Mid-term Results of Oxford Phase 3 Unicompartmental Knee Arthroplasties at a Small-Volume Center.

BACKGROUND AND AIMS: Unicompartmental knee arthroplasty is considered as an alternative to total knee arthroplasty for patients who have osteoarthritis limited to the medial compartment of the knee. The aim of this retrospective study was to find out clinical and radiological outcomes and related complications using the Oxford phase 3 prosthesis at a small-volume center. MATERIAL AND METHODS: In all, 95 Oxford unicompartmental knee arthroplasties (87 patients) were performed between 2000 and 2010 in North Karelia Central Hospital. Of these, five patients had undergone revision surgery. In all, 52 unicompartmental knee arthroplasties (46 patients) participated in this study. The mean age of patients was 61.4 years, and 78.2% of patients were females. Pain and function levels were evaluated by using the Knee Society score. Radiographic analyses were performed on preoperative and postoperative and follow-up radiographs. RESULTS AND CONCLUSIONS: The mean follow-up time was 6.5 years, and the Kaplan-Meier estimated 9-year implant survival rate was 88.9% (95% confidence interval = 78.7%-99.1%). The median Knee Society score of 77 (range: 18-93) at follow-up was considered good (range: 70-79). In this study, we found out that medial knee pain remains in 10% of unicompartmental knee arthroplasties several years after surgery, although the reason for the pain remained unclear. These mid-term results are promising, and good results can be achieved also at a small-volume center when strict patient selection is followed.

Effect of one-year post-operative alendronate treatment on periprosthetic bone after total knee arthroplasty. A seven-year randomised controlled trial of 26 patients.

Total knee arthroplasty (TKA) is known to lead to a reduction in periprosthetic bone mineral density (BMD). In theory, this may lead to migration, instability and aseptic loosening of the prosthetic components. Bisphosphonates inhibit bone resorption and may reduce this loss in BMD. We hypothesised that treatment with bisphosphonates and calcium would lead to improved BMD and clinical outcomes compared with treatment with calcium supplementation alone following TKA. A total of 26 patients, (nine male and 17 female, mean age 67 years) were prospectively randomised into two study groups: alendronate and calcium (bisphosphonate group, n = 14) or calcium only (control group, n = 12). Dual energy X-ray absorptiometry (DEXA) measurements were performed post-operatively, and at three months, six months, one, two, four, and seven years post-operatively. Mean femoral metaphyseal BMD was significantly higher in the bisphosphonate group compared with controls, up to four years following surgery in some areas of the femur (p = 0.045). BMD was observed to increase in the lateral tibial metaphysis in the bisphosphonate group until seven years (p = 0.002), and was significantly higher than that observed in the control group throughout (p = 0.024). There were no significant differences between the groups in the central femoral metaphyseal, tibial medial metaphyseal or diaphyseal regions of interest (ROI) of either the femur or tibia. Bisphosphonate treatment after TKA may be of benefit for patients with poor bone quality. However, further studies with a larger number of patients are necessary to assess whether this is clinically beneficial.

Obesity has a negative impact on clinical outcome after total knee arthroplasty.

BACKGROUND AND AIMS: Obesity has been linked to the development of osteoarthritis of the knee and since the incidence of obesity is increasing, the need for total knee arthroplasty (TKA) is likely to increase. Conflicting findings have been reported concerning the relationship between obesity and TKA. It has been shown in several studies, that obese patients have poorer clinical results after operation. On the other hand it has also been reported similar results for obese and non-obese patients. The purpose of this study was to analyze clinically and radiologically the results of total knee artrhoplasty in obese patients. MATERIAL AND METHODS: The study consisted of 48 patients who had a TKA. The patients were divided in two groups according their body mass index. Patients of BMI over 30 were regarded as obese. RESULTS: The obese patients had poorer clinical success at the final follow-up, their WOMAC scores were significantly higher compared to non-obese (pain 20.7 vs. 11.6; p = 0.021, stiffness 26.9 vs. 13.4; p = 0.006, physical function 26.5 vs. 14.4; p = 0.003). Differences were also found in the Knee (KS) and Function (FS) scores and a long-term postoperative ROM and (KS: 83.6 vs. 88.9; p = 0.01, FS: 63.6/76.3; p = 0.051, ROM: 104.6 vs. 109.6; p = 0.016). Non-obese patients reached better percentage improvement in the KSS compared to obese patients (KS change + 194.5% vs. + 59.5%, p = 0.03; FS change + 51.5% vs. + 14.9%, p = 0.19). CONCLUSIONS: Obesity has a negative impact on the outcome of TKA, assessed by patients' clinical function and satisfaction level.

Effect of alendronate on periprosthetic bone loss after total knee arthroplasty: a one-year, randomized, controlled trial of 19 patients.

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.

Measurement of bone density around total knee arthroplasty using fan-beam dual energy X-ray absorptiometry.

The clinical survival of joint arthroplasties is clearly associated with the quality of surrounding bone environment. Bone mineral density (BMD) is an important measure of bone strength and quality. Periprosthetic BMD can be measured by using dual-energy X-ray absorptiometry (DXA) with special software algorithms. We studied short-term reproducibility of the periprosthetic BMD measurements after total knee arthroplasty (TKA) in 30 patients with primary osteoarthrosis. The operated knees and the contralateral control knees were measured twice and the results were expressed as a coefficient of variation (CV%). The average precision error was 3.1% in femoral regions of interest (ROI) and 2.9% in tibial ROIs after TKA. In the prosthesis-free control knees, CV% were similar; 3.2% and 2.5%, respectively. The best precision was found in the femoral diaphyses above the implant (1.3%), whereas the least reproducible BMD was determined in the patellar region of the TKA knees (6.9%). Our results confirm that DXA measures precisely small bone mineral changes around TKA and makes it possible to follow bone remodeling DXA and may provide a feasible method for monitoring TKA in the future.