Short-term Precision Of High-resolution Peripheral Quantitative Computed Tomography Measures Of The Second Metatarsal Diaphysis

PURPOSE: The metatarsals (MT) are common sites for acute and overuse injuries, yet their properties are infrequently assessed. High-resolution peripheral quantitative computed tomography (HRpQCT) represents a potentially novel method of non-invasively and three-dimensionally evaluating MT bone properties. This study assessed the short-term precision of HRpQCT measures of the midshaft of the 2nd MT. METHODS: A convenience sample of 10 young, healthy individuals had two scans of the midshaft of the 2nd MT performed with interim repositioning between scans. Scans were performed in supine using an XtremeCT II HRpQCT scanner (Scanco Medical). Orthogonal scout views were performed to align the long axis of the 2nd metatarsal to the z-axis of the scanner. Bone length was measured on the scout view and 168 slices (voxel size = 60.7 μm) taken at the midshaft. The root mean square method (RMS) was used to compute overall standard deviation (RMS-SD, expressed in the respective unit of measure) and coefficient of variation (RMS-CV, %) of the precision error. RESULTS: RMS CV% values for length and density measures were ≤ 0.6% (Table). RMS CV% values for bone cross sectional size and estimated strength measures were ≤ 1.4% and ≤ 2.6%, respectively. CONCLUSIONS: HRpQCT measures of the 2nd MT midshaft were precise. Density measures were the most precise, followed by size and estimated strength measures. HRpQCT is a potentially useful modality for the non-invasive, in vivo assessment of three-dimensional MT bone properties. - Measure group Measure (units) Mean ± SD RMS SD RMS CV% Length Length (mm) 74.10 ± 5.48 0.49 0.64 Density Cortical volumetric bone mineral density (mgHA/cm3) 1028 ± 23 4.6 0.45 Total mineral density (mgHA/cm3) 859 ± 70 5.35 0.63 Bone mineral density (mgHA/cm3) 1096 ± 26 5.81 0.53 Area/Size Bone area (mm2) 43.9 ± 9.8 0.56 1.38 Total area (mm2) 55.4 ± 15.7 0.59 1.16 Bone area/total area (%) 80.4 ± 5.3 0.24 0.30 Cortical perimeter (mm) 28.9 ± 4.3 0.19 0.68 Cortical thickness (mm) 2.60 ± 0.25 0.026 1.06 Robustness (mm) 0.743 0.009 1.29 Porosity Cortical porosity (%) 1.33 ± 0.29 0.09 6.70 Cortical porosity diameter (mm) 0.19 ± 0.03 0.0058 3.13 Strength Polar moment of inertia (mm4) 511 ± 317 10.2 2.42 Maximum second moment of area (mm4) 316 ± 208 5.99 2.37 Minimum second moment of area (mm4) 194 ± 112 4.35 2.60 Stiffness (kN/mm) 43.23 ± 9.98 0.578 1.54 Failure load (kN) 3.76 ± 0.87 0.071 2.14