MODIFICATIONS IN THE SERUM LEVEL OF INTACT-PARATHYROID HORMONE IN A GROUP OF POSTMENOPAUSAL WOMEN SUFFERING FROM END-STAGE KNEE OSTEOARTHRITIS UNDERGOING TOTAL KNEE ARTHROPLASTY COMPARED WITH A CONTROL GROUP OF WOMEN UNDERGOING ELECTIVE NON-ORTHOPAEDIC OPERATIONS

Abstract

Introduction: Aim of this prospective study was the evaluation of the impact of TKA on the serum level of I-PTH, as continuously elevated levels of the latter may potentially play a negative role in an orthopaedic implant’s incorporation process.

Methods: The study-group was formed by 119 post-menopausal women suffering from end-stage idiopathic knee osteoarthritis scheduled to undergo TKA. Another 110 women that underwent elective non-orthopaedic operations were used as a control-group. The serum levels of I-PTH, Ca, P & creatinine were evaluated and the clearance of creatinine was calculated one day preoperatively and on the seventh postoperative day. Patients with abnormal preoperative values, suffering from endocrinopathies, rheumatoid or other secondary arthritis, osteoporosis or diseases interfering with bone homeostasis, as well as patients receiving medication affecting bone metabolism, were excluded. None had suffered any fracture or underwent any orthopaedic operation during the 36 months prior to her enrollment.

Results: The two groups were statistically comparable [age (p=0.72), weight (p=0.43), duration of menopause (p=0.31), serum creatinine level (p=0.49), creatinine clearance (p=0.74), preoperative serum I-PTH value (p=0.67)]. Sixteen patients of the study- (13.4%) and one of the control-group had abnormally elevated post-operative I-PTH values. Further analysis showed a statistically non-significant trend towards decrease in the post-operative I-PTH values of the study-group (p=0.16) compared with the control-group’s results were the I-PTH values remained statistically unchanged (p=0.55). No statistically significant difference was found in the postoperative serum I-PTH values between the two groups (p=0.21). The patients’ weight (p=0.76), age (p=0.77), serum creatinine (p=0.92) and creatinine clearance (p=0.96) did not have a statistically significant impact on the observed alteration of I-PTH values after TKA (study-group).

Discussion/Conclusion: The serum levels of I-PTH slightly decrease following TKA. This may attributed to the necrosis or apoptosis initiated immediately after implantation, leading to increased bone resorption and increased serum calcium concentrations that may well decrease the endogenous PTH production. Another possible explanation is the temporary immobilization of the patients undergoing TKA. A substantial number of our study-group’s women had abnormally elevated post-operative I-PTH values. Regardless of what actually caused it, the negative impact of continuously elevated PTH on bone formation, may interfere with the implant’s incorporation procedure, hence the evaluation of serum I-PTH before and after TKA is strongly recommended.