The effect of tibial rotation on knee medial and lateral compartment contact pressure.

PURPOSE: The progression of knee osteoarthritis (OA) is determined in part by mechanical effects on local structures. The mechanical influences of limb malalignment on cartilage loss are well known; however, the effect of rotational deformities on knee OA is not yet known. The aim of the current study was to evaluate the effect of tibial rotation on knee medial and lateral compartment contact pressure.

METHODS: The left knees of six fresh whole-body cadavers were used in this study. Fujifilm Prescale super-low type film was used for contact pressure measurement. The films were inserted into the joint after arthrotomy. The cadavers were stabilized with a custom-made device, and axial force of half body weight specific to each cadaver was applied to the plantar surface of the feet. The examination was repeated after osteotomy of the fibula and tibia, and the tibia was then rotated 15° or 30° internally (IR) or externally (ER) and securely fixed. The resulting films were scanned, and CP was determined using appropriate software.

RESULTS: The p values for increased medial compartment contact pressure at 15° and 30° IR and 30° ER were 0.016, 0.025, and 0.025, respectively. For decreased medial compartment contact pressure at 15° ER, the p value was 0.020. The p values for increased lateral compartment contact pressure at 15° and 30° ER were 0.010 and 0.030, respectively. In this compartment, contact pressure changes at 15° and 30° IR were not significant.

CONCLUSION: This experimental study demonstrated that 15° IR of the tibial shaft increased contact pressure and 15° ER decreased contact pressure over the knee medial compartment.