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1.
Using standard material testing techniques (bending stiffness, torsional stiffness, and maximum torque to failure or yield torque), the structural properties of interlocking nails (IN), canine femora, and IN/femur constructs were determined. Specimens that were tested included: 6 and 8 mm diameter IN with 5 to 10 screw holes (n = 18), and intact canine femora (n = 10), which also, with an IN inserted, formed the intact construct (IC) group, (n = 10). Specimens in the IC group were first tested with an 8 mm diameter IN with zero screws, followed by one and two screws (4.5 mm diameter) in the proximal and distal femur. A fracture model construct (FMC), (n = 14), consisting of a transverse femoral osteotomy with a 3 mm gap, was used with either 6 mm or 8 mm IN. In the 6 mm FMC, one and two 3.5 mm screws were used sequentially in the proximal and distal femoral segment. In the 8 mm FMC, one and two 3.5 mm screws and one and two 4.5 diameter screws were used similarly. When bending forces were applied parallel to IN screw holes, mean IN stiffness was 20% less than with forces perpendicular to the holes (n = 18), (P <.05). Eight-millimeter IN were 220% stiffer in torsion and 270% stiffer in bending than 6 mm IN (P <.05). Six-millimeter IN had approximately 32% of the bending stiffness and torsional stiffness of intact femurs (P <.05). Eight-millimeter IN had 93% and 79% of the bending stiffness and torsional stiffness, respectively, of intact femurs. Intact femur constructs (8 mm IN with four, 4.5 mm screws) had 147% of the bending stiffness (P <.05), and similar torsional stiffness and maximum torque, as intact femora (P >.05). The mean values of 6 mm FMC with four screws (3.5 mm) were 21% and 33% in torsional stiffness and bending stiffness, respectively, of intact femora values. When tested in torsion, 8 mm FMC failed by bone fracture; 6 mm FMC, in contrast, underwent plastic deformation. In comparing FMC stabilized with an 8 mm IN with two screws (4.5 mm diameter) in each bone segment, to intact femurs, the maximum torque was similar, FMC torsional stiffness was 40% (P <.05), and FMC bending stiffness was 65% (P <.05). These 8 mm FMC percentages are comparable to human IN fracture model construct values, indicating that the 8 mm IN/four screw construct should provide adequate stabilization for many canine diaphyseal femoral fractures.  相似文献   

2.
Objective: To determine whether the fatigue properties of an interlocking nail (ILN) construct are influenced by metaphyseal or diaphyseal location of the locking bolt. Study Design: Ex vivo mechanical investigation. Sample Population: Adult canine femora (n=19 pairs). Methods: Femora were implanted with a 6‐mm diameter ILN. In 1 femur, the ILN was locked with a 2.7 mm bolt placed in the diaphysis; the ILN in the contralateral femur was locked with a bolt placed in the metaphysis. Constructs were tested to failure in axial loading (9 pairs) or torsion (10 pairs), with failure defined as displacement>2 mm or a total of 500,000 cycles for axial loading, and rotation>45° for torsional loading. Outcome measures included initial construct stiffness, number of cycles to failure, peak load, and peak torque. After testing, microradiography and histology were used to determine the location and nature of construct failure. Results: Metaphyseal bolts failed at higher axial loads than diaphyseal bolts (P=.03), with bolt failure because of bending at the nail‐bolt interface. All of the metaphyseal bolt constructs survived torsional testing whereas 9 of 10 diaphyseal bolt constructs failed catastrophically because of spiral fracture through the adjacent cortical bone. Conclusions: Placement of a locking bolt in metaphyseal bone extends fatigue life under axial loading and decreases the incidence of catastrophic failure under torsional loading.  相似文献   

3.
OBJECTIVES: To compare the biomechanical properties, in full limb preparations, of intact second phalanx and a simulated comminuted second phalangeal fracture stabilized with either two bone plates or a custom Y-plate. STUDY DESIGN: In vitro biomechanical assessment of intact limbs and of paired limbs with a simulated second phalangeal fracture stabilized by one of two fixation methods. Animal Population-Thirteen pairs of equine cadaveric forelimbs. METHODS: A comminuted second phalangeal fracture was created in six paired cadaveric limbs. For each limb pair, the fracture was stabilized with two plates in one limb, and with a Y-plate in the contralateral limb. These limbs and seven pairs of intact limbs were subjected to axial compression in a single cycle until failure. Mechanical properties were compared with a mixed-model ANOVA and post hoc contrasts. Joint contact pressure, screw insertion torque, and final screw torque remaining after mechanical testing were also evaluated for constructs. RESULTS: No significant differences in mechanical testing variables were detected between construct types. However, the Y-Plate construct had significantly greater yield load, yield displacement and yield energy, and failure load and stiffness values than those for intact specimens, whereas the double-plate construct only had greater stiffness than intact specimens. There were no significant differences in joint contact pressures for both constructs. The final screw torque for proximal phalangeal screws was significantly greater for the Y-plate constructs than for double-plate constructs. CONCLUSIONS: The Y-plate was as effective as the double-plate technique for stabilization of simulated comminuted second phalangeal fractures in monotonically tested equine cadaveric forelimbs. CLINICAL RELEVANCE: This investigation supports evaluation of the Y-plate for repair of comminuted second phalangeal fractures in equine patients. Its specific design may facilitate repair of second phalangeal fractures, and may provide increased stability by allowing the proximal fragments of the second phalanx to be fixed with three screws placed through the plate.  相似文献   

4.
OBJECTIVE: To compare the structural properties and the interfragmentary motion in ostectomized canine femurs stabilized with either an 8-mm interlocking nail system (IN) or a 10-hole dynamic compression broad plate (DCP). ANIMAL OR SAMPLE POPULATION: Ten pairs of adult canine femurs with a 25-mm mid-diaphyseal gap. METHODS: Bone specimens were divided into 2 groups (10 femurs each). Left femurs were stabilized with a DCP and 8 bicortical screws; right femurs were stabilized with an IN and 3 screws. Mechanical tests were performed in eccentric axial loading and in craniocaudal bending. The testing was first conducted nondestructively and then until breakage. Structural properties, ie, stiffness, yield limits, and failure limits, were determined. Interfragmentary motion was measured during nondestructive tests with the use of an optoelectronic device. Axial, transverse, and rotational motions were calculated. Mean values of stiffness, yield and failure limits, and axial and shear motions for each fixation method were compared using a paired t test within each group (P <.05). RESULTS: Mean (+/-SD) values of stiffness and failure limit were significantly higher for IN constructs than for DCP constructs in compression, while there was little difference in the results between each tested group in bending. Mean yield load values were significantly higher for IN than for DCP specimens in compression as well as in bending. The axial-motion analysis revealed significant differences between IN and DCP groups during bending tests only. The highest score of transverse motion at the gap was recorded during bending tests, and was higher for DCP than for IN specimens. There were insignificant differences between the two groups with regard to rotation around the diaphyseal axis. CONCLUSIONS AND CLINICAL RELEVANCE: Structural properties and interfragmentary shear motion analysis demonstrated a much higher rigidity in the IN-bone than in the DCP-bone constructs.  相似文献   

5.
Femur fractures associated with canine total hip replacement   总被引：1，自引：0，他引：1  
OBJECTIVE: To report femur fracture as a complication of canine total hip replacement (THR) and to report the incidence, predisposing factors, treatment options, and outcome. STUDY DESIGN: Prospective clinical study. ANIMALS: Twenty-two client-owned dogs with 24 femoral fractures occurring during or after THR. METHODS: Cemented THR (BioMedtrix, Boonton, NJ) was performed. Medical records and radiographs were used to identify dogs that had femur fracture and to identify risk factors. Follow-up was obtained until dog death or study end. RESULTS: The overall incidence of femur fracture after THR was 2.9%. Femoral fractures occurred intraoperatively, immediately postoperatively, and up to 2196 days after THR. In 17 dogs, fractures resulted from a traumatic event. Osteopathy was present at THR in 5 dogs; all developed femoral fissures during reaming. Three dogs had fractures associated with cortical thinning secondary to aseptic loosening. Fracture treatment included euthanasia (1 dog), strict confinement (3 dogs), full cerclage wires on long oblique fractures (3 dogs), or plate and screw fixation (10 with, and 7 without, cerclage wires). All fractures extended near the distal tip of the femoral stem and all aggressively treated fractures healed. CONCLUSIONS: Predisposing risk factors for femur fracture after THR include osteopathy and iatrogenic fissures created during reaming. Trauma, excessive load concentration, and increased torque can lead to mid-diaphyseal fracture near the end of the femoral stem. Fracture did not disrupt THR implants. Cement fracture exposing the tip of the femoral stem did not affect fracture healing or rehabilitation. Immediate plate and screw fixation resulted in the most favorable outcome; healing occurred in 6-10 weeks. CLINICAL RELEVANCE: Femur fractures that occur after THR should be repaired using plate and screw fixation augmented with cerclage wire when needed. Forces on fissures should be neutralized to prevent propagation and fracture. Owners of high-risk patients (old dogs with osteopathies or previous hip surgery) should be counseled before THR. The prognosis is excellent when fractures are treated correctly.  相似文献   

6.
OBJECTIVE: To compare screw insertion variables and pullout mechanical properties between AO 6.5-mm cancellous and 7.3-mm cannulated bone screws in foal femoral bone. STUDY DESIGN: A paired, in vitro mechanical study. SAMPLE POPULATION: Seven pairs of femora from immature (1-7 months) foals. METHODS: The 6.5 cancellous and 7.3-mm cannulated screws were inserted at standardized proximal and distal metaphyseal, and mid-diaphyseal locations. Insertion torque, force, and time to drill, tap (6.5-mm cancellous), guide wire insertion (7.3-mm cannulated), and screw insertion were measured. Screw pullout properties (yield and failure load, displacement, and energy, and stiffness) were determined from mechanical tests. The effects of screw type and location on insertion variables and pullout properties were assessed with repeated measures ANOVA. Pairwise comparisons were examined with post hoc contrasts. Significance was set at P<.05 for all comparisons. RESULTS: Insertion torques for the 7.3-mm cannulated screws were significantly greater than for the 6.5-mm tap, but significantly lower than for the 6.5-mm cancellous screws. Total screw insertion times were similar. Pullout properties of both screws were similar at each femoral location. The holding power of both screws was significantly greater in the mid-diaphysis than in either metaphyseal location. Pullout failure occurred by bone shearing at the bone-screw interface in all specimens. CONCLUSIONS: The 6.5-mm cancellous and 7.3-mm cannulated screws vary in insertion properties, but have similar pullout properties in the mid-diaphysis, proximal, and distal metaphysis of foal femora. Both screw types have greater holding power at the mid-diaphyseal location compared with metaphyseal locations. Based on overall similar holding powers of 6.5-mm cancellous and 7.3-mm cannulated screws, it is unlikely that increasing the screw diameter beyond 6.5 mm will provide increased holding power in foal femoral bone. CLINICAL RELEVANCE: Use of the 7.3-mm cannulated screw should be considered for foal femoral fracture repair when greater accuracy is needed, or when bone threads for the 6.5-mm cancellous screw have been stripped.  相似文献   

7.
OBJECTIVE: To compare the biomechanical properties of intact immature horse femurs and 3 stabilization methods in ostectomized femurs. Animal or SAMPLE POPULATION: Eighteen pairs of femurs from immature horses aged 1 to 15 months, and weighing 68 to 236 kg. METHODS: 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. RESULTS: 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. CONCLUSIONS: In general, the 2DCP-femur construct provided superior strength and stiffness compared with the IIN and I/DCP-femur constructs under bending and torsion. CLINICAL RELEVANCE: 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.  相似文献   

8.
OBJECTIVE: To determine bone healing at 20 weeks, after either static fixation (SG) or after dynamization (DG) at 4 weeks in osteotomized canine femurs repaired with an interlocking nail (ILN) secured with a type I external skeletal fixator (ESF). STUDY DESIGN: Experimental study. ANIMALS: Ten adult beagle dogs. METHODS: After mid-diaphyseal femoral osteotomy, femurs in 10 dogs were repaired with an ILN secured with 4 (2 proximal, 2 distal) threaded custom pins (TP; 2.7-mm-diameter cortical screw with a 2-mm shaft attached to the screw head) to which 2 parallel connecting bars were attached in a type I ESF configuration. In 5 dogs, dynamization was performed at 4 weeks by removing the connecting bars and 2 distal screws. Limb function, range of motion of the stifle joint (ROMSJ), radiographic evidence of bone healing, and complications were studied for 20 weeks. RESULTS: Full limb function was achieved between 8 and 10 weeks in SG dogs, but a decreased ROMSJ was observed from 5 to 8 weeks. In DG dogs, full limb function occurred between 5 and 6 weeks except in 1 dog, and ROMSJ was considered normal in all dogs. Bone healing was not affected by dynamization. Average healing time for SG was 12.8 weeks, and for DG it was 13.6 weeks. Periosteal reaction at TP insertion points, osteolysis around the thread and head of TPs were observed in both groups. A windshield-wiper effect was observed at the tip of 1 ILN. CONCLUSION: ILN locked with a type I ESF can be used for fixation of mid-shaft femoral fractures. Dynamization at 4 weeks did not affect bone healing but did prevent stifle ankylosis and promoted earlier limb function. CLINICAL RELEVANCE: ILN locked with a type I ESF is seemingly a feasible method for repair of mid-shaft femoral fractures and may decrease risk of nail failure.  相似文献   

9.
OBJECTIVE: To evaluate a dorsoproximal extra-articular approach for insertion of 8.25-mm, solid-titanium, intramedullary (IM) interlocking nails into ostectomized foal third metacarpal (MC3) and third metatarsal (MT3) bones; to compare the monotonic mechanical properties of IM nail constructs with paired intact bones; and to determine the effects of age, body weight, fore- or hindlimb, and left or right limb on the mechanical testing variables. ANIMAL OR SAMPLE POPULATION: Twenty bone pairs (10 MC3, 10 MT3) collected from 10 foals of various weights and ages. METHODS: One bone from each pair was randomly selected to be ostectomized and stabilized using an 8.25-mm, solid-titanium IM nail, and four 3.7-mm titanium interlocking screws (construct). Constructs and contralateral intact bone specimens were tested in axial compression and palmaro-/plantarodorsal (PD) 4-point bending. Monotonic mechanical properties were compared between intact specimens and constructs with an ANOVA; significance was set at P <.05. RESULTS: Nail insertion caused bone failure in 6 MC3 and 2 MT3. In general, mean mechanical testing values indicated that intact specimens were significantly stronger and stiffer than constructs for all age and weight ranges when tested in compression and PD 4-point bending (P <.05). Bone strength and stiffness of intact specimens tested in compression and bending tended to increase linearly with age and weight. CONCLUSION: IM interlocking nail fixation of gap-ostectomized MC3 and MT3 with 8.25-mm IM nails and 3.7-mm interlocking screws did not achieve sufficient strength or stiffness to be recommended as the sole means of repair for comminuted MC3 and MT3 fractures in young foals. CLINICAL RELEVANCE: IM interlocking nail fixation of foal cannon bone fractures may be useful to decrease soft-tissue disruption at the fracture site; however, there is a risk of bone failure associated with extra-articular insertion. This method should be combined with other forms of external coaptation for added stability in axial compression and PD bending.  相似文献   

10.
OBJECTIVE: To determine the outcome of femoral fractures repaired with 4.0- and 4.7-mm interlocking intramedullary nails in cats. DESIGN: Retrospective study. ANIMALS: 12 cats with diaphyseal femoral fractures. PROCEDURE: Records of all cats in which the 4.0- and 4.7-mm interlocking nail system was used for repair of diaphyseal femoral fractures at the Animal Medical Center and Florida Veterinary Specialists between 1996 and 2000 were reviewed. Information included signalment, type of fracture, size of the implant, details of the surgery, intra- and postoperative complications, fracture healing, and clinical outcome. RESULTS: Femoral fractures in 12 cats were repaired. Eleven of the fractures were comminuted, with 2 of these being open. Clinical outcome was excellent in 7 cats, good in 3, and fair in 1. One resulted in a nonunion. Complications included screw breakage (1 cat) and fracture distal to the nail (1). Fracture distal to the nail occurred from a second trauma. CONCLUSION AND CLINICAL RELEVANCE: Use of the interlocking nail has been limited in cats because of the small diameter of the medullary canal. Use of the 4.0-mm nail will allow for greater application of this implant in small patients. Results of this study indicate that the 4.0- and 4.7-mm interlocking nails can be used to repair simple or comminuted diaphyseal femoral fractures in cats.  相似文献   

11.
Objective— To compare the biomechanical properties of five intramedullary (IM) pin fixation techniques for Salter-Harris type I fractures of the distal femur in dogs.
Study Design— Randomized, one-way factorial design composed of five treatment groups: (1) single IM pin, (2) dynamic IM crossed pins, (3) paired convergent pins, (4) crossed pins, and (5) crossed polyglycolic acid (PGA) rods.
Sample Population— Forty pairs of cadaver canine femurs.
Materials— One femur of each pair was manually fractured and subsequently repaired; the contralateral intact femur served as its control. Each femur was loaded in torsion until failure occurred and load-deformation curves were generated.
Results— The crossed-pin technique sustained the greatest load to failure (116.8%) followed by the paired convergent pins (104.8%), dynamic IM pins (90.6%), single IM pin (72.1%), and crossed PGA rods (71.9%). Statistically significant differences in strength at failure were detected between the crossed-pin and single IM pin and the crossed-pin and crossed PGA rod techniques. All fixation techniques underwent greater deformation (1.5 times as much) and had a lower stiffness (66% to 75%) compared with the intact controls; however, there was no significant difference between techniques. Failure in the paired convergent and crossed-pin techniques occurred by fracture of the bone; failure in the other techniques occurred by distraction at the fracture site.
Conclusion— The rotational stability of any of the fixation techniques appears to be primarily determined by the ability to prevent distraction and maintain interdigitation of the physis.
Clinical Relevance— When choosing a particular fixation technique for repair of a distal femoral physeal fracture, consideration should be given to the technique's relative biomechanical merits.  相似文献   

12.
OBJECTIVE--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 degrees. ANIMAL OR SAMPLE POPULATION--Twelve pairs of adult equine forelimbs intact from the midradius distally. METHODS--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 degrees) 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. RESULTS--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). CONCLUSIONS--No significant differences in biomechanical properties were identified between a standard interlocking nail and one with the screw holes offset by 30 degrees 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. CLINICAL RELEVANCE--The standard interlocking nail with parallel screw holes is superior to a modified interlocking nail with the screw holes offset by 30 degrees in ostectomized equine MC3 bones in vitro when tested in torsion.  相似文献   

13.
Twenty-four simple or comminuted supracondylar and diaphyseal femoral fractures in cats, which had been treated by retrograde insertion of a new 3.5 mm titanium interlocking nail (IN) from the intercondylar notch, were evaluated between June 2000 and October 2004 at the Ecole Nationale Vétérinaire d'Alfort. Patient data (species, breed, weight, and age), fracture characteristics, details of the surgery, post-operative complications and radiographic follow-up were recorded. The mean body weight was 3.75 kg and the cats ranged in age between four and 66 months (mean 29 months). The IN had a diameter of 3.5 mm and a length of 100, 109 or 119 mm, and were all fixed in a static position (two screws in seven cats, three screws in 10 cats and four screws in seven cats). Cerclage wires were used in seven cats and an autogenous bone graft was used in two cats. Screw or nail breakage were not recorded. Nineteen fractures healed without any complications, three cats died during the post-operative period from unknown causes, and two cats showed delayed bone healing. Twenty cats were considered to have an excellent limb function at one month. One cat with a sciatic injury was non-weight bearing for several months. Radiographic signs of degenerative joint disease of the stifle joint were not observed except in the cat with the sciatic nerve injury. The results of this study suggest that this new 3.5 mm titanium IN can be introduced from the intercondylar notch and be used in static fixation mode to stabilize supracondylar and diaphyseal femoral fractures in cats.  相似文献   

14.
The cross-pin technique for the treatment of distal femoral physis fractures (specifically, Salter-Harris Type I fractures) was investigated using femurs collected from beagle cadavers. The pin was inserted from the medial surface of the femur at an inclination of approximately 30 to 45° relative to the long axis of the femur in the anteroposterior direction; the pin exit was set proximal to the origin of the long digital extensor tendon. Digital and radiographic images of the femur in the anteroposterior and lateral directions were obtained. In both types of images, the insertion angle of the pin relative to the long axis was measured. Results suggest that when inserting a pin proximal to the fracture line, the ideal position can be achieved by inclining the pin approximately 20° cranially relative to the long axis of the lateral direction of the femur, in addition to the previously described criteria.  相似文献   

15.
Objective— To compare the biomechanical characteristics, failure mode, and effects of side (left or right limb) and end (forelimb or hindlimb) of different screws in 2-screw, parallel-screw proximal interphalangeal joint arthrodesis constructs in horses.
Study Design— In vitro experimental study.
Sample Population— Twenty limbs from 6 cadavers (4 complete limb sets, 2 partial sets—total of 4 forelimb and 6 hindlimb pairs).
Methods— Two parallel 5.5 mm cortical (AO) screws were inserted in lag fashion in 1 randomly allocated limb of a pair, and 2 parallel headless, tapered, variable-pitched, titanium compression screws (Acutrak-Plus®) were inserted in the contralateral limb. Constructs were tested in 3-point bending in a dorsopalmar (plantar) direction using a materials-testing machine at a loading rate of 5.83 mm/s. Maximal bending moment at failure and composite stiffness were calculated from data generated on load–displacement curves. Data were analyzed using a Friedman 2-way analysis of variance and Wilcoxon's signed-rank tests.
Results— No significant difference was detected for bending moment or stiffness values in proximal interphalangeal joint arthrodesis constructs using 2 parallel Acutrak-Plus® or AO screws for fixation. Mean stiffness values were significantly different between forelimb and hindlimb constructs.
Conclusions— Performance of 2 parallel Acutrak-Plus® screws was biomechanically comparable with 2 parallel AO 5.5 mm cortical screws in in vitro pastern arthrodesis constructs.
Clinical Relevance— Acutrak-Plus® screws may provide an alternative means of fixation for proximal interphalangeal joint arthrodesis.  相似文献   

16.
OBJECTIVE: To compare the biomechanical characteristics and mode of failure of 2 techniques using parallel 5.5 mm screws for pastern joint arthrodesis in horses. STUDY DESIGN: Randomized block design, for horse (1-5), method of fixation (two 5.5 mm screws versus three 5.5 mm screws), side (right, left), and end (front, hind). Constructs were tested to failure in 3-point bending. SAMPLE POPULATION: Twenty limbs (5 cadavers). METHODS: A combined aiming device was used to facilitate screw placement. Two parallel 5.5 mm screws were inserted in lag fashion in 1 limb of a pair, and three 5.5 mm screws were inserted in the contralateral limb. Constructs were then tested in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials testing machine at a loading rate of 19 mm/s. Maximal bending moment at failure and stiffness were obtained from bending moment-angular deformation curves. RESULTS: There was no significant difference between two and three 5.5 mm screw constructs for bending moment and stiffness (P<.05). All constructs ultimately failed by bone fracture or screw bending. For proximal interphalangeal (PIP) joint arthrodesis constructs loaded in 3-point bending, no significant effect of treatment, side, or end on maximal bending moment or stiffness was detected. CONCLUSIONS: Two 5.5 mm cortical screws inserted in parallel should provide a surgically simpler and equally strong PIP joint arthrodesis compared with three 5.5 mm cortical screws. CLINICAL RELEVANCE: Two 5.5 mm cortical screws inserted in parallel for PIP joint arthrodesis should perform similarly under conditions used in this study, as three 5.5 mm screws inserted in a similar manner, when loaded under bending.  相似文献   

17.
Lag screw fixation using single 4.5 mm cortical bone screws is a recommended technique for repair of mid-sagittal plane fractures of the distal phalanx in adult horses. However, implant infection and technical difficulties in obtaining adequate interfragmentary compression have made this surgical procedure somewhat controversial. We hypothesized that use of larger diameter screws would result in increased axial compression and improved stability of this fracture.Paired distal phalanges from the forelimbs of 10 adult horses were collected at necropsy and divided in half in the midsagittal plane. Using a randomized block study design, four types of bone screws (4.5 mm cortical, 5.5 mm cortical, 6.5 mm cancellous pre-tapped, and 6.5 mm cancellous non-tapped) were inserted to a depth of 15 mm. During screw insertion, the axial force generated under the screw head was measured with a load washer containing a piezoelectric force transducer, while torque of insertion was recorded with a torsional testing machine. The 6.5mm screw inserted after pre-tapping generated significantly greater axial force (2781 N) than the 4.5 mm (1522 N), 5.5 mm (2073 N) or 6.5 mm non-tapped (2295 N) screws. The relationship between maximal applied torque and axial force generated was linear for each screw type. Each unit of torque applied during insertion of cortical screws resulted in a greater increase in axial compression, as compared to cancellous screws. These data suggest that use of larger diameter screws would result in improved interfragmentary compression of distal phalangeal fractures.  相似文献   

18.
OBJECTIVES: To compare bone fragment compression and the mechanical pushout strength and stiffness of 6.5-mm Acutrak Plus (AP) and 4.5-mm AO cortical (AO) bone screws after stabilization of a simulated equine third metacarpal (MC3) bone complete lateral condylar fracture. STUDY DESIGN: In vitro biomechanical paired study of screw insertion variables, bone fragment compression, and screw pushout tests using a bone screw stabilized simulated lateral condylar fracture model. SAMPLE POPULATION: Six pairs of cadaveric equine MC3s. METHODS: Metacarpi were placed in a fixture and centered on a biaxial load cell in a materials testing system to measure torque, compressive force, and time for drilling, tapping, and screw insertion. Fragment compression was measured with a pressure-sensing device placed between the simulated fracture fragments during screw insertion for fragment stabilization. Subsequently, screws were pushed out of the stabilized bone fragments in a single cycle to failure. A paired t test was used to assess differences between site preparation, screw insertion, fragment compression, and screw pushout variables, with significance set at P <.05. RESULTS: Measured drilling variables were comparable for AO and AP specimens. However, the AP tap had significantly greater insertion torque and force. Mean maximum screw insertion torque was significantly greater for AO screws. For fragment compression, AP screws generated 65% and 44% of the compressive pressure and force, respectively, of AO screws. AP screws tended to have higher overall pushout strength. Pushout stiffness was similar between both screw types. CONCLUSION: The 6.5-mm tapered AP screw generated less interfragmentary compressive pressure and force but had similar pushout stiffness. Evaluation of failure patterns demonstrated that AP screws had greater pushout strength compared with 4.5-mm AO screws for fixation of a simulated complete lateral condylar fracture. CLINICAL RELEVANCE: The 6.5-mm tapered AP screw should provide ample holding strength but would provide less interfragmentary compression than 4.5-mm AO screws for repair of complete lateral condylar fractures in horses.  相似文献   

19.
A Salter-Harris type-II fracture of the proximal portion of the right femur in a 2-month-old filly was reduced and stabilized with three 6.5-mm-diameter, 100-mm-long cancellous bone screws through a dorsal approach to the right coxofemoral joint. The screws were removed after 11 months because the filly became lame in the affected limb. The surgical wounds dehisced despite preventive measures, most likely because of tightness of skin in the coxal region. Seven years after the original injury, the horse could perform vigorous paddock exercise without any disability. Early internal fixation of proximal femoral physeal fractures in foals can provide a good long-term prognosis.  相似文献   

20.
OBJECTIVES: To compare biomechanical properties of a prototype 5.5 mm tapered shaft cortical screw (TSS) and 5.5 mm AO cortical screw for an equine third metacarpal dynamic compression plate (EM-DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: Paired in vitro biomechanical testing of cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION: Adult equine cadaveric MC3 bones (n=12 pairs). METHODS: Twelve pairs of equine 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. An EM-DCP (10-hole, 4.5 mm) was applied to the dorsal surface of each, mid-diaphyseal osteotomized, MC3 pair. For each MC3 bone pair, 1 was randomly chosen to have the EM-DCP secured with four 5.5 mm TSS (2 screws proximal and distal to the osteotomy; TSS construct), two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws in the remaining holes. The control construct (AO construct) had four 5.5 mm AO cortical screws to secure the EM-DCP in the 2 holes proximal and distal to the osteotomy in the contralateral bone from each pair. The remaining holes of the EM-DCP were filled with two 5.5 mm AO cortical screws (most proximal and distal holes in the plate) and four 4.5 mm AO cortical screws. All plates and screws were applied using standard AO/ASIF techniques. 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 4-point bending yield load, yield bending moment, bending composite rigidity, failure load and failure bending moment of the TSS construct were significantly greater (P<.00004 for yield and P<.00001 for failure loads) than those of the AO construct. Mean cycles to failure in 4-point bending of the TSS construct was significantly greater (P<.0002) than that of the AO construct. The mean yield load and composite rigidity in torsion of the TSS construct were significantly greater (P<.0039 and P<.00003, respectively) than that of the AO construct. CONCLUSION: The TSS construct provides increased stability in both static overload testing and cyclic fatigue testing. CLINICAL RELEVANCE: The results of this in vitro study support the conclusion that the EM-DCP fixation using the prototype 5.5 mm TSS is biomechanically superior to the EM-DCP fixation using 5.5 mm AO cortical screws for the stabilization of osteotomized equine MC3.  相似文献   

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