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Medial Mobile-Bearing UKA with Twin-Peg Femoral Design and Enhanced Instrumentation

February 01, 2014

Contributors: Adolph V Lombardi Jr, MD; Jason M. Hurst, MD; Michael J. Morris, MD; Joanne B Adams, BFA, CMI; Keri L. Satterwhite, ; Michael A Sneller, BS; Keith R Berend, MD; Keith R Berend, MD

The femoral component of a mobile-bearing unicompartmental knee arthroplasty (UKA) implant was redesigned with an additional peg for more secure fixation and 15° of extra femoral surface for contact in deep flexion, and instrumentation was refined to facilitate surgical technique. To assess the benefit of these design and instrumentation changes, we compared early clinical results between the twin-peg versus earlier single-peg designs. A query of our practice's arthroplasty registry revealed 359 patients (428 knees) who underwent medial mobile-bearing UKA between August 2008 and December 2011. The twin-peg design was gradually and randomly phased into use with increasing availability, and 187 patients (222 knees) received the single-peg design, while 172 patients (206 knees) received the twin-peg design. The preoperative diagnosis was osteoarthritis in all cases. At mean follow-up of 2.8 years (maximum 4.7 years), there have been 10 revisions overall: 7 single-peg and 3 twin-peg. In the single-peg group, failure modes were one arthritic progression, three aseptic loosening, two medial pain secondary to tibial overload, and one unknown revised elsewhere. In the twin-peg group, failure modes were one arthritic progression, one tibial collapse, and one with a polyethylene insert revised at 14 months for varus/valgus instability and later revised to total knee arthroplasty elsewhere because of arthritic progression. Manipulation for treatment of ankylosis was performed in three single-peg knees versus no twin-peg knee (P = 0.04). Improvement in range of motion was similar between groups. The twin-peg group had more improvement than the single-peg group in KS pain (35.3 versus 31.4; P = 0.02), clinical scores (51.6 versus 47.9; P = 0.05), and function scores (19.6 versus 17.9; P = 0.05). Radiographic analysis revealed satisfactory position and alignment with no femoral or tibial radiolucencies in any surviving UKA. In this series with 2.8 years' mean follow-up, there have been no revisions for component loosening with the twin-peg femoral component. A lower manipulation rate and improvement in KS pain and clinical and function scores were observed with the initial twin-peg versus single-peg design.

Results for "Primary Knee Arthroplasty"

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