Modern implant systems offer a variety of options to address the posterior cruciate ligament (PCL) and afford stability in primary total knee arthroplasty (TKA). One system has three bearing options for cruciate retaining (CR) TKA: standard CR bearing (CR-S) with 3° posterior slope and no posterior lip; CR lipped bearing (CR-L) with no slope and small posterior lip, and deep-dished anterior stabilized bearing (CR-AS) with large anterior build-up to compensates for deficient or lax PCL. We previously reported on 1940 patients (2449 CR-TKA) at early follow-up comparing these three CR bearings and found CR-AS bearings had greater improvement in ROM and lower rate of manipulation despite their use in patients with greater preoperative deformity and lower ROM. The purpose of this study was to review a broader series by a single surgeon-designer with minimum 2-year follow-up to determine if there were differences between bearing types in terms of clinical outcomes and survival. From 2003 to 2014, 3348 patients (4500 knees) underwent primary CR-TKA and were available for review with minimum 2-year follow-up. An algorithmic approach to constraint was employed, choosing the least amount necessary to afford stability. Bearings used were 3883 CR-S (86%), 256 CR-L (6%), and 361 CR-AS (8%). CR-S bearings were used in patients with less preoperative tibiofemoral deformity (p=0.0316), less flexion contracture (p<0.0001), and better ROM (p<0.0001), but more mediolateral instability (p<0.0001) than CR-AS bearings.Introduction
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