PowerPoint Presentation

GOOD morning

Microvascular flaps

ContentsIntroductionHistory Advantages and disadvantagesPlanning- instrument setup, vessel preparation vascular anastomosis techniqueAnostomosis failure and its treatmentRecent advancesMicrovascular flapsconclusionReferences

IntroductionWith the introduction of micro vascular tissue transfer in the early 1970s, a new universe of reconstructive possibilities was opened. Meanwhile, this technique has proven to be one of the most important developments for our patients.Reconstruction of congenital, developmental, or acquired head and neck defects remains a signicant challenge for the oral and maxillofacial surgeon. In no other anatomic location is the quality of both form and function of the reconstructed part more critically appraised by the patient, surgeon, and society.

Reconstruction of head and neck defects was previously limited by the paucity of local tissues available to reconstruct complex wounds. The development of pedicled aps during the 1970s and 1980s (deltopectoral, pectoralis major)changed head and neck surgery and quickly became the workhorse procedures of the reconstructive surgeon.

History1950Jacobsen and Suarez anastomoses in animals1959 Seidenberg free jejunum segments to repair pharyngoesophageal defects. 1973 Daniels and Taylor free flap First free cutaneous flap 1976 Baker and Panje first free flap in head and neck cancer reconstruction Groin flap pedicled on the circumflex iliac artery

Advantages of free tissue transfer

Two team approachImproved vascularity and wound healingLow rate of resorptionDefect size of little consequencePotential for sensory and motor innervationPermits use of osseointegrated implants

Wide variety of available tissue types Large amount of composite tissue Tailored to match defect Wide range of skin characteristicsMore efficient use of harvested tissue Immediate reconstruction

THE ADVANTAGES OF MICROVASCULAR FREE FLAPS

Includes: (1) predictable composite tissue transfer from a variety of donor sites at a single stage (immediate reconstruction); (2) radiation tolerance; and (3) minimal donor site morbidity.

It has been shown to carry success rates of greater than 90% in experienced hands Oral Maxillofacial Surg Clin N Am 20 (2008) 521526

The shortcomings of Pedicled aps :the pedicled transfer of bone-containing soft tissue aps is unpredictable and limited because of extreme arcs of rotation;(2) large, axial pattern rotational aps, such as the pectoralis major myocutaneous ap, commonly result in unsightly contours and an unfavorable donor site defect; and (3) the use in midface and upper facial reconstruction is limited.

General consideration

Includes:Patient age, Tobacco use, Diabetes, Prior radiation, and prior operative procedures.

1. age:Patient age has not been demonstrated to be a contraindication for free tissue transfer in many studies. The success rates of free tissue transfer in patients over 65 has been shown to be similar to a younger. however, perioperative medical morbidities are more common in the older population.

2. Effect of radiation on vessels include perivascular fibrosis, endothelial damage, and microvascular occlusion, which can impair the quality of recipient vessels

3. In microvascular tissue transfer, studies have demonstrated that patients with diabetes are not at increased risk for ap failure or abnormal healing of the anastomosis as long as normoglycemia is maintained

4. Prior operative: Inadequate length of pedicle can be an issue when there are no appropriate vessels in the area of reconstruction. Most commonly this is remedied with interpositional vein grafting;

12

PLANNING FOR MICROVASCULAR SURGERY 1. Vascular status: selection of proper artery and vein: may require angiographic imaging/Duplex colour-flow Doppler 2. Wide exposure: Microsurgery is extremely dicult to perform deep in the neck without adequate access 3.Donor site: functional and cosmetic morbidity 4. Patient: Medical and oncologic status

Planning begins with the patients history and physical examination. Specic details regarding prior surgery, trauma, radiation, or disease process must be elicited in the preoperative phase.

13

INSTRUMENT SETUP :

Baby satinsky vascular clamp

VESSEL PREPARATIONArteries need to have strong pulsatile flowcut until it flows. Cut back beyond branches or ligate them if sufficiently distant from the anastomosis site.Intimal inspectionDilationRemoving the adventitia

IRRADIATED VESSELSTechnically more difficulteffects appear specific to arteriesVessel wall fibrosis, increased wall thickness, more intimal dehiscenceNo reported difference in outcome of microvascular anastomoses (Nahabedian MY, et al., 2004, Kroll SS, et al 1998)Microvascular anastomoses tolerate XRT well long-term (Foote RL., et al., 1994)Require careful handling, cut off clot (teasing thrombi may denude vessel wallsticky walls), smaller suture, needle introduced from lumen to outside wall (to pin intima to wall)

MICROVASCULAR ANASTOMOSISPrepare vesselsEvaluate vessel geometryTrim, irrigate, dilatePartial flap insetting (bony cuts and plating done at donor bed, if necessary)Arterial vs. venous anastomosis first with early or delayed unclamping of first vessel showed no difference. (Braun, et al., 2003)Anastomosis of remaining vesselComplete flap insetting

MICROVASCULAR SURGICAL TECHNIQUETrim adventitia2-3mmGentle handling (no full-thickness)Trim free edge, if neededDissect vessels from surrounding tissuesIrrigate and dilateHeparinized salineMechanical dilation (1 times normal paralyses smooth muscle)Chemical dilation, if necessarySuturing

MICROVASCULAR SUTURE TECHNIQUE3 guide sutures (120 degrees apart)Perpendicular piercingEntry point 2x thickness of vessel from cut endEqual bites on either sideMicroforceps in lumen vs. retracting adventitiaPull needle through in circular motionSurgeons knot with guide sutures, simple for othersAvoid backwalling2 bites/irrigation

SUTURE TECHNIQUE

Vessel size mismatch

Laminar flow vs. turbulent flow2:1, 3:1 end-to-side

End-to-end vs. End-to-sideRecent reports indicate end-to-side without increase in flap loss or blood flow rate.End-to-side overcomes size discrepancy, avoids vessel retraction, and IJ may act as venous siphon.End-to-side felt best when angle is less than 60 degrees (minimize turbulence)Vessel incision should be elliptical, not slitCan use continuous suture technique

End-to-side Anastomosis

Continuous suture techniqueMay significantly narrow anastomosisMay be used on vessels >2.5 mmDecreases anastomosis time by up to 50%Decreases anastomosis leakageMost commonly used for end-to-side anastomoses with large vessels

MECHANICAL ANASTOMOSISDevicesClipsCouplerLaserResultsIncreased efficiency and speed, use in difficult areasPatency rates at least equal to hand-sewn (Shindo, et al 1996, De Lorenzi, et al 2002)Can be used for end-to-end or end-to-side (DeLacure, et al 1999)Poorer outcome with arterial anastomosis20-25% failure (Shindo, et al 1996, Ahn, et al 1994)

VEIN GRAFTSUsed in situation where pedicle is not long enough for tension-free anastomosisUsually harvested from lower extremity (saphenous system)Valve orientation is necessaryAvoid anastomosis at level of vein valveKeep clamps in place until both anastomoses sewnPrognosis for success controversial (Jones NF, et al., 1996, German, et al. 1996)

2730% failure (vs. 5%) in 1993 study, German 1996 showed no difference, but revisions greater in vein graft cases (15% vs. 9%)

Anastomotic failure93-95% success rate expectedVenous thrombosis:Arterial thrombosis 4:1, ateriovenous loop, tobacco use significant factors (Nahabedian M., et al, 2004) Tobacco use as contribution controversial (4/5 failures in Nahabedian study - venous thrombosis)

Age, prior irradiation, DM (well-controlled), method of anastomosis, timing, vein graft, and specific arteries/veins not felt to contribute to failure rate

Anastomotic Failure--timeline15-20 minutes8 days Thin vs. thick flaps

Thrombus formationInjury to endothelium and media of vesselMechanical vs. thermalError in suture placementBackwall or loose suturesEdges not well-aligned (most common in veinsmost common site of thrombus)Intimal discontinuity with exposure of mediaOblique sutures, large needles, tight knotsInfection

VESSEL SPASMCausesTraumaContact with bloodVasoconstrictive drugs Phenylephrine--dose causing 30% increase in arterial pressure shows no effect on flap circulation (Banic A, et al., 1999) NicotineTemperature, dryingTreatmentWarmthXylocainePapavarine, thorazineVolume repletion

Treatment for anastomotic failureRevision of anastomosesExploration of woundWound care

StatisticsRevisions successful in 50%Revisions less successful after first 24-48hr>6 hrs of ischemia leads to poor survival12 hrs of ischemia leads to no-flow phenomenonAfter 5 days almost all flaps in rabbit model survived with loss of artery or vein (but not both)this is rational for other modalities after 48 hours

Post-operative careAttention to wound careFlap monitoring Nothing around neck that might compress pedicleAntibiotics No pressure/cooling of flap

Flap monitoringClinical flap checksMost commonly usedWarmthColorPin prickWound monitoring (hematoma, fistula)

MechanicalDoppler Implanted vs. external vs. color flow

Clinical flap monitoringNormal exam:Warm, good color, pinprick slightly delayed with bright red bloodVenous occlusion (delayed):Edema, mottled/purple/petechiae, tensePinprick immediate dark blood, wont stop

Arterial occlusion (usually