Intramuscular connective tissue differences in spastic and control muscle: a mechanical and histological study.

Cerebral palsy (CP) of the spastic type is a neurological disorder characterized by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks. Secondary to the spasticity, muscle adaptation is presumed to contribute to limitations in the passive range of joint motion. However, the mechanisms underlying these limitations are unknown.

Flexor carpi ulnaris tenotomy alone does not eliminate its contribution to wrist torque.

Background: Flexor carpi ulnaris muscle tenotomy and transfer to the extensor side of the wrist are common procedures used to improve wrist position and dexterity in patients with cerebral palsy. Our aim was to determine whether this muscle still influences wrist torque even after tenotomy of its distal tendon.

Methods: Intra-operatively, we determined in vivo maximal wrist torque in hemiplegic cerebral palsy patients (n=15, mean age 17 years) in three conditions: 1) with the arm and the muscle intact; 2) after tenotomy of the flexor carpi ulnaris just proximal to the pisiform bone, with complete release from its insertion; and 3) after careful dissection of the belly of the muscle from its fascial surroundings up until approximately halfway its length.

Myofascial force transmission and tendon transfer for patients suffering from spastic paresis: a review and some new observations.

The current rationale of clinical practice in spastic tendon transfer surgery is based on four assumptions: (1) changes in muscle fiber length (serial number of sarcomeres) determine the available length range and joint excursion, (2) muscle cross-sectional area determines the maximal force output, (3) fiber length and muscle force are invariable functions of muscle length, (4) there is an invariable relation between the elastic force and the active force exerted by the sarcomeres. The validity of these assumptions is discussed. Additionally, some new perspectives in muscle research are discussed and myofascial force transmission is introduced as a co-determinant for the outcome of tendon transfer by presenting some exploratory observations.

Adaptation of the properties of spastic muscle with wrist extension deformity.

To show that human muscle may adapt to tendon transfer, adaptation of flexor carpi ulnaris (FCU) function was studied by measuring active and passive length-force characteristics at initial operation and at reoperation in a case of extension deformity secondary to FCU tendon transfer. At reoperation, FCU was 20 mm shorter; active force decreased approximately 10%, indicating atrophy; and passive force increased, reflecting increased stiffness. FCU fiber length was unchanged.

Spastic muscle properties are affected by length changes of adjacent structures.

Recent animal experiments have shown that up to 37% of muscle force may be transmitted to adjacent structures rather than reach the insertion of the muscle's tendon, and that the extent of such force transmission depends on the length and relative position of these structures. We tested whether the force-length characteristics of the distally tenotomized human flexor carpi ulnaris muscle (FCU) of nine patients with cerebral palsy varied with the change of relative length of adjacent structures induced by a change of wrist position. In four patients, the FCU exerted up to 40% more active force in a flexed wrist position at short FCU length, whereas the active force was not significantly higher in the other five.

Overstretching of sarcomeres may not cause cerebral palsy muscle contracture.

To answer the question whether the muscle contracture in patients with cerebral palsy is caused by overstretching of in-series sarcomeres we studied the active and passive force-length relationship of the flexor carpi ulnaris muscle (FCU) in relation to its operating length range in 14 such patients with a flexion deformity of the wrist. Force-length relationship was measured intra-operatively using electrical stimulation, a force transducer, and a data-acquisition system. Muscle length was measured in maximally flexed and maximally extended position of the wrist.

Intraoperative measurement of force-length relationship of human forearm muscle.

The specific relationship between force and length is one of the most important characteristics of vertebrate muscle. The only accurate method to measure the force-length characteristics is to generate a set of isometric force-time plots at different muscle lengths. In humans, such force-length characteristics mostly are based on indirect measurements that have their limitations.

Progressive surgical dissection for tendon transposition affects length-force characteristics of rat flexor carpi ulnaris muscle.

Extramuscular connective tissue and muscular fascia have been suggested to form a myo-fascial pathway for transmission of forces over a joint that is additional to the generally accepted myo-tendinous pathway. The consequences of myo-fascial force transmission for the outcome of conventional muscle tendon transfer surgery has not been studied as yet. To test the hypothesis that surgical dissection of a muscle will affect its length-force characteristics, a study was undertaken in adult male Wistar rats.

Motor control impairment of the contralateral wrist in patients with unilateral chronic wrist pain.

Objective: Assessment of the quality of fine motor control in patients with unilateral chronic wrist pain seldom focuses on the possibility that control of movements is effector independent at the cerebral level. This mechanism may be involved in an impairment of motor function in the unaffected wrist. We studied the possible motor impairment in the unaffected wrist in patients with chronic wrist pain.