3D printing and pancreatic surgery

Introduction

The first and foremost rule every general surgical trainee is taught early in their apprenticeship is to “Eat when you can, sleep when you can, and do not mess with the pancreas!” Indeed, even in modern-day surgical training, a combination of high commitment, exhaustive effort, and extreme level of stress causes trainees to neglect their personal health and risk burning out, at the beginning of their aspired career in surgery. But why the pancreas out of all organs? What makes it so dangerous to treat with surgery?

In the following pages, we will briefly review the topography and chronology of the pancreas, obstacles, and breakthroughs in the field of pancreatic surgery. Evolution of multidetector computer tomography, 3D imaging, and 3D printing has contributed to the improvement of many surgical subspecialties. As their impact in modern-day medicine expands, hope for upgraded training, effectiveness, and reduced complications in pancreatic surgery is also growing. Perhaps, God created the pancreas and placed it in such a rough neighborhood, waiting for surgeons to train until they had enough simulated experience with personalized 3D printed models. The time has arrived when additive manufacturing could bring about advances in pancreatic surgery. Along with significant victories in the field of diagnosis and systemic treatment of pancreatic disease, this would supplementarily improve the lives of millions of sufferers around the world.

Anatomy

The pancreas is situated deep into the retroperitoneal space and is notorious for the difficulty to access surgically. It crosses the lumbar vertebrae anteriorly, roughly at level with the transpyloric plane. It can be divided into four parts: head, neck, body, and tail. The head is surrounded by the duodenal loop and gives out the uncinate process, extending posteriorly and below the superior mesenteric vessels as they emerge from behind the neck. The body tapers into the tail that extends to the splenic hilum.

Situated behind the pancreas lies the inferior vena cava, the portal vein formed by the confluence of the superior mesenteric and splenic veins behind the neck, the aorta, superior mesenteric vessels, diaphragmatic crura, celiac plexus, the left kidney, and suprarenal gland. In front of the pancreas lies the stomach forming part of the anterior wall of the lesser sac. The splenic artery undulates along the upper border of the pancreas, whereas the splenic vein travels behind it and receives the inferior mesenteric vein under the paraduodenal recess, laterally to the ligament of Treitz.

The common bile duct courses behind the pancreatic head, usually forming a groove in its lateral aspect. However, it can occasionally run through it to join with the main pancreatic duct of Wirsung and confluently drain into the medial aspect of the second part of the duodenum.

The arterial supply to the pancreatic head is common with the duodenum, derived from the superior (from the gastroduodenal artery) and inferior (from the superior mesenteric) pancreaticoduodenal arteries. The rest of the gland is perfused by branches of the splenic artery. Venous blood from the head and uncinate process drains to the right gastroepiploic and anterior-inferior pancreaticoduodenal veins. Together they form the gastrocolic trunk, which opens into the superior mesenteric vein on the right lateral side. Venous outflow from the body and tail ends into the splenic vein through short and fragile tributaries.

Lymph drains into peripancreatic lymph nodes along its upper and lower border, infra pyloric, portal, mesenteric, mesocolic, and aortocaval nodes. There are also lymph nodes around the splenic hilum, splenic artery, and tail of the pancreas.

Innervation of the pancreas is abundant. Pancreatic nerves carry nociceptive and visceral signals to the celiac plexus. Preganglionic efferent fibers of the greater, lesser, and least splanchnic nerves pass through the sympathetic chain and form the celiac ganglia, providing preganglionic input to the celiac plexus. Parasympathetic supply is derived from the left and right vagal trunks. The celiac plexus forms around the origin of the celiac axis and superior mesenteric artery.

Macroscopically, the gland is lobulated and covered by a fine capsule. The lobules consist of acini of epithelial secretory cells whose ductules drain into principal ducts. Between the pancreatic acini lie the hormone-secreting islets of Langerhans. The main duct occasionally drains separately into the duodenum and does not join with the common bile duct at the ampulla of Vater. The accessory duct (of Santorini) arises from the lower part of the head and crosses anterior to the main duct to drain into the duodenum proximal to it. It usually communicates with it, and sometimes it is absent.

Development of pancreatic surgery

Globally, there were 460,000 new cases of pancreatic cancer in 2018, making it the 12th most common cancer in men and the 11th most common cancer in women. In the United States, about 56,770 people (29,940 men and 26,830 women) will be diagnosed and 45,750 people (23,800 men and 21,950 women) will die from pancreatic cancer in 2019. By 2030, pancreatic cancer is expected to be the second commonest cause of cancer-related death. Despite progress in diagnosis and treatment, mortality from pancreatic cancer is expected to rise steeply in the following decades.

Surgery at an early stage represents the only hope for cure but only 15%–20% of patients are candidates for an operation at the time of diagnosis. Median postoperative survival is smaller than 20 months, 5-year survival is about 20%, and approximately 10% of patients are still alive after 10 years. Despite recent advances, long-term survival is uncommon even among patients eligible for surgical resection.

However, some decades ago, pancreatic resections were considered to be impossible owing to their deadly outcomes. Later, when mortality rates finally improved, they still were near 30%. Today, pancreaticoduodenectomy is the commonest type of pancreatic procedure and is safely carried out in high-volume centers (more than 19 cases per year) with mortality less than 2%.

The evolution of pancreaticoduodenectomy to its present form has been made possible by the efforts of several giants of the surgical legacy. This formidable type of surgery demands excellent surgical training and skills. Some of the important surgeons, operations, and dates in the evolution of pancreatic resections are listed below.

Alessandro Codivilla performed the first reported pancreaticoduodenectomy for carcinoma of the pancreas in 1898. He removed part of the pancreas, duodenum, distal stomach, and common bile duct. Reconstruction was achieved by Roux-en-Y gastrojejunostomy and cholecystojejunostomy. No anastomosis or closure of the pancreatic stump was performed. The patient died 18 days later from cachexia and diarrhea.

William Halsted performed the first successful resection of ampullary carcinoma by excising parts of the duodenum and pancreas in 1899.

Walther Kausch resected the bigger part of the duodenum en bloc with a significant part of the pancreas in 1912. Owing to the established ideas at the time, he did not complete the duodenectomy and restored continuity with a pancreaticoduodenostomy.

Allen Whipple published the first cases of a two-stage resection of the duodenum and greater part of the pancreatic head for ampullary cancer in 1935. Of the three operated patients, the first died the following day from anastomotic failure and the last survived for 2 years to finally succumb to liver metastases. Whipple is also credited with the first report of complete one-stage resection of the head of the pancreas and duodenum. While operating on a patient for pyloric ulcer, he observed that he also had a tumor in the pancreatic head. He continued to accomplish a distal gastrectomy, resection of the mass and choledochoduodenostomy. Pancreatic reconstruction was not performed in this patient but in later ones.

William Longmire reintroduced the concept of pylorus-preserving pancreatoduodenectomy in 1977, to control postgastrectomy syndrome. It was originally described by Kenneth Watson 30 years earlier. Despite early criticism on the radicality and oncological safety of the procedure, it proved to be equally effective with the traditional pancreaticoduodenectomy with the added advantages of shorter operative time, smaller blood loss. and better quality of life for long-term survivors.

Michel Gagner performed the first laparoscopic pylorus-preserving pancreatoduodenectomy in 1994. It was reported on a patient with pancreas divisum and chronic pancreatitis confined to the pancreatic head. In following years, many publications of successful distal pancreatectomy and pancreatoduodenectomy for neoplastic disease emerged from centers around the world.

Adoption of laparoscopic pancreatic surgery has been slow owing to the technical complexity, long learning curve, higher cost, and concerns about late complications and oncologic safety of the approach. The general advantages of laparoscopy over open surgery, such as diminished tissue trauma and blood loss, less requirement for analgesics, faster patient mobilization, and decreased length of stay, have been confirmed for laparoscopic pancreatic resections. Compared to open surgery, complications as pancreatic fistula and delayed gastric emptying have not been excessive, while abortion of the procedure after the initial inspection of the abdominal cavity spares the morbidity of an unnecessary laparotomy for patients with undiagnosed metastatic disease. Furthermore, similarly to the laparoscopic extirpation of other gastrointestinal malignancies, overall patient survival and incidence of positive resection margins after laparoscopic pancreatoduodenectomy for pancreatic head and periampullary cancer is comparable to open surgery.

Pier Giulianotti performed the first robotic pancreatectomy and reported his personal series of 13 robotic pancreatic resections 3 years later. Robotic surgery represents the latest development in the field of minimally invasive surgery. It was first used in the 1990s in military and major catastrophe applications and called telepresence surgery. It shares advantages of laparoscopic surgery such as small incisions, diminished blood loss, short length of stay, and faster recovery. Additionally, the robotic platform offers a better viewing experience in full high-definition 3D vision, improving hand-eye coordination. Compared to laparoscopy, it also reduces instrument tremor and abolishes the fulcrum effect, permitting 7° of mechanical freedom and allowing for easier and precise intracorporal maneuverability. Improvements in ergonomics provide a comfortable sitting for the surgeon who can perform longer operations with less fatigue and higher precision.

The prevailing commercially available system is the Da Vinci Surgical System (Intuitive Surgical, Sunnyvale, CA, USA). It consists of three fundamental elements: the surgeon's console where the surgeon seats wearing a 3D visor and using an interface for instrument control (Endowrist technology, Sunnyvale, CA, USA), the patient-side cart with four articulated arms (reproducing surgical manipulations in the operative field), and a vision control unit.

To date, the largest published series consisted of 250 consecutive robotic pancreatectomies, the majority of which for pancreatic adenocarcinoma. The reported rate of 30- and 90-day mortality was 0.8% and 2.0%, respectively, and overall postoperative morbidity was equivalent to open and laparoscopic operations in specialized high-volume centers. Conversion to open surgery was necessary in 6% of cases. There have also been reports of better oncologic results compared to laparoscopic resections, characterized by higher rates of negative resection margins and higher lymph node yields.

However, there is lack of evidence from multicentre randomized controlled trials, difficult to conduct because of high costs and limited availability of the robotic platform, surgical training, and patient consent issues. Level of evidence of the reported robotic pancreatic surgery studies is low and based mainly on single institution (and frequently single surgeon) series, with biased patient selection. This is likely to improve in the future with robotic technology improving continuously and becoming more affordable and accessible to healthcare applications.

Earlier diagnosis and evolution of neoadjuvant therapy are also expected to further improve the outcomes in pancreatic cancer treatment. Developments in surgical training and technique are similarly anticipated, possibly with the implementation of 3D printing, enabling surgeons to safely practice the operation in training facilities, on case-specific, exact anatomic models, before embarking on live surgery.