Avoiding dislocation after hip replacement: research reviews historical findings regarding prosthesis positioning

According to the "Journal of Bone and Joint Surgery", a study used artificial intelligence to analyze the X-rays of thousands of patients after hip replacement surgery to redefine the "safe zone" of the acetabulum to help avoid the risk of dislocation
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The magazine is published by Lippincott in collaboration with Wolters Kluwer

Two key angles-anteversion and tilt-have been used to assess the risk of dislocation after total hip arthroplasty (THA), defining the "safe area" of the acetabulum where the prosthesis is implanted
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Contrary to the results of an influential study 40 years ago, according to a new study by Mario Hevesi, MD, Daniel J.

Updated analysis proposes new safe areas to reduce the risk of THA dislocation

Placing the prosthesis in the acetabular safety zone is associated with a reduced risk of postoperative hip dislocation.
Hip dislocation is one of the most common complications after THA and has a high potential impact on the quality of life of patients
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The acetabulum is the socket of the hip joint, and the ball on the top of the thigh bone (femoral head) meets it

Although the study was innovative at the time, it also had important limitations, including that it was based on only 300 tha surgeries performed by 5 surgeons
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Subsequent research has shown that many of the measured values ​​of dislocated tha are in the so-called historical safety zone

In order to establish a more advanced, scientific and rigorous safety zone
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Hevesi, Berry and colleagues analyzed the X-rays of 9,907 primary THA surgeries out of 8081 patients

Dislocations occurred in 3% of cases after an average of two years
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X-ray analysis showed that the two angles used to measure the position of the acetabular cup and establish a safe zone (anterior tilt and tilt) have important clinical findings

For the acetabular tilt angle, the latest estimated safety range is 27 to 47 degrees-similar to the 30 to 50 degree range proposed in the 1978 paper
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When the two angles are considered at the same time, the forward tilt has a greater impact on the risk of dislocation than the tilt, especially when a satisfactory forward tilt is achieved

Although the location of the safe area for men and women is similar, it is found that the surgical approach will affect the topology of the safe area, and the anterior hip replacement surgery has less effect on low-level anteversion
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In general, men have a lower risk of THA dislocation, implantation in patients with larger femoral head sizes (36 mm or larger), and direct anterior approach

Although this study is not the first to raise questions about historical safe area measurement, it provides a new and reliable safe area perspective based on nearly 10,000 patients, reflecting modern THA technology and surgical experience
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"These findings are clinically relevant because they guide the positioning of the acetabulum, and doing so may reduce the risk of dislocation in an easy-to-implement way," Dr.
Berry and co-authors concluded
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They pointed out that current robotic or surgical navigation technology can more accurately place the prosthesis in the safe area of ​​the acetabulum during THA surgery
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