The sinus tarsi is an anatomical space bounded by the talus and calcaneum, the talocalcaneonavicular joint anteriorly and posterior facet of the subtalar joint posteriorly. It is medially continuous with the much narrower tarsal canal. The sinus tarsi contains the cervical ligament and the three roots of the inferior extensor retinaculum. The tarsal canal contains the interosseous talocalcaneal ligament and the deep and intermediate roots of the inferior extensor retinaculum. Both the sinus and the canal contain blood vessels - which are important for the nutrition of the talus - and nerves. The extensor digitorum brevis and bifurcate ligament lie anterior to the sinus tarsi.
The term "sinus tarsi syndrome" was first applied in O’Connor in 1958 to a syndrome of post-traumatic lateral hindfoot pain and instability which was relieved by the injection of local anaesthetic into the sinus tarsi. The same diagnostic criteria seem to have been applied reasonably consistently throughout the literature. The incidence of sinus tarsi syndrome following ankle injury has not been published, but it is not very common. Some authors use the term "sinus tarsi syndrome" to refer to lateral hindfoot pain associated with inflammatory conditions or hindfoot valgus, but we prefer to refer to this as "lateral subtalar impingement".
Pathological examination of tissue removed from patients with sinus tarsi syndrome include chronic inflammatory changes, fat necrosis, fibrosis and synovial cysts.
The cause of pain has been postulated to be vascular engorgement or nerve irritation, both due to fibrosis.
A recent paper by Frey et al suggests (on the basis of arthroscopic examination) that sinus tarsi syndrome is an inaccurate diagnosis which can always be refined by adequate investigation, particularly by subtalar arthroscopy. The following are the commonest underlying abnormalities found in this and other papers:
- interosseous talocalcaneal ligament tears
- subtalar instability
- osteochondral injuries of the subtalar joint
- arthrofibrosis of the subtalar joint
- degenerative disease of the subtalar joint
- fibrous tarsal coalition
- chronic inflammatory changes in the sinus tarsi connective tissues
Patients complain of pain in the sinus tarsi region. There is usually a history of ankle injury.
Clinical examination reveals tenderness over the sinus tarsi which is relieved by local anaesthetic injection. Pain may be exacerbated by varus tilting of the heel (unlike the pain of lateral impingement which is worse on valgus tilting of the heel) or walking on uneven ground. A feeling of subtalar opening may be felt on the varus tilt test. Abnormalities in the ankle are common: up to 50% have ankle instability and/or anterolateral synovitis.
Plain radiographs are generally normal, although degenerative arthritis of the subtalar joint may be seen. Stress views of the subtalar joint (lateral or Broden views) may show instability, but this is difficult to demonstrate and the diagnostic criteria are not clear. Subtalar arthrography may show obliteration of the anterior micro-recess but sensitivity is not very high.
MR shows inflammatory and fibrotic changes well. The interosseous talocalcaneal ligament may be shown to be torn but some observers find that non-specific changes make this difficult to visualise. MR also shows damage to the subtalar joint and surrounding structures. Lee (2008) assessed the diagnositic accuracy of MRI using subtalar arthroscopy as the reference standard. MRI had sensitivity of 44% and specificity of 60% for interosseous talocalcaneal ligament tears, 73% and 89% for cervical ligament tears, 71% and 92% for sinus tarsi fat alterations and 86% and 87% for synovial thickening. Complete agreement between MRI and arthroscopy was present in only 10% of patients
Taillard et al described various abnormalities on EMG examination of the peronei in patients with sinus tarsi syndrome compared with normal controls, including:
- reduced activity of peroneus longus or brevis or both during walking
- block contraction of both peronei during stance phase
The abnormalities disappeared after local anaesthetic injection of the sinus tarsi or successful surgery.
Non-surgical management should include:
- control of pain and inflammation with analgesics, anti-inflammatory medication and steroid injections. Komprda obtained cure in 73 and improvement in 25 of 116 patients with this regime.
- protection for selected patients with appropriate splintage: we use an Aircast ankle brace and customised orthotic devices when appropriate
- functional rehabilitation of Achilles tendon, peroneal muscles and proprioception
Two surgical techniques for sinus tarsi syndrome are described in the literature.
Excision of the entire contents of the sinus tarsi, including in some cases the interosseous talocalcaneal ligament was the treatment recommended by O'Connor in the original description of the condition. Results of this are reported very favourably, with most or all patients relieved of pain. Taillard et al summarise results from the literature as showing 88 cases treated surgically (including their own). There were 66 excellent, 16 good and six poor results. Half of these were in O'Connor's original paper and none of the papers describe outcome criteria in any detail.
Arthroscopic examination and debridement of the posterior subtalar joint and sinus tarsi allows diagnosis and treatment with low morbidity. 94% of 49 patients treated by Frey (1999) were improved at 1-7.75 years’ follow-up although half had some residual symptoms. Fey found that 36/49 atients had interosseous talocalcaneal ligament tears, 27 had soft tissue impingement lesions, 7 arthrofibrosis, 4 subtalar OA and 2 talocalcaneal coalitions. This paper leaves open some questions about patient selection and evaluation.
Lee (2008) reported 33 subtalar arthroscopies for sinus tarsi syndrome. 29 patients had ligament tears, 18 synovitis, 8 arthrofibrosis of the posterior subtalar joint and 7 soft tissue impingement. Mean VAS pain score improved from 7.3-2.7/10 and mean AOFAS score from 43-86/100, although several patients still had some pain.
In addition, surgical treatment may be indicated for concomitant ankle synovitis or instability, subtalar instability or foot deformity.
- Breitenseher MJ et al. MRI of the sinus tarsi in acute ankle sprain injuries. J Comput Assist Tomogr 1997 21(2):274-279
- Cahill DR. The anatomy and function of the contents of the human tarsal sinus and canal. Anat. Rec. 1965 153:1-18
- Frey C, Feder KS, DiGiovanni C. Arthroscopic evaluation of the subtalar joint: does sinus tarsi syndrome exist?. Foot Ankle Int. 1999 20(3):185-191
- Harper MC. The lateral ligamentous support of the subtalar joint. Foot Ankle 1991 11:354-358
- Klein MA, Spreitzer AM. MRI imaging of the tarsal sinus and canal. Radiology 1993 186(1):233-240
- Kuwada GT. Long-term retrospective analysis of the treatment of sinus tarsi syndrome. J Foot Ankle Surg 1994 33(1):28-29
- Lee KB et al. Subtalar arthroscopy for sinus tarsi syndrome: arthroscopic findings and clinical outcomes of 33 consecutive cases. Arthroscopy 2008; 24:1130-4
- Lee KB et al. Efficacy of MRI versus arthroscopy for evluaton of sinus tarsi syndrome. FAI 2008; 29:1111-6
- Taillard W et al. The sinus tarsi syndrome. Int Orthop 1981 5(2):117-130