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                                                                                    Figure 1:                 The Exogen unit
    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).

     METHODS: MODEL                                                                                             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
     A cost-effectiveness model estimates expected outcomes and costs in the 12-months following                factors include diabetes and smoking and others such as steroid use, obesity, osteoporosis, older
     first presentation for a cohort of patients with fresh fracture of the tibia. It evaluates the cost-       patient age and complicated fracture (Lane, et al, 1999).
     effectiveness 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         • For a population at risk of non-union whose probability of healing is 80% of the general
     diabetes).                                                                                                 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
     The model follows a Markov structure with monthly cycle length. The primary outcome measure                is at 70% of the general population (Table 2). This is less than the risk facing current and past
     is fracture healing. Each month there is a probability that an unhealed fracture will heal, and            smokers (63% and 68%) or patients with diabetes (61%). The greater is the risk of non-union, the
     each month the fracture remains unhealed there is a probability that the bone will become                  greater the relative advantage of Exogen.
     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).                         • 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
     Probability of healing. Estimates of the proportion of fracture patients healed within 6 months            surgical treatment by $130 per patient and increase fractures healed by 6.4%.
     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                  • 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
     Probability of osteomyelitis. The monthly probability that an unhealed fracture will develop               per patient (£5,578 versus £6,462). The increase in the number of fractures healed is 7.6% and
     osteomyelitis was derived from analysis of US Medicare claims data. This analysis used the 5%              6.4% respectively.
     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.
                                                                                                              Table 2:          Population at risk* of non-union (US costs)
     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                                                                Cons                 Cons + Exogen                   Increment
     patients with diabetes. The higher risk of non-union is reflected in a percentage reduction in the       Cost per patient                             $5,488                       $4,704                       -$744
     probability of healing. Probabilities are derived from the literature.
                                                                                                              Fractures healed                              90.2%                       97.8%                       +7.6%
                                                                                                              Cost per fracture healed                          -                           -                    Cost-saving

                                                                                                                                                           Surgery              Surgery + Exogen                  Increment
   Table 1:         Model parameters                                                                          Cost per patient                             $15,060                     $14,930                       -$130
   Fresh fracture                  Healed at six months           Source                                      Fractures healed                              87.3%                       93.7%                       +6.4%
    Conservative                           79.8%                  Busse et al., 2002
                                                                                                              Cost per fracture healed                          -                           -                    Cost-saving
    Conservative + Exogen                  93.6%                  Heckman et al., 1994 ; Busse et al., 2002
                                                                                                              * At 70% risk of healing, compared to the general population
    Surgery                                87.2%                  Busse et al., 2002 (non-reamed nail)
    Surgery + Exogen                       92.3%                  Lane et al., 1999
   Risk factor                Probability of healing (relative)   Source
    Current smoker                          63%                   Castillo et al., 1995 ; Cook et al., 1997
    Past smoker                             68%                   Castillo et al., 1995 ; Cook et al., 1997     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
    Diabetes                                61%                   Loder et al., 1988                            smoking (Cook et al, 1997) and other risk factors for non-union. Our analysis seeks to quantify the
   Osteomyelitis             Infection rate at twelve months      Source                                        economic value of these clinical benefits.

    Rate of osteomyelitis                  4.95%                  US Medicare claims data (2003-2004)           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
     METHODS: COSTS                                                                                             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).
     The model estimates expected cost per patient in the first year following presentation. Costs
                                                                                                                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
     • Cost of initial diagnosis and treatment – the cost depends on the treatment approach which is
                                                                                                                primary treatment choice. Relevant risk factors include diabetes, osteoporosis, smoking, steroid
     being considered (conservative or surgery). The cost of a course of Exogen therapy is included
                                                                                                                therapy and complicated fracture.
     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           REFERENCES
     weeks of outpatient IV antibiotics.
     • Cost of non-union surgery, rehabilitation and follow-up.                                                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.
     The analysis reflects costs to the payer – Medicare in the US, the National Health Service in the         An economic analysis of management strategies for closed and open grade 1 tibial shaft fractures. Acta Orthopaedica.
     UK. Healthcare resources (such as physician visits, physiotherapy sessions, X-rays) used to treat         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
     patients with fracture of the tibia were identified through interviews with expert orthopaedic            SD, Ryaby JP, McCabe J, et al. Acceleration of tibia and distal radius fracture healing in patients who smoke. Clin
     surgeons in the US and the UK.                                                                            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,
     Medicare payment rates for 2005 were used to assign costs to resource use in the US (including            Peterson M, Ryaby JP, Testa FL. Ultrasound treatment of 2126 fractures. Journal of Orthopaedic Trauma. 1999; 13 (4):
     DRG payments for inpatient procedures) Rates are US national average figures wherever                     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
     possible. For resources not covered by Medicare, typical managed care rates were used. In the             healing of closed fractures. Clin Orthop Relat Res. 1988; 232: 210-216. NHS Reference Costs, 2004 (March 2005).
     UK model costs refer where possible to the year 2004/2005 and were taken from NHS National                Unit Costs of Health and Social Care. 2005. Compiled by Curtis L and Netten A. Personal Social Services Research
     Reference Costs (2004) or Unit Costs of Health and Social Care (PSSRU, 2005).                             Unit, University of Kent. (

To top