Total knee arthroplasty (TKA) is one of the most common elective surgical procedures that alleviates pain and disability associated with knee osteoarthritis.1
The recent growing needs of the aging population have made this procedure, along with hip arthroplasty, the second most popular orthopedic surgery.2
Studies have shown that a dramatic increase has occurred in the TKA usage rate.3
Orthopedic surgeons worldwide are likely to face a growing list of patients awaiting TKA from all walks of life and with various socioeconomic statuses.
This study originated from Singapore at an Asian tertiary teaching hospital from a developed first-world country with a high level of health care standards and an infrastructure that is comparable with the best worldwide.4
The health care infrastructure in Singapore consists of public and private health care facilities, with both offering high-quality medical care but a generally different level of service and comfort. Citizens and permanent residents are entitled to subsidized government health care services through a compulsory national savings scheme. However, they may choose not to subscribe to subsidized health care even in the public hospitals should they prefer a higher level of service and comfort and the autonomy to choose their surgeon.
Misconceptions are rife in the advent of such a health care infrastructure and delivery system. One may assume that paying patients under the nonsubsidized scheme receive a higher quality of care and treatment by their attending physicians compared with their counterparts under the subsidized scheme. However, these misconceptions are not based on sound evidence.
Due to the aging population in Asia,5,6
the number of patients requiring TKA is likely to increase, which would cause a surge in the number of subsidized and nonsubsidized patients. This increase in demand will translate into growing waiting lists, especially for subsidized patients, as seen in various health care systems.7
To the authors’ knowledge, few studies in the literature have reported the effect of health care subsidies on TKA outcomes.
The authors assessed whether subsidized patients had good outcomes or whether they fared worse than their paying counterparts after undergoing conventional TKA.
Materials and Methods
Between January 2006 and May 2009, three hundred eighty-seven patients who underwent elective TKA in an Asian tertiary teaching hospital were retrospectively studied. Patients were selected if they underwent the same surgical technique and postoperative care. Eighteen patients were excluded for either symptomatic osteoarthritis in the contralateral knee (defined as self-reported knee pain greater than 4 on a 10-point, visual analog scale) or other lower-extremity orthopedic conditions or neurological impairments that limited function. The institutional review board approved this study.
All patients underwent unilateral posterior-stabilized TKA by a single surgeon (T.H.C.). All patients had a tourniquet applied to the operated limb throughout the surgery. Total knee arthroplasty was performed in a standard fashion for all patients. The medial parapatellar approach was used for patients with varus knees, and the lateral parapatellar approach was used for those with valgus knees. No patellar resurfacing was performed. Postoperative drains were inserted for all patients and removed on postoperative day 2 or when the drainage was less than 70 mL, depending on whichever occurred first. Resident and fellow involvement was encouraged more freely in the surgeries for the subsidized patients, although no change occurred in the primary surgeon.
All patients received standardized postoperative care, which included appropriate analgesia, pneumatic calf pumps, continuous passive motion from the first postoperative day, and daily physiotherapy assessment while they were inpatients. All patients began ambulation on postoperative day 2. No patient received oral chemoprophylaxis against venous thromboembolism because a previous study originating from the authors’ institution showed a low incidence of venous thromboembolism in patients undergoing TKA without anticoagulation.8
On discharge, patients were followed-up at the specialist outpatient clinic at 1- and 6-month and 1- and 2-year intervals. At each visit, patients reported pain scores and any other concerns they had. The surgeon also examined the knee for signs of wound or joint infection. A detailed review by the physiotherapist (C.H.C.), as outlined below, was conducted 6 months and 2 years postoperatively. Radiographs of the knee were also obtained immediately postoperatively and at 1-year follow-up.
All relevant demographic information was extracted from the standardized medical case notes. Health services usage data in the 6 months after discharge were extracted from the local health databases. These data included waiting time to surgery, length of stay, and readmission to hospitals within the country.
At the 6-month and 2-year follow-ups a physiotherapist determined the range of motion (ROM) of the operated knee using a goniometer. The authors also obtained Knee Society Scores,9
a Short Form 36 (SF-36),10
and an Oxford Knee Score.11
No data were missing with respect to the demographic details and functional outcomes for all of the patients who attended the required follow-ups.
Among the 369 patients, 95 were nonsubsidized and 274 were subsidized. Patients in the subsidized group (Table 1
) had a longer mean operative time (P<.001) and a longer waiting time to surgery (P<.001). Otherwise, no differences were identified in age, sex, medical status, length of stay, and discharge locations from acute care. Preoperatively (Table 2
), patients in the subsidized group had a lower mean function score (P=.002), lower mean Oxford score (P=.025), and lower mean SF-36 physical component score (P=.004).
Table 1: Patient Characteristics
Table 2: Preoperative ROM and Outcome Scores
Student’s t test and chi-square test were used to compare means and proportions respectively between the 2 groups. All statistical analyses were performed using SPSS version 17 software (IBM SPSS Statistics, Armonk, New York).
At 6-month follow-up (Table 3
), subsidized patients had a lower mean function score (P=.021) compared with nonsubsidized patients. This was also noted at 2-year follow-up (P=.019). At 6-month and 2-year follow-up, no differences were observed in the ROM or other outcome scores between the 2 groups.
Table 3: Postoperative ROM and Outcome Scores
The health care infrastructure in Singapore consists of public and private health care facilities that both offer high-quality medical care but generally have a different level of service and comfort. Patients are entitled to subsidized government health care services or may choose not to subscribe to subsidized health care and pay out-of-pocket or through privately purchased insurance, even in public hospitals, if they prefer a higher level of service and comfort and the autonomy to choose their surgeon. Due to the aging population in Asia,5,6
the number of patients requiring TKA is likely to increase, which would cause a surge in the number of subsidized and nonsubsidized patients. This increase in demand will translate into growing waiting lists, especially for subsidized patients, as is seen in various health care systems.7
To the authors’ knowledge, this is the first study in the region to report the effect of health care subsidies on TKA outcomes. Due to the unique health care policies in Singapore, it is difficult to find a study with a similar objective in the Western literature, although parallels can be inferred.12
The current authors assessed whether subsidized patients had good outcomes or if they fared worse than their paying counterparts after undergoing conventional TKA. In the United States, state-run Medicaid-managed care programs have been in place to improve health care access and usage rates for lower-income patients who cannot afford commercial health insurance.13
Similarly, in the United Kingdom, the National Health Service provides a comprehensive range of health services primary funded through general taxation rather than requiring insurance payments.14
In the current study, the subsidized patients receive health care benefits in a similar way to patients under the Medicaid managed care programs and the National Health Service. However, the nonsubsidized patients are the commercial payer-type.
In the current study, subsidized patients had good and acceptable results at both 6 months and 2 years after TKA, except for function score and mean SF-36 physical component score. Rowe et al15
reported that “110° of flexion would seem a suitable goal for the rehabilitation of motion in the knee.” In the current study, the subsidized patients had a mean ROM of 113° at 6-month follow-up and 117° at 2-year follow-up. Asif and Choon16
validated a grading system for the Knee Society Score in which a score of 80 to 100 was considered excellent; 70 to 79 was considered good; 60 to 69 was considered fair; and below 60 was considered poor. By these standards, the subsidized patients had good mean knee scores at both 6 months and 2 years. However, by the same standards, their mean function scores at 6 months and 2 years were fair. To the current authors’ knowledge, no studies have reported a grading system for the Oxford Knee Score and the SF-36 physical and mental component scores. However, a score of 50 is considered normal for the SF-36 questionnaire.10
The current subsidized patients had physical and mental component scores higher than 50 at 6 months and 2 years after TKA. Therefore, the subsidized patients had good results after TKA. These findings were consistent with those of Davis et al.17
The authors also assessed whether subsidized patients had worse post-TKA outcomes compared with nonsubsidized patients. The results showed that subsidized patients had lower function scores at both 6-month and 2-year follow-up. From evidence in the literature, this lower function postoperative score could be attributed to the poorer preoperative function scores seen in the subsidized patients.18
In the current study, subsidized patients had significantly poorer preoperative function scores compared with nonsubsidized patients. Hinman and Bozic12
evaluated whether patients under the Medicaid-managed care programs undergoing primary total hip arthroplasty differed from commercial-payer patients with respect to baseline demographic characteristics, social history, clinical outcomes, and resource usage. Similar to the current study, they reported that Medicaid patients had poorer preoperative function.12
Preoperative functional outcomes have consistently been the strongest determinant of postoperative functional outcomes, both immediately postoperatively and up to 2 years postoperatively.18,19
This could be the key determinant of the difference seen in the function scores at the 6-month and 2-year follow-ups. Hinman and Bozic12
attributed the poor preoperative function scores to poorer access to health care services. This was not the case for the current patients because all patients had equal access to health care services. However, a higher proportion of patients in Singapore have the subsidized scheme. As such, they have a longer waiting time for surgery (Table 1
). Desmeules et al20
reported that patients who waited longer for TKA had poorer function. In the current study, the longer waiting time for subsidized patients could have led to the poorer preoperative function seen in these patients.
Based on the current preoperative results, readers may wonder whether the longer operative time seen in the subsidized patients could account for the poorer postoperative function score. It is well known that residents and trainee surgeons actively participate in the care of patients with the subsidized scheme. They are talked through the various procedures and surgical techniques intraoperatively. This could have accounted for the longer operating time seen for the subsidized patients. This trend was also observed in a study reported by Woolson and Kang.21
However, they concluded that teaching and active participation from residents and fellows during total hip and knee arthroplasty did not have a detrimental effect on the early clinical results, except for a longer operative time.21
Although the current results showed a difference in the function score between the 2 groups, it is debatable whether this difference has clinical significance. Western studies have reported that differences in socioeconomic status and waiting times have no significant effect on short-term outcomes.5,20
Similarly, except for function score, no differences were seen in the ROM and outcome scores between the 2 groups at 6-month and 2-year follow-up in the current study.
The effect of health care subsidies on TKA outcomes in the long term remains inconclusive, in part due to few published studies in the literature. Much of this can be attributed to varying health care practices and controversies surrounding health care economics and policies. Patients in need of TKA, regardless of their socioeconomic status and subsidy levels, have access to equal and high-quality health care in Singapore. Although differences may exist in the levels of comfort, privacy, and autonomous surgeon choice, no difference existed in the standard of surgery performed and the postoperative rehabilitation for all patients.
The current study had limitations. First, the numbers of subsidized and nonsubsidized patients were not equal. Hence, statistical comparison between the 2 groups may be skewed. However, this imbalance in numbers reflects the true proportion of patients seen by the orthopedic surgeon in Singapore. Second, the authors only included patients from a single surgeon. Although this minimized the effect of selection bias and intra- and postoperative variability, including patients from weaker surgeons and hospitals may have yielded more accurate data. Third, the presence of unknown confounders is likely to have a significant effect on the results. However, a multivariate analysis was performed to evaluate the confounding effects of the other known variables in this study.
Subsidized patients undergoing conventional TKA in an Asian tertiary teaching hospital had good outcomes, and no major differences existed in the short-term outcomes except for function score compared with their nonsubsidized counterparts. Further prospective studies are required to validate the results of this study, which can also be applied to the context of Western health care. The way forward is to find ways to reduce waiting times for subsidized patients and to tailor preoperative rehabilitative regimes to improve their preoperative function scores to achieve comparable postoperative function scores.
- Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007; 89(4):780–785 doi:10.2106/JBJS.F.00222 [CrossRef] .
- Brady OH, Masri BA, Garbuz DS, Duncan CP. Rheumatology: joint replacement of the hip and knee–when to refer and what to expect. CMAJ. 2000; 163(10):1285–1291.
- Losina E, Thornhill TS, Rome BN, Wright J, Katz JN. The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic. J Bone Joint Surg Am. 2012; 94(3):201–207 doi:10.2106/JBJS.J.01958 [CrossRef] .
- World Health Organization. World Health Organization assesses the world’s health systems.
http://www.who.int/whr/2000/media_centre/press_release/en/. Accessed September 11, 2012.
- Holmes WR, Joseph J. Social participation and healthy ageing: a neglected, significant protective factor for chronic non communicable conditions. Global Health. 2011; 7:43 doi:10.1186/1744-8603-7-43 [CrossRef] .
- Shrestha LB. Population ageing in developing countries. Health Affairs. 2000; 19(3):204–212 doi:10.1377/hlthaff.19.3.204 [CrossRef] .
- The Canadian Institute for Health Information. Surgical Volume Trends, 2008: Within and Beyond Wait Time Priority Areas. Ottawa, Ont: CIHI; 2008.
- Bin Abd Razak HR, Soon AT, Dhanaraj ID, Tan AH. Incidence of clinically significant venous thromboembolic events in Asian patients undergoing total knee arthroplasty without anticoagulation. J Arthroplasty. 2012; 27(6):1128–1132 doi:10.1016/j.arth.2011.09.024 [CrossRef] .
- Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society Clinical Rating System. Clin Orthop Relat Res. 1989; (248):13–14.
- Ware JE Jr, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care. 1992; 30(6):473–483 doi:10.1097/00005650-199206000-00002 [CrossRef] .
- Dawson J, Fitzpatrick R, Murray D, Carr A. Questionnaire on the perceptions of patients about total knee replacement. J Bone Joint Surg Br. 1998; 80(1):63–69 doi:10.1302/0301-620X.80B1.7859 [CrossRef] .
- Hinman A, Bozic KJ. Impact of payer type on resource utilization, outcomes and access to care in total hip arthroplasty. J Arthroplasty. 2008; 23(6):9–14 doi:10.1016/j.arth.2008.05.010 [CrossRef] .
- Bowen G, Amy JD, Alshadye Y. Effects of Medicaid managed programs on health services access and use. Health Serv Res. 2003; 38(2):575–594 doi:10.1111/1475-6773.00134 [CrossRef] .
- O’Donnell O, Propper C. Equity and the distribution of UK National Health Service resources. J Health Econ. 1991; 10(1):1–19 doi:10.1016/0167-6296(91)90014-E [CrossRef] .
- Rowe PT, Myles CM, Walker C, Nutton R. Knee joint kinematics in gait and other functional activities measured using flexible electrogoniometry: how much knee motion is sufficient for normal daily life?Gait Posture. 2000; 12(2):143–155 doi:10.1016/S0966-6362(00)00060-6 [CrossRef] .
- Asif S, Choon DSK. Midterm results of cemented press fit condylar Sigma total knee arthroplasty system. J Orthop Surg. 2005; 13(3):280–284.
- Davis ET, Lingard EA, Schemitsch EH, Waddell JP. Effects of socioeconomic status on patients’ outcome after total knee arthroplasty. Int J Qual Health Care. 2008; 20(1):40–46 doi:10.1093/intqhc/mzm059 [CrossRef] .
- Lingard EA, Katz JN, Wright EA, et al. Predicting the outcome of total knee arthroplasty. J Bone Joint Surg Am. 2004; 86(10):2179–2186.
- Fortin PR, Penrod JR, Clarke AE, et al. Timing of total joint replacement affects clinical outcomes among patients with osteoarthritis of the hip or knee. Arthritis Rheum. 2002; 46(12):3327–3330 doi:10.1002/art.10631 [CrossRef] .
- Desmeules F, Dionne CE, Belzile E, Bourbonnais R, Fremont P. Waiting for total knee replacement surgery: factors associated with pain, stiffness, function and quality of life. BMC Musculoskelet Disord. 2009; 10:52 doi:10.1186/1471-2474-10-52 [CrossRef] .
- Woolson ST, Kang MN. A comparison of results of total hip and knee arthroplasty performed on a teaching service or a private practice service. J Bone Joint Surg Am. 2007; 89(3):601–607 doi:10.2106/JBJS.F.00584 [CrossRef] .
|Characteristic||Nonsubsidized Group (n=95)||Subsidized Group (n=274)||P|
| Mean age (range), y||66 (51–81)||66 (42–83)||.848|
| Female sex, No. (%)||72 (76)||224 (82)||.211|
| Mean BMI (range), kg/m2||27.1 (18.4–37.9)||27.6 (18.1–51.2)||.348|
| Primary diagnosis OA, No. (%)||93 (98)||269 (98)||1.000|
| Primary diagnosis inflammatory arthritis, No. (%)||2 (2)||5 (2)||.863|
| Cardiovascular disease, No. (%)||23 (24)||82 (30)||.798|
| Diabetes mellitus, No. (%)||28 (29)||98 (36)||.413|
| Mean±SD No. of comorbidities||2.2±1.7||2.6±2.2||.069|
|Health services usage|
| Mean±SD waiting time to surgery, mo||2.3 ±1.2||8.2±2.3||<.001|
| Mean±SD hospital LOS, d||4.8±2.6||5.2±2.7||.202|
| Discharge directly home, No. (%)||78 (82)||236 (86)||.699|
| Mean±SD operative time, min||64±12.2||74±15.4||<.001|
Preoperative ROM and Outcome Scores
|ROM and Outcome||Mean (Range)||P|
|Nonsubsidized Group (n=95)||Subsidized Group (n=274)|
|ROM, deg||117 (60–155)||118 (56–155)||.879|
|KSS||37 (0–91)||32 (0–83)||.057|
|KSS function score||56 (5–100)||49 (0–100)||.002|
|Oxford Knee score||35 (15–50)||37 (17–59)||.025|
|SF-36 physical component score||34 (14–59)||30 (9–58)||.004|
|SF-36 mental component score||50 (19–71)||50 (23–72)||.814|
Postoperative ROM and Outcome Scores
|ROM and Scores||Mean (Range)||P|
|Nonsubsidized Group (n=95)||Subsidized Group (n=274)|
| 6 mo||113 (40–142)||113 (65–144)||.984|
| 2 y||117 (45–141)||117 (75–150)||.894|
| 6 mo||80 (42–100)||79 (18–100)||.797|
| 2 y||86 (55–100)||83 (50–100)||.102|
|KSS function score|
| 6 mo||69 (5–100)||63 (0–100)||.021|
| 2 y||74 (20–100)||68 (20–100)||.019|
|Oxford Knee score|
| 6 mo||21 (12–40)||22 (12–52)||.381|
| 2 y||18 (12–41)||19 (12–55)||.087|
| 6 mo||53 (15–63)||54 (11–64)||.135|
| 2 y||59 (19–62)||58 (15–63)||.418|
| 6 mo||55 (29–71)||53 (14–75)||.647|
| 2 y||55 (20–71)||54 (17–73)||.894|