Research Review By Dr. Jeff Muir©

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Date Posted:

June 2014

Review Title:

Ankle Syndesmosis: Evaluation & Treatment

Studies Reviewed:

  1. Van Heest TJ & Lafferty PM. Injuries to the ankle syndesmosis. Journal of Bone & Joint Surgery (Am) 2014; 96:603-13.
  2. Miller TL & Skalak T. Evaluation and treatment recommendations for acute injuries to the ankle syndesmosis without associated fracture. Sports Medicine 2014; 44:179–188.

Background Information:

Ankle syndesmosis injuries, also referred to as ‘high ankle sprains’, are particularly common in athletic populations. Affecting the distal tibiofibular joint, the prevalence of this injury is estimated at 15 cases per 100,000 people in the population (1), occurring most often in sports requiring the ankle to be held in a fixed boot, such as skiing or hockey (2, 3). Up to 10% of ankle sprains (4, 5) and 23% of ankle fractures (6) involve trauma to the distal tibiofibular syndesmosis.

Despite the relative frequency of these injuries, disagreement exists amongst practitioners regarding the most appropriate and effective treatments. The potential damage to the lateral ligamentous structures presents special challenges for treatment, making this type of injury more difficult to diagnose and manage effectively (7).

This review examines two recent clinical publications regarding the diagnosis and management of ankle syndesmosis injuries, with special focus on surgical and conservative treatment options and their clinical efficacy.

Summary:

Anatomy:
The bony structures of interest in the ankle mortise include the distal tibiofibular joint and the tibiotalar joint. The distal tibiofibular joint is formed by the convex side of the medial distal fibula (also called the ‘incisura fibularis’), and the concave lateral distal tibia. Four distinct ligaments provide support to the distal tibiofibular articulation, creating a relatively stable joint characterized by widening of only 1 mm during normal gait (8). The orientation and location of the anterior and posterior branches of the fibular (peroneal) artery, which supply the tibiofibular ligaments, result in blood supply being at considerable risk of injury in this area.

Mechanism of Injury:
Injury to the ankle syndesmosis occurs most often via a combination of external rotation and hyperdorsiflexion, which, in addition to athletic injuries, can occur as a result of low-energy trauma, such as falling on stairs or slipping on ice.
high ankle sprain
Classification of Injury:
Injury classification has generally been based on a three-level grading system, including a simple sprain without diastasis (Grade I), latent diastasis present only on stress radiographs (Grade II) and a frank separation visible on routine films (Grade III). An alternate grading system, based on magnetic resonance imaging (MRI), adds a fourth grade. This system classifies injuries based on ligamentous involvement, ranging from injury to only the anterior ligament (Grade I), through injury to all four ligament (Grade IV).

Diagnosis:
Radiographs augment orthopaedic testing in diagnosing syndesmotic injuries. Both gravity/external rotation stress radiographs and traditional radiographs are useful for diagnosis, with stress films valuable for revealing frank diastasis. Orthopaedic testing relies on a number of stress tests (external rotation test, squeeze test, cross-leg test and forced dorsiflexion test – see below) which all challenge the tibiofibular joint and, in cases of syndesmotic injury, result in pain in the injured joint. Conversely, decreased pain with compression is suggestive of a syndesmotic injury.

Clinical Tests – Descriptions:
  • External Rotation Test: knee and ankle are stabilized at 90° flexion and the ankle is externally rotated (positive test = pain over the syndesmosis)
  • Squeeze Test: the proximal ends of the tibia/fibula are compressed – which should act to put an opening stress on the distal articulation (positive test = pain over the syndesmosis)
  • Cross-Leg Test: patient sits with both knees in 90° flexion and feet on the ground; the injured leg is lifted and the ankle is placed on the superior aspect of the uninjured knee; gentle downward pressure is applied to the knee of the injured leg (positive test = pain over the syndesmosis)
  • Forced Dorsi-Flexion Test: ankle is moved into end-range dorsiflexion, then the motion is repeated with compression over this distal tib-fib (positive test = decreased pain over the syndesmosis when compression is added)
Treatment of Syndesmosis Injuries:

Non-Operative Treatment:
A three-phase treatment plan has been proposed for conservative treatment (9).
  1. Phase I focuses on protecting the injury and managing pain and swelling through immobilization, limited weight-bearing, light motion exercises and rest/ice/compression/elevation.
  2. Patients then transition to Phase II (strength/proprioceptive/mobility exercises) when pain and edema are well controlled and the patient can walk with minimal antalgic gait.
  3. Phase III is generally reserved for patients wishing to return to athletic activities and includes rigorous strengthening exercises and sports-specific rehabilitation.
Operative Treatment:
Grade II and III injuries are unstable by nature and often require surgical intervention. Reduction quality has been shown to have a significant impact on long-term prognosis, as mal-reduction is a concern in cases of inadequate angulation of reduction (10).

Rigid fixation via open reduction and internal fixation (ORIF) with 3.5 mm cortical screws is considered the gold-standard for surgical fixation (11). Fixation hardware is typically removed between 12 and 16 weeks postoperatively to prevent breakage. The ideal fixation technique (one vs. two screws and capturing three vs. four cortices) remains under debate, as no study has shown biomechanical superiority.

Suture button fixation gained popularity in the 1990s and consists of passing a guide pin across both the distal tibiofibular joint approximately 1 cm proximal to the tibial plafond. The suture button is then passed through the guide pin tunnel. The non-absorbable suture ends are toggled to tighten the locking sutures and secure the fibula into its anatomic position. This technique does not require a second procedure to remove hardware, and has been shown to provide an improved anatomic reduction (12).

Posterior malleolar fixation, in cases of an intact posterior inferior tibiofibular ligament, also adequately stabilizes the syndesmosis (13). The posterior malleolus can be fixed utilizing percutaneous anterior-to-posterior screws when the fragment is minimally displaced.

Potential Surgical Complications:
Mal-reduction of the syndesmosis is the most significant complication and is of long-term concern, as it can lead to poor functional outcomes and post-traumatic osteoarthritis (14). In fact, anatomic reduction is of greater concern than over-compression during screw fixation (15).

Hardware failure and screw removal are concerns, as fixation limits fibular mechanics. As weight-bearing increases, the shear forces involved can result in screw breakage. Screw breakage has been reported to occur in 7% to 29% of patients who have had fixation, depending on the time of screw removal (16).

Obese patients, or those with neuropathic conditions such as diabetes mellitus, are at risk for implant complication. Patients with complicated diabetes are 3.4 times more likely to have malunion, nonunion, or Charcot arthropathy and five times more likely to need revision surgery following ankle fractures compared with patients with uncomplicated diabetes (17).

Heterotrophic ossification has been reported in between 1.7% to 18.2% of ankle fractures and, in athletic populations, has been reported as high as 50% in patients with syndesmotic sprains (18). This is a factor worth monitoring, particularly in higher-level athletes.

Clinical Application & Conclusions:

Injuries of the ankle syndesmosis ligaments have been strongly linked with a prolonged recovery and increased time to return to play – these are not regular ankle sprains and require a specialized level of careful assessment and management. As mentioned earlier, sports requiring the ankle to be in a fixed boot are at higher risk of this type of injury. While conservative care is adequate for many patients, a significant portion require surgical intervention, although a definitive treatment option has yet to be identified. Regardless of the type of treatment, recovery from this injury can be slow (something that should be effectively communicated with the patient to manage their recovery expectations). In addition to a thorough history and physical examination, appropriate imaging is necessary to effectively diagnose and classify this injury.

Study Strengths / Weaknesses

The authors of both reviews compiled a comprehensive review of the current knowledge regarding mechanism of injury, diagnosis and treatment of ankle syndesmotic injuries. While the background information is broad, the treatment focus falls largely on the surgical options, which may be expected, given that the authors themselves are surgeons. This provides a moderate limitation for those non-surgical practitioners, although the information provided is generally of good clinical value and should help to augment the treatment plans of all clinicians.

Additional References:

  1. van den Bekerom MP, Lamme B, Hogervorst M, Bolhuis HW. Which ankle fractures require syndesmotic stabilization? J Foot Ankle Surg 2007; 46(6): 456–63.
  2. Wright RW, Barile RJ, Surprenant DA, Matava MJ. Ankle syndesmosis sprains in national hockey league players. Am J Sports Med 2004; 32(8): 1941–5.
  3. Fritschy D. An unusual ankle injury in top skiers. Am J Sports Med 1989; 17(2): 282–5 (discussion 5–6).
  4. Dubin JC, Comeau D, McClelland RI et al. Lateral and syndesmotic ankle sprain injuries: a narrative literature review. J Chiropr Med 2011; 10(3): 204-19. Epub 2011 Jul 23.
  5. Kellett JJ. The clinical features of ankle syndesmosis injuries: a general review. Clin J Sport Med 2011; 21(6): 524-9.
  6. Purvis GD. Displaced, unstable ankle fractures: classification, incidence, and management of a consecutive series. Clin Orthop Relat Res 1982; 165: 91-8.
  7. Gerber JP, Williams GN, Scoville CR et al. Persistent disability associated with ankle sprains: a prospective examination of an athletic population. Foot Ankle Int 1998; 19(10): 653–60.
  8. Lin CF, Gross ML, Weinhold P. Ankle syndesmosis injuries: anatomy, biomechanics, mechanism of injury, and clinical guidelines for diagnosis and intervention. J Orthop Sports Phys Ther 2006; 36(6): 372–84.
  9. Williams GN, Jones MH, Amendola A. Syndesmotic ankle sprains in athletes. Am J Sports Med 2007; 35(7): 1197-207. Epub 2007 May 22.
  10. Miller AN, Barei DP, Iaquinto JM et al. Iatrogenic syndesmosis malreduction via clamp and screw placement. J Orthop Trauma 2013; 27(2): 100-6.
  11. Beumer A, Campo MM, Niesing R et al. Screw fixation of the syndesmosis: a cadaver model comparing stainless steel and titanium screws and three and four cortical fixation. Injury 2005; 36(1): 60–4.
  12. Naqvi GA, Cunningham P, Lynch B et al. Fixation of ankle syndesmotic injuries: comparison of tightrope fixation and syndesmotic screw fixation for accuracy of syndesmotic reduction. Am J Sports Med 2012; 40(12): 2828–35.
  13. Gardner MJ, Brodsky A, Briggs SM et al. Fixation of posterior malleolar fractures provides greater syndesmotic stability. Clin Orthop Relat Res 2006; 447: 165-71.
  14. Ramsey PL, Hamilton W. Changes in tibiotalar area of contact caused by lateral talar shift. J Bone Joint Surg Am 1976; 58(3): 356-7.
  15. Tornetta P, Spoo JE, Reynolds FA, Lee C. Overtightening of the ankle syndesmosis: is it really possible? J Bone Joint Surg (Am) 2001; 83(4): 489-92.
  16. Needleman RL, Skrade DA, Stiehl JB. Effect of the syndesmotic screw on ankle motion. Foot Ankle 1989; 10(1): 17-24.
  17. Wukich DK, Kline AJ. The management of ankle fractures in patients with diabetes. J Bone Joint Surg (Am) 2008; 90(7): 1570-8.
  18. Taylor DC, Englehardt DL, Bassett FH. Syndesmosis sprains of the ankle. The influence of heterotopic ossification. Am J Sports Med 1992; 20(2): 146-50.