Introduction
Hemipelvectomy is a procedure that can be performed in companion animals to treat neoplasms involving the pelvis or surrounding soft tissue.1 Hemipelvectomies can be characterized by type (internal or external) and location (cranial, middle, caudal, total), this terminology was derived from the human literature.2,3 External hemipelvectomy refers to removal of a portion of the pelvis and the ipsilateral pelvic limb. In contrast, internal hemipelvectomy spares the associated limb. Lesions can be categorized as either intercompartmental or extracompartmental.4,5 A tumor is classified as intercompartmental if the neoplasm is confined within a well-delineated anatomic compartment, whereas, extracompartmental neoplasms extend into other tissue planes or spaces.5 The cortical bone and articular cartilage aid as an anatomic compartment.5
Osteosarcoma (OSA) and chondrosarcoma (CSA) are the most common primary bone tumors of the canine pelvis.6,7 CSA is a malignant neoplasm arising from the cartilaginous tissue, that has a predilection for the medullary cavity of flat bones. The most common occurring pelvic neoplasm in adult humans is CSA.8 In veterinary medicine, CSA account for about 10% of bone neoplasms and predominantly occur in dogs.9,10 The most common location of pelvic chondrosarcoma in humans is the ilium followed by the pubis and ischium.11,12 CSAs in comparison to OSAs tend to be more slower growing and have a lower rate of metastasis in both animals and humans.13–15
In order to reduce the risk of local recurrence and prolong survival time, wide surgical resection is generally recommended for primary bone tumors. As such, the current standard of care for primary proximal femoral and pelvic bone tumors in dogs has been external hemipelvectomy.1,16–18 Currently, limited information is published within the veterinary literature regarding internal hemipelvectomy.8 If limb function can be retained without compromising surgical margins, a limb sparing procedure may be considered over an external hemipelvectomy.6 Three key areas need to be spared if an internal hemipelvectomy (i.e. limb sparing) is to be considered in human patients: the femoral neurovascular bundle, the sciatic nerve, and the acetabulum.6 Ideally one intact fascial plane about the circumference of the tumor is preserved.4 Internal hemipelvectomy is considered if tumor-free (clean) margins can be achieved, function of the limb is preserved, and the tumor does not involve major neurovascular structures.19
External hemipelvectomy requires patients to adapt to a novel method of ambulating post-operatively, can be contraindicated in patients with severe osteoarthritis, muscular or neurologic deficits, or may not be a consideration if the owner has a negative perception regarding amputation. Owner concerns may be influenced by anthropomorphism, concerns over aesthetic appearances, inability of their pet to adapt, or concerns for phantom pain.20,21 A phone survey conducted in the Netherlands revealed owners with older dogs reported a significant increase in negative response by acquaintances and were accused of being cruel to their companion for performing a limb amputation.21
Cranial internal hemipelvectomy was reported to be a feasible surgical alternative to external limb amputation in one dog with osteosarcoma.22 However, additional case reports are required to document the utility of internal hemipelvectomy for pelvic neoplasia in the veterinary literature. The purpose of this report was to document the long-term outcome of cranial internal hemipelvectomy for a marginally resected ilial chondrosarcoma in a dog followed by adjuvant radiation therapy.