Introduction

In addition to traditional posterior-stabilized (PS) designs with cam-post articulations, there are two new design concepts used in total knee replacement (TKR) to “substitute” for cruciate ligament function and restore anterior-posterior stability. These include i) guided-motion PS designs with a modified cam-post that is less restrictive to axial rotation; and ii) non-PS designs that incorporate progressive articular congruency to substitute the function of the resected anterior cruciate ligament (ACL-substituting). Early post-marketing surveillance of such new TKR designs is valuable because instability, loosening, and high complication rates within the initial 5 year follow-up interval have proven problematic for some design. This study reports the early clinical performance of sequential patients implanted with a new ACL-substituting TKR design at a German Center of Excellence for Arthroplasty (EPZ-Max) hospital.

A unique, laterally stabilized design concept (3D Knee-DJO Surgical, Inc) for total knee arthroplasty (TKA) without traditional post and cam construct was developed to allow surgeons to resurface the arthritic knee while choosing to maintain or sacrifice the posterior cruciate ligament (PCL). Reported complications with current ‘post and cam’ designs of PCL-substituting TKRs include higher polyethylene wear associated with cam-post impingement, increased bone interface shear stresses, and more distal femoral bone resection making revisions more complex and problematic. The effectiveness of this laterally stabilized TKA design has been extensively studied biomechanically using both in-vitro and in-vivo methods. It was hypothesized that for this total knee arthroplasty design; the mid-term clinical, radiographic and functional results would be the same for patients having two different surgical techniques in which the posterior cruciate ligament was either completely retained or completely resected. This study reports on eight year clinical results as well as in-vivo fluoroscopic results and retrieval data. Reported are 159 patients with 116 knees done by a surgeon who preserved the PCL with a bone block technique and 43 knees by a second surgeon who completely resected the PCL. Clinical results did not statistically differ between the two groups and found Knee Society Scores of 96 for Pain and 91 for Function. Average ROM was measured at 124 degrees. Comparative fluoroscopic imaging analysis of in-vivo dynamic flexion activities of thirty-three (20 PCL-preserved and 13 PCL resected) knees was performed demonstrating stable performance and only small (non-significant) mechanical differences. Analysis of two unrelated groups of tibial polyethylene inserts, the first retrieved from patients after 1–4 years in-vivo function (n = 14) and the second after in-vitro knee wear simulation (n = 4) showed low wear rates with no delamination. There was only one failure for mechanical loosening in the cruciate resected group and radiolucent lines of greater than 2 mm were only seen in 4% with none being progressive. Kaplan-Meier Survivorship, using mechanical loosening as the end point, was 99.2% at an average of 8.8 years. In summary, this laterally stabilized TKR design offers a very good alternative to standard ‘post and cam’ PCL sacrificing TKRs while still giving surgeons the ability to maintain the PCL if desired.

Introduction:

Femoral head surface roughness has been recognized as an important determinant of linear and volumetric polyethylene (UHMWPE) wear in total hip replacement (THR), particularly for metal heads. Fisher et al¹ found that a 2- μm scratch with a 1- μm buildup of metal debris produced a 70-fold increase in the wear rate. Ceramic materials and hard-on-hard bearing couples have been introduced to provide more scratch resistance. However, THR bearing surfaces of all materials can become damaged during in vivo function, potentially impacting wettability. The purpose of this study is to quantify surface roughness as related to distinct damage types on retrieved femoral heads and to assess wettability of common bearing materials.