The Utility of False-Profile Radiographs for the Detection of Osteoarthritis Progression in Acetabular Dysplasia

False-Profile Radiograph Sourcil-Edge and Bone-Edge Measurements Correlate to Different Weightbearing Regions of the Acetabulum: A 3-Dimensional Analysis

BACKGROUND

The acetabular sourcil is commonly interpreted as a reliable radiographic representation of the weightbearing dome of the acetabulum, despite limited modern data. Assessment of weightbearing acetabular coverage has been described using both the sourcil edge and bone edge as anatomic landmarks, leading to confusion and potential misguidance in surgical decision-making and thus compromised patient outcomes.

PURPOSE/HYPOTHESIS

The purpose of this study was to characterize the 3-dimensional (3D) anatomic correlates of the sourcil-edge and bone-edge radiographic measurements on false-profile radiographs. It was hypothesized that the sourcil edge would represent anterolateral coverage and the bone edge would represent anterior coverage.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 80 hips were grouped by large or small differences between bone-edge and sourcil-edge anterior center-edge angles, based on upper and lower quartiles of discrepancy. Three-dimensional surface mesh models and digitally reconstructed radiographs were generated from hip computed tomography scans. Sourcil-edge and bone-edge anterior center-edge angles were identified on digitally reconstructed radiographs and registered to the 3D models with fiducial markers. Intersections of bone-edge and sourcil-edge projection lines with the acetabular rim were obtained from the 3D models.

RESULTS

The bone-edge and sourcil-edge projections intersected the acetabular rim at clockface means of 2:05 ± 0:22 and 1:12 ± 0:25, respectively. The 3D models consistently demonstrated that, in both large- and small-discrepancy groups, the sourcil edge corresponded to the acetabular area just posterior to the anterior inferior iliac spine (AIIS) projection, and the bone edge corresponded to the weightbearing region inferior to the AIIS. Additionally, in large-discrepancy hips, the bone edge corresponded to more prominent acetabular coverage in the region inferomedial to the AIIS when compared with the small-discrepancy hips.

CONCLUSION

On false-profile radiographs, the sourcil edge corresponds to superior femoral head coverage, and the bone edge corresponds to anterosuperior coverage. Radiographs with a large discrepancy between sourcil-edge and bone-edge measurements demonstrate acetabular rim prominence in the region of the AIIS.

CLINICAL RELEVANCE

Characterizing the anatomic weightbearing regions of the acetabulum represented on false-profile radiographs facilitates improved clinical and intraoperative decision-making in hip preservation surgery, including acetabuloplasty and periacetabular osteotomy.

Range of Motion Measurements of the Hip Joint Are Useful in Screening for Acetabular Dysplasia in Healthy Young Japanese Women

The purpose of this study is to clarify whether a hip range of motion (ROM) measurement is useful in screening for early hip osteoarthritis with acetabular dysplasia (AD). Subjects were 58 healthy Japanese women volunteers (21.1 ± 0.7 (20 - 22)). We evaluated a total of 116 hip joints in these 58 cases. Sharp angle and centeredge angle were 44.1° ± 3.1° (37.0° - 51.5°) and 30.7°± 6.2° (19.5° - 47.0°), respectively. AD was present in 47.4%, but there were no severe cases. First, we compared the ROM of the hip joints with AD (AD group) and without AD (control group) according to the Mann-Whitney U test. Extension angles and external rotation angles in the AD group were significantly smaller than in the control group (18.9°± 6.1° VS. 22.1°± 4.2°, p= 0.01636, 26.3°± 8.9° VS. 34.1°± 8.8°, p= 0.001362, respectively). Next, we evaluated the following factors associated with AD by logistic regression analysis after adjustment for age: flexion, extension and internal and external rotation angles of the hip joint. As a result, internal rotation and external rotation were extracted as related factors. The area under the ROC curve was determined to have a moderate accuracy (0.72996). Cut off values of internal rotation and external rotation angles were 50 degrees and 35 degrees, respectively. Our findings suggest that ROM measurement of the internal and external rotation angles would be useful as a screening for AD in healthy young Japanese women without symptoms.

Bone morphology and physical characteristics of the pro-cyclist hip joint

PURPOSE

This study aimed to investigate the radiographic findings for the hip joint and hip range of motion in professional cyclists, and to determine their bone morphology and physical characteristics. The effects of physical characteristics on athletic performance were examined in terms of metabolic efficiency using simulation analysis.

METHODS

We performed a case-control research study on 22 hips in 11 male professional cyclists (average age 28.5, height 1.73 m, weight 77.6 kg). Thirty hips in 15 healthy male volunteers were selected as controls. As radiographic evaluations, acetabular dysplasia was assessed on standardized radiographs. During physical evaluations, the hip range of motion was examined. We used simulation analysis to investigate the metabolic efficiency in the different cycling forms.

RESULTS

The radiographic evaluations showed a significant difference in the incidence of acetabular dysplasia (p = 0.01): 59% (13/22 hips) in the pro-cyclist group versus 10% (3/30 hips) in the control group. The physical evaluations revealed significant differences in the hip internal rotation angle (p = 0.01), with greater ranges of internal rotation in the pro-cyclist group versus the control group. The simulation analyses showed that metabolism was reduced in the cycling form with hip internal rotation, especially in the lower extremities.

CONCLUSIONS

Pro-cyclists showed a high frequency of acetabular dysplasia and superior hip internal rotation. According to the cycling model analyses, hip internal rotation allowed pedaling with reduced metabolic power.

Management of chondral and osteochondral lesions of the hip : A comprehensive review

Chondral and osteochondral lesions encompass several acute or chronic defects of the articular cartilage and/or subchondral bone. These lesions can result from several different diseases and injuries, including osteochondritis dissecans, osteochondral defects, osteochondral fractures, subchondral bone osteonecrosis, and insufficiency fractures. As the cartilage has a low capacity for regeneration and self-repair, these lesions can progress to osteoarthritis. This study provides a comprehensive overview of the subject matter that it covers. PubMed, Scopus and Google Scholar were accessed using the following keywords: "chondral lesions/defects of the femoral head", "chondral/cartilage lesions/defects of the acetabulum", "chondral/cartilage lesions/defects of the hip", "osteochondral lesions of the femoral head", "osteochondral lesions of the acetabulum", "osteochondral lesions of the hip", "osteochondritis dissecans," "early osteoarthritis of the hip," and "early stage avascular necrosis". Hip osteochondral injuries can cause significant damage to the articular surface and diminish the quality of life. It can be difficult to treat such injuries, especially in patients who are young and active. Several methods are used to treat chondral and osteochondral injuries of the hip, such as mesenchymal stem cells and cell-based treatment, surgical repair, and microfractures. Realignment of bony anatomy may also be necessary for optimal outcomes. Despite several treatments being successful, there is a lack of head-to-head comparisons and large sample size studies in the current literature. Additional research will be required to provide appropriate clinical recommendations for treating chondral/osteochondral injuries of the hip joint.

Can we determine anterior hip coverage from pelvic anteroposterior radiographs? A study of patients with hip dysplasia

PURPOSE

Insufficient coverage causes hip joint instability and results in hip pain. Anterior hip coverage can be determined on both pelvic anteroposterior (AP) radiographs and false profile (FP) radiographs. Four parameters are commonly used to determine the anterior coverage on pelvic AP radiographs: the crossover index, crossover sign, anterior wall index (AWI), and rule of thirds. This study aims to clarify the relationship between these 4 parameters on AP radiographs and the anterior center edge angle (ACEA) on FP radiographs.

METHODS

In this study, 53 patients who underwent periacetabular osteotomy for hip dysplasia at our center between July 2020 and October 2020 were retrospectively reviewed. Four parameters on AP radiographs and the ACEA on FP radiographs before surgery and 6 months after surgery were measured and compared for each hip.

RESULTS

Upon examining the 53 hips in this study, there was no correlation between either the crossover index and the ACEA (P = 0.66) or the crossover sign before surgery. The postoperative correlation between the crossover index and the ACEA was weak (r = 0.36, P = 0.007), and that between the crossover sign and the ACEA was moderate (r = 0.41, P = 0.003). There was a weak correlation between the AWI and ACEA both before (r = 0.288, P = 0.036) and after (r = 0.349, P = 0.011) the operation. Evaluation of the anterior coverage by the rule of thirds was also not consistent when determining the anterior coverage with the ACEA.

CONCLUSION

Anterior coverage on AP radiographs is largely inconsistent with ACEA on FP radiographs, especially before the surgery. It is recommended to take FP radiographs routinely for determining anterior hip coverage.

Femoro-Epiphyseal Acetabular Roof (FEAR) Index and Anterior Acetabular Coverage Correlate With Labral Length in Developmental Dysplasia of the Hip

PURPOSE

The aim of this study was to evaluate the association between labral length and radiographic parameters of lateral and anterior acetabular coverage and the femoro-epiphyseal acetabular roof (FEAR) index in patients with developmental dysplasia of the hip (DDH).

METHODS

We retrospectively analyzed data from patients with DDH who visited our hip joint clinic for the first time due to hip symptoms. DDH presence was defined as a lateral center-edge angle (LCEA) of ≤25°. The labral lengths on the anterior and lateral sides were measured on central axial and central coronal slices of T1-weighted magnetic resonance imaging, respectively. The Pearson correlation coefficients (r) and simple linear regression analyses were performed to determine the association of the lateral and anterior labral lengths with the radiographic parameters, including the LCEA, acetabular roof obliquity, FEAR index, anterior wall index, and vertical center anterior angle.

RESULTS

This study included 88 patients, with a mean age of 39.6 ± 11.8 years. There were 65 women and 23 men. The lateral and anterior labral lengths correlated with all parameters of dysplasia. Specifically, the lateral labral length had a strong positive correlation with the FEAR index (R = 0.65, P < .001). The anterior labral length had a strong negative correlation with the anterior wall index (R = -0.66, P < .001).

CONCLUSIONS

The lateral labral length had a strong positive correlation with the FEAR index. Furthermore, the anterior labral length had a correlation with the anterior dysplasia.

LEVEL OF EVIDENCE

Level III, retrospective cross-sectional study.

Can the Femoro-Epiphyseal Acetabular Roof (FEAR) Index Be Used to Distinguish Dysplasia from Impingement?

BACKGROUND

Classifying hips with structural deformity on the spectrum from impingement to dysplasia is often subjective and frequently inexact. Currently used radiographic measures may inaccurately predict a hip's morphological stability in borderline hips. A recently described radiographic measure, the Femoro-Epiphyseal Acetabular Roof (FEAR) index, has demonstrated an ability to predict stability in the borderline hip. This measure is attractive to clinicians because procedures can be used on the basis of a hip's pathomechanics. This study was designed to further validate and characterize the FEAR index in a skeletally immature population, in hips with dysplasia/femoroacetabular impingement (FAI), and in asymptomatic hips.

QUESTIONS/PURPOSES

(1) What are the characteristics of the FEAR index in children and how does the index change with skeletal maturation? (2) How does the FEAR index correlate with clinical diagnosis and surgical treatment in a large cohort of symptomatic hips and asymptomatic controls? (3) How does the FEAR index correlate with clinical diagnosis in the borderline hip (lateral center-edge angle [LCEA] 20°-25°) group?

METHODS

A total of 220 participants with symptomatic investigational hips with a clinical diagnosis of dysplasia or FAI between January 2008 and January 2018 were retrospectively collected from the senior author's practice. Investigational hips were excluded if they had any femoral head abnormalities preventing LCEA measurement (for example, Perthes disease), Tönnis osteoarthritis grade greater than 1, prior hip surgery, or prior femoral osteotomy. In the 220 participants, 395 hips met inclusion criteria. Once exclusion criteria were applied, 15 hips were excluded due to prior hip surgery or prior femoral osteotomy, and 12 hips were excluded due to femoral head deformity. A single hip was then randomly selected from each participant, resulting in 206 investigational hips with a mean age of 13 ± 3 years. Between January 2017 and December 2017, 70 asymptomatic control participants were retrospectively collected from the senior author's institutional trauma database. Control hips were included if the AP pelvis film had the coccyx centered over the pubic symphysis and within 1 to 3 cm of the superior aspect of the symphysis. Control hips were excluded if there was any fracture to the pelvis or ipsilateral femur or the participant had prior hip/pelvis surgery. After exclusion criteria were applied, 16 hips were excluded due to fracture. One hip was then randomly selected from each participant, resulting in 65 control hips with a mean age of 16 ± 8 years. Standardized standing AP pelvis radiographs were used to measure the FEAR index, LCEA, and Tönnis angle in the investigational cohort. Standardized false-profile radiographs were used to measure the anterior center-edge angle (ACEA) in the investigational cohort. Two blinded investigators measured the FEAR index with an intraclass correlation coefficient of 0.92 [95% CI 0.84 to 0.96]. Question 1 was answered by comparing the above radiographic measures in age subgroups (childhood: younger than 10 years; adolescence: 10 to 14 years old; maturity: older than 14 years) of dysplastic, FAI, and control hips. Question 2 was answered by comparing the radiographic measures in all dysplastic, FAI, control hips, and a subgroup of operatively or nonoperatively managed dysplasia and FAI hips. Question 3 was answered by comparing the radiographic measures in borderline (LCEA 20°-25°) dysplastic, FAI, and control hips.

RESULTS

The FEAR index was lower in older dysplastic of hips (younger than 10 years, 6° ± 9°; 10 to 14 years, 4° ± 10°; older than 14 years, 5° ± 9°; p < 0.001) and control hips (younger than 10 years, -6° ± 5°; 10 to 14 years, -15° ± 4°; older than 14 years, -16° ± 7°; p < 0.001). The diagnosis and age groups were independently correlated with the FEAR index (p < 0.001). The relationship between the FEAR index and diagnosis remained consistent in each age group (p = 0.11). The FEAR index was higher in all dysplastic hips (mean 5° ± 10°) than in asymptomatic controls (mean -13° ± 7°; p < 0.001) and FAI hips (mean -10° ± 11°; p < 0.001). Using -1.3° as a cutoff for FAI/control hips and dysplastic hips, 81% (112 of 139) of hips with values below this threshold were FAI/control, and 89% (117 of 132) of hips with values above -1.3° were dysplastic. The receiver operator characteristics area under the curve (ROC-AUC) was 0.91. Similarly, the FEAR index was higher in borderline dysplastic hips than in both asymptomatic borderline controls (p < 0.001) and borderline FAI hips (p < 0.001). Eighty-nine percent (33 of 37) of hips with values below this threshold were FAI/control, and 90% (37 of 41) of hips with values above -1.3° were dysplastic. The ROC-AUC for borderline hips was 0.86.

CONCLUSION

The FEAR index was associated with the diagnosis of hip dysplasia and FAI in a patient cohort with a wide age range and with varying degrees of acetabular deformity. Specifically, a FEAR index greater than -1.3° is associated with a dysplastic hip and a FEAR index less than -1.3° is associated with a hip displaying FAI. Using this reliable, developmentally based radiographic measure may help hip preservation surgeons establish a correct diagnosis and more appropriately guide treatment.

LEVEL OF EVIDENCE LEVEL

III, diagnostic study.

Assessing precision and accuracy of false-profile hip radiographs

PURPOSE

The purpose of this study was to assess the accuracy and precision of pelvic rotation in existing false-profile (FP) radiographs and to devise a method to improve accuracy and precision of FP radiographs.

METHODS

An imaging protocol was developed to obtain FP radiographs. Pelvic rotation was calculated using the described method for FP images obtained in the 3 months prior to and after implementation of this protocol. Student's t-test and variance ratio tests were used to determine differences in mean and variance of pelvic rotation between the 2 cohorts. Pelvic rotation calculation methodology was validated by using fluoroscopic C-arm to obtain AP and rotated images of 10 osteologic pelvises. The ratio of the distance between hip centres of each rotated image and AP image (W_P/W) was determined. Intraclass coefficient correlation (ICC) was used to verify the relationship between W_P/W and pelvic rotation.

RESULTS

Mean W_P/W was 0.47 (95% CI, 0.45-0.49). There were significant differences in mean pelvic rotation of the pre-protocol group (47.6°; 95% CI, 45.6-49.5°) and the post-protocol group (60.0°; 95% CI, 58.7-61.3°, p < 0.0001). Additionally, there was a significantly wider distribution of measurements in the pre-protocol group (SD = 7.9°) compared to the post-protocol group (SD = 5.7°, p = 0.0035).

CONCLUSIONS

The quality of FP radiographs obtained in the clinical setting may be inconsistent. Standardising FP imaging produces more accurate images. Appropriate FP radiographs should have a distance between hip centres that is approximately 0.5 times the same distance found on an anteroposterior (AP) radiograph.

Assessment of the young adult hip joint using plain radiographs

Radiographic examination remains the mainstay of the initial assessment of the young adult hip; however, common parameters are required to assist in the formation of accurate diagnoses and appropriate management plans. This paper aims to summarise the most important aspects of the assessment of plain radiographs performed on the young adult hip joint.

Is lateral acetabular rotation sufficient to correct anterolateral deficiency in periacetabular reorientation osteotomy? A CT-Based simulation study

BACKGROUND

Residual acetabular deficiency after periacetabular reorientation osteotomy can result in suboptimal outcome. The optimal algorithm of acetabular fragment correction to achieve normal anterolateral acetabular coverage is not well characterized. The aim of this study was to determine the prevalence of residual anterolateral deficiency after lateral acetabular rotation and to evaluate the ability of additional sagittal and axial rotation of the acetabulum to normalize the acetabular coverage in periacetabular osteotomy.

METHODS

We performed computed tomography-based simulated periacetabular osteotomy on 85 patients (85 hips) with hip dysplasia. The acetabular fragment was rotated laterally to achieve a lateral center-edge angle (CEA) of 30°. For hips with residual anterolateral deficiency, which were identified based on the reference interval of the anterior CEA, the acetabulum was further rotated in the sagittal or axial direction in 5-degree increments from 5° to 20°, and the ability of these two manoeuvres to restore a normal anterior CEA was assessed.

RESULTS

After lateral acetabular rotation, 16 hips (19%) had residual anterolateral deficiency, 67 hips (79%) had normal acetabular coverage, and 2 hips (2.4%) had acetabular overcoverage. A preoperative anterior CEA <37° predicted residual deficiency (sensitivity, 94%; specificity, 81%). Additional anterior sagittal rotation was more effective than posterior axial rotation in normalizing the anterior CEA, while minimizing the decrease in posterior CEA. The highest number of hips with normal anterior and posterior CEA was noted at 10° sagittal rotation (81%), which was followed by 15° sagittal rotation (63%).

CONCLUSIONS

Normal anterolateral coverage was achieved in 79% of patients after rotating the acetabulum laterally. However, lateral rotation of the acetabulum may be insufficient to correct the anterolateral deficiency in patients with an anterior CEA of <37°. In them, additional 10°-15° anterior sagittal rotation may be appropriate to achieve sufficient anterolateral coverage while retaining posterolateral coverage.

Does Acetabular Coverage Vary Between the Supine and Standing Positions in Patients with Hip Dysplasia?

BACKGROUND

Although variation in physiologic pelvic tilt may affect acetabular version and coverage, postural change in pelvic tilt in patients with hip dysplasia who are candidates for hip preservation surgery has not been well characterized, and its clinical importance is unknown.

QUESTIONS/PURPOSES

The aim of this study was to determine (1) postural changes in sagittal pelvic tilt between the supine and standing positions; (2) postural changes in the acetabular orientation and coverage of the femoral head between the supine and standing positions; and (3) patient demographic and morphologic factors associated with sagittal pelvic tilt.

METHODS

Between 2009 and 2016, 102 patients underwent pelvic osteotomy to treat hip dysplasia. All patients had supine and standing AP pelvic radiographs and pelvic CT images taken during their preoperative examination. Ninety-five patients with hip dysplasia (lateral center-edge angle < 20°) younger than 60 years old were included. Patients with advanced osteoarthritis, other hip disease, prior hip or spine surgery, femoral head deformity, or inadequate imaging were excluded. Sixty-five patients (64%) were eligible for participation in this retrospective study. Two board-certified orthopaedic surgeons (TT and MF) investigated sagittal pelvic tilt, spinopelvic parameters, and acetabular version and coverage using pelvic radiographs and CT images. Intra- and interobserver reliabilities, evaluated using the intraclass correlation coefficient (0.90 to 0.98, 0.93 to 0.99, and 0.87 to 0.96, respectively), were excellent. Demographic data (age, gender, and BMI) were collected by medical record review. Sagittal pelvic tilt was quantified as the angle formed by the anterior pelvic plane and a z-axis (anterior pelvic plane angle). Using a 2D-3D matching technique, we measured the change in sagittal pelvic tilt, acetabular version, and three-dimensional coverage between the supine and standing positions. We correlated sagittal pelvic tilt with demographic and CT measurement parameters using Pearson's or Spearman's correlation coefficients.

RESULTS

Although functional pelvic tilt varied widely among individuals, the pelvis of patients with hip dysplasia tilted posteriorly from the supine to the standing position (mean APP angle 8° ± 6° versus 2° ± 7°; mean difference -6°; 95% CI, -7° to -5°; range -17° to 4.1°; p < 0.001; paired t-test).The pelvis tilted more than 5° posteriorly from the supine to the standing position in 39 patients (60%), and the change was greater than 10° in 12 (18%). In the latter subgroup of patients, the mean acetabular anteversion angle increased (22° ± 5° versus 27° ±5°; mean difference 5°; 95% CI, 4°-6°; p < 0.001) and the mean anterosuperior acetabular sector angle notably deceased from the supine to the standing position (91° ± 11° versus 77° ± 14°; mean difference -14°; 95% CI, -17° to -11°; p < 0.001; paired t-test). Postural change in pelvic tilt was not associated with any of the studied demographic or morphologic parameters, including patient age, gender, BMI, and acetabular version and coverage.

CONCLUSIONS

On average, the pelvis tilted posteriorly from the supine to the standing position in patients with hip dysplasia, resulting in increased acetabular version and decreased anterosuperior acetabular coverage in the standing position. Thus, assessment with a supine AP pelvic radiograph may overlook changes in acetabular version and coverage in weightbearing positions. We recommend assessing postural change in sagittal pelvic tilt when diagnosing hip dysplasia and planning hip preservation surgery. Further studies are needed to determine how postural changes in sagittal pelvic tilt affect the biomechanical environment of the hip and the clinical results of acetabular reorientation osteotomy.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Can the FEAR Index Be Used to Predict Microinstability in Patients Undergoing Hip Arthroscopic Surgery?

BACKGROUND

Atraumatic hip instability, or microinstability, is a challenging diagnosis for clinicians to make. Several radiographic parameters have been proposed to help identify patients with instability as a means to direct treatment. The Femoro-epiphyseal Acetabular Roof (FEAR) index was recently offered as a parameter to predict instability in a borderline dysplastic population.

PURPOSE

To evaluate the FEAR index in a series of predominantly nondysplastic patients undergoing hip arthroscopic surgery to determine if it can accurately predict patients with diagnosed microinstability at the time of surgery.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

A consecutive series of 200 patients undergoing hip arthroscopic surgery were evaluated for microinstability intraoperatively. Microinstability was diagnosed based on previously published criteria. Retrospectively, radiographic parameters were measured including the lateral center edge angle of Wiberg (LCEA), Tönnis angle, physeal scar angle, and FEAR index. Patients were excluded if they previously had any type of bony procedures performed, underwent prior open hip surgery or total hip arthroplasty of the ipsilateral hip, had osteoarthritis (Tönnis grade >1), or had any radiographic features of moderate-to-severe acetabular dysplasia including an LCEA <18°.

RESULTS

After applying exclusion criteria, 167 hips in 150 patients were analyzed. Based on an intraoperative assessment, 96 hips (57.5%) were considered stable, and 71 hips (42.5%) had signs of microinstability (unstable group). Patients in the unstable group had fewer radiographic findings of femoroacetabular impingement and higher rates of borderline dysplasia. All 4 measured angles were found to have excellent interobserver agreement. The FEAR index was significantly more positive in the unstable group compared with the stable group (-7.8° vs -11.3°, respectively; P = .004). A more positive FEAR index was also found in patients meeting intraoperative criteria for instability, with the exception of chondral wear pattern. Unstable nondysplastic patients (LCEA ≥25°, Tönnis angle ≤10°) also were found to have higher FEAR index values (-9.0° vs -12.0°, respectively; P = .012). A FEAR index cut-off of -5.0° was associated with a specificity of 92.4% and accuracy of 69.4% for predicting instability in a nondysplastic population.

CONCLUSION

The FEAR index was validated to improve the recognition of unstable patients preoperatively across a population with both borderline dysplastic and nondysplastic features.