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

Abstract

Hamstring (HS) use for anterior cruciate ligament reconstruction (ACLR) has increased greatly in the past 5 years. It has been said that the harvest is the most difficult part of HS ACLR and may require a learning curve of roughly 50 procedures. Use of a posterior mini-incision approach makes the harvest much simpler. The primary benefit of this approach is that it puts the incision in the area of the cross-connections of the semitendiosus and gracilis tendons, 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. 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 incident for 15 years since devising it after 6 years of experience with the traditional anterior approach. This chapter describes the technique.

Keywords

anterior incision, Gracilis tendon, Hamstring, harvesting, posterior incision, Semitendiosus tendon, tendon stripper, tibial tunnel drilling

Keywords

anterior incision, Gracilis tendon, Hamstring, harvesting, posterior incision, Semitendiosus tendon, tendon stripper, tibial tunnel drilling

Introduction

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. It has been said that the harvest is the most difficult part of HS ACLR and may require a learning curve of roughly 50 procedures.

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 incident 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. 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 can 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 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, in all but 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.

Surgical Technique

Patient Positioning

The patient is positioned supine. We use a lateral post rather than a circumferential leg holder, but the latter can be used if the surgeon desires.

Making the Posterior Skin Incision

The ST is the most prominent tendinous structure in the popliteal fossa and runs just medially to the midline. The affected lower extremity is externally rotated, and the knee is flexed about 30 degrees. The surgeon bends over the leg to see posteromedially. The incision should be made directly over it in the popliteal fossa, shading slightly anteromedially ( Fig. 20.1 ). If the ST cannot be felt, the incision can be put into the soft spot in the skin just medial to the midline. The location of this incision is not critical because the tendon can always be found by moving the highly mobile skin in this area. The incision should be made 3 cm in length initially, but need only be 2 cm in length once experience is gained. It should be put within or parallel to a skin crease. After the dermis is incised with a #15 blade, the subcutaneous tissue is opened by spreading with Metzenbaum scissors.

Finding the Semitendinosus

An index finger should probe the incision, fishing the tendon out bluntly. If it is not easily found in this manner, two Senne retractors can be used to open the incision, and the tendon can be found under direct visualization. Once the tendon is identified, a right-angle clamp is passed around it. A ¼-inch Penrose drain then captures it and is loosely clamped ( Fig. 20.2 ).

Finding the Semitendinosus Insertion

Once the tendon is identified, the surgeon runs his or her index finger under it to its tibial insertion. This may necessitate opening the fascia posteriorly slightly with Metzenbaum scissors. At the insertion, the surgeon can verify that he or she indeed has the ST and not the Gr, which is sometimes found first. The ST is the most distal tendinous insertion in the pes. If the Gr is found first, the surgeon can find the insertion of the ST adjacent to the insertion of the Gr. The surgeon can then pull his or her finger back to the posterior incision to find the ST there.

Making the Anterior Incision

The skin is tented just anterior to the posteromedial tibial border by the index finger inserted in the posterior incision under the ST. The surgeon makes a 2-cm longitudinal incision here with a #15 blade. This area is then opened with Metz scissors, and the superficial fascia is incised carefully to avoid scoring the tendons.

Identifying the Semitendinosus in the Anterior Incision

A right-angle clamp is inserted in the anterior incision and passed around the ST tendon to grasp a ¼-inch Penrose drain ( Fig. 20.3 ). The surgeon’s other index finger is still under the tendon and guides the clamp. The surgeon may insert the short end of an Army-Navy retractor and identify the tendon by direct visualization. A ¼-inch Penrose is then passed around the tendon and clamped with a right angle.