Search Results
inflammatory tissue reaction, and, in human research, survival probabilities of implanted PMMA have been upward of 50 years. 21 – 23 However, the chemical reaction occurring from mixing the PMMA polymer with the liquid monomer is exothermic, yielding
of multidrug-resistant bacterial infections increases, clinicians may use alternative methods to manage infections including treatment with natural antibacterial compounds such as honey or local application of antimicrobials in PMMA beads. 2 Newer
consequence, prevention of biofilm formation is imperative for successful patient outcome. One such prophylactic measure is the inclusion of antimicrobial additives in PMMA, which is a fixative commonly used in total joint arthroplasty, spinal fracture
stabilization of cervical vertebrae in dogs is application of an implant constructed from interbody smooth or threaded Steinmann pins placed in the vertebral bodies (traditional implant design) combined with overlying PMMA. This implant has been evaluated
equids and is gaining popularity for use in small animals. This approach relies on local delivery of antimicrobials to achieve higher tissue concentrations while avoiding systemic toxic effects. 5–7 Antimicrobial-loaded PMMA pellets are the most
spaces has not been sufficiently studied in veterinary medicine. In particular, with respect to distraction and fusion of the canine cervical vertebrae, various fixation methods that involve use of a metallic implant and PMMA or a plate with a locking
the host. 25,33 Polymethylmethacrylate is an acrylic bone cement, which has been used for plate luting 34 and total arthroplasties for almost 50 years. 24,35–37 Because PMMA is nonabsorbable, 2 interfaces will inevitably exist—1 between the implant
Abstract
Objective—To investigate the biomechanics of cervical vertebral motion units (VMUs) before and after a ventral slot procedure and after subsequent pin-polymethylmethacrylate (pin-PMMA) fixation and to assess the use of smooth and positive-profile threaded (PPT) pins in pin-PMMA fixation and intravertebral pin placement.
Sample Population—Cervical portions (C3 through C6 vertebrae) of 14 cadaveric canine vertebral columns.
Procedure—Flexion and extension bending moments were applied to specimens before and after creation of a ventral slot across the C4-C5 intervertebral space and after subsequent smooth or PPT pin-PMMA fixation at that site. Data for the C3-C4, C4-C5, and C5-C6 VMUs were compared among treatments and between pin types, and pin protrusion was compared between pin types.
Results—Compared with values in intact specimens, ventral slot treatment increased neutral zone range of motion (NZ-ROM) by 98% at the treated VMUs and appeared to decrease overall ROM at adjacent VMUs; pin-PMMA fixation decreased NZ-ROM by 92% at the treated VMUs and increased overall NZ-ROM by 19% to 24% at adjacent VMUs. Specimens fixed with PPT pins were 82% (flexion) and 80% (extension) stiffer than smooth–pin-fixed specimens. Overall, 41% of pins protruded into foramina; PPT pins were more likely to protrude into transverse foramina.
Conclusions and Clinical Relevance—Results indicated that fixation of a cervical VMU alters the biomechanics of adjacent VMUs and may contribute to degeneration of adjacent intervertebral disks. Use of threaded pins may lower the incidence of pin loosening and implant failure but enhances the likelihood of transverse foramina penetration. ( Am J Vet Res 2005;66:678–687)
Abstract
Objective—To evaluate the effect of an osteoconductive resorbable calcium phosphate cement (CPC) on the holding power of bone screws in canine pelvises and to compare the effect with that for polymethylmethacrylate (PMMA).
Sample Population—35 pelvises obtained from canine cadavers.
Procedure—Each pelvis was sectioned longitudinally. Within each pair of hemipelvises, one 4.0-mm cancellous screw was placed in the sacroiliac (SI) region and another in the iliac body. Similar regions on the contralateral- matched hemipelvis were assigned 1 of 3 augmentation techniques (CPC-augmented 4.0-mm cancellous screws, PMMA-augmented 4.0-mm cancellous screws, and CPC-augmented 3.5-mm cortical screws). Pullout force was compared between matched screws and between treatment groups prior to examination of cross sections for evaluation of cement filling and noncortical bone-to-cortical bone ratio.
Results—CPC and PMMA augmentation significantly increased pullout force of 4.0-mm screws inserted in the SI region by 19.5% and 33.2%, respectively, and CPC augmentation significantly increased pullout force of 4.0-mm cancellous screws inserted in the iliac body by 21.2%. There was no difference in the mean percentage augmentation between treatment groups at either location. Cement filling was superior in noncortical bone, compared with filling for cortical bone. Noncortical bone-to-cortical bone ratio was significantly greater in the sacrum (6.1:1) than the ilium (1.3:1).
Conclusions and Clinical Relevance—CPC and PMMA improve the ex vivo holding strength of 4.0-mm cancellous screws in the SI and iliac body regions and SI region, respectively. Cement augmentation may be more effective in areas with greater noncortical bone-to-cortical bone ratios. (Am J Vet Res 2005;66:1954–1960)
cannulated screws by use of a 3-point bending test and to evaluate whether those mechanical properties could be enhanced by filling the cannulated screws with material readily available to orthopedic surgeons such as PMMA bone cement alone or in combination
