Ch 72 MSK neoplasia and limb-spare Flashcards
What % of skeletal neoplasia is OSA?
What are the two reported peaks in age of onset?
85% of neoplasms of the skeleton
85%
- Small peak at 18-24m
- Larger peak at 10yr
risk factors
- large- and giant-breed dogs.
- Increasing height and weight
- Breed-associated changes identified in Golden Retriever and the Rottweiler
- early ovariohysterectomy or castration in Rottweiler
- timing of spay or neuter should be considered in predisposed breeds > research has inherent selection bias that exists in the pet population.
site of OSA
- predilection for the metaphyseal regions of long bones
- distal radius, femur, and tibia
- proximal humerus and tibia
distal radius and prox humerus most common
OSA types
- chrondro/osteoblastic
- fibroblastic
- endosteal - arises within the medullary canal (mst common)
- Periosteal and parosteal - arise from the periosteum
What is the MST with aggressive local and systemis treatment?
- In most cases of osteosarcoma, micrometastasis is present at the time of diagnosis
- MST 10-12m
Prognostic factors: postive (2) and negative (7)
**positive: **
- large tumour size
- proximal humerus
**negative: **
- flat bones,
- small dog,
- oral OSA (except maxilla)
- stage III not treated by metastatectomy (49d vs 232)
- lung (59d) vs bone (132) metastasis
- LN metastasis (MST 59d vs 318)
- ALP: total >110 U/L, bone isoenzyme >23 U/L
radiographic signs
- cortical lysis,
- periosteal reaction,
- extension of osteogenesis into adjacent soft tissue,
- loss of the fine trabecular pattern of the metaphysis,
- areas of fine punctuate lysis,
- lack of a distinct border between normal and abnormal bone
ddx (6)
- sarcomas (chondrosarcoma, fibrosarcoma, hemangiosarcoma),
- metastatic neoplasia,
- multiple myeloma,
- lymphoma,
- bacterial or fungal osteomyelitis
- bone cyst.
What is the accuracy rate of a bone biopsy and of an FNA?
Bone biopsy 80-90%
FNA 71% overall, increases to 92% for neoplastic processes (u/s guided, 20g)
- increased risk of path fracture with Michele
- Risks: lameness, fracture, nondiagnostic sample
- center of the radiographic lesion is the desired site
- biopsy tract is considered contaminated
- bipsy tracs increase risk of # with stereotactic radiosurgery
Jamshidi needle or a Michele trephine
What can be used to increase the diagnostic accuracy of FNA cytology for an OSA?
Staining with ALP
What is the rate of gross metastasis at time of diagnosis of OSA?
rate of ln mets?
rate of lung mets?
rate of bone mets?
15% gross metastasis
4%
Less than 10%
7.8%
staging
- two most common sites of metastasis are the lungs and another bone site
- Three-view thoracic radiographs are recommended for screening
- CT highly sensitive, but not specific
- Oblak et al.reported that long bone survey radiography had a low sensitivity to detecting bone metastasis
- Nuclear scintigraphy using technetium-99m is a very sensitive, but not specific
- radiography, bone scan, and whole body CT > bone scan was the only modality to definitively diagnose bone metastasis
- positron emission tomography (PET)-CT superior to bone scan
- regional lymph nodes should be palpated and aspirated
- rate of metastasis to nonlung and nonbone sites is low
- Complete blood count (CBC), serum biochemistry, and urinalysis geriatric patients with possible concurrent dz/other neoplasia
What sized thoracic mets can be seen on rads and on CT?
Nodules 7-9mm in diameter seen on rads
- 1mm seen on CT
When can bone lesions be seen on radiographs?
When there is over 30% bone loss and the lesion is over 2cm
What was the overall rate of bone mets when assessed with rads, nuclear scintigraphy (technetium 99m) and CT scan?
27%
Should not do an amuptation in a dog with bone mets in another limb….
what is Stage creep?
- increase in stage due to an increase in the sensitivity of the staging tests used, rather than an actual disease progression in the individual patient.
- Currently the prognostic effect of stage creep in cases that are radiography negative and CT positive for thoracic metastasis is not known.
What is the reported MST for dogs with LN mets vs not
MST with LN mets 59 days vs 318 days
What parameter on biochemistry has been shown to be a negative prognostic indicator?
Elevated total and bone ALP
Failure of bone ALP to decrease after amputation = shorter survival
local staging
- important part of surgical planning in the limb-sparing surgery
- radiographs, CT scan, magnetic resonance imaging (MRI), or scintigraphy.
- ## rads and CT were accurate, but may underestimated the extent vs other studies suggesting all overestimate extent > not appear to be a clear answer as to which diagnostic modality will provide the best
amputation
Goals
- prevent further metastasis,
- achieve local control,
- remove the source of pain
thorough orthopedic and neurologic examination should be performed before amputation
- Forequarter amputation (removal of the scapula) > thoracic limb
- entire pelvic limb with en bloc resection of the acetabulum > tumor of proximal part of the femur
- hip disarticulation > tumor of mid or distal portion of the femur
- hip disarticulation and amputation through the proximal part of the shaft > tumor of tibia
pathologic fracture
pathologic nature of the fracture may or may not be radiographically evident, - high index of suspicion> large- or giant-breed, fracture metaphyseal location, no hx of trauma.
- recommended treatment = limb amputation.
- fracture repair can be considered > if amp refused/not a candidate, staged negative for mets and chemo performed (MST was 166 days)
- fixation possibly has higher infection and failure rate
What are some hypothesised causes of fracture-associated OSA and TPLO-associated OSA?
- Comminuted fracture with complicated healing, implant loosening +/- infection
- Implant corrosion (Jonas pins, early TPLO)
- Chronic inflammation +/- infection
- delayed healing
- increased vascularity
cancerogenesis is multifactorial, it is likely more than one factor, including genetic predisposition
Fracture-Associated Osteosarcoma
- lag period of 5 years or longer
- diaphyseal neoplasms of large-breed dogs
- reported at the tibial plateau leveling osteotomy site in 5 of 472 and 6 of 1992 (very low rate)
- early-generation cast TPLO plates shown to have irregularities in the manufacturing process > but not all associated with these plates
- median survival time was 222 days, and it was 313 for dogs treated with limb amputation and adjuvant chemotherapy
Selmic 2018
association between TPLO and proximal tibial OSA
- dogs with history of TPLO → 40x more likely to develop proximal tibial OSA
- each 1kg increase → 11% increase in odds
- correlation with implant material not possible due to multiple implants in reported cases
What are the characteristics of a good candidate for a partial scapulectomy?
Proximal scapula effected
Has not extended into surrounding soft tissues
Can be removed with a 2-3cm distal margin with preservation of the shoulder joint
difference bwteen partial and subtotal scapulectomy?
partial: preservation of the acromion process, the acromial head of the deltoideus muscle, and the distal portion of the infraspinatus and supraspinatus muscles > greater stability of the shoulder compared to subtotal
subtotal: most of the scapula (as far distal as the scapular notch) while preserving the glenoid and the shoulder joint > loss of muscular support result in a greater dorsoventral excursion during weight bearing.
scapulectomy, holes can be drilled in the remaining scapula, and muscles can be sutured to their approximate origins or insertions
limb use after partial and especially subtotal scapulectomy is not completely normal. However, pain-free ambulation with a functional lameness is a reasonable expectation.
one study suggested no differnce bwteen how much scaula removed and function
DFI 210 days
MST 246 days
suggesting that the biologic behavior of scapular osteosarcoma is similar to that in other appendicular sites
Hemipelvectomy
- compartmental resection of the neoplasm with either 2- to 3-cm soft tissue and/or bone margins from the neoplasm, or a compartment of bone or fascia surrounding the neoplasm should be planned for a curative-intent resection.
- preoperative preparation for possible blood transfusion is recommended
- ensure ID urethra and rectum
Sx
- medial dissection: preserve sartorius, enicular and superficial circumflex artery, adductor magnus et brevis, gracilis, and pectineus muscles + abdomial muscles, ventral iliac wing exposed, external iliac artery and vein
- lateral: skin is elevated proximally to expose the lumbar fascia above the hip joint, between the semitendinosus and ischiocavernosus muscles, staying medial to the sacrotuberous ligament. The muscles of the pelvic diaphragm (levator ani and coccygeus muscles) can remain undisturbed, superfiical gluteal cut
- amputation: The limb is removed by an osteotomy of the ilium cranial to the acetabulum or disarticulation of the sacroiliac joint and by pubic osteotomy, medial muscle attachments are incised, lumbosacral plexus
- aggressive perioperative pain management is an essential part of this procedure.
tacking the omentum to the incision
What are the 4 historic classifications of hemipelvectomies?
- Total hemipelvectomy (from the pubic symphysis to the sacroiliac joint)
- Mid to caudal hemipelvectomy (from the pubic symphysis to the ilium just cranial to the acetabulum)
- Mid to cranial hemipelvectomy (from the sacroiliac joint to just caudal to the acetabulum)
- Caudal hemipelvectomy (pubic symphysis to just caudal to the acetabulum and allows for limb preservation)
total vs subtotal
Bray 2014
infrequent complications, usually minor, hemorrhage main intra-op complication, abdominal wall herniation 1 dog
- MST: HSA 179 days, chondrosarcoma 1232d, OSA 533d, STS 373d
- MDFI for local recurrence overall 257 days
- cats → 75% 1-year survival – higher than dogs
What can be used to reconstruct an abdominal wall defect after hemipelvectomy?
The sartorius muscle
Synthetic mesh
Medial thigh musculature (gracilus, adductor)
How much of the sacrum can be removed while retaining normal function of contralateral limb?
30%
caudal hemipelvelectomy
- Oblak and Boston
- removal of the ischium with limb preservation.
- ventraL: adductor, gracilis, and pectineus muscles) are dissected to be later reattached
- Lateral: biceps femoris muscle is tagged with suture for later reattachment. The sciatic nerve preserved. The semimembranosus and semitendinosus muscles are incised distal to their origin. sacrotuberous ligament is incised.
What are the main options for limb sparing surgery for distal radial OSA?
- Cortical allograft (out of favour)
- Endoprosthesis
- Pasteurised Autograft (65C for 40min)
- Vascularised Ulnar Transposition
- Bone transport osteogenesis (Distraction osteogenesis)
- Irradiated Autograft (not recommended)
- Stereotactic Radiosurgery (high risk of fracture 63%)
limb-sparing
- patient will not ambulate well with amputation of the limb (concurrent orthopedic or neurologic disease, the dog’s size)
- ideal candidate: distal radius, do not have a large amount of soft tissue involvement or evidence of pathologic fracture (to reduce recurrence)
- neoplasm should involve less than 50% of the length of the radius to reduce failure rate
corticoallograft
- high infection rate (approximately 50%) and the fact that the allograft is large and is not incorporated into the host bone within the patient’s remaining life span.
Endoprosthesis
- VOI: coated with hydroxyapatite to encourage bone ingrowth, and the screws are locking
- BioMedtrix (tantulum) trabecular metal. It is highly fatigue resistant
- Fitzpatrick Referrals
- failure involving the proximal screws
Charles Kuntz developed the original endoprosthesis
Ulnectomy
- reconstruction of the lateral collateral ligament may be necessary
- if gross instability is found at the time of surgery, plate stabilization should be performed (pancarpal arthodesis)
Partial Amputation and Endoprosthesis
- Intraosseous endoprosthesis after partial amputation
- case study: structure of the pores of the tantalum allowed for bone and skin ingrowth into the implant
- ITAP: intraosseous transcutaneous amputation prosthesis, and the exoprosthesis (study 4 dogs)
cats OSA
- 62% skeletal (50:50 axial vs appendicular)
- 38% extraskeletal
- Axial carries a worse prognosis > difficulty associated with achieving clean margin
- amputation without adjunctive chemotherapy. Staging with thoracic radiographs should be performed before surgery
- metastatic rate is much lower compared with canine osteosarcoma, and prolonged survival can be expected
Neoplasms of the Joint
3 types: SCS, HS, SM
- large-breed, older dogs
- incisional biopsy of affected bone and surrounding soft tissues for histopathology and immunohistochemistry
- histologic grade was found to be a significant prognostic indicator
- elbow and stifle joints were common sites
- Dogs with histiocytic sarcoma had significantly shorter mean survival time (5.3 months) compared synovial cell sarcoma and synovial myxoma.
- metastatic rate for histiocytic sarcoma high, 10 of 11 dogs (thus full staging b4 sx)
- Synovial myxoma mean survival of these dogs was 30.7 months.
- amputation is the recommended treatment for this disease if staging is negative
Intermuscular lipomas
- benign lipoma with a proclivity for caudal thigh,
- between the semimembranosus and semitendinosus muscles.
- firm, progressively enlarged thigh
- CT scan is useful for both diagnostic and surgical plannin
- sciatic nerve must be identified and protected during dissection
- excellent prognosis, with complete resolution
- no recurrence at a mean follow-up of 17 months.
seroma formation
Lateral manus translation for limb-sparing surgery in 18 dogs
with distal radial osteosarcoma in dogs
Bernard Séguin 2019
Retrospective case series.
Study population: Eighteen client-owned dogs.
lateral manus translation for distal radial osteosarcoma
- 66.6% complication (10/12 infection, 6/12 biomechanical)
- 33.3% recurrence
- median DFI 219d, MST 370d with adjuvant chemotherapy
Iliectomy with limb preservation in canines is feasible,
In this case, the dog developed an ischial fracture that ultimately
resulted in severe narrowing of the pelvic canal
Local recurrence was reported 385 days postoperatively
osteosarcoma
Novel radical pelvectomy technique to treat chondrosarcoma in a
large-breed dog
C Gordon 2021
AVJ
This case report is the first to demonstrate that removal of the entire
left ischium and both pubic bones with preservation of both hind
limbs was well tolerated and had a good clinical outcome in a largebreed
dog.
