Low-dose Preoperative Unshielded Radiation Is Effective in Heterotopic Ossification Prophylaxis and Does Not Affect Porous Fixation in Total Hip Arthroplasty at 2 Years Minimum Follow-up: A Radiographic Study.

Abstract

Heterotopic ossification (HO) is a frequent complication of total hip arthroplasty (THA). HO can cause pain, limitation of range of motion, and instability. Radiation therapy (RT) for HO prophylaxis is well established but may interfere with early porous ingrowth and pullout strength of implants, as suggested by two animal studies. Although shielding of the bone from irradiation may theoretically protect ingrowth, it has been found to reduce RT effectiveness. Despite the popularity of porous implants in THA, the frequency of HO, and use of RT in its prophylaxis, the effect of RT on porous implant fixation in THA has not been previously reported. At our institution, we use unshielded, single-dose, preoperative 700 to 800 centigrays RT for HO prophylaxis in high-risk patients. We hypothesize that this RT protocol is effective and the press-fit technique protects porous implants during early ingrowth; therefore, long-term implant fixation is not compromised. This was a retrospective study aiming to determine fixation of porous THA implants, healing of trochanteric osteotomies, and efficacy of HO prophylaxis with this RT protocol. Thirty-nine patients with follow-up of 24 to 144 months (average 59.7 months) were included. All 26 porous-coated femoral implants (11 revisions and 15 primary) were well fixed. There were 33 porous-coated acetabular implants (18 revisions and 15 primary). Thirty (91%) were well fixed, and three revision implants (9%) demonstrated radiolucent lines in two zones, but patients were clinically asymptomatic. All nine trochanteric osteotomies healed uneventfully. RT provided effective HO prophylaxis in 33 of 39 hips (85%). Single, low-dose, preoperative RT without shielding does not increase aseptic loosening of porous implants manufactured with plasma porous spray or nonunion of extended trochanteric osteotomies. This protocol provides effective HO prophylaxis in high-risk patients undergoing primary and revision THA.