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.

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