Summary

The predictive value of the “on-track/off-track” concept has been recently called into question by the introduction of the “Hill–Sachs interval to glenoid track width ratio” (H/G ratio), which can predict an increased risk of recurrent instability after arthroscopic Bankart repair

Abstract

Background

The predictive value of the “on-track/off-track” concept has been recently called into question by the introduction of a new threshold between peripheral and central on-track lesions: the so-called “Hill–Sachs interval to glenoid track width ratio” (H/G ratio). The aim of the present study was to analyze which pattern of bipolar lesion increases the risk of recurrent anterior gleno-humeral instability after arthroscopic Bankart repair.

Methods

A retrospective study was conducted. Patients affected by recurrent anterior gleno-humeral instability who underwent arthroscopic Bankart repair with a minimum of 12 months follow-up were included. A preoperative computed tomography (CT) scan was performed in all patients. Only patients with on-track bipolar defects were included. Subsequently, three-dimensional computer-based reconstruction of the Hill-Sachs and glenoid bone defect were performed using a dedicated software in order to obtain the H/G ratio following the formula: Hill Sachs interval/glenoid track width. Included patients were than divided into two groups according to the H/G ratio: group 1, patients with H/G ratio< 0.7; group 2, patients with H/G ratio > 0.7. The primary outcome was recurrent instability after surgery. Secondary outcomes were: Quick-DASH, ASES and WOSI score.
Comparison between groups was performed by use of chi-square test for categorical variables and unpaired t-test for discrete variables. Significance was set at p<0.5.

Results

The study included 36 males and 4 females. Mean age (+ SD) of patients was 25.7 ± 7.6 years. Each group was composed of 20 patients. Mean follow-up in group 1 was 54.6 + 30.68; while mean follow up in group 2 was 51 + 34.65. Comparison between groups did not show significant differences nor for baseline characteristics, neither at follow-up. Two recurrent instabilities occurred in group 2 (H/G ratio >0.7) (p<0.147).

Conclusions

Although two recurrent instabilities occurred only in group two, no significant differences could be found between central and peripheral track lesions.