Surgical Technique

The incision for the portals and the harvesting side of the hamstrings is infiltrated using 15 mL of 0.25% bupivacaine with 1:100,000 epinephrine solution. Another 15 mL of this solution is injected intra-articularly. This allows for harvest and reconstruction of the ACL without the use of a tourniquet. No arthroscopic legholder is used—only a lateral post.

With the knee flexed to 90 degrees, a 2-cm incision is used, parallel to the lines of the skin, to avoid damage to the inferior branch of the saphenous nerve and for cosmesis. The bursa of the pes is incised and split proximally.

Both the tendons are visualized and mobilized. First the gracilis tendon (GT) is grasped using a curved clamp. Maximal traction is applied, which releases the web-like fascia slips. The GT is inserted into an open stripper, which is advanced proximally about 25 cm. At this point, the tendon is cut by closing the stripper.

The tendon remains attached to the periosteum, and the semitendinosus tendon (ST) is harvested in the same manner. Being still attached to the tibia, the tendons are gently dissected free of muscle tissue using scissors. Finally, the tendons are stripped off the tibia with their periosteal insertion.

Graft Preparation

On the workstation, the ends of each tendon are tied together using a simple knot. The knots are maximally tightened under cyclic manual load and secured with four diverging U -shaped Ethibond 2 (DePuy Mitek Ethicon GmbH, Norderstedt, Germany) sutures. With the help of a Mersilene tape (DePuy Mitek Ethicon GmbH, Norderstedt, Germany), the loops are pulled one after the other through a measuring template in 0.5-mm steps in order to find the smallest diameter of both loops. The diameter of the knots should be 4 mm more than the diameter of the loops in order to prevent later knot slipping.

The loop length after knotting is equal to the cortical thickness, about 5–6 mm, plus the intra-articular graft length, about 30 mm, plus the length of the tibial tunnel at 45 degrees, about 40 mm. This makes a total of 75 mm for the ST and 85 mm for the GT. The GT loop must be longer because the knot of the GT will be proximal to the ST knot. Two Mersilene tapes are pulled through the ST and GT loops: one proximal at the knot and the other at the end of the loop. To distinguish between the ST and GT loops, Mersilene tapes are used in two colors. The ST graft is pulled into the femoral tunnel first, followed by the thinner GT graft.

Finally, the intra-articular portion of the graft is marked. A second mark is made 3 cm beyond the first mark. This mark should be seen at the intra-articular entrance into the tibial tunnel, when both grafts are inserted completely into the tunnels. Each loop is held by Mersilene tape. The lengths of the loops and the diameters of their knots are measured with a precision of up to 0.5 mm.

The C-arm was initially positioned at the end of the table. It is now moved to the joint for positioning of the tip of the Kirschner wire (K wire).

Under fluoroscopic control a 4-mm offset guide is inserted through the anteromedial portal. The tip of a K wire is inserted into the cortex to a depth of 1–2 mm at the 9:30–14:30 position, the anatomic center of the original ACL insertion, just between the center of the anteromedial and posterolateral bundles.

The ideal position of the tip is on an imaginary line continuing from the posterior cortex of the distal femur, about 5–7 mm inferior to Blumensaat line ( Fig. 33.1 ). Its correct position may be measured using the method of Bernard and Hertel. The knee is then flexed to 120 degrees and the K wire is advanced through the lateral condyle.

The ideal position of the anatomic anterior cruciate ligament insertion center lies on a sagittal view on the continuing dotted line of the posterior femur cortex.

Fig. 33.2 illustrates lateral fluoroscopic control with a K wire in place (1 mm in bone). Using a cannulated drill, a tunnel as thick as the loops (7.0–9.0 mm) is drilled until cancellous bone is reached. The drill may then be replaced by a bone-cutting tube if cancellous bone is needed to improve the press-fit on the tibia (e.g., females, revisions), and a transfemoral tunnel is cut. The cancellous bone is laid aside for later. A cannulated compactor with the same diameter as the drill used is introduced into the femoral tunnel to a depth of 10 mm. It serves as a stop for the subsequent drilling operation from the outside.

A, Impaction of the base of the lateral outside-in tunnel using a stepped compactor. B, Bottleneck principle.

The K wire is advanced to the level of the skin on the lateral thigh. A 12-mm incision is made over the pointing wire tip, and the underlying fascia is split longitudinally. The K wire is advanced and overdrilled down to the compactor with a drill bit of 11–13 mm, matching the knot diameter of the ST graft, until the impactor is reached.

As shown in Fig. 33.2A , next the drill is replaced by the stepped compactor, which is driven under arthroscopic vision until its graduated 10-mm long-stepped leading nose is seen in the tunnel entrance of the notch. In this process, the remaining cancellous bone is compacted against the cortex. This manifests as a change to a higher pitch of the blows driving in the compactor. This results in the tunnel having a step (bottleneck principle, Fig. 33.2B ). A Mersilene holding suture is passed through the joint with the aid of a K wire. The tibial drill guide is inserted with the knee in 90 degrees of flexion. A 2.5-mm guidewire is then inserted. Its position is again confirmed by C-arm imaging. An impingement probe is mounted over the guidewire. The knee is placed in full extension. On the x-ray image on the C-arm monitor, the impingement probe should have 2 mm of clearance to the notch roof.

The loops are introduced into the femoral and tibial tunnels from the lateral side, the ST loop in first position. A sudden jolt indicates that the loops have settled firmly within the bottleneck. The two loops are conditioned under maximal manual load (200 N per loop) by movement of the knee joint 20 times along its full range. A 4.5-mm drill bit is used to pierce the cortex 1 cm distal to the tibial tunnel exit. A curved forceps is passed through the underlying cancellous bone, from distal to proximal and from proximal to distal, to fashion a bony bridge. A passer is used to pull a traction suture under the bridge. This suture is placed through one end of each Mersilene tape, to railroad the tapes under the bridge, in a distal direction. With the knee flexed to about 10 degrees, maximum traction is exerted on the Mersilene tapes, and the ends of each tape are tied together.

Postoperative Rehabilitation

Postoperatively, an accelerated rehabilitation program is initiated. Partial weight bearing with crutches is recommended for the first 3 weeks. Thereafter progression to full weight bearing is encouraged, and patients discard crutches by the end of the fourth postoperative week. All patients should have regained their normal gait pattern by this point in time. Jogging is allowed at 3 months, provided the strength of the operated leg is 65% of that of the unaffected leg. A period of 6 months is required for the patient to feel comfortable enough to return to unrestricted athletic activity.

Biomechanical Studies

Biomechanical Testing

Kilger et al. tested eight fresh-frozen cadaveric knees (52 ± 7 years) using a robotic/universal force-moment sensor testing system. The knee kinematics of the intact, ACL-deficient, Endobutton-reconstructed, and knot/press-fit-reconstructed knee in response to both a 134 N anterior tibial load and a combined rotatory load at multiple knee flexion angles were determined. Differences among the four knee states were evaluated with a two-factor repeated-measures analysis of variance ( P < .05). To determine the stiffness and strength of the knot/press-fit fixation, the femur-graft-tibia complex was tested in uniaxial tension.

Clinical Results

This technique, which has been used on more than 3000 patients in the past 16 years, shows a particularly low rate of postoperative morbidity. The reason is probably to be found in the “waterproofing” of the bone tunnels, which leads to less postoperative bleeding and swelling. No drains were used. Rehabilitation was conducted following the same schemes as were followed for the reconstruction using patellar tendon grafts (accelerated-functional). The measured internal torque of the hamstrings and their flexion force returned to normal 12 months postoperatively.

A prospective study was initiated in 1998 to evaluate the short- and long-term results of this novel technique. Thirty-one ACL-insufficient patients (15 males, 16 females) without any concomitant sports injuries underwent ACL reconstruction using the previously described knot technique and rehabilitation, and took part in a prospective study. All patients underwent surgery between October 1998 and September 1999 by the author (H.H.P.). The average age was 34.2 years (range 26–64 years) at the time of surgery. All patients were examined 1 day preoperatively, and 3, 6, and 12 months and 8.23 years (range 8–9 years) postoperatively using the Tegner activity level, Lysholm score, and the International Knee Documentation Committee score. As objective parameters, KT-1000 arthrometer testing, one leg hop testing, kneeling and knee walking testing, and isokinetic testing were measured. At the latest follow-up, bilateral MRI was also performed to determine the cartilage defects of both the injured and uninjured knees according to the International Cartilage Research Society protocol, and this was compared with the preoperative status. We measured the defect size in square millimeters. For statistical analysis, we used Student’s t -test. The level of significance was P < .05.