In patients with concurrent hip and spine pathology, does it matter which condition is corrected first?
Click here to read the Cover Story “Aging spine poses challenges for acetabular cup positioning.”
No standard answer
With combined hip and spine disease, there is no standard answer for what is the preferred first operation. The surgeon must determine which disease is more painful and/or disabling. Total hip arthroplasty can be performed first without increased risk of dislocation after spine fusion. Instability risk after spine fusion is increased because postural change, such as with standing/sitting or bending, requires increased motion at the hip joint if the spinopelvic motion is stiff. It is mostly the mobility of the lower three lumbar vertebrae that are connected to hip mobility. Normal sitting is an angle of 60° to 70° at the hip and 20° to 30° of posterior pelvic tilt to biologically open the acetabulum for clearance of the hip, and the spine is straight. Standing is reversed, so the hip is at 170° to 190° and the pelvis is anteriorly tilted with the acetabulum more closed, and the spine is in lordosis. Bending forward involves 85° hip flexion with 12° internal rotation.
To avoid dislocation after spine fusion, the cup position for THA must accommodate the spine fusion position. If the spine fusion is in lordosis, then the pelvis will be anteriorly tilted and the acetabulum must be mechanically opened to compensate for the lost biological opening with posterior pelvic tilt. So, inclination should be at 45° and anteversion of the cup must allow combined anteversion of 35° to 45° (anteversion is most important). Conversely, if spine fusion creates a flat-back, the pelvis is posteriorly tilted and so the acetabulum is biologically opened and cup inclination can be 40° to 45° with combined anteversion of 30° to 35°. Dual-mobility articulation is a wise choice when spine fusion is present.
Therefore, the order of surgery is not important if the spine surgeon and hip surgeon communicate and THA implant positions accommodate the spine fusion position, either anticipated or completed.
Lawrence D. Dorr, MD, is professor of orthopedic surgery at the University of Southern California Keck School of Medicine in Los Angeles.
Disclosure: Dorr reports no relevant financial disclosures.
Consider patient factors
Recently, there has been increasing focus on this question due to reports of dislocations of the hip occurring more frequently in those who have had lumbar spine fusions. Overall, the literature on this topic is in its infancy. The overall increased risk, however, makes sense because the ability for the spine to move, reciprocating hip motion, is important to defining safe zones of the hip arthroplasty through the activities of daily living.
Theoretically, fusions that involve the L4/5 and L5/S1 segment will likely play a greater role than fusions at L1/2 or L2/3, or even fusions in the thoracic spine. This is due to the greater amount of lordosis the L4/S1 segments contribute to the lumbar spine relative to more cranial segments. Moreover, it is possible that fusions that are longer and have a distal instrumented vertebra to the pelvis will have an even greater risk.
My considerations that help me decipher which approach should be done first depend on a number of factors: Is the spine condition more debilitating? Is there neurologic compromise? Is there a hip flexion contracture? Will the fusion need to go to S1 with or without instrumentation to the Ilium?
If the answer to any of the above questions is yes, then I would consider performing the spine operation prior to the hip procedure.
The answer is not always black and white, and exceptions to this can be made on a case-by-case basis. Certainly, with more research, we will all have more data to support our approach to these patients and help our patients achieve maximal outcomes.
Han Jo Kim, MD, is an orthopedic spine surgeon at Hospital for Special Surgery in New York.
Disclosure: Kim reports no relevant financial disclosures.