ACL reconstruction with BPTB autograft and irradiated fresh frozen allograft

Objective： To analyze the clinical outcomes of arthroscopic anterior cruciate ligament （ACL） reconstruction with irradiated bone-patellar tendon-bone （BPTB） allograft compared with non-irradiated allograft and autograft. Methods： All BPTB allografts were obtained from a single tissue bank and the irradiated allografts were sterilized with 2.5 mrad of irradiation prior to distribution. A total of 68 patients undergoing arthroscopic ACL reconstruction were prospectively randomized consecutively into one of the two groups （autograft and irradiated allograft groups）. The same surgical technique was used in all operations done by the same senior surgeon. Before surgery and at the average of 31 months of follow-up （ranging from 24 to 47 months）, patients were evaluated by the same observer according to objective and subjective clinical evaluations. Results： Of these patients, 65 （autograft 33, irradiated allograft 32） were available for full evaluation. When the irradiated allografl group was compared to the autograft group at the 31 -month follow-up by the Lachman test, the anterior drawer test （ADT）, the pivot shift test, and KT-2000 arthrometer test, statistically significant differences were found. Most importantly, 87.8% of patients in the autograft group and just only 31.3% in the irradiated allograft group had a side-to-side difference of less than 3 mm according to KT-2000. The failure rate of the ACL reconstruction with irradiated allograft （34.4%） was higher than that with autograft （6.1%）. The anterior and rotational stabilities decreased significantly in the irradiated allograft group. According to the overall International Knee Documentation Committee （1KDC）, functional and subjective evaluations, and activity level testing, no statistically significant differences were found between the two groups. Besides, patients in the irradiated allograft group had a shorter operation time and a longer duration of postoperative fever. When the patients had a fever, the laboratory examinations of all patients were almost normal. Blood routine was normal, the values of erythrocyte sedimentation rate （ESR） were 5-16 mm/h and the contents of C reactive protein （CRP） were 3-10 mg/L. Conclusion： We conclude that the short term clinical outcomes of the ACL reconstruction with irradiated BPTB allograft were adversely affected. The less than satisfactory results led the senior authors to discontinue the use of irradiated BPTB allografl in ACL surgery and not to advocate using the gamma irradiation as a secondary sterilizing method.

Stable mechanical fixation in a bionic osteochondral scaffold considering bone growth

In the field of tissue engineering,there is significant subsidence of the porous design scaffold several months after implantation.To avoid stress shielding and stimulate bone and cartilage ingrowth,high scaffold porosity is needed to diminish the mechanical properties of the scaffold.The closer the mechanical properties of the scaffold are to those of surrounding tissues,the better biological properties it will get.Besides,adequate mechanical stability is needed as the scaffold needs to be well fixed in the target area and it will endure load after surgery.Evaluating the mechanical fixation of the scaffold at the initial stage and the long-term performance of a scaffold for in vivo study is hard,as no facility can be put into the target area for the friction test.This study investigated the mechanical stability of the biomimetic scaffold at the initial stage of implantation by finite element analysis(FEA).According to in vivo study,scaffold could not maintain its original position and would sink 1-2 mm in the target area.The simulation results suggested that mechanical loading is not the main reason for scaffold subsidence.