Bone Abstracts

Objectives: Prospective case-controlled study assessing whether the incidence of loosening of implants in patients undergoing Total Knee Arthroplasty (TKA) is higher among those with Secondary Hyperparathyroidism (SP) at the time of index operation.

Material and methods: Caucasian female patients with knee osteoarthritis who underwent TKA between November 2004 and March 2007 were enrolled. Exclusion criteria: endocrinopathies, rheumatoid or secondary arthritis, renal disease, fracture or orthopaedic surgery 24 months before enrollment. Patients with osteopenia/osteoporosis were not excluded. Serum intact PTH (I-PTH), calcium, phosphorus, creatinine, and the clearance of creatinine were determined pre-operatively. Case-notes were reviewed for any revision operation.

Results: Two hundred and eighty-three women aged 49–81 (mean 70) were enrolled; 100 had abnormally elevated I-PTH. Two with primary hyperparathyroidism were excluded from analysis. The incidence of SH was 35%. I-PTH correlated positively with age (P=0.008) and creatinine level (P=0.021) and negatively with the clearance of creatinine (P=0.004). In multiple regression analysis, 7.3% of the variance in I-PTH values (R²=0.073, P<0.001) was significant; creatinine level was the largest contributor (standardised β=0.275, P=0.08). 265 patients were available for re-evaluation at an average follow-up period of 115 (105–132) months. Three patients with SH and seven with normal I-PTH values (at the index operation) were re-operated due to aseptic loosening at an average period of 51.3 (26–90) and 49.9 (25–94) months respectively. The difference between the number of re-operated patients with pre-operative SH and normal I-PTH values, was statistically non-significant (P>0.005). The mean time to re-operation was also non-significant (P>0.005). One patient with SH and two with normal I-PTH, were re-operated due to septic loosening (P>0.005). The mean time to revision operation was 7.6 (4–12) months.

Conclusion(s): Our results show that SH does not enhance aseptic loosening of implants in TKA. Larger series are needed, especially as far as septic loosening and SH is concerned.