MR-Guided Focused Ultrasound for the Novel and Innovative Management of Osteoarthritic Knee Pain

Masashi Izumi; Masahiko Ikeuchi; Motohiro Kawasaki; Takahiro Ushida; Kazuo Morio; Hirofumi Namba; Thomas Graven-Nielsen; Yasuhiro Ogawa; Toshikazu Tani

Disclosures

BMC Musculoskelet Disord. 2013;14(267) 

In This Article

Results

The mean time used for preparing the system was 86 minutes (50–120 min) while the mean treatment time was 74 minutes (50–120 min). The mean therapeutic energy level was 735 Joules (491–952) and the mean number of sonication was 12.4 (10–20) per patient. The mean follow-up period was 9 (6–18) months after treatment. There were no adverse side effects or complications reported during and after treatment.

Pain Intensity Effects

The VAS scores were reduced 3 days, 10 days, and one month compared with pre-treatment in the 6 responders (Figure 4). In particular, four patients (Case 1, 4, 5, and 6) had long-lasting pain alleviation (mean VAS reduction at 6 months: 72.6%). One patient (Case 7) showed recurrence of pain at 6-month follow up. Two patients (Case 2 and 3) underwent total knee arthroplasty one month after MRgFUS treatment. One of the non-responders (Case 8) dropped out and switched to opioid therapy one month after MRgFUS treatment.

Figure 4.

VAS scores of the pain intensity during walking at each follow-up time point. Six patients (Case 1, 2, 4, 5, 6 and 7) showed good pain relief after treatment.

Pressure Pain Sensitivity

At pre-treatment and compared with the arm, the middle and posterior tibia plateau as well as posterior joint space showed significant lower PPTs (P < 0.05; Figure 5). In the 6 responders, the PPTs in medial knee were 358 kpa [290 - 431] at pre-treatment and 534 kpa [461 - 605] at post-treatment, which showed significant difference (p < 0.0001). In site-specific evaluation, the PPTs on middle, posterior joint space and tibia plateau were significantly increased after treatment (P < 0.05; Figure 5), suggesting that the nociceptive nerve terminals in the medial knee were successfully treated. In the two non-responders, the PPT values post-treatment were comparable with the pre-treatment values.

Figure 5.

PPTs at pre- and post-treatment. White bar indicates pre- treatment PPTs (n = 8). Gray and black bar indicate post-treatment PPTs of responder (n = 6) and non-responder (n = 2), respectively. # : p < 0.05 compared with Arm at pre-treatment. *: p < 0.05 compared with pre-treatment in responders. Sonications were applied to the site D, E, F.

Histopahological Evaluation

The cortical bone sample of the treated area was taken from 2 patients during TKA. Light microscopic assessment showed maintained bone morphology (Figure 6a) and normal osteocytes (Figure 6b), which demonstrated no significant focal bone necrosis due to MRgFUS treatment.

Figure 6.

Histology of the bone sample in the treated area. (a) low magnification, (b) high magnification. No significant focal bone necrosis was observed. Scale bar: 50 μm.

Case

A-82 year-old woman (Case 1) underwent MRgFUS treatment for her left knee. She had successfully undergone TKA for her right knee 5 months ago, and been scheduled surgery for her left knee. She had medial knee pain with the VAS of 78 mm and tenderness on her medial joint space and tibia plateau (pre-treatment median PPT values in the medial knee: 280 kPa). After treatment, she reported dramatic and long-lasting reduction in her left knee pain with PPTs increase (post-treatment median PPT values: 456 kPa). The clinical score was improved from 50 points in pre- to 75 points in post-treatment. At the 18-month follow-up, she was no longer suffering from severe knee pain in her daily life, and canceled her surgery. Figure 7 showed the radiological changes in this patient. MRI showed a low intensity curved line at the sonication site in T1 and T2 weighted images. In X-ray films, an osteosclerotic change was seen in accordance with the low intensity curved line in MRI. There were no findings of OA progression, osteonecrotic change, or segmental collapse of tibia plateau during follow-up period. The other patients also showed similar courses of radiographic change after treatment.

Figure 7.

Radiological changes between treatments. (a) MRI (pre-, T2WI), (b) MRI (3 months post-, T2WI), (c) MRI (3 months post-, T1WI), (d) X-p (pre-), (e) X-p (6 months post-), (f) X-p (12 months post-). Arrow heads in MRI indicate low intensity curved line at the sonication site. Arrows in X-p indicate osteosclerotic change in accordance with the line in MRI.

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