Joint distraction can induce tissue structure modification in knee osteoarthritis, possibly reversing structural damage to cartilage tissue and delaying the need for knee replacement surgery. This is according to results of an open 1-year pilot study reported in the August issue of Annals of the Rheumatic Diseases.
Endoprosthesis currently is the accepted method for treating pain caused by end-stage knee OA. However, the growing number of procedures carries a high price tag, and there is a higher risk of failure in patients aged younger than 65 years.
With that in mind, Dr. Femke Intema of the University Medical Center Utrecht (the Netherlands) and colleagues wanted to determine whether joint distraction could halt and possibly reverse joint degeneration in knee OA (Ann. Rheum. Dis. 2011;70:1441-6).
Courtesy of Dr. Floris P.J.G. Lafeber
Knee distraction
The study included 11 men and 9 women who had knee OA and in whom knee replacement surgery was indicated in 2006-2008. Patients were an average of 48 years old; 18 of them had predominant OA in the medial compartment; the remaining two had OA in the lateral compartment. Patients had a score of 60 mm or higher on the Visual Analogue Scale (VAS) of pain, as well as radiographic signs of joint damage, and primarily tibiofemoral OA.
Joint distraction was applied for 2 months via an external fixation frame. At the 1-year follow-up, researchers evaluated tissue structure modification according to the following:
• Radiographic analysis. This showed that the mean joint space width (JSW) of the most affected compartment increased from 2.7 mm to 3.6 mm between baseline and 12 months, whereas the minimum JSW increased from 1 mm to 1.9 mm.
• Quantitative MRI analysis. At 1 year, this showed an increase in the mean thickness of cartilage over total area of bone (ThCtAB) from 2.4 mm to 3 mm in the most affected compartment, and a decrease in mean percentage area of denuded bone (dABp) from 22% to 5%. The thickness of cartilage over area of bone covered with cartilage (ThCcAB), a secondary structural outcome parameter, showed a borderline increase from 2.9 mm to 3.1 mm.
• Biomarker analysis on serum and urine samples. These showed an 11% decrease of CTXII (a collagen type II breakdown marker), and a 103% increase in PILANP/CTXII (a collage type II synthesis marker), between 6 and 12 months. These findings suggest a net increase in collagen synthesis, the researchers said.
The primary outcome parameter of this study was the WOMAC (Western Ontario and McMaster Universities) osteoarthritis index questionnaire, which decreased from 55 points at baseline to 23 points at 1 year. In all, 18 of the 20 patients showed a greater-than-10% improvement, and 16 showed a greater-than-25% improvement. There were significant improvements in the individual components of the WOMAC index, namely pain, stiffness, and function.
One secondary measure, the VAS pain score, decreased from 73 mm at baseline to 31 mm at 1 year. Physical examination of the joint, which assessed crepitus, pain on palpation, pain with flexion, and joint effusion, showed improvement from 46% to 75%.
"This study is the first to demonstrate intrinsic tissue structure repair in OA," the researchers said. "Historically, the regenerative capacity of cartilage has been questioned owing to the slow turnover rate of cartilage matrix, especially of collagen. However, this study shows that a significant amount of cartilage tissue is formed within 1 year after the distraction, demonstrating that under certain conditions, cartilage has regenerative capacity."
There is uncertainty as to the underlying mechanism of the structural repair that was seen in this study. One possibility is that temporary distraction prevents mechanical stress on the cartilage, eliminates further wear and tear, and allows tissue repair to begin, the researchers said.
For now, the researchers are unsure which patients may benefit from this procedure, as the study included only those patients who were younger than 50 years, had severe OA, and were likely candidates for joint replacement surgery. Referrals from peripheral hospitals may have led to selection bias, the researchers say.
Safety concerns exist as well. Two patients developed lung emboli and required hospitalization and anticoagulative treatment. Also, 17 patients developed single or multiple pin-tract infections, all of which were successfully treated with antibiotics.
Larger and longer trials in a variety of OA populations are needed to optimize treatment, to determine which patients would benefit the most and for the longest period of time, and to pay attention to reducing the number of complications, the researchers said.
The authors had no relationships to disclose. The Dutch Arthritis Foundation provided financial support for this study.