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.