Fig 1.
A. Ovine patellar-tendon defect. B. Osteotomised tibial tuberosity with two suture anchors in situ. The defect was repaired with allograft in five sheep and with xenograft in the remaining five sheep. An interlocking Krakow suture technique was used to secure the DBM strip to the remaining proximal patellar tendon using a #2 FiberWire (Fig 1C). The distal end of the DBM strip overlying the tibial tuberosity was secured to the prepared flat surface using the two anchors and its margins sutured to the surrounding tissue to ensure consistent and complete contact with the bony footprint. The dimensions of the DBM strip were adjusted to match the length and width of the host patellar tendon prior to repair: averaged 20 mm wide and 100 mm long. The surgical wound was closed in layers using absorbable Vicryl sutures. The sheep were allowed to move freely postoperatively without restraint. Animals received intravenous Buprenorphine at a dose of 0.006–0.01 mg/kg for a maximum of four days after surgery. Digital lateral X-ray radiographs of both hind limbs were taken at 12 weeks. Fig 1C. Ovine patellar tendon defect repaired with allogenic DBM.
Fig 2.
Three morphological zones examined histologically.
Zone 1: DBM-patellar tendon interface; Zones 2: DBM in the region of the tendon defect; Zone 3: DBM neo-enthesis, examining the area of the new tendon enthesis over the tibial tuberosity.
Table 1.
Criteria for semi-quantitative analysis of demineralised bone matrix remodelling (Zones 1 and 2).
Table 2.
Criteria for semi-quantitative analysis of the tendon-bone interface (Zone 3).
Fig 3.
Box and whiskers plot showing percentage functional weight bearing of allogenic and xenogenic DBM groups at 6, 9 and 12 weeks.
Fig 4.
Photomicrographs showing appearance of DBM allograft and xenograft at 12 weeks.
Specimens stained with Toluidine Blue and Paragon. (a) Zone 1: Patellar tendon-DBM allograft interface characterized by well-organized, crimped collagen fibres with elongated fibroblast nuclei. (b) Zone 1: Patellar tendon-DBM xenograft interface characterized by well-organized, crimped collagen fibres with elongated fibroblast nuclei. (c) Zone 2: Tendon defect with complete remodeling of DBM allograft and large areas of well-organized, crimped collagen fibres with elongated fibroblast nuclei. (d) Zone 2: Tendon defect with complete remodeling of DBM xenograft and large areas of well-organized, crimped collagen fibres with elongated fibroblast nuclei. (e) Zone 3: Allogenic DBM neo enthesis comprising tendon (T), fibrocartilage (FC), mineralized fibrocartilage (MFC) and bone (B). (f) Zone 3: Xenogenic DBM neo enthesis comprising disorganised tendon (T), fibrocartilage (FC), mineralized fibrocartilage (MFC) and bone (B).