Background: Human costal cartilage remains widely used in the reconstruction of soft tissues, particularly within the field of plastic and orthopaedic surgery. The biologic expense of using autologous human costal cartilage has become superseded by the increasingly common use of irradiated costal cartilage allografts. To date, there has been no histologic investigation of such costal cartilage allografts. This study aims to characterize the histologic variations that exist between different costal cartilage specimens, and to quantify this between specimens in spite of their common anatomical derivation. Methods: Twenty-five specimens of cadaveric human costal cartilage were obtained from Australian Biotechnologies. Each specimen was irradiated, sectioned and stained with Haematoxylin and Eosin, Masson's trichrome and tetrachrome stains. After being analysed under light microscopy, specimen dimensions, chondrocyte counts and mineral content was quantified and measured. Results: The median specimen diameter was 8.20 mm, with an interquartile range (IQR) of 1.59 mm. The median measurement from the superficial to basal chondrocyte layer was 1409.91 μm (IQR = 885.59 μm), and the median measurement from superficial to calcified zone was 4146.26 μm (IQR 1441.83 μm). The median chondrocyte area was 442.74 μm 2 (IQR = 2622.72 μm 2 ) with their total chondrocyte count ranging from 289 to 591 chondrocytes per square millimetre. The median percentages of collagen and mineral content were 45.17% and 71.82%, respectively (IQR = 20.48%, 14.75%). Conclusion: These findings emphasize the histologic and biochemical degree of variation that exists between specimens of human cadaveric costal cartilage on a microscopic level. This has the potential to influence the selection of costal cartilage allografts for reconstructive purposes.

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Background: Numerous repair techniques have been described for closed flexor digitorum profundus (FDP) avulsion. One option is a pull-out suture tied over the nail plate (Bunnell repair). We modified the Bunnell repair by incorporating a portion of the distal interphalangeal (DIP) joint volar plate into the repair to improve strength and reduce gapping. The aim of this study is to compare gap formation and load to failure between the Bunnell repair and our modification in a turkey foot model. Methods: Twenty-four fresh-frozen cadaveric turkey feet were divided into two repair groups namely the conventional Bunnell pull-out suture technique and the modified Bunnell pull-out suture technique, incorporating the middle-third of the DIP joint volar plate into the repair. Both repairs were carried out with 3-0 prolene suture and underwent ex-vivo cyclic loading at 2-12 n in a sinusoidal wave for 100 cycles to simulate a passive range of motion (ROM) protocol. Subsequently, specimens were loaded to failure at 12 mm/minute. Gap formation and load to failure were measured. Results: No repair ruptures occurred during cyclical testing. Mean gap formation was 9.2 mm (±1.49) in the Bunnell repair, and 3.5 mm (±1.19) in the modified Bunnell repair (p < 0.0001). The mean load to failure for the Bunnell repair was 35.4 n compared to 45 n for the modified repair (p = 0.0017). Conclusions: Gap formation was reduced and load to failure increased by augmenting the Bunnell pull-out suture repair with the central portion of the DIP joint volar plate.