• Paul Monaro

Ankle Injuries - Syndesmosis Injury

Injury to the distal tibiofibular syndesmosis may be a more common injury than previously described. However it is a poorly recognized injury and often missed. There are three main ligaments that make up this complex the anterior inferior tibiofibular ligament, the interosseous ligament and the posterior inferior tibiofibular ligament. Support is also provided by the interosseous membrane.

An injury to this joint occurs with movements that cause separation (diastasis) of the tibia and fibula. Because large forces are required, there will often be associated injuries. There will often be tearing of the deltoid ligament complex. And frequently there will be an associated fracture of distal fibula and / or medial malleolus. Sometimes there will be a Maisonneuve fracture – at the upper shaft of the fibula. If there is diastasis on XRay, the whole fibula should be XRayed.

The injury can occur in conjunction with a severe lateral ankle sprain. Generally however the mechanism of injury is different, with the leg twisting (into external rotation) on a fixed foot rather than the foot rolling under the leg. This is common in contact sports, particularly rugby league, union, and American football. In these sports, tackles by one or multiple players put very large forces through the ankle, and players twist as they are wrestled to the ground. The mechanism is usually external rotation of the ankle relative to the leg.

These injuries are often misdiagnosed as lateral ankle ligament sprains. There is speculation that up to 10% of ankle injuries involve this joint, and up to 35% in the rugby codes.

Anatomy

The primary ligaments that stabilise the joint are the anterior inferior tibiofibular ligament (AITFL), the interosseous ligament (IOL), the posterior inferior tibiofibular ligament (PITFL) & the deltoid ligament complex. All syndesmosis injuries involve some degree of disruption to the AITFL and deep fibres of deltoid, while severe injuries may involve disruption of all four ligaments. Normally, no more than 1 mm of separation is possible between the distal tibia & fibula. 1.5 mm or more separation indicates instability and the need for surgery.

Examination

Clues to the injury include the mechanism, an inability to weight-bear with sensations of instability, difficulty pushing off the front of the foot, and early swelling with or without bruising that is high up on the ankle. On palpation, there will usually be tenderness over the AITFL, and often over the deltoid ligament. The entire fibula should be palpated, as syndesmosis injury is sometimes associated with a proximal fibular fracture (Maisonneuve fracture). Numerous physical tests have been described. The most reliable is the external rotation stress test. The patient sits with the knee and ankle at 90°. The examiner stabilizes the lower leg with one hand, while gripping the midfoot with the other hand & applying an external rotation force. Pain &/or apprehension adds to the suspicion of syndesmosis injury. The ‘squeeze test’ has also been described but is less reliable. Squeezing the tibia & fibula (medial and lateral force respectively) at mid-shin level results in separation of the syndesmosis & may produce pain.

The most widely used tests are:

1. Palpation. There will be tenderness superior to the ankle joint, and minimal swelling over the lateral ankle ligaments.

2. External rotation test. With the patient sitting and the leg hanging, the ankle is held plantargrade and is externally rotated on a fixed lower leg. This test has reasonably good reliability.

Radiology

The recommended x-ray views are weight-bearing antero-posterior, lateral, and mortise views. However, the patient is often hesitant to bear weight, and x-ray findings may be inconclusive. MRI is the imaging of choice, as it will provide additional information regarding soft-tissue injury to the relevant ligaments, including the extent of deltoid ligament disruption. It will also demonstrate concomitant osteochondral lesions, and injuries to other ligaments such as the lateral ligament complex, and the anterior tibiotalar ligament.

Treatment

If the injury is minor, the treatment will be rest and graduated rehabilitation, similar to the treatment for a standard ankle sprain. However these injuries generally heal significantly more slowly than lateral ankle ligament injuries. See more on rehabilitation below.

Surgery

When there is widening of the joint (any grade II or grade III injury) and particularly if there is associated fracture, surgery will be required. The ligaments will be repaired, and the joint stabilized with a screw or ‘tightrope’ wire. After healing, there may be a prolonged recovery time, as stiffness and recurrent swelling tend to settle slowly.

Traditionally, surgical stabilization has been achieved via screw fixation across the syndesmosis. More recently, the use of ‘tightrope’ fixation has increased in popularity. In cases of distal fibular or bi-malleolar fracture, some form of plate fixation will also be required.

Screw fixation:

A screw is placed proximal and parallel to the ankle joint, across the syndesmosis. Sometimes a second screw is implanted for added stability. While some surgeons prefer to keep the screw in place, up to 50% of the general population, and 75% of the athletic population, require a 2nd procedure for screw removal. While an inherently stable joint, the inferior tibiofibular joint does undergo a small degree of ‘spreading’ & rotation during weight-bearing, particularly that involving ankle dorsiflexion or external rotation. Screw fixation blocks this movement and is non-physiological. Failure to remove the screw is associated with high rates of screw breakage and osteolysis.

Suture button with tight-rope fixation:

A non-absorbable fibrewire suture is placed across the syndesmosis, and anchored on the bone on either side using an endobutton. The advantages of this procedure are that the wire allows physiologic mobility of the joint, there is a quicker recovery and return to sport, reduced risk of osteolysis, and most authors report that there is rarely any need for hardware removal. However, in one study with a 20-month follow-up, it was found that 1 in 4 patients required hardware removal.


Rehabilitation

It is recognized that, compared to moderate and severe lateral ankle sprains, syndesmosis injuries take at least twice as long to heal. After surgical stabilization, the time to return to sport is usually 4 to 6 months, although in recent studies where tightrope stabilization was used, return to play occurred in as little as 9 weeks.

The patient will often be nonweightbearing (NWB) initially, with between 4-6 weeks in a plaster or boot. Physiotherapy rehab may begin immediately for Grade I sprains, and within 2 to 6 weeks after surgical stabilisation.


Acute Phase (Wk 1-4): It is important to ensure the patient avoids ankle external rotation or forced dorsiflexion during this phase. They will usually be wearing a boot, which can be removed for physiotherapy. Treatment will focus on:

- R.I.C.E. for swelling and inflammation.

- Early gentle range of motion (ROM) in the sagittal plane. This will initially be NWB.

- Isometric strengthening using bands or weights.

- Progression to weightbearing calf strengthening.

- Manual therapy to the midfoot and superior tibiofibular joints.

- Strengthening for the large muscle groups of the lower body – gluteals, hamstrings, quadriceps.

- Maintenance of upper body strength and fitness.

- Exercise cycling.

- Prescription of orthoses, if necessary, to limit external rotation with weightbearing.

Subacute Phase (Wk 2-8): The focus during this phase will be to restore full ROM, assist the patient to resume normal ADLs, and ensure function and pain levels are adequate for more advanced training. The boot will usually be weaned off during the early part of this phase.

- Greater focus on stretching and ROM exercises, gradually pushing into restricted ranges. Forceful external rotation and dorsiflexion are still avoided.

- Manual therapy, including subtalar and ankle joint mobilization where necessary.

- Hydrotherapy, including pool running.

- Progression of strengthening

- Proprioceptive exercises, progressing from NWB to double leg, and later single leg weightbearing. This may include use of devices such as wobble boards, Bosu, mini trampoline, etc.

- Jogging may commence toward the end of this phase.

- Controlled introduction of change of direction drills.

- Progressive resistance added to calf exercises.

Advanced Phase (Wk 8+): Functional and sport-specific drills are introduced during this phase, with the goal being a return to full unrestricted sports training. Ideally, full ROM is present, although up to 36% of athletes were found to lack some flexibility at the time of return to sport2. The patient will have been transitioned to the use of an ankle brace or rigid strapping.

- More advanced change of direction drills.

- Advanced strengthening

- Plyometric drills

- Introduction of power drills

- Increasing speed, including rapid change-of-direction drills.

Return to full training will commence when the patient has:

- Normal ROM

- No pain or instability on advanced functional testing

- No pain / apprehension on external rotation stress test

- Equal to the non-injured side for strength and balance References

1. Degroot, H et al (2010). Outcomes of suture button repair of the distal tibiofibular syndesmosis. Foot & Ankle International, 32, 3, 250-256.

2. Del Buono, A et al (2013). Syndesmosis injuries of the ankle. Current Reviews in Musculoskeletal Medicine, 6, 313-319.

3. Latham, A et al (2017). Ankle syndesmosis repair & rehabilitation in professional rugby league players: a case series report. British Medical Journal, 3, e000175, 1-6.

4. Porter, D et al (2014). Optimal management of ankle syndesmosis injuries. Open Access Journal of Sports Medicine, 5, 173-182.

5. Williams, G & Allen, E (2010). Rehabilitation of syndesmotic (high) ankle sprains. Sports Health, 2, 6, 460-470.


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