Safety of thoracic pedicle screw application using the funnel technique in Asians: a cadaveric evaluation

Abstract

The objective of this cadaveric study is to determine the safety and outcome of thoracic pedicle screw placement in Asians using the funnel technique. Pedicle screws have superior biomechanical as well as clinical data when compared to other methods of instrumentation. However, misplacement in the thoracic spine can result in major neurological implications. There is great variability of the thoracic pedicle morphometry between the Western and the Asian population. The feasibility of thoracic pedicle screw insertion in Asians has not been fully elucidated yet. A pre-insertion radiograph was performed and surgeons were blinded to the morphometry of the thoracic pedicles. 240 pedicle screws were inserted in ten Asian cadavers from T1 to T12 using the funnel technique. 5.0 mm screws were used from T1 to T6 while 6.0 mm screws were used from T7 to T12. Perforations were detected by direct visualization via a wide laminectomy. The narrowest pedicles are found between T3 and T6. T5 pedicle width is smallest measuring 4.1 ± 1.3 mm. There were 24 (10.0%) Grade 1 perforations and only 1 (0.4%) Grade 2 perforation. Grade 2 or worse perforation is considered significant perforation which would threaten the neural structures. There were twice as many lateral and inferior perforations compared to medial perforations. 48.0% of the perforations occurred at T1, T2 and T3 pedicles. Pedicle fracture occurred in 10.4% of pedicles. Intra-operatively, the absence of funnel was found in 24.5% of pedicles. In conclusion, thoracic pedicle screws using 5.0 mm at T1-T6 and 6.0 mm at T7-T12 can be inserted safely in Asian cadavers using the funnel technique despite having smaller thoracic pedicle morphometry.

The use of fluoroscopic guided percutaneous pedicle screws in the upper thoracic spine (T1–T6): Is it safe?

“…36,[39][40][41][42][43][44][45][46] Despite none of the perforations caused screw-related complications in this study, there were a grade 2 medial perforation which may result in neurologic complications and a grade 2 as well as a grade 3 ( Figure 3) anterior perforation which may risk injury to mediastinal visceral structures. O'Brien et al 47 had reported a case of oesophageal injury after instrumentation of the T3 vertebrae due to backward pressure from the endotracheal tube and trachea that pushed the oesophagus unto the tip of the anterior perforated screws.…”

“…McLain et al 12 found that at T4, 61% of pedicles were too small, at T5, 67% were too small and at T6, 75% were too small to accept a 5.5-mm screws from dissection of 18 human cadavers. Others had documented the narrowest pedicle width was located at T4 [33][34][35] or at T5 15,[36][37][38] which may subject them to higher risks of perforation. In our study, we found that there was a peak in the perforation rate at T4 (14.0%) and T6 (14.5%).…”

Retrospective Analysis of Screw Malposition Following Instrumented Correction of Thoracic and Lumbar Spine Deformities

“…По другим данным [29], количество мальпозиций в грудном отделе достигает 31,6 %, в пояснич-ном -10,6 %. До 48,0 % мальпозиций в грудном отделе приходится на уро-вень Th 1 -Th 6 , что обусловлено мень-шим диаметром ножек позвонков [6]. Около 56 % некорректно установлен-ных винтов располагается на вогну-той стороне деформации [2], что мож-но объяснить структурной диспла-зией дужек и апикальной торсией.…”

“…Наиболее надежными являются транспедикулярные системы, требую-щие точной установки винтов в тела позвонков через корни дужек. Транс-педикулярная фиксация позволяет выполнять трехплоскостную коррек-цию деформаций с фиксацией трех колонн позвоночника, сохраняя мак-симальное количество позвоночно-двигательных сегментов [1,6,7,11,14,15,25,30]. Несмотря на очевидные преимущества транспедикулярной фиксации, ее широкое распростра-нение ограничено риском невроло-гических и сосудистых осложнений из-за мальпозиции винтов [7,14,36,40,43,46].…”

A comparison of feasibility and safety of percutaneous fluoroscopic guided thoracic pedicle screws between Europeans and Asians: is there any difference?

“…There had been evidences that showed differences in the thoracic pedicle morphometry between Caucasians and Asians [22][23][24] which may alter the feasibility or safety of percutaneous pedicle screw technique among Asians. Therefore, this study was done to directly compare the safety of fluoroscopic guided percutaneous thoracic pedicle screw placement between Caucasians and Asians.…”