James D. Bomar

Development and prevalence of femoroacetabular impingement-associated morphology in a paediatric and adolescent population: A CT study of 225 patients

We investigated the development of CT-based bony radiological parameters associated with femoroacetabular impingement (FAI) in a paediatric and adolescent population with no known orthopaedic hip complaints. We retrospectively reformatted and reoriented 225 abdominal CTs into standardised CT pelvic images with neutral pelvic tilt and inclination (244 female and 206 male hips) in patients ranging from two to 19 years of age (mean 10.4 years). The Tönnis angle, acetabular depth ratio, lateral centre-edge angle, acetabular version and α-angle were assessed. Acetabular measurements demonstrated increased acetabular coverage with age and/or progressive ossification of the acetabulum. The α-angle decreased with age and/or progressive cortical bone development and resultant narrowing of the femoral neck. Cam and pincer morphology occurred as early as ten and 12 years of age, respectively, and their prevalence in the adolescent patient population is similar to that reported in the adult literature. Future aetiological studies of FAI will need to focus on the early adolescent population.

Spectrum of Radiographic Femoroacetabular Impingement Morphology in Adolescents and Young Adults: An EOS-Based Double-Cohort Study

BACKGROUND Symptomatic femoroacetabular impingement is a known prearthritic condition. Impingement morphology is poorly defined in the adolescent population. The purpose of this study was to document the prevalence of radiographic impingement morphology in adolescents with no symptomatic hip problems. METHODS Ninety anteroposterior images of the hip in forty-five consecutive adolescents with scoliosis met the inclusion criteria. Sex distribution was equal. The second cohort (ninety hips) was an age-matched group with no scoliosis. None had symptomatic hip problems. Images were analyzed for coxa profunda, protrusio acetabuli, Tönnis angle, anteroposterior alpha angle, center-edge angle, acetabular crossover, ischial spine sign, and neck-shaft angle. RESULTS Of the 180 hips, 92.8% demonstrated at least one parameter suggesting impingement morphology, whereas 52.2% showed at least two signs. Evidence of coxa profunda was seen in 81.7% of the hips, while a negative Tönnis angle was seen in 31.1% and a center-edge angle indicative of acetabular overcoverage was seen in 15%. An acetabular crossover sign was detected in 27.2% of the hips, while an abnormal anteroposterior alpha angle was found in 5.6% of the hips in male patients and 6.7% of the hips in female patients. Statistical analysis revealed that abnormal alpha angles (p = 0.029), crossover signs (p = 0.029), and ischial spine signs (p = 0.026) were more common in the cohort without scoliosis, and coxa profunda was more common in females (p = 0.034). CONCLUSIONS There was a high prevalence of radiographic impingement morphology beyond the spectrum of normal in this double-cohort study of adolescents. Femoroacetabular impingement remains a dynamic problem, and we caution against relying only on the use of hard-set static radiographic parameters when evaluating femoroacetabular impingement. This study raises the important question of what morphologic characteristics should be defined as abnormal, when at least one finding of impingement morphology is noted in such a large segment of the population. On the basis of the normative data obtained, reference values for radiographic parameters of femoroacetabular impingement morphology should be redefined. Normal values for a Tönnis angle were between -8° and 14°, the upper limit of the center-edge angle was 44°, and the normal values for femoral neck-shaft angle were between 121° and 144°. Surgical indications should be tailored to physical examination findings and not radiographic findings alone.

Hip impingement in slipped capital femoral epiphysis: a changing perspective

BackgroundFemoroacetabular impingement (FAI) as a result of slipped capital femoral epiphysis (SCFE) has recently gained significant attention. Seen as an intermediate step toward the development of early osteoarthritis, symptomatic FAI develops in SCFE patients who have residual hip deformity characterized by relative posterior and medial displacement of the capital femoral epiphysis, leading to an anterolateral prominence of the metaphysis which abuts on the acetabular rim. This results in a decreased range of hip motion as well as progressive labral damage and articular cartilage injury, which cause symptoms of FAI. All degrees of slips from mild to severe can develop impingement.MethodsThe existing literature on the subject was thoroughly reviewed and all levels of studies that have made any meaningful changes to clinical practice were considered.ResultsBased on the literature review, current practice trends, and our own institutional practice pattern, all treatment options for SCFE in the impingement era have been presented with an open discussion regarding potential benefits and limitations.ConclusionsSeveral surgical options exist for the SCFE patient who develops FAI. These are largely determined by the degree of deformity present and severity of the initial slip. Extraarticular (intertrochanteric, base of the neck) as well as subcapital osteotomies can be utilized with a goal of restoring proximal femoral anatomy in order to minimize the effect of the anterolateral prominence in more severe deformities. Patients with milder deformities can undergo osteochondroplasty of the femoral head and neck to remove impinging structures via either an open or arthroscopic approach. Also, proximal femoral osteotomy and open head–neck recontouring can be combined. Finally, patients who develop pain very early after in situ pinning must also be examined for potential iatrogenic screw-head impingement as a source of their pain and decreased hip motion, in addition to abnormalities in the proximal femoral anatomy. There are many centers that are approaching acute unstable SCFE patients as well as the more displaced stable cases with open reduction techniques that seem to be demonstrating good mid-term results. The goal of treatment is to improve patient function, alleviate hip pain, and to delay or prevent the development of early degenerative changes in adolescents and young adults. Prospective multi-center studies will be necessary so as to determine what methods work best in treatment and delay the onset and progression of osteoarthritis.Level of evidenceV.

EOS Imaging of the Human Pelvis: Reliability, Validity, and Controlled Comparison with Radiography

BACKGROUND The EOS technique represents a unique imaging modality combining low radiation exposure with high image quality. As its applications for pelvic imaging may increase with time, we performed a pilot study to evaluate the validity and reliability of this technique for the assessment of gross pelvic and acetabular morphology. METHODS Consecutive conventional and EOS radiographs of a human cadaveric pelvis were made in 5° intervals of sagittal tilt and axial rotation (range, -15° to 15° for each). Six measurements were made on each image: (1) the vertical distance between the sacrococcygeal joint and the upper border of the pubic symphysis, (2) the horizontal distance between the midpoints of these structures, (3) the distance between the anterior superior iliac spines, (4) the distance between the facets of S1, (5) the Sharp angle, and (6) the Tönnis angle. Coxa profunda and crossover signs were also evaluated. The findings of the two imaging techniques were correlated with each other and with true linear measurements made on the cadaveric pelvis. All measurements were performed by two independent observers, and one observer repeated all measurements to assess reproducibility. Both observers were blinded to the true linear measurements made on the pelvis. RESULTS There was a strong correlation between the results of the conventional and EOS radiography (Pearson correlation coefficient, 0.644 to 0.998), and both modalities had high intraobserver and interobserver reproducibility (intraclass correlation coefficient, 0.795 to 1.000). Intraobserver and interobserver agreement on the presence of coxa profunda were both 100%. Intraobserver agreement (96.2%) and interobserver agreement (92.3%) on the presence of the crossover sign were marginally lower. Linear measurements differed significantly between the two modalities because of distortion caused by magnification effects in the conventional radiographic imaging (p < 0.05). CONCLUSIONS The EOS imaging technique proved reliable for the assessment of gross pelvic and acetabular morphology, and it may be an alternative to current radiography for primary imaging in the pediatric population and potentially in adults as well. This study did not evaluate the ability of EOS imaging to detect subtle radiographic anatomic abnormalities.

Pelvic Apophyseal Avulsion Fractures: A Retrospective Review of 228 Cases.

Background: The aim of this study was to assess the patient demographics, epidemiology, mechanism of injury, and natural history of pelvic apophyseal avulsion fractures. Methods: A retrospective records review of imaging and clinical documentation was performed for patients diagnosed with pelvic apophyseal avulsion fractures at our institution from 2007 to 2013. Patient’s Risser score, triradiate status, fracture location, size, and displacement were recorded based on initial injury radiographs. Further clinical and radiographic chart review was utilized to determine mechanism of injury, presence of multiple/bilateral injuries, nonunion, chronic pain, as well as any surgical interventions performed. Results: We identified 225 patients diagnosed with 228 apophyseal avulsion fractures with mean age of 14.4 years. Males represented 76% of the patients. Anterior inferior iliac spine (AIIS) avulsions were the most common, representing 49% of all avulsion fractures, followed by anterior superior iliac spine (30%), ischial tuberosity (11%), and iliac crest (10%). The most common mechanism of injury was sprinting/running (39%) followed by kicking (29%), but the mechanism varied by fracture type with 50% of AIIS avulsions caused by kicking. Multiple pelvic fractures were identified in 6% of patients. Pain >3 months out from initial injury was present in 14% of all patients and AIIS avulsion fractures were 4.47 times more likely to have chronic pain. Five nonunions were identified, 4 of which were ischial tuberosity avulsions. Initial fracture displacement >20 mm increased the risk of nonunion by 26 times. Surgical treatment was indicated in 3% of cases. Conclusions: In this series, nearly all pelvic avulsion fractures (97%) were managed successfully with a conservative approach. Contrary to prior studies, AIIS avulsions represented half of the avulsion fractures. AIIS and ischial tuberosity fractures are at increased risk of developing future pain and nonunions, respectively. Patients and families need to be counseled about this possibility because future intervention may be necessary. Level of Evidence: Level IV—therapeutic.

The role of capital realignment versus in situ stabilization for the treatment of slipped capital femoral epiphysis.

Introduction: Slipped capital femoral epiphysis (SCFE) can be treated by a variety of methods with the traditional method of in situ pin fixation being most commonly used. More recently, the Modified Dunn (Mod. Dunn) procedure consisting of capital realignment has been popularized as a treatment method for SCFE, particularly for more severe cases. Over the last 5 years, our institution has selectively used this method for more complex cases. The purpose of this article is to evaluate the differences between these 2 treatment methods in terms of avascular necrosis (AVN) rate, reoperation rate, and complication rate. Methods: Eighty-eight hips that were surgically treated for SCFE between July 2004 and June 2012 met our inclusion criteria. The in situ fixation group included 71 hips, whereas 17 hips were anatomically reduced with the Mod. Dunn procedure. Loder classification, severity, acuity, complication rate, and reoperation rate were determined for the 2 cohorts. The &khgr;2 analysis was performed to evaluate the relationship between the treatment method and outcome. Results: As expected, stable slips did well with in situ pinning with no cases of AVN, even in more severe slips. Ten stable slips were treated with the Mod. Dunn approach and 2 (20%) developed AVN. Unstable slips were more difficult to treat with 3 of the 7 hips stabilized in situ developing AVN (43%). Two of the 7 unstable slips treated by the Mod. Dunn procedure developed AVN (29%). The other outcomes studied (reoperation rate and complication rate) were not significantly related to the surgical treatment method (P=0.732 and 0.261, respectively). Conclusions: In situ pinning remains a safe and predictable method for treatment of stable SCFE with no AVN noted, even in severe slips. Attempts to anatomically reduce stable slips led to severe AVN in 20% of cases, thus this treatment approach should be considered with caution. Treatment of unstable slips remains problematic with high AVN rates noted whether treated by in situ fixation or capital realignment (Mod. Dunn). Level of Evidence: Level III retrospective comparative study.

Lateral Center-edge Angle on Conventional Radiography and Computed Tomography

BackgroundLateral center-edge angle (LCEA), originally described and validated on AP radiographs, has been used increasingly in CT-based studies, but it is unclear whether the measure is reliable and whether it correlates with that on AP radiographs.Question/PurposesWe therefore determined: (1) the interobserver and intraobserver reliabilities of the LCEA measured on AP radiographs; (2) the interobserver and intraobserver reliabilities of the LCEA measured on CT scans; and (3) the intermodality correlation of the LCEA between CT and AP radiography.MethodsWe reviewed the AP radiographs and CT scans of 22 patients treated for slipped capital femoral epiphyses. CT scans were reoriented to a neutral pelvic tilt and inclination. Three evaluators measured the LCEA on the unaffected hip on the AP and CT coronal images that corresponded to the center of the acetabulum on the axial slice.ResultsWe found an interobserver intraclass correlation (ICC) analysis of 0.84 for the AP radiographs and 0.88 for the CT scans. The intraobserver ICC for the AP radiographs was 0.96, and for the CT scans 0.98. The intermodality ICC for the CT scans and AP radiographs was 0.79, with a lower bound of 0.61 and an upper bound of 0.87.ConclusionsOur data suggest the LCEA measured on a CT scan is reliable and correlates with the LCEA on AP radiographs.

Is the Acetabulum Retroverted in Slipped Capital Femoral Epiphysis

BackgroundRecent biplanar radiographic studies have demonstrated acetabular retroversion and increased superolateral femoral head coverage in hips with slipped capital femoral epiphysis (SCFE), seemingly divergent from earlier CT-based studies suggesting normal acetabular version.Question/purposesWe therefore asked: Are there differences in (1) acetabular version at the superior ¼ of the acetabular dome (AVsup), (2) acetabular version at the center of the femoral head (AVcen), and (3) superolateral femoral head coverage (lateral center-edge angle [LCEA]) among affected SCFE hips, unaffected hips, and normal controls?MethodsWe identified 32 patients with SCFE who underwent CT between 2007 and 2012. Twenty-three met our inclusion criteria. Seventy-six age- and sex-matched normal patients comprised the control group. Pelvic rotation, tilt, and inclination were corrected on each CT. AVsup, AVcen, and LCEA were measured.ResultsThe mean AVsup of the affected hips (−1.71°) demonstrated retroversion compared to the unaffected hips and the control group; the mean AVsup of the unaffected hips was similar to that of the normal controls. Mean AVcen was similar among the three groups. The LCEA was higher in affected and unaffected SCFE hips than in the control group (34.3° versus 34.5° versus 28.9°, respectively), but we found no difference between affected and unaffected hips.ConclusionsOur data suggest an association of superior acetabular retroversion and increased superolateral femoral head coverage in SCFE. Whether this represents a primary abnormal morphology or a secondary pathologic response remains unclear. Further studies investigating the role of acetabular morphology in SCFE and its implications for development of symptomatic femoroacetabular impingement are warranted.

Reliability of plain radiographic parameters for developmental dysplasia of the hip in children

IntroductionFew studies have evaluated the reliability and reproducibility of the femoral neck-shaft angle (NSA), center-edge angle (CEA), and acetabular index (AI) in young children with developmental dysplasia of the hip (DDH). We wanted to determine whether these parameters could be used reliably by practitioners.MethodsFifty radiographs from 21 children with DDH were reviewed. Analysis was performed by three observers, at two time periods. The intra- and inter-observer reliability for each measure was assessed.ResultsAt time period one, we noted a “high” level of agreement between observers when measuring the NSA, a “low” level when measuring the CEA, and a “moderate” level when measuring the AI. At time period two, we noted a “very high” level of agreement between observers when measuring the NSA and a “high” level when measuring the CEA and AI. When comparing the measurements of observer 1 at the two different time periods, we noted nearly “very high” agreement when measuring the NSA, a “moderate” agreement when measuring the CEA, and a “high” agreement for the AI. In comparing the measurements of observer 2, we noted “very high” agreement for the NSA and “high” agreement for the CEA and AI. In comparing the measurements for observer 3, we noted nearly “very high” agreement for the NSA, nearly “high” agreement for the CEA, and “high” agreement for the AI.ConclusionIt is difficult to reliably measure three-dimensional pelvic morphology on a frontal plane radiograph, especially when important pelvic landmarks have yet to ossify.

The hip antero-superior labral tear with avulsion of rectus femoris (HALTAR) lesion: does the SLAP equivalent in the hip exist?

Background The purpose of this report is to describe a new lesion, the “Hip Antero-superior Labral Tear with Avulsion of Rectus femoris (HALTAR)”. This injury may be seen in both adolescent and skeletally mature athletes and shares several characteristics with the “Superior Labral tear from Anterior to Posterior (SLAP)” lesion in the shoulder. Methods We present a case example, as well as a detailed anatomic description of the pathological condition. Results As the rectus femoris crosses two joints it is exposed to substantial forces during muscle contraction. Considering the peri-articular origin of the reflected head at the superior aspect of the acetabular rim, a powerful eccentric contraction of the rectus femoris muscle or traction related to sudden knee flexion may cause an avulsion injury of the rectus femoris as well as a concomitant labral tear. Conclusions A strain injury of the rectus femoris muscle, which is common in young athletic patients, may cause a concomitant tear of the acetabular labrum. Therefore, we recommend further diagnostic work-up in cases with prolonged hip pain and impaired hip function following an AIIS injury in order to identify any associated peri- and intra-articular damage. In our experience these patients seldom need aggressive surgical management.