番茄社区

HONG KONG, March 23 -- Replacement of degenerative discs in the cervical spine with cadaver allografts shows early promise as an alternative to fusion or artificial discs, found researchers here.

In the first report of disc transplantation, all five patients had improved neurological symptoms and functional scores without immunoreaction, said Keith D. K. Luk, M.Ch., of the University of Hong Kong, and colleagues.

At the five-year follow-up, four patients had signs of mild disc degeneration but good motion and stability, they reported in the March 24 issue of The Lancet.

The results are promising despite the small size of the study, according to an accompanying editorial by Wafa Skalli, Ph.D., and Jean Dubousset, M.D., both of the Biomechanics Laboratory of ENSAM-CNRS in Paris.

"Nevertheless, the feasibility of the technique has now been shown and disc transplantation could be an attractive alternative for both fusion and artificial disc replacement," Drs. Skalli and Dubousset wrote.

While fusion remains the gold standard for treating disc pain unrelieved by conservative therapy, it limits motion and often speeds degeneration in adjacent segments. Many alternatives, including artificial discs, have been looked at but each has had motion, feasibility or other problems.

After 12 years experimenting with grafts in monkeys, the researchers attempted a series of five human transplantations from three young female donors who died of trauma.

The recipients, four men and one woman, ages 41 to 56 (mean 47), had single level degenerative disc herniation from cervical spondylotic myelopathy or traumatic disc herniation, typically at the C5-6 level.

The donor cervical spine segments were frozen, and then the desired disc with both endplates attached was thawed just before implantation. No internal fixation was used. Intravenous cefazolin (Ancef) 1-g twice daily was given for three days after surgery, but no immunosuppressive agents were used.

After the operation, all patients wore a cervical orthosis at all times for two weeks. Thereafter, it was worn part-time for four more weeks.

No immune reactions to the donor discs were seen. Erythrocyte sedimentation rate, C-reactive protein concentration level, peripheral white blood cell count, and differential counts were all within the normal range at short and long-term follow-up.

Dynamic active flexion-extension radiographs were taken two months after surgery then every three months.

At the five-year follow-up, the findings were:

• Neurological and functional status improved from a mean 11.0 to 14.75 on the Japanese Orthopedic Association scale that ranges from 1 to 17,

• The one patient with traumatic herniation improved from Frankel grade B paralysis to grade D on a scale of A to E,

• While most patients had no or little pain prior to surgery, none had persistent or clinically significant neck pain at rest or with movement,

• For range of motion, the mean total arc of flexion-extension was 10.1º before surgery, 5.8º at two months, and 8.7 at five years,

• Lordosis, anterior curving of the lower spine, was also well preserved,

• None of the grafts migrated or showed anterior or posterior translation, and

• Hydration status of the discs on MRI showed that two patients appeared to have live graft material.

Whereas adjacent disc degeneration has been a major problem with spinal fusion, transplantation appeared to yield only mild degeneration in the graft disc and none in the adjacent discs. The findings were:

• Mean disc height decreased, indicating mild degeneration (5.32 mm before, 5.88 mm immediately after, and 4.33 mm at five years),

• One patient developed spontaneous fusion posterior to the graft almost four years after transplantation, and

• No adjacent discs showed evidence of accelerated degeneration on radiographs or MRI.

Complications included one cases of recurrent upper limb numbness at 20 months after the operation and one case of a "foreign body in the throat" sensation in the first 18 months after surgery.

The researchers said they have done a second series of transplantations with modified techniques and are now pursuing using the grafts as a "scaffold" for cell and growth factor treatment.

"With further refinements, such transplantations could be an effective treatment for degenerative disc disease," the researchers concluded.

"Such disc transplantation could open a new dimension in the treatment of degenerative disc disease," they added.

Drs. Skalli and Dubousset agreed, and added, "This new approach could be of particular interest for younger patients for whom prevention of adjacent-level degeneration is important."

However, the editorialists cautioned that further study is needed.

"Definite conclusions require longer follow-up because allograft degradation can occur in the longer term, as in other othopaedic situations," they wrote.

The researchers reported no conflicts of interest.

Comment