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PubMed1994

Dynamic external fixation of unstable fractures of the distal part of the radius. A prospective, randomized comparison with static external fixation.

A prospective, randomized study was done to compare the results of dynamic external fixation (the Clyburn device) with those of static external fixation (the AO/ASIF device) in the treatment of fifty unstable fractures of the distal part of the radius. Mobilization of the wrist from neutral to 30 degrees of flexion was begun in the dynamic-fixator group at approximately two weeks, and full motion, allowing 30 degrees of extension, was started at approximately four weeks. The external fixation frames in both groups were kept in place for approximately ten weeks. Mobilization of the wrist in the dynamic-fixator group provided little gain in the mean motion of the wrist at the time of the removal of the fixator or at the one, six, or twelve-month evaluation. The static-fixator group had greater flexion of the wrist and radial deviation at the early and late follow-up examinations, while the dynamic-fixator group demonstrated only greater ulnar deviation one month after the fixator had been removed. Motion of the wrist in the dynamic-fixator group resulted in a statistically significant loss of radial length compared with that in the static-fixator group (four millimeters compared with one millimeter, p < 0.001). Complications were more frequent in the dynamic-fixator group. As evaluated with a modification of the scoring system of Gartland and Werley, 92 percent of the results at one year were excellent or good in the static-fixator group and 76 percent, in the dynamic-fixator group. The results of this study cannot support the concept of early mobilization with a dynamic external fixator for the treatment of unstable fractures of the distal part of the radius.

Adult↗
PubMed2003

A biomechanical comparison of facet screw fixation and pedicle screw fixation: effects of short-term and long-term repetitive cycling.

STUDY DESIGN: A biomechanical study was conducted to assess the stabilization performance of transfacet pedicle screw fixation. OBJECTIVE: To compare the biomechanical effects of short-term and long-term cyclic loading on lumbar motion segments instrumented with either a pedicle screw or a transfacet pedicle screw construct. SUMMARY OF BACKGROUND DATA: Facet screw fixation is an alternative to pedicle screw fixation that permits the use of a minimally invasive strategy. It is not known whether facet screw fixation can provide stability equivalent to pedicle screw fixation during cyclical loading. Therefore, transfacet pedicle screw fixation and standard pedicle screw fixation techniques were compared biomechanically. METHODS: Lumbar motion segments were tested under short-term and long-term cyclic loading conditions. For the short-term phase, specimens were tested intact for six cycles (to 400 N or 4 Nm) in compression, flexion, extension, lateral bending, and torsion. The specimens then were instrumented with bilateral semicircular interbody spacers and pedicle screw instrumentation or transfacet pedicle screws, and the testing sequence was repeated. For the long-term phase, 12 specimens were instrumented in a similar manner and loaded to 6 Nm of flexion bending for 180,000 cycles. RESULTS: For the short-term phase, both fixation systems had significantly greater stiffness and reduced range of motion, as compared with the intact state. No differences were observed between the fixation systems except in flexion, wherein transfacet pedicle screw specimens were significantly stiffer than traditional pedicle screw specimens. For the long-term phase, the stiffness and range of motion did not significantly increase or decrease over repetitive cycling of the instrumented specimens. Furthermore, no significant difference between the fixation systems was observed. CONCLUSIONS: The stability provided by both transfacet pedicle screw fixation and traditional pedicle screw fixation was not compromised after repetitive cycling. In this model, transfacet pedicle screw fixation appears equivalent biomechanically to traditional pedicle screw fixation.

Biocompatible Materials↗
PubMed1978

Fixation variables in horseradish peroxidase neurohistochemistry. I. The effect of fixation time and perfusion procedures upon enzyme activity.

In a series of neurohistochemical experiments the effect of aldehyde fixation upon the detection of horseradish peroxidase (HRP) was examined. These experiments demonstrated that: a) Increments in fixation of as little as 1 hr significantly decreased the number of labeled neurons; 12-hr fixation abolished HRP activity in many neuronal populations and significantly reduced the apparent size of the injection site. b) This negative fixation effect was greatest where the HRP concentration was low (e.g. in small, lightly labeled neurons) but was still evident in areas of high concentration (e.g. large, heavily labeled neurons). c) This effect was also most prominent when a less sensitive diaminobenzidine histochemical procedure was employed but was still apparent with a more sensitive benzidine dihydrochloride procedure. d) Immersion of the brain in fixative after perfusion produced a greater attenuation of HRP activity in more superficial areas. e) Immersion of the brain in buffer to terminate fixation produced a prolonged and unpredictable gradient of fixation. f) Excess, unbound fixative inhibited the histochemical reaction per se and had to be removed from the tissue but prolonged washing did not resurrect enzyme activity which was lost by fixation. To obviate these problems and optimize HRP enzyme activity a new perfusion-fixation procedure was developed. It entails 30 min fixation by perfusion which is terminated by a subsequent 30 min perfusion with cold sucrose-fuller to wash out unbound fixative. This allows the tissue to be processed immediately, produces a uniform and morphologically adequate fixation, and minimizes the negative effects of fixation on HRP enzyme activity.

Animals↗
PubMed2006

Initial fixation strength of a new hybrid technique for femoral ACL graft fixation: the bone wedge technique.

BACKGROUND: Aperture fixation with interference screws matching the diameter of the tunnel is associated with the risk of graft laceration and graft rotation. HYPOTHESIS: A hybrid fixation technique (extracortical and aperture fixation) with undersized interference screw placed behind a bone wedge provides a higher fixation strength as aperture fixation with a screw alone matching the size of the tunnel. STUDY DESIGN: Experimental laboratory study. METHODS: We evaluated the initial fixation strength (single cycle and cyclic loading tests) of hybrid and interference screw aperture fixation using different sized interference screws in porcine knees. RESULTS: Analysis of yield load, maximum load and stiffness in the single cycle loading test showed no statistically significant differences for hybrid fixation with a 1 mm undersized screw and aperture fixation with a screw matching the size of the tunnel. The use of an undersized screw alone resulted in low fixation strength. CONCLUSION: The initial fixation strength of the hybrid technique with undersized screws is comparable to that of interference screw fixation matching the size. CLINICAL RELEVANCE: The new "bone wedge fixation" is an alternative for ACL graft fixation without the risk of graft laceration and graft rotation.

Analysis of Variance↗
PubMed2002

Biomechanical comparison of hamstring and patellar tendon graft anterior cruciate ligament reconstruction techniques: The impact of fixation level and fixation method under cyclic loading.

PURPOSE: To mechanically test different reconstruction techniques of the anterior cruciate ligament (ACL) under incremental cyclic loading and to evaluate the impact of the level and method of graft fixation on tensile properties of each technique. TYPE OF STUDY: In vitro biomechanical study. METHODS: Four hamstring and 1 patellar tendon reconstruction techniques were performed on 40 young to middle-aged human cadaveric knees (average age, 39 years). An anterior drawer with increasing loads of 20 N increments was applied at 30 degree of knee flexion. Anatomic, direct interference screw fixation was tested in 2 hamstring and in the patellar tendon groups. Nonanatomic (extracortical) graft anchorage was tested in the remaining 2 hamstring groups with indirect graft fixations on both sides and the combination of indirect tibial and direct femoral fixation. Structural properties were determined throughout the cyclic loading test. RESULTS: The more anatomic reconstruction techniques provided significantly higher structural properties and smaller loss of fixation compared with nonanatomic, extracortical fixation, with indirect repair on both fixation sites resulting in the lowest structural properties. The tibial fixation site was the weakest link in all of the anatomic reconstructions. Patellar tendon fixation with attached bone blocks in both bone tunnels significantly improved construct stiffness and decreased graft slippage. CONCLUSIONS: The results of this study suggest that anatomic fixation should be preferred for anchorage of hamstring tendons and linkage materials should be avoided. Direct soft-tissue fixation with interference screws still allows considerable graft slippage, which can be limited by using a bone block or application of a backup or hybrid fixation, especially on the tibial fixation site.

Absorbable Implants↗
PubMed1999

Fracture healing of the sheep tibia treated using a unilateral external fixator. Comparison of static and dynamic fixation.

It is generally accepted that when a fracture is treated with external fixation, dynamization of the fixation accelerates formation of the bony callus by transferring part of the functional loads. The aim of the research presented here was to validate this principle using in vivo measurements of callus stiffness. We created a transverse fracture in the mid third of the tibial shaft in 12 sheep and maintained a 3 mm gap between the fragments for 3 weeks. Two types of unilateral external fixators were applied. Axial loading was permitted (dynamization) from the fourth week onwards in 6 animals. In the other 6 animals, fixation remained static for both types of fixation. Weekly measurements of callus stiffness were obtained using a goniometer and load cell to assess bending stiffness. Two slightly different fixators were used. Callus formed in all 12 animals. Callus stiffness increased exponentially to reach the degree of stiffness measured on the contralateral side. There was no clear difference in healing between the two types of fixations nor between dynamic and static fixation. If a unilateral fixator was applied which did not maintain absolutely rigid fixation, the fracture generally healed well even without contact between the fragment ends. If the process of callus formation had begun normally, dynamic fixation offered no further benefit. Measuring the stiffness of the callus with an adequate measurement apparatus in vivo indicated that the fixator could be removed earlier than would have been authorized on the basis of radiological evidence alone.

Animals↗
PubMed2006

Extramedullary fixation implants and external fixators for extracapsular hip fractures in adults.

BACKGROUND: Extramedullary fixation of hip fractures involves the application of a plate and screws to the lateral side of the proximal femur. In external fixators, the stabilising component is held outside the thigh by pins or screws driven into the bone. OBJECTIVES: To compare different types of extramedullary fixation implants and external fixators for fixing extracapsular hip fracture in adults. SEARCH STRATEGY: We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (July 2005), various other databases, conference proceedings and reference lists. SELECTION CRITERIA: All randomised or quasi-randomised controlled trials comparing extramedullary implants or external fixators for fixing extracapsular hip fracture in adults. DATA COLLECTION AND ANALYSIS: Two authors independently selected trials, assessed trial quality and extracted data. Data were pooled where appropriate. MAIN RESULTS: The 14 included trials tested seven comparisons in a total of 2222 mainly female and older participants. All trials had methodological flaws that may affect the validity of their results. Three trials comparing a fixed nail plate (Jewett or McLaughlin) with the sliding hip screw (SHS) found an increased risk of fixation failure for fixed nail plates. The two trials comparing the Resistance Augmented Bateaux (RAB) plate with the SHS had contrasting results, notably in terms of operative complications, fixation failure and anatomical restoration. One trial comparing the Pugh nail and the SHS found no significant difference between implants. Two trials compared the Medoff plate with the SHS. One trial reported higher blood losses and longer operation times for the Medoff plate. There was a lower risk of fixation failure with the Medoff plate for unstable trochanteric fractures. Two trials compared the Medoff plate with three different screw-plate systems. There were no statistically significant differences in outcome for trochanteric fractures. For subtrochanteric fractures, there was a lower fixation failure rate for the Medoff plate, but no evidence for differences in longer-term outcomes. Two trials comparing the Gotfried percutaneous plate with a SHS found a reduced blood loss with the Gotfried plate. A higher intra-operative fixation failure rate of the Gotfried plate may indicate some restriction to its use. Two trials found less operative trauma for external fixation when compared with the SHS. Final outcome appeared similar. AUTHORS' CONCLUSIONS: The markedly increased fixation failure rate of fixed nail plates compared with the SHS is a major consideration and thus the SHS appears preferable. There was insufficient evidence from other comparisons to draw definite conclusions.

Bone Plates↗
PubMed2002

Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology.

The advent of 'biological internal fixation' is an important development in the surgical management of fractures. Locked nailing has demonstrated that flexible fixation without precise reduction results in reliable healing. While external fixators are mainly used today to provide temporary fixation in fractures after severe injury, the internal fixator offers flexible fixation, maintaining the advantages of the external fixator but allowing long-term treatment. The internal fixator resembles a plate but functions differently. It is based on pure splinting rather than compression. The resulting flexible stabilisation induces the formation of callus. With the use of locked threaded bolts, the application of the internal fixator foregoes the need of adaptation of the shape of the splint to that of the bone during surgery. Thus, it is possible to apply the internal fixator as a minimally invasive percutaneous osteosynthesis (MIPO). Minimal surgical trauma and flexible fixation allow prompt healing when the blood supply to bone is maintained or can be restored early. The scientific basis of the fixation and function of these new implants has been reviewed. The biomechanical aspects principally address the degree of instability which may be tolerated by fracture healing under different biological conditions. Fractures may heal spontaneously in spite of gross instability while minimal, even non-visible, instability may be deleterious for rigidly fixed small fracture gaps. The theory of strain offers an explanation for the maximum instability which will be tolerated and the minimal degree required for induction of callus formation. The biological aspects of damage to the blood supply, necrosis and temporary porosity explain the importance of avoiding extensive contact of the implant with bone. The phenomenon of bone loss and stress protection has a biological rather than a mechanical explanation. The same mechanism of necrosis-induced internal remodelling may explain the basic process of direct healing.

Animals↗
PubMed2005

Biomechanical stability of high tibial opening wedge osteotomy: internal fixation versus external fixation.

PURPOSE: The goal of our study was to evaluate stability of internal fixation with a plate compared to external fixation in an opening wedge high tibial osteotomy model. Significance. To our knowledge, this is the only study to compare internal plate to external fixation in an opening wedge osteotomy model. The design of this cadaver study limits its direct application to clinical practice. MATERIAL AND METHOD: In each of the six pairs of fresh-frozen human cadaver knees one specimen was randomly assigned to internal plate fixation while the other was stabilized with an external fixation. The osteosynthesis plate incorporated a 12.5mm block that distracted the medial tibial cortices. Each knee was loaded on a mechanical testing machine to 700 N for 10,000 cycles to simulate immediate full weight bearing in a walking individual. SUMMARY OF RESULTS: The internal plate osteosynthesis provided significantly greater stiffness and smaller loss of correction (1.60mm) than the external fixation (3.22 mm) under cyclic loading condition (P<0.05). For static loading, the mean value of stiffness resulting in failure for the internal plate and external fixation, were respectively, 938 N/mm and 459 N/mm. Load to failure also showed two times greater stiffness in the plate osteosynthesis group. No hardware failure was observed in either construct. DISCUSSION AND CONCLUSION: Plate fixation was superior to external fixation in maintaining correction. However, progressive adjustment of the distraction with the external fixator allows precise "fine-tuning" during the healing process that is not possible with internal fixation.

Adult↗
PubMed1997

Pullout strength of tibial graft fixation in anterior cruciate ligament replacement with a patellar tendon graft: interference screw versus staple fixation in human knees.

The endoscopic single incision technique for anterior cruciate ligament (ACL) reconstruction with a femoral half-tunnel may lead to a graft/tunnel mismatch and subsequent protrusion of the block from the tibial tunnel. The typical tibial fixation with an interference screw is not possible in these cases. Fixation with staples in a bony groove inferior to the tunnel outlet can be used as an alternative technique. Current literature does not provide biomechanical data of either fixation technique in a human model. This study was performed to evaluate the primary biomechanical parameters of this technique compared with a standard interference screw fixation of the block. Fifty-five fresh-frozen relatively young (mean age 44 years) human cadaver knee joints were used. Grafts were harvested from the patellar tendon midportion with bone blocks of 25 mm length and 9 mm width. A 10-mm tibial tunnel was drilled from the anteromedial cortex to the center of the tibial insertion of the ACL. Three different sizes of interference screws (7 x 30, 9 x 20, 9 x 30 mm) were chosen as a standard control procedure (n = 40). For tibial bone-block fixation the graft was placed through the tunnel, and the screw was then inserted on the cancellous or the cortical surface, respectively. Fifteen knees were treated by staple fixation. A groove was created inferior to the tunnel outlet with a chisel. The bone block was fixed in this groove with two barbed stainless steel staples. Tensile testing in both groups was carried out under an axial load parallel to the tibial tunnel in a Zwick testing machine with a velocity of 1 mm/s. Dislocation of the graft and stiffness were calculated at 175 N load. Maximum load to failure using interference screws varied between 506 and 758 N. Load to failure using staples was 588 N. Dislocation of the graft ranged between 3.8 and 4.7 mm for interference screw fixation and was 4.7 mm for staples. Stiffness calculated at 175 N load was significantly higher in staple fixation. With either fixation technique, the recorded failure loads were sufficient to withstand the graft loads which are to be expected during the rehabilitation period. Staple fixation of the bone block outside of the tunnel resulted in a fixation strength comparable to interference screw fixation.

Adolescent↗
PubMed1982

Effects of glutaraldehyde fixative osmolarities on smooth muscle cell volume, and osmotic reactivity of the cells after fixation.

The contribution of glutaraldehyde (GA) to the effective osmolarity of GA fixatives, the osmotic reactivity of the cells after fixation in GA, and also the duration of fixation in GA on cell volume, were investigated using cultured smooth muscle cells (SMC) and spiral aortic strips. Four fixation procedures were studied. We found that GA contributes to the total effective osmolarity of the fixatives, and that the type of buffers used for the fixatives can also affect the cell volume differently during GA fixation. After GA fixation, the cells were still osmotically reactive, regardless of the buffer types for making up the GA fixatives, so that the osmolarity of the wash buffer after GA fixation is important. However, OsO4 eliminates osmotic responses, thus the osmolarity of OsO4 fixative and wash buffer have negligible influence on the cell volume. Longer fixation time up to 4 h had no effect of the cell volume.

Aldehydes↗
PubMedDate not supplied

Biomechanical comparison of a circular external skeletal fixator construct to pin and tension band wire fixation for the stabilization of olecranon osteotomies in dogs: a cadaveric study.

OBJECTIVE: To compare anatomic reduction and the biomechanical properties of a circular external skeletal fixator (CESF) construct to pin and tension band wire (PTBW) fixation for the stabilization of olecranon osteotomies in dogs. STUDY DESIGN: Cadaveric study. ANIMALS: Forelimbs from 12 skeletally mature mixed-breed dogs, weighing 23 to 28 kg. METHODS: An olecranon osteotomy was stabilized with either a CESF construct or PTBW fixation. A single distractive load to failure was applied to each specimen through the triceps tendon. Osteotomy reduction and biomechanical properties were compared between fixation groups. RESULTS: Reduction was not significantly different (gap: P =.171; malalignment: P =.558) between fixation groups. Osteotomies stabilized with the CESF had greater stiffness (P <.0001) and maximum load sustained (P <.0001) compared to PTBW fixation. There was no significant difference for yield load (P =.318) or for load at 1 mm of axial displacement (P =.997) between fixation groups. Failure of fixation occurred by bending of the intramedullary Steinmann pin and the fixation wires in the CESF specimens and by untwisting of the tension band wire knot with pullout and bending of the Kirschner wires in the PTBW specimens. CONCLUSIONS: Specimens stabilized with the CESF construct had similar reduction and yield load, greater stiffness and maximum load sustained, and less elastic deformation than specimens stabilized with PTBW fixation. CLINICAL RELEVANCE: The CESF construct may provide a biomechanically favorable alternative to PTBW fixation for stabilization of olecranon osteotomies in dogs, and its application warrants clinical investigation.

Animals↗
PubMed2004

Fixation stability using central and pericentral fixation targets in patients with age-related macular degeneration.

PURPOSE: To determine fixation stability for central and pericentral fixation targets in patients with age-related macular degeneration (AMD). DESIGN: Comparative study. PARTICIPANTS: Twelve patients having late-stage AMD involving the fovea and 10 age-matched controls having no other eye diseases and visual acuity better than 20/25. METHODS: Six different fixation targets (1 degrees cross; 1 degrees filled circle; 1 degrees letter x; small 4-point diamond; large 4-point diamond using dimensions as in a field analyzer; large-crossover whole-image diagonal with open 1 degrees center) were presented on a high-resolution monitor. Before examination, subjects were given verbal instructions to move their eye to see the center of the target best. Fixation stability was measured for the preferred eye, with the fellow eye occluded, using a gaze tracker. Fixation stability was quantified by calculating the bivariate contour ellipse area (BCEA) over 30 seconds for each target. For statistical analysis, BCEA values (minutes of arc2) were converted into their logarithms. The absolute retinal scotoma for the study eye was determined using a scanning laser ophthalmoscope. MAIN OUTCOME MEASURE: Bivariate contour ellipse area. RESULTS: Visual acuity in patients (age range, 57-87 years) ranged from 20/32 to 20/600. The lowest BCEA values were found for the 1 degrees letter x in patients (mean, 12052.2%+/-254.0%) and for the 1 degrees cross in normal subjects (mean, 1286.9%+/-47.8%); the highest BCEA values were found for the small 4-point diamond in patients (mean, 23109.5%+/-298.3%) and for the large 4-point diamond in normals (age range, 62-79 years) (mean, 3229.2%+/-105.4%). The difference between the targets was significant for normal subjects (analysis of variance [ANOVA], P<0.01) but not for patients (ANOVA, P>0.05). In normals, BCEA values were significantly lower for central fixation targets than for pericentral fixation targets (P<0.01). CONCLUSION: Fixation is significantly less stable for pericentral fixation targets in normal subjects, indicating an advantage for central fixation targets. These results are particularly significant for any clinical and experimental testing method that requires the patient to maintain stable fixation.

Aged↗
PubMed2006

Characterisation of ocular fixation in humans by analysis of saccadic intrusions and fixation periods: a pragmatic approach.

Eye movements during fixation were recorded in 55 normal subjects with ages ranging from 21 to 81 years. We analysed ocular fixation recordings using measurements of saccadic intrusion amplitudes and frequencies along with fixation periods and mean fixation displacement. Viewing conditions included monocular, binocular and presence or absence of a visual fixation target. Visual feedback reduced the saccadic intrusion amplitudes but had no effect on fixation periods or mean fixation displacements. Binocular viewing had no effect on saccadic intrusion amplitudes, fixation periods or mean fixation displacements. A decrease in fixation periods and an increase in the number of saccadic intrusions with age was observed. This approach could be a clinically useful tool to quantify ocular fixation in neurological disease.

Adult↗
PubMed1999

Initial fixation strength of modified patellar tendon grafts for anatomic fixation in anterior cruciate ligament reconstruction.

Recently it has been shown that anatomic tibial graft fixation in anterior cruciate ligament (ACL) reconstruction is preferable in order to increase isometry and knee stability. To facilitate anatomic patellar tendon graft fixation, customized graft length shortening is necessary. The purpose of this study was to compare the initial fixation strength of four different shortened patellar tendon grafts including three bone plug flip techniques and direct patellar tendon-to-bone interference fit fixation in a model with standardized bone density. Ninety calf tibial plateaus (22 to 24 weeks old) with adjacent patella and extensor ligaments were used. Tendon grafts were shortened by flipping the bone plug over the tendon leaving a tendon-tendon-bone (TTB) construct and, as the first modification in the opposite direction resulting in a tendon-bone-tendon (TBT) construct. The second modification consisted of the TBT construct with interference screw position at the lateral aspect of the bone plug (TBTlat). As the fourth modification the tendon graft was directly fixed (Tdirect) with an interference screw. In addition, a round-threaded titanium (RCI; Smith & Nephew DonJoy, Carlsbad, CA), a round-threaded biodegradable screw (Sysorb; Sulzer Orthopedics, Münsingen, Switzerland), and a conventional titanium interference screw (Arthrex Inc, Naples, FL) were compared. We found that TTB (mean 441 N for biodegradable screw, 357 N for RCI screw, 384 N for conventional screw) and TBT (mean 407 N for biodegradable screw, 204 N for RCI screw, 392 N for conventional screw) construct fixation achieves comparable fixation strength, although failure in the TTB was due to tendon strip off at its ligamentous insertion. The highest failure load was found in TBTlat fixation (mean 610 N for biodegradable screw, 479 N for RCI screw). Therefore, this technique should be recommended when using a tendon flip technique. The failure load for Tdirect fixation (mean 437 N for biodegradable screw, 364 N for RCI screw) was similar to that of TTB and TBT fixation, which may indicate that a patellar-tendon graft harvested without its patellar bone plug and directly fixed with an interference screw is equivalent to a flipped graft. This may additionally reduce harvest site morbidity and eliminates the risk of patellar fracture. The fixation strength of round-threaded biodegradable and conventional titanium interference screws was similar, whereas that of round-threaded titanium screws was significantly lower in the patellar tendon flip-techniques. However, it should be taken into consideration that round-threaded titanium screws are proposed for direct tendon-to-bone fixation.

Absorbable Implants↗
PubMed1995

Cost-effectiveness analysis of open reduction/nonrigid fixation and open reduction/rigid fixation to treat mandibular fractures.

OBJECTIVES: When open reduction and internal fixation is indicated for the management of mandibular fractures, it is generally agreed that nonrigid fixation and rigid fixation represent acceptable treatment alternative. Opinions vary, however, regarding the cost-effectiveness of the two alternative. The purpose of this study was to compare the costs of these treatments of mandibular fractures that required open reduction and internal fixation. STUDY DESIGN: Cost-effectiveness analysis was used to determine the most efficient resource used to treat mandibular fractures requiring open reduction and internal fixation. Cost-effectiveness was defined as the treatment charges per successfully treated patient. Data were collected retrospectively from patients with mandibular fractures treated between 1991 and 1994. The patient's medical record and hospital billing record were used as data sources. To estimate treatment charges, the sample was divided into three groups: (1) group 1, patients treated with nonrigid fixation without postoperative complications, (2) group 2, patients treated with rigid fixation without postoperative complications, and (3) group 3, patients treated with either procedure who had postoperative complications. The study variables were grouped into two categories: clinical information and charges. Treatment charges for both treatments were estimated and compared. RESULTS: Data were collected for 12 patients in group 1 and 11 patients in group 2. Costs for rigid fixation averaged $1,468 more per patient than for nonrigid fixation in uncomplicated cases. There were 11 patients in group 3. The average cost to treat a postoperative complication was $11,637. Given the institution-specific treatment cost and the probability of complications, rigid fixation was a more cost-effective treatment than nonrigid fixation. CONCLUSION: Cost estimates for treating mandibular fractures may vary widely depending on practice patterns and complication rates. Despite these cost variations, one may determine the most cost-effective treatment alternative by estimating treatment costs of both uncomplicated and complicated cases and the postoperative complication rate.

Adult↗
PubMedDate not supplied

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

OBJECTIVES: To compare the monotonic biomechanical properties and fatigue life of a broad, limited contact, dynamic compression plate (LC-DCP) fixation with a broad, dynamic compression plate (DCP) fixation to repair osteotomized equine 3rd 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: Twelve pairs of adult equine cadaveric MC3 bones. METHODS: Twelve pairs of equine MC3 were divided into 3 test 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 LC-DCP (8-hole, 4.5 mm) was applied to the dorsal surface of 1 randomly selected bone from each pair. One DCP (8-hole, 4.5 mm broad) was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard AO/ASIF techniques to MC3 bones that 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: The mean 4-point bending yield load, yield bending moment, composite rigidity, failure load, and failure bending moment of LC-DCP fixation were significantly greater (P<.01) than those of broad DCP fixation. Mean cycles to failure for 4-point bending was significantly (P<.001) greater for broad DCP fixation compared with broad LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion was significantly (P<.02) greater for broad LC-DCP fixation compared with broad DCP fixation. CONCLUSION: Broad LC-DCP offers increased stability in static overload testing, however, it offers significantly less stability in cyclic fatigue testing. CLINICAL RELEVANCE: The clinical relevance of the cyclic fatigue data supports the conclusion that the broad DCP fixation is biomechanically superior to the broad LC-DCP fixation in osteotomized equine MC3 bones despite the results of the static overload testing.

Animals↗
PubMedDate not supplied

An in vitro biomechanical comparison of a prototype equine metacarpal dynamic compression plate fixation with double dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare the monotonic biomechanical properties of a prototype equine third metacarpal dynamic compression plate (EM-DCP) fixation with a double broad dynamic compression plate (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. POPULATION: Twelve pairs of adult equine cadaveric MC3 bones. METHODS: Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional testing. The EM-DCP (10-hole, 4.5 mm) was applied to the dorsal surface of one randomly selected bone from each pair. Two DCPs, 1 dorsally (10-hole, 4.5 mm broad) and 1 laterally (9-hole, 4.5 mm broad) were applied to the contralateral bone from each pair. All plates and screws were applied using standard AO/ASIF techniques to MC3 bones that 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 4-point bending yield load, yield bending moment, bending composite rigidity, failure load and failure bending moment of the EM-DCP fixation were significantly greater (P<.0001) than those of the double broad DCP fixation. Mean cycles to failure in 4-point bending of the EM-DCP fixation was significantly greater (P<.0008) than that of the double broad DCP fixation. Mean yield load, composite rigidity, and failure load in torsion of the EM-DCP fixation were significantly greater (P<.0035) than that of the double broad DCP fixation. CONCLUSION: The EM-DCP provides increased stability in both static overload testing and cyclic fatigue testing. CLINICAL RELEVANCE: Results of this in vitro study support the conclusion that the prototype EM-DCP fixation is biomechanically superior to the double broad DCP fixation for the stabilization of osteotomized equine MC3.

Animals↗