(ii) Osteotomy for osteoarthritis of the knee

Summary

Osteotomy is a classic operation in the treatment of uni-compartimental osteoarthrosis of the knee. In the modern context it is used to correct initial varus, or valgus, deformity before slight chondral damages advance to become progressive irreversible articular disease. It has been presented as an alternative to prosthetic joint replacement, but the indications depend on the stage and articular spread of degenerative changes and on the patient's general state. Indications for surgery are very different, in most of the cases, from the indications for uni or total knee replacement.

Since the early nineties we have practiced a modern and relatively new technique in performing knee osteotomies based on a special dedicated system of instruments and plates. This opening wedge technique, when compared to Coventry's antivarus closing wedge osteotomy, inverts the method of correction, adding the wedge medially instead of removing it laterally; in case of valgus deformity osteotomy is carried out on the femoral side with a lateral opening wedge. Operative techniques of high tibial osteotomy and osteotomy of the distal femur will be illustrated with particular attention to all details of the two operations in ‘step by step’ descriptions.

Introduction

Deformity of the knee associated with osteoarthrosis (OA) is a common presenting complaint to the orthopaedic surgeon. In a normal knee, approximately 60% of the weight-bearing forces are transmitted through the medial compartment and 40% through the lateral compartment. The varus knee with uni-compartimental OA of the medial compartment has an altered alignment and consequently more load is distributed to the affected compartment. Then the medial half of the tibial plateau supports most of the body weight and the malalignment accentuates the stress on damaged articular cartilage, causing further degenerative changes and more angular deformity. In valgus deformity, the lateral plateau is the overloaded half of the joint with progressive chondral damage due to malalignment, which also makes the deformity worse as time goes by.

Osteotomy is the classic operation, in the standard orthopaedic armamentarium, to treat early degenerative arthritis of the knee and correct deformity. This procedure has a long history in orthopaedics. The first reports on osteotomies can be found in the German literature as early as the nineteenth century. Much later in modern English literature, Jackson,¹ in 1958, and Wardle,² in 1962, described the earliest techniques of proximal tibial valgus osteotomies with a lateral closing wedge.

Only in 1965 was the method popularised by Coventry.³ He modified the previously performed procedures by executing the osteotomy proximal to the tibial tubercle. This had several advantages. The osteotomy was performed closer to the area of the deformity, the bone involved was cancellous and tended to heal rapidly, and the patient could bear weight on the leg immediately, since the pull of quadriceps stabilised the osteotomy.

The medial opening wedge technique came about 10 years later. Hernigou et al.⁴ in 1987 presented a 10–13 years follow-up of 93 patients operated with the opening technique and considered that this was a suitable procedure for medial compartment narthrosis, but cautioned that ‘precise correction of malalignment is essential’ for a good long-term outcome. Fowler et al.⁵ in 2000 described a modification of the Puddu and co-workers6, 7 opening wedge technique and pointed out how ‘small corrections of 5° or less are technically easier to achieve than with a closing wedge osteotomy’.

Proximal tibial osteotomy is not so effective in cases of valgus knee, especially when the deformity is more than 10°. A major valgus deformity is often associated with a joint line that slopes superolaterally in the anterior–posterior plane, and this abnormal plane cannot be corrected unless the osteotomy is done proximal to the joint. Coventry⁸ in 1973 stated that if a knee is more than 12° valgus, or if the plane of the joint deviated from the horizontal by more than 10°, distal femoral varus osteotomy, rather than a proximal tibial varus osteotomy, should be done. The Manual of Internal Fixation, 1979 edition,⁹ contains a brief description of the use of the 90° offset blade-plate for the femoral osteotomy. More recently, some authors10, 11 discussed in detail their methods to perform the distal femoral osteotomy.

In the following paragraphs, we present our techniques to perform opening wedge osteotomies in the proximal tibia/distal femur using Puddu plates.