How Common Is Femoral Retroversion and How Is it Affected by Different Measurement Methods in Unilateral Slipped Capital Femoral Epiphysis?

BACKGROUND: Although femoral retroversion has been linked to the onset of slipped capital femoral epiphysis (SCFE), and may result from a rotation of the femoral epiphysis around the epiphyseal tubercle leading to femoral retroversion, femoral version has rarely been described in patients with SCFE. Furthermore, the prevalence of actual femoral retroversion and the effect of different measurement methods on femoral version angles has yet to be studied in SCFE. QUESTIONS/PURPOSES: (1) Do femoral version and the prevalence of femoral retroversion differ between hips with SCFE and the asymptomatic contralateral side? (2) How do the mean femoral version angles and the prevalence of femoral retroversion change depending on the measurement method used? (3) What is the interobserver reliability and intraobserver reproducibility of these measurement methods? METHODS: For this retrospective, controlled, single-center study, we reviewed our institutional database for patients who were treated for unilateral SCFE and who had undergone a pelvic CT scan. During the period in question, the general indication for obtaining a CT scan was to define the surgical strategy based on the assessment of deformity severity in patients with newly diagnosed SCFE or with previous in situ fixation. After applying prespecified inclusion and exclusion criteria, we included 79 patients. The mean age was 15 ± 4 years, 48% (38 of 79) of the patients were male, and 56% (44 of 79) were obese (defined as a BMI > 95th percentile (mean BMI 34 ± 9 kg/m2). One radiology resident (6 years of experience) measured femoral version of the entire study group using five different methods. Femoral neck version was measured as the orientation of the femoral neck. Further measurement methods included the femoral head's center and differed regarding the level of landmarks for the proximal femoral reference axis. From proximal to distal, this included the most-proximal methods (Lee et al. and Reikerås et al.) and most-distal methods (Tomczak et al. and Murphy et al.). Most proximally (Lee et al. method), we used the most cephalic junction of the greater trochanter as the landmark and, most distally, we used the center base of the femoral neck superior to the lesser trochanter (Murphy et al.). The orientation of the distal femoral condyles served as the distal reference axis for all five measurement methods. All five methods were compared side-by-side (involved versus uninvolved hip), and comparisons among all five methods were performed using paired t-tests. The prevalence of femoral retroversion (< 0°) was compared using a chi-square test. A subset of patients was measured twice by the first observer and by a second orthopaedic resident (2 years of experience) to assess intraobserver reproducibility and interobserver reliability; for this assessment, we used intraclass correlation coefficients. RESULTS: The mean femoral neck version was lower in hips with SCFE than in the contralateral side (-2° ± 13° versus 7° ± 11°; p < 0.001). This yielded a mean side-by side difference of -8° ± 11° (95% CI -11° to -6°; p < 0.001) and a higher prevalence of femoral retroversion in hips with SCFE (58% [95% CI 47% to 69%]; p < 0.001) than on the contralateral side (29% [95% CI 19% to 39%]). These differences between hips with SCFE and the contralateral side were higher and ranged from -17° ± 11° (95% CI -20° to -15°; p < 0.001) based on the method of Tomczak et al. to -22° ± 13° (95% CI -25° to -19°; p < 0.001) according to the method of Murphy et al. The mean overall femoral version angles increased for hips with SCFE using more-distal landmarks compared with more-proximal landmarks. The prevalence of femoral retroversion was higher in hips with SCFE for the proximal methods of Lee et al. and Reikerås et al. (91% [95% CI 85% to 97%] and 84% [95% CI 76% to 92%], respectively) than for the distal measurement methods of Tomczak et al. and Murphy et al. (47% [95% CI 36% to 58%] and 60% [95% CI 49% to 71%], respectively [all p < 0.001]). We detected mean differences ranging from -19° to 4° (all p < 0.005) for 8 of 10 pairwise comparisons in hips with SCFE. Among these, the greatest differences were between the most-proximal methods and the more-distal methods, with a mean difference of -19° ± 7° (95% CI -21° to -18°; p < 0.001), comparing the methods of Lee et al. and Tomczak et al. In hips with SCFE, we found excellent agreement (intraclass correlation coefficient [ICC] > 0.80) for intraobserver reproducibility (reader 1, ICC 0.93 to 0.96) and interobserver reliability (ICC 0.95 to 0.98) for all five measurement methods. Analogously, we found excellent agreement (ICC > 0.80) for intraobserver reproducibility (reader 1, range 0.91 to 0.96) and interobserver reliability (range 0.89 to 0.98) for all five measurement methods in healthy contralateral hips. CONCLUSION: We showed that femoral neck version is asymmetrically decreased in unilateral SCFE, and that differences increase when including the femoral head's center. Thus, to assess the full extent of an SCFE deformity, femoral version measurements should consider the position of the displaced epiphysis. The prevalence of femoral retroversion was high in patients with SCFE and increased when using proximal anatomic landmarks. Since the range of femoral version angles was wide, femoral version cannot be predicted in a given hip and must be assessed individually. Based on these findings, we believe it is worthwhile to add evaluation of femoral version to the diagnostic workup of children with SCFE. Doing so may better inform surgeons as they contemplate when to use isolated offset correction or to perform an additional femoral osteotomy for SCFE correction based on the severity of the slip and the rotational deformity. To facilitate communication among physicians and for the design of future studies, we recommend consistently reporting the applied measurement technique. LEVEL OF EVIDENCE: Level III, prognostic study.

What Is the Association Among Epiphyseal Rotation, Translation, and the Morphology of the Epiphysis and Metaphysis in Slipped Capital Femoral Epiphysis?

BACKGROUND: Contemporary studies have described the rotational mechanism in patients with slipped capital femoral epiphysis (SCFE). However, there have been limited patient imaging data and information to quantify the rotation. Determining whether the epiphysis is rotated or translated and measuring the epiphyseal displacement in all planes may facilitate planning for surgical reorientation of the epiphysis. QUESTIONS/PURPOSES: (1) How does epiphyseal rotation and translation differ among mild, moderate, and severe SCFE? (2) Is there a correlation between epiphyseal rotation and posterior or inferior translation in hips with SCFE? (3) Does epiphyseal rotation correlate with the size of the epiphyseal tubercle or the metaphyseal fossa or with epiphyseal cupping? METHODS: We identified 51 patients (55% boys [28 of 51]; mean age 13 ± 2 years) with stable SCFE who underwent preoperative CT of the pelvis before definitive treatment. Stable SCFE was selected because unstable SCFE would not allow for accurate assessment of rotation given the complete displacement of the femoral head in relation to the neck. The epiphysis and metaphysis were segmented and reconstructed in three-dimensions (3-D) for analysis in this retrospective study. One observer (a second-year orthopaedic resident) performed the image segmentation and measurements of epiphyseal rotation and translation relative to the metaphysis, epiphyseal tubercle, metaphyseal fossa, and the epiphysis extension onto the metaphysis defined as epiphyseal cupping. To assess the reliability of the measurements, a randomly selected subset of 15 hips was remeasured by the primary examiner and by the two experienced examiners independently. We used ANOVA to calculate the intraclass and interclass correlation coefficients (ICCs) for intraobserver and interobserver reliability of rotational and translational measurements. The ICC values for rotation were 0.91 (intraobserver) and 0.87 (interobserver) and the ICC values for translation were 0.92 (intraobserver) and 0.87 (intraobserver). After adjusting for age and sex, we compared the degree of rotation and translation among mild, moderate, and severe SCFE. Pearson correlation analysis was used to assess the associations between rotation and translation and between rotation and tubercle, fossa, and cupping measurements. RESULTS: Hips with severe SCFE had greater epiphyseal rotation than hips with mild SCFE (adjusted mean difference 21° [95% CI 11° to 31°]; p < 0.001) and hips with moderate SCFE (adjusted mean difference 13° [95% CI 3° to 23°]; p = 0.007). Epiphyseal rotation was positively correlated with posterior translation (r = 0.33 [95% CI 0.06 to 0.55]; p = 0.02) but not with inferior translation (r = 0.16 [95% CI -0.12 to 0.41]; p = 0.27). There was a positive correlation between rotation and metaphyseal fossa depth (r = 0.35 [95% CI 0.08 to 0.57]; p = 0.01), width (r = 0.41 [95% CI 0.15 to 0.61]; p = 0.003), and length (r = 0.56 [95% CI 0.38 to 0.75]; p < 0.001). CONCLUSION: This study supports a rotational mechanism for the pathogenesis of SCFE. Increased rotation is associated with more severe slips, posterior epiphyseal translation, and enlargement of the metaphyseal fossa. The rotational nature of the deformity, with the center of rotation at the epiphyseal tubercle, should be considered when planning in situ fixation and realignment surgery. Avoiding placing a screw through the epiphyseal tubercle-the pivot point of rotation- may increase the stability of the epiphysis. The realignment of the epiphysis through rotation rather than simple translation is recommended during the open subcapital realignment procedure. Enlargement of the metaphyseal fossa disrupts the interlocking mechanism with the tubercle and increases epiphyseal instability. Even in the setting of a stable SCFE, an increased fossa enlargement may indicate using two screws instead of one screw, given the severity of epiphyseal rotation and the risk of instability. Further biomechanical studies should investigate the number and position of in situ fixation screws in relation to the epiphyseal tubercle and metaphyseal fossa. LEVEL OF EVIDENCE: Level III, prognostic study.

Does a History of Slipped Capital Femoral Epiphysis in Patients Undergoing Femoroacetabular Osteoplasty for Femoroacetabular Impingement Affect Outcomes Scores or Risk of Reoperation?

BACKGROUND: Femoroacetabular impingement (FAI) can occur after slipped capital femoral epiphysis (SCFE) regardless of slip severity and even after in situ pinning. These patients represent a rare and unique demographic that is largely unreported on. It is important to further characterize the clinical presentation of these patients, associated treatment modalities, and the efficacy of these treatment modalities. QUESTIONS/PURPOSES: (1) How do patients with post-SCFE FAI typically present in terms of radiographic and surgical findings? (2) How do their hip-specific and general-health outcomes scores after mini-open femoroacetabular osteoplasty compare with those obtained in a matched group of patients with FAI caused by other etiologies? (3) How do those groups compare in terms of the proportion who undergo conversion to THA? METHODS: Between 2013 and 2017, 20 patients had femoroacetabular osteoplasty for post-SCFE FAI. During that time, general indications for this procedure were symptomatic FAI demonstrated on radiographs and physical exam. Of those, none was lost to follow-up before a minimum of 2 years, leaving all 20 available for matching, and all 20 had suitable matches in our database for patients who underwent femoroacetabular osteoplasty for other diagnoses. Matching was performed by surgeon, patient age, patient gender, and BMI. The matching group was drawn from a large database of patients who had the same procedure during the same period. We matched in a 1:3 ratio to arrive at 60 randomly selected control patients in this retrospective, comparative study. Patient demographics, medical history, clinical presentation, radiographic parameters, and intraoperative findings were compared between the two groups. At a minimum of 2 years of follow-up, the latest clinical functional outcome scores (Hip Disability and Osteoarthritis Outcome Score Jr and SF-12) and proportions of conversion to THA were compared between the groups. RESULTS: A greater percentage of patients with a history of SCFE than those without prior SCFE demonstrated full chondral lesions intraoperatively (90% [18 of 20] versus 32% [19 of 60], odds ratio 7 [95% confidence interval 1 to 178]; p < 0.01). A greater percentage of patients with a history of SCFE also demonstrated labral calcifications intraoperatively compared with those without prior SCFE (65% [13 of 20] versus 35% [21 of 60], OR 3 [95% CI 1 to 10]; p = 0.04). Radiographically, patients with SCFE had greater preoperative alpha angles than did patients without SCFE (94° ± 13° versus 72° ± 22°; p = 0.01) as well as lower lateral center-edge angles (25° ± 8° versus 31° ± 8°; p = 0.04). There was no difference in postoperative follow-up between patients with a history of SCFE and patients without a history of SCFE (4 ± 2 years versus 4 ± 2 years; p = 0.32). There was no difference in the mean postoperative outcome scores between patients with a history of SCFE and patients without (Hip Disability and Osteoarthritis Outcome Score Jr: 75 ± 28 points versus 74 ± 17 points; p = 0.95; SF-12 physical score: 40 ± 11 points versus 39 ± 8 points; p = 0.79). There was no difference with the numbers available in the percentage of patients who underwent conversion to THA (15% [3 of 20] versus 12% [7 of 60], OR 1.36 [95% CI 0 to 6]; p = 0.71). CONCLUSION: Patients with FAI after SCFE present with a greater degree of labral and chondral disease than do patients without a history of SCFE. However, at short-term follow-up, the proportion of patients who underwent conversion to THA and patients' postoperative outcome scores did not differ in this small, comparative series between patients with and without SCFE. Further evaluation with long-term follow-up is needed, especially given the more severe chondral damage we observed in patients with SCFE at the time of surgery. LEVEL OF EVIDENCE: Level III, therapeutic study.

Epiphyseal Translation as a Predictor of Avascular Necrosis in Unstable Slipped Capital Femoral Epiphysis.

BACKGROUND: Physeal instability has been shown to be associated with a higher risk of avascular necrosis (AVN) in patients with slipped capital femoral epiphysis (SCFE). The purpose of this study was to identify additional preoperative factors associated with AVN in patients with unstable SCFE. METHODS: Basic demographic information, chronicity of symptoms, and estimated duration of nonambulatory status were noted. Preoperative radiographs were used to measure the Southwick slip angle, slip severity by Wilson criteria, and epiphyseal translation. Translation was measured by 3 distinct radiographic parameters in the position demonstrating maximal displacement. Postoperative radiographs at the time of most recent follow-up were assessed for the presence of AVN. Translation measurements were tested for inter-rater reliability. Patients who developed AVN were compared with those that did not by Fisher exact test and Wilcoxon tests. Logistic regression assessed the effect of translation on the odds of developing AVN. Receiver operating characteristic curve was plotted to assess any threshold effect. RESULTS: Fifty-one patients (55 hips) out of 310 patients (16%) treated for SCFE were considered unstable. Seventeen hips' unstable SCFE (31%) showed radiographic evidence of AVN. Slip severity by Wilson grade (P=0.009) and epiphyseal translation by all measurements (P< 0.05) were statistically significantly greater among patients who developed AVN. Superior translation had the best inter-rater reliability (intraclass correlation coefficient=0.84). Average superior translation in hips that developed AVN was 17.2 mm compared with 12.9 mm in those that did not (P<0.02). Although the receiver operating characteristic curve did not demonstrate a threshold effect for AVN, it did effectively rule out AVN in cases with <1 cm of superior translation. Age, sex, laterality, chronicity of prodromal symptoms or inability to bear weight, Southwick slip angle, and method of treatment did not vary with the occurrence of AVN. CONCLUSIONS: Epiphyseal translation, either by Wilson Grade or measured directly, is associated with AVN in patients with an unstable SCFE. LEVEL OF EVIDENCE: Level II-development of diagnostic criteria.

The Role of Hyperinsulinemia in Slipped Capital Femoral Epiphysis.

BACKGROUND: Obesity in the prepuberal stage has been directly associated with slipped capital femoral epiphysis (SCFE). Serum insulin level increases in the prepuberal and adolescence stage, to a greater extent in the obese population. The main objective of this article was to analyze the relationship between insulin levels and SCFE. METHODS: A case-control study was conducted between January 2018 and April 2019. The study group was formed with patients with SCFE and the control group with patients from the pediatric obesity clinic of our hospital selected during their initial evaluation. None were being treated for obesity. Anthropometric measurements of size, weight, waist circumference, and blood pressure were taken. Body mass index (BMI) and waist-height index of all patients were calculated. According to BMI for age, they were classified as normal, overweight, or obese. Serum determinations of glucose, insulin, glycated hemoglobin, lipid profile, and complete blood count were analyzed. Insulin resistance was diagnosed with Homeostatic Model Assessment (HOMA) >3. Insulin levels >13 U/mL for girls and >17 U/mL for boys were considered as hyperinsulinemia. RESULTS: We studied 14 patients with SCFE and 23 in the control group. The mean age and BMI in both groups were similar. The elevation of serum insulin was significantly higher in the SCFE group (P=0.001) as was HOMA (P=0.005). Triglycerides and very-low-density lipoprotein were higher in the SCFE group (P=0.037 and 0.009, respectively). Glycemia, glycated hemoglobin, total cholesterol, high-density lipoprotein, low-density lipoprotein, and neutrophils showed no significant difference. CONCLUSIONS: Patients with SCFE showed elevated levels of insulin, HOMA, triglycerides, and very-low-density lipoprotein, even higher than the control group. Our study demonstrates a significant association between abnormally high serum insulin levels and SCFE. The known effects of insulin on growth cartilage may explain the physeal mechanical insufficiency to support the abnormally high or repetitive loads in accelerated growth stages that lead to SCFE. LEVEL OF EVIDENCE: Level III-case-control, prognostic study.

Capital Femoral Epiphyseal Cupping and Extension May Be Protective in Slipped Capital Femoral Epiphysis: A Dual-center Matching Cohort Study.

BACKGROUND: Peripheral cupping of the capital femoral epiphysis over the metaphysis has been reported as a precursor of cam morphology, but may also confer stability of the epiphysis protecting it from slipped capital femoral epiphysis (SCFE). The purpose of this study was to investigate the relationship between a novel morphologic parameter of inherent physeal stability, epiphyseal cupping, and the development of SCFE in a dual-center matched-control cohort study. METHODS: We performed a dual-center age-matched and sex-matched cohort study comparing 279 subjects with unilateral SCFE and 279 radiographically normal controls from 2 tertiary children's hospitals. All SCFE patients had at least 18 months of radiographic follow-up for contralateral slip surveillance. Anteroposterior and frog lateral pelvis radiographs were utilized to measure the epiphyseal cupping ratio and the current standard measure of inherent physeal stability, the epiphyseal extension ratio. RESULTS: Control hips were found to have greater epiphyseal cupping than the contralateral uninvolved hip of SCFE subjects both superiorly (0.28±0.08 vs. 0.24±0.06; P<0.001) and anteriorly (0.22±0.07 vs. 0.19±0.06; P<0.001). The 58/279 (21%) subjects who went on to develop contralateral slip had decreased epiphyseal cupping superiorly (0.25±0.07 vs. 0.23±0.05; P=0.03) and anteriorly (0.20±0.06 vs. 0.17±0.04; P<0.001). When we compared controls with hips that did not progress to contralateral slip and hips that further developed a contralateral SCFE, 1-way ANOVA demonstrated a stepwise decrease in epiphyseal cupping and epiphyseal extension ratio in the anterior and superior planes from control hips to contralateral hips without subsequent slip to contralateral hips that developed a SCFE (P<0.01 for each). CONCLUSIONS: This study provides further evidence that epiphyseal cupping around the metaphysis is associated with decreased likelihood of SCFE and may reflect increased inherent physeal stability. Epiphyseal cupping may represent an adaptive mechanism to stabilize the epiphysis during adolescence at the long-term cost of the eventual development of associated cam-femoroacetabular impingement deformity. LEVELS OF EVIDENCE: Level III-prognostic Study.

Treatment of Unstable Versus Stable Slipped Capital Femoral Epiphysis Using the Modified Dunn Procedure.

BACKGROUND: The modified Dunn procedure (open subcapital realignment via a surgical dislocation approach) has been shown to be a safe and effective way of treating acute, unstable slipped capital femoral epiphysis (SCFE). There is a paucity of literature comparing the modified Dunn procedure in stable SCFE. The purpose of this study was to compare acute, unstable versus chronic, stable SCFE managed with the modified Dunn procedure. METHODS: A retrospective chart review was performed on 44 skeletally immature patients who underwent the modified Dunn procedure for SCFE. Patients were divided into stable or unstable based on clinical presentation and intraoperative findings. Demographics, radiographic measurements, and complications were recorded and compared. χ and t tests were used to compare variables. RESULTS: In total, 31 consecutive hips (29 patients) with acute, unstable slips, and 17 consecutive hips (15 patients) with chronic, stable slips were reviewed. Average age was 12.5 and 13.8 years for acute and chronic, respectively (P=0.05). Mean follow-up was 27.9 months (unstable) and 35.5 months (stable). Average postoperative Southwick angle was 14.2 degrees; (unstable) and 25.3 degrees (stable) (P=0.001). Greater trochanteric height averaged 6.2 mm below the center of the femoral head in the acute group and 6.2 mm above center in the chronic group (P<0.001). Average femoral neck length measured 34.1 mm (unstable) and 27.1 mm (stable) (P<0.001). Two patients (6%) developed avascular necrosis (AVN) in the unstable group, with 5 patients (29.4%) in the stable group (P=0.027). All patients with hip instability (N=3) developed AVN. CONCLUSIONS: Although both acute, unstable and chronic, stable SCFE can be successfully treated with the modified Dunn procedure, the complication rate is statistically higher in patients with stable SCFE, specifically both AVN rate and postoperative instability. In addition, it is more difficult to establish normal anatomic indexes with regard to greater trochanteric height and femoral neck length. This procedure has great utility in the correction of the anatomic deformity associated with SCFE, but should be used with caution in patients with chronic, stable SCFE. LEVEL OF EVIDENCE: Level III-retrospective review.

Capital Femoral Epiphyseal Extension May Confer Physeal Stability in Slipped Capital Femoral Epiphysis.

BACKGROUND: Factors including obesity and morphologic parameters around the hip that increase physeal stress are associated with an increased risk of slipped capital femoral epiphysis (SCFE). Recent evidence suggests that superior epiphyseal extension may confer stability to the physis and help protect against SCFE. The purpose of this study is to investigate the relationship between epiphyseal extension and SCFE using an age-matched and sex-matched cohort study. METHODS: We generated 2 separate cohorts for comparison: 89 patients with unilateral SCFE and 89 healthy subjects with no evidence of hip disease or deformity. We utilized the anterior-posterior and lateral films of the hip to measure the Southwick angle and the epiphyseal extension ratio (EER), defined as the ratio of extension of the capital femoral epiphysis down the femoral neck relative to the diameter of the femoral head. We then compared these measurements between cohorts and in subgroup analysis based on slip stability and whether subjects progressed to a contralateral slip. RESULTS: The SCFE cohort demonstrated a decreased superior epiphyseal extension ratio compared with control (superior EER 0.71 vs. 0.68, P=0.002). There was also a significant downward trend in superior EER from the control subjects (0.71±0.07) to the stable slips (0.69±0.06) to the unstable slips (0.65±0.04) with an overall difference between the groups (P=0.001). Eighteen of 44 (41%) subjects with unilateral stable slips and at least 6 months of follow-up went on to develop SCFE of the contralateral limb. The subjects who developed contralateral slips were younger (11.6±1.2 vs. 12.7±1.4 y, P=0.008); however, there was no difference in superior or anterior epiphyseal extension (P=0.75 and 0.23, respectively). There was no significant linear correlation between Southwick angle and superior or anterior EER (r=0.13 and 0.17, respectively, P>0.05 for both). CONCLUSIONS: Increasing capital femoral epiphyseal extension may confer physeal stability in the setting of SCFE. We propose that this epiphyseal extension reflects an adaptive response to limit physeal stress and reduce the risk for progression to SCFE. LEVEL OF EVIDENCE: Level III-prognostic study.

Moderate and severe SCFE (Slipped Capital Femoral Epiphysis) arthroscopic osteoplasty vs open neck osteotomy-a retrospective analysis of results.

AIM: We intend to compare the outcomes of arthroscopic osteoplasty with open neck osteotomy for correction of the hip impingement and improvement of hip function in children with moderate to severe healed Slipped Capital Femoral Epiphysis (SCFE). Our aim is to verify if arthroscopic osteoplasty could achieve the same outcome as open procedures. PATIENTS AND METHODS: A retrospective analysis of the hospital hip database retrieved 187 cases of SCFE from 2006 to 2013. We found 12 patients underwent open neck osteotomy and deformity correction for moderate/ severe healed SCFE and ten underwent arthroscopic osteoplasty of the hip. We compared the outcomes between these groups. RESULTS: In the arthroscopy cohort, the mean age at surgery was 15.8 years (range 13-19 years) and mean follow-up was 46.1 months (range 33-66 months). In the neck osteotomy group, the mean age at surgery was 14.6 years (11-20 years) and mean duration of follow-up was 49 months (36-60 months). The outcomes in arthroscopic osteoplasty group vs. open neck osteotomy were as follows: antero-posterior (AP) slip angle 9.2° (0.3°- 28.8°) vs 10.8° (1°-17.9°) (p = 0.0003), lateral slip angle 44.8° (36.5°-64.2°) vs 13.5° (1°-28.5°) (p = 0.00001), oblique plane deformity 47.1° (40.2°-53.5°) vs 16.7° (1°-28.6°) (p = 0.0003), alpha angle 61.88° (52.1°-123°) vs.34.6° (23.2°-45.6°) (p = 0.0003), anterior offset 0 mm (0 mm-2 mm) vs. 5 mm (2-13 mm) (p = 0.0003), modified Harris hip score (MHHS) 75.5 (58.75-96.8) vs. 90 (86.2-99) (p = 0.003), non-arthroplasty hip score (NAHS) 67.12 (18.75-100) vs. 92.1 (81.25-100) (p = 0.002), internal rotation 20° (0-20°) vs. 50° (30°-70°) (p = 0.0002), respectively. CONCLUSION: Even though the radiographic correction lagged behind in the arthroscopic group, the functional outcomes achieved did convey the gain of function in this cohort. In carefully selected cases, arthroscopy could be a less invasive procedure which has desirable outcomes.

Similar femoral growth and deformity with one screw versus two smooth pins for slipped capital femoral epiphysis.

PURPOSE: To compare longitudinal growth and cam deformity of the proximal femur after treatment for slipped capital femoral epiphysis (SCFE) with one screw versus two smooth pins. METHODS: We studied 43 patients (29 males, 14 females; mean age, 12.1 years; range, 9.5-14 years) with idiopathic unilateral SCFE treated with in situ fixation with one cannulated screw (group A, n = 23) or two smooth pins (group B, n = 20). Anteroposterior and frog-leg radiographs of the pelvis were evaluated for each patient at initial presentation, post-operatively and at physeal closure. Longitudinal growth was evaluated using the femoral neck length (FNL), the caput-collum-diaphyseal (CCD) angle, and the articulo-trochanteric distance (ATD). Cam deformity was assessed using the anterior offset α-angle and the head-neck offset ratio (HNOR). The mean follow-up was 5.1 years (range, 4-7 years). RESULTS: Postoperatively, the mean CCD angle was 138.3°, the mean α-angle was 66.1° and the mean HNOR was - 0.030. At physeal closure, mean CCD angle significantly decreased to 133.6°, mean α-angle significantly reduced to 52.1°, and mean HNOR significantly improved to + 0.039. CCD, FNL, ATD, α-angle, and HNOR were not different between groups. CONCLUSIONS: One screw or two smooth pins result in similar longitudinal growth and deformity of the proximal femur after SCFE. The femoral head-neck junction remarkably improves until physeal closure; however, residual cam deformity is not avoided after in situ pinning. The complication rate with smooth pins is higher.

Continued Growth of the Femoral Neck Leads to Improved Remodeling After In Situ Fixation of Slipped Capital Femoral Epiphysis.

BACKGROUND: Globally, the most common method for in situ fixation of slipped capital femoral epiphysis (SCFE) is a threaded screw, which causes physeal arrest. The standard treatment in Sweden is unthreaded fixation using the Hansson hook-pin, which leads to continued growth of the femoral neck. Our purpose was to study remodeling during the remaining growth after fixation with the Hansson hook-pin. METHODS: We performed a retrospective study of 54 patients with SCFE who were treated with the Hansson hook-pin between 2001 and 2009. The immediate postoperative radiograph and the radiograph taken after physeal closure (mean interval, 34 mo) were analyzed. Three radiographic assessments were used: the head-shaft angle (HSA), the alpha angle (Nötzli), and the displacement from Klein's line. RESULTS: Significant remodeling was detected in all measured parameters. The mean postoperative HSA decreased by 9.0 degrees (P<0.001). The alpha angle improved by a mean of 14.5 degrees (P<0.001). Significant correlations were found between the reduction of the alpha angle and age (P<0.001, R=0.48) and longitudinal growth of the femoral neck (P<0.001, R=0.67). Displacement from Klein's line increased by a mean of 1.6 mm (P=0.006). CONCLUSIONS: Unthreaded fixation of SCFE using the Hansson hook-pin leads to substantial remodeling of the femoral neck. The positive correlation observed between the improvement of the alpha angle and femoral neck growth supports the use of a method that allows continuous growth, to reduce the risk of femoroacetabular impingement. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Early MRI Detection and Closed Bone Graft Epiphysiodesis May Alter the Course of Avascular Necrosis Following Unstable Slipped Capital Femoral Epiphysis.

BACKGROUND: Unstable slipped capital femoral epiphysis (SCFE) has an increased incidence of avascular necrosis (AVN). Early identification and surgical intervention for AVN may help preserve the femoral head. METHODS: We retrospectively reviewed 48 patients (50 hips) with unstable SCFE managed between 2000 and 2014. AVN was diagnosed based on 2 different postoperative protocols. Seventeen patients (17 hips) had a scheduled magnetic resonance imaging (MRI) between 1 and 6 months from initial surgery, and the remaining 31 patients (33 hips) were evaluated by plain radiographs alone. If AVN was diagnosed, we offered core decompression and closed bone graft epiphysiodesis (CBGE) to mitigate its affects. At final follow-up, we assessed progression of AVN using the Steinberg classification. RESULTS: Overall 13 hips (26%) with unstable SCFEs developed AVN. MRI revealed AVN in 7 of 17 hips (41%) at a mean of 2.5 months postoperatively (range, 1.0 to 5.2 mo). Six hips diagnosed by MRI received surgical intervention (4 CBGE, 1 free vascularized fibula graft, and 1 repinning due to screw cutout) at a mean of 4.1 months (range, 1.3 to 7.2 mo) postoperatively. None of the 4 patients treated with CBGE within 2 months postoperatively progressed to stage IVC AVN. The 2 patients treated after 4 months postoperatively both progressed to stage VC AVN.Plain radiographs demonstrated AVN in 6 of 33 hips (18%) at a mean of 6.8 months postoperatively (range, 2.1 to 21.1 mo). One patient diagnosed with stage IVB AVN at 2.4 months had screw cutout and received CBGE at 2.5 months from initial pinning. The remaining 5 were not offered surgical intervention. Five of the 6 radiographically diagnosed AVN, including the 1 treated with CBGE, progressed to stage IVC AVN or greater. CONCLUSIONS: Although all patients with positive MRI scans developed radiographic AVN, none of the 4 patients treated with CBGE within 2 months after pinning developed grade IVC or greater AVN. Early MRI detection and CBGE may mitigate the effects of AVN after SCFE. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

High Survivorship and Little Osteoarthritis at 10-year Followup in SCFE Patients Treated With a Modified Dunn Procedure.

BACKGROUND: The modified Dunn procedure has the potential to restore the anatomy in hips with slipped capital femoral epiphyses (SCFE) while protecting the blood supply to the femoral head and minimizing secondary impingement deformities. However, there is controversy about the risks associated with the procedure and mid- to long-term data on clinical outcomes, reoperations, and complications are sparse. QUESTIONS/PURPOSES: Among patients treated with a modified Dunn procedure for SCFE, we report on (1) hip pain and function as measured by the Merle d'Aubigné and Postel score, Drehmann sign, anterior impingement test, limp, and ROM; (2) the cumulative survivorship at minimum 10-year followup with endpoints of osteoarthritis (OA) progression (at least one Tönnis grade), subsequent THA, or a Merle d'Aubigné and Postel score < 15; (3) radiographic anatomy of the proximal femur measured by slip angle, α angle, Klein line, and sphericity index; and (4) the risk of subsequent surgery and complications. METHODS: Between 1998 and 2005, all patients who presented to our institution with SCFE were treated with a modified Dunn procedure; this approach was applied regardless of whether the slips were mild or severe, acute or chronic, and all were considered potentially eligible here. Of the 43 patients (43 hips) thus treated during that time, 42 (98%) were available for a minimum 10-year followup (mean, 12 years; range, 10-17 years) and complete radiographic and clinical followup was available on 38 hips (88%). The mean age of the patients was 13 years (range, 9-18 years). Ten hips (23%) presented with a mild, 27 hips (63%) with a moderate, and six hips (14%) with a severe slip angle. Pain and function were measured using the Merle d'Aubigné and Postel score, limp, ROM, and the presence of a positive anterior impingement test or Drehmann sign. Cumulative survivorship was calculated according to the method of Kaplan-Meier with three defined endpoints: (1) progression by at least one grade of OA according to Tönnis; (2) subsequent THA; or (3) a Merle d'Aubigné and Postel score < 15. Radiographic anatomy was assessed with the slip angle, Klein line, α angle, and sphericity index. RESULTS: The Merle d'Aubigné and Postel score improved at the latest followup from 13 ± 2 (7-14) to 17 ± 1 (14-18; p < 0.001), the prevalence of limp decreased from 47% (18 of 38 hips) to 0% (none in 38 hips; p < 0.001), the prevalence of a positive Drehmann sign decreased from 50% (nine of 18 hips) to 0% (none in 38 hips; p < 0.001), and both flexion and internal rotation improved meaningfully. Cumulative survivorship was 93% at 10 years (95% confidence interval, 85%-100%). Radiographic anatomy improved, but secondary impingement deformities remained in some patients, and secondary surgical procedures included nine hips (21%) with screw removal and six hips (14%) undergoing open procedures for impingement deformities. Complications occurred in four hips (9%) and no hips demonstrated avascular necrosis on plain radiographs. CONCLUSIONS: In this series, the modified Dunn procedure largely corrected slip deformities with little apparent risk of progression to avascular necrosis or THA and high hip scores at 10 years. However, secondary impingement deformities persisted in some hips and of those some underwent further surgical corrections. LEVEL OF EVIDENCE: Level IV, therapeutic study.

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.

Relationships Between Severity of Deformity and Impingement in Slipped Capital Femoral Epiphysis.

BACKGROUND: In situ pinning, a low-risk treatment for slipped capital femoral epiphysis (SCFE), leaves the slipped femoral head in place and may reduce range of motion (ROM) and cause impingement. It is unclear when a more complex surgery should be considered, because the relationships between severity, slip stability, remodeling, impingement, and ROM are unknown. RESEARCH QUESTIONS: (1) Do more severe acute SCFE deformities (no bony remodeling) result in a greater loss of flexion ROM?(2) Does the presence or location of impingement on the pelvis vary with severity of acute SCFE deformity? METHODS: We developed a 3D geometric model of acute SCFE deformity from 1 computed tomography scan of a normal adolescent hip. Ethics board approval was obtained from our institution. Bone models were created from the segmented pelvis, epiphysis, and subphyseal femur.In total, 3721 SCFE deformities were simulated by combining posterior and inferior slips in the axial and coronal planes, respectively. Southwick angles were estimated from a frog-leg lateral projection. Deformities were divided into mild (0 to 30 degrees), moderate (30 to 60 degrees), and severe (≥60 degrees) Southwick groups. Each joint was flexed in combination with internal/external rotation until contact occurred. A total of 121 ROM trials, with different degrees of internal/external rotation (0 to 90 degrees at 1.5-degree steps) were performed for each deformity. RESULTS: In total, 3355 simulated SCFE deformities (363 could not be rotated out of impingement) were analyzed.Increasing slip severity reduced flexion ROM across the range of internal/external rotation. Contact occurred for most mild deformities, and for all moderate and severe deformities in at least 1 ROM trial. Impingement was observed mainly on the anterosuperior aspect of the acetabulum. CONCLUSIONS: Increasing slip severity in acute SCFE reduced flexion and increased incidence of impingement, primarily occurring on the anterosuperior aspect of the acetabulum. The impingement patterns observed are consistent with damaged cartilage locations seen in clinical literature. CLINICAL RELEVANCE: In this experimental model, moderate and severe acute slips in SCFE lead to reduced ROM and impingement with the acetabulum. This suggests that in situ pinning may result in impingement of moderate and severe acute SCFE slips.

Validity and Clinical Consequences of a Rotational Mechanism for Slipped Capital Femoral Epiphysis.

BACKGROUND: Recent anatomic data supports a mechanism for slipped capital femoral epiphysis (SCFE) where the metaphysis rotates on the epiphysis through the eccentrically located epiphyseal tubercle as a pivot. The validity of such a mechanism and its clinical consequences have not been well investigated. METHODS: This cadaveric study defined the normal location of the calcar ridge line in 100 paired femora and compared them with 11 SCFE specimens, and with 25 immature femora where the metaphysis was rotated 30, 60, and 90 degrees on the epiphysis to model progressive SCFE. Coronal, sagittal, and axial plane deformity were measured on the rotational model to define the characteristic deformity caused by rotation, and lateral epiphyseal foramina stretch was measured to quantify the protective effect of an eccentric pivot. RESULTS: The posterior displacement of the fovea with respect to the calcar ridge line was 1±5 mm for the controls, versus 23±10 mm for the SCFE specimens (P<0.0005), and posterior displacement increased with incremental rotation in the rotational model (P<0.0005). The rotational model found minimal varus deformity, but substantial extension and retroversion, with deformities of 0±5, -16±12, and -38±9 degrees, respectively, at 90 degrees of rotation. The eccentric pivot mitigated lateral epiphyseal vessel stretch by 55% to 70%. CONCLUSIONS: This study provides strong anatomic support for a rotational mechanism for stable SCFE. When the metaphysis is rotated on the epiphysis acutely, minimal varus deformity is created, while substantial retroversion occurs. As this rotation occurs the eccentric pivot protects the lateral epiphyseal vessels, and likely accounts for the low rate of avascular necrosis observed in stable SCFE. CLINICAL RELEVANCE: If SCFE is treated in an open manner then the presence of a chronic rotational deformity should be considered. When planning osteotomies for deformity after a stable SCFE, any suspected varus component should be carefully investigated as it may represent retroversion deformity brought into view by external rotation posturing of the leg.

Prevalence of Hypertension in Pediatric Tibia Vara and Slipped Capital Femoral Epiphysis.

BACKGROUND: Slipped capital femoral epiphysis (SCFE) and tibia vara (Blount disease) are associated with childhood obesity. However, the majority of obese children do not develop SCFE or tibia vara. Therefore, it is hypothesized that other obesity-related biological changes to the physis, in addition to increased biomechanical stress, potentiate the occurrence of SCFE and tibia vara. Considering that hypertension can impose pathologic changes in the physis similar to those observed in these obesity-related diseases we set out to determine the prevalence of hypertension in patients with SCFE and tibia vara. METHODS: Blood pressure measurements were obtained in 44 patients with tibia vara and 127 patients with SCFE. Body mass index and blood pressure were adjusted for age, sex, and height percentiles utilizing normative distribution data from the CDC. These cohorts were compared with age-matched and sex-matched cohorts derived from an obesity clinic who did not have either bone disease. A multivariable proportional odds model was used to determine association. RESULTS: The prevalence of prehypertension/hypertension was significantly higher in the tibia vara (64%) and SCFE cohort (64%) compared with respective controls (43%). Patients diagnosed with either SCFE or tibia vara had 2.5-fold higher odds of having high blood pressure compared with age-matched and sex-matched obese patients without bone disease. Sex, age, and race did not have a significant effect on a patient's blood pressure. CONCLUSIONS: This is the first study to establish that the obesity-related bone diseases, SCFE and tibia vara, are significantly associated with high blood pressure. These data have immediate clinical impact as they demonstrate that children with obesity-related developmental bone disease have increased prevalence of undiagnosed and untreated hypertension. Furthermore, this prevalence study supports the hypothesis that hypertension in conjunction with increased biomechanical forces together potentiate the occurrence of SCFE and tibia vara. If proven true, it is plausible that hypertension may represent a modifiable risk factor for obesity-related bone disease. LEVEL OF EVIDENCE: Level III-case-control study.

Biomechanics of Slipped Capital Femoral Epiphysis: Evaluation of the Posterior Sloping Angle.

BACKGROUND: The posterior sloping angle (PSA) has been shown to be an objective and reproducible predictor of the risk of patients developing contralateral slipped capital femoral epiphysis (SCFE); however, prophylactic fixation remains controversial. This in vitro study investigates the biomechanical basis of using a 15-degree PSA as a threshold for prophylactic fixation. METHODS: Synthetic bone in vitro models of the proximal femur were constructed with a PSA of 10 degrees as a control (normal) group (n=6) by performing an osteotomy at the physis and gluing the head back onto the neck. SCFE groups were created with a PSA of 15, 20, 25, 30, 50, or 60 degrees, by excising a wedge from the posterior neck and gluing them back at the new angle with corresponding posterior translation proportional to the slip angle, and loaded superoinferiorly in compression, to failure. Ultimate strength, energy to failure, and stiffness were recorded. RESULTS: Increasing the PSA from 10 to 15 degrees only reduced ultimate strength by 13% (P>0.05; CI, -0.21 to -0.06), though a significantly lesser energy to failure was required (-58%, P<0.05; CI, -0.68 to -0.48). Increasing the angle to 20 degrees resulted in a further significant decrease in strength (-19%, P<0.05; CI, -0.28 to -0.10) and energy to failure (-45%, P<0.05; CI, -0.53 to -0.84). The severe SCFE (60-degree PSA) was significantly weaker and less rigid that the control, and the mild and moderate SCFE models (P<0.01). CONCLUSIONS: These biomechanical data support the threshold of 15-degree PSA as an objective measure for prophylactic fixation of the contralateral hip in SCFE. CLINICAL RELEVANCE: The number needed to treat with (minimally invasive) prophylactic fixation to prevent contralateral SCFE can be minimized if the above-mentioned threshold is used.

Modified Dunn Procedure is Superior to In Situ Pinning for Short-term Clinical and Radiographic Improvement in Severe Stable SCFE.

BACKGROUND: In situ pinning is the conventional treatment for a stable slipped capital femoral epiphysis (SCFE). However, with a severe stable SCFE the residual deformity may lead to femoroacetabular impingement and articular cartilage damage. A modified Dunn subcapital realignment procedure has been developed to allow for correction at the level of the deformity while preserving the blood supply to the femoral head. QUESTIONS/PURPOSES: We compared children with severe stable SCFE treated with the modified Dunn procedure or in situ pinning in terms of (1) proximal femoral radiographic deformity; (2) Heyman and Herndon clinical outcome; (3) complication rate; and (4) number of reoperations performed after the initial procedure. METHODS: In this nonmatched retrospective study, 15 patients treated with the modified Dunn procedure (between 2007 and 2012) and 15 treated with in situ pinning (between 2001 and 2009) for severe but stable SCFE were followed for a mean of 2.5 years (range, 1-6 years). During the period in question, the decision regarding which procedure to use was based on the on-call surgeon's discretion; six surgeons performed in situ pinning and three surgeons performed the modified Dunn procedure. A total of 15 other patients were treated for the same diagnosis during the study period but were lost to followup before 1 year; of those, 12 were in the in situ pinning group. Radiographs were reviewed to measure the AP and lateral alpha angles, femoral head-neck offset, and Southwick angle preoperatively and at the latest clinical visit. The Heyman and Herndon clinical outcome, complications, and subsequent hip surgeries were recorded. RESULTS: At latest followup, the median AP alpha angle (52°, range 41°-59° versus 76°, interquartile range [IQR]: 68°-88°; p = 0.0017), median lateral alpha angle (44°, IQR: 40°-51° versus 87°, IQR: 74°-96°; p < 0.001), median head-neck offset (7 mm, IQR: 5-9 mm versus -5, IQR: -11 to -4 mm; p < 0.001), and median Southwick angle (16°, IQR: 6°-23° versus 58°, IQR: 47°-66°; p < 0.001) revealed better deformity correction with the modified Dunn procedure compared with in situ pinning. Nine patients had good or excellent results in the modified Dunn group compared with four of 15 in the in situ pinning group (p = 0.0343; odds ratio, 5.86; 95% CI, 1.13-40.43). With the numbers available, there were no differences in the numbers of complications in each group (five versus three complications in the in situ and modified Dunn groups, respectively; p = 0.66), but there were more reoperations in the in situ pinning group (three versus seven; p = 0.0230). CONCLUSIONS: The modified Dunn procedure results in better morphologic features of the femur, a higher rate of good and excellent Heyman and Herndon clinical outcome, a lower reoperation rate, and a similar occurrence of complications when compared with in situ pinning for treatment of severe stable SCFE. LEVEL OF EVIDENCE: Level III, therapeutic study.

Pelvic Incidence and Acetabular Version in Slipped Capital Femoral Epiphysis.

BACKGROUND: The etiology of slipped capital femoral epiphysis (SCFE) is multifactorial, but the role of sagittal balance of the pelvis as a contributing factor to its development has not been well studied. Our primary purpose was to determine whether a smaller pelvic incidence (PI), a position-independent anatomic parameter that regulates pelvic orientation, could be a factor that increases shear stress in the epiphyseal growth plate and potentially contributes to the development of SCFE. We also set out to determine whether acetabular retroversion was associated with SCFE. METHODS: We obtained 14 cadaveric pelvi from the Hamann-Todd Osteological Collection whose femurs showed evidence of post-SCFE deformity. Two hundred age-matched, sex-matched, and race-matched pelvi were used as controls. PI and acetabular version were measured using standardized lateral photographs and goniometers, respectively. T tests were performed to evaluate for differences in measured parameters between groups. RESULTS: The mean PI was 40.6±6.1 degrees for SCFE specimens and 47.4±9.9 degrees for normal specimens (P=0.01). The mean version of SCFE and normal acetabula was 15±7 and 17±6 degrees, respectively (P=0.39). There was also no significant difference in version between SCFE acetabula and the contralateral, uninvolved acetabular of the same specimen (15±7 vs. 17±8 degrees, P=0.33). CONCLUSIONS: Specimens with SCFE deformity demonstrated a smaller PI than a large cohort of normal control specimens. We found no significant difference between acetabular version of specimens with and without SCFE deformity. Contralateral or unaffected acetabuli of SCFE specimens were not more retroverted than the affected side of the same specimen. CLINICAL RELEVANCE: Sagittal balance of the pelvis, and particularly decreased PI, may play an important role in the development of SCFE. The influence of mechanical factors beyond the hip joint in the development of SCFE should be considered by clinicians.