Background
- also known as LLIF / PLIF
Complications
- all branches of lumbar plexus in psoas muscle are at risk, particularly at L2–L4 levels, during exposure, dilation, and retraction.
Iliophypogastric / ilioinguinal Nerve Injury
- The retroperitoneal approach passes through the lateral abdominal wall muscles (external oblique → internal oblique → transversus abdominis).
- The iliohypogastric and ilioinguinal nerves run between these muscle layers.
- Retraction, splitting, or cautery in this area can injure or denervate these nerves, which control internal oblique and transversus abdominis.
- The external oblique and other intact muscles continue to contract normally, creating uneven tension. → lateral abdominal wall weakness and visible protrusion — a pseudohernia, not a true hernia.

Femoral Nerve Injury
🚨 Why Quadriceps Weakness Is Concerning (femoral nerve injury)
- Most common feared complications: femoral nerve injury (runs within or anterior to psoas)
- Loss of knee extension
- Weakness in hip flexion (iliopsoas involvement)
- Reduced or absent patellar reflex
🩻 Other (less critical but possible) weaknesses
Weakness | Likely cause | Comment |
Hip adduction | Obturator nerve injury | Through medial psoas |
Foot dorsiflexion / eversion | Peroneal branch of sciatic nerve | Rare, from traction or positioning |
Hip flexion only (without quad weakness) | Genitofemoral or psoas trauma | Usually transient |