Fentanyl Initiated Polymers Prepared by ATRP for Targeted Delivery.

The targeted delivery of polymers to neurons is a challenging yet important goal for polymer based drug delivery. We prepared a fentanyl based atom transfer radical polymerization (ATRP) initiator to target the Mu opioid receptor (MOR) for neuronal targeting. We incorporated our recently discovered rigid acrylate linking group into the initiator to retain a high degree of binding to the MOR and grafted random or block copolymers of poly(oligo(ethylene oxide) methacrylate)-block-(glycidyl methacrylate). Trifluoroethanol promoted amine ring opening of the glycidyl methacrylate was used for post-polymerization modification of the fentanyl initiated polymers to attach a near-infrared fluorescent dye (ADS790WS) or to build a targeted siRNA delivery system via modification with secondary amines. We examined the biocompatibility, cellular internalization, and siRNA binding properties of our polymer library in a green fluorescent protein expressing SY SH5Y neuroblastoma cell-line.

Pseudogout, an unconventional imitator of the lumbosacral spine with associated chronic epidural hematoma: illustrative cases.

BACKGROUND: Pseudogout, or calcium pyrophosphate dihydrate (CPPD) disease, is an inflammatory joint disease that most commonly involves the joints of the knees, ankles, and wrists. Pseudogout has also been known to involve the spine, especially the atlanto-occipital joint of the cervical spine, but there is limited documentation of its involvement in the lumbar spine. Though the atypical presentation of spinal pseudogout with findings consistent with discitis and epidural abscess has been documented, its presentation with associated chronic spinal epidural hematoma is a rare entity. OBSERVATIONS: The authors present two separate cases of pseudogout involvement of the lumbar spine, one case presenting with a clinical and radiographic picture consistent with discitis and epidural abscess and the other with radiographic and operative findings consistent with a chronic epidural hematoma. LESSONS: This case series demonstrates rare and atypical presentations of pseudogout within the lumbosacral spine.

A comparative study of three biomaterials in an ovine bone defect model.

BACKGROUND: Polyetheretherketone (PEEK), and more recently titanium-coated PEEK, have been given serious consideration as biomaterial design choices for spinal interbody implants. Shortcomings in these materials necessitate further innovation into materials research, for example, on PEKK. Common complications such as surface delamination (as with titanium coating) and lack of bone apposition (as with PEEK) indicate the need for a new material that inherently displays preferable bone growth characteristics without sacrificing structural integrity. PURPOSE: To compare three biomaterials with respect to their osseointegrative capacity. STUDY DESIGN: Evaluate the in vivo material characteristics of three separate biomaterials in an ovine bone defect model: PEEK, titanium-coated PEEK (Ti-coated PEEK), and 3D-printed PEKK. Biomechanical, histologic, and radiographic testing was the basis for evaluation and material characterization. METHODS: Eight ovine specimens were implanted with one of each of the three types of biomaterials tested in both left and right epicondyles using a femoral bone defect model, and were sacrificed at 8 and 16 weeks. Implants were then analyzed using a push-out method, histologic staining, and various radiographic tests. Industry funding was provided for the completion of this research study, followed by an independent third party review of all relevant data for publication. RESULTS: PEKK implants demonstrated bone ingrowth, no radiographic interference, no fibrotic tissue membrane formation, significant increase in bony apposition over time, and significantly higher push-out strength compared to standard PEEK. The PEKK implant displayed bone growth characteristics comparable to Ti-coated PEEK with significant improvements in implant integrity and radiographic properties. CONCLUSION: This study found that PEKK displayed preferable characteristics when compared to PEEK and Ti-coated PEEK, and is therefore a potential alternative to their use.

Comparative analysis of the lateral and posterolateral trajectories for fixation of the sacroiliac joint-a cadaveric study.

BACKGROUND: A number of minimally invasive sacroiliac (SI) joint fusion solutions for placing implants exist, with reduced post-operative pain and improved outcomes compared to open procedures. The objective of this study was to compare two MIS SI joint fusion approaches that place implants directly across the joint by comparing the ilium and sacrum bone characteristics and SI joint separation along the implant trajectories. METHODS: Nine cadaveric specimens (n = 9) were CT scanned and the left and right ilium and sacrum were segmented. The bone density, bone volume fraction, and SI joint gap distance were calculated along lateral and posterolateral trajectories and compared using analysis of variance between the two orientations. RESULTS: Iliac bone density, indicated by the mean Hounsfield Unit, was significantly greater for each lateral trajectory compared to posterolateral. The volume of cortical bone in the ilium was greater for the middle lateral trajectory compared to all others and for the top and bottom lateral trajectories compared to both posterolateral trajectories. Cortical density was greater in the ilium for all lateral trajectories compared to posterolateral. The bone fraction was significantly greater in all lateral trajectories compared to posterolateral in the ilium. No differences in cortical volume, cortical density, or cancellous density were found between trajectories in the sacrum. The ilium was significantly greater in density compared with the sacrum when compared irrespective of trajectory (p < 0.001). The posterolateral trajectories had a significantly larger SI joint gap than the lateral trajectories (p < 0.001). CONCLUSION: Use of the lateral approach for minimally invasive SI fusion allows the implant to interact with bone across a significantly smaller joint space. This interaction with increased cortical bone volume and density may afford better fixation with a lower risk of pull-out or implant loosening when compared to the posterolateral approach.