Abstract

The use of the hamstring tendons for anterior cruciate ligament (ACL) reconstruction has gained in popularity over the past several years. For those unfamiliar with the harvest technique of the hamstring tendons, this is often the most difficult part of the procedure. Several important steps in the procedure are described to avoid the common complication of cutting the grafts short.

Technique of Hamstring Graft Harvest

The graft harvest can be the most difficult aspect of this operation. Videotapes of this technique by Fowler, Prodromos, and Fox are available from the AAOS library.¹

The anatomy of the hamstrings has been described in the literature by Ferrari and Ferrari.² The strength of the hamstrings after harvest of the tendons was initially reported by Lipscomb et al³ to be the same as the opposite side. Since then, weakness of knee flexion above 90 degrees of knee flexion has been reported.⁴ Based on these reports, one should be cautious in recommending hamstring grafts for sprinters, who require full, active knee flexion strength. Yasuda et al⁵ have described the harvest site morbidity as minimal. Gobbi et al⁶ recommend preservation of the gracilis to prevent postoperative knee flexion weakness. The regeneration of the hamstring tendons after the harvest was described by Cross et al.⁷

Skin Incision

The skin incision for hamstring harvest should be made with the knee flexed in the figure-four position (Fig. 12-1). An oblique, 3-cm skin incision is made 5 cm below the joint line over the proximal edge of the pes anserine. The incision should start 1 cm medial to the tibial tubercle and then continue posteromedially. The oblique incision is preferable to the vertical incision for two reasons: It gives a greater exposure to the top of the pes anserine, and it also has less potential to injure the infrapatellar branch of the saphenous nerve. Plan to harvest the graft and drill the tibial tunnel through this incision. Incise the subcutaneous fat, and strip the fat off the pes anserine with a sponge.

Fig.12-1 The oblique anteromedial incision for hamstring harvest.

Exposure of the Tendon

Identify the superior border of the pes by palpating the superior edge with your finger. Lift up this superior border, and incise the fascia. Identify the bursa between the pes and the medial collateral ligament by placing the tip of the scissors in the space. With the scissors, continue the incision medially down the tibia, in an L-shaped fashion, removing the tendons distally. Use a Kocher to apply traction to this top corner. Turn the pes down to look on the underside for the most inferior tendon, the semitendinosus (Fig. 12-2). Lift the tendon up with the tip of the scissors, and grasp it with a Kocher. Lift up the gracilis, and grasp it in a similar fashion with a Kocher. Divide the conjoined tendon between the semitendinosus and the gracilis.

Fig. 12-2 The pes is turned down to visualize the tendons on the underside.

Tendon Release

Free the distal end of the tendon with the scissors. Make sure you get the full length distally. Grasp it with a Kocher, and pull it firmly into the incision. Many of the bands can be released with the traction and by blunt finger dissection. The main band that goes to the medial head of the gastrocnemius will usually have to be cut with the scissors (Fig. 12-3). Pull firmly on the tendon, and cut away from the tendon (to avoid cutting the tendon with the scissors) (Fig. 12-4). The tendon should not retract proximally if all the bands are cut. When the tendon is pulled distally, there is no dimpling posteriorly over the gastrocnemius.

Fig. 12-3 The bands from the tendon to the gastrocnemius are identified and cut.

Fig. 12-4 The scissors are used to cut the bands to the gastrocnemius.

Stripping of the Tendon

Advance the tendon stripper up over the tendon to free it from the muscle proximally (Fig. 12-5). The key to a successful harvest is to keep tension on the distal end. This will prevent the tendon from folding over and being cut off short (Fig. 12-6). Make sure that the tendon stripper is heading up the thigh in the same direction as the tendon. There is often resistance at the muscle tendon junction, and the stripper should be rotated to slip it up along the surface of the muscle. This gives extra length. The total length is usually 28 to 30 cm. Strip the gracilis tendon in a similar fashion.

Fig. 12-5 The tendon stripper is pushed up the tendon to remove it proximally from the muscle.

Fig. 12-6 One small band may kink the tendon, and the stripper will cut the tendon off short.

Preparation of the Graft

Preparation of the Four-Bundle Semitendinosus and Gracilis Graft

Take the graft to the graft master on the back table. Lay out, measure, and cut the graft to 22 cm. Remove the muscle with the periosteal elevator. Loop the two tendons over a #5 braided nonabsorbable suture to produce an 11-cm graft (Fig. 12-7). With this length, 2.5 cm is in the femur, 2.5 cm is intraarticular, and 5 cm is in the tibial tunnel. This ensures a small portion of the graft is at the cortex of the tibia for fixation with the screw. Whipstitch the individual ends of the tendons with a #2 nonabsorbable suture for a distance of 4 cm (Fig. 12-8). Make sure that each tendon has a suture in it. This allows you to tension each bundle of the composite graft. The completed four-bundle graft should be 11 cm in length. This four-bundle graft will be three times the strength of a single strand of semitendinosus, assuming all bundles are equally tensioned.⁸ Incorporate the graft into the bone tunnel by Sharpey fibers.⁹ This will take about 10 to 12 weeks to heal. This graft will have at least 2.5 cm of graft in each tunnel. The depth of graft in the tunnel can be determined by the suture marks at each end.

Fig. 12-7 The two tendons are looped over a suture.

Fig. 12-8 The tendon ends are whipstitched individually.

Graft Sizing

Measure the size of the composite graft to the nearest half centimeter (7.5 mm and 8 mm are the most common sizes) (Fig. 12-9). Drill the tunnels according to the size of the tendon.

Fig. 12-9 Sizing of the graft.

Tips for Harvesting the Hamstring Grafts to avoid complications