Trends of ankle fracture incidence in the United States are not well documented because these fractures are mostly treated in the outpatient setting and are therefore not consistently captured in large hospital nationwide databases. Our analysis used nationally representative claims databases to estimate an incidence of approximately 14.1 cases per 10,000 patient-years, of which 3.3 required surgical care. A further in-depth analysis of patients that required surgery showed that 37% of patients less than 65 (commercially-insured), and half of the Medicare patients (65 and above), presented with 2 or more fracture types, thus potentially complex cases. Post-operative complications were surprisingly common. Residual pain was very frequent: between 30% and 40% of patients experienced continuous pain more than 3 months after surgery. Joint derangements were also very common, with 25% of commercially-insured and 17% of Medicare patients reporting joint derangements in the post-operative period. Re-fracture and infection affected 11% and 10% of Medicare patients and 4% (each) of commercial patients, all other complications each affecting individually less than 5% of patients. Approximately 10% of patients underwent a secondary procedure (reoperation). Revision procedures, defined as a new ankle surgery or procedure at least 3-weeks after index, affected approximately 6% of patients. Interestingly, the majority of patients with joint derangements or pain did not have a reoperation within 12 months of index, suggesting conservative management of these post-operative conditions.
The increased risk of complications in Medicare patients vs. commercial patients may simply reflect age differences, and the fact that Medicare patients presented with far more comorbidities, as shown in Table 2. Hypertension (commercial: 19.9%, Medicare: 65.1%) and diabetes (commercial: 7.5%, Medicare: 27.2%) are 2 examples, but most rates of comorbidities were significantly greater in the Medicare cohort vs. the commercial cohort. These comorbidities have been shown to affect bone healing rates and increase risk for postoperative complications [27].
Our findings highlight the potential significant societal impact of ankle fracture in the United States: with relative high incidence rates, and complication and residual pain rates, ankle fracture may represent lasting burden on patients and healthcare systems.
Another recent analysis by Scheer et al. estimated the incidence of ankle fracture reported to emergency rooms at 4.2 per 10,000 person-years [1]. We found 14.1 fractures per 10,000 – observed in all care settings (not only emergency departments), of which 3.3 required surgical intervention. The 4.2 value reported by Scheer et al. is lower than our overall estimate of 14.1, possibly because not all fractures go to emergency departments, but higher than our estimate of fractures requiring surgery (3.3), as not all fractures identified in the emergency department may require a surgical fixation. Milstrey et al. evaluated distal fibula fractures in the German Federal Statistical Office, from 2005 to 2019, and reported an estimated 7.4 per 10,000 person/year (+/- 3.2) [28]. In our analysis, malleolus, bimalleolar and trimalleolar fractures (involving therefore the distal fibula) represented approximately 50% of all ankle fractures, thus about half of the 14.1 fractures per 10,000 person/year. Again, our estimate was therefore very close to the 7.4 reported in Germany. Finally, a Danish study from 2018 also reported incidence of overall ankle fracture of 16.8 per 10,000 patient-years [21].
The trends identified in our analysis, with increasing fractures in pediatrics, decreasing in adulthood until age 30 and increasing again, especially in female patients, with increasing age, has also been observed in Denmark by Elsoe et al. [21]. There are many causes for ankle fractures, childhood fractures are mostly linked to sports and high energy activity done in the presence of open growth plates, whereas fractures in older patients may be linked to increased rates of osteoporosis, propensity for falls, increased weight, and polypharmacy, which can lead to poor bone quality [29].
Surgery for the treatment of ankle fracture is particularly important when stability is compromised. Ankle fractures are commonly managed using open reduction and internal fixation. Whereas the long-term outcomes of these procedures are favorable, multiple articles have identified ongoing pain and stiffness in the early post-operative periods, as we have in our study. Specifically, Beckenkamp et al. reported reduced activity in patients with ankle fractures at 6-months post-index, due to ongoing stiffness and pain [30]. Another recent study further confirmed a slow return to pre-fracture activity and limitations in range of motion following surgery, up to 12 months post-index [31]. In our study, nearly a third of the commercial population, and more than a third of the Medicare population, had continuous pain. Our findings are therefore aligned with prior reports of relative slow recovery. An analysis of pain medication utilization was not included in this study and may constitute a limitation of this work.
The healthcare costs of ankle fracture, from the perspective of the payer, are not well documented. Pasic et al. evaluated cost of care from the perspective of the provider, reporting, as expected, higher costs in the inpatient vs. outpatient setting [32]. Our study identified the same trend, with ASCs having lower insurance payments than in- or outpatient sites. Severity of fracture was also a key determinant in index payments, with Gustilo III fractures being 2.5-fold higher payments than closed fractures. The difficulty of treating complex cases also explains why inpatient payments are higher: 85% of all Gustilo III fractures were treated in the inpatient setting, whereas more than 98% of all cases treated in the ASCs or outpatient cases were closed fractures. Incremental insurance payment analyses were conducted in the 12 months post-surgery, to understand the financial impact of post-operative complications. Continued pain, by itself, was associated with incremental payments exceeding $5K. Infection averaged an incremental payment of $27K.
The limitations of this study are mainly those inherent to the use of administrative claims data, which are not collected specifically for research purposes. Administrative data lack information, particularly clinical variables, limiting the inferences that can be made. They are also at risk of having clerical inaccuracies, recording bias secondary to financial incentives, and temporal changes in billing codes [33, 34]. As noted above, an addition limitation includes the fact that prescription patterns in relations to ankle fracture treatments were not analyzed in this study. This study is also limited in that the findings from this commercially-insured US population may not be generalizable to other patients with ankle fracture surgery, particularly those without health insurance or with other types of health insurance, and to patients in other countries. Despite these limitations, this study provides an informative overview of the experience of care among commercially-insured and Medicare-insured US patients with ankle fracture surgery. A key strength of our analysis is the inclusion of cases identified in the outpatient setting, in addition to those reported in the inpatient and emergency departments. Ankle fractures reported only in the outpatient setting are not consistently included in other studies that rely on hospital data, but as observed in our study, represent a large volume of patients [1, 35].
Conclusion
Our study identified an incidence of ankle fracture in the 2016–2019 time period of 14.1 per 10,000 patient-years, of which 3.3 required surgery. Complication rates were high, with approximately 10% of patients requiring a secondary surgery. Residual pain was the main complication and affected nearly a third of all patients. Due to its high incidence, and high complications at 12 months post-surgery, ankle fracture may have a significant societal impact in terms of patient quality of life and return to normal activities, and healthcare burden.
