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Hips

Normal anatomy of the hip joint

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Hip anatomy

   

Arthroscopy of the Hip

Overview

Hip pain in the athletic population is commonly diagnosed as a simple hip sprain or strain. However, the management of hip injuries has evolved substantially with the advancement in diagnostic tools such as magnetic resonance imaging and with new techniques and flexible instrumentation for hip arthroscopy. Hip injuries can be divided into intra-articular (central and peripheral compartment pathology), extra-articular (peritrochanteric space pathology, iliopsoas pathology, and musculotendinous injuries), or central pubic pain associated with athletic pubalgia. The most common cause for disabling intraarticular hip pain in the athletic population is secondary to labral tears. Currently, various hip pathology can be addressed arthroscopically including : labral tears, femoroacetabular impingement, traumatic hip dislocation or subluxation, hip instability, psoas impingement, snapping hip pathology (internal or snapping psoas; external or snapping iliotibial band), removal of loose bodies, cartilage injuries, injuries to the ligamentum teres, benign tumors of the hip joint (synovial chondromatosis, pigmented villonodular synovitis (PVNS), and osteochondroma) and peritrochanteric space pathology (recalcitrant trochanteric bursitis, and gluteus medius and minimus tears).

Treatment of Labral Tears

Injuries to the acetabular labrum are the most consistent pathologic findings identified during hip arthroscopy in athletes. The labrum is a fibrocartilaginous structure that provides some structural resistance to lateral and vertical motion of the femoral head within the acetabulum and has an important sealing function which limits fluid expression from the joint space in order to protect the cartilage layers of the hip. Mechanical symptoms and restricted range of motion are oftentimes present. Pain with hyperflexion, internal rotation and adduction (impingement position) is present in the majority of patients. Labral tears typically are the result of some underlying etiology including: traumatic subluxation or dislocation, atraumatic microinstability or capsular laxity, underlying bony abnormalities such as femoroacetabular impingement or dysplasia, and psoas impingement or symptomatic internal coxa saltans.
Treatment strategies for labral pathology include both labral debridement for irreparable tears, to labral repair for healthy tissue with good healing potential. Vascularity studies have demonstrated that there is a good vascular supply to the labrum stemming from the capsular side, however, the articular portion of the labrum remains largely avascular. With an increased understanding of the function of the labrum and its potential chondroprotective role, newer repair strategies have been described to improve the chance of labral preservation. It has become clear, however, that treatment of labral pathology in isolation, without addressing underlying bony pathology has a greater chance of failure. Arthroscopic treatment of labral tears has been shown to have variable rates of effectiveness, with at least 67%, and as high as 100% of patients satisfied with their outcomes. Satisfied patients have been shown to be able to return to their pre-injury level of athletic competition and have achieved good results by WOMAC or Harris hip scores.

Femoroacetabular Impingement

Femoroacetabular impingement is a well described pathologic condition that has been associated with predisposing factors including slipped capital femoral epiphysis, abnormal extension of the femoral head epiphysis, and acetabular retroversion. Impingement can occur as a result of femoral sided impingement (Cam impingement), acetabular rim impingement (pincer impingement), or a combination of both which is the case in the majority of patients. Cam lesions on the femoral head lead to shear forces of the nonspherical portion of the femoral head against the acetabulum resulting in a characteristic pattern of anterosuperior cartilage loss over the femoral head and corresponding dome, as well as labral tears. Labral tears associated with cam impingement are more commonly type 1 tears affecting the transition zone cartilage and leaving the labral tissue in fairly good condition.

The second category of femoroacetabular impingement is the "pincer" type lesion which is a result of repetitive contact stresses of a normal femoral neck against an abnormal anterior acetabular rim as a result of "over coverage". This situation results in degeneration, ossification and tears of the anterosuperior labrum, as well as the characteristic posteroinferior "contre-coup" pattern of cartilage loss over the femoral head and corresponding acetabulum. In this setting, the acetabular labrum fails first which leads to degeneration and eventual ossification, which worsens the over coverage (Type 2 tear). Overall, the pincer type lesion has limited chondral damage compared to the deep chondral inury associated with cam impingement.

Athletes with femoroacetabular impingement usually present with anterior groin pain exacerbated by hip flexion, internal rotation, and adduction, and physical examination reveals the "impingement sign." MRI usually demonstrates an anterosuperior labral tear, and an anterosuperior cartilage defect on the acetabulum. The alpha angle has been described as a radiographic and MRI measurement that indicates abnormal offset at the head neck junction. Normal alpha angles are less than 50 degrees with elevated values leading to increased cartilage and labral pathology consistent with the described mechanism of impingement. Rim impingement or pincer impingement can be seen on the anteroposterior pelvis plain radiograph as a "figure-of-eight sign" where the anterior wall of the acetabulum is lateral to the posterior wall suggestive of acetabular retroversion.

The surgical goal of decompression of the femoral-head neck junction (Cam decompression) is restoration of the normal head neck junction offset and clearance of the femoral head within the acetabulum with full flexion and rotation. At the completion of the bone resection, all bone debris is removed from the peripheral compartment, and dynamic arthroscopy is performed to confirm the absence of any residual impingement. A resection of less than 30% of the head neck junction is recommended because this has shown to preserve the load bearing capacity of the femoral neck.

Anterior overcoverage secondary to a pincer lesion can also be treated arthroscopically. This can be performed in either the central compartment or the peripheral compartment. First, the margins of the pincer lesion have to be defined by probing with a flexible instrument. This lesion is usually associated with a flattened, degenerative or cystic labrum. Pathologic pincer lesions require bony resection which can be performed using a motorized burr. Resection of the rim lesion oftentimes leads to destabilization or requires detachment of the labrum in order to fully visualize the pathology. Fluoroscopy can be used during this portion of the procedure to confirm reestablishment of the normal relationship between the anterior and posterior walls of the acetabulum. Following the rim resection, unstable but healthy residual labral tissue should be refixed to the acetabular rim using arthroscopic suture anchoring techniques.
Good results have been reported in the literature for patients treated arthroscopically for labral tears and associated femoroacetabular impingement, with as high as 93% of patients able to return to sports and 78% able to remain active at 1.5 years after surgery. While some studies suggest that patients with associated chondral lesions fair worse than patients with isolated labral tears, larger series have been unable to detect a correlation between chondral injury and clinical outcomes. Although the current volume and quality of outcomes literature is insufficient to conclude superior short-term outcomes when both the labral tear and underlying impingement were surgically addressed compared to treatment of the labral tear alone, reports on revision hip arthroscopy have demonstrated that the highest failure rates are associated with patients who have residual unaddressed bony impingement pathology.

Hip Dislocations and Subluxations

Athletes subject their hip to significant loads and can develop labral pathology as a result of both traumatic and atraumatic hip instability. The location of the labral pathology may be different than the most common anterosuperior location seen in the setting of impingement and dysplasia. Traumatic hip instability is typically the result of a posteriorly directed force and ranges from subluxation to dislocation with or without concomitant injuries. In addition to standard radiographic workup, the evaluation should include an MRI that may demonstrate the characteristic triad of findings described by Moorman et al: a hemarthrosis, a posterior acetabular lip fracture or posterior labral tear, and an iliofemoral ligament disruption. Anterior labral pathology is oftentimes present as well, and may represent a traumatic avulsion of the labrum or indicate the presence of some underlying bony impingement. The presence of a significant hemarthrosis may warrant aspiration under fluoroscopy to decrease intracapsular pressure. An MRI is also useful to detect AVN and help determine which patients may return safely to sports activity.

Hip subluxations and dislocations have been described in a variety of sporting activities including: American football, rugby, skiing, jogging, basketball, soccer, biking, and gymnastics. Most hip dislocations sustained during athletics are pure dislocations and, due to the relatively low energy mechanism, usually have no associated fractures or small acetabular rim fractures. Thus, surgical stabilization is often not warranted and active and passive range of motion can begin as soon as tolerated by the patient. Hip subluxation may be more subtle in its presentation and has been described with both contact injuries (fall on a flexed knee) as well as non-contact injuries while running with sudden changes in direction. Hip arthroscopy may play a role after both dislocation and subluxation to address femoral head pathology, loose bodies, chondral injuries and associated labral pathology. The optimal timing of the procedure is debatable due to the concern of placing a hip in traction in the acute phase of injury. If a loose body is not present, hip arthroscopy should be delayed for at least 6 weeks so that a repeat MRI can be performed to rule out the presence of early AVN before placing the hip in traction. However, if a significant loose body is present, hip arthroscopy is an option and may decrease the incidence of posttraumatic arthritis secondary to third body wear.

instaHip Instability

Atraumatic instability is a spectrum ranging from overuse injuries leading to microinstability to patients with generalized ligamentous laxity. Overuse injuries are common in athletes who particicpate in sports involving repetitive hip rotation with axial loading (i.e. golf, figure skating, football, baseball, ballet, martial arts, gymnastics, etc). The labrum or iliofemoral ligament may be damaged from these repetitive forces. These abnormal forces cause increased tension in the joint capsule which can lead to painful labral injury, capsular redundancy, and subsequent microinstability. The hip must rely more on the dynamic stabilizers for stability once the static stabilizers of the hip such as the iliofemoral ligament or labrum are injured. The spectrum of atraumatic instability also includes patients with hip pain secondary to more generalized ligamentous lxity, or, in the extreme form, in patients with connective tissue disorders such as Ehlers-Danlos syndrome or Marfan syndrome.

Psoas Impingement

Labral tears typically occur anterosuperiorly in association with femoroacetabular impingement or dysplasia. Less commonly, labral pathology may occur in an atypical direct anterior location in the absence of bony abnormalities. This direct anterior injury may be related to compression of the anterior capsule-labral complex by the psoas tendon as it crosses the anterior acetabular rim and results in a unique constellation of intra-articular findings reproducibly demonstrated at the time of arthroscopy. Arthroscopic findings are most notable for the intimate relationship between the labral pathology (inflamed labrum, or frank tear with mucoid degeneration) and the iliopsoas tendon, which lies directly anterior to the labral abnormality and sometimes is adherent or scarred to the anterior capsule. Torn labra can either be debrided or reattached to the acetabular rim depending on the pattern of the tear. Labral debridement or repair combined with lengthening of the iliopsoas has led to subjective improvement in symptoms and may be a logical treatment option for these patients.

Snapping Hip - Internal

Symptomatic internal snapping hip has been well described in the literature and is most commonly associated with painful displacement of the iliopsoas tendon over the iliopectineal eminence or over the femoral head. A variety of both open and arthroscopic techniques have been described for surgical release of a symptomatic painful snap.
Three different arthroscopic techniques have been described: 1. direct detachment of the tendon off of the lesser trochanter; 2. release of the tendon in the peripheral compartment; 3. release of the tendon in the central compartment. All three have been shown to be effective at eliminating the symptomatic snapping, however, release directly off of the lesser trochanter has resulted in some cases of the development of heterotopic ossification that has required subsequent excision.

Snapping Hip - External

External coxa saltans results from a thickened band of the posterior iliotibial band or anterior gluteus maximus tendon sliding over the greater trochanter. With the hip extended this band lies posterior to the greater trochanter, and during hip flexion this band slides anteriorly over it. Due to the tight attachments of the tensor fasica lata anteriorly, the gluteus maximus posteriorly, and association with aponeurosis of the gluteus medius, the iliotibial band remains tightly draped over the greater trochanter throughout hip range of motion. Any irritation or injury to the underlying bursa results in inflammation and the addition of pain with the snapping.

Diagnosis is confirmed by history, physical examination, and dynamic ultrasound displaying real time images of the iliotibial band snapping over the greater trochanter. Although conservative treatment is usually successful, small numbers of patients remain symptomatic. A variety of different open treatments for recalcitrant external coxa saltans have been described involving excision of an ellipsoid-shaped portion of the iliotibial band overlying the greater trochanter and removal of the trochanteric bursa. Endoscopic techniques are gaining in popularity and have demonstrated similar positive outcomes to the open surgical approaches.

Removal of Loose Bodies

Hip arthroscopy is ideally suited for the removal of loose bodies. Loose bodies may or may not be ossified, and are readily identified by radiographic studies only when calcium is present. If not evident on plain films, CT scans are highly sensitive for visualization; intraarticular fragments may be obscured with MR imaging. Symptoms are oftentimes described as mechanical locking or catching. When persistent symptoms are present even in the absence of clear evidence of ossified loose bodies, arthroscopy is a way to confirm the diagnosis suggested by clinical examination as well as provide simultaneous treatment with minimal associated morbidity.

Loose bodies may occur as an isolated fragment, such as after dislocation or with osteochondritis dissecans, or as multiple bodies or clusters such as is seen in synovial chondromatosis. In cases of multiple bodies, it is essential to fully explore the joint and be sure to remove all fragments. Often multiple bodies associated with synovial chondromatosis adhere to the synovium around the fovea and must be morsellized prior to removal by arthroscopy.

Cartilage Injury

Within the discipline of sports medicine, articular cartilage injuries in the hip have received considerably less attention than other joints, largely due to the difficulty that practitioners have had with accurate assessment. Non-arthritic cartilage injuries in the hip refer to focal chondral defects on either the femoral or acetabular side of the joint. Focal chondral defects on the femoral side are relatively uncommon, however, may result from axial loading, or shear injury of the head within the socket. Hip subluxation and dislocation oftentimes will result in a shear injury to the cartilage surfaces of the femoral head. These cartilage injuries may be treated with arthroscopic techniques to stabilize loose cartilage flaps and microfracture areas of exposed bone particularly if the injury is not in a weight-bearing zone. If the injury is in the weight-bearing zone of the femoral head, consideration should be given to cartilage transplant procedures which need to be performed as open procedures in the majority of cases. Byrd has described a more common mechanism of chondral injury to the femoral head with a direct blow to the greater trochanter, as can occur as the result of a fall or collision. This so-called "lateral impact mechanism" can result in an area of full-thickness articular cartilage loss caused by either shear or compressive forces on the medial aspect of the femoral head or chondronecrosis in the superomedial weight-bearing portion of the acetabulum. Similar arthroscopic or open surgical approaches can be used to address these chondral injuries.

Cartilage injuries on the acetabular side are more common and typically present as localized cartilage delamination
in the anterosuperior weight-bearing zone of the acetabular rim. The most common underlying condition resulting in these types of cartilage defects is femoroacetabular impingement which leads to damage of the transition zone cartilage with extension over time into the articular cartilage of the acetabulum due to Cam lesions entering the hip joint during flexion and rotation. These cartilage lesions may be treated with simple debridement to stabilize cartilage flaps, abrasion chondroplasty, or microfracture. Currently there are no studies to provide any long term data on the utility of any of these techniques.

Injuries to the Ligamentum Teres

The function of the ligamentum teres remains unclear. The presence of arteries around the ligamentum suggests a role in providing a blood supply to the developing hip. In addition, it has been suggested that this ligament plays a biomechanical role that contributes significantly to the stabilization of the hip. Analysis of the material properties of this ligament has demonstrated similarities to other ligaments and confirms its ability to resist dislocation forces applied to the femoral head. Patients suffering from ligamentum rupture as a result of trauma or dislocation will oftentimes suffer from symptoms of instability and pain.

Although some authors have reported a low incidence of ligamentum teres ruptures seen at arthroscopy, Byrd found these lesions to be the third most common problem encountered among athletes undergoing hip arthroscopy. Acute disruptions of the ligamentum are thought to occur as a result of exaggerated movements of adduction and external rotation, although hip abduction is oftentimes the injury mechanism described with patient history. Diagnosis of these injuries can be difficult and a high index of suspicion with careful attention to the injury mechanism and the physical examination are critical to accurate evaluation.

Ligamentum teres injuries in high impact sports such as football may lead to recurrent subluxation of the hip. The high incidence of degenerative arthritis associated with complete ligamentum teres ruptures has been attributed to the original injury in many cases, however, recurrent instability and subluxation episodes may cause repetitive injury to the femoral head and account for an increased incidence of AVN in these patients. Arthroscopy of persistently symptomatic lesions can clearly demonstrate ligamentum teres pathology, and athletes have been found to respond well to arthroscopic debridement of the disrupted and entrapped fibers.

Benign Tumors of the Hip Joint

Benign tumors of the hip joint can be the source of recalcitrant hip pain, and include disorders such as synovial chondromatosis, pigmented villonodular synovitis (PVNS), and osteochondroma. Synovial chondromatosis results in multiple loose bodies within the space between the femoral head and the acetabulum. Pigmented villonodular synovitis (PVNS) is a benign tumor of the inner lining of the joint capsule known as the synovium. It can be in a nodular or diffuse form. Osteochondromas are bony outgrowths that can occur anywhere throughout the body. When they occur within the hip joint, they can cause abrasive irritation of the cartilage surfaces within the joint.

Peritrochanteric Space

Disorders of the lateral or peri-trochanteric space, previously grouped into the "greater trochanteric pain syndrome", can now be addressed endoscopically. Recalcitrant trochanteric bursitis, and gluteus medius and minimus tears are entities that can effectively be treated within the lateral compartment of the hip.

Recalcitrant Trochanteric Bursitis

Trochanteric bursitis is characterized by chronic, intermittent aching pain over the lateral aspect of the hip. The diagnosis can typically be confirmed with accurate history and physical exam. Magnetic resonance imaging, although not necessary to make the diagnosis, may reveal increased signal intensity of the trochanteric bursa on T2 weighted images. Conservative treatment is the mainstay of therapy with physical therapy and the judicious use of a combined corticosteroid and local anesthetic preparation for diagnostic and therapeutic purposes. Numerous open surgical procedures have been described for failure of conservative treatment, and there is a growing interest in arthroscopic (or endoscopic) bursectomy in the treatment of trochanteric bursitis.

Gluteus Medius and Minimus Tears

Traditionally, greater trochanteric pain syndrome has been described as inflammation of the trochanteric bursae that lies predominantly over the posterior facet of the trochanter. There is increasing evidence to suggest that persistent pain and weakness in this region may, in fact, result from primary deficiencies in the tendon attachments of the gluteus medius and / or minimus. Tears of the gluteus medius and minimus tendons share similarities to tears of the rotator cuff tendons in the shoulder. As with cuff tears in the shoulder, it has been hypothesized that these "rotator cuff tears" of the hip are attritional injuries associated with increasing age. Physical examination reveals a slight trendelenberg gait, pain, and weakness with resisted abduction of the hip when compared to the contralateral extremity. The combination of abductor weakness, persistence of symptoms after conservative treatment and positive magnetic resonance imaging studies, showing increased signal in the tendon, confirm the diagnosis of abductor tears.

Summary

Sports-related hip pathology has gained increased recognition as a more complete understanding of the wide variety of intra and extra articular hip conditions has evolved. Currently the role of hip arthroscopy in the management of intra-articular injuries allows for reproducible surgical treatments for athletes who have failed conservative measures. Appropriate indications for hip arthroscopy include management of central compartment pathology involving the labrum, chondral surfaces, ligamentum teres, capsular tissue, and centrally located loose bodies. Peripheral compartment arthroscopy is effective for treatment of peripheral loose bodies, displaced labral flaps, and treatment of both cam and rim impingement lesions associated with femoroacetabular impingement. Pathologic conditions of the iliopsoas tendon can be addressed via the central or peripheral compartment. The peritrochanteric space or lateral compartment of the hip can be accessed endoscopically for effective treatment of recalcitrant cases of trochanteric bursitis, external snapping hip, and symptomatic abductor tendon tears.

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