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					ECONOMIC EVALUATION OF THE USE OF EXOGEN FOR FRESH FRACTURE OF THE TIBIA IN PATIENTS AT RISK OF NON-UNION
MJ Taylor1, Chaplin S1, Trueman P1, Searle R2, Posnett J2
1University

of York, York, United Kingdom, 2Smith & Nephew Wound Management, Hull, United Kingdom

BACKGROUND & OBJECTIVES
Fracture of the tibia is a common event, particularly among young adults. Incidence is reported to be highest among teenage males and is often a result of high-speed trauma. Most closed tibial fractures are treated conservatively or by surgical fixation. Most (80%-90%) will heal successfully but a proportion may experience delayed healing or non-union. Non-union is usually diagnosed at between 3 and 6 months post-fracture The objective of this study was to evaluate the relative cost-effectiveness of ultrasound stimulation (Exogen) as a complement to conservative therapy or surgical fixation in fresh fractures in patients at risk of non-union (non-union is defined at six months). The Exogen Bone Healing System has been shown to accelerate time to healing for conservatively treated tibia and distal radius fractures by 38% (Heckman et al.) and for surgically treated tibial fractures by 40% (Leung).

Figure 1:

The Exogen unit

RESULTS METHODS: MODEL
A cost-effectiveness model estimates expected outcomes and costs in the 12-months following first presentation for a cohort of patients with fresh fracture of the tibia. It evaluates the costeffectiveness of adding Exogen to conservative therapy (casting) or surgery (non-reamed intramedullary nailing) for patients at increased risk of non-union (e.g. smokers or patients with diabetes). The model follows a Markov structure with monthly cycle length. The primary outcome measure is fracture healing. Each month there is a probability that an unhealed fracture will heal, and each month the fracture remains unhealed there is a probability that the bone will become infected. Fractures which remain unhealed at 6 months are defined as non-unions. Monthly probabilities are derived from healing rates reported in the literature (Table 1). Probability of healing. Estimates of the proportion of fracture patients healed within 6 months were derived from a meta-analysis of relevant literature (Busse et al, 2002). These estimates were converted into monthly rates to give estimates of the monthly probability of healing Probability of osteomyelitis. The monthly probability that an unhealed fracture will develop osteomyelitis was derived from analysis of US Medicare claims data. This analysis used the 5% Sample Standard Analytic File for Part B carriers (2003-2004). All new cases of tibia fracture were identified in the year 2003 and those cases were followed forward for 12-months from first diagnosis to identify any occurrence of osteomyelitis. The annual incidence of osteomyelitis was converted to a monthly rate. The model allows the probability of healing to be varied to reflect the prognosis of patients with a higher than average risk of non-union. These groups include current and past smokers and patients with diabetes. The higher risk of non-union is reflected in a percentage reduction in the probability of healing. Probabilities are derived from the literature. The aim of the analysis was to evaluate the cost-effectiveness of Exogen as a complement to conservative therapy or surgery in fresh fractures in patients at risk of non-union. At-risk groups are defined as those whose probability of healing is less than that of the general population. Risk factors include diabetes and smoking and others such as steroid use, obesity, osteoporosis, older patient age and complicated fracture (Lane, et al, 1999). • For a population at risk of non-union whose probability of healing is 80% of the general population (or less), Exogen is cost saving irrespective of whether the patient is treated conservatively or with surgery. This case is illustrated for a population whose probability of healing is at 70% of the general population (Table 2). This is less than the risk facing current and past smokers (63% and 68%) or patients with diabetes (61%). The greater is the risk of non-union, the greater the relative advantage of Exogen. • In the US adding Exogen to conservative treatment reduces cost per patient by $744 and increases the number of fractures healed by 7.6% (Table 2). Adding Exogen reduces the cost of surgical treatment by $130 per patient and increase fractures healed by 6.4%. • In the UK adding Exogen to conservative treatment reduces cost per patient by £1,378 (£2,415 versus £3,793) and using Exogen as an adjunct to surgery reduces the cost of treatment by £884 per patient (£5,578 versus £6,462). The increase in the number of fractures healed is 7.6% and 6.4% respectively.

Table 2:

Population at risk* of non-union (US costs)
Cons Cons + Exogen $4,704 97.8% Surgery + Exogen $14,930 93.7% Increment -$744 +7.6% Cost-saving Increment -$130 +6.4% Cost-saving $5,488 90.2% Surgery

Cost per patient Fractures healed Cost per fracture healed

Table 1:
Fresh fracture Conservative

Model parameters
Healed at six months 79.8% 93.6% 87.2% 92.3% Probability of healing (relative) 63% 68% 61% Infection rate at twelve months 4.95% Source Busse et al., 2002 Heckman et al., 1994 ; Busse et al., 2002 Busse et al., 2002 (non-reamed nail) Lane et al., 1999 Source Castillo et al., 1995 ; Cook et al., 1997 Castillo et al., 1995 ; Cook et al., 1997 Loder et al., 1988 Source US Medicare claims data (2003-2004)

Cost per patient Fractures healed Cost per fracture healed

$15,060 87.3% -

Conservative + Exogen Surgery Surgery + Exogen Risk factor Current smoker Past smoker Diabetes Osteomyelitis Rate of osteomyelitis

* At 70% risk of healing, compared to the general population

CONCLUSIONS
There is evidence that ultrasound reduces healing time and the incidence of complications (Busse et al, 2002). There is also evidence that ultrasound can prevent the delayed healing effect of smoking (Cook et al, 1997) and other risk factors for non-union. Our analysis seeks to quantify the economic value of these clinical benefits. Exogen is most likely to be cost-effective in patients treated conservatively and/or where return to normal function is at a premium. Including lost productivity in the model the addition of Exogen to conservative treatment is cost-saving even for the general population of fresh fractures (cost per patient is reduced by -$2,136). Busse et al (2005) suggest that from an economic standpoint, while reamed intramedullary nailing is the treatment of choice for closed and open grade 1 tibial fractures, treatment with therapeutic ultrasound and casting may also be an economically sound intervention (for appropriate patients). In a population at risk of non-union, ultrasound is both less expensive and leads to better outcomes. Providing the risk is such that the probability of healing is 80% of the general population or less, adjunctive ultrasound appears to be a dominant strategy irrespective of the primary treatment choice. Relevant risk factors include diabetes, osteoporosis, smoking, steroid therapy and complicated fracture.

METHODS: COSTS
The model estimates expected cost per patient in the first year following presentation. Costs include: • Cost of initial diagnosis and treatment – the cost depends on the treatment approach which is being considered (conservative or surgery). The cost of a course of Exogen therapy is included where relevant ($2,800 in the US; £750 in the UK). • Cost of rehabilitation and follow-up care during the healing process. The intensity of follow-up care depends on whether the fracture is healing normally. Costs are higher in the case of delayed or non-union or if the bone is infected. • Cost of osteomyelitis – each month the fracture remains unhealed, the patient is at risk of infection. Treatment costs include a period of inpatient treatment (usually 1 week) followed by 5 weeks of outpatient IV antibiotics. • Cost of non-union surgery, rehabilitation and follow-up. The analysis reflects costs to the payer – Medicare in the US, the National Health Service in the UK. Healthcare resources (such as physician visits, physiotherapy sessions, X-rays) used to treat patients with fracture of the tibia were identified through interviews with expert orthopaedic surgeons in the US and the UK. Medicare payment rates for 2005 were used to assign costs to resource use in the US (including DRG payments for inpatient procedures) Rates are US national average figures wherever possible. For resources not covered by Medicare, typical managed care rates were used. In the UK model costs refer where possible to the year 2004/2005 and were taken from NHS National Reference Costs (2004) or Unit Costs of Health and Social Care (PSSRU, 2005).

REFERENCES
Busse JW, Bhandari M, Kulkarni AV, Tunks E. The effect of low-intensity pulsed ultrasound therapy on time to fracture healing: a meta-analysis. CMAJ 2002; 166: 437-41. Busse JW, Bhandari M, Sprauge S, Johnson-Masotti A, Gafni A. An economic analysis of management strategies for closed and open grade 1 tibial shaft fractures. Acta Orthopaedica. 2005; 76 (5): 705-712. Castillo RC, Bosse MJ, Mackenzie EJ, Patterson BM. Impact of smoking on fracture healing and complications in limb threatening open tibia fractures. Journal of Orthopaedic Trauma. 2005; 19: 151-157. Cook SD, Ryaby JP, McCabe J, et al. Acceleration of tibia and distal radius fracture healing in patients who smoke. Clin Orthop Related Res. 1997; 337: 198-207. Heckman JD, Ryaby JP, McCabe J, Frey JJ, Kilcoyne RF. Acceleration of tibial fracture-healing by non-invasive, low-intensity pulsed ultrasound. J Bone Joint Surg. 1994; 76: 26-34. Lane JM, Peterson M, Ryaby JP, Testa FL. Ultrasound treatment of 2126 fractures. Journal of Orthopaedic Trauma. 1999; 13 (4): 313-315. Leung KS, Lee WS, Tsui HF et al. Complex tibial fracture outcomes following treatment with low-intensity pulsed ultrasound. Ultrasound Med Biol 2004;30(3):389-95. Loder RT. The influence of diabetes mellitus on the healing of closed fractures. Clin Orthop Relat Res. 1988; 232: 210-216. NHS Reference Costs, 2004 (March 2005). Unit Costs of Health and Social Care. 2005. Compiled by Curtis L and Netten A. Personal Social Services Research Unit, University of Kent. (http://www.pssru.ac.uk/uc/uc2005contents.htm).


				
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