AAOS 2013：肥胖对膝关节置换术后直接医疗费用的影响

研究背景:在美国，肥胖病人的比例持续升高。在年轻和肥胖患者中，膝关节置换（total knee arthroplasty，TKA）手术的数量也在升高。本研究的目的就是观察肥胖对一个大样本TKA患者术后的手术并发症，住院时间以及直接医疗费用的影响。

方法：本研究纳入了8129名患者，其中有6475例行初次TKA以及1654例行TKA翻修术，地点是在美国一家大型的医疗中心，研究时间从2000年1月1日到2008年9月31日。排除了在90天窗口期内行双侧TKA的患者。在原始病例记录和关节注册中心，主要收集了病人的基线特征以及术后并发症（感染，血栓事件，关节不稳和周围骨折）。直接医疗费用的计算使用了标准的通货膨胀调整后费用，时间包括住院期间以及90天窗口期。病人根据体重指数（body mass index，BMI）分为8组。研究终点包括住院时间，90天窗口期内的并发症以及在住院期间和90天窗口期内的直接医疗费用。不同分组的研究结果依据未经调整和多因素风险调整分析进行了对比。使用了线性回归分析来观察随着体重指数的增加，直接医疗费用的变化。

结果：99.5%病人的体重指数是可收集的，范围从15-73。结果表明BMI在25-30和30-35两组病人的平均住院时间和直接医疗费用最低。BMI的增高并没有和更高的并发症有关联。但是在调整了年龄，性别，手术类型以及并发症进行分析表明，BMI的升高和更长的住院时间有关。在调整了年龄，性别，手术类型后进行分析表明，BMI在大于25以上每增加10个单位，平均直接医疗费用和90天内窗口期内的费用会分别增加648美元和724美元。这种变化在调整了并发症后，同样保持了明显的增加（BMI在大于25以上每增加10个单位，平均直接医疗费用和90天以内窗口期的费用分别增加了541和504美元。以上的结果关联同样适用于因为关节退化而行初次TKA的患者。对于这些行初次TKA的患者，BMI在25以上每增加10个单位，平均直接医疗费用和90天内的窗口期内的费用分别增加了575和510美元。当调整了并发症因素后，BMI和费用之间的关系没有统计学意义，提示肥胖对费用的影响是随着并发症的增多而增多的。

结论：在TKA中，肥胖看起来并没有增加90天内窗口期内的手术并发症，但是与住院时间和直接医疗费用有直接关系，一部分原因是增加的医疗花费可能是因为肥胖增加了手术并发症而引的。肥胖人群在TKA中的增加，可能会增加TKA患者的经济负担。

与膝关节相关的拓展阅读：

• AAOS 2013：全膝关节置换术（TKA）术后工作恢复率达99%
• JBJS：糖尿病患者全膝关节置换术后并无过高感染风险
• JAMA:补充维生素D 对膝关节骨性关节炎症状无益
• Science Trans Med：水凝胶促进膝关节软骨修复
• J Arthroplasty：后稳定型全膝关节置换术后前脱位
• JOA: 膝关节僵硬程度严重患者TKA术后功能恢复明显
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The Effect of Obesity on Direct Medical Costs in Total Knee Arthroplasty (TKA)
BACKGROUND
Obesity rates continue to rise in the United States. Total knee arthroplasty (TKA) procedures are increasingly performed in younger and obese patients. We sought to examine the effect of obesity on surgical complications, length of stay and direct medical costs in a large group of TKA patients.
METHODS
The study included 8,129 patients who had undergone 6,475 primary and 1,654 revision TKA procedures at a large U.S. medical center between 1/1/2000 and 9/31/2008. Patients with bilateral procedures during the 90-day window up to 90 days following index admission were excluded. Data on clinical, surgical characteristics and complications (infections, thrombovascular events, instability, fractures) were obtained from the original medical records and the institutional joint registry. Direct medical costs were calculated by using standardized, inflation-adjusted costs for services and procedures billed during hospitalization and the 90-day window. Patients were classified into eight groups based on body mass index (BMI). Study endpoints included hospital length of stay, occurrence of any complication during the 90-day time window and direct medical costs during hospitalization and the 90-day window. Endpoints were compared across the eight BMI categories in both unadjusted and multivariable risk-adjusted analyses. Logistic and linear regression models were used to determine the cost impact associated with increasing BMI and obesity.
RESULTS
BMI data were available for 99.5% of patients and ranged from 15 to 73. Among the eight BMI categories, mean length of stay and the direct medical costs were lowest for patients with a BMI of 25-30 and 30-35 kg/m2. Increasing BMI was not associated with a higher risk of complications (p=0.48) but it was associated with significantly longer hospital stays, after adjusting for age, sex, type of surgery and comorbidities. Adjusting for age, sex and type of surgery, every 10 unit increase in BMI beyond 25 kg/m2 was associated with $648 and $724 higher hospitalization and 90-day costs, respectively. This association remained significant upon further adjustment for comorbidities where every 10 unit increase in BMI beyond 25 kg/m2 was associated with $541 and $504 higher hospitalization and 90-day costs, respectively (p=0.0001 and 0.003). These associations remained significant when restricting analyses to primary TKA patients with degenerative arthritis. In these patients, every 10 unit increase in BMI beyond 25 kg/m2 was associated with $575 and $510 higher hospitalization and 90-day costs, respectively (p=0.0001 and 0.005). In analyses restricted to patients with no comorbidities, the association with BMI was not significant, suggesting that the impact of obesity on costs was mediated largely through increased prevalence of comorbidities.
DISCUSSION AND CONCLUSIONS
In TKA, obesity does not seem to increase the overall risk of 90-day complications, but it is associated with longer hospital stays and costs. The effect of obesity is in part mediated through obesity-related comorbid conditions. Increasing prevalence of obesity in the TKA population likely contributes to the financial burden of TKA.