Complication Rates Following Open Reduction
and Internal Fixation of Ankle Fractures
By Nelson F. SooHoo, MD, Lucie Krenek...
complications. Previous studies have attempted to identify the
risk factors that may lead to complications. However, most
...
specific code for revision procedures, we defined reoperation
for open reduction and internal fixation as any readmission
wit...
fractures, and trimalleolar fractures. Second, open fractures
were identified and the presence of an open injury was includ...
demographic information for the patients undergoing open
reduction and internal fixation. The mean age of the patient
popul...
associated with a higher rate of revision within five years after
the primary procedure in comparison with isolated lateral...
The current study clarifies some of the additional risks posed
by complicated diabetes and peripheral vascular disease. The...
3. Koval KJ, Zhou W, Sparks MJ, Cantu RV, Hecht P, Lurie J. Complications
after ankle fracture in elderly patients. Foot A...
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Complication Rates Following Open Reduction and Internal Fixation of Ankle Fractures

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Complication Rates Following Open Reduction and Internal Fixation of Ankle Fractures

  1. 1. Complication Rates Following Open Reduction and Internal Fixation of Ankle Fractures By Nelson F. SooHoo, MD, Lucie Krenek, MD, Michael J. Eagan, MD, Barkha Gurbani, BSN, Clifford Y. Ko, MD, MS, MSHS, and David S. Zingmond, MD, PhD Investigation performed at the Department of Orthopaedic Surgery, University of California at Los Angeles, Los Angeles, California Background: Ankle fractures are among the most common injuries treated by orthopaedic surgeons. The purpose of the present investigation was to examine the risks of complications after open reduction and internal fixation of ankle fractures in a large population-based study. Methods: With use of California’s discharge database, we identified 57,183 patients who had undergone open reduction and internal fixation of a lateral malleolar, bimalleolar, or trimalleolar ankle fracture as inpatients in the years 1995 through 2005. Short-term complications were examined on the basis of the rates of readmission within ninety days after discharge. The intermediate-term rate of reoperation for ankle fusion or arthroplasty was also analyzed. Logistic regression and proportional hazard regression models were used to determine the strength of the relationships between the rates of complications and fracture type, patient demographics and comorbidities, and hospital characteristics. Results: The overall rate of short-term complications was low, including the rates of pulmonary embolism (0.34%), mortality (1.07%), wound infection (1.44%), amputation (0.16%), and revision open reduction and internal fixation (0.82%). The intermediate-term rates of reoperation were also low, with ankle fusion or ankle replacement being performed in 0.96% of the patients who were observed for five years. Open fractures, age, and medical comorbidities were significant predictors of short-term complications. The presence of complicated diabetes was a particularly strong predictor (odds ratio, 2.30; p < 0.001), as was peripheral vascular disease (odds ratio, 1.65; p < 0.001). The intermediate-term rate of reoperation for ankle fusion or replacement was higher in patients with trimalleolar fractures (hazard ratio, 2.07; p < 0.001) and open fractures (hazard ratio, 5.29; p < 0.001). Treatment at a low-volume hospital was not significantly associated with either the aggregate risk of short-term complications or the risk of intermediate-term reoperation. Conclusions: By analyzing a large, diverse patient population, the present study clarifies the risks associated with open reduction and internal fixation of ankle fractures. Open injury, diabetes, and peripheral vascular disease were strong risk factors predicting a complicated short-term postoperative course. Fracture type was a strong predictor of reoperation for ankle fusion or replacement. Hospital volume did not play a significant role in the rates of short-term or intermediate-term complications. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence. B ecause of their high frequency and associated morbidity and mortality, musculoskeletal injuries place an enor- mous economic burden on society. Of the many injuries that occur, ankle fractures are increasingly common, trailing only hip fractures and wrist fractures in frequency among elderly patients1 . Among younger patients, ankle fractures likely rep- resent an even larger proportion of injuries2 . Surgical treat- ment of ankle fractures is frequently required, and appropriate treatment and recognition of potential risk factors are essential for optimizing outcomes. As with any surgical procedure, open reduction and in- ternal fixation of ankle fractures carries an inherent risk of Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated. A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM/DVD (call our subscription department, at 781-449-9780, to order the CD-ROM or DVD). 1042 COPYRIGHT Ó 2009 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED J Bone Joint Surg Am. 2009;91:1042-9 d doi:10.2106/JBJS.H.00653
  2. 2. complications. Previous studies have attempted to identify the risk factors that may lead to complications. However, most studies have relied on case series from single institutions or have focused on specific patient populations such as the elderly or those with diabetes3 . The purpose of the present study was to determine the short and intermediate-term complication rates and to clarify the role of patient and provider-related factors in predicting these rates. The use of a large, population-based dataset overcomes some of the biases inherent in existing case series and allows for the examination of a diverse set of patient and provider characteristics, including age, sex, race/ethnicity, insurance type, comorbidity, hospital type, and hospital volume. We hypothesized that the overall rate of postoperative complications requiring rehospitalization would be relatively low. However, we expected that certain patient populations, such as patients with diabetes, the elderly, and patients with multiple medical comorbidities, would have a significantly higher complication rate. The identification of high-risk groups of patients is useful for evaluating operative indications and for identifying the need for additional preventative mea- sures, such as altering the timing of surgery or postoperative management. Materials and Methods Data Source Data for all hospital discharges in California in the years 1995 through 2005 were obtained from the California Office of Statewide Health Planning and Development through the patient-discharge database. This database is compiled an- nually by the Office of Statewide Health Planning and Devel- opment and includes discharge abstracts from all nonfederal hospitals in California. Each discharge abstract includes codes for as many as twenty inpatient procedures and twenty-four diagnoses per hospitalization. All procedures and diagnoses are coded with use of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). Also in- cluded are patient demographic information (race, Hispanic ethnicity, sex, expected source of payment, age, and zip code of residence), outcomes (in-hospital mortality), and the site of hospitalization (indicated by a unique hospital identifier and postal code4 ). Deaths were identified from the state death file5 . The study protocol was reviewed and approved by the Uni- versity of California at Los Angeles institutional review board. Because of the nature of these secondary data analyses, waiver of patient consent was granted. Inclusion and Exclusion Criteria The sample consisted of adult patients who had undergone open reduction and internal fixation of a lateral malleolar, bi- malleolar, or trimalleolar ankle fracture during the study pe- riod. The specific ICD-9-CM procedure codes that were used to identify the cohort sample are available in the Appendix. Pa- tients with non-California postal codes were excluded as those patients were more likely to have been readmitted outside the state during the observation period. Patients with polytrauma were not excluded from the analysis. Outcomes Studied (Dependent Variables) The outcomes that were identified as dependent variables in- cluded both the short and the intermediate-term readmission rates for specific complications. The short-term outcomes of pulmonary embolism, below-the-knee amputation, readmission because of infection or wound complication, and reoperation for open reduction and internal fixation were reported for the first ninety days following discharge. These complications were identified with use of codes consistent with inpatient read- missions associated with these outcomes. Because there is not a TABLE I Ankle Fractures Requiring Open Reduction and Internal Fixation in California, 1995 through 2005 Number of Fractures (N = 57,183) Lateral Malleolar Fractures Bimalleolar Fractures Trimalleolar Fractures 9109 (16%) 25,639 (45%) 22,435 (39%) TABLE II Demographic Characteristics of Patient Sample (N = 57,183) Age* (yr) 51 (18 to 103) Age group† £50 yr 50% 51 to 75 yr 39% >75 yr 11% Sex† Male 37% Female 63% Race/ethnicity† White 70% Hispanic 18% Black 7% Asian-Pacific Islander 3% Other 3% Insurance type† Private 45% Medicare 26% Medicaid 10% Other 19% Charlson comorbidity score‡ (points) 0.43 ± 0.99 Uncomplicated diabetes† 8.24% Complicated diabetes† 2.13% Peripheral vascular disease† 1.02% Open fractures† 6.89% *The values are given as the mean, with the range in parentheses. †The values are given as the percentage of patients. ‡The values are given as the mean and the standard deviation. 1043 THE JOURNAL OF BONE & JOINT SURGE RY d JBJS.ORG VOLUME 91-A d NUMBER 5 d MAY 2009 COMPLICATION RATES FOLLOWING OPEN REDUCTION AND INTERNAL FIXATION OF ANKLE FRACTU RE S
  3. 3. specific code for revision procedures, we defined reoperation for open reduction and internal fixation as any readmission within ninety days that was associated with a procedure code consistent with open reduction and internal fixation. This definition also requires the assumption that the repeat code is for the same extremity because laterality is not recorded in the database (see Appendix). Mortality also was followed for ninety days postoperatively with use of linkage to the California state death file. The main intermediate-term complication that was an- alyzed was the rate of reoperation for an ankle fusion or ankle replacement during the study period. We excluded patients who underwent fusion or replacement during the first six months after the primary open reduction and internal fixation proce- dure as these early reoperations were more likely to be related to a short-term complication of the initial treatment than to intermediate-term degenerative arthritis. The intermediate-term complication of ankle fusion or replacement is reported for patients at intervals of one year and five years after the primary procedure. The specific ICD-9-CM codes used to identify re- admission for ankle fusion or replacement are available in the Appendix. Predictors (Independent Variables) The predictive variables of interest included patient and pro- vider characteristics, which were used in the regression models as covariates to adjust for their effect. These independent var- iables included patient demographic characteristics such as age, sex, race/ethnicity, and insurance type. Comorbid disease was assessed with use of the Charlson score as well as the separate inclusion of the presence of either complicated or uncompli- cated diabetes and peripheral vascular disease as covariates. Complicated diabetes was identified with use of the Charlson system of coding and included patients with end-organ dam- age6,7 . The Charlson comorbidity index assesses seventeen co- morbid conditions and has been validated for use in administrative database studies6,7 . Race and ethnicity are reported by the hos- pital on the basis of patient self-reports, and insurance type is also reported by hospitals for each patient. Patients were arbi- trarily categorized into three age groups: fifty years of age or less, fifty-one to seventy-five years of age, and more than seventy-five years of age. Hospital surgical volume was also included as a covariate. Surgical volume was defined as the average annual number of open reduction and internal fixation procedures involving the ankle performed during the study period. Hospitals were cat- egorized as low volume if they were in the lowest fortieth per- centile in terms of annual volume among hospitals where open reduction and internal fixation of ankle fractures was per- formed. Intermediate-volume hospitals were defined as those in the next fortieth percentile, and high-volume hospitals were defined as those in the remaining highest twentieth percentile. Additional hospital characteristics included rural location and teaching status, each of which is reported by hospitals in the Office of Statewide Health Planning and Development database. Injury severity was included as a covariate with use of two methods. First, fractures were classified according to severity into three categories: lateral malleolar fractures, bimalleolar TABLE III Ninety-Day Rates of Short-Term Complications Following Open Reduction and Internal Fixation for Ankle Fracture According to Fracture Type, Patient Comorbidities, and Hospital Characteristics Complication Rate N Pulmonary Embolism Wound Infection Revision Open Reduction and Internal Fixation Below-the-Knee Amputation Mortality Overall rate 57,183 0.34% 1.44% 0.82% 0.16% 1.07% Fracture type Lateral malleolar fracture 9109 0.27% 1.45% 0.83% 0.11% 0.77% Bimalleolar fracture 25,639 0.34% 1.70% 0.82% 0.21% 1.31% Trimalleolar fracture 22,435 0.36% 1.15% 0.81% 0.13% 0.91% Open fracture 3940 0.56% 4.57% 1.73% 0.69% 1.75% Patient comorbidities Uncomplicated diabetes 4710 0.38% 3.55% 1.40% 0.51% 2.53% Complicated diabetes 1219 0.33% 7.71% 4.43% 3.86% 4.27% Peripheral vascular disease 582 1.03% 6.87% 2.23% 3.44% 4.47% Age >75 yr 6233 0.51% 2.37% 1.09% 0.35% 4.91% Hospital characteristics Low volume 4639 0.22% 1.81% 0.78% 0.15% 1.40% Intermediate volume 22,155 0.34% 1.31% 0.85% 0.19% 1.11% High volume 30,389 0.35% 1.48% 0.80% 0.14% 0.98% Teaching hospital 9320 0.35% 2.14% 0.89% 0.18% 0.88% Rural location 4336 0.44% 1.34% 0.81% 0.07% 1.11% 1044 THE JOURNAL OF BONE & JOINT SURGE RY d JBJS.ORG VOLUME 91-A d NUMBER 5 d MAY 2009 COMPLICATION RATES FOLLOWING OPEN REDUCTION AND INTERNAL FIXATION OF ANKLE FRACTU RE S
  4. 4. fractures, and trimalleolar fractures. Second, open fractures were identified and the presence of an open injury was included as a covariate. The specific ICD-9-CM coding algorithms used to identify fracture type and the presence of an open injury are included in the Appendix. Statistical Analysis The patient sample is described with descriptive statistics. Re- sults that are reported with use of descriptive statistics include the demographic characteristics of the patients and the annual rates of open reduction and internal fixation. Raw rates of complications are also reported for patients according to frac- ture type and also separately for patients with the comorbidities of diabetes and peripheral vascular disease. We used multivariable regression techniques to identify the independent effect of the predictor patient and provider- related variables on the risk of complications. For the short- term complications (mortality, infection, pulmonary embolism, amputation, and readmission for open reduction and internal fixation), for which ninety-day follow-up was essentially com- plete for all patients in the cohort, we used multivariable logistic regression to analyze the aggregate risk of any of these outcomes occurring. We estimated the impact of fracture type and the presence of an open injury on the aggregate risk of these out- comes while accounting for patient demographic characteris- tics, comorbidities, and provider characteristics. The strength of the association between the aggregate risk of short-term com- plications and each of the provider and patient-related co- variates is expressed as an odds ratio for a complication with respect to a reference group. Ninety-five percent confidence intervals and p values are reported as well. For intermediate-term complications, defining a specific follow-up time would have excluded a large number of patients from analysis; therefore, we used a time-to-event analysis with Cox proportional hazard regression models. We performed separate analyses of the independent impact of the patient and provider characteristics on intermediate-term outcomes— reoperation for ankle fusion or replacement—with use of the same covariates as were used for the logistic regression models. The strength of the association between the risk of intermediate- term reoperation and each of the provider and patient charac- teristics is expressed as an adjusted hazard ratio (where the ‘‘hazard’’ is defined as the probability of the outcome occurring in a unit period of time) for complications relative to a reference group for each variable. Ninety-five percent confidence inter- vals and p values are also reported. Source of Funding No external funding was received for the present study. Results Patient Sample Atotal of 57,183 patients underwent open reduction and internal fixation of an ankle fracture during the eleven-year study period. Table I shows the proportion of cases according to fracture type. Lateral malleolar fractures accounted for 16% of the patient sample, bimalleolar fractures accounted for 45%, and trimalleolar fractures accounted for 39%. Table II lists TABLE IV Odds Ratios of Short-Term Complications and Hazard Ratios of Intermediate-Term Complications According to Fracture Severity, Patient Comorbidity, and Hospital Characteristics Reference Group Short-Term Complication Odds Ratio in Comparison with Reference Group* Intermediate-Term Complication Hazard Ratio in Comparison with Reference Group* Fracture severity Bimalleolar fracture Lateral malleolar fracture 1.00 (0.89 to 1.14, p = 0.96) 1.36 (0.99 to 1.87, p = 0.06) Trimalleolar fracture Lateral malleolar fracture 0.81 (0.70 to 0.94, p = 0.005) 2.07 (1.50 to 2.84, p < 0.001) Open fracture Closed fracture 4.00 (3.60 to 4.44, p < 0.001) 5.29 (4.17 to 6.72, p < 0.001) Patient comorbidity Uncomplicated diabetes Without diabetes 1.32 (1.17 to 1.49, p < 0.001) 1.37 (0.94 to 1.98, p = 0.10) Complicated diabetes Without diabetes 2.30 (1.90 to 2.79, p < 0.001) 3.36 (2.00 to 5.65, p < 0.001) Peripheral vascular disease Without peripheral vascular disease 1.66 (1.30 to 2.11, p < 0.001) 0.96 (0.35 to 2.61, p = 0.93) Age >75 yr Age £50 yr 1.73 (1.49 to 2.01, p < 0.001) 0.18 (0.10 to 0.30, p < 0.001) Hospital characteristics Low-volume hospital High-volume hospital 1.15 (0.95 to 1.41, p = 0.16) 0.82 (0.51 to 1.31, p = 0.41) Intermediate-volume hospital High-volume hospital 0.98 (0.86 to 1.12, p = 0.80) 1.09 (0.84 to 1.40, p = 0.52) Teaching hospital Non-teaching hospital 1.46 (1.21 to 1.75, p < 0.001) 1.01 (0.73 to 1.41, p = 0.93) Rural hospital Non-rural hospital 1.27 (1.04 to 1.55, p = 0.02) 0.88 (0.51 to 1.51, p = 0.64) *The 95% confidence interval and the p value are shown in parentheses. Significant findings (p < 0.05) are shown in bold. 1045 THE JOURNAL OF BONE & JOINT SURGE RY d JBJS.ORG VOLUME 91-A d NUMBER 5 d MAY 2009 COMPLICATION RATES FOLLOWING OPEN REDUCTION AND INTERNAL FIXATION OF ANKLE FRACTU RE S
  5. 5. demographic information for the patients undergoing open reduction and internal fixation. The mean age of the patient population was fifty-one years, and 63% of the patients were female. A total of 7% of the fractures were associated with an open injury. The prevalence of uncomplicated diabetes was 8%, whereas the prevalence of diabetes complicated by end- organ damage was 2%. One percent of the patients had asso- ciated peripheral vascular disease. Short-Term Complication Rates The overall rate of pulmonary embolism requiring readmission within ninety days after discharge was low (0.34%). Similarly, low rates of readmission within ninety days were seen for in- fection (1.44%), reoperation for open reduction and internal fixation (0.82%), below-the-knee amputation (0.16%), and mortality (1.07%). The rate of short-term complications ac- cording to fracture severity is shown in Table III. The rates of all five of the short-term complications that were analyzed were higher in association with open fractures than they were in association with closed injuries, and the difference in the ag- gregate rate was significant (p < 0.001) (Table IV). In contrast, patients who had trimalleolar and bimalleolar fractures did not have a significant increase in the aggregate rate of short-term complications in comparison with patients who had an iso- lated lateral malleolar fracture (Table IV). The rate of short-term complications was higher in pa- tients with the specific comorbidities of advanced age, com- plicated diabetes, and peripheral vascular disease (Table III). The rates of amputation (3.86%) and infection (7.71%) were notably high in patients with complicated diabetes. Peripheral vascular disease also was associated with increased rates of amputation (3.44%) and infection (6.87%). Compared with patients fifty years of age or younger, patients over the age of seventy-five years were noted to have a higher rate of mortality (4.91%) and wound infection (2.37%). The expected baseline ninety-day mortality rate for the population of patients not undergoing open reduction and internal fixation of an ankle fracture is not reported in the current analysis. Several patient- related factors demonstrated a significant association with the aggregate risk of short-term complications, including un- complicated diabetes (odds ratio, 1.32; p < 0.001), complicated diabetes (odds ratio, 2.30; p < 0.001), peripheral vascular dis- ease (odds ratio, 1.66; p < 0.001), and age of more than seventy-five years (odds ratio, 1.73; p < 0.001) (Table IV). Most of the hospital-related factors that were examined had less consistent associations with short-term outcomes as compared with patient comorbidities. High-volume and intermediate-volume hospitals were not significantly different from low-volume hospitals in terms of the aggregate rate of short-term complications (Table IV). Rural location and teach- ing status were associated with a higher aggregate risk for short- term complications (Table IV). Intermediate-Term Complication Rates The intermediate-term rate of reoperation for ankle replace- ment or ankle fusion was low, with a combined rate of 0.37% at one year and 0.96% at five years after the primary procedure. In addition, this rate may be overstated given that laterality is not specifically recorded in the database. Increasing fracture severity was the strongest predictor, with trimalleolar fractures being TABLE V One-Year and Five-Year Rates of Intermediate-Term Reoperation for End-Stage Arthritis Following Open Reduction and Internal Fixation for Ankle Fractures According to Fracture Type, Patient Comorbidities, and Hospital Characteristics One Year Five Years Sample Size (N) Rate of Reoperation for End-Stage Arthritis Sample Size (N) Rate of Reoperation for End-Stage Arthritis Overall rate 52,125 0.37% 30,728 0.96% Fracture type Lateral malleolar fracture 8331 0.25% 4975 0.64% Bimalleolar fracture 23,291 0.35% 13,393 0.85% Trimalleolar fracture 20,503 0.43% 12,360 1.21% Open fracture 3472 1.35% 1913 3.82% Patient comorbidities Uncomplicated diabetes 4093 0.88% 2011 1.69% Complicated diabetes 1056 3.31% 514 4.86% Peripheral vascular disease 517 0.58% 235 1.70% Age >75 yr 6233 0.38% 3120 0.71% Hospital characteristics Low volume 4315 0.37% 2730 0.99% Intermediate volume 20,193 0.38% 12,108 0.95% High volume 27,617 0.35% 15,890 0.96% Teaching hospital 8530 0.41% 5143 1.03% Rural location 3961 0.48% 2405 1.12% 1046 THE JOURNAL OF BONE & JOINT SURGE RY d JBJS.ORG VOLUME 91-A d NUMBER 5 d MAY 2009 COMPLICATION RATES FOLLOWING OPEN REDUCTION AND INTERNAL FIXATION OF ANKLE FRACTU RE S
  6. 6. associated with a higher rate of revision within five years after the primary procedure in comparison with isolated lateral malleolar fractures (1.21% compared with 0.64%) (Table V). This increased risk was reflected in the elevated hazard ratio of 2.07 (95% confidence interval, 1.50 to 2.84; p < 0.001) for patients with trimalleolar fractures in comparison with those with isolated lateral malleolar fractures (Table IV). Patients with open fractures also had a higher risk of fusion or replacement for the treatment of ankle arthritis, with a significant hazard ratio of 5.29 (95% confidence interval, 4.17 to 6.72; p < 0.001) in comparison with patients with closed fractures (Table IV). Complicated diabetes was also a significant predictor of reoperation for the treatment of end-stage ankle arthritis. The rate of reoperation at five years was 4.86%, with a hazard ratio of 3.36 (95% confidence interval, 2.00 to 5.65; p < 0.001) for patients with complicated diabetes in comparison with those without diabetes (Table IV). Elderly patients had a decreased rate of conversion to fusion or replacement, probably secondary to decreased activity demands or a higher likelihood of death prior to the need for reoperation for the treatment of chronic ankle degeneration. The volume of ankle open reduction and internal fixation procedures, teaching status, and rural location of the hospitals at which the primary open reduction and internal fixation procedure was performed had no significant association with intermediate-term rates of reoperation for arthrodesis or ar- throplasty of the ankle (Table IV). Discussion The present study analyzed a large, diverse population with regard to several important short and intermediate-term complications following open reduction and internal fixation of lateral malleolar, bimalleolar, and trimalleolar ankle fractures. The overall rate of complications was low, but complicated diabetes and peripheral vascular disease were found to be as- sociated with particularly high risks for severe complications, including infection and amputation. The results of the present study also indicate that provider-related factors such as hospital volume are relatively less consistent and less important as sig- nificant predictors of complication rates. These findings help to clarify the risks associated with the operative treatment of ankle fractures in a diverse patient sample. The rates of short-term complications that were observed in the present study were low and were consistent with those reported in previous studies3,8 . Koval et al. examined the Medi- care database and identified low rates of complications in elderly patients two years after surgery3 . The current study expands these findings to a broader sample of patients from all adult age categories and extends the observation period to examine intermediate-term rates of reoperation for the treat- ment of end-stage arthritis. Among the short-term complications that were studied, the rate of thromboembolic disease is of particular interest as there remains substantial uncertainty with regard to the opti- mum protocols for thromboprophylaxis following surgery in- volving the foot and ankle. The rate of pulmonary embolism resulting in readmission within ninety days after the primary open reduction and internal fixation procedure was 0.34% in the current study. The rate of pulmonary embolism following the treatment of ankle fractures has not been well documented in the literature, although cases of fatal pulmonary embolism have been reported9-11 . There have been attempts to analyze the rate of deep venous thrombosis. Specifically, one randomized placebo-controlled study showed no differences between 272 patients who were given either Dalteparin or placebo following ankle surgery12 . In addition, while the rate of distal asymp- tomatic deep venous thrombosis was high (>20%), the rates of proximal deep venous thrombosis were only 3% for the Dal- teparin group and 4% for the placebo group. Despite the high rate of deep venous thrombosis, most appeared to be asymp- tomatic and prophylaxis may not be warranted to prevent asymptomatic thromboses. Importantly, the California data- base does not specify the number of patients who received prophylaxis. However, the overall rate of pulmonary embolism was low given that one recent study indicated that as many as 80% of providers do not employ routine thromboprophylaxis following foot and ankle surgery13 . It is likely that higher-risk patients receive prophylaxis more frequently, and this may explain the low rates among those with comorbidities or ad- vanced age in the current study. A logical alternative to routine prophylaxis in all patients may be for older patients and those with medical comorbidities to receive consideration for throm- boprophylaxis and closer attention to symptoms suggesting thromboembolic disease postoperatively. The present study also highlights the importance of the specific patient comorbidities of diabetes and peripheral vas- cular disease in predicting the risks of the short-term compli- cations of mortality, infection, reoperation, and amputation. The rate of infection in patients with complicated diabetes was particularly notable (7.71%, compared with a 1.44% rate in the overall study population). Similarly, there was a striking in- crease in the rate of amputation among patients with compli- cated diabetes (3.86%) or peripheral vascular disease (3.44%) relative to the overall patient population (0.16%). Rates of amputation after open reduction and internal fixation of the ankle are rarely reported for the general population, probably because these rates are very low in the small series of patients that are typically available for study. Previous smaller series of patients with diabetes have demonstrated high rates of below- the-knee amputations; in one study, there were two amputations among twenty-one patients with an isolated ankle fracture14 . Diabetes has been known to be a risk factor for many post- operative complications. The reasons for this are multifactorial. Peripheral neuropathy may play a role in that these patients have impaired proprioception and nociception, predisposing them to additional injury and loss of fracture reduction. Studies also have revealed that bone healing is impaired as well, which places patients with diabetes at additional risk for malun- ions and the need for subsequent surgery15-17 . For these rea- sons, it has been suggested that patients with diabetes require longer immobilization and should receive longer postop- erative bracing compared with patients without diabetes18 . 1047 THE JOURNAL OF BONE & JOINT SURGE RY d JBJS.ORG VOLUME 91-A d NUMBER 5 d MAY 2009 COMPLICATION RATES FOLLOWING OPEN REDUCTION AND INTERNAL FIXATION OF ANKLE FRACTU RE S
  7. 7. The current study clarifies some of the additional risks posed by complicated diabetes and peripheral vascular disease. The magnitude of these risks supports recommendations for careful patient selection and heightened precautions in the perioper- ative period. The intermediate-term rate of conversion to ankle fusion or ankle replacement is also an area of uncertainty. The present study documented a low rate, with 0.96% of the patients who were available for observation at five years having undergone reoperation for arthrodesis or arthroplasty. The significant predictors for requiring fusion or replacement were the pres- ence of an associated open injury and the severityof the fracture. These findings confirm the findings of previous studies from single institutions that have demonstrated better intermediate- term prognoses for patients with isolated lateral or medial malleolar fractures than for those with more extensive bi- malleolar or trimalleolar injuries19-21 . The increased need for salvage procedures in patients with trimalleolar fractures is likely a result of the greater severity of the fracture, with more disruption of the articular surface and an increased risk for end-stage osteoarthritis. The results of the present study can be used when counseling patients on the intermediate-term risk of end-stage ankle arthritis requiring reoperation on the basis of injury severity. These findings are particularly rele- vant given that a large proportion of ankle arthritis cases are posttraumatic22 . The present study also demonstrated that hospital-related factors, including volume, rural location, and teaching status, were relatively less important as significant predictors of the short or intermediate-term complications that were analyzed. Provider volume has been shown to have an association with complication rates for a variety of other procedures, including total hip and total knee replacement4,23-26 . In the current study, low-volume hospitals were not significantly different from high-volume hospitals with regard to the aggregate rate of short- term complications. Thus, the operative treatment of ankle fractures may not be subject to the same level of variability in complication rates among providers as is seen with total joint replacement. This is an important reminder that provider volume may not be a significant consideration for all types of orthopaedic procedures. One of the major weaknesses of the present study is the limited types of data available in administrative databases. No report on functional outcomes is available, which would be helpful for clarifying long-term prognosis. In addition, proce- dures that are performed for the treatment of ankle fracture on an outpatient basis are not captured in the databases that we analyzed. The rates of outpatient procedures may have in- creased given the relatively stable number of inpatient proce- dures performed in the setting of a growing population in California. Similarly, the rates of complications not requiring readmission, such as superficial infections and minor pulmo- nary emboli, are not available for analysis. The reoperation rate also may be understated as only those requiring readmission are included in our analysis. Minor procedures that are rou- tinely performed in an outpatient setting, such as hardware removal, are not included in our study. Similarly, data on the patients seeking follow-up care outside of California are not captured. Some potentially important comorbidities, such as smoking and alcohol consumption, also were not available for analysis. We also were unable to analyze the effect of specific variations in care, such as the use of prophylactic antibiotics or antithrombotics. The present study evaluated population-based rates of complications with associated risk factors following the surgical treatment of ankle fractures in a diverse population of 57,183 patients. The rates of short-term complications were relatively low, with the notable exception of the rates among patients with complicated diabetes or peripheral vascular disease. This find- ing highlights the need for heightened caution in the periop- erative management of these patients. The intermediate-term rate of reoperation for end-stage arthritis was related to fracture severity but remained low even among patients with tri- malleolar and open fractures. Provider factors such as hospital volume did not play a consistent predictive role for the short or intermediate-term complications that were analyzed. These findings are useful for outlining the risks of operative treatment of ankle fractures, the role of patient comorbidities, and the comparatively small impact of hospital characteristics on com- plication rates. Appendix The coding algorithm used in the present study to identify inclusion criteria, exclusion criteria, diagnosis, and com- plications is available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on ‘‘Supplementary Material’’) and on our quarterly CD/DVD (call our subscription department, at 781-449-9780, to order the CD or DVD). n Nelson F. SooHoo, MD Lucie Krenek, MD Michael J. Eagan, MD Barkha Gurbani, BSN Clifford Y. Ko, MD, MS, MSHS David S. Zingmond, MD, PhD Department of Orthopaedic Surgery, University of California at Los Angeles, 10945 Le Conte Avenue PVUB #3355, Los Angeles, CA 90095. E-mail address for N.F. SooHoo: nsoohoo@mednet.ucla.edu References 1. Sporer SM, Weinstein JN, Koval KJ. 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