Aims

The aim of this study is to determine the effects of the UK lockdown during the COVID-19 pandemic on the orthopaedic admissions, operations, training opportunities, and theatre efficiency in a large district general hospital.

Recently, the osteoregenerative properties of allograft have been enhanced by addition of autogenous skeletal stem cells to treat orthopaedic conditions characterised by lost bone stock. There are multiple disadvantages to allograft, and trabecular tantalum represents a potential alternative. This metal is widely used, although in applications where there is poor initial stability, or when it is used in conjunction with bone grafting, loading may need to be limited until sound integration has occurred. Strategies to speed up implant incorporation to surrounding bone are therefore required. This may improve patient outcomes, extending the clinical applications of tantalum as a substitute for allograft.

Background

Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft). Aims. To investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone.

Background

Skeletal stem cells (SSCs) have been used for the treatment of osteonecrosis of the femoral head to prevent subsequent collapse. In isolation SSCs do not provide structural support but an innovative case series in Southampton, UK, has used SSCs in combination with impaction bone grafting (IBG) to improve both the biological and mechanical environment and to regenerate new bone at the necrotic site.

Aims

Disease transmission, availability and economic costs of allograft have resulted in significant efforts into finding an allograft alternative for use in impaction bone grafting (IBG). Biotechnology offers the combination of skeletal stem cells (SSC) with biodegradable polymers as a potential solution. Recently polymers have been identified with both structural strength and SSC compatibility that offer the potential for clinical translation.

The aim of this study was to assess whether increasing the porosity of one such polymer via super critical CO₂ fluid foaming (SCF) enhanced the mechanical and cellular compatibility characteristics for use as an osteogenic alternative to allograft in IBG.

Aims

Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft).

The aim of this study was to investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone.

The osteo-regenerative properties of allograft have recently been enhanced by addition of autogenous skeletal stem cells to treat orthopaedic conditions characterised by lost bone stock. There are however, multiple disadvantages to allograft, including cost, availability, consistency and potential for disease transmission, and trabecular tantalum represents a potential alternative. Tantalum is already in widespread orthopaedic use, although in applications where there is poor initial implant stability, or when tantalum is used in conjunction with bone grafting, loading may need to be limited until sound integration has occurred. Development of enhanced bone-implant integration strategies will improve patient outcomes, extending the clinical applications of tantalum as a substitute for allograft.

The aim of this study was to examine the osteoconductive potential of trabecular tantalum in comparison to human allograft to determine its potential as an alternative to allograft.

Human bone marrow stromal cells (500,000 cells per ml) were cultured on blocks of trabecular tantalum or allograft for 28 days in basal and osteogenic media. Molecular profiling, confocal and scanning electron microscopy, as well as live-dead staining and biochemical assays were used to characterise cell adherence, proliferation and phenotype.

Cells displayed extensive adherence and proliferation throughout trabecular tantalum evidenced by CellTracker immunocytochemistry and SEM. Tantalum-cell constructs cultured in osteogenic conditions displayed extensive matrix production. Electron microscopy confirmed significant cellular growth through the tantalum to a depth of 5mm. In contrast to cells cultured with allograft in both basal and osteogenic conditions, cell proliferation assays showed significantly higher activity with tantalum than with allograft (P<0.01). Alkaline phosphatase (ALP) assay and molecular profiling confirmed no significant difference in expression of ALP, Runx-2, Col-1 and Sox-9 between cells cultured on tantalum and allograft.

These studies demonstrate the ability of trabecular tantalum to support skeletal cell growth and osteogenic differentiation comparable to allograft. Trabecular tantalum represents a good alternative to allograft for tissue engineering osteo-regenerative strategies in the context of lost bone stock. Such clinical scenarios will become increasingly common given the ageing demographic, the projected rates of revision arthroplasty requiring bone stock replacement and the limitations of allograft. Further mechanical testing and in vivo studies are on-going.

Background

Skeletal stem cells can be combined with human allograft, and impacted to produce a mechanically stable living bone composite. This strategy has been used for the treatment of femoral head avascular necrosis, and has been translated to four patients, of which three remain asymptomatic at up to three year follow-up. In one patient collapse occurred in both hips due to widely distributed and advanced AVN disease, necessitating bilateral hip arthroplasty. However this has provided the opportunity to retrieve the femoral heads and analyse human tissue engineered bone.

Disease transmission, availability and economic costs of allograft have resulted in significant efforts into finding an allograft alternative for use in impaction bone grafting (IBG). Biotechnology offers the combination of skeletal stem cells (SSC) with biodegradable polymers as a potential solution. Recently polymers have been identified with both structural strength and SSC compatibility that offer the potential for clinical translation.

The aim of this study was to assess whether increasing the porosity of one such polymer via super critical CO2 dissolution (SCD) enhanced the mechanical and cellular compatibility characteristics for use as an osteogenic alternative to allograft in IBG.

High molecular weight PLA scaffolds were produced via traditional (solid block) and SCD (porous) techniques, and the differences characterised using scanning electron microscopy (SEM). The polymers were milled, impacted, and mechanical comparison between traditional vs SCD created scaffolds and allograft controls was made using a custom shear testing rig, as well as a novel agitation test to assess cohesion. Cellular compatibility tests for cell number, viability and osteogenic differentiation using WST-1 assays, fluorostaining and ALP assays were determined following 14 day culture with SSCs.

SEM showed increased porosity of the SCD produced PLA scaffolds, with pores between 50-100 micrometres. Shear testing showed the SCD polymer exceeded the shear strength of allograft controls (P<0.001). Agitation testing showed greater cohesion between the particles of the SCD polymer (P<0.05). Cellular studies showed increased cell number, viability and osteogenic differentiation on the SCD polymer compared to traditional polymer (P<0.05) and allograft (P<0.001).

The use of supercritical C02 to generate PLA scaffolds significantly improves the cellular compatibility and cohesion compared to traditional non-porous PLA, without substantial loss of mechanical shear strength. The improved characteristics are critical for clinical translation as a potential osteogenic composite for use in impaction bone grafting.

Impaction bone grafting with milled human allograft is the gold standard for replacing lost bone stock during revision hip surgery. Problems surrounding the use of allograft include cost, availability, disease transmission and stem subsidence (usually due to shear failure of the surrounding allograft).

The aim of this study was to investigate various polymers for use as substitute allograft. The ideal graft would be a composite with similar mechanical characteristics as allograft, and with the ability to form de novo bone.

High and low molecular weight (MW) forms of three different polymers (polylactic acid (PLA), poly (lactic co-glycolic) acid (PLGA) and polycaprolactone (PCL)) were milled, impacted into discs, and then tested in a custom built shear testing rig, and compared to allograft.

A second stage of the experiment involved the addition of skeletal stem cells (SSC) to each of the milled polymers, impaction, 8 days incubation, and then tests for cell viability and number, via fluorostaining and biochemical (WST-1) assays.

The shear strengths of both high/ low MW PLA, and high/low MW PLGA were significantly higher than those of milled allograft (P<0.001, P<0.001, P<0.005 and P<0.005) but high and low MW PCL was poor to impact, and had significantly lower shear strengths (P<0.005, P<0.001). Fluorostaining showed good cell survival on high MW PLA, high MW PCL and high MW PLGA. These findings were confirmed with WST-1 assays.

High MW PLA as well as high MW PLGA performed well both in mechanical testing and cell compatibility studies. These two polymers are good contenders to produce a living composite for use as substitute human allograft in impaction bone grafting, and are currently being optimised for this use via the investigation of different production techniques and in-vivo studies.

Background

Unicameral bone cysts (UBCs) are difficult to treat and have a high recurrence rate. Their pathogenesis is unknown making targeted therapies difficult. Attributed causes include venous and interstitial fluid obstruction, oxygen free radicals, lysosomal enzymes, prostaglandins and genetic factors. Skeletal stem cells (SSCs) are osteoblast precursors critical to bone formation and cyst fluid may influence their growth, however the association between SSCs and cyst fluid has never been investigated.

Background: Stress shielding in the proximal femur is a widely recognized sequel of total hip replacement. It is due to a discrepancy in the stiffness between the implant and the proximal femur. The strain characteristics of implants of differing materials on the femur have previously been demonstrated in the laboratory using strain gauges and photo-elastic techniques. These are however relatively crude techniques giving limited results. Finite element analysis has also been used, but this provides only a theoretical analysis. Digital Image Correlation is an extremely accurate technique for strain analysis previously used in micro and nano engineering research.

Methods: A stainless steel, a titanium, and a carbonfibre reinforced plastic (CFRP) femoral prosthesis of the same dimensions, were implanted without cement into 5 prosthetic femora. A 1kN load was applied using a compression device. The process was repeated with 5 other prosthetic control femora. Digital Image Correlation was used to give an extremely detailed 2D strain map of inner cortex of the proximal femora during laboratory simulated static physiological loading conditions.

Results: All implants caused stress shielding in the proximal calcar area. In Gruen zones 6–4, both the stainless steel and titanium implants caused statistically significant stress shielding, whereas the femora implanted with the CFRP prosthesis did not show a statistically different strain pattern from the control group. There was a reduction in strain experienced by the medial cortex of the femora beyond the tip of all of the implants.

Conclusion: Digital Image Correlation is a novel method for strain measurement within Orthopaedic research which produces extremely accurate strain maps and data that can be reliably used for statistical analysis. Using this technique, this laboratory based investigation indicates that a carbon-fibre reinforced plastic stem is a good candidate to avoid stress shielding in total hip replacement surgery.

Painful foot and ankle joints are often pointed out as an impeding factor for lack of mobility and weight reduction. There is an assumption that weight loss will occur after their surgery due to increased mobility. The current study aimed to evaluate the effect of surgery on post-operative body mass index (BMI) in patients who underwent mid-foot or hind-foot arthrodesis. Our secondary aim was to look at the effect of sex, pre-operative obesity and good pain relief (AOFAS> 80) on post-operative BMI.

All patients who underwent mid-foot and hind-foot arthrodesis between April 2005 and November 2006 were identified from the operating theatre records. Each patient’s BMI recorded pre-operatively was compared with that recorded at a minimum of 6 months postoperatively using the paired Student’s t-test.

There were 35 eligible patients. 3 patients were excluded because of multiple trauma and 1 patient died during the period of study. We had 31 patients with 33 procedures with a mean age of 61 years (range 41–80). There were 18 females and 13 males. It was found that there was a mean increase of BMI by 0.25 (95%CI of −.95 to.44; p-value=0.47). It was noted that BMI of patients in obese group (BMI> 30) increased post-operatively by 0.07 (95%CI of −1.52 to 1.66; p-value=0.92).

This study highlights the fact that there is no significant effect on BMI in obese patients after successful fusion surgery. The post-operative BMI is neither significantly affected by sex nor quality of pain relief.

Introduction: The volume of medical waste has increased in line with increasing medical, diagnostic and therapeutic procedures, and large joint arthroplasty is a major contributor. Demand for landfill sites due to increasing household, industrial and hospital waste loads, have made the current situation untenable.

Methods: A prospective observational study of the waste from non contaminated packaging in consecutive joint replacements was undertaken. The total weight and volume of waste, the cost of disposal, and percentage and constituents of recyclable items were recorded for each case.

Current costs and methods of local waste disposal were also investigated.

Results: The average non-contaminated waste from a primary joint replacement is 5.2 kg and less than 1% is non-recyclable. Paper waste constitutes 57%, plastic waste 36%, cardboard waste 16% and metallic waste < 1%. Landfill costs are between £60–70 per tonne with recent and projected increases in landfill taxes.

Revenue generated from recycling paper is between £50–80 per tone and plastic waste between £150–180 per tonne.

Conclusions: Currently all potentially recyclable waste from common orthopaedic procedures is going to landfill. Reduce, Reuse and Recycle are the cornerstones of waste management. Medical organisations and staff need to understand how best to segregate waste and take advantage of opportunities for reuse and recycling.

The introduction of a local or national recycling policy would make a definite impact on the environment, as well as potentially saving money.

Introduction: Obesity has become a major public health epidemic, with recent reports citing that 22% of English men and 24% of women are clinically obese. Painful foot and ankle joints are often pointed out as an impeding factor for lack of mobility and weight reduction. There is an assumption that weight loss will occur after their surgery due to increased mobility.

The current study aimed to evaluate the effect of surgery on post operative body mass index (BMI) in patients who underwent mid-foot or hind-foot arthrodesis.

Patients and Method: All patients who underwent mid-foot and hind-foot arthrodesis under the care of senior author from April 2005 to Nov. 2006 were identified from the operating theatre records. In total 33 procedures were done in 31 patients. Each patient’s BMI recorded pre-operatively was compared with that recorded at a minimum of 6 months postoperatively using the paired Student’s t-test. Analysis of the data was also conducted by stratifying pre-operative BMI, good pain relief (i.e AOFAS> 80), sex and fusion site.

Results: It was found that there was a mean increase of BMI by 0.25 (95% CI of −0.95 to 0.44) with p-value of 0.47.

It was noted that BMI of patients in obese group increased post-operatively by 0.07 (95% confidence interval of −1.52 to 1.66) with p-value of 0.9.

Discussion: This study highlights the fact that there is no significant effect on BMI in obese patients despite significant increase in mobility and pain levels after mid-foot and hind-foot arthrodesis. The change in BMI after fusion surgery is not significantly effected by sex nor quality of pain relief.

We implanted titanium and carbon fibre-reinforced plastic (CFRP) femoral prostheses of the same dimensions into five prosthetic femora. An abductor jig was attached and a 1 kN load applied. This was repeated with five control femora. Digital image correlation was used to give a detailed two-dimensional strain map of the medial cortex of the proximal femur. Both implants caused stress shielding around the calcar. Distally, the titanium implant showed stress shielding, whereas the CFRP prosthesis did not produce a strain pattern which was statistically different from the controls. There was a reduction in strain beyond the tip of both the implants.

This investigation indicates that use of the CFRP stem should avoid stress shielding in total hip replacement.

In an adult man the mean femoral anteversion angle measures approximately 15°, for which the reasons have never been fully elucidated.

An assortment of simian and quadruped mammalian femora was therefore examined and the anteversion angles measured. A simple static mathematical model was then produced to explain the forces acting on the neck of the femur in the quadruped and in man. Femoral anteversion was present in all the simian and quadruped femora and ranged between 4° and 41°. It thus appears that man has retained this feature despite evolving from quadrupedal locomotion.

Quadrupeds generally mobilise with their hips flexed forwards from the vertical; in this position, it is clear that anteversion gives biomechanical advantage against predominantly vertical forces. In man with mobilisation on vertical femora, the biomechanical advantage of anteversion is against forces acting mainly in the horizontal plane. This has implications in regard to the orientation of hip replacements.