*2.3. Dissection, Neurolysis, and Tenolysis*

A longitudinal/vertical incision was performed guided by the landmarks obtained with the aid of US and MRI. After dissecting the subcutaneous tissues, we identified the ischial tuberosity, torn hamstring tendons, and the entrapped sciatic nerve (Figure 3a). We carried out a careful distal-to-proximal exoneurolysis of the sciatic nerve and placed vessel-loops to visualize and avoid iatrogenic injury to the nerve during the surgery. Once identifying the stumps of both tendons that were retracted and entrapped by fibrotic tissue, we performed a careful tenolysis to free up both tendon stumps and freshen both stumps. In addition, we put Vicryl (Ethicon, Somerville, NJ, USA) sutures in each tendon stump, which served as control of the torn hamstring (Figure 3b).

**Figure 3.** Dissection, neurolysis, and tenolysis (**a**) After exoneurolysis, the sciatic nerve is identified and placed laterally in the surgical field. (**b**) Following tenolysis, Vycril sutures are placed for traction on both tendons.

## *2.4. STT Allograft Preparation*

Due to the impossibility of reinserting the hamstring tendon stumps into the ischial tuberosity, a free graft reconstruction with a 17 cm long STT allograft augmentation was carried out, allowing us to bridge the long gap (Figure 4a). The entire STT allograft was reinforced with a Hi-Fi Ribbon suture (ConMed, Largo, FL, USA), thereby endowing the reconstructed tendon augmentation with additional strength. The STT allograft was bent on itself, generating a double-thickness tendon allograft whose proximal section of 3 cm was reinforced with 2/0 Ethibond sutures (Ethicon, Somerville, NJ, USA), from which, were the two branches of the allograft stem toward the distal hamstring stumps in a "V inversion" shape (Figure 4b).

**Figure 4.** Semitendinosus tendon allograft preparation. (**a**) Description of allograft preparation and placement. (**b**) Intraoperative image showing the two branches of the allograft (inverted V-shaped).

#### *2.5. STT Allograft Placement*

After identification, dissection, and protection of the sciatic nerve, and following the correct anatomically location, we prepared the bony surface of the ischial tuberosity by curettage and rasp. Then, two self-punching Y-Knot RC (ConMed, Largo, FL, USA) suture anchors (two Hi-Fi, one blue and one white) were placed in the ischial tuberosity (Figure 5a). The first Y-Knot RC anchor was placed in a lateral and anterior position (corresponding to the SMT that is lateral and 3.1 cm proximal-to-distal and 1.1 cm medial-to-lateral). The second Y-Knot RC anchor was placed in a more posterior and medial location (the JT is medial 2.7 cm proximal-to-distal and 1.8 cm medial-to-lateral).

**Figure 5.** Semitendinosus tendon allograft placement. (**a**) Support with Ribbon resistance band. (**b**) Allograft to tendon suture.

Krakrow type stitches were passed with the blue strand of a Y-Knot RC in the external arm of the "V" of the double reinforcement of the allograft. We performed the same but using the white strand at the base of the medial arm of the "V". As it is a sliding thread, by pulling on another thread of the same color that remains free, the graft slides and is placed in the anatomical position at the level of the ischial tuberosity. Once this double suture is secured, we made a medial and lateral reinforcement suture with the blue and white threads left over in each Y-Knot RC to provide significant solidity in the insertional area.

We then took the two tendon ends: the joint tendon on one side and the semimembranosus tendon on the other side. Next, we passed one of the distal ends of the allograft through the semimembranosus tendon (deeper) with a Pulvertaft-type suture. We checked the tension after the two passes, and we carefully mobilized the knee in a range of 60 degrees, which allowed us to assess the right tension of our suture. After verifying that it was satisfactory, we made two more passes to provide a strong suture. We repeated the procedure with the joint tendon and performed four tendon passes with the Pulvertaft-type technique (Figure 5b).
