‘On-track’ and ‘off-track’ shoulder lesions

Abstract

Shoulder stability depends on the position of the arm as well as activities of the muscles around the shoulder. The capsulo-ligamentous structures are the main stabilisers with the arm at the end-range of movement, whereas negative intra-articular pressure and concavity-compression effect are the main stabilisers with the arm in the mid-range of movement.There are two types of glenoid bone loss: fragment type and erosion type. A bone loss of the humeral head, known as a Hill-Sachs lesion (HSL), is a compression fracture of the humeral head caused by the anterior rim of the glenoid when the humeral head is dislocated anteriorly in front of the glenoid. Four out of five patients with anterior instability have both Hill-Sachs and glenoid bone lesions, which is called a ‘bipolar lesion’.With the arm moving along the posterior end-range of movement, or with the arm in various degrees of abduction, maximum external rotation and maximum horizontal extension, the glenoid moves along the posterior articular margin of the humeral head. This contact zone of the glenoid with the humeral head is called the ‘glenoid track’.A HSL, which stays on the glenoid track (on-track lesion), cannot engage with the glenoid and cannot cause dislocation. On the other hand, a HSL, which is out of the glenoid track (off-track lesion), has a risk of engagement and dislocation. Clinical validation studies show that the ‘on-track/off-track’ concept is able to predict reliably the risk of a HSL being engaged with the glenoid. For off-track lesions, either remplissage or Latarjet procedure is indicated, depending upon the glenoid defect size and the risk of recurrence.Cite this article: EFORT Open Rev 2017;2:343-351.

Editorial Commentary: Glenoid Track Instability Management Score or Instability Severity Index Score—Will This Decrease Latarjet Abuse?

“…T he current prognostic study retrospectively evaluating the effectiveness of the Glenoid Track Instability Management Score (GTIMS) concludes that the GTIMS is a more refined prognosticator of which shoulder instability patients require the Latarjet procedure than the Instability Severity Index Score (ISIS) published in 2007. 1 The GTIMS incorporates the "ontrack" and "off-track" concept 2,3 with the same "nonbone loss" clinical risk factors in the ISIS scoring system (aged < 20 years, 2 points; competitive sports participation, 2 points; overhead or contact sports participation, 1 point; and shoulder hyperlaxity, 1 point). In the GTIMS, on-track lesions receive 0 points whereas offtrack lesions receive 4 points.…”

“…Similarly, Yang et al 9 reported that in 189 patients with recurrent anterior shoulder instability with off-track Hill-Sachs lesions and less than 25% glenoid bone loss, an arthroscopic Bankart procedure with remplissage achieved equivalent subjective results and revision rates to the Latarjet procedure. Finally, it is interesting that Itoi 3 opined that an arthroscopic Bankart procedure with remplissage may be a good procedure for off-track Hill-Sachs lesions with glenoid bone loss of less than 25%. His exceptions to this are overhead throwing athletes and contact or collision athletes.…”

Editorial Commentary: Open or Arthroscopic Surgery? Practice Makes Perfect…We Do Best What We Do Most Often

“…Many factors impact the incidence of recurrent instability 7 ; they include symptom duration, number of dislocations (especially 5 or more), revision cases, Hill-Sachs lesion sizes, glenoid bone loss, and "on-track" or "off-track" lesions. [7][8][9] The instability severity index score 10,11 and glenoid track instability management score 12 scoring systems include meaningful prognostic factors impacting surgical outcomes that were not appreciated in earlier case series: younger than 20 years of age, competitive sports participation, overhead or contact sports, and shoulder hyperlaxity. Significant glenoid bone loss is perhaps the most widely appreciated variable.…”

Editorial Commentary: Methodology of Measuring Bone Loss in Recurrent Shoulder Instability Surgery: Traditional Computed Tomography Scan and Magnetic Resonance Imaging Do Not Tell the Full Story

“…An on-track/ off-track determination was made using standard and prior well-referenced techniques. [7][8][9][10] Overall, the authors are to be congratulated for using multiple observers for the determination of these measurements. The average surface area from the circle method on CT scan was 18.4% and on MRI was 16.8%.…”