hip replacement

Redefining the acetabular safe zone to help avoid the risk of dislocation after hip replacement surgery

‘The Journal of Bone & Joint Surgery’ analyze the radiograph reports of approximately a thousand patients who underwent hip replacement surgery to finally conclude the acetabular the ‘safe zone’ helping avoid the risk of dislocation. 

Contradicting many studies conducted 40 years back in time about the acetabular zone, it is likely different from the conclusions of all the previous reports that many known organizations and reputed surgeons very well accept.

The latest analysis proposes a newer safe zone to reduce THA dislocation risk

The risk of dislocation post-surgery is likely reduced when the implants are placed within the acetabular zone. The complication of dislocation is a very common following THA that had a high impact on the patient’s life quality. The top of the thigh bone, also called the femoral head, fits into the acetabulum that is the socket of the hip’s joint. 

In 1978, the JBJS defined some “ideal” angles for safe hip implant placement, promoting a lesser chance of dislocation. This study was conducted years ago when the surgical methods weren’t as innovative as today. Also, only five surgeons participated in drawing the conclusion that is based on just 300 THAs. In the modern world, the techniques have been reformed, and many have been discovered, including capsular and soft repair and the growing popularity of the direct anterior approach.

According to the latest studies,the problem of dislocation occurs two years after the surgery in a total of three percent of patients who underwent hip-replacement surgery. The report’s analysis measuring acetabular cup positioning concludes the establishment of safe zones: inclination and anteversion. Patients who did not suffer a dislocation had an acetabular anteversion angle at 32 degrees that are 15 degrees higher than that of the “ideal” angle proposed by the reports of the study conducted in 1978. The latest studies further conclude that the most suitable anteversion angle with a seemingly lower dislocation risk rate lies between 18 to 38 degrees, which is still higher than a sustainable historical range of 2 to 25 degrees.

There have been many studies about the historical safe zone and all the related questions. Still, the latest reports have provided a newer set of safe zone angles that is based on almost 10,000 patients representing updated techniques and surgical experience.  

Dr Yugal Karkhur is an MBBS, MS, DNB, and MNAMS with a fellowship in Joint preservation & Adult Hip Reconstruction Surgery (Missouri Orthopaedic Institute, USA), fellowship in Joint placement surgery, hip replacement surgery in Gurgaon (Man Superspeciality Hospital, Saket, Delhi), and a fellowship in Knee and Shoulder Arthroscopy ( Sports Injury Centre Safdarjung Hospital, Delhi). 

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