Summary

TKA with standard metal alloy shows good results in patients with metal allergy/hypersensitivity

Abstract

Introduction

Metal allergy or hypersensitivity is a controversial topic in total knee arthroplasty (TKA). Data concerning the outcome of patients with a known metal allergy/hypersensitivity is sparse. The existing data gives no clear recommendation whether a hypoallergic implant is favorable compared to the standard metal alloys (cobalt, nickel, chromium). Aim of our study was to perform a retrospective follow up of all patients with known metal allergy/hypersensitivity and total knee arthroplasty (standard Sigma PFC implant) from January 2013 till March 2020.

Material And Methods

167 patients (182 knees) with known metal allergy/hypersensitivity to nickel, cobalt or chromium were treated with a cemented total knee arthroplasty using the Sigma PFC implant (DepuySynthes, Umkirch, Germany) between January 2013 and March 2020 in our institute. 134 patients could be enrolled into the trial. Clinical outcome was assessed comparing the NRS scale, the UCLA score and the WOMAC score, pre- and postoperatively. Furthermore, the Oxford Knee Score, the EQ5D3L and the revision rate was enquired.
The mean follow-up was 36.34 ± 22.28 (4.00-87.00) months. The patient collective consisted of 113 female patients with an average age of 61.5 ± 8.75 (42-83) years and 21 male patients with an average age of 59 ± 5.56 (49-71) years. 52 % of the included patients (n=70) had a proven metal allergy based on cutaneous and in-vitro testing. In the remaining 48 % (n=64), the metal allergy/hypersensitivity was suspected due to skin reaction to metallic objects observed by patients.

Results

Patient satisfaction on a numeric rating scale (NRS 0-10) showed good and very good results after TKA with a mean of 8 ±2. The queried pain level decreased significantly from 8,18 ±1,34 pre- to 1,72 ±2,02 postoperatively (p>0,0001). The UCLA and WOMAC score showed a similar positive performance and improved to 6,28 ± 1,37 (3,38 ± 1,40 preoperative) and 83,92 ± 18,79 (41,62 ± 16,64 preoperative) respectively (p>0,0001). The mean Oxford Knee Score was 39,88 ± 7,19 and the EQ5D showed good results in all 5 dimensions of the questionnaire after surgery. A total of 10 patients needed revision after TKA. Brisement force was performed in 5 patients, 3 patients were treated with open arthrolysis and inlay replacement and further 2 patients underwent synovectomy and biopsy. Implant loosening has not been observed during the follow-up.

Conclusion

The results of this study show similar outcomes compared to the non-allergic population displayed in the current literature after standard TKA, in short- and mid-term follow up. The use of a standard implant with a cobalt, nickel, chromium alloy does not seem to lead to inferior results in patients with known metal allergy/hypersensitivity compared to the general population. The non-inferiority theory of standard implants to hypoallergenic implants should be investigated in further studies comparing these implants.