Glenohumeral joint injuries frequently result in shoulder instability. However, the biomechanical effect of cartilage loss on shoulder stability remains unknown. The aim of the current study was to investigate biomechanically the effect of two severity stages of cartilage loss in different dislocation directions on shoulder stability. Joint dislocation was provoked for 11 human cadaveric glenoids in seven different dislocation directions between 3 o'clock (anterior) to 9 o'clock (posterior) dislocation. Shoulder stability ratio (SSR) and concavity gradient were assessed in intact condition, and after 3 mm and 6 mm simulated cartilage loss. The influence of cartilage loss on SSR and concavity gradient was statistically evaluated. Between intact state and 6 mm cartilage loss, both SSR and concavity gradient decreased significantly in every dislocation direction (p≤0.038), except the concavity gradient in 4 o'clock dislocation direction (p=0.088). Thereby, anterior-inferior dislocation directions were associated with the highest loss of SSR and concavity gradient of up to 59.0% and 49.4%, respectively, being significantly higher for SSR compared to all other dislocation directions (p≤0.04). The correlations between concavity gradient and SSR for pooled dislocation directions were significant for all three conditions of cartilage loss (p<0.001). From a biomechanical perspective, articular cartilage of the glenoid contributes significantly to the concavity gradient, correlating strongly with the associated loss in glenohumeral joint stability. The highest effect of cartilage loss was observed in anterior-inferior dislocation directions, suggesting that surgical intervention should be considered for recurrent shoulder dislocations in the presence of cartilage loss

Osteochondral glenoid loss is associated with recurrent shoulder instability. The critical threshold for surgical stabilization is multidimensional and conclusively unknown. The aim of this work was to provide a well- measurable surrogate parameter of an unstable shoulder joint for the frequent anterior-inferior dislocation direction. The shoulder stability ratio (SSR) of 10 paired human cadaveric glenoids was determined in anterior-inferior dislocation direction. Osteochondral defects were simulated by gradually removing osteochondral structures in 5%-stages up to 20% of the intact diameter. The glenoid morphological parameters glenoid depth, concavity gradient, and defect radius were measured at each stage by means of optical motion tracking. Based on these parameters, the osteochondral stability ratio (OSSR) was calculated. Correlation analyses between SSR and all morphological parameters, as well as OSSR were performed. The loss of SSR, concavity gradient, depth and OSSR with increasing defect size was significant (all p<0.001). The loss of SSR strongly correlated with the losses of concavity gradient (PCC = 0.918), of depth (PCC = 0.899), and of OSSR (PCC = 0.949). In contrast, the percentage loss based on intact diameter (defect size) correlated weaker with SSR (PCC=0.687). Small osteochondral defects (≤10%) led to significantly higher SSR decrease in small glenoids (diameter <25mm) compared to large (≥ 25mm) ones (p ≤ 0.009). From a biomechanical perspective, the losses of concavity gradient, glenoid depth and OSSR correlate strong with the loss of SSR. Therefore, especially the loss of glenoidal depth may be considered as a valid and reliable alternative parameter to describe shoulder instability. Furthermore, smaller glenoids are more vulnerable to become unstable in case of small osteochondral loosening. On the other hand, the standardly used percentage defect size based on intact diameter correlates weaker with the magnitude of instability and may therefore not be a valid parameter for judgement of shoulder instability

The laterjet procedure is an important option in both primary and revision surgeries, especially in anterior shoulder instabilities that progress with glenoid bone loss. 12 patients who had a history of unsuccessful arthroscopic bankart repair and who underwent laterjet procedure in Ankara Atatürk Research and Training Hospital between 2013 and 2017 were included in the study and the patients were evaluated retrospectively. The mean age of the patients was calculated as 27.7 (range 21 to 38 years). Rowe and Walch-Duplay scores and operated shoulder (OS)-healthy shoulder (HS) range of motion (ROM) measurements were used to evaluate patients clinically and functionally. The mean follow-up time of the patients was calculated as 5.5±1.8 years. Firstly, no dislocation history was recorded in any patient afer the laterjet procedure. The mean Rowe score was calculated as 82.5 (range 60–100). Accordingly, 8 patients had excellent result, 3 patients had good result and 1 patient had fair result. The mean Walch-Duplay score was 81.4 (range 55–100). It was determined as excellent result in 6 patients, good result in 4 patients and fair result in 2 patients. Another data, joint ROM of the OS-HS of patients are shown in the table. There was some limitation in OS compared to the HS. p<0.05 value was accepted as statistically significant. While there was a statistically significant difference in external rotation (OS:35.2º, HS:56.4º)(p=0.003), internal rotation (OS:65.7º, HS:68.1º)(p=0.008) and flexion (OS:171.2º, HS:175.9º)(p=0.012) degrees but there was no statistically significant difference in abduction degrees (OS:164.3º, HS:170.4º) (p=0.089). In radiological evaluation, partial graft resorption was detected in 1 patient, but it was asymptomatic. The osteoarthritis which is one of the complications of laterjet procedure, was not detected radiologically. There are some limitations of the study. Firstly, it is a retrospective study. Secondly, the demographic features of the patients such as age, gender, profession and dominant hand are excluded. Thirdly, the mean follow-up time is not too long. Finally, some of the scales filled in are based on the patient's declaration, which may not yield sufficient objective results. In conclusion, the laterjet procedure is a suitable and reliable technique even for revision surgery in the treatment of anterior shoulder instability. It gives positive results in terms of shoulder stability and function. The major disadvantage was found to be the limitation of external rotation. Longer follow-up is needed for another outcomes and late complications, such as osteoarthritis. For any figures or tables, please contact the authors directly