Since its introduction in total hip replacements in the 1960's, Ultra High Molecular Weight Polyethylene (UHMWPE) has played a major role as a bearing component material for joint arthroplasty. Concerns were raised when issues of wear resistance became apparent, and therefore Highly Crosslinked Polyethylenes were introduced. Such materials undergo a thermal treatment to quench the free radicals and reduce progressive oxidation.

However, said thermal treatment weakens the material mechanical properties and hence the use of antioxidants has been proposed and implemented in clinical use, mainly Vitamin-E. This can be added to the material before or after irradiation. If it is done before, part of the anti-oxydant is consumed during irradiation and so will not be available for its main purpose, and part reacts before irradiation with the free radicals thus reducing the crosslinking effect. If it is added after irradiation, high temperatures are required in order to diffuse it in the bulk material, and anyway the surface will be mainly rich in antioxidant. However, Vitamin-E tends to neutralize the free radicals on the oxidized lipid chain present in our body fluids and so in direct contact with the prosthetic components: such mechanism reduces the Vitamin-E quantity available for anti-oxidation purposes in the long run.

A UHMWPE doped with Hindered Amine Light Stabilizer (HALS) has been developed and tested for applications in large joint replacements where highest resistance to wear and tough mechanical properties are simultaneously required, such as tibial inserts for knee joints or acetabular inserts for large diameter heads.

Mechanical and biocompatibility tests were run in accordance with ASTM F 2565-06 and ISO 10993-1 with successful results and good reproducibility.

In particular, electro spin resonance exhibited a very high level of free radicals in the three samples, which confirms the properties of this new material. Free radicals are the result of the activation of the HALS molecules during irradiation, creating nitroxide radicals that will destroy the residual alkyl radicals responsible for the oxidation before and after implantation.

Biocompatibility tests proved absence of cytotoxicity, sensitization, irritation, genotoxicity or pyrogenic reactions.

The possible future applications for this new material in the arthroplasty field will be discussed along with the expected advances and advantages.

Introduction: We have investigated the accuracy of a serological marker to distinguish between septic and aseptic loosening of Total Hip Replacements (THR). We present the preliminary results of our on-going prospective study.

Methods: After obtaining Ethical Committee approval, 46 patients were collected in 3 groups; “control” primary THR, revision THR for aseptic loosening, and revision THR for infection. Serum IgG responses to an exocellular bacterial antigen (Lipid S) were determined by enzyme-linked immunosorbent assay (ELISA).

Results: Our results show that the test can accurately differentiate between the patients with infected joint replacements and the control group. The test, to date, has a specificity of 93% and a sensitivity of 100%.

Discussion and Conclusion: This simple and cheap test can reliably assist in the accurate evaluation of a painful hip arthroplasty, and planning for revision surgery. It will also be useful in the management of patients in whom the microbiology results are either negative or based on a single isolate of an organism, which may be either a contaminant or a possible pathogen. This, in turn, would have implications on financial costs and the optimum use of available resources.

Introduction and Aims: To confirm whether bacteria were present in disc material harvested at the time of discectomy; and to determine whether the presence of bacteria correlated with elevation of Anti Lipid S antibody levels; and to compare these results with antibody levels and disc specimens from patients undergoing surgery for indications other than radiculitis.

We have previously demonstrated significantly elevated IgG titres (ELISA) to a glycolipid antigen found in the cell wall of most gram-positive bacteria in patients with discogenic sciatica. This raised the possibility that the inflammation associated with disc protrusion might be initiated or accelerated by bacteria.

Method: A prospective study was performed using disc material harvested with stringent aseptic precautions from 207 microdiscectomy and 27 trauma, tumor or scoliosis patients (controls). Serology was obtained for all patients.

Results: In the Microdiscectomy group 76/207 (37%) had positive cultures after seven days incubation, of which 26 (34%) had positive serology. Forty-nine patients had Propionibacteria, 11 Coagulase-negative-Staphylococci (CNS), eight Propionibacteria and CNS, four other organisms and four mixed growth.

One hundred and thirty one (63%) patients had negative cultures of whom 15% had positive serology. There was a significant difference between patients with positive serology and culture, compared with those with negative serology and culture (Fischer exact test P< 0.01). In some patients, organisms were visible on microscopy prior to culture. Two of the patients undergoing surgery for other indications had positive cultures (P.acnes) of whom one had positive serology. Of those with negative cultures, six had positive serology.

There was a significant difference between positive cultures in those with sciatica and controls (P< .001).

Conclusion: A significant proportion of patients with discogenic radiculitis have positive cultures with low-virulence Gram-positive organisms (predominantly Propionibacteria ) and in proportion, a corresponding appropriate antibody response.

Introduction: We have previously demonstrated significantly elevated IgG titres (ELISA) to a glycolipid antigen found in the cell wall of most gram positive bacteria in patients with discogenic radiculitis (sciatica).

This raised the possibility that the inflammation associated with disc protrusion might be initiated or accelerated by the presence of bacteria.

Aim of the study: To confirm whether bacteria were present in the disc material harvested at the time of discectomy. To determine whether the presence of bacteria correlated with elevation of Anti Lipid S antibody levels. To compare these results with Antibody levels and disc specimens from patients undergoing surgery for indications other than radiculitis.

Methods: This was a prospective study. Recognising the frequency of contamination in clean wound culture stringent aseptic precautions were taken. Disc material was harvested from 108 microdiscectomy patients with sciatica.

Disc material was also obtained from 11 patients undergoing discectomy for other indications (trauma, tumour scoliosis). Serology was obtained for all these patients.

Results: In the microdiscectomy group 50/112 (45%) had positive cultures after seven days incubation, of which 15 (30%) had positive serology. Thirty-one patients had Propionibacteria, nine Coagulase negative Staphylococci (CNS), six Propionibacteria and CNS, one Corynebacterium and three mixed growth.

Sixty-two (55%) patients had negative cultures and all except one had negative serology. There was a significant difference between patients with positive serology and culture compared with those with negative serology and culture (Fischer exact test P< 0.01). In some patients organisms were visible on microscopy prior to culture.

Thirteen of those with postive cultures and 25 of those with negative cultures had had one or more epidural injections prior to surgery. Epidural injection was not found to be significantly associated with postive culture.

None of the patients undergoing surgery for other indications had positive serology or positive cultures.

Conclusion: A significant proportion of patients with discogenic radiculitis have positive cultures with low virulence Gram positive organisms (predominantly Propionibacteria) and in a proportion a corresponding appropriate antibody response.

Introduction: We have previously demonstrated significantly elevated IgG titres (ELISA) to a glycolipid antigen found in the cell wall of most gram positive bacteria in patients with discogenic radiculitis (sciatica).

This raised the possibility that the inflammation associated with disc protrusion might be initiated or accelerated by the presence of bacteria.

Aim of the Study: To confirm whether bacteria were present in disc material harvested at the time of discectomy. To determine whether the presence of bacteria correlated with elevation of Anti Lipid S antibody levels. To compare these results with Antibody levels and disc specimens from patients undergoing surgery for indications other than radiculitis.

Methods: This was a prospective study. Recognising the frequency of contamination in clean wound culture, stringent aseptic precautions were taken. Disc material was harvested from 62 microdiscectomy patients with sciatica. Disc material was also obtained from three patients undergoing decompression but without radiculitis and from three patients undergoing anterior correction of scoliosis. Serology was obtained for all these patients.

Results: In the Microdiscectomy group, 27/62 (43%) had positive cultures after seven days incubation, of which nine (33%) had positive serology. 22 patients had Propionibacteria, three Coagulase negative Staphylococci, one Corynebacterium and one mixed growth. Thirty five (56.4%) patients had negative cultures and all except one had negative serology. There was a significant difference between patients with positive serology and culture compared with those with negative serology and culture (Fischer exact test P< 0.001). In some patients organisms were visible on microscopy prior to culture.

Ten of those with positive cultures and fourteen of those with negative cultures had had one or more epidural injections prior to surgery. Epidural injection was not found to be significantly associated with positive culture.

None of the patients undergoing surgery for other indications had positive serology or positive cultures.

Conclusion: A significant proportion of patients with discogenic radiculitis have positive cultures with low virulence Gram positive organisms (predominantly Propionibacteria) and in a proportion, a corresponding appropriate antibody response.

Purpose of the study: Little is known about the impact of posterolateral arthrodesis on adjacent levels. In order to examine this question, we analyzed the radiological evolution of the lumbar spine in patients treated for lumbar stenosis, comparing cases where posterolateral arthrodesis was used with the other cases. Our aim was to determine whether the long-term radiographical modifications were affected by the arthrodesis.

Material and methods: Among our series of patients presenting with lumbar stenosis between 1984 and 1992, we retained two groups: patients in group 1 (n = 46) who underwent single-level decompressions at L4–L5 or L4–L5 and L5–S1 level; and patients in group II (n = 81) who underwent decompressions on the same levels associated with posterolateral arthrodesis extending from L4 to the sacrum with or without instrumentation. We compared the course of the two levels above the decompression (L2–L3 and L3–L4) between the two groups. We compared three radiological parameters: disc height, intervertabral slipping, and intersegmental mobility. We also examined the correlations between radiological modifications and functional outcome. Mean follow-up for these 127 patients was 9 years.

Results: The two groups were comparable for age, gender, follow-up, and presurgical functional score, disc height and intervertebral slipping at equivalent levels. At last follow-up, disc narrowing was observed at L2–L3 and L3–L4; it was significantly greater in the group with complementary arthrodesis. At L3–L4, intervertebral slipping also worsened more in the arthrodesis patients. Use of osteosynthesis significantly increased the risk of developing such radiological lesions. These lesions were associated, solely in the arthrodesis group, with poorer functional outcome.

Conclusion: Our findings allow the conclusion that, despite the effect of physiological aging, the observed long-term degenerative lesions in patients undergoing treatment of lumbar stenosis are related to the associated arthrodesis which increases their frequency and severity, deteriorating the functional outcome.