Hip osteoarthritis surgical profiles and morbid obesity: a case series and literature review

The disease known as hip osteoarthritis is a common highly painful disabling joint disease with no known cure affecting a large proportion of the adult population [1,2]. One potentially preventable factor that may mediate or moderate the onset and progression of hip osteoarthritis is obesity [3]. Moreover, even though surgery to replace a diseased joint is generally successful, the presence of extremely high body weights in excess of ideal body weight [4,5] may impact the outcome of surgery for hip osteoarthritis quite negatively, rather than improving health status [5-7].


Introduction
The disease known as hip osteoarthritis is a common highly painful disabling joint disease with no known cure affecting a large proportion of the adult population [1,2]. One potentially preventable factor that may mediate or moderate the onset and progression of hip osteoarthritis is obesity [3]. Moreover, even though surgery to replace a diseased joint is generally successful, the presence of extremely high body weights in excess of ideal body weight [4,5] may impact the outcome of surgery for hip osteoarthritis quite negatively, rather than improving health status [5][6][7].
Although a negative outcome could further exacerbate the original problem, even if surgery is technically successful, very few community based endeavors exist to assist the obese hip osteoarthritis patient to attain a healthful weight, and healthy related behaviors either before or after surgery. Moreover, very few treatment centers specifically designed for those cases suffering from excess obesity are evident, even though these could potentially reduce the need for surgery, or delay this, or permit more healthful surgical outcomes at the outset. To raise awareness about this issue for the clinician and patient, this brief provides a snapshot of prevailing data that highlight the relevance of the aforementioned ideas.
To this end, a sizeable cohort of subjects with disabling hip osteoarthritis undergoing surgery were examined first, to discern body mass distributions in general, and rates of cases presenting with evidence of excess or morbid obesity, in particular. Cases defined as being morbidly obese, referring to cases 59-100% above their ideal weight were assessed with respect to the presence of complications arising from prior surgeries, and/or the presence of comorbid health conditions, if any. In addition, given the controversy surrounding whether hip joint replacement surgery is appropriate for the morbidly obese, a systematic examination of the related literature was conducted.
We anticipated a small, but clinically important proportion of cases with hip osteoarthritis requiring some form of primary or secondary hip replacement surgery would be morbidly obese, meaning their body mass index would be equal to or exceed 40. Moreover, in the event body mass is a risk factor for osteoarthritis, we anticipated this sub group would include individuals younger than 65 years of age, and that a fair proportion of these cases would be found to experience severe complications, protracted hospital stays, and prevailing comorbid health conditions, regardless of age. We anticipated that the research in this area on the whole would reveal that morbidly obese hip osteoarthritis cases may be at high risk for complications after surgery, despite efforts to improve their condition.

Materials and methods
Body mass indices (BMIs) calculated retrospectively from available height and weight data of a sample of 1000 cases of hip osteoarthritis requiring unilateral or bilateral hip replacement, as well as revision surgery were examined. In addition to demographic data, the presence and type of accompanying chronic health conditions, and reasons for hospitalization noted on the chart, the body mass indices of the cohort were categorized into 4 broad categories: underweight (BMI <than 20 kg.m -2 ), normal weight (BMI 20-24.9 kg.m -2 ), overweight (BMI 25-29 kg.m -2 ), and obese (>29 kg.m -2 ) categories. Grade 1 obesity was categorized as having a BMI 30-35, grade II obesity cases has BMIs 36-39, and morbid obesity or obese grade III was denoted as a BMI of 40 kg.m -2 or greater. These data were systematically entered into SPSS version 17.0 files to generate descriptive data, and where data were amenable to quantitative analysis, an a priori significance level of 0.05 was adopted. Excluded were cases with rheumatoid arthritis and hip fractures.

Results
The mean age of the sample of 997 cases with complete date was 65.5 ± 12.98 years (range 23-94) and the majority (57%) were women. Calculations of body mass index showed most or 67% were overweight, on average. There were 40 excessively or morbidly obese cases, with body mass indices ranging from 40-68, and of these cases, 75% were 65 years of age or younger, and 22 were females and 18 were males. Among those in the excessively obese or morbidly obese category (BMI > 40 kg.m -2 ), 19% had diabetes compared to 11% among those in the healthy weight category, and 19/40 or approximately 50% of these excessively obese cases had comorbid hypertension histories (p < 0.01) and the mode for numbers of comorbid diseases was 2. Among the 35 cases who were categorized as being underweight, 5 or 14% had cardiovascular disease, 2 or approximately 6% had high blood pressure, and none had a diabetes or depression diagnosis and the mode for numbers of comorbid diseases was 1 (Tables 1 and 2).
As outlined in Table 2, among the cohort of patients undergoing primary or secondary surgeries, slightly more cases were excessively obese than underweight, and those who were morbidly obese were likely to be hospitalized for serious complications following prior hip surgery than those who were underweight, as well as those in any other weight category. Table 3 depicts the overall health status and functional ability and past history of 12 morbidly obese cases and shows that many had prior hip osteoarthritis or other joint problems, and multiple comorbid conditions, even though they were all deemed relatively young adults. Findings from the two superobese cases shown in Table 4 are generally consistent in showing the increased risk of sub optimal outcomes in the short and long term among the severely obese hip osteoarthritis surgical candidate. Table 5 reveals consistent evidence that caution is advised when patients are morbidly obese and recommended for hip replacement surgery.

Discussion
Although the relationship between overweight and hip joint osteoarthritis is not definitive, results of this present analysis suggest overweight, and especially being morbidly obese is an important element observed among cases with disabling hip osteoarthritis, especially younger cases. This subgroup is also at risk for severe complications such as infection. This is consistent with Changulani et al. [8] who found those in the morbidly obese range were almost 10 years younger on average than those in the normal weight category, and those with higher body weights were more likely to experience adverse surgical outcomes than those who were not. This also accords with Tai et al. [9] and with Guetner et al. [10]. As in Guetner et al.'s study, it appears younger adults, especially those who suffer from morbid obesity may be quite prone to developing hip joint osteoarthritis in both hips, as well as other disabling health conditions. They may also require early hip joint replacement surgery, while incurring an increased risk of poor surgical outcomes, and the onset of comorbid diseases that can prevent optimal outcomes. While Grotle et al. [2] found no association between body mass and hip osteoarthritis, obesity, an independent predictor of disability [12][13][14] and pain [16,17], can undoubtedly place excess biomechanical stress on the hip joint. It can also increase chances of adopting a  sedentary lifestyle, and hence not unsurprisingly, greater body weight and body mass index during early and middle adulthood [15].
Since being overweight could render individuals of any age subject to abnormal hip joint loading forces, hip joint destruction may be especially exaggerated in the morbidly obese individual. Moreover, associated high rates of pain, as well as joint destruction and postural changes in those who are excessively obese can be expected to impact the pathogenesis of hip joint osteoarthritis both before and after surgery more profoundly than non-obese situations [18,19]. Alternately, the constellation of obesity, immobility and pain can independently raise the risk for hip joint osteoarthritis, and its disability [21][22][23][24][25][26][27][28][29][30][31].
Morbid obesity is an enormous health care problem, and should not be ignored as an important factor impacting the onset and rate of hip osteoarthritis disability and its severity, as implied in Table 4-where the relatively young hip surgery candidates had had many prior years of joint dysfunction, and very poor outcomes at five days post-surgery compared to standard outcomes for most uncomplicated procedures among healthy or normal weight subjects. Since ample research shows obesity is a preventable situation related to energy balance, the importance of food intake and nutrition, and restoring functional mobility cannot be overlooked in this regard, in our view, even if this was not the view of McAlden et al. [31].
Consequently, although patients with hip osteoarthritis may routinely receive physical therapy for limited periods before and after surgery, more emphasis on the role good nutrition can have on the joint, and on reducing inflammation, while reducing the ratio of fat to muscle should be stressed, along with possibly routinely extending the pre operative period as well as the intensity and duration of post operative therapy.
Helping to prevent excess obesity in the formative years, and ensuring those affected are monitored for any emerging pain and disability is recommended as well. Other possible recommendations for reducing the adverse results shown in Tables 4 and 5, are the possible inclusion of nutrition educators in the team treating the hip osteoarthritis patient, and the design of foods that reduce diabetic complications, as well as vascular complications. Helping this sub group to reduce any proclivity towards depression is also indicated. As well, apprising the morbidly obese hip osteoarthritis surgical candidate of the increased risk of poor surgical outcomes at the outset, and encouraging weight loss is recommended.

Conclusion
Having a high body mass appears more characteristic than not of individuals hospitalized for purposes of total hip replacement, revision surgery, or severe complications from prior surgery. Whether this is a consequence of the disease, rather than a cause or risk factor it is important to consider:

1.
A small percentage of end stage hip osteoarthritis cases are morbidly obese.

2.
Those with excessively high body mass indices are younger on average than those 65 years of age.

3.
Excessively obese cases with BMIs ≥ 40 were more likely to have high rates of diabetes and blood pressure than those of normal weight.

4.
Being excessively obese is related to the presence of a severe surgical complication.
Hence despite the limitations of this cross-sectional study for pinpointing causation, this present overview implies efforts to minimize the onset and progression of obesity across the lifespan may prove highly beneficial, despite lack of consensus of a distinct correlation of these factors [25]. Moreover, those who are excessively obese and undergo surgery might be counseled about their situation and encouraged to lose weight prior to this intervention. Careful rehabilitation that takes into account the presence of comorbid conditions, may foster better  BMI=body mass index; #meds=number medications; #med cond=number medical conditions; # yrsimpaired=number years impaired

Authors Study procedures and Sample Results Conclusion
Arsoyet al. [32] The results of total hip arthroplasty in 42 primary total hip arthroplasties in super-obese patients (BMI ≥ 50) were reviewed.
Twenty-four of the THAs had at least one complication. At least one major complication occurred in 11 of the THAs and at least one minor complication in 14 THAs Caution should be used when proceeding with primary total hip arthroplasty with a BMI greater than 50.
Chee et al. [5] The authors analyzed outcomes of 55 consecutive total hip replacements performed on 53 morbidly obese patients with osteoarthritis with a matched group of 55 total hip replacements in 53 non-obese patients.
Survival at five years was 90.9% for morbidly obese and 100% for non-obese patients Harris Hip and the Short-form 36 scores were significantly better in non-obese group (p < 0.001) The morbidly obese patients had higher complication rates, which included dislocation, superficial and deep infection Morbidly obese patients should be advised to lose weight before undergoing total hip replacement, and counseled regarding the risk of complications.
Elson et al. [19] This evaluation was performed to determine if morbid obesity (BMI ≥35kg/m( 2 )) is a contributing risk factor to cup malpositioning.
There was a significant correlation between morbid obesity with respect to underanteversion; using multivariate analysis, there was a trend toward a combined underanteversion/overabduction of the acetabular cup.
Of all variables considered, high BMI was the most significant risk factor leading to malpositioning.
Houdeket al. [6] Studied the effect of morbid obesity as a risk factor for failure of two-stage revision total hip arthroplasty using medical records of 653 cases treated for periprosthetic joint infection over a 20 year period Compared with nonobese cases, morbidly obese cases had higher re infection, revision, and reoperation rates, Morbidly obese patients have increased risk of severe post-operative complications after revision total hip arthroplasty than nonobese patients Jamesenet al. [22] Examined one-year incidence of periprosthetic joint infections among 7181 primary hip and knee replacements.
The infection rate for those with normal body mass indices was 0.37$, while the rate for those who were morbidly obese was 4.66% Morbid obesity increases the risk for periprosthetic infection following primary hip or knee replacement Issaet al. [33] Assessed the outcomes of primary total hip arthroplasty in super-obese patients compared to a cohort who had a normal body mass index.
The super-obese patients had significantly lower mean Harris hip scores (84 vs 91 points) and higher complication rate at final follow-up.
Patients may benefit from a discussion with their orthopaedic surgeons to develop realistic expectations from the outcomes of their arthroplasty procedure.
Super-obese patients experienced significantly longer hospital stays and higher rates of major complications and readmissions than normal-weight and class I obese patients.
Despite improved function and satisfaction, morbidly obese group experience a significant increase in length of hospital stay and major complication and readmission rates.
Schwarzkopf et al. [38] Conducted a retrospective study to determine the difference in outcomes among the super-obese When categorized according to body mass index, the overall complication rate was higher for patients with BMI > 45 Super-obese patients had an increased odds of developing in-hospital complications Length of stay was increased by 13.8% for each 5-U increase in BMI above 45 There is a n increased risk of incurring complications among the super-obese, and this increases with BMIs greater than 45 overall long-term results. Research to examine this sub-group as a separate issue will potentially yield important understandings that can be applied to harm reduction efforts, as well as reparative efforts.