Autograft versus allograft tenodesis for chronic ankle instability: a single-center retrospective comparative study

Twenty-five patients affected by CAI treated at the Sports Traumatology Unit of The G. Pini Hospital in Milan, Italy were included in this retrospective single-center study and reviewed at an average follow-up of 10.5 years (range, 5–15 years). Ten consecutive patients who underwent allograft tenodesis between 2009 and 2011 were compared with 15 consecutive patients taken from a larger cohort of prospectively recruited subjects who underwent lateral tenodesis using a split peroneus brevis tendon between 1997 and 1998. Inclusion criteria were: age 18–40 years, positivity to anterior drawer greater than 5 mm and talar tilt greater than 9° on stress radiography, absence of previous ankle surgery, no cartilage defects requiring surgery. All the operations were performed by the same experienced senior surgeon. Mean age at surgery was 29.5 years (range: 18–40; Table 1).

Mean AOFAS and Karlsson–Peterson scores increased at follow-up compared with pre-operatory status in both groups, showing a significant difference (p < 0.05). Similarly both manual laxity tests and average radiographic anterior talar translation and talar tilt angle under varus stress documented a significant improvement from baseline (p < 0.05; Table 2). No statistically significant differences concerning AOFAS and Karlsson–Peterson scores were observed between the two groups (p = n.s.). Concerning sagittal ROM four patients in the autograft tenodesis group experienced 5° dorsiflexion limitation compared with the contralateral side, while one patient experienced 15° dorsiflexion limitations in the allograft group. A reduced value of average radiographic anterior talar translation was reported in the autograft group compared with the allograft group (1.4 and 4.0 mm respectively, p < 0.05), while no differences were reported in terms of radiographic talar tilt test (p = n.s.; Table 3). No donor-site morbidity was observed in the autograft group. No intra- nor postoperative fibular fractures occurred in proximity to the bone tunnel.

The findings of our study showed that both surgical techniques represent a valid treatment option in patients with chronic lateral ankle instability from both a subjective and objective standpoint. Patients who underwent autograft lateral tenodesis achieved increased anteroposterior ankle stability compared with those who underwent allograft lateral tenodesis.

Compared with the Gould modification of the Broström procedure [4] which is considered the gold standard treatment for CAI, external tenodesis possess the advantages of providing stability in case no viable ligamentous structures are present.

According to current literature, much emphasis is put in reproducing the course of the natural ligament in order to obtain proper joint stability [23–25]. Criticisms to non-anatomical tenodesis techniques include increased invasiveness, risks of neurovascular injuries and postoperative joint stiffness. The two techniques described in the present paper are not anatomical. However, the use of the base of the fifth metatarsal bone as an anchor for the suture, allows to address subtalar joint instability brought by the calcaneo-fibular ligament incompetence, thus leading to improved stability in both ankle and subtalar joint. Restricting subtalar motion may account for increased joint stiffness, and in our case series the presence of dorsiflexion deficit was noted in a relatively high percentage of patients (5/25, 20%), although it did not considerably affect the overall functional outcome.

In our case series patients showed significant ameliorations in both AOFAS and Karlsson–Peterson score and improved ankle stability without significant complications irrespectively of the surgical technique adopted. According to our findings, a reduced value of average radiographic anterior talar translation was reported in the autograft group compared with the allograft group.

The advantages of using an allograft tissue instead of a rerouted autograft tendon include shorter operative time, less postoperative pain and decreased donor site morbidity, since the muscle strength which is important for eversion of the ankle is preserved [26–28]. However, the increased anteroposterior motion reported in the allograft group compared with the autograft may be related to its reduced biomechanical properties. Although the issue is controversial and no consensus exist about allograft properties, host immunologic responses and decreased strength have been reported [29–31]; conversely, other studies report no disadvantages in terms of biomechanical properties for allograft tissues [32]. Additional concerns include risk of disease transmission and bacterial infection as well as increased costs [19,20].

Fibular fractures are potential although uncommon complications which may occur while drilling the bone tunnel during lateral ligament reconstruction procedures. In our case series we suffered no complications when drilling a 5 mm tunnel into the distal fibula. No donor-site morbidity was observed in the autograft group. Additional complications such as sural or superficial peroneal nerve injury or wound complications were not reported, thus supporting these procedure as safe and effective techniques. Eventually, we found no evidence for a learning curve given the small number of complications reported in this case series, probably because all the operations were performed by the same well-experienced surgeon.

Limitations of the present study include the small sample size and the retrospective nature of its analysis. Further possible weaknesses are that the AOFAS which is not a validated score was used and the two groups were not randomized and have different follow-up times. Long-term studies with larger cohorts are needed to test the long-term survival of the grafts with regards to joint stability and progression of degenerative changes affecting the ankle joint.

Both surgical techniques significantly improved subjective and objective outcomes in patients suffering from chronic ankle instability compared with pre-operatory status. Improved ankle stability was noted irrespectively of the surgical technique adopted, although objectively autograft stabilization provided reduced postoperative anterior talar translation compared with allograft tenodesis.

Study concepts/designing was done by A Ventura and C Legnani. Data acquisition was done by  C Legnani, E Borgo and V Macchi. Data analysis/interpretation and statistical analysis was performed by C Legnani and V Macchi.

This study was funded by the Italian Ministry of Health. No grant number is applicable. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

The authors state that they have obtained appropriate institutional review board approval or havec followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.