Glenoid Notch

Through an arthroscope, the variable-sized glenoid can normally be seen in its entirety, where it “…is described as a kidney bean or an inverted comma” [1,4,13]. The glenoid is a pear-shaped structure, with the inferior half being wider than the superior half [3].

The anterior margin of the glenoid bears a notch that varies in appearance, ranging from being very prominent to absent [Figure 3] [6,14]. At the glenoid notch, normal synovial outgrowths often occur, which may resemble “…fraying of the synovium and a small synovial fringe” [6,10].

In an anatomical study, Prescher and Klümpen [14] reported the glenoid notch to be present in 55% of scapulae, with such glenoids adopting a pear-shaped or an inverted comma-shaped configuration. The remaining 45% of scapulae, without a glenoid notch, were round or oval in shape [14]. No gender difference was noted regarding the incidence of the notch [14].

In a cadaveric study, Lehtinen et al. [15] reported variation in the anatomy of the glenoid rim angle, with it being slightly higher at the 3 o’clock position on the anterior rim than at the 9 o’clock position on the posterior rim. The posterior glenoid was shown to be concave, whilst the anterior glenoid extends almost straight medially [15].

In our study, the glenoid notch was found to be present in 46.2%, absent in 52.3%, and not visualised in 1.5% of cases. No other arthroscopic study has noted the prevalence of the glenoid notch. The results obtained show a slightly lower prevalence of the notch compared to those previously reported in an anatomical study [13], which found it to be present in 55% and absent in 45% of scapulae. The differences observed may be attributed to the often poorly visualised anterior margin of the glenoid during arthroscopy.

Both the anatomical study [13] and our study differ slightly with regard to the sex prevalence of the glenoid notch. No gender difference was found in the anatomical study [13], whereas we found it to be marginally more common in women.

A shallow notch was more frequently observed than a prominent one. No other study has commented on the prevalence of the shape of the glenoid notch.