Trauma Basic Science Abstracts (Subscribe)

50) this.border=1" alt="Bioabsorbable Antibiotic Delivery System in the Treatment of Fractures and Infections Preliminary Report"> OTA 2002 Posters OTA 2002 Posters Poster #9 Basic Science *Bioabsorbable Antibiotic Delivery System in the Treatment of Fractures and Infections: Preliminary Report Bruce H. Ziran, MD (b-Wright Medical Corp); Wade R. Smith, MD (b-Wright Medical Corp); N. Rao, MD; Ronald A. Hall, MD; University of Pittsburgh Department of Orthopaedics, Pittsburgh, Pennsylvania, USA

50) this.border=1" alt="Classification System for Distraction Osteogenesis"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #5, 8:47 AM A Validated Classification System for Distraction Osteogenesis and Its Correlation with Outcome in Adolescent and Adult Limb Lengthening Ru Li; M. Saleh; Les Coulton, MD ; Orthopaedic and Traumatic Surgery Research Group; University of Sheffield, Sheffield, United Kingdom Purpose: We designed and validated a new classification system of distraction osteogenesis and correlated the classification with healing. Methods: A series of radiographs, taken throughout the process >from osteotomy to fixator removal, were investigated to define callus appearance and morphology. The study involved 92 patients with a mean age of 24.7 years (range, 14 to 56) and approximately 6200 radiographs (54 femoral, 71 tibial). The patients had completed limb lengthening with use of monolateral, circular, or hybrid external fixators. The mean distraction consolidation index (DCI) was 72 days/cm (SD ±42). The mean percentage length gained was 23% (SD ±19). The mean length gained was 6.5 cm (SD ±3.3). The radiographic features of the distraction osteogenesis were classified into 5 shapes and 10 classification types which reflected the density of callus in the distraction phase, early and late consolidation phase, and the callus distribution (sparse, homogenous, heterogeneous, and lucent). Results: The classification was validated by inter- and intraobserver studies. The interobserver agreement (Kappa value) between four observers for shape was 0.51 ( P <0.001), and classification type was 0.6 ( P <0.001). Outcome was defined by the DCI; two groups were identified: good outcome, DCI <80 days/cm, and poor outcome, DCI >80 days/cm. The occurrence of classification type in the healing process was analyzed by use of the odds ratio and indicated the likelihood of a poor versus a good outcome. Classification types 2, 6, and 9 were indicative of a good outcome, and types 5 and 7 were indicative of a poor outcome ( P <0.05). Conclusion: This classification system is a convenient abbreviated way of describing distraction osteogenesis that can be used in clinical orthopedics to monitor progress, guide the treatment process, estimate prognosis, and predict complications.

50) this.border=1" alt="Coating of Titanium Implants Increases Biomechanical Strength"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #2, 8:22 AM *BMP-2 Coating of Titanium Implants Increases Biomechanical Strength and Accelerates Bone Remodeling in Fracture Treatment: A Biomechanical and Histological Study on Rats Gerhard Schmidmaier, MD ; Britt Wildemann, MD; Felix Cromme, MD; F. Kandziora, MD; Norbert P. Haas, MD; Michael Raschke, MD; Trauma and Reconstructive Surgery-Charité, Campus Virchow, Humboldt-University of Berlin, Berlin, Germany (a-Charitè Hospital Research Support) Purpose: Bone morphogenetic protein-2 (BMP-2), a member of the TGF-beta superfamily, is known to stimulate osteogenic cells. In vivo studies have shown that BMP-2 delivered from collagen sponges enhances healing of fractures [Welch RD, J Bone Miner Res 1998, 13:1483-1490]. This application technique requires opening of the fracture and may have possible side effects due to the use of bovine collagen. A newly developed coating method for implants based on biodegradable poly(D,L-lactide) allows the incorporation of growth factors and the controlled release of these factors during the healing process without the need for further devices. The effect of BMP-2 (5% weight-to-volume ratio) locally released from coated intramedullary implants on fracture healing was investigated with biomechanical and histologic analysis in rats. Methods: A standardized closed fracture of the right tibiae of 5-month old Sprague Dawley rats ( N = 80) was performed with a fracture device (impulse p = 1.12 Ns). The fractures were intramedullarly stabilized with uncoated versus coated titanium K-wires. The following groups were examined: group I, implant uncoated, 28 days ( N = 20); group II, implant coated with PDLLA + rh-BMP-2, 28 days ( N = 20); group III, implant uncoated, 42 days ( N = 20); and group IV, implant coated with PDLLA + rh-BMP-2, 42 days ( N = 20). After fracture of the right tibiae, x-ray examinations (posteroanterior and lateral) were performed throughout the experimental period. After sacrifice of the animals, both tibiae were dissected for biomechanical torsional testing using a material testing machine (Zwick 1455, Ulm, Germany). For histologic and histomorphometric analyses, the tibiae were fixed and embedded in methylmetacrylate; 5-µm sections were prepared and stained with Safranin O/light green and v. Kossa. The histomorphometry of the calli was analyzed using an image analyzing system (Zeiss KS 400). Results: A progressed callus consolidation was demonstrated in the BMP-2-treated groups compared with the uncoated groups at both time points. The histomorphometric analysis demonstrated a progressed callus remodeling with significantly higher mineralization of the cortices and higher mineralization and less cartilage of the periosteal callus. After 4 and 6 weeks, the local application of BMP-2 demonstrated a significantly ( t -test, P <0.05) higher maximum load and torsional stiffness in the biomechanical testing compared with controls. Discussion: The results clearly demonstrated that the local application of BMP-2 from PDLLA-coated implants significantly accelerated fracture healing. Two time points were investigated to analyze the effect of the BMP-2 coating on the healing process. The biomechanical torsional testing after 28 and 42 days revealed a higher torsional stability compared with that of the control groups. These data were supported by the histomorphometric results. The callus treated with BMP-2 demonstrated a progressed remodeling with significantly higher mineralization and less cartilage compared with controls. Conclusion: These results are in accordance with other studies investigating the effect of BMP-2 on fracture healing. However, local administration of growth factors from coated osteosynthetic implants could reduce clinical problems in fracture treatment without opening of the fracture, implantation of further devices, injections with the risk of infection, or side effects caused by the carrier.

50) this.border=1" alt="Effect of Early Stability on Fracture Repair"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #1, 8:16 AM The Effect of Early Stability on Fracture Repair Theodore Miclau, III, MD ; Zachary Thompson, BS; Celine Colnot, PhD; Diane Hu, MD; Zena Werb, PhD; Jill Helms, DDS; S. Huang; University of California, San Francisco, San Francisco General Hospital, Department of Orthopaedic Surgery, San Francisco, California, USA Introduction : Fracture repair is an ideal context for addressing the fundamental questions underlying skeletal tissue regeneration, remineralization, and remodeling. Fractures heal by two mechanisms: endochondral and intramembranous ossification. In both cases, in response to locally increased levels of growth factors and cytokines, mesenchymal cells migrate to the wound site, where they differentiate into chondrocytes or osteoblasts. The mechanical environment influences this cell fate decision; motion at the site of injury is associated with the formation of a cartilage intermediate, whereas rigidly stabilized fractures appear to heal by the direct differentiation of mesenchymal cells into osteoblasts. Precisely how cells perceive and respond to changes in the local mechanical environment is unclear, and when this cell fate commitment is made is unknown. Purpose : Our goal was to ascertain the time frame in which cells become irreversibly committed to either chondrogenic or osteoblastic cell fates. We compared fracture healing in mice in which the bone segments were left unstable for varying amounts of time, then stabilized and allowed to heal. The extent to which the fractures healed through intramembranous or endochondral ossification was determined by molecular, cellular, and histological analyses. Methods : Fracture Technique: All protocols were approved by the Institutional Committee on Animal Research. Adult mice were anesthetized by intraperitoneal injection of Avertin. Closed transverse fractures were created through the left tibial diaphysis by three-point bending and were confirmed by radiography. Surgical procedure ( stabilized fractures ): After shaving, the proximal and distal metaphyses of the left tibia were transfixed with use of four 0.25-mm pins oriented perpendicular to the long axis of the tibia, 90° to each other. An external fixation pin was positioned, and after creation of the transverse fracture, the second ring was secured to the distal pins. A third threaded rod was placed through proximal and distal rings to provide further stability at the time of definitive fixation. Mice were allowed to ambulate freely, which typically occurred within 24 hours. Groups : Animals were divided into three groups: mice in which closed fractures were stabilized for the entire healing period; mice in which the fractures were unstable for 24 hours, then stabilized for the remaining healing period; and mice whose bone segments were left unstabilized for 48 hours, then stabilized for the remaining healing period. The mice were allowed to heal for 10 days after fracture. Molecular and Cellular Analyses : The fracture callus tissues were prepared for standard histological and molecular analyses, including immunohistochemistry (platelet endothelial cell adhesion molecule, PECAM) and in situ hybridization ( collagen type II, Col2 cartilage), ( collagen type X , col10 , hypertrophic cartilage), and ( osteocalcin, bone). Results : Fractures that were stabilized for the entire healing period generated new bone through the direct differentiation of mesenchymal cells into osteoblasts, as evidenced by the presence of osteocalcin , and the absence of collagen type IIa transcripts in mesenchymal cells at the site of injury. Similarly, the majority of fractures that were unstable for 24 hours also healed by intramembranous ossification. Histologic staining and in situ hybridization analyses indicated that mesenchymal cells expressed osteocalcin but not collagen type IIa at multiple time points after fracture. In contrast, most fractures that were left unstable for 48 hours healed through endochondral ossification. Discussion/Conclusion : These data strongly suggest that the mechanical environment exerts its influence on bone regeneration within the earliest days of fracture healing. The results of this study provide evidence that regulating the mechanical environment during the initial inflammatory phase influences the differentiation of mesenchymal stem cells to an osteogenic or chondrogenic cell fate. Within 48 hours of sustaining an injury, cells at the fracture site have begun to express molecular markers that indicate their ultimate differentiation into osteoblasts or chondrocytes. We are currently exploring the molecular signals that are involved in transducing these mechanical stimuli during the early stages of fracture repair.

50) this.border=1" alt="Growth Factor Expression in a New Atrophic Nonunion Model"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #6, 8:53 AM Growth Factor Expression in a New Atrophic Nonunion Model: Implications for the Treatment of Fractures Anita Reed, DPhil; Clive Joyner, DPhil; Harry Brownlow, FRCS Orth; Hamish Simpson, Prof/FRCS Orth ; Nuffield Department of Orthopaedic Surgery, University of Oxford, Oxford, United Kingdom Purpose: The presence and distribution of important growth factors such as TGF-b, FGF, PDGF and BMP 2/4 has not previously been documented during abnormal bone healing at both early and late time points. Therefore, the aims of this study were to develop and validate a clinically relevant small animal atrophic nonunion model and to test the hypothesis that growth factor expression is diminished in atrophic nonunions. Methods: Twenty-eight adult female Wistar rats underwent application of a novel circular-frame external fixator to the right tibia. The periosteum was removed from 14 of the 28 animals and the intramedullary canal was curetted. Both insults were performed proximally and distally for a distance equivalent to one diameter of the tibia. A -mm gap was introduced. Animals were sacrificed at 1, 3, 8, and 16 weeks. Paraffin sections were immunohistochemically stained for TGF-b, FGF basic, PDGF and BMP 2/4. Results: At 8 and 16 weeks, all animals in which stripping was performed went on to form an atrophic nonunion. Those in which stripping was not performed united successfully. The immunohistochemical results were as follows. At 1 week, positive staining was observed in the hematoma in both groups and in the new bone matrix of the healing group. At 3 weeks, staining was similar in the two groups, with most tissues continuing to express growth factors. At 8 weeks, the periosteum in the healing group no longer expressed TGF-b and BMP 2/4 as it began to remodel. The nonunion group continued to express all four growth factors. At 16 weeks, as the healing group remodeled, staining of growth factors became weaker in all tissues and cells. The fibrous tissue in the nonunion group appeared to be more weakly stained than at earlier time points. Conclusion: These results may have relevance for new therapies that can be aimed at delivering growth factors to treat fracture nonunions. At 1, 3, and 8 weeks, the nonunion group appeared to stain similarly to the healing group. At 16 weeks, however, consistent with our hypothesis, there was less staining of the fibrous tissue in the nonunion gap than at earlier time points. These results may suggest that, at 16 weeks, the fibrous tissue within the nonunion gap had reached a steady state. Therefore, this may be a suitable time for the delivery of growth factors to the nonunion site.

50) this.border=1" alt="Intracellular Staphylococcus Aureus"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #3, 8:28 AM Intracellular Staphylococcus Aureus : A Proposed Mechanism for the Indolence of Osteomyelitis J. Kent Ellington, MS ; Mitchel B. Harris, MD; Lawrence X. Webb, MD; Beth P. Smith, PhD; Thomas Smith, PhD; Kim Tan, PhD; Michael C. Hudson, PhD; Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA Purpose/Hypothesis: Staphylococcus aureus is the bacterial pathogen responsible for nearly 80% of all cases of human osteomyelitis. It has previously been demonstrated that this bacterium can invade and persist within the intracellular environment of the human osteoblast. To date, the fate of intracellular S. aureus after host cell (osteoblast) death has not been established. The hypothesis of this study was that intracellular S. aureus will survive the death of their host osteoblasts and retain the capacity to invade other osteoblasts. Methods: Normal human osteoblasts were purchased and propagated in cell media. After cells reached 80% confluence (5 to 9 days), they were washed in growth media and seeded into six- well plates. The osteoblasts were then maintained in growth medium. S. aureus was grown in tryptic soy broth, harvested by centrifugation, and resuspended. The osteoblast containers were then infected at a multiplicity of infection at 250:1 with S. aureus . Following incubation (45 minutes at 37° C), the cultures were washed, and gentamicin was added to kill the extracellular S. aureus (gentamicin cannot penetrate the eukaryotic cells). Two methods were subsequently used to release the intracellular microorganisms. First, detergent-based cell lysis techniques were used as the osteoblast cultures were washed, lysed (0.1% Triton X-100), and then transferred to tryptic soy agar (TSA) plates for overnight incubation and bacterial enumeration. The second method used 0.025% trypsin-0.01% edetic acid instead of detergent. The trypsinized cultures were then transferred to TSA plates (allowed to die because of a lack of nutrients) for overnight incubation and bacterial enumeration. Following both of these methodologies, the previously intracellular bacteria were quantified at time zero (45 minutes), 24, and 48 hours after infection. These bacteria were then harvested, grown overnight, and used to infect other sterile osteoblast cultures. Following infection, the osteoblast cultures were incubated in gentamicin to eliminate extracellular bacteria. The new osteoblast cultures were lysed or trypsinized and plated on TSA plates for bacterial enumeration. In an effort to determine whether the length of time the bacteria had been intracellular had an effect on their subsequent ability to re-invade osteoblasts, cultures infected with the bacteria recovered at 45 minutes and 24 hours were compared to control infected osteoblast cultures (infected with S. aureus that had not previously been intracellular). Results: Dying and dead osteoblast cultures release viable S. aureus equivalent to those lysed by detergent. The respective colony counts demonstrated no statistically significant differences at times 0, 24, or 48 hours. Also, there was no statistical difference in the number of recovered S. aureus between the control group and the previously intracellular S. aureus cultures. Discussion/Conclusion: Human osteoblasts whose membranes are lysed and those that undergo cell death are capable of releasing viable S. aureus . These bacteria (once released from their intracellular environment) are capable of re-infecting additional cultures of normal human osteoblasts. The results of this study suggest a potential cellular mechanism responsible for the indolent and evanescent nature of bone infection.

50) this.border=1" alt="Near Infra-red Spectroscopy in the Diagnosis of Acute Compartment Syndrome"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #8, 9:12 AM *Near Infra-red Spectroscopy in the Diagnosis of Acute Compartment Syndrome Matthew J. Hope, MRCSE ; Carol Hajducka, RN; Hamish Simpson, MD; Margaret M. McQueen, MD, FRCS; Royal Infirmary of Edinburgh, Edinburgh, United Kingdom (a-Hutchinson Technology) Purpose: Near-infrared spectroscopy (NIRS), which measures soft tissue oxygenation (StO 2 ) noninvasively, is potentially a new noninvasive technique for the early detection of acute compartment syndrome (ACS). Animal models of ACS have shown that StO 2 correlates with perfusion pressure in the compartment. The first part of this study examined intracompartmental pressure and StO 2 among patients at risk of ACS. The second part investigated the influence of subcutaneous and intramuscular hematoma on NIRS in an ACS animal model. Methods: 1) Adult patients with tibial or radial diaphyseal fracture or gross soft tissue swelling were recruited on admission to the orthopaedic trauma unit. Noninvasive and invasive monitoring were carried out from admission until a minimum of 24 hours postoperatively. The differential pressure (DDP) was calculated as the compartment pressure subtracted from the diastolic blood pressure. The threshold for fasciotomy was a 'DDP' <30mmHg. StO 2 values were simultaneously recorded from the contralateral (uninjured) limb at the same site. The difference between the StO 2 value on the injured and uninjured sides was calculated (StO 2 difference). 2) Fifteen adult pigs were divided into three equal groups: plasma infusion alone, plasma infusion with SC hematoma (15 ml of blood) and whole blood infusion (intramuscular hematoma). An ACS was induced under general anesthesia by the above infusion into the anterior compartment of one rear leg of each animal. On both legs noninvasive StO 2 and compartment pressure monitoring were carried out. The development of an ACS was confirmed by absence of muscle twitch on electrical stimulation. Fasciotomy was performed 30 minutes later. DDP and 'StO 2 difference' (calculated as above) were compared. Results: 1) Three patients with thigh swelling, 73 with tibial fracture, and 2 with forearm fracture were recruited.   Mean 'StO 2 difference'    (%)  Mean 'DDP'  (mmHg)  no fasciotomy ( N = 59)  10.0   P = 0.003  52.6   P < 0.001  fasciotomy ( N = 18, all leg)  -2.7    24.5   2) An acute compartment syndrome was confirmed in all animals. Correlation between DDP (mmHg) and 'StO 2 difference' (%)  Plasma infusion ( N = 5)   r = 0.754   P = 0.01  Plasma infusion + SC hematoma ( N = 5)   r = 0.004   P = 0.95  Intramuscular hematoma ( N = 4)   r = 0.516   P = 0.01 Discussion/Conclusion: The StO 2 difference (measured noninvasively) was significantly lower among patients with an ACS, suggesting that NIRS can detect decreasing tissue oxygenation in trauma patients who are developing an ACS. The animal study confirms a strong correlation between DDP (mmHg) and StO 2 difference (%) in a plasma infusion and an intramuscular hematoma model. This correlation was lost in the presence of a SC hematoma. We are optimistic that NIRS will prove to be a reliable new noninvasive technique for the early detection of an acute compartment syndrome. The localization and avoidance of areas of SC hematoma will improve the diagnostic accuracy of NIRS in acute compartment syndrome.

50) this.border=1" alt="OTA 2002 - Session 1"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #7, 9:06 AM The Effect of Muscle Contusion on Cortical Bone and Muscle Perfusion after Reamed Intramedullary Nailing: A Novel Canine Tibia Fracture Model Henry Koo, MD; Alex Tov, MD; Emil H. Schemitsch, MD, FRCS(C) ; St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada Purpose: High-energy tibia fractures are often associated with significant soft tissue injury. The appropriate management of these injuries remains controversial. Previous studies have assessed perfusion of the fractured tibia and surrounding soft tissues in the setting of a normal soft tissue envelope. The purpose of this study was to determine the effects of muscle contusion on blood flow to the tibial cortex and muscle during reamed intramedullary nailing of a tibia fracture. Methods: Eleven adult canines were randomized into two groups: contusion or no contusion. Under general anesthesia, the left tibia of each canine underwent segmental osteotomy followed by limited reaming and locked intramedullary nailing. Six of the eleven canines had the anterior muscle compartment contused, at the level of the osteotomy, in a standardized fashion. Laser Doppler flowmetry (LDF) was used to measure cortical bone and muscle perfusion during each step of the procedure. Repeat LDF measurements were taken of the cortical bone and muscle 11 weeks later. The animals were then killed. Results: Following a standardized contusion, muscle perfusion in the contusion group was higher than in the no-contusion group ( P = 0.0001). This difference was transient because muscle perfusion returned to normal levels by the end of the procedure. The hyperemic response was most profound within the zone of injury. Reaming did not increase muscle perfusion. Bone perfusion decreased to a larger extent in the contusion group after contusion and osteotomy ( P = 0.003). The difference between the two groups remained significant throughout the procedure. At 11 weeks, muscle perfusion was similar in both groups. Site-specific analysis did not reveal any differences between the sites or between the two groups. There was a sustained decrease in overall bone perfusion in the contusion group, at 11 weeks, compared with the no-contusion group ( P = 0.001). Discussion: The results of this study show that injury to a soft tissue envelope has regional effects on blood flow to the bone and muscle. The hyperemic response observed in the muscle of the contusion group was not sustained. Furthermore, the larger decrease in bone perfusion observed in the contusion group was sustained. One possible explanation for the unsustained hyperemia of the damaged muscle is vasodilation during the acute inflammatory response. However, due to severe damage to the tissue and vessels, a sustained response was not possible. This explanation could also account for the sustained decrease in tibial blood flow. Acutely, the local hyperemic response in the muscle could have diverted blood flow away from the bone. Chronically, a damaged and dysfunctional soft tissue envelope may be unable to provide support to the intraosseous circulation. Conclusion: The results of our study show that injury to the soft tissue envelope may have deleterious effects on fracture healing by decreasing intraosseous circulation. In addition, the positive effects of reaming on muscle perfusion, as shown in previous studies, seem to be compromised when the muscle itself is damaged. This finding may influence the method of fixation in tibia fractures associated with significant soft tissue injury.

50) this.border=1" alt="OTA 2002 Posters"> OTA 2002 Posters OTA 2002 Posters Poster #6 Basic Science Fixation of Proximal Humerus Fractures with Use of a Spiral Blade Intramedullary Nail System Augmented with Norian Cement Michael S. Wildstein, MD; Yuhei H. An, MD; Jeffrey M. Conrad, MD; David G. Everman, MD; Stan Kmiec; Jim M. Green; Kathleen A. Hogan, MD; Langdon A. Hartsock, MD; Medical University of South Carolina, Charleston, South Carolina, USA Purpose: The purpose of this study was to test the strength of the newly developed spiral blade intramedullary nail system (SBIN) when augmented with the bioabsorbable bone cement, Norian. Methods: Six pairs of sawbones and six pairs of fresh frozen cadaveric humeral bones from cadavers with an average age of 69 years (range, 55 to 82) were obtained. Radiographs showed significant osteoporotic changes in the cadaveric bones. An osteotomy was made in each bone to reproduce a Neer two-part humeral fracture. Fractures were reduced and fixed with the SBIN construct either with (experimental) or without (control) Norian augmentation. Bones underwent torsional testing to ultimate failure with use of a hydraulic mechanical testing system. Results: There was a statistically significant difference between the augmented and non-augmented sawbone groups (cemented, 1035 ± 338N; non-cemented, 454 ± 249N; P = 0.00056). In the cadaveric humeri, there was a trend toward increased ultimate load in the Norian augmented specimens (cemented, 527 ± 103 N; non-cemented, 342 ± 126 N; P = 0.07). Discussion: The SBIN system appears to be an effective method for fixation of Neer two-part fractures of the proximal humerus, particularly in osteoporotic bone. This fixation modality may therefore be particularly useful for patients with osteoporotic bone.

50) this.border=1" alt="Potentiation of Osteo and Angiogenesis in Vivo"> OTA 2002 - Session 1 Session I - Combined Session (International Society for Fracture Repair) Fri., 10/11/02 Combined Session, Paper #4, 8:41 AM Potentiation of Osteo- and Angiogenesis in Vivo after Implantation of Hydroxyapatite Combined with Autogenous Growth Factors Olaf Kilian, MD ; Sabine Wenisch; Ingo Flesch; Reinhard Schnettler; Department of Trauma Surgery, University of Giessen, Giessen, Germany Purpose: There is accumulating evidence that growth factors accelerate wound healing by stimulating matrix production and potentiating angiogenesis. Use of hydroxyapatite (HA) combined with autogenous growth factors purified from pig platelets was investigated to determine whether analogous effects of growth factors could be observed during early phases of fracture healing. Methods: In the experimental procedure, two cylindrical defects were created within the intercondylar region of the pig femoral condylus. The proximal defect was filled with HA and the distal, with HA enriched with growth factors. Results: Ten and 20 days after surgery the specimens were examined immunohistochemically and ultrastructurally. Antibodies to factor VIII, ED-A, and ED-B fibronectin, and to alpha smooth muscle actin have been used to study angio- and osteogenesis, especially the formation of granulation tissue. Even after 10 days, comparative immunohistochemical data revealed distinct differences between the use of HA and HA in combination with growth factors. There was a significant increase of neovascularization >from the application of growth factors, as demonstrated with factor VIII and ED-B fibronectin antibodies. Moreover, granulation tissue formation was accelerated. After 10 days, intense labeling for alpha smooth muscle actin and ED-A fibronectin could be observed only in combination with growth factors. Discussion: Fibronectin expression precedes alpha smooth muscle actin deposition. Due to the effects of growth factors there is activation of resident fibroblasts to synthesize ED-A fibronectin necessary for the induction of myofibroblasts or pericytes by growth factors. Additionally, a few ED-B positive areas of woven bone, including osteoblasts, could be identified within the defect area after 10 days of local treatment with growth factors. This finding was confirmed ultrastructurally. It could be shown that the cells responsible for accelerated degradation of the implant enriched with growth factors were multinucleated giant cells.

50) this.border=1" alt="Thermal Effects of Intramedullary Reaming"> OTA 2002 Posters OTA 2002 Posters Poster #5 Basic Science Thermal Effects of Intramedullary Reaming Madhav A. Karunakar, MD; Elizabeth P. Frankenburg, MS; T. Toan Le, MD; Janette Hall, MS; University of Michigan, Ann Arbor, Michigan, USA ( OTA/Smith + Nephew Grant)