Faculty Bibliography
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Finite Element Analysis Applied to 3-T MR Imaging of Proximal Femur Microarchitecture: Lower Bone Strength in Patients with Fragility Fractures Compared with Control Subjects
Purpose To determine the feasibility of using finite element analysis applied to 3-T magnetic resonance (MR) images of proximal femur microarchitecture for detection of lower bone strength in subjects with fragility fractures compared with control subjects without fractures. Materials and Methods This prospective study was institutional review board approved and HIPAA compliant. Written informed consent was obtained. Postmenopausal women with (n = 22) and without (n = 22) fragility fractures were matched for age and body mass index. All subjects underwent standard dual-energy x-ray absorptiometry. Images of proximal femur microarchitecture were obtained by using a high-spatial-resolution three-dimensional fast low-angle shot sequence at 3 T. Finite element analysis was applied to compute elastic modulus as a measure of strength in the femoral head and neck, Ward triangle, greater trochanter, and intertrochanteric region. The Mann-Whitney test was used to compare bone mineral density T scores and elastic moduli between the groups. The relationship (R2) between elastic moduli and bone mineral density T scores was assessed. Results Patients with fractures showed lower elastic modulus than did control subjects in all proximal femur regions (femoral head, 8.51-8.73 GPa vs 9.32-9.67 GPa; P = .04; femoral neck, 3.11-3.72 GPa vs 4.39-4.82 GPa; P = .04; Ward triangle, 1.85-2.21 GPa vs 3.98-4.13 GPa; P = .04; intertrochanteric region, 1.62-2.18 GPa vs 3.86-4.47 GPa; P = .006-.007; greater trochanter, 0.65-1.21 GPa vs 1.96-2.62 GPa; P = .01-.02), but no differences in bone mineral density T scores. There were weak relationships between elastic moduli and bone mineral density T scores in patients with fractures (R2 = 0.25-0.31, P = .02-.04), but not in control subjects. Conclusion Finite element analysis applied to high-spatial-resolution 3-T MR images of proximal femur microarchitecture can allow detection of lower elastic modulus, a marker of bone strength, in subjects with fragility fractures compared with control subjects. MR assessment of proximal femur strength may provide information about bone quality that is not provided by dual-energy x-ray absorptiometry. (c) RSNA, 2014.
PMCID:4263634
PMID: 24689884
ISSN: 0033-8419
CID: 895822
Feasibility of three-dimensional MRI of proximal femur microarchitecture at 3 tesla using 26 receive elements without and with parallel imaging
PURPOSE: High-resolution imaging of deeper anatomy such as the hip is challenging due to low signal-to-noise ratio (SNR), necessitating long scan times. Multi-element coils can increase SNR and reduce scan time through parallel imaging (PI). We assessed the feasibility of using a 26-element receive coil setup to perform 3 Tesla (T) MRI of proximal femur microarchitecture without and with PI. MATERIALS AND METHODS: This study had institutional review board approval. We scanned 13 subjects on a 3T scanner using 26 receive-elements and a three-dimensional fast low-angle shot (FLASH) sequence without and with PI (acceleration factors [AF] 2, 3, 4). We assessed SNR, depiction of individual trabeculae, PI performance (1/g-factor), and image quality with PI (1 = nonvisualization to 5 = excellent). RESULTS: SNR maps demonstrate higher SNR for the 26-element setup compared with a 12-element setup for hip MRI. Without PI, individual proximal femur trabeculae were well-depicted, including microarchitectural deterioration in osteoporotic subjects. With PI, 1/g values for the 26-element/12-element receive-setup were 0.71/0.45, 0.56/0.25, and 0.44/0.08 at AF2, AF3, and AF4, respectively. Image quality was: AF1, excellent (4.8 +/- 0.4); AF2, good (4.2 +/- 1.0); AF3, average (3.3 +/- 1.0); AF4, nonvisualization (1.4 +/- 0.9). CONCLUSION: A 26-element receive-setup permits 3T MRI of proximal femur microarchitecture with good image quality up to PI AF2. J. Magn. Reson. Imaging 2014;40:229-238. (c) 2013 Wiley Periodicals, Inc.
PMCID:4004721
PMID: 24711013
ISSN: 1053-1807
CID: 1042112
MRI of the hip at 7T: Feasibility of bone microarchitecture, high-resolution cartilage, and clinical imaging
PURPOSE: To demonstrate the feasibility of performing bone microarchitecture, high-resolution cartilage, and clinical imaging of the hip at 7T. MATERIALS AND METHODS: This study had Institutional Review Board approval. Using an 8-channel coil constructed in-house, we imaged the hips of 15 subjects on a 7T magnetic resonance imaging (MRI) scanner. We applied: 1) a T1-weighted 3D fast low angle shot (3D FLASH) sequence (0.23 x 0.23 x 1-1.5 mm3 ) for bone microarchitecture imaging; 2) T1-weighted 3D FLASH (water excitation) and volumetric interpolated breath-hold examination (VIBE) sequences (0.23 x 0.23 x 1.5 mm3 ) with saturation or inversion recovery-based fat suppression for cartilage imaging; 3) 2D intermediate-weighted fast spin-echo (FSE) sequences without and with fat saturation (0.27 x 0.27 x 2 mm) for clinical imaging. RESULTS: Bone microarchitecture images allowed visualization of individual trabeculae within the proximal femur. Cartilage was well visualized and fat was well suppressed on FLASH and VIBE sequences. FSE sequences allowed visualization of cartilage, the labrum (including cartilage and labral pathology), joint capsule, and tendons. CONCLUSION: This is the first study to demonstrate the feasibility of performing a clinically comprehensive hip MRI protocol at 7T, including high-resolution imaging of bone microarchitecture and cartilage, as well as clinical imaging. J. Magn. Reson. Imaging 2013;. (c) 2013 Wiley Periodicals, Inc.
PMCID:3962810
PMID: 24115554
ISSN: 1053-1807
CID: 571382
Symptomatic atypical femoral fractures are related to underlying hip geometry
The benefits of bisphosphonates are well documented, but prolonged use has been associated with atypical femur fractures. Radiographic markers for fracture predisposition could potentially aid in safer medication use. In this case-control designed study, we compared hip radiographic parameters and the demographic characteristics of chronic bisphosphonate users who sustained an atypical femoral fracture with a group of chronic bisphosphonate users who did not sustain an atypical femur fracture and also a group who sustained an intertrochanteric hip fracture. Radiographic parameters included were neck-shaft angle (NSA), hip-axis length (HAL) and center-edge angle (CE). Multivariate regression was used to evaluate the relationship between radiographic measures and femur fracture. Receiver-operating characteristic analysis determined cut-off points for neck-shaft angle and risk of atypical femur fracture. Ultimately, pre-fracture radiographs of 53 bisphosphonate users who developed atypical fracture were compared with 43 asymptomatic chronic bisphosphonate users and 64 intertrochanteric fracture patients. Duration of bisphosphonate use did not statistically differ between users sustaining atypical fracture and those without fracture (7.9 [+/-3.5] vs. 7.7 [+/-3.3] years, p=0.7). Bisphosphonate users who fractured had acute/varus pre-fracture neck-shaft angles (p<0.001), shorter hip-axis length (p<0.01), and narrower center-edge angles (p<0.01). Regression analysis revealed associations between neck-shaft angle (OR=0.89 [95% CI=0.81-0.97; p=0.01), center edge angle (OR=0.89 [95% CI=0.80-0.99]; p=0.03), and BMI (OR=1.15 [95% CI=1.02-1.31; p=0.03) with fracture development. ROC curve analysis (AUC=0.67 [95% CI=0.56-0.79]) determined that a cut-off point for neck-shaft angle <128.3 degrees yielded 69% sensitivity and 63% specificity for development of atypical femoral fracture. Ultimately, an acute/varus angle of the femoral neck, high BMI, and narrow center-edge angle were associated with development of atypical femur fracture in long-term bisphosphonate users. Patients on long-term bisphosphonates should be regularly radiographically evaluated in order to assess for potential risk of atypical fracture.
PMID: 24565751
ISSN: 1873-2763
CID: 881722
No Advantage to rhBMP-2 in Addition to Autogenous Graft for Fracture Nonunion
Bone morphogenetic proteins are a necessary component of the fracture healing cascade. Few studies have delineated the efficacy of iliac crest bone graft and recombinant human bone morphogenetic protein 2 (rhBMP-2), especially, in comparison with the gold standard treatment of nonunion, which is autogenous bone graft alone. This study compared the outcome of patients with fracture nonunion treated with autogenous bone graft plus rhBMP-2 adjuvant vs patients treated with autogenous bone graft alone. A total of 118 consecutive patients who were to undergo long bone nonunion surgery with autogenous bone graft (50) or autogenous bone graft plus rhBMP-2 (68) were identified. Surgical intervention included either harvested iliac autogenous bone graft or autogenous bone graft plus 1.5 mg/mL of rhBMP-2 placed in and around the site of nonunion. No differences were found in the distribution of nonunion sites included within each group. Twelve-month follow-up was obtained on 100 of 118 patients (84.7%). Analyses of demographic characteristics (including tobacco), medical comorbidities, previous surgeries, and nonunion type (atrophic vs hypertrophic) did not differ. Postoperative complication rates did not differ. The percentage of patients who progressed to union did not differ. Mean time to union in the autogenous bone graft plus rhBMP-2 group was 6.6 months (+/-3.9) vs 5.4 (+/-2.7) months in the autogenous bone graft-only group (P=.06). Rates of revision (16.2% for rhBMP-2 plus autogenous bone graft vs 8% for autogenous bone graft) did not differ statistically (P=.19), nor did 12-month scores of pain and functional assessment. Although rhBMP-2 is a safe adjuvant, there was no benefit seen when rhBMP-2 was added to autogenous bone graft in the treatment of long bone nonunion. Given its high cost, rhBMP-2 should be reconsidered as an aid to autogenous bone graft in the treatment of nonunion.
PMID: 24972432
ISSN: 0147-7447
CID: 1051432
Are Race and Sex Associated With the Occurrence of Atypical Femoral Fractures?
BACKGROUND: Prior studies have suggested that Asian patients and women may be more likely to sustain atypical femoral fractures in association with bisphosphonate use. However, they do not account for confounders such as asymptomatic patients who are long-term bisphosphonate users or patients sustaining osteoporotic fractures. QUESTIONS/PURPOSES: The purpose of this study was to determine the differences in sex and racial association with atypical femoral fractures by comparing demographic characteristics of patients who sustained an atypical bisphosphonate-associated fracture with patients on long-term bisphosphonates without fractures and with patients who sustained osteoporotic fractures. METHODS: Three groups from prospective registries were identified: (1) patients with atypical femur fractures associated with long-term bisphosphonate use (BFF) (n = 54); (2) patients on long-term bisphosphonates but with no associated fractures (BNF) (n = 119); and (3) patients with osteoporotic proximal femur fractures not associated with bisphosphonates (PFF) (n = 216). Age, sex, and self-reported race/ethnicity were documented and compared. Multivariate and univariate analyses were done as well as age- and sex-stratified analyses. RESULTS: Age and sex distributions of the BFF and BNF patients were similar. There was a higher percentage of Asian patients in the BFF group (17%) than in the BNF group (3%; p = 0.004) as well as Hispanics (13% versus 3% in BNF; p = 0.011). Patients in the BFF group were younger than those in the PFF group (67.5 versus 78.4 years; p < 0.001) and had fewer males (7% versus 14%; p < 0.001). CONCLUSIONS: These data suggest that Asians are at higher risk for atypical bisphosphonate-associated fractures. We recommend closer followup in Asian patients who are taking bisphosphonates. LEVEL OF EVIDENCE: Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID:3916602
PMID: 24166075
ISSN: 0009-921x
CID: 779612
Ulnar variance as a predictor of persistent instability following Galeazzi fracture-dislocations
BACKGROUND: We investigated the radiographic parameters that may predict distal radial ulnar joint (DRUJ) instability in surgically treated radial shaft fractures. In our clinical experience, there are no previously reported radiographic parameters that are universally predictive of DRUJ instability following radial shaft fracture. MATERIALS AND METHODS: Fifty consecutive patients, ages 20-79 years, with unilateral radial shaft fractures and possible associated DRUJ injury were retrospectively identified over a 5-year period. Distance from radial carpal joint (RCJ) to fracture proportional to radial shaft length, ulnar variance, and ulnar styloid fractures were correlated with DRUJ instability after surgical treatment. RESULTS: Twenty patients had persistent DRUJ incongruence/instability following fracture fixation. As a proportion of radial length, the distance from the RCJ to the fracture line did not significantly differ between those with persistent DRUJ instability and those without (p = 0.34). The average initial ulnar variance was 5.5 mm (range 2-12 mm, SD = 3.2) in patients with DRUJ instability and 3.8 mm (range 0-11 mm, SD = 3.5) in patients without. Only 4/20 patients (20 %) with DRUJ instability had normal ulnar variance (-2 to +2 mm) versus 15/30 (50 %) patients without (p = 0.041). CONCLUSION: In the setting of a radial shaft fracture, ulnar variance greater or less than 2 mm was associated with a greater likelihood of DRUJ incongruence/instability following fracture fixation.
PMCID:3948522
PMID: 23989858
ISSN: 1590-9921
CID: 779622
The association of education level on outcome after distal radius fracture
BACKGROUND: Socioeconomic factors have been found to be predictors of outcome for other ailments. The purpose of this study was to evaluate the association of patient education level on pain and disability after distal radius fracture. METHODS: A series of patients with distal radius fractures (n = 335) were enrolled into a prospective research registry. Standard demographic information was obtained from patients, including a five-value categorical education variable. After treatment with closed reduction, external fixation, or internal fixation patients were evaluated for pain, function (Disability of the Arm, Shoulder, and Hand score [DASH]), range of motion (ROM), and grip strength at standard intervals until 12 months post-injury. A series of linear mixed effects models were developed to evaluate the relationship between time from injury and education level with each of the outcomes measured. RESULTS: Complete demographic and 12-month follow-up data were available on 227 patients (75 %). There were neither group differences in mode of injury, severity, nor treatment modality after stratification by education level. Mixed effects model analyses revealed a significant linear association between level of education and measured outcomes at each follow-up point. Overall, each increase in education level demonstrated a doubling of improvement in pain, ROM, grip strength, and DASH score. CONCLUSIONS: Outcome of distal radius fracture depends on acute care and follow-up rehabilitation; however, patient-related factors indicative of socioeconomic status are becoming increasingly relevant as predictors of outcome and should be considered by the orthopaedist.
PMCID:3928390
PMID: 24570641
ISSN: 1558-9447
CID: 820742
Do elderly patients fare worse following operative treatment of distal femur fractures using modern techniques?
BACKGROUND: The purpose of this study was to compare the functional outcomes and quality of life of older and younger patients with similarly treated distal femur fractures. METHODS: We conducted an assessment of 57 patients who sustained distal femur fractures (Orthopaedic Trauma Association Type 33B, C) and underwent surgical treatment at our academic medical center. Patients were divided into 2 groups for analysis: an elderly cohort of patients aged 65 or older and a comparison cohort of patients younger than age of 65. A retrospective review of demographics, preoperative ambulatory status, radiographic data, and physical examination data was collected from the medical records. Follow-up functional data were collected via telephone at a mean of 2.5 years (range 6 months-8 years) using a Short Musculoskeletal Functional Assessment (SMFA). All patients underwent standard operative treatment of either nail or plate fixation. RESULTS: There was no statistical difference in gender, fracture type, surgical technique, surgeon, or institution where the surgery was performed. The percentage of patients with healed fractures at 6-months follow-up was not significantly different between the cohorts. The elderly cohort had slightly worse knee range of motion at 3, 6, and 12 months postoperatively but there was not a statistically significant difference between the groups. The SMFA Daily Activity, Functional, and Bother indices were significantly worse in the older cohort (P < .01, P = .01, P = .02, respectively). However, there was no significant difference in the SMFA Emotional or Mobility indices. CONCLUSION: Despite lower quality of life and functional scores, this study suggests that relatively good clinical outcomes can be achieved with surgical fixation of distal femoral fractures in the elderly patients. Age should not be used as a determinate in deciding against operative treatment of distal femur fractures in the elderly patients.
PMCID:3962055
PMID: 24660097
ISSN: 2151-4585
CID: 897232
Scapula fractures: interobserver reliability of classification and treatment
OBJECTIVES: There is substantial variation in the classification and management of scapula fractures. The first purpose of this study was to analyze the interobserver reliability of the OTA/AO classification and the New International Classification for Scapula Fractures. The second purpose was to assess the proportion of agreement among orthopaedic surgeons on operative or nonoperative treatment. DESIGN: Web-based reliability study. SETTING: Independent orthopaedic surgeons from several countries were invited to classify scapular fractures in an online survey. PARTICIPANTS: One hundred three orthopaedic surgeons evaluated 35 movies of three-dimensional computerized tomography reconstruction of selected scapular fractures, representing a full spectrum of fracture patterns. MAIN OUTCOME MEASUREMENTS: Fleiss kappa (kappa) was used to assess the reliability of agreement between the surgeons. RESULTS: The overall agreement on the OTA/AO classification was moderate for the types (A, B, and C, kappa = 0.54) with a 71% proportion of rater agreement (PA) and for the 9 groups (A1 to C3, kappa = 0.47) with a 57% PA. For the New International Classification, the agreement about the intraarticular extension of the fracture (Fossa (F), kappa = 0.79) was substantial and the agreement about a fractured body (Body (B), kappa = 0.57) or process was moderate (Process (P), kappa = 0.53); however, PAs were more than 81%. The agreement on the treatment recommendation was moderate (kappa = 0.57) with a 73% PA. CONCLUSIONS: The New International Classification was more reliable. Body and process fractures generated more disagreement than intraarticular fractures and need further clear definitions.
PMID: 23629469
ISSN: 1531-2291
CID: 991952
