Health Sciences · Robert W. Jackson Arthroscopy
A knee hemiarthroplasty consisting of two parts:
2025.JAC.295.1: A thin metal tibial plateau with a smooth, slightly concave upper bearing surface and a textured bottom surface. Both upper and lower surfaces have divots on opposite sides that allow it to be gripped by instruments during handling and installation.
2025.JAC.295.2: A white plastic (likely high density polyethylene) femoral member whose bearing surface bearing corresponds to the femoral condyle. Its inner (non-bearing) surface 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.
Note that these two items were not necessarily packaged together when the collection was acquired. However, they correspond to a complete unit as described in U.S. patent 4,034,418 and were catalogued together for this reason.
Accession Number: 2025.JAC.295.1-2
Alternative Name:
Metal aloy (possibly Vitallium); Plastic (possibly high density polyethylene)
Markings: 2025.JAC.295.1-2
2025.JAC.295.1: Height = .4, Width = 4.5, Length = 3.2; -2025.JAC.295.2: Height = 5.4, Width = 2, Length = 2.
This is a partial knee replacement consisting of a metal tibial plateau and a plastic (likely HDPE) femoral component.
These items are likely prototypes of a design that did not make it to market. It is the reverse of the 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.
Both elements are in excellent condition and appear to be unused.
Associated Instruments:
This design is described in a patent assigned to the University of Toronto. It was likely manufactured by Osteo AG, based in Selzach, Switzerland.
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. Whether partial or complete, 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 reversed 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, assembled from loose artifacts within the Jackson collection, represents a complete example as described in the 1977 patent. The metal tibial component resembles the image shown in the patent diagram, though it differs in several ways from a “conventional” MacIntosh hemiarthroplasty as represented in this collection. These include the pattern of the textured surface on the bottom, the flattened area surrounding the bearing surface, and the divots included in the top and bottom surfaces to facilitate placement with a tool.
- Donated to UTSIC