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Technical Note

Intraoperative Fluoroscopy for Evaluation of Bony ResectionDuring Arthroscopic Management of Femoroacetabular

Impingement in the Supine Position

Christopher M. Larson, M.D., and Corey A. Wulf, M.D.

Abstract: There is a steep learning curve regarding many aspects of arthroscopic management offemoroacetabular impingement. One of the concerns with regard to this approach is verification ofappropriate bony resection for cam- and pincer-type pathology. Dynamic assessment and directvisualization of bony resection are the primary means of evaluating appropriate resection. Intraop-erative fluoroscopy, however, can be a helpful adjunct when performing the rim resection or femoralresection osteoplasty. We describe a predictable and reproducible fluoroscopic method for per-forming and verifying appropriate bony resection of pincer and cam lesions in an attempt to helpminimize the risk of under- and over-resection. Key Words: Hip arthroscopy—Femoroacetabularimpingement—Fluoroscopy.

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emoroacetabular impingement (FAI) has been treatedby open surgical dislocation, limited open approaches,

nd all-arthroscopic techniques.1-11 Open surgical dis-ocation allows for complete visualization of the fem-ral head-neck junction and acetabular rim for resec-ion and dynamic evaluation throughout the entireange of motion. Limited open approaches allow forirect visualization of the anterolateral femoral head-eck junction, with limited evaluation of the acetab-lar rim. All-arthroscopic techniques allow for evalu-tion of the anteroinferior to posterosuperior femoral

From the Minnesota Orthopaedic Sports Medicine Institute andwin Cities Orthopedics, Minneapolis, Minnesota, U.S.A.C.M.L. receives financial support for education from Smith &

ephew. C.A.W. reports no conflict of interest.Address correspondence and reprint requests to Christopher M.

arson, M.D., Department of Orthopaedics, Minnesota Sportsedicine Sports Fellowship Program, 775 Prairie Center Dr, Ste

50, Flagship Corporate Center, Eden Prairie, MN 55344, U.S.A.-mail: [email protected]© 2009 by the Arthroscopy Association of North America

s0749-8063/09/2510-$36.00/0doi:10.1016/j.arthro.2009.07.020

Arthroscopy: The Journal of Arthroscopic and Related Surg

ead-neck junction and the majority of the acetabularim. During arthroscopy, the femoral head and ace-abular rim are not visualized in 3 dimensions andnstead are visualized regionally through multiple por-als. This regional assessment can make evaluationf the bony pathology and subsequent resectionifficult. Potential complications related to im-roper orientation and poor visualization include inac-urate resection, under-resection, over-resection, or aombination thereof.12-16 We propose a reproducible in-raoperative fluoroscopic evaluation before, during, andfter bony resection for management of cam- and pincer-ype pathology as an adjunct to direct assessment duringrthroscopic management of FAI.

PREOPERATIVE EVALUATION

The patient is placed supine on the fracture table withenerous padding of bony prominences and the use of aell-padded perineal post. The nonoperative leg islaced in maximal abduction and external rotation. Theperative leg is placed in neutral abduction, 0° to 10° ofip flexion, and maximal internal rotation. The anterior-
uperior iliac spines are identified, and the bed is rotated
1183ery, Vol 25, No 10 (October), 2009: pp 1183-1192

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1184 C. M. LARSON AND C. A. WULF

n the axial plane, or “air planed” (typically to the oper-tive side), to have the anterior-superior iliac spinesarallel to the floor and/or ceiling. This helps to place theelvis in a neutral position. A fluoroscope is then intro-uced at a 45° angle between the legs, and an antero-osterior (AP) view of the operative hip is obtained withlight traction (Fig 1). Trendelenburg or reverse Tren-elenburg positioning of the patient is used to replicate aell-centered preoperative AP pelvis view of the patientith respect to the level of the acetabular crossover sign,hen present, and the relation between the ilioischial line

nd tear drop (Fig 1). The preoperative pelvis shouldave symmetric obturator foramina, and the tip of theoccyx should be centered over the symphysis with 0 tocm between these 2 structures so that acetabular ver-

ion can be properly evaluated. The fluoroscopy machinean be moved to the tip of the coccyx and symphysis tourther verify appropriate pelvic orientation.

After the fluoroscopic image replicates the preop-rative AP pelvis view, the femoral head-neck junc-ion is assessed with an “around-the-world” fluoro-copic evaluation. The AP image with the hip andnee in extension allows for evaluation of the superiornd inferior head-neck junction (Fig 2). AP images of

IGURE 1. The radiographic profile of the operative hip (left hip)ith a properly aligned (B) preoperative AP pelvis view. Specificosterior wall represented by a solid line and the anterior wall relioischial line (horizontal line) on both images.

he femur are obtained with the hip in maximal inter-afl

al rotation (Fig 3), neutral rotation (Fig 4), and max-mal external rotation (Fig 5). Hip rotation is obtainedy rotating the foot of the operative leg. Next, the hipnd knee are flexed to approximately 40° to evaluatehe anterior and posterior head-neck junction (Fig 2).ateral images of the proximal femur are obtained in

duced by comparing the (A) intraoperative fluoroscopic AP viewn is paid to the level and degree of acetabular crossover (with theted by a dashed line) and the relation between the tear drop and

IGURE 2. Our preferred terminology used to describe the direc-ion of reference in relation to the operative anatomy for a left hipn the AP orientation (the hip is in slight flexion, neutral rotation,

is reproattentiopresen

nd neutral abduction) and lateral orientation (the hip and knee areexed to 40°, with neutral rotation).

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1185FLUOROSCOPY AND FEMOROACETABULAR IMPINGEMENT

FIGURE 3. (A) Intraoperative positioning of left hip in extensionwith maximal internal rotation reproducing AP radiograph for eval-uation of superior and inferior head-neck junction and acetabularversion. (B) The intraoperative fluoroscopic image before resectionwith the hip in extension and maximal internal rotation shows thecrossover sign (with the posterior wall represented by a solid lineand the anterior wall represented by a dashed line) as indicated bythe anterior wall crossing lateral to the posterior wall. (C) Theintraoperative fluoroscopic image after resection with the hip in thesame position confirms bony resection and absence of the crossoversign (with the posterior wall represented by a solid line and theanterior wall represented by a dashed line). Nitinol guidewires(asterisks) are left in place to allow for re-establishment of portals ifnecessary.

IGURE 4. (A) The intraoper-tive fluoroscopic image beforeesection with the hip in exten-ion and the foot in neutral ro-ation shows the crossover signdashed arrow) as indicated byhe anterior wall crossing lat-ral to the posterior wall andam impingement (solid ar-ow). (B) The intraoperative flu-roscopic image after resectionith the hip in the same position

onfirms the absence of therossover sign (dashed arrow)nd presence of improved head-eck offset (solid arrow).

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aximal internal rotation (Fig 6), neutral rotation (Fig), and maximal external rotation (Fig 8). The neutralmage is similar to the modified Dunn view. Cam lesionsoted anteriorly on the lateral view indicate anterolateralsphericity, whereas cam lesions seen superiorly on theP view indicate superior extension. Finally, the fluo-

oscopy machine is rotated under the operative leg tobtain a cross-table lateral view for additional evaluationf the head-neck junction and femoral neck version withhe knee in neutral rotation (Fig 9).

Once the intraoperative fluoroscopic evaluation haseen performed, the surgeon can correlate the imagesith the preoperative templating from previously ob-

ained plain radiographs and computed tomographycans (Tables 1 and 2).

IGURE 6. (A) The intraoper-tive fluoroscopic image beforeesection with the hip flexed0° and in maximal internal ro-ation shows cam impingementarrow). (B) The intraoperativeuoroscopic image after resec-

ion with the hip in the sameosition confirms improved head-eck offset (arrow).

SURGICAL PROCEDURE

Our technique for arthroscopic management of FAIas been previously described.3 Traction is applied,nd typically 2 portals (anterolateral and anterior) arestablished for arthroscopic management of FAI. Apinal needle is placed in the posterolateral portal forutflow. The central compartment is first inspected,nd the labrum, acetabular rim, and labrochondralunction are evaluated to confirm the suspected patho-ogic forces. Preoperative and intraoperative radio-raphic findings need to be correlated with the en-ountered arthroscopic pathology when one is makingecisions about the management of any bony abnor-alities (Tables 1 and 2).

FIGURE 5. (A) The intraoper-ative fluoroscopic image beforeresection with the hip extendedand the foot maximally exter-nally rotated shows the cross-over sign (dashed arrow) as in-dicated by the anterior wallcrossing lateral to the posteriorwall and cam impingement(solid arrow). (B) The intraop-erative fluoroscopic image afterresection with the hip in thesame position confirms the ab-sence of the crossover sign(dashed arrow) and presence ofimproved head-neck offset (solidarrow).

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FIGURE 7. (A) Intraoperative positioning of the left hip in flexionwith neutral rotation reproducing the lateral radiograph of the femurfor evaluation of the anterior and posterior femoral head-neck junc-tion. (B) The intraoperative fluoroscopic image before resectionwith the hip in flexion and neutral rotation shows cam impingement(arrow). (C) The intraoperative fluoroscopic image after resectionwith the hip in the same position confirms improved head-neckoffset (arrow).

IGURE 8. (A) The intraoper-tive fluoroscopic image beforeesection with the hip in flexionnd maximal external rotationhows cam impingement (ar-ow). (B) The intraoperativeuoroscopic image after resec-

ion in the same position con-rms improved head-neck off-et (arrow).

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incer Resection

Once the decision has been made to manage theony impingement, we first address the pincer lesion.ifferent techniques for management of the labrum

ssociated with pincer impingement have been de-cribed.4,5,9,17,18 We prefer to preserve the labrumhenever possible. We routinely perform a labral

akedown and reattachment to the acetabular rim forincer lesions extending to or beyond the 12-o’clockosition. A bur is then introduced through the anteriorortal with the arthroscope in the anterolateral portal.he bur is placed on the anterior rim, and a fluoro-copic image is used to verify placement at or just
istal to the site of the anterior wall crossing the p
osterior wall (Fig 10A). It should be re-emphasizedhat fluoroscopic/radiographic findings need to be cor-elated with arthroscopic findings (Table 1). Aftererification of pincer pathology, the bur is used toesect the prominent anterior rim (Fig 10B). Fluoros-opy will show removal of the prominent anterior wallcrossover sign), and the bur is then moved up thecetabulum from anteroinferior to superior to verifyhat the anterior wall lies medial to the posterior wallnd that the 2 walls converge but do not cross supe-iorly. There should be a smooth transition from infe-ior to superior. Once the anterior prominence is re-ected, the arthroscope is placed into the anterior

GURE 9. (A) Intraoperative positioning to obtain a cross-tableeral image with the left hip in extension. (B) The intraoperativeoss-table lateral fluoroscopic image before resection shows campingement (arrow). (C) The intraoperative cross-table lateral flu-oscopic image after resection confirms improved head-neck offsetrrow).

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ortal. The superior area of rim resection is then com-leted. The goal should be to leave a lateral center-edgengle of at least 25°. The labrum is repaired with suturenchors after completion of the rim resection.

am Resection

Once the rim resection is completed, the hip isexed to approximately 40° and the peripheral head-

TABLE 1. Pincer Re

Preoperative 3-dimensional computed tomographas the location of os acetabuli and rim fractureresection.

If imaging studies show pincer-type pathology bpathology, bony resection is not clearly indica

If a crossover sign is associated with acetabulardeficiency/dysplasia, anterior rim resection shoacetabular structural instability.

If bony resection is not appreciated on intraoperaappropriate positioning, then further resectiondynamic testing for impingement, and preoper

When significant superior-lateral rim resection ison a well-aligned preoperative radiograph that

Superior rim resection is generally minimal excewith coxa profunda.

Acetabular coverage can be difficult to determinintermittent release of traction during rim resecoverage.

A posterolateral portal can be formally establisheresection are required (i.e., posterior labral oss

Arthroscopic management of protrusio acetabuliamount of rim resection and subsequent dynamapproach.

TABLE 2. Cam Res

Three-dimensional computed tomography scanstheir relation to the lateral retinacular vessels,superolateral head-neck junction on these scan

If imaging studies show cam-type pathology butbony resection is not clearly indicated.

When recontouring the femoral head-neck junctifluoroscopically by further externally rotating

If bony resection is not appreciated on intraoperaappropriate positioning, then further resectiondynamic testing for impingement, and preoper

The superolateral synovial fold is the site of thecarefully protected throughout the case and uspreoperative 3-dimensional computed tomogra

When the hip is brought into extension, further rjunction anteriorly can lead to a resection tooagain.

It is important to periodically dynamically assessover-resection and resultant loss of the labral s

Symptomatic posterior cam lesions are difficult t
with an open surgical dislocation.
eck junction is identified. Cam-type impingement,hen present, is then treated with a femoral resectionsteoplasty.3-6,8-11,19,20 The inferior-medial synovialold is at about the 5:30 position for a right hip, andhis is typically the most inferior extent of cam le-ions. A fluoroscopic image is taken, and the medialxtent of the resection follows a line that begins at thenferior head-neck junction and runs roughly perpen-

: Pearls and Pitfalls

valuable to evaluate acetabular version, as wellcan help template anterior and/or posterior rim

operative findings do not confirm the

rsion and superior and posterior acetabularavoided because this can lead to global

oroscopic imaging despite attempts atbe guided by direct arthroscopic visualization,diographic templating.d, the proposed rim resection should be drawncorrelated with intraoperative fluoroscopy.

ases of labral ossification typically associated

peratively with the hip in traction, andllows for a better evaluation of acetabular

n more posterior areas of acetabular rimn in the presence of coxa profunda).be undertaken with caution because theluation can be difficult with an arthroscopic

Pearls and Pitfalls

ful to evaluate the extent of cam lesions andcan be visualized as perforations at the

erative findings do not confirm the pathology,

area of resection will typically be seen.oroscopic imaging despite attempts atbe guided by direct arthroscopic visualization,diographic templating.lateral retinacular vessels and should belandmark for resection when correlating withns.n of the previously recontoured head-neckially when the hip is evaluated in flexion

pingement during the cam resection to avoid

ss arthroscopically and may be better managed

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icular to the femoral neck to the superior head-neckunction (Fig 11). This line should be confirmed byirect arthroscopic visualization of the head-neckunction and is simply a guide. The location of theonflict at the femoral head-neck junction is also eval-ated with dynamic assessment showing impingementf the femoral head-neck junction against the acetab-lar labrum. Once the medial extent of the resectionas been outlined with a bur, the surgeon recontourshe head-neck junction, working medial to lateralaway from the acetabulum/toward the greater andesser trochanters). The osseous lesion is graduallyemoved and tapered to the normal femoral neck lat-rally with occasional dynamic assessment to avoidver-resection and loss of the labral seal in flexionTable 2). The femoral resection is continued superi-rly, and a fluoroscopic image with the hip in externalotation will show improvement in femoral head-neck

IGURE 11. Intraoperative fluo-oscopic images of left hip withip in flexion and neutral rota-ion defining medial extent ofemoral resection osteoplastyith bur moving from postero-

nferior (A) to anterosuperiorB) head-neck junction. Theedial extent of the femoral re-

ection typically runs from thenferior femoral head-neck junc-ion along a line roughly perpen-icular to the femoral neckdashed line).

phericity. When the lateral view in external rotationhows improved femoral head-neck offset, which isonfirmed by direct arthroscopic visualization, the hips extended and the foot maximally internally rotated toomplete the more superior areas of femoral resection.he bur is placed where the most superior resection haseen completed and continued superiorly at the levelf the visualized head-neck junction (Fig 12). Thisill result in a radiograph with improved offset onoth AP and lateral views. At this point, a dynamicssessment under direct arthroscopic visualization iserformed with hip flexion, internal rotation, externalotation, abduction, and adduction to verify impinge-ent-free range of motion and maintenance of the

abral seal. This is followed by a repeat around-the-orld fluoroscopic evaluation identical to that per-

ormed before the procedure (Figs 3-9). This shouldhow a normal relation of the anterior and posterior

FIGURE 10. (A) Intraoperativefluoroscopic image of left hipwith arthroscope in anterolat-eral portal and bur in anteriorportal at inferior extent of an-terior wall (dashed line) cross-over sign (with posterior wallrepresented by solid line). (B)Intraoperative fluoroscopic im-age of bur after rim resection toanterosuperior aspect of ace-tabular rim.

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alls of the acetabulum and improved head-neck off-et seen on AP and lateral images.

DISCUSSION

Arthroscopic management of FAI continues tovolve, with excellent outcomes reported in the liter-ture at early-term follow-up.3-6,8-11 However, compli-ations such as femoral neck fracture and iatrogenicip instability have been reported.13,14,16,17,20,21 Theres an extremely steep learning curve with respect toaking the diagnosis and performing the procedure

hat even the most experienced hip arthroscopist con-inues to climb. Under-resection, over-resection, andn some cases both under-resection and over-resectionay lead to suboptimal outcomes as a result of resid-

al impingement or the creation of structural instabil-ty. It is imperative to use all resources includinghysical examination findings, preoperative imagingtudies, intra-articular anesthetic injections, and intra-perative findings to make the correct diagnosis. In-raoperative findings are the cornerstone with respecto evaluation of the pathologic forces at work, asell as verifying appropriate bony resection and

limination of the conflict. Because of the limitations of

IGURE 12. The superior head-neck junction osteoplasty is com-leted by bringing the leg into extension and maximal internalotation. This fluoroscopic image of the left hip shows the burompleting the resection at the superior femoral head-neck junctionith the hip in extension.

rthroscopic visualization, when compared with an open

urgical dislocation, we believe that this fluoroscopicechnique can help to orient the surgeon, further con-rm appropriate bony resection on the acetabulum andemur, and reduce the potential for under- and over-esection. We have used this technique on over 400atients with the primary diagnosis of FAI and haveublished our outcomes in this patient population.3,9

e have had no case of femoral neck fracture oratrogenic hip instability using this fluoroscopic tech-ique as part of an arthroscopic procedure for FAI.his fluoroscopic technique is not meant to replaceirect arthroscopic evaluation during the procedure,nd the surgeon should not rely on fluoroscopy alonehen performing this procedure.

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2. Clohisy JC, McClure JT. Treatment of anterior femoroac-etabular impingement with combined hip arthroscopy and lim-ited anterior decompression. Iowa Orthop J 2005;25:164-171.

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