RESEARCH - Spinal disk: New study expands range of candidates, but experts clash over appropriate use

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Spinal disk: New study expands range of candidates, but experts clash over

appropriate use

Rheumawire

Aug 26, 2005

Janis

New York, NY - Experience is slowly building with the first artificial

spinal disk, the SB Charité III (DePuy Spine/ & , Raynham,

MA), which was launched in the US late last year.

Five-year follow-up data for more than 700 patients who had total-disk

replacement (TDR) suggest that the device might be safe and effective in a

wider range of patients than previously thought, Dr Kang-jun Yoon (St

's Hospital, Seoul, Korea) and colleagues reported recently [1].

Results are good so far in elderly patients, in patients with both back pain

and radicular leg pain, and in those with two- or three-level disk

replacements, but not in obese patients.

Era of reconstruction in spinal surgery

Dr Blumenthal (Texas Back Institute, Plano), who conducted one of the

studies that led to FDA approval of this implant, tells rheumawire that this

study adds to the evidence that disk replacement should be viewed as an

alternative therapy to spinal fusion for lumbar degenerative-disk disease.

However, having this alternative changes the surgical management of

degenerative-disk disease from salvage surgery (spinal fusion) to joint

reconstruction. " We are many years behind hip and knee replacements, but we

are finally entering the era of reconstruction in spinal surgery, "

Blumenthal says.

However, Dr Russel C Huang (Hospital for Special Surgery, New York, NY), who

has also conducted studies of TDR, urges caution: " I think that the gold

standard remains fusion. TDR was approved for use in the US in October 2004,

and therefore domestic experience with the implants is very brief. In my

mind, the technology remains essentially experimental, as the long-term

performance of these implants is not well understood. "

Review five years after implantation

Yoon and colleagues analyzed outcomes of TDR in patients 21 to 81 years

(mean age 44.8 years) who had at least five years of follow-up. Most of

these patients had single-level procedures, most commonly at L4-L5, followed

by L5-S1. Yoon did two-level disk replacements in 92 patients and

three-level disk replacements in four patients.

The most significant observations in this study were:

No significant difference in outcomes between the single-level and

multilevel procedures.

No significant difference in outcomes between patients older than 65

and those younger than 65.

Outcomes were poor in obese patients with more than 40% body fat.

A 52% increase in disk height.

A 23% gain in intravertebral foramen.

A 5.3-point reduction in visual analog scale (VAS) scores for leg

pain.

A 4.6-point reduction in VAS scores for back pain.

Within two weeks of surgery, 85% of patients returned to work.

These data may expand the population of candidates for TDR. Huang previously

reported that only 5% of patients scheduled for lumbar fusion at his

hospital were candidates for TDR [2]. Most had two or more

contraindications, such as neural compression facet pathology, central or

lateral recess stenosis, facet arthrosis, herniated nucleus pulposus, and

radiculopathy (which is listed as a contraindication in the FDA approval).

Huang says that other contraindications are spondylolisthesis,

spondylolysis, end-plate defects (osteoporosis, interbody pseudoarthrosis),

and deformities such as scoliosis.

Yoon emphasizes that impeccable positioning of the implant is crucial: " On

the L4-L5 level, the iliolumbar vein was always ligated, and the sympathetic

chain was retracted laterally with a prepared annulus. " A vertebral body

retractor that Yoon designed himself was used to preserve the cartilage end

plate and to properly position the implant. This made it possible to

visualize and remove migrated disk material and to change the implant's

position without damaging the vertebral bodies or end plates.

Blumenthal and Huang agree that the long-term value of TDR likely depends on

whether it can reduce the chance that the spinal level adjacent to the one

with the new disk will degenerate. Blumenthal says that the Charité

artificial disk was designed to prevent that problem and that biomechanics

studies show that it should be successful. " But, " he adds, " we need at least

five years of clinical experience to determine whether it actually decreases

stress transfer to the next segment up, compared with the stress transferred

up from fused vertebral segments. "

" TDR probably will lower the rate of adjacent-level degeneration relative to

fusion. The question is how much, " Huang says. " Currently, there are no

class 1 data to prove that TDR reduces adjacent-level disease, only some

very circumstantial evidence that suggests the rate may be lowered by a

well-functioning TDR. "

Superior to spinal fusion?

The pivotal trial that led to FDA approval of the Charité disk in the US was

designed to determine whether the device was equivalent to spinal fusion.

However, Blumenthal tells rheumawire that new data on pain and function

outcomes suggest that TDR " may turn out to be superior " to spinal fusion.

Until such trials are completed and published, Huang says, " the management

of degenerative-disk disease " should not change. " In other words, we should

not extend our surgical indications now that we have a new implant. A

patient who is not a good candidate for spinal fusion is not a good

candidate for TDR. "

According to Huang, ideal candidates for TDR have minimal psychosocial

comorbidities, a concordant diskogram at the index level, a negative

diskogram at adjacent levels, and no contraindications (eg, stenosis,

osteoporosis, large herniated nucleus pulposus, instability, scoliosis, or

spondylolisthesis). " In addition, I consider female gender to be a relative

contraindication [because of] the risk of implant subsidence should the

patient develop significant osteoporosis in the future, " he says.

Sources

Yoon K, Hwange I, Ha S, et al. Artificial disc replacement

with Charité III in lumbar disc disease: 5 years follow up on 653 patients.

Spine Arthroplasty Society Global Symposium on Motion Preservation

Technology; May 4-7, 2005; New York, NY.

Huang RC, Lim MR, Girardi FP, et al. The prevalence of

contraindications to total disc replacement in a cohort of lumbar surgical

patients. Spine 2004; 29:2538-2541.

Not an MD

I'll tell you where to go!

Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org