Comparison of radiographic parameters for analysis of normal and dysplastic hips in the adult

Radiographic quantitation of the dysplastic hip in adults is difficult. This study compares the values for commonly used indices, the acetabular angle (AA), the center edge angle (CEA), and femoral head coverage, and the X-Y coordinate system on the anteroposterior pelvic radiograph in 30 adult patients with 60 normal hips, and 20 adult patients with 27 dysplastic hips. Dysplastic hips demonstrated significantly higher values for the AA and the X-Y coordinates, and significantly lower values for the CEA and femoral head coverage compared to normal hips. Femoral head coverage in dysplastic hips correlated best (negatively) with the Y coordinate, i.e., poorer coverage was associated with greater superior migration of the femoral head. The AA describes the slope of the acetabular roof, but does not take into account the relative position of the femoral head. The CEA measures the position of the femoral head in relation to the lateral lip of the acetabulum, but does not necessarily use the true acetabulum. The X-Y coordinate system relates the center of the femoral head to an identifiable acetabular landmark, the teardrop shadow. These coordinates are easily determined and can serve as an adjunct to other radiographic indices that quantitate the amount of subluxation in dysplastic hips in adults.     

伯尔尼髋臼周围截骨术对严重髋臼发育不良的治疗

目的 研究和分析使用伯尔尼髋臼周围截骨术治疗严重髋臼发育不良的中期临床和影像学结果.方法 1997年10月至2002年12月对18例(20髋)严重髋臼发育不良(Severin分级Ⅳb级)的患者接受了伯尔尼髋臼周围截骨术.患者手术时平均年龄21岁,平均随访时间6.2年.本组患者术前患髋均已出现疼痛,术前功能位片显示关节面吻合.术后影像学评价畸形的矫正范围,截骨处的愈合情况及关节炎的进展.临床结果和髋关节功能由Harris评分进行评价,术前Harris评分平均78.5分.结果 比较术前和术后X线片,外侧中心边缘角(CE角)、前方CE角和臼顶倾斜角均有显著改善.所有髂骨截骨均愈合.患者术后末次随访Harris评分平均91.1分.18例患者中的14例对手术效果表示满意.20髋中16髋临床结果优.但有5髋存在畸形矫正不足.结论 伯尔尼髋臼周围截骨术是治疗严重髋臼发育不良的有效术式.这一截骨术可以在各个平面对严重的骨缺损进行矫正,中期临床结果令人满意.     

Anteversion of the acetabulum and femoral neck in early walking age patients with developmental dysplasia of the hip

Computed tomography measurements were made to quantify the relationship between the anteversion of the acetabulum and femoral neck in 27 early walking age patients (age range; 18-48 months) with developmental dysplasia of the hip. The centre-edge angle and acetabular index were measured in standard pelvis radiographs, and anteversion of acetabulum and femoral neck were measured by use of two-dimensional computed tomography in 25 complete dislocated, 19 subluxated and 10 unaffected hips (a total of 54 hips). The diagnosis of dysplasia, subluxation and complete dislocation of developmental hip dysplasia were determined radiographically using Ishida's criteria. There were statistically significant differences between the three groups for the centre-edge angle, the acetabular index, and acetabulum anteversion. There was no statistically significant difference between the three groups for femoral neck anteversion. The acetabular anteversion was found to be 13.4+/-2.8 degrees (mean+/-SD) in unaffected hips, 16.7+/-1.9 degrees in subluxated hips and 19.8+/-2.5 degrees in complete dislocated hips. There was statistically significant difference between the three groups, with a wide range of acetabular anteversion values noted in all groups (9-26 degrees ). The acetabular anteversion was increased on the dislocated side in each patient and we found no retroverted acetabulum. On the other hand there was no significant difference between the groups with regards to femoral neck anteversion. We conclude that confirming anteversion of the acetabulum and the femoral neck by two-dimensional computed tomography is needed in treatment planning of early walking age patients with developmental hip dysplasia.     

Radiographic method to measure the inclination angle of the acetabulum

Background Various attempts have been made to assess the inclination angle of the acetabulum utilizing new imageprocessing technologies to enable three-dimensional reconstruction of the acetabulum. However, reliability of these methods has not been estimated in comparison with anatomical measurements. This study developed a geometric method for measuring the acetabular inclination with radiograms and evaluated the reliability of this method by comparing the anatomically measured acetabular inclination angle of the same dry pelvic bone. Methods One hundred and ten acetabulums from 55 human pelvis specimens were used. The uppermost, most frontal, and posterior lowermost points of the acetabular rim were determined, and an axis perpendicular to the triangular plane formed by these three points was defined as the anatomical inclination axis of the acetabulum. The anatomical lateral and anterior opening angles were directly measured using a tool we devised for this purpose. Posteroanterior and lateral radiograms of each pelvis were taken concurrently and three points were marked by small metal plates. Based on projections of these three points onto the posteroanterior and lateral images, we geometrically measured and calculated the lateral and anterior opening angles of the acetabulum. Results Anatomical measurements of the lateral opening angles ranged from 38° to 63° (mean 51.0°), and anterior opening angles from 10° to 36° (mean 20.8°). Geometric measurements of the lateral opening angles ranged from 40° to 61° (mean 50.5°), and anterior opening angles ranged from 7° to 35° (mean 20.8°). Geometrically measured acetabular inclination angles were highly correlated with the anatomically measured ones for both the lateral and anterior opening angles, with correlation coefficients of 0.803 and 0.822, respectively. Conclusions Our geometric measurement method of the acetabular inclination angle enabled us to calculate the lateral and anterior opening angles, which were very close to the corresponding anatomical measurements. This method allows three-dimensional evaluation of the anatomical structure of the hip and may be useful in predicting progression of coxarthrosis by measuring the femoral neck shaft and anteversion angles.     

Periacetabular osteotomy for the treatment of severe acetabular dysplasia

BACKGROUND: The optimal treatment of severe acetabular dysplasia with subluxation of the femoral head or the presence of a secondary acetabulum remains controversial. The purpose of this study was to analyze the extent of surgical correction and the early clinical results obtained with the Bernese periacetabular osteotomy for the treatment of severely dysplastic hips in adolescent and young adult patients. METHODS: Sixteen hips in thirteen patients with an average age of 17.6 years (range, 13.0 to 31.8 years) were classified as having severe acetabular dysplasia (Group IV or V according to the Severin classification). Eight hips were classified as subluxated, and eight had a secondary acetabulum. Preoperatively, all patients had hip pain and sufficient hip joint congruency on radiographs to be considered candidates for the osteotomy. All sixteen hips underwent a Bernese periacetabular osteotomy, and six of them underwent a concomitant proximal femoral osteotomy. Postoperatively, the hips were assessed radiographically to evaluate correction of deformity, healing of the osteotomy site, and progression of osteoarthritis. Clinical results and hip function were measured with the Harris hip score at an average of 4.2 years postoperatively. RESULTS: Comparison of preoperative and follow-up radiographs demonstrated an average improvement of 44.6 degrees (from -20.5 degrees to 24.1 degrees ) in the lateral center-edge angle of Wiberg, an average improvement of 51.0 degrees (from -25.4 degrees to 25.6 degrees ) in the anterior center-edge angle of Lequesne and de Seze, and an average improvement of 25.9 degrees (from 37.3 degrees to 11.4 degrees ) in acetabular roof obliquity. The hip center was translated medially an average of 10 mm (range, 0 to 31 mm). All iliac osteotomy sites healed. The average Harris hip score improved from 73.4 points preoperatively to 91.3 points at the time of the latest follow-up. Eleven of the thirteen patients (fourteen of the sixteen hips) were satisfied with the result of the surgery, and fourteen hips had a good or excellent clinical result. Major complications included loss of acetabular fixation, which required an additional surgical procedure, in one patient and overcorrection of the acetabulum and an associated ischial nonunion in another patient. Both patients had a good clinical result at the time of the latest follow-up. There were no major neurovascular injuries or intra-articular fractures. CONCLUSIONS: The periacetabular osteotomy is an effective technique for surgical correction of a severely dysplastic acetabulum in adolescents and young adults. In this series, the early clinical results were very good at an average of 4.2 years postoperatively; the two major complications did not compromise the good clinical results.     

Modified triple innominate osteotomy for acetabular dysplasia: for better femoral head medialization and coverage

Steel's triple innominate osteotomy was created for correcting dysplastic acetabulum in adolescents and young adults. We modified Steel's triple innominate osteotomy with two anterior incisions and ramus cuts close to the acetabulum to improve the mobility of the fragment for better coverage of the hip. The purpose of this study was to compare these two techniques with respect to acetabular morphology, femoral head coverage, and medialization. From 1989 to 2007, 22 hips from 19 adolescents and young adults underwent triple innominate osteotomy for symptomatic acetabular dysplasia with Tonnis grades 1 or 2. We divided patients into group A (11 hips from 10 patients), comprising patients who underwent classical Steel's osteotomy, and group B (11 hips from nine patients), comprising patients who underwent modified Steel's osteotomy, with a minimum follow-up of 2 years. Preoperative and postoperative radiographs of pelvis in the standing position were available for comparison. We used Sharp's angle, center-edge angle, femoral head extrusion index, and center-head distance discrepancy to evaluate hip morphology, femoral head coverage, and medialization, respectively. The paired t-test was used for statistical calculation with P-value less than 0.05 considered significant. The postoperative Sharp's angle, center-edge angle, femoral head extrusion index, and center-head distance discrepancy all had better results in group B with statistical significance. Other variants such as age, sex, and operation side did not have any significance. No postoperative complication was encountered. Our modified technique provided a better mobility of the rotated fragment in correcting acetabular dysplasia with a short learning curve. Most importantly, we provided greater coverage and medialization of the femoral head for better long-term results. Level of evidence: level III, retrospective comparative study.     

Subchondral cysts in dysplastic osteoarthritic hips communicate with the joint space: analysis using three-dimensional computed tomography

Introduction

Bone cyst formation in hips increases as osteoarthritis worsens. Although bone cysts in hips have been described in many studies, their etiology remains unclear and under debate. The purpose of this study was to investigate the communication between a bone cyst and the joint space, as well as the relationship between the severity of osteoarthritis and the formation of subchondral bone cysts in dysplastic hips.

Method

We studied bone cysts from 150 dysplastic hips in 97 patients by computed tomography (CT) and plain radiography. We investigated the distribution of the bone cysts and the presence or absence of a communication path between the cysts and the joint space by three-dimensional (3D) CT.

Result

Of the 150 hips, 94 acetabula and 55 femoral heads were found to contain cysts. Of the 94 hips containing acetabular cysts, 89 and 5 hips showed black lines and gray lines connecting the cyst and the joint space, respectively, on 3D-CT. The rate of cyst presentation in the hip increased as the joint space became narrower. The number of hips that possessed cysts in the anterior and/or middle portion was significantly higher than that in the posterior portions.

Conclusion

Bone cysts in dysplastic osteoarthritic hips were found to communicate with the joint space in all cases. This suggests that the formation and enlargement of the cysts in dysplastic hips may be greatly influenced by the joint fluid. Cyst formation was initially observed in the anterior acetabulum, gradually progressing to involve the entire joint, including the posterior acetabulum and the femoral head, with worsening of the osteoarthritis.     

Postoperative acetabular retroversion causes posterior osteoarthritis of the hip

We retrospectively reviewed 68 hips in 62 patients with acetabular dysplasia who underwent curved periacetabular osteotomy. Among the 68 hips, 33 had acetabular retroversion (retroversion group) and 35 had anteversion (control group) preoperatively. All hips were evaluated according to the Harris hip score. Radiographic evaluations of acetabular retroversion and posterior wall deficiency were based on the cross-over sign and posterior wall sign, respectively. The clinical scores of the two groups at the final follow-up were similar. In the retroversion group, 12 hips had anteverted acetabulum postoperatively. The posterior wall sign disappeared in these hips, but remained in 21 hips with retroverted acetabulum postoperatively. Among the 21 hips with retroverted acetabulum, posterior osteoarthritis of the hip developed postoperatively in five hips. When performing corrective osteotomy for a dysplastic hip with acetabular retroversion, it is important to correct the acetabular retroversion to prevent posterior osteoarthritis of the hip due to posterior wall deficiency.     

全髋置换术中应用髋臼内壁环形截骨术治疗成人髋臼发育不良

目的评价全髋置换中应用髋臼内壁环形截骨固定非骨水泥髋臼杯治疗成人髋臼发育不良的疗效。方法对29例髋臼发育不良继发骨性关节炎患者(29髋)在全髋置换术中应用髋臼内壁环形截骨术。手术指征为术前X线髋臼覆盖率70%。非骨水泥髋臼杯全部安放在真臼位置,附加操作:软组织松解17髋,治疗性股骨截骨2髋,结构性植骨1髋,股骨短缩3髋。手术前后进行临床及X线参数评价。结果患者均获得随访,时间4~8年。Harris评分从术前36~75(68.4±8.49)分提高到85~100(92.2±4.05)分(P0.05);其中优25髋,良4髋。影像学观察髋臼内壁截骨处愈合时间3~5个月,术后6~12个月时骨重塑。X线检查显示没有无菌性松动和透亮线,真臼固定稳定。结论在非骨水泥全髋置换术治疗髋关节发育不良中,应用髋臼内壁环形截骨术可以提供良好的髋臼位置、足够的髋臼覆盖及保留足够内壁厚度,并且无需植骨。     

Rotational acetabular osteotomy for the severely dysplastic hip in the adolescent and adult

Rotational acetabular osteotomy performed since 1968 is a circumacetabular osteotomy of the acetabulum for the dysplastic hip. The preoperative center-edge angle of Wiberg of 95 hips (89 patients) was -15 degrees or less. Forty-one hips (39 patients) form the basis of this report. They were followed from four years to 16 years and seven months (average, seven years and nine months). Twenty-one hips were classified as the Severin Group IV (subluxation) and 20 hips as the Severin Group V (a secondary acetabulum). A detailed assessment using a number of roentgenographic indices confirmed that the majority of the severely dysplastic hips could be corrected to nearly normal anatomy. The postoperative clinical results were assessed by the modified clinical classification of Severin proposed by Gibson and Benson. This procedure may be indicated for the severely dysplastic hip with subluxation or a secondary acetabulum in the adolescent and adult.     

Preoperative and postoperative assessment of rotational acetabular osteotomy for dysplastic hips in children by three-dimensional surface reconstruction computed tomography imaging

The three-dimensional relationship between the acetabulum and femoral head was evaluated using three-dimensional computed tomography (CT) reconstruction before and after rotational acetabular osteotomy. This method provides exact anatomic information on acetabular coverage so that precise operative planning is more easily made. Evaluation of six dysplastic hips indicated the possible dangers of anterolateral rotational shift of the acetabulum when there is marked posterior deficiency, such as in the case of a high decree of subluxated femoral head covered by a shallow false acetabulum. In these circumstances, it may be safer and preferable to plan a lateral shift instead of an anterolateral shift.     

Evaluation of acetabular versions after a curved periacetabular osteotomy for dysplastic hips

The purpose of this study is to investigate the early clinical and radiographic findings related to acetabular orientation after a curved periacetabular osteotomy (CPO). 106 dysplastic hips of 88 patients underwent CPO were investigated retrospectively with an average follow-up of 3.6 years. Conventional anteroposterior radiographs were used to measure the radiographic findings and range of motion were used for clinical evaluations. A significant improvement was noted in radiographic measurements including lateral centre-edge angle, acetabular index, and acetabular angle of Sharp. However, a high rate of postoperative acetabular retroversion was observed (62% hips) and a marked decrease in free flexion was noted. The Tönnis scale revealed a one-grade progression in most retroversion hips. Acetabular retroversion is a high risk factor leading to degenerative osteoarthritis of hip. Therefore, special consideration must be taken in surgical planning and careful intraoperative confirmation is required whilst manoeuvring the acetabular fragment in CPO.     

Factors which affect the progression of osteoarthritis after rotational acetabular osteotomy

We have investigated the factors which affect the progression of osteoarthritis after rotational acetabular osteotomy (RAO). Between 1984 and 1998, we treated 60 dysplastic hips by RAO. The mean age at surgery was 31.6 years (13 to 51) and the mean period of follow-up was 4.6 years (2 to 9.5). The thickness of the articular cartilage on the weight-bearing area, pre- and postoperative acetabular cover, and the sphericity of the femoral head were used for radiological assessment. The osteoarthritis did not progress in 39 hips. Significant factors which affected the radiological grade included sphericity of the femoral head and the postoperative acetabular cover. The surgical approach and preoperative acetabular cover did not affect the progression of osteoarthritis. Patients were divided into two groups according to the surgical approach used, either conventional (23 hips) or modified (37 hips). Significant factors included the postoperative acetabular cover in the modified approach, and the sphericity of the femoral head in the conventional approach. It is critical that the postoperative cover is sufficient, especially when RAO is carried out using our modified technique.     

The prevalence of acetabular retroversion among various disorders of the hip

BACKGROUND: Acetabular retroversion can result from posterior wall deficiency in an otherwise normally oriented acetabulum or from excessive anterior coverage secondary to a malpositioned acetabulum, or both. Theoretically, a retroverted acetabulum, which adversely affects load transmission across the hip, may occur more frequently in hips with degenerative arthritis. The aim of this study was to assess the prevalence of acetabular retroversion in normal hips and in hips with osteoarthritis, developmental dysplasia, osteonecrosis, and Legg-Calvé-Perthes disease. METHODS: We retrospectively examined anteroposterior radiographs of the pelvis of 250 patients (342 hips). Fifty-six patients (112 hips) had normal findings; sixty-six patients (seventy hips) had osteoarthritis; sixty-four (seventy-four hips), developmental dysplasia; thirty (thirty-six hips), osteonecrosis of the femoral head; and thirty-four (fifty hips), Legg-Calvé-Perthes disease. The sole criterion for a diagnosis of acetabular retroversion was the presence of a so-called cross-over sign on the anteroposterior radiograph of the pelvis. RESULTS: The prevalence of acetabular retroversion was 6% (seven of 112 hips) in the normal group, 20% (fourteen of seventy hips) in the osteoarthritis group, 18% (thirteen of seventy-four hips) in the developmental dysplasia group, 6% (two of thirty-six hips) in the group with osteonecrosis of the femoral head, and 42% (twenty-one of fifty hips) in the group with Legg-Calvé-Perthes disease. In patients with Legg-Calvé-Perthes disease, the prevalence of acetabular retroversion was 68% in twenty-five hips with Stulberg class-III, IV, or V involvement. In contrast, only four (16%) of twenty-five hips with Stulberg class-I or II involvement had acetabular retroversion. The difference was significant (p = 0.0002). Patients with osteoarthritis, developmental dysplasia, or Legg-Calvé-Perthes disease are significantly more likely to have acetabular retroversion than are normal subjects (p < 0.05). CONCLUSIONS: Acetabular retroversion occurs more commonly in association with a variety of hip diseases, in which the prevalence of subsequent degenerative arthritis is increased, than has been previously noted.     

Coverage of the femoral head by the acetabular labrum in dysplastic hips

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 ben described. We used radial MRI to measure the degree of coverage of the femoral head by the acetabu-lum and the labrum, corresponding to 7 positions on the acetabular rim at every 15° from anterosuperior 45° via midsuperior to posterosuperior 45°. 38 Japanese patients (51 hips) with dysplasia, and 11 healthy controls (22 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.     

Acetabular morphological variation in Asian patients with femoral neck fracture: A three-dimensional CT-based study

AimsThe acetabular morphology varies greatly among individuals, and hypoplasia is more common in Asia than in Europe. Dislocation after bipolar hip arthroplasty (BHA) for femoral neck fracture occurs at a constant rate, and is affected by the acetabular morphology. This study aimed to clarify individual differences in the acetabula of Asian patients with displaced femoral neck fractures.Patients and methodsFifty patients with displaced femoral neck fractures were assessed (50 fractured hips, 50 non-fractured hips). On CT corrected by the anterior pelvic plane, the 100 hips were assessed regarding acetabular coverage (six parameters), acetabular depth (two parameters), and acetabular opening angle (four parameters). Additional parameters related to the fracture and sex were examined. The percentile of each parameter was shown for all hips.ResultsThere was no patient with hip dysplasia defined as superior acetabular sector angle (SASA) less than 110° Compared with men, women had a significantly smaller anterior acetabular sector angle (AASA) (p = 0.016), and significantly larger acetabular inclination angle (p = 0.006) and acetabular index angle (p = 0.034). In the group with a normal SASA, seven hips (7.3%) had an anterior wall defect (AASA<50°) and five hips (5.2%) had a posterior wall defect (posterior acetabular sector angle<90°).ConclusionOlder adults with femoral neck fractures can have anterior wall and posterior wall defects, even if their SASA is normal. Hidden acetabular dysplasia may be related to post-BHA dislocation. So, our results suggest that is important to accurately evaluate the acetabulum of patients with femoral neck fracture before surgery.     

A computer simulation study of normal and abnormal hip joint contact pressure

The contact pressure on 112 normal hip joints and 66 acetabular dysplastic hip joints was analysed using a three-dimensional rigid body spring model. Geometric models were made from conventional anteroposterior radiographs, with the assumption that the acetabular surface was spherical. In normal hips, the distribution of contact pressure was almost even over the joint surface, and the maximum contact pressure was relatively low. However, in a dysplastic hip joint, the pressure was concentrated on the anterolateral edge of the acetabulum and increased enormously not only with the reduction in lateral coverage but also with the reduction in the anterior coverage of the acetabulum. This result indicates that a three-dimensional analysis is indispensable for estimating the mechanical effect on acetabular cartilage.     

髋关节发育不良的髋臼重建

目的　总结采用全髋关节置换术治疗髋关节发育不良继发骨关节炎和功能障碍的经验。方法　 1998年 4月至 2 0 0 2年 4月 ,对 96例 112髋 (双侧 16例 )成人髋关节发育不良继发骨关节炎患者进行了全髋关节置换术。其中 ,半脱位 73髋 ,低位脱位 18髋 ,高位脱位 2 1髋。髋臼侧均采用真臼位置重建 ,其中骨水泥固定 16髋 ,非骨水泥固定 96髋 ,植骨 11髋 ;采用常规置换 83髋 ;磨削加深髋臼后 ,安置小号髋臼假体 2 7髋 ;髋臼外上缘自体股骨头植骨加深髋臼后 ,安置小号髋臼假体 2髋。结果　患者术后伤口均一期愈合 ,未发生感染或血管神经损伤 ,患肢长度平均延长 1 7cm。随访 85例 98髋 ,平均随访 3 5年 ,关节疼痛缓解 ,活动功能满意 ,Harris评分由术前的平均 33 9分恢复到平均 89 3分 ,无假体松动和翻修病例。X线片显示 ,关节假体位置正常 ,人工髋臼的平均外展角4 4° ,宿主骨对臼杯的平均覆盖率为 96 6 % ,金属臼杯与宿主髋臼之间未见透光线 ;11髋髋臼侧植骨病例中 ,植骨块与宿主骨愈合良好 ,未见骨吸收现象。结论　全髋关节置换术是治疗髋关节发育不良继发骨关节炎患者的有效方法 ;术前应充分考虑髋关节发育不良的原发及继发性病理改变 ,尽可能在真臼位置重建髋臼