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Biomedical subjects

M F Swiontkowski

Publications and source records attributed to M F Swiontkowski.

At least 55 records · Page 3Linked to original sources
PubMed1996

X-ray film measurements for healed distal radius fractures.

In order to understand the effect of malunion on functional outcome, it is essential that deformity be measured in a consistent manner. A standardized method of measuring eight anatomic parameters at the distal radius was developed. By this method, six x-ray films of healed distal radius fractures were subsequently measured by 16 raters. Rater agreement was quantified by using the intraclass correlation coefficient. Tolerance limits were developed in order to estimate the expected margin of error for each parameter. Parameters measured with high rater agreement include ulnar variance, palmar tilt, and radial shift; however, even experienced clinicians did not readily agree on the size of step and gap deformity. Using the method of tolerance limits, one would expect that two randomly chosen clinicians measuring step and gap deformity on a random x-ray film will differ by more than 3 mm at least 10% of the time. Similarly, repeat step or gap measurements by the same observer are expected to differ by more than 2 mm at least 10% of the time. In view of our inability to measure deformity more accurately, the concept of a specific relationship between a given degree of deformity and outcome must be questioned. Prospective research is needed in order to improve our understanding of the precise relationship between malunion and functional outcome.

Fracture Healing↗
PubMed1996

Soft-tissue blood flow following reamed versus unreamed locked intramedullary nailing: a fractured sheep tibia model.

A study was performed to compare the effects of reamed versus unreamed locked intramedullary nailing on soft-tissue blood flow in a fractured sheep tibia model. After creation of a standardized short spiral fracture, each tibia was stabilized by insertion of a locked intramedullary nail. Ten animals were randomized into two groups: one that had reaming prior to nail insertion and one that did not. Blood flow was measured in real time, using laser Doppler flowmetry. Skin and muscle perfusion measurements were made at three locations (proximal diaphysis, fracture site, and distal diaphysis) and at five time intervals (postfracture; postnail insertion; and at 2-week, 6-week, and 12-week follow-ups). All animals were sacrificed at 12 weeks postoperatively. Muscle blood flow remained elevated longer in the reamed group than in the unreamed group, following completion of the procedure. Muscle perfusion was significantly greater in the reamed group than in the unreamed group (p < 0.033) and was significantly greater than skin perfusion at 2 weeks (p < 0.024). There was no difference in skin perfusion between the reamed and unreamed groups at any time interval. The study demonstrates that muscle perfusion is altered following reamed and unreamed intramedullary nailing. The findings demonstrate the change in blood flow in the surrounding soft-tissue envelope during the process of revascularization, following devascularization of a segment of tibial cortex by intramedullary nailing.

Animals↗
PubMed1996

Fatal group A streptococcal infection with toxic shock syndrome: complicating minor orthopedic trauma.

Since 1987, reports have appeared of a streptococcal toxic shock syndrome in various clinical settings. None have appeared in the orthopaedic literature. Between 1989 and 1991 at our institution three patients with relatively minor orthopaedic injuries or procedures died of group A streptococcal infections complicated by toxic shock syndrome. The manifestations of this syndrome included rapid progression of systemic sepsis, necrotizing soft-tissue infections, acute renal failure, adult respiratory distress syndrome, and coagulopathy. All three patients died despite aggressive resuscitative measures and surgical debridement. Optimal treatment of this life-threatening process requires early recognition, aggressive surgical debridement, appropriate antibiotic management, and intensive care unit support.

Adult↗
PubMed1996

Comparative biomechanical evaluation of different external fixation sidebars: stainless-steel tubes versus carbon fiber rods.

Carbon fiber rods were developed to provide radiolucent sidebars for external fixation. In the present study, a single-plane, half-pin, double-bar external fixator construct with either stainless-steel tubes or carbon fiber rods was applied on the anteromedial surface of an osteotomized synthetic human tibia and evaluated for fixation rigidity. Testing was performed with the bone fragments in cortical contact and with a 5-mm midshaft gap between the fragments. The sidebars then were loaded to failure in bending. The results of this study show (a) that the carbon fiber rods were 15% stiffer than the stainless-steel tubes (p = 0.009) and (b) that the external fixator with carbon fiber rods achieved approximately 85% of the fixation stiffness of the external fixator with stainless-steel tubes. The loss of stiffness of the external fixator with carbon fiber rods is most likely due to the clamps being less effective in connecting the carbon fiber rods rigidly to the Schanz screws.

Biomechanical Phenomena↗
PubMed1996

A comparative biomechanical evaluation of a noncontacting plate and currently used devices for tibial fixation.

The appearance of porous bone under fixation plates during fracture healing, attributed to disturbance of blood supply by the plate, has led to new plate designs with reduced plate to bone contact. The fixation stability afforded by these devices, in comparison to implants commonly used for fixation, is not well known. Therefore, the construct stiffnesses of osteotomized synthetic tibiae fixed with dynamic compression plates, external fixators, or two configurations of noncontact plates were compared in axial compression, bending, and torsion with and without cortical contact at the osteotomy site. The results of this study show that (1) the noncontact plated constructs achieve comparable fixation rigidity to constructs using dynamic compression plates or external fixators, if applied at a distance no greater than 5 mm from the surface of the tibia, and (2) the fixation rigidity of the noncontact plate decreases as the distance between plate and bone surface increases.

Biomechanical Phenomena↗
PubMed1996

Posttraumatic osteonecrosis in a swine model. Correlation of blood cell flux, MRI and histology.

We used a miniature swine femoral neck fracture model to demonstrate the effects of the fracture on blood flow, histologic appearance, MRI signal and the development of posttraumatic osteonecrosis. The fracture was created and internally fixed in the right hip of 11 swine, with the left hip serving as the control. Femoral head blood flow via Laser Doppler Flowmetry and MRI data was examined for the experimental hip preoperatively, postoperatively and at 1, 2, 4 and 8 weeks postfracture. At 8 weeks, the animals were killed and the femoral heads were evaluated. Femoral head blood flow decreased immediately postfracture and continued to diminish with time. MRI signal intensities in the femoral head at 4 and 8 weeks were significantly less when the fixation failed than when it was intact. Histologic grades (0-14 points) and bone densities were 7.6 and 49%, respectively, on the experimental side, compared to 1.6 and 56% on the control side. Histologic grading, bone density values and blood flow data had no relation to changes in MRI signal intensity.

Animals↗
PubMed1996

Consistency of AO fracture classification for the distal radius.

We sought to quantify agreement by different assessors of the AO classification for distal fractures of the radius. Thirty radiographs of acute distal radial fractures were evaluated by 36 assessors of varying clinical experience. Our findings suggest that AO 'type' and the presence or absence of articular displacement are measured with high consistency when classification of distal radial fractures is undertaken by experienced observers. Assessors at all experience levels had difficulty agreeing on AO 'group' and especially AO 'subgroup'. To categorize distal radial fractures according to joint displacement and AO type is simple and reproducible. Our study examined only whether distal radial fractures could be consistently classified according to the AO system. Validation of the classification as a predictor of outcome will require a prospective clinical study.

Acute Disease↗
PubMed1995

Comparison of the effect of reamed and unreamed locked intramedullary nailing on blood flow in the callus and strength of union following fracture of the sheep tibia.

This study was performed to compare the effects of reamed and unreamed locked intramedullary nailing on blood flow in the callus and early strength of union in a fractured sheep tibia model. After the creation of a standardized short spiral fracture by three-point bending with torsion, each tibia was stabilized by the insertion of a locked intramedullary nail. Ten animals were allocated randomly into two groups: one that had reaming prior to nail insertion and one that did not. Blood flow was measured in real time with use of laser Doppler flowmetry. Endosteal perfusion was determined at the fracture site before and after nail insertion. Perfusion of the callus was measured at three locations (proximal diaphysis, fracture site, and distal diaphysis) and at three time intervals (2, 6, and 12 week follow-up). All animals were killed 12 weeks postoperatively, and the tibiae were tested to failure in four-point bending. Nailing with reaming resulted in a larger decrease in overall endosteal perfusion than nailing without reaming (p < 0.015). The presence or absence of reaming did not affect blood flow within fracture callus. Perfusion of callus was greatest at 6 weeks of follow-up. Bending strength and stiffness were the same in both groups at 12 weeks. The study demonstrated that perfusion of callus and early strength of union are similar following intramedullary nailing with or without reaming.

Animals↗
PubMed1995

Cortical bone perfusion in plated fractured sheep tibiae.

The limited contact dynamic compression plate and partial contact plate were designed to decrease contact with cortical bone in an attempt to decrease cortical ischemia, remodeling, and eventual porosis under the plate after use of standard dynamic compression plates. This study quantified cortical bone blood flow beneath the plate with these three different designs in a sheep tibia fracture model. In 18 skeletally immature sheep, the right tibia was fractured and then was internally fixed with an interfragmentary screw and a dynamic compression plate, limited contact dynamic compression plate, or partial contact plate. At 12 weeks, cortical bone perfusion was assessed with laser Doppler flowmetry in nine areas beneath the plate. The baseline (before fracture) cortical bone cell flux averaged 100 +/- 60 mV. After fracture, this decreased to 60 +/- 48 mV (p < 0.0003); immediately after plating, the perfusion averaged 29 +/- 25 mV (p < 0.01). Cortical bone perfusion then increased to 106 +/- 52, 165 +/- 71, and 163 +/- 71 mV at 2, 6, and 12 weeks after fracture (p < 0.001 for all when compared with values after plating). No significant differences in cortical perfusion were seen between the types of plate. Cortical porosity under the plate was assessed with digital density analysis of microradiographs of this region. No significant difference was seen between the types of plate in this analysis or in biomechanical and disulphine blue perfusion analysis. Thus, no significant advantage was seen for the new plate designs used in this model. This lack of advantage may be a result of the immature animals used in the study, the protocol for blood flow measurement, the invasive periosteal stripping employed to create the fracture, or all three. However, as advantages with the new plate designs have been seen in other studies, this area warrants further investigation.

Analysis of Variance↗
PubMed1995

Cost and effectiveness issues in care of injured patients.

Injury remains the leading public health problem in the United States in terms of cost and years of life lost. It is the number 1 cause of death and disability from birth to 44 years old, which is the most economically productive segment of our population. In the current environment of rapid-pace health care system reform at the state and national levels, trauma care systems have evolved at the forefront; regionalization, continuous quality improvement systems, designation/accreditation systems, registry databases, and cost-effectiveness evaluations are being implemented in many states. In most states, these systems remain immature, but the critical framework is in place. This article attempts to present the current state of cost of injury and effectiveness data, the status of trauma registries, and the evolution of functional outcome research in trauma care.

Health Status Indicators↗
PubMed1995

Fractures of the proximal part of the femur.

The orthopaedic surgeon has a multitude of internal fixation devices and techniques available for use in the treatment of subtrochanteric fractures of the proximal femur. The successful use of second-generation locking nails is technically demanding. Close attention to positioning of the patient, reduction of the fracture, placement of the guide-wire, and insertion of the nail and of the proximal and distal locking screws is mandatory. The newer, high-strength hip-screws allow good fixation of a fracture that extends into the piriformis fossa. If medial comminution is present, this technique is best performed in conjunction with indirect reduction and bone-grafting. With proper technique, these devices allow the surgeon to manage predictably a complex subtrochanteric fracture that previously had to be treated with traction or extensive dissection and with (frequently inadequate) internal fixation.

Adult↗
PubMed1994

Evaluation of a laser Doppler flowmetry implantable fiber system for determination of threshold thickness for flow detection in bone.

Laser Doppler flowmetry (LDF) with the use of a standard metal shafted probe, has been successfully used to study bone blood flow in a wide variety of settings. The use of the standard probe is limited by the requirement that the probe be replaced onto the bone surface or driven into the bone with a trocar. In response to this, a system of implantable, detachable fibers was developed. This system allows repeated measurement over time without repeated surgical manipulation of the area of interest. This study was performed to evaluate the implantable fiber system by determining threshold thickness for flow detection in bone. A flow chamber with perpendicular and end-on flow was designed to collect results under controlled conditions for flow detection. Threshold thickness for bovine cortical and cancellous bone samples was determined after sequentially grinding the specimens and placing them in the flow chamber. A 2% solution of latex circulated in the chamber and each specimen was exposed to both flow directions and both types of probe. The laser Doppler probe was able to detect flow by resting on top of the sample, with the latex on the other side of the sample. The results showed a significantly greater threshold thickness for the standard probes than for the implantable probes, and a significantly greater threshold thickness for trabecular bone than for cortical bone. Despite the reduced threshold thickness with the implantable fiber, this new system was able to consistently detect depth of perfusion of 80-90% of the values for the standard probe.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Cortical bone blood flow in reamed and unreamed locked intramedullary nailing: a fractured tibia model in sheep.

We compared the effects of reamed versus unreamed locked intramedullary nailing on cortical bone blood flow in a fractured sheep tibia model. A standardized spiral fracture was created by three-point bending with torsion, and each tibia was stabilized by insertion of a locked intramedullary nail. Eleven animals were randomized into two groups: one that had reaming before nail insertion and one that did not. Blood flow was measured in real time using laser Doppler flowmetry. Cortical bone perfusion measurements were made at three locations (proximal diaphysis, fracture site, distal diaphysis) and at eight time intervals (prefracture, postfracture, postreaming, postnail insertion, postlocking, and at 2-, 6-, and 12-week follow-up). All animals were killed at 12 weeks postoperatively. After reamed nail insertion, cortical bone perfusion was significantly decreased (p < 0.0009). After unreamed nail insertion, perfusion was decreased less (p < 0.003). Insertion of locking screws did not affect blood flow. Cortical bone perfusion was greater in the unreamed group at completion of the procedure (p < 0.011), at 2-week follow-up (p < 0.006) and at 6-week follow-up (p < 0.027). The findings suggest that cortical revascularization had occurred by 6 weeks in the unreamed group but not until 12 weeks in the reamed group. The study demonstrates that cortical circulation is spared to a greater degree by unreamed nailing. This may be advantageous in severe open tibial fractures where blood supply is already significantly compromised.

Animals↗
PubMed1994

Extramedullary skeletal traction for intramedullary femoral nailing.

The through-and-through forms of femoral skeletal traction that are often used during intramedullary nailing for femur fractures can present two problems: (a) impingement with the intramedullary nail, requiring repositioning of the traction pin intraoperatively under radiographic control, to a position that may not optimally control the fracture; and (b) the risk of contaminating the intramedullary canal that will soon contain the metallic fixation device, especially when placed in the emergency room or at the bedside. Two new forms of extramedullary skeletal femoral traction are presented. The pullout strength and optimal positioning of these devices on the distal femur were evaluated. The first form of extramedullary traction evaluated was the large AO/ASIF pinless clamp. The second form of extramedullary traction, the extramedullary skeletal clamp, was based on a modification of the Gardner-Wells tong. These two forms of skeletal traction were compared with standard tensioned Kirschner wire (K-wire) through-and-through traction. Six fresh-frozen distal femora from donors (average age 29 years) were used to test the three femoral traction devices. Five of these specimens were skeletally mature. A total of 38 pullout tests were conducted. The pullout strength of the tested devices was in the following descending order: (a) tensioned K-wire; (b) extramedullary skeletal clamp (in the optimal metadiaphyseal position, 77% the strength of the K-wire); and (c) large ASIF pinless clamp (in the optimal metaphyseal position, 46% the strength of the K-wire). The mode of failure for each device was cut out through or from the bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗