The Peritubercle Lucency Sign is a Common and Early Radiographic Finding in Slipped Capital Femoral Epiphysis

Slipped capital femoral epiphysis: emphasis on early recognition and potential pitfalls

Slipped capital femoral epiphysis is a shearing injury through the growth plate of the proximal femur and is the most common hip disorder in adolescence. Delays in diagnosis persist across practice settings despite ongoing innovations in imaging. Recent insights into pathomechanics highlight the importance of femoral head surface morphology and rotational microinstability centered at the epiphyseal tubercle in causing early physeal changes, which can be detected on imaging prior to frank slip. Scrutiny of physeal morphology and comparison to the contralateral hip is critical at all stages of disease progression, and improper technique may result in undue diagnostic delay. Selective use of cross-sectional imaging can be helpful for troubleshooting equivocal early slips and can inform operative technique and adjuvant therapy candidacy in more severe cases. This review provides a comprehensive approach to imaging suspected slipped capital femoral epiphysis, with an emphasis on early detection and potential pitfalls.

The Peritubercle Lucency Sign as a Considerable Predictive Factor for Contralateral Hip Slippage in Unilateral Slipped Capital Femoral Epiphysis Cases

Objective  To determine whether the radiographic parameter at the epiphyseal tubercle region (peritubercle lucency sign) on the unaffected side can predict slipped capital femoral epiphysis (SCFE). Methods  We retrospectively reviewed patients who received an initial diagnosis of unilateral SCFE between 1995 and 2020 at a pediatric hospital in a Brazilian state's capital. The patients were monitored for at least 18 months. Two reviewers independently and blindly assessed the radiographs for the presence or absence of the sign. Disagreements were resolved by a third senior reviewer. Results  Out of the 115 cases reviewed, the peritubercle lucency sign was observed in 21 of the 30 patients who developed the disease in the contralateral hip. The sign was observed on an average of 21 days after the diagnosis on the initial side, and approximately 301 days prior to the condition affecting the contralateral hip. It was present in 95% and 85% of the cases on the lateral (frog-leg) and anteroposterior (AP) views, respectively. Interobserver reliability was measured using the Kappa test (k = 0.0801). There was a significant relationship between the presence of the sign and SCFE ( p  < 0.001). Conclusions:  We propose that the peritubercle lucency sign can be used as a supplementary tool in early diagnosis, for it is beneficial in the therapeutic planning. Level Of Evidence:  Level III - Diagnostic Study In Nonconsecutive Patients (Without Consistently Applied 'Gold Standard' As Reference).

Novelties in slipped capital femoral epiphysis imaging: A narrative review

Rationale and objectives

Imaging plays a key role in Slipped Capital Femoral Epiphysis diagnosis and severity assessment. In the last two decades, signs and measurements emerged in literature showed potential to help in SCFE diagnosis and tailoring treatment. The purpose of this review is to collect and discuss new imaging signs, measurements, and techniques according to investigations published after 2000 to improve SCFE diagnosis.

Material and methods

The PubMed, Scopus, and Science Direct databases were used to search for relevant articles related to imaging in SCFE diagnosis from January 2000 to March 2023. Article selection and review was performed by two board-certified radiologists). Article quality assessment were conducted by authors using QUADAS-2 and SANRA evaluation tools.

Results

The research resulted in a total of 2577 articles. After duplicates removal and abstract analysis, 28 articles were finally selected for full-text analysis. Seventeen articles were focused on Radiographs, 6 on CT, 1 on both Radiographs and CT, 4 on MRI. No study focused on ultrasound was selected.

Conclusions

Use of modified Klein's line and S-sign may improve radiographs accuracy in daily routine. Lucency sign may help in early diagnosis on radiographs. Preoperative CT may be useful in planning a tailored treatment predicting SCFE severity and instability. MRI is the most accurate modality to diagnose SCFE at early stage. Nevertheless, it cannot be used to predict the risk of contralateral SCFE. Risk prediction can be assessed with radiographs, using a new rapid mOBS. Further investigation and validation of these sign is needed.

Smaller epiphyseal tubercle in hips with slipped capital femoral epiphysis compared to the uninvolved contralateral hip

Recent investigations suggest that physeal morphologic features have a major role in the capital femoral epiphysis stability and slipped capital femoral epiphysis (SCFE) pathology, with a smaller epiphyseal tubercle and larger peripheral cupping of the femoral epiphysis being present in hips with progressive SCFE compared to healthy controls. Yet, little is known on the causal versus remodeling nature of these associations. This study aimed to use preoperative magnetic resonance imaging (MRI) of patients with unilateral SCFE to perform a comparison of the morphology of the epiphyseal tubercle, metaphyseal fossa, and peripheral cupping in hips with SCFE versus the contralateral uninvolved hips. Preoperative MRIs from 22 unilateral SCFE patients were used to quantify the morphological features of the epiphyseal tubercle (height, width, and length), metaphyseal fossa (depth, width, and length), and peripheral cupping height in three dimension. The quantified anatomical features were compared between hips with SCFE and the contralateral uninvolved side across the whole cohort and within SCFE severity subgroups using paired t-test. We found significantly smaller epiphyseal tubercle heights (p < 0.001) across all severities of SCFE when compared to their uninvolved contralateral side. There was a marginally smaller metaphyseal fossa length (p = 0.05) in SCFE hips compared to their contralateral uninvolved hips, with mild SCFE hips specifically having smaller fossa and epiphyseal lengths (p < 0.05) than their contralateral uninvolved side. There were no side-to-side differences in any other features of the epiphyseal tubercle, metaphyseal fossa and peripheral cupping across all severities (p > 0.05). These findings suggest a potential causal role of epiphyseal tubercle in SCFE pathogenesis.

Limited Hip Flexion and Internal Rotation Resulting From Early Hip Impingement Conflict on Anterior Metaphysis of Patients With Untreated Severe SCFE Using 3D Modelling

INTRODUCTION

Slipped capital femoral epiphysis (SCFE) is the most common hip disorder in adolescent patients that can result in complex 3 dimensional (3D)-deformity and hip preservation surgery (eg, in situ pinning or proximal femoral osteotomy) is often performed. But there is little information about location of impingement.Purpose/Questions: The purpose of this study was to evaluate (1) impingement-free hip flexion and internal rotation (IR), (2) frequency of impingement in early flexion (30 to 60 degrees), and (3) location of acetabular and femoral impingement in IR in 90 degrees of flexion (IRF-90 degrees) and in maximal flexion for patients with untreated severe SCFE using preoperative 3D-computed tomography (CT) for impingement simulation.

METHODS

A retrospective study involving 3D-CT scans of 18 patients (21 hips) with untreated severe SCFE (slip angle>60 degrees) was performed. Preoperative CT scans were used for bone segmentation of preoperative patient-specific 3D models. Three patients (15%) had bilateral SCFE. Mean age was 13±2 (10 to 16) years and 67% were male patients (86% unstable slip, 81% chronic slip). The contralateral hips of 15 patients with unilateral SCFE were evaluated (control group). Validated software was used for 3D impingement simulation (equidistant method).

RESULTS

(1) Impingement-free flexion (46±32 degrees) and IRF-90 degrees (-17±18 degrees) were significantly ( P <0.001) decreased in untreated severe SCFE patients compared with contralateral side (122±9 and 36±11 degrees).(2) Frequency of impingement was significantly ( P <0.001) higher in 30 and 60 degrees flexion (48% and 71%) of patients with severe SCFE compared with control group (0%).(3) Acetabular impingement conflict was located anterior-superior (SCFE patients), mostly 12 o'clock (50%) in IRF-90 degrees (70% on 2 o'clock for maximal flexion). Femoral impingement was located on anterior-superior to anterior-inferior femoral metaphysis (between 2 and 6 o'clock, 40% on 3 o'clock and 40% on 5 o'clock) in IRF-90 degrees and on anterior metaphysis (40% on 3 o'clock) in maximal flexion and frequency was significantly ( P <0.001) different compared with control group.

CONCLUSION

Severe SCFE patients have limited hip flexion and IR due to early hip impingement using patient-specific preoperative 3D models. Because of the large variety of hip motion, individual evaluation is recommended to plan the osseous correction for severe SCFE patients.

LEVEL OF EVIDENCE

Level III.

Proximal femoral changes related to obesity: an analysis of slipped capital femoral epiphysis pathoanatomy

Recent research has revealed the importance of the femoral epiphyseal tubercle and cupping height in the stability of the physis and its association with capital femoral slippage. To better understand the connection between the pathogenesis of slipped capital femoral epiphysis and obesity, we performed a retrospective analysis of proximal femur and acetabular anatomies using computed tomography (CT) scans in the hips of normal weight and obese pediatric patients. We measured morphologic characteristics of the proximal femur and acetabulum in developing hips of 31 obese adolescent patients and age-matched and sex-matched control group using pelvic CT scans. Measurements included physeal diameter, tubercle height, width, and volume, cupping height, acetabular rotation and inclination, and metaphyseal bone density. Measurements were performed on true coronal and sagittal views through the center of the epiphysis using previously described and validated techniques. Statistical analysis was performed to compare the measurements between obese and nonobese adolescents. The epiphyseal tubercle volume and average cupping size were similar between the two groups. Acetabular inclination and metaphyseal bone density were significantly different between the cohorts. Metaphyseal bone density was lower among obese patients. Obesity does not appear to cause morphologic changes to the capital femoral physis, though it is associated with a decreased metaphyseal bone mineral density which could indicate physeal instability. This could suggest increased metabolic activity in the metaphyseal bone in obese adolescents. Therefore, metabolic factors associated with obesity, rather than anatomical changes, may be responsible for physeal instability seen in obese adolescents.

Does the Capital Femoral Physis Bony MorphologyDiffer in Children with Symptomatic Cam-type Femoroacetabular Impingement

BACKGROUND

The epiphyseal tubercle, the corresponding metaphyseal fossa, and peripheral cupping are key stabilizers of the femoral head-neck junction. Abnormal development of these features in the setting of supraphysiologic physeal stress under high forces (for example, forces that occur during sports activity) may result in a cam morphology. Although most previous studies on cam-type femoroacetabular impingement (FAI) have mainly focused on overgrowth of the peripheral cupping, little is known about detailed morphologic changes of the epiphyseal and metaphyseal bony surfaces in patients with cam morphology.

QUESTIONS/PURPOSES

(1) Does the CT-based bony morphology of the peripheral epiphyseal cupping differ between patients with a cam-type morphology and asymptomatic controls (individuals who did not have hip pain)? (2) Does the CT-based bony morphology of the epiphyseal tubercle differ between patients with a cam-type morphology and asymptomatic controls? (3) Does the CT-based bony morphology of the metaphyseal fossa differ between patients with a cam-type morphology and asymptomatic controls?

METHODS

After obtaining institutional review board approval for this study, we retrospectively searched our institutional database for patients aged 8 to 15 years with a diagnosis of an idiopathic cam morphology who underwent a preoperative CT evaluation of the affected hip between 2005 and 2018 (n = 152). We excluded 96 patients with unavailable CT scans and 40 patients with prior joint diseases other than cam-type FAI. Our search resulted in 16 patients, including nine males. Six of 16 patients had a diagnosis of bilateral FAI, for whom we randomly selected one side for the analysis. Three-dimensional (3-D) models of the proximal femur were generated to quantify the size of the peripheral cupping (peripheral growth of the epiphysis around the metaphysis), epiphyseal tubercle (a beak-like prominence in the posterosuperior aspect of the epiphysis), and metaphyseal fossa (a groove on the metaphyseal surface corresponding to the epiphyseal tubercle). A general linear model was used to compare the quantified anatomic features between the FAI cohort and 80 asymptomatic hips (aged 8 to 15 years; 50% male) after adjusting for age and sex. A secondary analysis using the Wilcoxon matched-pairs signed rank test was performed to assess side-to-side differences in quantified morphological features in 10 patients with unilateral FAI.

RESULTS

After adjusting for age and sex, we found that patients with FAI had larger peripheral cupping in the anterior, posterior, superior, and inferior regions than control patients who did not have hip symptoms or radiographic signs of FAI (by 1.3- to 1.7-fold; p < 0.01 for all comparisons). The epiphyseal tubercle height and length were smaller in patients with FAI than in controls (by 0.3- to 0.6-fold; p < 0.02 for all comparisons). There was no difference in tubercle width between the groups. Metaphyseal fossa depth, width, and length were larger in patients with FAI than in controls (by 1.8- to 2.3-fold; p < 0.001 for all comparisons). For patients with unilateral FAI, we saw similar peripheral cupping but smaller epiphyseal tubercle (height and length) along with larger metaphyseal fossa (depth) in the FAI side compared with the uninvolved contralateral side.

CONCLUSION

Consistent with prior studies, we observed more peripheral cupping in patients with cam-type FAI than control patients without hip symptoms or radiographic signs of FAI. Interestingly, the epiphyseal tubercle height and length were smaller and the metaphyseal fossa was larger in hips with cam-type FAI, suggesting varying inner bone surface morphology of the growth plate. The docking mechanism between the epiphyseal tubercle and the metaphyseal fossa is important for epiphyseal stability, particularly at early ages when the peripheral cupping is not fully developed. An underdeveloped tubercle and a large fossa could be associated with a reduction in stability, while excessive peripheral cupping growth would be a factor related to improved physeal stability. This is further supported by observed side-to-side differences in tubercle and fossa morphology in patients with unilateral FAI. Further longitudinal studies would be worthwhile to study the causality and compensatory mechanisms related to epiphyseal and metaphyseal bony morphology in pathogenesis cam-type FAI. Such information will lay the foundation for developing imaging biomarkers to predict the risk of FAI or to monitor its progress, which are critical in clinical care planning.

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.

Intraobserver and Interobserver Reliability of the Peritubercle Lucency Sign in Slipped Capital Femoral Epiphysis

BACKGROUND

An area of enlargement of the metaphyseal socket around the epiphyseal tubercle, termed the peritubercle lucency sign, has recently been introduced as a possible predictor of contralateral slipped capital femoral epiphysis in patients with previous unilateral slipped capital femoral epiphysis. This study aimed to assess intraobserver and interobserver reliability for detecting the presence or absence of the peritubercle lucency sign.

METHODS

Thirty-five radiographs were presented to 6 fellowship-trained pediatric orthopaedic surgeons on 2 separate occasions 30 days apart, ensuring that the images were shown in a different order on the second exposure. Both times the reviewers recorded whether the peritubercle lucency sign was present or absent in each of the radiographs. Statistical analysis was performed to determine the intraobserver and interobserver reliability.

RESULTS

In the intraobserver analysis, percent agreement between the first and second time the radiographs were reviewed varied between 62.9% and 85.7%, for an average intraobserver agreement of 74.8%. κ values for the 6 reviewers varied between 0.34 and 0.716, with an average intraobserver κ value of 0.508. The interobserver percent agreement was 40.0% for the first time the radiographs were reviewed, 42.9% the second time, and the overall interobserver percent agreement was 29%. The interobserver κ value was 0.44 the first time the radiographs were reviewed, 0.45 the second time, and the overall interobserver κ value was 0.45.

DISCUSSION

On the basis of our findings, the peritubercle lucency has modest intraobserver and interobserver reliability at best and should be used with other currently used factors, such as age, presence of endocrinopathy, status of triradiate cartilage, posterior sloping angle, and modified Oxford score, in determining the need for prophylactic pinning. Further refinement of the definition of the peritubercle lucency sign may be needed to improve agreement and reliability of the sign.

LEVEL OF EVIDENCE

Level III-prognostic study.

Age- and sex-specific morphologic changes in the metaphyseal fossa adjacent to epiphyseal tubercle in children and adolescents without hip disorders

The epiphyseal tubercle plays an important role in epiphyseal stabilization. While the majority of studies have focused on tubercle morphology, there is a paucity of information on the morphological features of the metaphyseal fossa, where the tubercle sits on the metaphysis. The goal of this study was to determine the developmental changes in the capital femoral metaphyseal fossa. Computed tomography of the pelvis from 80 children and adolescents 8-15 years old were used to create three-dimensional models of the proximal femur. Depth, width, length, and surface area of the metaphyseal fossa were measured and the impact of age and sex on fossa morphology was assessed using the linear regression and two-way analysis of variance, respectively. The metaphyseal fossa was located in the posterosuperior quadrant of the metaphysis without any variations in the location with increasing age (P > .1). However, with increasing age, there was a reduction in all metaphyseal fossa measurements including the depth, length, width, and surface area (P < .01). No significant differences were noted for the metaphyseal fossa measurements between males and females (P > .1). The metaphyseal fossa reduces in size from 8 to 15 years of age in a similar fashion in males and females. As the metaphyseal fossa adjacent to the tubercle matches the area where a focal radiolucency has been observed in early slipped capital femoral epiphysis (SCFE), further studies should clarify the mechanisms by which the interlocking interaction of the epiphyseal tubercle and its fossa contributes to or is affected by SCFE.

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.

Increased body mass index percentile is associated with decreased epiphyseal tubercle size in asymptomatic children and adolescents with healthy hips

PURPOSE

To investigate whether body mass index (BMI) percentile impacts the morphology of the capital femoral epiphysis in children and adolescents without hip disorders.

METHODS

We assessed 68 subjects with healthy hips who underwent a pelvic CT for evaluation of appendicitis. There were 32 male patients (47%) and the mean age was 11.6 years (sd 2.3). The BMI (k/m²) was calculated for sex- and age-related percentiles according to the Centers for Disease Control and Prevention growth charts. CT images were segmented, and the epiphysis and metaphysis were reformatted using 3D software. We measured the epiphyseal tubercle (height, width and length), the metaphyseal fossa (depth, width and length) and the peripheral cupping of the epiphysis. All measurements were normalized to the diameter of the epiphysis. Pearson's correlation analysis was used to assess the correlations between the variables measured and BMI percentile adjusted for age.

RESULTS

Following adjustment to age, increased BMI correlated to decreased tubercle height (r =-0.34; 95% confidence interval (CI) -0.53 to -0.11; p = 0.005), decreased tubercle length (r = -0.32; 95%CI -0.52 to -0.09; p = 0.008) and decreased tubercle width (r = -0.3; 95% CI -0.5 to -0.07; p = 0.01). There was no correlation between BMI and metaphyseal fossa and epiphyseal cupping measurements.

CONCLUSION

The association between increased BMI percentile and decreased epiphyseal tubercle size, without changes of the metaphyseal fossa and peripheral cupping suggests another morphological change of the femur that may be associated with decreased growth plate resistance to shear stress. Further study is necessary to investigate whether the epiphyseal tubercle size plays a role in the pathogenesis of slipped capital femoral epiphysis in obese children and adolescents.

LEVEL OF EVIDENCE

Level IV.

The metaphyseal fossa surrounding the epiphyseal tubercle is larger in hips with moderate and severe slipped capital femoral epiphysis than normal hips

PURPOSE

To compare the 3D morphology of the metaphyseal fossa among mild, moderate and severe stable slipped capital femoral epiphysis (SCFE) and normal hips.

METHODS

We identified pelvic CT of 51 patients (55% male; mean 12.7 years (sd 1.9; 8-15)) with stable SCFE. In all, 16 of 51 hips (31%) had mild, 14 (27%) moderate and 21 (41%) severe SCFE. A total of 80 patients (50% male; mean age 11.5 years (sd 2.3; 8 to 15)) with normal hips who underwent pelvic CT due to abdominal pain made up the control cohort. CT scans were segmented, and the femur was reformatted using 3D software. We measured the metaphyseal fossa depth, width, length and surface area after the epiphysis was subtracted from the metaphysis in the 3D model.

RESULTS

The metaphyseal fossa width was significantly larger in severe (adjusted difference: 6.9%; 95% confidence interval (CI) 2.1 to 11.8; p = 0.001), moderate (6.5%; 95% CI 0.8 to 12.2; p = 0.02) and mild SCFE (6.2%; 95% CI 0.8 to 11.6; p = 0.01), in comparison with normal hips. Severe SCFE showed larger fossa length compared with mild SCFE (6.8%; 95% CI 0.6 to 13.0; p = 0.02) and normal hips (6.0%; 95% CI 1.4 to 10.6; p = 0.004). The fossa surface area was larger in severe (3.5%; 95% CI 1.3 to 5.7; p < 0.001) and moderate SCFE (2.7%; 95% CI 0.1 to 5.2; p = 0.03) when compared with normal hips. There were no differences in fossa depth between SCFE and normal hips.

CONCLUSION

The metaphyseal fossa is wider and more extensive but not deeper in hips with moderate and severe SCFE in comparison with normal hips. Although hips with severe SCFE had larger length and surface area than mild SCFE hips, further research is needed to clarify whether enlargement of the metaphyseal fossa is a consequence of slip progression.

LEVEL OF EVIDENCE

III.

Contralateral slip after unilateral slipped capital femoral epiphysis is associated with acetabular retroversion but not increased acetabular depth and overcoverage

Overcoverage of the femoral head by the acetabulum, increased acetabular depth and retroversion have been associated with the etiology of slipped capital femoral epiphysis (SCFE). However, limited evidence exists about the impact of the acetabular morphology on the development of a contralateral slip following an initial presentation of unilateral SCFE. We aimed to investigate whether acetabular overcoverage as assessed by an increased lateral center-edge angle (LCEA) and low Tönnis angle, increased acetabular depth assessed by the acetabular depth-width ratio (ADR) and the presence of coxa profunda; and acetabular retroversion assessed by the presence of the crossover sign were associated with a contralateral slip in patients presenting with unilateral SCFE. We evaluated 250 patients with initial diagnosis of unilateral SCFE (average age, 12.5 ± 1.7 years), who had not undergone prophylactic fixation on the contralateral hip for a median follow-up of 49 months (interquartile range: 25-76 months). Endpoints were the development of a contralateral slip (70 patients, 28%) or skeletal maturity assessed by complete closure of the proximal femoral growth plate (180 patients, 72%). We measured the LCEA, Tönnis angle, ADR, and the coxa profunda sign on an anteroposterior pelvic radiograph. The crossover sign was assessed in 208 hips who had a secondary ossification center in the posterior acetabular rim. For each additional degree of LCEA, the odds of contralateral slip decreased 8% [odds ratio = 0.92; 95% confidence interval (CI), 0.87-0.98; P = 0.009]. Tönnis angle (P = 0.11), ADR (P = 0.20) and coxa profunda (p = 0.37) had no association with a contralateral slip. The presence of crossover sign increased two and half times the odds for a contralateral slip (odds ratio = 2.5; 95% CI = 1.12-5.64; P = 0.03). Acetabular retroversion, but not acetabular overcoverage or increased acetabular depth, was associated with contralateral SCFE development in patients with unilateral SCFE. Level of evidence: prognostic level II.

What Is the Accuracy and Reliability of the Peritubercle Lucency Sign on Radiographs for Early Diagnosis of Slipped Capital Femoral Epiphysis Compared With MRI as the Gold Standard?

BACKGROUND

The diagnosis of slipped capital femoral epiphysis (SCFE) often is delayed. Although lack of clinical suspicion is the main cause of delayed diagnosis, typical radiographic changes may not be present during the initial phases of SCFE. The peritubercle lucency sign for follow-up of the contralateral hip in patients with unilateral SCFE may be beneficial in assisting the early diagnosis. However, the accuracy and reliability of this sign in patients with SCFE is unknown.

QUESTIONS/PURPOSES

(1) What is the accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the peritubercle lucency sign on radiographs for the early diagnosis of SCFE compared with MRI as the gold standard? (2) What are the interobserver and intraobserver reliabilities of the peritubercle lucency sign on radiographs?

METHODS

Between 2000 and 2017, 71 patients underwent MRI for an evaluation of pre-slip or a minimally displaced SCFE. Sixty percent of hips (43 of 71) had confirmed SCFE or pre-slip based on the presence of hip pain and MRI changes, and these patients underwent in situ pinning. Three independent experienced observers reviewed MR images of the 71 hips and agreed on the presence of a juxtaphyseal bright-fluid signal suggesting bone marrow edema in these 43 hips with SCFE, and absence MRI changes in the remaining 28 hips. The same three experienced observers and two inexperienced observers, including a general radiologist and an orthopaedic surgery resident, blindly assessed the radiographs for the presence or absence of the peritubercle lucency sign, without information about the diagnosis. Diagnostic accuracy measures including sensitivity, specificity, PPV, and NPV were evaluated. Intraobserver and interobserver agreements were calculated using kappa statistics.

RESULTS

The overall accuracy of the peritubercle lucency sign on radiographs was 94% (95% CI 91 to 96), sensitivity was 97% (95% CI 95 to 99), specificity was 89% (95% CI 90 to 96), PPV was 93% (95% CI 90 to 96), and NPV was 95% (95% CI 92 to 99). All accuracy parameters were greater than 85% for the five observers, regardless of experience level. Intraobserver agreement was perfect (kappa 1.0), and interobserver agreement was excellent for the peritubercle lucency sign on radiographs across the five observers (kappa 0.81 [95% CI 0.73 to 0.88]). The reliability was excellent for experienced observers (kappa 0.88 [95% CI 0.74 to 1.00]) and substantial for inexperienced observers (kappa 0.70 [95% CI 0.46 to 0.93]), although no difference was found with the numbers available (p = 0.18).

CONCLUSIONS

The peritubercle lucency sign on radiographs is accurate and reliable for the early diagnosis of SCFE compared with MRI as the gold standard. Improving the early diagnosis of SCFE may be possible with increased awareness, high clinical suspicion, and a scrutinized evaluation of radiographs including an assessment of the peritubercle lucency sign.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Smaller Epiphyseal Tubercle and Larger Peripheral Cupping in Slipped Capital Femoral Epiphysis Compared with Healthy Hips: A 3-Dimensional Computed Tomography Study

BACKGROUND

The inner surface of the capital femoral epiphysis is important for growth plate stability. However, abnormalities of epiphyseal morphology associated with the pathogenesis of slipped capital femoral epiphysis (SCFE) remain poorly understood. This study compares the 3-dimensional anatomy of the epiphyseal tubercle and peripheral cupping in hips with SCFE and normal hips.

METHODS

We created 3-dimensional models of the capital femoral epiphysis with use of computed tomography (CT) imaging from 51 patients with SCFE and 80 subjects without hip symptoms who underwent CT because of abdominal pain. The height, width, and length of the epiphyseal tubercle and the peripheral cupping were measured and normalized by the epiphyseal diameter and presented as a percentage. We used analysis of variance for the comparison of the measurements between SCFE and control hips after adjusting for age and sex.

RESULTS

Compared with normal hips, hips with mild SCFE had smaller mean epiphyseal tubercle height (0.9% ± 0.9% compared with 4.4% ± 0.4%; p = 0.006) and length (32.3% ± 1.8% compared with 43.7% ± 0.8%; p < 0.001). The mean epiphyseal tubercle height was also smaller in hips with moderate (0.6% ± 0.9%; p = 0.004) and severe SCFE (0.3% ± 0.8%; p < 0.001) compared with normal hips. No differences were observed for measurements of epiphyseal tubercle height and length between SCFE subgroups. The mean peripheral cupping was larger in hips with mild (16.3% ± 1.0%; p < 0.001), moderate (16.4% ± 1.1%; p < 0.001), and severe SCFE (18.9% ± 0.9%; p < 0.001) overall and when assessed individually in all regions compared with normal hips (10.6% ± 0.5%).

CONCLUSIONS

Hips with SCFE have a smaller epiphyseal tubercle and larger peripheral cupping compared with healthy hips. A smaller epiphyseal tubercle may be a predisposing morphologic factor or a consequence of the increased shearing stress across the physis secondary to the slip. Increased peripheral growth may be an adaptive response to instability as other stabilizers (i.e., epiphyseal tubercle and anterior periosteum) become compromised with slip progression. Future studies are necessary to determine the biomechanical basis of our morphologic findings.

A Novel Classification System for Slipped Capital Femoral Epiphysis Based on the Radiographic Relationship of the Epiphyseal Tubercle and the Metaphyseal Socket

Recent studies have suggested that the epiphyseal tubercle serves as a fulcrum for rotation in slipped capital femoral epiphysis (SCFE). However, radiographic evidence of the rotational mechanism is limited. In this study, we describe a novel radiographic staging system for SCFE based on the anatomic relationship between the epiphyseal tubercle and the metaphyseal socket.

Methods

We reviewed the cases of 469 patients with SCFE who were treated at our institution between 2000 and 2017. SCFE was classified according to our proposed staging system using the preoperative lateral radiograph. Normal hips were considered to be Stage 0. In Stage 1, the tubercle is concentric within its metaphyseal socket, which is enlarged and may present peritubercle radiolucency. In Stage 2, there is evidence of eccentricity of the tubercle, which remains in contact with the posterior wall of the socket. In Stage 3, the tubercle and metaphyseal lucency reach the posterior cortex of the femoral neck. A complete dislodgment of the tubercle from the metaphysis is present in Stage 4. Intra- and interobserver agreement, and correlations between the staging system and the traditional classifications of severity, stability, and chronicity, were estimated.

Results

The distribution by stage was as follows: 2% of the hips were classified as Stage 0, 19% were Stage 1, 48% were Stage 2, 15% were Stage 3, and 16% were Stage 4. The staging system had excellent intraobserver (κ = 0.89 [95% confidence interval (CI) = 0.83 to 0.96]) and interobserver agreement (κ = 0.87 [95% CI = 0.72 to 1.00]). There was a high correlation between the staging system and SCFE severity as assessed by the Southwick angle (r = 0.77 [95% CI = 0.73 to 0.82]; p < 0.001). There was a moderate correlation between the staging system and the Loder classification of stability (r = 0.55 [95% CI = 0.48 to 0.62]; p < 0.001) and a negligible correlation with the classification of chronicity (r = 0.19 [95% CI = 0.10 to 0.28]; p < 0.001).

Conclusions

The proposed staging system for SCFE is highly reliable and correlates well with the severity of SCFE based on the degree of displacement, with moderate correlation shown for stability. This new staging system helps in understanding the rotational mechanism of SCFE, warranting further investigation to determine its clinical application.

Clinical Relevance

The novel classification has the potential for the identification of hips that demonstrate subtle SCFE or are at pre-slip stage, or those at risk for osteonecrosis of the femoral head, failure of fixation, or slip progression.

Relative contribution of epiphyseal tubercle and peripheral cupping to capital femoral epiphysis stability during daily activities

Epiphyseal tubercle and peripheral cupping can influence the development of slipped capital femoral epiphysis (SCFE) and Cam morphology. During normal skeletal growth, epiphyseal tubercle shrinks while the peripheral cupping grows. We hypothesized that epiphyseal tubercle act as the primary stabilizer of the head-neck junction at early stages and this role is gradually transferred to epiphyseal cupping as the tubercle shrinks and cupping grows. From a cohort of 80 boys and girls (8-15 years old) with normal hips, CT scans of 5 subjects corresponding to minimum, 25th percentile, median, 75th percentile and maximum relative tubercle and cupping height were used to develop 3D finite element models. In vivo measured hip loads were used to study load sharing between the tubercle and peripheral cupping under combined and uniaxial loads exerted on femoral head during a range of daily activities. Lower epiphyseal tubercle height, larger epiphyseal cupping height and bigger differences in tubercle and cupping heights were strongly associated with increased epiphyseal cupping to epiphyseal tubercle stress ratios (R²  > 0.7). We found lower peripheral cupping stresses relative to the tubercle (cupping to tubercle stress ratio <1) in hips with larger tubercle and smaller cupping. The relative decreases in tubercle size along with increased in peripheral cupping in our models gradually shifted the load distribution to higher stresses in the periphery compared to the epiphyseal tubercle area (cupping to tubercle stress ratio >1). Both tubercle and cupping play a substantial role in sharing the generated stresses across the head-neck junction under all tested loading conditions. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1571-1579, 2019.

Evolving Understanding of and Treatment Approaches to Slipped Capital Femoral Epiphysis

PURPOSE OF REVIEW

To review slipped capital femoral epiphysis (SCFE), with a focus on new insights into its etiology and evolving methods of operative fixation.

RECENT FINDINGS

The epiphyseal tubercle and its size during adolescence are paramount to understanding the mechanism of SCFE. In chronic stable SCFE, the epiphysis rotates about the tubercle protecting the lateral epiphyseal vessels from disruption. In an acute unstable SCFE, the tubercle displaces, increasing the risk of osteonecrosis, also known as avascular necrosis (AVN). Intraoperative stability suggests that stable and unstable SCFE based on ambulation may be inaccurate. For stable SCFE, in situ pinning remains the most accepted treatment for mild slips with delayed symptomatic femoroacetabular impingement (FAI) management. Treatment of moderate to severe stable slips with realignment osteotomy leads to less femoral deformity and potentially better outcomes. However, it has a higher risk of complications, including AVN and chondrolysis. Our knowledge of the etiology for SCFE is evolving. The optimal technique for operative treatment of moderate to severe SCFE is controversial and varies by center. Well-controlled studies of these patients are needed to understand the best treatment for this difficult problem. Furthermore, increasing the awareness about SCFE is paramount to allow for early recognition and treatment of deformity at its early stages and avoiding severe SCFE deformity which has been associated with worse long-term outcomes.