Ortho and Palliation

Question 1

Location of bone mets

Answer 1

• Most frequently in axial skeleton (pain may be more diffuse and poorly localized)
• Mets to appendicular skeleton are most common in the femur (2/3 of all path fractures)or humerus (pain may be more discrete)
• Mets are less common in more distal regions

Question 2

Evaluation of patient with a bone lesion

Answer 2

In patients with a known primary who was thought to be disease free

• Imaging (initial primary, C/A/P/, rest of pelvis)
• Biopsy most accessible site to confirm disease recurrence

CUP and bone lesion

• CT C/A/P to examine viscera for primary or additional mets
• Bone scan for other mets
• Biopsy for histological type

Widely disseminated mets with known diagnosis

• Biopsy unnecessary
• Consider imagining to characterise location

Question 3

Imaging of patients with metastatic bony disease: UTD Approach

Answer 3

1. For suspected extremity lesions, XRs first. If impending or complete pathologic fracture suspected or XRs are ambiguous, consider CT or MRI without contrast to evaluate for surgical stabilization
2. In any case where a patient has significant back pain (even without neuro signs) or neurologic symptoms, get a spinal MRI without contrast to rule out cord compression. If symptoms persist but imaging is negative, consider a PET
3. Consider a PET scan if:
   - Need for comprehensive whole body cancer staging
   - Rapidly progressive mets with minimal reactive bone formation
   - Ewing sarcoma with primary lytic tumour
4. If the patient has myeloma
   - Primary lytic lesions - get a whole body plain radiograph skeletal survey
   - Primary sclerotic lesions - get a bone scan

Question 4

Imaging of patients with mets to bone: Plain XRs

Answer 4

• Useful to identify overall structural integrity of bone and planning surgical interventions
• Note insensitive for detecting mets (requires minimum lesion diameter of 1cm, bone mineral loss of >50%)
• ‘Moth eaten pattern’ - often with MM, typically more aggressive
• '’Permeative pattern’ - most aggressive
• ‘Geographic pattern’ - slow growing tumours

Question 5

Imaging of patients with mets to bone: Bone scintigraphy

Answer 5

• Useful to identify other bone lesions through the skeleton
• Detects disease progression ONLY when new bone formation is occurring
• Often false negatives with MM (due to lack of new bone deposition) or highly aggressive mets (e.g. lung CA or Melanoma)
• Sensitivity 75%, poor specificity

Question 6

Imaging of patients with mets to bone: CT scan

Answer 6

• Useful for assessment of structural integrity
• Helpful for preop planning in the pelvis and spine
• Can identify occult fractures in the setting of a metastatic lesion (more difficult to see on MRI due to marrow edema)
• More useful than plain XR as it better delineates bone involvement and can reveal soft tissue extension

Question 7

Imaging of patients with mets to bone: MRI

Answer 7

• Provides excellent contrast between normal bone marrow and tumour involved marrow space
• Unable to provide detail regarding structural integrity - typically used in conjunction with plain films and CT scan
• If there is concern re: spine, MRI spine is the most efficient way to assess

Question 8

Imaging of patients with mets to bone: PET

Answer 8

• PET uses a tracer that shows high uptake in cells with high metabolic activity
• Likely diagnostic potential in metastatic bone disease but cost often prohibitive

Question 9

Surgical treatment of metastatic bone disease

Answer 9

Goal:
- Increase QOL (decreased tumour burden and pain, improve mobility and function)
- Ultimately goal is immediate WBAT to facilitate quickest return to normal function
Indications for surgery
- Mechanical stabilization

Indications

• Impending or existing pathological fractures (ideally prior to fracture)
• If PS is too poor, or at EOL, casting or splinting may provide mechanical pain relief (but will not improve function)

Question 10

Casting for patients with metastatic bone disease

Answer 10

• Consider for patients who are too sick/close to EOL for surgery
• Ensure it is well padded and free of any significant areas of pressure so as to avoid skin breakdown/ulceration
• Avoid in limbs with lymphedema (may cause tissue damage or compartment syndrome)

Question 11

Assessment of fracture risk

Answer 11

• Patients with metastatic lesion at low risk of fracture are often best treated with non-surgical tx (rads, systemic tx)
• Consider use of scoring system for risk of pathologic fracture (Mirels’ scoring system) but may over or under estimate need for surgery
• Evidence to support benefit in terms of QOL is weak
• Surgery has best evidence in patients with a prognosis >6 months, otherwise post-op complications may limit benefit (though patients with short prognosis may still benefit)

Question 12

Impact of mets on bone biology/biomechanics

Answer 12

Lytic lesions

• Greater removal of mineral/organic components of bone, leading to greater loss in strength and stiffness
• Small osteolytic defects can lead to stress risers (areas of bone where stresses are concentrated around a small hole) and can lead to fracture in cases of pivoting or turning
• Larger metastatic lesions can create a hole in bone larger than the bone’s diameter

Blastic lesions

• No disruption to mineral content of bone but disrupt normal trabecular framework of the cancellous bone
• Lower likelihood of fracture

Question 13

Factors predicting life expectancy in the context of bony mets

Answer 13

• Multiple bone involvement
• Parenchymal organ involvement
• Low ANC
• Hypoalbuminemia
• Anemia
• Hypercalcemia

*Note this may be biased towards MM natural history

Question 14

Orthopedic surgical interventions: Tumour excision

Answer 14

1. Intralesional excision
   - Most common treatment choice
   - Provides pain reduction, associated with fewer fixation failures and lower risk of tumour progression at the site
2. Marginal or wide excision
   - Removes the bulk of the tumour by excising at the border of where normal/abnormal tissues meet
   - Typically performed in conjunction with arthroplasty
   - Can reduce risk of local recurrence and need for further surgery
   - More appropriate for patients with long prognosis and an isolated tumour

Question 15

Orthopedic surgical interventions: Prosthetic joint replacement (arthroplasty)

Answer 15

• Typically knee, hip, shoulder, and elbows
• Resection of one side (hemiarthroplasty) or both sides (total arthroplasty) of the joint surface with prosthetic replacement of the resected joint components

Indications
- Fractures involving the epiphyseal surface of joints (poor healing)

Technical considerations

• Stem of prosthetic component should bypass any distal lesions by twice the diameter of the involved bone to prevent later periprosthetic fracture
• Use cement because the bone ingrowth required for stability with a non-cemented compound is unlikely to ccur

Question 16

Orthopedic surgical interventions: Plate fixation

Answer 16

• Goal is to provide load-bearing stability to a fracture site by supporting weight through the bone until union of the fracture occurs
• Risk of screw and plate breakage, particularly if there is tumour progression at the site of the plate
• Most useful for where bone healing is expected to be quick (rare in pathologic fractures) or for patients with radiosensitive tumours that will heal after surgery with radiation treatment
• Typically does not allow weight bearing immediately after surgery

Question 17

Orthopedic surgical interventions: Intramedullary fixation

Answer 17

• Rod or bail placed down the centre of the medullar cavity of the bone, acting as a load bearing device
• Fracture less likely than with plate fixation as the device is in the centre of the bone and subjected to less bending force
• Most useful in diaphyseal fractures
• Can be augmented with cement to provide additional stability

Question 18

Orthopedic surgical interventions: Bone cement

Answer 18

• Useful adjuvant to stabilise a fracture site
• Can fill the detect remaining after excision/curettage of the lesion
• Barium contrast in the cement to facilitate monitoring with XR
• Emits heat while solidifying, destroying tumour cells and reducing tumour burden

Question 19

Orthopedic surgical interventions: Amputation

Answer 19

• Limited role in patients with metastatic disease
• Indications include a limb that cannot be reconstructed due to extensive disease involvements OR if complications leave no other options

Potentially:

• Fungating masses
• Recurrent infections that cannot be controlled with antibiotics
• Intractable pain in a limb that has failed treatment by other conventional methods

Question 20

Ortho Considerations: Epiphyseal fractures

Answer 20

Epiphyseal fractures

• Occurs at the end of the long bones near or involving the articular surface
• Poor healing rate, not easily stabilised in the setting of malignancy

Best treatment: Cemented arthroplasty

Question 21

Ortho Considerations: Metaphyseal fractures

Answer 21

Metaphyseal fractures

• Fracture in the ‘neck’ part of the bone
• Frequently occur where IM fixation is difficult

Best treatment: options are typically plate fixation (high failure rate) or arthroplasty

Question 22

Ortho Considerations: Diaphyseal fractures

Answer 22

Diaphyseal fractures
- Fracture in the shaft of a bone

Best treatment: Usually IM nails with complete curettage of the tumour and bone cement

Question 23

Ortho Considerations: Combinations of fractures

Answer 23

• Bones with both diaphyseal and epiphyseal or metaphyseal involvement, arthroplasty with a cemented long stem device is typically best

Question 24

Ortho Considerations: Pelvi and acetabular fractures

Answer 24

Treatment options:

1. Conventional THA
   - May fail if there is inadequate bone stock on the acetabular side to support the implant - evaluate with CT scan
   - If bone is deficient, will need alterations to technique
2. Saddle prosthesis
   - Consider for patients with complete destruction of the acetabulum
   - High risk of complications, especially in cases of disease progression into the retained ileum

Question 25

Kyphoplasty

Answer 25

• Balloon inserted through the pedicle into the vertebral body and inflated
• Re-expands collapsed vertebra and creates an opened space for injection of cement
• Avoid in patients with neuro findings or evidence of cord compromise

Advantages

• Restores vertebral body height and improves spine biomechanics
• Lowered risk of cement extrusion into the spinal canal (space created by balloon)
• Pain relief

Complications:

• Cement leak (can encroach on the epidural space and risk root or cord compression)
• Chemothermal damage to the cord
• Cement embolism (if there is a venous leak)

Question 26

Vertebroplasty

Answer 26

• Percutaneous injection of cement to re-expand collapsed vertebra
• Avoid in patients with neuro findings or evidence of cord compromise

Complications:

• Cement leak (can encroach on the epidural space and risk root or cord compression) - higher risk than kyphoplasty
• Chemothermal damage to the cord
• Cement embolism (if there is a venous leak)

Question 27

Radiofrequency ablation of bony mets

Answer 27

• Use of alternating electrical current to cause thermal necrosis of the cancerous tissue
• Useful for tumours >5cm and alternative to surgical stabilization for isolated small lesions in the extremity
• Also useful for lesions in the flat bones of the pelvis

Complications:

• Skin necrosis
• Damage to surrounding healthy tissue
• Fracture at the site of involvement

Inappropriate if impending path fracture is a concern

Question 28

Embolization of bony mets

Answer 28

• May be useful for very vascular tumours that metastasize to bone (e.g. renal and thyroid carcinomas)
• Risk of significant hemorrhage if disrupted surgically, and embolization can be a way to cause local tissue necrosis

Question 29

Osteoplasty

Answer 29

• Injection of bone cement into a painful lytic pelvic lesion in patients who cannot tolerate surgery or do not benefit from conventional tx (rads, meds)
• Immediate bone strengthening, improves mobility and pain control

Contraindications:

• Local infection
• Uncorrected coagulopathy

Complications:
- Inter articular injection (use fluoroscopy, especially when treating acetabular lesions)