PyroDisk Interposition Implant for Trapeziometacarpal Osteoarthritis
Authors: Pinho Romeu , Neto Altai Costa , Resende Vera , Teixeira José Manuel , Frada Ricardo 
Published: September 2016

Objective: Trapeziometacarpal osteoarthritis has a high prevalence. In the failure of conservative treatment, there are several surgical procedures, not having been proved to date the superiority of any of them. The PyroDisk interposition implant was introduced in 2005, and the few existing studies have short follow-ups. The objective of this study is to evaluate the clinical and radiological results of interposition arthroplasty with PyroDisk, after a minimum follow-up of 5 years. Materials and Methods: We conducted a retrospective, cross-sectional analytical study with a sample of patients undergoing arthroplasty with interposition PyroDisk between January 2008 and April 2010, with a minimum follow-up of 5 years. They were evaluated in individual interviews and through the clinical process: degree of satisfaction with the surgery, pain (through visual analogue scale), degree of capacity for the tasks of daily living (Disabilities of the Arm, Shoulder and Hand [DASH] score), palmar pinch and digital forces (through dynamometers), mobility (Kapandji score), and complications. We proceeded to assess the progression of osteolysis by analyzing postoperative radiographs and using Herren scale peri-implant radiolucency adapted to the trapeziometacarpal joint. The statistical data analysis was done through SPSS v20. We evaluated 26 patients corresponding to 29 arthroplasties (3 bilateral), 24 females and 2 males, average age 68.1 years. The dominant etiology was primary osteoarthritis (89.1%). The average follow-up was 84.2 months (range, 69-98 months). Results: We found a high degree of satisfaction (92.3%) and 84.6% repeat surgery and had a low degree of disability in daily living activities (average DASH 22.1), with an average pain score of 1.18. The average Kapandji score at follow-up was 8.56 (91% contralateral mobility). The mean grip strength was 13.0 kg/cm2 (91% of the contralateral force) and key pinch strength was 4.5 kg/cm2 (4.6 kg on the antero-lateral side). Radiological assessment (modified Herren scale) revealed the progression of osteolysis at revision for grade I (< 1 mm) in 18.5% of patients, for grade II (> 1 mm) in 59.3%, and for grade III (macroscopic deviation implant > 25% of the base of the first metacarpal) in 22.2%. There was no statistically significant relationship between the degree of osteolysis and the clinical results at revision ( P > 0.05). We registered three complications (10.3%): 2 dislocations and 1 superficial sensory branch neuroma. The implant survival at 5 years was 93.1%. Conclusions: Although the presence of peri-implant osteolysis has been universal in our study, we have not seen any relationship between the degree of osteolysis and implant failure, patient satisfaction, or clinical outcome. Our study confirms the good 5-year clinical results of interposition arthroplasty with PyroDisk. The observed lysis did not compromise the results. More research and greater follow-up are needed to study the effects of this long-term implant.