Proximal Humeral Nonunion Treated With an Intramedullary Tantalum Cylinder

Abstract

Nonunion is uncommon after proximal humerus fracture surgery. There is no agreement about preferred method of treatment. Traditional approaches have included laterally based locking plates, autogenous grafting, and endosteal support to provide improved biomechanical stability. Open reduction and internal fixation (ORIF) of proximal humeral nonunion has been performed with various methods, including blade plates and bone grafting, as well as intramedullary support with autologous or allogenic grafts. Both malunion and nonunion have occurred after ORIF with locking plates. Endosteal support in the form of a fibular allograft incorporated into the locking plate construct can increase mechanical stability in selected cases. An ideal implant for proximal humeral nonunion provides medial column mechanical support and osteoconductive and osteoinductive properties. Porous intramedullary tantalum metal may play a role in nonunion surgery as an alternative to fibular allograft because of its versatility of use and salutary biological effects. It offers many material advantages for use in nonunion surgery. Tantalum is extensively porous (75%-80%), has a stiffness close to that of native bone, and offers the possibility of being a carrier for osteoinductive materials. It may also be suitable for patients who refuse allograft material. This article describes a 65-year-old woman with recalcitrant proximal humeral nonunion who was successfully treated with revision ORIF with intramedullary tantalum cylinder augmentation with a lateral-based locking plate and autogenous cancellous bone grafting. At 5-year follow-up, she had excellent motion and clinical and radiographic union.

Structural Enzymology of Nitrogenase Enzymes

“…This observation contrasted with the findings of the first published report of a MoFe protein crystal structure determination (at 8 Å resolution, phased by direct methods) that indicated the two FeMo cofactors were sufficiently close to be bridged by N 2 . 18 The first crystal structures for the nitrogenase proteins were published in 1992 for the Azotobacter vinelandii MoFe protein 19,20 and Fe protein, 21 followed shortly by structures for the C. pasteurianum MoFe protein. 22,23 The resolutions of these structures were insufficient to unambiguously define the metallocluster architecture, and so the initial models integrated elemental analysis on the MoFe protein and isolated FeMo cofactor, stereochemical information from small molecule iron-sulfur cluster structures, and spectroscopic inferences.…”

“…The crystal structure of the A. vinelandii Fe protein confirmed these predictions and revealed the detailed molecular architecture. 21 The Fe protein dimer exhibits approximately two-fold molecular symmetry, with the rotation axis passing through the [4Fe:4S] cluster at one end of the dimer surface. The two chemically identical subunits fold as a single α/β domain of a type frequently observed in nucleotide binding proteins with a predominantly parallel β-sheet flanked by α-helices.…”

Outcome of Osteosynthesis of Late-Presenting Proximal Humerus Non-union: A Case Series

“…The autogenous intramedullary FSG helps obliterate the cavitation (scalloping) of the humeral head fragment, substitutes for bone stock deficiency, gives medial structural, and endosteal support, and avoids varus. Georgiadis and Georgiadis have used an intramedullary tantalum cylinder instead of FSG to provide endosteal support [ 28 ]. We have used a lateral PHILOS plate, through which some screws have been applied through FSG to enhance the strength of fixation.…”

Augmentation in proximal humeral fractures

“…Other augmentation approaches recently studied include humeral allograft, 23 femoral head allograft, 24,25 iliac crest allograft, 26 fibular autograft, 27 and intramedullary titanium cylinder augmentation, 28 which are beyond the scope of this review. This review focuses on augmentation of proximal humeral fractures using fibular allografts and injectable bone graft substitutes.…”