ABSTRACT
Undesired bone loss around implants is considered to occur mainly because of a stress-shielding phenomenon. Bone surrounding the total knee arthroplasty (TKA) adjusts its mineral density and structure to meet new mechanical demands. Immobilization, in combination with local operative trauma to the bone and soft tissues, has an additional impact on bone loss. The clinical survival of TKA is associated with the quality and quantity of the surrounding bone environment. Poor bone quality and quantity may predispose to aseptic implant loosening and periprosthetic fractures. We investigated the efficacy of oral bisphosphonate (alendronate, Fosamax) with calcium (Calcichew) for the inhibition of early bone mineral density (BMD) loss after TKA in a prospective, randomized, one-year follow-up study. Periprosthetic BMD changes were measured with fan-beam dual-energy X-ray absorptiometry (DXA) in 19 patients with knee osteoarthrosis. Patients (n = 8) treated with 10 mg alendronate and 500 mg calcium daily maintained distal femoral BMD values close to the baseline values (P > 0.04), while patients receiving only 500 mg of calcium daily (n = 11) showed significant bone loss during the one-year follow-up (P < 0.015). The treatment groups differed significantly in metaphyseal anterior, posterior, diaphyseal, and metaphyseal total regions of interest (ROIs) (repeated measures ANOVA analyses, P = 0.019, P = 0.010, P = 0.022, and P = 0.024, respectively). Our results indicate that oral alendronate reduces early postoperative periprosthetic bone loss significantly. This therapeutic strategy may improve the results and longevity of primary total knee arthroplasties.
Subject(s)
Alendronate/therapeutic use , Arthroplasty, Replacement, Knee , Bone Resorption/drug therapy , Calcium/therapeutic use , Osteoarthritis, Knee/therapy , Postoperative Complications , Absorptiometry, Photon , Aged , Bone Density , Bone Resorption/etiology , Disability Evaluation , Drug Therapy, Combination , Female , Hip Joint/diagnostic imaging , Humans , Male , Middle Aged , Osteoarthritis, Knee/complications , Osteoarthritis, Knee/physiopathology , Prospective Studies , Severity of Illness IndexABSTRACT
Periprosthetic bone loss, especially in the proximal part of the femur, is common after cemented and uncemented total hip arthroplasty (THA). Bone loss can be progressive and, in the extreme, may threaten survival of the prosthesis. To study whether alendronate therapy can reduce bone loss adjacent to prostheses, 13 uncemented primary THA patients were randomized to the study. They received 10 mg alendronate + 500 mg calcium (n = 8) or 500 mg calcium only (n = 5) daily for 6 months follow-up after THA. Periprosthetic bone mineral density (BMD) was measured with dual energy X-ray absorptiometry (DXA). Decreases in periprosthetic BMD in the alendronate-treated group were lower compared with the changes in the calcium-only group in the same regions of interest at the same follow-up time. In the proximal femur, the mean BMD decrease was 17.1% in the calcium-only group, whereas in the alendronate-treated group the decrease was only 0.9% (p = 0.019). The mean periprosthetic BMD change was also significantly different in the total periprosthetic area between the study groups at the end of the follow-up (calcium-only group -9.9% vs. alendronate-treated group -2.6%; p = 0.019). Alendronate therapy led to a significant reduction in periprosthetic bone loss after primary uncemented THA compared with the changes found in patients without therapy. This kind of bone response may improve the support of the prosthesis and may result in better survival of the prosthesis. However, in this study the follow-up time was too short and the study population was too small to make any long-term conclusions as to the prognosis for THA patients treated with alendronate.
Subject(s)
Bone Density/drug effects , Bone Resorption/drug therapy , Bone Resorption/etiology , Hip Prosthesis/adverse effects , Aged , Bone Cements , Bone Resorption/metabolism , Calcium, Dietary/administration & dosage , Female , Humans , Male , Middle Aged , Prospective Studies , Prosthesis FailureABSTRACT
Insertion of a metallic implant into the femur changes bone loading conditions and results in remodeling of femoral bone. To quantify changes in bone mass after uncemented total hip arthroplasty (THA), we monitored femoral bone with dual-energy X-ray absorptiometry (DXA). The periprosthetic bone mineral density (BMD) was measured with Lunar DPX densitometry in seven Gruen zones and the total periprosthetic area at scheduled time intervals in 22 patients during a 3-year follow-up. BMD decreased significantly almost in all Gruen zones during the first 3 months, ranging from 3.4% to 14.4% (p < 0.05 top < 0.001). At the end of the first year, the most remarkable decrease in BMD was found in the calcar (zone 7; -22.9%). During the second postoperative year, a slight restoration of periprosthetic bone mass was recorded. During the third year, no significant changes in BMD were found. The preoperative BMD was the only factor that was significantly related to the periprosthetic bone loss. Clearly, the early periprosthetic bone loss noticed during the 3 months after THA is caused by mainly limited weight bearing to the operated hip and stress shielding. We suggest that the restoration of bone mass is a sign of successful osteointegration between bone and metallic implant. DXA is a suitable tool to follow the bone response to prosthetization and will increase our knowledge on the behavior of bone after THA.
