Objective: To determine if the anatomical location of a tendon (hand or forearm) influences fibroblast function in the presence of physical forces.

Introduction Tendons are anatomical structures specialized to transmit high tensile loads from muscle to bone. When damaged, clinical recovery is slow and incomplete. Various authors have shown that application of tensile loading during recovery (such as in early active motion following hand flexor tendon repair) will accelerate the recovery of tensile strength. The mechanism is unknown and the optimum loading regime has not been quantitated. It is likely that similar influences are working in rheumatoid arthritis but there is clinical evidence that the response to applied load is very different. In this study a commercial system (Bio stretch) was used to apply different strain regimes to cells in culture, and then to assess the response by a series of quantitative methodologies

Materials Cells were obtained by the explant technique from tendons of the hand and forearm to generate confluent cultures. In this experiment fibroblasts cultured from intra-synovial tendons (Group 1)were compared with cultured fibroblasts of forearm tendons (Group II). We used the Biostretch Apparatus (ICCT Technologies Canada), to stretch fibroblasts in a gel foam (Helistat, Integra TM ) construct. The Biostretch apparatus uses a magnetic field to stretch cells within the gel foam. After seeding the gel foam pieces (1cm2) with a concentrated cell suspension (4 x105 cells/100 μlitre) , the apparatus was used at 40% stretch, with a burst time of 15 minutes and a rest time of 45 minutes at 37° C and 60 cycles a second for 24 hours. The experiment was performed in triplicate for both type of cells (Group I & II), with another group of cells serving as controls. At the end of 24 hours the BCA method was used to estimate Total Protein content while the Sircol method was used to determine Type 1 Collagen levels.

Results: Preliminary results indicate that there is a trend towards increased secretion of proteins and collagen in the stretched samples compared to the controls. Similarly the fibroblasts obtained from intra-synovial tendons seemed to produce more total protein and collagen as compared to the forearm. However both these observations failed to reach statistical significance.

Conclusions: Previous work (Evans CE et al. 2001) has shown no difference between collagen and protein production between flexor and extensor tendon, even under strain,. In this study the increased production of matrix proteins and collagen under the influence of physical strain may explain why flexor tendon injuries in the hand tend to heal with the formation of adhesions and poor functional results as compared with the forearm where the results tend to be uniformly better. However it must be stressed that these are preliminary results and further work will be required to provide definitive data.