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Object Incidental durotomy (dural tear) is a common complication of lumbar spine surgery. The purpose of this study was to clarify the anatomical location of and the specific causative factors for incidental durotomy during primary lumbar spine surgery. Methods The authors retrospectively reviewed 1014 consecutive cases involving patients (412 women and 602 men; mean age 57 years; age range 11–97 years) who underwent a surgical procedure for treatment of degenerative lumbar spinal disease at their institution between 2002 and 2008. In total, 1261 disc levels were treated surgically. Disease at the treated levels included 544 disc herniations, 453 instances of spinal canal stenosis without spondylolisthesis, 188 instances of lumbar spinal canal stenosis with spondylolisthesis (degenerative spondylolisthesis), 49 instances of combined stenosis (stenosis with disc herniation), and 22 juxtafacet cysts. In 5 of the treated levels, the condition was classified as “other” disease. Treatment included fenestration with discectomy in 547 levels, fenestration alone in 626, fenestration with resection of juxtafacet cysts in 22, unilateral recapping laminoplasty in 20, posterolateral spinal fusion or posterior lumbar interbody fusion in 17, microscopic discectomy with tubular retractor in 14, and “other” in 15. Results Unintended durotomy occurred in 4% of cases and in 3.3% of disc levels. The incidence of dural tear was significantly higher in women (5.6%) than in men (3%). The incidence of dural tear was 2% in disc levels with lumbar disc herniation, 1.8% with lumbar spinal canal stenosis without spondylolisthesis, 9% with degenerative spondylolisthesis, and 18.2% with juxtafacet cysts; the incidence was significantly higher in levels with degenerative spondylolisthesis or levels with juxtafacet cysts, than in those with other diseases. Incidental durotomy occurred in 4 critical anatomical zones, namely, the caudal margin of the cranial lamina, cranial margin of the caudal lamina, herniated disc level, and medial aspect of the facet joint adjacent to the insertion of the hypertrophic ligamentum flavum. Conclusions Risk factors for unintended durotomy were female sex, older age, degenerative spondylolisthesis, and juxtafacet cysts. In this study, the authors identified 4 high-risk anatomical zones that spine surgeons should be aware of to avoid dural tears.

The purpose of this study was to compare the biodegradation rate and quality of regenerated bone among four materials. A short time period of 8 weeks was chosen to examine early bone healing. The rod-shaped implants of commercially available two β-tricalcium phosphate (β-TCP) ceramics with porosity 60% and 71-80%, respectively, laboratory prepared octacalcium phosphate/gelatin composite (OCP/Gel), which has been proven to have a highly osteoconductive and biodegradable property in rat calvarial defect, and gelatin sponge (Gelatin) were implanted in rabbit tibia defect of 6 mm diameter and 7 mm depth for 2, 4 and 8 weeks. Analyses by μCT, histomorphometry and push-in test were carried out to evaluate the extent of the tissue regeneration and the material biodegradation in the long bone. OCP/Gel and Gelatin were completely resorbed but only OCP/Gel induced cortical bone bridge until 8 weeks that has strength compatible to that of the natural bone. β-TCP (71%-80%) and β-TCP (60%) were not completely resorbed and never induced the amount of new bone formation beyond that by OCP/Gel. The results indicate that the new bone having enough strength could be regenerated if the material shows not only higher biodegradation rate but also higher osteoconductivity. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2833-2842, 2016.

The present study was designed to investigate how octacalcium phosphate (OCP) induces an immune response and whether the response is involved in the biodegradation and subsequent bone formation by OCP implantation in bone defects.

Previous studies have suggested that the biodegradability of octacalcium phosphate-collagen (OCP/Col) composite by osteoclasts is accelerated in association with mechanical stress suffered by the host tissue around the implant. The present study was designed to investigate whether alleviation of mechanical stress restores the bone regenerative properties of OCP/Col, as previously shown in nonload-bearing sites. OCP/Col discs supported with a polytetrafluoroethylene (PTFE) ring, which has a higher modulus than OCP/Col, were implanted in a rat subperiosteal pocket for up to 12 weeks. The structural features of the implant and biological responses were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, histomorphometry, histochemistry, and tissue mRNA expression around the implants. The effect of compression was analyzed using mouse stromal ST-2 cells by deforming the cell-seeded OCP/Col discs in vitro with or without a PTFE ring. The results clearly indicated the restoration of bone formation by the alleviation of mechanical stress and the upregulation of osteoblast-related genes, such as osterix on the other hand, the implantation of OCP/Col on calvaria or in an in vitro test without PTFE support resulted in the upregulation of osteoclast-related genes, such as tartrate-resistant acid phosphatase (TRAP) and cathepsin K, in the tissues or receptor activator of the nuclear factor-kappaB ligand (RANKL) in ST-2 cells. The results confirmed that calvaria augmentation is enhanced by implanting OCP/Col if suitable conditions regarding mechanical stress are provided.