Editorial Commentary: Reducing the Tibial Tuberosity-Trochlear Groove Distance in Patella Stabilization Procedure. Too Much of a (Good) Thing?

Isolated Medial Patellofemoral Ligament Reconstruction in Patellar Instability: Does the Distance Between Tibial Tuberosity-Trochlear Groove Make a Difference?

Introduction

Medial patellofemoral ligament reconstruction (MPFLR) is used in most patellar instability surgeries, there is controversy on adding a tibial tuberosity osteotomy (TTO).

Objective

To describe the results of isolated MPFLR in patellar instability according to the Tibial Tuberosity-Trochlear Groove distance (TT-TG).

Methods

Retrospective study of patients with patellar instability with a mature skeleton in one center between 2016 and 2021, using isolated MPFLR. Patients with incomplete clinical and/or radiological records and less than one year follow-up were excluded. Pre-surgical demographic and radiological data (TT-TG, Caton-Deschamps (CD) index, patellar tilt, trochlear dysplasia) were recorded. Patients were divided into three groups according to TT-TG distance (Group 1: < 17 mm, Group 2: 17-19, Group 3: ≥ 20 mm). A pre and post-surgical Kujala score was performed. Local complications, satisfaction, recurrence and/or reintervention were recorded. Pre-surgical variables between groups, intra and inter-group Kujala differences were compared using Bartlett's test. Consent from the patients and approval from the local ethics committee were obtained.

Results

67 patients met the selection criteria, mean age of 23 years, 70% were women. There were no pre surgical, radiological nor follow-up differences between the groups (average 27 months). Pre and post-surgical Kujala score, respectively: Group 1: 37-78, Group 2: 37-78, Group 3: 39-79. All groups had a significant improvement (p < 0.05), there were no significant differences in improvement between groups (p > 0.05). There were three patients with a redislocation episode, all in group 1. One patient had a mobilization under anesthesia due to an arthrofibrosis (Group 2). 97% of all cases reported being satisfied.

Conclusion

Isolated MPFLR in patellar instability presents a functional improvement, with a low rate of complications and failure, regardless of the pre surgical TT-TG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-023-00906-6.

The patellofemoral morphology and the normal predicted value of tibial tuberosity-trochlear groove distance in the Chinese population

Background

Our objective was to obtain normal patellofemoral measurements to analyse sex and individual differences. In addition, the absolute values and indices of tibial tuberosity-trochlear groove (TT-TG) distances are still controversial in clinical application. A better method to enable precise prediction is still needed.

Methods

Seventy-eight knees of 78 participants without knee pathologies were included in this cross-sectional study. A CT scan was conducted for all participants and three-dimensional knee models were constructed using Mimics and SolidWorks software. We measured and analysed 19 parameters including the TT-TG distance and dimensions and shapes of the patella, femur, tibia, and trochlea. LASSO regression was used to predict the normal TT-TG distances.

Results

The dimensional parameters, TT-TG distance, and femoral aspect ratio of the men were significantly larger than those of women (all p values < 0.05). However, after controlling for the bias from age, height, and weight, there were no significant differences in TT-TG distances and anterior-posterior dimensions between the sexes (all p values > 0.05). The Pearson correlation coefficients between the anterior femoral offset and other indexes were consistently below 0.3, indicating no relationship or a weak relationship. Similar results were observed for the sulcus angle and the Wiberg index. Using LASSO regression, we obtained four parameters to predict the TT-TG distance (R² = 0.5612, p < 0.01) to achieve the optimal accuracy and convenience.

Conclusions

Normative data of patellofemoral morphology were provided for the Chinese population. The anterior-posterior dimensions of the women were thicker than those of men for the same medial-lateral dimensions. More attention should be paid to not only sex differences but also individual differences, especially the anterior condyle and trochlea. In addition, this study provided a new method to predict TT-TG distances accurately.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04454-8.

Tibial Tubercle Osteotomy May Not Provide Additional Benefit in Treating Patellar Dislocation With Increased Tibial Tuberosity-Trochlear Groove Distance: A Systematic Review

PURPOSE

To examine the indications and outcomes of medial patellofemoral ligament reconstruction (MPFLR) with or without tibial tubercle osteotomy (TTO) in treating recurrent or habitual patellar dislocation with an increased tibial tuberosity-trochlear groove (TT-TG) distance.

METHODS

We performed a literature search of the established medical databases Cochrane Central, PubMed-MEDLINE, EMBASE, and Web of Science. The inclusion criteria were as follows: skeletally mature patients with recurrent or habitual patellar dislocation and an increased TT-TG distance, treatment with MPFLR combined with a TTO procedure or isolated MPFLR, and reporting of clinical outcomes and complications. Each study was assessed for quality and the level of evidence. The general characteristics, indications, surgical techniques, TT-TG distance, clinical results, imaging evaluation findings, and complications of each study were recorded.

RESULTS

Nine studies consisting of 288 knees met the inclusion criteria. The average Coleman score was 71.56 (range, 55-83). The threshold for an increased TT-TG distance ranged from 16 to 20 mm in the included studies. Similar good postoperative outcomes were reported in patients with an increased TT-TG distance treated with MPFLR with versus without a TTO procedure. The mean postoperative Lysholm score ranged from 75.0 to 94.7 (I² = 87.6%) in the isolated MPFLR group and from 85.0 to 87.6 (I² = 16.3%) in the TTO-with-MPFLR group. Similar postoperative congruence angles were reported in both groups. The postoperative redislocation rate ranged from 0% to 4.2% in the TTO-with-MPFLR group, and no redislocation was found in the isolated MPFLR group. The postoperative apprehension sign was only reported in isolated MPFLR patients.

CONCLUSIONS

The outcomes of MPFLR with or without TTO to treat recurrent or habitual patellar dislocation with an increased TT-TG distance appeared similar. However, this study was limited by the considerable heterogeneity, variety of techniques, variety of TT-TG distances, and variability in patella alta and trochlear dysplasia among the included studies.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II to IV studies.

Tibial tuberosity-tibial intercondylar midpoint distance measured on computed tomography scanner is not biased during knee rotation and could be clinically more relevant than current measurement systems

PURPOSE

The purpose of this retrospective cross-sectional case-control study was to evaluate an alternative imaging test for lateralization of the tibial tuberosity, unbiased towards knee rotation.

METHODS

On axial CT images of 129 knees, classified as cases (two or more patellar luxations) and controls (no patellar luxations), two raters gauged the standard tibial tuberosity-trochlear groove (TT-TG) distance, tibial tuberosity-femoral intercondylar midpoint (TT-FIM) distance, and new tibial tuberosity-tibial intercondylar midpoint (TT-TIM) distance singly, and knee longitudinal rotation angles (LRAs), and the presence of femoral trochlear dysplasia (FTD) jointly.

RESULTS

All imaging tests intercorrelated and discriminated between stability groups. TT-TIM had the lowest values with the highest precision. Though poorly, TT-TG and TT-FIM negatively correlated with age and LRAs regarding femur, but positively with presence of FTD, whereas TT-TIM was unbiased. The accuracy of TT-TG (> 20 mm), TT-FIM (> 20 mm), and TT-TIM (> 13 mm) was good with almost perfect reproducibility. Only TT-TIM was sex-biased (p = 0.009), with > 12 mm cut-off in females and (presumably) > 14 mm in males.

CONCLUSION

TT-TIM is an alternative imaging test for lateralization of the tibial tuberosity, unbiased towards knee rotation.