The anatomic basis of a free vascularized bone graft based on the canine distal ulna

Ulnocarpal arthrodesis in a cat

A nine-year-old cat was presented with non-weight-bearing lameness of the right forelimb subsequent to an old fracture of the antebrachium previously treated by external stabilisation. Radiography showed severe atrophic non-union of the distal third of the radius and carpal luxation. Ulnocarpal arthrodesis was performed using a uniplanar external fixator. Follow-up radiography showed that bone fusion was slow but without complication. After 16 weeks, the external fixator was removed, and a Robert-Jones bandage was applied for one month. From postoperative week 2 onwards, the animal progressively made use of the limb in a weight-bearing capacity. At the last examination, one year postoperative, no lameness was observed.

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.

Comparison of the effects of the CO2 surgical laser and conventional surgical techniques on healing and wound tensile strength of skin flaps in the dog

OBJECTIVE

To determine if CO(2) laser was superior to conventional surgical techniques (CST) for creation of skin flaps in dogs as determined by hemostasis, wound healing, and wound tensile strength.

STUDY DESIGN

In-vivo model

ANIMALS

Six large, mixed-breed dogs.

METHODS

On each dog's trunk, 3 pairs of identical, dorsally based, pedicled skin flaps were created and sutured back into position. Based on a Latin Square design, flaps on one side were created with a CO(2) laser and on the other side by CST. Intraoperative hemorrhage was measured by weighing sponges used to absorb blood. On days 7, 10, and 14, specimens from the flap-skin junction and the central portion of each pair of flaps were collected. Specimens were subjected to tensile strength testing and histologic examination to evaluate wound healing.

RESULTS

Mean (+/- standard error of mean [SEM]) hemorrhage was significantly less (P =.02) with CO(2) laser (4.70 +/- 1.37 g) than CST (10.82 +/- 1.37 g). Wound tensile strength (N/m(2)) after CST (0.49 +/- 0.049) was significantly greater (P =.01) than with CO(2) laser (0.17 +/- 0.049). Laser incisions had partial necrosis of the wound edges and a more extensive inflammatory response; however, healing of the wound beds were similar regardless of technique.

CONCLUSIONS

The CO(2) laser provided better intraoperative hemostasis than CST. However, overall healing and increase in tensile strength of the skin-flap junction of the flaps created by the laser may be delayed during the first few weeks of wound healing.

CLINICAL RELEVANCE

Skin flaps used to repair large skin defects in dogs can be created and elevated with a CO(2) laser. In areas of increased skin mobility or tension, skin flaps created with CO(2) laser may be more susceptible to complications such as dehiscence, and care should be taken to minimize these complications.

Malignant transformation of an aneurysmal bone cyst in a dog

OBJECTIVE

To report malignant transformation of an aneurysmal bone cyst in a dog.

STUDY DESIGN

Case report.

SAMPLE POPULATION

Client-owned dog.

RESULTS

A 5-year-old male Labrador retriever was diagnosed with an aneurysmal bone cyst of the distal aspect of the right ulna. Surgical curettage resulted in remission of clinical signs for 33 months. Because of recurrence of clinical signs, a distal ulnar ostectomy was performed. Histopathologic examination of the excised specimen revealed a moderately differentiated chondrosarcoma at the level of the bone cyst. Limb function was normal for 17 months until a subcutaneous mass, determined to be a chondrosarcoma, occurred at the level of the shoulder. A right forequarter amputation was performed.

CONCLUSIONS

Aneurysmal bone cysts are benign but may be transformed into a malignancy after surgical manipulation. Complete surgical excision should be attempted where possible. In this case, distal ulnar ostectomy was an effective means of preserving limb function and preventing local recurrence of chondrosarcoma.

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.

Experimental carpal reverse-flow pedicle vascularized bone grafts. Part I: the anatomical basis of vascularized pedicle bone grafts based on the canine distal radius and ulna

We investigated the detailed extraosseous and intraosseous vascular anatomy of the distal radius and ulna in 55 pairs of canine forelimbs. Ten specimens were used for compartment identification. One hundred specimens were investigated after intra-arterial injection with red latex or Batson's compound. The extraosseous vascular network, including the nutrient artery location, was studied by delicate dissection and soft tissue digestion. Two superficial and 4 deep arteries were found on the dorsal aspect, with constant relationships to the retinaculum. On the palmar aspect, bony nutrient vessels rose from the branches of the radial artery (descriptive anatomy). The vascular supply of the canine distal forelimb was very consistent and enabled the design of 5 vascularized pedicle bone grafts similar to those described in humans (applied anatomy). These reverse-flow pedicle grafts may be placed in the carpus, allowing the canine forelimb to serve as an experimental model for the study of vascularized carpal bone grafting. (J Hand Surg 2000; 25A:34-45.

Microvascular free tissue transfer: results in 57 consecutive cases

OBJECTIVE

To evaluate the outcomes and complications in a consecutive series of animals undergoing microvascular reconstructive procedures at two veterinary institutions.

STUDY DESIGN

Retrospective study.

ANIMALS OR SAMPLE POPULATION

A total of 44 client-owned dogs and one red-necked wallaby.

METHODS

The medical records of all animals undergoing reconstructive microsurgical procedures at the Western College of Veterinary Medicine and Michigan State University were reviewed. Microvascular flap survival and related complications were described. Statistical analysis was performed to determine the significance of relationships between operative factors and outcome.

RESULTS

A total of 57 microvascular procedures were performed on 55 animals. Reconstruction was required after trauma in 42 animals, after ablative cancer surgery in 11 animals and for correction of congenital tissue aplasia in I animal. Donor tissues included the superficial cervical cutaneous, medial saphenous fasciocutaneous or musculofasciocutaneous, caudal superficial epigastric cutaneous, trapezius muscle or musculocutaneous, caudal sartorius muscle, latissimus dorsi muscle or musculocutaneous, cranial abdominal myoperitoneal, carpal footpad, digital footpad, and vascularized ulnar bone flaps. A total of 53 of 57 flaps (93%) survived. There was a significant relationship between flap failure and level of assistant surgeon experience (P < .05). Latissimus dorsi flaps were significantly more likely to fail when compared with pooled data from all other flap types (P < .01).

CONCLUSIONS

The success of microvascular tissue transfer in this case series compares favorably with those reported in human reconstructive microsurgery. Both the primary and assistant surgeon should be practiced in microsurgical technique. Failure of latissimus dorsi flaps was not likely caused by an inherently deficient flap design, but was more likely attributed to the location and severity of trauma at the recipient site, the difficulty in isolating suitable recipient vessels for anastomosis or the absence of a trained assistant surgeon during these procedures. Clinical Relevance-This retrospective study documents the successful application of microvascular technique in a series of clinical cases requiring tissue reconstruction.

Transplantation of the canine distal ulna as a free vascularized bone graft

An autogenous free vascular bone graft of the canine distal ulna was evaluated. The vascularity of the graft was based on a musculoperiosteal sheath supplied solely by the caudal interosseous artery and vein. Four autogenous heterotopic (ulna to tibia) vascular transfers were performed. Two avascular transfers were performed to provide baseline criteria from which the success of vascularized transfers could be assessed. Clinical lameness evaluation, serial radiographs, bone scintigraphy, and sequential fluorochrome bone labeling were performed after surgery in both vascular and avascular transfers. All dogs were free of lameness in the donor limb by the 26th postoperative day. Serial radiographs revealed rapid graft incorporation and hypertrophy in all vascularized grafts and severe bone resorption in nonvascularized grafts. Histology, microangiography, and evaluation of fluorochrome bone labels were performed 90 days after surgery to determine graft viability, incorporation and temporal remodeling patterns. Microangiography and fluorochrome assessment complemented the histological findings. Based on these findings the distal ulnar bone graft was determined to be both viable and structurally adequate for selected cases of long bone reconstruction.