Free Custom «Influence of Body Mass Index (BMI) On Age of Presentation and Functional Outcome of Total Knee Arthroplasty (TKA)» Essay Paper

Total knee arthroplasty (TKA; also known as total knee replacement) is a kind accurately performed operation aimed at the treatment of knee osteoarthritis (OA). This procedure requires a well-experienced and efficient team to carry out the operating technique within the minimal time possible to avoid long time wound exposure. Apparently, a lot of care and attention is needed during the operation to prevent possible incidences of post TKA complications. The most common indicator of TKA is a significant loss of intense pain that results from severe arthritis (16).

Osteoarthritis is a progressive musculoskeletal disease that mostly affects joints of the spine, hands, hip, and knee. In fact, it is found in about 6% to 12% of the adults and over 30% of the elderly population (1). Arthritis of the knee has a prevalence of about 6% in people aged 30 years and above with an increased prevalence rate of 10% in adults above the age of 55 years (2). Severe knee OA that has a poor response to medication can only be corrected by a total knee arthroplasty. Moreover, osteoarthritis has shown many variations in its etiology with some factors such as age, sex, body mass index (BMI), deformed anatomy, injuries of the joints becoming risk factors for development or progression of knee AO. The success of TKA may also depend on some of the factors that predispose an individual to knee AO including BMI (19).

Body mass index (BMI) defines whether an individual is obese, pre-obese, healthy, severely obese or morbidly obese. Specifically, this classification is as follows:

BMI <25 (healthy);

BMI between 25 and 29.9 (pre obese);

BMI between 30 and 34.9 (obese);

BMI between 35 and 39.9 (severely obese);

BMI above 40 (morbidly obese);

Therefore, BMI is a key factor of interest since it varies and is a significant risk factor for AO with corrective TKA (17, 4, 14). Other factors such as age and gender have shown variable results in response to TKA (19, 7, 15). Yeung et al. (20) demonstrated that patients with BMI greater than 30kg/m² have increased cases of complications with lower rates of implant survival and low score function after total knee arthoplasty. The WOMAC score result after TKA is lower in individuals with high BMI (>25kg/m²) than in those with lower BMI (<25 kg/m². In fact, it means that increasing BMI has a negative effect on functional outcome that follows TKA procedure (7). However, this is not the case with all studies of TKA functional outcome that raise a controversy which may be due to TKA studies involving different surgeons and use of small sample sizes in determining the score (11).

There is a trend between age and BMI, and studies have shown that BMI increases with age up to about 60-69 years of age. Moreover, BMI is a variable trait that can be modified. The age of 60-69, where the relationship of BMI and increasing age is at the peak, is the same age that is associated with increasing AO incidences in patients and TKA. It should be mentioned that this relationship across the population has raised queries regarding the functional output of obese patients to TKA in relation to age (16). This paper examines the influence of BMI on patients that undergo TKA within the care of one surgeon.

It is a prospective study with all data provided (including BMI of patient, pre-operation and post-operation knee society score (KSS), and WOMAC score). All the operations were done by one surgeon with all FDA approved implants. Moreover, these study asses the patient’s view on their ability in relation to TKA score measured by Knee Society Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC). The evaluation tools mentioned above are able to asses self-reported measure values of pain, emotional status and physical function of patients before and after a TKA procedure (10).

The study involved 192 patients, with 133 undergoing TKA under one surgeon. Specifically, 30 of the participants are male while 162 are female. The mean age of the participants is 63.88 for a period of 49.59 months. The pre-operation and post-operation knee society score is compared and results given in table one while the pre-operation and post-operation WOMAC is compared and results given in the table 2 below.

Variable	Mean ( SE)	p-value
HEALTHY	76.29 ( 1.47)	0.156
PREOBESE	79.21 (1.04)
OBESE	78.06 ( 1.48)
SEVERELY OBESE	80.04 ( 2.31)
MORBIDLY OBESE	78.90 (3.53)

Table 1. Comparison of post KSS1 score in between BMI group

• P> 0.05-No significant difference among group, good clinical outcome in all BMI group

Although there were little variations in the S.E values among the different BMI classes, they showed no statistically significant differences among the groups; hence, accepting the hypothesis that BMI does not influence TKA outcomes in the KSS score.

Variable	Mean ( SE)	p-value
HEALTHY	92.54 ( 1.06)	0.250
PREOBESE	94.68 (0.75)
OBESE	92.36 (1.07)
SEVERELY OBESE	94.99 (1.66)
MORBIDLY OBESE	92.78 (2.54)

Table 2. Comparison of post WOMAC score in between BMI group

• P> 0.05-No statistically significant difference among group, good clinical outcome in all BMI group

Although there were little variations in the S.E values among the different BMI classes, they showed no statistically significant differences among the groups; hence, accepting the hypothesis that BMI does not influence TKA outcomes in the WOMAC score.

Discussion

There has been a lot of debate on the role of BMI on the outcome of TKA. Worries of the increased effect of high BMI on TKA has resulted in the establishment of maximum BMI for patients who can have TKA in other health facilities. The research above aimed at addressing the effect of BMI on TKA outcome has found no statistically significant difference among the groups using both KSS and WOMAC. Therefore, the BMI of a patient does not affect the presentation and functional outcome in TKA with variations in age.

Comparative Studies

Moreover, further studies also demonstrated that the elderly had no negative outcomes after TKA except a few who could not generalize the findings (7, 10). Considering the literature reviewed, the effect of BML on TKA outcome is not yet clear (3, 5, 6). To continue, obese patients experienced more pain, inability to function well and depression before the TKA surgical procedure. One year after TKA, obesity was not the basis of the pain in the patients which demonstrates that obesity is not the cause of short term outcome of TKA (2). There are also studies that show an inability of the morbidly obese to walk, climb staircases of other activities which indicated that the BMI>40 was associated with certain inabilities. Therefore, this study affirms that higher BMI (>40) is a risk factor in functional outcomes after TKA. Based on this outcome, surgeons can advice patients that are severely obese and morbidly obese concerning their possibility of lower functional output after a TKA. In fact, this enables patients to have more realistic expectations as they go for TKA procedures. Secondly, the patients may consider reducing their BMI before going for a TKA procedure since BMI can be modified (9, 14).

Finally, some studies have identified complications after TKA that had a negative effect on the final stage of the procedure. However, one of the obese participants had a cardiac event requiring him to be transferred to the ICU just after the operation. In another study, among the overweighed group, one of the patients developed DVT, while another one was suffering from pneumonia and had to be taken to ICU. However, in the group of patients with normal BMI, there were no complications influencing the functional outcome (10, 12).

Conclusion

Most literature and surgeons advise differing TKA in morbidly obese patients due to higher complication and poor outcomes. Others argued that BMI exceeding 25kg/m² have lower functional outcome using WOMAC score in comparison with patients with BMI <25kg/m² (1, 2, 9). Therefore, the results of this study revealed comparable index in all categories and data showed higher BMI subgroups presenting for TKA at earlier age. However, long-terms follow up is needed to evaluate survivorship of the prosthesis.