Aims

Intraoperative pressure sensors allow surgeons to quantify soft-tissue balance during total knee arthroplasty (TKA). The aim of this study was to determine whether using sensors to achieve soft-tissue balance was more effective than manual balancing in improving outcomes in TKA.

Background

Signalling by growth differentiation factor 6 (GDF6/BMP13) has been implicated in the development and maintenance of healthy NP cell phenotypes and GDF6 mutations are associated with defective vertebral segmentation in Klippel-Feil syndrome. GDF6 may thus represent a promising biologic for treatment of IVD degeneration. This study aimed to investigate the effect of GDF6 in human NP cells and critical signal transduction pathways involved.

Introduction: Lumbar Total Disc Replacement (TDR) is an accepted treatment for recalcitrant Chronic Discogenic Low Back Pain. However, no studies have compared Lumbar TDR to non-operative intervention. The aim of this study was to investigate the two-year outcomes for con-current cohorts of chronic discogenic low back pain patients undergoing either Lumbar TDR or novel non-operative care.

Methods: Data for the TDR cohort was from prospectively collected data of patients who had undergone Prodisc II lumbar TDR during August 2003 to December 2005. Two-year data for the non-operative cohort was collected prospectively from 880 sequential patients who underwent non-operative intervention between January to December 2005 and who met the inclusion and exclusion criteria. Inclusion criteria: age > 20 and < 65, single/two level disc disease, low back pain > 6 months, had failed non-operative intervention. Exclusion criteria were: previous lumbar surgery, listhesis, facet disease, osteoporosis, pregnancy, red flag conditions, or poor command of English. Additional non-operative inclusion criteria were: attended a minimum of 3 non-operative sessions, completed the entry questionnaire. Novel non-operative care consisted of a cognition-driven motor relearning intervention, aimed at altering provocative movements and postures and reintegrating these alterations into daily life. Manual therapy and spinal injections were used as an adjunct where needed. Pre-treatment and two-year follow-up data for the following outcomes were collated from a modified NASS questionnaire: back/leg pain, activity limitation, and global perceived improvement. Data was expressed as mean difference with 95% confidence intervals for the difference between the means. Student-t test and paired student-t test were used to assess between group and within group differences.

Results: 16 patients (9 males) were identified in the lumbar TDR cohort with median age 43 years (29–57) and median duration of symptoms of 3.5 years (0.5–24). 16 patients (9 males) were also identified in the non-operative cohort with median age of 42 years (24–61) and median duration of symptoms of 2.5 years (0.5–24). There were no cross-overs, however one patient in the TDR cohort had previously undergone the non-operative care regime. There were no significant pre-treatment differences observed in age, sex, duration of symptoms and back pain intensity between cohorts. However, significant pre-treatment differences were observed with 25% greater leg pain and 25% greater activity limitation score in the TDR cohort when compared to the non-operative cohort. Following Lumbar TDR the mean differences at two years for back pain, leg pain and activity limitation favoured improvements of 3.6(2 to 5.1) and 3.4(1.8 to 4.9) and 30.5%(19.2–41.8) respectively when compared to pre-treatment. Similar improvements were observed for the non-operative cohort with 5.0(3.7–6.3), 2.8 (0.7–5.0) and 20.9%(9.4–32.4) for back pain, leg pain and activity limitation respectively. 71% of Lumbar TDR patients and 67% of Non-operative patients reported their relief of symptoms as exceeding 60% at the two-year follow-up.

Discussion: The data suggests that prior to treatment, patients undergoing lumbar TDR were worse off in activity limitation and leg pain than the non-operative cohort. However, improvements in back pain, leg pain, and activity limitation are clinically significant at two-year follow-up with either Prodisc II-L TDR or novel non-operative care for chronic discogenic low back pain patients. Clinically, it may be reasonable to offer patients with lesser leg pain intensity and activity limitation ongoing non-operative care. This level 3 evidence needs to be supported with more case cohorts or an otherwise ethically difficult to conduct RCT.

Introduction Bone morphogenetic protein-7 (BMP-7) is known to stimulate both cellular proliferation and extracellular matrix synthesis in the intervertebral disc but its protective role in apoptosis is unknown. The aim of this study was to determine whether BMP-7 protect cultured intervertebral disc cells following stimulation of apoptosis.

Methods Nucleus pulposus tissues were obtained from consent individuals under surgical procedures and digested with collagenase prior to culturing. Cellular apoptosis was achieved by either tumor necrosis factor-alpha (TNF-β) or hydrogen peroxide (H2O2) incubation. BMP-7 (Stryker) was used at 100ng/ml, 5 hours prior to the addition of apoptotic stimulation. Cellular apoptosis was detected by TUNEL assay, caspase-3 activity and caspase-3 protein expression. Cellular proliferation and viability was assayed by H3-thymidine incorporation and MTS assay respectively. Collagen II and aggrecan protein levels were measured using western blots and immunostaining. Proteoglycan synthesis was determined by (35)S-sulfate incorporation method. Nitric oxide and alkaline phosphatase activity were measured.

Results Both extrinsic and intrinsic apoptotic pathways were induced by TNF-β or hydrogen peroxide with increased proteolytic activity of caspase-3 as well as cellular shrinkage and nuclear condensation. Addition of BMP-7 prior to stimulation of apoptosis resulted in complete block of the apoptotic effects of both inducers as well as the cellular nitric oxide induced by TNF-β and BMP-7 increases cellular viability, proliferation and extracellular matrix production in an apoptotic environment with no osteoblastic activity induction of discal cells.

Discussion BMP-7 prevents apoptosis of cultured human disc cells induced by either tumor necrosis factor-alpha (TNF-β) or hydrogen peroxide. Induction of apoptosis led to down regulation of extracellular matrix proteins, decreased cell viability, morphological changes and activation of caspase-3, however addition of BMP-7 alone prevented the effects observed. One possible mechanism of the anti-apoptotic effects of BMP-7 was shown by its retardation of the elevated levels of TNF-β induced nitric oxide.

Introduction The present experiment is undertaken to determine if a single dose addition of OP-1 device (rhBMP-7 and TCP-CMC) will enhance posterolateral spinal fusion in an osteoporotic rat mode (estrogen deficiency). Posterolateral intertransverse process spinal fusion using recombinant human osteogenic protein (rhBMP-7) was performed in ovariectomised female rats. OP-1 can be manipulated to enhance fusion rates and fracture healing with or without osteoporosis. Osteoporosis is characterised by low bone mass and micro-architectural deterioration of bone structure, resulting in bone fragility and an increase in susceptibility to fracture. Ovariectomised rats have been used as an osteoporotic model for posterolateral intertransverse process fusion in BMP experimental studies. Many studies have shown rhBMP-7 promotes spinal fusions in posterolateral fusion animal models. Not only is OP-1 able to promote spinal fusion in a standard animal model, but also it has been shown to overcome the inhibitory effects of nicotine in a rabbit posterolateral spinal fusion model. OP-1 Putty (Stryker) is an osteoinductive and osteoconductive bone graft material which consists of the recombinant human Osteogenic Protein (rhBMP-7), and TCP putty containing carboxymethylcellulose sodium (CMC) and tricalcium phosphate. This standard OP-1 device is somewhat different from the one Moazzaz et al used (1). The implication of OP-1 in osteoporotic model will open a new therapeutic window for osteoporotic or osteopaenial patients for the requirements of spinal fusion.

Methods In present study, a total of 42 ovariectomised Sprague-Dawley female rats were randomly assigned to groups receiving 30 μg lactose + 400mg TCP-CMC, 90 μg lactose + 400 mg TCP-CMC, 30 μg rhBMP-7 + 400 mg TCP-CMC and 90 μg rhBMP-7 + 400 mg TCP-CMC. There was a group of rats receiving 400 mg TCP-CMC alone. Spinal fusion was evaluated by manual motion testing at each lumbar segment, Faxitron digital X-ray evaluation using the Lenke grading system, CT scans, DEXA scans and histology.

Results Ovariectomized rats receiving 30 μg lactose + 400mg TCP-CMC, 90 μg lactose + 400 mg TCP-CMC, and 400 mg TCP-CMC alone did not show spinal fusion. OVX rats receiving 90 μg rhBMP-7 + 400 mg TCP-CMC showed significantly higher fusion rates than other groups (P < 0.0001). However, the rats receiving 30 μg rhBMP-7 + 400 mg TCP-CMC did not show solid fusion either radiologically and histologically.

Discussion Therefore rhBMP-7, in dose of 90 μg, is able to overcome the inhibitory effects of estrogen deficiency on posterolateral spinal fusion and generate a relatively robust fusion. The effect of the OP-1 on osteoporotic spine is dose-dependent with/without carrier-dependent.

Introduction and Aims: There is good preliminary evidence that Bone Morphogenic Protein 7 (BMP-7) plays an integral role in fracture healing and metabolism of bone. It is not known, however, whether the implantation of an OP-1 device will enhance the rate of fracture healing in the presence of osteoporosis. The object of this study was to determine the effects of OP-1 on osteoporotic fracture healing in rats.

Method: An open fracture of the mid-shaft of the femur was created in 60, three months post-surgical ovarectomised female Sprague Dawley rats. Thirty rats had OP-1 device with CMC putty implanted into the fracture site and 30 rats had CMC putty implanted without OP-1. The fracture was stabilised with a 1.4mm K-wire. Muscle and skin closed. Ten rats from each group were sacrificed at three time points – 12, 20 and 31 days post-surgery, and bilateral femurs harvested. The fractured femurs were analysed by DEXA scanning, high-resolution radiography, cross-sectional area, biomechanical assessment and histology.

Results: There was a statistically significant acceleration of fracture healing with the use of OP-1 in DEXA, radiological, cross-sectional area and biomechanical analysis and a qualitative enhancement by histological analysis.

Conclusion: The results show that an OP-1 device can enhance fracture healing in the presence of osteoporosis in a rat.

Introduction The mechanisms underlying chronic back pain are not well understood, however, disc degeneration and facet joint arthrosis have been suggested to be two major pain sources. Nitric oxide (NO) is an oxygen free radical which is involved in variety physiological and pathological events. Increased concentrations of NO have been demonstrated with direct or indirect methods in temporomandibular (Takahashi T et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod.1999) and knee joints (Karan A et al. Clin Rheumatol. 2003) with osteoarthrosis. The aims of the study were 1. To investigate if real-time NO concentrations can be measured in the perifacetal region and 2. To estimate perifacetal NO levels in patients with facet joint osteoarthrosis associated chronic low back pain and compare it with that of healthy controls, and 3. To investigate if perifacetal NO levels is discriminative for subsets of patients with facet joint osteoarthrosis.

Methods Patients with at least six months duration of chronic low back pain with signs of facet joint osteoarthrosis on CT and/or MRI, were included in the study (n=26). Healthy volunteers were enrolled as controls (n=7). A detailed questionnaire including visual analogue scale (VAS) was completed by the patients before and six weeks after the NO measurements. Nitric oxide was measured with a custom designed electrochemical real-time nitric oxide sensor (World Precision Instruments, Sarasota, Fl). The NO sensor has a detection limit of less than 0.3 nM, a linear response to NO concentrations up to 100 μM and can discriminate between NO and closely related substances such as nitrite (Zhang X et al; Electroanalysis 2002). The NO sensor was inserted into the facet joint through a 20 gauge needle under fluoroscopic guidance in patients and controls. All patients received corticosteroids (0.4 ml Celestone®) and local anaesthetic (0.5–1.0 ml Marcain®) in the perifacetal region following the NO measurements. Descriptive parameters are expressed as mean (± SEM) and Mann-Whitney’s test was used for statistical comparison between groups.

Results It was possible to obtain NO measurements from all participants. No adverse effects were noted. The patients with chronic low back pain demonstrated 3-fold higher concentrations of nitric oxide in the perifacetal region compared to the healthy controls (1.66±1.39 vs. 0.46±0.37 nM, p=0.007). No association between nitric oxide concentration and pain-duration or pain-level (VAS) was detected. However, patients with a positive response to local anaesthetics and corticosteroid injection (detected as a reduction of VAS at a minimum of 20 mm) at the six week follow-up visit had 25% higher concentrations of nitric oxide when compared to patients who had a less than 20 mm decrease in VAS. p=0.02

Discussion The study demonstrates that measurement of NO with a real time-sensor around the facet joints is feasible and safe. The findings of higher concentrations of NO in the perifacetal region in chronic low back patients compared to healthy controls indicate that the degenerative process of the joints may cause increased NO production. Patients that responded to corticosteroid/local anaesthetic infiltration had higher NO concentrations in the perifacetal region compared to patients without response. This observation indirectly suggests a more pronounced inflammatory process in the responding patients.

Introduction Intervertebral disc degeneration may cause chronic low back pain. Disc degeneration is characterized by dysfunctional cells and a decrease in extra-cellular components. Bone marrow derived mononuclear cells are a heterogeneous cell population which contains mesenchymal stem cells. Transplantation of stem cells and progenitor cells may provide a new approach to treat disc degeneration, but it is unclear if transplanted cells can survive and differentiate in the non-vascularized disc.

Methods Bone marrow was collected from syngeneic Sprague-Dawley rats and mononuclear cells were isolated. The cells were labelled with a fluorescence dye (Cell Tracker Orange) and suspended in PBS. 10–20μl of the cell suspension (1–2x10⁵ cells/disc) was transplanted into coccygeal discs in 12 syngeneic rats. For each rat two discs were cell transplanted and one disc served as control. The rats were sacrificed after 0, 7, 14 or 21 days. For each time point the discs from one animal were saved for routine histological staining. The cell transplanted discs of the other animals (n=4 discs per time point) were formalin-fixed, frozen and sectioned together with the control discs. Frozen disc sections were visualized with fluorescence microscopy and the number of transplanted cells assessed. Expression of collagen II, a marker of chondrocytes and chondrocyte-like cells in the disc, was assessed in the transplanted cells using immunofluorescence technique.

Results All cell-suspension injected discs contained transplanted bone-marrow cells. The discs within each time-group demonstrated a large variation in number of detected cells. There was a decrease in detected cells at 7, 14 and 21 days compared to day 0. Transplanted cells expressed collagen II after 21 days but not after 7 and 14 days.

Discussion The results suggest that transplanted bone marrow-derived mononuclear cells can survive and differentiate within the intervertebral disc. Further studies in models of disc degeneration are warranted to investigate the regenerative potential of the disc following cell transplantation.

Nitric oxide (NO) is a free radical labile gas which has important physiological functions and is synthesised by the action of a group of enzymes called nitric oxide synthases (NOS) on L- arginine. We have shown that nitric oxide modulates fracture healing¹. Bone morphogenic proteins (BMP) are potent differentiating factors that augment the process of new bone formation. Recombinant human BMP-2 (rhBMP-2) enhances spinal fusion². With progression of fusion there is a remodelling of the fusion mass bone accompanied with a decrease in the fusion mass size. It is not known whether nitric oxide has a role in spinal fusion or rhBMP-2 enhanced spinal fusion.

We studied this in a novel rat intertransverse fusion model using a defined volume of bone graft (7 caudal vertebrae) along with 157 mm3 of absorbable Type-1 collagen sponge (Helistat®) carrier, which was compacted and delivered using a custom jig for achieving a similar graft density from sample to sample. The control groups consisted of a sham operated group (S, n=20), an autograft + carrier group (AC, n=28) and a group consisting of 43 μg of rhBMP-2 (Genetics Institute, Andover, MA) mixed with autograft + carrier (ACB, n=28). Two experimental groups received a nitric oxide synthase (NOS) inhibitor, N^G-nitro L-arginine methyl ester (L-NAME, Sigma Chemicals, St Louis, MO) in a dose of 1 mg/ml ad lib in the drinking water (ACL, n=28) and one of these experimental groups had rhBMP-2 added to the graft mixture at the time of surgery (ACLB, n=28). Rats were sacrificed at 22 days and 44 days, spinal columns dissected and subjected to high density radiology (faxitron) and decalcified histology. The faxitrons were subjected to image analysis (MetaMorph).

On a radiographic score (0–4) indicating progressive maturation of bone fusion mass, no difference was found between the AC and ACL groups, however, there was a significant enhancement of fusion when rhBMP-2 was added (ACB group, 3.3±0.2) when compared to the AC group (1±0) (p< .001). However, on day 44, the ACLB group (3.3±0.2) showed significantly less fusion progression when compared to the ACB group (4±0) (p< 0.01). There was a 25% (p< 0.05) more fusion-mass-area in day 44 of ACLB group (297±26 mm³) when compared to day 44 of the ACB group (225±16 mm³) indicating that NOS inhibition delayed the remodelling of the fusion mass. Undecalcified histology demonstrated that there was a delay in graft incorporation whenever NOS was inhibited (ACL and ACLB groups).

Our results show that the biology of autograft spinal fusion and rhBMP-2 enhanced spinal fusion can be potentially manipulated by nitric oxide pathways.