To The Editor:

We read the article,“Osteonecrosis of the Knee After Laser or Radiofrequency Assisted Arthroscopy: Treatment with Minimally Invasive Knee Arthroplasty”(1) with great interest and would like to express some comments.

The authors report that subchondral osteonecrosis was caused by laser and radiofrequency energy used during arthroscopic surgery(1), and there are published reports that have reached similar conclusions regarding the use of laser surgery(2-4). In contrast, there is only one case report that attributes osteonecrosis to radiofrequency energy(5).

We question how the authors made a preoperative diagnosis of osteonecrosis. Bonutti et al.(1)state that osteonecrosis was diagnosed by comparison of preoperative and postoperative MR images. In their figure 1 the MR images are T1-weighted. However, it is well known that an early finding of osteonecrosis, bone marrow edema, cannot be determined with T1-weighted MR images(6). Rather, fat- suppression T2-weighted images are diagnostic for the earliest stages of osteonecrosis. In additon, the duration between with the injury and MR imaging was not reported. During the first 4-6 weeks after injury, there may be a “window period” in which no pathological changes can be determined with MR imaging(7). Thus, osteonecrosis may have resulted from the initial injury, and may not have been attributable to the arthroscopic surgery.

As emphasized in the article, postmenisectomy syndrome is an important cause of osteonecrosis(1), but it is not clear from the article that the 10 patients who had been reported to have osteonecrosis due to radiofrequency energy had undergone menisectomy.(1). If menisectomy was performed, postmenisectomy syndrome may be the cause of osteonecrosis at least in some of these patients.

Pape et al.(7) reported the incidence of osteonecrosis in patients with knee pain to be 3.4% in patients over 50 years of age and 9,4% in patients older than 65.(8). Thus, the probability of spontaneous osteonecrosis as the etiology of osteonecrosis in the series reported by Bonutti et al., where the mean age of the patients was 69, cannot be excluded.

Experimental studies have shown that radiofrequency energy when used for chondroplasty can cause chondrocyte death (9,10). In a cadaver study, heat introduced by radiofrequency reached the subchondral bone (10).

In summary, the osteonecrotic effect of radiofrequency technique which is widely used to treat intrarticular lesions has not been proved with clinical studies. However, this does not mean that radiofrequency is a harmless surgical technique because it has been shown that radiofrequency energy, when used in contact with cartilage tissue during chondroplasty, causes some degree of chondrocyte death(9,10) and delivers heat to the subchondral bone(10). We believe that with appropriate probe and energy levels, clinically successful results with minimal chondrocyte death can be obtained when using radio-frequency techniques in cartilage surgery(11).

The authors of this did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

References:

1. Bonutti PM, Seyler TM, Delanois RE, McMahon M, McCarthy JC, Mont MA. Osteonecrosis of the knee after laser or radiofrequency assisted arthroscopy: treatment with minimally invasive knee arthroplasty. J Bone Joint Surg Am. 2006;88:69-75

2. Janzen DL, Kosarek FJ, Helms CA, Cannon WD, Wright JC. Osteonecrosis after contact neodymium: yttrium aluminum garnet arthroscopic laser menisectomy. AJR Am J Roentgenol 1997; 169:855-858

3. Fink B, Schneider T, Braunstein S, Schmielau G, Rüther W. Holmium: YAG laser-induced aseptic bone necroses of the femoral condyle. Arthroscopy 1996;12:217-223

4. Rozbruch SR, Wickiewicz TL, DiCarlo EF, Potter HG. Osteonecrosis of the knee following Arthroscopic laser menisectomy. Arthroscopy 1996; 12:245-250

5. Encalada I, Richmond JC. Osteonecrosis after arthroscopic menisectomy using radiofrequency. Arthroscopy 2004;20:632-636

6. Hofmann S, Kramer J, Vakil-Adil A, Aigner N, Breitenseher M. Painful bone marrow edema of the knee: differential diagnosis and therapeutic concepts. Orthop Clin North Am 2004;35:321-333

7. Pape D, Seil R, Kohn D, Schneider G. Imaging of early stages of osteonecrosis of the knee. Orthop Clin North Am 2004;35: 293-303

8. Pape D, Seil R, Fritsch E, Rupp S, Kohn D. Prevalence of spontaneous osteonecrosis of the medial femoral condyle in elderly patients. Knee Surg, Sports Traumatol, Arthrosc 2002;10:233-240

9. Lu Y, Edwards RB 3rd, Nho S, Cole BJ, Markel MD. Lavage solution temperature influences depth of chondrosit death and surface contouring during termal chondroplasty with temperature-controlled monopolar radiofrequency energy. Am J Sports Med 2002;30:667-673

10. Lu Y, Edwards RB 3rd, Cole BJ, Markel MD. Thermal chondroplasty with radiofrequency energy. An in vitro comparison of bipolar and monopolar radiofrequency devices. Am J Sports Med 2001;29:42-49.

11. Shellock FG. Radiofrequency energy induced heating of bovine articular cartilage: comparison between temperature-controlled, monopolar, and bipolar system. Knee surg Sports Traumatol Arthrosc 2001; 9:392-397