Question: In patients with adolescent idiopathic scoliosis, how do
the results of posterior spinal fusion compare when it is performed with and
without allograft bone?
Design: Randomized (allocation not concealed), blinded (surgeons, to
the point in surgery when bone graft was requested), controlled,
noninferiority trial with 2-year follow-up.
Setting: A children's hospital in Philadelphia, Pennsylvania.
Patients: 91 patients with adolescent idiopathic scoliosis who were
=21 years of age and were scheduled for posterior spinal fusion with a
multisegmented hook-screw and rod system and had a Risser score of =2.
Exclusion criteria included a preoperative curve of >80°. Follow-up was
83% (mean age, 15 y; 83% girls).
Intervention: The operation involved a standard posterior midline
incision and exposing the spine. After preparation of the hook sites and
before rod insertion, the cartilage of the lumbar facet and thoracic joints
was removed. The rods were inserted, the deformity was corrected, and a
wake-up test was done. According to the randomization schedule, the surgeon
was handed a bowl of crushed, freeze-dried corticocancellous allograft (n =
37) or an empty bowl (no graft; n = 39).
Main outcome measures: Definite pseudarthrosis (direct visualization
of a defect during surgical exploration of the fusion or broken
instrumentation seen on a radiograph) and possible pseudarthrosis (persistent
midline moderate-to-severe back pain, a defect in the fusion mass, an unfused
facet visible on a radiograph, or curve progression of >10° from that
seen on the initial erect postoperative radiograph).
Main results: No patient in the no-graft group compared with 1
patient in the allograft group had definite pseudarthrosis (0% vs 2.7%; p =
0.98). 2 patients in each group met the criteria for possible pseudarthrosis
(5.1% vs 5.4%; p = 0.65). 1 patient in the allograft group had a delayed deep
infection develop, and 1 patient in the no-graft group had a superficial wound
infection develop.
Conclusion: In patients with adolescent idiopathic scoliosis,
posterior spinal fusion with the multisegmented hook-screw and rod system is
effective without the use of supplemental bone graft.
A question facing scoliosis surgeons is what material is most effective at
achieving spinal fusion. Complications of iliac crest bone graft, such as a
24% rate of donor-site pain 4 years after surgery, have been well
described1. In
children undergoing rib resections, a substantial decline has been reported to
occur in the percent-predicted pulmonary function tests following
surgery2. In
contrast, allograft has few complications and the fusion rates are similar to
those with
autograft3.
The design of the study by Betz and colleagues goes one step further, by
using no bone graft at all. Autogenous bone harvested from spinous processes
or ribs was discarded, rather than used for bone graft, as is standard
clinical practice. While it is not the usual practice, this study makes its
point. The fact that the results showed no pseudarthrosis in the no-graft
group and an equal number with possible pseudarthrosis (n = 2) in both groups
is fascinating.
A limitation of the study was that clinical follow-up was <2 years in
20% of the no-graft group. However, 28 patients in the study had follow-up of
=5 years, with no sign of problems developing after 2 years. It remains to
be seen whether problems will develop later. Given a mean age of 14 years, and
a mean preoperative Cobb angle of 53°, one would expect a rate of
pseudarthrosis of <1%, and thus an n of 76 is insufficient to conclude that
there is no difference between groups.
If patients do well with intermediate follow-up under the extreme condition
of no bone graft at all, allograft bone combined with local autograft (spinous
process) should be sufficient in most patients with idiopathic scoliosis,
provided adequate facet destruction is performed at every level.
Skaggs DL, Samuelson MA, Hale JM, Kay
RM, Tolo VT. Complications of posterior iliac crest bone-grafting in spine
surgery in children. Spine.
2000;25:
2400-2.252400
2000
[PubMed][CrossRef]
Faro FD, Marks MC, Newton PO, Blanke K,
Lenke LG. Perioperative changes in pulmonary function after anterior scoliosis
instrumentation: thoracoscopic versus open approaches. Spine.
2005;30:
1058-63.301058
2005
[PubMed][CrossRef]
Price CT, Connolly JF, Carantzas AC,
Ilyas I. Comparison of bone grafts for posterior spinal fusion in adolescent
idiopathic scoliosis. Spine.
2003;28:
793-8.28793
2003
[PubMed]