1. Current Concepts Review
Femoroacetabular Impingement
Asheesh 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
ä Both arthroscopic and open operative treatment of femoroacetabular impingement (FAI) can reproducibly relieve
hip 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.
ä Between 75% and 90% of athletes undergoing FAI surgery return to sports at their pre-injury level of function. There
is no peer-reviewed evidence to date reporting on the efficacy of nonoperative treatment and return to play with FAI.
ä Successful operative treatment of impingement requires appropriate and complete correction of the mechanical
injury that led to the symptomatic labral pathology.
ä Early intervention prior to the onset of irreversible chondral damage is critical to the long-term success of FAI
surgery.
ä Complex deformities involving combinations of static and dynamic mechanical factors often coexist, so careful
preoperative 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 of
the hip joint and the impact of superimposed cyclic mechanical
loads and/or acute injuries of daily and athletic activity. Ganz
and colleagues have elucidated the complexities of the structural
anatomy of the hip joint and the various ways that pathologic hip
structure affects the loading characteristics of the hip1-3
. Femoro-
acetabular impingement (FAI) likely represents the most common
mechanism that leads to the development of early cartilage and
labral damage in the nondysplastic hip4-10
. While the combi-
nation of dynamic and static factors that impact the mechanics
of 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), or
combined impingement deformity. These anatomic abnormali-
ties of the proximal part of the femur and/or acetabulum result in
the 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 are
commonly 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 articular
cartilage within the acetabulum. The severity of the labral injury
and associated cartilaginous injury often depends on the duration
of the untreated injury, suggesting the importance of early di-
agnosis and treatment16-22
. The location of the injury pattern
depends highly on the osseous structure, and the ability for labral
and chondral healing is compromised by the relative avascularity
of the region23-25
.
Pathophysiology
Approximately 90% of patients with labral pathology have un-
derlying structural abnormalities in femoral and/or acetabular
morphology17,26
. 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 any
aspect 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 this
work, 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 had
any 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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2. 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 static
mechanical factors.
Static factors result in abnormal stress and asymmetric
load between the femoral head and acetabulum in the standing
position. These mechanical stresses lead to hip pain related to
insufficient congruency between the femoral head and the socket,
which leads to asymmetric wear of the chondral surfaces of the
acetabulum and femoral head with or without associated insta-
bility of the hip. Hip pain related to static overload does not
require motion across the hip. In contrast, dynamic factors result
in abnormal stress and contact between the femoral head and
acetabular rim with terminal motion of the hip. These me-
chanical stresses result in reactive hip pain with movement of
the 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 in
changes in the dynamic muscle forces and strains across the pelvis
and 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 commonly
contribute to prearthritic hip pain, especially in young athletic
males45,46
. Cam-type lesions on the femoral head lead to shear
forces of the aspherical portion of the femoral head against the
acetabulum (Fig. 2-A)47
. Repetitive entry of this cam-type le-
sion into the hip joint, typically during flexion and internal
rotation, results in a characteristic pattern of shear injury to the
transition zone and adjacent articular cartilage48
. Resulting
chondral 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), abrasion
chondroplasty, 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 is
predictable on the basis of the location and topography of the
cam-type lesion (Fig. 3).
Labral tears with cam-type impingement result from
compression of the labrum between the aspherical femoral
head 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, these
tears have more favorable healing rates after repair because of
the improved tissue quality and vascular supply from the
capsule at this peripheral location23-25
. Beck et al.5,50
found that
cam-type impingement caused damage to the anterosuperior
acetabular cartilage, with separation between the labrum and
cartilage. During flexion, the nonspherical femoral head re-
sulted in chondral delamination but was relatively sparing of
associated labral injury. Johnston et al.20
studied the relation-
ship between the size of cam-type lesions, as quantified by the
radiographic alpha angle, and the presence of cartilage damage,
labral injury, and change in the range of motion in hips with
FAI. The alpha angle51
defines the concavity of the head-neck
junction by measuring the point of deviation of femoral-head
sphericity 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 with
the 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 the
labrum 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 cadaveric
and 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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3. 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 and
recorticalization occurs in the majority of patients during the
first two years80-82
. Using preoperative and postoperative alpha-
angle measurements on extended-neck lateral radiographs, Bedi
et al.83
identified no significant difference in achieved correction
between surgical dislocation (thirty patients) and arthroscopic
decompression (thirty patients).
Cephalad Retroversion of the Acetabulum
(Pincer-Type Lesions)
A focal rim lesion, or cephalad retroversion of the acetabulum, is
a distinct dynamic mechanical cause of FAI that is common in
females2,3,84
and that results in repetitive contact stresses of a
normal femoral neck against an abnormal area of focal acetab-
ular overcoverage (Fig. 2-B). On a well-aligned anteroposterior
radiograph with neutral tilt and rotation, this focal anterosu-
perior overcoverage may present as a crossover and/or ischial
spine sign, but this method has limited reliability compared with
computed tomography6,85-88
. These findings result from relative
or absolute retroversion of the acetabulum anterosuperiorly and
more normal anteversion inferomedially. Focal rim lesions need
to 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 after
periacetabular osteotomy91,92
.
Repetitive abutment of the femoral head-neck junction on
the abnormal acetabular rim in flexion and rotation results in
degeneration and tearing of the labrum anterosuperiorly, and
the characteristic posteroinferior contrecoup pattern of cartilage
loss of the femoral head and acetabulum6,93
. Contrecoup chon-
dral injury may result from flexion or rotation of the hip beyond
engagement of the focal rim lesion, leading to levering of the
femoral head and abnormal shear forces on the posterior
chondral surfaces2,19,72
. In contrast to cam-induced injury,
rim-impingement lesions typically induce primary, intra-
substance labral injury and are often less reparable. Heterotopic
bone apposition often occurs on the osseous rim adjacent to the
base 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 the
labrum may be absent on imaging6,94
. Overall, a focal rim lesion
results in relatively limited chondral damage as compared with
the deep chondral injury and delamination that are associated
with cam-type impingement2,5,50
.
Pincer-type impingement secondary to prominence of
the anterior inferior iliac spine below the acetabular margin has
been reported as a potential cause of pathologic impingement
with direct hip flexion and/or internal rotation95
. Impingement
of the anterior inferior iliac spine on the subspine may be
developmental or the result of a prior anterior inferior iliac
spine avulsion or pelvic osteotomy. Subspine decompression in
these select cases has been reported with satisfactory clinical
outcome40
.
Impingement Patterns
Mixed impingement with both femoral and acetabular defor-
mity is the most common FAI pattern2,5,50
. Allen et al.11
reported
on 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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4. deformity of at least one hip. Bilateral cam-type deformity was
present in eighty-eight patients (77.9%), while only twenty-three
(26.1%) of those had bilateral hip pain. Painful hips had a mean
alpha angle that was significantly higher than that of asymp-
tomatic hips (69.9° versus 63.1°, p < 0.001). Among 201 hips
with a cam-type impingement deformity, 42% also had a focal
rim 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 been
delivered at the primary research institution in 1989; 1062 were
excluded 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 868
male and 1192 female participants, respectively, as follows:
posterior wall sign, 203 (23.4%) and 131 (11.0%); and excessive
acetabular coverage, 127 (14.6%) and fifty-eight (4.9%) (all p <
0.001, according to sex distribution). The crossover sign was
seen on radiographs in 446 (51.4%) and 542 (45.5%) of the male
and female participants, respectively (p = 0.004). A high degree
of coexistence (odds ratio [OR] >2) among most FAI findings
was reported96
.
Relative or absolute femoral retroversion can exacerbate
symptoms and loss of motion from FAI because reduced hip
flexion and/or internal rotation is necessary for engagement of a
cam-type or rim-type lesion. Even in the absence of femoral or
acetabular 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 femoral
anteversion may not be symptomatic until the terminal range of
hip flexion and internal rotation with no substantial restriction
in range of motion, whereas this same lesion in a retroverted
femur may engage the rim with minimal internal rotation,
resulting in substantial pain and loss of internal rotation with
daily activities6,17,97
.
Dynamic instability occurs with posterior hip subluxation
as a result of early contact of the femoral head against the ace-
tabulum98-102
. The spectrum of posterior instability of the hip
ranges from subluxation to frank dislocation. The most com-
mon traumatic mechanism of injury in athletic competition is a
fall on a flexed and adducted hip with a posteriorly directed
force. Atraumatic and lower-energy mechanisms of hip insta-
bility have also been described98-103
. It has been proposed that
capsular tissue laxity or abnormal osseous morphology may
predispose the athlete to hip instability104
. The arthroscopic
management of a traumatic dislocation of a hip that had pre-
disposing anterior impingement pathology has recently been
reported105
. Ilizaliturri et al., who reported on seventeen patients
who were surgically treated for mechanical symptoms after
traumatic posterior dislocation of the hip, reported the presence
of 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 acetabular
dysplasia in association with deformity of the proximal part
of the femur, which resulted in hip dysfunction. The authors
concluded that a periacetabular osteotomy combined with
concurrent femoral procedures can provide comprehensive de-
formity correction and improved hip function for this complex
pattern of FAI and dysplasia107
.
Etiology
The etiology of the cam-type and rim-type impingement mor-
phology in humans remains controversial and incompletely
defined. Evolutionary explanations have been offered. Hogervorst
et al.109,110
described two stereotypical mammalian hips (i.e.,
coxa recta and coxa rotunda) as possible adaptations that
occurred 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, and
can explain the pincer-type impingement that occurs in as-
sociation with coxa profunda109
. Slipped capital femoral
epiphysis or related injury has also been implicated in the
etiology of FAI111-113
, and the aspherical osteocartilaginous
bump could be associated with an extended physis that re-
sults from increased loading of the hip during late childhood
and early adolescence114
.
Genetic factors may have a role in the etiology of FAI.
Pollard et al.115
studied ninety-six siblings of sixty-four patients
treated for primary impingement and compared them with a
spouse control group of seventy-seven individuals. The siblings
of patients with a cam-type deformity had a relative risk of 2.8
of having the same deformity, and the siblings of patients with a
pincer-type deformity had a relative risk of 2.0 of having the
same deformity. Bilateral deformity occurred more often in the
sibling group than it did in the spouse control group.
Geographical variation also plays a part in the incidence
of FAI. The prevalence is low in the Eastern world, with only six
preoperative cases reported among 946 primary hip replace-
ments for osteoarthritis116
.
Management Options
Nonoperative Treatment
Nonoperative management is often advisable for FAI and typi-
cally consists of activity modification, anti-inflammatory medi-
cation, abductor strengthening, and hip-motion exercises. The
physical therapy program should be individualized on the basis of
factors 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 and
restore strength of the hip abductors and periarticular muscu-
lature but also emphasize improved neuromuscular control and
postural balance. Adjustments in posture and core strength may
create subtle changes in the position of the lumbar spine and
pelvis to avoid impingement in terminal motion. However, there
are no data demonstrating the efficacy of these interventions
with regard to achieving functional improvement or altering the
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5. natural history of progressive degenerative changes in patients
with symptomatic FAI. The effect of nonoperative management
on the natural history and progression of degenerative changes in
patients with FAI is also unknown. Hartofilakidis et al.117
retro-
spectively examined the outcome of ninety-six asymptomatic
hips in ninety-six patients (mean age, 49.3 years) for whom there
was 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 of
development of osteoarthritis on the asymptomatic side.
Operative Treatment
Operative treatment of symptomatic FAI should primarily ad-
dress all contributory mechanical factors to the symptomatic
impingement 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 of
the hip, the Smith-Petersen approach or Heuter anterior ar-
throtomy, and anteversion periacetabular osteotomy2,61,71
. Surgical
dislocation, described by Ganz et al.1
, utilizes a trochanteric slide
osteotomy and protects the short external rotators to preserve the
blood 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 and
labral pathology. Naal et al.118
reported on twenty-two male ath-
letes (mean age plus standard deviation, 19.7 ± 2.2 years) at a
mean 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 competing
professionally and eighteen (82%) were satisfied with their hip
surgery118
. 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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6. exposure to the native hip, but complications of this technically
demanding 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-wall
insufficiency90
. Siebenrock et al.90
reported on twenty-nine hips
in twenty-two patients who underwent periacetabular osteot-
omy for symptomatic anterior impingement secondary to ace-
tabular retroversion. Arthrotomy was performed in twenty-six
hips 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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7. femoral head-neck offset. At a mean follow-up of thirty months,
the average ranges of internal rotation, flexion, and adduction
increased significantly. The mean Merle d’Aubign´e-Postel score
increased 2.9 points (p < 0.001), and the result was good or
excellent for twenty-six hips90
. The return to competitive athletic
play after periacetabular osteotomy for symptomatic impinge-
ment, however, has not been reported. Periacetabular osteotomy
is also very technically demanding. Complications may include
inadequate correction of deformity, intra-articular osteotomy,
nonunion of the superior pubic ramus, loss of fixation and
correction, symptomatic implants, and neurovascular injury120
.
Arthroscopic techniques have evolved to allow for ef-
fective and comprehensive treatment of various impingement
patterns. Techniques for extensile arthroscopic capsulotomies
have allowed for improved central and peripheral compartment
exposure and access for labral takedown, refixation, treatment of
chondral 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 an
improved 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 made
between the lateral and medial synovial folds and parallel with
the femoral neck to avoid injury to the retinacular perfusing
branches of the medial and lateral femoral circumflex arteries. At
the conclusion of the procedure, the medial and lateral capsular
flaps 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 underwent
either open (surgical hip dislocation) or arthroscopic surgery
for symptomatic FAI. Thirty patients underwent arthroscopic
osteochondroplasty with labral debridement and/or refixation
for the treatment of cam-type impingement deformity and/or
rim defects; and thirty underwent open surgical dislocation,
osteochondroplasty for the treatment of cam-type impingement
deformity and/or rim defects, and labral debridement or refix-
ation. In the arthroscopic group, the extended-neck lateral alpha
angle was reduced by a mean of 17.2° (28.3%, p < 0.05), the
anterior femoral head-neck offset was improved by 5.0 mm
(111%, p < 0.05), and the beta angle was increased by a mean
of 23.1°. In the open dislocation group, the extended-neck
lateral alpha angle was reduced by a mean of 21.2° (30.7%, p <
0.05), the anterior femoral head-neck offset was improved by
6.56 mm (108%, p < 0.05), and the beta angle was increased
by a mean of 18.35°. There were no significant differences in
deformity correction between the two treatment groups83
.
Botser et al.123
recently assessed differences in outcomes after
arthroscopic, open, or combined surgical approaches for
symptomatic hip impingement (1462 hips in 1409 patients).
Labral repair was performed more frequently in open surgical
dislocation (45%) and combined approach (41%) procedures
than in arthroscopies (23%). Mean improvement in the modified
Harris hip score after surgery was 26.4 points for arthroscopy,
20.5 points for open surgical dislocation, and 12.3 points for the
combined approach. A higher rate of return to sport was reported
for arthroscopy in professional athletes than for open surgical
dislocation. The overall rate of complication was highest in the
combined approach group (16%)123
.
Outcomes
Numerous studies have established, on the basis of available
short-term to midterm follow-up (Appendix), that open surgical
dislocation, mini-open approaches, and arthroscopy are all
effective methods to treat symptomatic FAI118,124-130
. To our
knowledge, there is no peer-reviewed literature available to date
on the efficacy of nonoperative management for symptomatic
FAI. On the basis of a systematic review of the literature from
1980 to 2008, Bedi et al.13
reported that open surgical dislo-
cation with labral debridement and osteochondroplasty was a
successful treatment for FAI, with a good correlation between
patient satisfaction and favorable outcomes (at a mean of forty
months after surgery) as defined by the Harris hip score or Merle
d’Aubign´e-Postel score. A common finding in all series was an
increased incidence of failure among patients with substantial
preexisting osteoarthritis. Patients treated arthroscopically for a
labral tear and associated FAI did well13
. The substantial range
and variation in clinical outcome reflect the heterogeneous pa-
tient populations, inclusion criteria, and surgical techniques that
were utilized.
Additional systematic reviews and analyses of the literature
have reported similar results. Clohisy et al.7
reviewed eleven
level-III or level-IV studies of FAI that together had a mean
follow-up of 3.2 years. The Merle d’Aubign´e-Postel score was
most 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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8. points. Reduced pain and improvement in hip function were
reported in 68% to 96% of patients. Poor prognostic factors
included 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 hip
function, patient satisfaction was not universally positive, and
worse outcomes were noted in patients with T¨onnis grade-2
osteoarthritis on preoperative imaging and/or Outerbridge
grade-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, and
arthroscopic surgical approaches for FAI (six, four, and eight
studies, 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 was
found 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 lateral
femoral cutaneous nerve injury. The arthroscopic approach
had equivalent clinical outcomes with a lower rate of major
complications when performed by experienced surgeons131
.
The literature consists of only level-III and level-IV evi-
dence, and, to our knowledge, no prospective or randomized
controlled trials have been performed to compare the efficacy of
nonoperative management with that of operative management, or
open approaches with that of arthroscopic approaches (Table I).
The impact of surgery on long-term clinical results, the
natural history of FAI, or the prevention of or delay in the onset
of osteoarthritis has not been established. The current litera-
ture supports surgical intervention for the treatment of FAI to
provide pain relief and improved function in active patients in
whom osteoarthritis is not severe, but it does not support
prophylactic surgical intervention in asymptomatic individuals
to prevent degenerative changes of the hip (Table I).
Recent studies have reliably demonstrated improved
in vivo hip kinematics after surgical correction of FAI29,132
. Bedi
et al.132
reported on ten patients with symptomatic, focal cam-
type and/or pincer-type impingement lesions who underwent
high-resolution computed tomography scans and computer-
assisted three-dimensional modeling of the involved hip before
and 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 both
hip flexion (3.8°; p = 0.002) and internal rotation (9.3°; p =
0.0002), and was correlated with significant improvement in
the mean Harris hip score from 65.86 ± 6.66 to 89.1 ± 13.02, at
a 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 in
eleven patients with FAI during level walking. Overall sagittal-
plane range of motion of the hip increased on the affected side
from 27.6° ± 5.0° to 30.7° ± 4.3° (p = 0.02). Additionally, pain
decreased and activity level increased postoperatively133
. Kennedy
et al.28
also quantified the effect of cam-type FAI on the in vivo
three-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), frontal
range of motion (p = 0.003), and attenuated pelvic frontal range
of motion (pelvic roll) (p = 0.004) as compared with matched
controls (n = 14) during level gait28
.
Conclusion
Both open and arthroscopic hip preservation surgery have grown
exponentially in popularity over the past ten years as interventions
for early hip disease. FAI is the most common indication for hip
preservation surgery and is the most common mechanism that
leads to the development of earlycartilage and labral damage in the
nondysplastic hip. However, a careful physical examination and
radiographic assessment are critical to define strict surgical indi-
cations that reproducibly achieve favorable clinical outcomes. The
anatomic abnormalities of the proximal part of the femur and/or
the acetabulum are more complex than the originally described
cam-type and pincer-type lesions that provided the foundation for
the development of this field. The precise osseous anatomy and
mechanics of the hip joint lead to a predictable pattern of injury to
the 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 precipitate
not only direct intra-articular damage, but also compensatory
injury patterns to the surrounding musculature about the hip
joint. Both the direct intra-articular damage and the compensatory
injuries lead to pain and loss of function and may result in early
osteoarthritic changes and periarticular muscular dysfunction.
Appendix
Tables showing important radiographic findings and con-
siderations in the evaluation of femoroacetabular impinge-
ment, participant demographics for studies evaluating operative
treatment of femoroacetabular impingement, and clinicaloutcomes
TABLE I Grades of Recommendation for Femoroacetabular
Impingement (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 or
against recommending intervention, B = fair evidence (level-II or
level-III studies with consistent findings) for or against recom-
mending intervention, C = poor-quality evidence (level-IV or level-V
studies with consistent findings) for or against recommending
intervention, and I = insufficient or conflicting evidence, therefore
not allowing a recommendation for or against intervention.
89
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9. reported from studies evaluating FAI are available with the online
version of this article as a data supplement at jbjs.org. n
Asheesh Bedi, MD
MedSport, University of Michigan Orthopaedics,
Domino’s Farms, Lobby A,
24 Frank Lloyd Wright Drive,
Ann Arbor, MI 48106.
E-mail address: abedi@umich.edu
Bryan T. Kelly, MD
Center for Hip Pain and Preservation,
Hospital for Special Surgery,
541 East 71st Street,
New York, NY 10021
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