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Chondrosarcoma (CS) is the second most common primary bone tumour and the most common in adults. These range from low to high grade malignant cartilage tumours which may metastasise to the lungs. They are relatively insensitive to chemo or radiotherapy meaning that surgery is the principal intervention. Five year survival ranges from 99% for low grade to 24% for dedifferentiated chondrosarcomas. Resection of a tumour from the proximal femur requires reconstruction of the large bone and soft-tissue defect. Achieving adequate surgical margins to ensure the tumour is excised-bloc is the guiding oncological principle to avoid local recurrence.
Endoprosthetic replacements of the proximal femur are one of the most common limb-salvage procedures undertaken to reconstruct massive bone defects secondary to tumour, trauma or infection. The complications of such surgery from a systematic review include dislocation (5.8%), prosthetic joint infection (5.2%), local recurrence (4.7%) and peri-prosthetic fracture (0.6%). These are both reliable and durable implants that offer immediate mobility and return to function; however in the long-term complications and failure mean that ten year endoprosthesis survival without revision surgery is approximately 75%.
INDICATIONS
The indications for proximal femoral endoprosthetic replacement are to reconstruct massive bone defects following malignancy, infection, trauma or failed arthroplasty. In oncology, tumours may either be primary or metastatic (secondary) bone tumours, or soft tissue sarcomas which have invaded the bone. Within this group pathological fractures may develop, where by the bone is weakened to the point of failure by the presence of the tumour.
The incidence of deep prosthetic joint infection following total hip replacement is approximately 1%. The treatment for infected hip replacements may involve explanting the infected prosthesis and insertion of a new prosthesis. Recurrent infections may be difficult to treat particularly when dealing with bone loss from previous surgeries which may necessitate endoprosthetic reconstruction.
Failed internal fixation of proximal femoral bone loss, particularly in osteoporotic bone, may lead to severe bone loss: endoprostheses replace this lost bone expeditiously which may be essential in comorbid patients with osteoporosis.
SYMPTOMS & EXAMINATION
Patients with primary bone tumours present principally with pain and swelling, with or without limitation of motion and reduced ability to bear weight.
Biopsy tract, range of motion of hip and knee, limb length, deformity, neurovascular status, skin quality including previous scars and sinuses, abductor function, availability of local soft tissue flaps as required.
IMAGING
Plain radiographs usually delineate the size and location of the tumour as well as extra-osseous extension. Radiographs are assessed for the extracellular matrix deposition of the tumour be that osteoid (e.g. osteosarcoma), chondroid (e.g. chondrosarcoma) or fibrous (fibrosarcoma of bone) which hints at the diagnosis. The age and anatomical location (epiphyseal, metaphyseal, diaphyseal) are important clues in narrowing the differential diagnosis.
In the proximal femur necessary radiographs include measured radiographs of the whole femur AP and lateral and pelvic AP radiograph.
Patients undergo biopsy to confirm the histological diagnosis. In our centre biopsies either occur in the operating theatre using a Jamshidi needle and fluoroscopy or CT guidance via a direct lateral approach. The positioning of the biopsy tract is crucial to ensure that is does not cross more than one anatomical compartment or compromise vital structures as the biopsy tract is excised en-bloc at the time of surgery. Typically the histological biopsy results take 7 to 10 days to be reported and are discussed at the sarcoma multi-disciplinary team (MDT) meeting comprising orthopaedic surgeons, radiologists, pathologists and oncologists.
Prior to surgery patients are ‘staged’, which involves local staging of the affected bone (i.e. MRI scan of the whole femur including the hip and knee joints) and distal staging to include CT chest and whole-body imaging e.g. bone scintigraphy, whole-body MRI or whole-body PET-CT, to exclude metastatic disease. If metastases are identified at the time of diagnostic staging this may influence the extent of surgical and systemic treatment but may not preclude surgical excision of the primary tumour; all of these details are considered at the sarcoma MDT when deciding upon the optimum treatment by all involved specialists.
ALTERNATIVE OPERATIVE TREATMENT
For primary malignant bone tumours of the proximal femur, alternatives to endoprosthetic replacement include allograft or allograft prosthetic composite. The former involves reconstructing the proximal femur with an allograft proximal femur matched in all dimensions to the planned resection, secured with plates and screws. The latter involves pre-operative insertion of a prosthetic femoral component and then attachment of the allograft to the residual distal femur with plates and screws. In some centres, allografts are augmented with vascularised fibula autografts (Capanna technique) to encourage host bone incorporation and minimise fracture and non-union rates.
NON-OPERATIVE MANAGEMENT
For chondrosarcoma the principle treatment is en-bloc excision and reconstruction as these are relatively chemo- and radiotherapy insensitive tumours.
For other primary bone tumours, patients typically receive pre-operative chemotherapy, then surgical resection and reconstruction followed by further post-operative chemotherapy. Some tumours, such as Ewing’s sarcoma are relatively sensitive to radiotherapy also.
CONTRAINDICATIONS
If the patient was medically unfit to undergo major surgery or if the staging revealed that the disease had already spread to the lungs with a very poor prognosis then surgery may be contraindicated although palliative surgery to control pain may still be contemplated.
GA + spinal
Prophylactic antibiotics, ultra clean theatre
Lateral decubitus position with hip props, pillow between calves, exclusion drape
Double alcoholic skin preparation, hip and thigh exposed, calf and foot excluded, ioban skin incisional drapes
VTE prophylaxis: early mobilisation protected weight bearing with crutches, LMWH chemoprophylaxis dose at least 6 hours post-operatively for 4 weeks, thigh lengths TED stockings for 6 weeks and foot pumps or flowtrons (calf compression devices) until mobile
VTE prophylaxis: early mobilisation protected weight bearing with crutches, LMWH chemoprophylaxis dose at least 6 hours post-operatively for 4 weeks, thigh length TED stockings for 6 weeks and foot pumps or flowtrons (calf compression devices) until mobile
Wound check 14 days
3 post-operative doses of antibiotics
X-rays when safe, AP right proximal femur and hip
Crutches 6 weeks, then wean to one crutch 6-12 weeks
Readmission for inpatient hydrotherapy after 6 to 8 weeks to facilitate weaning off crutches
Sarcoma surveillance: all patients with primary bone sarcomas undergo post-operative surveillance to monitor for local recurrence and metastasis. International guidelines mandate that patients are seen 3-monthly for the first two years, then 6-monthly until year five, then annually until year ten. At our institution we do chest radiographs at each visit plus radiographs of the proximal femur and endoprosthesis.
Proximal femoral endoprostheses are durable and reliable reconstructions even in patients with comorbid conditions (Khajuria et al. Hip Int 2017) and recently were shown to have eliminated the risk of dislocation when used with hemiarthroplasty heads in the short term (Stevenson et al. Bone Joint Journal 2018;100: 101-8). Implant survival after five years is between 87% and 95%, and approximately 75% at ten years.
Causes of implant failure and revision include infection, aseptic loosening, dislocation, local tumour recurrence and structural failure. For the purposes of standardising the reporting of endoprosthetic related complications the Henderson classification is now used to subdivide the modes of failure into: soft-tissue failures (Type 1), aseptic loosening (Type 2), structural failures e.g. implant fracture (Type 3), infection (Type 4), and tumor progression (Type 5) (Henderson et al. Failure mode classification for tumour endoprostheses: retrospective review of five institutions and a literature review. JBJS Am 2011;93(5):418-29.)
Reference
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