Introduction

The legacy constrained condylar knee prosthesis (LCCK, Zimmer.) is designed for primary and revision total joint arthroplasties that need additional stability due to ligament deficiency and to compensate for bone defects. In this follow-up we present our mid term results.

Background: A continuing controversy in total knee arthroplasty is the question whether the posterior cruciate ligament should be retained or substituted. This report reviews a series of total knee arthroplasties with a fixed bearing posterior cruciate ligament retaining implant (Nex Gen^© CR, Zimmer Inc., Warsaw, IN).

Methods: Between May 1997 and April 2001 197 patients were provided with 218 primary implants. There were 142 females and 55 males with an average age of 71 years (range 53–88 years) and a BMI of 28,9 kg/m² (range 19,1–41,2 kg/m²). The diagnosis was osteoarthritis in 212 patients, 3 cases of aseptic osteonecrosis, 1 fracture of the tibia plateau, 1 prior infection and 1 psoriatic arthritis. 84 knees had prior operations including high tibial osteotomies and menisectomies.

The operations were performed by 11 surgeons, with more than 80% done by 5 surgeons. 162 (74%) femur components and 181 (83%) tibia components were cemented. Patella resurfacing was performed in 135 (62%) cases.

We evaluated the results prospectively with a clinical inspection, radiographs (AP and lateral, longleg standing, patella sunrise view), and the use of the Knee Society Score, Quality-of-Life Short Form-36 and WOMAC rating score.

149 patients were examined at a mean follow up of 5,9 years (range 4,1–8,2 years). 29 were questioned on the telephone, 29 deceased, 7 revisions had to be performed and 4 (2%) were lost to follow up.

Results: The range of motion improved from 101° to 115° (range 80°–140°). All knees had sufficient antero-posterior and mediolateral stability. The Knee society score improved from 35 to 83 (good result) and the function score improved from 52 to 76 (good result).

Early complications included 12 haematoma, 10 wound healing problems, 5 early infections, 2 thrombosis and 1 non lethal pulmonary embolism. 7 revisions had to be performed: 3 late infections (2 one-stage revisions with synovectomy and exchange of polyethylene inlay, one two-stage revision with semi-constrained implant LCCK© Zimmer Inc.), 3 patella resurfacing due to anterior knee pain and 1 exchange of cemented tibia plateau due to aseptic loosening. Survivorship at 6 years including any reason of failure was 96,5%.

Conclusion: At a mid term follow up of 6 years this fixed bearing posterior cruciate retaining implant achieved a reasonable survivorship with good clinical results, kinematics and patient satisfaction.