Operative technique

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Functioning free muscle transfer for Volkmann's ischemic contracture

This difficult and complex procedure is best performed by a two-team approach. The gracilis muscle is ideal for such a transfer from the anatomic and physiologic perspectives [20,21]. Because of extensive scarring and previous surgical debridement, the surgical preparation of the forearm can be difficult and tedious. The incision along the volar forearm should be carefully planned. In the proximal forearm, the incision should allow for adequate exposure of the medial epicondyle and the neurovascular recipient structures that are going to be used. In the distal forearm, anticipation of skin flap cover should be taken into consideration. This is required for coverage of the tendon repairs to facilitate tendon gliding (Fig. 4).

Generally, it is preferable to begin the dissection proximally, where healthy undamaged tissue can be identified. The dissection then continues distally, using the median nerve and brachial artery as guides to the depth of dissection. It is helpful to preserve any large superficial vein in the proximal forearm because this may be preferable to any vena comitans of the deeper vasculature. For finger and thumb flexion, the best nerve to use is the anterior interosseous nerve, which is

Fig. 4. Volar forearm incision.

a branch of the median nerve. Adjacent to its takeoff from the median nerve are the anterior interosseous vessels, which can also provide an excellent vascular supply for the transplanted muscle. The anterior interosseous vessels and nerve can be exposed by transecting the insertion of the pronator teres. As this is reflected, the neurovascular bundle should come into view. Even in severe cases of Volkmann's ischemic contracture, there may be small areas of residual musculature that can be stimulated. Using the nerve stimulator on the anterior interosseous nerve, one may see some contraction of residual musculature. This is not effective from a clinical standpoint because it does not produce movement. Nevertheless, it confirms the viability and functionality of the anterior interosseous nerve. Thus, this maneuver can be important and reassuring to the surgeon. Once the anterior inter-osseous nerve has been clearly identified and the anterior interosseous artery has been prepared, attention can be directed to the central and distal forearm. The skin flaps should be elevated such that there is no tension on the muscle with closure. In the incision in the distal forearm, it is particularly important to provide a skin flap for cover over the tendon repairs. As one enters the distal forearm, the profundus tendons are identified. The superficialis tendons can often be divided because they are not useful in this procedure. The profundus tendons are divided and then sutured to one another in a balanced fashion. In this way, when traction is applied to the tendons, the fingers move down into the flexed position in unison. The flexor pollicis longus should also be identified and divided in the forearm. If it is to be incorporated into the single muscle transplant, it should flex slightly after the fingers. In this way, the thumb is not caught in the palm, thus decreasing the effectiveness of the grip. It should flex down after the fingers to provide for thumb-index apposition. The flexor pollicis longus is then sutured to the balanced four profundus tendons, and the preparation of the forearm is complete. Much of this dissection can be done under tourniquet control. Confirmation of an adequate arterial supply to vascularize the muscle should be obtained as the tourniquet is deflated, however. Also with the tourniquet deflated, one should confirm that the anterior interosseous nerve is functional by stimulating it and observing any contraction of residual muscle.

In unusual cases in which the anterior inter-osseous nerve is not available, branches of the ulnar nerve that innervate the ulnar profundus muscles may be used as a second choice.

In certain situations, it is helpful to have a degree of independence of finger flexion and thumb flexion. This may be possible with the use of the anterior interosseous nerve. The anterior interosseous nerve courses distally, giving off separate branches to the profundi and a separate branch to the flexor pollicis longus. The branches that go to the profundi course ulnarward. The branches that go to the flexor pollicis longus course radially. Thus, it is possible to separate the motor components for finger flexion and thumb flexion. When transplanting the gracilis muscle, it may also be possible to separate the fibers according to fascicular territory. In this way, a separate longitudinal section of muscle with its tendinous unit and innervated by a separate fascicle can be created. With appropriate positioning and identification of the motor components and the tendinous components, one can achieve a degree of separation of function between the thumb and the fingers (Fig. 5).

The volar forearm is now fully prepared as outlined in Box 3. To summarize, the medial epi-condyle has been exposed, and this anchors the muscle origin. The motor nerve to be used has been carefully prepared and confirmed to have adequate function. Frozen section evaluation by a neuropathologist can often confirm the presence of healthy axons. Adequate vascular input is ensured by releasing the tourniquet and testing the arterial flow. A superficial vein is often helpful when a deep vein is not present or is involved in extensive venous communications. In the distal forearm, the four profundus tendons are divided and sutured in unison with a side-to-side woven technique. With traction on this unit, finger median nerve radial artery median nerve radial artery

Fig. 5. Schematic of separation of function for thumb and finger flexion.

flexion in unison is produced. The flexor pollicis longus may be incorporated into the profundus tendon if a single nonsplit gracilis transplant is to be performed. The thumb is incorporated so that it lags slightly behind the unified finger flexors. If a split gracilis muscle transplant is to be performed, the anterior interosseous nerve is appropriately split and dissected and the finger and thumb flexors are left separate.

Gracilis muscle preparation

The muscle is harvested simultaneous to the forearm preparation using a two-team approach (see Box 3). Many muscles have been used for transplantation, but the gracilis seems to be best for forearm reconstruction. It has an appropriate anatomic configuration with a muscular belly proximally and a tendinous insertion distally. With intrafascicular nerve stimulation, it is also possible to split the gracilis into two distal

Box 3. Key points in gracilis muscle harvest

1. Incision is made posterior to the interval between the gracilis muscle and adductor longus

2. Musculocutaneous perforator can identify the level of the pedicle

3. Motor nerve enters the muscle at the vascular pedicle at an angle of 45° and lies on top of the adductor longus taking origin from the obturator nerve

4. Mark the muscle at 5-cm intervals in the fully stretched position to aid in establishing appropriate tension when it is transferred musculotendinous units. This may be suitable for providing at least partial independence of finger versus thumb flexion. The neurovascular structures of the gracilis render it ideal for transplantation. It has a dominant pedicle with a single artery and vena comitans. It also has a large single motor nerve. As a strap muscle, it provides adequate strength and excursion for forearm reconstruction. Thus, on an anatomic basis as well as on a dynamic physiologic basis, the gracilis muscle is preferred for forearm reconstruction in Volk-mann's ischemic contracture.

The gracilis muscle lies in the medial thigh just posterior to the adductor longus. It takes its origin from the pubis and ischium as it courses distally along the inner thigh. Its insertion is by means of a strong tendon just posterior to the tibial tubercle on the medial shaft of the tibia. One can easily palpate the origin of the adductor muscle in the upper inner thigh. This provides the landmark for the gracilis incision. The incision is made just posterior to the adductor longus, and the muscle interval between the adductor and the gracilis can often be palpated in thin patients (Fig. 6). The incision should parallel this muscle interval in the upper inner thigh and course distally to the junction of the middle and distal thirds of the thigh. The dissection proceeds deep toward the muscle, which is usually easily identified. The neurovascu-lar pedicle is then approached by elevating the adductor longus anteriorly. As the adductor longus is elevated, the vascular pedicle comes into view. It generally enters the muscle approximately 8 to 12 cm from its origin and on to the deep surface. This is the major pedicle, and it has a dominant artery and two venae comitans. The motor nerve enters the pedicle just proximal to the vessels at

Fig. 6. Gracilis harvest incisions.

an angle of 45°. The vascular pedicle is dissected back to easily identifiable branches going upward into the adductor longus. These are divided, and the remainder of the pedicle is easily visualized going deeper to its takeoff from the profunda femo-ris artery with its vena comitans. Often, the paired venae comitans unite at the takeoff from the profunda femoris vein. The motor nerve to the graci-lis is a branch of the anterior division of the obturator nerve (L2-L3). It takes an oblique course between the adductor longus and adductor magnus. In general there are two to three fascicles in this nerve, and with intraoperative stimulation, each fascicle can be stimulated and the appropriate motor territory observed. This is often facilitated by palpation, with identification of distinct longitudinal sections (Fig. 7). It is then possible to split the distal musculotendinous unit for potential reconstruction of independent finger and thumb flexion.

The entire gracilis is elevated from the thigh, except for its origin, tendinous insertion, and neurovascular pedicle. Marking the muscle to

Fig. 7. Segmental contraction of gracilis with individual fascicle stimulation. (A) Muscle segments pulled out to length. (B) Stimulation of a single fascicle with selective contraction of one segment of muscle.

provide tension guides after transplantation is important at this stage. The muscle is placed in a fully stretched position by abducting the hip and extending the knee. Markers are placed at 5-cm intervals with the muscle in this position. This can be done with sutures so that they can be identified readily after transplantation (Fig. 8). After the markings have been placed at 5-cm intervals along the course of the muscle, the origin and insertion are divided. This leaves the muscle attached only by its neurovascular pedicle. Only when the forearm dissection is complete and is ready to receive the transplant should the neurovascular pedicle should be divided. In this way, one can minimize muscle ischemia time.

Gracilis muscle transfer to the forearm

The muscle is then removed from the thigh and transplanted to the forearm (Fig. 9). The donor site in the thigh is closed in layers, taking care to close the fascia loosely to reduce the likelihood ofmuscle herniation. Usually, a suction drain is used.

The muscle is positioned in the forearm so as to minimize the distance between the nerve repair and the muscle itself (Box 4). This reduces the time required for reinnervation and assists in the return of adequate muscle function. Placing the muscle in the appropriate position for nerve repair then allows the surgeon to place the muscle belly adequately over the medial epicondyle for the origin and the tendon over the distal forearm for the insertion. The surgeon can then stretch the muscle to its fully stretched position as indicated by the tension guide sutures. One can then visualize the location of the origin and insertion and potentially shorten the muscle bellies or shorten the tendon to allow for optimal positioning of the muscle.

Fig. 8. Tension guide sutures placed at 5-cm intervals on muscles in stretched position in the thigh.
Cuadriceps
Fig. 9. Muscle removed from the thigh and ready for insertion in the forearm.

The muscle origin is then securely fixed to the medial epicondyle, and the neurovascular structures are repaired. Under the operating microscope, the pedicle of the gracilis is prepared. The larger vena comitans is isolated and prepared for microvascular anastomosis. It is often necessary to separate this vena comitans from the artery to facilitate repair. The microvascular venous repair is performed first to a superficial vein in the proximal forearm or to the vena comitans of the anterior interosseous artery. Next, the artery to the gracilis is repaired to the anterior interosseous artery. These small vessels require technically

Box 4. Key points in transferring

the gracilis muscle to the forearm

1.

Set the muscle in the forearm so as to

minimize the distance between the

nerve coaptation and transferred

muscle

2.

Securely fix the muscle origin to the

medial epicondyle

3.

Profundus tendons should be sutured

together to recreate the natural

cascade

4.

Secure woven distal tendon repair

5.

Beware of the thumb being potentially

too tight and interfering with finger

flexion

6.

Provide good skin coverage to

facilitate tendon gliding

7.

Be prepared to do a tenolysis

(6 months after surgery)

perfect anastomoses, with every attempt made to avoid thrombosis. Revision is possible but increases the ischemia time, and thus increases the likelihood of the muscle being irretrievably damaged. After revascularization is performed, the entire muscle should appear healthy and revascu-larized and should contract on direct stimulation. This is often the best guide to muscle viability at this stage of revascularization. Next, the motor nerve is repaired. The nerve repair should be done as close to the gracilis muscle as possible to minimize reinnervation time. The fascicles are accurately aligned under high magnification and tacked together as perfectly as possible. If a split gracilis is required, the nerve repairs must be evaluated carefully. The fascicle of the anterior interosseous nerve that innervated the profundi is coapted to the fascicle of the gracilis motor nerve that innervates the section of the gracilis carrying out finger flexion. Similarly, the fascicle of the anterior interosseous nerve that innervates the flexor pollicis longus is coapted to the fascicle of the gracilis motor nerve that innervates the section of the gracilis performing thumb flexion. Again, these nerve repairs should be perfect, under no tension, and as close to the muscle as possible.

The tendon repairs should then be performed. To facilitate this, the muscle is stretched out to its fully stretched position as indicated by the previously placed tension guide markers. The wrist and the fingers are also placed into the fully extended position, and the location of the tendon repair is then noted (Fig. 10). Thus, wrist and finger extension is possible, and flexion of the muscle takes place at its most mechanically advantageous position. The site of tendon repair is marked, and the wrist and fingers can then be brought into a flexed position and a woven secure tendon repair performed without tension. If a split gracilis is required, the portion of the gracilis tendon that is going to be used for finger flexion is woven through the balanced profundi. The portion of the gracilis that is going to be used for thumb flexion is woven through the flexor pollicis longus. The thumb flexor should be in a slightly more lax position relative to the fingers. With contraction, the thumb is not pulled prematurely into the palm, thus diminishing grip. It is exceedingly important to place the muscle under appropriate tension if one is to optimize muscle function.

Soft tissue cover is then provided after the tendon repairs have been performed. It is important to have a healthy flap over the site of tendon repair to allow for tendon gliding. Conversely, the

Fig. 10. (A) Muscle in the forearm being pulled out to length, as confirmed by tension guide sutures and site of tendon repair marked. (B) Tendon of the gracilis repaired by the woven technique to balanced tendons of the forearm at the designated site.

muscle belly can be covered with split-thickness skin grafts to avoid the excessive tension that may be caused by flap cover. The adjacent skin flaps on either side of the incision can be used to cover the crucial areas of the vascular and neural repairs, with the central segment of the muscle belly left open with split-skin coverage. Drains are placed at a distance from the vascular repairs. On completion of the procedure, the extremity is immobilized. It is preferable to have the elbow at 90° and the wrist slightly flexed to take the tension off the origin and insertion of the muscle. The finger metacarpophalangeal joints should be maintained in a flexed position of 90°, and the thumb should be abducted with the interphalan-geal joint slightly flexed (Fig. 11).

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