Aims. Studies of infant hip development to date have been limited by considering only the changes in appearance of a single ultrasound slice (Graf’s standard plane). We used 3D ultrasound (3DUS) to establish maturation curves of normal infant hip development, quantifying variation by age, sex, side, and anteroposterior location in the hip. Methods. We analyzed 3DUS scans of 519 infants (mean age 64 days (6 to 111 days)) presenting at a tertiary children’s hospital for suspicion of developmental dysplasia of the hip (DDH). Hips that did not require ultrasound follow-up or treatment were classified as ‘typically developing’. We calculated traditional DDH indices like α angle (α. SP. ), femoral head coverage (FHC. SP. ), and several novel indices from 3DUS like the acetabular contact angle (ACA) and osculating circle radius (OCR) using custom software. Results. α angle, FHC, and ACA indices increased and OCR decreased significantly by age in the first four months, mean α. SP. rose from 62.2° (SD 5.7°) to 67.3° (SD 5.2°) (p < 0.001) in one- to eight- and nine- to 16-week-old infants, respectively. Mean α. SP. and mean FHC. SP. were significantly, but only slightly, lower in females than in males. There was no statistically significant difference in DDH indices observed between left and right hip. All 3DUS indices varied significantly between anterior and posterior section of the hip. Mean 3D indices of α angle and FHC were significantly lower anteriorly than posteriorly: α. Ant. = 58.2° (SD 6.1°), α. Post. = 63.8° (SD 6.3°) (p < 0.001), FHC. Ant. = 43.0 (SD 7.4), and FHC. Post. = 55.4° (SD 11.2°) (p < 0.001). Acetabular rounding measured byOCR indices was significantly greater in the anterior section of the hip (p < 0.001). Conclusion. We used 3DUS to show that hip shape and normal growth pattern vary significantly between anterior and posterior regions, by magnitudes similar to age-related changes. This highlights the need for careful selection of the Graf plane during 2D ultrasound examination. Whole-joint evaluation by obtaining either 3DUS or manual ‘sweep’ video images provides more comprehensive DDH assessment. Cite this article: Bone Jt Open 2022;3(11):913–923

Background: Information on embryological hip development has been obtained from post mortem examination. There is less information on normal foetal hip. Magnetic resonance imaging (MRI) allows development to be followed in the healthy baby. AIM: To assess the value of MRI of the foetus and neonate to provide information on normal and abnormal hip development. To establish normal patterns of hip development. To obtain charts that could be used to detect abnormality earlier. There are three aspects to this study:. Validation – analysing MRI scans of babies hips prior to post mortem (the gold standard) would verify MRI as a valid tool for such studies. Measurements will be gained for foetus in utero. Similarly for pre and term babies. PATIENT SELECTION: 30 patients for each aspect of this pilot study, 90 in total (3). For the initial validation process, parents who had consented to post mortem were asked to consider additionally an MR scan of their neonate’s hips, a total of 30 cases. Method: MR images in axial and coronal planes were obtained using a high resolution T2 weighted sequences (4). Measurements were made, by two independent observers, of the width and depth of the acetabulum and the radius & diameter of the femoral head, volume and area were calculated. Inter-observer variation was assessed. Results: The babies ranged in gestation from 17 – 42 weeks. With the exception of the acetabular width each dimension showed little development until week 20 when the line of growth rose exponentially. The acetabular width showed only a slow rate of growth despite the changes seen in the femoral head. Levels of observer agreement were high (ICCs = 0.98) for all but depth (ICCs = 0.86). The measurements for all dimensions were in line with previous post mortem studies. CONCLUSION: MRI is a valid and acceptable alternative to post mortem in the assessment of hip development eventually allowing early detection of abnormal hip development

Background Information on embryological hip development has been obtained from post mortem examination (1). There is less information on normal fetal hip (2). Magnetic resonance imaging (MRI) allows development to be followed in the healthy baby. Aim To assess the value of MRI of the foetus and neonate to provide information on normal and abnormal hip development. To establish normal patterns of hip development. To obtain charts that could be used to detect abnormality earlier. There are three aspects to this study:. Validation – analysing MRI scans of babies hips prior to post mortem (the gold standard) would verify MRI as a valid tool for such studies. Similarly for a) fetuses in utero b) pre and term babies. Patient selection 30 patients for each aspect of this pilot study, 90 in total (3). For the initial validation process, parents who had consented to post mortem were asked to consider additionally an MR scan of their neonate’s hips, a total of 30 cases. Method MR images in axail and coronal planes were obtained using a high resolution T2 weighted sequences (4). Measurements were made, by two independent observers, of the width and depth of the acetabulum and the radius & diameter of the femoral head, volume and area were calculated. Inter-observer variation was assessed. Results The babies ranged in gestation from 17 – 42 weeks. With the exception of the acetabular width each dimension showed little development until week 20 when the line of growth rose exponentially. The acetabular width showed only a slow rate of growth despite the changes seen in the femoral head. Levels of observer agreement were high (ICCs 95% = 0.98) for all but depth (ICCs 95% = 0.86). The measurements for all dimensions were in line with previous post mortem studies. Conclusion MRI is a valid and acceptable alternative to post mortem in the assessment of hip development eventually allowing early detection of abnormal hip development

Purpose: To study the development of the hip and the relationship of radiological angles between acetabulum and proximal femur in children 0–3 years and thus the influence of walking and weight bearing on hip development. Material and Methods: A study mesuring radiological angles in antero-posterior X-rays of pelvis in 334 children between 0 a 3 years of age (1997–2005), including acetabular index (AI) and physeal proximal angle (PPA (Alsberg’ angle) with goniometer (error ± 1°). Patients with pelvis or femur fractures or inflammatory diseases were excluded. Age distribution was of 1 (69.2%), 2 (22.2%) and 3 years (8.7%). 36.8% were males and 63.2% females. Descriptive statistics, T- test, Spearman correlation and ANOVA were used. Level of significance p< 0.05. Results: The mean AI was 20.2°, 19.9° and 17.3°, in 1, 2 and 3 years. The AI angle diminishes significatively in children older than 2 years of age (p = 0.002). The mean PPA was 79.5°, 74.9° and 74.2°, in 1,2 y 3 years respectively. The Alberg’s angle reduced significatively at 1 year of age (p = 0.0005). AI and PPA was higher in females after 1 year of age (p = 0.02 and p = 0.04). There are not significative correlation between AI and Alsberg’ angle in different groups of children (r = 0.03). The age was important factor in both angles changes (p = 0.0005), but female patients (p = 0.002) and left side (p = 0.02) influenced only in AI. Conclusions: AI and PPA angles reduced with age specially in 2 and 1 year, respectively, suggesting the effect of weight bearing and walking on hip shape. There was not relation between both angles in different groups of age

Femoroacetabular impingement (FAI) causes pain and chondrolabral damage via mechanical overload during movement of the hip. It is caused by many different types of pathoanatomy, including the cam ‘bump’, decreased head–neck offset, acetabular retroversion, global acetabular overcoverage, prominent anterior–inferior iliac spine, slipped capital femoral epiphysis, and the sequelae of childhood Perthes’ disease.

Both evolutionary and developmental factors may cause FAI. Prevalence studies show that anatomic variations that cause FAI are common in the asymptomatic population. Young athletes may be predisposed to FAI because of the stress on the physis during development. Other factors, including the soft tissues, may also influence symptoms and chondrolabral damage.

FAI and the resultant chondrolabral pathology are often treated arthroscopically. Although the results are favourable, morphologies can be complex, patient expectations are high and the surgery is challenging. The long-term outcomes of hip arthroscopy are still forthcoming and it is unknown if treatment of FAI will prevent arthrosis.

Introduction and Aims: In the management of newborn’s hips, ultrasonography (US) has proven to be a useful tool. However, the progression of measurements at different ages in normal hips has not been thoroughly investigated. This prospective study assessed the longitudinal development of clinically stable hips from birth to the age of 12 weeks.

Method: Forty newborn children (80 hips) with clinically stable hips were assessed by ultrasound at three points in time – namely within the first few days of life, at six weeks of age and finally at 12 weeks of age. Femoral Head Coverage (FHC) as well as Graf’s alpha and beta angles were measured.

Results: A significant change in all values occurred between the three points in time (p< 0.001). The mean FHC progressed from 58% at birth, to 65% and 69% at six weeks and at 12 weeks respectively. The mean alpha angle improved from 70 degrees to 77 degrees and then 80 degrees at birth, six weeks and at 12 weeks, respectively. The mean beta angle progressed from 52 degrees to 46 degrees and then 43 degrees at birth, at six weeks and at 12 weeks, respectively.

Conclusion: In clinically stable hips, the FHC, alpha and beta angles change significantly over time. It is important, therefore, to consider the baby’s age when interpreting US images, especially when making management decisions regarding splintage. This has important implications if ultrasound is used as a screening tool.

Introduction and Objectives: The aim of this study is to analyze changes seen on X-ray of the acetabular index, Wiberg’s angle, Sharp’s angle and the continuity of Shenton’s line after osteotomy performed by means of the Dega technique in developmental dysplasia of the hip (DDH).

Materials and Methods: We retrospectively analyzed 72 histories of children that underwent surgery performed using the Dega technique at the Niño Jesús Hospital over the last 15 years. We measured the rupture of the Shenton line, the acetabular index, Wiberg’s centre-edge angle and Sharp’s acetabular angle preoperatively; and then approximately 1 year after surgery and at the last X-ray control in the medical history.

Results: The acetabular index changed from 33° preoperatively to 24° one year after surgery. At the last X-ray control the acetabular index was 23°. Wiberg’s centre-edge angle is normalized by osteotomy, and changed from 6° preoperatively to 20° after surgery. At the last X-ray it was 23°. However, Sharp’s acetabular angle only suffered slight modifications. It changed from 50° to 48° with surgery.

Discussion and Conclusions: The Dega osteotomy is an effective technique to provide acetabular coverage in hips suffering from dysplasia before the closure of the triradiate cartilage. Both the acetabular index and Wiberg’s angle vary significantly with surgery, and become normalized in most cases. This correction is stable over time. However, the same cannot be said for Sharp’s acetabular angle which barely changes with osteotomy.

Software to segment and to analyse connective CT-scan images of the bone-cement-stem complex was developed and validated. Parameters assessed included: volumes (cortical bone, cancelous bone, cement, stem, air in bone and air in cement), cement mantle thickness, cortical & cancelous bone thickness, contact surface area between cement and bone, degree of centralisation (stem in cement, stem and cement in cancelous and in cortical bone). To validate and assess intra- and interob-server reliability two models were implanted in two dried macerated cadaver femurs using a third generation cementing technique. In the first a polished tapered stem (CPT, Zimmer) was cemented and removed after cement curing. The air filled cavity within the cement mantle could be identified as implant, avoiding metallic scatter artefacts. The second model (SLA) used a plastic stem prototype produced by computer design and a rapid prototyping stereolithographic technique. This model does not need to be removed before CT-scanning and allows assessment of whatever femoral implant. Validation occurred by comparing 41 manually segmented femoral cross-sections (25 CPT, 16 SLA) with data of corresponding CT-scan slices. Inter-observer reliability was assessed by having the same person performing the CT-scan and the analysis of both models four times. To assess intra-observer reliability, four different observers segmented 97 representative CT-images (46 CPT, 51 SLA). The average accuracy for surfaces areas (bone, cement, stem) within CT-images was 7.47 mm2 (1.80%), bone & cement mantle thickness: 0.51 mm (9.39%), distances between centroids (stem-cement, stem-bone, cement-bone): 0.38 mm (18.5%) and contours (bone, cement): 0.27 mm (2.57%). The intra- and interobserver reliability of air content in bone and cement was suboptimal (intraclass-correlation coefficient (ICC) as low as 0.54, average ICC: 0.85). All other variables assessed were reliable (ICC > 0.81, average ICC: 0.96). Validity and reliability were comparable when assessed separately for the proximal, middle and distal third of both models. This in vitro technique can assess characteristics of cement mantles produced by different cementing techniques, centralizers and existing femoral implants or stem prototypes.

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells. Cite this article: Bone Joint Res 2020;9(12):857–869

Avascular necrosis (AVN) of the femoral head is a potentially devastating complication of treatment for developmental dysplasia of the hip (DDH). AVN most commonly occurs following operative management by closed (CR) or open reduction (OR). This occurrence has frequently been examined in single centre, retrospective studies, however, little high-level evidence exists to provide insight on potential risk factors. The purpose of this observational, prospective multi-centre study was to identify predictors of AVN following operatively-managed DDH. A multi-centre, prospective database of infants diagnosed with DDH from 0–18 months was analyzed for patients treated by CR and/or OR. At minimum one year follow-up, the incidence of AVN (Salter criteria) was determined from AP pelvis radiographs via blinded assessment and consensus discussion between three senior paediatric orthopaedic surgeons. Patient demographics, clinical exam findings and radiographic data were assessed for potential predictors of AVN. A total of 139 hips in 125 patients (102 female, 23 male) underwent CR/OR at a median age of 10.4 months (range 0.7–27.9). AVN was identified in 37 cases (26.6% incidence) at a median 23 months post-surgery. Univariate logistic regression analysis comparing AVN and no AVN groups identified sex, age at diagnosis, age at surgery, pre-surgery IHDI grade and time between diagnosis and surgery as potential predictive factors. Specifically, male sex (OR 2.21 [0.87,5.72]), IHDI grade IV, and older age at diagnosis (7.4 vs. 9.5 months) and surgery (10.2 vs. 13.6 months) were associated with development of AVN. Likewise, increased time between diagnosis and surgery (2.9 vs. 5.5 months) was also associated with a higher incidence. No association was found with surgery type (CR vs. OR), pre-surgery acetabular index or surgical hip. Development of AVN occurred in 26.6% of hips undergoing CR or OR at a median 23 months post-surgery. Male sex, older age at diagnosis and surgery, dislocation severity and increased time between diagnosis and surgery were associated with AVN. Longer-term follow-up and larger numbers will be required to confirm these findings. Early outcomes from this prospective patient cohort suggest that AVN is an important complication of operative management for DDH, and appears to occur at a comparable rate whether the reduction is performed open or closed. Male patients may be more susceptible to developing AVN and merits further exploration. Potential predictive factors of older age and length of time between diagnosis and surgery emphasize the importance of early detection and treatment to minimize complications and optimize outcomes

Aims

Eccentric reductions may become concentric through femoral head ‘docking’ (FHD) following closed reduction (CR) for developmental dysplasia of the hip (DDH). However, changes regarding position and morphology through FHD are not well understood. We aimed to assess these changes using serial MRI.

Aims. Femoroacetabular impingement (FAI) is a potential cause of hip osteoarthritis (OA). The purpose of this study was to investigate the expression profile of matrix metalloproteinases (MMPs) in the labral tissue with FAI pathology. Methods. In this study, labral tissues were collected from four FAI patients arthroscopically and from three normal hips of deceased donors. Proteins extracted from the FAI and normal labrums were separately applied for MMP array to screen the expression of seven MMPs and three tissue inhibitors of metalloproteinases (TIMPs). The expression of individual MMPs and TIMPs was quantified by densitometry and compared between the FAI and normal labral groups. The expression of selected MMPs and TIMPs was validated and localized in the labrum with immunohistochemistry. Results. On MMP arrays, most of the targeted MMPs and TIMPs were detected in the FAI and normal labral proteins. After data normalization, in comparison with the normal labral proteins, expression of MMP-1 and MMP-2 in the FAI group was increased and expression of TIMP-1 reduced. The histology of the FAI labrum showed disorderly cell distribution and altered composition of thick and thin collagen fibres. The labral cells expressing MMP-1 and MMP-2 were localized and their percentages were increased in the FAI labrum. Immunohistochemistry confirmed that the percentage of TIMP-1 positive cells was reduced in the FAI labrum. Conclusion. This study established an expression profile of MMPs and TIMPs in the FAI labrum. The increased expression of MMP-1 and MMP-2 and reduced expression of TIMP-1 in the FAI labrum are indicative of a pathogenic role of FAI in hip OA development. Cite this article:Bone Joint Res. 2020;9(4):173–181

Between June 1988 and December 1997, 332 babies with 546 dysplastic hips were treated in the Pavlik harness for primary Developmental Dysplasia (DDH) as a product of the Southampton selective screening program. Each was managed by a strict protocol including ultrasonic monitoring of treatment within the harness. The group was prospectively studied over a mean duration of 6. 5 years (SD=2. 7y) with 89. 1% follow-up. The Acetabular Index (AI) and Centre-Edge angle of Wiberg (CEA) were measured on annual radiographs to determine the natural history of hip development following treatment in the Pavilik harness. These were compared to published normal values. We observed a failed reduction rate of 15. 2% of all complete hip dislocations; these required alternative surgical treatment. The development of those hips of infants successfully treated in the harness showed no significant difference from the normal values of Acetabular Index for female left hips, after eighteen months of age. Of those dysplastic hips that were successfully reduced in the harness; 2. 4% exhibited persisting significant late dysplasia (CEA< 20°) and 0.2% demonstrated persistent severe late dysplasia (CEA< 15 °) All such cases could be identified at sixty months. Dysplasia was clinically deemed sufficient to merit innominate osteotomy in 0. 9% dysplastic hips treated. Avascular necrosis was noted in 1% of hips treated in the harness. We conclude that using our protocol, successful initial treatment of DDH with the Pavlik harness appears to revert the natural history of hip development to that of the normal population. We recommend that regular radiographic surveillance up to 60 months of age constitutes safe and effective practice

Aims

This study aimed to evaluate sagittal spinopelvic alignment (SSPA) in the early stage of rapidly destructive coxopathy (RDC) compared with hip osteoarthritis (HOA), and to identify risk factors of SSPA for destruction of the femoral head within 12 months after the disease onset.

Aims

The lateral centre-edge angle (LCEA) is a plain radiological measure of superolateral cover of the femoral head. This study aims to establish the correlation between 2D radiological and 3D CT measurements of acetabular morphology, and to describe the relationship between LCEA and femoral head cover (FHC).

Purpose. Following closed or open reduction for developmental dysplasia of the hip (DDH), assessment of reduction is essential. With potentially poor accuracy in confirming reduction, the risk of abnormal hip development and ultimately poor outcome exists if reduction is not achieved. Computed tomography (CT) has been used in recent years to assess reduction. The aim of this study was to compare the accuracy in confirming hip reduction following closed or open reduction in children with DDH, using CT and plain radiographs and to decide whether CT scans improved the assessment of reduction. Methods. We retrospectively reviewed 6 patients treated for DDH at an Academic Hospital. The patients were treated with either closed or open reduction. Post operatively radiographs and CT scans were obtained to assess reduction. Reduction was assessed using Shenton's line, medial joint space, a femoral mid-cervical line through the tri-radiate cartilage and a tri-radiate intersectional line on axial CT. The CT scans were analyzed using Osirix on an Apple Macintosh computer. Results. We were able to obtain measurements in all parameters in only one radiograph, whereas in the CT images all parameters were determined. One patient had radiographs in which no values could be measured. The CT scan however confirmed reduction of that hip. In one patient we assessed a hip as reduced using all the parameters, whereas the tri-radiate intersectional line on axial CT and the Shenton's line on the coronal slice showed that in fact the head was posteriorly subluxed. Conclusion. We conclude that although CT scans did not change our management in this small patient series, CT scans did provide a better means of confirming hip reduction than plain radiographs for patients with DDH following closed or open reduction in a hip spica. NO DISCLOSURES

Background and Aims: Concentric pressure of the femoral head on acetabulum is the necessary prerequisite for normal hip development. In the case of diminished hip joint area an elevation of hip joint pressure ensues. If this pressure elevation lasts for a long period of time early degenerative changes are proposed to occur. The aim of our study is to substantiate the connection between hip joint pressure and occurrence of hip osteoarthritis in dysplastic hips. Methods: From 1955 to 1965 112 patients were treated non-operatively for hip dysplasia in developmental dysplasia of the hip in Dept. of Orthopaedic Surgery, Ljubljana. Using mathematical model of the hip, peak joint stress was measured in 27 patients, which met the enrolment criteria consisting of: a.) initial rentgenograph taken at least 20 years ago, b.) closed triradiate cartilage and no rentgenographic signs of osteoarthritis at the time of initial radiograph, c.) no neurological deþcit of lower limbs and no operative procedure during follow up period. All hips were re-examined clinically in year 2000. Results: Mean age at the latest follow up was 47 years (35 years to 61 years). Mean time interval between the rentgenograph from which the hip joint stress was measured and clinical examination was 27 years (20 years to 33 years). Signiþcant correlation was found between peak hip joint stress and Harris hip score (p 0.0013). Discussion and conclusions: Our results indicate that occurrence osteoarthritis of the hip could be related to the degree of hip dysplasia at the end of skeletal growth. The correlation between peak hip joint stress and Harris hip score was one order of magnitude larger than the corresponding correlation between CE angle and Harris hip score, which indicates that hip joint stress represents a valuable parameter describing the status of the hip joint

Early detection and management of developmental dysplasia of the hip (DDH) yields simpler and more effective the treatment. Diagnosis by ultrasound has changed the clinical view of the disease. However, the need and the way of ultrasound screening is still controversial. Diagnosis by ultrasound has shown that morphological abnormalities may not be associated with clinical signs. In Hungary all newborns are screened clinically within the first and also the third week of life, and controlled at the age of four month. Clinical examination is performed by an Ortopaedic specialist. Ultrasound screening is first performed for children with clinical signs and for children at risk at three weeks of age. Radiological examination, when necessary, is first performed at the age of four month. In the five year timeline (2001–2005) that was re-evaluated 7339 children presented 9706 times for screening for DDH at the University of Szeged (Hungary) Department of Orthopaedics. Out of these cases 6991 (95.2%) children were found to be healthy and 348 (4.8%) were diagnosed for DDH. Children with dysplasia presented 896 times for treatment and follow-up. Patient compliance in the DDH group was average 2.5 visits, while for the healthy group it was only average 1.2 visits. Because of clinical signs or risk factors 1569 (21%) children had ultrasound examination, all-together 2169 times. 84% of the initial ultrasound examination showed Graf stage Ia hip. Out of the diagnosed 348 DDH cases 31 patients (Graf IIa-IIc) were administered with Pavlik harness, and 314 (Graf Ib-IIa) were treated with splinting. Remaining 3 cases were diagnosed late, where no ultrasound examination was performed. In the DDH cases 832 ultrsonographic examination was performed during the treatment (average 2.4 examination/case). Radiographic control of all treated children excluded avascular necrosis in all cases. For this population 14 first operative procedure was needed so far. In our experience clinical screening and selective ultrasound examination is effective in the screening and early detection of developmental dyspalsia of the hip. In our practice, we promptly treated all patients with detected morphological changes as a deficiency in hip development. This way selective screening has helped us in the management of developmental dyspalsia of the hip. Hopefully, with the selective indication the number of false positive cases was reduced, while the „silent” clinical instabilities were given a chance for better long term development

Clinical screening aims to identify and treat infants with neonatal hip instability in order to reduce the risk of subsequent hip displacement but risks failures of diagnosis and treatment (abduction splinting) and potential iatrogenic effects. The Hip Trial aims to assess the clinical effectiveness of ultrasound (US) imaging compared to clinical assessment alone to guide the further management of infants with clinical hip instability. Infants with clinical hip instability confirmed by a second senior doctor were recruited from 33 UK centres and randomised to standardised US hip examination at age 2–8 weeks [US group: n=314] or clinical assessment alone [no ultrasound (NU) group: n=315. ] Primary outcomes by two years were hip X-ray appearances, operative treatment, abduction, splinting and walking. Analysis was ‘intention to treat’. Key prognostic factors were similar between the randomised groups. Protocol compliance was high (90% US; 92% NU). X-ray information was available for 91% by 12–14 months and 85% by two years. Fewer children in the US group had abduction splinting in the first two years (RR 0. 78; 95% CI 0. 65–0. 94; p=0. 01). Operative treatment was required by 21 US (6. 7%) and 25 NU (7. 9%) infants (RR 0. 84; 95% CI 0. 48–1. 47. ) By two years, subluxation, dislocation, acetabular dysplasia or avascular necrosis were identified on X-ray on one or both hips of 21 US and 21 NU children (RR 1. 00; 95% CI 0. 56 – 1. 80. ) One US and 4 NU children were not walking by two years (RR 0. 25; exact 95% CI 0. 03–2. 53; p=0. 37). The use of US imaging in infants with screen-detected clinical hip instability allows abduction splinting rates to be reduced, and is not associated with an increase in abnormal hip development or higher rates of operative treatment by two years of age

Aims

Our retrospective analysis reports the outcome of patients operated for slipped capital femoral epiphysis using the modified Dunn procedure. Results, complications, and the need for revision surgery are compared with the recent literature.