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FIGURE 1

FIGURE 2

Indications

• Bone deficiency, a common theme in revision total knee arthroplasty (TKA) that has several etiologies:

  • Asymptomatic loosening resulting in direct mechanical bone loss

    • Figure 1 shows a failed TKA secondary to aseptic loosening of the femoral and tibial components resulting in bone loss in both the femur and tibia.

    • Upon removal of the respective femoral and tibial components (Fig. 2), significant deficiencies of the distal femur and proximal tibia are noted. Stems, wedges, augments, and the possibility of allograft should be considered in reconstruction.

  • Periprosthetic fracture

    • Comminuted periprosthetic distal femoral fractures represent one type of revision arthroplasty that can be handled with a bulk distal femoral allograft (Fig. 3).

  • Polyethylene wear–induced osteolysis

  • Stress shielding

  • Septic loosening

  • Iatrogenic bone loss resulting from implant removal

• Structural allografts are indicated for noncontained bony deficits greater than 15 mm.

  • The workhorse of revision arthroplasty is a varus-valgus constrained condylar device with stemmed femoral and tibial components.

  • Minimal deficiency of the medial tibial plateau is handled with a block augment (Fig. 4).

  • Deficiency of the posterior femoral condyle and distal femoral condyle of less than 15 mm can be handled with metallic augments (Fig. 5).

    Examination/Imaging

• History to include:

  • Preoperative diagnosis for primary arthroplasty

  • Details of perioperative course

  • Onset of pain

  • Systemic symptoms consistent with aseptic process

• Physical examination

  • Assessment of hip as well as foot and ankle

  • Assessment of skin and soft tissues

  • Location of previous incisions

  • Overall limb alignment

  • Medial-lateral and anteroposterior (AP) stability

FIGURE 3

Treatment Options

• When preparing for surgical intervention in the face of bone deficiency, a preoperative treatment plan should be developed. The authors’ treatment algorithm for bone loss management in revision TKA is outlined at the beginning of the Procedure section.

• The most important requisite is to have an appropriate revision arthroplasty system with both cemented and cementless stems of varying lengths. Structural bone graft options include femoral heads, distal femurs, and proximal tibias.

FIGURE 4

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FIGURE 5

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• Radiographs to include:

  • AP, lateral, obliques, and Merchant’s views

  • Metal substractions

  • Computed tomography scans to assess extent of bone involvement

• Review of any pertinent records, including operative reports from original surgical intervention

  Surgical Anatomy

• The anatomy of the distal femur for component positioning is critical.

• The size of the distal femur and proximal tibia can be addressed by comparison to the contralateral limb. Also, one can evaluate the size of the components removed.

• With the loss of the AP axis and the posterior condylar axis, femoral rotation is best determined by combination of the transepicondylar axis and 90° to the tibial shaft axis.

• Joint line placement is also determined by the transepicondylar axis.

  • The distal and posterior femoral joint line is on average 2.5 cm distal to the medial epicondyle (Fig. 6). Additionally, the tibial joint line is generally 1.5–2 cm proximal to the fibular head.

  • The relative location of the patella and reconstruction of an Insall-Salvati ratio of 1 can also be used to assist with joint line placement.

    Equipment

    • Leg-holding devices can be used at the surgeon’s discretion. These devices generally allow for positioning of the extremity at varying degrees of flexion during the surgical procedure.

    • Alternatively, two sandbags can be placed on the operating table, one that will hold the extremity flexed at 45° and another that will hold the extremity flexed at 90°.

     

    Positioning

• The patient is placed in supine positioning. A tourniquet is applied proximally on the limb to avoid interference with the surgical incision.

• Standard prepping and draping is performed so that the extremity is free and bony landmarks such as the anterior superior iliac spine and the medial and lateral malleoli are palpable.

• An Alvarado boot is placed on the lower limb to help stabilize the extremity during the surgical procedure.

   

  2.5 cm

  2 cm

   

   

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  FIGURE 6

   

   

  P EARLS

  • Long incisions are preferred to avoid damage to the quadriceps tendon or patellar tendon.

     

  • A standard medial parapatellar arthrotomy is most versatile and extensile.

     

  • In a modular system, remove the tibial polyethylene insert prior to flexing the knee.

     

    P ITFALLS

  • Failure to respect previous incisions can result in wound necrosis.

     

  • Failure to respect the patellar tendon insertion can result in patellar tendon avulsion.

   

  Portals/Exposures

  • A long midline incision is generally preferred, followed by a standard medial parapatellar arthrotomy.

  • When multiple prior incisions exist, the most lateral incision through which an arthroplasty can be performed should be chosen.

  • Once the arthrotomy is performed, excise all peripatellar scar tissue that is present and all scar tissue present about the patellar tendon.

    • Reestablish the medial and lateral retinacular folds.

    • Sublux the patella laterally rather than evert the patella.

    • Place a pin at the insertion of the patellar tendon to avoid avulsion of the patellar tendon.

  • If there is still difficulty obtaining exposure, then consider an extensile exposure, such a quadriceps snip or tibial tubercle osteotomy.

     

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    Procedure

    Rules of the Road for Bone Loss Management in TKA

• Contained defects

  • 5 mm: polymethylmethacrylate fill

  • 5–10 mm: reinforced polymethylmethacrylate

  • 10 mm: morselized allograft or porous metal augments

• Noncontained defects

  • 5 mm: polymethylmethacrylate fill

    Instrumentation/ Implantation

    • Appropriate instruments required include:

      • Oscillating and reciprocating saws

      • Curved and straight osteotomes in a variety of sizes

      • Gigli saw for removal of cementless femoral components

      • Standard burr and high-speed burr

      • Ultradrive with varying tools to remove cement

      • Component removal devices

     

  • 5–10 mm, less than 50% femoral condyle/tibial plateau: reinforced polymethylmethacrylate

  • 5–15 mm, greater than 50% femoral condyle/tibial plateau: TKA modular systems with stems, augments

  • 15 mm: structural allografts, megaprostheses, or porous metal augments

     

    Step 1: Implant Removal

• Atraumatic removal of implants is the key to success.

• Carefully and meticulously disrupt the prosthesis-bone or prosthesis-cement interface with a combination of saws, osteotomes, ultradrive, and high-speed burr to facilitate removal of the component with minimal bone loss.

• Once components are removed, remove any of the remaining polymethylmethacrylate and debris.

   

  Step 2: Establish Tibial Joint Line

• Ream the tibial canal until cortical chatter is appreciated, and sufficient length is obtained to place a diaphyseal-engaging stem.

• Using the reamer as an intramedullary guide, perform a cleanup resection of the proximal tibia.

  • If there is deficiency of one or the other of the tibial plateaus, do not resect down to the level of this deficiency. Only perform a cleanup resection on the intact plateau.

• Note that the tibial joint line is typically 1.5 cm proximal to the fibular head.

• Determine size of the tibial component and the need for offset.

• Address bony deficiency according to treatment algorithm.

• In the case of deficiency that is noncontained, femoral head or proximal tibial allografts can be utilized.

   

   

   

   

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  FIGURE 7

   

  • Proximal tibial deficiency involving both the medial and lateral tibial plateau without compromise

    of the tibial tubercle can be handled with a proximal tibial allograft. This may be either an intussuception allograft or, as shown in Figure 7, an onlay graft stabilized by the intramedullary stem.

  • When there is deficiency of the proximal tibia down to the level of the tibial tubercle, and involving the tibial tubercle, a proximal tibial allograft with an attached extensor mechanism allograft represents a viable option.

  • In the case of an entire proximal tibial allograft, the allograft should be cemented to the prosthesis and fixation afforded by the tibial stem.

  • When using femoral heads, male and female acetabular-type reamers are required. The tibial deficit is prepared with appropriate-sized male acetabular reamers and the femoral head is prepared by reaming with appropriate female reamers. A femoral head holding device from DePuy (Warsaw, IN) is helpful is this preparation.

  • Alternatively, a medial-lateral tibial plateau can be fashioned from a proximal tibial allograft and secured with screws.

     

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    Step 3: Appropriate Placement of the

    Femoral Component

• Factors to be considered in the positioning of the femoral component are:

  • AP position

  • Medial-lateral position

  • Rotation

  • Distal femoral joint line

  • Posterior femoral joint line

• Begin with reaming of the femoral canal until cortical chatter is appreciated and ream to an appropriate length for a diaphyseal-engaging stem.

• Using the reamer as a guide, perform a distal femur cleanup resection. Do not resect to the level of the deficient condyle.

• The AP and medial-lateral position of the component is dictated by the position of the boss on the femoral component. This has been selected to be an anatomic mean, and therefore should not require significant variation.

• The distal and posterior femoral joint line should be approximately 2.5–3 cm distal to the medial epicondyle.

• The femoral component should be rotated in line with the transepicondylar axis, which should correlate to 90° to the tibial shaft axis.

• If deficiencies of the distal femur cannot be handled with the stems and wedges available, then allograft options should be considered.

  • Intussuception allografting is a technique of handling massive contained deficits of either the distal femur or proximal tibia. Distal femoral allografting is necessary when deficits are greater than 15 mm and involve the medial and lateral condyles (Fig. 8). These are stabilized by an intramedullary stem and the use of plates, screws, or cerclage cables and strut grafts.

  • Noncontained deficiencies of the entire distal femur are best treated with an entire distal femoral allograft.

• Using the size of the component removed and sizing from the contralateral knee, an appropriate femoral allograft is selected.

• The allograft may be fashioned on the back operating room table. The distal end of the femoral allograft is cut and shaped to fit the prosthetic implant.

   

   

   

   

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  FIGURE 8

   

  • The canal is reamed to the size of the reamer, which obtains a press-fit in the remaining host bone. Therefore, the AP placement and the varus-valgus positioning of the component will be determined by the stem of the implant.

  • Rotation will be determined by a perpendicular to the tibial shaft axis. The host allograft junction may either be step cut or cut transversely. The implant is cemented into the allograft.

     

     

     

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    FIGURE 9

     

• The host allograft junction is stabilized by a combination of the press-fit of the stem into the host bone with or without the addition of supplementary fixation such as a cerclage, a strut allograft, or a plate and screws (Fig. 9). In these cases, the joint line is best established by reestablishing the appropriate Insall-Salvati ratio but also determining the length at which full extension is attainable.

• In cases in which host epicondyles remain, these should be attached into the allograft while the knee is flexed at the appropriate medial and lateral epicondylar region (see Fig. 9).

• The degree of constraint selected—posterior stabilized, posterior stabilized constrained, or rotating hinge—depends on the intregrity of the reconstructed soft tissue sleeve.

   

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  Postoperative Care and Expected Outcomes

  • Since these are rather extensive operative interventions, it is recommended to use a drain for at least the first 24 hours postoperatively. All patients are immobilized in a Robert Jones dressing with plaster splints in full extension for the first 24 hours.

  • The exposure and ultimate reconstruction will dictate how the patient is handled with respect to active extension and range-of-motion (ROM) exercises. In those patients who require extensile exposure, such as a tibial tubercle osteotomy or a quadriceps turndown, ROM is limited to the degree that placed tension on the repair at the time of surgical closure. Active extension exercises are also discouraged for the first 6–8 weeks.

  • In cases in which a posterior stabilized or a posterior stabilized constrained articulation has been utilized, patients are placed in a hinged knee brace for 6–8 weeks.

  • Toe-touch weight bearing is continued for 6–8 weeks. After 8 weeks and if the radiographs remain stable, patients are allowed to increase the amount of weight on the extremity. Full weight bearing is allowed when there is some evidence of union at the host-graft junction.

  • Because of the complexity of these operative interventions and the length of surgical time required, infection is always a concern. The authors suggest the patients be treated with a first-generation cephalosporin (or, if penicillin allergic, clindamycin) and gentamycin preoperatively and for 48 hours postoperatively. Patients are then continued orally on the first-generation cephalosporin or, if penicillin allergic, cleocin for 5 days.

  • Additionally, because these patients have difficulty resuming all activities, it is advised that they be placed on deep venous thrombosis prophylaxis to start when the wound is hemodynamically stable and continued for 4 weeks postoperatively.