Our prospective study was performed in accordance with the principles of the 1964 Declaration of Helsinki (2013 revision) and approved by the Research Ethics Committee of Hospital Beata María. All participants gave their informed consent to participate in the study and for their clinical and imaging data to be collected and analyzed. The specimens were provided by the Department of Anatomy of University Lasalle, Madrid, Spain. We used 7 fresh anatomical specimens (4 left and 3 right) including the knee, calf, ankle, and foot. All authors contributed to patient selection, procedure and application of scores.
All ultrasound scans were performed using an E-CUBE 15 equipped with an L8-17X multifrequency linear transducer (Alpinion Medical Systems, Bothell, WA, USA) and the Needle Vision Plus™ software package (Alpinion Medical Systems, Bothell, WA, USA).
The ultrasound-guided technique described below was performed on cadaveric specimens.
We then applied the ultrasound-guided technique to repair ATRs in 11 patients. Both in cadaveric specimens and in patients we used a straight needle kit (1.6 mm) and high-strength N°2 FiberWire® suture (Arthrex), although a high strength reabsorbable suture could equally be used [25].
Pre-clinical study: development of the surgical procedure
The cadaveric specimens were placed prone, and a complete percutaneous tenotomy of the Achilles tendon was performed 5 cm proximal to the insertion on the calcaneus, simulating a complete rupture. The sural nerve was then mapped throughout its course using ultrasound to accurately place the portals for surgery and prevent nerve entrapment or damage (Fig. 1).
Sural nerve mapping with US
No skin incisions were made. At the point where the proximal and distal sutures meet, minimal stretching of the skin was performed with the tip of forceps to avoid skin bridges between the stitches.
We used a symmetrical Bunnell-type suture configuration, starting 6–8 cm proximal to the ATR. The proximal suture ends at the proximal end of the tendon stump. Each medial-to-lateral or lateral-to-medial cross-suture was advanced approximately 2 cm (Figs. 2 and 3, and Fig. 4).
The sural nerve usually runs from lateral, in the distal area, posterior to the fibular malleolus, lateral to the Achilles tendon, to medial in the medial third of the calf, crossing over the gastrocnemius tendon. Care is required to pass the suture without trapping the sural nerve. The first pass is normally deep to the nerve and, at some point distally, depending on the anatomy of the nerve, the suture is superficial to the tendon.
In the proximal stump, the needle and thread must be advanced carefully in the lateral area to avoid damaging or trapping the sural nerve. The procedure was performed under ultrasound guidance to avoid damaging the sural nerve and to ensure that the tendon was appropriately sutured (Fig. 2).
Ultrasound-guided passage of the needle and suture in the lateral area of the proximal stump with direct vision of the sural nerve
In the distal stump, passage of the needle and suture is usually medial to the nerve, as this runs from distal and lateral to proximal and medial
We repeated the procedure with another suture starting in the distal portion stump of the tendon and advancing proximally.
The distal ends of the suture were guided through the distal puncture of the proximal end suture to tie the proximal suture to the distal one. Reliable approximation of both ends of the tendon was thus achieved and verified with ultrasound.
We finished the Bunnell-type suture emerging at the point of the proximal ends of the suture (Fig. 4). Therefore, we did not need to enlarge the emergence points of the suture more than 1–2 mm if a skin bridge remains between the two stitches.
In addition, we achieved maximum tension when we tie the proximal and distal ends of 2 independent sutures by driving one suture to the point where the other one ends.
The ankle was kept in full plantar flexion while the sutures were tied (Fig. 4).
The ends of both the proximal and the distal sutures are tied in the lateral and medial aspects of the ruptured tendon. The approximation of the ends of the Achilles tendon is verified using ultrasound
Postsurgical dissection enabled us to verify that the sural nerve was not damaged, and that full juxtaposition of the tendon stumps had been was achieved (Fig. 5).
Verification of the sural nerve via dissection of the specimen
Clinical study
The clinical series comprised 11 patients (10 males and 1 female; mean age: 54 years (range 42 to 65) in whom the ATR was located by ultrasound and the sural nerve was carefully identified (Fig. 6). TThe time elapsed from the rupture of the Achilles tendon until the surgery was performed was 8.6 days (3–14). No patients had systemic diseases.
The skin was prepared in the usual fashion, obtaining a sterile field. Anesthesia involved sedation and local infiltration with 20 mL of local anesthetic (20 mL bupivacaine/adrenaline, 5 mg/mL + 0.005 mg/mL) in the puncture areas and tendon defects, approximately 4 to 6 cm proximal and distal to the tendon defect (Fig. 7). No tourniquet was used.
At the end of the procedure, the patient was immobilized in a below knee cast, with maximum plantar flexion of the ankle.
Achilles tendon tear: ultrasound image of acute Achilles tendon tear in the sagittal plane. G: gap (tendon lesion); PS: proximal stump; DS: distal stump; T: tibia
Bunnell-type criss-cross suture, knotting the proximal end with the distal end
Post‑operative protocol
Patients were discharged from the hospital on the same day. The full cast was kept in place for 3 weeks.
Patients walked using crutches without weight bearing for 3 weeks. The cast was removed at that stage, and an Aircast boot (XP Walker, DJO Ltd, Guilford, England, UK) with 3 heel wedges was appliied. Partial weight bearing with the Aircast boot was allowed at 4 weeks following the index procedure (one week after removal of the casr). The aptients were allowed to progressively increase their weight bearing status until full weight bearing was achieved 6 weeks after the percutaneous repair.
Nine weeks after surgery, and over the course of a further 2 weeks, patients were instructed to remove the orthosis for 1 to 4 h in the morning and again in the evening. At this stage, when not wearing the splint, patients bore their full weight on the operated leg and were instructed to wear a 15 mm heel wedge.
After complete removal of the Aircast boot, patients wore the heel wedge for a further month, by which time they had usually regained a fully plantigrade foot. Only at this stage (after approximately 12 weeks) were they permitted to begin eccentric exercises of the gastrocsoleus complex. At 5 months, patients were allowed to return to their normal activities, including running, when they felt confident to do so.
An early clinical examination was performed 2–3 weeks after the surgical procedure, and all patients underwent ultrasound assessment of the approximated stumps. The area innervated by the sural nerve was examined for tenderness, numbness, or any other complication. The Tinel test was performed along the entire course of the sural nerve.