Kinematic MRI of ischiofemoral impingement

Hip External Rotation Decreases Ischiofemoral Distance: A Positive Correlation Between Cadaveric and Fluoroscopic Studies

PURPOSE

To determine the effect of hip external rotation or extension/adduction on minimizing the ischiofemoral distance (IFD) and assess the correlation between cadaveric and fluoroscopic IFD measurements in different hip positions.

METHODS

This cadaveric study involved 33 hip joints from 17 embalmed cadavers. IFD, the distance between the lesser trochanter and lateral ischium, was measured in different hip positions: neutral, external rotation at 30°, and external rotation at 60° with the hip in both neutral extension and adduction as well as 10° hip extension and 10° hip adduction. Differences in IFD related to positions and correlation between cadaveric and fluoroscopic measurements were analyzed.

RESULTS

IFD measurements showed that the greatest reduction occurred at 60° of external hip rotation, with a significant difference observed only between neutral and 60° external rotation in cadaveric groups (7.60 ± 4.68 vs 5.05 ± 3.48, 95% CI, 0.14-4.96; P = .036). No substantial difference was observed between the extension and adduction positions. Positive correlations were observed between cadaveric and fluoroscopic measurements, especially in the neutral position (r = 0.492, P = .004), external rotation at 30° (r = 0.52, P = .002), external rotation at 60° (r = 0.419, P = .015), and the extension/adduction positions combined with neutral rotation (r = 0.396, P = .023).

CONCLUSIONS

The IFD significantly decreased with increasing degrees of hip external rotation, particularly at 60°. No significant reduction was observed in the extension/adduction positions. In addition, positive correlations were observed between cadaveric and fluoroscopic measurements for specific hip positions: neutral rotation, external rotation at 30° and 60°, and extension/adduction at 10° with neutral rotation.

CLINICAL RELEVANCE

Surgeons can use this knowledge to improve hip impingement assessment through radiography, focusing on positions in which IFD reduction is most notable. Understanding the relationship between hip positions and IFD can enhance the diagnosis of ischiofemoral impingement syndrome and benefit patient care and outcomes.

MRI 3D simulation of hip motion in female patients with and without ischiofemoral impingement

OBJECTIVE

To utilize hip MRI 3D models for demonstration of location and frequency of impingement during simulated range-of-motion in ischiofemoral impingement (IFI) compared to non-IFI hips.

MATERIALS AND METHODS

Sixteen hips (N = 7 IFI, 9 non-IFI) from 8 females were examined with high-resolution MRI. We performed image segmentation and generated 3D bone models and simulated hip range-of-motion and impingement. We examined the frequency and location of bone contact in early external rotation and early extension (0-20°), isolated maximum external rotation, and isolated maximum extension. Frequency and location of impingement at varied combinations of external rotation and extension and areas of simulated bone impingement at early external rotation and extension were compared between IFI and non-IFI.

RESULTS

Higher frequency of bony impingement occurred more often in IFI hips at each simulated range-of-motion combination (P < 0.05). Impingement involved the lesser trochanter more often in IFI hips (P < 0.001) and occurred at early degrees of external rotation and extension. In isolated maximum external rotation, only the greater trochanter, intertrochanteric area, or both combined were involved, in 14%, 57%, and 29% in IFI hips. In isolated maximum extension, the lesser trochanter, intertrochanteric area, or both combined were involved in 71%, 14%, and 14% in IFI hips. The simulated area of bone impingement was significantly higher in IFI hips (P = 0.02).

CONCLUSION

Hip MRI 3D models are feasible for simulated range-of-motion and show a higher frequency of extra-articular impingement at early stages of external rotation and extension in IFI compared to non-IFI hips.

Hip MRI in flexion abduction external rotation for assessment of the ischiofemoral interval in patients with hip pain-a feasibility study

OBJECTIVES

To assess the feasibility of flexion-abduction-external rotation (FABER) magnetic resonance imaging (MRI) of the hip to visualize changes in the ischiofemoral interval and ability to provoke foveal excursion over the acetabular rim.

METHODS

IRB-approved retrospective single-center study. Patients underwent non-contrast 1.5-T hip MRI in the neutral and FABER position. Two readers measured the ischiofemoral interval at three levels: proximal/distal intertrochanteric distance and ischiofemoral space. Subgroup analysis was performed for hips with/without high femoral torsion, or quadratus femoris muscle edema (QFME), respectively. A receiver operating curve with calculation of the area under the curve (AUC) for the prediction of QFME was calculated. The presence of foveal excursion in both positions was assessed.

RESULTS

One hundred ten patients (121 hips, mean age 34 ± 11 years, 67 females) were evaluated. FABER-MRI led to narrowing (both p < .001) of the ischiofemoral interval which decreased more at the proximal (mean decrease by 26 ± 7 mm) than at the distal (6 ± 7 mm) intertrochanteric ridge. With high femoral torsion/ QFME, the ischiofemoral interval was significantly narrower at all three measurement locations compared to normal torsion/no QFME (p < .05). Accuracy for predicting QFME was high with an AUC of .89 (95% CI .82-.94) using a threshold of ≤ 7 mm for the proximal intertrochanteric distance. With FABER-MRI foveal excursion was more frequent in hips with QFME (63% vs 25%; p = .021).

CONCLUSION

Hip MRI in the FABER position is feasible, visualizes narrowing of the ischiofemoral interval, and can provoke foveal excursion.

CRITICAL RELEVANCE STATEMENT

FABER MRI may be helpful in diagnosing ischiofemoral impingement and detecting concomitant hip instability by overcoming shortcomings of static MR protocols that do not allow visualization of dynamic changes in the ischiofemoral interval and thus may improve surgical decision making.

KEY POINTS

• FABER MRI enables visualization of narrowing of the ischiofemoral interval proximal to the lesser trochanter. • Proximal intertrochanteric distance of ≤ 7 mm accurately predicts quadratus femoris muscle edema. • Foveal excursion was more frequent in hips with quadratus femoris muscle edema.

Quadratus femoris muscle edema in children

OBJECTIVE

To assess the prevalence and clinical relevance of quadratus femoris muscle edema (QFME) in pediatric pelvic MRI.

MATERIALS AND METHODS

The axial T2-W with fat saturation sequence of pelvic/hip MRI examinations of pediatric patients (≤ 18 years) and a control group of young adults aged 19-45 years was retrospectively and independently evaluated by two musculoskeletal radiologists for the presence of QFME in each hip. Demographics, indication for imaging studies, and pain location were documented. The prevalence of QFME was compared between the groups on a patient level and on a hip level.

RESULTS

The study group included 119 children (164 MRI examinations; F:M 1:1.08, mean age 11.4 ± 3.6 years), and 120 young adults, > 18, < 45 years old, served as controls (F:M 1:0.9, mean age 33.7 ± 6.4 years). QFME was significantly more prevalent among the study compared to the control group, both on a patient level (15% and 4.2%, respectively, p < 0.05) and on a hip level (12.1% and 2.5%, respectively, p < 0.05). This significant difference was also seen in the subgroup of MRI studies performed for orthopedic indications but not for non-orthopedic indications. There was no correlation between the side of localized pain and the side with QFME.

CONCLUSION

QFME is significantly more prevalent in pediatric patients compared to adults under 45 years old, especially in subjects scanned for orthopedic indications. The clinical relevance of QFME in children and adolescents is unclear.

What Factors Are Associated With Postoperative Ischiofemoral Impingement After Bernese Periacetabular Osteotomy in Developmental Dysplasia of the Hip?

BACKGROUND

Any abnormal structures that contribute to the narrowing of the ischiofemoral space could induce ischiofemoral impingement. Bernese periacetabular osteotomy (PAO) medializes the hip center and, therefore, decreases contact stress on the cartilage in developmental dysplasia of the hip (DDH). However, medialization of the hip center might also narrow the ischiofemoral space, which may increase the risk of postoperative ischiofemoral impingement in patients with acetabular dysplasia who are undergoing PAO. Furthermore, the dysplastic hip has less ischiofemoral space and less space for the quadratus femoris. A few studies have focused on the amount of medialization of the hip center, but the proportion of postoperative ischiofemoral impingement after PAO has not been investigated.

QUESTIONS/PURPOSES

(1) What proportion of patients develop ischiofemoral impingement after undergoing unilateral PAO for DDH? (2) What radiographic factors are associated with postoperative ischiofemoral impingement in patients who underwent PAO for DDH? (3) How much hip center medialization is safe so as to avoid postoperative ischiofemoral impingement during PAO?

METHODS

Between 2014 and 2016, we treated 265 adult patients who had symptomatic residual acetabular dysplasia (lateral center-edge angle less than 20°) using PAO. During that time, we generally offered PAO to patients with acetabular dysplasia when the patients had no advanced osteoarthritis (Tönnis grade < 2). Of those, we considered only patients who underwent primary PAO without femoral osteotomy as potentially eligible. Based on that, 65% (173 of 265) were eligible; a further 9% (24 of 265) were excluded due to leg length discrepancy, spine disorders, or joint replacement in the contralateral side, and another 6% (17 of 265) of patients were lost before the minimum study follow-up of 2 years or had incomplete datasets, leaving 50% (132 of 265) for analysis in this retrospective study at a mean of 2.70 ± 0.71 years. The diagnosis of ischiofemoral impingement was defined by symptoms, MRI, and diagnostic ischiofemoral injection. We ascertained the percentage of patients with this diagnosis to answer the first research question. To answer the second question, we divided the patients into two groups: PAO patients with ischiofemoral impingement and PAO patients without ischiofemoral impingement. The demographic data and preoperative imaging parameters of patients in both groups were compared. There were statistical differences in acetabular version, ischial angle, neck-shaft angle, the presence of positive coxa profunda sign, McKibbin index, ischiofemoral space, quadratus femoris space, anterior acetabular section angle, and the net amount of hip center medialization. To investigate potential factors associated with postoperative ischiofemoral impingement in patients who underwent PAO, these factors underwent binary logistic regression analysis. To answer the third question, the cutoff value of the net amount of hip center medialization was evaluated using receiver operator characteristic curve and the Youden index method.

RESULTS

We found that 26% (35 of 132) of PAO dysplastic hips had postoperative ischiofemoral impingement. After controlling for confounding variables such as acetabular version, ischial angle, femoral neck version, McKibbin index, and ischiofemoral space, we found that an increasing neck-shaft angle (odds ratio 1.14 [95% confidence interval 1.01 to 1.29]; p = 0.03), a positive coxa profunda sign (OR 0.13 [95% CI 0.03 to 0.58]; p < 0.01), and an increasing net amount of hip center medialization (OR 2.76 [95% CI 1.70 to 4.47]; p < 0.01) were associated with postoperative ischiofemoral impingement in patients with DDH who underwent PAO (R 2 = 0.73). The cutoff values of neck-shaft angle was 138.4°. The cutoff values of the net amount of hip center medialization was 1.9 mm.

CONCLUSIONS

Postoperative ischiofemoral impingement could occur in patients with acetabular dysplasia who have undergone PAO after hip center medialization. An increasing neck-shaft angle, a positive coxa profunda sign on preoperative imaging, and excessive medialization of the hip center are factors associated with ischiofemoral impingement development in these patients. Therefore, we suggest that physicians measure the ischiofemoral space on a preoperative CT when patients with DDH have an increasing neck-shaft angle (> 138.4°) or a positive coxa profunda sign on radiological imaging. During PAO, the amount of hip center medialization should be carefully controlled to keep these patients from developing postoperative ischiofemoral impingement.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Increased Combined Anteversion Is an Independent Predictor of Ischiofemoral Impingement in the Setting of Borderline Dysplasia With Coxa Profunda

PURPOSE

To investigate the differences in radiologic parameters between borderline dysplasia hips (BDDH) +/- coxa profunda and normal hips and to evaluate the correlations between these parameters and the prevalence of ischiofemoral impingement (IFI) in borderline dysplasia.

METHODS

The imaging of patients with BDDH (18° ≤ lateral center edge angle <25°) treated in our hospital from January 2018 to December 2019 was retrospective reviewed. These patients were divided into BDDH with coxa profunda (acetabular fossa touches the ilioischial line, pBDDH) and without coxa profunda (nBDDH) groups. The groups were compared with a control group with normal acetabular coverage. Neck-shaft angle, femoral offset, acetabular versions, acetabular coverage, ischial angle, femoral neck version, and combined anteversion were reviewed and analyzed using computed tomography imaging using one-way analysis of variance.

RESULTS

There were 43 patients (36 female/7 male, 26.13 ± 4.96 years) in the pBDDH group, 22 patients (17 female/5 male, 28.60 ± 5.89 years) in the nBDDH group, and 23 patients (14 female/9 male, 27.67 ± 5.98 years) in the control group. The pBDDH group had increased femoral version, ischial angle, acetabular versions, and decreased ischiofemoral space (IFS)/quadratus femoris space (QFS) than the other 2 groups. The IFS/QFS correlated with neck-shaft angle, femoral offset, femoral neck version, acetabular versions, ischial angle, femoral neck-lesser trochanter angle, posterior acetabular coverage, and combined anteversion in patients with BDDH. Combined anteversion at the 3-o'clock level was an independent predictor of a decreased IFS (beta = -0.348, P = .007) and QFS (beta = -0.255, P = .01, R² = .550). Binary logistic regression demonstrated that patients with BDDH with large combined anteversion at the 3-o'clock level had a greater prevalence of IFI (odds ratio 1.148; P = .001, R² = .505).

CONCLUSIONS

In patients with borderline dysplasia, the QFS/IFS significantly correlated with combined anteversion at the 3-o'clock level on clock face of acetabulum. BDDH with coxa profunda might have a greater prevalence of IFI because of large combined anteversion.

LEVEL OF EVIDENCE

III, retrospective comparative observation study.

Arthroscopic Lesser Trochanter Osteoplasty, Quadratus Femoris Debridement, and Sciatic Neurolysis via Posterior Approach for Ischiofemoral Impingement

Ischiofemoral impingement (IFI) syndrome is considered the narrowing of the ischiofemoral space (IFS), leading to pathological changes in the quadratus femoris and sciatic nerve, causing posterior hip and sciatica-like pain. Open or arthroscopic resection of the lesser trochanter to enlarge the IFS is the main surgical procedure. However, there is a lack of research on isolated IFI, and currently known surgical procedures are at risk of weakening the flexion strength of the hip joint. In this study, four patients, who were diagnosed with isolated IFI and had undergone arthroscopic treatment with partial resection of the lesser trochanter, debridement of the quadratus femoris, and decompression of the sciatic nerve, were reviewed. To the best of our knowledge, this is the first study to describe the management of IFI using a series of surgical procedures via a posterior approach as an effective treatment option. The outcomes of this study broadened the strategies for IFI management.

Interpretation of ischiofemoral impingement via a clinical test using hip triaxial dynamic magnetic resonance imaging

BACKGROUND

The present study aimed to use magnetic resonance (MR) to explore the dynamic changes of the ischiofemoral space (IFS) under the triaxial motion of the hip joint and verify the clinical test mechanism for ischiofemoral impingement (IFI).

METHODS

A prospective design was used to screen 37 patients with clinically confirmed IFI, which included a total of 67 lateral hips, and 39 healthy controls with a total of 69 lateral hips. A dynamic MR examination was performed in positions designed by a simulated IFI test (adduction, adduction with 30° external rotation, 30° internal rotation, supine with 30° flexion, and prone with 30° backward extension). The IFS (mm) and quadratus femoris space (QFS, mm) were measured in different positions. All the data were evaluated independently by three musculoskeletal radiologists. The differences between the two groups were compared using the two-tailed t-test.

RESULTS

The IFS and QFS in the case group were smaller than those in the control group. The IFS and QFS were significantly reduced in the prone with backward extension and adduction with external rotation positions of the hip. The correlation coefficients of the IFI test and long-stride walking (LSW) test were -0.621 and -0.715 for IFS and -0.653 and -0.696 for QFS, respectively.

CONCLUSIONS

In this study, the mechanism of the IFI-specific clinical examination (IFI and LSW tests) was verified by triaxial dynamic MR imaging of the hip joint, which provided a dynamic imaging basis for the clinical application of the IFI-specific impingement test. The IFI impingement test can be used as a specific clinical test for IFI screening.

Pain relief and good functional outcomes after hip endoscopy via posterior approach in patients with ischiofemoral impingement

PURPOSE

Ischiofemoral impingement is considered to be an uncommon and difficult pathology to diagnose with respect to hip pain etiology. The objective was to describe the clinical results of endoscopic lesser trochanter resection via a posterior approach in patients with Ischiofemoral impingement.

METHODS

This was a retrospective observational study of consecutive patients with Ischiofemoral impingement, who underwent endoscopic resection of the lesser trochanter via a posterior approach, between 2015 and 2018. Clinical results were evaluated using the ischiofemoral impingement test, long-stride walking test, modified Harris Hip Score (mHHS) and the Oxford scale to assess the strength of the iliopsoas muscle as well as the presence of complications. Preoperative and postoperative ischiofemoral space was measured to assess whether the resection of the lesser trochanter was adequate.

RESULTS

16 hips in 13 patients (mean age: 34.4 ± 12.1 years, 11 women) with a follow-up period between 24 and 59 months were included. Preoperative ischiofemoral space ranged from 6.4 to 22.4 mm, a measure > 17.0 mm was achieved in 15 hips without the presence of pain in IFI test and long-strides walking test. Function improved postoperatively, as reflected by a higher mean mHHS (preoperative: 44.6 ± 21.5, postoperative: 81.2 ± 15.1, p < 0.05). After surgery, the strength of the iliopsoas muscle was not decreased compared to the preoperative measure. Three complications were reported, including two cases that required revision surgery.

CONCLUSIONS

Endoscopic resection of the lesser trochanter via posterior approach provides satisfactory outcomes with symptom relief and good functional results in patients with Ischiofemoral impingement. It is important to discuss the benefits and risks when offering this treatment choice.

LEVEL OF EVIDENCE

Level IV.

Ischiofemoral Impingement Syndrome: Effect of Morphological Variations on the Diagnosis

OBJECTIVE

The purpose of this study is to clarify which morphologic variations of the hip on MRI are associated with the development of ischiofemoral impingement.

METHODS

Hip MRIs of patients who have been referred to our department between 2016-2017 were retrospectively reviewed and assessed for pathological signal changes in the quadratus femoris muscle and ipsilateral hip or buttock pain. After assessment, ischial angle, inclination angle, ischiofemoral space, quadratus femoris space, intertuberous distances and femur neck angle, femoral torsion angle and knee angle were measured and compared in 37 hips of 20 patients and 56 hips of 28 age-gender matched control subjects.

RESULTS

There were statistically significant differences between the patient and control groups in all MRI parameters except for intertuberous distances (p<0.05). Quadratus femoris space (p<0.001) and ischiofemoral space (p<0.001) were significantly lower and femoral torsion angle (p=0.02), femur neck angle (p=0.001), ischial angle (p=0.01) and inclination angle (p=0.03) values were significantly higher in patients compared with the control group.

CONCLUSION

Decreased ischiofemoral space and quadratus femoris space, increased femoral torsion angle, femur neck angle, ischial angle and inclination angle are found to be associated with IFI on MRI. These pelvic anatomical variations may predispose to ischiofemoral impingement and should be kept in mind for patients with hip pain.