Clinical History: A 53 year-old female complains of progressive pain around the area of the iliac crest with no history of trauma. T2-weighted fat suppression images in the coronal (1a) and axial (1b) planes of the pelvis are provided.
What are the findings? What is your diagnosis?
Proximal Iliotibial Band Syndrome
Strain injuries of the iliotibial band (ITB) at the iliac tubercle enthesis were first discussed as a distinct entity by Sher and others in 2011 1, who coined the term Proximal Iliotibial Band Syndrome. ITB Syndrome relates to a strain injury of the ITB enthesis where the ITB attaches to the iliac tubercle. Abnormalities of the ITB distal to the iliac tubercle, including larger traumatic tears and abnormalities of the ITB at the level of the greater trochanter, are not included in this syndrome. Because this is a newly described syndrome, very little is known about the cause, prevalence, demographics, and optimal treatment.
To better delineate the anatomy of the ITB at the iliac tubercle, Sher and others performed 16 cadaver dissections 1 and Huang and others performed 40 cadaver dissections. 2 The dissections showed that the fascia lata (FL) attaches to the entire extent of the inferior aspect of the iliac crest. In the upper and lateral thigh, the FL receives fibrous contributions from the gluteus maximus and tensor fascia lata (TFL) to form the ITB. At the level of the iliac tubercle, a bony prominence on the lateral aspect of the crest 5 cm posterior to the anterior superior iliac spine, the FL is preferentially thickened and this represents the origin of the ITB. The ITB distally inserts on the Gerdy tubercle along the anterolateral tibia. 1,2
Huang describes the ITB as having three layers: superficial, intermediate, and deep, which coalesce at the level of the greater trochanter. 2 The superficial layer is superficial to the TFL. The intermediate layer originates from the ilium inferior to the TFL origin and is deep to it. More inferiorly, the superficial and intermediate layers fuse with the deep layer that originates from the supraacetabular fossa. The gluteal aponeurotic (GA) fascia arises from the posterior and lateral iliac crest and extends distally covering the gluteus medius muscle and inserts on the ITB and the gluteal tuberosity of the femur. The iliac crest origins of the ITB and GA fascia are a continuous aponeurotic complex.
The prevalence of proximal ITB strain injuries is unknown. Very few reports exist in the literature specific to this injury. It is uncertain if the injury is uncommon or common and seldom imaged. Sher and others reported a prevalence in their practice of 10% in 67 patients undergoing bony pelvic MR. 1 It is possible this high prevalence is due to a selection bias of their patient population and/or their awareness of the entity. The presence of mild signal intensity changes at the proximal ITB enthesis is common and most patients are asymptomatic. (3) The term ITB syndrome is not an imaging diagnosis and should be reserved for those situations where both the imaging and clinical findings support the diagnosis. In our experience at Radsource, proximal ITB syndrome is uncommon. In a retrospective review of our database, only 12 patients were recognized as having clinical and imaging findings consistent with proximal ITB syndrome.
In Sher’s study, patients with ITB Syndrome were divided into athletic and non-athletic groups. 1 Four patients were runners and three were non-athletic. The runners presented with gradual onset of pain centered on the iliac tubercle that worsened with activity for 1-2 months prior to imaging consistent with a chronic overuse injury. The three non-athletes had no history of inciting trauma and two were moderately overweight and these tears may have been degenerative. One patient in their study was treated for hip related disease although the pain was at the iliac crest level. In our experience there were five patients who were runners, one patient with a hang gliding accident and six patients who presented with pain and no trauma.
In the small number of patients with proximal ITB syndrome reported to date, there is a strong female predisposition. This is similar to the strong female predominance with abnormalities of the abductor complex of the hip. 3 Different investigators have discussed gender differences that predispose females to acquired lower extremity abnormalities. 4 5. In the report by Sher and others, all seven patients were female. 1 In our experience at Radsource, eleven of the twelve patients were female. The male patient was a marathon runner. (4a and 4b) The age distribution in Sher’s study was 34-67 years. In our experience the age distribution was 32-62 years (mean 48.5 years). In our experience, the ITB syndrome presented on the left in eight patients and on the right in four patients.
Huang divides abnormalities of the ITB and GA fascia into four categories: overuse injuries, traumatic injuries, degenerative lesions and inflammatory lesions. 2 Overuse injuries, as previously discussed, typically occur in runners and involve the proximal ITB. Traumatic injuries occur with sports, falls or high-energy trauma and can involve the GA fascia, ITB and TFL. The injuries range from sprain injuries to complete tears, are typically larger than overuse injuries and in severe cases can include fractures and muscle herniations through fascial defects. Degenerative tears occur without trauma or occur with minimal exertion and present with pain. This category likely includes the non-athletic patients in Sher’s study 1 and the Radsource cohort. In some patients with degenerative tears, the exact time of onset can be recollected and in some patients the pain immediately follows a “popping” sensation. According to Huang, muscle herniations can occur in chronic degenerative tears of the FL. Inflammatory lesions include patients with greater trochanteric pain syndrome (GTPS) which is primarily caused by trochanteric tendinosis or tendinobursitus. Huang includes these patients because the FL may be secondarily involved but away from the area of the proximal ITB. 2
The differential diagnosis for pain at the anterior aspect of the iliac crest includes osseous abnormalities of the iliac crest such as stress reactions of the anterior superior iliac spine, fractures, impaction injuries and neoplastic lesions. Soft tissue abnormalities that can be confused with ITB syndrome include traumatic ITB injuries distal to the iliac tubercle and symptoms related GTPS.
Conventional radiography does not have the contrast resolution to evaluate the proximal ITB. CT could potentially diagnose larger tears of the proximal ITB but the lack of contrast resolution compared to MR imaging would restrict any reason to use it for this purpose. Bass and others described using sonography to evaluate the TFL. 6 Sonography probably has the ability to also resolve the proximal ITB although no such studies have yet to be published.
MR imaging is likely to have a prominent role in the evaluation of ITB syndrome. MR imaging is an excellent modality for evaluating the musculoskeletal system and it can be expected that MR evaluation of the ITB enthesis would be no exception. The articles from Sher and Huang demonstrate that the findings typical of ITB syndrome are well demonstrated with MR imaging. 1, 2
The scanning protocol with MR imaging should be done with imaging in the coronal and axial planes with proton density and/or T2 weighted images preferably with fat suppression technique. T1 weighted imaging should be performed in at least one imaging plane. The imaging should be done with a field of view that includes only the iliac crest of interest. If the imaging protocol for a hip is used, the proximal ITB will not be optimally visualized and may be partially or completely excluded from the field of view.
MR Imaging findings
With MR imaging, proximal ITB tears present as areas of increased signal intensity on T2 weighted images adjacent to iliac tubercle. In lower grade injuries, the proximal ITB remains intact (5a) and possibly thickened. Surrounding soft tissue edema can involve the adjacent gluteal musculature and fascial planes. Higher grade injuries present with partial or complete interruption of ITB elements. (5b) In Sher’s report there were four partial tears of the ITB substance and three that presented as expansion and edema of the ITB substance. According to Huang and others, overuse injuries tend to be low-grade partial tears confined to the iliac attachment. Marrow edema of the iliac tubercle is a common finding and Huang and others attributed it to enthesopathy from chronic microtrauma. In some patients, enthesophyte formation can occur at the level of the iliac tubercle. (5c and 5d)
Treatment and Prognosis
There are no published treatment protocols for proximal ITB strain injuries. It is likely that most if not all of the proximal ITB abnormalities, whether low or high grade injuries, are treated conservatively. In one patient not included in our series because the ITB tear was diffuse and not preferentially involving the proximal segment, follow-up imaging showed complete healing with conservative treatment. (6a and 6b)
Proximal ITB syndrome is a recently described entity. As defined in the original description, it is a strain injury of the proximal ITB enthesis at the iliac tubercle. The reports to date have been retrospective and little is known about the true incidence. Early results suggest that most patients who are imaged are female, some are runners, some are non-athletic and some have a specific antecedent traumatic event. The appropriate therapy is unknown and is likely conservative in most patients. MR imaging appears to be an excellent modality for diagnosing and evaluating the severity of Proximal ITB Syndrome.
- Sher I, Umans H, Downie SA, Tobin K, Arora R, Olson TR. Proximal iliotibial band syndrome: what is it and where is it? Skeletal radiology. 2011;40(12):1553-6. ↩
- Huang BK, Campos JC, Michael Peschka PG, Pretterklieber ML, Skaf AY, Chung CB, et al. Injury of the gluteal aponeurotic fascia and proximal iliotibial band: anatomy, pathologic conditions, and MR imaging. Radiographics : a review publication of the Radiological Society of North America, Inc. 2013;33(5):1437-52. m ↩
- Kingzett-Taylor A, Tirman PF, Feller J, McGann W, Prieto V, Wischer T, et al. Tendinosis and tears of gluteus medius and minimus muscles as a cause of hip pain: MR imaging findings. AJR American journal of roentgenology. 1999;173(4):1123-6. ↩
- Ferber R, Davis IM, Williams DS, 3rd. Gender differences in lower extremity mechanics during running. Clinical biomechanics. 2003;18(4):350-7. ↩
- Chumanov ES, Wall-Scheffler C, Heiderscheit BC. Gender differences in walking and running on level and inclined surfaces. Clinical biomechanics. 2008;23(10):1260-8. ↩
- Bass CJ, Connell DA. Sonographic findings of tensor fascia lata tendinopathy: another cause of anterior groin pain. Skeletal radiology. 2002;31(3):143-8. ↩