A case of a traumatic sciatic nerve paralysis was successfully treated with the transfer of the long digital extensor tendon of origin to the vastus lateralis muscle after a portion of the latter had been separated from its insertion on the patella. A second procedure was necessary to shorten the distal tendon of the long digital extensor muscle to create the proper tension needed to fully extend the digits. Within 11 weeks after the surgery the dog was successfully returned to training and field trial competition. Viability of the transfer was further demonstrated by electrical stimulation of the vastus lateralis one year later.
Damage to the radial or sciatic nerves is a fairly common sequel to certain humeral, pelvic or proximal femoral fractures. Reports on treatment for peripheral nerve palsy in veterinary medicine have been scant compared to human medicine where the transfer of muscles and their tendons in such diseases as spina bifida, neuromuscular atrophies, cerebral palsy and especially poliomyelitis has been practiced frequently and successfully. A tendon transfer is defined as the shifting of "a tendinous insertion from its normal attachment to another location so that its muscle may be substituted for a paralyzed muscle in the same region. A tendon transplant is the relocation of a whole segment of tendon, or tendon and muscle, whereas a tendon transfer is the relocation of the tendinous insertion only. Tendon transfers have been reported for the treatment of both radial and peroneal nerve paralysis in the dog and cat. The alternative consists of arthrodesing the carpus or tarsus and digits, or amputating the leg.
With peroneal nerve paralysis one of the flexors of the crus (the tibialis caudalis or the flexor digitorum longus) can be transferred, but when both the peroneal and the tibial nerves are affected these flexors are nonfunctional. This report describes a case where transfer of the long digital extensor muscle (LDEH) tendon of origin to the vastus lateralis muscle was used to correct the effects of a traumatic sciatic nerve paralysis.
A 1 ½ year old, female, Irish setter weighing 20 kg was referred to our hospital because of a left side sciatic paralysis which occurred secondary to a previously treated pelvic fracture. An attempt had been made to fuse the left hock joint in its natural position by inserting a Steinmann pin across the tibiotarsal joint.
At presentation there was 10 degree range of motion in the tibiotarsal joint and a full range of motion in the stifle. The digits were in flexion contracture despite the referring veterinarian's attempts to prevent this with splinting. The dog would bear weight on the leg but usually on the dorsal surface of the paw. No ulceration was present on the dorsal surface of the paw. There was significant muscle atrophy in the thigh and especially the crus.
Two procedures were planned. First the distal tendons of the flexor digitorum profundus and the flexor digitorum superficialis were lengthened with a step-cut in the metatarsal area. They were resutured with the toes parallel to the axis of the metatarsal bones.
In the second procedure the tendon of origin of the LDEM was detached from the lateral condyle of the femur. Through the same incision the vastus lateralis was separated and freed including its tendinous insertion of the patella (Fig. 2). These 2 tendons were sutured with 4-0 nylon after threading the tendon of origin of the LDEM through 2 stab incisions in the vastus lateralis tendon (Fig. 3). The LDEM was apparently adhered due to the extensive atrophy of the muscles of the crus and had to be mobilized in order to actively extend the digits. This was accomplished with manipulation by exerting tension non the origin of the muscle. The entire leg was placed in a heavy cotton bandage with a posterior fiberglass splint extending from the calcaneal process distally. This bandage remained on for 10 days and the splint for an additional 2 weeks.
After the splint was removed the dog would walk on the ends of her digits. Further surgery was necessary to bring the paw into the required degree of extension (dorsiflexion) to allow weight bearing on the plantar pads. The need for further surgery could have been prevented by placing more tension on the LDEM before suturing it to the vastus lateralis during the first operation, but the necessary angle of dorsiflexion had been miscalculated. By this time the flexors were starting to contract once again. Therefore they were incised by not sutured and the tendon of insertion of the LDEM was shortened just distal to the distal transverse ligament of the tarsus (Fig. 4). The tendon was folded on itself and sutured with 4-0 nylon (Fig. 4), pulling the digits into the normal position of weight bearing. A fiberglass splint maintaining the digits in dorsiflexion was applied for ten days and then used at home for half an hour BID for a further 3 weeks.
When seen 1 month postoperatively the dog was consistently walking on the plantar pads and there was about 160 degree range of motion at the metatarsal-phalangeal joint. By six weeks significant return of muscle mass was evident in the quadriceps and gluteal muscles. Ten degrees range of motion still remained in the tibiotarsal joint. The owners reported that the dog never placed the paw down on the dorsal surface while walking or standing (Fig. 5), and had been returned to training and even successful competition in field trials.
The tendon transfer was electrically evaluated 12 months later using a Grass S44 stimulator and Teflon-coated wire passed through a 20 ga needle into the vastus lateralis muscle. A positive electrode was placed subcutaneously in the opposite leg as a ground and a needle and Teflon wire was also placed in the rectus.