THA Patients May Have Muscle Atrophy

Jennie McKee

The iliopsoas muscle plays an important part in flexing the hip joint and supporting the lumbar spine and pelvis. Atrophy of this muscle has not been noticed clinically in patients with hip osteoarthritis (OA), but it may be found in patients who undergo total hip arthroplasty (THA), according to data presented in Scientific Poster P001.

Coauthors Koh Shimizu, MD, and Sara Shimizu, MD, of the Center of Bone and Joint Surgery, Chiba Rohsai Hospital, Japan, found more muscle atrophy in the iliopsoas muscle compared with the gluteus medius muscle in patients prior to surgery, and also found that atrophic muscles did not recover sufficiently after the THA.

“The lack of improvement may be the result of inactivity during the painful preoperative OA years and the lack of activity even after successful THA,” noted Dr. Shimizu.

The researchers used magnetic resonance imaging (MRI) to preoperatively evaluate the psoas, iliacus, and gluteus medius muscles in 800 patients (116 males, 684 females; mean age, 66 years) with severe hip OA. Researchers were able to follow 458 (76 males, 382 females) for more than 3 years after surgery to investigate recovery of the muscles.

Using both coronal and transverse sections of bilateral muscles, the investigators evaluated T1-weighted images to determine the ratios of the muscle diameter and area and calculate the percentage of muscle atrophy both before and after THA.

Dr. Shimizu reported that the decreased ratio of the area in transverse sections was measured before surgery, at 1 year after surgery, and at 3 years after surgery. For the psoas muscle, they found a 52 percent decrease in muscle area prior to surgery, but the muscle gradually recovered after surgery until, at 3 years postoperatively, the decrease was just 33 percent.

Similar changes were noted for the iliacus muscle (a 43 percent decrease in muscle area prior to surgery compared with a 34 percent decrease 3 years after surgery) and the gluteus medius muscle (35 percent decrease in muscle area prior to surgery compared with a 25 percent decrease 3 years after surgery).

“We were surprised to see that the iliopsoas had more muscle atrophy than the gluteus medius muscle in patients with hip OA, not only as measured by area, but also as measured by diameter on the coronal MRI sections both preoperatively and postoperatively,” said Dr. Shimizu.

The researchers also found correlations between muscle atrophy and both duration of symptoms and limitations in range of motion. Dr. Shimizu noted that OA patients’ lack of activity before and after THA surgery may have an impact on the overall lack of muscle improvement.

“As far as we know, our study is believed to be the first to use MRI to describe the remarkable atrophy of the iliacus and psoas in hip OA patients,” noted Dr. Shimizu.

According to Dr. Shimizu, the results of this study indicate that rehabilitation after THA should include hip flexion exercises to help strengthen the iliopsoas muscle and hip abduction exercises to strengthen the gluteus medius muscle.

To view Scientific Poster P001, “Iliopsoas Muscle Atrophy was Evident in the Patients with Hip Osteoarthritis – MRI Analysis of 800 Cases,” visit Academy Hall B; to view it as an iPoster, visit http://aaos.posterview.com

Disclosure information: Neither author reports any conflicts.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS6_3_21.asp