Total Knee Arthroplasty: Pie-Crusting Technique and Balancing of PCL Technique

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PRE-PROCEDURE
INDICATIONS
  • General indications for total knee arthroplasty
    • Severe arthritis that is not responsive to conservative treatment measures
    • Osteonecrosis with subchondral collapse of femoral condyle
  • Specific indications for techniques described herein:
    • The pie-crusting technique was originally described as a soft-tissue release for the severe valgus knee.
      • The pie-crusting technique has been used as a soft-tissue release for both varus and valgus knees using lamina spreaders.
    • Balancing the PCL is necessary when a cruciate-retaining implant is used.
CONTRAINDICATIONS
  • Recent or current knee sepsis
  • A remote source of ongoing infection
  • Extensor mechanism discontinuity or severe dysfunction
  • Recurvatum deformity secondary to muscular weakness
  • Presence of a painless, well-functioning knee arthrodesis
EQUIPMENT

The equipment required generally depends on the knee arthroplasty set being used.

ANATOMY
Kinematics
  • Knee motion during gait occurs in flexion and extension, abduction and adduction, and rotation about the long axis of the limb.
  • Flexion axis
    • Varies in a helical fashion in the normal knee
      • Medial femoral condyle: 2 mm of posterior translation on the tibia during flexion
      • Lateral femoral condyle: 21 mm of posterior translation
        • This pattern of medially based pivoting of the knee explains the observed external rotation of the tibia on the femur during extension, known as the "screw-home mechanism," and internal rotation of the tibia during knee flexion.
Axial Alignment
  • Tibial articular surface
    • Normally in 3 degrees of varus with respect to the mechanical axis
    • Tibial components are generally implanted perpendicular to the mechanical axis of the tibia in the coronal plane
      • Sagittal plane has varying amounts of posterior tilt.
  • Femoral articular surface
    • Corresponding 9 degrees of valgus
    • Femoral components usually are implanted in 5 to 6 degrees of valgus, the amount necessary to reestablish a neutral mechanical axis of the limb.
Rotational Alignment
  • Rotation of femoral component effects
    • Balancing of flexion space
      • Because the proximal tibial cut is made perpendicular to the mechanical axis of the limb instead of in the anatomically correct 3 degrees of varus, rotation of the femoral component also must be altered from its anatomic position to create a symmetrical flexion space.
    • Patellofemoral tracking
Patellofemoral Joint
  • The primary function of the patella is to increase the lever arm of the extensor mechanism about the knee, thus improving the efficiency of quadriceps contraction.
  • The quadriceps and patellar tendons insert anteriorly on the patella.
  • The thickness of the patella displaces the respective force vectors of the tendons away from the center of rotation of the knee.
    • This displacement or lengthening of the extensor lever arm changes throughout the arc of the knee.
      • The extensor lever arm is greatest at 20 degrees of flexion, and the quadriceps force required for knee extension increases significantly in the last 20 degrees of extension.
  • Patellofemoral stability
    • Maintained by a combination of the articular surface geometry and soft-tissue restraints
    • Patella does not contact the trochlea in early flexion.
      • Lateral subluxation during early flexion is resisted by the vastus medialis obliquus muscle fibers.
    • As flexion increases, bony and prosthetic constraints play a dominant role in preventing subluxation.
      • Most femoral component designs have a more prominent lateral flange of the trochlea to produce a more anatomically correct reconstruction.
Blood Supply to the Knee
  • Intrinsic and extrinsic sources
    • Five intrinsic sources
      • Superior medial and superior lateral genicular arteries
        • Arise from the popliteal artery superior to the joint line
      • Middle (posterior) genicular artery
        • Arises as a single vessel from the popliteal artery behind the distal femoral intercondylar region
        • Supplies the anterior cruciate and medial collateral ligaments
      • Inferior lateral and inferior medial genicular arteries
        • Arise from the popliteal artery slightly distal to the posterior knee joint line
        • Each runs forward around its respective tibial condyles, deep to the collateral ligaments.
    • Three extrinsic sources
      • Descending genicular artery
        • Branch of superficial femoral artery
      • Recurrent anterior tibial artery
      • Descending branch of lateral femoral circumflex artery

PROCEDURE
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POST-PROCEDURE
TECHNIQUES
  • Post-Procedure: Pie-Crusting Technique
  • Post-Procedure: Balancing of Posterior Cruciate Ligament

Post-Procedure: Pie-Crusting Technique

POST-PROCEDURE CARE
  • Postoperative physical therapy and rehabilitation greatly influence the outcome of total knee arthroplasty.
    • Range-of-motion exercises, muscle strengthening, gait training, and instruction in performing activities of daily living are important.
    • >
  • Deep venous thrombosis prophylaxis must be undertaken in the postoperative period.
    • The Seventh Consensus Conference on Antithrombotic Therapy of the American College of Chest Physicians recommended in 2004 that low-molecular-weight heparin (LMWH), warfarin, or fondaparinux be used for at least 10 days for deep venous thrombosis prophylaxis in patients who have had total knee arthroplasty.
COMPLICATIONS
  • Thromboembolism
    • Prevalence of deep venous thrombosis after total knee arthroplasty without any form of mechanical or pharmaceutical prophylaxis has been reported to range from 40% to 84%.
  • Infection
    • Incidence ranges between 1.6% and 2.6%.
    • Most common organisms causing postoperative infection are Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus species.
  • Patellofemoral complications
    • Patellofemoral instability
    • Patellar fracture
    • Patellar component failure
    • Patellar clunk syndrome
    • Extensor mechanism rupture
  • Neurovascular complications
    • Arterial compromise
      • Occurs in 0.03% to 0.2% of patients, with up to 25% resulting in amputation
    • Peroneal nerve palsy
      • Only commonly reported nerve palsy after total knee arthroplasty
      • Occurs primarily with correction of combined fixed valgus and flexion deformities
  • Aseptic failure
    • Component loosening
      • Tibial component loosening more common than femoral component loosening
    • Polyethylene wear
      • This can result in loosening and osteolysis.
      • More rarely, can be catastrophic failure through polyethylene fracture
  • Periprosthetic fractures
ANALYSIS OF RESULTS
  • Ranawat developed the pie-crusting technique, and his 2004 paper presents excellent long-term results.
  • Prosthesis survival at 10 years is between 90% and 95%.
OUTCOMES AND EVIDENCE
  • Prosthesis survival
    • The original total condylar prosthesis has been demonstrated in three long-term series to have a longevity of 95% at 15 years and 91% at 21 and 23 years.
    • PCL-retaining and PCL-substituting designs have documented 10-year survivorship of 95% and better.
Procedure: Pie-Crusting Technique

Post-Procedure: Balancing of Posterior Cruciate Ligament

POST-PROCEDURE CARE
  • Postoperative physical therapy and rehabilitation greatly influence the outcome of total knee arthroplasty.
    • Range-of-motion exercises, muscle strengthening, gait training, and instruction in performing activities of daily living are important.
    • >
  • Deep venous thrombosis prophylaxis must be undertaken in the postoperative period.
    • The Seventh Consensus Conference on Antithrombotic Therapy of the American College of Chest Physicians recommended in 2004 that low-molecular-weight heparin (LMWH), warfarin, or fondaparinux be used for at least 10 days for deep venous thrombosis prophylaxis in patients who have had total knee arthroplasty.
COMPLICATIONS
  • Thromboembolism
    • Prevalence of deep venous thrombosis after total knee arthroplasty without any form of mechanical or pharmaceutical prophylaxis has been reported to range from 40% to 84%.
  • Infection
    • Incidence ranges between 1.6% and 2.6%.
    • Most common organisms causing postoperative infection are Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus species.
  • Patellofemoral complications
    • Patellofemoral instability
    • Patellar fracture
    • Patellar component failure
    • Patellar clunk syndrome
    • Extensor mechanism rupture
  • Neurovascular complications
    • Arterial compromise
      • Occurs in 0.03% to 0.2% of patients, with up to 25% resulting in amputation
    • Peroneal nerve palsy
      • Only commonly reported nerve palsy after total knee arthroplasty
      • Occurs primarily with correction of combined fixed valgus and flexion deformities
  • Aseptic failure
    • Component loosening
      • Tibial component loosening more common than femoral component loosening
    • Polyethylene wear
      • This can result in loosening and osteolysis.
      • More rarely, can be catastrophic failure through polyethylene fracture
  • Periprosthetic fractures
ANALYSIS OF RESULTS
  • Ranawat developed the pie-crusting technique, and his 2004 paper presents excellent long-term results.
  • Prosthesis survival at 10 years is between 90% and 95%.
OUTCOMES AND EVIDENCE
  • Prosthesis survival
    • The original total condylar prosthesis has been demonstrated in three long-term series to have a longevity of 95% at 15 years and 91% at 21 and 23 years.
    • PCL-retaining and PCL-substituting designs have documented 10-year survivorship of 95% and better.
Procedure: Balancing of Posterior Cruciate Ligament
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