Arthroscopic Management of Femoroacetabular Impingement

Alexis Chiang Colvin, MD

Jorge Chahla, MD, PhD

Shane J. Nho, MD, MS

Dr. Colvin or an immediate family member serves as a board member, owner, officer, or committee member of the American Academy of Orthopaedic Surgeons. Dr. Nho or an immediate family member has received royalties from Ossur; serves as a paid consultant to or is an employee of Ossur and Stryker; has received research or institutional support from Allosource, Arthrex, Inc., Athletico, DJ Orthopaedics, Linvatec, Miomed, Smith & Nephew, and Stryker; and serves as a board member, owner, officer, or committee member of the American Orthopaedic Society for Sports Medicine and the Arthroscopy Association of North America. Neither Dr. Chahla nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

PATIENT SELECTION

Femoroacetabular impingement syndrome (FAIS) is a condition in which there is bony incongruity, which results in a cascade of pathologic issues in the hip joint. This incongruity can originate from the femoral side (a cam deformity), the acetabular side (a pincer deformity), or both. Labral or cartilage tears or both can result, leading to pain. Patients typically report groin pain, but pain lateral and posterior to the hip can also occur. Pain occurs primarily with activity, such as walking, running, or sports. Patients may also have difficulty sitting for long periods of time and putting on socks and shoes. Some patients may experience a clicking or catching sensation in the hip joint.

When evaluating a patient for possible FAIS, a complete history and physical examination should be performed. The history should include asking about any childhood hip abnormalities, previous trauma, or infection. The physical examination should evaluate both the range of motion of the hip and the strength of the hip muscle groups. Particular emphasis should be placed on the results of tests for intra-articular pathology, including the Stinchfield test (examiner resists active hip flexion), the posterior impingement test, FADIR (flexion, adduction, and internal rotation), and the FABER (flexion, abduction, and external rotation) tests. Ruling out other orthopaedic and nonorthopaedic sources of pain in the hip area, such as hernias, or other extra-articular pathology is also imperative. Responsiveness to an intra-articular anesthetic injection is highly correlated with an intra-articular pathology and should be performed in cases of unclear pain etiology.¹

PREOPERATIVE IMAGING

Standard AP pelvis and a lateral (ie, 45° Dunn, 90° Dunn, frog leg, cross-table) hip radiographs should be obtained. A well-positioned AP pelvis is critical to evaluate the orientation of the acetabulum. In males, the distance between the pubic symphysis and the tip of the sacrococcygeal junction should be 32 mm; in females, it should be 47 mm.³ Measurement of the lateral center-edge angle (LCEA) will quantify the amount of lateral coverage. The LCEA between 20° and 24° is considered borderline normal, and an angle less than 20° is considered dysplastic. Global overcoverage of the femoral head by the acetabulum, known as pincer impingement, can be defined as an LCEA greater than 39°.⁴ A false-profile view is useful for measuring the anterior center-edge angle. The Dunn view can be obtained at 45° or 90° and is used to evaluate the femoral head sphericity and contour of the femoral head-neck junction. The alpha angle allows quantitative characterization of the degree of anterior deformity associated with cam-type FAIS. Alpha angles greater than 50° are consistent with cam-type deformity. Articular surface damage should be suspected when alpha angles are large. Importantly, the Tönnis angle has been reported to be the most representative radiographic measurement of acetabular volume and femoral head coverage and is measured off a horizontal line drawn from teardrop to teardrop and a line tangential to the weight-bearing dome (ie, sourcil) of the acetabulum. A normal Tönnis angle lies between −10° and 10°, whereas a Tönnis angle of more than 10° is indicative of acetabular dysplasia and a Tönnis angle
below −10° is indicative of a pincer deformity. Images should be assessed for acetabular version as well as the presence or absence of a cam deformity (Figure 1), herniation pits in the femoral neck, joint space narrowing, and os acetabuli. CT with three-dimensional reconstructions also can be helpful in determining FAIS pathomorphology as well as femoral version abnormalities.

FIGURE 1 AP pelvis radiograph demonstrates bilateral cam lesions.

Magnetic resonance arthrography has been found to have a better correlation (100%) with the identification of labral tears at arthroscopy than does conventional MRI (85%).⁵ The two techniques are similar for the detection of cartilage abnormalities.⁵ Other MRI findings of FAIS include paralabral cysts (Figure 2), herniation pits at the head-neck junction, and os acetabuli.

VIDEO 10.1 Arthroscopic Management of Pincer- and Cam-Type Femoroacetabular Impingement. Christopher M. Larson, MD; Rebecca M. Stone, ATC (8 min)

View Quicktime Video

Video 10.1

FIGURE 2 Sagittal T2-weighted magnetic resonance arthrogram demonstrates a paralabral cyst (arrow) and a perforation in the anterosuperior labrum (arrowhead).

PROCEDURE

Room Setup/Patient Positioning

The patient is positioned supine on a fracture table or a flat table using a hip distractor (Figure 3). After induction of anesthesia, an examination of the hip should be performed, assessing for any side-to-side differences in range of motion. The patient is then positioned as follows: the feet should be well padded. An oversized, well-padded peroneal post distances the post from the area of the pudendal nerve and helps to add a slight transverse component to the direction of the traction vector. The pelvis should be positioned at the level of the peroneal post and slid toward the nonsurgical side. The hip is positioned in approximately neutral flexion, 0° of abduction, and 20° of internal rotation of the foot. The ipsilateral arm is padded and positioned over the chest away from the surgical field. Slight traction should be placed on the nonsurgical leg before distracting the surgical side to stabilize the torso. Fluoroscopy is used to confirm that adequate distraction can be obtained on the hip. Traction is then released while preparation and draping are performed.

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