Small intestinal submucosa as a potential bioscaffold for intervertebral disc regeneration.

STUDY DESIGN: To evaluate the capacity of porcine small intestine submucosa to support the in vitro proliferation of human disc cells and the synthesis of extracellular matrix that could restore the biochemical properties of the disc. OBJECTIVE: To evaluate if porcine small intestine submucosa is a potential bioactive scaffold for rescuing degenerative disc cells. SUMMARY OF BACKGROUND DATA: Discogenic back pain is associated with alterations of the disc and abnormal turnover of the disc extracellular matrix. We hypothesize that a biodegradable and biocompatible acellular scaffold such as small intestine submucosa, which contains entrapped growth factors, may stimulate disc cells to synthesize extracellular matrix, thereby arresting the degeneration, or even promoting the regeneration, of the disc. METHODS: Human degenerative anulus and nucleus cells were seeded onto small intestine submucosa scaffolds, and evaluated over a 3-month period for cell growth (proliferation assay, deoxyribonucleic acid content) and matrix composition (glycosaminoglycan and collagen contents). RESULTS: As hematoxylin and eosin staining revealed, more than 70% of seeded cells attached to the small intestine submucosa surface and invaded throughout the scaffold. The macroscopic appearance of cell-seeded scaffolds was dramatically modified over time. Cell metabolic activity was confirmed for up to 3 months. Seeded scaffolds showed a higher glycosaminoglycan content as compared to control scaffolds. Toluidine blue staining detected large areas of proteoglycans. Positive gene expression for collagens I, II, and X, aggrecan, and Sox-9 confirmed deposition of new extracellular matrix components. CONCLUSIONS: This pilot study shows that small intestine submucosa is a promising bioactive material that could potentially serve as a temporary scaffold for intervertebral disc regeneration.

In vivo evaluation of plasmid DNA encoding OP-1 protein for spine fusion.

STUDY DESIGN: A posterolateral lumbar interbody arthrodesis animal model was selected to evaluate the percutaneous delivery of OP-1 plasmid DNA. OBJECTIVE.: To evaluate the feasibility of achieving ectopic bone formation using nonviral gene delivery with a minimally invasive technique, by coinjecting plasmid DNA encoding OP-1 with collagen into the paraspinal muscle. SUMMARY OF BACKGROUND DATA: Osteoinductive proteins show great promise for achieving spine fusion but suffer from poor bioavailability. Viral gene transfer can produce therapeutic and sustained levels of osteoinductive proteins to achieve osteogenesis in a variety of animal models. Toxicity and immunogenicity concerns, however, limit the appeal of viral gene therapy for spine fusion. METHODS: Single-level posterior lumbar arthrodesis was attempted at L5-L6 in 64 adult Sprague-Dawley rats bilaterally. OP-1 plasmid DNA was injected with and without collagen carrier above the L5 transverse process either percutaneously or after open surgery. Bone formation was evaluated at 2 and 4 weeks by manual palpation, posterolateral radiographs, and nondecalcified histology. Control animals received the rhOP-1 protein. RESULTS: Bone formation was detected histologically after the percutaneous and open surgical delivery of 25 microg or 500 microg, respectively, of OP-1 plasmid DNA (pVR1055-OP1) and collagen (bone formation = 75% and 50%), but was weaker than that observed after injection of 30 microg of rhOP-1 protein and collagen (bone formation = 100%). Single-level spine fusion was only achieved in groups receiving percutaneous OP-1 protein and collagen (30 microg protein, fusion rate = 100%) or high concentrations of OP-1 protein alone (40 microg protein, 100%), as confirmed through manual palpation, histology, and radiography. CONCLUSIONS.: These data confirm that OP-1 plasmid DNA can successfully generate bone formation in vivo.

Interaction of human mesenchymal stem cells with disc cells: changes in extracellular matrix biosynthesis.

STUDY DESIGN: To evaluate the in vitro interactions between human mesenchymal stem cells (MSCs) and degenerative disc cells. OBJECTIVES: To demonstrate the potential of MSCs in regulating the extracellular matrix synthesis of degenerative disc cells. SUMMARY OF BACKGROUND DATA: Culture of degenerative disc cells followed by their reinsertion into a disc can retard the degeneration process in an animal model. However, harvesting cells without accelerating degeneration is problematic. Autologous MSCs can be safely harvested from the bone marrow and transplanted into degenerative discs. METHODS: Human degenerative nucleus pulposus (NP), anulus fibrosus (AF) cells, and MSCs were cultured as pellets, and coculture pellets were formed by addition of MSCs to disc cells (50:50 ratio). Glycosaminoglycan (GAG) and DNA content were measured. Proteoglycan synthesis was analyzed by RT-PCR and western blot. Type II collagen expression was assessed by immunohistochemistry. RESULTS: Coculture pellets formed by the addition of MSCs to AF cells were superior in size to all other pellets. AF/MSC pellets showed higher experimental GAG content than the predicted values represented by the sum of individual control pellets, with 10.2 versus 5.6 microg/pellet at week 3, respectively. The effect was not observed in the NP/MSC coculture, or when chondrogenic medium was used. Close contact between cells was necessary to obtain this enhancement of GAG content. Proteoglycan and collagen expression in both individual and coculture pellets was confirmed by PCR analysis and western blot. CONCLUSION: Addition of MSCs to AF cells resulted in an up-regulation of the proteoglycans synthesis. This study provides the rationale for further investigation of the potential of MSC therapy in treating intervertebral disc degeneration.

Temperature-responsive hydroxybutyl chitosan for the culture of mesenchymal stem cells and intervertebral disk cells.

Temperature-responsive polymers are attractive candidates for applications related to injectable delivery of biologically active therapeutics, such as stem cells. In this study, we evaluate the potential of thermosensitive hydroxybutyl chitosan (HBC) as a biomaterial for the culture of human mesenchymal stem cells (hMSC) and cells derived from the intervertebral disk, with the eventual goal of using the HBC polymer as an injectable matrix/cell therapeutic. Conjugation of hydroxybutyl groups to chitosan renders the polymer water soluble and thermally responsive. Below its lower critical solution temperature, a solution of HBC can be maintained indefinitely in its solvated state. Upon exposure to a 37 degrees C environment, within 60 s, a 3.8 wt% HBC solution rapidly forms a gel that can be maneuvered with forceps. Upon cooling, the gel once again is able to revert to its solvated state. The gel exhibits a dramatic increase in both G' and G'' with increasing temperature, signifying a temperature-dependent enhancement of gel mechanical properties. Although a solid structure upon gelation, due to its physical nature of polymer interaction and gel formation, the gel exhibits a fluid-like viscoelastic behavior when exposed to shear stresses of up to 10% strain, with both G' and G'' approaching zero with increasing shear stress. Formulations of HBC gels presented in this study have gelation temperatures ranging from 13.0 to 34.6 degrees C and water contents of 67-95%. Minimal cytotoxicity in MSC and disk cell cultures was observed with these polymers up to a concentration of 5 wt%. Detection of metabolic activity, genetic analysis of synthesized mRNA, and histological staining of MSC and disk cell cultures in these gels collectively indicate cell proliferation without a loss in metabolic activity and extracellular matrix production. This study suggests the potential of HBC gel as an injectable carrier for future applications of delivering therapeutics to encourage a biologically relevant reconstruction of the degenerated disk.

Functional and radiographic outcome of sacroiliac arthrodesis for the disorders of the sacroiliac joint.

BACKGROUND CONTEXT: The sacroiliac joint is known to be a possible cause of chronic low back pain, but the diagnosis and treatment of disorders of the sacroiliac joint have been difficult and controversial. PURPOSE: To describe the outcome of sacroiliac joint arthrodesis for sacroiliac joint disorders, with the hypothesis that sacroiliac arthrodesis leads to improved postoperative function. STUDY DESIGN/SETTING: Consecutive case series performed in an academic medical institution. PATIENT SAMPLE: The patient population consisted of 20 patients undergoing sacroiliac joint arthrodesis between December 1994 and December 2001. Patients undergoing concomitant procedures at the time of sacroiliac joint arthrodesis were excluded. The 3 men and 17 women in the study group had an average age of 45.1 years (range 21.8-66.4 years), a mean duration of symptoms of 2.6 years (range 0.5-8.0 years), and a mean follow-up period of 5.8 years (range 2.0-9.0 years). OUTCOME MEASURES: Outcome measures included general health and function, clinical evaluation, and radiographic assessment. METHODS: For all 20 patients, nonoperative treatment had failed, and for all, the diagnosis was confirmed by pain relief with intraarticular sacroiliac joint injections under fluoroscopic guidance. Sacroiliac joint arthrodesis (via a modified Smith-Petersen technique) was recommended only when a positive response to the injection was noted, and patients had recurrence of symptoms after the initial positive response. Preoperative and postoperative general health and function were assessed via the 36-item Short-Form (SF-36) Health Survey and American Academy of Orthopaedic Surgeons (AAOS) Modems Instrument, which were collected prospectively. Medical records and plain radiographs were reviewed retrospectively to determine the clinical and radiographic outcome. RESULTS: Multiple etiologies of sacroiliac symptoms were observed: sacroiliac joint dysfunction (13 patients), osteoarthritis (5 patients), and spondyloarthropathy and sacroiliac joint instability (1 each). Seventeen patients (85%) had solid fusion. Fifteen patients (75%) completed preoperative and postoperative SF-36 forms. Significant (p< or =.05) improvement occurred in the following categories: physical functioning, role physical, bodily pain, vitality, social functioning, role emotional, and neurogenic and pain indices. Improvement (not statistically significant) was also noted in general and mental health. CONCLUSIONS: For carefully selected patients, sacroiliac arthrodesis appears to be a safe, well-tolerated, and successful procedure, leading to significant improvement in functional outcome and a high fusion rate. To the authors' knowledge, the current report is the largest series to document the functional and radiographic outcome of sacroiliac joint arthrodesis.

Evaluation of the biological response of wear debris.

STUDY DESIGN: An animal study was conducted to evaluate the biological response to titanium particles from an artificial intervertebral disc in terms of serology and histologic changes. OBJECTIVES: To determine the biological response to wear debris in the retroperitoneal and epidural space. SUMMARY OF BACKGROUND DATA: Few wear studies exist about mechanical artificial discs. METHODS: Twenty-three New Zealand white rabbits were used for two approaches of the lumbar spine. In a retroperitoneal group (10 rabbits), lateral flank approach at the L2-L3 area was used. In an epidural group (13 rabbits), a dorsal laminotomy of L2 was performed. The wear debris was obtained from mechanical test cycling of the implantable intervertebral disc. At 4 and 12 weeks postoperatively, five or six animals from each group were killed. The tissues, including deposition site, regional lymph nodes and major organs, were evaluated with hematoxylin and eosin staining. RESULTS: At death all rabbits were found to be healthy. Blood results from the predeath samples were found to be consistent with the preoperative blood work values. Scar tissue was minimal with good healing. All organs were found to be normal in appearance. On histopathology sections, adverse reactions such as fibrosis, granuloma formation or necrosis were not found in any tissues. Free particles were found sparingly in all tissue sections with minimal cellular response. No remarkable difference was found according to groups or time intervals. Smaller particles were found to be engulfed in macrophages without adverse biological consequences. CONCLUSION: Titanium particles traveled from the sites of deposition but elicited no to minimal biological response.

Concepts in nuclear replacement.

This article describes the pathogenesis of early nuclear failure and current philosophical approaches to artificial, biological, and bioartificial nucleus replacement. Necessary in this review is an overview of current approaches to nucleus replacement with prosthetics and various gel materials.

Surgeon perceptions of the complications and value of threaded fusion cages as a spine fusion technique: results of a consensus survey.

BACKGROUND CONTEXT: Threaded cage technology has had a meteoric rise in usage. It has been touted as a procedure with low risk and minimal complications. PURPOSE: To gauge the spine surgical community's general consensus regarding cage usage and its complications. STUDY DESIGN/SETTING: A canvassing questionnaire regarding threaded cage usage and complications was sent to members of the North American Spine Society. PATIENT SAMPLE: A total of 665 doctors reported on their perception of 22,585 cages placed by the second year after pre-market approval from the Food and Drug Administration approval. OUTCOME MEASURES: A nonscientific canvassing questionnaire was thought to give a consensus of surgical outcome perception in a large number of caregivers with hopes of understanding general trends. METHODS: Simple statistical measurements were used to report perceived complications by surgeons involved in performing threaded cage surgical procedures. RESULTS: Sixty-nine percent of doctors reported at least one complication with threaded cages, but the complication incidence was low. Visceral injuries were reported in 0.1%; vascular injuries, 1.0%; cage displacement and dislodgement, 1.4%; temporary and permanent neurologic injuries, 2.25% and 0.56%, respectively; infection 0.34%; retrograde ejaculation 1.2% and revision surgery recorded for 2.7%. Those rating cages as fair to poor (16.5%) were those physicians reporting the longest experience with this technology. CONCLUSIONS: The general consensus is that threaded cages have low complication rates and high satisfaction rates, 83.5%. The data represent a convenience sampling and is not scientific.

Functional outcome and radiographic correction after spinal osteotomy.

STUDY DESIGN: A prospective clinical trial to study the radiographic parameters and functional outcome in patients undergoing spinal osteotomy. OBJECTIVES: To determine whether correction of specific radiographic parameters is associated with improved functional outcome. SUMMARY OF BACKGROUND DATA: Although vertebral osteotomies have been shown to improve functional outcome in patients with spinal deformity, no prospective reports have studied whether correction of specific radiographic parameters is associated with improvement in functional outcome. METHODS: Eighty-three patients with fixed sagittal and/or coronal deformity were followed over a 7-year period. Patients were evaluated clinically and radiographically and completed a SF-36 Health Survey and American Academy of Orthopedic Surgeons Modems Instrument questionnaire. Spearman correlation analysis was used to determine the association between correction of radiographic parameters and functional outcome. RESULTS: Mean preoperative lumbar lordosis measured -14.2 degrees (i.e., kyphosis) with an average postoperative correction of 27.9 degrees. Mean preoperative lumbar scoliosis measured 40.1 degrees with an average postoperative correction of 15.1 degrees. Mean preoperative plumb sagittal and coronal plane alignment was 8.37 cm and 4.22 cm, respectively; after surgery they improved to 3.33 cm and 2.31 cm, respectively. A significant association was found between sagittal angular correction and physical function (P = 0.034) and role-physical (P = 0.01) when postoperative lumbar lordosis was >25 degrees. A significant association was also found between plumb coronal correction and physical function (P = 0.041), vitality (P = 0.05), and social function (P = 0.047) when postoperative plumb coronal alignment was <2.5 cm. CONCLUSIONS: Correction of sagittal and coronal deformity is important in the treatment of spinal deformity. A significant association was found between outcomes and radiographic correction of coronal and/or sagittal deformity if postoperative sagittal lordosis was >25 degrees and if postoperative plumb coronal alignment was <2.5 cm. Therefore, these radiographic parameters should be the goal of a spinal osteotomy. The surgery has a relatively high complication rate.

Role of femoral ring allograft in anterior interbody fusion of the spine.

A review was carried out on 59 patients (10 males and 49 females) who had anterior interbody fusion performed with femoral ring allograft packed with autograft bone chips with a minimum follow up of 2 years. The average age at the time of surgery was 49.1 year old (26 to 75). The total number of levels grafted was 141. The diagnosis consisted of multiple degenerative disease in 6, degenerative change below the long segment of fusion for scoliosis in 9, osteoporosis with collapsed fracture in 3, pseudarthrosis after posterior laminectomy and fusion in 35, congenital scoliosis in 3, scoliosis in 2 and paralytic scoliosis due to multiple sclerosis in one. The distribution of levels fused was T12-L1 in 6, L1-2 in 12, L2-3 in 17, L3-4 in 22, L4-5 in 35 and L5-S1 in 39. The remaining 10 levels were in the lower thoracic areas (T7-T12). The operations were performed as anterior fusion alone in 13 patients, one-stage anterior and posterior fusion in 26 patients and two-stage surgery in 20 patients. Anterior instrumentation was used in all 141 levels. At average follow-up (33.7 months) there was no significant change in allograft angles (average = 1.6 degrees ). Fusion of the allograft was classified by Bridwell's grading system. At 24 months of the follow up, 97 % of the allografts were in grade I (fully incorporated) and 3% were in grade II (partially incorporated). Compared to 12 months follow-up only 76.2% of the grafts were in grade I, 28 % were in grade II and 0.8% were in grade III. Two patients had deep posterior infections which required further surgery (without resorption of the allograft anteriorly). One patient had a screw migration anteriorly which required removal. Three patients had persistence of radiolucent line at one of the vertebral end plates - graft interfaces but no subsidence of the graft or pain. In conclusion, the femoral ring allograft appeared to benefit the anterior interbody fusion in complex spinal surgery.