Research

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Researchers in Tromsø (Norway) have set out to answer one of the remaining difficult dilemmas in knee research: that of the osteochondral lesion.¹ Although there have been a large number of papers published on a variety of new methods of regeneration, the production of hyaline cartilage following a chondral lesion remains a controversial area, with the ‘definitive’ treatment and study probably yet some way off. There are still proponents of the simple ‘microfracture’ citing simplicity, ease of surgical technique and well published longer-term outcomes, while other surgeons prefer other, more complex procedures ranging from stem cell therapies to platelet-rich plasma and collagen sponges. We were delighted to read this updated report of a previously reported, randomised controlled trial comparing autologous chondrocyte implantation (ACI) to microfracture. Last reported at mid-term (five-year) follow-up, this cohort did not previously show an advantage to the ACI approach, and we were very pleased to see that these investigators have published their long-term results. The initial cohort consisted of 80 patients, all with an isolated symptomatic cartilage defect, randomised to one treatment or another. Outcomes were assessed using the International Cartilage Repair Society, Lysholm, SF-36, and Tegner scores along with objective weight-bearing radiographs. The bottom line — perhaps surprisingly — is that at long-term follow-up there were no differences between the two groups with regard to the clinical scores. However, there was a higher rate of failure in the ACI group (17 vs 13 patients) and more patients subsequently required total knee arthroplasty (6 vs 3 patients). However, those patients for whom treatment was effective appear to have gone on to have long-term success with significant improvements in scores relative to baseline. The message here is perhaps somewhat confusing, nevertheless it appears that, when successful, microfracture and ACI are equally effective in the long-term and about equivalent. While the study team raise some concerns about the failure rate of the ACI being higher than that of microfracture, chondrocyte implantation technology has definitely moved on somewhat in the last 15 years, and this paper certainly serves as proof of concept: when it works, it appears to work at least moderately well.

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The difficulty with radiostereometric analysis (RSA) studies is in knowing how to interpret the results. The method is sensitive for early subsidence and loss of fixation of components, for estimating wear rates, and has been used as an early surrogate marker for failure of components. One of the tricky things is that the components usually have to be modified to carry the tantalum markers. It is rare to see comparative RSA studies and, as such, only inferences can be made about the potential success or otherwise of the implant in question. We were delighted to come across this comparative study from Nijmegen (The Netherlands) where the group set out to compare the potential benefits of different fixation strategies following revision knee arthroplasty in a randomised controlled trial, using RSA as an outcome tool.² A total of 32 patients were randomly allocated to either cemented or hybrid (uncemented) stem fixation, and RSA radiographic measures were taken at regular follow-up to 24 months. In addition to reporting migration in all degrees of freedom, the investigators also reported clinical outcomes using a variety of outcome scores. Despite the accuracy of RSA as a technique and the gamut of outcome measures selected, there were no differences in any outcome measure at 24 months, however, perhaps surprisingly, there was an incidence of around one third of patients demonstrating subclinical micromotion of >1° or 1 mm of motion, despite the absence of radiographic loosening. It would appear that despite the unexpected incidence of instability, both methods of fixation are equally successful even when assessed using the most exacting radiographic and clinical outcomes possible.

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The push for a ‘gold standard’ in tissue diagnosis of periprosthetic joint infection continues to produce more and more research papers with proponents of new technologies continuing to produce evidence to support their use. Sonication is the use of ultrasound to agitate prosthesis and tissue taken from patients with a suspected periprosthetic infection, followed by the use of either traditional culture or molecular diagnostic methods on the resulting ‘sonicate’. A study from Izola (Slovenia) would seem to suggest that there is some mileage in the use of sonication, with a reported series of 87 patients all undergoing revision arthroplasty.³ The samples taken in theatre were all analysed using the polymerase chain reaction (PCR) technique, specifically aimed at the 16S gene. The authors diagnosed infection in 27 patients using the sonication method, while this was positive in just 22 cases when using the traditional tissue methods. Interestingly, in six of seven patients with a positive sonicate, the culprit was a low virulence bacteria. Despite some mixed literature surrounding the benefit or otherwise of sonication, it appears that, in this series at least, a positive benefit was definitively seen with the addition of sonication to the usual battery of microbiological tests. We do not think it will be long before the inclusion of sonication in laboratory analyses becomes the ‘standard of care’ for diagnosis of periprosthetic joint infection.

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It is rare for orthopaedic studies to be printed in the Lancet, so we were excited to read this study from Sydney (Australia) where the authors have reported their randomised controlled trial of vertebroplasty versus placebo.⁴ The trial reports the outcomes of 120 patients, all with painful acute vertebral fractures seen within six weeks of presentation. The patients were randomised to either treatment or placebo and all had numeric rating scale (NRS) back pain scores of 7 in 10, or greater, prior to enrolment in the study. Outcomes were assessed using an intention-to-treat principle and NRS pain scales, with the primary outcome measure being the proportion of patients with an NRS score < 4 at 14 days post-operatively. There was a marked difference between the groups with regard to the primary outcome score, with 44% of patients in the vertebroplasty group having pain scores of < 4 as compared with 21% in the placebo group. Vertebroplasty is a relatively benign procedure and although significant, complications are reported in the literature including cement extravasation and thermal injury, though they are few and far between. This study clearly demonstrates that significant improvements in pain outcomes can be expected in patients offered vertebroplasty following a painful osteoporotic spinal fracture.

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There is now no debate that the use of tranexamic acid during total joint arthroplasty reduces bleeding complications including transfusion. There are a number of randomised and non-randomised trials which demonstrate this to be the case. Interest has now turned to the administration route; there are a number of studies that have compared topical with intravenous administration with surprisingly little difference. Investigators in Chicago, Illinois (USA) have perhaps taken this approach to its logical conclusion and their randomised controlled trial (RCT) was designed to establish if the route of administration really needs to be parenteral or if oral administration will suffice.⁵ Their study randomised 71 patients to either oral administration (1.95 g, two hours pre-operatively) or intravenous (IV) administration (1 g prior to wound closure). The primary outcome measure was the post-operative haemoglobin and the study itself was powered only for equivalence. There were no differences in the primary outcome measure, with a mean drop of 3.45 g/dL in the oral group and 3.31 g/dL in the IV group. There were few differences in total recorded blood loss, and a single patient in each group required transfusion. However, the difference was clear to see regarding the cost, with oral formulations reported as being up to $90 cheaper than the IV preparation. This paper is a nicely executed study which seems to suggest that there is an equivalent and cheaper option to IV preparations – certainly something to at least make one pause for thought.

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Are we falling into the same trap again? Picking up on the new fad without evidence? Anterolateral ligament (ALL) reconstruction is all the rage in sport surgery camps, and like all things ‘new’, it seems that now everyone is doing some kind of extra reconstruction. Researchers in Vail, Colorado, (USA) have set out to establish what, if anything, is the benefit of additional reconstructions.⁷ Their hypothesis was that all reconstruction would offer increased rotational stability to the knee. They undertook a cadaveric study using ten fresh frozen specimens. Each knee underwent a kinematic assessment within a range of states. Initially the intact knee was tested, then progressive reconstructions were undertaken:

• Anatomic single-bundle repair (ASBR) with intact ALL

• ASBR with divided ALL

• ASBR with ALL reconstruction in angles ranging from 0° – 90°

• Unreconstructed knee

The results were surprising; it appears that the reconstruction of the ALL resulted in overconstraint when the knee was flexed beyond 30° in terms of internal rotation in all graft positions. The authors quite rightly caution that before this trend is more widely adopted, some further work is clearly required here. Overconstraint of the knee will have implications for long-term degenerative change, as well as potentially resulting in impaired function.

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Meniscal scaffolds can be used in cases of a meniscal tear or previous partial meniscectomy, with the logic being that painful irreparable meniscal defects - given time - lead to further tears, increased contact stresses in the knee joint, and ultimately to degenerative change. The concept is that the use of a biodegradable scaffold will result in the right patient in biointegration and improved functional outcomes. Of course, given the relatively poor results of meniscal repair itself in the medium to longer term, particularly in the older patient, many surgeons have treated polyurethane scaffolds with some considerable cynicism. A team from Ghent (Belgium) have reported their own experience of polyurethane scaffolds used in a relatively large number of patients and followed up over five years.⁸ The surgical team implanted 44 scaffolds for irreparable partial meniscal defects. The outcomes were assessed in terms of survival of the implant and functional outcomes. The authors report a five-year survival of just 62% and a stable cartilage status on MRI scan of a worrying 47%, perhaps reinforcing the belief in many surgical quarters that these implants are rarely indicated and have poor success even in the short term. However, when it works it does seem to improve knee function with significant clinical improvements in visual analogue scale, and knee injury and osteoarthritis KOOS scores maintained over the five years of the study.