Introduction

Since its introduction in the mid-1990s, the use of robotic assistance in the operating room has allowed the development and refinement of minimally invasive alternatives to a number of surgical procedures with applications in urology, gynecology and cardiac and general surgery [1, 2]. More hospitals are acquiring surgical robots, despite the cost of this technology, and the applications continue to expand. In head and neck surgery robotic assistance, by virtue of its combination of magnification, illumination and stereoscopic vision, allows unsurpassed access to the pharynx, soft palate and base of tongue, without the need for extensive and morbid access incisions. The effectiveness of trans-oral robotic surgery (TORS) in the management of oropharyngeal and supraglottic carcinoma has been demonstrated in several studies [3–6]. A natural extension of this experience is to apply this technology to the reconstruction of the resultant defects left by tumor extirpation and other processes for which a minimally invasive approach is appropriate. This report describes our experience with robot-assisted management of soft tissue defects created during the treatment of malignant and non-malignant conditions in a series of 12 patients.

Patients and methods

Twelve patients were treated jointly by the Otolaryngology and Plastic Surgery services at the University of Pittsburgh Medical Center over a nine-month period for a variety of problems for which a TORS approach was felt to be indicated (Table 1). Diagnoses included malignant neoplasms involving the soft palate, base of tongue and pharyngeal walls in ten patients and one patient each with post-surgical velopharyngeal insufficiency (VPI) and velopharyngeal stenosis. The malignancies included squamous cell carcinoma in eight, melanoma in one and sarcoma in one. Procedures performed included FAMM (facial artery musculo-mucosal flap) flaps in five cases, free flaps in four, uvular filleted flaps in two, and a pharyngeal flap in one. Free flaps performed included two ALT (anterolateral thigh) flaps and two radial forearm flaps.

Table 1 Diagnosis, defect size and procedure in twelve patients treated with robotic-assisted transoral reconstruction
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In each case, an attempt was made to reconstruct the resection defect anatomically and the choice of method was dictated by the size of the defect created. In general, smaller defects, especially those less than 5 × 2 cm in size and those involving one half or less of the length of the soft palate, were amenable to closure with local techniques. Larger and more complex defects, involving significant portions of the tongue or more than one half of the soft palate length, were addressed with free tissue transfer. Superficial defects of the posterior and lateral pharyngeal walls were allowed to heal spontaneously by contraction and mucosalization. Radial forearm flaps were preferred to manage defects of the soft palate where more than 3 cm of the palatal length was removed, as these defects were felt to exceed the capabilities of local flaps. These palatal defects usually extended onto one lateral pharyngeal wall and a long and relatively thin radial forearm flap was found to be ideal for reconstruction. For defects of the tongue, ALT flaps were chosen. The thigh skin thickness in these patients was a good match for the defect and this flap allowed provision of a little more bulk at the base of the tongue by incorporating a portion of vastus lateralis muscle, if necessary. In all patients requiring free flap reconstruction, a neck dissection was performed as part of the treatment of the tumor involved and so the cervical vessels were readily available for an external anastomosis. The pedicles easily reached the neck vessels through bluntly dissected tunnels and a 2-inch Penrose drain assisted in passing the vascular pedicle from the site of reconstruction to the external cervical incision.

Following induction of anesthesia, the operating table was rotated 180° and a shoulder roll was positioned to help extend the head. A Mayo stand was positioned over the patient’s chest and the end of the retractor was hooked over the lip of the stand to provide stable retraction. Feyh–Kastenbauer and Dingman retractors proved effective for exposure and positioning. To protect the teeth from the retractor and from the robotic instruments a guard was fashioned from thermoplastic splint material and placed over the upper and lower dentition. The robotic patient cart was positioned to the patient’s left side and the arms aligned in the standard recommended positions. The assistant was positioned above the patient’s head (Fig. 1). Flaps were harvested after tumor margins were cleared by pathology. The harvesting of free flaps was begun concurrently with neck dissection. Flaps were inset with absorbable material in all cases. Monofilament suture on small, tapered needles cut to lengths of about 15 cm was most effective for insetting.

Fig. 1
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View of the operating room set-up of the patient, patient cart, assistant and surgeon console

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Case examples

Case 1 (patient 9)

A 49-year-old male presented with a newly diagnosed squamous cell carcinoma involving the soft palate just to the left of the base of the uvula. Resection with frozen section margin control was accomplished with the robot; the tumor was found to extend to the right uvular margin and onto the lateral pharyngeal wall (Fig. 2). A left-sided facial artery musculomucosal (FAMM)flap was designed and elevated. The flap was inset with two layers of 3-0 braided absorbable sutures, anatomically filling the defect (Fig. 3). The postoperative course was unremarkable and the patient was discharged on the fifth post-operative day. A minor dehiscence occurred at the juncture of the flap with the remaining soft palate at the tip of the flap, which closed spontaneously. The patient developed symptomatic VPI which had almost fully resolved at the time of the latest follow-up. A modified barium swallow 6 weeks following surgery showed only minimal regurgitation.

Fig. 2
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The resection defect with FAMM flap outlined on the left buccal mucosa

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Fig. 3
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FAMM flap transposed and sutured in place

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Case 2 (patient 11)

A 65-year-old woman presented with recently diagnosed melanoma involving the posterior border of the soft palate (Fig. 4). Complete excision of the defect included the entire soft palate and extended down the right pharyngeal wall with exposure of the carotid sheath. A bilateral neck dissection was performed allowing exposure of vessels for anastomosis. A radial forearm flap was chosen to provide thin vascularized tissue consistent with the defect. The anastomosis was completed in standard fashion externally under loupe magnification. The flap was inset with braided absorbable sutures (Fig. 5). The post-operative course was benign and the patient was discharged on the seventh post-operative day. The patient experienced some mild symptomatic obstruction with nasal breathing early in the post-operative period due to flap edema, which improved with time. She subsequently returned to a full oral diet and her gastrostomy tube was removed 6 weeks post-operatively, after successful completion of external beam radiation therapy.

Fig. 4
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Patient with malignant melanoma involving the posterior border of the soft palate

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Fig. 5
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Defect in the patient following radial free flap reconstruction

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Results

Operative time ranged from 2 h 24 min to 15 h 20 min. The time required for docking and un-docking the robot contributed significantly to the length of the procedures. Estimated blood loss ranged from 50 to 300 ml. Length of stay ranged from 3 to 17 days with the youngest patient in this series requiring a 17-day stay, including initiation of adjuvant therapy. The next longest post-operative stay was 9 days.

There were no major complications in this group of patients. Minor wound healing complications were not uncommon, occurring in four patients. These consisted of minor areas of dehiscence and developed in the group of patients who underwent limited resections of the soft palate with local flap reconstruction. These did not seem to correlate with closure technique and tended to develop at the points of inset of the tips of the transferred flaps. It is our impression that contributing factors may have involved intermittent and recurrent tension across the velum during activities such as swallowing, coughing and speaking, which are difficult to control during the early post-operative period. Two patients, one with a fistula and one with a dehiscence, underwent minor revisions at the time of subsequent surgical procedures planned as part of the management of their malignant disease with good results. Another patient underwent revision of a modestly bulky flap pedicle, again at the time of a subsequent planned secondary procedure. The other two patients healed completely by secondary intention.

Discussion

The surgical robot is an exciting and state-of-the-art technology which enhances both surgical precision and the ability to offer minimally invasive alternatives to commonly performed procedures across a number of surgical specialties. Robotic assistance can enhance more standard and accepted endoscopic and minimal access surgical techniques by augmenting the technical capability of the surgeon. Initially it was thought that the robot could be used to provide surgical capabilities at distant locations; however, experience has demonstrated that the robot–surgeon interface can enhance the surgeon’s capabilities in any setting [2]. The robot augments visual capabilities through optics which provide magnification, stereoscopic vision and co-axial illumination via limited-access portals and in restricted operative fields. In addition, motion scaling––the ability to scale up or down the magnitude of the motions made by the surgeon––suppression of tremor and articulated arms, which are not only smaller and finer than the surgeon’s hands but also possess the capability of greater degrees of range of motion, enhance the surgeon’s physical capabilities. An assistant can also access the third arm during the procedure without significantly degrading the visual or manual capabilities of the surgeon. Finally, there are potential ergonomic advantages compared with standard operating arrangements where the surgeon is forced to lean over the patient for hours at a time to complete the procedure.

The advantages of robotic surgery have already been established in urologic and gynecologic surgery and are gaining acceptance in cardiac surgery, general surgery and endocrine surgery. In these applications the robot adapts easily to laparoscopic or endoscopic port incisions. More recently the concept of the TORS approach to the oral cavity and nasopharynx has allowed a re-assessment of the application of primary surgical approaches to the treatment of malignant neoplasms of the base of the tongue, soft palate and pharynx. Previously, access to these areas generally required the use of long and inflexible instruments under conditions of limited lighting and vision or the use of lip and/or mandible splitting procedures which resulted in significant additional morbidity, the need for a tracheostomy and unsightly scars. As a result, concurrent chemoradiotherapy has become a standard primary treatment for locally advanced malignant lesions of the oropharynx [7, 8]. Unfortunately, chemoradiation has significant limitations in terms of accurate staging and exposure of the patient to major long-term functional complications and sequellae [1, 7, 8]. The TORS approach has been associated with improved functional outcomes and in addition more complete pathologic tissue examination may result in more accurate tumor staging and more precisely directed adjuvant therapy [1, 8, 9]. In the authors’ experience, the improved visualization and dexterity offered by the operating robot when compared with conventional closure techniques is particularly advantageous in the posterior and lateral pharyngeal walls, as well as the base of the tongue.

TORS represents an alternative to the management of patients with oropharyngeal pathology but also necessitates attention to the development and assessment of reconstructive approaches using the robotic platform. This application of the robot to oral reconstruction is new and the description of these techniques is limited, and only a few small series mentioning robotic-assisted oropharyngeal reconstruction have been published so far [10–13]. The numbers of patients reported and the discussion of specific approaches and techniques have been limited.

A number of reconstructive options exist for management of defects of the oropharynx, as we have demonstrated. Small defects are managed with local tissue transfer techniques including mucosal undermining and advancement, pharyngeal flaps, and the use of the uvula as a filleted flap. Fortunately, the robot is easily adapted to such techniques as local tissue reconstruction with FAMM and pharyngeal wall flaps as well as to the insetting of free flaps. Our preference is to use the FAMM flap for the reconstruction of defects which involve 2 cm or less of the length of the soft palate and defects not amenable to closure with undermining and advancement or other local flaps. The standard FAMM flap will extend easily to the palatal midline. It is necessary in most situations to carry the superior incision of the FAMM flap behind the maxillary tuberosity to create a trough for the flap so it can reach the defect. Tumors often extend onto the lateral and sometimes posterior pharyngeal wall. We feel that coverage of the vessels of the neck, when exposed, is important. It does not, however, seem necessary to completely close the entire pharyngeal defect, particularly the posterior wall. Whenever possible, at least two layers of sutures are placed, one in the deeper soft tissues and one in the mucosa. We have not attempted to provide separate nasal mucosal lining when using FAMM flaps.

Free tissue transfer is used for defects which exceed the size limitations of local flaps. The robot adapts easily to insetting of free flaps. We have found it necessary to carefully design these flaps, and this includes precise evaluation and measurement of the defect and the resected tissue specimen as well as the creation and use of templates. There is limited opportunity for tailoring and modification of the flap once insetting has commenced, due to the limited size of the oropharynx. Thin flap donor sites such as the radial forearm and the anterior lateral thigh work well. Larger and more bulky flaps create visual limitations with insetting the distal portions of the flaps. We have tried “parachute” sutures but, unfortunately, these seem to get in the way when more than two or three are placed at one time and therefore their use is limited. Fortunately the robotic instrument shafts themselves, when correctly positioned, tend to retract the tissues as the instruments are used and aid in visualization during insetting.

In most if not all cases, microvascular anastomosis may be performed using standard techniques via an external cervical incision with pull-through of the vascular pedicle through a bluntly dissected tunnel. Care must be taken to avoid injury to surrounding structures and to the vascular pedicle during this process. We have found a 2-inch Penrose drain useful in passing the flap pedicle to minimize traction and trauma to the vessels. Insetting is begun on the distal or deepest border of the flap. Eventually, robotic technology may allow routine anastomotic coupling of vessels completely within the oral cavity. Monitoring is performed with the aid of the Cook–Swartz implantable Doppler probe (Cook Medical, Bloomington, IN, USA). In addition, a Doppler probe site can usually be identified on the intra-oral surface of the flap.

Minor degrees of dehiscence, probably due to a combination of tension and the dynamic pull created by swallowing and talking, are not uncommon. Edema and stiffness of the soft tissues also contribute to post-operative dysfunction. Fortunately both nasopharyngeal obstruction and VPI, when present post-operatively, seem to improve as edema resolves, the tissues soften and pharyngeal scars contract. Given the fact that reconstruction involves replacing the functional muscle of the velum, which acts in coordination with the remaining oral and pharyngeal components, with adynamic flaps of skin or mucosa, the level of function observed post-operatively was relatively good.

Because its application to head and neck cancer treatment is very new, the role of the robot is undergoing definition at this time and the ideal applications have not yet been thoroughly established [10]. By virtue of its current capabilities, there exists the potential to offer local resection and reconstruction as primary treatment to more patients with early stage malignancies and to avoid or modify the need for chemoradiation therapy and its attendant morbidity. As we have demonstrated, the robot is also adaptable to the reconstructive needs of non-malignant conditions.

The future potential of this device may be further enhanced by the development of haptic feedback, flexible multiport access devices, multiplace (multiple surgeon) capability and by progressive miniaturization of its component parts. There is a need for studies to document the efficacy of this technology in the resection and reconstruction of tumors of the oropharynx as well as in the treatment of non-malignant conditions, to establish the limitations of this approach, to refine techniques and address current technical challenges, such as microsurgical anastomosis, to standardize effective reconstructive techniques and further define their anatomic basis and to develop instruments and sutures better suited to the capabilities of this device. As these issues are resolved the robot will likely expand the treatment options and improve outcomes for patients with head and neck pathology.