Disc Allograft Research Articles

ID: 216940 Retrospective Analysis of Safety and Efficacy of Disc Allograft Supplementation for Discogenic Low Back Pain

Low back pain has a prevalence of 60-70% in industrialized countries, and combined with neck pain, they made up the third costliest medical condition in 2013, at an estimated 87.6 billion dollars in medical spending.1,2 Intervertebral disc disruption accounts for greater than 42% of the back pain population, making it the most common causative etiology.3 A vital function of the intervertebral disc is to absorb shock and vibrations from activities of daily living, which preserves the spinal structure. The sponginess of the disc is attributed to proteoglycans and its’ watered structure, creating hydraulic properties within the nucleus pulposus. The disc relies on subchondral bone for nutrient and waste transfer. With aging there is desiccation and loss of mechanical integrity, leading to further degeneration of the surrounding structures.1

Effect of age on outcomes after allogeneic disc tissue supplementation in patients with chronic discogenic low back pain in the VAST trial.

Aim:To explore the effects of viable allogeneic disc tissue supplementation in younger patients with discogenic chronic low back pain (CLBP). Patients & methods: VAST was a randomized placebo-controlled trial of disc allograft supplementation in 218 patients with discogenic CLBP. We conducted a post hoc analysis of change from baseline to 12months in Oswestry Disability Index (ODI) and visual analog scale for pain intensity scores stratified by patient age. Results: Patients aged <42years receiving allograft experienced greater improvement in ODI (p=0.042) and a higher ODI response rate (≥10-, ≥15- and ≥20-point reductions in ODI) than those receiving saline (p=0.001, p=0.002 and p=0.021, respectively). Conclusion: Young patients with discogenic CLBP may have significant functional improvement following nonsurgical disc allograft supplementation.

Viable Disc Tissue Allograft Supplementation; One- and Two-level Treatment of Degenerated Intervertebral Discs in Patients with Chronic Discogenic Low Back Pain: One Year Results of the VAST Randomized Controlled Trial

Background: A viable disc tissue allograft has been developed to supplement tissue loss associated with degenerative lumbar disc disease and the development of chronic discogenic lower back pain. Objectives: Viable disc allograft was injected into painful degenerated discs to evaluate safety and determine whether it can improve pain and function. Study Design: Patients received an active treatment of allograft or saline, or continued with nonsurgical management (NSM). Prior to entering the study, patients had back pain for a minimum of 6 months before treatment that was recalcitrant to nonoperative treatment modalities. Standardized outcome measures were used to evaluate the patient’s condition before and after treatment. Primary endpoints included improvement in Oswestry Disability Index (ODI) and Visual Analog Scale of Pain Intensity (VASPI). Conventional radiographs and magnetic resonance imaging scans were used to assess disc space height and spinal alignment, and to determine the degree of disc degeneration. Patients were followed for one year after enrollment. The NSM group could cross over to the allograft group after 3 months. Setting: This multicenter trial was completed in outpatient surgical centers and office injection suites. A total of 218 patients with chronic low back pain secondary to single-level or 2-level degenerative disc disease were enrolled. Inclusion criteria included pretreatment VASPI &gt;= 40 mm, ODI score &gt;= 40 and symptoms present longer than 6 months. Patients were blinded and randomized to receive intradiscal injections of either viable disc allograft or saline. Patients randomized to the NSM group continued existing treatment. Patients were assessed at 6 and 12 months. Adverse events (AEs) were continually assessed. Methods: The VAST trial is a prospective, multicenter, blind, randomized clinical trial (RCT) for patients with single-level or 2-level degenerative lumbar disc disease. Results: At 12 months, clinically meaningful improvements in mean VASPI and ODI scores were achieved in the investigational allograft and saline groups. A responder analysis demonstrated a clinically meaningful reduction in ODI of &gt;= 15 points at 12 months that was statistically significant; 76.5% of patients randomized to allograft were responders (P = 0.03) compared to 56.7% in the saline group. A responder group characterized by a ? 20 point reduction in pain at 12 months achieved a statistically significant reduction in pain compared to the saline group (P = 0.022). In the allograft group, 11 safety adverse events occurred in 141 patients (3.5%) and there were no persistently symptomatic AEs. Limitations: Limitations of this study include a comparison to saline that has been shown to be more representative of an active comparator as opposed to a placebo. In addition, 36 patients were lost to follow-up; this loss resulted in the saline and NSM/crossover groups being smaller than the predetermined group size to have an appropriately powered analysis. Conclusions: This large, prospective blinded RCT demonstrated safety and efficacy results indicating that viable disc tissue allograft may be a beneficial nonsurgical treatment for patients who have chronically painful lumbar degenerative discs. Further studies would be optimal to confirm efficacy Key words: Viable disc tissue allograft, discogenic back pain, allograft supplementation, degenerative disc disease, low back pain, intervertebral disc, intradiscal injection

58. Viable disc tissue allograft supplementation in the treatment of degenerated intervertebral discs the one-year results of a randomized control trial

58. Viable disc tissue allograft supplementation in the treatment of degenerated intervertebral discs the one-year results of a randomized control trial

91. The viable disc tissue allograft supplementation (VAST) randomized controlled trial in patients with chronic discogenic low back pain: Correlating age with clinical outcome

<h3>BACKGROUND CONTEXT</h3> The development of chronic low back pain (LBP) results from internal disc disruption within the nucleus pulposus and is the most common etiology of LBP in young to middle-age adults. A viable disc tissue allograft has been developed to supplement tissue loss associated with degenerative lumbar disc disease and the development of chronic discogenic LBP. <h3>PURPOSE</h3> In this study, the clinical outcomes of patients in the VAST study were analyzed on the basis of patient age (above and below the median age of all patients). <h3>STUDY DESIGN/SETTING</h3> Randomized, controlled, multicenter study in US. <h3>PATIENT SAMPLE</h3> A total of 218 patients with chronic low back pain secondary to single-level or two-level degenerative disc disease were enrolled in the study. Patients had back pain for a minimum of 6 months that was recalcitrant to nonoperative treatment modalities. Inclusion criteria also included pretreatment VASPI ≥ 40 and ODI Score ≥ 40. <h3>OUTCOME MEASURES</h3> Oswestry Disability Index (ODI) and visual analog scale of pain intensity (VASPI), neurological exam and adverse events. Plain film radiographs and magnetic resonance (MR) imaging scans were used to assess disc space height and spinal alignment and to determine the degree of disc degeneration. <h3>METHODS</h3> Prospective, multicentered, blinded, randomized clinical trial for subjects with single or two-level degenerative lumbar disc disease was conducted. Patients had back pain for a minimum of 6 months, which was recalcitrant to nonoperative treatment modalities. Patients were blinded and randomized to receive intradiscal injections of either viable disc allograft or saline, or to continue nonblinded with nonsurgical management (NSM). The NSM group could cross over to the allograft group after 3 months. All patients crossed over into the investigational allograft treatment group. Patient data based on age comparing younger patients (19-42 years, 104 patients) to older patients (43-73 years, 114 patients) across all three groups were analyzed. Statistical analyses were performed based on 12-month post treatment improvements in ODI and VAS. <h3>RESULTS</h3> In the younger patient group, a significantly larger improvement in ODI of 29.7 points in the allograft treated group and 45.0 points in the cross over group was observed vs 17.4 points with the saline group (Overall p-value =.004). This effect was also observed in multiple responder analyses with a significantly higher percentage of allograft-treated patients demonstrating ≥15 and ≥20-point improvements in ODI vs the saline group. 69.1% of the younger patients treated with viable allograft vs 35.3% of the saline group showed clinically meaningful improvement of ODI ≥20-points (Overall p-value=.004). No significant interaction between treatment and age in VAS, and no significant benefits of allograft treatment on VAS in younger vs older patients was observed. Adverse events were reported in 30.9%, 10.5% and 17.6% of younger patients in the allograft, placebo, and conservative care groups, respectively (overall p value=0.155), compared to 28.8%, 15.8%, and 9.1% of older patients in these groups (overall p value=0.136), most commonly back pain. <h3>CONCLUSIONS</h3> This subgroup analysis indicates that younger patients (≤ 42 years) have more favorable clinical outcome vs older patients at 12 months. This data suggests that a viable disc tissue injection can effectively treat chronic discogenic LBP nonsurgically with meaningful results demonstrated in a younger patient population. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

P53. Allogeneic disc matrix as treatment for disc degeneration: improvement in pain and function at 1- and 2-levels

BACKGROUND CONTEXT Chronic back pain has been linked to genetic, metabolic, and mechanical imbalance, and although physical therapy, dieting, core strengthening, and anti-inflammatory medication have offered symptomatic relief, to date there has been no remedy for tissue regeneration of the disc or replenishing tissue loss to degeneration. PURPOSE This study evaluated whether placement of a supplemental structural cellular allograft matrix at either 1 or 2 levels could effectively augment tissue lost to degeneration. Safety, and efficacy over a minimum of 6 months are presented. STUDY DESIGN/SETTING Following IRB approval, a prospective, randomized 3-arm study was designed. Safety and efficacy of structural disc allograft matrix was evaluated up to 6 months. (ClinicalTrials.gov NCT03709901). PATIENT SAMPLE This study compares 204 enrolled patients 6 months following the index procedure. Subjects consisted of 43% females and 57% males. OUTCOME MEASURES Visual analog scale (VAS), and Oswestry Disability Index (ODI) were the primary symptomatic assessments. METHODS Following IRB approval, a prospective, randomized 3-arm study was designed. Safety and efficacy of structural disc allograft matrix was evaluated up to 6 months. (ClinicalTrials.gov NCT03709901).; demographics of age 42.7 (19-73), and BMI 27.6 (17-35.4) were similar between the groups. Subjects were randomized to receive allogeneic disc tissue matrix consisting of disc material with a cellular component, saline placebo, or continue in conservative care. Patients received intradiscal injections at 1 or 2 levels. Subject distribution included 134 active allograft, 38 receiving saline placebo, and 32 continuing conservative care. There were 119 subjects with 1-level intervention, and 85 received 2-level. Visual Analog Scale (VAS), and Oswestry Disability Index (ODI) were the primary symptomatic assessments at 6 months. RESULTS Back pain, as measured by VAS was reduced in all subjects treated by active agents. All conservative management subjects crossed over at 3 months due to persistent pain. Allograft pain scores decreased from 64.33 to 33.27 (31.06; 48.3% reduction); saline placebo decreased from 66.06 to 43.87 (22.19; 33.6% reduction); and conservative care after cross over to structural allograft decreased from 68.67 to 21.27 (47.40; reduction 69%). A greater than 20-point improvement in ODI mean scores was reported in both active allograft and cross-over groups at 6 months. The crossover group with 2 levels treated reported most significant improvements in pain and function across all three groups. Pain scores decreased from 63.6 to 12.8 and ODI decreased from 51.7 to 19. CONCLUSIONS Intradiscal allograft demonstrated symptomatic relief and provided the largest improvement in ODI at either 1- or 2-levels treated, whether randomized and blinded, or after crossover with open label compared to placebo (saline). Subjects in the conservative treatment arm after three additional months of conservative care achieved comparable symptomatic relief to the initial treatment arm, despite the time lapse of 3 months. Functional improvements and pain reduction were linked to the number of levels treated, suggesting that disc height improvement might bridge more than single levels. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Lumbar intervertebral disc allograft transplantation: the revascularisation pattern.

Fresh frozen intervertebral disc allograft transplantation has been reported to be a viable treatment option for advanced degenerative disc diseases, but rapid degeneration of the postoperative allograft was found. Loss of nutrient supply is believed to be the most likely inducer because the disc allografts have to endure in an ischaemic environment until the nutrient pathway is re-established. The aim of this study was to focus on the revascularisation of the disc allograft after transplantation in goats. Twenty male goats were used in this study. Intervertebral disc allograft transplantation was performed at L4/L5. Groups of five goats were killed at 1.5, 6 and 12m postoperatively, respectively. The transplanted segments were harvested, fixed, sagittally cut and decalcified for H&E staining and immunochemistry to observe the blood vessel formation at the endplates, anterior outer annulus, posterior outer annulus, inner annulus and the nucleus. The blood vessel density and the sectional vessel area were measured. Blood vessels were first found in the marrow space of the bony endplate and the outer annulus at 1.5month postoperatively. Then, they were able to penetrate to reach the cartilaginous endplate and the inner annulus after 6months. Interestingly, the endplate area possessed the most abundant blood vessels, with the highest level of vessel density and area at the final follow-up. None of these newly formed vessels invaded the nucleus during the observation period. Revascularisation of the postoperative disc allograft has been determined, but its pattern was different from that in adult normal discs, suggesting that the typical nutrient diffusion pattern may be affected after transplantation.

The dorsal skinfold chamber: A versatile tool for preclinical research in tissue engineering and regenerative medicine.

Previous human study suggested that fresh-frozen intervertebral disc allograft transplantation can relieve neurological symptoms and restore segmental kinematics. Before wide clinical application, research into the pathophysiology of the postoperative disc allograft is needed. One important question that remains to be answered in disc allografting is the healing process of the host-graft interface and the subsequent change of the endplates. With the goat model for lumbar disc allografting, histology, micro-computed tomography analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy mapping were applied to evaluate the healing of the host-graft interfaces, the remodelling of subchondral bone, and the changes of the bony and cartilaginous endplates after transplantation. It was found that healing of the host-graft interfaces started at 1.5 months and was completed at 6 months by natural remodelling. This bony remodelling was also noted in the subchondral bone area after 6 months. The bony endplate was well preserved initially, but was gradually replaced by trabecular bone afterwards; on the other hand, the cartilaginous endplate became atrophic at 6 months and nearly disappeared at the final follow-up. Collectively, after intervertebral disc allograft transplantation, bony healing and remodelling were seen which ensured the stability and mobility of the disc-transplanted segment, but the integrity of bony and cartilaginous endplates was gradually lost and nearly disappeared finally.

Lumbar intervertebral disc allograft transplantation: long-term mobility and impact on the adjacent segments.

Fresh-frozen intervertebral disc (IVD) allograft transplantation has been successfully performed in the human cervical spine. Whether this non-fusion technology could truly decrease adjacent segment disease is still unknown. This study evaluated the long-term mobility of the IVD-transplanted segment and the impact on the adjacent spinal segments in a goat model. Twelve goats were used. IVD allograft transplantation was performed at lumbar L4/L5 in 5 goats; the other 7 goats were used as the untreated control (5) and for the supply of allografts (2). Post-operation lateral radiographs of the lumbar spine in the neutral, full-flexion and full-extension positions were taken at 1, 3, 6, 9 and 12months. Disc height (DH) of the allograft and the adjacent levels was calculated and range of motion (ROM) was measured using the Cobb's method. The anatomy of the adjacent discs was observed histologically. DH of the transplanted segment was decreased significantly after 3months but no further reduction was recorded until the final follow-up. No obvious alteration was seen in the ROM of the transplanted segment at different time points with the ROM at 12months being comparable to that of the untreated control. The DH and ROM in the adjacent segments were well maintained during the whole observation period. At post-operative 12months, the ROM of the adjacent levels was similar to that of the untreated control and the anatomical morphology was well preserved. Lumbar IVD allograft transplantation in goats could restore the segmental mobility and did not negatively affect the adjacent segments after 12months.

Surgical technique for lumbar intervertebral disc transplantation in a goat model.

Fresh-frozen intervertebral disc transplantation was determined to be an effective treatment for degenerative disc diseases in rhesus monkeys and in humans. Further research in improving different aspects of disc allografts transplantation is needed and will be investigated in large animal models. This study reports the detailed surgical technique of intervertebral disc transplantation without internal fixation and the important notes to ensure success in goats. Fifty-one male goats were used in this study. Ten goats were used as intervertebral disc allograft donors; the remaining forty-one goats were used to develop the surgical technique for intervertebral disc allograft transplantation. Radiographs, ex vivo MRI and gross observation were used to monitor the stability and healing of the disc allografts at 3 months, postoperatively. Size matching of the disc allograft, preservation of the anterior longitudinal ligament and an appropriate portion of the annulus fibrosus at the recipient site were crucial for stable graft retention. Additionally, a slightly reduced height of the disc allograft compared to that of the recipient slot may avoid graft endplate fracture. Lumbar intervertebral disc transplantation without internal fixation can be successfully performed in goats.

The effect of gamma irradiation on the biological properties of intervertebral disc allografts: in vitro and in vivo studies in a beagle model.

Study DesignAn animal experiment about intervertebral disc allograft.ObjectiveTo explore the feasibility to decellularize disc allografts treated by 6°Co Gamma Irradiation, and simultaneously, to assess the possibility to make use of the decellularized natural disc scaffold for disc degeneration biotherapy.Summary of Background DataStudies of both animal and human disc allograft transplantation indicated that the disc allograft may serve as a scaffold to undertake the physiological responsibility of the segment.Methods Experiment in vitro: 48 discs of beagles were harvested and divided randomly into four groups including a control group and three irradiated groups. Immediate cell viability and biomechanical properties of the discs were checked and comparisons were made among these groups. Experiment in vivo: 24 beagles accepted single-level allografted disc treated with different doses of gamma irradiation. Plain X-rays and MRIs were taken before and after surgery. Then, the spinal columns were harvested en bloc from the sacrificed beagles and were examined morphologically.ResultsThere were significant differences of both the annulus fibrosus and nucleus pulposus immediate cell viabilities among the various groups. There were no obvious differences of the biomechanical properties among the four groups. The disc height and range of motion decreased significantly in all groups as time went on. The observed indexes in irradiated groups were much smaller than those in the control group, but the indexes in 18-kGy group were larger than those in 25-kGy and 50-kGy groups. Both MRI and macroscopic findings showed that the segmental degeneration in the control and 18-kGy group was less severe than that in 25-kGy and 50-kGy groups.ConclusionGamma Irradiation can decellularize disc allograft successfully to provide natural scaffold for the study of degenerative disc disease therapy, and also can be used as an effective method to produce adjustable animal models.

Lumbar Intervertebral Disc Transplantation: Healing and Remodeling of the Bony Structure

Introduction A previous human study suggested that intervertebral disc allograft transplantation in the cervical spine can relieve neurological symptoms and restore segmental kinematics. We have demonstrated that lumbar intervertebral disc transplantation could restore the global and segmental mobility after 12 months using a goat model. However, the healing process of the bone-bone interface and the subsequent remodeling of the bony endplate of the disc allograft are still unknown. This study examines this issue in a large animal model. Materials and Methods A total of 20 male goats between 6 and 9 months weighing between 17.5 and 25 kg were used in this study. Five goats served as disc allograft donors, and 15 goats as allograft recipients. Disc allograft transplantation without internal fixation was performed at lumbar L4/L5 using the retropsoas approach as previously described. Radiological healing was assessed with lateral radiographs of the lumbar spine at 1, 3, 6, 9, and 12 months posttransplantation. Five goats were sacrificed at 1.5, 6, and 12 months postoperatively, respectively. The transplanted segments together with the adjacent levels were then harvested en bloc and fixed in 10% formalin. Micro-CT scanning and three-dimensional reconstructions were conducted. Three volumes of interests (VOIs) were placed at the anterior, center, and posterior of the osteotomy sites; two VOIs were selected at the center of adjacent vertebral bodies near the epiphyseal line. Mean of the values at the three positions of osteotomy sites was calculated and compared with that of two adjacent vertebral VOIs as normal control to evaluate bone formation according to the following parameters: bone volume over total volume (BV/TV, %), bone surface density (BS/TV, 1/mm), trabecular thickness (Tb.Th, mm), trabecular number (Tb.N, 1/mm), trabecular separation (Tb.Sp, mm), trabecular pattern factor (Tb.Pf, 1/mm), structure model index (SMI), degree of anisotropy (DA), and connectivity density (Conn.Dn, 1/mm3). Sequentially, the sample was mid-sagittally cut. One half was decalcified for histological staining to morphologically observe new bone formation and bone remodeling; the other without decalcification was used for SEM and line-scan EDX analysis for assessing distribution profile of calcium (Ca) and phosphate (P) as well as the ratio of Ca/P at the newly formed bone of healing sites. Results Radiographically, increased radio-opacity was seen at the host-graft interface at 1 month postoperative, and bony union was seen after 3 months. Micro-CT images demonstrated more new bone formation with plate-like and well-connected architecture at the osteotomy sites at 1.5 months postoperative. These sites had higher BV/TV, BS/TV, Tb.N, and Conn.Dn, and had lower Tb.Pf and SMI than the mean of the control ( p &lt; 0.05). As the bone remodeling proceeds, the number (Tb.N), internal connection (Tb.Pf), and the structure (SMI, rod-like) of trabecular bone at the healing sites became similar with those of the control and remained unchanged until the final follow-up ( p &gt; 0.05). But the means of BV/TV, BS/TV, Tb.Th, and Conn.Dn were significantly greater than those of the control, while lower Tb.Sp at the healing site ( p &lt; 0.05). After 12 months, there was no difference between the healing site and the control in all 3D indices except the average of Conn.Dn ( p &lt; 0.01) and DA ( p &lt; 0.05). Despite the architecture of the remodeled trabecular bone was a little different than those from the control after 6 months, the profiles of Ca and P distribution as well as the ratio of Ca/P were comparable without significant difference. Histologically, resorption of the redundant vertebral bones and extensive new bone formation were noted in the healing site at 1.5 months; the subchondral bone and bony endplate of the disc allograft were still well preserved. In the form of creeping substitution, the subchondral bone was gradually replaced by dense and mature trabecular bone at 6 months postoperative. After continuous remodeling, the bony architecture became similar with that of the trabecular bone in the controls after 12 months. Conclusion Healing and remodeling of the host-graft bony interface was basically completed at 6 months posttransplantation. The bony structure of the disc allograft was replaced by newly formed trabecular bone through creeping substitution. Disclosure of Interest None declared Reference Ruan D, He Q, Ding Y, Hou L, Li J, Luk KD. Intervertebral disc transplantation in the treatment of degenerative spine disease: a preliminary study. Lancet 2007;369(9566):993–999

Tissue-Engineered Allograft Intervertebral Disc Transplantation for the Treatment of Degenerative Disc Disease: Experimental Study in a Beagle Model

To investigate whether the intervention of nucleus pulposus (NP) cells or human telomerase reverse transcriptase (hTERT) gene-transfected NP cells can prevent the degeneration process after allograft total disc transplantation. Eighteen canine lumbar intervertebral discs were obtained from five canines and cryopreserved in liquid nitrogen. Canine nucleus pulposus cells were isolated and transduced with recombinant adeno-associated virus (rAAV)-hTERT. The cells were injected into the discs to construct a tissue-engineered allograft disc (group A). NP cells and DMEM/F12 were used for positive control (group B) and blank control (group C). 18 beagle dogs received the three groups of allograft intervertebral disc (IVD) composites implantation, respectively. Radiographic examinations were performed at 4, 8, and 12 weeks postimplantation. At 12 weeks after operation, all dogs were sacrificed and the lumbar spines were harvested for the biomechanical analysis, and then the allografts underwent histological analysis, ectogenic NP cell tracing, and hTERT mRNA analysis. Bony fusion between the intervertebral disc allograft and the adjacent host intervertebral body were observed in all animals. The disc height and T2 signal intensity preservation in group A and B was better than group C. Magnetic resonance images (MRI) showed typical degenerative changes in group C. In group A, the normalized grayscale of the transplanted disc on MRI was significant higher compared with the controls at 12 weeks. A biomechanical test showed a poor stability preservation in group C compared to group A and B. PKH-26-positive cells were identified within the allograft discs in group A at 12 weeks, providing evidence of cell survival. Histological analysis showed the NP cell morphology, cell number, and distribution of the allograft discs was better preserved in group A and B compared to group C at a 12-week follow-up. The present study demonstrated that NP cells or hTERT-loaded NP cells intervention could effectively resist the degeneration of the allogenic transplanted intervertebral discs in a beagle model. The hTERT-loaded NP cells had a better antidegeneration effect on the transplanted disc than NP cells. This modified disc regeneration technique through NP cell injection or manipulation may have the potential to ensure the long-term function preservation of allograft disc transplantation.

The Effect of Remodeling on the Kinematics of the Malpositioned Disc Allograft Transplantation

A postoperative biomechanical study. This study aimed to assess whether the mal-alignment of the intervertebral disc (IVD) allograft during transplantation would negatively affect the biomechanics of the spinal segment. Studies of human IVD allograft transplantation have observed remodeling of the allograft implant, suggesting that the remodeling of the allograft may be able to restore the natural mechanics of the IVD. Eighteen male goats (age: 6-12 months; weight: 25-30 kg) were randomly assigned into control (n = 5), aligned (n = 5), or malpositioned (n = 5) groups. Transplantation of a size-matched cryopreserved IVD allograft was performed in the lumbar region (L4-L5) after disc excision. In the aligned group, the IVD allografts were placed aligned and flush with the anterior vertebral margin. In the malpositioned group, the allografts were placed proud anteriorly by 25% of the anterior-posterior diameter of the allograft. The lumbar spines were harvested at 6 months after transplantation. Three-dimensional kinematic assessment of the lumbar spines was performed using an MTS testing machine and an optoelectronic camera system. The range of motion, neutral zone, and instantaneous axis of rotation were calculated. No significant difference in range of motion was noted between the groups in flexion, axial rotation, and lateral bending. Significance was noted with extension range of motion as detected in both the aligned (17.51 ± 1.97 degrees; P = 0.019) and malpositioned groups (16.61 ± 2.35 degrees; P = 0.027) compared with the control (10.11 ± 1.03 degrees). No significant difference was detected in the neutral zone between the groups. Significant difference in the instantaneous axis of rotation orientation between the malpositioned and control groups was detected in the sagittal plane during lateral bending motion (P = 0.036). Kinematic parameters in both the aligned and malpositioned allograft were similar to those of the intact spine. This suggests that precise positioning of the IVD allograft may not be an essential factor affecting the biomechanics of the spinal segment after transplantation.

The role of cryopreservation in the biomechanical properties of the intervertebral disc

Implantation of intervertebral disc (IVD) allograft or tissue engineered disc constructs in the spine has emerged as an alternative to artificial disc replacement for the treatment of severe degenerative disc disease (DDD). Establishment of a bank of cryopreserved IVD allografts enables size matching and facilitates logistics for effective clinical management. However, the biomechanical properties of cryopreserved IVDs have not been previously reported. This study aimed to assess if cryopreservation with different concentrations of cryopreservant agents (CPA) would affect the dynamic viscoelastic properties of the IVD. Whole porcine lumbar IVDs (n = 40) were harvested and processed using various concentrations of CPA, 0 % CPA, 10 % CPA and 20 % CPA. The discs were cryopreserved using a stepwise freezing protocol and stored in liquid nitrogen. After four weeks of storage, the cryopreserved IVDs were quickly thawed at 37 °C for dynamic viscoelastic testing. The apparent modulus, elastic modulus (G'), viscous modulus (G") and loss modulus (G"/G') were calculated and compared to a fresh control group. Cryopreserved IVD without cryopreservants was significantly stiffer than the control. In the dynamic viscoelastic testing, cryopreservation with the use of CPA was able to preserve both G' and G" of an IVD. No significant differences were found between fresh IVD and IVD cryopreserved with 10 % CPA or 20 % CPA. This study demonstrated that CPAs at an optimal concentration could preserve the mechanical properties of the IVD allograft and can provide further credence for the application of long-term storage of IVD allografts for disc transplantation or tissue engineered construct applications.

A Prospective, Pilot Study of Cervical Disc Allografting: A Minimum 10-Year Follow-Up

The authors have reported previously successful transplantation of fresh-frozen intervertebral disc allograft in humans with good clinical outcomes at the 5-year follow-up. This current study addresses the long-term 10-year clinical follow-up in such subjects.

Minimizing cryopreservation-induced loss of disc cell activity for storage of whole intervertebral discs

Severe intervertebral disc (IVD) degeneration often requires disc excision and spinal fusion, which leads to loss of spinal segment mobility. Implantation of an allograft disc or tissue engineered disc construct emerges as an alternative to artificial disc replacement for preserving the motion of the degenerated level. Establishment of a bank of cadaveric or engineered cryopreserved discs enables size matching, and facilitates clinical management. However, there is a lack of understanding of the behaviour of disc cells during cryopreservation, as well as how to maximize their survival, such that disc graft properties can be preserved. Here, we report on the effect of alterations in cooling rates, cryoprotective agents (CPAs), and duration of pre-cryopreservation incubation in CPA on cellular activity in whole porcine lumbar discs. Our results indicated that cooling rates of -0.3 degrees C/min and -0.5 degrees C/min resulted in the least loss of metabolic activity in nucleus pulposus (NP) and annulus fibrosus (AF) respectively, while metabolic activity is best maintained by using a combination of 10% dimethylsulphoxide (DMSO) and 10% propylene-glycol (PG) as CPA. By the use of such parameters, metabolic activity of the NP and the AF cells could be maintained at 70% and 45%, respectively, of that of the fresh tissue. Mechanical testing and histological evaluation showed no significant differences in mechanical properties or alterations in disc structure compared to fresh discs. Despite the limitations of the animal model, our findings provide a framework for establishing an applicable cryopreservation protocol for human disc allografts or tissue-engineered disc constructs.

Intervertebral disc transplantation in the treatment of degenerative spine disease: a preliminary study

Spinal fusion can be complicated by accelerated degeneration of the adjacent segments. Artificial disc replacements have been developed, but results are variable. Successful transplantations of intervertebral disc autografts, fresh allografts, and fresh-frozen allografts-ie, a non-fusion strategy-in which the mobility and stability of the spinal segment were preserved have been done in a primate model. Our aim was to determine the feasibility, safety, and long-term clinical results of disc transplantation in human beings. Five patients, average age 47 years, with cervical disc herniation underwent transplantation of fresh-frozen composite disc allografts after disc excision. Serial MRI and static and dynamic radiographs were used to monitor the status of the grafts and the sagittal stability and mobility of the segment. Good union of the graft endplates was seen by the end of 3 months after surgery in all patients. At a minimum follow-up of 5 years, the neurological symptoms of all patients had improved from before surgery levels. No immunoreaction was encountered. There was no olisthesis and only mild degenerative changes of the transplanted discs. All except one of the discs showed preservation of 7.0-11.3 degrees of sagittal motion at the final follow-up. MRI at 5 years showed preservation of hydration in at least two discs. Despite signs of mild disc degeneration, the motion and stability of the spinal unit was preserved after transplantation of fresh-frozen allogenic intervertebral discs in our patients. With further refinements, such transplantations could be an effective treatment for degenerative disc disease.

P3. Frozen intervertebral disc allografting in management of cervical discal disorders

P3. Frozen intervertebral disc allografting in management of cervical discal disorders

Fresh frozen intervertebral disc allografting in a bipedal animal model.

An in vivo experimental study to examine the possibility of using fresh frozen intervertebral disc allograft in disc transplantation. To investigate the long-term radiographic, pathologic, biochemical, and biomechanical changes of fresh frozen disc allograft in a bipedal animal model. It has been shown that intervertebral disc autograft is able to survive and maintain some degree of tissue metabolism and segmental mobility after transplantation in a bipedal animal model. However, the long-term results of disc allografting and the associated problems of graft rejection are unknown. Seventeen rhesus monkeys (15 male, 2 female) between 5 and 8 years of age and weighing between 6.7 and 11.8 kg were used in this study. Of these 17 subjects, two were used as intervertebral disc donors and three were used as controls for the biomechanical testing. The remaining 12 monkeys were randomly divided into a short-term group (n = 4, followed up for 2, 4, 6, and 8 weeks, respectively), a midterm group (n = 6, 6 months), and a long-term group (n = 2, 24 months). Radiologic, histologic, biochemical, and biomechanical changes were investigated. Radiography and macro- and microhistologic examination showed severe disc degeneration at 24 months of follow-up. Disc height decreased mainly in the early postoperative stage. Decreased water, proteoglycan, and hydroxyproline contents of the allograft were observed at 6 and 24 months of follow-up. The biomechanical properties of the transplanted allograft were similar to those of control. Fresh frozen disc allografts can survive and maintain some degree of cell metabolism and segmental mobility at 24 months after transplantation. However, severe disc degeneration is also observed at this stage.