Mechanical assessment of two hybrid plate designs for pancarpal canine arthrodesis under cyclic loading

Pancarpal canine arthrodesis (PCA) sets immobilization of all three carpal joints via dorsal plating to result in bony fusion. Whereas the first version of the plate uses a round hole (RH) for the radiocarpal (RC) screw region, its modification into an oval hole (OH) in a later version improves versatility in surgical application. The aim of this study was to mechanically investigate the fatigue life of the PCA plate types implementing these two features–PCA-RH and PCA-OH. Ten PCA-RH and 20 PCA-OH stainless steel (316LVM) plates were assigned to three study groups (n = 10). All plates were pre-bent at 20° and fixed to a canine forelimb model with simulated radius, RC bone and third metacarpal bone. The OH plates were fixed with an RC screw inserted either most proximal (OH-P) or most distal (OH-D). All specimens were cyclically tested at 8 Hz under 320 N loading until failure. Fatigue life outcome measures were cycles to failure and failure mode. Cycles to failure were higher for RH plate fixation (695,264 ± 344,023) versus both OH-P (447,900 ± 176,208) and OH-D (391,822 ± 165,116) plate configurations, being significantly different between RH and OH-D, p = 0.03. No significant difference was detected between OH-P and OH-D configurations, p = 0.09. Despite potential surgical advantages, the shorter fatigue life of the PCA-OH plate design may mitigate its benefits compared to the plate design with a round radiocarpal screw hole. Moreover, the failure risk of plates with an oval hole is increased regardless from the screw position in this hole. Based on these findings, the PCA plate with the current oval radiocarpal screw hole configuration cannot be recommended for clinical use

PLOSONEcomplete data set. (TPLO alignment jig-saw guide)

Raw data collected for two groups of clinically performed TPLOs (a crescent osteotomy of the proximal tibia designed to alter the craniotibial shear force as a result of a cranial cruciate deficient knee). Group 1 (2005-2007): freehand osteotomies with jig only; Group 2 (2013-2015): freehand osteotomies with jig only. Group 1 follows recommendation at that time to place proximal jig pin through center of medial collateral ligament (MCL). Group 2 follows the later recommendation to place the jig pin behind the MCL. The objective of the study is to determine if a saw guide attached to the jig can match the positions of the osteotomy performed by experienced surgeons, and also is it can replicate the ideal osteotomy location. The data file are all measurements obtained from these clinical cases that compares guide-to-osteotomy fit and the appropriateness of the osteotomy based upon current published guidelines. All methods are described in the manuscript

Novel TPLO Alignment Jig/Saw Guide Reproduces Freehand and Ideal Osteotomy Positions

<div><p>Objectives</p><p>To evaluate the ability of an alignment jig/saw guide to reproduce appropriate osteotomy positions in the tibial plateau leveling osteotomy (TPLO) in the dog.</p><p>Methods</p><p>Lateral radiographs of 65 clinical TPLO procedures using an alignment jig and freehand osteotomy performed by experienced TPLO surgeons using a 24 mm radial saw blade between Dec 2005–Dec 2007 and Nov 2013–Nov 2015 were reviewed. The freehand osteotomy position was compared to potential osteotomy positions using the alignment jig/saw guide. The proximal and distal jig pin holes on postoperative radiographs were used to align the jig to the bone; saw guide position was selected to most closely match the osteotomy performed. The guide-to-osteotomy fit was categorized by the distance between the actual osteotomy and proposed saw guide osteotomy at its greatest offset (≤1 mm = excellent; ≤2 mm = good; ≤3 mm = satisfactory; >3 mm = poor).</p><p>Results</p><p>Sixty-four of 65 TPLO osteotomies could be matched satisfactorily by the saw guide. Proximal jig pin placement 3–4 mm from the joint surface and pin location in a craniocaudal plane on the proximal tibia were significantly associated with the guide-to-osteotomy fit (<i>P</i> = 0.021 and <i>P</i> = 0.047, respectively).</p><p>Clinical Significance</p><p>The alignment jig/saw guide can be used to reproduce appropriate freehand osteotomy position for TPLO. Furthermore, an ideal osteotomy position centered on the tibial intercondylar tubercles also is possible. Accurate placement of the proximal jig pin is a crucial step for correct positioning of the saw guide in either instance.</p></div

The distribution of frequency for each saw guide position as the best guide-to-osteotomy fit for freehand osteotomies based on group.

<p>The distribution of frequency for each saw guide position as the best guide-to-osteotomy fit for freehand osteotomies based on group.</p

The proximal jig pin is inserted (dot) parallel to the joint surface and perpendicular to the tibial long axis, 3–4 mm distal to the joint and just caudal to the medial collateral ligament (MCL).

<p>The proximal jig pin is inserted (dot) parallel to the joint surface and perpendicular to the tibial long axis, 3–4 mm distal to the joint and just caudal to the medial collateral ligament (MCL).</p

The distribution of frequency for each saw guide position as the best guide-to-osteotomy fit for the proposed ideal osteotomy location (IOL) based on group.

<p>The distribution of frequency for each saw guide position as the best guide-to-osteotomy fit for the proposed ideal osteotomy location (IOL) based on group.</p

Depiction of the osteotomy options available with each of the twelve positions and ±30° from a baseline of 90° angulation of the proximal jig arm.

<p>Each shaded area is a result of angulating the jig arms in each of the positions selected (ABC/1234).</p

Digital representation of the method used to align the jig and guide onto a true-to-size printed postoperative lateral radiograph.

<p>The alignment jig/saw guide was aligned with the long axis of the tibia using the proximal and distal jig pin holes. The saw guide was then positioned to achieve the best fit over the osteotomy by angling the jig arms (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161110#pone.0161110.g003" target="_blank">Fig 3</a>). The widest offset along the radial osteotomy between the actual and saw guide osteotomy position was recorded (≤1 mm = excellent; ≤2 mm = good; ≤3 mm = satisfactory; >3 mm = poor).</p

The DePuy Synthes TPLO saw guide has a combination of 12 possible positions for attachment to the jig; three angular positioning slots on the guide for the jig pin (A, B, C) and four bolt hole choices for securing the guide to the jig (1, 2, 3, 4).

<p>The DePuy Synthes TPLO saw guide has a combination of 12 possible positions for attachment to the jig; three angular positioning slots on the guide for the jig pin (A, B, C) and four bolt hole choices for securing the guide to the jig (1, 2, 3, 4).</p