An experimental flexor tendon repair in zone II that allows immediate postoperative mobilization

Active mobilisation after flexor tendon repair: comparison of results following injuries in zone 2 and other zones

PURPOSE

To prospectively study the role of active mobilisation after flexor tendon repair.

METHODS

The standard modified Kessler's technique was used to repair 46 digits in 32 patients with flexor tendon injuries. Early active mobilisation of the repaired digit was commenced on the third postoperative day. Range of movement was monitored and recovery from injury in zone 2 was compared with injury in other zones.

RESULTS

There were 24 and 22 injuries in zone 2 and other zones respectively. The total active motion score of the American Society for Surgery of the Hand was measured. Patients with zone-2 injuries achieved similar results to those with other-zone injuries apart from a 3-week delay in recovery. The final results were good to excellent in 71% and 77% of zone-2 and other-zone cases respectively (p < 0.05). There were 2 ruptures in zone-2 and one rupture in zone-3 repairs (6.5%).

CONCLUSION

Preliminary results of this study showed that active mobilisation following flexor tendon repair provides comparable clinical results and is as safe as conventional mobilisation programmes although recovery in patients with zone-2 injury was delayed.

Splinting programmes for tendon injuries

It is beyond doubt that splinting programmes have often been an integral and important part of the rehabilitation process in tendon injuries. Over the past three decades, hand splints for tendon injuries of various designs and different mobilisation programmes have been developed in the hope of pursuing better clinical and functional outcome for patients. In this paper, the development of different splinting programmes in flexor and extensor tendon injuries and the current practice in some acute hospitals in Hong Kong were discussed.

Zone II tendon repairs augmented with autogenous dorsal tendon graft: a biomechanical analysis

We investigated the biomechanical properties of a new technique for tendon repair that reinforces a standard suture with an autogenous tendon graft. A dynamic in situ testing apparatus was used to test 40 flexor digitorum profundus tendons harvested from fresh-frozen cadaver hands. The tendons were cut and repaired using 1 of 4 suture techniques: 2-strand modified Kessler, 4-strand modified Kessler, 6-strand modified Savage, and 2-strand modified Kessler augmented with autogenous dorsal tendon graft. The augmented repair uses 1 slip of the flexor digitorum superficialis tendon secured to the dorsal surface of the repair site with a continuous stitch. Ultimate tensile strength, resistance to gap formation, and work of flexion were measured simultaneously on an in situ tensile testing apparatus. No significant difference in tensile strength was found between the augmented repair and the 6-strand Savage repair. The augmented repair and the 6-strand Savage repair showed significantly greater ultimate tensile strength than the 2- and 4-strand repairs. The augmented repair had significantly greater resistance to 2 mm gap formation than the other 3 repairs. We were unable to show a significant difference in work of flexion between the repairs with the numbers tested (n = 10). Our findings suggest that the augmented repair is strong enough to tolerate the projected forces generated during active motion without dehiscence or gap formation at the repair site.

Flexor tendon suture methods: a quantitative analysis of suture material within the repair site

This study compared the cross-sectional area and volume occupied by suture material at the repair site in three common methods of flexor tendon repair. A total of 51 human cadaveric tendons were studied. Zone II flexor digitorum profundus tendon lacerations were created and then repaired using the techniques described by Kessler, Tajima, and Savage. Quantitative cross-sectional area and volumetric measurements of suture material within each repair site were determined using a digital image analysis system. The Tajima repair occupied 27% of the tendon area at the repair site, while the Savage and Kessler repairs occupied 18% and 2%, respectively.

Results of dynamic splintage following extensor tendon repair

We report a prospective study of dynamic splintage following extensor tendon repair. Eighty-four patients with 101 extensor tendon injuries were studied. Using Dargan's evaluation system, there were 97% excellent results for the thumb and 93% excellent and good results for the fingers. The average total active motions were 107 degrees for thumbs and 245 degrees for fingers. Over 80% of patients regained good power grip. Patients with associated digital fractures or with ragged lacerations had poorer results. Overall, we found that dynamic splintage was a satisfactory method after extensor repair.

Augmented Becker versus modified Kessler tenorrhaphy in monkeys: dynamic mechanical analysis

The strength and gliding efficiency of an augmented Becker and Kessler tendon repair techniques were compared in fresh cadaver macaque monkey hands. Gliding efficiency was determined by comparing tendon work and load measurements made during tendon excursion to full fist with the same measurements made after tendon repair. Repair strength was then determined by tendon distraction to complete repair rupture. Data were gathered by computer controlled tensiometer and analyzed by factorial and repeated measures ANOVA. The augmented Becker repairs were significantly stronger than Kessler repairs. Repaired tendons required more load and work to bring the fingers into full fist; both repair types resulted in gliding efficiencies of 30% compared to intact controls. The augmented Becker repair is significantly stronger in situ than the modified Kessler and is recommended when early postoperative motion regimens are planned.

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.

An in vitro model of fibroblast activity and adhesion formation during flexor tendon healing

We studied fibroblast activity during tendon healing with an in vitro tendon culture model. Tendons were embedded in a translucent collagen gel matrix whose porous nature permitted free nutrient diffusion, fibroblast migration out of the tendon, and microphotographic documentation of fibroblast activity. Experiments were performed using one or more tendons cultured in the same collagen gel. We identified three zones of fibroblast activity in the gel. Zone I was an area of randomly dispersed cells directly adjacent to the tendon where collagen synthesis and remodeling were probably taking place. In zone II, spindle-shaped fibroblasts were aligned pointing away from the cut tendon end forming a sunburst-like aggregate of cells. Zone II fibroblasts were responsible for formation of migration trails by exerting a mechanical force on the collagen matrix, which was evident as a local gel contraction. Zone III was the leading edge of the sunburst populated by the fastest moving fibroblasts, which responded to guidance by other cut tendon ends. We speculate that the collagen gel used in the culture system may help maintain a chemotactic concentration gradient that allows fibroblasts to locate other distal cut tendon surfaces also embedded in the collagen gel.

Mechanical analysis of tendon suture techniques

The relative strengths of seven methods of tendon repair were measured by mechanical disruption in an effort to determine the quality of a technique using loaded criss-crossing sutures and a running epitenon stitch. Fifty-seven calcaneus tendons were harvested from adult New Zealand white rabbits and randomized for transection. Standardized oblique transections were repaired with nylon using modified Halsted peripheral suture; modified Kessler technique; Kessler core stitch alone; running peripheral epitenon stitch; modified Becker technique #1; modified Becker technique #2; and a new augmented Becker repair. Sixteen additional rabbits each had bilateral tendon repairs in situ, one leg by Kessler and the other by the new augmented Becker repair technique. Half were lethally injected after 2 weeks and half after 4 weeks. Tenorrhaphies were pulled apart at constant speed until a gap of 1 mm was observed. Strength (maximum stress) and toughness (energy absorption to gap formation) were calculated. At time 0 the new augmented Becker repairs were the strongest, followed by the Kessler and Becker #2 tenorrhaphies. Kessler repairs were weaker at 2 weeks and then gained in strength; new augmented Becker repairs did not weaken at the 2-week point and demonstrated significant gains in strength after 4 weeks in vivo. The new augmented Becker repair was the strongest by a significant margin at all time points.

Tensile strength of the end-weave flexor tendon repair. An in vitro biomechanical study

A study was designed to investigate the tensile strength of the end-weave method of tendon repair. Flexor tendons were removed from 13 fresh-frozen human cadavers, transected and repaired with the end-weave technique varying from one to five weaves, with two suture techniques, the commonly used horizontal mattress suture and a new method we have termed the cross stitch. The repairs were then tested in tension to failure on a Materials Test System (MTS) biomechanical testing device. Comparisons were also made to tensile strengths of intact whole tendons, tendon-bone insertions, and distal reinsertion techniques. Tensile strength increased linearly with the number of weaves for both suture methods. The cross stitch was found to have significantly greater strength per weave compared to the horizontal mattress suture (P < 0.05). Three out of five trials of five weaves done with the cross stitch actually failed at the tendon itself first, rather than through the repair, which was the failure mode for all other trials. The results from this in vitro model suggest that active rehabilitative exercises might safely be performed in the immediate post-operative period after procedures that involve tendon weaving.

Early active mobilization after flexor tendon repairs

Traditional methods of treatment for flexor tendon injuries required cumbersome splinting and a high degree of patient compliance to prevent joint contractures of adherent tendons. In Belfast in 1985 a pilot study was set up to investigate the feasibility of simple splinting of the hand and full-range passive movement into flexion and extension, with active movement of the repaired tendon commencing within 48 hours of surgery. The study was repeated in Sheffield, which confirmed the methodology established in Belfast. This report describes the treatment regimen and summarizes the results of three studies undertaken. It is concluded that the key to the success of early active mobilization is the simplicity of the regimen for both patient and staff, with only one plaster application requiring no alteration throughout the treatment, thus providing a safe environment for patients to undertake full passive and active movements from 48 hours post repair.

In vitro biomechanical analysis of suture methods for flexor tendon repair

This study was designed to compare five different suture methods that are used clinically for tendon repair. The flexor digitorum profundus tendons from the digits of adult mongrel dogs and adult human cadavers were used as models. The tendons in zone II of the hand, defined as the region from the distal palmar crease to the insertion of the flexor digitorum superficialis tendon at the middle phalanx, were transected and then were repaired by one of the suture methods developed by Kessler, Tsuge, Tajima, Savage, or Lee. The gliding function and tensile properties of the repaired tendons were evaluated biomechanically at time zero. The Tajima and Savage methods produced better gliding function than the other techniques. In the canine specimens that had been repaired by one of these two methods, the rotation of the distal interphalangeal joint was more than 60% of the rotation of the canine control specimens; only the Savage technique produced a rotation 124% that of the human control specimens. After the Tajima repair, the rotation of the proximal interphalangeal joint was 113% that of the canine control specimens and 157% that of the human controls. In the canine specimens that had had the Tajima or Savage repair, excursion of the tendon was greater than 55% that of the controls. The tendons repaired by the Savage method tolerated a significantly higher ultimate load to failure (14 and 25% that of the canine and human control specimens, respectively) than the other methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical analysis of a step-cut technique for flexor tendon repair

We compared the strength of a new step-cut technique for flexor tendon repair with that of the widely used Kessler-Tajima technique, giving special attention to the relative contributions of the core and epitendinous sutures. 36 flexor digitorum profundus tendons from human cadavers were used. Corresponding digits from the same donor were paired, and the two tendons of each pair were placed in the Kessler-Tajima and step-cut groups, respectively. Each group had three subcategories of repair: (1) core repair alone; (2) epitendinous repair alone; and (3) full repair. In the Kessler-Tajima repair, the core stitch contributed more to ultimate tensile strength, while the epitendinous stitch contributed more to gap formation resistance. In the step-cut repair, however, the epitendinous stitch contributed more to both measures of strength. The full step-cut repair was 65% stronger in resisting gap formation and had 84% more ultimate tensile strength than the full Kessler-Tajima repair. We attribute the greater strength of the step-cut repair to the additional number of epitendinous loops, which lie perpendicular to the long axis of the tendon.

The effects of frequency and duration of controlled passive mobilization on tendon healing

This study was designed to determine the effects of frequency and duration of controlled passive motion on the healing flexor tendon following primary repair. Adult mongrel dogs were divided into two groups based on frequency of controlled passive motion. In one group, motion was applied manually at a frequency of 12 cycles/min for 5 min/day; in the other group, a continuous passive motion machine was used to apply motion at a lower frequency of 1 cycle/min for 60 min/day, making the number of cycles each day for both groups identical. Gliding function and tensile properties of repaired tendons were evaluated biomechanically at 3 and 6 weeks postoperatively. Results showed that gliding function in both groups was similar, but tensile properties, as represented by linear slope, ultimate load, and energy absorption, were significantly improved in the higher frequency group. It was concluded that frequency of controlled passive motion rehabilitation is a significant factor in accelerating the healing response following tendon repair, and higher frequency-controlled passive motion has a beneficial effect.

Double loop locking suture: a technique of tendon repair for early active mobilization. Part I: Evolution of technique and experimental study

This article describes a technique of tendon repair and two variations using double loop locking sutures. Experimental study on human tendon specimens showed that the average tensile strength of tendon junctures was 4400 grams by double loop locking sutures and 2252 grams by Kessler's technique. The study also showed that the weakest point of the tendon juncture by double loop locking sutures was the sutures.

Excursion of the flexor digitorum profundus tendon: a kinematic study of the human and canine digits

The most common problem following primary flexor tendon repair is the failure of the tendon apparatus to glide, secondary to the formation of adhesions. Early motion following tendon repair has been shown to be effective in reducing adhesions between the tendon and the surrounding sheath. Therefore, it is important to determine the amount of flexor tendon excursion along the digit during joint motion. In this study, the excursion between the flexor digitorum profundus (FDP) tendon and the sheath was examined in both human and canine digits. Based on roentgenographic measurements and joint kinematic analysis, the motion of the bones, the FDP tendon, and the sheath were measured with respect to joint rotations. It was found that the canine flexor tendon apparatus behaved similarly to that of the human for the motions studied. The amount of tendon excursion was very small in regions distal to the joint in motion (approximately 0.1 mm/10 degrees of joint rotation). There was little displacement of the sheath (0.2-0.3 mm), except at the metacarpal joint region during metacarpophalangeal (MCP) joint motion and at the proximal interphalangeal (PIP) joint region during PIP joint motion. Tendon excursion relative to the tendon sheath was the largest in zone II during PIP joint rotation (1.7 mm/10 degrees of joint rotation). These results suggest that PIP joint motion may be most effective in reducing adhesions following tendon repair in zone II.

Early active mobilisation following flexor tendon repair in zone 2

In a prospective study, 114 patients with 138 zone 2 flexor tendon injuries were treated over a three-year period. Early active mobilisation of the injured fingers was commenced within 48 hours of surgery. 98 patients (86%) were reviewed at least six months after operation. Using the grading system recommended by the American Society for Surgery of the Hand, the active range of motion recovered was graded excellent or good in 77% of digits, fair in 14% and poor in 9%. Dehisence of the repair occurred in 11 digits (9.4%) and in these an immediate re-repair followed by a similar programme of early active mobilisation resulted in an excellent or good outcome in seven digits.

Flexor Tendon Surgery

We have attempted to review the development and current status of flexor tendon surgery. The methods of acute flexor tendon repair, conventional free tendon grafting, staged flexor tendon reconstruction, tenolysis and pulley restoration have been discussed, with the published results included for each procedure. The role of rehabilitation has also been reviewed and the ongoing quest for an active flexor tendon prosthetic implant has been briefly mentioned. It may be seen that flexor tendon surgery is a complex and difficult art which requires a thorough appreciation of the normal flexor tendon system, the exact status of that system following injury and surgery and a strong understanding of the techniques which may be best utilised to restore tendon gliding and digital joint motion. The procedures described require both technical skill and experience and the post-operative therapy programmes must be carefully chosen for each patient. With the important laboratory and clinical advancements occurring in many areas of flexor tendon surgery, it is realistic to believe that in the future the techniques described here will be substantially altered and modified and to hope that results will continue to improve until the patient and surgeon can expect to restore most digits to nearly full function after flexor tendon interruption.