In pathology where there is grossly deficient bone stock the B-PTM knee System contains modular revision components which provide stem fixation to augment the usual compressive surface fixation. A stem may also be used to traverse shaft fractures. The stems used are those of the B-PTM Integrated Hip system and are available in diameters ranging from 10 through 20mm in 1mm increments, and lengths of 25 to 200mm in 25m increments. The connection is reliable, convenient and free of micro-motion.
COMPONENT DESCRIPTION
MODULAR TRICOMPARTMENTAL FEMORAL COMPONENT
The Femoral Component is designed to replace the complex geometry of the femoral articular surface while maintaining an anatomical valgus angle. The radii of curvature decrease from anterior to posterior in a coordinated fashion to provide full flexion while maintaining excellent bearing congruity with either tibial component. Its geometry also congruently accommodates varus-valgus and rotary motions. It accepts a large variety of diameters and lengths of extension stems. This component accepts the modular stems of the B-PTM Hip System.
PATELLAR COMPONENT
The Patella Component consists of a patella bearing, mounted on a metallic anchoring plate. The bearing congruently matches the spherical anterior flange segments and sulcus of the femoral component. The metallic, three peg, anchoring plate is used to protect the prosthesis-cement and prosthesis-bone interfaces. It also functions as a substrate for porous-coating.
UHMWPE PATELLAR COMPONENT
This component provides fully congruent contact on its lateral face except near full extension where contact pressures are low. The medial face, which sees much lower loading, is in line contact with the femoral component.
TIBIAL BEARING
This component is used in the absence of viable cruciate ligaments to provide functional stability by use of proper tension control of the surrounding soft tissues of the knee. These bearings come in a variety of thicknesses to allow flexibility in bone resection of the tibia, to correct gross deformities, and can be extremely useful in revision arthroplasties. A modular bearing with a removable stem is available to ease bearing replacement with the metallic components in situ.
MODULAR TIBIAL COMPONENT
This tibial component accepts the same extension stems that are used with the MODULAR TRICOMPARTMENTAL FEMORAL COMPONENT. This stop does not engage the bearing unless spinout is induced. If this occurs, spin is limited so that normal compression of the joint results in self reduction of the bearing to a normal orientation.
MODULAR STEMS
The stems used are those of the B-PTM Integrated Hip system and are available in diameters ranging from 10 through 20mm in 1mm increments and lengths of 25 to 200mm in 25mm increments. The connection is reliable, convenient and free of micro-motion.
REBAR® SCREWS
These are used to support the implants during the healing of bone grafts used to support the implants, or if cement is used, to support the implants before and during cementation. The knurled regions of the screws enhance their integration into the bone or cement mass used to support the implants. These screws are available in lengths of 20, 25, 38 and 50mm
INSTRUMENTATION AND TRIALS
The primary instruments and trials as well as available hip stem reamers in one mm increments are used in the implantation of the revision components. There are a few specialized revision instruments. These are shown in the “Revision Knee Surgical Procedure’ section in the ‘Surgeons’ menu.
