SpineAnterior odontoid fixation using a 4.5-mm Herbert screw: the first report of 20 consecutive cases with odontoid fracture
Introduction
Anterior screw fixation provides the best anatomical and functional results for type II odontoid process fractures with intact transverse ligament, and it is considered as a treatment of choice for type II-P fractures [2], [8], [17]. Recently, its simple procedures and satisfactory results brought popularity for treatment even in type II-A and type II-N fractures. Several kinds of screws are available for the procedure. One or two 3.5- or 4.0-mm-diameter, titanium or stainless, cannulated or noncannulated, cancellous and half-threaded screws are usually used [1], [8], [12], [13], [16], [18], [19], [20], [21]. Because Knöringer [14] first described the technique of anterior odontoid screw fixation using double-threaded compression screw in 1987, the report by Chang et al [4] only described clinical series in 13 patients using 1 (4.5 mm) or 2 (3.0 mm) Herbert screw fixation of displaced type II odontoid fracture, which has double threads with different pitches on the distal and proximal ends and has no head.
The author has recently used a 4.5-mm Herbert screw in 20 consecutive patients of anterior odontoid screw fixation. The purpose of this study is to evaluate the clinical result and advantage of a 4.5-mm Herbert screw in anterior odontoid screw fixation. To the best of our knowledge, this is the first clinical study to describe anterior odontoid screw fixation using a 4.5-mm Herbert screw.
Section snippets
Materials
Between April 1995 and December 2005, 58 patients with types II and III odontoid process fractures were treated with anterior screw fixation. The Herbert screw was used in the recent 20 consecutive patients from May 2003 to November 2005.
Herbert screw
The Herbert screw is manufactured from Tivanium Ti-6Al-4V Alloy (Zimmer, Warsaw, IN), which provides excellent strength and biocompatibility (Fig. 1). This implant has double threads, with different pitches on the leading and trailing threads. Because of this
Results
The preoperative clinical and radiologic findings of 20 patients are listed in Table 1. There were 16 male and 4 female patients whose ages ranged from 15 to 76 years (mean, 43.7 years). The fracture type was type II-A in 4 patients, II-N in 9 patients, II-P in 5 patients, and III in 2 patients. The fracture line was posterior oblique in 10 cases, anterior oblique in 4 cases, and horizontal in 6 cases (Table 2). The range of follow-up was 3 to 36 months (mean, 18.6 months).
In all cases, a
Discussion
Because various methods of treatments exist for types II and III odontoid process fractures, considerable controversy exists regarding the best method for stabilizing these fractures [15]. Initial treatment has relied primarily on immobilization by using a rigid orthosis such as a halo vest or a Minerva jacket. However, relatively high failure rate associated with this method of treatment has led several authors to attempt operative treatment of C1-2 posterior fusion as a primary treatment [1],
Conclusion
The Herbert screw is very useful in anterior fixation of variable type of odontoid process fracture. This screw has double threads, with a different pitch on the distal and proximal ends. Because of a unique design, odontoid fracture reduction and compression are combined to provide rigid internal fixation. It also provides minimal damage at soft tissue and C3 vertebra. The Herbert screw provides significant advantages over fixation techniques using conventional bone screws.
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