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For further reading see Bailey and Love, Chapter 8.What is a controlled clinical trial?
A controlled trial is a scientific experiment in which one or more treatments are compared with a control treatment. The controls may be non-treatment, placebo or a standard clinical practice.
What is a crossover design for clinical trials?
In crossover designs, the patient acts as his or her own control.
Treatments are compared and their order is randomised.
What is randomisation?
Randomisation is a method of assigning subjects to an experimental or control arm of a study. Each patient has an equal chance of appearing in either treatment group. It helps avoid selection bias.
What is meant by blinding?
Blinding is a method used to eliminate any bias inherent in the data collection. A study is single-blinded if the patient is unaware of the treatment allocation. In the best randomised controlled trials, neither patient nor researcher is aware of which therapy has been used until after the study has been conducted (double-blinded).
What are type I and type II errors?
■ Type I errors occur when the null hypothesis (HO) is rejected when it is in fact true. In other words, benefit is perceived when really there is none (false positive).
Research and statistics
■ Type II errors occur when the null hypothesis (HO) is not rejected when it is in fact false. In other words, benefit is missed when it was there to be found (false negative).
What is the power of a trial?
The power measures the sensitivity of the trial to detect a difference and is equal to a type II error.
What does it mean to state that a result is ‘statistically significant’?
The result is unlikely to have occurred by chance. Normally this equates to a p-value of less than 0.05 (5 per cent).
What is a ‘confidence interval’ (CI)?
It is an interval estimate of any population parameter. It is used to indicate the reliability of an estimate. The CI provides the probability that a true population is contained within a range from a sample mean and its standard error.
Fractures
B&L
For further reading see Bailey and Love, Chapter 27.What is a fracture?
A fracture is a break in the continuity of a bone. It may be complete or incomplete (based on whether both cortices are involved), or open or closed (based on whether the overlying skin is intact).
What are the phases of bone healing?
■ Reactive phase: fracture and inflammation, followed by granulation tissue formation
■ Reparative phase: callus formation and lamellar bone deposition
■ Remodelling phase: remodelling to the original bone contour.
What classification do you know for proximal femoral fractures?
The Garden classification:
■ I: incomplete fractures (including impacted valgus fracture)
■ II: complete fracture without displacement
■ III: complete fracture with partial displacement
■ IV: complete fracture with full displacement.
How may fractures be treated?
The treatment of bone fractures depends on the type and location of the fracture and the patient’s age and medical history. However, four phases can be identified (the 4 Rs):
■ Resuscitation
■ Reduction (open or closed)
■ Restriction (immobilisation) (cast splint, functional brace, continuous traction, internal fixation, external fixation)
■ Rehabilitation (physiotherapy).
Section 3: Applied surgical science
What are the early complications of fractures?
Local
■ Vascular injury causing haemorrhaging (internal or external)
■ Visceral injury causing damage to the surrounding organs (e.g. brain, lung or bladder)
■ Damage to surrounding soft tissue, nerves or skin
■ Haemarthrosis
■ Compartment syndrome (or Volkmann’s ischaemia)
■ Wound infection.
Systemic
■ Fat embolism
■ Shock
■ Thromboembolism (pulmonary or venous)
■ Exacerbation of underlying diseases (diabetes, ischaemic heart disease)
■ Pneumonia.
What are the late complications of fractures?
Local
■ Delayed union
■ Non-union
■ Mal-union
■ Joint stiffness
■ Contractures
■ Infection
■ Myositis ossificans
■ Avascular necrosis
■ Algodystrophy (Sudeck’s atrophy)
■ Osteomyelitis
■ Growth disturbance or deformity.
Systemic
■ Gangrene, tetanus, septicaemia
■ Fear of mobilising (compensation neurosis)
■ Osteoarthritis.
Sterilisation
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For further reading see Bailey and Love, Chapter 15.What is meant by cleaning?
Cleaning is the process of physical removal of organic debris (e.g. blood, tissue and other body fluids) but does not necessarily destroy micro-organisms.
Sterilisation
What is disinfection?
Disinfection reduces the number of viable organisms.
What is sterilisation?
Sterilisation refers to the process that kills or eliminates transmissible viable micro-organisms (bacteria, viruses, fungi, spores, cysts).
How may the methods of sterilisation be classified?
Physical sterilisation
■ Heat sterilisation with moist heat (pressurised steam autoclaves) at 134°C
■ Heat sterilisation with dry heat at 160°C
■ Radiation sterilisation.
Chemical sterilisation
■ Ethylene oxide
■ Ozone
■ Chlorine bleach
■ Formaldehyde
■ Glutaraldehyde
■ Hydrogen peroxide
■ Peracetic acid
■ Ethanol (70 per cent).
Give some examples of sterilisation.
■ Moist heat sterilisation (steam autoclaves) for trays of surgical instruments
■ Dry heat sterilisation for non-aqueous liquids and ointments
■ Ionising radiation for swabs, catheters and syringes
■ Ethylene oxide for sutures and electrical equipment
■ Formaldehyde for plastics
■ Glutaraldehyde for endoscopes.
Does sterilisation destroy prions?
No.
Prior to sterilisation of your surgical instruments, what do you need to do?
All instruments need to be cleaned and thoroughly dried before they are sterilised. There are three main cleaning methods: hand scrubbing, ultrasonic cleaning and automated washing.
What types of disinfectants do you use when scrubbing?
See Fig. 3.6.
Chlorhexidine gluconate is an aqueous quaternary ammonium
compound. It has a residual effect and is effective for more than 4 hours.
It has potent antiseptic activity against Gram-positive and Gram-negative organisms and some viruses, but only moderate activity against the tubercle bacillus. It has poor activity against spores and fungi.
Section 3: Applied surgical science
Povidone-iodine is a potent bactericidal, fungicidal and viricidal agent.
There is some activity against bacterial spores and good activity against tubercle bacillus. The iodine penetrates cell walls to produce antimicrobial effects. Iodine has some residual effects but these are not sustained for more than 4 hours. In addition, it may cause irritation to the skin or allergic reactions.
Alcohols are rapid-acting antimicrobial agents with broad-spectrum activity. They are effective in destroying Gram-positive and Gram-negative bacteria, fungi, viruses and tubercle bacillus. However, they are not sporicidal.