National registry should assess implant outcome

Dr Ravi Gupta
Medical Superintendent, GMCH, Chandigarh

The withdrawal of “Metal on Metal” (MoM) total hip replacement system of Johnson and Johnson  (DePuy), and the indictment of the company by the government recently for paying compensation to the suffering patients who underwent this surgery is a matter of concern for medical men, health administrators and society. 

A committee constituted by the Government of India has recently recommended compensation to the sufferers of this procedure. The amount recommended by the committee is Rs 20 lakh to each affected patient. But the main problem is to trace the patients who suffered problems with this implant. The expected number of patients who are untraceable is more than 3,600.  Many Western countries have their dedicated hip joint registries at the national level where all the patients are registered after surgery. Due to this close monitoring, some countries, including Australia and the UK, had reported inferior outcomes in terms of early failures on an average of 7-8 years in comparison to 15 years for standard hip implants. 

As per the observations of the government committee, MoM hip prosthesis was removed from the Australian market in 2009. This was done on the recommendations and intervention from the Therapeutic Goods Administration (TGA) of Australia. The TGA took this harsh decision on the basis of the data of Australian National Joint Replacement Registry (NJRR) that showed an alarmingly high revision surgery rate in patients who underwent this surgery.

The hip replacement system in question consisted of a ball and socket component, wherein both the components were made of metal (cobalt, chromium, molybdenum).  

Cause of problem and symptoms

Due to continuous friction of the two metal components, the wear particles of the metal get collected in the tissues in the vicinity of the operated joint and tend to create inflammation and tissue necrosis. 

The collected wear particles and the inflammatory reaction of the body may present as a timorous mass known as “pseudotumour”.  This local collection of wear particles and inflammation may cause local symptoms, which may require revision surgery. It has been observed that the local symptoms are seen in approximately 18 per cent of the population which may include:

• Loosening of implant causing pain
• Pain, fever, local redness
• Creaking sound on moving the hip

Further, the worn out metal particles also enter the blood circulation and can affect the other vital organs of the body, thus giving symptoms of metal toxicity, known as metallosis. The metallosis causing general symptoms is observed in around 5 per cent of the population. The general symptoms may include:

• Cardiac symptoms (related to heart)
• Convulsions
• Headache neuropathy
• Cognitive dysfunction
• Anxiety, depression etc.
• Rashes on the skin
• Symptoms related to thyroid gland dysfunction
• Symptoms related to vision impairment in eye

The risk  of these complications are higher in obese persons, females, more active individuals, patients with bilateral hip replacement, patients with renal problems and patients with the suboptimal alignment of the implant. 

What is hip replacement & the options?

Hip replacement surgery is performed in patients whose hip joint (ball and socket) get destroyed due to ageing (degenerative joint disease) or due to other causes like inflammation, trauma and avascular necrosis etc.

Of the two components of ball and socket, the stem of the ball is fixed in the hollow canal of the thigh bone (femur), either with a fixing material (bone cement) or the step is made tight fit into the hollow canal on which there is a possibility of growth of bone due to special kind of sprays on the stem.

The socket can similarly be fixed either with bone cement or can be uncemented.

The traditional joint invented by Sir John Charnley from the UK had a small diameter of the ball (22 cm) and moved in a plastic socket. Both the components were cemented. This was the cheapest option for hip replacement with reasonably superior outcome. But the procedure required a good learning curve for the surgeon and precision at surgery was important. 

To reduce the learning curve and the zeal to further improve the outcome of surgeries, many new designs were invented across the  world. With every new design, there were changes in the nature of metal/plastic and/or size of the ball and socket and/or modularity of the implant and the original Charnley implant was monoblock.

Also, with every new design the cost of the implant was increased.  The cost of the original Charnley implant in our country is around Rs 40,000  while the cost of new designs can go upto 1.5 lakh or more. It is worth mentioning here that the outcome of the original Charnley implant in the hands of masters is no less than any of the newer designs.

Lessons to be learnt from MoM episode

1. It is high time for our country to have our own national registries for important surgeries like hip replacement so that we can assess our outcome and complications instantly as well as to ensure that tracing the patients is not a problem. 

2. We should be more stringent in granting licences to new designs of the devices, especially when the existing devices have reasonable outcomes. 

3. Lastly, sharing my personal experience, I never jump to adopt a new medical technology when the existing devices are giving good results in my hand. I usually wait for five years, during which time I am able to see the outcome and complications of the device used by others in our country or abroad.