Unpacking the Tibial Tubercle–Trochlear Groove Distance: Evaluation of Rotational Factors, Trochlear Groove and Tibial Tubercle Position, and Role of Trochlear Dysplasia

Abstract

Background: The tibial tubercle to trochlear groove (TT-TG) distance is often utilized for determining the surgical treatment for patients with patellar instability (PI). It is thought to directly represent the position of the TT on the tibia. Recent work has shown that the measurement of the TT-TG distance is multifactorial. Purpose: To investigate the relationship between relative tibial external rotation (rTER) and trochlear dysplasia (TD), as well as the location of the TG and TT in patients with and without PI, and to correlate these and other anatomic measurements with the TT-TG distance. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 89 patients with PI who underwent magnetic resonance imaging were identified with 92 matched control patients. A standardized measurement protocol on axial magnetic resonance imaging determined rTER, the proximal and distal TG lateralization (pTGL and dTGL, respectively) ratios, and the TT lateralization (TTL) ratio. Other measures of interest included the lateral trochlear inclination angle, sulcus angle, and lateral patellar inclination angle. Univariate regression was used to determine the associations of TD (lateral trochlear inclination angle, sulcus angle) with rTER and the TG position, and multivariate regression was used to model associations among all the variables with the proximal and distal TT-TG distances. Results: rTER was significantly higher in the study group ( P < .001), and univariate regression showed a significant association between dysplasia measures and rTER ( P < .001). The pTGL ratio was lower in the study group ( P = .025), but there was no difference in the dTGL ratio ( P = .090) or the TTL ratio ( P = .098) between the groups. There were no associations between dysplasia measures and the pTGL and dTGL ratios ( P > .05). Multivariate regression showed that the proximal TT-TG distance is predicted by the sulcus angle, pTGL ratio, rTER, and TTL ratio ( P < .05) and that the distal TT-TG distance is predicted by the lateral patellar inclination angle, dTGL ratio, sulcus angle, rTER, and TTL ratio ( P < .05). Conclusion: rTER had a significant association with TD. The position of the proximal TG was more medial in patients with PI. There was no significant difference in the TTL ratio between patients with and without PI. The TT-TG distance was associated with multiple anatomic measures and was not solely predicated on the position of the TT.

No significant difference in thick versus thin osteochondral flap trochleoplasty in the treatment of trochlear dysplasia: A systematic review

“…Meanwhile, the systematic review by Ren et al compared outcomes following isolated trochleoplasty (three studies, n = 111 patients) versus trochleoplasty + MPFL reconstruction (three studies, n = 81 patients) [30]. At the final follow‐up, Kujala score was found to increase significantly ( p < 0.00001) in both the isolated trochleoplasty group (21.4 points, mean follow‐up 39 months) and trochleoplasty + MPFL reconstruction group (24.9 points, mean follow‐up 29.8 months) [26]. Similarly, Guan‐Yan et al analysed 17 studies comparing trochleoplasty to other patellar stabilising procedures (MPFL reconstruction, medial retinaculum repair and Insall proximal realignment) in the setting of severe trochlear dysplasia [33].…”

Trochlear Shape and Patient-Reported Outcomes After Arthroscopic Deepening Trochleoplasty and Medial Patellofemoral Ligament Reconstruction: A Retrospective Cohort Study Including MRI Assessments of the Trochlear Groove

“…3,27 We assessed the TT-TG distance using the most distal and proximal axial slice displaying full cartilage coverage of the trochlear groove and the most proximal slice of the patellar tendon insertion on the tibial tuberosity. 28,31 The TT-TG was defined as the distance between the midpoint of the tibial insertion of the patellar tendon and the deepest point of the trochlear groove when measured parallel to the tangent along the posterior femoral condyles (posterior condylar axis).…”

Increased TT–TG distance caused by excessive tibiofemoral rotation predicts poor clinical outcomes after tibial tubercle osteotomy in recurrent patellar dislocation

“…The TT–TG distance is a widely used parameter to evaluate the lateral offset of the distal extensor mechanism, which is of importance given that it represents a risk factor for RPD and is often included in algorithmic treatment of RPD [5]. Recently, many researchers have turned their attention towards the underlying causes of increased TT–TG distance [3, 20, 26, 27, 29]. Interestingly, some radiologic studies have found that TT–TG distance is more affected by tibiofemoral rotation (TFR) than by actual tibial tubercle lateralisation (TTL) [26, 29], suggesting that the impact of actual TTL on the TT–TG distance is less important than previously thought.…”