Summary

A recent study published in The Lancet, that researchers have found several factors- specifically surgery following trauma or inflammatory arthropathy increased the risk of revision for infection in the long-term, but patients receiving a patellofemoral, unicondylar or uncemented total knee replacement had a lower risk of late revision for infection.

The US National Institutes of Health in a factsheet describes Osteoarthritis (OA) as “a degenerative disease, caused by a breakdown of cartilage (the tissue that covers the ends of bones where they form a joint). Healthy cartilage allows bones to glide over one another, and it absorbs energy from the shock of physical movement. In osteoarthritis, the surface layer of cartilage breaks down and wears away. This results in bones under the cartilage rubbing together, causing pain, swelling, and stiffness. Bone spurs develop, permanently changing the joint’s shape.”

The progression of the disease and the symptoms (pain around the knee, swelling, tenderness; stiffness after getting out of bed; altered joint function and a crunching feeling or sound of bone rubbing on bone) are very upsetting and depressing especially for those who want to be physically active. Patients must receive proper counselling from his/her physician to manage the condition and to choose suitable treatment.

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Total knee replacement (TKR) surgery is an instance in point. What are the possible risk factors for TKR? Are physicians aware of the best data on risk factors?

In a paper published on line on April 17, 2019, in The Lancet Infectious Diseases, the researchers, Lenguerrand and colleagues from the Musculoskeletal Research Unit at the University of Bristol reported having identified the most important risk factors for developing severe infection after knee replacement.

They confirmed that deep infection, affecting about one per cent of patients is a rare, but serious, “devastating complication” of knee replacement surgery. This causes considerable distress and often requires long and protracted treatments including revision surgery.

The patients with increased risk of having the joint replacement redone (known as revision) due to infection are those who are under 60 years of age, males, those with chronic pulmonary disease, diabetes, liver disease, and a higher body mass index. Patient, surgical, and health-care related factors influence the risk of developing joint infection

The researchers clarified that the heterogeneity in populations studied, short follow-up and inadequate statistical power, limit the existing evidence. Also, it does not differentiate early prosthetic joint infection which is most likely related to the intervention, from late infection, more likely to occur due to spread of bacteria via blood to other parts of the body. The researchers assessed the overall and time-specific associations of these factors with the risk of revision due to prosthetic joint infection following primary knee replacement.

“Some of these factors are modifiable, and the use of targeted interventions or strategies could lead to a reduced risk of revision for prosthetic joint infection” the researchers noted.

“Non-modifiable factors and the time-specific nature of the effects we have observed will allow clinicians to appropriately counsel patients preoperatively and tailor follow-up regimens”, they added.

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Details of the study cohort

In this largest cohort study, researchers analysed primary knee replacements, numbering about 6,79,010 done between 2003 and 2013 in England and Wales and the procedures subsequently revised for prosthetic joint infection between 2003 and 2014. They used the data from the National Joint Registry linked to the Hospital Episode Statistics data in England and the Patient Episode Database for Wales.

The follow up period for each primary replacement was a minimum of 12 months until the end of the observation period (Dec 31, 2014) or until the date of revision for prosthetic joint infection, revision for another indication, or death (whichever occurred first).

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Findings from the study

A press release from the University of Oxford highlighted the following facts:

1. This study showed the reason for surgery, the type of procedure performed and the type of prosthesis and its fixation, influenced the risk of needing revision surgery for infection.
2. Surgery performed following trauma, inflammatory arthropathy or a history of previous infection in the operated joint were more likely to be revised for an infection.
3. Cemented total knee replacements were more likely to be revised for infection compared to patients with an un-cemented implant.
4. The risk of revision was increased for patients with a posterior stabilised fixed-bearing implant or a constrained condylar (CC) implant compared to those with an unconstrained (or cruciate retaining) fixed-bearing implant.
5. And finally, the experience of the surgeon and the size of the orthopaedic centre had no or only small effects on the risk of revision for infection.

The researchers uniquely found that these important factors have a different effect depending on the post-operative period, with liver diseases or inflammatory arthropathy increasing the risk of revision for infection in the long-term but patients receiving a patellofemoral, unicondylar or uncemented total knee replacement had a lower risk of late revision for infection.

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In an accompanying comments column in the Journal, Thorsten Gehrke, Christian Lausmann, Mustafa Citak, Department of Orthopaedics, Helios ENDO-Klinik Hamburg, Germany acknowledged that to the best of their knowledge, “this is the largest cohort study to date analysing the risk factors for periprosthetic joint infection following primary total knee replacement.”

However, they criticised the study on many grounds. Although Lenguerrand and colleagues presented various patient- related risk factors for prosthetic joint infection following primary knee arthroplasty, they did not include important information such as surgical time or germ spectrum in their statistical analyses.

The commentators cited three studies that disputed convincingly the researchers’ conclusion that high-volume hospitals have a higher risk for prosthetic joint infection than low-volume hospitals.

Lenguerrand and colleagues reported that un-cemented total knee replacement cases had a lower risk of revision for prosthetic joint infection than cemented total knee replacement cases contrary to other studies of several randomised clinical trials and conclusions arrived at internationally. The critics recommended that further studies are warranted to elucidate the optimal preoperative protocol to avoid complications following total knee replacement.

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Status in India

The ICMR published an eminently readable document titled ‘Standard Treatment Guidelines- Management of Osteoarthritis Knee' in January 2017.

According to this document, the prevalence of OA knee in India was 3.28% in Delhi; 5.81% in Dibrugarh and 6.52% in Jodhpur. It also noted that a community-based cross sectional study across five sites in India conducted in a big city, a small city, a town, and a village was reported in 2016 to be as high as 28.7% (Pal et al, 2016).

Patients gather health information from the internet. It may not be authentic and at times biased because of conflict of interests. Some patients who underwent the expensive surgery may exaggerate the benefits. Is there any irrefutable evidence that private surgeons are motivated by monetary considerations to recommend total knee replacement?

A physician’s claim that his very old patient who suffered from Diabetes Mellitus and Parkinson’s disease and who had symptomatic left knee Osteoarthritis could walk within a few hours after a computer-navigated total knee replacement surgery and was fit to go home within two days may be, if true, a rare event Such anecdotal information may lead to unrealistic expectations.

Patients may ask for surgery as a prophylactic step. A truly dedicated surgeon may not rightly agree with the demand. However, brushing aside the patient’s concerns brusquely widens the communication gap. The specialist must travel an extra mile to address the concerns.

Patients must also recognise that a physician’s time is precious; they must appreciate the limitations of treatments and help to create a shared atmosphere in which the patient and the physician can take crucial treatment decisions jointly with mutual respect.

Orthopaedic surgeons may examine whether they can confidently use the objective conclusions of the Lancet study as a priceless resource in their counselling programme. To help the patient to appreciate the limitations and merits of the treatments they can share with them the summary of the recommendations from the clinical practice guidelines titled “Treatment of Osteoarthritis of the knee 2nd edition” published by the American Academy of Orthopaedic Surgeons (AAOS). An NIH fact sheet gives past, present and future developments in the field.

The tyranny of technology should not adversely impact on the shared patient-physician relationship.

Disclaimer- The views and opinions expressed in this article are those of the author's and do not necessarily reflect the official policy or position of M3 India.

Dr K S Parthasarathy is a freelance science journalist and a former Secretary of the Atomic Energy Regulatory Board. He is available at ksparth@yahoo.co.uk