IAT is a common sports injury, and its pathogenesis is not clear. It is often thought that excessive exercise causes repeated microinjury of the Achilles tendon, which can also be caused by degeneration or by abnormal development of the calcaneus, such as Haglund’s deformity. The common pathological changes associated with IAT are fat deposition, heterotopic ossification, calcification, inflammation around the Achilles tendon and anterior bursitis of the Achilles tendon. For IAT patients with heterotopic ossification, the effect of conservative treatment is often not ideal, and surgical treatment is frequently needed. The purpose of the operation is to remove the ossification and calcification of the Achilles tendon and the inflammatory tissue around the tendon. In order to remove heterotopic ossification of the Achilles tendon, it is often necessary to detach the tendon at its insertion, cut away the heterotopic ossification, and reattach the tendon in its original position. It has been reported that the risk of Achilles tendon rupture after operation is small when the insertion is detached by less than 50%[2, 5], but when it is more than 50%, the risk of rupture is increased; in such cases, it is necessary to reattach the tendon with anchors at its insertion[1, 21, 22]. In this study, when the heterotopic ossification was being removed, the insertion of the Achilles tendon was completely detached and cleaned; the footprint of the tendon was reconstructed with anchors afterward. Patients' AOFAS, VAS, and VISA-A scores were significantly improved after the operation, indicating a good clinical outcome. The average time to recover normal walking ability was 9.1 weeks (4–15 weeks), and the recovery time of exercise ability was 10 weeks (8–12 weeks). The recovery rate of exercise was 80% at 6 months after the operation. All of the patients soon returned to ordinary daily activities and exercise.
There are many methods for treating IAT with heterotopic ossification. The usual method is to detach the Achilles tendon from the calcaneus, remove the heterotopic ossification, and reattach the tendon to the calcaneus. Johnson et al. [21]used a bone anchor to reattach the Achilles tendon after debridement of degenerated or calcified portions with a central tendon-splitting incision. The average follow-period was 34 months. The AOFAS score increased from 53 preoperatively to 89 at the last follow-up. Nunley et al. [23]reported the use of the central tendon-splitting technique with a posterior incision. They performed a retrospective analysis of 27 patients. Two 3.5 mm suture anchors were used for fixation. One patient developed superficial wound infection. After an average follow-up period of 4 years, the average AOFAS score was 96. At the 7-year follow-up, 96% of the patients were pain free. Zhuang et al. [15]reported that the central tendon-splitting approach was an effective surgical method for the treatment of Achilles tendon disease. However, there are no reports on reconstructing the footprint of the Achilles tendon on the calcaneus. After detaching the Achilles tendon and removing the osteophyte, the surgeon reconstructs the footprint of the tendon on the calcaneus with a suture bridge by placing anchors at the proximal vertex of the footprint and external screws at the distal vertex. These attachment points cause the detached Achilles tendon to adhere to its original anatomical footprint on the calcaneal tubercle to restore the anatomical form and function as much as possible. The mean AOFAS, VAS and VISA-A scores at the latest follow-up were 94.2 ± 5.00, 0.4 ± 0.51 and 81.4 ± 8.83, respectively. All of these measures were significantly improved compared with their preoperative values. This study had several strengths: first, the anatomical reconstruction of the footprint provides an increased contact area between the Achilles tendon and its footprint on the calcaneus, which promotes tendon–bone healing; second, the anatomical reconstruction of the footprint can provide increase the initial pull-out strength, which helps patients carry out early weight-bearing exercise; third, the anatomical reconstruction of the footprint can restore the anatomical morphology of the Achilles tendon to restore its function. The biomechanical properties of the Achilles tendon-calcaneus complex were restored, and the rate of Achilles tendon rerupture was effectively reduced.
The Achilles tendon consists of the gastrocnemius tendon and soleus tendon. The anatomical study of the Achilles tendon shows that the tendons of the soleus and the medial and lateral heads of the gastrocnemius are inserted into the posterior parts of the calcaneus. As the gastrocnemius and soleus tendons extending to the distal end, they internally rotate to some extent[24]. PeKala et al. [20]carried out a cadaver study and assessed the degree of rotation of the Achilles tendon, classifying each tendon as type I, type II or type III accordingly. These three classifications of internal rotation affected the biomechanical properties of the Achilles tendon, determining the level of stress that it sustained. The attachment points of the three component tendons also have an important influence on the mechanical properties of the Achilles tendon as a whole. Therefore, it is very important to reconstruct the footprint of the detached Achilles tendon on the calcaneus in the treatment of Achilles tendinopathy. In this study, an "L"-shaped incision posterior to the Achilles tendon was used to expose and remove the Achilles tendon enthesopathy, and the shape of the footprint of the Achilles tendon was marked. According to the shape of the footprint, internal and external anchors were implanted to reattach the Achilles tendon to the footprint area. The results showed that the average time to recover normal walking ability was 9.1 weeks (4–15 weeks), the time to recover exercise ability was 10 weeks (8–12 weeks), and the exercise recovery rate was 80% at 6 months postoperatively. The proportion of patients with excellent or good postoperative functional scores was 100%.
Heterotopic ossification in IAT is a common pathological manifestation affecting the insertion of Achilles tendon. Traditional surgical treatment methods detach the insertional Achilles tendon, remove the heterotopic ossified tissue, and then reattach the Achilles tendon to the calcaneal tubercle. Plaster fixation is often needed postoperatively, but it brings a high risk of rerupture, slow recovery, and functional implications such as a low rate of return to sports. Johnson et al. [21]suggested that, after the application of bone anchors from the posterior median approach to repair the insertion of the Achilles tendon, the limb requires 3 weeks of non-load-bearing recovery. Deorio et al. [8]suggested that the injured limb should not bear weight within 3–5 weeks after operation according to the degree of detachment of the Achilles tendon; DeVries et al.[9] also advised that the injured limb should not bear weight within 3–5 weeks after the use of a bone anchor for reattachment of a surgically detached Achilles tendon. Wagner et al.[25] reported that, when a bone anchor is used to repair the reattached IAT, the limb requires a weight-free recovery period of up to 8 weeks. McGarvey et al.[22] used the posterior median approach to treat the Achilles tendon. After the removal of inflammatory tissue, the Achilles tendon was fixed at the insertion with bone anchor nails. For 2 months after the operation, the patients could not fully load the limb when walking. Three months after the operation, only 15 of 22 patients were fully able to perform normal work again, and 2 patients did not return to work at all because of continuous symptoms. Hardy et al.[14] studied 46 patients with IAT. After the Achilles tendon was completely stripped from the bone, the limb needed plaster fixation for 6 weeks, after which the patients wore Achilles tendon boots for weight-bearing walking. A total of 89.1% of patients had no pain while running, and 71.7% of patients were able to return to their premorbid activity levels. In recent years, there have been an increasing number of reports on the reconstruction of the Achilles tendon with double-row anchors, and the mechanical stability of this reconstruction technique has been improved, which has enabled patients to resume weight-bearing activities early and expedited their return to exercise. Research shows that, for patients with extensive tendon debridement, double-row Achilles tendon suture bridge technology has a biomechanical advantage over single-row anchorage sutures [26]. Rigby et al.[27] reviewed 43 cases of insertional Achilles tendon reconstruction treatment with suture bridge technology. The patients did not need plaster fixation after the operation and could bear weight early, at an average of 10 days after the operation. The average AOFAS score was 90 (65–100). The VAS score improved from 6.8 (2–10) to 1.3 (0–6). Forty-two cases (97.6%) were able to return to their daily activities. However, the double-row reconstruction did not consider the restoration of the Achilles tendon footprint, and its long-term effect is uncertain. Considering that the Achilles tendon is composed of three bundles of tendons rotating and twisting, we adopted the method of anatomical footprint reconstruction of the Achilles tendon insertion to restore the biomechanical properties of the Achilles tendon–-calcaneus complex as much as possible. This method provides high initial biomechanical strength after the operation, and no postoperative plaster fixation is required. Therefore, the patients can be ordered to carry out active non-weight-bearing exercises with the ankle joint soon after the operation; the incision sutures are removed 2 weeks after the operation, at which time the patients were allowed to bear weight within tolerance. After 6 weeks, the patients could gradually begin adaptive jogging exercise. In this group, the average recovery time of normal walking ability was 9.1 weeks (4–15 weeks), and the recovery time of exercise ability was 10 weeks (8–12 weeks). The exercise recovery rate was 80% at 6 months postoperatively. Thus, the procedure allowed rapid recovery and a return to exercise.
The shortcomings of this study include the small number of cases and the short follow-up time. Despite its limitations, this study provides a method for the treatment of IAT with heterotopic ossification. Large sample studies and biomechanical studies are needed to further confirm the therapeutic effect of anatomical footprint reconstruction of IAT.