Introduction
Medial opening-wedge high tibial osteotomy is a widely accepted procedure for the treatment of medial compartment arthritis of the knee. However, this procedure has some disadvantages including the cartilage degeneration in the patellofemoral joint and the increase of sagittal tibial slope because of a supra-tubercle osteotomy. With the aim of avoiding these potential problems, some authors support a medial opening-wedge infra-tubercle osteotomy, i.e. distal tibial osteotomy (OW-DTO). In the OW-DTO, the fibular osteotomy is not necessary as well. We have performed a medial opening-wedge distal tibial osteotomy using hemicallotasis (OWDTO-HCO) as an option of OW-DTO until now, without fibular osteotomy. However, the effect of this OWDTO-HCO on the proximal tibiofibular joint (PTFJ) is not clear.
Purpose
The purpose of this study is, first, to examine the effect of our OWDTO-HCO on the PTFJ cartilage using a quantitative T1rho magnetic resonance imaging (MRI), and, second, to clarify the relationship between the correction angle (CA) and the articular cartilage change of PTFJ.
Methods
Twenty knees (20 patients) with medial compartment osteoarthritis of the knee were enrolled in this study. The averaged age at surgery was 70 y.o. The unilateral OWDTO-HCO was carried out for those knees. No fibular osteotomy was done. Before surgery and one year postoperatively, all patients were evaluated using the standing AP radiograph of whole limb, and using the coronal T1rho 3-Tesla MRI. In MRI analysis, T1rho relaxation time was measured at a region of interest on a coronal image of the center of PTFJ.
Results
In all knees, the fibular head was displaced upward postoperatively, while the position of the distal tip of the fibula was not changed. The averaged CA was 15º (ranged from 9º to 21º), and seven out of 20 knees had the CA more than 15º. The upward transposition of the fibular head showed an positive correlation with increase of CA. In addition, in the knees with CA less than 15º, the averaged T1rho relaxation time was 40.1 millisecond (ms) preoperatively, and 40.3 ms at one-year after surgery, showing no significant postoperative change. On the other hand, those with CA more than 15º had 38.4 ms preoperatively, and 41.4 ms at one-year after surgery, which showed the significant higher postoperative value (Mann-Whitney U test, p=0.02). A significant correlation between CA and the amount of postoperative increase in T1rho relaxation time was found (r=0.78, p=0.03).
Conclusions
In OWDTO-HCO without fibular osteotomy, the fibular head was displaced more upward as the CA increased. T1rho relaxation mapping has been reported a sensitive noninvasive marker for quantitatively predicting and monitoring the status of macromolecules in early OA. In the previous study, we showed that the T1rho relaxation time of PTFJ cartilage were not affected by aging or cartilage degeneration in the femorotibial joint, and those value showed a constant range from 35 ms to 40 ms. Accordingly, our results suggested that the PTFJ cartilage might have a degenerative change postoperatively if we perform the tibial valgus correction more than 15º using the OWDTO-HCO with no fibular osteotomy.