Basic dissecting techniques in ultrasound-guided surgery

Abstract

Ultrasound-guided surgery is an area of minimally-invasive surgery where surgical procedures are performed with the aid of ultrasound imaging throghout the operation. This requires the operator to posses a certain degree of experience in endoscopic procedures, and to be adeptly skillfull in conducting US examinations. It is combining and finely tuning together these two elements that allows to perform efficiently an ultrasound-guided surgical procedure. Accessing an affected site correctly is of utmost importance in surgery, being oftentimes decisive in terms of the procedure's final outcome. In ultrasound-guided procedures, the operative site is accessed percutaneously, with a single point incision, yet tissues situated deeper within are dissected with dissecting techniques in a fluid evironment, typical for this area of surgery. Dissecting techniques in ultrasound-guided surgery are currently divided into basic ones which employ either a hydrodissection needle, surgical instruments, electrosurgical instruments, a thread, or a combination thereof, and advanced ones where either a balloon, a hook dissection technique, or a hybrid one is used. Hydrodissection with a needle was devised based on the rule of complementarity, and is the most frequently applied technique in ultrasound-guided surgery. The immense possibilities that go along with this modality will be of huge benefit to any surgeon, regardless of their field. Dissection with a variety of surgical instruments and electrosurgery instruments is a standard practice in all surgery areas, yet the method of imaging we employ in ultrasound-guided surgery results in certain modifications of these techniques. It is, however, learning the thread technique that facilitates a precise and oftentimes extensive dissection. This technique is successfully applied for dissecting muscle, ligament, tendon, vascular and other structures. Having mastered dissecting techniques allows to perform any minimally-invasive procedure efficiently, be they ultrasound-guided, artroscopic, or endoscopic ones. Various surgical techniques are bridged, resulting in applying the so-called hybrid ones. Their strength lies in excellent imaging results allowing to conduct a surgical procedure both in a body cavity and within a parenchymal organ.

Learn, do what you have learnt, teach it to others.

Professor Józef Dzielicki

Introduction

Accessing the operative site in a correct way is an art as ancient as surgery itself. It was the rupturing of the skin that made way for the development of surgery, regardless whether the skin was rendered open at the hand of a physician or a warrior. Presumably, wounds sustained in a battle required an adequate and technically correct treatment, thus facilitating a rapid progress in traumatic surgery. The kinds of weapons used required physicians to continuously extend their skill and knowledge to be able to remove arrowheads, spearheads and bullets, as well as to treat and dress gash wounds. The practical skills and observations acquired in the course of wars were subsequently applied when treating common people in peace times, and passed on to the next generations of physicians.

Incision-free surgery is still unthinkable, yet we attempt to incise with more consideration. The old surgical maxim stating: “a great surgeon cuts big, a meager surgeon cuts small” is gradually being forgotten. Great surgeons performing advanced surgical procedures try to minimize the incision and perform endoscopic surgical procedures.

In endoscopic surgery, the operative site is accessed in a specific way. The skin incisions are made solely to introduce an optical set and endoscopic instruments inside. The maneuvering space and at the same time the operative site are the “inflated” or, in other words, insufflated, natural body cavities: peritoneal, pleural or joint (synovial) cavity. The skin still covers the operated area, hence the application of the optical system giving a view into the operative site is indispensable. Thereby, the idea that the skin and tissues should be minimally traumatized in the course of an endoscopic procedure facilitates the development of novel operating techniques. These include: LESS (laparo-endoscopic single site surgery), and SILS (single incision laparoscopic surgery) which both permit to carry out a surgical procedure with a single access site (SAS), or, in other words, a single port access (SPA). It is important that the equipment used and the skills of the operator are adequate to the conditions⁽¹⁾.

Anthony Kalloo, having professed in 1997 that one day a surgeon would be able to perform a cholecystectomy without leaving visible scars on the patient's body, proved to be a man of boundless imagination. In result, NOTES (natural orifice transluminal endoscopic surgery) was developed⁽²⁾, with transabdominal cholecystectomy or transvaginal splenectomy being fine examples thereof.

Owing to the currently used optical sets and camera systems, endoscopically operated structures are visible in 2D images. The lack of the third dimension, and particularly the lack of depth, initially tends to be quite troublesome for the surgeon. Learning to determine the distance is very challenging, yet is crucial for endoscopic surgery. It is, thankfully, made easier by the mobility of the optical set, and by real-time imaging. Oftentimes, nonetheless, the operator needs to insert various measuring tools, e.g. prior to incising, or matching an implant, etc. It is a natural course of progress, therefore, to develop optical sets which provide a 3D endoscopic image. There is a very dynamic turnover of methods for registering and presenting 3D images, yet it seems that a particularly promising one is the modality known as head-mounted display (HMD), known form computer games and providing a separate image for every eye. Should the possibility for a fusion of a previously obtained CT image with an endoscopic image appear, which is described as an augmented reality (AR) image⁽³⁾, we would, and surely will, enter a terrain which is practically unavailable for the classical endoscopic surgery, namely the area beyond the wall of the operated cavity. It will allow to identify important structures based on a pre-operative CT scan. So far, the only way of locating a “lesion” properly within the operated organ has been the application of an intraoperative ultrasound or radiological examination. Particularly, laparoscopic ultrasonography (LUS) and endoscopic ultrasonography (EUS) have been in extensive use⁽⁴⁾. The introduction of these modalities initiated further research into the development of subsequent methods, termed as extraperitoneal laparoscopy and extra articular endoscopy (EAE), used in orthopedic procedures⁽⁵⁾.

In our practice, we perform ultrasound-guided procedures under the control of image generated by a mid-range ultrasound device equipped with 3D/4D modality, image enlargement option, Doppler modality, and capable of rendering precise lesion measurement. Numerous other options for evaluating a “lesion” with the aid of an ultrasound device, such as contrast application, or elastography should not be overlooked either. The application of all these capabilities of ultrasound devices in the course of a surgical procedures renders them superior to the current state-of-the-art endoscopic equipment.

The authors of this article perform typical ultrasound-guided procedures under the sole control of ultrasound image, without using additional optical sets. Every stage is ultrasound-guided, from accessing the lesion, to suturing. This sets ultrasound-guided surgery apart from other endoscopic methods. No iatrogenic damage of important structures is caused due to them being visualized as they are being accessed, which unquestionably improves procedure safety. This is why many surgeons access operated sites under the control of ultrasound image, and continue the procedure in like manner.

Dissection techniques

Ultrasound-guided surgery is a surgical discipline like any other, hence all procedures must be conducted in aseptic conditions, and respecting all rules of the surgical art. Every ultrasound-guided procedure begins with ultrasound topography (which we call a sonotopogram), followed by accessing the lesion.

The routine mapping of the operated site with the aid of US examination immediately preceding any surgical procedure we have termed a sonotopogram. It allows to familiarize the operator with the topographic anatomy of a treated area, which facilitates accessing the site correctly. Practically all anatomical structures can be found and evaluated in a US examination, thus rendering ultrasound topography (a sonotopogram) unquestionably and universally helpful in any invasive procedure⁽⁶⁾.

Single-incision percutaneous approach is used for ultrasound-guided insertion of instruments or a cannula. The operative site is most commonly accessed during dissection, following hydrodissection and preceding dissection with instruments. During the dissection, local or regional anesthesia is applied, which is typical for ultrasound-guided procedures in adults, this being a highly practical and economical practice.

In children, we tend to perform all ultrasound-guided procedures under general anesthesia, the reason being not actual pain, but young patients’ fear of invasive procedures. Local anesthesia of the operative site is applied as an accessory procedure.

Ultrasound-guided dissecting techniques have been divided into:

Ultrasound-guided dissecting techniques have been divided into:

1. Basic ones:

   1. Hydrodissection (with a needle);
   2. Dissection with surgical instruments;
   3. Dissection with electrosurgical instruments;
   4. Dissection with thread;
   5. Combined.
2. Advanced:

   1. Balloon dissection;
   2. Hook dissection;
   3. Hybrid.

We feel inclined to recommend hydrodissection technique using saline solution containing an anesthetic agent. The application of the needle allows to separate tissues very accurately when dissecting. Two mechanisms are at work here, complementing each other: the separating action of the jet of fluid, and the application of the needle blade acting as a knife. This is an example of complementarity employed in ultrasound-guided procedures⁽⁷⁾ (fig. 1A, B), whereby simultaneously the operative site is anesthetized and the operative tissues are separated thus facilitating easy access with surgical instruments. Additionally, the fluid injected improves the quality of the ultrasound image and serves as a temperature buffer for exothermic procedures. The presented technique was devised based on a very simple technique, widely used in invasive ultrasound-guided surgery, namely administering a medication under the guidance of ultrasound image. The important thing is the method of the administration (different from infiltrative administration), whereby a small amount of skin- and subcutaneous tissue- anesthetizing solution is topically administered in the approach site, and the remaining part of the anesthetic is administered into the operative site, in such a way as to separate the laminated tissues with the effect of a fluid space forming. The amount of the solution administered into the intervention site can be substantial, and may be administered in portions, with the anesthetic solution being gradually replaced by saline solution.

Fig. 1A, B.

Hydrodissection – a view of the surgery field and the sonogram

Commonly, special probes, guides, and dissectors are used in ultrasound-guided surgery. These are most typically employed following hydrodissection, in the way of a complementary procedure. Rigid instruments have been in wide use for many years now, yet flexible ones are becoming increasingly popular (fig. 2A, B). Electrosurgical instruments have found their application in various situations, most commonly for tackling blood vessels and for mechanical or thermal tissue removal (fig. 3A, B). This tends to be conducted in the fluid space which accumulates heat and facilitates the separation and then the removal of tissue fragments. It is easy to collect specimens for histopathology while dissecting tissues as well.

Fig. 2A, B.

Dissection with surgical instruments – a view of the surgery field and the sonogram

Fig. 3A, B.

Use of shaver – a view of the surgery field and the sonogram

The introduction of the thread technique for ultrasound-guided procedures came as a breakthrough, and has enabled surgeons to conduct reconstructive procedures very efficiently. This technique enables to dissect extensive muscle, tendon, ligament and vascular structures. Being applied under the control of ultrasound image, it is a very safe technique. Due to its universality, it is used with great success in other surgery fields also (fig. 4).

Fig. 4.

Thread technique – a view of the surgery field

Among the techniques listed above, hydrodissection with a needle is the only one that can be used on its own, as it allows both for dissection and applying local anesthesia at the same time. In most cases, combined techniques are used due to their effectiveness, which is an approach widely practiced in all surgery areas.

Conclusion

Surgical equipment and technique never cease evolving. At our disposal we have operative equipment which is ever more advanced technologically. This, in turn, allows to conduct surgical procedures with increasingly sophisticated methods. Nonetheless, the components of a surgical procedure remain the same. The time and method in which they are tackled may evolve and change, yet given stages of a procedure, such as pre-operative mapping or devising an ultrasound topography, or accessing the operative site remain unalterable components of each and every surgical procedure, regardless of the adopted technique.

Pre-operative mapping is a particularly important action taken before any ultrasound-guided procedure, or, for that matter, any surgical procedure. This is a simple and safe procedure undertaken by a growing number of surgeons and other practitioners attempting invasive procedures of various kinds⁽⁸⁾.

Ultrasound-guided access to the lesion is characterized by very good cosmetic outcomes, minimal post-operative symptoms, a low proportion of complications, and a speedy recovery, thereby considerably improving the post-operative quality of life.

Attempting a comparison of ultrasound and endoscopic imaging, a number of advantages and disadvantages, or limitations of both techniques could be pointed out. Nonetheless, when a lesion/ operative site is accessed under the guidance and control of ultrasound image, a feasibly high degree of patient's safety is ensured⁽⁹⁾.

The best training one can obtain in ultrasound surgery is by watching a genuine Master at work. Despite all the surgical atlases that we have at our disposal, nothing can ever replace the actual show of surgical technique. This is an art that we learn and acquire under a Master's watchful, careful eye, realizing at the same time that we are obliged to pass the acquired skills and expertise on to our younger, less experienced colleagues. In surgery and the entire medical field a universal rule holds true, which says: “Learn, do what you have learnt, teach it to others”. This is how the science has been able to survive whole millenia, and is still evolving and developing.

Conclusions

1. Ultrasound-guided dissection techniques are simple, friendly and safe.

2. Local anesthesia is applied in the course of dissecting, thereby relatively lowering the cost of a procedure.

3. Ultrasound-guided access to the lesion/ operative site allows a continuous observation of the treated area and should be recommended for other endoscopic techniques too.

Conflict of interest

Authors do not report any financial or personal links with other persons or organizations, which might affect negatively the content of this publication and/or claim authorship rights to this publication.