Chapter 13 Posterior Mini-Incision Hamstring Harvest Approach for Anterior Cruciate Ligament Reconstruction*

Overview

Hamstring (HS) use for anterior cruciate ligament reconstruction (ACLR) has increased greatly in the past 5 years as improved fixation techniques have allowed stability rates to meet or exceed those of bone–patellar tendon–bone (BPTB) grafts.¹ It has been said that the harvest is the most difficult part of HS ACLR² and may require a learning curve of roughly 50 procedures.³

The primary difficulty is that the intertendinous cross-connections of the semitendinosus (ST) and gracilis (Gr) must be sectioned before the tendon stripper is used to harvest the tendons. If they are not, the tendons can be cut too short to use, necessitating an unplanned switch to a different graft. These cross-connections, however, are significantly posterior to the traditional anterior harvest incision, requiring often-difficult retraction and dissection to reach. The primary benefit of the posterior approach is that it puts the incision in the area of the cross-connections, thus facilitating their visualization and sectioning.

The second benefit of the technique is that it allows easier location and identification of the ST and Gr in the posterior incision, where they are separate from each other and easy to find. In the area of the traditional anterior approach, the tendons exist as a single insertional structure, which requires posterior dissection for positive identification of individual tendons. This is made more difficult by the close apposition of the superficial fascial sheath anteriorly, whereas posteriorly the fascia is separated from the tendons by fat. The anterior incision, when used in conjunction with the posterior mini-incision, is then used only for tibial tunnel drilling and tibial fixation. It can thus be made much smaller than in the traditional anterior technique, only about 1 inch in length.

The author has used this technique continuously without problem for 15 years since devising it after 6 years of experience with the traditional anterior approach.

Anatomy

The accessory ST tendon is the primary structure leading to premature amputation of the ST tendon after tendon harvesting. This structure is not described in any standard anatomy texts. However, several papers have described it.⁴^–⁶ It is present in about 70% of patients. Other cross-connections exist variably from the ST and Gr tendons. In some patients they are thin and will be easily cut with a tendon stripper. However, the accessory ST in particular can be almost as thick as the main trunk of the ST. Especially in these cases, the tendon stripper can easily sever the main trunk of the ST, rendering it too short to use. The variability of the anatomy is such that it is difficult to devise a consistent plan for freeing the tendon using the traditional approach, except to run a scissors along both sides of both tendons. Branches of the saphenous nerve, and indeed its main trunk, are very close by, and saphenous neurapraxia is very common after these dissections. The takeoff of the accessory ST was shown in our studies to be an average of 5 to 6 cm posterior to the tibial crest. Although orthopaedic surgeons rarely operate posteriorly and may be apprehensive about a posterior approach, the posterior approach does not subject neurovascular structures to significant risk. Our cadaver studies showed that the closest neurovascular structure was the popliteal artery, but in eight specimens it was always at least 2.9 cm away from the ST tendon. It was also shielded from the ST tendon by the semimembranosus muscle.