ACL reconstruction

Anterior Cruciate Ligament reconstruction design

Our experimental design for ACL reconstruction (ACL-R) included a variety of steps. In figure 2, a flow diagram demonstrates and summarises the overall surgical procedure. Each step will be explained in detail below:

Step 1: Semitendinosus graft harvest

The semitendinosus tendon is usually harvested from the ipsilateral leg.11 The semitendinosus is one of the three muscles that build up the hamstrings muscle group which locates at the posterior and medial aspect of the thigh. The use of semitendinosus autograft for ACL-R is advantageous because semitendinosus harvest is a relatively safe, reproducible, and elegant technique that has been widely used. The vertical minimal incision used to harvest the semitendinosus can lower the possibility of saphenous nerve injury and offer a cosmetic advantage at the same time.12 However, anterior knee pain, sensory deficits due to lesions of the infrapatellar branches of the saphenous nerve, decreased flexion strength and internal rotation strength can be complications associated with the HS autograft. The donor site problems thus have led to the search for allografts. A lack of harvest site morbidity, shorter operative time, and reduced postoperative pain are the advantages of using allografts.9,14 With standard screening required in the United States, the risk of disease transmission is minimal.9,14

Step 2: Semitendinosus graft preparation

With graft preparation, there are a variety of variables we need to take in account. For example, suture material and suturing technique. In the literature review, Ethibond no. 2 sutures were commonly used. However, procuring these was difficult so we opted for a similar material: prolene, a monofilament suture. Our design was chosen because both suture materials are non-absorbable. Using the suture, we decide to conduct whipstitch technique as seen in figure 4 c). This is a common suture technique in the medical world used by surgeons. Often 6-7 whip stitches are used for preparation on each end in human grafts. Using proportionality we calculated that for a rabbit graft 3 stitches was suitable.

Step 3: ACL Transection

Using a medial parapatellar incision, we created a opening in the knee to access the ligament. Once we have located the ACL between the femoral head and tibial plateau, we used a hook to "grab" the ACL and transect it using a scalpel.

Step 4: Bone Drilling

The drilling angles and starting points were standardized with the measurements from sagittal, coronal, and transverse planes in micro-CT analysis. In this way, the tunneling diameter and orientation can be consistent with the presence of protractor every time. Tibial tunneling is created using an outside-in method and femoral drilling is created using an inside-out method.

Step 5: Graft Fixation

The graft is passed through the bone tunneling and secured with the metal screws. The graft fixation design is chosen based on the human ACL reconstruction methods and the feasibility in rabbit knees. #2 ½ inches stainless steel metal screw was chosen based on literature research and the measurements of the femoral condyle and tibial plateau from the microCT scan. The size was determined to ensure a secure fixation of the passing graft while minimizing damage to the bone. The orientation of the screw was chosen due to the ease of operation and feasibility.

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