Timing of venous thromboembolism prophylaxis initiation and complications in polytrauma patients with high-risk bleeding orthopedic interventions: A nationwide analysis.

INTRODUCTION: There are no clear recommendations for the perioperative timing and initiation of venous thromboembolism pharmacologic prophylaxis (VTEp) among polytrauma patients undergoing high-risk bleeding orthopedic operative intervention, leading to variations in VTEp administration. Our study examined the association between the timing of VTEp and VTE complications in polytrauma patients undergoing high-risk operative orthopedic interventions nationwide. METHODS: We performed a retrospective cohort study of trauma patients 18 years or older who underwent high-risk bleeding operative orthopedic interventions for pelvic, hip, and femur fractures within 24 hours of admission at American College of Surgeons-verified trauma centers using the 2019-2020 American College of Surgeons Trauma Quality Improvement Program databank. We excluded patients with a competing risk of nonorthopedic surgical bleeding. We assessed operative orthopedic polytrauma patients who received VTEp within 12 hours of orthopedic surgical intervention compared with VTEp received beyond 12 hours of intervention. The primary outcome assessed was overall VTE events. Secondary outcomes were orthopedic reinterventions within 72 hours after primary orthopedic surgery, deep venous thromboembolism, and pulmonary embolism rates. RESULTS: The study included 2,229 patients who underwent high-risk orthopedic operative intervention. The median time to VTEp initiation was 30 hours (interquartile range, 18-44 hours). After adjustment for baseline patient, injury, and hospital characteristics, VTEp initiated more than 12 hours from primary orthopedic surgery was associated with increased odds of VTE (adjusted odds ratio, 2.02; 95% confidence interval, 1.08-3.77). Earlier initiation of prophylaxis was not associated with an increased risk for surgical reintervention (hazard ratio, 0.90; 95% confidence interval, 0.62-1.34). CONCLUSION: Administering VTEp within 24 hours of admission and within 12 hours of major orthopedic surgery involving the femur, pelvis, or hip demonstrated an associated decreased risk of in-hospital VTE without an accompanying elevated risk of bleeding-related orthopedic reintervention. Clinicians should reconsider delays in initiating or withholding perioperative VTEp for stable polytrauma patients needing major orthopedic intervention. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level III.

Statistical fragility analysis of reported outcomes associated with surgical management of acetabular labral pathology.

INTRODUCTION: The purpose of this study was to analyse the robustness of comparative research that evaluated arthroscopic labral reconstruction versus other surgical management of labral pathology. Key measures of statistical fragility include the fragility index and fragility quotient.ß. METHODS: 12 comparative studies that evaluated the use of arthroscopic labral reconstruction were included in this study. Particular attention was placed on evaluating trends, either statistically significant or not, of functional improvement, complication rates, need for total hip arthroplasty (THA) and revision rates with associated p-values. The analysis involved in this study was the Fragility Index, which is the median number of events required to change the statistical significance of a particular outcome, thus changing the study conclusions. Fragility quotient was calculated for each study as the fragility index divided by sample size. RESULTS: Of the 12 studies that were included for analysis, there were a total of 25 reported outcomes, 8 of which were statistically significant (p < 0.05). The statistical fragility for the significant outcomes were 2.5 (interquartile range [IQR]: 1.5-3.5), whereas the median statistical fragility for insignificant results was 6 (IQR 4-9). The overall fragility index was 4 (IQR 3-7). The median of fragility quotients was 0.04 (IQR 0.01-0.07). CONCLUSIONS: This study demonstrated that comparative research regarding arthroscopic techniques of labral reconstruction may not be as statistically stable as previously hoped. In many of the reported outcomes, particularly the ones that were statistically significant, only a small percentage of event changes was required to change the significance of the study conclusions. This fragility is worrisome, since clinical decisions that rely on these reported outcomes may have a significant impact on long-term patient outcomes. It is, therefore, crucial to optimise patient outcomes by incorporating past literature and reported outcomes.

Do All Fractures Need Surgery?

Common fractures managed by orthopaedic surgeons include ankle fractures, proximal humerus fractures in patients older than 60 years, humeral shaft fractures, and distal radius fractures. Recent trends indicate that surgical management is the best option for most fractures. However, there is limited evidence regarding whether most of these fractures need surgery, or whether there is a subset that could be managed without surgery, with no change in outcomes, or even possibly having improved results with lower complication rates with nonsurgical care.

Postoperative Complications of Hip Fractures Patients on Chronic Coumadin: A Comparison Based on Operative International Normalized Ratio.

In current clinical practice, orthopedic surgeons often delay the surgery intervention on geriatric hip fracture patients to optimize the international normalized ratio (INR), in order to decrease the risk of postoperative hematological complications. However, some evidence suggests that full reversal protocols may not be necessary, especially for patients with prior thromboembolic history. Our study aims to compare the surgical outcomes of patients with normal versus elevated INR values. We conducted a retrospective chart review on 217 patients who underwent surgeries on hip fractures at two academic trauma centers. We found that in our group (n = 124) of patients with an INR value of 1.5-3.0, there was only one reoperation for a hematoma, but there was a trend for more blood transfusions. There was no statistically significant difference in the odds of reoperation or overall complications. Nevertheless, there were significantly more events of postoperative anemia in this high INR patient group.

Surgical Hip Dislocation for Small Posterior Wall Fracture After Hip Subluxation.

This case demonstrates a recognized association between an acetabular injury pattern and underlying morphology of the hip. In the patient discussed, hyperflexion of the hip results in the engagement of the present CAM lesion, and the resulting subluxation leads to a fracture of the posterior wall and instability of the hip. This combination of pathologies was addressed with a surgical dislocation approach to address both the CAM lesion and fix the posterior wall.

The Past, Present, and Future of Orthopedic Education: Lessons Learned From the COVID-19 Pandemic.

The COVID-19 global pandemic has upended nearly every medical discipline, dramatically impacted patient care and has had far-reaching effects on surgeon education. In many areas of the country, elective orthopedic surgery has completely stopped to ensure that resources are available for the critically ill and to minimize the spread of disease. COVID-19 is forcing many around the world to re-evaluate existing processes and organizations and adapt to carry out business, of which medicine and education are not immune. Most national and international orthopedic conferences, training programs, and workshops have been postponed or canceled, and we are now critically evaluating the delivery of education to our colleagues as well as residents and fellows. This article describes the evolution of orthopedic education and significant paradigm shifts necessary to continue to teach ourselves and the future leaders of our noble profession.

Patient Outcomes Following Total Joint Replacement Surgery: A Comparison of Hospitals and Ambulatory Surgery Centers.

BACKGROUND: For several years, many orthopedic surgeons have been performing total joint replacements in hospital outpatient departments (HOPDs) and more recently in ambulatory surgery centers (ASCs). In a recent shift, the Centers for Medicare and Medicaid Services began reimbursing for total knee replacement surgery in HOPDs. Some observers have expressed concerns over patient safety for the Medicare population particularly if Centers for Medicare and Medicaid Services extends the policy to include total hip replacement surgery and coverage in ASCs. METHODS: This study used a large claims database of non-Medicare patients to examine inpatient and outpatient total knee replacement and total hip replacement surgery performed on a near-elderly population during 2014-2016. We applied propensity score methods to match inpatients with ASC patients and HOPD patients with ASC patients adjusting for risk using the HHS Hierarchical Condition Categories risk adjustment model. We conducted statistical tests comparing clinical outcomes across the 3 settings and examined relative costs. RESULTS: Readmissions, postsurgical complications, and payments were lower for outpatients than for inpatients. Within outpatient settings, readmissions and postsurgical complications were lower in ASCs than in HOPDs but payments for ASC patients were higher than payments for HOPD patients. CONCLUSION: Our findings support the argument that outpatient total joint replacement is appropriate for select patients treated in both HOPDs and ASCs, although in the commercially insured population, the latter services may come at a cost. Until further study of outpatient total joint replacement in the Medicare population becomes available, how this will extrapolate to the Medicare population is unknown.

The first MICCAI challenge on PET tumor segmentation.

INTRODUCTION: Automatic functional volume segmentation in PET images is a challenge that has been addressed using a large array of methods. A major limitation for the field has been the lack of a benchmark dataset that would allow direct comparison of the results in the various publications. In the present work, we describe a comparison of recent methods on a large dataset following recommendations by the American Association of Physicists in Medicine (AAPM) task group (TG) 211, which was carried out within a MICCAI (Medical Image Computing and Computer Assisted Intervention) challenge. MATERIALS AND METHODS: Organization and funding was provided by France Life Imaging (FLI). A dataset of 176 images combining simulated, phantom and clinical images was assembled. A website allowed the participants to register and download training data (n = 19). Challengers then submitted encapsulated pipelines on an online platform that autonomously ran the algorithms on the testing data (n = 157) and evaluated the results. The methods were ranked according to the arithmetic mean of sensitivity and positive predictive value. RESULTS: Sixteen teams registered but only four provided manuscripts and pipeline(s) for a total of 10 methods. In addition, results using two thresholds and the Fuzzy Locally Adaptive Bayesian (FLAB) were generated. All competing methods except one performed with median accuracy above 0.8. The method with the highest score was the convolutional neural network-based segmentation, which significantly outperformed 9 out of 12 of the other methods, but not the improved K-Means, Gaussian Model Mixture and Fuzzy C-Means methods. CONCLUSION: The most rigorous comparative study of PET segmentation algorithms to date was carried out using a dataset that is the largest used in such studies so far. The hierarchy amongst the methods in terms of accuracy did not depend strongly on the subset of datasets or the metrics (or combination of metrics). All the methods submitted by the challengers except one demonstrated good performance with median accuracy scores above 0.8.

Outcomes after plating of olecranon fractures: A multicenter evaluation.

INTRODUCTION: The aim of this study was to report the physical and functional outcomes after open reduction internal fixation of the olecranon in a large series of patients with region specific plating across multiple centres. PATIENTS/METHODS: Between January 2007 and January 2014, 182 consecutive patients with a displaced olecranon fracture treated with open reduction internal fixation were included in this study. Retrospective review across four trauma centres collected elbow range of motion, DASH scores, hardware complications, and hardware removal. Postoperative visits in the outpatient clinic were at two, six, and twenty-four weeks. After 24 weeks, patients were eligible for hardware removal if symptomatic. All patients were contacted, at least 1 year following surgery, to determine if hardware was removed. RESULTS: 182 patients (75 women, 105 men) average age 50 (16-89) with 162 closed and 19 open displaced olecranon fractures were treated with one region specific plate. Nineteen were lost to followup leaving 163 for analysis with all patients united. The most common deficiency was a lack of full extension with 39% lacking at least 10° of extension. Hardware was asymptomatic in 67%, painful upon leaning in 20%, and restricted activities in 11% resulting in a 15% rate of hardware removal. Hardware complaints were more common if a screw was placed in the corner of the plate (P=0.004). When symptomatic, the area of the plate that was bothersome encompassed the whole plate in 39%, was at the edge of the plate in 33%, and was a screw head in 28%. The DASH scores, collected at final follow-up of 24 weeks, was 10.1±16, indicating moderate disability was still present. Patients who lacked 10° of extension had a DASH of 12.3 as compared with 10.5 for those with near full extension, but this was not significant (P=0.5). CONCLUSION: Plating of the olecranon leads to predictable union. The most common complication was lack of full extension with 39% lacking more than 10°, although this did not have any effect on DASH scores. Overall results indicate that disability still exists after 6 months with an average DASH score of 10. LEVEL OF EVIDENCE: Therapeutic level III.

Healing Time and Complications in Operatively Treated Atypical Femur Fractures Associated With Bisphosphonate Use: A Multicenter Retrospective Cohort.

OBJECTIVES: The purpose of this study was to characterize demographics, healing time, and complications of a large series of operatively treated atypical femur fractures. DESIGN: Retrospective multicenter review. SETTING: Seventeen academic medical centers. PATIENTS: Bisphosphonate-related fractures as defined by American Society of Bone and Mineral Research. Fractures had to be followed for at least 6 months or to union or revision. INTERVENTION: Operative treatment of bisphosphonate-related fracture. MAIN OUTCOME MEASUREMENTS: Union time and complications of treatment, as well as information about the contralateral limb. RESULTS: There were 179 patients, average age 72, average body mass index 27.2. Average follow-up was 17 months. Twenty-one percent had a previous history of fragility fracture; 34% had prodromal pain. Most (88%) lived independently before injury. Thirty-one percent had radiographic changes suggesting stress reaction. Surgical fixation was with cephalomedullary nail (51%), IM nail (48%), or plate (1%). Complications included death (4), PE (3), and wound infection (6). Twenty (12%) patients underwent revision at an average of 11 months. Excluding revisions, average union time was 5.2 months. For revisions, union occurred at an average of 10.2 months after intervention. No association was identified between discontinuation of bisphosphonates and union time (P = 0.5) or need for revision (P = 0.7). Twenty-one percent sustained contralateral femur fractures; 32% of these had pain and 59% had stress reaction before contralateral fracture. CONCLUSIONS: In this series, surgery had a 12% failure rate and delayed average time to union. Twenty-one percent developed contralateral femur fractures within 2 years, underscoring the need to evaluate the contralateral extremity. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The Clinical and Economic Impact of Preoperative Transthoracic Echocardiography in Elderly Patients with Hip Fractures.

PURPOSE: The purpose of this study was to evaluate preoperative transthoracic echocardiography (TTE) on cardiac intervention, length of stay (LOS), inpatient mortality, and costs. METHODS: A retrospective series of 43 preoperative TTE and 161 non-TTE (control) hip fracture patients (> 65 years) was reviewed. The data collected included ASA score, comorbidities, indication for TTE, perioperative cardiac intervention, LOS, inpatient mortality, and cost. RESULTS: One of 43 (2.4%) (TTE) had a cardiac intervention (PTCA/CABG). Zero interventions occurred in the control group. The average time to operation was 1.5 days (TTE) and 0.93 days (control) (p < 0.001). The average LOS was 7.2 days (TTE) and 6.0 days (control), (p = 0.04). Patients (American Society of Anesthesiologists Physical Status Classification 3 and 4 patients), LOS was 7.3 days (TTE) and 6.3 days (control) (p = 0.18). Inpatient mortality was 2.3% (TTE) and 3% (control) (p = 0.493). There was no correlation between TTE and anesthesia. Hospital costs were different between groups (TTE $24,445 and control $18,429, p = 0.02). CONCLUSIONS: Preoperative TTE in elderly patients with hip fractures resulted in a low cardiac intervention rate. Patients undergoing preoperative TTE prior to surgery had longer times to operation, LOS, and higher hospital costs. The utility of TTE as a preoperative screening tool is limited in the geriatric hip fracture population and does not appear to effect perioperative mortality rates.

Long Term Treatment Results for Deep Infections of Total Knee Arthroplasty.

This study aims to identify the long-term outcomes of total knee arthroplasty (TKA) treated for deep infection. 3270 consecutive primary and 175 revision TKAs were followed prospectively. There were 39 deep infections (1.16%): 29 primary (0.9%) and 10 revision (5.7%) cases. Two-stage resection and re-implantation procedure was performed in 13 primary cases with 10/13 (77%) successfully resolved. Early (<1 month) Irrigation and Debridement (I&D) was performed in 16 primary cases with 100% success. Late (>4 months) I&D was performed in 6 cases with 5/6 (83.3%) successful. Infection following revision TKA resulted in poor outcomes with both two-stage (2/4 successful) and I&D (2/6 successful). Deep infection after primary TKA can be successfully resolved with I&D and appropriate antibiotic treatment in the early postoperative course.

Revision surgery occurs frequently after percutaneous fixation of stable femoral neck fractures in elderly patients.

BACKGROUND: Femoral neck fractures are a major public health problem. Multiple-screw fixation is the most commonly used surgical technique for the treatment of stable femoral neck fractures. QUESTIONS/PURPOSES: We determined (1) the proportion of hips that had conversion surgery to THA, and (2) the proportion of hips that underwent repeat fracture surgery after percutaneous screw fixation of stable (Garden Stages I and II) femoral neck fractures in patients older than 65 years and the causes of these reoperations. METHODS: We performed a retrospective study of all patients older than 65 years with stable femoral neck fractures secondary to low-energy trauma treated surgically at our institution between 2005 and 2008. We identified 121 fractures in 120 patients older than 65 years as stable (Garden Stage I or II); all were treated with percutaneous, cannulated screw fixation in an inverted triangle without performing a capsulotomy or aspiration of the fracture hematoma at the time of surgery. The average age of the patients at the time of fracture was 80 years (range, 65-100 years). Radiographs, operative reports, and medical records were reviewed. Fracture union, nonunion, osteonecrosis, intraarticular hardware, loss of fixation, and conversion to arthroplasty were noted. Followup averaged 11 months (range, 0-5 years) because all patients were included, including those who died. The mortality rate was 40% for all patients at the time of review. RESULTS: Twelve patients (10%) underwent conversion surgery to THA at a mean of 9 months after the index fracture repair (range, 2-24 months); the indications for conversion to THA included osteonecrosis, nonunion, and loss of fixation. Two others had periimplant subtrochanteric femur fractures treated by surgical repair with cephalomedullary nails and two patients had removal of hardware. CONCLUSIONS: Revision surgery after osteosynthesis for stable femoral neck fractures was more frequent in this series than previously has been reported. The reasons for this higher frequency of reoperation may be related to poor bone quality, patient age, and some technical factors, which leads us to believe other treatment options such as nonoperative management or hemiarthroplasty may be viable options for some of these patients. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Periacetabular osteotomy after failed hip arthroscopy for labral tears in patients with acetabular dysplasia.

BACKGROUND: Chronic mechanical overload of the acetabular rim may lead to acetabular labral disease in patients with hip dysplasia. Although arthroscopic debridement of the labrum may provide symptomatic relief, the underlying mechanical abnormality remains. There is little information regarding how the results of periacetabular osteotomy are affected by a prior primary treatment for labral disease in the presence of acetabular dysplasia. METHODS: In a retrospective matched-cohort study, seventeen patients who had arthroscopic labral debridement prior to periacetabular osteotomy (the arthroscopy group) were compared with a control group of thirty-four patients who did not undergo arthroscopic labral debridement prior to periacetabular osteotomy (the non-arthroscopy group). Two control patients were randomly matched to each experimental patient from a pool of controls. Functional outcomes were assessed with use of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Failure of periacetabular osteotomy was defined as conversion to a total hip replacement. RESULTS: Changes in the preoperative and postoperative WOMAC scores of arthroscopy and non-arthroscopy patients were comparable, and the differences between the two treatment groups were not significant. We were unable to show a significant difference between the seventeen arthroscopy and thirty-four non-arthroscopy patients with regard to the risk of having to undergo a total hip replacement. CONCLUSIONS: When arthroscopic labral debridement fails to improve symptoms in patients with labral disease secondary to acetabular dysplasia, periacetabular osteotomy may still be considered as a joint-preserving procedure that can achieve good functional results.

Patient-Perceived Quality of Life after Total Hip Arthroplasty: Elective versus Traumatological Surgery.

Purpose. The aim was to evaluate and compare patient's health-related quality of life after THA for osteoarthritis and femoral neck fracture. The postoperative outcome was retrospectively evaluated in patients who underwent THA with an intracapsular femoral neck fracture (Group A) or with an hip osteoarthritis (Group B). Methods. Length discrepancy was measured on postoperative X-rays. Study groups were compared as to age, results of WOMAC and SF-36 tests, limb length discrepancy (LLD) by independent group t-test. Correlations between LLD and results obtained atWOMAC test were performed. 117 patients were enrolled. The 2 groups were similar as to age, type of implanted stem and sex. Mean follow up was 2,4 years for group A and 2,3 years for group B. Results. WOMAC score was found higher in group A in all items examinated. Correlation tests did not indicate a statistically significant linear relationship between LLD and WOMAC score in both groups. Conclusions. Patients who received THA for arthritis have better perception of quality of life than traumatologic patients. Although LLD should always be strongly considered by the surgeons performing a THA, LLD alone can't be considered as an indicator of patient dissatisfaction or clinical bad result after a 2-year followup.

Epiphyseal reperfusion after subcapital realignement of an unstable SCFE.

We present a case of epiphyseal reperfusion in a 12-year-old boy following subcapital realignment of a unstable slipped capital femoral epiphysis. The case demonstrates that even if delayed, anatomical surgical realignment of the femoral head can be successful in preserving or reestablishing blood flow to the femoral epiphysis.

The history of the anterior approach to the hip.

The anterior approach is a safe, reliable, and feasible technique for total hip arthroplasty, permitting optimal soft tissue preservation. Since Hueter first described this interval, many surgeons have approached the hip anteriorly to perform a myriad of surgical procedures. The anterior approach allows optimal muscle preservation, and it is a truly internervous approach to the hip. An understanding of the evolution of the anterior approach to the hip will help the orthopedic community understand these advantages and why so many have used this approach in the treatment of hip pathology and for the implantation total hip arthroplasty.

Periacetabular osteotomy for acetabular dysplasia in patients older than 40 years: a preliminary study.

The functional outcomes of periacetabular osteotomy (PAO) and factors predicting outcome in the older patient with acetabular dysplasia are not well understood. We therefore retrospectively determined the functional outcome of 70 patients (87 hips) over age 40 treated with PAO in three institutions; we also determined whether preoperative factors, particularly the presence of osteoarthritis, influenced the survival of the hip or time to total hip arthroplasty after PAO. The average age at surgery was 43.6 years. The minimum followup was 2 years (mean, 4.9 years; range, 2-13 years). Twenty-one hips (24%) had undergone total hip arthroplasty (THA), at a mean of 5.2 years after PAO (range, 1.9-7.6 years). Surviving hips had a mean improvement in Harris hip score from 60.7 to 90.3 and in total WOMAC pain score from 8.7 to 3. We observed no differences in preoperative or postoperative radiographic measurements or preoperative clinical function scores (HHS, WOMAC) in hips surviving and hips having THA. The risk of THA at 5 years after PAO was 12% in hips with preoperative Tönnis Grade 0 or 1 and 27% for Tönnis Grade 2. Our preliminary study suggests that PAO will give satisfactory functional and pain scores in patients over age 40 having dysplastic hips with mild or no arthrosis.

Diagnosis of femoral neck fractures in patients with a femoral shaft fracture. Improvement with a standard protocol.

BACKGROUND: An ipsilateral fracture of the femoral neck is seen in association with 1% to 9% of femoral shaft fractures, and 20% to 50% of these injuries are missed initially. Recognition of an associated femoral neck fracture prior to stabilization of the femoral shaft fracture is imperative to avoid or minimize complications of displacement and osteonecrosis. METHODS: A protocol to look for a femoral neck fracture in all patients with a femoral shaft fracture was instituted at a single level-I trauma center. This protocol consisted of a dedicated anteroposterior internal rotation plain radiograph, a fine (2-mm) cut computed tomographic scan through the femoral neck, and an intraoperative fluoroscopic lateral radiograph prior to fixation as well as postoperative anteroposterior and lateral radiographs of the hip in the operating room prior to awakening the patient. A chi-square analysis comparing pre-protocol and post-protocol fracture prevalences was used to assess the relative risk of missing an associated femoral neck fracture. RESULTS: Two hundred and sixty-eight consecutive patients with a femoral shaft fracture formed the basis of the study group. Of 254 who were followed for at least two months, sixteen were identified as having an associated ipsilateral femoral neck fracture with use of the protocol. Thirteen associated femoral neck fractures were identified before the patient entered the operating room for definitive fixation, and twelve of them were identified with the fine-cut computed tomographic scan. One fracture was identified intraoperatively. There was one iatrogenic fracture and one delayed diagnosis of a femoral neck fracture. With this protocol, we reduced the delay in diagnosis by 91% as compared with our experience in the year prior to the initiation of the protocol. CONCLUSIONS: In the presence of a femoral shaft fracture, evaluation of the femoral neck with fine-cut computed tomography and dedicated internal rotation hip radiographs significantly improves the ability to diagnose an associated femoral neck fracture.

Osteogenic effects of traumatic brain injury on experimental fracture-healing.

BACKGROUND: Heterotopic bone formation has been observed in patients with traumatic brain injury; however, an association between such an injury and enhanced fracture-healing remains unclear. To test the hypothesis that traumatic brain injury causes a systemic response that enhances fracture-healing, we established a reproducible model of traumatic brain injury in association with a standard closed fracture and measured the osteogenic response with an in vitro cell assay and assessed bone-healing with biomechanical testing. METHODS: A standard closed femoral fracture was produced in forty-three Sprague-Dawley rats. Twenty-three of the rats were subjected to additional closed head trauma that produced diffuse axonal injury similar to that observed in patients with a traumatic brain injury. Twenty-one days after the procedure, all animals were killed and fracture-healing was assessed by measuring callus size and by mechanical testing. Sera from the animals were used in subsequent in vitro experiments to measure mitogenic effects on established cell lines of committed osteoblasts, fibroblasts, and mesenchymal stem cells. RESULTS: Biomechanical assessment demonstrated that the brain-injury group had increased stiffness (p = 0.02) compared with the fracture-only group. There was no significant difference in torsional strength between the two groups. Cell culture studies showed a significant increase in the proliferative response of mesenchymal stem cells after exposure to sera from the brain-injury group compared with the response after exposure to sera from the fracture-only group (p = 0.0002). This effect was not observed in fibroblasts or committed osteoblasts. CONCLUSIONS: These results support data from previous studies that have suggested an increased osteogenic potential and an enhancement of fracture-healing secondary to traumatic brain injury. Our results further suggest that the mechanism for this enhancement is related to the presence of factors in the serum that have a mitogenic effect on undifferentiated mesenchymal stem cells.