Introduction

Femoral periprosthetic fractures above TKA are commonly treated with retrograde intramedullary nailing (IMN). This study determined if TKA design and liner type affect the minimum knee flexion required for retrograde nailing through a TKA.

The current ‘gold’ standard surgical intervention for critical size bone defect repair involves autologous bone grafting, that risks inadequate graft containment and soft tissue invasion. Here, a new regenerative strategy was explored, that uses a barrier membrane to contain bone graft. The membrane is designed to prevent soft tissue ingrowth, whilst supporting periosteal regrowth, an important component to bone regeneration. This study shows the development of a collagen-based barrier membrane supportive of periosteal-derived mesenchymal stem cell (P-MSC) growth.

P-MSC-homing barrier membranes were successfully obtained with nonaligned fibres, via free-surface electrospinning using type I collagen and poly(E-caprolactone) in 1,1,1,3,3,3-Hexafluoro-2-propanol. Introduction of collagen in the electrospinning mixture was correlated with decreased mean fibre diameter (d: 319 nm) and pore size (p: 0.2–0.6 μm), with respect to collagen-free membrane controls (d: 372 nm; p: 1–2 μm). Consequently, as the average MSC diameter is 20 μm, this provides convincing evidence of the creation of a MSC containment membrane.

SEM-EDX confirmed Nitrogen and therefore collagen fibre localisation. Quantification of collagen content, using Picro Sirius Red dye, showed a 50% reduction after 24 hours (PBS, 37 °C), followed by a drop to 25% at week 3. The collagen-based membrane has a significantly higher elastic modulus compared to collagen-free control membranes. P-MSCs attached and proliferated when grown onto collagen-based membranes, imaged using confocal microscopy over 3 weeks. A modified transwell cell migration assay was developed, using MINUSHEET® tissue carriers to assess barrier functionality. In line with the matrix architecture, the collagen-based membrane proved to prevent cell migration (via confocal microscopy) in comparison to the migration facilitating positive control.

The aforementioned results obtained at molecular, cellular and macroscopic scales, highlight the applicability of this barrier membrane in a new ‘hybrid graft’ regenerative approach for the surgical treatment of critical size bone defects.

Introduction: UHMWPE wear particles induce osteolysis and loosening of total joint replacements. Much effort has been directed at reducing the wear volume of UHMWPE, such as crosslinking treatments [1]. Recently, interest in UHMWPE with vitamin E (VE) has increased due to its improved wear resistance in knee prostheses [2], as well as improved mechanical properties. The aim of this study was to culture human peripheral blood mononuclear cells (PBMNCs) with known volumes of clinically relevant wear debris from UHMWPE with and without VE in order to quantify and compare their respective biological activities.

Methods: For UHMWPE with VE, GUR1050 UHMWPE powder was mixed with VE at 0.3% (w/w) and 3% (w/w) using a screw cone mixer. The wear rates were evaluated using a six-station multidirectional pin on plate wear simulator against a smooth CoCr plate (Ra 0.01–0.03 micrometres), in 25% bovine serum, under a load of 160N and a frequency of 1 Hz. Endotoxin-free clinically relevant wear debris was generated aseptically for cell culture studies, using a single-station multidirectional pin on plate wear rig housed in a class II safety cabinet. PBMNCs were isolated from blood collected from three healthy donors then cultured with debris at particle volume (μm3) to cell number ratios of 100:1 using the agarose gel technique [3]. Cells without particles were used as the negative control, and LPS at 200 ng/ml was the positive control. Cell viability was assessed by ATP-Lite assay, and TNF-alpha, interleukin (IL)-1beta, IL-6 and IL-8 were measured by ELISA at 12 and 24 h.

Results: The 3% VE UHMWPE was found to have a higher wear rate than both the Virgin and the 0.3% VE UHMWPE, although there were no significant differences. Particle size and volume distributions were similar for all materials, with the mode of the frequency distributions being in the 0.1–1 micron size range. Cell viability was not adversely affected by any of the treatments. Cells cultured with virgin UHMWPE debris secreted significantly higher quantities (P< 0.05) of TNF-alpha compared to debris from both the 0.3% and the 3% VE UHMWPE, which released comparable levels of TNF-alpha to the cell only control group. The results for the other cytokines, IL-1beta, IL-6 and IL-8, and for the two additional donors showed similar trends as the results for TNF-alpha.

Discussion: The biological response to wear particles is strongly influenced by particle size and volume [3]. Cells cultured with wear debris of UHMWPE containing VE released very low levels of cytokines in comparison with virgin UHMWPE, even there were no significant differences in particle size. Differences in the chemical composition of the particles or different rates of protein adsorption may explain these differences. VE has anti-inflammatory properties, which may act by free radical scavenging. VE has been shown to reduce production of reactive oxygen species and pro-inflammatory cytokines such as TNF-alpha and IL-1beta from monocytes [4]. The anti-inflammatory effects of UHMWPE particles containing VE are currently being investigated.

With an alarming 10% increase in disability payments for backpain annually, the importance of early management of backpain within the first 6 weeks is paramount. The problems of a long and often agonising waiting time for a hospital consultation has been overcome by setting up of the Alexandra Hospital Backpain Assessment Clinic (ABPAC) with initial and immediate consultation by a trained clinical physiotherapist.

From the period March 1995 to March 1999 a total of 1881 patients werw reviewed by the ABPAC and an analysis of these cases is presented. 640/1881 (34%) patients were assessed, advised and discharged. 535/1881 (28%) patients were assessed, given supervised physiotherapy, advised and discharged. 169/1881 (16%) patients were assessed, investigated and discharged. In all 292/1881 (16%) patients needed actual review by consultant, out of which only 48 (2.5%) needed surgery. Only 63/1881 patients needed an MRI scan. There were only 2 patients who were found to have serious pathology in the form of spinal metastasis and only 5 were inappropriate because non-spinal pathology was picked up at initial assessment. There were no “missed” diagnosis.

Thus the clinic with its emphasis on examination and advice rather than “treatment” does not allow for repeated series of consultations nor the development of “regulars” who become dependent on the hospital for treatment, saving the NHS serious money and consultant time. This study proves that such a clinic apart from being safe, is also well accepted by patients and referring G.Ps alike. An outline of its working and the management algorithms is presented.