Health Sciences · Robert W. Jackson Arthroscopy
A self-seal sterilization bag includes MacIntosh knee plateau made of Vitallium alloy, and a white plastic femoral component whose bearing surface bearing corresponds to the femoral condyle. The inner (non-bearing) surface of the femoral component has a complex shape that is meant to fit into slots cut into the femoral condyle. Within this portion of the implant is a channel containing a metal wire assembly that is used to locate the implant on an x-ray.
The femoral component contains large traces of bone cement. It is missing one edge, and the bearing surface is cracked and damaged, suggesting that the implant failed and was removed.
Accession Number: 2025.JAC.298
Alternative Name:
Tibial plateau is of Vitallium alloy. The femoral component is likely likely high density polyethylene.
Stamped into the tibial plateau: “[Vittalium symbol] 3S”
The bag, unfolded is aproximately: Height = 1.5, Width = 26, Length = 12.
This is a partial knee replacement consisting of a metal MacIntosh tibial plateau and a plastic (likely HDPE) femoral component. It has been removed from a patient following the failure of the femoral component.
These items likely came from a clinical trial. The evident failure of the femoral component likely indicates the results of such testing and explains why the femoral component was never produced. This prototype design is the reverse of the now-conventional arrangement for knee implants in which a metal femoral component bears on an HDPE insert that serves as the tibial bearing surface. However, this prototype was developed before the convention was firmly established.
The bearing surface of the femoral component is heavily damaged with one edge mostly missing (see image three). Bone cement fills most of the central longitudinal groove. The bearing surface of the tibial component has very little wear. The two components have not been removed from the sterilization pouch in which they were received.
Associated Instruments:
Manufacturer:
Date of Manufacture: c. 1970s
This and other items related to the development of a partial knee replacement based on a MacIntosh plateau and a plastic femoral component were likely gathered by Dr. Robert W. Jackson during his time on staff at the Division of Orthopedic Surgery of Toronto General Hospital.
The Robert W. Jackson Arthroscopy Collection was acquired by the University of Toronto from Dr. Jackson’s family on November 12th, 2020.
Robert W. Jackson, Frederick P. Dewar, David L. MacIntosh, John P. Kostuik, and Robin Black. US4034418A: Artificial knee joint. US Patent. Awarded July 12, 1977.
The MacIntosh hemiarthroplasty (tibial plateau) was developed at the Toronto General Hospital (TGH) beginning in 1954. It is named for its inventor, orthopedic surgeon David L. MacIntosh (1914 – 2013). This was a platform that replaced the bearing surface of a tibial condyle. Though various materials were tried, after 1965 they were made exclusively of Vitallium alloy. A detailed history of that development can be found here.
At some point, possibly in the late 1960s, efforts began to create a femoral implant to match the tibial plateau in order to create a complete partial knee replacement. Little is known so far about this effort. However, the Jackson Collection contains several intriguing prototype artifacts. The best source is a 1977 patent (US patent 4,034,418), led by Robert W. Jackson and assigned to the University of Toronto, which describes a mature version of this arrangement.
An Unconventional Arrangement
With the benefit of decades of experience, medical manufacturers have settled on a conventional arrangement for an artificial knee joint. This consists of a metal tibial component that serves as a platform for a plastic (high-density polyethylene HDPE) tibial liner that forms the tibial bearing surface. The metal femoral implant component bears upon this lower plastic liner.
The developmental efforts towards a partial knee replacement that emerged from the MacIntosh hemiarthroplasty is the reverse of this arrangement, with a plastic (likely HDPE) femoral implant on top and a metal tibial component on the bottom. This arrangement was tested and likely proved unworkable. This technology did not make it to market, though prototypes were provided by a major manufacturer.
This example appears to be part of a clinical testing phase for which no documentation has yet been found. Clearly, the plastic femoral component failed in this instance. Whether this is indicative of fundamental flaws in the design is possible but unclear.
This example is interesting as it includes a conventional MacIntosh tibial plateau, rather than the thinner example described in the 1977 patent and shown in this catalogue entry.