The effect of acetabular cup orientations on limiting hip rotation.

The orientation of the acetabular cup and position of lip augmentation (if present) may improve postoperative total hip replacement stability by decreasing dislocation caused by hip prosthesis impingement during rotation. To determine how these cup parameters affect dislocation, the range and amount of rotation for two standard femoral components was determined in a Sawbones hemipelvis model. The parameters that allowed for maximal range of rotation were a cup angle of inclination between 35 degrees and 45 degrees and cup anteversion between 0 degrees and 10 degrees. Cup anteversion angles greater than 20 degrees and cup angles of inclination greater than 45 degrees significantly limited internal and external rotation, particularly for hip flexion greater than 60 degrees. The position of the cup lip augmentation did not affect the amount of rotation except when the hip was flexed and the lip superiorly oriented. Although there are currently devices to facilitate a particular cup position, hip stem type and orientation are other important factors affecting range of rotation that must be considered.     

全髋关节表面置换术治疗成人髋关节发育不良中假体的安放技术和临床疗效分析

目的探讨全髋关节表面置换术治疗髋关节发育不良（DDH）术中假体安放位置的控制和临床效果。方法2005年1月至2007年9月，对42例45髋因DDH继发骨关节炎的患者行全髋关节表面置换术。其中女39例，男3例，平均年龄46．3岁，单侧39例39髋，双侧3例6髋。按Crowe分型，Ⅰ型17例18髋，Ⅱ型17例19髋，Ⅲ型6例6髋，Ⅳ型2例2髋。术前通过CT三维重建测量股骨颈干角、股骨颈前倾角。入路采用改良后外侧Gibson入路，根据术前测量结果，对于颈干角小于135°，手术时适当增加至135°，大于135°则维持原有角度；DDH患者股骨前倾角均有增加，术中应适当减少，并减少髋臼前倾角和外展角。采用X线检查和Harris功能评分评估术后疗效。结果术前股骨颈干角平均134．1°，术后平均138.2°，其中术前颈干角小于135°的34髋，平均131．7°，术后平均137°；术前颈干角大于135°的12髋，平均140.9°，术后平均141．5°。股骨前倾角术前平均34．5°。术后X线显示所有髋臼均为真臼重建，髋臼外展角平均42°。双侧肢体长度差别术前平均2.1cm，术后平均0．5cm。平均随访14．6个月。Harris功能评分术前平均43．6分，最后一次随访功能评分为平均88．4分。随访期内无股骨颈骨折和假体松动等并发症发生。结论对年青DDH并骨关节炎患者采用髋关节表面置换术的近期效果满意，术中根据个体情况调整假体安放位置有助于提高临床效果。     

数字技术在人工全髋关节置换术中的应用研究

目的探索把数字技术应用于人工全髋关节置换术,为临床选择更适配的人工全髋关节假体提供新的方法。方法6例成人病变的髋关节和42-56号的髋臼假体和01-04号钛合金股骨柄(矩形,HA微孔)假体连续CT扫描,将CT扫描数据经Mimics软件处理,3D计算建立髋关节和假体的数字模型。将数据输入SPSS 17.0进行统计学分析。根据术前选择的假体施行手术,术后6个月根据Harris评分进行评价,并与同期6例行传统人工全髋关节置换术患者髋关节Harris评分进行统计学比较。结果 6例骨盆三维模型数据测量结果分析:髋臼前倾角、外展角与身高、性别、侧别因素无显著性差异;股骨颈前倾角及颈干角与侧别、性别及身高因素无统计学差异。结论数字技术可以指导选择更匹配的全髋关节假体,提高人工全髋关节置换术的近期效果,为临床术前选择全髋关节假体提供一种新的方法。     

Verbesserte Implantationstechnik der Oberflächenendoprothese des Hüftgelenks

OBJECTIVE: Prevention of incorrect positioning of the surface replacement, whereby the center of the femoral head for the implantation of the replacement surface is ascertained by central drilling of the femoral neck under image intensifier control. INDICATIONS: An arthritically damaged, but not too severely deformed femoral head that can be reamed without injuring the femoral neck. CONTRAINDICATIONS: Hip ankylosis. Femoral head necrosis. Severe deformity of the femoral head. State after varus osteotomy. SURGICAL TECHNIQUE: Using a 6-mm drill bit, the femoral neck of the affected hip is drilled from lateral to medial under anteroposterior and lateral imaging deliberately perforating the femoral head. The hip joint is exposed through a minimized invasive anterolateral, lateral, or posterior approach and dislocated. A guide rod corresponding in size to the 6-mm drill channel is inserted into the drill hole; it serves as a guide for all subsequent preparations of the femoral head, depending on the type of prosthesis. After implantation of the corresponding acetabular component, resurfacing of the femoral head is done. Reduction of the joint completes surgery. RESULTS: In the first 14 hips the midpoint of the femoral head was ascertained by using the manufacturer's centering device. In 31 subsequent hips the midpoint of the femoral head was found by central drilling of the femoral neck. Using the centering device, the average deviation of the angle of the prosthesis from the preoperative CCD angle was 7 degrees (+/- 5.7 degrees ); for central drilling of the femoral neck it was only 3 degrees (+/- 3.4 degrees ). The exact alignment of the resurfacing component is crucial for the success of surgery. It is achieved with greater precision with central drilling of the neck than with the manufacturer's centering device.     

计算机导航系统辅助下全髋关节表面置换的初步经验

目的 初步评估计算机辅助下行全髋关节表面置换的手术方法及假体植入的精确性.方法 对40例患者分成导航组(20例)和对照组(20例),分别采用计算机导航系统辅助和标准常规技术完成全髋关节表面置换术.比较两组手术时间、术中失血量、Harris髋关节评分(HHS),以及髋臼杯外展角和前倾角的偏移度及股骨假体柄干角和前倾角的偏移度.结果 手术时间导航组较对照组长38.7min(P＜0.05),术中平均出血量导航组较对照组多109.4 ml(P＜0.05).随访平均14.5个月,HHS评分两组比较差异无统计学意义(P＞0.05).对照组髋臼杯外展角偏移度(7.3°±4.3°)大于导航组(1.9°±1.3°)(P＜0.05),对照组髋臼杯前倾角偏移度(3.9°±2.3°)大于导航组(2.4°±1.5°)(P＜0.05).导航组股骨假体柄干角偏移度(1.5°±1.0°)小于对照组(11.3°±1.3°)(P＜0.05),导航组股骨假体前倾角偏移度(1.8°±2.3°)小于对照组(6.5°±5.3°)(P＜0.05).结论 计算机导航系统辅助下行全髋关节表面置换术可以提高假体植入的精确性,避免股骨颈皮质骨切迹,降低股骨颈骨折的风险.     

The effect of the orientation of the acetabular and femoral components on the range of motion of the hip at different head-neck ratios

BACKGROUND: Prosthetic impingement due to poor positioning can limit the range of motion of the hip after total hip arthroplasty. In this study, a computer model was used to determine the effects of the positions of the acetabular and femoral components and of varying head-neck ratios on impingement and range of motion. METHODS: A three-dimensional generic hip prosthesis with a hemispherical cup, a neck diameter of 12.25 millimeters, and a head size ranging from twenty-two to thirty-two millimeters was simulated on a computer. The maximum range of motion of the hip was measured, before the neck impinged on the liner of the cup, for acetabular abduction angles ranging from 35 to 55 degrees and acetabular and femoral anteversion ranging from 0 to 30 degrees. Stability of the hip was estimated as the maximum possible flexion coupled with 10 degrees of adduction and 10 degrees of internal rotation and also as the maximum possible extension coupled with 10 degrees of external rotation. The effects of prosthetic orientation on activities of daily living were analyzed as well. RESULTS: Acetabular abduction angles of less than 45 degrees decreased flexion and abduction of the hip, whereas higher angles decreased adduction and rotation. Femoral and acetabular anteversion increased flexion but decreased extension. Acetabular abduction angles of between 45 and 55 degrees permitted a better overall range of motion and stability when combined with appropriate acetabular and femoral anteversion. Lower head-neck ratios decreased the range of motion that was possible without prosthetic impingement. The addition of a modular sleeve that increased the diameter of the femoral neck by two millimeters decreased the range of motion by 1.5 to 8.5 degrees, depending on the direction of motion that was studied. CONCLUSIONS: There is a complex interplay between the angles of orientation of the femoral and acetabular components. Acetabular abduction angles between 45 and 55 degrees, when combined with appropriate acetabular and femoral anteversion, resulted in a maximum overall range of motion and stability with respect to prosthetic impingement. CLINICAL RELEVANCE: During total hip arthroplasty, acetabular abduction is often constrained by available bone coverage, while femoral anteversion may be dictated by the geometry of the femoral shaft. For each combination of acetabular abduction and femoral anteversion, there is an optimum range of acetabular anteversion that allows the potential for a maximum range of motion without prosthetic impingement after total hip arthroplasty. These data can be used intraoperatively to determine optimum position.     

Idiopathic Increased Anteversion of the Femoral Neck: Radiological and Clinical Study in Non-operated and Operated Patients

The development of femoral neck angles in children with idiopathic increased anteversion was investigated. The anteversion (AV) angle in 16 non-operated patients (n = 32) decreased from a mean of 45 degrees at the age of 7.3 years (median) to 31 degrees at the age of 15.7 years. The neckshaft (CCD) angle remained unchanged.

A subtrochanteric derotational osteotomy was performed in 24 patients (n = 48) aged 7.7 years (median). The AV angle was corrected from 47 to 3 degrees, and the CCD angle from 134 to 124 degrees. At follow-up at the age of 16.5 years the AV and the CCD angles had increased to 14 and 135 degrees respectively. The internal rotation of the hip was increased to the same extent in the two patient groups. The degree of external rotation as well as total rotation was significantly larger in the non-operated patients compared to the patients who needed an operation.

At follow-up the rotational movements of the hip and the external torsion of the leg/foot were measured and compared with the corresponding measurements for a control group of 26 healthy subjects whose median age was 16.3 years. In the non-operated patients the internal rotation was reduced at a rate corresponding to the spontaneous reduction of the femoral anteversion, while the external rotation was unchanged. In the operated patients the rotational movements were normalized, as was the anteversion of the femoral neck. No differences in external torsion of the leg/foot were found in the three groups.

Based on these results we conclude that cases of idiopathic increased anteversion of the femoral neck are not corrected spontaneously as the child grows up. With a subtrochanteric derotational osteotomy slight overcorrection may be indicated, but simultaneous varus correction of the femoral neck seems to be unnecessary. The degree of external rotation of the hip determines gait symptoms in patients with increased femoral anteversion. No regular compensatory external torsion of the leg/foot develops during growth.     

True femoral anteversion during primary total hip arthroplasty: use of postoperative computed tomography-based sections

This study investigated a reference line that is closer to the true femoral anteversion on only the cutting surface of the proximal femoral neck during a femoral stem insertion in a cementless total hip arthroplasty. A postoperative computed tomography of both hips from 33 consecutive patients after a unilateral primary cementless total hip arthroplasty with an avascular necrosis of the femoral head was taken to observe the positioning of the stem and its correlation with the true anteversion of the contralateral side. The average of the midcortical angle was 14.1 degrees +/- 6.8 degrees on the lesion side and 0.1 degrees +/- 1.3 degrees more than the true anteversion on the contralateral side. This study has shown that anteversion using a midcortical line between the anterior cortical line and the posterior cortical line is compatible with the true femoral anteversion. However, further investigation is required to confirm the true femoral anteversion.     

Movement Mapping as dynamic preoperative surgical planning in total hip replacement

The purpose of the present study was to develop and present a computer program for preoperative simulation of implant components placement in total hip alloarthroplasty, and its influence on the possible range of motion (ROM). We evaluated a computer simulation for preoperative estimation of range of motion (movement mapping) in total hip replacement. The computer program was based on Borland C++. The system had an open data port, so the data could be transferred to an Excel spreadsheet for statistical evaluation. With the developed virtual computer simulation, a practical model was established. The model showed range of motion patterns which correspond to clinical experience. ROM was best at a shaft anteversion between 20 degrees and 30 degrees. ROM had its maximum with a CCD angle of 120 degrees -130 degrees. Acetabular cup anteversion was optimal between 10 degrees and 20 degrees, and cup inclinations were optimal below 40 degrees. The presented movement mapping system seems to be a reliable option for dynamic preoperative planning, which may be a prerequisite for the use of intraoperative navigation systems.     

Compliant positioning of total hip components for optimal range of motion.

Impingement between femoral neck and endoprosthetic cup is one of the causes for dislocation in total hip arthroplasty (THA). Choosing a correct combined orientation of both components, the acetabular cup and femoral stem, in manual or computer-assisted implantation will yield a maximized, stable range of motion (ROM) and will reduce the risk for dislocation. A mathematical model of a THA was developed to determine the optimal combination of cup inclination, cup anteversion, and stem antetorsion for maximizing ROM and minimizing the risk for cup-neck impingement. Single and combined hip joint motions were tested. A radiographic definition was used for component orientation. Additional parameters, such as stem-neck (CCD) angle, head-neck ratio, and the design of the acetabular opening, were also considered. The model showed that a maximized and safe ROM requires compliant, well-defined combinations of cup inclination, cup anteversion, and stem antetorsion depending on the intended ROM. Radiographic cup anteversion and stem antetorsion were linearly correlated. Additional internal rotation reduced flexion, and additional external rotation reduced extension, abduction and adduction. The articulating hemispheric surface of acetabular cups should be oriented between 40 degrees and 45 degrees of radiographic inclination, between 20 degrees and 28 degrees of radiographic cup anteversion, and should be combined with stem antetorsion so that the sum of cup anteversion plus 0.7 times the stem antetorsion equals 37 degrees. Final component orientation must also consider cup containment, implant impingement with bone and soft tissue, and preoperative skeletal contractures or deformities to achieve the optimal compromise for each patient.     

Computer-assisted navigated cup placement in primary and secondary dysplastic hips

AIM: The positioning of an acetabular implant has great influence on the range of motion as well as the charger of dislocation of total hip arthroplasty. Using modern CAS systems the reproduction of the cup position after three-dimensional planning based on computed tomography is possible. We investigated the reliability of the position of the acetabular implant in primary and secondary dysplastic cases. METHOD: Within a prospective randomised study in a total of 100 hip replacements with postoperatively controlled cup position using a computed tomography, we reinvestigated especially the 18 dysplastic and two secondary dysplastic cases. RESULTS: In the dysplastic cases we could realise nearly the same anteversion angles (22.4 degrees to 21.5 degrees) with a bigger standard deviation (+/- 7.68 degrees to +/- 7.29) than in the normal collective. Even the inclination angles (44.5 degrees +/- 5.47 degrees) could be realized nearly the same as in the normal cases (42.3 degrees +/- 4.31 degrees). The depth of the cup implantation could be realised in 15 of 18 cases. CONCLUSION: The CAS system is helpful even in dysplastic cases. The advantage of three-dimensional preoperative CT-based planning is apparent. The surgeon is not able to plan and realise the ideal cup position in some individual.     

Bilateral varus osteotomies in hip deformities: are early interventions superior?

Coxa valga (with or withour excessive femoral anteversion) combined with acetabular dysplasia is a well-known cause of early osteoarthritis. Many authors have stated that the best result of an osteotomy can be achieved at an early stage of these osteoarthritic changes. In this study, we present 26 patients with a symmetrical hip deformity for which we performed a therapeutic osteotomy on the symptomatic hip. The contralateral hip had the same anatomical predisposition to develop an OA, but there were only minor to no complaints. We advised and performed an early osteotomy on these hips. On radiological evaluation, an average Sharp angle of 42.2 degrees and an average CCD of 142 degrees was present. During an average follow-up period of 19.9 years (range 15.0-25.9), 14 hips were converted to THR after the primary osteotomy, whereas there were only 6 after the early osteotomy (chi-square P<0.05). Using a Pearson correlation analysis, the age, preoperative grade of OA, preoperative Merle d'Aubigne score and excessive femoral anteversion were significantly correlated with the outcome. Our results show that the effect of an early, more prophylactic varus osteotomy in patients with a coxa valga with excessive femoral anteversion and acetabular dysplasia can be superior to the results achieved when surgery is postponed until the complaints and arthrosis have become more severe.     

Femoral anteversion in normal adults. Ultrasound measurements in 50 men and 50 women.

The femoral anteversion (AV) angles were measured by ultrasound in a normal group of 100 adult subjects to find the normal range of anteversion, to determine the normal left/right difference, to assess the interobserver variation, and to find the correlation between AV angle and clinical hip rotation. All the ultrasound measurements were performed independently by 2 observers. The mean AV angle was 18 degrees in the women and 14 degrees in the men. The mean left/right difference in AV was 3.8 degrees, and the upper normal limit of side difference (mean +/- 2 SD) was 9.8 degrees. The mean (SD) interobserver variation was only 1.9 degrees (1.3 degrees). The correlations between AV angles and internal and external hip rotation were significant, but not very high (r = 0.49 and -0.49, respectively). We conclude that ultrasound is appropriate for measurement of femoral anteversion. Our results could be used as a basis when evaluating patients with clinically suspected rotational disorders of the femur.     

成人常见髋关节疾病双侧髋关节解剖参数的研究

目的探讨行全髋关节置换术中利用对侧相对正常髋关节的解剖参数作为模板重建患侧髋关节的准确性。 方法选取2019年9月至2020年12月于大连医科大学附属第一医院关节外科行首次单侧全髋关节置换术的患者作为研究对象。纳入标准：患侧诊断为髋关节骨关节炎、股骨头坏死或髋关节发育不良Crowe Ⅰ型；对侧髋关节形态不影响测量。排除标准：患侧髋关节既往手术史；畸形严重影响测量；髋关节发育不良Crowe Ⅱ型及以上。最后共纳入82例患者，其中33例男性，49例女性，年龄范围29~74岁。根据患者X线及CT影像数据，分别测量患者患侧及对侧髋臼前倾角、髋臼外展角、股骨前倾角、颈干角以及股骨偏心距，并计算其各自的联合前倾角。运用t检验、Pearson相关性分析等统计学方法分析双侧髋关节解剖参数的对称性。 结果对股骨头坏死及髋关节骨关节炎患者来说，除双侧股骨偏心距患侧小于对侧外(t＝0.523，P <0.05)，余双侧髋关节解剖参数包括髋臼前倾角、髋臼外展角、股骨前倾角、联合前倾角及颈干角的差异均无统计学意义(均为P>0.05)。Pearson相关性分析显示股骨头坏死及骨关节炎患者股骨偏心距的不对称性与颈干角有相关性(r＝-0.519，P<0.001)，颈干角的不对称性与股骨前倾角(r＝0.303，P＝0.041)以及股骨偏心距有相关性，联合前倾角的不对称性与髋臼外展角(r＝0.311，P＝0.035)、颈干角(r＝0.049，P＝0.032)有相关性。Crowe Ⅰ型髋关节发育不良患者的髋臼前倾角(t＝2.081，P＝0.045)、股骨偏心距(t＝3.934，P<0.001)患侧小于对侧，颈干角患侧大于对侧(t＝3.792，P＝0.001)；而双侧髋臼外展角、股骨前倾角、联合前倾角差异均无统计学意义(均为P>0.05)。Pearson相关性分析发现股骨偏心距的不对称性与颈干角(r＝-0.709，P<0.001)、股骨前倾角(r＝-0.349，P＝0.037)有相关性。Crowe Ⅰ型髋关节发育不良患者的股骨偏心距小于股骨头坏死患者或髋关节骨关节炎患者，而髋臼前倾角、髋臼外展角、颈干角大于后者。 结论对于股骨头坏死患者及髋关节骨关节炎患者来说利用对侧肢体作为模板重建患侧髋关节是可行的。而Crowe Ⅰ型髋关节发育不良患者双侧髋关节解剖形态差异较大，对这类患者的全髋关节置换术需个体化。     

The combined anteversion technique for acetabular component anteversion

The combined anteversion technique for acetabular component placement of total hip arthroplasty is beneficial because of the surgeons' limited ability to control the anteversion of a cementless femoral stem. Our data show that the cementless stem anteversion can be 15 degrees different than anticipated. By determining femoral stem anteversion before positioning cup anteversion, the cup anteversion can be adjusted for the stem anteversion. The combined anteversion technique should provide a mean near 35 degrees with a safe zone of 25 degrees to 50 degrees.     

Assessment of implant position of CTX-custom-made stems with EBRA-FCA in 107 cases of total joint replacement

AIM: The aim of this study was to assess the ratio of correct and malpositioned stems in a THR population with custom-made stems. Furthermore, any relation of the extent of deviation from the exact stem position and defined patient variables was evaluated. METHODS: Preoperatively, in three-dimensional virtual reality, CTX-individual hip stems were positioned in femora reconstructed from the individual patient's CT data until a stable cortical fit was achieved. Postoperative femoral stem position was measured with EBRA-FCA (EinzelBildRontgenAnalyse-Femoral Component Analysis). Differences of planned and actual depth of stem position were calculated for 107 CTX-custom-made hip stems implanted at one institution. RESULTS: Compared to preoperative planning 59 hip stems were placed too high, while 16 were placed exactly to within one millimeter and 32 were positioned too low. Deviations of postoperative stem position from preoperative planning did not correlate with previous femoral osteotomy found in one-third of femora or femoral anteversion exceeding 25 degrees as present in two-thirds of patients. CONCLUSION: In 71 % the intraoperative stem position did match the preoperative CTX-implant fitting into virtual patient femora. 29 % of implanted stems were malpositioned, i. e., deviations were greater plus or minus 5 mm to preoperative computer planning. None of the examined variables such as body mass index, previous femoral osteotomy, surgical approach, abnormal anteversion angle served as a predictive value for CTX-stem position in this cohort.     

Changes of biomechanical parameters in dysplasia of the hip by total hip replacement

AIM: Dysplastic hips or dislocated hips lead to loss of muscle strength claudication, and finally to coxarthrosis. This study analytically compares the hip joint forces in normal, dysplastic hips and hips after implantation of a hip prosthesis for several positions. METHOD: The results of 173 total hip replacements in 153 cases of either severe congenital dysplasia or dislocation were analyzed. A 2 dimensional mathematical model of the hip was developed to evaluate the effects of surgically achievable mechanical alterations such as acetabular placement, femoral shaft-prosthetic neck angle, and neck length of the femoral prosthesis. RESULTS: 63 % of the hip prosthesis were implanted on the right, 72 % on the left. Before implantation, the femoral shaft-prosthetic neck angle in mean was 146 degrees +/- 10 degrees, after implantation it was 135 degrees. The hip centre was displaced on in average 10 mm distally. Postoperatively hip joint force was increased 21 %. CONCLUSION: Minimum joint contact forces occurred when the femoral shaft prosthetic neck angles were small. The loads on the hip were lowered significantly by placing the centre of the acetabulum as far inferiorly and medially as possible. Another important finding is that displacement of the hip centre distally has a great effect on muscle performance and hip joint force.     

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.     

Die intertrochantäre Korrekturosteotomie nach Imhäuser

OBJECTIVE: Surgical correction of deformities of the proximal femur caused by epiphyseal displacement by restorative (usually inflection and internal rotation) osteotomy at the intertrochanteric level with the aim of reducing both the offset disorder of the coxal end of the femur that is causing impingement and the prevalence of secondary coxarthrosis. INDICATIONS: Chronic and subacute manifestations of slipped capital femoral epiphysis with an epiphyseal dislocation in the radiographic axial view of 30-60 degrees (ET angle) and DeltaED > 20 degrees (CCD angle minus ED angle) in the anteroposterior view. CONTRAINDICATIONS: Acute phase or course of slipped capital femoral epiphysis. Secondary coxarthrosis (after slipped capital femoral epiphysis). Traumatic epiphyseolysis. SURGICAL TECHNIQUE: Exposure of the proximal femur (anterior femoral neck, intertrochanteric plane, proximal femoral diaphysis) through an anterolateral approach; fixation of the femoral epiphysis with two 3.0-mm Steinmann nails positioned parallel in a posteromedial direction; the seating chisel is hammered in according to the planned, usually inflectional axial correction; intertrochanteric osteotomy by excision of a wedge oriented in accordance with preoperative planning; adaptation of the osteotomy surfaces and osteosynthesis with a 90 degrees AO adolescent plate under interfragmentary compression. POSTOPERATIVE MANAGEMENT: Mobilization on underarm crutches with unloading of the extremity for 2 months postoperatively; gradual increase in loading depending on osseous consolidation of the osteotomy; radiographic assessment 2 and 4 months postoperatively, further clinical and radiologic follow-up until growth is completed (closure of the growth plate); removal of implants at 1 year postoperatively or thereafter. RESULTS: Retrospective follow-up of 51 patients with unilateral, moderate to severe slipped capital femoral epiphysis (indication: epiphyseal displacement angle of 30-60 degrees, average preoperative displacement angle 45 degrees) that was corrected surgically by Imh?user intertrochanteric osteotomy and epiphyseal nailing. After an average observation time of 24 years (range: 20-29 years), 28 (55%) of the 51 hip joints were clinically asymptomatic and radiologically free of degenerative changes; moderate clinical and radiologic changes were recorded for 14 hip joints (28%), and advanced changes for nine (17%). Complications related to surgery were apparent in a total of six hip joints: in one case, the Steinmann nail broke after being damaged by the plate blade; in two cases, revision osteosynthesis of the intertrochanteric osteotomy was necessary due to incorrect implant positioning; partial femoral head necrosis developed in one hip joint; there were two cases of low-grade osteomyelitis that healed after implant removal.