Complete avulsion of the brachial plexus in adults can be devastating for patients due to loss of function in the upper extremity. Patients with complete avulsion injuries lose shoulder abduction, external rotation, elbow flexion, and animation and sensation in the hand. These injuries are typically caused by high-energy traumatic impact with a stationary object, such as occurs in vehicular accidents, including motorcycle and snowmobile collisions.
As more patients survive these serious accidents, there is a greater need for more robust brachial plexus reconstruction options, particularly in the setting of complete avulsion, or when treatment is delayed 12 months or more resulting in denervation and irreversible muscle atrophy.
More robust reconstruction techniques are now emerging and being refined due to enhanced understanding of complex nerve and muscle pathophysiology. Improved results rely on microsurgical techniques, including the use of functioning free muscle transfer (FFMT) in recent years. FFMT is indicated when nerve grafting is not possible, when all nerve roots are avulsed from the spinal cord, or when nerve reconnection is unlikely to succeed.
Importantly, such repairs seldom restore function to the wrist and hand, explains Alexander Y. Shin, M.D., an orthopedic reconstructive microsurgery and hand specialist on Mayo Clinic's brachial plexus surgical team. "At Mayo, we combine traditional brachial plexus reconstruction of nerve transfers or grafts with free tissue transfer options, including double functioning free muscle transfer of the gracilis. The concept is that if one muscle is good for restoring function, then two are better," says Dr. Shin.
Adds Dr. Shin's reconstructive microsurgeon colleague, hand specialist Allen T. Bishop, M.D.: "The double gracilis functioning free muscle transfer is an essential tool in the management of brachial plexus injury because it offers the patient the possibility of expanded functionality to include simple grasp, in addition to restoration of shoulder and elbow motion, hand sensation, and triceps function."
Neurosurgeon Robert J. Spinner, M.D., is the third specialist on the Mayo brachial plexus team. "The key to our approach is the multidisciplinary team," he says. "We now have vast experience with an algorithm that relies on simultaneous surgeries in a single complex procedure — which is much less traumatic and disruptive for patients."
The double gracilis FFMT was pioneered as a two-stage, two-operation procedure in Japan in 1997. In stage I, the first gracilis transfer, powered by the spinal accessory nerve, restores elbow flexion and finger extension. In stage II, a second gracilis transfer, powered by intercostal motor nerves, expands function to include finger and thumb flexion (grasp).
The Mayo Clinic specialty team of brachial plexus surgeons has modified the procedure. Since 2005 they have occasionally performed both stage I and II of the double gracilis transfer in a single operation, generally in 10 to 12 hours. The three surgeons begin the surgery together, one at each anatomical station of neck, chest and leg. They divide the surgical tasks according to the algorithm they devised, technical needs of the case and nerve selection preferences.
Another Mayo modification has been to emphasize wrist rather than finger extension in stage I. Strong wrist extension improves finger flexion through a tenodesis effect.
A third Mayo modification improves distal muscle function by detaching and relocating the distal portion of the flexor carpi ulnaris to cross the elbow, and thus minimizing the "bowstringing" of the first muscle by creating an elbow-level pulley. The result is improved muscle excursion and strengthened wrist extension. To conduct motor neurotization of the gracilis muscle, the fifth and sixth intercostal motor nerves are used.
At Mayo Clinic, data for the double gracilis transfer show that approximately 80 percent of patients recover M4 elbow flexion strength and 50 percent are able to perform a simple hand grasp-release. Compliance with postoperative therapy is a key determinant in recovery of prehension.
Patient attitude and expectations must be managed preoperatively to understand the role compliance plays in recovery, as well as the range of recovery possible for prehension. Double gracilis FFMT is an evolving surgical option that can expand the possibilities for functional recovery after complete brachial plexus injury. The key to optimal outcomes is obtaining early and appropriate care at an advanced orthopedic center specializing in reconstructive microsurgery and brachial plexus repairs.