枢椎侧方椎弓的临床解剖学测量

Clinical anatomic study of lateral arch of axis

目的:探讨国人行枢椎椎弓根螺钉内固定的可行性。方法:测量57例干燥枢椎标本侧弓前部内倾角α s、上倾角Y、上宽Ws、中宽Wm、下宽W、上高Hup下高Hip及上关节突厚度Hsa,Ebraheim进针点O距下关节突外缘和下缘距离Lla和Hia钉道表观长度Ls、实际长度La,O点距上关节突后缘和峡部的距离Los和Loi。结果:左／右αs=37.78°±7.87°／40.23°±7.73°,y=62.92°±9.25°／62.41°±8.41°,Ws=7.40±1.69 mm／6.86±1.71 mm,Wm=5.18±1.48 mm／5.17±1.40 mm,Wi=4.17±1.13 mm／4.21±0.98 mm.Hsa2+07±0.94 mm／1.97±0.87 mm,Hup=5 09±1.39 mm／5.00±1.43 mm,Hip=6.05±1.48 m／5.84±1.20 mm.Lla=4.19±1.17 mm／3.94±1.06 mm,Hia=9.38±1.60 mm／9.44±1.82 mm,Ls=29.43±2.61 mm／30.02±2.70 mm,La=26.63±2.37 mm／26.42±2.72 mm,Los=6.37±1.48 mm／4.96±1.54 mm,Loi=4.42±1.30 mm／2.64±1.25 mm。左右侧分别有45.6％(26)／47.3％(27)例的Wm≤5.0 mm(3.5 mm螺钉的安全界限)。如以仅α作为进针方向,左、右侧分别有63.2％(36)、70.2％(40)的螺钉将进入对侧。结论:国人Wm偏小,3.5 mm椎弓根螺钉内固定风险较大。Ebraheim进针点偏前、偏内、偏上,进钉的内倾角偏大、上倾角偏小。应行调整。

objective: To assess the feasibility of pedicle screw fixation in the treatment of Hangman's fracture based on the anatomical observation and measurement of lateral arch of axis. Methods: Medial inclination of anterior portion(α s) and posterior portion (βs) of lateral arch (separated from posterior portion (isthmus) by transverse process)from superior aspect, and superior inclination of anterior portion(Y ) and posterior portion(5 ) of lateral arch from lateral aspect of 57 dry axes were measured respectively. The superior, middle and inferior width of anterior portion of lateral arch (Wu,Wm and Wi), thickness of superior articular process (Hsa), superior and inferior height of anterior portion of lateral arch (Hup and Hip), horizontal distance from Ebraheim's entrance point(O) to lateral edge of inferior articular process (Lla), posterior edge of superior articular process (Los) and mid-position of isthmus (Loi) on superior aspect, and vertical distance from O to inferior edge of inferior articular process (Hia) on lateral aspect was documented respectively. The apparent and actual pedicle screw length projection (Ls and La) on horizontal plane was also measured. Results: Left/Right αs=37.78°±7.87° /40.23°±7.73°,βs = 6.46°±4.82°/5.20°±2.92°, 7=62.92°±9.25°/62.4°1±8.41°, 8=62.92°±9.25°/62.41°±8.41°.Ws=7.40±1.69 mm/6.86±1.71 mm, Wm=5.18±1.48 mm/5.17±1.40 mm. Wm in 26 (45.61% )left and 27 (47.37% )right side was less than 5.00 mm. Wi=4.17±1.13 mm/ 4.21 ±0.98 mm, Hsa= 2.07±0.94 mm/1.97±0.87 mm, Hup=5.09±1.39 mm/5.00±1.43 mm,Hip=6.05±1.4 mm/5.84±1.20 mm, Lla=4.19±1.17 mm /3.94±1.06 mm, Los= 6.37±1.48 /4.96±1.54, Loi=4.42±1.30 /2.64±1.25 Hia= 9.38±1.60 mm /9.44±1.82 mm,Ls=29.43±2.61 /30.02±2.70,La= 26.63±2.37/26.42±2.72.(left/right). If set a s as medial inclination of pedicle screw insertion, 63.2 % (36) left screws and 70.2 % (40) right ones would penetrate into the corresponding half portion of anterior structure of axis before they reached the anterior surface, if set p s as medial inclination of pedicle screw insertion ,all screws would penetrate into the transverse foramen, and if set Y as superior angle for pedicle screw insertion, all would violate the superior facet of axis. Conclusions: Neither medial nor superior inclination provided by any portion -of the lateral arch could guarantee safe and applicable pedicle screw insertion, the entrance point determined by standard medial and superior inclination of anterior portion of lateral arch for screw insertion was too closer to the lateral edge of inferior articular process and the middle portion of the isthmus. If set 5.0mm width of middle part of anterior portion of lateral arch as technically difficult limit for 3.5mm screw insertion,45.6 % (26) left and 47.4 % (27) right lateral arches are not suitable.