Technical NoteApplication of Piezosurgery in En Bloc Laminectomy for the Treatment of Multilevel Thoracic Ossification of Ligamentum Flavum
Introduction
Since being first described in the 1920s, ossification of the ligamentum flavum (OLF) has been reported to be the most important cause for thoracic myelopathy, especially in the East Asian population.1 OLF is found more commonly in patients aged 40–60 years than in other age group, and the overall prevalence of OLF has been reported as 6.2% for male patients and 4.8% for female patients in the Japanese population.2, 3 Thoracic OLF can result in muscle weakness and various degrees of difficulty walking, numbness, and sensory disturbance in the lower limbs, and in severe cases, complete paraplegia. The incidence of sphincter dysfunction in advanced stage is also relatively high.4, 5 Surgical treatment is indicated for symptomatic thoracic OLF because conservative treatment is usually ineffective.6
Laminectomy is the most frequently used strategy for the treatment of thoracic OLF, and it can be divided into piecemeal laminectomy and en bloc laminectomy according to the resection method.7, 8 Compared with the piecemeal method, en bloc resection of lamina and the OLF with high-speed drill has several advantages. First, the drilling technique is less likely to damage spinal cord because no instrument enters the spinal canal during the decompression procedure. Second, en bloc resection can reduce cord compression at all levels simultaneously, and this could avoid spinal cord herniation.8 However, using the high-speed drill is technically demanding, which may cause injuries of the spinal cord and dura mater with inappropriate handling.9, 10 In addition, surgical time and intraoperative blood loss are both problematic issues in the treatment of multilevel thoracic ossification of ligamentum flavum (MTOLF).3, 6, 8
Piezosurgery is a relatively new osteotomy technique based on microvibrations that are generated by the so-called piezoelectrical effect and has therefore selective bone-cutting properties with preservation of adjacent soft tissue. It can ensure a greater cutting precision and safety. So far, application of the piezosurgery has been described in patients undergoing anterior cervical decompression and posterior cervical laminoplasty, with good success.11, 12, 13 However, few studies have focused on its safety and effectiveness in treating cases with thoracic OLF.
Based on our previous experiences in treating cervical ossification of posterior longitudinal ligament (OPLL), we have routinely used piezosurgery for the treatment of thoracic OLF and OPLL since 2015. To evaluate effectiveness and safety of the piezosurgery technique in en bloc laminectomy for the treatment of MTOLF, comparisons in perioperative events including surgical time, intraoperative blood loss, and complications, as well as neurologic improvement between cases using piezosurgery and a high-speed drill were carried out. According to our knowledge, this is the first report on using piezosurgery for the treatment of MTOLF.
Section snippets
Methods
This study was approved by the appropriate ethics committee and was performed in accordance with the Declaration of Helsinki ethical standards.
Results
Differences in general information preoperatively between the 2 groups were not significant, as shown in Table 1. A total of 187 segments (Group A: n = 105; Group B, n = 82) were involved, and the details are shown in Figure 2. The most involved levels were the lower thoracic spine in both Group A (68.6%) and Group B (62.2%). Distribution of the OLF in upper, middle, and lower thoracic spine wasn’t significantly different between the 2 groups (P = 0.591). Mean decompression extent was 4.8 ± 1.6
Discussion
Decompression surgery is recommended for cases with symptomatic thoracic OLF when conservative treatment is ineffective. Progression of the ossificated mass may aggravate neurologic deterioration, and longer duration of myelopathy also indicates poor neurologic recovery.14, 15 Laminectomy with piecemeal resection of the OLF has been wildly carried out in previous studies, and the mean neurologic recovery rate could be more than 50%.7 However, due to pre-existing static compression pathologies
Conclusions
For cases with MTOLF, application of the piezosurgery in en bloc laminectomy is safe and effective, and it could significantly reduce the operation time and intraoperative blood loss when compared with the high-speed drill.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.