Ankle Injuries and Fractures in the Obese Patient




Ankle fractures are a common orthopedic injury. Certain ankle injuries have been associated with patient demographics such as obesity and smoking. Obese patients are more prone to severe ankle injuries. Naturally, these injuries affect the lower extremity mobility significantly, which itself is a risk factor for obesity. Although obese patients have increased complications across the board, there are specific techniques that can be used to assure the best possible outcome. The perioperative, surgical, and postoperative considerations as well as the outcomes are discussed in this article.


Ankle fractures are a common orthopedic injury, occurring at an annual incidence of 187 fractures per 100,000 people. Certain ankle injuries have been associated with patient demographics such as obesity and smoking. Unlike fractures of the distal radius, hip, and spine, osteoporosis does not seem to be a major risk factor for ankle fractures. A study of more than 3500 patients with ankle fracture revealed their average body mass index (BMI), calculated as the weight in kilograms divided by height in meters squared, to be higher than the general population across all age and gender categories. Naturally, these injuries affect the lower extremity mobility significantly, which itself is a risk factor for obesity. Although overweight adults with disabilities are generally as likely to attempt weight loss as those without disabilities, overweight adults having difficulty walking or using a mobility aid are the exception. In part, this stems from physicians not counseling this population on the importance of physical exercise. Physicians may focus more on diet than exercise in light of limited mobility; however, recent studies suggest that reduced energy expenditure is more causative than increased food intake in the development of obesity.


The implications to one’s health of being overweight are numerous. More than 80% of type 2 diabetes can be attributed to obesity, which may also account for many diabetes-related deaths. The association between diabetes and complications of ankle injuries has been well documented. In addition, obesity has been associated with an increased risk of deep vein thrombosis (DVT) and pulmonary embolus (PE), which are concerns with any lower extremity injury. Finally, obesity syndrome predisposes patients to osteoarthritis by altering cartilage and bone metabolism independent of weight bearing, as evidenced by the involvement of non-weight-bearing joints. The tibiotalar joint is subject to joint reaction forces of 4.5 times the body weight during walking and 10 times the body weight with running. Posttraumatic arthritis in the setting of a biologic predilection for osteoarthritis can be devastating to mobility. Although there may be some protective effect of obesity on bones, with recent evidence showing that leptin resistance in obese individuals may have a favorable effect on bone mass, ankle injuries in the setting of obesity are fraught with complications.


Epidemiology


Data on ankle injuries in the obese population require well-defined parameters of obesity. Technically, overweight refers solely to excess body weight, whereas obesity is excess fat. The 2 commonly used definitions are ideal body weight, based on one’s height and gender, and BMI, which correlates with body fat and relatively unaffected by height. A study of 314 ankle fractures over a 3-year period revealed 39% of cases to have resulted from slips and falls in obese individuals, defined as greater than 120% ideal body weight, compared with a general prevalence of obesity less than 20% at the time of study. The study also demonstrated almost double the prevalence of diabetes in the cohort with ankle injuries than would be expected in the general population. The latest data compiled in 2008 detailed an obesity rate (BMI>30) of 33.8% in the United States among those aged 18 years and older, with 68% being overweight (BMI>25). Another retrospective review of 279 ankle fractures reported a similar increased incidence of concomitant obesity, with 35.5% incidence in patients with BMI greater than 30.


Fracture pattern also seems to be affected by obesity. Although sustaining an open versus closed injury for distal tibial fractures does not seem to be a consequence of body mass, obese individuals were more likely to sustain Orthopaedic Trauma Association type B and C fractures, and less likely to have type A fractures than nonobese patients, at rates of 1% and 11%, respectively. Furthermore, the mean BMI of patients with displaced fractures is significantly higher than those with nondisplaced fractures, with one study demonstrating 83% of displaced fractures in overweight patients. Almost one-third of patients with displacement had a BMI more than 30, whereas only 1 of 24 significantly obese patients had a nondisplaced fracture.




Perioperative considerations


Given the high prevalence of obesity in patients with type 2 diabetes, one must pay particular attention to the risks and benefits of surgery in this specific population. There has been much data to contradict the misconception that increased surgical risks in the diabetic population should influence one toward or against operative management of ankle injuries. A study of 42 closed ankle fractures in diabetic patients with matched controls demonstrated that surgery was not associated with an increased risk of infection and nonsurgical treatment did not increase the risk of malunion, nonunion, or Charcot neuroarthropathy. Another source suggests that closed treatment of unstable ankle fractures is less likely to be successful in obese patients due to sporadic accidental moments of early full weight bearing. In light of conflicting evidence and advances in perioperative patient care, management decisions should be based on standard parameters such as fracture pattern and ability to undergo surgery.


From the surgical booking to the postoperative splinting, once a decision is made between the surgeon and patient to undergo operative management, there are considerations specific to the obese population. Often a preoperative medical assessment or anesthesia evaluation is undertaken, in which a patient is deemed a reasonable candidate for surgery and medically optimized. An important part of optimization for obese patients with concomitant diabetes is appropriate glucose management. Tight blood glucose control has traditionally been advocated, although recent evidence suggests that occasional hypoglycemia associated with lower level of hemoglobin A 1c may actually increase cardiovascular risks. In addition, with obese individuals having a higher incidence of coronary artery disease, they may be on an anticoagulant such as aspirin. The surgeon should assess for such medication use when evaluating the patient and planning surgery. It is the authors’ general practice to hold aspirin intake for 1 week before the date of surgery and restart it on the first postoperative day, although this practice is adjusted in extenuating circumstances such as high cardiac risk or intraoperative bleeding concerning for hematoma formation. If there is a medical contraindication to a period without anticoagulation preoperatively or if bleeding risks or renal function preclude the use of postoperative chemoprophylaxis, a retrievable inferior vena cava filter can be placed for interim protection from PE. One study examined the use of retrievable filters in orthopedic patients, including patients with ankle fractures, and demonstrated no complications of insertion and successful retrieval in 64% of patients. Reasons for leaving filters in place include thrombosis around the filter and filter incorporation into the vessel wall, each occurring at a rate of 8%. Another consideration is comorbidities such as sleep apnea, which may require specialized equipment such as positive airway pressure machines, precluding the use of ambulatory surgery facilities if unequipped or possibly mandating an overnight stay in the hospital for monitoring.


Specialized operating room equipment and additional staff may need to be requested ahead of time. Bookings may need to include extended block time for fracture cases involving morbidly obese patients, because cases can take double the standard operative time, much of which may be spent in positioning. Standard operating room tables support a maximum of 205 kg, although extrawide tables capable of holding up to 455 kg are available. Position is an important consideration, primarily because the obese patient poorly tolerates poses that restrict chest or abdominal motion because they can compromise ventilation. This positioning may affect surgical approach because a surgeon preferring a posterior approach in prone position may want to consider a lateral approach in the better-tolerated lateral decubitus position, with the bulk of the panniculus adiposus displaced off the abdomen. Meticulous attention should be given to padding pressure points during positioning because obese patients are more prone to neural injuries. Peroneal compartment syndrome can result from the lateral decubitus position in the dependent leg. If a tourniquet is used, there are several pearls to application on the large thigh to prevent slipping or a venous tourniquet. An assistant can hold or pull back the soft tissue distally as one applies a tourniquet that ideally overlaps only a couple inches at the edges. When the soft tissue is released, it helps hold the tourniquet in place. Most commonly the authors use a supine position with the normal leg padded and the affected limb elevated on a soft foam pad ( Fig. 1 ).




Fig. 1


Supine positioning of an obese patient using a foam pad to elevate the injured leg for both padding and intraoperative fluoroscopy access.


Choice of anesthetic is also influenced by body mass. Although regional anesthesia is associated with higher rates of block failure and complications, stemming from difficulty locating landmarks and using longer needles, overall failure rates remain low. If general anesthesia is used, rapid induction is paramount in this population with an inherently high risk of aspiration. Similar to the method of anesthesia, no definitive recommendations exist for antibiotic prophylaxis in patients undergoing foot and ankle surgery. The authors think that appropriate preoperative antibiotics should be given, although standard dosing should be adjusted. The current recommendations are to increase preoperative dosing to 2 g of cefazolin for patients weighing more than 80 kg, administer antibiotics 1 hour before incision (2 hours for vancomycin), complete the infusion before tourniquet inflation, and readminister cefazolin every 2 to 5 hours (6–12 hours for vancomycin). Paiement and colleagues showed no difference in infection rates with or without the use of preoperative antibiotics in 122 patients undergoing open reduction internal fixation of closed ankle fractures in a double-blind, randomized, prospective study; however, the study may have been underpowered. A meta-analysis of more than 8000 patients demonstrated single-dose antibiotic prophylaxis to significantly lower the surgical site infections in patients undergoing surgery for several types of closed fractures, with no superior results from multiple doses. For standard closed ankle fractures, the authors’ practice is to use preoperative antibiotics alone for ambulatory surgery patients and to continue parenteral antibiotics for less than 24 hours for patients requiring overnight hospital stay. Lastly, skin preparation should be meticulous because obese patients are more prone to surgical site infections.




Perioperative considerations


Given the high prevalence of obesity in patients with type 2 diabetes, one must pay particular attention to the risks and benefits of surgery in this specific population. There has been much data to contradict the misconception that increased surgical risks in the diabetic population should influence one toward or against operative management of ankle injuries. A study of 42 closed ankle fractures in diabetic patients with matched controls demonstrated that surgery was not associated with an increased risk of infection and nonsurgical treatment did not increase the risk of malunion, nonunion, or Charcot neuroarthropathy. Another source suggests that closed treatment of unstable ankle fractures is less likely to be successful in obese patients due to sporadic accidental moments of early full weight bearing. In light of conflicting evidence and advances in perioperative patient care, management decisions should be based on standard parameters such as fracture pattern and ability to undergo surgery.


From the surgical booking to the postoperative splinting, once a decision is made between the surgeon and patient to undergo operative management, there are considerations specific to the obese population. Often a preoperative medical assessment or anesthesia evaluation is undertaken, in which a patient is deemed a reasonable candidate for surgery and medically optimized. An important part of optimization for obese patients with concomitant diabetes is appropriate glucose management. Tight blood glucose control has traditionally been advocated, although recent evidence suggests that occasional hypoglycemia associated with lower level of hemoglobin A 1c may actually increase cardiovascular risks. In addition, with obese individuals having a higher incidence of coronary artery disease, they may be on an anticoagulant such as aspirin. The surgeon should assess for such medication use when evaluating the patient and planning surgery. It is the authors’ general practice to hold aspirin intake for 1 week before the date of surgery and restart it on the first postoperative day, although this practice is adjusted in extenuating circumstances such as high cardiac risk or intraoperative bleeding concerning for hematoma formation. If there is a medical contraindication to a period without anticoagulation preoperatively or if bleeding risks or renal function preclude the use of postoperative chemoprophylaxis, a retrievable inferior vena cava filter can be placed for interim protection from PE. One study examined the use of retrievable filters in orthopedic patients, including patients with ankle fractures, and demonstrated no complications of insertion and successful retrieval in 64% of patients. Reasons for leaving filters in place include thrombosis around the filter and filter incorporation into the vessel wall, each occurring at a rate of 8%. Another consideration is comorbidities such as sleep apnea, which may require specialized equipment such as positive airway pressure machines, precluding the use of ambulatory surgery facilities if unequipped or possibly mandating an overnight stay in the hospital for monitoring.


Specialized operating room equipment and additional staff may need to be requested ahead of time. Bookings may need to include extended block time for fracture cases involving morbidly obese patients, because cases can take double the standard operative time, much of which may be spent in positioning. Standard operating room tables support a maximum of 205 kg, although extrawide tables capable of holding up to 455 kg are available. Position is an important consideration, primarily because the obese patient poorly tolerates poses that restrict chest or abdominal motion because they can compromise ventilation. This positioning may affect surgical approach because a surgeon preferring a posterior approach in prone position may want to consider a lateral approach in the better-tolerated lateral decubitus position, with the bulk of the panniculus adiposus displaced off the abdomen. Meticulous attention should be given to padding pressure points during positioning because obese patients are more prone to neural injuries. Peroneal compartment syndrome can result from the lateral decubitus position in the dependent leg. If a tourniquet is used, there are several pearls to application on the large thigh to prevent slipping or a venous tourniquet. An assistant can hold or pull back the soft tissue distally as one applies a tourniquet that ideally overlaps only a couple inches at the edges. When the soft tissue is released, it helps hold the tourniquet in place. Most commonly the authors use a supine position with the normal leg padded and the affected limb elevated on a soft foam pad ( Fig. 1 ).




Fig. 1


Supine positioning of an obese patient using a foam pad to elevate the injured leg for both padding and intraoperative fluoroscopy access.


Choice of anesthetic is also influenced by body mass. Although regional anesthesia is associated with higher rates of block failure and complications, stemming from difficulty locating landmarks and using longer needles, overall failure rates remain low. If general anesthesia is used, rapid induction is paramount in this population with an inherently high risk of aspiration. Similar to the method of anesthesia, no definitive recommendations exist for antibiotic prophylaxis in patients undergoing foot and ankle surgery. The authors think that appropriate preoperative antibiotics should be given, although standard dosing should be adjusted. The current recommendations are to increase preoperative dosing to 2 g of cefazolin for patients weighing more than 80 kg, administer antibiotics 1 hour before incision (2 hours for vancomycin), complete the infusion before tourniquet inflation, and readminister cefazolin every 2 to 5 hours (6–12 hours for vancomycin). Paiement and colleagues showed no difference in infection rates with or without the use of preoperative antibiotics in 122 patients undergoing open reduction internal fixation of closed ankle fractures in a double-blind, randomized, prospective study; however, the study may have been underpowered. A meta-analysis of more than 8000 patients demonstrated single-dose antibiotic prophylaxis to significantly lower the surgical site infections in patients undergoing surgery for several types of closed fractures, with no superior results from multiple doses. For standard closed ankle fractures, the authors’ practice is to use preoperative antibiotics alone for ambulatory surgery patients and to continue parenteral antibiotics for less than 24 hours for patients requiring overnight hospital stay. Lastly, skin preparation should be meticulous because obese patients are more prone to surgical site infections.

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Oct 6, 2017 | Posted by in ORTHOPEDIC | Comments Off on Ankle Injuries and Fractures in the Obese Patient
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