For unrepairable nerve defects, to date autogenous nerves are considered the golden standard, but donor site morbidity, limited availability and operation time prolongation are relevant problem. Acellular nerves from cadaveric donor, introduced since more than one decade ago, represent a novel promising alternative to bridge unrepairable nerve gaps.

Aim of this study is to provide a new tool to ameliorate the assistance of the numerous patients suffering from traumatic, oncological and jatrogenic nerve lesions. For this purpose, our project is promoting a progress beyond the state of the art of nerve gaps bridging surgery by developing a new technique to obtain acellular nerve allografts (ANAs).

Several methods to examine the effect of detergents on nerve tissue morphology and protein composition have been previously reported. Most of them are too expensive and time consuming. The presented novel decellularization technique is a modification of the Michigan detergent-based organic material removal, to speed up myelin and cellular debris detachment. The previously published Hudson's method¹has been chosen as control of the decellularization process). To validate the new nerve decellularization method, in terms of histological characteristics, outcomes were estimated through morphological and immunohistochemical studies in vitro and in vivo. The in vivo study consisted of a 1 cm defect in the tibial nerve of 3 new Zealand rabbits. This nerve defect was microsurgically replaced with a “Rizzoli” acellular nerve allograft. Rabbits were sacrificed 12 weeks after surgery. Endpoints were nerve conduction studies and histology.

Histological analysis of processed acellular nerve have been performed to evaluate the preservation of the structure and almost complete clearance of donor cells and cellular debris. Immunostaining analysis confirmed absence of Schwann cells and the maintenance of basal lamina. In vivo studies showed an effective and abundant nerve regeneration through the microsurgically reconstructed nerve defects. This was histologically proven. However no electophysiological return of function was showed.

The novel method will allow the storing of acellular nerve allografts. First results obtained by morphological analysis and immunofluorescence experiments and in vivo studies indicate that the internal structure of native nerve is maintained. It is then possible to decellularize nerves with the novel technique reducing both manufacturing times and costs. The relatively inexpensive method of decellularization will facilitate the number of patients that will benefit from reconstruction of nerve defects with ANAs.

We undertook a randomised controlled trial to compare bipolar hemiarthroplasty (HA) with a novel total hip replacement (THR) comprising a polycarbonate–urethane (PCU) acetabular component coupled with a large-diameter metal femoral head for the treatment of displaced fractures of the femoral neck in elderly patients. Functional outcome, assessed with the Harris hip score (HHS) at three months and then annually after surgery, was the primary endpoint. Rates of revision and complication were secondary endpoints.

Based on a power analysis, 96 consecutive patients aged > 70 years were randomised to receive either HA (49) or a PCU-THR (47). The mean follow-up was 30.1 months (23 to 50) and 28.6 months (22 to 52) for the HA and the PCU group, respectively.

The HHS showed no statistically significant difference between the groups at every follow-up. Higher pain was recorded in the PCU group at one and two years’ follow-up (p = 0.006 and p = 0.019, respectively). In the HA group no revision was performed. In the PCU-THR group six patients underwent revision and one patient is currently awaiting re-operation. The three-year survival rate of the PCU-THR group was 0.841 (95% confidence interval 0.680 to 0.926).

Based on our findings we do not recommend the use of the PCU acetabular component as part of the treatment of patients with fractures of the femoral neck.

Cite this article: Bone Joint J 2013;95-B:609–15.

Introduction

We evaluated the osteogenic potential of a novel biomimetic bone paste (DBSint®), made of a combination of a human demineralized bone matrix (hDBM) and a nano-structured magnesium-enriched hydroxyapatite (Mg-HA), in a standardized clinical model of high tibial osteotomy for genu varus.

Ceramic-on-ceramic bearing is an attractive alternative to metal-on-polyethylene bearing due to the unique tri-bological advantages of alumina. However, despite the long-term satisfactory results obtained so far in the vast majority of patients, failure may occur in a few cases.

Clinical, radiographic, laboratory and microbiological data of 30 consecutive subjects with failed alumina-on-alumina total hip arthroplasties (THA) were analyzed to define if foreign body reaction to wear debris may be responsible for periprosthetic bone resorption, as in conventional metal-to-polyethylene bearings. In all cases, clinical and radiographical material was reviewed, retrieved implants were examined, and histology of periprosthetic tissues was analyzed. Massive osteolysis was never observed. Apart from 5 five patients for which revision surgery was necessary due to the occurrence of late infection, in all other cases failure had occurred due to secondary implant instability (as in the case of screwed sockets, 19 cases) or to malpositioning of the implant (5 cases). One patient suffered from chronic dislocation.

In the vast majority of cases, ceramic wear debris was absent or scarce, and did not induce any tissue reaction. In a few cases with severe wear, debris was evident in clusters of perivascular macrophages, notably in the absence of foreign body multinucleated cells, confirming the excellent biocompatibility of ceramics.

These findings indicate that wear debris and peri-prostetic bone resorption were the effect rather than the cause of failure, differently from revised metal-on-polyethylene bearings, in which foreign body cell reaction is the main pathogenetic mechanism of failure. On the contrary, mechanical problems, due to incorrect surgical technique or to inadequate prosthetic design, may cause instability of the implant, in turn resulting in wear debris production and moderate if any biological reaction.

We investigated the role of ion release in the assessment of fixation of the implant after total knee replacement and hypothesised that ion monitoring could be a useful parameter in the diagnosis of prosthetic loosening. We enrolled 59 patients with unilateral procedures and measured their serum aluminium, titanium, chromium and cobalt ion levels, blinded to the clinical and radiological outcome which was considered to be the reference standard. The cut-off levels for detection of the ions were obtained by measuring the levels in 41 healthy blood donors who had no implants. Based on the clinical and radiological evaluation the patients were divided into two groups with either stable (n = 24) or loosened (n = 35) implants.

A significant increase in the mean level of Cr ions was seen in the group with failed implants (p = 0.001). The diagnostic accuracy was 71% providing strong evidence of failure when the level of Cr ions exceeded the cut-off value. The possibility of distinguishing loosening from other causes of failure was demonstrated by the higher diagnostic accuracy of 83%, when considering only patients with failure attributable to loosening.

Measurement of the serum level of Cr ions may be of value for detecting failure due to loosening when the diagnosis is in doubt. The other metal ions studies did not have any diagnostic value.

Aim: To assess the effect of lyophilised bone grafts, autologous platelet gel and autologous medullary cells on bone repair processes after tibial osteotomy for genu varum

Methods: Thirty patients, divided into 3 groups by the generation of random sampling numbers, were treated by valgus osteotomy for genu varum with a minimum correction of 8 mm and fixation using a titanium plate (TITAN plate® Citieffe).

The groups were thus divided:

Group 1: lyophilised bone chips.

Group 2: lyophilised bone chips + platelet gel

Group 3: lyophilised bone chips + platelet gel + packed autologous medullary cells (Buffy coat).

At six weeks X-rays, MRI and needle biopsies were carried out. The tissue underwent morphological and microstructural tests.

Results confirmed that the use of platelet gel and packed medullary cells as adjuvant for the lyophilised bone aid bone repair and graft integration. Morphological and morphometric tests showed that at six week the newly formed bone of group 3 had better mechanical properties.

Conclusions: This study shows that the use of platelet gel and packed autologous medullary cells combined with lyophilised bone chips produces a faster and mechanically stronger recovery of bone stock in the treatment of bone defects.

Modern metal-on-metal bearings produce less wear debris and osteolysis, but have the potential adverse effect of release of ions. Improved ceramic-on-ceramic bearings have the lowest wear of all, but the corrosion process has not been analysed.

Our aim was to measure the serum ion release (ng/ml) in 23 patients having stable hip prostheses with a ceramic-on-ceramic coupling (group A) and to compare it with the release in 42 patients with a metal-on-metal bearing (group B) in the medium term. Reference values were obtained from a population of 47 healthy subjects (group C). The concentrations of chromium, cobalt, aluminium and titanium were measured.

There was a significant increase of cobalt, chromium and aluminium levels (p < 0.05) in group B compared with groups A and C. Group A did not differ significantly from the control group. Despite the apparent advantage of a metal-on-metal coupling, especially in younger patients with a long life expectancy, a major concern arises regarding the extent and duration of ion exposure. For this reason, the low corrosion level in a ceramic-on-ceramic coupling could be advantageous.

There is no diagnostic, non-invasive method for the early detection of loosening after total hip arthroplasty. In a pilot study, we have analysed two serum markers of bone remodelling, procollagen I C-terminal extension peptide (PICP) and cross-linked N-terminal telopeptide (NTx), as well as the diagnostic performance of NTx for the assessment of osteolysis. We recruited 21 patients with loosening (group I), 18 with a well-fixed prosthesis (group II) and 17 at the time of primary arthroplasty for osteoarthritis (OA) (group III). Internal normal reference ranges were obtained from 30 healthy subjects (group IV).

The serum PICP level was found to be significantly lower in patients with OA and those with loosening, when compared with those with stable implants, while the NTx level was significantly increased only in the group with loosening, suggesting that collagen degradation depended on the altered bone turnover induced by the implant. This hypothesis was reinforced by the finding that the values in the pre-surgery patients and stable subjects were comparable with the reference range of younger healthy subjects.

A high specificity and positive predictive value for NTx provided good diagnostic evidence of agreement between the test and the clinical and radiological evaluations. The NTx level could be used to indicate stability of the implant. However, further prospective, larger studies are necessary.

Aim: to assess the effect of lyophilized bone grafts, autologous platelet gel and autologous medullary cells on bone repair processes after tibial osteotomy for genu varum.

Methods: thirty patients, divided into 3 groups by the generation of random sampling numbers, were treated by valgus osteotomy for genu varum with a minimum correction of 8 mm and fixation using a titanium plate (TITAN plateA8 Citieffe).

The groups were thus divided:

Group 1: lyophilized bone chips.

At six weeks X-rays, MRI and needle biopsies were carried out. The tissue underwent morphological and microstructural tests.

Results: preliminary results confirmed that the use of platelet gel and packed medullary cells as adjuvant for the lyophilized bone aid bone repair and graft integration. Morphological and morphometric tests showed that at six week the newly formed bone of group 3 had better mechanical properties.

Conclusions: this study shows that the use of platelet gel and packed autologous medullary cells combined with lyophilized bone chips produces a faster and mechanically stronger recovery of bone stock in the treatment of bone defects.

The world-wide experience with metallic implants provides the evidence for biocompatibility of modern cobalt- and titanium-based alloys. However, a corrosion process leading to release of ions has to be taken into account, and controversial data are available about the ‘endogenous’ metal exposure resulting from implants.

Adverse tissue reactions, cytotoxicity and toxic/ sensitizing effects of corrosion products on the immune system, as well as an involvement of metal ions in the pathogenesis of prosthesis loosening, are the main undesired effects. Moreover, metal ions could be responsible of long-term toxic effects, such as genotoxicity and carcinogenicity.

The aim of our study was to analyze the levels of serum metal ions in a large series of patients who underwent total hip and knee replacement (THR and TKR, respectively); both stable and loosened implants were considered. Furthermore, a group of subjects with fracture fixation devices was evaluated.

A consecutive series of 471 individuals (193 M; 278 F) was enrolled in the study, including 151 with hip prosthesis loosening (Group A: 52 M; 99 F; median age 67; median follow up 90 months) and 100 patients with stable hip prosthesis (Group B: 44 M; 56 F; median age 59; median follow up 34 months). Group A and B comprised implants with different coupling, i.e. ceramic-on-ceramic (alumina), metal-on-metal and metal-on-polyethylene, and different stem alloy (TiAlV-THR and CoCrMo-THR). 20 patients with knee prosthesis loosening (Group C: 3 M; 17 F; median age 67; median follow up 25 months), and 12 subjects with failed fracture fixation devices (Group D: 6 M; 6 F; median age 35; median follow up 12 months) were enrolled, too. Osteoarthritis was the most frequent disease that led to joint replacement (59%), followed by hip dysplasia (19%), and trauma (13%). Ion reference ranges were obtained from 188 subjects (88 M; 100 F; median age 52), including 56 healthy subjects and 132 candidates to primary THR or TKR. Serum samples were analyzed for chromium (Cr), cobalt (Co), molybdenum (Mo), nickel (Ni), aluminum (Al), titanium (Ti) and vanadium (V) content, in relation with the presence in the implant alloy, using a graphite furnace atomic absorption spectrometer (GFAAS), equipped with double background correction Deuterium/ Zeeman, autosampler and pyrolytic carbon-coated graphite tubes (Unica Solaar 939 QZ, Cambridge, UK). The highest value found for subjects with no implant was considered the upper reference limit for each element.

Group A (loosened THR) and B (well-fixed THR) patients, compared with controls, showed different behaviour depending on the prosthesis coupling and stem composition.

Metal-on-PE coupling and CoCrMo/Ni stem: a significant increase of Cr and Co serum values was observed, in both groups, even if the increase in loosened implants was higher than in the stable ones. Mo and Ni concentration did not show a significant variation.

A serum Co, Cr increase was demonstrated in Group C patients, too, who had a failed knee prosthesis, and a Cr, Ni increase was observed in Group D patients with stainless steel fracture fixation devices.

Metal corrosion leading to ion release needs further consideration, because it may enhance the inflammatory reaction, depress the immune system, and facilitate peri-prosthetic bacterial growth. Especially metal-on-metal coupling introduces additional biologic risks associated with increased degradation products of prosthetic materials. Otherwise, histiocytic/giant-cell reaction and peri-prosthetic osteolysis induced by polyethylene particles represent the main problem in knee and hip joint implants with metal/PE coupling, and the systemic effects due to the ion release become negligible. On the contrary, ceramic-on-ceramic coupling represents a good alternative, as demonstrated by the absence of metal release in stable implants, even if, in case of loosening, a serum ion increase is observed, probably due to the fretting at the head/neck connection.

Also, metal corrosion of fixation devices is a concern; consequently, it could be appropriate to remove the implants, as early as their function is accomplished.

In conclusion, ion profile should be carefully monitored and the epidemiological survey implemented, in order to establish the tolerance values in patients with implants, especially in young patients, where a long-term ‘endogenous’ exposure has to be faced. In particular, concerning systemic toxic effects, the ‘gene expression profiling’, through the use of microarray technology, could contribute to an improved understanding of the biological responses to metal ions released from orthopedic implants. In such a way a real risk-to-benefit ratio for the patient could be established.

Finally, ion monitoring, as demonstrated by the different serum ion levels in stable and loosened implants, could allow to detect early signs of failure, when radiographic and clinical data are unclear, and to avoid the need of revision using a proper treatment.

We aimed to assess whether the immunological abnormalities which have been observed in patients with loose total hip replacements (THRs) are present in patients with a well-fixed prosthesis.

We examined blood samples from 39 healthy donors, 22 patients before THR and 41 with well-fixed THRs of different types (15 metal-on-metal, 13 metal-on-polyethylene, 13 ceramic-on-ceramic). Before THR, the patients showed a decrease in leukocytes and myeloid cells in comparison with healthy donors, and a prevalence of type-1 T lymphocytes, which was confirmed by the increase in ratio of interferon-γ to interleukin 4. Moreover, patients with metal-on-metal or metal-on-polyethylene implants showed a significant decrease in the number of T lymphocytes and a significant increase in the serum level of chromium and cobalt, although no significant correlation was observed with the immunological changes. In the ceramic-on-ceramic group, leukocytes and lymphocyte subsets were not significantly changed, but a significant increase in type-2 cytokines restored the ratio of interferon-γ to interleukin 4 to normal values.

We conclude that abnormalities of the cell-mediated immune response may be present in patients with a well-fixed THR, and that the immunological changes are more evident in those who have at least one metal component in the articular coupling.

Our aim was to determine if the serum levels of bone-resorbing cytokines (IL-1β, TNF-α, IL-6, GM-CSF) are altered in patients with aseptic loosening of a total hip prosthesis, and if such levels are influenced by the type of implant. We determined cytokine levels in sera from 35 patients before revision for failed total hip arthroplasty and compared them with those in 25 healthy donors. We also assessed the soluble receptor of interleukin-2 (sIL-2r) in serum as an indication of a specific immune reaction against the implant.

Our findings showed that the sIL-2r and TNF-α serum level did not change. The IL-6 level was not significantly altered, but was higher in patients with TiAlV prostheses than in those with a CrCoMo implant and in patients with cemented prostheses. The IL-1β level was found to be higher in those with a TiAlV cemented prosthesis than in the control group (p = 0.0001) and other groups of patients (p = 0.003 v uncemented TiAlV, p = 0.01 v cemented CrCoMo, p = 0.001 v uncemented CrCoMo). The GM-CSF level significantly increased in patients compared with healthy subjects (p = 0.008), and it was higher in those with cemented than with uncemented implants (p = 0.01). Only patients with cementless CrCoMo prostheses had levels of GM-CSF similar to those of the control group. The highest GM-CSF concentrations were observed in patients treated with non-steroidal anti-inflammatory drugs (NSAIDs) in the last months before revision (p = 0.04). In addition, when massive osteolysis was observed, the level of GM-CSF tended to decrease to that of the control group.