Protocol and validity testing of femoroacetabular posterior translation with dynamic hip ultrasonography.

OBJECTIVE: To describe femoroacetabular posterior translation (FAPT) using dynamic hip ultrasonography (DHUS), and to determine the inter- and intra-rater reliability of hip ultrasound measurements of FAPT. MATERIALS AND METHODS: The study design was a feasibility study of 13 healthy young adults (26 hips) using test-retest analysis. The data was collected prospectively over a 2-week time period. Three DHUS measurements (posterior neutral (PN), flexion, adduction, and internal rotation (PFADIR), and stand and load (PStand) were measured by four independent raters (2 senior who divided the cohort, 1 intermediate, 1 junior) at two time points for bilateral hips of each participant. Reliability was assessed by calculating the intraclass correlation coefficient (ICC) along with 95% confidence intervals (CIs) for each rater and across all raters. RESULTS: A total of 468 US scans were completed. The mean age of the cohort was 25.7 years (SD 5.1 years) and 54% were female. The inter-rater reliability was excellent for PFADIR (ICC 0.85 95% CI 0.76-0.91), good for PN (ICC 0.69 95% CI 0.5-0.81), and good for PStand (ICC 0.72 95% CI 0.55-0.83). The intra-rater reliability for all raters was good for PFADIR (ICC 0.60 95% CI 0.44-0.73), fair for PN (ICC 0.42 95% CI 0.21-0.59), and fair for PStand (ICC 0.42 95% CI 0.22-0.59). CONCLUSION: This is the first study to present a protocol using dynamic ultrasonography to measure FAPT. DHUS measure for FAPT was shown to be reliable across raters with varying levels of ultrasound experience.

Risk Factors for Suboptimal Outcome of FAI Surgery in the Adolescent Patient.

BACKGROUND: Surgical treatment for adolescent patients with femoroacetabular impingement (FAI) is increasing. The purpose of this study was to determine the clinical outcomes of FAI surgery in a multicenter cohort of adolescent patients and to identify predictors of suboptimal outcomes. METHODS: One hundred twenty-six adolescent hips (114 patients < 18 years of age) undergoing surgery for symptomatic FAI were studied from a larger multicenter cohort. The group included 74 (58.7%) female and 52 male hips (41.3%) with a mean age of 16.1 (range 11.3 to 17.8). Clinical outcomes included the modified Harris Hip Score (mHHS), Hip disability and Osteoarthritis Outcome Score (5 domains), and University of California Los Angeles activity score. Failure was defined as revision surgery or clinical failure (inability to reach minimally clinical important differences or patient acceptable symptoms state for the mHHS). Statistical analysis was used to identify factors significantly associated with failure. RESULTS: There was clinically important improvement in all patient-reported outcomes for the overall group, but an 18.3% failure rate. This included a revision rate of 8.7%. Females were significantly more likely than males to be classified as a failure (25.7 vs. 7.7%, P =0.01), in part because of lower preoperative mHHS (59.1 vs. 67.0, P < 0.001). Mild cam deformity (alpha angle <55 degrees) was present in 42.5% of female hips compared with 17.3% male hips. Higher alpha angles were inversely correlated with failure. Alpha angles >63 have a failure rate of 8.3%, between 55 and 63 degrees, 12.0% failure rate, and <55 degrees (mild cam) failure rate of 37.5%. Patients who participated in athletics had a 10.3% failure rate compared with nonathletes at 25.0% ( P =0.03, RR (relative risk) 2.4). CONCLUSIONS: Adolescent patients undergoing surgical treatment for FAI generally demonstrate significant improvement. However, female sex, mild cam deformities, and lack of sports participation are independently associated with higher failure rates. These factors should be considered in surgical decision-making and during patient counseling. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

What Are the Early Outcomes of True Reverse Periacetabular Osteotomy for Symptomatic Hip Overcoverage?

BACKGROUND: Acetabular overcoverage is associated with pincer-type femoroacetabular impingement (FAI). A subtype of acetabular overcoverage is caused by a deep acetabulum with a negatively tilted acetabular roof, in which acetabular reorientation may be a preferable alternative to rim trimming to uncover the femoral head. We introduced the true reverse periacetabular osteotomy (PAO) in 2003, which in contrast to an anteverting PAO, also flexes and abducts the acetabulum relative to the intact ilium to decrease anterior and lateral femoral head coverage and correct negative tilt of the acetabular roof. To our knowledge, the clinical results of the true reverse PAO have not been evaluated. QUESTIONS/PURPOSES: For a group of patients who underwent reverse PAO, (1) Do patients undergoing reverse PAO demonstrate short-term improvement in pain, function, and hip ROM, and decreased acetabular coverage, as defined by lateral and anterior center-edge angle and Tönnis angle? (2) Are there identifiable factors associated with success or adverse outcomes of reverse PAO as defined by reoperation, conversion to THA, or poor patient-reported outcome scores? (3) Are there identifiable factors associated with early complications? METHODS: Between 2003 and 2017, two surgeons carried out 49 reverse PAOs in 37 patients. Twenty-five patients had unilateral reverse PAO and 12 patients had staged, bilateral reverse PAOs. To ensure that each hip was an independent data point for statistical analysis, we chose to include in our series only the first hip in the patients who had bilateral reverse PAOs. During the study period, our general indications for this operation were symptomatic lateral and anterior acetabular overcoverage causing FAI that had failed to respond to previous conservative or surgical treatment. Thirty-seven hips in 37 patients with a median (range) age of 18 years (12 to 41; interquartile range 16 to 21) were included in this retrospective study at a minimum follow-up of 2 years (median 6 years; range 2 to 17). Thirty-four patients completed questionnaires, 24 patients had radiographic evaluation, and 23 patients received hip ROM clinical examination. However, seven patients had not been seen in more than 5 years. The clinical and radiographic parameters of all 37 hips that underwent reverse PAO in 37 patients from a longitudinally maintained institutional database were retrospectively studied preoperatively and postoperatively. Adverse outcomes were considered conversion to THA or a WOMAC pain score greater than 10 at least 2 years postoperatively. Patient-reported outcomes, radiographic measurements, and hip ROM were evaluated preoperatively and at most recent follow-up using a paired t-test or McNemar test, as appropriate. Linear regression analysis was used to assess for identifiable factors associated with clinical outcomes. Logistic regression analysis was used to assess for identifiable factors associated with adverse outcomes and surgical complications. All tests were two-sided, and p values less than 0.05 were considered significant. RESULTS: At a minimum of 2 years after reverse PAO, patients experienced improvement in WOMAC pain (-7 [95% CI -9 to -5]; p < 0.001), stiffness (-2 [95% CI -3 to -1]; p < 0.001), and function scores (-18 [95% CI -24 to -12]; p < 0.001) and modified Harris Hip Score (mHHS) (20 [95% CI 13 to 27]; p < 0.001). The mean postoperative hip ROM improved in internal rotation (8° [95% CI 2° to 14°]; p = 0.007). Acetabular coverage, as defined by lateral center-edge angle (LCEA), anterior center-edge angle (ACEA), and Tönnis angle, improved by -8° (95% CI -12° to -5°; p < 0.001) for LCEA, -12° (95% CI -15° to -9°; p < 0.001) for ACEA, and 9° (95% CI 6° to 13°; p < 0.001) for Tönnis angle. The postoperative severity of radiographic arthritis was associated with worse WOMAC function scores such that for each postoperative Tönnis grade, WOMAC function score increased by 12 points (95% CI 2 to 22; p = 0.03). A greater postoperative Tönnis grade was also correlated with worse mHHS, with an average decrease of 12 points (95% CI -20 to -4; p = 0.008) in mHHS for each additional Tönnis grade. Presence of a positive postoperative anterior impingement test was associated with a decrease in mHHS score at follow-up, with an average 23-point decrease in mHHS (95% CI -34 to -12; p = 0.001). Nineteen percent (7 of 37) of hips had surgery-related complications. Four hips experienced adverse outcomes at final follow-up, with two patients undergoing subsequent THA and two with a WOMAC pain score greater than 10. We found no factors associated with complications or adverse outcomes. CONCLUSION: The early clinical and radiographic results of true reverse PAO compare favorably to other surgical treatments for pincer FAI, suggesting that reverse PAO is a promising treatment for cases of pincer FAI caused by global acetabular overcoverage. However, it is a technically complex procedure that requires substantial training and preparation by a surgeon who is already familiar with standard PAO, and it must be carefully presented to patients with discussion of the potential risks and benefits. Future studies are needed to further refine the indications and to determine the long-term outcomes of reverse PAO. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Slipped Capital Femoral Epiphysis in Children without Obesity.

OBJECTIVE: To evaluate rates and characteristics of slipped capital femoral epiphysis (SCFE) in children who are not obese to prevent missed diagnoses and subsequent complications. STUDY DESIGN: A multicenter, retrospective review identified all patients with SCFE from January 1, 2003 to December 31, 2012. Patients were excluded if they received previous surgery at an outside institution, had no recorded height and weight, or had medical co-morbidity associated with increased risk of SCFE. Body mass index (BMI) percentile for age was calculated and categorized for each patient (patients without obesity vs with obesity). RESULTS: In total, 275 patients met inclusion criteria. Average BMI was 91.2 percentile (range: 8.4-99.7). Thirteen percent (34 patients) were considered "normal weight" (BMI 5%-85%), 17% (48 patients) were considered "overweight" (BMI 85%- 95%), and 70% (193 patients) were considered "obese" (BMI >95%). Average BMI percentile was higher in male than female patients (93.2 ± 12.7 vs 88.5 ± 21.4, P = .034). Patients without obesity were older compared with patients with obesity (12.2 ± 1.7 vs 11.7 ± 1.6 years, P = .015). Fewer patients without obesity were seen at the hospital in the southwest. The southwest had fewer patients without obesity than the northeast (18.3% vs 36.1%, P = .002). Patients without obesity were more likely to present with a severe slip as graded by Wilson percent displacement (27.2% vs 11.4%, P = .007) and an unstable slip (32.9% vs 14.7%, P = .001). CONCLUSION: Rates of nonobese SCFE in this study are higher than reported in the previous literature. Normal weight patients with SCFE are more likely to be older, female, and present with a severe and unstable SCFE.

What Proportion of Patients Undergoing Bernese Periacetabular Osteotomy Experience Nonunion, and What Factors are Associated with Nonunion?

BACKGROUND: The Bernese periacetabular osteotomy (PAO) is one of the most-used surgical techniques to treat symptomatic acetabular dysplasia. Although good functional and radiographic short-term and long-term outcomes have been reported, several complications after PAO have been described. One complication that may compromise clinical results is nonunion of an osteotomy. However, the exact prevalence and risk factors associated with nonunion are poorly elucidated. QUESTIONS/PURPOSES: (1) What proportion of patients have complete bony healing versus nonunion during the first year after PAO? (2) What is the clinical and functional impact of nonunion at a minimum of 1 year after PAO, as assessed by the modified Harris hip score (mHHS) and the Hip Disability and Osteoarthritis Outcome Score (HOOS)? (3) What patient-specific or surgery-specific factors are associated with nonunion at 6 months and at a minimum of 1 year postoperatively? METHODS: Between January 2012 and December 2015, we retrospectively identified 314 patients who underwent PAO at our institution. During this period, 28 patients with a diagnosis different from symptomatic acetabular dysplasia (reverse PAO for acetabular over-coverage: n = 25; PAO for skeletal chondrodysplasia: n = 3) underwent PAO but were ineligible to participate. Hence, 286 patients underwent PAO to treat symptomatic acetabular dysplasia during the study period and were considered eligible. Inclusion criteria were patients with a complete set of postoperative radiographs (AP, Dunn lateral, and false-profile) at 12 months or more postoperatively. Eighteen percent (51 of 286) of the patients underwent staged, bilateral PAOs, but we only included the first PAO. Finally, 14% (41 of 286) of the patients were excluded because they had an incomplete set of postoperative radiographs at 12 months or more. The study comprised 245 patients. Eighty-five percent (209 of 245) of the patients were female and the mean age at surgery was 24 years ± 9 years. The healing status (complete healing vs. nonunion) was recorded for ischial, superior pubic, supraacetabular, and posterior column osteotomies at each subsequent visit. Nonunion was defined as noncontiguous osseous union with a persistent radiolucent line across any osteotomy site and was recorded at 3 months, approximately 6 months, and approximately 12 months postoperatively. Calculation of Cohen's kappa statistic coefficients showed the classification had perfect interobserver agreement (0.53; 95% confidence interval, 0.12-0.93), but there was moderate intraobserver agreement between those who healed and those with nonunion. The HOOS and mHHS were collected preoperatively and at a minimum of 1 year after PAO. The HOOS contains five separate subscales for pain, symptoms, activity of daily living, sport and recreational function, and hip-related quality of life. The HOOS responses are normalized on a scale of 0 (worst) to 100 (best). The mHHS includes pain and function scales and is overall interpreted on a scale from 0 (worst) to 100 (best). Eighty-six percent (211 of 245) of the patients with a complete set of images at their 12-month visit completed the mHHS and 89% (217 of 245) completed the HOOS. We collected information from the patients' medical records about their symptomatic status and additional treatment for nonunion. A logistic regression analysis was used to investigate factors associated with nonunion at 6 and 12 months postoperatively. RESULTS: Only 45% (96 of 215) of the patients had complete radiographic healing of all osteotomy sites at the 6-month visit and 55% (119 of 215) had not healed completely. However, 92% (225 of 245) demonstrated complete radiographic healing of all osteotomy sites at approximately 1 year postoperatively. The proportion of nonunion at a minimum of 12 months after PAO was 8% (20 of 245 patients). There was no difference in the mHHS after 1 year or more of follow-up between patients with nonunion and patients with complete healing after PAO (nonunion mean mHHS: 73; 95% CI, 62-85 versus healed: 82; 95% CI, 80-85; p = 0.13) and HOOS pain (nonunion mean HOOS pain: 80; 95% CI, 71-90 versus healed: 86; 95% CI, 83-88; p = 0.16). Similarly, no difference was identified for HOOS symptoms (nonunion mean: 72; 95% CI, 63-80 versus healed: 78; 95% CI, 75-81; p = 0.11), HOOS activities of daily living (nonunion mean: 86; 95% CI, 78-94 versus healed: 91; 95% CI, 89-93; p = 0.09), HOOS sports and recreation (nonunion mean: 70; 95% CI, 57-83 versus healed: 78; 95% CI, 75-82; p = 0.18); and HOOS quality of life (nonunion mean: 60; 95% CI, 46-75 versus healed: 69; 95% CI, 65-72; p = 0.28). After controlling for potentially confounding variables such as gender, age, chisel type, and preoperative anterior center-edge angle, we found that higher BMI (per 1 k/m; odds ratio 1.14; 95% CI, 1.06-1.22; p < 0.01), older age (per 1 year; OR 1.05; 95% CI, 1.01-1.08; p < 0.01) and more-severe acetabular dysplasia as assessed by a decreased preoperative lateral center-edge angle (per 1°; OR 1.06; 95% CI, 1.02-1.11; p < 0.01) were independently associated with nonunion of one or more osteotomy sites at 6 months postoperatively. Only age was an independent predictor of nonunion at 12 months postoperatively (per 1 year; OR 1.06; 95% CI, 1.01-1.11; p = 0.02). CONCLUSIONS: Our study helps us to understand radiographic healing during the first year after PAO to treat symptomatic acetabular dysplasia. Fewer than half of the patients had complete healing of their osteotomies at 6 months postoperatively. More than 90% of patients can expect to have completely healed osteotomy sites at 12 months postoperatively. Surgeons should avoid unnecessary interventions if nonunion is observed radiographically at 6 months postoperatively. Although there was no difference in the HOOS and mHHS between patients with nonunion and those with complete healing, further research with a larger cohort is needed to clarify the impact of nonunion on clinical and functional outcomes after PAO. Surgeons should consider using strategies to enhance osteotomy healing in those who undergo PAO, such as optimizing vitamin D levels and using local bone grafts in older patients, those with a high BMI, and patients with severe acetabular dysplasia. LEVEL OF EVIDENCE: Level III, therapeutic study.

Vascular Supply to the Femoral Head in Patients With Healed Slipped Capital Femoral Epiphysis.

BACKGROUND: Slipped capital femoral epiphysis (SCFE) is one of the most common hip disorders. The vascularity of the lateral epiphyseal vessels supplying the femoral head in patients with healed SCFE has not been well defined. The purpose of this study was to characterize the location and number of lateral epiphyseal vessels in young adults with healed SCFE. METHODS: This was a retrospective study of 17 patients (18 hips) with a diagnosis of SCFE and a matched control group of 17 patients (17 hips) with developmental dysplasia of the hip. All patients underwent high-resolution contrast-enhanced magnetic resonance imaging to visualize the path of the medial femoral circumflex artery and the lateral epiphyseal arterial branches supplying the femoral head. RESULTS: There were 5 unstable SCFEs and 13 stable SCFEs with an average slip angle of 31 degrees. (All patients had been treated with in situ pinning and screw removal). Average age at time of magnetic resonance imaging was 24.5 years (range, 15 to 34 y). The lateral epiphyseal vessels reliably inserted on the posterior-superior aspect of the femoral neck from the superior-anterior to the superior-posterior position in both the SCFE and control groups. An average of 2 (±0.8) retinacular vessels were identified in the SCFE group compared with 5.2 (±0.7) retinacular vessels in the control group (P<0.001). CONCLUSIONS: In healed SCFE, the lateral epiphyseal vessels reliably insert in the same anatomic region as patients with hip dysplasia; however, the overall number of vessels is significantly lower.

Periacetabular Osteotomy Improves Pain and Function in Patients With Lateral Center-edge Angle Between 18° and 25°, but Are These Hips Really Borderline Dysplastic?

BACKGROUND: The treatment of mild or borderline acetabular dysplasia is controversial with surgical options including both arthroscopic labral repair with capsular closure or plication and periacetabular osteotomy (PAO). The degree to which improvements in pain and function might be achieved using these approaches may be a function of acetabular morphology and the severity of the dysplasia, but detailed radiographic assessments of acetabular morphology in patients with a lateral center-edge angle (LCEA) of 18° to 25° who have undergone PAO have not, to our knowledge, been performed. QUESTIONS/PURPOSES: (1) Do patients with an LCEA of 18° to 25° undergoing PAO have other radiographic features of dysplasia suggestive of abnormal femoral head coverage by the acetabulum? (2) What is the survivorship free from revision surgery, THA, or severe pain (modified Harris hip score [mHHS] < 70) and proportion of complications as defined by the modified Dindo-Clavien severity scale at minimum 2-year followup? (3) What are the functional patient-reported outcome measures in this cohort at minimum 2 years after surgery as assessed by the UCLA Activity Score, the mHHS, the Hip disability and Osteoarthritis Outcome Score (HOOS), and the SF-12 mental and physical domain scores? METHODS: Between January 2010 and December 2014, a total of 91 patients with hip pain and LCEA of 18° to 25° underwent a hip preservation surgical procedure at our institution. Thirty-six (40%) of the 91 patients underwent hip arthroscopy, and 56 hips (60%) were treated by PAO. In general, patients were considered for hip arthroscopy when symptoms were predominantly associated with femoroacetabular impingement (that is, pain aggravated by sitting and hip flexion activities) and physical examination showed a positive anterior impingement test with negative signs of instability (negative anterior apprehension test). In general, patients were considered for PAO when symptoms suggested instability (that is, pain with upright activities, abductor fatigue now aggravated by sitting) and clinical examinations demonstrated a positive anterior apprehension test. Bilateral surgery was performed in six patients and only the first hip was included in the study. One patient was excluded because PAO was performed to address dysplasia caused by surgical excision of a proximal femoral tumor associated with multiple epiphyseal dysplasia during childhood yielding a total of 49 patients (49 hips). There were 46 of 49 females (94%), the mean age was 26.5 years (± 8), and the mean body mass index was 24 kg/m (± 4.5). Radiographic analysis of preoperative films included the LCEA, Tönnis acetabular roof angle, the anterior center-edge angle, the anterior and posterior wall indices, and the Femoral Epiphyseal Acetabular Roof index. Thirty-nine of the 49 patients (80%) were followed for a minimum 2-year followup (mean, 2.2 years; range, 2-4 years) and were included in the analysis of survivorship after PAO, complications, and functional outcomes. Kaplan-Meier modeling was used to calculate survivorship defined as free from revision surgery, THA, or severe pain (mHHS < 70) at minimum 2 years after surgery. Complications were graded according to the modified Dindo-Clavien severity. Patient-reported outcomes were collected preoperatively and at minimum 2 years after surgery and included the UCLA Activity Score, the mHHS, the HOOS, and the SF-12 mental and physical domain scores. RESULTS: Forty-six of 49 hips (94%) had at least one other radiographic feature of dysplasia suggestive of abnormal femoral head coverage by the acetabulum. Seventy-three percent of the hips (36 of 49) had two or more radiographic features of hip dysplasia aside from a LCEA of 18° to 25°. The survivorship of PAO at minimum 2 years for the 39 of 49 (80%) patients available was 94% (95% confidence interval, 80%-90%). Three of 39 patients (8%) developed a complication. At a mean of 2.2 years of followup, there was improvement in level of activity (preoperative UCLA score 7 ± 2 versus postoperative UCLA score 6 ± 2; p = 0.02). Hip symptoms and function improved postoperatively, as reflected by a higher mean mHHS (86 ± 13 versus 64 ± 19; p < 0.001) and mean HOOS (386 ± 128 versus 261 ± 117; p < 0.001). Quality of life and overall health assessed by the physical domain of the SF-12 improved (47 ± 11 versus 39 ± 12; p < 0.001). However, with the numbers available, no improvement was observed for the mental domain of the SF-12 (52 ± 8 versus 51 ± 11; p = 0.881). CONCLUSIONS: Hips with LCEA of 18° to 25° frequently have other radiographic features of dysplasia suggestive of abnormal femoral head coverage by the acetabulum. These hips may be inappropriately labeled as "borderline" or "mild" dysplasia on consideration of LCEA alone. A more comprehensive imaging analysis in these hips by the radiographic features of dysplasia included in this study is recommended to identify hips with abnormal coverage of the femoral head by the acetabulum and to plan treatment accordingly. Patients with LCEA of 18° to 25° showed improvement in hip pain and function after PAO with minimal complications and low proportions of persistent pain or reoperations at short-term followup. Future studies are recommended to investigate whether the benefits of symptomatic and functional improvement are sustained long term. LEVEL OF EVIDENCE: Level IV, therapeutic study.

What Is the Reliability and Accuracy of Intraoperative Fluoroscopy in Evaluating Anterior, Lateral, and Posterior Coverage During Periacetabular Osteotomy?

BACKGROUND: Periacetabular osteotomy (PAO) is an established treatment for acetabular dysplasia in the skeletally mature individual. Fluoroscopy is used intraoperatively for osteotomy completion and to judge fragment correction. However, a comprehensive study validating fluoroscopy to judge anterior, lateral, and posterior coverage in PAO has not been reported. QUESTIONS/PURPOSES: (1) Are radiographic and fluoroscopic measures of anterior, lateral, and posterior acetabular coverage reliable? (2) Do fluoroscopic measures of fragment correction accurately measure anterior, lateral, and posterior coverage when compared with postoperative radiographs? METHODS: We performed a retrospective study of patients undergoing PAO with a primary diagnosis of acetabular dysplasia. Between 2012 and 2014 two surgeons performed 287 PAOs with fluoroscopy. To be included in this retrospective study, patients had to be younger than 35 years old, have a primary diagnosis of dysplasia (not retroversion, Perthes, or skeletal dysplasia), have adequate radiographic and fluoroscopic imaging, be a primary PAO (not revision), and in the case of bilateral patients, only the first hip operated on in the study period was included. Based on these criteria, 46% of the PAOs performed were included here (133 of 287). A total of 109 (82%) of the patients were females (109 of 133), and the mean age of the patients represented was 24 years (SD, 7 years). Pre- and postoperative standing radiographs as well as intraoperative fluoroscopic images were reviewed and lateral center-edge angle (LCEA), Tönnis angle (TA), anterior center-edge angle (ACEA), anterior wall index (AWI), and posterior wall index (PWI) were measured. Two fellowship-trained hip preservation surgeons completed all measurements with one reader performing a randomized sample of 49 repeat measurements 4 weeks after the initial reading for purposes of calculating intraobserver reliability. Intra- and interrater reliability was assessed using an intraclass correlation coefficient (ICC) model. Agreement between intraoperative fluoroscopic and postoperative radiographic measures was determined by estimating the ICC with 95% confidence intervals and by Bland-Altman analysis. RESULTS: Intrarater reliability was excellent (ICC > 0.75) for all measures and good for postoperative AWI (ICC = 0.72; 95% confidence interval [CI], 0.48-0.85). Interrater reliability was excellent (ICC > 0.75) for all measures except intraoperative TA (ICC = 0.72; 95% CI, 0.48-0.84). Accuracy of fluoroscopy was good (0.60 < ICC < 0.75) for LCEA (ICC = 0.73; 95% CI, 0.55-0.83), TA (ICC = 0.66; 95% CI, 0.41-0.79), AWI (ICC = 0.63; 95% CI, 0.48-0.74), and PWI (ICC = 0.72; 95% CI, 0.35-0.85) and excellent (ICC > 0.75) for ACEA (ICC = 0.80; 95% CI, 0.71-0.86). Bland-Altman analysis for systematic bias in the comparison between intraoperative fluoroscopy and postoperative radiography found the effect of such bias to be negligible (mean difference: LCEA 2°, TA 2°, ACEA 1°, AWI 0.02, PWI 0.11). CONCLUSIONS: Fluoroscopy is accurate in measuring correction in PAO. However, surgeons should take care not to undercorrect the posterior wall. Based on our study, intraoperative fluoroscopy may be used as an alternative to an intraoperative AP pelvis radiograph to judge final acetabular fragment correction with an experienced surgeon. However, more studies are needed including a properly powered direct comparative study of intraoperative fluoroscopy and intraoperative radiographs. Moreover, the impact of radiographic correction achieved during surgery should be studied to determine the implications for patient-reported outcomes and long-term survival of the hip. LEVEL OF EVIDENCE: Level IV, diagnostic study.

Can Dynamic Ultrasonography of the Hip Reliably Assess Anterior Femoral Head Translation?

BACKGROUND: Hip microinstability has gained attention recently as a potential cause of hip pain. Currently there is a lack of evidence-based objective diagnostic criteria surrounding this diagnosis. Previous studies have shown translation of the femoral head during extreme hip positions. However, reliable assessment of femoral head translation is lacking. QUESTIONS/PURPOSES: (1) How precise is musculoskeletal ultrasound for measuring anterior femoral head translation during the hip anterior apprehension test? (2) What is the intra- and interrater reliability of dynamic ultrasonography in assessing anterior femoral head translation? METHODS: We recruited 10 study participants (20 hips) between the ages of 22 and 50 years with no history of hip pain or functional limitations. Test-retest methodology was used. Seven females and three males were enrolled. The mean age of study participants was 27 years (SD 8.7 years); mean body mass index was 22.6 kg/m (SD 2.2 kg/m). All study participants underwent dynamic hip ultrasonography by three different physicians 1 week apart. Each hip was visualized in two neutral positions (neutral and neutral with the contralateral hip flexed [NF]) and two dynamic positions, which sought to replicate the apprehension test, although notably study participants had no known hip pathology and therefore no apprehension. The first maintained the hip in extension and external rotation off to the side of the examination table (EER1), and the second held the hip off of the bottom of the examination table (EER2). One hundred twenty ultrasound scans (480 images) were performed. Mean and SD were calculated using absolute values of the difference in ultrasound measurements (mm) between positions NF and EER1 and NF and EER2 calculated for each physician as well as an average of all three physicians. Intraclass correlation coefficient (ICC) analysis was used to examine intra- and interrater reliability. RESULTS: The mean absolute difference for NF and EER1 was 0.84 mm (SD 0.93 mm) and for NF and EER2 0.62 mm (SD 0.40 mm) on Study Day 1. Similarly, on Study Day 2, the mean absolute difference for NF and EER1 position was 0.90 mm (SD 0.74 mm) and for NF and EER2 1.03 mm (SD 1.18 mm). Cumulative values of ICC analysis indicated excellent intrarater reliability in all four positions: neutral 0.794 (95% confidence interval [CI], 0.494-0.918), NF 0.927 (95% CI, 0.814-0.971), EER1 0.929 (95% CI, 0.825-0.972), and EER2 0.945 (95% CI, 0.864-0.978). Similarly, interrater ICC analysis cumulative values were excellent for NF, EER1, and EER2 and fair to good for the neutral position: neutral 0.725 (95% CI, 0.526-0.846), NF 0.846 (95% CI, 0.741-0.913), EER1 0.812 (95% CI, 0.674-0.895), and EER2 0.794 (95% CI, 0.652-0.884). CONCLUSIONS: This study offers the first ultrasound protocol of which we are aware for measuring anterior femoral head translation. Hip dynamic ultrasound may assist in providing precise objective clinical-based diagnostic evidence when evaluating complex hip pain and suspected microinstability. Musculoskeletal ultrasound is a reliable office-based method of measuring anterior femoral head translation that can be utilized by physicians with varying experience levels. Future studies are needed to investigate ultrasound anterior femoral head translation taking into account sex, prior hip surgery, hip osseous morphology, and ligamentous laxity. LEVEL OF EVIDENCE: Level III, diagnostic study.

The borderline dysplastic hip: when and how is it abnormal?

Borderline acetabular dysplasia refers to mildly sub-normal patterns of acetabular shape and coverage that might predispose children to mechanical dysfunction and instability. Borderline dysplasia generally includes children with a lateral center edge angle (CEA) of 18-24°. Some children with borderline radiographic measurements have normal joint mechanics and function while others benefit from acetabular reorienting surgery. Although radiographic findings of borderline dysplasia might suggest instability, the ultimate diagnosis is based on history and physical exam in addition to imaging. Children with borderline acetabular dysplasia sometimes benefit from other cross-sectional imaging studies such as MR imaging to evaluate for secondary evidence of instability, including damage along the acetabular rim, or labral degeneration and hypertrophy. CT is also helpful for depiction of 3-D acetabular morphology for preoperative assessment and planning. Pediatric radiologists are often the first to identify borderline or mild dysplasia on radiographs. It is imperative that pediatric radiologists serve as effective consultants and offer appropriate recommendations as part of a cohesive multidisciplinary approach to this complex patient population.

Iatrogenic Hip Instability Is a Devastating Complication After the Modified Dunn Procedure for Severe Slipped Capital Femoral Epiphysis.

BACKGROUND: The modified Dunn procedure facilitates femoral capital realignment for slipped capital femoral epiphysis (SCFE) through a surgical hip dislocation approach. Iatrogenic postoperative hip instability after this procedure has not been studied previously; however, we were concerned when we observed several instances of this serious complication, and we wished to study it further. QUESTIONS/PURPOSES: The purpose of this study was to evaluate the frequency, timing, and clinical presentation (including complications) associated with iatrogenic instability after the modified Dunn procedure for SCFE. METHODS: Between 2007 and 2014, eight international institutions performed the modified Dunn procedure through a surgical dislocation approach in 406 patients. During the period in question, indications varied at those sites, but the procedure was used only in a minority of their patients treated surgically for SCFE (31% [406 of 1331]) with the majority treated with in situ fixation. It generally was performed for patients with severe deformity with a slip angle greater than 40°. Institutional databases were searched for all patients with SCFE who developed postoperative hip instability defined as hip subluxation or dislocation of the involved hip during the postoperative period. We reviewed in detail the clinical notes and operative records of those who presented with instability. We obtained demographic information, time from slip to surgery, type of fixation, operative details, and clinical course including the incidence of complications. Followup on those patients with instability was at a mean of 2 years (range, 1-5 years) after the index procedure. Complications were graded according to the modified Dindo-Clavien classification. Radiographic images were reviewed to measure the preoperative slip angle and the presence of osteonecrosis. RESULTS: A total of 4% of patients treated with the modified Dunn procedure developed postoperative hip instability (17 of 406). Mean age of the patients was 13 years (range, 9-16 years). Instability presented as persistent hip pain in the postoperative period or was incidentally identified radiographically during the postoperative visit and occurred at a median of 3 weeks (range, 1 day to 2 months) after the modified Dunn procedure. Eight patients underwent revision surgery to address the postoperative instability. Fourteen of 17 patients developed femoral head avascular necrosis and three of 17 patients underwent THA during this short-term followup. CONCLUSIONS: Anterolateral hip instability after the modified Dunn procedure for severe, chronic SCFE is an uncommon yet potentially devastating complication. Future studies might evaluate the effectiveness of maintaining anterior hip precautions for several weeks postoperatively in an abduction brace or broomstick cast to prevent this complication. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Is Increased Acetabular Cartilage or Fossa Size Associated With Pincer Femoroacetabular Impingement?

BACKGROUND: Surgical treatment for pincer femoroacetabular impingement (FAI) of the hip remains controversial, between trimming the prominent acetabular rim and reverse periacetabular osteotomy (PAO) that reorients the acetabulum. However, rim trimming may decrease articular surface size to a critical threshold where increased joint contact forces lead to joint degeneration. Therefore, knowledge of how much acetabular articular cartilage is available for resection is important when evaluating between the two surgical options. In addition, it remains unclear whether the acetabulum rim in pincer FAI is a prominent rim because of increased cartilage size or increased fossa size. QUESTIONS/PURPOSES: We used reformatted MR and CT data to establish linear length dimensions of the lunate cartilage and cotyloid fossa in normal, dysplastic, and deep acetabula. METHODS: We reviewed the last 200 hips undergoing PAO, reverse PAO, and surgical dislocation for acetabular rim trimming at one institution. We compared MR images of symptomatic hips with acetabular dysplasia (20 hips), pincer FAI (29 hips), and CT scans of asymptomatic hips from patients who underwent CT scans for reasons other than hip pain (20 hips). These hips were chosen sequentially from the underlying pool of 200 potential subjects to identify the first 10 male and the first 10 female hips in each group that met inclusion criteria. As a result of low numbers, we included all hips that had undergone reverse PAO and met inclusion criteria. Cartilage width was measured medially from the cotyloid fossa to the lateral labrochondral junction. Cotyloid fossa linear height was measured from superior to inferior and cotyloid fossa width was measured from anterior to posterior. Superior lunate cartilage width (SLCW) and cotyloid fossa height (CFH) were measured on MR and CT oblique coronal reformats; anterior lunate cartilage width (ALCW), posterior lunate cartilage width (PLCW), and cotyloid fossa width (CFW) were measured on MR and CT oblique axial reformats. Cohorts were compared using multivariate analysis of variance with Bonferroni's adjustment for multiple comparisons. RESULTS: Compared with control acetabula, dysplastic acetabula had smaller SLCW (2.08 ± 0.29 mm versus 2.63 ± 0.42 mm, mean difference = -0.55 mm; 95% confidence interval [CI] = -0.83 to -0.27; p < 0.01), ALCW (1.20 ± 0.34 mm versus 1.64 ± 0.21 mm, mean difference = -0.44 mm; 95% CI = -0.70 to -0.18; p = 0.00), CFH (2.84 ± 0.37 mm versus 3.42 ± 0.57 mm, mean difference = -0.59 mm; 95% CI = -0.96 to -0.21; p < 0.01), and CFW (1.98 ± 0.50 mm versus 2.77 ± 0.33 mm, mean difference = -0.80 mm; 95% CI = -1.16 to -0.42; p < 0.0001). Based on the results, we identified two subtypes of deep acetabula. Compared with controls, deep subtype 1 had normal CFH and CFW but increased ALCW (2.09 ± 0.42 mm versus 1.64 ± 0.21 mm; p < 0.001) and PLCW (2.32 ± 0.36 mm versus 2.00 ± 0.32 mm; p = 0.04). Compared with controls, deep subtype 2 had increased CFH (4.37 ± 0.51 mm versus 3.42 ± 0.57 mm; p < 0.01) and CFW (2.76 ± 0.54 mm versus 2.77 ± 0.33 mm; p = 1.0) but smaller SCLW (2.12 ± 0.40 mm versus 2.63 ± 0.42 mm; p < 0.01). CONCLUSIONS: Deep acetabula have two distinct morphologies: subtype 1 with increased anterior and posterior cartilage lengths and subtype 2 with a larger fossa in height and width and smaller superior cartilage length. CLINICAL RELEVANCE: In patients with deep subtype 1 hips that have increased anterior and posterior cartilage widths, rim trimming to create an articular surface of normal size may be reasonable. However, for patients with deep subtype 2 hips that have large fossas but do not have increased cartilage widths, we propose that a reverse PAO that reorients yet preserves the size of the articular surface may be more promising. However, these theories will need to be validated in well-controlled clinical studies.

Continuing Delay in the Diagnosis of Slipped Capital Femoral Epiphysis.

OBJECTIVE: To evaluate whether the time from symptom onset to diagnosis of slipped capital femoral epiphysis (SCFE) has improved over a recent decade compared with reports of previous decades. STUDY DESIGN: Retrospective review of 481 patients admitted with a diagnosis of SCFE at three large pediatric hospitals between January 2003 and December 2012. RESULTS: The average time from symptom onset to diagnosis of SCFE was 17 weeks (range, 0-to 169). There were no significant differences in time from symptom onset to diagnosis across 2-year intervals of the 10-year study period (P = .94). The time from evaluation by first provider to diagnosis was significantly shorter for patients evaluated at an orthopedic clinic (mean, 0 weeks; range, 0-0 weeks) compared with patients evaluated by a primary care provider (mean, 4 weeks; range, 0-52 weeks; r = 0.24; P = .003) or at an emergency department (mean, 6 weeks, range, 0-104 weeks; r = 0.36; P = .008). Fifty-two patients (10.8%) developed a second SCFE after treatment of the first affected side. The time from the onset of symptoms to diagnosis for the second episode of SCFE was significantly shorter (r = 0.19; P < .001), with mean interval of 11 weeks (range, 0-104 weeks) from symptom onset to diagnosis. There were significantly more cases of mildly severe SCFE, as defined by the Wilson classification scheme, in second episodes of SCFE compared with first episodes of SCFE (OR, 4.44; P = .001). CONCLUSION: Despite reports documenting a lag in time to the diagnosis of SCFE more than a decade ago, there has been no improvement in the speed of diagnosis. Decreases in both the time to diagnosis and the severity of findings for the second episode of SCFE suggest that the education of at-risk children and their families (or providers) may be of benefit in decreasing this delay.

Periacetabular Osteotomy Redirects the Acetabulum and Improves Pain in Charcot-Marie-Tooth Hip Dysplasia With Higher Complications Compared With Developmental Dysplasia of the Hip.

BACKGROUND: The Bernese periacetabular osteotomy (PAO) is a well-accepted reorientation pelvic osteotomy used to treat symptomatic acetabular dysplasia secondary to developmental dysplasia of the hip (DDH). However, there are limited data regarding PAO in patients with symptomatic hip dysplasia secondary to Charcot-Marie-Tooth disease. METHODS: We compared patients who underwent PAO for the treatment of Charcot-Marie-Tooth disease hip dysplasia (CMTHD group) with patients who underwent PAO for treatment of hip dysplasia secondary to DDH in terms of (1) modified Harris Hip scores; (2) radiographic correction of acetabular dysplasia; and (3) the rate of complications. Twenty-seven subjects with Charcot-Marie-Tooth disease who underwent a PAO between January 1991 and December 2010 were matched to 54 subjects with DDH on the basis of sex, age, date of surgery, and body mass index. Preoperative and postoperative hip functional scores and radiographic data were collected with a minimum 2-year follow-up. The modified Harris Hip Scores (mHHS) assessed functional hip outcomes. Radiographic variables included lateral (LCEA) and anterior (ACEA) center-edge angles, Tönnis angle and Tönnis grade of arthritis. Postoperative complications were classified according to a modified Dindo-Clavien system. RESULTS: At latest follow-up mHHS improved in the CMTHD group (preoperative median 63; (interquartile range [IQR]=54-70 to postoperative median 88; IQR=74-91); P=0.004) and in the DDH groups (preoperative median 71; IQR=58-83 to postoperative median 86; IQR=73-96; P=0.002) with no difference between the 2 groups (P=0.631). Radiographic improvement (LCEA: mean difference, 36 degrees, 95% confidence interval [CI], 30-41 degrees, P<0.001; ACEA: mean difference, 27 degrees, 95% CI, 20-33 degrees, P<0.001; Tönnis angles: mean difference, 21 degrees, 95% CI, 15-26 degrees, P<0.001) was achieved in the CMTHD group. Similarly, radiographic improvements in LCEA (mean difference, 33 degrees, 95% CI, 29-37 degrees, P<0.001), ACEA (mean difference, 18 degrees, 95% CI, 13-23 degrees, P<0.001) and Tönnis angles (mean difference, 13 degrees, 95% CI, 9-17 degrees, P<0.001) were also achieved in the DDH group. After PAO, 33% of the patients in the CMTHD group and 13% in the DDH group developed a complication that required treatment (odds ratio, 3.4; 95% CI, 1.1-10.4; P=0.035). CONCLUSIONS: The Bernese PAO is capable of comprehensively achieving improvement in patient-reported outcome scores and redirecting the acetabulum in symptomatic acetabular dysplasia secondary to CMTHD. However, patients with CMTHD have a higher risk for developing complications. LEVEL OF EVIDENCE: Level III-therapeutic study.

Does periacetabular osteotomy have depth-related effects on the articular cartilage of the hip?

BACKGROUND: Osteoarthritis may result from abnormal mechanics leading to biochemically mediated degradation of cartilage. In a dysplastic hip, the periacetabular osteotomy (PAO) is designed to normalize the mechanics and our initial analysis suggests that it may also alter the cartilage biochemical composition. Articular cartilage structure and biology vary with the depth from the articular surface including the concentration of glycosaminoglycans (GAG), which are the charge macromolecules that are rapidly turned over and are lost in early osteoarthritis. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) enables noninvasive measurement of cartilage GAG content. The dGEMRIC index represents an indirect measure of GAG concentration with lower values indicating less GAG content. GAG content can normally vary with mechanical loading; however, progressive loss of GAG is associated with osteoarthritis. By looking at the changes in amounts of GAG in response to a PAO at different depths of cartilage, we may gain further insights into the types of biologic events that are occurring in the joint after a PAO. QUESTIONS/PURPOSES: We (1) measured the GAG content in the superficial and deep zones for the entire joint before and after PAO; and (2) investigated if the changes in the superficial and deep zone GAG content after PAO varied with different locations within the joint. METHODS: This prospective study included 37 hips in 37 patients (mean age 26 ± 9 years) who were treated with periacetabular osteotomy for symptomatic acetabular dysplasia and had preoperative and 1-year follow up dGEMRIC scans. Twenty-eight of the 37 also had 2-year scans. Patients were eligible if they had symptomatic acetabular dysplasia with lateral center-edge angle < 20° and no or minimal osteoarthritis. The change in dGEMRIC after surgery was assessed in the superficial and deep cartilage zones at five acetabular radial planes. RESULTS: The mean ± SD dGEMRIC index in the superficial zone fell from 480 ± 137 msec preoperatively to 409 ± 119 msec at Year 1 (95% confidence interval [CI], -87 to -54; p < 0.001) and recovered to 451 ± 115 msec at Year 2 (95% CI, 34-65; p < 0.001), suggesting that there is a transient event that causes the biologically sensitive superficial layer to lose GAG. In the deep acetabular cartilage zone, dGEMRIC index fell from 527 ± 148 msec preoperatively to 468 ± 143 msec at Year 1 (95% CI, -66 to -30; p < 0.001) and recovered to 494 ± 125 msec at Year 2 (95% CI, 5-32; p = 0.008). When each acetabular radial plane was looked at separately, the change from before surgery to 1 year after was confined to zones around the superior part of the joint. The only significant change from 1 to 2 years was an increase in the superficial layer of the superior zone (1 year 374 ± 123 msec, 2 year 453 ± 117 msec, p < 0.006). CONCLUSIONS: This study suggests that PAO may alter the GAG content of the articular cartilage with a greater effect on the superficial zone compared with the deeper acetabular cartilage zone, especially at the superior aspect of the joint. Some surgeons have observed that surgery itself can be a stressor that can accelerate joint degeneration. Perhaps the decrease in dGEMRIC index seen in the superficial layer may be a catabolic response to postsurgical inflammation given that some recovery was seen at 2 years. The decrease in dGEMRIC index in the deep layer seen mainly near the superior part of the joint is persistent and may represent a response of articular cartilage to normalization of increased mechanical load seen in this region after osteotomy, which may be a normal response to alteration in loading. CLINICAL RELEVANCE: This study looks at the biochemical changes in the articular cartilage before and after a PAO for dysplastic hips using MRI in a similar manner to using histological methods to study alterations in articular cartilage with mechanical loading. Although PAO alters alignment and orientation of the acetabulum, its effects on cartilage biology are not clear. dGEMRIC provides a noninvasive method of assessing these effects.

Periacetabular osteotomy restores the typically excessive range of motion in dysplastic hips with a spherical head.

BACKGROUND: Residual acetabular dysplasia is seen in combination with femoral pathomorphologies including an aspherical femoral head and valgus neck-shaft angle with high antetorsion. It is unclear how these femoral pathomorphologies affect range of motion (ROM) and impingement zones after periacetabular osteotomy. QUESTIONS/PURPOSES: (1) Does periacetabular osteotomy (PAO) restore the typically excessive ROM in dysplastic hips compared with normal hips; (2) how do impingement locations differ in dysplastic hips before and after PAO compared with normal hips; (3) does a concomitant cam-type morphology adversely affect internal rotation; and (4) does a concomitant varus-derotation intertrochanteric osteotomy (IO) affect external rotation? METHODS: Between January 1999 and March 2002, we performed 200 PAOs for dysplasia; of those, 27 hips (14%) met prespecified study inclusion criteria, including availability of a pre- and postoperative CT scan that included the hip and the distal femur. In general, we obtained those scans to evaluate the pre- and postoperative acetabular and femoral morphology, the degree of acetabular reorientation, and healing of the osteotomies. Three-dimensional surface models based on CT scans of 27 hips before and after PAO and 19 normal hips were created. Normal hips were obtained from a population of CT-based computer-assisted THAs using the contralateral hip after exclusion of symptomatic hips or hips with abnormal radiographic anatomy. Using validated and computerized methods, we then determined ROM (flexion/extension, internal- [IR]/external rotation [ER], adduction/abduction) and two motion patterns including the anterior (IR in flexion) and posterior (ER in extension) impingement tests. The computed impingement locations were assigned to anatomical locations of the pelvis and the femur. ROM was calculated separately for hips with (n = 13) and without (n = 14) a cam-type morphology and PAOs with (n = 9) and without (n = 18) a concomitant IO. A post hoc power analysis based on the primary research question with an alpha of 0.05 and a beta error of 0.20 revealed a minimal detectable difference of 4.6° of flexion. RESULTS: After PAO, flexion, IR, and adduction/abduction did not differ from the nondysplastic control hips with the numbers available (p ranging from 0.061 to 0.867). Extension was decreased (19° ± 15°; range, -18° to 30° versus 28° ± 3°; range, 19°-30°; p = 0.017) and ER in 0° flexion was increased (25° ± 18°; range, -10° to 41° versus 38° ± 7°; range, 17°-41°; p = 0.002). Dysplastic hips had a higher prevalence of extraarticular impingement at the anteroinferior iliac spine compared with normal hips (48% [13 of 27 hips] versus 5% [one of 19 hips], p = 0.002). A PAO increased the prevalence of impingement for the femoral head from 30% (eight of 27 hips) preoperatively to 59% (16 of 27 hips) postoperatively (p = 0.027). IR in flexion was decreased in hips with a cam-type deformity compared with those with a spherical femoral head (p values from 0.002 to 0.047 for 95°-120° of flexion). A concomitant IO led to a normalization of ER in extension (eg, 37° ± 7° [range, 21°-41°] of ER in 0° of flexion in hips with concomitant IO compared with 38° ± 7° [range, 17°-41°] in nondysplastic control hips; p = 0.777). CONCLUSIONS: Using computer simulation of hip ROM, we could show that the PAO has the potential to restore the typically excessive ROM in dysplastic hips. However, a PAO can increase the prevalence of secondary intraarticular impingement of the aspherical femoral head and extraarticular impingement of the anteroinferior iliac spines in flexion and internal rotation. A cam-type morphology can result in anterior impingement with restriction of IR. Additionally, a valgus hip with high antetorsion can result in posterior impingement with decreased ER in extension, which can be normalized with a varus derotation IO of the femur. However, indication of an additional IO needs to be weighed against its inherent morbidity and possible complications. The results are based on a limited number of hips with a pre- and postoperative CT scan after PAO. Future prospective studies are needed to verify the current results based on computer simulation and to test their clinical importance.

Medial versus anterior open reduction for developmental hip dislocation in age-matched patients.

BACKGROUND: The difference between medial (MAOR) and anterior (AAOR) approaches for open reduction of developmental hip dysplasia in terms of risk for avascular necrosis (AVN) and need for further corrective surgery (FCS, femoral and/or acetabular osteotomy) is unclear. This study compared age-matched cohorts undergoing either MAOR or AAOR in terms of these 2 primary outcomes. Prognostic impact of presence of ossific nucleus at time of open reduction was also investigated. METHODS: Institutional review board approval was obtained. Nineteen hips (14 patients) managed by MAOR were matched with 19 hips (18 patients) managed by AAOR based on age at operation (mean 6.0; range, 1.4 to 14.9 mo). Patients with neuromuscular conditions and known connective tissue disorders were excluded. Primary outcomes assessed at minimum 2 years' follow-up included radiographic evidence of AVN (Kalamchi and MacEwen) or requiring FCS. RESULTS: MAOR and AAOR cohorts were similar regarding age at open reduction, sex, laterality, and follow-up duration. One hip in each group had AVN before open reduction thus were excluded from AVN analysis. At minimum 2 years postoperatively (mean 6.2; range, 1.8 to 11.7 y), 4/18 (22%) MAOR and 5/18 (28%) AAOR met the same criteria for AVN (P=1.0). No predictors of AVN could be identified by regression analysis. Presence of an ossific nucleus preoperatively was not a protective factor from AVN (P=0.27). FCS was required in 4/19 (21%) MAOR and 7/19 (37%) AAOR hips (P=0.48). However, 7/12 (54%) hips failing closed reduction required FCS compared with 4/26 (16%) hips without prior failed closed reduction (P=0.024). Cox regression analysis showed that patients who failed closed reduction had an annual risk of requiring FCS approximately 6 times that of patients without a history of failed closed reduction (hazard ratio=6.1; 95% CI, 1.5-24.4; P=0.009), independent of surgical approach (P=0.55) or length of follow-up (P=0.78). CONCLUSIONS: In this study of age-matched patients undergoing either MAOR or AAOR, we found no association between surgical approach and risk of AVN or FCS. In addition, we identified no protective benefit of a preoperative ossific nucleus in terms of development of AVN. However, failing closed reduction was associated with a 6-fold increased annual risk of requiring FCS. SIGNIFICANCE: To the best of our knowledge, this is the first study comparing these 2 surgical techniques in an age-matched manner. It further corroborates previous studies stating that there may be no difference in risk of AVN based on surgical approach or presence of ossific nucleus preoperatively. LEVEL OF EVIDENCE: Level III-retrospective comparative study.