Fluoroscopic Demonstration of Femoroacetabular ImpingementDuring Hip Arthroscopy
Cara Beth Lee, M.D., and John Clark, M.D.
Abstract: Femoroacetabular impingement is a cause of hip pain that in selected cases can be treatedby removal of impinging bone (osteoplasty). No absolute parameters for osteoplasty exist. Wepresent a technique for dynamic evaluation of bony impingement and control of arthroscopicosteoplasty using intraoperative fluoroscopy. With the patient supine on a fracture table, the C-armis positioned between the legs. Femoral anteversion is measured with the C-arm vertical and the hipflexed 90° (Dunn view). The C-arm is then tilted back 25° from vertical to create a profile view ofthe anterior rim, and the hip is flexed under fluoroscopy to find the location of maximum head/neckdeformity. Because the distance between rim and neck is apparent, a spot view in that position is usedto plan the osteoplasties. Impingement is demonstrated by forced internal rotation and is obvious asbony contact, movement of the pelvis, or joint subluxation. Osteoplasty of the neck is performed withthe hip extended and the C-arm tilted to reproduce the view of the maximum neck deformity. Thedynamic examination is repeated to confirm adequacy of the osteoplasty and improvement in internalrotation. Hip deformities could be efficiently identified and individually corrected.
As femoroacetabular impingement (FAI) has gainedrecognition as a clinically significant condition, sur-
ical management including removal of impinging bonerom the femoral neck or acetabular rim (osteoplasty) hasecome accepted practice in cases not responding toonservative measures.1 The location and size of the
femoral head-neck deformity causing “cam” impinge-ment are variable, and impingement can occur anywhereover an arc of about 100° on the acetabular margin.2,3
For these reasons, the extent and placement of an osteo-plasty cannot be standardized.
From Group Health Central Specialty Center, Seattle, Washing-ton, U.S.A.
Received December 1, 2010; accepted January 20, 2011.Address correspondence to Cara Beth Lee, M.D., Orthopaedic
Surgery, Group Health Central Specialty Center, 125 16th Ave E,Seattle, WA 98112, U.S.A. E-mail: [email protected]
994 Arthroscopy: The Journal of Arthroscopic and Related S
Ilizaliturri4 observed that failure to recognize oradequately reshape impinging bone may be the mostcommon complication when treating FAI arthroscopi-cally. Cadaveric studies show that arthroscopic trim-ming of the anterior femoral neck and acetabular rimis subject to error, even in a laboratory setting.5-7 Useof special radiography, either for preoperative plan-ning or for intraoperative computer-assisted naviga-tion, is complex and may not improve the accuracy ofosteoplasty.8-10
Recently, Larson and Wulf11 and Matsuda12 havedescribed techniques wherein fluoroscopy is used tocontrol the femoral or acetabular osteoplasty duringarthroscopy. In our transition from open to ar-throscopic treatment of FAI, we also adopted fluo-roscopic control of the bone resection, but first, weexamine the hip under fluoroscopy and use spotviews to plan the osteoplasty. Even with experi-ence, we were not satisfied with direct arthroscopicobservation for control of the femoral osteoplasty or
for evaluation of impingement as the hip was flexed
beyond 90°. Given wide variation in patient anat-omy, bone resection— even with fluoroscopic con-trol—is best individualized on the basis of repeatedintraoperative observation, but such maneuverscomplicate the procedure. The spot views provideddocumentation of the bony deformities and the ef-fects of forced internal rotation (IR) and served asan acceptable substitute for the dynamic examina-tion possible with surgical dislocation. This methodhas improved our understanding of the mechanicsof FAI and efficiency of our surgery.
This report explains the technique and describes our
intraoperative observations of FAI (Tables 1-3).
TECHNIQUE
All patients were treated for anterior FAI diagnosedby history, limited IR in flexion, and magnetic reso-nance arthrography including radial reconstructions.13
Arthroscopy is performed with the patient in a supineposition with distraction through a fracture table hold-ing the operative limb in neutral abduction and thenonoperative hip in extension/maximum abduction.The anterior spines serve as a horizontal reference,and pelvic tilt is judged by the position of the sym-physis. The operative hip is internally rotated to place
URE 1. Capture of special views by fluoroscopy. (A) Position ofrm during evaluation. When possible, the plane of C-arm rotationld be perpendicular to the femoral neck axis, as shown here. (B)
rm views used for arthroscopy. Femoral anteversion is determinedan AP view with the hip flexed to 90° and abducted. The “rim”used for the dynamic examination and creation of a “beta” view
btained by tilting the arm back 25° from the vertical (AP) position.s tested in this position, and this “stress” view is also recorded.ause this provides a false-profile view of the acetabulum, anyormal anterior overhang or deficiency will be evident. The “neck”
used for osteoplasty of the femoral neck is variable, and the exactrm tilt is determined by the location of the apex of the neckrmity found during the dynamic examination. (C) Dynamic ex-
nation stress view. The hip is flexed while held in neutral rotationthe region of greatest deformity located. After the beta view isn in neutral rotation, “impingement” is documented by testingimum IR in this position of flexion, as shown here.
positioned between the legs with the arm perpendic-ular to the axis of the femoral neck (Fig 1A). Ifpositioning is ideal, the X-ray beam remains perpen-dicular to the neck as the arm is rotated from ananteroposterior (AP) (vertical) to a lateral (horizontal)view (Fig 1B).
Dynamic Fluoroscopic Examination and Spot Views
Before the skin preparation, the foot is released andfluoroscopic evaluation of the femoral neck is per-formed. To measure neck version, a Rippstein-Dunnlateral view of the femoral neck14,15 is obtained withthe C-arm vertical (AP view) and the hip flexed 90°and abducted (Fig 2). A guidewire can serve as ahorizontal reference. In subjects with abnormal over-hang or a short neck, the AP view is used to assessimpingement in abduction or external rotation. TheC-arm is then rotated back 25° from vertical (rimview, Figs 1B and 3). This position provides a 15°external oblique view of the anterior-superior acetab-ular margin, similar to the “false-profile” view ofLequesne and Laredo16 but with a slight cephalad tilt.With the neck centered on the fluoroscopic view, thehip is flexed from 0° to 90°, the position of hip flexionthat shows maximum head-neck deformity is located,and a spot (“beta”) view is taken with the hip in
FIGURE 2. Determination of femoral anteversion. By use of theAP view, anteversion is measured with the hip flexed 90° andabducted. In this case the neck has only 2° of anteversion based ona horizontal reference.
neutral rotation/abduction (Fig 3B). The � and � an-
les of Nötzli et al.17,18 can be used to characterize thedeformity. The � angle provides a measure of anterioread offset. The � angle (i.e., the angular distance
between the acetabular rim and the femoral neck) isdrawn on a printout by use of the method of Wyss etal.18 (Fig 3B). The flexed hip is then rotated internallyto document actual IR to the point of impingement.Impingement can be identified on this stress view asthe point where the pelvis starts to move, a vacuumsign appears in the joint (Figs 4-6), or the hip sublux-ates (Fig 7). Bone-to-bone contact sometime occursbut is rare. To complete the dynamic fluoroscopicexamination, IR at 90° of flexion and IR at maximumflexion are observed and correlated to the preoperativeexamination.
TABLE 1. Pointers for Dynamic FluoroscopicExamination
Bone-against-bone impingement is sometimes seen, but moreoften, interposed soft tissue separates the neck and rim duringthe test of IR.
An anterior neck prominence can be narrow or broad, so youmay need to repeat the examination several times to locate theapex of the deformity.
The point of maximum femoral deformity is not always a bump;in many cases the junction will simply be flat. Also look atposterior head displacement and relative width of the neck asclues for maximum deformity.
When testing IR, you have found the limit of hip motion whenthe pelvis starts to move or the hip subluxates.
A detached labrum can fold into the joint and act as a fulcrum.Thick periosteum is often present over or adjacent to a “camlesion” in young patients, and this contributes to impingement.In both circumstances the neck and rim are separated by a gapeven during stress IR.
When repeating the examination after osteoplasty, motion maynot improve as much as expected. At the limit of IR, thepelvis moves but the gap separating the rim and neck is largerthan before.
Hip motion and the point of impingement change with repair ofthe labrum. For this reason, you may wish to repeat thedynamic fluoroscopic examination after rim resection andlabral repair but before any femoral osteoplasty.
Calcified labral fibrocartilage on the acetabular margin often isnot visible by fluoroscopy. Complete removal of the calcifiedmaterial creates room for motion and exposes fresh bone forrepair.
Because the C-arm is positioned at about 40° to the body axis,the 25° tilt (rim) view provides a false-profile view of theacetabulum. Anterior acetabular insufficiency as well asabnormal anterior overhang should be evident with this view.
Especially with distraction, a detached labrum will hang into thejoint, obscuring the acetabular margin. Use a probe and therim view to locate the bony margin of the acetabulum in this
circumstance.
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Use of Dynamic Examination to ExecuteOsteoplasty
Once the initial dynamic examination is complete,the limb is placed in extension for diagnostic arthros-copy, rim resection, removal of unstable cartilage, andlabrum refixation. Rim resection and placement ofsuture anchors are performed with distraction and byuse of the rim view (i.e., with the C-arm tilted 25°).
The beta view is used to plan the osteoplasties (Figs3B, 4B, 5A, and 6B). Our general goal has been toemove enough bone to increase IR in 90° of flexiono 35°.19 This is accomplished by femoral osteoplastylone or in combination with recession of the acetab-lar rim. The beta view permits one to estimate rotationhat can be gained by a bone resection that removes lesshan 30% of the width of the neck20 and does not com-
promise acetabular coverage (Figs 3 and 6).For the anterior femoral osteoplasty, traction is re-
moved and peripheral access established. With the hipin full extension, the C-arm must be rotated back to amore horizontal position to reproduce the view ofmaximum neck deformity (neck view, Figs 1B and3C). This tilt varies but can be estimated from the hipflexion required to display it during the dynamic ex-amination or by use of the “around-the-world tech-nique” of Larson and Wulf.11 If, for example, themaximum deformity is straight anterior, it would bemost visible at 65° to 70° of flexion on the dynamicexamination and reproduced by tilting the C-arm intoa horizontal (lateral) position when the hip is in fullextension. After the osteoplasty progresses, the extentof the osteoplasty is monitored by rotating the armabove and below the initial neck view position. Afterthe osteoplasty is completed, the foot is released andthe dynamic examination and beta view are repeatedto document restoration of concavity of the anterior-superior head-neck junction (� angle), the clearanceetween the anterior neck and the acetabular rim ineutral rotation (� angle), and actual improvement in
IR (Figs 4C, 4D, 5B, 6C, and 6D).
Observations
The location and shape of the anterior femoralneck deformity varied but could be reliably visual-ized by this method because, in our series, the pointof greatest deformity was always located in theanterior/superior quadrant of the head-neck junc-tion, or straight anterior. The deformity appeared aseither a frank prominence (“cam” lesion, Fig 4) oras insufficient head offset (Fig 6). Our preference
has been to treat cases of mild acetabular or femoral
retroversion by osteoplasty of the femoral neck, andthe beta view permitted us to determine whetherthis can be accomplished without removal of anexcessive amount of femoral neck, as defined byMardones et al.20
If the C-arm is rotated in a consistent plane, theimages could be readily interpreted and referencedto the spot views. Because the neck view repro-
TABLE 2. Pointers for Performing Osteoplasty
Use the spot view in neutral rotation to plan the osteoplastieswith the goal of removing a minimum of healthy acetabulararticular surface and �30% of the width of the femoral neck.ost impingement cases are “mixed” cam and pincer, and somecases of acetabular retroversion and profunda can be addressedlargely by reshaping a concomitant femoral neck deformity,thus preserving acetabular coverage.
egin the femoral osteoplasty at the apex of the deformity,where the most bone will be removed. This helps avoidcreation of a step-off at the articular margin and facilitatesshaping of a spherical head.femoral neck cyst or focal sclerosis is often present at theapex of the deformity and can be used as a visual landmark.uring the actual osteoplasty, it helps to think in distances ratherthan angles. Thirty degrees of IR requires 12 to 14 mm ofclearance between neck and rim. As the femoral osteoplastyextends the spherical articular surface of the head, one canestimate its adequacy based on size, using the bur as areference.
ase your resection on preoperative IR at 90° of flexion, whichis normally about 30°. If a patient has 10°, you only need togain 20° based on the beta view.
he anterior neck deformity (“cam lesion”) can be narrow orwide. Look medially and laterally for the transition to normalneck contour (1) to circumscribe your resection, (2) to use asa visual template for your reshaping, and (3) to avoid thelateral retinacular vessels.
phericity of the head is difficult to judge arthroscopically; relyon fluoroscopy for initial shaping if you wish to create aspherical surface.s the femoral osteoplasty extends proximally to the articularsurface, the shape of the head should be judged visually,because an apparent bony prominence seen on the fluoroscopicimage may actually be covered by normal spherical articularcartilage.
he reshaped head-neck junction can be assessed visually forsphericity by moving it under the labrum with mild hipflexion. In this position the labrum or acetabular margin servesas a visual template for curvature. We perform this test earlybecause it does not require freeing the foot.ften, an unstable labrum must be surgically mobilized toexpose the acetabular margin, reshape the rim, and effect asecure repair. Detachment from the non-articular side is oftenpreferable, especially when the labrum hangs distally into thejoint. Once this repair is done, the rim can be used as a visualguide for femoral head sphericity.
duces the neck profile seen on the beta view, the
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998 C. B. LEE AND J. CLARK
femoral osteoplasty drawn on the beta view couldbe accurately executed with the hip in extension(Figs 3B and 3C). The arthroscopic view of the neckwas easier to interpret when C-arm control was usedto mark the proximal and distal extents of theplanned resection by use of the ablator. At thebeginning of this series, we used a limited anteriorarthrotomy for the osteoplasty, but after 9 cases, wefound that arthroscopic osteoplasty under C-armcontrol was more efficient than direct exposurethrough the anterior incision. With experience, thenumber of repeat examinations needed for comple-tion of the osteoplasty decreased.
Actual bone-to-bone impingement during the dy-namic examination was observed only when thelabrum was fully ossified, as in Fig 5. Otherwise, therim and neck typically remained separated by what wefound to be interposed labrum (Fig 7) or thickenedperiosteum on the neck. IR was noticeably increasedby refixation of a detached, interposed labrum. Camlesions on the anterior neck did not pass into the jointduring dynamic testing; instead, the aspherical necklevered against the articular side of the rim as the jointsubluxated (Fig 4B). This contact was associated witharthroscopic findings of a chondral ulceration at thelabrochondral junction. Full-thickness cartilage loss incam impingement correlated with bone-to-bone con-tact seen during dynamic examination.
Because head offset was increased by removal of acam deformity, the point of potential conflict betweenthe acetabular rim and femoral neck moved distally onthe femoral neck. Improvement of IR and of flexion inneutral rotation required reshaping of the entire ante-rior femoral neck, sometimes to the point of capsularinsertion (Fig 4D). This phenomenon could only beappreciated by repeated dynamic examination of IR.Simple creation of the conventional 10- to 15-mmgroove along the head-neck junction19,20 reduced the� angle to normal ranges but did not provide satisfac-ory motion in this circumstance.
Repeat examination of forced IR often showed that,espite completion of the planned osteoplasties, rota-ion at 90° of flexion did not always improve to ouroal of 35°. Instead, the pelvis would move despite theresence of a generous separation between head andeck (Fig 4D). We believe that this is a result ofosterior (external rotator or capsular) tightness, be-ause other signs of impingement, specifically luxa-ion or bony encroachment, were absent.
It was not uncommon for there to be no clearanceor IR on the initial beta view (Figs 4-6). That is, the
� angle was 0. This was confirmed by testing IR.
Generally, IR was less than what was measured in theoffice, we assume because the fluoroscopic techniqueshows subtle pelvic movement that we do not detectby physical examination.
The initial measurement of femoral version was avaluable adjunct in cases where retroversion contributedto impingement (Fig 2). Specifically, femoral retrover-sion may cause impingement in the presence of modestabnormalities in head offset or acetabular overhang.
Potential Problems
In our setup the pelvis tends to tilt, especiallywhen traction is released, and the plane of the pelvisshould be checked frequently. A large perineal postinterfered with the neck osteoplasty, and for thisreason, we usually removed it when traction was nolonger required. This method does not address pos-terior impingement or acetabular retroversion, butthose conditions can be identified before any sur-gery. If a patient has poor abduction on the oppositeside, the C-arm cannot easily be aligned perpendicular tothe neck. The ideal tangential view of the femoral neck(neck view) changes if the hip is flexed, which is pre-ferred by many surgeons for developing peripheral ac-cess. This problem can be solved by adjusting theamount of C-arm tilt or by using the around-the-world
TABLE 3. Cautions With Technique
Not every patient has bony impingement despite the appearanceof deformities on preoperative images and limited motion.This is sometimes discovered during the dynamic fluoroscopicexamination. The most common reason is a large displacedlabral segment, although thick femoral periosteum and othersoft-tissue masses can contribute. Assessment of motioncannot be completed until the tissue is repaired or removed.
Forward pelvic tilt distorts the examination and limitsarthroscopic access. This tilt can sometimes be reduced byelevation of both feet, which relaxes anterior contractures. Thetable should provide support out to the ischium and avoidthick padding under the lumbar spine.
Be vigilant for the effects of femoral retroversion, acetabularretroversion, and acetabular protrusion with negativeacetabular inclination. Although these patients will benefitfrom labral repair, osteoplasty may not be indicated.
Not every patient will regain normal IR intraoperatively, despitecompletion of the planned repair and osteoplasty. This isbecause of soft-tissue constraints, and wider bony resectionshould not be attempted.
A thick perineal post distorts the examination, and we remove itfor the initial examination, as well as after the traction isreleased.
technique of Larson and Wulf.11 The addition of the
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999FAI AND FLUOROSCOPY
dynamic examinations adds to total operative time andfluoroscopy time but not to traction time. During thefollow-up dynamic examination of IR, the neck may stillcontact the labrum, potentially disrupting a repair, al-though we did not experience this problem.
DISCUSSION
The role of osteoplasty for FAI is to restore im-
FIGURE 3. Rim, beta, and neck views. (A) AP pelvis view of 18-yresonance imaging. Because this patient is young and his femoral nosteoplasty and thus preserve the articular surface. (B) Beta view.The hip also has been flexed to the position showing the greatest nal.17 and � angle of Wyss et al.18 are measured. The � angle—hereis available is before bony contact occurs. In this example of pincangle is 7°. Femoral osteoplasty (dashed line) is planned from tBecause of this patient’s malpositioned acetabular articular surfacethe beta view. This image shows distal reshaping of the femoral nto the junction of neck and trochanter.
ingement-free flexion/rotation without unnecessary
compromise of neck strength, joint surface area, orjoint stability. To accomplish these objectives, thesurgeon must understand how diminished head off-set, acetabular overhang, and femoral retroversioncontribute to impingement and have some methodto plan and monitor bony resection in each case.Lavigne et al.21 described “dynamic evaluation” ofthe osteoplasty during the open “surgical disloca-tion” technique introduced by Ganz et al.22 With
d man with protrusio acetabuli and labral detachment by magneticroad, our objective is to provide improved motion through femoral-arm has been tilted back 25° from vertical to create a rim view.formity (beta view). From this beta view, the � angle of Nötzli etepresents the angular distance between neck and rim and, thus, IRingement due to protrusio acetabuli, the � angle is 44° and the �view. (C) Intraoperative neck view during femoral osteoplasty.
tion was carried out solely by femoral osteoplasty as planned fromthe osteoplasty progresses, the impingement point moves distally
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1000 C. B. LEE AND J. CLARK
areas of impingement in positions of flexion, IR,and adduction. When we undertook hip arthros-copy, we could not find an equivalent to this openexamination, even during the time when we used an
FIGURE 4. Evaluation of cam impingement. (A) Initial beta viewIR from this neutral position. (B) Dynamic examination of IR. WithThe femoral head levers posteriorly, and a vacuum sign (black arroan estimate for improvement in IR. (C) Post-osteoplasty beta v
ost-osteoplasty dynamic examination of IR. The femoral head rorom neck, indicating that impingement does not occur with forceell beyond the head-neck junction.
anterior arthrotomy as an adjunct. The dynamic
fluoroscopic examination with spot views (Dunnview, beta view, and stress IR view) was a reliableand efficient solution.
Larson and Wulf11 and Matsuda12 also use fluoros-
an � angle of 50°; the � angle is 0°, which indicates no potentialIR, the point of asphericity (the cam lesion) abuts the acetabulum.ident. The planned osteoplasty is outlined (dashed line), providinghe � angle is reduced to 41° by the femoral osteoplasty. (D)ncentrically within the acetabulum, and a large gap separates rimon. The point of potential impingement (white arrow) has moved
showsforced
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1001FAI AND FLUOROSCOPY
refer to repeated use of a “dynamic assessment” toverify adequacy of the resection. Our approach is
FIGURE 5. Evaluation of pincer impingement. (A) On this beta view,he � angle is 44°; the � angle is 0°. Because the head/neck contours normal, save for a reactive prominence at the site of impingement,mproved motion must be gained primarily by rim resection. Thecetabular osteoplasty will be performed by use of this view. Plannedesection to the arrow should create a 22° improvement in IR. (B)ynamic test of IR after rim trimming. IR has increased 23° from thereoperative dynamic view (not shown). The femoral neck osteoplastyas limited to removal of the small prominence.
different in that we use a stress view initially to
characterize the mechanism of impingement and wecreate a spot view (the beta view) to plan the entireosteoplasty. The oblique rim view provided a betterview of anterior overhang than did the AP view usedin alternative methods. We prefer to create a congru-ent spherical contour for the segment of the femoralosteoplasty that passes into the joint, but we foundsphericity difficult to judge with the arthroscope. Fur-thermore, we could not easily visualize the neck withflexion greater than about 90°. These factors pushedus to be more reliant on intraoperative fluoroscopy forcontrol of the bony work. The specificity of the betaview also made us less reliant on special preoperativeimaging for planning osteoplasties.
Wyss et al.18 showed that in FAI, clinical deficits inR correlate closely with the angular distance betweenhe acetabular rim and femoral neck measured byagnetic resonance imaging scans performed in 90°
f hip flexion (� angle). Our beta view approximatesthe Wyss view but with the hip flexed precisely to theposition that places the point of maximum neck de-formity opposite the anterior-superior acetabular rim.This view, together with the estimate of femoral ver-sion from the Rippstein-Dunn view, provides a com-prehensive picture of individual anatomic factors con-tributing to potential impingement and a template forplanning each osteoplasty.
In critical ways, this picture is more accurate thanmost preoperative imaging. Impingement is com-monly not appreciated on standard AP or lateralradiographs because the anatomic deformities cre-ating FAI are distributed over a wide arc on thefemoral neck and acetabular rim.2,8,23,24 With this
oint in mind, Meyer et al.14 proposed a “45° Dunniew” (AP with hip flexed 45°), which produces anmproved view of head offset in cam-type FAI, and
yss et al.18 used reconstructed magnetic reso-nance images to visualize the relation of the ace-tabulum to the neck in 90° of flexion. Brunner etal.25 describe a � angle measured from AP pelvisviews taken with the subject seated, which is easierto accomplish in most offices. With the ability tomove the hip under fluoroscopy, our dynamic ex-amination allows more precise localization of theapex of the femoral deformity and documents truemaximum IR (before and during osteoplasty). Froma quantitative standpoint, finding the point of max-imum neck deformity enables one to measure themaximum “� angle”17 and plan a safe and appro-priate osteoplasty based on individual anatomy. An-terior acetabular overhang caused by acetabula pro-
funda or cranial acetabular retroversion is also seen
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1002 C. B. LEE AND J. CLARK
in the modified false-profile view inherent in thebeta view. Because both aspects of anterior FAI areaddressed, the net increase in potential IR (� angle)
FIGURE 6. Evaluation of combined cam and pincer impingement.and a flat head-neck junction. The � angle is 68°; the � angle is 0eep surface of the acetabular rim (black arrow), the femoral head ssteoplasty is planned on this view. (C) Intraoperative dynamic evn IR is minimal and that additional femoral osteoplasty is needed tond rim trimming. The � angle is now 38°; the � angle is 32°. To a
The width of the femoral neck was reduced by only 22% and thushelp maintain the joint seal.
can be observed in real time by testing IR (Fig 6C).
In summary, these 2 fluoroscopic spot views pro-vide a useful and cogent basis for executing arthroscopicosteoplasty of the anterior femoral neck using a setup
beta view reveals the combination of anterior acetabular overhangDynamic view of IR. With minimal IR, the neck impinges on thees posteriorly, and a vacuum sign (white arrow) is visible. Femoraln of IR after acetabular rim resection shows that the improvemente congruent motion. (D) Beta view after completion of osteoplastyodate full IR, the osteoplasty extends distally on the neck (arrow).not risk fracture. The reshaped femoral head is made spherical to
(A) A°. (B)ubluxataluatioimprovccomm
that is already standard for hip arthroscopy. The bony
1003FAI AND FLUOROSCOPY
deformities in FAI vary in each patient, and the fluoro-scopic examination reveals these variations. We havefound the pre- and post-osteoplasty dynamic fluoro-scopic evaluation to be the best substitute for directopen observation only possible with surgical disloca-tion.
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