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Digital Replantations
Komatsu and Tamai performed the first successful replantation of a fully severed thumb in 1965. Since then, the field of digital replantation has evolved considerably. There has been extensive progress in terms of the development of suture materials, microsurgical instruments and microscopes. There are now organized microsurgical courses to specifically train surgeons to perform this type of surgery. This combined progress in microsurgical training of surgeons and equipment development has led to a steady improvement in success rates. Digital replantation is now performed regularly in specialized centers. The increase in number of cases has propelled the field forward and advanced its goals. Surgeons no longer just aim for the long-term survival of the finger. Instead, digital replantations are now planned with the aim of restoring global function to the patient's injured hand.
Microsurgical Equipment
Instruments
The basic microsurgical instrument tray should contain a needle holder, a pair of microscissors and two smooth fine-tip forceps. Modern instruments are counterbalanced. Instead of being short, they are long enough to rest in the surgeon's first webspace. Rounded handles are preferred because this cylindrical shape allows for more precise handling of the instrument. The needle holder, for example, can be held like a pencil. This type of grip assists in the axial rotation of the instrument, which is necessary to guide the needle through the thin vessel walls of a digital artery ( Fig. 15.1 ). Microsurgical instruments should be protected in their own dedicated storage and sterilization case. They should be handled and cleaned only by specially trained operating room personnel.
Suture Materials
Monofilament nylon is the most common suture material used. It has the appropriate level of tissue reactivity and knot-holding ability for use in microsurgery. Microsutures are now available in different sizes and needle configurations. Three suture sizes (9-0, 10-0 and 11-0) on 50- to 100-µm taperpoint needles are sufficient to address all digital replantations. The needles are “3/8th of a circle,” which is an ideal shape for the repair of small vessels. Generally, repair of the palmar digital artery at the base of an adult finger is carried out with 9-0 monofilament nylon sutures with 100-µm needles, whereas 10-0 sutures with 75-µm needles are used for digital artery repair in the vicinity of the proximal interphalangeal (PIP) joint. All very distal digital artery anastomoses in the fingertip are performed with 11-0 sutures on 50-µm needles. This size of suture is suitable for repair of very thin-walled central pulp artery and pulp veins.
Accessory Instruments
Accessory Instruments: Irrigation Needles, Vessel Clamps, Backgrounds, Spears
Aside from the instruments and sutures, several items are helpful when performing microsurgery ( Figs. 15.2–15.4 ).
Blunt-tip needles (see Fig. 15.2, top ) are used for endoluminal flushing of the vessels. They are mounted on a syringe containing diluted heparin solution. It is possible to bend the needles to 60 degrees between the thumb and index finger without obstructing the lumen. This way the most ergonomically suitable instrument is obtained. When the syringe is held between the thumb and index finger of the person performing the surgery, the needle readily becomes oriented in the axis of the vessel. Alternatively, endoluminal irrigation can also be done with a 5-mL syringe mounted on a 24-gauge Angiocath.
Vascular clamps are used to temporarily occlude the vessel during surgery without damaging the vessel wall. Disposable single-use clamps are made of plastic and do not refract light. Vessel clamps are available as single or double clamps (see Fig. 15.2 , bottom ). Double clamps are two single clamps linked by a sliding bar and are used to help align and oppose the two vessel ends being repaired. These clamps are manipulated by mosquito forceps. Double clamps take up space and may not be useful when only short vessel ends are available for repair. For vessels 1 mm in size, closing pressure of the clamp should not exceed 30 g/mm.
A colored background or contrast is often used to isolate the vessel ends from surrounding tissue and blood. It improves visualization of vessel ends and facilitates handling of suture by preventing it from sticking to or getting lost in adjacent tissues. It can be made of any material (plastic or rubber) in contrasting color (green or blue) that is cut to size and slid under the vessel or nerve ends. The hands of the surgeon performing microsurgery are stabilized by resting the ulnar borders on a white-covered cushion. This cushion is assembled using a stack of drapes covered by a white penny towel. The white color facilitates visualization of the fine black sutures used (see Fig. 15.3 ).
Microsponges (“spears”) are also useful (see Fig. 15.4 ). The surgical field is often flooded by blood oozing from adjacent areas despite use of a tourniquet. Irrigation of vessel ends also causes pooling of fluid that complicates suture handling. Because suctioning is prohibited around fine vessels, these triangular and compact sponges provide a good substitute for the use of gauze.
Microscope
The operating microscope provides the much-needed visualization that allows precise suture placement in 1- to 2-mm vessels ( Fig. 15.5 ).
Two face-to-face optical systems allow the surgeon and his assistant to sit facing each other and work in the same operating field. Its positioning in the field is facilitated by a multijoint arm and a steady suspension system. Foot-controlled magnification and focusing help keep the operating field steady when shifting from high to low magnification, such as when shifting from needle insertion (requires high magnification) to knot tying (easier at low magnification). Sterile drapes are available to allow surgeons to position the optics at their desired spot.
Preservation of Amputate
Tolerance to Ischemia
Successful replantations of amputated fingers with cold ischemia time of 24–30 hours have been reported. This is made possible by proper preservation of the amputated part. The referring center must be given specific instructions on how the amputated finger should be transported. It can tolerate 6 hours of warm ischemia time and up to 12 hours of cold ischemia because it contains no skeletal muscle. Devascularized striated muscle undergoes irreversible cell damage after 4 hours in ambient temperature. It should be emphasized that cooling is currently the only effective method to increase tolerance to ischemia.
Sterility
No time should be lost trying to clean the amputated finger prior to dispatch. A simple rinse with saline is enough. If saline is not available, such as at the accident site, the part should be placed directly into a sealed container. Cleaning can be performed once the patient and the part reach the hospital. Bleeding from the stump end is controlled by compression of the finger and hand elevation. A tourniquet is not necessary and is dangerous, especially if applied without any deliberate time monitoring. Blind ligation of vessels is also not advised; it may cause further vessel injury.
Packaging
The amputate should be wrapped in a saline-soaked gauze and placed in a sealed container. The sealed container is then placed on ice. The amputated part itself should not be frozen or placed directly on ice to avoid freezing injury to its cells and microvasculature.
Surgical Team and Preoperative Preparation
Surgical Team
Once the patient and the amputated finger arrive in the emergency room, the replantation team should discuss with the patient the indications and contraindications for replantation. Each patient will have different functional demands, and it is the surgeon's role to help the patient decide whether replantation should be attempted. Once decided, the replantation team can divide into two subteams. While one team is preparing the patient for surgery, the other team led by the performing surgeon takes the amputated part to the operating theater, where it is debrided and prepared. This preparation can be performed with the part continuously cooled by a sterile saline ice slush placed under layers of penny towels. One should remember to take an x-ray of the amputated finger to decide on the technique of shortening and fixation or fusion. Critical structures are tagged with small vascular clips to avoid frustration and save time later on. The team with the patient should assess the patient's fitness for prolonged anesthesia and help the patient decide between general and regional anesthesia, keeping in mind that the operation can last for 4 to 6 hours for a single finger replant.
Anesthesia
The vast majority of digital replantations can be performed under axillary block (see Chapter 1 ), with general anesthesia being reserved for very young children and for locoregional anesthesia failures. When the digital amputation has occurred in a young child, general anesthesia is the only option.
Microsurgical Techniques for Digital Replantations
Performing a digital replantation requires full mastery of the usual techniques for vascular and neural anastomosis. Again we emphasize that these are techniques that need to be learned in a laboratory setting.
Our objective is not to provide an exhaustive catalog of techniques available elsewhere, but to simply elaborate on those we have adopted and that are used daily.
As noted earlier, stabilization of the surgeon's hands is ensured by a pack of drapes covered with a white surface like a penny towel. This allows the sutures to be found easily.
End-to-End Artery Anastomosis
Each arterial end is located and dissected. The vessel is handled with very fine straight forceps. Once a sufficiently long section of vessel is obtained on both sides, it is placed in a clamp. It is best to use a small version of a double Tamai clamp at its maximal deployment to bring the vessels ends together rather than setting the clamp jaws to a narrower position. This way a greater length of the vessel is available, which makes handling easier. Trimming of the artery is done using microscissors held perpendicular to the axis of the vessel. In the case of a clean-cut amputation, this trimming is only done to remove the contused wall of the vessel. The importance of taking great care when performing this will be seen with the treatment of digital avulsions.
At the end of this procedure, there will be a discrete gap between the ends that are to be repaired. This will allow the tension for tying the knots required to coapt the two ends together to be judged, and it will help with continuous visualization ( Fig. 15.6a ).
Adventicectomy
This follows after the clamp has been placed. It is performed with microscissors. A straight forceps takes hold of the adventitia close to the arterial end and is used to gently pull the adventitia along the axis of the vessel (see Fig. 15.6b ). A clean cut is then made perpendicular to the axis of the vessel. The adventitia is then allowed to retract freely. This single measure allows a circumferential adventicectomy to be performed in one go.
Dilation-Irrigation
The adventicectomy sometimes causes the vascular lumen to be reopened. In some cases, however, it remains collapsed owing to the effect of having been crushed as an inevitable result of the cutting. The vessel appears flattened, and its lumen is linear. By exerting “equatorial” pull with two straight jeweler's forceps, the luminal opening can be restored. One of the two jaws of the straight microdissection forceps can then be introduced gently, and progressive dilation can be performed (see Fig. 15.6d, e ). The lumen of the vessel is then irrigated copiously with heparinized saline (see Fig. 15.6f ).
Suture Placement
Digital replantation involves working with small-caliber vessels (diameters of 0.3–0.4 mm for most distal replantations). In light of the small vessel size, distribution of the stitches becomes highly important. Furthermore the cramped surgical field and the fragility of the vessel walls can prevent maneuvers that involve flipping the clamp or preclude their use altogether. We have therefore adopted a technique that can be used at all levels of digital replantation. It can readily be adapted for use with or without a clamp, helps with the distribution of stitches and limits maneuvers involving axial torsion of the vessels.
Eversion of the vessel allows placement of the first posterior stitch at 6 o'clock (see Fig. 15.6g ). This is knotted with one of the strands kept long; the second stitch is an anterior stitch placed symmetrically to the other at 12 o'clock. When the needle is placed through both walls without pulling it through, it is easy to ensure proper placement of the second stitch based on tension across the two hemicircumferences. If this tension is not symmetric, the second stitch should be repositioned and one of the sutures left long as a traction suture (see Fig. 15.6h ).
Once these two equatorial stitches have been placed, the two hemicircumferences are sutured one at a time. An axial torsion movement limited to 90 degrees suffices to successfully expose each of the two hemicircumferences without having to flip the clamp over (see Fig. 15.6i ). The surgeon and the assistant each grasp one of the traction sutures. The traction creates tension in the vessel wall and allows easier placement of the subsequent stitches. Axial torsion of the vessel is only possible if a sufficient length of vessel is held between the sets of jaws of the clamp. Two additional sutures on each of the hemicircumferences—in other words a total of six sutures—generally suffice for a digital artery. Once these two initial “lateral” stitches have been placed, the surgeon and assistant exchange their traction sutures, thereby exposing the other lateral hemicircumference. By inspecting the lumen, it is then easy to ensure that neither of the two prior knots have caught the opposite wall (see Fig. 15.6j ).
It will not be possible to control the last two sutures, because they will permanently occlude the lumen of the vessel. Upon putting in the fifth knot, the remaining luminal gap still allows introduction of a thin-tipped dissection forceps into the lumen. The fifth stitch is then passed between the tips of these forceps, thereby avoiding any engagement with the posterior wall. This will no longer be possible for the placement of the sixth stitch. Also, when a very small vessel is involved, we use a method aimed at preventing the risk of catching the opposite wall: after suturing the fifth stitch, it is not knotted. Instead the surgeon pulls on the suture until one end is just long enough to tie the knot. The needle then readily transfixes the two vascular walls again. The needle is temporarily left through the two vessel walls, and the fifth stitch is tied off. Once the ends of this stitch are cut, the knot for the sixth stitch can then be finished (see Fig. 15.6k ).
End-to-Side Anastomosis
In the setting of replantation, the only end-to-side anastomosis performed is when a vein graft is required for revascularization of the thumb to the radial artery. Our technique consists of performing the back wall anastomosis first. This has the advantage of ensuring that the lumen is patent until the last suture is placed ( Fig. 15.7 ).
End-to-End Vein Anastomosis
The principles stated above can apply to performing an end-to-end vein anastomosis. The difficulty here lies with the flaccidness of the wall, which makes identifying the lumen difficult. It is easier at times to work with the vein ends immersed in a pool of heparinized saline, particularly for very small veins. Here again, the distribution of the stitches is profoundly important.
Nerve Repair
Nerve repair techniques are presented in detail in Chapter 14 . Their technical execution does not have any particular requirements when it comes to replantations. In the event that primary end-to-end repair cannot be performed, primary nerve grafting should be done.
Preparation for Replantation
The indication for replantation is reviewed. Other prognostic factors that may influence the nature of the surgical intervention also need to be evaluated. These factors include time since the accident, duration of cold or warm ischemia and mechanism of injury.
Mechanism of Injury
Guillotine-Type Injury
Guillotine-type injuries that occur with industrial cutting blades and shearing devices are the most favorable type of mechanism for replantation. They are also the least commonly encountered type in our practice. With this type of injury, replantation is possible without the need to shorten the bone, as well as without the need for a graft. The expected functional recovery in such distal guillotine-type injuries is excellent, especially in children, who are able to achieve good sensory recovery.
Less-sharp devices cause amputations that are crushing in nature. Replantation will often require bone shortening and the possible use of grafts.
Amputation by Industrial Pressing Machines
These types of injuries are crushing and cause a wide zone of injury. Often there is extensive contamination of the wound, with areas of subepidermal bruising seen. In such a setting, replantation is not possible.
Avulsion
When the amputation occurs by a sudden violent pull along the axis of the finger, it is called an avulsion amputation. A ring avulsion injury is an example of this, but there are some industrial machines that can cause a similar type of injury in the absence of any band or ring on the finger. The extent of the injury is typical: the tendons are often ruptured at the musculotendinous junction of the forearm. The level of bony injury is variable and most commonly seen distal to the level of the soft tissue degloving injury. The prognosis of such amputations is poor and often necessitates the use of nerve and vein grafts. Despite the lack of bony injury, the extensive soft tissue component usually results in the finger being stiff.
Door Injuries
This mechanism of injury is crushing in nature. It is most commonly seen in children and can cause an amputation, often distal to the distal interphalangeal (DIP) joint. Despite the mechanism of injury, microsurgical replantation is often possible.
Surgical Preparation of the Amputate
This can begin before the patient is brought into the operating theater, thereby allowing for surgical preparation of the amputate as the regional block is administered. The amputate is gently scrubbed and irrigated with normal saline before bench work can commence ( Fig. 15.8 ).
This preparation can be done with the use of surgical loupes. Bench work saves precious time, especially if there is multiple digit involvement. Preparation begins with soft tissue debridement. Longitudinal midline incisions are made, and skin flaps are retracted by the use of stay sutures. Thereafter, digital nerves and vessels are identified, tagged and dissected free. Nerves can be tagged with methylene blue and arteries with microclips. At this stage, flexor tendon repair can commence by the placement of a core suture. Tagging these critical structures is important for identification purposes. The vessels are prepared using a microscope after the completion of bench work and bone fixation. Dorsal veins are difficult to identify, especially over the middle phalanx and DIP joint, because they are collapsed. Therefore vein identification can be delayed until after one arterial anastomosis is completed, because the veins will be distended from back bleeding. After bench work is completed, the amputate can be placed in a surgical glove and placed back on ice.
Preparation of the Stump
Overall the procedures for preparation of the stump are similar to the preceding ones. Longitudinal midlateral incisions are made, soft tissue debridement is performed and digital nerves and vessels are identified.
Subsequently the proximal aspect of the retracted flexor tendon has to be retrieved from its sheath, and this should be performed before bone fixation is carried out.
Technique of Replantation at Middle Phalangeal Level
The best indication for a replant is when the level of amputation is distal to the PIP joint. When the mobility of this joint is maintained, the functional outcome is good.
Bone Shortening
Aside from some cases of perfectly clean-cut amputations, shortening the bone is routine prior to fixation. This will allow for tension-free repair of vessels, nerves and tendons, as well as enabling easier soft tissue coverage. Sufficient bone shortening allows for a primary anastomosis to be performed. There is no specific rule with regard to how much shortening is required. Depending on the injury, Wood recommends a shortening of 5–10 mm. The method of bone stabilization should be decided on prior to shortening, because it affects the nature and extent of the shortening required.
Even in the diaphyseal area, bone shortening has few functional consequences. If the replanted finger has reduced mobility, it is due to general postoperative factors rather than the shortening itself.
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