Summary

Proximal tibiofibular dislocation during a CWHTO produces radiological lateral instability when is compared with a fibular head osteotomy.

Abstract

Purpose

To determine if the proximal tibiofibular joint (TFJ) dislocation increased lateral compartment gapping more than a fibular head osteotomy (FHO) following a closing-wedge high tibial osteotomy (CWHTO). A second objective was to determine if lateral compartment gapping affects clinical outcomes.

Methods

Prospective randomized clinical study. The study included 36 patients; 18 in group 1 (fibular head osteotomy) and 18 in group 2 (tibiofibular joint dislocation). An a priori sample size was calculated. To detect a difference of 2mm in both groups with a=0.05 and a power of 80%, 18 patients were needed in each group. A maximum patient loss of 10% of was considered.
Both groups were comparable in terms of age, sex, BMI, previous femorotibial angle and the number of corrected degrees. All the patients were studied preoperatively and 6 months postoperatively with varus-stress radiograph at full extension and 30° of knee flexion in both knees. Lateral compartment gapping was measured in millimetres. The knee section of the Knee Society Score (KSS) was used to assess clinical stability.
Statistics; Mean and standard deviations were calculated for each continuous variable. The results were statistically analysed and compared by using the Student’ t-test for parametric data with a normal distribution. In the case of a non-parametric distribution, the Mann-Whitney test was used. The SPSS program was used for the statistical analysis and a p-value of 0.05 was considered statistically significant.

Results

The difference between the pre- and post-operative measurements relative to the gapping in the knee lateral compartment at 0º degrees of knee flexion was 1.3mm (SD1.8) in group 1 and 4.5mm (SD2.4) in group 2 (p=0.006). At 30° of knee flexion, this difference was 1.9mm (SD1.2) in group 1 and 5.2mm (SD3.1) in group 2 (p=0.01). The differences in gapping in the healthy knee were not statistically different.
Preoperatively, both groups presented similar KSS knee values: Group 1 with 54.7 (SD11.7) and group 2 with 54.8 (SD11.1) (n.s.). Postoperatively, these values were also similar in both groups: Group 1 with 93.2 (SD 7.4) and group 2 with 93.5 (SD 5.5) (n.s.).

Conclusion

In patients who have undergone a CWHTO, TFJ dislocation increases knee lateral compartment gapping when compared to a FHO at 0° and 30° of knee flexion. However, this fact does not have any repercussion on the clinical and functional status of the knee measured with the KSS.