A new tilt on pelvic radiographs: a pilot study

Three-Dimensional Computed Tomography Reconstructions May Detect Pincer Lesions With Higher Sensitivity Than Radiographs in Patients With Femoroacetabular Impingement Syndrome

Purpose

To assess the diagnostic capability of radiographs (XRs) to detect pincer lesions compared with 3-dimensional (3D) computed tomography scans in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS).

Methods

We performed a retrospective review of all patients who underwent hip arthroscopy for FAIS between September 1, 2020, and October 2, 2022. Preoperative imaging was reviewed. Pincer lesions were defined as a lateral center-edge angle greater than 40°; a Tönnis angle greater than 0°; the presence of the ischial spine, crossover, or posterior wall sign; and the presence of overcoverage greater than 80%. Under "select criteria," patients were classified as having a pincer lesion on XRs and 3D computed tomography reconstructions (CTRs) based on the lateral center-edge angle or Tönnis angle alone, whereas "all criteria" added the presence of the crossover sign and coverage percentage. Statistical analysis was performed to determine the diagnostic accuracy of XRs compared with 3D CTRs.

Results

A total of 69 patients met the inclusion criteria. There were 21 male patients (30.4%) and 48 female patients (69.6%). The mean age was 33 ± 13.5 years. χ2 Analysis for select criteria found that 3D CTR was more likely than XRs to detect a pincer lesion. χ2 Analysis for all criteria found that 3D CTR was more likely than XRs to detect a pincer lesion. χ2 Analysis further showed that when using XRs, a pincer lesion was more likely to be detected under all criteria than under select criteria. Likewise, when using 3D CTR, a pincer lesion was more likely to be detected under all criteria than under select criteria.

Conclusions

In this study, we found that 3D CTR detected pincer lesions in patients undergoing hip arthroscopy for FAIS with significantly higher sensitivity than XRs alone.

Level of Evidence

Level III, retrospective cohort study.

Is Stage 2 idiopathic osteonecrosis of the hip joint associated with version angles on imaging methods?

Objectives

In this study, we aimed to investigate whether anatomical variations of acetabulum were associated to idiopathic osteonecrosis (ON) of the femoral head.

Patients and methods

Between January 2014 and March 2020, a total of 46 patients (32 males, 14 females; mean age: 43 years; range, 18 to 66 years) who were diagnosed with unilateral or bilateral ON of the hip joint and 44 healthy age- and sex-matched controls (30 males, 14 females; mean age: 46 years; range, 18 to 79 years) with no signs of ON of the hip joint were retrospectively analyzed. For both groups, measurements were taken of the anatomic parameters, including the acetabular version angle (VA), the sharp angle (SA), and the center-edge angle (CEA) on anteroposterior pelvic radiographs and magnetic resonance imaging (MRI) scans.

Results

The mean VA of both hips was found to be significantly smaller in Group 1 than in Group 2 on both MRI and X-ray (14.9±4.1 and 14.4±3.1 vs. 17.3±3.9 and 18.0±3.7, respectively; p=0.004, p<0.001). The mean SA of both hips was found to be significantly smaller in Group 1 than in Group 2 on both MRI and X-ray (39.0±2.9 and 38.9±2.8 vs. 41.6±3.9 and 40.8±4.9, respectively; p=0.001, p=0.036). The mean CEA of both hips was found to be significantly larger in ON group than in control group on both MRI and X-ray (36.7±6.1 and 36.9±7.0 vs. 32.0±6.0 and 31.5±7.5, respectively; p<0.001, p=0.001).

Conclusion

Version angles were found to be smaller in patients with ON and more acetabular coverage was observed. Greater coverage of the acetabulum may indicate early collapses of the femoral head even in Stage 2 ON patients. The smaller version angles may be associated with ON.

The Musculoskeletal Manifestations of Marfan Syndrome: Diagnosis, Impact, and Management

Purpose of Review

Marfan syndrome (MFS) is an autosomal dominant heritable disorder of fibrillin-1 (FBN1) with predominantly ocular, cardiovascular, and musculoskeletal manifestations that has a population prevalence of approximately 1 in 5–10,000 (Chiu et al. Mayo Clin Proc. 89(1):34–42, 146, Dietz 3, Loeys et al. J Med Genet. 47(7):476–85, 4).

Recent Findings

The vascular complications of MFS still pose the greatest threat, but effective management options, such as regular cardiac monitoring and elective surgical intervention, have reduced the risk of life-threatening cardiovascular events, such as aortic dissection. Although cardiovascular morbidity and mortality remains high, these improvements in cardiovascular management have extended the life expectancy of those with MFS by perhaps 30–50 years from an estimated mean of 32 years in 1972 (Dietz 3, Gott et al. Eur J Cardio-thoracic Surg. 10(3):149–58, 147, Murdoch et al. N Engl J Med. 286(15):804–8, 148). The musculoskeletal manifestations of MFS, which to date have received less attention, can also have a significant impact on the quality of life and are likely to become more important as the age of the Marfan syndrome population increases (Hasan et al. Int J Clin Pract. 61(8):1308–1320, 127). In addition, musculoskeletal manifestations are often critically important in the diagnosis of MFS.

Summary

Here, we review the main clinically relevant and diagnostically useful musculoskeletal features of MFS, which together contribute to the “systemic features score” (referred to hereafter as systemic score), part of the revised Ghent nosology for MFS. We discuss current treatment strategies and highlight the need for a multidisciplinary approach to diagnosis and management. Finally, we review new pharmacological approaches that may be disease modifying and could help to improve the outcome for individuals with this syndrome.

Effects of acetabular rim trimming on hip joint contact pressures: how much is too much?

BACKGROUND

In patients with femoroacetabular impingement (FAI), acetabular rim trimming removes the offending area of the acetabular deformity in patients with pincer-type and mixed-type FAI to improve hip joint kinematics. Although the rationale for arthroscopic acetabular rim trimming in patients with FAI is well established, the amount of rim resection has not been quantified, and the threshold at which excessive rim resection results in abnormal hip contact pressures has not been described.

PURPOSE

To investigate the changes in contact areas, contact pressures, and peak forces within the hip joint with sequential acetabular rim trimming.

STUDY DESIGN

Controlled laboratory study.

METHODS

Six fresh-frozen, nondysplastic, human cadaveric hemipelvises were analyzed utilizing thin-film piezoresistive load sensors to measure the contact area, contact pressure, and peak force after anterosuperior acetabular rim trimming at depths of 0 mm (intact), 2 mm, 4 mm, 6 mm, and 8 mm. Each specimen was examined at 20° of extension and 60° of flexion. Analysis was performed on 2 regions of interest: the acetabular rim and the acetabular base (deep part of the acetabulum). After each experimental condition, the acetabulum was normalized with respect to the intact state to account for specimen variability. Statistical analysis was conducted through 1-way analysis of variance with post hoc Games-Howell tests.

RESULTS

At the acetabular base, there were significant increases in the contact area after 4-mm resection (60°: 169.12% ± 30.64%; P = .0138), contact pressure after 6-mm resection (60°: 292.76% ± 79.07%; P = .009), and peak force after 6-mm resection (60°: 166.00% ± 34.40%; P = .027). At the acetabular rim, there were significant decreases in the contact area after 6-mm resection (60°: 66.32% ± 18.80%; P = .0354) (20°: 65.47% ± 15.87%; P = .0127), contact pressure after 6-mm resection (60°: 50.77% ± 11.49%; P < .001) (20°: 58.01% ± 23.10%; P = .0335), and peak force after 6-mm resection (60°: 60.67% ± 9.29%; P < .001) (20°: 74.44% ± 9.84%; P = .007).

CONCLUSION

Resecting more than 4 to 6 mm of the acetabular rim during hip arthroscopic surgery to address a pincer deformity may dramatically increase contact pressures by 3-fold at the acetabular base. The study suggests that excessive rim resection may lead to increased loads in the hip joint and may predispose to premature joint degeneration.

CLINICAL RELEVANCE

Resecting more than 4 to 6 mm of the acetabular rim may significantly alter hip joint biomechanics, increasing joint reactive forces and subsequent chondrolabral degeneration.

Analysis of Protrusio Acetabuli Using a CT-based Diagnostic Method in Korean Patients with Marfan Syndrome: Prevalence and Association with Other Manifestations

A new CT-based diagnostic method of protrusio acetabuli (PA) was introduced. However, prevalence of PA by this method and correlation between PA and other manifestations of Marfan syndrome (MFS) is unknown in Korean MFS patients. This study aimed to investigate the prevalence of PA diagnosed by a CT-based method in Korean patients with MFS, the association of PA with other manifestations of MFS, and the contribution of PA to MFS diagnosis. We retrospectively reviewed the records of 146 MFS patients with the presence of a causative FBN1 mutation and 146 age- and sex-matched controls from a single tertiary care center. All MFS patients underwent a complete assessment of criteria based on the revised Ghent nosology. PA was assessed quantitatively using a CT-based circle-wall distance (CWD) method. PA was diagnosed in 77.4% of patients in the MFS group and in 11.0% of the control group. CWD was significantly different between the two groups (1.50 mm vs. -0.64 mm, P<0.001). The presence of PA did not correlate with the presence of ectopia lentis, aortic root diameter, or history of aortic dissection. The presence of PA did not have a significant impact on the final diagnosis of MFS. Even though the presence of PA does not related to the cardinal clinical features of MFS or influence MFS diagnosis, its presence may be helpful for the suspicion of MFS when aortic dissection or aneurysm is found on CT angiography of the aorta because of the high frequency of PA in MFS patients.

Bony abnormalities of the hip joint: a new comprehensive, reliable and radiation-free measurement method using magnetic resonance imaging

OBJECTIVES

To develop comprehensive and reliable radiation-free methods to quantify femoral and acetabular morphology using MRI.

METHODS

32 hips (16 subjects, 6 with intra-articular hip disorder (IAHD); 10 controls) were included. A 1.5T magnetic resonance system was used to obtain 3D fat suppressed gradient echo images at the pelvis and distal femora. After acquisition, pelvic images were post-processed to correct for coronal, axial and sagittal rotation. Measurements performed included acetabular version (AV), femoral version (FV), lateral center edge angle (LCEA), femoral neck angle (FNA) and alpha angle (AA) at 3, 2, 1 and 12 o'clock. Two experienced raters, a musculoskeletal radiologist and an orthopaedic physical therapist, and a novice rater, a research assistant, completed reliability testing. Raters measured all hips twice with minimum 2 weeks between sessions. Intraclass Correlation Coefficients were used to determine rater reliability; standard error of measurements was reported to estimate the reasonable limits of the expected error in the different raters' scores.

RESULTS

Interrater reliability was good to excellent for all raters for AV, FV, FNA, and LCEA (ICCs: 0.82-0.98); good to excellent between experienced raters (ICCs: 0.78-0.86) and poor to good between novice and experienced raters (ICCs: 0.23-0.78) for AA. Intrarater reliability was good to excellent for all raters for AV, FV and FNA (ICCs: 0.93-0.99); for one experienced and novice rater for LCEA (ICCs: 0.84-0.89); moderate to excellent for the experienced raters for AA (ICCs: 0.72-0.89). Intrarater reliability was poor for the second experienced rater for LCEA (ICC: 0.56), due to a single measurement error and for the novice rater for AA (ICCs: 0.17-0.38).

CONCLUSION

We described MRI methods to comprehensively assess femoral and acetabular morphology. Measurements such as AV, FV and FNA and the LCEA can be made reliably by both experienced and novice raters, however the AA measurement was reliable only among experienced raters.

Measuring limb length discrepancy using pelvic radiographs: the most reproducible method

Leg length inequality following total hip replacement remains common. In an effort to reduce this occurrence, surgeons undertake pre-operative measurements, templating and use various forms of intraoperative measurements, including computer navigation. This study aims to delineate which measurement technique is most appropriate for measuring leg length inequality from a pelvic radiograph. Three observers took a total of 9600 measurements from 100 pelvic radiographs. Four lines were constructed on each of the radiographs, bisecting the acetabular teardrops, ischial spines, inferior sacroiliac joint and inferior obturator foramen. Measurements were taken from these lines to the most prominent medial point on the lesser trochanter and to the tip of the greater trochanter. The effect of pelvic positioning was also assessed using radiographs of a synthetic pelvis and femur. Intra-observer and inter-observer variability were calculated. Measuring from the inferior aspect of the ischial tuberosities to the most prominent medial point on the lesser trochanter appears to be the best method for measuring LLD however large error margin still exist, even when corrected for magnification errors.

Quantifying the characteristics of the acetabulum and proximal femur using a semi-automated hip morphology software programme (SHIPS)

BACKGROUND

Hip-joint shape is an important factor that affects an individual's risk of developing osteoarthritis (OA). However, validated tools to quantify these morphological characteristics on clinical plain radiographs are few. We developed a Matlab-based Semi-automated HIP Software programme (SHIPS) that measures 10 morphologic characteristics of the hip that are risk factors for OA using a plain digitised antero-posterior pelvic radiograph. In this study we validated the accuracy and repeatability of this freeware-tool.

METHODS

Software accuracy was assessed using a test pelvic radiograph, and by repeated measurements of an AP-pelvic radiograph digitally recreated from pelvis computed-tomography images reformatted to create images rotated in 2-dimensions (2.5° increments, range -15° to +15°). Intra- and inter-observer repeatability was assessed using pelvic radiographs from 30 subjects analysed twice using the software by two readers, and expressed as coefficient of variation (CV). Clinical-repeatability was assessed by measuring sequential pelvic radiographs taken on the same day after re-positioning in 23 subjects.

RESULTS

Software accuracy was within 0.1% for linear-ratios and 0.4° for angular-measurements. Changes in pelvic inclination and rotation of ±15° resulted in <14% change in linear-measurement ratios and <7° change in angular-measurements. The intra-observer CV was between 0.3 to 4.1%, and inter-
observer CV 0.7 to 9.7% with the exception of horizontal-toit-externa (HTE, 14.6 and 24.2% respectively). Short-term clinical-repeatability varied from 0.4 to 6.1%, with the exception of HTE (37.4%).

CONCLUSION

The software showed good accuracy and repeatability for measurement of most hip-joint morphologic risk factors for OA apart from HTE. This tool has particular value in studying large or 
retrospective datasets where cross-sectional imaging is not feasible or available.

Atypical hip impingement

OBJECTIVE

This article summarizes how atypical forms of hip impingement can be assessed with radiographs, CT, and MRI.

CONCLUSION

Subspine impingement, ischiofemoral impingement, and iliopsoas impingement are atypical forms of hip impingement and are less common than classic femoroacetabular impingement. Additional forms of atypical impingement, such as abnormal femoral antetorsion, abnormal pelvic and acetabular tilt, and extreme hip motion, can occur combined with classic femoroacetabular impingement or as separate entities.

Defining a reference range of acetabular inclination and center-edge angle of the hip in asymptomatic individuals

PURPOSE

Acetabular morphology is an important predictor of the severity of osteoarthrosis and survival of hip prostheses but there is limited data on the normal range of acetabular measurements on plain radiographs. The aim of this project was to determine the statistically normal ranges of acetabular inclination (AI) and center-edge angle (CEA).

METHOD

One hundred coronal CT localizers (50 men and 50 women aged 20-30 years) were included in this study. All the patients underwent CT examination for thoracic or intra-abdominal indications. Patients with pelvic disease, fractures, history of serious trauma, or previous pelvic surgery were excluded. One pair of independent observers measured the AI and pelvic tilt (PT), and a further pair measured the center-edge angle (CEA), using electronic calipers on a high-resolution PACS workstation.

RESULTS

AI and CEA measurements were obtained for 200 hips. There was very good intra-class correlation between the observers (r = 0.7-0.8). The mean AI was 38.8° (2SD 32.1-45.5°). That in men was 38.0° (2 SD 31.8-44.1°) and 39.6° (2 SD 32.7-46.8°) in women, which was statistically significantly different (p < 0.001). The mean CEA measurement for all patients was 36.3° (SD 13.8°), for men 37.7° (SD 10.8°) and for women 34.9° (SD 11.4°) with a statistically significant gender difference (p < 0.001). The mean pelvic tilt measurement (sacro-coccygeal-pubic symphysis) was 38.3 mm (2 SD 18.3-58.3 mm) with a significant gender difference (p < 0.001).

CONCLUSIONS

The results of this study define reference ranges of two common measures of acetabular morphology and confirm statistically significant differences between men and women.

A quantitative method to assess focal acetabular overcoverage resulting from pincer deformity using CT data

BACKGROUND

Current assessment techniques for focal acetabular overcoverage are neither consistent nor quantitatively accurate.

QUESTIONS/PURPOSES

We propose: (1) a method to precisely quantify the amount of focal acetabular overcoverage in a patient's pincer deformity based on CT data; (2) to evaluate the consistency of this method; and (3) to compare the method with conventional radiographic assessments.

METHODS

We developed a method to assess focal acetabular overcoverage using points selected from CT scans along the acetabular rim after realigning the pelvis into a neutral position. Using four resampled and segmented pelvic CT scans of cadaveric specimens with virtually induced impingement, two observers independently tested the algorithm's consistency. Our algorithm assessed the amount of focal acetabular overcoverage using CT data and projected data from reconstructed radiographs.

RESULTS

(1) We successfully showed the feasibility of the software to produce consistent, quantitative measurements. (2) Testing showed the average difference between observers in aligning the pelvis was 0.42°, indicative of a consistent approach. (3) Differences between measurements on three-dimensional (3-D) CT and simulated radiographs were significant.

CONCLUSIONS

The proposed method represents a new avenue in consistently quantifying focal acetabular overcoverage using CT models while correcting for pelvic tilt and rotation. Our analysis confirms AP hip radiograph simulations overestimate the amount of overhanging acetabular rim in a pincer deformity.

CLINICAL RELEVANCE

This technique has potential to improve preoperative diagnostic accuracy and enhance surgical planning for correction of a pincer deformity resulting from focal acetabular overcoverage.

CT of the hips in the investigation of protrusio acetabuli in Marfan syndrome. A case control study

OBJECTIVES

To establish the prevalence of protrusio acetabuli (PA) in adults fulfilling the Ghent criteria for Marfan syndrome (MFS), and in a normal adult population.

METHODS

105 adults with probable MFS and 107 controls were included. CT of the hips was obtained. A qualitative assessment of PA was performed. A new method for estimating the degree of PA was introduced with measurement of the parameter CWD (circle-wall distance). Results were compared to an alternative method based on MRI [1].

RESULTS

87 of the study group fulfilled the Ghent criteria of MFS (Ghent positives), and 18 did not (Ghent negatives). PA was diagnosed qualitatively in 74.7% of Ghent positive persons, in 27.8% of Ghent negative persons, and in 3.7% of the controls. CWD was significantly different between the three groups (p < 0.001). A slight but significant gender difference was found in Ghent positive persons only. The alternative method did not differentiate between the groups with respect to PA, but showed a significant difference between genders.

CONCLUSIONS

PA was found significantly more often in MFS persons than in controls. Our method was found to be robust and highly reproducible, giving a direct measurement of pelvic protrusion irrespective of pelvic shape.

Acetabular rim reduction for the treatment of femoroacetabular impingement correlates with preoperative and postoperative center-edge angle

PURPOSE

The purpose of this study was to quantify the change in degrees in the center-edge (CE) angle for each millimeter of acetabular rim resected in hips undergoing arthroscopic acetabular rim trimming.

METHODS

Preoperative and postoperative CE angle and millimeters of rim reduction were prospectively collected in 58 hips that underwent arthroscopic rim reduction. There were 35 women and 23 men. The mean age was 32 years. The inclusion criterion was hip arthroscopy for femoroacetabular impingement in patients without dysplastic hips. Two orthopaedic surgeons made independent measurements of the CE angle on preoperative and postoperative anteroposterior pelvis radiographs. To determine the amount of rim reduction intraoperatively, the lunate surface was measured with an arthroscopic ruler at the 12-o'clock position before and after rim trimming. The rim trimming was performed by a single surgeon using a 5.5-mm motorized bur.

RESULTS

For the 58 hips included in this study, the mean rim reduction performed was 3.2 mm (range, 1 to 9 mm). The mean change in CE angle was 3.9 degrees (range, 0 degrees to 17 degrees ). All numbers were normally distributed. By use of a regression model, the change in the CE angle could be determined by the following formula: Change in CE angle = 1.8 + (0.64 x rim reduction in millimeters). The interobserver intraclass correlation coefficient for radiographic measurement of the CE angle was 0.92 (95% confidence interval, 0.87 to 0.95), indicating excellent interobserver reliability.

CONCLUSIONS

The amount of change in the CE angle can be estimated by the amount of bony resection performed at the 12-o'clock position on the lunate surface in the arthroscopic treatment of femoroacetabular impingement. We found that 1 mm of bony resection equals 2.4 degrees of change in the CE angle and 5 mm of bony resection equals 5 degrees of change in the CE angle.

LEVEL OF EVIDENCE

Level II, diagnostic study.