Intraoperative ultrasonography assistance for minimally invasive repair of the acute Achilles tendon rupture

Achilles tendon (AT) rupture is a common injury of the foot and ankle, which mostly occurs in the 30–40-year age group, and the incidence is increasing in recent years [1]. The optimal treatment for acute Achilles tendon rupture is still controversial since now. Treatment can be classified into conservative and surgical types. Conservative management using a short-leg resting cast or brace in an equinus position was shown to be associated with an increased re-rupture incidence of, about 10–12% compared with about 4–5% in patients undergoing surgery [2, 3]. Surgical treatment can be subdivided into open sutures with or without augmentation, minimally invasive, and percutaneous repairs. In comparison with conservative management, surgical repair can decrease the tendon re-rupture rate, and get earlier functional treatment, less calf atrophy, and stronger push off [4]. However, the possible surgical complications included wound infection and sural nerve (SN) injury.

Percutaneous repair, first described by Ma and Griffith [5] in 1977, has the advantage of less chance of wound breakdown, but this technique has two potential risks. The first risk is sural nerve injury owing to the close anatomic neighborhood with the path the needle takes and the nerve. The recent literatures reported a range of 0–27% of sural neuritis after percutaneous repair [2, 3, 6‐9]. The second risk is an inability to assess the quality of the tenodesis because this technique does not use a surgical incision that allows exposure of the tendon ends. Kakluchi [10] described a new method that combined the advantages of open and percutaneous techniques in 1994. Assal et al. [11] developed a device called the Achillon to improve on the method reported by Kakluchi. They conducted a preliminary study using 16 fresh cadavers and reported their satisfactory clinical results of a multicenter, prospective study of 87 patients in 2002 [11]. Based on the Achillon method, Chen et al. [12] conducted a new method, which is called channel-assisted minimally invasive repair (CAMIR), to avoid sural nerve injury and yield essentially identical clinical and functional outcomes compared with open repair. But these devices (Achillon or CAMIR) are too expensive to apply beyond some patients’ affordability in our hospital. Some authors reported that the ultrasound examination was used to determine the passage of the sural nerve relative to the Achilles tendon or the small saphenous vein (SSV) [13, 14]. Therefore, intraoperative ultrasonography was used to assist minimally invasive repair of acute AT rupture [15‐17]. In this present study, we assessed the outcomes of a minimally invasive repair assisted with intraoperative ultrasonography in patients diagnosed as acute AT rupture, and evaluated the effect and advantage of the intraoperative ultrasonography assistance for minimally invasive repair of the acute Achilles tendon rupture. We used ultrasonography to identify the small saphenous vein and sural nerve and marked them in advance to achieve the purpose of minimally invasive treatment without damage to the sural nerve. This study mainly carries on research in this aspect.

From January 2015 to December 2017, 36 consecutive patients diagnosed as acute AT rupture were treated with minimally invasive repair assisted with intraoperative ultrasonography. The AT ruptures were left in 15 cases and right in 21 cases. The inclusion criteria consisted of an acute close AT rupture with no calcaneal fracture, a palpable gap between the ruptured ends, a positive Thompson test, and a distal stump more than 2 cm from the insertion confirmed by ultrasonography. Patients with re-ruptures, Achilles rupture of more than 3 weeks, previous history of local surgery or injury, history of steroid injection, chronic diseases, a distal tendon stump less than 2 cm or more than 8 cm from its insertion [15], were excluded from this study. The patients’ characteristics were listed in Table 1. The career of the patients almost included the athlete, the amateur, or the sportsman, who were more easily suffering from the AT rupture. The reason for injury was a sports injury in 36 patients, including basketball, football, badminton, and running. Simultaneously, MRI or ultrasonography was performed to confirm the AT rupture and the relationship of SSV and SN (Fig. 1).

None of the patients developed superficial or deep infections in the surgical site and there was no wound healing problem in all patients. No sensory loss in the foot or ankle associated with SN injury or no re-rupture was observed among patients in this group during the surveillance period. And no clinical evidence of deep vein thrombosis or pulmonary embolism was observed in this study.

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 persist [1, 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 treatment [17, 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 the percutaneous suture technique based on Bunnell sutures for AT rupture in 1977 [5]. However, Klein reported a 13% rate of iatrogenic sural nerve injury with the Ma–Griffith technique for percutaneous repair of fresh ruptured tendon Achilles [20]. 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 technique [21]. 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 device [6] 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 China [12], 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 the 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 11 cm proximally, respectively [13]. 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 2.5 mm, calculated as the distance between the clinical measurement and the ultrasound images [23]. In Zappia’s cadaveric study [24], the average distance between the suture and the sural nerve was 2.1 mm, less than the result (2.5 mm) reported by Flavin et al. [23].

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 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 consuming [25]. In our study, there was no SN injury, re-rupture, superficial or deep infections, or wound healing problem among patients, which was the result from the ultrasonography assistance and the minimal invasion.

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 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 cases [16]. Therefore, the suture needle was punctured through the medial side of the SSV with the 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 infection [29]. The Achilles tendon is more susceptible to infection than other parts of the ankle because of its poor blood supply [30]. Paavola 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 infection [31]. The percutaneous repair of the Achilles tendon is known to reduce the risk of wound site infection compared with open surgery methods [32], 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 in selective bias. The number of patients was not large enough to provide a valid conclusion. 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, it should be proven whether this technique influences the blood supply of the Achilles tendon.

The minimally invasive repair assisted with intraoperative ultrasonography can yield good clinical outcomes, less surgical time, and less complications, especially sural nerve injury. The technique can save the cost of surgery with the comparison of the Achillon device. In our study, the surgeon does not accept the radiological training, it is easy to identify the course of the SSV by intraoperative ultrasonography. The suture needle punctures the medial side of the SSV to avoid SN injury. This technique effectively reduces the risk of sural nerve injury in this study. This study shows that minimally invasive repair assisted with intraoperative ultrasonography is an efficient, reliable, and safe method for acute AT rupture.