Sunday, December 2, 2012

Management of peri-prosthetic fracture of the humerus with severe bone loss and loosening of the humeral component after total shoulder replacement JBJS B

Management of peri-prosthetic fracture of the humerus with severe bone loss and loosening of the humeral component after total shoulder replacement.

This article emphasizes the difficulty in managing periprosthetic fractures of the humerus. The fractures occurred in older individuals (average age 75, range up to 90 years). The great majority were in women. All but three of the 22 cases were in shoulders with cemented humeral components. 18 patients had severe osteopenia and 4 had mild osteopenia. 17 of the fractures were near the distal tip of the humeral component. While some of the fractures were treated with long stemmed prostheses, others required endoprosthetic replacement of the humerus to the level of the fracture. The authors report a 60% five-year survivorship of these revisions along with complications ranging from instability, component failure, non-union, infection, and nerve palsies.

These authors are to be commended on their valiant attempts to reconstruct these fractures in older individuals with soft bone.

Perhaps the real lesson to be derived from this study is that we need to better understand the factors that might predispose patients to this devastating complication. See our previous posts on the topic. The authors list risk factors as including female gender, revision surgery, press-fit humeral components, rheumatoid arthritis, over-reaming of the humeral canal, proximal humeral deformity or malunion, soft-tissue contracture, aggressive manipulation and osteopenia. It is apparent that any humeral technique that stiffens the upper half of an osteopenic humerus will risk fracture at the tip of the prosthesis. Thus cemented components (as shown in the study) can place the humerus at risk as can press fit components with a tight fit of the prosthetic tip in the diaphysis.

We have sought to minimize the risk of intraoperative and postoperative humeral fractures by avoiding cement (which can create a stress riser at the end of the cement), by avoiding endosteal reaming (which can create a stress riser by notching the inside of the diaphysis), by avoiding a tight cortical fit of the prosthetic stem (which can create a stress riser at the tip of the prosthesis), and by avoiding forcing a too-large prosthesis into smallish bone.

Instead we use intramedullary reamers only to size the canal, stopping as soon as the reamer engages the endosteal surface ('love a first bite') avoiding any notching of the diaphysis as shown on the right below.

We then use impaction grafting (also shown here and here) to build up the inside of the humeral shaft so that a snug fit is achieved without tight contact between the metal stem and the cortex.

Here is a recent post op films of the left shoulder of an 82 year old woman. The humeral component was securely fixed with impaction grafting leaving the tip of the component free of contact with the diaphysis - ergo no stress riser.

Our preferred method for managing periprosthetic fractures is shown here.


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