Guide to trainees for the orthopaedic oncology rotation

We have compiled the following unofficial guide to trainees coming to the North of England Bone and Soft Tissue Tumour Service. It contains key topics in the curriculum to which you may get exposure in this attachment, competence levels for surgical procedures and other useful information.

Orthopaedic Oncology Syllabus

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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:
  1. Where is the lesion?
  2. How large is the lesion?
  3. What is the lesion doing to the bone?
  4. What is the bone doing in response?
  5. Is the lesion making matrix?
  6. Is the cortex eroded?
  7. 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:

  1. Plan carefully in conjunction with the specialist surgical team
  2. Don’t contaminate new compartments or critical anatomical structures unnecessarily
  3. Needle biopsies are the “industry standard”
  4. 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
  5. Talk to the pathologist – some specimens go fresh
  6. 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.