We report the case of a 12-year-old boy with flexion loss in the left elbow caused by deficient of the concavity corresponding to the coronoid fossa in the distal humerus. The range of motion (ROM) was 15°/100°, and pain was induced by passive terminal flexion. Plain radiographs revealed complete epiphyseal closure, and computed tomography (CT) revealed a flat anterior surface of the distal humerus; the coronoid fossa was absent. Then, the bony morphometric contour was surgically recreated using a navigation system and a three-dimensional elbow joint model. A three-dimensional model of the elbow joint was made preoperatively and the model comprising the distal humerus was milled so that elbow flexion flexion of more than 140° could be achieved against the proximal ulna and radius. Navigation-assisted surgery (contouring arthroplasty) was performed using CT data from this milled three-dimensional model. Subsequently, an intraoperative passive elbow flexion of 135° was obtained. However, active elbow flexion was still inadequate one year after operation, and a triceps lengthening procedure was performed. At the final follow-up one year after triceps lengthening, a considerable improvement in flexion was observed with a ROM of −12°/125°. Plain radiographs revealed no signs of degenerative change, and CT revealed the formation of the radial and coronoid fossae on the anterior surface of the distal humerus. Navigation-assisted surgery for deformity of the distal humerus based on a contoured three-dimensional model is extremely effective as it facilitates evaluation of the bony morphometry of the distal humerus. It is particularly useful as an indicator for milling the actual bone when a model of the mirror image of the unaffected side cannot be applied to the affected side as observed in our case.

Introduction: In general a loose-balanced total knee arthroplasty (TKA) are believed to gain good postoperative range of motion (ROM), however, too much laxity is thought to be a cause for persistent pain and catastrophic long-term results.

Materials and methods: We measured the antero-posterior and medio-lateral laxity to evaluate the influence of stability after cruciate-retaining TKA on ROM, pain score in Knee Society score and Functional score at 4–7 years after the operation. Twenty-one knees in 15 patients with an average age of 68 years (range, 58–78) who had a PCL retaining TKA for osteoarthrosis were examined (YS-4, 16 knees; AGC-S, 5 knees). There were 12 women and 3 men. Anteroposterior laxity was examined using a KT 2000 arthrometer at 30-degree knee flexion. Mediolateral laxity was examined at full extension with manual stress x-rays.

Results: Average ROM was 112 degrees (range, 90–140 degrees), antero-posterior laxity was 9.7 mm (range, 2–27 mm) and mediolateral laxity was 10.6 degrees (range, 5–22 degrees). Knee Society pain score was 47 (range, 10–50) and Functional score was 82 (range, 40–100). No significant difference in ROM and clinical scores were noted between the lax and the stable knees. Correlations between ROM and anteroposterior or medio-lateral laxity were not significant (P = 0.55, P = 0.05, respectively; Spearman’s correlation efficient).

Discussion and conclusion: A loose-balanced TKA did not gain good post-operative ROM. No parameters suggested that lax knees got better flexion angle, worse pain score and functional score than stable knees.