Currently, there have been different opinions concerning whether conservative or surgical treatment should be applied for infectious spondylitis. Surgery was performed only in patients with unsatisfactory conservative treatment, failed infection control, progressive neurological impairment, and progressive spinal deformity[8–11]. In this study, all patients underwent at least 3 weeks of conservative treatment, and still experiencing persisted symptoms. The number of infectious spondylitis patients is increasing year by year, and due to medical development and population aging, the infected population gradually shifts from teenagers and middle-aged people to the elderly. Almost half of the infected people were aged over 50. The main surgical methods for infectious spinal inflammation are anterior decompression and anterior decompression combined with posterior fixation and fusion, both of which require general anesthesia and are accompanied by large blood loss and long operation time. Pee performed anterior lesion removal and bone graft fusion and posterior pedicle screw internal fixation in 60 patients, with an average operation time of 263.8 ± 83.0 min and an average blood loss of 810 ± 49.6 ml. For elderly infected with spinal inflammation, due to their poor physical condition and autoimmune state, it is difficult for them to tolerate the trauma caused by traditional surgery, large blood loss and long anesthesia time. It has been reported that anterior fusion surgery has a 15% incidence of perioperative complications and a 4–5% mortality. In this study, the average age of the patients was 71.03 ± 13.91 years old, which was generally old. Most of the patients were rated as ASA level III with one or more internal diseases including diabetes, stroke, renal failure, etc., and had been lied in bed for at least 3 weeks before surgical treatment, with poor physical condition and were unsuitable or at high risk of receiving general anesthesia. Compared with the traditional operation, PEDD and PPSF are all performed under local anesthesia, which induces a lower risk compared to general anesthesia by avoiding endotracheal intubation and thus reducing the likely incidence of postoperative pneumonia, and associated difficulty in exhaling management. Traditional open surgery requires complex and lengthy preoperative preparation and adjustment. For patients with neurological defects, PEDD can relief nerve root compression and rescue neurological function in the shortest time.
Intraoperatively, a scraping spoon was used to remove the adjacent vertebral endplate. In adults, where there is no vascular tissue in the intervertebral disc, intra-osseous infusion extends into the terminal artery at about age 30. In adults, the subchondral spongiform bone is supplied with nutrients from the terminal artery, where small septic emboli may stay in and begin to proliferate, leading to infarct and subsequent osteomyelitis. As infection reaches to the subchondral space, it usually continues to spread to the disc, causing osteomyelitis and discitis. The infection can then spread to the adjacent vertebral endplate through the disc. Therefore, in our opinion, the removal of the endplate during the operation can make the lesion removal more thorough and contributes to a lower recurrence rate, which can't be achieved by other minimally invasive methods except for direct vision using an endoscope. At the same time, the scraping of adjacent vertebral endplates also promoted the spontaneous fusion of vertebral bodies. The primary objective of conservative treatment is to apply a large amount of antibiotics to control the infection and wait for spontaneous fusion of the adjacent vertebral bodies of the infected segment, a process that often takes 3 months. However, the lesion clearance of PEDD and the vertebral stability brought by PPSF all facilitate the spontaneous fusion among vertebral bodies, enabling patients to perform early functional exercise, reduce bed immobilization, and reduce the incidence of perioperative complications such as thrombotic pulmonary embolism.
The main clinical manifestations of infectious spondylitis are intractable back pain. The primary manifestation of infectious spondylitis is the erosion of intervertebral space. Low back pain caused by infection and inflammatory stimulation can be further aggravated by slight changes in position or movement (such as turning over) due to damage to the vertebral space and endplate. Conservative treatment often relieves pain by immobilizing in bed to avoid movement between the adjacent vertebral bodies. Nasto et al. compared the differences between the treatment of infectious spondylitis with percutaneous posterior fixation and conservative treatment with traditional supports, the results showed that VAS in the fixation group were lower than those in the conservative group. In our study, 33 patients had significant pain relief after surgery. It is notable that the VAS decreased from 8.20 ± 0.83 points to 6.20 ± 0.44 points for the 5 patients who received the second-stage operation after the first-stage PEDD. This means after receiving PPSF in the second phase, the score further decreased to 2.40 ± 0.89 (p < 0.005). We believe that PEDD can rapidly solve the patients' lower back pain by debridement and lavage of intervertebral space under the endoscope, and further clear the lesions by continuous irrigation and drainage after the catheter placement. However, other than the destruction of posterior ligament complex and paravertebral muscle caused by open surgery, all of the disc, the adjacent soft tissues and vertebral endplate were scraped in PEDD. The stability of the vertebral body was still affected before the formation of spontaneous fusion, therefore the persistent back pain occurred after the operation. PPSF, as a minimally invasive fixation technique, further enhances spinal stability and alleviates symptoms after infection control by PEDD, and provides a firm fixation of the spine through the minor trauma. Tsunemasa also suggested that PPSF should be considered as an additional surgery for patients with infectious spondylitis who underwent percutaneous drainage lavage in the presence of persistent postoperative low back pain or refractory pathogens that are not sensitive to antibiotics. In our study, we demonstrate that PEDD can alleviate the pain and the additional PPSF can improve the outcome on this basis.
In addition, we believe that the application of PPSF can bring long-term benefits to patients. Infectious spinal inflammation inevitably leads to bone destruction, long term spontaneous intervertebral fusion and spinal deformity. Also, chronic spinal instability can cause underlying pain and neurological symptoms. Adequate isolation of infected segments is therefore essential for the management of infectious spinal inflammation . Deininger et al. demonstrated that after posterior PPSF alone, the mean Cobb Angle increased by 3.4° in during the 9 months follow-up period. Pee used anterior lesion removal and bone graft fusion with posterior PPSF to treat spondylodiscitis. The average follow-up time was 35.8 months. 91.3% of bone union and an average lordosis change of 4.5 ± 9.0° were reported. Nasto reported an average increase in Cobb Angle by 1.86 ± 4.78° during the 9 months follow-up period after simple posterior PPSF[12, 13, 19, 20]. In the above studies, the intervertebral space was either treated by bone grafting or left untouched. However, in our study, the lesions in the intervertebral space were cleared without bone grafting. The local cavity is inevitably formed after the operation, which undoubtedly destroys the stability of the spine and promotes the development of spinal deformity. This may be the reason why kyphosis was developed in Ito’s patients after PEDD treatment alone (the Cobb Angle increased by an average of 12°). However, the purpose of both conservative treatments using thoracolumbar braces and internal fixation devices is to fix infected segments, promote spontaneous healing, maintain spinal stability and slow down the progression of spinal deformity. Although the treatment of infectious spinal inflammation with posterior internal fixation remains controversial, studies have shown that posterior internal fixation provides better orthopedic results and promotes faster fusion of adjacent vertebrae, without increasing the risk of infection. In our study spanning an average follow-up period of 7.84 ± 4.29 months, local Cobb Angle in patients increased by 3.9 ± 6.7°, and the intervertebral bridge or fusion occurred in 90.9% of the patients. Therefore, we believe that the combination of PPSF and PEDD can be more effective in delaying the progress of kyphosis than PEDD alone, and providing better long-term efficacy to patients. However, a larger sample size and control group may be required to determine the effect of PEDD combined with PPSF on the long-term kyphosis deformity and stability.
There are many minimally invasive surgical methods alternative to open surgery in clinical practice. The main objective is to remove diseased tissue while minimizing trauma occurrence and performing subsequent microbial culture for the tissue. For infectious spinal inflammation, identification of pathogen species, while not necessary for diagnosis, is essential for successful treatment. Blood culture and tissue culture are common methods to diagnose pathogenic bacteria. In general, the positive rate of blood culture can reach to 50%, while the positive rate of tissue culture can reach to 70%. In this group, 7 of the 33 patients tested positive for blood culture (21.2%), while 24 (72.7%) tested positive for intraoperative tissue culture through PEDD. Clinically, needle aspiration pathology is often used or pathology study is performed using CT, X-ray or ultrasound. However, the positive rates of tissue culture vary a lot according to methods used. Fouquet achieved a 36% positive rate through needle culture. Yang obtained a positive rate of 47% for CT guided biopsy. Staatz obtained a positive rate of 76% for CT guided biopsy. Chew and Kline achieved a 91% positive rate [21–24] of CT guided biopsy in 43 patients with active infection. Yang pointed out that there were too many factors that might lead to a negative result for culturing, such as too few samples and sampling errors for the needle aspiration biopsy and imaging guided biopsy. In the literature of PEDD, the positive rate of pathological culture of PEDD can reach to 80–90% . The advantages of PEDD include the direct extraction of pathological tissues, guarantee of sample size, reduction of sampling errors, and avoiding excessive radiographic guidance, huge trauma and potential complications caused by open surgery. Higher positive rate of culture can be obtained through PEDD, and early identification of pathogenic strains can also greatly reduce the likelihood of patients needing further open surgery. In our study, the positive rates of blood culture and tissue culture were low, which may be related to the fact that patients received antibiotics before surgery. Kim's study showed that the negative results of microbial culture were closely related to the use and length of antibiotics. However, while reducing the positive rate of microbial culture, the application of inappropriate antibiotics can lead to the colonization of bacteria resistant to the whole class of antibiotics. More importantly, the colonization of antibiotic-resistant pathogens may increase the risk of subsequent infection with these highly toxic microorganisms. Current research suggests that patients with spinal infections who undergo frequent biopsies or surgery should not be treated with routine antibiotics. Therefore, we believe that early identification of infectious strains is particularly critical. PEDD can achieve debridement and high positive rate for microbial culture.
In accordance with Yang's study, we used a large amount of dilute Beta iodized salt water with a concentration of 3.5% during the operation to obtain the optimal bactericidal effect. In the previous literature on PEDD, the drainage tube was mostly implanted into the intervertebral disc area with the negative pressure after the operation, focus on the intervertebral space drainage to further clear the infected lesions[21, 27–30]. Compared with the previous study, we focus on the postoperative irrigation. In this study, a disposable epidural anesthesia catheter was inserted through the channel as an inlet pipe and an outlet pipe with a diameter of about 3.5 mm. Walters infected the intervertebral space of the sheep with staphylococcus aureus and then applied cefazolin to it. Finally, the concentration of antibiotics in the blood was significantly higher than that in the annulus fibrosus, and there was no significant correlation between the two concentrations. This suggests that when intra - disc infection occurs, antibiotics cannot reach the affected area no matter how high the intravenous antibiotic concentration is. This also reflects the limitations of conservative treatment for infectious spinal disease. However, we placed double tubes under the channels for postoperative continuous lavage and drainage, the inlet pipe was removed until the rinsing solution was clear and the outlet pipe was retained for drainage. For patients with positive microbial culture results after the operation, they were given relatively sensitive antibiotic irrigation through the inlet pipe. The antibiotic can reach the disc area directly, which can obviously improve the drug concentration in the lesion area. At the same time, local application of antibiotics, drugs do not go through the portal vein system, avoid long-term use of antibiotics side effects. After a large amount of intraoperative flushing to remove inflammation and diseased tissues, the continuous application of local drugs after the operation will undoubtedly enable infectious spinal inflammation to be further controlled.