William D. Lack

Motion Predicts Clinical Callus Formation: Construct-specific Finite Element Analysis of Supracondylar Femoral Fractures

BACKGROUND Mechanotransduction is theorized to influence fracture-healing, but optimal fracture-site motion is poorly defined. We hypothesized that three-dimensional (3-D) fracture-site motion as estimated by finite element (FE) analysis would influence callus formation for a clinical series of supracondylar femoral fractures treated with locking-plate fixation. METHODS Construct-specific FE modeling simulated 3-D fracture-site motion for sixty-six supracondylar femoral fractures (OTA/AO classification of 33A or 33C) treated at a single institution. Construct stiffness and directional motion through the fracture were investigated to assess the validity of construct stiffness as a surrogate measure of 3-D motion at the fracture site. Callus formation was assessed radiographically for all patients at six, twelve, and twenty-four weeks postoperatively. Univariate and multivariate linear regression analyses examined the effects of longitudinal motion, shear (transverse motion), open fracture, smoking, and diabetes on callus formation. Construct types were compared to determine whether their 3-D motion profile was associated with callus formation. RESULTS Shear disproportionately increased relative to longitudinal motion with increasing bridge span, which was not predicted by our assessment of construct stiffness alone. Callus formation was not associated with open fracture, smoking, or diabetes at six, twelve, or twenty-four weeks. However, callus formation was associated with 3-D fracture-site motion at twelve and twenty-four weeks. Longitudinal motion promoted callus formation at twelve and twenty-four weeks (p = 0.017 for both). Shear inhibited callus formation at twelve and twenty-four weeks (p = 0.017 and p = 0.022, respectively). Titanium constructs with a short bridge span demonstrated greater longitudinal motion with less shear than did the other constructs, and this was associated with greater callus formation (p < 0.001). CONCLUSIONS In this study of supracondylar femoral fractures treated with locking-plate fixation, longitudinal motion promoted callus formation, while shear inhibited callus formation. Construct stiffness was found to be a poor surrogate of fracture-site motion. Future implant design and operative fixation strategies should seek to optimize 3-D fracture-site motion rather than rely on surrogate measures such as axial stiffness.

Any Cortical Bridging Predicts Healing of Tibial Shaft Fractures

BACKGROUND There is no consensus regarding the optimal radiographic criteria for predicting the final healing of fractures. The purpose of this study was to determine if the time to the radiographic appearance of cortical bridging predicted the final healing of tibial shaft fractures, to examine the reliability of this assessment, and to determine when it is most accurate during the postoperative period. METHODS We retrospectively reviewed the data on 176 tibial fractures (OTA [Orthopaedic Trauma Association] 42-A, B, and C) treated with intramedullary nailing at a level-I trauma center from 2007 through 2010. Postoperative radiographs were assessed for varying degrees of cortical bridging, and interobserver reliability was calculated. Receiver operating characteristic (ROC) curve and chi-square analyses determined the accuracy of cortical bridging assessments in predicting union. RESULTS The nonunion rate was 7%. Any cortical bridging within four months was an excellent predictor of final healing (accuracy = 99%, area under the curve [AUC] = 0.995, p < 0.0001) and was the most reliable criterion (kappa = 0.90). All fractures that showed unicortical bridging eventually showed bridging of three cortices without additional intervention. CONCLUSIONS Assessment for any cortical bridging by four months postoperatively is a reliable, accurate predictor of tibial shaft fracture-healing. This relatively early radiographic finding discriminates between fractures that will undergo late union with observation alone and those destined for nonunion. LEVEL OF EVIDENCE Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Mechanism of Injury Differentiates Risk Factors for Mortality in Geriatric Trauma Patients.

Objectives: To evaluate the relationship between mechanism of injury and mortality in geriatric trauma patients and the ability of existing injury severity indices (ISIs) to assess mortality. Design: Retrospective review. Setting: Urban level 1 trauma center. Participants: Four thousand five hundred forty-five trauma patients age ≥55 presenting between 2008 and 2011. Intervention: Low-energy (LE-GTP) and high-energy (HE-GTP) geriatric trauma patient cohorts were created based on ICD-9 injury codes. Existing ISIs were evaluated for their ability to predict in-hospital mortality using the area under the receiver-operating characteristic curve (AUROC). Main Outcome Measures: Mortality. Results: The Trauma Score–Injury Severity Score (TRISS) was the most predictive ISI for both cohorts and was deemed to have moderate predictive capacity (AUROC: 0.82) in LE-GTP and excellent predictive capacity (AUROC: 0.91) in the HE-GTP. For, HE-GTP each 1-year increase in age was associated with a 12% increase risk of mortality versus 6% for LE-GTP. Preexisting conditions (PECs) were distributed differently between the cohorts with significantly more PECs in the LE-GTP (P < 0.01). Conclusions: Existing ISIs have fair-to-moderate predictive capacity for in-hospital morality in LE-GTPs and moderate-to-excellent predictive capacity in HE-GTPs. LE-GTPs and HE-GTPs are distinct cohorts that should be evaluated separately. Combining the cohorts underestimates both the effect of age on HE-GTPs and the effect of PECs on LE-GTPs while overestimating the effect of PECs on HE-GTPs. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Risk of Radiation-Induced Malignancy With Heterotopic Ossification Prophylaxis: A Case–Control Analysis

PURPOSE To determine the risk of radiation-induced malignancy after prophylactic treatment for heterotopic ossification (HO). METHODS AND MATERIALS A matched case-control study was conducted within a population-based cohort of 3489 patients treated either for acetabular fractures with acetabular open reduction internal fixation or who underwent total hip arthroplasty from 1990 to 2009. Record-linkage techniques identified patients who were diagnosed with a malignancy from our state health registry. Patients with a prior history of malignancy were excluded from the cohort. For each documented case of cancer, 2 controls were selected by stratified random sampling from the cohort that did not develop a malignancy. Matching factors were sex, age at time of hip treatment, and duration of follow-up. RESULTS A total of 243 patients were diagnosed with a malignancy after hip treatment. Five patients were excluded owing to inadequate follow-up time in the corresponding control cohort. A cohort of 238 cases (control, 476 patients) was included. Mean follow-up was 10 years, 12 years in the control group. In the cancer cohort, 4% of patients had radiation therapy (RT), compared with 7% in the control group. Of the 9 patients diagnosed with cancer after RT, none occurred within the field. The mean latency period was 5.9 years in the patients who received RT and 6.6 years in the patients who did not. Median (range) age at time of cancer diagnosis in patients who received RT was 62 (43-75) years, compared with 70 (32-92) years in the non-RT patients. An ad hoc analysis was subsequently performed in all 2749 patients who were not matched and found neither an increased incidence of malignancy nor a difference in distribution of type of malignancy. CONCLUSION We were unable to demonstrate an increased risk of malignancy in patients who were treated with RT for HO prophylaxis compared with those who were not.

Defining the Lower Limit of a "Critical Bone Defect" in Open Diaphyseal Tibial Fractures.

Objectives: To determine healing outcomes of open diaphyseal tibial shaft fractures treated with reamed intramedullary nailing (IMN) with a bone gap of 10–50 mm on ≥50% of the cortical circumference and to better define a “critical bone defect” based on healing outcome. Design: Retrospective cohort study. Patients: Forty patients, age 18–65, with open diaphyseal tibial fractures with a bone gap of 10–50 mm on ≥50% of the circumference as measured on standard anteroposterior and lateral postoperative radiographs treated with IMN. Intervention: IMN of an open diaphyseal tibial fracture with a bone gap. Setting: Level-1 trauma center. Main Outcome Measurements: Healing outcomes, union or nonunion. Results: Forty patients were analyzed. Twenty-one (52.5%) went on to nonunion and nineteen (47.5%) achieved union. Radiographic apparent bone gap (RABG) and infection were the only 2 covariates predicting nonunion outcome (P = 0.046 for infection). The RABG was determined by measuring the bone gap on each cortex and averaging over 4 cortices. Fractures achieving union had a RABG of 12 ± 1 mm versus 20 ± 2 mm in those going on to nonunion (P < 0.01). This remained significant when patients with infection were removed. Receiver operator characteristic analysis demonstrated that RABG was predictive of outcome (area under the curve of 0.79). A RABG of 25 mm was the statistically optimal threshold for prediction of healing outcome. Conclusions: Patients with open diaphyseal tibial fractures treated with IMN and a <25 mm RABG have a reasonable probability of achieving union without additional intervention, whereas those with larger gaps have a higher probability of nonunion. Research investigating interventions for RABGs should use a predictive threshold for defining a critical bone defect that is associated with greater than 50% risk of nonunion without supplementary treatment. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Payer status and increased distance traveled for fracture care in a rural state.

Objectives: To assess the volume and distance traveled for fracture care at a rural trauma center and how this varied over time by case type and by payer. Design: A retrospective review of the electronic record. Setting: A rural level 1 trauma center. Patients/Participants: Adults presenting with operative orthopaedic trauma at a rural level 1 trauma center between 1990 and 2007. Intervention: Not applicable. Main Outcome Measurements: County of residence was used to calculate distances traveled to the tertiary care center. Case volume and distance traveled for care were compared by case type, early (1990–1997) and late (1998–2007) time periods, and by payer status. Injury severity score was compared by case type and time period. Results: The presentation of simple injuries to the referral center increased throughout the study period without an increase in injury severity. The percentage of patients with simple injuries covered by standard Medicaid doubled from 11.8% to 21.2% between the early and late time periods. The average distance traveled by patients with simple injuries increased over time from 35.2 to 51 miles, and the distance was greater for Medicaid patients (59.7 vs 42.6 miles). Medicaid patients with emergent injuries also traveled farther for care (77.4 vs 66.1 miles). Conclusions: Increasing volume of orthopaedic trauma at a rural level 1 trauma center was associated with increasing travel distance for patients. Specifically, there was a dramatic increase in the volume of patients presenting for the care of simple orthopaedic injuries, these patients traveled greater distances with time and were more likely to beon Medicaid. Patients presenting with emergent injuries were also more likely to be on Medicaid. The appropriate triage of orthopaedic injuries requires a well-designed trauma system, including local on-call orthopaedists who can appropriately direct the care of patients with a variety of injuries. The effect of payer status on travel distance may be addressed through changes in reimbursement. Long-distance referral of orthopaedic trauma deserves further study as it affects patient outcomes, cost, and convenience of care.

Advanced Imaging Lacks Clinical Utility in Treating Geriatric Pelvic Ring Injuries Caused by Low-Energy Trauma

Objectives: Is advanced imaging necessary in the evaluation of pelvic fractures caused by low-energy trauma in elderly patients? Design: Retrospective review. Setting: Single institution, Level 1 Trauma Center. Patients: Age ≥60 years old treated for low-energy traumatic pelvic ring injuries. Intervention: None. Main Outcomes: Posterior pelvic ring injuries diagnosed on advanced imaging, radiographic displacement, admission status, hospital length of stay, change in weight-bearing status recommendations, and whether operative treatment was pursued. Results: Eighty-seven patients met the inclusion criteria, of which 42 had advanced imaging to evaluate the posterior pelvic ring (10 magnetic resonance imaging, 32 computed tomography). More posterior pelvic ring injuries were identified with advanced imaging compared with radiographs alone (P < 0.001). There was no statistically significant difference in rate of admission (P = 0.5) or hospital length of stay (P = 0.31) between patients with radiographs alone compared with patients evaluated with radiographs plus advanced imaging. The rate of displacement >1 cm at presentation and 6-week follow-up was unaffected by the presence of a posterior injury diagnosed on advanced imaging. Treatment for all 87 patients remained weight-bearing as tolerated with assist device irrespective of advanced imaging findings, and no patient underwent surgical intervention by 12-week follow-up. Conclusions: Despite frequent identification of posterior pelvic ring injuries in patients evaluated with advanced imaging, admission status, length of hospital stay, radiographic displacement, and treatment recommendations were unaffected by these findings. The use of advanced imaging in elderly patients with low-energy traumatic pelvic ring fractures may not be necessary. Level of Evidence: Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Prehospital Antibiotic Prophylaxis for Open Fractures: Practicality and Safety

Abstract Objective: Early antibiotic administration has been associated with a significant decrease in infection following open fractures. However, antibiotics are most effective at a time when many patients are still being transported for care. There is limited evidence that antibiotics may be safely administered for open fractures when being transported by life-flight personnel. No such data exists for ground ambulance transport of patients with open fractures. The purpose of the study was to assess the safety and feasibility of prophylactic antibiotic delivery in the prehospital setting. Methods: We performed a prospective observational study between January 1, 2014 and May 31, 2015 of all trauma patients transferred to a level 1 trauma center by a single affiliated ground ambulance transport service. If open fracture was suspected, the patient was indicated for antibiotic prophylaxis with 2 g IV Cefazolin. Exclusion criteria included penicillin allergy, higher priority patient care tasks, and remaining transport time insufficient for administration of antibiotics. The administration of antibiotics was recorded. Patient demographics, associated injuries, priority level (1 = life threatening injury, 2 = potentially life threatening injury, 3 = non-life threatening injury), and timing of transport and antibiotic administration were recorded as well. Results: EMTs identified 70 patients during the study period with suspected open fractures. Eight reported penicillin allergy and were not eligible for prophylaxis. The patient’s clinical status and transport time allowed for administration of antibiotic prophylaxis for 32 patients (51.6%). Total prehospital time was the only variable assessed that had a significant impact on administration of prehospital antibiotics (<30 minutes = 29% vs. >30 minutes = 66%; p < 0.001). There were no allergic reactions among patients and no needle sticks or other injuries to EMT personnel related to antibiotic administration. Conclusions: EMT personnel were able to administer prehospital antibiotic prophylaxis for a substantial portion of the identified patients without any complications for patients or providers. Given the limited training provided to EMTs prior to implementation of the antibiotic prophylaxis protocol, it is likely that further development of this initial training will lead to even higher rates of prehospital antibiotic administration for open fractures.

Any Cortical Bridging Predicts Healing of Supracondylar Femur Fractures After Treatment With Locked Plating

Objectives: To determine the accuracy and reliability of radiographic cortical bridging criteria in predicting the final healing of supracondylar femur fractures after treatment with locked plating. Design: Retrospective review. Setting: Two Level 1 trauma centers. Patients/Participants: Patients who presented with supracondylar femur fractures (OTA/AO 33A, C) and were treated with locking plate fixation between January 1, 2004, and January 1, 2011. The final study population included 82 fractures after excluding patients with open physes (n = 4), nondisplaced fractures (n = 4), early revision for technical failure (n = 4), or inadequate follow-up (n = 42). Intervention: Distal femur locking plate fixation. Main Outcome Measurements: Postoperative radiographs until final follow-up were assessed for cortical bridging at each cortex on anterior–posterior and lateral views. Images were analyzed independently by 3 orthopaedic traumatologists to allow for assessment of reliability. Final determination of union required both radiographic and clinical confirmation. Results: Assessment for any cortical bridging was the earliest accurate predictor of final union (95.1% accuracy at 4 months postoperatively), compared with criteria requiring bicortical bridging (93.9% accuracy at 6 months) and tricortical bridging (78% accuracy at 21 months). Any cortical bridging demonstrated a higher interobserver reliability (kappa = 0.73) relative to bicortical (kappa = 0.27) or tricortical bridging (kappa = 0.5). Conclusions: Our results for plate fixation of supracondylar distal femur fractures mirror those previously described for intramedullary nailing of tibia shaft fractures. Any radiographic cortical bridging by 4 months postoperatively is an accurate and reliable predictor of final healing outcome after locking plate fixation of supracondylar femur fractures. Assessment for bicortical or tricortical bridging is less reliable and inaccurate during the first postoperative year. Level of Evidence: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Evaluation of Common Fractures of the Hip in the Elderly

Hip fractures in the geriatric population are a common injury encountered in the emergency department. The recommendations for preoperative medical workup and management of these patients have recently been evaluated. Although medical therapies have been designed in an attempt to decrease the rate of these fractures, attempts to medically manage osteoporosis has created a new “atypical” fracture pattern that must be recognized and managed appropriately. The current recommendations for preoperative medical evaluation and management of patients with hip fractures will be reviewed. In addition, the epidemic of new fractures created by long-term bisphosphonate use will be described, and the current recommendations for the management of these fractures detailed.