Research

Vitamin D levels and revision arthroplasty

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It never ceases to amaze us here at 360 how orthopaedics, and orthopaedic research in particular, run in trends and fashions. Just at this point in time, vitamin D is very much in vogue for the retrospective registrar paper. Although not all of this research is valuable, and there is a danger of poor study design and a ‘me too’ attitude, there is certainly some worth in these investigations as vitamin D deficiency is easily correctable medically. This retrospective review from Charleston, South Carolina (USA) of 126 patients undergoing revision joint replacement surgery sets out to compare a number of different outcome measures between patients with normal pre-operative vitamin D levels and patients with low vitamin D levels.¹ Although there was not a huge number of patients here, the authors’ first finding was that patients whose levels were low were at statistically increased risk of periprosthetic joint infection (PJI). As such, the authors undertook a regression analysis; this therefore allowed them to control for PJI itself, following which they still discovered an increased risk of all complications at 90 days, and a higher all-cause 90-day re-operation rate. The take home message from this straightforward paper is that vitamin D deficiency should be considered a pre-operative modifiable risk factor in this patient cohort. Although the authors did not demonstrate a non-causal relationship, and a number of other variables might also warrant further consideration, this is a simple test for a simple problem that may potentially reduce morbidity and cost following revision surgery, and, as such, it merits closer scrutiny.

What is the effect of age on risk of revision?

It is widely acknowledged that not only are primary joint replacement rates increasing in the general population, but there is a specific increase in the number of patients younger than 60 years who are undergoing these procedures. The authors of this study from Oxford (United Kingdom) highlight that this is a topic of concern as joint registries have shown that the ten-year revision rates in this group are much higher than for older patient groups.² The majority of surgeons quote the joint registry data for longevity because other studies with longer follow-up are usually less representative, being restricted to specific prostheses, small populations or single-surgeon series. There is a gap in knowledge about the true effect of age and its influence on joint replacement longevity. This novel study published in The Lancet aims to determine the lifetime risk of undergoing a revision procedure after primary total hip arthroplasty (THA) or total knee arthroplasty (TKA), with data obtained from the Clinical Practice Research Datalink (based on computerised primary care medical records of a patient population of 6.5 million from 433 contributing representative UK practices) and the Office for National Statistics. From the database, the authors identified 63 158 patients who underwent a THA, and 54 276 who underwent a TKA. A total of 15% of patients were aged between 50 and 60 years, and the estimated lifetime risk of revision increased with decreasing age at the time of primary operation. In patients of 70 years, the lifetime risk of revision was between 4.4% and 7.7%. In patients aged between 60 and 70 years at the time of their original surgery, the lifetime risk of revision increased with decreasing age, reaching 15% for both TKA and THA at 60 years. The risk was higher in male patients. For women between 50 and 60 years, the lifetime risk of revision does not change much, but in men the lifetime risk is 29.6% for THA and 35% for TKA for the youngest patient group of 50 to 54 years. For those patients undergoing revision, this peaked within five years of the primary operation in all age ranges. The important message from this paper is that patients under 60 years of age stand a significant chance of revision of up to 35% should they undergo a primary THA or TKA, but not only that – the timing to revision in the majority of cases is under five years. This is of particular concern as patients of this age undergoing a revision tend to have poorer outcomes and are likely to spend most of their lives with a revision implant as opposed to their primary implant. While implant survival is just one indicator of success following a joint replacement, this paper carries an important message and the information it contains should be reflected on carefully by surgeons who perform joint replacements in patients under the age of 60 years.