Hip Arthroscopy for Challenging Deformities: Global Pincer Femoroacetabular Impingement Dean K. Matsuda, M.D., Nikhil Gupta, B.S., and Dylan Hanami, B.S.

Abstract: Pincer femoroacetabular impingement occurs in focal or global forms, the latter having more generalized and typically more extreme acetabular overcoverage. Severe global deformities are often treated with open surgical dislocation of the hip. Arthroscopic technical challenges relate to difficulties with hip distraction; central-compartment access; and instrument navigation, acetabuloplasty, and chondrolabral surgery of the posterior acetabulum. Techniques addressing these challenges are introduced permitting dual-portal hip arthroscopy with central-compartment access, subtotal acetabuloplasty, and circumferential chondrolabral surgery. The modified midanterior portal in combination with a zonespecific sequence of acetabular rim reduction monitored with fluoroscopic templating enables precision subtotal acetabuloplasty. Guidelines for acetabular rim reduction include the following suggested radiographic endpoints: postoperative center-edge angle of 35
, a neutral posterior wall sign, and an anterior margin ratio of 0.5. Arthroscopic zone-specific chondrophobic rim preparation and circumferential labral reparative and reconstructive techniques and tools permit the arthroscopic treatment of these challenging deformities.

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ith the rapid growth of hip arthroscopy1 and recent evidence of efficacy and safety in the treatment of femoroacetabular impingement (FAI) using this approach,2,3 there has been a gravitation toward the arthroscopic management of many but not all of these deformities. Pincer FAI occurs in focal or global forms, the latter having more generalized and typically more extreme acetabular overcoverage. These deep sockets classically have a radiographic centeredge angle (CEA) of 40
or greater4 and include protrusio acetabuli and the more prevalent coxa profunda (Fig 1). Severe global deformities have traditionally been treated with open surgical dislocation of the hip,5,6 and protrusio acetabuli has been considered a relative contraindication of hip arthroscopy.7 Arthroscopic technical challenges relate to difficulties with hip distraction; central-compartment (CC) access; and instrument navigation, acetabuloplasty, and chondrolabral surgery From Kaiser West Los Angeles Medical Center (D.K.M.), Los Angeles, California; Jefferson Medical School (N.G.), Philadelphia, Pennsylvania; and Saint Louis University Medical School (D.H.), St. Louis, Missouri, U.S.A. The authors report the following potential conflict of interest or source of funding: D.K.M. receives royalties from ArthroCare and Smith & Nephew. Received August 29, 2013; accepted September 24, 2013. Address correspondence to Dean K. Matsuda, M.D., Kaiser West Los Angeles Medical Center, 6041 Cadillac Ave, Los Angeles, CA 90034, U.S.A. E-mail: [email protected] Ó 2014 by the Arthroscopy Association of North America 2212-6287/13628/$36.00 http://dx.doi.org/10.1016/j.eats.2013.09.021

of the posterior acetabulum. Cam FAI often accompanies these deformities. Moreover, global acetabular deformities often occur in patients with relatively high body mass indexes,8 adding to the aforementioned technical challenges. We present the arthroscopic techniques, pearls, and pitfalls that have enabled us to perform arthroscopic surgery in the treatment of severe global pincer FAI.

Technical Note Dual-portal supine hip arthroscopy is performed with the patient under general anesthesia with muscular paralysis to aid hip distraction. Pelvic orientation is standardized to a raised vertical C-arm fluoroscopy device even before traction is applied.9 With countertraction applied to the nonoperative lower extremity and by use of a well-padded large-diameter perineal post lateralized toward the operative hip, traction is progressively applied to the operative lower extremity with the hip in 10
of flexion (which relaxes the iliofemoral ligament), 20
of abduction, and maximal internal rotation (which relaxes the ligamentum teres,10 compensates for hip anteversion, and opens the anterior CC11). Typically, larger amounts of traction force are required to distract hips with global acetabular overcoverage.12 Although the goal is to achieve 10 mm of distraction between the articular surfaces of the hip (i.e., 15 mm between corresponding subchondral surfaces on fluoroscopy), often asymmetric hip distraction occurs

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D. K. MATSUDA ET AL. Table 1. Techniques for CC Access in Patients With Severe Global Acetabular Overcoverage Distal portal entry through midanterior portal or MMAP Capsulotomy-first approach Inside out Outside in Acetabuloplasty-first approach

Fig 1. AP pelvis radiograph of 20-year-old woman showing bilateral severe coxa profunda with extreme global pincer and cam FAI. The more symptomatic right hip has a CEA of 62
.

with less distraction at the lateral sourcil.12-14 A typical example might be 6 mm of central distraction viewed on anteroposterior (AP) fluoroscopy and 2 mm of lateral distraction. We have observed occasional small changes in distraction widths with adjustments in hip abduction/ adduction but not with adjustments in hip flexion/ extension. Moreover, we sometimes observe a decrement in hip distraction with neutral or external rotation (from our initial internally rotated position). Capsular venting may be performed with a 17-gauge entry needle to aid hip distraction by releasing intracapsular negative pressure. However, our experience has been inconsistent, with typically minimal or no gained distraction even with the intracapsular instillation of air with a syringe. We surmise that, at least in the setting of severe global overcoverage, either more capsuloligamentous contracture exists (perhaps through a timedependent process of limited range of motion from skeletal constraints causing further capsuloligamentous contracture) or venting of the peripheral compartment (intracapsular but extra-articular) may not overcome a CC (intracapsular and intra-articular) retained labral suction seal. Because of severe acetabular overcoverage, entry needle access into the CC is often blocked from the anterolateral portal commonly used to gain initial CC access. This may be exacerbated in the setting of coexisting coxa vara or breva. Hence we will try 1 of several options (Table 1):  Distal portalefirst approach: Initial CC access in made through a distal portal (we prefer the modified midanterior portal15,16 [MMAP], which is 3 cm anterior and 4 to 5 cm distal to the anterolateral

portal when the latter is made with the hip in internal rotation), enabling a more collinear path into the anterior CC.  Capsulotomy-first approach: An initial anterolateral capsulotomy may enable improved hip distraction so that CC access may then be safely achieved. It may be performed through either an inside-out or outside-in arthroscopic technique. 14 B The capsulotomy-first approach from inside out entails initial peripheral-compartment access, instrument triangulation, and subsequent capsulotomy with an arthroscopic knife, mechanical shaver, and/or radiofrequency probe. 14,17 B The capsulotomy-first outside-in variation entails the arthroscopic creation of a space anterior to the hip capsule with subsequent capsulotomy into the peripheral compartment remaining distal to the underlying labrum.  Acetabuloplasty-first approach:13,14 If arthroscopic capsulotomy provides insufficient hip distraction, arthroscopic rim trimming from the peripheral compartment (on the capsular side of the labrum) is performed until sufficient to permit CC access. We use the fluoroscopic templating technique,9 which enables real-time assessment of arthroscopic rim reduction. The technique involves matching the pelvis under the desired amount of hip distraction to a vertical fluoroscopic C-arm image intensifier so that a horizontal AP hip image appears on the viewing monitor. An erasable marking pen is used to draw the desired area of planned acetabular rim resection directly on the viewing monitor screen. Intermittent fluoroscopic images with the raised stationary C-arm device allow assessment of superolateral and, importantly, anterior and posterior rim resections. We image the burr first along the superolateral rim and then along the anterior and posterior rims to define and differentiate their respective extent of overcoverage. By placing a metallic burr on each respective rim, incremental acetabuloplasty is performed until the burr tip “reaches” the predetermined medial border of the fluoroscopic template, “erasing” the contents within the template for controlled and precise completion of planned rim reduction. For global acetabuloplasty, we first demarcate the desired postoperative CEA to approximately 35
. We then draw our template from this “set point” to achieve a neutral posterior wall sign passing “through” the center of the femoral head and an

GLOBAL PINCER FEMOROACETABULAR IMPINGEMENT

Fig 2. Preoperative fluoroscopic template of right hip. The 1 represents the first templating step, and the yellow dot is the set point for the desired CEA (in this case set at 35
). The 2 represents the second step, drawing the anterior rim template (blue line) to the lateral radiographic border of the pubis (blue dot). The 3 represents the third step, drawing the posterior rim template (red line) to the lateral border of the ischium (red dot). The posterior rim template passes through the radiographic center of the femoral head (green dot) and the anterior rim template passes superior and medial to the same landmark.

anterior rim superior and medial to the same radiographic landmark14 (Fig 2). We have revised our fluoroscopic templating technique9 so that the template is made with a horizontal fluoroscopic image of the hip under lower traction force than required for central compartment access. This permits minimization of cumulative traction force, especially relevant with global acetabuloplasty and chondrolabral procedures, while permitting a few millimeters of hip distraction to protect the femoral head from iatrogenic damage during acetabuloplasty. Femoroplasty is performed without traction. We use a zone-specific sequence of rim trimming for global acetabular deformities. We begin with superolateral rim trimming to “set the stage” for subsequent anterior and posterior rim reductions. As shown in Video 1, we reduce the CEA from 62
to 36
, thereby making an arthroscopically created reference point for anterior and posterior acetabuloplasty. We “sculpt” a gentle arc toward the lateral border of the pubis (anterior structure) for the anterior rim and toward the lateral border of the ischium (posterior structure) for the posterior rim. For the anterior rim, we desire an

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Fig 3. Intraoperative AP fluoroscopic image showing metallic burr adjacent to posterior rim at midway point of arthroscopic posterior acetabuloplasty. The black lines encompass the entire region of posterior wall resection, and the red line highlights the remaining posterior wall to be resected to the solid black line, indicating desired postoperative rim reduction. The asymmetric hip distraction should be noted. (Dotted black line, original border of the posterior acetabular wall.)

anterior margin ratio18,19 of about 0.5, although an optimal ratio has not been defined. For the posterior rim, we try to create a neutral posterior wall sign (reducing the posterior rim so that it passes through the femoral head center on the AP projection) to avoid posterior insufficiency while eliminating posterior overcoverage (Fig 3). Initial superolateral acetabuloplasty not only facilitates anterior and posterior rim reductions by providing a bony reference but also improves visualization of the posterior rim, aiding posterior acetabuloplasty (Fig 4). Anterior rim reduction improves clearance for instrument navigation from the MMAP to the posterior rim, as do transient increases in hip distraction, which move the femoral head “out of the way.” Hence the preferred sequence for arthroscopic global acetabuloplasty is superolateral, anterior, and posterior (Table 2). The region and width of rim reduction are more extensive with global or subtotal acetabuloplasty. Whereas focal pincer FAI may have anterior and/or superolateral rim reduction of perhaps 2 to 5 mm, our experience with global pincer FAI is resection approximating 10 mm. Auto-detachment of the labrum often occurs with the extent of rim reduction required for treating severe global deformities. If the labrum is of sufficient quantity and quality (e.g., not ossified), we will perform labral

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Fig 4. Arthroscopic image of right hip during supine arthroscopy. The 70
arthroscope is in the anterolateral portal aimed posteroinferior showing the posterior acetabular rim (AR) during arthroscopic posterior acetabuloplasty using a burr (Flat-top; Smith & Nephew, Andover, MA) in the MMAP to resect excess bone (asterisk) near the direct posterior acetabular rim (9). One should note the protective posterior position of the burr sheath and adjacent muscle belly of the obturator internus, behind which lies the sciatic nerve.

refixation. Otherwise, we will typically perform labral reconstruction with gracilis autograft harvested from the ipsilateral knee.10,15,16 In our case example the adjacent capsule was adhered to the thin labrum. During an acetabuloplasty-first approach (Fig 5), which enables access to the CC, we preserve a cuff of capsulolabral tissue for later reconstruction. Rim preparation is performed with zone-specific chondrophobic drilling (Table 3). Desiring suture anchor placement in proximity but not violation of the acetabular articular cartilage, anterior drill holes are made with the drill positioned parallel to the floor. Because pelvic orientation has been standardized at the onset of surgery, this technique avoids iatrogenic chondral damage. By visualizing the adjacent acetabular cartilage while engaging tactile feel to detect even subtle increased resistance to drill advancement (suggesting unwanted subchondral bone violation), the surgeon ensures safe

Fig 5. Arthroscopic image of right hip after arthroscopic subtotal acetabuloplasty. One should note the exposed femoral head (FH), which was originally fully covered by extreme global acetabular overcoverage and enabled access to the central compartment. The asterisk shows preserved capsular tissue that adhered to the labrum. (AR, acetabular rim.)

anterior suture anchor placement. At the superolateral rim, 2-dimensional AP fluoroscopic spot imaging can confirm a drill path engaging bone while diverging from the articular cartilage. For the posterior rim, the drill path is inherently chondroprotective; by nature of its posterior vector from the MMAP, it diverges from the posterior chondral surface. However, the posterior rim may be particularly thin,20 and posterior wall “blowout” with compromised anchor fixation may occur. We often drill all of the anticipated anchor sites along the acetabular rim in a single stage before passing the first suture. Although we used to initiate drilling with the anterior-most anchor site and progress posteriorly, we now prefer drilling the most challenging posterior or posteroinferior anchor site first to prioritize its safe anchor placement and then base our subsequent perimetric anchor locations off of this reference. Although our experience with posterior labral refixation and reconstruction has been uneventful using the MMAP with straight instrumentation, we have on Table 3. Zone-Specific Chondrophobic Acetabular Rim Drilling

Table 2. Suggested Zone-Specific Sequencing Procedure

Anterior

Superolateral

Posterior

Zone

Description

Templating Acetabuloplasty Rim drilling Labral refixationy

Second Second Third First

First First Second Second

Third Third First* Third

Anterior Superior Posterior

Drill path parallel to floor Fluoroscopic divergent drill path Divergent drill path*

*One should prioritize the position of the most challenging posterior anchor. yOne should prioritize the position of the most challenging reconstruction.

*The posterior-most drill site is the most challenging and should be addressed before the final drill site. If treated as the final drill site, anchor spacing may dictate that far-posterior drilling is performed in a region most susceptible to posterior wall fracture with compromised labral refixation.

GLOBAL PINCER FEMOROACETABULAR IMPINGEMENT

Fig 6. Arthroscopic image of right hip after arthroscopic subtotal acetabuloplasty and capsulolabral reconstruction (asterisks). The visible femoral head (FH) and extensively trimmed acetabular rim should be noted. (10, posterior acetabular rim just above equator; 12, direct superior acetabular rim.)

occasion used a small-diameter suture-based anchor (JuggerKnot soft anchor; Biomet, Warsaw, IN) with straight and curved drill guides to achieve refixation along the posterior or posteroinferior rim. The curved guide is oriented anteriorly away from the posterior cortex to avoid iatrogenic posterior wall blowout. In labral reconstruction we overlap our terminal anchor sites with stable labral margins; the most posterior anchor site is often located in this far-posterior zone. We have also used arthroscopic labralization21 to restore the labral fluid seal function when severe labral insufficiency remains after global acetabuloplasty; this technique has been particularly helpful in cases of farposterior labral insufficiency. After arthroscopic subtotal acetabuloplasty and often circumferential labral refixation or reconstruction (Fig 6), incremental arthroscopic femoroplasty is performed with intermittent arthroscopic dynamic testing to confirm eradication or guide further reduction of ongoing mechanical impingement throughout various combined arcs of hip motion. Partial capsulectomy and placement of the burr tip in proximity to the arthroscopic field of view permit fine adjustment of suction outflow to optimize dynamic arthroscopic visualization. Particular attention is given to the intraoperative anterior impingement test. We desire at least 30
of unrestricted internal rotation and no visible encroachment of the anterolateral or anteromedial22 femoral head-neck region with the anterior acetabular rim. Additional femoroplasty is performed at points of visualized mechanical conflict with the adjacent burr until cam decompression is complete while avoiding

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Fig 7. Detail of postoperative AP pelvis radiograph showing reshaped acetabulum after arthroscopic subtotal acetabuloplasty with reduction of anterior rim (blue line), posterior rim (red line), and superolateral rim (arrowhead) with CEA measuring 36
. One should note the neutral posterior wall sign passing through the radiographic center of the femoral head, as well as the area of superior femoroplasty (arrow).

over-resection. Fluoroscopic and arthroscopic confirmation of sufficient posterior decompression with the hip in the flexedeabductedeexternally rotated position is also performed. We have found posterior acetabuloplasty to a neutral posterior wall alignment to be sufficient without causing iatrogenic posterior insufficiency (Fig 7). Occasional arthroscopic posterosuperior femoroplasty23 is performed proximal to the critical posterolateral vessels supplying the femoral head. These procedures are performed as outpatient operations with the same postoperative protocols as those in patients undergoing arthroscopic surgery for more focal deformities.

Discussion The arthroscopic treatment of extreme global pincer FAI is feasible and offers an attractive less invasive alternative to traditional open surgical dislocation. The challenges of difficult hip distraction and CC access, as well as instrument navigation, acetabuloplasty, and chondrolabral surgery of the posterior acetabulum, can be overcome using the described techniques. However, we recommend that arthroscopic surgery for severe global pincer deformities be performed by surgeons with significant arthroscopic experience in the treatment of less severe focal deformities. Several techniques and pearls have broader application in the treatment of less severe deformities. Standardization of pelvic orientation by the fluoroscopic

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Table 4. Suggested Postoperative Radiographic Endpoints for Global Pincer FAI Endpoint Superolateral rim Anterior rim Posterior rim




CEA, 35 AMR, 0.5 Neutral posterior wall sign

AMR, anterior margin ratio.

templating technique encourages precision arthroscopic acetabuloplasty and safe acetabular rim drilling for suture anchor placement, particularly in the anterior zone (Table 3). Fluoroscopic templating permits intraoperative assessment of not only superolateral but also anterior and posterior rim reductions without altering the vertical C-arm position. The raised C-arm position permits unobstructed maneuvering of even posteriordirected instruments using dual-portal supine hip arthroscopy when combined with the MMAP.9 The MMAP is a utilitarian portal encouraging a distal chondrophobic path for suture anchor placement while allowing access to the posterior acetabulum for rim reduction and chondrolabral surgery. Moreover, it facilitates arthroscopic femoroplasty when needed outside of the classic anterolateral femoral head-neck region into the anteromedial “critical corner”20 and, when indicated, the posterosuperior region proximal to the deep retinacular vessels supplying the femoral head.23 We perform dual-portal arthroscopy for even extreme global pincer and large cam deformities, often without interportal instrument exchange. The amount of rim reduction is guided by fluoroscopic templating and the location/severity of acetabular rim chondral damage. Circumferential chondrolabral damage may occur with severe global deformities especially when accompanied by cam FAI; global rim trimming may eradicate this chondral pathology. Until such time that an optimal acetabular volumetric reduction is determined, we believe a CEA of 35
, an anterior margin ratio18 of 0.5, and a neutral posterior wall sign are reasonable guidelines (Table 4). Complications from hip arthroscopy tend to be low in incidence and severity,24 but arthroscopic surgery for global pincer FAI can require more traction (both time and force) and longer surgery times commensurate with the severity of the deformity and associated pathology, which may increase complication risks, of which we will discuss a few. The sciatic nerve is susceptible to injury from traction and from inadvertent direct trauma. Traction times should not exceed 2 hours, and traction forces should be minimized when CC access is not necessary.25 Prudent traction “timeouts” during which femoroplasty may be performed may be followed by judicious and perhaps partial reapplication of traction only as needed. One must also avoid hip traction in significant hip flexion.26 We

Table 5. Technical Options for Arthroscopic Surgery of Posterior Acetabular Rim Straight suture anchor system through MMAP Optional posterolateral portal Optimization of path to posterior rim Anterior acetabuloplasty Transient reapplication of hip distraction (moves femoral head out of path) Curved suture anchor system aimed anterior, away from posterior cortical wall Small-diameter suture anchors Soft implant suture anchors

typically do not expose the sciatic nerve during posterior acetabuloplasty because the nerve lies posterior to the superior gemellus, obturator internus, and inferior gemellus and medial to the typical region of posterior rim resection. At this anatomic level, it would likely be susceptible to direct injury with excessive trimming of the posteroinferior rim. We recommend keeping the activated burr tip in contact with the posterior rim with the protective sheath between the burr tip and adjacent deep external rotator muscles. Intra-abdominal fluid extravasation is potentially lifethreatening.27 Avoidance of high arthroscopic fluid pressures (we typically perform these procedures at pump pressures of 50 to 60 mm Hg), intermittent palpation of the draped abdomen, intraoperative monitoring of core body temperature and hemodynamic stability, and performance of any indicated iliopsoas tenotomy toward the termination of surgery are recommended.28 With a larger surface area of acetabular bone resection and commensurately more osseous debris generation, patients undergoing the described procedure may be at greater risk of iatrogenic heterotopic ossification. We use chemoprophylaxis with nonsteroidal anti-inflammatory drugs in our patients without medical contraindications and have used indomethacin in the initial postoperative period because of recently reported improved efficacy.29 Acetabular rim preparation for suture anchor placement typically involves drilling along the rim. Care must be taken to avoid iatrogenic violation of the acetabular articular cartilage or, even worse, penetration of a hard anchor implant into the hip joint. A safe angle of approximately 10
has been suggested in a previous study, but it focused on the anterosuperior rim.19 A recent study determined that the 3-o’clock position or direct anterior rim had the smallest margin for error.30 However, the authors acknowledged that portal placement and tissue constraints of the in vivo scenario were not taken into account. We submit that the posterior and posteroinferior acetabular rim may present the most challenging region for drilling and suture anchor placement using the aforementioned

GLOBAL PINCER FEMOROACETABULAR IMPINGEMENT

arthroscopic technique (Table 5). Because safe angles increase with greater depths of rim trimming, the relatively large amounts of rim resection at the posterior rim may enable safe arthroscopic suture anchor placement. Arthroscopic access and surgery of the posterior acetabular rim may be performed with the addition of a posterolateral portal. This portal, by nature of its angle of approach to the posterior rim, would decrease the risk of posterior wall fracture but would actually increase the risk of iatrogenic posterior chondral damage. The posterior portal is in relatively close proximity to the sciatic nerve; however, sciatic complications rarely have been reported. Acetabular rim safe angles19,30 also increase with smaller drill depths and drill diameters. Hence, especially for far-posterior labral refixation, one may consider suture anchor systems that incorporate this technology. We have successfully used 1.4-mm suturebased suture anchors (JuggerKnot soft anchors) with straight and curved guides. These soft anchors may offer an extra degree of safety when compared with harder implants, lessening the risk of posterior wall blowout, articular cartilage violation, and iatrogenic femoral head damage from an exposed hard implant.

Outcomes Encouraging outcomes from arthroscopic surgery for global pincer FAI are beginning to emerge. Successful early outcomes from arthroscopic surgery for protrusio acetabuli have recently been reported.12,31 A multicenter prospective study comparing global (coxa profunda) versus focal pincer FAI found comparable successful outcomes.32

3.

4.

5.

6.

7. 8.

9.

10. 11.

12.

13.

Conclusions Severe global pincer FAI may be treated with arthroscopic techniques, harnessing the advantages of less invasive outpatient surgery. Indeed, hip arthroscopy may be the preferred method to treat these deformities.33 The surgical technique is challenging but feasible. The combined application of fluoroscopic templating, the MMAP, and zone-specific sequencing enables global acetabuloplasty and circumferential chondrolabral surgery. If emerging successful outcomes can be verified with further studies, one may envision gravitation toward the arthroscopic treatment of global acetabular overcoverage.

14.

15. 16.

17.

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18.

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27. Bartlett CS, DiFelice GS, Buly RL, Quinn TJ, Green DS, Helfet DL. Cardiac arrest as a result of intraabdominal extravasation of fluid during arthroscopic removal of a loose body from the hip joint of a patient with an acetabular fracture. J Orthop Trauma 1998;12:294-299. 28. Kocher MS, Frank JS, Nasreddine AY, et al. Intraabdominal fluid extravasation during hip arthroscopy: A survey of the MAHORN group. Arthroscopy 2012;28: 1654-1660. 29. Bedi A, Zbeda RM, Bueno VF, Downie B, Dolan M, Kelly BT. The incidence of heterotopic ossification after hip arthroscopy. Am J Sports Med 2012;40:854-863. 30. Hernandez JD, McGrath BE. Safe angle for suture anchor insertion during acetabular labral repair. Arthroscopy 2008;24:1390-1394. 31. Safran MR, Epstein NP. Arthroscopic management of protrusio acetabuli. Arthroscopy 2013;29:1777-1782. 32. Matsuda DK, Gupta N, Sehgal B, Bourchette R. Arthroscopic surgery for global versus focal femoroacetabular impingement: Are the outcomes different? (SS-34). Arthroscopy 2013;29:e16-e17 (suppl, abstr). 33. Parvizi J. FAI done arthroscopic with mini open is better. Presented at the International Society for Hip Arthroscopy 2012 Annual Meeting, Boston, MA, September 27, 2012.