Zone 1 is compromised by all causes of implant failure, and further bone loss can occur at implant removal. To allow fixation in Zone 1, it is necessary to establish a stable surface, free of sclerotic bone, avascular membrane and loose cement debris. Where bone stock allows, flat aligned cuts with augmentation improve implant stability and fixation. Augmentation by cement, bone graft or metal augment is possible but in Zone 1 reliable fixation is only achieved with PMMA cement. Where augmentation is needed, fixation in at least one other zone is necessary. The geometry of the diaphysis and that of the epiphysis are not congruent; therefore, an offset is sometimes needed to optimise Zone 1 coverage and avoid medial overhang of the tray.

Bone reacts to loading with increased bone density, and when unloaded, bone will be reabsorbed [9, 10]. Traditional revision knee replacement systems bypass the metaphysis concentrating on diaphyseal and joint surface (Zones 3 and 1) fixation. However, fixation in the metaphysis (Zone 2) allows fixation closer to the point of articulation and makes restoration of the joint line easier. The geometry of the metaphysis and that of the joint surface are similar therefore obviating the need for an offset on the tibial implant. Similarly, fixation in Zone 2 allows posterior translation of the femoral component and the use of shorter stems, to mitigate against femoral bowing which moves implants anteriorly. Failure to utilise Zone 2 can lead to uncontrolled biomechanical sheer stress and instability of augment fixation in Zone 1 potentially leading to early failure of the revision [11–13].

There are currently only two options for direct fixation in Zone 2, cement [14] or metaphyseal sleeves (DePuy Synthes) [15, 16]. Cement fixation in metaphyseal bone is not costly, is readily available and can be used with either cemented or uncemented stems. Metaphyseal sleeves have been available since 1975 but have been most widely used as part of the S-ROM Noiles, rotating hinge system which has shown good midterm results [15]. Metaphyseal sleeve fixation optimises load transfer to improve bone regrowth (“Wolff’s law”) and ongrowth [16]. Fixation closer to the joint space provides better restoration of joint line and axial/rotational fixation stability even in the presence of cortical or cancellous bone defects [17, 18]. Metaphyseal sleeves as part of mobile-bearing revision systems have been available for over 30 years but have only belatedly gained popularity, showing good early to midterm results [19–21]. The concept of metaphyseal sleeves was introduced more than 30 years ago and has shown good midterm results [17, 18]. If Zone 1 is sufficiently preserved to accept a worthwhile cement mantle, additional fixation in Zone 3 might not be necessary. However, insufficient data on stemless metaphyseal sleeve fixation exist for general use to be recommended.

Metaphyseal sleeves are the only method available that provides both bone reconstruction and direct implant fixation. Indirect metaphyseal fixation in Zone 2 is possible when reconstruction has been achieved first. As with Zone 1 augmentation, Zone 2 reconstruction can be achieved with cement and bone graft (bulk allograft or morsellised impaction graft) [22] or by the use of a trabecular metal cone (Zimmer) which acts as metal bone graft and is used as a reconstruction ring. Trabecular metal has a structure similar to cancellous bone and is highly biocompatible and osteoconductive [23, 24]. Once metaphyseal reconstruction is secure and stable, secondary Zone 2 fixation is achieved with bone cement. Trabecular metal cones offer the advantages of availability and intraoperative press-fit stability, allowing immediate weight bearing [25, 26]. Zone 2 reconstruction, however achieved, should be supported by secure Zone 3 fixation with either cemented or uncemented stems.

Fixation by diaphyseal stems in Zone 3 will offload the metaphysis, protecting the implant/cement interface from potential failure. Cemented or uncemented stems can be used; both offer long-term survival, but both have individual limitations. In cemented stem fixation, bone resorption occurs in the metaphysis over time [27]. Using cementless stems seems to be beneficial for the bone of the metaphysis [28, 29]; however, radiolucent lines around the stems can be observed in many cases with time. The geometry of the diaphysis and that of the epiphysis are not congruent; therefore, an offset is occasionally needed. With this concept, an optimised coverage of the joint surface can be assured. However, it is still unclear whether a cemented or an uncemented fixation of the stems is advantageous, and optimal length and optimal thickness of the stems are also still unclear [30].

Management options are based on the severity of defect and the chosen method of bone reconstruction, which range from bone cement, allograft and metal augmentation to megaprosthesis. Recently, new alloys with high porosity have been introduced with satisfactory short-term results [31, 32]; however, it should be recognised that all methods of managing bone loss have different pros and cons [33]. Selection of the best treatment method is based on many factors, including defect size and location, the patient’s age and health and ability to participate in the necessary postoperative rehabilitation. Metaphyseal sleeves and porous tantalum cones are a major addition in dealing with large, central, contained and uncontained defects. The use of stem extensions in cases of bone deficits is helpful in enhancing fixation and lessening stresses to weakened condylar bone [34].