Biomechanical evaluation of FDS (flexor digitorum superficialis), 1/2FDS, and palmar fascia in the correction of claw fingers and the clinical exploration of 5 cases with 1/2FDS as tendon stiffness

Abstract

Purpose FDS (flexor digitorum superficialis), 1/2FDS, and palmar fascia are 3 surgical procedures commonly used to correct the deformities of claw fingers after ulnar nerve injury. FDS and palmar fascia traditionally are the more common procedures. The fomer requires the whole FDS, while the latter sometimes causes the recurrence of deformity because of its transfiguration. The of 1/2FDS spare the motor tendon and the recurernce rate is expected to be lower. A biomechanical study was performed to determine whether the biomechanical character of the three tissues is suit for surgery procedure; Another follow-up study was performed to determine the clinical outcome with the 1/2FDS loop tenodesis operation in treatment of patients with ulnar claw fingers. Methods Ten fresh symmetrical arms in adults were tested, whose palmar fascias and FDSs of each finger were cut down respectively. And then 5 of the 10 FDSs were split into two tails equally. All samples were tested by an Instron Universal Test Instrument (model AG-10TA; made in Japan), which would control the stress and strain exerted on the test sample automatically, and print out the data of each load, elongation, stress and strain, then the curve of stress compared with elongation. 5 patients presented 5 affected 5 hands with ulnar claw fingers, had the 1/2FDS loop tenodesis procedure from May 1990 to March 2010. Each hand was assessed before surgery and at follow-up evaluation by predetermined angle measurements, power grip, motion, mechanical function, and patients'satisfaction. Results Biomechanical study showed that FDS and that in half could endure large amount of stress exerted on it with less elongation in size. The difference between half FDS with palmar fascia group was statistically significant (P<0.05) in maximum stress and in maximum elongation in size. The maximum stress of half FDS was ten times larger than that of palmar fascia, while the maximum elongation in size of palmar fascia was two times bigger than that of half FDS. In the aspect of modulus of elasticity, there was no significant difference between the two groups of FDS integrated and that in half (P>0.05)f, but it was significant weaker in half FDS than palmar fascia(P<0.05). After an average follow-up period of 34 months, Corrections of deformity with the 1/2FDS loop tenodesis procedure was satisfactory in all patients without recurrence. Power grip remained static in most cases. Motion and function of the fingers were satisfactory. Conclusion The 1/2FDS provided us a better procedure for tenodesis than palmar fascia by biomechanical testing. It avoids the disadvantage to sacrifice large amount of FDSs that would result in new disorders of hand.