Treatment/Prognosis Flashcards
What is the role of Sg in the Tx of HO?
Clinically relevant HO should be surgically removed. The risk of subsequent recurrence may be lower if the ectopic bone is removed after it has reached maturity. At the time of Sg, prophylaxis against future HO should be taken.
Other than RT, are there any other effective methods for prophylaxis against HO?
For prophylaxis against HO, indomethacin and ibuprofen (prostaglandin synthesis inhibitors) have been shown to decrease the incidence of HO compared to placebo. (Fransen M et al., Cochrane Database Syst Rev 2004)
What should be the RT dose and fractionation for prophylaxis against HO?
There have been multiple randomized trials and retrospective series on the RT dose and fractionation for prophylaxis against HO:
Sylvester J et al. (IJROBP 1988) compared 20 Gy in 10 fx vs. 10 Gy in 5 fx, and Pellegrini V et al. (J Bone Joint Surg Am 1992) looked at 8 Gy × 1 fx vs. 10 Gy in 5 fx. There were no differences b/t those doses and fractionation schemes. More recent studies looked at using lower doses.
Healy W et al. (J Bone Joint Surg Am 1995) compared 7 Gy × 1 fx against 5.5 Gy and concluded that 5.5 Gy is not a sufficient dose.
Padgett D et al. (J Arthroplasty 2003) looked at 5 Gy × 2 fx or 10 Gy in 5 fx. There was a trend toward increased HO of any grade in the 5-Gy group.
Milakovic et al. (Radiotherapy and Oncology 2015) performed a meta-analysis and found that there seems to be no relationship b/t BED greater or less than 2,500 cGy and the efficacy of HO prophylaxis. They also report that multiple fx seem to be more effective than single-fx radiotherapy in preventing HO progression.
What is the efficacy of preop RT for HO prophylaxis c/w PORT? What are the advantages and disadvantages of preop RT vs. PORT?
In 1 study, preop RT at 7–8 Gy × 1 fx gave the same rates of prophylaxis as the same dose given PORT. (Gregoritch S et al., IJROBP 1994) Preop RT decreases pt discomfort associated with transport and positioning for RT but is often not feasible d/t scheduling issues. A meta-analysis by Milakovic E et al. (Radiotherapy and Oncology 2015) looked at 12 randomized trials comparing preop RT vs. PORT. They concluded that there was no difference b/t postop or preop radiotherapy in preventing HO progression
How soon should PORT be given after Sg for prophylaxis against HO?
PORT prophylaxis against HO should be given no later than 4 days and ideally within 3 days of Sg. (Seegenschmiedt M et al., IJROBP 2001)
What is the timeframe for giving preop RT for HO prophylaxis?
The randomized trial comparing preop RT vs. PORT for HO prophylaxis using 7–8 Gy × 1 fx (Gregoritch S et al., IJROBP 1994) gave preop RT within 4 hrs of Sg. Other nonrandomized series have suggested that preop RT can be given as early as 8 hrs preop without a significant decrease in efficacy. (Seegenschmiedt M et al., IJROBP 2001)
Are there randomized trials comparing RT against indomethacin in HO prophylaxis?
Yes. Burd T et al. (J Bone Joint Surg Am 2001) randomized 166 pts to rcv either indomethacin or RT postoperatively for HO prophylaxis. Grades 3–4 HO occurred in 14% of the indomethacin group as c/w 7% of the RT group, but the results were not SS (p = 0.22).
A meta-analysis by Pakos E et al. (IJROBP 2004) looked at 7 randomized trials comparing RT vs. NSAIDs. They concluded that RT postop >6 Gy tended to be more effective than NSAIDs in preventing Brooker grade 3 or 4 HO, but the absolute difference was only 1.2%.
What is the typical RT field for HO prophylaxis?
The RT fields for HO prophylaxis typically includes the usual area at risk for HO. When treating the hip for HO prophylaxis, the cranial border is usually 3 cm above the acetabulum and inferiorly includes two-thirds of the shaft of the implant. Field size is usually around 14 × 14 cm. The prosthesis may be blocked from RT if a cementless fixation is used, but observational data suggest that this blocking strategy is associated with higher rates of subsequent HO.
