ACL-Restoration with Semitendinosus Tendon

Operative Technique

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Steps of the Operation:

	Preparation and Positioning of the Patient
	Graft-Harvest
	Graft-Preparation
	Debridement and Notch-Plasty
	Femoral Socket
	Tibial Socket
	Graft-Passage
	Graft-Fixation
	Postoperative Procedure

Preparation and Positioning of the Patient

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The patient is placed in the supine position on the operating table. Next to the thigh is an abduction post. The knee is flexed to 90° and the foot is supported with a roll fixed to the table. The knee-joint can be fully flexed and stabilized in this position by the roll in front of the toes and the lateral abduction post.
The arthroscopy portals and skin incisions are marked on the skin with a marking pen. The camera portal is just lateral to the patellar tendon at the level of the inferior patellar pole. The working portal lies medial to the tendon just above the joint line. The 4 cm long transverse high medial parapatellar incision lies approximately 1 cm distal to the superior patellar rim and is centered over the medial border of the patella. The 4 cm long incision for the harvest of the semitendinosus tendon lies 2 cm distal and 1 cm medial to the tibial tuberosity and follows the skin lines. The whole procedure can be performed without a tourniquet if the incisions and the knee-joint are infiltrated with epinephrine / buivacain solution.

Graft-Harvest

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The leg is externally rotated and the knee-joint flexed to 60°. The skin is incised 2 cm distally and 1 cm medially to the tibial tuberosity along Langer's lines approximately 4 cm in length. The incision should be centered over the inferior part of the pes anserine, whose superior margin often can be palpated fairly distinctly underneath the skin. The most superficial layer of the pes anserine, the thin fascia of the sartorius muscle, is opened in line with the skin incision. The gracilis- and semitendinosus-tendon can be identified by palpation as they separate and pass over the postero-medial border of the tibia. The more inferior of the two tendons, the semitendinosus-tendon, is delivered from the posterior part of the incision using a curved Kelly clamp. The tendon is further liberated using closed Metzenbaum scissors in addition to the Kelly clamp. All tendinous slips to the fascia of the medial Gastrocnemius muscle have to be identified and transected.
The tendon is pulled as far as possible out of the wound and a Linvatec® tendon stripper is attached to the tendon proximally to all tendon slips. With a slight oscillating motion the tendon stripper is advanced to about 17 cm length and the tendon is transected.
The free end of the tendon is captured with a large resorbable suture using a modified Bunnel stitch (fishing hook). The needle is left attached to the suture for later use.
The tendon is freed distally up to its bony insertion. All weak divergent tendon parts are dissected leaving a 10 mm wide strip. To allow the later insertion of the graft into the knee-joint, the semitendinosus tendon is harvested with a small bone plug attached from its distal insertion into the tibia. A specially designed chisel, which is shaped like a pyramid, is used exactly at the tendon attachment site to indent the cortical bone in order to make a small trough. The 10 mm Helical Tube Saw (HTS)-Osteotom (Kaltec®^,Edwardstown, South Australia) is fed around the tightly held tendon. The surgeon stabilizes the osteotom in the bony trough with his fingers. Using light oscillating motions a 15 mm long bone plug is harvested.. In this area the cortical bone is very brittle and breaks easily if the helical tube saw is not held steadily and oscillated very carefully. Once the desired length is obtain the osteotom is angled away from the bone in order to detach the bone. The graft is completely separated from the tibia using a scalpel.

Graft-Preparation

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All soft-tissue debris is cleaned off the graft. After predrilling the bone plug with a 1.5 mm drill-bit a threaded K-wire is inserted into the whole. It is imperative that the K-wire sits well in order to achieve a successful graft passage into the joint. Sometimes it is recommended that the K-wire be inserted into the cortical bone obliquely to the long axis of the plug. Drilling is facilitated by the use of the drill-guide-clamp. The smooth end of the K-wire (the bone plug is on the threaded end) is slightly bent and fixed tightly into the 2 mm hole of the working station. The tendon is folded to one third of its original length and is placed in such a manner over the top of the bone plug that the free end of the tendon is approximately 5 mm shorter than the tendinous sling. In this position the tendon is secured to the bone plug using a 3-0 resorbable suture.
The previously attached suture of the free end of the tendon is pierced through the axilla of the tendon loop. That way the free end of the tendon will rest inside the tendon loop which itself is secured with a large non-absorbable suture (Syntofil®). Both holding sutures are pulled around the hook at the end of the working station. They are tensioned so that the K-wire bends in a curve and there is approximately a 45° angle between the bony end and the tendinous part of the graft. In this position the sutures are clamped together. Using a baseball stitch and absorbable suture material the three tendon strands are sewn to each other at the area where they will be held with the interference screw inside the femoral socket. The length and the diameter of the graft is checked using the sizing holes of the working station.
The graft is covered with a moist sponge and stored until its insertion inside the groove of the working bench.

Debridement and Notch-Plasty

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During the graft-preparation a second surgeon can begin the arthroscopy. The arthroscope is introduced through a high infrapatellar lateral portal. Via the low medial working portal just above the joint line all remnants of the old ACL are removed. This portal should not perforate the hoffa-fat-body but rather pass it medially. If the view to the posterior part of the notch is insufficient, one should remove 2 or 3 mm of bone form the lateral wall. The femoral as well as the tibial attachments of the old ACL should be cleaned of all soft-tissues. Often one has to remove additional hypertrophic hoffa flaps in order to visualize clearly the future site of the tibial socket.

Femoral Socket

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With the knee bent to 90° one can palpate the posterior cortical border of the notch using an angled bone pick. The tool is pulled 5 mm forward and a pilothole is made in the left knee at 10-11 O'clock and in the right at 1-2 O'clock. In this way only approximately 2 mm of bony bridge will remain posteriorly. In order to avoid difficulties during insertion and fixation of the graft, this area should be fairly clean of all soft-tissue.
The knee-joint is now fully bent and the foot is placed on the table in front of the roll. By fully flexing the knee joint the pilothole is well visualized without hindrance by the so-called resident's ridge. The Synos screwdriver should be used turning counterclockwise to penetrate the cancellous bone. The femoral 7 mm dilator is pushed into the bone using a mallet. The blade of the dilator should be held vertically in order to allow the blade to be deviated anteriorly and not to penetrate the hard posterior wall. Once the 40 mm long dilator is fully inserted, an oscillating motion of the dilator will create a cylindrical hole. The correct shape and depth of the socket can be verified using a 7 mm sizer. Depending on the previously measured cross section of the graft, the socket may have to be enlarged to 8 or 9 mm. At the superior border of the entrance of the socket a small indentation is created using the screw notcher. This indentation will later prevent the screw from accidentally rotating around the graft during screw insertion.

Tibial Socket

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The angled pick is introduced through the anteromedial arthroscopy portal. In different angles of extension under direct arthroscopic vision the center of the future tibial socket is marked. The center of the socket should lie in the postero-medial aspect of the original ACL were it intercepts a line drawn from the posterior border of the anterior horn of the lateral meniscus to the medial tibial spine. This point should also be as medial as possible so the graft will cross the notch in front of the posterior cruciate ligament. However, the graft should insert into the tibia as far forward as possible without being impinged by the roof in full extension. There is always a tendency to place the socket too far laterally so that at the end of the operation some additional millimeters of bone have to be removed from the lateral wall of the notch.
With the knee joint bent to 90° a 4 cm long vertical skin incision is made just at the medial border of the patella and 1 cm distal to the superior patellar pole. The skin is mobilized subcutaneously and 10 mm of the underlying capsule is opened in line with the skin incision. The Sysorb® screw driver is pushed into the previously made hole of the tibia as parallel as possible to the long axis of the tibia. The hole is enlarged to 9 mm width and 20 mm depth using the sharply cut tibial dilator. The dilator should not be fully inserted until the most superior cortical and subchondral bone is opened by fully rotating motions. The socket is completed using the 10 mm dilator.
Soft tissue debris and sharp edges are removed from the edge of the socket using a shaver or rasp. An indentation with the screw notcher is made at the antero-lateral border where the interference screw will be placed later.

Graft-Passage

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The knee-joint is fully flexed, using a 2.4 mm beath pin a suture is pulled via the anteromedial arthroscopy portal through the femoral socket and out through the lateral femoral condyle.
With the knee-joint flexed to 90° an arthroscopic grasping clamp is used to pull the suture form the anteromedial arthroscopy portal out the medial parapatellar incision. Both ends of the suture are fixed together with a clamp.
The graft is introduced into the parapatellar incision and pushed carefully into the tibial socket. Occasionally a hypertrophic medial plica prevents the passage and has therefore to be removed. Sometimes slight extension of the knee-joint facilitates the passage of the graft beneath the patella. A mallet is tapped onto the guide wire until the tibial end is fully seated. Once the graft is fully seated inside the tibial socket the guide wire is removed using a vise-grip.
The holding sutures from the femoral end of the graft are put through the sling of the pull-through suture. With slight extension of the knee-joint, first the pull-through suture and subsequently under direct arthroscopic vision the femoral end of the graft are pulled into the femoral socket.

Graft-Fixation

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The knee is flexed to 100° and the first Sysorb®-screw is inserted from the parapatellar incision into the tibial socket. The previously created notch prevents the screw from spinning around the graft. The graft is held tightly with the holding-sutures to prevent the screw from catching some of the superficial graft-fibers. Difficulties can occur during this part of the operation if the visualization to the tibial socket is impaired by a hypertrophic hoffa. The tibial screw is screwed just underneath the joint surface.
80 Newton of tension is applied to the femoral graft and the joint is brought several times through a full arc of motion. The knee is fully bent and the femoral Sysorb®-screw is inserted via the anteromedial arthroscopy portal.
A nerve hook is used to assure that all graft-bundles are tight and there is no wall- or notch-impingement. If there is any impingement at this time an additional notch-plasty is performed. If the Lachman test (KT 1000) is satisfactory, the femoral holding sutures are removed.
The parapatellar incision is closed in layers, but the arthroscopic portals are left open to allow postoperative drainage.

Postoperative Procedure

Neither CPM nor splintage is required. During the first week cold therapy is frequently used (PolarCare®) and at least three times a day the knee joint is held in full extension for 20 minutes while the heel rests on a pillow. Full weight bearing is encouraged in full extension only.

After the second week unrestricted active and passive physical therapy is began. Crutches can be used for comfort as long as the patient desires, but most of the patients do not use them for more than one week. After full range of motion is obtained (usually after one month) strengthening exercises can be added.

Usually patients are allowed back to sports third month after surgery, once they have regained their agility, strength and coordination.

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Send comments or questions to kruzlifix@staehelin.ch