Measurement of Patellar Proximodistal Positioning with Limited Joint-Angle Sensitivity

Abstract

Objective Patellar luxation can be associated with abnormal proximodistal positioning of the patella. The current gold standard index (Insall–Salvati) for referencing this position is poorly suited to postoperative use, if the tibial tuberosity is moved surgically, but has the advantage of changing minimally with altered joint angles. The aim of this study was to identify an alternative index, which was simple to use, joint-angle insensitive and suitable for postoperative use. Study Design Candidate indices based on the angle between stifle joint landmarks were screened across a wide range of joint angles for insensitivity to joint angle changes using vulpine and canine stifle radiographs. Intraobserver and interobserver agreements were assessed for a single candidate index using canine radiographs. Results An angular index based on the caudal aspect of the femoral and tibial condyles and the apex of the patella was largely insensitive to joint angle variation. Intra- and interobserver agreements appeared suitable for clinical use, with low within-subject standard deviations (<1.3°) and coefficients of variations (<2.2%), and high intraclass correlation coefficients (>0.89). Conclusion Patellar proximodistal position can be acceptably assessed at a variety of caudal joint angles using the described angular index. Further work is required to define reference intervals across a range of canine breeds.

Examination of the proximodistal patellar position in small dogs in relation to anatomical features of the distal femur and medial patellar luxation

“…Thus, the ratio of the patellar ligament length to patellar length (PLL/PL) based on the Insall-Salvati index in humans was introduced as an index that is minimally affected by the stifle angle [6,[9][10][11]. Although some studies have introduced other indices to evaluate the proximodistal patellar position [2,12,13], these indices have not been used in clinical cases as often as the PLL/PL. Many canine studies have focused on the PLL/PL to discuss the proximodistal alignment between the patella and the femoral trochlea [1][2][3][4][5][6][7][8].…”

Patellar Proximo-Distal Displacement following Modified Maquet Technique Is Not Predictive of Patellar Luxation

“…11 To overcome these limitations, a recent study by Allberg and Miles proposed several easy-to-use osseous landmarks to be identified on radiographs in order to measure the position of the patella with a very limited impact of the SOA. 15 The same study suggests the fact that tibial osteotomies such as MMT could induce patellar luxation. 15 The objectives of this retrospective study were to verify in a large cohort of dogs the low sensitivity of the Allberg and Miles index (AM index) to SOA, evaluate the position of the patella in dogs pre-and post-MMT via that particular index and assess the incidence of patellar luxation post-MMT.…”

“…15 The same study suggests the fact that tibial osteotomies such as MMT could induce patellar luxation. 15 The objectives of this retrospective study were to verify in a large cohort of dogs the low sensitivity of the Allberg and Miles index (AM index) to SOA, evaluate the position of the patella in dogs pre-and post-MMT via that particular index and assess the incidence of patellar luxation post-MMT.…”

“…11 To overcome these limitations, a recent study by Allberg and Miles proposed several easy-to-use osseous landmarks to be identified on radiographs in order to measure the position of the patella with a very limited impact of the SOA. 15 The same study suggests the fact that tibial osteotomies such as MMT could induce patellar luxation. 15…”

Canine medial patellar luxation

“…2020). Additionally, concerns have been raised regarding whether the IS index is appropriate for use postoperatively when the TT has been moved (Allberg & Miles 2020). Due to this, a novel angular index, based on the caudal aspect of the femoral and tibial condyles and the apex of the patella has been proposed (Allberg & Miles 2020).…”