All patients received standard perioperative antibiotics (three doses of cefazolin or two doses of vancomycin) and pharmacologic thromboembolic prophylaxis with low molecular weight heparin or warfarin depending on surgeon preference. The patients received the standard postoperative rehabilitation protocol for THA without any modification. All patients were mobilized on day one following surgery and were allowed to bear weight as tolerated. The patients received physical therapy for walking assistance with a walker and stair climbing. After discharge the patients were allowed activity as tolerated and advised to follow precautions against dislocation which included limitation of hip flexion to less than 90°, avoidance of adduction, and avoidance of excessive external rotation.
The postoperative followup was at 3 and 6 months, 1 year, and then annually for all patients with AP pelvis and cross table lateral radiographs obtained at each followup. Clinical exam at each visit consisted of inspection of the wound, gait, range of motion, and Trendelenburg tests. We obtained Harris hip scores (HHS) on all patients.
Three observers (SBJ, PSR, and DGL) independently reviewed the pre- and postoperative radiographs independently by (SBJ, PSR, and DGL) for all the patients, including the ones who died. While all available radiographs were reviewed, final followup radiographs were compared with the initial postoperative and 2- and 3-year followup radiographs for detailed assessment of loosening. The observers used the criteria laid out by Yoder et al.  to assess acetabular loosening with any lucency entirely around the acetabular component greater than or equal to 2 mm or a position change greater than 4 mm involving the center of rotation of the hip as measured by the cup height and cup horizontal distance or greater than 4° change in the angulation of the cup.
We performed survivorship analysis using the Kaplan-Meier log curve analysis for overall patient survival. The primary endpoints for our study were death or revision due to any reason, and the secondary endpoint was radiological evidence of loosening of acetabular component. We performed statistical calculations using Microsoft® Excel version 2003 SP3 (Microsoft®, Redmond, WA, USA) using descriptive statistics and paired t-tests as indicated.
No patients, alive or deceased, required a revision for any reason. Oncologic survival of the cohort at 10 years was 50% as estimated by the Kaplan-Meier analysis (Fig. 4).
The mean preoperative HHS was 36 (range, 19-63), while the mean 5-year HHS was 80 (range, 60-100) (p < 0.001). The hips were fully functional at the time of latest followup for the patients who were lost to followup or who had died.
We observed no implant migration or progressive lucent lines in any of the hips at final followup. Two hips had stable nonprogressive lucencies in Zone 1, and one hip had a Zone 2 stable nonprogressive radiolucency, while one hip had evidence of lucency in both Zones 1 and 2, which was stable and nonprogressive at final followup. Three additional hips had Zone 1 lucencies which were not present at final followup.
One patient developed an intraoperative proximal femur fracture treated with cerclage fixation. Early postoperative complications included one urinary tract infection, one case of lower lobe pneumonia, and one case of cellulitis involving the distal operative extremity; all were successfully managed with antibiotic therapy. Three patients developed postoperative blood loss anemia that required transfusion. One patient developed multiple subsegmental pulmonary emboli without hemodynamic compromise or untoward outcomes, despite prophylactic anticoagulation without any evidence of deep vein thrombosis. No patient developed prosthetic joint infection. There were no late postoperative complications at final followup.
THA following pelvic radiation presents challenges in terms of durability of fixation (Table 1). Most studies have shown high rates of fixation failure with conventional implants [4, 10, 15]. The reported acetabular loosening rates of 44% to 52% at 2 to 6 years [10, 15] highlighted the difficulty in obtaining durable acetabular fixation in this patient population. There has been a need for secure long-term fixation in this cohort, with 50% of the patients alive at the 10-year mark (Fig. 4). Our study aimed to determine if the 100% short-term implant survival experienced by our group in our initial report  with the use of porous tantalum acetabular components persisted at the 5- to 10-year followup interval and assessed function and radiographic loosening.
Our study had several limitations. First, the sample size of 29 patients (34 hips) was modest, and we were able to include only 17 patients (22 hips) for the survivorship analysis at a minimum 5-year followup because of patient demise. However, the number of patients having large doses of radiation to the pelvis is not large, and will likely decrease with contemporary radiation therapy. Second, since many patients lived a great distance from our center, followup was often by correspondence with local physicians, and some patients who were clinically doing well failed to provide radiographs at their final followup. For this reason, mean radiographic followup was 73 months, while mean clinical followup was 78 months for surviving patients. Third, we had no direct comparison group of alternative implants for this relatively rare condition. Finally, since we had no reoperations or autopsy retrievals, we were unable to confirm true osseointegration of the implants.
We observed no clinical or radiographic failures in the 17 surviving patients undergoing 22 arthroplasties following pelvic radiation at a minimum 5-year followup (Table 2). Kim et al.  demonstrated no loosening rates at a minimum 2-year followup; however, their study included only males with prostate cancer. Our study involved a diverse population (Table 2), thus improving the generalizability of the study. The uniform survivorship of the implants in this study was in contrast to most prior reports [4, 10, 15]. This may have been secondary to the combination of the bone ingrowth and biomechanical properties of porous tantalum we used. This implant provided a high coefficient of friction and allowed the use of multiple screws in an array across the dome, posterior column, and base of the ischium in a 180° arc, providing rigid initial fixation. The technique of cementing polyethylene liners into acetabular shells was first described for use during revision of well-fixed acetabular components, which has had a reliable mid-term survival [11, 22]. The multihole tantalum revision shell design provided for the use of a cemented liner combined with multiple screws placed into the shell. The cement also provided a locking effect to the screw heads and unified the polyethylene liner with the porous tantalum shell, preventing backside wear. This strategy was designed to maximize initial fixation and prevent motion during the early postoperative period, allowing bony ingrowth to occur from the scattered islands of viable bone remaining in the periacetabular region. Supplemental fixation with an antiprotrusion cup-cage construct, tantalum augments, or both were used to achieve rigid fixation for six cases in which the surgeon judged the bony stock to be particularly poor. We presumed that the extensive fixation (multiple screws and augments as necessary) and high coefficient of friction of tantalum allowed for successful bony ingrowth of these implants. Apart from the early complications, none of the patients developed late complications that threatened implant survival.
Malignancies and their treatment with chemotherapy, radiation, or surgery can lead to morbidity and disability. This cohort is far more debilitated from their condition compared to patients presenting with primary degenerative joint disease for THA. Patients in this study had a widely variable delay (mean, 90 months; median, 56 months; range, 1-800 months) between therapeutic radiation therapy and THA for disabling symptoms with a mean preoperative HHS of 36 (range, 9-63). These data were consistent with prior studies (Table 1). Kim et al.  reported a mean preoperative HHS of 47 (range, 8-81), and Jacobs et al.  reported a mean preoperative HHS of 41 (range, 31-55). Massin et al.  did not use the HHS system to assess function, which prevented direct comparison; however, they concluded that this cohort suffered rapid functional decline at varying periods after radiation, and was very different from patients with primary osteoarthritis. We observed an improvement in function, as measured by HHS, at a 5-year followup for all cases. The final HHS scores were also not as high as seen after primary THA at similar followup, highlighting the challenge presented by this patient population. However, the function compare favorably with other reports in the literature (Table 1).
Tantalum trabecular metal acetabular components provided durable reconstruction in patients undergoing THA following prior pelvic radiation. There were no clinical or radiographic failures at the minimum 5-year followup, and we observed substantial improvements in functional scores. These findings build on those previously reported with this technique to establish the durability of this reconstruction .
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