Effect of pelvic tilt on acetabular retroversion: a study of pelves from cadavers

Does spinopelvic alignment affect femoral head cartilage and the proximal femoral physis in slipped capital femoral epiphysis? A finite element analysis

BACKGROUND

Slipped capital femoral epiphysis is a prevalent pediatric hip disorder. Recent studies suggest the spine's sagittal profile may influence the proximal femoral growth plate's slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how various spinopelvic alignments affect shear stress and growth plate slip.

METHODS

A finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through reorientation. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum growth plate Tresca (shear) stress.

FINDINGS

Posterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants hip contact and growth plate Tresca stress compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear.

INTERPRETATION

Our findings suggest that posterior pelvic tilt and high pelvic incidence may lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially leading to slip.

Accuracy of cup placement compared with preoperative surgeon targets in primary total hip arthroplasty using standard instrumentation and techniques: a global, multicenter study

BACKGROUND

Acetabular cup positioning in total hip arthroplasty (THA) is closely related to outcomes. The literature has suggested cup parameters defined by the Lewinnek safe zone; however, the validity of such measures is in question. Several studies have raised concerns about the benefits of using the Lewinnek safe zone as a predictor of success. In this study we elected to use prospective surgeon targets as the basis for comparison to see how successful surgeons are positioning their cup using standard instruments and techniques.

METHODS

A prospective, global, multicenter study was conducted. Cup positioning success was defined as a composite endpoint. Both cup inclination and version needed to be within 10° of the surgeon target to be considered a success. Radiographic analysis was conducted by a third-party reviewer.

RESULTS

In 170 subjects, inclination, target versus actual, was 44.8° [standard deviation (SD 0.9°)] and 43.1° (SD 7.6°), respectively (p = 0.0029). Inclination was considered successful in 84.1% of cases. Mean version, target versus actual, was 19.4° (SD 3.9°) and 27.2° (SD 5.6°), respectively (p < 0.0001). Version was considered successful in 63.4% of cases, and combined position (inclination and version) was considered successful in 53.1%.

CONCLUSION

This study shows that with traditional methods of placing the cup intraoperatively, surgeons are only accurate 53.1% of the time compared with a predicted preoperative plan. This study suggests that the inconsistency in cup positioning based on the surgeon's planned target is potentially another important variable to consider while using a mechanical guide or in freehand techniques for cup placement in THA.

TRIAL REGISTRATION

This study is registered on ClinicalTrials.gov, NCT03189303.

Influence of acetabular and femoral morphology on pelvic tilt

Aims

The aim of this study was to investigate whether anterior pelvic plane-pelvic tilt (APP-PT) is associated with distinct hip pathomorphologies. We asked: is there a difference in APP-PT between young symptomatic patients being evaluated for joint preservation surgery and an asymptomatic control group? Does APP-PT vary among distinct acetabular and femoral pathomorphologies? And does APP-PT differ in symptomatic hips based on demographic factors?

Methods

This was an institutional review board-approved, single-centre, retrospective, case-control, comparative study, which included 388 symptomatic hips in 357 patients who presented to our tertiary centre for joint preservation between January 2011 and December 2015. Their mean age was 26 years (SD 2; 23 to 29) and 50% were female. They were allocated to 12 different morphological subgroups. The study group was compared with a control group of 20 asymptomatic hips in 20 patients. APP-PT was assessed in all patients based on supine anteroposterior pelvic radiographs using validated HipRecon software. Values in the two groups were compared using an independent-samples t-test. Multiple regression analysis was performed to examine the influences of diagnoses and demographic factors on APP-PT. The minimal clinically important difference (MCID) for APP-PT was defined as > 1 SD.

Results

There were no significant differences in APP-PT between the control group and the overall group (1.1° (SD 3.0°; -4.9° to 5.9°) vs 1.8° (SD 3.4°; -6.9° to 13.2°); p = 0.323). Acetabular retroversion and overcoverage groups showed higher mean APP-PTs compared with the control group (p = 0.001 and p = 0.014) and were the only diagnoses with a significant influence on APP-PT in the stepwise multiple regression analysis. All differences were below the MCID. The age, sex, height, weight, and BMI showed no influence on APP-PT.

Conclusion

APP-PT showed no radiologically significant variation across different pathomorphologies of the hip in patients being assessed for joint-preserving surgery.

Pelvic flexion/extension and its impact on functional acetabular alignment and stability following total hip replacement

PURPOSE

Dislocation following total hip arthroplasty (THA) remains a significant clinical problem and can occur even with optimal implant alignment. We hypothesized that different patterns of pelvic flexion/extension (PFE) during daily activities may influence acetabular alignment and contribute to impingement and instability following THA. Recently, there has been an increased interest in spinopelvic alignment and its impact on THA. Therefore, this study aimed to identify different patterns of PFE that could be predictive of instability following THA.

METHODS

A range of motion (ROM) simulator was used to demonstrate the effects of different patterns of PFE on ROM and impingement. The findings were applied to PFE measurements obtained from 84 patients in standing and sitting positions.

RESULTS

Three different categories of PFE were identified: normal, hypermobile, and stiff. ROM simulator revealed that changes in PFE had affected ROM and impingement significantly. Patients in the stiff pelvis category, even with "optimal" implant alignment, were more susceptible to implant impingement.

CONCLUSIONS

The different patterns of PFE during daily activities could affect acetabular alignment and stability following THA. We propose a classification system that can identify different types of PFE and predict their effects on the stability of prostheses following THA. Hence, we believe that patients with unfavorable PFE may require modified cup alignment.

Femoroacetabular Impingement Measurements Obtained From Two-Dimensional Radiographs Versus Three-Dimensional-Reconstructed Computed Tomography Images Result in Different Values

Purpose

To compare the reliability and accuracy of radiographic measurements obtained from 2-dimensional (2D) radiographs and 3-dimensional (3D)-reconstructed computed tomography (CT) images in the assessment of femoroacetabular impingement syndrome (FAIS).

Methods

Consecutive patients with FAIS from January 2018 to December 2020 were identified and included in this study. Two fellowship-trained surgeons and 2 fellows performed blinded radiographic measurements. Lateral center-edge angle (LCEA) and Tönnis angles were measured on anteroposterior pelvic radiographs, and alpha angles were measured on frog lateral radiographs. Reliability coefficients for individual measurement accuracy were performed using the Cronbach alpha and intra- and inter-rater intraclass correlation coefficients (ICCs). Composite measurements for LCEA, Tönnis angle, and alpha angle were compared with the corresponding 3D value using paired sample t-tests.

Results

Fifty-three patients with FAIS with standardized 2D radiographic and 3D-reconstructed CT imaging were included. All reliability metrics met thresholds for internal reliability. Inter-rater ICCs for LCEA, Tönnis angle, and alpha angle were (0.928, 0.888, 0.857, all P < .001). When we compared 2D radiographic measurements with 3D-reconstructed CT values, there was a significant difference in the LCEA for 2 authors: surgeon 1 (mean [M] = -9.14, standard deviation [SD] = 5.7); t(52) = -11.6, P < .001, and surgeon 2 (M = -5.9°, SD = 4.7); t(52) = -9.2, P < .001. Significant differences were seen for Tönnis angle for 2 authors: fellow 2 (M = 3.9°, SD = 5.6); t(52) = 5.1, P < .001, and surgeon 2 (M = -2.6°, SD = 4.1); t(52) = -4.6, P < .001. Alpha angle measurements compared to the 3D-reconstructed alpha angle at 2 o'clock was significantly different for 3 authors: fellow 1 (M = 11.9°, SD = 16.2); t(52) = 5.3, P < .001; fellow 2 (M = 10.4°, SD = 18.6); t(52) = 4.1, P = .002; and surgeon 2 (M = -6.5°, SD = 16.2); t(52) = -2.9, P = .005. Positive mean values indicate 2D radiographic measurements overestimated 3D reconstruction values and negative mean values indicate underestimation.

Conclusions

The use of 2D radiographs alone for preoperative planning of FAIS may lead to inaccuracies in radiographic measurements.

Level of Evidence

Level, III retrospective cohort study.

The Duration of Hardware Retention After Radiologic Union of Surgically Treated Femoral Neck Fractures in Children May Predict the Aggravation or Occurrence of Avascular Necrosis of the Femoral Head or Neck After Hardware Removal

BACKGROUND

The incidence of aggravation or occurrence of avascular necrosis (AVN) following hardware removal in surgically treated pediatric femoral neck fractures who achieved radiologic consolidation is unknown. This study aimed to investigate the risk factors for this complication.

METHODS

Seventy-one pediatric (mean age: 9.8±3.9 y) were retrospectively analyzed. Risk factors (age, sex, laterality, severity of initial displacement, type of fracture, time from trauma to reduction, reduction and fixation method, quality of reduction, time required to achieve radiologic union, duration of hardware retention, presence of AVN before hardware removal and follow-up time) were recorded. The severity of AVN was assessed based on radiographs with Ratliff's classification.

RESULTS

Following hardware removal, the aggravation/occurrence of AVN was detected in 11 hips (15.5%). Among the 5 hips (7%) with aggravation of AVN, 1 (1.4%) with type II AVN and 3 (4.2%) with type III AVN exhibited aggravation of type I AVN, while the remaining hip (1.4%; type I) showed enlargement of the involved AVN area. Six hips (8.5%) developed AVN following hardware removal: 2 (2.8%) were classified as type I and 4 (5.6%) as type III. Receiver operating characteristic curve analysis indicated that hardware retention >7 months after union is associated with a decreased rate of aggravation or occurrence of AVN of the femoral neck or head following hardware removal.

CONCLUSIONS

The incidence of aggravation or occurrence of AVN following hardware removal in surgically treated pediatric femoral neck fractures is 15.5%; hardware retention >7 months after radiologic union may reduce the risk of aggravation or occurrence of AVN of the femoral neck or head postimplant removal.

LEVEL OF EVIDENCE

Level III.

Pelvis radiographs in children with cerebral palsy: effects of patient positioning on calculating migration percentages

BACKGROUND

Hip displacement in children with cerebral palsy (CP) is monitored by measuring migration percentage on anteroposterior pelvis radiographs. However, proper positioning for radiography in children with spasticity is difficult. The reliability and accuracy of migration percentage as a function of patient positioning is unknown.

OBJECTIVE

To determine the effects of patient positioning on migration percentage measurements in children with CP.

MATERIALS AND METHODS

We identified children with CP (≤18-year-old) with pelvis CT and anteroposterior pelvis radiograph obtained <6 months apart (10/2018-11/2021). Digitally reconstructed radiographs were generated from each pelvis CT, to simulate nine different patient positions: neutral; 10° and 20° lordosis and kyphosis; and 10° and 20° right rotation and left rotation. Two radiologists measured migration percentages from the simulated and real pelvis radiographs. We used Spearman's rho to assess inter-rater reliability, and Wilcoxon signed rank test to determine statistical significance.

RESULTS

We studied sixty-three children (male=41; median age=8 years; range=4-18 years). The two radiologists' migration percentage measurements were highly correlated with each other across all simulated and real radiographs (Spearman's rho=0.86-0.99, P<0.01). For both readers and hips, migration percentages measured from real radiographs were significantly different from those measured from neutral simulated radiographs (P<0.01), with median absolute difference=5-6 percentage points (PP) and interquartile range (IQR)=9-12 PP. When comparing migration percentage measurements from neutral simulated radiographs to those in kyphosis/lordosis and right/left rotations, median absolute differences were 2-4 PP (IQR=3-8 PP) and 4-15 PP (IQR=6-17 PP), respectively.

CONCLUSION

Inter-rater reliability of measured migration percentages is high, but accuracy decreases with patient positional changes.

The Influence of Compensatory Pelvic Tilt on Patient-reported Outcome Measurements in FAI Patients Who Received Arthroscopic Treatment

OBJECTIVE

Pelvic compensation is common in femoroacetabular impingement (FAI) patients to reduce symptoms and increase range of motion. However, little attention was given to the postoperative clinical effect of pelvic compensation. Therefore, this study aims to compare the outcomes between pelvic compensation and normal pelvic position in femoroacetabular impingement (FAI) patients after hip arthroscopy.

METHODS

The retrospective study was conducted from January 2019 to June 2022, recruited consecutive patients who were diagnosed with FAI and received subsequent arthroscopic treatment. All patients completed an X-ray in the anterior-posterior standing position before and 4 weeks after surgery. Patients with pelvic compensation were compared with those who did not. Functional outcomes included hip disability and osteoarthritis outcome score (HOOS), modified Harris (mHHS) score, and lower-extremity activity scale (LEAS). Secondary outcomes included the EuroQol Five Dimensions Questionnaire (EQ-5D) and patient satisfaction. The intraclass correlation coefficient (ICC) was used to analyze interobserver and intraobserver reliability.

RESULTS

Ninety patients with a mean age of 39.40 years were included in the study. No significant compensation changes were noted within groups after the elimination of impingement. The functional scores showed no significant difference between groups (p(HOOS) = 0.352, p(mHHS) = 0.183, p(LEAS) = 0.865). The EQ-5D revealed statistically better performance in usual activities in the compensatory group (p = 0.044). There are no significant between-group differences in patients' satisfaction evaluations.

CONCLUSION

As assessed by Patient-Reported Outcome Measures (PROMs), patients with compensatory pelvic tilt demonstrated similar clinical outcomes without extra adverse events to patients with normal pelvic positioning in short-term follow-ups. Furthermore, compensatory pelvic tilt did not significantly enhance the range of motion or functional outcome at short-term follow-ups.

Patient positioning during the radiographic procedure affects the radiological signs of acetabular retroversion - A systematic review

Young adults presenting with non-traumatic hip pain may suffer from acetabular retroversion (AR). The previous studies have suggested that patient positioning during the radiographic procedure, that is, pelvic tilt and/or rotation may alter the appearance of the acetabulum. The purpose of this systematic review was to explore and collate existing literature on the correlation between pelvic positioning in weight-bearing anterior-posterior radiographs and the radiographic signs of AR, namely, the ischial spine sign (ISS) the cross-over sign (COS) and posterior wall sign (PWS). The preferred reporting items for systematic reviews and meta-analysis guidelines were followed. MEDLINE, EMBASE, PubMed, The Cochrane Library, and CINAHL were searched. The search string included the following keywords: Pelvic, tilt, rotation, positioning, inclination, incidence, AR, ISS, COS, PWS, and acetabular version. Two authors independently screened the studies identified in the search, extracted data, and critically assessed included studies for quality using the Quality Assessment of Diagnostic Accuracy Studies 2 tool. In total, 2289 publications were screened. Fifteen articles were found eligible for full-text screening, and four articles met the inclusion criteria. Although the studies varied methodologically, all reported that pelvic positioning impacted radiographic signs of AR investigated. One study suggested that more than 9° of pelvic inclination would result in positive COS. No other benchmark values on the degree of pelvic tilt and rotation that would compromise the diagnosis of AR, that is, the detection of ISS, COS, and PWS were reported. At present, literature reporting on the correlation between patient positioning and AR is sparse. Four studies met the inclusion criteria, and they all reported a link between pelvic positioning and the radiographic appearance of AR.

Prediction of Change in Pelvic Tilt After Total Hip Arthroplasty Using Machine Learning

BACKGROUND

A postoperative change in pelvic flexion following total hip arthroplasty (THA) is considered to be one of the causes of dislocation. This study aimed to predict the change of pelvic flexion after THA integrating preoperative and postoperative information with artificial intelligence.

METHODS

This study involved 415 hips which underwent primary THA. Pelvic flexion angle (PFA) is defined as the angle created by the anterior pelvic plane and the horizontal/vertical planes in the supine/standing positions, respectively. Changes in PFA from preoperative supine position to standing position at 5 years after THA were recorded and which were defined as a 5-year change in PFA. Machine learning analysis was performed to predict 5-year change in PFA less than -20° using demographic, blood biochemical, and radiographic data as explanatory variables. Decision trees were constructed based on the important predictors for 5-year change in PFA that can be handled by humans in clinical practice.

RESULTS

Among several machine learning models, random forest showed the highest accuracy (area under the curve = 0.852). Lumbo-lordotic angle, femoral anteversion angle, body mass index, pelvic tilt, and sacral slope were most important random forest predictors. By integrating these preoperative predictors with those obtained 1 year after the surgery, we developed a clinically applicable decision tree model that can predict 5-year change in PFA with area under the curve = 0.914.

CONCLUSION

A machine learning model to predict 5-year change in PFA after THA has been developed by integrating preoperative and postoperative patient information, which may have capabilities for preoperative planning of THA.

A retrospective evaluation of supine pelvic radiography image quality using centring points and anatomical axial rotation, including reliability of measurements (ARLEX-P STUDY)

INTRODUCTION

Pelvic radiographs are commonly used for the investigation of a variety of conditions. Comparison between examinations requires a consistent radiographic technique but variations in image quality and radiographic centring points are frequently reported in the literature. The aim of this study was to establish the amount of variation in the radiographic centring point (RCP) and pelvic axial rotation (PAR), with a secondary aim of reporting the reliability of such measures.

METHODS

Using a previously acquired imaging archive, 633 adult pelvis/hip radiographs were identified on a Picture Archiving and Communication System (PACS). Radiographs with bilateral prostheses, evidence of acute pelvic trauma, projections acquired on a stretcher/trolley and those demonstrating large discontinuity between the detector and X-ray field centre were excluded. To determine centring point variation (+ values denote superior variations) and axial rotation multiple measurements were obtained from each radiograph. A video was used to train five observers and each of these reviewed ten random cases to determine inter- and intra-rater reliability. One of the five observers then performed the measurements on all remaining radiographs.

RESULTS

Following exclusions 380 radiographs were evaluated. The median (IQR) RCP deviation from the inter-acetabular line was +22 (+2 to +43) mm where both iliac crests were present and -29 (-45 to -12) mm where they were not. Eleven (3%) cases demonstrate RCP variation from the midline of greater than 25 mm (no bias towards the left or right side). The median (IQR) PAR was 0.0 (-1.5 to 1.4) degrees with greater variance in PAR for male participants (p = 0.004). Almost 60% of inter-rater ICC measurements were categorised as excellent, good or moderate.

CONCLUSION

Variations in RCP and PAR exist when evaluating a sample of routinely acquired pelvis radiographs. Some initial factors, such as sex and sub-examination type (full pelvis [XPEL] or low centred pelvis [XHIPB]) have been identified as having a statistical affect on variability. Further research and methods to standardise radiographic techniques is required and must be multidimensional in nature.

IMPLICATIONS FOR PRACTICE

Selection of radiographic technique, including RCP, appears to influence components of the pelvis radiograph. Given the increasing clinical requirements for pelvic radiography further standardisation alongside individual optimisation is warranted.

Defining the Borderline Dysplastic Hip: High Variability in Acetabular Coverage and Femoral Morphology on Low-Dose Computed Tomography

BACKGROUND

Borderline acetabular dysplasia is commonly radiographically defined as a lateral center-edge angle (LCEA) of 20° to 25°. While the variability of plain radiographic assessment of this population has been reported, an understanding of the variability of 3-dimensional (3D) hip morphology remains to be better defined.

PURPOSE

To investigate the variability of 3D hip morphology present on low-dose computed tomography (CT) in the setting of symptomatic borderline acetabular dysplasia and to determine if plain radiographic parameters correlate with 3D coverage.

STUDY DESIGN

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

METHODS

A total of 70 consecutive hips with borderline acetabular dysplasia undergoing hip preservation surgery were included in the current study. Plain radiographic evaluation included LCEA, acetabular inclination, anterior center-edge angle (ACEA), anterior wall index (AWI), posterior wall index (PWI), and alpha angles on anteroposterior, 45° Dunn, and frog-leg views. All patients underwent low-dose pelvic CT for preoperative planning, which allowed detailed characterization of 3D morphology relative to normative data. Acetabular morphology was assessed with radial acetabular coverage (RAC) calculated according to standardized clockface positions from 8:00 (posterior) to 4:00 (anterior). Coverages at 10:00, 12:00, and 2:00 were classified as normal, undercoverage, or overcoverage relative to 1 SD from the mean of normative RAC values. Femoral morphology was assessed with femoral version, alpha angle (measured at 1:00 increments), and maximum alpha angle. Correlation was assessed with the Pearson correlation coefficient (r).

RESULTS

Lateral coverage (12:00 RAC) was deficient in 74.1% of hips with borderline dysplasia. Anterior coverage (2:00 RAC) was highly variable, with 17.1% undercoverage, 72.9% normal, and 10.0% overcoverage. Posterior coverage (10:00 RAC) was also highly variable, with 30.0% undercoverage, 62.9% normal, and 7.1% overcoverage. The 3 most common patterns of coverage were isolated lateral undercoverage (31.4%), normal coverage (18.6%), and combined lateral and posterior undercoverage (17.1%). The mean femoral version was 19.7°± 10.6° (range, -4° to 59°), with 47.1% of hips having increased femoral version (>20°). The mean maximum alpha angle was 57.2° (range, 43°-81°), with 48.6% of hips having an alpha angle ≥ 55°. The ACEA and AWI were poorly correlated with radial anterior coverage (r = 0.059 and 0.311, respectively), while the PWI was strongly correlated with radial posterior coverage (r = 0.774).

CONCLUSION

Patients with borderline acetabular dysplasia demonstrate highly variable 3D deformities, including anterior, lateral, and posterior acetabular coverage; femoral version; and alpha angle. Plain radiographic assessments of anterior coverage are poorly correlated with anterior 3D coverage on low-dose CT.

Does pelvic tilt change with a peri-acetabular osteotomy?

Change in pelvic tilt (PT) during and after peri-acetabular osteotomy (PAO) is important for surgical planning. The aims of this study were to (i) determine how PT varies throughout the course of treatment in patients undergoing PAO, (ii) test what factors influence the change in PT and (iii) assess whether changes in PT influenced achieved correction. This is an retrospective, single-centre, consecutive case series of 111 patients treated with PAO for global (n = 79), posterior (n = 49) or anterior dysplasia (n = 6) (mean age: 27.3 ± 7.7 years; 85% females). PT was determined on supine, anteroposterior pelvic radiographs pre-, intra-, 1 day, 6 weeks and 1 year post-operatively, using the sacro-femoral-pubic (SFP) angle, a validated, surrogate marker of PT. An optimal acetabular correction was based on the lateral centre-edge angle (25°-40°), acetabular index (-5° to 10°) and cross-over ratio (<20%). There was a significant difference across pre- (70.1° ± 4.8°), 1-day (71.7° ± 4.3°; P < 0.001) and early post-operative SFP (70.6° ± 4.7°; P = 0.004). The difference in SPF between pre-operative and 1-year post-operative was -0.5° ± 3.1° (P = 0.043), with 9% of cases having a difference of >5°. The difference in SFP did not correlate with age, sex, body mass index, type of dysplasia or achievement of optimal acetabular correction (P = 0.1-0.9). In the early post-operative period, PT is reduced, leading to a relative appearance of acetabular retroversion, which gradually corrects and is restored by annual follow-up. The degree of change in PT during PAO did not adversely affect fragment orientation. PT does not significantly change in most patients undergoing PAO and therefore does not appear to be a compensatory mechanism.

Acetabular Rim Ossification Variants Are Found in Almost 20% of Patients Presenting With Hip Pain

Purpose

To determine the prevalence of 4 different types of acetabular rim ossifications, including partial labral ossification or punctate calcification, true os acetabuli, acetabular rim stress fracture, and complete labral ossification, and to determine whether different types of periacetabular ossifications are linked to demographic or radiological factors.

Methods

We retrospectively reviewed the medial records of patients presenting for hip-related complaints at 2 sports medicine practices from September 2007 to December 2009. An anteroposterior radiograph of both hips and a lateral radiograph of each hip was obtained for all patients and reviewed for findings of cam and pincer femoroacetabular impingement, degenerative changes (Tönnis grade), and periacetabular calcifications for both hips. These parameters were also evaluated with respect to symptoms, sex, and age.

Results

Four hundred ninety-one consecutive patients (982 hips) presented to 2 orthopaedic surgeons at 2 centers for "hip"-related complaints. There were 223 males and 268 females (age 39 ± 14 years). The overall prevalence of periacetabular calcifications in hips was 17.6%, with 56.6% of calcifications in the symptomatic hip and 43.4% in the contralateral hip. Four basic patterns of calcification were identified: punctuate calcifications within the labrum (8.0% hips), large rounded calcifications (os acetabuli) (4.2% hip), large fragments with a vertical line of the superior-lateral acetabular rim, consistent with healed or non-healed stress fracture (2.0% hips), and complete ossification of the labrum (3.4% hips). Overall, male sex (P = .002), increased lateral center-edge angle (P = .046), and higher Tönnis grade (P < .001) statistically predicted the presence of periacetabular ossification. Punctate calcifications were more prevalent in males (P = .002). Higher Tönnis grade (P = .029) and increased alpha angle (P = .046) were more prevalent with os acetabuli. Younger age (P = .001), male sex (P = .048), increased alpha angle (P = .012), and increased lateral center-edge angle (P < .001) were more prevalent in acetabular rim fractures. No factors were statistically significant at predicting the presence of an ossified labrum.

Conclusions

Periacetabular calcifications are not uncommon. Four particular patterns of calcification are identified: punctate labral calcifications (8%), larger rounded calcifications (i.e., os acetabuli) (4.2%), acetabular rim stress fractures (2%), and complete ossification of the labrum (3.4%) for a combined prevalence of 17.6% in patients presenting to an orthopaedic surgeon with "hip"-related complaints. Nearly half were in the asymptomatic hip. Male sex had a higher prevalence of periacetabular calcifications. An increased lateral center edge angle and higher Tönnis grade also had a higher prevalence of periacetabular calcifications. Younger male patients are more likely to have acetabular rim stress fractures. Patients with an increased alpha angle have a higher prevalence of os acetabuli and rim stress fractures.

Clinical Relevance

This study aims to identify, quantify, and categorize periacetabular calcifications about the hip. Their clinical relationships and relevance have been discussed, but no study has distinctly categorized the various types and their prevalence. This study provides a framework for identification and categorization.

Using virtual reality simulation for training practical skills in musculoskeletal wrist X-ray - A pilot study

OBJECTIVES

Using virtual reality (VR), students of radiography can practice acquisition and positioning of musculoskeletal radiographs and get immediate feedback on their performance within the simulator. The purpose of this study was to assess usability of a newly developed VR simulator and to explore self-perceived clinical readiness (SPCR) of radiography students before and after training acquisition of wrist radiographs in the VR simulator.

MATERIAL AND METHODS

A prospective methodology was applied where the students (n = 10) estimated their own SPCR in regard to acquisition of wrist radiographs pre- and post-VR training. A questionnaire on usability, realism, and educational value of the simulator was answered post-VR training. Usability and SPCR scores were calculated. The student's paired t-test was applied to explore the impact of VR training on SPCR.

RESULTS

The students (90%) reported that the simulator was realistic and they thought that it could contribute to learning. The pre- and post-SPCR scores were 75 (95% confidence interval [CI]: 54-96) and 77 (95% CI: 59-95), respectively. There was no significant difference (P = 0.4574) between the pre- and post-SPCR scores.

CONCLUSION

Results indicated that the concept of training acquisition and positioning of wrist radiographs in a VR simulator is feasible with positive feedback from the students. The SPCR scores improved slightly, although not statistically significant, after completion of the training session.

Does robot-assisted surgery reduce leg length discrepancy in total hip replacement? Robot-assisted posterior approach versus direct anterior approach and manual posterior approach: a propensity score-matching study

BACKGROUND

Advocates of robot-assisted technique argue that robots could improve leg length restoration in total hip replacement. However, there were few studies to compare the robot-assisted posterior approach (RPA) with conventional posterior approach (PA) THA and direct anterior approach (DAA) THA in LLD. This study aimed to determine whether robot-assisted techniques could significantly reduce LLD compared to manual DAA and manual PA.

METHODS

We retrospectively reviewed the cohort of consecutive ONFH patients who underwent THA robot-assisted posterior, manual posterior, and manual DAA from January 2018 to December 2020 in one institution. One experienced surgeon performed all procedures. We calculated the propensity score to match similar patients in different groups by multivariate logistic regression analysis for each patient. We included confounders consisting of age at the time of surgery, sex, body mass index (BMI), and preoperative LLD. Postoperative LLD and Harris hip scores (HHS) at two years after surgery of different cohorts were compared.

RESULT

We analyzed 267 ONFH patients treated with RPA, DAA, or PA (73 RPA patients, 99 DAA patients, and 95 PA patients). After propensity score matching, we generated cohorts of 40 patients in DAA and RPA groups. And we found no significant difference in postoperative LLD between RPA and DAA cohorts (4.10 ± 3.50 mm vs 4.60 ± 4.14 mm, p = 0.577) in this study. The HHS at 2 years postoperatively were 87.04 ± 7.06 vs 85.33 ± 8.34 p = 0.202. After propensity score matching, we generated cohorts of 58 patients in manual PA and RPA groups. And there were significant differences in postoperative LLD between the RPA and PA cohorts. (3.98 ± 3.27 mm vs 5.38 ± 3.68 mm, p = 0.031). The HHS at 2 years postoperatively were 89.38 ± 6.81 vs 85.33 ± 8.81 p = 0.019. After propensity score matching, we generated cohorts of 75 patients in manual DAA and PA groups. And there were significant differences in postoperative LLD between the DAA and PA cohorts. (4.03 ± 3.93 mm vs 5.39 ± 3.83 mm, p = 0.031) The HHS at 2 years postoperatively were 89.71 ± 6.18 vs 86.91 ± 7.20 p = 0.012.

CONCLUSION

This study found no significant difference in postoperative LLD between RPA and DAA, but we found a significant difference between RPA and manual PA, DAA and manual PA in ONFH patients. We found a significant advantage in leg length restoration in primary total hip arthroplasty with robot-assisted surgery.

Correlations Analysis of Different Pelvic Tilt Definitions: A Preliminary Study

Background: Pelvic tilt (PT) is described as the pelvic orientation along the transverse axis, yet 4 PT definitions were established based on radiographic landmarks: anterior pelvic plane (PTa), the center of femoral heads to sacral plate (PTm), pelvic outlet (PTh), and sacral slope (SS). These landmarks quantify a similar concept, yet understanding of their relationships is lacking, and their differences are sometimes ignored. Purpose: This study aimed to examine the correlations and differences of PT definitions for education and research purposes. Methods: This study reviewed 105 sagittal pelvic radiographs of patients (68 men and 37 women) awaiting hip surgery at a single clinic. Hip hardware and spine pathologies were examined for subgroup analysis. Two observers annotated 4 PTs in a gender-dependent manner and repeated it after 6 months. The linear regression model and intraclass correlation coefficient (ICC) were applied with a 95% confidence interval. Results: The SS showed no correlation to the other 3 PT definitions, except for females in the hip hardware subgroup (n = 17). PTm demonstrated very strong linear correlation to PTh (r > 0.9) under the linear model PTm = 0.951 × PTh - 68.284. Conclusion: The PTm and PTh can be calculated from each other under a simple linear regression equation, which enables comparisons between them. SS presented poor correlations to the other PT parameters, except for the female subgroup with hip implant that required further analysis; PTa-related comparisons showed high anatomical variations between patients.

Standard radiographic values for the acetabulum in Japanese adolescents: a cross-sectional study

BACKGROUND

Most previous reports of normal acetabular radiographic values focused on adults or elderly people. Recent reports have described premature hip osteoarthritis in adolescents not caused by acetabular dysplasia. In addition, there is a certain failure rate of surgical treatment for young patients with borderline acetabular dysplasia. Accurate indices for treatment of adolescent hips are unclear because standard measurement values of the adolescent acetabulum have not been reported.

METHODS

This cross-sectional study involved 552 Japanese adolescents aged 12-18 years who had scoliosis or suspected scoliosis and asymptomatic hips. All persons underwent plain standing anteroposterior whole-spine radiography, and measurements were obtained using the pelvic part of the radiograph. We excluded persons who were unable to correctly perform measurements because of conditions such as pelvic rotation or lateral inclination and persons in whom closure of the triradiate cartilage or closure of the secondary ossification centers of the acetabulum had not yet occurred. In 1101 hips, we measured the lateral center-edge angle (LCEA), Tönnis angle, Sharp angle, acetabular head index (AHI), lateral subluxation (LS), vertical subluxation (VS), and peak-to-edge distance (PED). We evaluated the correlation coefficient and coefficient of determination between each parameter and age, height, body weight, and body mass index (BMI) and assessed the intra- and inter-rater reliability of each radiographic parameter.

RESULTS

Among all hips, the mean of each parameter was as follows: LCEA, 27.9° ± 4.8°; Tönnis angle, 5.0° ± 3.7°; Sharp angle, 44.1° ± 3.1°; AHI, 82.1% ± 5.5%; LS, 5.4 ± 1.4 mm; VS, 0.3 ± 1.2 mm; and PED, 14.0 ± 2.3 mm. The correlation between each parameter and age, height, body weight, and BMI was considerably low. Intra- and inter-rater reliability was moderate or good for almost all parameters.

CONCLUSIONS

The values for each radiographic parameter of the acetabulum in this study are considered standard for the adolescent acetabulum without age-related changes. Some parameters differ slightly from the normal values for adults or elderly people in previous reports; thus, we suggest careful evaluation of these parameters for adolescents.

A radiomics approach to the diagnosis of femoroacetabular impingement

Introduction

Femoroacetabular Impingement (FAI) is a hip pathology characterized by impingement of the femoral head-neck junction against the acetabular rim, due to abnormalities in bone morphology. FAI is normally diagnosed by manual evaluation of morphologic features on magnetic resonance imaging (MRI). In this study, we assess, for the first time, the feasibility of using radiomics to detect FAI by automatically extracting quantitative features from images.

Material and methods

17 patients diagnosed with monolateral FAI underwent pre-surgical MR imaging, including a 3D Dixon sequence of the pelvis. An expert radiologist drew regions of interest on the water-only Dixon images outlining femur and acetabulum in both impingement (IJ) and healthy joints (HJ). 182 radiomic features were extracted for each hip. The dataset numerosity was increased by 60 times with an ad-hoc data augmentation tool. Features were subdivided by type and region in 24 subsets. For each, a univariate ANOVA F-value analysis was applied to find the 5 features most correlated with IJ based on p-value, for a total of 48 subsets. For each subset, a K-nearest neighbor model was trained to differentiate between IJ and HJ using the values of the radiomic features in the subset as input. The training was repeated 100 times, randomly subdividing the data with 75%/25% training/testing.

Results

The texture-based gray level features yielded the highest prediction max accuracy (0.972) with the smallest subset of features. This suggests that the gray image values are more homogeneously distributed in the HJ in comparison to IJ, which could be due to stress-related inflammation resulting from impingement.

Conclusions

We showed that radiomics can automatically distinguish IJ from HJ using water-only Dixon MRI. To our knowledge, this is the first application of radiomics for FAI diagnosis. We reported an accuracy greater than 97%, which is higher than the 90% accuracy for detecting FAI reported for standard diagnostic tests (90%). Our proposed radiomic analysis could be combined with methods for automated joint segmentation to rapidly identify patients with FAI, avoiding time-consuming radiological measurements of bone morphology.

CT-based morphological study of the pelvis in patients with gluteal muscle contracture

BACKGROUND

In the clinic, gluteal muscle contracture (GMC) causes pelvic structural changes, including acetabular retroversion. However, its causes and forms are not well understood. This study aimed to investigate and analyse the clinical significance of pelvic structural differences between GMC patients and healthy individuals.

METHODS

As the GMC group, we identified 100 GMC patients who received treatment and met the inclusion criteria between January 2019 and January 2020. Control subjects were drawn from the hospital's emergency trauma patients who had no history of pelvic or hip joint disease. All subjects underwent CT scans to measure their pelvic rotation, including the superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA), and acetabular coverage, which includes anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), horizontal acetabular sector angle (HASA), and superior acetabular sector angle (SASA).

RESULTS

The SIA, IIA, IPA, and PASA of the GMC group were considerably smaller than those of the control group, while the AASA of the GMC group was higher, indicating a statistically significant difference (P < 0.05). The HASA and SASA of the GMC group, on the other hand, were not considerably different from those of the control group. The angles in the GMC group were relativized as follows: The HASA had a positive correlation with the AASA and PASA (r = 0.750, P < 0.01; r = 0.749, P < 0.01); the SASA had a positive correlation with the AASA, PASA, and HASA (r = 0.555, P < 0.01; r = 0.273, P < 0.01; r = 0.552, P < 0.01); the AASA had a negative correlation with the SIA, IIA and IPA (r = - 0.355, P < 0.01; r = - 0.551, P < 0.01; r = - 0.30, P < 0.01); the PASA had a positive correlation with the IIA (r = 0.315, P < 0.01) and had no correlation with the SIA and IPA (P > 0.05); and the IIA had a positive correlation with both the SIA and IPA (r = 0.664, P < 0.01; r = 0.465, P < 0.01).

CONCLUSION

Individuals with GMC have an abnormal pelvic morphology, with acetabular retroversion caused by ilial rotation rather than dysplasia of the acetabular wall.

Change in functional biomechanics following a targeted exercise intervention in patients with acetabular retroversion and femoroacetabular impingement syndrome

BACKGROUND

Acetabular retroversion is a form of hip dysplasia that may cause femoroacetabular impingement syndrome (FAIS), leading to pain and restricted hip range of motion. An exercise intervention aiming at altering pelvis tilt and related functional biomechanics may be a useful first-line intervention for patients who are not eligible for surgical repositioning.

RESEARCH QUESTION

Does squat and gait biomechanics change following an 8-week targeted exercise program in individuals with symptomatic acetabular retroversion and FAIS?

METHODS

This prospective intervention study used participants as their own controls. Examinations were conducted at three time-points: T1 baseline; T2 following an 8-week control period; T3 after 8 weeks' intervention. At each time-point, three-dimensional motion analysis of a deep squat and level gait was performed, and pain intensity was recorded using a numerical rating scale (NRS 0-10). The intervention consisted of a home-exercise program to improve core stability and pelvic movement. Differences in waveforms between time-points across pelvis and lower-limb biomechanics were evaluated using statistical parametric mapping. Delta (Δ, differences between T1-T2 and T2-T3) was used to evaluate changes in spatiotemporal gait parameters and pain.

RESULTS

Nineteen patients (18 females), mean age 22.6 (SD 4.5) years, BMI (kg/m2) 23.0 (SD 4.1), were included. Changes (Δ T1-T2 vs. Δ T2-T3) in squat biomechanics were observed as: (i) decreased anterior pelvic tilt, (ii) deeper vertical pelvis position, and (iii) increased knee flexion angle. Contrary, no significant changes in gait biomechanics, Δ walking speed, Δ step length, or NRS for pain were found.

SIGNIFICANCE

Following a targeted exercise intervention, participants were able to squat deeper, potentially allowing better hip function. The deepened squat position was accompanied by increased knee flexion and reduced anterior pelvic tilt. Gait biomechanics and patient-reported pain remained unchanged post-intervention. These findings are important for future design of exercise interventions targeting pelvic tilt in symptomatic individuals.

Measurement of pelvic tilt and rotation on AP radiographs using HipRecon: Validation and comparison to other parameters

In this paper, we present and evaluate HipRecon, a noncommercial software package that simultaneously calculates pelvic tilt and rotation from an anteroposterior pelvis radiograph. We asked: What is the (1) accuracy and precision, (2) robustness, and (3) intra-/interobserver reliability/reproducibility of HipRecon to analyze both pelvic tilt and rotation on conventional AP pelvis radiographs? (4) How does the prediction of pelvic tilt on AP pelvis radiographs using HipRecon compare to established measurement methods? We compared the actual pelvic tilt of 20 adult human cadaveric pelvises with the calculated pelvic orientation based on an AP pelvis radiograph using HipRecon software. The pelvises were mounted on a radiolucent fixture and a total of 380 AP pelvis radiographs with different configurations were acquired. In addition, we investigated the correlation between actual tilt and the tilt calculated using HipRecon and seven other established measurement methods. The calculated software accuracy was 0.2 ± 2.0° (-3.6-4.1) for pelvic tilt and 0.0 ± 1.2° (-2.2-2.3, p = 0.39) for pelvic rotation. The Bland-Altman analysis showed values that were evenly and randomly spread in both directions. HipRecon showed excellent consistency for the measurement of pelvic tilt and rotation (intraobserver intraclass-correlation coefficient [ICC]: 0.99 [95% CI: 0.99-0.99] and interobserver ICC 0.99 [95% CI: 0.99-0.99]). Of all eight analyzed methods, the highest correlation coefficient was found for HipRecon (r = 0.98, p < 0.001). In the future, HipRecon could be used to detect changes in patient-specific pelvic orientation, helping to improve clinical understanding and decision-making in pathologies of the hip.

Impact of intraoperative fluoroscopic beam positioning relative to the hip and pelvis on perceived acetabular component position

Background

Parallax is poorly understood and can mislead surgeons using intraoperative fluoroscopy (IF) to guide cup placement during anterior approach (AA) total hip arthroplasty. The purpose of this study was to examine how changes in fluoroscopic beam positioning in relation to the hip and pelvis affects the projected acetabular image.

Methods

An acetabular component was positioned in an anatomic pelvis model in 45° and 20° of abduction and anteversion, respectively using a computer assisted cup targeting system. Fluoroscopic images were taken at various caudal and cranially directed angles with the fluoroscopic beam centered over the hip then pelvis. In each position, four independent observers measured the abduction and anteversion angles of the projected cup image using the same computer targeting system.

Results

Cup abduction and anteversion measured 43.5° and 19.5° when IF was centered over the hip and 40.5 and 27.5° when centered over the pelvis in the neutral position. Increasing the caudal direction of the beam 20° increased the projected abduction/anteversion angles by approximately 7°/12° and 9°/16° when centered over the hip and pelvis respectively. Increasing the cranial direction of the beam 20° decreased the measured abduction/anteversion angles by roughly 4°/20° and 4°/24° when centered over the hip and pelvis, respectively.

Conclusion

The projected image of the acetabular component can change dramatically depending on fluoroscopic beam position relative to the hip and pelvis. Recognizing the approximate direction and magnitude of change with differing fluoroscopy positions may help surgeons avoid cup malpositioning.

Comparison of Transfer Learning Models in Pelvic Tilt and Rotation Measurement in Pediatric Anteroposterior Pelvic Radiographs

The rotation and tilt of the pelvis during anteroposterior pelvic radiography can lead to misdiagnosis of developmental dysplasia of the hip (DDH) in children. At present, no method exists for accurately and conveniently measuring the precise rotation and tilt angles of pelvic on radiographs. The objective of this study was to develop several rotation and tilt measurement models using transfer learning and digital reconstructed radiographs (DRRs), and to compare their performances on pelvic radiographs. Based on the inclusion criteria, 30 of 92 children who underwent 3D hip CT scans at Xijing Hospital from 2015 to 2020 were included in the study. Using DRR techniques, radiographs were generated by rotating and tilting the pelvis in CT datasets at - 12 to 12° (projected every 3°) and were randomized to a 2:1:1 ratio of training dataset, validation dataset, and test dataset. Five pre-trained networks, including VGG16, Xception, VGG19, ResNet50 and InceptionV3 were used to develop pelvic rotation measurement models and tilt measurement models, and these models were trained with training dataset. The callback function was used during the training to slow down the learning rate when learning was stalled. Then, the validation set was used to optimize each model and compare their performances. At last, we tested the final performances of optimal rotation measurement model and optimal tilt measurement model on test dataset. The mean absolute error (MAE) was employed to assess the performance of the models. A total of 2430 pelvic DRRs were collected based on 30 CT datasets. Among 5 pre-trained transfer learning models, VGG16-Tilt achieved the best tilt prediction performance at the same BS and different LR. VGG16-Tilt model achieved its best performance on validation set at LR = 0.001 and BS = 4, and the final MAE on the test set was 0.5250°. In terms of rotation prediction, VGG16-Rotation also achieved the best performance, and it achieved its best performance on validation set at LR = 0.002 and BS = 8. The final MAE of VGG16-Rotation on the test set was 1.0731°. Pretrained transfer learning models worked well in predicting tilt and rotation angles of the pelvis on radiographs in children. Among them, VGG16-Tilt and VGG16-Rotation had the best effect in dealing with such problems despite their simple structures. These models deployed in devices can give orthopedic surgeons a powerful aid in DDH diagnosis.

Utilizing Three-Dimensional Head-Lesser Trochanter Distance Could Further Reduce Leg Length Inequality in Primary Bipolar Hemiarthroplasty

Background: The aim of this study was to investigate whether the use of three-dimensional (3-D) computed tomography (CT)-based head-lesser trochanter distance (HLD) could reduce leg length discrepancy (LLD) more than the use of a two-dimensional (2-D) plain film method in primary bipolar hemiarthroplasty. Methods: Propensity score matching (PSM) analysis was used to adjust the confounding factors. A retrospective comparative analysis of 128 patients was performed. In the control group, the leg length was equalized using the 2-D, plain film-based HLD. In the study group, primary bipolar hemiarthroplasty was performed using the 3-D CT-based HLD method. Postoperative LLDs were compared between the two groups using the method of Ranawat. In addition, the Harris hip score (HHS) was evaluated and compared at one year after surgery. Results: A significant difference was observed in mean postoperative LLD between the 2-D HLD group and the 3-D CT HLD group: 1.6 ± 1.2 mm (range, 0.1−6.0 mm) and 1.1 ± 1.2 mm (range, 0.1−5.1 mm), respectively (p < 0.05). Additionally, a higher percentage of patients in the 3-D CT HLD group had an LLD of less than 2 mm. The mean HHS at one year after surgery showed no significant difference between the two groups. Conclusions: To minimize the occurrence of LLD, HLD measurement from a CT scanner may be more accurate than an X-ray. The 2-D and 3-D HLD differences in the 3-D CT HLD group were statistically significant. Using a 3-D, CT-based HLD method might decrease the possibility of an LLD over 2 mm.

Exercise in patients with acetabular retroversion and excessive anterior pelvic tilt: A feasibility and intervention study

BACKGROUND

Acetabular retroversion is associated with femoroacetabular impingement syndrome (FAIS). Anterior pelvic tilt enhances risk of FAIS.

OBJECTIVES

To investigate feasibility and change in patient-reported symptoms of a home-based exercise intervention in patients with acetabular retroversion and excessive anterior pelvic tilt, in comparison with a prior control period.

DESIGN

Prospective intervention study.

METHODS

Patients (18-40 years) not eligible for surgery, with radiographic signs of acetabular retroversion and excessive anterior pelvic tilt were recruited. An 8-week control period was followed by an 8-week training period. The home-based intervention consisted of education and exercises for core stability, muscle strengthening and stretching for reducing anterior pelvic tilt. Feasibility assessments were dropout (≤10%), adherence (≥75% of sessions), exercise-related pain, and adverse events. Primary outcome was change in the Copenhagen Hip and Groin Outcome Score (HAGOS) pain-subscale. Pelvic tilt was measured by EOS scanning.

RESULTS

Forty-two patients (93% female, mean age 22.2 ± 4.2 years) were included. Dropout rate was 7% and satisfactory adherence was demonstrated by 85%. Exercise-related pain and adverse events were acceptable. Between-period mean change score for HAGOS-PAIN was 5.2 points (95% CI: -0.3-10.6) and -1.6° (95% CI: -3.9-0.7) of anterior pelvic tilt. Patients responding positively (≥10 points) (n = 10, 26%), had pre-exercise moderate pain (HAGOS-PAIN 47.5-70 points).

CONCLUSIONS

Current exercise intervention was feasible. However, we found no clinically relevant changes in self-reported hip-related pain or anterior pelvic tilt. Post hoc responder analysis revealed that patients with moderate pain at baseline might benefit from this exercise.

The effect of pelvic ring rotation and tilt on the radiographic teardrop distance: an important consideration in the assessment of dynamic displacement on stress radiographs

PURPOSE

The purpose of this study was to determine the effect of rotation and tilt on the radiographic teardrop distance (TD) on anteroposterior (AP) pelvis radiographs.

METHODS

Radiographic examination of a pelvis models was conducted utilizing increasing degrees of beam rotation and tilt on portable C-arm fluoroscopy. The TD, x-plane rotation (symphyseal-mid-sacrum distance (SMS)), and y-plane tilt (sacroiliac joint-symphysis distance (SIS)) were measured by four independent observers. Interobserver reliability was assessed using intraclass correlations.

RESULTS

TD was altered by less than 2 mm with up to 7.5° fluoroscopic rotation (SMS: 3 cm) and up to 30° of inlet and 15° of outlet (SIS: ± 3.3 cm). SMS distance effectively corresponded to the degree of rotation present (r = 1.00, CI: 0.97 to 1.00, p < 0.0001) and was strongly correlated to TD (r = -0.95, CI: -0.99 to -0.67, p = 0.001). SIS distance effectively corresponded to the degree of tilt present (r = -0.97, CI: -0.99 to -0.88, p < 0.0001) and was correlated to TD (r = 0.94, CI: 0.75 to 0.99, p = 0.0001). Linear regression models determined that, with every degree of rotation and tilt, TD was altered by 0.4 mm and 0.09 mm, respectively (p = 0.0004, r² = 0.93 and p < 0.0001, r² = 0.94, respectively). Interobserver reliability among observers was excellent (0.92).

CONCLUSION

The TD has excellent interobserver reliability and is minimally impacted by up to 7.5° of rotation, 30° inlet tilt, and 15° of outlet tilt. Utilization of these thresholds may ensure reliability of TD measurements when assessing pelvis stress radiographs.

Do the Number, Size, and Position of Partially Threaded Screws Affect the Radiological Healing of Surgically Treated Displaced Femoral Neck Fractures? A Review of 136 Children

Background and Objectives: The quantity, size, and position of implants might affect the fracture healing process of surgically treated displaced pediatric femoral neck fractures (PFNFs). The aim of this retrospective multicenter study was to evaluate the correlation between the time needed to achieve radiological union and the number, size, and location of the partially threaded cannulated screws (PTCSs) in children with displaced PFNFs. Materials and Methods: A retrospective review of 136 children (mean age: 10.6 ± 3.8 years) with displaced PFNFs treated by two (n = 103) or three (n = 33) PTCSs was carried out. Student’s t-tests, one-way ANOVA, Cox regression analysis, and multiple linear regression analyses were performed to investigate the variables affecting the time needed to achieve radiological fracture healing according to the number, size, and position of PTCSs, as assessed on plain radiographs. Results: A total of 132 hips achieved union at an average of 3.2 ± 1.6 months after the initial surgery. The time needed to achieve union in the patients treated with two or three PTCSs was comparable (p = 0.36). Among the fractures treated by two PTCSs, the time needed to achieve union did not correlate with the size of the implant (p = 0.122), or with the angulation between the PTCSs on anterior–posterior (p = 0.257) and lateral radiographs (p = 0.547). The time needed to achieve union in the fractures that were fully compressed by the implants was similar to the partially compressed fractures (p = 0.08). Conclusions: The number, size, and position of the PTCSs do not affect the radiological healing in the children with displaced PFNFs treated surgically.

Intraoperative Fluoroscopy Allows the Reliable Assessment of Deformity Correction during Periacetabular Osteotomy

We aimed to determine the accuracy and reliability of measures characterizing anterior, lateral, and posterior acetabular coverage on intraoperative fluoroscopic images compared to postoperative radiographs when performing periacetabular osteotomies (PAOs). A study involving 100 PAOs was initiated applying a standardized intraoperative imaging protocol. Coverage was determined by the lateral center edge angle (LCEA), the Tönnis angle (TA), and the anterior and posterior wall index (AWI, PWI). An intraclass correlation coefficient (ICC) model was used to assess interrater (ICC (3,2)) and intrarater (ICC (2,1)) reliability. The ICC (2,2) between analyses obtained from intraoperative fluoroscopy and postoperative radiographs and the corresponding 95% confidence interval (CI) were determined and complemented by Bland–Altman analysis, the mean difference, and 95% limits of agreement (LOA). The ICCs were 0.849 for the LCEA (95% CI 0.783–0.896), 0.897 for the TA (95% CI 0.851–0.930), 0.864 for the AWI (95% CI 0.804–0.907), and 0.804 for the PWI (0.722–0.864). The assessed interrater reliability was excellent except for the AWI, which was graded good (ICC = 0.857, 95% CI 0.794–0.902). Interrater agreement was generally good and fair for the AWI (ICC = 0.715, 95% CI 0.603–0.780). For each postoperative radiograph, interrater reliability was good with ICCs ranging from 0.813 (TA) to 0.881 (PWI). Intrarater reliability was good for all measurements and excellent for the preoperative TA (ICC = 0.993, 95% CI 0.984–0.997) and PWI (ICC = 0.954, 95% CI 0.919–0.97). In summary, we confirm the validity and reliability of intraoperative fluoroscopy as an alternative imaging modality to radiography to evaluate acetabular fragment orientation during PAO. We affirm the LCEA and TA as precise measures for lateral head coverage, and show the suitability of the AWI and PWI to steadily assess acetabular version.

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.

Effects of pelvic obliquity and limb position on radiographic leg length discrepancy measurement: a Sawbones model

Purpose

Potential sources of inaccuracy in leg length discrepancy (LLD) measurements commonly arise due to postural malalignment during radiograph acquisition. Preoperative planning techniques for total hip arthroplasty (THA) are particularly susceptible to this inaccuracy, as they often rely solely on radiographic assessments. Owing to the extensive variety of pathologies that are associated with LLD, an understanding of the influence of malpositioning on LLD measurement is crucial. In the present study, we sought to characterize the effects of varying degrees of lateral pelvic obliquity (PO) and mediolateral limb movement in the coronal plane on LLD measurement error (ME).

Methods

A 3-D sawbones model of the pelvis with bilateral femurs of equal-length was assembled. Anteroposterior pelvic radiographs were captured at various levels of PO: 0°, 5°, 10°, and 15°. At each level of PO, femurs were individually rotated medio-laterally to produce 0°, 5°, 10°, and 15° of abduction/adduction. LLD was measured radiographically at each position combination. For all cases of PO, the right-side of the pelvis was designated as the higher-side, and the left as the lower-side.

Results

At 0° PO, 71% of tested variations in femoral abduction/adduction resulted in LLD ME < 0.5-cm, while 29% were ≥ 0.5-cm, but < 1-cm. ME increased progressively as one limb was further abducted while the contralateral limb was simultaneously further adducted. The highest ME occurred with one femur abducted 15° and the other adducted 15°. Similar magnitudes of ME were seen in 98% of tested femoral positions at 5° of PO. The greatest ME (~ 1 cm) occurred at the extremes of right-femur abduction and left-femur adduction. At 10° of PO, a higher prevalence of cases exhibited LLD ME > 0.5-cm (39%) and ≥ 1-cm (8%). The greatest errors occurred at femoral positions similar to those seen at 5° of PO. At 15° of PO, half of tested variations in femoral position resulted in LLD ME > 1-cm, while 22% of cases produced errors > 1.5-cm. These clinically significant errors occurred at all tested variations of right-femur abduction, with the left-femur in either neutral position, abduction, or adduction.

Conclusion

This study aids surgeons in understanding the magnitude of radiographic LLD ME produced by varying degrees of PO and femoral abduction/adduction. At a PO of ≤5°, variations in femoral abduction/adduction of up to 15° produce errors of marginal clinical significance. At PO of 10° or 15°, even small changes in mediolateral limb position led to clinically significant ME (> 1-cm). This study also highlights the importance of proper patient positioning during radiograph acquisition, demonstrating the need for surgeons to assess the quality of their radiographs before performing preoperative templating for THA, and accounting for PO (> 5°) when considering the validity of LLD measurements.

Dissociation of liner from cup in THA: does liner damage affect the risk of dissociation?

INTRODUCTION

A rare catastrophic failure of modular component Total Hip Arthroplasty is dissociation between liner and cup, which has been associated with component malposition and/or impingement and seems to be more frequently associated with the Pinnacle system. The goal of this study was to evaluate the resistance of a polyethylene liner to lever-out-forces of the Pinnacle locking mechanism and the locking mechanisms of two other current cup/liner systems using a standardized testing method (ASTM).

MATERIALS AND METHODS

Five of each of the following cups were evaluated with their corresponding polyethylene liners: Pinnacle Multihole cup with and without intact anti-rotation tabs (ART's); Allofit-S-Alloclassic and Plasmafit Plus7 cups. The ASTM test set-up was used to evaluate the lever-out force resulting in liner dissociation for each construct.

RESULTS

The Pinnacle construct with intact ARTs required the greatest force (F) to achieve dissociation (263.2 ± 79.2 N) followed by the Plasmafit Plus7 (185.8 ± 36.9 N) and the Allofit-S (101.4 ± 35.3 N) constructs, respectively. However, after removal of the ARTs, the Pinnacle system required the least force to achieve dissociation (75.1 ± 22.2 N) (p < 0.001).

CONCLUSIONS

The intact Pinnacle system appeared the most stable in lever-out tests when compared to the other systems. However, after removal of the ARTs, the Pinnacle system required the least force for dissociation, consistent with locking mechanism failure, and suggesting that the ARTs are a critical component of the locking mechanism. Our findings are consistent with the clinical experience of dissociated Pinnacle constructs displaying damaged or missing ARTs, and that damage to these may increase risk of liner dissociation.

Pelvic tilt from supine to standing in patients with symptomatic acetabular retroversion of the hip

AIMS

Acetabular retroversion is a recognized cause of hip impingement and can be influenced by pelvic tilt (PT), which changes in different functional positions. Positional changes in PT have not previously been studied in patients with acetabular retroversion.

METHODS

Supine and standing anteroposterior (AP) pelvic radiographs were retrospectively analyzed in 69 patients treated for symptomatic acetabular retroversion. Measurements were made for acetabular index (AI), lateral centre-edge angle (LCEA), crossover index, ischial spine sign, and posterior wall sign. The change in the angle of PT was measured both by the sacro-femoral-pubic (SFP) angle and the pubic symphysis to sacroiliac (PS-SI) index.

RESULTS

In the supine position, the mean PT (by SFP) was 1.05° (SD 3.77°), which changed on standing to a PT of 8.64° (SD 5.34°). A significant increase in posterior PT from supine to standing of 7.59° (SD 4.5°; SFP angle) and 5.89° (SD 3.33°; PS-SI index) was calculated (p < 0.001). There was a good correlation in PT change between measurements using SFP angle and PS-SI index (0.901 in the preoperative group and 0.815 in the postoperative group). Signs of retroversion were significantly reduced in standing radiographs compared to supine: crossover index (0.16 (SD 0.16) vs 0.38 (SD 0.15); p < 0.001), crossover sign (19/28 hips vs 28/28 hips; p < 0.001), ischial spine sign (10/28 hips vs 26/28 hips; p < 0.001), and posterior wall sign (12/28 hips vs 24/28 hips; p < 0.001).

CONCLUSION

Posterior PT increased from supine to standing in patients with symptomatic acetabular retroversion. The features of acetabular retroversion were less evident on standing radiographs. The low PT angle in the supine position is a factor in the increased appearance of acetabular retroversion. Patients presenting with symptoms of hip impingement should be assessed by supine and standing pelvic radiographs to highlight signs of acetabular retroversion, and to assist with optimizing acetabular correction at the time of surgery. Cite this article: Bone Joint J 2022;104-B(7):786-791.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

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

RESULTS

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

CONCLUSION

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

Effects of degree of translation or rotation of acetabular fragment of periacetabular osteotomy procedure on pelvic X-ray parameters

The present study aims to investigate the effect of amount of lateralization and/or anteversion of the point where the iliac cut meets with the posterior column cut of periacetabular osteotomy (PAO), on X-ray parameters such as Center of edge (CE) angle, retroversion index (RVI) and sharp angle. Fourteen patients with symptomatic hip dysplasia (CE° < 20°) were included. Pelvis Computerized tomography (CT) sections were used for 3D printing. PAO was then performed on these models. The point (A), 1 cm lateral to the pelvic brim, is marked where the iliac cut intersects the posterior column cut. In Group I (1.5–0), point A is lateralized parallel to the osteotomy line for 1.5 cm. In Group II (1.5–0.5), it is additionally anteverted for 0.5 cm. In Group III (3–0), point A is lateralized for 3 cm and then additionally anteverted for 1 cm (Group IV: 3–1). Radiographs were taken in each stage. The lateral CE angle, RVI and sharp angle were measured. All had an increase in the CE angle and RVI and a decrease in the sharp angle compared to the control group (P < 0.05). The amount of CE angle (ΔCE) or RVI increase (ΔRV) was as follows: 3–1(38°, 0.3) > 3–0(27°, 0.2) and 1.5–0.5(25°, 0.1) > 1.5–0(17°, 0.07) (P < 0.05) (with no difference between groups 1.5–0.5 and 3–0, P = 0.7). The amount of sharp angle decrease was as follows: 3–1(20°), 3–0(18°) < 1.5–0.5(11°) < 1.5–0(8°) (P < 0.05). The lateralization of the intersection point where the iliac wing cut meets with the posterior column cut along the cut surface led to an increase of lateral cover and focal retroversion. Additional anteversion leads to further increases in those parameters, while groups 1.5–0.5 and 3–0 did not differ between.

A New Parameter of Hip Instability in Developmental Dysplasia of the Hip (DDH): Teardrop Distance

Background

Hip instability is one of the etiologies of accelerated onset of osteoarthritis in developmental dysplasia of the hip (DDH). There are some radiological parameters for hip instability in hip dysplasia like broken shenton’s line, elevated acetabular index, reduced lateral center edge angle (LCEA), upsloping lateral sourcil. We have discovered a new index of teardrop distance (TD) for assessing instability. Herein, we hypothesized that increased TD could be used as evidence of hip instability in DDH patients, which we verified using TD as an auxiliary diagnostic parameter for DDH, from supine to standing position.

Methods

Female DDH patients undergoing Bernese periacetabular osteotomy (PAO) were enrolled in the DDH group, and normal female volunteers were in the control group. Anteroposterior radiographs of the pelvis in the supine and standing positions were taken, and LCEA, Tönnis angle (TA), sharp angle (SA), and TD were tested using Stata software to analyze the changes between supine and standing anteroposterior pelvic radiographs.

Results

There were 26 female volunteers with 52 hips in the control group: supine TD 6.80 ± 0.98 mm, standing TD 6.65 ± 1.3 mm (P > 0.05). A total of 78 patients with 135 hips were included in the DDH group: supine TD 10.51 ± 3.50 mm, standing TD 10.93 ± 4.23 mm (P < 0.05). In either supine or standing position, TD in the DDH group was significantly wider than that in the control group (P < 0.05). In the DDH group, TD was correlated with TA and LCEA (rp 0.494–0.588, P < 0.05); TD was not correlated with SA, weight, or BMI (P > 0.05). There was a weak correlation between TD difference and standing LCEA (rp −0.276, P < 0.05).

Conclusion

TD > 10 mm was a common imaging feature of DDH. It increased from supine to standing position, thus indicating hip instability in DDH patients. The hip parameters of both positions should be compared, fully considering the factors of hip stability.

Long-term outcomes of hip reconstruction surgery in children with GMFCS III diplegic cerebral palsy

INTRODUCTION

The results of hip reconstruction surgery are known for non-walking (GMFCS IV and V) and walking (GMFCS I and II) patients. Few studies deal with GMFCS III patients in isolation. Their intermediate functional status can be deteriorated by asymmetrical contractures, hip dislocation, multi-level deformities of the lower limbs, leading to motor function degradation, and possibly losing their ability to walk. The aim of our study was to establish whether surgical results were maintained over time and whether the functional status changed.

MATERIAL AND METHODS

Fifteen patients with GMFCS III spastic diplegia, treated for hip subluxation, were reviewed. The mean age at the time of surgery was 10 years old. The mean follow-up after surgery was 11 years. Reconstructive surgery was performed on 21 hips including pelvic osteotomy in all cases, with associated femoral osteotomy in 19 cases. Clinical (pain, joint mobility, walking aids, walking distance, GMFCS level) and radiological data (Melbourne Cerebral Palsy Hip Classification, standard coxometry) were recorded preoperatively and at the last follow-up.

RESULTS

Preoperatively, 6 patients were losing their ability to walk due to pain and flexion-adduction contracture. At the last follow-up, no patients had pain and joint mobility was improved in all cases. For one patient, recovery to their previous functional state required a period of two years. In the long term, 14 patients were GMFCS III and only one patient was GMFCS IV due to reasons unrelated to hip surgery. The radiological parameters improved significantly. The Melbourne score was IV preoperatively for all patients. At the last follow-up, 10 hips were grade I, 6 hips were grade II and 5 hips were grade III.

DISCUSSION

Correction of architectural disorders of the subluxed hip by pelvic osteotomy, in most cases associated with femoral osteotomy, improves functional and radiological status for GMFCS III patients. This improvement is maintained in the long-term. Complementary surgeries correcting the other deformities of the lower limbs were necessary in more than half of the patients.

LEVEL OF EVIDENCE

IV.

Evaluation of Crossover Sign in Pelvis Models Made with a Three-Dimensional Printer

Introduction

Investigation of the crossover sign (COS) in different degrees of tilt in pelvises made by three-dimensional printing of CT scans among patients with normal hip versions was carried out.

Methods

Radiology CT scans of 8 normal pelvises reconstructed in 3D and the effect of sequential tilting on the presence of the false-positive COS in 48 radiographs were investigated.

Results

The COS was seen in 77% of the AP radiographs during tilt changes. The average distance between the tip of the coccyx and the symphysis pubis was 32.06 ± 10.99 mm. Also, COSs were present in all radiographs from 6 degrees tilt and above.

Conclusion

Minor tilting of the pelvis can result in a false-positive crossover sign on AP plain radiographs.

Accuracy and Reliability of Software Navigation for Acetabular Component Placement in THA: An In Vitro Validation Study

Background and Objectives: Intraoperative fluoroscopy can be used to increase the accuracy of the acetabular component positioning during total hip arthroplasty. However, given the three-dimensional nature of cup positioning, it can be difficult to accurately assess inclination and anteversion angles based on two-dimensional imaging. The purpose of this study is to validate a novel method for calculating the 3D orientation of the acetabular cup from 2D fluoroscopic imaging. Materials and Methods: An acetabular cup was implanted into a radio-opaque pelvis model in nine positions sequentially, and the inclination and anteversion angles were collected in each position using two methods: (1) a coordinate measurement machine (CMM) was used to establish a digitalized anatomical coordinate frame based on pelvic landmarks of the cadaveric specimen, and the 3D position of the cup was then expressed with respect to the anatomical planes; (2) AP radiographic images were collected, and a mathematical formula was utilized to calculate the 3D inclination and anteversion based on the 2D images. The results of each method were compared, and interrater and intrarater reliably of the 2D method were calculated. Results: Interrater reliability was excellent, with an interclass correlation coefficient (ICC) of 0.988 (95% CI 0.975–0.994) for anteversion and 0.997 (95% CI 0.991–0.999) for inclination, as was intrarater reliability, with an ICC of 0.995 (95% CI 0.985–0.998) for anteversion and 0.998 (95% CI 0.994–0.999) for inclination. Intermethod accuracy was excellent with an ICC of 0.986 (95% CI: 0.972–0.993) for anteversion and 0.993 (95% CI: 0.989–0.995) for inclination. The Bland–Altman limit of agreement, which represents the error between the 2D and 3D methods, was found to range between 2 to 5 degrees. Conclusions: This data validates the proposed methodology to calculate 3D anteversion and inclination angles based on 2D fluoroscopic images to within five degrees. This method can be utilized to improve acetabular component placing intraoperatively and to check component placement postoperatively.

Prone Apprehension Relocation Test significantly correlates with radiological instability scores of the hip

Recently, there was a debate about whether borderline dysplastic hips should be treated surgically with hip arthroscopy or periacetabular osteotomy (PAO). Current studies recommend a classification into stable and unstable hips. Therefore, radiological scores have been described in recent years. Likewise, a new clinical stability test with the Prone Apprehension Relocation Test (PART) has been described. However, there has been no correlation between the modern radiological scores and the PART. We prospectively studied a consecutive group of patients who presented to our clinic. The PART and radiological scores were assessed in these patients. We divided the patients into a PART-positive and a PART-negative group and analyzed the associated clinical and radiological findings. Out of 126 patients (126 hips) included, 36 hips (29%) were evaluated as PART positive. There were significantly more females in the PART positive group (P = 0.005). Comparing the PART groups, significant differences (P < 0.0001) were found for the lateral center edge angle (LCEA), Femoro-Epiphyseal Acetabular Roof (FEAR) index, Gothic arch angle (GAA), anterior wall index (AWI), the occurrence of the upsloping lateral sourcil (ULS) and signs of acetabular retroversion. The correlation analysis showed an association between LCEA, FEAR index, GAA, AWI, ULS and the PART. A chi-square automatic interaction detection algorithm revealed that the strongest predictor of positive PART was the GAA. In conclusion, a high correlation between the PART and known radiological instability parameters was found. Consequently, a combination of clinical instability testing and radiological instability parameters should be applied to detect unstable hips.

Acellular Matrix-Induced Chondrogenesis Technique Improves the Results of Chondral Lesions Associated With Femoroacetabular Impingement

PURPOSE

The study's main objective was to evaluate, in the short-term, the result of the autologous acellular matrix-induced chondrogenesis (AMIC) technique in a selected group of patients with 2-4 cm² full-thickness chondral lesions, undergoing hip arthroscopy for femoroacetabular impingement (FAI).

METHODS

A retrospective single-center Level IV case series of 25 patients (28 hips) who underwent an arthroscopic hip surgery with a liquid acellular collagen matrix. Inclusion criteria for implantation were FAI diagnosis (cam or pincer type), grade IV chondral lesions (Outerbridge size 2-4 cm²); Tönnis stage 0-II, minimum follow-up of 24 months, and 1 year (12-15 months) evaluation with very high field 3-T MRI arthrography. Exclusion criteria were Tönnis III, joint space <2 mm, center-edge angle <20°, and <24 months of follow-up. Clinical assessments involved symptoms duration until surgery, changes in physical and work activity and range of motion, modified Harris Hip Score, reporting percentages of patient acceptable symptomatic state (PASS) and minimal clinically important difference (MCID), pain with a VAS, and level of satisfaction. Radiological assessments: Tönnis stage, articular space, alpha and lateral center edge angle (Wiberg), and generated tissue characteristics at 1 year (based on the MOCART score), through 3-T MRI.

RESULTS

25 patients (28 hips) treated; 19 men and 6 women (mean age: 40.5 years; range: 25-55). Two women underwent joint replacement surgery. Thus, 23 patients (26 hips) were analyzed. At 29 months following surgery (range: 24-48), a significant improvement was obtained in all parameters assessed, focusing on the characteristics of the generated tissue in the MRI (MOCART scores). 95% of the patients met the MCID (improvement >12 points in the modified Harris Hip Score), and 100% scored >74 points, achieving the PASS. Patients' satisfaction was 86.6% (SD 16.4). All patients who practiced sports resumed them.

CONCLUSIONS

The liquid AMIC is a safe technique that shows good clinical and radiological outcomes in a 2-year follow-up in patients with femoroacetabular impingement and grade IV acetabular 2-4 cm² chondral defects.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases

BACKGROUND

The correlation between the number, size, and location of cannulated screws and the incidence of avascular necrosis (AVN) in children with femoral neck fractures treated surgically is uncertain.

METHODS

We retrospectively reviewed 153 children (mean age: 10.6±3.7 y) with femoral neck fractures treated by internal fixation with 2 (n=112) or 3 (n=41) cannulated screws. The severity of initial displacement was divided into incomplete (type I) and complete (type II, angulation <50 degrees; type III, angulation >50 degrees) fractures. The diameter of the screw was measured and recorded as a percentage of the femoral neck width. The distance (D) between the mid-point of each screw at the base (B) of the femoral neck and at the tip (T) of each screw and the superior and anterior cortices of the femoral neck, respectively, were measured on anteroposterior (AP) and lateral (L) radiographs. Values were expressed as the ratio between the measured distance and the width of the femoral neck (BDAP%, TDAP%, BDL%, and TDL%). The correlation between the number, size, and location of the screws and AVN was analyzed.

RESULTS

Patients with type II of initial displacement treated with 2 cannulated screws had a lower AVN rate (21.4%) than those treated with 3 screws (44.8%) (P=0.027). Screw diameter (19%) in patients with AVN was larger than (17%) in patients without AVN (P<0.001); patients with AVN had a lower BDAP% (48.6%) than those without AVN (56.4%) (P<0.001). Screw size and BDAP% were risk factors for AVN (P<0.05). Further, screw diameter >16.5% and BDAP% <51.6% of the femoral neck width were the cutoff values for an increased AVN rate (P<0.05).

CONCLUSIONS

Patients treated with 2 cannulated screws showed a lower rate of AVN than patients treated with 3 screws. Screws of larger size and screws closer to the piriformis fossa on AP radiographs increased the risk of AVN in children with femoral neck fractures treated surgically.

LEVEL OF EVIDENCE

Level III.

Acetabular retroversion is prevalent and proportional to the severity of slipped upper femoral epiphysis

Aims

Slipped upper femoral epiphysis (SUFE) has well documented biochemical and mechanical risk factors. Femoral and acetabular morphologies seem to be equally important. Acetabular retroversion has a low prevalence in asymptomatic adults. Hips with dysplasia, osteoarthritis, and Perthes’ disease, however, have higher rates, ranging from 18% to 48%. The aim of our study was to assess the prevalence of acetabular retroversion in patients presenting with SUFE using both validated radiological signs and tomographical measurements.

Methods

A retrospective review of all SUFE surgical cases presenting to the Royal Children’s Hospital, Melbourne, Australia, from 2012 to 2019 were evaluated. Preoperative plain radiographs were assessed for slip angle, validated radiological signs of retroversion, and standardized postoperative CT scans were used to assess cranial and mid-acetabular version.

Results

In all, 116 SUFEs presented in 107 patients who underwent surgical intervention; 47 (52%) were male, with a mean age of 12.7 years (7.5 to 16.6). Complete radiological data was available for 91 patients (99 hips) with adequate axial CT imaging of both hips. Overall, 82 patients (82%) underwent pinning in situ (PIS), with subcapital realignment surgery (SRS) performed in 17 patients (18%) (slip angles > 75°). Contralateral prophylactic PIS was performed in 72 patients (87%). On the slip side, 62 patients (68%) had one or more radiological sign of retroversion. Tomographical acetabular retroversion was more pronounced cranially than caudally of the acetabulum on both the affected side and the contralateral side (p < 0.001) as expected in the normal population. Increasing severity of the slip was found to be directly proportional to the degree of reduction in cranial and central acetabular version (p < 0.05) in the SUFE hips.

Conclusion

Acetabular retroversion is more prevalent in patients with SUFE than previously reported, and have been shown be correlated to the severity of the slip presentation. The presence of radiological signs of acetabular retroversion could be used to justify prophylactic contralateral pinning.

Cite this article: Bone Jt Open 2022;3(2):158–164.

Inzidenz, Biomechanik und Diagnostik der Hüftgelenkdysplasie

Die Hüftdysplasie ist eine komplexe dreidimensionale Pathomorphologie des gesamten Hüftgelenks. Die mangelhafte Überdachung des Hüftkopfes führt zur Instabilität des Gelenks. Das schräg aufsteigende Dach ist Scherkräften ausgesetzt, die zu einer Überlastung der Erkerregion führen. Die Folge sind Schäden am chondrolabralen Komplex, welche die Ursache für auftretende Schmerzen sind und in weiterer Folge die Dysplasiearthrose induzieren. Die Inzidenz der Hüftdysplasie variiert nach geografischen Regionen und ethnischen Gruppen. Unterschiede in der Definition der Hüftdysplasie und ihrer Diagnose machen Literaturvergleiche schwierig. Die Biomechanik der dysplastischen Hüfte wird von der knöchernen Formgebung, aber auch von der Belastung und Muskelkräften beeinflusst. Die Behandlung sollte die Herstellung einer physiologischen Biomechanik zum Ziel haben, die in den meisten Fällen mehr eine Domäne der offenen Chirurgie als der Arthroskopie darstellt. Die Diagnosestellung der Hüftdysplasie ist herausfordernd. Eine genaue Anamnese, standardisierte klinische Tests und Röntgenaufnahmen, die durch den Chirurgen selbst beurteilt werden müssen, sind essenziell. Weiterführende Untersuchungen wie die Magnetresonanztomographie (MRT) sind für die Beurteilung von Knorpel- und Labrumschäden hilfreich.

Acetabular Cartilage Thickness Differs Among Cam, Pincer, or Mixed-Type Femoroacetabular Impingement: A Descriptive Study Using In Vivo Ultrasonic Measurements During Surgical Hip Dislocation

OBJECTIVE

To investigate acetabular cartilage thickness among (1) 8 measurement locations on the lunate surface and (2) different types of femoroacetabular impingement (FAI).

DESIGN

Prospective descriptive study comparing in vivo measured acetabular cartilage thickness using a validated ultrasonic device during surgical hip dislocation in 50 hips. Measurement locations included the anterior/posterior horn and 3 locations on each peripheral and central aspect of the acetabulum. The clock system was used for orientation. Thickness was compared among cam (11 hips), pincer (8 hips), and mixed-type (31 hips) of FAI. Mean age was 31 ± 8 (range, 18-49) years. Hips with no degenerative changes were included (Tönnis stage = 0).

RESULTS

Acetabular cartilage thickness ranged from 1.7 mm to 2.7 mm and differed among the 8 locations (P < 0.001). Thicker cartilage was found on the peripheral aspect at 11 and 1 o'clock positions (mean of 2.4 mm and 2.7 mm, respectively). At 5 out of 8 locations of measurement (anterior and posterior horn, 1 o'clock peripheral, 12 and 2 o'clock central), cartilage thickness was thinner in hips with pincer impingement compared to cam and/or mixed-type of FAI (P ranging from <0.001 to 0.031). No difference in thickness existed between cam and mixed-type of impingement (P = 0.751).

CONCLUSION

Acetabular cartilage thickness varied topographically and among FAI types. This study provides first baseline information about topographical cartilage thickness in FAI measured in vivo. Thinner cartilage thickness in pincer deformities could be misinterpreted as joint degeneration and could therefore have an impact on indication for hip preserving surgery.

The use of image analysis software increases the accuracy of the periacetabular osteotomy fragment placement

The purpose of this study was to report on the use of image analysis technology to enhance accuracy of intra-operative imaging and evaluation of periacetabular osteotomy (PAO) correction. This was a retrospective study reporting on the first 25 cases of PAO performed with the use of an image analysis tool. This technology was used intra-operatively to assess the position of the supine coronal image in comparison to pre-operative standing images using a ratio of pelvic tilt (PT). Intra-operative PT, Tönnis angle, lateral center–edge angle (LCEA) and anterior wall index were compared to post-operative images. Post-operative radiographic parameters in the study group were compared with a control group of PAO cases performed prior to the implementation of the new software. The image analysis software was able to obtain intra-operative supine imaging that was equivalent to pre-operative standing imaging. When comparing the PAOs performed with the use of the software versus those without, the study group trended toward being more likely within the surgeon’s defined target range of radiographic values, which was statistically significant for LCEA. This tool can be used to assure the surgeon that the intra-operative image being used for surgical decision-making is representative of the functional radiograph. PAOs performed with the use of this technology showed enhanced accuracy of surgical correction for the parameters within our defined target ranges. This may increase the ability of the surgeon to place the acetabular fragment more precisely within his or her goal parameters for acetabular reorientation correction.

Surgical correction for adult spinal deformity increases acetabular lateral coverage of femoral heads

BACKGROUND

Studies explaining the relationship between hip and spine reported that spinal corrective surgery affected acetabular orientation and changes in pelvic tilt were capable of influencing radiographic measures of acetabular coverage. This study aimed to assess the change in coronal parameters for acetabular coverage as a result of adult spinal deformity (ASD) correction and to analyze the relationship between the postoperative changes in sagittal spinopelvic parameters and coronal acetabular coverage parameters.

METHODS

Fifty-two consecutive patients who had undergone multilevel spinal surgical correction were enrolled and evaluated. Coronal acetabular coverage parameters included Tönnis angle (TA), lateral center edge angle (LCEA), and the angle of Sharp (SA). All radiographic parameters were evaluated at the preoperative and the postoperative 1 year. Paired t test was used to determine whether there were significant changes between the time points. Bivariate correlation and linear regression analysis were used to assess the relationship between the postoperative changes of spinal alignment and acetabular orientation.

RESULTS

The surgical correction resulted in significant decrease of TA, increase of LCEA and SA, respectively (p < 0.001). The changes in pelvic tilt (PT) demonstrated weak correlation on TA (β = 0.117, p < 0.001 for right; β = 0.111, p < 0.001 for left).

CONCLUSIONS

Although the surgical correction of ASD significantly changed PT resulting in increased acetabular lateral coverage parameters, the correlation between the changes of PT following sagittal correction of ASD and acetabular coverage parameters was low.

TRIAL REGISTRATION

This study was retrospectively registered with approval by the institutional review board (IRB) of our institution (approval number: KHNMC-2020-10-010).

Hip morphology in slipped capital femoral epiphysis

Several mechanical factors have been related to slipped capital femoral epiphysis (SCFE). Main aim of this study is to investigate the acetabular coverage and acetabular version in unilateral SCFE hips in order to detect a potential pincer-type deformity as predisposing factor; second, we compared those measurements either to the contralateral, uninvolved hips either to a matched healthy control population. A total of 85 patients treated for unilateral SCFE were retrospectively reviewed. The lateral center-edge angle (LCEA) and the Tönnis angle were used to assess acetabular coverage, whereas acetabular retroversion was defined by positive prominent ischial spine (PIS), cross-over sign (COS) and posterior wall sign (PWS). Angles and signs of the affected hips were compared to the contralateral hips and to a matched cohort undergoing an abdominal/pelvic computed tomography for nonorthopedic-related diseases. Affected and unaffected hips of patients with unilateral SCFE had similar morphology in terms of LCEA 28.7° vs. 28° (P = 0.4), Tönnis angle 9° vs. 9° (P = 0.1) and retroversion signs with concomitant rate of PWS and COS 57.6% vs. 50.5% (P = 0.4), PIS 56.4% vs. 49.4% (P = 0.4). Matched healthy controls vs. the affected hips showed a lower LCEA (P < 0.001) and higher Tönnis angle (P < 0.001) in conjunction with a lower incidence of acetabular retroversion: PWS and COS 40% vs. 57.6% (P = 0.01), PIS 43% vs. 56.4% (P = 0.07). A significant retroversion and increased overcoverage were observed in SCFE patients compared to matched healthy controls. In unilateral SCFE, the involved and uninvolved hips showed a substantial symmetry.

Acetabular Morphology and Spinopelvic Characteristics: What Predominantly Determines Functional Acetabular Version?

Background:

In addition to the relative size of the acetabular rim and how the pelvis is positioned in space, the plane in which the acetabular version is calculated also affects its measurement.

Purpose:

To determine the relative contribution of pelvic and acetabular characteristics on morphological version (measured relative to the anterior pelvic plane angle [APPA]) and functional version (measured relative to the horizontal table).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Included were 50 acetabular dysplasia patients and 109 asymptomatic controls. Using image analysis software, morphological parameters of the pelvis and acetabulum were determined from 2-dimensional computed topography: pelvic incidence, pelvic tilt angle, sacral slope, APPA, morphological and functional acetabular versions, and subtended angles (measure of acetabular rim prominence relative to the femoral head center) around the acetabular clockface in 30° increments. Correlation and multivariable regression analyses were performed with morphological and functional version as dependent variables and spinopelvic and acetabular parameters as independent variables.

Results:

Morphological version was moderately associated with differences between anterior and posterior subtended angles (R = 0.68 [P < .001] and R = 0.57 [P < .001] for differences at 165° and 15° and 135° and 45°, respectively). Functional version was moderately associated with pelvic tilt angle (R = 0.56; P <.001) and the difference in subtended angles between anterior and posterior rims (R = 0.61 [P < .001] and R = 0.50 [P < .001] for differences at 165° and 15° and 135° and 45°, respectively). Multivariate analysis revealed a good model for predicting morphological version (R² = 0.44; P < .01) and functional version (R² = 0.58; P < .01). Subtended angle difference between 165° and 15° (B = 0.36 [95% CI, 0.24-0.49]; P < .001) was most strongly related to morphological version, and pelvic tilt angle (B = 0.57 [95% CI, 0.46-0.68]; P < .001) was most strongly related to functional version.

Conclusion:

Functional acetabular version was influenced most strongly by pelvic tilt angle rather than the relative prominence of the acetabular rims. Before determining surgical management for version abnormalities, it would be prudent to assess pelvic mobility and characteristics in different functional positions. In patients with minimal pelvic tilt change dynamically, corrective osteotomy would be the treatment of choice to improve functional version.