In the late 1970s and early 1980s, the acetabular labrum was implicated in the evolution of hip arthritis and was cited as a potential cause for hip pain with normal-appearing radiographs. On the heels of clinical success with knee and shoulder arthroscopy, hip arthroscopy emerged in the mid 1980s, predominantly as a treatment modality for removal of loose bodies and evaluation and resection of acetabular labral defects.
With the development of arthroscopic techniques and the recognition of the considerably wider spectrum of intra-articular hip pathology amenable to arthroscopic evaluation, the techniques of hip arthroscopy have continued to evolve. Most recently, with renewed interest in minimally invasive surgical techniques, hip arthroscopy is being explored as a potential adjunct to other surgical interventions designed to address a wider array of hip pathology.
Anatomic Considerations
The acetabulum represents the convergence and subsequent fusion of the three ossification centers of the pelvis: the pubis, ischium, and ilium. Normal hip anatomy includes a ball-and-socket configuration with deep intrinsic stability. The femoral head articulates at a neck shaft angle typically of 130 degrees and 10 degrees of anteversion. Developmental variances provide a wide spectrum of head coverage. This variability is compounded by the degree of anteversion of the acetabular opening and the flexural position of the pelvis relative to the lumbar spine. The motion of the hip is typically considered in three planes: sagittal, frontal, and transverse. The greatest degree of motion occurs in the sagittal plane.
The acetabular labrum is a triangular cartilaginous structure that rims the edge of the acetabulum. The labrum originates anteriorly at the transverse acetabular ligament. The anterior and superior aspects of the acetabular labrum are typically triangular. Posteriorly, the labrum is less pronounced and more rounded. A small sulcus is present between the labrum and the articular margin of the acetabular cartilage. This sulcus is typically more pronounced posteriorly. The hip capsule is composed of dense fibrous tissue and can anatomically be divided into three ligaments. These include the iliofemoral ligament or Y ligament of Bigelow, which extends from anterior superiorly on the ileum down to the anterior intertrochanteric ridge. The ischial femoral ligament is typically considered a capsular thickening, which wraps forward from the posterior acetabular rim to the piriformis fossa. The third component of the hip capsule is a pubofemoral ligament, which extends inferiorly from the pubis to the posterior inferior femoral neck. The patulence of the hip capsule is greatest inferiorly, and is constricted around the neck of thefemur by circular oriented fibers of the hip capsule, forming the zona orbicularis.
The arthroscopic approach to the hip must transverse the subcutaneous tissues, abductor muscle mass, and the capsular structures. Because of the intimate configuration of the ball-and-socket joint, arthroscopic visualization of the articular surface generally requires distraction of the hip to allow access between the femoral head and the acetabulum. The thick muscular envelope and often thick subcutaneous layer require exacting techniques of portal placement to ensure optimal mobility of the instruments within the hip joint.
The acetabular labrum derives its blood supply from vessels originating from the acetabular bony rim. Nociceptors are present within the labral tissue. Consequently, damage to the acetabular labrum can result in pain, and tearing of the acetabular labrum away from the acetabular rim may devascularize the labral fragment. The dysvascular labral tear has limitedpotential for spontaneous healing.
The iliofemoral and ischiofemoral ligaments both are tighter in hip extension than in slight hip flexion.
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Consequently, hip distraction typically is best achieved with slight hip flexion. The ligamentum teres remains recessed within the acetabular fossa. In the neonate, blood supply to the femoral epiphysis occurs via the terminal branches of the medial femoral circumflex artery via the ligamentum teres. In the adult, the ligamentum teres exists primarily as a tendinous structure attached to the base of the acetabulum at the confluence of the transverse acetabular ligament and the fovea on the femoral head. In the adult, the artery of the ligamentum teres supplies only a vestige of blood supply to the femoral head (Fig. 8-1A, B).
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Figure 8-1 A: Midcoronal cross-sectional drawing of the right hip. B: Right hip pericapsular structures. |
Surgical Indications
Hip arthroscopy has benefited from an increased understanding of hip anatomy, improvements in distraction techniques, and instrumentation designed specifically to address hip pathology arthroscopically. Prior to hip arthroscopy, open exploration of the hip with dislocation of the hip was the only method to address many intra-articular problems including loose bodies, acetabular labral tears, bone spurs, and synovial pathology.
Proposed current indications for hip arthroscopy include diagnostic evaluation of the painful hip, excision of loose bodies, management of synovial chondromatosis, resection of labral tears and chondral flaps, diagnostic evaluation of osteonecrosis, treatment of torn ligamentum teres, partial synovectomy, foreign body removal, posttraumatic excision of osteochondral fragments, lavage in crystalline arthropathy or early sepsis as well as capsular shrinkage in conditions of instability such as Ehlers-Danlos. Additionally, hip arthroscopy has been used in removal of loose bodies following total hip arthroplasty and as an adjunct for management of extra-articular conditions such as snapping psoas tendon, bursectomy, and soft tissue releases. The indications will be discussed individually below.
Labral Tears
Labral tears occur most commonly in the anterior superior quadrant of the acetabulum. When present, a labral tear can produce functionally limiting symptoms typically characterized as catching or occasionally popping. Arthroscopic visual inspection can delineate areas of degenerative tearing that are amenable to resection and/or stabilization techniques. Acetabular labral stabilization, although inherently appealing, is technically challenging and is typically reserved for acute traumatic tears of the acetabular labrum. Arthroscopy provides excellent visualization and access to the acetabular labrum (Fig. 8-2A, B).
Loose Bodies
Loose bodies are commonly associated with catching or locking presentation. They may be ossified but commonly are cartilaginous. These loose bodies within the hip are notoriously difficult to visualize with either plain x-ray views or other radiographic studies. Synovial osteochondromatosis can result in accumulation of dozens of loose bodies within the hip joint. Arthroscopic techniques are particularly helpful in the management of loose bodies because removal is associated with a high degree of symptom relief.
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Chondral Lesions of the Acetabulum or Femoral Head
Full-thickness chondral lesions often present in association with loose bodies. These lesions are distinguished from degenerative wear within the hip, which results in a widespread thinning of the articular cartilage and exposure of subchondral bone. Full-thickness osteochondral lesions may occur as a result of impact injury but more commonly are associated with the delamination of the chondral surface in association with other entities, including labral tears and femoro-acetabular impingement (Fig. 8-3). Resection of chondral flap injury to stable margins is associated with a high degree of symptom resolution. Clinical outcome is predicated on the size and location of the articular cartilage injury. The prognosis is typically poor when full-thickness chondral injury is present on both the acetabulum and femoral head. Additionally, when acetabular chondral lesions exceed 1 cm square, the shouldering effect of the cartilage is diminished and the prognosis is more guarded.
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Figure 8-2 A: Tears of the acetabular labrum often occur at the junction of the labrum and the articular cartilage of the acetabulum. The distracted femoral head is visible at the right of the field. B: Flexible thermal ablation probes are quite useful in resection of degenerative labral tears. |
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Figure 8-3 Chondral delamination is often seen at the anterior origin of the acetabulum in association with labral tears. |
Ligamentum Teres—Rupture or Impingement
Clinical subluxation of the hip as a result of trauma may result in tearing and degenerative change within the ligamentum teres. The tendinous ligament, when avulsed from the fovea of the femoral head, may result in impingement or a catching/locking pain pattern. Arthroscopic resection of the ligamentum teres from the fovea typically results in near complete pain relief.
Synovial Abnormalities
Inflammation of the hip synovium can result from several pathologic conditions including crystalline arthropathy, collagen vascular disease, mechanical irritation, or viral cause. An effusion of the hip joint can be quite painful and is visible on T2-weighted MRI. When diagnostic uncertainty exists, aspiration of the hip is not conclusive, and other serum-based testing fails to yield a diagnostic conclusion, hip arthroscopy may be used for lavage as well as for synovial biopsy. Additionally, for conditions that are synovium based, such as synovial chondromatosis, which result in synovial tissue production of chondral or osteochondral loose bodies, arthroscopic excision of the loose bodies and thermal ablation of the visible synovial tissues can lead to symptom resolution.
Other synovium-based pathologies such as pigmented villonodular synovitis may be treated in a temporizing manner or even potentially eradicated with arthroscopic techniques. Collagen vascular diseases such as lupus, juvenile rheumatoid arthritis, or rheumatoid arthritis may manifest first with hip pain. Synovial biopsy can prove diagnostic when these patients are seronegative.
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Infection
Hip arthroscopy has been used effectively in lavage and management of acute pyarthrosis of the hip. Clinical series in the literature support use of hip arthroscopy in both the adult and pediatric population following the early onset of symptoms, and good results have been reported in patients with favorable host parameters and susceptible bacteria. After lavage of the hip joint and arthroscopic assessment of the cartilaginous surfaces, a small drain can be left within the hip capsule temporarily to facilitate decompression. Obviously, arthroscopic management is performed in conjunction with appropriate antibiotic treatment.
Femoral Acetabular Impingement
The role for hip arthroscopy in femoral acetabular impingement is evolving. There are reports of patients in whom the offending femoral neck impingement is adequately decompressed arthroscopically. However, no large series to date substantiates these findings. Hip arthroscopy also can be used as an adjunct to open arthrotomy for more involved femoral acetabular impingement. Arthroscopy allows a more intimate and detailed evaluation of the acetabular labrum in the area of impingement as well as an assessment of the articular cartilage prior to initiation of a surgical dislocation of the hip for femoral neck contouring procedures.
Surgical Techniques
Patient positioning can be either lateral or supine. Most hip arthroscopists use a distraction apparatus specifically designed for hip arthroscopy or a fracture table (Fig. 8-4). To adequately visualize the inner aspects of the acetabulum and to assess intra-articular pathology, the femoral head must be distracted from the acetabulum. The orientation of the traction must affect a resultant force parallel to the femoral neck. This is typically achieved with a peroneal post and longitudinal distraction. The hip is slightly flexed and slightly externally rotated to relax the anterior hip capsular structures. Image intensification is used to assess joint distraction, and these cases are typically performed under general anesthesia with skeletal muscle relaxation to reduce the distraction force (Fig. 8-5).
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Figure 8-4 A fracture table is useful to assist with distraction of the hip. Note the positioning of fluoroscopy, which is draped within the surgical field. |
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Figure 8-5 Axial traction is accompanied by lateral traction via the peroneal post. The resultant traction vector is in line with the femoral neck, allowing the femoral head to lift out of the acetabulum. |
Modern arthroscopy sets contain 14-gauge 6-inch spinal needles that can be advanced into the hip capsule. A small nitinol wire is passed through the needle, then various cannula and sleeves can be advanced safely over the wire into the hip joint.
Portal Placement
Typically three working portals are used in hip arthroscopy. These include the anterior and posterior peritrochanteric portals and a direct anterior portal. The location of the peritrochanteric portal is approximately 1 to 2 cm proximal to the bony tip of the greater trochanter and located at the anterior and posterior margins of the trochanteric profile. The direct anterior portal typically is localized by drawing a vertical line from the anterior superior iliac spine down on the anterior thigh and a horizontal line from the top of the greater trochanter intersecting the anterior superior iliac spine (ASIS) line. From this point on the horizontal, the portal is lateralized to the junction of the middle third and medial third of the horizontal line from the tip of the trochanter. This location will avoid injury to the superficial femoral cutaneous nerve. The anterior and posterior peritrochanteric portals provide excellent visualization of the entire intra-articular hip. The direct anterior portal facilitates a working portal in the anterior inferior quadrant of the hip (Fig. 8-6A, B).
Both 30-degree and 70-degree arthroscopes are used. Most hip arthroscope sets provide longer instrumentation, scope cannulae, and lenses. Flexible and maneuverable thermal ablation probes provide the ability to manipulate synovial and chondral structures, and a combination of
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shavers and burrs are used to assist with contouring and loose body removal.
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Figure 8-6 A: The trochanteric outline is used to localize the anterior and posterior peritrochanteric portals. B: The anterior portal is typically lateral to the anterior superior iliac crest. |
The inferior sulcus of the hip capsule, in the region of the zone orbicularis, can be accessed for loose body removal via the anterior peritrochanteric and direct anterior portals. The femoral head is allowed to reduce into the acetabulum as traction is released. The hip joint is flexed approximately 45 degrees with slight adduction, which provides increased patulence in the inferior recess of the hip capsule. Fluoroscopy is helpful in achieving cannula positioning.
Complications and Contraindications
Hip arthroscopy has been shown in a large series to be a relatively safe operative intervention. The complication rate in the largest series reported to date by Villiar was 1.4%, which included transient sciatic palsy, transient femoral palsy, vaginal tear, and hematoma. Avoiding major complications including severe neurovascular injury requires exacting techniques on the part of the surgeon and fluoroscopic assistance in portal placement. The surgeon should carefully pad the perineum and the ankle as considerable distraction forces are applied during the course of the surgical procedure. Distraction time should be limited, typically to >2 hours.
Conditions that preclude distraction of the joint such as ankylosis; severe petrusio or heterotrophic ossification should discourage attempted arthroscopy due to the risk of injury from distraction and obstruction at typical portals from the surrounding bone. Because of the depth of the hip joint, morbid obesity remains a relative contraindication.
Summary
Hip arthroscopy provides excellent visualization of the articular surfaces of the acetabulum and femoral head. Modern arthroscopy techniques facilitate management of a myriad of pathologic conditions within the hip joint and permit modulation of early hip disease. Refinement of indications for hip arthroscopy will continue as longer-term outcome studies emerge.
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