Treatment of Ankle Fractures in Diabetic Patients

Ian L.D. Le, M.D, FRCSC
University of Calgary
Calgary, AB

In 2007, the Public Health Agency of Canada reported that more than two million Canadians (six percent of the population) were living with a diagnosis of diabetes. This is projected to increase six percent each year such that an estimated 2.8 million Canadians will have diabetes by 20121. It is inevitable that orthopaedic surgeons will need to have a sound approach to the management of ankle fractures in the diabetic population as this patient population expands.

 

Pre and Postoperative Glycemic Control
Patients with diabetes mellitus have an increased complication rate following both operative and non-operative management of ankle fractures. The risk of complication is greater in patients with either long standing diabetes or poor glycemic control as a consequence of the higher prevalence of co-morbidities such as neuropathy or vasculopathy. The hemoglobin A1C level is an excellent marker of long-term glycemic control and may be an indicator of compliance. A reduction of the hemoglobin A1C level by one percent can result in a 25-30% reduction in the rate of complications2. Optimization of glycemic control requires a multidisciplinary approach but is paramount in minimizing potential treatment complications.

Evaluation for Diabetic Neuropathy and Vasculopathy
Pre-existing neuropathy or peripheral vascular disease are associated with higher complications rates in diabetic ankle fractures and must be evaluated upon initial evaluation2.

Up to 40% of patients with a ten-year history of diabetes and 50% of all diabetics over the age of 65 will have some degree of peripheral neuropathy3. Evaluation for neuropathy can be determined using a 5.07 Semmes-Weinstein monofilament test for light touch sensation or a 128Hz tuning fork for vibration sensitivity. Patients with loss of protective sensation have a sevenfold increase in the risk of foot ulceration4.

Compromised macrovascular and microvascular circulation results in relative tissue hypoxia and impaired bone and wound healing. Initial evaluation must include examination of vascular status of the limb. The presence of palpable pedal pulses typically signifies adequate perfusion for healing. The absence of a palpable pedal pulse warrants further investigation. The ankle brachial index (ABI) can be a useful evaluation tool but can be falsely elevated in diabetic patients due to vascular calcification. A transcutaneous oxygen pressure (tcPO2) measurement of 30mmHg is the minimum required for diabetic wound healing5. Doppler toe pressure measurement is another option for assessment with a threshold of 30mmHg indicating adequate limb perfusion.

Delayed Fracture Healing
Several clinical and basic science studies have demonstrated impaired bone healing in patients with diabetes. Loder demonstrated increased observed-to-expected healing time ratio for ankle fractures treated non-operatively (1.42) and operatively (1.86)6. A cohort study of patients with lower extremity fractures showed a diabetic fracture healing time was more than double of that of a matched fracture in a non-diabetic7. The pathogenesis behind the delay in bone and fracture healing is multifactorial involving alteration in inflammatory response, metabolic activity, and impaired perfusion. Consequently, it is recommended that consideration be given to prolonged immobilization and possible delay in weight-bearing in diabetic patients compared to non-diabetic patients.

 

Treatment Strategies
Irrespective of treatment strategy, it is imperative to appreciate the elevated risk of complication associated with even low energy rotation ankle fractures in the diabetic population. Infection, ulceration, malunion, delayed union, nonunion, and the development of Charcot arthropathy are all possible with or without surgical intervention.

Initial assessment must include prompt reduction and splinting of the deformity to minimize further soft tissue insult. Splinting must be well moulded to secure the reduction while maintaining appropriate padding of the malleoli and bony prominences especially in neuropathic patients.

Treatment decisions should be made with a multidisciplinary team approach for medical optimization regardless of whether surgical or non-surgical treatment is decided.

Nondisplaced Ankle Fractures
Nondisplaced ankle fractures can be treated non-operatively in a cast. If non-operative treatment is chosen, prolonged immobilization is advocated for a duration up to two to three times that of non-diabetic patients to minimize the risk for malunion, nonunion, or Charcot arthropathy2. Frequent cast changes and soft tissue inspection is critical to monitor for ulceration or infection which can still occur in the absence of surgery especially in patients with pre-existing neuropathy. One study reported an infection rate of 32% in diabetic ankle fractures and the rate of infection was actually higher in patients treated non-operatively8. This was postulated to be a result of poor compliance and neuropathy. These factors highlight the importance of patient education and compliance in addition to diligent follow-up.

Displaced Ankle Fractures
There exists debate as to the role of non-operative treatment for displaced ankle fractures in diabetic patients. A Canadian study by McCormack9 examined the relative risk of complication in the treatment of displaced malleolar ankle fractures in diabetic compared to matched non-diabetic patients. This case-controlled study reported an overall 42% incidence of complications in diabetic patients compared to no complications in the non-diabetic group. Of the 19 diabetic patients treated surgically, six patients (31%) developed major complications including one malunion, one wound necrosis requiring a flap, and four infections resulting in two cases of deep sepsis, amputation and death. There was a high rate of malunion in the non-operatively treated group but the malunion resulted in few symptoms. It was concluded that older diabetic patients with low functional demands can be treated non-operatively with an acceptance of malunion.

For higher demand diabetic patients, several studies have advocated early operative treatment of displaced ankle fractures. Anatomic stabilization of the fracture minimizes further injury to the soft tissue envelope and reduces the incidence of malunion, nonunion, and the development of Charcot arthropathy. Schon10 reported a 100% incidence of nonunion or malunion in 13 diabetic patients with displaced ankle fractures treated with casting. In a study by Connolly, 40% of displaced diabetic ankle fractures treated in casts developed an infection and 40% developed a Charcot arthropathy11. These authors advocated early surgical stabilization while minimizing further soft tissue insult.

Diabetic patients with ankle fractures should be prioritized for early stabilization to prevent further soft-tissue compromise from displacement that may not be recognized due to altered sensation. Furthermore, diabetic patients benefit from early morning surgery to minimize the time they are NPO and to prevent the catabolic metabolic response that impairs glycemic control.

Several surgical techniques have been described to obtain rigid internal fixation in the setting of a poor soft tissue envelope and osteopenia. Consideration should be given to the implementation of temporary or long-term external fixation to mitigate further soft tissue damage. Locking plate and supplementary k-wires can be employed to combat osteopenia. Techniques to increase stability have been described by Schon10 with the use of multiple tetracortical fibula-to-tibia screws to increase stability of fixation. Jani12 reported on the use of supplemental trans-articular calcaneal-talar-tibial Steinmann pins; and Koval13 described the use of a single fibular intramedullary 1.6 k-wire to increase fibular screw purchase and pull out strength.

Operative fixation of ankle fractures in diabetic patients is not without significant risk of complication. Particular attention needs to be given to preventing infection, malunion, nonunion, and the development of Charcot arthropathy. A meta-analysis of five studies involving 140 diabetic ankle fractures (127 operative; 13 non-operative) demonstrated an overall complication rate of 30% in the operative group compared to 77% in the non-operative group and 7% in the non diabetic group14. The infection rate was 25% in the operative group; 31% in the non-operative group; and 6% in the non diabetic group.

Summary
Routine ankle fractures in the diabetic population can prove both challenging and humbling. Careful preoperative evaluation must include assessment of co-existing neuropathy and vasculopathy. Management of diabetic ankle fractures includes a multidisciplinary team and an understanding of the increased inherent risks of both operative and non-operative management.

References

  1. Report from the National Diabetes Surveillance System: Diabetes in Canada 2009. In: Public Health Agency of Canada, Government of Canada; 2009.
  2. Bibbo C., Patel D.V. Diabetic neuropathy. Foot Ankle Clin 2006;11(4):753-74.
  3. Kumar S., Ashe H.A., Parnell L.N., et al. The prevalence of foot ulceration and its correlates in type 2 diabetic patients: a population-based study. Diabet Med 1994;11(5):480-4.
  4. Wukich D.K., Kline A.J. The management of ankle fractures in patients with diabetes. J Bone Joint Surg Am 2008;90(7):1570-8.
  5. Ballard J.L., Eke C.C., Bunt T.J., Killeen J.D. A prospective evaluation of transcutaneous oxygen measurements in the management of diabetic foot problems. J Vasc Surg 1995;22(4):485-90; discussion 90-2.
  6. Loder R.T. The influence of diabetes mellitus on the healing of closed fractures. Clin Orthop Relat Res 1988(232):210-6.
  7. Cozen L. Does diabetes delay fracture healing? Clin Orthop Relat Res 1972;82:134-40.
  8. Flynn J.M., Rodriguez-del Rio F., Piza P.A. Closed ankle fractures in the diabetic patient. Foot Ankle Int 2000;21(4):311-9.
  9. McCormack R.G., Leith J.M. Ankle fractures in diabetics. Complications of surgical management. J Bone Joint Surg Br 1998;80(4):689-92.
  10. Schon L.C., Marks R.M. The management of neuroarthropathic fracture-dislocations in the diabetic patient. Orthop Clin North Am 1995;26(2):375-92. Connolly J.F., Csencsitz T.A. Limb threatening neuropathic complications from ankle fractures in patients with diabetes. Clin Orthop Relat Res 1998(348):212-9.
  11. Jani M.M., Ricci W.M., Borrelli J., Jr., Barrett S.E., Johnson J.E. A protocol for treatment of unstable ankle fractures using transarticular fixation in patients with diabetes mellitus and loss of protective sensibility. Foot Ankle Int 2003;24(11):838-44.
  12. Koval K.J., Petraco D.M., Kummer F.J., Bharam S. A new technique for complex fibula fracture fixation in the elderly: a clinical and biomechanical evaluation. J Orthop Trauma 1997;11(1):28-33.
  13. Lillmars S.A. MB. Acute trauma to the diabetic foot and ankle. Curr Opin Orthop 2001;12:100-5.

 

 

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