George S. Martin

In vitro biomechanical comparison of locking compression plate fixation and limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVE To compare monotonic biomechanical properties and fatigue life of a broad locking compression plate (LCP) fixation with a broad limited contact dynamic compression plate (LC-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION Cadaveric adult equine MC3 bones (n=12 pairs). METHODS MC3 were divided into 3 groups (4 pairs each) for: (1) 4-point bending single cycle to failure testing; (2) 4-point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8-hole, 4.5 mm LCP was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8-hole, 4.5 mm LC-DCP) was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment, under 4-point bending, single cycle to failure, of the LCP fixation were significantly greater than those of the LC-DCP fixation. Mean cycles to failure for 4-point bending was significantly greater for the LCP fixation compared with LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load under torsional testing, single cycle to failure was significantly greater for the broad LCP fixation compared with the LC-DCP fixation. CONCLUSION The 4.5 mm LCP was superior to the 4.5 mm LC-DCP in resisting the static overload forces (palmarodorsal 4-point bending and torsional) and in resisting cyclic fatigue under palmarodorsal 4-point bending. CLINICAL RELEVANCE The results of this in vitro study may provide information to aid in the selection of a biological plate for the repair of equine long bone fractures.

An in vitro biomechanical comparison of a 5.5 mm limited-contact dynamic compression plate fixation with a 4.5 mm limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES To compare monotonic biomechanical properties and fatigue life of a 5.5 mm broad limited-contact dynamic compression plate (5.5-LC-DCP) fixation with a 4.5 mm broad LC-DCP (4.5-LC-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. SAMPLE POPULATION Adult equine cadaveric MC3 bones (n=18 pair). METHODS MC3 were divided into 3 test groups (6 pairs each) for: (1) 4-point bending single cycle to failure testing; (2) 4-point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8-hole, 5.5 mm broad LC-DCP (5.5-LC-DCP) was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8-hole, 4.5 mm broad LC-DCP (4.5-LC-DCP) was applied dorsally to the contralateral bone from each pair. Plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment under 4-point bending, single cycle to failure, of the 5.5-LC-DCP fixation were significantly greater (P<.024) than those of the 4.5-LC-DCP fixation. Mean cycles to failure for 4-point bending was significantly (P<.05) greater for the 4.5-LC-DCP fixation compared with the 5.5-LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion for the 5.5-LC-DCP fixation was not significantly different (P>.05) than those with the 4.5-LC-DCP fixation. CONCLUSION 5.5-LC-DCP fixation was superior to 4.5-LC-DCP fixation in resisting the static overload forces under palmarodorsal 4-point bending. There was no significant difference between 5.5-LC-DCP fixation and 4.5-LC-DCP fixation in resisting static overload forces under torsion; however, the 5.5-LC-DCP offers significantly less stability (80% of that of the 4.5-LC-DCP) in cyclic fatigue testing. CLINICAL RELEVANCE The results of this in vitro study may provide information to aid in the selection of a biological plate for long bone fracture repair in horses.

An In Vitro Biomechanical Comparison of Equine Proximal Interphalangeal Joint Arthrodesis Techniques: An Axial Positioned Dynamic Compression Plate and Two Abaxial Transarticular Cortical Screws Inserted in Lag Fashion Versus Three Parallel Transarticular Cortical Screws Inserted in Lag Fashion

OBJECTIVES To compare in vitro monotonic biomechanical properties of an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (DCP-TLS) with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (3-TLS) for the equine proximal interphalangeal (PIP) joint arthrodesis. STUDY DESIGN Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. SAMPLE POPULATION Cadaveric adult equine forelimbs (n=15 pairs). METHODS For each forelimb pair, 1 PIP joint was stabilized with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion and 1 with 3 parallel transarticular 5.5 mm cortical screws inserted in lag fashion. Five matching pairs of constructs were tested in single cycle to failure under axial compression, 5 construct pairs were tested for cyclic fatigue under axial compression, and 5 construct pairs were tested in single cycle to failure under torsional loading. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P<.05. RESULTS Mean yield load, yield stiffness, and failure load under axial compression and torsion, single cycle to failure, of the DCP-TLS fixation were significantly greater than those of the 3-TLS fixation. Mean cycles to failure in axial compression of the DCP-TLS fixation was significantly greater than that of the 3-TLS fixation. CONCLUSION The DCP-TLS was superior to the 3-TLS in resisting the static overload forces and in resisting cyclic fatigue. CLINICAL RELEVANCE The results of this in vitro study may provide information to aid in the selection of a treatment modality for arthrodesis of the equine PIP joint.

A mechanical comparison of equine proximal interphalangeal joint arthrodesis techniques: an axial locking compression plate and two abaxial transarticular cortical screws versus an axial dynamic compression plate and two abaxial transarticular cortical screws.

OBJECTIVES To compare in vitro monotonic biomechanical properties of an axial 3-hole, 4.5 mm narrow locking compression plate (ELCP) using 5.0 mm locking screws and 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (ELCP-TLS) with an axial 3-hole, 4.5 mm narrow dynamic compression plate (DCP) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion (DCP-TLS) for equine proximal interphalangeal (PIP) joint arthrodesis. DESIGN Experimental. ANIMAL POPULATION Cadaveric adult equine forelimbs (n = 18 pairs). METHODS For each forelimb pair, 1 PIP joint was stabilized with an axial ELCP using 5.0 mm locking screws and 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion and 1 PIP joint with an axial 3-hole narrow DCP (4.5 mm) using 5.5 mm cortical screws in conjunction with 2 abaxial transarticular 5.5 mm cortical screws inserted in lag fashion. Six matching pairs of constructs were tested in single cycle to failure under axial compression, 6 construct pairs were tested for cyclic fatigue under axial compression, and 6 construct pairs were tested in single cycle to failure under torsional loading. Mean values for each fixation method were compared using a paired t-test within each group with statistical significance set at P < .05. RESULTS Mean yield load, yield stiffness, and failure load under axial compression, single cycle to failure, of the DCP-TLS fixation were significantly greater than those of the LCP-TLS fixation. There was no significant difference between the mean number of cycles to failure in axial compression of the LCP-TLS and the DCP-TLS fixations. Mean yield load, yield stiffness, and failure load under torsion, single cycle to failure, of the LCP-TLS fixation were significantly greater than those of the DCP-TLS fixation. CONCLUSION The DCP-TLS construct provided significantly greater stability under axial compression in single cycle to failure than the ELCP-TLS construct, the ELCP-TLS construct provided significantly greater stability under torsional loading in single cycle to failure than the DCP-TLS construct, and there was no significant difference in stability between the 2 constructs for cyclic loading under axial compression.

In Vitro Biomechanical Comparison of a Modified 5.5 mm Locking Compression Plate Fixation with a 5.5 mm Locking Compression Plate Fixation of Osteotomized Equine Third Metacarpal Bones

OBJECTIVES To compare number of cycles to failure for palmarodorsal 4-point bending of a modified 5.5 mm broad locking compression plate (M5.5-LCP) fixation with a 5.5 mm broad LCP (5.5-LCP) fixation used to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN In vitro biomechanical testing. ANIMAL POPULATION Adult equine cadaveric MC3 bones (n=6 pairs). METHODS An 8-hole, M5.5-LCP, obtained by having a 1.0 mm thickness removed from the bone contact portion of the 5.5-LCP, was applied to the dorsal surface of 1 randomly selected MC3 from each pair, and an 8-hole, 5.5-LCP was applied dorsally to the contralateral bone from each pair using a combination of cortical and locking screws. Plates and screws were applied using standard ASIF techniques to MC3 bones with a mid-diaphyseal osteotomy. MC3 constructs had palmarodorsal 4-point bending cyclic fatigue testing. Mean cycles to failure for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS Mean±SD cycles to failure of the M5.5-LCP fixation (188,641±17,971) was significantly greater than that of the 5.5-LCP fixation (166,497±15,539). CONCLUSION M5.5-LCP fixation was superior to 5.5-LCP fixation of osteotomized equine MC3 bones in resisting cyclic fatigue under palmarodorsal 4-point bending. CLINICAL RELEVANCE This suggests that biological plate fixation is not the ideal choice for osteotomized equine MC3 bones.

An In Vitro Biomechanical Comparison of Equine Proximal Interphalangeal Joint Arthrodesis Techniques: Two Parallel Transarticular Headless Tapered Variable Pitch Screws Versus Two Parallel Transarticular AO Cortical Bone Screws Inserted in Lag Fashion

OBJECTIVES To compare the mean number of cycles to failure under axial compression of equine proximal interphalangeal (PIP) joint arthrodesis constructs created by 2 parallel transarticular Acutrak Plus screws (AP-TS) or 2 parallel transarticular 5.5 mm cortical screws inserted in lag fashion (AO-TLS). STUDY DESIGN Paired in vitro biomechanical testing of 2 methods of stabilizing cadaveric adult equine forelimb PIP joints. SAMPLE POPULATION Cadaveric adult equine forelimbs (n=5 pairs). METHODS For each forelimb pair, 1 PIP joint was stabilized with AP-TS and 1 with AP-TLS. The 5 construct pairs were tested for cyclic fatigue under axial compression. Mean number of cycles to failure for each fixation method were compared by a paired t-test within each group with statistical significance set at P<.05. RESULTS The mean number of cycles to failure under axial compression for AO-TLS fixation and AP-TS fixation were 57,723±8488 and 35,322±4698, respectively. CONCLUSION The AO-TLS was superior to the AP-TS in resisting cyclic fatigue under axial compression.

In Vitro Biomechanical Comparison of Dynamic Compression Plates with a Rough Contact Surface and a Polished Contact Surface for Fixation of Osteotomized Equine Third Metacarpal Bones

OBJECTIVES To compare the number of cycles to failure of 4.5 mm broad dynamic compression plates (DCP), 4.5 mm broad limited-contact dynamic compression plates (4.5-LC-DCP), and 5.5 mm broad limited-contact dynamic compression plates (5.5-LC-DCP) having a rough (denoted by a prefix R-) versus a standard smooth contact surface for the fixation of osteotomized equine 3rd metacarpal (MC3) bones. STUDY DESIGN Experimental. ANIMAL POPULATION Fifteen pairs of adult equine cadaveric MC3 bones. METHODS Fifteen pairs of equine MC3 were divided into 3 test groups (5 pairs each) for comparison of (1) R-DCP fixation with DCP fixation, (2) R-4.5-LC-DCP fixation with 4.5-LC-DCP fixation, and (3) R-5.5-LC-DCP fixation with 5.5-LC-DCP fixation to repair osteotomized equine MC3 bones under palmarodorsal 4-point bending cyclic fatigue testing. For each group an 8-hole plate with rough contact surface was applied to the dorsal surface of one randomly selected bone from each pair and a corresponding 8-hole plate with smooth contact surface was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard ASIF techniques. All MC3 bones had mid-diaphyseal osteotomies. Mean number of cycles to failure for each method were compared using a paired t-test within each group. Significance was set at P < .05. RESULTS Mean cycles to failure ± standard deviation was significantly greater for the R-DCP fixation (230,025 ± 23,129) compared with the DCP fixation (103,451 ± 14,556), for the R-4.5-LC-DCP fixation (99,237 ± 14,390) compared with the 4.5-LC-DCP fixation (46,464 ± 6325) and for the R-5.5-LC-DCP fixation (65,113 ± 7796) compared with the 5.5-LC-DCP fixation (34,224 ± 3835). CONCLUSION For the fixation of osteotomized MC3 bones, the constructs with plates having rough contact surface were superior to the corresponding constructs with plates having standard smooth contact surfaces in resisting cyclic fatigue under palmarodorsal 4-point bending.