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)

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.

 

 

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.