Free Hand Pedicle Screw Placement in the Thoracic Spine: Is it Safe?

Purpose: To evaluate the safety and accuracy of a free hand technique of pedicle screw placement in the thoracic spine by a single spine surgeon at a single institution over a 10 year experience.

Methods: 273 consecutive patients who underwent posterior stabilization utilizing 2199 transpedicular thoracic screws by a single surgeon from 1992 to 2001 were analyzed. The mean age was 26 years (range 5-83 years) at the time of surgery. Etiologic diagnoses were: pediatric scoliosis in 141, pediatric kyphosis in 14, other pediatric spinal disease in 4, adult scoliosis in 43, adult kyphosis in 17, other adult spine disease such as tumor or fracture in 54. Pedicle screws were inserted using a free hand technique, similar to that used in the lumbar spine, in which anatomic landmarks and specific entry sites were used to guide the surgeon. A 2mm tip pedicle probe was carefully advanced free hand down the pedicle into the body. Careful palpation of all bony borders (floor and 4 pedicle walls) was performed before and after tapping. Next, the screw was placed, followed by triggered EMG and radiographic (AP and lat) confirmation. An independent spine surgeon using medical records and roentgenograms taken during treatment and followup retrospectively reviewed all the patients.

Results: The number of the screws inserted at each level were as follows (total n=2199): T1 n=10; T2 n=41; T3 n=128; T4 n=190; T5 n=188; T6 n=163; T7 n=157; T8 n=180; T9 n=175; T10 n=230; T11 n=332; T12 n=405. According to the diagnoses, the number of screws placed were: 1320 screws for pediatric scoliosis, 118 pediatric kyphosis, 320 adult scoliosis, 132 adult kyphosis, 24 pediatric tumor and fracture, and 285 adult tumor and fracture. 546 screws out of 1890 screws inserted into the deformed thoracic spine were randomly evaluated by thoracic CT scan to assess for screw malposition. 35 screws (6.41%) were inserted with moderate cortical perforation which means the central line of the pedicle screw is out of the outer cortex of the pedicle wall and included 10 screws (1.83%) that violated the medial wall. Twenty five screws (4.58%) were inserted between the lateral pedicle and rib. There were screws (out of the entire study group of 2199) with any neurologic or vascular complications, clinical sequelae, or revision surgery needed at up to 10 years follow-up.

Conclusions: The free hand technique of thoracic pedicle screw placement performed in a step-wise, consistent and compulsive manners is an accurate, reliable, and safe method of insertion to treat a variety of spinal disorders, including spinal deformity.