Knee

Hyaluronic acid equivalent to steroid injections in knee osteoarthritis

Accelerated discharge may be more successful in selected patients

One of the difficulties with the two competing pressures applied by modern healthcare funders – shorter hospital stay and reduced unplanned readmissions – is that interventions to improve one are likely to adversely affect the other. An arthroplasty group in Stratford, New Jersey (USA) took a novel approach to risk stratification, to reduce length of hospital stay without resulting in higher unplanned emergency department attendances.² The study focuses on the outcomes of 995 patients, all of them inpatients undergoing primary total knee arthroplasty. The group was arbitrarily divided into short (< 3 days) or longer stays. The cohort was then analysed according to comorbidities, length of stay, deep vein thrombosis history, discharge location and requirement for post-discharge emergency department visits. The authors established that the likelihood of return to hospital after discharge could be explained by risk stratification for patient comorbidities alone. When the authors went on to further evaluate the outcomes of the emergency department visits, just 50% resulted in an admission, suggesting that emergency room visits could be decreased by resolving problems in the outpatient setting.

Cardiac Risk Index: a way of making arthroplasty safer?

All-polyethylene offers little over modular components

This very useful systematic review from Rome (Italy) and Melbourne (Australia) revisited the age-old question, should we be using all-polyethylene tibial components?⁴ Since the 1970s, materials have changed considerably, and several recent survivorship studies have demonstrated that more modern all-polyethylene tibial components have at least equivalent, and in some cases superior, rates of survival, as well as comparable clinical outcomes when compared with metal-backed tibial components for total knee arthroplasty (TKA). The advantages of all-polyethylene tibial components have been well documented, and include minimal backside wear, low component migration and minimal bone resection at the time of implantation. What’s more, all-polyethylene components are cheap! Metal-backed tibial components were developed in the late 1970s to increase the polyethylene component strength. A number of biomechanical and clinical outcome studies subsequently demonstrated improved survivorship coupled with the advantage of modular intra-operative flexibility and the option for liner exchange revision. Modular components, however, introduce the concern of backside wear due to the micromotion between the metal tray and the polyethylene insert. A total of 32 papers were included in the analysis, reporting the outcomes of 58 942 patients. The average age at surgery was 69 years for the all-polyethylene group and 70 years for the metal-backed group. Follow-up was reported to an average of six years (range 2-22 years). Clinical outcomes reviewed included clinical scores such as the Knee Society Score (KSS), Knee Society Functional Score (KSS(F)) and the Hospital for Special Surgery (HSS) score, as well as an objective assessment of range of movement. The authors were able to conclude that there was no statistically significant difference in the majority of outcome scores except for the KSS(F) between metal-backed and all-polyethylene components. On the other hand, there were significant differences in terms of complications and revision rates, with fewer complications (1.92% metal-backed vs 2.22% all-polyethylene) and revisions (1.85% metal-backed vs 2.02% all-polyethylene) in the metal-backed group. The authors estimated that the additional cost of using metal-backed components compared with all-polyethylene comes to a total of $95 000 per 100 patients, however, this is just an indirect cost estimate and does not include the costs of higher revision and complication rates associated with the all-polyethylene components. Before dismissing all-polyethylene components entirely, the authors raise an interesting point. Since elderly patients (> 70 years) are less active, possibly all-polyethylene components could be considered in this age group. Alternatively, in the younger age group, metal-backed tibial components may convey advantages of a lower revision rate and therefore justify the increased cost. These are interesting theories and ones that are currently not examined in the medical literature but with an ageing population with an increasing demand for TKA, all-polyethylene tibial components may experience a renaissance in the not-too-distant future!

Tranexamic acid: better by both routes?

Vascular calcification a poor pre-operative observation

It is hardly uncommon to notice the calcified popliteal artery prior to undertaking a knee arthroplasty; in some patients the appearance is almost like that of an angiogram. Here at 360 we have often wondered if this is associated with excess complications. It’s certainly a sign of vascular disease, however, does that equate to complications? This observational study from a study group in Ulm (Germany) was designed to establish if the presence of visible calcification on plain radiographs was associated with an increased complication rate.⁶ Their two-year study encompassed 825 patients, all undergoing total knee arthroplasty. The study team excluded patients with an absent pulse or occult vascular pathophysiology. There were signs of calcification in 268 patients, of which 54 were medial type and 214 intimal type. Whilst there were no differences in major vascular complications (just two across the whole cohort, one with and one without vascular complications), there was a higher rate of minor vascular complications (essentially wound healing problems) in patients with intimal calcification when compared with either of the other groups (6.1% vs 1.9% and 1.6%). This simple paper has quantified the excess risk associated with a commonly remarked upon radiographic sign. Quite clearly, although there is no evidence to support major complications associated with intimal calcification, the rate of minor complications is significantly higher. A simple sign with a relevant clinical message.

Robotic surgery reaching its zenith?

Robotic and computer-assisted surgery in orthopaedics have really been a solution without a problem. The accuracy of bony cuts is not limited by the surgeon’s skill but by the limitation of the power tools, and in the absence of evidence to the contrary, robotic surgery has failed to gain traction in orthopaedics. Surgeons in Glasgow (UK), presumably reasoning that achieving accurate positioning with a unicompartmental knee may well be an area in which a robot may be helpful (given the variable data on outcomes in the literature), designed a randomised prospective single-blinded study, reviewing the outcomes of 139 patients. The patients were randomly assigned to treatment with either a robotic-assisted surgical procedure using the Mako robot (Stryker, Kalamazoo, MI) or conventional surgery to implant the Zimmer Biomet (Warsaw, IN) Oxford phase 3 unicompartmental knee.⁷ Final follow-up assessed 120 patients who were available, who underwent a CT scan at three months to confirm component positioning. Although the robot was far from perfect, it did improve the positioning accuracy, with 57% positioned within 2° of the target position as compared with 26% with traditional implantation. This study does demonstrate that implantation can be made more accurate using a robot. Nonetheless, we are slightly sceptical about the study design. The use of an arbitrary 2° of the target position as the surrogate outcome measure is slightly concerning in this study, which essentially demonstrates that the robot is slightly more accurate. If 3° or 4° had been used, would there have been any difference? And perhaps most important of all, the unanswered question is still: where should the knee be placed?

Revising the stiff knee?

Surgeons in Toronto (Canada) offer insight into perhaps one of the trickiest of clinical decisions to make: when, and how, to revise a stiff knee?⁸ Undoubtedly, patients whose post-operative result includes some significant stiffness are a bit of a mixed bag. Some will have had considerable pre-operative stiffness, some difficulties with physiotherapy, and some will have a degree of component malalignment. These authors describe the outcomes of 48 patients where they have taken the plunge and undertaken a revision arthroplasty for stiffness. The authors were able to report on a relatively large cohort of 48 patients, all presenting with a stiff knee following total knee arthroplasty. The mean age at revision was 65.5 years and all surgeries were performed by a single surgeon with pre-operative arc of stiffness < 70° or flexion contracture of > 15°. Essentially, the authors describe an open revision and arthrolysis combined with a downsizing of the polyethylene liner by 4 mm, giving a ‘sloppy’ revision. There are no long-term outcomes published for this approach (which may well open the door for catastrophic wear and macroscopic failure). However, within the constraints of the outcomes reported, this can be described as a successful approach. At a mean of 60 months’ follow-up, the authors report a mean improvement in composite flexion arc of nearly 45° – a remarkable achievement. It is easy to be either sceptical about the results presented here, or simply to write this off as a series of ‘overstuffed’ knees at initial surgery. However, it is an interesting technique and from a reputable unit it would be churlish to ignore such an honest account of treating complications.