Sebastian Oenning

Background: In the presence of anterior glenoid bone loss (aGBL), options for bony glenoid augmentation include Latarjet procedures and free bone block transfers. Bone graft placement is challenging, and malposition causes complications, such as recurrent instability or osteoarthritis. Hypothesis: With minimal changes in bone block positioning, osteochondral shoulder stability cannot be restored sufficiently. Study Design: Controlled laboratory study. Methods: In a robotic test setup, 14 human cadaveric scapulae were included. Soft tissue was resected, and matching artificial humeri were selected for each specimen. Testing was performed in 60° of glenohumeral abduction with 50 N of glenohumeral compression and anterior-directed translational force to the humerus. Application of 20% aGBL and screw fixation of artificial bone blocks (artBBs) with different buildup shells allowed the following testing stages: (1) intact, (2) 20% aGBL, (3) flush artBB, (4) 1-mm medialized artBB, and (5) 1-mm lateralized artBB. The stability ratio (SR) and medial-lateral humeral head starting position were assessed. Results: Specimens with 20% aGBL provided lower mean SRs than native joints (20.6% [SD, 4.7%] vs 27.8% [SD, 6.7%]; P < .0001). Flush artBB placement (mean, 35.4%; SD, 7.7%) led to an increased SR compared with both native joints ( P = .002) and 20% aGBL ( P < .0001). The mean SR in 1-mm medialized artBBs (21.5%; SD, 5.7%) did not differ compared with that for 20% aGBL ( P = .908). One-millimeter lateralized artBBs (mean, 40.8%; SD, 5%) provided higher SR and more lateral humeral head starting positions compared with flush artBB ( P = .003 and P = .003, respectively). Conclusion: In the presence of aGBL, flush bone block placement restores osteochondral glenohumeral stability, while a 1-mm medialized bone block fails to increase stability. Bone block lateralization of 1 mm provides higher stability but is associated with humeral head lateralization. Clinical Relevance: Glenoid bone block augmentations are established in patients with glenohumeral instability and aGBL. In the case of bone block malposition, complications like recurrent instability or the development of osteoarthritis can occur. This study underlines the importance of accurate bone block placement since only minimum bone block malposition relevantly affects osteochondral shoulder biomechanics.

Introduction: In displaced pediatric proximal humerus fractures (PHF), surgical treatment ranges from closed to open procedures. Soft tissue interposition can impede closed reduction, making open techniques necessary. While K-wire fixation and elastic stable intramedullary nailing (ESIN) lead to good results, plate fixation could be an alternative in patients with limited growth potential and highly unstable or insufficiently retained fractures. Only few studies with low sample sizes have assessed plate fixation, yet. In this study, the outcome of pediatric PHFs treated with plate fixation was evaluated. Materials and methods: We present a retrospective case series of 18 patients with open growth plates and unilateral, displaced PHFs, treated with plate fixation. The mean age at trauma was 12.1 years (± 2.4), the mean follow-up was 6.52 years (± 4.37). A mean fracture angulation of 32.3° (± 10.89°) was seen. Postoperative assessments included range of motion, clinical scores [Simple Shoulder Test (SST), Subjective Shoulder Value (SSV), American Shoulder and Elbow Surgeons (ASES) Shoulder Score, Pediatric/Adolescent Shoulder Score (PASS), Disabilities of Arm, Shoulder and Hand (DASH) Score], radiological parameters and subjective satisfaction. Results: All patients showed excellent results in SST (99.4% ± 0.02), SSV (98.3% ± 0.04), ASES-score (100% ± 0) and PASS (0.99 ± 0.01). In the DASH-score, 17 patients had excellent results, one patient showed a good outcome. Fracture healing occurred in all patients without complications. Eight patients complained about bothering scars. Age, gender and fracture morphology did not affect the outcome. Revision surgery after secondary fracture dislocation did not show a worsened outcome compared to primary plate fixation. Physeal growth plate bridging implants did not worsen the outcome. The timing of implant removal within the first 6 months postoperatively did not affect long-term function. Conclusion: Plate fixation is a safe option in pediatric patients with limited growth potential and highly displaced PHFs. Plate fixation led to a good to excellent functional outcome, regardless of fracture morphology and implant positioning. A higher invasiveness and the need for implant removal must be considered.

Background: The treatment of bony glenoid defects after anteroinferior shoulder dislocation currently depends on the amount of glenoid bone loss (GBL). Recent studies have described the glenoid concavity as an essential factor for glenohumeral stability. The role of glenoid concavity in the presence of soft tissue and muscle forces is still unknown. Hypothesis: Glenoid concavity would have a major impact on glenohumeral stability in an active-assisted biomechanical model including soft tissue and the rotator cuff's compression forces. Study Design: Controlled laboratory study. Methods: In 8 human shoulder specimens, individual coordinate systems were calculated based on anatomic landmarks. The glenoid concavity was measured biomechanically and based on computed tomography. Static load was applied to the rotator cuff tendons and the deltoid muscle. In a robotic test setup, anteriorly directed force was applied to the humeral head until translation of 5 mm (N_ant) was achieved. N_ant was used as a parameter indicating shoulder stability. This was performed in the following testing stages: (1) intact joint, (2) labral lesion, (3) 10% GBL, and (4) 20% GBL. The 8 specimens were divided equally into 2 subgroups (low concavity [LC] versus high concavity [HC]), with 4 specimens each, according to the previously measured concavity. Results: Anterior glenohumeral stability was highly correlated with the native glenoid concavity ( R² = 0.8). In the testing stages 1 to 3, we found a significantly higher mean stability in the HC subgroup compared with the LC subgroup ( P≤ .0142). The HC subgroup still showed higher absolute N_ant values with 20% GBL; however, there was no significant difference from the LC subgroup. The loss of stability in 20% GBL was correlated with the initial concavity ( R² = 0.86). Thus, a higher loss of N_ant in the HC subgroup was observed ( P = .0049). Conclusion: In an active-assisted model with intact soft tissue surrounding and muscular compression forces, the glenoid concavity correlates with shoulder stability. In bony defects, loss of concavity is an essential factor causing instability. Due to their significantly higher native stability, glenoids with HC can tolerate a higher amount of GBL. Clinical Relevance: Glenoid concavity should be considered in an individualized treatment of bony glenoid defects. Further studies are required to establish reference values and develop therapeutic algorithms.