Bone marrow aspiration and trephine biopsy

The indications for performing bone marrow aspiration and trephine biopsy procedures have previously been discussed (p. 19). In this section the practical aspects of obtaining these samples are outlined. More detailed accounts can be found in books of practical procedures, but ultimately the only way to perfect techniques is to practise under expert supervision.

Although the anterior iliac crest is occasionally preferred, most operators get the best specimens from the posterior iliac crest. The sternum is now rarely used. This is, in part, due to the small risk of causing catastrophic damage to the mediastinum, but mainly because it is not possible to obtain a trephine biopsy. Only the posterior iliac crest approach is described here.

Bone marrow aspiration

As for all procedures the sequence of events should be explained to the patient, reassurance given and consent obtained. A degree of discomfort should be acknowledged but it should be emphasised that this is transitory. In most adults, local analgesia is adequate but sedation is considered where patients are unusually anxious. A general anaesthetic is the norm in children. A clean, no touch technique is mandatory and operators should wear gloves. Stringent asepsis is needed in immunosuppressed cases.

The patient lies in the left or right lateral position and the skin over the posterior iliac crest is cleaned with antiseptic prior to screening with sterile drapes. The crucial next stage is to properly identify the bony landmarks (Fig 53.1). This is straightforward in most patients but can be problematic in obese subjects. If there are real difficulties in locating the posterior iliac crest then the anterior crest or the sternum may be considered or the procedure may be performed under CT guidance. A local anaesthetic is infiltrated into the skin and then down to the periosteum. Before use it should be checked that the marrow aspirate needle stylet is easily withdrawn and the guard is removed (this is only required for sternal aspirates). The needle (Fig 53.2) is inserted through the skin and subcutaneous tissues at the site of local anaesthetic infiltration until the periosteum is encountered. It is pushed through the periosteum with a deliberate screwing motion (alternating clockwise and anti-clockwise) – a ‘give’ is felt as the marrow cavity is entered. The stylet is withdrawn and a syringe attached to the needle (Fig 53.3). Approximately 0.5 mL of marrow is aspirated into the syringe. The patient should be warned that this stage often causes pain but that it is momentary.