Lumbar Spinal Fusion
Do you suffer from chronic lower back pain? Aches and pains don’t have to be an irreversible part of aging.
Painful discs can often lead to chronic lower back pain, but you don’t have to suffer through it. There are two types of lumbar spinal fusion – posterolateral and interbody fusion – that can reduce pain, facilitate movement, and help you live a more enjoyable life. The two procedures differ in where the bone graft is placed in the spine to complete the fusion.
Posterolateral Lumbar Spinal Fusion
In posterolateral fusion, the bone graft, which functions as a bridge between vertebrae, is placed between the transverse processes. This arrangement facilitates healing of the bone from one vertebra to the other.
A posterolateral fusion is typically completed using pedicle screw fixation. Each vertebral segment in the lumbar spine contains pedicles. By fixing screws into the pedicles and joining them with a metal rod, the segments can be connected.
Most posterolateral fusions fall under one of two categories:
A one level fusion joins two vertebrae using four screws and two metal rods.
A two level fusion joins three vertebrae using six screws and two metal rods.
Your doctor will determine whether posterolateral fusion is the best option to relieve your lower back pain and recommend either a one or two level fusion depending on how many vertebrae must be joined.
Interbody Lumbar Spinal Fusion
Interbody lumbar spine fusion involves placing the bone graft in a cage between the vertebral bodies surrounding the spinal disc. To accomplish this, the disc must be removed and the vertebral endplates cleaned and prepared for graft entry. Disc removal allows the separated vertebral bodies to fuse together via the endplates.
There are two main approaches to interbody fusion:
Anterior lumbar interbody fusion (ALIF) involves placing the bone graft through an abdominal incision, or from the front. ALIF-designed cages are relatively round and large.
Posterior lumbar interbody fusion (PLIF) involves placing the bone graft through an incision in the back. PLIF cages are generally rectangular in shape. Transforaminal lumbar interbody fusion (TLIF) is a subcategory of PLIF that requires a specific placement angle. TLIF cages can either be shaped like a rectangle, or curved to resemble a boomerang.
Types of Bone Cages
Bone cages can be constructed from various materials, each offering unique benefits and drawbacks:
Poly Ethyl Ethyl Ketone (PEEK) cages mimic the strength of a durable plastic and will not obstruct view of the bone under X-ray.
Carbon Fiber cages offer similar benefits as PEEK cages while being made of a similarly tough material.
Titanium cages provide the strongest support, but may hinder X-ray views of the bone.
Cortical cages are not as strong or durable as synthetic options, but can naturally incorporate into fusions over time.
Choosing the Right Lumbar Spinal Fusion Procedure
In general, interbody fusion better facilitates spinal fusion than posterolateral fusion. This is due to the greater surface area afforded for bone joining and the transfer of part of the anterior spinal pressure to the bone graft. In certain situations, a doctor may recommend a 360-degree fusion, in which a surgeon performs a posterolateral fusion reinforced by an interbody fusion. This procedure offers the highest rate of success.