The economic burden of osteoarthritis has been increasing in the United States, in part due to an increase in the prevalence of disease, and to increasing costs of treatment (both surgical and non-surgical) [7
]. At the same time, concerns have been raised regarding the costs associated with TJA, due to an increase in the number of procedures performed annually in the U.S., management of post-surgical complications, and increased adoption of newer, more expensive implant technologies [9
]. TJA has been shown to be a cost-effective intervention relative to non-operative treatment [10
] and has been associated with dramatic improvements in quality of life in patients who suffer from debilitating OA of the hip and knee [5
]. Several investigators have shown that when performed in younger patients, TJA can expedite return to work and a more active, productive lifestyle [16
While previous authors have reported that OA is associated with substantial direct and indirect medical expenditures [6
], relatively little is known about the direct medical costs before and after hip and knee arthroplasty in patients with OA. Hawker and colleagues undertook a nested case-control study to examine total and arthritis-attributable costs in the periods before and after TJA among persons with disabling arthritis of the hip and/or knee in Ontario, Canada [18
]. The pre-surgery period was defined as the 1-year period ending 6 weeks prior to TJA; the peri-operative period, as beginning 6 weeks prior to TJA and ending 6 months following TJA; and the post-surgery period, the 1-year period thereafter. The authors found that while mean arthritis-attributable costs during post-surgery decreased from pre-surgery levels by $278 (Canadian dollars, expressed in calendar-year [CY] costs), total healthcare costs increased by $1978. In their analyses of total healthcare costs of patients who underwent TJA for any reason (exclusive of bone cancers) during the 3-year periods immediately before and after surgery, Graver et al. [19
] reported total healthcare costs of $8762, $10,076, and $11,475 in the third, second, and year immediately prior to TJA, respectively; corresponding values for the 3 years immediately following and including the surgery were $37,445, $11,980, and $11,307. While Graver and colleagues did not account for the peri-operative period, which render direct comparisons between their work and ours somewhat difficult, we note that their reported costs in the second year subsequent to TJA are higher than those reported in the year prior to surgery (statistical significance testing not undertaken).
Our results indicate that although utilization of healthcare services decreased for most services during the first year following TJA (exclusive of the peri-operative period) in commercially insured patients with OA of the hip or knee, mean total healthcare costs increased, largely due to increased costs associated with inpatient care. Given that the mean length of stay during the peri-operative period (a 3-month "window" that includes the admission for the initial TJA as well as any subsequent readmission) was only 6.9 days, and that 75% of patients spent no more than 8 days in hospital during this time, our findings are most likely associated with readmissions, rather than stays in hospital for the initial TJA of > 91 days. Hospital readmissions following elective surgical procedures such as TJA have become the focus of great debate and concern among healthcare policymakers [20
], and have led to calls for changes in payment policy to incentivize better coordination of post-discharge care among providers [21
]. Based on our findings, further investigation is warranted into the cause of and strategies to decrease the rate of hospital readmissions following elective TJA.
Despite the interesting findings, our study has several limitations. First, our database consisted of administrative claims for patients enrolled in private insurance plans, who tend on average to be younger than the "typical" cohort who undergoes TJA for OA. Specifically, while patients aged ≥65 years comprise approximately two-thirds of all patients who undergo TJA in the US [23
], they only represented about 17% of patients in our sample. However, we would note that as the indications for TJA have expanded to include younger, more active patients, an increasing number of patients under the age of 65 are undergoing TJA [24
Second, our analysis relied upon administrative claims data, which have been shown to have an imperfect correlation with the clinical record [25
]. It is possible that certain costs may have been over- or under-estimated in both the pre-surgery and follow-up period due to the reliance on administrative claims data. However, we believe that the majority of healthcare costs experienced by patients in the periods immediately before and after TJA are captured within the database. Because the principal purpose of administrative databases such as the one we used in this study are to support reimbursement, we believe that our study yields a fairly comprehensive view of "real-world" utilization and cost of healthcare services in commercially insured patients who undergo TJA.
Third, and somewhat related to the second, we did not attempt to adjust for price inflation by expressing costs in terms of a particular "base year". The principal reason that we did not undertake such an adjustment was that we thought it important to examine (and report) actual amounts paid in "real-word" clinical practice during the periods before and after joint replacement. Were we to have expressed all costs in terms of a "base year", such information would not be available. We also note that identification of an appropriate "price index" to adjust healthcare costs is not straightforward. In most instances where this method is employed, a single index (e.g., the medical-care component of the US consumer price index) is used to adjust values; implicit in use of this single index, however, is the assumption that all goods and services (e.g., pharmacotherapy, physician office visits, hospitalizations, durable medical equipment) experience the same relative change in pricing in a given year. The degree to which that assumption is valid within any given year is unknown. Regardless, to the extent that differences between pretreatment and follow-up costs reflect price inflation, our findings may overestimate differences in healthcare costs between these two periods.
Fourth, although recovery from TJA surgery is variable, it is possible that some patients were not fully recovered from surgery by 90 days [26
], and therefore some of the costs included in the follow-up period may have been related to recovery from TJA. The 90-day window for the peri-operative period chosen because this is considered the 'global period' by most insurers, during which time all costs that are incurred are considered attributable to the index procedure. This limitation is further mitigated by the fact that the major difference in costs between the pre-surgery and follow-up period was related to inpatient care, and it is unlikely that these costs would be considered routine follow-up costs. Since our goal was to evaluate the impact of TJA on healthcare resource utilization and total direct healthcare spending during the first 15 months following surgery from a healthcare system perspective, we did not attempt to separate out costs that were directly attributable to OA or TJA, which may account for the difference in our findings from those of Hawker, et al. [18
] Additionally, we were unable to include indirect or time costs in our analysis, and it is quite possible that the increase in direct medical costs during the follow-up period could be offset by reductions in indirect or time costs associated with earlier return to work and increased productivity, especially given the relatively young average age (57.3 years) of the commercially insured patients who were included in our study. Additionally, we only measured costs during the 15 months immediately following the index TJA procedure, while the benefits of TJA are known to accrue over many years and in some cases decades. Nonetheless, it is anticipated that most patients (especially the younger patients included in this study) recover completely from surgery within 3 months, and therefore, their use of healthcare services and the associated costs would be expected to decrease after that time.