20. Surgery under magnification: Microsurgery / Microvascular Surgery

20. Surgery under magnification
Microsurgery / Microvascular surgery

1. Craftsmen have used magnification in their work long before specialist surgeons took advantage of this optical science. A watch maker using a mono-ocular lens or a goldsmith using rudimentary spectacles with convex lenses has been a familiar sight for more than a century at least. The identification of inherent defects in diamonds was done with the help of magnification and is still called “sighting” and when diamonds came to be cut with diamond tipped tools these tips were also fabricated with the help of magnification.
2. While almost all surgical specialists now use magnification to facilitate their work the one important difference between them and the plastic surgeons is that the former almost always use it only to improve their vision and only occasionally use it for reconstruction for e.g. ossicles in the ear. Because reconstruction is the raison d’etre of a plastic surgeon (and therefore called a plastic and reconstructive surgeon), he / she uses magnification not only to see better but also to repair and reconstruct tissue. A plastic surgeon who uses a microscope to repair and reconstruct is called a microsurgeon and this speciality is called microsurgery.
3. Successful replantation of limbs and the description of axial pattern flaps in the seventies of the last century formed the background of development of microsurgery which pari passu was accompanied by better optics, use of fibre-optic lights and last and probably equally important, the fabrication of ultra thin needles and suture materials.
4. Magnification can be achieved with spectacles, mounted with convex lenses or with two convex lenses at some distance which gives a compounded magnification but has the drawback of losing some clarity in the peripheral field of vision. With new technology the space between the two convex lenses has come to be occupied by multiple reflective surfaces which has improved the definition and the sharpness of the image. The weight of the viewing system increases with each additional sophistication but it also improves comfort appropriate working distance. The last mentioned is traditionally called a loupe. Most surgeons will order a loupe suitable for their inter-pupillary distance and their refractory error. This is called a custom made loupe; though off the shelf loupes are also available. By a general consensus it is now accepted that a good loupe may allow the surgeon to perform routine microvascular work and it is helpful if the assistant is also wearing a loupe though a microscope delivers the ideal circumstance for surgery.
5. A proper compound microscope with an in-built fiber optic light system and even better, a diploscope where the assistant can also view the operating field is considered ideal for performing any procedure particularly if the vessel or nerve size is in the range of around 1 or 2 mm. A fiber optic light is less injurious to tissue as compared to normal overhead operation theatre lights and such fiber optic lights are now incorporated within the optics of the microscope. In addition a camera is also provided to record the procedures. The modern lights in theaters are also now sufficiently modified not to produce abnormal heating of tissue. A recent addition is a battery operated LED light which can be worn on the head together with the loupes. When using a microscope the surgeon’s and assistant’s comfort is a very important consideration particularly to avoid any strain on the back or the neck because the procedure might last several hours and the head may not be taken away from the microscope for long durations during the procedure.
6. Most surgeons who transfer flaps start their dissection with a loupe and then as the vessels are identified switch to a microscope. The speed of dissection can be increased if liga clips are used to achieve hemostasis. When two teams are working the recipient area can be prepared simultaneously if the donor and the recipient areas are spaced apart and this consideration is important while planning a flap.
7. The actual anastomosis must be preceded by removal of adventitia over the minute vessel. There is a learning curve in the procedure in which the adventitia is removed just enough so that the tunica media is not traumatized particularly in the vein where this layer is much thinner. Only a very small area adjacent to anastomotic site is cleared completely of the adventitial tissue so that the needle goes through the media alone for a better approximation and this area should have enough width to allow it to be everted so that the actual site of approximation of the blood vessels is somewhat external to the lumen. This avoids the greatest danger to the anastomosis, that of formation of a thrombosis or a clot. This atraumatic method must also ensure that the throw or the sweep of the needle is pointed upwards rather than towards the lumen. The suture size is determined by the diameter of the vessel, 8/0 to 11/0, and is usually made of nylon.
8. During the anastomosis the vessels are steadied by atraumatic clamps. This allows a bloodless field. The area is subject to gentle, intermittent irrigation with saline and the vessels are usually placed over a material which enhances a contrast for a better visualization of vessels. Prior to suturing the vessels they are cleared of any clots, if present, and they may have to be dilated gently with a tip of a needle holder or a very fine blunt tipped needle or a cannula.
9. That the vessels require to be clamped during anastomosis to prevent blood flow interfering with the anastomosis is well accepted. But which side should be anastomosed first, the arterial or the venous is not quite clearly established. If the arterial side is done first and later the veins are clamped to facilitate anastomosis, there is a danger that a flap may get congested but on the other hand blood flow through the veins starts almost immediately after their anastomosis. If the venous side is completed first, there is a time lag till the arterial side is completed leading to a possible early thrombotic episode near the venous anastomotic site. This is particularly relevant in a muscle flap. Both protocols have their adherents. In another method clamps are released simultaneously only after both the anastomosis are performed. As to whether two veins need to be anastomosed when two venae commitantis are available there are too many variables in comparing series of cases to come to a firm conclusion. Whether two or three stay sutures should be employed prior to the actual anastomosis also remains a matter of choice of the individual surgeon and does not appear to have any bearing on the final result. Generally speaking the trend is to take intermittent sutures than a single continuous stitch. An end to side anastomosis is preferred when there is a mismatch between the vessels to be anastomosed.
   

   Steps in end to side anastomosis. Above left: Area of anastomosis stripped of adventatia. Vessels show inequality in size. Top right: Areteriotomy made. Bottom left: Suture of posterior wall completed. Bottom right: Anterior wall sutured and anastomosis is complete. Clinical pictures for corroboration below.

   

   Photographs and illustrations courtesy: Gautam Biswas, PGI, Chandigarh

   

   A standard end-to-end anastomosis. How the vessels are prepared is shown in illustrations above. In this case two veins have been used. Photograph courtesy: Sitaram Prasad, Mumbai

   A flow through flap is one where there is a vascular compromise in the distal part of a limb in addition to a defect in the proximal part which requires flap cover and when a flap with its vessels is used to not only cover the defect but also to re-establish vascular continuity. In these circumstances as well, an end to side anastomosis might have to be performed because there is a disparity between the flap vessel and the interrupted major vessel in the limb.

10. When the recipient vessels are of a poor quality either due to disease or because a healthy segment of a recipient vessel (as in cases of trauma) is too far from the site where flap cover is required, a vein graft may have to be employed to bridge the gap in both the arterial as well as the venous side. This increases the number of anastomosis by two fold and as a consequence the rates of re-exploration as well as failures are likely to increase.
    

    Above left – An end to end and a end to side anastomosis, Above centre – Two ends of an artery held with clamps to be bridged with a vein graft, Above-right – Tell tale sign of anastomotic failure: clot around the anastomosis, Bottom left – A thrombus clearly seen in the vein graft, Bottom right – Vein graft replaced with a new vein graft. These pictures are included not only to show how to diagnose a block but also to stress that the incidence might be slightly higher with vein grafts because of the increased number of anastomosis. Photographs courtesy: Samir Kumta, Mumbai

11. A piece of tissue being transferred as a free flap cannot be compared in its vascularity to when it is in situ. Surgical islanding takes away its collateral perfusion from its surroundings and also denervates its sympathetic supply. The latter is to the surgeon’s advantage because it leads to reduction in resistance. All surgical cutting however is a stimulus to vasospasm, both in the capillary network as well as the main vessels. Vasospasm of the vessels that are being anastomosed is usually a passing phase and reverts to normal if enough patience is shown during which the vessel is observed or it is very gently irrigated with a solution of local anaesthetic. But here in a strange paradox, a very dilute solution of this local anaesthetic can produce a spasm while higher concentrations relieve the spasm and effect dilatation.
12. No concrete evidence is available to indicate that pharmacological intervention helps in survival of flaps or that events leading to a flap failure can be reversed by any specific agent. Except in very very few cases where the reasons for failure of a flap remain unresolved, in the vast majority an actual failure or an impending failure is caused by thrombogenic activity or formation of a clot, more on the arterial side than the venous side and is almost always in the intimal area which may have been damaged during the dissection or at the time of suturing. Failure of flaps has been discussed at some length in chapter 14 titled ‘The How and Why of the Failure of Flaps”.
13. Most surgeons take a front or anterior suture first and then use it to flip the vessel and insert the other sutures. The only exception is when the recipient vessel is situated at a depth and cannot be flipped easily, when the suturing begins from behind forwards. After the anastomosis is completed clamps are released to confirm that the anastomosis is leak proof. If there is a leak an additional suture is essential. A naturally sealed leak may mean clotting and this clot can enlarge and block the anastomotic site. When a satisfactory anastomosis is completed the flow in the anastomosed vessel can be checked by applying clamps and releasing them to actually watch the flow which is easy to see. The lie of the anastomosis site is confirmed to be without tension and, if in the extremity, the limb is moved a little to gauge if it affects the anastomotic site. Meticulous haemostasis is achieved, a waiting period of several minutes is spent and the flow in the vessel is checked again and only then is closure begun. During closure the area over the anastomotic site is closed last to confirm that the closure has not had any untoward pressure effects on the anastomosis by checking again for a normal flow. A drain is frequently used under the flap. After closure the transferred part is dressed in a manner to allow inspection of the flap and is immobilized suitably. At the earliest sign of a failure of a free flap re-exploration of the flap is essential. The blocked anastomosis may need to be redone or a blood clot might have to be evacuated which may have caused abnormal pressures. Unlike other local, regional or distant flaps a free flap either survives fully or necroses completely and the success of salvage is inversely proportional to the time elapsed from when the first signs of failure are recognized.
14. For some reason manual anastomosis remains the first choice of most microsurgeons though very fine ring like appliances are available which allow a faster anastomosis and have a marginally higher success rate. Robots are still in early stages of experimentation for small vessel anastomosis. Though conduits are now universally used for obstructed coronary vessels and temporary artificial AV fistulae are now not infrequently created by tubes in patients undergoing dialysis for short duration, similar very fine conduits have still not been used in reconstructive microsurgery. But with nano-technology making progress and a graphene sheet of only single atoms arranged in a row having been created, that kind of advance might soon be available in the form of a conduit in reconstructive microsurgery.

The compiler wishes to thank Dr. Subramaniam Iyer, Amrita Institute, Kochi and Dr. Gautam Biswas, PGIMER, Chandigarh for the help in constructing this chapter.

Phil Sykes, our archivist from England adds that the major difference between vascular surgery per se and microvascular surgery lies in the fact that often vascular surgery is performed on patients who have vascular disease. In contrast microvascular surgery is usually performed on an average in healthier individuals and there is always the option of using vein grafts should the zone of trauma or any extensive laceration should necessitate such a graft. He stresses that such grafts should be used even when there is the slightest doubt about the donor and recipient vessels.

Robert Acland : A short biography

As to who performed (and where) the first free tissue transfer with the help of magnification will continue to arouse interest. But for his life long dedication to the speciality of microsurgery, Robert Acland’s name will always occupy a place of distinction. Robert Acland, a British plastic surgeon was one of the earliest to recognize the value of microsurgical technique (in the midst of general skepticism) and doggedly pursued his interests, first in London (England), then in Glasgow (Scotland) at the Canniesburn Hospital and later from the mid-1970’s in Louisville (Kentucky, USA) where he is now the head of the renowned fresh tissue dissection laboratory. His early papers included the importance of gentle technique, identification of patency across anastomotic sites, delicate vascular clamps which could hold stay sutures, fabrication of very fine needles and instruments and all this basic work would be effectively and rapidly transferred in a clinical setting for patients. Recently he has pioneered a new technique of anatomical videography that gives the viewer a clear three dimensional understanding of the spatial relationship of tissue.

– Phil Sykes and Ravin Thatte