Redefining the acetabular protected zone to assist keep away from the chance of dislocation after hip substitute surgical procedure


A research utilizing synthetic intelligence to investigate radiographs from 1000’s of sufferers after hip substitute surgical procedure redefines the acetabular “protected zone” to assist keep away from the chance of dislocation, stories The Journal of Bone & Joint Surgical procedure. The journal is printed within the Lippincott portfolio in partnership with Wolters Kluwer.

Two key angles – anteversion and inclination – have been traditionally measured to evaluate the chance of dislocation following whole hip arthroplasty (THA), defining an acetabular “protected zone” for implant placement. Opposite to the findings of an influential research from 40 years in the past, the acetabular protected zone is probably going totally different than beforehand reported, in accordance with the brand new analysis by Mario Hevesi, MD, PhD, Daniel J. Berry, MD, and colleagues on the Mayo Clinic, Rochester, Minn. For orthopaedic surgeons, making certain that these angles are precisely reproduced throughout hip substitute could also be a readily carried out step to assist scale back postoperative dislocation danger.

Up to date evaluation proposes new protected zone to scale back THA dislocation danger

Placement of implants inside the acetabular protected zone is related to a decreased danger of postoperative hip dislocation, which is likely one of the most typical problems following THA and has a excessive potential impression on affected person high quality of life. The acetabulum is the socket of the hip joint into which the ball on the prime of the thigh bone (the femoral head) matches. A landmark 1978 paper printed in JBJS outlined the “perfect” angles for hip implant placement to create a “protected zone” and decrease the chance of dislocation.

Though progressive in its time, that research had vital limitations, together with that it was based mostly on simply 300 THAs carried out by 5 surgeons. Subsequent analysis has proven that many THAs that dislocate have measurements inside the so-called historic protected zone. In the meantime, there have been many advances in surgical strategies over the many years, together with capsular and delicate tissue restore in addition to the popularization of the direct anterior strategy.

To ascertain a extra up-to-date and scientifically rigorous protected zone , Drs. Hevesi, Berry, and colleagues analyzed radiographs from 9,907 main THA procedures in 8,081 sufferers. The procedures have been carried out by 35 totally different orthopaedic surgeons on the Mayo Clinic between 2000 and 2017. To handle this massive quantity of radiographic measurements, the researchers used a beforehand validated, extremely exact synthetic intelligence neural community strategy.

Dislocation occurred in three p.c of instances at a mean of two years postoperatively. Evaluation of radiographs confirmed clinically vital findings for the 2 angles used to measure acetabular cup place and set up the protected zone – anteversion and inclination. The typical acetabular anteversion angle was noticed to be 32 levels amongst sufferers who didn’t have a dislocation, which was considerably increased than the “perfect” anteversion angle of 15 levels proposed by the earlier 1978 research. The researchers carried out additional analyses to optimize the acetabular protected zone and located that dislocation danger was lowest at an anteversion angle between 18 and 38 levels which was once more considerably increased than that of the historic vary of 5 to 25 levels.

For the acetabular inclination angle, the newly estimated protected zone was 27 to 47 levels – just like the 30- to 50-degree vary proposed within the 1978 paper. When the 2 angles have been thought of collectively, anteversion had a larger impression on dislocation danger than did inclination, notably offered that passable anteversion was achieved.

Whereas the placement of the protected zone values have been comparable for women and men, surgical strategy was discovered to have an effect on the topology of the protected zone, with anterior-based hip substitute approaches penalizing low values of anteversion to a lesser extent. General, the chance of THA dislocation was decrease for males, for sufferers with bigger implanted femoral head sizes (36 millimeters or bigger), and with the usage of the direct anterior strategy.

Though the research just isn’t the primary to boost questions on historic protected zone measurements, it gives a brand new and sturdy set of protected zone angles based mostly on nearly ten thousand sufferers, reflecting fashionable THA strategies and surgical expertise.

These findings are clinically related in that they information acetabular positioning and, in doing so, might mitigate dislocation danger in a readily carried out method.”

Daniel J. Berry, MD, Mayo Clinic

They word that present robotic or surgical navigation strategies might facilitate extra exact placement of implants inside the acetabular protected zone throughout THA procedures.


Journal reference:

Mario, H., et al. (2021) Redefining the 3D Topography of the Acetabular Protected Zone. A Multivariable Research Evaluating Prosthetic Hip Stability. The Journal of Bone and Joint Surgical procedure.

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