral hemiplegia and severe involvement of the upper limbs the incidence of dislocation was very high (59%), while in those with diplegia and little involvement of the upper limbs, only 6.5% were affected. There was no evidence of dysplasia or instability of the hip in any of the patients with unilateral hemiplegia. A strong correlation was found between the stability of the hip and the patients' ability to walk. These findings have a bearing on clinical surveillance and also on the indications for prophylactic surgery.

A case of early closure of the triradiate cartilage, probably secondary to neonatal septic arthritis of the right hip, is reported. Tomograms of the hip showed the triradiate cartilage closed posteriorly, with the anterior portion still open. These findings were confirmed at operation. An arthrogram and a CT scan of the right hip showed subluxation of the femoral head. This unique complication, after an episode of septic arthritis of the hip, has not before been reported in the literature.

We have reviewed 19 consecutive patients admitted to the Odense University Hospital after traumatic dislocation of the hip. We aimed to perform computerised tomography as soon as possible after closed reduction; this was accomplished in 15 patients. The CT scans revealed intra-articular fragments of bone in five hips, and fractures of the femoral head or acetabulum in six. In two cases the CT scans excluded fractures or intra-articular fragments which had been suspected on conventional radiography. CT scanning is a useful diagnostic tool in traumatic dislocation of the hip; we consider that it makes an important contribution to management.

Stereoradiography with a base shift of the source of illumination was used to produce pairs of radiographs to be measured by stereophotogrammetric techniques. The direction of shift was parallel with the longitudinal axis of the body, so that each radiograph in the stereopair could be used for other clinical purposes. A base shift of 10 centimetres with a distance of 100 centimetres between the focus and the film gave acceptable value of stereoscopic parallax. The radiographs were measured using a Hilger and Watts medical stereometer. This method was checked with test specimens, namely an osteotomised pelvis in which one acetabulum could be rotated and an osteotomised femur in which the whole upper portion could be rotated against the shaft. Measurements made on the acetabulum and its radiographs showed a correlation coefficient of 0.9838 over the range 0 to 30 degrees of anteversion, with a mean error +2.54 degrees and a standard deviation of +/- 1.52 degrees (n = 21). For the femoral neck, over the range from 10 degrees of retroversion to 80 degrees of anteversion, the correlation coefficient was 0.9979, the mean error +2.46 and the standard deviation +/- 1.48 degrees (n = 30).