A novel method for in vivo measurement of dynamic ischiofemoral space based on MRI and motion capture.

Purpose: To use a novel in vivo method to simulate a moving hip model. Then, measure the dynamic bone-to-bone distance, and analyze the ischiofemoral space (IFS) of patients diagnosed with ischiofemoral impingement syndrome (IFI) during dynamic activities. Methods: Nine healthy subjects and 9 patients with IFI were recruited to collect MRI images and motion capture data. The motion trail of the hip during motion capture was matched to a personalized 3D hip model reconstructed from MRI images to get a dynamic bone model. This personalized dynamic in vivo method was then used to simulate the bone motion in dynamic activities. Validation was conducted on a 3D-printed sphere by comparing the calculated data using this novel method with the actual measured moving data using motion capture. Moreover, the novel method was used to analyze the in vivo dynamic IFS between healthy subjects and IFI patients during normal and long stride walking. Results: The validation results show that the root mean square error (RMSE) of slide and rotation was 1.42 mm/1.84° and 1.58 mm/2.19°, respectively. During normal walking, the in vivo dynamic IFS was significantly larger in healthy hips (ranged between 15.09 and 50.24 mm) compared with affected hips (between 10.16 and 39.74 mm) in 40.27%-83.81% of the gait cycle (p = 0.027). During long stride walking, the in vivo dynamic IFS was also significantly larger in healthy hips (ranged between 13.02 and 51.99 mm) than affected hips (between 9.63 and 44.22 mm) in 0%-5.85% of the gait cycle (p = 0.049). Additionally, the IFS of normal walking was significantly smaller than long stride walking during 0%-14.05% and 85.07%-100% of the gait cycle (p = 0.033, 0.033) in healthy hips. However, there was no difference between the two methods of walking among the patients. Conclusions: This study established a novel in vivo method to measure the dynamic bone-to-bone distance and was well validated. This method was used to measure the IFS of patients diagnosed with IFI, and the results showed that the IFS of patients is smaller compared with healthy subjects, whether in normal or long stride walking. Meanwhile, IFI eliminated the difference between normal and long stride walking.

Multifocal concomitant scapulothoracic and subgluteal-ischiofemoral elastofibromas.

PURPOSE: To evaluate the frequency, imaging findings, and patient demographics of synchronous elastofibroma dorsi (ED) and pelvic elastofibromas. METHODS: Image archives between 2011 and 2021 were retrospectively searched for CT and MRI reports including the keyword "elastofibroma". Patients with concomitant CT and/or MRI of the chest and pelvic regions were included. The greatest thickness and side of ED were noted. Subsequently, pelvic soft tissues were evaluated for a soft tissue mass with similar radiological features to ED. When detected, its location, greatest transverse diameter, and ischiofemoral space widths were noted. Wilcoxon matched-pairs signed-rank and Mann-Whitney U-tests were performed when appropriate. Pearson's correlations were used to assess the association of presence of subgluteal-ischiofemoral elastofibromas (SGIFE) and ED thickness. The model discrimination of ED thickness was evaluated by calculating the AUC of the ROC. RESULTS: Eighty-eight patients (Male:Female = 8:80) with a mean age of 70.6 (±10.3) years were included. 96.6 % of patients had bilateral ED. 18.2 % of patients (all females) had at least one concomitant SGIFE. Patients with SGIFE had significantly thicker ED (p < 0.001 right; p = 0.049 left). There was a significant positive correlation between the thickness of ED and presence of SGIFE (r = 0.43, p < 0.001 right; r = 0.25, p = 0.019 left). An AUC of 0.781 (p < 0.001, 95 %-CI:0.675-0.887) and 0.659 (p = 0.049, 95 %-CI:0.523-0.794) were revealed regarding the presence of ipsilateral right and left SGIFE, respectively. CONCLUSION: Concomitant SGIFE may accompany ED in up to 18.2% of cases, particularly in women with thick ED. Knowledge of this co-occurrence and the described SGIFE characteristics can facilitate correct diagnosis.

Síndrome de pinzamiento isquiofemoral: reporte de un caso inusual / Ischiofemoral impingement syndrome: Report of an unusual case

El síndrome de pinzamiento isquiofemoral suele ser una patología infradiagnosticada que forma parte de uno de los diagnósticos diferenciales a tener en cuenta en el dolor de cadera. Inicialmente fue descrito con procedimientos quirúrgicos, pero con el paso del tiempo se han ido describiendo diferentes entidades médicas, así como técnicas y posturas mantenidas, que puede agravar el cuadro, pudiendo asociar incluso afectación neurológica. En la actualidad el tratamiento es inicialmente conservador con medidas de reposo, analgesia, frío e inicio progresivo de ejercicios dirigidos a la musculatura lumbar, glútea y de miembros inferiores, pero no existe un protocolo de actuación establecido unificado.(AU)

Ischiofemoral impingement syndrome is usually underdiagnosed; this syndrome forms part of the differential diagnoses to be included in hip pain. It was initially described with surgical procedures but, with the passage of time, various medical entities have been described, as well as techniques and postures that can aggravate this syndrome, which can even be associated with neurological involvement. Current treatment is initially conservative, consisting of rest, analgesia, cold and progressive exercises aimed at the lumber and gluteal muscles and lower extremities but there is no established standard of care.(AU)

[Ischiofemoral impingement syndrome: Report of an unusual case]. / Síndrome de pinzamiento isquiofemoral: reporte de un caso inusual.

Ischiofemoral impingement syndrome is usually underdiagnosed; this syndrome forms part of the differential diagnoses to be included in hip pain. It was initially described with surgical procedures but, with the passage of time, various medical entities have been described, as well as techniques and postures that can aggravate this syndrome, which can even be associated with neurological involvement. Current treatment is initially conservative, consisting of rest, analgesia, cold and progressive exercises aimed at the lumber and gluteal muscles and lower extremities but there is no established standard of care.

Ischiofemoral space dimensions for ischiofemoral impingement: is it different in children?

OBJECTIVE: This study intended to analyze alterations in ischiofemoral space (IFS) dimensions in normal children between the ages of 1 and 18 years for the ischiofemoral impingement. MATERIALS AND METHODS: This study retrospectively focused on computed tomography images of 360 hips of 180 (90 boys and 90 girls) pediatric subjects (mean age: 9.50 ± 5.20 years, range: 1-18 years) without any hip disorders to measure IFS, femoral neck angle (FNA), and ischial angle (IA). RESULTS: Mean IFS, FNA, and IA were measured as 14.64 ± 7.24 mm, 34.61 ± 11.47°, and 131.52 ± 4.22°, respectively. IFS increased in children aged between 1 and 18 years, whereas FNA and IA decreased. IFS was similar in infancy and early childhood periods but then increased up to postpubescent period. FNA decreased proportionally from birth, whereas IA decreased in an irregular pattern. Linear functions were detected as y = 3.451 + 1.178 × years for IFS, as y = 48.555 - 1.468 × years for FNA, and as y = 132.535 - 0.107 × years for IA. CONCLUSION: Our findings indicate that IFS tends to increase in size with age during childhood but decreases with further aging. Therefore, age-specific values for IFS, FNA, and IA may be beneficial for clinicians and radiologists for the diagnosis of ischiofemoral impingement.

The Utility of MRI to Diagnose Ischifemoral Impingement by Assessing the Ischiofemoral and Quadratus Femoris Spaces During Femoral External Rotation.

OBJECTIVE: The purpose of this study was to explore if the dimensions of the ischiofemoral space on MRI vary with changes in external femoral rotation in Ischifemoral Impingement patients relative to healthy control; if so, to determine the optimal diagnostic cutoff values of these dimensions in Ischifemoral Impingement. METHODS: The study included 43 clinically confirmed Ischifemoral Impingement patients and 50 healthy volunteers. All subjects underwent hip MRI examinations with their hips externally rotated at 0°, 30° and 60°. The IFS and QFS were measured respectively at each angle. The measurements were compared between the IFI group and the control group to determine the optimal diagnostic cutoff values for diagnosing IFI by using IFS and QFS measurements. RESULTS: In the IFI group, the spaces were smaller than those of the control group at all rotation angles (P < 0.05 for each). When external rotation angles were increased, the IFS and QFS tended to decrease. QFSs were smaller in the case group than the control group at each rotation angle. The receiver operating characteristic areas under the curves of IFS and QFS in a neutral position of 0° were highest. CONCLUSION: Both of the IFS and QFS spaces of IFI patients were found to be smaller than those of control group, regardless of the external hip rotation angles. A neutral position of 0° was deemed the best position for diagnosing IFI. The diagnostic cutoff values of IFS and QFS were 2.44cm and 1.34cm in the neutral position, respectively.

The ischiofemoral space of the hip is influenced by the frontal knee alignment.

PURPOSE: The ischiofemoral distance (IFD), defined as the distance between the ischial tuberosity and the lesser trochanter of the femur, is gaining recognition as an extra-articular cause of hip pain. It is unknown whether the IFD is influenced by the frontal knee alignment. The aim of this study was to determine the influence of realignment surgery around the knee on the IFD. It was hypothesized that valgisation osteotomy around the knee is associated with reduction of the IFD. METHODS: A consecutive series of 154 patients undergoing frontal realignment procedures around the knee in 2017 were included in this study. Long-leg standing radiographs were obtained before surgery and postoperatively. The IFD was measured between the ischium and the lesser trochanter at three different levels (proximal, middle and distal margins of the lesser trochanter parallel to the horizontal orientation of the pelvis) on standardized long-leg radiographs with the patient in upright standing position. The knee alignment was determined by measuring the hip knee ankle angle, mechanical lateral distal femur angle and the medial mechanical proximal tibia angle. Linear regression was performed to determine the influence of the change of frontal knee alignment on the IFD. RESULTS: Linear regression showed a direct influence of the overall change in frontal knee alignment on the IFD of the hip, regardless of the site of the osteotomy (ß-0.4, confidence-interval - 0.5 to - 0.3, p < 0.001). Valgisation osteotomy around the knee induced a significant reduction of the ipsilateral IFD (p < 0.001), while varisation osteotomy induced a significant increase (p < 0.001). The amount of ISD change was 0.4 mm per corresponding degree of change in frontal knee alignment. CONCLUSION: These findings are relevant to both the hip and knee surgeons when planning an osteotomy or arthroplasty procedure. Correction of a malalignment of the knee may resolve an ischiofemoral conflict in the hip. The concept deserves inclusion in the diagnostic workup of both the hip and knee joints. LEVEL OF EVIDENCE: IV.

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.

Utility of False Profile View for Screening of Ischiofemoral Impingement.

PURPOSE: Ischiofemoral impingement (IFI)-primarily diagnosed by magnetic resonance imaging (MRI)-is an easily overlooked disease due to its low incidence. The purpose of this study was to evaluate the usefulness of false profile view as a screening test for IFI. MATERIALS AND METHODS: Fifty-eight patients diagnosed with IFI between June 2013 and July 2017 were enrolled in this retrospective study. A control group (n=58) with matching propensity scores (age, gender, and body mass index) were also included. Ischiofemoral space (IFS) was measured as the shortest distance between the lateral cortex of the ischium and the medial cortex of lesser trochanter in weight bearing hip anteroposterior (AP) view and false profile view. MRI was used to measure IFS and quadratus femoris space (QFS). The receiver operating characteristics (ROC), area under the ROC curve (AUC) and cutoff point of the IFS were measured by false profile images, and the correlation between the IFS and QFS was analyzed using the MRI scans. RESULTS: In the false profile view and hip AP view, patients with IFI had significantly decreased IFS (P<0.01). In the false profile view, ROC AUC (0.967) was higher than in the hip AP view (0.841). Cutoff value for differential diagnosis of IFI in the false profile view was 10.3 mm (sensitivity, 88.2%; specificity, 88.4%). IFS correlated with IFS (r=0.744) QFS (0.740) in MRI and IFS (0.621) in hip AP view (P<0.01). CONCLUSION: IFS on false profile view can be used as a screening tool for potential IFI.

Utility of False Profile View for Screening of Ischiofemoral Impingement / 대한고관절학회지

PURPOSE: Ischiofemoral impingement (IFI)-primarily diagnosed by magnetic resonance imaging (MRI)-is an easily overlooked disease due to its low incidence. The purpose of this study was to evaluate the usefulness of false profile view as a screening test for IFI. MATERIALS AND METHODS: Fifty-eight patients diagnosed with IFI between June 2013 and July 2017 were enrolled in this retrospective study. A control group (n=58) with matching propensity scores (age, gender, and body mass index) were also included. Ischiofemoral space (IFS) was measured as the shortest distance between the lateral cortex of the ischium and the medial cortex of lesser trochanter in weight bearing hip anteroposterior (AP) view and false profile view. MRI was used to measure IFS and quadratus femoris space (QFS). The receiver operating characteristics (ROC), area under the ROC curve (AUC) and cutoff point of the IFS were measured by false profile images, and the correlation between the IFS and QFS was analyzed using the MRI scans. RESULTS: In the false profile view and hip AP view, patients with IFI had significantly decreased IFS (P < 0.01). In the false profile view, ROC AUC (0.967) was higher than in the hip AP view (0.841). Cutoff value for differential diagnosis of IFI in the false profile view was 10.3 mm (sensitivity, 88.2%; specificity, 88.4%). IFS correlated with IFS (r=0.744) QFS (0.740) in MRI and IFS (0.621) in hip AP view (P < 0.01). CONCLUSION: IFS on false profile view can be used as a screening tool for potential IFI.

Ischiofemoral impingement: defining the lesser trochanter-ischial space.

PURPOSE: The purpose of this study was to define changes in the ischial-lesser trochanteric space associated with medial and lateral hip rotation in neutral and 10° of extension and adduction. METHODS: Twenty-five hip joints from 14 embalmed cadavers (7 males and 7 females) were used for this study. The pelvic region of each cadaver was skeletonized, and the hip capsule released distally. With the hip joint in 0° flexion-extension/abduction-adduction, the distance between the lesser trochanter and ischium was measured in: neutral rotation, 40° medial rotation, and 60° lateral rotation. A one-way ANOVA with post hoc analysis determined the difference in the ischiofemoral space in these three positions. An additional position was then tested by laterally rotating the femur with the hip joint positioned in 10° extension and adduction. RESULTS: The average distance between the lesser trochanter and ischium was different (p < .0005) in neutral rotation, 40° medial rotation, and 60° lateral rotation at 2.8 cm (SD 1.1), 4.3 cm (SD 1.2), and 1.4 cm (SD 0.7), respectively. With the hip joint laterally rotated from a starting position of 10° extension and adduction, 21 of 25 (84 %) hips made contact between the lesser trochanter and ischium at an average position of 29° (SD 20) of lateral rotation. CONCLUSIONS: The lesser trochanter is closest to the ischium in lateral rotation and is furthest away in medial rotation when the hip is in neutral flexion-extension/abduction-adduction. The lesser trochanter approximates the ischium when the hip is laterally rotated in 10° extension and adduction. The information gained through this investigation helps to define the pathomechanics associated with ischiofemoral impingement and validate clinical tests to diagnose ischiofemoral impingement.

Variability of ischiofemoral space dimensions with changes in hip flexion: an MRI study.

OBJECTIVE: The primary aim of this study was to determine if ischiofemoral space (IFS) dimensions vary with changes in hip flexion as a result of placing a bolster behind the knees during magnetic resonance imaging (MRI). A secondary aim was to determine if IFS dimensions vary between supine and prone hip neutral positions. DESIGN: The study employed a prospective design. SETTING: Sports medicine center within a tertiary care institution. PARTICIPANTS: Five male and five female adult subjects (age mean = 29.2, range = 23-35; body mass index [BMI] mean = 23.5, range = 19.5-26.6) were recruited to participate in the study. METHODS: An axial, T1-weighted MRI sequence of the pelvis was obtained of each subject in a supine position with their hips in neutral and flexed positions, and in a prone position with their hips in neutral position. Supine hip flexion was induced by placing a standard, 9-cm-diameter MRI knee bolster under the subject's knees. The order of image acquisition (supine hip neutral, supine hip flexed, prone hip neutral) was randomized. The IFS dimensions were then measured on a separate workstation. The investigator performing the IFS measurements was blinded to the subject position for each image. MAIN OUTCOME MEASUREMENTS: The main outcome measurements were the IFS dimensions acquired with MRI. RESULTS: The mean IFS dimensions in the prone position were 28.25 mm (SD 5.91 mm, standard error mean 1.32 mm). In the supine hip neutral position, the IFS dimensions were 25.1 (SD 5.6) mm. The mean difference between the two positions of 3.15 (3.6) mm was statistically significant (95 % CI of the difference = 1.4 to 4.8 mm, t19 = 3.911, p = .001). The mean IFS dimensions in the hip flexed position were 36.9 (SD 5.7) mm. The mean difference between the two supine positions of 11.8 (4.1) mm was statistically significant (95 % CI of the difference = 9.9 to 13.7 mm, t19 = 12.716, p < .001). CONCLUSIONS: Our findings demonstrate that the IFS measurements obtained with MRI are dependent upon patient positioning with respect to hip flexion and supine versus prone positions. This finding has implications when evaluating for ischiofemoral impingement, an entity resulting in hip and/or buttock pain secondary to impingement of the quadratus femoris muscle within a pathologically narrowed IFS. One will need to account for patient hip flexion and supine versus prone positioning when evaluating individuals with suspected ischiofemoral impingement.

Ischiofemoral Impingement in Children: Imaging With Clinical Correlation.

OBJECTIVE: The purpose of this study is to correlate the MRI finding of quadratus femoris edema in children with established measures of ischiofemoral impingement in adults and to determine their clinical significance. MATERIALS AND METHODS: A case-control retrospective review was performed of MR images of 12 hips of nine children (mean age, 10 years) that showed abnormal signal intensity in the quadratus femoris muscle. The findings were compared with those for 13 hips in 13 control subjects (mean age, 9.8 years). Two musculoskeletal radiologists independently measured the ischiofemoral space, quadratus femoris space, inclination angle, and hamstring tendon area. Quadratus femoris muscle edema, tears, or fatty replacement were assessed visually. Statistical analysis determined inter- and intraobserver variability and statistical differences between the two subject groups. RESULTS: Subjects with abnormal signal in the quadratus femoris muscle had a statistically significantly narrower ischiofemoral space (mean, 11.5 vs 20.7 mm; p < 0.05) and quadratus femoris space (mean, 7.2 vs 14.3 mm, p < 0.05) compared with control subjects. Inclination angles were statistically significantly larger in affected subjects (145.5° vs 138.7°; p < 0.05). No statistically significant difference was found in hamstring tendon area. Four of 12 patient hips had no symptoms or symptoms unrelated to the abnormality. Inter- and intraobserver variability scores were strong for all continuous variables. CONCLUSION: Ischiofemoral impingement is a cause of hip pain in children and should be considered with the combination of quadratus femoris muscle edema and narrowing of ischiofemoral space and quadratus femoris space. Coxa valga may contribute to narrowing of these parameters and predispose to ischiofemoral impingement. The MRI features of ischiofemoral impingement, however, are nonspecific and may be seen in patients with pain localized to that hip or in patients with symptoms unrelated to the abnormality.