Posterolateral Fusion

Posterolateral fusion is a fusion performed across the back parts of the spine — laying bone graft over the transverse processes and the joints at the back, and holding the segment with pedicle screws and rods — so that the vertebrae fuse together at the back. Crucially, it does not involve entering the disc space or placing a cage in the front column. It is one of the oldest and most established fusion techniques, and it can achieve a solid union, but it works only on the posterior part of the spine.

Here is my honest reasoning. Because posterolateral fusion leaves the front column — the disc space — untouched and unsupported, it does two things I regard as shortcomings. First, it does not restore the segmental lordosis, the forward curve of the level; the disc space is not opened up and rebuilt, so the shape of that segment is largely left as it is. For a surgeon who treats every case as a deformity and who wants to set the alignment deliberately, that is a fundamental limitation. Second, without the load-bearing support of a cage in the disc space, the fusion has to knit across the back alone, and the rate of a solid union is lower than when an interbody is added, with a higher chance of a non-union, or pseudarthrosis. So a posterolateral fusion on its own neither restores the alignment I want nor gives the fusion the best mechanical chance. For those reasons it is not, on its own, my operation of choice.

Where posterolateral fusion earns its place in my practice is as the posterior component of a circumferential, or 360-degree, fusion. In that setting, an interbody cage — placed from the front, the side, or through the back — restores the anterior column, the disc height and the lordosis, and does the work of alignment and indirect decompression. The posterolateral fusion and the pedicle-screw instrumentation then add a strong posterior tension band, laying bone across the back to complete a solid, circumferential union. Front and back together — the interbody restoring the shape, the posterolateral fusion locking it in from behind — give both the alignment and the union I am aiming for. In that combined role, posterolateral fusion is genuinely valuable.

The comparative literature aligns closely with this reasoning. Meta-analyses consistently show that interbody fusion achieves higher radiographic fusion rates than posterolateral fusion alone, because the interbody provides load-bearing support in the disc space, whereas posterolateral fusion leaves the anterior column unsupported and is more prone to non-union. The same studies show interbody techniques are better at restoring segmental lordosis and disc height, while posterolateral fusion frequently fails to restore the segmental shape. This is the evidence base for combining an interbody with a posterolateral fusion in a 360-degree construct. It is also honest to note that several randomised trials have found that, for well-selected, mechanically stable, well-aligned single-level cases, posterolateral fusion alone can give good results without the added cost and morbidity of an interbody — so it is not that the technique lacks value, but that in the deformity-and-alignment framework I apply, and where anterior column support is needed, I prefer to include an interbody.

Where posterolateral fusion is used as part of a 360-degree operation, recovery follows that of the combined procedure — a hospital stay of several days, help to get up and move as soon as it is safe, and a graded return to activity over the following weeks and months while the fusion becomes solid. The fused levels are now stiff, sitting within a spine whose alignment has, ideally, been restored by the interbody component. The spine is followed up over the longer term.

• —Levin JM, et al. Posterolateral fusion versus posterior lumbar interbody fusion: systematic review and meta-analysis of RCTs. (PMID 33977761 / PMC9344525)
• —Zhou ZJ, et al. Meta-analysis of instrumented posterior interbody fusion versus posterolateral fusion in the lumbar spine. (PMID 21619404)
• —McAnany SJ, et al. Posterolateral fusion versus interbody fusion for degenerative spondylolisthesis: systematic review and meta-analysis. (PMC5544162)
• —de Kunder SL, et al. TLIF versus posterolateral instrumented fusion: randomized clinical trial with 2-year follow-up. (PMID 23584162 / PMC3777065)
• —de Kunder SL, et al. TLIF versus posterolateral fusion in degenerative lumbar spondylosis: a meta-analysis. (PMID 27749558 / PMC5059060)
• —Fujimori T, et al. Does TLIF have advantages over posterolateral fusion for degenerative spondylolisthesis? (PMID 25844282)
• —Levin DA, et al. Does adding interbody fusion to posterolateral fusion increase success in degenerative spondylolisthesis? (PMID 29385121)
• —Liu XY, et al. Systematic review with meta-analysis of posterior interbody fusion versus posterolateral fusion in spondylolisthesis. (PMC3897839)
• —Moshirfar A, et al. Fusion rates of instrumented lumbar arthrodesis by surgical approach: systematic review of RCTs. (PMC3042168)
• —Dorward IG, et al. Lumbar fusion rates with local bone in posterolateral and combined posterolateral and interbody approaches. (PMC6903817)
• —Kim KT, et al. Management of chronic disabling low back pain with 360-degree fusion (concurrent PLIF, posterolateral fusion, and pedicle screws). (PMID 10528382)
• —Lidar Z, et al. RCT comparing TLIF and uninstrumented posterolateral fusion in the degenerative lumbar spine. (PMID 26225282)