Abstract
Background
Total Knee Arthroplasty (TKA) is one of the most effective treatment modalities for chronic knee pain and disability. A strong association exists between obesity and early knee osteoarthritis. Various studies on outcomes of TKA in obese patients have been inconclusive. The purpose of this retrospective evaluation is to assess the influence of obesity on outcomes of TKA in Indian patients.
Methods
This retrospective study conducted from 2010 to 2016 included 402 knees in 213 patients with Body Mass Index (BMI) between 30 and 39.99 kg/m2 followed up for a minimum of 12 months. All cases of revision TKAs and those with follow up less than a year were excluded from the study. Patients were followed up regularly for examining their wound healing, post operative complications if any and knee range of motion. Regular radiographs were taken to observe any evidence of loosening. Post-operative knee society scores(KSS) were recorded at each follow up. Improvement in the scores and activity level was noted.
Results
The objective KSS improved from 55.88 to 93.01 at the last follow up while the functional scores improved from 52.91 to 80.63. Post surgery improvement in activity level was seen in 71.83% patients. Complications seen in the study included patello-femoral pain, superficial wound infections, deep vein thrombosis and delayed wound healing. No cases of deep infection or revision surgeries were seen in our series.
Conclusions
The outcome of TKA in non-morbidly obese patients is comparable to non-obese patients with excellent post-operative objective and functional scores. The benefits are sustainable over a long duration of time. The complication rates in obese patients is no different than non-obese patients.
Keywords: Obesity, Total knee arthroplasty, Contraindication
1. Introduction
Total Knee Arthroplasty (TKA) is one of the most effective treatment modalities for chronic knee pain and disability.1 The application of this surgery for chronic knee arthritis has been on a rise in India.2 The popularity of this surgical treatment can be gauged by the fact that WHO has predicted a six fold increase in the number of TKAs performed in 2030.3
As per the WHO, obesity is defined as BMI ranging from 30 to 40 kg/m2, has reached an epidemic proportion worldwide.4 Numerous studies have found a strong association between excessive body weight and early degenerative disease of the knee.5,6 Hence along with the increase in the number of TKAs performed the proportion of obese patients opting for this surgery is also on an increase. Canadian registry quotes 55% of all TKA surgeries done in the year 2002–2003 were on obese patients.
Obesity magnifies the stress on the underlying bone and the implant material thereby adversely affecting prosthetic longevity and functional gain.7 Literature reports the following ill effects of obesity on clinical outcomes of total knee arthroplasty: prolonged wound drainage; delayed wound healing; higher infection rates, more medical complications, lower tolerance of physical therapy and poorer functional gains.8
Various studies on outcomes of TKA in obese patients have been inconclusive; while some studies have shown a poorer outcome in obese patients some others show no difference in the outcome.9 Most of these studies published, are however in the western literature and none show the effects of obesity on the outcomes of TKA in the Indian population. The most important question that remains unanswered is, whether the risk benefit ratio of TKA is adverse in obese patients or not?
The purpose of this retrospective evaluation is to assess the influence of obesity on outcomes of TKA in Indian patients. We assess the patients in terms of their clinico-radiological outcomes, the Knee Society Score and complications encountered.
2. Materials and methods
This retrospective study was conducted in a single institution by a single surgeon from January 2010 to December 2016. During this time frame 1156 TKAs were performed of which 546 knees in 281 patients were found to be in the body mass index (BMI) range of 30–39.99 kg/m2. 68 patients did not follow up for the minimum requirement of 12 months. The study finally included 402 knees in 213 non-morbidly obese patients followed up for a minimum of 12 months.
After obtaining clearance from the institutional review board this retrospective analysis was performed. All cases were performed using posterior stabilised high flexion Genesis II system(Smith and Nephew, Memphis, Tennessee, USA). All cases of revision TKAs and those with follow up less than a year were excluded from the study. Based on these criteria, 213 patients were included in the study with eight being diagnosed cases of rheumatoid arthritis and 205 cases of osteoarthritis. 189 patients were operated for bilateral knees while others underwent unilateral knee arthroplasty. Necessary patient consents were taken before subjecting them to the procedure and pre-operative KSS was recorded.
All the surgeries were performed using the standard anterior midline incision and medial parapatellar approach with the patient supine and tourniquet applied. Using a thin oscillating saw blade and an electrocautery patellaplasty was done in all cases.10 Upper tibial cut taken using an extra-medullary jig and a 3° posterior slope. A 4° valgus distal femoral cut taken using an intra-medullary jig. Posterior referencing done for sizing and 3° external rotation given in respect to the posterior condyles. Flexion and extension gap balancing done, patellar tracking noted. All components were fixed with cement after trialling and knee joint reduced. Concealed cosmetic closure was done for all patients.16
The patients were mobilised and knee flexion initiated on day one post operatively. Radiographs of the operated knee in antero-posterior and lateral views were taken. Standard deep vein thrombosis (DVT) prophylaxis in the form of DVT pumps, compression stockings and low molecular weight heparin done in all patients as routine unless contra-indicated. Patients were discharged on the 3rd to 5th post-operative day.
Patients were followed up for a minimum of one year at regular intervals of 2 weeks, 6 weeks, 3 months, 6 months and 1 year. Patients were examined for their wound healing, post operative infection, development of deep vein thrombosis, pain and other complications if any. At each follow up knee range of motion was noted. Regular radiographic evaluation was done to observe any evidence of radioluciency/loosening. Post-operative knee society scores(KSS) were observed at each follow up. Improvement in the post-operative KSS compared to the pre-operative scores was noted.
Patients’ activity level both pre and post TKA was classified as follows11:
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1 = sedentary (wheel-chair, bedridden)
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2 = semi-sedentary (light duty)
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3 = light labor (yard work)
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4 = moderate labor (can lift ≤23 kg and walk >5 km)
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5 = heavy manual labor, vigorous sports.
Our records were tabulated in an excel sheet for analysis. The results thus obtained were compared with the data published in the standard literature to observe whether obesity has any adverse effects in the recovery of patients offered a total knee arthroplasty.
3. Results
The study included 69 (32.39%) males with an average age of 62.70 (51–72) years and 144 (67.61%) females with an average age of 61.75 (48–71) years. While 189 (88.73%) patients underwent bilateral TKAs only 24 (11.27%) were operated on one side. Eight (3.76%) cases of rheumatoid arthritis and 205 (96.24%) cases of osteoarthritis were included in the study.
Medical co-morbidities observed in our study included cardio-vascular diseases in 93 patients (43.66%), diabetes in 104 patients (48.83%) and respiratory disorders in 41 patients (19.25%). An association of these factors with the occurrence of adverse events was evaluated individually using chi-square tests. These tests were statistically insignificant suggesting these factors were not associated with increased incidence of complications.
The Body mass index of the patients varied from 30.01 to 39.91 kg/m2 (mean = 34.13). The female patients had higher mean BMI 34.29 kg/m2 (30.07–39.91) than the male patients (33.81 kg/m2, range = 30.01–39.42). The patients were followed up at two weeks, six weeks, three months, six months, 12 months followed by regular six monthly follow up. The follow up duration of the patients ranged from 14 to 84 months with 60.09 months being the mean duration.
At every follow up patients were evaluated for their objective and functional knee society scores. Wound check was done to check for signs of inflammation or infection. Calf examination to look for signs of DVT was done. Radiographs were taken every six monthly to check for any signs of loosening. Return to activity was an important parameter evaluated in this study.
The average pre-operative objective knee society score was 55.88 (range-34 to 74) which improved to 71.84 (range-51 to 89) at six weeks and to 92.79 (range-71 to 100) at six months. Following this improvement the scores remained steady at the last follow up with mean score being 93.01 (range-72 to 100). (Fig. 1).
Fig. 1.
Graph comparing pre and post operative objective knee scores.
The objective scores were classified into excellent(90–100), good(80–89), fair (70–79) and poor(less than 70)11. In our study, we found 85.32% patients with excellent, 13.68% patients with good and 1% patients with fair outcome.
The functional knee scores before surgery averaged 52.91 (range-30 to 75). The score at six weeks were 62.33 (range-35 to 85) which improved significantly at six months to 80.63 (range- 45 to 100). The scores at the last follow up remained the same as 12 months follow up (Fig. 2).
Fig. 2.
Graph comparing pre and post operative functional knee scores.
The following graph shows the activity level before surgery and at the last follow up. 114(53.52%) patients moved one level above and 39(18.31%) patients moved two levels above in their routine activity level. 60(28.17%) patients recorded no change in the activity level (Fig. 3).
Fig. 3.
Bar diagram showing pre and post operative activity levels.
Blood transfusions were needed only in four(1.88%) patients of which three patients needed one packed cells and one patient needed two packed cells transfusion. Three knees(0.75%) showed non progressive tibial loosening which was clinically not significant. Three knees(0.75%) developed patello-femoral pain post-operatively of which one patient was managed conservatively and two patients had to undergo additional patella resurfacing surgery achieving good results.
Deep vein thrombosis was observed in five(1.24%) legs. Superficial wound infection noted in five(1.24%) knees which healed with extended antibiotic treatment. Eight knees (1.99%) had delayed wound healing which resolved with compression dressing and conservative management.
4. Discussion
This retrospective study was conducted to evaluate the mid-term outcomes of total knee arthroplasty performed using a single implant type in non-morbidly obese patients. The results of our study are encouraging for this sub group of patients. The most important result from our study was an excellent improvement in both objective and functional knee society scores following surgery. The complication rates encountered in our study too were within the acceptable limits for a total knee arthroplasty according to the literature.
The average gain in the objective and functional knee society score(KSS) after surgery in our paper is 37.13 and 27.72 points respectively. These are very encouraging results for this particular subset of patients. There are various studies in the literature which have shown comparable results of TKA in non-obese and obese patents. Our study is unique in terms of its large patient population and a long duration of follow up.
In a study by Spicer et al.12 in 2001, they found no significant difference in the post-operative KSS between non-obese and obese patients at a mean follow up of 75.9 months, although the post-operative KSS was lower in morbidly obese patients. At 10 years survivorship was similar in both obese and non-obese patients. Our study has similar results in terms of good outcome in obese patients we have however achieved better post-operative knee society scores.
In a study published by Mont et al.,13 comparing the results of cement-less knee arthroplasties, the post-operative objective KSS of the obese and non-obese patients were 88 and 91 respectively. These scores were not significantly different. These scores are similar to our paper. We however have a significantly bigger sample size(78 versus 402) with better scores for obese patients at five year follow up.
Griffin et al.,15 in their 10 year follow up of 32 obese and 41 non-obese knees found no difference in their post-operative hospital for special surgery scores and knee society scores. Revision rates at 10 years were also similar in both these sub groups. This study has a very limited sample size. Similar results have been reported Amin AK et al.,17 at their five year follow up.
There are certain studies which have reported negative outcomes in obesity. Stern and Insall,14 have reported a 30% incidence of patello-femoral symptoms in moderate to severely obese patients. Similarly Griffin et al.15 have reported a higher incidence of patello-femoral symptoms in obese patients. These studies have a higher incidence of patella-femoral complications due to use of older implant designs. Using Agarwala, S et al.10 technique of patellaplasty the incidence of patello-femoral pain was observed in only three patients post-operatively in our series which is significantly lower than the above mentioned studies, thus achieving better results of total knee arthroplasty in obese patients.
Foran JR et al.11 compared the KSS of non-obese to the obese patients and found that the scores were significantly different with obese patients fairing worse than the non-obese patients. Our scores compared to their non-obese patients did not show any significant difference. This study is limited by very small patient population and non matched groups (Table 1).
Table 1.
Comparison of pre and post operative knee society scores with the study done by Foran JR et al11.
| Non-obese patients | Obese patients | OUR STUDY | |
|---|---|---|---|
| Pre-op objective score | 57 ± 9 | 59 ± 11.7 | 55.88 |
| Post-op objective score | 94 ± 6.5 | 90 ± 12.7 | 93.01 |
| Pre-op functional score | 53 ± 16.2 | 51 ± 16.9 | 52.91 |
| Post-op functional score | 78 ± 23.4 | 71 ± 23.1 | 80.63 |
We have also observed in our study that the maximum gain in the KSS occurs in the first six months post surgery. After which the scores remained constant unto the last follow up averaging 60.09 months.
Most of our patients had an improved activity level post surgery. A comparison of the post-operative level of activity with that seen in article by Foran JR et al.11 is shown in the table below (Table 2):
Table 2.
Comparison of post operative activity level with study done by Foran JR et al.11.
| Non-obese | Obese | OUR STUDY | |
|---|---|---|---|
| Level 1 | 28% | 24% | 0.47% |
| Level 2 | 29% | 29% | 28.64% |
| Level 3 | 32% | 20% | 60.09% |
| Level 4 | 9% | 4% | 10.80% |
| Level 5 | 1% | 1% | 0% |
We observed a better level of activity post-operatively in our patients probably due to aggressive and fast track knee rehabilitation. In a study by Dowsey MM et al.17 cardiovascular disorders and diabetes as factors affecting the outcome of TKA were individually analysed and no association was found. This is in accordance to our study.
Literature has been varied in terms of the complication rates seen in obese patients undergoing TKA. McElroy MJ et al.8 in their study found a significant difference in the post-operative complication rates between the non-obese (9%), obese (15%) and morbidly obese (22%) patients. They have attributed this difference to increased incidence of medical comorbidities in obese and morbidly obese patients. Similarly Dowsey MM et al.17 in their study have shown higher surgical complications in obese and morbidly obese patients attributing them to increased technical difficulty. They also observed that for each unit increase in the BMI the risk of incurring an adverse event increased by 8% after age and gender adjustment. Ayyar et al.7 in their study on the influence of obesity on patient reported outcomes of TKR showed no significant difference in both the local and systemic complication rates (p value - 0.13 and 0.14 respectively) between obese and non obese patients. Amin AK et al.,18 in their five year follow up study showed no statistical difference between the complication rates in the non-obese and obese groups. The complication rates in our study are comparable to their study (Table 3).
Table 3.
Comparison of complication rates with study done by Amin AK et al.17.
| Non-obese | Obese | OUR STUDY | |
|---|---|---|---|
| Superficial infection/wound healing complications | 2.8% | 4.3% | 3.23% |
| Deep infection | 0.9% | 0.6% | 0% |
| DVT | 0.5% | 1.2% | 1.24% |
| Revision rates | 1.4% | 2.5% | 0% |
No implant loosening was noted in our study. Only 3 knees (0.75%) showed radioluciencies around the tibial base plate. However on regular follow up these were found to be non-progressive and clinically not significant. A systematic review by Vaishya R et al.19 has shown that though there was an increased incidence of radioluciencies in morbid obese patients following TKA most did not progress to loosening.
Our study has certain limitations. It is a non-comparative, retrospective analysis. The survivorship of the prosthesis can be assessed only after a longer follow up period. However, our study reports the outcome of total knee arthroplasty in one of the largest series of knees with a mean follow up duration of 60.08 months which is longer than most of the other published reports.
5. Conclusion
From our study we conclude that the outcome of total knee arthroplasty in obese patients is comparable to that seen in non-obese patients. With an aggressive post-operative rehabilitation good functional recovery is a rule. Post operative activity level in most patients improves. The benefits of surgery in terms of functional scores and activity level are sustainable for a long time. Intra-operative and post-operative complications are not significantly different from those seen in non obese patients.
Thus, total knee arthroplasty gives excellent results in non-morbidly obese patients giving them a better quality of life and a chance to regain their original level of activity at no added risks. It is therefore not necessary for the patients to lose weight or go in for bariatric surgeries before doing a successful TKR.
Disclosure
No conflict of interest to be disclosed.
Footnotes
Supplementary data to this article can be found online at https://doi.org/10.1016/j.jcot.2018.11.016.
Contributor Information
Sanjay Agarwala, Email: drsa2011@gmail.com.
Chintan Jadia, Email: chintanjadia.87@gmail.com.
Mayank Vijayvargiya, Email: maksy.doc37@gmail.com.
Appendix A. Supplementary data
The following is the Supplementary data to this article:
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