Ultrasound-Guided Bar Edge Labeling in the Perioperative Assessment of Nuss Bar Removal

Introduction

The minimally invasive repair of pectus excavatum (MIRPE) is a procedure through which one or more bended metal bars secured with stabilizers are inserted behind the sternum to push it forward to a normal position. The implant is usually left in place for ∼3 years and then removed. Bar removal in uncomplicated cases usually entails 1 to 2 days of hospitalization. A few techniques have been proposed for safe removal of Nuss bars with encouraging results.^1,2 Although bar removal is thought to be a safe operation, complications sometimes occur. Life-threatening complications following bar removal, which require subsequent sternotomy or bilateral thoracotomy, are reported.^3,4 It is well known that a fibrous sheath forms around the metal implant and, especially in adult patients, ossifications have been described, challenging the surgeon who performs the removal and eventually adding potential morbidity in those patients whose bar edges are undetectable at intraoperative palpation.^3–5

Ultrasound is a bed-to-side, repeatable, low-cost technique that has already been used in patients who underwent MIRPE with the purpose of evaluating compression on internal mammary arteries to assess flow obstruction and to monitor the introducer edge during the bar insertion procedure.^6,7 We hypothesized that ultrasound may play a role to identify and label bar edges in the perioperative assessment to make the procedure quicker and safer; this concept may be relevant especially for those patients whose bar edges are not clearly identified at palpation. Herein we describe a strategy that allows to clearly identify bar edges in patients who undergo implant removal procedure.

Technique

A perioperative scan is performed by means of portable ultrasonograph (Logiq e - General Electric, Co., Fairfield, CT) a few minutes before the operation. The patient is recumbent, and the chest is exposed. The operator, visualizing the scar in one hemithorax, handles the chest wall looking for the bar end and the stabilizer, whenever present. The probe type is chosen according to the patient's anatomical features, skin thickness, and age. In most of the cases, especially in slender patients, a linear probe (8.0–10.0 MHz) is placed onto the scar following longitudinal, oblique, and transversal orientation. The bar edge stabilizer is then detected as a hyperechogenic image with concentric crescents, while the bar is detected as a hyperechogenic dashed line with net edges (Fig. 1a). The bar, as previously described, may be followed up to the contralateral scar even in its intrathoracic passage, with the probe kept in transverse and longitudinal position (Fig. 1a). If the operator is unable to follow up the bar from side to side, especially in the part under the sternum, for better penetration it is possible to use a convex probe (5.0 MHz), although details will appear less magnified. By means of the same technique, the procedure is repeated on the opposite side where either the bar end or the bar end stabilizer is detected (Fig. 1b). As the scan is performed, and the actual image is projected on the skin, the metal plaque bulk is then labeled on the patient's chest by an ink marker.

OPEN IN VIEWER

FIG. 1.

(a) A longitudinal scan obtained with a linear probe (10 MHz): the bar edge stabilizer complex is detected as a hyperechogenic image with two overlapped crescents marked as arrows, while the bar is identified as a hyperechogenic dashed line with net edges marked as yellow arrow. (b) The patient recumbent before the operation exposes the chest and the scars are visualized on each side, and a linear probe is handled looking for stabilizer bar edge complex, which is followed up to the contralateral side and labeled by means of an ink marker.

Discussion

To date, peri- and intraoperative localization of stabilizers is based only on palpation of the metallic bulk, which in selected cases might be difficult because it is embedded into fibrotic and osseous tissue, dislocated from the scar, and difficult to ascertain from actual ribs. ⁸ A safe exposure of the bar edge with minimal morbidity in some cases may be challenging for the surgeon; when a blind dissection is performed, operative time increases and dissection toward the bar edge stabilizer may lead to intercostal vessel damage or possible deep intercostal muscle injury, which in turn increases postoperative pain control and recovery.

In this article, we reported a quick perioperative strategy to promptly localize the metal implant. Moreover, within an additional few seconds, by means of the same technique it is possible to detect, at the same time, internal mammary artery flow, the presence of pleural effusion, and lung “sliding” sign as in pneumothorax.^3,4

Although a double cohort prospective study is still warranted to justify this procedure as a routine approach, we believe that with such simple expedient, operative time and morbidity as in blood loss, postoperative pneumothorax, postoperative pain, and eventual hospitalization could be improved for those patients whose implant is barely detected when about to be removed.