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fixation, and other orthopedic and neurologic procedures. 13–15 Polymethylmethacrylate impregnated with gentamicin is widely available for use in human and veterinary orthopedics. 16–19 Local delivery of gentamicin is thought to provide higher
Biomed Mater Res . 1997 ; 38 ( 2 ): 155 – 182 . doi: 10.1002/(SICI)1097-4636(199722)38:2<155::AID-JBM10>3.0.CO;2-C 22. Mok D , Schwarz J . The use of polymethyl-methacrylate (Artecoll) as an adjunct to facial reconstruction . Can J Plast Surg
uniform application of PMMA that incorporated all of the ventral ends of the pins. Polymethylmethacrylate f was mixed as per manufacturer instructions, poured into the standard plastic mold to cover all pin ends, and allowed to cure for a minimum of 20
pin or screw, dorsal vertebral fixation with a pin or pedicle screw and polymethylmethacrylate (PMMA), dorsal vertebral fixation with a pedicle screw and rod, and fixation with a locking plate. 2 , 6 – 10 , 14 , 15 , 20 – 23 A previous autopsy study
polymethylmethacrylate. b An appropriate amount of time was allowed for the polymethylmethacrylate to harden before the surgical site was closed in a routine manner. Implant positioning was confirmed by evaluation of postsurgical radiographs. MRI sequences
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)
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)
mL of sterile saline (0.9% NaCl) solution. l Polymethylmethacrylate beads m were prepared according to the manufacturer's instructions; a portion was mixed with gentamicin n (50 mg/g of cement), and a portion was mixed with cefazolin o (100 mg
-wires. Three simple interrupted encircling sutures of 4-0 polyglyconate b were placed to hold the femur and the pin in close apposition ( Figure 2 ). Polymethylmethacrylate c was molded around the positive-profile pin and the protruding K-wires to secure the
