This study uses a biomechanical model to compare the strength of intraosseous and extraosseous insertion of tendon into the second phalanx of rabbits. Two matched groups were used by incising the profundus tendon in the 2nd and 3rd toes of rabbits. One group received repairs of the 2nd toe tendon by an intraosseous method while the 3rd toe was repaired in an extraosseous manner. The second group received the opposite. Half of each group was sacrificed at 3 weeks following repair and these were evaluated for signs of healing and load to failure. The remaining rabbits were sacrificed at 8 weeks. These failures were compared to unoperated controls within the same animals.
All specimens showed signs of healing at 3 and 8 weeks. All but two repaired tendons incurred failure at the suture site during testing. At 3 weeks the control group load to failure was 91 N and 100 N at 8 weeks. Intraosseous repair strengths were 17N at 3 weeks and 45N at 8 weeks. Extraosseous repair strengths were 15N at 3 weeks and 58N at 8 weeks. There was no statistical difference between the two groups.
This article concluded that, in the rabbit model, repaired flexor tendons have a lower load to failure than those that are healing. No differences seem to exist regarding the method of tendon reattachment.