Introduction
The treatment of chronic Achilles tendon tears, including chronic ruptures, is a challenge for most orthopedic surgeons [
10]. Several techniques have been described; however, the superiority of one technique over the others has not been demonstrated and the best surgical management of chronic Achilles tendon ruptures still remains controversial [
14,
19,
23,
24,
33,
34,
36]. Chronic injuries are associated with a higher rate of postoperative infection and more prolonged recovery, that is why minimally invasive techniques may be advantageous compared with open techniques [
26,
31].
Therefore, it has been recently aimed at establishing new technique of Achilles reconstruction to minimize the wound healing problems and to reduce the rate of infection [
30]. Using semitendinosus and gracilis tendons with Endobutton (Smith & Nephew, USA) stabilization, an Achilles tendon reconstruction in a minimally invasive way with as little as eight small skin incisions and immediate weight-bearing of the injured foot after the surgery has been performed.
Assessment of the long-term outcomes of the minimally invasive Achilles tendon reconstruction technique [
30] was the primary aim of this study. Presented method has been hypothesized to be potentially beneficial to all patients when it comes to both, restored Achilles tendon function as well as patients satisfaction with the reconstruction outcomes.
Results
Biomechanical tests
All the tested specimens survived two loading blocks (at least 500 cycles). With three specimens, it was possible to perform the third cyclic loading block and two specimens survived the fourth block. The overall number of cycles reported for cadavers ranged from 507 to 1000.
Clinical evaluation
All patients were reviewed at the average follow-up of 15.3 months (range 12–24). The subjective outcomes reported by patients 12 months after the surgical treatment are given in Table
1.
Table 1The subjective outcomes of the surgical procedure
Early complications (donor site pain) | None | 17 |
Moderate | 1 |
Severe | 0 |
Late complications (donor site pain) | None | 17 |
Moderate | 1 |
Severe | 0 |
Daily activity limitations | None | 13 |
Moderate | 5 |
Severe | 0 |
Strength limitations | None | 11 |
Moderate | 7 |
Severe | 0 |
Loss of lateral foot sensitivity | None | 18 |
Moderate | 0 |
Severe | 0 |
Pre-operative ATRS score improved significantly after the surgery (p < 0.001). The injured leg showed slightly decreased maximum calf circumference than the opposite leg in almost all cases, but the difference was not significant. All patients returned to normal daily activities. Sixteen of the eighteen patients returned to the sport pre-injury level. Two patients did not return to sport, including one due to the ACL surgery.
The median reported pain and satisfaction level according to the VAS scale was 1.0 (± 1.3) and 9.0 (± 1.7), respectively. None of the patients scored 5 points (extreme problems) to any of the particular EQ-5D-5L questions. The median value of the actual comfort was amounted to 80.0 (± 18.6) and maximum score of 100 points was recorded in three cases.
Functional evaluation
The differences in performing the weight-bearing lunge test and single leg hop for distance for the injured and non-injured extremity were not statistically significant (Table
2). The differences in performing the heel rise endurance test for the injured and non-injured extremity were statistically significant (
p = 0.0002). The largest difference in number of repetitions was 13 (14 for the uninjured limb and 1 for the injured limb in one case and 22 for the non-injured limb and 9 for injured one in another case). No difference was observed in one case.
Table 2Functional tests results for non-injured and injured limb
The weight-bearing lunge test (cm) | 12.0 ± 4.0 (5.0–18.0) | 10.0 ± 3.2 (4.0–15.0) | n.s |
The heel rise endurance test (no. of repeats) | 10.5 ± 6.4 (2.0–22.0) | 7.0 ± 5.2 (1.0–18.0) | 0.0002 |
Single leg hop for distance (cm) | 100.0 ± 25.8 (70.0–160.0) | 85.0 ± 38.8 (65.0–160.0) | n.s |
Isokinetic evaluation
The results of most of strength and endurance muscle parameters were comparable for injured and non-injured extremities (Table
3,
p value n.s.). The flexors strength parameters measured during the isometric contraction: isometric flexors peak torque (
p = 0.0006) showed significant difference for injured and non-injured leg.
Table 3Isokinetic test results for non-injured and injured limb
Isometric flexors peak torque (Nm) | 105.0 ± 34.5 (48.0–186.2) | 71.6 ± 38.7 (30.4–156.7) | 0.0006 |
Isometric flexors peak torque/bodyweight (%) | 111.5 ± 30.6 (60.6–164.7) | 91.3 ± 39.8 (39.9–160.6) | n.s |
Isometric extensors peak torque (Nm) | 54.1 ± 12.7 (31.4–77.7) | 58.3 ± 11.4 (32.6–68.6) | n.s |
Isometric extensors peak torque/bodyweight [%] | 60.5 ± 11.7 (37.0–69.0) | 58.3 ± 27.9 (34.0–171.8) | n.s |
Peak torque concentric contraction (Nm) | 160.5 ± 48.8 (88.9–261.7) | 153.2 ± 49.6 (76.0–241.7) | n.s |
Peak torque/bodyweight concentric contraction (%) | 176.9 ± 57.4 (141.1–212.3) | 185.3 ± 54.6 (114.8–240.9) | n.s |
Peak torque eccentric contraction (Nm) | 168.6 ± 50.4 (76.5–265.5) | 167.2 ± 51.3 (143.5–249.2) | n.s |
Peak torque/bodyweight eccentric contraction (%) | 187.2 ± 60.8 (143.5–234.4) | 192.6 ± 56.4 (117.4–333.2) | n.s |
CON/ECC ratio (%) | 103.4 ± 54.6 (98.2–309.7) | 103.2 ± 70.4 (100.7–309.9) | n.s |
Work concentric contraction (J) | 478.2 ± 178.5 (164.1–775.6) | 410.5 ± 204.7 (164.1–941.8) | n.s |
Power concentric contraction (W) | 40.2 ± 15.3 (12.8–71.3) | 38.1 ± 15.2 (20.8–69.5) | n.s |
Work eccentric contraction (J) | 746.8 ± 256.4 (247.0–1023.0) | 570.4 ± 217.6 (214.9–985.5) | n.s |
Power eccentric contraction (W) | 61.3 ± 23.7 (23.4–90.5) | 54.4 ± 18.0 (22.2–73.5) | n.s |
Discussion
The most important finding of the present study is that an Achilles tendon reconstruction using a minimally invasive surgical procedures with semitendinosus and gracilis tendons as well as Endobutton stabilization allows for a proper reconstruction of chronic Achilles tendon tears. A detailed and extensive biomechanical, clinical, functional and isokinetic evaluation has been performed as a follow-up post-operative study. Eight fresh-frozen human cadaveric specimens with Achilles tendon tear have been treated with the surgical procedure. The cadavers have been enrolled in the biomechanical tests equivalent to the rehabilitation program. Moreover, 18 patients with Achilles tendon chronic tears have been enrolled in the postoperative evaluation.
To date, several techniques for Achilles tendon reconstruction have been described; however, the best surgical management of chronic Achilles tendon ruptures has not been defined [
28,
32]. Neglected cases have a tendency to show poor functional results. However, good functional results after the surgery have been shown in several recent studies [
9,
18,
24‐
29]. In the present study, a statistically significant improvement of the ATRS, VAS and EQ-5D-L after the surgery has been noticed. This suggests that patients with severe chronic Achilles tendon dysfunction experienced high improvement after the repair, starting from poor position.
Chronic injuries are associated with a possibility to develop postoperative complications, reported in 20% of patients undergoing a free gracilis tendon graft procedure [
28], 6% of patients undergoing peroneus brevis tendon transfer [
27] or 18% of patients undergoing a free semitendinosus tendon graft procedure [
32]. In the present series, no patients have developed any wound infection, suggesting that the minimally invasive approach is associated with a lower risk of infections when compared with other open techniques [
31]. These results stay in line with conclusions from minimally invasive peroneus brevis tendon transfer [
25].
Another crucial advantage is that the post-operative treatment has been conducted with immediate weight-bearing of the injured limb and decreased up to two weeks period of immobilization comparing to other studies [
20,
24,
26,
28]. It has been reasoned that it is of great advantage when patients are able to walk normally very fast [
6]. This has been confirmed by biomechanical analysis of humans gait and forces upon Achilles tendon during walking as well as by the calf circumference measurements on both affected and contralateral sides [
1]. Maximum calf circumference was slightly decreased on the affected side. This finding is in inconsistency permanent calf muscle atrophy following Achilles tendon repair after patients’ immobilization [
15,
16,
18,
21,
25]. It has been shown that the rapid return to walking had a positive influence on repair, avoiding negative effects of long immobilization on tendon healing, as previously suggested [
5‐
7].
A decrease in the endurance of the calf muscles in the injured limb has been indicated during the functional heel rise endurance test. Asymmetry of muscle endurance indicates an increased risk of injury for patients active in sports [
8]. Therefore, it might be necessary to intensify exercises to improve muscular endurance after surgical treatment, with particular emphasis on functional aspects.
A comparative analysis of the isokinetic test results for the non-injured and injured limb has also been performed. It allowed to assess the ability of the muscles to perform work in postoperative rehabilitation of patients. Both strength and endurance of the lower leg muscles have been properly and functionally restored. Decrease in isometric strength parameters suggest putting more efforts in isometric exercises of calf muscles. It could be beneficial but needs more studies on that. Additionally, an important parameter of percentage of the peak torque of the concentric and eccentric calf muscle strength (CON/ECC Ratio%) indicated a correct dynamic balance of ankle joint. This result was of special importance because a correct balance of concentric and eccentric strength ensures the dynamic stabilization of the joint and reduces the risk of injury [
8]. In terms of recovery of isokinetic strength at 12 months after the surgery, there seems to be no differences between minimally invasive and open surgery techniques [
13]. The flexors muscles had no isokinetic strength deficit, as previously reported [
11,
17,
22], even though different speeds were used (30°/s and 90°/s).
There are some limitations to this study. First, this is a short-term prospective study with small number of cases. Second, a prominent heterogeneity of the studied group has been noticed. Both these aspects, however, could not be excluded because all patients treated with the minimally invasive procedure were qualified to the surgery usually after long and unsuccessful treatment. Therefore, in most cases, the procedures might have been regarded as a last chance for restoration of Achilles tendon normal function. Although the clinical and radiological results of 1-year follow-up are encouraging, more cases and longer follow-up time of two and five years after treatment are needed to provide stronger evidences in control clinical trials.
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