**5. Surgical management**

400 Recent Advances in Arthroplasty

Fig. 9. (a) Aseptic knee prosthesis failure in a 58 years old patient. (b) Intraoperatively a severe confined cavitary deficiency of the medial and lateral tibial plateau was found. (c) The defect was filled with TMT cone and cancellous allograft. (d) Postoperative radiological

Custom-made prostheses represent an excellent biomechanical solution; nevertheless they

result.

**4.6 Custom-made prostheses** 

 Delay until the implant is available. Poor versatility during surgery.

show some disadvantages:

High costs.

Whatever classification used to determine best treatment and whatever any surgical option is available (Table 4), always have to be considered some rules.

Careful component removal is critical to preserve bone stock; the cancellous bone is much weaker away from the native articular surface.

We prefer the use of a small sagittal saw and flexible osteotomes to loosen the components and their fixation interfaces. After careful and successful exposure and component removal, the surgeon assesses the bone defects and begins the reconstruction.

Tibia influences the flexion and extension spaces and establishes a platform for the subsequent arthroplasty. The surgeon must recognize severe proximal tibial bone loss, and recreate the appropriate height to allow for proper component placement and gap balancing. With contained defects, the goal is to obtain firm seating of the tibial tray on a rim of viable bone along with rigid press fixation of an intramedullary stem. Likewise, femoral condyle bone loss can influence femoral component's size and sagittal position. The joint line is an average of 25 mm from the lateral epicondyle and 30 mm from the medial epicondyle; the distance from the epicondyles to the posterior joint line is similar to the distal joint line and is helpful in confirming the correct femoral component size.

Adjustments to ensure correct femoral component rotation usually require augmentation of the posterolateral condyle; additional modification to the position and size of the femoral component may be needed as the flexion and extension gaps are balanced. Once the gaps are equal and stable, the tibial polyethylene is correctly sized.

Management of Bone Loss in Primary and Revision Knee Replacement Surgery 403

Fig. 11. (a,b) Lateral radiographs of total knee prosthesis revision, with patella extremely

This happens in severe patello-femoral arthritis or inammatory arthropathy, when the patella may be thin and track laterally before and during arthroplasty. Treatment depends on the quality of the remaining bone stock and options include non-resurfacing, retention of the remaining thin patellar shell or total patellectomy (Pagnano et al., 1998). Nevertheless these solutions have been associated with lower functional results compared with resurfaced patella. A patellar bone grafting procedure has been described to provide patellar bone for possible future revision (Hassen, 2001). The "gull wing" patellar osteotomy (Kelly et al., 2002) has also been proposed in case of low demand patients, whereas in some cases it is possible to rebuild a damaged patella with K-wires in a reinforcing conguration to support the pegs of the patellar implant using the so called "rebar" technique (Tigani et al, 2009). Trabecular metal patella represents a viable therapeutic option for severe damaged patella; we experienced use with this technique (Tigani et al., 2009) in revision cases with more than 50% amount of residual bone, obtaining reliable bony xation despite the quality

We therefore exclude TM patella in cases of previous patellectomy, where soft tissue have to be used for xation of the TM implant, because of reported migration and loosening of the

dug out, long and thin on preoperative. (c) Note lateral patella subluxation, and reestablishment of correct balancing after TMT patella prosthesis implantation.

of residual bone (Fig. 11).

implant in these difficult cases.


If there is functional loss of the medial or lateral collateral ligaments, soft tissue instability, inability to balance the flexion and extension spaces, or a severe valgus deformity, then a constrained condylar prosthesis is necessary.

Table 4. Surgical algorithm according to bone defect size.
