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External fixation. Its use in podiatric surgery.

Rigid fixation of osseous fragments with the ability to supply additional compression or distraction at will is achieved only by external fixation. Of course, the treatment of nonunions, infections, fixation of osteotomies, fusion of joints, and lengthening of bone can be accomplished by other satisfactory means with and without fixation. External fixation is only one method of fixation. From this list the practitioner can choose the method of fixation best suited to the contemplated procedure and the one with which the surgeon feels most comfortable. However, a good surgeon will have prepared alternative methods of fixation if, in fact, the first and preferable method of fixation fails. It would be wonderful if our plans became a reality; quite often they do not and this is what one must prepare for. External fixation in many of the cases presented was not the original form of fixation to be used; in a few cases it had not been seriously considered. Fortunately, however, it was considered and allowed a difficult situation to be remedied with relative ease. Although elaboration of the categories in which external fixation was employed has been brief, the numerous presentations lend themselves to further investigation into external fixation.

Adult↗

Biomechanical analysis of anterior cervical spine plate fixation systems with unicortical and bicortical screw purchase.

Anterior plate fixation with unicortical screw purchase does not involve the risk of posterior cortex penetration and possible injuries of the spinal cord. However, there are very few biomechanical data about the immediate stability of non-locking plate fixation with unicortical or bicortical screw placement. The aim of the present study was to evaluate the immediate biomechanical properties in terms of flexibility of a non-locking anterior plate system with 4.5-mm screw fixation and unicortical or bicortical screw purchase applied to a single destabilized cervical spine motion segment. Using fresh cadaveric cervical spine specimens C3-C7, multidirectional flexibility was measured at the level C4-C5 before and after destabilization and fixation with an anterior plate with either unicortical or bicortical screw purchase. The results showed that fixed cervical spine segments with anterior plate and bicortical screw purchase were more rigid than intact specimens in all modes of testing. The difference was statistically significant for flexion and extension ( P<0.001). Plate fixation with unicortical screw purchase had statistically significant decreased ranges of motion compared to the intact specimen only in extension. Neither unicortical nor bicortical screw purchase decreased the range of motion significantly in axial rotation compared to the intact specimens. This in vitro study documented that neither unicortical nor bicortical screw purchase with non-locking plate fixation can increase stability in all modes of testing, in axial rotation in particular. Direct comparison between the group with uni- and that with bicortical screw fixation did not reveal significant differences, and therefore no advantage was shown for either type of screw fixation. Therefore, we demonstrated that both uni- and bicortical screw purchase with non-locking plate fixation can decrease immediate flexibility of the tested motion segment, with better results for bicortical purchase. No significant differences were found comparing the two groups of screw fixation. These data suggest that unicortical screw fixation can be used for anterior plate fixation with a comparable immediate stability to bicortical screw fixation.

Adolescent↗

Biomechanics of initial tibial fixation in posterior cruciate ligament reconstruction.

PURPOSE: Clinical success of posterior cruciate ligament (PCL) reconstruction continues to lag behind that of its anterior counterpart. The tibial site of PCL graft fixation has been a focus of recent research. This study examined the effect of combined distal and proximal tibial fixation on the ability of a transtibial PCL reconstruction to restore intact knee kinematics and in situ forces of the intact PCL. TYPE OF STUDY: Biomechanical study. METHODS: Ten human cadaveric knees were tested. A 134-N posterior tibial load was applied using a robotic/universal force moment sensor testing system at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion. Each knee was tested under 4 conditions: intact, PCL-deficient, single-bundle transtibial reconstruction with distal tibial fixation, and single-bundle transtibial reconstruction with combined distal and proximal tibial fixation. Knee kinematics in 5 degrees of freedom for each condition were recorded and in situ forces of the intact PCL and the PCL grafts were determined. RESULTS: Reconstruction with combined fixation resulted in significantly less posterior tibial translation than reconstruction with distal fixation at 30 degrees, 90 degrees, and 120 degrees (P < .05), and restored intact knee kinematics at 90 degrees and 120 degrees (P > .05). Reconstruction with combined fixation more closely restored intact PCL in situ forces at 90 degrees (P < .05). CONCLUSIONS: Transtibial reconstruction with combined fixation more closely restores intact knee kinematics and in situ forces in the PCL at initial fixation than does reconstruction with distal tibial fixation. The improved kinematics and in situ forces seen with the combined fixation may be attributed to decreased functional graft length and increased stiffness of the PCL graft. CLINICAL RELEVANCE: Combined tibial fixation may provide a more stable reconstruction at initial fixation.

Achilles Tendon↗

Initial biomechanical properties of staple-anchor Achilles tendon allograft and interference screw bone-patellar tendon-bone autograft fixation for anterior cruciate ligament reconstruction in a cadaveric model.

PURPOSE: Anterior cruciate ligament (ACL) reconstruction is a common procedure that has a fairly high success rate. Despite such success, controversy exists with regard to fixation and graft type. The purpose of this study was to quantify the maximum load to failure for staple-anchor freeze-dried Achilles tendon allograft fixation compared with interference screw bone-pattelar tendon-bone autograft fixation at the time of insertion for ACL reconstruction. METHODS: Eleven pairs of cadaveric knees were prepared for ACL reconstruction by disarticulation before graft insertion. The tibia and femur were mounted separately onto an MTS machine and were loaded to failure in line with the tunnels. Femoral fixation for the allograft was provided by a staple anchor; tibial fixation was provided by a suture anchor. Titanium interference screws on the femoral and tibial sides provided autograft fixation. A paired t test was performed to compare mechanical testing results in the 2 groups. RESULTS: Mean maximum load to failure for the allograft was 58.7 N (range, 32.3 to 92.6 N) and 119.6 N (range, 82 to 165.9 N) for the femur and the tibia, respectively, compared with 228.2 N (range, 74.2 to 352 N) and 232.9 N (range, 65.1 to 553.1 N) for the autografts. This difference was statistically significant (P < .001) for femoral fixation, but it was not statistically significant for tibial fixation (P = .186). CONCLUSIONS: Soft tissue Achilles tendon allograft with staple fixation is a significantly weaker fixation construct when compared with autograft bone-patellar tendon-bone with interference screw fixation. CLINICAL RELEVANCE: This study shows significantly weaker fixation in the staple-alograft construct and yet this construct has had at least equivalent results over a 5-year time frame, indicating that rigid femoral fixation may not be a critical factor in long-term results.

Achilles Tendon↗

Effects of knee position, graft tension, and mode of fixation in posterior cruciate ligament reconstruction: a cadaveric knee study.

PURPOSE: Many knees exhibit residual ligament laxity after posterior cruciate ligament (PCL) reconstruction, which is believed to be technique related. The purpose of this study was to investigate the optimal graft tension, the best angle of knee flexion, and the mode of fixation in PCL reconstruction. TYPE OF STUDY: Anatomic biomechanical study. METHODS: A testing apparatus with frictionless bearing that allows other degrees of freedom except for flexion and extension of the knee joint was designed. The normal PCL tension at different angles of knee flexion was measured with a force transducer, and the optimal tension of the PCL graft that allows full range of knee motion was studied with a tensiometer in 12 cadaver knees. The modes of fixation failure between interference screw fixation and post fixation were studied with an Instron (Canton, MA) machine in 8 cadaver knees. RESULTS: The lowest PCL tension in normal knees was noted at 20 degrees to 30 degrees of knee flexion and the highest at 90 degrees. The optimal tension of PCL graft, which allows full range of knee motion, was 15 lb (68 N). The average load of graft failure was 417 (179-730) N with interference screw fixation and 367 (149-701) N with post fixation when the patellar bone-tendon-bone graft was tested. There was no statistical difference in the failure load between interference screw fixation and post fixation (P =.753); however, the modes of failure differ. The sites of failure for interference screw fixation were 25% caused by rupture of ligament substance and 75% bone plug pullout; those of post fixation were 25% caused by rupture of ligament substance, 37.5% caused by fracture, and 37.5% as a result of suture breakage. CONCLUSIONS: The results of this study suggested that a 15-lb tension to the graft at 20 degrees to 30 degrees of knee flexion is optimal in PCL reconstruction. There was no statistical difference in the failure load between interference fixation and post fixation despite different modes of fixation failure.

Biomechanical Phenomena↗

Central fixations are inadequately controlled by instructions alone: implications for studying cerebral asymmetry.

A fundamental concern when using visual presentations to study cerebral asymmetry is to ensure that stimuli are presented with the same degree of retinal eccentricity from a central fixation point in either visual field. However, a widely used procedure intended to control fixation location merely instructs participants to fixate appropriately without any other means of ensuring that central fixations actually occur. We assessed the validity of assuming that instructions alone ensure central fixation by using the traditional RVF advantage for words and either (a) only instruction to fixate centrally, or (b) eye-tracking device that ensured central fixation on every trial. Experiments 1 and 2 found that when only instructions were given, the vast majority of fixations were not central, and more occurred to the right of centre than to the left. Moreover, the prevalence of non-central fixations was otherwise disguised by the finding that both fixation procedures produced similar RVF advantages in overt performance. The impact of typical non-central fixations on performance was revealed by systematically manipulating fixation location in Experiment 3, where deviations in fixation of only 0.25 degrees from centre had a reliable impact on visual field effects. Implications of these findings for studies of cerebral asymmetry are discussed.

Adult↗

Pelvic or lumbar fixation for the surgical management of scoliosis in duchenne muscular dystrophy.

STUDY DESIGN: This retrospective study evaluates two groups of patients with scoliosis and Duchenne muscular dystrophy, treated with two different surgical stabilization methods. OBJECTIVE: To determine whether fixation to the sacropelvis is always necessary for adequate stabilization of scoliosis in Duchenne muscular dystrophy. SUMMARY OF BACKGROUND DATA: Pelvic fixation is generally recommended for scoliosis in Duchenne muscular dystrophy. Recent studies describe a more selective approach toward lumbar or pelvic fixation. Pelvic fixation is reserved for larger curves and established pelvic tilt. METHODS: Fifty cases of Duchenne muscular dystrophy, operated in two different centers and followed up for a minimum of 3 years, were reviewed. In the first group (Oswestry), 31 patients had fixation to the pelvis, using standard Luque instrumentation and pelvic fixation. The Galveston technique was used in 9 cases and L-rod configuration in 22 cases. In the second group (Nottingham), 19 cases had fixation to L5 using pedicle screws in the lumbar spine and sublaminar wires in the thoracic spine. These cases were operated on early, usually shortly after becoming wheelchair dependent. RESULTS: In the pelvic fixation group, the mean age at the time of surgery was 14 years, and forced vital capacity was 44%. The mean Cobb angle and pelvic obliquity were 48 degrees and 19.8 degrees at the time of surgery, 16.7 degrees and 7.2 degrees immediately after surgery, and 22 degrees and 11.6 degrees at the final follow-up (mean 4.6 years), respectively. The mean blood loss was 4.1 L, and the average hospital stay was 17 days. There were five major complications, including a deep wound infection in one case, revision of instrumentation prominence at the proximal end in two cases, and loosening of pelvic fixation in two cases. In the lumbar fixation group, the mean age at the time of surgery was 11.7 years, and forced vital capacity was 58%. The mean Cobb angle and pelvic obliquity were 19.8 degrees and 9 degrees at the time of surgery, 3.2 degrees and 2.2 degrees immediately after surgery, and 5.2 degrees and 2.9 degrees at the final follow-up (mean 3.5 years), respectively. The mean estimated blood loss (3.3 L) and mean hospital stay (7.7 days) were much less compared with the pelvic fixation group. Pelvic obliquity was corrected and maintained below 10 degrees in all but two cases, who had an initial pelvic obliquity exceeding 20 degrees. One patient had instrumentation failure at the proximal end, and one had a deep wound infection. CONCLUSION: Lumbar fixation to L5 is adequate if the surgery is performed early, soon after becoming wheelchair bound, and with smaller curves and minimal pelvic obliquity. Use of pedicle screws in lumbar spine provides a solid foundation to maintain the correction over the period of relatively short life expectancy of these children. Pelvic fixation may be necessary in older children, who have larger curves and established pelvic obliquity. In the presence of deteriorating lung function, this is associated with a greater morbidity and higher complication rate.

Adolescent↗

A biomechanical evaluation of transcondylar femoral fixation of anterior cruciate ligament grafts.

BACKGROUND: Interference screw fixation of the graft in anterior cruciate ligament reconstruction is considered the gold standard, but limited clinical experience suggests that transcondylar fixation is equally effective. PURPOSE: To compare transcondylar and interference screw fixation. STUDY DESIGN: Ex vivo biomechanical study. METHODS: Twenty pairs of unembalmed knees underwent anterior cruciate ligament reconstruction with patellar tendon autografts. In 1 knee of each pair, the bone plug was stabilized in the femoral tunnel with standard interference screws; in the other knee, transcondylar screws were used. Testing to failure occurred immediately or after 1000 cycles of sinusoidal loading (30 to 150 N) (20 paired reconstructions each). Fixation stiffness, strength, graft creep, displacement amplitude, and change in amplitude were measured and compared (repeated measures anaylsis of variance with Tukey test; P <.05). RESULTS: There was no significant difference in acute strength, maximum load within 3 mm, or stiffness between transcondylar fixation (410 +/- 164 N, 183 +/- 93 N, and 49.6 +/- 28 N/mm, respectively) and interference fixation (497 +/- 216 N, 206 +/- 115 N, and 61 +/- 37.8 N/mm, respectively). Similarly, there was no significant difference in cyclic strength, maximum load within 3 mm, or stiffness between transcondylar fixation (496 +/- 214 N, 357 +/- 82.9 N, and 110 +/- 27.4 N/mm, respectively) and interference fixation (552 +/- 233 N, 357 +/- 76.2 N, and 112 +/- 26.8 N/mm, respectively). Predominant modes of failure were bone plug pullout (transcondylar fixation) and tendon failure or bone plug fracture (interference fixation). CONCLUSIONS: Transcondylar screw fixation of the patellar tendon autograft into the femoral tunnel performed mechanically as well as interference screw fixation. CLINICAL RELEVANCE: The results suggest that transcondylar and interference screws provide similar fixation for anterior cruciate ligament reconstruction.

Aged↗

Femoral press-fit fixation of the hamstring tendons for anterior cruciate ligament reconstruction.

BACKGROUND: Press-fit fixation of patellar tendon-bone anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. For hamstring tendon grafts, no biomechanical data exist of a press-fit procedure. HYPOTHESIS: Press-fit femoral fixation of hamstring tendons is mechanically equivalent to press-fit patellar tendon-bone fixation. STUDY DESIGN: Controlled laboratory study. METHODS: Patellar and hamstring tendons of 30 human cadavers (age, 53.8 +/- 18.0 years) were used. An outside-in press-fit fixation with a knot in the semitendinosus and gracilis tendons and an inside-out and outside-in fixation with the tendons wrapped around a bone block were compared with patellar tendon-bone press-fit fixation in 30 ovine femora. Constructs were cyclically strained and then loaded until failure. Maximum load to failure, stiffness, and elongation during failure testing and cyclical loading were investigated. RESULTS: The maximum load to failure was 561 +/- 309 N for the patellar tendon, 599 +/- 234 N for the semitendinosus/gracilis tendons knot construct, 678 +/- 231 for the semitendinosus/gracilis tendons bone construct inserted outside in, and 339 +/- 236 for the semitendinosus/gracilis tendons bone construct inserted inside out (inferior to the others; analysis of variance, Dunn test, P < .01). Stiffness of the constructs averaged 134 +/- 32 N/mm for the patellar tendon, 124 +/- 21 N/mm for the knot construct, 118 +/- 27 N/mm for the outside-in fixation, and 117 +/- 23 N/mm for inside-out fixation. Elongation during initial cyclical loading was 0.7 +/- 0.6 mm for the patellar tendon, 1.6 +/- 0.5 mm for the knot construct, 1.9 +/- 1.2 mm for the outside-in fixation, and 1.9 +/- 0.9 mm for the inside-out fixation (significantly larger for all semitendinosus/gracilis tendon techniques, P < .05). CONCLUSIONS: Failure loads for the semitendinosus/gracilis tendons bone construct inserted outside in and the semitendinosus/ gracilis tendons knot construct were within the confidence interval of the patellar tendon press-fit fixation. All semitendinosus/ gracilis tendon graft techniques exhibited larger elongation during initial cyclical loading than the patellar tendon graft. There was no difference in stiffness between all techniques. CLINICAL RELEVANCE: Two of the 3 hamstring press-fit fixation techniques showed loads to failure similar to the patellar tendon fixation. Preconditioning of the constructs is critical. These results must be interpreted with care because of high standard deviations.

Adolescent↗

Displaced intracapsular hip fractures in fit, older people: a randomised comparison of reduction and fixation, bipolar hemiarthroplasty and total hip arthroplasty.

OBJECTIVES: To compare internal fixation, bipolar hemiarthroplasty and total hip arthroplasty for the management of displaced subcapital fracture of the hip in previously fit patients of 60 years or older. DESIGN: A prospective randomised clinical trial. SETTING: This multicentre trial was carried out in 11 Scottish hospitals with acute orthopaedic trauma units. PARTICIPANTS: The participants were 298 previously fit patients of 60 years or older with displaced subcapital hip fractures. INTERVENTIONS: The three surgical interventions for comparison were reduction and fixation, bipolar hemiarthroplasty and total arthroplasty (total hip replacement). Participating surgeons elected to randomise patients either among all three types of operation (three-way randomisation) or just between fixation and hemiarthroplasty (two-way randomisation). MAIN OUTCOME MEASURES: Clinical outcomes were mortality rates, reoperation rates and the complication rates associated with each procedure. Functional outcome was measured using a hip specific questionnaire [Johanson Hip Rating Questionnaire (HRQ)] and a general health status questionnaire [EuroQol 5 Dimensions (EQ-5D)]. Economic analysis compared the costs in the randomised groups of hospital treatment for the initial and subsequent admissions for up to 2 years. RESULTS: Altogether, 207 patients were randomised among all three trial operations, and 91 between just fixation and bipolar hemiarthroplasty. There were no statistically significant differences in clinical outcomes, but confidence intervals (CIs) were wide. At 2 years fixation failure reached 37% among those allocated fixation and 39% had undergone further surgery. Further surgery rates after hemiarthroplasty and total hip replacement were 5% and 9%, respectively. The group allocated fixation had significantly worse HRQ and EQ-5D scores than both arthroplasty groups at 4 and 12 months. At 24 months the results still favoured arthroplasty, but the overall HRQ and EQ-5D scores were no longer statistically significant. Total hip replacement had the best patient-assessed outcome scores. At 24 months the overall HRQ and EQ-5D scores for total hip replacement were significantly better than for hemiarthroplasty. The mean costs for the initial episode ranged from 6384 pounds Sterling for fixation to 7633 pounds Sterling for total hip replacement. The cost differences were largely due to differences in theatre costs and the cost of prostheses and hardware. The cumulative cost over 2 years of hemiarthroplasty was around 3000 pounds Sterling lower than for fixation (95% CI 1227 pounds Sterling to 7192 pounds Sterling). Compared with total hip replacement, both fixation and hemiarthroplasty were characterised by increased costs arising from hip-replacement admissions. When total (initial episode and subsequent hip-related admissions) hip-related costs are compared, total hip replacement conferred a cost advantage of around 3000 pounds Sterling per patient (versus hemiarthroplasty, 95% CI -pounds Sterling 1400 to 7420 pounds Sterling). CONCLUSIONS: In fit, older patients the results of the study show a clear advantage for arthroplasty over fixation; arthroplasty was more clinically effective and probably less costly over a 2-year period postsurgery. The results suggest that total hip replacement has long-term advantages over bipolar hemiarthroplasty, but these findings are less definite. This study provided support for the use of total hip replacement to treat displaced intracapsular hip fractures in fit, older patients. A larger trial comparing total versus hemiarthroplasty for these fractures could help to verify these findings. It would also be useful to know whether the findings of this study apply to patients aged 60 years or less who are usually treated with reduction and fixation. A clinical trial comparing arthroplasty versus fixation in patients older than 40 years would be a logical extension of the current study.

Aged↗

New fixation device for photorefractive surgery and its effect on corneal epithelial wound healing.

PURPOSE: A new eyeball fixation device during photorefractive surgery was designed and tested. The device fixates the eyeball by means of a suction ring, and is then fixated to the headrest of the patient's chair via clipper and metal frames. METHODS: Photorefractive keratectomy (PRK) was performed on PMMA contact lenses placed over the patient's cornea (n=6) to evaluate smoothness of the ablated surface and on rabbit (n=24) and patient (n=30) corneas for evaluation of wound healing time. Decentration with fixation was examined using videokeratography after PRK. RESULTS: After fixation, only small amounts of corneal movement from the patient's pulsating heart were noted. The mean smoothness (root mean square) of the PMMA contact lens ablated surface was 0.43 +/- 0.16 microm in non-fixated eyes and 0.26 +/-0.05 microm in fixated eyes. Mean epithelial healing rate was 47.93 +/- 21.80 microm/hr in non-fixated rabbit eyes and 66.49 +/- 20 microm/hr in fixated rabbit eyes. Mean epithelial healing time was 3.47 +/- 1.11 days in non-fixated human eyes and 2.53 +/- 0.51 days in fixated human eyes. Mean decentration after PRK was 0.30 +/- 0.28 mm in fixated human eyes. CONCLUSION: Fixating the eyeball allows less movement of the eye and achieves a smoother ablation surface for more rapid epithelial healing after PRK.

Adult↗

[The clinical application and biomechanical study of reconstruction of anterior and posterior cruciate ligament with hamstring tendons knot implant fixation].

OBJECTIVE: To investigate the feasibility of reconstruction of anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) with hamstring tendons knot implant fixation. METHODS: Fifty-two cases of ACL and PCL old injury were reconstructed under the arthroscopy with double bundles hamstring tendons knot implant fixated in the bottle-necked femoral tunnel. The tibia side were fixated by tendon weave suture cross tied a knot at the bone bridge of tibia. In this group reconstruction of ACL was in 25, PCL and ACL at the same time reconstruction in 15, PCL in 12. The failure test and displacement evaluation were used to study the biomechanics of reconstruction of ACL by hamstring tendon knot implant fixation (n = 13) in porcine knees. The control group were reconstructed with bone-patellar tendon-bone B-PT-B and interference screw (n = 11). The tibia side tendon weave suture immobility by cross tied a knot at the tibia bone bridge (n = 7) and interference screw in the tibia tunnel (n = 8). RESULTS: Forty-nine cases were followed up, average 14.6 months. The results of Lanchman test was negative in 46 cases, positive in 3 cases. Preoperative Lysholm score was 56.7, and postoperative was 92.8. According to the knee joint effective evaluate standard, 46 were excellent and 3 good. The maximal pull-out force of hamstring tendons knot implanted fixation had been greater than B-PT-B fixation by interference screw. There were similar displacement in 100 N and 400 N load between hamstring tendons knot implant fixation and B-PT-B (P > 0.05). Peak force test maximal displacement evaluation and failure energy absorption measurement showed that hamstring tendons knot implant fixation was significantly greater than B-PT-B (P < 0.01). The failure test and displacement evaluation of tendon fixation by weave suture knot at the tibia bone bridge cross tie were greater than B-PT-B fixation by interference screw. CONCLUSION: The methods of reconstruct of ACL and PCL by hamstring tendons knot implant fixation are feasible. The advantages include: it is biological fixation, not machine fixation; it may benefit for tendons with bone tunnel healing and decrease medical cost. Decreasing or eliminating displacement is helpful to prevent relaxation after reconstruction of ACL and PCL.

Animals↗

The effect of external fixation stiffness on early healing of transverse osteotomies.

The effect of bending stiffness of external fixators on the early healing of transverse tibial osteotomies was studied in a canine model to determine whether there is a particular range of fixation stiffness where healing is poor. Five unilateral fixators with different stiffnesses were developed and employed along with a dynamic compression plate to fix experimental osteotomies of dog tibias and the contralateral intact tibias served as controls. The six experimental fixation devices were: plate (P), stainless steel sidebar fixator (SS), stiff aluminum sidebar fixator (SA), intermediate aluminum sidebar fixator (IA), flexible aluminum sidebar fixator (FA), and Delrin sidebar fixator (D). Compared with human tibial fixation methods, the fixators ranged from a rigidity greater than a plate on a human tibia to a flexibility similar to a plaster cast on a human lower leg. Sixty-four adult male mongrel dogs (29 +/- 3 kg) underwent surgery and 52 completed the 9-week study, leaving 7 to 10 dogs in each experimental group (P = 8, SS = 7, SA = 9, IA = 9, FA = 10, D = 9). After the 9-week survival period the experimental tibias were radiographed and callus area was digitized. Both the experimental and control tibias were then tested to failure in four-point bending, and failure moment, stiffness, and energy to failure were determined. Of the 52 osteotomies, only four developed nonunions: 3 of 10 in the FA group and 1 of 7 in the SS group. Using analysis of variance, no statistical differences were detected in failure force, stiffness, or energy to failure as a function of fixator groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

A meta-analysis of outcomes of external fixation versus plate osteosynthesis for unstable distal radius fractures.

PURPOSE: External fixation and open reduction and internal fixation have been the traditional techniques for surgical fixation of unstable distal radius fractures. The existing literature has not identified which is superior, primarily because of the lack of comparative trials. We performed a comprehensive systematic review and meta-analysis of the current literature on external fixation and internal fixation of distal radius fractures to determine the dominant strategy based on available scientific evidence. METHODS: We searched MEDLINE and EMBASE for English-language articles published between 1980 and 2004 that satisfied predetermined inclusion and exclusion criteria. The outcomes of internal and external fixation were compared using continuous measures of grip strength, wrist range of motion, and radiographic alignment and categoric measures of pain, physician-rated outcome scales, and complication rates. Outcomes were pooled by random-effects meta-analysis and meta-regression analysis was used to control for patient age, presence of intra-articular fracture, duration of follow-up period, and date of publication. Sensitivity analyses were used to test the stability of the meta-analysis results under different assumptions. RESULTS: Forty-six articles were included in the review with 28 (917 patients) external fixation studies and 18 (603 patients) internal fixation studies. Meta-analysis did not detect clinically or statistically significant differences in pooled grip strength, wrist range of motion, radiographic alignment, pain, and physician-rated outcomes between the 2 treatment arms. There were higher rates of infection, hardware failure, and neuritis with external fixation and higher rates of tendon complications and early hardware removal with internal fixation. Considerable heterogeneity was present in all studies and adversely affected the precision of the meta-analysis. CONCLUSIONS: The current literature offers no evidence to support the use of internal fixation over external fixation for unstable distal radius fractures. Comparative trials using appropriately sensitive and validated outcome measurements are needed to guide treatment decisions.

Bone Plates↗

Supplemental maxillomandibular fixation with miniplate osteosynthesis.

Monocortical miniplate fixation provides biomechanical fixation of mandibular fractures. The ability of this system to adequately fixate fractures clinically has not been fully accepted. We analyzed our use of supplemental maxillomandibular fixation with miniplate osteosynthesis during a 5-year period, in 287 patients with 499 mandible fractures. A retrospective, matched pairing of identical fractures fixated with identical plating-schemes was carried out. Sixty-five pairs of patients undergoing intraoral monocortical plating were identified. Patients in group 1 were treated with supplemental maxillomandibular fixation after surgery, whereas patients in group 2 were treated without postoperative maxillomandibular fixation. The rate of major complications was 11% with supplemental maxillomandibular fixation and 9% without supplemental maxillomandibular fixation (p > 0.05). The total rate of complications was 17% with supplemental maxillomandibular fixation and 20% without supplemental maxillomandibular fixation (p > 0.05). No statistically significant outcome advantage could be attributed to the use of maxillomandibular fixation.

Bone Plates↗

Fixation technique influences the monotonic properties of equine mandibular fracture constructs.

OBJECTIVE: To determine the optimal fixation technique for equine interdental space fractures by evaluating the biomechanical characteristics of 4 fixation techniques. STUDY DESIGN: In vitro randomized block design. SAMPLE POPULATION: Twenty-seven adult equine mandibles. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. CLINICAL RELEVANCE: 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.

Animals↗

Fixation of soft tissue surrounded by bone with microwave irradiation: electron microscopic observation of guinea pig inner ear.

When electron microscopy is performed on organs such as the inner ear that cannot be removed immediately after decapitation of animals, it is necessary to fix the target organ or tissue by systemic or regional perfusion fixation. However, such methods of fixation can increase vascular pressure or perilymphatic pressure, making it difficult to perform precise morphological observation of the vascular endothelial cells and membranous labyrinth. We recently attempted fixation of the cochlea by microwave irradiation. Guinea pigs were decapitated. The bullas were then removed from each animal and fixed in a mixture of 2% paraformaldehyde and 0.5% glutaraldehyde. Microwave (300 W) irradiation was then applied to the specimen for 1 minute. The fixative was immediately replaced with new fixative (4 degrees C). This sequence of manipulations was repeated 10 times, for a cumulative microwave irradiation time of 10 minutes. During the microwave irradiation period, the fixative temperature was kept at about 30 degrees C. After the last round of irradiation, the specimens were kept immersed in the fixative for 1 hour. After a small slit was created in the bone on the lateral wall of the cochlea, the specimens were post-fixed in osmic acid and embedded in Epon 812. Each specimen was cut into halves along the plane containing the modiolus of the cochlea. After the bone on the lateral wall of the cochlea was cut off under a stereoscopic microscope, ultrathin sections were prepared for observation under a transmission electron microscope. With this technique, the stria vascularis and the organ of Corti were fixed to a degree comparable to or better than that achieved with the conventional method of fixation. Fixation with microwave irradiation is relatively simple and can solve the problems associated with perfusion fixation, and thus provides an excellent means of fixation. This technique appears to be particularly promising for fixation for soft tissue surrounded by bone.

Animals↗

Conversion of external fixation to intramedullary nailing for fractures of the shaft of the femur in multiply injured patients.

BACKGROUND: From 1989 to 1997, 1507 fractures of the shaft of the femur were treated with intramedullary nailing at The R Adams Cowley Shock Trauma Center. Fifty-nine (4 percent) of those fractures were treated with early external fixation followed by planned conversion to intramedullary nail fixation. This two-stage stabilization protocol was selected for patients who were critically ill and poor candidates for an immediate intramedullary procedure or who required expedient femoral fixation followed by repair of an ipsilateral vascular injury. The purpose of the current investigation was to determine whether this protocol is an appropriate alternative for the management of fractures of the femur in patients who are poor candidates for immediate intramedullary nailing. METHODS: Fifty-four multiply injured patients with a total of fifty-nine fractures of the shaft of the femur treated with external fixation followed by planned conversion to intramedullary nail fixation were evaluated in a retrospective review to gather demographic, injury, management, and fracture-healing data for analysis. RESULTS: The average Injury Severity Score for the fifty-four patients was 29 (range, 13 to 43); the average Glasgow Coma Scale score was 11 (range, 3 to 15). Most patients (forty-four) had additional orthopaedic injuries (average, three; range, zero to eight), and associated injuries such as severe brain injury, solid-organ rupture, chest trauma, and aortic tears were common. Forty fractures were closed, and nineteen fractures were open. According to the system of Gustilo and Anderson, three of the open fractures were type II, eight were type IIIA, and eight were type IIIC. Intramedullary nailing was delayed secondary to medical instability in forty-six patients and secondary to vascular injury in eight. All fractures of the shaft of the femur were stabilized with a unilateral external fixator within the first twenty-four hours after the injury; the average duration of the procedure was thirty minutes. The duration of external fixation averaged seven days (range, one to forty-nine days) before the fixation with the static interlocked intramedullary nail. Forty-nine of the nailing procedures were antegrade, and ten were retrograde. For fifty-five of the fifty-nine fractures, the external fixation was converted to intramedullary nail fixation in a one-stage procedure. The other four fractures were associated with draining pin sites, and skeletal traction to allow pin-site healing was used for an average of ten days (range, eight to fifteen days) after fixator removal and before intramedullary nailing. Follow-up averaged twelve months (range, six to eighty-seven months). Of the fifty-eight fractures available for follow-up until union, fifty-six (97 percent) healed within six months. There were three major complications: one patient died from a pulmonary embolism before union, one patient had a refractory infected nonunion, and one patient had a nonunion with nail failure, which was successfully treated with retrograde exchange nailing. The infection rate was 1.7 percent. Four other patients required a minor reoperation: two were managed with manipulation under anesthesia because of knee stiffness, and two underwent derotation and relocking of the nail because of rotational malalignment. The rate of unplanned reoperations was 11 percent. The average range of motion of the knee was 107 degrees (range, 60 to 140 degrees). CONCLUSIONS: We concluded that immediate external fixation followed by early closed intramedullary nailing is a safe treatment method for fractures of the shaft of the femur in selected multiply injured patients.

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