MRI of Quadratus Femoris Muscle Tear: Another Cause of Hip Pain

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1 MRI of Quadratus Femoris Muscle Tear Musculoskeletal Imaging Clinical Observations Seth D. O Brien 1 Liem T. Bui-Mansfield 1,2,3 O Brien SD, Bui-Mansfield LT Keywords: hip pain, MRI, muscle tear, quadratus femoris muscle DOI: /AJR Received April 12, 2007; accepted after revision June 1, The opinions and assertions contained herein are those of the authors and should not be construed as official or as representing the opinions of the Department of the Army or the Department of Defense. 1 Department of Radiology, San Antonio Uniformed Services Health Education Consortium (SAUSHEC), Brooke Army Medical Center, 3851 Roger Brooke Dr., Fort Sam Houston, TX Address correspondence to L. T. Bui-Mansfield (liem.mansfield@gmail.com). 2 Department of Radiology, Wake Forest University, Winston-Salem, NC Department of Radiology, Uniformed Services University of the Health Sciences, Bethesda, MD AJR 2007; 189: X/07/ American Roentgen Ray Society MRI of Quadratus Femoris Muscle Tear: Another Cause of Hip Pain OBJECTIVE. The objective of this study is to report the MR appearance of quadratus femoris muscle tear, another cause of hip pain. We will review the pertinent anatomy of the quadratus femoris muscle, summarize the current literature on quadratus femoris muscle tear, and report our experience in the diagnosis of quadratus femoris muscle tear on MRI. CONCLUSION. MRI is an important tool in assisting clinicians to make a correct diagnosis for the patient who presents with hip pain. Although quadratus femoris muscle tear is an uncommon injury, radiologists should be aware of this entity to assist with making a diagnosis that is usually unsuspected clinically. uadratus femoris tears are uncommon injuries that usually cause Q hip pain, but the true incidence is unknown. The injury may be acute or chronic and can have concomitant posterior gluteal pain or groin pain or both, which makes accurate diagnosis difficult. Another challenge in the evaluation of hip pain is the complex anatomy of the hip joint. In addition, the differential diagnosis of hip pain is broad and includes a multitude of abnormalities, many of which are either unsuspected or difficult to diagnose without advanced imaging. MRI with its superior soft-tissue resolution and multiplanar capability provides excellent visualization and characterization of a wide range of abnormalities. Therefore, MRI is an excellent adjunct to physical examination because it shows the anatomic location of the abnormality, aiding the clinician to make unsuspected diagnoses. MRI allows accurate diagnosis, which may influence treatment. Materials and Methods Three consecutive cases of quadratus femoris tears were diagnosed by one or another of two fellowship-trained musculoskeletal radiologists in routine clinical practice using standard protocol hip MRI. A fourth case with the initial diagnosis of an obturator externus muscle tear was retrospectively reevaluated after the detection of a series of cases of quadratus femoris tears and found to be a quadratus femoris muscle partial tear by both reviewers in consensus. The subjects were seen in our department from September 2006 to March Images were obtained on a Picker Eclipse 1.5-T scanner (Philips Medical Systems) with a standard receive-only coil, supplied by the manufacturer, using our standard departmental protocol. MR sequences included coronal T1 fast spin-echo (TRrange/TE, /17) and STIR sequence (TR/TE, 4,911/11) of the pelvis followed by axial T2 fast spin-echo with fat-suppression (3,000/96); coronal T2 fast spin-echo with fat suppression (3,000/96); and sagittal proton density with fat-suppression (2,000/15) sequences of the painful hip. Coronal T1 fast spin-echo and STIR images of the pelvis were obtained with a standard thickness of 5 mm and a matrix size of The remaining sequences of the painful hip had a slice thickness of 4 mm with a matrix size of In one patient, gadolinium-enhanced axial T1 (681/12) fat-suppressed imaging was added to the standard protocol because of concern for a possible mass. Standard hip radiographs were obtained in all patients before MRI in accordance with departmental protocol. All images were retrospectively reviewed by both musculoskeletal radiologists for any associated abnormality. All the clinical records were reviewed for demographic data, symptom, duration of symptom, activity or mechanism of injury, and presumed clinical diagnosis. The study did not require approval from the institution investigation review board. However, the Brooke Army Medical Center department of clinical investigation reviewed and approved the manuscript for publication. A literature search was conducted on the MED- LINE database using PubMed. A total of three articles were found; all were case reports, and none was in the radiology literature [1 3]. AJR:189, November

2 TABLE 1: Summary of Findings in Patients with Quadratus Femoris Muscle Tear Patient Age (y) Sex Side Symptom Duration Activity 1 43 F Left Upper posterior thigh pain Results Table 1 summarizes the clinical and imaging findings in patients with quadratus femoris muscle tear. Patients 1 4 are from the authors experience. Patients 5 7 are collected from the literature. In the authors series, all patients were women. The age range was years. Three of the patients injuries were judged to be chronic, with symptoms present for months. The remaining patient had an acute presentation to the emergency department after orienteering activity. A week later, an MR examination was performed to exclude a stress fracture. The respective clinical diagnoses were sciatica, stress fracture, and snapping hip syndrome. Unspecified months Clinical Diagnosis Review of the radiographs in all cases did not show any radiographic abnormalities of the painful hip. Patient 2 had a healed stress fracture of the contralateral femoral neck. The most common (4/5, 80%) finding in the authors series was edema or hemorrhage at the musculotendinous junction of the quadratus femoris seen easily on axial images, located between the lesser and ischial tuberosity (Figs. 1A and 2A), but present on all three planes. In the second case, there was complete rupture of the quadratus femoris tendon from its insertion, causing the tendon to be retracted medially (Fig. 3A). This patient also had hemorrhage adjacent to Muscle Injury Grade Location of Injury Associated Findings Unknown Sciatica II Musculotendinous None 2 37 F Right Hip pain 3 d Orienteering Stress fracture III Tendon attachment Partial tear of gluteus medius and hamstring tendons 3 35 F Right Hip pain 5 mo Fall on crutch Snapping hip syndrome 4 18 F Left and right Hip pain Unspecified months Unknown Snapping hip syndrome II Musculotendinous Mild right greater bursitis II Musculotendinous None 5 27 F Right Deep gluteal pain 1 d Badminton Hamstring injury II Musculotendinous None 6 30 F Right Groin pain 6 wk Lifting box Adductor tendinitis II Musculotendinous None 7 17 M Left Proximal posterior thigh pain 5 d Tennis Hamstring strain II Musculotendinous None Note Patients 1 4 are from the authors experience; patients 5 7 are from the literature [1 3]. Muscle injury grade I = muscle strain, II = partial tear, and III = complete tear. Fig year-old woman with partial tear of quadratus femoris muscle. A, Axial T2-weighted fat-suppressed image shows edema and small focal fluid hemorrhage within muscle belly of left quadratus femoris muscle located between ischial tuberosity (i) and lesser (t). B, Sagittal proton density fat-suppressed image shows edema within muscle belly of quadratus femoris muscle posterior to lesser (t). C, Coronal T2-weighted fat-suppressed image shows edema and small focal fluid hemorrhage within muscle belly of left quadratus femoris muscle lateral to ischium (i). the site of injury and associated partial tear of the gluteus medius and hamstring tendons. One patient had bilateral quadratus femoris muscle tears. Therefore, there were a total of five cases of quadratus femoris muscle tears. In our experience, the sagittal proton density fat-suppressed images were helpful in confirming the diagnosis of quadratus femoris injury because they showed a characteristic comma-shaped appearance of abnormal edema at the musculotendinous junction within the quadratus femoris located posterior to the lesser. An identical appearance was seen in both cases of partial tears (Figs. 1B and 2B). Diffuse abnormality was 1186 AJR:189, November 2007

3 MRI of Quadratus Femoris Muscle Tear also present in this region in the case of avulsion of the quadratus femoris tendon (Fig. 3B). Fig year-old woman with partial tear of quadratus femoris muscle. A, Axial T2-weighted fat-suppressed image shows edema within right quadratus femoris muscle (arrow) at musculotendinous junction consistent with partial tear located posterior to lesser (t). B, Sagittal proton density fat-suppressed image of right hip shows edema within quadratus femoris muscle posterior to lesser (t). C, Coronal T2-weighted fat-suppressed image of right hip shows edema within right quadratus femoris muscle (arrow) just lateral to ischium (i). Fig year-old woman with complete rupture of quadratus femoris tendon. A, Axial T2-weighted fat-suppressed image reveals disruption and proximal retraction of right quadratus femoris muscle fibers between lesser (t) and ischial tuberosity (i). Note additional finding of partial tear of hamstring at its attachment on ischial tuberosity. B, Sagittal proton density fat-suppressed image reveals disrupted muscle fibers with edema and hemorrhage within quadratus femoris muscle located posterior to lesser (t). C, Coronal T2-weighted fat-suppressed image of entire pelvis reveals hemorrhage and edema with disruption of fibers of right quadratus femoris muscle just lateral to ischium (i). Discussion The quadratus femoris muscle is a flat, quadrilateral muscle that arises from the upper external border of the ischial tuberosity and inserts on the linea quadrata or quadrate tubercle of the femur [4]. The linea quadrata is a slight area of vertically oriented thickening usually arising from the middle of the interic crest on the posterior aspect of the femur [4] (Fig. 4A). The quadratus femoris muscle acts as a hip external rotator and assists with adduction. Injury to the quadratus femoris has been described as a cause of groin pain and gluteal pain that can radiate distally from the posterior thigh, presumably by irritation of the sciatic nerve either from hematoma or edema [1, 2]. In this regard, quadratus femoris injury is similar on clinical grounds to a hamstring injury, which presents with similar pain and tenderness to palpation on the ischial tuberosity [1]. In correlating the anatomy with imaging, there are at least two considerations. Because of the muscle s orientation in the coronal plane (Fig. 4B), the abnormal signal may be difficult to visualize on routine coronal images, particularly if the field of view is large and the injury is mild. In addition, because of its posterior position, the muscle may only be partially included in the field of view on coronal imaging, AJR:189, November

4 Lesser Head Neck Fig. 4 Pertinent anatomy of hip joint. A, Posterior view of proximal femur shows locations of insertion of obturator externus and quadratus femoris tendons. B, Posterior coronal view of proximal femur shows sites of insertion of posterior hip muscles. C, Sagittal view shows hip joint and surrounding muscles and tendons. Trochanteric fossa Interic crest Insertion of obturator externus Greater Insertion of quadratus femoris Ilium Anterior inferior iliac spine Femur, neck increasing the diagnostic difficulty. In our patient series, although all injuries were visualized in the coronal plane with a small field of view, they were considered to be more conspicuous in the axial and sagittal planes. Familiarity with the complex anatomy of the hip joint and this specific injury also aids in the diagnosis. One of the cases presented was initially mistaken for a partial tear of the obturator externus muscle by an experienced radiologist. Based on their close proximity, the misdiagnosis is easily understood. The obturator externus muscle is inserted in the ic fossa, which is located medial to the posterior aspect of the greater (Fig. 4B). Therefore, on T2-weighted MR images, a tear of the obturator externus muscle should show edema medial to the greater in the posterior thigh. In contrast, a tear of the quadratus femoris muscle has edema posterior to the lesser on the sagittal plane (Fig. 4C). A Gluteus maximus Adductor magnus Semitendinosus Piriformis Gluteus medius Gluteus minimus Gemellus superior Obturator internus Gemellus inferior Biceps femoris Quadratus femoris Gluteus medius Greater Obturator externus Gluteus maximus Vastus lateralis Gluteus medius m. Gluteus maximus m. The incidence of injury to the quadratus femoris muscle is unknown because there are only three case reports in the medical literature to our knowledge. In addition, one of the confounding issues is the difficulty in making the correct clinical diagnosis based on the history and physical examination [1 3]. In all previous case reports, the correct diagnosis was made on MRI. A 5-year study of European soccer players does shed some light on the relative incidence of lower extremity muscle strains. In this highly active population, lower extremity muscle strains accounted for 30% of all injuries [5]. Of the muscle strains diagnosed, the quadriceps (32%) was the most common, followed by hamstring (28%), adductor (19%), and gastrocnemius (12%) [5]. Quadratus femoris strains were not diagnosed in this active population, which may be secondary to the rarity of the injury or the difficulty in making the diagnosis or a combination of both [5]. B Piriformis t. Gemellus superior t. Obturator internus t. Gemellus inferior m. Obturator externus t. Femur, lesser Quadratus femoris m. Adductor magnus m. C Quadratus femoris muscle tears occur predominantly in women; the female-tomale ratio is 6:1. They affect the right side almost twice as often as the left. The majority (83%) of the tears were isolated grade II injuries. The case reports describe different activities that patients were participating in during the time of injury including badminton, lifting, and tennis [1 3]. Including our cases of quadratus femoris muscle tear, there was no common activity accounting for the tear. In one, the authors theorized that the quadratus femoris muscle strongly eccentrically fired as it tried to control internal hip rotation during the follow-through phase of tennis serving [3]. This explanation is in keeping with current concepts regarding musculotendinous injuries that suggest that muscular noncontact injuries are the result of eccentric exercise [6]. However, the authors could not explain why no other deep hip external rotator was involved [3]. The published case reports on the subject suggest that the diagnosis can be difficult to make clinically and that MRI was critical in making the diagnosis [1 3]. In one of the case reports, the initial diagnosis was a hamstring injury. This mistake can be easily understood because of the common attachment on the ischial tuberosity [1]. Of the three case reports, one was reported as a chronic injury, possibly incited by previous tendinitis after picking up a box from the ground, a combined movement of hip extension and adduction [2]. In none of the cases was a quadratus femoris tear suspected clinically [1 3]. Different treatment techniques were used for the patients including a Depo- Medrol injection (methylprednisolone acetate, Pfizer) [2], transcutaneous neurostimulation and sonography [1], and proper stretching exercise technique [3], which were reported as effective because all patients were able to return to full activities. Our case series, the largest in the medical literature to our knowledge, provides additional information on the characteristic MR appearance of quadratus femoris muscle injuries. In addition, one patient had associated injuries involving the gluteus medius and hamstring muscles, presumably from the same mechanism of injury. The rarity of this diagnosis in the imaging literature may be due to mistaken diagnosis (one of our cases was initially diagnosed as obturator externus muscle tear), subtleness of the imaging findings, and lack of knowledge by the interpreting radiologist AJR:189, November 2007

5 MRI of Quadratus Femoris Muscle Tear In conclusion, MRI remains an important tool in assisting clinicians to make a correct diagnosis for the myriad causes of hip pain. Although quadratus femoris muscle tear is an uncommon injury, radiologists should be aware of this entity to assist with making a diagnosis that is usually unsuspected clinically. Quadratus femoris tears have characteristic findings on MRI. On axial T2-weighted fat-suppressed images, edema is seen between the lesser and ischial tuberosity. On sagittal T2-weighted or proton density fat-suppressed images, edema is seen posterior to the lesser. FOR YOUR INFORMATION Acknowledgments We thank Michael C. Vernon and Robert Rios from the department of medical illustration of Brooke Army Medical Center for their beautiful illustrations. References 1. Peltola K, Heinonen OJ, Orava S, Mattila K. Quadratus femoris muscle tear: an uncommon cause for radiating gluteal pain. Clin J Sport Med 1999; 9: Klinkert P Jr, Porte RJ, de Rooij TP, de Vries AC. Quadratus femoris tendinitis as a cause of groin pain. Br J Sports Med 1997; 31: Willick SE, Lazarus M, Press JM. Quadratus femoris muscle strain. Clin J Sport Med 2002; 12: Gray H. Anatomy of the human body, 30th ed. Philadelphia, PA: Lea & Febiger, 1985: Volpi P, Melegati G, Tornese D, et al. Muscle strains in soccer: a five-year survey of an Italian major league team. Knee Surg Sports Traumatol Arthrosc 2004; 12: Garrett WE. Muscle strain injuries. Am J Sports Med 1996; 24[6 suppl]:s2 S8 The comprehensive book based on the ARRS 2007 annual meeting categorical course on Neuroradiology is now available! For more information or to purchase a copy, see AJR:189, November