Studies on the External Fixator Pin-Bone Interface: The Effect of Pin Design and Pin Cooling in an In Vivo Sheep Tibia Model

SummaryThe purpose of this study was to examine the effect of pin design and drill/pin cooling on the biological response of bone in the near (entry) and far (exit) cortices of mature intact sheep tibiae. Two pins with markedly different characteristics were used; the AO Schanz screw, a traditional pyramidal tipped design, and the fluted, tapered end Howmedica Apex pin. Our hypothesis was that cooling of hardware would reduce thermal necrosis of bone at the pin-bone interface (PBI). When the effect of pin design was controlled for, the cooled pins resulted in better pin bone interfaces at the near cortex but not the far cortex. It is possible that the drill bits and pins warmed significantly after traversing the more vascular bone marrow space, thus the cooling effect was lost before drilling the far cortex. Secondly, the Howmedica Apex pin resulted in more bone at the pin bone interface than the AO Schanz pin indicating that the former’s more advanced design follows the pilot hole and creates threads more accurately, resulting in a better pin-bone fit and less mechanical damage.The purpose of this study was to examine the effects of pin design and drill/pin cooling on the remodelling response of cortical bone at the pin-bone interface in an in vivo sheep tibia model. No significant differences were found between pin designs or between pins that were implanted at 4° C and those that were inserted at 20° C. More bone was retained at the near cortex pin-bone interface (PBI) than the far cortex PBI when the pins were cooled, but the opposite was true when the pins were not cooled.</jats:p

The Effect of External Fixator Pin Geometry and Dynamic Loading on Bone Remodelling at the Pin-Bone Interface (PBI), in an In Vivo Sheep Tibia Model

SummaryThe purpose of this study was to study the effects of pin design and dynamic loading on the biological response of bone at the pin-bone interface (PBI). An electro-pneumatic pin-loading device was used to mimic the forces that would be experienced by external fixator pins, during patient ambulation following repair of a fracture with external skeletal fixation. The remodelling response was assessed histologically with fluorescence microscopy of plasticembedded undecalcified pin-bone sections, and surface-stained histomorphometry.There were no significant differences between the AO Schanz and Howmedica Apex 5.0 mm diameter self-tapping pin designs when they were inserted in 4.5 mm diameter predrilled pilot holes. When pin type was controlled for, significant differences (p&lt;0.05) existed between loaded and control groups as well as between entry (near) and exit (far) cortices. Less bone resorption was observed in the non-loaded group in comparison to the dynamically loaded group, and bone resorption in the near cortex consistently exceeded the amount of bone resorption in the far cortex for both treatment groups.The purpose of this study was to examine the effects of pin design and dynamic pin loading on the remodelling response of cortical bone at the pin-bone interface (PBI) of intact sheep tibiae. No significant differences were demonstrated between pin designs; however, significant differences (p&lt;0.05) existed between loaded versus control pins, as well as between entry and exit cortices.</jats:p

Barbed Suture for Gastrointestinal Closure: A Randomized Control Trial

In an effort to make laparoscopic suturing more efficient, the V-Loc advanced wound closure device (Covidien, Mansfield, MA) has been produced. This device is a self-anchoring barbed suture that obviates the need for knot tying. The goal of this initial feasibility study was to investigate the use of the barbed suture in gastrointestinal enterotomy closure. A randomized study of 12 pigs comparing enterotomy closure with barbed versus a nonbarbed suture of similar tensile strength was performed. To this end, 25 mm enterotomies were made in the stomach (1 control, 1 treatment), jejunum (2 controls, 2 treatments), and descending colon (1 control, 1 treatment). Animals were killed at 3, 7, and 14 days postoperatively (4 each group) and their gastrointestinal tracts harvested; 6 of the 8 enterotomies from each pig underwent burst strength testing. The remaining 2 were fixed in formalin and sent for histological examination. All 12 pigs survived until they were killed without any major complications. Enterotomy closure with barbed suture revealed adhesion scores, burst strength pressures, and histology scores that were similar to those for the control. Jejunal closures resulted in 6 failures at 7 days (3 control, 3 barbed) and 4 failures at 14 days (2 control, 2 barbed). The barbed suture significantly reduced suturing time in the stomach, jejunum, and colon. The V-Loc wound closure device appears to offer comparable gastrointestinal closure to 3-0 Maxon while being significantly faster. Further studies with V-Loc are required to assess its use in laparoscopic surgery. </jats:p