Iliac bone grafting of the intact glenoid improves shoulder stability with optimal graft positioning

BACKGROUND: Bone grafting procedures are increasingly popular for the treatment of anterior shoulder instability. In cases with high risk of recurrence, open coracoid transplantation is preferred but can be technically demanding. Free bone graft glenoid augmentation may be an alternative strategy for high-risk patients without significant glenoid bone loss. This biomechanical cadaver study aims to assess the stabilizing effect of free iliac crest bone grafting of the intact glenoid and the importance of sagittal graft position. METHODS: Eight fresh frozen cadaver shoulders were tested. The bone graft was fixed on the glenoid neck at three sagittal positions (50%, 75% and 100% below the glenoid equator). Displacement and reaction force were monitored with a custom device while translating the humeral head over the glenoid surface in both anterior and antero-inferior direction. RESULTS: Peak force (PF) increased significantly from the standard labral repair to the grafted conditions in both anterior (14.7 (±5.5 N) vs. 27.3 (±6.9 N)) and antero-inferior translation (22.0 (±5.3 N) vs. 29.3 (±6.9 N)). PF was significantly higher for the grafts at the 50% and 75% positions, compared to the grafts 100% below the equator with anterior translation. Antero-inferior translation resulted in significantly higher values for the 100% and 75% positions compared to the 50% position. CONCLUSIONS: This biomechanical study confirms improved anterior glenohumeral stability after iliac crest bone graft augmentation of the anterior glenoid. The results also demonstrate the importance of bone graft position in the sagittal plane, with the ideal position determined by the direction of dislocation

Developing a temporal framework for past natural resource exploitation in the Sonian Forest using optically stimulated luminescence dating

The Sonian Forest (Central Belgium) has recently been added to UNESCO’s List of World Heritage as an example of the extraordinary evolution of the beech ecosystem since the last Ice Age. Interestingly, and while often considered as “untouched” natural heritage, the Sonian forest in fact preserves an undisturbed and extremely vast archive of its (pre)historical exploitation by man, and intensive iron and charcoal production in particular. So far, the chronology of these features has been entirely based on 14C-dating of charcoal from above-ground kilns. Most of these ages indicate post-1650 CE charcoal production, a period over which 14C is of little use. This implies a major gap in our understanding of the chronological order of events and activities during the past couple of centuries. This study reports on an Optically Stimulated Luminescence (OSL) dating methodology that aims at establishing chronologies for post-1650 CE features with a high temporal resolution. The investigations use sand-sized quartz extracted from sediments that were heated as a result of charcoal production and iron extraction, in combination with the single-aliquot regenerative-dose (SAR protocol). We first document the luminescence characteristics in terms of signal intensity, dose response, a variety of procedural tests (such as recuperation, recycling, dose recovery and dependence on thermal pre-treatments) and completeness of resetting. We address potential problems associated with the (near)surficial position of the investigated features in terms of post-depositional processes and calculation of the dose rate. As a test of accuracy, the obtained quartz SAR OSL ages are compared with 14C-dates for multiple pre-1650 CE charcoal kilns and roasting places. Finally, the approach is applied to a few younger features as an illustration of its potential. We discuss the time-resolution that can be achieved, with a focus on the temporal resolution that can be achieved to distinguish between generations of charcoal and iron production sites, rather than assigning numerical ages to them. We conclude that OSL signals from heated sedimentary quartz hold considerable potential for dating the remains of past natural resource exploitation in the Sonian Forest, which is of particular relevance for features that are not older than a few hundred years. In addition, our study provides a firm methodological framework for addressing the chronometric issues pertaining to the vast number of similar structures that are archived within the loamy forest soils of Northwest and Central Europe