Aims. Complex total hip arthroplasty (THA) with subtrochanteric shortening osteotomy is necessary in conditions other than developmental dysplasia of the hip (DDH) and septic arthritis sequelae with significant proximal femur migration. Our aim was to evaluate the hip centre restoration with THAs in these hips. Methods. In all, 27 THAs in 25 patients requiring THA with femoral shortening between 2012 and 2019 were assessed. Bilateral shortening was required in two patients. Subtrochanteric shortening was required in 14 out of 27 hips (51.9%) with aetiology other than DDH or septic arthritis. Vertical centre of rotation (VCOR), horizontal centre of rotation, offset, and functional outcome was calculated. The mean followup was 24.4 months (5 to 92 months). Results. The mean VCOR was 17.43 mm (9.5 to 27 mm) and horizontal centre of rotation (HCOR) was 24.79 mm (17.2 to 37.6 mm). Dislocation at three months following acetabulum reconstruction required femoral shortening for offset correction and hip centre restoration in one hip. Mean horizontal offset was 39.72 (32.7 to 48.2 mm) compared to 42.89 (26.7 to 50.6 mm) on the normal side. Mean Harris Hip Score (HHS) of 22.64 (14 to 35) improved to 79.43 (68 to 92). Mean pre-operative shortening was 3.95 cm (2 to 8 cm). Residual limb length discrepancy was 1.5 cm (0 to 2 cm). Sciatic neuropraxia in two patients recovered by six months, and femoral neuropraxia in one hip recovered by 12 months. Mean Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was 13.92 (9 to 19). Mean 12-item short form survey (SF-12) physical scores of 50.6 and mental of 60.12 were obtained. Conclusion. THA with subtrochanteric shortening is valuable in complex hips with high dislocation. The restoration of the hip centre of rotation and offset is important in these hips. Level of evidence IV. Femoral shortening useful in conditions other than DDH and septic sequelae. Restoration of hip centre combined with offset to be planned and ensured

Using radiography and computer tomography (CT) we studied the morphology of 83 hips in 69 Caucasian adults with osteoarthritis secondary to developmental dysplasia of the hip (DDH). A previously published series of 310 hips with primary osteoarthritis was used as a control group. According to the Crowe classification, 33 of the dysplastic hips were graded as class I, 27 as class II and 23 as class III or class IV. The intramedullary femoral canal had reduced mediolateral and anteroposterior dimensions in all groups compared with the control group. Only in Crowe class II hips was the femoral neck-shaft angle increased. The proximal femur had more anteversion in all the developmental dysplasia of the hip groups, ranging from 2° to 80°. Templated measurement of acetabular dimensions for plain radiography closely matched measurements taken by CT. The results of our study confirm the observations previously confined to the Japanese population

Aims. Open reduction in developmental dysplasia of the hip (DDH) is regularly performed despite screening programmes, due to failure of treatment or late presentation. A protocol for open reduction of DDH has been refined through collaboration between surgical, anaesthetic, and nursing teams to allow same day discharge. The objective of this study was to determine the safety and feasibility of performing open reduction of DDH as a day case. Methods. A prospectively collected departmental database was visited. All consecutive surgical cases of DDH between June 2015 and March 2020 were collected. Closed reductions, bilateral cases, cases requiring corrective osteotomy, and children with comorbidities were excluded. Data collected included demographics, safety outcome measures (blood loss, complications, readmission, reduction confirmation), and feasibility for discharge according to the Face Legs Activity Cry Consolidability (FLACC) pain scale. A satisfaction questionnaire was filled by the carers. Descriptive statistics were used for analysis. Results. Out of 168 consecutive DDH cases, 16 patients fit the inclusion criteria (age range 10 to 26 months, 13 female). Intraoperative blood loss ranged from "minimal" to 120 ml, and there were no complications or readmissions. The FLACC score was 0 for all patients. The carers satisfaction questionnaire expressed high satisfaction from the experience with adequate information and support provided. Conclusion. Open reduction in DDH, without corrective osteotomy, is safe and feasible to be managed as a day case procedure. It requires a clear treatment pathway, analgesia, sufficient counselling, and communication with carers. It is even more important during the COVID-19 pandemic when reduced length of hospital stay is likely to be safer for both patient and their parents. Cite this article: Bone Joint Open 2021;2(4):271–277

Aims. Open reduction is required following failed conservative treatment of developmental dysplasia of the hip (DDH). The Ludloff medial approach is commonly used, but poor results have been reported, with rates of the development of avascular necrosis (AVN) varying between 8% and 54%. This retrospective cohort study evaluates the long-term radiographic and clinical outcome of dislocated hips treated using this approach. Patients and Methods. Children with a dislocated hip, younger than one year of age at the time of surgery, who were treated using a medial approach were eligible for the study. Radiographs were evaluated for the degree of dislocation and the presence of an ossific nucleus preoperatively, and for the degree of AVN and residual dysplasia at one and five years and at a mean of 12.7 years (4.6 to 20.8) postoperatively. Radiographic outcome was assessed using the Severin classification, after five years of age. Further surgical procedures were recorded. Functional outcome was assessed using the Pediatric Outcomes Data Collection Instrument (PODCI) or the Hip Disability and Osteoarthritis Outcome Score (HOOS), depending on the patient’s age. Results. A total of 52 children (58 hips) were included. At the latest follow-up, 11 hips (19%) showed signs of AVN. Further surgery was undertaken in 13 hips (22%). A total of 13 hips had a poor radiological outcome with Severin type III or higher. Of these, the age at the time of surgery was significantly higher (p < 0.05) than in those with a good Severin type (I or II). The patient-reported outcomes were significantly worse (p < 0.05) in children with a poor Severin classification. Conclusion. This retrospective long-term follow-up study shows that one in five children with DDH who undergo open reduction using a medial surgical approach has poor clinical and/or radiological outcome. The poor outcome is not related to the presence of AVN (19%), but due to residual dysplasia. Cite this article: Bone Joint J 2018;100-B:822–7

Osteoarthritis is extremely common and many different causes for it have been described. One such cause is abnormal morphology of the affected joint, the hip being a good example of this. For those joints with femoroacetabular impingement (FAI) or developmental dysplasia of the hip (DDH), a link with subsequent osteoarthritis seems clear. However, far from being abnormal, these variants may be explained by evolution, certainly so for FAI, and may actually be normal rather than representing deformity or disease. The animal equivalent of FAI is coxa recta, commonly found in species that run and jump. It is rarely found in animals that climb and swim. In contrast are the animals with coxa rotunda, a perfectly spherical femoral head, and more in keeping with the coxa profunda of mankind. This article describes the evolutionary process of the human hip and its link to FAI and DDH. Do we need to worry after all?

Aims. A clicky hip is a common referral for clinical and sonographic screening for developmental dysplasia of the hip (DDH). There is controversy regarding whether it represents a true risk factor for pathological DDH. Therefore a 20-year prospective, longitudinal, observational study was undertaken to assess the relationship between the presence of a neonatal clicky hip and pathological DDH. Patients and Methods. A total of 362 infants from 1997 to 2016 were referred with clicky hips to our ‘one-stop’ paediatric hip screening clinic. Hips were assessed clinically for instability and by ultrasound imaging using a simplified Graf/Harcke classification. Dislocated or dislocatable hips were classified as Graf Type IV hips. Results. The mean age at presentation was 13.8 weeks (12.8 to 14.7). In all 351 out of 362 children (97.0%) had Graf Type I hips (normal) that required no treatment. Nine children (2.5%) had Graf Type II hips but all resolved to Graf Type I hips on follow-up scans. One child (0.3%) had Graf Type III hip dysplasia and one child (0.3%) had an irreducible hip dislocation. The two pathological hips were associated with unilateral limited hip abduction. Mean referrals increased from 12.9 to 23.3 each year (p = 0.002) from the first decade of the study to the second, driven by increasing primary care referrals (5.5 versus 16.7 per year, p < 0.001). Conclusion. Most clicky hips required no treatment other than reassurance to parents. Clicky hips with a normal hip examination should be considered a variant of normal childhood and not a risk factor for DDH. However, an abnormal hip examination including unilateral limited hip abduction should prompt urgent further investigations. Cite this article: Bone Joint J 2017;99-B:1533–6

Aims. Despite the presence of screening programmes, infants continue to present with late developmental dysplasia of the hip (DDH), the impact of which is significant. The aim of this study was to assess infants with late presenting dislocation of the hip despite universal clinical neonatal and selective ultrasound screening. Patients and Methods. Between 01 January 1997 to 31 December 2011, a prospective, longitudinal study was undertaken of a cohort of 64 670 live births. Late presenting dislocation was defined as presentation after three months of age. Diagnosis was confirmed by ultrasound and plain radiography. Patient demographics, referral type, reason for referral, risk factors (breech presentation/strong family history) and clinical and radiological findings were recorded. Results. There were 31 infants with an irreducible dislocation of the hip, an incidence of 0.48 (95% confidence interval (CI) 0.34 to 0.68) per 1000 live births. Of these, 18 (0.28 (95% CI 0.17 to 0.44) per 1000 live births; 58%) presented late. All infants had a documented normal newborn clinical examination and no abnormality reported in the six to eight week check. Of the 18 late presenting cases 72% (n = 13) had no risk factors: 16 were referred by GPs and two were late due to administrative issues (missed appointments). The mean time to diagnosis was 62.4 weeks (19 to 84). Conclusion. Despite universal clinical neonatal and selective ultrasound screening, late cases of irreducible hip dislocation still occur. We recommend an update of the national screening programme for DDH, a review of training and education of healthcare professionals involved in the physical examination of neonates and infants, and the addition of a further assessment after the six to eight week check. Cite this article: Bone Joint J 2017;99-B:1250–5

Aims. The aim of this study was to identify the association between asymmetrical skin creases of the thigh, buttock or inguinal region and pathological developmental dysplasia of the hip (DDH). Patients and Methods. Between 1 January 1996 and 31 December 2016, all patients referred to our unit from primary or secondary care with risk factors for DDH were assessed in a “one stop” clinic. All had clinical and sonographic assessment by the senior author (RWP) with the results being recorded prospectively. The inclusion criteria for this study were babies and children referred with asymmetrical skin creases. Those with a neurological cause of DDH were excluded. The positive predictive value (PPV) for pathological DDH was calculated. Results. A total of 105 patients met the inclusion criteria. There were 71 girls and 34 boys. Only two were found to have pathological DDH. Both also had unilateral limited abduction of the hip in flexion and a positive Galeazzi sign with apparent leg-length discrepancy. Thus, if the specialist examination of a patient with asymmetrical skin creases was normal, the PPV for DDH was 0%. Conclusion. Isolated asymmetrical skin creases are an unreliable clinical sign in the diagnosis of pathological DDH. Greater emphasis should be placed on the presence of additional clinical signs to guide radiological screening in babies and children. Cite this article: Bone Joint J 2018;100-B:675–9

Aims. This study presents the long-term survivorship, risk factors for prosthesis survival, and an assessment of the long-term effects of changes in surgical technique in a large series of patients treated by metal-on-metal (MoM) hip resurfacing arthroplasty (HRA). Patients and Methods. Between November 1996 and January 2012, 1074 patients (1321 hips) underwent HRA using the Conserve Plus Hip Resurfacing System. There were 787 men (73%) and 287 women (27%) with a mean age of 51 years (14 to 83). The underlying pathology was osteoarthritis (OA) in 1003 (75.9%), developmental dysplasia of the hip (DDH) in 136 (10.3%), avascular necrosis in 98 (7.4%), and other conditions, including inflammatory arthritis, in 84 (6.4%). Results. The mean follow-up time was 10.5 years (1 to 20). Using revision for any reason as the endpoint, the overall survivorship at 15 years was 89.4% (95% confidence interval (CI) 86.8 to 91.4). There was a substantial increase between the first and second generation of surgical technique (86.6% vs 90.1%; p = 0.05). Men with idiopathic OA had a 15-year survivorship of 94.5% and women, 82.2% (p = 0.001); gender was not a risk factor after stratification by component size and aetiology. Using revision for excessive wear (ion levels > 7 µg/l associated with symptoms or adverse local tissue reactions) as the endpoint, the 15-year survivorship was 98.5%. Risk factors for revision for all modes of failure were an underlying pathology of hip dysplasia, a contact patch to rim (CPR) distance of 7 mm or less, an age at surgery of 55 years or less, and a femoral component size of 46 mm or less. Specific risk factors for aseptic failure of the femoral component were early surgical technique, a cementless metaphyseal stem, and a body mass index of 24 kg/m. 2. or less. Conclusion. HRA is a viable concept; metal-on-metal bearings are well suited for this procedure when a well-designed device is properly implanted. The best results were obtained in men with OA, but survivorship was better for other underlying pathologies and for women after changes were made to the technique of implantation. Lifetime durability is a possible outcome for many patients despite a high level of activity. Cite this article: Bone Joint J 2018;100-B:1424–33

Developmental dysplasia of the hip (DDH) should be diagnosed as early as possible to optimise treatment. The current United Kingdom recommendations for the selective screening of DDH include a clinical examination at birth and at six weeks. In Northern Ireland babies continue to have an assessment by a health visitor at four months of age. As we continue to see late presentations of DDH, beyond one year of age, we hypothesised that a proportion had missed an opportunity for earlier diagnosis. We expect those who presented to our service with Tonnis grade III or IV hips and decreased abduction would have had clinical signs at their earlier assessments. We performed a retrospective review of all patients born in Northern Ireland between 2008 and 2010 who were diagnosed with DDH after their first birthday. There were 75 856 live births during the study period of whom 645 children were treated for DDH (8.5 per 1000). The minimum follow-up of our cohort from birth, to detect late presentation, was four years and six months. Of these, 32 children (33 hips) were diagnosed after their first birthday (0.42 per 1000). With optimum application of our selective screening programme 21 (65.6%) of these children had the potential for an earlier diagnosis, which would have reduced the incidence of late diagnosis to 0.14 per 1000. As we saw a peak in diagnosis between three and five months our findings support the continuation of the four month health visitor check. Our study adds further information to the debate regarding selective versus universal screening. . Cite this article: Bone Joint J 2015;97-B:1572–6

Aims. There is no consensus about the best method of achieving equal leg lengths at total hip arthroplasty (THA) in patients with Crowe type-IV developmental dysplasia of the hip (DDH). We reviewed our experience of a consecutive series of patients who underwent THA for this indication. Patients and Methods. We retrospectively reviewed 78 patients (86 THAs) with Crowe type-IV DDH, including 64 women and 14 men, with a minimum follow-up of two years. The mean age at the time of surgery was 52.2 years (34 to 82). We subdivided Crowe type-IV DDH into two major types according to the number of dislocated hips, and further categorised them into three groups according to the occurrence of pelvic obliquity or spinal curvature. Leg length discrepancy (LLD) and functional scores were analysed. Results. Type-I included 53 patients with unilateral dislocation, in which 25 (category A) had no pelvic obliquity or spinal deformity, 19 (category B) had pelvic obliquity with a compensated spinal curvature and nine (category C) had pelvic obliquity and decompensated spinal degenerative changes. Type-II included 25 patients with one dislocated and one dysplastic hip, in which there were eight of category A, 15 of category B and two of category C. Pre-operatively, there were significant differences between the anatomical and functional LLD in type-IB (p = 0.005) and -IC (p < 0.001), but not in type-IA, -IIA or -IIB. Post-operatively, bony LLD increased significantly in types-IB, -IC and -IIB, whereas functional LLD decreased significantly in each type except for IIA. The mean functional LLD decreased from 30.7 mm (standard deviation (. sd. ) 18.5) pre-operatively to 6.2 mm (. sd. 4.4) post-operatively and the mean anatomical LLD improved from 35.8 mm (. sd. 19.7) pre-operatively to 12.4 mm (. sd. 8.3) post-operatively. Conclusion. Pelvic and spinal changes are common in patients with Crowe type-IV DDH and need to be taken into consideration when planning THA, in order to obtain equal leg lengths post-operatively. The principal subdivisions of Crowe type-IV DDH which we describe proved effective in achieving equal leg lengths and satisfactory outcomes. Cite this article: Bone Joint J 2017;99-B:872–9

Twins are often considered to be at an increased risk of developmental dysplasia of the hip (DDH); we therefore investigated whether multiple births have a higher incidence of DDH, and if selective ultrasound scanning should be considered for these infants. We reviewed our records of all live births between 1 January 2004 and 31 December 2008 and included 25 246 single and 990 multiple births. Multiple births did not have a significantly higher incidence of DDH compared with single births (0.0030 vs 0.0023, p = 0.8939). Of the 990 multiple births, 267 had neonatal ultrasound scans and one case of DDH was diagnosed and treated successfully with a Pavlik harness. There were two late-presenting cases at eight and 14 months of age, neither of whom had risk factors for DDH and consequently had not had a neonatal scan. Whereas selective ultrasound scanning of multiple births would have led to earlier detection and treatment of the late-presenting cases, they did not have a significantly higher incidence of DDH compared with single births. We conclude that being a twin or triplet in itself is not a risk factor for DDH and that selective ultrasound scanning is not indicated for this population. Cite this article: Bone Joint J 2013;95-B:132–4

The incidence of clinically significant avascular necrosis (AVN) following medial open reduction of the dislocated hip in children with developmental dysplasia of the hip (DDH) remains unknown. We performed a systematic review of the literature to identify all clinical studies reporting the results of medial open reduction surgery. A total of 14 papers reporting 734 hips met the inclusion criteria. The mean follow-up was 10.9 years (2 to 28). The rate of clinically significant AVN (types 2 to 4) was 20% (149/734). From these papers 221 hips in 174 children had sufficient information to permit more detailed analysis. The rate of AVN increased with the length of follow-up to 24% at skeletal maturity, with type 2 AVN predominating in hips after five years’ follow-up. The presence of AVN resulted in a higher incidence of an unsatisfactory outcome at skeletal maturity (55% vs 20% in hips with no AVN; p < 0.001). A higher rate of AVN was identified when surgery was performed in children aged < 12 months, and when hips were immobilised in ≥ 60°of abduction post-operatively. Multivariate analysis showed that younger age at operation, need for further surgery and post-operative hip abduction of ≥ 60° increased the risk of the development of clinically significant AVN. Cite this article: Bone Joint J 2014;96-B:279–86

In a prospective study over 11 years we assessed the relationship between neonatal deformities of the foot and the presence of ultrasonographic developmental dysplasia of the hip (DDH). Between 1 January 1996 and 31 December 2006, 614 infants with deformities of the foot were referred for clinical and ultrasonographic evaluation. There were 436 cases of postural talipes equinovarus deformity (TEV), 60 of fixed congenital talipes equinovarus (CTEV), 93 of congenital talipes calcaneovalgus (CTCV) and 25 of metatarsus adductus. The overall risk of ultrasonographic dysplasia or instability was 1:27 in postural TEV, 1:8.6 in CTEV, 1:5.2 in CTCV and 1:25 in metatarsus adductus. The risk of type-IV instability of the hip or irreducible dislocation was 1:436 (0.2%) in postural TEV, 1:15.4 (6.5%) in CTCV and 1:25 (4%) in metatarsus adductus. There were no cases of hip instability (type IV) or of irreducible dislocation in the CTEV group. Routine screening for DDH in cases of postural TEV and CTEV is no longer advocated. The former is poorly defined, leading to the over-diagnosis of a possibly spurious condition. Ultrasonographic imaging and surveillance of hips in infants with CTCV and possibly those with metatarsus adductus should continue

We performed MRI on 13 infants after operative reduction for developmental dysplasia of the hip (DDH). Using an axial gradient-echo sequence, MRI accurately depicted the acetabular anatomy and confirmed adequate reduction in 12 patients. The one patient with redislocation after surgery was correctly identified. MRI can be carried out quickly, inexpensively and without risk of radiation and is the investigation of choice to confirm adequate reduction in DDH

The medial approach for the treatment of children with developmental dysplasia of the hip (DDH) in whom closed reduction has failed requires minimal access with negligible blood loss. In the United Kingdom, there is a preference for these children to be treated using an anterolateral approach after the appearance of the ossific nucleus. In this study we compared these two protocols, primarily for the risk of osteonecrosis. Data were gathered prospectively for protocols involving the medial approach (26 hips in 22 children) and the anterolateral approach (22 hips in 21 children) in children aged <  24 months at the time of surgery. Osteonecrosis of the femoral head was assessed with validated scores. The acetabular index (AI) and centre–edge angle (CEA) were also measured. . The mean age of the children at the time of surgery was 11 months (3 to 24) for the medial approach group and 18 months (12 to 24) for the anterolateral group, and the combined mean follow-up was 70 months (26 to 228). Osteonecrosis of the femoral head was evident or asphericity predicted in three of 26 hips (12%) in the medial approach group and four of 22 (18%) in the anterolateral group (p = 0.52). The mean improvement in AI was 8.8° (4° to 12°) and 7.9° (6° to 10°), respectively, at two years post-operatively (p = 0.18). There was no significant difference in CEA values of affected hips between the two groups. Children treated using an early medial approach did not have a higher risk of developing osteonecrosis at early to mid-term follow-up than those treated using a delayed anterolateral approach. The rates of acetabular remodelling were similar for both protocols. Cite this article: Bone Joint J 2014;96-B:406–13

The results of the Ferguson medial approach for open reduction of developmental dysplasia of the hip (DDH) were reviewed for 49 hips with a follow-up of more than 48 months. The mean age at operation was 12.3 months (6 to 23). The mean length of clinical and radiological follow-up was 82 months (48 to 148). Three redislocations occurred. Group I avascular necrosis according to the classification of Kalamchi and MacEwen was seen in four hips, group II in two hips and group III in one hip; 92% of the hips were classified as Severin class I and II. The acetabular index and centre edge (CE) angles were within normal limits at final follow-up, but were still significantly different from the unaffected side. We conclude that the Ferguson procedure is safe and reliable for low dislocations in children aged six to 18 months

In developmental dysplasia of the hip (DDH), a bone defect is often observed superior to the acetabulum after the reconstruction at the level of the true acetabulum during total hip replacement (THR). However, the essential amount of uncemented acetabular component coverage required for a satisfactory outcome remains controversial. The purpose of this study was to assess the stability and function of acetabular components with a lack of coverage > 30% (31% to 50%). A total of 760 DDH patients underwent THR with acetabular reconstruction at the level of the true floor. Lack of coverage above the acetabular component of > 30% occurred in 56 patients. Intra-operatively, autogenous morcellised bone grafts were used to fill the uncovered portion. Other than two screws inserted through the acetabular shell, no additional structural supports were used in these hips. In all, four patients were lost to follow-up. Therefore, 52 patients (52 hips, 41 women and 11 men) with a mean age of 60.1 years (42 to 78) were available for this study at a mean of 4.8 years (3 to 7). There were no instances of prosthesis revision or marked loosening during the follow-up. The Harris hip score improved from a mean of 40.7 points (. sd. 12.2) pre-operatively to 91.1 (. sd. 5.0) at the last follow-up. Radiological analysis with medical imaging software allowed us to calculate the extent of the uncoverage in terms of the uncovered arc of the implant as viewed on the anteroposterior pelvic radiograph. From this we propose that up to 17 mm of lateral undercoverage in the presence of a stable initial implantation in the presence of bone autografting, with an inclination angle of the acetabular component between 40° and 55°, is acceptable. This represents undercoverage of ≤ 50%. Cite this article: Bone Joint J 2013;95-B:1178–83

Between 1985 and 1998, 12 331 patients were included in the general neonatal ultrasound hip screening programme for developmental dysplasia of the hip (DDH). Patients who needed treatment (604) were compared with a second group of 73 unscreened children treated conservatively and surgically for DDH. The incidence of Graf sonographic hip types IIc to IV varied throughout the observation period. Femoral and pelvic osteotomies were almost entirely restricted to the unscreened group of patients. The six to ten per year recorded in the period 1985 to 1990 declined subsequently to three or less per year. The yearly admissions to hospital fell noticeably after six years of screening. Late presentations of DDH were reduced to three or less per year from 1990 to 1994, none between 1995 and 1998 and one or two per year from 2000. We conclude that general neonatal sonographic hip screening can reduce significantly surgical procedures, hospitalisation and late presentation of DDH

We report the six-year results of a prospective, controlled demographic trial of developmental dysplasia of the hip (DDH) treated in the Pavlik harness using ultrasound supervision. Our aim was to assess the value of ultrasound and its role in monitoring reduction in the harness, in terms of progression or failure of reduction at an early state. From 1988 to 1994, a total of 221 patients with 370 ultrasonographically abnormal hips was treated in the Pavlik harness. This represents a treatment rate for the Southampton district of 5.1 per 1000 live births. Sixteen hips in 12 patients were not reduced in the harness and required surgical treatment; 95.7% were successfully reduced. One case of mild avascular necrosis (0.3%) was identified in those treated by harness alone. Of the 221 patients 87.8% remain under radiological review, with 3.2% of affected hips showing continued, mild acetabular dysplasia. We conclude that ultrasound monitoring has led to an acceptably low level of intervention, a high reduction rate and minimal iatrogenic complications. The trial is continuing