Abstract
The primary objective of this review is further education of the general practitioner, or family medicine physician, on an important, but often missed, cause of hip pain in the adolescent and young adult population, femoroacetabular impingement (FAI) syndrome. We hope that further understanding of the etiology, examination, diagnosis, and treatment of FAI, will lead to more accurate diagnosis and timely referral to the Orthopedic hip specialist for definitive treatment and management. Thus, preventing the complications, or late sequelae, associated with the condition.
Femoroacetabular Impingement (FAI) Syndrome
Femoroacetabular impingement, or FAI, syndrome refers to the constellation of signs and symptoms related to abnormal morphology of the acetabulum, proximal femur, or both. Abnormal anatomy at the hip leads to altered mechanics abnormal loading of the hip joint. As a result, labral injury, chondral delamination, and more diffuse, non-focal degeneration of the hip articular surface can occur.1 The severity of these injuries correlates with time to diagnosis and definitive treatment.2,3 According to Clohisy et al., the average delay to definitive diagnosis from the onset of symptoms in FAI patients is approximately 3 years. Also of concern, these patients see an average of 4.1 healthcare providers before definitive diagnosis and specialist referral for appropriate management.4
More recently, FAI syndrome has been recognized as one of the most common causes of early arthritis in the non-dysplastic hip.5,6 As the primary physician is often the first to evaluate these patients, it is important that FAI syndrome is on their differential. This will hopefully result in decreased time to accurate diagnosis and facilitation of early referral to the orthopedic hip specialist.
Classification
CAM-type FAI
CAM-type FAI is characterized by abnormal anatomy of the proximal femur at the head-neck junction, in which there is typically an aspherical portion of the femoral head-neck junction that, with hip flexion and internal rotation, results in compression and shear forces to the labrum and acetabular rim, respectively. Over time, repetitive trauma resulting from a CAM-type FAI can lead to labral tears, chondral delamination and detachment.7,8,9
Pincer-type FAI
Pincer-type FAI is characterized by abnormal anatomy of the acetabular rim. This can cause either a focal, or more global, over coverage of the acetabulum over the normal anatomic femoral head and neck. As a result, ROM is limited when the femoral neck comes into contact with the acetabular labrum, again with hip flexion. This force is subsequently transmitted to the acetabular cartilage and labrum. With repeated bouts of micro trauma in this fashion, there is focal degeneration of the labrum with eventual ossification in a well described and recognized pattern.5,10 Another associated lesion with pincer type impingement is the contra-coup cartilage lesion of the femoral head.5,11 Development of these lesions further compromises biomechanical forces across the hip, predisposing the hip to progressive, diffuse, degenerative changes over time.
Mixed FAI
This type of FAI presents with both CAM-type and pincer-type deformities with abnormal morphology of both the proximal femur and acetabulum, along with their associated characteristic lesions. Recent reports indicate that this may be the most common pattern of FAI.1,5,12
Diagnosis
History and Physical Examination
The diagnosis of FAI syndrome cannot reliably be made with only one modality. Rather the accurate diagnosis is made by combining the findings of a good history, physical exam including specific provocative tests, and appropriate imaging. According to the PROCESS survey performed by Ayeni et al., the majority of orthopedic surgeons made the diagnosis of FAI based on a history of groin pain (81.7%), and the physical exam finding of pain with rotation of the affected hip (78.7%).13 Clohisy et al. looked at 51 patients in which the diagnosis of FAI was made. The average age of their patient population was 35 years old, and most participants were relatively active and high demand. The researchers noted that the majority of their patients reported pain of insidious onset. The pain was localized to the groin in 88%, however, many patients also reported discomfort in the lateral hip, thigh, low back and buttock. Clohisy et al. stressed the importance of recognizing the clinical presentation of FAI to facilitate timely and improved orthopedic care in efforts towards joint preservation and prevention of osteoarthritis.4
Tijssen et al., performed a systematic review to determine the accuracy and validity of physical tests reported in the literature that are utilized in making the diagnosis of FAI and labral pathology in the hip. They concluded that there were only three physical tests of good quality, which include the anterior hip impingement test (FADIR test), the FABER test, and the resisted straight leg raise (RSLR) test.14
The anterior hip impingement test is performed with the patient in the supine position. The leg is passively flexed to 90 degrees, adducted, and internally rotated until end range of motion. Reproduction of the patient’s pain with this test is considered a positive result.14,15,16 Ayeni et al. reported that 70% of orthopedic surgeons that were surveyed utilized the FADIR test in making the clinical diagnosis of FAI.13
The FABER test is performed with the patient in the supine position. The leg is passively flexed at the hip and knee, abducted, and externally rotated until the lateral ankle rests just proximal to the knee on the contralateral extremity. The pelvis is then stabilized and a downward force is applied on the flexed knee, pushing it towards the exam table. A positive test is reported as either reproduction of pain or decreased ROM compared to the non-affected limb.14,15,16
The RSLR test is also performed with the patient in the supine position. The patient actively flexed the straight leg at the hip to 30–45 degrees of flexion. They are then asked to resist manual downward force on the leg applied just proximal to the knee. A positive test is reported as recognizable pain or weakness.14,15,16 Although the aforementioned physical tests may be helpful tools, Tijssen et al. conclude that these tests are not able to reliably confirm or discard the diagnosis of FAI, when viewed in isolation. 14
Diagnostic Imaging
Diagnostic imaging is utilized by most orthopedic surgeons in confirming the diagnosis of FAI. As described above, clinical history and physical exam alone, have not proven reliable in making a definitive diagnosis of FAI, therefore further studies are warranted.17 The PROCESS survey reports that 66.3% and 70.8% of surgeons obtain plain radiographs and MRI, respectively, in confirming the diagnosis.13
At our institution, four plain film views are obtained in accordance with literature supported FAI radiographic assessment protocols. This protocol includes standing AP pelvis, standing false profile, supine modified Dunn lateral, and frog-leg lateral views. Each of these views provides specific information regarding the anatomy of both the acetabulum and proximal femur. Once familiar with the radiographic features of FAI, a reliable diagnosis should be able to be made by the practitioner.
In general, the standing AP pelvis and false profile views provides most useful information pertaining to the morphology of the acetabulum. From these views one can estimate the acetabular depth, inclination, and version, and measure the anterior and lateral center edge angles. These measurements are useful in estimating the amount of acetabular coverage of the femoral head.18
The supine modified Dunn lateral and frog-leg lateral views are most helpful when assessing morphology of the proximal femur. Head sphericity, as determined by gross inspection, or with the use of concentric circles, is determined using these radiographs. Femoral head-neck offset and head-neck junction deformities are often identified using these lateral views. The alpha angle is one useful quantitative measure used to evaluate these deformities.18
The alpha angle is determined by drawing a line through the center of the femoral neck and through the center of the femoral head. A circle is then drawn around the femoral head, using the spherical portion of the femoral head within the acetabulum as a guide to determine the radius of the sphere. A second line is drawn from the center of the femoral head to the anterolateral aspect of the head-neck junction where the radius exceeds that of the previously drawn sphere based off of the normal morphology. This is demonstrated in Figure 4 below. According to Clohisy et al, alpha angle greater than 42 degrees is indicative of femoral head-neck offset deformity, or CAM lesion. 18
Figure 4.
Demonstration of alpha angle calculation from the frog leg lateral view of the hip.
Source: http://clinicalgate.com/cam-type-femoroacetabular-impingement/
Treatment
Once the diagnosis of FAI is suspected or confirmed, early referral to the orthopedic hip specialist is recommended for timely evaluation and management. Conservative measures in the form of activity modification, physical therapy, non-steroidal anti-inflammatory medications, and pain medication may be trialed prior to more invasive techniques. However, as FAI is a syndrome that is mechanical in nature, and tends to be diagnosed in young, active adults, many patients do not improve clinically with conservative measures.19, 20 Failed conservative management has been generally accepted as an indication for surgical intervention in this patient population.
Orthopedic surgeons propose surgical treatment for the direct correction of anatomic deformities associated with FAI, as well as the associated lesions resulting from the abnormal morphology. Current surgical options include arthroscopy, open surgery with surgical hip dislocation, or a combination of the two. Surgical management is tailored to address the specific pathology and needs of each patient, and is also influenced by surgeon training and experience. Surgical intervention is also dictated by concomitant hip pathology. Especially when diagnosis is delayed, patients presenting with FAI and associated late sequelae, such as advanced osteoarthritis, are not ideal candidates for surgery aimed at correction of the FAI lesion. These patients are likely better served with joint arthroplasty.
Conclusion
FAI is a common cause of hip pain in young adults and adolescents that often goes unrecognized and untreated. This syndrome can lead to early degenerative disease of the hip in otherwise young and healthy individuals. Therefore, delays in diagnosis and treatment may have significant long-term consequences. Early diagnosis of FAI is vital to joint preservation, pain relief and restoration of function, and may improve quality of life in this patient population. As the primary physician is often the first practitioner to evaluate these patients, it is critical that they be familiar with the diagnosis and treatment of FAI, to expedite the appropriate management of these young patients to prevent the high morbidity associated with the disease process.
Figure 1.
FAI can be subdivided into three categories based on morphology: CAM-type, Pincer-type, and Mixed.
Source: https://www.thornleighphysio.com.au/news/2015/12/4/is-it-hip-to-be-fai
Figure 2.
AP radiograph of the right hip demonstrating pincer-type femoroacetabular impingement.
Figure 3.
This is a frog leg lateral radiograph of the right hip demonstrating CAM-type FAI.
Source: http://clinicalgate.com/cam-type-femoroacetabular-impingement/
Biography
Chsistopher Shaw, MD, is Assistant Professor in the Department of Orthopaedic Surgery at the University of Missouri - Kansas City.
Contact: cmshaw5@gmail.com
Footnotes
Disclosure
None reported.
References
- 1.Bedi A, Kelly BT. Femoroacetabular impingement. J Bone Joint Surg Am. 2013;95(1):82–92. doi: 10.2106/JBJS.K.01219. [DOI] [PubMed] [Google Scholar]
- 2.Ito K, Leunig M, Ganz R. Histopathologic features of the acetabular labrum in femoroacetabu-lar impingement. Clin Orthop Relat Res. 2004;(429):262–71. doi: 10.1097/01.blo.0000144861.11193.17. [DOI] [PubMed] [Google Scholar]
- 3.Johnston TL, Schenker ML, Briggs KK, Philippon MJ. Relationship between offset angle alpha and hip chondral injury in femoroacetabular impingement. Arthroscopy. 2008 Jun;24(6):669–75. doi: 10.1016/j.arthro.2008.01.010. Epub 2008 Mar 17. [DOI] [PubMed] [Google Scholar]
- 4.Clohisy JC, Knaus ER, Hunt DM, Lesher JM, Harris-Hayes M, Prather H. Clinical presentation of patients with symptomatic anterior hip impingement. Clin Orthop Relat Res. 2009;467:638–644. doi: 10.1007/s11999-008-0680-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of dam-age to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J. Bone Joint Surg. Br. 2005;87:1012–1018. doi: 10.1302/0301-620X.87B7.15203. [DOI] [PubMed] [Google Scholar]
- 6.Chaudhry H, Ayeni OR. The etiology of femoroacetabular impingement: what we know and what we don’t. Sports Health. 2014;6:157–161. doi: 10.1177/1941738114521576. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Johnston TL, Schenker ML, Briggs KK, Philippon MJ. Relationship between offset angle alpha and hip chondral injury in femoroacetabular impingement. Arthroscopy. 2008 Jun;24(6):669–75. doi: 10.1016/j.arthro.2008.01.010. Epub 2008 Mar 17. [DOI] [PubMed] [Google Scholar]
- 8.Kelly BT, Weiland DE, Schenker ML, Philippon MJ. Arthroscopic labral repair in the hip: surgical technique and review of the literature. Arthroscopy. 2005 Dec;21(12):1496–504. doi: 10.1016/j.arthro.2005.08.013. [DOI] [PubMed] [Google Scholar]
- 9.Nepple JJ, Zebala LP, Clohisy JC. Labral disease associated with femoroacetabular impingement: do we need to correct the structural deformity? J Arthroplasty. 2009 Sep;24(6 Suppl):114–9. doi: 10.1016/j.arth.2009.06.003. [DOI] [PubMed] [Google Scholar]
- 10.Seldes RM, Tan V, Hunt J, et al. Anatomy, histologic features, and vascularity of the adult acetabular labrum. Clin Orthop. 2001;382:232–40. doi: 10.1097/00003086-200101000-00031. [DOI] [PubMed] [Google Scholar]
- 11.Khan M, Bedi A, Fu F, Karlsson J, Ayeni OR, Bhandari M. New perspectives on femoroace-tabular impingement syndrome. Nat Rev Rheumatol. 2016;12(5):303–10. doi: 10.1038/nrrheum.2016.17. [DOI] [PubMed] [Google Scholar]
- 12.Ganz R, Leunig M, Leunig-Ganz K, Harris WH. The etiology of osteoarthritis of the hip: an integrated mechanical concept. Clin Orthop Relat Res. 2008 Feb;466(2):264–72. doi: 10.1007/s11999-007-0060-z. Epub 2008 Jan 10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Ayeni OR, et al. Results of the PeRception of femOroaCetabular impingEment by Sur-geons Survey (PROCESS). Knee Surg. Sports Traumatol. Arthrosc. 2014;22:906–910. doi: 10.1007/s00167-014-2882-z. [DOI] [PubMed] [Google Scholar]
- 14.Tijssen M, Van cingel R, Willemsen L, De visser E. Diagnostics of femoroacetabular im-pingement and labral pathology of the hip: a systematic review of the accuracy and validity of physical tests. Arthroscopy. 2012;28(6):860–71. doi: 10.1016/j.arthro.2011.12.004. [DOI] [PubMed] [Google Scholar]
- 15.Martin RL, Irrgang JJ, Sekiya JK. The diagnostic accuracy of a clinical examination in determining intra-articular hip pain for poten-tial hip arthroscopy candidates. Arthroscopy. 24(2008):1013–1018. doi: 10.1016/j.arthro.2008.04.075. [DOI] [PubMed] [Google Scholar]
- 16.Maslowski E, Sullivan W, Forster Harwood J. The diagnostic validity of hip provocation maneuvers to detect intra-articular hip pathology. PM R. 2(2010):174–181. doi: 10.1016/j.pmrj.2010.01.014. [DOI] [PubMed] [Google Scholar]
- 17.Reiman MP, Goode AP, Cook CE, Hölmich P, Thorborg K. Diagnostic accuracy of clinical tests for the diagnosis of hip femoroacetabular impingement/ labral tear: a systematic review with meta-analysis. Br. J. Sports Med. 2015;49:811. doi: 10.1136/bjsports-2014-094302. [DOI] [PubMed] [Google Scholar]
- 18.Clohisy JC, Carlisle JC, Beaulé PE, et al. A systematic approach to the plain radiographic evaluation of the young adult hip. J Bone Joint Surg Am. 2008;90(Suppl 4):47–66. doi: 10.2106/JBJS.H.00756. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Parvizi J, Leunig M, Ganz R. Femoroacetabular impingement. J Am Acad Orthop Surg. 2007;15(9):561–70. doi: 10.5435/00124635-200709000-00006. [DOI] [PubMed] [Google Scholar]
- 20.Imam S, Khanduja V. Current concepts in the diagnosis and management of femoroacetabu-lar impingement. Int Orthop. 2011;35(10):1427–35. doi: 10.1007/s00264-011-1278-7. [DOI] [PMC free article] [PubMed] [Google Scholar]