Longitudinal Bone Transport for Treatment of Primary Bone Tumors in Dogs: Technique Description and Outcome in 9 Dogs

Impact of microwave ablation treatment on the biomechanical properties of the distal radius in the dog: A cadaveric study

OBJECTIVE

To determine whether microwave ablation (MWA) modifies the biomechanical properties of the normal distal radius in the dog to better estimate the clinical impact of MWA as a tool for the treatment of neoplastic bone lesions.

STUDY DESIGN

Biomechanical experimental study.

SAMPLE POPULATION

Sixteen pairs of dog forelimbs from 16 canine cadavers.

METHODS

From each pair of forelimbs, one radius was randomly assigned to an MWA group, and the other radius was randomly assigned to a control group. Bone tunnels were created in each distal radial epiphysis for a length of 6 cm toward the middiaphysis. In the MWA group, the ablation probe was inserted into the bone tunnel for a series of three ablation treatments. Specimens were then tested in three-point bending to acute failure with the middle point located 3 cm from the distal articular surface (middle of the ablated zone). Load and displacement were continuously recorded to determine maximum displacement and peak load before failure. Data were analyzed with noninferiority tests.

RESULTS

The mean peak loads for the control group and MWA group were 1641.9 N and 1590.9 N, respectively. Microwave ablation-treated radii were not biomechanically inferior to control radii (P < .0001).

CONCLUSION

Microwave ablation of normal cadaveric dog distal radii did not affect the maximum displacement and peak load before failure.

CLINICAL SIGNIFICANCE

Microwave ablation does not affect biomechanical bending properties of the distal radius in the dog. Future studies, both cadaveric and in vivo, are required to evaluate the impact of MWA on neoplastic bone.

Distraction Osteogenesis in Two Wild Raptors

Distraction osteogenesis was used in 2 wild raptor patients for the repair of tibiotarsal fractures. The first case was a hatching year female peregrine falcon (Falco peregrinus) admitted with an open oblique right distal tibiotarsal fracture. The fracture was surgically managed with the external skeletal fixator intramedullary pin tie-in technique (ESF-IM pin tie-in). Appropriate healing of the fracture site occurred with the ESF-IM pin tie-in. However, there was significant pelvic limb shortening of the affected leg, and the bird consequently developed pododermatitis on the contralateral foot. The second case was an adult female great horned owl (Bubo virginianus) that was admitted with a closed, partially healed, overriding right tibiotarsal fracture. Because of the advanced stage of this fracture, which presented with a fibrous callus, and the already apparent pelvic limb shortening, the ESF-IM pin tie-in was not used. Both patients were fitted with a circular external skeletal fixator (CESF), and distraction osteogenesis was performed until the length of the pelvic limb was deemed anatomically adequate. It is critical that rehabilitated raptors be released without any physical conditions that may reduce their ability to survive and reproduce in the wild. Pelvic limb shortening can potentially predispose a raptor patient to pododermatitis, even with fatal consequences, in both captive and wild environments. The orthopedic technique used here proved useful to repair the limb shortening in both raptor cases, and each bird fully recovered and was released.

Limb-sparing in dogs using patient-specific, three-dimensional-printed endoprosthesis for distal radial osteosarcoma: A pilot study

Limb-sparing for distal radial osteosarcoma has a high rate of complications. Using personalized three-dimensional (3D)-printed implants might improve outcome. The goals of this study were to optimize use of patient-specific, 3D-printed endoprostheses for limb-sparing in dogs in the clinical environment and to report the outcome. This was a pilot study where five client-owned dogs were enrolled. Computed tomography (CT) of the thoracic limbs was performed, which was used to create patient-specific endoprostheses and cutting guides, and repeated on the day of surgery. Intra-arterial (IA) carboplatin was introduced in the clinical management. Limb-sparing was performed. Outcome measures were time required to produce the endoprosthesis and cutting guide, fit between cutting guide and endoprosthesis with host bones, gait analysis, size of the tumour, percent tumour necrosis, complications, disease-free interval (DFI) and survival time (ST). Four dogs received IA carboplatin. Excessive tumour growth between planning CT and surgery did not occur in any dog. The interval between the CT and surgery ranged from 14 to 70 days. Fit between the cutting-guide and endoprosthesis with the host bones was good to excellent. At least one complication occurred in all dogs. Two dogs were euthanized with STs of 192 and 531 days. The other dogs were alive with a follow up of 534 to 575 days. IA chemotherapy is a promising strategy to minimize the risk of excessive tumour growth while waiting for the endoprosthesis and cutting-guide to be made. The design of the cutting-guide was critical for best fit of the endoprosthesis with host bones.

Modification of the metal endoprosthesis limb-salvage procedure for excision of a large distal radial osteosarcoma in a dog: A case report

OBJECTIVE

To report modification of the endoprosthesis surgical limb-salvage technique to treat a locally extensive osteosarcoma in a dog and associated functional outcome.

STUDY DESIGN

Clinical case report.

ANIMALS

One client-owned dog.

METHODS

A 9-year-old dog was presented for treatment of a locally extensive distal radial osteosarcoma. A limb-salvage surgery was performed with a second-generation Veterinary Orthopedic Implants (VOI) endoprosthesis to reconstruct the radial segmental and carpal osseous defect. The endoprosthesis was stabilized with a 16-mm-wide locking VOI limb-salvage plate. The level of the osteotomy of the radius/ulna was 3 cm proximal to the periosteal reaction seen on radiographs, and the distal osteotomy extended through the proximal metacarpal bones (II-V), 3 cm from the distal extent of the soft tissue component of the tumor. A 3.5-mm SOP (String of Pearls) plate was used as adjunct fixation.

RESULTS

The postoperative functional outcome was classified as acceptable. Ambulation was normal, with mild subjective lameness on the treated limb at examinations 20, 43, and 63 days after surgery. The dog was euthanized 92 days after surgery because of progressive metastatic disease.

CONCLUSION

The modified endoprosthetic technique allowed complete excision of the carpal joint, which resulted in acceptable functional outcomes in the dog described here.

CLINICAL SIGNIFICANCE

Distal ostectomies may include part of the manus during limb salvage surgery of locally extensive distal radial osteosarcoma and using an endoprosthesis implant to reconstruct the defect.

Orthogonal bone plate stabilization for limb-sparing surgery

This report describes limb-sparing surgery in a 35 kg, six-year-old Hungarian Vizsla with a distal radial lytic bone lesion. Preoperative biopsy had suggested a bone cyst, however histopathology on the excised bone segment was indicative of an osteosarcoma. Following excision of the tumour, the bone defect was filled with a composite bone graft and stabilized with a custom-made dorsal 3.5/2.7 mm pancarpal arthrodesis plate and an orthogonally positioned medial 2.7 mm compression plate. This technique has not previously been described for limb-sparing procedures. No complications were encountered, and despite the owners declining adjunctive chemotherapy, the dog was alive 34 months postoperatively with near normal limb function.

Long-term outcome of dogs treated with ulnar rollover transposition for limb-sparing of distal radial osteosarcoma: 27 limbs in 26 dogs

OBJECTIVE

To determine outcomes in dogs with distal radial osteosarcoma treated with ulnar rollover transposition (URT) limb-sparing surgery including: viability of the ulnar graft, complications, subjective limb function, disease-free interval (DFI), and survival time (ST).

STUDY DESIGN

Retrospective case series.

ANIMALS

Twenty-six client-owned dogs with distal radial osteosarcoma and no involvement of the ulna.

METHODS

Data of dogs treated with URT were collected at the time of surgery and retrospectively from medical records and by contacting owners and referring veterinarians.

RESULTS

URT technique was performed on 27 limbs in 26 dogs. The ulnar graft was determined to be viable in 17 limbs, nonviable in 3, and unknown in 7. Complications occurred in 20 limbs. Infection was diagnosed in 12 limbs. Biomechanical complications occurred in 15 and local recurrence in 2 limbs. Limb function graded by veterinarians or owners was poor in 2 limbs, fair in 4, good in 14, excellent in 3, and unknown in 4. Median DFI was 245 days and median ST was 277 days.

CONCLUSION

The URT technique maintained the viability of the ulnar graft. The complication rate was high but limb function appeared acceptable. Although sufficient length of the distal aspect of the ulna must be preserved to perform this technique, local recurrence was not increased compared to other limb-sparing techniques when cases were appropriately selected.

Outcome and complications in dogs with appendicular primary bone tumors treated with stereotactic radiotherapy and concurrent surgical stabilization

OBJECTIVE

To document the outcome of dogs with appendicular primary bone tumors treated with stereotactic radiotherapy (SRT) and concurrent stabilization.

STUDY DESIGN

Multi-institutional retrospective case series.

ANIMALS

Eighteen dogs with presumptive or definitive diagnosis of appendicular osteosarcoma.

METHODS

Medical records of dogs with appendicular primary bone tumors treated with SRT and stabilization were reviewed for signalment, preoperative staging and diagnostics, radiation dose, stabilization method, and outcome.

RESULTS

The distal radius was affected in 13/18 cases. Osteosarcoma or sarcoma was confirmed cytologically or histologically in 15/18 cases. Seven dogs were diagnosed with a pathological fracture at the time of treatment, and 11 were considered at high risk for pathological fracture. Dogs received a single dose (n = 5) or 3 doses (n = 13) of SRT. Surgical stabilization was performed under the same anesthetic event as the final dose of SRT in 10 dogs. Stabilization was achieved with a bone plate (n = 15) or interlocking nail (n = 3). Seventeen dogs received adjuvant chemotherapy. Complications occurred in 16/17 dogs, 15/17 of those being considered major complications. Four dogs experienced more than one complication. Infection was the most common complication, diagnosed in 15/17 cases, and considered as a major complication in 13/15 cases. Postoperative fracture was recorded as a major complication in 3 cases. Nine dogs were amputated at a median of 152 days. The median survival time was 344 days.

CONCLUSION

Treatment of bone tumors with SRT and concurrent stabilization was associated with a prohibitively high complication rate in dogs. Alternative methods for limb salvage should be considered for dogs at risk for pathologic fracture.

Mechanical properties of canine osteosarcoma-affected antebrachia

OBJECTIVE

To determine the influence of neoplasia on the biomechanical properties of canine antebrachia.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Osteosarcoma (OSA)-affected canine antebrachia (n = 12) and unaffected canine antebrachia (n = 9).

METHODS

Antebrachia were compressed in axial loading until failure. A load-deformation curve was used to acquire the structural mechanical properties of neoplastic and unaffected specimens. Structural properties and properties normalized by body weight (BW) and radius length were compared using analysis of variance (ANOVA). Modes of failure were compared descriptively.

RESULTS

Neoplastic antebrachia fractured at, or adjacent to, the OSA in the distal radial diaphysis. Unaffected antebrachia failed via mid-diaphyseal radial fractures with a transverse cranial component and an oblique caudal component. Structural mechanical properties were more variable in neoplastic antebrachia than unaffected antebrachia, which was partially attributable to differences in bone geometry related to dog size. When normalized by dog BW and radial length, strength, stiffness, and energy to yield and failure, were lower in neoplastic antebrachia than in unaffected antebrachia.

CONCLUSIONS

OSA of the distal radial metaphysis in dogs presented for limb amputation markedly compromises the structural integrity of affected antebrachia. However, biomechanical properties of affected bones was sufficient for weight-bearing, as none of the neoplastic antebrachia fractured before amputation. The behavior of tumor invaded bone under cyclic loading warrants further investigations to evaluate the viability of in situ therapies for bone tumors in dogs.

Outcomes of Limb-Sparing Surgery Using Two Generations of Metal Endoprosthesis in 45 Dogs With Distal Radial Osteosarcoma. A Veterinary Society of Surgical Oncology Retrospective Study

OBJECTIVE

To report outcomes in dogs with distal radial osteosarcoma (OSA) treated with metal endoprosthesis limb-sparing surgery and compare outcomes between 2 generations of endoprosthesis.

STUDY DESIGN

Multi-institutional retrospective case series.

ANIMALS

Forty-five dogs with distal radial OSA treated with endoprosthesis and chemotherapy.

METHODS

Data of dogs treated with either first-generation endoprosthesis (GEN1) or second-generation endoprosthesis (GEN2) were sourced from medical records and radiographs. Surgical outcomes included postoperative lameness assessment and the presence, severity, and time to onset of complications. Oncologic outcomes included presence of local recurrence or metastasis, time to onset of local recurrence, metastasis-free interval (MFI), and survival time. Results for surgical and oncologic outcomes were compared between GEN1 and GEN2.

RESULTS

Twenty-eight dogs received GEN1 and 17 dogs received GEN2. There were 39 complications (96%, 14 minor, 29 major) including infection (78%), implant-related complication (36%), and local recurrence (24%). Metastatic frequency was 67% and median MFI was 188 days (95% confidence interval [CI]: 126-250 days). Survival time ranged from 34 days to 6.1 years with a median of 289 days (95% CI: 207-371 days). There was no significant difference in complication severity, frequency, time to complication, MFI, or survival time between dogs receiving GEN1 and GEN2.

CONCLUSION

There was no significant difference in outcomes between dogs receiving GEN1 and GEN2 for limb-sparing surgery of the radius. Metastatic frequency and survival time for metal endoprosthesis were similar to that of amputation with curative intent chemotherapy.

Mechanics of Supplemental Drop Wire and Half-Pin Fixation Elements in Single Ring Circular External Fixator Constructs

OBJECTIVE

Evaluate the effects of supplemental fixation elements on the mechanical properties of a single ring circular fixator construct.

STUDY DESIGN

In vitro mechanical testing.

SAMPLE POPULATION

Five construct configurations (six replicates of each configuration) were used to stabilize a 1.6 cm diameter Delrin rod bone model.

METHODS

Constructs were assembled using 66 mm complete rings, 1.6 mm olive wires, and 3.2 mm diameter half-pins. Construct configurations tested were a base single ring construct, constructs with 1 supplemental drop wire or constructs with 1, 2, or 3 supplemental half-pins. Constructs were loaded in axial compression, caudocranial and mediolateral bending, and torsion. Strain was measured in individual fixation elements during axial loading.

RESULTS

A supplemental drop wire or half-pin significantly increased bending and torsional stiffness. The supplemental half-pin increased caudocranial stiffness significantly more than placing a drop wire. Placing a 2nd or 3rd pin afforded significantly greater increases in construct stiffness in all modes of loading, with 3 half-pin constructs having significantly greater axial and caudocranial stiffness than 2 half-pin constructs. Placing a single supplemental pin induced cantilever bending resulting in angular displacement of the Delrin rod during axial loading and high strain in both the fixation wire secured distal to the ring and the pin. Supplemental half-pins incrementally reduced strain in all fixation elements and resulted in linear displacement of the Delrin rod during axial loading.

CONCLUSION

If using supplemental half-pins as fixation elements, insertion of 2 or 3 pins is preferred over a single pin.

Contralateral bone widening and transfer for limb sparing in a cat

OBJECTIVE

To report on a novel surgical procedure to treat a long segmental tibial defect in a five-year-old 5 kg spayed female Main Coon cat using transverse distraction osteogenesis in the contralateral tibia to create a free autograft.

METHODS

A long free bone segment was created from the cranial half of the normal tibia. A circular external fixator was constructed to give the segment 7 mm of cranial distraction. After 42 days the widened section of tibial bone was removed and transferred to the defect in the contralateral tibia. Locking plates were used to stabilize the graft and to protect the donor tibial sites.

RESULTS

By 27 months, both tibias were healed, all implants had been removed, function was excellent, and the overall limb length was 90% of the normal side.

CLINICAL RELEVANCE

Compared with longitudinal distraction osteogenesis in long bone defects, transverse distraction of a normal bone requires a significantly shorter distraction distance to produce a similar amount of bone. Thus, distraction time is reduced, with less likelihood of significant soft tissue damage. New bone may be more reliably regenerated in a normal limb due to better tissue health, and native bone may be more readily incorporated than allografts in compromised sites. Disadvantages include the increased morbidity, as well as the risk and expense associated with involvement of a normal limb.

Evaluation of outcome and prognostic factors for dogs living greater than one year after diagnosis of osteosarcoma: 90 cases (1997-2008)

OBJECTIVE

To evaluate clinical characteristics, outcome, and prognostic variables in a cohort of dogs surviving > 1 year after an initial diagnosis of osteosarcoma.

DESIGN

Retrospective case series.

ANIMALS

90 client-owned dogs.

PROCEDURES

Medical records for an 11-year period from 1997 through 2008 were reviewed, and patients with appendicular osteosarcoma that lived > 1 year after initial histopathologic diagnosis were studied. Variables including signalment, weight, serum alkaline phosphatase activity, tumor location, surgery, and adjuvant therapies were recorded. Median survival times were calculated by means of a Kaplan-Meier survival function. Univariate analysis was conducted to compare the survival function for categorical variables, and the Cox proportional hazard model was used to evaluate the likelihood of death > 1 year after diagnosis on the basis of the selected risk factors.

RESULTS

90 dogs met the inclusion criteria; clinical laboratory information was not available in all cases. Median age was 8.2 years (range, 2.7 to 13.3 years), and median weight was 38 kg (83.6 lb; range, 21 to 80 kg [46.2 to 176 lb]). Serum alkaline phosphatase activity was high in 29 of 60 (48%) dogs. The most common tumor location was the distal portion of the radius (54/90 [60%]). Eighty-nine of 90 (99%) dogs underwent surgery, and 78 (87%) received chemotherapy. Overall, 49 of 90 (54%) dogs developed metastatic disease. The median survival time beyond 1 year was 243 days (range, 1 to 1,899 days). Dogs that developed a surgical-site infection after limb-sparing surgery had a significantly improved prognosis > 1 year after osteosarcoma diagnosis, compared with dogs that did not develop infections.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of the present study indicated that dogs with an initial diagnosis of osteosarcoma that lived > 1 year had a median survival time beyond the initial year of approximately 8 months. As reported previously, the development of a surgical-site infection in dogs undergoing a limb-sparing surgery significantly affected prognosis and warrants further study.

Canine osteosarcoma: a naturally occurring disease to inform pediatric oncology

Osteosarcoma (OSA) is the most common form of malignant bone cancer in children and dogs, although the disease occurs in dogs approximately 10 times more frequently than in people. Multidrug chemotherapy and aggressive surgical techniques have improved survival; however, new therapies for OSA are critical, as little improvement in survival times has been achieved in either dogs or people over the past 15 years, even with significant efforts directed at the incorporation of novel therapeutic approaches. Both clinical and molecular evidence suggests that human and canine OSA share many key features, including tumor location, presence of microscopic metastatic disease at diagnosis, development of chemotherapy-resistant metastases, and altered expression/activation of several proteins (e.g. Met, ezrin, phosphatase and tensin homolog, signal transducer and activator of transcription 3), and p53 mutations, among others. Additionally, canine and pediatric OSA exhibit overlapping transcriptional profiles and shared DNA copy number aberrations, supporting the notion that these diseases are similar at the molecular level. This review will discuss the similarities between pediatric and canine OSA with regard to histology, biologic behavior, and molecular genetic alterations that indicate canine OSA is a relevant, spontaneous, large animal model of the pediatric disease and outline how the study of naturally occurring OSA in dogs will offer additional insights into the biology and future treatment of this disease in both children and dogs.

Durations of bone consolidation and external fixation after distraction osteogenesis in dogs

OBJECTIVE

To evaluate the influence of epidemiologic, surgical, and mechanical factors on the durations of bone consolidation and external fixation after distraction osteogenesis in dogs.

STUDY DESIGN

Retrospective cohort study.

SAMPLE POPULATION

Dogs (n = 115) that had corrective osteotomy with circular external fixation (CEF; n = 152) METHODS: Medical and radiographic records (1992-2012) of dogs that had corrective osteotomies were reviewed. Putative variables included age, weight, gender, and breed. Surgery date, delay before distraction, rate and duration of distraction, mechanical complications, and frame removal date were recorded. Radiographic data included bone operated, bone length, osteotomy site, bone and limb size at osteotomy site, distraction distance, and CEF frame size and stiffness.

RESULTS

Mean ± SD bone consolidation period was 56 ± 33 days. Mean duration of external fixation was 77 ± 35 days. Twelve fixation failures occurred. Radii healed faster than tibiae (P < .001). Failure of fixation (P = .002) and stiff frames (P = .033) increased duration of bone consolidation. For the tibia, durations of bone consolidation and external fixation decreased with larger bone size relative to limb size (P = .004). For the radius, bone consolidation duration decreased as distraction amount increased (P = .03).

CONCLUSION

Radii healed faster than tibiae. Wearing frames with low or moderate stiffness, the absence of mechanical complications, a larger distraction distance, and a larger bone size accelerated bone consolidation. Optimizing these factors should accelerate bone consolidation and reduce the duration of external fixation.

Accuracy of computed tomography in determining lesion size in canine appendicular osteosarcoma

Multidetector contrast enhanced computed tomography with acquisition of 0.625-mm thick transverse images was used to measure the extent of appendicular osteosarcoma in 10 dogs. The measured length of tumor based on CT was compared to the true length of tumor using histopathology. There was a statistically significant association with good correlation between the true length of osteosarcoma compared to the length of intramedullary/endosteal abnormalities on CT with a mean overestimation of 1.8% (SD = 15%). There was not a statistically significant association between the true tumor length and the length of periosteal proliferation on CT with a mean overestimation of 9.7% (SD = 30.3%). There was a statistically significant association, but with poor correlation, between the true tumor length compared to the length of abnormal contrast enhancement with a mean overestimation of 9.6% (SD = 34.8%). The extent of intramedullary/endosteal CT abnormalities assessed from submillimeter transverse images may be of value in assessing patient candidacy and surgical margins for limb-sparing surgery.

Loss of implant-bone interface following distal radial locking-plate endoprosthesis limb-sparing surgery in a dog

An eight-year-old, neutered female Rottweiler was presented with lameness of seven days duration. Radiographs were consistent with a distal radial bone tumour. Limb-sparing surgery was performed using a commercially available endoprosthesis with a locking bone plate. Histopathological examination of the resected bone revealed an intraosseous fibrosarcoma, and postoperative adjuvant chemotherapy was initiated three weeks after surgery. Despite initial satisfactory limb function, lameness worsened four months after surgery. Radiographs revealed large areas of bone lysis around the proximal and distal screws, leading to significant resorption of the radius and radial carpal bone with subsequent construct failure. Further treatment was declined by the owner and the dog was subsequently euthanased. This case illustrates that implant failure is not necessarily averted by the use of locking (compared with non-locking) implants combined with an endoprosthesis to treat distal radial tumours in dogs.

Use of an interlocking nail-hybrid fixator construct for distal femoral deformity correction in three dogs

Our purpose was to report the use of an interlocking nail-hybrid external fixator construct to correct distal femoral deformities in three dogs. Radiographs, computed tomography and a three-dimensional model were used to plan the surgical procedure. A femoral osteotomy or ostectomy was performed at the level of the centre of rotation of angulation in all three dogs. Angular and rotational deformities were corrected acutely. Distraction osteogenesis was performed to lengthen each femur postoperatively. All three dogs had additional anatomic abnormalities of the affected hindlimb complicating the correction of the distal femoral deformity. While the interlocking nail-hybrid fixator construct allowed for stable distraction of the femur, all three dogs developed complications during the postoperative convalescent period, and each had some degree of residual lameness. Lengthening the femur following acute deformity correction is problematic and additional experimental and clinical studies are warranted to decrease postoperative morbidity and improve functional results.

Effect of zoledronic acid and amputation on bone invasion and lung metastasis of canine osteosarcoma in nude mice

Osteosarcoma (OSA) is an aggressive, highly metastatic and lytic primary bone neoplasm commonly affecting the appendicular skeleton of dogs and children. Current treatment options include amputation of the afflicted limb, limb-sparing procedures, or palliative radiation with or without adjunct chemotherapy. Therapies that inhibit bone resorption, such as the bisphosphonates, may be an effective palliative therapy by limiting the local progression of OSA in those patients that are not viable candidates for amputation. We have developed a mouse model of canine skeletal OSA following intratibial inoculation of OSCA40 cells that spontaneously metastasized to the lungs. We demonstrated that therapy with a nitrogen-containing bisphosphonate, zoledronic acid (Zol), reduced OSA-induced bone lysis; however, Zol monotherapy or in combination with amputation was not effective at inhibiting pulmonary metastasis. While not reaching statistical significance, amputation of the tumor-bearing limb reduced the average incidence of lung metastases; however, this effect was nullified when Zol was added to the treatment protocol. In untreated mice, the magnitude of proximal tibial lysis was significantly correlated with the incidence of metastasis. The data support amputation alone for the management of appendicular OSA rather than combining amputation with Zol. However, in patients that are not viable candidates for amputation, Zol may be a useful palliative therapy for OSA by reducing the magnitude of lysis and therefore bone pain, despite the risk of increased pulmonary metastasis.

Transverse ulnar bone transport osteogenesis: a new technique for limb salvage for the treatment of distal radial osteosarcoma in dogs

OBJECTIVE

To develop instrumentation and a technique for transverse ulnar bone transport osteogenesis in dogs.

STUDY DESIGN

Cadaveric study and in vivo validation (1 dog).

SAMPLE POPULATION

Paired cadaveric antebrachii (n=10 dogs) and 1 live dog.

METHODS

Circular fixator constructs were applied and fitted with reeling or linear motors designed to transport an ulnar segment transversely into a defect created by excising the distal 50% of the ipsilateral radius. A longitudinal osteotomy of the adjacent ulna was created and the segment was transported across the radial defect. Pre- and post-distraction CT scans were used to compare the efficacy of each construct. The procedure was performed unilaterally in a live dog using the reeling motor (RM) construct.

RESULTS

Both constructs effectively transported the ulnar segment into the defect. Subjectively, the RMs were easier to apply and operate. No significant differences were observed in the objective measures of efficacy between the 2 construct types. The live dog produced viable regenerate bone after transverse ulnar bone transport.

CONCLUSIONS

Transverse ulnar bone transport should be considered a potential method for limb salvage in dogs with osteosarcoma (OSA) of the distal radius. The RMs were effective and clinically applicable.

CLINICAL RELEVANCE

Transverse ulnar bone transport osteogenesis affords the benefits of longitudinal radial bone transport osteogenesis, allowing resolution of large longitudinal radial defects in a substantially less time as a result of shortening the transport distance. This would be beneficial when treating conditions such as OSA where minimizing convalescence and maximizing quality of life is a priority.

Ulnocarpal arthrodesis and limb lengthening for the management of radial agenesis in a dog

Radial agenesis was diagnosed in a nine-week-old boxer. An ulnocarpal arthrodesis was performed when six months of age to improve limb alignment and enable weight bearing. When the dog was 10 months old, a hinged circular fixator was applied to the limb to gradually lengthen the ulna and correct angular and rotational deformity. The fixator was removed at 16 months of age. At this time, there was 1.7 cm (6 per cent) shortening of the affected antebrachium-metacarpus and 2.6 cm (15 per cent) compensatory overgrowth of the humerus compared with the contralateral limb. Inability to extend the digits was a complication that improved with physiotherapy. Follow-up at 23 months of age showed good limb use when walking and running. Radiographs of the elbow showed periarticular osteophytes and subcoronoid sclerosis of the ulna.

Intraoperative Radiation for Limb Sparing of the Distal Aspect of the Radius Without Transcarpal Plating in Five Dogs

OBJECTIVES

To evaluate intraoperative irradiation (IORT) as a method of limb spare with preservation of the radiocarpal joint.

STUDY DESIGN

Prospective case series.

ANIMALS

Dogs (n=5) with stage II sarcoma of the distal aspect of the radius.

METHODS

A bone segment containing the tumor was isolated surgically, treated by IORT, reimplanted, and secured by internal fixation. In 1 dog, the postradiation tumor bed was curetted and filled with bone cement. Dogs were administered alternating adriamycin and carboplatin starting 2 weeks after IORT and monitored at regular intervals.

RESULTS

Four dogs had osteosarcoma and 1 had undifferentiated sarcoma. Implant failure (n=3), deep tissue infection (3), and pathologic fracture (3) resulted in amputation (3) or pancarpal plating (2). The dog with undifferentiated sarcoma was euthanatized because of suspected tumor recurrence 4 months postoperatively. Osteotomy healing was documented by radiography (1), histopathology (2), or by direct observation (2).

CONCLUSIONS

A technique for limb-sparing surgery of the distal portion of the radius in dogs using IORT had advantages include healing of the autograft and a source for a perfectly fitting autograft but did not appear to offer any advantage with respect to infection rate. Long-term preservation of the radiocarpal joint was not successful.

CLINICAL RELEVANCE

It was not possible to preserve the function of the radiocarpal joint and so this technique cannot be recommended currently. Further study is needed to evaluate whether or not IORT can be considered in combination with pancarpal plating and possibly curettage and cementation of the tumor to prevent subchondral bone collapse.

Cortical allograft and endoprosthesis for limb-sparing surgery in dogs with distal radial osteosarcoma: a prospective clinical comparison of two different limb-sparing techniques

OBJECTIVE

To compare surgical and oncologic outcome in dogs with osteosarcoma (OSA) of the distal aspect of the radius treated with limb-sparing surgery, using either a cortical allograft or endoprosthesis, and postoperative chemotherapy; and to evaluate predictive factors for outcome.

STUDY DESIGN

Prospective cohort study.

ANIMALS

Dogs (n = 20) with spontaneous, non-metastatic OSA of the distal aspect of the radius.

METHODS

Dogs were prospectively randomized for limb-sparing surgery with either a cortical allograft (n = 10) or endoprosthesis (10) and full-course adjuvant chemotherapy using single or dual agent protocols of cisplatin, carboplatin, and/or doxorubicin. Surgical (intraoperative findings, postoperative infection, construct failure) and oncologic (local tumor recurrence, metastasis, survival) outcomes were compared. The influence of intraoperative and postoperative variables on surgical and oncologic outcome were evaluated.

RESULTS

No clinically significant differences in surgical and oncologic outcome were detected between groups. The percentage of radius replaced by the implant was significantly greater in the endoprosthesis group (60.9% compared with 48.6%, P = .008). Median survival time (MST) for dogs with construct failure, regardless of implant type, was 685 days and significantly greater than MST of dogs without construct failure (322 days, P = .042; hazard ratio [HR] 16.82). Median metastasis-free interval and MST (685 days versus 289 days; P = .034, HR 24.58) were significantly greater in dogs with postoperative infection. Disease-free and overall limb-salvage rates were 70% and 85%, respectively. Overall MST was 430 days.

CONCLUSIONS

For dogs with OSA of the distal aspect of the radius, a cortical allograft or endoprosthesis can be used for limb-sparing surgery. Construct failure and postoperative infection significantly improve survival time regardless of implant type.

CLINICAL RELEVANCE

An endoprosthesis is an attractive alternative to cortical allografts for limb-salvage of the distal aspect of the radius in dogs because surgical and oncologic outcomes are similar, but the endoprosthesis is an immediately available off-the-shelf implant which is not complicated by the bone harvesting and banking requirements associated with cortical allografts. Mechanisms whereby postoperative infection improves survival time requires further investigation and, if elucidated, may provide the opportunity to improve the outcome of dogs and humans with OSA.

Cortical Bone Graft and Endoprosthesis in the Distal Radius of Dogs: A Biomechanical Comparison of Two Different Limb-Sparing Techniques

OBJECTIVE

To compare the biomechanical properties of cortical bone and surgical steel endoprosthesis for limb-sparing surgery of the distal radius in dogs and evaluate the role of the ulna in providing stability to the reconstructed limb.

STUDY DESIGN

Cadaveric biomechanical study.

ANIMALS

Twelve pairs of normal canine thoracic limbs.

METHODS

Paired limbs were divided into 4 groups: endoprosthesis and cortical bone graft, with and without preservation of the ulna. In each limb pair, the distal segment of the radius resected from the limb to be reconstructed with an endoprosthesis was used as the cortical bone graft in the contralateral limb. The ulna was resected en bloc with the radius and at the same level as the radial osteotomy in limbs where the ulna was not preserved. Limbs were tested in axial loading until failure. The load-deformation curve was used to acquire the biomechanical properties of each construct, which were compared using 2-way ANOVA. Failure modes were compared descriptively.

RESULTS

Limbs reconstructed with the endoprosthesis had significantly greater yield load, energy at yield, and ultimate load compared with limbs reconstructed with a cortical bone graft. There were no significant differences in either energy to failure or stiffness between the 2 constructs. Preservation of the ulna did not significantly improve any of the biomechanical properties tested with either endoprosthesis or cortical bone graft constructs. The modes of failure in all 4 groups were variable and inconsistent.

CONCLUSIONS

Limbs reconstructed with an endoprosthesis were biomechanically superior to limbs reconstructed with a cortical bone graft in axial loading to failure. Preservation of the ulna is not required to improve the stability in axial compression after limb-sparing surgery of the distal radius.

CLINICAL RELEVANCE

The endoprosthesis may provide another option for limb-sparing surgery of the distal radius in dogs. It has potential advantages when compared with cortical bone grafts, including better biomechanical performance and resistance to implant failure in axial compression, immediate availability, and no requirement for bone banking facilities. The ulna can be resected en bloc with the radius without having a negative impact on construct stability. En bloc resection of the ulna and radius may decrease the risk of local tumor recurrence after limb-sparing surgery.