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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The success of anterior cervical arthrodesis adjacent to a previous fusion

STUDY DESIGN

A retrospective review of all patients surgically treated for adjacent segment disease of the cervical spine over a 20-year period.

OBJECTIVES

To determine the clinical and radiographic success of discectomy with interbody grafting and corpectomy with strut grafting in the treatment of adjacent segment disease of the cervical spine.

SUMMARY OF BACKGROUND DATA

Up to 25% of all patients undergoing anterior cervical fusion have new disease due to degeneration of an adjacent segment within 10 years. The success of surgical treatment in these patients with adjacent segment disease has not been reported.

METHODS

Thirty-eight patients were surgically treated for adjacent segment disease by discectomy with interbody grafting or corpectomy with strut grafting. Arthrodesis was evaluated by flexion-extension lateral radiographs and clinical outcomes were assessed using Robinson's criteria at least 2 years after surgery. Fusion rates were compared by Fisher's exact test, and outcomes were compared by rank-sum analysis.

RESULTS

The rate of arthrodesis was significantly lower in the 24 patients treated by discectomy with interbody grafting at one or more levels (63%) than in the 14 patients treated by corpectomy with strut grafting (100%; P = 0.01). Clinical outcomes were similar for the corpectomy and discectomy groups (P = 0.55). There was a trend toward better outcomes in patients who achieved a solid arthrodesis (P = 0.13).

CONCLUSIONS

Achieving fusion is more difficult when anterior cervical arthrodesis is performed adjacent to a prior fusion. Strut grafting resulted in a significantly higher rate of arthrodesis than interbody grafting.

Comparison of lumbar sagittal alignment produced by different operative positions

STUDY DESIGN

This study is a prospective evaluation of the effects of commonly used spinal tables on lumbar sagittal alignment.

OBJECTIVES

The objective was to determine the differences, if any, in lumbar sagittal alignment produced by different positions on routinely used spinal operating tables.

SUMMARY OF BACKGROUND DATA

Earlier studies have documented the advantages of the knee-chest position in lumbar decompressive procedures. When simultaneous fusion is performed and augmented with internal fixation, intraoperative position is the critical determinant of sagittal plane balance. Other investigators have documented an association between the knee-chest position and decreased lumbar lordosis.

METHODS

Ten asymptomatic volunteers underwent a series of four lateral lumbar radiographs, as follows: standing, prone on the Jackson (Orthopaedic Systems, Inc., Hayword, CA) spinal table, and prone on the Andrews (Orthopaedic Systems, Inc.) table with the hips flexed 60 degrees and 90 degrees, respectively. Intervertebral body angle measurements were obtained from L1 to S1. Lordosis values were compared and analyzed for each of the positions. Standing lordosis was assumed to be physiologic.

RESULTS

Physiologic lordosis values were produced only on the Jackson operative table. Both positions on the Andrews table resulted in a statistically significant decrease in lumbar lordosis. Decreasing hip flexion on the Andrews table from 90 degrees to 60 degrees produced a statistically significant increase in lumbar lordosis. However, this change did not reproduce physiologic values.

CONCLUSION

When instrumentation is used to augment lumbar fusions, positions incorporating hip flexion should be avoided to ensure maintenance of sagittal plane balance.

Optimizing imaging parameters for MR evaluation of the spine with titanium pedicle screws

OBJECTIVE

This study examined the contribution and interdependence of multiple imaging parameters in clinical imaging sequences to aid practicing radiologists in minimizing artifacts during MR imaging of the spine after implantation of titanium pedicle screws.

MATERIALS AND METHODS

A lumbar spine specimen with titanium pedicle screws implanted in the pedicle was imaged with a 1.5-T scanner. Sequence type, voxel volume, TE, and bandwidth varied. Different voxel volumes were achieved by altering section thickness, field of view (FOV), and matrix size. Artifact size was measured on sagittal and axial images at the midpedicle level. Artifact size was expressed as a percentage of actual screw size, and mean artifact size was calculated for each sequence. Analysis of variance without replication was done.

RESULTS

Mean artifact size ranged from 231% to 364% of actual screw size. Artifact size was independent of voxel volume for voxels greater than 3 MM3 (p<.001). Artifact size decreased significantly (p<.001) when voxel volume was less than 1 mm3. When we increased slice thickness and maintained a constant voxel volume, artifact size decreased. Decreases in artifact size correlated with a reduction in the ratio of the FOV to the number of pixels in the frequency-encoding direction (Nx). Artifact sizes were smallest when fast spin-echo sequences were used. Conventional spin-echo sequences produced artifacts that were smaller than the artifacts produced by the gradient-echo sequences. Decreasing the TE did not diminish artifact size for conventional spin-echo images in larger voxel volume.

CONCLUSION

Although voxel volume has been recognized as a factor that affects artifact size, the role of other contributing factors--slice thickness, number of phase-encoding steps, and FOV/Nx--has not been evaluated before. Artifact reduction proved to be dependent only on FOV/Nx. Artifact size was reduced by the use of fast spin-echo sequences. With conventional spin-echo sequences, TE should be minimized, although other technical factors may outweigh the gain in artifact reduction.

The role of distraction in improving the space available for the cord in cervical spondylosis

STUDY DESIGN

This study analyzed the effects of distraction via strut graft insertion on the canal dimensions in spondylotic human cadaver cervical spines. Transverse and anteroposterior diameters and cross-sectional areas were measured by transverse computed tomography imaging before and after distraction without direct decompression.

OBJECTIVES

This experiment was designed to address whether distraction across the disc space without direct canal decompression can improve the space available for the cord.

SUMMARY OF BACKGROUND DATA

Smith-Robinson anterior discectomy and fusion have been shown to improve clinical symptoms of radiculopathy and myelopathy even in the absence of direct decompression. This has been postulated to be the result of gradual resorption of intruding osteophytes. However, the immediate effects of indirect distraction alone have not been previously investigated.

METHODS

Four cadaver spines from elderly donors were harvested intact. The transverse diameter, anteroposterior diameter, and cross-sectional area of the spinal canal were measured before and after discectomy and distraction via insertion of fibular strut graft by digitization of contiguous computed tomography scan slices.

RESULTS

The spinal canal dimensions before distraction were found to vary in a sinusoidal pattern around the disc space, with the maximum measurements located at the pedicle and the minimum measurements at the spondylotic ridge above or below the disc space. Distraction via strut graft insertion significantly increased the anteroposterior diameter and cross-sectional area, but had a negligible effect on transverse diameter.

CONCLUSIONS

Anterior discectomy and distraction with a strut graft can significantly improve the space available for the cord in cervical spondylosis. Osteophyte debridement, which risks iatrogenic injury to the cord, may not always be necessary for improving clinical radiculopathy and myelopathy.

Review of Harrington rod treatment of spinal trauma

Harrington rod treatment for spinal trauma has become the gold standard against which other treatment modalities are judged. A review of the results of Harrington rod treatment is essential to establish a baseline level of efficiency in terms of rehabilitation time, correction of deformity, canal decompression, motion segment loss, and device-related complications. With economic concerns becoming more important in medical treatment, the value of newer techniques must be clearly superior to established methods. Harrington rod-augmented spine fusion is reliable and cost-effective in the thoracic and thoracolumbar spine. The risks of rod failure and late complications related to lost motion segments in the lumbar spine make pedicle screw systems a better option in this region.

Mechanics of anatomic reduction of thoracolumbar burst fractures. Comparison of distraction versus distraction plus lordosis, in the anatomic reduction of the thoracolumbar burst fracture

The adequate reduction of vertebral burst fractures is dependent on successful application of distractive forces in combination with the restoration of normal spinal lordosis. However, the optimal sequence of distraction in comparison to distraction plus lordosis in the anatomic restoration of the fractured thoracolumbar spine has not been described. Burst fractures of the L1 vertebra were first created and the reduced in vitro using three differing reduction techniques. In six fresh human cadaver spine specimens, the mean fracture severity based on the degree of canal compromise was 31% (SD +/- 20%) after fracture. Reductions were performed using the AO Fixator Intern, the Reduction Fixation (RF) Device, and the Steffee plate systems following standard clinical techniques. The AO Fixator Intern provided independent but variable control of distraction and lordosis, the RF device provided variable distraction with independent, but preset, correction of lordosis and the Steffee system provided set distraction and stabilization. Both the AO and RF devices restored the lordosis (7.6 degrees +/- 5.2 degrees and 9.7 degrees +/- 4.5 degrees, respectively) better than the Steffee plate system (0 degrees +/- 1.6 degrees). However, the AO device provided poorest restoration of the posterior vertebral body height (92% vs 96% for the RF device and 99% for the Steffee plate). The RF device, which restored both lordosis and posterior vertebral body height to the near anatomic prefracture level, provided significantly better canal clearance (9% +/- 8%) than the other techniques, P < 0.05. The study demonstrates that instrumentation systems that provide independent correction of distraction and lordosis can best restore anatomic alignment, with indirect neurodecompression of the compromised spinal canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of cervical spine motion on the neuroforaminal dimensions of human cervical spine

A nerve root impingement within a stenotic neuroforamen is a common sequela of cervical degenerative arthritis and herniated nucleus pulposus. Understanding of the effects of cervical position on foraminal size is important in the assessment of pathology and injury, for selection of a provocative maneuver to elicit symptoms and in selecting a position of immobilization for the management of nerve root impingement syndrome. This biomechanical study of human cadaver cervical spines reports the measured variations in the sizes of neuroforamina as a function of cervical positioning. Five fresh frozen adult human cadaver cervical spines (C2-T1) were tested with combinations of flexion-extension and rotational position. Ten pounds of axial load was applied to simulate a normal loading of a cervical spine. The foramina of C5, C6, and C7 were directly measured using a set of finely graded circular probes. Compared to the foraminal diameter at the neutral position, there were statistically significant reductions in the foramen diameter of 10% and 13%, at 20 degrees and 30 degrees of extension respectively (P < 0.01). Conversely, in flexion, there were statistically significant increase of 8% and 10% at 20 degrees and 30 degrees of flexion respectively (P < 0.01). Though there was a reduction in the foraminal size with ipsilateral 20 degrees rotation, and an increase with contralateral 20 degrees rotation, these changes were not significantly different from the mean of the control. Combinations of flexion or extension position with axial rotation did not significantly change the foraminal size compared to the respective sagittal position with no axial rotation.(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression of proteoglycan synthesis in chondrocyte cultures derived from canine intervertebral disc

Chondrocytes were dissociated enzymatically from canine nucleus pulposus. After attaining monolayer growth, the cells were subpassaged and incubated with sodium salicylate, indomethacin, or sodium meclofenamate (10(-2) M to 3 x 10(-6) M). When incubated with nonsteroidal anti-inflammatory drug concentrations mimicking therapeutic plasma levels, proteoglycan synthesis was significantly suppressed. After 24 hours of incubation, there was a 15% decrease in radioactive sulfate (35SO4) incorporation for salicylate (10(-3) M), a 29% decrease for indomethacin (3 x 10(-6) M), and a 75% decrease for sodium meclofenamate (10(-5) M). This inhibition was both dose- and time-dependent. Despite the effect of these nonsteroidal anti-inflammatory drugs on quantitative proteoglycan synthesis, there was no demonstrable effect of these drugs on the size of proteoglycan monomers or the degree to which proteoglycan aggregate formation occurred.

Evidence that a humoral immune response to autologous cartilage proteoglycan can participate in the induction of cartilage pathology

We examined antiproteoglycan antibodies as an autoimmune response for induction of synovitis. This hypothesis was studied by monitoring humoral antiproteoglycan antibody following IgG induction of experimental immune synovitis, localization in the articular cartilage of an autologous immune response, and loss of proteoglycan from cartilage following intravenous administration of antiproteoglycan monoclonal antibodies. The data support the hypothesis that autoimmunity to cartilage macromolecules may play a role in the etiopathogenesis of arthritis.

Analysis of experimental immune synovitis cartilage using monoclonal antibodies reactive to rabbit proteoglycan

This study details the macromolecular changes in cartilage involving proteoglycan molecules in an animal model of rheumatoid arthritis. In experimental chronic immune synovitis, fluorescein-conjugated mouse IgG and three monoclonal antibodies (MAbs 2G2, 2E9, and 6C9) portraying differing fine antigenic specificity for rabbit cartilage proteoglycan monomer were utilized to detail alterations in cartilage proteoglycan. In normal and IgG-immune animals, fluorescein isothiocynate (FITC)-conjugated MAbs 2G2 and 2E9 stained cellular/pericellular (C/PC) region intensely. FITC-MAb 2G2 stained cartilage interterritorial matrix as well. FITC-MAb 6C9 stained only C/PC area lightly but did not stain matrix. A marked decrease in staining intensity with FITC-MAb 2G2 was noted in cartilage sections derived from animals with immune synovitis. A corresponding increase in staining of cartilage was noted with FITC-MAb 6C9. The augmented staining of articular cartilage with FITC-MAb 6C9 was most prominent in femoral condyle tissue sections, which corresponded to the cartilaginous area, with the greatest severity in gross pathology. There was a slight augmentation of staining with FITC-MAb 2E9, especially in the C/PC area of medial/femoral cartilage. In addition, the animals with immune synovitis showed abortive cartilage repair exemplified by the presence of chondrocyte cloning (up to 20 cells) which correlated with increased FITC-MAb 2G2 staining. The differential MAb staining patterns of cartilaginous tissues obtained utilizing FITC-conjugated monoclonal antibodies with known fine antigenic specificity indicates a modulation of proteoglycans involving predominantly core protein epitopes in the articular cartilage of animals with chronic immune synovitis.

Structural characteristics of articular cartilage proteoglycan in IgG induced experimental immune synovitis

The early changes (five weeks) in the structure of newly synthesised and endogenous articular cartilage sulphated proteoglycans were studied in lapine IgG induced experimental immune synovitis. Rabbits with immune synovitis (IS-IgG) were compared with animals with a developed hypersensitivity to IgG (I-IgG) and with non-treated normal weight matched controls. Medial and lateral femoral condyle and tibial plateau cartilage was pooled and radiolabelled for 24 h in vitro with 35SO4. The samples constituted tissue from regions underlying pannus and from pannus free sites. Cartilage from animals with IS-IgG showed a significantly diminished amount of newly synthesised and endogenous proteoglycan aggregate and an increased amount of hydrodynamically small proteoglycans. Newly synthesised (obtained by in vivo radiosulphate labelling) and endogenous proteoglycans showed a similar profile. The proteoglycan monomer fraction from animals with IS-IgG failed to form proteoglycan aggregates in the presence of excess hyaluronic acid. In the group with IS-IgG linear regression analysis showed a statistically significant relationship between the synovial pathology scores (but not cartilage pathology score) and diminished newly synthesised and endogenous proteoglycan aggregate.

Epitopes of proteoglycans eliciting an anti-proteoglycan response in chronic immune synovitis

This study details the immune response to cartilage proteoglycan in experimental chronic IgG-induced immune synovitis. Antibodies reactive with purified rabbit proteoglycan monomer were observed in nine of nine rabbits with immune synovitis. IgG-immunized but nonsynovitic control animals with no pathology showed no antibody response. A panel of murine monoclonal antibodies with defined specificity towards rabbit proteoglycan were utilized to characterize the epitope specificity of the immune synovitis polyclonal anti-proteoglycan response. One murine monoclonal antibody, 6C11, inhibited the binding of the polyclonal antisera to proteoglycan in all nine animals with significant (greater than 40%) inhibition in six of nine rabbits. Further inhibition studies utilizing DEAE-cellulose-resolved proteoglycan tryptic peptides revealed that peptides poor in chondroitin sulfate were strong inhibitors of binding of the polyclonal antibodies to the proteoglycan substrate. In particular, keratan sulfate-containing tryptic peptides were most inhibitory on a per weight basis. These results indicate that, in chronic IgG-induced immune synovitis, anti-proteoglycan antibodies elicited are heterogeneous with regard to specificity, but a relatively large proportion predominantly recognized a portion of the proteoglycan molecule containing core protein and associated keratan sulfate.