Joint contact areas after radial head arthroplasty: a comparative study of 3 prostheses.

BACKGROUND: Contact stresses of radial head prostheses remain a concern, potentially leading to early capitellar cartilage wear and erosion. In particular, point contact or edge loading could have a detrimental effect. The purpose of this study was to compare 3 different types of radial head prostheses in terms of joint contact areas with each other and with the native situation. The hypothesis was that the joint contact areas would be lower after monopolar arthroplasty. METHODS: Seven fresh-frozen cadaveric upper limbs were used. Radiocapitellar contact areas of a monopolar design, a straight-neck bipolar design, and an angled-neck bipolar design were compared with each other and with the native joint. After standardized preparation, polysiloxane was injected into the loaded radiocapitellar joint to create a cast from which the joint contact area was measured. Measurements were performed at 3 angles of elbow flexion and in 3 different forearm positions. RESULTS: In the native elbow, contact areas were highest in supination. Elbow flexion had no significant effect on native and prosthetic joint contact areas. Contact areas were decreased for all types of arthroplasties compared with the native joint (from 11% to 53%). No significant contact area difference was found between the 3 designs. However, bipolar prostheses showed lateral subluxation in neutral forearm rotation, resulting in a significant decrease in the contact areas from pronation to the neutral position. CONCLUSIONS: All types of radial head prostheses tested showed a significant decrease in radiocapitellar contact area compared with the native joint. Bipolar designs led to subluxation of the radial head, further decreasing radiocapitellar contact.

Percutaneous, Transtrapezial Fixation without Bone Graft Leads to Consolidation in Selected Cases of Delayed Union of the Scaphoid Waist.

Purpose We evaluated clinical and radiographic outcome of percutaneous transtrapezial fixation of the scaphoid delayed union or nonunion using a headless bone screw without bone grafting. Methods Sixteen patients with delayed union or nonunion of the scaphoid were included in this retrospective study between 2006 and 2011. All patients had a delayed presentation of scaphoid fracture, and none of them was treated conservatively elsewhere. Patients with bone graft, sclerotic bone debridement, or displacement of the fragment at the nonunion site were excluded. A percutaneous transtrapezial fixation technique was used in all cases. Patients were reviewed until clinical and radiographic union was observed. At the final follow-up, DASH (Disabilities of the Arm, Shoulder and Hand) and PRWHE (Patient-Rated Wrist and Hand Evaluation) outcome scores were completed. Results Radiographic union was obtained in 15 out of 16 patients (94%) at an average follow-up of 36 months (range: 12-98 months). No complications from the percutaneous technique were noted. The average DASH score was 6 (range: 0-39) and the average PRWHE score was 10 (range: 0-56). No statistical significant difference in range of motion and grip strength was found between the operated side and the contralateral side. Conclusion Percutaneous transtrapezial screw fixation for delayed or nonunion of selected scaphoid fractures without bone grafting is promising. At a mean of 4 months, 94% union was obtained with good functional results when there was no sclerosis, minimal osteolysis, and no displacement at the scaphoid nonunion site. Type of Study Therapeutic study. Level of Evidence IV.