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Posterior approaches to the hip joint were developed by Langenbeck and Kocher in the nineteenth century. Letournel created the term Kocher-Langenbeck approach which became one of the most important approaches to the hip joint. The further extension of this approach by digastric trochanteric osteotomy and subsequently by surgical hip dislocation enables visualization of the entire hip joint which allows complete evaluation of articular joint damage, quality of reduction and confirmation of extra-articular hardware. With the increasing incidence of acetabular fractures in the elderly there is a concomitant increase of complicating factors, such as multifragmentary posterior wall fractures, dome impaction, marginal impaction and femoral head damage. These factors are negative predictors and compromise a favorable outcome after acetabular surgery. With direct joint visualization these factors can be reliably recognized and corrected as adequately as possible. Surgical hip dislocation thus offers advantages in complex posterior wall, transverse and T-shaped fractures with or without posterior wall involvement. For these fracture types surgical hip dislocation represents a standard approach in our hands.

Background: Developmental dysplasia of the hip (DDH) and acetabular retroversion represent distinct acetabular pathomorphologies. Both are associated with alterations in pelvic morphology. In cases where direct radiographic assessment of the acetabulum is difficult or impossible or in mixed cases of DDH and retroversion, additional indirect pelvimetric parameters would help identify the major underlying structural abnormality., Questions/purposes: We asked: How does DDH and retroversion differ with respect to rotation and coronal obliquity as measured by the pelvic width index, anterior inferior iliac spine (AIIS) sign, ilioischial angle, and obturator index? And what is the predictive value of each variable in detecting acetabular retroversion?, Methods: We reviewed AP pelvis radiographs for 51 dysplastic and 51 retroverted hips. Dysplasia was diagnosed based on a lateral center-edge angle of less than 20° and an acetabular index of greater than 14°. Retroversion was diagnosed based on a lateral center-edge angle of greater than 25° and concomitant presence of the crossover/ischial spine/posterior wall signs. We calculated sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve for each variable used to diagnose acetabular retroversion., Results: We found a lower pelvic width index, higher prevalence of the AIIS sign, higher ilioischial angle, and lower obturator index in acetabular retroversion. The entire innominate bone is internally rotated in DDH and externally rotated in retroversion. The areas under the ROC curve were 0.969 (pelvic width index), 0.776 (AIIS sign), 0.971 (ilioischial angle), and 0.925 (obturator index)., Conclusions: Pelvic morphology is associated with acetabular pathomorphology. Our measurements, except the AIIS sign, are indirect indicators of acetabular retroversion. The data suggest they can be used when the acetabular rim is not clearly visible and retroversion is not obvious., Level of Evidence: Level III, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Background: Understanding acetabular pathomorphology is necessary to correctly treat patients with hip complaints. Existing radiographic parameters classify acetabular coverage as deficient, normal, or excessive but fail to quantify contributions of anterior and posterior wall coverage. A simple, reproducible, and valid measurement of anterior and posterior wall coverage in patients with hip pain would be a clinically useful tool., Questions/purposes: We (1) introduce the anterior wall index (AWI) and posterior wall index (PWI), (2) report the intra- and interobserver reliability of these measurements, and (3) validate these measurements against an established computer model., Methods: We retrospectively reviewed 87 hips (63 patients) with symptomatic hip disease. A validated computer model was used to determine total anterior and posterior acetabular coverage (TAC and TPC) on an AP pelvis radiograph. Two independent observers measured the AWI and PWI on each film, and the intraclass correlation coefficient (ICC) was calculated. Pearson correlation was used to determine the strength of linear dependence between our measurements and the computer model., Results: Intra- and interobserver ICCs were 0.94 and 0.99 for the AWI and 0.81 and 0.97 for the PWI. For validation against the computer model, Pearson r values were 0.837 (AWI versus TAC) and 0.895 (PWI versus TPC). Mean AWI and PWI were 0.28 and 0.81 for dysplastic hips, 0.41 and 0.91 for normal hips, 0.61 and 1.15 for hips with a deep acetabulum., Conclusions: Our data suggest these measures will be helpful in evaluating anterior and posterior coverage before and after surgery but need to be evaluated in asymptomatic individuals without hip abnormalities to establish normal ranges., Level of Evidence: Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Femoroacetabular impingement (FAI) is a pathomechanical concept describing the early and painful contact of morphological changes of the hip joint, both on the acetabular, and femoral head sides. These can lead clinically to symptoms of hip and groin pain, and a limited range of motion with labral, chondral and bony lesions. Pincer impingement generally involves the acetabular side of the joint where there is excessive coverage of the acetabulum, which may be focal or more diffuse. There is linear contact of the acetabulum with the head/neck junction. Cam impingement involves the femoral head side of the joint where the head is associated with bony excrescences and is aspheric. The aspheric femoral head jams into the acetabulum. Imaging appearances are reviewed below. This type is evident in young males in the second and third decades. The main features of FAI are described., (Copyright © 2011. Published by Elsevier Ireland Ltd.)

Background: Patients after Legg-Calvé-Perthes disease (LCPD) often develop pain, impaired ROM, abductor weakness, and progression of osteoarthritis (OA) in early adulthood. Based on intraoperative observations during surgical hip dislocation, we established an algorithm for more detailed characterization of the underlying pathomorphologies with a proposed joint-preserving surgical treatment., Questions/purposes: We asked if patients after LCPD treated with our algorithm experienced (1) reduced pain; (2) improved hip function; and/or (3) prevention of OA progression; we then determined (4) the intraoperative damage patterns; (5) the survival of the hip; and (6) factors predicting the need for a conversion to THA; radiographic progression of OA; a Merle d'Aubigné-Postel score below 15 at last followup; and/or the need for revision surgery., Methods: We retrospectively reviewed 53 patients after LCPD who underwent joint-preserving surgery (40 surgical hip dislocations, eight acetabular osteotomies, four combined procedures, and one intertrochanteric osteotomy). We obtained Merle d'Aubigné-Postel scores to assess pain; OA was assessed using Tönnis grades. Survival and predictive factors were calculated with the univariate Cox regression. Fifty of the 53 patients were evaluated at a minimum of 5.1 years (mean, 8.2 years; range, 5.1-12.8 years)., Results: Pain and hip function improved at followup from a median of 4 points to 5 points. The mean increase in Tönnis grades at last followup was 0.3 to 0.8. The survival of surgery at 5 years was 86%; 13 factors related to survival., Conclusion: Patients with symptoms resulting from pathomorphologic deformities after LCPD benefit from joint-preserving surgery with specific treatment of individual structural abnormalities.

Background: Legg-Calvé-Perthes disease (LCPD) often results in a deformity that can be considered as a complex form of femoroacetabular impingement (FAI). Improved preoperative characterization of the FAI problem based on a noninvasive three-dimensional computer analysis may help to plan the appropriate operative treatment., Questions/purposes: We asked whether the location of impingement zones, the presence of additional extraarticular impingement, and the resulting ROM differ between hips with LCPD and normal hips or hips with FAI., Methods: We used a CT-based virtual dynamic motion analysis based on a motion algorithm to simulate the individual motion for 13 hips with LCPD, 22 hips with FAI, and 27 normal hips. We then determined the motion and impingement pattern of each hip for the anterior (flexion, adduction, internal rotation) and the posterior impingement tests (extension, adduction, external rotation)., Results: The location of impingement zones in hips with LCPD differed compared with the FAI/normal groups. Intra- and extraarticular impingement was more frequent in LCPD (79% and 86%, respectively) compared with normal (15%, 15%) and FAI hips (36%, 14%). Hips with LCPD had decreased amplitude for all hip motions (flexion, extension, abduction, adduction, internal and external rotation) compared with FAI or normal., Conclusions: Hips with LCPD show a decreased ROM as a result of a higher prevalence of intra- and extraarticular FAI. Noninvasive assessment of impingement characteristics in hips with LCPD may be helpful in the future for establishment of a surgical plan.

Background: The evidence supporting continued use of shelf acetabuloplasty in Legg-Calvé-Perthes disease (LCPD) is not well-defined, and there is controversy regarding the long-term benefits related to clinical and functional improvement., Questions/purposes: Our goals were to determine whether shelf arthroplasty for LCPD (1) prevents the onset of early osteoarthritis; (2) improves pain, ROM, activity, and functional outcomes; (3) maintains or improves femoral head containment, sphericity, and congruency; (4) changes the acetabular index; and (5) is associated with a low rate of complications., Methods: We performed a systematic review of the medical literature from 1966 to 2009 using the search terms Perthes, shelf procedure, and acetabuloplasty. We excluded reports using multiple/combined treatment methods and those not clearly stratifying outcomes. Thirteen studies met the criteria. There were no Level I studies, one Level II prognostic study, five Level III therapeutic studies, and seven Level IV studies. Mean followup ranged from 2.6 to 17.9 years., Results: Only one study reported progression to early osteoarthritis in one patient. We found no evidence for improvement in ROM and continued pain relief at long-term followup. Mean decrease in lateral subluxation ratio was 13% to 30%, demonstrating an improvement in femoral head containment. Mean acetabular cover percentage improved 16% to 38%, and mean acetabular and center-edge angles improved 4° to 14° and 8° to 33°, respectively. There were no reports of any major complications after the procedure., Conclusions: While radiographic measurements indicate improved coverage of the femoral head after shelf acetabuloplasty for LCPD, available evidence does not document the procedure prevents early onset of osteoarthritis or improves long-term function.

Objectives: To classify the fracture patterns of gunshot wounds to the acetabulum; identify the associated injuries and complications; determine the predictors of poor outcome and deep infection; and propose a treatment algorithm based on the results., Design: Retrospective review of two trauma registry databases over a 13-year period., Setting: Multicenter study., Patients: Thirty-nine gunshot wounds to the acetabulum (38 patients)., Intervention: Treatment strategy was based on infection control by treating bowel and bladder injury, presence/absence of intra-articular lead, pattern, and stability of the fracture., Main Outcome Measurements: Merle d'Aubigné score, rate of failures, and complications. Multivariate logistic regression analysis to detect predictors of poor outcome and deep infection., Results: There were 32 simple (82%) and seven (18%) associated fracture patterns. Bowel injuries were the most common associated injures. There was a 54% major complication rate. Significant predictors of poor outcome were high-velocity missile, involvement of the acetabular dome, abdominal injury, nerve injury, vascular injury, and male gender. Significant factors associated with deep infection were presence of a bowel injury with primary anastomosis of the bowel and an associated fracture pattern., Conclusions: The Letournel classification system can be applied to describe these injuries. The successful treatment of the bowel injury directly correlates to infection control. Diverting colostomy is associated with a reduction of the infection rate. Overall, gunshot wounds to the acetabulum are catastrophic injuries with a high complication rate and poor functional outcome. A multidisciplinary algorithm is proposed for treatment of these complex injuries., Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Background: The iliocapsularis muscle is a little known muscle overlying the anterior hip capsule postulated to function as a stabilizer of dysplastic hips. Theoretically, this muscle would be hypertrophied in dysplastic hips and, conversely, atrophied in stable and well-constrained hips. However, these observations have not been confirmed and the true function of this muscle remains unknown., Questions/purposes: We quantified the anatomic dimensions and degree of fatty infiltration of the iliocapsularis muscle and compared the results for 45 hips with deficient acetabular coverage (Group I) with 40 hips with excessive acetabular coverage (Group II)., Patients and Methods: We used MR arthrography to evaluate anatomic dimensions (thickness, width, circumference, cross-sectional area [CSA], and partial volume) and the amount of fatty infiltration., Results: We observed increased thickness, width, circumference, CSA, and partial volume of the iliocapsularis muscle in Group I when compared with Group II. Additionally, hips in Group I had a lower prevalence of fatty infiltration compared with those in Group II. The iliocapsularis muscle typically was hypertrophied, and there was less fatty infiltration in dysplastic hips compared with hips with excessive acetabular coverage., Conclusion: These observations suggest the iliocapsularis muscle is important for stabilizing the femoral head in a deficient acetabulum. This muscle serves as an anatomic landmark when performing a periacetabular osteotomy. Additionally, preoperative evaluation of morphologic features of the muscle can be used as an adjunct for decision making when treating patients with borderline hip dysplasia or femoroacetabular impingement.

An automated algorithm for detection of the acetabular rim was developed. Accuracy of the algorithm was validated in a sawbone study and compared against manually conducted digitization attempts, which were established as the ground truth. The latter proved to be reliable and reproducible, demonstrated by almost perfect intra- and interobserver reliability. Validation of the automated algorithm showed no significant difference compared to the manually acquired data in terms of detected version and inclination. Automated detection of the acetabular rim contour and the spatial orientation of the acetabular opening plane can be accurately achieved with this algorithm., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objectives: Gunshot wounds (GSW) affecting the genitourinary (GU) system in civilians are uncommon. This study describes the incidence, anatomic distribution, demographics, associated injuries, management, and outcomes after civilian GU GSW., Methods: A Level 1 Trauma Center Registry was used to retrospectively identify all patients who sustained GU GSW (January 1997-December 2008). Patient information was abstracted from the Registry, medical, and autopsy records. Multivariate regression detected significant factors associated with mortality., Results: Of 2941 civilian GSW patients, 309 (10.5%) sustained GU injury with/without associated injuries. Mean age was 30.4 ± 11.9 years (range 6.6-80.6 years); 289 patients (93.5%) were male. Mean Injury Severity Score (ISS) 22.2 ± 15.4 (1-75). Incidence of GU GSW increased during the study period. GSW affected the kidneys (55%), scrotum (21%), bladder (19%), testicle (12%), penis (8%), some patients having more than 1 GU organ injured. A total of 284 patients (92%) experienced at least 1 other organ injury. Most GU GSW were managed surgically (mean 2.2 ± 2.0; 0-13 surgeries/patient). There was a 27% (n = 84) overall mortality, with 16% (n = 50) dead on arrival. Mortality and ISS were correlated (P = 0.002; hazard ratio = 3.0; 95% confidence interval 3.0-3.0CI). Large vessel, head/neck, kidney, vascular, heart, lung, spine, and spinal cord injury were statistically significant risk factors for death., Conclusions: GU injury occurred in 10.5% of 2941 civilian GSW patients. Associated injuries were very common, with many cases involving multiple organs. Most injuries (90%) were managed surgically. Mortality is usually the result of associated nongenitourinary injuries. A high index of suspicion for injuries affecting other organs is necessary in managing GU GSW trauma patients., (Copyright © 2010 Elsevier Inc. All rights reserved.)

We introduce a new method for computerized real-time evaluation of femoroacetabular impingement (FAI). In contrast to previously presented stress analyses, this method is based on two types of predictions of penetration depths for two rotating bodies: curvilinear and radial penetration depth. This intuitive method allows the analysis of both bony and soft tissue structures (such as cartilage and acetabular labrum) in real time. Characteristic penetration depth patterns were found for different subtypes of FAI, such as cam and pincer pathologies. In addition, correlation between the penetration depths (estimated by applying this method) and the existing contact stresses (estimated by applying the finite element method) of various hip morphologies were found. A strong correlation with predicted stress values existed, with a mean correlation coefficient of 0.91 for the curvilinear and 0.80 for the radial penetration method. The results show that the penetration depth method is a promising, fast, and accurate method for quantification and diagnosis of FAI., ((c) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Seventeen bones (sixteen cadaveric bones and one plastic bone) were used to validate a method for reconstructing a surface model of the proximal femur from 2D X-ray radiographs and a statistical shape model that was constructed from thirty training surface models. Unlike previously introduced validation studies, where surface-based distance errors were used to evaluate the reconstruction accuracy, here we propose to use errors measured based on clinically relevant morphometric parameters. For this purpose, a program was developed to robustly extract those morphometric parameters from the thirty training surface models (training population), from the seventeen surface models reconstructed from X-ray radiographs, and from the seventeen ground truth surface models obtained either by a CT-scan reconstruction method or by a laser-scan reconstruction method. A statistical analysis was then performed to classify the seventeen test bones into two categories: normal cases and outliers. This classification step depends on the measured parameters of the particular test bone. In case all parameters of a test bone were covered by the training population's parameter ranges, this bone is classified as normal bone, otherwise as outlier bone. Our experimental results showed that statistically there was no significant difference between the morphometric parameters extracted from the reconstructed surface models of the normal cases and those extracted from the reconstructed surface models of the outliers. Therefore, our statistical shape model based reconstruction technique can be used to reconstruct not only the surface model of a normal bone but also that of an outlier bone., (Copyright 2010 IPEM. Published by Elsevier Ltd. All rights reserved.)

Surgical dislocation of the hip in the treatment of acetabular fractures allows the femoral head to be safely displaced from the acetabulum. This permits full intra-articular acetabular and femoral inspection for the evaluation and potential treatment of cartilage lesions of the labrum and femoral head, reduction of the fracture under direct vision and avoidance of intra-articular penetration with hardware. We report 60 patients with selected types of acetabular fracture who were treated using this approach. Six were lost to follow-up and the remaining 54 were available for clinical and radiological review at a mean follow-up of 4.4 years (2 to 9). Substantial damage to the intra-articular cartilage was found in the anteromedial portion of the femoral head and the posterosuperior aspect of the acetabulum. Labral lesions were predominantly seen in the posterior acetabular area. Anatomical reduction was achieved in 50 hips (93%) which was considerably higher than that seen in previous reports. There were no cases of avascular necrosis. Four patients subsequently required total hip replacement. Good or excellent results were achieved in 44 hips (81.5%). The cumulative eight-year survivorship was 89.0% (95% confidence interval 84.5 to 94.1). Significant predictors of poor outcome were involvement of the acetabular dome and lesions of the femoral cartilage greater than grade 2. The functional mid-term results were better than those of previous reports. Surgical dislocation of the hip allows accurate reduction and a predictable mid-term outcome in the management of these difficult injuries without the risk of the development of avascular necrosis.

Objective: Elimination of an intraarticular femoroacetabular impingement conflict. Creation of a pain-free, normal range of motion of the hip., Indications: Femoroacetabular impingement of any type (cam/pincer) and any localization (anterior/posterior)., Contraindications: Absolute: advanced hip osteoarthritis, local infections around the hip. Relative: excessive acetabular retroversion with deficiency of the posterior wall., Surgical Technique: Lateral decubitus position. Straight lateral incision centered over the greater trochanter. Entering of the Gibson interval. Digastric trochanteric osteotomy with protection of the medial circumflex femoral artery. Opening of the interval between the piriformis and the gluteus minimus muscle. Z-shaped capsulotomy. Dislocation of the femoral head. Detachment of the labrum. Trimming of the excessive acetabular rim. Refixation of the labrum. Creation of a sufficient femoral head-neck offset. Suture of the capsule. Refixation of the trochanter., Postoperative Management: During hospital stay, intensive mobilization of the hip joint using a continuous passive motion machine with a maximum flexion of 90 degrees . No active abduction and passive adduction over the body's midline. Maximum weight bearing 10-15 kg for 6 weeks. Subsequently, first clinical and radiographic follow-up. Deep venous thrombosis prophylaxis until full weight bearing., Results: Short- and mid-term results showed an improvement of the postoperative clinical score (Merle d'Aubigné Score) in 95% of all patients, depending on the individual degenerative joint alterations at the time of surgery. Good to excellent results were obtained in 91% of all cases. Cumulative 5-year survival was 91% (endpoint total hip arthroplasty or poor Merle d'Aubigné Score). Long-term results are not available yet.

Although the ischial spine sign (ISS) has been advocated to detect acetabular retroversion, it is unknown whether the sign is valid on anteroposterior (AP) pelvic radiographs with tilted or rotated pelves. We therefore evaluated reliability of the ISS as a tool for diagnosing acetabular retroversion in the presence of considerable pelvic tilt and/or malrotation. We obtained radiographs of 20 cadaver pelves in 19 different malorientations resulting in 380 pelvis images (760 hips) for evaluation. In addition, 129 clinical radiographs of patients' hips that had varying pelvis orientations were reviewed. We found an overall sensitivity of 81% (90%), specificity of 70% (71%), positive predictive value of 77% (80.7%), and negative predictive value of 75% (85%) in the cadaver (patient) hips. Our data suggest the ISS is a valid tool for diagnosing acetabular retroversion on plain radiographs taken using a standardized technique regardless of the degree of pelvic tilt and rotation.

Introduction: A novel computerized algorithm for hip joint motion simulation and collision detection, called the Equidistant Method, has been developed. This was compared to three pre-existing methods having different properties regarding definition of the hip joint center and behavior after collision detection. It was proposed that the Equidistant Method would be most accurate in detecting the location and extent of femoroacetabular impingement., Materials and Methods: Five plastic pelves and ten plastic femora with modified acetabula and head-neck junctions, allowing for 50 different morphologic combinations, were examined, along with six cadaver hips. First, motions along anatomically relevant paths were performed. These motions were tracked by a navigation system and impingement locations were digitized with a pointer. Subsequently, previously generated 3D models of all the specimens, together with the recorded anatomic motion paths, were applied to all four simulation algorithms implemented in a diagnostic computer application. Collisions were detected within the motion paths, and the linear and angular differences regarding the location as well as the size of the detected impingement areas were compared and analyzed., Results: The Equidistant Method detected impingement with significantly higher linear and angular accuracy compared to the other methods (p < 0.05). The size of the detected impingement area was smaller than that detected with the other methods, but this difference was not statistically significant., Conclusions: The increased accuracy of the Equidistant Method is achieved by implementing a dynamic hip joint center, more closely resembling the natural characteristics of the hip joint. Clinical application of this algorithm might serve as a diagnostic adjunct and support in the planning of joint-preserving surgery in patients with femoroacetabular impingement.

Suture materials in orthopaedic surgery are used for closure of wounds, repair of fascia, muscles, tendons, ligaments, joint capsules, and cerclage or tension band of certain fractures. The purpose of this study was to compare the biomechanical properties of eleven commonly used sutures in orthopaedic surgery. Three types of braided non-absorbable and one type of braided absorbable suture material with different calibers (n=77) underwent biomechanical testing for maximum load to failure, strain, and stiffness. All samples were tied by one surgeon with a single SMC (Seoul Medical Center) knot and three square knots. The maximum load to failure and strain were highest for #5 FiberWire and lowest for #0 Ethibond Excel (p<0.001). The stiffness was highest for #5 FiberWire and lowest for #2-0 Vicryl (p<0.001). In all samples, the failure of the suture material occurred at the knot There was no slippage of the knot in any of the samples tested. This data will assist the orthopaedic surgeon in selection and application of appropriate suture materials and calibers to specific tasks.

Our goal was to validate accuracy, consistency, and reproducibility/reliability of a new method for determining cup orientation in total hip arthroplasty (THA). This method allows matching the 3D-model from CT images or slices with the projected pelvis on an anteroposterior pelvic radiograph using a fully automated registration procedure. Cup orientation (inclination and anteversion) is calculated relative to the anterior pelvic plane, corrected for individual malposition of the pelvis during radiograph acquisition. Measurements on blinded and randomized radiographs of 80 cadaver and 327 patient hips were investigated. The method showed a mean accuracy of 0.7 +/- 1.7 degrees (-3.7 degrees to 4.0 degrees) for inclination and 1.2 +/- 2.4 degrees (-5.3 degrees to 5.6 degrees) for anteversion in the cadaver trials and 1.7 +/- 1.7 degrees (-4.6 degrees to 5.5 degrees) for inclination and 0.9 +/- 2.8 degrees (-5.2 degrees to 5.7 degrees) for anteversion in the clinical data when compared to CT-based measurements. No systematic errors in accuracy were detected with the Bland-Altman analysis. The software consistency and the reproducibility/reliability were very good. This software is an accurate, consistent, reliable, and reproducible method to measure cup orientation in THA using a sophisticated 2D/3D-matching technique. Its robust and accurate matching algorithm can be expanded to statistical models.

Introduction: The purpose of this study was to prospectively evaluate the 5-13-year results of a cementless total hip arthroplasty with a special focus on the survivorship,occurrence of osteolysis, incidence of intraoperative femoral fractures, thigh pain, and cortical hypertrophy of the femoral stem. The femoral component used in this study was titanium fluted, slotted, symmetrical component that was prepared with intraoperative machining. The proximal third of the stem had hydroxyl-apatite coating and horizontal steps., Methods: The clinical and radiographical results of a consecutive series of 157 total hip arthroplasties (124 patients)with this stem were investigated. Minimum follow-up was 5 years. The average age of the patients at the time of surgery was 47 years. Three patients died and ten patients were lost to follow-up, leaving 142 hips for evaluation. The clinical result was evaluated on the basis of the Merled’Aubigné score, complications and thigh pain. A detailed radiographic analysis was performed at each follow-up visit. Kaplan–Meier survivorship analysis was performed to evaluate stem, cup, and bearing survivorship., Results: The mean follow-up was 8.5 years (range 5-13 years). The average Merle d’Aubigné score improved from 10.5 points preoperatively to 17.4 points postoperatively.The cumulative 10-year survival rate was 99% for the femoral component, 99% for the acetabular component,and 69% for the bearing. Thigh pain was identified in three patients (2%). There was no distal femoral osteolysis.Seventy-nine percent of all the hips had endosteal spot welds around the coated, proximal one-third of the prosthesis.51% had radio dense lines around the distal tip of the prosthesis,and 3% had cortical hypertrophy. One undersized stem and one cup were revised for aseptic loosening, and 25 bearings were exchanged., Conclusions: Uncemented, machined, fluted titanium canal-filling femoral components achieve reliable fixation in this young patient population. They have a decreased incidence of activity-related thigh pain, lower rate of intraoperative femur fractures and cortical hypertrophy with comparable bone-ingrowth in comparison to other second generation uncemented femoral components described in literature. Bearing wear and the need for bearing exchange was the only limitation of these constructs.

Objective: Anatomic reduction and stable fixation by means of tissue- preserving surgical approaches. INDICATIONS Displaced acetabular fractures. Surgical hip dislocation approach with larger displacement of the posterior column in comparison to the anterior column, transtectal fractures, additional intraarticular fragments, marginal impaction. Stoppa approach with larger displacement of the anterior column in comparison to the posterior column. A combined approach might be necessary with difficult reduction. CONTRAINDICATIONS Fractures > 15 days (then ilioinguinal or extended iliofemoral approaches). Suprapubic catheters and abdominal problems (e.g., previous laparotomy due to visceral injuries) with Stoppa approach (then switch to classic ilioinguinal approach)., Surgical Technique: Surgical hip dislocation: lateral decubitus position. Straight lateral incision centered over the greater trochanter. Entering of the Gibson interval. Digastric trochanteric osteotomy with protection of the medial circumflex femoral artery. Opening of the interval between the piriformis and the gluteus minimus muscle. Z-shaped capsulotomy. Dislocation of the femoral head. Reduction and fixation of the posterior column with plate and screws. Fixation of the anterior column with a lag screw in direction of the superior pubic ramus. Stoppa approach: supine position. Incision according to Pfannenstiel. Longitudinal splitting of the anterior portion of the rectus sheet and the rectus abdominis muscle. Blunt dissection of the space of Retzius. Ligation of the corona mortis, if present. Blunt dissection of the quadrilateral plate and the anterior column. Reduction of the anterior column and fixation with a reconstruction plate. Fixation of the posterior column with lag screws. If necessary, the first window of the ilioinguinal approach can be used for reduction and fixation of the posterior column., Postoperative Management: During hospital stay, intensive mobilization of the hip joint using a continuous passive motion machine with a maximum flexion of 90 degrees . No active abduction and passive adduction over the body's midline, if a surgical dislocation was performed. Maximum weight bearing 10-15 kg for 8 weeks. Then, first clinical and radiographic follow-up. Deep venous thrombosis prophylaxis for 8 weeks postoperatively., Results: 17 patients with a mean follow-up of 3.2 years. Ten patients were operated via surgical hip dislocation, two patients with a Stoppa approach, and five using a combined or alternative approach. Anatomic reduction was achieved in ten of the twelve patients (83%) without primary total hip arthroplasty. Mean operation time 3.3 h for surgical hip dislocation and 4.2 h for the Stoppa approach. Complications comprised one delayed trochanteric union, one heterotopic ossification, and one loss of reduction. There were no cases of avascular necrosis. In two patients, a total hip arthroplasty was performed due to the development of secondary hip osteoarthritis.

The widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior (AP) radiograph is known inaccurate, largely due to the wide variability in individual pelvic orientation relative to X-ray plate. 2D-3D image registration methods have been introduced for an accurate determination of the post-operative cup alignment with respect to an anatomical reference extracted from the CT data. Although encouraging results have been reported, their extensive usage in clinical routine is still limited. This may be explained by their requirement of a CAD model of the prosthesis, which is often difficult to be organized from the manufacturer due to the proprietary issue, and by their requirement of either multiple radiographs or a radiograph-specific calibration, both of which are not available for most retrospective studies. To address these issues, we developed and validated an object-oriented cross-platform program called "HipMatch" where a hybrid 2D-3D registration scheme combining an iterative landmark-to-ray registration with a 2D-3D intensity-based registration was implemented to estimate a rigid transformation between a pre-operative CT volume and the post-operative X-ray radiograph for a precise estimation of cup alignment. No CAD model of the prosthesis is required. Quantitative and qualitative results evaluated on cadaveric and clinical datasets are given, which indicate the robustness and the accuracy of the program. HipMatch is written in object-oriented programming language C++ using cross-platform software Qt (TrollTech, Oslo, Norway), VTK, and Coin3D and is transportable to any platform.

Femoroacetabular impingement (FAI) of the hip joint is increasingly being recognized as one of the causes of hip pain and restriction of hip motion in young adults. The main subtypes are Pincer and Cam types. MRI digagnostic and relevant surgical information is presented.

Femoroacetabular impingement (FAI) is a pathologic condition of the hip joint in young adults that, if untreated, leads to end-stage osteoarthritis. It is characterized by early pathologic contact between primary osseous prominences of the acetabular rim (so-called pincer FAI) and/or the femoral head-neck junction (cam FAI). Conventional radiographs are often considered normal because classic radiographic signs of osteoarthritis are not present initially. The physician should be aware of the radiographic features for both types of impingement to recognize subtle pathologies.

The purpose of this study was to validate the accuracy, consistency, and reproducibility/reliability of a new method for correction of pelvic tilt and rotation of radiographic hip parameters for pincer type of femoroacetabular impingement on an anteroposterior pelvic radiograph. Thirty cadaver hips and 100 randomized, blinded AP pelvic radiographs were used for investigation. To detect the software accuracy, the calculated femoral head coverage and classic hip parameters determined with our software were compared to reference measurements based on CT scans or conventional radiographs in a neutral orientation as gold standard. To investigate software consistency, differences among the different parameters for each cadaver pelvis were calculated when reckoned back from a random to the neutral orientation. Intra- and interobserver comparisons were used to analyze the reliability and reproducibility of all parameters. All but two parameters showed a good-to-very good accuracy with the reference measurements. No relevant systematic errors were detected in the Bland-Altman analysis. Software consistency was good-to-very good for all parameters. A good-to-very good reliability and reproducibility was found for a substantial number of the evaluated radiographic acetabular parameters. The software appears to be an accurate, consistent, reliable, and reproducible method for analysis of acetabular pathomorphologies., ((c) 2008 Orthopaedic Research Society)

Introduction: We report the results of a titanium acetabular reinforcement ring with a hook (ARRH) in primary total hip arthroplasty (THA), which was introduced in 1987 and continues to be used routinely in our center. The favorable results of this device in arthroplasty for developmental dysplasia and difficult revisions motivated its use in primary THA. With this implant only minimal acetabular reaming is necessary, anatomic positioning is achieved by placing the hook around the teardrop and a homogenous base for cementing the polyethylene cup is provided., Materials and Methods: Between April 1987 and December 1991, 241 THAs with insertion of an ARRH were performed in 178 unselected, consecutive patients (average age 58 years; range 30-84 years) with a secondary osteoarthrosis in 41% of the cases., Results: At the time of the latest follow-up, 33 patients (39 hips) had died and 17 cases had been lost to follow-up. The median follow-up was 122 months with a minimum of 10 years. Eight hips had been revised, leaving 177 hips in 120 living patients without revision. Six cups were revised because of aseptic loosening. Two hips were revised for sepsis. The mean Merle d'Aubigné score for the remaining hips was 16 (range 7-18) at the latest follow-up. For aseptic loosening, the probability of survival of the cup was 0.97 (95% confidence interval, 0.94-0.99). However, analysis of radiographs implied loosening in seven other cups without clinical symptoms., Conclusions: The results of primary THA using an acetabular reinforcement ring parallel the excellent results of these implants often observed in difficult primary and revision arthroplasty at a minimum of 10 years. Survivorship is comparable to modern cementless implants. Medial migration that occurs with loosening of the acetabular component seems to be prevented with this implant. Radiographic loosening signs can exist without clinical symptoms.

Objective: The purpose of this article is to show the important radiographic criteria that indicate the two types of femoroacetabular impingement: pincer and cam impingement. In addition, potential pitfalls in pelvic imaging concerning femoroacetabular impingement are shown., Conclusion: Femoroacetabular impingement is a major cause for early "primary" osteoarthritis of the hip. It can easily be recognized on conventional radiographs of the pelvis and the proximal femur.

Modern imaging techniques are an invaluable tool for assessing pathomorphological changes of the hip. Thorough diagnostic analysis and therapeutic decision making mainly rely on correct interpretation of conventional radiographic projections as well as more modern techniques, including magnetic resonance arthrography. This article gives an overview of the imaging techniques that are routinely used for assessing pathological conditions of the hip, with a special focus on diagnostic findings in developmental dysplasia of the hip as well as in femoroacetabular impingement.

Total hip arthroplasty (THA) still carries a higher failure rate in patients with avascular necrosis of the femoral head (AVN) than in a similar patient population with THA for other reasons. This is particularly true for the acetabular component. One of the major factors accounting for this is the compromised acetabular bone quality with structural defects subsequent to collapsing of the femoral head in high-grade AVN. In this study we implanted an acetabular reinforcement ring with hook (ARRH), which had been used successfully for other indications with acetabular bone stock deficiency, in 32 consecutive THA's in 29 patients with AVN. Five patients died during the observation period of causes unrelated to the surgery, one patient was lost to follow-up and one patient could not be followed up due to chronic illness, leaving 25 hips (23 patients) with a minimum follow-up of ten years (mean: 11.8; range: 10-15). The mean Merle d'Aubigne score increased significantly from 7.7 preoperatively to 16.6 postoperatively (p < 0.001). One revision was performed for aseptic stem loosening. Of the unrevised hips, one acetabular component was classified as definitively loose. The cumulative 12-year survivorship for THA with ARRH in AVN was 95.2% (confidence interval: 86.1-100%) for both components, 100% for the cup and 95.2% for the stem (86.1-100%).

Unlabelled: Structural deformities of the femoral head occurring during skeletal development (eg, Legg-Calvé-Perthes disease) are associated with individual shapes of the acetabulum but it is unclear whether differences in acetabular shape are associated with differences in proximal femoral shape. We questioned whether the amount of acetabular coverage influences femoral morphology. We retrospectively compared the proximal femoral anatomy of 50 selected patients (50 hips) with developmental dysplasia of the hip (lateral center-edge angle [LCE] < or = 25 degrees ; acetabular index > or = 14 degrees ) with 45 selected patients (50 hips) with a deep acetabulum (LCE > or = 39 degrees ). Using MRI arthrography we measured head sphericity, epiphyseal shape, epiphyseal extension, and femoral head-neck offset. A deep acetabulum was associated with a more spherical head shape, increased epiphyseal height with a pronounced extension of the epiphysis towards the femoral neck, and an increased offset. In contrast, dysplastic hips showed an elliptical femoral head, decreased epiphyseal height with a less pronounced extension of the epiphysis, and decreased head-neck offset. Hips with different acetabular coverage are associated with different proximal femoral anatomy. A nonspherical head in dysplastic hips could lead to joint incongruity after an acetabular reorientation procedure., Level of Evidence: Level IV, retrospective comparative study. See the Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Although current concepts of anterior femoroacetabular impingement predict damage in the labrum and the cartilage, the actual joint damage has not been verified by computer simulation. We retrospectively compared the intraoperative locations of labral and cartilage damage of 40 hips during surgical dislocation for cam or pincer type femoroacetabular impingement (Group I) with the locations of femoroacetabular impingement in 15 additional hips using computer simulation (Group II). We found no difference between the mean locations of the chondrolabral damage of Group I and the computed impingement zone of Group II. The standard deviation was larger for measures of articular damage from Group I in comparison to the computed values of Group II. The most severe hip damage occurred at the zone of highest probability of femoroacetabular impact, typically in the anterosuperior quadrant of the acetabulum for both cam and pincer type femoroacetabular impingements. However, the extent of joint damage along the acetabular rim was larger intraoperatively than that observed on the images of the 3-D joint simulations. We concluded femoroacetabular impingement mechanism contributes to early osteoarthritis including labral lesions., Level of Evidence: Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Objective: The purpose of this article is to show the important radiographic criteria that indicate the two types of femoroacetabular impingement: pincer and cam impingement. In addition, potential pitfalls in pelvic imaging concerning femoroacetabular impingement are shown., Conclusion: Femoroacetabular impingement is a major cause for early "primary" osteoarthritis of the hip. It can easily be recognized on conventional radiographs of the pelvis and the proximal femur.

The range of motion of normal hips and hips with femoroacetabular impingement relative to some specific anatomic reference landmarks is unknown. We therefore described: (1) the range of motion pattern relative to landmarks; (2) the location of the impingement zones in normal and impinging hips; and (3) the influence of surgical débridement on the range of motion. We used a previously developed and validated noninvasive 3-D CT-based method for kinematic hip analysis to compare the range of motion pattern, the location of impingement, and the effect of virtual surgical reconstruction in 28 hips with anterior femoroacetabular impingement and a control group of 33 normal hips. Hips with femoroacetabular impingement had decreased flexion, internal rotation, and abduction. Internal rotation decreased with increasing flexion and adduction. The calculated impingement zones were localized in the anterosuperior quadrant of the acetabulum and were similar in the two groups and in impingement subgroups. The average improvement of internal rotation was 5.4 degrees for pincer hips, 8.5 degrees for cam hips, and 15.7 degrees for mixed impingement. This method helps the surgeon quantify the severity of impingement and choose the appropriate treatment option; it provides a basis for future image-guided surgical reconstruction in femoroacetabular impingement with less invasive techniques.

This paper addresses the problem of estimating postoperative cup alignment from single standard X-ray radiograph with gonadal shielding. The widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior radiograph is known inaccurate, largely due to the wide variability in individual pelvic position relative to X-ray plate. 2D-3D image registration methods have been introduced to estimate the rigid transformation between a preoperative CT volume and postoperative radiograph(s) for an accurate estimation of the postoperative cup alignment relative to an anatomical reference extracted from the CT data. However, these methods require either multiple radiographs or a radiograph-specific calibration, both of which are not avaiable for most retrospective studies. Furthermore, these methods were only evaluated on X-ray radiograph(s) without gonadal shielding. In this paper, we propose to use a hybrid 2D-3D registration scheme combining an iterative landmark-to-ray registration with a 2D-3D intensity-based registration to estimate the rigid transfromation for a precise estimation of cup alignment. Quantitative and qualitative results evaluated on clinical and cadaveric datasets are given which indicate the validity of our approach.

A CT-based method ("HipMotion") for the noninvasive three-dimensional assessment of femoroacetabular impingement (FAI) was developed, validated, and applied in a clinical pilot study. The method allows for the anatomically based calculation of hip range of motion (ROM), the exact location of the impingement zone, and the simulation of quantified surgical maneuvers for FAI. The accuracy of HipMotion was 0.7 +/- 3.1 degrees in a plastic bone setup and -5.0 +/- 5.6 degrees in a cadaver setup. Reliability and reproducibility were excellent [intraclass correlation coefficient (ICC) > 0.87] for all measures except external rotation (ICC = 0.48). The normal ROM was determined from a cohort of 150 patients and was compared to 31 consecutive hips with FAI. Patients with FAI had a significantly decreased flexion, internal rotation, and abduction in comparison to normal hips (p < 0.001). Normal hip flexion and internal rotation are generally overestimated in a number of orthopedic textbooks. HipMotion is a useful tool for further assessment of impinging hips and for appropriate planning of the necessary amount of surgical intervention, which represents the basis for future computer-assisted treatment of FAI with less invasive surgical approaches, such as hip arthroscopy., ((c) 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

From June 1997 to June 2003 we performed 194 total hip arthroplasties on 173 patients using alumina ceramic-on-ceramic bearings as part of a prospective United States Food and Drug Administration/Investigational Device Exemption study. The average patient age at surgery was 49.9 years. Minimum followup time was 2 years (mean 4.3 years, range 2-9 years). We evaluated survival rate, implant- and nonimplant-related complications. Clinical outcomes included the Merle d'Aubigné score. We assessed radiographs for signs of osteolysis, component loosening, and implant wear. No patients had osteolysis and there were no hip dislocations. Implant survivorship for all hips with aseptic revision of any component was 96% (CI, 91-100) at 9 year; survivorship for hips without prior surgery was 99.3%, (CI, 98-100). There was a 1.7% incidence of implant-related complications. Our data help confirm two United States FDA/IDE studies on alumina ceramic-on-ceramic total hip arthroplasty that reported low aseptic revision rates and low revision rates for instability. Total hip arthroplasty using alumina ceramic-on-ceramic implants is a safe and reliable procedure in the comparably young and active patient.

Less invasive methods of performing total hip arthroplasty have been considered controversial after increased complication rates and component malpositioning were reported. A new method of performing total hip arthroplasty through an incision in the superior capsule, posterior to the abductors and anterior to the posterior capsule, was developed with the aim of producing a technique that maintained the joint stability of the transgluteal exposure and the rapid abductor recovery of the posterior exposure. We assessed the recovery and complications of this technique performed with surgical navigation. The study group was compared with similar subjects who had conventional total hip arthroplasty, without surgical navigation, using the transgluteal exposure. There were 185 consecutive total hip arthroplasties in the study group and 189 nonconsecutive historical total hip arthroplasties in the control group. The two groups were controlled for complexity and had no differences in body mass index, gender, diagnosis, operative side, bilateral operations, and previous surgeries. Patients were evaluated for clinical recovery and perioperative complications at 9 and 24 weeks. The study group recovered faster at both followup examinations. The study group had fewer perioperative and postoperative complications compared with the control group. Accuracy of component positioning was not compromised compared to the control group. Less invasive surgery with the philosophy of maximally preserving the abductors, posterior capsule, and short rotators may result in a safer operation with faster recovery than traditional techniques.

Using navigation systems in general orthopaedic surgery and, in particular, knee replacement is becoming more and more accepted. This paper describes the basic technological concepts of modern computer assisted surgical systems. It explains the variation in currently available systems and outlines research activities that will potentially influence future products. In general, each navigation system is defined by three components: (1) the therapeutic object is the anatomical structure that is operated on using the navigation system, (2) the virtual object represents an image of the therapeutic object, with radiological images or computer generated models potentially being used, and (3) last but not least, the navigator acquires the spatial position and orientation of instruments and anatomy thus providing the necessary data to replay surgical action in real-time on the navigation system's screen.

The number and type of operative procedures involving the hip continue to increase, placing a greater emphasis on characterizing patient postoperative condition accurately. Optimal postoperative imaging evaluation may involve multiple modalities, including conventional radiography, radionuclide scintigraphy, and cross-sectional imaging. Many of the surgical procedures involve the placement of metallic joint replacements or fixation that can make the imaging evaluation of the postoperative anatomy challenging. Clinical examination of patients combined with the type of procedure performed direct the appropriate imaging evaluation; adequate clinical knowledge of these procedures and how to optimally image them provide an opportunity to attain the most accurate evaluation possible.

Objective: To compare six different parameters described in literature for estimation of pelvic tilt on an anteroposterior pelvic radiograph and to create a simple nomogram for tilt correction of prosthetic cup version in total hip arthroplasty., Design: Simultaneous anteroposterior and lateral pelvic radiographs are taken routinely in our institution and were analyzed prospectively. The different parameters (including three distances and three ratios) were measured and compared to the actual pelvic tilt on the lateral radiograph using simple linear regression analysis., Patients: One hundred and four consecutive patients (41 men, 63 women with a mean age of 31.7 years, SD 9.2 years, range 15.7-59.1 years) were studied., Results: The strongest correlation between pelvic tilt and one of the six parameters for both men and women was the distance between the upper border of the symphysis and the sacrococcygeal joint. The correlation coefficient was 0.68 for men (P<0.001) and 0.61 for women (P<0.001). Based on this linear correlation, a nomogram was created that enables fast, tilt-corrected cup version measurements in clinical routine use., Conclusion: This simple method for correcting variations in pelvic tilt on plain radiographs can potentially improve the radiologist's ability to diagnose and interpret malformations of the acetabulum (particularly acetabular retroversion and excessive acetabular overcoverage) and post-operative orientation of the prosthetic acetabulum.

Using a total of 30 cadaveric hips, the accuracy of a fluoroscopy-based computer navigation system for cup placement in total hip arthroplasty (THA) was investigated and an error analysis was carried out. The accuracy of placing the acetabular component within a predefined safe zone using computer guidance was compared to the precision that could be achieved with a freehand approach. Accurate control measurements of the implanted cup were obtained using fiducial-based matching to a pre-operative CT scan with respect to the anterior pelvic plane. A significantly higher number of cups were placed in the safe zone with the help of the navigation system. The variability of cup placement could be reduced for cup abduction but not substantially for cup version. An error analysis of inaccurate landmark reconstruction revealed that the registration of the mid-pubic point with fluoroscopy was a potential source of error. Keeping this pitfall in mind, fluoroscopy-based navigation in THA is a useful tool for registration of the pelvic coordinate system, particularly those points that cannot be reached by direct pointer digitization with the patient in the lateral decubitus position.

Unlabelled: Pelvic tilt and rotation can drastically affect the apparent cup orientation on conventional anteroposterior pelvic radiographs. It was hypothesized that nonstandardized radiographic cup version and abduction can differ significantly from the corresponding anatomic angles if not measured to the anterior pelvic plane, defined by the pubic tubercles and the anterior superior iliac spine. Differences in preoperative and postoperative pelvic orientation and their influence on radiographic measurements of the two angles were analyzed. Conventional radiographs and preoperative and postoperative computed tomography scans of 37 total hip arthroplasties were compared. Calculations were made with the preoperative planning station of a computer navigation system. Significantly smaller values of cup version were seen on nonstandardized radiographs, whereas abduction could be measured reliably when referenced to horizontal pelvic landmarks seen on radiographs. The underlying cause for this difference was the variation of pelvic tilt that ranged 27 degrees (range, -7 degrees -20 degrees). Influence of pelvic tilt on the apparent cup orientation can be seen with simple nomograms. The orientation of the anterior pelvic plane before and after surgery did not differ. We think that version measurement on nonstandardized radiographs without anatomic referencing is highly inaccurate., Level of Evidence: Diagnostic study, Level II-1 (development of diagnostic criteria on basis of consecutive patients--with universally applied reference "gold" standard). See Guidelines for Authors for a complete description of levels of evidence.

The outcome of 33 total hip arthroplasties using an acetabular reinforcement ring with hook for osteoarthritis associated with developmental dysplasia of the hip was reevaluated after a minimal follow-up of 10 years (average, 10.8 years). Most cases comprised Crowe type II (22 hips) and type III (7 hips) dysplasia. The mean D'Aubigné score increased from 7 to 15 points. Three revisions (9%) were performed for aseptic loosening, 2 of them had a structural autograft. None of the unrevised 30 acetabular reconstructions showed definite radiographic signs of loosening. These results compare favorably with the literature and the acetabular reinforcement ring with hook presents a versatile tool for acetabular bone stock deficiencies.

Untreated femoro-acetabular impingement is a common cause of osteoarthrosis of the hip. Surgical debridement of the adult hip with femoro-acetabular impingement recently has been advocated with the aim of relieving symptoms and slowing or halting progression of the arthrosis. At surgery, femoral sources of impingement are relieved by debriding the aspheric peripheral portion of the femoral head and the adjacent femoral neck. Acetabular sources of impingement can be relieved by debridement of the anterior rim. The most fundamental questions concerning these procedures relate to the preoperative and postoperative function, postoperative survivorship of these hips and the incidence of osteonecrosis. The current study assesses a group of 23 hips in 23 patients treated by surgical debridement for impingement. Twenty-two patients were treated by full surgical dislocation and one patient was treated by relief of impingement without dislocation. Followup ranged from a minimum of 2 years to 12 years. At most recent evaluation, seven patients had been converted to total hip arthroplasty, one had arthroscopic debridement of a recurrent labral tear, and 15 patients have had no further surgery. No hips developed osteonecrosis. Of the seven patients who had to have their procedure converted to total hip arthroplasty, three of these hips failed early and four patients' hips recovered and functioned well and subsequently deteriorated with total hip arthroplasty done between 6.4 and 9.5 years after debridement. Hips at greatest risk of failure have advanced arthrosis or a combination of impingement and instability preoperatively. The procedure effectively treats hips with impingement and without considerable secondary arthrosis or instability.

We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8 degrees +/-10.1 degrees (range: 23.0-71.5 degrees ) and mean anteversion angle was 27.3 degrees +/-15.0 degrees (range: -23.5 degrees to 59.0 degrees ). We compared the results to the "safe" position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al. [13] was only achieved in a minority of the cups that were implanted freehand.

Aim: The purpose of the current study was to determine the accuracy of free hand and computer-assisted (CAS) cup placement., Material and Methods: Between June 1985 and August 2001, 105 free-hand and from March to November 1999 80 total hip arthroplasties under computer assistance were implanted in the above mentioned centers. To determine the accuracy of the cups, the inclination and anteversion angles were measured. In all cases the cup position was measured with a CT-investigation of the pelvis. Statistical analysis was performed with the F-test., Results: With regard to the inclination and anteversion angles the variability of the cup position was significantly higher in the group of free hand implanted cups. In the CAS group we could not find any "extreme" positions., Conclusion: Using computer-assisted surgery a significantly higher reproducible cup position can be obtained. Long time survey may present a lowering of the rate of early and late complications caused by better prostheses alignment in the follow up.