Posterior Cruciate Ligament–Retaining Total Knee Arthroplasty

P ITFALLS

• Contraindications include severe fixed deformities; anatomic abnormality, degeneration,

or absence of the PCL; and technical inability to properly balance the PCL.

 

PCL-Retaining TKA

 

Indications

• End-stage joint destruction due to osteoarthritis, or due to primary synovial conditions, crystal deposition disease, rheumatoid arthritis and other inflammatory arthritides, osteonecrosis, and posttraumatic arthritis

• Structurally intact posterior cruciate ligament (PCL)

• Fixed flexion of less than 30°

• Varus of less than 20°

  Controversies

  • The surgeon’s ability to balance the PCL is critically important.

  • A PCL that is too tight may result in decreased range of motion and abnormal

    polyethylene wear patterns, and may be a source of pain.

  • A PCL that is too loose may result in anterior-posterior instability causing pain, effusion, malfunction, and poor wear characteristics due to increased contact stresses.

   

• Valgus of less than 25°

• Joint subluxation of less than 1 cm

• Technical ability of the surgeon

  Examination/Imaging

• In addition to examination of the knee, a thorough general history and physical examination are essential to ensure symptoms are indeed originating from the knee joint.

• Any previous knee surgeries or injuries need to be documented.

• It is essential to determine the presence of any chronic or acute infections that require treatment prior to joint replacement surgery.

  Treatment Options

  • When possible, nonoperative management (activity modifications, injections, oral anti-inflammatory and/or pain medications, weight loss, etc.) should be entertained before total joint replacement.

   

• Examination of the knee should include accurate range of motion, documentation of any flexion contracture, stability of the joint and integrity of ligamentous structures (in particular the PCL by posterior drawer testing or presence of posterior sag), and patellar tracking.

• Plain radiographs

  • Standing anteroposterior and lateral views, with patellar views

  • Long-leg standing hip-to-ankle views to evaluate overall alignment of the limb.

    Surgical Anatomy

• Tibial attachment of the PCL is posterior and distal to the tibial plateau, making that structure vulnerable to injury during the tibial bone resection.

• Excessive bone resection from the proximal tibia or a large posteriorly sloped cut may jeopardize the tibial attachment of the PCL. Posterior tibial slope should not exceed 10°.

• It is also possible to injure the PCL during correct tibial resection by making an overaggressive cut with the saw blade traveling too far posterior.

• The PCL can be protected during the tibial resection by placing an osteotome anterior to it (Fig. 1).

   

   

   

  PCL-Retaining TKA

   

  FIGURE 1

   

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  Positioning

  • Supine positioning on standard operating room table is used.

  • A thigh-high tourniquet should be utilized.

     

    P EARLS

    • If possible, incisions from previous procedures should be used.

       

    • Large skin flaps and undermining of the subcutaneous tissues should be avoided, as this can lead to devascularization of skin margins.

     

    Portals/Exposures

  • Routine surgical exposure for total knee arthroplasty (TKA) should be utilized.

  • This typically involves an anterior longitudinal skin incision just medial to the midline followed by medial parapatellar arthrotomy.

  • Following the skin incision, dissection is continued directly to the interval between the quadriceps tendon and the vastus medialis.

  • The quadriceps tendon is incised sharply in one layer, leaving several millimeters of tendon attached to the vastus medialis to allow tendon-to-tendon closure at the conclusion of the procedure.

  • The medial parapatellar arthrotomy continues with the capsular incision extending around the medial aspect of the patella, extending just medial and distal to the tibial tubercle.

  • Approximately 1 cm of soft tissue medial to the tibial tubercle is preserved to allow repair of the capsule at the time of closure.

   

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  P EARLS

  • Maintenance of the correct epicondylar axis of the femur is critical to ensure correct patellar tracking and extensor mechanism function, improve knee kinematics, and minimize the need for collateral ligament releases (Fig. 3).

     

  • Femoral notchplasty can help avoid impingement of the PCL (Fig. 4).

     

  • Posterior femoral osteophytes should be removed to remove tension from the posterior capsule (Fig. 5) and prevent flexion contracture (Fig. 6A and 6B).

   

  PCL-Retaining TKA

   

  Procedure

  Step 1

  • After exposure of the knee joint, the bone cuts are performed (femur-first or tibia-first according to surgeon preference).

  • In the absence of a flexion contracture and to most accurately reproduce the joint line, the distal femoral cut should be 2 mm less than the thickness of the actual femoral component.

    • This will account for lost distal femoral articular cartilage, and minimize the chance of creating an imbalance in the femoral-tibial gaps.

  • The amount of proximal tibia removed from the less involved plateau should be equal to the composite thickness of the tibial component.

  • Once the tibial plateau bone has been removed, any remaining bone island anterior to the PCL can be trimmed to allow flush placement of the tibial component (Fig. 2).

   

   

   

   

  FIGURE 2

   

   

   

  FIGURE 3

   

   

   

   

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  PCL-Retaining TKA

   

  FIGURE 4

   

  FIGURE 5

   

   

   

   

   

  A B

  FIGURE 6

   

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  P EARLS

  • PCL tension is best tested with the trial components in place.

   

  PCL-Retaining TKA

   

  Step 2

  • After the femoral and tibial bone cuts have been completed, trial components are placed and PCL tension is assessed.

  • Preservation and correct balancing of the PCL are key goals to this surgery.

  • Balance of the PCL should be assessed after any varus or valgus ligamentous imbalance has been corrected.

  • As usual, soft tissue balancing should always be tested with the knee in both flexion and extension.

    • Ideally, the flexion and extension gaps should be within 1–2 mm of each other.

  • A useful test of the balance of the PCL is the “pull-out, lift-off” (POLO) test (Scott and Chmell, 2008).

     

    P EARLS

    • Increased tibial bone resection is only appropriate if the knee is tight in both flexion and extension.

       

    • If the knee is tight only in extension, the posterior slope of the tibial cut should be assessed. Increasing the posterior tibial slope relaxes the PCL. Posterior tibial slope should not exceed 10° to avoid potential injury to the tibial attachment of the PCL.

       

    • If more than 75% of the PCL is released, a PCL-substituting prosthesis should be considered,

      as the remaining PCL fibers may rupture with activity, leading to instability.

       

      P ITFALLS

    • If the knee is tight only in flexion, increasing tibial bone resection leaves the knee lax in extension, resulting in instability.

     

    • The “pull-out” portion of the test is performed with the knee in 90° of flexion with trial components in place. Using the handle attached to the trial tibial component, an attempt is made to pull the tibial trial component out from under the posterior femoral condyles. If the tray can be pulled out with the knee in flexion, PCL tension and flexion stability are inadequate.

    • The “lift-off” portion of the test is performed with the tibial handle removed, and the extensor mechanism reduced into anatomic position. The knee should be put through a range of motion up to 120° while closely examining the anterior tibial tray–bone interface. If the trial component books open or lifts off the tibial bone surface, the test

      is positive and the PCL is too tight. This occurs because the tight PCL pulls the femoral component posteriorly against the posterior upslope of the polyethylene tibial insert, forcing the tray down posteriorly and up anteriorly.

      Step 3

  • If the PCL is excessively tight, the tension within the ligament needs to be decreased.

  • PCL recession can be accomplished by several techniques from either the femoral origin or the tibial insertion, or within the ligament itself.

    • Release of the anterior 10–20% of the ligament, which usually results in correct soft tissue balance

    • Release of the anterior PCL at its femoral origin

      (Fig. 7)

    • Release of the PCL at its tibial insertion (Fig. 8)

       

       

       

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      PCL-Retaining TKA

       

      FIGURE 7 FIGURE 8

       

      • Release of the PCL utilizing a “pie-crusting” technique (Fig. 9)

        • Once balancing is complete, the final components are placed (Fig. 10).

           

           

           

           

           

          FIGURE 9 FIGURE 10

           

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          PCL-Retaining TKA

           

          Postoperative Care and Expected Outcomes

  • Postoperative care and rehabilitation should follow standard TKA protocols as dictated by surgeon preference.

  • Excellent results have been encountered with cemented condylar knee components with cruciate-sacrificing, cruciate-substituting, and cruciate-retaining implants.

  • Survivorship free of revision for any reason for cemented cruciate-retaining implants ranges from 90% to 98% at 9–15 years.

  • If performed correctly and the PCL remains intact, PCL-retaining designs limit posterior instability by preserving the PCL and may offer improved range of motion as compared with cruciate-sacrificing total condylar designs.

  • Complications are similar to those with any TKA and include deep prosthetic infection, patellofemoral problems, aseptic loosening, and wear.

  • A complication unique to cruciate-retaining designs is delayed rupture of the PCL resulting in posterior instability in flexion.

  • Flexion instability after cruciate-retaining TKA is likely an under-recognized cause of persistent pain and functional problems. Patients usually present with pain, recurrent knee effusions, generalized tenderness, above-average TKA motion, and a sense of instability about the knee (Pagnano et al., 1998).

  • If the symptoms have been present since the index surgery, the flexion gap was likely left unbalanced at the time of surgery. This is likely the most common cause of flexion instability, followed by late PCL rupture.

Evidence

Dennis DA, Clayton ML, O’Donnell S, Mack RP, Stringer EA. Posterior cruciate condylar total knee arthroplasty: average 11-year follow-up evaluation. Clin Orthop Relat Res. 1992;(281):168-76.

 

This study reviews 42 TKAs of the posterior cruciate condylar design performed from 1975 until 1978. Good results can be expected if satisfactory lower extremity alignment is attained. PCL retention has provided a slightly improved postoperative range of motion. Residual problems appear to be centered about the patellofemoral joint. (Level IV evidence [Therapeutic Study])

 

Dixon MC, Brown RR, Parsch D, Scott RD. Modular fixed-bearing total knee arthroplasty with retention of the posterior cruciate ligament: a study of patients followed for a minimum of fifteen years. J Bone Joint Surg [Am]. 2005;87:598-603.

 

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PCL-Retaining TKA

 

This study describes a consecutive series of 139 TKAs in 109 patients, performed by one surgeon using a nonconforming PCL-retaining prosthesis. In this single-surgeon series, modular fixed-bearing PCL-retaining TKAs had good clinical and radiographic results with excellent survivorship for up to 15 years. (Level IV evidence [Therapeutic Study])

 

Gill GS, Joshi AB. Long-term results of cemented, posterior cruciate ligament-retaining total knee arthroplasty in osteoarthritis. Am J Knee Surg. 2001;14:209-14.

 

This study reviews 254 TKAs in 223 patients with osteoarthritis. It shows that longterm results of cemented, PCL-retaining TKA for osteoarthritis are excellent in terms of improved clinical function and pain relief. (Level IV evidence [Therapeutic Study])

 

Gill GS, Joshi AB. Long-term results of retention of the posterior cruciate ligament in total knee replacement in rheumatoid arthritis. J Bone Joint Surg [Br]. 2001;83: 510-2.

 

This study analyzed the long-term results, with a mean follow-up of 10.2 years, of 66 total knee replacements in 42 patients with rheumatoid arthritis. In all cases the PCL was retained. The clinical, radiologic, and survivorship analyses show that the PCL-retaining knee arthroplasty performs well in rheumatoid arthritis. (Level IV evidence [Therapeutic Study])

 

Pagnano MW, Cushner FD, Scott WN. Role of the posterior cruciate ligament in total knee arthroplasty. J Am Acad Orthop Surg. 1998;3:176-87.

 

This study focuses on the relative merits of the cruciate-retaining and posterior-stabilized TKA designs. It discusses theoretical concerns and early clinical data; presents a summary of the latest research, with particular attention to direct comparisons of cruciate-retaining and posterior-stabilized designs; and looks at areas of agreement and future research directions.

 

Pagnano MW, Hanssen AD, Lewallen DG, Stuart MJ. Flexion instability after primary posterior cruciate retaining total knee arthroplasty. Clin Orthop Relat Res.

1998;(356):39-46.

 

This study suggests that flexion instability can be a cause of persistent pain and functional impairment after PCL-retaining TKA. A revision operation that focuses on balancing the flexion and extension spaces, in conjunction with a posterior-stabilized knee implant, seems to be a reliable treatment for symptomatic flexion instability after PCL-retaining TKA. (Level IV evidence [Therapeutic Study])

 

Scott RD, Chmell MJ. Balancing the posterior cruciate ligament during cruciate-retaining fixed and mobile-bearing total knee arthroplasty: description of the pull-out lift-off and slide-back tests. J Arthroplasty. 2008;23:605-8.

 

This study describes two simple intraoperative tests that assess PCL tension in fixed-and mobile-bearing TKA. Performance of the “pull-out, lift-off” (POLO) test in fixed-bearing knees and the “slide-back test” in rotating platform knees will assure appropriate PCL tension after TKA by determining that the PCL is neither too loose nor too tight. (Level V evidence [Expert Opinion])

 

Vessely MB, Whaley AL, Harmsen WS, Schleck CD, Berry DJ. The Chitranjan Ranawat Award: Long-term survivorship and failure modes of 1000 cemented condylar total knee arthroplasties. Clin Orthop Relat Res. 2006;(452):28-34.

 

This study examined factors affecting survivorship, and reasons for reoperation and revision of a cemented modular condylar TKA. Survivorship at 15 years for revision for any reason, revision for mechanical failure, and revision for aseptic loosening was 95.9%, 97.0%, and 98.8%, respectively. (Level IV evidence [Therapeutic Study])