Taliah Schmitt

Human flexor tendon tissue engineering: in vivo effects of stem cell reseeding.

Background: Tissue-engineered human flexor tendons may be an option to aid in reconstruction of complex upper extremity injuries with significant tendon loss. The authors hypothesize that human adipose-derived stem cells remain viable following reseeding on human tendon scaffolds in vivo and aid in graft integration. Methods: Decellularized human flexor tendons harvested from fresh-frozen cadavers and reseeded with green fluorescent protein–labeled pooled human adipose-derived stem cells were examined with bioluminescent imaging and immunohistochemistry. Reseeded repaired tendons were compared biomechanically with unseeded controls following implantation in athymic rats at 2 and 4 weeks. The ratio of collagen I to collagen III at the repair site was examined using Sirius red staining. To confirm cell migration, reseeded and unseeded tendons were placed either in contact or with a 1-mm gap for 12 days. Green fluorescent protein signal was then detected. Results: Following reseeding, viable cells were visualized at 12 days in vitro and 4 weeks in vivo. Biomechanical testing revealed no significant difference in ultimate load to failure and 2-mm gap force. Histologic evaluation showed host cell invasion and proliferation of the repair sites. No increase in collagen III was noted in reseeded constructs. Cell migration was confirmed from reseeded constructs to unseeded tendon scaffolds with tendon contact. Conclusions: Human adipose-derived stem cells reseeded onto decellularized allograft scaffolds are viable over 4 weeks in vivo. The movement of host cells into the scaffold and movement of adipose-derived stem cells along and into the scaffold suggests biointegration of the allograft.

Augmentation of tendon healing with an injectable tendon hydrogel in a rat Achilles tendon model.

Background: Many unsolved problems in plastic and hand surgery are related to poor healing of acute and chronic tendon injuries. The authors hypothesized that tendon healing could be augmented by the addition of a tendon-derived, extracellular matrix hydrogel that would guide tissue regeneration. Methods: Both Achilles tendons of 36 Wistar rats were given full-thickness injuries approximately 5 mm long and 0.5 mm wide from the tendon insertion at the calcaneus to the midsubstance. The hydrogel was injected into the injury site of one leg and compared with control saline in the other. The ultimate failure load, ultimate tensile stress, and stiffness were evaluated at 2, 4, and 8 weeks. Tendon cross-sections underwent histologic analysis (hematoxylin and eosin and picrosirius red) after the animals were killed. Statistical analysis of biomechanical data was performed using a paired t test. Results: There was no significant difference in strength between gel and saline injections in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.42), or stiffness (p = 0.76) at 2 weeks. However, there was a significant difference in ultimate failure load (74.8 ± 11.6 N versus 58.4 ± 14.2 N; p = 0.02) at 4 weeks. The difference in ultimate tensile stress (p = 0.63) and stiffness (p = 0.08) remained insignificant. By 8 weeks, there was no significant difference in strength in ultimate failure load (p = 0.15), ultimate tensile stress (p = 0.39), or stiffness (p = 0.75). Conclusions: Treatment with the tendon hydrogel significantly increases the ultimate failure load of tendons at the critical 4-week time point, and is a promising method for augmentation of tendon healing.

Physicochemical decellularization of composite flexor tendon-bone interface grafts.

Background: Extremity injuries involving tendon attachment to bone are difficult to address. Clinically, tendon-bone interface allografts must be decellularized to reduce immunogenicity. Composite grafts are difficult to decellularize because chemical agents cannot reach cells between tissues. In this study, the authors attempted to optimize tendon-bone interface graft decellularization. Methods: Human flexor digitorum profundus tendons with attached distal phalanx were harvested from cadavers and divided into four groups. Group 1 (control) was untreated. Group 2 (chemical) was chemically treated with 5% peracetic acid, 0.1% ethylenediaminetetraacetic acid, and 0.1% sodium dodecyl sulfate. Group 3 (low-power) underwent targeted ultrasonication for 3 minutes (22,274 J, 126W) followed by chemical decellularization. Group 4 (high-power) underwent targeted ultrasonication for 10 minutes (88,490 J, 155W) followed by chemical decellularization. Decellularization was assessed histologically with hematoxylin and eosin stain and stains for major histocompatibility complex I stains. Cell counts were performed. The ultimate tensile load of decellularized grafts (group 4) were compared with pair-matched untreated grafts (group 1). Results: Average cell counts were 100 ± 41, 27 ± 10, 12 ± 11, and 6 ± 11 per high-power field for groups 1, 2, 3, and 4, respectively (p < 0.001). Decellularization using physical and chemical treatments (groups 3 and 4) resulted in substantial reduction of cells and major histocompatibility complex I molecules. There was no difference in ultimate tensile load between treated (group4) and untreated (group 1) samples (p > 0.5). Conclusions: Physicochemical decellularization of tendon-bone interface grafts using targeted ultrasonication and chemical treatment resulted in near-complete reduction in cellularity and maintenance of tensile strength. In the future, these decellularized composite scaffolds may be used for reconstruction of tendon-bone injuries.

Decellularized tendon-bone composite grafts for extremity reconstruction: an experimental study.

Background: Restoration of biomechanical strength following surgical reconstruction of tendon or ligament insertion tears is challenging because these injuries typically heal as fibrous scars. The authors hypothesize that injuries at the tendon-bone interface would benefit from reconstruction with decellularized composite tendon-bone grafts. Methods: Tendon-bone grafts were harvested from Sprague-Dawley rats. Grafts subjected to decellularization were compared histologically and biomechanically with untreated grafts ex vivo and in a new in vivo model. Wistar rats underwent Sprague-Dawley allograft reconstruction using a pair-matched design. The rats were killed at 2 or 4 weeks. B-cell and macrophage infiltration was determined using immunohistochemistry, and explants were tested biomechanically. Results: Decellularization resulted in a decrease in cells from 164 ± 61 (untreated graft) to 13 ± 7 cells per high-power field cells (p < 0.005) and a corresponding significant decrease in DNA content, and preserved scaffold architecture of the tendon-bone interface. Biomechanical comparison revealed no difference in failure load (p = 0.32), ultimate tensile stress (p = 0.76), or stiffness (p = 0.22) between decellularized grafts and untreated controls. Following in vivo reconstruction with tendon-bone interface grafts, decellularized grafts were stronger than untreated grafts at 2 weeks (p = 0.047) and at 4 weeks (p < 0.005). A persistent increase in B-cell and macrophage infiltration was observed in both the capsule surrounding the tendon-bone interface and the tendon substance in untreated controls. Conclusion: Decellularized tendon-bone grafts display better biomechanical properties at early healing time points and a decreased immune response compared with untreated grafts in vivo.

Decellularized Human Tendon–Bone Grafts for Composite Flexor Tendon Reconstruction: A Cadaveric Model of Initial Mechanical Properties

PURPOSE After complex hand trauma, restoration of tendon strength is challenging. Tendon insertion tears typically heal as fibrous scars after surgical reconstruction and create a weak point at the tendon-bone interface. In addition, major tendon loss may overwhelm the amount of available autograft for reconstruction. An off-the-shelf product may help address these challenges. We hypothesized that decellularized human flexor digitorum profundus and distal phalanx tendon-bone composite grafts were a feasible option for flexor tendon reconstruction after complex hand trauma. By replacing the entire injured composite segment, the need for tendon repair within the tendon sheath, reconstruction of the tendon-bone interface, and use of limited autograft could be eliminated. METHODS Paired human cadaver forearms were dissected to obtain the flexor digitorum profundus tendon with an attached block of distal phalanx. Tendon-bone grafts were pair-matched and divided into 2 groups: decellularized grafts (n = 12) and untreated (control) grafts (n = 11). Grafts in the decellularized group were subjected to physiochemical decellularization. Pair-matched tendon-bone grafts (decellularized and untreated) were placed back into the flexor tendon sheath and secured distally using a tie-over button and proximally by weaving the graft into the flexor digitorum superficialis tendon in the distal forearm. The ultimate load, location of failure, and excursion were determined. RESULTS Decellularized tendon-bone composite grafts demonstrated no significant difference in ultimate failure load or stiffness compared with untreated grafts. Both groups eventually failed in varied locations along the repair. The most common site of failure in both groups was the tie-over button. The decellularized group failed at the tendon-bone insertion in 3 specimens (25%) compared with none in the untreated group. Both groups demonstrated an average tendon excursion of approximately 82 mm before failure. CONCLUSIONS Decellularization of human flexor tendon-distal phalanx tendon-bone constructs did not compromise initial strength despite chemical and mechanical decellularization in a cadaveric model. At the time of repair, decellularized flexor tendon-bone grafts can exceed the strength and excursion needed for hand therapy immediately after reconstruction. CLINICAL RELEVANCE These tendon-bone grafts may become an option for complex hand reconstruction at or near tendon-bone insertions and throughout the tendon sheath. Further work is required to assess the role of reseeding in an in vivo model.

New Concepts and Technologies in Reconstructive Hand Surgery

Complex traumatic injuries and degenerative conditions of the hand continue to lead to significant impairment and disability. From technical innovations to regenerative concepts, this article presents the latest advances in the dynamic field of hand surgery in which worldwide efforts are made around the globe to repair, regenerate, or restore each composite tissue forming the hand. The systematic method by which finger replantation is performed, from bony fixation to skin closure, provides a platform for discussion of the newest innovations available to reconstructive hand surgeons.

Abstract: Lower Body Lift in the Massive Weight Loss Patient

videos was 13.1 (SE = .18) out of a possible 26. The videos found under the search “nose reshaping” had the lowest mean score (10.24 SE = .74) while “eyelid surgery” and “buttock lift” had the highest (14.36 SE = .83, 14.36 SE = .70). Videos with physician authorship, (59% of included videos), were found to have a higher mean EQIP score and video views than those posted by patients.. Whether the search term used was the appropriate medical terminology for the procedure or a non-expert description, such as “otoplasty” versus “ear surgery,” influenced how many of the top 50 videos were relevant to plastic surgery and the average EQIP score for that search.

Abstract: Post-Massive Weight Loss Chest Contouring

videos was 13.1 (SE = .18) out of a possible 26. The videos found under the search “nose reshaping” had the lowest mean score (10.24 SE = .74) while “eyelid surgery” and “buttock lift” had the highest (14.36 SE = .83, 14.36 SE = .70). Videos with physician authorship, (59% of included videos), were found to have a higher mean EQIP score and video views than those posted by patients.. Whether the search term used was the appropriate medical terminology for the procedure or a non-expert description, such as “otoplasty” versus “ear surgery,” influenced how many of the top 50 videos were relevant to plastic surgery and the average EQIP score for that search.