Chan Chris Yin Wei, Kwan Mun Keong, Saw Lim Beng
Department of Orthopaedic Surgery, Faculty of Medicine, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia.
Surg Radiol Anat. 2011 Jan;33(1):19-25. doi: 10.1007/s00276-010-0726-1. Epub 2010 Sep 17.
Pedicle screw instrumentation has superior biomechanical as well as clinical outcome. Thoracic pedicles show great variation in different population groups, particularly in Asians who have been shown to have smaller pedicle dimensions. Although plain radiographs are widely performed prior to spine surgery, no studies have been done so far to investigate whether the thoracic pedicle profile on plain radiographs affect thoracic pedicle screw insertion. Therefore, this is a cadaveric study aimed to determine the relationship between plain radiographic thoracic pedicle profile in Asians and the outcome of pedicle screw insertion in the thoracic spine.
A pre-insertion radiograph with an enlargement reference scale was performed and surgeons were blinded to the plain radiographic morphometry of the thoracic pedicles. From the pre-insertion radiograph, the normalized pedicle width and height (which controls for any magnification error) as well as the pedicle width:body width (PWBW) and pedicle width:pedicle height (PWPH) ratio was derived. 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 wide laminectomies after pedicle screw insertion. The outcome of thoracic pedicle screw insertion was correlated with the radiological profile using independent t-test. Pearson correlation coefficient was used to investigate the correlation between the ratios and the normalised pedicle width and height.
The narrowest pedicle width is from T3 to T6 determined from normalized measurement of the pedicle width. T5 pedicle width is the smallest measuring 4.1 ± 1.3 mm. The overall perforation rate is 10.4% (25 perforations). There is only one significant perforation. There were twice as many lateral and inferior perforations compared to the medial perforations. 48% of the perforations occurred at T1, T2 and T3. Pedicles <4.0 mm in width and upper thoracic pedicles are risk factors for pedicle perforation. The normalised pedicle width has a high degree of linear correlation with PWBW and a normalised pedicle width of 4.0 mm correlated with a PWBW ratio of 0.3.
Plain radiographic thoracic pedicle morphometry has an influence on the outcome of thoracic pedicle screw insertion in Asian cadavers. Pedicle width <4.0 mm is associated with higher risk of pedicle perforation. This critical value corresponds to a PWBW ratio of 0.3. Identification of such pedicle profile warrants full evaluation of the morphometry of the thoracic pedicles and possibly extra-pedicular techniques should be employed to avert the risk of critical pedicle perforation.
椎弓根螺钉内固定术具有卓越的生物力学性能以及临床效果。不同人群的胸椎椎弓根差异很大，尤其是亚洲人，其椎弓根尺寸较小。尽管在脊柱手术前广泛进行普通X线片检查，但迄今为止尚未有研究调查普通X线片上的胸椎椎弓根形态是否会影响胸椎椎弓根螺钉的置入。因此，本尸体研究旨在确定亚洲人普通X线片上的胸椎椎弓根形态与胸椎椎弓根螺钉置入结果之间的关系。
在置入螺钉前拍摄带有放大参考标尺的X线片，外科医生对胸椎椎弓根的普通X线片形态测量结果不知情。从置入螺钉前的X线片上得出标准化的椎弓根宽度和高度（可控制任何放大误差）以及椎弓根宽度与椎体宽度之比（PWBW）和椎弓根宽度与椎弓根高度之比（PWPH）。使用漏斗技术在10具亚洲尸体上从T1至T12置入240枚椎弓根螺钉。T1至T6使用5.0 mm的螺钉，T7至T12使用6.0 mm的螺钉。在置入椎弓根螺钉后通过广泛椎板切除术直接观察来检测穿孔情况。使用独立t检验将胸椎椎弓根螺钉置入结果与放射学形态进行相关性分析。使用Pearson相关系数来研究这些比率与标准化椎弓根宽度和高度之间的相关性。
根据椎弓根宽度的标准化测量，最窄的椎弓根宽度位于T3至T6。T5椎弓根宽度最小，为4.1±1.3 mm。总体穿孔率为10.4%（25处穿孔）。仅有1处严重穿孔。外侧和下方穿孔的数量是内侧穿孔的两倍。48%的穿孔发生在T1、T2和T3。宽度<4.0 mm的椎弓根以及上胸椎椎弓根是椎弓根穿孔的危险因素。标准化椎弓根宽度与PWBW具有高度线性相关性，标准化椎弓根宽度为4.0 mm时对应的PWBW比率为0.3。
普通X线片上的胸椎椎弓根形态测量对亚洲尸体的胸椎椎弓根螺钉置入结果有影响。椎弓根宽度<4.0 mm与更高的椎弓根穿孔风险相关。这一临界值对应的PWBW比率为0.3。识别这种椎弓根形态需要对胸椎椎弓根形态进行全面评估，可能应采用椎弓根外技术以避免严重椎弓根穿孔的风险。
