Surgical Technique

Patient Positioning

In a previously reported method [18,22,23], the patient is placed in the modified supine position with the operative hip in 10° of flexion, 15° of internal rotation, 10° of lateral tilt, and 30° of abduction. An extra wide peroneal post is used to minimize the risk of pudendal nerve injury. Traction is first applied to break the joint's vacuum seal. The leg is then slightly adducted over the post, thereby venting the capsule and laterally displacing the femoral head. Additional traction, typically requiring 25 to 50 pounds of force, is then required to create approximately 10 mm of joint distraction for safe surgical instrument clearance. Minimal countertraction is also applied to the contralateral leg to reduce the amount of traction necessary on the operative leg.

Portal Placement

Two portals (anterolateral and anterior) are recommended for safe and adequate decompression of FAI and treatment of associated intraarticular pathologies. We have previously described a method of establishing the portals [22,23]. Using the 70° arthroscope, the anterolateral portal provides a view of the anterior triangle (anterior capsule, labrum, and anterior chondral surface of the femoral head), iliofemoral ligament, iliopsoas tendon, cotyloid fossa, liga-mentum teres, transverse ligament, and most of the acetabulum. The postero-superior labrum, posterior capsule, posterior recess, and ligamentum teres may be visualized through the anterior portal. Additionally, the anterior portal provides a good view of the anterior femoral neck, head-neck junction, zona orbicularis, and distal insertion of the capsular ligaments [22].

Cam Procedure

The first step in treating cam impingement is to address the associated intraar-ticular pathology. This may include labral repair or debridement, and microfracture chondroplasty of femoral or acetabular chondral defects. The next step occurs after the impinging lesion has been visualized with the scope in the anterior portal (Fig. 3A). A long motorized shaver is introduced through the lateral portal to debride any capsular tissue that may be obstructing a complete view of the femoral head-neck junction. Osteoplasty of the impinging lesion is then performed with a long motorized burr through the lateral portal (Fig. 3B). Throughout the procedure, the hip may be flexed and extended, abducted and adducted, and internally and externally rotated to dynamically assess the impinging lesion. In these hip positions, the motorized burr may be used to resect any impinging bone. Caution should be taken when approaching the antero-lateral and posterolateral aspects of the head-neck junction because branches of the medial circumflex artery (lateral retinacular vessels) perforate the joint

Fig. 3. Sequence for treatment of cam-type impingement (A) A sclerotic bony bump is observed arthroscopically in the region of the anterior femoral head-neck junction. (B) A long motorized burr resects the region of sclerotic bone to a depth of approximately 5 to 8 mm and as far circumferentially as needed, carefully avoiding the anterolateral and posterolateral regions of the head-neck junction. (C) Joint clearance is assessed arthroscopically postosteoplasty with the operative hip flexed beyond 90° and internally rotated.

Fig. 3. Sequence for treatment of cam-type impingement (A) A sclerotic bony bump is observed arthroscopically in the region of the anterior femoral head-neck junction. (B) A long motorized burr resects the region of sclerotic bone to a depth of approximately 5 to 8 mm and as far circumferentially as needed, carefully avoiding the anterolateral and posterolateral regions of the head-neck junction. (C) Joint clearance is assessed arthroscopically postosteoplasty with the operative hip flexed beyond 90° and internally rotated.

capsule and run along these regions of the femoral neck [24,25]. Understanding the anatomy of the vasculature is critical to avoid avascular necrosis following osteoplasty.

The goal of cam debridement is to eliminate the bony prominence that impinges the labrum and acetabular rim, and restore the anatomic offset between the femoral head and neck. An obvious concern that has been raised in FAI decompression is how much bone can be removed without increasing the risk of femoral neck fracture. A recent study in cadavers demonstrated that resection of up to 30% of the anterolateral head-neck junction of a morphologically normal femur did not alter the load-bearing capacity [26]. A resection larger than 30%, however, did result in structural compromise of the femoral neck. Although this study should be used as a guideline for maximal resection, it is difficult to interpret the results with regards to morphologically abnormal head-neck junctions. In our experience, burring to a depth of approximately 5 to 8 mm has been clinically observed to be a safe and effective procedure.

Fig. 4. Placement of the third arthroscopic portal approximately 1 cm anterior to the anterolateral portal and 4 cm distal with the operative hip flexed to 45°.

To assess joint clearance following osteoplasty, the operative hip should be flexed beyond 90° and internally rotated under direct visualization through the anterior portal (Fig. 3C). Furthermore, the leg should be brought into full abduction and again flexed to 90°, and internally and externally rotated. This "butterfly" test simulates the hockey goalie stance, a position frequently found to trigger impingement signs in athletes. If impingement is visualized in this position, further resection of the lesion is needed. Successful decompression is concluded when no further impingement between the femoral head-neck, the labrum, and the acetabular rim is observed during the dynamic testing.

Although the senior author (MJ.P.) prefers a two-portal approach to decompressing FAI, an additional distal lateral accessory portal may be used, if necessary, to access the site of the lesion (Fig. 4). This portal is typically the last to be placed, as the traction needs to be slowly released and the operative leg flexed to 45°. The arthroscope should be placed in the anterior portal to visualize the anterior femoral head and neck. Upward pressure on the scope will reduce the risk of chondral injury to the femoral head as the hip is flexed. The arthroscope can then easily slide anteriorly and distally over the femoral head, in a position peripheral to the labrum. With the hip flexed to 45° and in neutral rotation, the anterior capsule will distend and provide excellent visualization of

Fig. 5. A spinal needle is directed through the capsule in the region of the zona orbicularis (ZO) for the placement of the third arthroscopic portal. FH, femoral head; FN, femoral neck.

the head-neck junction and any impinging lesion. Once the scope is in position, a skin incision is made approximately 1 cm anterior to the anterolateral portal and 4 cm distal. Under direct visualization, a spinal needle is directed through the capsule in the region of the zona orbicularis (Fig. 5). A guide wire is then inserted through the spinal needle, and a cannulated blunt trochar is used to safely establish the portal.

Postoperative complications following cam debridement include capsular adhesions and the slight risk of femoral neck fracture, avascular necrosis, and myositis ossificans.

Pincer Procedure

Pincer impingement in the hip occurs when the acetabulum provides anterior overcoverage of the femoral head. The first step to resecting a pincer lesion is defining the margins by probing with a flexible instrument (Fig. 6A). As mentioned above, other clues to recognizing pincer impingement may include observing a bruised, flattened, degenerative, or cystic labrum [6]. After assess-

Fig. 6. Sequence for treatment of pincer-type impingement (A) A sclerotic bony overhang is observed arthroscopically in the region of the anterosuperior acetabular rim (A). L, labrum; FH, femoral head. (B) An arthroscopic osteotome resects small portions of the anterosuperior acetabular rim (A) until a majority of the lesion is removed. L, labrum. (C) A motorized burr completes the resection by reshaping the acetabulum (A) into its normal contour. L, labrum. (D) The labrum is reattached to the anterosuperior acetabular rim using suture anchor repair.

Fig. 6. Sequence for treatment of pincer-type impingement (A) A sclerotic bony overhang is observed arthroscopically in the region of the anterosuperior acetabular rim (A). L, labrum; FH, femoral head. (B) An arthroscopic osteotome resects small portions of the anterosuperior acetabular rim (A) until a majority of the lesion is removed. L, labrum. (C) A motorized burr completes the resection by reshaping the acetabulum (A) into its normal contour. L, labrum. (D) The labrum is reattached to the anterosuperior acetabular rim using suture anchor repair.

ing the lesion, three different surgical options may be pursued depending on the size of the lesion. If the overhang is slight and the labral attachment is intact, it may be possible to perform a cam-type procedure to create more clearance on the femoral side. However, medium to large pincer lesions require resection of the acetabulum to avoid excessive bony resection at the distal femoral neck and potential injury to the lateral epiphyseal vessels.

After the margins of a pincer lesion have been recognized, a motorized shaver is used to clear all soft tissue from the overhanging acetabulum and to define the plane between the labrum and the acetabular rim. If the lesion is moderately sized, a motorized burr is inserted into the anterior portal and the overhang is carefully resected in a "rim trimming" procedure. If the lesion is large, an arthroscopic osteotome may be used through the anterior portal to carefully separate the anterosuperior labrum from its insertion on the pincer lesion. The osteotome is then placed on the anterosuperior acetabulum and small portions of the rim are resected until a majority of the lesion has been removed (Fig. 6B). The motorized burr then completes the resection by reshaping the acetabulum (Fig. 6C). A maximum of approximately 5 mm of acetabular rim should be removed. It is critical to avoid overresection of the rim to prevent future instability in the patient. In all resections of the acetabular rim, microfracture of the subchondral bone should be performed until punctate bleeding is achieved. If detached during the pincer procedure, the labrum should be reattached to the superior acetabular rim with suture anchors [22,23] (Fig. 6D).

Following resection of the pincer impingement, it is important to slide the arthroscope into the peripheral compartment through the anterior portal to visualize the head-neck junction. Mixed cam-pincer impingement disorders are a very common finding [2] and for best postoperative outcomes, it may be necessary to surgically address both pathologies.

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