Variation in tibial tuberosity lateralization and distance from the tibiofemoral joint line: An anatomic study.

BACKGROUND: To describe variation in tibial tuberosity position in a normal adult population and inter-rater reliability of measurements of tibial tuberosity position.

METHODS: Surface models of 161 proximal tibia specimens (83 female, 78 male; 80 black, 81 white; age 28.7years, SD 7.5) were created with a three-dimensional laser scanner. Percent lateralization, tuberosity-eminence angle, and distance from joint surface were measured for each specimen. Variation in tuberosity position by sex, race, age, height, and BMI was calculated. Multivariate regression was used to assess for demographic factors independently associated with tuberosity positioning.

RESULTS: Mean percent lateralization was 57.9% (SD 2.4, range 52.4-64.9%). Tuberosity-eminence angle mean was 11.03° (SD 2.8, range 0-18.7°). Percent lateralization and tuberosity-eminence angle were not influenced by sex, race, age, height or, BMI (p>0.05). Mean tuberosity distance from joint surface was 29.2mm (SD 3.5, range 16.6-38.6mm) and larger in males than females (30.7mm (SD 2.9), 27.6mm (SD 3.3); p<0.001). Tuberosity distance from joint surface increased 0.18mm on average per 1.0cm increase in height (p<0.001). Inter-rater reliability was high for distance from joint surface (Cronbach alpha=0.99) and percent lateralization.

CONCLUSIONS: Tibial tuberosity percent lateralization falls in a narrow range for individuals, whereas tuberosity-eminence angle and distance from joint line are more variable. Inter-rater reliability is high for percent lateralization and distance for the joint surface. Distance of tibial tuberosity from joint surface is associated with sex and height.