Origins of the
Ream & Run
The normal shoulder joint consists of a ball (the humeral head) and socket (the glenoid) which are covered by smooth articular cartilage.
In shoulder arthritis this cartilage is lost, and the ball and socket lose their normal shape
A common surgical procedure for managing severe shoulder arthritis is a total shoulder arthroplasty in which a polyethylene (plastic) implant (yellow arrow) is inserted to resurface the glenoid along with a metal ball to replace the arthritic humeral head (red arrow).
Total shoulder arthroplasty is a reliable method for resurfacing the joint and usually improves shoulder comfort and function for many years. Because the glenoid implant is “prefabricated” to the desired shape, the restoration of the joint surfaces is accomplished at the time of surgery.
However, wear and loosening of the plastic glenoid socket has been and remains one of the most important causes of failure of total shoulder arthroplasty. Concern about glenoid component failure has led many surgeons to limit patients’ activities after this procedures.
The University of Washington’s Shoulder Research Program has studied the problem of the arthritic glenoid since 1988 – these investigations have led to the development of the ream and run procedure.
What follows is a brief summary of our work, explaining how we got to where we are today. For those wishing to learn more, we’ve provided “hot links” to some of the articles we have published, clicking on the title will bring up an abstract of the article.
Glenoid component failure in total shoulder arthroplasty identifies loosening of the component and wear of the joint surface as two important modes of failure. The challenge of fitting and securing the component to the bone of the glenoid is pointed out in Edge displacement and deformation of glenoid components in response to eccentric loading. The effect of preparation of the glenoid bone and in The radiographic evaluation of keeled and pegged glenoid component insertion . The problem of wear of the surface of the plastic glenoid component is assessed in Alterations in surface geometry in retrieved polyethylene glenoid component and Observations on retrieved polyethylene glenoid components
One of our early observations was that in many cases, shoulders with failed glenoid components could be satisfactorily treated by simply removing the component and allowing the bone to heal as shown in the examples below.
This led us to investigate whether simply reaming the glenoid bone surface to the desired shape and matching this shape to a metal humeral head could allow healing of a new joint surface.
In our study, Healing of reamed glenoid bone articulating with a metal humeral hemiarthroplasty: a canine model we showed that indeed the reamed glenoid could heal over with fibrocartilage that was biologically bonded to the underlying bone, avoiding the problem of attaching a plastic socket replacement to the bone. The figures below show (a) a normal glenoid, (b) a reamed glenoid, (c) the healing glenoid surface at 10 weeks after reaming and (d) the healed glenoid surface at 24 weeks.
On the higher magnification views below, one can see the regenerating fibrocartilage (red) emerging from the reamed bone surface (blue).
Importantly, the new fibrocartilage is firmly bonded to the bone, avoid the problem of fixing a plastic glenoid component to bone.
Our next question was whether the bony glenoid could be reamed in a manner that provided the same stability offered by a polyethylene glenoid component. In the study. Optimizing the Glenoid Contribution to the Stability of a Humeral Hemiarthroplasty without a Prosthetic Glenoid we used a cadaver model to compare the stability angles in different directions for (a) normal glenoids, (b) glenoids denuded of cartilage and labrum, (c) bony glenoids reamed to a radius of curvature of 25 mm, and (d) bony glenoids reamed to a radius of curvature of 22.5 mm, each shown in the figure below.
The figure below shows the stability (measured as balance stability angle) for different directions around the face of the glenoid (superior is 0 degrees, anterior is 90 degrees, inferior is 180 degrees, and 270 is posterior). Note that the stability of the normal glenoid (cream color) is dramatically reduced by denuding the glenoid of articular cartilage and labrum (teal color). Spherical reaming to a radius of curvature of 25 mm (gold color) restores the normal stability. Reaming to this degree provides the same stability as a polyethylene glenoid component with a radius of curvature of 25 mm. Reaming to a radius of 22.5 mm further increases the stability.
This basic research set the stage for the clinical application of this procedure for patients with shoulder arthritis who wished to avoid the risks and limitations associated with a polyethylene glenoid component. From this point our research has been directed at optimizing the clinical outcomes of this procedure through advances in patient selection, surgical technique and rehabilitation.
While the formal name of this procedure is “humeral hemiarthroplasty with non-prosthetic glenoid arthroplasty”, it is most widely known by the nickname “ream and run”. The “ream” indicates that the glenoid is reamed and not replaced. The “run” indicates the importance of immediate postoperative motion to minimize the risk of stiffness and to mechanically induce the formation of fibrocartilage on the reamed glenoid surface.