Femoroactabular impingement

Current Concepts Review

Femoroacetabular ImpingementAsheesh Bedi, MD, and Bryan T. Kelly, MD

Investigation performed at the University of Michigan, Ann Arbor, Michigan, and the Center for Hip Pain and Preservation,Hospital for Special Surgery, New York, NY

� Both arthroscopic and open operative treatment of femoroacetabular impingement (FAI) can reproducibly relievehip pain with correction of the underlying osseous deformity and treatment of the associated labral pathology,particularly in patients without substantial articular cartilage injury at the time of surgery.

� Between 75% and 90% of athletes undergoing FAI surgery return to sports at their pre-injury level of function. Thereis no peer-reviewed evidence to date reporting on the efficacy of nonoperative treatment and return to play with FAI.

� Successful operative treatment of impingement requires appropriate and complete correction of the mechanicalinjury that led to the symptomatic labral pathology.

� Early intervention prior to the onset of irreversible chondral damage is critical to the long-term success of FAIsurgery.

� Complex deformities involving combinations of static and dynamic mechanical factors often coexist, so carefulpreoperative evaluation of the underlying structural anatomy is critical to successful treatment planning.

The development of symptomatic hip disorders in the non-arthritic hip is related to the underlying structural anatomy ofthe hip joint and the impact of superimposed cyclic mechanicalloads and/or acute injuries of daily and athletic activity. Ganzand colleagues have elucidated the complexities of the structuralanatomy of the hip joint and the various ways that pathologic hipstructure affects the loading characteristics of the hip1-3. Femoro-acetabular impingement (FAI) likely represents the most commonmechanism that leads to the development of early cartilage andlabral damage in the nondysplastic hip4-10. While the combi-nation of dynamic and static factors that impact the mechanicsof the hip joint are complex, the most common structural de-formities are a loss of femoral head-neck offset (cam-type lesion),focal or global acetabular overcoverage (pincer-type lesion), orcombined impingement deformity. These anatomic abnormali-ties of the proximal part of the femur and/or acetabulum result inthe occurrence of repetitive collisions during dynamic hip mo-tion, which leads to regional loading of the femoral head-neck

junction against the acetabular rim and precipitate labral injury,chondral delamination, and a degenerative cascade of more ex-tensive, nonfocal intra-articular injuries3,11-15. These injuries arecommonly localized to the anterosuperior region of the acetab-ular rim and frequently are associated with concomitant carti-laginous injury to the adjacent transition zone of the articularcartilage within the acetabulum. The severity of the labral injuryand associated cartilaginous injury often depends on the durationof the untreated injury, suggesting the importance of early di-agnosis and treatment16-22. The location of the injury patterndepends highly on the osseous structure, and the ability for labraland chondral healing is compromised by the relative avascularityof the region23-25.

PathophysiologyApproximately 90% of patients with labral pathology have un-derlying structural abnormalities in femoral and/or acetabularmorphology17,26. Historically, alterations in hip joint mechanics

Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of anyaspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of thiswork, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has hadany other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work.The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.

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COPYRIGHT � 2013 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED

J Bone Joint Surg Am. 2013;95:82-92 d http://dx.doi.org/10.2106/JBJS.K.01219

have been thought of as a continuum between so-called un-dercoverage (dysplasia) and overcoverage (FAI). Often, however,there are complex combinations of both dynamic and staticmechanical factors.

Static factors result in abnormal stress and asymmetricload between the femoral head and acetabulum in the standingposition. These mechanical stresses lead to hip pain related toinsufficient congruency between the femoral head and the socket,which leads to asymmetric wear of the chondral surfaces of theacetabulum and femoral head with or without associated insta-bility of the hip. Hip pain related to static overload does notrequire motion across the hip. In contrast, dynamic factors result

in abnormal stress and contact between the femoral head andacetabular rim with terminal motion of the hip. These me-chanical stresses result in reactive hip pain with movement ofthe hip into the flexed position, resulting in abnormal en-gagement between the femoral head and the acetabulum6,27-29.These alterations in the mechanics of the hip joint can result inchanges in the dynamic muscle forces and strains across the pelvisand typically affect the adductor longus, proximal hamstrings,hip abductors, iliopsoas, and hip flexor muscles (Fig. 1)30-44.

Loss of Femoral Head-Neck Offset (Cam-Type Lesions)Loss of femoral head-neck offset and asphericity commonlycontribute to prearthritic hip pain, especially in young athleticmales45,46. Cam-type lesions on the femoral head lead to shearforces of the aspherical portion of the femoral head against theacetabulum (Fig. 2-A)47. Repetitive entry of this cam-type le-sion into the hip joint, typically during flexion and internalrotation, results in a characteristic pattern of shear injury to thetransition zone and adjacent articular cartilage48. Resultingchondral delamination and detachment ensues over time16-22,49.These cartilage lesions may be treated with simple debride-ment, reattachment with adhesives (e.g., fibrin glue), abrasionchondroplasty, or microfracture, although the long-term struc-tural outcomes of these treatments remain unknown. The lo-cation of the labral tear and cartilage delamination injury ispredictable on the basis of the location and topography of thecam-type lesion (Fig. 3).

Labral tears with cam-type impingement result fromcompression of the labrum between the aspherical femoralhead and acetabular rim and more commonly result in de-tachment at the transition-zone cartilage rather than intra-substance injury. As compared with intrasubstance tears, thesetears have more favorable healing rates after repair because ofthe improved tissue quality and vascular supply from thecapsule at this peripheral location23-25. Beck et al.5,50 found thatcam-type impingement caused damage to the anterosuperioracetabular cartilage, with separation between the labrum andcartilage. During flexion, the nonspherical femoral head re-sulted in chondral delamination but was relatively sparing ofassociated labral injury. Johnston et al.20 studied the relation-ship between the size of cam-type lesions, as quantified by theradiographic alpha angle, and the presence of cartilage damage,labral injury, and change in the range of motion in hips withFAI. The alpha angle51 defines the concavity of the head-neckjunction by measuring the point of deviation of femoral-headsphericity relative to a central head-neck axis (Fig. 4, Appen-dix). In eighty-two patients who underwent operative inter-vention, a higher offset alpha angle (Fig. 4) was associated withthe presence of chondral defects of the acetabular rim (p £0.044) and full-thickness delamination of the acetabular car-tilage (p £ 0.034). Patients with detachment of the base of thelabrum had a higher offset alpha angle (p £ 0.016).

Cam-type lesions can effectively be addressed with ar-throscopy or open surgical dislocation and osteoplasty8,50,52-79.Mardones et al.80,81 compared these techniques in both cadavericand clinical studies and found no significant differences in any of

Fig. 1

A list of static and dynamic mechanical factors for prearthritic hip pain.

AIIS = anterior inferior iliac spine, FAI = femoroacetabular impingement,

SI = sacroiliac joint, and ITB = iliotibial band.

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TH E J O U R N A L O F B O N E & JO I N T SU R G E RY d J B J S . O R G

VO LU M E 95-A d NU M B E R 1 d JA N UA RY 2, 2013FE M O R OAC E TA B U L A R IM P I N G E M E N T

the measurements of resection. Whether the procedure is per-formed in an open or arthroscopic fashion, the deformity cor-rection achieved with the osteochondroplasty is maintained andrecorticalization occurs in the majority of patients during thefirst two years80-82. Using preoperative and postoperative alpha-angle measurements on extended-neck lateral radiographs, Bediet al.83 identified no significant difference in achieved correctionbetween surgical dislocation (thirty patients) and arthroscopicdecompression (thirty patients).

Cephalad Retroversion of the Acetabulum(Pincer-Type Lesions)A focal rim lesion, or cephalad retroversion of the acetabulum, isa distinct dynamic mechanical cause of FAI that is common infemales2,3,84 and that results in repetitive contact stresses of anormal femoral neck against an abnormal area of focal acetab-ular overcoverage (Fig. 2-B). On a well-aligned anteroposteriorradiograph with neutral tilt and rotation, this focal anterosu-perior overcoverage may present as a crossover and/or ischialspine sign, but this method has limited reliability compared withcomputed tomography6,85-88. These findings result from relativeor absolute retroversion of the acetabulum anterosuperiorly andmore normal anteversion inferomedially. Focal rim lesions needto be distinguished from global overcoverage and impingement,which can result from coxa profunda, coxa protrusio, true ace-tabular retroversion9,89,90, or even iatrogenic overcorrection afterperiacetabular osteotomy91,92.

Repetitive abutment of the femoral head-neck junction onthe abnormal acetabular rim in flexion and rotation results indegeneration and tearing of the labrum anterosuperiorly, and

the characteristic posteroinferior contrecoup pattern of cartilageloss of the femoral head and acetabulum6,93. Contrecoup chon-dral injury may result from flexion or rotation of the hip beyondengagement of the focal rim lesion, leading to levering of thefemoral head and abnormal shear forces on the posteriorchondral surfaces2,19,72. In contrast to cam-induced injury,rim-impingement lesions typically induce primary, intra-substance labral injury and are often less reparable. Heterotopicbone apposition often occurs on the osseous rim adjacent to thebase of the labrum and can progress to ossification of the entire,damaged labrum anterosuperiorly. In later stages, the bone for-mation cannot be distinguished from the native bone, and thelabrum may be absent on imaging6,94. Overall, a focal rim lesionresults in relatively limited chondral damage as compared withthe deep chondral injury and delamination that are associatedwith cam-type impingement2,5,50.

Pincer-type impingement secondary to prominence ofthe anterior inferior iliac spine below the acetabular margin hasbeen reported as a potential cause of pathologic impingementwith direct hip flexion and/or internal rotation95. Impingementof the anterior inferior iliac spine on the subspine may bedevelopmental or the result of a prior anterior inferior iliacspine avulsion or pelvic osteotomy. Subspine decompression inthese select cases has been reported with satisfactory clinicaloutcome40.

Impingement PatternsMixed impingement with both femoral and acetabular defor-mity is the most common FAI pattern2,5,50. Allen et al.11 reportedon 113 patients who had a symptomatic cam-type impingement

Fig. 2-A Fig. 2-B

Fig. 2-A Extended-neck (Dunn) lateral radiograph demonstrating an anterior cam-type lesion (arrow) with loss of femoral head-neck offset. Note that the

normal cortical shadow of the head-neck junction can be visualized. Fig. 2-B Anteroposterior radiograph of the right hip. The arrow demonstrates a focal

rim lesion with cephalad retroversion of the acetabulum. Note that there is also a broken rim fragment (arrow), which is consistent with a pincer-type

lesion.

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deformity of at least one hip. Bilateral cam-type deformity waspresent in eighty-eight patients (77.9%), while only twenty-three(26.1%) of those had bilateral hip pain. Painful hips had a meanalpha angle that was significantly higher than that of asymp-tomatic hips (69.9� versus 63.1�, p < 0.001). Among 201 hipswith a cam-type impingement deformity, 42% also had a focalrim deformity11. Laborie et al.96 reported on the population-based prospective follow-up of 2081 (874 male and 1207 female)young adults from a larger study cohort of 4006 young adults.The cohort was composed of all 5068 newborns who had beendelivered at the primary research institution in 1989; 1062 wereexcluded from the follow-up because of death or emigration.Cam-type deformities were seen in the 868 male and 1192 fe-male participants, respectively, as follows: pistol-grip deformity,187 (21.5%) and thirty-nine (3.3%); focal femoral neck prom-inence, eighty-nine (10.3%) and thirty-one (2.6%); and flat-tening of the lateral femoral head, 125 (14.4%) and seventy-four(6.2%). Pincer-type deformities were seen in those same 868male and 1192 female participants, respectively, as follows:posterior wall sign, 203 (23.4%) and 131 (11.0%); and excessiveacetabular coverage, 127 (14.6%) and fifty-eight (4.9%) (all p <0.001, according to sex distribution). The crossover sign wasseen on radiographs in 446 (51.4%) and 542 (45.5%) of the maleand female participants, respectively (p = 0.004). A high degreeof coexistence (odds ratio [OR] >2) among most FAI findingswas reported96.

Relative or absolute femoral retroversion can exacerbatesymptoms and loss of motion from FAI because reduced hipflexion and/or internal rotation is necessary for engagement of acam-type or rim-type lesion. Even in the absence of femoral oracetabular deformity, retroversion of the femur increases func-tional external rotation and reduces internal rotation of the hip6.A cam-type lesion in a patient with normal or increased femoralanteversion may not be symptomatic until the terminal range ofhip flexion and internal rotation with no substantial restrictionin range of motion, whereas this same lesion in a retrovertedfemur may engage the rim with minimal internal rotation,resulting in substantial pain and loss of internal rotation withdaily activities6,17,97.

Dynamic instability occurs with posterior hip subluxationas a result of early contact of the femoral head against the ace-tabulum98-102. The spectrum of posterior instability of the hipranges from subluxation to frank dislocation. The most com-mon traumatic mechanism of injury in athletic competition is afall on a flexed and adducted hip with a posteriorly directedforce. Atraumatic and lower-energy mechanisms of hip insta-bility have also been described98-103. It has been proposed thatcapsular tissue laxity or abnormal osseous morphology maypredispose the athlete to hip instability104. The arthroscopicmanagement of a traumatic dislocation of a hip that had pre-disposing anterior impingement pathology has recently beenreported105. Ilizaliturri et al., who reported on seventeen patientswho were surgically treated for mechanical symptoms aftertraumatic posterior dislocation of the hip, reported the presenceof labral tears and chondral injury consistent with anterior im-pingement in fourteen patients106.

The combination of dysplasia and FAI can also occur107,108.Clohisy et al.107 reported on a series of patients with acetabulardysplasia in association with deformity of the proximal partof the femur, which resulted in hip dysfunction. The authorsconcluded that a periacetabular osteotomy combined withconcurrent femoral procedures can provide comprehensive de-formity correction and improved hip function for this complexpattern of FAI and dysplasia107.

EtiologyThe etiology of the cam-type and rim-type impingement mor-phology in humans remains controversial and incompletelydefined. Evolutionary explanations have been offered. Hogervorstet al.109,110 described two stereotypical mammalian hips (i.e.,coxa recta and coxa rotunda) as possible adaptations thatoccurred in response to the activities of running (coxa recta)and climbing and swimming (coxa rotunda). The evolu-tionary conflict between upright gait and the birth of a large-brained fetus is expressed in the female pelvis and hip, andcan explain the pincer-type impingement that occurs in as-sociation with coxa profunda109. Slipped capital femoralepiphysis or related injury has also been implicated in theetiology of FAI111-113, and the aspherical osteocartilaginousbump could be associated with an extended physis that re-sults from increased loading of the hip during late childhoodand early adolescence114.

Genetic factors may have a role in the etiology of FAI.Pollard et al.115 studied ninety-six siblings of sixty-four patientstreated for primary impingement and compared them with aspouse control group of seventy-seven individuals. The siblingsof patients with a cam-type deformity had a relative risk of 2.8of having the same deformity, and the siblings of patients with apincer-type deformity had a relative risk of 2.0 of having thesame deformity. Bilateral deformity occurred more often in thesibling group than it did in the spouse control group.

Geographical variation also plays a part in the incidenceof FAI. The prevalence is low in the Eastern world, with only sixpreoperative cases reported among 946 primary hip replace-ments for osteoarthritis116.

Management OptionsNonoperative TreatmentNonoperative management is often advisable for FAI and typi-cally consists of activity modification, anti-inflammatory medi-cation, abductor strengthening, and hip-motion exercises. Thephysical therapy program should be individualized on the basis offactors such as athletic demands, restriction in range of motion,and objective weakness in muscle strength-testing. The rehabil-itation program must not only improve soft-tissue mobility andrestore strength of the hip abductors and periarticular muscu-lature but also emphasize improved neuromuscular control andpostural balance. Adjustments in posture and core strength maycreate subtle changes in the position of the lumbar spine andpelvis to avoid impingement in terminal motion. However, thereare no data demonstrating the efficacy of these interventionswith regard to achieving functional improvement or altering the

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natural history of progressive degenerative changes in patientswith symptomatic FAI. The effect of nonoperative managementon the natural history and progression of degenerative changes inpatients with FAI is also unknown. Hartofilakidis et al.117 retro-spectively examined the outcome of ninety-six asymptomatichips in ninety-six patients (mean age, 49.3 years) for whom therewas radiographic evidence of FAI. Overall, seventy-nine hips(82.3%) remained free of osteoarthritis for a mean of 18.5 years(range, ten to forty years). Only the presence of idiopathic os-teoarthritis of the contralateral diseased hip was predictive ofdevelopment of osteoarthritis on the asymptomatic side.

Operative TreatmentOperative treatment of symptomatic FAI should primarily ad-dress all contributory mechanical factors to the symptomaticimpingement and secondarily address the resultant intra-articular pathology6. The specific approach must be individ-ualized and depends on the pattern and extent of pathology.

Independent of approach, the goals of surgery are to relieve pain,improve function and return to activity, and prevent degen-eration of the hip joint6,9.

Open surgical approaches include surgical dislocation ofthe hip, the Smith-Petersen approach or Heuter anterior ar-throtomy, and anteversion periacetabular osteotomy2,61,71. Surgicaldislocation, described by Ganz et al.1, utilizes a trochanteric slideosteotomy and protects the short external rotators to preserve theblood supply to the femoral head, allowing for direct, circum-ferential visualization of the acetabular rim and femoral head-neck junction to address osseous deformity and chondral andlabral pathology. Naal et al.118 reported on twenty-two male ath-letes (mean age plus standard deviation, 19.7 ± 2.2 years) at amean of 45.1 months after surgical hip dislocation for the treat-ment of symptomatic hip impingement. At the time of follow-up,twenty-one of twenty-two patients (95%) were still competingprofessionally and eighteen (82%) were satisfied with their hipsurgery118. Surgical dislocation can safely achieve an extensile

Fig. 3

Figs. 3-A, 3-B, and 3-C Young athlete with symptomatic femoroacetabular impingement of the right hip. Fig. 3-A Preoperative anteroposterior radiograph of

the pelvis (left) and extended-neck lateral radiograph of the right hip (right). Fig. 3-B T1-weighted sagittal (left) and axial (right) magnetic resonance images

demonstrating anterosuperior labral tear (yellow arrow).

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exposure to the native hip, but complications of this technicallydemanding procedure may include trochanteric osteotomy non-union, osteonecrosis of the femoral head, heterotopic ossification,and persistent weakness of the hip abductor musculature93,119.

The anteversion periacetabular osteotomy is an uncom-monly performed treatment for pincer-type rim impingement

secondary to global acetabular retroversion and posterior-wallinsufficiency90. Siebenrock et al.90 reported on twenty-nine hipsin twenty-two patients who underwent periacetabular osteot-omy for symptomatic anterior impingement secondary to ace-tabular retroversion. Arthrotomy was performed in twenty-sixhips to visualize intra-articular lesions and improve a low

Fig. 4

Anteroposterior (Fig. 4-A) and Dunn lateral (Fig. 4-B) radiographic images depicting alpha (a), beta (b), and center-edge (CE) angles as well as the femoral

head-neck offset.

Fig. 3-C

Fig. 3-C Intraoperative arthroscopic images of the central compartment, demonstrating the labral tear and delaminating chondral injury.

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femoral head-neck offset. At a mean follow-up of thirty months,the average ranges of internal rotation, flexion, and adductionincreased significantly. The mean Merle d’Aubigne-Postel scoreincreased 2.9 points (p < 0.001), and the result was good orexcellent for twenty-six hips90. The return to competitive athleticplay after periacetabular osteotomy for symptomatic impinge-ment, however, has not been reported. Periacetabular osteotomyis also very technically demanding. Complications may includeinadequate correction of deformity, intra-articular osteotomy,nonunion of the superior pubic ramus, loss of fixation andcorrection, symptomatic implants, and neurovascular injury120.

Arthroscopic techniques have evolved to allow for ef-fective and comprehensive treatment of various impingementpatterns. Techniques for extensile arthroscopic capsulotomieshave allowed for improved central and peripheral compartmentexposure and access for labral takedown, refixation, treatment ofchondral injury, and osteochondroplasty of the femoral head-neck junction and acetabular rim (Fig. 5)6,60,74,121. The man-agement of the capsule can be critical and must allow for animproved exposure without compromising stability and kine-matics of the hip. If an extensile capsulotomy to address pe-ripheral compartment pathology is necessary, it should be madebetween the lateral and medial synovial folds and parallel withthe femoral neck to avoid injury to the retinacular perfusingbranches of the medial and lateral femoral circumflex arteries. Atthe conclusion of the procedure, the medial and lateral capsularflaps are anatomically reduced, restoring the tension and stabi-lizing function of the iliofemoral ligament122.

Recent studies have established that open surgical dislo-cation and an arthroscopic approach may have comparable effi-cacy in achieving a surgical correction of impingement deformity.

Bedi et al.83 reported on sixty active, male patients who underwenteither open (surgical hip dislocation) or arthroscopic surgeryfor symptomatic FAI. Thirty patients underwent arthroscopicosteochondroplasty with labral debridement and/or refixationfor the treatment of cam-type impingement deformity and/orrim defects; and thirty underwent open surgical dislocation,osteochondroplasty for the treatment of cam-type impingementdeformity and/or rim defects, and labral debridement or refix-ation. In the arthroscopic group, the extended-neck lateral alphaangle was reduced by a mean of 17.2� (28.3%, p < 0.05), theanterior femoral head-neck offset was improved by 5.0 mm(111%, p < 0.05), and the beta angle was increased by a meanof 23.1�. In the open dislocation group, the extended-necklateral alpha angle was reduced by a mean of 21.2� (30.7%, p <0.05), the anterior femoral head-neck offset was improved by6.56 mm (108%, p < 0.05), and the beta angle was increasedby a mean of 18.35�. There were no significant differences indeformity correction between the two treatment groups83.Botser et al.123 recently assessed differences in outcomes afterarthroscopic, open, or combined surgical approaches forsymptomatic hip impingement (1462 hips in 1409 patients).Labral repair was performed more frequently in open surgicaldislocation (45%) and combined approach (41%) proceduresthan in arthroscopies (23%). Mean improvement in the modifiedHarris hip score after surgery was 26.4 points for arthroscopy,20.5 points for open surgical dislocation, and 12.3 points for thecombined approach. A higher rate of return to sport was reportedfor arthroscopy in professional athletes than for open surgicaldislocation. The overall rate of complication was highest in thecombined approach group (16%)123.

OutcomesNumerous studies have established, on the basis of availableshort-term to midterm follow-up (Appendix), that open surgicaldislocation, mini-open approaches, and arthroscopy are alleffective methods to treat symptomatic FAI118,124-130. To ourknowledge, there is no peer-reviewed literature available to dateon the efficacy of nonoperative management for symptomaticFAI. On the basis of a systematic review of the literature from1980 to 2008, Bedi et al.13 reported that open surgical dislo-cation with labral debridement and osteochondroplasty was asuccessful treatment for FAI, with a good correlation betweenpatient satisfaction and favorable outcomes (at a mean of fortymonths after surgery) as defined by the Harris hip score or Merled’Aubigne-Postel score. A common finding in all series was anincreased incidence of failure among patients with substantialpreexisting osteoarthritis. Patients treated arthroscopically for alabral tear and associated FAI did well13. The substantial rangeand variation in clinical outcome reflect the heterogeneous pa-tient populations, inclusion criteria, and surgical techniques thatwere utilized.

Additional systematic reviews and analyses of the literaturehave reported similar results. Clohisy et al.7 reviewed elevenlevel-III or level-IV studies of FAI that together had a meanfollow-up of 3.2 years. The Merle d’Aubigne-Postel score wasmost commonly utilized, and improvement ranged from 2.4 to 5

Fig. 5

Intraoperative arthroscopic photograph demonstrating osteochondroplasty for

restoration of femoral head-neck offset. A T-capsulotomy has been performed

to allow for thorough medial-lateral and proximal-distal correction of the de-

formity and is followed by side-to-side repair of the capsular flaps.

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points. Reduced pain and improvement in hip function werereported in 68% to 96% of patients. Poor prognostic factorsincluded advanced preoperative osteoarthritis, advanced chon-dral degeneration, and older age7. Ng et al.114 reported on twenty-three case studies (970 cases) on the surgical treatment of FAI.Although treatment of FAI consistently improved mean hipfunction, patient satisfaction was not universally positive, andworse outcomes were noted in patients with Tonnis grade-2osteoarthritis on preoperative imaging and/or Outerbridgegrade-3 or 4 cartilage damage noted intraoperatively114.

Matsuda et al.131 recently performed a comparative sys-tematic review of the open surgical dislocation, mini-open, andarthroscopic surgical approaches for FAI (six, four, and eightstudies, respectively), concluding that all approaches were ef-fective in pain relief and improvement in function with short-term to midterm follow-up. Open surgical dislocation wasfound to have a higher incidence of major complications re-lated to the trochanteric osteotomy and associated implants,and mini-open approaches had a greater incidence of lateralfemoral cutaneous nerve injury. The arthroscopic approachhad equivalent clinical outcomes with a lower rate of majorcomplications when performed by experienced surgeons131.

The literature consists of only level-III and level-IV evi-dence, and, to our knowledge, no prospective or randomizedcontrolled trials have been performed to compare the efficacy ofnonoperative management with that of operative management, oropen approaches with that of arthroscopic approaches (Table I).

The impact of surgery on long-term clinical results, thenatural history of FAI, or the prevention of or delay in the onsetof osteoarthritis has not been established. The current litera-ture supports surgical intervention for the treatment of FAI toprovide pain relief and improved function in active patients inwhom osteoarthritis is not severe, but it does not supportprophylactic surgical intervention in asymptomatic individualsto prevent degenerative changes of the hip (Table I).

Recent studies have reliably demonstrated improvedin vivo hip kinematics after surgical correction of FAI29,132. Bediet al.132 reported on ten patients with symptomatic, focal cam-type and/or pincer-type impingement lesions who underwenthigh-resolution computed tomography scans and computer-assisted three-dimensional modeling of the involved hip beforeand after corrective FAI surgery. The mean alpha angle im-proved from 59.8� to 36.4�. Corrective femoral and rim os-teochondroplasty resulted in significant improvements in bothhip flexion (3.8�; p = 0.002) and internal rotation (9.3�; p =0.0002), and was correlated with significant improvement inthe mean Harris hip score from 65.86 ± 6.66 to 89.1 ± 13.02, ata mean follow-up of 10.9 ± 7.4 months132. Rylander et al.133

recently completed an in vivo motion capture analysis of pre-operative and postoperative sagittal-plane hip kinematics ineleven patients with FAI during level walking. Overall sagittal-plane range of motion of the hip increased on the affected sidefrom 27.6� ± 5.0� to 30.7� ± 4.3� (p = 0.02). Additionally, paindecreased and activity level increased postoperatively133. Kennedyet al.28 also quantified the effect of cam-type FAI on the in vivothree-dimensional kinematics of the hip and pelvis during

walking. A unilateral cam-type impingement group (n = 17)had significantly lower peak hip abduction (p = 0.009), frontalrange of motion (p = 0.003), and attenuated pelvic frontal rangeof motion (pelvic roll) (p = 0.004) as compared with matchedcontrols (n = 14) during level gait28.

ConclusionBoth open and arthroscopic hip preservation surgery have grownexponentially in popularity over the past ten years as interventionsfor early hip disease. FAI is the most common indication for hippreservation surgery and is the most common mechanism thatleads to the development of early cartilage and labral damage in thenondysplastic hip. However, a careful physical examination andradiographic assessment are critical to define strict surgical indi-cations that reproducibly achieve favorable clinical outcomes. Theanatomic abnormalities of the proximal part of the femur and/orthe acetabulum are more complex than the originally describedcam-type and pincer-type lesions that provided the foundation forthe development of this field. The precise osseous anatomy andmechanics of the hip joint lead to a predictable pattern of injury tothe labrum and cartilage during dynamic hip motion, with re-gional loading of the femoral head-neck junction against the ac-etabular rim. The resulting abnormal kinematics can precipitatenot only direct intra-articular damage, but also compensatoryinjury patterns to the surrounding musculature about the hipjoint. Both the direct intra-articular damage and the compensatoryinjuries lead to pain and loss of function and may result in earlyosteoarthritic changes and periarticular muscular dysfunction.

AppendixTables showing important radiographic findings and con-siderations in the evaluation of femoroacetabular impinge-

ment, participant demographics for studies evaluating operativetreatment of femoroacetabular impingement, and clinical outcomes

TABLE I Grades of Recommendation for FemoroacetabularImpingement (FAI)

Grade*

Pathophysiology B

Injury patterns B

Etiology C

Nonoperative treatment I

Surgical treatment B

Open versus arthroscopic approach I

Improvement in hip kinematics C

Prevention of osteoarthritis I

*A = good evidence (level-I studies with consistent findings) for oragainst recommending intervention, B = fair evidence (level-II orlevel-III studies with consistent findings) for or against recom-mending intervention, C = poor-quality evidence (level-IV or level-Vstudies with consistent findings) for or against recommendingintervention, and I = insufficient or conflicting evidence, thereforenot allowing a recommendation for or against intervention.

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reported from studies evaluating FAI are available with the onlineversion of this article as a data supplement at jbjs.org. n

Asheesh Bedi, MDMedSport, University of Michigan Orthopaedics,Domino’s Farms, Lobby A,

24 Frank Lloyd Wright Drive,Ann Arbor, MI 48106.E-mail address: [email protected]

Bryan T. Kelly, MDCenter for Hip Pain and Preservation,Hospital for Special Surgery,541 East 71st Street,New York, NY 10021

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