Distal Radioulnar oint Prosthesis

The semiconstrained DRUJ prosthesis: blessing or curse?

PURPOSE

There are numerous operative procedures to treat osteoarthritic changes or a significant instability of the distal radioulnar joint (DRUJ). The key problem of most methods is the destabilization of the forearm leading to secondary painful impingement between the radius and ulna, as well as a significant limitation of forearm rotation. The Aptis-Prosthesis designed by Scheker represents a complete substitute for the DRUJ. It is mostly used after the failure of various treatment options to solve the primary problems (arthritis, instability). We have used this type of prosthesis mostly after multiple operative treatments for more than 25 years.

METHODS

In the following retrospective study, we analyzed the data of patients that received an Aptis-prosthesis between 2016 and 2021. We have implanted this prosthesis in 13 cases (11 female, 2 male). Routinely, we document the clinical outcome concerning range of motion (ROM), grip strength, and pain according to numeric rate scaling (NRS) after more than 12 months (month 12-24). In addition, complications, osseous changes, and the rate of loosening of the prosthesis were registered. Furthermore, DASH-Score and patients ' satisfaction were evaluated. Also-as with other implants-follow-up x-rays were performed.

RESULTS

Removal or significant revision of any of the prostheses was not needed. The ROM was 68.1° ± 19.7° for pronation and 72.3° ± 20.9° for supination, grip strength amounted to 27.7 kg ± 11.0 kg equaling 83% of the contralateral side. NRS was 0 at rest and 1.2 (0-2) under weight-bearing. A lysis margin of the radial tap was noted in the radiological examination in 2 patients but without any signs of loosening. The DASH-Score added up to 31.8 ± 13.8 (13-55). All patients were satisfied or very satisfied having this implant.

CONCLUSION

The semiconstrained Aptis-prosthesis is a safe and efficient treatment option after failed DRUJ surgeries. It is striking that of the 20 implanted prostheses no significant revision or explantations were necessary over a period of 25 years.

Finite element analysis of intraosseous distal radioulnar joint prosthesis

BACKGROUND

Joint replacement is one of the options to retrieve the interosseous distal radioulnar joint (DRUJ) function. DRUJ prosthesis has recently been introduced clinically to treat DRUJ instability. This article analyzes the biomechanical behavior of the prosthesis during different loadings by the finite element method.

METHODS

CT images of a healthy 33 years old man were used to construct the three-dimensional geometry of the forearm bone. Then two models, a healthy foreman (Model A) and a damaged model with an inserted interosseous prosthesis (Model B), were constructed to analyze and compare the foreman's biomechanical behavior under different loading conditions using the finite element method. Both models were examined during pronation and supination with 500, 1000, 2000, and 5000 N.mm values. Also, both models were subjected to volar and dorsal loads with values of 10, 30, and 50 N and traction force with 100, 150, and 200 N.

RESULTS

Maximum and minimum principal stresses were evaluated for bones in all conditions, and von Mises stress was considered for the prosthesis and fixing screws. In supination, the maximum stress in Model A is significantly higher than the Model B. However, the maximum principal stress of both models is similar during volar and dorsal loading. In Model A, the maximum principal stress in traction is much smaller than in Model B. The absolute value of minimum principal stress in pronation and supination in Model B is higher than in Model A. The prostheses and screws are subjected to higher stresses during pronation than supination. Also, the amount of stress created in prostheses and screws during volar and dorsal loading is almost equal. In traction loading, screws are subjected to significantly high stresses.

CONCLUSION

Our study indicates that the interosseous DRUJ prosthesis can perform the foreman's normal daily activities. This prosthesis provides the ability similar to a normal hand.

LEVEL OF EVIDENCE

IV.

Distal Radioulnar Joint Instability: Diagnosis and Treatment

Distal radioulnar joint (DRUJ) instability and triangular fibrocartilage complex (TFCC) tears are more usual than estimated and are frequently overlooked. Diagnosis is often clinical, which can be confirmed using computed tomography (CT) scan and magnetic resonance imaging (MRI). In doubtful cases, bilateral computed tomography in neutral forearm rotation, supination, and pronation should also be performed. Wrist arthroscopy can be diagnostic and therapeutic for ulnar-sided wrist pain. Two systematic reviews showed equivalent outcomes between open and arthroscopic repair of the TFCC. There is scant proof to advise one technique over the other in clinical practice. TFCC repair and reconstruction are contraindicated when there is a bony deformation of the radius or ulna or osteoarthritis of the DRUJ. With the advancement of implant arthroplasty, salvage procedures are less desirable. Constrained distal radioulnar arthroplasty is stable, and the longevity is encouraging.