By definition, isthmic spondylolisthesis is the forward slippage of one vertebra over another (the one below it). It happens because there is a defect (usually a tiny crack) in the pars interarticularis (one of the supporting columns of the vertebra). That defect develops early in life before the bones are fully grown and fused.
The last lumbar vertebra (L5) is the one most likely to slip forward (over the sacrum, S1). But isthmic spondylolisthesis can develop anywhere in the lumbar spine, particularly at the L4-L5 or L3-L4 levels.
Most cases of spondylolisthesis can be treated conservatively (without surgery). This is especially true for the low-grade type. Low-grade spondylolisthesis means up to 50 per cent of the vertebral body has shifted forward. A shift forward of more than 50 per cent is classified as a high-grade slippage.
Conservative (nonsurgical) care involves physical therapy, activity modification, and sometimes bracing and/or pain relieving medications. Physical therapists teach the patients lifelong skills of management including core training, correct posture and lifting, stretching, and aerobic conditioning.
Surgery is reserved for severe cases that are extremely painful and accompanied by neurologic symptoms. At age 16, she has probably completed her growth and will be more likely to be treated as an “adult”. Conservative care is almost always recommended first — even in difficult cases.
Your surgeon will advise you as to the best treatment approach for your daughter. The decision will be made based on the grade of slippage, desired activity level, symptoms, and patient/family preferences.