The Modified Mid-Anterior Portal for Hip Arthroscopy

Abstract

The modified mid-anterior portal is a utilitarian hip arthroscopy working portal that permits dual-portal comprehensive surgery for femoroacetabular impingement and related chondrolabral procedures without the need for interportal exchange. Its distal location facilitates labral reparative and reconstructive procedures while minimizing iatrogenic acetabular chondral damage. The relatively lateral location permits instrument navigation not only along the anterosuperior acetabular rim and anterolateral proximal femur typically required for acetabuloplasty and femoroplasty but even to the posterior regions of the hip in cases of global pincer femoroacetabular impingement and posterior extensions of cam morphology and the anteromedial proximal femur while avoiding direct injury to the lateral femoral cutaneous nerve.

Hip arthroscopy is the fastest growing orthopaedic procedure,¹ with expanding indications across multiple orthopaedic disciplines. However, the learning curve is substantial, and the rate of hip arthroscopy complications, though typically small in prevalence and severity, may be higher than initially appreciated.² Historically, 3 portals were typically used for hip arthroscopy: anterolateral portal (ALP), posterolateral portal, and anterior portal (AP). The ALP continues to be popular and remains the primary viewing portal, often used with a 70° arthroscope. The posterolateral portal is less frequently used, often for cases in which posterior hip access is desired. The AP provides a useful working portal for commonly encountered anterior hip pathology (e.g., anterior or anterosuperior labral tears, classic cam and/or pincer femoroacetabular impingement [FAI]), but its relative proximal location limits its utility in arthroscopic labral reparative and reconstructive procedures. Often, accessory distal portal(s) are required to safely drill and seat suture anchors in close proximity without violating the acetabular rim articular cartilage.³

The mid-anterior portal (MAP) is a popular distal-based portal that facilitates labral repair because of its relative distal location.⁴ It is significantly anterior and distal to the typical ALP. During our use of this portal, we modified its location and found that our ability to perform arthroscopic acetabuloplasty, labral refixation, and femoroplasty was further enabled. We began using the modified mid-anterior portal (MMAP) for all of our dual-portal arthroscopic hip procedures in 2005 and discovered that it enabled arthroscopic access to expanding areas of the acetabular rim and proximal femur, which facilitated the development of procedures such as arthroscopic posterior cam decompression,⁵ arthroscopic femoroplasty of the anteromedial “critical corner,”⁶ arthroscopic decompression of subspine impingement,⁷ and arthroscopic surgery for global pincer deformities including severe coxa profunda⁸ and protrusio acetabuli.⁹

Technique

Because the MMAP is established in relation to the anterolateral viewing portal (ALP), it is important to establish this viewing portal with precision and consistency. Likewise, the relation of both portals to the acetabulum will change with setup positioning of the operative hip. Hence we standardize our supine arthroscopic setup by aligning the pelvis in the coronal and sagittal planes to a vertical C-arm fluoroscopic imaging device by the fluoroscopic templating technique.¹⁰ Hip distraction is performed with the operative hip in 10° of hip flexion (which relaxes the iliofemoral ligament), 20° of abduction, and approximately 30° of internal rotation (which relaxes the ligamentum teres while preferentially opening the anterior central compartment space under distraction and optimizes femoral head position to minimize instrument obstruction).

The ALP is established at the intersection of the anterior and superior borders of the greater trochanter. The MMAP is typically 3 cm anterior and 4 to 5 cm distal to the ALP with commensurate adjustment for very small or large patients. Once the ALP has been established under fluoroscopic guidance and a 70° arthroscope inserted into the central compartment, we use fluoroscopic and arthroscopic guidance as an entry needle penetrates the anterior capsular triangle (Table 1). Infrequently, the needle may be blocked by the anterior femoral head. If this occurs, the surgeon should alter the needle trajectory, increase hip internal rotation, and/or adjust the percutaneous needle entry site slightly more anterior. On occasion, the needle may enter the anterior capsular triangle too close to or even “behind” the anterosuperior labrum. If not easily remedied by a subtle change of the needle path, a technical pearl is to proceed with nitinol wire exchange followed by careful insertion of the arthroscopic cannula and matching cannulated blunt trocar through the capsule. While the tip of the blunt nitinol wire is retained, the stiffer obturator/cannula permits repositioning of the nitinol wire for atraumatic placement “over” rather than through the labrum. Simultaneous removal of the trocar and nitinol wire prevents inadvertent wire breakage. The arthroscopic cannula is retained for the insertion of an arthroscopic knife and then removed to permit immediate interportal capsulotomy performed under initial “dry” arthroscopic visualization and procession to the specific arthroscopic hip procedure(s).

Table 1.

Key Steps

Distract the hip in internal rotation; this aids distraction by relaxing the ligamentum teres and opens the anterior central compartment.

Establish the ALP under fluoroscopic guidance, entering the capsule at or slightly anterior to the mid-coronal plane of central compartment for typical anterior-based pathology.

Establish the MMAP 3 cm anterior and 4-5 cm distal to the ALP.

Perform entry of the MMAP needle in the anterior capsular triangle under fluoroscopic and arthroscopic guidance.

Perform dry arthroscopy for interportal capsulotomy; this minimizes “red out” from blood that obstructs visualization and is quick and efficient.

Video 1 shows the location and utility of the MMAP as used in various dual-portal supine hip arthroscopic applications.

Discussion

Recognizing that there is no perfect portal for all arthroscopic hip applications, we have found the MMAP to be a user-friendly portal with several benefits. The MMAP is presented as a utilitarian hip arthroscopy working portal that permits dual-portal comprehensive surgery for FAI and related chondrolabral procedures without the need for interportal exchange. Although using additional portals or interportal exchange is preferred by some surgeons and may provide inherent advantages in specific instances, the MMAP permits freedom of choice.

The MMAP's distal location facilitates central compartment access through a favorable angle of approach collinear to the anterior space created with traction and hip internal rotation. We have yet to convert to an arthrotomy for central compartment access and have resorted to an arthroscopic acetabuloplasty-first approach only for the most challenging cases of extreme global pincer FAI.^8,9 Perhaps more importantly, the distal location facilitates labral reparative and reconstructive procedures while minimizing iatrogenic acetabular chondral damage.² We are typically able to safely place suture anchors from the anteroinferior acetabulum (generic 4-o'clock position) to the posterior acetabulum (9-o'clock position), the latter being used in cases of posterior labral tears or global pincer FAI (coxa profunda and protrusio acetabuli).^8,9,11 Although the typical labral tear is seen in the anterosuperior or superior region, anterior tears occur and may be related to iliopsoas impingement.¹² The MMAP facilitates transcapsular iliopsoas release under traction near the anteroinferior acetabular location, but we perform this step (if indicated) at the end of any given arthroscopic procedure to minimize the risk of abdominal compartment syndrome.¹³ Although the MMAP encourages safe suture anchor placement through spatial geometric positioning of the skin portal, acetabular geometry,¹⁴ and its resultant angle of approach into the acetabular rim, it does not ensure this. A straight drill at the superolateral rim via the MMAP diverges from the cartilage on a chondro-protective path and may be confirmed with anterior-posterior fluoroscopy. By keeping the drill parallel to the floor on the anterior rim, safe drilling and anchor placement is enabled. And the MMAP encourages an inherently chondro-protective trajectory along the posterior rim, where the major risk is not chondral violation but posterior wall blowout. On occasion, we have used small suture-based anchors with curved drill guides (Juggerknot Long; Biomet, Warsaw, IN) via the MMAP; aimed anteriorly, the curved drill diverges from the articular cartilage at the anterior rim and diverges from the posterior wall on the posterior rim.

The MMAP's relatively lateral location permits instrument navigation not only along the anterosuperior acetabular rim and anterior and anterolateral proximal femur typically required for acetabuloplasty and femoroplasty but even to the posterior regions of the hip in cases of global pincer^8,9,11 and posterior cam FAI⁵ while avoiding direct injury to the lateral femoral cutaneous nerve. This nerve is in proximity to the classic AP.⁴

The original MAP described by Robertson and Kelly⁴ is the apex of an inverted or proximal-based equilateral triangle made with the classic ALP and AP forming the other apices. This has been estimated as approximately 7 cm distal and anterior to the ALP, whereas the MMAP is relatively more proximal and lateral (Fig 1). The MMAP was derived from some admittedly poor attempts at the MAP. As we inadvertently noticed improved instrument “reach” and reduced surgical times (from less capsular development, as discussed later), we began modifying this portal to enhance acetabular rim suture anchor placement with intentional lateralization and proximalization of the portal to more closely “match” the angle of approach to acetabular rim geometry while accounting for femoral head positioning. The MAP is in proximity to a terminal branch of the ascending lateral femoral circumflex artery that does not provide a significant blood supply to the femoral head.⁴ The MMAP is more distant from this small vessel, and we have not experienced clinically significant bleeding from this portal for either central or peripheral compartment surgery. The relative proximal location of the MMAP (compared with the MAP) requires less capsulotomy/capsulectomy for arthroscopic femoroplasty. Its angle of approach yields a relatively proximal capsular entry site for any given region of femoroplasty; less capsular resection is needed for sufficient instrument navigation (e.g., mechanical burr), which increases surgical efficiency (by decreasing capsular development time) and safety (by decreasing capsular resection and potential hip instability). Moreover, the MMAP permits a seamless transition from typical acetabular- to femoral-sided procedures; once acetabuloplasty and labral refixation have been performed, traction is released and immediate capsular development and femoroplasty may follow without the need for the establishment of another skin or capsular portal.

Fig 1.

MMAP in relation to other common portals in a right hip. One should note their relation to the anterior superior iliac spine and greater trochanter skeletal landmarks. (ALP, anterolateral portal; W, posterolateral portal; X, anterior portal; Y, mid-anterior portal; Z, distal anterolateral accessory portal.)

Popular distal portals include the MAP, MMAP, and distal accessory lateral portal. The MMAP is more posterior than the former and more anterior than the latter. The MMAP may have a favorable overall position by yielding a safer angle of approach for anterior and superior acetabular rim labral refixation/reconstruction (Fig 2) than the MAP¹⁵ while having less instrument obstruction from the femoral head than the distal accessory lateral portal. The more proximal location of the MMAP also minimizes femoral head obstruction.

Fig 2.

Favorable angle of approach for acetabular rim preparation (drilling) and suture anchor placement for labral reparative and reconstructive procedures, shown in a right hip.

The MMAP facilitates arthroscopic femoroplasty by permitting access beyond the typical anterior/anterolateral regions for cam decompression. The more anteromedial, or critical, corner—which has been implicated recently in cam impingement⁶—is readily accessed through hip flexion with varying degrees of external rotation bringing the more anteromedial head-neck region toward the arthroscopic field of view. On occasion, we have performed posterior femoroplasty for cam deformities extending into the posterolateral “no man's land.”⁵ Under strict arthroscopic visualization, the MMAP has permitted access to this region, in which we have performed uneventful femoroplasty proximal to the retinacular vessels near the lateral synovial fold that supply the femoral head.

Despite the proximity of the ALP to the MMAP (Fig 3), the relative lateral location of the MMAP has allowed unobstructed external instrument navigation when using the fluoroscopic templating technique¹⁰ with the stationary vertical C-arm. A variety of advanced arthroscopic hip (e.g., labral reconstruction,^16-18 global acetabuloplasty [Fig 4], posterior cam decompression [Fig 5], osteosynthesis of an anterior acetabular fracture [Fig 6] and femoral head osteochondritis dissecans,¹⁹ and inferior capsular plication²⁰) and peritrochanteric procedures have been performed using the ALP and MMAP. However, the addition of the AP has been helpful in the performance of arthroscopic osteosynthesis of acute and malunited femoral head fractures.^20-24

Fig 3.

External view of a supine right hip showing the 70° arthroscope in the ALP and the plastic cannula in the MMAP during arthroscopic osteosynthesis of a femoral head fracture. One should note the use of 2 guide pins for percutaneous insertion of headless screws.

Fig 4.

Supine arthroscopic view of right hip from ALP during global acetabuloplasty for severe global pincer FAI. One should note the posterior acetabular rim (AR) and the burr (Flat-top; Smith & Nephew, Andover, MA) resecting a remnant of posterior rim (asterisk) inferior to the direct posterior 9-o'clock location (9). Circumferential labral reconstruction was then performed. All procedures were performed through the MMAP.

Fig 5.

Supine arthroscopic view of right hip from ALP after arthroscopic posterior cam decompression. One should note the region of anterolateral (AL) and posterolateral (PL) femoroplasty. The latter is proximal to the retinacular vessels (asterisk) supplying the femoral head (FH).

Fig 6.

Supine arthroscopic view of right hip from ALP during arthroscopic internal fixation of anterior column acetabular fracture. The 2 large-fragment cannulated screws (arrow) were inserted through the MMAP. Concurrent arthroscopic femoroplasty, acetabuloplasty, and labral refixation were performed. (AR, acetabular rim; FH, femoral head; L, labrum.)

Although the MMAP typically permits easy access to the central compartment, obstruction by the femoral head occasionally occurs. The anterior femoral head chondral surface may be scuffed by forceful insertion of the entry needle or other instruments along an obstructed path. This complication is easily avoided by implementation of 1 or more of the aforementioned technical pearls (Table 2).

Table 2.

Pearls

Problem	Solution
The femoral head obstructs MMAP needle access into the central compartment.	Adjust the entry needle trajectory (which moves the needle path away from the femoral head).
	Increase hip internal rotation (which moves the femoral head away from the needle path).
	Make MMAP skin entry slightly more anterior (which moves the needle path away from the femoral head).
The labrum obstructs MMAP needle access into the central compartment.	Attempt maneuvering the nitinol wire over the labrum. If unable, proceed to the following steps:
	1. Exchange the sharp stylet with nitinol wire.
	2. Insert a cannulated obturator over the nitinol wire.
	3. Manipulate the stiffer assembly over the labrum.
	4. Advance the nitinol wire safely into the central compartment while retaining the arthroscopic cannula.
	5. Insert an arthroscopic knife (under arthroscopic guidance) through the cannula and then remove the latter before performing capsulotomy (dry).

Because the MMAP is our working portal, the incision is approximately 1 cm, slightly longer than that for the ALP, so as to accommodate an 8.25-mm plastic cannula for labral refixation or reconstruction. We recommend subcutaneous reapproximation with an absorbable stitch before skin closure.

The MMAP is a safe, surgeon-friendly portal that facilitates the performance of hip arthroscopy. We believe that it offers several advantages for dual-portal hip arthroscopy, including extended reach, permitting global osteoplastic, reparative, and reconstructive procedures often without the need for interportal exchange. Through a “less is more” principle, the MMAP may simplify decision making as the sole working portal while expanding arthroscopic applications; by so doing, this portal may enable the performance of hip arthroscopy by more surgeons.

Supplementary Data

Video 1

Location and utility of MMAP as used in various dual-portal supine hip arthroscopic applications.