A review of cyclic testing protocols for flexor tendon repairs.

Area of Science:

• Orthopedic biomechanics
• Biomaterials science
• Regenerative medicine

Background:

• Cyclic testing is crucial for evaluating flexor tendon repairs, simulating post-operative rehabilitation more effectively than static testing.
• Existing cyclic testing protocols exhibit significant variability, hindering direct comparisons of flexor tendon repair outcomes.
• Standardization is needed to enhance the rigor and comparability of flexor tendon repair research.

Purpose of the Study:

• To systematically review and categorize existing cyclic testing protocols for flexor tendon repairs.
• To identify common parameters such as preload, cyclic load, cycle count, frequency, and displacement rate.
• To propose standardized protocols for simulating passive and active mobilization in flexor tendon rehabilitation.

Main Methods:

• A comprehensive literature search was conducted to identify studies utilizing cyclic testing for flexor tendon repairs.
• Protocols were analyzed and categorized based on key testing parameters: preload, cyclic load, number of cycles, frequency, and displacement rate.
• Data from 35 studies encompassing 42 distinct protocols were compiled and analyzed.

Main Results:

• Thirty-five studies contributed 42 unique cyclic testing protocols, with 31 being single-staged and 11 multi-staged.
• Preload varied across protocols, commonly set at 2 N, while cyclic loads typically ranged from 11 to 20 N.
• Most protocols employed 100-1000 cycles at frequencies below 1 Hz and displacement rates between 0-20 mm/min.

Conclusions:

• The heterogeneity in current cyclic testing protocols complicates the evaluation and comparison of flexor tendon repairs.
• Two standardized single-staged protocols are proposed: one for passive mobilization (15 N cyclic load) and one for active mobilization (38 N cyclic load).
• These proposed protocols aim to improve the design, comparison, and clinical evaluation of flexor tendon repair strategies.