We enrolled 15 patients who underwent anterior sta-bilization of the cervical spine and subsequently presented with signs of clinical and radiological instability at the operated level. the group included 7 males and 8 females aged 43 to 58 years (mean 49.5).
five of them were operated originally due to rheuma-toid arthritis leading to cervical spine instability, six due to cervical discopathy, three due to cervical trauma and one due to extradural tumor causing destruction of c3 and c4 vertebral bodies.
there was no neurological improvement after surgery in five cases, deterioration after short improvement in six, and new neurological deficits with signs of vertebrobasilar circulation insufficiency in four.
all patients underwent routine and flexion/extension X-rays and ct or mri cervical scans. in four of them there were signs of anterior construct destabilization in the form of anterior plate “kick out” (fig. 1). vertebral body c4 compression fracture was found in one (fig. 2) and signs of vertebral body movement of the stabilized segment on flexion/extension Xrays (Fig. 3) in ten.
All patients underwent reoperation of the anterior con-struct and posterior stabilization during the same surgery
25
Posterior cervicAl lAterAl mAss fiXAtion
the anterior one in the clinical setting. it is very difficult to estimate the sufficiency of anterior stabilization before surgery. in the majority of cases, proper anterior decom-pression supplemented with anterior instrumentation secure appropriate stability of the spine. However, if the posterior column of the spine is substantially compromised, anterior stabilization may not be able to bear loads in the angular and rotatory range of motion. this possibility should be considered especially if three or more levels of the cervical spine are involved [4, 5]. only one of our patients had one-level discopathy. in this case, additional posterior instru-mentation lead to transient improvement with subsequent deterioration after four months. follow-up revealed no signs of spine instability and confirmed proper position of anterior and posterior construct elements. three or more levels were involved in the remaining patients and the surgical outcome was satisfactory. therefore, persistence of one-level instability despite anterior stabilization should be considered in the light of inappropriate anterior surgery or other causes of the neurological problem before poste-rior stability aspects are dealt with. still, there are no firm criteria which could be helpful to predict insufficiency of anterior stabilization in cases of multilevel disease.
Posterior stabilization is an extensive procedure cau-sing more immediate postoperative discomfort than anterior surgery due to substantial muscle preparation. there also remains the possibility of serious complications. screw placement in the lateral masses of the cervical vertebra can lead to spinal cord and nerve root injury as well as vertebral artery injury [6].
nevertheless, there were no intraoperative complica-tions in our patients who were able to return to normal life after a short post-operative period. radiological follow-up ascertained that the operated spine segments and constructs elements maintained their proper position during a mean follow-up period of more than one year. taking under consideration that initial anterior stabilization was lost in these cases, we conclude that additional posterior fixation substantially improved spinal stability.
conclusions
1.Posterior cervical lateral mass fixation significantly improves cervical spine stability in cases of insufficiency of anterior stabilization.
2. there is a need for further investigations regarding criteria helpful to predict insufficiency of anterior stabili-zation in cases of multisegmental cervical spine disease.
references
1. Adams M.S. et al.: Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating. spine 2003, 15, 2352–2358.
session. For posterior fixation we used poliaxial screws introduced in the lateral masses of cervical vertebras (additionally in occipital bone in four cases), connected subsequently by rods in the longitudinal axis (summit si system). the screws were introduced according to the roy-camille method.
Post-operative imaging (X-ray and ct scan) was done during first postoperative days and 6 months after surgery (fig. 4).
Fig. 4. Postoperative scan in patient from fig. 2. A – restabilized anterior construct after c4 vertebrectomy and iliac bone autograft placement.
Posterior stabilization involving the occiput, c3, c4 and c5.
B – cT showing position of the screws in lateral masses Ryc. 4. obraz pooperacyjny chorego z ryciny 2. A – restabilizacja struktur przednich; wertebrektomia c4 i implant z kości biodrowej.
B – obraz kTśruby w masach bocznych
a B
results
follow-up ranged from 6 to 18 months (mean 13 months). during that period
neurological symptoms resolved completely in 10 patients and in 5 there was substantial improvement. one patient complained of dizziness and shoulder pain which appeared four months after surgery. in this case radiology failed to reveal cervical spine instability or other pathology.
no complications were observed during surgery, postope-rative period, and ambulatory follow-up.
discussion
Anterior stabilization is often used after decompres-sion of the cervical spinal canal. However, the pathological process in some situations leads to changes in anterior and posterior spine structures that make this form of stabiliza-tion insufficient to stabilize the spine, producing overload of the anterior construct with subsequent pullout of the anterior plate and screws or even compression fractures of the vertebral bodies. it was shown in laboratory biomecha-nical investigations that posterior stabilization substantially improves stability when combined with the anterior one [1, 2, 3]. despite in vivo observations demonstrating the im-portance of this problem there is lack as to our knowledge of studies on posterior cervical fixation as an adjunct to
26 LesZek M. sagan, Marek B. LickendorF 2. Deen H.G. et al.: Lateral mass screwrod fixation of the cervical spine:
a prospective clinical series with 1-year follow –up. spine J. 2003, 3, 489–495.
3. Singh K. et al.: Biomechanical comparison of cervical spine reconstru-ctive techniques after a multilevel corpectomy of the cervical spine.
spine, 2003, 15, 2352–2358.
4. Kirkpatrick J.S. et al.: reconstruction after multilevel corpectomy in the cervical spine. A sagital plane biomechanical study. spine, 1999, 15, 1186–1190.
5. Swank M.L. et al.: rigid internal fixation with lateral mass plates in multilevel anterior and posterior reconstruction of the cervical spine.
spine, 1997, 22, 274–278.
6. Heller J.G., Silcox D.H., Sutterlin C.E.: comlications of posterior cervical plating. spine, 1995, 15, 2442–2448.
comments
sir,i read with interest “the role of posterior cervical lateral mass fixation in cases of insufficient anterior stabi-lization” by sagan L.M. and Lickendorf M. B. The article appears to be important in demonstrating the usefulness of additional posterior stabilization in case of unsuccessful anterior stabilization. i would like to comment on a few aspects of the study.
cervical spine instability and spine stabilization pose significant problems for the managing surgeon. These in-clude: (1) the risk of treatment failures; (2) the significant multiplanar forces affecting this region causing multidi-rectional instabilities; and (3) the difficulties associated with the attainment of a solid fusion, when the stability is multisegmental.
solid arthrodesis is relatively difficult to achieve in craniocervical and cervical region particularly in multi-segmental posttraumatic instability and in very devastating pathological processes, for instance metastases. Flexion, extension and rotation are extensive in the upper cervical spine, therefore simply restricting flexion and extension may not be enough. rotation may interfere with the fusion process enough to render it unsuccessful.
in traumatic fracture-dislocation injuries the post-traumatic instability affects all three vertebral columns.
although biomechanical data indicates that anterior fixation alone in unstable cervical injuries may not provide adequate stability, reports of clinical series indicate general success with this method of treatment.
The specific contribution of posterior column insta-bility to overall cervical sine stainsta-bility following anterior stabilization has been evaluated in very few studies. sagan and lickendorf report about the group of 15 patients who
underwent additional posterior fixation due to destabili-zation of anterior one. Unfortunately no exact evaluation of destabilizing factors in these cases is given in the ar-ticle. The secondary and definitive operative treatment of presented patients was correct; therefore the results were very good.
i think that the study gives quite new and important information about the usefulness of additional posterior stabilization in case of failed anterior stabilization. the documented insufficient anterior stabilization originates probably from inappropriate operation technique or multidi-rectional instabilities of cervical spine that should be quali-fied primarily to combined ventral and dorsal stabilization in one operative procedure. i agree with authors indicating the need for further investigation regarding criteria helpful to predict insufficiency of anterior stabilization.
ass. Prof. andrzej Bohatyrewicz, M.d.
July 11th, 2005 department of orthopaedics and traumatology Pomeranian medical University
*
We are very thankful to dr Bohatyrewicz for his com-ment to our paper.
as he noticed no exact evaluation of destabilizing fac-tors had been given. Patients included in the analyzed group were admitted with signs of instability of instrumented an-teriorly spine level. in six cases deterioration evolved after short time of improvement and there was no improvement or even immediate deterioration afer initial anterior surgery in nine cases. in all cases initial postoperatiye radiologi-cal investigation revelead appropriate decompression and construct position. on that basis we assumed that original operations were performed properly, however majority of this patients were not operated in our institution and we did not have insight in the operative record.
in all but one case original surgery involved several movement units. this implies signifcant role of multidi-rectional load which could not be sufficiently managed by anterior stabilization alone.
Analysis of appropriateness of preoperative planing and biomechanical conditions unique for presented cases would undoubtedly contribute to answer on question put in point 2 of our concłusions. However, we decided that it would have oversized the scope and aim of presented paper.
Authors
An nAles AcAdemiAe medicAe steti nensis, 2005, 51, 27–31
r o c z n i k i p o m o r s k i e j a k a d e m i i m e d y c z n e j w s z c z e c i n i e AnnAls of tHe PomerAniAn medicAl University, 2005, 51, 27–31
tom li/1 2005 volUme li/1
damian czepiTa