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PubMedDate not supplied

[War injuries of the extremities. Use of the CMC fixator].

The injuries of the extremities in the military setting, during hostilities, are classified to be the most frequent in general. Among them there are those caused by the missiles from rifles and automatic and semiautomatic weapons and those due to mine and shell fragments. The characteristics of modern array of weapons are missiles of high kinetic energy provoking extensive tissue injuries, often together with fractures of the long bones. When taking care of such fractures, in addition to surgical treatment of the wounds, the administration of medicine and prevention, the immobilization of the fragments is of fundamental significance. All modern armies in the world use external fixators for the immobilization of the fragments, those fixators being the most reliable and the most uncomplicated means of immobilization. The paper presents a new type of the external fixator to be used in war surgery. It is called the CMC fixator (Croatian Medical Corps). The fixator is made according to the original designs in the factory (Instrumentarija) at Zagreb. Following its biomechanic characteristics the fixator is classified into the group of unilateral or joining external fixators. It is designed for fixation of the long bone fractures in the war setting and disaster conditions. It may be used for two purposes: 1. for the transport immobilization to a medical facility where the problem is to be finally solved, 2. as the means of an external immobilization until the final secondary bone-healing. The fixator has only three elements and the universal kee. It is easily applied. The way how to apply this fixator is described in details. The first experiences in the field have given satisfactory results.

External Fixators↗
PubMed1988

[Combination of external fixator and internal synthesis in fractures and pseudoarthrosis of the leg. Principle indications and results].

A combination of internal and external fixation has been used on 58 occasions in fractures and pseudarthroses in the leg. In almost two-thirds of the cases, the fractures were compound. Several situations favour this combination of fixation: internal fixation complements an initial external fixation by stabilising the fracture site in the shaft or by allowing reconstruction of joint surfaces, external fixation complements any inadequate internal fixation due to comminution of the fracture or poor skin cover that only allows a minimum of internal fixation, external fixation secondarily comes to the help of internal fixation in cases of skin necrosis or secondary bone infection. The authors believe that a combination of internal and external fixation has real advantages and that, when used with good sense, it should not lead to any specific complications.

Adolescent↗
PubMed1995

Evaluation of three fixation techniques for repair of mandibular fractures in dogs.

Bilateral midbody hemimandibular osteotomies were performed between premolars 3 and 4 in 18 adult dogs. Hemimandibles were repaired by use of monocortically applied bone plates (n = 6), an interdental fixator composed of an Erich arch bar and acrylic (n = 6), or a type I external skeletal fixator (n = 6). At the immediate postoperative evaluation, hemimandibles stabilized with interdental fixators had an osteotomy gap distance (mean +/- SEM, 1.6 +/- 0.2 mm) that was significantly (P < 0.05) greater than for hemimandibles stabilized with external skeletal fixators (1.2 +/- 0.3 mm). Osteotomy gap distance of hemimandibles stabilized with external skeletal fixators (1.5 +/- 0.2 mm) was significantly (P < 0.05) greater at weeks 4 (1.1 +/- 0.2 mm) and 8 (0.8 +/- 0.3 mm) after surgery than the osteotomy gap distance of hemimandibles stabilized by application of bone plates. By week 16, significant differences in osteotomy gap distance were not detected between groups. Immediately after surgery, mandibular alignment measurements were not significantly different for dogs with bone plates (0.3 +/- 0.1 mm), interdental fixators (0.3 +/- 0.1 mm), and external skeletal fixators (0.9 +/- 0.5 mm). Mandibular alignment scores were not significantly different between treatment groups during the remaining postoperative period. Occlusal measurements were not significantly different between evaluations performed before surgery and 16 weeks after surgery, regardless of treatment group. Radiographic evidence of healing in hemimandibles stabilized with external skeletal fixators was significantly (P < 0.05) less at 4 and 8 weeks, compared with hemimandibles stabilized with bone plates and interdental fixators; however, radiographic evidence of bone healing was not significantly different between fixation groups at 16 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[The AO external clamp fixator. New techniques in external stabilization of tibial fractures].

A serious disadvantage of conventional external fixators is the opening of the medullary canal. This creates a direct communication between the canal and the exterior. The new pinless external fixator does not have this disadvantage. The clamps of the new fixator system do not penetrate cortical bone, they simply rest on the cortical surface. The clinical indications of this easily managed system are fractures of the tibial shaft in cases in which primary internal fixation is precluded either by precarious local or general conditions, or even by a lack of infrastructure. In such situations the pinless external fixator is an excellent device to achieve a good fracture stabilisation rapidly, while leaving open all subsequent alteration of treatment. In case of secondary change to an intramedullary nail the pinless fixator facilitates the procedure, because this fixator can be also used as an distractor during nailing. Furthermore this fixator can be combined with any intramedullary nail to increase the stability in case of very proximal or distal as well as highly instable shaft fractures. The clamps of the pinless external fixator set are used in combination with the standard AO fixator system.

Adult↗
PubMedDate not supplied

[Personal experience in the care of open fractures using external fixation during the hostilities in Osijek and surrounding region].

In the period of aggression of the Federal Army and Serbian paramilitary forces on the City of Osijek and its surrounding, beginning in the summer of 1991, 4036 wounded were treated at the Department of Surgery, Osijek General Hospital. Extremity injuries were documented in 3889 patients, including 959 bone fractures. The majority of patients had wounds caused by highly destructive explosives filled with metal fragments of different shapes and dimensions, and having sharp and uneven edges. One hundred and forty wounded were treated by external fixators. In 102 patients this mode of fixation was applied for gun- and explosive-related long bone fractures of the lower extremities. External fixator for the upper and forearm fractures was used in 38 cases. During this period, different types of external fixators were used and experience in this work has been gained. Stability of both open and unstable bone fractures of the extremities, caused by explosive devices, has been obtained by the external fixation mostly in one plane, regardless of the type of external fixator used. The advantages of use of external fixators of the types Instrumentarija Zagreb 1 and 2 for the treatment of long bone fractures has been emphasized as well as the possibility of the subsequent corrections owing to the technical construction of the bone spike. The usefulness of the longitudinal bar of the AO/ASIF fixator for the healing of fractures of the upper leg with subsequent callus formation is also stressed. The same stability has been achieved by the CMC fixator. The external fixators of a type Zagreb 2 have been a satisfactory treatment for forearm fractures as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Croatia↗
PubMed1996

Closed reduction and type-II external fixation of comminuted fractures of the radius and tibia in dogs: 23 cases (1990-1994).

OBJECTIVE: To describe a technique for closed reduction of and application of a type-II external fixator to comminuted fractures of the radius and tibia in dogs and to evaluate outcome of the technique in a series of client-owned dogs. DESIGN: Retrospective case series. ANIMALS: 23 dogs that underwent closed reduction of severely comminuted (> or = 5 fragments); mid-diaphyseal radial (n = 9); and tibial (n = 14) fractures and stabilization with a type-II external fixator. PROCEDURE: Radiographs were made postoperatively and every 4 to 6 weeks until the fixator was removed. The effect of type of fracture (open vs closed), type of pins (threaded vs smooth), and number of fixation pins on surgery time, time between surgery and development of bridging callus, and time between surgery and removal of the fixator was evaluated using one-sided Student's t-tests. RESULTS: 21 fractures healed after a single surgery. Two dogs with radial fractures required a second procedure because of complications. All fractures healed with the original fixation device in place. Mean time between surgery and the development of bridging callus was 11.4 weeks (range, 4 to 22 weeks), and mean time between surgery and fixator removal was 14.7 weeks (range, 4 to 27 weeks). Type of fracture, type of pins, and number of fixation pins did not have a significant effect on surgery time, time to development of bridging callus, or time to fixator removal. CLINICAL IMPLICATIONS: Closed reduction and application of a type-II external fixator was an effective method of treating severely comminuted radial and tibial fractures.

Animals↗
PubMed1997

Open reduction and bone plate stabilization, compared with closed reduction and external fixation, for treatment of comminuted tibial fractures: 47 cases (1980-1995) in dogs.

OBJECTIVE: To compare open reduction and bone plate fixation with closed reduction and external skeletal fixation as treatment for severely comminuted fractures of the tibia. Limb alignment, fracture reduction, operating time, hospitalization time, postoperative care, time to unrestricted activity, bone healing, complications, and number of surgical procedures were considered. DESIGN: Retrospective case series. ANIMALS: 47 dogs with severely comminuted fractures of the tibia treated with open reduction and bone plate application (22 dogs) or closed reduction and external fixation (25 dogs). PROCEDURE: Medical records of all dogs included in this study were reviewed. Postoperative and follow-up radiographs were evaluated by 2 independent observers. RESULTS: Differences were not found in hospitalization time, time to unrestricted activity, or time to earliest radiographic evidence of bone healing between dogs with fractures treated with a bone plate and dogs with fractures treated with an external fixator. Fractures treated with an external fixator had more caudal malalignment, and fractures treated with a bone plate had more valgus malalignment. Malalignments were determined not to be related to clinical problems. Dogs with fractures treated with an external fixator had shorter surgery times and more recheck examinations. Dogs with fractures treated with a bone plate had more complications. CLINICAL IMPLICATIONS: Open reduction with bone plate fixation and closed reduction with external fixation were both effective for treatment of comminuted tibial fractures. External fixation was associated with shorter surgery time, but dogs required more extensive postoperative care. Bone plate fixation was associated with more complications.

Animals↗
PubMedDate not supplied

Mandibular angle fractures: two-miniplate fixation and complications.

BACKGROUND: Noncompression monocortical miniplate fixation of the mandibular angle is an accepted and reliable method for providing rigid internal fixation. High complication rates have been reported for internal fixation of angle fractures. OBJECTIVE: To analyze the outcome and complications in cases in which patients were treated with 2-miniplate fixation at the mandibular angle. DESIGN: A retrospective analysis of outcomes for a case series. SETTING: Treatment performed at a level 1 trauma-rated teaching hospital. METHODS: From May 1992 to September 2001, a total of 88 patients with angle fractures of the mandible were treated with 2-miniplate fixation. Sixty-eight of the 88 patients, with 70 angle fractures, were included in the study; 13 were unavailable for follow-up and 7 had less than the minimum follow-up of 6 weeks. The time of trauma to treatment, cause of injury, and associated fractures were recorded. Postoperative complications, including infection, malunion, nonunion, dehiscence, osteomyelitis, and nerve injury due to surgical manipulation, were tabulated. Follow-up examinations were performed up to 12 weeks after surgery, with additional examinations if necessary. Postreduction panoramic radiographs were obtained in most cases. RESULTS: No patients treated with monocortical 2-miniplate fixation had malunion, nonunion, or osteomyelitis. Twelve (17.6%) of the 68 patients were identified as having at least 1 postoperative complication. Postoperative infection occurred in 2 patients (2.9%). Infection was controlled with oral antibiotic therapy. One patient required removal of miniplates after the acute phase resolved. Occlusal disturbances were noted in 4 patients (5.9%) (2 with a slight anterior open bite, 1 with a crossbite, and 1 with premature contact of a molar) after surgery. Three of the 4 patients had associated midfacial or multiple mandibular fractures. None required further surgery. Wound dehiscence, with exposure of an underlying plate, occurred in 4 patients (5.9%); the wounds were treated conservatively and subsequently resolved. Nerve injury due to surgical manipulation occurred in 3 patients (4.4%). CONCLUSIONS: Monocortical 2-miniplate fixation of the mandibular angle is a reliable and effective technique for providing rigid fixation. The complications were minimal in our study, and the infection rate was 2.9%, which is comparable to or better than the infection rate reported with the use of a single miniplate fixation technique in other studies. Disturbances of occlusion were associated with midfacial or additional mandibular fractures. In view of the contradictory published results, further studies are needed to determine the ideal approach for noncompression monocortical plate fixation of angle fractures.

Bone Plates↗
PubMed1994

The fixation area of the cat superior colliculus: effects of electrical stimulation and direct connection with brainstem omnipause neurons.

The superior colliculus has long been recognized as an important structure in the generation of saccadic displacements of the visual axis. Neurons with presaccadic activity encoding saccade vectors are topographically organized and form a "motor map." Recently, neurons with fixation-related activity have been recorded at the collicular rostral pole, at the area centralis representation or fixation area. Another collicular function which deals with the maintenance of fixation behavior by means of active inhibition of orientation commands was then suggested. We tested that hypothesis as it relates to the suppression of gaze saccades (gaze = eye in space = eye in head + head in space) in the head-free cat by increasing the activity of the fixation cells at the rostral pole with electrical microstimulation. Long stimulation trains applied before gaze saccades delayed their initiation. Short stimuli, delivered during the gaze saccades, transiently interrupted both eye and head components. These results provide further support for a role in fixation behavior for collicular fixation neurons. Brainstem omnipause neurons also exhibit fixation-related activity and have been shown to receive a direct excitatory input from the superior colliculus. To determine whether the collicular projection to omnipause neurons arises from the fixation area, the deep layers of the superior colliculus were electrically stimulated either at the rostral pole including the fixation area or in more caudal regions where stimulation evokes orienting responses. Forty-nine neurons were examined in three cats. 61% of the neurons were found to be orthodromically excited by single-pulse stimulation of the rostral pole, whereas only 29% responded to caudal stimulation. In addition, stimuli delivered to the rostral pole activated, on average, omnipause neurons at shorter latencies and with lower currents than those applied in caudal regions. These results suggest that excitatory inputs to omnipause neurons from the superior colliculus are principally provided by the fixation area, via which the superior colliculus could play a role in suppression of gaze shifts.

Animals↗
PubMedDate not supplied

Binocular eye orientation during fixations: Listing's law extended to include eye vergence.

Any eye position can be reached from a position called the primary position by rotation about a single axis. Listing's law states that for targets at optical infinity all rotation axes form a plane; the so-called Listing plane. Listing's law is not valid for fixation of nearby targets. To document these deviations of Listing's law we studied binocular eye positions during fixations of point targets in the dark. We tested both symmetric (targets in a sagittal plane) and asymmetric vergence conditions. For upward fixation both eyes showed intorsion relative to the position that would have been taken if each eye followed Listing's law. For downward fixation we found extorsion. The in- or extorsion increased approximately linearly with the vergence angle. The direction of the Listing axis and the turn angle about this axis can be described by rotation vectors. Our observations indicate that for fixation of nearby targets the rotation vectors of the two eyes become different and are no longer located in a single plane. However, we find that it is possible to decomose the rotation vector of each eye into the sum of a symmetric and an anti-symmetric part, each with its own properties. (1) The symmetric part is associated with eye version. This component of the rotation vector is identical for both eyes and lies in Listing's plane. In contrast to the classical form of Listing's law, this part of the rotation vector lies in Listing's plane irrespective of the fixation distance. (2) The anti-symmetric part of the rotation vector is related to eye vergence. This component is of equal magnitude but oppositely directed in each eye. The anti-symmetric part lies in the mid-sagittal plane, also irrespective of fixation distance. For fixation of targets at optical infinity the anti-symmetric part equals zero and the eye positions obey the classical form of Listing's law. Thus, the symmetric and anti-symmetric parts of the rotation vectors are restricted to two perpendicular planes. Combining these restrictions in a model, with the additional restriction that the vertical vergence equals zero during fixation of point targets, we arrive at the prediction that the cyclovergence is proportional to the product of elevation and horizontal vergence angles. This was well born out by the data. The model allows to describe the binocular eye position for fixation of any target position in terms of the bipolar coordinates of the target only (i.e. using only three degrees of freedom instead of the six needed for two eyes).

Eye Movements↗
PubMed1996

Fixation conditions, the foveola and saccadic latency.

Saccades are often elicited in the laboratory by the abrupt step-displacement of a single lit point which is initially the foveolar fixation point and then the eccentric refixation target. This was our Control condition. Four experiments modified the fixation arrangements to examine the effect of altered foveolar stimulation on saccadic latency and accuracy to targets within the central +/- 6 deg of the visual field. (1) No foveolar fixation point: The subject fixated the empty space midway between a pair of fixation guides, which later collapsed into a single refixation target. Latencies for small saccades were similar to the Control values. (2) No foveolar fixation point and no real refixation target: A pair of fixation guides underwent a yoked displacement, and it was easy to fixate and track the invisible midpoint. The smallest saccades were hypermetric, and the typical pattern of latency variation with retinal eccentricity was exaggerated in scale. (3) Spatial effects of a persistent non-target: The precise position of a non-target was important, latency increases being in the ipsilateral hemifield when the non-target was intrafoveolar and unilateral, bilateral when intrafoveolar and on the midline, and local when the non-target was extrafoveolar. (4) Temporal effects of a foveolar fixation point: Blanking an otherwise persistent fixation point for as little as 1 msec at the time of target presentation reduced the expected latency increase. We conclude that the position and timing of foveolar illumination can be critical for saccades of all sizes.

Fixation, Ocular↗
PubMed2005

Long-term follow-up of fixation patterns in eyes with central scotomas from geographic atrophy that is associated with age-related macular degeneration.

PURPOSE: To study whether fixation patterns changed over time in patients with central scotomas from geographic atrophy from age-related macular degeneration. DESIGN: Prospective cohort study. METHODS: setting: Institutional. patient or study population: Prospective natural history study of geographic atrophy included 34 eyes of 25 patients with baseline acuity between 20/80 and 20/200 and with subsequent follow-up. observation procedures: Baseline and annual follow-up visits included best-corrected visual acuity, scanning laser ophthalmoscope macular perimetry, reading rate, and clinical evaluation. main outcome measures: Location of eccentric preferred retinal locus for fixation (PRL). RESULTS: At baseline, 77% of study eyes had a PRL. At the final visit (median follow-up, 5.3 years), 91% of study eyes had a PRL, with 81% of the eyes retaining the baseline PRL location. Fixation with the scotoma to the right and fixation with the scotoma superior were the first and second most common fixation patterns, respectively. Reading rates of <50 words/min were present in 54% of eyes. Eyes fixating with the scotoma to the left tended to have lower reading rates than eyes fixating with right or superior patterns. CONCLUSION: Fixation with right pattern remained the most common fixation pattern, both in patients with a PRL at baseline and in patients who had a PRL during follow-up. Eyes with a PRL at baseline generally retained this pattern. The reading rate data suggest an advantage of fixation with right or superior pattern, rather than left. Reading rate declined further during follow-up in most patients.

Aged↗
PubMed2004

Internal fixation of radial neck fractures: an in vitro biomechanical analysis.

OBJECTIVE: To assess the fixation rigidities of a custom designed blade plate, a 2.7 mm T-plate and 3.0 mm cannulated screws. DESIGN: A cadaveric non-comminuted radial neck fracture model was employed to test the three fixation methods, using a multi-directional shear loading protocol. BACKGROUND: The management of displaced radial neck fractures in adults remains unsatisfactory due to failure of internal fixation with secondary loss of reduction, and non-unions. METHODS: The stiffness of the various fixation methods was measured in five directions of loading in the transverse plane. Failure testing was performed on the final testing condition for each specimen, in a posteroulnar to anteroradial direction. RESULTS: The direction of specimen loading did not have a significant effect on the stiffness of the various methods of fixation (P = 0.4). There was no significant difference in the fixation stiffness between the 3.0 mm screws or blade plate, however, both were superior to the T-plate (P < 0.05). CONCLUSIONS: Although the 2.7 mm T-plate has been reported in the literature as a viable method of fixation for radial neck fractures, it may not be optimal from the viewpoint of fixation stability. In the setting of a non-comminuted radial neck fracture, the use of cross-cannulated screws or blade plate fixation is preferred.Relevance This study supports the use of cross-cannulated screws or blade plate fixation for non-comminuted fractures of the radial neck.

Aged↗
PubMed2004

Three-dimensional load measurements in an external fixator.

On the basis of a six-degree-of-freedom adjustable fracture reduction hexapod external fixator, a system which can be used for measuring axial and shear forces as well as torsion and bending moments in the fixator in vivo was developed. In a pilot study on 9 patients (7 fresh fractures and 2 osteotomies of the tibia), the load in the fixator during the healing process was measured after 2, 4, 8 and 12 weeks and at fixator removal. The measured values enabled both the type of fracture to be determined as well as the monitoring of the healing process. In well-reduced type A3 fractures small axial (direction of the bone axis) forces were found in the fixator. A2, B2 and C3 fractures showed distinct axial forces, which decreased during the healing process, according to an increasing load transfer over the bone. Bending moments in the fixator showed good correspondence with the clinical healing process, except in the case of a C3 fracture. A combination of bending moment and axial force proved to be particularly suitable to assess fracture healing. In transverse fractures, the well-known resorption phenomenon of bone in the fracture gap at approximately 4 weeks was detected by the system. Compared with other external fixator load measurements in vivo, the hexapod offers the advantage of being able to measure all forces and moments in the fixator separately and with a relatively simple mechanical arrangement. In our opinion, it will be possible to control fracture healing using this system, thereby minimizing radiation exposure from radiographs. Furthermore, the measurement system is a step towards the development of external fixator systems that enable automatic adjustments of the callus mechanical situation ("automatic dynamization") and inform the patients about the optimal weight bearing of their extremity ("intelligent fixator").

Equipment Design↗
PubMedDate not supplied

Degenerative changes following spinal fixation in a small animal model.

OBJECTIVE: The objective of this study was to evaluate changes of the lumbar vertebral column following fixation. DESIGN: Using an established small animal (rat) model of spinal fixation (hypomobility), 3 contiguous lumbar segments (L4, L5, L6) were fixed with a specially engineered vertebral fixation device. Spinal segments of control rats were compared with those of animals with 1, 4, or 8 weeks of fixation. Subgroups of these fixation animals subsequently had the fixation device removed for 1, 2, 4, 8, or 12 weeks to evaluate the effects of attempting to reestablish normal forces to the vertebral segments following hypomobility. SETTING: This Institutional Animal Care and Use Committee (IACUC) approved study was conducted in a university animal facility. ANIMALS: Eighty-seven animals (23 controls animals and 64 fixation animals) were used in this study. Main Outcome Measures Outcome measures were degenerative changes of the vertebral bodies (VBs) and intervertebral disks (IVDs), zygapophysial (Z) joint osteophyte formation, and Z joint articular surface degeneration (ASD). Changes found in vertebral segments that were fixed (hypomobile) were compared with changes in adjacent nonfixed vertebral segments, and changes among fixation animals were compared with nonfixed controls. Main Results Very few degenerative changes were identified on the VBs and IVDs. Z joint changes were significant, both for osteophyte formation (analysis of variance [ANOVA], P <.0001) and ASD (ANOVA, P <.0001). Fixed segments had more degenerative changes than nonfixed segments for all Z joint parameters (ANOVA, P <.0001). Osteophyte formation and ASD were directly dependent on duration of fixation. CONCLUSIONS: These findings indicate that fixation (hypomobility) results in time-dependent degenerative changes of the Z joints.

Analysis of Variance↗
PubMed2006

Effects of paraformaldehyde fixation on nicotinic acetylcholine receptor binding in adult and developing rat brain sections.

In vitro receptor autoradiography requires unfixed tissue sections, but incubation and washing procedures often result in substantial tissue damage in sections from developing brain, hindering quantitative and qualitative analysis. Formaldehyde fixation greatly preserves morphology. However, fixation can interfere with pharmacological properties of receptors, increase in non-specific background labeling, or even destroy ligand binding sites. Two mild fixation protocols, 0.2% paraformaldehyde (pFA) and pFA vapor fixation, were compared for their ability to improve tissue morphology in postnatal day 7 (P7) brain slices and maintain binding of [125I]-epibatidine and [125I]-alpha-bungarotoxin to heteromeric and homomeric nicotinic acetylcholine receptors, respectively. Fixation greatly improved the ability of P7 brain slices to withstand incubation and washing procedures during binding, resulting in minimal or no loss of tissue after prior 0.2% pFA or vapor fixation, respectively. In adults, distribution pattern of [125I]-epibatidine was identical in fixed and unfixed slices, with no difference in total and non-specific labeling. Distribution of [125I]-alphaBTX labeling was similarly unaffected by 0.2% pFA fixation, but vapor fixation increased total and non-specific binding signal. Thus, mild fixations greatly improve tissue quality during receptor binding procedures and can preserve pharmacological properties of nicotinic acetylcholine receptors. However, different receptors or ligands might exhibit differential sensitivity to fixation protocols.

Age Factors↗
PubMed1997

The influence of fixation delay on mitotic activity and flow cytometric cell cycle variables.

Proliferation variables such as mitotic activity and the percentage of S-phase cells have been shown to be of prognostic value in many tumors, especially in breast cancer. However, some studies reported a decrease in mitotic activity caused by delay in fixation of the tissue. In contrast, other studies showed that the identifiability of mitotic figures decreases after fixation delay, but the total number of mitotic figures and also the percentage of S-phase cells remain unchanged. Most studies have been done on small numbers of experimental tumors, thus introducing the risk of selection bias. The aim of this study was to reinvestigate the influence of fixation delay on mitotic activity and cell cycle variables assessed by flow cytometry in an adequate number of resected human tissues to reach firmer conclusions. Resection specimens of 19 and 21 cases, respectively, for the mitotic activity estimate and the flow cytometric percentage of S-phase calculation were collected directly from the operating theater using lung, breast, and intestinal cancers and normal intestinal mucosa. The tissues were cut in pieces, and from each specimen, pieces were fixed in 4% buffered formaldehyde (for mitosis counting) as well as snap frozen (for flow cytometry) immediately after excision, as well as after a fixation delay of 1, 2, 4, 6, 8, 18, and 24 hours. Moreover, during the fixation delay, one series from each specimen was kept in the refrigerator and the second at room temperature. Thus, a total of 304 (19 X 16) and 336 (21 X 16) specimens were investigated for the mitotic activity estimate and the percentage of S-phase cells calculation, respectively. With regard to the estimation of the mitotic activity, both clear and doubtful mitotic figures were registered separately, obtaining an "uncorrected" and "corrected" (for doubtful mitotic figures) mitotic activity estimate. The percentage of S-phase cells was obtained by cell cycle analysis of flow cytometric DNA-histograms. The results showed that the quality of the material decreased during the fixation delay, as reflected by poorer cellular morphology in the hematoxylin-and-eosin-stained slides, resulting in more difficult identification of mitotic figures and a more time-consuming procedure with regard to the mitosis counts, but not in a worse intraobserver and interobserver reproducibility, which was acceptable. The reduction in quality of the tissues also was shown by the flow cytometric measurements because the coefficient of variation and percentage of debris increased after 4 hours or more of fixation delay. However, the mean values of the "uncorrected" mitotic activity and the "corrected" mitotic activity showed no decreasing trend; neither did the average percentage of S-phase cells. In conclusion, within the time investigated, fixation delay has no clear influence on the proliferation features studied. Because of the decreasing quality of the histological sections, resulting in more difficult identification of mitoses and interpretation of DNA histograms, fixation delay should be kept as short as possible, keeping the tissue at 4 degrees C until fixation.

Flow Cytometry↗
PubMed1992

Instrumentation for external fixation.

External skeletal fixation is a very useful technique for managing many orthopedic problems in veterinary practice. The Kirschner apparatus has been the most widely used fixator for many years in veterinary orthopedics because of its versatility, simplicity, and economy in use. The medium-sized device has the widest indications and is easiest to begin with. The small size can be acquired later for use on cats and small dogs. The new "raised thread" fixation pin designs improve bone-pin integrity and can be used in combination with nonthreaded pins to decrease the incidence of postoperative complications and for economy. Acrylic-pin external fixators are particularly useful for treatment of mandibular fractures and transarticular application since they allow nonlinear placement of fixation pins in highly contoured bones. A commercial system, currently being developed, will have all the equipment and materials necessary for their application in a convenient kit. Circular fixators (Ilizarov design) use thin K wires placed under tension to replace rigid fixation pins. Their unique adjustability characteristics make them useful in the treatment of limb deformity and shortening. Many other human fixators can be used for veterinary application if the basic principles of fixators are followed. Instrumentation required for external fixator application include a pin driver, pin cutter, and wrenches. Although surgical versions of these materials are available, less expensive alternatives are available using gas sterilization instead of autoclaving. The use of selected orthopedic instrumentation such as a periosteal elevator, bone clamps, and curets will facilitate fracture management.

Animals↗