Use of Stems: Cemented and Uncemented
Graham D. Pallante
Daniel J. Berry
Stems are indicated in almost all revision total knee arthroplasty (TKA). Data show that routine use of stems in revision TKA leads to fewer failures than discretionary use of stems.
Stems provide the benefit of enhanced mechanical fixation while distributing the load over a greater area, which is important in total knee arthroplasty revision (TKAR) because bone quality and quantity usually are compromised by failure of the previous implant, stress shielding, or bone loss related to implant removal.
Conceptually, there are 3 main areas for implant fixation in TKAR: (1) the bone surfaces of the femur and tibia, (2) the metaphyses of the femur and tibia, and (3) the diaphysis of the femur and tibia. The bone surfaces typically are fixed with cement. Metaphyseal fixation may be with cement or with uncemented sleeves or cones. Diaphyseal fixation is with stems, which may be cemented or uncemented.
Both cemented and uncemented stems can provide reliable, stable fixation in revision TKA. Each has advantages and disadvantages.
Stem choice should be based on available implants, remaining bone stock, presence of bony deformity, and ease of extraction.
Most uncemented stems obtain a press fit in the diaphysis but do not provide true biologic fixation because most do not have bone ingrowth or ongrowth surfaces. Uncemented stems may be easier to insert and extract than cemented stems. Final implant position is dictated by the diaphysis. This can sometimes be modified with offset stems. When bone deformity is present, uncemented stems allow less latitude to compensate than cemented stems. Pain at the stem tip has been reported in some patients with uncemented stems.
Cemented stems provide immediate and long-term fixation. They provide more versatility in the presence of bone deformity than uncemented stems but in the presence of normal anatomy provide less alignment guidance. Cemented stems allow for local antibiotic delivery from the cement. Cemented stems typically are more difficult to extract than uncemented stems.
Despite advantages and disadvantages of each method, cemented or uncemented stems can be used in most cases, depending on surgeon preference (Figures 62.1 and 62.2).
Suggested indications for uncemented stems:
Good diaphyseal bone quality, favorable canal geometry, minimal or reconstructible metaphyseal bone loss that allows a good cement interface.
Suggested indications for cemented stems:
Poor diaphyseal bone quality, unfavorable canal geometry for uncemented implant.
Sterile Instruments and Implants
Revision TKA instrumentation
Reamers for cemented or uncemented stems
Trial implants for cemented or uncemented stems
Power and hand reaming instruments for the stems
Pulse lavage with femoral attachment for canal irrigation
Metaphyseal cones, sleeves as needed
Bone grafts as needed
Figure 62.2 ▪ A, Radiograph of patient after resection arthroplasty for infection with static antibiotic-loaded cement spacer in place. B and C, Radiographs after reconstruction with uncemented stems.
Intraoperative radiography capability
For cemented stems: cement gun, cement restrictor, vacuum cement mixer
Uncemented stems (with instrumentation) in multiple lengths and diameters, with offset options if desired
Cemented stems (with instrumentation) in multiple lengths and diameters
Revision TKA: femoral and tibial implants
Standard, midline approach with median parapatellar arthrotomy is preferred. Considerations should be made for previous skin incisions or soft tissue defects.
Extensile knee approaches such as quadriceps snip or tibial tubercle osteotomy may be required. See Section IV-B, Chapter 2 for details.
Obtain previous operative reports and implant records.
Obtain full-length hip-to-ankle radiograph. Determine the desired mechanical alignment and determine which stem configurations can help achieve this.
If the tibial or femoral component will be retained, review the manufacturer’s revision instrumentation options. Custom or seldom used implants may require shipment from the device company.
Template femoral and tibial stem length, diameter, and component position. Anticipate use of uncemented or cemented stems.
Bone, Implant, and Soft Tissue Techniques
Perform the desired approach to the knee, employing an extensile approach if needed. If possible, it is preferable to use the previous incision. If multiple incisions are present, utilizing the most lateral incision possible is desirable.
Remove implants, being careful to preserve as much bone as possible (see Section IV-B, Chapter 3).