CT Procedure Helps Identify Cause of Unexplained Pain after MoM Hip ReplacementJul 16, 2015
A recently published study demonstrated that single photon emission tomography/CT (SPECT-CT) can be useful in identifying the cause of pain in patients with unexplained pain after undergoing metal-on-metal hip replacement.
Researchers identified 15 patients who had a total of 19 metal-on-metal hip replacement devices and were experiencing unexplained pain. The researchers compared the patients before and after SPECT-CT, comparing each patient's diagnosis and treatment plan, Healio reports.
Using a chi-square test, the researchers assessed the utility of SPECT-CT to establish whether SPECT-CT data changed the diagnosis or treatment of patients' pain. The researchers report that SPECT-CT was useful for all patients, with changes in clinical management decisions made in 13 of the 19 patients with unexplained pain. The other six patients continued to have unexplained pain, but SPECT-CT confirmed the initial non-operative treatment plan should be continued. Following SPECT-CT, loosening was observed in three femoral stems and one acetabular cup and these four patients were advised to undergo revision surgery, Healio reports. In one patient with a normal SPECT-CT, there was evidence of intracapsular joint fluid on the MRI, That patient was given a local anesthetic hip injection to relieve the pain, and the revision surgery was recommended.
In patients who receive metal-on-metal hip implants, when the hip's metal components rub together during movement they create minute metallic debris that can enter the patient's bloodstream and severely damage tissue and muscle, the New York Times reports. In addition to metallic debris in the bloodstream, recipients MoM hips have reported injuries including pain, loosening of the joint, hip dislocation, difficulty walking, and cysts around the joint. Many of these patients have undergone additional surgery (revision surgery) to remove and replace metal hips with safer, more reliable models.
MoM hip implants have been problematic worldwide, with reports of higher than expected early failure rates for the devices and high rates of injuries and complications, which have led to additional surgery for many recipients, Consumers Union reports. Manufacturers including DePuy Orthopaedics, Biomet, Stryker, and Smith & Nephew have recalled their hips. Thousands of hip recipients have sued device manufacturers over injuries and complications they allege are due to the MoM hips' defective designs. Stryker and Biomet have reached settlements in multidistrict litigations over their MoM hips.
In October 2014, the European Commission's Scientific Committee on Emerging and Newly Identified Health Risks (SCENHIR) issued an opinion on the safety of metal-on-metal hip devices. SCENHIR recommended annual follow-up for the life of the joint for patients who receive large-head devices and for patients with special risk factors like small component size and female gender. SCENHIR recommends all patients undergo clinical and radiographic examination during follow-up. The committee recommends metal ion testing on a routine basis for patients with large-head MoM hips and for hip resurfacing patients in the first postoperative years and thereafter depending on device performance.
The SPECT-CT study was published in April in the Journal of Arthroplasty. The researchers concluded that SPECT-CT should be reserved as a specialist test in cases where conventional investigations fail to identify potential causes of hip pain.