Even if an intervention results in a positive clinical outcome in patients with knee osteoarthritis, another important factor to consider is whether that treatment’s benefits justify its costs. Increasingly, cost effectiveness studies are comparing OA interventions to determine value.
By Daniel Pinto, PT, PhD
Nearly half the older population complains of joint pain.1,2 From a public health perspective, hip and knee osteoarthritis (OA) are considered the most serious disorders of the muscles, bones, and joints.1,3 Hip and knee OA have a substantial societal impact, with the economic burden equaling roughly 1% to 2.5% of the gross national product in many Western nations.4 This impact is projected to grow due to increased prevalence of the condition stemming from aging societies and higher rates of obesity.5
Zhang et al found more than 50 forms of treatment for individuals with hip or knee OA, but relatively little is known about the cost effectiveness of these interventions. For patients with hip or knee OA, conservative nonpharmacological nonsurgical treatments for which cost effectiveness data have been reported include exercise, acupuncture, bracing and foot orthoses, multimodal self care, advice about weight loss, and rehabilitation.6,7
In clinical guidelines, these treatments are suggested as either primary or adjunctive interventions before more invasive treatments such as joint replacement surgery.8,9 In addition, many patients prefer conservative interventions because they perceive them as lower risk than invasive treatments.10 A number of studies in the literature have attempted to identify whether conservative interventions for the treatment of hip or knee OA provide good value for money.
What is good value?
The scarcity of healthcare resources has facilitated greater research in cost effectiveness. An important goal is identifying good outcomes that can be attained efficiently.11 For simplicity, this discussion of value will assume absolute certainty of the results following a comparison of two treatments. All economic evaluations are comparisons between two treatment alternatives, and the mean difference in costs and effects are the metrics from which all other cost effectiveness statistics are derived.
Figure 1 shows the cost effectiveness plane (CE plane), a graphic that displays the point representing the net difference in health outcome and cost for a treatment (treatment A) relative to an alternative (treatment B). If treatment A improves health outcomes (does more) and costs less relative to treatment B, treatment A is a good value. This intervention falls in the southeast quadrant of the CE plane and is represented by the dot in Figure 1. Treatments are not good value if they cost more and reduce health (do less) relative to another treatment; these treatments fall in the northwest quadrant of the CE plane.
If treatments fall into the northeast or southwest quadrants of the CE plane a further consideration needs to be made before making a value judgment. Interventions that improve health (do more) relative to a treatment alternative at a higher cost (costs more) may be considered cost effective if the additional cost is acceptable. To make this judgment one must identify what society is willing to pay for the additional benefit.
In the US $50,000 has been used as a threshold price that society is willing to pay for an additional year of life at full health (a quality-adjusted life year [QALY]). Therefore, treatments associated with cost effectiveness estimates that are lower than $50,000 per quality-adjusted life year would be considered good value whereas those associated with estimates higher than this amount would not.
The southwest quadrant is the most controversial. Some authors suggest a treatment that decreases health should not be considered for implementation;12 an argument could be made, however, for the consideration of such a treatment if it frees enough resources to fund other health improvements. The amount that society is willing to accept for a loss of health is roughly double what it is willing to pay for an improvement in health.13
As mentioned earlier, this discussion of value and cost effectiveness includes the central caveat of having absolute certainty of results. This is seldom, if ever, true. When interpreting cost effectiveness study results, important considerations particular to methodology include the selection of treatment alternatives, the health outcomes reported (disease-specific outcomes versus generic health outcomes), the specific cost items captured when measuring cost, and the handling of uncertainty. Additional resources for further discussion of these economic study components can be found in works by Drummond et al12,15 and Glick et al.16
In the management of hip and knee OA, exercise is recommended for all patients “irrespective of age, comorbidity, pain severity and disability,”8 according to the National Institute for Health and Clinical Excellence (NICE) in the UK. The NICE recommends exercise be aimed at specific joints rather than delivered as a general fitness program.8 Exercise therapy for management of OA often includes an emphasis on muscle strengthening, muscle stretching, or neuromuscular control.17,18 Exercise appears to be more beneficial in individuals with knee OA than those with hip OA, though research has also demonstrated small improvements in pain in individuals with hip OA.9
Multiple studies have assessed the cost effectiveness of various forms of exercise including facility-based exercise,19 class-based exercise,20,21 home exercise,22-24 and water-based exercise.25,26 Additionally, Segal et al considered the cost effectiveness of exercise in a priority-setting model.7 Thomas et al,24 Barton et al,22 and Patrick et al 26 found their exercise programs, which involved, home-based exercise, lifestyle changes, and aquatic exercise, respectively,
resulted in higher costs relative to treatment alternatives. All studies assessing the cost effectiveness of exercise found, on average, an incremental improvement in the health outcome studied relative to the comparison treatment.
The study by Patrick et al was the only study to suggest that exercise was not good value because it produced more benefit at a higher cost than society is typically willing to pay.26 In the remaining studies, exercise was found to both improve health outcomes and reduce costs relative to the comparison treatment.19-21,23,25
These studies assessed different forms of exercise and used different cost items, making direct comparison difficult. Many of the studies referred to here were considered in a recent systematic review6 that found the results by McCarthy et al to be the most compelling with regard to cost effectiveness when taking study bias in the estimate of cost and effect into account. McCarthy et al studied the addition of a physical therapist-supervised class-based exercise program to a comprehensive home exercise program.20,21 The exercise program produced greater health outcomes at a lower cost than the control program, making it a cost saving intervention.
Lifestyle modifications for hip and knee OA include patient education, self-care programs, and obesity management. Patient education is designed to encourage positive changes in behaviors, increase competence with respect to living with a chronic disease, and improve quality of life.27 Education programs for managing OA may include instruction on self-help principles, emotion management, exercise instruction, the disease process, communication skills, pain management, relaxation techniques, and healthy eating. In general, these programs have produced relatively small improvements in health outcomes.8,9 For individuals who are overweight, weight loss is recommended as a core treatment for managing hip and knee OA.8,28 However, there is stronger evidence for its benefit in individuals with knee OA29 than in those with hip OA. Lifestyle modifications are consistently recommended in international guidelines.9
Several studies have investigated the cost effectiveness of lifestyle modifications for OA, with mixed results. Lord et al31 assessed the cost effectiveness of a four-session patient education program for patients with knee OA and found a small improvement in outcome and higher costs for the treatment compared with conventional management. The program was not good value for money according to usual standards.6,30 Patel et al assessed a six-session self-management program in addition to the provision of an education booklet for patients with hip OA, knee OA, or both. They found the self management program resulted in improvement in the physical and mental health components of the Short Form (SF)-36 Health Survey compared with the booklet alone; the intervention, however, also resulted in a nonsignificant decrease in quality-adjusted life years.31 Barton et al26 found that quadriceps strengthening exercises resulted in improved health outcomes and higher costs compared with provision of an advice leaflet. The additional cost per quality-adjusted life year was within the range considered good value. However, the confidence interval for this estimate was wide and the resulting probability that this intervention was good value at the maximum value that society is willing to pay for an additional quality-adjusted life year was low.22
Although these interventions are not necessarily cost effective, the UK’s NICE guidelines present them as an integral part of informed decision making.8
Acupuncture is a traditional Chinese medical therapy that uses hair-thin metal needles to puncture the skin along meridians in the body or in tender points to relieve pain and promote wellbeing.32 Although less well-controlled studies have shown clinically meaningful improvement, the results from placebo controlled studies have not been clinically meaningful.33 In studies by Reinhold et al and Whitehurst et al cost-effectiveness analyses of acupuncture for the treatment of individuals with knee OA reported an improvement in health outcomes at an additional cost.34,35 Reinhold et al compared acupuncture with “delayed acupuncture,” i.e., acupuncture that was promised to the nonintervention group at the end of the study.34 In the study by Whitehurst et al acupuncture was administered in addition to advice and exercise and was compared with two alternatives, advice and exercise alone and advice and exercise plus sham treatment.35
Many biomechanical strategies such as bracing and foot orthoses attempt to reduce the high knee external adduction moment associated with medial tibiofemoral compartment compression and severity of medial knee OA.36 Thin-soled flexible shoes, lateral wedge shoe inserts, and valgus knee braces can all decrease loading on the medial compartment of the knee36 and have been associated with improvements in patient outcome.5 Although no trial has specifically assessed the cost effectiveness of foot orthoses or bracing, the cost effectiveness of bracing for knee OA was considered in a priority setting model conducted by Segal et al.7 The authors found that bracing for knee OA improved health outcomes and increased healthcare costs. The cost for an additional quality-adjusted life year was under the threshold price society is willing to pay for such a benefit and therefore was considered cost effective.
Rehabilitation programs for treatment of OA are typically multimodal programs that include any combination of strengthening and stretching exercises, range of motion exercises, and functional training.37-39 Rehabilitation programs have been studied in individualized or group formats and cost effectiveness analyses of such programs have produced conflicting results. For example, a behavioral-graded activity program aimed at gradually increasing participants’ activity levels via short-term and long-term goal setting and the integration of new activities into daily life resulted in poorer health outcomes and lower costs compared with conventional physical therapy.39,40 These results are not good value because the treatment did not free up enough resources to be considered cost effective.6
Three other rehabilitation studies evaluated the ESCAPE (Enabling Self-Management and Coping of Arthritic Knee Pain Through Exercise)-knee pain rehabilitation program, which included discussions with patients about topics such as self-management and coping strategies as well as an individualized, progressive exercise routine.38,41,42 The ESCAPE-knee pain group showed an increase in the number of participants achieving significant improvements in WOMAC (Western Ontario McMasters Universities Arthritis Index) function scores at six-month follow-up compared with usual medical care, but the program was not cost effective when quality-adjusted life years were the measure of benefit.42
A follow-up study evaluated a shortened ESCAPE-knee pain rehabilitation program to make it more clinically applicable and added a booster session at four months to promote long-term adherence to exercise.38 In the original program participants were expected to adhere to the self-management program and exercises. Relative to usual physiotherapy, the modified ESCAPE-knee pain program was cost saving (cost perspective unspecified). This cost saving estimate, based on mean differences in cost and effect, was not associated with statistically significant improvements in the QALY or WOMAC subscale scores. (Although statistical significance is important when judging clinical effectiveness, this is not necessarily the case for claims of cost effectiveness; here the discussion of value has been broadened to include the concept of cost effectiveness findings based on mean differences.)
In the 30-month follow up to the original ESCAPE-knee pain study, Hurley et al reported continued health improvements when using the WOMAC scale, but, in contrast to the findings in the short-term follow up, the ESCAPE-knee pain program resulted in lower costs relative to usual medical care.41 The authors did not report health outcomes in quality-adjusted life years in the follow-up report.
A call to action
Of all of the cost effectiveness analyses that reported findings considered good value for money, Pinto et al had the most confidence in the analysis by McCarthy et al.20 This was based on low risks of methodological bias for the clinical trial and the economic analysis.6 McCarthy et al found that a class-based exercise program supervised by a physical therapist increased positive health outcomes and decreased costs when added to a comprehensive home exercise program.20 This supports several guideline suggestions by NICE,8 OARSI (Osteoarthritis Research Society International),9 and OASIS (Osteoarthritis Service Integration System)43 that recommend patients be given joint-specific exercise individualized to their needs8 along with professional assistance in the instruction of exercise9,43 (OARSI guidelines specify a physical therapist).9
Unfortunately, despite guideline emphasis on nonpharmacological treatment as the cornerstone of care, current clinical management of OA is often limited to the use of analgesics, anti-inflammatory medications, and cautious waiting.44 A recent review found that up to 29% of general practitioners believe rest is the optimal management approach in patients with chronic knee pain, and nearly half the time general practitioners do not advise their patients with OA to exercise.45 Patients are rarely provided specific exercise instruction by general practitioners, and many individuals with OA do not know how to proceed.46
Combined, these findings suggest there is an increased need to advocate exercise as a treatment for patients with hip and knee OA. Importantly, where one is not able to appropriately guide an exercise program, a referral to another clinician who can provide such care is warranted. This recommendation is supported by findings of both clinical effectiveness and cost effectiveness.
Daniel Pinto, PT, PhD, is an assistant professor in the Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, at Northwestern University in Chicago.
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