Michiel Kreulen

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. During progressive dissection of the flexor carpi ulnaris muscle, isometric length‐force characteristics were measured using maximal electrical stimulation of the ulnar nerve. After fasciotomy, muscle active force decreased by approximately 20%. Further dissection resulted in additional decline of muscle active force by another 40% at maximal dissection. The muscle length at which the muscle produced maximum active force increased by approximately 0.7 mm (i.e. 14% of the measured length range) after dissection. It is concluded that, in rats, the fascia surrounding the flexor carpi ulnaris muscle is a major determinant of muscle length‐force characteristics.

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. Using biopsies, we compared mechanical as well as histological properties of flexor carpi ulnaris muscle (FCU) from CP patients (n = 29) and healthy controls (n = 10). The sarcomere slack length (mean 2.5 µm, SEM 0.05) and slope of the normalized sarcomere length-tension characteristics of spastic fascicle segments and single myofibre segments were not different from those of control muscle. Fibre type distribution also showed no significant differences. Fibre size was significantly smaller (1933 µm2, SEM 190) in spastic muscle than in controls (2572 µm2, SEM 322). However, our statistical analyses indicate that the latter difference is likely to be explained by age, rather than by the affliction. Quantities of endomysial and perimysial networks within biopsies of control and spastic muscle were unchanged with one exception: a significant thickening of the tertiary perimysium (3-fold), i.e. the connective tissue reinforcement of neurovascular tissues penetrating the muscle. Note that this thickening in tertiary perimysium was shown in the majority of CP patients, however a small number of patients (n = 4 out of 23) did not have this feature. These results are taken as indications that enhanced myofascial loads on FCU is one among several factors contributing in a major way to the aetiology of limitation of movement at the wrist in CP and the characteristic wrist position of such patients.

Three-dimensional video analysis of forearm rotation before and after combined pronator teres rerouting and flexor carpi ulnaris tendon transfer surgery in patients with cerebral palsy.

The effect of combined pronator teres rerouting and flexor carpi ulnaris transfer on forearm rotation was prospectively studied by comparison of pre- and postoperative three-dimensional analysis of forearm range of motion in ten patients with cerebral palsy. One year postoperatively, surgery had improved maximal supination of the forearm in all patients by an average of 63°, but there was also a mean loss of 40° pronation. Forearm range of motion increased by a mean of 23°. The centre of the range of motion on average shifted 52° in the direction of supination. Based on these results of objective forearm range of motion analysis, we conclude that the common combination of pronator teres rerouting and flexor carpi ulnaris transfer in patients with cerebral palsy effectively facilitates active supination but impairs active pronation.

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. A method of direct, in vivo measurement of force-length characteristics of the human flexor carpi ulnaris muscle using relatively simple equipment during transposition surgery is presented. The method is proven reproducible, with an overall estimated error of 2.8%.

Fine motor assessment in chronic wrist pain: the role of adapted motor control

Objective: To show whether a difference in fine motor control exists between patients with chronic, undiagnosed wrist pain (CUWP) and healthy controls. Furthermore, a method to assess fine motor function of the wrist is evaluated. Design: A case–control study. Setting: The Academic Medical Center in Amsterdam, the Netherlands. Subjects: Twenty-seven CUWP patients were compared with 50 healthy control subjects. Interventions: Subjects performed horizontal stroke patterns on a digital writing tablet connected to a computer. The control subjects were tested twice to obtain test–retest reliability. A visual analogue scale was used to assess subjective pain. Main outcome measures: Fluency of movement and average velocity were measured. Intraclass correlation, ANOVA repeated measures statistics and Pearson correlation were calculated. Results: There is a significant difference in fluency of motion between patients and controls, possibly due to a disturbed motor control, since there is no relationship between pain and test score, nor do CUWP patients have any abnormality in the wrist that can explain the disturbance in motor function. The test method is reliable (ICC = 0.78) and valid. Conclusions: The disturbed fine motor control in CUWP patients is suggested to maintain chronic wrist pain through ‘strain injury, causing’ pain evasive adaptation of the motor control system. This might lead to new perspectives regarding treatment of CUWP patients.

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. FINDINGS After tenotomy of the flexor carpi ulnaris muscle, the maximal wrist torque decreased 18% whereas dissection of the muscle resulted in an additional decrease of 18%. INTERPRETATION We conclude that despite the tenotomy of its distal tendon, the flexor carpi ulnaris still contributes to the flexion torque at the wrist through myofascial force transmission. Quantification of this phenomenon will help in the study of the effects of fascial dissection on the functional results of tendon transfer surgery.

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

Smeulders MJC, Kreulen M, Hage JJ, Ritt MJPF, Mulder T: Motor control impairment of the contralateral wrist in patients with unilateral chronic wrist pain. Am J Phys Med Rehabil 2002;81:177–181. ObjectiveAssessment 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. DesignEighteen patients with chronic wrist pain in their dominant hand and 20 healthy controls performed, using their nondominant hand, back-and-forth, left-to-right stroke patterns with a pen on a digital writing tablet connected to a computer. Fluency of movement, defined as the number of zero-crossings of the acceleration curve (pZC), average stroke size, and average velocity were calculated. ResultsThe controls moved significantly more fluently than the patients (pZC, 0.26 ± 0.07 for controls and 0.46 ± 0.20 for patients;P < 0.001), suggesting that long-term afferent disturbances may compromise cerebral motor control mechanisms. ConclusionThis result is in accordance with the view that chronic pain complaints may be maintained by persistently abnormal cerebral motor control. This finding opens a new perspective on the understanding and treatment of chronic wrist pain.

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 ∼10%, indicating atrophy; and passive force increased, reflecting increased stiffness. FCU fiber length was unchanged. The presented case shows that human forearm muscle may adapt to a transferred function. Muscle Nerve, 2006