Allograft-Reconstructed Iliac Bone Graft Donor Site Remodels to Viable Bone and Its Feasibility for Revision Fusion.

BACKGROUND: Bone autograft options may be limited in revision spinal fusion cases. Reconstruction of the iliac bone graft (IBG) donor site with cancellous bone allograft allows for reharvest for patients who subsequently have another fusion. This study examined viability of the reconstructed IBG (RIBG) donor sites. Secondarily, we assessed the feasibility of whether the RIBG sites could be reharvested for obtaining a successful arthrodesis for a secondary fusion. METHODS: Prospectively collected data of 154 consecutive lumbar revision fusions were reviewed, of which 17 cases had their IBG donor site backfilled with allograft bone at the time of their primary fusion and subsequently had secondary surgery for a pseudarthrosis repair or fusion extension. Biopsies of the RIBG and computed tomography (CT) images were obtained at the time of secondary fusion. Histology analyzed the ratio of filled to unfilled lacunae and marrow cellularity. Histology controls were from normal iliac crest. Clinically, postoperative CT and >2-year outcomes (visual analog scale [VAS] and Oswestry Disability Index [ODI]) evaluated the feasibility of the secondary fusion surgery using RIBG. The RIBG fusion rate and outcomes were compared with clinical control revision groups that had IBG and/or bone morphogenetic protein (BMP) used for their revision fusion. RESULTS: CT images prior to RIBG harvest found bony healing of the original graft donor site in all except 1 case. RIBG bone marrow histology found lower cellularity vs controls, but this characteristic did not appear to compromise bone viability with filled lacunae in 83% ± 14% in the RIBG group, vs 88% ± 8% for iliac controls. After revision fusion, often combined with bone growth stimulator or BMP, repeat CT demonstrated solid spinal fusions in 16 of 17 patients, whereas control revision group fusion rates were approximately 80%. Clinical improvement was significant (VAS decrease = 3.8, ODI decrease = 16.5) and comparable with the IBG revision controls. CONCLUSION: RIBG using allograft remodels into viable predominately cancellous bone and is clinically feasible for revision fusion if IBG or BMP is unavailable. CLINICAL RELEVANCE: Reconstructed iliac bone graft is viable and may be used as a bone graft option.

Chiropractic Care of a Female Veteran After Cervical Total Disk Replacement: A Case Report.

Objective: The purpose of this case study is to describe chiropractic care of the cervical spine for a patient who previously underwent cervical total disk replacement (CTDR) of the C5-6 and C6-7 disks. Clinical Features: A 42-year-old female veteran of the U.S. Army presented to a Veterans Affairs chiropractic clinic with chronic cervical pain and radiculopathy. She had previously undergone CTDR surgery of the C5-6 disk 9 years earlier, but the pain had become severe and radicular symptoms had returned in the upper left extremity. Imaging taken before the chiropractic referral demonstrated significant joint space narrowing and disk herniation of the C6-7 disk with protrusion to the left side. Intervention and Outcome: The patient received spinal manipulative therapy, trigger-point therapy, and manual traction to the cervical spine. However, these treatments were not effective in reducing her cervical pain and radiculopathy. She then opted for CTDR of the C6-7 disk. After surgery, the patient reported that radicular symptoms were mostly relieved and cervical pain had decreased by 50%. After 6 additional spinal manipulative therapy treatments, she reported having no neurologic symptoms and that her pain had decreased more than 70% from presurgery levels. Conclusion: This case report is the first reported example of chiropractic care after CTDR within an integrated health care environment. The patient's cervical pain and radiculopathy improved with CTDR along with postsurgical chiropractic care.

Value of single-level circumferential fusion: a 10-year prospective outcomes and cost-effectiveness analysis comparing posterior facet versus pedicle screw fixation.

PURPOSE: To compare the clinical and economic outcomes of facet versus pedicle screw instrumentation for single-level circumferential lumbar spinal fusion. METHODS: Outcomes included self-assessment of back and leg pain, pain drawing, ODI, pain medication usage, and procedure success. The CEA was based on the 10-year data collected, and the base-case was from a US payer perspective. Costs included the index surgery, additional surgeries, outpatient/ED visits, and medications. To determine quality-adjusted life years (QALYs), ODI scores were used to predict SF-6D utilities. Sensitivity analyses were performed from a modified payer perspective including device costs and from a societal perspective including productivity loss. Discounted and undiscounted incremental costs and QALYs were calculated. Bootstrapping was performed to estimate the distribution of incremental costs and effects. RESULTS: Clinical improvement was significant from pre-op to 10-year follow-up for both groups (p < 0.01 for all outcomes scales). Outcomes were significantly better for back pain and ODI for the facet versus pedicle group at all follow-up periods > 1 year (p < 0.05). In the CEA base-case, facets had more QALYs (0.68) and lower costs (- $8650) per person compared with pedicle screws. Therefore, facets were dominant (i.e., provided cost savings and greater QALYs) compared with pedicle screws. Facets had a 97% probability of being below a willingness-to-pay threshold of $20,000 per QALY gained and were estimated to be dominant over pedicle screws in 84% of the simulations. CONCLUSION: One-level circumferential spinal fusion using facet screws was clinically superior and provided cost savings compared with pedicle screw instrumentation in the USA.

Postoperative Care Pathways Following Lumbar Total Disc Replacement: Results of a Modified Delphi Approach.

STUDY DESIGN: A modified Delphi method was used to establish consensus. Subject matter experts were invited to participate as the expert panel. Best practice statements were distributed to the panel. Panel members were asked to mark "agree" or "disagree" after a series of statements during several rounds until either consensus could be obtained or the practice method was deemed unable to achieve consensus. OBJECTIVE: Lumbar total disc replacement (TDR) is acknowledged as an alternative to spinal fusion in appropriately selected patients. There is a lack of unanimity on the appropriate postoperative patient protocols and rehabilitation expectations for the procedure. The long-term viability of Lumbar TDR, further adoption in the community setting and specific patient outcomes are contingent on the existence of appropriate postoperative recovery programs. SUMMARY OF BACKGROUND DATA: Currently there are no established methods for postoperative care following lumbar TDR. Establishing a postoperative clinical pathway algorithm may improve patient outcomes with respect to lumbar TDR. METHOD: A lumbar TDR expert panel of 22 spine surgeons employed a modified Delphi method to drive consensus on postoperative care following single-level Lumbar TDR. The panel first reviewed literature and guidelines relevant to postoperative care following lumbar TDR. Panel members considered 21 survey questions intended to determine "standard-practice" postoperative care recommendations for patients who have undergone lumbar TDR for the initial recovery phase (0-4 wk) and rehabilitation (4-20 wk). Each panel member participated in a round of anonymous voting followed by a group discussion. Consensus was defined as 80% agreement or higher among the respondents. RESULTS: Consensus was achieved in 11 of the 21 survey questions. There was a high degree of consensus around the key goals for both the initial recovery and rehabilitation phases, ceased use of narcotics for pain management by 4 weeks postoperative, unrestricted walking immediately following surgery, timelines for physical therapy (within 2-4 wk) and return to work based on level of activity (as early as 1 wk postoperative). Lack of agreement included the use of back bracing and timing of postoperative visits. Generally, panel members felt that patient expectations regarding return to function were different following lumbar TDR versus fusion and warrant further study. CONCLUSION: Surgeon and patient alignment around postoperative expectations may significantly affect the long-term results of lumbar TDR. This surgeon consensus study found agreement for immediate postoperative ambulation, rapid reduction in opioids within the first month, and early return to work. When expectations are appropriately set with patients preoperatively, both provider and patient have shared goals in the return-to-function process. LEVEL OF EVIDENCE: 5.

Five-year Results of a Randomized Controlled Trial for Lumbar Artificial Discs in Single-level Degenerative Disc Disease.

STUDY DESIGN: A prospective, multicenter, randomized, controlled, investigational device exemption (IDE) noninferiority trial. OBJECTIVE: The aim of this study was to compare the 5-year safety and effectiveness of the activL Artificial Disc with Control Total Disc Replacement (TDR) systems (ProDisc-L or Charité) in the treatment of patients with symptomatic single-level lumbar degenerative disc disease (DDD). SUMMARY OF BACKGROUND DATA: The activL Artificial Disc received Food and Drug Administration approval in 2015 based on 2-year follow-up data. METHODS: Eligible patients presented with symptomatic, single-level, lumbar DDD who failed ≥6 months of nonsurgical management. At entry, 324 patients were randomly allocated (2 : 1) to treatment with activL (n = 218) or Control (n = 106, including n = 65 ProDisc-L and n = 41 Charité) TDR. At 5-year follow up, a total of 261 patients (176 activL patients and 85 Control patients) were available for analysis. RESULTS: The primary composite endpoint at 5 years for activL patients was noninferior to Control TDR. Relative to baseline, reductions in back pain severity and improvements in Oswestry Disability Index (ODI) were maintained for both the activL and Control TDR groups through 5 years. The activL group showed significantly better range of motion for flexion-extension rotation, flexion-extension translation, and disc angle, compared with Control TDR. Freedom from a serious adverse event through 5 years was 64% in activL patients, 47% in Control patients (log-rank P = 0.0068). Freedom from index-level and adjacent-level reoperation was high for TDR patients, ranging between 94% and 99%, respectively. CONCLUSION: Long-term evidence supports lumbar total disc replacement as safe. The next-generation activL Artificial Disc is more effective at preserving range of motion than first-generation lumbar TDRs (ProDisc-L and Charité) and offers a higher safety profile. Other primary and secondary outcomes are similar between disc designs. LEVEL OF EVIDENCE: 2.

Safety and Efficiency of Cervical Disc Arthroplasty in Ambulatory Surgery Centers vs. Hospital Settings.

BACKGROUND: Outpatient surgery has been shown safe and effective for anterior cervical discectomy and fusion (ACDF), and more recently, for 1-level cervical disc arthroplasty (CDA). The purpose of this analysis is to compare the safety and efficiency of 1-level and 2-level CDA performed in an ambulatory surgery center (ASC) and in a hospital setting. METHODS: The study was a retrospective collection and analysis of data from consecutive CDA patients treated in ASCs compared to a historical control group of patients treated in hospital settings who were classified as outpatient (0 or 1-night stay) or inpatient (2 or more nights). Surgery time, blood loss, return to work, adverse events (AEs), and subsequent surgeries were compared. RESULTS: The sample consisted of 145 ASC patients, 348 hospital outpatients, and 65 hospital inpatients. A greater proportion of 2-level surgeries were performed in hospital than ASC. Surgery times were significantly shorter in ASCs than outpatient or inpatient 1-level (63.6 ± 21.6, 86.5 ± 35.8, and 116.7 ± 48.4 minutes, respectively) and 2-level (92.4 ± 37.3, 126.7 ± 43.8, and 140.3 ± 54.5 minutes, respectively) surgeries. Estimated blood loss was also significantly less in ASC than outpatient and inpatient 1-level (18.5 ± 30.6, 43.7 ± 35.9, and 85.7 ± 98.0 mL, respectively) and 2-level (21.1 ± 12.3, 67.8 ± 94.9, and 64.9 ± 66.1 mL). There were no hospital admissions and no subsequent surgeries among ASC patients. ASC patients had 1 AE (0.7%) and hospital patients had 10 AEs (2.4%). Working patients returned to work after a similar number of days off, but fewer ASC patients had returned to work by the end of the 90-day period. CONCLUSIONS: Both 1- and 2-level CDA may be performed safely in an ASC. Surgeries in ASCs are of shorter duration and performed with less blood loss without increased AEs.

Anterior Cervical Discectomy and Fusion Outcomes over 10 Years: A Prospective Study.

STUDY DESIGN: Prospective cohort study with >10-year follow-up. OBJECTIVE: To assess the long-term, >10-year clinical outcomes of anterior cervical discectomy and fusion (ACDF) and to compare outcomes based on primary diagnosis of disc herniation, stenosis or advanced degenerative disc disease (DDD), number of levels treated, and preexisting adjacent level degeneration. SUMMARY OF BACKGROUND DATA: ACDF is a proven treatment for patients with stenosis and disc herniation and results in significantly improved short- and intermediate-term outcomes. Motion preservation treatments may result in improved long-term outcomes but need to be compared to long-term ACDF outcomes reference. METHODS: Patients who had disc herniation, stenosis, and DDD and underwent ACDF with or without decompression were prospectively enrolled and followed for a minimum of 10 years with outcome assessment at various intervals. All 159 consecutive patients had autogenous tricortical iliac crest bone graft and plate instrumentation used. Outcomes included visual analog scale for neck and arm pain. pain drawing, Oswestry Disability Index, and self-assessment of procedure success. Preoperative adjacent-level disc degeneration, pseudarthrosis, and secondary operations were analyzed. RESULTS: For all diagnostic groups, significant outcomes improvement was seen at all follow-up periods for all scales relative to preoperative scores. Outcomes were not related to age, gender, number of levels treated, and minimally to preexisting degeneration at the adjacent level. The use of narcotic pain medication decreased substantially. Neurological deficits almost all resolved. Patient self-reported success ranged from 85% to 95%. Over the long term, additional surgery for pseudarthrosis (10%) occurred in the early follow-up period, and for adjacent segment degeneration (21%), which occurred linearly during the >10-year follow-up period. CONCLUSION: ACDF leads to significantly improved outcomes for all primary diagnoses and was sustained for >10 years' follow-up. Secondary surgeries were performed for pseudarthrosis repair and for symptomatic adjacent-level degeneration. LEVEL OF EVIDENCE: 2.

Foreword: Proceedings From the First Annual Lumbar Total Disc Replacement Summit.

: This publication focuses on proceedings from the First Annual Lumbar Total Disc Replacement Summit, held October 25, 2016 in Boston, MA. The Summit brought together 17 thought leading surgeons who employed a modified-Delphi method to determine where consensus existed pertaining to the utilization of lumbar total disc replacement as a standard of care for a subpopulation of patients suffering from degenerative disc disease.

Defining the Ideal Lumbar Total Disc Replacement Patient and Standard of Care.

: Lumbar total disc replacement, now in use since 2004, was determined by the panel to be a standard of care for the treatment of symptomatic single-level lumbar degenerative disc disease in the active patient subpopulation as outlined by the investigational device exemption study criteria. The large body of evidence supporting this statement, including surgeons' experiences, was presented and discussed. Consensus statements focusing on decision-making criteria reflected that efficacy, long-term safety, clinical outcomes with validated measures, and cost-effectiveness should form the basis of decision-making by payers. Diagnostic challenges with lumbar degenerative disc disease patients were discussed among the panel, and it was concluded that although variably used among surgeons, reliable tools exist to appropriately diagnose discogenic back pain.

Morphologic and biomechanical comparison of spinous processes and ligaments from scoliotic and kyphotic patients.

The spinous processes and supraspinous and interspinous ligaments (SSL and ISL, respectively) limit flexion and may relate to spinal curvature. Spinous process angles and mechanical properties of explanted human thoracic posterior SSL/ISL complexes were compared for scoliosis (n=14) vs. kyphosis (n=8) patients. The median thoracic coronal Cobb angle for scoliosis patients was 48°, and sagittal angles for kyphosis patients was 78°. Spinous processes were gripped and four strain steps of 4% were applied and held. Percent relaxation was calculated over each step, equilibrium load data were fit to an exponential equation, and a Kelvin model was fit to the load from all four curves. Failure testing was also performed. Median ligament complex dimensions from scoliosis and kyphosis patients were, respectively: ISL width=16.5mm and 16.0mm; SSL width=4.3mm and 3.8mm; ISL+SSL area=17.2mm and 25.7mm; these differences were not significant. Significant differences did exist in terms of spinous process angle vs. spine axis (47° for scoliosis and 32° for kyphosis) and SSL thickness (2.1mm for scoliosis and 3.0mm for kyphosis). Fourth-step median relaxation was 42% for scoliosis and 49% for kyphosis. Median linear region stiffness was 42N/mm for scoliosis and 51N/mm for kyphosis. Median failure load was 191N for scoliotic and 175N for kyphotic ligaments. Differences in loading, relaxation, viscoelastic and failure parameters were not statistically significant, except for a trend for greater initial rate of relaxation (T1) for scoliosis ligaments. However, we found significant morphological differences related to the spinous processes, which suggests a need for future biomechanical studies related to the musculoskeletal aspects of spinal alignment and posture.

Flexibility and fatigue evaluation of oblique as compared with anterior lumbar interbody cages with integrated endplate fixation.

OBJECTIVE: This study was undertaken to quantify the in vitro range of motion (ROM) of oblique as compared with anterior lumbar interbody devices, pullout resistance, and subsidence in fatigue. METHODS: Anterior and oblique cages with integrated plate fixation (IPF) were tested using lumbar motion segments. Flexibility tests were conducted on the intact segments, cage, cage + IPF, and cage + IPF + pedicle screws (6 anterior, 7 oblique). Pullout tests were then performed on the cage + IPF. Fatigue testing was conducted on the cage + IPF specimens for 30,000 cycles. RESULTS: No ROM differences were observed in any test group between anterior and oblique cage constructs. The greatest reduction in ROM was with supplemental pedicle screw fixation. Peak pullout forces were 637 ± 192 N and 651 ± 127 N for the anterior and oblique implants, respectively. The median cage subsidence was 0.8 mm and 1.4 mm for the anterior and oblique cages, respectively. CONCLUSIONS: Anterior and oblique cages similarly reduced ROM in flexibility testing, and the integrated fixation prevented device displacement. Subsidence was minimal during fatigue testing, most of which occurred in the first 2500 cycles.

Lumbar Total Disc Replacement for Discogenic Low Back Pain: Two-year Outcomes of the activL Multicenter Randomized Controlled IDE Clinical Trial.

STUDY DESIGN: A prospective, multicenter, randomized, controlled, investigational device exemption (IDE) noninferiority trial. OBJECTIVE: The aim of this study was to evaluate the comparative safety and effectiveness of lumbar total disc replacement (TDR) in the treatment of patients with symptomatic degenerative disc disease (DDD) who are unresponsive to nonsurgical therapy. SUMMARY OF BACKGROUND DATA: Lumbar TDR has been used to alleviate discogenic pain and dysfunction while preserving segmental range of motion and restoring stability. There is a paucity of data available regarding the comparative performance of lumbar TDR. METHODS: Patients presenting with symptomatic single-level lumbar DDD who failed at least 6 months of nonsurgical management were randomly allocated (2:1) to treatment with an investigational TDR device (activL, n = 218) or FDA-approved control TDR devices (ProDisc-L or Charité, n = 106). The hypothesis of this study was that a composite effectiveness outcome at 2 years in patients treated with activL would be noninferior (15% delta) to that in controls. RESULTS: The primary composite endpoint of this study was met, which demonstrated that the activL TDR was noninferior to control TDR (P < 0.001). A protocol-defined analysis of the primary composite endpoint also confirmed that activL was superior to controls (P = 0.02). Radiographic success was higher with activL versus controls (59% vs. 43%; P < 0.01). Mean back pain severity improved by 74% with activL and 68% with controls. Oswestry Disability Index scores decreased by 67% and 61% with activL and controls, respectively. Patient satisfaction with treatment was over 90% in both groups at 2 years. Return to work was approximately 1 month shorter (P = 0.08) with activL versus controls. The rate of device-related serious adverse events was lower in patients treated with activL versus controls (12% vs. 19%; P = 0.13). Surgical reintervention rates at the index level were comparable (activL 2.3%, control 1.9%). CONCLUSION: The single-level activL TDR is safe and effective for the treatment of symptomatic lumbar DDD through 2 years. LEVEL OF EVIDENCE: 2.

Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit: a prospective randomized study with follow-up at sixteen to twenty-two years.

BACKGROUND: Studies comparing operative with nonoperative treatment of a stable burst fracture of the thoracolumbar junction in neurologically intact patients have not shown a meaningful difference at early follow-up. To our knowledge, longer-term outcome data have not before been presented. METHODS: From 1992 to 1998, forty-seven consecutive patients with a stable thoracolumbar burst fracture and no neurological deficit were evaluated and randomized to one of two treatment groups: operative treatment (posterior or anterior arthrodesis) or nonoperative treatment (a body cast or orthosis). We previously reported the results of follow-up at an average of forty-four months. The current study presents the results of long-term follow-up, at an average of eighteen years (range, sixteen to twenty-two years). As in the earlier study, patients at long-term follow-up indicated the degree of pain on a visual analog scale and completed the Roland and Morris disability questionnaire, the Oswestry Disability Index (ODI) questionnaire, and the Short Form-36 (SF-36) health survey. Work and health status were obtained, and patients were evaluated radiographically. RESULTS: Of the original operatively treated group of twenty-four patients, follow-up data were obtained for nineteen; one patient had died, and four could not be located. Of the original nonoperatively treated group of twenty-three patients, data were obtained for eighteen; two patients had died, and three could not be located. The average kyphosis was not significantly different between the two groups (13° for those who received operative treatment compared with 19° for those treated nonoperatively). Median scores for pain (4 cm for the operative group and 1.5 cm for the nonoperative group; p = 0.003), ODI scores (20 for the operative group and 2 for the nonoperative group; p <0.001) and Roland and Morris scores (7 for the operative group and 1 for the nonoperative group; p = 0.001) were all significantly better in the group treated nonoperatively. Seven of eight SF-36 scores also favored nonoperative treatment. CONCLUSIONS: While early analysis (four years) revealed few significant differences between the two groups, at long-term follow-up (sixteen to twenty-two years), those with a stable burst fracture who were treated nonoperatively reported less pain and better function compared with those who were treated surgically.

Two-Level Circumferential Lumbar Fusion Comparing Midline and Paraspinal Posterior Approach: 5-Year Interim Outcomes of a Randomized, Blinded, Prospective Study.

STUDY DESIGN: A prospective randomized and blinded comparative study of 2 patient groups with >5-year follow-up. OBJECTIVE: To compare the clinical outcomes and postoperative posterior muscle changes in patients with advanced degenerative disk disease undergoing 2-level circumferential spinal fusion using a posterior midline versus a paraspinal approach. SUMMARY OF BACKGROUND DATA: Lumbar spinal fusion is often performed using a circumferential (anterior and posterior) technique. Paraspinal muscle alterations occur during the retraction of the muscles required for posterior instrumentation and fusion bed preparation, which may adversely affect outcomes. METHODS: Patients with advanced 2-level lumbar degenerative disk disease were randomized into 2 groups of 25 each for the approach to the posterior spine for their anterior-posterior fusion. A midline posterior skin incision was universal, but all patients were blinded to the fascial incision and exposure to the posterior spine. All had intertransverse and facet joint fusions with pedicle screw instrumentation. Outcomes (visual analog back and leg pain scale, pain drawing, Oswestry disability index, and self-assessment of procedure success) were assessed at various periods postoperatively. Preoperative and >1-year postoperative magnetic resonance images (MRI), including paraspinal muscles, were read by a radiologist who was blinded to the surgical approach and outcomes. RESULTS: No difference in operative time, blood loss, implant costs, or any other intraoperative parameter existed between the 2 patient groups. Although clinical improvement for all outcome scales was significant for both groups postoperatively, there was no difference between groups. Postoperative MRI T2 relaxation values were significantly increased at the operative levels and distally, but the changes were similar for both groups. CONCLUSIONS: Midline and paraspinal approaches result in similar outcomes in 2-level spinal fusions. We were unable to demonstrate that a paraspinal muscle-splitting approach to 2-level fusion was superior to the muscle-stripping midline approach. However, the study has low statistical power.

Outcomes of posterior facet versus pedicle screw fixation of circumferential fusion: a cohort study.

PURPOSE: To compare single-level circumferential spinal fusion using pedicle (n = 27) versus low-profile minimally invasive facet screw (n = 35) posterior instrumentation. METHOD: A prospective two-arm cohort study with 5-year outcomes as follow-up was conducted. Assessment included back and leg pain, pain drawing, Oswestry disability index (ODI), pain medication usage, self-assessment of procedure success, and >1-year postoperative lumbar magnetic resonance imaging. RESULTS: Significantly less operative time, estimated blood loss and costs were incurred for the facet group. Clinical improvement was significant for both groups (p < 0.01 for all outcomes scales). Outcomes were significantly better for back pain and ODI for the facet relative to the pedicle group at follow-up periods >1 year (p < 0.05). Postoperative magnetic resonance imaging found that 20 % had progressive adjacent disc degeneration, and posterior muscle changes tended to be greater for the pedicle screw group. CONCLUSION: One-level circumferential spinal fusion using facet screws proved superior to pedicle screw instrumentation.

Compressive properties of fibrous repair tissue compared to nucleus and annulus.

The wound healing process includes filling the void between implant and tissue edges by collagenous connective repair tissue. This fibrous repair tissue may load share or stabilize implants such as spinal disc replacements. The objective of this study was the biomechanical characterization of human fibrous tissue compared to annulus fibrosus and nucleus pulposus. Human lumbar discs (10 nucleus and annulus) and 10 lumbar deep wound fibrous tissue specimens were sectioned into 12mm diameter×6mm high cylindrical samples. Confined compression testing, after 2h swelling at 0.11MPa, was performed at 5%, 10% and 15% strain over 3.5h. Unconfined dynamic testing (2-0.001Hz) was performed at 5-15% strain. Semi-quantitative histology estimated the proportion of proteoglycan to collagen. Fibrous tissue exhibited a decrease in height during the swelling period whereas annulus and nucleus tissues did not. The aggregate modulus was significantly less for fibrous tissue (p<0.002). Percent stress relaxation was greatest for the fibrous tissue and similar for annulus and nucleus. Dynamic testing found the storage modulus (E') was greater than the loss modulus (E″) for all tissues. Annulus were found to have greater E' and E″ than nucleus, whereas E' and E″ were similar between annulus and fibrous tissue. Fibrous tissue had the greatest increase in both moduli at greater frequencies, but had the lowest hydration and proteoglycan content. Fibrous tissue would not be a substitute for native tissue within the disc space but if adjacent to a disc prosthesis may impart some degree of intersegmental stability during acute loading activities.

Feasibility of the runt cow for in vivo testing of a spinal interbody prosthesis with preliminary results.

BACKGROUND: The optimal lumbar spinal disc prosthesis has yet to be developed. Failures of clinical device studies may be minimized by appropriate large animal preclinical studies. The lumbar spine of the mature "runt" cow, Corrientes breed, has been shown to have a number of desirable characteristics to the human. This study assessed the feasibility of the "runt" cow for in vivo testing of human-sized lumbar interbody implants and the ability to perform common analyses of explants. METHODS: Eight cows (four experimental and four controls) were compared. The experimental animals had transosseous implantation of the disc prosthesis at L4-L5, and their spines were harvested at four or six months. They were evaluated for the ease of surgical access and healing, motion segment mobility, ability to remove the implant nondestructively, and microradiography and histomorphology. RESULTS: All animals had successful implantation. All explantations were performed without alteration to the devices. All animals had surgical healing and intended device motion, and histology found device stability by demonstrating bone ingrowth into the device's porous plates. There was a significant 46% increase in the amount of trabecular bone adjacent to the implants. CONCLUSION: The mature runt cow allows for implantation of human-sized interbody and intrabody spinal prostheses. This animal model allowed for macro- and histological analysis of the implant and surrounding tissues. In vivo stability was demonstrated for the disc prosthesis while also allowing for evaluation of intended mobility. Additionally, this is the first study to suggest increased bone density supporting an interbody prosthesis.

Percutaneous vertebral body cement augmentation for back pain related to occult osteomyelitis/diskitis.

Although complications related to vertebroplasty or kyphoplasty are few, we treated 2 patients with vertebroplasty or kyphoplasty for pain, presumed to be due to vertebral compression fractures, which were subsequently found to be due to occult osteomyelitis/diskitis. The onset of their infections appeared to have preceded their vertebral body augmentation procedures and was possibly due to prior interventional procedures for histories of back pain.An 86-year-old woman had had 3 prior kyphoplasty procedures for fractures at T10, T11, and L1. She reported continued severe pain, and subsequent magnetic resonance imaging was misinterpreted for another fracture at T12, resulting in her fourth kyphoplasty. She became septic and had some improvement with antibiotics, but she declined specialty care and died. A 74-year-old man with chronic back pain had recently undergone lumbar facet joint injections. Computed tomography and subsequent bone scan found uptake at both L2 and L3. Despite abnormal erythrocyte sedimentation rate and C-reactive protein level and normal radiographic vertebral height, he underwent a vertebroplasty. His pain increased, and subsequent workup found L2-3 diskitis. He recovered with antibiotics and specialty care. Similar to prior reports of spondylodiskitis, both patients had multiple medical comorbidities.This article emphasizes the need for clinical reevaluation and scrutiny in the interpretation of imaging studies, including for infection in patients with continued pain after spinal procedures. The differential diagnosis of infectious etiology is an important consideration prior to vertebral cement augmentation for presumed fragility fracture.