gms | German Medical Science

Objectives/Interrogation: K-now total elbow is a non-constrained elbow prosthesis designed and manufactured in Japan. K-now total elbow arthroplasty (TEA) is mainly indicated in the elbow with rheumatoid arthritis. The most significant feature of this prosthesis is that humeral component is modular and condylar size can be adjusted with different size of humeral stem. Since we started using this prosthesis, ten years has passed. We reviewed the mid-term results of this total elbow and tried to elucidate inherent complications.

Methods: Since 2007, we started using K-now TEA in patients with rheumatoid arthritis with severe elbow joint destruction. Between 2007 and 2013 we performed 20 K-now TEAs on 19 cases with RA. At a follow-up of seven years two months on average, one had died of unrelated cause. There were 17 women and two men with a mean age of 63 years (34 to 72). All of them except the deceased were reviewed radiologically and clinically assessed using Japanese Orthopaedic Association elbow performance score (JOA elbow score). The joint destruction was rated as Larsen grade 4 in 11 elbows, grade 5 in seven elbows and one ankylosed elbow.

Campbell approach was used to expose the joint. Sizes of the ulnar component, condylar component and the humeral stem are predetermined. At surgery, trial component is inserted to see the snug fit. Then, condylar component and the humeral stem is assembled and firmly fixed by tightening the posterior screw. Ulnar component is fixed using bone cement. Soft tissues are sutured primarily, and the elbow is kept in the splint for 10 days.

Results and Conclusions: One patient developed metallosis in the affected elbow joint and condylar prosthesis was revised after three years four months. At revision, diffuse metallosis was noted and the screw fixing the condylar prosthesis to the humeral stem was found to be loose. In no other patients, metallosis, breakage or loosening of the either stem was found radiologically. The averaged JOA elbow score improved from preoperative 51 points to postoperative 83 points, including the revised patient. The mean arc of flexion/extension improved from preoperative 116/29 degrees to postoperative 131/26 degrees on average. Pronation/supination improved from preoperative 52/68 degrees to postoperative 72/78 degrees.

In conclusion, K-now total elbow arthroplasty has proved to be a durable elbow prosthesis. However, there is a risk of development of metallosis when the screw that connects condyle and the stem becomes loose.