Markus W. Kroeber

Effects of controlled dynamic disc distraction on degenerated intervertebral discs: An in vivo study on the rabbit lumbar spine model

Study Design. An in vivo study on the rabbit lumbar spine model. Objectives. Effects of temporary dynamic distraction on intervertebral discs were studied on the lumbar spine rabbit model to characterize the changes associated with disc distraction and to evaluate feasibility of temporary disc distraction to previously compressed discs in order to stimulate disc regeneration. Summary of Background Data. Studies have shown that accelerated degeneration of the intervertebral disc results from altered mechanical loading conditions. The development of methods for the prevention of disc degeneration and the restoration of disc tissue that has already degenerated are needed. Methods. New Zealand white rabbits (n = 32) were used for this study. The rabbits were randomly assigned to one of five groups. In 12 animals, the discs were first loaded for 28 days using a custom-made external loading device to stimulate disc degeneration. After 28 days loading time, the discs in six animals were distracted for 7 days and in six animals for 28 days using the same external device, however, modified as dynamic distraction device. In six animals, the discs were distracted for 28 days without previous loading; and in six animals, the discs were loaded for 28 days and afterwards the loading device removed for 28 days for recovery without distraction. Six animals were sham operated. The external device was situated; however, the discs remained undistracted and they also served as controls. After 28 to 56 days loading and distraction time, the animals were killed and the lumbar spine was harvested for examination. Disc height, disc morphology, cell viability, relative neutral zone, and tangent modulus were measured. Results. After 28 days of loading, the discs demonstrated a significant decrease in disc space. Histologically, disorganization of the architecture of the anulus occurred. The number of dead cells increased significantly in the anulus and cartilage endplate. These changes were re-versible after 28 days of distraction. The disc thickness increased significantly as compared with the specimens from the 28 days loading group without distraction. Histologically, the discs showed signs of tissue regeneration after 28 days of distraction. The number of dead cells decreased significantly in comparison with the loaded discs without distraction. The flexibility of compressed discs was higher than of compressed/distracted discs. Conclusions. The results of this study suggest that disc regeneration can be induced by axial dynamic distraction in the rabbit intervertebral disc. The decompressed rabbit intervertebral discs showed signs of tissue recovery on a biologic, cellular, and a biomechanical level after 28 days of distraction.

Clinical Outcome of Deep Wound Infection After Instrumented Posterior Spinal Fusion : A Matched Cohort Analysis

Study Design. Retrospective case control study. Objective. Determine the impact of infection on clinical outcome in patients undergoing posterior spinal fusion surgery. Summary of Background Data. The outcome of patients treated for infection after spinal surgery is not well established because of variability in cohort identification, definition of infection, outcomes instrument, use of a control group, and/or sample size. Methods. Thirty-two patients were included. Sixteen patients (“infection group”) met inclusion criteria of deep wound infection after spinal fusion with posterior segmental instrumentation (including combined approach). A 1:1 matched cohort (“control group”) was created based on primary or revision status, length of fusion, diagnosis, and age. Postoperative patient outcomes were evaluated using the physical components of SF-36 v2.0 with minimum 2-year follow-up. Results. No significant difference in the Physical Function, Role Physical, Bodily Pain, and General Health domains was detected between the infection group and control group. Mean follow-up was 62 months. Mean Physical Component Summary was 41.4 in the infection group and 44.3 in the control group (P = 0.6). Infection occurred early in 12 patients and late in 4 patients. Most common organisms isolated were Staphylococcus epidermidis, Enterococcus sp., and Staphylococcus aureus. Multiple debridements were significantly associated with polymicrobial infections and later pseudarthrosis requiring reoperation. Conclusion. An aggressive approach to deep wound infection emphasizing early irrigation and debridement allowed preservation of instrumentation and successful fusion in most cases. At the conclusion of treatment, patients can expect a medium-term clinical outcome similar to patients in whom this complication did not occur.

Stimulation of gene expression and loss of anular architecture caused by experimental disc degeneration--an in vivo animal study.

Study Design. An external compression model was used to evaluate gene and protein expression in intervertebral discs with moderate disc degeneration. Objective. To determine messenger ribonucleic acid and protein expression levels of relevant disc components. Summary of Background Data. An animal model of mechanically induced disc degeneration was developed and characterized histologically. However, little is known at the molecular level in moderate disc degeneration. Methods. There were 8 New Zealand white rabbits subjected to monosegmental posterior compression to induce moderate disc degeneration. Twelve animals served as controls or sham controls. Discs were analyzed using immunohistochemistry for collagen type 1 (COL1), COL2, aggrecan, and bone morphogenetic protein-2/4 (BMP-2/4). For gene analysis, conventional and quantitative polymerase chain reactions were used for COL1A2, COL2A1, aggrecan, BMP-2, biglycan, decorin, osteonectin, fibromodulin, fibronectin, matrix metalloproteinase-13 (MMP-13), and tissue inhibitor of MMP-1. Gene expression for nontreated, sham-treated, and compressed discs was quantified in relation to the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase. Results. Immunohistochemistry of compressed discs showed a loss of anular architecture, and a significant reduction of BMP-2/4 and COL2 positive cells. Gene expression analysis showed a significant up-regulation of COL1A2, osteonectin, decorin, fibronectin, tissue inhibitor of MMP-1, BMP-2, and MMP-13 in compressed discs. Conclusions. Experimental moderate disc degeneration is characterized by a loss of BMP-2/4 and COL2 positive cells, although gene expression of disc constituents, catabolic enzymes, and growth factors is stimulated to reestablish disc integrity.

Disc distraction shows evidence of regenerative potential in degenerated intervertebral discs as evaluated by protein expression, magnetic resonance imaging, and messenger ribonucleic acid expression analysis.

Study Design. An animal model of degeneration was used to determine the effects of disc distraction, and was evaluated with magnetic resonance imaging (MRI) as well as gene and protein expression levels. Objective. To investigate gene expression and MRI effects of distraction. Summary of Background Data. Disc degeneration can result from hyper-physiologic loading. Distracted discs with degeneration showed histologic signs of tissue recovery. Methods. There were 18 rabbits that underwent 28 days of compression (200 N) to induce moderate disc degeneration followed by 28 days of distraction (120 N; attached and loaded distraction device) or sham distraction (attached but unloaded distraction device). Comparison was performed with 56 days of compressed discs without distraction. Quantitative outcome measures were MRI signal intensity and gene expression analysis to determine: messenger ribonucleic acid levels for extracellular matrix genes, including collagen 1, collagen 2, biglycan, decorin, aggrecan, fibromodulin, and osteonectin; and matrix-regulative genes, including matrix metalloproteinase-13, tissue-inhibitor of matrix metalloproteinase-1, and bone morphogenetic protein (BMP)-2. Immunohistology was performed for collagen 2 and BMP-2 to label cells semiquantitatively by staining of the cell-surrounding matrix. Results. A total of 28 days of compression decreased signal intensity. Distraction over the same period reestablished physiologic signal intensity, however, a persistent reduction was found in sham distraction. Distraction resulted in gene expression up-regulation of collagen 1 (5.4-fold), collagen 2 (5.5-fold), biglycan (7.7-fold), and decorin (3.4-fold), while expression of fibromodulin (0.16-fold), tissue-inhibitor of matrix metalloproteinase-1 (0.05-fold), and BMP-2 (0.15-fold) was decreased, as compared with 56 days compression. Distracted discs showed more BMP-2 (19.67 vs. 3.67 in 56 days compression) and collagen 2 (18.67 vs. 11.33 in 56 days compression) positive cells per field. Conclusions. Distraction results in disc rehydration, stimulated extracellular matrix gene expression, and increased numbers of protein-expressing cells.

Apoptotic Pathways in Degenerative Disk Lesions in the Wrist

PURPOSE Degenerative articular disk perforations of the triangular fibrocartilage (TFC) of the wrist could result from chronic loading of the ulnocarpal joint. Apoptosis played a crucial role in fibrocartilage cell loss, and the purpose of this study was to clarify which apoptotic pathway was involved in the development of degenerative disk lesions. We also investigated whether ulna length played an etiologic role in the occurrence of fibrocartilage cell loss. METHODS Included in the study were 17 patients with degenerative articular disk tears of the TFC (Palmer type 2C). After arthroscopic debridement of the TFC, histologic sections were examined to assess the presence of apoptosis. Apoptosis was determined by use of caspase 3, caspase 8, and caspase 9 immunohistochemistry. Furthermore, Fas ligand and BID (BH3 interacting domain death) agonist were applied for immunohistochemical analysis. RESULTS Cells positive for caspase 3, caspase 8, caspase 9, Fas ligand, and BID were found in all specimens. The number of cells positive for caspase 3 and BID was significantly increased in specimens from patients with an ulna-positive variance. In contrast, for cells positive for caspase 8, caspase 9, and Fas ligand, no significant difference was found between specimens from patients with an ulna-positive variance and those from patients with an ulna-neutral/ulna-negative variance. CONCLUSIONS The extrinsic and intrinsic apoptotic pathways are involved in the development of degenerative disk lesions. Fibrocartilage cell loss occurs mainly through the intrinsic apoptotic pathway. The accumulation of apoptotic cells is not significantly different between the 3 zones of the TFC. It could be verified that ulna length is correlated with fibrocartilage cell loss. CLINICAL RELEVANCE Ulnar shortening is a valuable treatment option for degenerative TFC lesions. Knowledge of the specific apoptotic pathway that is causing degenerative disk lesions is critical in selecting the appropriate and most beneficial therapeutic treatment to halt further cell loss and the degeneration of the TFC.

Cartilage cell proliferation in degenerative TFCC wrist lesions

IntroductionThe central zone of the triangular fibrocartilage complex (TFCC) of the wrist is thought to be avascular and is generally considered to lack any healing potential.AimThe purpose of this study was to investigate, if cartilage cells of degenerative disc lesions possess any healing or proliferation potential and whether ulna length plays a significant role in the proliferation process.ResultsCells positive for proliferating cell nuclear antigen (PCNA) were found in all specimens. Specimens of patients with ulna positive variance showed a decreased number of PCNA positive cells than specimens of patients with either negative or neutral ulna variance.ConclusionWe found that cartilage cells of Palmer type 2C lesions undergo mitotic cell division, thus exhibiting proliferation capability. It could not be shown that ulnar length is significantly correlated with the number of PCNA positive cells.

Biomechanical Testing of Bioabsorbable Cannulated Screws for Slipped Capital Femoral Epiphysis Fixation

This study compared cannulated 4.5-mm bioabsorbable screws made of self-reinforced poly-levolactic acid to cannulated 4.5-mm steel and titanium screws for resistance to shear stress and ability to generate compression in a polyurethane foam model of slipped capital femoral epiphysis fixation. The maximum shear stress resisted by the three screw types was similar (self-reinforced poly-levolactic acid 371 +/- 146 MPa, steel 442 +/- 43 MPa, and titanium 470 +/- 91 MPa). The maximum compression generated by both the self-reinforced poly-levolactic acid screw (68.5 +/- 3.3 N) and the steel screw (63.3 +/- 5.9 N) was greater than that for the titanium screw (3 +/- 1.4 N, P <.05). These data suggest cannulated self-reinforced poly-levolactic acid screws can be used in the treatment of slipped capital femoral epiphysis because of their sufficient biomechanical strength.

Shortening spinal column reconstruction through posterior only approach for the treatment of unstable osteoporotic burst lumber fracture: a case report

Study designCase report.Clinical questionThis study reports if shortening reconstruction procedure through posterior approach only can be used in osteoporotic unstable fracture as well as post-traumatic burst fracture.MethodsAn 80-year-old female patient with unstable burst osteoporotic fracture of L1 underwent posterior approach corpectomy and shortening reconstruction of the spinal column by non-expandable cages.ResultThe surgery was uneventful, with average blood loss. Using of small profile cages has helped us to avoid root injury. Augmentation of the screw with cement and the compressive force applied to the spine column aids in obtaining a rigid construct with good alignment without any neurological complication.ConclusionShortening reconstruction procedure through only posterior approach is a viable option in treating unstable osteoporotic fracture as well as post-traumatic fractures. Using non-expandable cage is advocated to avoid cage subsidence.

Expression of leptin, leptin receptor, and connective tissue growth factor in degenerative disk lesions in the wrist.

PURPOSE The purpose of this study was to identify whether leptin and connective tissue growth factor (CTGF) occur in the degenerative fibrocartilage disk and whether cartilage cells express leptin receptors. METHODS The study included 23 patients diagnosed with degenerative articular disk tears of the triangular fibrocartilage (TFC) (Palmer type 2C). Patients were divided into 2 groups based on ulna length: 1 group consisted of patients with an ulna-positive variance (group A), and the other group included patients with ulna-negative or -neutral variance (group B). After arthroscopic debridement of the TFC, histologic sections of biopsy specimens were prepared. The biopsy specimens were immunohistochemically analyzed, and the quantity of leptin-, CTGF-, and leptin receptor-positive cells was assessed. RESULTS Cells positive for leptin, leptin receptor, and CTGF were found. The number of cells positive for leptin was significantly increased in specimens of patients with an ulna-negative variance (group B). In contrast, no significant difference was found for leptin receptor and CTGF in biopsy specimens of patients with ulna-positive or ulna-negative/neutral variance. The inner, middle, and outer zones of the disk do not express significantly different quantities of marker-positive cells. CONCLUSIONS Degenerative fibrocartilage disk tissue cells exhibit leptin receptors and are exposed to the markers leptin and CTGF, providing evidence of a local paracrine system and regenerative processes. Cells of disks from patients with an ulna-neutral/negative length express significantly higher numbers of leptin-positive cells. LEVEL OF EVIDENCE Level II, diagnostic study.

Beneficial effects following microsurgical decompression in an adult with congenital thoraco-lumbar kyphoscoliosis with spina bifida aperta and myelomeningocele: an interesting case report

Study designCase report.Clinical questionTo report successful surgical therapy for spinal canal stenosis in an adult patient with congenital thoraco-lumbar kyphoscoliosis with spina bifida aperta and myelomeningocele.MethodsA 65-year-old woman with a history of congenital thoraco-lumbar kyphoscoliosis with spina bifida aperta and myelomeningocele presented with severe radicular pain and weakness in her left lower limb.ResultsThe patient underwent microsurgical decompression at the level of L3/S1 on the left side. Postsurgery, the patient showed significant amount of pain relief and improvement in weakness in the left lower limb.ConclusionSurgery for spinal canal stenosis in patients with severe thoraco-lumbar scoliosis can be effective in relieving radicular pain, weakness and numbness, and while not curative can greatly improve the quality of life.