Observation and measurement of applied anatomical features for thoracic intervertebral foramen puncture on computed tomography images

BACKGROUND: Thoracic intervertebral foramen puncture is the key step for interventional therapy on the thoracic nerve roots or dorsal root ganglia. The anatomical features of the thoracic spine are complex, and puncture injury to the pleura, blood vessels, spinal cord, and other tissues may cause serious complications. The spatial anatomical characteristics and related parameters for thoracic intervertebral foramen puncture remain poorly understood. AIM: To observe and summarize the spatially applied anatomical characteristics for intervertebral foramen puncture on different vertebral segments. METHODS: A total of 88 patients (41 males and 47 females) who underwent thoracic minimally invasive interventional treatment at Nanjing Drum Tower Hospital from January 2019 to June 2020 were included. Computed tomography images of 167 thoracic vertebral segments scanned in the prone position were collected. The width of the intertransverse space (D(P)), the height of the rib neck/head above the lower transverse process (D(R)), the width of the lateral border of the articular process/lamina (W(P)), and the width of the posterior border of the vertebral body (W(V)) were measured. At the upper 1/3 of the intervertebral foramina, the horizontal inclination angle (α) from the lateral border of the articular process/lamina to the posterolateral border of the vertebral body was measured. The ratios D(R)/D(P )and W(P)/W(V )were calculated. The intervertebral foramen parameters were compared between segments. RESULTS: No rib head/neck occlusion (D(R)/D(P )> 0) was found in the intertransverse spaces of T1-2 and T12-L1. The incidence of occlusion for the upper thoracic segments (T1-5, n = 138), middle thoracic segments (T5-9, n = 116), and lower thoracic segments (T9-L1, n = 80) were 76.81%, 100%, and 82.50%, respectively. The incidence of occlusion for the middle thoracic segments was significantly higher than that for the upper and lower thoracic segments (P < 0.05). The incidence of > 1/2 occlusion (D(R)/D(P )> 1/2) for the upper, middle, and lower thoracic segments was 7.97%, 74.14%, and 32.50%, respectively. The incidence of > 1/2 occlusion for the middle thoracic segments was significantly higher than that for the upper and lower thoracic segments (P < 0.05). W(P )was longer than W(V )on T1-2 to T9-10 and shorter than W(V )on T10-11 to T12-L1. The horizontal puncture angle (α) into the external opening of the intervertebral foramina was positively correlated with the segments of the thoracic vertebrae from the cephalic to caudal portion (left: r = 0.772, P < 0.01; right: r = 0.771, P < 0.01), and the horizontal inclination angle for T11-12 and T12-L1 was 90°. CONCLUSION: It is necessary to identify the spatial impact of the rib head/neck on the puncture path of the intervertebral foramina and design appropriate puncture angles for different segments.