In this study, we designed and manufactured a posterior lumbar interbody fusion cage for osteoporosis patients using 3D-printing. The cage structure conforms to the anatomical endplate’s curved surface for stress transmission and internal lattice design for bone growth. Finite element (FE) analysis and weight topology optimization under different lumbar spine activity ratios were integrated to design the curved surface (CS-type) cage using the endplate surface morphology statistical results from the osteoporosis patients. The CS-type and plate (P-type) cage biomechanical behaviors under different daily activities were compared by performing non-linear FE analysis. A gyroid lattice with 0.25 spiral wall thickness was then designed in the internal cavity of the CS-type cage. The CS-cage was manufactured using metal 3D printing to conduct in vitro biomechanical tests. The FE analysis result showed that the maximum stress values at the inferior L3 and superior L4 endplates under all daily activities for the P-type cage implantation model were all higher than those for the CS-type cage. Fracture might occur in the P-type cage because the maximum stresses found in the endplates exceeded its ultimate strength (about 10 MPa) under flexion, torsion and bending loads. The yield load and stiffness of our designed CS-type cage fall into the optional acceptance criteria for the ISO 23089 standard under all load conditions. This study approved a posterior lumbar interbody fusion cage designed to have osteoporosis anatomical curved surface with internal lattice that can achieve appropriate structural strength, better stress transmission between the endplate and cage, and biomechanically tested strength that meets the standard requirements for marketed cages.
IntroductionEsophagogastric varices bleeding is a common complication due to portal hypertension in patients with liver cirrhosis. With the advancement of nonoperative management including vasoactive agents, endoscopic hemostasis or transjugular intrahepatic portosystemic shunt, surgical management has played a lesser role in recent decades. The present report describes a patient with hepatitis B (HBV)-related liver cirrhosis and portal vein thrombosis with recurrent esophagogastric varices bleeding despite the use of medical and endoscopic therapy. The modified Sugiura procedure was performed as an alternative bridge surgery for liver transplantation in order not to change the anatomic structure of the great vessels and to avoid hepatic encephalopathy related to shunting procedures like the transjugular intrahepatic portosystemic shunt.Case presentationA 56-year-old Chinese man with a history of portal hypertension due to HBV-related liver cirrhosis and known former recurrent esophageal varices bleeding status post Sengstaken-Blakemore tube tamponade was referred to our hospital for liver transplantation evaluation because of persistent esophagogastric varices bleeding with hypovolemic shock, even after medical and endoscopic therapies in a local hospital. As a result, liver cirrhosis with Child-Pugh class B function was diagnosed. Despite the use of vasoactive agents, and endoscopic hemostasis management, esophagogastric varices bleeding still occurred episodically with hypovolemic shock, which could not be reversed by blood transfusion or Sengstaken-Blakemore tube tamponade. The modified Sugiura procedure, as an alternative bridge therapy for patients who are candidates for liver transplantation, was performed, despite the fact that his liver transplantation was not yet completed. He then received a living donor liver transplantation with the right lobe of liver from his daughter. The postoperative course was uneventful, and he was discharged two weeks later. He had no evidence of recurrent esophagogastric varices bleeding during the six-month follow-up.ConclusionsThe treatment experience of this case gave us not only the idea but also the practical way of applying the modified Sugiura operation as a bridge and rescue therapy without alteration of the vascular anatomy and hemodynamic stability for patients who have experienced refractory esophagogastric varices bleeding, despite the use of medication and endoscopic treatment, and are candidates for receiving a liver transplantation.
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