Hexagonal grafts in mosaicplasty: Biomechanical comparison of standard cylindrical and novel hexagonal grafts in calf cadaver model.

OBJECTIVE: Cylindrical grafts are currently used to cover defected area in mosaicplasty. However, there are some difficulties with cylindrical grafts, such as potential dead space between grafts and insufficient coverage. Hexagonal graft (honeycomb model) was created and evaluated in this biomechanical study. Hypothesis was that harvesting grafts with hexagonal shape, which has the best volume geometry characteristics in nature, would be biomechanically advantageous and provide superior pull-out strength. METHODS: Total of 24 fresh calf femurs were divided into 3 equal groups. In the first group, 1 cylindrical and 1 hexagonal graft were compared. Second group consisted of 3 cylindrical and 3 hexagonal grafts. Third group was designed to evaluate effect of graft depth; hexagonal graft implanted at 5 mm depth was compared with 20-mm-deep hexagonal graft. All specimens were subjected to pull-out test. Friction field and graft surface area were also evaluated. RESULTS: Pull-out strength comparison of 15-mm-deep triple cylindrical grafts and 15-mm-deep triple hexagonal grafts in second group revealed statistically significant difference in favor of hexagonal grafts (p < 0.05). Surface area of cylindrical graft with 9-mm diameter was calculated to be 50.27 mm2, while hexagonal graft surface area was 55.425 mm2. Volume ratio of cylindrical and hexagonal grafts was 753.98 mm3 and 831.375 mm3, respectively. CONCLUSION: This biomechanical study demonstrated that graft geometry, especially in multiple graft applications, is a factor that influences stability. Hexagonal grafts appear to be more stable than cylindrical grafts in multiple applications, and they may be used to cover a larger defected area.

Pure Intrathoracic Scapular Dislocation.

Scapular dislocation, also known as locked scapula or scapulothoracic dislocation, is a rare entity that can be identified as extrathoracic or intrathoracic dislocation, depending on the penetration of the scapula into the thoracic cavity. The 3 reported cases of intrathoracic scapular dislocations in the literature are associated with a preexisting condition, such as sternoclavicular separation, prior rib fracture, thoracotomy for a lung transplant procedure, or surgical resection of superior ribs during breast or pulmonary tumor excisions. There are also 3 published cases of intrathoracic scapular impaction, involving comminuted scapular fractures with intrathoracic impaction of the inferior fragment through intercostal space. We report an intrathoracic scapular dislocation that was not associated with fracture of the scapula or predisposing factors. To our knowledge, this is the first case of pure intrathoracic dislocation.