Prepare or allow access to the ipsilateral anterolateral thigh for harvest of a split-thickness skin graft.
After inflation of an upper-arm tourniquet, the laceration should be extended so as to provide adequate exposure and to facilitate skin grafting over muscle should direct closure be impossible. A transverse incision should be extended radially and ulnarly to the borders of the forearm. This incision may be then made into a “T” or an “H” by adding an ulnar longitudinal limb or ulnar and radial limbs, respectively (Fig. 7).
Oblique lacerations should be incorporated into a longitudinal ulnar incision. Many surgeons are familiar with a forearm fasciotomy incision that creates a large, rounded, ulnarly based flap of forearm skin. We favor a more ulnar, longitudinal incision when possible (Fig. 8). An ulnar and longitudinal incision creates a less conspicuous scar and is more likely to expose the FCU than the other flexor tendons should the incision gap. The FCU’s distal muscle belly will support a skin graft or granulate, whereas the bare FDS tendons will not.
With lacerations at or near the wrist flexion crease, a carpal tunnel release may be necessary to expose and repair the median nerve and to properly identify the flexor tendons. In joining a carpal tunnel incision to the patient’s laceration, the palmar cutaneous branch of the median nerve should be avoided (Fig. 9).
Start in normal tissue, either slightly proximally in the forearm or distally in the carpal tunnel. Work toward the laceration. Hematoma should be washed away, and blood-filled tenosynovium should be excised. There are potentially 2 major arteries, 2 major nerves, and 12 tendons in play. Laying eyes on the entire zone of injury and each involved structure is more important, at this stage, than precise identification or matching of stumps. Over dissection may distort relationships that are useful in the next step.
Identification of Nerves and Arteries
Frayed nerve and artery stumps may be tagged with vascular clips, anticipating resection of 1–2 ml of tissue to which the clips are applied. Do not ignore the palmar cutaneous branch of the median nerve or the dorsal sensory branch of the ulnar nerve. Large, mixed nerves are grossly similar in appearance to tendons, but on close inspection, are more cylindrical and different in sheen. Fascicles at clean, cut ends of the median and ulnar nerve are evident.
Tendon and nerve ends have been sutured together by mistake.3 We assume this devastating error occurs in the setting of limited exposure, poor lighting, and a bloody surgical field.
Tendon Matching, Repair, and Inventory
Sew the flexor tendons as you go. In other words, once the ends of the deepest tendons can be matched, repair them. Although it is possible to identify and tag each stump before suturing, this is tedious and results in numerous tagged tendons, which then have to be re-matched! Start by identifying the proximal stumps of the flexor pollicis longus or FDP. Pull potential distal matches and observe the digits. Stump caliber and the obliquity of lacerations may assist with matching.
Perform each repair. Epitendinous sutures are required in Zone 2 to prevent adhesions to and binding within the flexor tendon sheath. There are no true sheaths in forearm, therefore Kessler or figure-of-8 3-0 polyester (eg, Ethibond) stitches are expedient. Although suturing should be meticulous, some bulging at the repair sites is acceptable.
After the deep FDP and flexor pollicis longus tendons are repaired, the FDS tendons and FCR tendon may be addressed. Knowledge of cross-sectional anatomy of the FDS tendons in the carpal tunnel, that is, the superficial location of the ring and long finger FDS tendons, aids in matching. Suture of the FCU should be delayed, for the sake of exposure, if the ulnar nerve and artery require repair.
If present, the palmaris longus tendon should be repaired, anticipating that it may be used as a donor tendon in the future. In the unlikely event that the palmaris longus crosses a wound to be skin grafted, the tendon may be resected.
An inventory should be kept on the surgical drapes or card from a sterile gown. If you take a cell phone picture of this inventory, the status of each forearm structure, for example, “OK,” or “repaired,” may be conveniently included in the operative report. This careful documentation is valuable for the surgeon and hand therapist postoperatively (Fig. 10).
Hemorrhagic or frayed nerve ends should be resected, taking care not to create an irreparable gap. A clean, perfectly transverse neurectomy is difficult to make. A piece of sterile glove or Esmarch bandage may be wrapped around the nerve stump and held tightly with a hemostat. This stabilizes the fascicles while they are cut. The wrist should be positioned in neutral during nerve coaptation. A tension-free repair should be possible if a single 8-0 nylon epineural stitch approximates the stumps. If tension-free nerve repairs cannot be performed with the wrist in neutral, nerve grafts should be considered.
An attempt should be made to repair cut nerves so that they match on cross-section. Vasae nervorum may be lined up, as may the fascicles of each stump. Individual fascicular repair is difficult and of no proven benefit.4 Circumferential epineural stitches are placed under magnification.
Do not forget to repair the palmar cutaneous branch of the median nerve and the dorsal sensory branch of the ulnar nerve.
Ideally, the previous steps are accomplished in less than 2 hours. At this point, the tourniquet is deflated. Some hand surgeons worry that a single-artery hand may become cold-intolerant. There is little evidence to support this suspicion and some evidence to the contrary.5 The authors still advocate repair of both major arteries. Much of the effort to repair a single artery involves microscope set up. Once the microscope is in place, a second arterial repair adds little time to the operation.
If both the radial and ulnar arteries are cut, and the hand is dysvascular (which is not always the case), both arteries should be repaired. This will save the hand if one of the repairs clots. Arterial repair is done under the operating microscope with 8-0 nylon suture.
Once the ulnar nerve and artery are repaired, do not forget to the repair the FCU tendon.
Close the skin if possible. Any residual wound should be prepared for a split-thickness skin graft. Muscle will accept a skin graft. Tendon, particularly without paratenon, will not. If the FCR tendon is exposed, as is often the case, underlying FDS muscle may be drawn over and sutured above it. Split-thickness skin grafting may be undertaken immediately; however, use of a vacuum sponge may permit delayed closure or result in decreased area to be grafted.
Persistently exposed tendons are a particular problem. An attempt at coverage with a collagen dermal substitute is reasonable if the area of exposed tendon is small and if this area is surrounded by particularly healthy tissue. Flap coverage is otherwise required.
A dorsal plaster splint should be used to hold the wrist in neutral, the metacarpophalangeal joints in 90 degrees of flexion, and the interphalangeal joints straight.
The vascular status of the hand after arterial repair may be monitored with pulse oximeters placed on the digits. This allows untrained observers to screen for problems and to call for a skilled examination if necessary.6
Flexor tendon lacerations in the wrist and forearm need not be moved early like flexor tendon repairs in Zone 2. Whereas extended immobilization would create debilitating adhesions in the fingers, there are no sheaths in the forearm for tendons to attach to. Three weeks of splinting allows sufficient healing for the patient to begin a rehabilitation protocol based on active, unresisted range of motion. Forceful gripping should begin 3 months after surgery.
Dorsal splints that hold the metacarpophalangeal joints in flexion during the first 6–8 weeks of recovery ease tension and prevent full extension of the repaired tendons. Although perhaps counterintuitive to patients and hand therapists, this technique creates tenodesis at the metacarpophalangeal joints and prevents clawing in the setting of median and ulnar nerve lacerations. Synchronous, full flexion of the digits should be prioritized over full extension.
Nerve regrowth occurs at roughly a millimeter a day. Age and smoking status are predictors of neurologic recovery and patients should be counseled accordingly.
OUTCOMES AND COMPLICATIONS
Patients should expect a functional but imperfect recovery.1,7–15 Recovery of ulnar innervation is less predictable than that of the median nerve.1,7–9 Adults often achieve protective sensation at the finger tips but loose forceful intrinsic muscle function. Compartment syndrome, possibly as a result of occult bleeding, and loss of arterial patency are early risks. Stiffness and neuropathic pain are notable long-term problems as is cold intolerance. Cold intolerance, when it does occur, likely has more to do with neurologic rather than vascular injury.5,16,17
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Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Plastic Surgeons. All rights reserved.
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