A three‐dimensional computed tomographic volume rendering methodology to measure the tibial torsion angle in dogs

Abstract

Objective To describe a three‐dimensional (3D) computed tomographic (CT) methodology to measure the tibial torsion angle (TTa) and to evaluate intrarater and interrater agreements and accuracy through comparison with anatomic measurements. Study design Ex vivo cadaveric study. Sample population Thirty‐six tibiae from 18 dogs. Methods Tibial torsion angle of each tibia was measured by using two CT techniques (axial and 3D volume rendering) by three raters who blindly measured TTa in duplicate. A semitransparent bone filter was used to enhance the visibility of the target anatomical landmarks for the 3D volume rendering CT technique. Tibial torsion angle was also quantitated in tibial specimens. Intrarater and interrater agreements were analyzed by using intraclass coefficients (ICC). Accuracy was evaluated by using adjusted R2 coefficients (R2 > 80% was considered acceptable). Results The 3D volume rendering CT technique had excellent intrarater and interrater agreements (ICC > 0.94) and an R2 value of 97%. The axial CT technique had good to excellent intrarater and interrater agreements (0.8 < ICC < 0.95) and an R2 of 86%. No difference was found between axial and 3D CT techniques. A mean internal TT angle of approximately −6° was found with CT and anatomic measurements. Conclusion The 3D volume rendering and axial CT techniques were precise and accurate for measuring TTa in dogs unaffected by patellar luxation. Clinical relevance Combining 3D bone manipulation with application of a semitransparent filter allows simultaneous visualization of anatomic landmarks, which may facilitate the evaluation of complex bone deformations. Internal tibial torsion may be present in nonchondrodystrophic dogs without patella luxation.

Efficacy of two reduction methods in conjunction with 3-D–printed patient-specific pin guides for aligning simulated comminuted tibial fractures in cadaveric dogs

“…The length of each tibia, frontal, and sagittal angulation and degree of tibial torsion were measured according to methods previously described. [40][41][42] The cadavers were stored in a -30° C cooler until custom guides were designed and printed. Each dog's right and left pelvic limbs were randomly assigned by coin toss to an RG and an EF group.…”

Three‐dimensional volume rendering planning, surgical treatment, and clinical outcomes for femoral and tibial detorsional osteotomies in dogs

“…CT scans were reconstructed in DICOM (digital imaging and communications in medicine) software (Osirix, version 5.8, Pixmeo Sarl). Femoral and tibial torsion angles were measured by two authors (FL, TN) using a CT 3D volume rendered approach, similarly to what has previously been described 11,12 …”

“…Femoral and tibial torsion angles were measured by two authors (FL, TN) using a CT 3D volume rendered approach, similarly to what has previously been described. 11,12 The anatomic lateral distal femoral angle (aLDFA) and the mechanical medial proximal tibial angle (mMPTA) were also measured using literature guidelines. 20,21 Abnormal varus was defined if aLDFA >102 , abnormal valgus when aLDFA <88 .…”

“…Although the reported range for physiological femoral torsion is wide, 8,15 a torsion angle of 27° is used as the reference value for FTA 16 . An internal tibial torsion angle of −3° to −6° has been reported in medium to large size healthy dogs 9,12 …”

“…16 An internal tibial torsion angle of À3 to À6 has been reported in medium to large size healthy dogs. 9,12 A recent study presented a CT graphical approach to plan FT correction. 17 The cortical geometrical arch and chord length were measured on 3D femoral models to quantify the amount of rotation needed to correct FT.…”