Development of the acetabulum and hip: computed tomography analysis of the axial plane

Roles of combined femoral and acetabular anteversion in pathological changes of hip dysplasia and hip reconstructive surgery

Combined femoral and acetabular anteversion is the sum of femoral and acetabular anteversion, representing their morphological relationship in the axial plane. Along with the increasing understanding of hip dysplasia in recent years, numerous scholars have confirmed the role of combined femoral and acetabular anteversion in the pathological changes of hip dysplasia. At present, the reconstructive surgery for hip dysplasia includes total hip replacement and redirectional hip preservation surgery. As an important surgery index, combined femoral and acetabular anteversion have a crucial role in these surgeries. Herein, we discuss the role of combined femoral and acetabular anteversion in pathological changes of hip dysplasia, total hip replacement, and redirectional hip preservation surgery.

Hip Joint Stability during and after Femoral Lengthening in Congenital Femoral Deficiency

BACKGROUND

Hip stability remains a major preoccupation during femoral lengthening in Congenital Femoral Deficiency (CFD). We aimed to review hip stability in Paley type 1a CFD patients undergoing femoral lengthening.

METHODS

A total of 33 patients with unilateral CFD, who were treated between 2014 and 2023, were retrospectively reviewed. In 20/33 cases (60.6%) the SUPERhip preparatory surgery was performed at a mean age of 4.3 years (range 2.7-8.1). The femoral lengthening using an external fixator was performed at a mean age of 7.8 years (range 4.3-14.3).

RESULTS

All patients presented with a stable hip joint after preparatory surgery and during femoral lengthening. Six cases of hip instability at a mean of 637 days after the external fixator removal were observed (range 127 to 1447 days). No significant differences between stable and unstable hips were noted for (1) Center-Edge Angle: 23.7 vs. 26.1 deg; (2) Acetabular Inclination: 12.8 vs. 11.7 deg; and (3) Ex-Fix Index: 35.6 days/cm vs. 42.4 days/cm; p > 0.05. Late hip instability was related to Coxa Vara and decreased femoral antetorsion before lengthening.

CONCLUSIONS

Late hip joint instability in Paley type 1a CFD patients may occur long after femoral lengthening despite hip morphology appearing to be normal on radiograms before and at the end of femoral lengthening. Coxa Vara, femoral torsional deformity, and posterior acetabular deficiency might be risk factors for hip instability.

How Often Do Patients Presenting With Severe Adolescent Idiopathic Scoliosis Have Underlying Hip Dysplasia?

INTRODUCTION

Adolescent idiopathic scoliosis radiographic screening will often include the hips. The purpose of this study is to evaluate the prevalence of hip dysplasia by lateral center edge angle (LCEA) on scoliosis radiographs in patients presenting with severe range (>45 deg) idiopathic curves.

METHODS

We reviewed 200 consecutive patients (400 hips) with idiopathic scoliosis with major coronal curves ≥45 degrees between October 2009 and October 2022. The presenting scoliosis radiograph PA were reviewed for the following variables: major coronal curve direction, coronal balance, and lateral center edge angles. An LCEA value ≤18 was considered dysplastic. To assess potential measurement variability related to parallax of the scoliosis radiographs, the intermodality intraclass correlation coefficient (ICC) was measured from a subset of 20 hip LCEA values from patients with both scoliosis and pelvis radiographs.

RESULTS

A total of 200 patients [mean age: 13.6 (1.8) years; Female: 79%] were reviewed. The mean major curve (SD) was 58.6 degrees (11.4 deg). Overall 19% (37/200) patients or 11% (43/400) of hips had hip dysplasia. Of the dysplastic hips, 16% (6/43, P <0.001) were bilateral and 57% (21/43, P =0.04) were right sided. There was no association between dysplastic hip laterality and ipsilateral or contralateral coronal balance ( P =0.26) or curve direction ( P =0.49). The interobserver ICC for assessment of LCEA on scoliosis radiographs was 0.85, and the intermodality ICC between pelvic and scoliosis radiographs was 0.78.

CONCLUSION

Hip dysplasia was present in 19% of patients presenting with large major curves, and many of these patients had right sided hip dysplasia. There was no association between hip dysplasia laterality and the patient's major curve direction or coronal balance. There was good intermodality reliability (ICC=0.78) between LCEA values in patients who had both scoliosis and pelvis radiographs, and good inter-rater reliability between raters. Radiographic interpretation of adolescent idiopathic scoliosis should focus not only on the description of the curve and ruling out underlying segmentation anomalies but should also include critical assessment of the hips to exclude co-existing hip dysplasia.

LEVEL OF EVIDENCE

Therapeutic study-level IV.

Definition of Tweener: Consensus Among Experts in Treating Early-onset Scoliosis

BACKGROUND

The term "Tweener" is colloquially used to refer to early-onset scoliosis (EOS) patients whose age and development make them candidates for multiple surgical options. The purpose of this study was to establish expert consensus on a definition to formally characterize the Tweener population.

METHODS

A 3-round survey of surgeons in an international EOS study group was conducted. Surgeons were provided with various patient characteristics and asked if each was part of their definition for Tweener patients. Responses were analyzed for consensus (≥70%), near-consensus (60% to 69%), and no consensus (<60%).

RESULTS

Consensus was reached (89% of respondents) for including chronological age in the Tweener definition; 8 to 10 years for females and 9 to 11 years for males. Surgeons agreed for inclusion of Sanders score, particularly Sanders 2 (86.0%). Patients who have reached Sanders 4, postmenarche, or have closed triradiate cartilage should not be considered Tweeners. Bone age range of 8 years and 10 months to 10 years and 10 months for females (12 y for males) could be part of the Tweener definition.

CONCLUSIONS

This study suggests that the Tweener definition could be the following: patients with open triradiate cartilage who are not postmenarche and have not reached Sanders 4, and if they have one of the following: Sanders 2 or chronological age 8 to 10 years for females (9 to 11 y for males) or bone age 8 years and 10 months to 10 years and 10 months for females (12 y for males). This definition will allow for more focused and comparative research on this population.

LEVEL OF EVIDENCE

Level V-expert opinion.

The Anatomical Position of Graf’s Standard Plane and Its Relationship With Pelvic Morphology: A Computed Tomography-Based Study

Objective

The Graf method is the most widely used ultrasonographic method for evaluating developmental dysplasia of the hip (DDH), and it relies on a set standard plane. However, no previous reports have discussed the detailed anatomical location of the plane. The aim of this study was to evaluate the exact anatomical position of Graf’s standard plane in the pelvis and to ascertain the correlation between this position and pelvic morphology in children without abnormal pelvic morphology.

Methods

We retrospectively assessed the pelvic CT data of 32 children (64 hips) aged three to five years without abnormal pelvic morphology and measured the pelvic winging and acetabular anteversion and coverage. We defined the coronal plane that passed through the center of the bilateral femoral head as plane A. We determined that Graf’s standard plane could be approximated by rotating plane A until the outer wall of the ilium was parallel to the sagittal plane, and we defined this as plane A′. AA′ was defined as the angle from plane A to plane A′ on the sagittal plane. The anterior rotational angle (clockwise, viewing from the right side) was measured as the positive AA′. Moreover, we measured the pelvic rotation, acetabular anteversion, and acetabular coverage and evaluated the correlation between AA′ and these morphological parameters.

Results

The average AA′ was -8.27° and AA′ had a significant correlation with acetabular anteversion (Spearman’s ρ=0.40**, p<0.01).

Conclusions

We found that Graf's standard plane, as determined by the CT scan, tilts slightly posteriorly. This information may be useful in improving the ease of ultrasonographic examination of DDH.

Outcomes for the Arthroscopic Treatment of Femoroacetabular Impingement Syndrome With Acetabular Retroversion: A 3D Computed Tomography Analysis

BACKGROUND

Increased attention has been directed toward the acetabular morphology in the management of patients with femoroacetabular impingement syndrome (FAIS). Whether acetabular version influences patient-reported outcomes remains poorly understood.

PURPOSE

To use computed tomography (CT)-based 3-dimensional (3D) bone models to (1) quantify acetabular version in patients with FAIS, (2) compare acetabular version on 3D bone models with current plain radiographic parameters, and (3) explore the relationship between the magnitude of acetabular version and minimum 2-year clinical outcomes after hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Three-dimensional models of the pelvis and femur were generated by semiautomated segmentation and aligned to a standard coordinate system. Acetabular version was quantified at the 3-o'clock position, and 3 groups were identified: acetabular retroversion (AR; <15°), normal acetabular version (NV; 15°-25°), and acetabular anteversion (AA; >25°). Patient demographic characteristics, plain radiographic parameters, and clinical outcomes were analyzed, including the Hip Outcome Score-Activities of Daily Living, Hip Outcome Score-Sports Subscale, modified Harris Hip Score (mHHS), International Hip Outcome Tool (iHOT-12), and visual analog scale (VAS) for pain and satisfaction.

RESULTS

Preoperative CT scans were acquired in 105 consecutive patients before hip arthroscopy for FAIS, of which 84 (80.0%) completed minimum 2-year patient-reported outcomes. The mean ± SD age and body mass index of patients were 33.9 ± 12.6 years and 26.0 ± 5.4, respectively; 70.2% were female. The number of patients and the mean central acetabular version within each group were as follows: AR (n = 12; 11.3°± 2.7°), NV (n = 56; 20.7°± 2.9°), and AA (n = 16; 28.5°± 2.7°). Posterior wall sign was the only plain radiographic parameter that was significantly more observed in the AR group than in the other 2 groups. At minimum 2-year follow-up, significant between-group differences in the mHHS, iHOT-12, and VAS for pain and satisfaction (P < .05) were appreciated, while post hoc analysis with Bonferroni correction (P < .0167) found lower scores on the mHHS, iHOT-12, and VAS for pain and satisfaction in patients with AR as compared with NV. Lower scores on the VAS for satisfaction were reported in patients with AR when compared with AA (P = .006) but not on the mHHS (P = .023), iHOT-12 (P = .032), or VAS for pain (P = .072).

CONCLUSION

Traditional plain radiographic indices to describe AR, including crossover sign and ischial spine sign, were not reliable in defining AR according to 3D models derived from CT scans. Only the posterior wall sign was observed in a higher proportion in the AR group. Patients with AR demonstrated inferior outcomes when compared with patients with NV and AA after hip arthroscopy for FAIS.

Proximal femoral epiphyseal spurs and their association with acetabular labral tears on MRI in symptomatic patients

OBJECTIVE

Femoral epiphyseal spurs are developmental projections that form at the edge of the physis. Although considered incidental, their association with acetabular labral tears has never been examined. Our aim was to assess the prevalence of femoral epiphyseal spurs in symptomatic patients with mechanical hip pain and explore if they are associated with labral tears on MRI.

MATERIALS AND METHODS

Hip MRI scans performed on a Siemens 3 T MRI using femoroacetabular impingement protocol were retrospectively reviewed. All patients were referred by orthopaedic surgeons for mechanical hip pain. Two musculoskeletal radiologists blinded to initial reports evaluated MRI images for the presence of an epiphyseal spur and acetabular labral changes. A consensus was achieved on all cases by the two readers. The association between epiphyseal spurs and labral changes was assessed using Fisher's exact test.

RESULTS

A total of 115 patients (178 hip MRI scans) were reviewed; the mean age was 28.8 years (SD 7.1). There were 52 females (45.2%) and 63 males (54.8%). There were 115 hips with labral tears (64.6%). Fourteen hips (7.8%) in ten patients (8.7%) demonstrated epiphyseal spurs and all of them showed labral tears (100%). There was statistically significant association between epiphyseal spurs and labral tears on MRI (p value = 0.0024).

CONCLUSION

Femoral epiphyseal spurs were observed in 8.7% of our defined patient population, and all patients with epiphyseal spurs demonstrated labral tears. Epiphyseal spurs should be documented on imaging reports due to their potential association with labral tears. Future research is needed to further delineate and guide management of these entities.

Labral tears with axial plane disorders

OBJECTIVES

This study aims to determine if there is an axial plane coverage insufficiency in patients with symptomatic labral tears compared to the contralateral asymptomatic side and healthy control subjects.

PATIENTS AND METHODS

This retrospective study was conducted between December 2017 and January 2019. Thirty patients (21 males, 9 females; mean age 28 years; range, 20 to 36 years) operated due to unilateral symptomatic acetabular labral tears secondary to femoroacetabular impingement were evaluated. Twenty asymptomatic patients (13 males, 7 females; mean age 27±9 years; range, 19 to 36 years) were included in the control group. The relationship between acetabular morphology and labral tear was investigated with the comparison of unilateral symptomatic hips with contralateral asymptomatic hips and the control group by using radiological parameters on plain radiographs and computed tomography.

RESULTS

When the patient group symptomatic side was compared to the control group, acetabular anteversion angle (A A A) and alpha (α) angle were higher, while posterior acetabular sector angle and horizontal acetabular sector angle were lower. When the asymptomatic side was compared to the control group, AAA was higher in the patient group. There was no difference between the symptomatic and asymptomatic sides in the patient group; the symptomatic side yielded a higher α; angle.

CONCLUSION

Posterior axial plane coverage deficiency in combination with cam deformity (increased α angle) seems to play a role in the pathogenesis of symptomatic acetabular labral tears, even creating a side-to-side difference in some individuals.

Acetabular Version Increases During Adolescence Secondary to Reduced Anterior Femoral Head Coverage

BACKGROUND

Acetabular version influences joint mechanics and the risk of impingement. Cross-sectional studies have reported an increase in acetabular version during adolescence; however, to our knowledge no longitudinal study has assessed version or how the change in version occurs. Knowing this would be important because characterizing the normal developmental process of the acetabulum would allow for easier recognition of a morphologic abnormality.

QUESTIONS/PURPOSES

To determine (1) how acetabular version changes during adolescence, (2) calculate how acetabular coverage of the femoral head changed during this period, and (3) to identify whether demographic factors or hip ROM are associated with acetabular development.

METHODS

This retrospective analysis of data from a longitudinal study included 17 volunteers (34 hips) with a mean (± SD) age of 11 ± 2 years; seven were male and 10 were female. The participants underwent a clinical examination of BMI and ROM and MRIs of both hips at recruitment and at follow-up (6 ± 2 years). MR images were assessed to determine maturation of the triradiate cartilage complex, acetabular version, and degree of the anterior, posterior, and superior acetabular sector angles (reflecting degree of femoral head coverage provided by the acetabulum anteriorly, posteriorly and superiorly respectively). An orthopaedic fellow (GG) and a senior orthopaedic resident (PJ) performed all readings in consensus; 20 scans were re-analyzed for intraobserver reliability. Thereafter, a musculoskeletal radiologist (KR) repeated measurements in 10 scans to test interobserver reliability. The intra- and interobserver interclass correlation coefficients for absolute agreement were 0.85 (95% CI 0.76 to 0.91; p < 0.001) and 0.77 (95% CI 0.70 to 0.84), respectively. All volunteers underwent a clinical examination by a senior orthopaedic resident (PJ) to assess their range of internal rotation (in 90° of flexion) in the supine and prone positions using a goniometer. We tested investigated whether the change in anteversion and sector angles differed between genders and whether the changes were correlated with BMI or ROM using Pearson's coefficient. The triradiate cartilage complex was open (Grade I) at baseline and closed (Grade III) at follow-up in all hips.

RESULTS

The acetabular anteversion increased, moving caudally further away from the roof at both timepoints. The mean (range) anteversion angle increased from 7° ± 4° (0 to 18) at baseline to 12° ± 4° (5 to 22) at the follow-up examination (p < 0.001). The mean (range) anterior sector angle decreased from 72° ± 8° (57 to 87) at baseline to 65° ± 8° (50 to 81) at the final follow-up (p = 0.002). The mean (range) posterior (98° ± 5° [86 to 111] versus 97° ± 5° [89 to 109]; p = 0.8) and superior (121° ± 4° [114 to 129] to 124° ± 5° [111 to 134]; p = 0.07) sector angles remained unchanged. The change in the anterior sector angle correlated with the change in version (rho = 0.5; p = 0.02). The change in version was not associated with any of the tested patient factors (BMI, ROM).

CONCLUSIONS

With skeletal maturity, acetabular version increases, especially rostrally. This increase is associated with, and is likely a result of, a reduced anterior acetabular sector angle (that is, less coverage anteriorly, while the degree of coverage posteriorly remained the same). Thus, in patients were the normal developmental process is disturbed, a rim-trim might be an appropriate surgical solution, since the degree of posterior coverage is sufficient and no reorientation osteotomy would be necessary. However, further study on patients with retroversion (of various degrees) is necessary to characterize these observations further. The changes in version were not associated with any of the tested patient factors; however, further study with greater power is needed.

LEVEL OF EVIDENCE

Level II, prognostic study.

Age-related change and gender differences in pelvic morphology of healthy children

BACKGROUND

An increasing number of studies about the hip joint morphology with childhood-specific hip diseases have been reported. But there have been few reports on pelvic morphology of healthy children. The purpose of this study was to assess the pelvic morphology of healthy children in detail and clarify the age-related change and gender difference of it.

METHODS

We retrospectively assessed the pelvic morphology of 97 healthy children (3-18 years old) using their pelvic computed tomography (CT) data. Superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA) as the parameters of pelvic winging, and acetabular anteversion and anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), superior acetabular sector angle (SASA) as the parameters of acetabular coverage, are measured. Pearson's correlation coefficient was used for examining the correlation between the each measurement and the age of cases. Multiple linear regression analysis was performed to investigate the possibility of association of age and sex with each measurement.

RESULTS

In female, it was found that IIA, AASA, PASA, SASA were significantly correlated with the age of the cases. And in male, SIA, IIA, IPA, AASA, PASA were significantly correlated with the age. Multiple linear regression analysis revealed the significant difference of the distribution between males and females was observed in IIA, IPA, AVcen, PASA, and these measurements were lager for female.

CONCLUSIONS

In this study, we revealed the age-related change and gender difference of the pelvic morphology of healthy children, and this could be useful information in evaluating the hip with what appears to be an abnormal acetabular anteversion and acetabular inclination in the patients with childhood specific hip disease. Additionally, it will also help us to make operation plans pertaining to the hip.

Periacetabular quadruple osteotomy of the pelvis in older children: computed tomography scan analysis of acetabular retroversion and anterior overcoverage of the hip, preventing femoral acetabular impingement

The periacetabular quadruple osteotomy of the pelvis (QOP), with the osteotomy of ischial spine to release the sacrospinal ligament, is reserved for older children with low potential of remodeling. Different parameters were studied with computed tomography (CT) scan before (pre-OH) and after surgery (post-OH) and for nonoperated hip (NOH). The study determined an optimal method to avoid retroversion and excessive anterior coverage. Fifteen QOP were performed in 13 patients, ranging in age from 10 to 15 years. The morphology of pelvis was analyzed with a CT scan before the surgery and 2 years after. Pathologies were Legg-Calve-Perthes (seven hips) and dysplasia (eight hips). The two-dimensional exam measured the acetabular index, the coverage, and the version of the acetabulum. The three-dimensional images measured the frontal lateral inclinations of the lips and the sagittal anterior acetabular inclination. The mean anterior acetabular index was 50.4° (NOH), 56° (pre-OH), and 58.7° (post-OH). The posterior acetabular index was 48.5° (NOH), 52.2° (pre-OH), and 40° (post-OH). The anterior coverage angle was 37.1° in (pre-OH), 27.6° (post-OH), and 30.1° (NOH). The posterior coverage was 20.4° (pre-OH), 17.2° (post-OH), and 12.4° (NOH). The acetabular version was 2.1° (pre-OH), 8.3° (post-OH), and 2.5° (NOH). The anterolateral lip inclination was 50.3° (pre-OH), 35.3° (post-OH), and 43.8° (NOH). The posterolateral lip inclination was 56.7° (pre-OH), 43.7° (post-OH), and 55.8° (NOH). The anterior acetabular inclination was 21.3° (pre-OH), 15.6° (post-OH), and 18° (NOH). The QOP enabled significant range of coverage of the hip in adolescents in whom the potential of remodeling is very low. External rotation related to figure-of-four should be omitted, whereas the maneuver to be applied, preventing the anterior impingement and decrease of the posterior coverage, should be performed by placing the acetabular fragment below the iliac bone, with a lateral inclination in the frontal plane similar to a steering wheel movement. This maneuver preserves comparable morphology of the OH with NOH and avoids retroversion with the excessive anterior coverage responsible for pain and early osteoarthritis.

Ischemic femoral head osteonecrosis in a piglet model causes three dimensional decrease in acetabular coverage

Legg-Calve-Perthes disease (LCPD) is a childhood form of ischemic osteonecrosis marked by development of severe femoral head deformity and premature osteoarthritis. The pathogenesis of femoral head deformity has been studied extensively using a piglet model of ischemic osteonecrosis, however, accompanying acetabular changes have not been investigated. The purpose of this study was to determine if acetabular changes accompany femoral head deformity in a well-established piglet model of LCPD and to define the acetabular changes using three dimensional computed tomography (3-D CT) and modeling. Twenty-four piglets were surgically induced with ischemic osteonecrosis on the right side. The contralateral hip was used as control. At 8 weeks postoperative, pelvi were retrieved and imaged with CT. Custom software was used to measure acetabular morphologic parameters on 3-D CT images. Moderate to severe femoral head deformities were present in all animals. Acetabula with accompanying femoral head deformity had a significant decrease in acetabular version and tilt (p < 0.001) and in coverage angle in the superior, posterior, and inferior quadrants (p < 0.05). These findings indicate that the development of femoral head deformity following ischemic osteonecrosis produces specific and predictable changes to the shape of the acetabulum. Acetabular changes described in patients with LCPD were observed in the piglet model. This model may serve as a valuable tool to elucidate the relationship between femoral head and acetabular deformities. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1173-1177, 2018.

Can Computed Tomography Accurately Measure Acetabular Anterversion in Developmental Dysplasia of the Hip? Verification and Characterization Using 3D Printing Technology

BACKGROUND

One of the important pathologic changes in developmental dysplasia of the hip (DDH) is increased acetabular version angle (AA). Reasonable correction for excessive AA is an important step in the treatment of DDH, making accurate AA measurement very crucial. However, the results of different AA measurement methods vary. Thus, this study aimed to compare the difference in AA measurements between 2-dimensional computed tomography (2D-CT) and 3-dimensional computed tomography (3D-CT) in children with DDH and to identify the AA degree in children with DDH to guide treatment.

METHODS

AA was measured by 2D-CT and 3D-CT in 186 children with DDH, and the measurement results were compared with the physical measurement result in the 3D-printed pelvis (3D-PP) model. The 3D-PP was a 1:1 model identical to the human pelvis. All patients were unilaterally affected.

RESULTS

The results of AA measurement through 2D-CT, 3D-CT, and 3D-PP of normal hips were 14.0±6.6, 11.9±5.3, and 11.9±3.4 degrees, respectively, whereas those of the dislocated hips were 24.9±8.9, 19.8±5.2, and 19.5±4.3 degrees, respectively. In both the normal and dislocated hip groups, the results between 2D-CT and 3D-CT was significantly different (P<0.05), but there was no difference between the results of 3D-CT and 3D-PP (P>0.05). The AA of the normal and dislocated hips as measured by 3D-PP was 11.9±3.6 and 19.6±4.3 degrees, respectively, with statistically significant difference (P<0.05). In the dislocated hips, a significant positive correlation was found between age and AA (r=0.756, P<0.05) and between AA and degree of dislocation (r=0.837, P<0.05).

CONCLUSIONS

3D-CT is more accurate than 2D-CT for AA measurement, and compared with normal hips, AA in dislocated hips increased by ∼7.7 degrees on average. AA increases as age and degree of dislocation increase.

LEVEL OF EVIDENCE

Level II.

Acetabular overcoverage in the horizontal plane: an underdiagnosed trigger of early hip arthritis. A CT scan study in young adults

INTRODUCTION

Acetabular overcoverage promotes hip osteoarthritis causing a pincer-type femoroacetabular impingement. Acetabular coverage in the horizontal plane is usually poorly defined in imaging studies and may be misdiagnosed. The goal of this study was to analyze the role of acetabular overcoverage measured in the frontal plane and in the horizontal plane by CT scan and to determine its relationship with other anatomic features in the onset of hip arthritis in young adults.

MATERIALS AND METHODS

We compared prospectively CT scans from two groups of adults of 55 years or younger: the patient group (n = 30) consisted of subjects with diagnosis of early hip arthritis (Tönnis Grade I or II) and the control group (n = 31) consisted of subjects with healthy hips. Two independent observers analyzed centre edge angle (CEA), acetabular anteversion angle (AAA), anterior sector acetabular angle (AASA), posterior sector acetabular angle (PASA), horizontal acetabular sector angle (HASA), femoral anteversion angle (FAVA), alpha angle (AA), and Mckibbin Instability Index (MI).

RESULTS

Angles measuring the acetabular coverage on the horizontal plane (AASA, PASA and, HASA) were significantly higher in the patient group (p < 0.001, p = 0.03 and p < 0.001, respectively). Pearson's correlation coefficient showed a positive correlation between CEA and HASA in patients (r = 0.628) and in controls (r = 0.660). However, a high CEA (> 35º) was strongly associated with a high HASA (> 160º) in patients (p = 0.024) but not in controls (p = 0.21), suggesting that pincer should be simultaneously present in the horizontal and frontal plane to trigger hip degeneration. No significant association was detected between a high alpha angle (> 60º) and a high CEA (> 35º suggesting that a mixed pincer-cam aetiology was not prevalent in our series. Multivariate regression analysis showed the most significant predictors of degenerative joint disease were HASA (p = 0.008), AA (p = 0.048) and ASAA (p = 0.004).

CONCLUSIONS

Acetabular overcoverage in the horizontal plane plays an important role in the onset of early hip arthritis. Considering that this condition is usually underdiagnosed, we suggest the anterior sector acetabular angle, the posterior sector acetabular angle, and the horizontal acetabular sector angles be routinely included in decision-making algorithms in hip conservative surgery to better define hips-at-risk of developing early hip osteoarthritis.

Acetabular Version Increases After Closure of the Triradiate Cartilage Complex

BACKGROUND

Although the etiology of primary femoroacetabular impingement (FAI) is considered developmental, the underlying pathogenic mechanisms remain poorly understood. In particular, research identifying etiologic factors associated with pincer FAI is limited. Knowledge of the physiologic growth patterns of the acetabulum during skeletal maturation might allow conclusions on deviations from normal development that could contribute to pincer-related pathomorphologies.

QUESTIONS/PURPOSES

In a population of healthy children, we asked if there were any differences related to skeletal maturation with regard to (1) acetabular version; (2) acetabular depth/width ratio; and (3) femoral head coverage in the same children as assessed by MRIs obtained 1 year apart.

METHODS

We prospectively compared 129 MRIs in 65 asymptomatic volunteers without a known hip disorder from a mixed primary/high school population (mean age, 12.7 years; range, 7-16 years). All participants underwent two MRI examinations separated by a minimum interval of 1 year. Based on the status of the triradiate cartilage complex (open versus closed [TCC]), all hips were allocated to the following groups: "open-open" = open TCC at both MRIs (n = 45 hips [22 bilateral]); "open-closed" = open TCC at initial and closed TCC at followup MRI (n = 26 hips [13 bilateral]); and "closed-closed" group = closed TCC at both MRIs (n = 58 hips [29 bilateral]). We assessed acetabular version in the axial plane at five different locations (5, 10, 15, 20 mm below the acetabular dome and at the level of the femoral head) as well as three-dimensional (3-D) acetabular depth/width ratio and 3-D femoral head coverage on six radial MRI sequences oriented circumferentially around the femoral neck axis. Using analysis of variance for multigroup comparisons with Bonferroni adjustment for pairwise comparisons, we compared the results between the initial and followup MRI examinations and among the three groups.

RESULTS

Acetabular version was increased in hips of the "open-closed" group at the followup MRI compared with the initial MRI at 5 mm (-6 ± 4.6 [95% confidence interval {CI}, -7.6 to -3.6] versus -1 ± 5.0 [95% CI, -3.3 to 0.7]; p < 0.001), 10 mm (0 ± 4.0 [95% CI, -1.6 to 2.1] versus 7 ± 4.6 [95% CI, 4.4-8.7]; p < 0.001), and 15 mm (8 ± 5.0 [95% CI, 6.1-10.2] versus 15 ± 4.6 [95% CI, 13.3-17.4]; p < 0.001) below the acetabular dome. Acetabular version did not change between the initial and followup MRI in the "open-open" and "closed-closed" groups. Independently of the groups, acetabular version was increased in all hips with a fused TCC compared with hips with an open TCC (mean difference measured at 5 mm below the acetabular dome at initial MRI examination: 2° ± 5.9° [95% CI, 0.2°-3.4°] versus -9° ± 4.4° [95% CI, -9.9° to -7.8°]; p < 0.001; at followup MRI examination: 1° ± 5.7° [95% CI, 0.1°-2.7°] versus -9° ± 3.8° [95% CI, -10° to -7.6°]; p < 0.001). Both acetabular depth/width ratio and femoral head coverage did not differ among the groups or between the initial and followup MRI examinations within each group.

CONCLUSIONS

Although acetabular depth/width ratio and femoral head coverage remain relatively constant, acetabular version increases with advancing skeletal maturity. There seems to be a relatively narrow timeframe near physeal closure of the TCC within which acetabular orientation changes to more pronounced anteversion. Further studies with greater numbers and longer followup periods are required to support these findings and determine whether such version changes may contribute to pincer-type pathomorphologies.

LEVEL OF EVIDENCE

Level II, prospective study.

Age- and gender-related characteristics of the pubic symphysis and triradiate cartilage in pediatric computed tomography

BACKGROUND

There is little information on the pubic symphysis' normal CT appearance in children.

OBJECTIVE

We sought to generate age-, gender- and maturity-related symphyseal width appearances in CT scans.

MATERIALS AND METHODS

Pelvic CT scans performed for any reason during a 6-year period in patients younger than 18 years were retrospectively analyzed. The symphysis width was measured in the axial plane and the triradiate cartilage was classified as open or closed.

RESULTS

Four hundred twenty-seven CT scans were evaluated and 350 remained for analysis. Age- and gender-related measurements of the symphysis width are illustrated on various centile graphs. When grouping children by age in years 0-6, 7-11, 12-15 and 16-17, mean (standard deviation) symphysis width was 5.4 mm (0.9), 5.3 mm (1.1), 4.1 mm (1.1) and 3.5 mm (1.0), respectively, in girls and 5.9 mm (1.3), 5.4 mm (1.2), 5.2 mm (1.1) and 4.0 mm (1.0), respectively, in boys. Boys and girls were significantly different in the age groups 12-15 years (P<0.001) and 16-17 years (P=0.04). In the mature pelvis, the symphyseal gap is significantly (P<0.001) shorter in both genders, and in girls compared to boys (P=0.04).

CONCLUSION

The pubic symphysis width in children differs according to age, gender and maturity. The reference values published herein may help detect symphyseal injury.

Magnetic resonance imaging evaluation of acetabular orientation in normal Chinese children

There are no data regarding the acetabular orientation on magnetic resonance imaging (MRI); this study investigates the changes of acetabular orientation with age in normal Chinese children.We retrospectively analyzed the medical records of children who underwent hip MRI examination at our hospital from January 2009 to December 2015. A total of 180 patients with normal MRI reading of the hip joints were included and were divided into 14 groups according to age: from 6 months of age and then for each year from 1 to 16 years. The bony and cartilage acetabular anteversion angle (AAA), acetabular inclination angle (AIA), and acetabular index (AI) were measured. Total bony and cartilage femoral head coverage angles were measured on axial section total femoral head coverage angle (a-TCA) and coronal section total femoral head coverage angle (c-TCA).The mean bony AAA and AIA were 12.2 ± 2.5° and 50.9 ± 2.5°, respectively; both of them stayed constant from the age of 6 months to 16 years. Similar results were found in cartilage AAA (12.1 ± 2.5°) and AIA (41.2 ± 3.0°). There was no difference between bony and cartilage AAA, but bony AIA was significantly larger than cartilage AIA. Bony AI was 24.1 ± 2.4° at the age of 6 months, decreasing to 12.5 ± 2.3° by 12 to 13 years of age; cartilage AI (5.9 ± 1.7°) maintained a steady value with age. The mean bony a-TCA and c-TCA at 6 months were 117.0 ± 5.8° and 127.5 ± 5.1°, increasing to 144.5 ± 4.6° and 140.7 ± 2.5° at the age of 16 years. However, the cartilage a-TCA (145.2 ± 7.2°) and c-TCA (154.1 ± 5.7°) did not change significantly with age.Both bony and cartilage AAA and AIA remain constant up to the age of 16 years in normal Chinese pediatric population. Although the cartilage coverage of femoral head by the acetabulum remains unchanged with age, the bony coverage of femoral head increases.

Surgical Hip Dislocation is Safe and Effective Following Acute Traumatic Hip Instability in the Adolescent

BACKGROUND

A traumatic hip dislocation in the pediatric patient is a rare but potentially catastrophic injury. The purpose of this study was to review our early clinical results and radiographic morphology of hips treated with a surgical hip dislocation (SHD) approach for intra-articular hip pathology resulting from traumatic instability in pediatric and adolescent patients.

METHODS

This is a retrospective analysis of a consecutive series of patients presenting with nonconcentric reduction after traumatic hip instability. All patients were treated with a transtrochanteric SHD with concomitant procedures based on intra-articular findings. Radiographic evaluations and Harris Hip Scores were completed at final follow-up.

RESULTS

Eleven male patients, mean age of 12.3 years (range, 9.3 to 16.1 y) and mean body mass index 19.6 kg/m (range, 15.4 to 28.0 kg/m). Intraoperative findings included: labral tear (8), femoral cartilage injury (5), acetabular rim fracture (4), acetabular cartilage delamination (3), loose body (2), and femoral head osteochondral fracture (1). Postoperatively, 1 patient developed a transient peroneal nerve palsy. At a mean 24.5 months (range, 12.0 to 48.1 mo) postoperatively, no hips have radiographic evidence of osteonecrosis. The mean lateral center edge angle was 20 degrees (range, 9 to 38 degrees) with 6 hips of <20 degrees; mean acetabular index 9 degrees (range, -2 to 23 degrees) with 5 hips of >10 degrees; mean α-angle 56 degrees (range, 48 to 62 degrees) with 6 hips of >55 degrees; mean acetabular version 12 degrees (range, 8 to 16 degrees) with 8 hips of <15 degrees. At 1-year follow-up, the mean Harris Hip Score was 95.8 (range, 84.7 to 100).

CONCLUSIONS

Early results suggest that SHD is a safe approach to treat an incomplete reduction following posterior hip instability and is effective for identification and treatment of acute intra-articular pathology. Acetabular dysplasia, relative acetabular retroversion, and/or decreased femoral offset may be risk factors for posterior hip instability in adolescents.

LEVEL OF EVIDENCE

Level IV.

FEMORAL ANTEVERSION AND THE NECK-SHAFT ANGLE: RELATIONSHIP WITH HIP OSTEOARTHRITIS

OBJECTIVE

To compare the existence of agreement between measurements of anteversion of the femoral neck and the degrees of osteoarthritis and abnormality of the neck-shaft angle in patients with unilateral idiopathic hip osteoarthritis, among three evaluators.

METHODS

Forty-two patients with unilateral hip osteoarthritis were evaluated by means of simple radiography and computed tomography.

RESULTS

It was observed that there was no significant variation in femoral anteversion between the diseased and healthy hips. There was strongest agreement between observers 1 and 2 in relation to both the diseased hips (cases) and the healthy hips (controls). Moreover, no significant agreement was found between observers 1 and 3 (p = 0.13) and between observers 2 and 3 (p = 0.12), in relation to the neck-shaft angle of the control hips.

CONCLUSION

Although there was no relationship between femoral anteversion and the neck-shaft angle in the patients with unilateral hip osteoarthritis, the present study showed that there was also no relationship with these angular deviations.

Sex Differences in Cartilage Topography and Orientation of the Developing Acetabulum: Implications for Hip Preservation Surgery

BACKGROUND

Increased attention is being placed on hip preservation surgery in the early adolescent. An understanding of three-dimensional (3-D) acetabular development as children approach maturity is essential. Changes in acetabular orientation and cartilage topography have not previously been quantified as the adolescent acetabulum completes development.

QUESTIONS/PURPOSES

We used a novel 3-D CT analysis of acetabular development in children and adolescents to determine (1) if there were sex-specific differences in the growth rate or surface area of the acetabular articular cartilage; (2) if there were sex-specific differences in acetabular version or tilt; and (3) whether the amount of version and tilt present correlated with acetabular coverage.

METHODS

We assessed acetabular morphology in 157 patients (314 hips); 71 patients were male and 86 were female. Patient ages ranged from 8 years to 17 years. A 3-D surface reconstruction of each pelvis was created from CT data using MIMICs software. Custom MATLAB software was used to obtain data from the 3-D reconstructions. We calculated articular surface area, acetabular version, and acetabular tilt as well as novel measurements of acetabular morphology, which we termed "coverage angles." These were measured in a radial fashion in all regions of the acetabulum. Data were organized into three age groups: 8 to 10 years old, 10 to 13 years old, and 13 to 17 years old.

RESULTS

Male patients had less acetabular anteversion in all three age groups, including at maturity (7° versus 13°, p<0.001; 10° versus 17°, p<0.001; 14° versus 20°, p<0.001). Males had less acetabular tilt in all three age groups (32° versus 34°, p=0.03; 34° versus 38°, p<0.001; 39° versus 41°, p=0.023). Increases in anteversion correlated with increased posterior coverage angles (r=0.805; p<0.001). Increases in tilt were correlated with increases in superior coverage angles (r=0.797; p<0.001). The posterosuperior regions of the acetabulum were the last to develop and this process occurred earlier in females compared with males. Articular surface area increased from 18 (8-10 years) to 24 cm(2) (13-17 years) in males and from 17 (8-10 years) to 21 cm(2) (13-17 years) in females. [corrected]. Articular surface area was higher in males beginning in the 10- to 13-year-old age group (p=0.001).

CONCLUSIONS

Using a novel technique to analyze acetabular morphology, we found that acetabular development occurs earlier in females than males. The posterosuperior region of the acetabulum is the final region to develop. The articular cartilage surface area and articular cartilage coverage of the femoral head are increasing in addition to total coverage of the femoral head during the final stages of acetabular development.

LEVEL OF EVIDENCE

Level III, prognostic study.

How are dysplastic hips different? A three-dimensional CT study

BACKGROUND

Surgical correction of acetabular dysplasia can postpone or prevent joint degeneration. The specific abnormalities that make up the dysplastic hip are controversial.

QUESTIONS/PURPOSES

(1) What are the relative size, shape, and orientations of the typical nondysplastic hip? (2) How do these variables differ in the developmentally dysplastic hip? (3) Are there version differences between the acetabuli of dysplastic and nondysplastic hips? (4) Are there pairs of variables in which the change in one is always accompanied by a change in the other for both nondysplastic and dysplastic acetabuli?

METHODS

Of 117 consecutive three-dimensional (3-D) CT scans performed for hip dysplasia between March 1988 and October 1995, 48 met criteria of developmentally dysplastic hips by plain radiography. These were retrospectively compared with 55 pelvic 3-D CT scans culled from 81 consecutive scans performed for reasons other than hip dysplasia (ie, hip pain, trauma, infection) that did not affect the hip or pelvic landmarks. The 3-D reconstructions were orientated anatomically for standardization of the measurements to be compared. Representative 3-D volumes of the acetabular space were constructed from which we could measure anatomic positions and dimensional information. One author performed all image orientation and measurements.

RESULTS

Nondysplastic acetabuli are essentially hemispheric with height equal to width and twice the depth. The dysplastic acetabuli were elongated in females (52.4 ± 6.2 mm for dysplastic versus 46.5 ± 4.6 mm for nondysplastic (mean difference, 5.0; 95% confidence interval [CI], 1.9-8.0; p = 0.002) and shallower in both females (18.7 ± 4.9 mm for dysplastic versus 23.6 ± 4.0 mm for nondysplastic; mean difference, 6.5; 95% CI, 4.4-8.5; p < 0.0001) and males (21.1 ± 4.8 mm for dysplastic versus 25.0 ± 4.3 mm for nondysplastic, mean difference, 5.3; 95% CI, 2.6-8.1; p = 0.0002); width was similar to that of nondysplastic hips. Acetabular openings were slightly more vertical than nondysplastic hips in females (5°; 95% CI, 1.9-8.1; p = 0.002) but not in male subjects. The dysplastic acetabuli were smaller in volume (18% in females, p = 0.002, and 19% in males, p = 0.0012) and had less space occupied by the femoral head compared with nondysplastic hips (p < 0.0001 for females, p < 0.0001 for males). Dysplastic hip midacetabulum was 4° more anteverted in females (95% CI, 0.5-6.8; p = 0.022) but not for males (p = 0.538). The upper dysplastic acetabulum was more retroverted in females and males (10.2°; 95% CI, 5.5-15; p < 0.0001, and 7.0°; 95% CI, 0.6-13.4; p = 0.032, respectively). Acetabular volumes in nondysplastic and dysplastic hips were related to acetabular width but not to length.

CONCLUSIONS

Developmentally dysplastic acetabuli are not deficient in merely a single dimension but are globally deficient. The subluxated femoral head lies in the elongated and retroverted superior acetabulum, which becomes progressively shallower as the acetabulum increases in length. Focally deficient anterior or posterior femoral head coverage is uncommon. Current procedures that redirect the acetabulum, no matter how technically successful, cannot fully compensate for the incongruence of a spherical femoral head within a shallow and elongated acetabulum unless corrected at an early age when acetabular remodeling is possible. Early detection and treatment of acetabular dysplasia should be emphasized.

LEVEL OF EVIDENCE

Level III, prognostic study.

How do acetabular version and femoral head coverage change with skeletal maturity?

BACKGROUND

Normal changes in acetabular version over the course of skeletal development have not been well characterized. Knowledge of normal version development is important because acetabular retroversion has been implicated in several pathologic hip processes.

QUESTIONS/PURPOSES

The purpose of this study was to characterize the orientation of the acetabulum by measuring (1) acetabular version and (2) acetabular sector angles in pediatric patients during development. We also sought to determine whether these parameters vary by sex in the developing child.

METHODS

We evaluated CT images of 200 hips in 100 asymptomatic pediatric patients (45 boys, 55 girls; mean age, 13.5 years; range, 9-18 years) stratified by the status of the triradiate physis and sex. We determined the acetabular anteversion angle at various levels in the axial plane as well as acetabular sector angles at five radial planes around the acetabulum.

RESULTS

For both genders, anteversion angle was greater for the closed physis group throughout all levels (p < 0.001) and both open and closed physis groups were more anteverted as the cut moved caudally away from the acetabular roof (p < 0.001). At the center of the femoral head, the mean anteversion angle (± SD) in girls was 15° ± 3° in the open group and 19° ± 5° in the closed group (p < 0.001). In boys, the mean anteversion angle increased from 14° ± 4° in the open group to 19° ± 4° in the closed group (p = 0.003). In the superior, posterosuperior, and posterior planes, the acetabular sector angles were greater in the closed compared with the open physis group for both boys and girls with the largest increase occurring in the male posterosuperior plane (approximately 20°) (all p < 0.05).

CONCLUSIONS

This study demonstrates that acetabular anteversion and acetabular sector angles in both male and female subjects increase with skeletal maturity as a result of growth of the posterior wall. This suggests that radiographic appearance of acetabular retroversion may not be attributable to overgrowth of the anterior wall but rather insufficient growth of the posterior wall, which has clinical treatment implications for pincer-type impingement.

Hip dysplasia is more severe in Charcot-Marie-Tooth disease than in developmental dysplasia of the hip

BACKGROUND

Patients with Charcot-Marie-Tooth disease may develop hip dysplasia. Hip geometry in these patients has not been well described in the literature.

QUESTIONS/PURPOSES

We compared the hip morphometry in Charcot-Marie-Tooth hip dysplasia (CMTHD) and developmental dysplasia of the hip (DDH) in terms of extent of (1) acetabular dysplasia and subluxation, (2) acetabular anteversion and osseous support, (3) coxa valga and femoral version, and (4) osteoarthritis.

METHODS

Fourteen patients with CMTHD (19 hips; mean age, 23 years) presenting for periacetabular osteotomy were matched to 45 patients with DDH (45 hips; mean age, 21 years) based on age, sex, and BMI. We assessed acetabular dysplasia and subluxation using lateral center-edge angle (LCEA), anterior center-edge angle (ACEA), and acetabular roof angle of Tönnis (TA) on plain pelvic radiographs and acetabular volume, area of femoral head covered by acetabulum, and percentage of femoral head covered by acetabulum on three-dimensional CT reconstruction models. Acetabular version and bony support, femoral version, and neck-shaft angle were measured on two-dimensional axial CT scans. Hip osteoarthritis was graded radiographically according to Tönnis criteria.

RESULTS

Acetabular dysplasia was more severe in CMTHD, as measured by smaller LCEA (p < 0.001), ACEA (p < 0.001), and acetabular volume (p = 0.0178) and larger TA (p = 0.025). Hip subluxation was more pronounced in CMTHD, as demonstrated by lower area of femoral head covered by acetabulum (p = 0.034) and percentage of femoral head covered by acetabulum (p = 0.007). CMTHD was associated with higher acetabular anteversion (p < 0.001), lower anterior (p < 0.001) and posterior (p = 0.072) osseous support, and more severe coxa valga (p < 0.001). More (p = 0.006) arthritic hips were found in CMTHD.

CONCLUSIONS

The extent of acetabular dysplasia, hip subluxation, acetabular anteversion, coxa valga, and hip osteoarthritis was more severe in CMTHD. These findings are important in choosing the appropriate surgical strategy for patients affected by CMTHD.

Effect of pelvic inclination and torsional deformity on canine acetabular morphology with computed tomography. A phantom study

OBJECTIVES

To evaluate how the inclination and torsional deformity of the hemipelvis using extra-rotation as a model affect acetabular angle (AA) and dorsal acetabular rim angle (DARA) assessment with computed tomography (CT).

METHODS

A normal canine hemipelvis positioned in dorsal recumbency was scanned with a 16-slice multidetector CT scanner, with different degrees of torsional deformity, using extra-rotation around the long axis (0-5-10-15°) of the hemipelvis. Each degree of extra-rotation was acquired at 0°, +20° and -20° of gantry tilt, to mimic different pelvic inclinations on its transverse axis. Cranial and central individual acetabular angles (IAA) and central DARA were calculated and correlated with inclination and torsional deformity.

RESULTS

A very strong negative correlation was found between cranial and central IAA, pelvic inclination, and torsional deformity. A very strong positive correlation was found between DARA, pelvic inclination, and torsional deformity.

CLINICAL SIGNIFICANCE

Pelvic inclination and torsional deformity affect acetabular angles assessment with CT. The greater the inclination (ilia far from the tabletop in dorsal recumbency) and torsional deformity of the pelvis, the worse the acetabulum appeared. A standardized scanning protocol for acetabular morphology assessment is needed and it should consider pelvic inclination. The actual relevance of pelvic torsional deformity is not well known and it should be investigated more thoroughly.

Standard radiographs and computed tomographic scan underestimating pediatric acetabular fracture after traumatic hip dislocation: report of 2 cases

Posterior wall acetabular fractures are rare in the pediatric patient but require proper management to prevent significant complications. Plain radiographs and computed tomography scans are standard diagnostic imaging used with clinical examination of hip stability to determine if the injury requires open reduction and internal fixation. Two cases are presented of adolescent traumatic hip dislocations and posterior wall fractures in which radiography underestimated the extent of the posterior wall fracture. In one case, a magnetic resonance imaging study more clearly characterized the injury. Because the ossification of the posterior wall occurs throughout adolescence, magnetic resonance imaging may be a useful tool in characterizing these fractures and assisting with surgical planning.

Pelvic positioning creates error in CT acetabular measurements

BACKGROUND

CT allows for accurate measurement of acetabular orientation and shape, but malpositioning of the pelvis may lead to measurement variance.

PURPOSE

We therefore sought to determine: (1) whether acetabular anteversion measurements using the femoral head centers differed from those using the posterior ischia, and (2) the extent to which changing obliquity, rotation, and tilt of a pelvis in a CT scanner affected the measurement of acetabular variables.

METHODS

A radiopaque human pelvis model with articulated hips was suspended from a plastic sheet as part of an adjustable frame. Changes in the transverse and sagittal planes created rotation and tilt, while rotating the frame in the coronal plane created obliquity. CT scans were obtained, varying the combinations of obliquity, rotation, and tilt by intervals of 5°, up to 20°. Acetabular anteversion (AA), anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), and horizontal acetabular sector angle (HASA) were measured.

RESULTS

The two methods for measuring AA yielded values differing by 1° to 4° but correlated (r = 0.981) across the spectrum of pelvis positioning. Pelvic obliquity and tilt were linearly associated with changes in the measurements. For each 1°-increase in pelvic obliquity, AA changed -0.4°, and AASA, PASA, and HASA changed 1.93°, 0.99°, and 2.80°, respectively. For each 1°-increase in pelvic tilt, AA changed 0.8°, and AASA, PASA, and HASA changed -1.07°, 0.52°, and -0.51°, respectively. Rotation had no affect on the variables.

CONCLUSIONS

Small changes in pelvic obliquity and tilt were associated with variances in acetabular measurements. The measured changes were directly proportional to the changes in obliquity and tilt, and were additive. Pelvic rotation created no changes in measurement.

Surgical treatment of developmental dysplasia of the hip presenting in children above 10 years

BACKGROUND

Management of developmental dysplasia of the hip in older children remains controversial. The objective of this study was to evaluate the results of surgical treatment of developmental dysplasia of the hip in children older than 10 years.

METHOD

Sixty-three patients (75 hips) whose mean age at the time of surgery was 11.5 years (range 10-19 years) were treated using Salter osteotomy, Pemberton acetabuloplasty, Dega osteotomy, or Westin osteotomy. Subtrochanter transverse femoral shortening and derotation osteotomy were performed for all patients. A long leg cast, rather than a spica cast, was applied postoperation, and progressive flexion and extension exercises of the hip joint were initiated 2 weeks after the surgery.

RESULT

All 63 patients (75 hips) were followed for an average of 7.6 years (range 5-10 years) after surgery. According to the McKay criteria and Severin X-ray criteria, the fineness ratios were 82.7 and 82.6%, respectively. After surgery, there were 4 cases of semiluxation (6.3%); 4 of femoral head ischemia necrosis (6.3%), and 9 of hip joint stiffness (14.3%).

CONCLUSION

We believe that preoperation overall evaluation and personalized operation plans, experience with the surgical procedure, and commencement of functional exercise soon after the operation are the main reasons for the satisfactory therapeutic effects achieved in this study after surgery for developmental dysplasia of the hip presenting in children older than 10 years.

Axial plane coverage and torsion measurements in primary osteoarthritis of the hip with good frontal plane coverage and spherical femoral head

INTRODUCTION

Mechanical factors play a role in pathogenesis of primary osteoarthritis of the hip. Torsion measures were made to detect whether there is a causal relationship between increase or decrease of femoral anteversion, acetabular anteversion, and osteoarthritis. There are no studies in the literature indicating a relationship between axial plane coverage and osteoarthritis of the hip. Deficient axial plane coverage of femoral head may also play a role in pathogenesis of osteoarthritis.

MATERIALS AND METHODS

Thirty patients with primary osteoarthritis of the hip and 29 control cases were included in the study. We used the method of Anda et al. (Acta Radiol Diagn 27:443-447, 1986; Comput Assist Tomogr 15:115-120, 1991) to measure axial plane anterior, posterior coverages in patients with primary osteoarthritis of the hip. The computerized tomography sections and pelvic radiographs indicated good frontal plane coverage and spherical femoral head. In addition to anterior acetabular sector angle, posterior acetabular sector angle, horizontal acetabular sector angles for axial plane coverage detection, femoral anteversion, acetabular anteversion, and McKibbin instability index were also measured.

RESULTS

Posterior coverage was lower at osteoarthritic hips than the control group's hips (96.0 ± 16.7, 104.2 ± 10.6) (p < 0.05).

CONCLUSION

The results may indicate that in addition to other mechanical factors, axial plane coverage, especially the posterior coverage deficiency, may play a role in the pathogenesis of hip osteoarthritis.

Steel syndrome: dislocated hips and radial heads, carpal coalition, scoliosis, short stature, and characteristic facial features

BACKGROUND

A syndrome of children with short stature, bilateral hip dislocations, radial head dislocations, carpal coalitions, scoliosis, and cavus feet in Puerto Rican children, was reported by Steel et al in 1993. The syndrome was described as a unique entity with dismal results after conventional treatment of dislocated hips. The purpose of this study is to reevaluate this patient population with a longer follow-up and delineate the clinical and radiologic features, treatment outcomes, and the genetic characteristics.

METHODS

This is a retrospective cohort study of 32 patients in whom we evaluated the clinical, imaging data, and genetic characteristics. We compare the findings and quality of life in patients with this syndrome who have had attempts at reduction of the hips versus those who did not have the treatment.

RESULTS

Congenital hip dislocations were present in 100% of the patients. There was no attempt at reduction in 39% (25/64) of the hips. In the remaining 61% (39/64), the hips were treated with a variety of modalities fraught with complications. Of those treated, 85% (33/39) remain dislocated, the rest of the hips continue subluxated with acetabular dysplasia and pain. The group of hips that were not treated reported fewer complaints and limitation in daily activities compared with the hips that had attempts at reduction.

CONCLUSIONS

Steel syndrome is a distinct clinical entity characterized by short stature, bilateral hip and radial head dislocation, carpal coalition, scoliosis, cavus feet, and characteristic facial features with dismal results for attempts at reduction of the hips.

LEVEL OF EVIDENCE

Prognostic Study Level II.

Normal development of the hip: a geometrical analysis based on planimetric radiography

The existing studies on the development of the hip joint predominantly focus on either the acetabulum or the proximal femur. This paper investigates the parallel geometrical development of both, the proximal femur and the acetabulum during growth. Six hundred and seventy-five hips with an age from 9 months to 16 years were studied by means of planimetric radiography; angles and lever arms were determined. Although the apophyseal angles remain virtually unchanged throughout growth, the epiphyseal angles and the neck-shaft angle undergo typical changes until the age of 10 years. Subsequently, there are no major changes in the angular conformation of the proximal femur, whereas acetabular coverage and its centric alignment continue to develop further until the end of skeletal growth. The load and muscle lever arms increase until the end of growth with their ratio remaining constant after the age of 10 years. We present correlated data on the geometrical development of the acetabulum and the proximal femur. The interpretation of our findings is to some extent limited by the two-dimensionality of planimetric radiography. Our results do, however, support the timing of corrective osteotomies of the proximal femur relatively soon after the age of 10 years.

Does Salter innominate osteotomy with transiliac lengthening effect triradiate cartilage or cause posterior coverage insufficiency?

INTRODUCTION

To treat neglected developmental dysplasia of the hip (DDH), we performed Salter innominate osteotomy with a modification of transiliac lengthening. We asked whether this modified technique caused posterior coverage problems and triradiate cartilage injury.

METHODS

We retrospectively reviewed 45 patients with unilateral DDH treated by open reduction and femoral shortening and modified Salter innominate osteotomy. The age at operation was 38.44 +/- 19.79 months (mean +/- standard deviation). Minimum follow-up was 24 months (mean +/- standard deviation 49.84 +/- 27.73 months; range 24-112 months). We measured the tilt of the iliac bone (difference of preoperative and postoperative acetabular index values). We divided the hips into two groups. There were 29 hips in Group 1 (deviation amount <20 degrees ) and 16 hips in Group 2 (deviation amount > or =20 degrees ). At the latest follow-up, frontal and axial plane computed tomographic analyses were performed. We measured medial wall thickness, teardrop width, and hemipelvis heights to evaluate triradiate cartilage intactness indirectly. Posterior center edge angle, which reflects posterior coverage of the hip, was also measured.

RESULTS

We found no differences between groups regarding all measured parameters.

CONCLUSIONS

Modified Salter osteotomy with transiliac lengthening can be performed safely in the treatment of neglected DDH.

Evolution of the hip and pelvis

Man's evolution features two unique developments: growing a huge brain and upright gait. Their combination makes the pelvis the most defining skeletal element to read human evolution. Recent revival in joint preserving hip surgery have brought to attention morphological variations of the human hip that appear similar to hips of extant mammals. In man, such variations can produce hip osteoarthrosis through motion. We reviewed the evolution of the hip and pelvis with special interest in morphology that can lead to motion induced osteoarthrosis in man. The combination of giving birth to big brained babies and walking upright has produced marked differences between the sexes in pelvis and hip morphology, each having their characteristic mode of hip impingement and osteoarthrosis.

Measurement of acetabular anteversion in developmental dysplasia of the hip in children by two- and three-dimensional computed tomography

This study assessed the angle of acetabular anteversion (AA) in 66 children with developmental dysplasia of the hip (132 hips: 24 left, 25 right, 17 bilateral and 49 unaffected hips as controls). The AA was measured by two- and three-dimensional computed tomography (2D-CT and 3D-CT). Measurements were taken by three observers and repeated 2 weeks later by one of these observers. Intra- and inter-observer agreement was analysed using the intra-class correlation coefficient. For all hips, the mean AA (+/-SD) measured by 2D-CT versus 3D-CT was statistically significantly different (15.76 +/- 5.23 degrees versus 16.76 +/- 4.43 degrees , respectively). The mean (+/-SD) AA by 3D-CT in unaffected and affected hips was also statistically significantly different (13.92 +/- 3.95 degrees versus 18.44 +/- 3.82 degrees , respectively). A significant positive correlation between age at presentation and AA was found in affected, but not unaffected, hips. The 3D-CT showed better intra- and inter-observer agreement than 2D-CT for assessing AA hence is a more reliable measurement of AA. An increased AA is one component of anatomical abnormalities in developmental dysplasia of the hip and the abnormality appears to worsen with age.

Is there a relation between hip torsion, coverage and osteoarthritis of the knee?

PURPOSE

Biomechanic factors play a role in the pathogenesis of knee osteoarthritis. The aim of the study was to find out whether there is a relation between femoral, acetabular anteversions, anterior, posterior acetabular coverages and primary osteoarthritis of the knee.

METHODS

Thirty patients with primary osteoarthritis of the knee and 29 control subjects were enrolled into the study. Femoral anteversion, acetabular anteversion, McKibbin's instability index, anterior acetabular sector and posterior acetabular sector angles were measured using tomographic scanograms.

RESULTS

There was no difference between groups for each parameter (P > 0.05).

CONCLUSION

This study did not show any relationship between the axial plane changes in the hip joint and primary knee osteoarthritis.

[Indications and results of corrective pelvic osteotomies in developmental dysplasia of the hip]

BACKGROUND

Joint-preserving reconstructive surgeries in children and adolescents remain challenging for orthopaedists with regard to indication and surgical technique. Besides skeletal maturity and tissue quality at the time of surgery, the kind and degree of deformity, the causative pathologies in secondary dysplasias, and the prognosis have to be considered when deciding for or against a surgical procedure. Developmental dysplasia of the hip (DDH) is the most frequent deformity that indicates reorienting surgery on the hip joint in children and adolescents. The aim of these procedures is to prevent early secondary osteoarthritis. For patients and families as well as for the orthopaedist, risk-benefit analysis is of major interest.

METHODS

In this study, the surgical techniques and specialties of different reconstructive operations are presented. Based on a review of the literature, the results of defined surgical methods are discussed and compared with own experiences.

RESULTS

Only limited information is available about the clinical long-term outcome after defined reconstructing surgery on the hip joint in children and adolescents. The degree of the deformity, the age of onset, and the surgical experience of the orthopaedist are crucial factors in decision making for or against a surgical treatment. In early childhood, acetabuloplasty and Salter osteotomy are widely accepted to correct DDH. Triple and periacetabular osteotomies are preferred and have shown promising results in late adolescence and young adults. When the triradiate cartilage (growth plate) is closed, good outcomes can be achieved by the Ganz osteotomy. Intertrochanteric varus and derotation osteotomies of the femur may serve as additional procedures for pelvic osteotomies and are rarely indicated as a single procedure today.

CONCLUSION

Reconstructive surgery on the hip joint improves function and may prevent early osteoarthritis and delay progression of cartilage degeneration in most patients when the indication and surgical technique are appropriate.

Two-dimensional computed tomographic measurement of acetabulum--reliability, validity, and limitation

BACKGROUND

The shape of the dysplastic acetabulum has been generally determined by 2-dimensional computed tomography (CT) measurements (transaxial CT indices), such as the anterior and posterior acetabular indices and acetabular anteversion. However, their reliability and validity in evaluating the acetabular coverage have not been confirmed.

METHODS

This study examined the reliability and validity of the transaxial CT indices using 2- and 3-dimensional CT analyses of the acetabulum before and after a Dega osteotomy. Twenty-two acetabuli from 16 patients with cerebral palsy with hip instability were examined. Interobserver and intraobserver reliability tests were performed, and the preoperative and postoperative measurements were compared for the concurrent and construct validity test.

RESULTS

The transaxial CT indices revealed substantial intraobserver and interobserver reliability. The concurrent validity of the anterior acetabular and posterior acetabular indices before osteotomy was moderate (r = 0.45, 0.49), whereas the construct validity after osteotomy was low when compared with 3-dimensional methods.

CONCLUSION

The transaxial CT indices are reliable and valid for assessing the acetabular coverage in the preoperative status. However, care should be taken when using these indices to assess the outcome of a pelvic-reshaping osteotomy because of their insufficient construct validity.

LEVEL OF EVIDENCE

Level III of diagnostic study.

The development of acetabular retroversion in children with Legg-Calvé-Perthes disease

BACKGROUND

Ezoe et al showed that the prevalence of acetabular retroversion in adults with Legg-Calvé-Perthes disease (LCPD) was 42% versus 6% in normal controls. Our purpose was to study the development of acetabular retroversion in children with LCPD and perhaps draw conclusions regarding cause and effect.

METHODS

We reviewed all 271 patients with LCPD seen at our institution to identify those patients with axial imaging before closure of the triradiate cartilage. Fifty-three hips (44 patients) formed our study population; the 35 normal hips in those patients with unilateral disease served as an internal control. Acetabular version was measured on the axial cut with the largest femoral head cross-section. Diseased versus control hips were compared using a paired t test. Two disease-severity subgroups, Herring A or B (42 hips) and B/C or C (11 hips), were compared using an independent-samples t test. In those patients followed past skeletal maturity (16 of 53 hips), we evaluated final AP pelvic radiographs for acetabular retroversion (presence of a crossover sign).

RESULTS

Before skeletal maturity, all but 1 patient in our series demonstrated positive acetabular version (anteversion). We found no significant difference between the diseased and control hips: mean acetabular version in LCPD hips was 13.6 +/- 4.3 versus 15.4 +/- 5.4 degrees in unaffected hips. More severe cases (B/C or C) exhibited significantly more relative retroversion (10.8 degrees) than less severe cases (14.6 degrees, P = 0.047). Of the 16 hips followed past skeletal maturity, 5 demonstrated crossover signs on anteroposterior pelvic radiographs, indicating a 31% prevalence of acetabular retroversion.

CONCLUSION

Early after diagnosis, the prevalence of acetabular retroversion in our skeletally immature children with LCPD was extremely rare (1.8%), and there was no significant difference in version between the normal hips and hips with LCPD. However, over time, a child with a more deformed femoral head is more likely to develop acetabular retroversion, suggesting a cause-and-effect relationship.

LEVEL OF EVIDENCE

Level III (case-control).

Relationships among measurements obtained by use of computed tomography and radiography and scores of cartilage microdamage in hip joints with moderate to severe joint laxity of adult dogs

OBJECTIVE

To evaluate correlations among measurements on radiographic and computed tomography (CT) images with articular cartilage microdamage in lax hip joints of dogs.

ANIMALS

12 adult mixed-breed hounds.

PROCEDURES

Pelvic CT and radiography were performed. Hip joints were harvested following euthanasia. Orthopedic Foundation for Animals (OFA) and PennHIP radiograph reports were obtained. Norberg angle (NA) and radiographic percentage femoral head coverage (RPC) were determined. Center-edge angle (CEA), horizontal toit externe angle (HTEA), ventral acetabular sector angle (VASA), dorsal acetabular sector angle (DASA), horizontal acetabular sector angle (HASA), acetabular index (AI), and CT percentage femoral head coverage (CPC) were measured on 2-dimensional CT images. Femoral head-acetabular shelf percentage was measured on sagittal 3-dimensional CT (SCT) and transverse 3-dimensional CT (TCT) images. Light microscopy was used to score joint cartilage. Relationships of OFA confirmation and PennHIP osteoarthritis scores with radiography, CT, and cartilage variables and relationships of cartilage scores with radiography and CT measurements were evaluated with Spearman rank correlations. Pearson correlation was used for relationships of distraction index (DI) with radiography, CT, and cartilage variables.

RESULTS

Significant relationships included PennHIP osteoarthritis score with cartilage score, CEA, HTEA, DASA, AI, CPC, and TCT; OFA confirmation score with cartilage score, NA, RPC, CEA, HTEA, DASA, AI, CPC, and TCT; cartilage score with NA, RPC, CEA, HTEA, DASA, HASA, AI, and TCT; and DI with cartilage score, CEA, HTEA, DASA, HASA, AI, and CPC.

CONCLUSIONS AND CLINICAL RELEVANCE

CT appeared to be a valuable imaging modality for predicting cartilage microdamage in canine hip joints.

Imaging in the surgical management of developmental dislocation of the hip

Although the use of ultrasound in the diagnosis and early treatment of developmental dysplasia of the hip (DDH) has reduced the number of patients diagnosed late and decreased the number of operative procedures, surgical treatment is still needed in some patients. Late cases continue to occur as a result of missing the screening examination, being normal at initial screening and missing followup. Dysplasia may persist despite appropriate nonoperative or operative treatment. Many of these patients subsequently undergo closed or open reduction and femoral or acetabular reconstruction. Ultrasound of the hips is generally used up to 6 or 8 months of age, during which time the hips are largely cartilaginous, and radiographs after that time when bony development is more complete. Options to supplement ultrasound and radiography include arthrography, computed tomography, and magnetic resonance imaging. Several advances have been made in the imaging of DDH and its complications including acetabular labral pathology and of femoroacetabular impingement (FAI). We review imaging techniques other than ultrasound used in the management of DDH.

LEVEL OF EVIDENCE

Level V, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Morphometric changes in the acetabulum after Dega osteotomy in patients with cerebral palsy

We carried out a morphometric analysis of the acetabulum following Dega osteotomy in patients with cerebral palsy using three-dimensional CT. We assessed 17 acetabula in 12 patients with instability of the hip. A Dega osteotomy and varus derotation femoral osteotomy were performed in all 17 hips. Three-dimensional CT scans were taken before and approximately one year after operation. Acetabular cover was evaluated using anterosuperior, superolateral and posterosuperior acetabular indices, and the change in the acetabular volume was calculated. Inter- and intra-observer reliability was assessed using the intraclass correlation coefficient. After the osteotomy, the anterosuperior, superolateral and posterosuperior cover had improved significantly towards the value seen in a control group. The mean acetabular volume increased by 68%.

Three-dimensional computed tomography analysis and anteversion study after periacetabular osteotomy of pelvis in children

PURPOSE

Three-dimensional computed tomography (CT) is the method of choice in understanding the morphological changes after periacetabular osteotomy in children. We studied different parameters and compared aspects of operated hip (OH) with non-operated hip (NOH) to define the maneuver that promotes normalization of the hip during repositioning of the acetabulum.

METHODS

A total of 22 patients with 25 OHs underwent CT control scans an average of 4 years after surgery. The patients, with a mean age of 6.8 years, had either Legg-Calvé-Perthes disease (12 cases) or dysplasia (10 cases).The measurements included the anterior and posterior coverage angles of the hip and version of the acetabulum on axial CT views. The 3D reconstructed images measured the inclination of the antero- and postero-lateral lips, the external rotation and the anterior inclination of the acetabulum.

RESULTS

The mean anterior coverage angle was 27 degrees for OHs, 31 degrees for NOHs, and 12 degrees versus 10.3 degrees for the posterior coverage angle. Acetabular anteversion was 2 degrees for OHs (6.3 degrees in the dysplastic OHs) and 6 degrees for NOHs. The mean angle of inclination of the antero-lateral lip was 37 degrees for OHs, 47 degrees for NOHs, and the postero-lateral lip inclination was 56 degrees for OHs and 67 degrees for NOHs. Inferior 3D views showed a mean internal acetabular rotation of 1.5 degrees (4.8 degrees in the dysplastic OH), 3 degrees for NOH. The anterior acetabular inclination angle measured with lateral 3D views was 6 degrees for OHs, 11 degrees for NOHs.

CONCLUSION

Our analysis demonstrated a mean anteversion of the acetabulum despite normalization of the anterior coverage of the hip, particularly in the dysplastic group, in which the osteotomized fragments had anteversion superior to NOH. The unexpected external rotation used to improve anterior coverage of a coax magna in Legg-Calvé-Perthes disease was responsible for the retroversion and the decrease of the posterior coverage.

The use of computed tomography to assess acetabular morphology in Morquio-Brailsford syndrome

PURPOSE

Morquio-Brailsford syndrome (MS) is an autosomal recessive lysosomal storage disorder, a mucopolysaccharidosis, characterized by abnormal metabolism of glycosaminoglycans. Major treatable concerns in patients with MS involve C1 to C2 instability, genu valgum, and hip subluxation. Untreated hip subluxation has been shown to predispose to early onset of arthritis of the hip. Early appropriate pelvic osteotomies may restore (improve) load transmission and retard the onset of arthritis. Computed tomographic (CT) measurements can help determine the site and severity of acetabular deficiency, aiding in selection of the appropriate acetabular procedure. Acetabular morphology in MS has not been described in the literature. The purpose of this study was to evaluate morphology (shape) of the acetabulum in MS using two-dimensional (2-D) CT scans.

METHODS

To assess the acetabular roof, the acetabular index was measured on anteroposterior radiographs of the pelvis. Various CT measures were used to assess the acetabular anatomy in the axial plane.

RESULTS

The average acetabular index on the anteroposterior radiographs of the pelvis was 33 degrees (average age-matched difference from normal, 12 degrees). Two-dimensional CT (axial cuts) showed that the average acetabular anteversion angle was close to normal, measuring 10.9 degrees. The average anterior acetabular index was 58.8 degrees (average age-matched difference from normal, 10.6 degrees), and posterior acetabular index was 53.8 degrees (average age-matched difference from normal, 3.8 degrees). Calculated axial acetabular index ranged from 90 to 133 degrees (mean, 112.6 degrees; average difference from normal, 14.5 degrees).

CONCLUSIONS

Two-dimensional CT of the hip in patients with MS demonstrated a severe dysplasia of the anterior acetabular wall and the roof of the acetabulum, although the acetabular version was normal. Treatment of hip dysplasia in MS should focus on increasing the overall depth of the acetabulum to better contain the femoral head. Two-dimensional CT is recommended before bony acetabular procedures to assess the degree of acetabular deficiencies.

SIGNIFICANCE

Computed tomography of the acetabulum is helpful in preoperative decision making and planning before an acetabular procedure in patients with Morquio-Brailsford syndrome.

Role of the triradiate cartilage in predicting curve progression in adolescent idiopathic scoliosis

Braces are commonly used to treat progressive adolescent idiopathic scoliosis. Several previous studies have reported a correlation between the success of brace treatment and skeletal maturity markers. These studies have not focused on the status of the triradiate cartilage (TRC) as it relates to successful brace treatment for adolescent idiopathic scoliosis. The authors retrospectively evaluated all patients at their institution from 1990 to 1997 with a diagnosis of adolescent idiopathic scoliosis who were treated in a Boston brace. Sixty-two patients met inclusion criteria. At presentation, the average age was 12.87 years, the average Risser sign was 0.56, and 45% of patients had an open TRC. The average follow-up was 2.92 years. Greater than 5 degrees of progression at discontinuation of bracing was considered a failure. Curves with a closed TRC failed bracing 21% of the time, whereas those with an open TRC failed 54% of the time (P = 0.0069). Those curves with a closed TRC progressed 3.12 degrees on average, whereas curves with an open TRC progressed 6.86 degrees. Curves associated with a closed TRC at initiation of bracing progressed less frequently and to a lesser degree than those associated with an open TRC (P = 0.027). Although the TRC is not an independent predictor of curve stability, it is an additional indicator of skeletal maturity and may prove most useful in patients with otherwise borderline indications for brace treatment.

Residual axial plane deformities after hip reconstruction for developmental dysplasia of the hip after walking age

Children with developmental dysplasia of the hip after walking age can be treated with one-stage combined operations. In these procedures, complex deformity corrections at both frontal and axial planes are performed in the guidance of intraoperative stability tests. The reports about the results of these procedures focus on frontal plane assessments but neglect to assess axial plane corrections. We aimed to find out whether hips with unilateral developmental dysplasia of the hip, treated by one-stage combined procedures after walking age and which had good frontal plane containment at the last follow-up, had any axial plane deformities. Twenty-one patients were included in this study according to our described criteria. Mean age at the operation time was 38.04 months (range: 20-86 months), mean follow-up time was 55.54 months (range: 24-117 months) and mean age at latest follow-up was 93.46 months (range: 52-150 months). Femoral anteversions, acetabular anteversions and acetabular sector angles were measured bilaterally in the computed tomography examination. Operated hip measurements were compared with the contralateral hips. One-way variance analysis was used for statistical analysis. Femoral anteversion, acetabular anteversion and posterior acetabular sector angle values of the operated hips were found to be statistically lower than those of the contralateral hips. Our findings suggest that using the intraoperative stability test alone for planning osteotomies may lead to unsuitable femoral head coverage in axial plane although successful frontal plane containment can be obtained. We believe that strict preoperative planning that can be accomplished by a preoperative computed tomography examination should be performed in order to decide innominate osteotomy type and correction amounts.

The assessment of acetabular index: is there still a place for plain radiography?

This is a series of 7 children (14 hips) with a mean age of 7.3 years (range, 3.3-10.5 years) and an underlying diagnosis of developmental dysplasia of the hips and no previous open-hip surgery who underwent plain radiographic and magnetic resonance imaging (MRI) measures of bony acetabular index. There was a significant correlation between the measurement of acetabular index using plain radiography and MRI, with a Spearman correlation coefficient of 0.88 (95% confidence interval, 0.61-0.96; P<0.001) and a mean difference between the 2 measures of 0.36+/-6.5 degrees. Furthermore, the bony and cartilaginous acetabular indexes as measured by MRI had a significant correlation with a Spearman correlation coefficient of 0.88 (95% confidence interval, 0.80-0.98; P<0.001). We suggest that plain radiography is still an appropriate tool for follow-up for the nonoperated hip with developmental dysplasia and may be a good indicator of hip cartilaginous development.

Anteversion of the acetabulum and femoral neck in early walking age patients with developmental dysplasia of the hip

Computed tomography measurements were made to quantify the relationship between the anteversion of the acetabulum and femoral neck in 27 early walking age patients (age range; 18-48 months) with developmental dysplasia of the hip. The centre-edge angle and acetabular index were measured in standard pelvis radiographs, and anteversion of acetabulum and femoral neck were measured by use of two-dimensional computed tomography in 25 complete dislocated, 19 subluxated and 10 unaffected hips (a total of 54 hips). The diagnosis of dysplasia, subluxation and complete dislocation of developmental hip dysplasia were determined radiographically using Ishida's criteria. There were statistically significant differences between the three groups for the centre-edge angle, the acetabular index, and acetabulum anteversion. There was no statistically significant difference between the three groups for femoral neck anteversion. The acetabular anteversion was found to be 13.4+/-2.8 degrees (mean+/-SD) in unaffected hips, 16.7+/-1.9 degrees in subluxated hips and 19.8+/-2.5 degrees in complete dislocated hips. There was statistically significant difference between the three groups, with a wide range of acetabular anteversion values noted in all groups (9-26 degrees ). The acetabular anteversion was increased on the dislocated side in each patient and we found no retroverted acetabulum. On the other hand there was no significant difference between the groups with regards to femoral neck anteversion. We conclude that confirming anteversion of the acetabulum and the femoral neck by two-dimensional computed tomography is needed in treatment planning of early walking age patients with developmental hip dysplasia.

Microcomputed tomography imaging of skeletal development and growth

Skeletogenesis is an exquisitely orchestrated and dynamic process, culminating in the formation of highly variable and complex mineralized structures that are optimized for their function. While cellular and molecular biology studies have provided tremendous recent progress toward understanding how patterns of bone formation are regulated, high resolution imaging techniques such as microcomputed tomography (micro-CT) can provide complementary quantitative information about the progressive changes in three-dimensional (3-D) skeletal morphology and density that occur during early skeletal development and postnatal growth. Furthermore, recently developed in vivo micro-CT systems promise to be a powerful and efficient tool for noninvasively monitoring normal skeletogenesis, as well as for evaluating the effects of genetic or environmental manipulation. This review focuses on the use of micro-CT imaging and analysis to better understand normal and abnormal skeletal development and growth.

Computed tomographic measurements of the hip morphology of 10 healthy German shepherd dogs

Linear measurements were made by computed tomography of the diameter of the femoral head, the width and depth of the acetabulum and the dorsal and ventral acetabular rim distances in 10 healthy German shepherd dogs, and angular measurements were made of the axial acetabular index, acetabular anteversion, and the dorsal and ventral centre-edge angles. There were no significant differences between the measurements made on the left and right sides. The width of the acetabulum was about twice its depth, and was a little larger than the diameter of the femoral head. The mean values of the axial acetabular index, acetabular anteversion, and ventral and dorsal centre-edge angles were 100.9 degrees, 25.1 degrees, 48.0 degrees and 12.2 degrees, respectively.

Selective anterior fusion of thoracolumbar/lumbar curves in adolescents: when can the associated thoracic curve be left unfused?

STUDY DESIGN

A retrospective multicenter study was conducted to investigate patients with a major thoracolumbar/lumbar adolescent idiopathic scoliosis and an associated minor thoracic curve treated with an anterior instrumentation and fusion of the lower curve.

OBJECTIVE

To establish criteria for determining when such curves can be successfully treated by an anterior only procedure of the lower curve with acceptable spinal balance and residual thoracic curve.

SUMMARY OF BACKGROUND DATA

Anterior spinal instrumentation techniques have been proved effective for the management of isolated thoracolumbar/lumbar scoliosis with small compensatory thoracic curves. The success of a selective anterior fusion when the associated thoracic curve had some structural changes in a small preliminary study was variable and was the stimulus for this study.

METHODS

A multicenter study involved 49 adolescent patients with a major thoracolumbar/lumbar curve in which the associated minor thoracic curve measured between 30 degrees and 55 degrees. In all the patients, the apical vertebra of the lower curve lay outside the midsacral line, and the thoracic apical vertebra fell outside a line dropped from the center of C7. Multiple radiographic parameters were evaluated. The Risser sign, height, weight, onset of menses, and closure of the triradiate cartilages were studied to access the patients' maturity. All the patients were observed at least 2 years. Patients were considered to have a satisfactory result if the thoracic curve at the final follow-up assessment measured 40 degrees or less, if balance and sagittal alignment were reasonable, and if additional procedures were not required.

RESULTS

At final follow-up assessment, two groups emerged. Group 1 (n = 43) had satisfactory results. The preoperative thoracic curve in this group averaged 40 degrees and 26 degrees after surgery. The lumbar curve averaged 56 degrees before surgery and 22 degrees after surgery. Group 2 (n = 6) had unsatisfactory results. The average thoracic curve was 49 degrees before surgery 54 degrees after surgery, whereas the lumbar curve averaged 59 degrees before surgery and 27 degrees after surgery. Three of these patients underwent posterior thoracic instrumentation and fusion.

CONCLUSIONS

Statistical analysis showed that a successful surgical outcome was dependent on both the structural changes in the thoracic curve and the patient's maturity. The thoracolumbar/lumbar-thoracic (TL/L:T) Cobb ratio in combination with the degree of the thoracic curve on lateral bending was the best predictor among the structural indexes. Of 44 patients with a TL/L:T Cobb ratio of 1.25 or greater and/or a thoracic curve, which bent out to 20 degrees or less, 42 had a satisfactory result. The best predictor among the maturity indexes was closure of the triradiate cartilages. Of 43 patients in whom the triradiate cartilages were closed, 42 had satisfactory results. When this data is combined, the outcome for the thoracic curve can be reasonably predicted.