Introduction

The cause of hip osteoarthritis is a controversial topic. Historically, it was believed that arthritis was the result of intrinsic cartilage abnormalities and a biomechanical mismatch with axial loading that led to joint overload and subsequent cartilage wear. Recently, femoroacetabular impingement (FAI) has been shown to cause chondrolabral damage and leads to osteoarthritis. Although the pistol grip deformities have been described, the biomechanical concept of FAI as a unifying principle that explains how abnormal osseous parameters lead to arthritis is unique. FAI is a dynamic phenomenon that causes chondrolabral damage from repetitive hip motion, especially flexion and internal rotation. These “at-risk” hips have osseous structural abnormalities on either the femoral side, the acetabular side, or both. During the range of motion of the hip, particularly during flexion and internal rotation, these abnormalities produce the mechanical impingement of the femoral head against the acetabular cartilage or the femoral neck against the adjacent labrum. With time, repetitive impingement leads to acetabular cartilage damage, and this is followed by early osteoarthritis.

Two distinct mechanisms of FAI have been described; these are commonly referred to as cam disease and pincer disease (Figure 28-1, A through D). The descriptions of these conditions were based on the skeletal morphology and the pattern of chondrolabral damage observed during surgical hip dislocations. However, these morphologic patterns are not mutually exclusive; it is quite common for patients to have components of both cam and pincer types of impingements. With cam FAI, there is an abnormal bony prominence at the femoral head–neck junction that is often located anterosuperiorly. During hip flexion, the abnormal contoured femoral head engages the anterosuperior acetabulum and produces shear forces that lead to chondral abrasion, delamination, and, eventually, full-thickness cartilage loss. The natural history of this impingement process is initially acetabular cartilage injury, which is followed by labral injury and ultimately joint arthrosis. At first the labrum is uninvolved, but, with further impingement, labral injury results from the further loosening of the labrum at the transition zone between the peripheral cartilage and the labrum itself. With pincer FAI, there is increased acetabular coverage that leads to linear contact between the femoral head–neck junction and the acetabular rim. Acetabular overcoverage may be either generalized, as in coxa profunda and protrusio acetabuli, or localized, as in acetabular retroversion and anterior acetabular overhang. Unlike what occurs with cam FAI, the labrum is the first to get injured with intrasubstance degeneration, cyst formation, and bone apposition at the rim, which further deepens the socket and exacerbates the problem. The prominent acetabular rim abuts with the femoral neck and causes the femoral head to lever in the acetabulum. This chronic levering of the head generates shear forces and injury to the posterior cartilage. Over time, this contrecoup mechanism leads to posteroinferior chondral damage and joint space narrowing.

Figure 28–1 The two forms of femoroacetabular impingement (FAI) are shown. A, Cam FAI occurs when the lack of offset of the femoral neck (arrow) leads to mainly anterosuperior damage through repetitive inclusion of the femoral neck with subsequent shearing injury of the acetabular cartilage. B, During hip flexion, impingement causes chondral labral injury. C, Pincer FAI occurs as a result of acetabular overcoverage (arrow). D, Pincer impingement causes anterosuperior impaction and subsequent leverage with contrecoup injury to the cartilage of the posteroinferior acetabulum during hip flexion.

Redrawn from Leunig, M., Robertson, W., and Ganz, R. Femoroacetabular impingement: diagnosis and management including open surgical technique. Tech Sports Med 15:178-188, 2007.

Basic science

The major breakthrough in impingement surgery was the safe surgical dislocation of the hip. The key to this procedure is an in-depth understanding of the blood supply to the femoral head. A recent latex injection study demonstrated that the medial femoral circumflex artery (MFCA) is the main blood supply to the femoral head. The vessel was surgically dissected and found to cross the obturator externus posteriorly and to then pass anteriorly to the short external rotators before perforating the joint capsule at the level of the superior gemellus. The study also demonstrated that the vessel remained undamaged during a controlled surgical hip dislocation, providing that the short external rotators and obturator externus remained intact. As a result of this study, an operative technique was developed that allowed for the safe surgical dislocation of the femoral head. Unlike the commonly used posterior approach, which requires the division of the short external rotators, a surgical dislocation protects these structures and, in doing so, preserves the blood supply to the femoral head.

Another critical basic science concept is that, in most cases, chondral injury usually leads to labral tears (and not vice versa). On the basis of our observations during several hundred surgical dislocations, the pattern of disease in cam FAI is that osseous abnormalities create mechanical “outside-in” shear forces and chondral damage, and, subsequently, the uninvolved labrum gets injured. This concept is supported by the fact that the majority of so-called labral tears occur at the anterosuperior portion of the acetabulum at the transition zone between the labrum and the articular cartilage and not the capsular margin. In addition, in early cam FAI, chondral damage is often observed without labral tears. Intrasubstance labral tears that are less frequently associated with chondral injuries have been observed in patients with early pincer FAI. Labral tears in the anterosuperior portion of the acetabulum are the result of FAI and not isolated traumatic injuries; this idea is supported by the observations that the majority of labral tears are also associated with chondral damage and radiographic evidence of abnormal skeletal morphology.

Treatment, indications, and contraindications

Conservative treatment is usually attempted first, and this includes activity modification; rest; nonsteroidal antiinflammatory drugs; and a physical therapy regimen that focuses on core, lower back, and hip flexor strengthening. On occasion, one may use intra-articular injections for both diagnostic and therapeutic uses. We do not routinely perform intra-articular hip injections; however, for select cases in which the origin of a patient’s symptoms remains unclear, we will perform a diagnostic intra-articular injection. In many cases, conservative management strategies may only partially relieve symptoms, and often they only mask symptoms. Attempts by physical therapists to improve the passive range of motion are often not beneficial and in fact may be counterproductive, because the limitation of internal rotation in patients with FAI is the result of abnormal osseous morphology. Although some patients receive temporary benefits from these conservative measures, young athletic patients often have difficultly complying with activity modifications.

The most important indications for FAI surgery are physical examination and radiographic findings that are consistent with FAI (Box 28-1). Proper imaging studies are critical to confirm and quantify the deformity and to assess the degree of arthritis. Unnecessary treatment delays also should be avoided.

The next critical issue is determining the surgical technique that should be used. Although this decision depends on numerous patient factors, the type, magnitude, and location of the underlying osseous abnormality are important. Although arthroscopy is an emerging technique for the treatment of FAI, it is technically challenging, and it has its limitations. Arthroscopy can easily handle the soft-tissue or secondary effects of FAI (e.g., the chondrolabral pathology), although how well it can handle the underlying osseous abnormalities remains debatable. Alternatively, a surgical dislocation of the hip provides a wide, safe exposure with the complete visualization of both the acetabular and femoral pathologies. In addition, the structural morphologic changes (e.g., the lack of an anterior femoral neck offset, acetabular overcoverage) can be addressed with relative ease. It has also been shown that the failure to address the underlying bony abnormality is likely to lead to continued symptoms, progressive joint degeneration, and poor outcomes. Another advantage of a surgical dislocation is that it is provides versatile exposure of the hip joint. It enables the surgeon to perform numerous impingement procedures as well as other procedures for soft-tissue injuries, osseous Bankart lesions, avascular necrosis, hip resurfacing, loose bodies, osteochondromatosis, and other non-FAI diagnoses. Contraindications for this technique are few, but the most obvious are extensive arthritic changes (e.g., a score of more than 2 on the Tönnis scale) and extensive destruction and deformity of the femoral head. Other contraindications include significant acetabular protrusio and dysplasia.

History and physical examination

FAI typically presents with an insidious onset of groin pain in young adults. Although patients often mistakenly associate the condition with a traumatic event, it is a more chronic process with intermittent pain and occasionally with acute exacerbations from activities that require forceful hip flexion and internal rotation. As a result of the often subtle findings on routine radiographs, these patients may experience a delay in diagnosis and be subjected to extensive nonorthopedic workups. Pincer-type FAI is more common among women, and it is often quite painful as a result of the crushing of the sensitive labrum between the acetabular rim and the femoral neck. This symptom often acts as a warning sign that causes patients with the condition to seek earlier orthopedic evaluation before significant chondral damage occurs. Alternatively, cam-type FAI is more common among young males. These patients have a pain pattern that involves more deep-seated groin symptoms, which are usually less severe than those experienced by patients with pincer-type FAI, because the labrum is commonly spared. These patients often do not seek evaluation until they have developed significant chondral injury.

It is crucial that all FAI patients receive a thorough physical examination, because there are many extra-articular diagnoses that can present with hip pain. The examination begins with detailed motor and sensory examinations. Next, the range of motion is assessed. Limited internal rotation of the flexed and adducted hip is seen in both cam and pincer FAI, but a greater loss of internal rotation is seen with cam FAI. This is followed by FAI-specific tests. An impingement test (Figure 28-2) is performed with the patient in the supine position; the affected hip is adducted and internally rotated as it is passively flexed. In patients with FAI, the femoral head–neck junction and the acetabulum abut, thus producing shear forces on the labrum and reproducing a sharp pain in the groin. A posteroinferior FAI test is performed with the patient supine on the edge of the examination table with the legs dangling free from the end. The examiner then extends and externally rotates the affected hip. Deep-seated groin pain during this maneuver is indicative of posteroinferior FAI, and it is frequently combined with limited external rotation. Finally, other critical examination maneuvers are performed to find associated pathology of the psoas, the iliotibial band, the lower back, and other related structures.

Figure 28–2 Clinical examination of the impingement test.

Redrawn from Leunig, M., Robertson, W., and Ganz, R. Femoroacetabular impingement: diagnosis and management including open surgical technique. Tech Sports Med 15:178-188, 2007.

Imaging

A correctly performed anteroposterior pelvic radiograph is the most essential imaging study for the assessment of impingement. The radiograph should be standardized to ensure proper rotation (i.e., the sacrum bisects the pubis) and pelvic inclination (i.e., 2 cm to 5 cm of pubic–sacrococcygeal distance). Slight deviations in either of these parameters can lead to an inaccurate assessment of acetabular coverage, inclination, and anteversion.

After the adequacy of the radiograph has been verified, it should be reviewed in a systematic fashion. First, the radiograph should be assessed for the coverage of the femoral head (i.e., center edge angle and Tönnis angle) or for gross arthritic changes (i.e., Tönnis scale). Next, the acetabulum should be inspected for pincer-type FAI. Five radiographic structures must be identified: 1) the medial acetabular wall; 2) the ilioischial line; 3) the anterior wall of the acetabulum; 4) the posterior wall of the acetabulum; and 5) the femoral head. By understanding the relationship of these radiographic structures, all of the common causes of pincer FAI can be diagnosed. In a patient with coxa profunda, the medial acetabular wall approaches and overlaps (if it does not pass medial to) the ilioischial line, which causes a deep socket. In a patient with protrusio, the femoral head is medial to the ilioischial line. In a patient with true acetabular retroversion, the anterior and posterior acetabular walls overlap; they also have a positive crossover sign and a prominent ischial spine (Figure 28-3, A). In these cases, there may or may not be a sufficient posterior wall, but there is always a relative anterior overhang. Finally, one must assess for os acetabuli, which can represent either broken pincer lesions or unfused portions of the acetabulum (i.e., true os acetabuli).

Figure 28–3 A, Anteroposterior radiograph that shows a crossover sign indicating acetabular retroversion. B, Cross-table lateral view that shows a lack of femoral offset. L, left; R, right.

On the femoral side, cam FAI is readily diagnosed with the proper radiographs. Given its mostly anterosuperior location, the cam lesion is often underappreciated on a standard anteroposterior radiograph, and it may be obstructed by the greater trochanter on a frog-leg lateral view. The aspheric head–neck junction is best visualized with either a 45-degree Dunn view or a cross-table lateral view with the leg in 15 degrees of internal rotation. The Dunn view, which is also known as an extended neck lateral view, is taken with the patient’s hip in neutral rotation, flexed 45 degrees, and abducted 20 degrees. The internally rotated cross-table lateral view is often more practical for routine use, because positioning the patients for the Dunn view requires a leg holder or an assistant. Either image can be used to measure the head–neck offset and the alpha angle, both of which are abnormal parameters that can be used to assess cam FAI (see Figure 28-3, B). In addition, the femoral neck shaft angle should also be assessed for any significant varus deformities.

In addition to radiographs, we routinely obtain a magnetic resonance arthrogram to accurately assess chondral delamination and full-thickness cartilage defects. In many cases of FAI, hips that produce normal radiographs (as defined by Tönnis grade) in fact have extensive chondral injury. Magnetic resonance imaging also assesses for labral pathology or subtle signs of FAI, such as fibrocystic changes at the head–neck junction; these changes are also known as synovial herniation pits. The magnetic resonance imaging should involve the use of cartilage-specific sequences, and it should be performed in radial-directed sections for the accurate measurement of angulation and the translation of the impingement lesions in the radiologic reference planes (Figure 28-4). Standard magnetic resonance imaging of the pelvis is often less sensitive, because it does not occur in the correct sequence plane with a resolution being far too low. In addition, although computed tomography scans provide a superior assessment of femoral anteversion, acetabular version, and femoral offset, they require radiation exposure during 20 radiologic pelvic overviews; thus, computed tomography should be used quite judiciously. Other advantages of obtaining a magnetic resonance image include the evaluation of stress fractures and soft-tissue abnormalities as well as the measurement of the alpha angle and acetabular version.

Figure 28–4 Radial sequence magnetic resonance image of the right hip showing cam-type FAI with a decreased head/neck offset.

Surgical technique

The fundamental principle of the surgical treatment of impingement is an exposure that preserves the blood supply to the femoral head. The approach combined and made use of features from several previously described approaches, with the general principle being that of an anterior dislocation of the femoral head from a posterolateral approach. However, to protect the MFCA, the external rotators are left intact, and the joint capsule is exposed anteriorly with the use of a trochanteric osteotomy. The surgical technique is explained in detail later in this chapter.

General or spinal anesthesia is used. The patient is placed in the lateral decubitus position in well-padded bolsters, and care is taken to also protect the nonoperated limb. Correct orientation is important to allow for the accurate assessment of acetabular orientation during the procedure. The skin is cleansed with a standard preparation solution over the trochanteric region. The patient is prepared and draped in standard sterile fashion (Figure 28-5, A) with a free leg sterile bag drape placed on the opposite side of the operating table to receive the lower leg during hip dislocation (see Figure 28-5, B). A second-generation cephalosporin antibiotic is given for prophylaxis and continued for 24 hours. Image intensifying and laser Doppler flowmetry are not routinely used, but both can be helpful for either osteotomy fixation or to monitor the perfusion of the femoral head.

Figure 28–5 A, The lateral decubitus position for surgical hip dislocation. This technique provides for the exposure of the entire femoral head and the acetabulum, which allows for the identification and treatment of femoroacetabular impingement. B, With the hip in flexion and external rotation, the femoral head can be dislocated to allow for an almost circumferential inspection of the entire acetabulum.

Redrawn from Leunig, M., Robertson, W., and Ganz, R. Femoroacetabular impingement: diagnosis and management including open surgical technique. Tech Sports Med 15:178-188, 2007.

A straight lateral incision of approximately 20 cm to 25 cm in length is made along the anterior border of the greater trochanter. This incision has been more cosmetically favorable than a traditional Kocher-Langenbeck incision; in cases with excessive adipose tissue and the latter type of incision, unaesthetic bulges developed posteriorly toward the distal end of the incision. As a general rule, the more adipose tissue present, the longer the incision necessary for the adequate visualization for the trochanteric osteotomy and for the dislocation maneuver. The fascia lata is incised in line with the incision and extended proximally without any violation of the gluteus maximus fibers, as described by Gibson. The advantage of this approach is that it affords a wide exposure without any splitting of the gluteus maximus, thus avoiding damage to the muscle and its neurovascular supply. To locate the anterior margin of the gluteus maximus, the perforant vessels to the muscle are identified by undercutting the epifascial layer of the fatty tissue in an anterocephalic direction. Care is taken to incise the intermediate fascia that rests on the gluteus medius and to retract it posteriorly with the mass of gluteus maximus muscle fibers, because this fascial plane retains the blood supply and innervation to the anterior part of the gluteus maximus. The intergluteal space is then developed with the hip in extension and internal rotation.

The next step is to make a gentle incision of the trochanteric bursa close to its lateral edge and to then retract it in an anterior direction. The innominate tubercle and the border of the vastus lateralis origin are now visible. By careful, superficial exposure of the posterior margin of gluteus medius, the posterocranial tip of the trochanter with the tendinous insertions of the gluteus medius can be seen and palpated. A small trochanteric branch of the MFCA can be identified running anteriorly along the posterior border of the trochanteric crest and should be hemocauterized.

Before starting the osteotomy, one should inspect the trochanter. The osteotomy fragment should provide continuity between the gluteus medius and the gluteus minimus (specifically the long tendon anteriorly) proximally and the vastus lateralis via the osteotomy fragment distally. Thus, the osteotomy is trigastric rather than digastric in nature. Conversely, the piriformis and the short external rotators should remain attached to the nonosteotomized femur (i.e., the stable trochanter). If done properly, the osteotomy should undercut the tendinous origin of the vastus lateralis distally and a few remaining incoming gluteus medius fibers proximally at the tip of the trochanter. This will increase the certainty that the major part of the underlying piriformis muscle tendon will remain on the stable trochanter.

The trochanteric osteotomy begins with the internal rotation of the leg of about 20 degrees to 30 degrees on a Mayo stand to expose the posterior border of the gluteus medius. The osteotomy is generally performed with an oscillating saw at an angle that is roughly parallel to the rotation of the affected extremity. The osteotomy should run from the posterosuperior border of the greater trochanter distally toward the posterior border of the vastus lateralis muscle, and it should remain parallel with the long axis of the femoral shaft.

Although the osteotomy was originally described as a single plane cut, we now recommend using a triplanar osteotomy to increase the mechanical stability of the osteotomy fragment, especially among older patients, who may have compromised bone. The osteotomy should commence at the posterosuperior border of the greater trochanter with two broad chevron-type cuts, leaving a step of 5 mm between them. The distal cut should end more medial than the proximal one to offset the pull of the abductors. Moreover, it is recommended that the osteotomy not perforate the anterior cortex of the trochanteric crest but rather be left incomplete. An osteotome is used to lever the fragment forward with a controlled fracture of the anterior cortex. This creates a third plane to the osteotomy, because the anterior cortex typically detaches with an anterior lip of cortex attached. The advantages of this triplanar osteotomy are its increased stability and the ease of the anatomic refixation of the fragment.

The resulting mobile fragment should be approximately 10 mm to 15 mm in diameter. If the trochanteric osteotomy is too thick, the tendon of the piriformis muscle will adhere completely to the mobile trochanteric fragment. This may lead to insufficient mobilization of the trochanteric fragment and endanger the anastomosis with the inferior gluteal artery or the deep branch of the MFCA itself, with the consequent risk of femoral head necrosis. Alternatively, if the trochanteric osteotomy is too thin, fixation difficulties and the risk of fracture of the trochanteric fragment may arise.

The osteotomy fragment is then mobilized. Initially, an 8-mm Hohmann retractor is placed in the osteotomy site, and the fragment is retracted and mobilized anteriorly. The mobile osteotomy fragment is in continuity with the gluteus medius and the vastus lateralis. The fibers of the vastus lateralis originating at the posterior femur are gradually released to the middle of the height of the gluteus maximus tendon. The mobile fragment can now be tilted more anteriorly, especially after the anterolateral part of the vastus lateralis has been released subperiosteally from the femur with the hip in external rotation, flexion, and abduction. Proximally, the residual tendon insertions of the gluteus medius that are still attached to the stable part of the trochanter are cut. After releasing these fibers, the piriformis tendon becomes visible. Ideally, approximately 25% of the piriformis tendon should be attached to the mobile osteotomy fragment to ensure the appropriate thickness of the osteotomy. These residual piriformis fibers on the mobile fragment are then released to further mobilize the osteotomy fragment. Care must be taken during this portion of the procedure to avoid any damage to the short external rotators, because they protect the MFCA.

The next step is to develop and expose the hip capsule between the interval of the gluteus minimus and the piriformis. The limb is placed in extension and slight internal rotation. The interval between the gluteus minimus and the posterior capsule is carefully dissected posteriorly down to the acetabular rim; this interval offers the most certainty that the blood supply to the femoral head will be preserved. Furthermore, the constant anastomosis between the inferior gluteal artery and the deep branch of the MFCA is protected; this runs along the lower margin of the piriformis tendon, and it is of fundamental importance because it alone can guarantee the vascularization of the femoral head if there is injury to the deep branch. Finally, the limb is placed in abduction, flexion, and external rotation again. The anterosuperior capsular insertions of the gluteus minimus muscle are then released while preserving the long tendon insertion into the mobile fragment. After the gradual release of the posterior, superior, and anterior insertions of the gluteus minimus from the capsule, the hip capsule is completely exposed; however, the short external rotators have always remained protected and attached to the stable trochanter.

With the hip capsule completely exposed, a Z-shaped capsulotomy (for the right hip) or an inverse Z-shaped capsulotomy for the left hip is performed. It begins with a linear incision along the line of the femoral neck close to the superior border of the stable trochanter. The capsulotomy then runs posterosuperior along the acetabular rim from the inside out in a proximal direction to avoid injury to the retinaculum, the cartilage, and the labrum. Finally, an inferomedial extension of the capsulotomy is performed over the front of the anterior capsule and headed toward the lesser trochanter. It is important to avoid extending the capsulotomy cut past the lesser trochanter to protect the MFCA, and the posterosuperior extension should not extend past the piriformis tendon, because the vessel may also be injured at this point. The labrum and the chondral surfaces are best preserved by an “inside-out” arthrotomy, which ensures the visualization of these structures at all times.

The next critical step is the careful dislocation of the femoral head and the appropriate positioning of the retractors to visualize the pathology. First, an 8-mm Hohmann hook is hammered into the bone below the capsular margin but above the labrum to hold the soft tissues back at the 12-o’clock position; a Langenbeck hook may also be adequate for this purpose. A bone hook is then placed around the femoral calcar, and the hip is gently subluxed with traction, flexion, and external rotation as the limb is prepared to be placed into the sterile leg bag. The ligamentum teres, which prevents complete dislocation, is then cut with parametrium scissors, with care taken not to damage the chondral surfaces of the acetabulum or the femoral head. On rare occasions, the hip is only subluxed, and all operative work is then performed with the limb in this position. The lower extremity is then dislocated anteriorly and placed in the sterile leg bag. Two additional retractors are placed: one at the anterior acetabular rim and the other inferiorly by the transverse acetabular ligament. There is now a 360-degree view of the entire acetabulum. Posterior retractors can also be placed, if necessary. Finally, a bump is placed on the femur to provide slight abduction, and a posterior force is placed on the femur by an assistant to assist with acetabular visualization.

The hip can now be inspected for evidence of injury as a result of FAI. Open inspection initially begins with a capsu-lotomy when the amount of synovial effusion and the degree of synovitis are documented. Next, attention turns to the acetabular chondrolabral surfaces. Note that, as soon as the cartilage is exposed, it should be protected from drying out with a constant trickle of physiologic salt solution. Damage to the acetabular cartilage and labrum is documented. A blunt probe can be used to examine the labrum for detachments or tears and to assess the cartilage for softening or delamination. By altering the position of the leg in flexion, all articular surfaces can be visualized, and any chondrolabral injuries in both the anterosuperior and posterosuperior regions are documented. If labral tears are unrepairable, then the labrum might be debrided or even replaced by graft tissue (round ligament, hamstrings, IT band, etc.). Likewise, grade IV contained chondral lesions are often microfractured. Larger lesions, particularly of the femoral head, might require cartilage repair techniques such as ACT, AMIC, or others.

If pincer FAI is noted preoperatively and confirmed intraoperatively, then an acetabular rim trimming is performed (Figure 28-6, A through D). First, the labrum must be detached from the acetabular rim with the use of sharp dissection. Because the typical location of acetabular rim lesions is the anterosuperior margin, the excessive rim segment can be removed with a curved osteotome. The amount of rim resected depends on the location of the crossover sign and the femoral head coverage (e.g., the value of the lateral center-edge angle, femoral head extrusion) seen on the preoperative plain radiograph. Ultimately, however, intraoperative tests are performed to assess the degree of overcoverage. These tests are performed after both the acetabular and femoral resections, if needed. Rim excision is performed until no impingement exists but not at the expense of creating instability or dysplasia. If there are full-thickness chondral lesions, then a microfracture is performed with angled awls. The labrum is then reattached with the use of two to four small bone anchors placed into the bed of bleeding cancellous bone approximately 10 mm to 15 mm apart. The nonabsorbable suture of the anchor should be passed through the base of the labrum and tied with the labrum firmly seated against the acetabular bone so that the knot lies on the nonarticular surface of the labrum.

Figure 28–6 A, The resection of excessive anterior rim in a case of acetabular retroversion can be performed with a curved osteotome B, after labral detachment as part of the approach to the acetabular rim. C, After sufficient rim resection, D, labral refixation is performed with the use of bone anchors.

Redrawn from Leunig, M., Robertson, W., and Ganz, R. Femoroacetabular impingement: diagnosis and management including open surgical technique. Tech Sports Med 15:178-188, 2007.

Attention now turns to the femoral side. The retractors are gently removed, the knee is lowered, and the femoral head can be elevated out of the wound so that, with rotation, about three fourths of the head circumference can be seen. First, the posterosuperior retinaculum and the vessels are identified and protected. Next, the sphericity of the femoral head can be assessed after two blunt retractors are placed under the femoral neck. Nonsphericity is tested with the use of appropriately sized transparent spheric templates. With these templates, a safe resection is predictable, and the risk of femoral neck fracture is minimized. A previous study has shown that up to 30% of the femoral neck can be resected.

The most common location for this pathology is the anterosuperior head–neck junction, with the abnormal cartilage having a slightly hypervascular, pink appearance. The presence of a cyst near the peripheral border of the nonspheric segment is sometimes noted, which indicates the point of maximum impingement. The abnormal bone can be removed carefully with the use of curved chisels until a normal head–neck offset is recreated, with great care taken not to laterally injure the terminal branches of the MFCA in the posterosuperior retinaculum (Figure 28-7, A and B). Unfortunately, this area may also be nonspheric, in which case the debridement should start proximally on the neck and reach the point at which the vessels enter their intraosseous course. A periosteal elevator may also be used to strip a portion of the retinaculum off of the bone as well. Femoral resection should be performed cautiously with regular reassessment with the use of the spheric templates to avoid over-resection, which both increases the risk of femoral neck fracture (only with excessive resections) and endangers the loss of the labrum’s suction seal effect with the femoral head.

Figure 28–7 Resection osteoplasty from the femoral head–neck junction can be used to recreate the normal concave contour of the femoral neck. A, Transparent templates are used to determine the sphericity of the femoral head. B, Femoral osteochondroplasty is performed to restore the insufficient offset.

Redrawn from Leunig, M., Robertson, W., and Ganz, R. Femoroacetabular impingement: diagnosis and management including open surgical technique. Tech Sports Med 15:178-188, 2007.

Before relocation, the ligamentum teres is debrided. Per-fusion should be assessed by observing bleeding from the fovea or from the raw cancellous surface that was created after the neck debridement. Bone wax (ideally resorbable) can be applied to the debrided surface before relocation. Hip relocation can be achieved with simple traction and controlled internal rotation, with care taken not to avulse the repaired labrum. Alternatively, although bone anchors have been placed during the acetabular preparation, the sutures can be tightened after the femoral head relocation, thus reducing the risk for avulsing labral refixation. After relocation, the range of motion can be assessed to look for any residual impingement before closure.

Capsular closure is performed without excessive tension to avoid the compression of the retinacular vessels. The trochanteric fragment is reduced anatomically according to the triplanar osteotomy step cuts, and it is reattached with the use of 3.5-mm or 4.5-mm screws. With the triplanar trochanteric osteotomy, 3.5-mm screws are sufficient for fixation, but if the patient develops any reactive bursitis, these screws are slightly more difficult to remove. Alternatively, 4.5-mm screws are much easier to remove if the patient becomes symptomatic. The fascia lata and the fat and cutaneous layers are then carefully closed in a layered fashion. Drains are rarely indicated. Box 28-2 reviews technical pearls for this procedure.

Rehabilitation and postoperative management

A postoperative radiograph is obtained in the recovery department (Figure 28-8). The patient is usually immobilized postoperatively on crutches, with toe-touch weight bearing for 6 weeks for triplanar osteotomy or 8 weeks for classic slide osteotomy. The patient is prohibited from performing hip flexion of more than 70 degrees (or of more than 90 degrees after a triplanar procedure) and from actively abducting or adducting the hip to allow for the proper healing of the osteotomy site. Continuous passive motion with flexion limited to 70 degrees is started on postoperative day 1 and continued until discharge to prevent the formation of intra-articular adhesions between the femoral osteochondroplasty and the capsule. If a microfracture was performed, then the use of continuous passive motion is extended for up to 8 weeks. The patient is usually discharged after 5 days. All patients receive low-molecular-weight heparin until full mobilization occurs.

Figure 28–8 Postoperative A, anteroposterior and B, lateral radiographs after bilateral surgical dislocations through a transtrochanteric approach with acetabular rim trimming, labral refixation, and femoral offset correction.

If after 6 to 8 weeks the radiograph shows evidence of healing at the osteotomy site, then weight-bearing and motion restrictions are advanced. If there is any concern, then therapy advancement is postponed for another 3 to 4 weeks. Full activities are allowed after the patient has regained full motion and strength, which usually takes about 3 months.

Results

A review of the literature and of the results of open impingement surgery is given in Table 28-1. To date, there have been seven series with approximately 199 patients. The patient’s prognosis generally depends on the extent of articular damage. Stated another way, the extent of preoperative arthritis is an important predictor of outcome. In addition, it has been shown that labral refixation appears to yield better clinical and radiographic results, whereas cases that involve both impingement and instability have been shown to have worse results.

Complications

General complications such as infection, blood loss, and venous thrombosis are quite rare. Specific complications of this procedure include iatrogenic head femoral necrosis, osteotomy nonunion, symptomatic hardware, undercorrection, overcorrection, and femoral neck fracture.

Although the risk of osteonecrosis is possible, in numerous series, the condition has not been reported. If one has a thorough understanding of the course of the MFCA, this potential complication is completely preventable. Similarly, these reports have all reported minimal trochanter fixation problems. If trochanter failure develops, then a repeat stable osteosynthesis is recommended. With the new triplane osteotomy, trochanter nonunions have been almost eliminated. Alternatively, symptomatic hardware is not infrequent. If indicated, this situation requires a small day procedure to remove the hardware, but minimal disability is associated with this condition and the procedure. Finally, undercorrection and overcorrection are also rare problems that can be eliminated with proper preoperative radiographic assessment in conjunction with carefully performed intraoperative impingement testing. Likewise, femoral neck fractures can be avoided with the use of templates to avoid excessive resection.

Conclusion

The open treatment of FAI with a surgical dislocation has many potential advantages. It is a safe, reproducible, and versatile procedure. It also allows the surgeon to perform a real-time assessment of the impingement. The best mid-term results have been seen among patients with the least amount of osteoarthritis. As indications are better defined, clinical outcomes will continue to improve. By eliminating FAI, progressive osteoarthritic changes will hopefully be delayed or even prevented.