The presence of Waddell signs depends on age and gender, not diagnosis.

AIMS: The aim of this study was to determine if positive Waddell signs were related to patients' demographics or to perception of their quality of life. PATIENTS AND METHODS: This prospective cross-sectional study included 479 adult patients with back pain from a university spine centre. Each completed SF-12 and Oswestry Disability Index (ODI) questionnaires and underwent standard spinal examinations to elicit Waddell signs. The relationship between Waddell signs and age, gender, ODI, Mental Component Score (MCS), and Physical Component Score (PCS) scores was determined. RESULTS: Of the 479 patients, 128 (27%) had at least one positive Waddell sign. There were significantly more women with two or more Waddell signs than men. The proportion of patients with at least one positive Waddell sign increased with age until 55 years, and then declined rapidly; none had a positive sign over the age of 75 years. Functional outcome scores were significantly worse in those with a single Waddell sign (p < 0.01). With one or more Waddell signs, patients' PCS and ODI scores indicated a perception of severe disability; with three or more Waddell signs, patients' MCS scores indicated severe disability. With five Waddell signs, ODI scores indicated that patients perceived themselves as crippled. CONCLUSION: Positive Waddell signs, a potential indicator of central sensitization, indicated a likelihood of having functional limitations and an impaired quality of life, particularly in young women. Cite this article: Bone Joint J 2018;100-B:219-25.

Lumbar magnetic resonance imaging findings in patients with and without Waddell Signs.

BACKGROUND CONTEXT: Waddell Signs (WS), introduced as a method to establish patients with substantial psychosocial components to their low back pain, carry a negative association despite no literature evaluating whether physical disease is associated with them. PURPOSE: To compare lumbar magnetic resonance imaging (MRI) findings between the patients with and without WS. STUDY DESIGN: Retrospective cohort study based on prospectively collected data. PATIENT SAMPLE: Thirty patients aged 35 to 55 years with an Oswestry Disability Index (ODI) score >50 randomly selected such that there was an even distribution of patients based on the number of WS. OUTCOME MEASURES: ODI and Short Form-12 scores, number of WS, presence and severity of spinal pathology. METHODS: MRIs were reviewed by three spine specialists blinded to clinical exam findings, number of WS, and patient identity. Type and severity of pathology and presence of surgical and non-surgical lesions were assessed, and findings were rank ordered based on the overall impression of the pathology. There was no external funding or potential conflicts of interest for this study. RESULTS: There were significantly more individual pathologic findings in patients without WS (p=.02). However, there was no difference in the severity of pathology based on WS (p=.46). Furthermore, the rank ordering based on overall impression of severity showed no difference between the patients with and without WS (p=.20). Although 100% of the patients without WS showed pathologic findings on MRI, 70% of WS patients also had significant pathology on MRI. The prevalence of spondylolisthesis, stenosis, and disc herniation was similar (p=.41, p=.22, and p=.43, respectively). The prevalence and mean number of lesion amenable to surgery did not differ based on presence of WS (p=.21 and p=.18, respectively). CONCLUSIONS: Patients with WS present a difficult diagnostic challenge for the physician as their organic symptoms are often coexistent with emotional fear avoidance behavior. Although there is more overall pathology in patients without WS, a significant number of these patients appear to have comparable spinal pathology with equivalent severity, which may be contributing to patients' symptoms and disability. Presence of these non-organic symptoms often makes us doubt these patients. However, as part of effective treatment, physicians should better understand both the physical and psychological components of patient disability.

Adverse events associated with anterior cervical spine surgery.

Anterior cervical procedures for neurologic decompression and fusion, including cervical diskectomy and cervical corpectomy, are commonly performed by orthopaedic surgeons and spinal neurosurgeons. These procedures are highly successful in treating most patients with persistent pain and neurologic symptoms that have not responded to nonsurgical methods. Adverse events occur infrequently, but several have been described, including esophageal injury, vertebral artery injury, dural tear, postoperative airway compromise, spinal cord injury, hematoma, dysphagia, dysphonia, and graft dislodgement. Newer procedures, such as cervical total disk replacement and the use of bone morphogenetic protein as a supplement to fusion, have raised unique concerns. Appropriate strategies must be utilized to avoid these adverse events, and the treating surgeon should have an understanding of how to detect and manage such events when they do arise.

Use of a postoperative lumbar corset after lumbar spinal arthrodesis for degenerative conditions of the spine. A prospective randomized trial.

BACKGROUND: Lumbosacral corsets and braces have been used to treat a variety of spinal disorders. Although their use after lumbar arthrodesis for degenerative conditions has been reported, there is a lack of evidence on which to base guidelines on their use. The purpose of this study was to evaluate the effect of a postoperative corset on the outcome of lumbar arthrodesis. METHODS: A prospective randomized trial was performed in which patients who wore a postoperative lumbar corset for eight weeks full-time after a posterior lumbar arthrodesis for a degenerative spinal condition were compared with those who did not use a corset after such an operation. Ninety patients were randomized to one of the two treatments. A history was recorded and patients were assessed with a physical examination, radiographs, and functional outcome questionnaires (the Dallas Pain Questionnaire [DPQ] and the Short Form-36 [SF-36]) preoperatively and at one year and two years following the surgery. The primary outcome measure of the study was the DPQ, a disease-specific patient-derived functional measure of the spine, and secondary end points included the SF-36 scores, complications, rates of fusion as determined radiographically, and reoperation rates. RESULTS: Follow-up analysis was performed for seventy-two patients, thirty-seven randomized to the brace (experimental) group and thirty-five randomized to the control group. Regardless of the treatment method, the patients had substantial improvement in the disease-specific and general health measures by two years postoperatively. At two years, there was no difference in the DPQ category scores (the primary outcome parameter) of the two treatment groups. There was also no difference in the mean SF-36 component scores at two years. Postoperative complications occurred in 22% and 23% of patients in the experimental and control groups, respectively, and a subsequent lumbar spinal operation was performed in 19% and 14%, respectively. Seven patients (five in the experimental group and two in the control group) with radiographic evidence of nonunion underwent revision surgery. CONCLUSIONS: This study does not indicate a significant advantage or disadvantage to the use of a postoperative lumbar corset following spinal arthrodesis for degenerative conditions of the lumbar spine. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Ascorbate-enhanced chondrogenesis of ATDC5 cells.

The ATDC5 cell line exhibits the multistep chondrogenic differentiation observed during endochondral bone formation. However, it takes up to two months to complete the process of cell expansion, insulin addition to promote differentiation and further changes in culture conditions effectively to induce hypertrophy. We sought to produce consistent chondrogenesis with significant hypertrophic differentiation with simpler conditions in a more practical time period. By adding ascorbate, the prechondrogenic proliferation phase was shortened from 21 to 7 days, with production of cartilaginous nodules during the chondrogenic phase, after insulin addition, that were greater in number and larger in size. Immunohistochemistry indicated much greater matrix elaboration and the mRNA expression of sox9, aggrecan and collagen type II were all significantly increased earlier and to a much higher degree when compared with controls. Moreover, there was a robust induction of hypertrophy: Col10a1, Runx2 and Mmp13 were all induced within 7-10 days. In conclusion, addition of ascorbate to ATDC5 cultures shortened the prechondrogenic proliferation phase, produced earlier chondrogenic differentiation, heightened gene expression and robust hypertrophic differentiation, abrogating the need for extended culture times and the changes in culture conditions. This simple modification considerably enhances the practicality of this cell line for studies of chondrogenesis.

Cyclic hydrostatic pressure enhances the chondrogenic phenotype of human mesenchymal progenitor cells differentiated in vitro.

Much attention has been given to the influences of bioactive factors on mesenchymal progenitor cell differentiation and proliferation, but few studies have examined the effect of mechanical factors on these cells. This study examined the effects of cyclic hydrostatic pressure on human bone marrow-derived mesenchymal progenitor cells undergoing chondrogenic differentiation. Aggregates of bone marrow-derived mesenchymal progenitor cells were cultured in a defined chondrogenic medium and were subjected to cyclic hydrostatic pressure. Aggregates were loaded at various time points: single (day 1 or 3) or multiple (days 1-7). At 14 and 28 days, aggregates were harvested for histology, immunohistochemistry, and quantitative DNA and matrix macromolecule analysis. The aggregates loaded for a single day did not demonstrate significant changes in proteoglycan and collagen contents compared with the non-loaded controls. In contrast, for the multi-day loaded aggregates, statistically significant increases in proteoglycan and collagen contents were found on both day 14 and day 28. Aggregates loaded for seven days were larger and histological staining indicated a greater matrix/cell ratio. This study indicates that hydrostatic pressure enhances the cartilaginous matrix formation of mesenchymal progenitor cells differentiated in vitro, and suggests that mechanical forces may play an important role in cartilage repair and regeneration in vivo.

BMP-2 induction and TGF-beta 1 modulation of rat periosteal cell chondrogenesis.

Periosteum contains osteochondral progenitor cells that can differentiate into osteoblasts and chondrocytes during normal bone growth and fracture healing. TGF-beta 1 and BMP-2 have been implicated in the regulation of the chondrogenic differentiation of these cells, but their roles are not fully defined. This study was undertaken to investigate the chondrogenic effects of TGF-beta 1 and BMP-2 on rat periosteum-derived cells during in vitro chondrogenesis in a three-dimensional aggregate culture. RT-PCR analyses for gene expression of cartilage-specific matrix proteins revealed that treatment with BMP-2 alone and combined treatment with TGF-beta 1 and BMP-2 induced time-dependent mRNA expression of aggrecan core protein and type II collagen. At later times in culture, the aggregates treated with BMP-2 exhibited expression of type X collagen and osteocalcin mRNA, which are markers of chondrocyte hypertrophy. Aggregates incubated with both TGF-beta 1 and BMP-2 showed no such expression. Treatment with TGF-beta 1 alone did not lead to the expression of type II or X collagen mRNA, indicating that this factor itself did not independently induce chondrogenesis in rat periosteal cells. These data were consistent with histological and immunohistochemical results. After 14 days in culture, BMP-2-treated aggregates consisted of many hypertrophic chondrocytes within a metachromatic matrix, which was immunoreactive with anti-type II and type X collagen antibodies. In contrast, at 14 days, TGF-beta 1 + BMP-2-treated aggregates did not contain any morphologically identifiable hypertrophic chondrocytes and their abundant extracellular matrix was not immunoreactive to the anti-type X collagen antibody. Expression of BMPR-IA, TGF-beta RI, and TGF-beta RII receptors was detected at all times in each culture condition, indicating that the distinct responses of aggregates to BMP-2, TGF-beta 1 and TGF-beta 1 + BMP-2 were not due to overt differences in receptor expression. Collectively, our results suggest that BMP-2 induces neochondrogenesis of rat periosteum-derived cells, and that TGF-beta 1 modulates the terminal differentiation in BMP-2 induced chondrogenesis.

Hyaluronan-based polymers in the treatment of osteochondral defects.

Articular cartilage in adults has limited ability for self-repair. Some methods devised to augment the natural healing response stimulate some regeneration, but the repair is often incomplete and lacks durability. Hyaluronan-based polymers were tested for their ability to enhance the natural healing response. It is hypothesized that hyaluronan-based polymers recreate an embryonic-like milieu where host progenitor cells can regenerate the damaged articular surface and underlying bone. Osteochondral defects were made on the femoral condyles of 4-month-old rabbits and were left empty or filled with hyaluronan-based polymers. The polymers tested were ACP sponge, made of crosslinked hyaluronan, and HYAFF-11 sponge, made of benzylated hyaluronan. The rabbits were killed 4 and 12 weeks after surgery, and the condyles were processed for histology. All 12-week defects were scored with a 29-point scale, and the scores were compared with a Kruskall-Wallis analysis of variance on ranks. Untreated defects filled with bone tissue up to or beyond the tidemark, and the noncalcified surface layer varied from fibrous to hyaline-like tissue. Four weeks after surgery, defects treated with ACP exhibited bone filling to the level of the tidemark and the surface layer was composed of hyaline-like cartilage well integrated with the adjacent cartilage. At 12 weeks, the specimens had bone beyond the tidemark that was covered with a thin layer of hyaline cartilage. Four weeks after surgery, defects treated with HYAFF-11 contained a rim of chondrogenic cells at the interface of the implant and the host tissue. In general, the 12-week defects exhibited good bone fill and the surface was mainly hyaline cartilage. Treated defects received significantly higher scores than untreated defects (p < 0.05), and ACP-treated defects scored significantly higher than HYAFF-11-treated defects (p < 0.05). The introduction of these hyaluronan-based polymers into defects provides an appropriate scaffolding and favorable microenvironment for the reparative process. Further work is required to fully assess the long-term outcome of defects treated with these polymers.

Tortuous course of the vertebral artery and anterior cervical decompression: a cadaveric and clinical case study.

STUDY DESIGN: Both the cadaveric and clinical examples of anomalous vertebral artery courses are described. The incidence of this anomaly in the general population and recognition, complications, and treatment options for these patients when undergoing anterior cervical decompression are discussed. OBJECTIVES: Cadaveric study: In this study vertebral artery's course through the cervical spine in the adult population was analyzed. The relation between an abnormal vertebral artery course and surgical landmarks are described. Clinical study: Complications and alternative treatment methods for decompression in patients with the anomaly are described. SUMMARY OF BACKGROUND DATA: The incidence of anomalous vertebral artery course is low, but failure to recognize a medially located vertebral artery may result in a life-threatening iatrogenic injury during decompression. Neither the relation between the vertebral arteries and the surgical landmarks nor the guidelines for decompression in the face of a tortuous vertebral artery have been well described. METHODS: Transverse foramens of the cervical spine were measured in 222 cadaveric spines. The measurements were taken describing the relation between transverse foramens and other surgical landmarks. Three patients with anomalies were identified in clinical practice. The complications and treatment options are identified in these patients. RESULTS: In the cadaveric specimens, a 2.7% incidence of tortuous vertebral artery course was identified. In these abnormal specimens, the transverse foramen was located an average of 0.14 mm medial to the joint of Luschka. In one patient, the abnormal course of the vertebral artery was recognized after laceration of the artery during a routine corpectomy. Anomalies in the other two patients were recognized before surgery, and the patients underwent modified anterior decompression by combining a discectomy at the anomalous level with a corpectomy at other levels. Vertebral artery ectasia is identifiable on axial magnetic resonance or computed tomographic images. CONCLUSIONS: Aberrant vertebral artery is rare. Preoperative recognition and appropriate modification of anterior decompression can yield excellent clinical results without risking significant complications.

Chondrogenitor cells and gene therapy.

The development of isolation and culture techniques for mesenchymal progenitor cells from various tissues has promoted interest in the use of these cells for repair and regeneration of musculoskeletal tissues. The chondrogenic differentiation of these pluripotential cells seems to be mediated by numerous cytokines most of which belong to the transforming growth factor-beta superfamily. Strategies to repair articular cartilage have focused on delivery of these cytokines or progenitor cells to the area of damage. More recently, with the development of gene transfer techniques, these cells have become the target of in vivo gene therapy, which involves direct injection of viral and nonviral vectors carrying transgenes. Furthermore, they are viewed as potential carriers of the transgenes for ex vivo gene therapy, in which the gene transfer is done in vitro with culture-expanded cells that then are implanted or injected. In vitro data suggest that the chondrogenic potential of these cells is maintained with virally mediated ex vivo gene transfer. By transducing these cells with chondroinductive factors, the bioactive factors and the target cells are delivered to the repair site.

Morphologic considerations of C2 isthmus dimensions for the placement of transarticular screws.

STUDY DESIGN: This study examines the C2 vertebrae using both direct anatomic and computed tomographic measurements. OBJECTIVE: To define the relation of the C2 vertebrae bony elements to the vertebral artery and the spinal canal, to determine individuals at risk for vertebral artery injury during C1-C2 transarticular screw placement. SUMMARY OF BACKGROUND DATA: Recent literature assessing the safety of upper cervical spine transarticular screws has concentrated on technique, including the optimal point of entry and path projection of the screw. The actual dimensions of the C2 isthmus of the pars interarticularis has not been examined in a large number of specimens. METHODS: C2 isthmus width and height measurements were made on 205 human cadaveric C2 vertebrae. Vertebrae predicted to be at risk for vertebral arterial injury were imaged by computed tomography. RESULTS: There were 102 female and 103 male specimens with mean isthmus widths of 8.2 +/- 1.5 mm and 7.2 +/- 1.3 mm, respectively. Five specimens (2.4%) had an isthmus width less than 5 mm. The mean isthmus heights were 8.6 +/- 2.0 mm and 6.9 +/- 1.5 mm for male and female specimens, respectively. In twenty-four specimens (11.7%), one or both isthmi had a height of less than 5 mm. Six of these specimens were male and 18 were female. The right C2 isthmus was generally smaller than the left. Computed tomographic measurements closely approximated those of the actual dimensions of the isthmi. CONCLUSIONS: Placing a 3.5 mm screw in a patient with narrow C2 isthmus dimensions (smaller than 5 mm in either the height or width) is technically difficult. Because of narrow C2 isthmus width and/or height, approximately 10% of patients may be at risk for a vertebral artery injury with placement of C1-C2 transarticular screws.

High variability in rabbit bone marrow-derived mesenchymal cell preparations.

The rabbit has been extensively used for preclinical models, especially in orthopedic applications. One of the more troubling features of this model is the high interindividual variability that is encountered and that requires a careful experimental design with sufficient sample size to make judgments valid. We have processed 241 individual preparations of rabbit bone marrow-derived mesenchymal progenitor cells (MPCs) over the last 3 years and have kept detailed records of the performance of these cells in various assays. This communication details the lack of correlation between the analyzed parameters. Bone marrow was harvested from 4-month-old rabbits; the cells were centrifuged, resuspended, and cultured. When cells reached 80% of confluence, they were removed from the plates with trypsin and assayed for their osteo- and chondrogenic potential. The average yield of the 241 individual MPC preparations exhibited a coefficient of variation of 77. An in vivo implantation assay with porous calcium phosphate ceramic cubes exhibited scores with a coefficient of variation of 65. Lastly, an in vitro assay of alkaline phosphatase enzyme activity exhibited the most variability with a coefficient of variation of 132. All of the cell preparations tested in an in vitro aggregate culture assay underwent chondrogenic differentiation. No relationships between any of these parameters were found. The variability of the results within the different assays is interpreted to be the result of the heterogeneity of the preparations. The lack of correlation between the parameters studied shows the importance of the conditions intrinsic to the different assays. These results serve to emphasize that any experimental design involving rabbit progenitor cells must include a sufficiently large sample size to allow statistically significant and rigorous conclusions.

Autologous mesenchymal progenitor cells in articular cartilage repair.

The lack of repair of articular cartilage where the damage does not penetrate the subchondral bone indicates the importance of marrow components in the repair of the articular cartilage. In adult animals, there is an inability of articular cartilage chondrocytes to heal chondral defects, but if the damage extends beyond the subchondral bone, a repair process ensues in which mesenchymal progenitor cells migrate into the injured site and undergo chondrogenic differentiation. However, analysis of animal models and human biopsy samples indicates that fibrocartilage, rather than true articular cartilage is the predominant tissue synthesized. To improve this outcome, the use of cell based implants of culture expanded progenitor cells from various sources has been proposed and attempted. This paper describes some of the age related differences in the natural repair of osteochondral defects, the in vitro characterization of the chondrogenic potential of certain mesenchymal cell types, and some of the characteristics required of cell and matrix constructs that may be used for repair or regeneration of articular cartilage.

A quadripotential mesenchymal progenitor cell isolated from the marrow of an adult mouse.

Adult marrow contains mesenchymal progenitor cells (MPCs) that have multiple differentiation potentials. A conditionally immortalized MPC clone, BMC9, has been identified that exhibits four mesenchymal cell phenotypes: chondrocyte, adipocyte, stromal (support osteoclast formation), and osteoblast. The BMC9 clone, control brain fibroblasts and another marrow-derived clone, BMC10, were isolated from a transgenic mouse (H-2Kb-tsA58) containing a gene for conditional immortality. To test for chondrogenic potential, cells were cultured in defined medium containing 10 ng/ml transforming growth factor beta and 10-7 M dexamethasone in 15-ml polypropylene tubes ("aggregate cultures"). Adipogenic potential was quantitated by flow cytometry of Nile Red-stained cells cultured for 1 and 2 weeks in medium containing isobutyl methylxanthine, indomethacin, insulin, and dexamethasone. Support of osteoclast formation was measured by quantitating multinucleated tartrate-resistant acid phosphatase-positive cells in spleen cell cocultures of test clones (immortomouse clones and positive control ST2 cells) cultured in the presence of 10-7 M vitamin D3 and 150 mM ascorbate-2-phosphate. In vivo osteogenic potential was assayed by histologic examination of bone formation in subcutaneous implants, into athymic mouse hosts, of a composite of cells combined with porous calcium phosphate ceramics. The bone marrow-derived clone BMC9 has the potential to express each of the four mesenchymal characteristics tested, while brain fibroblasts, tested under identical conditions, did not exhibit any of these four mesenchymal characteristics. BMC10 cells exhibited osteogenic and chondrogenic phenotypes, but showed only minimal expression of adipocytic or osteoclast-supportive phenotypes. Clone BMC9 is, minimally, a quadripotential MPC isolated from the marrow of an adult mouse that can differentiate into cartilage and adipose, support osteoclast formation, and form bone. The BMC9 clone is an example of an adult-derived multipotential progenitor cell that is situated early in the mesenchymal lineage.

Augmentation of spinal arthrodesis with autologous bone marrow in a rabbit posterolateral spine fusion model.

STUDY DESIGN: Posterolateral spinal fusion with autologous bone marrow aspirate in addition to autograft iliac crest bone graft in a rabbit model. OBJECTIVE: To demonstrate that the addition of autologous bone marrow can have positive effects on bone formation and spinal fusion. SUMMARY OF BACKGROUND DATA: Bone marrow has been shown to contain osteoprogenitor cells. A number of studies have demonstrated that bone formation is possible with autologous marrow injection into orthotopic sites such as that performed in femur fracture models. METHODS: A bone paucity model of posterolateral spine fusion was developed. The control animals received 0.8 g of morselized autogenous iliac crest bone graft harvested from a single iliac crest. The graft was mixed with 2 mL of clotted peripheral blood. In the experimental group, 2 mL of bone marrow aspirated from the opposite iliac crest was substituted for the peripheral blood clot. All rabbits were killed at 12 weeks, and the specimens were subjected to evaluation by posteroanterior radiography for the presence of fusion, computed tomography for bone volume, and biomechanical testing for stiffness. RESULTS: Successful fusion was achieved in 61% of the animals in the experimental group versus 25% in the control group (P < 0.05). The fusion mass in the experimental group had a mean volume of 919 +/- 387 mm3 versus 667 +/- 512 mm3 for the control group, as measured from computed tomography images. The results of the biomechanical testing validated the radiographic scoring system. The stiffness in specimens, graded as having a radiographic score of 4, was significantly greater than in specimens with radiographic scores of 1 and 2. CONCLUSION: In cases for which an adequate quantity of autogenous bone graft is not available, addition of bone marrow may facilitate greater bone formation and successful fusion.

Chondroprogenitor cells of synovial tissue.

OBJECTIVE: To assess the chondrogenic potential of cells within the synovium. METHODS: Explants of synovium taken from various sites in the joint were embedded in agarose and cultured with transforming growth factor beta1 (TGFbeta1) to assess their chondrogenic potential. Isolated synovial cells were also tested for their chondrogenic potential by culturing them as aggregates in a chemically defined medium with TGFbeta1. Cartilage formation was determined with histologic staining and immunohistochemistry. The osteochondral potential of the isolated cells was also assessed after subcutaneous implantation of the cells, loaded into porous calcium phosphate ceramic cubes, in athymic mice. RESULTS: A total of 48 synovial explants were cultured in agarose with TGFbeta1. The formation of cartilage was observed in the outer region of 21 explants, and type II collagen was localized in that region by immunohistochemistry. A larger percentage of TGFbeta1+ explants from the inner synovium sites formed cartilage compared with those from the outer synovium sites. Chondrogenesis occurred in aggregates incubated with TGFbeta1 as early as day 7, and by day 14, all TGFbeta1+ aggregates demonstrated chondrogenesis. In contrast with the results of the in vitro aggregate assay for chondrogenesis, no formation of cartilage or bone was evident in any section containing synovial cell-loaded ceramic cubes that were harvested at either 3 or 6 weeks after implantation subcutaneously in athymic mice. CONCLUSION: Synovial explants and isolated synovial cells will undergo chondrogenesis when cultured in the presence of TGFbeta1. The data indicate a possible synovial origin for the chondrocytic cells found in rheumatoid pannus. Furthermore, these data are consistent with the clinical findings of synovial chondrogenesis leading to synovial chondromatosis.

In vitro chondrogenesis of bone marrow-derived mesenchymal progenitor cells.

A culture system that facilitates the chondrogenic differentiation of rabbit bone marrow-derived mesenchymal progenitor cells has been developed. Cells obtained in bone marrow aspirates were first isolated by monolayer culture and then transferred into tubes and allowed to form three-dimensional aggregates in a chemically defined medium. The inclusion of 10(-7) M dexamethasone in the medium induced chondrogenic differentiation of cells within the aggregate as evidenced by the appearance of toluidine blue metachromasia and the immunohistochemical detection of type II collagen as early as 7 days after beginning three-dimensional culture. After 21 days, the matrix of the entire aggregate contained type II collagen. By 14 days of culture, there was also evidence for type X collagen present in the matrix and the cells morphologically resembled hypertrophic chondrocytes. However, chondrogenic differentiation was achieved in only approximately 25% of the marrow cell preparations used. In contrast, with the addition of transforming growth factor-beta 1 (TGF-beta 1), chondrogenesis was induced in all marrow cell preparations, with or without the presence of 10(-7) M dexamethasone. The induction of chondrogenesis was accompanied by an increase in the alkaline phosphatase activity of the aggregated cells. The results of RT-PCR experiments indicated that both type IIA and IIB collagen mRNAs were detected by 7 days postaggregation as was mRNA for type X collagen. Conversely, the expression of the type I collagen mRNA was detected in the preaggregate cells but was no longer detectable at 7 days after aggregation. These results provide histological, immunohistochemical, and molecular evidence for the in vitro chondrogenic differentiation of adult mammalian progenitor cells derived from bone marrow.

The chondrogenic potential of human bone-marrow-derived mesenchymal progenitor cells.

Mesenchymal progenitor cells provide a source of cells for the repair of musculoskeletal tissue. However, in vitro models are needed to study the mechanisms of differentiation of progenitor cells. This study demonstrated the successful induction of in vitro chondrogenesis with human bone-marrow-derived osteochondral progenitor cells in a reliable and reproducible culture system. Human bone marrow was removed and fractionated, and adherent cell cultures were established. The cells were then passaged into an aggregate culture system in a serum-free medium. Initially, the cell aggregates contained type-I collagen and neither type-II nor type-X collagen was detected. Type-II collagen was typically detected in the matrix by the fifth day, with the immunoreactivity localized in the region of metachromatic staining. By the fourteenth day, type-II and type-X collagen were detected throughout the cell aggregates, except for an outer region of flattened, perichondrial-like cells in a matrix rich in type-I collagen. Aggrecan and link protein were detected in extracts of the cell aggregates, providing evidence that large aggregating proteoglycans of the type found in cartilaginous tissues had been synthesized by the newly differentiating chondrocytic cells; the small proteoglycans, biglycan and decorin, were also detected in extracts. Immunohistochemical staining with antibodies specific for chondroitin 4-sulfate and keratan sulfate demonstrated a uniform distribution of proteoglycans throughout the extracellular matrix of the cell aggregates. When the bone-marrow-derived cell preparations were passaged in monolayer culture as many as twenty times, with cells allowed to grow to confluence at each passage, the chondrogenic potential of the cells was maintained after each passage.

The role of osteochondral progenitor cells in fracture repair.

The repair of a fracture necessarily entails synthesis of osseous tissue requiring the transformation of undifferentiated osteochondral progenitor cells to mature osteoblasts and chondrocytes. Owen and Friedenstein proposed that there are stem cells for all mesenchymal tissues, resident in bone marrow throughout life, that have a lineage comparable to that described for hematopoiesis. Subsequent with this initial study, marrow derived and periosteal derived progenitor cells have been shown to produce bone and cartilage in numerous in vivo and in vitro studies. The differentiation process appears to depend heavily on the influences of numerous cytokines, especially the transforming growth factor beta superfamily. Initial cartilage formation from progenitor cells is important in any secondary fracture repair. In the in vitro study of chondrogenesis, the marrow derived progenitor cells were shown to differentiate into their terminal phenotype, the hypertrophic chondrocyte, as indicated by the detection of Type X collagen messenger ribonucleic acid and protein. A concomitant elevation in the alkaline phosphatase level suggests that these cells are ready to mineralize. Despite the importance of these cells in fracture repair, the characterization of these cells and the mechanism of their differentiation have only begun to be explored.

Accuracy of using computed tomography to identify pedicle screw placement in cadaveric human lumbar spine.

STUDY DESIGN: Utility of using computed tomography to predict pedicle screw misplacement. OBJECTIVE: This study defines the sensitivity and specificity of predicting pedicle screw placement by experienced clinicians using a CT scan image. SUMMARY OF BACKGROUND DATA: In clinical and research settings, the method most commonly used to evaluate pedicle screws placement has been computed tomography. However, no current literature describes the accuracy of this method of evaluating screw placement. METHOD: Cobalt-chrome and titanium alloy pedicle screws of identical size were placed in six cadaveric human lumbar spine. Wide laminectomy was performed to allow complete visualization of the pedicles. Three consecutive lumbar levels were instrumented in each spine, giving 36 pedicle screw placements to identify. The instrumented spines were imaged, and four orthopaedic spine surgeons and a musculoskeletal radiologist were asked to read the images to identify the accuracy of screw placement within the pedicles. RESULTS: The sensitivity rate of identifying a misplaced screw was 67 +/- 6% for cobalt-chrome screws compared with 86 +/- 5% for titanium screws (P < 0.005). The specificity rates of radiographic diagnosis of misplaced pedicle screws were 66 +/- 10% for cobalt-chrome screws and 88 +/- 8% for titanium screws (P < 0.005). Similarly, a statistically significant difference was found in the sensitivity rates of identifying screws placed correctly in the pedicle: 70 +/- 10% for cobalt-chrome screws versus 89 +/- 8% for titanium screws (P < 0.005). Overall accuracy rates were 68 +/- 7% for cobalt chrome screws versus 87 +/- 3% for titanium screws (P < 0.002). CONCLUSION: Reliance on the computed tomography scan data alone in determining accuracy of pedicle screws can lead to inaccuracies in both clinical and research conditions.