Purpose. Periacetabular osteotomy (PAO) is a versatile acetabular reorienting procedure that is most commonly used to provide greater femoral head coverage in adolescent hip dysplasia. However, PAO can also be used to reorient the acetabulum in the opposite direction to treat femoroacetabular impingement (FAI) due to acetabular over-coverage. We describe the indications, surgical technique, and early results of reverse PAO to reduce femoral head coverage in symptomatic hips with FAI due to acetabular over-coverage. Methods. IRB approval was obtained to retrospectively review cases of symptomatic acetabular over-coverage treated with reverse PAO and that had a minimum of two years follow-up. All hips had atypical intraoperative positioning of the acetabular fragment to uncover the lateral and anterior aspects of the femoral head, with or without anteverting the acetabulum. Prospectively collected pre- and post-operative demographics, WOMAC scores, Modified Harris Hip Score (MHHS), and radiographic measurements consisting of the lateral center edge angle (LCEA), Tönnis angle (TA), and anterior center edge angle (ACEA) were compared using student's t-test. Results. Between 2004 and 2015, 31 hips (18 left, 13 right) in 26 patients (18 female, 8 male) met the inclusion criteria. Average age at the time of surgery was 19.4 years. Average length of follow-up was 30.4 months. After reverse PAO, femoral head coverage significantly decreased (LCEA 41.7° to 35.3°, p<.001; TA −7.4° to −3.7°, p<.01; ACEA 44.0° to 35.3°, p<.0001). Patients experienced improved post-operative pain, with decreases in WOMAC pain score (from 8.8 to 4.2, p<.001) and WOMAC stiffness score (from 3.5 to 1.9, p<.001). Patients also experienced improvements in function and quality of life with improvements in WOMAC function score (from 24.8 to 10.0, p<.001) and MHHS (from 60.8 to 83.2, p<.0001). Conclusion. Reverse PAO is a technically challenging procedure that provides clinical and radiographic improvement in patients with symptomatic FAI due to acetabular over-coverage. Significance. Reverse PAO is an especially useful and appropriate alternative to arthroscopic acetabular rim-trim in complex FAI pathomorphologies

Introduction. The outcome of periacetabular osteotomy in dysplastic hips is dependent on the absence of pre-operative osteoarthritis [OA]. The purpose of this study was to analyze whether Tonnis grading is a reliable predictor of OA in patients with hip dysplasia. Methods. Thirty patients were identified who had undergone hip arthroscopy surgery to assess their suitability for periacetabular osteotomy. Radiographs were assessed for anterior centre edge angle, lateral centre edge angle, Tonnis angle and Tonnis grade for OA changes. The radiographic grading of OA was compared with arthroscopic findings. Results. The average age at the time of arthroscopy was 35 [16–53 yrs] (28 females). Tonnis grade did not correlate with arthroscopic findings (p=0.082). There was a trend for patients with a higher Tonnis grade to have more OA changes. Of the 30 patients, all 3 with grade 0 were fit for periacetabular osteotomy, while only 8 out of 24 with grade I, and 1 out of 3 with grade II were fit for periacetabular osteotomy. Discussion. This study reports that even when radiographic grading showed minimal OA changes, arthroscopy findings indicated significant OA changes. Hence radiographic grading is a poor indicator of OA and other diagnostic modality should be sought before proceeding with joint preserving surgery in this highly selected subgroup of dysplastic hips

Arthroscopic hip procedures have increased dramatically over the last decade as equipment and techniques have improved. Patients who require hip arthroscopy for femoroacetabular impingement on occasion require surgery on the contralateral hip. Previous studies have found that younger age of presentation and lower Charlson comorbidity index have higher risk for requiring surgery on the contralateral hip but have not found correlation to anatomic variables. The purpose of this study is to evaluate the factors that predispose a patient to requiring subsequent hip arthroscopy on the contralateral hip. This is an IRB-approved, single surgeon retrospective cohort study from an academic, tertiary referral centre. A chart review was conducted on 310 primary hip arthroscopy procedures from 2009-2020. We identified 62 cases that went on to have a hip arthroscopy on the contralateral side. The bilateral hip arthroscopy cohort was compared to unilateral cohort for sex, age, BMI, pre-op alpha angle and centre edge angle measured on AP pelvis XRay, femoral torsion, traction time, skin to skin time, Tonnis grade, intra-op labral or chondral defect. A p-value <0.05 was deemed significant. Of the 62 patients that required contralateral hip arthroscopy, the average age was 32.7 compared with 37.8 in the unilateral cohort (p = 0.01) and BMI was lower in the bilateral cohort (26.2) compared to the unilateral cohort (27.6) (p=0.04). The average alpha angle was 76.3. 0. in the bilateral compared to 66. 0. in the unilateral cohort (p = 0.01). Skin to skin time was longer in cases in which a contralateral surgery was performed (106.3 mins vs 86.4 mins) (p=0.01). Interestingly, 50 male patients required contralateral hip arthroscopy compared to 12 female patients (p=0.01). No other variables were statistically significant. In conclusion, this study does re-enforce existing literature by stating that younger patients are more likely to require contralateral hip arthroscopy. This may be due to the fact that these patients require increased range of motion from the hip joint to perform activities such as sports where as older patients may not need the same amount of range of motion to perform their activities. Significantly higher alpha angles were noted in patients requiring contralateral hip arthroscopy, which has not been shown in previous literature. This helps to explain that larger CAM deformities will likely require contralateral hip arthroscopy because these patients likely impinge more during simple activities of daily living. Contralateral hip arthroscopy is also more common in male patients who typically have a larger CAM deformity. In summary, this study will help to risk stratify patients who will likely require contralateral hip arthroscopy and should be a discussion point during pre-operative counseling. That offering early subsequent or simultaneous hip arthroscopy in young male patients with large CAMs should be offered when symptoms are mild

Background. BHA is popular surgery for femoral neck fractures expecially elderly patients. However, clinical results are variable that factors affecting results are questionable. Therefore we investigated radiologic fators, dysplastic hip whether influences results of BHA. Methods. Between 2004 and 2009, 200 patients undergoing bipolar hemiarthroplasty for femoral neck fracture were divided two groups; a lateral center edge (LCE) angle of < 16 degree or > 16 degree on anteroposterior radiographs. All surgical procedures were performed by a single surgeon. Dermogrpahic data, the harris hip score, WOMAC index, Koval activity level, and complication were recorded. The minimum follow up interval was 4 years (mean, 7.8 years). Result. Late postoperative complications such as periprosthetic joint infection, acetabular erosion, and subluxation of bioplar head were commonly observed in a group <16 degree of center edge angle. Clinical score was significantly lower in dysplastic group. Revision rate was higher in dysplastic group compared with group LCE angle of above the 16 degree. Conclusion. These results suggest that the dysplastic nature might be affected result of bipolar hemiarthroplasty in femroal neck fracture especially elderly patients

To determine the effect that preoperative use of 3D printed models has on the outcomes for femoroacetabular impingement (FAI) surgery. Ninety patients that underwent FAI surgeries by the same surgeon were retrospectively analyzed. Patients were age- and sex-matched for two groups - those who had pre-operative 3D printed hip models (n=45) and those with conventional planning using X-rays and/or CT scan (n=45) were identified. Radiographic parameters on pre- and post-operative radiographs that include the alpha angle (45 Dunn view), center edge angle (CEA) (weight bearing AP pelvis), and head-neck offset ratio (cross-table lateral) were obtained. Clinical outcomes were assessed by analyzing iHOT and HOS scores pre- and post-operatively. Ninety patients (3D printed group 45, Conventional group 45) with a mean age of 36 years were evaluated. Mean follow-up time was 28 months. For all of the radiological variables (CEA and alpha angle), there was a significant improvement seen for both groups (p=0.001). However, the 3D printed group showed significantly better resection of bone to a normal alpha angle (< 5 5) than did the Conventional group. Additionally, head-neck offset was significantly better in the 3D printed group (p=0.001). Statistically significant improvements were seen in both groups on the HOS and iHOT-33 (p=0.001). Planning FAI surgery using 3D hip models helps in achieving better resection, especially in CAM-type FAI

Hip dysplasia has traditionally been classified based on the lateral centre edge angle (LCEA). A recent meta-analysis demonstrated no definite consensus and a significant heterogeneity in LCEA values used in various studies to define hip dysplasia and borderline dysplasia. To overcome the shortcomings of classifying hip dysplasia based on just LCEA, a comprehensive classification for adult acetabular dysplasia (CCAD) was proposed to classify symptomatic hips into three discrete prototypical patterns of hip instability, lateral/global, anterior, or posterior. The purpose of this study was to assess the reliability of this recently published CCAD. One thirty four consecutive hips that underwent a PAO were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior or psosterior. Based on the prevalence of individual dysplasia and using KappaSize R package version 1.1, seventy four cases were necessary for reliability analysis: 44 dysplastic and 30 normal hips were randomly selected. Six blinded fellowship trained raters were then provided with the classification system and they looked at the x-rays (74 images) at two separate time points (minimum two weeks apart) to classify the hips using standard PACS measurements. Thereafter, a consensus meeting was held where a simplified flow diagram was devised before a third reading by four raters using a separate set of 74 radiographs took place. Intra-rater results per surgeon between Time 1 and Time 2 showed substantial to almost perfect agreement amongst the raters. With respect to inter-rater reliability, at time 1 and time 2, there was substantial agreement overall between all surgeons (kappa of 0.619 for time 1 and 0,623 for time 2). Posterior and anterior rating categories had moderate and fair agreement at time 1 and time 2, respectively. At time 3, overall reliability (kappa of 0.687) and posterior and anterior rating improved from Time 1 and Time 2. The comprehensive classification system provides a reliable way to identify three categories of acetabular dysplasia that are well-aligned with surgical management. The term borderline dysplasia should no longer be used

Introduction. Acetabular dysplasia, also known as developmental dysplasia of the hip, has been shown to contribute to the onset of osteoarthritis. Surgical correction involves repositioning the acetabulum in order to improve coverage of the femoral head. However, ideal placement of the acetabular fragment can often be difficult due to inadequate visualization. Therefore, there has been an increased need for pre-operative planning and navigation modalities for this procedure. Methods. PubMed and EBSCO Host databases were queried using keywords (preoperative, pre-op, preop, before surgery, planning, plan, operation, surgery, surgical, acetabular dysplasia, developmental dysplasia of the hip, and Hip Dislocation, Congenital [Mesh]) from 1974 to March 2019. The search generated 411 results. We included all case-series, English, full-text manuscripts pertaining to pre-operative planning for congenital acetabular dysplasia. Exclusion criteria included: total hip arthroplasty (THA) planning, patient population mean age over 35, and double and single case studies. Results. A total of 12 manuscripts met our criteria for a total of 186 hips. Preoperative planning modalities described were: Amira (Thermo Fischer Scientific; Waltham, MA, USA) − 12.9%, OrthoMap (Stryker Orthopaedics; Mahwah, NJ, USA) − 36.5%, Amira + Biomechanical Guidance System (Johns Hopkins University) − 5.9%, Mills et al. method − 16.1%, Klaue et al. method − 16.1%, Armand et al. method − 6.5%, Tsumura et al. method − 3.8%, and Morrita et al. method − 2.2%. Virtual implementation of the Amira software yielded increases in femoral head coverage (p<0.05) and a significant decrease in lateral center edge angle (LCEA) (p<0.05). A significant decrease in post-surgical complications (0.0% navigated group vs. 8.7% non-navigated group, p<0.01) was found with usage of OrthoMap related planning. Conclusion. There was a notable lack of prospective studies demonstrating the efficacy of these modalities, with decreased post-surgical complications being the only added benefit of their use. Additionally, small sample sizes and lack of commercial availability for many of these programs further diminishes their applicability. Future studies are needed to compare computer assisted planning with traditional radiographic assessment of ideal osteotomy orientation. Furthermore, these programs must be readily accessible rather than be solely available to the researchers who wrote the program. For any figures or tables, please contact authors directly

During a periacetabular osteotomy (PAO), intra-operative assessment of correction of acetabular parameters is typically performed using fluoroscopy of the hip, a technique that has not been shown to produce predictable measurements. Furthermore, paralysing agents are used in order to facilitate dissection and fragment mobilization. The effect of paralysing agents on spino-pelvic posture is yet to be investigated. This study aims to: 1. Compare the reliability of intra-operative x-rays versus hip fluoroscopy in the assessment of acetabular fragment correction and 2. Evaluate the effect of changes in spino-pelvic alignment on the assessment of acetabular correction. An IRB approved, retrospective review of all patients who underwent a PAO at our institution between 2006–2018 was performed. Patient demographic data was collected and all available imaging studies were retrieved. Patients were excluded if there was no available to review intra-operative AP pelvis x-ray or intra-operative fluoroscopic PA image of the hip. Using a validated hip analysis software (Hip2Norm), the lateral center edge angle (LCEA) and acetabular index (AI) of plain radiographs were measured. The sacro-femoral-pubic angle (SFP), along with the LCEA and AI of the fluoroscopic image were measured using ImageJ. A oneway ANOVA was used to detect differences between measured parameters in the intra-operative x-ray, the post-operative x-ray and the fluoroscopic image. A total of 93 patients were identified. 26 patients were excluded due to missing data. The mean LCEA in the post-operative, intra-operative, and fluoroscopic groups were as follows: 33.67° (range 5.3° to 52.4°), 30.71°(range 9° to 55.6°), and 29.23°(range 12.4° to 51.4°) respectively. The mean AI in the post-operative, intra-operative, and fluoroscopic groups were as follows: −0.65° (range −18.10° to 27.30°), 0.35°(range −16.10° to 17.20°), and 5.54°(range −11.66° to 27.83°) respectively. When comparing intra-operative to post-operative plain radiographs, there was no statistically significant difference in AI (ΔAI −1±1.29° p=0.71) or LCEA (ΔLCEA 2.95±1.38° p=0.09). When comparing fluoroscopy to post-operative plain radiographs, there was a statistically significant difference in AI (ΔAI −6.21±1.29° p < 0 .0001) as well as LCEA (ΔLCEA 4.44±1.38° p < 0 .0001). Statistical analysis revealed no influence of demographics (age, BMI, gender), on acetabular correction parameters. The mean SPF angles measured from intra-operative and post-operative x-rays were 69.32±5.11° and 70.45±5.52°. There was a statistically significant difference between these 2 measurements with a ΔSFP of 1.03° (p < 0 .0001). The results of our study show that the use of intra-operative x-ray for the assessment of LCEA and AI is more reliable than fluoroscopic images. Further, we found a difference in SFP angle, which offers an indirect assessment of pelvic tilt, between the intra-operative and the post-operative plain x-rays. This suggests that there are changes in pelvic tilt during the surgery, which can be attributed to either patient positioning or changes in spino-pelvic posture secondary to the paralysing agents used by the anesthetists. The use of intra-operative x-rays as well as the effect of paralysing agents on spino-pelvic alignment should be considered by surgeons performing PAO's

Purpose of Study. Multiple measurements have been described for the assessment of developmental dysplasia of the hip (DDH). In particular, the centre edge angle (CEA) has been described by Wiberg to assess the position of the femoral head in relation to the acetabular edge in patients over the age of five years. The purpose of this study is twofold. Firstly to assess the reliability of all measurements available in the literature and secondly to evaluate whether or not the CEA can be reliably measured below five years of age. Methods. Eighty seven patients were included for assessment. Radiographs were measured within six months of spica cast/Batchelor cast removal, depending on whether closed or open reduction was performed. A web based computer programme was used to store the radiographs electronically and with the help of an electronic template the following measurements were recorded: CEA, AI, centre head distance discrepancy ratio (CHDDR), Smith's c/b and h/b ratios. Three readers recorded measurements at two intervals, to determine intra and inter reader reliability. Results. The mean age at measurement was 2.26 years (Range 0.60–5.99). Regarding intra reader reliability, the AI and CEA were the most reliable measurements with a mean intraclass correlation coefficient (ICC) of 0.87 [CI 0.78–0.94] and 0.78 [CI 0.43–0.94] respectively. Regarding inter reader reliability, the CEA was the most reliable measurement with a mean ICC of 0.84 [CI 0.79–0.90]. Conclusion. This study confirms the reliability of the CEA, AI, CHDDR, Smith's c/b and h/b ratios in children with DDH. It also describes the reliable use of the CEA at a younger age in DDH than previously described which has prognostic implications. NO DISCLOSURES

Aims. To determine whether there is any benefit using a minimally invasive trans-sartorial approach as described by Professor Søballe compared to the ilio-femoral for peri-acetabular osteotomy. Methods. 30 consecutive patients were operated on by a single surgeon. The first 15 underwent an ilio-femoral (I-F) approach whilst the following 15 had a trans-sartorial (T-S) approach. Fixation was achieved with 3 or 4 screws. All other aspects of surgery and rehabilitation were the same. Data was collected prospectively and included operation time, intra-operative blood loss and length of stay. Acetabular correction was measured using the sourcil and centre edge angle (CEA) on pre and post-operative radiographs. Results. Both groups had acceptable radiographic corrections with CEA improving from mean 14.5 to 38.7 degrees (T-S) and 14 to 39 degrees (I-F). The sourcil angle improved from mean 17.8 to 2 degrees (T-S) and 19.5 to −1.5 (I-F). Minimally invasive surgery reduced anaesthetic time by 62 minutes. Haemoglobin loss was reduced by 1 gram/L and there was no requirement for transfusion. Hospital stay reduced by 0.8 days. There were no major adverse complications although two partial femoral neurapraxias were noted early in the series. These fully resolved. Conclusion. We have found significant benefit from changing to minimally invasive PAO. Our patients have smaller wounds, a shorter operative time, reduced bleeding and a shorter length of stay. We found no adverse effects. The time savings have also corresponded to a cost saving for our institution. We recommend this technique although recognise that it has a learning curve and should be initiated by surgeons with previous PAO experience

Purpose. Introduction: The Dega osteotomy is a versatile procedure that is widely used to treat neuromuscular hip dysplasia. There is a paucity of English-language literature on its use in acetabular dysplasia seen in developmental dysplasia of the hip (DDH). Method. A retrospective radiographic and chart review was performed for all patients diagnosed with DDH who underwent a modified Dega osteotomy between March 1995 and December 2008 at the Shriners Hospital for Children or the Montreal Children's Hospital (Montréal, Canada) by two orthopedic surgeons. Radiographic parameters were measured at the preoperative, immediate postoperative and final follow-up time points. These parameters included the acetabular index (AI), center edge angle (CEA), Reimer's extrusion index, Shenton's line and grading by the Severin classification. Results. A total of 21 patients (22 hips) of which 18 were female, underwent a modified Dega osteotomy at an average age of 55.4 months (range: 20 to 100 months). Out of the 22 hips (1 bilateral and 19 single cases), 9 involved the right side and 13 involved the left side. Prior to surgery, 10 patients had a subluxated hip, 7 had a dislocated hip and 5 had a dysplastic hip. Twelve hips underwent concomitant procedures including 10 open reductions with capsulorraphy. The AI improved from 36 degrees (St. Dev 8) preoperatively to 19 degrees (St. Dev 7) on the date of last visit. The CEA improved from 4 (St. Dev 17) to 22 degrees (St. Dev 12). Conclusion. Results from this study demonstrate that the modified Dega osteotomy produces nearnormal lateral coverage parameters in children with DDH

Rotational acetabular osteotomy (RAO) for developmental dysplasia of the hip (DDH) may not restore normal hip range of motion (ROM) due to the inherent deformity of the hip and it may lead to femoro-acetabular impingement. The purpose of this study was to investigate morphological factors of the pelvis and femur influencing on simulated ROM after RAO with a fixed target for femoral head coverage. We retrospectively reviewed CT images of 52 DDHs with an average lateral centre edge angle (CEA) of 7.9° (−12° to 19°). After virtual RAO with 30° of lateral CEA and 55° of anterior CEA producing femoral head coverage similar to that of the normal hips, we measured simulated flexion ROM using pelvic and femoral computer models reconstructed from the CT images. Pelvic sagittal inclination, acetabular anteversion, lateral CEA, femoral neck anteversion, femoral neck shaft angle (FNSA), alpha angle and the position of the anterior inferior iliac spine (AIIS) were investigated as morphological factor. When the most prominent point of the AIIS existed more distally than the cranial tip of the acetabular joint line in a lateral view of the pelvis model in supine position, the subjects were defined as AIIS-Type1; the remaining subjects were defined as Type 2. There were 10 hips with Type 1 and 42 hips with Type 2 AIIS. The Kappa value of inter-observer reproducibility to classify AIIS was 0.82. Multiple regression analyses were performed to analyse the relationship between ROM and the morphological parameters. We also analysed the relationship between the probability of flexion ROM being less than 110° and the factors which influenced on flexion ROM. FNSA and AIIS-Type independently influenced on simulated flexion ROM after RAO (standard regression coefficient: −0.51 and 0.37, respectively. p&lt; 0.001). The multiple correlation coefficient was 0.68. Flexion ROM after RAO with a fixed femoral head coverage similar to that of the normal hips ranged from 95° to 141° with an average of 121°±8°. The probability of ROM being less than 110° was significantly higher in subjects with AIIS-Type 1 than in those with Type 2 (odds ratio: 13.3, p&lt;0.01). It was also significantly higher in subjects with more than 135° of FNSA than in those with less than 135° of FNSA (odds ratio: 9.5, p&lt;0.05). FNSA and the type of AIIS influenced on flexion ROM after RAO with approximately 40° of variation in spite of a fixed target for femoral head coverage. A large FNSA and a distal positioning of AIIS were independently associated with smaller flexion ROM after RAO

Introduction. This study was to investigate the association of developmental dysplasia of the hip (DDH) and primary protrusion acetabuli (PPA) with Vitamin D receptor polymorphisms TaqI and FokI and oestrogen receptor polymorphisms Pvu II and XbaI. Methods. 45 patients with DDH and 20 patients with PPA were included in the study. Healthy controls (n=101) aged 18-60 years were recruited from the same geographical area. The control subjects had a normal acetabular morphology based on a recent pelvic radiograph performed for an unrelated cause. DNA was obtained from all the subjects from peripheral blood. Genotype frequencies were compared in the three groups. The relationship between the genotype and morphology of the hip joint, severity of the disease, age at onset of disease and gender were examined. Results. The oestrogen receptor XbaI wild-type genotype (XX, compared with Xx and xx combined) was more common in the DDH group (55.8%) than controls (37.9%), though this just failed to achieve statistical significance (p=0.053, odds ratio=2.1, 95% CI=0.9-4.6). In the DDH group, homozygosity for the mutant TaqI Vitamin D receptor t allele was associated with higher acetabular index (Mann-Whitney U-test, p= 0.03). Pvu II pp oestrogen receptor genotype was associated with low centre edge angle (p=0.07). Conclusion. This study suggests a possible correlation between gene polymorphism in the oestrogen and vitamin D receptors and susceptibility to, and severity of DDH. The TaqI vitamin D receptor polymorphisms may be associated with abnormal acetabular morphology leading to DDH while the XbaI oestrogen receptor XX genotype may be associated with increased risk of developing DDH. No such correlations were found in the group with PPA

Opinions about the treatment of Perthes' disease vary widely. However there is no disagreement about the need for containment during fragmentation stage to create an optimum biomechanical environment for remodelling of femoral head. Types of containment may vary. Younger children do well irrespective of the method of containment. Older children usually require surgical containment. The present study was aimed at evaluating the results of different methods of surgical containment in different age group and identifying specific factors that alter the final outcome and prognosis. 107 cases were reviewed retrospectively. 21 cases were excluded due to lack of records. 86 hips were available for clinical and radiological evaluation. 31 patients were under 7 years and required Varus osteotomy (VO). 55 patients were above 7 years. VO was performed in 30 hips and Shelf containment was done in 25. Case notes were reviewed for demographic details, surgical details and clinic letters. Radiographs were reviewed for Herring's grading, Stulberg staging, containment indices, centre edge angle, lateral pillar height, Mose index, neck shaft angle and shelf width. In all patients, there was an improvement in pre-operative symptoms and summated range of motion, especially abduction. Good functional and radiological outcome was seen in age group < 7 years. In older children, outcome was good to satisfactory with Herring grade B. Stulberg grading worsened with advancing age and Herring grade C, irrespective of the method of containment. Persistence of varus neck shaft angle and trochanteric overgrowth were significant problems with VO. Although all containment indices improved with Shelf group, Stulberg grading remained poor in most patients. The lateral pillar classification and age strongly correlate with final outcome. Herring group C had the least favourable result. Stulberg staging remained poor in older children irrespective of the method of containment

Introduction. Herniation pits had been considered as a normal variant, a cystic lesion formed by synovial invagination. On the contrary, it was also suggested that herniation pits were one of the diagnostic findings in femoroacetabular impingement (FAI) because of the high prevalence of herniation pits in the FAI patients. To date, the exact etiology is still unknown. The purpose of this study was to evaluate whether there is an association between the presence of herniation pits and morphological indicators of FAI based on computed tomography (CT) examination. Materials and methods. We reviewed the CT scans of 245 consecutive subjects (490 hips, age: 21–89 years) who had undergone abdominal and pelvic CT for reasons unrelated to hip symptom from September, 2010 to June, 2011. These subjects were mainly examined for abdominal disorders. We confirmed by the questionnaire survey that there were no subjects who had symptoms of hip joints. We reviewed them for the presence of herniation pits and the morphological abnormalities of the femoral head and acetabulum. Herniation pits were diagnosed when they were located at the anterosuperior femoral head-neck junction with a diameter of more than 3 mm. We measured following four signs as indicators for FAI: α angle, center edge angle (CE angle), acetabular index (AI), and acetabular version. Mann-Whitney U-test was used for statistical analysis. Results. Herniation pits were identified in 61 of the 245 subjects or, with respect to individual hips, in 85 (17%) of 490 hips. The prevalence of herniation pits in younger subjects (<60 years, 240 hips) and elderly subjects (≥60 years, 250 hips) were 16.3% and 18.4%, respectively. Among 85 hips, the mean diameter of herniation pits was 5.9 ± 2.4 mm and it was significantly larger (p<0.01) in the elderly subjects (7.1 ± 2.4 mm) than in the younger subjects (4.7 ± 1.7 mm). In terms of the α angle, there were significant differences between the group with (49.8 ± 16.6°) and without herniation pits (40.7 ± 6.7°) in the elderly subjects, whereas not significantly different among the younger subjects. Measurements of the acetabular coverage (CE angle, AI) and the acetabular version showed no significant difference between the subject with and without herniation pits. Discussion. In the present study, the prevalence of herniation pits was 17% in asymptomatic Japanese general population. The fact that the size of the herniation pits enlarge with age may suggest these cystic lesions have degenerative characteristics with no association with FAI. Although large α angles have been recognized as a predictor of cam impingement especially in young population, it was impossible to show the relationship between α angle and presence of herniation pits in young population. These results suggest that the presence of the herniation pits has little relevance to FAI diagnosis

Introduction:. Most cases of hip osteoarthritis (OA) are believed to be caused by alterations in joint contact mechanics resulting from pathomorphologies such as acetabular dysplasia and acetabular retroversion. Over the past 13 years, our research group has focused on developing approaches for patient-specific modeling of cartilage and labrum in the human hip, and applying these approaches to study hip pathomorphology. The long term objective is to improve the understanding of the etiology of OA related to hip pathomorphology, and to improve diagnosis and treatment. The objectives of this presentation are to provide a summary of our subject-specific modeling approach, and to describe the results of our analysis of hips from three populations of subjects: normal, traditional dysplastic, and retroverted. Methods:. A combined experimental and computational protocol was used to investigate contact mechanics in ten normal subjects (normal center edge angles (CEA), no history of hip pain), ten subjects with hip pain secondary to acetabular dysplasia (CEA less than 25°), and ten patients with a radiographic crossover sign, pain and clinical exams consistent with acetabular retroversion. CT arthrography was used to image cartilage and bone. Volumetric image data were segmented and discretized, and subject-specific finite element models were produced using validated methods [Fig. 1]. Boundary and loading conditions were obtained from instrumented implant and gait data. Contact mechanics were evaluated on the acetabular cartilage and labrum. Labrum contact area and peak contact stress were evaluated. Cartilage contact area, peak and average contact stress were evaluated in six anatomical regions in the acetabulum. Results:. Hip contact patterns were subject-specific, but distinct patterns emerged in the groups. Dysplastic hips had a larger contact area in the lateral region of the acetabulum, while normal hips demonstrated a more distributed contact pattern. The labrum in dysplastic hips supported significantly more load than the labrum in normal hips in all activities [Fig. 2]. Contact in retroverted hips tended to be focused medially and superiorly [Fig. 3]. Retroverted subjects had smaller contact stress and area in most regions. Discussion:. The differences in labrum mechanics between the normal and dysplastic groups provide clear support for the mechanical importance of the acetabular labrum in dysplastic hips. There were only minor differences in cartilage contact stress and area between normal and dysplastic groups, because of a lateral shift in the location of contact and subsequent loading on the acetabular labra in the dysplastic hips. The larger labrum load support and contact area in dysplastic hips indicates that the labrum compensates for the shallow acetabula. Clinically, this may account for the pattern of OA onset in dysplastic hips. The results for the retroverted group do not support the commonly held belief that concentrated posterior loading in retroverted hips leads OA because there were lower contact stresses and areas in the posterior regions of retroverted hips. Further, these results suggest that rim trimming may be appropriate for retroverted hips. The preferred surgery likely depends on subtle patient specific aspects of hip pathoanotomy in both retroverted and dysplastic hips

Introduction. We perform PAO via a modified Smith-Petersen approach. The purpose of this study was to investigate the result of PAO via a modified Smith-Petersen approach at a minimum 10-years' follow-up. Methods. We retrospectively reviewed 209 hips in 179 patients with acetabular dysplasia who underwent PAO with a modified Smith-Petersen approach from August 1995 to April 2010. Exclusion criteria were as follows: under 10 year follow-up, incomplete clinical or radiographic data. Harris hip score (HHS) was investigated preoperatively, at the time of most improvement and at the final follow-up for clinical evaluation. Tönnis classification was investigated preoperatively and at the final follow-up for evaluation of osteoarthritis. Center edge (CE) angle and acetabular roof obliquity (ARO) were investigated preoperatively, postoperatively and at the final-follow up for radiographic evaluation. Tönnis classification and radiographic parameters were investigated on anterior-posterior radiographs. Patients of conversion of PAO to total hip arthroplasty (THA) were investigated for preparing Kaplan Myer survival analysis. The Wilcoxon signed-rank test was used to compare changes in HHS and radiographic parameters between the preoperative and the postoperative values. Statistical significance was defined a priori as p < 0.05. Results. Eighty-seven hips in 79 patients (44.1%) were included in this study. 100 patients were excluded from this study. The average age of the patients at the time of surgery was 39 years (rang, 15 to 65 years) and the mean follow-up period was 12 years and 2 months (range, 10 years to 18 years and 3 months). The mean HHS improved from 74 points (range, 38 to 98 points) preoperatively to 95 points (range, 62 to 100 points) at the time of most improvement (p < 0.01) and decrease slightly to 89 points (range, 32 to 100 points) at final follow-up. Tönnis classification was as follows: grade 0 was 4 hips preoperatively and 2 hips at the final follow-up, grade 1 was 55 hips preoperatively and 50 hips at the final follow-up, grade 2 was 25 hips preoperatively and 24 hips at the final follow-up, grade 3 was 3 hips preoperatively and 11 hips at the final follow-up. The mean CE angle improved from 5° (range, −19 to 24°) preoperatively to 30° (range, 2 to 56°) postoperatively (p < 0.01) and increased 38° (range, 12 to 68°) at final follow-up. The mean ARO improved from 24° (range, 6° to 45°) preoperatively to 6° (range, −14° to 48°) postoperatively (p < 0.01) and increased to 12° (range, −24 to 45°) at final follow-up. THA was performed on 5 hips in 5 patients (5.7%) after PAO. The mean duration between PAO and THA was 9 years and 6 months (range, 1 year and 4 months to 15 years 4 months). Ten-year survival rate was 97 % with conversion THA as the end point. Discussion & Conclusion. Clinical data and radiographic parameter were improved in patients who underwent PAO satisfactory. PAO was instrumental as time-saving surgical treatment of symptomatic acetabular dysplasia or slightly osteoarthritis because of 97% survival rate at 10 years