Once the surgeon has classified the bone defect, a starter reamer is used to open the metaphyseal bone until the desired symmetry is achieved for subsequent sleeve placement [42]. Trial sizing of components is performed, and once the appropriate size is selected, the sleeve is placed. Usually a tapered junction that is system specific is used to connect the sleeve to the stem, rather than cement [8]. Both cemented and cementless stems are available for use. When using a cemented stem proximal to the femoral sleeve or distal to the tibial sleeve, the combination sleeve and stem is cemented by filling the femoral and tibial canals with cement prior to insertion of the components. In a cementless system, the stems are impacted into the metaphyseal-diaphyseal bone of the distal femur and/or proximal tibia in order to achieve adequate axial and rotational press fit. Bone graft is used to fill any voids that exist between the host bone and the sleeve.

The advantages of this approach include a straightforward surgical technique that can be effectively used in mild to moderate bone loss. The disadvantages of this approach are that the preparation broaches can be difficult to use in sclerotic bone, and these sleeves are intrinsically specific to one implant system.

The surgical technique for porous tantalum metaphyseal cones has previously been described [8, 27, 43, 44]. Once the surgeon has decided to use a metaphyseal cone, a trial intramedullary stem or reamer may be used to create the appropriate positioning of the cone. Trial sizing of the cone is done by inverting the cone to match the size most closely to the proximal part of the defect in the tibia or the distal part of the defect in the femur. Due to the variability of bone defects, cones can be contoured, usually to accommodate large defects. The bone is then contoured free hand with a high-speed burr to ensure optimal press fit. The cone is impacted into its final position, and trial components and stems are inserted. The final sized implant and stem are inserted through the cone into the correct rotational alignment. The interface between the cone and stemmed implant is reinforced with cement. It is our preference to only utilize cemented stems. When using a cemented stem proximal to the femoral cone or distal to the tibial cone, the stem is passed through the cone, placed in the cement, and held in place until the cement hardens. Bone graft is used to fill any voids that exist between the host bone and the cone.

The advantages of these metaphyseal cones are that there are multiple shapes and sizes to accommodate a large spectrum of bone defects in the moderate to severe range of bone loss. Additionally, the porous tantalum can be cut with a high-speed burr to alter the shape and size if needed. The primary disadvantage of these cones is that the bone preparation is done with high-speed burrs in a freehand manner, which results in a less than optimal bone preparation in many cases and is often quite time-consuming. Additionally, the size and shape of these implants often require considerable bone removal, and this is particularly true of the femoral cones.

Once the surgeon has decided to use a metaphyseal cone, the canal is reamed up to a diameter so that the reamer is stable within the canal. Based upon the intended size of the prosthesis, a target range of cone sizes can be anticipated to gauge the depth of the central symmetric cone reamer (Fig. 10.5). In the tibia, a determination can then be made as to whether or not it is desirable to proceed with additional bone preparation for the lobed-shaped cone. If so, a side reamer is used in the appropriate position to prepare the lobe portion of the bone preparation (Fig. 10.6). Symmetric and lobe-shaped trials are then used to judge final position of the cone in relation to the prosthesis. In the femur, the cones are bilobed. The femoral bone preparation is also medullary guided, initiated with a central reamer, and then finally with two-side lobe reamers (Fig. 10.7).

It is important to note that both the tibial and femoral cones are inserted with a stem trial to guide appropriate implant position. The final sized implant and stem are inserted through the cone into the correct rotational alignment. The interface between the cone and stemmed implant is reinforced with cement. It is our preference to only utilize cemented stems. When using a cemented stem proximal to the femoral cone or distal to the tibial cone, the stem is passed through the cone, placed in the cement, and held in place until the cement hardens. Bone graft is generally not required to fill any voids that exist between the host bone and the cone because of the precise nature of the bone milling preparation (Figs. 10.8a, b).

The advantages of these 3-D printed porous titanium cones include more precise and rapid bone preparation, less bone removal, and better axial alignment due to the use of a medullary guided bone preparation system. The disadvantages of this system are yet unknown as there have been no clinical studies yet reported.

Metaphyseal sleeves have been available for revision TKAs for almost four decades, yet most data is relatively short term (Table 10.1). In 2014 , Barnett et al. [48] retrospectively reviewed 34 revision TKAs using stepped porous titanium metaphyseal sleeves (DePuy) in 34 patients (13 females, 21 males; mean age 66 years). The patients had a mean of 0.22 (range, 0–2) prior knee revisions after the primary TKA, and classification of bone loss, performed intraoperatively, included Type 2A [14], Type 2B [15], and Type 3 [5]. At the final follow-up (mean 38 months), all 34 sleeves showed radiographic evidence of osseointegration, and there were no signs of implant migration or fracture. Three patients required reoperation for the following reasons: failure of femoral adaptor [1], supracondylar femoral fracture [1], and intractable end-of-stem pain [1]. The Knee Society functional scores improved by a mean of 34 points, and knee scores improved by a mean of 47 points.