Results
Histopathological evaluation was consistent with a chondrosarcoma and the tumor was incompletely excised as expected (Figure 2). The chondrosarcoma was determined to be a grade II based on exhibited moderate pleomorphism with no undifferentiated areas and 1 mitotic figure observed per 10 high magnification fields.23–25
As previously mentioned, the dog was scheduled to begin radiation therapy twenty-seven days after the iliectomy. At that time, the dog had an intermittent non-weight bearing lameness of the right pelvic limb when running but ambulated well otherwise. Physical examination was unremarkable other than mild pain elicited with flexion of the right coxofemoral joint. Diagnostics included a urinalysis and urine culture via cystocentesis, thoracic and pelvic radiographs. CT scan and radiation therapy had to be rescheduled due to technical issues. Urinalysis was unremarkable and the culture recovered very light growth of Escherichia coli and Enterococcus hirae . Thoracic radiographs revealed no evidence of metastatic pulmonary disease. Pelvic radiographs demonstrated an overlapping fracture of the left pubic bone as well as corresponding fracture of the left ischial arch (Figure 3). There was evidence of callus formation over the fracture sites. Other significant findings included mild bilateral coxofemoral and stifle degenerative joint disease. The fractures did not appear to be causing the dog marked discomfort; but carprofen (1.7 mg/kg, q12hrs, orally) was prescribed.
Fifty-three days after iliectomy, the dog re-presented for initiation of radiation therapy (nineteen 3 Gy fractions). Physical examination was unremarkable. The following diagnostics were performed: urinalysis via cystocentesis and culture, pelvic radiographs, and CT. Urinalysis was unremarkable, and no bacteria were cultured. Pelvic radiographs revealed progressive coxofemoral degenerative joint disease and healed pelvic fractures. The fracture of the left ischium had a callus around the fracture gap. The margins of the remaining right ilium were irregular and consistent with healing. The mesh overlaying the right hemipelvis region was in place. The dog was premedicated with hydromorphone (0.05 mg/kg, IM), induced with thiopental (10 mg/kg, IV), and maintained with isoflurane. CT was acquired with 5mm slices from the cranial aspect of L5 through the entire pelvis (Figure 4). After completion of full-course radiation therapy the plan for re-evaluation was for physical examination and thoracic radiographs to be performed at one month and then every three months for two years. At the one, six, and nine month re-evaluations pelvic radiographs were also recommended. Upon serial re-evaluations neither pulmonary metastases nor tumor recurrence was ever appreciated. Six months post-radiation therapy, there was progression of new bone formation within the right hemipelvis in the region where the hemipelvectomy was performed cranial to the coxofemoral joint.
Between the fifteen and eighteen month rechecks, the dog was noted to have some stiffness in her right hindlimb. Thoracic and pelvic radiographs were performed. Thoracic radiographs were unremarkable. Pelvic radiographs revealed mild increased new bone at the iliectomy site and osteopenia region of the right proximal femur which was apparent on multiple views (Figure 5). This was thought to be due to late effects of radiation therapy causing decreased vascularity and subsequent decreased mineralization of the right proximal femur. Carprofen that had been discontinued around three months post-operatively was reinstituted to help with patient comfort.
The referring veterinarian treated the dog for an abscess that had developed at the surgical site prior to the eighteen month recheck. The prolene mesh was removed, a drain was placed, and a course of Cephalexin (unknown dose) was prescribed. On physical examination there was a ~8 mm open draining tract with a mild amount of purulent discharge was appreciated at the cranial end of her scar.
At 9.5 years of age, almost 42 months post-iliectomy the dog succumbed to a suspected cardiac arrhythmia. The dog suddenly collapsed and was presented to a local veterinary emergency facility. Upon presentation, the dog was tachycardic. No treatments or diagnostics were performed. The dog was discharged with an unknown medication. The dog collapsed again shortly thereafter and died. There was presumably no recurrence of CSA at the time of death, however, a necropsy was not performed for confirmation. The owner was contacted for follow-up and relayed that she was very pleased with the outcome. The dog had some mild atrophy appreciated on the right pelvic limb at the time of death, however, there was no evidence of lameness or pain. Following iliectomy, the dog was able to continue living an apparently normal life that including running and playing.