Vibrotactile evaluation: osseointegrated versus socket-suspended transfemoral prostheses

This study investigated detection thresholds of vibrometric stimuli in patients with transfemoral amputation supplied with osseointegrated (OI) and socket-suspended prostheses. It included 17 patients tested preoperatively with socket-suspended prostheses and after 2 yr with OI prostheses and a control group (n = 17) using socket-suspended prostheses, evaluated once. Assessments on the prosthetic and intact feet were conducted at six frequencies (8, 16, 32, 64, 125, and 250 Hz). Furthermore, measurements were conducted to investigate how vibrometric signals are transmitted through a test prosthesis. The results showed that the OI group had improved ability to detect vibrations through the prosthesis at 125 Hz (p = 0.01) at follow-up compared with the preoperative measurement. Compared with the control group, the OI group at follow-up had better ability to detect high frequency vibrations through the prosthesis (125 Hz, p = 0.02; 250 Hz, p = 0.03). The vibrometric signal transmitted through the test prosthesis was reduced at 8, 125, and 250 Hz but was amplified at 16, 32, and 64 Hz. Differences between the OI and the control groups were found in the highest frequencies in which the test prosthesis showed reduction of the vibrometric signal. The study provides insight into the mechanisms of vibration transmission between the exterior and bone-anchored as well as socket-suspended amputation prostheses.

Increase of sodium channels (nav 1.8 and nav 1.9) in rat dorsal root ganglion neurons exposed to autologous nucleus pulposus

Purpose:

It has been assumed that nucleus pulposus-induced activation of the dorsal root ganglion (DRG) may be related to an activation of sodium channels in the DRG neurons. In this study we assessed the expression of Nav 1.8 and Nav 1.9 following disc puncture.

Method:

Thirty female Sprague-Dawley rats were used. The L4/L5 disc was punctured by a needle (n=12) and compared to a sham group without disc puncture (n=12) and a naive group (n=6). At day 1 and 7, sections of the left L4 DRG were immunostained with anti-Nav 1.8 and Nav 1.9 antibodies.

Result:

At day 1 after surgery, both Nav 1.8-IR neurons and Nav 1.9-IR neurons were significantly increased in the disc puncture group compared to the sham and naive groups (p<0.05), but not at day 7.

Conclusion:

The findings in the present study demonstrate a neuronal mechanism that may be of importance in the pathophysiology of sciatic pain in disc herniation.

A novel osseointegrated percutaneous prosthetic system for the treatment of patients with transfemoral amputation

Patients with transfemoral amputation (TFA) often experience problems related to the use of socket-suspended prostheses. The clinical development of osseointegrated percutaneous prostheses for patients with a TFA started in 1990, based on the long-term successful results of osseointegrated dental implants.

Between1999 and 2007, 51 patients with 55 TFAs were consecutively enrolled in a prospective, single-centre non-randomised study and followed for two years. The indication for amputation was trauma in 33 patients (65%) and tumour in 12 (24%). A two-stage surgical procedure was used to introduce a percutaneous implant to which an external amputation prosthesis was attached. The assessment of outcome included the use of two self-report questionnaires, the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) and the Short-Form (SF)-36.

The cumulative survival at two years’ follow-up was 92%. The Q-TFA showed improved prosthetic use, mobility, global situation and fewer problems (all p < 0.001). The physical function SF-36 scores were also improved (p < 0.001). Superficial infection was the most frequent complication, occurring 41 times in 28 patients (rate of infection 54.9%). Most were treated effectively with oral antibiotics. The implant was removed in four patients because of loosening (three aseptic, one infection).

Osseointegrated percutaneous implants constitute a novel form of treatment for patients with TFA. The high cumulative survival rate at two years (92%) combined with enhanced prosthetic use and mobility, fewer problems and improved quality of life, supports the ‘revolutionary change’ that patients with TFA have reported following treatment with osseointegrated percutaneous prostheses.

Cite this article: Bone Joint J 2014;96-B:106–13.

Evoked thalamic neuronal activity following DRG application of two nucleus pulposus derived cell populations: an experimental study in rats

PURPOSE

To investigate the effects on evoked thalamic neuronal activity of application of notochordal cells and chondrocyte-like cells derived from nucleus pulposus (NP) onto a dorsal root ganglion (DRG) and to compare these effects with a previously reported increased thalamic activity induced by NP.

METHODS

Nucleus pulposus was harvested from tail discs of adult rats and the disc cells were separated into two cell populations, notochordal cells and chondrocyte-like cells. The two cell populations were applied separately, or in combination, to the L4 DRG of anaesthetised female Sprague-Dawley rats during acute electrophysiological experiments. In control experiments, cell suspension medium was applied on the DRG. Recordings from the contralateral thalamus were sampled for 40 min while electrically stimulating the ipsilateral sciatic nerve at above Aδ-fibre thresholds.

RESULTS

Application of notochordal cells resulted in a decrease in evoked thalamic activity within 10 min while chondrocyte-like cells did not induce any changes during the 40 min of recording. The difference in evoked thalamic activity 40 min after notochordal and chondrocyte-like cell application, respectively, was statistically significant. Neither an increased concentration of chondrocyte-like cells alone nor a combination of the two cell populations induced any changes in thalamic activity.

CONCLUSIONS

Separate exposure of the DRG to the two NP-derived cell populations induced different effects on evoked thalamic activity, but none of the tested cell samples induced an increase in neuronal activity similar to that previously observed with NP. This indicates a high complexity of the interaction between NP and nervous tissue.

Electron microscopy analysis of neurites extending from dorsal root ganglia in vitro following exposure to intervertebral disc cells

Nucleus pulposus cells from the intervertebral disc have been shown to have inhibiting effects on neurite outgrowth in vitro. The nucleus pulposus consists of at least 2 cell populations, notochordal cells and chondrocyte-like cells. The aim of this study was to analyze the morphology of the neurites, from rat dorsal root ganglia (DRG) in a culture system, after exposure of these 2 cell populations. DRG from perinatal rats was harvested and placed in culture dishes for 24 h. Nucleus pulposus cells from donor rats were separated into 2 populations and applied to the DRG and neurite culture for a further 24 h and compared to control cultures exposed to culture medium without cells. The DRG and neurites were thereafter prepared for scanning or transmission electron microscopy (SEM/TEM). Descriptive SEM and TEM analyses and calculations of the neurite diameter were performed. The visual appearance after SEM and TEM preparation was similar in the three different culture conditions. However, there was a statistically significant reduction of the neurite diameter for the cultures exposed to notochordal cells compared to the cultures exposed to medium and chondrocyte-like cells (TEM preparation). Prominent and frequent pathologic abnormalities in peripheral nerve diseases have been observed with changes in axonal caliber. This study may suggest that a preserved small amount of notochordal cells, as seen in human adults, may play a role in clinical situations where nerve tissue is exposed to disc material, i.e. in disc herniation or degeneration.

Effect of methotrexate on fracture healing

Low doses of methotrexate (MTX) are safe and effective for treating adult and juvenile rheumatoid arthritis. However, because this powerful anti-inflammatory drug might negatively influence the healing of wounds and fractures, MTX administration is often stopped during surgical procedures. The present study assesses the effects of low- and high-dose MTX on early inflammatory processes and bone healing in an experimental model of fracture. Thirty male Sprague-Dawley rats were assigned to low- and high-dose MTX and control groups. A femur was cut using a reciprocating saw and a 2-mm fracture gap was made using a fixator. One or four weeks thereafter, macrophages were immunostained and new bone formation was histomorphometrically measured. Significantly less new bone was formed in the high-dose MTX, than in the control group (p< 0.01), whereas bone formation did not significantly differ between the low-dose MTX and control groups. These results suggested that a low dose of MTX does not affect the early process of endochondral bone formation during fracture healing, whereas a high dose might delay the progress of new periosteal bone formation. Although more macrophages were found in the groups treated with MTX, their impact on surrounding inflammatory processes remains unclear.

An external fixation method and device to study fracture healing in rats

We wished to establish a reproducible model for fracture fixation to be used in fracture healing research and therefore developed an external fixation construct and surgical procedure adapted to Sprague-Dawley rats. We evaluated the mechanical properties of the construct in brass rods and rat bone, in an Instron test machine with axial and transverse loading, and the in vivo performance. We found that the mechanical properties of the construct in brass rods were predictable and could be repeated in rat femora. In all tests, the axial load was about 10 times the transverse for the same degree of deformation. The stiffness among fixators was uniform. 1 mm pins caused about 50% less stiffness than 1.2 mm pins in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) as well as in transverse loading of brass rods (p < 0.001). Loosening of 1 or 2 screws that lock the pins to the fixator reduced stiffness by about 50% in axial loading of rat bone (p = 0.009) and brass rods (p = 0.05). A change in the distance between the bone surface and the fixator was linearly related to the stiffness in axial loading of rat bone (p < 0.001) and brass rods (p < 0.001) and in transverse loading of brass rods (p < 0.001). If the bone ends touched each other, the axial stiffness of the construct increased almost 10 times (265 N/mm), as compared to a fracture gap size of 2 mm (31 N/mm). In vivo experiments had a complication rate of less than 10% when we used 1.2 mm pins, 6 mm offset and rats weighing 350-450 g. Our method and device for experimental external fixation of rat femora are reliable and the findings are reproducible. These can be used in bone repair and fracture healing research.

Autologous nucleus pulposus primes T cells to develop into interleukin-4-producing effector cells: an experimental study on the autoimmune properties of nucleus pulposus

An autoimmune response to herniated nucleus pulposus has been proposed to constitute a pathophysiologic mechanism for inducing sciatica based on the fact that nucleus pulposus under normal conditions is excluded from the development of immunological tolerance. The manifestation of an autoimmune response comprises different steps starting with antigen capture, continuing with activation of T helper (T(H)) cells and ending with production of autoantibodies. Activated T(H) cells differentiate into either T(H)1 cells, predominately producing proinflammatory cytokines such as interferon gamma (IFNgamma) or a T(H)2 subset mainly producing anti-inflammatory cytokines such as interleukin-4 (IL-4). The aim of the present study was to examine if exposure of autologous nucleus pulposus (NP) to the immune system for 3 weeks is potent enough to prime T(H) cells to differentiate into T(H)2 cells. The study was performed in a pig model allowing the exposure of NP to the immune system. To assess the polarization of T(H) cells the intracellular production of IFNgamma and IL-4 was measured in T cells by using flow cytometry. The revealed predominant production of IL-4 together with low production of IFNgamma in T cells after NP exposure to the immune system indicates that nucleus pulposus may prime T(H) cells to develop into IL-4-producing T(H)2 cells after being exposed to the immune system, for example, in association with disc herniation.

Osseointegrated trans-femoral amputation prostheses: prospective results of general and condition-specific quality of life in 18 patients at 2-year follow-up

This is the first report on prospective outcome for individuals treated with bone-anchored trans-femoral amputation prostheses (OI-prostheses) using the method of osseointegration. The aim was to analyze general and condition-specific health related quality of life (HRQL) at 2-year follow-up as compared to the preoperative situation. The study population consists of the first 18 consecutively treated patients (8 male/10 female, mean age 45 years) in a clinical investigation with amputations mainly caused by trauma and tumour. At inclusion the mean time since the amputation was 15 years (10 months - 33 years). Two self-report questionnaires were answered preoperatively and at follow-up: the SF-36 Health Survey (SF-36) and the Questionnaire for persons with a Transfemoral Amputation (Q-TFA). At follow-up 17/18 patients used the OI-prosthesis; one did not due to pain and loosening of the implant. Four of the scales of the SF-36 (Physical Functioning, Role Functioning Physical, Bodily Pain and Physical Component Score) and all four scores of Q-TFA (Prosthetic Use, Prosthetic Mobility, Problems and Global Health) were statistically significantly improved at follow-up showing superior general physical HRQL, increased prosthetic use, better prosthetic mobility, fewer problems and a better global amputation situation. Thus, osseointegrated prostheses represent a promising development in the rehabilitation of individuals with transfemoral amputation and increase their quality of life.

Autoimmune properties of nucleus pulposus: an experimental study in pigs

STUDY DESIGN

Assessment of activated T and B cells in a subcutaneous chamber filled with autologous nucleus pulposus using flow cytometry and immunohistochemistry.

OBJECTIVES

To examine if subcutaneously placed autologous nucleus pulposus may attract activated T and B cells in an animal model.

SUMMARY OF BACKGROUND DATA

Nucleus pulposus has been suggested to trigger an autoimmune response if exposed to the immune system, for example, in association with disc herniation. T-cell activation represents a hallmark in the generation of an autoimmune response, subsequently leading to the differentiation of B cells, but a causal association between the exposure of nucleus pulposus to the systemic circulation and T and B cell activation is still lacking.

METHODS

Autologous nucleus pulposus was harvested from the intervertebral disc of 9 pigs and placed subcutaneously in perforated titanium chambers. In order to control for the effect of the titanium chamber, an additional empty chamber was placed subcutaneously in each pig. After 7 days, the pigs were killed and the chambers were harvested. Flow cytometry and immunohistochemistry were used for analysis of T-helper cells (CD4+), cytotoxic T cells (CD8+), and B cells (Igkappa) in the chamber exudates and T cells (CD45RC) in the remaining blood clot tissue of the chamber.

RESULTS

As compared with the empty chambers, the proportion of activated T cells (CD4+ and CD8+) was significantly higher in the exudate of the nucleus pulposus filled chamber. The proportion of activated B cells expressing immunoglobulin kappa (Igkappa) was also significantly elevated in the exudate of the nucleus pulposus chambers. The analysis of the remaining chamber tissue revealed a significantly higher amount of T cells (CD45RC) in the nucleus pulposus chambers than in the empty chambers.

CONCLUSIONS

The present findings indicate that nucleus pulposus attracts activated T and B cells. However, since the cell population in the nucleus pulposus of young pigs may differ from that of adult humans, the obtained data may not be directly transferred to the human situation of a disc herniation. The observations in the present study may nevertheless explain some of the local tissue reactions occurring in association with disc herniation and nerve root involvement, thereby providing further insight into the pathophysiology of sciatica.

Production of tumor necrosis factor-α from porcine nucleus pulposus cells at various time points in cell culture under conditions of nutritional deficiency

Nucleus pulposus (NP) in the epidural space induces spinal nerve damage not only by mechanical but also chemical mechanism. NP has been shown to be capable of producing tumor necrosis factor-alpha (TNF). TNF may play key roles in the NP-induced chemical damage. One of the main pathways to reach the avascular NP is diffusion from the blood supply of the vertebral body through the cartilage endplate. On disk herniation, when NP moves to the epidural space, the distance from the endplate to the herniated NP are longer in the herniated disk than in the intact disk. That is, it seems more difficult to receive adequate nutritional supply from the endplate in the sequestrated type. However, there have been only a few reports of the appearance of TNF in NP. The present study was performed to investigate TNF production in porcine NP under conditions of nutritional deficiency. NP cells were cultured and processed for immunohistochemistry using antisera to TNF, and for ELISA to measure TNF production. The latter was compared longitudinally. The immunoreactivity increased over time. On the other hand, the results of ELISA showed a peak in TNF production 12h, and lower amounts 1 day and 2 days after application of PBS. These observations may suggest that a nutritional deficit is a possible turn-on switch for TNF up-regulation in the NP.

Changes in pain behavior and histologic changes caused by application of tumor necrosis factor-alpha to the dorsal root ganglion in rats

STUDY DESIGN

Histologic changes in the dorsal root ganglion (DRG) and the nociceptive stimulation thresholds were studied in rats.

OBJECTIVE

To examine the effects of tumor necrosis factor-alpha (TNF) with special reference to pain behavior and histology of the DRG.

SUMMARY OF BACKGROUND DATA

Recently, it was reported that local application of nucleus pulposus induces a characteristic tissue reaction at the surface of the DRG. However, to our knowledge, there have been no previous reports about the relationship between the histologic changes and pain behavior caused by cytokines.

METHODS

Recombinant TNF was applied to the L4 DRG. Mechanical and thermal nociceptive thresholds were tested. The L4 DRG was sectioned and observed by light microscopy.

RESULTS

After the application of 5 ng/microL TNF, significant differences were observed in mechanical and thermal stimulation thresholds. At the site of application of TNF, a characteristic a semilunar-shaped enlargement was observed. The average width of the part was significantly larger in the 5 ng/microL TNF application, as compared to the 0.5-ng/microL TNF application.

CONCLUSIONS

The higher concentration of TNF used induced allodynia and hyperalgesia responses. Because the region showing the histologic changes was significantly larger after application of the higher concentration of TNF, the reaction of the DRG may be related to pain.

Nucleus pulposus-induced apoptosis in dorsal root ganglion following experimental disc herniation in rats

STUDY DESIGN

The mechanisms behind the formation of a characteristic tissue reaction at the surface of the dorsal root ganglion (DRG) exposed to nucleus pulposus was studied with special reference to apoptosis using electron microscopy and immunohistochemistry in rats.

OBJECTIVES

To study the mechanism of the characteristic tissue reaction at the surface of the DRG exposed to nucleus pulposus.

SUMMARY OF BACKGROUND DATA

Recently, it was observed that local application of nucleus pulposus may induce a characteristic tissue reaction at the surface of the DRG. This change occurred as early as 1 day after the application of nucleus pulposus. METHODS.: Herniation of nucleus pulposus was created in the L4-L5 disc in rats. The L4 DRG were resected 3 and 24 hours after surgery. The sections of the specimens were observed using light and electron microscopy. The sections were processed for immunohistochemistry using antibodies to single-stranded DNA (ssDNA), caspase 3, and tumor necrosis factor alpha (TNF).

RESULTS

There were typical changes of the cell nuclei observed by light and electron microscopy, especially those of the small-sized cells, in the DRG 24 hours after application of nucleus pulposus, indicating the presence of apoptosis. The presence of ssDNA, caspase 3, and TNF further enhanced the impression that there was apoptosis in the DRG. Nucleus pulposus induced apoptosis in the DRG at the site of application within as little as 24 hours.

CONCLUSIONS

Nucleus pulposus herniated from the disc induced apoptosis in at the surface of the DRG exposed to nucleus pulpous as early as 24 hours after exposure.

Effects of lumbar sympathectomy on pain behavioral changes caused by nucleus pulposus-induced spinal nerve damage in rats

It has been suggested that lumbar sympathectomy can reduce pain behavior, including mechanical allodynia and thermal hyperalgesia, caused by ligation of the spinal nerve. One well-characterized model, which involves application of nucleus pulposus to the spinal nerve and displacement of the adjacent nerve, shows behavioral changes in rats. However, there have been no previous reports regarding sympathectomy performed in this model. Disk incision and adjacent spinal nerve displacement were performed with (n=6) or without (n=6) sympathectomy. Sham surgery was also performed with (n=6) or without (n=6) sympathectomy. The animals were tested for 3 days before surgery and on days 1, 3, 7, 14, and 21 after surgery. Non-noxious mechanical thresholds were tested by determining the hind paw withdrawal response to von Frey hair stimulation of the plantar surface of the footpad using a touch stimulator. Thermal nociceptive thresholds were tested using a sensitive thermal-testing device. While rats in the disk incision with displacement surgery group showed allodynia and hyperalgesia after surgery on the experimental side, sympathectomized animals did not. No allodynia was observed in the sham groups. Sympathectomy seemed to prevent the pain behavioral changes caused by the combination of disk incision and nerve displacement.

Incision of the intervertebral disc induces disintegration and increases permeability of the dorsal root ganglion capsule

STUDY DESIGN

The origin and the barrier properties of the characteristic reaction at the surface of the dorsal root ganglion (DRG) exposed to the nucleus pulposus was studied using Alcian-Blue staining, van Gieson staining, and the application of Evans Blue Albumin (EBA) complex in rats.

OBJECTIVE

To study the origin and the barrier properties of the capsule, including the characteristic reaction, at the surface of the DRG exposed to the nucleus pulposus.

SUMMARY OF BACKGROUND DATA

Local application of nucleus pulposus may induce a characteristic reaction at the surface of the DRG. This reaction histologically resembles an acute inflammatory reaction. However, it is not evident if this is a swelling of the DRG capsule, if it is located between the capsule and neurons of the DRG, or if it is only an attached nucleus pulposus.

METHODS

Nucleus pulposus from the discs was obtained. The nucleus pulposus was smeared on glass slides. Alcian-Blue with hematoxylin and eosin staining was performed for each smear. Herniation of the nucleus pulposus was made in the L4-L5 disc in rats. The L4 DRGs were resected 3, 24, and 72 hours after surgery, and sectioned. The sections were processed for Alcian-Blue staining, van Gieson staining, and EBA complex infiltration. The sections were observed using light or fluorescent microscopy.

RESULTS

Smear of nucleus pulposus was stained bright blue indicating mucins. A characteristic reaction, "inflammatory crescent," was confirmed at the surface of the DRG exposed to the nucleus pulposus. No mucins were observed in the crescent using Alcian-Blue. The results of van Gieson staining showed that the reaction started both inside and outside the elastic fiber layer, the DRG capsule, within 3 hours. The EBA complex was capable of infiltrating into the DRG capsule 24 hours after disc incision.

CONCLUSIONS

The disintegrated capsule showed an increased permeability even for a large molecule as albumin, which indicates a possible entrance route for various substances induced by locally applied nucleus pulposus.

Torsional stiffness in healing fractures: influence of ossification: an experimental study in rats

BACKGROUND

Different fracture fixation techniques and fracture environment influence bone formation in healing fractures. However, the influence on the development of biomechanical properties has not been clear described. We evaluated the influence of fracture fixation stability and fracture environment on mechanical properties in healing femoral fractures in rats.

METHODS

Animals were treated surgically with external fixation: 1 group (27 rats) with 0-mm fracture gap size with bone ends touching, corresponding to an axial stiffness of 265 (SD 34) N/mm, and a second group (27 rats) with 2-mm fracture gap size corresponding to an axial stiffness of 30 (SD 2.1) N/mm. From each group, 6-7 animals were killed at 2, 4, 6 and 12 weeks. Torsional test revealed a delay in torsional stiffness in fractures in group 2 compared to group 1. In group 2, the torsional stiffness of the contralateral femora was found to be greater at 12 weeks than the torsional stiffness in group 1.

INTERPRETATION

We found that during fracture healing, the development of torsional stiffness corresponds to the magnitude of endochondral ossification and late response of bone formation. A significantly increased torsional stiffness in the non-fractured leg of rats with delayed fracture healing was also found, possibly indicating a response to loading conditions or a systemic stimulation of bone mass.

Effects of selective tumor necrosis factor-alpha inhibition to pain-behavioral changes caused by nucleus pulposus-induced damage to the spinal nerve in rats

Application of nucleus pulposus to the spinal nerve and displacement of the adjacent nerve results in behavioral changes in rats. It has been reported that treatment with the tumor necrosis factor-alpha (TNFalpha) inhibitor, infliximab, significantly reduces spontaneous pain behavior in this animal model. However, there have been no reports of the effects of infliximab on mechanical or thermal hyperalgesia using this model. Disk incision and adjacent spinal nerve displacement were performed with (n = 6) or without (n = 6) injection of infliximab. A control group also underwent sham surgery (n = 6). The animals were tested for 3 days before and on days 1, 3, 7, 14, and 21 after surgery. Non-noxious mechanical thresholds were tested by determining the hind paw withdrawal response to von Frey hair stimulation of the plantar surface of the footpad with a touch stimulator. Thermal nociceptive thresholds were tested using a sensitive thermal testing device. While disk incision with displacement surgery rats showed mechanical and thermal hyperalgesia after surgery on the experimental side, neither rats treated with infliximab nor the sham operation controls showed these effects. Injection of infliximab seemed to prevent mechanical and thermal hyperalgesia caused by the combination of disk incision and nerve displacement.

Disc related cytokines inhibit axonal outgrowth from dorsal root ganglion cells in vitro

STUDY DESIGN

Application of nucleus pulposus and disc related cytokines in vitro on cultured dorsal root ganglion (DRG) cells.

OBJECTIVES

To study if tumor necrosis factor (TNF) and interleukin-1beta (IL-1beta) may induce similar inhibition of axonal outgrowth from cultured DRG cells as application of nucleus pulposus and to compare a new assessment method to previous data.

SUMMARY OF BACKGROUND DATA

Pro-inflammatory cytokines related to the intervertebral disc have been suggested to affect adversely neurons following local application, with implications for the nucleus pulposus-induced nerve injury seen in various studies. Nucleus pulposus is known to inhibit axonal outgrowth from cultured DRG cells, thereby indicating a neurotoxic potential. The mechanisms were not understood, but it was suspected that the effect was mediated by pro-inflammatory cytokines produced by the nucleus pulposus.

METHODS

DRG were harvested from newborn rats and put in culture. The axonal outgrowth was determined 24 hours after starting the culture. Twenty-four hours after exposing the cultured cells to nucleus pulposus, frozen nucleus pulposus, TNF, or IL-1beta, the axonal outgrowth was reassessed, and the outgrowth during the exposure time was calculated.

RESULTS

Nucleus pulposus clearly reduced the axonal outgrowth. Also, application of TNF and IL-1beta reduced the outgrowth but not as pronounced as the nucleus pulposus. Frozen nucleus pulposus had no effects on the outgrowth. Overall, the data were similar regarding frozen and nonfrozen nucleus pulposus compared to a previous study.

CONCLUSIONS

It was evident that the 2 studied cytokines inhibited the outgrowth of axons from cultured DRG cells, thus suggesting a neurotoxic potential. However, the inhibition was not as pronounced as for nucleus pulposus. These data may increase our understanding for cytokine induced nerve injury, with implications for future treatment strategies for such conditions.

Nerve growth factor content in dorsal root ganglion as related to changes in pain behavior in a rat model of experimental lumbar disc herniation

STUDY DESIGN

The time courses of nerve growth factor content and pain-related behavior were examined using experimental disc herniation models.

OBJECTIVES

To investigate a relationship between nerve growth factor level and pain behavior.

SUMMARY OF BACKGROUND DATA

An induction of nerve growth factor in the periphery is regarded as a major contributor of inflammatory hyperalgesia and neuropathic pain. However, it has not been clarified quantitatively whether disc herniation induces changes in nerve growth factor levels in the dorsal root ganglion in relation to pain-related behavior.

METHODS

A total of 140 rats were used in this study. The animals had their left L4 nerve roots and associated dorsal root ganglion exposed and were equally divided into 4 groups: L4-L5 disc puncture, displacement of L4 nerve roots/dorsal root ganglion, the combination of disc puncture and displacement, and sham exposure. The content of nerve growth factor in the affected dorsal root ganglion was assessed by enzyme-linked immunosorbent assay as well as pain behavior during a postoperative 21-day period.

RESULTS

Disc puncture resulted in nerve growth factor induction at postoperative day 3, but not apparent behavioral changes. Mechanical displacement induced nerve growth factor at postoperative day 1 and mechanical allodynia at postoperative day 3, respectively (P < 0.05). In the combination model, there were more pronounced changes in nerve growth factor induction and both mechanical and thermal threshold during 7 days after surgery (P < 0.05).

CONCLUSIONS

These data suggest the possibilities that elevated nerve growth factor level is partly involved in pain behavior and further the combined model mimicking the clinical situation, which causes the marked neuronal responses, is helpful to advance the understanding of the mechanisms underlying sciatica due to lumbar disc herniation.

Macrophage appearance in the epineurium and endoneurium of dorsal root ganglion exposed to nucleus pulposus

Recently, it was observed that local application of nucleus pulposus may induce a characteristic reaction at the surface of the dorsal root ganglion (DRG). This change was inflammatory in nature and occurred as early as 1 day after the application of nucleus pulposus. Herniation of the nucleus pulposus was surgically induced in the L4-5 disc in rats. The L4 DRGs were resected 3, 24, and 72 h after surgery and sectioned. The sections were processed for immunohistochemistry using antisera to the macrophage marker ED1 and observed using light microscopy. The appearance of macrophages was confirmed 3, 24, and 72 h after the surgery. Macrophages were mainly distributed in the epineurial space of the DRG 3 h after disc incision and also in the endoneurial tissue 24 and 72 h after disc incision. The immunoreactivity was significantly stronger at 24 and 72 h than at 3 h in the parts of the DRG without apparent changes in the disc incision series (p < 0.01). Within the epineurium adjacent to application of nucleus pulposus, the number was significantly higher at 3 h than at 24 and 72 h (p < 0.05). We conclude that experimental disc herniation with leakage of nucleus pulposus results in macrophage recruitment to the epineurium of the DRG 3 h after disc incision and to the endoneurium 24 and 72 h after disc incision.

Selective inhibition of tumor necrosis factor-alpha prevents nucleus pulposus-induced histologic changes in the dorsal root ganglion

STUDY DESIGN

The possibility to prevent nucleus pulposus-induced structural changes of the dorsal root ganglion (DRG) by selective tumor necrosis factor-alpha (TNF-alpha) inhibition was assessed in an experimental model in the rat spine.

OBJECTIVES

To evaluate the role of TNF-alpha in the mediation of nucleus pulposus-induced structural changes by using selective inhibition and to confirm the effect of TNF-alpha inhibitor at the point of histologic findings.

SUMMARY OF BACKGROUND DATA

TNF-alpha is known to be released from the nucleus pulposus, and has been suggested to play a key role in chemical damage of the adjacent nerve tissue. The TNF-alpha inhibitor prevents the reduction of nerve conduction velocity and may limit the nerve fiber injury, intracapillary thrombus formation, and intraneural edema formation caused by nucleus pulposus. However, there is no report on the effect of the inhibitor regarding histologic findings and the appearance of the TNF-alpha in the DRG exposed to nucleus pulposus.

METHODS

1) Rats were treated with an intraperitoneal injection of infliximab. Nucleus pulposus from the disc was obtained 1, 3, 7, 14, and 21 days after the injection. The TNF-alpha-positive cells were observed using immunohistochemistry. 2) Disc herniation of the nucleus pulposus was made on the L4-L5 disc in rats. Two groups were treated with selective TNF-alpha inhibitor 1 day before or 3 hours after surgery. The other group received no TNF-alpha inhibitor. The L4 DRG was resected 1, 3, 7, 14, and 21 days after surgery. The specimens were processed for hematoxylin and eosin staining and immunohistochemistry using rabbit antisera to TNF-alpha. The histologic findings and TNF-alpha-positive cells were observed by light microscopy.

RESULTS

1) While positively stained immunoreactive TNF-alpha appeared between 7 and 21 days, no immunoreactive TNF-alpha was observed 1 and 3 days after injection in the nucleus pulposus. 2) The histologic changes of the DRG caused by nucleus pulposus were smaller in the infliximab treatment group than those in the nontreatment group. The number of immunoreactive TNF-alpha cells was high 1 and 3 days after surgery in the DRGs of disc herniation rats that were treated without an injection of the inhibitor, low on day 7 and 14, and very low on day 21 after surgery. No immunoreactive TNF-alpha was observed in the DRGs of the TNF-alpha inhibitor treatment groups on day 1, 3, and 21 after surgery. Weakly stained cells were sometimes observed in rats at day 7 and 14 after surgery.

CONCLUSIONS

Infliximab may prevent the histologic damage induced by nucleus pulposus. When rats were given a single intraperitoneal injection of infliximab at the beginning of disc herniation, the histologic damage seemed to be reduced in comparison with the nontreated rats.

Distribution and appearance of tumor necrosis factor-alpha in the dorsal root ganglion exposed to experimental disc herniation in rats

STUDY DESIGN

Distribution and appearance of tumor necrosis factor-alpha (TNF-alpha) in the dorsal root ganglion (DRG) exposed to experimental disc herniation were investigated using an immunohistochemical method in rats.

OBJECTIVES

To study the distribution and appearance of TNF-alpha in the DRG following experimental disc herniation in rats.

SUMMARY OF BACKGROUND DATA

Nucleus pulposus in the epidural space induces spinal nerve root injury not only by mechanical but also chemical mechanisms. Cytokines may play a key role in the chemical damage. There is, however, no report on the distribution and appearance of TNF-alpha in the DRG exposed to nucleus pulposus.

METHODS

Nucleus pulposus from the discs was smeared on the glass slides and processed for immunohistochemistry by the avidin-biotinylated peroxidase complex technique using rabbit antisera to TNF-alpha in rats. A herniation of the nucleus pulposus was made by incision of the L4-L5 disc in rats. The L4 and L5 DRGs were resected 1, 3, 7, 14, and 21 days after surgery. The specimens were processed for immunohistochemistry using rabbit antisera to TNF-alpha. The TNF-alpha-positive cells were observed and counted using light microscopy. Distribution of the TNF-alpha products was compared on each day after surgery.

RESULTS

A positive staining was seen in the cell bodies and in the matrix between the cells in the smeared nucleus pulposus. In the L4 DRG sections, the number of positive cells was significantly higher in the disc incision group than in the sham group at 1, 3, 7, and 14 days after surgery (P < 0.05). The positive cells showed a decrease in number day by day after surgery. On the contrary, in the L5 DRG, only a few positive cells were observed in the disc incision group after surgery. There was no statistically significant difference between disc incision and the sham groups at each day after surgery for the L5 DRGs.

CONCLUSIONS

The immunoreactivity of TNF-alpha in the DRG directly exposed to nucleus pulposus increases during 2 weeks. A collapse of the positive cells was seen in the DRG directly exposed to the nucleus pulposus.

Infliximab attenuates immunoreactivity of brain-derived neurotrophic factor in a rat model of herniated nucleus pulposus

STUDY DESIGN

The effect of infliximab, a chimeric monoclonal antibody to TNF-alpha, on induction of brain-derived neurotrophic factor (BDNF) was examined using an experimental herniated nucleus pulposus (NP) model.

OBJECTIVES

To investigate whether treatment of infliximab could attenuate an induction of BDNF, which functions as a modulator of pain, following NP application to the nerve root.

SUMMARY OF BACKGROUND DATA

Evidence from basic scientific studies proposes that TNF-alpha is involved in the development of NP-induced nerve injuries. However, the therapeutic mechanisms of infliximab against pain have not been elucidated experimentally.

METHODS

Twenty rats were used in this study. In the test groups, the animals underwent application of NP to the L4 nerve roots and received a single systemic (intraperitoneal) injection of infliximab at the time of surgery (Infli-0 group, n = 5) or at 1 day after operation (Infli-1 group, n = 5). As a control treatment, sterile water was administered intraperitoneally to 5 rats with NP application (NP group) and to 5 sham-operated rats (sham group). On day 3 after surgery, the L4 dorsal root ganglion (DRG) and L4 spinal segment were harvested and assessed regarding BDNF immunoreactivity. RESULTS.: Application of NP induced a marked increase of BDNF immunoreactivity in number in the DRG neurons and within the superficial layer in the dorsal horn compared with the sham group (P < 0.01). Infliximab treatment in the Infli-0 and Infli-1 groups reduced the BDNF induction in both DRG and spinal cord (P < 0.05).

CONCLUSION

These findings indicate that infliximab attenuates the elevated BDNF levels induced by NP. The present study therefore further indicates the importance of TNF-alpha in sciatica due to disc herniation and the possible therapeutic use of a TNF-alpha inhibitor for this condition.

Effects of fracture fixation stability on ossification in healing fractures

Temporal distribution of intramembranous and endochondral bone formation was studied in experimental fracture defects in rats under different stability of fracture fixation and fracture environments. Animals were surgically treated with a specially developed external fixation construct: Group 1 had 42 rats with a 0-mm fracture gap with bone ends touching corresponding to an axial stiffness of 265.00 +/- 34.00 N/mm and Group 2 had 42 rats with a 2-mm fracture gap corresponding to an axial stiffness of 30.38+/- 2.07 N/mm. From each group, six animals were sacrificed at 4 days and 1, 2, 3, 4, 6, and 12 weeks. Qualitative histologic and morphometric analyses revealed that less fixation rigidity and increased fracture gap induces a later response of bone formation and greater endochondral bone formation leading to prolonged time for full ossification. Furthermore, in the early phase of fracture healing temporal distribution and histologic characteristics of periosteal and intramedullary bone formation are similar and not influenced by rigidity and fracture environment. Results also showed that if tissues associated with the intramedullary region are preserved, intramedullary bone formation is substantial. Finally, histologic data indicate that woven bone might be a prerequisite for the differentiation process of endochondral bone formation.

Immunoreactivity of brain-derived neurotrophic factor in rat dorsal root ganglion and spinal cord dorsal horn following exposure to herniated nucleus pulposus

The pain mechanisms underlying radiculopathy due to disc herniation are still incompletely understood. This study assessed changes in brain-derived neurotrophic factor (BDNF) expression, a modulator of nociceptive information, in the dorsal root ganglion (DRG) and spinal cord dorsal horn following experimental disc herniation. Immunohistochemical analysis revealed an increase in percentage of BDNF-immunoreactive (IR) neurons profiles in the affected DRG and marked elevation in the BDNF-IR regions within both the superficial and deep layers at the corresponding spinal level with a peak at 3 days after nucleus pulposus (NP) application. These results thus show that herniated NP increases the BDNF production in the pain-processing neurons. Such changes can contribute to the development of inflammatory hyperalgesia.

Local application of disc-related cytokines on spinal nerve roots

STUDY DESIGN

To analyze the effects of tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma on cauda equina function and to define if any of these cytokines could induce nerve root dysfunction comparable with the situation with application of nucleus pulposus.

SUMMARY OF BACKGROUND DATA

Proinflammatory cytokines derived from the intervertebral disc have been suggested to mediate the nucleus pulposus-induced nerve root injury following local application of nucleus pulposus. However, it is not known if such cytokines may induce similar injury if applied separately.

METHODS

A total of 29 pigs were used. Nucleus pulposus was harvested from lumbar discs and applied to the sacrococcygeal cauda equina following laminectomy of the first coccygeal vertebra in seven pigs. Five pigs received 1.66 microg of tumor necrosis factor-alpha, five pigs received 0.85 microg of interleukin-1beta, and five pigs received 1.66 microg of interferon-gamma. Seven pigs received autologous fat for control. Nerve conduction velocity was studied by local electrical stimulation and recordings in the tail muscles 7 days after the application.

RESULTS

Application of nucleus pulposus and fat induced similar effects as seen in previous studies, with normal nerve conduction velocity for fat and a significant reduction for nucleus pulposus. Application of both interleukin-1beta and IFN-gamma induced slight reductions of nerve conduction velocity compared with fat, but they were not statistically significant. Tumor necrosis factor-alpha, however, induced a reduction of the velocity that was even more pronounced than for nucleus pulposus.

CONCLUSION

Based on previous observations and the data of the present study, one may conclude that tumor necrosis factor-alpha from nucleus pulposus cells seems to be intimately involved with the basic pathophysiologic events leading to both nerve root dysfunction and pain after local, epidural application of nucleus pulposus. One may therefore also suspect that pharmacologic inhibition of tumor necrosis factor-alpha may at least theoretically be considered in the clinical situation with disc herniation and sciatica.

Glycosphingolipid antibodies in serum in patients with sciatica

STUDY DESIGN

Serum antibody titers against 10 different glycosphingolipids were investigated by enzyme-linked immunosorbent assay in three groups of patients: patients with acute sciatica (Group IA, radicular pain for 32 +/- 36 days, n = 68), a subgroup of these patients 4 years later (Group IB, n = 23), and patients undergoing lumbar discectomy because of disc herniation (Group II, n = 37).

OBJECTIVES

To investigate the immunologic response in sciatica patients by analyzing circulating autoantibodies against glycosphingolipids, molecules highly expressed in cells from the nervous system, and the possible correlation of such antibodies to clinical and imaging findings as well as to subjective symptoms.

SUMMARY OF BACKGROUND DATA

The titers of glycosphingolipid antibodies are elevated in neurologic diseases with autoimmune stimulation such as Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy.

METHODS

Antiglycosphingolipid antibodies were assayed by a microtiter enzyme-linked immunosorbent assay method. Antibody titers were related to a healthy population by a method that judges all positive results (positive result = patient sera/pooled blood donor serum >2, at titer 1/400) as indicating a pathologic condition.

RESULTS

Increased levels of circulating antibodies against one or more glycosphingolipids were detected in 71% of patients with acute sciatica, in 61% of sciatica patients at a 4-year follow-up visit (eight antigens analyzed) and in 54% in patients undergoing discectomy. These frequencies were somewhat higher than, and in the last group similar to, those reported for generalized nervous system disorders with autoimmune involvement. In the acute sciatica patients, positive neurologic findings were associated with increased levels of two of the examined antibodies: 3'LM1 (immunoglobulin M and/or immunoglobulin G), P = 0.023, and GD1a (immunoglobulin M), P = 0.017.

CONCLUSION

The presence of glycosphingolipid antibodies in patients with sciatica and disc herniation suggests an activation of the immune system and thus a process possibly involved in the pathophysiology of sciatica. The autoimmune response was not limited to antibodies against one specific glycosphingolipid target; rather, an overall increase in autoantibodies against nervous system-associated glycosphingolipids was observed. These results encourage further studies of the pathophysiologic and clinical relevance of autoimmune responses in patients with sciatica and disc herniation.

Proinflammatory cytokines in cerebrospinal fluid and serum in patients with disc herniation and sciatica

Proinflammatory cytokines have been identified in herniated intervertebral discs in humans, and such cytokines have experimentally been demonstrated to be important in the pathophysiological mechanisms of disc herniation. Cerebrospinal fluid (CSF) and serum concentrations of interleukin (IL)-1beta IL-6, IL-8, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha were investigated using the enzyme-linked immunosorbent assay (ELISA) technique in 39 patients with lumbar disc herniation and sciatica. Pain duration and pain intensity (visual analogue scale, VAS) were recorded at inclusion, and a clinical examination was performed evaluating neurological findings. The extent of disc herniation (protrusion or extrusion/sequestration) was evaluated perioperatively. Normal concentrations of IL-1beta, IL-6, IFN-gamma and TNF-alpha were present in CSF and serum in almost all patients with lumbar disc herniation. The concentrations of IL-8 in CSF were increased in 12 out of 39 patients, and these increased levels of IL-8 correlated to a short duration of pain and to more pronounced herniation (extrusion or sequestration). No relationship between IL-8 concentrations in CSF and pain intensity, positive neurological findings or a positive straight leg-raising (SLR) test was found. The observation of increased concentrations of IL-8 in CSF in patients with a short duration of symptoms supports the concept of the initial involvement of inflammatory mechanisms after a disc herniation. The finding that most of the patients with increased concentrations of IL-8 in CSF had an extrusion or a sequestration may suggest that the increase in IL-8 is related to mechanical nerve root compression, but may also indicate a biochemical effect exerted by the herniated disc on the surrounding tissue. Further studies on the potential role of IL-8 as a biomarker for disc herniation are warranted.

Effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression

STUDY DESIGN

The effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression were evaluated in a setup using an established pig model.

OBJECTIVE

To assess the effects of two potent nonsteroidal antiinflammatory drugs, diclofenac and ketoprofen, in experimental nerve root compression.

SUMMARY OF BACKGROUND DATA

Compression of spinal nerve roots is recognized to be of major etiologic importance for several common spinal pain syndromes. Secondary inflammatory changes, induced by microvascular permeability changes and leakage of inflammatory mediators into the endoneural tissue, have been proposed as important for the induction of spinal nerve root injury by chronic compression.

METHODS

This study involved 21 pigs. An ameroid constrictor was used to induce compression. Seven pigs were treated with daily intramuscular injections of diclofenac 3 mg/kg for 7 days. Seven other pigs were treated with daily intramuscular injections of ketoprofen 4 mg/kg. For a control, seven pigs did not receive any drug treatment. After 7 days, the pigs were reanesthetized, and the nerve conduction velocity in the compressed nerve root segments was determined.

RESULTS

The nerve conduction velocity was significantly higher (P < 0.05, Student's t test) in the pigs treated with diclofenac (50 +/- 16 m/second) than in the untreated pigs (32 +/- 15 m/second). The nerve conduction velocity also was significantly higher (P < 0.05) in the pigs treated with ketoprofen (59 +/- 16 m/second) than in the untreated pigs. There were no significant differences in nerve conduction velocity between pigs treated with ketoprofen and those treated with diclofenac.

CONCLUSIONS

The findings indicate that intramuscular administration of diclofenac or ketoprofen, both potent antiinflammatory drugs, may reduce nerve root dysfunction induced by compression of spinal nerve roots in an experimental pig model.

Effects of anulus fibrosus and experimentally degenerated nucleus pulposus on nerve root conduction velocity: relevance of previous experimental investigations using normal nucleus pulposus

STUDY DESIGN

Nerve conduction velocity was measured in the pig cauda equina after local application of anulus fibrosus or in vitro/postmortem degenerated nucleus pulposus from the same pig.

OBJECTIVES

To analyze the effects of anulus fibrosus and degenerated nucleus pulposus on nerve conduction velocity.

SUMMARY OF BACKGROUND DATA

Previous studies on nucleus pulposus-induced effects on nerve roots have used normal, nondegenerated nucleus pulposus. Because both anulus fibrosus and degenerated nucleus pulposus are commonly seen in the clinical situation of disc herniation, the value of the previous work could be questioned.

METHODS

Anulus fibrosus and nucleus pulposus were harvested using a retroperitoneal approach. The nucleus pulposus was degenerated artificially either by addition of sodium lactate with HCl added to form a pH of either 6.0 or 3.5 (in vitro degeneration), or by storing the nucleus pulposus at 4 C until a pH of 6.0 (postmortem degeneration) was reached. After epidural application, the nerve conduction velocity was determined at 7 days (anulus fibrosus) or 3 days (degenerated nucleus pulposus).

RESULTS

Application of anulus fibrosus did not induce any reduction of nerve conduction velocity. In vitro and postmortem degenerated nucleus pulposus induced a reduction of nerve conduction velocity similar to that of normal nucleus pulposus.

CONCLUSIONS

Although only nerve function and not pain was assessed, it seems likely that previous experiments using normal nucleus pulposus may be relevant for evaluating the pathophysiologic mechanisms behind the nucleus pulposus-induced nerve root injury, also in a clinical perspective.

Selective inhibition of tumor necrosis factor-alpha prevents nucleus pulposus-induced thrombus formation, intraneural edema, and reduction of nerve conduction velocity: possible implications for future pharmacologic treatment strategies of sciatica

STUDY DESIGN

The possibility to prevent nucleus pulposus-induced functional and structural nerve root injury by selective tumor necrosis factor-alpha inhibition was assessed in an experimental model in the pig spine.

OBJECTIVE

The objective of the study was to evaluate the role of tumor necrosis factor-alpha in the mediation of nucleus pulposus-induced nerve injury by using selective inhibition.

SUMMARY OF BACKGROUND DATA

The cytokine tumor necrosis factor-alpha has been suggested to play a key role in the nerve root injury induced by local application of nucleus pulposus. However, previous studies have not been able to distinguish the effects between tumor necrosis factor-alpha and other disc-related cytokines because of the use of nonspecific cytokine inhibition.

METHODS

Autologous nucleus pulposus was harvested from a lumbar disc and applied to the porcine sacrococcygeal cauda equina. The pigs were simultaneously treated with two selective tumor necrosis factor-alpha inhibitors (etanercept n = 8 and infliximab n = 5), a heparin analogue (enoxaparin n = 5) or saline for control (n = 5). After 7 days the nerve conduction velocity over the application zone was determined and samples of the exposed nerve roots were collected for light microscopic evaluation.

RESULTS

The two tumor necrosis factor-alpha inhibitors prevented the reduction of nerve conduction velocity and also seemed to limit the nerve fiber injury, the intracapillary thrombus formation, and the intraneural edema formation. However, treatment with enoxaparin did not seem to be different from control regarding reduction of nerve conduction velocity or histologic changes.

CONCLUSIONS

The data clearly indicate that tumor necrosis factor-alpha is involved in the basic pathophysiologic events leading to nerve root structural and functional changes after local application of nucleus pulposus. The study therefore provides a basic scientific platform with potential clinical implications regarding the use of anti-tumor necrosis factor-alpha medication as treatment in patients with disc herniation and sciatica.

A long-term (4- to 12-year) follow-up study of surgical treatment of lumbar spinal stenosis

Limited data are available about the long-term outcome of surgical treatment for lumbar spinal stenosis, and there is a wide variation in reported success rates. There is also a controversy regarding differences in long-term outcome between patients undergoing decompressive surgery alone and those undergoing both decompression and fusion. The aim of this study was to evaluate the long-term clinical outcome and possible complications of decompressive surgery, with special reference to possible differences between patients undergoing fusion, with or without instrumentation, and those undergoing decompression alone. All 124 patients undergoing first-time surgery for lumbar spinal stenosis between 1982 and 1991 at our department were included, and their medical records were reviewed retrospectively. Ninety-six of the patients were available for follow-up and were re-examined by an independent investigator and assessed with a questionnaire after a mean follow-up period of 7.1 (range 4.0-12.2) years. Sixty-five percent of all the patients at the follow-up were subjectively satisfied. Eighty-eight percent of the patients reported constant or daily leg pain preoperatively compared to 43% at follow-up. Constant or daily low back pain was reported by 83% of the patients preoperatively compared to 45% at follow-up. Improvement in walking capacity was found in most patients, and only 4% of the patients who had a preoperatively documented maximum walking distance reported a decreased walking capacity. Twenty-four (25%) of all patients used analgesics daily at the time of follow-up, 34 patients (35%) occasionally and 38 patients (40%) never. The patients with fusions, instrumented or non-instrumented, did not differ significantly from the unfused patients regarding any of the above-mentioned parameters. The results of the study showed that most patients demonstrated a considerable improvement in walking capacity at follow-up. This improvement was significant (P < 0.001) and of clinical importance. A significant improvement regarding both low back pain and leg pain was found postoperatively compared to preoperatively (P < 0.001). There were no statistical differences, judged by all the evaluated parameters, regarding the clinical outcome between patients who were fused and those who were not. Neither were any significant differences found between instrumented fusions compared to uninstrumented fusions. In accordance with most other long-term follow-up studies, about two-thirds (65%) of the patients claimed a satisfactory result at follow-up.

Transport of epidurally applied horseradish peroxidase to the endoneurial space of dorsal root ganglia: a light and electron microscopic study

The route by which an epidurally applied macromolecule might reach the endoneurial space of spinal nerve roots was assessed with light and electron microscopy in a pig model established to explore the pathophysiology of disk herniation. Horseradish peroxidase (HRP) dissolved in saline was infused epidurally. Animals were sacrificed after 5 minutes (n = 5) or 30 minutes (n = 5). Two control animals received only a saline infusion and were sacrificed after 30 minutes. Nerve root specimens were collected, fixed, and exposed to the HRP substrate, 3.3'-di-amino-benzidine (DAB). The distribution of HRP reaction product in the nerve tissue was studied with light and electron microscopy. In 5-minute specimens, HRP was found in epidural and intradural vessel walls. At the nerve root level, HRP was detected in meningeal membranes but was not seen in periaxonal space. In addition to engaging the outer cell layers of the dorsal root ganglion (DRG) capsule, HRP was detected as a gradient among the peripherally located nerve cell bodies and sometimes among the emerging afferent axons. The 30-minute group demonstrated similar findings. The results confirm that HRP can reach the periaxonal spaces of lumbar DRG within 5 minutes after epidural application. Although the transport mechanism is not fully understood, the DRG may constitute an anatomical location allowing epidurally applied macromolecules entrance to the endoneurial space, either by direct diffusion or via vascular transport. The demonstrated transport route may have implications in the pathophysiology of sciatica in conjunction with lumbar disc herniation.

Methylprednisolone reduces the early vascular permeability increase in spinal nerve roots induced by epidural nucleus pulposus application

Autologous nucleus pulposus is known to have injurious effects on spinal nerve roots when applied epidurally. Both inflammatory and immunological mechanisms have been implicated in this regard. Various proinflammatory substances might be released or activated by nucleus pulposus and might affect the endoneural nerve root vessels. The present study assessed nucleus pulposus-induced early vascular reactions and the possibility of blocking these reactions with intravenous, high-dose, methylprednisolone pretreatment. In 25 pigs, the S2 and S3 nerve roots were exposed. In five pigs (control group), retroperitoneal fat was applied epidurally on the nerve roots, and the other 20 pigs had nucleus pulposus applied. This group was sub-divided into the treatment group (n = 8), in which the pigs were pretreated with intravenous high-dose methylprednisolone (30 mg/kg body weight), and the nontreatment group (n = 12), in which the pigs received a corresponding volume of saline solution. After 2 hours, Evans blue labeled albumin was injected intravenously 5 minutes before death. Endoneural extravasation of Evans blue labeled albumin was evaluated with fluorescence microscopy. A marked albumin leakage was found in 67% of the nontreated animals, in 25% of those in the treatment group, and in none of the control animals. These results demonstrate that nucleus pulposus can induce a rapid increase in endoneural vascular permeability in spinal nerve roots after epidural application. This increase can be partially prevented by pretreatment with high-dose methylprednisolone.

Nitric oxide as a mediator of nucleus pulposus-induced effects on spinal nerve roots

Nerve root dysfunction and sciatic pain in disc herniation are considered to be caused by mechanical compression and related to the presence of nucleus pulposus in the epidural space. Autologous nucleus pulposus has been shown to induce endoneural edema and to decrease nerve-conduction velocity in spinal nerve roots in experimental disc herniation models, and inflammatory mediators have been suggested to be involved in these mechanisms. Nitric oxide, a potent inflammatory mediator, is implicated in vasoregulation, neurotransmission, and neuropathic pain. Nitric oxide synthesis can be induced by different cytokines, e.g., tumor necrosis factor-alpha, which recently was shown to be of pathophysiological importance in experimental disc herniation. The enzyme nitric oxide synthase mediates the production of nitric oxide. Three series of experiments were performed in rat and pig disc herniation models to (a) investigate nitric oxide synthase activity in spinal nerve roots after exposure to autologous nucleus pulposus and (b) evaluate the effects of systemic treatment with aminoguanidine, a nitric oxide synthase inhibitor, on vascular permeability and nerve-conduction velocity. In a disc herniation model in the rat, calcium-independent nitric oxide synthase activity was measured in nerve roots exposed to nucleus pulposus; however, no nitric oxide synthase activity was detected in nerve roots from animals that underwent a sham operation, reflecting increased inducible nitric oxide synthase activity. In nucleus pulposus-exposed spinal nerve roots in the pig, the edema was less severe after systemic aminoguanidine administration than without aminoguanidine treatment. Aminoguanidine treatment also significantly reduced the negative effect of nucleus pulposus on nerve-conduction velocity in spinal nerve roots in the pig. These results demonstrate that nucleus pulposus increases inducible nitric oxide synthase activity in spinal nerve roots and that nitric oxide synthase inhibition reduces nucleus pulposus-induced edema and prevents reduction of nerve-conduction velocity. Furthermore, the results suggest that nitric oxide is involved in the pathophysiological effects of nucleus pulposus in disc herniation.

Evaluation of the psychophysical detection threshold level for vibrotactile and pressure stimulation of prosthetic limbs using bone anchorage or soft tissue support

In the present study the psychophysical detection threshold levels mechanical stimulation of 32 prosthetic limbs were determined. Prosthetic limbs were anchored to the bone by means of an implant (n=17) or supported by a socket enclosing the amputation stump (n=15). Detection threshold levels were assessed for pressure and vibratory stimulation of the prosthesis and the limb at the contralateral side (control). Following vibratory stimulation, thresholds were increased on an average 20% for socket prostheses. but approached those of the control for bone-anchored prostheses. For pressure stimulation, thresholds were increased up to 60% for socket prostheses and 40% for bone-anchored prostheses compared to the control. While bone-anchored prostheses yielded significantly lower threshold levels than socket prostheses, there was no significant difference between both treatments regarding pressure stimulation. Results were applicable to both upper and lower limb amputees. It could be concluded that detection thresholds for pressure and especially vibratory stimulation of prosthetic limbs were generally higher than for control limbs. The outcome was related to the prosthetic limb design with bone-anchored prostheses yielding better perception than socket prostheses.