Using Black Bone Magnetic Resonance Imaging in Craniofacial Virtual Surgical Planning: A Comparative Cadaver Study.

BACKGROUND: The use of magnetic resonance imaging (MRI) for virtual surgical planning has not yet been described. In the United States, over 600,000 computed tomographic (CT) scans are performed annually on children, who are at higher risk than adults of developing cancer caused by ionizing radiation. The aim of this study was to demonstrate whether three-dimensionally-printed craniofacial surgical guides created from "black bone" MRI are comparable in accuracy to those created from CT scans. METHODS: A mock craniosynostosis surgery translocating four calvarial segments was virtually planned and performed in 10 cadavers. For five specimens, planning was performed and three-dimensionally-printed guides were created using black bone MRI scans. Five specimens underwent standard planning using CT scans. Reconstructed skulls underwent CT scans and three-dimensional reconstruction. Accuracy was compared to that of virtually planned surgeries. RESULTS: The preoperative black bone MRI scan had an average deviation from the preoperative CT scan of 1.37 mm. There was no statistically significant difference in the fit accuracy of MRI versus CT-created guides. Average deviation of postoperative anatomy from preoperative plan was within 1.5 mm for guides created from either scanning modality, with no statistically significant difference in accuracy between the two methods. Planned versus postoperative skull volume was not statistically significantly different when MRI versus CT was used. CONCLUSIONS: This study demonstrates that virtual surgical planning and three-dimensional craniofacial surgical guide creation can be performed using black bone MRI with accuracy comparable to that of CT. This could dramatically reduce radiation exposure of craniofacial reconstruction patients.

Algebraic connectivity of brain networks shows patterns of segregation leading to reduced network robustness in Alzheimer's disease.

Measures of network topology and connectivity aid the understanding of network breakdown as the brain degenerates in Alzheimer's disease (AD). We analyzed 3-Tesla diffusion-weighted images from 202 patients scanned by the Alzheimer's Disease Neuroimaging Initiative - 50 healthy controls, 72 with early- and 38 with late-stage mild cognitive impairment (eMCI/lMCI) and 42 with AD. Using whole-brain tractography, we reconstructed structural connectivity networks representing connections between pairs of cortical regions. We examined, for the first time in this context, the network's Laplacian matrix and its Fiedler value, describing the network's algebraic connectivity, and the Fiedler vector, used to partition a graph. We assessed algebraic connectivity and four additional supporting metrics, revealing a decrease in network robustness and increasing disarray among nodes as dementia progressed. Network components became more disconnected and segregated, and their modularity increased. These measures are sensitive to diagnostic group differences, and may help understand the complex changes in AD.

Angular versus spatial resolution trade-offs for diffusion imaging under time constraints.

Diffusion weighted magnetic resonance imaging (DW-MRI) are now widely used to assess brain integrity in clinical populations. The growing interest in mapping brain connectivity has made it vital to consider what scanning parameters affect the accuracy, stability, and signal-to-noise of diffusion measures. Trade-offs between scan parameters can only be optimized if their effects on various commonly-derived measures are better understood. To explore angular versus spatial resolution trade-offs in standard tensor-derived measures, and in measures that use the full angular information in diffusion signal, we scanned eight subjects twice, 2 weeks apart, using three protocols that took the same amount of time (7 min). Scans with 3.0, 2.7, 2.5 mm isotropic voxels were collected using 48, 41, and 37 diffusion-sensitized gradients to equalize scan times. A specially designed DTI phantom was also scanned with the same protocols, and different b-values. We assessed how several diffusion measures including fractional anisotropy (FA), mean diffusivity (MD), and the full 3D orientation distribution function (ODF) depended on the spatial/angular resolution and the SNR. We also created maps of stability over time in the FA, MD, ODF, skeleton FA of 14 TBSS-derived ROIs, and an information uncertainty index derived from the tensor distribution function, which models the signal using a continuous mixture of tensors. In scans of the same duration, higher angular resolution and larger voxels boosted SNR and improved stability over time. The increased partial voluming in large voxels also led to bias in estimating FA, but this was partially addressed by using "beyond-tensor" models of diffusion.

Evidence for ordering of Alzheimer disease biomarkers.

OBJECTIVE: To empirically assess the concept that Alzheimer disease (AD) biomarkers significantly depart from normality in a temporally ordered manner. DESIGN: Validation sample. SETTING: Multisite, referral centers. PARTICIPANTS: A total of 401 elderly participants in the Alzheimer's Disease Neuroimaging Initiative who were cognitively normal, who had mild cognitive impairment, or who had AD dementia. We compared the proportions of 3 AD biomarker values (the Aß42 level in cerebrospinal fluid [CSF], the total tau level in CSF, and the hippocampal volume adjusted for intracranial volume [hereafter referred to as the adjusted hippocampal volume]) that were abnormal as cognitive impairment worsened. Cut points demarcating normal vs abnormal for each biomarker were established by maximizing diagnostic accuracy in independent autopsy samples. MAIN OUTCOME MEASURES: Three AD biomarkers (ie, the CSF Aß42 level, the CSF total tau level, and the adjusted hippocampal volume). RESULTS: Within each clinical group of the entire sample (n = 401), the CSF Aß42 level was abnormal more often than was the CSF total tau level or the adjusted hippocampal volume. Among the 298 participants with both baseline and 12-month data, the proportion of participants with an abnormal Aß42 level did not change from baseline to 12 months in any group. The proportion of participants with an abnormal total tau level increased from baseline to 12 months in cognitively normal participants (P = .05) but not in participants with mild cognitive impairment or AD dementia. For 209 participants with an abnormal CSF Aß42 level at baseline, the percentage with an abnormal adjusted hippocampal volume but normal CSF total tau level increased from baseline to 12 months in participants with mild cognitive impairment. No change in the percentage of MCI participants with an abnormal total tau level was seen between baseline and 12 months. CONCLUSIONS: A reduction in the CSF Aß42 level denotes a pathophysiological process that significantly departs from normality (ie, becomes dynamic) early, whereas the CSF total tau level and the adjusted hippocampal volume are biomarkers of downstream pathophysiological processes. The CSF total tau level becomes dynamic before the adjusted hippocampal volume, but the hippocampal volume is more dynamic in the clinically symptomatic mild cognitive impairment and AD dementia phases of the disease than is the CSF total tau level.

3.0-Tesla MR angiography of intracranial aneurysms: comparison of time-of-flight and contrast-enhanced techniques.

PURPOSE: To determine whether 3.0-T elliptical-centric contrast-enhanced (CE) magnetic resonance (MR) angiography is superior to 3.0-T elliptical-centric time-of-flight (TOF) MR angiography in the detection and characterization of intracranial aneurysms, and to determine whether increasing the acquisition matrix size in 3.0-T CE MR angiography improves image quality. MATERIALS AND METHODS: A total of 50 consecutive patients referred for MR angiographic evaluation of a known or suspected intracranial aneurysm underwent MR angiography, including three-dimensional TOF and elliptical-centric CE techniques at 3.0 T. The 3.0-T three-dimensional TOF and 3.0-T CE examinations were graded for image quality. A blind review identified the presence and location of aneurysms. RESULTS: A total of 28 aneurysms were identified in 23 of the 50 patients. The 3.0-T TOF MR angiography had a higher mean score for image quality than the 3.0-T elliptical-centric CE MR angiography (P < 0.0001). A total of 14 patients with aneurysms had conventional angiography for comparison. The 3.0-T TOF showed all the aneurysms, whereas 3.0-T CE MR angiography did not show 1 of 19 aneurysms when conventional angiography was the reference standard. CONCLUSION: For imaging intracranial aneurysms, 3.0-T TOF MR angiography offers better image quality than 3.0-T CE MR angiography using the elliptical-centric technique.

A comparison of combined arthroscopic triangular fibrocartilage complex debridement and arthroscopic wafer distal ulna resection versus arthroscopic triangular fibrocartilage complex debridement and ulnar shortening osteotomy for ulnocarpal abutment syndrome.

PURPOSE: Treatment of ulnocarpal abutment (UAS) syndrome involves decompression of the pressure and impingement, or abutment of the ulnocarpal articulation. Debridement of triangular fibrocartilage complex (TFCC) tears alone in the patient with UAS may have a failure rate of as much as 25% to 30%. Ulnar shortening osteotomy (USO) can be an effective treatment of failed TFCC debridement. Good results have been reported with combined arthroscopic TFCC debridement and mechanical arthroscopic distal ulnar resection. Similar results have been reported with both ulnar shortening osteotomy and open wafer distal ulnar resections in the UAS patient. Because all of these treatment choices appear to yield similar relief of symptoms, determination of the optimal treatment protocol remains a point of debate. The purpose of this study was to evaluate 2 different surgical treatments for UAS. TYPE OF STUDY: Retrospective review. METHODS: Eleven combined arthroscopic TFCC debridement and arthroscopic distal ulna resections (arthroscopic wafer procedures; AWP) were compared with 16 arthroscopic TFCC debridement and USOs. All patients had diagnostic wrist arthroscopy and arthroscopic TFCC debridement. All patients presented with ulnar wrist pain or neutral or positive ulnar variance, and all experienced at least 3 months of failed conservative management. RESULTS: At mean follow-up times of 21 and 15 months, respectively, 9 of 11 patients showed good to excellent results after arthroscopic TFCC debridement and AWP compared with 11 of 16 after arthroscopic TFCC debridement and USO. A statistically significant difference (P <.05) in the complication rates was identified, including secondary procedures and tendonitis. One secondary procedure and 2 cases of tendonitis were seen in the arthroscopic wafer group. CONCLUSIONS: Combined arthroscopic TFCC debridement and arthroscopic wafer procedure provides similar pain relief and restoration of function with fewer secondary procedures and tendonitis when compared with arthroscopic TFCC debridement and USO, for the treatment of UAS. LEVEL OF EVIDENCE: Level III.

Flexor tendon suture: a description of two core suture techniques and the Silfverskiöld epitendinous suture.

Flexor tendon injuries are commonly treated by orthopedic, plastic, and hand surgeons. Bunnell referred to zone 2 injuries as being in "no-man's land," plagued by poor results after surgical repair. Over the last 30 years, a better understanding of the biology of flexor tendon injuries, advanced surgical techniques, and perhaps most important, improved rehabilitation protocols, have afforded consistently good to excellent results after surgical repair at all levels of injury. Complications such as restrictive adhesions, joint contracture, and repair rupture, although less frequent, can compromise functional recovery.

Laser-assisted arthroscopic ulnar shortening.

The purpose of this study is to evaluate arthroscopic ulnar shortening with the holmium:yttrium-aluminum-garnet (Ho:YAG) laser for the treatment of ulnocarpal abutment syndrome (UAS). This is a retrospective review of the experience of a single surgeon using this technique between 1994 and 2000. Unloading the ulnocarpal joint is the recognized treatment of UAS. Ulnar shortening via a diaphyseal osteotomy and plating (USO) has been used with good results; however, nearly 50% of patients will require hardware removal. Researchers have reported similar results between open distal ulnar resection (the wafer procedure) and USO for the treatment of UAS. Researchers have also reported similar results with mechanical arthroscopic distal ulnar resections (arthroscopic wafer distal ulnar resection [AWP]) for UAS. Eleven patients who underwent Ho:YAG laser-assisted arthroscopic distal ulnar resection were retrospectively evaluated. The average follow-up time was 31 months, with a range of 7 to 61 months. Evaluation using Darrow' s criteria revealed 64% excellent (7 of 11), 18% good (2 of 11), 9% fair (1 of 11), and 9% poor (1 of 11) results. The average return to work time was 4.7 months, with a range of 1.5 to 16 months. Complications included 1 repeat surgery for ulnocarpal scar formation, 2 cases of transient tendonitis, and 1 portal site erythema without drainage that was treated with antibiotics. One patient (the one with a poor result) has not returned to work for unrelated reasons. chi- square analysis (P <.05) was unable to identify a statistical difference between the reported results of arthroscopic wafer procedures, USOs, and open wafer procedures. We concluded that Ho:YAG laser-assisted arthroscopic ulna shortening procedures show similar results to those reported for arthroscopic wafer procedures, open wafer procedures, and USOs. Return to work times are similar to those reported by other researchers, as is the return to preoperative occupation rate. There is no need for late removal of hardware, as is sometimes associated with USO. Our experience has been that the Ho:YAG laser removes hyaline cartilage and subchondral bone rapidly and with little debris, and thus facilitates the ulna shortening procedure.