Femoroacetabular impingement syndrome: a narrative review for the chiropractor

Abstract

Objective: To familiarize the chiropractic clinician with the clinical presentation, radiographic features, and conservative versus surgical treatment options for managing femoroacetabular impingement (FAI) syndrome.

Background: FAI syndrome is a relatively new clinical entity to be described in orthopedics, and has been strongly linked with pain and early osteoarthritis of the hip in young adults. Hip joint radiographs in these patients often appear normal at first-particularly if the clinician is unfamiliar with FAI. The role of conservative therapy in managing this disorder is questionable. Surgical treatment ultimately addresses any acetabular labral or articular cartilage damage, as well as the underlying osseous abnormalities associated with FAI. The most commonly used approach is open surgical hip dislocation; however, more recent surgical procedures also involve arthroscopy.

Conclusion: In FAI syndrome-a condition unknown to many clinicians (including medical)-chiropractors can play an important role in its diagnosis and referral for appropriate management.

Keywords: acetabulum/abnormalities; femoral neck/abnormalities; hip joint; osteoarthritis.

Figure 1

Femoroacetabular impingement. Normal configuration of the hip with sufficient joint clearance allows unrestricted range of motion (top). Excessive acetabular coverage leads to early linear contact between the femoral head–neck junction and acetabular rim, resulting in labrum degeneration and significant cartilage damage. The posteroinferior portion of the joint can be damaged (i.e. contrecoup lesion) due to subtle subluxations (centre). With abnormal morphology of the proximal femur, the aspherical portion of the femoral head–neck junction is jammed into the acetabulum (bottom) (Source: Reprinted with permission M. Tannast, K.A. Siebenrock, S.E. Anderson, Femoroacetabular Impingement: Radiographic Diagnosis—What the Radiologist Should Know, AJR Am J Roentgenol, 188(6), p. 1541, © 2007 American Roentgen Ray Society.)

Figure 2

Impingement types. Diagram showing a normal acetabular fossa along with the typical concavity of the anterolateral femoral head-neck junction (A), the aspherical femoral head/convex anterolateral head-neck junction in the cam-type deformity (B), excessive acetabular coverage in the pincer-type (C), and mixed cam and pincer (D). (Source: Reprinted with permission from M. Lavigne, J. Parvizi, M. Beck, K.A. Siebenrock, R. Ganz, and M. Leunig, Anterior Femoroacetabular Impingement Part I. Techniques of Joint Preserving Surgery, Clin Orthop, 418, p. 62, © 2004 Lippincott Williams & Wilkins.)

Figure 3A and 3B

Slipped capital femoral epiphysis (SCFE) and the “pistol-grip” deformity. AP pelvic radiographs of a 16-year-old male patient showing a right-sided SCFE (A), and a cam-type (or pistol-grip) deformity (arrow) of the same hip, along with an os acetabulum (arrowhead), after two year follow-up from in situ surgical pinning (B).

Figure 4

Hip impingement test. The patient’s hip is forcibly rotated internally, while in adduction and 90º of flexion. This manoeuvre approximates the anterolateral femoral head-neck junction with the anterosuperior acetabular rim, creating a shearing pressure on the acetabular labrum (or adjacent articular cartilage). A positive test produces anterior groin pain.

Figure 5A and 5B

Femoral head-neck offset and alpha angle. (A) Right frog-leg radiograph of a 57-year-old female patient with a normal anterior femoral head-neck junction. The head-neck offset (os) and alpha angle (α) are indicated. (B) Right frog-leg, post-surgical radiograph (of the same patient in Figure 3) showing a small anterior femoral head-neck offset (os’) and large alpha angle (α’)—both characteristic of cam FAI

Figure 6

Cam FAI. AP pelvis radiograph of a 47-year-old male patient with bilateral cam-type FAI (arrows). Note the herniation pit within the superolateral femoral neck on the right (crossed arrow), and the small ossicle (os acetabulum) along the superior acetabular rim on the left (arrowhead). A normal anteverted acetabulum is highlighted on the right, where the anterior wall (AW) projects medial to the posterior wall (PW).

Figure 7

Focal acetabular over-coverage. Acetabular retroversion is visualized on AP pelvic radiographs by carefully tracing the anterior (AW) and posterior (PW) walls of the acetabular fossa to form the ‘crossover sign.’ A normal acetabulum is anteverted with the anterior rim projecting medial to the posterior rim (see Figure 6). In a retroverted acetabulum, the anterior rim projects lateral to the posterior rim proximally and crosses over in a medial direction distally. (Source: Reprinted with permission M. Tannast, K.A. Siebenrock, S.E. Anderson, Femoroacetabular Impingement: Radiographic Diagnosis – What the Radiologist Should Know, AJR Am J Roentgenol, 188(6), p. 1545, © 2007 American Roentgen Ray Society.)

Figure 8

General acetabular over-coverage. AP pelvic radiograph of a 43-year-old female patient with bilateral pincer-type FAI. General acetabular over-coverage is characterized by a deepened acetabular fossa. In this case, bilateral coxa profunda is evident, and highlighted on the right, with the medial floor of the acetabular fossa (AF) overlapping the ilioischial line (IIL – a line drawn tangentially along the margin of the pelvic inlet and outer border of the obturator foramen; in protrusio acetabuli, the femoral head crosses this line). Note also the large herniation pits located within the superolateral femoral head-neck junction, bilaterally (arrows).

Figure 9A and 9B

‘Pseudo’ pistol-grip deformity. AP pelvic radiographs of a 37-year-old male patient without the femurs internally rotated 15° (A) – giving the appearance of a ‘pseudo’ pistol-grip deformity on the right (arrow), and with the femurs internally rotated 15° (B) – clearly showing the concavity of a normal lateral head-neck junction (crossed arrow).

Figure 10A and 10B

MR arthrography in FAI. (A) Oblique sagittal fat-saturated T1-weighted MR arthrographic image (600/8) of the hip in a patient with cam FAI. An abnormal anterior femoral head-neck offset (short arrow) and anterosuperior labral tear (long arrow) are shown. (Source: Reprinted with permission A. Kassarjian, L.S. Yoon, E. Belzile, S.A. Connolly, M.B. Millis, W.E. Palmer, Triad of MR Arthrographic Findings in Patients with Cam-Type Femoroacetabular Impingement, Radiology, 236(2), p. 592, © 2005 RSNA.) (B) Coronal spin-echo sequence T1-weighted MR image (524/14) showing ossification of the acetabular labrum in a patient with pincer FAI. Bone marrow signal (arrowheads) extends into the substance of the acetabular labrum (arrow). (Source: Reprinted with permission C.W.A. Pfirrman, B. Mengiardi, C. Dora, F. Kalberer, M. Zanetti, J.Hodler, Femoroacetabular Impingement: Characteristic MR Arthrographic Findings in 50 Patients, Radiology, 240(3), p. 784, © 2006 RSNA.)

Figure 11A and 11B

End-stage hip degeneration in FAI. AP pelvis (A) and frog-leg right hip (B) radiographs of an 80-year-old female patient with bilateral pincer FAI, and severe right hip joint OA. Note the posteroinferior (i.e. contrecoup) joint space narrowing (arrow) and multiple osteophytes (arrowheads) on the right; coxa profunda is also evident. Protrusio acetabuli is evident and highlighted on the left, with the femoral head (FH) overlapping the ilioischial line (IIL). Note also the linear indentation (small arrow) and reactive cortical thickening (small crossed arrow) on the superolateral head-neck junction of the left femur.

Figure 12

Medial proximal femoral angle (MPFA). AP radiograph of the left hip joint (in a 36-year-old male patient) showing the modified MPFA. A line is drawn from the superior tip of the greater trochanter through to the centre of the femoral head. A second line is drawn (representing the anatomical axis of the proximal femur) from the midpoint of the most distally visible aspect of the femoral shaft, and up proximally through the piriformis fossa. The medial angle formed by these two lines is the MPFA (normal range = 80º to 89º). Note the ossification of the lateral acetabular labrum (arrowhead), resulting in pincer FAI.