Each month during the coming year, OrthoBuzz will bring you a current commentary on a “classic” article from The Journal of Bone & Joint Surgery. These articles have been selected by the Editor-in-Chief and Deputy Editors of The Journal because of their long-standing significance to the orthopaedic community and the many citations they receive in the literature. Our OrthoBuzz commentators will highlight the impact that these JBJS articles have had on the practice of orthopaedics. Please feel free to join the conversation about these classics by clicking on the “Leave a Comment” button in the box to the left.
This classic investigation on periprosthetic bone loss (J Bone Joint Surg Am 1992; 74:849–863) was conducted by Tom Schmalzried in the early 1990s working in William Harris’ laboratory. Specimens from osteolytic lesions both near and far from the articular surface in 34 total hip arthroplasties were studied by plain and polarized light microscopy, as well as transmission electron microscopy.
The authors emphasized the role of activated macrophages containing micron and submicron polyethylene particles in the bone resorption evident in the areas of osteolysis. They speculated that the polyethylene-laden joint fluid migrated and penetrated far from the bearing surface to the points of least resistance. Thus, the concept of an effective joint space (i.e., all periprosthetic regions that are accessible to joint fluid and its particulate debris by the pumping action of the joint) was introduced into the orthopaedic lexicon.
Although the findings identified in this study were not necessarily new, the insights proffered by the authors radically altered our thoughts about osteolysis. Using this concept of effective joint space, subsequent investigators and innovators identified methods and designs of hip replacements to retard osteolysis by limiting the generation and spread of particulate debris.
Thus, the 1990s were marked by the development of solid acetabular cups, nonmodular monoblock components, improved liner locking mechanisms to avoid backside wear, circumferentially coated femoral stems, highly crossed-linked polyethylene to lessen abrasive wear, and metal and ceramic bearing surfaces. As appreciated by most orthopaedic residents, the article also led to a generation of questions on the Orthopaedics In-Training Exam (OITE) about the importance of macrophages in the pathogenesis of osteolysis.
Recently, some investigators speculate on a more significant mechanical effect of metal-on-metal joint fluid in causing the pseudotumors and muscle damage/necrosis that is frequently evident. Regardless of whether the primary effect of small particle-laden joint fluid is biologic or mechanical, I believe that the theory of effective joint space remains a valid anatomic concept for all arthroplasty surgeons.
Robert Bucholz, MD
JBJS Deputy Editor for Adult Reconstruction and Trauma