Everyone knows someone who has had “rods” and “screws” inserted into his spine, right? Or “pins.” Same thing.
What he (or she) is referring to is a fusion operation. This literally entails anchoring multiple vertebral bodies to one another with titanium hardware in order to stabilize the spine (or more specifically the affected spinal levels). Fusions are performed for a variety of reasons: spinal instability (due to pathology itself or due to the destabilizing nature of the procedure necessary to address said pathology), spondylolisthesis, deformity and discogenic low back pain (provided the specific pain generator is isolated). Fusions are most often performed in the context of a decompressive operation (i.e. laminectomy). In such cases, the neural elements are decompressed (described elsewhere) and the bones subsequently fused together.
The fusion portion of a particular procedure may be accomplished many different ways. Dr. Osborn utilizes two standard, time-tested techniques, PLIF and TLIF:
- PLIF (Posterior Lumbar Interbody Fusion): Through a standard laminectomy, the intervertebral disc is removed (in a near-total manner, through cautious retraction of the nerve roots). Spacers (or cages) filled with harvested or cadaveric bone are placed into the disc space (under tension) and serve to reestablish height, stabilize the spine (anterior and middle columns) and provide additional surface area for fusion. [The cages are made of PEEK (polyetheretherketone), a plastic-like polymer that has nearly the same hardness (tissue modulus) as bone.] The fusion construct is further strengthened with a pedicle screw/rod construct. Essentially, bone screws are inserted into the vertebrae and affixed to one another with titanium rods. Bone graft (harvested or cadaveric) is placed on the sides of the spine and ultimately hardens to form a solid fusion mass. This typically occurs in 6-12 weeks.
- TLIF (Transforaminal Lumbar Interbody Fusion): Unlike a PLIF, this procedure is performed through an angled approach (instead of midline as in the PLIF described above). This trajectory allows for a lesser amount of nerve root retraction (and therefore minimizes risk to these structures). In this procedure, the spinal canal is accessed by removing the (facet) joint on one side (unilateral facetectomy). This grants access to the disc space as well as both the superior and inferior nerve roots (i.e. if one is performing an L4/5 TLIF, both the L4 and L5 nerve roots are visualized). This distinguishes the procedure from a PLIF as does the placement of the PEEK cage. In a TLIF, a single cage is placed into the disc space on an angle and rotated (in order to cover the maximal amount of surface area with anterior aspect of the spinal column). In a PLIF, two cages are placed vertically (straight down) into the disc space. The TLIF is “backed up” with a pedicle screw/rod construct as in the case of a PLIF.
The PLIF and TLIF are similar procedures in that they accomplish the same thing: neural element decompression and bony fusion. All decompressive procedures create space where there is no space, freeing up the nerves and/or the sac that contains the nerves and spinal cord. The fusion portion of the procedure stabilizes the spine and slows/stops the degenerative process cold (the impetus for arthritis development is abnormal motion within a spinal segment; fusion eliminates motion entirely).
WHAT YOU WANT TO KNOW
“How long will I be laid up after surgery?”
Lumbar (or thoracolumbar) fusion procedures are typically the most painful of spinal surgeries. This is due to the muscle dissection required to expose the bones, in particular the entry points for the pedicle screws and the “lateral elements” where bone graft is placed. Muscle is a pain-sensitive structure and its manipulation responsible for the majority of postoperative pain. That said, Dr. Osborn makes every effort to preemptively control pain with aggressive usage of local anesthesia at time of surgery and opioids postoperatively (in patch and IV forms).
“How long is the typical hospital stay?”
Patients may be discharged home within 24-48 hours postoperatively. Others require longer hospital stays specifically to manage their pain. Postoperative pain is dependent on a variety of factors: number of levels exposed (operated on) at time of surgery, girth of the patient (larger patients require more dissection and therefore experience more pain postoperatively), mental attitude (a positive attitude makes a tremendous impact on one’s perception of pain) and gender (women tend to experience lesser pain than for ill-defined reasons). You will be discharged home when your pain is manageable and you are walking safely. You may otherwise require a short inpatient stay at a rehabilitation center.
“What are the chances of a failed fusion (or pseudoarthrosis)? What is the infection rate?”
Failed fusions occur for a variety of reasons and occur with an incidence of 5-10% (depending upon the literature source). Smoking dramatically impedes bony fusion so smoking cessation is MANDATED preoperatively. Poor bone quality (osteopenia) also is a risk factor for psuedoarthrosis and frank hardware dislodgement. To augment bone quality, one should supplement with vitamin D3 and calcium pre and postoperatively.
Similarly, one should aggressively supplement with vitamins C and A to improve the chances of wound healing. Wound infection (superficial and deep) occurs in approximately 5% of those undergoing lumbar fusions (much higher than those undergoing smaller, non-instrumented procedures such as a lumbar microdiscectomy). Risk factors for infection include tobacco smoking, diabetes, obesity, malnutrition and vascular disease to name a few.
Should you develop an infection, antibiotics will be prescribed. In the event these fail (or if the infection is deep-seated), Dr. Osborn will wash the surgical site out (during a second surgical procedure). This is called an I & D (incision and drainage). Antibiotics in these cases are prescribed for 12 weeks. Patients typically heal without incident.
“How long does the fusion take to occur?”
6-12 weeks. In a healthy, non-smoker and well-nourished individual, bony fusion may occur sooner. Think of the last time you had your arm or leg casted for a fracture. Same process. The implanted hardware in these cases serves as “the cast.” It is necessary only until bony fusion occurs (serving as a scaffold for fusion). It is NOT removed as a cast is thereafter however.
“I’m scared that I’ll break the screws and rods after I return to exercise. Is this possible?”
Frank hardware breakage occurs with relatively low incidence (< 1%) in uncomplicated procedures. Those procedures in which there is high stress placed upon the construct (deformity correction, for example) are associated with a higher incidence of failure. This may or may not warrant reoperation. A fractured screw on postoperative x-rays may be an incidental finding and not require surgery (in the context of a well-appearing patient without pain complaints).
Dr. Osborn is an advocate of early strength training in the wake of surgery. This will accelerate recovery times and alleviate stress on the implanted hardware (as the more rigid and stronger low back will serve as an “internal brace,” stabilizing the spine). Exercise is typically reintroduced 6 weeks postoperatively and gradually escalated in intensity over the next 4-6 months. The chances of an exercise-related hardware failure overall are extremely low.