Aims. Periacetabular osteotomy (PAO) is an established treatment for acetabular dysplasia. It has also been proposed as a treatment for patients with acetabular retroversion. By reviewing a large cohort, we aimed to test whether outcome is equivalent for both types of morphology and identify factors that influenced outcome. Methods. A single-centre, retrospective cohort study was performed on patients with acetabular retroversion treated with PAO (n = 62 hips). Acetabular retroversion was diagnosed clinically and radiologically (presence of a crossover sign, posterior wall sign, lateral centre-edge angle (LCEA) between 20° and 35°). Outcomes were compared with a control group of patients undergoing PAO for dysplasia (LCEA < 20°; n = 86 hips). Femoral version was recorded. Patient-reported outcome measures (PROMs), complications, and reoperation rates were measured. Results. The mean Non-Arthritic Hip Score (NAHS) preoperatively was 58.6 (SD 16.1) for the dysplastic hips and 52.5 (SD 12.7) for the retroverted hips (p = 0.145). Postoperatively, mean NAHS was 83.0 (SD 16.9) and 76.7 (SD 17.9) for dysplastic and retroverted hips respectively (p = 0.041). Difference between pre- and postoperative NAHS was slightly lower in the retroverted hips (18.3 (SD 22.1)) compared to the dysplastic hips (25.2 (SD 15.2); p = 0.230). At mean 3.5 years’ follow-up (SD 1.9), one hip needed a revision PAO and no hips were converted to total hip arthroplasty (THA) in the retroversion group. In the control group, six hips (7.0%) were revised to THA. No differences in complications (p = 0.106) or in reoperation rate (p = 0.087) were seen. Negative predictors of outcome for patients undergoing surgery for retroversion were female sex, obesity, hypermobility, and severely decreased femoral anteversion. Conclusion. A PAO is an effective surgical intervention for acetabular retroversion and produces similar improvements when used to treat dysplasia. Femoral version should be routinely assessed in these patients and when extremely low (< 0°), as an additional procedure to address this abnormality may be necessary. Females with signs of hypermobility should also be consulted of the likely guarded improvement. Cite this article: Bone Jt Open 2021;2(9):757–764

Aims

The aim of this study was to evaluate the long-term clinical and radiographic outcomes of the Birmingham Interlocking Pelvic Osteotomy (BIPO).

Traditional radiographic criteria might underestimate or fail to detect subtle types of acetabular dysplasia. Acetabular sector angles (ASA) can measure the degree of anterior and posterior coverage of the femoral head on computed tomography (CT). This study aims to determine ASA values at different axial levels in a cohort of (1) asymptomatic, high-functioning hips without underlying hip pathology (controls); and (2) symptomatic, dysplastic hips that underwent periacetabular osteotomy (PAO). Thereby, we aimed to define CT-based thresholds for hip dysplasia and its subtypes. This is an IRB approved cross-sectional study of 51 high functioning, asymptomatic patients (102 hips) (Oxford Hip Score >43), without signs of osteoarthritis (Tönnis grade≤1), who underwent a CT scan of the pelvis (mean age: 52.1±5.5 years; 52.9% females); and 66 patients (72 hips) with symptomatic hip dysplasia treated with peri-acetabular osteotomy (PAO) (mean age: 29.3±7.3 years; 85.9% females). Anterior and posterior acetabular sector angles (AASA & PASA) were measured by two observers at three CT axial levels to determine equatorial, intermediate, and proximal ASA. Inter- and intra-observer reliability coefficient was high (between 0.882–0.992). Cut-off values for acetabular deficiency were determined based on Receiver Operating Characteristic (ROC) curve analysis, area under the curve (AUC) was calculated. The dysplastic group had significantly smaller ASAs compared to the Control Group, AUC was the highest at the proximal and intermediate PASA. Controls had a mean proximal PASA of 162°±17°, with a cut-off value for dysplasia of 137° (AUC: 0.908). At the intermediate level, the mean PASA of controls was 117°±11°, with a cut-off value of 107° (AUC 0.904). Cut-off for anterior dysplasia was 133° for proximal AASA (AUC 0.859) and 57° for equatorial AASA (AUC 0.868). Cut-off for posterior dysplasia was 102° for intermediate PASA (AUC 0.933). Measurement of ASA on CT is a reliable tool to identify dysplastic hips with high diagnostic accuracy. Posterior ASA less than 137° at the proximal level, and 107° at the intermediate level should alert clinicians of the presence of dysplasia

The periacetabular osteotomy (PAO) is a well-described procedure for symptomatic acetabular dysplasia. For severe acetabular deformities, the efficacy of acetabular reorientation remains controversial and the literature on mid to long-term outcomes is limited. The purpose of this study was to analyze average 10-year clinical and radiographic results of the PAO for severe acetabular dysplasia. We retrospectively analyzed a consecutive series of patients undergoing PAO for severe acetabular dysplasia as defined by LCEA < 5˚. Patient demographics, radiographic measurements, modified Harris Hip score (MHHS), UCLA activity, SF-12, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were assessed. Sixty-eight patients (82 hips; 54 females) with an average age 20.7 and BMI of 24.4 kg/m2 were included. Mean follow-up was follow up was 10.3 years. . The LCEA and ACEA improved a mean of 32.8˚ (8.4˚ to 24.4˚, p<0.0001) and 31.6˚ (−4.9˚ to 26.7˚, p< 0.0001), respectively. MHHS improved an average of 17.5 points (64.6 to 82.3, p<0.0001), WOMAC Pain subscore improved an average of 21.1 points (65.7 to 85.0, p = 0.004), and SF-12 physical improved 11.8 points (from 40.3 to 50.6, p = 0.006). Activity improved as indicated by a 1.5-point increase in the UCLA Activity score (6.4 to 7.9, p=0.005). Six hips (9.1%) converted to THA at average 6.8 years post-PAO. Kaplan-Meier survival analysis with THA as the endpoint was 92% at 15 years (95% confidence interval [CI] (81%–96%). Multivariable linear regression analysis revealed concurrent osteochondroplasty was associated with a decreased risk of PAO failure. PAO is an effective treatment for severe acetabular dysplasia. At average 10.3 years, clinical and radiographic outcomes demonstrate pain relief, improved hip function, and major deformity correction. We observed minimal clinical deterioration over time

Finite element analysis (FEA) has been applied for the biomechanical analysis of acetabular dysplasia, but not for biomechanical studies of periacetabular osteotomy (PAO) or those performing analysis taking into consideration the severity of acetabular dysplasia. This study aimed to perform biomechanical evaluation of changes in stress distribution following PAO and to determine the effect of the severity of developmental dysplasia of the hip (DDH) using three-dimensional FEA. A normal model was designed with a 25° center-edge (CE) angle and a 25° vertical-center-anterior margin (VCA) angle. DDH models were designed with CE and VCA angles each of 10, 0, or −10°. Post-PAO models were created by separating each DDH model and rotating the acetabular bone fragment in the anterolateral direction so that the femoral head was covered by the acetabular bone fragment, with CE and VCA angles each at 25°. Compared to the normal hip joint model, the DDH models showed stress concentration in the acetabular edge and contacting femoral head, and higher stress values; stress increased with decreasing CE and VCA angles. Compared to the DDH models, the post-PAO models showed near-normal patterns of stress distribution in the acetabulum and femoral head, with stress concentration areas shifted from the lateral to medial sides. Stress dispersion was especially apparent in the severe acetabular dysplasia models. PAO provided greater decreases in the maximum values of von Mises stress in the load-bearing area of the acetabulum and femoral head when applied to the DDH models of higher degrees of severity, although the values increased with increasing severity of DDH. PAO is expected to provide biomechanical improvement of the hip joint, although the results also suggest a limitation in the applicability of PAO for the patients with severe acetabular dysplasia

Aims. The aim of the current study was to assess the reliability of the Ottawa classification for symptomatic acetabular dysplasia. Methods. In all, 134 consecutive hips that underwent periacetabular osteotomy were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior, or posterior. A total of 74 cases were selected for reliability analysis, and these included 44 dysplastic and 30 normal hips. A group of six blinded fellowship-trained raters, provided with the classification system, looked at these radiographs at two separate timepoints to classify the hips using standard radiological measurements. Thereafter, a consensus meeting was held where a modified flow diagram was devised, before a third reading by four raters using a separate set of 74 radiographs took place. Results. Intrarater results per surgeon between Time 1 and Time 2 showed substantial to almost perfect agreement among the raters (κappa = 0.416 to 0.873). With respect to inter-rater reliability, at Time 1 and Time 2 there was substantial agreement overall between all surgeons (Time 1 κappa = 0.619; Time 2 κappa = 0.623). Posterior and anterior rating categories had moderate and fair agreement at Time 1 (posterior κappa = 0.557; anterior κappa = 0.438) and Time 2 (posterior κappa = 0.506; anterior κappa = 0.250), respectively. At Time 3, overall reliability (κappa = 0.687) and posterior and anterior reliability (posterior κappa = 0.579; anterior κappa = 0.521) improved from Time 1 and Time 2. Conclusion. The Ottawa 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. Cite this article: Bone Joint Res. 2020;9(5):242–249

Metal-on-metal hip resurfacing was performed for developmental dysplasia in 96 hips in 85 patients, 78 in women and 18 in men, with a mean age at the time of surgery of 43 years (14 to 65). These cases were matched for age, gender, operating surgeon and date of operation with a group of patients with primary osteoarthritis who had been treated by resurfacing, to provide a control group of 96 hips (93 patients). A clinical and radiological follow-up study was performed. The dysplasia group were followed for a mean of 4.4 years (2.0 to 8.5) and the osteoarthritis group for a mean of 4.5 years (2.2 to 9.4). Of the dysplasia cases, 17 (18%) were classified as Crowe grade III or IV. There were five (5.2%) revisions in the dysplasia group and none in the osteoarthritic patients. Four of the failures were due to acetabular loosening and the other sustained a fracture of the neck of femur. There was a significant difference in survival between the two groups (p = 0.02). The five-year survival was 96.7% (95% confidence interval 90.0 to 100) for the dysplasia group and 100% (95% confidence interval 100 to 100) for the osteoarthritic group. There was no significant difference in the median Oxford hip score between the two groups at any time during the study. The medium-term results of metal-on-metal hip resurfacing in all grades of developmental dysplasia are encouraging, although they are significantly worse than in a group of matched patients with osteoarthritis treated in the same manner

In a longitudinal case-control study, we followed 81 subjects with dysplasia of the hip and 136 control subjects without dysplasia for ten years assessing radiological evidence of degeneration of the hip at admission and follow-up. There were no cases of subluxation in the group with dysplasia. Neither subjects with dysplasia nor controls had radiological signs of ongoing degenerative disease at admission. The primary radiological discriminator of degeneration of the hip was a change in the minimum joint space width over time. There were no significant differences between these with dysplasia and controls in regard to age, body mass index or occupational exposure to daily repeated lifting at admission. We found no significant differences in the reduction of the joint space width at follow-up between subjects with dysplasia and the control subjects nor in self-reported pain in the hip. The association of subluxation and/or associated acetabular labral tears with dysplasia of the hip may be a conditional factor for the development of premature osteoarthritis in mildly to moderately dysplastic hips

Patients with acetabular dysplasia commonly undergo peri-acetabular osteotomy after skeletal maturity to reduce the risk of the late development of osteoarthritis. Several studies have suggested that deformity of the femoral head influences the long-term outcome. We radiologically examined 224 hips in 112 patients with acetabular dysplasia and early-stage osteoarthritis. There were 103 women and nine men with a mean age of 37.6 years (18 to 49). A total of 201 hips were placed in the acetabular dysplasia group and 23 in a normal group. The centre–edge angle and acetabular head index were significantly smaller (both p < 0.001), and the acetabular angle, acetabular roof angle and roundness index were significantly greater in the acetabular dysplasia group than those in the normal group (all p < 0.001). There were significant correlations between the roundness index and other parameters. Femoral head shape may be influenced by the severity of the acetabular dysplasia. Cite this article: Bone Joint J 2013;95-B:1192–6

MCID and PASS are thresholds driven from PROMS to reflect clinical effectiveness. Statistical significance can be derived from a change in PROMS, whereas MCID and PASS reflect clinical significance. Its role has been increasingly used in the world of young adult hip surgery with several publications determining the thresholds for Femoro-acetabular impingement FAI. To our knowledge MCID and PASS for patient undergoing PAO for dysplasia has not been reported. 593 PAOs between 1/2013 and 7/2023 were extracted from the Northumbria Hip Preservation Registry. Patients with available PROMS at 1year and/or 2years were included. PAOs for retroversion, residual Perthes and those combined with FO were excluded. MCID was calculated using the distribution method 0.5SD of baseline score(1). PASS was calculated using anchor method, ROC analysis performed, and value picked maximizing Youden index. A Logistic Regression analysis was performed to determine which independent variables correlated with achieving MCID and PASS. The MCID threshold for iHOt12 was 8.6 with 83.4 and 86.3 % of patients achieved it at 1 and 2 years respectively. The PASS score at 1 and 2 year follow up was 43 and 44 respectively, with 72.6 and 75.2% achieving it at 1 and 2 year postop. At 2 years a Higher preop iHOT 12 was associated with not achieving MCID and PASS (p<0.05). Preop acetabular version was negatively correlated with achieving MCID and previous hip arthroscopy was negatively correlated with PASS. The % of patients achieving MCID and PASS mimics that of FAI surgery (2). The negative correlation with preop iHOT12 reaffirms the importance of patient selection. The negative correlation of hip arthroscopy highlights the importance of having a high index of suspicion for dysplasia prior to hip arthroscopy and poorer outcomes of patients with mixed CAM and dysplasia pathology

Aims. Some patients presenting with hip pain and instability and underlying acetabular dysplasia (AD) do not experience resolution of symptoms after surgical management. Hip-spine syndrome is a possible underlying cause. We hypothesized that there is a higher frequency of radiological spine anomalies in patients with AD. We also assessed the relationship between radiological severity of AD and frequency of spine anomalies. Methods. In a retrospective analysis of registry data, 122 hips in 122 patients who presented with hip pain and and a final diagnosis of AD were studied. Two observers analyzed hip and spine variables using standard radiographs to assess AD. The frequency of lumbosacral transitional vertebra (LSTV), along with associated Castellvi grade, pars interarticularis defect, and spinal morphological measurements were recorded and correlated with radiological severity of AD. Results. Out of 122 patients, 110 (90.2%) were female and 12 (9.8%) were male. We analyzed the radiographs of 122 hips (59 (48.4%) symptomatic left hips, and 63 (51.6%) symptomatic right hips). Average age at time of presentation was 34.2 years (SD 11.2). Frequency of LSTV was high (39% to 43%), compared to historic records from the general population, with Castellvi type 3b being the most common (60% to 63%). Patients with AD have increased L4 and L5 interpedicular distance compared to published values. Frequency of pars interarticularis defect was 4%. Intraclass correlation coefficient for hip and spine variables assessed ranged from good (0.60 to 0.75) to excellent (0.75 to 1.00). Severity of AD did not demonstrate significant correlation with frequency of radiological spine anomalies. Conclusion. Patients with AD have increased frequency of spinal anomalies seen on standard hip radiographs. However, there exists no correlation between radiological severity of AD and frequency of spine anomalies. In managing AD patients, clinicians should also assess spinal anomalies that are easily found on standard hip radiographs. Cite this article: Bone Joint J 2021;103-B(8):1351–1357

Introduction. Acetabular dysplasia is typically characterised by insufficient antero-superior femoral head coverage. It is postulated (yet unproven) that patients with dysplasia compensate by reducing pelvic tilt (anterior pelvic rotation), effectively retroverting their acetabulum to improve antero-superior cover. We aimed to 1) define pelvic tilt (PT) in patients with bilateral and unilateral dysplasia, and 2) quantify PT changes following a successful periacetabular osteotomy (PAO). Patients/Materials and Methods. We retrospectively reviewed 16 patients (14 females) who underwent successful, bilateral, staged, PAOs (32 PAOs). These cases were matched for age and gender with 32 unilaterally dysplastic hips that underwent successful PAO for a similar degree of acetabular dysplasia as per pre-operative imaging. Supine and AP radiographs pre-PAO and at latest follow-up were used to measure centre-edge-angle (CEA) and Tönnis-angle (TA). PT was measured using two validated methods (Sacro-Femoral-Pubic (SFP) angle and Pubic-Symphysis to Sacro-Iliac (PS-SI) Index with excellent correlation (ρ=0.8, p<0.001). Results. Post-operatively, the TA/CEA improved from 20°±8/11°±9 to 5°±5/33°±6, respectively, with similar improvements between the unilateral and bilateral hips (p=0.9). PT pre-operatively was similar between unilaterally (8°±5) and bilaterally dysplastic hips (7°±5) (p=0.87). The change in PT was −1°±3; changing by >5° (all increased) in 6 patients (13%; 3 with unilateral PAOs and 3 with bilateral PAOs). Discussion. Patients with unilateral and bilateral hip dysplasia demonstrate similarities in PT. In 87% of cases PT remained the same following PAO, therefore was unlikely to have been compensatory. PT increased in 13% of cases post-PAO illustrating that a change in PT is possible and suggesting that the reduced tilt pre-PAO may have been compensatory to improve functional femoral head coverage in these patients. Conclusion. This is the first clinical and radiological evidence that patients with bilateral or unilateral dysplasia demonstrate similar pre- and post-operative PT, which remains unchanged in almost 90% of cases

The aim of this study was to investigate the incidence of dysplasia in the ‘normal’ contralateral hip in patients with unilateral developmental dislocation of the hip (DDH) and to evaluate the long-term prognosis of such hips. A total of 48 patients (40 girls and eight boys) were treated for late-detected unilateral DDH between 1958 and 1962. After preliminary skin traction, closed reduction was achieved at a mean age of 17.8 months (4 to 65) in all except one patient who needed open reduction. In 25 patients early derotation femoral osteotomy of the contralateral hip had been undertaken within three years of reduction, and later surgery in ten patients. Radiographs taken during childhood and adulthood were reviewed. The mean age of the patients was 50.9 years (43 to 55) at the time of the latest radiological review. In all, eight patients (17%) developed dysplasia of the contralateral hip, defined as a centre-edge (CE) angle < 20° during childhood or at skeletal maturity. Six of these patients underwent surgery to improve cover of the femoral head; the dysplasia improved in two after varus femoral osteotomy and in two after an acetabular shelf operation. During long-term follow-up the dysplasia deteriorated to subluxation in two patients (CE angles 4° and 5°, respectively) who both developed osteoarthritis (OA), and one of these underwent total hip replacement at the age of 49 years. In conclusion, the long-term prognosis for the contralateral hip was relatively good, as OA occurred in only two hips (4%) at a mean follow-up of 50 years. Regular review of the ‘normal’ side is indicated, and corrective surgery should be undertaken in those who develop subluxation. Cite this article: Bone Joint J 2014; 96-B:1161–6

Background. Hip dysplasia has traditionally been classified based on the lateral center 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. Methods. One hundred thirty-four consecutive hips that underwent a PAO were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior or posterior. 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. Five surgeons (3 fellowship trained in hip preservation) did a first reading (Time 1) to classify the hips, followed by four raters for a second reading (Time 2) minimum two weeks apart. 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. Results. There was substantial and almost perfect intra-rater agreement for 4 surgeons between Time 1 and Time 2. At time 1 and time 2, there was substantial agreement overall between all surgeons; however, posterior and anterior rating categories had moderate and fair agreement at time 1 and time 2, respectively. At time 3, overall reliability and posterior and anterior rating improved from Time 1 and Time 2. Conclusion. This 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

In Japan, osteoarthritis (OA) of the hip secondary to acetabular dysplasia is very common, and there are few data concerning the pathogeneses and incidence of femoroacetabular impingement (FAI). We have attempted to clarify the radiological prevalence of painful FAI in a cohort of Japanese patients and to investigate the radiological findings. We identified 176 symptomatic patients (202 hips) with Tönnis grade 0 or 1 osteoarthritis, whom we prospectively studied between August 2011 and July 2012. There were 61 men (65 hips) and 115 women (137 hips) with a mean age of 51.8 years (11 to 83). Radiological analyses included the α-angle, centre–edge angle, cross-over sign, pistol grip deformity and femoral head neck ratio. Of the 202 hips, 79 (39.1%) had acetabular dysplasia, while 80 hips (39.6%) had no known aetiology. We found evidence of FAI in 60 hips (29.7%). Radiological FAI findings associated with cam deformity were the most common. There was a significant relationship between the pistol grip deformity and both the α-angle (p < 0.001) and femoral head–neck ratio (p = 0.024). Radiological evidence of symptomatic FAI was not uncommon in these Japanese patients. Cite this article: Bone Joint J 2013;96-B:172–6

We followed up 76 consecutive hips with symptomatic acetabular dysplasia treated by acetabular shelf augmentation for a mean period of 11 years. Survival analysis using conversion to hip replacement as an end-point was 86% at five years and 46% at ten years. Forty-four hips with slight or no narrowing of the joint space pre-operatively had a survival of 97% at five and 75% at ten years. This was significantly higher (p = 0.0007) than that of the 32 hips with moderate or severe narrowing of the joint-space, which was 76% at five and 22% at ten years. There was no significant relationship between survival and age (p = 0.37) or the pre- and post-operative centre-edge (p = 0.39) and acetabular angles (p = 0.85). Shelf acetabuloplasty is a reliable, safe procedure offering medium-term symptomatic relief for adults with acetabular dysplasia. The best results were achieved in patients with mild and moderate dysplasia of the hip with little arthritis

Aims. Acetabular dysplasia is frequently associated with intra-articular pathology such as labral tears, but whether labral tears should be treated at the time of periacetabular osteotomy (PAO) remains controversial. The purpose of this study was to compare the clinical outcomes and radiographic corrections of PAO for acetabular dysplasia between patients with and without labral tears pre-operatively. Patients and Methods. We retrospectively reviewed 70 hips in 67 patients with acetabular dysplasia who underwent PAO. Of 47 hips (45 patients) with labral tears pre-operatively, 27 (25 patients) underwent PAO alone, and were classified as the labral tear alone (LT) group, and 20 (20 patients) underwent combined PAO and osteochondroplasty, and were classified as the labral tear osteochondroplasty (LTO) group. The non-labral tear (NLT) group included 23 hips in 22 patients. Results. There were no significant differences between groups for post-operative Harris hip scores, degree of progression of osteoarthritis or rate of reoperation. The pre-operative alpha angle was significantly larger in the LTO group compared with the other groups (p < 0.0001). Conclusion. PAO provides equivalent short-term relief of pain and functional outcome in patients with or without labral tears. The rate of progression of osteoarthritis and reoperation was not significantly increased in patients with labral tears. Take home message: PAO provides equivalent short-term pain relief and functional outcomes in patients with acetabular dysplasia with and without labral tears. We did not find significantly increased risks of progression of osteoarthritis or re-operation in those with labral tears. Cite this article: Bone Joint J 2016;98-B:741–6

Introduction. Acetabular dysplasia is associated with an increased risk of hip pain and early development of osteoarthritis (OA). The Bernese peri-acetabular osteotomy (PAO) is the most well-established technique in the Western world for the treatment of symptomatic acetabular dysplasia. This case-control study aims to assess whether the severity of acetabular dysplasia has an effect on outcome following Peri-Acetabular Osteotomy (PAO) and/or the ability to achieve desired acetabular correction. Patients/Materials & Methods. A prospective, multicentre, longitudinal cohort of consecutive PAOs was reviewed. Of the available 381 cases, 61 hips had pre-PAO radiographic features of lesser-dysplasia [Acetabular-Index (AI)<15° and Lateral-Centre-Edge-Angle (LCEA)>15°) and comprised the ‘study-group’. ‘Study-Group’ was matched for all factors known to influence outcome post-PAO [age, gender, BMI, Tönnis-grade and joint congruency (p=0.6–0.9)] with a ‘Comparison-Group’ of pronounced dysplasia (n=183). Clinical outcomes, complications and the ability to achieve optimum correction (LCEA: 25°–40°/AI: 0°–+10°) were compared. Results. At a mean follow-up of 4(±1.5) years, 3 hips had a THA and 13 underwent further procedures; 21 major complications occurred. The mean improvement in HOOS was 28(±23). No differences in complication- or re-operation- rates were detected between study- and comparison groups (p=0.29). Lesser-dysplastic hips had inferior HOOS compared to pronounced dysplastic hips, both pre- (52Vs.59) and post-operatively (73Vs.78); however, similar improvements were seen. Amongst the lesser dysplastic hips, those that required a femoral osteochondroplasty at PAO had significantly inferior pre-operative HOOS (48±18), compared to those that didn't require an osteochondroplasty (60±17) (p=0.04). Increased ability to achieve optimum acetabular correct was seen (80Vs59%, p=0.4) in the lesser dysplastic hip. Discussion. A PAO is safe and efficacious in the treatment of lesser dysplasia. The mildly dysplastic hips with cam deformity that required concurrent FOCP and PAO, were the most symptomatic. Future studies should aim to optimize diagnosis and management in this challenging, combined deformity cohort

Purpose. Patients with acetabular dysplasia demonstrate altered biomechanics during gate and other activities. We hypothesized that these patients exhibit a compensatory increase in the anterior pelvic tilt during gait. Materials & Methods. Twelve patients were included in this prospective radiographic and gait analysis study prior to the PAO. All were women. The mean age was 27 years (+/− 8 yrs). Tonnis grade was zero in nine, and one in three hips. All patients performed multiple one-minute walking trials on the level, the incline, and the decline treadmill surfaces in an optical motion capture lab. Anterior pelvic tilt is reported in (+), while the posterior pelvic tilt is reported in (–) values. Results. Radiographic Data. : The mean alpha angle measured from the Dunn and the frog lateral images was 63.0º±17.4, and 54.7º±16.4, respectively. The mean LCEA was 14.9°±6.1, and the mean anterior center edge angle was 18.3°±8.9. the mean acetabular version at 1, 2, and 3 o'clock were 12.1°±11.6, 29.2°±9.9, and 23.3°±7.4, respectively. Intra-class correlation coefficient (ICC) for these measurements were 0.934, 0.895, and 0.971, respectively. The mean femoral anteversion, as measured on the 3D CT scan was 21.3°±16.1. The mean hip flexion range was 107.1°± 7.2. The mean pelvic tilt was 88.7 mm ± 14.4 using the PS-SI distance with an ICC of 0.998. Gait Data. : Baseline measurements were done in the standing position. On the leveled surface, 5 patients had anterior (+) while 7 had posterior (−) pelvic tilt. The mean posterior pelvic tilt was 1.0° with the range of −2.8° to +0.67°. On the inclined surface, all patients had posterior (−) pelvic tilt. The mean pelvic tilt was −4.9° with the range of −6.4° to −3.1°. On the declined surface, 8 patients had anterior (+) while 4 patients had posterior (−) pelvic tilt. The mean pelvic tilt was −0.39° with the range of −1.9° to +1.0°. The pelvic tilt was negatively correlated with the PS-SI distance on all three surfaces with the Spearman coefficients of −0.27, −0.04, and −0.18 on the 3 different surfaces, respectively. Conclusion. Our results demonstrated that the patients with hip dysplasia exhibit variable degrees of the pelvic tilt while walking on different surface inclinations. Weak negative correlation with the standing pelvic tilt measurements from the radiographs suggests that those patients with more anterior standing pelvic tilt tend to have greater compensatory posterior tilt during gait

The purpose of this study was to examine a cohort of patients with minor acetabular dysplasia features in order to identify the preoperative clinical characteristics and imaging findings that differentiate patients with hip instability from patients with impingement. A retrospective cohort study of patients with borderline acetabular dysplasia was performed. All patients were identified by prospective radiographic evaluation with an LCEA between 20° and 25°. Multivariate statistical analyses were used to identify independent predictors of disease type. Of the 143 hips in the cohort, 39.2% (n=56) had the diagnosis of instability, while 60.8% (n=87) had the diagnosis of impingement. The cohort included 109 females (76.2%) and 34 males (23.8%). Hips with instability had a lower LCEA (21.8° vs. 22.8°; p<0.001), lower ACEA (23.3° vs. 26.6°; p=0.002), a higher AI (11.8° vs. 8.5°; p<0.001), and a lower maximum alpha angle (54.4° vs. 61.1°; p=0.001). The odds of instability increased 1.7 times for each one-degree decrease in LCEA, 1.4 times for each one-degree decrease in ACEA, and 1.1 times for each one-degree increase in acetabular inclination (all p0.003). Female sex was strongly associated with instability. The instability subgroup had greater range of motion (IRF, 22.7° vs. 12.4°, p<0.001) and total arc of motion (IRF+ERF, 61.2° vs. 47.4°, p<0.001). We identified predictors of diagnosis including: acetabular inclination (1.49, p<0.001), ACEA (0.89, p=0.007), crossover sign (0.27, p=0.014), preoperative mHHS (0.96, p=0.014), IRF (1.10, p=0.001), and age (0.88, p=0.001). Patients with symptomatic instability tend to have increased acetabular inclination, decreased ACEA, greater functional limitations, younger, greater IRF, while hips with impingement demonstrate the opposite trends