Summary

The lateral closed wedge HTO might be more protective for the patellofemoral joint than the medial open wedge HTO with a significant medial tilt, valgus rotation as well as a significant posterior and distal displacement of the patella, but both HTO procedures provides satisfactory postoperative clinical outcomes.

Abstract

Purpose

There has been little in-vivo clinical information about the effect of high tibial osteotomy (HTO) on the three-dimensional patellofemoral relationship. This study aimed to investigate the postoperative three-dimensional change of patellofemoral relationship after HTO, and to compare the change between medial open wedge (MOW) and lateral closed wedge (LCW) procedures.

Methods

From January 2019 to July 2022, 17 patients (MOWHTO for 8 patients and LCWHTO for 9 patients), who were relatively active and underwent HTO for medial early knee osteoarthritis with varus deformity and underwent three-dimensional computed tomography (CT) scans preoperatively and 1 year postoperatively, were enrolled. Patients with a concomitant cruciate ligamentous injury or combined surgical procedures affecting the patellofemoral joint were excluded. Age and body mass index were comparable (MOWHTO; 57±10 years and 25±2, LCWHTO; 57±8 years and 27±4), whereas there was a significant difference in terms of sex (MOWHTO; male/female: 3/5, LCWHTO; male/female: 8/1). MOWHTO was performed for the patients with a coronal correction angle within 10°, while LCWHTO was performed with the correction angle more than 10° and/or a combined apparent degeneration in the patellofemoral joint. Postoperatively, range-of-motion exercise was started 1 week and partial weightbearing was started 2–3 weeks followed by full weightbearing at 4–5 weeks in both groups. During CT examinations, the patients were laid in a spine position and asked to relax their muscular contraction with their knees extended. Then, three-dimensional models of the femur and patella and coordinate systems were created at each time point. Using a surface registration technique, the three-dimensional change of patellofemoral relationship through HTO was calculated and compared between the two surgical techniques. Moreover, the Knee Injury and Osteoarthritis Outcome Score (KOOS) more than 2 years postoperatively was compared.

Results

There was no patient with any complication such as infection, non-union, or correction loss. After MOWHTO, the patella displaced posteriorly (0.8±0.6mm, p=0.02), medially (0.7±1.3mm, non-significant), and distally (1.3±1.8mm, p<0.01) as well as rotated internally (medial tilt by 2.7°±1.7°, p=0.02) and valgus (1.7°±1.1°, p<0.01). After LCWHTO, the patella displaced posteriorly (0.2±0.5mm, non-significant), laterally (0.4±0.7mm, non-significant), and proximally (2.3±1.1mm, p<0.01) as well as rotated externally (lateral tilt by 0.7°±0.5°, p<0.01) and valgus (1.2°±2.2°, non-significant). In comparison of these parameters, there were significant differences in the proximal–distal displacement and internal–external rotation between the two surgical procedures. The postoperative KOOS after both MOWHTO and LCWHTO were successful (symptom, 94±6 and 89±12, non-significant; pain, 93±6 and 93±9, non-significant; daily activities, 97±4 and 94±9, non-significant; sports, 85±10 and 84±20, non-significant; quality of life, 84±16 and 86±12, non-significant).

Conclusion

Both HTO procedures provides satisfactory postoperative clinical outcomes whereas caused three-dimensional positional change of the patella such as axial rotation (tilt) and proximal or distal displacement. However, considering the less axial and coronal rotational change as well as proximal displacement of the patella after LCWHTO, LCWHTO might be more protective for the patellofemoral joint.