How to critique a paper Liddle
Thanks to Alex Liddle for this excellent presentation discussing how to critique a scientific paper.
Category Archives: Exam specials
Guide to trainees for the orthopaedic oncology rotation
We have compiled the following unofficial guide to trainees coming to an Orthopaedic Oncology attachment. It contains key topics in the curriculum to which you may get exposure in the attachment, competence levels for surgical procedures and other useful information.
Principles for the surgical treatment of metastatic bone disease
- Know the diagnosis
- Consider other modalities of treatment
- Treat the whole bone
- Assume it won’t heal
- Avoid load sharing devices (eg DHS)
Seven questions to ask when looking at an x-ray
A good approach to looking at an X-ray demonstrating an abnormality in the bone is to ask seven questions:
- Where is the lesion?
- How large is the lesion?
- What is the lesion doing to the bone?
- What is the bone doing in response?
- Is the lesion making matrix?
- Is the cortex eroded?
- Is there a soft tissue mass?
(from Levesque et al. A Clinical Guide to Primary Bone Tumours)
The Musculoskeletal Tumour Society staging system
The MSTS (Enneking) staging system for sarcomas is another exam classic. This is a very straightforward system which allows the user to describe the extent of the tumour locally and systemically. Tumours are either low grade (Stage 1, <15% risk of metastasis), high grade (Stage 2, >15% risk of metastasis) or metastatic (Stage 3).
Intracompartmental tumours are classified as “A” and extracompartmental tumours as “B”.
For example, an osteosarcoma of the distal femur, which has an associated soft tissue mass but no detectable metastases would be staged as “2B” in this system.
Other systems include the AJCC system for staging.
Reference:
Enneking WF, Spanier SS, Goodman MA. Current concepts review. The surgical staging of musculoskeletal sarcoma. J Bone Joint Surg Am 1980;62(6):1027-30.
Describing surgical margins
The description of surgical margins requires an understanding of the local behaviour of sarcomas. Classically, sarcomas grow centrifugally, and around the central tumour is a “reactive zone” comprising compressed normal tissues, inflammatory cells and small numbers of tumour cells. Tumours also tend to stay within osteofascial anatomical compartments. These concepts were popularised by Enneking, in the era before the widepsread availability of cross-sectional imaging.
The text-book answer is that surgical margins are described as follows:
- Intralesional – when the resection passes through tumour
- Marginal – when the resection passes through the reactive zone
- Wide – when the resection passes through normal tissue
- Radical – when the whole of the involved compartment is removed.
However, given that the majority of tumours are close to critical neurovascular structures for at least part of their circumference, most resections are technically marginal. A more helpful description is often whether or not the margin is microscopically positive (tumour at or within 1mm of the resection margin) or microscopically negative.
The surgical margin achieved is the strongest predictor of the risk of local recurrence in several large series.
Taking a history
Taking a history from a patient with a suspected bone or soft tissue tumour requires a different emphasis from the rest of orthopaedics. Particular features to note include:
- Length of history (is this a preexisting mass that has changed?)
- Rate of growth
- Pain history (site, character, severity, radiation, modifying factors, periodicity – is there mechanical or night pain?)
- Previous surgery at the site of interest (ie is this a local recurrence?)
- History of malignancy (could this be a metastasis?)
- History of a predisposing condition (eg Hereditary Multiple Exostoses)
- Previous radiotherapy
- Family history (think inherited disorders like Li Fraumeni syndrome)
- Symptoms suggestive of malignancy (eg weight loss, lethargy)
How to biopsy a musculoskeletal tumour
This is a classic exam question, and one every surgeon should know. Even if you think you won’t be doing biopsies, you need to stay out of trouble by being prepared.
The main issue is that sarcomas are highly implantable and the biopsy track needs to be removed with the tumour. That means that biopsies need to be planned with the surgical team who are going to remove the tumour. An inappropriate biopsy can jeopardise limb sparing surgery, particularly in difficult anatomical areas like the popliteal fossa and the pelvis.
Principles can be summarised as follows:
- Plan carefully in conjunction with the specialist surgical team
- Don’t contaminate new compartments or critical anatomical structures unnecessarily
- Needle biopsies are the “industry standard”
- If you do an open biopsy, use a vertical incision (easier to reexcise), make sure you have good haemostasis and if you need to drain, take it out close to or through the wound
- Talk to the pathologist – some specimens go fresh
- Make sure you get enough tissue
My preference is to use a trucut needle for soft tissue masses (usually in outpatients), or a bone needle (eg the Islam needle) for bone biopsies. Trucut biopsies are very good at distinguishing benign and malignant tumours, slightly less good at typing the tumour.
Excision biopsies are only performed for small (<5cm) superficial tumours which do not involve the deep fascia. If tumours like these turn out to be sarcomas, the whole scar can be excised along with the deep fascia.
Image guided biopsies are helpful in some anatomical areas or for vascular tumours.
What are the referral guidelines for soft tissue masses?
Soft tissue lumps are common: malignant ones are rare, but detecting them early is important. Delay in diagnosis is a significant problem in the treatment of sarcomas, as is unplanned excision. An unplanned excision occurs when a soft tissue lump is removed by a surgeon (or General Practitioner) without any thought about whether the lump might be malignant. (these are called “whoops” operations by sarcoma teams). Both of these problems can be minimised by using the referral guidelines.
A soft tissue lump exhibiting any of the following four following criteria should be considered malignant until proven otherwise:
- increasing in size
- size >5cm
- deep to the deep fascia
- painful
Patients with lumps such as these are best referred to a specialist centre for further investigation, which would start with imaging (eg USS or MRI).
UK soft tissue sarcoma guidance can be found here.
Guidance for referral to the London Sarcoma Service can be found here.
The North of England Bone and Soft Tissue Tumour Service has a fax for urgent referrals: 0191 223 1328.
What is a sarcoma?
A sarcoma is a malignant tumour arising from connective tissues (the embryonic mesenchymal layer), and also, by convention, neurological tissues. Sarcomas are rare and comprise a large number of diagnoses. They are classified according to their histological appearance (eg liposarcoma, synovial sarcoma).
