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Biomedical subjects

J A Goulet

Publications and source records attributed to J A Goulet.

At least 19 recordsLinked to original sources
PubMed2000

Increased distraction rates influence precursor tissue composition without affecting bone regeneration.

The effect of increased distraction rate on bony tissue differentiation was studied using a paired bilateral model of rat femur lengthening. After a 6-day latency period, one randomly selected femur for each rat was distracted at 0.5 mm/day (normal rate) for 12 days, and the contralateral femur was distracted at 1.5 mm/day (increased rate) for 4 days. Femoral lengthening for each side was 6.0 mm, leaving the increased rate leg with an extra 8 days of consolidation compared with the normal rate limb. Group I rats (n = 9) were killed at day 18 postsurgery and analyzed for cartilage tissue composition and distribution. Group II rats (n = 7) were killed on day 36 postsurgery and analyzed by three-dimensional microcomputed tomography (MCT) for changes in new bone volume. Digital color analysis of slides stained with type II collagen antibody showed increases in cartilaginous tissue formation on the increased rate side (1.51 mm2 vs. 0.83 mm2; p = 0.10). No differences in new bone volume were detected between increased rate limbs and their contralateral controls (46.13 mm3 vs. 42.69 mm3; p = 0.63). These findings suggest that intermediate distraction rates may influence precursor tissue composition without affecting the final amount of new bone formed. Because damage to the tissue was not detected at either time point, these changes in chondrogenesis may reflect sensitivity of the pluripotential gap tissue to tension accumulation during lengthening. Future work with this in vivo model is focused on improving our understanding of the mechanisms behind this strain sensitivity.

Animals↗
PubMed1999

Marrow-derived progenitor cell injections enhance new bone formation during distraction.

Bilateral femoral distraction was performed in rats to investigate whether injections of marrow-derived mesenchymal progenitor cells could be used to facilitate new bone formation. The cells were isolated from whole marrow of 2-6-month-old Sprague-Dawley rats. One-year-old recipient Sprague-Dawley rats were divided into five experimental groups. Rats in groups I, II, and III received injections of mesenchymal progenitor cells on days 6 (beginning), 12 (middle), and 18 (end of distraction) after surgery, respectively. Those in group IV received injections of serum and carrier gel alone, and those in group V received no injections. Distraction zones were harvested at 36 days and analyzed for new bone volume within the distraction gap by three-dimensional microcomputed tomography. Significant increases in new bone volume were observed for femora injected with marrow-derived progenitor cells compared with contralateral femora and controls (no injection). The timing of the cell injections appeared to have no effect on the experimental outcome. Histologic analyses demonstrated active formation of new trabecular bone with marked osteoblastic activity and osteoid production. No qualitative differences in histologic appearances of new bone among rats in any of the five groups were seen. The results of in vitro lysis assays indicated that donor and recipient rats were not completely syngenic, leaving some doubt as to the reasons for observed increases in new bone formation. Future work will focus on attempting to repeat these experiments in a fully syngenic rat model. This rat distraction model can be used to explore the molecular and cellular behavior of these progenitor cells in a clinically relevant in vivo environment.

Animals↗
PubMed1999

Severity of injuries associated with traumatic hip dislocation as a result of motor vehicle collisions.

BACKGROUND: Previous reports have shown a high rate of associated injuries in patients who sustain traumatic hip dislocation. Since these earlier reports appeared, improvements have been made in passenger safety systems and the rate of restraint usage has increased. The purpose of this study was to review the associated injuries present in a current series of patients who sustained traumatic hip dislocation as a result of motor vehicle collisions. METHODS: We retrospectively reviewed our trauma registry and identified 66 patients who sustained traumatic hip dislocation as a result of motor vehicle collisions. Thirty patients (45%) were restrained and 36 (55%) were unrestrained. Airbags were known to have deployed in 14 cases. RESULTS: The incidence of associated injuries was 95% (63 patients). Orthopedic injuries alone were seen in 22 patients (33%), whereas associated injuries were seen in 44 patients (67%). Abdominal injuries were present in 10 patients (15%), thoracic injuries were present in 14 patients (21%), closed head injuries were present in 16 patients (24%), and craniofacial injuries were present in 14 patients (21%). Acetabular fractures were seen in 46 patients (70%), femoral head fractures were identified in 9 patients (14%), and other extremity fractures occurred in 26 patients (39%). The average Injury Severity Score for all patients was 17.4 (range, 9-59). The average Injury Severity Score of the restrained patients was not statistically different from that of the unrestrained patients (p = 0.491). CONCLUSION: Although improvements in automotive safety features and restraint usage have occurred since previous reports appeared, there continues to be a high rate of severe injuries associated with traumatic hip dislocation that occur in motor vehicle collisions. We believe that all patients who sustain traumatic hip dislocation warrant a general surgery trauma evaluation to rule out any potential associated injuries.

Accidents, Traffic↗
PubMed1999

Viscoelastic characterization of mesenchymal gap tissue and consequences for tension accumulation during distraction.

Nonlinear viscoelastic analysis was used to characterize the time-dependent behavior of mesenchymal gap tissue generated during distraction osteogenesis. Six (n = 6) lengthened tibiae were harvested from New Zealand white rabbits at 18 days. This gap tissue was subjected to a series of step displacement tests of increasing magnitude, and force relaxation behavior was monitored. Isochrones in stress-strain space were fit to odd cubic functions of strain. An analytic expression, linear in both e and e3, was developed to predict stress accumulation within the gap tissue as a function of time during distraction. Stress relaxation functions were described well by two-term Prony series. The two time constants determined from mechanical testing results were consistent, suggesting the presence of two fundamental physiologic relaxation processes. Gap tissue stresses were predicted to rise considerably during early stages of lengthening when distraction magnitudes exceeded the clinical norm of 0.25 mm. These differences in tension accumulation were less pronounced by the time lengthening was completed. Specifically, these results may in part explain clinical observations of decreased bone regeneration and altered tissue proliferation and differentiation at higher distraction rates. More generally, this work provides a framework for the rigorous characterization of the viscoelastic properties of biologic tissues ordinarily exposed to step strains.

Animals↗
PubMed1999

Reduced gap strains induce changes in bone regeneration during distraction.

A bilateral New Zealand white rabbit model of distraction osteogenesis (DO) was used to investigate the relationship between strain environment and bone regeneration during limb lengthening. In seven (n = 7) rabbits, a stiffener was applied to the fixator on one side to reduce strains within the gap tissue after lengthening was completed. Animals were euthanized six days later and their distraction zones were harvested and analyzed for changes in new bone volume and architecture. Nonlinear finite element analyses (FEA) were performed to predict changes in the gap strain environment. FEA results predicted a nearly uniform sevenfold decrease in average strain measures within the distraction zone. No change in total average new bone volume and significant decreases in both bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) were observed in tibiae in which gap strains were reduced experimentally, compared to contralateral controls. These results suggest that fixator stiffening influenced the architecture but not the amount of newly formed bone. This animal model of distraction might be used to study the mechanisms by which strain fields affect events in bone repair and regeneration, such as cell proliferation, precursor tissue differentiation, and altered growth factor and nutrient delivery to tissues.

Animals↗
PubMed1999

Temporal and spatial characterization of regenerate bone in the lengthened rabbit tibia.

A rabbit model of bilateral tibial lengthening was used to investigate temporal and spatial changes in new bone volume and architecture during regenerate bone formation. Tibiae were lengthened 9.0 mm at 0.75 mm/day after a 6-day latency period. Animals were euthanized at four time points, and new bone volume and architecture within the distraction gap were assessed by microcomputed tomography and histomorphometry. New bone formation began before day 18 postsurgery and increased markedly between day 18 (completion of distraction) and day 24. This period of high bone formation activity might therefore be optimal for biologic and mechanical interventions aimed at enhancing bone regeneration. Regions of both endochondral and intramembranous bone formation were observed throughout the consolidation period. Significant increases in bone volume fraction were observed early in the consolidation period and were attributed to significant increases in trabecular thickness. This suggested that increased mineral density in the gap tissue with time was a consequence of increased osteoblast activity and associated trabecular thickening. New bone formation was shown to be highly oriented toward the distraction axis throughout lengthening. More bone formed consistently in lateral and proximal regions of the distraction gap, perhaps due to improved blood supply or progenitor cell availability in these areas. No differences in trabecular architecture were detected between regions having more or less bone volume, suggesting that bony tissue differentiation in all regions of the distraction gap was similar. Homotypical variations in measures of bone architecture were small; thus, these outcome variables seem appropriate for determining the effects of biological and mechanical interventions on bone regeneration in this animal model.

Animals↗
PubMed1998

Evaluation of the mechanical environment during distraction osteogenesis.

Physical forces have been hypothesized to direct the process of bone regeneration during distraction osteogenesis. However, despite significant clinical experience, relatively little is known about how the mechanics of distraction influence bone formation. This study investigated net fixator forces and strains in the distraction callus during bilateral lengthening of tibiae in New Zealand White rabbits. Distractions yielded a classic viscoelastic response with a sharp increase in fixator force, followed immediately by significant relaxation. Tension acting on mesenchymal gap tissue caused by distraction was estimated to reach more than 30 N by the time full lengthening was achieved. Average maximum cyclic strains within the distraction zone during ambulation were estimated to be 14% to 15% and supported by the results of fluoroscopic imaging. Paradigms for fracture healing have hypothesized that such strains are incompatible with new bone formation. The documented clinical success of distraction osteogenesis at stimulating large volumes of new bone suggests that other mechanisms that warrant additional investigation may be at work during distraction.

Animals↗
PubMed1998

Bone regeneration and fracture healing. Experience with distraction osteogenesis model.

The relation between physical forces and the processes of bone regeneration and healing remains incompletely understood. Gaps in understanding of these processes stem in part from models that produce inadequate amounts of new bone for study. Bone created through the use of distraction osteogenesis provides an attractive substrate for the study of mechanical forces and their effects on bone formation because this technique produces large volumes of new bone in a controlled fashion. The optimal mechanical environment in which bone formation occurs clinically has not been fully determined. In laboratory studies, however, the mechanical environment can be manipulated, and resultant changes in bone formation can be measured. To investigate how changes in strain environment influence patterns of bone formation, a bilateral New Zealand White rabbit model of bilateral distraction osteogensis was implemented. When a stiffener was applied to the external distractor, computation analyses predicted a sevenfold to eightfold decrease in all strain measures. These reductions in gap strains appeared to induce significant decreases in bone volume fraction and mean trabecular thickness. When osteotomies were created at a 30 degrees angle to the bony axis to generate more shear within the gap tissue, changes in the distribution of gap strains and resultant new bone architecture were observed. Specific correlations between changes in tissue level strains and the pattern of bone regeneration were seen in both experiments. These results provide direct in vivo evidence that pluripotential gap tissues are sensitive to their physical surroundings. Mechanisms responsible for this sensitivity might include vascularity, stem cell supply, and scaffolding architecture. The process of bone formation in distraction osteogenesis appears to be related to bone formation processes associated with more common conditions. The distraction osteogenesis model described suggests a mechanism for bone formation that seems applicable to other more common processes associated with bone formation, including fracture healing and impaired fracture healing.

Adult↗
PubMed1997

Extracorporeal life support for patients with significant orthopaedic trauma.

Extracorporeal life support is a therapeutic modality that can provide cardiorespiratory support for multiply injured patients. Fourteen patients with multiple trauma who sustained pelvic or long bone fractures were referred for treatment with extracorporeal life support at the University of Michigan Medical Center. All patients were considered morlbund secondary to their pulmonary injury. Six of the 14 patients had bilateral pulmonary contusions. The mean Injury Severity Score was 19. Twelve of the 14 patients had femoral or pelvic fractures or both. Eight patients had orthopaedic injuries initially treated with traction. The most common complication during extracorporeal life support management was bleeding, which occurred in eight of 14 patients. Eight of the 14 patients survived. Seven of eight patients with less than 6 days of mechanical ventilation before initiation of extracorporeal life support survived. Only one of six patients with six or more days of mechanical ventilation before initiation of extracorporeal life support survived. Patients with significant orthopaedic trauma and severe pulmonary compromise have an extremely high mortality risk. Appropriate aggressive fracture management remains the most important intervention to decrease the risk of pulmonary compromise. Early initiation of extracorporeal life support can be an additional lifesaving intervention in select patients with orthopaedic trauma who have respiratory failure refractory to conventional mechanical ventilation.

Adolescent↗
PubMed1997

Autogenous iliac crest bone graft. Complications and functional assessment.

Functional outcomes and complications experienced by adult patients who underwent iliac crest bone grafting were evaluated to assess the effect of bone grafts on patient function. In addition to retrospective chart reviews, patients completed the Sickness Impact Profile and a detailed questionnaire on pain. One hundred ninety-two patients met study inclusion criteria. Major complications were recorded in four (2.4%) patients in whom infections developed requiring readmission. Thirty-seven (21.8%) patients had minor complications. One hundred nineteen of 170 patients were available for followup; of these 119 patients, 87 (73.1%) returned completed questionnaires. Thirty-three of 87 (37.9%) patients reported pain 6 months postoperatively. The incidence of pain decreased with time, with 16 of 87 (18.7%) patients continuing to report pain more than 2 years postoperatively. Proportionately more spine patients reported pain at all time points. The mean Sickness Impact Profile score for patients completing questionnaires was nine, suggesting most patients were functioning well 2 years postoperatively. The morbidity of iliac crest grafting remains substantial. Pain symptoms in this study sample seemed to last longer in more patients than earlier series have indicated. Minimizing muscle dissection around donor sites and the advent of bone graft substitutes may help alleviate these problems.

Activities of Daily Living↗
PubMed1997

Hip screw augmentation with an in situ-setting calcium phosphate cement: an in vitro biomechanical analysis.

OBJECTIVES/HYPOTHESIS: This study was performed to determine whether a new, in situ-setting calcium phosphate cement would have sufficient mechanical integrity to reinforce compression screw fixation of unstable intertrochanteric fractures. We compared the cut-out resistance of screws augmented with calcium phosphate cement to the cut-out resistance of screws augmented with polymethylmethacrylate (PMMA). We used PMMA as the standard for comparison because it is currently used clinically. Our hypothesis was that initial fixation strength with PMMA and calcium phosphate cement augmentation would not be significantly different from one another. STUDY DESIGN: Cut-out testing of compression hip screws in paired human cadaveric proximal femurs was performed before and after augmentation with PMMA or calcium phosphate cement. Bilateral testing was performed to allow pairwise comparisons of the materials used for augmentation, and repeated testing was done to provide an internal control for the effects of bone quality. The initial fixation of screws augmented with calcium phosphate cement was compared with that of screws augmented with PMMA. METHODS: Ten paired human femurs (mean age, 75 +/- 9.2 years) were implanted with Richards AMBI compression hip screws. Basicervical osteotomies were then performed, yielding isolated proximal fragments for mechanical testing. Preaugmentation cut-out tests were performed under displacement control, with cut-out continuing to five millimeters at two millimeters per second. The screws were then removed, and the screw tracks were filled with 2.0 cubic centimeters of PMMA (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted and the cements were allowed to harden for twenty-four hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the initial fixation strength of screws augmented with calcium phosphate cement was compared with the initial fixation strength of screws augmented with PMMA using a two-way repeated measures analysis of variance. RESULTS: The cut-out behavior of screws augmented with calcium phosphate cement was not significantly different from the cut-out behavior of screws augmented with PMMA. With calcium phosphate cement, yield strength increased by 15.8 percent (from 1,354 +/- 632 newtons to 1,568 +/- 320 newtons); with PMMA, the yield strength increased by 26.8 percent (from 1,477 +/- 526 newtons to 1,834 +/- 225 newtons). However, only the increase with PMMA augmentation was significant at p < 0.05). The energy to yield increased significantly (41 percent, p < 0.05) with both types of augmentation (from 2,399 +/- 1,186 newton-millimeters to 3,378 +/- 857 newton-millimeters for calcium phosphate cement, and from 2,635 +/- 1,113 newton-millimeters to 3,741 +/- 426 newton-millimeters for PMMA), whereas the stiffness increased only slightly with PMMA augmentation (6.2 percent, from 481 +/- 180 newtons per millimeter to 511 +/- 92 newtons per millimeter) and fell slightly with calcium phosphate cement augmentation (10 percent, from 457 +/- 201 newtons per millimeter to 411 +/- 663 newtons per millimeter). CONCLUSIONS: The in situ-setting calcium phosphate cement investigated in this study compared favorably with PMMA in a single-cycle cut-out test of augmented compression hip screws in senile trabecular bone. Our results suggest that these materials may have promise as substitutes for PMMA in the salvage of compression hip screw fixation in elderly osteopenic patients with complex intertrochanteric fractures and that further study of their use in this application is warranted.

Aged↗
PubMed1994

The use of ultrasound mean acoustic attenuation to quantify bone formation during distraction osteogenesis performed by the Ilizarov method. Preliminary results in five dogs.

RATIONALE AND OBJECTIVES: Management of distraction during Ilizarov limb lengthening remains primarily clinical and empirical. Estimates of tissue acoustic attenuation were evaluated for their ability to quantify bone formation within the distraction gap. METHODS: Five dogs had tibias lengthened by the method of Ilizarov. Mean acoustic attenuation measurements at multiple positions across the distraction gap were compared with corresponding x-ray computed tomography attenuation measurements. RESULTS: Computed tomography and ultrasound attenuation displayed similar quantitative behavior across the gap. Linear correlation between them ranged from R2 = .878 to R2 = .131. Fibrous interzone width estimates based on computed tomography and ultrasound attenuation measurements were correlated, based on our preliminary data with R2 = .519. These estimates are independent of the width of distraction. CONCLUSIONS: Ultrasound parallels computed tomography as a measure of bone formation within the distraction gap. Future studies are needed to improve acoustic attenuation data acquisition techniques and to evaluate their potential as a tool for optimizing early distraction rates in patients at risk for rate-related complications.

Acoustics↗
PubMed1994

Mortality after fracture of the hip in patients who have end-stage renal disease.

Thirteen fractures of the hip in twelve patients who had end-stage renal disease were treated over a ten-year period; these injuries included one intertrochanteric fracture, seven non-displaced fractures of the femoral neck, and five displaced fractures of the femoral neck. Twelve of the thirteen fractures were treated with an operation. Six patients (who had a total of six fractures) died within one year after the fracture. Two patients died as the result of sepsis related to the wound; the other four deaths were not directly related to the operation. Although the mortality rate in this group of patients was higher than that in a group of matched patients who had a fracture of the hip but who did not have end-stage renal disease, we were not able to demonstrate that this difference was significant, perhaps because of the small size of the sample. The mortality rate in these twelve patients was significantly higher, however, than that in matched patients who had end-stage renal disease but who did not have a fracture of the hip (p = 0.01).

Adult↗
PubMed1994

Comminuted fractures of the posterior wall of the acetabulum. A biomechanical evaluation of fixation methods.

Reproducible simple fractures and osteotomies of the posterior wall of the acetabulum were created in twenty paired hemipelves from fresh human cadavera. Comminution was created with an additional fracture line that was either parallel (concentric comminution) or perpendicular (transverse comminution) to the posterior rim of the acetabulum. Under simulated weight-bearing, the stiffness of fixation of the transversely comminuted fractures that had been achieved with use of a reconstruction plate and screws was significantly higher than that achieved with fixation with screws alone (p < 0.05). The load to failure of the fixation of transversely comminuted fractures treated with a reconstruction plate and screws was also significantly higher than that of fixation of such fractures with screws alone (p = 0.05). The load to failure of the fixation of concentrically comminuted fractures was significantly higher when a reconstruction plate and accessory spring plates had been used than when a reconstruction plate alone had been employed (p < 0.05).

Acetabulum↗
PubMed1993

Physical therapy management of patients undergoing limb lengthening by distraction osteogenesis.

Limb lengthening by distraction osteogenesis and external fixation is used increasingly in the United States for a variety of orthopaedic conditions. Maintenance of joint motion, critical for successful outcomes, can be difficult to achieve. The rate of growth needed for distraction osteogenesis is faster than that of normal growing bone. Histogenesis of soft tissues must also occur to maintain the motion in joints above and below the limb being lengthened. Physical therapists in patients' home communities need to be knowledgeable about the aggressive management needed to prevent the loss of joint motion. This article introduces physical therapists to a commonly used external fixator, the procedure of distraction osteogenesis, and the role of functional loading. To assist in treatment planning, a physical therapy management plan is presented. Two case examples illustrate how therapists can assess a patient's status relative to the goals in the management plan and determine intervention priorities.

Adolescent↗