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      Magnetic resonance imaging evaluation of the effects of closed reduction in infants with developmental dysplasia of the hip

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      Chinese Medical Journal
      Lippincott Williams & Wilkins

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          Abstract

          To the Editor: Manual closed reduction has become the most common treatment for infants with developmental dysplasia of the hip (DDH), especially those under 18 months old, because it can minimize the limitations of the post-operative range of motion of the hip joint and reduce iatrogenic avascular necrosis.[1] As 90% of children with symptomatic DDH have lesions on the acetabular labrum, we initiated a magnetic resonance imaging (MRI) study of acetabular labrums of dysplastic hips to determine how magnetic resonance-based parameters and contents of joint space could be used to evaluate the therapeutic effect of closed reduction in DDH patients.[2] This is a descriptive and retrospective study. A total of 23 patients (four male and 19 female) were included in the study, all of them were less than 18 months old and undergone closed reduction surgery in the Third Affiliated Hospital of Southern Medical University from January 2016 to December 2017 during the study period. Patients were inspected using a 1.5-T MRI scanner (Ingenia, Philips, the Netherlands) with the femurs at an abduction angle of 60°. Clear and qualified MRI data of the hip were collected within one week before and after the surgery. One study[3] found that the MRI-based parameters, such as labral angle (LA) and zone of compressive force (ZCF), could be used to evaluate the structure of the labrum. Figure 1A shows the measurement of LA, which is the angle between the labrum and the acetabulum. Line H is a baseline that was drawn horizontally through the superior aspect of the triradiate cartilage, and a second line was drawn through the bony margin of the acetabulum. Following this, a line was determined representing the direction of the labrum (Line A), which is the midline between the inner and outer appendages (points B and C) and the distal apex. Figure 1B shows the determination of ZCF. ZCF is a zone entered by a line perpendicular to Line H, then tilted inward 16° (the resultant force of partial body weight and the abductor muscle group) and passed through the center of the femoral head, which is used to assess the relationship between the affected hip and the compression force acting on it.[4] The upper part of the acetabular bone is divided into three equal areas, which are numbered as 2, 3, and 4, with zone 1 consisting of the labrum alone. All parameters were measured three times on proton-density-weighted spectral pre-saturation attenuated inversion recovery sequence by two radiologists with more than 10 years of experience, then averaged. We observed and classified three kinds of post-operative conditions in DDH patients, including concentric reduction, near reduction, and mild subluxation, which are different from the clinical classification. These assessments were based on the MRI results of LA∗ (affected-unaffected side), ZCF, and joint space content. Figure 1 The determination of the MRI-based parameters and the MRI examples of three kinds of post-operative conditions. (A) Measurement of LA; (B) Determination of the ZCF; (C) PDW-SPAIR image showing that the left hip achieved concentric reduction after surgery; (D) PDW-SPAIR image showing that the left hip achieved near reduction after surgery. (E) PDW-SPAIR image showing that the right hip achieved mild subluxation after surgery. LA: Labral angle; MRI: Magnetic resonance imaging; PDW-SPAIR: Proton-density-weighted spectral pre-saturation attenuated inversion recovery; ZCF: Zone of compressive force; AI: acetabular index. Results indicated that eight cases experienced a complete concentric reduction, eight cases experienced near reduction, and seven cases displayed mild subluxation. Figures 1C–E show the MRI examples of concentric reduction, near reduction, and mild subluxation, respectively. The LA∗ values of the cases with concentric reduction were all <0° (average −15°). Additionally, all ZCF measures were in the 3-area and transverse acetabular ligaments were observed. The LA∗ of the cases with near reduction were all <0° (average −4.5°). As for the ZCF assessment, two cases were in area 2, two cases were in area 4, and the remaining five cases were in area 3, and there were transverse acetabular ligaments and fibrous tissue observed in the hip joint space. Seven cases showed mild subluxation, with an average LA∗ value of 1°. ZCF assessment yielded four cases in area 4 and four cases in area 3. There were transverse acetabular ligaments, iliac ligaments, and fibrous tissue embedded within the hip joint gap. Through comparative observations of MRI of patients pre- and post-operation, most cases were found to achieve concentric and near reduction. After multiple follow-up surveys, most patients showed no sequelae or defects in movement. We believe closed reduction to be the appropriate method for treating DDH in infants. In many dysplastic hips and hips in which treatment had failed, the labrum was less elastic than normal, and, in abduction, the labrum does not return to the normal position. Accordingly, we observed that LA is larger before the procedure, and reduced after restoration. The lower the post-operative LA value, the better the surgical effect. The epiphyses of femoral heads were mostly located in the 3-region of the ZCF, which was the best position of the femoral head relative to acetabulum. Further, if area 3 could not be reached, it was preferable for the femoral head to be located in area 4 rather than area 1 during restoration.[4] It can be observed by MRI that patients with DDH often have materials embedded in the joint space, which may cause reduction failure. For refractory or complicated DDH, we can analyze the contents of joint space via MRI to ascertain the cause of the contents and determine the most suitable treatment. In conclusion, this study demonstrated that MRI can be used as a tool to evaluate the curative effect of DDH in young children after closed reduction and plaster external fixation. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients’ guardians have given their consent for their images and other clinical information to be reported in the article. The patients’ guardians understand that their names and initials will not be published and due efforts will be made to conceal the identity of the patient, although anonymity cannot be guaranteed. Acknowledgements The authors thank Dr. Xue-Mei Lin of the pediatric orthopedics department for providing clinical case data. Funding This study was supported by the grants from the Science and Technology Planning Project of Guangdong Province (No. 2017ZC0099) and the Science and Technology Planning Project of Tianhe district of Guangzhou City (No. 201704KW037). Conflicts of interest None.

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          Long-term results of closed reduction for developmental dislocation of the hip in children of walking age under eighteen months old

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            MR-based Parameters as a Supplement to Radiographs in Managing Developmental Hip Dysplasia

            Background Some dysplastic hips with favorable radiographic parameters fail to develop normally, suggesting that we should consider cartilaginous or soft tissue structures for further information regarding the condition of the hip. The purpose of this study was to provide a clear definition of concentric reduction in developmental dysplasia of the hip (DDH) based on magnetic resonance imaging (MRI), and to determine how radiographic and MR-based parameters could be used together to treat dysplastic hips. Methods We studied range of motion (ROM)-MRI of 25 patients with unilateral hip dysplasia (mean age at the time of MR imaging, 44.1 months). Each ROM-MRI consisted of a set of bilateral hip scans in the following positions: neutral; abduction; abduction- internal rotation; abduction-internal rotation-flexion; and adduction. Before MR scanning, the 25 patients received the following primary treatments: closed reduction (n = 15; at a mean age of 14.5 months); and open reduction (n = 10; at a mean age of 10.0 months). The following new parameters appear to be useful in treating DDH: 1) the labral angle, the angle the labrum makes with the acetabulum; 2) the uncorrected labral deformity (ULD), the "residual deformity" (deflection of the labrum) when the affected labrum is freed from pressure in abduction; and 3) the zone of compressive force (ZCF), the region of the acetabulum through which the body weight acts on the femoral head. Results A concentrically-reduced hip is one in which the labrum points downward in the neutral position, at the same angle as that of the normal side; and in which the ZCF is zone 3, the inner acetabular zone as defined herein. The ULD and the ZCF may be determined precisely as we have done, or the physician may simply observe the changes in the orientation of the labrum and compare the changes qualitatively to the unaffected side, and likewise for the medial joint space. Conclusions Detailed analysis of the labrum as permitted by ROM-MRI, together with acetabular index and other parameters measured from radiographs, provides important information for physicians treating childhood hip dysplasia.
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              Inverted Acetabular Labrum: An Analysis of Tissue Embedment in Hip Joint in 15 Patients with Developmental Dysplasia of the Hip

              Introduction The acetabular labrum is a triangular fibrocartilaginous structure that forms a horseshoe-shaped attachment to the acetabular rim, which connects the acetabulum to the underlying transverse acetabular ligament [Figure 1a].[1] Up to 90% of symptomatic patients with developmental dysplasia of the hip (DDH) are found to combine with lesions of acetabular labrum.[2] The most common presentations of the acetabular labrum lesions are hypertrophy, laceration, and/or cyst formation.[3 4] Nevertheless, a unique hip joint condition is observed recently in several symptomatic DDH patients [Figure 1b]. A layer of abnormal disk-shaped soft tissue embedded in the acetabulum. The outer layer was connected to the acetabular labrum, whereas the inner layer could be lifted and separated from the acetabular cartilage by surgical probe. Figure 1 Appearance of normal acetabular labrum (a) and abnormal acetabulum with embedded tissues (b). The appearance of acetabulum after embedded tissues excised (c). The black arrow shows the acetabular cartilage which was abraded by the embedded tissue. Ross et al.[3] suggested that gradually increased shear stress at the acetabular margin was due to anterolateral migration of the femoral head in dysplastic hips. The continuous effect of this chronic outward shear stress could lead to hypertrophy of the acetabular labrum, and secondary damage to the acetabular cartilage connected to the labrum. Meanwhile, the labrum-cartilage complex is always integrate. Ganz et al.[5] proposed that cam deformity at the junction of the femoral head and neck in some DDH patients could result in impingement on the rim of the acetabulum during hip flexion. Shering caused by impingement led to an inward delaminating injury of the acetabular cartilage. This mechanism would also cause the acetabular cartilage delaminated from the subchondral bone, while the labrum was still attached to the torn cartilage. However, it remains unclear whether tissue damage is primarily caused by acetabular cartilage tears or inverted acetabular labrum. Therefore, this study aimed to assess whether abnormal tissue embedded in the hip joint is avulsed acetabular cartilage, inverted acetabular labrum, or other types of tissues such as aberrant ligamentum teres, we harvested the disk-like abnormal tissue from the hip joint during surgery and performed histological staining to investigate its property. Methods Patients Fifteen DDH patients, who were hospitalized in Department of Orthopedics, the First Affiliated Hospital of the Chinese PLA General Hospital from June 2013 to December 2014, were included in this study. The tissue embedments in the hip joint of all patients were detected by magnetic resonance imaging. The findings were confirmed by hip joint incision during surgery. One male and 14 females (average age: 23 years; range: 15–30 years) were included in the study. Nine left hip joints and six right hip joints were involved. In addition to the 15 young adult cases, five cases with avascular necrosis of the femoral head were also studied as normal controls (including three males and two females; average age: 51 years; range: 45–61 years). Source of specimen and specimen preparation The hip surgeries were performed on 15 DDH patients. Seven patients were treated by anterior hip dislocation. The other eight patients were treated by surgical hip dislocation. Embedded tissues in the acetabulum were harvested and labeled for further histological study. Normal acetabular labrum in five patients with avascular necrosis of the femoral head was observed during total hip arthroplasty. The normal acetabular labrum, acetabular cartilage, and ligamentum teres of the femur were harvested and labeled for further histological studies. The following steps were taken to prepare the specimens for study: (1) fixation: Specimens collected from the above patients were immersed in 10% formalin; (2) dehydration and clearing: Tissue samples were dehydrated gradually by graded ethanol (low to high concentration) and cleared in xylene; (3) paraffin embedding: Samples were embedded in paraffin and cooled to solidified blocks; (4) sectioning: The tissues were sectioned into 5–8 μm sections and placed onto glass slides to dry in a 45°C incubator; and (5) dewaxing: Paraffin was removed by xylene, rehydrated in gradient ethanol (high to low concentration), and washed in distilled water. Hematoxylin and eosin staining Hematoxylin and eosin (HE) staining was used to enhance the differentiation of various parts and structures in tissues to allow better tissue examination. Hematoxylin is a basic dye that stains the nuclei and ribosomes of basophilic cells blue and purple. Meanwhile, eosin is an acidic dye that stains the cytoplasm of eosinophilic cells red or pink. Stained slides were observed under the microscope and images of the tissue sections were recorded. Results Raw observation of embedded tissues in hip joint While the disk-shaped tissue was connected with the acetabular labrum to the acetabular rim, the labrum cartilage complex was normal and showed no direct connection with the articular cartilage in acetabulum. These tissues were identified in various sites of the acetabulum, including the anterosuperior quadrant in two cases, both anterosuperior and anteroinferior quadrants in five cases, anterosuperior and posterosuperior quadrants in seven cases, and posterosuperior quadrant in one case. Thinning, roughness, darkness, and degeneration of the acetabular cartilage at the corresponding sites of tissue embedment were observed in all 15 patients after tissue excision [black arrow in Figure 1c]. Observation of stained embedded tissues from hip joint under the microscope The matrix for each of the 15 tissue samples was rich in parallel or staggered collagen fiber bundles (pink). Small numbers of round hyaline cartilage cells (nuclei stained blue) were distributed among collagen fiber bundles in the cartilage lacuna as single cells or isogenous groups. All characteristics were consistent with stained structures of fibrous cartilage [Figure 2a]. Figure 2 Embedded tissues from hip joint (a) and normal acetabular labrumunder (b) under the microscope. Acetabular cartilage (c) and ligamentum teres of femur (d) under the microscope. Scale bar = 100 μm (Hematoxylin and eosin staining). Observation of stained normal acetabular labrum under the microscope The matrix, stained color, shape of the cells, and shape of fibers from acetabular labrum samples in five normal cases appeared no pathologically differences from stained embedded tissues [Figure 2b]. Observation of stained acetabular cartilage under the microscope The matrix of acetabular cartilage samples demonstrated numerous round hyaline cartilage cells (nuclei stained blue) in the cartilage lacuna as single cells or isogenous groups [Figure 2c]. Observation of stained ligamentum teres of femur under the microscope The matrix of acetabular cartilage samples was filled with regularly or irregularly oriented collagenous fibers (pink), whereby some demonstrated scattered spindle-shaped fibroblasts (nuclei stained blue). There was no cartilage lacuna around fibroblasts that could be distinguished from chondrocytes. These characteristics were consistent with stained structures of fibrous connective tissues [Figure 2d]. HE staining demonstrated that embedded tissue structures from hip joints of 15 DDH patients were the same as normal acetabular labrum while being consistent with stained fibrous cartilage structures. However, this tissue was different from acetabular hyaline cartilage and ligamentum teres of the femur since acetabular cartilage is made up of hyaline cartilage cells, whereas the ligamentum teres of the femur is comprised of fibrous connective tissues. These findings demonstrated that embedded tissues we identified in hip joints of symptomatic DDH patients were inverted acetabular labrum rather than torn acetabular cartilage or aberrant ligamentum teres of femur. Thinning, roughness, darkness, and degeneration of the acetabular cartilage were observed at sites of tissue embedment in all 15 patients after excision of tissue from hip joints. Discussion In a recent multicenter and large-scale study, Sankar et al.[6] summarized the morphological characteristics of acetabular labrum in 942 symptomatic DDH patients (972 hips). In 553 hips, the morphology of the labrum was categorized as hypertrophic, normal, hypoplastic, and ossified. Among those 553 hips, 355 hips demonstrated labral tears. The majority of labral damages in these cases were degeneration (52.3%), delamination (38.7%), full-thickness tear (7.2%), and ossification (0.6%) according to the Beck classification. Moreover, Haene et al.[7] studied 128 radiographs of arthroscopically-diagnosed acetabular labral tears, and found that 59 (46.1%) cases could be classified as DDH. Among these 59 cases, 27 (45.8%) could be described as the radial flap type, 13 (22.0%) longitudinal peripheral, 14 (23.7%) radial fibrillated, and 5 (8.4%) unclassified, using the classification described by Lage et al.[8] To date, no studies have reported the observation of disk-shaped abnormal soft tissue in symptomatic DDH patients. It always located between the acetabulum and the femoral head and connected to the labrum. Ross et al.[3] hypothesized that one type of injury in DDH involved a partial dislocation injury of the acetabular cartilage while the labrum cartilage complex still remained intact. Ganz et al.[5] suggested that cam impingement may cause tearing of the acetabular cartilage from the subchondral bone at the anterosuperior acetabular region without affecting the labrum, while the torn cartilage remains connected with the labrum. The present study suggested that abnormal disk-shaped tissue, which was found overlying the surface of the acetabulum and connected with the labrum during surgery, were inverted acetabular labrum rather than torn acetabular cartilage or other tissues (e.g., aberrant ligamentum teres of the femur). We demonstrated that the labrum-cartilage complex remained intact, thereby excluding the possibility that the disk-shaped tissue was the result of inner tearing of the complex. This study showed a novel type of intra-articular lesion, as characterized by inverted acetabular labrum, in symptomatic DDH patients. In a recent prospective study, Fukui et al.[9] examined nine patients with rapidly destructive hip osteoarthritis (OA) and found that the anterosuperior portion of the acetabular labrum had inverted into the articular space in each patient, which was accompanied by numerous articular cartilage fragments on the surface in each case. Moreover, subchondral insufficiency fractures of the femoral head was observed under the inverted labra in eight of nine patients, suggesting that the inverted acetabular labrum may be involved in the rapid narrowing of the joint space associated with subchondral insufficiency fractures in rapidly destructive hip OA. Nevertheless, radiographic hip scans of all nine patients did not show any adverse changes in hip joint development. While performing surgery on eight patients with idiopathic degenerative arthritis of the hip, it was found that the labrum was located between the femoral head and the acetabulum in each patient. Although no patient had a history or current radiographic evidence for DDH or hip dislocation, following exposure of the acetabulum during surgery, the labrum was found to penetrate into the joint overlying the acetabular rim. After excising the inverted labrum, a crescent-shaped surface could be observed at the corresponding sites in the acetabulum as well as in the areas above the femur head. Histological results of the inverted labrum demonstrated that the tissues were fibrous cartilage, which suggested that the inverted acetabular labrum was the cause of the degenerative arthritis. Although this study also found a pistol grip-like deformity in the femoral neck, it remained unclear whether this abnormality is associated with the inverted acetabulum labrum. Similarly, other studies have demonstrated that thinning, roughness, darkness, and early cartilage degeneration occurred at corresponding areas in the acetabular cartilage after excising the inverted labrum from all 15 patients. These indicated that the inverted acetabular labrum, as a foreign intra-articular structure, was wearing down the acetabular cartilage during hip movement, and thereby accelerated the degeneration of dysplastic hip. Embryological studies on the hips of 11 fetuses aged from 8 weeks to full term by Cashin et al.[10] demonstrated that the anterior acetabular cartilage was covered by a hat-shaped anterior margin of the labrum cartilage complex, while the intra-articular projection of the labrum into the joint resulted in the formation of a crypt between the acetabular cartilage surface and the labrum. However, the posterior labrum was directly attached to the acetabular cartilage in the absence of an intra-articular projection. Therefore, the study suggested that the anterior intra-articular projection of the labrum may be a normal type of structural variation. Moreover, an animal study demonstrated that inverted labrum could affect the development of the acetabulum and occurrence of acetabular dysplasia by causing damages to the metaphyseal cartilage at the acetabular rim. As a result, the acetabulum lost its contact with the femoral head, leading to femoral head subluxation. These data suggested that the inverted acetabular labrum was caused by incorrect fitting between the femoral head and the acetabulum in the dysplastic hip. As a result, the labrum was pushed into the femoral head-acetabulum space during femoral head movement, while gradually becoming hyperplastic and hypertrophic. Although filling of the intra-articular space by the inverted labrum provides stabilization in the early period, the inverted labrum could eventually wear down the cartilage at the surface of the hip joint, inducing hip OA. To the best of our knowledge, this study has identified a new type of hip joint pathology in symptomatic DDH patients. This unique hip joint pathology was characterized by the presence of abnormal disk-shaped soft tissue that overlied the acetabulum and connected to the labrum. Our histological study suggested that this tissue was inverted acetabular labrum. This study observed that cartilage wearing and degeneration occurred in the corresponding attachment sites of the inverted labrum in the acetabulum of patients, suggesting that inversion of the acetabular labrum was an adverse pathological change of the hip joint, leading to accelerated occurrence of hip OA. Thus, we suggested that it is necessary to excise any identified inverted labrum when correcting skeletal deformity of the hip. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
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                Author and article information

                Journal
                Chin Med J (Engl)
                Chin Med J (Engl)
                CM9
                Chinese Medical Journal
                Lippincott Williams & Wilkins (Hagerstown, MD )
                0366-6999
                2542-5641
                5 March 2021
                03 December 2020
                : 134
                : 5
                : 611-613
                Affiliations
                Department of Medical Imaging, The Third Affiliated Hospital, Southern Medical University, Guangzhou, Guangdong 510000, China.
                Author notes
                Correspondence to: Ling-Yan Zhang, Department of Medical Imaging, The Third Affiliated Hospital, Southern Medical University, Guangzhou, Guangdong 510000, ChinaE-Mail: sdzly@ 123456smu.edu.cn
                Article
                CMJ-2020-678 00024
                10.1097/CM9.0000000000001269
                7929600
                33278095
                b5fd3128-0706-40ab-8d2c-66c434deb41e
                Copyright © 2021 The Chinese Medical Association, produced by Wolters Kluwer, Inc. under the CC-BY-NC-ND license.

                This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0

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                : 11 August 2020
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