Extended healing validation of an artificial tendon to connect the quadriceps muscle to the Tibia: 180-day study

Attaching artificial Achilles and tibialis cranialis tendons to bone using suture anchors in a rabbit model: assessment of outcomes

Objective

The purpose of this study was to investigate the factors associated with outcomes of attaching artificial tendons to bone using suture anchors for replacement of biological tendons in rabbits.

Study Design

Metal suture anchors with braided composite sutures of varying sizes (USP #1, #2, or #5) were used to secure artificial tendons replacing both the Achilles and tibialis cranialis tendons in 12 New Zealand White rabbits. Artificial tendons were implanted either at the time of (immediate replacement, n=8), or four weeks after (delayed replacement, n=4) resection of the biological tendon. Hindlimb radiographs of the rabbits were obtained immediately after surgery and approximately every other week until the study endpoint (16 weeks post-surgery).

Results

All suture anchors used for the tibialis cranialis artificial tendons remained secure and did not fail during the study. The suture linkage between the Achilles artificial tendon and anchor failed in 9 of 12 rabbits. In all cases, the mode of failure was suture breakage distant from the knot. Based on radiographic analysis, the mean estimated failure timepoint was 5.3±2.3 weeks post-surgery, with a range of 2-10 weeks. Analysis of variance (ANOVA) tests revealed no significant effect of tendon implantation timing or suture size on either the timing or frequency of suture anchor failure.

Conclusion

Based on the mode of failure, suture mechanical properties, and suture anchor design, we suspect that the cause of failure was wear of the suture against the edges of the eyelet in the suture anchor post, which reduced the suture strength below in vivo loads. Suture anchor designs differed for the tibialis cranialis and did not fail during the period of study. Future studies are needed to optimize suture anchor mechanical performance under different loading conditions and suture anchor design features.

Replacement of tibialis cranialis tendon with polyester, silicone-coated artificial tendon preserves biomechanical function in rabbits compared to tendon excision only

BACKGROUND

Artificial tendons may be an effective alternative to autologous and allogenic tendon grafts for repairing critically sized tendon defects. The goal of this study was to quantify the in vivo hindlimb biomechanics (ground contact pressure and sagittal-plane motion) during hopping gait of rabbits having a critically sized tendon defect of the tibialis cranialis and either with or without repair using an artificial tendon.

METHODS

In five rabbits, the tibialis cranialis tendon of the left hindlimb was surgically replaced with a polyester, silicone-coated artificial tendon (PET-SI); five operated control rabbits underwent complete surgical excision of the biological tibialis cranialis tendon in the left hindlimb with no replacement (TE).

RESULTS

At 8 weeks post-surgery, peak vertical ground contact force in the left hindlimb was statistically significantly less compared to baseline for the TE group (p = 0.0215). Statistical parametric mapping (SPM) analysis showed that, compared to baseline, the knee was significantly more extended during stance at 2 weeks post-surgery and during the swing phase of stride at 2 and 8 weeks post-surgery for the TE group (p < 0.05). Also, the ankle was significantly more plantarflexed during swing at 2 and 8 weeks postoperative for the TE group (p < 0.05). In contrast, there were no significant differences in the SPM analysis among timepoints in the PET-SI group for the knee or ankle.

CONCLUSIONS

Our findings suggest that the artificial tibialis cranialis tendon effectively replaced the biomechanical function of the native tendon. Future studies should investigate (1) effects of artificial tendons on other (e.g., neuromuscular) tissues and systems and (2) biomechanical outcomes when there is a delay between tendon injury and artificial tendon implantation.

Effect of polyester-based artificial tendons on movement biomechanics: A preliminary in vivo study

Artificial tendons may be valuable clinical devices for replacing damaged or missing biological tendons. In this preliminary study, we quantified the effect of polyester-suture-based artificial tendons on movement biomechanics. New Zealand White rabbits underwent surgical replacement of either the Achilles (n = 2) or tibialis cranialis (TC, n = 2) biological tendons with artificial tendons. Once pre-surgery and weekly from 2 to 6 weeks post-surgery, we quantified hindlimb kinematics and ground contact pressures during the stance phase of hopping gait. Post-surgical movement biomechanics were either consistent or improved over time in both groups. However, the Achilles group had greater overall biomechanical and muscle deficits than the TC group. In the TC group, at 6 weeks post-surgery, foot angles were about 10° greater than those in healthy controls during the first 30 % of stance. At 6 weeks post-surgery, the Achilles group exhibited lesser (i.e., more dorsiflexed) ankle angles (minimum angle = 31.5 ± 9.4°) and vertical ground reaction forces (37.4 ± 2.6 %BW) during stance than those in healthy controls (65.0 ± 11.2° and 50.2 ± 8.3 %BW, respectively). Future studies are needed to quantify long-term biomechanical function with artificial tendons, the effect of artificial tendons on muscle function and structure, and the effect of formal rehabilitation.

Repair of Tendon Disruption Using a Novel Synthetic Fiber Implant in Dogs and Cats: The Surgical Procedure and Three Case Reports

Surgical management of tendon rupture is challenging. One concern is to provide adequate tensile strength to prevent distraction during weight-bearing and gap formation following repair, associated with an increased risk of repair failure. Additional challenges may arise from the nature or the chronicity of the lesion. In the event of avulsion, when the tendon is torn off at the bone insertion, its reinsertion on the bone is generally difficult and may even be impossible in the presence of an avulsion fracture, especially when the bone fragment is too small or fragmented. Repair management is also complicated in chronic cases, as degeneration of the tendon may lead to excessive scar tissue formation, tendon retraction, and muscle atrophy, resulting in a large gap and inadequate tissue for reconstruction. The authors describe the surgical procedure for implanting a novel implant, illustrated by three characteristic clinical cases: (1) an acute Achilles tendon avulsion; (2) a chronic patellar tendon rupture; and (3) a chronic avulsion fracture of the triceps tendon. In these three cases, complete recovery of the function was observed at the last clinical evaluation (6 or 8 months), and no complication was noted. A splinted dressing (6 to 8 weeks) was used successfully in two cases. A resin cast (8 weeks) was preferred in case 1, a very active dog. In conclusion, this novel implant represents a simple procedure for the effective repair of chronic tendon rupture, as well as an effective tendon reinsertion on the bone and adequate support for bone tendon healing in the treatment of tendon avulsion, even in cases of fragmented bone fracture. The thinness of the implant facilitates its insertion into the native tendon, while the bone-screw-implant interface provides immediate and lasting mechanical support. This may facilitate the healing process and potentially shorten the period of immobilization.

Implanted passive engineering mechanism improves hand function after tendon transfer surgery: a cadaver-based study

PURPOSE

The purpose of this study was to investigate if a new tendon transfer surgical procedure that uses an implanted passive engineering mechanism for attaching multiple tendons to a single donor muscle in place of directly suturing the tendons to the muscle improves hand function in physical interaction tasks such as grasping.

METHODS

The tendon transfer surgery for high median ulnar palsy was used as an exemplar, where all four flexor digitorum profundus (FDP) tendons are directly sutured to the extensor carpi radialis longus (ECRL) muscle to restore flexion. The new procedure used a passive hierarchical artificial pulley system to connect the muscle to the tendons. Both the suture-based and pulley-based procedures were conducted on N = 6 cadaver hands. The fingers' ability to close around four objects when the ECRL tendon was pulled was tested. Post-surgery hand function was evaluated based on the actuation force required to create a grasp and the slip between the fingers and the object after the grasp was created.

RESULTS

When compared with the suture-based procedure, the pulley-based procedure (i) reduced the actuation force required to close all four fingers around the object by 45 % and (ii) improved the fingers' individual adaptation to the object's shape during the grasping process and reduced slip by 52 % after object contact (2.99° ± 0.28° versus 6.22° ± 0.66°).

CONCLUSIONS

The cadaver study showed that the implanted engineering mechanism for attaching multiple tendons to one muscle significantly improved hand function in grasping tasks when compared with the current procedure.