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Large and load-bearing bone defects are challenging to treat and cause pain and disfigurement. The design of efficacious bone scaffolds for the repair of such defects involves a range of length scales from the centimeter down to the micrometer-scale. Here, we assess the influence on bone regeneration of scaffold rod spacing (>300 μm) and microporosity (<50 μm), as well as the combination of different structures and materials in the same scaffold, i.e., at the millimeter scale. We use four single-domain scaffolds, microporous (MP) or nonmicroporous (NMP) and with either a “small” or “large” rod spacing. Multidomain scaffolds combine four regions corresponding to the macro- and microarchitectures of the single-domain scaffolds. The scaffolds are implanted in pig mandibles for 3 weeks and bone regeneration is assessed by measuring the average bone volume fraction, BVF̅, the bone distribution and the trabecular thickness from micro-CT data. For the single-domain scaffolds, BVF̅was 45 ± 3% for MP-small, 39 ± 2% for MP-large, 25 ± 2% for NMP-small, and 25 ± 2% for NMP-large. MP scaffolds have significantly higher BVF̅and a more uniform bone distribution compared to NMP, regardless of rod spacing. The average trabecular thickness is significantly larger in MP compared to NMP, and in “large” compared to “small” scaffolds. Microporosity affects trabecular thickness throughout the scaffold, while rod spacing affects it only at the scaffold periphery. In multidomain scaffolds, MP-large and NMP-large domains have similar BVF̅as compared to their respective single-domain counterparts. These results suggest that combining different architectures into one scaffold conserves the properties of each domain. Hence, bone growth and morphology can be tailored by controlling scaffold architecture from the millimeter down to the micrometer level. This will allow the customization of scaffold designs for the treatment of large and load-bearing bone defects.

This report evaluates the effect of a suture loaded with basic fibroblast growth factor (bFGF) on acute rotator cuff healing in an ovine model.

The purpose of this study was to evaluate the effects of a nonsteroidal anti-inflammatory medication in a monopolar radiofrequency energy induced canine model of osteoarthritis.

The rate and patterns of longitudinal bone growth are affected by many different local and systemic factors; however, uncompromised growth is usually considered to be smoothly continuous, with predictable accelerations and decelerations over periods of months to years. The authors used implanted microtransducers to document bone growth in immature lambs. Bone length measurements were sampled every 167 seconds for 21 to 25 days. The authors show that at least 90% of bone elongation occurs during recumbency and almost no growth occurs during standing or locomotion. The authors hypothesize that growth may also occur in children during rest or sleep, thus supporting the concept of nocturnal growth and perhaps a relationship to growing pains.

To investigate the harvest and application of hamstring grafts for canine cranial cruciate ligament (CrCL) reconstruction.Experimental study.Four adult female hounds, weighing 26.3 ± 1.6 kg (mean ± SEM).One stifle in each dog was randomly chosen for hamstring graft CrCL reconstruction after native CrCL transection. Arthroscopy was performed to evaluate graft integrity at 12 weeks. Gait analysis and stifle radiographs were performed preoperatively and up to 52 weeks after graft placement. Dogs were killed 12 ( n = 2) or 52 weeks ( n = 2) after CrCL reconstruction. Tissues were evaluated grossly and with light and confocal laser microscopy. Hamstring grafts were intact in all stifles at 12 weeks ( n = 4) and 52 weeks ( n = 2). Grossly, there was no osteoarthritis in stifles at 12 weeks and only chondrophytes along the trochlear ridges at 52 weeks. Minimal radiographic evidence of osteoarthritis developed in stifles with grafts during the study. Lameness in limbs with grafts resolved by 52 weeks. Graft tissue was highly vascular, ligamentized, and undergoing active remodeling at 12 weeks. Fifty-two weeks after graft placement, intraarticular graft tissue was well vascularized, mature, and encapsulated by synovium, and graft-bone interfaces were characterized by Sharpey's fiber insertions. There was no evidence of graft necrosis using confocal laser microscopy at either time point. The hamstring graft technique may be a viable method of canine CrCL reconstruction.Hamstring grafts may be an alternative technique for canine CrCL reconstruction. Further study is needed before clinical application.

To determine the optimal fixation technique for equine interdental space fractures by evaluating the biomechanical characteristics of 4 fixation techniques.In vitro randomized block design.Twenty-seven adult equine mandibles.Mandibles with interdental osteotomies were randomly divided into 4 fixation groups ( n = 6/group). Fixation techniques were the following: (1) dynamic compression plates (DCP), (2) external fixator (EF), (3) external fixator with interdental wires (EFW), and (4) intraoral splint with interdental wires (ISW). Three intact (nonosteotomized) mandibles were tested as controls. Mandibles were subjected to monotonic cantilever bending until failure. Angular displacement data (radians) were derived from continuously recorded gap width measurements provided by extensometers placed across the osteotomy site. Osteotomy gap width data (mm) at 50 and 100 Nm were selected for standardized comparison of gap width before the yield point and failure point, respectively of all constructs tested. Stiffness (Nm/radian), yield strength (Nm), and failure strength (Nm) were determined from bending moment-angular displacement curves and were compared using ANOVA with appropriate post hoc testing when indicated. Radiographs were obtained prefixation, postfixation, and posttesting. Bending stiffness, yield, and ultimate failure loads were greatest for intact mandibles. Among osteotomized mandibles, stiffness was greatest for DCP constructs ( P < .05 ) and was not significantly different among EF, EFW, and ISW constructs. Yield load was greatest for ISW constructs ( P < .05 ) and was not significantly different among DCP and EFW constructs. Yield and ultimate failure loads were lowest ( P < .05 ) and osteotomy gap width at 50 and 100 Nm were greatest for EF constructs ( P= .09 and P < .05 , respectively). There was no significant difference in failure loads and osteotomy gap widths among DCP, EFW, and ISW constructs ( P < .05 ). Failure occurred through the screw-bone interface (DCP), acrylic splint (ISW), acrylic connecting bar and/or pin-bone interface (EF, EFW), and wire loosening (EFW). All 3 intact mandibles fractured through the vertical ramus at its attachment to the testing apparatus. Among osteotomized mandibles, DCP fixation had the greatest stiffness under monotonic bending to failure; however, the relatively low yield value may predispose it to earlier failure in fatigue testing without supplemental fixation. Techniques using tension-band wiring (EFW and ISW) were similar to DCP constructs in yield, failure, and osteotomy displacement, whereas EF constructs were biomechanically inferior to all other constructs.DCP fixation is most likely the most stable form of fixation for comminuted interdental space fractures. However, for simple interdental space fractures, ISW fixation may provide adequate stability with minimal invasiveness and decreased expense. Tension-band wiring significantly enhances the strength of type II external skeletal fixators and should be used to augment mandibular fracture repairs.

To determine changes to the cells and collagenous and amorphous extracellular matrix (ECM) structure in ruptured canine cranial cruciate ligaments (CCL).Prospective clinical study.CCL specimens obtained from 29 dogs with ruptured CCL and 6 young dogs with intact CCL.Ligament fibroblast number density and phenotype were determined in the core and epiligamentous regions. ECM birefringence and crimp structure in the core region were also studied.Loss of fibroblasts from the core region of ruptured CCL was seen ( P < .001 ), whereas, in the epiligamentous region, cell number densities were similar in ruptured and intact CCL ( P= .7 ). In ruptured CCL, numbers of typical ligament fibroblasts (fusiform and ovoid cells) were decreased, and numbers of cells exhibiting chondroid transformation (spheroid cells) were increased in the core region ( P < .001 ). Expansion of the volume of the epiligamentous region was also seen, although bridging scar tissue was not seen between the ends of ruptured CCL. The structure of the ECM collagen in the core region was extensively disrupted in ruptured CCL. This was, in part, because of decreased birefringence and elongation of the crimp in the remaining collagen fibers when compared with intact CCL ( P < .01 ). Extensive alterations to the cell populations and collagenous ECM structure were seen in ruptured CCL. Although a proliferative epiligamentous repair response was seen in ruptured CCL, there was a lack of any bridging scar between the ruptured ends of the CCL.The cellular and ECM changes in ruptured CCL that we have described appear to result from the cumulative effects of remodeling and adaptation to mechanical loading and microinjury. Treatment of early cruciate disease in dogs will need to inhibit or reverse these progressive changes to CCL tissue, which are directly associated with partial or complete structural failure of the CCL under conditions of normal activity.

To compare the biomechanical characteristics and mode of failure of two different dynamic compression plate (DCP) techniques for proximal interphalangeal joint (PIPJ) arthrodesis in horses.Randomized block-design blocking on horse (1–5), method of fixation (two 7-hole, 3.5-mm broad DCP vs two 5-hole, 4.5-mm narrow DCP), side (left, right), and end (front, hind). Constructs were loaded to failure in 3-point bending in a dorsal-to-palmar (plantar) direction.Ten paired limbs from 5 equine cadavers.Two 7-hole, 3.5-mm broad dynamic compression plates (bDCP) were used in 1 limb of a pair, and two 5-hole 4.5-mm narrow dynamic compression plates (nDCP) were used on the contralateral limb. Plates were positioned abaxially across the dorsomedial and dorsolateral aspect of the PIPJ. Arthrodesis constructs were loaded (19 mm/s) in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials-testing machine. Composite stiffness, yield point, and maximal bending moment at failure were obtained from bending moment—angular deformation curves. Data were analyzed using ANOVA, χ2 analysis, and Fisher's exact tests; the power of the test was calculated when differences were not significant. There were no significant differences in composite stiffness ( P > .05; power = 0.8 @δ= 21.9% ), yield point ( P > .05; power = 0.8 @δ= 34.4% ), or maximal bending moment ( P > .05; power = 0.8 @δ= 17.8% ) between the two fixation techniques. For bDCP constructs, 11% (15 of 140) of the 3.5-mm screws were damaged; 7 of the screw heads pulled through plates where the plates bent, 1 screw head broke off, and 7 screws were bent or pulled out of the phalanx. For nDCP constructs, 8% (8 of 100) of the 4.5-mm screws were damaged; 1 screw head pulled through a plate, 1 screw head broke off, and 6 screws were bent or pulled out of the phalanx. There were no biomechanical or failure differences between bDCP and nDCP fixation of the PIPJ in horses when evaluated in single-cycle 3-point bending to failure.There is no biomechanical advantage to the use of two 7-hole, 3.5-mm bDCP in equine proximal interphalangeal arthrodesis compared with two 5-hole, 4.5-mm nDCP. Two 5-hole, 4.5-mm nDCP may be easier to place, whereas two 7-hole, 3.5-mm bDCP may provide more versatility in fracture repair.

Purpose:To evaluate the effect of monopolar radiofrequency energy (RFE) on intact and lacerated meniscal tissue. Type of Study:In vitro study. Application of monopolar RFE to soft tissue for treatment of various musculoskeletal disorders has been explored recently, although its effect on meniscal tissue has not been critically evaluated. Monopolar RFE denatures and fuses collagen. Given that menisci are composed primarily of type I collagen, we proposed that RFE could be applied to meniscal tears with minimal effect on healthy meniscal tissue. Methods:Adult sheep menisci were given 1 of 2 treatments (65°C, 15 W or 75°C, 10 W) with a monopolar RFE generator. Specimens were processed for scanning electron microscopy (SEM), transmission electron microscopy (TEM), light microscopy, and confocal laser microscopy. A computer-based area-determination program was used to calculate the treated area in confocal laser images. Results:SEM changes in treated tissue consisted of surface smoothing with collagen fibril fusion. Changes apparent with TEM included tissue homogenization with loss of cross-striations and fusion of collagen fibrils. Histologic changes consisted of fusion and loss of collagen fiber individualization, pyknosis of fibrochondrocyte nuclei, and loss of lacunae surrounding fibrochondrocytes. There were clear demarcations between treated and untreated tissue with both treatments. There were no discernible differences between treatment groups on SEM, TEM, or histologic examination. Confocal laser microscopic evaluations showed distinct treatment areas. The mean area affected ranged from 6.6% for 65°C, 15 W to 8.8% for 75°C, 10 W. Conclusions:The primary effects of monopolar RFE treatment of menisci in this study were consistent with thermal tissue damage limited to the treatment area. Monopolar RFE treatment of a meniscal laceration may stabilize the tear by fusing collagenous tissue in the surrounding area and prevent propagation along tissue lines. This study presents preliminary in vitro results. Further studies are necessary before clinical applications can be recommended.

To compare the biomechanical characteristics and mode of failure of 2 parallel-screw techniques for proximal interphalangeal joint arthrodesis in horses.Randomized block design, blocking for horse (1–5), method of screw fixation (three 4.5-mm vs two 5.5-mm), side (left limb vs right limb), and end (front limb vs hind limb). Constructs were loaded to failure in 3-point bending in a dorsal-to-palmar (plantar) direction.Twenty limbs (10 limb pairs) from 5 equine cadavers.A combined aiming device was used to facilitate consistent screw placement. Three parallel 4.5-mm cortical screws were placed in lag fashion in 1 limb of a pair, and 2 parallel 5.5-mm cortical screws were placed in lag fashion in the contralateral limb. Arthrodesis constructs were tested in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials-testing machine. Loading rate was 19 mm/s. Maximal bending moment at failure and composite stiffness were obtained from bending moment—angular deformation curves. Data were analyzed using ANOVA and χ2 analysis. There were no significant differences in bending moment ( P > .05 , power = 0.8 @δ= 19%) or composite stiffness ( P > .05 , power = 0.8 @δ= 19%) between the 2 fixation techniques. Higher maximal bending moment was found in front limbs than hind limbs, and front limbs with two 5.5-mm screws than hind limbs with two 5.5-mm screws. In all cases, constructs completely failed. A greater number of 4.5-mm cortical screws failed than 5.5-mm cortical screws. In pastern arthrodesis constructs loaded in 3-point bending, end (front limb vs hind limb) affected maximal bending moment at failure of constructs. There was no significant effect of horse, treatment, or side on maximal bending moment or stiffness. Two 5.5-mm cortical screws should provide a surgically simpler pastern arthrodesis than three 4.5-mm cortical screws while maintaining similar biomechanical characteristics.Three 4.5-mm screws or two 5.5-mm screws will provide similar biomechanical characteristics in bending when performing equine pastern arthrodesis.

To compare the mechanical properties of 2 interlocking-nail systems for fixation of ostectomized equine third metacarpi (MC3): (1) a standard interlocking nail with 2 parallel screws proximal and distal to a 1-cm ostectomy; and (2) a modified interlocking nail with 2 screws proximal and distal to a 1-cm ostectomy with the screws offset by 30°.Twelve pairs of adult equine forelimbs intact from the midradius distally.Twelve pairs of equine MC3 were divided into 2 test groups (6 pairs each): torsion and caudocranial 4-point bending. Standard interlocking nails (6-hole, 13-mm diameter, 230-mm length) were placed in 1 randomly selected bone from each pair. Modified interlocking nails (6-hole, 13-mm, 230-mm length, screw holes offset by 30°) were placed in the contralateral bone from each pair. All bones had 1-cm mid-diaphyseal ostectomies. Six construct pairs were tested in caudocranial 4-point bending to determine stiffness and failure properties. The remaining 6 construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t test within each group. Significance was set at P < .05 . Mean (±SEM) values for the MC3-standard interlocking-nail composite and the MC3-modified interlocking-nail composite, respectively, in 4-point bending were: composite rigidity, 3,119 ± 334.5 Nm/rad (newton · meter/radian) and 3,185 ± 401.2 Nm/rad; yield bending moment, 205.0 ± 18.46 Nm and 186.7 ± 6.17 Nm; and failure bending moment, 366.4 ± 21.82 Nm and 378.1 ± 20.41 Nm. There were no significant differences in the biomechanical values for bending between the 2 fixation methods. In torsion, mean (±SEM) values for the MC3-standard interlocking-nail composite and the MC3-modified interlocking-nail composite were: composite rigidity, 135.5 ± 7.128 Nm/rad and 112.5 ± 7.432 Nm/rad; gap stiffness, 207.6 ± 10.57 Nm/rad and 181.7 ± 12.89 Nm/rad; and yield load, 123.3 ± 2.563 Nm and 107.5 ± 8.353 Nm, respectively. Composite rigidity and gap stiffness for standard interlocking-nail fixations were significantly higher than the modified interlocking-nail fixation technique in torsion. Yield load had a tendency to be higher for the standard interlocking-nail fixation ( P= .15 ). No significant differences in biomechanical properties were identified between a standard interlocking nail and one with the screw holes offset by 30° in caudocranial 4-point bending. The standard interlocking nail was superior to the modified interlocking nail in torsional gap stiffness and composite rigidity. The torsional yield load also tended to be higher for the standard interlocking nail.The standard interlocking nail with parallel screw holes is superior to a modified interlocking nail with the screw holes offset by 30° in ostectomized equine MC3 bones in vitro when tested in torsion.

To compare the biomechanical properties of intact immature horse femurs and 3 stabilization methods in ostectomized femurs.Eighteen pairs of femurs from immature horses aged 1 to 15 months, and weighing 68 to 236 kg.Thirty-four immature horse femurs were randomly assigned to 1 of 5 test groups: 1) interlocking intramedullary nail (IIN) ( n = 6); 2) IIN with a cranial dynamic compression plate (I/DCP) ( n = 6); 3) 2 dynamic compression plates (2DCP) ( n = 8); 4) intact femurs tested to failure in lateromedial (LM) bending ( n = 6); and 5) intact femurs tested to failure in caudocranial (CaCr) bending ( n = 8). Mid-diaphyseal ostectomies (1 cm) were performed in all fixation constructs. Biomechanical testing consisted of 4 nondestructive tests: CaCr bending, LM bending, compression, and torsion, followed by bending to failure. All groups were tested to failure in LM bending with the exception of 1 group of intact femurs tested to failure in CaCr bending. Stiffness and failure properties were compared among groups. The 2DCP-femur construct had greater structural stiffness in nondestructive bending than the IIN-femur construct in either LM or CaCr bending, and the I/DCP-femur construct in LM bending. Only the I/DCP and 2DCP fixations were similar to intact bone in nondestructive-bending tests. In addition, the 2DCP-femur construct had greater structural and gap torsional stiffness than the I/DCP-femur construct, and greater gap torsional stiffness than the IIN-femur construct. However, all of the fixation methods tested, including the 2DCP-femur construct, had lower structural stiffness in torsional loading compared with intact bone. No significant differences in structural stiffness were found between intact bones and femur constructs tested nondestructively in compression. In resistance to LM bending to failure, the 2DCP-femur construct was superior to the IIN-femur construct, yet similar to the I/DCP-femur construct. Also, evaluation of yield and failure loads revealed no significant differences between intact bone and any of the femur constructs tested to failure in LM bending.In general, the 2DCP-femur construct provided superior strength and stiffness compared with the IIN and I/DCP-femur constructs under bending and torsion.Double plating of diaphyseal comminuted femoral fractures in immature horses may be the best method of repair, because in general, it provides the greatest strength and stiffness in bending and torsion.

This study compared the effect of augmentation of allograft–host bone junctions with recombinant human bone morphogenetic protein‐2 (rhBMP‐2) on an absorbable collagen sponge (ACS), autogenous cancellous bone graft (CBG), and a collagen sponge alone in a canine intercalary femoral defect model repaired with a frozen allograft. Outcome assessment included serial radiographs, dual energy X‐ray absorptiometry scans, and gait analyses, and mechanical testing and histology of post‐mortem specimens. The distal junction healed more quickly and completely with rhBMP‐2 than ACS alone based on qualitative radiography and histologic evaluations. The primary tissue in the unhealed gaps in the ACS group was fibrous connective tissue. The proximal allograft–host bone junction had complete bone union in the three treatment groups. There was significantly greater new bone callus formation at both junctions with rhBMP‐2 than with CBG or ACS alone that resulted in increased bone density around the allograft–host bone junctions. All dogs shifted their weight from the treated leg to the contralateral pelvic limb immediately after surgery. Weight bearing forces were redistributed equally between the pelvic limbs at 12 weeks after surgery with rhBMP‐2, at 16 weeks after surgery with CBG, and at 24 weeks after surgery with ACS alone. Bending and compressive stiffnesses of the whole treated femora were equal to the contralateral control femora in all treatment groups, whereas torsional rigidities of the whole treated femora for the CBG and ACS groups were significantly less than the control. Both the proximal and distal junctions the treated with rhBMP‐2 had torsional stiffnesses and strengths equal to intact control bones. Ultimate failure torques of the proximal junctions of the CBG group and of both junctions of the ACS group were significantly less than the BMP‐treated bones. Augmentation of the allograft–host bone junctions with rhBMP‐2 on an ACS gave results for all parameters measured that equaled or exceeded autogenous graft in this canine intercalary femoral defect model. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.

Thermal modification of joint capsule and ligament has gained great popularity among orthopaedic surgeons as a treatment method for joint instability. Heating joint capsular tissue to approximately 70°C to 80°C by laser or radiofrequency energy produces significant dimensional alterations shrinkage and thickening of the tissue treated, resulting in postoperative stabilization of the joint. In vitro experimental studies have demonstrated that joint capsular tissue is significantly shortened by thermal energy, although significant loss of the tissue's mechanical properties occurs after this treatment. In vivo experimental studies have demonstrated initial deleterious effects of thermal energy application, followed by an active reparative response, with concomitant improvement of mechanical properties. Other studies have shown that despite significant immediate postoperative tissue shrinkage, the tissue stretches over time if it is subjected to physiologic loading. Currently, radiofrequency applications to other musculoskeletal tissues such as cartilage are being explored. Thermal modification of musculoskeletal tissues has the potential to enhance joint stability and may become a prominent modality in the treatment of joint disorders. However, it should be emphasized that thermal treatment does cause initial deleterious effects to the tissue's properties, and that longterm results have yet to be evaluated.

This study used radiography, gait analysis, gluteal muscle mass, mechanical testing, and qualitative histology to compare three methods of gluteal muscle attachment to an allograft/endoprosthetic composite of the proximal 25% of the femur in an in vivocanine model. The three methods of gluteal muscle attachment were identical to those used clinically in human patients for hip revision and proximal femoral limb salvage: the host gluteal tendon sutured to the allograft tendon (tendon group), the host greater trochanter with intact gluteal tendons secured to the allograft with a cable‐grip system (grip group), and periosteally vascularized proximal femoral bone onlay with intact tendons wrapped around the allograft (wrap group). On the basis of radiographs taken every 2 months, the tendon group had more graft fractures than did the grip or wrap group. Radiographic union of the graft‐host bone junction occurred more rapidly and there was less graft resorption in the wrap group than in the other two groups. In all dogs, peak vertical ground‐reaction forces in the treated limb decreased immediately after surgery and then slowly increased over the length of the study. The dogs in the wrap group regained normal weight‐bearing on the treated limb more quickly than did those in the other groups. The constructs in the tendon group were weaker and less stiff immediately after surgery than were those in the other groups or in intact controls. Histologic analysis confirmed that the wrap technique resulted in complete union of the host bone‐allograft junction more often than did the other techniques. The wrap method had the best functional outcome after 9 months when an allograft/endoprosthetic composite was used during total hip arthroplasty in this canine model.

To compare the mechanical properties of two stabilization methods for ostectomized equine third metacarpi (MC3): (1) an interlocking nail system and (2) two dynamic compression plates.Ten pairs of adult equine forelimbs intact from the midradius distally.Ten pairs of equine MC3 were divided into two test groups (five pairs each): caudocranial four-point bending and torsion. Interlocking nails (6 hole, 13-mm diameter, 230-mm length) were placed in one randomly selected bone from each pair. Two dynamic compression plates one dorsally (12 hole, 4.5-mm broad) and one laterally (10 hole, 4.5-mm broad) were attached to the contralateral bone from each pair. All bones had 1 cm mid-diaphyseal ostectomies.Five construct pairs were tested in caudocranial four-point bending to determine stiffness and failure properties. The remaining five construct pairs were tested in torsion to determine torsional stiffness and yield load. Mean values for each fixation method were compared using a paired t-test within each group. Significance was set at P < .05. Mean (±SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite, respectively, in four-point bending were: composite rigidity, 3,454 ± 407.6 Nm/rad and 3,831 ± 436.5 Nm/rad; yield bending moment, 276.4 ± 40.17 Nm and 433.75 ± 83.99 Nm; failure bending moment, 526.3 ± 105.9 Nm and 636.2 ± 27.77 Nm. There was no significant difference in the biomechanical values for bending between the two fixation methods. In torsion, mean (±SEM) values for the MC3-interlocking nail composite and the MC3-double plate composite were: composite rigidity, 124.1 ± 16.61 Nm/rad and 262.4 ± 30.51 Nm/rad; gap stiffness, 222.3 ± 47.32 Nm/rad and 1,557 ± 320.9 Nm/rad; yield load, 94.77 ± 7.822 Nm and 130.66 ± 20.27 Nm, respectively. Composite rigidity, gap stiffness, and yield load for double plate fixation were significantly higher compared with interlocking nail fixation in torsion.No significant differences in biomechanical properties were identified between an interlocking nail and double plating techniques for stablilization of ostectomized equine MC3 in caudocranial four-point bending. Double plating fixation was superior to interlocking nail fixation in torsion.Double plate fixation is biomechanically superior to interlocking nail fixation in vitro in ostectomized equine MC3 bones.

Recurrence of large colon displacement or volvulus is a rare but significant occurrence in horses. Prevention of these lesions has been attempted by three basic approaches. They include removal of the displacing colon, obliteration of the space into which the colon displaces, and colopexy of the large colon. Large colon resection is useful for horses with strangulating lesions of the large intestine. For horses with a viable large colon, colopexy of the left large colon to the abdominal wall appears to be the best method for prevention of recurrence.

An in vitrostudy was performed to compare the effects of augmenting interlocking nails of one of two diameter (5 or 6 mm) with intramedullary polymethylmethacrylate. Subsequently, an in vivostudy was performed to compare the effects of augmenting the interlocking nail with five combinations of intramedullary polymethylmethacrylate and autogenous cancellous bone applied to the periosteal surface or within the medullary canal. Dogs were killed 6 months after the procedure for biomechanical evaluation of the femora in axial compression, mediolateral and craniocaudal bending, and torsion. Results from the in vitrostudy at the proximal osteotomy indicated the 6‐mm inteilocking nail with intramedullary polymethylmethacrylate had greater stiffness than the 5‐mm interlocking nail without it (p < 0.05). At the distal osteotomy, regardless of the diameter of the interlocking nail, the addition of intramedullary polymethylmethacrylate increased stiffness (p < 0.05). Results from the in vivostudy indicated greater global construct stiffness with an interlocking nail alone, an interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface, and an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface (p < 0.05). At the osteotomy level, the interlocking nail augmented with intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface had greater stiffness than did an interlocking nail alone or an interlocking nail augmented with either intramedullary polymethylmethacrylate. cancellous bone within the medullary canal, or cancellous bone at the periosteal surface (p < 0.05) but produced the same results as an interlocking nail augmented with cancellous bone within the medullary canal and at the periosteal surface. The results suggest that augmenting interlocking nail fixation with intramedullary polymethylmethacrylate by itself offers no advantage but that acombination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface improves structural properties at 6 months.

This study was designed to compare bone mineral density, periosteal callus production. new bone formation, bone porosity, histologic appearance, and union of mid‐diaphyseal segmental allografts of the femur stabilized with an interlocking nail technique in a canine model 4 months after the procedure. An in vivostudy was performed to compare the effects of augmenting interlocking nail fixation with an interlocking nail alone, intramedullary polymethylmethacrylate, intramedullary polymelhylmethacrylate and autogenous cancellous bone applied to the periosteal surface of the host‐allograft junction, autogenous cancellous bone applied to the endosteal surface of the allograft, autogenous cancellous bone applied to the periosteal surface of the host‐allograft junction, and autogenous cancellous bone applied to the periosteal surface of the hostallograft junction and to the endosteal surface of the allograft. There were no differences among treatments for bone mineral density at any time interval. Callus area 4 weeks after the procedure was greater along the lateral and cranial surfaces for treatments with periosteal cancellous bone (p < 0.05). New bone within the allograft segment did not differ among treatments and was reduced compared with the host‐allograft junctions (p < 0.05). The amount and quality of bone tissue at the host‐allograft junctions were greatest with treatments of intramedullary polymethylmethacrylate and autogenous cancellous bonc applied to the periostcal surface of the host‐allograft junction and of autogenous cancellous bone applicd to the periosteal surface of the host‐allograft junction and to the endosteal surface of the allograft (p < 0.05). The rate of bone union was lower, and there was a greater gap (non‐bone tissue) remaining between host and allograft bone with treatment involving just intramedullary polymethylmethacrylate than with other treatments (p < 0.05). The results suggest that augmenting interlocking nail fixation with intramedullary polyrnethylmethacrylate by itself offers no advantage but that a combination of intramedullary polymethylmethacrylate and cancellous bone at the periosteal surface or of cancellous bone within the medullary canal and at the periosteal surface improves the quality of healing at 6 months.

Peritonitis and adhesions in the horse are best managed through prevention. Perioperative antimicrobial therapy, nonsteroidal anti-inflammatory therapy, experienced personnel, and good surgical techniques should minimize complications after surgery. Despite preventative measures, some horses still develop peritonitis after surgery. Immediate, intensive treatment is necessary to enhance their chances for survival.