TENDON LENGTHENING FOR MUSCLE CONTRACTURES
Wise Young, Ph.D., M.D.
W. M. Keck Center for Collaborative Neuroscience
Rutgers, State University of New Jersey, Pisacataway, NJ 08854
Email: email@example.com, Updated: 21 June 2006
Several people have written to me about tendon lengthening to relieve spasticity. I thought that it might be useful to describe and comment on the procedure.
Spasticity and Contractures. Spasticity induces and is aggravated by muscle contractures. Muscles contain receptors called spindles that monitor tension and feeds back to the spinal cord to maintain muscle length. Injury to the spinal cord increases excitabilty of neural circuits that control muscle tension. Spastic muscles resist changes of tension by contracting. Prolonged and continuous muscle spasticity may lead to muscle contracture or shortening of muscles. Contractures interfere with standing and walking. While drugs such as baclofen and tizanidine moderates spasticity, they usually cannot moderate muscle contractures.
Treatments of contractures. Clnicians use three ways to relieve spasticity muscle contractures. One is to inject a toxin called Botox which damages motor nerves and, in high doses, the motoneurons that innervate muscles. The other is to inject phenol, a chemical, that damages both motor and sensory nerves. A third way is to cut the muscle tendon and lengthen the tendon to relieve the tension on the muscle. The first two methods damage motoneurons or axons, sometimes irreversibly, and may cause weakness of muscles. For people who have some muscle function, tendon lengthening is the method of choice.
Tendon lengthening. The basic tendon lengthening procedure involves cutting the tendon partway at two points and a cut down the middle of the tendon. This allows the two halves of the tendon to be slid along each other and then sewed together, as illustrated in the diagram below. The procedure is simplified for illustrative purposes but it shows how the cuts (left image) can allow two strands of tendon to be slid alongside each other (middle image), and sewed together (right image). Note that there are other ways to cut the tendon, including methods that involving creating four strands and splicing these strands together. Once healed, the tendon is longer and the cut parts will fill out with scar tissues.
Strength of repaired tendons. Tendon lengthening procedures have been carried out for many decades. In fact, I use to participate in such surgeries for children with cerebral palsy and idiopathic toe walking (Source). Children who undergo tendon lengthening even of big musles such as the leg flexors (Source) can return to athletic activities. Many athletes of course rupture their tendons, undergo tendon repair, and then return to their previous activity. Repaired tendons have a scar and the strength of the scar depends on how it healed. The tendon should be immobilized for about four weeks the healing to take place (Source). Properly healed tendons are reasonably strong.
Complications. Making the tendons too long or not lengthening the tendon sufficiently can result in weakening of the muscle (Source) or insufficient resolution of the spasticity. Both surgical experience and judgment is required to get the proper lengthening without significantly weaking the muscle. For obvious reasons, it is not good to go in numerous times to repair the tendon. Repeated surgeries and scar tissues will cause stiffening of the tendon and lost of elastic recoil. Muscle weakness due to immobilization and non-use may be a problem and full function may not return to pre-operative levels for as long as 9 months after surgery, even with intensive physical therapy (Source). The change in one muscle group may affect the balance of other muscles, resulting in abnormal gait (Source).
In summary, tendon lengthening surgery has been practiced for many decades. The procedure does reduce spasticity of major muscle groups and well-healed tendons are strong enough to permit renewal of athletic activity. However, the operation requires experience and good surgical judgment. Like all operations of this nature, complications may occur. Immobilization of the tendon is important for proper healing. Overlengthening, repeated operations, and muscle weakness may occur. The advantages of tendon lengthening is that it may correct specific orthopedic problems and spasticity without damaging nerves or motoneurons.