Three-dimensional computer analysis of complex acetabular insufficiency

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.

Minimally Invasive Radiographic Evaluation of the Dysplastic Hip Joint Configuration in Terms of Surgical Treatment with Hip Preservation by PAO

Introduction

Residual developmental dysplasia of hip (RDDH) is a factor of early osteoarthritis of the hip. The main problems are pain and instability of the hip joint due to inadequate coverage of the femoral head by the acetabulum. The purpose of this study was to radiologically evaluate RDDH after Bernese periacetabular osteotomy (PAO) and to compare RDDH to healthy hips.

Materials and Methods

The radiological parameters of RDDH treated by PAO were retrospectively evaluated. Digital AP pelvic radiographs were taken, including parameters of central edge angle and femoral head coverage, medialization, distalization, and ilio-ischial angle. Clinical assessment is based on the VAS scale. The study group consisted of patients with RDDH, and the control group consisted of patients without RDDH.

Results

After PAO radiological parameters decreased: medialization by 2.68 mm, distalization by 3.65 mm, and ilio-ischial angle by 2.62°. However, there was an increase in the parameters: CEA by 17.61° and FHC by 16.46%. There was a mean 3 point decrease in pain on the VAS scale. There was also a statistically significant radiological difference in the structure of dysplastic hip joints before surgery and healthy hip joints of the control group.

Conclusions

Radiological studies confirmed the effectiveness of the PAO method in the treatment of RDDH. Based on all radiological parameters, differences between healthy and dysplastic hip joints were demonstrated. We believe that a thorough understanding of the values of radiological parameters used to describe dysplastic hip joints will allow us to improve the imaging diagnosis of this condition.

Comparison of Acetabular Measurements Between 2 Validated Software Programs Used in Hip Preservation Surgery

BACKGROUND

Validated software tools (Clinical Graphics [CG] and Hip²Norm) permit measurement of the percentage of femoral head coverage (%FHC), which aids in morphological classification and prediction of outcome after hip preservation surgery.

PURPOSE

(1) To assess whether acetabular parameter measurements determined from 2 commonly used software systems are comparable. (2) To determine which parameters influence the correlation or differences between software outputs and measurements.

STUDY DESIGN

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

METHODS

The study included 69 patients (90 hips) who underwent periacetabular osteotomy and had comprehensive preoperative imaging available. Lateral center-edge angle (LCEA), acetabular index (AI), and %FHC were determined using 3-dimensional computed tomography (CT) measurements by CG and Hip²Norm software. Images of 18 pelvises were segmented to determine spinopelvic parameters and subtended acetabular angles. Between-group measurements were compared using correlation coefficients and Bland-Altman analyses. The difference in the outputs of the 2 programs was defined as delta (Δ). Radiographic parameters were tested to assess whether they were responsible for differences in %FHC between software programs.

RESULTS

Strong correlations between LCEA (ρ = 0.862) and AI (ρ = 0.825) measurements were seen between the Hip²Norm and CG programs. However, weak correlation was seen in the estimate of %FHC (ρ = 0.358), with the presence of a systematic error. Hip²Norm consistently produced lower anterior, posterior, and total %FHC values than CG. The %FHC determined by CG, but not Hip²Norm, correlated with acetabular subtended angles (P < .05). Pelvic tilt measured on CT did not correlate with pelvic tilt estimated by Hip²Norm (P = .56), and ΔPelvicTilt strongly correlated with the difference in %FHC by the 2 software programs (ρ = 0.63; P = .005), pelvic incidence (ρ = 0.73; P < .001), and pelvic tilt (ρ = -0.91; P < .001) as per CT.

CONCLUSION

The correlation of %FHC between Hip²Norm and CG was weak (ρ = 0.358). The difference in measurements of %FHC correlated with ΔPelvicTilt. The %FHC determined by CG strongly correlated with the segmented acetabular subtended angles and thus more likely reflected true values. Hip preservation surgeons should be aware of these measurement differences because %FHC is important in the diagnosis and prognosis of acetabular dysplasia.

Avascular Necrosis of the Hip Compromises Gait Balance Control in Female Juveniles With Unilateral Developmental Dysplasia Treated in Toddlerhood

Avascular necrosis of the hip (AVN) is one of the most severe complications of surgical reduction when treating developmental dysplasia of the hip (DDH). The current study identified the differences in the balance control during walking in terms of the inclination angle (IA) of the center of pressure (COP) to the center of mass (COM), and the rate of change of IA (RCIA) between female juveniles with and without secondary AVN at the hip who were treated for unilateral DDH during toddlerhood as compared to their healthy peers. When compared to female healthy controls, the non-AVN group showed bilaterally similar compromised balance control with significantly decreased IA (p < 0.05) but increased RCIA (p < 0.04) in the sagittal plane during single-limb support (SLS) of the unaffected side, and in the frontal plane during terminal double-limb support (DLS) of the affected side. In contrast, the AVN increased between-side differences in the sagittal IA (p = 0.01), and sagittal and frontal RCIA during DLS (p < 0.04), leading to bilaterally asymmetrical balance control. Secondary AVN significantly reduced IA and RCIA in the sagittal plane (p < 0.05), and reduced range of RCIA in the frontal plane during initial DLS (p < 0.05). The trend reversed during terminal DLS, indicating a conservative COM-COP control in the sagittal plane and a compromised control in the frontal plane during body weight acceptance, with a compromised COM-COP control in the frontal plane during weight release. The current results suggest that increased between-side differences in the sagittal IA, and sagittal and frontal RCIA during DLS are a sign of AVN secondary to treated unilateral DDH in female juveniles, and should be monitored regularly for early identification of the disease.

3-D acetabular morphology of the neuromuscular hip: implications for preoperative planning

The importance of precisely understanding the pathoanatomy of acetabular dysplasia prior to surgical treatment has long been recognized. Acetabuloplasties for neuromuscular hip dysplasia have typically aimed to improve the acetabulum by increasing posterior-superior coverage, as previous three-dimensional (3-D) computed tomography (CT) studies have shown that acetabular dysplasia in neuromuscular hips is primarily in the direction of posterior-superior subluxation or dislocation. The purpose of this study was to identify differences in 3-D morphology between normal hips and dysplastic neuromuscular hips, specifically to identify areas of acetabular deficiency to guide preoperative decision-making. Patients treated for neuromuscular hip dysplasia at a single institution between 2009 and 2017 with a preoperative high-resolution pelvic CT scan (28 hips) were evaluated with custom software to measure acetabular morphology. Acetabuli were divided into equal octants; coverage angles were measured for each octant of interest. Variables were compared with age- and sex-matched normal controls (56 hips). We found a wide range of hip pathology in our study cohort. Five hips had no sectors with abnormal coverage. One hip (4%) was overcovered anteriorly. The remaining pathology was undercoverage located anteriorly [n = 7 (25%)], superiorly [n = 6 (21%)], posteriorly [n = 4 (14%)] or globally [n = 5 (18%)]. Our findings indicate that individual patients with neuromuscular acetabular dysplasia have unique deformities that do not uniformly conform to a specific area of acetabular deficiency. It is imperative to define the specific 3-D acetabular deficiency location and magnitude for accurate preoperative planning. Level of evidence: Level III.

Radiographic hip screening for children with cerebral palsy: an imaging and reporting update

Children with cerebral palsy are at increased risk of hip dislocation. Detecting hip subluxation through radiographic hip screening is an essential component of hip surveillance and has been shown to prevent hip dislocations. Large-scale hip surveillance programs are being implemented nationwide, highlighting the importance of uniform technical and reporting standards.

3D Characterization of Acetabular Deficiency in Children with Developmental Dysplasia of the Hip

BACKGROUND

The purpose of this study is to determine if a quantitative method can be used to identify differences in 3D morphology between normal and developmentally dysplastic hips and to identify specific areas of undercoverage in children with DDH compared to age- and sex-matched controls.

METHODS

Subjects were included if they were typically developing children with no other underlying conditions affecting their musculoskeletal system and had an available pelvic CT scan (67 hips). Custom software was used to measure standard variables defining acetabular morphology (version, tilt, surface area). Acetabuli were divided into equal octants; coverage angles were measured for each octant of interest. Variables were compared with age- and sex-matched controls (128 hips) using analysis of variance or the Mann-Whitney test.

RESULTS

Hips with DDH were more anteverted compared to normal hips (DDH: 22.6˚, Control: 16.4˚, p < 0.001). The surface area was similar between groups. 28% of hips had a global deficiency, 24% were anteriorly deficient, 19% were laterally deficient, 10% were anteverted (under covered anteriorly and over covered posteriorly), 3% were posteriorly deficient, and 15% of hips had borderline undercoverage. None of the hips in this cohort were found to be retroverted.

CONCLUSIONS

This is the first study to quantify the 3D acetabular deficiency in children with DDH compared to age- and sex-matched controls. We found wide variability in coverage patterns among dysplastic hips. It is imperative to define the specific acetabular deficiency for each individual patient prior to surgical correction.

LEVEL OF EVIDENCE

III - Case-control study.

Inter-rater and Intrarater Reliabilities of the Identification of a "Gothic Arch" in the Acetabulum of Children With Cerebral Palsy

BACKGROUND

Progressive hip displacement in children with cerebral palsy (CP) is monitored by measuring migration percentage (MP) on anteroposterior (AP) pelvis radiographs. Accurate measurement of MP requires the lateral margin of the ossified acetabulum to be identified for the placement of Perkin's line. It has been suggested that when there is an erosion of the acetabular rim, described as a gothic arch, the midpoint of the arch be used for the placement of Perkin's line. However, this requires that there be agreement on what constitutes a gothic arch. The purpose of this study was to evaluate the inter-rater and intrarater reliabilities of identifying a gothic arch on pelvis radiographs.

METHODS

An online survey with 100 AP pelvis images (200 hips) of children with CP was sent to international experts. Participants were asked to identify which hip(s) had a gothic arch (left, right, both, and neither). The Fleiss κ statistic for inter-rater reliability was calculated. Eight weeks later, the images were shuffled and redistributed to calculate intrarater reliability.

RESULTS

The initial survey was completed by 10 participants with 9 participants completing the second survey. The average inter-rater κ value was 0.18 [95% confidence interval (CI), 0.14-0.23] and 0.19 (95% CI, 0.14-0.24) for the 2 surveys, respectively. Among the pediatric orthopaedic surgeons subgroup, the κ values were 0.06 (95% CI, 0.02-0.1) and 0.08 (95% CI, 0.03-0.13). The average intrarater reliability κ value was 0.61 (95% CI, 0.2-1), ranging from 0.32 to 0.86.

CONCLUSIONS

There were poor inter-rater and moderate intrarater reliabilities in identifying a gothic arch on AP pelvis radiographs in children with CP. Further characterization and clarification of what constitutes a gothic arch are required. The lack of agreement on the identification of a gothic arch may negatively impact the measurement of MP and referrals to a pediatric orthopaedic surgeon.

Is the Gothic Arch a reliable radiographic landmark for migration percentage in children with cerebral palsy?

INTRODUCTION

Reimers migration percentage (MP) is the gold standard for measuring hip displacement in children with cerebral palsy (CP). Hip surveillance registries proposed using the top of the Gothic arch (GA) as a modification in patients with acetabular dysplasia because the classical method (CM) described by Reimers may underestimate hip migration. The aim of this study is to assess the inter- and intra-observer reliability of the modified method (MM) versus the CM and identify their effect on the MP.

METHODS

We performed a retrospective review of 50 children with CP, who had a hip radiograph at our institution between 1st April 2014 and 28th February 2018. All hip radiographs were carefully selected to show the presence of a GA. Four observers measured the MP using the CM and MM for each patient. Interclass coefficient was used to estimate inter- and intra-observer reliability.

RESULTS

Inter-observer reliability was excellent for the CM with ICC 0.96 (95% CI 0.94 to 0.97) and good for the MM, ICC 0.78 (95% CI 0.51 to 0.89) p < 0.001. Intra-observer reliability was excellent for both methods raging from ICC 0.94 to 0.99 for the CM and ICC 0.89 to 0.95 for the MM. The mean MP was 19% for the CM and 28% for the MM (p < 0.001).

CONCLUSION

The CM is more reliable than the MM to measure hip migration in children with CP. If the CM is used and acetabular dysplasia with a GA are present on the hip radiograph, then a 9% hip migration underestimation should be considered on decisions for both referral and surgical management.

LEVEL OF EVIDENCE

II.

Reliability of Radiographic Assessments of the Hip in Cerebral Palsy

INTRODUCTION

Children with cerebral palsy are at risk for progressive hip displacement. Since surveillance for hip displacement uses specific radiographic measurements to guide decision making, it is important to establish the reliability of these measurements, which include Reimer's migration percentage (MP), acetabular index or acetabular angle (AI or AA), and pelvic obliquity (PO). The purpose of this study was to determine the intraobserver and interobserver reliability of these radiographic measures among an international group of pediatric orthopaedic surgeons participating in the prospective international multicenter Cerebral Palsy Hip Outcomes Project (CHOP) currently underway to evaluate the outcomes of hip interventions in cerebral palsy.

METHODS

Two compact discs (CDs) containing the same 25 anteroposterior pelvis radiographs in Digital Imaging and Communications in Medicine (DICOM) format were provided to participating surgeons at least 2 weeks apart. To reduce the likelihood of recall or any effects of learning or fatigue, the order of the radiographs varied on the 2 CD versions, and participating surgeons received the 2 CDs in random order. The intraclass correlation coefficients (ICCs) were calculated to assess interobserver and intraobserver reliability. Mean absolute differences of hip measurements obtained at 2 time points were also calculated.

RESULTS

The MP had the highest reliability followed by PO, AI, and AA with a mean intrarater ICC (SD; range) of 0.95 (0.04; 0.84 to 0.98); 0.92 (0.03; 0.85 to 0.97); 0.84 (0.05; 0.75 to 0.92); and 0.82 (0.14; 0.51 to 0.98); respectively. The mean interrater ICC (SD; range) for MP, PO, AI, and AA were 0.94 (0.05; 0.78 to 0.99); 0.90 (0.04; 0.76 to 0.99); 0.79 (0.08; 0.52 to 0.93); and 0.69 (0.23; 0.42 to 0.98) for MP, PO, AI, and AA, respectively. The mean (SD; 95% confidence interval) for the absolute difference between the 2 measurements for the raters was 4.9% (2.9%; 3.4%-6.4%); 3. 8 degrees (1.2 degrees; 3.1-4.5 degrees); 2.6 degrees (1.5 degrees; 1.7-3.5 degrees); and 1.3 degrees (0.3 degrees; 1.29-1.31 degrees) for MP, AI, AA, and PO, respectively.

CONCLUSIONS

MP is a reproducible measure with excellent intrarater and interrater reliability. However, differences in MP of <7% should be treated with caution as these might be a consequence of measurement error. Although we found a high level of intrarater and interrater reliability of the AI, AA, and PO, these measurements are more variable and not ideal for use as discrete outcome measures. Instead, these parameters might be useful for prognostication and decision making when consistent trends are observed longitudinally over time which might be better indications of true change.

Femoral and Dega osteotomies in the treatment of habitual hip dislocation in Down syndrome patients - is it efficient or not?

PURPOSE

The purpose of this case series study is to report on the intermediate-term outcomes following a femoral varus derotational osteotomy (FVDO) performed in conjunction with a Dega osteotomy (DO) in management of hip -instability in Down syndrome (DS) patients.

METHODS

Ten hips in seven children with DS suffering from hip dislocation were included. All patients included in this study had hip dislocation in the habitual phase and painless mobile hip to full abduction. All patients were firstly subjected to FVDO. An additional DO was added if intraoperative assessment demonstrated posterior instability. The mean age at time of surgery was 5.6 years (3 to 7). There were three male and four female patients. All patients were followed up after two years with a mean follow-up of 3.27 years (2 to 5). All operations were performed by the first author.

RESULTS

There was improvement of neck shaft angles (130° to 175°, median = 160° preoperatively, to 120° to 140°, median =130° postoperatively). The Shenton line was restored in all our cases. There was also improved percentage of the femoral head uncovered by the lateral wall of the acetabulum (25° to 100° with median = 45° preoperatively, to 0° to 15° with median = 5° postoperatively) and improved posterior acetabular coverage, which was assessed by CT.

CONCLUSION

FVDO combined with DO without -capsulorrhaphy is efficient in the management of hip instability in DS, as it corrects hip biomechanics and increases posterior acetabular coverage.

LEVEL OF EVIDENCE

IV - retrospective case series.

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.

Pedobarographic Analysis Following Pemberton's Pericapsular Osteotomy for Unilateral Developmental Dysplasia of the Hip: An Observational Study

Successful clinical and radiographic outcomes have been reported in patients with unilateral developmental dysplasia of the hip (DDH) following Pemberton pericapsular osteotomy (PPO). However, residual gait deviations are seen in both the affected and unaffected limbs. To date it is not known whether these deviations result in abnormal plantar pressure in such patients. This study investigated this possibility by performing pedobarographic, clinical, and radiographic examinations after PPO in 20 patients (age: 102.5 ± 19.0 months) with unilateral DDH who underwent PPO at 34.2 ± 9.8 months of age. Plantar pressure was evaluated using the Footscan pressure plate (RsScan International, Olen, Belgium). Each foot was subdivided into 10 zones and peak pressure, force-time integral as a percentage of total FTI, and contact time as a percentage of total stance time was estimated. The minimum duration of follow-up was 24 months (mean: 68.3 ± 20.3 months). The data were compared with 20 age- and weight-matched healthy controls. Despite clinical and radiographic examinations showing satisfactory results according to modified McKay and Severin criteria, significant differences in plantar pressure parameters were identified between the affected limbs, the unaffected limbs, and normal controls. No significant differences were found between patients classified as "excellent or good" and those rated as "fair" according to the modified Severin criteria. Pedobarographic results showed the existence of the residual plantar pressure deviations during walking in patients treated with PPO for unilateral DDH. Longer follow-up will be needed to more fully evaluate the effect of these deviations on gait.

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.

Associations between early radiographic and computed tomographic measures and canine hip joint osteoarthritis at maturity

OBJECTIVE

To evaluate associations of measures assessed by radiography, 2-D CT, and 3-D CT of the hip joints of immature dogs with osteoarthritis in the same joints at maturity.

ANIMALS

46 hound-type dogs from a colony predisposed to osteoarthritis.

PROCEDURES

Images of hip joints (1/dog) were obtained at 16, 32, and 104 weeks of age. Radiographic measures included Norberg angle, distraction index, and osteoarthritis score. Two-dimensional CT measures included acetabular index, percentage of femoral head coverage, and center edge, horizontal toit externe, acetabular anteversion, and ventral, dorsal, and horizontal acetabular sector angles. Three-dimensional CT measures were femoral head and neck volume, femoral neck angle, and femoral head and neck radius. Differences among measures at 16 and 32 weeks in dogs with different osteoarthritis scores at later time points, relationships among variables at each time point, and relationships of single and combined measures with the presence of osteoarthritis at 104 weeks were evaluated.

RESULTS

The 16- and 32-week distraction index, center edge angle, dorsal acetabular sector angle, horizontal acetabular sector angle, percentage of femoral head coverage, acetabular index, and Norberg angle and the 32-week femoral neck angle varied significantly with osteoarthritis severity at 104 weeks. Presence of osteoarthritis in mature dogs was most strongly associated with 16-week combined measures of distraction index and center edge angle and 32-week combined measures of dorsal acetabular sector angle and Norberg angle.

CONCLUSIONS AND CLINICAL RELEVANCE

Changes in hip joint morphology associated with radiographic signs of osteoarthritis were detectable as early as 16 weeks of age and varied with osteoarthritis severity in adult dogs. The use of combined hip joint measures may improve early identification of dogs predisposed to hip joint osteoarthritis.

Imaging evaluation of developmental hip dysplasia in the young adult

OBJECTIVE

The purpose of this article is to review the clinical and imaging features as well as the potential complications of hip dysplasia in the young adult. Hip dysplasia is an important cause of secondary osteoarthrosis, which accounts for a significant proportion of patients requiring total hip arthroplasty. The radiographic diagnosis of mild hip dysplasia in the young adult may be subtle and is primarily based on the detection of deficient coverage of the femoral head by the acetabulum.

CONCLUSION

Cross-sectional imaging, including CT and MRI, afford improved detection and characterization by providing morphologic information about acetabular deficiency. MRI also allows evaluation of potential associated injuries to the articular cartilage, the labrum, and the ligamentum teres. Familiarity with the radiographic and cross-sectional imaging findings of mild hip dysplasia in the young adult may allow a timely diagnosis and implementation of treatment strategies, which may prevent or delay the development of early osteoarthritis.

Evaluation of femoral head coverage following Chiari pelvic osteotomy in adolescents by three-dimensional computed tomography and conventional radiography

INTRODUCTION

Currently, the cover of the femoral head was mainly assessed using conventional plain films after Chiari pelvic osteotomy in most studies. The purpose of the current study was to observe whether the femoral head coverage measured by three-dimensional computed tomography (3D-CT) was consistent with the radiographic findings.

PATIENTS AND METHODS

A total of 24 patients (24 hips) with an average age of 11.5 years, underwent Chiari osteotomy due to acetabular dysplasia, and 15 subjects (30 hips) of normal control with a mean age of 12 years were involved in the study. The pre- and postoperative coverage of femoral head was measured by using conventional plain film and 3D-CT on the anterior 1/4, middle 1/2, and posterior 1/4 coronal plane. The anterolateral, mediolateral and posterolateral coverage measured by 3D-CT were compared with the coverage measured by plain radiograph, and which were also compared with the normal control individuals.

RESULTS

The postoperative anterolateral, mediolateral coverage measured by 3D-CT was significantly smaller than that measured by radiography (P < 0.01). No significant difference was found between the 3D-CT measurements on the posterolateral coverage and the radiographic results. The anterolateral femoral head coverage in the patients following Chiari pelvic osteotomy was also smaller than that in the normal control individuals (P = 0.026). In contrast, the postoperative posterolateral coverage in the patients was more excessive than that in the normal control individuals (P = 0.001).

CONCLUSION

Conventional radiographs may show sufficient cover of the femoral head after Chiari osteotomy, whereas in fact, the cover may be not perfect, especially on the anterolateral part. Therefore, the postoperative 3D-CT is beneficial for evaluating the outcome of Chiari osteotomy, especially when the anterolateral coverage o

The early detection and management of unstable concentric closed reduction of DDH with percutaneous K-wire fixation in infants 6 to 12 months of age

BACKGROUND

In some infants with developmental dysplasia of the hip, concentric closed reduction, although initially achievable, cannot be maintained even by casting because of a deficient posterior acetabular wall. Usually, these hips will redislocate in the cast and a rereduction will be necessary, often requiring an open reduction subsequently.

METHODS

A 3-year retrospective review of 88 infants, (M/F; 14/74) 6 to 12 months of age with 124 dislocated hips, was conducted to assess the efficacy of percutaneous Kirschner wire fixation in achieving permanent hip stability. A "hip-at-risk" instability test was developed to detect potentially unstable hips at the time of closed reduction that might redislocate in the hip spica cast, and these hips were stabilized with a percutaneous K-wire through the greater trochanter into the pelvic bone.

RESULTS

The hip instability test was positive in 27 hips and negative in 97. Percutaneous K-wire fixation was used to stabilize 21 hips with a positive hip instability test. All 21 unstable hips that were stabilized with the K-wire technique maintained their concentric reduction and went on to stable development. No K-wire breakage was encountered and only 1 superficial pin tract infection occurred.

CONCLUSIONS

K-wire stabilization of unstable closed reductions is a safe, reliable technique for maintaining concentric hip reduction in infants 6 to 12 months of age with developmental dislocation of the hips.

LEVEL OF EVIDENCE

Level II retrospective study.

Virtual Bernese osteotomy using three-dimensional computed tomography in hip dysplasia

BACKGROUND

Accurate assessment of acetabular morphology and its relationship to the femoral head is essential for planning a periacetabular osteotomy. We observed the acetabular coverage after virtual Bernese osteotomy using computer-aided technique.

METHODS

Three-dimensional computed tomography of 18 normal hips and 3 symptomatic dysplastic hips were analyzed. Through the center of the femoral head, vertical images were obtained at 10° intervals from 0° to 180° of rotation, using multiplanar reformation technique. Subsequently we measured 19 center-edge angles (CEAs) from each acetabulum. Four types of virtual osteotomy were performed on the three dysplastic hips. The adequacy of acetabular coverage after osteotomy was determined by comparing CEAs after correction with normal CEAs.

RESULTS

Pearson correlation coefficients between the CEAs measured from normal cases and postoperative cases after lateral rotation of osteotomized fragments were 0.906 in case 1, 0.975 in case 2, 0.976 in case 3. Additional anterior rotation increased anterior acetabular coverage and simultaneously decreased posterior coverage in all three cases.

CONCLUSION

Computer-aided virtual surgery technique based on three-dimensional computed tomography information enabled acetabular coverage to be quantified preoperatively in Bernese osteotomy. Lateral rotation of osteotomized acetabular fragments improved anterior and posterior coverage as well as lateral coverage.

Can excessive lateral rotation of the ischium result in increased acetabular anteversion? A 3D-CT quantitative analysis of acetabular anteversion in children with unilateral developmental dysplasia of the hip

BACKGROUND

The purposes of this study were to observe whether increased acetabular anteversion was a universal finding and whether excessive lateral rotation of the ischium was correlated with increased acetabular anteversion.

METHODS

We retrospectively reviewed 90 patients with unilateral developmental dysplasia of the hip (DDH), including 77 female patients and 13 male patients with an average age of 18 months (range, 6 to 60 mo). A total of 31 children were involved in the normal control group, including 14 girls and 17 boys with an average age of 21 months (range, 7 to 48 mo). The acetabular anteversion angle (AA), pubic relative length (PRL), ischiac relative distance (IRD), lateral rotational angle of the ischium (IA), and pubic rotational angle were compared between the affected hips and the unaffected hips in the unilateral DDH group and between the right hips and left hips in the normal control group.

RESULTS

No retroverted acetabulum was found in any hip. No significant differences in AA, IA, pubic rotational angle, IRD, and PRL were found between the left and right hips in the normal control group. However, the PRL was shorter in the affected hips than in the unaffected hips (P < 0.05). The average IA, AA, and IRD in the affected hips were larger than that in the unaffected hips (P < 0.05). The IA was positively correlated with AA and IRD in the DDH group.

CONCLUSIONS

Increased acetabular anteversion in affected hips is a universal finding in unilateral DDH. The deficiency of the anterior wall in the acetabulum is not a unique reason for increased acetabular anteversion in unilateral DDH, because it is also correlated with excessive lateral rotation of the ischium.

LEVEL OF EVIDENCE

IV.

Adolescents after Pemberton's osteotomy for developmental dysplasia of the hip displayed greater joint loading than healthy controls in affected and unaffected limbs during gait

Patients after reduced developmental dysplasia of the hip (DDH) are at higher than normal risk of developing avascular necrosis (AVN) of the femoral head and degenerative hip osteoarthritis (OA) that are closely related to abnormal loadings. We aimed to determine the lower limb loadings in adolescents after Pemberton's osteotomy for unilateral DDH. Eleven females (age: 10.6 ± 1.0 years), who had received Pemberton's osteotomy for unilateral DDH at 1.6 ± 0.5 years of age, and 12 age-matched healthy controls were studied using gait analysis. Compared to the normal controls, the patients were displayed greater peak axial forces at the hip, knee, and ankle in both limbs, with greater loading rates in the ground reaction force (GRF) and at the hips (p < 0.05 for all comparisons). The increased rates of repetitive loading around heel strike in both hips suggest that patients treated for unilateral DDH using Pemberton's osteotomy may be at higher risk of premature hip OA. The increased axial forces at the affected hip may be a contributing factor to the development of AVN of the femoral head in these patients, especially when incomplete coverage, insufficient congruency, and/or damaged articular surfaces remain after the osteotomy. Therefore, monitoring the loading condition at the hip is necessary for a more accurate assessment of the risk of developing joint pathology in patients after reduced DDH.

Relationships of hip joint volume ratios with degrees of joint laxity and degenerative disease from youth to maturity in a canine population predisposed to hip joint osteoarthritis

OBJECTIVE

To assess relationships of acetabular volume (AV), femoral head volume (FV), and portion of the femoral head within in the acetabulum (FVIA) with each other and with degrees of hip joint laxity and degenerative joint disease from youth to maturity in dogs predisposed to developing hip joint osteoarthritis (OA).

ANIMALS

46 mixed-breed half- or full-sibling hound-type dogs.

PROCEDURES

The distraction index (DI), AV, FV, FVIA, and degree of osteoarthritis (OA score) were quantified in 1 hip joint at 16, 32, and 104 weeks of age. Relationships among variables were evaluated within and between ages. Ratios corresponding to OA scores were compared within ages. Differences among 16-week ratios corresponding to 32-week OA scores and among 16- and 32-week ratios corresponding to 104-week OA scores were evaluated.

RESULTS

Significant positive relationships existed between FV and AV across ages as well as between FVIA/FV and FVIA/AV and between DI and OA score across and within most ages. Such relationships also existed within these variables across most ages. Negative relationships of DI and OA scores with FVIA/FV and FVIA/AV within and among all ages were significant. Sixteen-week AVs, FVs, and FVIAs were greater and FV/AVs and OA scores were less than 32- and 104-week values. The 32-week FVIA/FV was less than 16- and 104-week values, and the 32-week FVIA/AV was less than the 104-week value. The FVIA/FV and FVIA/AV were lower and the DI was higher with higher OA scores within and among most ages.

CONCLUSIONS AND CLINICAL RELEVANCE

Structural volumes in lax canine hip joints changed predictably relative to each other during growth, despite degenerative changes. Measures developed in this study may augment current diagnosis and treatment strategies for hip dysplasia in dogs.

Percutaneous innominate pelvic osteotomy without the use of bone graft for femoral head coverage in children 2-8 years of age

Percutaneous innominate pelvic osteotomy without the use of bone graft as treatment for hip diseases is proposed as another tool to handle this pathology, which occurs frequently in our area, without changing postural correction at the level of the pelvis by secondary transiliac lengthening through an unilateral iliac bone graft at the lower extremity. This technique was developed by biomechanical studies in corpses and was later performed on children. This was a prospective, multicentric, longitudinal study of a case series in children between 2 and 8 years of age with developmental hip dysplasia, Legg-Calve-Perthes disease, aseptic or avascular necrosis, congenital or acquired lesions of the femoral head having obtained previous consent from the parents. In 121 patients with increases in femoral head coverage in a concentric hip joint, the average follow-up period was 4.1 years (range 6 months to 5 years). The vertical-center-anterior angle of Lequesne and the center-edge angle of Wiberg, both of which showed significant improvement in the coverage of the femoral head with an average of acetabular presurgical index of 38.2 degrees (P=0.002) and a postsurgical average of 19.8 degrees (P=0.003), angles of lateral uncovering of the femoral head of 12.3 degrees (P=0.0019) and a postsurgical angle of 23.2 degrees (P=0.004). The registered complications were 2.7% (P=0.047). The results offer many advantages over the current treatments on handling congenital diseases or acquired diseases of the hip and can indicate an alternative to the other methods of treatment which is possibly less aggressive and with a better future for the patient.

Interobserver repeatability of measurements on computed tomography images of lax canine hip joints from youth to maturity

OBJECTIVES

To determine interobserver repeatability of measurements on computed tomography (CT) images of lax canine hip joints at different ages and in the presence of degenerative joint disease at maturity.

STUDY DESIGN

Longitudinal observational investigation.

ANIMALS

Sibling crossbreed hounds.

METHODS

Pelvic CT was performed at 20, 24, 32, 48, 68, and 104 weeks of age. Measures were performed on 3 contiguous two-dimensional (2D) transverse CT images of both hips at each time point by 3 investigators. Center-edge angle (CEA), horizontal toit externe angle (HTEA), ventral (VASA), dorsal (DASA), and horizontal (HASA) acetabular sector angles, acetabular index (AI), and percent femoral head coverage (CPC) were measured. Interobserver repeatability was quantified with the intraclass correlation coefficient (ICC). Satisfactory repeatability was considered when ICC >or=0.75.

RESULTS

DASA, CEA, and CPC were repeatable in all age groups. HASA and HTEA were repeatable for all but 1 time point. At 20 weeks of age, all measures but AI were repeatable, and at 104 weeks of age, DASA, CEA, CPC, and HASA were repeatable. Measures were repeatable in hips with and without degenerative changes with the exceptions of AI and HASA in normal hips and VASA and HTEA in osteoarthritic hips.

CONCLUSIONS

Most 2D CT measurements examined were repeatable regardless of age or joint disease.

CLINICAL RELEVANCE

Two-dimensional CT measures may augment current techniques for assessing joint changes in lax canine hips.

Triple pelvic osteotomy in complex hip dysplasia seen in neuromuscular and teratologic conditions

BACKGROUND

The site of acetabular deficiency in hip dysplasia associated with neuromuscular or teratologic conditions is described as posterolateral or global unlike the anterosuperior location in developmental dysplasia of the hip. The triple pelvic osteotomy is a redirectional osteotomy that provides complete control over acetabular fragment placement and can be used to optimize coverage in complex hip dysplasia in skeletally immature hips in which other pelvic osteotomies are ineffective, incomplete, or counterproductive.

METHODS

Thirty-one hips in 26 patients (11 females and 15 males) that had complex hip dysplasia associated with neuromuscular or teratologic conditions were treated with triple pelvic osteotomies. The patients were divided into 2 groups: spastic and nonspastic. Nine of the 15 spastic patients were nonambulatory whereas 1 of the 11 nonspastic patients was nonambulatory. The average age of the patient was 9.6 years and time since surgery was 3 years. Preoperative and postoperative migration index, lateral center-edge angles, and changes in Shenton's line were noted. Computed tomography scans were also compared when available. The surgical technique is described.

RESULTS

The average preoperative lateral center-edge angles and migration index were 1.1 and 42.8 and postoperatively were 39 and 3.7. There was 1 nonunion of the pubic ramus with sciatic nerve palsy. Two patients continued to have persistent hip subluxation.

CONCLUSIONS

We conclude that triple pelvic osteotomy provides adequate mobility of the acetabular fragment to optimize coverage and improve stability in skeletally immature individuals with complex hip dysplasia associated with neuromuscular and teratologic conditions.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Novel three-dimensional MRI technique for study of cartilaginous hip surfaces in Legg-Calvé-Perthes disease

Treatment of Legg-Calvé-Perthes disease (LCPD) may improve if new knowledge can be obtained regarding how articular cartilage changes shape during the course of this disorder. A new technique is presented showing how analyses of magnetic resonance images can be used to quantify the three-dimensional changes in the femoral and acetabular articulating cartilage surfaces of children with LCPD. Ten male subjects (8 +/- 1 years) with unilateral LCPD were enrolled in this IRB approved study. Sets of magnetic resonance images of both hips were obtained at three different times. Three-dimensional virtual models of the cartilage were created from these images, and mathematical spheres were fit to the articulating surfaces. Five parameters (size, shape deformity (sphericity error), radial growth rate, joint fit, and joint incongruity) were used to quantify cartilage surface shape. Data were analyzed by using a linear mixed-model. Joint incongruity, i.e., the distance between the centers of the femoral and acetabular spheres, was slightly more than 2.5 times larger (p = 0.001) in LCPD hips than the contralateral normal hips. Cartilage shape deformity was 65% larger in hips with LCPD than in normal hips. Growth rates of the femoral head and the opposing acetabular surface showed that distortion of the femoral surface occurred first and the opposing acetabular surface followed. Mean radial difference (acetabular surface radius minus femoral surface radius) in LCPD hips was less than half (p < 0.01) the value of normal hips. Interobserver variability was approximately 10% of the value attributable to LCPD. This is the first known report presenting a technique that quantifies the three-dimensional size, deformity, growth, fit. and incongruity of the femoral and acetabular articulating cartilaginous surfaces of LCPD and contralateral normal hips. The data obtained support the use of this technique and provide pilot data for a future clinical study of LCPD. Objective assessment of cartilage shape enabled by this technique may aid future diagnoses, enable monitoring of three-dimensional femoral and acetabular remodeling, and permit quantitative assessment of treatment efficacy.

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.

Three-dimensional computed tomography analysis of non-osteoarthritic adult acetabular dysplasia

OBJECTIVE

Little data exists on the original morphology of acetabular dysplasia obtained from patients without radiographic advanced osteoarthritic changes. The aim of this study was to investigate the distribution and degree of acetabular dysplasia in a large number of patients showing no advanced degenerative changes using three-dimensional computed tomography (3DCT).

MATERIALS AND METHODS

Eighty-four dysplastic hips in 55 consecutive patients were studied. All 84 hips were in pre- or early osteoarthritis without radiographic evidence of joint space narrowing, formation of osteophytes or cysts, or deformity of femoral heads. The mean age at the time of CT scan was 35 years (range 15-64 years). 3D images were reconstructed and analyzed using recent computer imaging software (INTAGE Realia and Volume Player). Deficiency types and degrees of acetabular dysplasia were precisely evaluated using these computer software.

RESULTS

The average Harris hip score at CT scans was 82 points. Twenty-two hips (26%) were classified as anterior deficiency, 17 hips (20%) as posterior deficiency, and 45 hips (54%) as lateral deficiency. No significant difference was found in the Harris hip score among these groups. The analysis of various measurements indicated wide variations. There was a significant correlation between the Harris hip score and the acetabular coverage (p < 0.001).

CONCLUSION

Our results indicated wide variety of deficiency type and degree of acetabular dysplasia. Hips with greater acetabular coverage tended to have a higher Harris hip score.

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.

MR measurement of articular cartilage thickness distribution in the hip

OBJECTIVE

To develop a method to determine the distribution of articular cartilage in the hip and to evaluate the potential of the method in a study of normal weight-bearing effects in asymptomatic young volunteers.

DESIGN

Six volunteers were scanned after periods of standing and lying supine, using 3D gradient-echo magnetic resonance imaging (MRI). The protocol was repeated for two successive weeks to determine reproducibility. The femoral and acetabular cartilage layers were segmented as a single unit and thickness distribution maps were calculated using a spherical bone model as a frame of reference. Thickness maps were combined over the population using the bone model and post-weight-bearing and post-resting maps were compared.

RESULTS

Mean thickness values were compared using an analysis of variance and a significant increase in cartilage thickness of 0.05 mm (P=0.02) was observed. The reproducibility of the method, assessed using test-retest coefficient of variation was 2.5%.

CONCLUSIONS

The technique is reproducible, sensitive to sub-millimetre changes in thickness and may be useful in monitoring changes due to disease progression in patients with arthritis of the hip.

Automated analysis of MR image of hip: geometrical evaluation of the Legg–Calvé–Perthes disease

This study proposes semi-automatic determination of geometrical features in hip magnetic resonance (MR) images in order to evaluate the Legg-Calvé-Perthes disease (LCPD). Nine anatomical points on a hip image are selected by a clinician; then eight geometrical indexes of the hip joint are calculated: acetabulum head index (AHI), Wiberg angle (VCE), inner acetabular coverage angle (VCI), acetabular inclination angle (HTE), femoral shaft-neck angle (CC'D), circularity (C), convex deficiency factor (CDF) and pillar height deficiency factor (HDF) for the head region. The geometrical parameters are evaluated on 46 hip images of young patients with unilateral LCPD: 23 images concern the affected hip and 23 the unaffected hip. The extraction of the region of interest is done with a seeded region growing method. All the data were centered and reduced, and were subjected to principal component analysis. Supervised classification is applied with discriminant analysis and k-nearest neighbours classification. The AHI appears to be the best discriminant attribute (maximum between-class variance ratio). Cross-validation tests indicate that we can at most reduce the parameters to five (AHI, CC'D, DHF, DCF and VCE). The classification error rate for the linear discriminant method is 12.5%.

Posterior acetabular wall deficiency in Down syndrome

Trisomy 21 or Down syndrome is the most common chromosomal anomaly and is associated with musculoskeletal abnormalities related to a generalized ligamentous laxity. Approximately 1% to 7% of Down syndrome patients have hip instability. Prior studies on the topic recommend Salter innominate osteotomy, capsular plication, and a varus derotational osteotomy of the proximal femur, which typically is in an anteverted and valgus position. The authors present a previously unreported bilateral finding in two patients noted on three-dimensional reconstruction computed tomography: deficiency of the posterior acetabular wall. Each was treated using a modification of the Pemberton osteotomy in which a wedge of iliac crest graft is placed posteriorly to hinge the posterior wall into a position of better posterior coverage of the femoral head. Both patients' hips have remained stable more than 10 years postoperatively. Follow-up imaging demonstrates well-remodeled osteotomy sites and excellent posterior coverage of the femoral heads.

The use of a reconstructed three-dimensional solid model from CT to aid the surgical management of a total knee arthroplasty: a case study

The use of a rapid prototyping method was utilised to produce a pre-operative solid model of the proximal tibia in a patient with a massive defect of the medial tibial plateau. The solid model was reconstructed from aligned sequential CT images of the knee. This was then used to determine the level of bone resection of the proximal tibia for the optimum placement of the tibial component of a total knee replacement. This technique gives the surgeon both the three-dimensional anatomical information needed to ascertain whether there is adequate bony support after cutting for the prosthesis, as well as a solid model on which to carry out the proposed surgery, before undertaking the procedure on the patient.

Retroversion of the acetabular dome after Salter and triple pelvic osteotomy for congenital dislocation of the hip

Retroversion of the acetabular dome has been associated with hip pain and osteoarthritis in several studies. Nevertheless, this acetabular alignment received little attention when studying the radiological outcome of pelvic osteotomies in childhood. We therefore reviewed the charts and X-rays of 73 patients with congenital dislocations, who underwent 97 pelvic osteotomies in childhood. We focussed our attention on anterior overcoverage or retroversion of the acetabular dome, respectively. Eighty-six Salter and 11 LeCoeur osteotomies were performed on patients with a mean age of 4.8 years. The mean age at last X-ray documentation was 16.5 years. The version of the acetabular dome was estimated qualitatively from the relationship of the anterior and posterior border to each other and measured semiquantitatively using templates developed by Hefti. According to Lequesne's criteria 94% of the hips were normal or borderline at maturity. A retroverted acetabular dome was present in 27% and averaged -15 degrees. It was more frequent (60% versus 24%) and more pronounced (-16 degrees versus +5 degrees) after Le Coeur's than after Salter's osteotomy and in the residually dysplastic hips (83% versus 22%; -15 degrees versus +3 degrees). It is suggested that anterior overcoverage of the femoral head results from ignorance, when choosing the type and performing the pelvic osteotomy, of where coverage needs to be improved in an individual hip. We question the long-term outcome of these hips because such rotational misalignment has been suggested to be associated with early hip pain and osteoarthritis. In order to avoid such misalignment, preoperative evaluation of where coverage needs to be improved in an individual hip and efforts for better intraoperative control of acetabular reorientation should be made.

Radiographic imaging for treatment and follow-up of developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a spectrum of abnormalities that can range from a very mild disturbance to a very severe process that is incapacitating later in life. This article considers the causative factors and natural history of DDH, as well as anatomic abnormalities, physical examination findings, and both surgical and nonsurgical treatment options. The goal of this article is to place in perspective the use of advanced imaging techniques in the diagnosis and follow-up of patients with DDH. Ultrasound, computed tomography (CT), and magnetic resonance (MR) findings are reviewed with respect to the diagnosis of DDH, treatment complications, and long-term problems that may occur in treated and untreated patients.

Evaluation of acetabular dysplasia using a top view of the hip on three-dimensional CT

We assessed coverage over the femoral head, using three-dimensional computed tomography (CT) imaging on 20 hips in 18 patients before rotational acetabular osteotomy, and on 18 normal hips as control. In particular, we introduced a "top view of the hip" in three-dimensional CT evaluation in order to detect posterolateral deficiency, which needs special attention in regard to rotational transfer of the acetabular fragment. We determined the horizontal plane passing through 5 mm cranial to the top of the femoral head on the coronal view of a multiplanar reconstruction image. Then, we erased the images of the ilium that were more cranial than this horizontal plane from the conventional cranial view of the pelvis and the proximal femur, and defined this view as the "top view of the hip". This top view clearly showed any uncovered area on the femoral head. Of the 20 hips, 6 were deficient anterolaterally (anterolateral type), 9 were deficient laterally (lateral type), and 5 were deficient posterolaterally (posterolateral type). On plain anteroposterior radiographs, 7 of the 20 hips had the cross-over sign of Reynolds. Five of these 7 hips with the cross-over sign were the posterolateral type in top view, while none of the 13 hips without the cross-over sign was the posterolateral type. We recommend preoperative evaluation using a top-view on three-dimensional CT images in patients who have the cross-over sign on an anteroposterior radiograph.

CT-generated 3-dimensional models for complex acetabular reconstruction

Before undergoing complex acetabular reconstruction, 10 patients who met prospectively established criteria for severe acetabular bone deficiency received plain radiographs, computed tomography (CT) scans, and CT-generated 3-dimensional pelvic models. The radiographs, CT scans, and models each were graded according to the American Academy of Orthopaedic Surgery (AAOS) classification for acetabular deficiency. The classifications for the radiographs, CT scans, and models were then compared with findings at surgery. The models predicted acetabular deformity and AAOS classification significantly better than the other imaging modalities. The models agreed with the surgical findings in 9 of 10 cases, compared with 2 of 10 for the CT scans (P = .016) and 4 of 10 for the plain radiographs (P = .063). The models closely predicted the available space for the hemispheric acetabular shells, based on the size of the last reamer used, for the 6 hips reconstructed with standard components. Four patients required custom acetabular components; in 2 of those 4, the need for custom components was not anticipated by plain radiographs or CT scans. Three-dimensional CT-generated acetabular models were found to be useful in preoperative planning of complex acetabular reconstructions.

Planning acetabular redirection osteotomies based on joint contact pressures

Acetabular redirection osteotomy can be used to relieve pain, improve function, and extend the life of dysplastic hip joints. To understand better the factors that may determine the acetabular reorientation that minimizes pressures, joint contact pressures were calculated by computer assisted methods in 70 dysplastic and 12 normal hips (82 patients). Calculated pressures were consistent with pressures estimated and measured by other investigators. Contact areas were 26% smaller, and contact pressures were 23% higher, in the dysplastic hips compared with the normal hips. When the acetabula were reoriented to minimize contact pressures for an activity such as the midstance phase of gait, then contact pressures were elevated for dissimilar activities such as stair ascent. Contact pressures in the dysplastic hips were reduced when the acetabula were rotated in the frontal plane to increase lateral coverage or rotated in the sagittal plane to increase anterior coverage. In most of the dysplastic hips, contact pressures were reduced twice as much when the acetabulum was rotated in the frontal and the sagitta' planes. Computer assisted methods to quantify joint contact pressures can be used to assess potential candidates for reconstruction, plan acetabular redirection surgery, and possibly may improve the long term success of acetabular redirection osteotomy.

Advanced imaging concepts: a pictorial glossary of CT and MRI technology

This article serves as an illustrative glossary of concepts related to computed tomography (CT) and magnetic resonance imaging (MRI) technology. The principles of tomography, digital processing, image resolution, CT windowing, CT gray levels, contrast enhancement, and MRI spin echo pulse sequences are reviewed. Techniques not commonly described for use in animal patients are also introduced, and include gradient echo, short time of inversion recovery, fluid attenuated inversion recovery and fat saturation pulse sequences, fast imaging, MRI angiography, perfusion and diffusion imaging, brain activation, CT angiography/functional CT, interventional procedures, and three-dimensional CT.