Pedicle Screw Disease

  Pedicle screw, one of the great innovations in spinal implants since Harrington rod  for correction of scoliosis. It has been used successfully in treating spinal fracture, deformities, and spinal metastasis, thanks to its provided rigidity.  Pedicle screw is indispensable in some spinal disorders from top to bottom of the spine.

  But unfortunately, its use in lumbar degenerative disorders is anther story. Also, pedicle screw placement is a technically demanding procedure with a high complication rate. Let's take a look at U.S. FDA's ruling of pedicle screw in 1998:

``Warning: The safety and effectiveness of pedicle screw ..only for.. significant mechanical instability...degenerative spondylolisthesis with..neurologic impairment, fracture, dislocation, scoliosis, kyphosis, spinal tumor, and failed previous fusion (pseudarthrosis). The safety and effectiveness..for any other conditions are unknown.'' ``Precaution:..pedicle screw..performed only by experienced..surgeons with specific training..this is a technically demanding procedure presenting a risk of serious injury to the patient.'' 

 Globally, surgeons have used pedicle screw to an extent of indiscretion (excuse me, folks, I am not pointing the finger at you.)  especially at the degenerative lumbar spines.

12 years later, we have enough literature regarding complications of pedicle screw,  of varying severity in 54% of the patients:

1. deep infection: more than 4%. According to my associate, Dr. SH Chen, who once worked at a gigantic spine unit, he said the actual infection rate was around 6%, higher than the reported statistics; some were devastating, resulting in quadriparesis or paraplegia, even death.

2. permanent nerve root Injury: 2.3% . crippled.

3. Misplacement of screw: 11-20% , some were inside the spinal canal.

4. Back muscle injury: weakness of the back.

5. Late backache requiring screw removal: 23%

6. Adjacent segment disease (ASD):  16.5% at five years and 36.1% at ten years, requiring additional surgery.

The rate of symptomatic ASD is higher in patients with transpedicular instrumentation (12.2–18.5%) compared with patients fused with other forms of instrumentation or with no instrumentation (5.2–5.6%)

(Left) Deep infection after pedicle screw fixation, Wound Dehiscence .  Right: Pus flew out flooding all over the dura sac. (Courtesy of Dr. SH Chen)

Angulation of L1-2 level (ASD), fortunately no nerve injury. 62 years lady.

T12-L1 ASD, 70 years old male, crippled, underwent 4 spine surgeries in 2 years, including once for deep infection. T12-L1 ASD, screw penetrating the disc and all screws were loosened.

 

The sad and grim scientific evidences shown above indicate that we need to rethink the use of pedicle screw, particularly in degenerative lumbar vertebrae.

Note: I invented the term: Pedicle Screw Disease, all rights reserved (joke). 

Live Lateral fusion Surgery for Malaysian Doctors & XLIF

  The Malaysian doctors encountered some trouble when performing XLIF (NuVasive).  They flied to Taipei and wanted to know what was the difference between XLIF and my designed cage using lateral access.
  They were told by XLIF Co. that stand-alone XLIF cage was effective. Also, by elevating the disc height, posterior spinal stenosis might  be relieved (so called indirect decompression) and no need to do decompression.
 My replies were: 
1. stand-alone cage has been shown that it cannot control extension and rotation. This biomechanical fact has been repeated in several papers, unless XLIF rectangular cage has some secret stabilizing mechanism built-in (a case report of XLIF cage migration).  I am wondering whether NuVasive says the same to all western surgeons including Asian ones.
2. Indirect decompression by using cage to elevate disc height is a wishful thinking. I would like to say that decompression procedure is such a simple job. Why not spend a little time to do it and go home sleep tight? Instead of leaving the decompression to the cage, and worrying about the actual outcome?
  They said it took about an hour to setup the whole operating set including probing the nerves inside the psoas muscle before starting lateral fusion procedure. I was joking that when you finish the setup, I had already left the operating table and sipping a cup of espresso. 
  Even they used neuromonitoring, patients still had paresthesia of the thigh.  Some most recent papers show that there was no safe zone or narrow margin of safety for the nerves when performing trans-psoas approach. The most secure way is to retract the psoas muscle and use the muscle to protect the nerves. 
  I told them my principle: respect the anatomy, don't burn the bridge, you or others may have to go back again.