1887

Microsurgery

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Abstract

Although the use of operating loupes and surgical microscopes has been commonplace in human neurosurgery, ophthalmic surgery and reconstructive surgery for decades, experience with microvascular free tissue transfer is limited in veterinary surgery. Despite this fact, the utility of microvascular free tissue transfer for one-stage reconstruction of difficult problems, particularly of the distal limbs and the oral cavity, has been established. Early reconstruction of traumatic tissue loss using vascularized tissue is feasible, as is functional and cosmetic reconstruction after ablative cancer surgery. Tissues transferred in this manner are referred to as ‘microvascular free tissue transfers’, ‘free flaps’, ‘microvascular free flaps’, or ‘autogenous vascularized grafts’. Topics discussed are as follows: Microvascular technique; and Specific flaps in the dog and cat. : End-to-end anastomosis; End-to-side anastomosis; Raising a trapezius muscle flap; Raising a latissimus dorsi muscle flap; and Harvesting a vascularized ulnar graft.

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Figures

Image of 10.2
10.2 An operating microscope is needed for successful microvascular surgery. This microscope is fitted with a ‘beam splitter’, allowing two surgeons to view the same surgical field with stereoscopic vision. A foot pedal control facilitates adjustment of the microscope, leaving the surgeon’s hands free. This foot pedal has adjustments for zoom, focus, and an ‘X–Y’ axis that allows repositioning of the field of vision.
Image of 10.3
10.3 Fine microsurgical instruments are required for atraumatic handling and dissection of small vessels. An assortment of fine adventitial scissors, vessel dilators, jewellers’ forceps and vascular clips is shown. Fine suture materials and needles are also required: the recommended sizes are shown in Figure 10.4 .
Image of 10.5
10.5 Vascular approximating clamps are available in various sizes and as single or double clamps. It is important that clamp size is matched to vessel size to ensure security of the vessel during anastomosis, but to avoid vessel injury from excessive clamp pressure.
Image of 10.6
10.6 The surgical approach to flap harvest. All pertinent anatomical landmarks are identified prior to incision. Landmarks and proposed incision for harvest of the trapezius myocutaneous flap are indicated. Skin incision is made and small bleeding vessels are carefully controlled using electrocautery. Dissection is begun distant from and continued towards major vascular pedicles. Vascular pedicles must be identified and preserved during flap dissection. The vascular pedicle is skeletonized after its identification. As much length of the vascular pedicle as possible should be harvested. Final appearance of the dissected myocutaneous flap, showing the vascular pedicle and its associated muscle and skin territories. (Illustrated using a cadaver specimen.)
Image of 10.7
10.7 Necrotic and heavily contaminated tissue must be excised prior to wound reconstruction. Aggressive debridement and open wound management has converted this heavily contaminated forelimb injury to a clean contaminated state over a 3-day period.
Image of 10.8
10.8 End-to-end arterial anastomosis results in diversion of arterial flow away from distal structures normally nourished by the recipient artery. End-to-side arterial anastomosis allows revascularization of the transferred tissue while maintaining distal arterial flow. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
Image of 10.9
10.9 The venous occlusion test is a safe and reliable method to assess patency and the venous anastomoses. Gentle occlusion of the recipient vein ‘downstream’ from the anastomosis results in distension of the vein ‘upstream’. Rapid distension reveals a patent arterial anastomosis. Rapid relief of venous distension following release of the vein is compatible with a patent venous anastomosis. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
Image of 10.10
10.10 The empty and refill test can be used to test both arterial and venous patency. The vessel is grasped gently using two jewellers’ forceps ‘downstream’ from the anastomosis. Blood is ‘milked’ from a vessel segment. Release of the ‘upstream’ forceps should result in rapid refill of the emptied segment.
Image of 10.11
10.11 Harvest of the fifth digital footpad flap. The incision is initiated laterally over the fifth metatarsal bone and curves distally to end on the dorsal aspect of the coronary band. The phalangeal bones are dissected extraperiosteally. Care is necessary to avoid damage to neurovascular structures in the surrounding soft tissues. The vascular pedicle, consisting of the superficial dorsal metatarsal vein (SDMV), the deep plantar metatarsal artery (DPMA) and deep plantar metatarsal nerve (DPMN), is identified. The broken line indicates the level of skin incision through the interdigital skin to complete flap formation. Appearance of the dissected flap, as viewed from the deep surface. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
Image of 10.12
10.12 Anatomical landmarks for dissection of the carpal footpad flap. Circumferential skin incision around the footpad is extended proximally, parallel to the cephalic vein (CV). Deep subcutaneous dissection is initiated from the lateral aspect until the small arterial branch to the footpad is identified. The accessory carpal bone (AC) and the transverse carpal ligament (TCL) are shown. After dissection through the carpal canal, the caudal interosseous artery (CIA) and a superficial branch of the ulnar nerve (UN) are identified as they course between the transverse carpal ligament and the accessory metacarpeum ligament (AML). The pedicle closely parallels the tendon of the superficial digital flexor muscle (SDF). Venous drainage is provided by the cephalic vein. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
Image of 10.13
10.13 Shear stresses acting upon weightbearing incisions frequently result in partial dehiscence and flap migration. Minor revisional procedures are often required after footpad transfer.
Image of 10.14
10.14 Radiograph of the vascular territory of the prescapular branch of the superficial cervical artery. The vascular pedicle is in the centre. The trapezius muscle is shown in the lower left, a segment of the omotransversarius muscle in the centre, and the cutaneous territory in the upper portion.
Image of 10.15
10.15 Transferred muscle rapidly undergoes neurogenic atrophy. Bulky appearance of a trapezius muscle transfer with overlying skin graft immediately after transfer. Appearance of the same flap, in profile, 6 weeks after transfer.
Image of 10.16
10.16 Perfusion patterns of the forelimb in a specimen after injection of barium into the brachial artery. The ulna derives its vascular supply from the caudal interosseous artery, which arises from the short common interosseous artery and extends distally in the interosseous space between the radius and the ulna.
Image of Vessel ends in approximation, held in a double microvascular approximating clamp.
Vessel ends in approximation, held in a double microvascular approximating clamp. Vessel ends in approximation, held in a double microvascular approximating clamp.
Image of Loose adventital tissue is excised from the vessel ends.
Loose adventital tissue is excised from the vessel ends. Loose adventital tissue is excised from the vessel ends.
Image of Suture placement at 10 and 2 o’clock.
Suture placement at 10 and 2 o’clock. Suture placement at 10 and 2 o’clock.
Image of The ‘front wall’ is completed.
The ‘front wall’ is completed. The ‘front wall’ is completed.
Image of The ‘back wall’ is brought into view by inverting the approximating clamp.
The ‘back wall’ is brought into view by inverting the approximating clamp. The ‘back wall’ is brought into view by inverting the approximating clamp.
Image of Closure is complete and the approximating clamp has been removed.
Closure is complete and the approximating clamp has been removed. Closure is complete and the approximating clamp has been removed.
Image of With the recipient vessel secured in a double microvascular approximating clamp, adventitial tissue is dissected and an opening made for the donor vessel.
With the recipient vessel secured in a double microvascular approximating clamp, adventitial tissue is dissected and an opening made for the donor vessel. With the recipient vessel secured in a double microvascular approximating clamp, adventitial tissue is dissected and an opening made for the donor vessel.
Image of Blood is flushed from the recipient vessel using heparinized saline.
Blood is flushed from the recipient vessel using heparinized saline. Blood is flushed from the recipient vessel using heparinized saline.
Image of Simple interrupted sutures are placed at the 3 and 9 o’clock positions.
Simple interrupted sutures are placed at the 3 and 9 o’clock positions. Simple interrupted sutures are placed at the 3 and 9 o’clock positions.
Image of Retraction of the donor vessel in one direction facilitates closure of one side of the anastomosis. Retraction in the opposite direction allows completion of the anastomosis.
Retraction of the donor vessel in one direction facilitates closure of one side of the anastomosis. Retraction in the opposite direction allows completion of the anastomosis. Retraction of the donor vessel in one direction facilitates closure of one side of the anastomosis. Retraction in the opposite direction allows completion of the anastomosis.
Image of Anatomical landmarks. X = position of direct cutaneous artery. Dashed line = proposed incision. The dog’s head is in a direction towards upper right.
Anatomical landmarks. X = position of direct cutaneous artery. Dashed line = proposed incision. The dog’s head is in a direction towards upper right. Anatomical landmarks. X = position of direct cutaneous artery. Dashed line = proposed incision. The dog’s head is in a direction towards upper right.
Image of Elevating the trapezius muscle along its dorsal and fascial attachments. Vascular branches are identified on the deep surface of the muscle. Branches extending into deep cervical musculature are ligated.
Elevating the trapezius muscle along its dorsal and fascial attachments. Vascular branches are identified on the deep surface of the muscle. Branches extending into deep cervical musculature are ligated. Elevating the trapezius muscle along its dorsal and fascial attachments. Vascular branches are identified on the deep surface of the muscle. Branches extending into deep cervical musculature are ligated.
Image of After identification of the vascular pedicle, cranial and ventral dissection of the trapezius muscle is completed.
After identification of the vascular pedicle, cranial and ventral dissection of the trapezius muscle is completed. After identification of the vascular pedicle, cranial and ventral dissection of the trapezius muscle is completed.
Image of Skeletonized vascular pedicle. Perfusion is maintained with the flap protected in moist sponges until the recipient site is prepared.
Skeletonized vascular pedicle. Perfusion is maintained with the flap protected in moist sponges until the recipient site is prepared. Skeletonized vascular pedicle. Perfusion is maintained with the flap protected in moist sponges until the recipient site is prepared.
Image of Landmarks for dissection. Ventral dotted line = proposed skin incision. The head is to the left.
Landmarks for dissection. Ventral dotted line = proposed skin incision. The head is to the left. Landmarks for dissection. Ventral dotted line = proposed skin incision. The head is to the left.
Image of Elevation of the skin reveals the superficial aspect of the latissimus dorsi muscle.
Elevation of the skin reveals the superficial aspect of the latissimus dorsi muscle. Elevation of the skin reveals the superficial aspect of the latissimus dorsi muscle.
Image of The muscle is dissected from its origin towards its insertion. Several segmental intercostal vessels must be ligated and transected near the muscle’s origin. The thoracodorsal vascular pedicle is shown on the deep surface of the muscle near its insertion.
The muscle is dissected from its origin towards its insertion. Several segmental intercostal vessels must be ligated and transected near the muscle’s origin. The thoracodorsal vascular pedicle is shown on the deep surface of the muscle near its insertion. The muscle is dissected from its origin towards its insertion. Several segmental intercostal vessels must be ligated and transected near the muscle’s origin. The thoracodorsal vascular pedicle is shown on the deep surface of the muscle near its insertion.
Image of Arcuate skin incision over caudolateral aspect of forelimb.
Arcuate skin incision over caudolateral aspect of forelimb. Arcuate skin incision over caudolateral aspect of forelimb.
Image of Fasciotomy of extensor and flexor muscle groups facilitates their evaluation. Vascular branches to the extensor muscles are identified laterally and mark the level of the medially located common interosseous vessels.
Fasciotomy of extensor and flexor muscle groups facilitates their evaluation. Vascular branches to the extensor muscles are identified laterally and mark the level of the medially located common interosseous vessels. Fasciotomy of extensor and flexor muscle groups facilitates their evaluation. Vascular branches to the extensor muscles are identified laterally and mark the level of the medially located common interosseous vessels.
Image of Medial dissection of the ulna is carried into the interosseous space, taking care to preserve a myoperiosteal soft tissue cuff surrounding the bone.
Medial dissection of the ulna is carried into the interosseous space, taking care to preserve a myoperiosteal soft tissue cuff surrounding the bone. Medial dissection of the ulna is carried into the interosseous space, taking care to preserve a myoperiosteal soft tissue cuff surrounding the bone.
Image of Osteotomy
Osteotomy Osteotomy
Image of Dissection of the specimen has been completed. The short common interosseous vascular pedicle is shown.
Dissection of the specimen has been completed. The short common interosseous vascular pedicle is shown. Dissection of the specimen has been completed. The short common interosseous vascular pedicle is shown.
Image of Distal ulnar graft. The caudal interosseous vessels form the vascular pedicle.
Distal ulnar graft. The caudal interosseous vessels form the vascular pedicle. Distal ulnar graft. The caudal interosseous vessels form the vascular pedicle.

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