The objective of the present study was to perform an in vivo assessment of a novel silk-collagen scaffold for anterior cruciate ligament (ACL) reconstruction. First, a silk-collagen scaffold was fabricated by combining sericin-extracted knitted silk fibroin mesh and type I collagen to mimic the components of the ligament. Scaffolds were electron-beam sterilized and rolled up to replace the ACL in 20 rabbits in the scaffold group, and autologous semitendinosus tendons were used to reconstruct the ACL in the autograft control group. At 4 and 16 weeks after surgery, grafts were retrieved and analyzed for neoligament regeneration and tendon-bone healing. To evaluate neoligament regeneration, H&E and immunohistochemical staining was performed, and to assess tendon-bone healing, micro-CT, biomechanical test, H&E and Russell-Movat pentachrome staining were performed. Cell infiltration increased over time in the scaffold group, and abundant fibroblast-like cells were found in the core of the scaffold graft at 16 weeks postoperatively. Tenascin-C was strongly positive in newly regenerated tissue at 4 and 16 weeks postoperatively in the scaffold group, similar to observations in the autograft group. Compared with the autograft group, tendon-bone healing was better in the scaffold group with trabecular bone growth into the scaffold. The results indicate that the silk-collagen scaffold has considerable potential for clinical application.

BackgroundIt remains unclear whether conservative treatment should be used to treat the common undisplaced femoral neck fractures that develop in the elderly. Herein, we systematically review the rates of union and avascular necrosis after conservative and surgical treatment of undisplaced femoral neck fractures.MethodsWe searched the EMBASE, PubMed, OVID, Cochrane Library, Web of Science, and Scopus databases for randomized controlled trials or observational studies that assessed the outcomes of conservative or surgical treatments of undisplaced femoral neck fractures. No language or publication year limitation was imposed. Statistical analyses were performed with the aid of the chi-squared test. We evaluated the quality of each publication and the risk of bias.ResultsTwenty-nine studies involving 5071 patients were ultimately included; 1120 patients were treated conservatively and 3951 surgically. The union rates were 68.8% (642/933) and 92.6% (635/686) in the former and latter groups, respectively (p < 0.001). The avascular necrosis rate in the conservatively treated group was 10.3% (39/380), while it was 7.7% (159/2074) in the surgically treated group (p = 0.09).ConclusionsSurgery to treat undisplaced femoral neck fractures was associated with a higher union rate and a tendency toward less avascular necrosis than conservative treatment.

BackgroundThe objective of this study was to investigate the potency of platelet-rich plasma (PRP) combined with bone marrow mesenchymal stem cells (BMSCs) to promote tendon–bone healing in a rabbit model.MethodsIn the in vitro study, the effects of PRP on osteogenic induction of BMSCs were analysed. Later, PRP with or without BMSCs was used in the rabbit model of anterior cruciate ligament reconstruction. Specimens were harvested 8 weeks postoperatively to evaluate tendon–bone healing by histology, radiology, and biomechanical testing.ResultsThe in vitro study revealed that collagen I, osteocalcin, and osteopontin expression was higher in BMSCs co-cultured with PRP for 14 days. The in vivo study revealed a more mature tendon–bone interface using light microscopy, a more newly formed bone at the bone tunnel walls detected by micro-computed tomography, and a significantly higher failure load as assessed by biomechanical testing in the BMSC + PRP group than in the control and PRP groups.ConclusionsThese results indicate that the combination of PRP and BMSCs promotes tendon–bone healing and has potential for clinical use.Electronic supplementary materialThe online version of this article (doi:10.1186/s13018-016-0433-7) contains supplementary material, which is available to authorized users.

Background To investigate osteointegration at the graft-bone interface and the prevention of osteoarthritis after anterior cruciate ligament (ACL) reconstruction using a silk-collagen scaffold with both ends modified by hydroxyapatite (HA) in a rabbit model. Methods The HA/silk-collagen scaffold was fabricated using a degummed, knitted silk scaffold, collagen I matrix, and simulated body fluid (SBF). The HA/silk-collagen scaffold was rolled up to make a graft for replacing the native ACL in the experimental group (HA group), and the silk-collagen scaffold was used in the control (S group). All specimens were harvested at 16 weeks postoperatively to evaluate graft-bone healing and osteoarthritis prevention. Results Histological staining revealed the massive formation of more mature bone at the tendon-bone interface, and immunohistochemistry staining revealed more collagen I and osteocalcin deposition in the HA group than in the S group. Higher signals indicating more bone mineral formation were detected in the HA group than in the S group, which was consistent with the results of biomechanical testing. Better osteoarthritis prevention was also observed in the HA group, indicating a more stable knee joint in the HA group than in the S group. Conclusion The HA/silk-collagen scaffold promotes osteointegration at the tendon-bone interface after ACL reconstruction and has great potential for clinical applications.

The objective of this study was to investigate whether intermittent administration of parathyroid hormone [1–34] (PTH[1–34]) promotes tendon-bone healing after anterior cruciate ligament (ACL) reconstruction in vivo. A rat model of ACL reconstruction with autograft was established at the left hind leg. Every day, injections of 60 μg PTH[1–34]/kg subcutaneously were given to the PTH group rats (n = 10) for four weeks, and the controls (n = 10) received saline. The tendon-bone healing process was evaluated by micro-CT, biomechanical test, histological and immunohistochemical analyses. The effects of PTH[1–34] on serum chemistry, bone microarchitecture and expression of the PTH receptor (PTH1R) and osteocalcin were determined. Administration of PTH[1–34] significantly increased serum levels of calcium, alkaline phosphatase (AP), osteocalcin and tartrate-resistant acid phosphatase (TRAP). The expression of PTH1R on both osteocytes and chondrocyte-like cells at the tendon-bone interface was increased in the PTH group. PTH[1–34] also enhanced the thickness and microarchitecture of trabecular bone according to the micro-CT analysis. The results imply that systematically intermittent administration of PTH[1–34] promotes tendon-bone healing at an early stage via up-regulated PTH1R. This method may enable a new strategy for the promotion of tendon-bone healing after ACL reconstruction.