The value of MRI undertaken immediately after reduction of the hip as a predictor of long-term acetabular dysplasia

Hip Morphology on Post-Reduction MRI Predicts Residual Dysplasia 10 Years After Open or Closed Reduction

BACKGROUND

There is limited evidence supporting the value of morphological parameters on post-reduction magnetic resonance imaging (MRI) to predict long-term residual acetabular dysplasia (RAD) after closed or open reduction for the treatment of developmental dysplasia of the hip (DDH).

METHODS

We performed a retrospective study of 42 patients (47 hips) undergoing open or closed reduction with a minimum 10 years of follow-up; 39 (83%) of the hips were in female patients, and the median age at reduction was 6.3 months (interquartile range [IQR], 3.3 to 8.9 months). RAD was defined as additional surgery with an acetabular index >2 standard deviations above the age- and sex-specific population-based mean value or Severin classification grade of >2 at last follow-up. Acetabular version and depth-width ratio, coronal and axial femoroacetabular distance, cartilaginous and osseous acetabular indices, transverse ligament thickness, and the thickness of the medial and lateral (limbus) acetabular cartilage were measured on post-reduction MRI.

RESULTS

At the time of final follow-up, 24 (51%) of the hips had no RAD; 23 (49%) reached a failure end point at a median of 11.4 years (IQR, 7.6 to 15.4 years). Most post-reduction MRI measurements, with the exception of the cartilaginous acetabular index, revealed a significant distinction between the group with RAD and the group with no RAD when mean values were compared. The coronal femoroacetabular distance (area under the receiver operating characteristic curve [AUC], 0.95; 95% confidence interval [CI], 0.90 to 1.00), with a 5-mm cutoff, and limbus thickness (AUC, 0.91; 95% CI, 0.83 to 0.99), with a 4-mm cutoff, had the highest discriminatory ability. A 5-mm cutoff for the coronal femoroacetabular distance produced 96% sensitivity (95% CI, 78% to 100%), 83% specificity (95% CI, 63% to 95%), 85% positive predictive value (95% CI, 65% to 96%), and 95% negative predictive value (95% CI, 76% to 100%). A 4-mm cutoff for limbus thickness had 96% sensitivity (95% CI, 78% to 100%), 63% specificity (95% CI, 41% to 81%), 71% positive predictive value (95% CI, 52% to 86%), and 94% negative predictive value (95% CI, 70% to 100%).

CONCLUSIONS

Coronal femoroacetabular distance, a quantitative metric assessing a reduction's concentricity, and limbus thickness, a quantitative metric assessing the acetabulum's cartilaginous component, help to predict hips that will have RAD in the long term after closed or open reduction.

LEVEL OF EVIDENCE

Diagnostic Level IV . See Instructions for Authors for a complete description of levels of evidence.

MRI hip morphology is abnormal in unilateral DDH and increased lateral limbus thickness is associated with residual DDH at minimum 10-year follow-up

Purpose:

The purpose of the study was to compare the post-reduction magnetic resonance imaging morphology for hips that developed residual acetabular dysplasia, hips without residual dysplasia, and uninvolved contralateral hips in patients with unilateral developmental dysplasia of the hip undergoing closed or open reduction and had a minimum 10-year follow-up.

Methods:

Retrospective study of patients with unilateral dysplasia of the hip who underwent open/closed hip reduction followed by post-reduction magnetic resonance imaging. Twenty-eight patients with a mean follow-up of 13 ± 3 years were included. In the treated hips, residual dysplasia was defined as subsequent surgery for residual acetabular dysplasia or for Severin grade > 2 at latest follow-up. On post-reduction, magnetic resonance imaging measurements were performed by two readers and compared between the hips with/without residual dysplasia and the contralateral uninvolved side. Magnetic resonance imaging measurements included acetabular version, coronal/ axial femoroacetabular distance, acetabular depth–width ratio, osseous/cartilaginous acetabular indices, and medial/lateral (limbus) cartilage thickness.

Results:

Fifteen (54%) and 13 (46%) hips were allocated to the “no residual dysplasia” group and to the “residual dysplasia” group, respectively. All eight magnetic resonance imaging parameters differed between hips with residual dysplasia and contralateral uninvolved hips (all p < 0.05). Six of eight parameters differed (all p < 0.05) between hips with and without residual dysplasia. Among these, increased limbus thickness had the largest effect (odds ratio = 12.5; p < 0.001) for increased likelihood of residual dysplasia.

Conclusions:

We identified acetabular morphology and reduction quality parameters that can be reliably measured on the post-reduction magnetic resonance imaging to facilitate the differentiation between hips that develop with/without residual acetabular dysplasia at 10 years postoperatively.

Level of evidence:

level III, prognostic case-control study.

Correlation of postoperative magnetic resonance image measurements with persisting acetabular dysplasia in open reduction of developmental hip dysplasia

Objectives

The aim of this study was to evaluate correlation of post-reduction magnetic resonance imaging (MRI)-based parameters with residual acetabular dysplasia in developmental dysplasia of the hip (DDH) patients who underwent open reduction.

Patients and methods

A total of 62 hips of 54 children (5 males, 57 females; mean age: 8.5±3.5 months; range, 0 to 24 months) with a diagnosis of DDH who underwent open reduction between January 2012 and January 2017 were retrospectively analyzed. The acetabular head index (AHI), head coverage index (HCI), sphericity, bony acetabular index (BAI), cartilage acetabular index (CAI), anterior acetabular index (AAI), posterior acetabular index (PAI), abduction angle (AA), and acetabular medial wall thickness were measured by MRI. The correlation between MRI measurements and residual acetabular dysplasia was evaluated.

Results

The mean follow-up was 23.7±10.1 (range, 12 to 56) months. The mean age at the final examination was 47.6±10.4 months. The age at the time of operation (r=0.250, p=0.049), medial wall thickness (r=0.304, p=0.016), AAI (r=0.729, p<0.001), PAI (r=0.590, p<0.001), and early postoperative AI (r=0.900, p<0.001) at the third postoperative month were positively correlated with the last follow-up AI. The AHI (r=-0.512, p<0.001), sphericity (r=-0,661, p<0.001), and HCI (r=-0.554, p <0.001) were negatively correlated with the last follow-up AI.

Conclusion

Post-reduction MRI parameters can be used to evaluate correlation with persistent acetabular dysplasia in DDH patients.

Imaging of developmental dysplasia of the hip: ultrasound, radiography and magnetic resonance imaging

Developmental dysplasia of the hip (DDH) describes a broad spectrum of developmental abnormalities of the hip joint that are traditionally diagnosed during infancy. Because the development of the hip joint is a dynamic process, optimal treatment depends not only on the severity of the dysplasia, but also on the age of the child. Various imaging modalities are routinely used to confirm suspected diagnosis, to assess severity, and to monitor treatment response. For infants younger than 4 months, screening hip ultrasound (US) is recommended only for those with risk factors, equivocal or positive exam findings, whereas for infants older than 4-6 months, pelvis radiography is preferred. Following surgical hip reduction, magnetic resonance (MR) imaging is preferred over computed tomography (CT) because MR can not only confirm concentric hip joint reduction, but also identify the presence of soft-tissue barriers to reduction and any unexpected postoperative complications. The routine use of contrast-enhanced MR remains controversial because of the relative paucity of well-powered and validated literature. The main objectives of this article are to review the normal and abnormal developmental anatomy of the hip joint, to discuss the rationale behind the current recommendations on the most appropriate selection of imaging modalities for screening and diagnosis, and to review routine and uncommon findings that can be identified on post-reduction MR, using an evidence-based approach. A basic understanding of the physiology and the pathophysiology can help ensure the selection of optimal imaging modality and reduce equivocal diagnoses that can lead to unnecessary treatment.

Quality of reduction and prognosis of developmental dysplasia of the hip: a retrospective study

INTRODUCTION

Using limited MRI we evaluated the quality of closed reduction and prognosis in a group of patients with developmental dysplasia of the hip (DDH).

METHODS

Limited MRI was performed on 28 DDH patients (41 hips) after closed reduction. All the hips were divided into deep and incomplete concentric reduction groups according to the femoral head-acetabular distance (FAD) and the shape of the labrum on limited MRI. The abduction angle of the hips, and the initial and final acetabular index (AI) were measured. Presence or absence of the ossification centre of the femoral head before treatment, the Tönnis classification and avascular necrosis of the femoral head and types (Bucholz and Ogden type) were recorded. The data of the 2 groups were analysed with SPSS software.

RESULTS

We found no significant differences in age, gender, side, preoperative ossification centre of the femoral head, preoperative AI, decreased postoperative AI and abduction angles of hips between the 2 groups. There were significant statistical differences in the preoperative Tönnis grade, FAD after reduction, AI at the final follow-up, severe residual deformity and severe avascular necrosis of the femoral head (p&lt;0.05). The cure rate showed a significant trend (p = 0.052).

CONCLUSIONS

Limited MRI enables effective determination of the quality of reduction immediately after closed reduction. The prognosis of the deep concentric reduction group was better than the group with incomplete concentric reduction.

Reliability of indices measured on infant hip MRI at time of spica cast application for dysplasia

PURPOSE

Infants with persistent developmental dysplasia of the hip (DDH) after harness treatment may be treated by operative reduction and spica casting, with post-reduction hip alignment assessed by magnetic resonance imaging (MRI), which can demonstrate three-dimensional hip geometry. This may provide valuable information regarding prognosis and adequacy of management, but such scans are difficult to assess due to limited spatial resolution and artefacts caused by patient motion. This may account for the limited success in correlating MRI findings to clinical outcomes to date. As a first step to improving these results we tested whether MRI indices of hip deformity and quality of femoral head reduction could be reliably measured.

PROCEDURES

We retrospectively studied children with DDH, post-spica-cast MRI, and radiographic follow-up. We measured MRI indices adapted from other reports using computed tomography (CT) and MRI, and added new indices. Inter-observer reliability and inter-index correlations were evaluated and indices adapted during the process.

FINDINGS

We observed 55 dysplastic hips in 41 infants. Despite difficulties inherent to infant hip MRI, several indices were measured with substantial agreement (kappa up to 0.88, intra-class correlation ICC up to 0.91), with highly significant (p<0.01) correlation with each other (up to r = 0.72). Reliable indices included coronal acetabular angle, pulvinar fat-pad thickness, presence of a barrier to reduction, and grades of subluxation and dysplasia.

CONCLUSION

Indices on MRI scan post hip spica cast placement can be measured reliably, assessing acetabular geometry, degree of hip reduction and barriers to reduction.

Utility of magnetic resonance imaging (MRI) after closed reduction of developmental dysplasia of the hip

PURPOSE

Magnetic resonance imaging (MRI) has been successfully used in the determination of the adequacy of the surgical reduction of congenitally dislocated hips in children. We present the results of a prospective series of patients treated conservatively. MRI was performed in all hips after positioning was deemed adequate on radiographs after spica cast application. The goal of this study was to evaluate the usefulness of MRI in this indication.

METHODS

After the study was approved by our local ethics committee, 31 patients for a total of 36 dislocated hips were included. After the traction period, hip testing was performed and a hip spica cast was applied under general anaesthesia. All children had MRI within 1 week of reduction, without the need for contention or general anaesthesia. Hip reduction was assessed on axial and coronal MRI images.

RESULTS

The concentric reduction of the hip was confirmed in 30 cases out of 36. In three cases, the dislocation was retrospectively suspected on radiographs and then confirmed. In the three remaining cases, hip dislocation was only diagnosed on MRI.

CONCLUSIONS

MRI screening of congenitally dislocated hips after reduction procedures is a safe and reliable procedure to assess the concentric reduction of the hip. Even in doubtful cases, MRI detected persistent hip dislocations and was conducive to iterative reduction and satisfactory outcome and result.

Magnetic resonance evaluation of acetabular residual dysplasia in developmental dysplasia of the hip: a preliminary study of 27 patients

Thirty-one hips in 27 young girls, treated for developmental dysplasia of the hip in the authors' institute since 2003, showed persistent radiographic evidence of residual acetabular dysplasia. These hips were registered as candidates for pelvic osteotomy. A prospective study was conducted and these hips were evaluated by magnetic resonance imaging (MRI); the average age of the patients was 5 years. MRI measurement of acetabular angle and acetabular head index in 2 different landmarks (bone and cartilage) was performed. The results were correlated with plain radiographic film evolution. MRI studies revealed sufficient cartilaginous acetabular coverage in 27 hips, cartilaginous acetabular dysplasia in 2 hips, and short acetabulum in 2 others. The 27 hips with thick cartilage of the acetabular roof were subsequently followed up by plain radiographs. The average follow-up period was 2.1 years. The authors observed a spontaneous progressive ossification of the cartilaginous acetabular roof in all the 27 cases. In 4 cases, the correction of the acetabular angle was complete. They concluded that MRI promotes more accurate selection of patients for pelvic osteotomy and aids in the choice of the most appropriate type of osteotomy. Clinical imaging examples are presented and need to be further evaluated.

Radiographic study of the acetabulum and proximal femur between 1 and 3 years of age

BACKGROUND

The angle formed by the intersection of the line between triradiate cartilage of both hips (Hilgenreiner's line) and a line drawn between triradiate cartilage and the external roof of the acetabulum is called the acetabular index (AI), the angle formed by line of proximal femoral physis and middiaphysis axis of femur is called the epiphyseal angle (EA). Both decrease with age, but it is not described whether there is a relation between them in this development. It would be very useful to compare its evolution in children with normal hips, in order to compare them with dysplasic hips in the same groups of age.

OBJECTIVE

To study the radiographic angles and the relationship between the acetabulum and the proximal femur.

MATERIALS AND METHODS

Retrospective study was performed on pelvic X-rays in 224 children between 1 and 3 years of age. Children with injuries, sepsis or inflammatory disease were excluded. We measured by goniometer (error +/-1 degrees ): the AI, and the angle of the proximal femoral physis (EA). We have compared statistically the parameters.

RESULTS

The AI was 21.1 degrees (+/-3.8), 19.9 degrees (+/-3.5), and 16.1 degrees (+/-4.2) and EA was 75.8 degrees (+/-5.1), 75.9 degrees (+/-6.3), and 75.6 degrees (+/-4.7), at the ages of 1, 2, and 3 years, respectively. A significant difference was noted for AI between 2 and 3 years old (P = 0.003), but there was not significative EA decrease. No significant correlation was found between AI and EA among the different groups, nor overall (r = 0.03). Sex or side was not a significant factor for both angles.

CONCLUSION

The AI decreases significantly between 1 and 3 years of age, but not the EA. No significant relation was found between them in the different age groups. Normal children's hips have a tendency to spontaneously improve its acetabular morphology during the first 3 years of life.

Imaging in the surgical management of developmental dislocation of the hip

Although the use of ultrasound in the diagnosis and early treatment of developmental dysplasia of the hip (DDH) has reduced the number of patients diagnosed late and decreased the number of operative procedures, surgical treatment is still needed in some patients. Late cases continue to occur as a result of missing the screening examination, being normal at initial screening and missing followup. Dysplasia may persist despite appropriate nonoperative or operative treatment. Many of these patients subsequently undergo closed or open reduction and femoral or acetabular reconstruction. Ultrasound of the hips is generally used up to 6 or 8 months of age, during which time the hips are largely cartilaginous, and radiographs after that time when bony development is more complete. Options to supplement ultrasound and radiography include arthrography, computed tomography, and magnetic resonance imaging. Several advances have been made in the imaging of DDH and its complications including acetabular labral pathology and of femoroacetabular impingement (FAI). We review imaging techniques other than ultrasound used in the management of DDH.

LEVEL OF EVIDENCE

Level V, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.