Ten-Year Results of Primary and Revision Condylar-Constrained Total Knee Arthroplasty in Patients with Severe Coronal Plane Instability

Objective : To retrospectively review the results at minimum ten years after surgery of a consecutive series of total knee arthroplasties (TKAs) performed using a constrained condylar implant in patients with severe coronal plane instability. Materials and Methods : The series comprised of 44 patients (45 knees) who received primary (19 knees) or revision (26 knees) TKA with a constrained condylar implant between 2001 and 2003 at a single institution. Results : There were no revisions or any other surgery related complications at a mean implantation time of 11.0 years. In 38 patients (15 knees in the primary group and 24 knees in the revision group) who were available for clinico-radiographic follow-up at a minimum of ten years, there was no sign of radiographic loosening. Two patients showed cortical hypertrophy at the extension stem tip but none complained of pain around the stem tip. According to the TLKSS score grading, 73% of the patients in the primary group had results categorized as good or excellent, while 54% of the patients in the revision group had fair results. Four patients (one (7%) in the primary group and three (13%) in the revision group) had poor results. The median WOMAC Index was 80.2% (interquartile range: 74.0% - 81.2%) and 74.0% (interquartile range: 72.1% - 75.8%) in the primary and in the revision groups, respectively (p=0.010). Conclusion : This study showed satisfactory clinical outcomes with no re-operations at minimum ten years after implantation in patients who had undergone primary or revision TKA with a condylar constrained implant.

Finite Element Analysis of TMJ Implant

The TMJ is a bilateral joint of the jaw that functions as a single entity during normal masticatory activities, speaking, yawning and swallowing. TMJ replacement has been indicated in cases of joint trauma, advanced degenerative disease, tumors, developmental anomalies and ankylosis of the joint following injury. Alloplastic replacement of the TMJ (an artificial replacement in the form of a TMJ condylar implant with a glenoid fossa component that articulates with the undersurface of the skull on the temporal bone) renders the anatomical space devoid of the natural mandibular condyle (Fig. 1). Compared to hip and knee prostheses, TMJ implants have not been studied in detail. The goals of this study were to quantify the stress distribution in a commercially available TMJ implant (TMJ Implants, Inc, CO), bone and implant-bone interface, to compare the stresses and strains with different bone conditions, and to compare the stresses and strains with different implant materials using a finite element software package.