Getting Up the Down Escalator
to tame the TJR queue will require a doubling of efforts

Dennis Jeanes
Special to the Canadian Orthopaedic Association

On any given day during 2004-05 in Ontario, 26,725 patients were waiting for total hip or knee arthroplasty, and with each passing month, the number of new decisions for surgery exceeded the actual number of surgeries by more than 20%, adding another 500 patients to the waiting list.

It's not very often that a reverse trend can be captured quite so crisply, but then that's the kind of picture Dr. Robert B. Bourne, chief of orthopaedics at the London Health Sciences Centre, is able to extrapolate from the Ontario Joint Replacement Registry (OJRR) and the Canadian Joint Replacement Registry. These findings got their start in 2005, when Alan Hudson, head of Ontario's wait-times strategy, asked Bourne for an educated guess of what the demand might be for total joint replacement (TJR) in the next and ensuing 10 to 12 years. "We were able to say we would have to increase by 9000 surgeries the first year and then gradually increase the numbers from thereon," says Bourne. "While this data is based on Ontario data, these recommendations might be applied to any province across Canada".

Certainly there will be a continued increase in demand, not only from real growth in the usual 65-74 demographic cohort but also from other factors. For example, epidemiologist Dr. Elizabeth Badley "has predicted that 55% of her large population study in Ontario will show some knee arthritis," says Bourne, "of which 7% will be severe enough to consider total knee replacement. About 2% receive surgery now." This forecast has led Badley and her colleagues to suggest a gap of unmet needs in the 5% range, which is likely feeding into the rise in demand for TJR.

Bourne also notes with interest that the major increase in the general trends regarding demand for TJR - especially total knee replacement (TKR) - are at the tails of the bell curve, where among men in the 45-54 cohort demand went up by 164% from 1994-2002. Among women, the demand increased by 207.6%. And there are similarly high numbers among the 85-plus cohort, where demand for TKR during the same time period increased by 136.5% for men and 116% for women. Although less striking, demand for total hip replacement also increased during the same eight-year span among younger patients (m: 62.5%; w: 70.3%) and older patients (m: 82.6%; w: 90.2%). "People are more accepting of the surgery," says Bourne. "I think in the past, they felt they were too young, so they either put up with it, or perhaps they had an osteotomy or something that didn't work quite as well. So what we're seeing now is that the fastest growing cohort for both hips and knees is the 45-54 age group." Trends for 2005 and 2006 are quite similar.

Given all the complexities that must be factored into the equation to answer this straightforward, yet far-reaching, question about demand for TJR, Bourne felt he should be "a little more scientific about it." So he approached biostatistician Dr. Greg Zaric at the Richard Ivey School of Business, showed him some of the data available in the OJRR and then asked his help in predicting the number of joint replacements that might have to be done in the next ten years. Zaric responded with enthusiasm and assigned one of his graduate students, Lauren Cipriano, to the project. Indeed, she based her MA thesis on the work and has just published the results, "Predicting joint replacement waiting times," in Health Care Management Science.

"To perform this analysis, we took into account the predicted growth in the patient group 55 years and older plus the increased willingness of patients with hip and knee arthritis to undergo THR or TKR surgery, as noted in utilization rates over the past decade, then applied queuing theory to this data". Estimating that demand would grow annually by 8.7%, they developed incremental scenarios based on patients receiving surgery within the optimal six-month benchmark over the next ten years. Queuing theory helped reveal that to reduce wait times within a decade, the annual supply of surgery would have to increase by at least 12%: "If you increase surgeries by 12% annually from 2004-05 levels, then in 2015 about 70% of patients in Ontario would have their surgery within six months. We then looked at all sorts of other scenarios. If you want to get to 100% within six months, you would have to increase surgeries by 14% a year, but that would take up to 2015 to do that. If you want to do it quicker, you'd have to increase by 22% per year to get 100% of patients done by 2010."

"Prior to 2005, the annual increase in THR and TKR surgeries in Ontario was 6.7%, well below the predicted 8.7% annual growth noted in this study. It is no wonder that a patient backlog developed over the preceding ten years. Dealing with this backlog plus increasing future patient demand will stress our health care system. If the findings of this study are correct, there will be no turning back on increasing the supply of THR/TKR surgeries, as the number of THRs and TKRs performed in Ontario will have to increase from the current 31,488 to 50,000 five years from now and 70,000 in 2014-15! The implications of this increased demand on resources and manpower are obvious."

Cipriano's paper also identifies regional disparities in patient demand among Ontario's Local Health Integrated Networks that call into doubt the effectiveness of allocating surgeries purely on a population basis. Different hospitals may have different factors (human resources, ORs, etc.) affecting their growth in surgical capacity, and thus coordinated and targeted increases may achieve better results. However, Cipriano warns that if there is a large supply shortage combined with a large unmet need, then a very large supply increase may be the only means to generate reductions in wait times: "We have shown that the benefits of special targeted funding to reduce waiting times can be lost if the long-term rates of supply increase are not greater than the rate of patients joining the waiting list. We are not aware of others who have modeled a short-term burst in capacity as a potential solution to waiting time problems."

Calling the study "long overdue and something we should be applying to every discipline," Bourne reflects on the clinical realities behind the numbers: "We increased surgeries by roughly a third in the first year of our efforts to reduce wait times, but then the hospitals started running out of capacity. Hospitals didn't have enough ORs, nurses or anesthetists. Now we don't have enough surgeons. I think we did the easy part first. It shows that you have to plan for growth. It's clear that the whole enterprise is growing, which means we have to do things more efficiently."

Perhaps the last word for now on patient demand should go to Lauren Cipriano, who in her final thoughts for the journal article noted the inherent limits of modeling: "A wide range of demand predictions were tested here, but the actual demand for surgery over the next ten years remains unknown. There are currently no systems for tracking the underlying need for TJR surgery in the province or the number of new decisions to join a waiting list, nor is the actual number of patients currently waiting for surgery in Ontario known. This study identifies the critical importance of knowing demand and thus identifies a critical shortfall of the current Ontario total joint replacement system that must be addressed to ensure that neither a shortage of supply nor an excess of waste, through excess allocations, occur in the future."