Commentary & Perspective

Commentary & Perspective on
"Medial Opening-Wedge High Tibial Osteotomy with Use of Porous Hydroxyapatite to Treat Medial Compartment Osteoarthritis of the Knee"
by Tomihisa Koshino, MD, PhD, et al.

Commentary & Perspective by
Allan E. Gross, MD, FRCSC*,
Mount Sinai Hospital, Toronto, Ontario, Canada

While osteotomy around the knee for the treatment of osteoarthritis has decreased in North America¹, its use has increased dramatically as an adjunct to cartilage transplantation and also to ligament reconstructive procedures in the field of sports medicine. These new applications, recent advances in the surgical technique of realignment osteotomy, and an increasing prevalence of osteoarthritis of the knee in relatively young high-demand patients will, I believe, create a renewed interest in the use of realignment osteotomy to treat osteoarthritis of the knee.

Traditionally, realignment osteotomy around the knee was done with a closing-wedge technique². Recently, however, the use of opening-wedge osteotomy, particularly that of the proximal tibia, has become more popular because³ it facilitates balancing of the collateral and cruciate ligaments and realignment of the weight-bearing axis; it preserves bone stock; and it makes subsequent total knee replacement technically easier to perform than it is after a closing-wedge osteotomy⁴.

Among its disadvantages, opening-wedge osteotomy is associated with an increased incidence of delayed union, particularly if a large correction is attempted. Also, the slope of the joint line in the sagittal plane can be altered by an opening-wedge osteotomy just as it can be after a closing-wedge osteotomy. Altering the slope of the joint line can be beneficial in cases of anterior or posterior cruciate insufficiency. However, if the osteotomy is performed only for purposes of realignment, the possibility of adversely altering the slope of the joint line must be considered.

A major difficulty in performing an opening-wedge osteotomy is obtaining appropriate biological material to maintain correction. The best material is autograft bone, but obtaining enough for large corrections necessitates harvesting bone from the iliac crest. Allograft bone could also be used for this purpose as long as morselized autograft bone was used around the allograft wedge to enhance union. In some countries, however, allograft bone is not easily available or is not used in orthopaedic practice.

In this article by Koshino et al., the authors have described the use of hydroxyapatite wedges to maintain the angle of correction. In addition to the hydroxyapatite wedge, the authors used autograft bone that was taken from the ipsilateral fibula. A 2-cm segment was resected from the midpart of the fibular shaft and divided longitudinally into four pieces. The amount of osteotomy-site opening was determined with use of a goniometer set at the angle of correction, and an appropriate hydroxyapatite wedge was then inserted. Two plates were applied with screws to hold the osteotomy. Quadriceps and range-of-motion exercises were started on the first day after surgery to obtain knee motion and were continued for three to four weeks when partial weight-bearing was started after application of a long leg cylinder cast. Full weight-bearing was started eight weeks after surgery, and the cast was removed after no changes in the opening angle of the osteotomy site were noted.

Using this technique, the authors were able to obtain an excellent correction radiographically as well as good clinical results, and they reported no recurrence of the varus deformity or collapse of the wedges.There were no nonunions, and union was noted by eight weeks. Radiographs made up to ten years postoperatively revealed that the wedges had maintained their position and original shape in the osteotomy site.

I believe that Koshino et al. have described an excellent technique. I would emphasize, however, that whether hydroxyapatite wedges or wedge-shaped allografts are used, autograft bone must still be included to enhance union. Hydroxyapatite wedges can be stored on the shelf and carry no risk of disease transmission in comparison with allograft bone.

There are, however, certain potential drawbacks of this technique. The resection of a 2-cm segment of the midpart of the fibular shaft to obtain autograft bone could lead to a nonunion of the fibula and resultant symptoms. The other preferable source of autogenous bone would be the iliac crest, but its harvest usually creates greater postoperative pain. With a closing-wedge osteotomy, of course, this is not a problem.

Another potential problem, associated with the use of hydroxyapatite wedges, involves the apparent delay in bone remodeling, which may not be favorable for performance of a subsequent total knee replacement. Also, the authors used two fixation plates, whereas most techniques involve use of only one plate or staples. Currently, there are not enough available data to determine whether total knee replacement after an opening-wedge osteotomy is likely to be easier or more difficult to perform than it would be after a closing-wedge osteotomy. Since there is no loss of bone stock, total knee replacement should be at least potentially easier to perform after an opening-wedge osteotomy. There is also the possibility that an opening-wedge osteotomy of great enough magnitude could cause leg-lengthening.

Overall, I think that the medial opening-wedge high tibial osteotomy with use of hydroxyapatite wedges is a good technique. The advantages of an opening-wedge osteotomy, in comparison with a closing-wedge osteotomy, are that it is somewhat easier to perform and is less likely to be associated with injury to the peroneal nerve, since the surgery is carried out on the medial side. There is the added advantage of achieving ligament balancing which has made this technique particularly attractive in the field of sports medicine. The major disadvantages are the potential for delayed union and nonunion and the limited degree of correction that can be obtained. The use of a bone-graft substitute that can be stored on the shelf and kept in various sizes is extremely attractive, particularly when it is accompanied by information that enables the surgeon to determine the correction that can be achieved with each wedge size and the angle at which the wedge should be inserted. There is no question that the use of opening-wedge osteotomy, despite its limitations, has caused a resurgence in the use of realignment osteotomy as a treatment modality for young patients with knee osteoarthritis, and, for this reason, this study is a very important contribution to the literature.

*The author did not receive grants or outside funding in support of the research or preparation of this manuscript. He did not receive 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, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Wright J, Heck D, Hawker G, Dittus R, Freund D, Joyce D, Paul J, Young W, Coyte P. Rates of tibial osteotomies in Canada and the United States. Clin Orthop. 1995;319;266-75.
2. Coventry MB, Ilstrup DM, Wallrichs SL. Proximal tibial osteotomy. A critical long-term study of eighty-seven cases. J Bone Joint Surg Am. 1993;75:196-201.
3. Hernigou P, Medevielle D, Debeyre J, Goutallier D. Proximal tibial osteotomy for osteoarthritis with varus deformity. A ten to thirteen-year follow-up study. J Bone Joint Surg Am. 1987;69:332-54.
4. Gill T, Schemitsch EH, Brick GW, Thornhill TS. Revision total knee arthroplasty after failed unicompartmental knee arthroplasty or high tibial osteotomy. Clin Orthop. 1995;321;10-8.