RSU study aims to improve outcomes in intervertebral disc surgery

Writers: Aleksejs Repņikovs, Lecturer, Doctoral Student, RSU Department of Orthopaedics;
Sigita Kazūne, Associate Professor, RSU Department of Anaesthesiology, Intensive Care and Clinical Simulation

Patients usually consult a spine surgeon when they have specific concerns about their spinal health, such as whether they should undergo surgery and what their next steps should be.

In this article, we explain the different types of surgery available for disc protrusion or herniation and discuss in greater detail an innovative study* conducted by Rīga Stradiņš University (RSU) that aims to further improve surgical outcomes.

In milder cases, treatment of intervertebral disc involves relieving pressure on the root of the nerve by removing a fragment of the disc or a bony growth (osteophyte) that is compressing the nerve. Symptoms often subside significantly after the intervention. Such a procedure is referred to as less extensive or “minor” surgery.

However, in cases where conservative treatment or “minor” surgery is insufficient, or where there are significant structural changes in the spine, reconstructive stabilisation surgery may be required. During stabilisation surgery, a segment of the spine is stabilised using screws and other implants placed within and between the vertebrae, ensuring stable fixation and restoring the spine’s supporting function.

Intervertebral discs have a specific structure. They provide both shock absorption and spinal mobility and stability; however, they have a very limited blood supply due to the absence of direct vascularisation and are therefore considered avascular structures. The discs receive nutrients through their endplates by diffusion from the bodies of adjacent vertebrae. For this reason, all regenerative processes within the discs occur slowly.

During surgery, all patients are given intravenous antibiotics prophylactically to ensure adequate antibiotic concentrations in the soft tissues and to reduce the risk of infection. In this way, patients are appropriately protected against the risk of postoperative infections. These are not common complications; however, when they do occur, recovery is considerably more difficult and involves prolonged treatment, inability to work, and a significant burden on the healthcare system.

Nowadays, we often talk about antibiotic resistance — the phenomenon whereby antibiotics are becoming increasingly ineffective against micro-organisms. Therefore, it is very important to use antibiotics as little as possible, but when they are truly necessary, to ensure the most appropriate dosage is used so as not to promote antibiotic resistance.

We have extensive data on how much and in what situations to administer antibiotics intravenously; we know with considerable precision what concentrations will be achieved in the blood. However, during intervertebral disc surgery, the aim is not to reduce the concentration of micro-organisms in the blood, but rather in specific tissues. In intervertebral disc surgery, it is difficult to determine, due to the poor blood supply mentioned earlier, what concentrations will be present in peripheral tissues.

For example, if the disc is severely degenerated, its electrical charge may change. This means that if an antibiotic is positively charged, it may bind more readily to the disc.

In contrast, if a negatively charged antibiotic is used, it may be repelled from the disc.

From a scientific perspective, we were interested in how to optimise the concentration of antibiotics so that the most appropriate dosage could be used.  This led to the RSU study* on factors influencing antibiotic concentrations. Are comorbidities a factor? What about local changes? The stage of disc degeneration? We had the opportunity to collaborate with the RSU Faculty of Pharmacy and the Laboratory of Finished Dosage Forms, which enabled us to measure concentration of antibiotics in intervertebral disc tissue.

As part of the study, we collect intervertebral disc material from surgeries performed at the Traumatology and Orthopaedics Hospital (TOS)**, which is then sent for analysis to the RSU Laboratory of Finished Dosage Forms. In this way, we aim to identify the factors that most strongly influence antibiotic concentrations. Currently, we are beginning to develop a mathematical model of antibiotic concentration tailored to a patient with specific parameters.

We are currently in the data analysis phase of the study and have already presented the results at international conferences.

This is our opportunity to contribute to the collective knowledge of antibacterial therapy / prophylaxis.

* Fundamental and applied research project Optimisation of prophylactic antibacterial therapy in spinal surgery through mechanical PKPD modelling to reduce the emergence of antibiotic-resistant bacteria (OPATS-PKPD)
** Aleksejs Repņikovs is Deputy Director of the Spinal Surgery Centre and a spine surgeon, and Sigita Kazūne is an anaesthesiologist and intensive care specialist at the Anaesthesiology and Intensive Care Unit