Locking Screws Extend Lifespan of Wrist Implants

Figure 1

Total wrist arthroplasty (TWA) has become an increasingly viable alternative to total wrist fusion for patients with severe wrist conditions. However, the long-term effectiveness of TWA, particularly concerning the role of locking screws, has been the subject of ongoing debate. A recent case study by Dr. Ingo Schmidt from Private Othopaedic Practice in Germany, published in the Journal of Hand Surgery Global Online, sheds new light on this topic through an eight-year follow-up of a patient who underwent TWA with a second-type Maestro wrist prosthesis.

Dr. Schmidt details the extremely rare case of a middle-aged woman diagnosed with a Campanacci grade II giant cell tumor in the capitate bone of her right  wrist. Initially treated with intralesional curettage and bone grafting. However, the patient experienced recurring wrist pain, leading to a series of interventions, including four-corner fusion and the eventual implantation of a second-type Maestro wrist prosthesis. This prosthesis, notable for its use of locking screws, was inserted after two failed motion-preserving procedures (Figure 1).

Over the eight-year follow-up, the patient showed complete but asymptomatic avascular necrosis of all previously inserted bone grafts around the capitate peg, but without any evident loosening of the carpal component (Figure 2). However, in contrast to these remarkable radiographic findings, the patient reported high satisfaction levels in conjunction with excellent functional outcomes and only minimal pain under load conditions (Figure 3). A revision of the implant became not necessary.

The study underscores the crucial role of locking screws in enhancing the durability and functionality of TWA. According to Dr. Schmidt, “the use of locking screws significantly improves the longevity of total wrist arthroplasty by mimicking external or internal fixation for large bony defects in long bones.” 

Interestingly, the case study revealed that while the patient experienced progressive bone resorption leading to avascular necrosis, this did not translate to clinical symptoms or reduced functionality. The patient maintained excellent wrist function, with a significant range of motion and grip strength comparable to the unaffected wrist. This highlights the potential of locking screws to ensure the mechanical stability of wrist implants, even in the presence of bone necrosis.

The findings from this case report emphasize the importance of selecting appropriate wrist implants equipped with locking screws for patients undergoing TWA. Dr. Schmidt suggests that the two supporting locking screws minimized unfavorable shear forces at the implant-screw-bone interface, thereby preventing loosening. This stability is crucial, especially in cases where the capitate is replaced by bone grafts, as nonlocking screws may not provide longstanding sufficient fixation. 

The Maestro prosthesis was the world’s first wrist implant to allow fixation of the carpal component with locking screws. However, despite the superiority of the Maestro both in terms of survivorship and functional outcome over all other third-generation TWA types (or fourth-generation types when declaring the silicone implants as first type), this implant was incomprehensibly withdrawn from the marketplace in 2018, suggesting that the implant was no longer profitable for the company.

The long-term success of TWA with locking screws, as demonstrated in this case, challenges previous concerns about the durability of wrist implants. It suggests that the correct use of locking screws can significantly extend the lifespan of TWA, reducing the need for revision surgeries. However, Dr. Schmidt cautions that while the current results are promising, the potential for future loosening remains, necessitating ongoing monitoring.

Dr. Schmidt’s study contributes valuable insights into the long-term management of TWA, particularly regarding the choice of implants and fixation methods. It highlights the necessity of considering locking screws in TWA procedures to enhance implant stability and patient outcomes. As wrist arthroplasty continues to evolve, these findings will inform future surgical practices and implant designs, ensuring better care for patients with severe wrist conditions.