Robert T. Trousdale
An osteotomy about the knee is a reliable treatment for unicompartmental arthrosis of the knee. Alignment correction procedures about the knee have been used since their introduction by Langenbeck in the 19th century and were popularized by Jackson, Coventry, and Maquet. Paramount to success is understanding the biomechanics and pathophysiology, as well as proper patient selection and surgical execution. In this chapter the pathogenesis, diagnosis, surgical indications, surgical technique, results, and potential complications will be discussed.
Pathogenesis and Diagnosis
Osteoarthritis of the knee has many causative factors including genetic factors, major trauma or trauma from overload secondary to obesity, and/or mechanical malalignment. A concentration of force greater than that which the articular cartilage and subchondral bone can tolerate is a common theme leading to secondary knee osteoarthritis. Malalignment of the limb in excessive varus or valgus will overload the medial or lateral compartments, respectively, and is an important factor in the development of unicompartmental arthritis of the knee. The rationale for realignment osteotomy is to correct the malalignment at the knee by decreasing the excessive load across the affected compartment.
Clinical features of this disease include activity-related knee pain, which is typically located in the affected compartment. Examination should focus on knee range of motion, ligamentous stability, and excluding extra-articular causes of pain (hip, back, vascular, and soft tissue problems). Proper imaging includes radiographs of the knee in three planes and a flexed posterior-anterior weight-bearing view. A long-leg weight-bearing radiograph is essential for preoperative planning. In selected situations, MRI or bone scan may be used to study the status of the noninvolved compartment and meniscus and to look for associated chondral lesions. In most cases prior to considering surgery, patients should have pain sufficient to justify an operation and have failed a structured nonoperative treatment program including appropriate activity modification, weight reduction, use of nonsteroidal anti-inflammatory agents, bracing, and shoe wedges.
Treatment
Proper patient selection is critical. The classic indication for osteotomy is unicompartmental osteoarthritis with a secondary varus or valgus malalignment. Osteotomy also has been used for patients with localized avascular necrosis, cartilage defects, and concurrently with osteochondral allografts although little is known about the long-term results of the procedure in these conditions. Ligamentous stability is necessary, although cruciate instability is not an absolute contraindication as ligament reconstruction can be done at the same time or staged with the osteotomy. A reasonable range of motion is necessary with at least 110 degrees of flexion and no more than 10 degrees loss of extension. Age over 60 to 65 years is a relative contraindication, but physiologic age and activity are more important considerations. Inflammatory arthritis, diffuse osteoarthritis, and marked femoral-tibial subluxation are absolute contraindications. Obesity, osteoporosis, chondrocalcinosis, and marked malalignment (>20 degrees) are not strict contraindications, but the success rate and prognosis are compromised.
In general, patients with varus malalignment are best corrected on the tibial side of the joint and those with valgus malalignment are best dealt with on the femoral side to minimize postoperative joint line obliquity. Patients with severe malalignment occasionally should be corrected on both sides of the joint to minimize joint line obliquity. This chapter will focus on the correction of the more commonly seen varus-malaligned limb.
Once indications for high tibial osteotomy are obtained, the decision of whether to do a closing wedge versus an opening wedge needs to be made. Both have advantages and disadvantages (Table 23-1).
Proper Preoperative Planning
Preoperative planning is essential to achieve a proper postoperative mechanical axis. There are multiple ways to plan for an osteotomy, and below is one such technique.
P.160
|
TABLE 23-1 Advantages and Disadvantages of A Closing Wedge Versus an Opening Wedge |
||||||||||||||||||
|
||||||||||||||||||
Step 1
Using a full-length radiograph, use transparent paper to draw the contours of the whole limb. One should take into account instability of the lateral collateral ligament to avoid overcorrection with the osteotomy. If there is marked lateral collateral ligament instability, stress views can facilitate how much deformity is corrected by the instability versus bony deformity and help determine the proper correction. Depending on the severity of the medial cartilage loss, the new axis is planned to be located 10% to 40% into the lateral compartment. With increasing severity of medial compartment arthritis, the amount of correction is increased.
|
Figure 23-1 Drawing with present mechanical axis placed from center of femoral head to center of ankle. |
|
Figure 23-2 Drawing with planned mechanical axis from center of head through lateral compartment. |
Step 2
Draw the malaligned mechanical axis from the center of the hip joint to the center of the ankle (Fig. 23-1).
Step 3
Draw the new planed mechanical axis from the femoral head through the desired point in the lateral compartment (10% to 40%) to the ankle (Fig. 23-2).
Step 4
The hinge of the osteotomy is defined and connected distally to the new and old center of the ankle. This gives the angle of desired correction (Fig. 23-3).
Surgical Technique
Closing Wedge
A lateral or midline incision can be used. The anterolateral tibia is exposed to the fibula head. If a major correction is planned (>10 to 12 degrees) resection of the tibia-fibular joint can be performed with an osteotome and/or rongeur. Osteotomy of the tibia is then performed under fluoroscopic control. A K-wire is placed parallel to the joint line, approximately 2.5 cm distal to the joint line. A second K-wire is placed distally, creating a closing wedge at an angle that equals the desired amount of correction. Fluoroscopy can confirm correct size angle of the wedge. The osteotomies are then performed, protecting the posterior structures and patellar tendon. It is important to maintain the integrity of the medial cortex as this serves as a tension band when the osteotomy is closed. The bony wedge is removed, and the osteotomy is closed and fixed with staples or a small laterally based L-plate (Fig. 23-4). Prior to fixation, with the osteotomy closed, it is important to check for overall
P.161
alignment using fluoroscopy. An electrocautery cord or a long metal rod may be superimposed over the center of the hip and center of the ankle to ensure correct placement of the restored mechanical axis into the lateral compartment.
|
Figure 23-3 Hinge point identified and planned correction angle generated from hinge point to old and new ankle center. |
Opening Wedge
The knee is exposed by a longitudinal anterior or anterior-medial incision. A 2-mm K-wire is drilled parallel to the joint line, 3.5 to 4.5 cm distal to the joint line, engaging the opposite cortex. Proper position is confirmed with fluoroscopy. The osteotomy is performed distal to the K-wire to prevent intra-articular fracture into the lateral compartment. The osteotomy is performed proximal to the tibial tuberosity. The posterior structures are protected, and the osteotomy is performed leaving the lateral cortex intact, provided that no sagittal correction is needed. The posterior soft tissues are released to avoid increasing the posterior slope when the osteotomy is opened. The osteotomy is opened slowly using stacked osteotomes or a manufactured wedge to the desired correction. Proper correction is confirmed using intraoperative fluoroscopy with a long rod or a electrocautery cord.
Fixation can be obtained with a T-plate or various opening wedge plates designed for this procedure (Fig. 23-5). Small corrections (<10 degrees) can be left alone, but most surgeons favor using allograft bone or bone graft substitute to fill the defect. The plate is placed distally under the pes anserine tendons. Closure is routine over drains.
|
Figure 23-4 Ten-year postoperative radiograph after closing wedge osteotomy fixed with two staples. |
|
Figure 23-5 Postoperative radiograph after opening wedge osteotomy with simultaneous ligament reconstruction. |
Complications
Complications after upper tibial osteotomy can occur after closing or opening wedge procedures. Neurovascular problems can be avoided by proper technique and careful retraction. Fracture into the joint is probably more common with the open wedge technique and can be avoided by making sure one has osteotomized at least 90% to 95% across the proximal tibia and gradual opening of the osteotomy. Fracture of the lateral cortex or medial cortex may occur, especially in young patients with hard bone. If this occurs, making sure one obtains stable fixation will minimize the risk of this becoming problematic. Poor correction can be avoided by careful technique and the use of intraoperative fluoroscopy, but this is a relatively crude technique. Inadvertent changing of the tibial slope is more difficult to monitor. Making sure that the osteotomy is done properly in the sagittal plane and that distraction or closure of the wedge is done properly can minimize this problem. One may want
P.162
to alter the slope intentionally in three situations: (i) In patients with extension lags, decreasing the posterior tibial slope will improve extension; (ii) in patients with hyperextension, increasing the posterior tibial slope will help limit overextension; (iii) in patients with posterior knee instability, increasing the slope will improve stability in extension as the femur slides posteriorly and the tibia anteriorly in this position. Delayed or nonunions can be avoided by maximizing bony apposition and obtaining proper stability. DVT, infection, hematoma, and compartment syndrome have been described.
Postoperative Management
Antibiotics are administered for 24 hours. Drains are removed on the second postoperative day. Mobilization and partial weight bearing (approximately 15 to 20 kg) are begun immediately. With closing wedge osteotomy and good fixation, range of motion is begun at 4 or 5 days with or without a removable splint. Patients with closing wedge osteotomy fixed with staples may be immobilized in a cast for 4 to 6 weeks. If at 6 weeks radiographs show consolidation, progressive weight bearing is allowed. Opening wedge osteotomy patients can begin range of motion immediately and weight bearing after 6 to 8 weeks.
Results
Most studies with long-term results have been performed in patients treated with a closing wedge technique. Multiple authors have shown that clinical results deteriorate with time. Insall showed that at 2-year follow-up, 97% of patients had a good or excellent result. The outcome deteriorates to 85% at 5 years and 59% at 9 years. Multiple authors have also reported successful outcome, although with shorter follow-up, with an opening wedge technique. Hernigou has reported on 93 knees treated with opening wedge technique with 90% having a good result at 5 years. Success depends on multiple factors including proper correction, preoperative condition of the noninvolved compartment meniscus, and severity of obesity.
Conclusion
Realignment osteotomy for the young active patient with osteoarthritis secondary to limb malalignment is a reliable and somewhat durable procedure. Proper patient selection and surgical execution will help optimize outcome.
Suggested Readings
Aglietti P, Rinonapoli E, Stringa G, et al. Tibial osteotomy for the varus osteoarthritic knee. Clin Orthop.1983;176:239–251.
P.163
Coventry MB. Osteotomy of the upper portion of the tibia for degenerative arthritis of the knee. A preliminary report. J Bone Joint Surg. 1965;47A:984.
Fowler PJ, Tan JL, Brown GA. Medial opening wedge high tibial osteotomy: how I do it. Op Tech Sports Med. 2000;1:32–38.
Hernigou P. Open wedge tibial osteotomy: combined coronal and sagittal correction. Knee. 2002;9:15–20.
Hernigou P, Medevielle D, Debeyre J, et al. Proximal tibial osteotomy for osteoarthritis with varus deformity. A ten to thirteen-year follow-up study. J Bone Joint Surg 1987;69A:332–354.
Insall JN, Joseph DM, Msika C. High tibial osteotomy for varus gonarthrosis. J Bone Joint Surg. 1984;66A:1040–1048.
Jackson JP. Osteotomy for osteoarthritis of the knee. Proceedings of the Sheffield Regional Orthopaedic Club. J Bone Joint Surg. 1958;40B:826.
Jacobi M, Jakob RP. Open wedge osteotomy in the treatment of medial osteoarthritis of the knee. Tech Knee Surg. 2005;4:70–78.
Langenbeck B. Die subkutane Osteotomie. Dtsch Klin. 1854;6:327.
Maquet P. Valgus osteotomy for osteoarthritis of the knee. Clin Orthop. 1976;120:143–148.
Puddu G, Fowler PJ, Amendola A. Opening Wedge Osteotomy System by Arthrex: Surgical Technique. Naples, FL: Arthrex; 1998.