Current evidence advocates use of a new pathologic tibial tubercle–posterior cruciate ligament distance threshold in patients with patellar instability

Nickolas Boutris, Domenica A. Delgado, John Scott Labis, Patrick McCulloch, David M. Lintner, Joshua D. Harris

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Purpose: To determine (1) whether a correlation exists between tibial tubercle–posterior cruciate ligament (TT-PCL) and tibial tubercle–trochlear groove (TT-TG) distances in patellar instability patients; (2) reliability when measuring TT-PCL distance; (3) whether TT-PCL distances measured on MRI are equivalent to those on CT; and (4) whether a correlation exists between TT-PCL distance and number of instability events or recurrence of instability following stabilization surgery. Methods: A systematic review was performed using PRISMA guidelines. Clinical studies investigating the relationships of TT-PCL with TT-TG on CT and/or MRI in patellar instability patients were sought. English language studies with Levels of evidence I–IV were eligible for inclusion. Results: Four studies (285 subjects [300 knees] with patellar instability [74.2% female; mean age 26.1 ± 8.2 years]; 114 controls [144 knees; 77% female; mean age 23.1 years]) were included. Mean TT-PCL of instability and control groups was 21.1 ± 4.1 and 18.8 ± 4.0 mm (p < 0.0001), respectively. Two studies reported significant positive (strong and moderate) correlations between TT-PCL and TT-TG MRI measurements in instability patients. All four investigations reported excellent interobserver and intraobserver reliability in MRI measurement of TT-PCL distance. No study compared TT-PCL distances on MRI and CT. No study assessed correlation between TT-PCL distance and number of instability events or recurrence of instability after surgery. Conclusion: A moderate-to-strong positive correlation exists between TT-PCL and TT-TG measurements taken from MRIs of patellar instability patients. There is excellent interobserver and intraobserver reliability when taking TT-PCL measurements using MRI. This review advocates use of a new pathologic TT-PCL threshold of 21 mm. Level of evidence: Level III, systematic review of Level II–III studies.

Original languageEnglish (US)
Pages (from-to)1-10
Number of pages10
JournalKnee Surgery, Sports Traumatology, Arthroscopy
DOIs
StateAccepted/In press - Sep 16 2017

Keywords

  • Patellar dislocation
  • Patellar instability
  • Tibial tubercle–posterior cruciate ligament
  • Tibial tubercle–trochlear groove
  • TT-PCL
  • TT-TG

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

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