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Role of the Posterior Cruciate Ligament in Total Knee Arthroplasty

Role of the Posterior Cruciate Ligament in Total Knee Arthroplasty. James M. Steinberg, D.O. Introduction. What to do with the PCL? Save Sacrifice Partial release or recession Substitute Controversial topic Debate continues

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Role of the Posterior Cruciate Ligament in Total Knee Arthroplasty

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  1. Role of the Posterior Cruciate Ligament in Total Knee Arthroplasty James M. Steinberg, D.O.

  2. Introduction • What to do with the PCL? • Save • Sacrifice • Partial release or recession • Substitute • Controversial topic • Debate continues • Excellent long term results with cruciate sacrificing, substituting and retaining implants

  3. Historical Perspective:Cruciate Sacrificing • 1974: total condylar prosthesis • cemented & cruciate sacrificing • relied on soft tissue balancing • 1978: modified to posterior stabilized • cam & post design • functional substitute for PCL • 1980: metal backed tibial component • 1987: modified to modular posterior stabilized

  4. Historical Perspective:Cruciate Retaining • 1940s: early designs • 1960s: polycentric knee • promote femoral rollback & a moving instant center of rotation • 1970s: condylar knee designs • 1980s: designs moved away from conformity at the tibiofemoral articulation • increased poly wear • 1990s: Poly wear addressed • reemergence of moderate conformity • selective release or recession of the PCL

  5. The Issues • Kinematics • Range of motion • Wear • Loosening • Proprioception • Gait & Stair Climbing ability • Correction of deformity • Bone loss • Stability • Patella & Joint line

  6. Save the PCL • Needed for stability in coronal & sagittal planes • Femoral rollback • increased flexion • More efficient quadriceps mechanism • better stair climbing • Improved proprioception • Glide between femoral & tibial components • dec wear • Requires strict soft tissue balancing

  7. Sacrifice the PCL • Easier surgical technique • better exposure • Improved ability to correct deformity & restore alignment • Congruent prostheses • less stress to poly • Relies on the principle of balanced flexion and extension gaps

  8. Kinematics • Preservation of the PCL: • preserve femoral roll back • increase ROM • preserve anterior tibiofemoral contact • Posterior stabilized: • dictated by conforming geometry of the tibiofemoral articulation • post & cam

  9. Steihl et al.JBJS 1995;77:884-889 • Fluoroscopic analysis of 5 normal knees & 47 cruciate retaining TKAs • Tibiofemoral contact point posterior in extension and anteriorly translated in flexion • Paradoxical anterior femoral translation • Cruciate retaining TKAs had a discontinous ROM

  10. Mahoney et al.J Arthroplasty 1994;9:569-578 • Biomechanical study of the PCL in TKA • Cruciate retaining and posterior stabilized vs normal knee: • less femoral rollback • less quadriceps efficiency • Femoral rollback decreased by 36 % in cruciate retaining • Femoral rollback decreased by 12 % in posterior stabilized

  11. Range of Motion • Original cruciate total condylar design: • lacked femoral rollback • 0-95 degrees • Posterior stabilized design: • post and cam • allowed flexion of 105 to 115 degrees • Cruciate retaining: • maximum flexion of 100 to 110 • several recent studies have reported flexion of 110 to 115 with recession techniques

  12. Hirsch et al.Clin Orthop 1994;309:64-68 • 242 TKAs • Compared cruciate retaining, cruciate sacrificing and posterior stabilized • Posterior stabilized mean ROM 112 degrees • Cruciate sacrificing mean ROM 103 degrees • Cruciate retaining mean ROM 104 degrees

  13. Cruciate Sacrificing

  14. Cruciate Substituting

  15. Cruciate Retaining

  16. Wear • Cruciate sacrificing total condylar design: • moderately conforming tibiofemoral articulation • shear forces across conforming articulation & prosthesis bone interface • Cruciate retaining: • most designs are less conforming atricular geometries • flat on flat: subject to edge loading • nonconforming designs are subject to high contact stresses

  17. Articulation & Wear

  18. Wear • Majority of literature implicates cruciate retaining designs:(Swany & Scott J Arthroplasy 1993, Landy, J Arthroplasy 1988) • flat on flat • thin tibial inserts • heat pressed poly • Advocates of PCL retention recommend techniques to balance the PCL to avoid overtightening (Rand, Reconstructive Surgery of the Joints,1994, Scott Clin Orthop 1994, Ritter J Arthroplasy 1988)

  19. PCL Balancing

  20. Loosening • Postulated that PCL retention can relieve stress from the cement bone prosthesis interface • Aseptic loosening of cemented condylar knees with cruciate retention, sacrifice and posterior stabilized designs is rare

  21. Proprioception • Mechanoreceptors exist in both the ACL & PCL • Amount of preoperative arthritis is correlated with joint proprioception • Current literature does not support a particular design in regard to a patients’ “feel”

  22. Becker et al.Clin Orthop, 1991:271:122-124 • 30 patients with bilateral TKA; one cruciate retaining and one cruciate substituting • No significant advantage of one design over the other • Half the patients were unable to select one knee over the other when asked to express a preference • Remaining patients were divided equally as to which knee was preferred

  23. Gait Analysis • All knee designs have demonstrated gait abnormalities in level walking: • shorter stride length • reduced midstance flexion • abnormal flexion & extension moments at the knee • Better stair climbing ability has long been attributed to cruciate retaining knees

  24. Wilson et al.J Arthroplasty 1996;11:359-367 • 16 patients with posterior stabilized and compared to 32 age matched controls • No significant difference in knee ROM during stair climbing • Compared to historical controls: • posterior stabilized equivalent to cruciate retaining

  25. Correction of Deformity • Proponents of cruciate retention argue that it is possible to correct varus & valgus deformities • Advocates of posterior stabilized designs argue that PCL excision makes ligamentous balancing technically easier • Ritter stesses need for PCL recession with fixed preoperative deformities • no difference in results with cruciate retention with fixed deformity than those without

  26. Laskin,Clin Orthop 1996;331:29-34 • 115 TKAs with a preoperative varus deformity of at least 15 degrees: • 65 cruciate retaining & 50 posterior stabilized • Ten year follow up: • cruciate retaining: more pain, increase in radiolucencies beneath prosthesis, decreased final ROM, and decreased surviorship

  27. Bone Loss • Posterior stabilized designs require greater resection of bone from the intercondylar notch • Bone in this region is of poor quality • Most revision TKAs use posterior stabilized design • Revision components allow for management of bone deficiency

  28. Stability • Cruciate retaining designs: • less conforming to allow PCL to share the load on the implant interface • require an intact PCL to prevent posterior subluxation • Normal strain pattern in the PCL is difficult to achieve • Posterior stabilized: • require balance of flexion & extension gaps to prevent posterior dislocation

  29. Stability • Incavo et al.Clin Orthop 1994;309:88-93: • Biomechanical study of 8 knees with cruciate retaining implant • PCL too loose in 3 • PCL too tight in 3 • Mahoney et al.J Arthroplasty 1994;9:569-578: • tested implants of several cruciate retaining designs • overtightening of the PCL occurred frequently

  30. Stability • Pagnano et al.Clin Orthop 1999 & Laskin Clin Orthop 1996: • delayed rupture of PCL after cruciate retianing TKA • symptomatic flexion instability • Ritter et al.J Arthroplasty 1988: • reported no problems with late rupture or instability with PCL recession

  31. Patella • Original posterior stabilized design: • patella complication rate ~12% • patella clunk and fracture • Design modifications have decreased rate to ~3 %, equal to cruciate retention

  32. Joint Line • Cruciate retention: • prosthetic joint line must be close to preoperative position 2-3mm • balance PCL to achieve a good ROM • Posterior stabilized: • joint line may be elevated as much as 10mm • Soft tissue balance is important to avoid instability

  33. Conclusions • Considerable literature supporting use of cruciate sacrificing and retaining designs • ROM and survivorship are relatively comparable • Rare problem of dislocation with posterior stabilized design is matched by the late problem of PCL rupture and subsequent flexion instability in cruciate retaining designs • Debate that is going to continue

  34. Considerations • Is PCL recession reproducible? • Balancing the PCL: • Too tight, too loose, just right….. • “Maintaining appropriate tension while preserving the ligament may be a matter of luck”- John Insall, M.D. • PCL sacrificing makes restoring alignment & correcting deformities easier • Sacrifice of the PCL allows for more reproducible TKA • “Same way every time” & “If you really want to learn watch me do surgery” 9/25/00 - Paul Drouillard, D.O.

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