Lateral Lumbar Interbody Fusion (LLIF)

In a traditional posterior approach, the surgeon accesses the spine through the back, which requires retracting or detaching the paraspinal muscles and sometimes removing bone to reach the disc space. The lateral approach accesses the spine through a small incision on your side, working through the natural muscle planes of the flank. This avoids disrupting the strong back muscles, typically results in less blood loss and post-operative back pain, and allows for a larger interbody spacer to be placed, which improves spinal alignment and provides indirect decompression of the nerves. Dr. Kazarian will recommend the approach that is best suited to your specific condition.

Lateral lumbar interbody fusion surgery typically takes between two and four hours, depending on the number of spinal levels being treated, the complexity of your condition, and whether supplemental posterior fixation with robotic percutaneous pedicle screws is required. A single-level procedure generally takes about two to three hours, while multi-level procedures may take longer. You should plan to be at the hospital for the entire day of surgery, including pre-operative preparation and initial recovery time in the post-anesthesia care unit.

Pain management after lateral lumbar interbody fusion involves a multi-layered approach to keep you as comfortable as possible. In the hospital, you will receive pain medication through your IV. Before discharge, you will transition to oral medications. Dr. Kazarian will send you home with the following medications as needed: • Tylenol (acetaminophen) 500–1000 mg every 6 hours for mild pain • Flexeril (cyclobenzaprine) 5 mg every 6 hours for muscle spasms or soreness • Oxycodone 5–10 mg every 4–6 hours for moderate to severe pain not controlled by Tylenol alone Ice therapy and frequent short walks also help reduce pain and swelling. Most patients are able to gradually wean off prescription pain medications within four to six weeks and transition to over-the-counter options. Your care team will work closely with you to adjust your pain management plan throughout your recovery.

Recovery from lateral lumbar interbody fusion is a gradual process that occurs in stages. Most patients spend one to three days in the hospital after surgery. The first two weeks at home are focused on managing pain, protecting the surgical site, and gradually increasing walking distance. Many patients notice improvement in their symptoms within the first few weeks. By six weeks, most patients experience significant improvement and should be weaning off of most pain medications. Bending, twisting, and lifting restrictions are in place for the first six weeks. At the six-week mark, most patients are performing activities of daily living, physical therapy begins, and activity increases gradually from there. The bone graft takes approximately six to twelve months to fully fuse into solid bone, and Dr. Kazarian will monitor fusion progress with periodic imaging at your follow-up appointments.

As with any major surgery, lateral lumbar interbody fusion carries certain risks, though serious complications are uncommon. Potential risks include infection at the surgical site, bleeding, blood clots in the legs or lungs, nerve injury that could cause new numbness or weakness, and adverse reactions to anesthesia. Risks specific to spinal fusion include nonunion (pseudoarthrosis), which means the bone graft does not fully fuse and may require additional treatment, and hardware complications such as screw loosening or rod breakage. There is also a long-term consideration called adjacent segment disease, in which the disc levels above or below the fusion may experience increased stress over time. Dr. Kazarian will discuss your individual risk profile based on your health, anatomy, and the specifics of your planned procedure. Choosing an experienced spine surgeon and carefully following your post-operative instructions significantly reduces the likelihood of complications.

Temporary numbness, tingling, or a burning sensation along the front or outer portion of the thigh is one of the more common side effects of the lateral approach. It occurs because the surgical corridor passes through or near the psoas muscle, which surrounds the lumbar plexus, a network of nerves that provides sensation to the thigh. During surgery, these sensory nerves may be gently stretched or temporarily affected. For most patients, this thigh numbness improves gradually over several weeks to a few months. In a small number of cases, some degree of altered sensation may persist longer. Your surgical team monitors nerve function with real-time neuromonitoring during the procedure to minimize this risk.

Hip flexor weakness refers to temporary difficulty lifting your thigh toward your chest on the side of the surgical approach. It can make activities such as climbing stairs, getting in and out of a car, or lifting your leg feel more challenging. This occurs because the psoas muscle, which is the primary hip flexor, is gently retracted during surgery to create a path to the spine. The vast majority of patients see significant improvement in hip flexor strength within four to eight weeks, and physical therapy exercises specifically targeting hip flexor recovery can help speed this process. Dr. Kazarian and your physical therapist will monitor your progress closely.

In the vast majority of cases, the titanium screws, rods, and interbody cage remain in your spine permanently and do not need to be removed. Titanium is biocompatible, meaning your body tolerates it very well, and the hardware is designed to last a lifetime. Once the bone has fully fused (typically within six to twelve months), the screws and rods serve a secondary role since the solid bone fusion itself provides the primary stability. In rare cases, hardware may need to be removed if it causes persistent discomfort, becomes loose, or if an infection develops around it. The hardware is safe for most MRI scans, though you should always inform any medical provider that you have spinal implants. You will receive an implant card with details about your specific hardware for your records.

Dr. Kazarian requires a lumbar brace (also called a lumbar orthosis or LSO) to be worn for six weeks after fusion surgery. The brace should be worn as much as possible during this period, as it provides external support to the healing spine, limits excessive bending and twisting, and serves as a helpful reminder to maintain good posture and body mechanics. In some cases, Dr. Kazarian may also prescribe a bone stimulator to help promote fusion healing. It is important to wear the brace exactly as directed, as consistent use during the first six weeks supports the best possible outcome.

Physical therapy is a critical component of your recovery and plays a major role in achieving the best possible outcome. Therapy typically begins at six weeks after surgery, once your incision has healed and Dr. Kazarian gives clearance. Early sessions focus on gentle core activation, posture training, and safe body mechanics for daily activities such as sitting, standing, and walking. As healing progresses, your therapist will introduce progressive core strengthening, flexibility exercises, and functional training tailored to your goals. Most patients attend physical therapy two to three times per week for two to four months. A home exercise program will also be prescribed for you to perform on the days between therapy visits. Consistent participation in physical therapy helps rebuild the muscular support around your spine, improves mobility, and reduces the risk of future problems.

Most patients are cleared to resume driving approximately six to eight weeks after lateral lumbar interbody fusion, though this timeline can vary based on your individual recovery, the number of levels fused, and Dr. Kazarian's assessment. You should not drive while taking any narcotic or sedating pain medications, as they impair your reaction time and judgment. Before resuming driving, you should be able to sit comfortably for at least 20 to 30 minutes, move your foot quickly and confidently between the gas and brake pedals, and check your mirrors by turning your upper body without significant pain. Dr. Kazarian will let you know when it is safe to get back behind the wheel. For the first few drives, consider starting with short trips in low-traffic areas to rebuild your confidence.

Your return-to-work timeline depends primarily on the physical demands of your occupation. Patients with sedentary or desk-based jobs can often return to work within four to six weeks, initially on a part-time or modified-duty basis if possible. Jobs requiring light physical activity such as occasional walking or standing may require eight to twelve weeks of recovery. Occupations involving moderate to heavy lifting, prolonged standing, bending, or manual labor typically require three to six months before a safe return, and Dr. Kazarian may recommend a gradual return-to-duty program. Your surgical team can provide work restriction documentation for your employer and will clear you for progressive increases in activity at each follow-up visit based on your healing progress.

The bone graft in a lateral lumbar interbody fusion typically takes six to twelve months to mature into solid, fully healed bone, though the exact timeline varies from patient to patient. Early signs of fusion are often visible on X-rays by three to four months, but solid bridging bone throughout the entire graft site generally requires nine to twelve months. Factors that influence fusion healing time include your age, nutritional status, bone density, whether you use tobacco products (which significantly impairs bone healing), and the number of levels fused. Dr. Kazarian will monitor fusion progress with periodic imaging at your follow-up appointments. It is important to understand that while you will feel progressively better during this time, the biological process of bone fusion continues working beneath the surface for many months. Following your activity restrictions and avoiding smoking are two of the most important things you can do to support successful fusion.

Dr. Kazarian completed his undergraduate education at Princeton University and earned his medical degree from the University of Michigan Medical School. He completed his orthopaedic surgery residency at Harvard Medical School and Massachusetts General Hospital, followed by a fellowship in spine surgery at the Mayo Clinic.