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.     

Biomechanical comparison of cortical radial graft versus ulnar transposition graft limb-sparing techniques for the distal radial site in dogs

OBJECTIVE: To compare the biomechanical properties of radial graft (RG) versus ulnar transposition graft (UTG) limb-sparing techniques in the dog. STUDY DESIGN: Cadaveric study. ANIMALS: Six pairs of normal canine thoracic limbs. METHODS: In each pair of limbs, 1 limb was subjected to the RG technique and the other to the UTG technique. Limbs were tested in axial loading until failure. Modes of failure and biomechanical properties were compared between the 2 groups. Percent coverage of the metacarpal bone by the plate was retrospectively compared between the limbs that failed by fracture of the metacarpal bones and those that did not. RESULTS: RG limbs had significantly greater stiffness, yield load, maximum load, maximum energy, and post-yield energy. All UTG limbs failed by cranial bending of the plate. Half of the RG limbs failed by caudal bending of the plate and half by fracture of the third metacarpal bone at the distal end of the plate. Limbs with <80% plate coverage of the metacarpal bone were significantly more likely to fail by metacarpal fracture. CONCLUSIONS: The RG technique was biomechanically superior to the UTG technique under the conditions studied. At least 80% plate coverage of the metacarpal bone should be achieved. CLINICAL RELEVANCE: Exercise restriction and coaptation bandages should be considered for patients undergoing the UTG technique to minimize potential biomechanical complications.     

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.     

Ipsilateral vascularised ulnar transposition autograft for limb-sparing surgery of the distal radius in 2 dogs with osteosarcoma

Canine osteosarcoma is the most commonly diagnosed primary bone tumour in the dog, affecting mainly large and giant breed dogs with the predilection site being the metaphysis of long bones, specifically the distal radius, proximal humerus, distal femur and proximal tibia and fibula. Treatment options are either palliative or curative intent therapy, the latter limb amputation or limb-sparing surgery together with chemotherapy. This article describes the use of an ipsilateral vascularised ulnar transposition autograft as well as chemotherapy in 2 dogs with osteosarcoma of the distal radius. Both dogs showed minimal complications with the technique and both survived over 381 days following the surgery. Complications seen were loosening of the screws and osteomyelitis. The procedure was well tolerated with excellent limb use. This technique is indicated for use in cases with small tumour size that have not broken through the bone cortex.     

Use of an ipsilateral vascularized ulnar transposition autograft for limb-sparing surgery of the distal radius in dogs: an anatomic and clinical study

OBJECTIVE: To develop a surgical technique for using the distal aspect of the ulna as a transposition autograft in a distal radial defect and to assess patency of vascular supply and viability of the distal ulna in a heterotopic position. STUDY DESIGN: Cadaveric study and clinical cases. ANIMALS: Twenty-two normal canine thoracic limbs; 3 dogs with distal radial osteosarcoma. METHODS: The arteries and veins of 12 limbs were injected with latex. Barium sulfate suspension was injected into the brachial artery of 10 other limbs after removal of the distal radius only (n = 2), ulna transposition (UT) (n = 6), or no procedure (n = 2). The distal ulna grafts were then harvested and decalcified in formic acid. The grafts were cut into 3-5 mm transverse sections and radiographed with a nonscreen film system to determine filling of intramedullary vessels with barium suspension. UT was performed in 3 dogs with distal radial osteosarcoma. Bone scintigraphy was performed 2-7 days after surgery to assess viability of the transposed ulna graft. RESULTS: Angiography confirmed patency of the caudal interosseous artery in all but 2 limbs in which the UT technique was performed; however, barium-filled vessels were identified in the medullary cavity of all ulnar grafts. Scintigraphy confirmed graft viability in the 3 dogs, all of which had good to excellent limb function. CONCLUSIONS: The distal aspect of the canine ulna can be used as a vascularized transposition autograft to replace distal radial defects, and viability can be maintained. CLINICAL RELEVANCE: The UT technique appears to be an acceptable limb-sparing technique for dogs with tumors of the distal aspect of the radius.     

Vascularized ulnar bone grafts for limb-sparing surgery for the treatment of distal radial osteosarcoma

The objective of this retrospective study was to compare vascularized free or roll-in ulnar bone grafts for limb-sparing surgery in dogs with radial osteosarcoma with the cortical allograft, metal endoprosthesis, or distraction osteogenesis techniques. Overall, the ulnar graft techniques used in this study demonstrated excellent healing properties. Complications included recurrence of the tumor in 25% (2/8) of the dogs, metastasis in 50% (4/8) of the dogs, implant loosening in 37.5% (3/8) of the dogs, implant failure in 12.5% (1/8) of the dogs, and infection in 62.5% (5/8) of the dogs. Mean survival time was 29.3 mo (range, 9 to 61 mo). The mean metastasis-free interval was 33.67 mo (range, 8 to 54 mo). Tumors recurred locally in two dogs at 10 mo and 20 mo postoperatively. This study yielded similar long-term complications as other limb-sparing options (such as cortical allografts and metal endoprostheses) and allowed dogs to bear weight on the operated limb with acceptable limb function. More research is needed regarding specific healing times for ulnar vascularized grafts, time until implant removal, and the extent of radial bone that could ultimately be replaced by the ulna.     

Microvascular transplantation of a free omental graft to the distal extremity in dogs

OBJECTIVE: To assess the survival of a free omental graft applied to an experimentally created wound on the distal extremity in dogs. STUDY DESIGN: A free omental graft was evaluated as a primary method of treatment for dogs with distal extremity wounds in an experimental model. ANIMALS OR SAMPLE POPULATION: Five adult intact female mixed breed dogs weighing 21.8 kg to 25.0 kg. METHODS: A free omental graft was harvested from the abdomen and transferred to a wound bed overlying the medial aspect of the tibia. A microvascular anastomosis was performed between the graft vessels and vessels at the recipient site. Daily clinical assessment of graft viability was performed. Angiography and 99mTechnetium labeled macroaggregated albumin (99mTc MAA) scintigraphic perfusion scans were performed on either day 4, 5, or 7. Postmortem collection of tissues for histopathologic analysis was performed immediately after imaging. Total operative time and graft ischemia time were evaluated for effects on graft survival. RESULTS: Two of seven grafts survived to the end of the study, three of seven grafts failed because of ischemia, and two of seven grafts failed because of self-trauma. There was no clinically significant morbidity associated with the abdominal portion of the procedure. Because of the small number of surviving grafts, the effects of operative time and graft ischemia time could not be statistically evaluated. CONCLUSIONS: Microvascular transplantation of a free omental graft can result in a viable tissue covering of a distal extremity wound, however, the failure rate is unacceptably high. CLINICAL RELEVANCE: A free omental graft may not have sufficient durability to be an acceptable wound covering by itself. Further studies combining omentum with a skin graft or other tissues may result in a clinically useful technique.     

A histopathological comparison of two techniques for soft palate resection in normal dogs

Eighteen dogs were used to compare histopathological findings following excision of the soft palate using either a bipolar sealing device or a carbon dioxide laser. Histopathological comparisons were done at 48 and 96 hours after soft palate resection. Mean depths of tissue injury at 96 hours were 3.5 and 3.33 mm for bipolar sealing device and carbon dioxide laser, respectively. Control of hemorrhage was excellent in all dogs, and none of the dogs developed signs of respiratory compromise after soft palate resection. Using the bipolar sealing device for soft palate resection was significantly faster than using the carbon dioxide laser, although both techniques were fast.     

A comparison of two pamidronate dosing protocols on bone turnover in normal dogs and dogs with osteosarcoma

Introduction: Dogs with appendicular osteosarcoma (OSA) excrete higher concentrations of urine cross‐linked N‐telopeptide of type I collagen (NTx) than normal dogs. NTx is a specific biochemical marker of osteoclastic activity. Pamidronate is a bone‐modulating agent that exerts potent inhibitory effects on osteoclasts. The use of pamidronate is currently being evaluated for the management of osteolytic bone pain in dogs with appendicular osteosarcoma. Despite pamidronate's increasing usage in veterinary oncology, optimal dosing has yet to be determined. Commonly utilized dosages range from 1–2 mg/kg, given intravenously (IV) as a 2‐hour constant rate infusion every 28 days. The purpose of this prospective study was to compare the biological activity of two pamidronate doses (1 mg/kg vs. 2 mg/kg) in the suppression of urine NTx excretion in normal dogs and dogs with appendicular osteosarcoma. Methods: Seventeen OSA dogs receiving single‐agent pamidronate as palliative therapy were evaluated. Group 1A (n = 10) received a dose of 1 mg/kg and group 2A (n = 7) received a dose of 2 mg/kg IV. Urine NTx level were measured at day 0 and 28 using a commercial ELISA (Ostex International). Urine NTx level were also measured in 6 normal dogs: Group 1B (n = 3) received a dose of 1 mg/kg and group 2B (n = 3) received a dose of 2 mg/kg. In normal dogs, urine NTx levels were recorded weekly for six consecutive weeks. Results: In dogs with osteosarcoma, greater reductions in urine NTx excretion from baseline values were demonstrated at 2 mg/kg versus 1 mg/kg (57% and 23%, respectively). Likewise, in normal dogs, urine NTx excretion was suppressed to a greater extent with a dosage of 2 mg/kg versus 1 mg/kg (69% and 23%, respectively). Conclusion: Pamidronate possesses biologic activity in both normal dogs and in dogs with osteosarcoma, as assessed by reductions in urine NTx excretion. Based upon reductions in urine NTx excretion, a dosage of 2 mg/kg appears more effective than 1 mg/kg.     

Microcrack density and length in the proximal and distal metaphyses of the humerus and radius in dogs

OBJECTIVE: To compare microcrack density and length in the proximal and distal metaphyses of the humerus and radius in dogs. SAMPLE POPULATION: Left humerus and radius from each of 10 dogs of medium to large size. PROCEDURE: Metaphyseal specimens were bulk stained in 1% basic fuchsin in graded alcohols and embedded in methylmethacrylate. For quantification of fatigue-induced microscopic damage, transverse sections were prepared from proximal and distal metaphyseal regions, and length and density of microcracks were determined, using light microscopy. RESULTS: Bone region, age, and body weight were not significantly associated with microcrack density or length. CONCLUSIONS AND CLINICAL RELEVANCE: The hypothesis that fatigue-induced injury (increased microcrack density and length) caused by cyclic loading associated with daily activity is greater in bone regions prone to development of osteosarcoma was not supported by data from this study.     

Angiographic examination of the forelimb in dogs with abnormal growth of the distal radius and ulna

Brachial angiograms were performed on 13 forelimbs from 12 dogs with growth-plate disorders of the distal radius and ulna. Eight angiograms were considered normal and five showed failure of individual arteries to fill, in two cases associated with hypertrophy of other vessels. Angiography was too insensitive to identify the small vessels which supplied the growth plates.     

Evaluation of a free vascularized medial tibial bone graft in dogs

OBJECTIVE: To develop a free vascularized tibial bone graft based on the periosteal saphenous blood supply. STUDY DESIGN: Preliminary anatomic study of medial tibial blood supply. In vivo comparison of a vascularized and avascular tibial bone graft. ANIMALS: Nine canine cadavers; 14 healthy adult dogs that weighed 25 to 32 kg. METHODS: An anatomic study of the vascular supply of the medial aspect of the tibia was performed using the Spalteholz technique. A bone graft consisting of the medial aspect of the tibia was transferred to a mandibular defect as a vascularized graft in 7 dogs and as an avascular graft in 7 dogs. Bone scans were performed to evaluate graft perfusion. Radiographic evaluation of the mandibles and tibias was performed. The dogs were killed after 60 days, five mandibles from each group were examined histologically, and two from each group were evaluated using the Spalteholz technique. RESULTS: The saphenous vascular pedicle provides vascular perfusion to the medial tibial cortex. Bone scans and radiographic evaluations were consistent with viable bone in the vascularized grafts, and nonviable bone in the avascular grafts. Histological examination revealed live, healing bone in vascular grafts and necrotic bone in avascular grafts. Spalteholz evaluation revealed many small arborizing vessels in the vascular grafts and no organized vasculature in the avascular grafts. CONCLUSIONS: The vascularized medial tibial cortical bone graft survived and proceeded to bony union in the mandibular body defect more readily than the avascular graft in this experimental model. CLINICAL RELEVANCE: A vascularized medial tibial bone graft is a suitable free graft for use in reconstructing bone defects in dogs.     

Complications after two transphyseal bridging techniques for treatment of angular limb deformities of the distal radius in 568 Thoroughbred yearlings

Reasons for performing study: Surgical correction of carpal angular limb deformities by growth retardation is commonly undertaken with a screws and tension band wire loop technique (S&W) or a single transphyseal screw (STS). This study compares complications after S&W and STS bridging in the distal radius of Thoroughbred yearlings. Objective: To compare the prevalence of complications serious enough to require follow‐up radiographs following either S&W or STS surgery for growth manipulation in the distal radius of Thoroughbred yearlings. Methods: Medical records and radiographs from Thoroughbred yearlings (age range 261–457 days) treated for carpal angular limb deformities at a single hospital over 2 years were reviewed. Each of the techniques was used exclusively during a single year. The complication threshold criterion for inclusion was the need for nonroutine radiographs of the operated site anytime after implant insertion or removal. Results: Of 568 horses, 253 received S&W and 315 received STS. Horses were of similar age at the time of surgery for STS and S&W. Single transphyseal screws were left in place for a significantly shorter amount of time (16 days). Sex, the limb(s) treated and medial vs. lateral placement were not significantly different between techniques. Complications included physitis post implant removal, metaphyseal collapse post implant removal, infection, overcorrection and seroma formation severe enough to require radiography. Physitis and metaphyseal collapse occurred significantly more frequently with STS compared with S&W. Infection, overcorrection and seromas were not significantly different between techniques. Conclusion: The STS and S&W techniques are both viable treatment options for correction of carpal angular limb deformities. However, horses treated with the STS technique have a significantly increased risk of developing physitis or metaphyseal collapse. Potential relevance: Horses treated with STS bridging have a significantly increased risk of developing the post correction complications of moderate to severe physitis and metaphyseal collapse compared with horses treated with S&W bridging.     

A comparison of five different bone resorption markers in osteosarcoma-bearing dogs, normal dogs, and dogs with orthopedic diseases

BACKGROUND: Various bone resorption markers in humans are useful for supporting the diagnosis of malignant skeletal pathology, with certain bone resorption markers appearing to be more discriminatory for detecting cancer-induced osteolysis than others. Canine osteosarcoma (OSA) is characterized by focal bone destruction, but a systematic investigation for determining which bone resorption marker best supports the diagnosis of OSA in dogs has not been reported. HYPOTHESIS: Dogs with OSA will have increased concentrations of bone resorption markers compared with healthy dogs and dogs with orthopedic disorders. Differences will exist among various bone resorption markers for their ability to support the diagnosis of malignant osteolysis in dogs with OSA. ANIMALS: Single time point, cross-sectional, cohort study including dogs with OSA (n = 20) or orthopedic disorders (n = 20) and healthy dogs (n = 22). METHODS: Basal concentrations of urine and serum N-telopeptide (NTx), urine and serum C-telopeptide (CTx), and urine deoxypyridinoline (DPD) were compared among all 3 groups. RESULTS: Compared with healthy dogs and dogs with orthopedic disorders, urine NTx, serum NTx, and serum CTx concentrations were significantly increased in dogs with OSA. For urine NTx and serum NTx, the calculated lower and upper 95% confidence limits in dogs with OSA did not overlap with dogs diagnosed with orthopedic disorders or healthy dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Of the markers evaluated in this study, urine NTx and serum NTx appear to be the most discriminatory resorption markers supporting the diagnosis of focal malignant osteolysis in dogs with OSA.     

A comparison of two techniques for the determination of serum bone-specific alkaline phosphatase activity in dogs

Bone-specific alkaline phosphatase (BALP) shows potential as a marker of bone formation in the dog. Recent studies have indicated that serum BALP may provide a useful, non-invasive indicator of skeletal health in dogs, and as a diagnostic and prognostic marker in the management of dogs with musculoskeletal or metabolic disorders. Two assay techniques (one based on wheatgerm lectin precipitation followed by a simple enzymatic reaction, the second on a specific enzyme-linked immunoassay) were used to measure serum levels of BALP in 35 dogs of different ages.As expected, BALP concentrations decreased with age. For the enzymatic assay, mean (+/-SD) serum concentrations of BALP activities were 100.3 (+/-11.6) U/liter in dogs under 1 year of age, 25.3 (+/-6.8) U/L in dogs 1 to 2 years of age, 16.5 (+/-7.3) U/L in dogs 2 to 3 years of age, 14.3 (+/-5.6) U/L in dogs 3 to 7 years of age, and 12.3 (+/-4.8) U/L in dogs aged 8 years and older. Corresponding results from the immunoassay were 56.3 (+/-9.8) U/L, 10.7 (+/-4.5) U/L, 7.0 (+/-2.5) U/L, 6.7 (+/-3.6) U/L and 7.0 (+/-2.9) U/L. There was excellent correlation between the results from the two assay techniques (r = 0. 96; P < 0.0001). The correlation between BALP and total ALP activities was poor (r = 0.20 for enzymatic BALP, r = 0.31 for immunoreactive BALP), indicating that total ALP should be considered unreliable as an indicator of BALP activity in canine serum. The immunoassay demonstrated acceptable (13 per cent) cross-reactivity with the liver isoform of ALP.The commercial immunoassay kit is simple and provides fast results. Although the wheatgerm lectin/enzymatic technique is preferred in situations where the activities of all three isoforms of ALP are required, the immunoassay should be considered whenever the activity of BALP is the focus of interest.     

Bone plate fixation of distal radius and ulna fractures in small- and miniature-breed dogs.

Bone plate fixation was reviewed in 29 distal radial fractures of small- and miniature-breed dogs. Twenty-two fractures in 18 dogs were available for follow-up. Number of complications and return to function were evaluated. Complications occurred in 54% of the fractures. Catastrophic complications occurred in 18% of fracture repairs with follow-up, while minor complications occurred in 36%. Sixteen (89%) of 18 dogs had a successful return to function. Bone plate fixation is a successful repair method for distal radius and ulna fractures in small-breed dogs, compared to previously reported methods.     

Assessment of postoperative pain after unilateral mastectomy using two different surgical techniques in dogs

Background

There are few studies reporting pain and postoperative analgesia associated with mastectomy in dogs. The aim of this study was to evaluate postoperative pain after unilateral mastectomy using two different surgical techniques in the dog.

Findings

Twenty female dogs were assigned (n=10/group) to undergo unilateral mastectomy using either the combination of sharp and blunt dissection (SBD) or the modified SBD (mSBD) technique, in which the mammary chain is separated from the abdominal wall entirely by blunt (hand and finger) dissection except for a small area cranial to the first gland, in a prospective, randomized, clinical trial. All dogs were premedicated with intramuscular acepromazine (0.05 mg/kg) and morphine (0.3 mg/kg). Anesthesia was induced with intravenous ketamine (5 mg/kg) and diazepam (0.25 mg/kg), and maintained with isoflurane. Subcutaneous meloxicam (0.2 mg/kg) was administered before surgery. Postoperative pain was evaluated according to the University of Melbourne pain scale (UMPS) by an observer who was blinded to the surgical technique.. Rescue analgesia was provided by the administration of intramuscular morphine (0.5 mg/kg) if pain scores were >14 according to the UMPS. Data were analyzed using t-tests and ANOVA (P>0.05). There were no significant differences between the groups for age, weight, extubation time, and duration of surgery and anesthesia (P>0.05). There were no significant differences for postoperative pain scores between groups. Rescue analgesia was required in one dog in each group.

Conclusions

The two surgical techniques produced similar surgical times, incidence of perioperative complications and postoperative pain. Multimodal analgesia is recommended for treatment of postoperative pain in dogs undergoing unilateral mastectomy.