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KneeFurther Opinion

One-stage versus two-stage bilateral unicompartmental knee replacement

WCW Chan, P Musonda, AS Cooper, MMS Glasgow, ST Donell, NP Walton

J Bone Joint Surg [Br] 2009;91-B:1305-9.


Osteoarthrosis of the knee is often a bilateral disease and a significant proportion of patients present with symptoms in both knees severe enough to warrant arthroplasty.  There has been considerable debate for some time now regarding bilateral total knee replacement.  Should the surgery be carried out in one sitting or staged?  The risks of doubling the surgical trauma have to be balanced against the benefits to the patient of only needing one hospital admission.  Certainly in the present economic environment where the job security of patients still working may not be all it might be then one period of time off work will be advantageous.  There are possibly also cost savings although these should not influence patient safety.  As in every controversial topic in medicine there are enthusiastic supporters for both courses of action.  If the surgery is carried out under the same anaesthetic then there are two options, simultaneous with two surgical teams or consecutive with the same team and a tea break in the middle.  As far as I am aware this issue has not been studied with respect to unicompartmental knee replacement specifically replacement of the medial compartment.  This is a large study and will be of interest to those many surgeons who carry out unicompartmental knee replacement.  The authors are honest enough to list the shortcomings but it does reflect “the shop floor” as it were.  The mean time between operations was 1.5 years which as the authors state means that at least some of the patients did not have bilateral disease at presentation but I think that this is unlikely to change the findings or conclusion.   

Thromboembolism is the main concern here.  The authors state that there is no evidence that chemical prophylaxis would reduce this risk.  As far as I am aware there is also no evidence that it would not and I must say that after reading this paper my inclination would be to use chemical prophylaxis for a one-stage bilateral case.  I would feel quite vulnerable in the present climate if a patient had a fatal pulmonary embolism and chemical prophylaxis had not been used particularly now that an oral agent is available for hip and knee replacement prophylaxis.  The three patients with cardiac complications were all ASA 3 and two had a history of cardiac disease.  In the past one of the messages from studies of one-stage bilateral knee replacement has been that the procedure should not be carried out in patients with significant medical co-morbidity.  Also looking at Figure 1 over 30% of the one-stage cases were over 70 years old (with 7.5% over 80 years).  This is a lot of surgical trauma for an older patient to cope with.  It is also of interest that none of the simultaneous one-stage cases had problems but the number is very small.  Clearly the risk in general terms is likely to be less if the anaesthetic is half as long.  Not many units however have the necessary resources to carry this out, particularly with respect to surgeon availability.  I work in a large District General Hospital but with the reduction in junior doctor’s hours I seem to have a different trainee for virtually every list that I do and there is no way I can plan to have even a trained assistant for a specific list let alone a second trained surgeon.  Private patients expect the consultant to carry out their surgery and I could envisage problems if the knee operated on by the other surgeon did badly. 

After reading this paper my conclusion is that one-stage consecutive bilateral unicompartmental knee replacement does have a place but only after careful consideration and only for younger patients who are ASA 1 or 2 with chemical thromboembolism prophylaxis.


Allum R, FRCS

Wexham Park Hospital, Berkshire, United Kingdom