The acetabular rim syndrome. A clinical presentation of dysplasia of the hip.

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

The Rarely Encountered Rim Fracture That Contributes to Both Femoroacetabular Impingement and Hip Stability: A Report of 2 Cases of Arthroscopic Partial Excision and Internal Fixation

Femoroacetabular impingement (FAI) can be associated with labral ossification, acetabular rim fractures, and os acetabuli. Typically, these fragments can be completely excised as part of a femoroacetabular impingement correction procedure. In rare instances, however, larger, weight-bearing fragments contribute to pincer-type impingement, but complete removal might create structural instability or dysplasia. We report the results of 2 such cases where partial resection of a rim fracture and internal fixation of the remaining fragment were performed to correct the impingement while preserving adequate acetabular coverage. Predictable pain relief, healing of the stabilized rim fragment, and improved outcome scoring were achieved in both cases at 2-year follow-up evaluation.     

Pathomorphologic characteristics of posttraumatic acetabular dysplasia

OBJECTIVES: The pathomorphology of posttraumatic acetabular dysplasia differs fundamentally from the classic developmental dysplasia of the adolescent. The aim of this report is to qualify and quantify the pathomorphologic characteristics of the posttraumatic acetabular dysplasia and to define the requirements for adequate corrective surgery in this type of dysplasia. DESIGN AND MATERIAL: Retrospective review of the anteroposterior (AP) radiographs of ten patients with symptomatic posttraumatic acetabular dysplasia. In five cases, false profile views and in five cases computed tomography (CT) scans were also available for investigation. Measurements of distances and angles on radiographs and CT scans were made by pencil and goniometer. RESULTS: On the AP radiographs, posttraumatic acetabular dysplasia shows uniformly deformed true pelvis with an angular deformation of the innominate bone averaging 20 degrees in the region of the acetabular fossa that causes the concavity of the pelvic brim to increase in direction of the involved acetabulum and creates both a lateral and a caudal displacement of the acetabulum, averaging twenty-three millimeters and nine millimeters, respectively. The increased width of the inner wall of the acetabulum, measuring an average of eleven millimeters, makes lateralization of the center of the femoral head reach a mean of forty-three millimeters. The acetabular deformity in all cases shows a pronounced lateral deficiency. Ventral deficiency is moderate. All ten posttraumatic dysplastic acetabuli show marked retroversion averaging 27 degrees. In contrast, the contralateral acetabuli shows a mean anteversion of 23 degrees. CONCLUSIONS: The morphology of this kind of acetabular dysplasia is uniform and differs significantly from that seen in classic developmental dysplasia of the hip. For reconstructive surgery of such a hip, the challenge to abolish the lateralization of the hip joint to restore normal body weight lever arm is imperative. Because acetabular retroversion is a reproductive feature of posttraumatic dysplasia, it is important to avoid further reduction of the posterolateral containment of the femoral head and augmentation of the anterior acetabular wall, increasing the risk of anterior impingement.     

髋臼翻转造盖术治疗成人髋臼发育不良的生物力学研究

目的探讨髋臼翻转造盖术治疗成人髋臼发育不良的力学机理。方法收集适宜行髋臼翻转造盖术的成人髋臼发育不良12例的术前术后X线片,建立有限元网格,分析其力学变化并与正常髋关节进行对照研究。结果术后与术前各部位受力明显改变具有显著性差异(P<0·01),其中术前髋臼应力集中于外上缘,术后髋臼应力分布于臼顶,应力分散,与正常髋臼受力接近。结论髋臼翻转造盖术可明显改善髋臼局部受力情况,使成人髋臼发育不良术后髋关节受力趋于正常。     

Growth disorders of the acetabular roof after acetabuloplasty in congenital hip dysplasia

PURPOSE: The aim of this long-term study was to evaluate whether the Lance acetabuloplasty for congenital dysplasia of the hip causes a growth disturbance of the acetabular roof during or after puberty. METHOD: 71 hips of 58 patients were followed clinically and radiologically over a maximum time of 16 years after the operative procedure of a Lance acetabuloplasty. The average age of the patients at the time of operation was 2.8 years (1-6 years). In order to assess the growth of the acetabulum in the early and long-term postoperative phase quantitative parameters (acetabular index of Hilgenreiner, CE angle of Wiberg, ACM angle of Idelberger) as well as qualitative parameters (disturbance of the ossification of the acetabulum and the femoral head) were determined in standardized X-rays of the pelvis, done routinely 6 months, 3 years, 5 years, 8 years and at an average of 11 years as the last follow-up examination after the operation. The assessment of these metrical parameters were carried out in accordance to the classification of the study-group "hip dysplasia" of the DGOT (normal--slight pathological--serious pathological) respecting the different age-groups and degrees of dysplasia. RESULTS: Although in the early postoperative phase the acetabular roof showed a positive development (65% of the CE angles could be considered normal 3 years after operation), the further growth of the acetabulum was disturbed in the period of puberty (8 years after operation only 33% of the CE angles could be considered normal, 51% were extremely pathological). And also in the last X-ray control after an average follow-up time of 11 years a significant retardation of the acetabular roof was seen in 51% of all cases. CONCLUSION: The Lance acetabuloplasty seems to damage the Ossa acetabuli, which are as centers of ossification the essential anatomic structures for the growth of the acetabular rim in adolescence. CLINICAL RELEVANCE: Other procedures such as the Salter osteotomy are to be preferred for the therapy of hip dysplasia.     

髋臼旋转截骨术时髋臼后上方植骨前后髋关节生物力学的改变及其对比

目的探讨在偏心性髋臼旋转截骨术时于髋臼后上缘旋出部分上方进行植骨并检测植骨前、后髋关节生物力学的变化,为临床进行该类手术时髋臼后上方是否需要植骨提供必要的理论依据。方法将7具人体防腐骨盆标本建立成髋关节发育不良模型,测定每具标本模型髋关节所受应力的初始应变值仅,在每具标本的同一侧做偏心性髋臼旋转截骨术,再测定应变值β,然后,于旋转截骨后的髋臼后上缘旋出部分上方加骨块进行植骨,再测定应变值β’。应用配对资料的t检验比较植骨前后髋关节间应力的改变程度在不同压力负荷时有无差别。结果植骨前后组的对比中,当压力负荷为100N时,t=0．254,P〉0．05;200N时,t=-0．542,P〉0．05,可以认为植骨前后两组问数值差异无统计学意义;但植骨组多数标本的绝对数值要优于非植骨组。结论髋臼旋转截骨后,在髋臼旋出部分后上方进行植骨,能使股骨头所受的应力更趋于合理分布,而且,待植骨块与宿主骨完全愈合后,能较好地增加髋臼后上方骨的储备量。     

Developmental dysplasia of the hip: A computational biomechanical model of the path of least energy for closed reduction

This study utilized a computational biomechanical model and applied the least energy path principle to investigate two pathways for closed reduction of high grade infantile hip dislocation. The principle of least energy when applied to moving the femoral head from an initial to a final position considers all possible paths that connect them and identifies the path of least resistance. Clinical reports of severe hip dysplasia have concluded that reduction of the femoral head into the acetabulum may occur by a direct pathway over the posterior rim of the acetabulum when using the Pavlik harness, or by an indirect pathway with reduction through the acetabular notch when using the modified Hoffman–Daimler method. This computational study also compared the energy requirements for both pathways. The anatomical and muscular aspects of the model were derived using a combination of MRI and OpenSim data. Results of this study indicate that the path of least energy closely approximates the indirect pathway of the modified Hoffman–Daimler method. The direct pathway over the posterior rim of the acetabulum required more energy for reduction. This biomechanical analysis confirms the clinical observations of the two pathways for closed reduction of severe hip dysplasia. The path of least energy closely approximated the modified Hoffman–Daimler method. Further study of the modified Hoffman–Daimler method for reduction of severe hip dysplasia may be warranted based on this computational biomechanical analysis. © 2016 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:1799–1805, 2017.

     

Familial hip dysplasia with short acetabular roofs

A longtime observation of a mother and her three children with too short but not flattened acetabular roofs as contrasted with shallow acetabuli is presented, probably on a hereditary basis. The development of these short roofs from acetabular dysplasia may be recognized towards the end of the first decade of life at the latest. The short roof as such seems to be little amenable to conservative treatment. Adduction osteotomies, if necessary, later are preferable to the acetabuloplasties aiming more at improvement of a shallow than a short acetabulum, with the exception of Chiari's osteotomy.     

A stress analysis of acetabular reconstruction in protrusio acetabuli

We are reporting the results of a finite-element analysis of acetabular reconstruction for total hip replacement in the presence of protrusio acetabuli. In a protruded acetabulum, cortical bone stresses on the medial part of the pelvic wall increase with medial placement of the acetabular component, while normal placement of the component (more lateral placement) reduces these stresses. Metal backing of a polyethylene acetabular component causes a reduction in the peak cement and trabecular-bone stresses. A metal protrusio ring about only the periphery of the acetabular component increases stress levels within the lateral part of the pelvic cortex and has little effect on stresses in the medial part of the pelvic wall. A complete metal protrusio cup increases stresses in the lateral part of the pelvic cortex while decreasing substantially the stresses in the medial part of the cortex and the trabecular bone. Prosthetic reinforcement of the medial part of the acetabular wall has little effect on stress patterns in the acetabular region. Clinical Relevance: The major long-term problem with cemented total hip prostheses is loosening. Loosening is probably related in part to the stress state in the cement and surrounding bone. The protruded acetabulum is particularly difficult to reconstruct in a manner that ensures longevity of the total hip replacement. In patients with protrusio acetabuli, the prosthetic acetabulum should be placed in a normal and not in a protruded position. A metal-backed acetabular component or a complete metal cup incorporated within the cement reduces stress levels within the medial aspect of the pelvic bone and thus may reduce the incidence of loosening.     

成人髋臼发育不良Bernese经髋臼周围骨盆截骨术的两维有限元分析

目的：建立成人髋臼发育不良Bernese经髋臼周围骨盆截骨术后模型，并进行生物力学有限元分析。方法:制备尸体标本成人髋臼发育不良模型，并利用Ansys 6．0软件，对髋臼发育不良Bernese术后矫枉过正及合适矫正模型进行生物力学分析。结果：术后矫枉过正模型组外侧、前侧髋臼边缘出现应力增加趋势，作用于髋臼及股骨头的水平分力及剪应力是正常组的2—3倍。结论：探讨髋臼合适矫正的标准Bernese术后髋臼矫枉过正，将会导致髋臼进行性的向前侧、外侧突起畸形及股骨头颈髋臼盂唇撞击综合征。久之导致骨性关节炎。     

髋臼发育不良的光弹性生物力学研究

目的 从生物力学角度探讨髋臼发育不良继发骨关节炎的发病机理,为髋臼旋转截骨术提供依据。方法 用环氧树脂制作骨盆、股骨模型,其中包括４个不同Ｓｈａｒｐ角、３个不同软骨厚度及３个颈干角模型,采用二维光弹性方法进行生物力学分析。结果 随着Ｓｈａｒｐ角的增大,髋关节的合力增大,生物应力向髋臼外侧缘移动;关节软骨缺损一半时,髋关节合力未见明显变化,当关节软骨不存在时,生物应力为正常时的２．５倍;随着颈干角的增大,生物应力集中的位置没有变化,但生物应力及合力随之增大。结论 髋臼发育不良因生物力学因素可继发骨关节炎,髋臼旋转截骨术是对其有效的治疗方法。     

Center edge angle measurement for hip preservation surgery: technique and caveats

Anterior and lateral center edge angles have traditionally been used to determine acetabular coverage, and thereby strongly influence the decision to perform acetabular reorientation versus osteochondroplasty in patients with dysplasia and/or femoroacetabular impingement. We propose templating the center of the contained articular femoral head in aspherical hips to provide reliable assessment of acetabular coverage. Digital radiographs of 30 patients with various combinations of femoral and acetabular morphologies were evaluated using 2 methods to identify the anterior center edge angle and lateral center edge angle. The control method used an estimated femoral head center for angle apex. The study technique determined the center of the femoral head by templating the congruent aspect of the femoral head contained by the acetabulum while ignoring the increasing lateral and anterior radius associated with cam deformities. Four readers measured lateral center edge angles on anteroposterior radiographs and anterior center edge angles on false-profile radiographs. Two reads were performed by each reader using both the estimated and the templated methods for a total of 4 reads. Interobserver reliability using the proposed method compared to the standard was much improved for anterior center edge angles (intraclass correlation coefficient of 0.76 vs 0.55) as well as with lateral center edge angles (ICC of 0.80 vs 0.42). Decreased correlation was most commonly associated with abnormal sourcil morphology, posterior wall deficiency combined with calcified labra, and os acetabuli. Including the anterolateral cam deformity in identifying the center of the femoral head for measuring center edge angles leads to an underestimation of acetabular coverage, which may negatively affect hip preservation surgical decision making.     

Über acetabuläre Ossifikationszentren und periartikuläre Verkalkungen bzw. Verknöcherungen,ihre Entstehung und ihre Bedeutung

Zusammenfassung Die Abhandlung befaßt sich mit den Gesetzmäßigkeiten der Osteogenese der Hüftgelenkspfanne, den primären und sekundären Ossifikationszentren und ihrer Bedeutung. Dabei wird im besonderen auf die Pfannendysplasie, das anatomische und röntgenologische Os acetabuli, auf die Apophysenlösung und Osteochondropathie der Spina il. ant. inf., auf die Periarthrosis coxae und das Os ad acetabulum eingegangen.

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Summary The paper treats of the laws governing the osteogenesis of the socket of the hip-joint, the primary and secondary ossification centres and their significance, special emphasis being placed on the dysplasia of the socket, on the anatomic and radiological os acetabuli, on the lysis of the apophysis and osteochondropathy of the Spina il. ant. inf., on the periarthrosis coxae and the os ad acetabulum.

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Résumé L'auteur traite les lois de l'ostéogenèse de la cavité cotyloide de l'articulation coxofémorale, des centres d'ossification primaires et secondaires et leur importance. En outre il s'occupe en particulier de la dysplasie de la cavité articulaire, de l'os acetabuli anatomique et radiologique, de la lysis apophysaire et de l'ostéochondropathie du spina il. ant. inf., de la periarthrosis coxae et de l'os ad acetabulum.

     

Primary stability of acetabular reinforcement implants in revision surgery

It was the purpose of this biomechanical in vitro study to characterize the initial mechanical stability of 3 different acetabular reinforcement prostheses as a function of implant design and bone stock conditions. Müller and Ganz rings and Burch-Schneider cage (Protek, Münsingen, CH) were fixed using 3 screws in normal acetabuli and in acetabuli with 5 different simulated conditions of segmental bone-stock defects. A servohydraulic testing machine (Instron, Canton, USA) was used for the inquiry. Preparations were tested to determine axial stability (2354 N). Three electromagnetic displacement transducers (Micro-Epsilon, Ortenburg, D) were placed in the 3 main quadrants of the acetabular rim to detect the micromotion of the implant. The amount of micromotion depended on the size of the defect and contact area of the prosthesis. All of the implants were stable (< 123 microns) in all quadrants of normal acetabuli and in case of ectasis, protrusio, and ventral defects. Displacement of more than 200 microns was observed at the ilium with the Muller implant in acetabuli with cranial defect (p < 0.05) and with both rings in acetabuli with dorsal defect. The Burch-Schneider cage was stable in all conditions, but displacement of more than 350 microns was observed in acetabula with pseudoarthrosis. The 3 reinforcement implants showed low displacement rates in most of the acetabular bony defects. The experimental data suggests that careful preoperative evaluation and intraoperative assessment to match bone defects and reinforcement implants are of paramount importance to achieve good stability.     

The Exeter method—acetabular impaction grafting with cemented reimplantation

Objective

Restoration of acetabular anatomy and biomechanics at revision hip surgery by replacing deficient acetabular bone through impaction of allograft and/or autograft bone chips.

Indications

Aseptic loosening of the socket due to osteolysis, bone loss from infection, iatrogenic bone loss due to implant removal, and in the primary setting protrusio acetabuli, dysplasia and previous acetabular fracture.

Contraindications

Large segmental peripheral acetabular defects which cannot be contained, the presence of untreated infection, unstable acetabular fractures, previous radiotherapy to the affected hip area.

Surgical technique

Sound exposure of the acetabulum with delineation of the bony defect. Creation of a host environment suitable for bone graft and containment of segmental defects using rim mesh or porous augments. Impaction grafting using layered allograft or autograft bone chips of 0.8–1 cm³, packed using hemispherical impactors, followed by cementing of a polyethylene acetabular component with pressurisation.

Postoperative management

Partial weight bearing 6 weeks, modified depending on level of containment and intra-operative findings.

Results

A successful and reproducible technique with survival up to 87?% at 20 years for aseptic loosening in the revision setting.     

Coverage of the femoral head by the acetabular labrum in dysplastic hips: quantitative analysis with radial MR imaging

Hip dysplasia is an important cause of osteoarthrosis of the hip, especially in Japanese. Recently, the role of the acetabular labrum in hip diseases has attracted the attention of researchers, but the condition of the labrum in the dysplastic hips has not been described. We used radial MRI to measure the degree of coverage of the femoral head by the acetabulum and the labrum, corresponding to 7 positions on the acetabular rim at every 15 degrees from anterosuperior 45 degrees via midsuperior to posterosuperior 45 degrees. 38 Japanese patients (51 hips) with dysplasia, and 11 healthy controls 122 hips) were studied. In the dysplastic hips, the labrum was larger than in the controls. We found no correlation between the coverage of the acetabulum in the anterosuperior positions and the size of the labrum among the dysplastic hips.     

Long-term results of primary hip total prosthesis with acetabulum reinforcement ring

The Müller acetabular reinforcement ring has proven very useful, especially in total hip revision when the bone of the acetabulum is of poor quality or deficient. However, the acetabular reinforcement ring may also be indicated in primary total hip replacement, especially in the case of poor quality bone in the acetabular bone stock, e.g. in chronic polyarthritis or protrusio acetabuli, or of deficient morphology of the acetabulum, e.g. in hip dysplasia. We analysed the results recorded in 145 patients operated on between 1977 and April 1983. Each of these patients had received a total hip prosthesis for the first time, with the polyethylene cup supplemented by an acetabular reinforcement ring. This patient group cannot be compared with the usual patient populations reported on in connection with primary hip replacement, since most of our 145 patients had several risk factors and had undergone previous surgery on up to seven occasions on the hip ultimately replaced by a prosthesis. Radiological analysis did not show a significant correlation between malposition of the acetabular reinforcement ring and signs of loosening, except when the acetabular component had been implanted in a most atypical manner. The infection rate was 4.8%, but it must be borne in mind that from 1977 to 1983 there was no routine prophylaxis with antibiotics. The incidence of aseptic loosening of the acetabular reinforcement ring necessitating revision was 0.7% after a mean follow-up of 7.7 years (range 5.5-11 years).(ABSTRACT TRUNCATED AT 250 WORDS)     

成人髋臼发育不良伴骨关节炎行髋臼结构性植骨重建关节置换术的力学分析

目的：利用三维有限元力学分析方法,研究髋关节发育不良患者髋臼外上缘结构性植骨重建髋臼、增加臼杯假体包容对髋臼假体-骨界面间的应力分布情况的影响。方法选取髋关节发育不良患者的骨盆为实验对象,用螺旋CT做全长连续扫描,然后利用计算机仿真技术对CT图像进行三维重建,建立髋关节发育不良骨盆模型。在计算机环境中对重建模型进行髋臼外上缘结构性植骨重建髋臼并臼杯植入的模拟手术,利用有限元分析软件对重建模型进行有限元网格化及力学分析。结果髋臼植骨重建后,臼杯置入无需突破髋臼底,髋臼外上缘得到植骨块的包容覆盖,臼杯接触面积增大,单位面积所受应力相对较少,应力集中的情况得到明显改善。同时,植骨块及原髋臼外上缘区域承担了臼杯较多的应力。结论结构性植骨重建髋臼使骨床与臼杯接触面积较大,单位面积所受应力较小且均匀,有利于臼杯的稳定,植骨块承担了臼杯较多的应力,若臼杯外上缘外露面积过大,而过多的靠植骨块来弥补骨床的覆盖,使植骨块所受应力过大则臼杯松动的风险较大。     

Protrusio acetabuli in Marfan syndrome. History, diagnosis, and treatment

Marfan syndrome is an autosomal dominant disorder of connective tissue, with ocular, skeletal, and cardiovascular manifestations. Protrusio acetabuli is a criterion for the diagnosis of Marfan syndrome. Prolonged protrusio acetabuli may result in secondary osteoarthritic changes in the hip joint. Radiographic criteria for protrusio acetabuli include an abnormally positioned acetabular line, a center-edge angle of Wiberg of >40 degrees, and crossing of the teardrop by the ilioischial line. In a skeletally immature patient with Marfan syndrome in whom the triradiate physis of the acetabulum is still open, closure of the triradiate physis can interrupt and decrease the progression of the deformity. In older patients, valgus intertrochanteric osteotomy and eventually total hip arthroplasty are the only methods available for correction of the protrusio acetabuli.     

Diagnosis and therapy of hip dysplasia in the older child

Diagnosis of congenital hip dysplasia is based on normal values of the acetabulum, but also criteria such as deficiency of the acetabular rim and an increased distance from the tear drop figure. Instability of the hip joint is seen in arthography. Acetabuloplasty is the way to treat it. Unstable joints will deteriorate, stable ones are frequently improving spontaneously. The technique of open reduction from an inguinal approach medial of the psoas muscle is described. There are many advantages. Simultaneous shortening osteotomy and acetabuloplasty to permit immediate movements out of the hip spica are recommended to avoid stiffening and contractures. Hip dysplasia is corrected by a lateral acetabuloplasty that levers down the acetabular roof in the triradiate cartilage. After consolidation of the cartilage triple pelvic osteotomy for acetabular rotation is the method to correct dysplasia in adolescents and adults. The closer the osteotomies are performed to the hip joint, the better rotation is possible. Our technique has proved successful now in 12 years.