Chapter 72 Musculoskeletal Neoplasia/Limb Sparing Sx

Question 1

1. Osteosarcoma

- Most common Neoplasia accounting for 85% of skeletal neoplasm

• Appendicular - predominant in large and giat breeds
• Risk Factor - increasing height, weight, adolescent body weight, radius and ulnar circumference

What is the signalment?

Answer 1

Signalment - Older dogs, median 7 years,

• 2 peaks of onset, 18-24 months (Small peak), and 10 years (Large peak).
• May be hormonally related in Rottweilers increasing risk in early OVH and castration.
• Clinical signs - Chronic progressive lameness responsive to NSAIDS. Firm swelling, Acute lameness, pathologic fracture.
• Predilection for metaphyseal bone. Distal radius, femur, and tibia, and proximal humerus and tibia.
• Distal radius and proximal humerus most common.
• Distal radius associated with more favouble prognosis.
• Proximal humerus - worse prognosis.
• Most patients succumb to metastatic disease

Question 2

What are the treatment options for OSA

Answer 2

Palliative intent (Positive for metastasis

• Amputation and chemotherapy
• Anagesia and euthanasia
• Radiation, analgesics, bisphosphanates, and chemotherapy

Curative intent (negative for metastasis)

• Amputation and chemotherapy
• Limb savage, stereotactiv radiation and chemotherapy.

Question 3

Diagnosis and staging

Radiographic findings

• Cortical lysis,
• Periosteal reaction
• Osteogenesis extension into soft tissues
• loss of trabecular pattern
• punctuate lysis
• lack of distinch border between normal and abnormal bone
• Note - Sharp demarcation more suggestive of infectious process or bone cyst then neoplasia

Answer 3

• Most common OSA -s endosteal (medullary canal origin).
• Periosteal and parosteal OSA less common

DDx - Sarcoma, metastatic neoplasia, lymphoma, multiple lyeloma, osteomyelitis, bone cyst

Question 4

BIOPSY

• Biopsy more important in areas or endemic fungal disease
• Lesion not in typical location
• Clinical picture not completely consistent with primary bone neoplasia

Answer 4

How to perform Biopsy

• Jamshidi or Michele trephine
• Accuracy - 80-90%
• Michele trephine higher risk of pathological fx compared to Jamshidi.
• Michele trephine - take single core. Jamshidi - take multiple core.
• Reserve sample for bacterial and fungal culture

Question 5

Risk of bone biopsy

• worsene lameness and fracture
• non diagnostic sample - take sample from centre. periphery = periosteal reaction.

Biopsy considerations - prevent seeding

• Biopsy tract considered contaminated
• Take biopsy from single skin incision
• Do not penetrate opposite cortex

Answer 5

FNA?

• 71% accurate for bone lesion, but 92% for neoplastic process
• 20g needle, use ultrasound to identify cortical break
• diagnostic in 32/36 cases
• 16g vs 22g? - 95% vs 85% diagnostic rate
• CT may be used to guide aspiration

Question 6

Staging?

- Gross metastasis at presentation - 15%

- Most common in lungs and another bone site

- Lung lesion 7-9mm visible on radiograph

- CT scan - detect 1mm nodule

- Eberle et al 2011 - Pulmonary nodules were detected radiographically in 5% of cases, whereas the CT imaging showed that pulmonary nodules were evident in 28% of cases

Stage creep - negative on rads but positive on CT. Ct would suggest increased burden and worse prognosis

Answer 6

What if there is bone metastasis?

• Bone metastasis precludes limb amputation
• Jankoswski 2003 - Technetium 99m of dogs with OSA, N 399, bone metastatic rate of 7.8%
• Oblak et al 2015 - Survey rads low sensitivity to bone mets. Bone lesions not detectable until >30% bone loss and lesion >2cm

Question 7

Nuclear Scintigraphy

• Sensitive but not specific for bone mets - cannot differentiate between bone neoplasm, infection, fracture or others
• Abnormal ares should be evaluated by CT
• Oblak et al - bone scan was only modality that could diagnosis bone metastasis. Bone met rate of 27%
• CT sensitive for lung lesions but not for bone metastases. Pet-CT combines bone scan with CT but not available

Answer 7

Lymph Node

• Hillers 2003 - 4.4% regional met rate. Dogs with OSA treated with amp and chemo had MST 59 when LN positive vs MST 318 when LN negative.
• FL - axillary and prescap. HL popliteal and inguinal.
• Sarcornrattana et al - 3/118 (2.5%) mets detected by abdominal ultrasound
• Wallace et al - 4/80 (5%) diagnosed with another primary neoplasia based on abdo U/S, 0% metastatic disease by OSA
• Metastatic disease to non-lung and non-bone is low.
• Work up -
• - CBC, biochem, urinalysis
• - chemo may be nephrotoxic
• ALP may indicate poor prognosis. Failure of ALP to normalise post amputation associated with shorter survival and disease free interval.
• High ALP reflection of disease burden

Question 8

Local Staging

- Important in radius for limb sparing sx.

- Stage using rads, CT, MRI, or scintigraphy

- Davis et al - CT and rads mroe accurate than MRI for extent of neoplasia but underestimated lenght. MRI least accurate but did not underestimate neoplasia lenght. MRI superior for local staging for limb sparing sx

- Wallack - MRI considered most accurate compared to rads and CT and bone scan in contrast to Davis. No consensus on more accurate modaility.

- Scintigraphy overestimates extent of disease

Answer 8

Treatment options

• Amputation - Most dogs tolerate even if OA present in other limbs. Scapulectomy for FL, hip disarticulation for HL.
• Pathologic fracture - Suspect in large breeds with metaphyseal fx without trauma.
• Boston 2011 vet surg - Internal fixation of pathologic fractures - MST 166 days (18-897). Guidelines for fx repair - amp not an option, negative metastatic disease, fracture feasable, or follow up chemotherapy.
• Covey 2014 - N = 6. 2 fx at preso, 4 fx after stereotactic radiation. Infection 5/6, implant failure 3/6.

Question 9

Fracture associated OSA

• Reported in dogs and 2 cats
• in dogs - hx of comminuted fx and complciated healing, infection, implant loosening. Occurs after lag period of 5 years or more after fx repair
• Older dogs > 7 years
• Cause unknown. Hypothesis - implant corrosion - Jonas pins. . Chronic inflammation, infection, implant corrosion, delayed healing, reduced vascularity all thought to contribute. Also patient genetics
• TPLO related OSA - early gen TPLO plates had irregularities and increased corrosion. BUT Sartor et al 2014 VCOT - Incidence of TPLO OSA is low, 5/472 and 6/1992. All plates were early gen TPLO plates
• Selmic 2014 JAVMA - 18/22 case - early gen TPLO plate. Survival MST 222 days, 313 MST for ampuitation and chemo.

Answer 9

Scapulectomy

• Scapular neoplasia - forequarter emputation, partial or subtotal scapulectomy with limb preservation
• Partial scapulectomy - remove proximal scapula, preserve acromion process, deltoideus, and distal infra/supraspinatus.
• Subtotal scapulaectomy - remove all but glenoid and shoulder joint.
• Good candidates - disease limited to proximal scapula and disease can be removed with 2-0 cm margin and shoulder joint preserved.
• Scapulectomies associated with good to excellent outcome in 3 small case series
• Montinaro et al 2013 - largest retrospective study. partial scapulectomy in 24, subtotal in 13, total in 5 dogs. limb use considered fair to excellent. No asociation between amount of scapula removed and function. Positive correlation with increased body weight and reduced limb function. Complication - seroma. Pain free and functional lameness is reasonable expectation after surgery.

Question 10

Hemipelvectomy

• Categorise into - total hemipelvectomy, mid to caudal hemi, mid to cranial hemipelvectomy, , and caudal
• OR - total vs subtotal. Type of subtotal depends on portion to be removed.
• Bray et al 2014 - 84 dogs, 16 cats with neoplasia. Intraoperative complications rare. 7 experienced substatial blood loss, 2 required blood transfusion. 1 iatrogenic urethral laceration.
• Post op- abdominal wall herniation, scrotal swelling, urine retention, aspiration pneumonia, wound complications.
• Long term function excellent in 94 patients
• 33 sarcoma, OSA, 9 CSA, 6 hemangiosarcoma, 5 infiltrative lipoma. Cats - fibrosarcoma, OSA, and chondro sarcm
• MST chondrosarcoma 1232, OSA 533, STS 373. Cats 1 years survival 75%
• CT recommended fort staging and planning.
• rectum and urethra at risk of iatrogenic damage

Answer 10

Limb sparing surgery

• Consider if concurrent orthopaedic or nero disease or previous amputation in another limb.
• Distal radial OSA most amenable
• Options for radial OSA - cortical allograft, pasteurized autograft, intraop radiation, bone transport osteogenesis.
• Ideal candidate - small soft tissue involvement, no pathologic fx. neoplasm <50% of radius to decrease implant failure

Cortical allograft

- High infection rate - 50%, allograft not incorporated into host bone within life span. allograft often becomes sequestrum. implant failure by fatigue or loosening in longer term survivors. This technique has fallen out of favour

Endoprostehesis

Kuntz - 122mm 316L stainless steel bar with flared ends. 2 screws secure endoprosthesis to bone plate. 24 hole limb sparing plate.available in 98 and 122mm.

No difference in infection, surgical time, limb use, implant fail rate, or outcome for allograft vs endoprosthesis.

Mode of failure - allograft failed in distal screw, enroprosthesis failred in proximal screw. Cadavaric study - endoprosthesis biomechanically superior to allograft.

Pasteurized autograft

Radial autograft removed and pasteurised in sterile saline at 65C for 45 minutes

Morello et al:Complications similar to allograft - local recurrence, infection, and implant failure. risk of failure greater due to preexisting lysis of diseased bone and because autograft not filled with bone cement. Advantage - no need for bone bank. osteotomy will eventuually heal to autograft and radial carpal bone.

Kuntz - autoclave autograft for 75C for 10 minutes medullary canal filled with bone cement. 7/9 developed infection. Autograft resorbed leaving only bone cement radiographically.

Vascularised ulnar transposition.

• Uses ipsilateral distal ulnar to replace radial defect. Must not have neoplastic involvement of ulnar
• Preserve caudal interosseous artery, vein, attachment of abductor pollicis longus, and pronator quadratus muscle. Ulnar is osteotomised and rolled over to radial defect
• Advantage - graft is vascularised and may hypertrophy.
• Disadvantage - may cause limb shortening. biomechanically weaker than allograft.
• Alternative techniques - ulnar transposition with lateral manus translation to contact RC bone. N = 8, good to excellent function. 5 infections and 1 recurrence (Seguin)

Bone Transport Osteogenesis

• Progressive prolonged distraction by intramembranous ossification.
• Distraction commences 3-7 days post op, 1mm a day over 3-4 distractions a day. Cancellous bone graft once there is 5mm cap to RC bone. Transport segment distracted for 1-3 days after contacting RC bone for compression then locked until fusion.
• Ehrhart - Mean time to docking 123 days. MEan time until ESH removal 205 days.
• Advantage - vasculatised bone resistant to infection. and no implant failure once ESF removed.
• Disadvantage - labour intensive.

Irradiated Autograft

• Not recommended. Intention to preserve antebrachiocarpal joint but major complication of collapse of articular cartilage and subchondral bone due to lysis from neoplasia and radiation.

Stereotactic Radiosurgery

• Delivers single dose accurately with minimal radiation to surrounding tissues
• risk - high fracture rates. Consider prophylactic plating.
• Covey 2014 - N = 6, 2 dogs with pathological Fx at admission, 4 dogs fractured after SRS. 5/6 infections and 3/6 implant failure when plated after SRS.

Question 11

Complications of Limb sparing sx

• Local recurrence, implant failure, and infection
• Infection rate - 40-75% - lack of vascularity.
• Antibiotic impregnated beads vs lifelong antibiotics
• Infection may increase survival time. MST 480 - 685 days infected vs 228 - 289 days in noninfected group.
• Local recurrence 25%
• Implant failure 40% (Liptak et al) when N=20 underwent allograft or endoprothesis limb spare sx. Allograft failures distally, endoprosthesis failure occured proximally.
• Implant failure - MST 685 days vs 322 days no implant failure - unknown mechanism.

Answer 11

Other limb sparing methods and sites

• Intercalary limb-sparing surgery for diaphyseal OSA
• Ulnectomy + PCA for Ulnar OSA.
• Proximal humerus limb sparing - not recommended. SRS more appropriate.
• Partial Amputation and endoprosthesis.
• ITAP

Question 12

Chemotherapy

• Amputation alone - 19 weeks NST.
• Chemo + Sx - Doxorubicin MST 52.3 weeks.
• Doxo + carboplatin MST 235-320 days
• Carboplatin single agent less side effects than doxo single agent. No difference in survival time compared to doxo + carbo.

Radiation

• 2-4 doses 8gy course fractionated radiation
• Improves pain and inflammation.
• Less expensive than SRS
• Use when evidence of mets but amputation not practical
• Risk pathological fx. 50-93% response rate. MST 122-313 days
• Full course fractionated curative intent radiation not recommended - lack survival benefits and more soft tissue side effects.

Answer 12

Palliative therapy

• Multimodal
• Palliative radiation + analgesics
• Chemotherapy + palliative radiation.
• Bisphosphanates - inhibits osteoclast
• Pamidronate - 1-2mg/kg IV a month.Associated with shorter survival but unknown why
• Zoledronate - more expensive, easier to administer. Optimal dose unknown.

Question 13

Appendicular chondrosarcoma in dogs

• Rare - 5-10% primary bone neoplasm
• Lower met rates, longer survival and potential cure with amp.
• MST 979 days, met rate 28%
• Grade 1 - 0% met rate, grade 2 31% met rate, grade 3 50% met rate
• MST - Grade 1 6 years, grade 2 2.7 years, grade 3 0.9 years
• Unknown if chemotherapy beneficial.

Answer 13

OSA in cats

• Rare
• 65% appendicular, 35% axial
• Met rate 10%
• Amputation alone - MST 16.7 to 64 months
• Axial OSA - poorer prognosis.
• Recurrence 44%
• Recommended radial excision without chemotherapy

Question 14

Joint neoplasm

• Synovial cell sarcoma vs histiocytic sarcomas vs synovial myxoma. Immunohistochem to differentiate.
• Periarticular histiocystic sarcoma (Bernease mountain dog) carries better prognosis comapred to otherlocations but MST (5.3 months) shorter than synovial cell sarcoma and myxoma.
• Amputation recommended if no mets.
• Myxoma - Doberman pinscher, MST 30.7 months.

Answer 14

Muscle neoplasm

• Rhabdomyosarcoma - either wide or radical excision based on staging
• Hemangiosarcoma - Excision with chemotherapy - MST 272 days. Consider wide or radical excision

Neoplasm of adipose tissue

• Intermuscular lipomas - between semimembranosus and semitendinosus. Surgery is curative
• Infiltrative lipoma - invades into adjacent muscles - needs radical excision. . Recurrence rate 36. cytoreductive sx with adjunctive radiation - 40 months MST
• Liposarcoma - locally aggressive, low metas. MST 694 days. . Wide excision 1188 days, margical excision 649 days. Excellent prognosis if local control obtained.

Question 15

Neoplasm of digit

• 53.5-61% malignant
• SCC, melanoma
• Subungual SCC - 95% survival.. Digital SCC 60%. Met rate 8-29%
• Melanoma - met rate 50-58%. MST 1 year. . With vaccine, MST 351 days.
• Consider partial foot amputation, 8/11 dogs got clean margins, 8 dogs had lameness resolved.
• In cats - 10% malignant - SCC, fibrosarc, adenocarc, OSA, hemangiosarc, MST, histiocytoma. Adenocarcinoma - metastases from bronchial adenocarcinoma (lung digit syndrome). . Short MST 67 days.