RECONSTRUCTION 2023, Jan, 08 | 12:00 am

Hinged Total Knee Arthroplasty

Indications

  • Hinged total knee arthroplasty is utilized as a salvage procedure for complex primary or revision total knee arthroplasty. Indications include:

    • Limb salvage following periarticular tumor resection

    • Severe bony deficiency requiring segmental replacement

       

      P ITFALLS

      • Fixed hinges such as the Waldius and Guepar were associated with high rates of loosening and infection (Fig. 4A). With the advent of the modern rotating hinge design, there is no current indication for the use of fixed hinges (Fig. 4B).

       

    • Medial collateral ligament disruption

    • Extensor mechanism disruption

    • Significant flexion and extension gap mismatch

    • Treatment of periprosthetic fracture about the knee with associated with severe bone loss in low-demand patients (Fig. 1)

    • Salvage of previous nonunion/malunion of periprosthetic fracture about the knee (Fig. 2)

    • Recurvatum deformity secondary to quadriceps weakness (underlying neurologic disorder or previous cerebrovascular accident) (Fig. 3)

 

 

 

 

 

FIGURE 1

 

FIGURE 2

 

 

 

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FIGURE 3

 

 

 

Controversies

  • Controversies exist regarding the use of hinged total knee arthroplasty for treatment of periprosthetic fracture associated with significant bone loss or poor-quality bone. The general consensus is that hinged total knee arthroplasty in elderly, low-demand patients allows for quicker mobilization and recovery (Fig. 5A and 5B).

 

A B

FIGURE 4

 

 

 

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Hinged Total Knee Arthroplasty

 

A

FIGURE 5

B

 

Examination/Imaging

Preoperative Examination

  • Examination of skin for color, temperature changes, and effusion that would indicate infection

  • Evaluation of old incisions

  • Vascular and neurologic status of the limb

  • Range of motion

  • Collateral ligament stability

  • Function of the extensor mechanism

  • Presence of recurvatum deformity

    Preoperative Planning

  • As with any primary or revision total knee arthroplasty, preoperative planning is essential.

  • Appropriate radiographs include a standing anteroposterior view, lateral view, and Merchant’s

     

     

     

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    Hinged Total Knee Arthroplasty

     

    A B

    FIGURE 6

     

    view. Each of these radiographs should be evaluated to assess bone loss and quality of remaining host bone. In addition, a long leg hip-to-ankle view may be utilized to assess the overall mechanical alignment of the extremity and to assess for other hardware that may interfere with placement of a long-stem hinged total knee arthroplasty (e.g., total hip arthroplasty above a total knee arthroplasty).

    • Templating of both the femoral (Fig. 6A) and tibial (Fig. 6B) components is mandatory. In addition to estimating the size of the components, templating is utilized to estimate bone resection levels and the need for augmentation as well as the length, position, and size of intramedullary stems.

    • If performing the reconstruction for bone sarcomas, preoperative imaging studies such as computed tomography scans and magnetic resonance imaging studies of the extremity should be reviewed to determine a safe resection level about the femur or tibia in order to gain adequate tumor-free margins.

 

 

Sciatic nerve

 

Popliteal

artery

Superficial femoral artery

 

 

 

Tibial nerve

Peroneal nerve

 

 

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Hinged Total Knee Arthroplasty

 

FIGURE 7

Surgical Anatomy

  • In patients with severe distal femoral or proximal tibial bone loss or neoplastic disease, resection of the distal femur or proximal tibia may be required. As such, familiarity with the distal femoral and popliteal space anatomy is important to avoid damage to the superficial femoral artery during distal femoral resection, the popliteal artery and sciatic nerve during posterior dissection, and the tibial artery, tibial nerve, and peroneal nerve during proximal tibial dissection and resection (Fig. 7).

     

    P EARLS

    • If a large exposure is required, a sterile tourniquet should be utilized in order to allow exposure to the proximal aspect of the thigh, groin, and pelvis.

     

    Positioning

  • The patient is placed supine on the operating table.

  • A nonsterile tourniquet is placed on the upper thigh.

  • Positioning should allow for free mobility of the knee through the full range of flexion and extension. A leg positioner should be used to allow the knee to flex and rest at 90° of flexion to assist in femoral and tibial preparation.

  • In cases in which large-scale resection of the femur or tibia may be required, the entire extremity, including the groin and pelvis, should be prepped and draped.

     

    485

     

     

    P ITFALLS

    • Because hinged total knee arthroplasty is often used in a salvage situation, most patients have had multiple previous incisions. Large exposures and bony resection may often compromise the already tenuous soft tissue envelope. Consultation with a plastic surgeon preoperatively to assess the need for soft tissue coverage at the time of the procedure may be warranted in some cases.

     

    Hinged Total Knee Arthroplasty

     

    Portals/Exposures

    • Utilize prior incisions.

    • When multiple incisions are present, use the most laterally based incision. Any flaps that are created should be full thickness to avoid compromise of the blood supply to the skin.

    • A standard medial parapatellar approach or extensile exposures may be required.

    • Once they are exposed, removal of the failed tibial and femoral components should proceed, preserving as much of the remaining bone as possible. Remove all cement and debris and débride all bony surfaces down to good-quality bone.

       

      P EARLS

      • Ensure the tibial reamers remain in line with the shaft of the tibia when reaming. Retained cement, sclerotic bone, or tibial deformity may influence reamer position and lead to cortical perforation.

         

        P ITFALLS

      • In patients with substantial proximal bony deficiency, a long-stem cemented or cementless tibial implant may be required for fixation. In patients with metaphyseal or diaphyseal deformity, an offset stem may be required to obtain appropriate alignment in the intramedullary canal.

       

      Procedure

      Step 1: Tibial Preparation

    • Prepare the tibial canal and establish a proximal tibial supportive bony platform perpendicular to the mechanical axis.

      • The tibial surface may be cut utilizing extramedullary or intramedullary instrumentation (Fig. 8).

       

       

       

      FIGURE 8

       

       

       

      486

       

      Hinged Total Knee Arthroplasty

       

      FIGURE 9 FIGURE 10

       

      • The tibial canal is prepared by reaming to the appropriate size and depth based on preoperative templating or until cortical contact is made

        (Fig. 9).

      • Determine the appropriate depth of the tibial resection. The purpose of this cut is to obtain a flat, supportive bony platform. It may be unnecessary to cut below all defects as these may be filled in with bone graft or augmented.

        Instrumentation/ Implantation

        • Straight reamers in 0.5-mm increments should be available.

        • If deformity on the tibial diaphysis exists, flexible reamers may be utilized.

         

      • Cut the proximal tibia using the preferred instrumentation. Determine the need for block or wedge augmentation and make the appropriate bony cuts on the tibia. The tibal baseplate can then be sized. A trial tibial component with the appropriate-length stem and augments can then be inserted (Fig. 10).

        Step 2: Femoral Preparation

  • Femoral canal preparation

    • Identify and progressively ream the femoral canal to the appropriate size based on preoperative templating or until cortical contact is made. Avoid eccentric reaming of the femoral shaft.

    • If a bowed femoral stem is to be utilized, the femoral canal should be flexibly reamed.

  • The size of the femoral component is determined by preoperative templating and the amount of remaining host bone.

     

     

    P EARLS

    • If distal femoral segmental replacement is necessary, the distal femur should be resected first. When a diaphyseal resection is required, it is imperative to mark the rotation of the deepest section of the trochlear groove on the remaining diaphyseal segment. This will allow for correct femoral prosthesis rotational alignment (Fig. 12).

     

     

    Hinged Total Knee Arthroplasty

     

    FIGURE 11

     

    487

     

    • Femoral component rotation

      • The rotation of the femoral component is critical to achieving proper flexion gap symmetry and patellofemoral mechanics. In the revision setting, however, many of the key bony landmarks used to determine femoral component rotation, such as the transepicondylar axis, posterior condylar axis, and trochlear groove, are absent or damaged

        (Fig. 11).

         

         

         

        FIGURE 12

         

        488

         

        Hinged Total Knee Arthroplasty

         

      • In these situations, the tibial shaft axis should be utilized to establish femoral component rotation and ensure a symmetric rectangular flexion gap and appropriate external rotation of the femoral component (see Fig. 11).

  • Once the femoral size and rotation have been determined, the appropriate jig system should be used to complete the cuts on the femur. At this juncture, note the areas of bony deficiency that may require augmentation.

    Step 3: Balance the Knee in Flexion and Extension

  • Balancing the knee in flexion

  • Keeping in mind that a hinged total knee arthroplasty is often indicated to treat a significant flexion-extension gap mismatch (10 mm), an attempt should be made to maximize stability in flexion.

  • As assessment of the flexion and extension gap asymmetry may be made by several methods, including direct measurement and spacer blocks (Fig. 13A and 13B).

  • Flexion gap stability is achieved by maximizing femoral component anteroposterior distance and filling this gap with appropriate posterior femoral augmentation.

     

     

     

    A B

    FIGURE 13

     

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    Hinged Total Knee Arthroplasty

     

    • Balance the knee in extension

      • Extension gap stability is achieved by distal augmentation of the femur (loose extension gap) or further resection of the distal femur (tight extension gap).

         

        P EARLS

        • Particular attention should be paid to patellofemoral tracking, one of the most common complications associated with hinged total knee arthroplasty. If patellar tracking is inappropriate, femoral component rotation must be evaluated and adjusted accordingly.

         

      • Most hinge systems will allow a certain degree of hyperextension. This is usually limited with an extension stop bumper. It is important to limit any hyperextension so as to avoid stress on the bumper that could result in implant breakage.

        Step 4: Trial Reduction and

        Radiographic Evaluation

    • Perform a trial reduction.

    • When reasonable gap balance is achieved, assemble the trial components with the appropriate stem length and diameter.

    • Distal and posterior femoral augments and tibial augments should be utilized based on the intraoperative assessment of gap balancing and to accommodate for bony deficiency.

    • With the appropriate trial components in place (Fig. 14), the knee should be taken through a range of motion to ensure proper stability and patellar tracking.

    • The hinged components will substitute for coronal and sagital plane imbalance.

 

 

 

FIGURE 14

 

 

 

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Hinged Total Knee Arthroplasty

 

A

FIGURE 15

B

 

  • Intraoperative radiographs with trial components in place are crucial to ensure appropriate alignment of the extremity, restoration of the joint line, and position of the stems within the intramedullary canal of the femur (Fig. 15A and 15B).

     

    P EARLS

    • Each rotating hinge system that is available has a different mechanism of linked constraint between the femoral and tibial component. It is important for the surgeon to be familiar with the system being used to ensure proper assembly.

     

    Step 5: Assembly and Insertion of

    Final Components

  • If intraoperative trialing and radiographs confirm appropriate alignment, stability, and patellofemoral tracking, the final implants should be opened

(Fig. 16).

  • Meticulous care and attention should be paid to assembly of the final components. The operating surgeon or an experienced assistant should assemble the final components on the back table (Fig. 17A–17C).

  • Ensure the appropriate augments, stem length, diameter, and offset match from the intraoperative trial components. If necessary, insert the final components provisionally into the bone to ensure proper fit.

     

     

     

     

     

     

     

     

    Hinged Total Knee Arthroplasty

     

     

     

     

     

    491

     

    FIGURE 16

     

    A

     

    B

     

    C

     

    FIGURE 17

     

     

    Controversies

    • With the additional constraint that is achieved with the use of a hinged component, additional fixation with intramedullary stems is required. Both cemented and cementless stem fixation is available for most systems. If cementless stems are to be used, they should be press-fit, diaphysis-engaging stems.

     

    Hinged Total Knee Arthroplasty

     

    • The femoral and tibial canals should be copiously lavaged and dried. The distal diaphyseal bone of the femur and tibia should be restricted with a canal plug if cemented stems are to be used.

    • The tibial and femoral components should be cemented separately under separate mixing conditions, allowing for the cement to fully cure before proceeding to cementing the next component.

    • Once all components have been cemented, the linked polyethylene is assembled. Care should be taken to ensure proper assembly of the linking mechanism (Fig. 18A–18C).

    • Stability and patellar tracking should again be assessed, ensuring proper patellofemoral tracking.

 

 

 

492

 

A B

 

 

 

C FIGURE 18

 

493

 

Complications

  • Common complications following hinged total knee arthroplasty include:

    • Wound complications

    • Patellofemoral complications

    • Deep periprosthetic infection

    • Hardware failure

 

Hinged Total Knee Arthroplasty

 

Postoperative Care and Expected Outcomes

  • Suction drainage should be utilized and left in place until drainage is less than 30 mL in 8 hours.

  • Standard postoperative antibiotics are administered for 24 hours.

  • Meticulous care should be take with regard to the soft tissue envelope. Oftentimes large exposure and lengthy surgical time can lead to soft tissue healing issues.

  • Institution of physical therapy can be started when the soft tissue envelope allows, and progressed as tolerated.

  • In general, patients are allowed to bear weight as tolerated with an assistive device until quadriceps strength is adequate to allow for transfer to a cane.