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Unicondylar Arthroplasty

Unicondylar Arthroplasty. Jeff Easom, D.O. Garden City Hospital. Overview. Utilized for either medial or lateral compartment OA Controversy exists over the durability of a UKA compared to a TKA Patient selection criteria important for probability of success with UKA.

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Unicondylar Arthroplasty

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  1. Unicondylar Arthroplasty Jeff Easom, D.O. Garden City Hospital

  2. Overview • Utilized for either medial or lateral compartment OA • Controversy exists over the durability of a UKA compared to a TKA • Patient selection criteria important for probability of success with UKA

  3. Rarely considered for OA patient < 60 y.o. • UKA is an acceptable alternative for the young, active patient with OA if clinical results are predictable and if UKA does not compromise TKA conversion in the future • Advantages in patients who are elderly and sedentary are evident(no immobilization, ^ ROM when compared to HTO).

  4. Selection Criteria, Scott et alJBJS 71-A, No. 1, January 1989 • Age - > 60 y.o. • Weight - < 180 lbs. • Activity level - No heavy laborers or excessively physically active patients • Pain - Preoperative rest pain should be minimum • ROM - Pre-op flexion to 90 degrees and no greater than 5 degrees flexion contracture

  5. Angular deformity - Should be less than 15 degrees that is passively correctable

  6. UKA v TKA • Final decision made after arthrotomy • Direct visual examination of articular surfaces. Small erosion in non-weight-bearing areas of opposite compartment is not a contraindication to UKA • PF pain - Relative contraindication to UKA, while chondromalacia patella is not

  7. Exposed subchondral bone beneath patella or in a weight-bearing area on the opposite compartment - TKA is recommended • RA and chondrocalcinosis are not suitable candidates for UKA because of increased risk of degeneration in the opposite compartment

  8. Selection Criteria for UKAInsall et al., CORR, No. 286, January 1993 • Prospective evaluation of 165 consecutive pts (228 knees) • Intraoperative evaluation of cartilage at time of TKA • 35 knees (15%) - UKA candidates based solely of inspection of cartilage • 22 of this 35 did not meet other selection criteria - only 6%(13 knees) met criteria

  9. Theoretical Advantages of UKA • Rapid rehabilitation - ^ ROM • Bone-sparing procedures - controversial. Barrett and Scott, JBJS 69:1328, 1987 - 50 of UKA conversions required some form of augmentation • ACL and PCL preservation for future TKA • PF joint preservation and preservation of articular surface of opposite side

  10. Goals of Surgery • Relieve pain • Restore alignment of knee to neutral, and avoid overcorrection of varus to valgus • Use adequate poly thickness to avoid accelerated wear • Place tibial component over rim to avoid subsidence

  11. Major Causes for Clinical Failure of UKA • Prosthetic design • Surgical technique • Patient selection • Overall, aseptic loosening of the tibia component or progressive arthritic changes in the opposite compartment have led to failure

  12. Perioperative Morbidity • Fewer systemic complications • Fewer wound problems • Transfusion rarely needed • MUA and extensor mechanism problems after TKA are less likely with UKA • Need for post-op ambulatory aids less with UKA than TKA

  13. Revision TKA After Failed UKA or HTO • ABILITY to revise either must always be considered in the decision-making process for treatment of unicompartmental arthritis • UKA - Concern of bone loss • HTO - Concern over gaining adequate exposure and re-establishing alignment, as well as soft-tissue balance with revision TKA

  14. Thornhill et al., CORR No. 321, pp 10-18 • Retrospective analysis • 30 TKA after failed UKA • 30 TKA after failed HTO • Minimum f/u - 2 years(avg. 3.8) • Blindly matched according to age, gender, primary disease, length of f/u within 1 year and Knee Society scores

  15. Results • Avg. time to conversion TKA in HTO group - 6.5 years • Most common problem at revision was obtaining adequate exposure • Avg Knee Society Knee Score was 87.3 • 6 pts had PF pain when rising from chair, 5 had pain while standing, 6 pts use ambulatory aids, and 17 could walk unlimited distance, with 9 walking 10 blocks

  16. Avg time to conversion TKA from UKA - 6.7 years • Mean poly thickness - 11.3 mm • Most commonly encountered problem with TKA - loss of bone stock • Significant femoral and medial tibial bone loss requiring reconstruction present in 23 knees (77%)

  17. Additional problems - Patellar inversion • Avg ROM at 3.8 years was 2 to 104 degrees • 6 pts had PF pain when rising from chair, 4 had pain with standing, 7 had pain with ambulation ,16 used a support for ambulation • 7 pts - no limitations with distance walked, and 19 had diff walking 10 blocks • Knee Society Score in UKA group -67.7

  18. No significant difference in radiolucent lines between the 2 groups • Poor results - Defined as Knee Score > 1 standard deviation from mean score of both groups, or a pt. Requiring revision from initial TKA - 3 poor results in HTO group and 12 in UKA group

  19. Scott et al, CORR, No. 271, October, 1991 • 8 to 12 year f/u • 100 UKA - 64 studied at f/u • 90% survivorship at 9 years, 85% at 10 years, and 82% at 11 years • 87% had no significant pain • Avg knee flexion - 115 degrees • 15% (avg age - 80 y.o.) used a cane but not for knee

  20. 60% had radioulucent lines at tibial bone-cement interface • 13 knees that required revision would not have been treated with UKA if current selection criteria had been used.

  21. Marmor, CORR, No. 226, January 1988 • 10 to 13 year f/u study on UKA • 60 knees - minimum 10 year f/u • 30 excellent, 8 good, 4 fair and 18 poor results • Pain relief accomplished in 86.6% of pts. • Of 21 failures, majority due to poor pt selection and material problems (6mm poly)

  22. Stockelman et al, CORR, No. 271, October, 1991 • Retrospective study • 44 knees - Medial UKA • Poly at least 9 mm in all cases • F/U 5 to 12 years (avg 7.4 years) • F/u based on questionnaire, PE and radiographs • Mean age - 64.5

  23. Results • 89.6 good or excellent results • HSS scores higher in > 55 y.o. group • Radiograph showed 68.2% of pts had a radiolucent line > 1mm on AP, but only 20.5% seen on lateral projection • Younger age group had less ROM and lower HSS scores

  24. Engh et al, ICL, Volume 48, 1999 • UKA as option for high demand patient • Addresses 4 basic questions - 1)Clinical results and durability of UKA in young pts. 2)Comparison of morbidity and complications of UKA to other procedures 3)Difficulty of revision of UKA or conversion to TKA 4)Durability of TKA following revision of a failed UKA

  25. Results of UKA • No study specifically addresses UKA and it’s durability in the young(<60 y.o.) pt. • Authors stratified UKA in 5 long-term studies - 290 knees with avg f/u of 10 years • 51/290 (18%) required revision at 10 years • Most common reason for revision was aseptic loosening and progressive arthritis

  26. Aseptic loosening most commonly caused by thin tibial poly component • Progressive arthritis most commonly caused by overcorrection of varus deformity to valgus deformity

  27. 46 UKA on age 40 to 60 y.o. at Anderson Clinic. • Avg weight - 191 lbs • Avg f/u - 7.1 years • Revision rate at 7 years - 28% (13/46) • 10 of 13 failures due to polyethylene wear in 6 mm metal backed components (actual poly thickness of 4 mm)

  28. Revision of UKA • Barrett and Padgett studies each suggested > 50 and 70% of UKA conversions required bone-grafting or long-stemmed components to fill bony defect from UKA

  29. Durability of Revision TKA • Related to age and activity level of patient, extent of bone loss, and management of bony defects • 35 pts at Anderson clinic in age 40 to 60 y.o. hav undergone revision of UKA to TKA - Reason was poly wear in 26 cases and aseptic loosening in 9 cases with overall success rate of 94%.

  30. Conclusion • Controversy still exists regarding the use of UKA in single compartment OA. • Long-term studies have shown that UKA MAY provide an approx 76% survival rate at 8 to 10 years. • Newer components have addressed the failure issues associated with thin tibial components, which were used in most of the long-term studies published.

  31. Overall, the most important clinical decision is the stringent criteria used in selecting patients for UKA, if one chooses to perform these

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