J. W. Thomas Byrd and MaCalus V. Hogan
DEFINITION
Soft tissue pathology of the hip includes labral tears, articular damage, and lesions of the ligamentum teres, all of which share several common features.
The clinical presentations may be indistinguishable, and these lesions often coexist. They represent significant causes of disabling hip pain that can be elusive to clinical detection.
The diagnosis sometimes is based just on maintaining an index of suspicion. Often these lesions have gone undiagnosed and untreated, with the patient simply resigned to living within the constraints of their symptoms.
ANATOMY
The horseshoe or lunate articular surface of the acetabulum surrounds the acetabular fossa (FIG 1).
The articular surface of the femoral head forms about two thirds of the sphere, with an indentation medially where the ligamentum teres attaches at the fovea capitis.
The diameter of the femoral neck normally is 65% of the diameter of the femoral head, allowing clearance of the acetabulum during range of motion (ROM).
The fibrocartilaginous labrum is triangular in cross section, forming a rim around the articular surface of the acetabulum.
Inferiorly, it is contiguous with the transverse acetabular ligament, which traverses the inferior aspect of the fossa. Its morphology and size can be quite variable, especially anterior and superior.
The shape of the posterior labrum is the most consistent and least often damaged landmark, representing a useful reference in the arthroscopic assessment of labral pathology.
Unlike the shoulder, there is no capsulolabral complex; the capsule attaches directly to the acetabulum separate from the labrum. Thus, acetabular labral pathology is not as synonymous with instability as that of the glenoid.
Konrath et al17 have shown that the labrum has minimal mechanical properties for distributing forces across the acetabular surface. Similarly, Ferguson13 has demonstrated that the labrum has minimal mechanical properties for stabilizing the joint, but its hydraulic seal is important.
The ligamentum teres has a serpentine course from its acetabular attachment in the posterior fossa to the fovea capitis of the femoral head. Its precise function remains an enigma.
FIG 1 • Macroscopic anatomy of the hip joint. (Courtesy of Delilah Cohn.)
In childhood, its vessel contributes to the blood supply of the femoral head. Its redundant nature implies that it contributes little to joint stability, but it may have nociceptive and proprioceptive functions.
Gray and Villar15 have postulated that its windshield wiper effect during ROM may facilitate joint lubrication. Its dimensions are variable, and sometimes it is absent in adulthood.
PATHOGENESIS
The etiologies of soft tissue lesions in the hip are numerous and variable. Breakdown may result from supraphysiologic loads on normal tissue, physiologic loads on abnormal tissue, or, commonly, mildly supraphysiologic loads on mildly abnormal tissue.
Supraphysiologic loads may be the result of macrotrauma or repetitive microtrauma.
Athletes are especially prone to pushing their bodies beyond the physiologic limits where breakdown occurs.
Once this point has been passed, reversal of the damage often is incomplete, even with surgical intervention. Variable joint morphology often is a contributing factor.
Labral tears can occur from compression, commonly associated with impingement; traction associated with excessive translation of the femoral head; and shear forces, typically associated with acetabular dysplasia.
Articular damage can be caused by acute trauma or degenerative disease. A propensity for acute articular fracture has been identified in physically fit young men, resulting from a direct lateral blow to the trochanter.2
There is little adipose tissue over the trochanter to cushion the blow; and with high bone density fracture does not occur, so the force is delivered directly to the joint surface.
Lesions of the ligamentum teres can occur from acute trauma or degeneration.
The ligament is most taut with adduction and external rotation, but acute rupture has been identified with a variety of mechanisms.
Deterioration of the ligament occurs with degenerative disease, and the ligament is sometimes hypertrophied, making it more susceptible to degenerate rupture.
Femoroacetabular impingement (both pincer and cam type) has been recognized as a causative factor in the development of soft tissue joint damage.14 It is the soft tissue damage that then becomes symptomatic, necessitating treatment.
Pincer impingement is associated primarily with labral pathology due to excessive compression and then secondary development of articular breakdown (FIG 2A).
Cam impingement is associated with selective articular delamination of the anterolateral acetabulum with a variable amount of associated labral pathology (FIG 2B).
Dysplasia is associated with breakdown of the labrum, articular surface, and ligamentum teres.4
The labrum often is enlarged, with more weight-bearing responsibility, making it susceptible to a breakdown from shear forces. It also can become inverted within the joint and susceptible to deterioration.
The reduced surface area of the acetabulum results in increased contact forces, which may exceed the structural integrity of the articular cartilage.
Hypertrophy of the ligamentum teres occurs in association with dysplasia, and the hypertrophied ligament is more susceptible to degenerative rupture.
NATURAL HISTORY
The natural history of these soft tissue lesions is variable. Some conditions deteriorate quickly, whereas others may remain stable for a protracted period of time, and some become asymptomatic.
FIG 2 • A. Pincer impingement: mechanism of labral breakdown. B. Cam impingement: mechanism of articular delamination.
Labral degeneration has been observed as an unavoidable consequence of age and is found to be uniformly present in persons over 70 years of age.18
Abnormal hip morphology, including impingement and dysplasia, may be found even in absence of joint pathology.
When symptomatic soft tissue pathology occurs, it is important to assess for predisposing morphology. Some conditions may remain stable for an indefinite period; however, progressive worsening of symptoms usually dictates more proactive intervention.
PATIENT HISTORY AND PHYSICAL FINDINGS
Examination of the hip joint is fairly straightforward.3 Much of the assessment revolves around ruling out other problems.
Patients with chronic hip joint pathology will start to develop other conditions secondarily as they compensate for the joint.
The secondary conditions, such as gluteal pain or trochanteric bursitis, may be more evident, obscuring the underlying diagnosis. In addition, other conditions such as lumbar spine disease may coexist with hip joint disease.
There is a significant correlation between hip joint pathology and athletic pubalgia in athletes.
Increased pelvic motion compensates for restricted hip motion, placing more stress on the pelvic stabilizers and resulting in the soft tissue breakdown characterized by athletic pubalgia.
The history of injury is variable, with some patients describing a major traumatic event. Others may recount an acute episode such as twisting. In these circumstances, however, the clinician should look closely for predisposing factors, because a healthy joint should be able to withstand these forces.
Some patients simply describe the insidious or gradual onset of symptoms, further indicative of underlying disease.
A history of a significant traumatic event indicates a more favorable prognosis of a potentially correctable problem.
Similarly, mechanical symptoms such as sharp stabbing pain, catching, or locking are favorable indicators for surgical intervention.
Simply having pain, with or without activity, is a poorer prognostic indicator for the success of arthroscopy.
Numerous characteristic features of hip joint symptoms have been identified.3
Straight plane activities, including running, often are well tolerated.
Pivoting and twisting maneuvers usually are more troublesome.
Squatting and prolonged hip flexion such as sitting often will exacerbate hip symptoms.
Patients may experience a catching sensation when rising from a seated position.
Ascending and descending stairs or inclines is more troublesome than walking on level surfaces.
Entering and exiting an automobile is very characteristic for recreating symptoms, because it loads the hip in a flexed position while introducing a torsional component.
Dyspareunia due to hip pain is uniformly present in sexually active individuals.
Difficulty getting shoes and socks on and off usually indicates restricted motion and more advanced disease.
Localization of the symptoms starts with an understanding that the L3 nerve root serves as the principal innervation of the hip.
Symptoms, therefore, are sometimes referred to the L3 dermatome, explaining the presence of medial-sided thigh and knee pain.
The C-sign is very characteristic of hip joint pathology.
Describing their symptoms, patients will cup their hand in the shape of a C above the greater trochanter, gripping their fingers into the groin.
Most patients describe groin or anterolateral pain.
Posterior pain rarely is indicative of hip joint pathology, but may occasionally be a presenting feature.
It is important to record ROM in a consistent fashion for comparing sides as well as for comparison on subsequent examination.
Recording flexion and extension must take into account the contributing components of pelvic and lumbar motion. Rotational motion is different when measured in extension versus flexion.
The log roll test is the most specific test for hip joint pathology:
The leg is rolled back and forth, rotating only the femoral head in relation to the acetabulum and capsule, without tensioning any of the surrounding soft tissue structures.
The impingement test generally has been found positive for virtually any irritable hip joint, regardless of the nature of the pathology.
The leg is placed in maximal flexion, adduction, and internal rotation.
This maneuver is more sensitive for hip joint pathology, but may be uncomfortable even in a healthy hip. Thus, it is important to compare the symptomatic to the asymptomatic side.
It also is important to distinguish whether this test recreates the type of symptoms that the patient experiences with activity, more than simply whether or not it is uncomfortable.
Abduction with external rotation also can be sensitive for eliciting hip joint symptoms.
It may impinge upon posterior lesions or exacerbate anterior symptoms from translation of the femoral head and, thus, is not especially specific for the location or type of intraarticular pathology.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs are important for assessing hip morphology.
A properly centered anteroposterior pelvis radiograph is essential for assessing the morphology of the hip and comparing the affected to the unaffected side (FIG 3).
The optimal lateral view has yet to be determined, but a standardized reproducible lateral radiograph of the affected hip should be obtained in every case.
Radiographs usually are normal with regard to specific findings indicative of soft tissue pathology in the hip.
The soft tissue disease usually is far advanced before any radiographic indices emerge.
Thus, it is important to scrutinize the radiographs carefully, assessing for subtle indicators of change.
For example, slight joint space narrowing usually indicates advanced intra-articular disease, and should be viewed as a cautious indicator in counseling patients on the role of arthoscopy.
FIG 3 • An AP radiograph allows comparison of the affected and unaffected hips as well as an assessment of the surrounding bony architecture. It must be properly centered without rotation to assess the radiographic indices of hip morphology accurately. (Courtesy of J. W. Thomas Byrd, MD.)
MRI can be useful for the evaluation of hip pathology.
Low-resolution studies (eg, open magnets and small scanners) are unreliable at detecting hip joint pathology.
High-resolution scans (eg, 1.5-Tesla magnet, surface coils) are superior but still present limitations.5
They are best at detecting labral pathology but generally poor at assessing the articular surface or the status of the ligamentum teres.
Caution is necessary in assessing labral lesions, because these have been identified in studies of asymptomatic volunteers and occur uniformly as a consequence of age.
Indirect findings often are the most reliable.
Evidence of an effusion in a symptomatic hip is highly indicative of joint pathology.
Paralabral cysts are pathognomonic of labral damage and subchondral cysts are indicative of associated articular damage.
Gadolinium arthrography with MRI (MRA) has a greater sensitivity than MRI, but introduces some risk of overinterpreting pathology.5
A particular challenge is differentiating a labral tear from a normal labral cleft.
Assessment of the patient's symptomatic response to the anesthetic effect of an intra-articular injection is the most reliable diagnostic feature.
The intra-articular injection always should include a long-acting anesthetic (eg, bupivacaine).
However, this evaluation depends on the patient being able to perform activities that recreate pain prior to injection so that the same activities can be recreated postinjection to assess the amount of pain relief.
CT can be superior to MRI for assessing bony architecture.
Three-dimensional reconstructions are especially useful in assessing cam impingement.
Bone scans are relatively inexpensive, provide a good skeletal survey tool, and can be helpful in assessing osseous homeostasis around the hip.
DIFFERENTIAL DIAGNOSIS
Hip flexor or adductor strain
Hernia
Athletic pubalgia
Nerve entrapment
Upper lumbar disc
Referred from visceral origin (eg, gastrointestinal, genitourinary, gynecologic)
NONOPERATIVE MANAGEMENT
Nonoperative management begins with informing the patient on the nature of the disorder; and education regarding warning signs of progressive damage, especially worsening symptoms.
Activity modification often is necessary to modulate associated discomfort. This may be temporary while managing the acute phase of an injury, or may be long-term for patients coping with a chronic process.
Distraction mobilization techniques may reduce discomfort and improve function while optimizing ROM.
Closed-chain stabilization exercises usually are well tolerated and help to protect the joint.
Trunk and core strengthening are integral to functional recovery.
SURGICAL MANAGEMENT
Surgical intervention is indicated for mechanical symptoms in the presence of clinically suspected joint pathology.
Conservative treatment may be appropriate for stable, manageable symptoms. A more proactive approach may be indicated if the symptoms are not manageable or demonstrate progressive worsening with time.
In selecting patients for surgical management, the most important assessment tools are the history and physical examination.5
Imaging studies are helpful only when interpreted in the context of the overall clinical evaluation.
The surgeon should not be lured by false-positive interpretations or dissuaded by false-negative results.
Preoperative Planning
Numerous intra-articular hip lesions may have similar clinical presentations.
Imaging studies may only partly reflect the extent of pathology.
Recent radiographs should be available for review in addition to any other tests that have been performed.
Radiographic evidence of joint deterioration can occur within a few months; thus, old radiographs are not useful.
Findings of progressive joint space loss may contraindicate a planned arthroscopic procedure.
The patient must be properly informed regarding the suspected nature of the joint pathology and also any comorbid conditions that will not be addressed by the procedure.
The patient should have reasonable expectations of what can be accomplished and the uncertainty regarding what associated pathology may be encountered.
Positioning
Arthroscopy of the intra-articular (“central”) compartment of the hip requires distraction.
FIG 4 • A. The patient is positioned on the fracture table so that the perineal post is placed as far laterally as possible toward the surgical hip resting against the medial thigh. B. The optimal vector for distraction is oblique relative to the axis of the body and coincides more closely with the axis of the femoral neck than the femoral shaft. This oblique vector is created partially by abduction of the hip and accentuated by a small transverse component to the vector created by lateralizing the perineal post. C. The surgical area remains covered in sterile drapes while the traction is then released and the hip flexed 45 degrees. The figure shows the position of the hip without the overlying drape. (A:Reprinted with permission from The supine approach. In: Byrd JWT, ed. Operative Hip Arthroscopy, ed 2. New York: Springer, 2005:145–169; B: Courtesy of Delilah Cohn; C: Courtesy of J. W. Thomas Byrd, MD.)
Proper positioning is essential to the safety and efficacy of the procedure.
A well-padded perineal post should be secured against the ischium but lateralized against the medial thigh (FIG 4A).
This keeps the post away from the pudendal nerve and aids in achieving the optimal vector for distraction.
Applying slight counter-traction to the nonoperative leg stabilizes the pelvis and keeps the post from shifting as traction is then applied to the operative leg.
The amount of abduction of the operative leg can be variable.
Less abduction may be necessary with a varus hip to make it possible to introduce the cannulas above the trochanter but enter the joint underneath the lateral lip of the acetabulum.
Neutral rotation during portal placement maintains a consistent relationship between the greater trochanter and the joint.
Slight flexion (10 degrees) relaxes the capsule and may facilitate distraction (FIG 4B).
Excessive flexion should be avoided, because it can place tension on the sciatic nerve and reduce anterior access to the joint.
Most standard fracture tables can accomplish the positioning necessary for hip arthroscopy.
Specialized positioning devices are more practical for ambulatory surgery centers. These are more affordable and transportable, adapting to standard OR tables.
Arthroscopy of the peripheral compartment is performed with traction released and hip flexed (FIG 4C).
Traction is released only after the instruments have been removed from the central compartment.
Flexion relaxes the capsule, opening the space within the periphery.
Approach
For the intra-articular (“central”) compartment, three standard portals (anterior, anterolateral, and posterolateral) allow access for virtually all procedures (FIG 5A,B).10
The lateral two portals usually are the easiest to position, but the anterior portal provides the greatest versatility and access to the medial joint space.
Eighty percent of the intra-articular pathology resides in the anterior half of the hip and is accessible from the two anteriormost portals.
However, the posterolateral portal is important for routine inspection of the posterior recesses as well as access for posteriorly based lesions and the acetabular fossa.
Two portals usually are sufficient for the peripheral compartment, but the positioning is widely variable, depending on the nature and location of the pathology to be addressed (FIG 5C,D).
FIG 5 • A. The site of the anterior portal coincides with the intersection of a sagittal line drawn distally from the anterior superior iliac spine and a transverse line across the superior margin of the greater trochanter. The direction of this portal courses approximately 45 degrees cephalad and 30 degrees toward the midline. The anteroand posterolateral portals are positioned directly over the superior aspect of the trochanter at its anterior and posterior borders. B.The relation of the major neurovascular structures to the three standard portals is demonstrated. The femoral artery and nerve lie well medial to the anterior portal. The sciatic nerve lies posterior to the posterolateral portal. Small branches of the lateral femoral cutaneous nerve lie close to the anterior portal. Injury to these is avoided by using proper technique in portal placement. The anterolateral portal is established first, because it lies most centrally in the safe zone for arthroscopy. C. From the anterolateral entry site, the arthroscope cannula is redirected over the guidewire through the anterior capsule, onto the neck of the femur. D. With the arthroscope in place, prepositioning is performed with a spinal needle for placement of an ancillary portal distally. (A,B:Courtesy of Delilah Cohn.)
LABRAL DÉBRIDEMENT
Most symptomatic labral tears are managed with selective débridement of the damaged portion (TECH FIG 1).
Emphasis is given to preserving healthy tissue, because removal of normal labrum can lead to poorer results.
A complete joint survey is performed with thorough inspection and palpation of the labrum, identifying its damaged portion.
Most labral resection is carried out with a power shaver, debulking the damaged tissue.
Hand instruments and an arthroscopic knife may aid in this resection.
It is important to preserve the healthy tissue but create a stable transition zone when completing the débridement.
A radiofrequency device is especially useful for this because of the limited maneuverability imposed by the architecture of the joint.
Diseased tissue has an increased water content and responds selectively to the thermal device.
TECH FIG 1 • Arthroscopic view of a right hip from the anterior portal. A. A fragmented labral tear with degeneration within its substance is identified. B. Débridement is initiated with the power shaver. C.A portion of the comminuted labral tear is conservatively stabilized with a radiofrequency probe. D. The damaged portion has been removed, preserving the healthy substance of the labrum.
LABRAL REPAIR
Labral repair is best suited for young patients when it is believed that simple débridement may result in inordinate sacrifice of healthy tissue (TECH FIG 2).
An optimal pattern is a tear at the articulolabral junction where a large segment of otherwise healthy tissue has been detached.
Labral function is most dependent on its fluid seal.2 Thus, the goal of repair is to reapproximate the labrum to the adjacent acetabulum.
The mechanical properties of the labrum are minimal; therefore, the recreation of a bolster effect such as that in the shoulder is not necessary.
TECH FIG 2 • A. Sagittal MRA image demonstrates an anterior labral tear (arrow). B. Arthroscopy reveals a traumatic detachment of the anterior labrum (indicated by the probe). C. An anchor has been placed with suture limbs passed in a mattress fashion through the detached labrum. D. The labrum has been reapproximated to the articular edge. E. Viewing the peripheral aspect of the labrum, the suture is seen on its capsular surface, avoiding contact with the articular surface of the femoral head. (Courtesy of J. W. Thomas Byrd, MD.)
An anchor should be placed adjacent to the articular edge; it is not necessary for it to be placed on its surface.
The angle created by the articular surface and the bony edge of the acetabulum is more acute than its counterpart in the shoulder, which is created by the articular surface and bony face of the glenoid.
Thus, the direction of anchor entry is more critical, especially to avoid perforation of the articular cartilage. This direction is dictated by the position of the cannula.
The standard portal placements lend themselves well to anchor placement, but if the direction of entry does not seem appropriate, it is best to simply establish another portal with the proper angle for anchor entry.
The anchor is seated adjacent to the articular surface, between it and the detached labrum.
Passage of the suture limbs through the detached labrum can then be accomplished with various suturepassing devices.
It is important that the sutures not be left interposed between the labrum and the articular surface of the femoral head, because this can result in third-body wear on the articular cartilage.
Passing the sutures in a mattress fashion accomplishes reapproximation of the labrum, recreating the seal and avoiding interposed suture in the joint.
CHONDROPLASTY
Chondroplasty of unstable articular fragments is performed in the hip, just as in other joints.
Technical challenges are imposed by the limited instrument maneuverability.
Curved shaver blades aid in navigating the constrained joint architecture (TECH FIG 3A–C).
Radiofrequency devices can further assist in ablating damaged tissue, even within the constraints of the joint. Judicious use is imperative to avoid thermal injury.
Like other joints, microfracture of select grade IV lesions can be performed (TECH FIG 3D–G).
Microfracture is indicated primarily for discrete lesions with healthy surrounding articular surface.
TECH FIG 3 • A. Coronal MRI demonstrates evidence of labral pathology (arrow). B. Arthroscopy reveals extensive tearing of the anterior labrum (*) as well as an adjoining area of grade III articular fragmentation (arrows). C. The labral tear has been resected to a stable rim (arrows), and chondroplasty of the grade III articular damage (*) is being performed. D. Coronal MRI demonstrates evidence of labral pathology (arrow). E.Arthroscopy reveals the labral tear (arrows), but also an area of adjoining grade IV articular loss (*). F. Microfracture of the exposed subchondral bone is performed. G. Occluding the inflow of fluid confirms vascular access through the areas of perforation. (Courtesy of J. W. Thomas Byrd, MD.)
ARTHROSCOPIC REPAIR OF LESIONS OF THE LIGAMENTUM TERES AND PULVINAR
Disrupted fibers of the ligamentum teres, whether from trauma or degeneration, can be quite painful, creating soft tissue impingement within the joint.
Associated with this soft tissue impingement, the pulvinar tissue often is hyperplastic or fibrosed and also can create painful symptoms.
Indiscriminate débridement of the ligamentum teres should be avoided and intact fibers preserved; however, débridement of the disrupted portion can be quite beneficial (TECH FIG 4).
Most of the contents of the acetabular fossa are best accessed from the anterior portal.
However, a portion of the posterior contents often is best accessed with instrumentation introduced from the posterolateral portal.
Between these two sites most pathologic processes can be accessed with combinations of straight, curved, and flexible instruments.
TECH FIG 4 • A. Arthroscopic view from the anterolateral portal reveals disruption of the ligamentum teres (*). B. Débridement is begun with a synovial resector introduced from the anterior portal. C. The acetabular attachment of the ligamentum teres in the posterior aspect of the fossa is addressed from the posterolateral portal. (Reprinted with permission from Byrd JWT, Jones KS. Traumatic rupture of the ligamentum teres as a source of hip pain. Arthroscopy 2004;20:385–391.)
POSTOPERATIVE CARE
For most soft tissue procedures, weight bearing is allowed as tolerated, with crutches needed only until the patient's gait has been normalized, typically 5 or 6 days.
Home exercises and supervised physical therapy are begun within the first few days.
Gentle ROM, closed-chain exercises, stabilization, and subsequent functional activities are allowed to progress as dictated by the pathology encountered, the procedure performed, the resources available to the patient, and the patient's goals for returning to activities.
For labral repairs, patients are kept on a protective weightbearing status for 6 weeks, with avoidance of external rotation and maximal hip flexion.
For microfracture, a strict protective weight-bearing status is maintained for 2 months during early maturation of the fibrocartilaginous healing response.
OUTCOMES
Successful outcomes from labral débridement range from 68% to 82%.1,12,20
Diminished results are observed with associated articular damage, which is present in most cases.
The poorest results are reported in patients with radiographic evidence of arthritis.
These observations are supported by a recent study reporting 82% continued successful outcomes at 10-year follow-up for patients undergoing labral débridement in absence of arthritis.9 Among those with associated arthritis, 79% had been converted to total hip arthroplasty.
Considerable experience has been gained in labral repair, but few outcome data have been published, with preliminary studies reporting success in two thirds of cases.16,19
These results will improve with a better understanding of patient selection.
Microfracture of grade IV articular lesions has demonstrated successful outcomes in 86% of properly selected cases.6
Successful results also have been reported with excision of painful unstable fragments caused by macrotrauma.
Soft tissue impingement due to disrupted fibers of the ligamentum teres tends to be quite painful and responds remarkably well to arthroscopic débridement, with success comparable to loose body removal.7
The results of many of these procedures will continue to improve with better understanding of underlying causative factors such as femoroacetabular impingement.
COMPLICATIONS
The reported complication rate for hip arthroscopy among large cohorts ranges from 1.3% to 6.4%.8 Most complications are minor or transient, but a few major problems have been reported.
Iatrogenic intra-articular damage may be the most common complication. Occasional joint scuffing may not be avoidable, but the concerns can be minimized by use of meticulous technique.
Traction neuropraxia can be associated with prolonged or excessive traction, but also can occur even when surgery is performed within established guidelines.
Direct trauma to major neurovascular structures should be avoidable, but, rarely, a partial neuropraxia of the lateral femoral cutaneous nerve can occur in association with the anterior portal.
Life-threatening intra-abdominal fluid extravasation has been reported, emphasizing the importance of maintaining an awareness of fluid use during surgery.
REFERENCES
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