## 1 Introduction  
Hip osteoarthritis is one of the most common musculoskeletal pathologies, affecting more than 1.5 billion people worldwide [1]. This pathology can lead to pain and functional impairment, which can severely alter patients' quality of life [1]. The treatment of hip osteoarthritis includes both conservative treatments, such as weight loss, physiotherapy, non-steroidal anti-inflammatory drugs (NSAIDs), and surgical treatment, which is mostly represented by total hip arthroplasty. This surgical procedure is one of the most frequently performed orthopedic surgical procedures worldwide. There are two types of total hip arthroplasty, depending on fixation, which are cemented and cementless. In contrast to cemented total hip arthroplasties, cementless total hip arthroplasties require bone ingrowth at the implant site for proper fixation of the component, a process called osseointegration. There is no consensus among orthopedic surgeons on whether or not to fully weight-bear the patients during the first 6 to 8 weeks postoperatively. Despite research papers supporting the safety of early total weight-bearing, some surgeons consider that the presence of early periprosthetic bone loss could produce an early femoral migration during total weight-bearing [2]. Most cementless total hip arthroplasty patients experience good functional results, and the implant survival is around 95% at 10 years postoperatively [3]. Nevertheless, late complications can occur, leading to important medical and socio-economic consequences [4]. The most common late complication of total hip arthroplasty is represented by aseptic loosening, meaning a mechanical failure at the bone-implant interface [4]. Aseptic loosening can lead to pain, which can alter all physical activities, including walking [4]. The treatment of aseptic loosening is represented by revision surgeries, which are complex and high-risk surgeries that result in lower patient satisfaction compared to the primary surgical procedure [4]. Multiple factors can prevent aseptic loosening in total hip arthroplasties, such as implant characteristics, surgical technique, patient-related factors, and postoperative factors [4]. The postoperative factors have been the least studied, although they can provide an inexpensive and low-risk option to prevent aseptic loosening in total hip arthroplasty [5]. Two postoperative factors leading to an enhanced osseointegration process in the animal model are represented by bisphosphonates and statins [5]. Previous studies showed that both alendronate and simvastatin could limit the periprosthetic bone loss following cementless total hip arthroplasty [5]. Nevertheless, there has never been a direct comparison between these two drugs to decide which has the superior effect on the early periprosthetic bone loss following cementless total hip arthroplasty. The use of alendronate and simvastatin can also have side effects. Alendronate use can most commonly lead to abdominal pain, nausea, dysppepsia, constipation, diarrhea, musculoskeletal pain, and headache. On the other hand, the most common side effects of simvastatin are represented by gastrointestinal disorders, mayalgia, and arthraglia. The early bone formation process can be detected by examinations such as bone mineral density scan (DEXA) or bone serum markers [6]. The bone serum markers are represented by bone formation markers, such as alkaline phosphatase (ALPL), and bone resorption markers, such as beta cross-laps (\(\beta\)-CTx) [6]. This study aimed to test and compare the efficiency of alendronate and simvastatin in terms of the early bone formation process following cementless total hip arthroplasty. The study was performed on osteoporotic patients previously diagnosed using a DEXA scan. Moreover, the patients were not allowed full weight-bearing for the first 6 weeks postoperatively, as this was the standard postoperative protocol of the institution.