Microsurgery

Microsurgery uses an operating microscope and specialized instruments to repair small nerves, blood vessels, and tissue in the hand and upper limb.

Microsurgery is not a single operation but a technique: operating under a microscope, with instruments and sutures finer than a human hair, on structures that cannot be repaired reliably by eye. It makes it possible to join blood vessels under a millimetre across, align the internal architecture of a nerve, and move living tissue from one part of the body to another with its own blood supply. In hand surgery it underpins replantation, free tissue transfer, nerve grafting and reconstruction after tumour or trauma. Its defining characteristic is that the margin for error is measured in fractions of a millimetre, which is why it is done slowly and by a surgeon who does it regularly.

Patients whose problem cannot be solved without working at this scale: amputation of a digit, hand or limb where replantation is being considered; soft-tissue loss exposing tendon, bone or joint that will not heal with a simple graft and needs a flap; nerve injury requiring grafting or nerve transfer; vascular injury or compromised circulation to a digit; complex trauma with injury to several tissue types at once; and reconstruction after excision of a tumour. Suitability depends on the condition of the tissue, the time since injury, and general health — smoking, uncontrolled diabetes and peripheral vascular disease all measurably reduce the chance of a free tissue transfer surviving, and are addressed beforehand where there is time.

The operation is done under general anaesthesia and is long — several hours is usual, and complex reconstruction can take considerably longer. The damaged tissue is debrided until only healthy tissue remains, because a repair into unhealthy tissue fails. Bone is stabilised first to give a stable framework, then vessels, nerves and tendons are repaired in a planned sequence under the microscope. Arterial and venous anastomoses are performed with sutures typically in the 9-0 to 11-0 range, and flow is confirmed before moving on. Where tissue must be imported, a flap is raised with its artery and vein, transferred, and its vessels joined to recipient vessels at the defect. The result is monitored continuously afterwards, because the window in which a failing anastomosis can be salvaged is short.

An inpatient stay is usual after free tissue transfer or replantation, commonly five to seven days, with the circulation to the transferred tissue checked frequently in the first 48 to 72 hours, when most failures occur. The limb is elevated and kept warm, and smoking and caffeine are prohibited because both cause vessel spasm. Protected movement under hand therapy begins once the reconstruction is stable, usually in the first two weeks. The functional recovery then follows whichever structures were repaired — bone union at six to twelve weeks, tendon rehabilitation over three to six months, and nerve regeneration over six to eighteen months. Full recovery after complex microsurgical reconstruction is measured in a year or more, and often involves further planned procedures.

The specific risk of microsurgery is failure of the anastomosis, causing partial or complete loss of the transferred or replanted tissue; salvage depends on detecting it early, and a proportion cannot be salvaged. Bleeding, haematoma, infection and wound breakdown occur. Donor-site morbidity — scarring, numbness, weakness or, for some flaps, a functional deficit — is part of the trade and is discussed specifically. Prolonged anaesthesia carries its own risks. Stiffness, cold intolerance and incomplete sensory recovery are common in the long term. Further surgery is frequently required, whether planned in stages or to refine the result. Replantation in particular restores a part, not a normal part: a replanted digit that is stiff and painful can function worse than a well-managed amputation, and that comparison is made honestly before proceeding.