Midcarpal Arthrodesis Biomechanics: Memory Staples versus Cannulated Screws

Background: Midcarpal arthrodesis is a treatment of choice in patients with midcarpal arthritis. Traditionally a four corner fusion has been favoured, however recent research has shown improved results when the triquetrum and scaphoid are excised. There is no clear evidence as to which remaining bones should be fused or which implants should be used. The purpose of this study is to compare the biomechanics of midcarpal arthrodesis after scaphoid and triquetrum excision, using memory staples or cannulated screws, in recognised construct patterns. Methods: 36 identical sets of carpal bones were 3D printed from acetyl butyl styrene. Midcarpal arthrodeses were performed in three configurations with shape memory alloy staples or headless compression screws. This gave 6 treatment groups; lunocapitate single staple or screw, lunocapitate with 2 staples or screws, three corner fusion with 2 staples or screws. Peak torque to distraction was measured and analysed. Results: The peak torque to distraction was significantly greater in almost all constructs utilizing screws compared to staples, with two lunocapitate screws having the highest peak torque at both 1 and 3 mm distraction with 244 Nmm and 749 Nmm respectively (p < 0.05). Conclusions: Constructs utilizing screws have a peak torque to distraction significantly higher when compared to staples. Our recommendation when performing a midcarpal arthrodesis after scaphoid and trapezium excision is to fuse the midcarpal joint with 2 headless compression screws.

Outcomes after Scaphoid Excision and Midcarpal Arthrodesis for SNAC and SLAC Wrist Arthritis

Background. Persistent, long-lasting pseudoarthrosis of the scaphoid or scapholunate dissociation results in arthrosis of the radio-scaphoid joint termed scaphoid non-union advanced collapse (SNAC) or scapholunate advanced collapse (SLAC), which causes pain, reduction in wrist movements and weakness of the hand grip. Scaphoid resection followed by „four-corner” midcarpal arthrodesis is a recognized treatment for this condition. Material and methods. The study evaluated the results of treatment of 27 patients with arthrosis of the wrist type SNAC (n = 15) and SLAC (n = 12) after an average of 4 years after surgery (range from 2 to 8 years) Results. The mean numerical pain score for wrist movements was 3.6 (range: 1-5). The mean active range of wrist movement (affected vs healthy hand) was: flexion 27° vs 58° (46%), extension 27° vs 52° (53%), ulnar deviation 16° vs 26° (62%), radial deviation 9° vs 17° (53%), total grip strength 22 kG vs 29 kG (76%), The mean DASH score was 22 (range: 4-36) and the mean Mayo score was 72 (range: 65-80). None of the patients required revision surgery. Of the 16 patients employed prior to the surgery, 10 returned to work after a mean of 4 months of sick leave. Conclusions. 1. The results of the treatment presented in this stu­dy, after a relatively long follow-up period, show a beneficial effect of the surgery on pain intensity and improvement of hand dexterity, at the cost of a mild reduction in wrist movements. 2. It seems that this technique offers good, predicta­ble outcomes and may be recommended for Wa­t­son 2° and 3° SNAC or SLAC wrist arthrosis.

Proximal row carpectomy, scaphoidectomy with midcarpal arthrodesis or midcarpal tenodesis: when and how to use

I report my personal experience over three decades in the treatment of carpal collapse due to scapholunate collapse and scaphoid nonunion. I have used the proximal carpal row resection performed through palmar approach, the scaphoidectomy and double-column midcarpal arthrodesis, and scaphoidectomy with midcarpal tenodesis. Diagnostic arthroscopy is essential for staging and surgical decision making regarding the type of treatment. The details of the surgical techniques, tips, results and possible complications are described for each method. The advantage of the proximal row carpectomy by palmar approach is the early permitted rehabilitation with better recovery of wrist motility in comparison with the traditional technique. The advantage of the double-column midcarpal arthrodesis lies in its ease of execution. The midcarpal tenodesis is an excellent intervention from the conceptual point of view even if over time there is a progressive carpal collapse even in absence of symptoms.