Most recent meta-analyses have reported that a significantly lower risk of re-rupture with open repair techniques compared with conservative treatment, but the risks of wound-related complications and skin adhesions persist1,3,17,18. Percutaneous and minimally invasive techniques have several advantages to reduce these complications. For example, the risk of wound problems is lower than the open repair, and the risk of re-rupture is lower compared with the conservative treatment17,19. It was known that there was a major problem of sural nerve injury during minimally invasive suturing of the AT rupture. Ma and Griffith firstly described percutaneous suture technique based on Bunnell sutures for AT rupture in 19775. However, Klein reported a 13% rate of iatrogenic sural nerve injury with the Ma-Griffith technique for percutaneous repair of fresh ruptured tendo Achillis20. Haji reported the risk of sural nerve injury was 10.5% in 38 patients who underwent repair of acute AT rupture using a modified Ma and Griffith percutaneous technique21. Although there have been no clinical reports that the Achillon technique produces sural nerve injury, Porter’s cadaveric study showed a 27% risk of sural nerve violation during percutaneous Achilles tendon repair using Achillon device6, because the sural nerve displayed a highly variable anatomical course. The other minimally invasive technique, which was called Channel-assisted minimally invasive repair (CAMIR) and designed by Dr. Chen from China12, could minimize the possibility of sural nerve injury and yield essentially identical clinical and functional outcomes compared with open repair. But this CAMIR device is so expensive that limits its clinical application. The intraoperative ultrasound was used to decrease the risk of sural nerve injury to assist minimally invasive repair of the acute AT rupture.
The sural nerve (SN) is a sensory nerve in the lower extremity which branches to supply the skin on the distal posterolateral third of the lower limb. Typically, the SN is sought along the course of the small saphenous vein (SSV), where it is complete after the union of the medial sural cutaneous nerve (MSCN) and the peroneal communicating nerve (PCN) 22.Kammar et al. reported that the mean distance between the sural nerve and the Achilles tendon was 21.48, 11.47, 5.8, and 0.81 mm lateral to the tendon as measured at the insertion , and 4, 8, and 11cm proximally, respectively13. Falvin et al. have proposed a clinical method to locate the sural nerve before the surgical procedure. In their study, the average of the error of distance of the method was 2.5mm, calculated as the distance between the clinical measurement and the ultrasound images 23. In Zappia’s cadaveric study24, the average distance between suture and sural nerve was 2.1mm, less than the result (2.5mm) reported by Flavin et al23.
Intraoperative high-resolution real-time ultrasound can be of assistance during percutaneous repair of AT rupture, with no complication related to the ultrasonography. In Giannetti S et al study, no surgery-related complications, such as wounds or deep infections, sural nerve injury, were detected at follow-up7. The ultrasonography control was performed to notice the position of the needle during the needle puncture. But it must be considered that the use of high resolution real time ultrasonography does require the presence of an experienced imaging specialist and its more time and cost consuming25.
The relationship of the sural nerve and the small saphenous vein may be helpful for the Orthopaedic surgeon to repair the AT rupture with a minimally invasive technique. Eid, E. M. et al dissected anatomical variations of the sural nerve and its role in clinical and surgical procedures in 24 Egyptian legs and feet, they found that the small saphenous vein passed along the medial side of the sural nerve in all cases16. Therefore, the suture needle was punctured through the medial side of the SSV with Bunnell suture method as a result the risk of sural nerve injury was avoided theoretically. It is difficult to accurately locate the SSV and the SN intraoperatively for an Orthopaedic surgeon. According to Eid, E. M. results, the course of the SSV instead of the SN, can be detected with the intraoperative ultrasonography, because the SSV is easier to be found than the SN with the intraoperative ultrasonography for an Orthopaedic surgeon without an experienced imaging technique. Therefore, the suture needle was punctured through the medial side of the SSV to avoid the possibility of the sural nerve injury. In our study, the rupture of the Achilles tendon and the course of the SSV were detected with the intraoperative ultrasonography after anesthesia on prone position. The SN injury was not found in our cases after surgery with the Bunnell percutaneous repair method assisted with the intraoperative ultrasonography.
Some studies reported that open surgery around the Achilles tendon had a wound-related complication rate of between 8.2% and 34.1%26-28, of which at least half are due to infection29. The Achilles tendon is more susceptible to infection than other parts of the ankle because of its poor blood supply30. Paavola M et al reported that the use of tourniquets might be detrimental to wound healing and the retraction of soft tissue during surgery might increase the risk of wound infection31. The percutaneous repair of the Achilles tendon is known to reduce the risk of wound site infection compared with open surgery methods32, but sural nerve injuries may be a risk factor with this treatment method. The tourniquet was not used in the case with this minimally invasive method. The paratenon, which is located between the tendon and the skin, provides a valuable blood supply to the repaired tendon and avoids skin tethering to the AT, it also prevents superficial infection spreading into the deep layers. A 2.0-cm vertical incision was made in the paratenon to display the ruptured Achilles tendon, the paratenon was completely closure after the tendon was repaired. The suture knots were located outside the repaired tendon. All of these conditions protect the blood supply to the AT and promote tissue healing. In our study, there were no wound related complications and no case of re-rupture with our minimally invasive repair method.
Although we achieved satisfactory and good clinical outcomes, there were several limitations in this study. First, this is a retrospective non- controlled study with a relatively small number of patients result to the selective bias. The number of patients was not large enough to provide a valid conclusion. A prospective, randomized, controlled study of the various methods for AT repair should be conducted in the future. Second, the suture method in this study is based on the Bunnell suture and modified, the suture knots located outside of the repaired tendon. Whether this technique can achieve good strength of AT repair needs to be further biomechanically compared with the open repair and other minimally invasive repair methods. Finally, whether this technique influence the blood supply of Achilles tendon, the anatomical study should be applied in the future.