The most important finding of this study is the reporting of many epidemiological variables of an uncommon injury. This was made possible by the large data sample in the SFR.
The present study shows that bony Bankart lesions are more common in the population over 50 years of age. This is contrary to the soft-tissue Bankart lesion which usually occurs in the young population (30). One reason why a bony Bankart lesion is more typical in older patients could be biomechanical and biological changes leading to reduced elasticity of the joint capsule (31, 32).
There was a predominance of bony Bankart lesions in males (58.7%), which is much lower when compared with the soft-tissue Bankart lesions (75%) in the same group (30). A simple, low-energy fall was one of the most common causes of this injury. This study further reveals a seasonal variation in the distribution of bony Bankart lesions. This type of injury is more common during the winter period, possibly related to slippery conditions.
Most bony Bankart lesions were treated non-surgically, particularly in females. This could be related to fracture size, the position of the fracture related to differences in ligament laxity, bone quality or other factors (32, 33). The age of the patients did not affect the treatment strategy.
A higher prevalence of non-surgical treatment could be related to the relatively low degree of dislocation of the bony Bankart fragment, a low complication rate and good bone-to-bone healing potential (23, 34, 35). Olds et al. reported a low risk of recurrent instability in the presence of a bony Bankart lesion (14). Robinson et al. reported an increased risk of recurrence in the presence of a glenoid rim fracture during the first six weeks following a first-time traumatic anterior shoulder dislocation in only 3.2% of patients(36).
One-third of bony Bankart lesions; 225/734 (30.7%)) were treated surgically, which is similar to previously published data on the treatment of soft-tissue Bankart lesions (37, 38). In the present study, we found that the majority of the bony Bankart lesions were due to low-energy trauma and were mostly treated non-surgically (71% of all patients), compared with high-energy bony Bankart lesions, which were treated surgically to a greater extent. Almost half the patients (48%) with bony Bankart lesions induced by high-energy trauma were treated surgically, which could be related to more dislocated and larger bony Bankart fragments due to high-energy forces.
It is difficult to draw any definitive conclusion in terms of patient quality of life one year after injury due to the limited response rate. However, quality of life appears to decrease slightly in both groups, especially in the non-surgically treated group. These results were statistically significant, albeit not clinically relevant, since the minimal clinically important change on the EQ-VAS has been shown to supersede the attained values (39).
Further, we compared the data with previously published epidemiological studies based on the SFR analysing other types of fractures (40–42). Some differences and common features were found. Most fractures had a similar seasonal variation with an increased number of injuries during the winter months and a higher incidence after the age of 40 years. The main difference between studies was the distribution of gender. The majority of bony Bankart lesions occurred in males and decreased dramatically after the age of 75 years compared with other fractures (40–42).
These results may suggest that bony Bankart injuries are probably not related to fragility or reduced bone mineral density.
There are several limitations to the present study. One of them was the low response rate in PROMS, especially at the one-year follow-up. Another limitation is that the modified Euler and Rüedi classification could lead to misclassification, causing difficulties for surgeons to classify the fracture in some non-standard cases. The simplicity of this classification that has been used to classify different types of glenoid fracture in the SFR is an advantage, compared with the AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification of scapular fractures from 2013. However, it is incomplete and can make it difficult to distinguish isolated anterior glenoid fractures with a large anterior fragment from bony Bankart lesions in several patients (43).
One of the main strengths of this study is the large amount of data from the Swedish Fracture Register, including non-surgically treated fractures. The current register-based study provides reliable data on bony Bankart occurrence in Sweden.