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High Tibial Osteotomy: Does Navigation Improve Results?

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Abstract

Between January 2003 and March 2006, the authors performed 67 open-wedge high tibial osteotomies (HTO) for treatment of genu varum and osteoarthritis. Through comparison of two groups, the study sought to answer whether computed tomography (CT)-free navigation is feasible for HTO and will provide a more accurate correction angle without giving rise to additional complications. The results showed a significantly higher accuracy in achieving the proper leg axis correction (P<.016) when HTO was performed with navigation. Navigation in HTO, which allows intraoperative calculation of the leg axis, seems to be a reliable and safe procedure. Knowing that clinical results of HTO in varus deformity of the leg axis are closely connected to correct postoperative valgus alignment and avoiding overcorrection and undercorrection, the study lead to the conclusion that the use of navigation will contribute to better clinical outcomes.

With the growing popularity of partial and total knee arthroplasties (TKA), the frequency of high tibial osteotomy (HTO) interventions had decreased over recent years. However, with the advent of cartilage reconstructive surgery, accompanied by growing awareness of complications following joint arthroplasty especially, in younger patients, HTO has become popular again in both prevention and therapy of varus osteoarthritis of the knee. It is well known that long-term results of HTO depend strongly on the quality of correction. In this context, the quality of correction means achieving an adequate postoperative alignment of the leg and preserving this alignment for a long time. Exact preoperative planning is indispensable but also difficult. Measuring and controlling the quality of correction intraoperatively was significantly more difficult in the past, however. The authors’ goal, therefore, was to investigate whether intraoperative navigation could solve these problems and improve the accuracy of HTO surgery.

Materials and Methods

Between January 2003 and March 2006, the authors performed 67 HTOs with the open-wedge technique described by Staubli, using Tomofix stabilization (Synthes, West Chester, Pa) (Figure 1). The aim of this procedure was to achieve a postoperative genu valgum of 3° (2°-5°), meaning that the load line must be brought to the Fujisawa point in the lateral aspect of the joint compartment. In all cases, preoperative planning was based on full-leg radiography and standard anterioposterior (AP)-view and lateral-view radiography. Planning included the drawing of the weight-bearing axis, the intended correction, and the opening wedge required for a 3° valgus. For the intraoperative measurement of the leg axis, the OrthoPilot system (HTO version 1.3, B. Braun Aesculap, Tuttlingen, Germany) was used in 44 patients. The system uses computed tomography (CT)-free infrared registration of kinematic joint centers (hip, knee, ankle) with additional percutaneous palpation of landmarks. Two additional stab incisions were necessary for fixating two rigid bodies to the femur and tibia.

Prior to the patient being discharged, another full-leg radiograph was obtained, and the postoperative leg axis was examined in relation to intraoperative measurements and preoperative planning.

Results

The first 23 HTOs were performed without navigation and the next 44 were carried out using the navigated technique. Of the patients, 33 were female. The right leg was navigated in 41 patients, and the left leg was navigated in 26 patients. Most of the patients were between 50 and 70 years old (Figure 2). The HTOs performed without navigation showed a clear tendency toward undercorrection. With the OrthoPilot navigation system, the authors found fewer outliers and fewer patients with undercorrection (Figures 3 and 4).

Discussion

Varus misalignment of the knee can be either the cause or the result of unicompartmental knee osteoarthritis. To manage this situation, especially in young and active patients, surgical correction of the leg axis through HTO has been widely used. With the benefits of partial and total knee arthroplasty, HTO seemed to become less common for a while, but with ongoing research and improving performance of reconstructive cartilage surgery, and because knee arthroplasty still presents problems and complications, HTO returned as an increasingly popular procedure.

The correction of the leg axis by HTO can be carried out either as closed-wedge surgery or as open-wedge surgery.¹ However, because of complications related to closed-wedge osteotomy (eg, compartment syndrome and peroneal nerve palsy), and because additional fibula osteotomy is necessary with the technique, many surgeons prefer open-wedge osteotomy through a medial approach. Morbidity can be ruled out for this procedure, because bone grafting does not occur from the iliac crest. In this series, the authors did not fill the osteotomy gap with any material, but instead relied on callus formation under the protection of plate osteosynthesis with interlocking screws. This biological technique makes this type of surgery even more attractive. The osteotomy was performed in the manner described by Staubli et al,² (ie, L-shaped with additional cutting behind the tibial tuberosity). Contraindications against this procedure (eg, smoking) should be considered.

Patient selection and the decision about whether arthroplasty is the preferred option are important and difficult issues.³ Therefore, patients are often given the choice between osteotomy and partial or total knee arthroplasty. Surgeons must take into account criteria described by Spahn et al⁴. Smoking, obesity, symptoms persistent for longer than 24 months, narrowing of the medial joint width to less than 5 mm, and grade VI cartilage damage present a poor prognosis for osteotomy.⁴ In this study, the authors treated many patients older than 60 years. Other authors suggest that patients with an inclination toward high impact physical activities should not be excluded.⁵

Many authors confirm the correlation between overcorrection or undercorrection, loss of correction, and poor results.⁶ Maximal valgus deformity is known to be difficult to handle in total knee arthroplasty, yet questions remain. What is “exact alignment”? What degree of valgus correction is necessary and useful?

Most authors recommend an anatomic axis between the femur and tibia of 8° to 10° or a mechanical leg axis of 3° to 5° valgus. The Mikulicz line intersects the total width of the tibia plateau lateral from the eminentia at a point at 62% to 66% of the distance from the medial border, called the Fujisawa point. The importance of preoperative planning for optimal result is stressed by many authors. Standard radiographs of the knee in AP and lateral views as well as full-leg radiographs with weight on both legs are indispensable.

Planning methods vary and suffer from an inherent lack of accuracy, primarily because of difficulties with full-leg radiographs, especially with an extension deficit of the knee.^7,8 Another crucial problem is the intraoperative implementation of preoperative planning. Presently, many surgeons still rely on the accuracy of visual inspection, even if they use the cable method.⁹ Other authors, however, were encouraged by good navigation results in knee arthroplasty procedures to try navigation for calculating the correction angle intraoperatively in leg axis correction surgery.¹⁰ Early results are encouraging, and navigation seems to provide more accuracy than other procedures. The results are confirmed by surgical data and experience. The authors found a good correlation, not only between preoperative planning and preoperative computed navigation regarding the angle of varus deformity, but also between the navigated correction angle and postoperative measurements in another full-leg view. Use of navigation resulted in fewer outliers and statistically significant higher accuracy of the postoperative leg axis within a range of 3° to 5° valgus.

The quality of the results suggests preoperative planning could be abandoned altogether, but that would be unwise. Preoperative planning allows the surgeon to monitor the computer system and to continue surgery without navigation if any failure in the navigation system occurs. In agreement with other investigators, the authors did not observe any major complications in the series due to navigation. The operating time is extended by about 10 minutes, but the extension, as well as the two additional scars from the stab incisions for the rigid bodies, is acceptable. Operating time extensions of about 23 minutes, as found in studies with other navigation systems, did not occur with OrthoPilot navigation.¹⁰

Conclusion

The OrthoPilot navigation system for HTO helps compensate for the shortcomings of preoperative planning. Intraoperative calculation of leg axis and correction angle is much more accurate than with traditional procedures. Navigation for HTO appears to be a reliable and safe procedure that does not need CT or intraoperative fluoroscopy. Navigation itself was straightforward and did not give rise to any complications in this study. The effect of slightly longer operating times is negligible, considering the possible benefits in terms of long-term results. Naturally, more studies are required to confirm early data, but, nevertheless, HTO promises to be advantageous for both patient and surgeon.

References

1. Mont MA, Stuchin SA, Paley D, et al. Different surgical options for monocompartmental osteoarthritis of the knee: high tibial osteotomy versus unicompartmental knee arthroplasty versus total knee arthroplasty: indications, techniques, results, and controversies. Instr Course Lect. 2004; 53:265-283.
2. Staubli AE, De Simoni C, Babst R, Lobenhoffer P. Tomofix: a new LCP–concept for open wedge osteotomy of the medial proximal tibia -early results in 92 cases. Injury. 2003; 34:B55-B62.
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4. Spahn G, Kirschbaum S, Kahl E. Factors that influence high tibial osteotomy results in patients with medial gonarthritis: a score to predict the results. Osteoarthritis Cartilage. 2006; 14:190-195.
5. Wright JM, Crockett HC, Slawski DP, et al. High tibial osteotomy. J Am Acad Orthop Surg. 2005; 13:279-289.
6. Pape D, Adam F, Rupp S, Seil R, Kohn D. Stability, bone healing and loss of correction after valgus realignment of the tibial head. A roentgen stereometry analysis [in German]. Orthopade. 2004; 33:208-217.
7. Fujisawa Y, Masuhara K, Shiomi S. The effect of high tibial osteotomy on osteoarthritis of the knee. An arthroscopic study of 54 knee joints. Orthop Clin North Am. 1979; 10:585-608.
8. Pape D, Seil R, Adam F, Rupp S, et al. Imaging and preoperative planning of high tibial head osteotomy [in German]. Orthopade. 2004; 33:122-134.
9. Hooper G, Leslie H, Burn J, Schouten R, Beci I. Oblique upper tibial opening wedge osteotomy for genu varum. Oper Orthop Traumatol. 2005; 17:662-673.
10. Saragaglia D, Roberts J. Navigated osteotomies around the knee in 170 patients with osteoarthritis secondary to genu varum. Orthopedics. 2005; 28:S1269-S1274.

Authors

Drs Maurer and Wassmer are from the Department of Traumatology and Orthopedic Surgery, Hospital St Elisabeth, Oberschwabenklinik, Ravensburg Germany.