Endoscopic anterior cruciate ligamentreconstruction using doubled gracilis and semitendinosus tendons and endobutton femoral fixation

ENDOSCOPIC ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION USING DOUBLED GRACILIS AND SEMITENDINOSUS TENDONS AND ENDOBUTTON FEMORAL FIXATION CHARLES H. BROWN, JR, MD and JOSEPH H. SKLAR, MD

Donor site complications associated with the use of patellar tendon autografts have resulted in increased interest in the use of multiple-stranded hamstring tendon grafts (semitendinosus and gracilis tendons) for anterior cruciate ligament (ACL) reconstruction. Two major advantages of hamstring tendon grafts are their high initial strength and stiffness, and their harvest results in minimal donor site morbidity. The EndoButton (Smith and Nephew, Andover, MA) provides a quick, simple, strong, and reproducible endoscopic method of securing the femoral end of hamstring tendon grafts. This article describes our technique of endoscopic ACL reconstruction using a doubled semitendinosus and gracilis autograft with EndoButton femoral fixation. KEY WORDS: ACL reconstruction, EndoButton, hamstring tendons

Due to the well-recognized donor site morbidity associated with the use of autogenous patellar tendon grafts, four-stranded hamstring tendon grafts have become an increasingly popular choice for reconstruction of a torn anterior cruciate ligament (ACL). Although the initial tensile strength of hamstring tendon grafts has been questioned, biomechanical studies have shown that equally tensioned doubled gracilis and semitendinosus grafts are the strongest and stiffest autogenous ACL replacement graft currently available. 1-3 Hamstring tendon grafts also appear to result in less postoperative pain and donor site morbidity compared with other autogenous grafts. 4 Harvest of the hamstring tendons can be performed using a small, cosmetically acceptable incision, and the procedure is easily performed as an outpatient procedure. We favor the use of hamstring tendon grafts for ACL reconstruction in the following settings: patients with extensor mechanism problems; patients whose religion, occupation, or sport requires kneeling or crawling; and revision of failed patellar tendon ACL reconstructions. Relative contraindications for use of hamstring tendon grafts include the hamstring-dominant athlete, the patient with chronic grade IV anterior laxity, and the patient with generalized ligamentous laxity. Previous pes transfer or open medial-sided surgery may result in scarring and alter normal hamstring anatomy, making hamstring tendon harvest difficult and unpredictable. In these settings, we From the Department of Orthopaedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (CHB), and Boston university School of Medicine, Boston MA, and New England Orthopaedic Surgeons, Springfield, MA (JHK). Address reprint requests to Charles H. Brown, Jr, MD, Department of Orthopaedic Surgery, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115. This article is adapted and reprinted with permission from Lippincott Williams & Wilkins from Brown CH, Jr, Sklar JH: Endoscopic anterior cruciate ligament reconstruction using quadrupled hamstring tendons and endobutten femoral fixation. Tech Orthop 13(3):281-298, 1998.

favor use of a patellar tendon or quadriceps tendon autograft.

SURGICAL PREPARATION The surgery is usually performed as an outpatient procedure under either general or epidural anesthesia. A thighlength TED antiembolism stocking (Kendall Co, Mansfield, MA) and a foam rubber heel pad are applied to the well leg. A padded pneumatic tourniquet is applied high on the thigh of the operative leg. Standard arthroscopic equipment is required. Use of an infusion pump allows the procedure to be performed without inflating the tourniquet. One gram of a first-generation cephalosporin is given intravenously, followed by a 15 or 30 mg intravenous bolus of ketorolac, and a continuous infusion of ketorolac at 4 m g / h , before making the skin incision, s We have found that preemptive injection of the knee joint with a solution of 4 mg of morphine sulfate mixed with 25 mL of 0.25% bupivacaine with 1:100,000 epinephrine is particularly helpful in reducing intra-articular bleeding and postoperative pain. If the status of the ACL is in doubt, diagnostic arthroscopy is performed before harvesting the hamstring tendons. However, the hamstring tendons should be harvested before performing an inside-out meniscal repair to avoid injury to the meniscal repair sutures by the tendon stripper.

SURGICAL TECHNIQUE Graft Harvest

The regional anatomy of the hamstring tendons is well described in articles by Brown et al,4,6,7Ferrari and Ferrari, 8 Ivey,9 Levy and Prud'homm@ ° Pagnani et a l y and Warren and MarshalU 2 These articles should be reviewed before surgery. Harvest of the hamstring tendons can be per-

Operative Techniques in Sports Medicine, Vol 7, No 4 (October), 1999: pp 201-213

201

formed through a vertical or an oblique incision centered over the pes anserinus (Fig 1). In an average-sized patient, the most cephalad edge of the gracilis tendon is approximately one fingerbreadth below the tibial tubercle or three fingerbreadths below the medial joint line. In thin patients, the two tendons can often be palpated as they course around the posteromedial corner of the tibia. In revision cases involving a failed primary patellar tendon reconstruction, the distal portion of the original vertical incision is extended distally 2 to 3 cm below the tibial tubercle. 13 This incision permits simultaneous removal of tibial fixation hardware and hamstring tendon harvest. The proposed skin incision is infiltrated with 10 mL of a 0.25% bupivacaine with 1:100,000 epinephrine solution to help control bleeding. The grafts can be routinely harvested without inflating the tourniquet. The skin is incised, and blunt dissection is carried through the subcutaneous fat to expose layer 1, the sartorius or crural fascia. 12 The gracilis and semitendinosus tendons can be palpated as two small bumps, and can also be seen lying beneath the thin crural fascia. Since the tendons fuse together and become flat as they insert into the crest of the tibia, it is easier to palpate and identify them as they cross over the posteromedial corner of the tibia and the superficial medial collateral ligament (MCL). At

Fig 1. Skin incisions. A vertical (A) or an oblique (B) incision can be used to harvest the hamstring tendons. (Reprinted with permission. 4)

202

Fig 2. Exposure of the crural fascia. The outline of the gracilis tendon can be seen lying beneath the crural fascia. A small branch of the infrapatellar division of the saphenous nerve is visible above the lower limb of the self retaining retractor.

this location they can be felt as two separate round structures, and can be seen to move under the crural fascia (Fig 2). We recommend that the following technique be used for harvesting the two tendons. First, a horizontal incision is made through the crural fascia about 3 mm above the gracilis tendon, taking care to avoid injury to the underlying medial collateral ligament. A vertical incision in line with the skin incision, just medial to the crest of the tibia, is made through the crural fascia and the conjoined insertion of the two tendons is divided using an electrocautery pencil. The resultant inverted-L-shaped fascial flap is grasped with an Allis or Kocher clamp, and reflected distally, exposing the deep aspect of both tendons (Fig 3). Blunt dissection is used to release the thin web-like fascia slips that connect the undersurface of the crural fascia to the MCL and the posteromedial corner of the tibia. Release of these thin fascial slips allows the crural fascia and the underlying hamstring tendons to be retracted away from the MCL, increasing exposure of the tendons as they travel up into the thigh. The two tendons are most easily separated from one another and the overlying crural fascia by using a no. 15 knife blade to score the interval between them at their tibial insertion. The two tendons are then bluntly separated off the crural fascia with a right-angle clamp and scissors (Fig 4). The crural fascia is carefully preserved for later closure over the tibial fixation hardware. The next task is to free the tendons from the many highly variable fascial slips that connect the tendons to the tibia and the crural fascia itself. Visualization of these fascial slips and connections can be improved by placing the long end of a Army-Navy or similar type of right-angle retractor under the crural fascia and towing the retractor in, placing these connections under tension. The dissection proximally into the thigh is most safely performed using a combination of blunt scissors and finger dissection, taking care to orient the tips of the scissors away from the tendons. The freed end of the gracilis tendon is grasped with an Allis clamp and dissected free first. Care must be taken to BROWN AND SKLAR

Fig 3. (A) Human cadaveric specimen (right knee). A transverse incision through the crural fascia is used to expose the superior border of the gracilis tendon (arrow). Note the superficial medial collateral ligament seen lying beneath the crural fascia. The MCL is at risk during this exposure, and care must be taken to protect it. (B) The two tendons are detached from their conjoined tibial insertion using a vertical incision placed medial to the tibial crest. (C) The resultant inverted L-shaped fascial flap is reflected distally, exposing the deep aspect of both tendons (gracilis, straight arrow; semitendinosus, curved arrow).

avoid straying superiorly during dissection of the gracilis tendon to avoid injury to the saphenous nerve. 7m The nerve crosses the gracilis tendon at the posteromedial corner of the knee and can be injured by extraneous dissection 7m (Fig 5). After freeing approximately 6 to 8 cm of the gracilis tendon, the end of the tendon is whipstitched with a no. 2 braided polyester suture on a tapered needle (Ethibond Excel suture D-5757, Ethicon Inc, Sommerville, NJ). Firm traction on the sutures at this point strips many of the remaining attachments to the gracilis. Depending on the surgeon's preference, the tendons may be harvested with either a slotted or closed tendon stripper (available in 5-mm or 7-mm sizes). The long end of an Army-Navy right-angle retractor or a Langenbeck type of retractor is used to retract the crural fascia. Traction is applied to the gracilis tendon using the whip stitch, and the tendon stripper is advanced along the tendon under direct vision, keeping the stripper parallel to the tendon at all times (Fig 6). The stripper is advanced using a slow and steady sliding motion up into the thigh. When the tendon stripper reaches the hiatus through which the tendon courses, increased resistance will be felt. At this point, traction on the tendon is decreased, and the tendon ENDOSCOPIC ACL RECONSTRUCTION

stripper can be felt to slip through the hiatus, allowing further advancement of the stripper up into the thigh with a smooth, sliding type of sensation. If the tendon stripper fails to advance smoothly, it is best to remove the stripper and use blunt finger or scissors dissection to release the area of obstruction. The stripper is advanced all the way up into the thigh, and the tendon is released from its muscle belly by holding the stripper in place and slowly pulling the tendon out of the incision using the whip stitch. The tendon is carefully wrapped in a moist laparotomy pad and passed off the field. The semitendinosus is harvested in a similar fashion; however, there are crural fascial connections from the semitendinosus tendon to the medial head of the gastrocnemius that lie approximately 7 cm from the tendon's tibial insertion that must be sharply divided under direct vision to avoid a false harvest 4,6-11(see Fig 5). More proximally in the thigh, the surgeon may encounter a second potential troublesome area at a band of thickened semimembranosus fascia that courses inferior and medial to the semimembranosus and forms a sling for the semitendinosus tendon, suspending it beneath the semimembranosus 6-8 (Fig 5). According to Ferrari and Ferrari, 8 this area of fascial

203

Saphenousnerve: Infrapatellarbr. Sartorial~ . ~

A or c,,,s

tendon~

XZ.\

Sartoriusm.

~ ~ ~ ~ d d uctormagnus "--~, ~\',~.~,~--,"~- /tendon

e0,

gastroenemius m. ~ " ~ u ~ s ~'~ "~ / / Semim/embranos on Fascial Semitendinosus tendon

sling

Fig 5. Relationship of the saphenous nerve to the gracilis tendon, fascial connection between the semitendinosus tendon and the medial head of the gastrocnemius, and fascial sling, which suspends the semitendinosus beneath the semimembranous.

Fig 4. Blunt dissection with a right-angle clamp is used to free the two tendons from the crural fascia. (A) gracilis, (B) semitendinosus.

the tendons are gently dissected free using a large curette or a wing-tip type of periosteal elevator. The two tendons are cut to the same length, and the proximal end of each tendon is tubularized with a running baseball-style whipstitch using a no. 2 Ethibond suture (Ethicon, Inc, Somerville, NJ). Each tendon graft is looped around a no. 5 Ethibond suture, and the free ends are equalized in length (Fig 8). The graft is presized using a 0.5-mm incremental sizing block (Arthrex, Naples, FL) or 0.5-mm incremental sizing tubes (Smith & Nephew, Inc, Andover, MA). The size of the combined grafts is usually between 7 and 9mm. Depending on the total length of the grafts, a surgical marking pen is used to make a circumferential mark at a distance of 25 to 35 mm from the looped end of the graft. This mark will be used to set the length of graft to be inserted into the femoral socket, and represents the amount of graft available to undergo healing within the femoral

thickening is approximately 12 to 15 cm proximal to the tibial insertion of the semitendinosus tendon. This sling or area of thickened fascia should be released with blunt finger or scissors dissection, and the tunnel through which the semitendinosus tendon travels should be dilated with the surgeon's finger, to ensure easy passage of the tendon stripper up into the thigh. Failure to release this band a n d / o r dilate the tunnel can cause the tendon stripper to pass outside of the tendon's normal pathway, resulting in premature amputation of the graft 6-8 (Fig 7). If the stripper does not easily pass beyond the 12-cm mark, it should be removed and further finger or scissors dissection performed. The semitendinosus is harvested as previously described for the gracilis.

Graft Preparation Preparation of the tendons is facilitated by use of a graft preparation board (Graft Master, Smith & Nephew Inc, Andover, MA). The muscle fibers on the proximal end of

204

Fig 6. A closed tendon stripper is used to harvest both tendons. The tendon stripper is kept parallel to the tendon and advanced into the thigh while maintaining traction on the tendon using the whip stitch. Exposure of the tendons can be enhanced by retracting the crural fascia with a right-angletype retractor. BROWN AND SKLAR

Intercondylar Notch Preparation Semitendinosus~ ~ ' ~ " - ~ = - - tendon ~ , / / --,N , ~ ~ " ~ . ' ~ . ~ -

nerve

~

. . . . . ~'~'~'

, Sartorius

"7'.-..7.~--..

Fig 7. Passage of the tendon stripper outside of the hiatus or tunnel created by the fascial bands running beneath the semimembranous may result in premature amputation of the semitendinosus graft. (Reprinted with permission. 8)

tunnel. It is our feeling that to maximize bone-tendon healing a minimum of 20 to 25 m m of graft should be inserted into the femoral socket. The no. 2 sutures from the gracilis and semitendinosus tendons on each limb of the graft are tied together, creating a loop of suture on each end of the grafts. These loops will be used during the cycling and tensioning phase of the procedure to attempt to produce equal tension in all four graft strands. If an EndoButton with continuous loop (Smith & Nephew Inc, Andover, MA) is to be used, the tendons are looped around the tensioning post and provisionally tensioned to 5 lb. The appropriate-length implant is selected when the femoral socket has been drilled and its length measured directly. If the surgeon chooses to use the conventional EndoButton and tape, the EndoButton is placed into the EndoButton holder and a loop of 5-mm EndoButton Tape (Smith & Nephew Inc, Andover, MA) is created by passing the ends of the tape through the two central holes in the EndoButton. If the surgeon chooses to use 5-mm Mersilene tape (Ethicon Inc, Somerville, NJ), we recommend doubling the tape by passing it twice through the two central holes of the EndoButton to increase its tensile properties. 7 One limb of the EndoButton Tape is passed through the axilla of the looped hamstring tendon graft, and one throw of a square knot made. The tape loop is shortened, and the loop provisionally secured by a hemostat. The tape span will be set later in the procedure once the length of the femoral tunnel is known. The graft is pretensioned to 5 lb while the remainder of the procedure is completed (Fig 9).

Preparation of the intercondylar notch is one of the most important aspects of ACL reconstruction with quadrupled hamstring tendon grafts. Proper notch preparation is necessary to allow visualization of the femoral attachment site and to avoid impingement of the ACL graft. Fourstranded hamstring tendons have a greater cross-sectional area than patellar tendon grafts, making impingement a greater concern. 1-3,14 Judgement is required to determine the extent of the notchplasty. The location and amount of bone removal will depend on the following factors: the size and shape of the notch, the cross-sectional area of the graft, and the sagittal position of the tibial tunnel. 14-17 Tibial Tunnel

A tibial ~Jnnel length of 40 to 45 m m is optimal because this will allow an adequate length of graft to be inserted into the femoral tunnel (>20 ram), and will result in enough graft exiting the tibial tunnel to permit direct fixation to the tibia. In general, if the tibial aimer is set between 45 ° and 50 °, these goals will be accomplished. The recommendations of Olson et al is with regard to the starting position of the tibial tunnel (halfway between the tibial tubercle and the posteromedial edge of the tibia) are generally followed. In most knees, this starting position will produce a femoral tunnel length of between 45 and 60 mm. A tibial tunnel oriented in this fashion will prevent the femoral guide pin from exiting too proximal on the thigh a n d / o r too close to the midline. A too-proximal exit of the femoral guide pin will result in a long femoral tuiznel, necessitating a tong loop of connecting tape, decreasing the stiffness of the femur-hamstring tendon-tibia complex (Fig 10).19 The large cross-sectional area of four-strand hamstring tendon grafts makes sagittal placement of the tibial tunnel especially important if roof impingement is to be avoided. We follow the recommendations of Howell et a116,17 and Jackson and Gasser 2° for the sagittal placement of the tibial guide pin, attempting to place the tibial guide pin at the junction of the middle and posterior third of the tibial footprint. This anterior-posterior position will result in the guide pin being positioned approximately two thirds of the way up the slope of the medial tibial spine in most knees. Since the typical four-stranded hamstring tendon graft has a smaller diameter than a 10-mm patellar tendon graft, use of a tibial aimer that is designed to position the

Fig 8. Doubled gracilis and semitendinosus graft. Note the large cross-sectional area of the graft.

ENDOSCOPICACL RECONSTRUCTION

205

Fig 9. (A) The hamstring tendon graft is equalized in length, passed through the provisional loop of EndoButton Tape, and pretensioned to 5 Ib. (B) If an EndoButton with continuous loop is to be used, the grafts are looped around a tensioning post and pretensioned.

tibial guide pin 7 mm anterior to the posterior cruciate ligament (PCL) (leaving a 1 to 2 mm posterior wall) will result in a posterior wall of between 2.5 and 3.5 mm if used for hamstring tendon grafts. The ideal medial/lateral position of the tibial guide pin is along a depression just lateral to the medial tibial spine, a°, If necessary, the tibial guide pin position can be checked by taking an intraoperative anterior-posterior, and a true lateral radiograph with the knee in maximum extension. Radiographs may be particularly helpful in revision cases in which improper placement of the tibial tunnel was the cause of failure of the primary reconstruction. To prevent anterior drift of the tibial tunnel, a cannulated rear-entry-style reamer is used to drill the tibial tunnel. 21In the case of odd-sized grafts (6.5 turn, 7.5 mm, 8.5 ram), the tibial tunnel is drilled using the closest l-ram incremental drill bit, and following the drilling of the femoral tunnel, both bone tunnels are dilated using a smooth tunnel dilator (Arthrex, Naples, FL) that corresponds to the size of the graft. A half-round or angled chamfering rasp is used to smooth the posterior lip of the tibial tunnel to minimize graft abrasion.

Femoral Tunnel The length of the femoral tunnel is critical to the success of the EndoButton technique. The ideal femoral tunnel length is between 50 and 60 mm. Assuming that the four-stranded hamstring tendon graft is long enough to permit 25 to 30 mm of graft to be inserted into the femoral socket, this range of femoral tunnel length will result in a 20 to 35-mm loop of connecting material. As discussed earlier, the external starting position of the tibial tunnel is an important determinant of femoral tunnel length. A second determinant of femoral tunnel length is the knee flexion angle at the time of femoral guide pin placement. Assuming that the tibial tunnel was drilled with the tibial aimer set at 45 °, a knee flexion angle of 70 ° to 90 ° should result in a satisfactory femoral tunnel length. A knee flexion angle of less than 70 ° may result in an excessively long femoral tunnel, whereas a knee flexion angle greater than 90 ° may result in a shorter-than-desired femoral tunnel (Fig 11). With the knee flexed to 90 °, a small angled curette is hooked behind the lateral femoral condyle to identify the over-the-top position. Because the typical hamstring tendon graft has a smaller diameter than a 10-mm patellar tendon graft, endoscopic femoral aimers designed for a 10-mm

206

patellar tendon graft (6 to 7 mm offset) will result in the guide pin being placed too anterior in the notch. Unlike patellar tendon grafts where the orientation of the femoral bone block can be adjusted to position the collagen fibers to lie along the posterior wall of the femoral tunnel, due to their cylindrical shape, hamstring tendon grafts will occupy the entire diameter of the femoral tunnel. Therefore it is important to position a hamstring tendon graft so that there is no more than I mm of cortical backwall. For hamstring tendon grafts, an endoscopic femoral aimer with an offset 0.5 to i mm larger than the measured radius of the graft should be used. This offset size will result in a femoral tunnel with 1 mm or less of posterior femoral cortex remaining. Since the EndoButton fixation method is based solely on the integrity of the lateral femoral cortex, a blowout of the posterior femoral cortex does not preclude endoscopic fixation, and is in fact desirable in small knees. The endoscopic femoral aimer is positioned high in the notch at the 11 o'clock position in a right knee, and at the 1 o'clock position in a left knee with the knee between 70 ° and 90 ° of flexion. A 2.7-mm drilled tipped passing pin (Smith & Nephew Inc, Andover, MA) is drilled through the lateral femoral cortex and out through the skin of the lateral thigh. Since fixation of the EndoButton is based on maintaining the integrity of the lateral femoral cortex, it is extremely important to avoid reaming the endoscopic femoral tunnel completely through the lateral femoral cortex. This complication is most likely to occur in cases in which the femoral tunnel length is less than 45 mm. Although it is possible to drill the closed-end endoscopic femoral tunnel first, until experience is gained with the technique, we recommend first drilling through the lateral femoral cortex with the 4.5-mm EndoButton drill bit. The markings on the EndoButton drill can be used to estimate the length of the femoral tunnel the moment the lateral femoral cortex is breached. Having an estimate of the femoral tunnel length before drilling the femoral socket will help prevent perforation of the lateral femoral cortex. The closed-end femoral socket is drilled with an endoscopic drill bit to avoid injury to the PCL. The endoscopic drill bit is inserted into the drill chuck and manually advanced through the tibial tunnel and past the PCL before the power is connected. A motorized shaver with the blade window left open can be used to remove bone debris from the back of the knee, improving visualization of the calibrated marks on the drill bit. The femoral BROWN AND SKLAR

j~' ,!

I,

•

\

A

B

C

socket depth must allow for the length of the hamstring graft to be inserted into the femur (25 to 35 mm) plus an extra 10 mm for the EndoButton to clear the lateral femoral cortex and flip. Although it is possible for the EndoButton to flip if the endoscopic femoral socket is overdrilled only 6 mm (half the radius of the EndoButton), in practice because of the large size of the EndoButton Tape knot, we have found it helpful to overdrill the femoral socket by at least 10 mm to prevent the graft from hitting the end of the tunnel and bottoming out before the EndoButton has cleared the lateral cortex. In the case of odd-sized grafts (6.5 ram, 7.5 mm, 8.5 ram), a smooth tunnel dilator corresponding to the measured size of the graft is used to dilate the tibial and femoral tunnels simultaneously. The 2.7-mm passing pin is removed, and a more accurate measurement of the femoral tunnel length is obtained by using the endoscopic depth gauge (Smith & Nephew, Inc, Andover, MA). Since the cylindrical hamstring tendon graft will fill the entire femoral tunnel and contact the tunnel edges, it is extremely important at this point to ensure that the femoral tunnel is properly chamfered, to decrease graft abrasion. 22 If the lateral femoral cortex is violated during the drilling of the closed-end femoral socket, there are two options for salvaging the operation. The first option is to change the flexion angle of the knee and redrill the 2.7-ram passing pin through the lateral femoral cortex at a new location, making it possible to drill a new EndoButton tunnel. A disadvantage of this technique is that two 4.5-mm holes are drilled through the lateral femoral cortex, creating a possible stress concentration effect. Weiner and Siliski 23 have recently reported a distal femoral shaft fracture that was attributed to stress concentration after drilling three holes through the lateral femoral cortex during an endoscopic ACL reconstruction. An alternative technique is to use a two-hole 2.7-mm AO stainless steel DCP plate (8 × 20 mm) or a four-hole 2.4-iran titanium LC-DCP plate (6.5 × 31 mm) (Synthes, Ltd, Paoli, PA). The hamstring tendon graft is prepared as previously described, and passed and deployed in the normal fashion (F. Ezzat, A1 Razi Orthopaedic Hospital, Kuwait, personal communication, October 1995). In this situation intraoperative fluoroscopy or radiographs should be taken to verify proper placement of the implant. Setting of the T a p e S p a n

Fig 10. Effect of tibial tunnel starting position on the femoral tunnel length. Tunnel A is too close to the tibial tuberosity, resulting in a long, vertically oriented femoral tunnel, and necessitating a long loop of connecting material. Tunnel C is too close to the proximal edge of the MCL, resulting in a short, horizontally oriented femoral tunnel; a short loop of connecting material; and the inability to insert more than 25 mm of graft into the femoral socket. Tunnel B is ideal and results in a femoral tunnel length of 50 to 60 mm.

ENDOSCOPIC ACL RECONSTRUCTION

The simplest w a y to set the length of the tape span is to place a circumferential mark with a surgical marker at the distance representing the desired amount of tendon to be inserted into the femoral tunnel (25 to 35 mm) from the looped end of the graft. Place the graft under tension and shorten or lengthen the span of tape such that the surgical mark lines up with the millimeter number on the EndoButton holder that corresponds to the direct measurement of the femoral tunnel. This will automatically set the tape span such that when the EndoButton is anchored on the lateral femoral cortex, the mark on the hamstring tendon graft will lie at the entrance of the femoral tunnel. The tape is then tied with five secure square throws. 207

A

,

~

C '!. -

- .

~

':

ii

Fig 11. Effect of knee flexion angle on femoral tunnel length. A knee flexion angle between 70 ° and 90 ° (A) usually will result in a femoral tunnel length of 50 to 60 mm. A knee flexion angle > 9 0 ° (B) may result in a short femoral tunnel and distal placement of the EndoButton. A knee flexion angle < 7 0 ° (C) may result in a long femoral tunnel, necessitating a long loop of connecting material.

Before passing the graft, it is important that the tape knot be positioned away from the EndoButton, about halfway between the folded ends of the graft and the EndoButton. As a result of its large size, the EndoButton Tape knot will not pass through the 4.5-mm EndoButton tunnel, making it impossible to secure the graft.

Continuous LoopTechnique An EndoButton with a factory-attached continuous polyester loop has recently been developed (Smith & Nephew, Inc, Andover, MA), eliminating the need for knot tying of the connector material. Elimination of knot tying reduces operative time, eliminates elongation of the hamstring tendon graft construct caused by knot slippage, and eliminates the possibility that a bulky knot will prevent passage of the graft. This new implant is available with continuous polyester loops in 5-mm increments from 20 to 50 mm. Biomechanical testing of the femurEndoButton continuous loop-hamstring tendon graft complex (20 mm loop) in young human femora (n = 11); mean age, 46 years (age range, 42 to 50 years); after cyclical loading at 50 to 250 N at I Hz for a 1,000 cycles showed a

mean failure load of 1,345 + 179 N, stiffness of 178 + 39 N / m m , maximum graft-bone displacement of 2.1 + 0.3 mm, and a steady-state graft-turmel displacement of 0.51 _+ 0.14 ram. The surgical technique for the continuous loop EndoButton is identical to that described earlier in this article. To maximize the stiffness of the femur-EndoButton-hamstring graft complex, we recommend that a 25-mm or 30-mm continuous loop be used. Assuming that a 30-mm length of hamstring tendon graft is to be inserted into the femoral socket, a femoral tunnel length of 55 to 60 mm will be required. The required continuous loop length is calculated by subtracting the amount of graft to be inserted into the femoral socket from the directly measured femoral tunnel length. For example, assuming that the femoral tunnel length measured 58 mm and 30 mm of graft has been selected for insertion into the femoral socket, the required continuous loop is calculated as follows: 58 mm - 30 m m = 28 mm. Since the implants come in 5-ram increments, an EndoButton with a 30-mm continuous loop would be selected. The appropriate-size EndoButton with continuous loop is placed into the EndoButton holder, and the

Fig 12. (A) Doubled gracilis and semitendinosus graft and conventional EndoButton with EndoButton Tape ready for passing. Note the position of the knot. If the knot is positioned too close to the EndoButton, its large size may prevent the EndoButton from passing through the 4.5-mm EndoButton tunnel, thus making it impossible to deploy the EndoButton. No. 5 passing suture (upper left arrow), and no. 2 flipping suture (lower left arrow) are seen. If necessary, the graft can be removed using the no. 5 suture that exits the tibial tunnel. (B) Doubled gracilis and semitendinosus graft and EndoButton with continuous loop ready for passing. 208

BROWN AND SKLAR

hamstring graft is passed through the loop and the ends of the graft are equalized in length. Graft Passage

The 2.7-mm passing pin is manually reinserted into the tibial and femoral tunnels under arthroscopic control, and passed out through the previous puncture hole on the lateral side of the thigh. A full-length no. 5 Ethibond suture (passing suture) and a full-length no. 2 Ethibond suture (flipping suture) are passed through the end holes of the EndoButton. A second no. 5 Ethibond suture (safety su-

ture) can be inserted into the same hole as the no. 2 flipping suture and passed alongside the graft and out of the tibial tunnel. If necessary, this safety suture can be used to remove the graft (Fig 12). A no. 5 Ethibond suture is passed through the eyelet of the 2.7-mm passing pin and tied to itself, creating a large passing loop. The no. 5 and no. 2 EndoButton sutures are loaded into the passing toop, and the passing pin is used to pull the passing loop and sutures across the joint and out the lateral thigh. Under arthroscopic visualization, the no. 5 suture attached to the EndoButton is used to pull the EndoButton

Fig 13. (A) EndoButton with continuous loop. The graft is advanced into the femoral socket using the no. 5 suture. The no. 2 flipping suture is clearly seen in this intraoperative photograph. The no. 5 trailing suture exiting the tibial tunnel can be used to remove the graft if necessary. (B) Continuous polyester loop is seen connecting the EndoButton, which has entered the femoral tunnel, and the doubled gracilis and semitendinosus graft, which is exiting the tibial tunnel. (C) For the EndoButton to flip and anchor on the lateral femoral cortex, the insertion mark must be advanced out of view into the femoral socket. (D) If the measurements are correct and the EndoButton has deployed on the surface of the femoral cortex, the insertion mark should lie at the entrance of the femoral tunnel, as shown here.

ENDOSCOPICACL RECONSTRUCTION

209

and the attached hamstring tendon graft across the joint, and into the femoral socket. The graft must be advanced until the previously placed insertion mark is seen to disappear into the socket (Fig 13). The no. 2 suture attached to the EndoButton is then pulled in a proximal direction parallel to the femoral tunnel, and the EndoButton will be felt to flip against the lateral femoral cortex. Correct deployment can be verified by pulling on the no. 2 and no. 5 sutures, and the EndoButton should be felt to teeter-totter against the lateral femoral cortex. If any doubt exist about secure deployment of the EndoButton, intraoperative radiographs or fluoroscopy can be used to check the position of the EndoButton. Tension is applied to the distal end of the graft, and the previously placed insertion mark will be seen to slide back down the tunnel. If the measurements

B

I

4

and setting of the synthetic tape length are correct, this mark should lie at the entrance of the femoral tunnel. If it is desirable to remove the graft, the no. 5 passing suture can be pulled, thus tipping the EndoButton while simultaneously pulling on the safety suture that exited the tibial tunnel. The EndoButton will then disengage from the cortex and slip back down the EndoButton hole, allowing removal of the graft. If an EndoButton with continuous loop is used, the grafts are looped through the continuous loop, and the implant is passed as described above. If the surgeon wishes to change the length of the polyester loop, the EndoButton can be removed as described earlier using the no. 5 safety suture, the polyester loop can be cut, and EndoButton Tape can be used as the connecting material.

F

Fig 14. Tibial fixation options. (A) Two 13.5 mm x 4,0 mm AO plastic spiked ligament washers. (B) Washerloc, (C) 17 mm plastic spiked ligament washer with 9 mm x 25 mm unicortical fixation screw. (D) Two barbed ligament staples. (E) Sutures tied around a 9 mm x 25 mm unicortical fixation post and metal washer, (F) 9 mm x 28 mm biointerference screw,

t

I' 1 210

BROWN AND SKLAR

Graft Fixation and Tensioning

Based on the biomechanical studies of Sklar et a124 and Magen et al, 25 the most secure method of fixing hamstring tendon grafts to the tibia is using two 13 × 4-mm plastic spiked ligament washers (Synthes Ltd, Paoli, PA) with bicortical 4.5-mm cortical screws. There are two potential disadvantages of this fixation technique; first, in some patients (especially thin patients) the hardware may be prominent and may require later removal. The second potential disadvantage of using this type of tibial fixation is that in some patients the gracilis tendon may be too short to be fixed under the second washer, compromising the fixation strength. Other suitable tibial fixation options

include the Washerloc (Arthrotek, Inc, Warsaw, IN), a 9 m m × 25 m m unicortical fixation screw and 17-mm plastic spiked channel washer (Smith & Nephew Endoscopy, Andover, MA), two barbed ligament staples (Smith & Nephew Richards, Memphis, TN), sutures tied around a fixation post, and direct tendon fixation using a metal soft tissue interference screw (Smith & Nephew Don Joy, Andover, MA) or a bioabsorbable soft tissue interference screw (Fig 14). Based on the results of preliminary biomechanical testing in our laboratory, two AO spiked washers (Synthes, Ltd, Paoli, PA) are the strongest fixation, followed by (in decreasing order of strength) the Washerloc, no. 2 nonabsorbable sutures tied around a fixation post and

Fig 15. Doubled gracilis and semitendinosus grafts with EndoButton femoral fixation. (A) A 6-week second look shows that the graft has been revascularized. (B) A 3-month second look shows synovialization of the graft. (C) A 2-year second look, showing that the graft has a close resemblance to that of the normal ACL. (D) A 6-year postoperative MRI scan shows a healthy-looking graft.

ENDOSCOPICACLRECONSTRUCTION

211

washer, a single 17-mm plastic spiked channel ligament w a s h e r fixed to the tibia with a unicortical 9 m m × 25 m m fixation screw, and, finally, a 9 m m × 28 m m bioabsorbable screw. If a bioabsorbable screw is used, we r e c o m m e n d dilation of the tibial tunnel to the nearest 0.5 m m , use of a 9 × 28-ram screw, and advancing the screw until it is just flush with the anterior tibial cortex. Although it has been s h o w n in a robotic m o d e l using porcine bone that graft fixation inserted close to the joint line (anatomic fixation) leads to i m p r o v e d stability c o m p a r e d with fixing the graft more distally, w e have f o u n d that u n d e r cyclical loading conditions the a m o u n t of graft slippage is greater and the ultimate failure load lower for bioabsorbable screws advanced to the level of the joint line c o m p a r e d with screws that are left flush with the anterior tibial cortex. 26 If any d o u b t exists about the security of the tibial interference screw fixation, we r e c o m m e n d that this fixation be backed up b y tying the sutures a r o u n d a fixation post or button. Before fixing the grafts to the tibia, it is critical to cycle the knee to allow stress relaxation of the hamstring t e n d o n graft, stretching of the connecting material, settling of the E n d o B u t t o n against the lateral femoral cortex, and settling of the hamstring t e n d o n graft a r o u n d the connector material, and for potential knot slippage to occur. We recomm e n d that the knee be cycled a m i n i m u m of 60 times before tibial fixation. At the present time the knee flexion angle and the a m o u n t of tension that should be applied to the ACL graft at the time of surgery is u n k n o w n . If t a n d e m AO ligament washers or Washerloc is used for tibial fixation, the strength and fixation of this graft construct is such that similar to patellar tendon grafts, one must be careful to avoid overtensioning the graft and capturing the knee. If these fixation m e t h o d s are used, w e advocate tensioning and fixing the tibial end of the graft at 0 ° to avoid potentially overconstraining the joint. For other fixation methods, the knee is positioned b e t w e e n 20 ° and 30 ° of flexion depending on the a m o u n t and the pattern of graft lengthening. The stability and the range of m o t i o n of the knee are checked once the tibial end of the graft has been fixed. The arthroscope is inserted back into the knee, the graft tension is assessed, and a check for roof and lateral wall impingem e n t is made, Roof i m p i n g e m e n t is best assessed b y viewing with a 70 ° arthroscope in the notch (Fig 15).

Closure and Postoperative Dressings The crural fascia that was p r e s e r v e d d u r i n g harvest of the hamstring tendons is closed over the tibial h a r d w a r e with a no. 0 absorbable suture. The subcutaneous tissue is closed in layers with fine absorbable sutures. A running 3-0 Prolene (Ethicon, Inc) subcuticular stitch produces a v e r y cosmetic closure. Before leaving the operating room, the joint is injected with a second solution of 4 m g of m o r p h i n e and 25 mL of 0.25% Marcaine with 1:100,000 epinephrine for pain control. A light dressing is applied over the w o u n d , followed b y a thigh-length TED antiembolism stocking. A Cryocuff (Aircast Corp, Summit, NJ) is applied over the elastic stocking before leaving the operating room.

POSTOPERATIVE MANAGEMENT The p r o c e d u r e is routinely p e r f o r m e d as an outpatient procedure. Before discharge from the d a y surgery unit, the

212

patient is fitted with a knee immobilizer and crutches. We allow full unrestricted motion, and weight bearing as tolerated. The patient is w e a n e d from the knee immobilizer w h e n good quadriceps control of the leg is reestablished (usually 1 to 2 weeks). Crutches are continued until the patient has a normal gait pattern. Riding on a stationary bicycle can be started w h e n the patient has at least 100 ° of flexion. Closed-chain strengthening exercises such as a stairclimber, leg presses, ski machine, and rowing machine are started a r o u n d 4 to 6 weeks after surgery. During the first 6 to 8 weeks after surgery, the hamstring d o n o r site must be protected b y avoiding strenuous hamstring muscle stretching (bending d o w n to tie shoes with the knee straight) and isolated hamstring strengthening exercises such as leg curles with the leg in an extended position. Isolated hamstring strengthening exercises p e r f o r m e d with the knee at 90 ° (seated leg curles) can be started at 8 weeks. We allow jogging and running at 3 to 4 months; side-toside and cutting exercises at 4 to 5 months, and a return to sports at 6 months. In revision cases we r e c o m m e n d that sports be delayed until 9 months.

REFERENCES 1. Hamner DL, Brown CH, Steiner ME, et ah Hamstring tendon grafts for reconstruction of the anterior cruciate ligament: Biomechanical evaluation of the use of multiple strands and tensioning techniques. J Bone Joint Surg Am 81:549-557,1999 2. Brown CH, Hamner D, Hecker AT,et ah Biomechanicsof semitendinosus and gracilis tendon grafts. Book of Abstracts, pp 39-40, Sports Medicine 2000 Meeting, Stockholm,Sweden, June 6-8, 1995 3. Hecker AT, Brown CH, Definer KT, et ah Tensileproperties of young multiple stranded hamstring tendon grafts. Final Program Book of Abstracts and Outlines. SpecialtyDay,American Orthopaedic Society for Sport Medicine, February 16, 1997,San Francisco,California,p 8 4. BrownCH, Steiner ME, Carson EW: The use of hamstring tendons for anterior cruciate ligament reconstruction: Technique and results. Clin Sports Med 12:723-756,1992 5. Shelbourne KD, Liotta FJ, Goodloe SL: Preemptive pain management program for anterior cruciate ligament reconstruction. Am J Knee Surg 11:116-119,1998 6. Brown CH, Steiner ME: Anterior cruciate ligament injuries, in SitiskiJ (ed): Traumatic Disorders of the Knee. New York, NY, SpringerVerlag, 1994,pp 193-284 7. Brown CH, SklarJH: Endoscopicanterior cruciate ligament reconstruction using quadrupled hamstring tendons and EndoButton femoral fixation. TechOrthop 13:281-298,1998 8. Ferrari JD, Ferrari DA: The semitendinosus: Anatomic considerations in tendon harvesting. Orthop Rev 20:1085-1088,1991 9. Ivey M: Surgical technique for harvesting the gracilis and semitendinosus tendons. Contemporary Orthopaedics 26:369-372,1993 10. Levy M, Prud'homme J: Anatomic variations of the pes anserinus: a cadaver study. Orthopedics 16:601-606,1993 11. Pagnani MJ, Warner JJ, O'Brien SJ, et al: Anatomic considerations in harvesting the semitendinosus and gracilis tendons and a technique of harvest. Am J Sports Med 21:565-571,1993 12. Warren LF, Marshall JL: The supporting structures and layers on the medial side of the knee. J Bone Joint Surg 61A:56-62, 1979 13. Brown CH, Carson EW: Revision anterior cruciate ligament surgery. Clinics Sports Med 18:109-171,1999 14. Cooper DE, Deng XH, Burstein AL, et ah The strength of the central third patellar tendon graft. A biomechanical study. Am J Sports Med 21:818-824, 1993 15. Tanzer M, Lenczner E: The relationship of intercondylar notch size and content to notchplasty requirement in anterior cruciate ligament surgery. Arthroscopy 6:89-93,1990 16. Howell SM, Clark JA, Farley TC: A rationale for predicting anterior cruciate graft impingement by the intercondylar roof: an MRI study. Am J Sports Med 19:276-281,1991 BROWN AND SKLAR

17. Howell SM, Clark JA: Tibial tunnel placement in anterior cruciate ligament reconstructions and graft impingement. Clin Orthop 283:187195,1992 18. Olson EJ, Fu FH, Harner CD, et al: Towards optimal tibial tunnel placement in endoscopic anterior cruciate ligament reconstruction. Poster exhibit no. 57 at the Annual Meeting of the American Academy of Orthopaedic Surgeons, San Francisco, California, February 1993 19. Steiner ME, Hecker AT, Brown CH, et al: Anterior cruciate ligament graft fixation: comparison of hamstring and patellar tendon grafts. Am J Sports Med 22:240-246, 1994 20. Jackson DW, Gasser SI: Tibial tunnel placement in ACL reconstruction. Arthroscopy 10:124-131, 1994 21. Goble EM, Downey DJ, Wilcox TR: Positioning of the tibial tunnel of anterior cruciate ligament reconstruction. Arthroscopy 11:688-695, 1995 22. Graf BK, Henry J, Rothenberg M, et al: Anterior cruciate ligament

ENDOSCOPICACL RECONSTRUCTION

23.

24.

25.

26.

reconstruction with patellar tendon. An ex vivo study of wear-related damage and failure at the femoral tunnel. Am J Sports Med 22:131135, 1994 Wiener DF, Siliski JM: Distal femoral shaft fracture: a complication of endoscopic anterior cruciate ligament reconstruction. A case report. Am J Sports Med 24:244-247, 1996 Sklar JH, Brown CH, Hecker AT, et al: Endoscopic ACL Graft Fixation: Comparison of Hamstring and Patellar Tendon Techniques. Presented at 2nd World Congress on Sports Trauma/AOSSM 22nd Annual Meeting, Lake Buena Vista, Florida, June 16-20,1996 Magen HE, Howell SM, Hull ML: Structural properties of six tibial fixation methods for anterior cruciate ligament soft tissue grafts. Am J Sports Med 27:35-43,1999 Ishibashi Y, Rudy TW, Livesay GA, et al: A robotic evaluation of the effect of ACL graft fixation site at the tibia on knee stability. Arthroscopy 13:177-182, 1997

21 3