Morizane Kazuaki, Goto Koji, Kawai Toshiyuki, Fujibayashi Shunsuke, Otsuki Bungo, Shimizu Takayoshi, Matsuda Shuichi
The Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawaharacho, Sakyo-ku, Kyoto 602-8570, Japan.
Materials (Basel). 2021 Mar 17;14(6):1458. doi: 10.3390/ma14061458.
Composites of unsintered hydroxyapatite (HA) and poly(-lactide) (PLLA) reinforced by compression forging are biodegradable, bioactive, and have ultrahigh strength. However, foreign body reactions to PLLA and physical irritation can occur when not covered by bone. We aimed to confirm the relationships between the depth of the implanted HA-PLLA threaded pins and the new bone formation. We inserted HA-PLLA composite threaded pins (diameter: 2.0 or 4.5 mm) into the femoral and tibial bones of 32 mature male Japanese white rabbits (weight 3.0-3.5 kg) with the pin head 1 or 0 mm below or protruding 1 or 2 mm above surrounding cortical bone. Eight euthanized rabbits were radiologically and histologically assessed at various intervals after implantation. Bone bridging was complete over pins of both diameters at ~12 weeks, when inserted 1 mm below the surface, but the coverage of the pins inserted at 0 mm varied. Bone was not formed when the pins protruded >1 mm from the bone surface. No inflammation developed around the pins by 25 weeks. However, foreign body reactions might develop if composites are fixed above the bone surface, and intraosseous fixation would be desirable using double-threaded screws or a countersink to avoid screw head protrusion.
通过模锻增强的未烧结羟基磷灰石（HA）和聚（-丙交酯）（PLLA）复合材料具有生物可降解性、生物活性且强度超高。然而，当未被骨覆盖时，可能会发生对PLLA的异物反应和物理刺激。我们旨在确认植入的HA-PLLA螺纹钉深度与新骨形成之间的关系。我们将HA-PLLA复合螺纹钉（直径：2.0或4.5毫米）插入32只成熟雄性日本白兔（体重3.0 - 3.5千克）的股骨和胫骨中，钉头在周围皮质骨下方1或0毫米处或突出于其上方1或2毫米。在植入后的不同时间间隔，对8只安乐死的兔子进行放射学和组织学评估。当插入表面下方1毫米时，在约12周时两种直径的钉上骨桥接均完成，但插入在0毫米处的钉的覆盖情况有所不同。当钉从骨表面突出>1毫米时未形成骨。到25周时，钉周围未出现炎症。然而，如果复合材料固定在骨表面上方，可能会发生异物反应，使用双螺纹螺钉或埋头孔进行骨内固定以避免螺钉头突出是可取的。
