Radiologic findings in femoroacetabular impingement: a pictorial review

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1 Radiologic findings in femoroacetabular impingement: a pictorial review Poster No.: P-0035 Congress: ESSR 2015 Type: Educational Poster Authors: J.-H. Opsahl, A. P. Parkar ; Drammen/NO, Bergen/NO Keywords: Musculoskeletal joint, MR, CT, Conventional radiography, Diagnostic procedure, Normal variants, Image verification, Athletic injuries DOI: /essr2015/P Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 30

2 Learning objectives After reading this poster the viewer will: Understand the underlying anatomic configuration of the femur and acetabulum Understand how anatomy affects function and causes restricted range of motion in the hip joint. Be able to identify and evaluate radiologic findings associated with femoroacetabular impingement (FAI). Background Hip pain in young adults is a relatively common and difficult diagnostic challenge. Several differentials are possible: adductor tendinopathy, pubic stress fractures, osteoid osteoma, athlethic pubalgia and ischiofemoral or femoroacetabular impingement (1). In the last two decades, research has provided a better understanding of the different pathologicanatomic disease mechanisms and thus, more precise diagnostics. Detection of subtle bony and soft tissue changes in young active people with hip pain has gained recognition as a contributing factor for premature osteoarthritis (2-5). In patients with symptoms, early intervention may help prevent joint degeneration in predisposed individuals (6). The concept of femoroacetabular impingement (FAI) is a relatively new entity which has changed our view on the aetiology of hip osteoarthritis and the population groups affected. As early as 1963 and 1975 a correlation between abnormal hip morphology and subsequent osteoarthritis was described (7,8). Even so, it was not until the 1990's the concept of FAI as we know it today developed through several studies on different hip morphology types, imaging techniques, treatment and follow up (2,9). FAI in itself is not a disease, but rather a spectrum of anatomic-morphologic changes which in turn can predispose to labral and articular pathology. Bone deformity or angular malorientation of the femoral head-neck junction or acetabulum leads to reduction of the range of motion. Recurrent abutment between the acetabular rim and the proximal femur causes subsequent damage to the soft tissue structures inbetween; the labrum and adjoining articular cartilage. Patients typically experience restricted range of motion and pain in flexion, adduction and internal rotation, and for some patients, cessation of activities with extreme range of motion can be sufficient to achieve complete symptom relief (10,11). Page 2 of 30

3 Two major forms of FAI are distinguished: The cam type is an aspherical femoral headneck junction with reduced anterosuperior or lateral femoral head-neck offset (Fig 1). The pincer variant is focal or general acetabular overcoverage of the femoral head (Fig 2). Both configurations lead to repetetive contact between the labrum and acetabular edge with concurrent degenerative changes. Most patients have a combination of both forms - referred to as "mixed type impingement" (12,13). Furthermore, some individuals can present with early degenerative change due to supraphysiologic range of motion without morphologic abnormality. Thus the FAI-concept includes both static and dynamic considerations, which the clinician must consider when designing treatment and intervention plans (6,11). With recognition and the ability to early detection of FAI, both conservative and surgical measures has shown promise in relieving hip pain and possibly preventing premature osteoarthritis in young adults (14-17). Images for this section: Page 3 of 30

4 Fig. 1: Fig. 1: Cam-type. Osseous bump at the femoral head-neck interface. Page 4 of 30

5 Fig. 2: Fig. 2: Deep acetabular fossa (coxa profunda) with overcoverage of the femoral head, both by the ileal (red arrow) and ischial (white arrow) part of the acetabulum. Page 5 of 30

6 Imaging findings OR Procedure Details Clinical findings Patients most often present with gradually increasing hip or groin pain, with reduced range of motion in flexion, adduction and internal rotation. The pain is classically described as deep, diffuse groin pain, which is provoked by both active and passive flexion acivities. Clinical tests are generally unspecific with a resulting broad spectrum of differential diagnosis, including tendinopathies, stress fractures, athletic pubalgia, osteitis pubis and ischiofemoral impingement (2,18,19). Imaging The primary investigation is conventional x-rays. A standard anteroposterior (AP) projection of the pelvis and a cross-table lateral view of the affected hip allows for evaluation of bony abnormalities associated with impingement. It is also useful for excluding of some other pathologies, such as rheumatoid arthritis and avascular necrosis. Correct angulation and patient positioning is essential for diagnostic quality (3,5). The AP-projection will detect different pincer configurations, including Wibergs centreedge angle and acetabular retroversion, as well as a lateral cam deformity (also called "pistol grip-deformity"). (Fig. 3,4). A cross-table lateral view is useful for measuring the #-angle and anterior/anterosuperior offset. (Fig. 5). Alternatively, one can supplement with a Dunn/modified Dunn projection with 90 /45 hip flexion and 20 hip abduction (Fig. 6,7). The modified Dunn view has shown the highest sensitivity in detecting anterosuperior cam deformity (3,5,6) MRI or MR-arthrography are considered to be the best modalities for evaluating labral and chondral changes, and detect other intraarticular pathology (20-23). Cartilage specific sequences, such as three-dimensional spoiled gradient-echo (3D SPGR), are still mostly used in research, as they have the disadvantage of long imaging times and the limited ability to evaluate other relevant structures. New MR cartilage mapping techniques (dgemric, T2-mapping, T1 rho, sodium imaging and diffusion tensor imaging) shows promise in assessing biochemical and structural cartilage integrity, allowing for even earlier detection of degenerative change (6,24). Cam impingement Page 6 of 30

7 Cam configuration put easy is "too much femur". Bone protrusion at the femoral headneck junction results in an aspheric femoral head, and reduces the difference in radius between the head and neck. The reduction can be more prominent anterosuperiorly or laterally ("pistol grip-deformity"). The relatively broad femoral neck will compress the labrum and adjacent articular cartilage at an early stage in the normal range of motion. Repetetive microtrauma causes separation at the labrum-cartilage interphase and medial compression of cartilage near the acetabular rim (Fig. 8). The cartilage layer can separate from the bone surface in a waveform; a so-called "chondral flap-tear" (Fig. 9-12). Rupture and degenerative change of the labrum is found to be less common than separation at the transition-zone and cartilage damage. Angular deformities of the femoral neck such as coxa vara and femoral retrotorsion will also predisopse for cam-type impingement (11,25). Cam impingement is most often seen in young, active males between 20 and 40 years of age. Suggested possible causes for cam impingement are: idiopathic, developmental angular anomalies (coxa vara, femoral retrotorsion), posttraumatic (femoral neck fractures), child diseases (Perthes disease, slipped capital femoral epiphysis) and iatrogenic angular abnormality after femoral osteotomy (4,5,11,25). Pincer impingement The pincer variants put easy is "too much acetabulum", resulting in a general or focal overcoverage of the femoral head-neck junction. The repeated contact between these two in the end-spectrum of range of motion causes labral degeneration and, later on, ossification of the acetabular rim. In contrast to cam impingement, chondral damage is less pronounced, often confined to a thin, circumferentially distribuated perilabral strip. (Fig ). Early anterosuperior contact due to overcoverage can also cause subluxation of the femoral head, resulting in excessive compression and a "contre-coup lesion", with cartilage damage in the posteroinferior aspect of the acetabulum. Pincer impingement is most frequently seen in middle-aged active women in their 40s and 50s. Acetabular retroversion, coxa profunda, protrusio acetabuli and a protruding os acetabuli are all recognized predisposing factors (4,5,11,25). Essential radiographic measurements and signs Cam type Coxa vara: The angle between the femoral neck and diaphysis <120 is called coxa vara. The normal range is An angle >140 is called coxa valga. Page 7 of 30

8 Pistol grip deformity: reduced lateral femoral head-neck offset, seen on APradiographs (Fig 3). #-angle: This is the angle between the femoral neck axis and a line from the femoral head center to the point where asphericity of the head-neck contour begins. An angle >50-55 is considered abnormal, with some conflict in the literature regarding the best cut-off value (Fig. 16). Anterior offset is defined as the difference in radius between the anterior femoral head and neck on a cross-table axial view, with a suggested normal value of > 8 mm (Fig 17). The offset ratio is the ratio between the anterior offset and the diameter of the head. Corresponding to a normal offset value of > 8 mm, a normal offset ratio should be > Femoral retroversion: Femoral version is defined as the angular difference between axis of femoral neck and transcondylar axis of the knee, with a normal range between 8 and 14 in adults. Angles > 8 represents femoral retroversion. Pincer type Coxa profunda/protrusio acetabuli: Deep acetabular socket, best avaluated on AP radiographs. In coxa profunda, the floor of the fossa acetabuli is seen touching or overlapping the ilioischial line (Fig. 18). In protrusio acetabuli, the medial border of the femoral head reaches or overlaps the ilioischial line (Fig. 19,20). Acetabular retroversion: the cranial part of the anterior acetabular rim crosses over and lies lateral to the posterior wall on AP radiographs of the hip, the so-called "cross over sign" or "figure eight sign" (Fig. 21). Lateral center edge angle (of Wiberg): The angle between a vertical line and a line connecting the femoral head center with the lateral edge of the acetabulum. Normal values are between 25 and 39. An angle < 25 defines dysplasia, and values above 39 indicates acetabular overcoverage (Fig. 21,22). Acetabular index (acetabular roof angle): the angle between a horizontal line and a line connecting the medial point of the sclerotic zone with the lateral center of the acetabulum. In hips with coxa profunda og protrusio acetabuli, the acetabular index is 0 or negative. Posterior wall sign: Normally, the outline of the posterior acetabular rim runs approximately through the femoral head center. In a prominent posterior wall, this line will project laterally to this center. On the other hand, a deficient posterior wall will be seen projected medially. Secondary signs such as herniation pits, labral ossification and os acetabuli can also be helpful indicators. Treatment options Page 8 of 30

9 Conservative measures consists of activity modification, anti-inflammatory medication, strengthening of stabilizing musculature (especially abductors), and hip-motion exercises. It is of the essence that physical therapy and training programs are individualized according to the patients athletic demands, motion restriction and stability/ strength deficits. Training programmes should also be designed to improve core strength, postural and neuromuscular control, as stability of the lumbar spine and pelvis is essential in avoiding impingement in terminal motion. Even so, there is at present no convincing evidence of conservative measures causing functional improvement or slowing of osteoarthrosis development in patients with symptomatic FAI (6,11,26). Operative treatment can be performed with an arthroscopic or open approach with hip dislocation. Surgical debridement and repair of the damaged labrum, chondroplasty, shaving of the acetabular edge, capsulotomy and femoral osteocohdroplasty seek to correct anatomic and morphologic abnormalities and possibly prevent or slow the ongoing osteoarthrosis development. There is still conflicting evidence as to which approach producing the best long-time results, and the best timing of preservative surgery. However, studies showing preoperative osteoarthrosis correlating negatively with postoperative results give support to early intervention (5,6,11,26,27) Images for this section: Page 9 of 30

10 Fig. 3: Bilateral "pistol grip-deformity" with reduced lateral femoral head-neck offset. Page 10 of 30

11 Fig. 4: Frog leg view of a left hip shows an osseous bump (white arrow), typical of cam type FAI. Page 11 of 30

12 Fig. 5: Positioning for cross-table lateral view Page 12 of 30

13 Fig. 6: Dunn view positioning. Page 13 of 30

14 Fig. 7: Dunn view with nice exposure of the anterosuperior aspect of the femoral headneck, also demonstrating a degenerative herniation pit (white arrow). Page 14 of 30

15 Fig. 8: Coronal STIR-sequence. Cam-type with separation at the labrum-cartilage interphase (white arrow) and adjacent irregular chondral surface. Page 15 of 30

16 Fig. 9: Coronal MR-arthrogram (PD SPIR, 3 Tesla magnet): Cam-type impingement with extensive labral degeneration (white arrow), and adjacent chondral delamination (red arrow). (Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaall/NO) Page 16 of 30

17 Fig. 10: Same patient as in fig. 9 - more anterior view. (Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaal/NO) Page 17 of 30

18 Fig. 11: Same patient as fig. 9. Sagittal PD-sequence demonstrating delamination and chondral degeneration. (Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaal/ NO) Page 18 of 30

19 Fig. 12: Same patient as in fig. 9. Sagittal PD SPAIR-sequence. (Picture courtesy of Dr. Anvar, Oslo University Hospital). Page 19 of 30

20 Fig. 13: Coronal STIR-sequence. Pincer type with acetabular overcoverage, degenerative cyst in the acetabular roof (white arrow), and adjacent irregular chondral surface. Page 20 of 30

21 Fig. 14: Sagittal MR arthrogram. Anterosuperior labral rupture (blue arrow) in a patient with pincer type impingement. Page 21 of 30

22 Fig. 15: Same patient with pincer type-impingement. Coronal MRA shows chondral damage at both femoral head and acetabular surfaces in the anterosuperior location. Page 22 of 30

23 Fig. 16: Lateral view with #-angle measurement. Page 23 of 30

24 Fig. 17: Lateral view. Anterior offset. Page 24 of 30

25 Fig. 18: Coxa profunda. The floor of the fossa acetabuli overlaps the ilioischial line. Page 25 of 30

(Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaal/NO). Fig.

26 Fig. 19: Protrusio acetabuli. The medial border of the femoral head reaching the ilioischial line. (Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaal/NO). Fig. 20: Same patient as in fig 19. Axial CT-image demonstrating deep acetabular fossa bilaterally. (Picture courtesy of Dr. Anvar, Oslo University Hospital, Ullevaal/NO) Page 26 of 30

27 Fig. 21: Mixed type. Pistol grip-deformity. A lateral center edge angle of 46 in the left hip. Cross-over sign: the anterior acetabular rim (white arrow) crosses the posterior rim (red arrow) in the cranial aspect of the hip. Page 27 of 30

28 Fig. 22: Lateral center edge angle of Wiberg. Borderline measurement of 38. Page 28 of 30

29 Conclusion Femoroacetabular impingement is commonly seen in young adults. Recognition of the typical imaging signs and findings is important for the correct follow-up of symptomatic patients. References Adkins III SB, Figler RA. Hip pain in athletes. Am Fam Physician Apr 1; 61: Ganz R et al. Femoroacetabular impingement: a cause for osteoarthritis of the hip. Clin Orthop Relat Res 2003; 417: 1-9. Tanzer M, Noiseux N. Osseous abnormalities and early osteoarthritis. Clin Orthop Relat Res 2004; 429: Tannast T, Siebenrock KA, Anderson SE. Femoroacetabular impingement: Radiographic diagnosis - what the radiologist should know. AJR 2007; 188: Leunig M, Beaulé PE, Ganz R. The concept of femoroacetabular impingement. Current status and future perspectives. Clin Orthop Relat Res 2009; 467: Sangal RB, Waryasz GR, Schiller JR. Femoroacetabular impingement: A review of current concepts. Rhode Island Medical Journal 2014; 97: Herndon CH, Heymann CH, Bell DM. Treatment of slipped capital femoral epiphysis by epiphysiodesis and osteoplasty of the femoral neck. J Bone Joint Surg Am. 1963; 45: Stulberg SD et al. Unrecognized childhood hip disease: a major cause of idiopathic osteoarthrosis of the hip. Presentation at: The hip: Proceedings of the third open scientific meeting of the hip society, Ganz R et al. Cervico-acetabular impingement after femoroacetabular impingement (german text). Unfallchirurg. 1991; 94: Ito K, Leunig M, Ganz R. Histopathologic features of the acetabular labrum in femoroacetabular impingement. Clin Orthop Relat Res 2004; 429: Bedi A, Kelly BT. Current concepts review. Femoroacetabular impingement. J Bone Joint Surg Am. 2013; 95: Beck M et al. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br 2005; 87: Ganz R et al. The etiology of osteoarthritis of the hip: an integrated mechanical concept. Clin Orthop Relat Res. 2008;466: Peters CL et al. Hip-preserving surgery: understanding complex pathomorphology. J Bone Joint Surg Am. 2009; 91: Page 29 of 30

30 15. Bedi A, Chen N, Robertson W, Kelly BT. The management of labral tears and femoroacetabular impingement of the hip in the young, active patient. Arthroscopy 2008; 24: Clohisy JC, St John LC, Schutz AL. Surgical treatment of femoroacetabular impingement: a systematic review of the literature. Clin Orthop Relat Res 2010; 468: Ng VY et al. Efficacyof surgery for femoroacetabular impingement: a systematic review. Am J Sports Med. 2010; 38: Bedi A et al. Static and dynamic mechanical causes of hip pain. Arthroscopy. 2011; 27: Burnett RS et al. Clinical presentation of patients with tears of the acetabular labrum. J Bone Joint Surg Am. 2006; 88: Beaule PE, Zaragoza E, Copelan N. Magnetic resonance imaging with gadolinium arthrography to assess acetabular cartilage delamination. A report of four cases. J Bone Joint Surgery Am. 2004; 86: Kassarjian A et al. Triad of MR arthrographic findings in patients with camtype femoroacetabular impingement. Radiology. 2005; 236: Pfirrmann CW et al. Cam and pincer femoroacetabular impingement: characteristic MR arthrographic findings in 50 patients. Radiology. 2006; 240: Thomas JD et al. Imaging of the acetabular labrum. Semin Musculoskelet Radiol. 2013; 17: Zilkens C et al. Magnetic resonance imaging of hip joint cartilage and labrum. Orthopedic Reviews. 2011; volume 3:e Beck M et al. Hip morpholgy influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br. 2005; 87: Byrd JW. Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 2014; 42: Zingg PO et al. Surgical hip dislocation versus hip arthroscopy for femoroacetabular impingement: clinical and morphological short-term results. Arch Orthop Trauma Surg. 2013; 133: Opsahl Fysiomed Normal 0 21 false false false NO-BOK JA X-NONE Personal Information Page 30 of 30

The condition occurs when the proximal femur repeatedly comes into contact with the native acetabular rim during normal hip range of motion.

RIM SYNDROME [femoroacetabular impingement] It has been suggested to be a preosteoarthritic mechanism. The condition occurs when the proximal femur repeatedly comes into contact with the native acetabular