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July2010 Vol.47 Issue:      3 (Supp.) Table of Contents
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Evaluation of the Image Guided Pedicle Screw Insertion: Limited Experience

Sherif Al-Mekawi, Amr K. Elsamman

 

Department of Neurosurgery, Cairo University; Egypt

 



ABSTRACT

Background: Image-guided technology has greatly broadened the scope of modern surgery. Objective: Evaluation of the accuracy of pedicle screw placement using navigation and the safety offered to the surrounding structure during screw placement and affection of the workflow. Methods: eight patients with dorsal and dorso-lumber instability were operated upon by pedicle screw fixation using 3D image guidance. BrainLAB Vector Vision (BrainLAB, Inc.). all patients had preoperative, intra-operative and postoperative imaging. Results: no vascular or neural complications were encountered, accuracy in choosing the entry point was high (100%) and accepted in medio-lateral inclination (62.5% perfect match and the rest showed minimal deviation less than five degrees). Conclusion: The use of spine navigation in the placement of pedicular screws provides higher accuracy, and is safer to the patient with less percentage of misplacement. [Egypt J Neurol Psychiat Neurosurg. 2010; 47(3): 471-476]

 

Key Words: instrumentation, spine navigation, spine instability.

 

Correspondence to Sherif AlMekawi, 30 Mourad st., first floor, flat no. 109, Giza, Egypt.

Tel:+20122124128. Email: almekawi_sherif@hotmail.com.





INTRODUCTION

 

               The use of pedicle screw instrumentation was described by Boucher in 1950s, and was popularized by Roy- Camille et al in 1960s. The initial use of pedicle screws began in the lumbar spine and as the surgeons became more comfortable with the complex anatomy required for accurate screw placement, they evolved the use of pedicle instrumentation in the thoraco-lumbar and thoracic spine.1

Transpedicular screw fixation has many advantages over other spinal instrumentations such as Harrington rod fixation, Luque’s instrumentation, etc., in various pathologies. Pedicle screws also prevent the need to place instrumentation within the spinal canal like sublaminar wiring, which creates the risk of neurological injury.1

Safety concerns on the violation of the spinal canal leading to potential harm to vascular, neural and other vital structures have been encouraging surgeons to improve the accuracy of pedicle screw placement by trying various approaches.2

The reported pedicle screws misplacement in historical spinal literature can be as high as 20-39.8%, but only a small number leads to complications (neurological, vascular or visceral injuries). But these complications can be potentially life and limb threatening.3.

The accuracy of pedicle screw placement has been discussed, as misplacement rates of up to 30% in the lumbar spine an up to 55% in the thoracic spine have been reported. Different techniques of pedicle screw placement have been described in the past. However, none of these techniques reduced the incidence of misplacement.4

Image-guided technology has greatly broadened the scope of modern surgery. Studies indicated that pedicle screw insertion accuracy could be significantly improved with image-assisted systems compared with conventional approaches. Among them, computed tomography-based navigation was the most popular.2

 

Aim of the work:

               Evaluation of the accuracy of pedicle screw placement using navigation and the safety offered to the surrounding structure during screw placement and affection of the workflow.

 

PATIENTS AND METHODS

 

Eight patients with spine instability needing stabilization were operated upon by pedicle screw fixation in national bank hospital, Egyptian ministry of Health, in the period between September 2009 and February 2010 using the neuro-navigation BrainLAB Vector Vision (BrainLAB, Inc.). All cases were subjected to complete history taking, general and neurological examinations and routine laboratory investigations. All patients had preoperative x rays of area of pathology, computed tomography with 3D reconstruction and magnetic resonance imaging in most of the cases.

The technique of screw placement was the same in all patients. After registration was accomplished, navigation accuracy was confirmed by touching anatomical landmarks with the image-guided probe. The intra-operative planning function on the image-guided system, which places a phantom screw on the tip of the probe, was then used to ascertain the entry point and trajectory of the screw. The optimal length and diameter of the screw were also determined using this function, and it should be noted that in each case effort was made to place the maximum diameter screw that the anatomy could accommodate. This intra-operative plan was locked into place, and all subsequent drilling/probing was done with image-guided instruments through this plan. After the pedicle was either probed or drilled, a pedicle feeler was then used to confirm that there was no pedicle breach, and the hole was then tapped in the same trajectory. After a pedicle feeler again confirmed no pedicle breach, the screw was placed. Navigation accuracy was briefly checked again prior to placement of the next screw by touching anatomical landmarks. In most cases, the tap and screwdriver were not image guided.

After completing the procedure, intra-operative X-ray of the surgery site was routinely done to confirm proper placement of the instrumentation.

Routine plain X-ray film, both antero-posterior and lateral on the second day post-operative were done, in some cases, post-operative CT scan at the surgery site was also done.

Technical notes:

During the procedure, good care should be taken at the time of registration. The degree of inclination and rotation of the vertebral body should considered and should corrected on the navigation screen.

Proper exposure and good dissection of the soft tissue off the spinous process, the lamina, and the pedicles should be achieved, to reach the highest accuracy percent.

Using the navigation added about 10 to 15 more mints to the time of surgery. This time was spent during the process of registration. On the other hand it reduces the need to use the intra-operative fluoroscopy and hence decreased the radiation exposure time for the operating room personnel.

 

RESULTS

 

               Out of eight patients (Three females and five males, with age ranging from 25 years to 56 years with a mean of 40.5 years), three cases had fracture in the dorsal spine, two of which were traumatic (D10 and D11), and one case was pathological fracture (D6-7). The other 5 cases had degenerative spondylolithesis, (L4-5 in three cases, and L5S1 in two cases).(Table 1)

All patients complained of back pain before surgery. In the post-traumatic cases, none of them had spinal cord compression, and hence there was no weakness in the lower limbs, or sphincteric dysfunction. (Table 2)

All patients with degenerative spondylolithesis had back pain and radiculopathy, with failure of medical treatment that was tried for an average of three months. None of these patients had weakness or sphincteric dysfunction pre-operatively.

Thirty six pedicle screws were used in this study using the spinal navigation. All the screws appeared in good position in the post-operative plain X-ray. We didn’t have any breaches in our study. The accuracy of the procedure was checked.  We compared the points, angles and endpoints we chose on the planning screen and the postoperative CT scans we have done to the patients and the results were matching. The entry points with 100% accuracy as planned. Five patients out of eight had matching angles on medio-lateral inclination with 62.5% accuracy. The remaining cases had deviation not exceeding 5 degrees.

Figures (1,2) are case presentations showing pre- intra and postoperative images.

 

 

Table 1. Level of the pathology in patients with spinal instability

Number of patients

Level of the Pathology

Percentage (%)

1

Traumatic fracture of D10

12.5%

1

Traumatic fracture of D11

12.5%

1

Pathological fracture of D6-7

12.5%

3

L4-5 first degree spondylolithesis

37.5%

2

L5S1 degenerative spondylolithesis

25%

 

Table 2. Pre-operative complaints in patients with spinal instability

Complaint

Number of patients

Percentage (%)

Back pain

8

100%

Leg pain

5

62.5%

Weakness in the lower limbs/ sphincteric dysfunction

0

0%

 


F

E

D

C

B

A

   

 

   

 

Figure 1. Case 1: Pathological fracture of the dorsal spine: (A) Pre-operative MRI for a case of pathological fracture dorsal spine (B) Intra-operative Plain X-ray during leveling (C) Intra-operative, during level definition using navigation (D) Starting registration (E) Intra-operative checking of the screw after insertion (F) Post-operative Plain X-ray.

A

B

 


C

 

D

 


 

 

Figure 2. Case 2: Degenerative L5,S1 Spondylolithesis: (A)Pre-operative MRI LSS. (B)Intra-operative during verifying registration. (C) Intra-operative during screw navigation. (D) Post-operative plain X-ray LSS.


DISCUSSION

 

Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers.4

Pedicle screw fixation was long used with the aid of intra-operative fluoroscopy. Even some surgeons with long practice don’t feel the need to use it especially in the lumbar spine. However, a number of complications are present in the literature related to misplacement of screws.

In a meta-analysis of the published literature on accuracy of PS placement, Kosmopoulos and Schizas5, reported a median accuracy of 90.3% in 12, 299 PSs placed in vivo without navigation versus a median accuracy of 95.2% in 3059 PSs placed in vivo with navigation. In another cohort, Nottmier and colleagues6, studied their results with 1084 screws placed using the navigation and they had no vascular or visceral complications. Two nerve root injuries occurred in 1084 screws placed, resulting in a 0.2% per screw incidence and a 0.9% patient incidence of nerve root injury. Neither nerve root injury was associated with a motor deficit. The breach rate was 7.5%. Grade 1 and minor antero-lateral “tip out” breaches accounted for 90% of the total breaches.

We didn’t have any breaches in our study; however we can’t state that we did better than Nottmier’s work due to the significant difference in the number of cases.

Pedicular screw placement using navigation has been used in this case study in different forms of pathologies, and at different levels. It was of real help in cases with fracture spine. During registration, orientation of the rotation and inclination of the vertebral body due to the fracture using the navigation helped in safe screw placement.

Moreover, the value of having higher safety margin during introduction of the pedicular screw, but the less time of radiation exposure is weighted against the more time consumed during surgery by using the navigation.

 

Conclusion

The use of spine navigation in the placement of pedicular screws provides higher accuracy, and is safer to the patient with less percentage of misplacement.

 

[Disclosure: Authors report no conflict of interest]

 

REFERENCES

 

1.      Modi HN, Suh SW, Fernandez H, Yang JH, Song HR. Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique. Eur Spine J. 2008; 17: 1686-96.

2.      Tian NF, Xu HZ. Image-guided pedicle screw insertion accuracy: a meta-analysis. Int Orthop. 2009 Aug; 33 (4): 895-903.

3.      Verma R, Krishan S, Haendlmayer K, Mohsen A. Functional outcome of computer-assisted spinal pedicle screw placement: a systematic review and meta-analysis of 23studies including 5992 pedicle screws. Eur Spine J. 2010 Mar; 19(3): 370-5.

4.      Tjardes T, Shafizadeh S, Rixen D, Paffrath T, Bouillon B, Steinhausen ES, et al. Image guided spine surgery: state of the art and future directions. Eur Spine J. 2010 Jan; 19 (1): 25-45.

5.      Kosmopoulos V, Schizas C. Pedicle screw placement accuracy: a meta-analysis. Spine. 2007; 32: E111-20.

6.      Nottmeier EW, Seemer W, Young PM. Placement of thoracolumbar pedicle screws using three-dimensional image guidance: experience in a large patient cohort. J Neurosurg Spine. 2009; 10:33-9.


 

 

الملخص العربى

 

إن الاستخدام جهاز الملاح الجراحى فى جراحات المخ والعمود الفقرى ترجع بداياته إلى خمسينيات القرن الماضى وتعود أهميه استخدام الجهاز إلى أن نسبه الخطاء فى توجيه مسامير العمود الفقرى تصل إلى 39.8% وتكمل خطورة هذا الخطاء فى التوجيه من حدوث مضاعفات للمريض وتزيد خطورة ونسبه  هذه المضاعفات  فى المنطقة العنقية والصدرية أكثر من المنطقة القطنية والعجزية.

يهدف هذا البحث إلى تقيم دقه توجيه مسامير تثبيت العمود الفقرى باستخدام جهاز الملاح الجراحى ومدى الفائدة العائدة من استخدامه.

تم إجراء هذا البحث على ثمانية مرضى يعانون من عدم ثبات العمود الفقرى وتم إجراء الجراحات بمستشفى البنك الاهلى للرعاية المتكاملة فى الفترة من سبتمبر 2009 إلى فبراير 2010.

تم تركيب 36 مسمار فى هذا البحث, جميع الأشعات أثناء وما بعد الجراحة مرضيه وبمقارنه ما تم التخطيط له على شاشه جهاز الملاح الجراحى وأشعات ما بعد الجراحة لاحظنا الاتى:

100% دقه فى اختيار نقطه دخول المسمار, 62.5% دقه فى زاوية الدخول مع ملاحظه أن باقى 37.5% كان نسبه الخطأ لا تتعد 5 درجات.

لايوجد اى اختراق للفقرة من الجانب أو من الأمام أو من الأسفل .

فى النهاية نستخلص أن جهاز الملاح الجراحى يوفر دقه أكثر فى توجيه المسامير ولا يتطلب وقت اضافى ملاحظ أثناء سير الجراحة وينصح به دائما



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