Due to well-known disadvantages of the autologous bone graft, many alternatives have been studied for a reliable spinal fusion. Herein, we aimed to investigate the effects of human recombinant epidermal growth factor (EGF) on posterolateral lumbar fusion in a rat model. 36 male SD rats underwent posterolateral fusion at L4-5 level. They were randomly assigned to 3 groups: Sham control group, Hydoxyapatite β-tricalcium phosphate (HA/β-TCP) group and HA/β-TCP + EGF group. Rats were euthanized at 8 weeks post-surgery. 6 rats from each group were selected for manual palpation examination, micro-computed tomography analysis and histologic analysis; and the rest was used for biomechanical analysis. Based on manual palpation, there was no fusion in the sham control group. Fusion rate was 33.3% in the HA/β-TCP group and 66.7% in the HA/β-TCP + EGF group (p=0.085). Micro-CT results revealed that new bone formation was higher in the HA/β-TCP + EGF group (BV/TV: 40% vs. 65%) (p=0.004). Histologically newly formed bone tissue was more pronounced in the EGF group and compacted and bridging bone spicules were observed. The median maximum bending moment values were 0.51 Nmm (0.42– 0.59), 0.73 Nmm (0.49– 0.88) and 0.91 Nmm (0.66– 1.03) in the sham control, HA/β-TCP and HA/β-TCP + EGF groups, respectively (p=0.013). The median stiffness values were 1.69 N/mm (1.12–2.18), 1.68 N/mm (1.13–2.74) and 3.10 N/mm (1.66–4.40) as in the previous order (p=0.087). This study demonstrates that EGF enhances posterolateral lumbar fusion in the rat model. EGF in combination with ceramic grafts increased the fusion rates

Our study establishes a rabbit model of disc degeneration which requires neither a chemical nor physical injury to the disc. Disc degeneration similar to that seen in man was created at levels proximal (L4-L5) and caudal (L7-S1) to a simulated lumbar fusion and was studied for up to nine months after arthrodesis. Loss of the normal parallel arrangement of collagen bundles within the annular lamellae was observed in intervertebral discs adjacent to the fusion at three months. By six months there was further disorganisation as well as loss of distinction between the lamellae themselves. By nine months the structure of the disc had been replaced by disorganised fibrous tissue, and annular tears were seen. There was an initial cellular proliferative response followed by loss of chondrocytes and notochordal cells in the nucleus pulposus. Degeneration was accompanied by a decrease in the monomer size of proteoglycans. Narrowing of the disc space, endplate sclerosis and the formation of osteophytes at adjacent disc spaces were observed radiologically

Introduction. In daily clinical practice, progression of spinal fusion is typically monitored during clinical follow-up using conventional radiography and Computed Tomography scans. However, recent research has demonstrated the potential of implant load monitoring to assess posterolateral spinal fusion in an in-vivo sheep model. The question arises to whether such a strain sensing system could be used to monitor bone fusion following lumbar interbody fusion surgery, where the intervertebral space is supported by a cage. Therefore, the aim of this study was to test human cadaveric lumbar spines in two states: after a transforaminal lumbar interbody fusion (TLIF) procedure combined with a pedicle-screw-rod-construct (PSR) and subsequently after simulating bone fusion. The study hypothesized that the load on the posterior instrumentation decreases as the segment stiffens due to simulated fusion. Method. A TLIF procedure with PSR was performed on eight human cadaveric spines at level L4-L5. Strain sensors were attached bilaterally to the rods to derive implant load changes during unconstrained flexion-extension (FE), lateral bending (LB) and axial rotation (AR) loads up to ±7.5Nm. The specimens were retested after simulating bone fusion between vertebrae L4-L5. In addition, the range of motion (ROM) was measured during each loading mode. Result. The ROM decreased in the simulated bone fusion state in all loading directions (p≤0.002). In both states, the measured strain on the posterior instrumentation was highest during LB motion. Furthermore, the sensors detected a significant decrease in the load induced rod strain (p≤0.002) between TLIF+PSR and simulated bone fusion state in LB. Conclusion. Implant load measured via rod strain sensors can be used to monitor the progression of fusion after a TLIF procedure when measured during LB of the lumbar spine. However, further research is needed to investigate the influence of daily loading scenarios expected in-vivo on the overall change in implant load

Background

Posterolateral fusion (PLF) is a commonly accepted surgical procedure and overall the most common technique performed to obtain fusion in the lumbar spine. Harvesting autologous bone from the iliac crest is associated with increased operation time, blood loss, and chronic donor site pain. Allograft material has an insufficient osteoinductive potential. Bone marrow concentrate (BMC) could be an option how to promote allograft PLF healing. The purpose of the presented study was to investigate the validity of BMC addition to allografts in instrumented lumbar PLF surgery.

Lateral lumbar interbody fusion (LLIF) has biomechanical advantages due to the preservation of ligamentous structures (ALL/PLL), and optimal cage height afforded by the strength of the apophyseal ring. We compare the biomechanical motion stability of multiple levels LLIF (4 segments) utilising PEEK interbody 26mm cages to stand-alone cage placement and with supplemental posterior fixation with pedicle screw and rods. Six lumbar human cadaver specimens were stripped of the paraspinal musculature while preserving the discs, facet joints, and osteoligamentous structures and potted. Specimens were tested under 5 conditions: intact, posterior bilateral fixation (L1-L5) only, LLIF-only, LLIF with unilateral fixation and LLIF with bilateral fixation. Non-destructive testing was performed on a universal testing machine (MTS Systems Corp) to produce flexion-extension, lateral-bending, and axial rotation using customized jigs and a pulley system to define a non-constraining load follower. Three-dimensional spine motion was recorded using a motion device (Optotrak). Results are reported for the L3-L4 motion segment within the construct to allow comparison with previously published works of shorter constructs (1-2 segments). In all conditions, there was an observed decrease in ROM from intact in flexion/extension (31%-89% decrease), lateral bending (19%-78%), and axial rotation (37%-60%). At flexion/extension, the decreases were statistically significant (p<0.007) except for stand-alone LLIF. LLIF+unilateral had similar decreases in all planes as the LLIF+bilateral condition. The observed ROM within the 4-level construct was similar to previously reported results in 1-2 levels for stand-alone LLIF and LLIF+bilateral. Surgeons may be concerned about the biomechanical stability of an approach utilizing stand-alone multilevel LLIF. Our results show that 4-level multilevel LLIF utilizing 26 mm cages demonstrated ROM comparable to short-segment LLIF. Stand-alone LLIF showed a decrease in ROM from the intact condition. The addition of posterior supplemental fixation resulted in an additional decrease in ROM. The results suggest that unilateral posterior fixation may be sufficient

The use of lumbar fusion procedures in the USA and Europe has rapidly increased over the last decade and a large number of these procedures involve the use of bone grafts. Despite of technical progress of spinal surgery and operative materials the risk of vertebral fusion failure occurs in 5 – 35 % of cases. Autografting has been considered the gold standard for bone graft procedures. However, the harvesting from the iliac crest can be associated with short and long-term morbidity in up to 22 % of cases. Main goal of this experimental study was to compare newly developed hybrid biodegradable nanocomposit porous implant (HBNPI) against bone craft from iliac crest as a new and better alternative for lumbar interbody fusion. 24 male pigs 4 months old weighting around 40 Kg were included in our study. These pigs were divided into two study groups depending on fusion method. Group A – 12 pigs underwent lateral lumbal interbody fusion (L2/3) with implantation of iliac crest bonegraft. Group B - 12 pigs underwent lateral lumbal interbody fusion (L2/3) with newly developed HBNPI. Each group were divided into two subgroups from these 6 spines were harvested 8 weeks (subgroup A1, B1) and 6 spines 16 weeks (group A2, B2) after surgery. After sacrifice, the lumbar spines were taking out and micro-CT, biomechanical testing and histomorphological analysis in all groups were performed to evaluate a quality of intervertebral fusion. As controls (group N), 6 cadaveric intact lumbar spines underwent biomechanical, micro-CT and histological testing. All 24 animals recovered from general anesthesia without unusual events. The operations lasted between 50–90 minutes (mean 70) in Group A and between 35–72 minutes (mean 43) in Group B. All of the pigs from group A could stand up and were mobile within 20 hours (range 7–20). When bone graft harvesting was not necessary (group B) this time was shortened, ranging from 1 – 1,5 hour. All pigs from Group A were limping on the first postoperative day. No limping animal was observed in group B. Total body weight of the pigs increased from 37 kg (range 36–40) at the start to 85 (range 80–89) at sacrifice. Biomechanics evaluation shows that extension flexural stiffness values are statistically significantly different between A2 (16 weeks post-implant) and A1 (8 weeks post-implant). Group A2 achieves higher values than Group A1, which is attributed to the adhesion of the implant to the surrounding vertebrae. Similarly, this also applies to groups B2 and B1. The flexural stiffness at group B2 extension is statistically significantly higher than the A2 group and also than the native N group. Biomechanical evaluation supports findings on micro-CT and histological specimens, where both adjacent vertebrae are completely fused in groups B2, unlike in group A2, where there is no or incomplete fusion. Newly developed HBNPI represents new possibility how to do intervertebral fusion, and simultaneous become chance how to improve and accelerate bone healing process against standard procedures

The objective of this study was to investigate the effects of different doses rhBMP-2 on bone healing in an ovine lumbar interbody fusion model. In this study 22 sheep underwent two level lumbar interbody fusion using a ventrolateral approach with secondary dorsal fixation at L1/2 and L3/4. After randomization in one level a PEEK-cage was implanted filled with one of three doses rhBMP-2 (0,5mg; 1mg; 2mg) delivered on an ACS. The other level received an empty PEEK-cage or ACS filled cage. Animals were sacrificed after 3 and 6 months and decalcified histology was performed. This included histomorphological analysis well as histomorphometry of the tissues within the cage. At 3 months after surgery the groups treated with rhBMP-2 showed higher amounts of bone tissue within the cage. At 6 months the amounts of bone tissue increased in all groups, were still lower in the groups without growth factor. At 3 months there was only one active osteolysis in the cage/ACS. 7 of 8 segments of the rhBMP-2 groups had a compromised bone structure around the implant. These areas were filled with fibrous tissue and fibrocartilage. This finding was not detected in the groups without rhBMP-2 at 3 months. At 6 months most of the segments with an empty cage or cage/ACS showed a chronic inflammation. Predominant cells were macrophages and giant cells. The groups treated with rhBMP-2 showed only a few mild chronic inflammatory reactions. The well-known dose dependent effect of rhBMP-2 on bone healing could also be recognized in our study. Attention has to be payed to the proinflammatory properties of the growth factor. Consistent with other studies we found 2 strong inflammatory reactions, each one in the lowest and highest dose group. Also, the potential for causing transient bone resorptions, according to the results of others, was demonstrated. At 3 months 7 of 8 segments treated with rhBMP-2 showed compromised peri-implant bone. Osteoblasts, but not osteoclasts, were seen in the periphery of these areas. It can be concluded that there where bone resorptions which already merged into an increased osteoblastic activity. Usually resorptions occur between 2 and 12 weeks and are followed by a period of increased osteoblastic activity. This finding wasn't recognized at 6 months anymore. Striking is that at 6 months most of the segments without rhBMP-2 showed a compromised bone structure around the implant with a mild to mainly moderate chronic inflammatory reaction. This cannot be attributed to the growth factor. Also, the ACS is degraded at 6 months and is unlikely a possible explanation. Therefore, the cage as a reason must be considered and it has to be questioned whether PEEK is the optimal material for interbody cages

We have examined the process of fusion of the intertransverse processes and bone graft in the rabbit by in situ hybridisation and evaluated the spatial and temporal expression of genes encoding pro-α1 (I) collagen (COL1A1), pro-α1 (II) collagen (COL2A1) and pro-α1 (X) collagen (COL10A1).

Beginning at two weeks after operation, osteogenesis and chondrogenesis occurred around the transverse process and the grafted bone at the central portion of the area of the fusion mass. Osteoblasts and osteocytes at the newly-formed woven bone expressed COL1A1. At the cartilage, most chondrocytes expressed COL2A1 and some hypertrophic chondrocytes COL10A1. In some regions, co-expression of COL1A1 and COL2A1 was observed. At four weeks, such expressions for COL1A1, COL2A1 and COL10A1 became prominent at the area of the fusion mass. From four to six weeks, bone remodelling progressed from the area of the transverse processes towards the central zone. Osteoblasts lining the trabeculae expressed a strong signal for COL1A1. At the central portion of the area of the fusion mass, endochondral ossification progressed and chondrocytes expressed COL2A1 and COL10A1.

Our findings show that the fusion process begins with the synthesis of collagens around the transverse processes and around the grafted bone independently. Various spatial and temporal osteogenic and chondrogenic responses, including intramembranous, endochondral and transchondroid bone formation, progress after bone grafting at the intertransverse processes. Bone formation through cartilage may play an important role in posterolateral spinal fusion.

The use of intraoperative navigation and robotic surgery for minimally invasive lumbar fusion has been increasing over the past decade. The aim of this study is to evaluate postoperative clinical outcomes, intraoperative parameters, and accuracy of pedicle screw insertion guided by intraoperative navigation in patients undergoing lumbar interbody fusion for spondylolisthesis. Patients who underwent posterior lumbar fusion interbody using intraoperative 3D navigation since December 2021 were included. Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey-36 (SF-36) were assessed preoperatively and postoperatively at 1, 3, and 6 months. Screw placement accuracy, measured by Gertzbein and Robbins classification, and facet joint infringement, measured by Yson classification, were assessed by intraoperative Cone Beam CT scans performed at the end of instrumentation. Finally, operation time, intraoperative blood loss, hospital stay, and screw insertion time were evaluated. This study involved 50 patients with a mean age of 63.7 years. VAS decreased from 65.8±23 to 20±22 (p<.01). ODI decreased from 35.4%±15 to 11.8%±14 (p<.01). An increase of SF-36 from 51.5±14 to 76±13 (p<.01) was demonstrated. The accuracy of “perfect” and “clinically acceptable” pedicle screw fixation was 89.5% and 98.4%, respectively. Regarding facet violation, 96.8% of the screws were at grade 0. Finally, the average screw insertion time was 4.3±2 min, hospital stay was 4.2±0.8 days, operation time was 205±53 min, and blood loss was 169±107 ml. Finally, a statistically significant correlation of operation time with hospital stay, blood loss and placement time per screw was found. We demonstrated excellent results for accuracy of pedicle screw fixation and violation of facet joints. VAS, ODI and SF-36 showed statistically significant improvements from the control at one month after surgery. Navigation with intraoperative 3D images represents an effective system to improve operative performance in the surgical treatment of spondylolisthesis

Pelvic tilt can vary over time due to aging and the possible appearance of sagittal spine disorders. Cup position in total hip arthroplasty (THA) can be influenced due to these changes. We assessed the evolution of pelvic tilt and cup position after THA and the possible appearance of complications for a minimum follow-up of ten years. 343 patients received a THA between 2006 and 2009. All were diagnosed with primary osteoarthritis and their mean age was 63.3 years (range, 56 to 80). 168 were women and 175 men. 250 had no significant lumbar pathology, 76 had significant lumbar pathology and 16 had lumbar fusion. Radiological analysis included sacro-femoral-pubic (SFP), acetabular abduction (AA) and anteversion cup (AV) angles. Measurements were done pre-operatively and at 6 weeks, and at five and ten years post-operatively. Three measurements were recorded and the mean obtained at all intervals. All radiographs were evaluated by the same author, who was not involved in the surgery. There were nine dislocations: six were solved with closed reduction, and three required cup revision. All the mean angles changed over time; the SFP angle from 59.2º to 60º (p=0.249), the AA angle from 44.5º to 46.8º (p=0.218), and the AV angle from 14.7º to 16.2º (p=0.002). The SFP angle was lower in older patients at all intervals (p<0.001). The SFP angle changed from 63.8 to 60.4º in women and from 59.4º to 59.3º in men, from 58.6º to 59.6º (p=0.012). The SFP angle changed from 62.7º to 60.9º in patients without lumbar pathology, from 58.6º to 57.4º in patients with lumbar pathology, and from 57.0º to 56.4º in patients with a lumbar fusion (p=0.919). The SFP cup angle was higher in patients without lumbar pathology than in the other groups (p<0.001), however, it changed more than in patients with lumbar pathology or fusion at ten years after THA (p=0.04). Posterior pelvic tilt changed with aging, influencing the cup position in patients after a THA. Changes due to lumbar pathology could influence the appearance of complications long-term

Cervical and lumbar spine fusion procedures are increasing every year. Nonetheless, these procedures are associated with high infection rates, resulting in additional cost burden. The conundrum of achieving efficient spinal fusions with minimum complications requires an ideal bone graft with osteoconductive, osteoinductive, osteogenic and structural characteristics. Synthetic bone graft substitutes with or without autograft, allograft or synthetic bone substitutes have been commonly used for fusion procedures. We carried out a meta-analysis of comparative studies and prospective case series (n = 29) with cervical and lumbar fusion procedures using synthetic bone graft substitutes, autograft or allograft and other biologics. Synthetic bone graft substitutes analysed included HA (Hydroxyapatite), β-TPC (Tri Calcium Phosphate), β-TSC (Tri Calcium Sulfate), PMMA (Polymethylmetacrylate), Surgibone, BOP (Biocompatible Osteoconductive Polymer). The analysis revealed suboptimal evidence for the efficacy and safety of synthetic products used in spinal fusion procedures. Further studies are needed to determine beneficial effects of synthetic substitutes. However, the infection rate could be highly decreased with surface and composition modification of widely used polyether ether ketone (PEEK) implants. Laser modification of surface characteristics and collagen fleeces with micro and nano pore structures can prove to be excellent surface for increased osteoblasts cell proliferation and vitality

Introduction and Objective. Posterior and transforaminal lumbar interbody fusion (PLIF, TLIF) represent the most popular techniques in performing an interbody fusion amongst spine surgeons. Pseudarthrosis, cage migration, subsidence or infection can occur, with subsequent failed surgery, persistent pain and patient’ bad quality of life. The goal of revision fusion surgery is to correct any previous technical errors avoiding surgical complications. The most safe and effective way is to choose a naive approach to the disc. Therefore, the anterior approach represents a suitable technique as a salvage operation. The aim of this study is to underline the technical advantages of the anterior retroperitoneal approach as a salvage procedure in failed PLIF/TLIF analyzing a series of 32 consecutive patients. Materials and Methods. We performed a retrospective analysis of patients’ data in patients who underwent ALIF as a salvage procedure after failed PLIF/TLIF between April 2014 to December 2019. We recorded all peri-operative data. In all patients the index level was exposed with a minimally invasive anterior retroperitoneal approach. Results. Thirty-two patients (average age: 46.4 years, median age 46.5, ranging from 21 to 74 years hold- 16 male and 16 female) underwent salvage ALIF procedure after failed PLIF/TLIF were included in the study. A minimally invasive anterior retroperitoneal approach to the lumbar spine was performed in all patients. In 6 cases (18.7%) (2 infection and 4 pseudarthrosis after stand-alone IF) only anterior revision surgery was performed. A posterior approach was necessary in 26 cases (81.3%). In most of cases (26/32, 81%) the posterior instrumentation was overpowered by the anterior cage without a previous revision. Three (9%) intraoperative minor complications after anterior approach were recorded: 1 dural tear, 1 ALIF cage subsidence and 1 small peritoneal tear. None vascular injuries occurred. Most of patients (90.6%) experienced an improvement of their clinical condition and at the last follow-up no mechanical complication occurred. Conclusions. According to our results, we can suggest that a favourable clinical outcome can firstly depend from technical reasons an then from radiological results. The removal of the mobilized cage, the accurate endplate and disc space preparation and the cage implant eliminate the primary source of pain reducing significantly the axial pain, helping to realise an optimal bony surface for fusion and enhancing primary stability. The powerful disc distraction given by the anterior approach allows inserting large and lordotic cages improving the optimal segmental lordosis restoration

Introduction. The objective of this study was to investigate the effects of different doses rhBMP-2 on bone healing in an ovine lumbar interbody fusion model. Methods. In this study 22 sheep underwent two level lumbar interbody fusion using a ventrolateral approach with secondary dorsal fixation at L1/2 and L3/4. After randomization in one level a PEEK-cage was implanted filled with one of three doses rhBMP-2 (0,5mg; 1mg; 2mg) delivered on an ACS. The other level received an empty PEEK-cage or ACS filled cage. Animals were sacrificed after 3 and 6 months and decalcified histology was performed. This included histomorphological analysis as well as histomorphometry of the tissues within the cage. Results. At 3 months after surgery the groups treated with rhBMP-2 showed higher amounts of bone tissue within the cage. At 6 months the amounts of bone tissue increased in all groups, but were still lower in the groups without growth factor. At 3 months there was only one active osteolysis in the cage/ACS. 7 of 8 segments of the rhBMP-2 groups had a compromised bone structure around the implant. These areas were filled with fibrous tissue and fibrocartilage. This finding was not detected in the groups without rhBMP-2 at 3 months. At 6 months most of the segments with an empty cage or cage/ACS showed a chronic inflammation. Predominant cells were macrophages and giant cells. The groups treated with rhBMP-2 showed only a few mild chronic inflammatory reactions. Discussion. The well-known dose dependent effect of rhBMP-2 on bone healing could also be recognized in our study. Attention has to be payed for the proinflammatory properties of the growth factor. Consistent with other studies we found 2 strong inflammatory reactions, each one in the lowest and highest dose group. Also the potential for causing transient bone resorptions, according to the results of others, was demonstrated. At 3 months 7 of 8 segments treated with rhBMP-2 showed compromised peri-implant bone. Osteoblasts, but not osteoclasts, were seen in the periphery of these areas. It can be concluded that there where bone resorptions which already merged into an increased osteoblastic activity. Usually resorptions occur between 2 and 12 weeks and are followed by a period of increased osteoblastic activity. This finding wasn”t recognized at 6 months anymore. Striking is that at 6 months most of the segments without rhBMP-2 showed a compromised bone structure around the implant with a mild to mainly moderate chronic inflammatory reaction. This cannot be attributed to the growth factor. Also the ACS is degraded at 6 months and is unlikely a possible explanation. Therefore, the cage as a reason must be considered and it has to be questioned whether PEEK is the optimal material for interbody cages

Statement of Purposes. Functional Restoration (FR) and spinal fusion are both used as treatment for patients with chronic low back pain however opinions are divided over their long term efficacy. This study examines the 18 month to 8 year outcomes of stand-alone lumbar fusion (STALIF) at L5/S1 and FR in similar groups of patients. Methods. A prospective audit was undertaken using data routinely collected from the practice of the senior author. Pain (VAS), disability (ODI) and patients' subjective appraisals were used as comparable outcome measures. SPSS was used for statistical analysis. Results. STALIF patients had sustained significant improvements in their VAS and ODI scores at study end, compared to the pre-operative assessments. FR patients demonstrated significant improvements in their VAS scores and measurable functionality on discharge from the programme, but these deteriorated by the one-month follow-up. At study end there was a significant deterioration in the outcomes compared to discharge. Patient perceived success was 85% in the STALIF patients and 58% in the FR. 24% of FR patients subsequently required surgery. Conclusions. Both groups demonstrated statistically significant improvements in pain and disability/functionality scores during the period of the study however improvements in the FR groups occurred only during the active phase and significantly reduced by study end. The low patient satisfaction rating for the FR group and the need for 25% to subsequently undergo surgery indicates that further robust investigation to clarify “real” sustainability and rule out short-term benefits that arise from psychological cushioning or simply a training effect is required. Conflicts of Interest. None. Source of Funding. None. This abstract has not been previously published in whole or substantial part nor has it been presented at a national meeting

PEMF is currently approved by the FDA for adjunctive treatment of lumbar/cervical spine fusion and for treatment of long-bone non-unions. Soft tissues are a potential new therapeutic application for PEMF due to pre-clinical studies showing a reduction of inflammatory markers following PEMF exposure. The aim was therefore to investigate the structural/functional effects of PEMFs on tendon-to-bone and tendon-to-tendon healing in a rotator-cuff (RC) and Achilles tendon (AT) repair model, respectively. RC study: Adult male rats (n=280), underwent bi-lateral supraspinatus tendon transections with immediate repair followed by cage activity until sacrifice (4, 8, and 16 weeks). Non-controls received PEMF for 1, 3, or 6 hours daily. AT study: Male rats underwent acute, complete transection and repair of the Achilles tendon (FULL, n=144) or full thickness, partial width injury (PART, n=160) followed by immobilization for 1 week. Sacrifice was at 1, 3, and 6 weeks. Outcome measures included passive joint mechanics, gait analysis, biomechanical assessments, histological analysis of the repair site and mCT (humerus) assessment (FULL only). RC study: Significant increases in modulus, stiffness, bone mineral content and improved collagen organization was observed for the PEMF groups. No differences in joint mechanics and ambulation were observed. AT study: A decrease in stiffness and limb-loading rate was observed for the PEMF groups for the FULL groups, whereas an increase in stiffness with no change in range-of-motion was seen for the PART groups. The combined studies show that PEMF can be effective for soft tissue repair but is dependent on the location of application

Introduction. Augmentation of spinal fusion using bone grafts is largely mediated by the osteoinductive potential of mesenchymal stem cells (MSC) that reside in cancellous bone. Iliac crest (IC) is a common autograft, but its use presents an increased risk for donor-site pain, morbidity and infection. Degenerative facet joints (FJ) harvested during facetectomy might servce as alternative local grafts. In this study, we conducted an intra-individual comparison of the osteogenic potential of MSC from both sources. Methods. IC and degenerative FJ were harvested from 8 consecutive patients undergoing transforaminal lumbar interbody fusion surgery for spinal stenosis. MSC were isolated by collagenase digestion, selected by plastic adherence and minimally expanded for downstream assays. Clonogenic and osteogenic potential was evaluated by colony formation assays in control and osteogenic culture medium. Osteogenic properties, including alkaline phosphatase (ALP) induction, matrix mineralization and type I collagen mRNA and protein expression were characterized using quantitative histochemical staining and reverse transcription PCR. Spontaneous adipogenesis was analysed by adipocyte enumeration and gene expression analysis of adipogenic markers. Results. Average colony-forming efficiency in osteogenic medium was equal between IC (38±12%) and FJ (36±11%). Osteogenic potential at the clonal level was 55±26 and 68±17% for IC and FJ MSC, respectively. Clonogenic and osteogenic potential were significantly negatively associated with donor age. Osteogenic differentiation led to significant induction of ALP activity in IC (6-fold) and FJ (8-fold) MSC. Matrix mineralization quantified by Alizarin red staining was increased by osteogenic differentiation, yet similar between both MSC sources. Protein expression of type I collagen was enhanced during osteogenesis and significantly greater in IC MSC. Correspondingly, COL1A2 mRNA expression was higher in osteogenically differentiated MSC from IC. Adipocyte numbers showed significant differences between IC (63±60) and FJ (18±15) MSC under osteogenic conditions. Negative (GREM1) and positive (FABP4) adipogenic markers were not differentially expressed between sources. Conclusion. MSC from IC and degenerative FJ largely display similar clonogenic and osteogenic properties in vitro. Differences at the molecular level are not likely to impair the osteoinductive capacity of FJ MSC. Facetectomy samples are viable bone autografts for intervertebral spinal fusion

In a study on ten fresh human cadavers we examined the change in the height of the intervertebral disc space, the angle of lordosis and the geometry of the facet joints after insertion of intervertebral total disc replacements. SB III Charité prostheses were inserted at L3-4, L4-5, and L5-S1. The changes studied were measured using computer navigation sofware applied to CT scans before and after instrumentation.

After disc replacement the mean lumbar disc height was doubled (p < 0.001). The mean angle of lordosis and the facet joint space increased by a statistically significant extent (p < 0.005 and p = 0.006, respectively). By contrast, the mean facet joint overlap was significantly reduced (p < 0.001). Our study indicates that the increase in the intervertebral disc height after disc replacement changes the geometry at the facet joints. This may have clinical relevance.