Background The AscensionTM MCP-implant acc. to Beckenbaugh is an unconstrained endoprosthesis consisting of a graphite core with a pyrocarbon coating. Long term results published by the Mayo Clinic gave rise to the hope of good ingrowth properties and a long durability due to the optimum wear resistance of the material. Purpose of this study was the evaluation of the early results of this implant applied on the patients of a rheumatoid arthritis surgery department.
Methods In a prospective manner we evaluated the data of 18 patients with 19 involved hands in which we implanted a total of 29 Ascension endoprostheses between July, 2000 and Oktober, 2002. The mean follow up time was 39.7 months. We assessed hand function (SODA-score), mobility, radiographic appearance and the subjective parameters pain, functionality, power, cosmetic appearance and global satisfaction.
Results The SODA score increased from 82.8 preoperatively to 92.9 (maximum 108) at follow up. With 50.9 and 51.3 deg. respectively the range of motion remained almost unchanged. On a visual analogue scale from 0 – 10 the subjective results were: pain 2.1 (−5.2), functionality 6.5 (+3.0), power 5.3 (+2.3), cosmetic appearance 8.0 (+3.4), global satisfaction 8.1.
Radiographically we observed suspicious radiolucent lines around 17 of 58 implanted components (29%), three of them progressive. Around the tips of three stems an osteolytic area with minimal progression was found. Three stems showed a slight migration. The following intraoperative complications were observed: Two bone fissures and three lacerations of a collateral ligament, which all healed uneventfully. Five endoprostheses were converted into a flexible hinge silicone implant for persistent pain and loosening between 12 and 48 months p.o. One more implant had to be revised due to a late haematogenous infection 4 years p.o.
Conclusion With the AscensionTM MCP implant a good pain relief can be obtained in almost every case but only rarely an improvement in the range of motion can be seen. The subjective results were predominantly good. But the apparently inconstant bony ingrowth resulted in a rate of revisions for aseptic loosening as high as 17% at a mean follow up of 3 ½ years. A modification of the implant leading to a better bony fixation would be required before a wider clinical use of this implant can be recommended.
