In the reconstruction of the anterior cruciate ligaments of the knee, early loading of the leg is usually desirable. Thus, it is of a great interest to evaluate the early stability of screws used for tibial fixation of the ligament, rather than long-term stability of such devices when the neoligament is certainly integrated. The purpose of this study (controlled laboratory study) was to investigate the early osteointegration and biodegradation of hydroxyapatite (HA)/poly(L-lactide)(PLLA) (HA/PLLA) composite screws compared with tricalcium-phosphate (TCP)/PLLA (TCP/PLLA) composite screws used for tibial fixation in the reconstruction of the anterior cruciate ligaments.

We used two types of resorbable screws: BioRCI (Smith& Nephew) composite screws (30% HA and 70% PLLA) and Biocryl (Mitek) composite screws (30% TCP and 70% PLLA) that were inserted into the distal femur of three skeletally mature sheep. Each animal received one HA/PLLA composite screw and one TCP/ PLLA composite screw. The three sheep were sacrificed 20, 40 and 60 days after surgery. Results were evaluated by radiological (RX, TC and RMN), histological and microradiographic analyses.

The amount of bone tissue osteointegrating the screw was higher for TCP/PLLA screws than for HA/PLLA screws. No sign of real biodegradation was observed in any of the specimens.

In conclusion, TCP/PLLA composite screws provide a favourable early osteointegration compared to HA/PLLA composite screws; this could provide an early loading of the leg, which is the primary goal of clinicians and patients in this case. In addition, this could provide a considerable reduction of medical expenses, due to the decrease in hospitalisation and rehabilitation time.