Residual FAI

Residual femoroacetabular impingement (FAI) is one of the most important causes of persistent or recurrent symptoms after hip arthroscopy. In the 2025 systematic review of revision arthroscopy, unaddressed FAI was the most common indication for revision. Residual FAI can be due to residual deformity that was incompletely removed in the primary procedure, or regrowth of a bony deformity.

Residual morphology: Residual cam morphology is the most common residual abnormality. The portion most easily missed is the superior to posterolateral head-neck junction, where visualization and fluoroscopic assessment are more difficult.

· Residual cam: incomplete restoration of head-neck offset, particularly at the superolateral or posterolateral extent of the original lesion.

· Residual pincer: persistent focal or global acetabular overcoverage, including an incompletely treated anterior rim or acetabular retroversion.

· Combined residual FAI: persistent cam and acetabular-sided morphology. This is common in revision series and may be missed when attention is focused on only one side of the joint.

Femoral and acetabular version should also be reconsidered in a failed case. Abnormal version changes where impingement occurs and can make a seemingly insignificant deformity cause symptoms.

Recurring morphology: Recurrent bony deformities are rare but theoretically may occur. A radiographic study of 47 patients found no meaningful recurrence of cam morphology 2 years post-operatively.

Suggestive symptoms: Patients with residual FAI often describe the same mechanical groin pain that was present before surgery. Pain that never meaningfully improved after the index procedure raises concern for incomplete bony correction or an incorrect original diagnosis. Initial improvement followed by recurrent pain should prompt a broader search for a new or progressive problem. Common associated causes include a recurrent or new labral tear, capsulolabral adhesions, cartilage progression, capsular insufficiency or instability, or extra-articular pain generators.

Evaluation of suspected residual FAI: Revision surgery should not be based on a postoperative radiograph alone. CT scans can also be considered in patients with suspected residual FAI to further characterize the morphology. Like pre-operative evaluation, imaging findings must correlate with history and exam findings as well as possible diagnostic injections. .

When to revise: There is no single postoperative time point at which revision becomes appropriate. Some revisions are performed within the first 6 months, whereas published series report average intervals of approximately 18-28 months between primary and revision surgery. In practice, the timeline for revision is often dependent on symptom severity and duration, patient preference, and surgical wait times.

Revision arthroscopy is most reasonable when all the following are present:

· Persistent or recurrent symptoms that are mechanically consistent with impingement and remain functionally important despite appropriate rehabilitation.

· Objective residual morphology that corresponds to the symptomatic arc of motion.

· A hip that remains suitable for preservation surgery, without advanced osteoarthritis or other structural problems that are better treated with a different operation.