AT THE EULAR 2015 CONGRESS
ROME (FRONTLINE MEDICAL NEWS) – Knee joint distraction – a method of relieving mechanical stress on the joint by temporarily pinning it – could help some patients with osteoarthritis avoid the need for a knee prosthesis, judging from preliminary findings from a randomized, controlled, comparative trial.
At 1-year follow-up, all subscales of the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Total KOOS score were significantly and progressively improved from baseline in patients who underwent knee distraction (P < .001). Overall the mean change in the Total KOOS score was not significantly different from that in the group of patients who underwent total knee replacement (TKR); although the KOOS subscale of quality of life did show greater improvement with the prosthesis than with distraction (P = .027), it was felt that this will “level out” when data on all 60 patients included in the trial are available. This research, performed at the UMC [University Medical Center] Utrecht and Sint Maartenskliniek in Woerden in the Netherlands, highlights how knee distraction may offer a valuable alternative to TKR, particularly in younger patients with OA, according to Simon Mastbergen , Ph.D., who studies tissue degeneration and regeneration in the department of rheumatology and clinical immunology at UMC Utrecht, and associates ( Ann. Rheum. Dis. 2015;74:359-60 ).
“When you have a total knee prosthesis at a relatively young age, the outcome is not as successful as most people think,” Dr. Mastbergen said in an interview during a poster session at the European Congress of Rheumatology. Around 40% of TKRs are performed in people under the age of 65 years, he observed, and younger patients have a higher risk of revision failure because of mechanical failure as they tend to be more active than elderly patients with knee OA. Indeed, it’s been estimated that around 44% of younger patients who have TKR will need revision surgery at some point, and as secondary procedures are more difficult to perform and can be much more disabling “we need a joint-saving treatment.” Joint distraction is a surgical procedure that aims to gradually separate the two bony ends of a joint for a certain length of time. The method used by the Dutch team involved patients wearing an external frame bridging the knee that consisted of two long tubes with coiled springs inside with pins coming out that are inserted into the opposing soft tissue and bones and moved by about 5 mm each time. Patients wear the frame for 6-8 weeks and are encouraged to try to bear weight on the affected knee, with the aid of crutches if needed. The idea behind the method is that it will allow the joint to repair itself, and the team has already shown that cartilaginous tissue repair does indeed seem to occur ( Cartilage 2013;21:1660-7 ).
Dr. Mastbergen noted that patients who underwent knee joint distraction in the study directly comparing it to TKR exhibited significant widening in the joint space, which is good because it indicates that cartilage has been regained. “We feel that knee joint distraction is an alternative for those [patients] who are ready for total knee prosthesis but are actually too young for [it],” he said.
Other randomized controlled trial data from the team was presented during an oral abstract session at the meeting ( Ann. Rheum. Dis. 2015;74:108 ) and showed that knee joint distraction is also as good as high tibial osteotomy, which is another method aimed at relieving mechanical stress on the knee joint. The senior author of the team Floris Lafeber , Ph.D., who presented data on behalf of colleague Dr. Jan Ton van der Woude, noted that there were several similarities between the two procedures in that they were both joint saving and could potentially postpone TKR and had been shown to improve bone turnover and cartilaginous tissue repair.
To compare the two methods, the researchers studied almost 70 patients aged 65 years or younger with medial compartment knee OA who were indicated for high tibial osteotomy. Patients were randomized 2:1 to the two procedures, with 45 undergoing osteotomy and 22 knee joint distraction. Significant improvements in total Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ), visual analog pain, and quality of life ( EQ-5D ) scores were seen in both groups when compared with the preoperative values (P < .05). None of the parameters showed any statistically significant difference between the two procedures at 1-year follow-up. The data led to the conclusion that knee joint distraction had a clinical benefit that was comparable to osteotomy.
However, both the minimum and mean joint space width showed a steeper increase in patients randomized to the knee joint distraction group, suggesting that cartilaginous tissue repair might be better with the latter method.
The potential clinical benefit of knee joint distraction was further highlighted in another poster from the team, presented by Dr. Natalia Kuchuk, which showed the effects of the procedure were maintained at 5-year follow-up. Importantly, 80% of the 20 patients studied in this open study still had their own knee joint. The mean age of patients at the time of distraction was 48.5 years. “In young patients, knee joint distraction effectively postpones total knee arthroplasty and is the only treatment which allows regeneration of cartilage,” she said in an interview.
Dr. Lafeber also commented in an interview on the practicalities of the procedure, which is still in its experimental phases. “It’s a rather an invasive procedure but if you compare it to a total knee replacement or high tibial osteotomy it’s less invasive,” he said.
“The surgical procedure takes about half an hour, we place a few pins through soft tissue and bone and the distraction tubes are placed mediolaterally to these pins, so in fact it’s less invasive than many of the other surgical techniques.” The distraction itself is not painful, he added, and actually alleviates OA pain but patients may need painkillers and perhaps antibiotics for short periods during the method.Next steps for the team are to follow up patients in the randomized trials for a longer period of time and refine the distraction device. “This is an off-the-shelf, ‘proof-of-concept’ device, and we are now developing a more patient-friendly, smaller, lighter frame device which is also easier to place by orthopedic surgeons,” Dr. Lafeber said. “Then we will do a comparison with the proof-of-concept device.”
Reumafonds (the Dutch Arthritis Foundation), ZonMw (The Netherlands Organization for Health Research and Development), UMC Utrecht, and Sint Maartinskliniek funded the research. Dr. Mastbergen, Dr. Lafeber, and Dr. Kuchuk had no disclosures to report.
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