Lateral Center-edge Angle Research Articles

Radiographic Outcome Following Treatment of Residual Hip Dysplasia with Pemberton Versus Salter Osteotomy: Comparison of Results in Patients Followed to Skeletal Maturity.

Salter osteotomy (SO) and Pemberton acetabuloplasty (PA) are procedures to treat skeletally immature patients with developmental dysplasia of the hip (DDH). The purpose of this study was to compare the radiographic results and rate of residual dysplasia (RD) after treatment with SO and with PA. This was a retrospective analysis of pediatric patients treated with either SO or PA for DDH between 1980 and 2013 who were skeletally mature at the time of follow-up. The preoperative and postoperative acetabular index (AI) and postoperative lateral center-edge angle (LCEA) and anterior center-edge angle (ACEA) were collected. RD was defined as an LCEA or ACEA of <20° or an acetabular inclination (AIn) of >15° at skeletal maturity. Continuous variables were compared between treatment groups with 2-sample t tests, and categorical variables were compared using chi-square tests. Multivariable analysis was used to identify risk factors for RD with p < 0.05. The study included 113 hips in 102 patients with a mean follow-up of 10.5 years. The SO group had 73 hips treated at a mean patient age of 5.4 years, and the PA group had 40 hips treated at a mean age of 5.3 years. The preoperative AI did not differ between the treatment groups (32.2° versus 31.3°, p = 0.658), nor did the immediate postoperative AI (20.0° versus 20.2°, p = 0.459). At the time of final follow-up, the SO group had a significantly smaller AIn (8.6° versus 13.2°, p = 0.001), a trend toward a greater LCEA (26.2° versus 21.6°, p = 0.056), and a similar ACEA (24.1° versus 26.1°, p = 0.808). By the abovementioned definition, 36 hips (31.9%) had evidence of RD, with a lower rate in the SO group (26.0% versus 42.5%, p = 0.07). Patients who had a positive family history of hip dysplasia were more likely to have RD (odds ratio = 4.311, 95% confidence interval = 1.125 to 16.528). Patients with RD could be effectively treated with either SO or PA, with overall good radiographic outcomes. However, SO achieved a better AI and may thus yield better long-term health of the affected hip. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Impact of a Unilateral High Tibial Osteotomy With a Large Correction on Functional Lateral Acetabular Coverage of the Hip Joint.

Changes in limb length and coronal pelvic tilt, which occur along with changes in limb alignment, may affect the functional lateral acetabular coverage of the hip joint under weightbearing conditions. To analyze the functional lateral acetabular coverage after unilateral closed-wedge and open-wedge high tibial osteotomies with a large wedge correction of ≥10 mm. Cohort study; Level of evidence, 3. A retrospective analysis was conducted for 107 unilateral closed-wedge high tibial osteotomies (CWHTOs) and 100 unilateral open-wedge high tibial osteotomies (OWHTOs) with a wedge correction of ≥10 mm and without correction loss during a 2-year follow-up. Limb length and coronal pelvic tilt were measured. Functional lateral acetabular coverage was evaluated using the lateral center-edge angle (LCEA), acetabular index, sharp angle, and femoral head extrusion index (FHEI) with reference to the ground horizontal line. Appropriate ranges of the LCEA (22° to 40°), acetabular index (-8° to 14°), sharp angle (34° to 43°), and FHEI (11% to 27%) were investigated. Limb length significantly decreased after CWHTO (-7.2 mm) and increased after OWHTO (11.5 mm). The pelvis of the operative limb tilted downward after CWHTO (-1.0°) and upward after OWHTO (2.1°). The mean parameters for functional lateral acetabular coverage significantly changed toward more coverage after CWHTO and less coverage after OWHTO (change in LCEA, acetabular index, sharp angle, and FHEI = 1.2°, -1.1°, -1.0°, and -0.7%, respectively, in CWHTO and -1.3°, 1.8°, 1.6°, and 2.7%, respectively, in OWHTO). When evaluating the appropriateness of each parameter for coverage, cases of conversions from undercoverage to appropriate coverage (1.9% to 4.7%) and appropriate to overcoverage (0.9% to 5.6%) after CWHTO and from overcoverage to appropriate coverage (0% to 8%) and appropriate to undercoverage (2% to 7%) after OWHTO were observed. The functional lateral acetabular coverage increased after CWHTO and decreased after OWHTO. Surgeons may want to consider the acetabular coverage of the ipsilateral hip joint when performing a unilateral high tibial osteotomy with a large correction.

Erect weight-bearing pelvic radiographs are superior to supine radiographs for diagnosis of mixed type acetabular retroversion plus developmental dysplasia hip deformity

PurposeThis study focused on the mixed-type deformities of acetabular retroversion (AR) and developmental dysplasia hip deformity (DDH) and aimed to ascertain the changes in pelvic tilt from a supine to a standing position in these cases and identify potential underlying mechanisms. MethodsA retrospective study was conducted on cases with symptomatic DDH from January 1, 2019, to April 30, 2023. DDH was defined as LCEA < 20°. AR was diagnosed by using a crossover index threshold of 0.2 in standing pelvic X-ray. Two observers assessed the supine and weight-bearing pelvic radiographs, along with computed tomography (CT) scans. The evaluated parameters included pelvic tilt (sacrofemoral-pubic angle (SFP), symphysis to sacrococcygeal distance (PSSC), pubic symphysis to sacroiliac (PSSI)), acetabular retroversion (crossover index, posterior wall sign), acetabular coverage (lateral center-edge angle (LCEA), ischial spine sign (ISS)), and axial rotation of the hemipelvis (pelvic width index, obturator index, and ilio-ischial angle). Acetabular orientation and coverage was measured by CT through anterior sector angle (ASA), posterior sector angle (PSA) and acetabular anteversion (AA). Cases with acetabular retroversion plus DDH were defined as the mixed-type deformity. Comparative analyses between mixed-type deformities and DDH cases were performed along with subgroup and correlation analyses within mixed-type cases. Inter-observer and intra-observer reliabilities were assessed using intraclass correlation coefficients. ResultsA total of 85 were included. 26 cases (30.59%) had mixed-type deformity, where transition from the supine to standing position led to an increased posterior pelvic tilt (SFP (supine: 64.35±4.6°, standing: 74.75±4.16°, p<0.001), PSSC (supine: 6.37±2.47, standing: 2.08±1.32, p<0.001) and PSSI (supine: 9.47±1.66, standing: 6.33±1.08, p<0.001)). Compared to cases with DDH, CT examination revealed a significantly greater anterior acetabular coverage and less posterior superior coverage, with smaller posterior sector angle and greater anterior sector angle (ASA) (p<0.05) for cases with AR. The superior iliac wing angle (mixed type: 45.63±9.22°, isolated type: 50.70±8.77°, p=0.013), inferior iliac wing angle(mixed type: 60.77±8.24°, isolated type: 65.24±8.02°, p=0.013), and ischiopubic angle (IPA) (mixed type: 32.27±3.19°, isolated type: 36.71±5.38°, p<0.001) were significantly reduced in AR cases, suggesting external rotation of the hemipelvis. Subgroup analysis showed that cases with a higher crossover index had a significantly higher PSSC and a significantly lower IPA. ConclusionAR was observed in 31% of DDH cases and was associated with a notable posterior pelvic tilt during postural transitions. This tilt appeared to be a compensatory mechanism affecting the AR diagnosis. Key changes in the acetabular coverage, including increased anterior coverage and decreased superior posterior coverage, were also observed. Additionally, external rotation of the hemipelvis in mixed-type cases correlated strongly with the extent of AR and anterior acetabular coverage, suggesting that it may be a key contributor to the underlying mechanism of this mixed-type deformity. Level of evidenceIII, retrospective case series.

Staged Hip Arthroscopy and Periacetabular Osteotomy in Active Patients 45 Years and Older Produces Comparable Improvements in Outcome Scores to Younger Patients

PurposeTo determine staged hip arthroscopy and periacetabular osteotomy (PAO) mid-term outcomes in active patients aged 45 years and older compared with a younger group. Materials and MethodsAll patients aged ≥45 years old who underwent staged arthroscopy and PAO between 2015 and 2021 were retrospectively analyzed and compared to a case-matched control of younger patients. All patients underwent at least 6 months of non-operative management prior to surgery. Prior to PAO, all patients underwent hip arthroscopy to address any intra-articular pathology. The experimental group consisted of dysplastic patients >45 years of age without significant osteoarthritis who underwent PAO and reported a minimum of 1-year postoperative PROs. Patient-reported outcomes (PROs) were quantified using the International Hip Outcomes Tool (iHOT-12) and Non-Arthritic Hip Score (NAHS). ResultsThe cohort consisted of 35 patients (44 hips) with a mean age of 49.4 ± 3.8 years. The lateral center edge angle significantly improved from preoperatively (20.1 ± 4.5 degrees) to postoperatively (33.2 ± 3.2 degrees) (p<0.001). Mean follow up in the PAO ≥45 cohort was 2.80 (±1.3) years postoperatively. Patients reported significant improvement of iHOT-12 (preoperative: 36.6 ± 14.1, latest follow-up: 81.2 ± 21.0; p<0.001) and NAHS scores (preoperative: 59.2 ± 15.5, latest follow-up: 87.4 ± 13.1; p<0.001). Compared to the control, the older cohort did not report significantly different iHOT-12 scores between groups at any point, and age did not significantly affect either outcome score (p>0.05). ConclusionsPatients ≥45 years of age reported a statistically significant improvement in hip function and pain following staged hip arthroscopy and PAO, with outcome scores comparable to a younger cohort. Our findings demonstrate that appropriately selected older dysplastic patients without significant preexisting hip osteoarthritis experience clinically meaningful improvements in hip pain and function following hip preservation surgery. Level of EvidenceIII, retrospective comparative case series

Radiographs Underestimate Lateral Center Edge Angle and Tonnis Angle Measurements Compared to CT Scan in Assessment of Borderline and Frank Acetabular Dysplasia

Radiographs Underestimate Lateral Center Edge Angle and Tonnis Angle Measurements Compared to CT Scan in Assessment of Borderline and Frank Acetabular Dysplasia

Functional and radiological outcomes and complications of bernese periacetabular osteotomy through modified Stoppa approach.

The Smith-Peterson approach and its modifications provide an extensive exposure and allow osteotomies through a single incision. However, the risk of complications increases when the quadrilateral surface, ischial and pubic osteotomy sites cannot be seen. This study aimed to evaluate the surgical characteristics, complications, and functional and radiological outcomes of patients with acetabular dysplasia who underwent Bernese periacetabular osteotomy (PAO) through modified Stoppa approach and plate-screw fixation. The study included 31 patients (41 hips) who had undergone PAO using a modified Stoppa approach. The characteristics of patients and the surgical procedure were described. The lateral centre-edge angle (LCEA) and Tönnis roof angle were evaluated in the radiological outcome evaluation. The modified Harris Hip Score (mHHS) was used to evaluate functional outcome. Furthermore, complications were described. The mean age of the patients was 20.4 ± 9.0 years. Of the 31 patients, 21 underwent unilateral Bernese PAO and 10 underwent bilateral Bernese PAO. The mean follow-up period was 25.1 ± 8.8 months. Postoperatively, the mean mHHS improved significantly (68.8 ± 9.4 vs. 88.8 ± 10.0, p < 0.001). Postoperatively, the mean LCEA and Tönnis roof angle improved significantly (17.7 ± 6.0 vs. 42.2 ± 4.8, p < 0.001 for LCEA and 18.3 ± 5.5 vs. 8.0 ± 2.2, p < 0.001 for Tönnis roof angle). There was no significant correlation between preoperative to postoperative improvement in LCEA or Tönnis roof angle and improvement and mHHS (p > 0.005). 5 complications were identified: 1 transient sciatic nerve palsy, 1 external iliac vein injury, 1 infection, and 2 screw irritations of acetabulum. Performing Bernese PAO through a modified Stoppa approach with plate-screw fixation results in acceptable complication rates, immediate early weight-bearing opportunity, and improved functional and radiological outcomes in patients with acetabular dysplasia.

Hip shelf acetabuloplasty in borderline dysplasia, an alternative between Periacetabular Osteotomy and arthroscopic procedures.

Surgical treatments for symptomatic borderline dysplastic hips (Lateral Center-Edge Angle: LCEA 18-25°) remain challenging, instability being the primary issue. Currently, treatment options include arthroscopic procedures or peri-acetabular osteotomy (PAO). Although the popularity of the acetabular shelf bone block has declined in favor of PAO, it may still be relevant as a hip joint stabilizer and coverage area, rather than for increasing coverage area by cartilage. We analyzed clinical and radiographic outcomes of 23 borderline hips after undergoing shelf procedure with a minimum follow-up of two years. This is a retrospective descriptive study. Clinical evaluations (modified Harris Hip Score: mHHS, Non-Arthritic Hip Score: NAHS, International Hip Outcome Tool: iHOT12) and radiographic assessments were performed before and after surgery. We collected data on revision surgery rates, associated surgical procedures (labrum, impingement), complications, arthrosis progression, and conversion to total hip replacement (THR). The mean LCEA was 21°, and the mean follow-up period was five years (2 to 14 years). Clinical scores showed significant improvement at the last follow-up, mHHS increasing from 47 to 72 (p < 0.001), NAHS from 42 to 68 (p < 0.001), iHOT12 from 28 to 52 (p < 0.001), and pain levels decreasing from 7 to 3. Revision surgery rate was 13%, and complication rate was 8%. No osteoarthritis beyond Tönnis grade 2, and no cases required conversion to THR. Arthroscopic procedures and PAO have shown promising results in the treatment of borderline hips. The hip shelf procedure appears to be a simple and effective treatment for stabilizing borderline hips, with favorable outcomes for 80% of patients and a low rate of arthritic progression. Shelf procedure could be a valuable addition to the therapeutic options for painful borderline dysplasia of the hip.

A Computer Modeling-Based Target Zone for Transposition Osteotomy of the Acetabulum in Patients with Hip Dysplasia.

This study aimed to determine the acetabular position to optimize hip biomechanics after transposition osteotomy of the acetabulum (TOA), a specific form of periacetabular osteotomy, in patients with hip dysplasia. We created patient-specific finite-element models of 46 patients with hip dysplasia to simulate 12 virtual TOA scenarios: lateral rotation to achieve a lateral center-edge angle (LCEA) of 30°, 35°, and 40° combined with anterior rotation of 0°, 5°, 10°, and 15°. Joint contact pressure (CP) on the acetabular cartilage during a single-leg stance and simulated hip range of motion without osseous impingement were calculated. The optimal acetabular position was defined as satisfying both normal joint CP and the required range of motion for activities of daily living. Multivariable logistic regression analysis was used to identify preoperative morphological predictors of osseous impingement after virtual TOA with adequate acetabular correction. The prevalence of hips in the optimal position was highest (65.2%) at an LCEA of 30°, regardless of the amount of anterior rotation. While the acetabular position minimizing peak CP varied among patients, approximately 80% exhibited normalized peak CP at an LCEA of 30° and 35° with 15° of anterior rotation, which were the 2 most favorable configurations among the 12 simulated scenarios. In this context, the preoperative head-neck offset ratio (HNOR) at the 1:30 clock position (p = 0.018) was an independent predictor of postoperative osseous impingement within the required range of motion. Specifically, an HNOR of <0.14 at the 1:30 clock position predicted limitation of required range of motion after virtual TOA (sensitivity, 57%; specificity, 81%; and area under the receiver operating characteristic curve, 0.70). Acetabular reorientation to an LCEA of between 30° and 35° with an additional 15° of anterior rotation may serve as a biomechanics-based target zone for surgeons performing TOA in most patients with hip dysplasia. However, patients with a reduced HNOR at the 1:30 clock position may experience limited range of motion in activities of daily living postoperatively. This study provides a biomechanics-based target for refining acetabular reorientation strategies during TOA while considering morphological factors that may limit the required range of motion.

Identifying Risk Factors for Disease Progression in Developmental Dysplasia of the Hip Using a Contralateral Hip Model

Background: Developmental dysplasia of the hip (DDH) can cause pain and premature osteoarthritis. The risk factors and timing for disease progression in adolescents and young adults have not been fully defined. This study aimed to determine the prevalence of and risk factors for contralateral hip pain and surgery after periacetabular osteotomy (PAO) on a dysplastic hip. Methods: Patients undergoing unilateral PAO for DDH were followed for at least 2 years and categorized into contralateral pain and no-pain groups and contralateral surgery and no-surgery groups. Pain was defined with the modified Harris hip score. Univariate analysis tested group differences in demographics, radiographic measures, and range of motion. Kaplan-Meier survival analysis was used to assess pain development and surgery in the contralateral hip over time. Multivariable regression identified risk factors for contralateral pain and surgery. Contralateral pain and surgery predictors were secondarily assessed after categorization of the contralateral hips as dysplastic, borderline, and non-dysplastic and in subgroups based on the lateral center-edge angle (LCEA) and acetabular inclination (AI) in 5° increments. Results: One hundred and eighty-four patients were followed for a mean of 4.6 ± 1.6 years (range, 2.0 to 8.8 years), during which 51% (93) reported contralateral hip pain and 33% (60) underwent contralateral surgery. Kaplan-Meier analysis predicted 5-year survivorship of 49% with contralateral pain development as the end point and 66% with contralateral surgery as the end point. Painful hips exhibited more severe dysplasia compared with no-pain hips (LCEA = 16.5° versus 20.3°, p &lt; 0.001; AI = 13.2° versus 10.0°, p &lt; 0.001). AI was the sole predictor of pain, with every 1° increase in the AI raising the risk by 11%. Surgically treated hips also had more severe dysplasia (LCEA = 14.9° versus 20.0°, p &lt; 0.001; AI = 14.7° versus 10.2°, p &lt; 0.001) and were in younger patients (21.6 versus 24.1 years, p = 0.022). AI and a maximum alpha angle of ≥55° were predictors of contralateral surgery. Conclusions: At 5 years after hip PAO, approximately 50% of contralateral hips will have pain and approximately 35% can be expected to need surgery. More severe dysplasia, based on the LCEA and AI, increases the risk of contralateral hip pain and surgery, with AI being a predictor of both outcomes. Knowing these risks can inform patient counseling and treatment planning. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Development of a novel rabbit model for femoroacetabular impingement through surgically induced acetabular overcoverage.

There is a lack of validated small animal models for femoroacetabular impingement (FAI) that induce intra-articular lesions and cause osteoarthritis (OA) progression. The gene expression profile of articular cartilage in patients with FAI has not been characterized in animal studies. The purpose of this study is to describe a novel rabbit model for FAI with validated induction of intra-articular lesions and OA progression and to characterize the gene expression pattern in impinged cartilage using this model. Thirty 6-month-old New Zealand White rabbits underwent unilateral endobutton implant placement at the acetabular rim to surgically create overcoverage. Radiological assessment confirmed secure placement of endobutton at the acetabular rim for all operated hips with a mean alteration in lateral center-edge angle (ΔLCEA) of 16.2 ± 6.6°. Gross inspection revealed secondary cartilage injuries in the anterosuperior region of the femoral head for the operated hips. Cartilage injuries were shown to exacerbate with increased impingement duration, as demonstrated by the modified Outerbridge scores and Mankin scores. Immunostaining and quantitative real-time polymerase chain reaction revealed elevated expression of inflammatory, anabolic and catabolic genes in impinged cartilage. RNA sequencing analysis of cartilage tissue revealed a distinct transcriptome profile and identified C-KIT, CD86, and CD68 as central markers. Our study confirmed that the novel rabbit FAI model created acetabular overcoverage and produced articular cartilage injury at the impingement zone. Cartilage from the impingement zone demonstrated a heightened metabolic state, corroborating with the gene expression pattern observed in patients with FAI.

Radiographically Apparent Acetabular Sourcil Landmarks Are Created by Comparable Regions of the Pelvis With Extraarticular Bone Variably Confounding Estimates of Joint Coverage.

The severity of hip dysplasia is characterized by radiographic measurements that require user definition of the acetabular sourcil edge, a bony landmark for which the corresponding three-dimensional (3D) anatomy is not well defined in any imaging plane. To use digitally reconstructed radiographs to determine: (1) What 3D anatomy is contributing to the "acetabular sourcil" location used to make lateral center-edge angle (LCEA) and anterior center-edge angle (ACEA) measurements in standing AP and false-profile radiographic views, respectively? (2) How do intraobserver and interobserver agreement in LCEA and ACEA translate into agreement of the 3D anatomy being evaluated? (3) How distinct are regions around the acetabular rim circumference that are evaluated by LCEA and ACEA measurements on radiographs? Between January 2018 and May 2019, 72 patients were indicated for periacetabular osteotomy to treat hip dysplasia or acetabular retroversion at our institution. From these patients, a series of 10 patients were identified of the first 12 patients in 2018 who were treated with periacetabular osteotomy, excluding two with missing or low-quality clinical imaging. A second series of 10 patients was identified of the first 11 patients in 2019 who were treated with periacetabular osteotomy and concurrent hip arthroscopy, excluding one who was missing clinical imaging. Pelvis and femoral bone surface models were generated from CT scans of these two series of 10 patients. There were 15 female and five male patients, with a median patient age of 18 years (IQR 17 to 23 years), a preoperative LCEA of 22° (IQR 18° to 24°), and a preoperative ACEA of 23° (IQR 18° to 27°). Exclusion criteria included missing preoperative CT or standard clinical radiographic imaging or severe joint incongruity. To address our first study question, digitally reconstructed radiographs matching each patient's standing AP and false-profile clinical radiographs were created from the segmented CT volumes. A board-certified orthopaedic surgeon and three trained researchers measured LCEA and ACEA on the digitally reconstructed radiographs, and the selected sourcil points were projected back into coordinates in the 3D anatomic space. To address our second study question, intraobserver and interobserver agreement in radiographic coverage angles were related to variations in 3D coordinates of the selected bony anatomy. Lastly, to address our third study question, 3D locations around the acetabular rim identified as contributing to the lateral and anterior sourcil points were summarized across patients in a clockface coordinate system, and statistical analysis of the "time" separating the 3D acetabular contributions of the sourcil edges was performed. The 3D anatomy contributing to the lateral sourcil was a variable length (27 mm [IQR 15 to 34 mm]) span of the laterosuperior acetabular edges, with contributions by the anterior inferior iliac spine in 35% (7 of 20) of hips. The anterior sourcil reflected a 28-mm (IQR 25 to 31 mm) span of bone from the medial ilium (posterior-medial to the anterior-inferior iliac spine and anterior-lateral to the arcuate line) to the anterior and lateral edges of the acetabulum. Interobserver variability was good for LCEA (intraclass correlation coefficient [ICC] 0.82 to 0.83) and moderate to good for ACEA (ICC 0.73 to 0.79), whereas the agreement in identified 3D sourcil locations varied widely (ICC 0.32 to 0.95). The acetabular edge of the 3D anatomy contributing to the anterior sourcil overlapped the circumferential range of the acetabular rim contributing to the lateral sourcil. Projection of two-dimensional radiographic landmarks contributing to the diagnosis of structural hip deformity into 3D allowed for the identification of the overlapping bony anatomy contributing to radiographically visible anterior and lateral sourcil edges. This work leveraging digitally reconstructed radiographs and 3D pelvis anatomy has found that bone outside the joint contributes to the radiographic appearance of the sourcil and may variably confound estimates of joint coverage. Furthermore, the substantial overlap between the acetabular bone contributing to measurement of the LCEA and ACEA would indicate that these angles measure similar acetabular deformity, and that additional measures are needed to assess anterior coverage independent of lateral coverage.

Imaging characteristics of hip joint microinstability: a case-control study of hip arthroscopy patients.

Hip microinstability is a clinical entity increasingly recognized and treated but challenging to diagnose with a lack of objective criteria. This study assessed the prevalence and diagnostic accuracy of different imaging findings for hip microinstability on radiograph and MR. A retrospective case-control study of 224 hips treated with arthroscopic surgery by a single orthopedic surgeon, 112 hips with clinical microinstability and 112 controls without. Pre-operative radiograph and MRI/MRA imaging were evaluated by two musculoskeletal radiologists to assess morphological parameters and imaging signs reportedly associated with hip microinstability. Four imaging features reached significance as predictors of microinstability via three-step logistic regression: labral hyperplasia and decreased lateral center edge angle on MR (OR 2.45 and 0.93, respectively) and the absence of positive ischial spine sign and absence of osteophytes on radiographs (OR 0.47 and 0.28, respectively). Increased acetabular anteversion and absence of cam lesions were more likely in the microinstability group (p = 0.02 and 0.04, respectively), but not independent predictors. Labral tears, chondral loss, abnormal ligamentum teres, anterior capsule thinning, iliocapsularis to rectus femoris ratio, posterior crescent sign, cliff sign, and femoro-epiphyseal acetabular roof (FEAR) index were not associated with microinstabillity. Imaging features may be predictive of hip microinstability in some cases. Decreased LCEA, increased acetabular anteversion, and labral hyperplasia were associated with microinstability in this study, while many other published imaging findings were not. Imaging remains complementary, but not definitive, in the diagnosis of hip microinstability.

DXA images vs. pelvic radiographs: Reliability of hip morphology measurements

ObjectiveDual-energy x-ray absorptiometry (DXA) images are increasingly used to study hip morphology. Whether hip morphology measurements are consistent between DXA images and radiographs is unknown. Therefore, we investigated the agreement and reliability of the measurements performed on DXA images and radiographs. DesignWe included participants from the Rotterdam study, a population-based cohort study, who received a hip DXA image and pelvic radiograph on the same day. The acetabular depth-width ratio (ADR), modified acetabular index (mAI), alpha angle (AA), Wiberg and lateral center edge angle (WCEA, LCEA), extrusion index (EI) and triangular index ratio (TIR) were automatically determined on both imaging modalities. The intraobserver and intermethod agreement were studied using Bland-Altman methods, and the reliability was assessed using intraclass correlation coefficients (ICC). Secondly, the diagnostic agreement regarding dysplasia, cam, and pincer morphology was assessed using percent agreement and Cohen’s kappa. Results750 hips from 411 individuals, median age 67.3 years (range 52.2 – 90.6), 45.5% male, were included. The following intermethod ICCs (95% CI) were obtained: ADR 0.85 (0.74-0.91), mAI 0.75 (0.52-0.85), AA 0.72 (0.68-0.75), WCEA 0.81 (0.74-0.85), LCEA 0.93 (0.91-0.94), EI 0.88 (0.84-0.91), and TIR 0.81 (0.79-0.84). We found comparable intraobserver ICCs for each morphological measurement. ConclusionDXA images and pelvic radiographs could both reliably be used to study hip morphology. Due to the lower radiation burden, DXA images could be an excellent alternative to pelvic radiographs for research purposes.

Association Between Hip Translation and Hip Rotation and Anatomy: A Pilot Quasi-static MRI Study.

There is little known about translation of the hip and the relationship with hip rotation and morphology in asymptomatic patients. (1) Femoral head would exhibit significant translations in asymptomatic hips, (2) femoral head translations would correlate to femoral rotations, and (3) range of femoral head translations would correlate to hip morphology. Cross-sectional study; Level of evidence, 3. A total of 11 individuals (age, 23-47 years; 64% female) with asymptomatic hips underwent hip magnetic resonance imaging (MRI) in the following postures: neutral (supine), midflexion, maximum-flexion, internal rotation, internal rotation + midflexion, internal rotation + maximum-flexion, adduction, flexion-abduction-external rotation (FABER), extension, and lateral abduction. All rotations were passive. MRI-generated 3-dimensional hip models were used to quantify femoral rotations and translations. Femoral head diameter, acetabular diameter, lateral center-edge angle, alpha angle, femoral anteversion, acetabular version and inclination, and neck-shaft angle were measured from MRI. A t test was used if measured translations were statistically significant. Linear regression was used to assess the associations between translation and rotation. Pearson correlation was used to assess the relationships between hip anatomy and range of femoral head translations. In all tested positions, the femoral head translated anteriorly by 2 ± 1 mm (maximum 5 mm, P < .001), posteriorly by 1 ± 1 mm (maximum 6 mm, P < .001), superiorly by 2 ± 2 mm (maximum 7 mm, P < .001), inferiorly by 2 ± 2 mm (maximum 6 mm, P < .001), laterally by 1 ± 1 mm (maximum 4 mm, P < .001), and medially by 2 ± 1 mm (maximum 5 mm, P < .001), relative to the rested supine position. Femoral flexion was associated with posterior translation of the femoral head (P = .038). Femoral abduction was associated with medial translation of the femoral head (P = .042). Higher femoral anteversion and smaller alpha angle were associated with a higher total magnitude of femoral head translation in the anterior-posterior direction (P < .04). Smaller femoral anteversion, higher acetabular inclination, smaller lateral center-edge angle, and lower neck-shaft angle were associated with a higher total magnitude of femoral head translation in the superior-inferior direction (P ≤ .03). Our study demonstrated that, during passive physiologic movement, asymptomatic hips on average translated up to 2 mm (with up to 7 mm maximum translation in some positions), which is potentially related to hip rotations and morphology. Further investigations are warranted to understand the normal and pathologic hip translations and their impact on hip function (ie, instability and impingement).

Borderline Hip Dysplasia - Best Treated with Hip Arthroscopy or Periacetabular Osteotomy?

As the field of hip preservation evolves, the diagnosis of borderline dysplasia (defined as a lateral center edge angle between 18°-25°) has shown itself to be one of the more challenging diagnoses to treat. As the nuances of acetabular coverage have come to light, the question of whether borderline hip dysplasia is best treated with isolated hip arthroscopy, periacetabular osteotomy, or whether a combined procedure is best, is now top of mind. The goal of these procedures is to not only improve patient symptoms, but to correct underlying pathology and ideally slow the development of hip osteoarthritis. The purpose of this review is to summarize the recent literature and clinical findings regarding both isolated hip arthroscopy and periacetabular osteotomy in the surgical management of borderline hip dysplasia. Current research demonstrates improved postoperative clinical outcome scores for both patients who had isolated hip arthroscopy in the setting of borderline hip dysplasia and for those patients who underwent periacetabular osteotomy. Mid-term outcomes for patients in both groups have showed low rates of conversion to total hip arthroplasty. No gold standard in the surgical management of borderline hip arthroscopy exists. Improved clinical outcomes have been seen postoperatively in patients who undergo hip arthroscopy and in patients who undergo periacetabular osteotomy. Successful clinical outcomes seem to rely on treatment of the underlying clinical pathology and are largely based on the appropriate surgical indications and appropriate surgical techniques. Surgical decision making in this patient population should be individualized based on a comprehensive evaluation of the patient.

Three-dimensional acetabular reorientation during periacetabular osteotomy: an intraoperative navigation method using an external fixator for periacetabular osteotomy.

Bernese periacetabular osteotomy (PAO) is an effective procedure for treating acetabular dysplasia. However, limited visual control of the acetabular position during surgery may result in under- or overcorrection or changes in acetabular version resulting in residual dysplasia or femoroacetabular impingement. Thus, we wanted to develop a simple and straightforward navigation method that provides information about acetabular correction in all three planes during surgery. Intraoperatively, acetabular coordinates are shown in coronal, sagittal, and transverse plane by two perpendicular tubes of an external fixator mounted onto a third tube that is fixed to the mobilized acetabular fragment with two Schanz screws. The application and fixation of the external fixator on the pelvis are demonstrated in this article. We used this analog navigation method on 27 PAOs, where we mainly performed a lateral rotational correction. The pre- and postoperative radiographs of these 27 hips were analyzed regarding the radiological hip parameters, taking into account the pelvic tilt. The mean preoperative lateral center edge angle (LCEA) of the 27 PAOs improved from 16° (+-6) to a mean of 34° (+-6°) and the mean acetabular index (AI) was corrected from 15° (+-4) to 2° (+-4). This implements highly physiologic postoperative values for lateral coverage in this population. In this case series, no postoperative acetabular retroversion was measured in any of the 27 PAOs. Three-dimensional control of the acetabular orientation during periacetabular osteotomy is important to avoid over- and undercorrection. Using a fixateur externe as an analog navigation method this three-dimensional control can be implemented intraoperatively for PAOs.

Prognosticating Residual Dysplasia at Skeletal Maturity Following Closed Reduction for Developmental Dysplasia of the Hip: A Long-Term Study with an Average 20-Year Follow-up.

Patients with developmental dysplasia of the hip (DDH) are at risk for residual acetabular dysplasia even after successful closed reduction. The aim of this study was to identify predictors of long-term outcomes in order to guide prognostication and management. Patients who were treated for DDH at 2 institutions between 1970 and 2010 and had follow-up until skeletal maturity were screened for inclusion. Hips that underwent open reduction were excluded to reduce iatrogenic confounding. Syndromal (including neuromuscular and arthrogrypotic) hip instability with collagenopathies were excluded. Demographic characteristics, Tönnis grade, age at the time of the reduction, surgical treatment, acetabular index, lateral center-edge angle, residual dysplasia graded using the Severin classification, and the presence and type of proximal femoral growth disturbance categorized using the Bucholz and Ogden classification were assessed. In addition, the the acetabular angle was recorded at the latest follow-up before secondary procedures, and the Oxford Hip Score and 5-level EuroQoL (EQ)-5 Dimension score were recorded at the latest follow-up. To account for repeated measures, generalized estimating equations (GEE) logistic regression was utilized for the multivariable analysis. A support vector machine model and a receiver operating characteristic curve analysis were utilized to identify prognostication thresholds. One hundred and seven hips (96 female, 11 male) that were followed to skeletal maturity, with a mean follow-up of 20 years (range, 10 to 54 years), were included in the analysis. Eighty-nine hips (83%) demonstrated a good outcome at skeletal maturity, with a Severin grade of I or II. Major growth disturbances of Bucholz and Ogden types II, III, or IV were present in 13 hips (12%). At the latest follow-up after skeletal maturity (before any secondary procedures), the mean acetabular angle was 45° ± 4° and the mean lateral center-edge angle was 26° ± 8°. The mean Oxford Hip Score and EQ visual analog scale values were 47 and 86, respectively. A GEE logistic regression analysis of 1,135 observations revealed that the acetabular index (odds ratio [OR], 1.16 per degree; p < 0.001) and age (OR, 1.20 per year; p = 0.003) were significant predictors of a poor outcome (i.e., Severin grade III, IV, or V). Significant differences in acetabular indices across all age groups were found between hips with a good outcome and those with a poor outcome. Age-specific acetabular index prognostication cutoff values are presented. This long-term follow-up study demonstrated that the age-specific acetabular index remains an important predictor of residual dysplasia at skeletal maturity. The proposed prognostication chart and thresholds herein can help to guide orthopaedic surgeons and parents when contemplating the use of an intervention versus surveillance to optimize long-term outcomes. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Three-dimensional assessment of subchondral arc and hip joint coverage angles in the asymptomatic young adult hip.

The primary objective of this study was to develop a custom algorithm to assess three-dimensional (3D) acetabular coverage of the femoral head based on surface models generated from computed tomography (CT) imaging. The secondary objective was to apply this algorithm to asymptomatic young adult hip joints to assess the regional 3D acetabular coverage variability and understand how these novel 3D metrics relate to traditional two-dimensional (2D) radiographic measurements of coverage. The algorithm developed automatically identifies the lateral- and medial-most edges of the acetabular lunate at one-degree intervals around the acetabular rim based on local radius of curvature. The acetabular edges and the center of a best-fit sphere to the femoral head are then used to compute the mean 3D subchondral arc angles and hip joint coverage angles in five acetabular octants. This algorithm was applied to hip models generated from pelvis/hip CT imaging or abdomen/pelvis CT angiograms of 50 patients between 17 and 25 years of age who had no history of congenital or developmental hip pathology, neuromuscular conditions, or bilateral pelvic and/or femoral fractures. Corresponding 2D acetabular coverage measures of lateral center edge angle (LCEA) and acetabular arc angle (AAA) were assessed on the patients' clinical or digitally reconstructed radiographs. The 3D subchondral arc angle in the superior region (58.0 [54.6-64.8] degrees) was significantly higher (p < 0.001) than all other acetabular subregions. The 3D hip joint coverage angle in the superior region (26.2 [20.7-28.5] degrees) was also significantly higher (p < 0.001) than all other acetabular subregions. 3D superior hip joint coverage angle demonstrated the strongest correlation with 2D LCEA (r = 0.649, p < 0.001), while 3D superior-anterior subchondral arc angle demonstrated the strongest correlation with 2D AAA (r = 0.718, p < 0.001). The 3D coverage metrics in the remaining acetabular regions did not strongly correlate with typical 2D radiographic measures. The discrepancy between standard 2D measures of radiographic acetabular coverage and actual 3D coverage identified on advanced imaging indicates potential discord between anatomic coverage and the standard clinical measures of coverage on 2D imaging. As 2D measurement of acetabular coverage is increasingly used to guide surgical decision-making to address acetabular deformities, this work would suggest that 3D measures of acetabular coverage may be important to help discriminate local coverage deficiencies, avoid inconsistencies resulting from differences in radiographic measurement techniques, and provide a better understanding of acetabular coverage in the hip joint, potentially altering surgical planning and guiding surgical technique.

Alpha Angle Values Predict the Severity of Hip Chondral Damage in Patients With Cam-Type Femoroacetabular Impingement Syndrome: A Systematic Review and Meta-analysis

To assess the role of alpha angle (AA) in predicting the severity of hip chondral damage in patients with cam-type femoroacetabular impingement (FAI) syndrome. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines, a systematic review was performed to summarize and critically appraise studies analyzing the prognostic capability of AA values in predicting the severity of intraoperatively evaluated hip chondral damage in patients with cam-type FAI syndrome. The risk of bias was assessed through the Quality In Prognosis Studies tool. Meta-analyses based on groups and individual data from studies with a low risk of bias were conducted. We employed a cumulative link mixed model to analyze the relationship between AA and the ordinal outcome (chondral damage). The model was adjusted for sex, age, and the lateral center-edge angle (LCEA). Interactions between sex and AA were also investigated, and probabilities were calculated. Twelve studies with 4,564 patients were included in a qualitative review (aged 30-39 years, 1,822 women [40%]). Studies with a low risk of bias (n= 4; 2,945 patients) indicated that AA values are significantly smaller (mean difference [95% confidence interval] of 10.5° [6.5°-15°]) in the low-grade chondral damage group (grades 0/I/II) compared with the high-grade chondral damage group (III/IV). The cumulative link mixed model with individual patient data from studies with low risk of bias (n= 3; 1,460 patients) indicated that for each 1° increase in AA, the odds of being in a greater category of chondral damage increased by a factor of 1.04 (odds ratio 1.04, P < .0001). Men were at significantly greater risk (odds ratio 2.11, P < .0001) than women, but no significant interaction between sex and AA was observed (P= .054). We estimate the average probability of having high-grade chondral damage to be greater than 33% when AA values surpass 71° for men and 90° for women, and greater than 50% when 89° for men and 108° for women. However, the heterogeneity observed across studies should be considered. The AA is a significant predictor of hip chondral damage severity in patients with cam-type FAI syndrome, regardless of sex and independently of age and LCEA. In addition, men are at a greater risk of chondral damage than women, and this risk increases with aging but decreases with the magnitude of the LCEA. Level III, systematic review of Level II and III studies.

The Measurement of the Lateral Center-Edge Angle Is Underestimated on Radiographs Compared With 3-Dimensional Computed Tomography

PurposeTo determine if there is a significant difference using Femoral Heads (FH) as anatomical horizon when measuring the LCEA compared to Floor (F), Acetabular Teardrops (AT), and Ischial Tuberosities (IT) and to determine their accuracy by comparing to CT scan with commercially available software. MethodsBetween June 2019 and May 2020, patients with preoperative supine anteroposterior (AP) pelvis radiographs and CT scans were included and retrospectively analyzed. The LCEA was measured on all preoperative supine AP pelvis radiographs four times per hip, using the four methods. The four anatomical horizons used to measure LCEA were compared to each other to determine statistically significant difference. The LCEA measured in the CT scan at the 12 o’clock position was used to compare and determine radiographs’ LCEA accuracy. ResultsNinety-six patients (100 hips) met the inclusion criteria. Sixty-two were females (65%), and the mean age was 35.2 ± 15 years. The mean value for LCEA in CT was 32.2 and 31.1 for the four anatomical horizons in X-ray (P < 0.001). The lowest mean difference between CT scan and X-ray was obtained using the FH (2.3 ± 2.4). Less mean difference was obtained between FH and IT (1.0 ± 0.8). ConclusionIn this study, radiographic measurements underestimated LCEA compared with those from CT scans. Using the FH as an anatomic horizon on radiographs was a more accurate method to measure LCEA than using AT, IT, or F. While this difference is statistically significant, it is not likely to be clinically significant.