An interesting article was published recently in The Journal of Arthroplasty by my friend and spine colleague, Associate Professor Aaron J. Buckland.
Traditionally, the acetabular component in a total hip arthroplasty (THA) has been placed in the same position for all patients. More recently, a number of studies have confirmed that the relationship between the lower spine and pelvis varies widely between individuals and should be taken into account when planning THA.
Patients with lumbar spine degeneration tend to lose the natural curve of their lower spine (lumbar lordosis) and develop the characteristic deformity known as “flatback”. This is turn causes a progressive loss of their protective posterior pelvic tilt and may predispose them to instability of their THA.
A retrospective analysis was performed on patients who had undergone THA. All participants had a preoperative analysis of their spinopelvic mechanics using sagittal x-rays in the sitting and standing position. They were then divided into three groups based on the severity of their lumbar flatback deformities – normal, degenerative and severe.
The three groups demonstrated significant differences in both standing and sitting sagittal alignment. The normal group had the most amount of spinopelvic tilt when transitioning from standing to sitting, whilst the severe group had the least.
Severe lumbar flatback deformities result in loss of the normal protective posterior pelvic tilt during postural changes. This appears to predispose these patients to an increased rate of THA dislocations when compared to those with normal lumbar spine mechanics.
The relationship between spine and pelvis movement varies greatly between individuals, especially for those with degenerative disease of their lumbar spine. Preoperative planning may identify these at risk patients and avoid unnecessary THA dislocations.
To view the Journal Article written by Associate Professor Aaron J. Buckland click here.
