SCORE FINANCIERO

*Marc R. Safran, MD

Introduction

Hip pain in the athletic population is commonly diag- nosed as a simple hip strain or pull. However, the man- agement of hip injuries has evolved substantially with better understanding of the hip and its pathomechanics and advances in diagnostic modalities such as MRI and hip arthroscopy, with new techniques and flexible instru- mentation. Hip pain can be caused by an injury to the joint itself or the soft tissue surrounding the joint or by referred pain. Hip injuries can be divided into intra- articular, extra-articular, or central pubic. Intra-articular sources of hip pain include labral tears, chondral dam- age, ligamentum teres tears, loose bodies, femoroacetab- ular impingement, hip displasia, and hip instability.

Disabling intra-articular hip pain in the athletic pop- ulation is most often the result of a labral tear. How- ever, labral tears may occur as an isolated phenomenon and often are the result of a bony abnormality, such as femoroacetabular impingement or dysplasia.

Evaluation of the Athlete With Hip Pain

The differential diagnosis of hip pain is quite broad in the athletic population. Without an appropriate work- up, hip pain in an athlete should not be simply diagnosed as muscle strain or soft-tissue contusion. A detailed his- tory and physical examination help to narrow the dif- ferential diagnosis. Careful evaluation is critical to de- lineate the source of the pain. Soft-tissue pain can be caused by trochanteric bursitis, muscle tears, contusions, iliopsoas bursitis, snapping hip, and piriformis syn- drome. Remote sites leading to referred pain can include the spine, the abdomen, the genitourinary system, and the knee. Pain from the hip joint itself can be caused by arthritis, stress fractures, synovial pathology, labral in- juries, trauma, fractures, dislocation, chondral lesions, loose bodies, osteonecrosis, stiffness, and instability.

Patient History

A careful history should include the qualitative nature of the discomfort (clicking, catching, stiffness, instabil- ity, decreased performance, weakness), the location of the discomfort, and the precipitating cause of symp- toms (insidious or traumatic onset). It is important to determine if the symptoms are acute and began after an inciting event or have been ongoing. Pertinent findings include a history of trauma; instability; inciting or ag- gravating activities; mechanical symptoms; or weak- ness. The location of the pain, such as over the groin, thigh, or greater trochanter, may provide a clue to the diagnosis. Intra-articular pathology is frequently mani- fested as groin pain. Details about medical history, sur- gical history, social history, and medications provide pertinent information. Further, questions about sports participation are important because certain types of sports activities are associated with hip pathology, such as golf, running, ballet, and football.

Physical Examination

The physical examination should determine if the pain originates from intra-articular or extra-articular pathol- ogy and confirm that the pain is not referred from a remote source, such as the spine, genitourinary system, or abdomen. Most intra-articular pathologies can be aggravated by passive motion of the hip joint such as log-rolling, and placement of the hip in the impinge- ment position (flexion, internal rotation, and adduc- tion). Extra-articular conditions more typically will be aggravated by localized palpation or resisted muscular contraction.

For physical examination of the hip, the patient should undress to shorts or undergarments. During the first part of the examination, gait and posture are observed. The way a patient sits (slouched to reduce hip flexion, off to one side to unload a hip) may provide a clue about the source of hip pain. The way a patient arises from a chair may also provide important information, particularly whether the hands must be used to raise up, and whether hip flexion or standing on the affected leg is avoided. It is important to observe and evaluate for an antalgic or Trendelenburg gait; a positive Trendelenburg sign indicates hip abductor weakness.

During the next part of the examination, palpation over the site of pain can help determine whether the

*Mark R. Safran, MD or the department with which he is affili- ated has received research or institutional support from Smith & Nephew; holds stock or stock options in Cool Systems, Inc; and is a consultant for or an employee of Cool Systems, Inc.

2: Hip

pain is deep, muscular, or bursal related, or possibly caused by trochanteric bursitis, an anterior superior il- iac spine avulsion fracture, or osteitis pubis.

After palpation and with the patient supine, both ac- tive and passive ranges of motion, including flexion, abduction, and internal and external rotation, should be tested. Strength should be tested and compared with that of the contralateral side.

Finally, hip-specific and provocative tests that should be performed include a resisted straight-leg raise, the Ober test (for hip abductor tightness), the Thomas test (for flexion contracture), the Patrick test (placing the leg in a figure-of-4 position while the patient is supine to assess for sacroiliac joint conditions and psoas pain or tightness from hip pathology), the labral stress test (extending, adducting, and internally rotating the hip while it is flexed, abducted, and externally rotated, as well as extending, abducting, and externally rotating

the flexed, adducted, and internally rotated hip to as- sess for pain and/or clunk). The impingement test (pas- sive flexion and gradual internal rotation of the ad- ducted hip) will elicit groin pain (Figure 1) that corresponds to labral tears, and a positive impingement test may be seen with femoroacetabular impingement. Log rolling of the lower extremity can be performed to test for intra-articular hip pain. A positive McCarthy sign (with both hips fully flexed, the pain is reproduced by extending the affected hip first in external rotation, then in internal rotation) also corresponds to intra- articular pathology.

Radiographic Evaluation

Plain Radiographs

According to a 2004 study, 87% of patients with labral tears had evidence of osseous abnormalities detected on plain radiographs.1_{An AP pelvic and true (cross table)}

lateral (or Dunn lateral) radiographs of the hip may show evidence of abnormalities in bony contour and shape, such as malunited femoral neck fractures, os- teonecrosis, developmental dysplasia, slipped capital femoral epiphysis, Legg-Calvé-Perthes disease, and fem- oroacetabular impingement (Figure 2). If underlying dysplasia is suspected, a false-profile view should be obtained.

The AP pelvic radiograph allows comparison be- tween both proximal femora. The center edge angle, the acetabular version, the head-neck angle, and the femoral offset all can be measured. Radiographs should be evaluated for joint space narrowing, osteophytes, cysts, erosions, osseous lesions, and calcification. Spe- cific signs such as the figure-of-8 sign or crossover sign indicate excess anterior bony rim and relative retrover- sion of the acetabular roof.2 _{In addition, attention}

should be paid to the head-neck junction, and the ante- rolateral neck should be compared with that of the un- affected side to identify reactive bone changes and bone associated with femoroacetabular impingement(Figure 2, A and B).

Figure 1 The impingement test of the hip is performed with the patient supine. The hip is flexed to 90º, then adducted, and finally internally rotated. A positive test is defined as pain with internal ro- tation in this position.

Figure 2 Bony variants associated with hip pain. A, Radiograph from a 32-year-old woman with right hip pain and evidence of hip dysplasia. B, AP radiograph of the pelvis of a 40-year-old man showing bony changes consistent with com- bined type femoroacetabular impingement. The femoral head-neck junction reveals reduced offset laterally; coxa profunda and a positive crossing sign are seen, findings that are consistent with relative retroversion of the upper acetabulum. C, Radiograph from the same patient with an obvious bump at the anterior femoral head-neck junc- tion, seen with cam impingement.

2: Hip

Lateral radiographs may help determine loss of fem- oral head-neck offset in femoroacetabular impingement and evaluate dysplasia. Plain radiographs will show signs of trauma, including fractures, dislocations, and loose bodies.

Avulsion fractures from the anterosuperior iliac spine, the anteroinferior iliac spine, or the ischial tuberosity may all be seen on plain radiographs. Osteitis pubis has classic radiographic findings of cystic changes and scle- rosis at one or both margins of the pubic symphysis.

Stress fractures can occur as a result of chronic load- ing and high stress to the femoral neck and may lead to serious complications, including complete and dis- placed fracture with possible resultant osteonecrosis of the femoral head. Fractures may be seen on plain radio- graphs; if not, a bone scan or MRI may confirm the presence of fractures. Other stress fractures, including those of the acetabular roof, ischium, sacrum, and pel- vis, may occur about the hip.

To assess trauma about the hip, inlet and outlet views as well as Judet views may be helpful. Additional imag- ing studies may be warranted if intra-articular pathol- ogy or underlying bony impingement or dysplasia are suspected.

Bone Scans

Bone scans are more sensitive than plain radiographs for assessing bony injury and may be positive within 24 hours after injury. Bone scans allow a survey view of the entire pelvis and lower extremities and can be used to determine the presence of fractures, arthritis, neo- plasms, and infections but have a low specificity for intra-articular abnormalities such as loose bodies, la- bral tears, and chondral defects.

Computed Tomography

CT can help delineate the osseous geometry of the hip. After hip dislocation, CT helps define fractures and loose bodies.3 _{CT also can be used for preoperative}

planning for acetabular fractures. In patients with fem- oroacetabular impingement, CT (particularly three-

dimensional CT) can show bony anatomy, including the acetabular version and bony prominence of the an- terior femoral head-neck junction(Figure 3).

Magnetic Resonance Imaging

MRI helps differentiate soft tissue, myotendinous inju- ries, inflammation, synovitis, neoplasms, infections, and stress fractures. Magnetic resonance arthrography detects intra-articular pathology of the hip, such as la- bral tears, chondral injuries, and ligamentum teres. The sensitivity and accuracy of magnetic resonance arthrog- raphy for the diagnosis of a hip labral tear(Figure 4)

may approach 100% and 95%, respectively.4,5_{At some}

institutions, high-contrast imaging has reportedly been achieved without intra-articular contrast agents. MRI has high specificity and sensitivity for labral lesions; chondral softening, chondral delamination, and small defects are less consistently detected by MRI.

Fluoroscopically-Guided Injections

Fluoroscopically-guided intra-articular injection of lo- cal anesthetic as an adjunct to clinical and radiographic examination has been the most highly sensitive indica- tor of an intra-articular abnormality, with a reliability of greater than 90%.6_{This finding has led to the use of}

intra-articular anesthetic along with gadolinium during magnetic resonance arthrography as an adjunctive di- agnostic tool.

Specific Diagnoses of Intra-articular Sources of Hip Pain

The more common sources of intra-articular pain in athletes are labral tears and chondral lesions, which may be seen together in patients with femoroacetabular impingement and/or hip dysplasia, ligamentum teres tears, and loose bodies. Other sources of hip pain in athletes include hip dislocations, more subtle hip insta- bility such as hip subluxation, and adhesive capsulitis.

Figure 3 CT scans of the hip of a 36-year-old man who plays competitive football and has right hip pain and evidence of a superolateral acetabular stress fracture. A, Axial cut CT scan. B and C, Three-dimensional CT reconstructions show- ing mild cam femoroacetabular impingement and clearly demonstrating the fracture fragment.

2: Hip

Femoroacetabular Impingement

Femoroacetabular impingement occurs when there is abnormal abutment between the femur and the acetab- ulum.7_{It has recently received increased attention as a}

structural entity associated with early arthritis of the hip.8 _{Predisposing factors associated with femoroace-}

tabular impingement include altered femoral neck mor- phology (which may be caused by slipped capital fem- oral epiphysis; anteverted femoral neck, femoral neck nonunion, developmental dysplasia of the hip, Legg- Calvé-Perthes disease, osteonecrosis, a pistol grip fem- oral neck, and coxa vara as well as acetabular morpho- logic variants such as a retroverted acetabulum and a deep acetabular socket (coxa profunda and protrusio). Impingement can occur as a result of femoral-sided im- pingement (cam impingement), acetabular rim impinge- ment (pincer impingement), or, most commonly, a com- bination of both. Cam lesions on the femoral head- neck region lead to shear forces of the nonspherical portion of the femoral head against the acetabulum, re- sulting in a characteristic pattern of anterosuperior car-

tilage loss over the femoral head and corresponding dome, as well as labral tears.9 _{Labral tears associated}

with cam impingement are more commonly labral- chondral separation lesions affecting the transition zone cartilage that leave the labral tissue in fairly good condition. The chondral damage tends to begin with softening, followed by debonding and delamination of the articular cartilage from the underlying acetabular bone(Figure 5). These chondral lesions are located in the anterosuperior region of the acetabulum and extend deeper into the acetabulum than chondral lesions be- cause of pincer impingement.

Pincer type lesions result from repetitive contact stresses of a normal femoral neck against an abnormal anterior acetabular rim as a result of overcoverage. This situation results in degeneration, ossification, and tearing of the anterosuperior labrum, as well as the characteristic posteroinferior contrecoup pattern of car- tilage loss over the femoral head and corresponding ac- etabulum.9_{In this setting, the acetabular labrum failure}

leads to degeneration and eventual ossification, which worsens the overcoverage. Overall, the pincer type le- sion has chondral damage that is limited to near the rim but occurs more globally around the circumference of the acetabulum in comparison with the deep chon- dral injury associated with cam impingement.

Patients with femoroacetabular impingement com- monly present with anterior groin pain, and deep hip pain that is worse with hip flexion and internal rota- tion. The typical patient is middle aged and is younger than the typical patient with degenerative joint disease. The typical patient with a cam lesion is a young adult male in his 20s, whereas the typical patient with a pin- cer lesion is an active middle-aged female in her 40s.9

The pain and symptoms usually are related to activity. On physical examination, patients often exhibit de- creased internal rotation and adduction with the hip flexed to 90°. The impingement test is positive, and there is pain with passive adduction and gradual inter- nal rotation of the flexed hip(Figure 1).

Plain radiographs detect pistol grip deformity; flat-

Figure 4 Magnetic resonance arthrography of a labral tear. A, MRI of a 40-year-old woman with evidence of labral chondral separation. B, MRI of a 46-year-old woman with evidence of an intrasubstance labral tear.

Figure 5 Arthroscopic view of chondral delamination, seen with cam femoroacetabular impingement.

2: Hip

tening of the femoral head; synovial herniation pits; and prior deformity of the femoral head, neck, and ac- etabulum in young patients with hip pain. A positive figure-of-8 sign seen on an AP hip radiograph may sug- gest relative acetabular retroversion.2,7_{MRI can show}

anterosuperior labral tears and anterosuperior cartilage defects on the acetabulum. Theα angle is an MRI mea- surement that indicates abnormal offset at the head- neck junction.10 _Normal α angles are less than 50°,

with elevated values leading to increased cartilage and labral pathology consistent with the described mechan- ism of impingement.10,11

Nonsurgical treatment such as anti-inflammatory medications and activity modification may improve hip impingement symptoms, but because the pain is caused by a mechanical block, surgery is likely necessary. Un- less the impingement is caused by an anteverted pelvis (seen with increased lumbar lordosis), physical therapy usually is not beneficial.12 _{When patients have symp-}

toms attributable to an intra-articular source (pain re- lieved with intra-articular anesthetic) and the bony anatomy of impingement, the treatment is usually sur- gical, either arthroscopic or open.

Hip Dysplasia

Hip dysplasia occurs when there is less acetabular bony coverage over the femoral head (Figure 2, C). Often, the acetabular labrum will be hypertrophied to com- pensate for the deficient bony coverage(Figure 6). Con- comitant femoral head enlargement is occasionally present. Although deficient bony coverage of the roof is a common sequelae of congenital hip dislocation, many individuals will function well with a properly reduced hip joint. Some sports activities (such as ballet) select for individuals who have greater hip motion such as that seen in hip dysplasia, where there is reduced bony constraint. However, increased stresses on the labrum may result when there is increased anteroposterior mo- bility of the femoral head within the acetabulum. This abnormal mechanical stress leads to a labral degenera- tion or tearing, resulting in further motion within the joint and edge loading of the acetabulum, resulting in chondral damage and premature arthritis.13 _Further,

lateral subluxation of the femoral head within the ace- tabulum caused by loss of bony constraint also can cause damage to the ligamentum teres. As a result, pa- tients with hip dysplasia more commonly suffer from labral tears, chondral damage, and ligamentum teres hypertrophy, elongation, or tears.

The typical patient is a woman in her 30s or early 40s with hip pain that may worsen with physical activ- ity. The patient often has groin pain or mechanical symptoms. Pain is reproduced with the impingement sign as well as by hyperextending the hip or placing the hip in the FABER (flexion-abduction external rotation) position; the leg is placed in a figure-of-4 position while the patient is supine. There often is increased range of motion of both hips, although the affected hip may have less motion, limited by pain. Plain radiographs

will show the signs of dysplasia, including a reduced center-edge angle and retroversion; CT may help con- firm this. Magnetic resonance arthrography can help identify the labral damage, although coexistent chon- dral damage, beginning at the acetabular rim, is often present but may not be seen on MRI.

Although arthroscopy may detect the damage to the labrum, ligamentum teres, and/or chondral flaps, treat- ment is focused on the bony deficiency, which is cur- rently beyond the realm of arthroscopy. Return to sports participation, especially at the elite level, after surgery for dysplasia is not likely.

Hip Instability

Hip instability is much less common than that of the shoulder. The hip is subject to both traumatic and atraumatic instability. The hip relies less on soft-tissue stability because of the intrinsic stability provided by the bony architecture. Previous hip dislocations lead to capsular laxity of the hip and the possibility of recur- rent hip instability. Traumatic hip instability is typically the result of a posteriorly directed force, such as land- ing on a bent knee or being tackled with the hip and knee flexed. The spectrum of injury ranges from sub- luxation to dislocation with or without concomitant in- juries. Most athletic-related dislocations are posterior, and the classification is the same as with trauma, whether there is an associated fracture or not.

In addition to a standard radiographic workup, the