Local physiotherapy aiming to reduce synovitis, and an ankle rehabilitation programme, are often helpful, although possibly less than in patients with anterior symptoms. Patients whose problems are provoked by activities in equinus need a period of avoidance followed by graduated reintroduction of these activities. Local steroid injection can be used for those who fail physiotherapy or cannot follow the programme because of pain. Messiou et al (2006) reported resolution of pain in all of 9 professional athletes after ultrasound-guided steroid injection, with recurrence at 3 months in one.
Michelson (2005) reported improvement in about 50% of patients with posterior ankle pain due to FHL tendonopathy treated with a stretching programme.
Arthroscopic view of the hindfoot after os trigonum excision
In some ankles posterior debridement can be accomplished from anterior portals, but posterior portals, keeping lateral to the FHL tendon, are increasingly used. Posterior ankle arthroscopy, often combined with subtalar arthroscopy, is done with the patient prone. Portals are either side of the Achilles tendon at the level of the tip of the lateral malleolus. Access is kept lateral to FHL to protect the tibial neurovascular bundle. The sural nerve is also at risk. The method of accessing the ankle and subtalar joint is described with excellent illustration in Scholten (2008). The arthroscope trocar and sheath are inserted down to the joint through the posterolateral portal, aiming towards the first webspace. A shaver is inserted into the posteromedial portal and passed to engage the sheath. The sheath and scope are withdrawn until the shaver comes into view. The shaver is now used to clear the space at the back of the ankle and subtalar joints until the joints, posterior talar tubercle and FHL tendon come into view.
Arthroscopic excision of the os trigonum has been reported (Marumotu and Ferkel 1997). Willitts et al (2008) reported a variety of posterior arthroscopic procedures, including excision of os trigonum, debridement of posterior talar process and FHL tendon and loose body removal, in 23 patients. At short-term follow-up the mean AOFAS ankle score was 91 and there were "no permanent neurovascular injuries". It is important to assess the joint surface: osteochondral lesions were present in 4/25 of Koulouris’ (2003) series.
Scholten (2008) described 55 patients who underwent posterior hindfoot endoscopy for posterior impingement, defined by the presence of a posterior impingement sign and the absence of osteochondral lesions or loose bodies. Two-thirds had a history of injury, and ¾ had a bony impingement lesions, usually an os trigonum, and half of these had FHL tendonopathy. In the post-traumatic group, median return to work was 1 week and to sports 11 weeks, and the median AOFAS score was 90/100. In the overuse group, return to work was 2.5weeks and to sports 8 weeks and the median AOFAS score was 100/100. Patient satisfaction was slightly higher in the overuse group. There was no difference between the results of treatment of bony and soft-tissue impingement.
An injured or hypertrophic os trigonum or posterior talar process can be excised through an open posterior approach. Abramowitz (2003) reported a mean AOFAS hindfoot score of 87/100 at 2-6y follow-up after open surgery, although this was lower in those with symptoms for more than 2y prior to surgery. They also reported four temporary and four permanent sural nerve injuries.
Michelson (2005) reported open surgical decompression of the FHL in the fibrous tunnel behind the ankle in 20 patients, with complete relief of pain in 50% and marked improvement in the remainder. The length of follow-up for the surgical patients in this study was not clear.