In Italy, thyroidectomy is the fifth most frequently performed operation in the Departments of General Surgery [11
]. It is a procedure commonly performed across the country, in both large volume centres and small hospitals. MI techniques for thyroid surgery—not only MIVAT but many other approaches [12
]—are proposed with increasing frequency but they require a high level of competence to minimise the length of the learning curve, which is otherwise rather long [13
]. It has been stated that the "widespread application of this technique has been somewhat limited and, for practical purposes, has been confined to high-volume surgeons who have plentiful skilled assistants” [14
]. No clear advantage of MI techniques in terms of medium-long term outcomes has been demonstrated [15
], it is therefore reasonable to aim for standardisation and technical advancement of the conventional open technique in order to reduce the invasiveness of the procedure.
Our observational study was based on the underlying hypothesis that there is a latent tendency to over-estimate the difficulty of the operation and to create a wider incision than is strictly needed. We empirically showed that the main factors related to the length of the incision are gender, neck circumference and thyroid volume. Diagnosis and pathology had an influence, but these factors could be relevant in an indirect way, because of their influence on thyroid volume. Neither diagnosis nor the presence of thyroiditis was related to DO. These findings are consistent with the findings of Brunaud [7
], who also found a correlation of LI with BMI that was stronger than the one we found. This difference could be due to a difference in the samples. Our patients tended to be over-weighted (mean BMI
27.07), which could have counteracted the effect of this factor. BMI as a risk factor has been studied in a large database of patients [16
] and was positively correlated with a longer operation time and with higher morbidity but not to a clinically significant extent. In our opinion NC is a better candidate than BMI as an element on which to base the decision regarding the incision length, but a study specifically tailored to this goal should be designed.
We found only a weak correlation among the assessed factors, including the length of the incision (r
0.33) and the duration of the operation. In particular, when patients with thyroid of similar volume were operated upon with incisions of varying lengths, the time needed for the operation was not significantly different for smaller incisions compared to the longer ones.
] proposed a classification system for MI thyroid surgery, based on two factors: size of the largest nodule and BMI. The authors then divided the continuum of possible incision lengths (from 0 to >6
cm) into four classes. These classes were defined a priori
and then validated by retrospectively grouping a series of 359 patients. Information on DO was not available, but the results of clustering yielded mean incision lengths of 2.0, 3.3, 4.9 and 8.3
cm for the four classes, respectively. These results coincide only partially with ours, regarding the range of incisions used (4÷7
cm). In particular, there is a wide gap between the third and the fourth class. Our work provides further elements to set guidelines to assist the surgeon in the choice of a better incision for use in open surgery and that the limits of incision length in open surgery can be lowered.
A limitation of this study was that—because of the prospective design—the surgeon knew that his decision about the length of the incision was going to be recorded; this could have altered his judgement. To limit this bias, the interim results of the on-going study were not disclosed. Comparison between the figures of the first and the last set of operations during the study showed that the performance remained relatively stable regarding mean LI and DO, as if the on-going study had not altered the surgeon’s behaviour. The decision was always made according to his subjective evaluation, without any formal decision process based on empirical data. In this sense the surgeon’s decision regarding length was a consequence of his assessment of the expected technical difficulty of the operation.