title: Radiographic and Anatomic Evaluation of Tibial Tubercle to Trochlear Groove Distance.
abstract: BackgroundA lateralized tibial tubercle is an important anatomic predictor of patellar instability and can be used as an indication for a distal realignment procedure. Currently, tibial tubercle to trochlear groove (TT-TG) distance is measured on computed tomography (CT); however, radiographs could be a safer and more efficient modality. The aim of this study is to evaluate and compare TT-TG measurements obtained using CT, anatomical dissections, and a novel radiographic technique. Furthermore, we evaluated the effects of knee flexion and tibial rotation on these measurements.MethodsTT-TG distances were measured on 11 fresh cadaver specimens with CT and compared with anatomic measurements obtained from dissection in full knee extension and 90-degree flexion. Both imaging- and dissection-derived measurements were obtained in neutral, external, and internal tibial rotation. The TT-TG distance was also measured on a modified sunrise X-ray view (knee at 90 degrees).ResultsThe TT-TG distance obtained on CT was 13.00 ± 1.05 mm and was comparable to measurements derived from anatomic dissections in extension (14.88 ± 1.10 mm) and 90 degrees (12.40 ± 1.93 mm) (p≥ 0.05). The X-ray measurements of TT-TG distance (5.62 ± 1.16 mm) were significantly different than those measured on CT (p≤ 0.05). TT-TG distances in neutral tibial position measured on CT and dissection were significantly different than distances measured in full external (19.79 ± 1.33 and 20.92 ± 1.15 mm, respectively) and internal tibia rotation (6.45 ± 1.00 and 10.33 ± 1.19 mm, respectively) (p≤ 0.05).ConclusionsTT-TG distance measured on CT is comparable to measurements from dissections in both full extension and 90-degree flexion. Tibial rotation has a significant effect on TT-TG measurements. Radiographic measurements did not correlate with CT and anatomic measurements.Clinical RelevanceCT-derived TT-TG measurements are accurate throughout knee range of motion; however, it is important to maintain neutral lower leg rotation to not generate a false-positive or false-negative measurement. Radiographic measurement of TT-TG ration is not currently recommended.
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Alicia
authors.initials: A
authors.lastname: Worden
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Scott
authors.initials: S
authors.lastname: Kaar
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Joshua
authors.initials: J
authors.lastname: Owen
authors.affiliation: Department of Orthopaedic Surgery, Saint Louis University, Saint Louis, Missouri.
authors.forename: Adnan
authors.initials: A
authors.lastname: Cutuk
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017760:Bone Malalignment / Q000517:prevention & control; D002102:Cadaver; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D057071:Patellofemoral Joint; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed