The results demonstrate that, once past the learning curve, the use of the harmonic scalpel during thyroidectomy significantly reduces operative time and postoperative hypocalcaemia, and is as safe as conventional surgery with regard to voice change and bleeding.
The harmonic scalpel is commonly used in laparoscopic surgery.1
Its ultrasonically activated coagulation shears use high-frequency ultrasound (55 kHz) to divide vessels of up to 5 mm during thyroidectomy. The active blade vibrates longitudinally against an inactive blade, combining cutting and coagulation. It operates at a relatively low temperature (80°C); consequently, there is potentially less thermal damage to surrounding tissues than electrocautery and laser. There are possible benefits of using the harmonic in thyroidectomy. First, a reduction in operative time, as repetitive ‘clip, cut and tie’ routines are avoided.2
This also permits less need for surgical assistants. The reduction in postoperative hypocalcaemia may occur as a consequence of less injury to the parathyroids and surrounding structures through lateral dispersion of heat. Excellence in haemostasis may also permit a better view of these and other important structures to preserve when operating. However, potential increased cost and the skill required in overcoming the learning curve are possible disadvantages. Although no definition of the learning curve for this technique exists (and is likely to be different for each surgeon), we report our results here ‘beyond the learning curve’ following 2 years' experience with the harmonic scalpel during thyroid surgery, by which time the technique was established in our unit and in routine use.
The difficulties of performing a randomised, controlled trial in comparing surgical techniques are self-evident. The outcomes of a novel technique might be confounded by the learning curve phenomenon.3
Once the novel technique is established, advantages may be seen and randomisation at this point becomes difficult. We undertook a retrospective review of patients undergoing thyroid surgery over two separate 12-month periods. The first cohort was taken from 2003 and consisted of 77 patients. This group underwent surgery prior to the introduction of the harmonic scalpel, using conventional ‘clip, cut and tie’ routines with additional small metal clips (Ligaclips, Ethicon UK) to secure haemostasis. The second cohort included 106 patients whose surgery was performed in 2006, two years following experience of the harmonic scalpel, at a time when all involved felt comfortable with the technology.
With regard to cost, the contract price for the disposable items and generator will vary across different health authorities, but constant in the equation will be the absence of metal clips, sutures or ties, a quicker turnaround time permitting on average another case to be done per list,4
and less hospital stay and expense relating to the correction of hypocalcaemia.