Allograft alone versus allograft with bone marrow concentrate for the healing of the instrumented posterolateral lumbar fusion.

BACKGROUND CONTEXT

Spondylodesis in the operative management of lumbar spine diseases has been the subject of numerous studies over several decades. The posterolateral fusion (PLF) with pedicle screw fixation is a commonly used procedure.

PURPOSE

To determine whether the addition of bone marrow concentrate (BMC) to allograft bone increases fusion rate after instrumented posterior lumbar fusion.

STUDY DESIGN

The study was prospective, randomized, controlled, and blinded.

METHODS

Eighty patients with degenerative disease of the lumbar spine underwent instrumented lumbar or lumbosacral PLF (22 men, 58 women; body mass index less than 35 for a good visualization of the PLF in the X-rays). In 40 cases, the PLF was done with spongious allograft chips alone (Group I, age 62.7 years in average, range 47-77 years, level of fusion 1-2). In another 40 cases, spongious allograft chips were mixed with BMC (Group II, age 58.5 years in average, range 42-80, level of fusion 1-3), including the mesenchymal stem cells (MSCs). Patients were scheduled for anteroposterior and lateral radiographs 12 and 24 months after the surgery and for computed tomography scanning 24 months after the surgery. Fusion status and the degree of mineralization of the fusion mass were evaluated separately by two radiologists blinded to patient group affiliation. The bony mass was judged as fused if there was uninterrupted bridging of well-mineralized bone between the transverse processes or sacrum, with trabeculation indicating bone maturation on least at one side of the spines.

RESULTS

In Group I at 12 months, the bone graft mass was assessed in X-rays as fused in no cases (0%) and at 24 months in four cases (10%). In Group II, 6 cases (15%) achieved fusion at 12 months and 14 cases (35%) at 24 months. The statistically significant difference between both groups was proven for complete fusion at both 12 (p=.041) and 24 months (p=.011). Computed tomography scans showed that 16 cases (40%) in Group I and 32 cases (80%) in Group II had evidence of at least unilateral continuous bridging bone between neighboring vertebrae at 24 months (p<.05).

CONCLUSIONS

We have confirmed the hypothesis that the autologous BMC together with the allograft is a better alternative for PLF than the allograft alone. The use of autologous MSCs in form of BMC in combination with allograft is an effective option to enhance the PLF healing.