Abstract
Purpose
In total elbow arthroplasty (TEA), especially for elbows with condyle defect due to rheumatoid arthritis or trauma, determination of rotation alignment of implants is often difficult. To develop a navigation system for TEA, selecting bony landmarks that can be identified intraoperatively is important. Therefore, we developed a new roentgen free navigation system such as special alignment jigs for TEA based on CT data of normal elbows. The aim of this study was to evaluate alignments of implants after MIS-TEA using the new systems. And also, we reported that 6 bony landmarks on the elbow showed small variability in normal elbows by CT examinations and were considered to be usable as intraoperative landmarks for determining rotational position of implants last year. Especially in RA elbow, posterior aspect of humerus and ulnar aspect of proximal part of ulna were able to be identified even if there is a large bone defect that extends to the lateral or/and medial epicondyle.
We used a new roentgen free navigation system in TEA with using Solar elbow from 2009. The aim of this study was to evaluate alignments of implants after MIS-TEA using the new systems by CT examinations.
MATERIALS AND METHODS
For determination of alignment and anatomical landmarks to develop the jigs, 3D-CT data of 11 normal elbows was investigated. The posterior aspect of humeral shaft and ulnar aspect of proximal ulna were selected as bony landmarks. Because these can be identified intraoperatively and remain in elbows with extensive bone loss. MIS-TEA with Solar Elbow (Stryker) using these new systems were investigated with postoperative 3D-CT in 14 elbows of 13 patients. Their average age was 68.8 years old. Basic diseases were 10 rheumatoid arthritis and 4 distal humerus injuries. The alignments of humeral and ulnar component were measured on postoperative 3D-CT.
RESULTS
Rotational alignment (humerus / ulna) was pronation 6.8° ± 5.7° / pronation 4.6° ± 9.1°; frontal alignment was valgus 0.1° ± 2.7° / valgus 0.1° ± 3.7°; and sagittal alignment was extension 0.6° ± 3.0° / extension 8.9° ± 2.5°. In condyle-defect group (n=5), comparable alignment with condyle-preserved group was obtained.
DISCUSSION
The new systems were effective in determining intraoperative alignment even in elbows with extensive bone defect. Extension alignment of the ulna component is because the short component of Solar Elbow was placed along the center axis of the proximal ulna, which inclines in the extension direction relative to the axis of distal ulna.
