Donald L. Pruitt

Biomechanical and histologic characteristics of canine flexor tendon repair using early postoperative mobilization.

The purpose of this experimental study was to evaluate the mechanical and histologic healing of flexor tendon repairs using an early active motion protocol. Three different flexor tendon repair techniques in zone II were used. Forty-seven lacerated canine flexor profundus tendons from 25 dogs were repaired and evaluated at 5, 10, and 21 days after surgery. Eight of 9 Kessler repairs ruptured at days 5 and 10. None of the 19 Savage repairs or the 19 dorsal tendon splint repairs ruptured; 3 of 19 dorsal tendon splint repairs failed owing to adhesions. Smooth tendon gliding was obtained in all specimens in which repair was successful. The gap strength values for both the Savage and dorsal tendon splint repairs improved significantly for day-21 specimens compared to day-5 or day-10 specimens. The ultimate tensile strength showed no reduction during the 3-week period of tendon healing for both repairs. Histologically, there was evidence of progressive healing without surrounding adhesions. The improved suture techniques have the potential to withstand the stress produced by active digital motion protocols.

Cyclic stress analysis of flexor tendon repair

A method of evaluating flexor tendon repair techniques with the use of cyclic testing is presented. This type of evaluation complements the presently used load-to-failure tests by providing more detailed information about gap formation at the repair site. During load-to-failure testing in this study, core sutures alone demonstrated initial gap formation at 0.85 kg tensile force or more; yet on cyclic testing all techniques demonstrated gap formation of 1.9 mm or greater at 0.5 kg tensile force. Thus cyclic testing demonstrated gap formation not readily apparent on load-to-failure testing. An epitenon stitch placed circumferentially around the laceration site added strength in both load-to-failure and cyclic tests, and significantly reduced gap formation regardless of the core suture technique.

Effect of motion and tension on injured flexor tendons in chickens

This study was undertaken to evaluate the individual effects of motion and tension on the healing response of injured flexor profundus tendons in chickens. Partial midsection transverse lacerations of the profundus tendons were produced in 53 chickens. Postoperatively, they were assigned randomly to four management groups: both motion and tension; only motion, no tension; no motion, only tension; no motion and no tension. Biomechanical results at 4 weeks showed that breaking strength significantly increased with both motion and tension, significantly decreased with neither, and was intermediate with only motion or only tension. Histologic evaluation generally showed the greatest cellular activity with both motion and tension, the least with neither, and an intermediate response with one or the other alone. Collagen fiber staining was increased primarily in the tension groups. The finding that both motion and tension enhance the tendons response to injury encourages the development of active mobilization protocols following tendon repair.

Mechanical properties of various circumferential tendon suture techniques

We evaluated the mechanical properties of six different circumferential tendon sutures with a variable number of suture strands. Seventy-two human cadaver flexor profundus tendons were cut and repaired using only a 6/0 polypropylene circumferential suture. The six running suture techniques were: Simple; Simple-locking; Lembert; Halsted; Cross-stitch; Lin-locking; using 10, 14 and 18 suture passes. The increased suture passes increased both tensile and gap strengths. The tensile strength of the Lin-locking technique (29 to 63 N) was significantly stronger than the others, followed by Cross-stitch (27 to 38 N), Halsted (21 to 27 N), Lembert (20 to 27 N), Simple (11 to 22 N) and Simple-locking (10 to 17 N). The gap strength values were between 3 to 14 N, with no significant differences between the techniques. The resistance to gliding, as measured by work of flexion, was not affected by the number of strands. However, the Lin-locking significantly increased the resistance to gliding (33-36%) compared to the other techniques (6-21%); there were no significant differences between these five techniques.

Work of Flexion after Tendon Repair with Various Suture Methods A human cadaveric study

After flexor tendon repair there is often increased resistance to tendon gliding at the repair site, which is greater for techniques using increased suture strands or suture material. This increased “friction” may be measured as the “work of flexion” in the laboratory setting. Tendon repairs performed in zone 2 in human cadaver hands using the two strand Kessler, the lateral Becker, the six strand Savage, internal and dorsal tendon splint, or the external mesh sleeve techniques, had “work of flexion” measurements made both before and after the laceration and repair. The average increase in work of flexion was 4.8% for Kessler; 6.5% for Becker; 10.9% for Savage; 19.3% for the internal tendon splint, 16.2% for the dorsal tendon splint and 44.3% for the external mesh sleeve. The work of flexion was found to increase in direct proportion to the amount of suture material at the repair site.

Computed tomography scanning with image reconstruction in evaluation of distal radius fractures

Seventeen patients with 18 intraarticular distal radius fractures underwent computed tomography (CT) scanning and image reconstruction to evaluate their distal radius fractures. All patients were selected prospectively because of intraarticular extension and/or displacement of their fractures on pre- or post reduction plain films. Patients who were not surgical candidates for open reduction and internal fixation of their fracture were not included in the study. X-ray films and CT scans were viewed separately and in random order by a senior radiologist not familiar with the cases. Both x-ray films and CT scans readily showed extension of fracture lines into the radiocarpal joint, radial shaft, and the ulnar styloid, but CT scans were better than x-ray films at demonstrating fracture involvement of the distal radioulnar joint, the extent of articular surface depression, and the amount of comminution. Due to the cost, it is recommended that the test only be used for patients who are surgical candidates for open reduction and internal fixation or when more information about the extent of comminution and joint depression is required.

Effect of suture knot location on tensile strength after flexor tendon repair

This study investigated the effect of increased suture material within the flexor tendon repair site on tensile strength in a canine model after in vivo healing. Four-strand modified Savage suture repairs with the knots located either inside or outside the repair site were performed in dogs. The tendons were placed on a passive-motion protocol after surgery and were biomechanically tested at 1, 3, and 6 weeks of in vivo healing. The knots-outside technique initially was 1.14 kg stronger on load-to-failure testing. After 6 weeks of healing, the knots-inside tendons had equal tensile strength (3.91 +/- 0.50 kg [inside] vs 4.16 +/- 0.66 kg [outside]). Relative tensile strength compared to initial strength showed an increase of 20% for the knots-outside technique and an increase of 67% for the knots-inside technique after 6 weeks. Suture material within the repair site did not have any deleterious effects on tensile strength and may stimulate tendon healing.

Effect of cyclic tension on lacerated flexor tendons in vitro

The effect of tension on tendon healing was evaluated in vitro using cyclic tension and no tension groups of chicken flexor digitorum profundus tendons and histologic and immunohistologic techniques. A Vitrodyne force-loading machine was used for application of cyclic tension on partially lacerated chicken flexor tendons in culture media. Laceration sites under cyclic tension after 14 days were covered by newly proliferated fibroblasts, aligned in the direction of tension. This new growth was much thicker than that seen in the no tension group at the same time interval. Procollagen synthetic activity began at 3 days of culture in both groups. At 21 days, newly formed fibroblasts in the cyclic tension group were stained positive more strongly at the surface layer than in the deeper layers. In the no tension group, the staining was primarily in the surface layer. Cyclic tension stimulated the intrinsic response of lacerated flexor tendons significantly more than no tension did by enhancing proliferation and migration of fibroblasts, as well as stimulating collagen synthesis.

Effect of Suture Knots on Tensile Strength of Repaired Canine Flexor Tendons

59 dog cadaver flexor digitorum profundus tendons were repaired with one or two knots inside or outside the tendon, using two, four and six suture strands. The ultimate tensile strength and gap strengths were compared. Locating the knots outside rather than within the tendon repair site showed significantly higher ultimate tensile strength for two, four, and six strand sutures. The strength was greater in one knot than in two knot sutures; the value of the six-strand suture using the one knot outside technique was the greatest. Similarly, increased gap strength was also obtained from the one-knot-outside technique. We concluded that the knots should be located away from the tendon repair site and there should be as few as possible.

Tendon repair using flexor tendon splints: An experimental study

Mechanical strength of tendon repair using Dacron tendon splints across the laceration site were evaluated in human cadaver profundus tendons; the splints were placed both on the dorsal surface and internally within the tendon substance. Comparison was made to modified Kessler, Becker, and Savage repair techniques. Ultimate tensile strength was 2.55 kgf for the Kessler, 3.00 kgf for the Becker, 8.29 kgf for the Savage, 8.46 kgf for the internal tendon splint, and 8.10 kgf for the dorsal tendon splint; the Savage and both Tendon Splints techniques had significant higher tensile strength than the Kessler and Becker. Gap strength was 1.44 kgf for the Kessler, 2.22 kgf for the Becker, 2.45 kgf for the Savage, 2.05 kgf for internal tendon splint, and 3.15 kgf for the dorsal tendon splint. The dorsal tendon splint technique showed significant greater gap strength than the other four techniques. There was no significant difference in the magnitude of the gap during cyclic testing of these techniques; however, three of seven Kessler repairs failed and one of six Becker repairs failed. The results of these cadaver studies suggest that both tendon splint repair techniques are comparable to the Savage and may have sufficient strength to allow postoperative active motion against minimal resistance. Further in vivo testing is in order.