Minimally Invasive Lumbar Fusion

Lumbar fusion surgery is commonly done to treat a variety of lumbar spine conditions that may be degenerative, traumatic, or tumor-related. With the advancement of minimally invasive surgery (MIS) techniques in other fields of surgery, these techniques are increasingly being used in spine surgeries such as lumbar fusion. Compared to traditional open techniques, the minimally invasive surgery techniques offer faster recovery, less postoperative pain, and fewer complications.

 

Lumbar fusion surgery may be performed by either fusion of the vertebrae from the back, front, or sides. Lumbar fusion surgery typically involves the fusion of the adjacent vertebral bodies by removal of the intervertebral disc but may involve only the fusion of the facet joints. The lumbar fusion surgery also involves the removal of any bony or soft tissue structure impinging upon the dural tissue or spinal nerve/roots.

The fusion of the adjacent vertebrae is achieved by placing a bone graft in between the two vertebrae that heals by forming a rigid bone bridge. The height of the vertebrae after removal of the intervertebral disc is maintained by the introduction of a cage along with the bone graft. The cage may be made of metal, plastic polymer, or machined bone graft.

The fusion construct is further stabilized by the addition of screws and rods or plate and screws. The instrumentation of the segment allows the patient the ability to move without compromising the healing bone graft.

The traditional approach to the lumbar fusion construct involves an open approach. The open approach may be done from the front known as an anterior lumbar interbody fusion or from the back known as the posterior lumbar interbody fusion. Both the traditional approaches involve a large incision and cutting of significant tissues to visualize the bony landmarks and removal of compressing tissues.

Although successful, the traditional open approach is being replaced by minimally invasive techniques that achieve the same degree of fusion results. The minimally invasive techniques may be applied to either anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), or transforaminal interbody fusion (TLIF).

The minimally invasive techniques utilize smaller incisions of about 1-2 inches that may be single or multiple depending upon the procedure. More importantly, rather than the smaller incision, the minimally invasive lumbar fusion involves less cutting of the tissues.

Traditional open surgeries for lumbar fusion involve significant cutting of the paraspinal muscles when performed from the back. The cutting of the paraspinal muscles and their rigorous manipulation during the surgery often results in prolonged back pain and decreased muscle strength after the surgery. The minimally invasive techniques employed in posterior surgeries minimize the trauma to the paraspinal muscles by the use of serial dilators. The serial dilators are introduced and they dilate the space between the paraspinal muscle instead of cutting them.

The open approach from the front is often associated with a greater risk of damage to the major blood vessels and parasympathetic chain of nerves along with the cutting of the tissues to gain exposure. The minimally invasive anterior lumbar interbody fusion minimizes damage to the blood vessels/nerves and involves less cutting of the tissues to achieve fusion.

While performing lumbar interbody fusion from the back using the traditional approach the covering of the nerves known as dural sheath may be damaged. The damaged dural sheath may become scared that may make any future surgery in the area difficult. The minimally invasive surgery circumvents the route for achieving the fusion from the back that has minimum effect on the dural sheath.

Lumbar fusion surgery utilizing a minimally invasive technique involves the use of special instruments and implants. The surgeon uses a microscope/endoscope to illuminate and magnify the narrow field of the surgery. The surgeon uses tubular dilators to retract the soft tissue structures in order to reach the bony landmarks.

Once reaching the bony landmarks, the surgeon then uses the specialized instruments through the tubular dilators to remove parts of the posterior vertebrae and to remove the intervertebral disc. The surgeon then introduces the cage/spacer to maintain disc height along with bone graft material. Similar smaller percutaneous incisions are then used to introduce pedicle screws from the back. The rod on either side is then tightened over the screws to form a solid construct.

After the end of the construct, the operating surgeon withdraws the tubular dilators and the incisions are closed in layers. The procedure may be performed in an outdoor patient setting and the patient may be able to go home the same day of the procedure.

Minimally invasive lumbar fusion may be used to treat a wide range of conditions such as spondylolisthesis, herniated discs, deformity correction, and degenerative lumbar disc disease, etc. The minimally invasive lumbar fusion offers the advantage of less blood loss and lower risk of infection. The less cutting of tissues ensures reduced postoperative pain and less use of analgesics. The patients are able to get back to their day-to-day activities faster than the traditional open lumbar fusion.

Although the minimally invasive lumbar fusion offers various advantages, it is not indicated in every patient, and in some patients, the open approach may be better suited. The orthopedic surgeon attending to the patient will assess the patient’s condition and discuss the type of surgery indicated in his/her case.