Efficacy of total knee arthroplasty (TKA) revision surgery depends upon the indication for revision : a systematic review.

The number of revision total knee arthroplasty (TKA) surgeries has increased over the years and it is expected that its number will keep rising. Most frequent reasons for revision are known to be aseptic loosening, infection, instability, periprosthetic frac- ture, arthrofibrosis and component malposition. The influence of the indication for revision on the outcome scores is not fully understood. Therefore, this work will evaluate and review the existing literature regarding outcome scores after revision TKA surgery. We conducted a sensitive and comprehensive search for published and unpublished studies relevant to the review question. We restricted our search to English studies published between January 2008 and December 2018. Our systematic review was done according to PRISMA guidelines. We withheld 19 studies (1419 knees) for inclusion. Of these, 9 papers reported outcome scores after TKA revision for aseptic loosening, 10 reported on revision for instability, 10 reported on stiffness or arthrofibrosis and 4 papers reported on component malposition. Although we found some papers suggesting that there is no difference in postoperative outcome scores depending on the aetiology of revision surgery, the majority of the included studies suggest differently. This review suggests there is a tendency for relative higher outcome scores after revision for aseptic loosening. Revision for malrotation might give comparable postoperative outcome scores and satisfaction ratios. Revision for instability tends to give lower postoperative outcome scores than aseptic loosening, although certain subgroups of instability show comparable results. Lowest postoperative scores might be found after revision for stiffness and arthrofibrosis.

Effects of Histidine and ß-alanine Supplementation on Human Muscle Carnosine Storage.

PURPOSE: Carnosine is a dipeptide composed of ß-alanine and L-histidine and is present in skeletal muscle. Chronic oral ß-alanine supplementation can induce muscle carnosine loading and is therefore seen as the rate-limiting factor for carnosine synthesis. However, the effect of L-histidine supplementation on carnosine levels in humans is never established. This study aims to investigate whether 1) L-histidine supplementation can induce muscle carnosine loading and 2) combined supplementation of both amino acids is more efficient than ß-alanine supplementation alone. METHODS: Fifteen male and 15 female participants were equally divided in three groups. Each group was supplemented with either pure ß-alanine (BA) (6 g·d), L-histidine (HIS) (3.5 g·d), or both amino acids (BA + HIS). Before (D0), after 12 d (D12), and after 23 d (D23) of supplementation, carnosine content was evaluated in soleus and gastrocnemius medialis muscles by H-MRS, and venous blood samples were collected. Muscle biopsies were taken at D0 and D23 from the vastus lateralis. Plasma and muscle metabolites (ß-alanine, histidine, and carnosine) were measured by high-performance liquid chromatography. RESULTS: Both BA and BA + HIS groups showed increased carnosine concentrations in all investigated muscles, with no difference between these groups. By contrast, carnosine levels in the HIS group remained unaltered. Histidine levels were significantly decreased in plasma (-30.6%) and muscle (-31.6%) of the BA group, and this was prevented when ß-alanine and L-histidine were supplemented simultaneously. CONCLUSION: We confirm that ß-alanine, and not L-histidine, is the rate-limiting precursor for carnosine synthesis in human skeletal muscle. Yet, although L-histidine is not rate limiting, its availability is not unlimited and gradually declines upon chronic ß-alanine supplementation. The significance of this decline still needs to be determined, but may affect physiological processes such as protein synthesis.