Not to be Missed: Part 2: The Syndesmosis Complex

The tibiofibular syndesmosis joint plays a primary role in providing the stability and congruency to the mortise of the talocural joint under axial loads. Immediate recognition and prompt management of syndesmotic injuries should minimise complications and improve the prognosis and return to sport timeframes.

This article aims to provide sports physiotherapists with the framework to be able to diagnose and effectively manage an acute syndesmotic injury to a successful return to sport.

Injuries to the syndesmotic tibiofibular joint are less likely to occur than lateral ankle sprains. Beumer et al., (2004) estimates that the incidence of acute syndesmotic injury varies from 1-11% of all ankle injuries. Sports that involve high intensity twisting and cutting maneuvers or those with limited mobility, such as wearing a boot in skiing or ice hockey, have the highest incidence of this injury. Delayed or poor initial management of a syndesmosis injury will increase the likelihood of the athlete developing secondary complications. These complications can include heterotrophic ossification, joint synovitis, anterior impingement, osteoarthritis, oesteochondral lesions and chronic ankle pain.

The syndesmosis complex forms the distal articulation between the tibia and fibula. The articulation is anchored by a number of ligaments that are crucial to the normal function of the joint. These ligaments include the interosseous membrane (IOM), the anterior inferior tibiofibular ligaments (AITFL), the posterior inferior tibiofibular ligaments (PITFL), the interosseous ligament and the transverse tibiofibular ligaments (TTFL). This ligamentous structure provides a very strong and stable ankle mortise. Subsequently injury to this complex is often caused by high load and force.

syndesmois1

Image 1: The AITFL & IOM

posterior ankle

Image 2: The posterior ankle: PITFL & TTFL

The kinematics of the syndesmosis complex is an important component during rehabilitation in order to restore the ankles natural glide and rotation. The distal tibiofibular joint acts as a ‘spring’ to spread the mortise to accommodate the wider portion of the talus with dorsiflexion and then recoils when the joint returns to plantarflexion. Changes to the mechanics of the joint can lead to secondary problems with in the ankle joint and complications further up the kinetic chain. Van den Bekeron (2007) state a lateral talar displacement greater than 2 mm may result in greater than 90% chance of degenerative joint changes if left unaddressed because of increased pressure with decreased contact area.

MECHANISM

Image 3: Mechanicm of injury- Forced external rotation of the foot on the ankle

Image 3: Mechanism of injury- Forced external rotation of the foot on the ankle

The most commonly reported mechanism of a syndesmosis injury involves a forced external rotation of the foot on the tibia. This may occur when the athlete rapidly pivots internally off a foot that is planted in external rotation. Less common mechanisms reported in theliterature involve hyper-dorsiflexion of the ankle, which occurs when an individual falls forward over the planted foot; inversion of the ankle with a planar-flexed foot and internal rotation of the foot and ankle complex (Williams, N., Allen, J., 2010).

ASSESSMENT

The classic sign of a syndesmotic injury is tenderness on palpation over the anterior and posterior tibiofibular ligaments. As the severity of the injury increases, tenderness may increase proximally over the insertion of IOM That is 2-3cm proximal to the ankle joint.Severe swelling and ecchymotic discolouration, which is observed in lateral ankle sprains, is rare. This is due to the tissue damaged in a syndesmotic sprain to be considered more extra capsular. Range of motion is typically limited into plantar and dorsiflexion with a possible painful or empty end feel. If the athlete is unable to weight bear a few steps following the injury the Ottawa ankle rules should be applied in order to determine first line radiographs. Ligamentous tests are contraindicated until bony fractures have been ruled out.

X-ray is considered first line imaging to assess for diastasis and a potential fracture.  These radiographs should be conducted in a weight bearing position and include A-P, lateral and mortise views. A syndesmosis injury is present when the ankle joint exhibits greater than 1 mm lateral subluxation or greater than 5 mm separation between the distal fibula and tibia on the mortise view (Taylor et al 2007). Radiograph measurements however should not be relied upon for ruling out a syndesmotic injury due to the high rate of false negatives (Takao, 2013 & Nielson, et al., 2005). The A-P and lateral views should extend the entire length of the tibia and fibula to rule out a Maisonneuve fracture. A Maisonneuve fracture involves the complete rupture of the medial deltoid ligaments, the AITFL, IOM as well as a proximal fibula fracture.

MRI’s sensitivity and specificity for the diagnosis of syndesmosis injuries is close to 100% and is the investigation of choice for the assessment of soft tissue damage.

SPECIAL TESTS

Most of the clinical tests for syndesmosis injuries use the reproduction of symptoms , i.e. pain, as opposed to the perceived amount of laxity. The diagnostic accuracy and prognostic potential of these tests are yet to be validated.

Image 3: The Squeeze Test

Image 3: The Squeeze Test

The Squeeze Test: The therapist applies an approximation of the middle third of the tibia. This is best conducted with the athlete sitting over the edge of the plinth. Reproduction of the athletes ankle pain is considered a positive test.

The Dorsiflexion- Compression Test: The athlete performs a lunge/squat maneuver driving the tibia over the foot as far as possible. An inclinometer is used to assess the tibial angle at the end of range position or where the athletes symptoms are reproduced. This is then repeated with the therapist providing compression over the syndesmosis joint. An improvement in the angle recorded with the compression indicates a positive test.

Dorsiflexion- External Rotation Test (Kleiger test): This involves the therapist stabilising the leg and providing an external rotation force with the ankle in maximal dorsiflexion. Reproduction of pain indicates a positive test. This test has the highest degree of inter- rater reliability and the lowest rate of false positives.

The Cotton (Shuck) Test: The therapist alternates medial and lateral forces to the talus with the ankle in a neutral position. This test is designed to assess the degree of bony translation available as opposed to assessing pain reproduction itself.  The test is considered positive if there is excessive translation or a boggy end feel.

Heel Thump Test: With the athlete sitting over the edge of the plinth, the therapist applies a firm thump to the bottom of the heel in line with the long axis of the tibia. The test is positive if the thump briefly aggravates the athlete’s pain above the ankle or in the distal leg.

It should be noted that as no one single test alone is able to produce an accurate diagnosis. A cluster of positive tests should raise the therapist’s suspicion of an injury to the syndesmosis complex. Research by Alonso (1998) indicates that a positive dorsiflexion compression test, a positive squeeze and palpatory tenderness of the AITFL indicate a protracted recovery from a syndesmosis injury.

PROGNOSIS

Nussbaum et al., (2004) developed a return to competition formula to guide prognosis of syndesmosis injuries with the exclusion of  fracture or frank diastasis. This formula is based on distance from tip of medial malleolus to the most proximal point of tenderness on the anterior portion of the IOM.

Time to return to play= 5+ (0.93 x Tenderness length in cm)) -/+ 3.72 days

SURGERY Vs. CONSERVATIVE

Syndesmotic surgical repair is generally indicated for a fibular fracture at least two centimeters above the ankle joint in the presence of a deltoid ligament disruption or with complete diastasis (Mulligan 2010). Conservative management is indicated for stable sprains where by there is no to minimal radiographic widening of the mortise upon external rotation stress.

 Conservative management programs generally involve early rigid immobilization and pain relief strategies. The severity of injury and degree of instability is used to dictate early immobilisation and weight bearing status. Grade I sprains that are considered stable will likely require immobilsation in a moon boot for 3 -14 days depending on injury severity.  The average return to sports will be between 4-8 weeks. Surgical reduction should be considered for grade II injuries, where stress views on radiographs demonstrate diastasis.. Porter (2009) states grade II injuries, which are occultly unstable, may be overlooked and treated too conservatively (non-surgically), leading to latent complications.. For stable grade II sprains, a more conservative approach may be considered. This will typically involve weight bearing immobilsation in a moon boot for 4-6 weeks. Syndesmosis injuries with frank diastasis or fracture are considered grade III injuries and should be treated with surgical reduction.

Internal fixation with trans-syndesmotic screws is the most common surgical intervention for tibiofibular stabilization. The screws and plate involved in this operation are typically removed 2–4 months after surgery. More recent surgical advancements have seen a shift in the preferred fixation to the Suture-button or ‘Tightrope; procedure. This involves the use of an interosseous fibrewire suture spanning the tibiofibular joint and secured by an endobutton. Results of this technique have been positive with improved joint mobility, faster return to weight bearing & sport, no osteolysis and no need for hardware removal. (Porter et al 2014).

REHABILITATION

As there is limited evidence based research on the management guidelines for syndesmosis injuries, the therapist must rely on experience and sound clinical reasoning to guide the athletes progressions.

The primary aim of rehabilitation is to restore the function of the ankle joint with respect to the kinematics, range of motion and dynamic control to provide a safe return to sport. For post surgical atheltes, external rotation of ankle is not permtted in the six weeks in the setting of a deltoid tear (Porter et al 2014). End of range subtalar eversion and loaded exercises in the abducted foot position should also be avoided in the early stages until the ligements have healed.

Dorsiflexion should be introduced with caution in the rehabilitation program as excessive dorsiflexion can cause further separation of the syndesmosis and lead to impaired tissue healing. A heel lift may be used initially and cycling with a higher seat to limit end of range dorsiflexion is advised in the early stages before progressing towards full range.  Porter et al (2014) state 95-100% of the pre injury range of motion must be regained before athletes initiate strength exercises. Furthermore they comment on the importance of regaining range of motion within the first six weeks as only a slight change will occur thereafter.

Strength is based around restoring the eccentric control of the pronatory forces by the tibialis posterior and the eccentric control of dorsiflexion to protect against weight bearing dorsiflexion stress on the syndesmosis. Proprioceptive balance retraining is imperative throughout the rehabilitation ideally implemented with training of gluteus medias and maximus (Bullocak- Saxton 1994) for proximal control.

Taping or bracing of the syndesmosis may be used as a protective effect for the athletes return to sports specific movements. A medial sub talar sling taping technique is advocated by Wilkerson 2002 to reduce strain on AITFL. Circumferential straps as the distal tibiofibular joint with secure distal compression should also be protective of the tibiofibular ligaments. Orthotic intervention may be required to minimise over pronation, which can stress the medial deltoid and tibiofibular ligaments.

The ability to perform a repetitive, painless hop test is a common indicator that the athlete is ready to transition to the final phase of rehabilitation. Running will  commence once the athlete has restoredpre-injury range of motion, strength and endurance compared to the uninjured side.  This will then progress to gradually introducing the athlete back into athletic movements that are specific to their sport such cutting, bounding & plyometric training.

A through return to sport testing should be conducted with 80-90% symmetry with single leg jumps tests and the star excursion balance test,  comfort with push off and cutting maneuvers, and a normal foot and ankle disability index (FADI). See our future sportsmedicinephysiotherapy.com article on return to sport testing and outcome measures coming soon.

CONCLUSION

Syndesmosis injuries have gained considerable awareness in recent years however sufficient evidence remains limited with respect to accuracy of clinical tests and management guidelines. Syndesmosis injuries that may be misdiagnosed or mismanaged often develop secondary complications such as ankle impingement, restricted range of motion, heterotrophic ossification, synovitis and chronic pain. Early surgical intervention appears to result in a quicker return to sport with reduced complications for unstable syndesmosis injuries. Conservative management is indicated for stable grade I-II sprains and involves a period in rigid immobilization. The athlete’s rehabilitation must be guided by clinical judgment with respect to tissue healing times, response to loading, range of motion, proprioception, strength and functional sports specific training. Early accurate diagnosis with prompt management will reduce return to sport timeframes and provide a more successful long-term outcome for your athlete.

Nick Kane

Editing by Kelly Taylor Lewis

REFERENCES

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Mulligan EP. Evaluation and Management of ankle syndesmosis injuries, Physical Therapy in Sport 2011 12: 57-69

Beumer A, Swiertra BA, Mulder PG. Clinical diagnosis of syndesmotic ankle instability: evaluation of stress tests behind the curtains. Acta Orthpaedica Scandinavica 2002 73, 667-669

Nussbaum E.D., Hosea T.M., Sieler S.D., et al: Prospective evaluation of syndesmotic ankle sprains without diastasis. Am J Sports Med  2001; 29:31-35

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Nielson, J.H., Gardner M.J., Peterson, Margaret G.E., Sallis, Julian J.G, Potter, Hollis G.D, David L. Lorich D.G., Radiographic Measurements Do Not Predict Syndesmotic Injury in Ankle Fractures: An MRI Study. Clinical Orthopaedics & Related Research: 2005 Vol. 436: 216-221

Porter, D.A, Jaggers, R.R.,
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