Comparative anatomical study of standard percutaneous and modified medialised percutaneous Bunnell type repair for artificial Achilles tendon rupture: positive effect of medialisation of the stitches with lower risk of sural nerve injury

Background: Less invasive percutaneous acute Achilles tendon rupture (AATR) repair techniques gain popularity because of lower risk of surgical wound complications. But these approaches have an increased risk of sural nerve iatrogenic injury as this sensory nerve is usually not visualised during minimally invasive operative procedures. We compared standard percutaneous Bunnell type and our proposed modified-medialised percutaneous technique in a cadaver study to evaluate potential advantages. Materials and methods: Ten pairs of fresh frozen specimens were divided into two groups for comparative anatomical study. Tenotomies of Achilles tendons were made and wounds sutured. Ten standard and 10 modified-medialised repairs were applied for artificially performed ruptures. All sutured tendons were dissected meticulously. We carefully looked at repaired Achilles tendon end-to-end contact and adaptation, distance from Achilles insertion in calcaneal tubercle to place where sural nerve crosses lateral border of the Achilles tendon and possible sural nerve and vein entrapment. Groups were compared using Fisher’s exact and Student-T tests. Results: All ends of sharply dissected tendons in both groups were in sufficient contact. No measurable diastasis between tendon ends was found in all cases. No entrapment of sural nerve or vein was found in modified percutaneous Bunnell suture technique group, whereas 7 of 10 sural nerves and 9 small saphenous veins were entrapped when using standard percutaneous Bunnell type technique. Average distance from Achilles tendon insertion in tuber calcanei to sural nerve crossing the lateral border of Achilles was 93 mm. Conclusions: Medialisation of percutaneous suture in AATR repair shows clear advantages compared to standard non medialised technique ensuring a possible lower incidence of sural nerve entrapment injury. Our modified percutaneous Bunnell type technique allows sufficient adaptation of ruptured Achilles tendon.

In silico testing of the semi-closed loop infusion system with a new simulator

Goal directed fluid therapy (GDFT) implies the flow-related parameters guided infusion of fluids. It requires adherence to complex clinical algorithms and fluid protocols, as well as simultaneous monitoring of several parameters and evaluation of their fluid responsiveness or actual response to fluid challenges. Automated clinical decision support systems (ACDSS) are used to ease the task. However, they are based on the flow-related (hemodynamic) parameters – arterial blood pressure, cardiac output, etc. Meanwhile, infusions guided by hemodynamic endpoints may lead to edema. A mini Volume Loading Test (mVLT) may be helpful in detection of imminent edema from changes in hemodilution during stepwise infusion which is conventionally used for hemodynamic optimization. We developed an ACDSS which is based on evaluation of both hemodynamic and hemodilution parameters. It operates on the basis of our unique algorithm which implies interchangeable application of fluid loading, vasopressor injection and red cell transfusion. This ACDSS is used in our PC-based command centre of a prototype semi-closed loop (SCL) infusion system. We developed a simulator – ‘Virtual Patient’ – on the basis of our previous clinical records aiming to test a new controller, as well as train the research team before starting a clinical trial. In silico testing continued for 12 hours on five occasions. Primary endpoint was the compliance of a controller with our clinical algorithm and the stability of operation in a spectrum of arterial hypotension and bleeding scenarios. The prototype SCL infusion system was found ready for clinical validation