Clinical characteristics and surgical outcome of thoracic myelopathy caused by ossification of the ligamentum flavum: a retrospective analysis of 85 cases

Abstract

Study design: A retrospective comparative study. Objectives: To describe the clinical features and radiological findings, to assess the safety and effectiveness of posterior decompressive laminectomy and resection of the ossification of the ligamentum flavum (OLF), and to determine which presurgical and surgical variables were most closely related to postsurgical prognosis of thoracic myelopathy (TM) caused by OLF in China. Methods: Eighty-five patients with the diagnosis of TM caused by OLF received surgical treatment from July 1998 to May 2012. Clinical data were collected from medical and operative records. Correlations between the surgical outcome and various factors were also analyzed. Results: All cases were followed up for a mean of 49.2 months (range, 24-190 months) postoperatively. The mean Japanese Orthopaedic Association score was 3.8 points preoperatively and 8.2 points at the final follow-up, yielding a mean recovery rate of 63.0%. Postoperative complications included transient neurological deficits (9 cases), persistent neurological deficits (4 cases), dural tears (17 cases), cerebrospinal fluid leakage (9 cases), wound dehiscence (2 cases) and wound infection (3 cases). The OLF level (middle thoracic), preoperative duration of symptoms, intramedullary signal change on T2WI and preoperative severity of myelopathy were important predictors of surgical outcome. Conclusions: Biomechanical and anatomical factors may have a key role in thoracic OLF progression. Posterior decompressive laminectomy and resection of the OLF can be considered an effective, reliable and safe alternative procedure. The OLF level, preoperative duration of symptoms, intramedullary signal change on T2WI and preoperative severity of myelopathy were confirmed and significantly correlated with the surgical outcome.

Outcomes and Complications Following Laminectomy Alone for Thoracic Myelopathy due to Ossified Ligamentum Flavum

“…13,14,32 Concurrent posterior instrumentation and fusion has been proposed as a strategy to prevent progression of thoracic kyphosis from surgical decompression, although this remains controversial. 11,32 However, two studies in this meta-analysis specifically proposed that good clinical results can be achieved with decompression alone without fusion. 1,23 The late-onset complication of thoracic kyphosis was not reported in these two studies at a follow-up period of 17.3 and 53.2 months, respectively.…”

“…While there are no prospective studies in the literature examining outcomes or complications following surgical treatment of thoracic myelopathy secondary to OLF for comparison, Li et al 11 performed one of the larger retrospective studies of laminectomy with and without fusion in 85 patients with thoracic myelopathy due to OLF and found a complication rate of 51%. Another retrospective study performed by Onishi et al 10 examining laminectomy with and without fusion for thoracic myelopathy of various etiologies ( e.g ., OLF, disc herniation, spinal stenosis, ossified posterior longitudinal ligament) demonstrated an overall complication rate of 21% in 73 patients.…”

“…Our findings are consistent with previous studies that have reported the incidence of dural tears and CSF leaks to be 11% to 32%. 7,11,12,24,25 One potential explanation for the significant rate of dural tears and CSF leaks is the potential technical challenge encountered by the presence of dural ossification, which has been described by several authors. 16,17,19 The pathophysiology of OLF can lead to ossification of the dura mater, resulting in fusion of the ligamentum flavum and dura into a single inseparable layer of bony tissue.…”

“…However, Li et al ’s retrospective study of surgical outcomes after laminectomy with or without fusion for myelopathy due to OLF reported an infection rate of 3.5%, which is fairly consistent with our findings. 11 Potential risk factors for infection include failure of intraoperative hemostasis that can be the result of an unknown or occult coagulopathy or failure of a surgical drain. 11 The development of a hematoma is a potential sequelae of inadequate intraoperative hemostasis and the hematoma may become a nidus for postoperative infection.…”

“…9–14 Even with successful surgical decompression, there can be marked variation in clinical outcomes and the incidence of postoperative complications is not infrequent. 9,11,14–17 …”