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Chondrocyte death after drilling and articular screw insertion in a bovine model.

Research paper by D A DA Houston, A K AK Amin, T O TO White, I D M ID Smith, A C AC Hall

Indexed on: 23 Feb '13Published on: 23 Feb '13Published in: Osteoarthritis and Cartilage



Abstract

Intra-articular screws are used for internal fixation of osteochondral fragments after fracture or osteochondritis dissecans. This causes cartilage injury potentially leading to chondrocyte death. We have visualised/quantified the hole and zone of cell death (ZCD) in cartilage after drilling/insertion of various articular screws.Using an ex vivo bovine model with transmitted light and confocal laser scanning microscopy (CLSM), the holes and ZCD following drilling/insertion of articular screws (cortical screw, headless variable pitch metallic screw, headless variable pitch bioabsorbable screw) were evaluated. In situ chondrocyte death was determined by live/dead cell viability assay. An imaging/quantification protocol was developed to compare hole diameter and ZCD from drilling/insertion of screws into cartilage. The effect of saline irrigation during drilling on the ZCD was also quantified.Screw insertion created holes in cartilage that were significantly (P ≤ 0.001) less than the diameters of the equipment used. With a 1.5 mm drill, a ZCD of 580.2 ± 124 μm was produced which increased to 637.0 ± 44 μm following insertion of a 2 mm cortical screw although this was not significant (P > 0.05). The ZCD from insertion of the variable pitch headless screws (diam. 3.5 mm) was lower for the metallic compared to the bioabsorbable design (800.9 ± 159 vs 1,236.4 ± 212 μm, respectively; P < 0.01). The ZCD from drilling was reduced ∼50% (P < 0.001) by saline irrigation.Cartilage injury during intra-articular screw fixation caused a ZCD around the hole irrespective of screw design. Saline irrigation significantly reduced the ZCD from drilling into cartilage.