As a minimally invasive technique for treatment of LDH that PELD only requires an eight-mm skin incision and promotes faster recovery for patients. Previously, it has been widely believed that PELD associated with minimal blood loss based on the intra-operative observation. However, significant perioperative HBL is frequently unaccounted for.
In 2000, Sehat et al 13 gave further support to the concept of HBL when they reported that HBL during total hip replacement represented 49% of the total blood loss. Recently, HBL has received increased attention among spine surgeons. HBL was shown to constitute approximately 40% of total blood loss during primary and revision posterior spinal fusion surgeries 14. Wen et al 15 reported that significant HBL occurred in patients who underwent posterior lumber fusion surgery for degeneration, especially in cases of multi-level fusion. An additional study concluded that HBL was underestimated and accounted for a large percentage of total blood loss in minimally invasive transforaminal lumbar interbody fusion 16. HBL was calculated to range from 678 to 1,267 mL in two- or three-level posterior lumbar decompression and fusion 17, suggesting the need to consider HBL in patient management. Furthermore, for patients with rheumatoid arthritis undergoing posterior lumbar interbody fusion, while total blood loss, intraoperative bleeding, and operation time showed no variation, HBL was greater than that for patients without rheumatoid arthritis, particularly for long-segmental surgery 18. Despite these findings, HBL during PELD is not widely recognized and has not been characterized in the literature. To the best of our knowledge, it is the first prospective observational study of HBL in patients undergoing PELD.
Percutaneous kyphoplasty (PKP) is also a minimally invasive procedure used to treat osteoporotic vertebral compression fractures without drainage, and HBL during PKP is difficult to estimate. Wu et al 19 concluded that HBL should not be ignored during the peri-operative period for vertebroplasty, especially in patients who are frail and/or have multiple fractures and have PKP. However, the causes of PELD-associated HBL are still unknown. Several possible sources of HBL in PELD include hemolysis, extravasation of blood into surrounding tissues, residual blood in a dead space, or simple under-estimation of blood loss. In addition, the Hct method has been identified as a reliable way to estimate HBL20.
The concept of percutaneous posterolateral nucleotomy was introduced in 1973, and PELD was subsequently applied for the treatment of lumbar disc herniation 21. PELD refers to both percutaneous endoscopic transforaminal discectomy (PETD) and percutaneous endoscopic interlaminar discectomy (PEID). As a minimally invasive spinal procedure, PELD has gained popularity due to its small incision, quick recovery, short hospitalization, and equivalent clinical outcomes compared to open surgery 22. In the present study, all patients were discharged within 1–2 days post-operation. By comparing with the 25th -percentile and 75th -percentile cases for HBL, we found that surgical approach, surgical time and decompression procedure make a difference and try to make further investigation about risk factors.
The transforaminal approach is the procedure used most commonly to treat most types of herniated nucleus pulposus, except for the intra-canalicular type at L5/S1 with a high iliac crest9. Herein, we found that the lateral approach was associated with approximately 50 mL more HBL than the interlaminar approach. The improvements in VAS, JOA, and ODI scores on post-operative day 1 were similar with both surgical approaches. While one study reported no significant differences in estimated blood loss, post-operative periods in bed or hospitalization time between PETD and PEID 23, there remains a lack of sufficient evidence to compare these two approaches. In the present study, a transforaminal approach was elected for treating L4/L5, and an interlaminar approach for treating L5/S1, based on the hypothesis that a transforaminal approach would require cutting through more muscle and induce more trauma. However, our multivariable linear regression analysis showed that the surgical approach in PELD was not associated with the amount of HBL.
Our analysis did reveal a positive correlation between increased HBL and increased surgical time. Greater soft tissue damage may have partially accounted for this correlation. Generally, the greatest sources of HBL during surgery have been considered to extravasation of blood into surrounding tissues and hemolysis 24,25. In patients who receive treatment for LSS and also undergo foraminoplasty or ventral facetectomy, high-speed drilling and/or trephine reamers are applied, which increases bone-derived bleeding. In the present study, we found that application of decompression procedures was positively correlated with HBL.
The present study has several limitations. The cohort size was small, and control groups were not included. Additionally, the data analysis was not done in a blinded manner. Moreover, post-operative Hct and Hb levels were measured only on post-operative day 1. In future studies, these levels will need to be measured at later time points in order to analyze the return to normal levels. Although core body temperature was monitored and maintained during surgery, a large amount of fluid flushing and other hypothermia factors were difficult to avoid. Fluid shifts had likely already occurred in these patients, which may have confounded Hct estimation.