Patients with anterior groin pain referable to the anterior thigh, greater trochanteric area, and medial knee often have hip problems. The clinician must distinguish if the source is from an intra-articular or extra-articular origin. A history of mechanical symptoms such as clicking, catching, locking, or buckling or a restricted range of motion (ROM) when plain radiographs are within normal limits gives reasonable suspicion for an intra-articular problem. A positive McCarthy sign (with both hips fully flexed, the patient’s pain is reproduced by extending the affected hip, first in external rotation, then in internal rotation)31; inguinal pain with flexion, adduction, and internal rotation of the hip; and anterior inguinal pain with ipsilateral resisted straight leg-raising are significantly correlated with an intra-articular condition.30,31 The pain may have come about suddenly or have developed after a traumatic event such as a fall or twisting injury. Generally the pain is exacerbated with activity and does not respond to conservative treatment such as ice, rest, nonsteroidal anti-inflammatory drugs (NSAIDS), and physical therapy.
Radiologic studies including plain radiographs, arthrography, bone scintigraphy, and computerized tomography (CT) to evaluate intractable hip pain often do not confirm the diagnosis. Plain radiographs may show loose bodies or degenerative arthritis, but overall they do not identify intra-articular pathology including the early stages of degenerative joint disease. Bone scintigraphy has a low specificity for intra-articular abnormalities such as loose bodies, labral tears, and chondral defects. Edwards et al11 prospectively studied 23 patients who had magnetic resonance imaging (MRI) followed by hip arthroscopy within a 3-week period. Magnetic resonance imaging without contrast often failed to identify chondral defects smaller than 1 cm, osteochondral loose bodies, and labral tears, which they noted were identified readily and treated with hip arthroscopy.11 The addition of contrast agents in conjunction with CT and MRI help in the identification of labral tears but cannot show labral fraying or degeneration consistently.18,42 McCarthy and Busconi30 showed 74% sensitivity, 83% specificity, and a 78% accuracy for magnetic resonance arthrography in diagnosing anterior labral pathology. There was an 80% false-negative rate for plain radiography, bone scintigraphy, CT, MRI, and arthrography. At surgery, 52 of 94 patients (55%) had acetabular labral injuries, all of which were observed and debrided at arthroscopy. The presence of loose bodies within the hip joint, whether ossified or not, was correlated with locking episodes and anterior inguinal pain. Acetabular labral tears detected arthroscopically correlated with symptoms of anterior inguinal pain, painful clicking episodes, transient locking, or giving way and with a painful click going from flexion to extension. A chondral defect of the femoral head or acetabulum correlated with anterior inguinal pain but no other specific findings. Although radiologically confirmed intra-articular injection into the hip joint may help to alleviate joint symptoms temporarily it does not clarify the source of irritation (whether it is labral, chondral, synovial, or loose body etiology).
Although certain hip-specific radiologic views can ascertain developmental abnormalities (retroverted acetabulum, diminished anterior femoral head offset47), currently there is no radiologic study that reproduces impingement or the direct relationship between bony changes and intra-articular chondral lesions.
Our purpose is to detail the specific indications and contraindications for hip arthroscopy, the lesions that can be clearly viewed and treated in contrast to radiologic studies, and to provide technical pearls to facilitate safe access to the hip joint.
Subsequent advances in technology and technique such as endoscopic instruments and distraction equipment designed specifically for hip surgery have overcome historical limitations, allowing comprehensive access to the hip arthroscopically. This has facilitated minimally invasive treatment of an evolving series of conditions in and around the hip joint.
Labral tears most often present with mechanical symptoms such as buckling, clicking or catching and painful, restricted ROM. These tears most frequently occur on the articular nonvascular white zone and will not heal with conservative treatment.35 Chondral lesions are one of the most elusive sources of hip joint pain. These lesions are most frequently found in association with a labral tear but also may occur with other conditions including but not limited to loose bodies, posterior dislocation, osteonecrosis, slipped capital femoral epiphysis (SCFE), dysplasia, and degenerative arthritis. The extent or thickness of the cartilage injury is the most decisive predictor of surgical outcome.5,12,31,33 Even mild dysplasia may produce hyperplasia of the labrum, making it more susceptible to impingement and tearing. Massie and Howorth27 defined mild dysplasia as a center edge angle of Wiberg between 22° and 28°, and moderate dysplasia between 16° and 22°. Labral debridement will alleviate mechanical symptoms such as locking, catching, or buckling in mild dysplasia. Labral and chondral lesions most often occur in the anterior quadrant of the joint. The preponderance of lesions in this region have several possible explanations including higher mechanical demand on the anterior labrum associated with repetitive or strenuous twisting and pivoting motions.35 Pain associated with anterior labral and chondral lesions is usually reproduced when the leg is brought full extension after the hip is flexed and externally rotated (McCarthy sign).31 In this case radiographic findings usually are limited to mild dysplasia. If the pain is reproduced when the hip is flexed and internally rotated (impingement sign) and radiographic findings include a loss of femoral offset and anterior femoral neck osteophytes.24,45 Then an osteochondroplasty of an impinging bump can be done in addition to the intra-articular treatment of the cartilage lesion.
Calcified loose bodies are identified readily by radiographic studies. However, if they are not evident on plain radiographs, CT or MR scanning with or without contrast can be more sensitive. Loose bodies may occur as isolated fragments or they may be multiple (2-300) as seen in synovial chondromatosis. In synovial chondromatosis the bodies typically aggregate together in grapelike clusters and often are adherent to the synovium about the fovea. Mechanical symptoms such as locking or catching can corroborate clinical suspicion. Arthroscopy establishes the diagnosis as well as providing simultaneous treatment using a minimally invasive technique.
Arthroscopy also allows minimally invasive synovial biopsy, evaluation of the extent of the synovitis. Arthroscopic synovectomy can be useful in the treatment of inflammatory conditions such as rheumatoid arthritis, gout, and pseudogout.19,23 Labral and chondral articular surfaces can be evaluated and treated simultaneously when there is a history of mechanical symptoms. Janssens et al21 described arthroscopic synovectomy as an adjunct to diagnosis and treatment of pigmented villonodular synovitis.
The absence of joint space narrowing, osteophyte formation, subchondral sclerosis, and cystic changes by conventional radiographs does not exclude osteoarthritis.10,32,40 Asymmetric, focal chondral degenerative changes, particularly in the anterior or anterosuperior aspect of the femoral head or acetabulum, may appear normal on anteroposterior (AP) pelvic radiographs. Arthroscopic examination will identify the exact extent and location of chondral degeneration and exclude other pathology. Accurate staging of the lesions is useful when subsequent surgical procedures such as osteotomy or arthroplasty are considered. If the chondral cartilage is well preserved or the damage is minimal the osteotomy would be a viable option, whereas if there is extensive chondral damage an arthroplasty may be a more appropriate option.
There is increasing awareness of the role that impingement may have in producing inguinal pain, chondral injury, and loss of motion. Patients with hips with mild developmental deformities may have reduced femoral head offset or anterior osteophytes. When high-resolution studies (flexion CT scan, contrast MRI) have confirmed contact between the femoral neck and the anterior acetabulum on images taken with the hip in flexion, treatment is done either by open surgical dislocation or more recently by arthroscopic means. To date, however, no outcome studies on arthroscopic treatment have been done to verify its impact.
There is a limited role for arthroscopy in patients with osteonecrosis. It should be reserved for those patients in early stages with mechanical symptoms. Arthroscopy can be done simultaneously with a core decompression in order to evaluate the chondral surfaces thoroughly.36,43 A patient with osteonecrosis may remain symptomatic from an untreated chondral lesion. Arthroscopy allows a comprehensive mapping of the femoral head and acetabular joint surfaces, the labrum and the synovium, but has no role in treating end-stage disease involving a collapsed femoral head.
Most patients with a painful replaced hip do not require arthroscopic evaluation. When unexplained symptoms persist despite appropriate conservative treatment combined with a negative workup, arthroscopy can be valuable. The senior author (JCM) successfully has removed intra-articular third bodies such as broken trochanteric wire, porous beads, and an acetabular screw that showed progressive backing out on xrays. A diagnosis was established on a patient with a metal-on-metal articulating surface who had a large inguinal cyst with repeated negative joint aspirations. There was metal-on-metal corrosion at the head-neck articulation and numerous porous beads throughout the joint, including at the head-shell interface.
Posttraumatic hematomas can be evacuated; chondral loose bodies and labral injuries (often posterior with trauma) are intra-articular conditions that may be amenable to endoscopic repair. Dislocations and fracture dislocations also can produce shear damage to the chondral surfaces of the femoral head or acetabulum not often seen by MRI scanning. Intra-articular foreign bodies such as bullet fragments can affect the hip with or without an associated fracture.9,16,37,46 Symptoms associated with rupture or injury to the ligamentum teres also can be addressed arthroscopically.6,17,22
Iliopsoas bursitis, snapping hip syndrome, and iliotibial band tendonitis are extra-articular conditions amenable to evolving endoscopic repair.
Absolute contraindications to arthroscopy include hip pain referred from extra-articular sources such as a compression fracture of the lumbar spine. Osteonecrosis or synovitis in the absence of mechanical symptoms do not warrant arthroscopy. Acute skin lesions or ulceration, especially in the vicinity of portal placement, or sepsis with accompanying osteomyelitis or abscess formation would exclude arthroscopy. Conditions that limit the potential for hip distraction may preclude arthroscopy. These include joint ankylosis, dense heterotopic bone formation, or substantial protrusio. Advanced osteoarthritis also is a contraindication for arthroscopy.
Morbid obesity is a relative contraindication for arthroscopy, not only because of distraction limitations but also because of the requisite length of instruments necessary to access and maneuver within the deeply recessed joint.
Moderate dysplasia needs to be evaluated judiciously before arthroscopic intervention. If there is evidence of instability (actual subluxation of the hip as compared to hyperlaxity), femoral head translation (coxa valga deformity with a neck-shaft angle of greater than 140°),25 or an upsloping sourcil [Horizontal toite externe angle (HTE) greater than 10°]25 then arthroscopy is not warranted and these patients should be evaluated further for periacetabular osteotomy.
Judicious patient selection is a key factor in predicting successful surgical outcomes. This includes those patients with mechanical symptoms (catching, locking, or buckling) that persist despite normal radiographic findings and failed conservative therapy. Positive examination findings as mentioned earlier combined with a history of mechanical symptoms and/or failed conservative therapy may warrant more specific diagnostic testing such as a gadolinium contrast MRI. Occasionally an intra-articular joint injection with a steroid and marcaine done under fluoroscopic control may help to clarify whether the source of pain is intra-articular. Comprehensive preoperative teaching should include associated risks including issues specific to distraction of the leg. A detailed explanation of what can and cannot be addressed arthroscopically helps provide patients with realistic recovery expectations. Postoperative activity levels, when physical therapy is and is not indicated, and back to work expectations all are key components of the preoperative discussion.
Hip arthroscopy can be done either in supine or lateral decubitus position. The choice is based on the surgeon’s preference and the availability of positioning equipment specific to the approach. In the supine position the patient is placed on a fracture table with a heavily padded peroneal post lateralized against the medial thigh to effect a lateral force on the hip. After initial distraction of the hip, flexion and internal rotation of the limb allows relaxation of the anterior aspect of the capsule which facilitates arthrocentesis. The three standard portals used in the supine position are the anterior, anterolateral, and posterolateral. The anterolateral portal is established over the anterosuperior margin of the greater trochanter about 4.4 cm cephalad from the superior gluteal nerve.4 The anterolateral portal is located at the intersection of a sagittal line from the anterior superior iliac spine and transverse line across the superior greater trochanter about 3 to 4 cm from the femoral nerve. The lateral femoral cutaneous nerve and ascending branch of the lateral circumflex artery also are in close proximity. The posterolateral portal enters the joint at the posterosuperior margin of the greater trochanter slightly cephalad and anterior converging on the anterolateral portal. It averages about 4 cm from the gluteal nerve and 2.9 cm from the sciatic nerve.4
The lateral approach requires a fracture table or specialized distractor. The lateral decubitus position allows direct access to the joint along the superior, anterior, or posterior femoral neck.14,28 Because the hip capsule is thinner laterally along the neck and the muscle envelope is not as thick, the arthroscope can be inserted more easily.15 The trochanter acts as a constant anatomic landmark, and the femoral neck can be used as a palpable structure with the trocar to assist with orientation during instrument placement. Additionally, because a considerable amount of the pathology addressed in the hip with hip arthroscopy occurs in the anterior aspect of the joint, a superior trochanteric portal allows observation of the anterior aspect of the joint with a wide-angle 30° scope instead of the 70° scope often necessary with the anterolateral portal.
Regional or general anesthesia with adequate skeletal muscle relaxation is required to overcome the forces that resist distraction of the hip. Adequate distraction is required to separate the femoral head away from the acetabulum for observation of joint surfaces and to allow passage of instruments into the recesses of the joint without scuffing chondral surfaces or skewering the labrum. A modified fracture table usually is used for the supine position. In the lateral decubitus position a dedicated hip distractor can be positioned on a regular operating room table (Fig 1). The distractor has considerable mechanical advantage because it is adjustable in multiple planes allowing six-axis joint motion. A well-padded perineal post is positioned and adjusted before applying traction. Axial traction is applied using a carefully padded foot boot with the heel firmly seated and secured. The traction device is adjusted such that the foot can be maintained in neutral position to avoid undue stress to the ligamentous structures on either side of the ankle. Distraction is applied with the leg abducted between 0° and 20°, depending on the patient’s neck-shaft angle and the depth of the acetabulum. The hip then is placed in slight forward flexion of approximately 10° to 20°.
A tensiometer on the hip distraction device may be a considerable help in preventing overzealous distraction. Adequate distraction is 7 to 10 mm for ease of instrument entrance. The majority of hip arthroscopies can be done with distraction forces between 25 and 100 pounds of direct axial traction. Fluoroscopic images determine the relative distraction of the femoral head from the acetabulum. It also can verify intra-articular placement of cannulae. Adequate distraction and complete observation has allowed successful completion of more than 1500 consecutive patients treated with this technique. Continuous traction should be avoided for more than 1.5 hours at a time. Inadvertent loss of traction while instruments are in the joint may result in harm to the articular cartilage or instrument breakage within the joint.
Once distraction is achieved intra-articular joint position is initiated with two 6-inch, 18-gauge spinal needles. The spinal needles are advanced into the hip capsule and then the joint is injected with approximately 30 to 60 mL of normal saline. This eliminates the normal negative joint pressure and facilitates distraction.
The principal portals providing access to the hip joint include the anterior and posterior superior trochanteric, anterior and posterior paratrochanteric, anterior, anterolateral, and inferior. The anterior portal is placed at the intersection of a line directly below the anterior superior iliac spine (ASIS) and a horizontal line at the level of the superior trochanter. The anterolateral portal is placed midway between the trochanteric and anterior portals. The inferior portal is placed anteroinferior to the trochanter at the level of the vastus tubercle. The anterior superior trochanteric portal is placed at the junction of the anterior and mid ⅓ of the superior trochanteric ridge as close to bone as possible and is aimed cephalad parallel to the femoral neck. The posterior superior trochanteric portal is placed at the junction of the mid and posterior ⅓ of the superior trochanteric ridge (Fig 2).
The cannulae can be placed over guide wires that have been passed through spinal needles. The senior author’s preference is to enter the joint with conical tipped telescoping cannulae and then to switch to the arthroscope using a switching stick. A 30° arthroscope initially is placed in the posterior superior trochanteric portal to view the posterior portion of the joint that includes the posterior ¾ of the femoral head, acetabulum, labrum, synovium, and ligamentum teres. The second cannula placed in the anterior superior trochanteric portal facilitates outflow and surgical instrument passage. The telescoping cannulae will allow portal dilatation as needed. Several options are available to complete intra-articular observation. An arthroscope can be changed to a 70° scope, the arthroscope can be switched to the anterior superior trochanteric portal, or it can be reinserted through an additional capsular puncture using the cannula. An anterior portal can be placed if a third portal is needed to complete observation.
The majority of surgical procedures are done in the central compartment. Loose bodies can be extracted with alligator graspers or suction basket graspers. Large or conglomerated loose bodies may need to be morselized with a shaver and brought out through the telescoping cannula. A synovial biopsy can be obtained with a pituitary ronguer or basket forceps. Labral tears are debrided with straight or curved extra-length shavers. Chondral flaps require chondroplasty using straight and curved shavers, angled basket forceps, and electrothermal tools with straight and flexible tips (Fig 3). Microfracture of full-thickness chondral lesions may be done with straight or angled picks. Lesions of the ligamentum teres are addressed with curved shavers and/or electrothermal shrinkage.
If surgery needs to be done in the peripheral compartment, the anterior and inferior paratrochanteric portals are used for this approach. Traction is released and the hip then is flexed between 30° and 45°. Impinging osteophytes can be resected with unhooded burrs under fluoroscopic guidance. A partial synovectomy can be done using straight and curved extra-length shavers. Loose bodies sometimes also are found in the peripheral compartment (Fig 4). Posttraumatic impinging heterotopic bone also can be removed from extra-articular spaces using fluoroscopic guidance.
Complication rates for hip arthroscopy range between 1.34% and 6% are reported for the supine and lateral approaches.3,8,44 Arthroscopy complications can be described as permanent or transient. Sciatic or femoral palsy, avascular necrosis, compartment syndrome, fluid extravasation, and broken instruments have all been reported.2,8,13,44 The most frequently occurring complications are transient peroneal or pudendal neuropraxia and chondral scuffing, which are associated with difficult or prolonged distraction. Osteonecrosis is a very rare complication after hip arthroscopy. Sampson44 reported one case in 530. In the senior author’s experience of more than 2000 arthroscopic procedures, there are no known cases of osteonecrosis; however, only 5% of these patients have had postoperative MRIs. Complications are best avoided with sufficient distraction (7-10 mm) kept under 60 minutes, proper hip instruments, and precise surgical skills. Hip arthroscopy involves a high learning curve. Meticulous attention to positioning, distraction time, and portal placement are essential.
Techniques and Pearls
The distraction time should be kept to less than 1 hour to avoid complications. If further surgery is required the traction should be released temporarily. To achieve distraction the thigh muscles must be paralyzed completely. In order to facilitate distraction the leg is positioned with the hip slightly flexed and abducted and with the foot slightly externally rotated. A well-padded lateral peroneal post is positioned transverse to the long axis of the torso approximately 10 to 15 cm distal to the ischial tuberosity and is adjusted for the abduction force.
To reduce iatrogenic labral or chondral injury fluoroscopic imaging is used to ensure the superior cartilage surface of the femoral head is distracted 7 to 10 mm from the inferior edge of the labrum (Fig 5). The capsule is injected with saline for full distention before insertion of instruments.
Surgeons always should have a complete set of arthroscopic hip instruments at the start of the procedure and should have a routine sequence for observation of the entire central compartment. Procedures in the central compartment (within the articulating joint surfaces) should be completed before entering the peripheral compartment (lateral access to the femoral neck and head).
The labrum is an important anatomic structure in the hip joint with many functions; therefore, the least intrusive means of resecting or stabilizing a labral tear should be emphasized and overresection of labral tissue should be avoided, especially in dysplasia.29 The labrum is resected judiciously back to stable healthy cartilage to alleviate intra-articular catching of the torn cartilage flap. The labrum is not repaired because of the hypovascularity of the tissue.35 The capsular portion of the labrum always should be maintained. No available outcome data exist to support routine capsular shrinkage. At the completion of the procedure the joint can be injected with marcaine for enhanced analgesia. Steroids should not be used because of the potentially increased risk of postoperative infection.1,39
Arthroscopy of the hip has lagged behind endoscopic procedures of the other major joints. The formidable anatomic constraints, the relative thickness and inelasticity of the iliofemoral ligament, and the curvilinear articulating surfaces have made access to this joint challenging. More recently development of hip-specific distraction equipment, hand tools, portal-preserving cannulas and the interchange of 30° and 70° arthroscopes has facilitated the evolving use of this procedure.
Although originally constructed as an ancillary diagnostic procedure in some centers, direct viewing of the chondral and synovial joint surfaces during arthroscopy has resulted in distinct improvements in our understanding of hip joint pathology and treatment. Direct witnessing that labral tears occur has spawned many investigational efforts: it illuminated the lack of sensitivity and specificity of conventional CT and MR scanning and stimulated the development of high resolution, thin-cut multiplaning MRI imaging and intra-articular gadolinium-enhanced magnetic resonance arthrography.30,38,40,41 In addition, recognition of labral pathology stimulated a microvascular study showing the vascular zone to be confined to the capsular margin of the labrum.35 The predominant occurrence of labral tears on the nonhealing portion of this tissue has facilitated development of improved treatment techniques.
Chondral lesions also are viewed readily arthroscopically and previously were unrecognized by radiologic testing. In some series chondral injuries were even more prevalent than labral lesions. The full-thickness nature of many of these lesions may presage development of early arthrosis of the joint. Joint fluid being pumped underneath these chondral lesions has been shown to be the pathogenesis of anterior subchondral acetabular cysts.35
Arthroscopy of the hip has allowed further recognition of synovial conditions of the joint, such as pseudogout and pigmented villonodular synovitis. Arthroscopy also has shown that synovial chondromatosis is also prevalent in the hip. The senior author has treated more than 30 patients with this disease. Even current radiographic studies may fail to diagnose this condition, especially if the bodies are nonossified.
There are several limitations to this procedure, however. Of the many potential etiologies of inguinal pain, arthroscopy only allows observations of the intraarticular sources of symptoms. As is true with other joints, judicious clinical and radiographic acumen is necessary to determine extra-articular or referred sources of pain. Other technical limitations include the inability to achieve intra-articular access, inadequate distraction, iatrogenic labral injury or femoral head scuffing, and inability to reach pathology in the fovea or transverse ligament area of the hip. Additionally, current arthroscopes are straight and rigid with a limited field of view, a disadvantage in a joint with a curvilinear surface.
One of the principle limitations of this procedure is the lack of long-term followup in treated patients. Although a validated outcome measurement tool has been developed, its use in large cohorts or prospective controlled series has not been completed yet.7
The advent of hip arthroscopy has also caused controversy. The effect of treatment for a labral tear versus the natural history of this lesion’s effect on the joint still are unclear. It similarly is not known whether all labral tears are the result of bony impingement as espoused by some reported studies20,24,26 or if they happen independently as a result of a dynamic load or torque, as is true in the knee joint. Is the watershed injury34 (labral and chondral lesion), as opposed to an isolated labral injury, the harbinger of inevitable joint disease progression or will its treatment retard or prevent that occurrence? The answers to these questions await further biomechanical and clinical research.
1. Armstrong RW, Bolding F: Septic arthritis after arthroscopy: The contributing roles of intraarticular steroids and environmental factors. Am J Infect Control 22:16-18, 1994.
2. Bartlett CS, DiFelice GS, Buly RL, et al: Cardiac arrest as a result of intraabdominal extravasation of fluid during arthroscopic removal of a loose body from the hip joint of a patient with an acetabular fracture. J Orthop Trauma 12:294-299, 1998.
3. Byrd JW: Complications associated with hip arthroscopy. In Byrd JW (ed).Operative Hip Arthroscopy. New York, Thieme 171-176, 1988.
4. Byrd JW: Hip arthroscopy utilizing the supine position. Arthroscopy 10:275-280, 1994.
5. Byrd JW, Jones KS: Prospective analysis of hip arthroscopy with 2-year follow-up. Arthroscopy 16:578-587, 2000.
6. Byrd JW, Jones KS: Hip arthroscopy in athletes. Clin Sports Med 20:749-761, 2001.
7. Christensen CP, Althausen PL, Mittleman MA, et al: The nonarthritic hip score: Reliable and validated. Clin Orthop Relat Res 406:75-83, 2003.
8. Clarke MT, Arora A, Villar RN: Hip arthroscopy: complications in 1054 cases. Clin Orthop Relat Res 406:84-88, 2003.
9. Cory JW, Ruch DS: Arthroscopic removal of a.44 caliber bullet from the hip. Arthroscopy 14:624-626, 1998.
10. Dvorak M, Duncan CP, Day B: Arthroscopic anatomy of the hip. Arthroscopy 6:264-273, 1990.
11. Edwards DJ, Lomas D, Villar RN: Diagnosis of the painful hip by magnetic resonance imaging and arthroscopy. J Bone Joint Surg 77B:374-376, 1995.
12. Farjo LA, Glick JM, Sampson TG: Hip arthroscopy for acetabular labral tears. Arthroscopy 15:132-137, 1999.
13. Funke EL, Munzinger U: Complications in hip arthroscopy. Arthroscopy 12:156-159, 1996.
14. Glick JM: Hip arthroscopy using the lateral approach. Instr Course Lect 37:223-231, 1988.
15. Glick JM, Sampson TG, Gordon RB, et al: Hip arthroscopy by the lateral approach. Arthroscopy 3:4-12, 1987.
16. Goldman A, Minkoff J, Price A, Krinick R: A posterior arthroscopic approach to bullet extraction from the hip. J Trauma 27:1294-1300, 1987.
17. Gray AJ, Villar RN: The ligamentum teres of the hip: An arthroscopic classification of its pathology. Arthroscopy 13:575-578, 1997.
18. Hodler J, Yu JS, Goodwin D, et al: MR arthrography of the hip: Improved imaging of the acetabular labrum with histologic correlation in cadavers. AJR Am J Roentgenol 165:887-891, 1995.
19. Holgersson S, Brattstrom H, Mogensen B, Lidgren L: Arthroscopy of the hip in juvenile chronic arthritis. J Pediatr Orthop 1:273-278, 1981.
20. Ito K, Minka II MA, Leunig M, et al: Femoroacetabular impingement and the cam-effect: A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg 83B:171-176, 2001.
21. Janssens X, Van Meirhaeghe J, Verdonk R, et al: Diagnostic arthroscopy of the hip joint in pigmented villonodular synovitis. Arthroscopy 3:283-287, 1987.
22. Kelly BT, Williams III RJ, Philippon MJ: Hip arthroscopy: current indications, treatment options, and management issues. Am J Sports Med 31:1020-1037, 2003.
23. Krebs VE: The role of hip arthroscopy in the treatment of synovial disorders and loose bodies. Clin Orthop Relat Res 406:48-59, 2003.
24. Lavigne M, Parvizi J, Beck M, et al: Anterior femoroacetabular impingement: Part I. Techniques of joint preserving surgery. Clin Orthop Relat Res 418:61-66, 2004.
25. Lequesne M: Rev Rhum Mal Osteoartic 30:479-485, 1963. [Coxometry. Measurement of the basic angles of the adult radiographic hip by a combined protractor.]
26. Leunig M, Beck M, Woo A, et al: Acetabular rim degeneration: a constant finding in the aged hip. Clin Orthop Relat Res 413:201-207, 2003.
27. Massie WK, Howorth MB: Congenital dislocation of the hip: Part I. Method of grading results. J Bone Joint Surg 32A:519-531, 1950.
28. McCarthy JC: Hip arthroscopy: Applications and technique. J Am Acad Orthop Surg 3:115-122, 1995.
29. McCarthy J (ed): Early Hip Disorders Advances in Minimally Invasive Treatment. New York, Springer-Verlag, 2003.
30. McCarthy JC, Busconi B: The role of hip arthroscopy in the diagnosis and treatment of hip disease. Orthopedics 18:753-756, 1995.
31. McCarthy JC, Lee JA: Acetabular dysplasia: A paradigm of arthroscopic examination of chondral injuries. Clin Orthop Relat Res 405:122-128, 2002.
32. McCarthy JC, Lee JA: Arthroscopic intervention in early hip disease. Clin Orthop Relat Res 429:157-162, 2004.
33. McCarthy JC, Noble PC, Schuck MR, et al: Acetabular and labral pathology. In McCarthy JC (ed). Early Hip Disorders: Advances in Detection and Minimally Invasive Treatment. New York, Springer-Verlag 113-134, 2003.
34. McCarthy JC, Noble PC, Schuck MR, et al: The watershed labral lesion: Its relationship to early arthritis of the hip. J Arthroplasty 16:81-87, 2001.
35. McCarthy JC, Noble PC, Schuck MR, et al: The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease. Clin Orthop Relat Res 393:25-37, 2001.
36. McCarthy JC, Puri L, Barsoum W, et al: Articular cartilage changes in avascular necrosis: An arthroscopic evaluation. Clin Orthop Relat Res 427S:S64-S70, 2003.
37. Meyer NJ, Thiel B, Ninomiya JT: Retrieval of an intact, intraarticular bullet by hip arthroscopy using the lateral approach. J Orthop Trauma 16:51-53, 2002.
38. Mintz DN, Hooper T, Connell D, et al: Magnetic resonance imaging of the hip: Detection of labral and chondral abnormalities using noncontrast imaging. Arthroscopy 21:385-393, 2005.
39. Montgomery SC, Campbell J: Septic arthritis following arthroscopy and intra-articular steroids. J Bone Joint Surg 71B:540, 1989.
40. Newberg AH, Newman JS: Imaging the painful hip. Clin Orthop Relat Res 406:19-28, 2003.
41. Palmer WE: MR Arthrography of the Hip. Semin Musculoskelet Radiol 2:349-362, 1998.
42. Petersilge CA: MR arthrography for evaluation of the acetabular labrum. Skeletal Radiol 30:423-430, 2001.
43. Ruch DS, Satterfield W: The use of arthroscopy to document accurate position of core decompression of the hip. Arthroscopy 14:617-619, 1998.
44. Sampson TG: Complications of hip arthroscopy. Clin Sports Med 20:831-835, 2001.
45. Tanzer M, Noiseux N: Osseous abnormalities and early osteoarthritis: The role of hip impingement. Clin Orthop Relat Res 429:170-177, 2004.
46. Teloken MA, Schmietd I, Tomlinson DP: Hip arthroscopy: A unique inferomedial approach to bullet removal. Arthroscopy 18:E21, 2002.
47. Trousdale RT, Ekkernkamp A, Ganz R, Wallrichs SL: Periacetabular and intertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg 77A:73-85, 1995.