[Postoperative radiotherapy in the prevention of heterotopic ossification after endoprosthetic hip joint replacement].
BACKGROUND
Following total hip arthroplasty high-grade heterotopic ossification occurs with a range of 0.5 to 27%. Local postoperative hip irradiation using different dosage and fractionation schedules reduces the incidence in high-risk cases on an average of 8%. The present retrospective study compares results after conventionally fractionated and high-dose radiotherapy.


METHODS
A total of 50 hips (46 patients) from 2 different risk groups had complete follow-up. In group I (40 hips [80.0%]) radiotherapy was indicated after surgical excision of pre-existing high-grade heterotopic ossification, in group II (10 hips [20.0%]) for several risk factors (contralateral heterotopic ossification [n = 7], hypertrophic osteoarthritis [n = 2], spondylosis hyperostotica [n = 1]). In 28/50 cases (56.0%) conventionally fractionated irradiation with total doses ranging from 12.0 to 20.0 Gy was given, in 22/50 hips (44.0%) a high-dose irradiation consisting of 10.0 Gy given in 2 fractions on each of the first 2 postoperative days was applied. After a minimal observation period of 6 months (median: 22 months, range: 6 to 56 months) roentgenograms were analysed using a modified Brooker score.


RESULTS
At follow-up, 2 hips in group I had recurrence of high-grade heterotopic ossification with the stages IIIA and IVB. In 1 case radiotherapy was interrupted after 3 x 2.0 Gy due to sepsis (IIIA), in the other case ectopic bone recurred from bony islands which layed outside the radiation portal (IVB). In group II, 9 patients had stage 0 and 1 patient stage IA. Statistical analysis using the Wilcoxon test showed a highly significant reduction of the amount of pre-existing heterotopic ossification (p < 0.0001) for both fractionation schedules. The comparison of both fractionation groups with the Whitney-Mann-U-test (p = 0.92) showed no statistical significant difference.


CONCLUSIONS
The data about the high therapeutic efficacy of postoperative radiotherapy for prevention of heterotopic ossification were confirmed. Both fractionation schedules led to a sufficient reduction of high-grade heterotopic ossification in the 2 treated risk groups.
Heyd
R
R
Abteilung für Strahlentherapie und Onkologie, J.-W.-Goethe-Universität, Frankfurt a. M.
Strassmann
G
G
Kirchner
J
J
Schopohl
B
B
Böttcher
H D
HD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005069:Evaluation Studies as Topic; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D009999:Ossification, Heterotopic / Q000517:prevention & control* / Q000532:radiotherapy; D011182:Postoperative Care; D011183:Postoperative Complications / Q000517:prevention & control* / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D018714:Radiotherapy, Adjuvant / Q000379:methods / Q000706:statistics & numerical data; D012307:Risk Factors
Postoperative Strahlentherapie zur Prävention heterotoper Ossifikationen nach endoprothetischem Huftgelenkersatz.