Question: In patients with degenerative disc disease (DDD), is total
disc replacement (TDR) with the CHARITE artificial disc at least as good as
anterior lumbar interbody fusion (ALIF)?
Design: Randomized (unclear allocation concealment), unblinded,
controlled trial with 24-month follow-up.
Setting: 14 centers in the United States.
Patients: 304 patients (mean age, 40 y; 52% men) with single-level
discography-confirmed DDD at L4-L5 or L5-L1 who had back or leg pain without
nerve root compression with a score of =40 on a visual analogue scale
(VAS), ranging from 0 to 100, and an Oswestry Disability Index (ODI) score of
=30 for =6 months. Exclusion criteria were multilevel symptomatic DDD,
previous thoracic or lumbar fusion, previous or current lower lumbar fracture,
osteoporosis, spondylolisthesis of >3 mm, spondylosis, or scoliosis of
>11°. 265 patients (87%) were available for clinical success measures
at 24 months.
Intervention: Patients were allocated (2:1 ratio) to TDR with the
CHARITE artificial disc (n = 205) or to ALIF (n = 99). Patients in both groups
had a complete discectomy, and the disc space was prepared similarly. In the
group that received the CHARITE artificial disc (DePuy Spine, Raynham,
Massachusetts), the prosthesis end plates were inserted into the disc space in
a trajectory parallel to the vertebral end plates with positioning determined
by lateral fluoroscopy. In the ALIF group, corticocancellous autograft was
harvested from the iliac crest and packed into 2 cages (BAK Interbody Fusion
System; Zimmer Spine, Minneapolis, Minnesota) and placed in the disc
space.
Main outcome measures: Clinical success was defined as a =25%
improvement in ODI score at 24 months, no device failure, no major
complications, and no neurological deterioration. Secondary outcomes were
radiographically confirmed flexion-extension segmental range of motion,
restoration of operative level intervertebral disc height, maintenance of disc
height, and restoration of neuroforaminal height.
Main results: The groups did not differ for operative time or blood
loss. Patients in the CHARITE group had a shorter hospital stay than patients
in the ALIF group (mean, 3.7 vs 4.2 d; p = 0.004). Patients in the CHARITE
group had greater improvement in ODI and VAS scores than patients in the ALIF
group at all time-points but 24 months
(Table). Clinical success was
64% in the CHARITE group and 56% in the ALIF group, supporting the hypothesis
that CHARITE was at least as good as ALIF. Range of motion increased by 13.6%
in the CHARITE group at 24 months and decreased by 82.5% in the ALIF group.
Patients in the CHARITE group also had better restoration and maintenance of
disc height (p < 0.05).
Conclusion: In patients with degenerative disc disease, total disc
replacement with the CHARITE artificial disc was as effective as anterior
lumbar interbody fusion.
Sources of funding: Corporate and industry funds.
This trial comparing artificial disc and interbody fusion cages with
clinical and radiographic follow-up of 91.5% and 89.2%, respectively,
represents the "cleanest" comparison study for surgical treatment
of lumbar disc degeneration. The authors concluded that the CHARITE disc is a
safe and effective alternative to anterior interbody fusion for symptomatic
single-level lumbar disc degeneration based on clinical success as determined
by the ODI, VAS, complications, and neurologic status.
However, 18% of the patients undergoing fusion had persistent iliac-crest
pain. Because the ODI and VAS scales cannot discriminate lumbar from
iliac-crest pain, the iliac-crest pain may have negatively affected the
outcome in the fusion group. Furthermore, because patients knew that they
received a "motion sparing" device, this may have influenced their
perception of outcome, especially if they expected the prosthesis but received
a fusion. Unfortunately, the extent of the influence cannot be assessed with
the available data.
A perceived advantage of the artificial disc is the potential to reduce the
incidence of symptomatic adjacent level disease. Frymoyer et al., however,
comparing lumbar fusion with lumbar discectomy, found that symptomatic
degenerative disease above the fusion "appears to be an uncommon
clinical problem." By prolonging the follow-up of the present study to 5
to 10 years, the answer to this issue may be found. Furthermore, degeneration
of the facets, a potential new or continued source of pain after disc
replacement, was not addressed in this study.
Disc replacement is a surgical option with the caveat that meticulous
attention be paid to patient selection, surgical technique, and long-term
follow-up.
Frymoyer JW, Hanley EN Jr, Howe J,
Kuhlmann D, Matteri RE. A comparison of radiographic findings in fusion and
nonfusion patients ten or more years following lumbar disc surgery.
Spine. 1979;4:
435-40.4435
1979
[PubMed][CrossRef]