Does Femoral Component Cementation Affect Costs or Clinical Outcomes After Hip Arthroplasty in Medicare Patients?

Journal Pre-proof Does Femoral Component Cementation Affect Costs or Clinical Outcomes After Hip Arthroplasty in Medicare Patients? Jason H. Oh, MD, William Yang, BS, Tara Moore, MSc, Kristina Dushaj, MA, H. John Cooper, MD, Matthew S. Hepinstall, MD PII:

S0883-5403(20)30072-3

DOI:

https://doi.org/10.1016/j.arth.2020.01.035

Reference:

YARTH 57743

To appear in:

The Journal of Arthroplasty

Received Date: 19 August 2019 Revised Date:

23 December 2019

Accepted Date: 12 January 2020

Please cite this article as: Oh JH, Yang W, Moore T, Dushaj K, Cooper HJ, Hepinstall MS, Does Femoral Component Cementation Affect Costs or Clinical Outcomes After Hip Arthroplasty in Medicare Patients?, The Journal of Arthroplasty (2020), doi: https://doi.org/10.1016/j.arth.2020.01.035. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Inc. All rights reserved.

TITLE: Does Femoral Component Cementation Affect Costs or Clinical Outcomes After Hip Arthroplasty in Medicare Patients?

AUTHORS: Jason H. Oh MD1, William Yang BS1, Tara Moore MSc1, Kristina Dushaj MA1, H. John Cooper MD2, Matthew S. Hepinstall MD1

1

Department of Orthopaedic Surgery

Lenox Hill Hospital 130 E 77th St., 11th Floor New York NY 10075

2

Department of Orthopaedic Surgery

Columbia University Medical Center 622 W 168th St., PH 11 – Center New York NY 10032

CORRESPONDING AUTHOR: Jason H. Oh, MD Department of Orthopaedic Surgery Lenox Hill Hospital 130 E 77th St., 11th Floor New York NY 10075 Phone: (212) 434-6880 Fax: (212) 434-2268 Email: [email protected]

1

TITLE:

2

Does Femoral Component Cementation Affect Costs or Clinical Outcomes After Hip Arthroplasty in

3

Medicare Patients?

4 5

Abstract

6 7

Background: Bundled payment initiatives were introduced to reduce costs and improve quality of care.

8

Cemented versus cementless femoral fixation is a modifiable variable that may influence the cost and

9

quality of care. New bundled payments data from the Centers for Medicare and Medicaid Services

10

(CMS) allowed us to study the influence of femoral fixation strategy on 90-day costs and clinical

11

outcomes.

12 13

Questions/purposes: How does the method of femoral fixation affect (1) 90-day costs; (2) readmission

14

rates; (3) reoperation rates; (4) length of stay (LOS); and (5) discharge disposition for Medicare patients

15

undergoing THA?

16 17

Methods: We retrospectively studied 1671 primary THA Medicare cases, comparing 359 patients who

18

received cemented femoral fixation to 1312 who received cementless fixation. CMS cost data as well as

19

clinical data were reviewed. Demographic differences were present between the two cohorts. Statistical

20

analyses were performed, including multiple regression models to adjust for baseline differences.

21 22

Results: Controlling for cohort differences, cemented patients were significantly more likely to be

23

discharged home compared to cementless patients. Cemented patients also demonstrated trends

24

toward lower costs, lower readmission rates, and shorter LOS compared to cementless patients. All

25

reoperations within the early postoperative period occurred in patients managed with cementless

26

femoral fixation.

27 28

Conclusion: Among Medicare patients, cemented femoral fixation outperformed cementless fixation

29

with respect to discharge disposition and also trended toward superiority with regards to LOS,

30

readmission, cost of care, and reoperation. Cemented femoral fixation remains relevant and useful

31

despite the rising popularity of cementless fixation.

32 1

33

Keywords: Medicare, bundled payments, hip, arthroplasty, cement, cost, outcomes

34 35

Introduction

36

The rising demand for total hip arthroplasty (THA)[1] has been met with increasing scrutiny from the US

37

government. The Bundled Payment for Care Improvement (BPCI) initiative and the Comprehensive Care

38

for Joint Replacement (CJR) model were introduced by the Centers for Medicare and Medicaid Services

39

(CMS) in 2013 and 2016, respectively, to rein in costs and improve quality of care. Orthopaedic surgeons

40

have thus been challenged to maximize quality metrics while minimizing costs of delivering care to the

41

hip arthroplasty patient, particularly within the 90-day episode of care.

42

Femoral fixation strategy is one variable that may influence the cost and quality of care. Utilization of

43

cemented versus cementless femoral components varies widely by geography and may be influenced by

44

non-patient factors such as surgeon training, familiarity and preference. As such, it represents a

45

possible target for quality improvement under the BPCI and CJR initiatives. There has been increasing

46

use of cementless components in recent decades with utilization estimated as high as 86-93% in the

47

United States[2,3]. Proponents of cementless femoral fixation cite reduced operative time and blood

48

loss, as well as the potential for biological integration, as primary advantages[4,5]. Others tout

49

avoidance of potential complications relating to cement use, such as pulmonary complications,

50

thromboembolic events, and early perioperative mortality[6–12]. When possible future revision surgery

51

is considered, many arthroplasty surgeons prefer to avoid the occasionally arduous task of thorough

52

cement removal. Nevertheless, the increasing prevalence of cementless femoral fixation runs counter to

53

established registry data showing fewer early reoperations and superior survival with use of cemented

54

components[2]. In addition, many reports have refuted the claims of increased cardiopulmonary

55

complications, thromboembolic events, and mortality among cemented patients, assuming the use of

56

modern surgical technique and appropriate medical co-management[13–22]. Furthermore, it has been

57

well established that cemented fixation is superior for the treatment of proximal femur fractures in frail

58

and elderly patients with osteoporosis[23–28]. The American Academy of Orthopaedic Surgeons (AAOS)

59

has issued a moderate-strength recommendation to use cemented fixation in arthroplasty treatment of

60

displaced femoral neck fractures[29].

61

Given the current spotlight on cost-effective care that optimizes quality while preventing complications,

62

it is possible that the trend towards increasing utilization of cementless fixation in patients over the age

63

of 65 should be reconsidered. We sought to utilize recently available CMS data on groups of BPCI and

64

CJR patients in our healthcare system to assess whether cemented femoral fixation was associated with 2

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(1) lower total 30-day and 90-day costs, or (2) improved early clinical outcomes including readmission,

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reoperation, length of stay, and discharge disposition, when compared to cementless fixation.

67 68

Materials and Methods

69

ICD-9 and ICD-10 data were used to identify 1671 cases of primary THA among Medicare patients who

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underwent surgery from January 2014 through October 2017 across nine hospitals in our healthcare

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network. Data was available for all patients with Medicare as the primary insurance, including patients

72

with a secondary private insurance. The hospitals included five tertiary-care academic facilities as well as

73

four community hospitals, all of whom were participating in either BPCI or CJR during the study period.

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One primary academic center represented the BPCI payment cohort, whereas the remaining eight

75

facilities comprised the CJR payment cohort. BPCI data was collected from January 2014 through

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October 2017, and CJR data was collected from January 2016 through October 2017. Revision

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procedures were excluded.

78

Demographics including age, gender, Charlson Comorbidity Index (CCI) values and the total number of

79

emergency department (ED) visits within the six months prior to the index surgery had been recorded

80

prospectively in the hospital electronic record and were extracted digitally. The CCI is a validated clinical

81

tool that quantifies the severity of a patient’s medical comorbidities; increasing CCI score is correlated

82

with increased likelihood of postoperative mortality as well as increased costs of care[30–33]. The

83

number of ED visits within the six months leading up to surgery has been found to predict risk of

84

postoperative ED utilization, readmission, and early postoperative mortality[34–36]. Length-of-stay

85

(LOS) data were also extracted from our healthcare network electronic medical record. ICD-9/10 codes

86

were used to determine whether each THA was performed on an elective basis (i.e., primary

87

osteoarthritis, rheumatoid arthritis, etc.) or for a proximal femoral fracture. ICD-10 data was used to

88

determine whether femoral cementation was performed at the time of surgery. In cases where ICD-10

89

data was not available, operative implant logs and operative reports were consulted. Femoral

90

cementation status was successfully verified for all patients.

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CMS data was queried for discharge disposition and total costs in the episode of care. Within the BPCI

92

cohort, an episode of care includes the operative admission as well as the 30 days following discharge.

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The CJR episode of care includes the operative admission as well as the 90 days following discharge.

94

Therefore, total cost per episode of care was available as 30 days post-discharge for the BPCI group and

95

90 days post-discharge for the CJR group. These costs were inclusive of initial hospital charges as well as

96

costs incurred by readmissions, at-home and outpatient services, skilled nursing facility costs, and 3

97

Medicare Plan B costs. CMS data allowed capture of cost and readmission data to hospitals and

98

providers outside of our healthcare network. Only total perioperative costs were available and recorded,

99

not itemized charges (e.g., cost per implant or per procedure). For all readmissions within our health

100

system, electronic health records were reviewed to determine whether a reoperation at the surgical site

101

occurred.

102

Given the retrospective nonrandomized nature of this investigation, the cemented and cementless

103

cohorts were compared with regard to potential confounding variables including age, gender, CCI,

104

frequency of emergency department visits, and indication for surgery (elective surgery versus urgent

105

surgery for fracture). Outcome measures included total cost per episode of care and early clinical

106

outcomes consisting of LOS, discharge disposition (i.e., to home versus to skilled nursing facilities or

107

acute rehabilitation facilities), readmissions and reoperations. The Shapiro-Wilk test was applied to

108

confirm whether data was normally distributed. Inter-group comparisons of continuous variables with

109

normally distributed data were assessed via a T-test and inter-group comparisons of continuous

110

variables with data that is not normally distributed were examined using the Mann-Whitney U test.

111

Comparison of the distribution of categorical variables in the different groups were performed with

112

Fisher's exact test or the χ 2 test.

113

Univariate analysis was performed to determine differences in outcomes between patients currently

114

treated with cemented and cementless fixation in our health system. Outcomes of interest were total

115

costs, LOS, discharge disposition, readmissions, and reoperations at the surgical site. LOS and discharge

116

disposition analysis was performed for the pooled BPCI and CJR cohorts whereas readmissions,

117

reoperations and total costs were analyzed separately for the BPCI and CJR cohorts due to differences in

118

follow-up duration (30 vs. 90 days, respectively).

119

Multiple regression analysis was employed to determine the association between fixation strategy and

120

outcomes while adjusting for the baseline differences between the cemented and cementless cohorts.

121

As the fixation cohorts differed with regard to age, gender, CCI score, the number of ED visits in the six

122

months preceding the index surgery, and fracture versus elective indication for surgery, each of these

123

potential covariates was included in the regression. Multiple linear regressions were employed to assess

124

the association between costs, length-of-stay, and cemented status while controlling for age, gender,

125

CCI, frequency of prior emergency department visits, and indication for surgery (elective surgery versus

126

urgent surgery for fracture). Multiple logistic regressions were employed to assess the association

127

between discharge disposition, readmissions, and cemented status while controlling age, gender, CCI,

128

frequency of prior emergency department visits, and indication for surgery. BPCI and CJR cohorts were 4

129

again analyzed separately when assessing costs and readmissions and combined when assessing LOS

130

and discharge disposition. Multiple regression analysis was not performed for reoperations as the low

131

number of cases (11 reoperations total among 1671 primary surgeries) resulted in a lack of statistical

132

validity to study multiple variables. All statistical analyses were performed with SPSS v22 and statistical

133

significance was set at P < 0.05.

134 135

Results

136

Across the overall study population of 1671 Medicare patients, 359 (21.5%) received cemented femoral

137

fixation while 1312 (78.5%) received cementless femoral fixation. Analysis of baseline characteristics

138

revealed significant differences between the groups receiving cemented and cementless fixation with

139

regards to age, gender, CCI, the number of emergency department visits in the prior six months, and

140

indication for surgery (Table 1). Patients receiving cemented femoral fixation were older (81.4 vs 74.5

141

years; p<0.001), were more likely to be female (78.8% vs 61.1%; p<0.001), had a higher CCI (4.90 vs 3.74;

142

p<0.001), had a higher number of ED visits in the six months prior to surgery (1.05 vs 0.50; p<0.001),

143

were more frequently being treated for a proximal femur fracture than for an elective indication (53.1%

144

vs. 15.5%; p<0.001), and in the hospital participating in BPCI compared to the hospitals participating in

145

CJR (51.5% vs. 41.8%; p=0.001).

146

Univariate Analyses:

147

Univariate analysis of the data is presented in Tables 2 and 3. Before accounting for the baseline

148

differences between the cemented and cementless cohorts, patients receiving cemented fixation were

149

observed to have significantly higher total costs ($32,166 vs. $25,578; p<0.001). This held true for both

150

the BPCI and CJR cohorts as well as the study population overall. Patients receiving cemented fixation

151

also demonstrated trends toward higher rates of readmission (8.4% vs. 6.6%; p=0.24) and lower rates of

152

reoperation at the surgical site (0% vs. 0.84%; p=0.135). Although the observed difference was not

153

statistically significant, it is notable that there were no instances of reoperations at the surgical site

154

within the early postoperative period among all of the 359 cemented patients, whereas 11 reoperations

155

occurred among the 1312 cementless patients. These included 4 periprosthetic fractures, 3 cases of

156

recurrent dislocation, 2 cases of femoral implant subsidence, and 2 periprosthetic infections (Table 4).

157

Upon analyzing the aggregated data, statistically higher LOS (4.9 days vs. 3.8 days; p<0.001) and lower

158

rates of discharge to home (38.4% vs. 57.9%; p<0.001) were observed with the cemented patient

159

cohort.

160

Multivariate Analyses: 5

161

Due to the significant baseline differences between the cemented and cementless cohorts, multiple

162

regression analyses were performed to determine the influence of fixation choice while statistically

163

controlling for the impact of known confounding variables. The results of these analysis are reviewed

164

individually below. Multiple regression analysis was not performed for reoperations as the low number

165

of cases (11) would result in a lack of statistical validity.

166

Costs:

167

Following multiple linear regression analysis with the inclusion of confounding variables, there was no

168

significant difference in total cost of care between cemented and cementless patients in either the CJR

169

or BPCI cohorts. The observed trend was toward lower costs among the cemented patients in the CJR

170

cohort (p=0.57) and in the BPCI cohort (p=0.46), but this did not approach statistical significance. Within

171

the CJR cohort, higher costs were significantly associated with increasing age, female gender, more

172

emergency department visits within the prior six months, and diagnosis of femoral neck fracture. Within

173

the BPCI cohort, higher costs were significantly associated with increasing age, higher CCI scores, more

174

emergency department visits within the prior six months, and diagnosis of femoral neck fracture (Table

175

5).

176

Readmissions:

177

Following multiple logistic regression analysis with the inclusion of confounding variables, there was no

178

significant difference in readmission rates between cemented and cementless patients in either the CJR

179

or BPCI cohorts. The trend was toward fewer readmissions among the cemented patients with p=0.09 in

180

the CJR cohort and p=0.46 in the BPCI cohort. Within the CJR cohort, significantly higher readmission

181

rates were associated with more emergency department visits within the prior six months. Within the

182

BPCI cohort, higher CCI scores were significantly associated with more readmissions (Table 6).

183

LOS:

184

Following multiple linear analysis with the inclusion of confounding variables, there was no significant

185

difference in LOS between cemented and cementless patients. The trend was toward shorter LOS

186

among the cemented patients with p=0.21. Increasing age, higher CCI scores, more emergency

187

department visits within the prior six months, and hip fracture diagnoses were significantly associated

188

with higher LOS (Table 7).

189

Discharge disposition:

190

Following multiple logistic analysis with the inclusion of confounding variables, cemented patents were

191

significantly more likely to be discharged home (p=0.019) as opposed to a rehabilitation or other nursing

192

facility. Younger age, male gender, lower emergency department usage in the prior six months, and 6

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elective (i.e., non-fracture) indications for surgery were also significantly associated with a higher

194

likelihood of discharge home (Table 8).

195 196

Discussion

197

There is a growing trend in the United States as well as worldwide toward the adoption of cementless

198

femoral component fixation for hip arthroplasty. In 2009, a survey of surgeons at the annual meeting of

199

the American Association of Hip and Knee Surgeons (AAHKS) showed that 47% of respondents preferred

200

to use cementless femoral components in all hip arthroplasty cases, and another 47% used cementless

201

fixation in over 75% of cases[37]. There has been concern that femoral cementing technique may

202

become a “lost art” as enthusiasm for cementless fixation continues to build. There exists a strong

203

argument that surgeons in training should become competent with femoral cementation technique and

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a legitimate question as to whether we should be using cemented femoral fixation more frequently in

205

patients over 65 years of age to improve clinical outcomes and decrease costs and morbidity associated

206

with complications of cementless fixation.

207

Ours is the first study to our knowledge to leverage the new ability to combine patient-level CMS cost

208

and readmissions data with a large institutional database to compare economic and clinical outcomes

209

between cemented and cementless femoral fixation in the Medicare population. Patients who received

210

cemented femoral fixation were significantly older, more commonly female, had more medical

211

comorbidities, had more emergency department utilization, and were more likely to present with

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proximal femoral fracture than patients receiving cementless femoral fixation. Likely as a result of

213

demographics, patients receiving cement fixation had inferior short-term outcomes (with the exception

214

of reoperation) on univariate analysis. If these results are typical of health systems in which a relatively

215

small percentage of THAs receive cement fixation, the choice may be self-reinforcing; communities of

216

surgeons who choose cement primarily for hip fracture patients and the frail elderly may come to

217

perceive cement fixation to be associated with inferior outcomes.

218

After controlling for these differences, however, we found that cement fixation was associated with

219

superior performance over cementless fixation with regards to discharge disposition, suggesting earlier

220

return of function. Cemented fixation also trended toward superiority with regards to LOS, readmission

221

rates, reoperations at the surgical site, and total costs. These trends were present within a community

222

of surgeons that elected cementless fixation for 80% of Medicare patients, but only became evident

223

with multivariable analysis. Communities of surgeons with routine utilization of cement fixation beyond

7

224

fracture patients and the frail elderly might more easily perceive the benefits of cement fixation

225

demonstrated in registry data, however.

226

Our demographic analyses were consistent with prior reported findings, revealing generally improved

227

short-term outcomes associated with younger age, male gender, fewer comorbid conditions, lower rates

228

of pre-operative emergency department usage, and elective surgery rather than proximal femoral

229

fracture diagnosis[23–28,38]. It is notable that these demographic variables were significantly

230

associated with total costs whereas the study variable most within surgeon control, femoral fixation

231

strategy, was not. All of these key components were incorporated into our multivariate analysis to

232

better understand the true effect of femoral fixation strategy in this retrospective analysis.

233

We believe that a critical advantage of cemented fixation is the avoidance of early reoperation

234

secondary to periprosthetic femur fracture, implant subsidence and failure of osseointegration. Aside

235

from being a devastating complication in its own right, periprosthetic fracture is a significant risk factor

236

for subsequent readmission, reoperation, permanent loss of function, and mortality[39,40]. Although

237

our study was not powered to demonstrate statistical significance with regards to early reoperation,

238

there exists strong published evidence supporting the superiority of cemented fixation in the reduction

239

of both intraoperative and postoperative periprosthetic fractures, particularly in the frail and/or

240

elderly[13,22–24,27,41,42]. Accordingly, all 11 reoperations occurred in the cementless fixation group;

241

these included four instances of periprosthetic fracture as well as two additional cases of femoral

242

revision for early subsidence with mechanical failure of cementless fixation.

243

Our findings should be interpreted in the context of prior studies, many of which were performed

244

outside of the United States in regions with greater utilization of cemented technique. Pennington et al.

245

found in a large English and Welsh joint replacement registry study that femoral cementation yielded

246

lower costs and higher quality-adjusted life years than cementless fixation[43]. Veldman et al.

247

performed a meta-analysis of 5 randomized control trials (RCTs) that found that cementless fixation

248

generated more complications, particularly implant-related complications, than cemented fixation[41].

249

Chammout et al. also found that uncemented femoral fixation was significantly more likely to result in

250

early hip-related complications than cemented fixation in a single-blinded RCT, with similar rates of

251

mortality and functional outcome scores[13]. Moerman et al. found in another RCT that cementless

252

patients had greater rates of complication than cemented, with similar functional outcome scores and

253

pain[42]. Taylor et al. also found higher rates of complication in cementless patients in their own RCT,

254

with similar pain and trends toward improved mobility and function in the cemented group[16]. In a

8

255

systematic review, Luo et al. found that cemented fixation tends to provide better pain relief and

256

function with no additional risk with regards to mortality, complication, or reoperation[17].

257

Although our findings support a trend toward improved outcomes with cemented fixation for every

258

measure of interest, prior reports favoring cementless fixation should also be considered. In a

259

retrospective review of patients treated for displaced femoral neck fractures, Fuchs et al. found that

260

perioperative mortality was higher after cemented hemiarthroplasty than cementless THA, though hip-

261

related surgical complications remained higher in the THA group[11]. There may have been an element

262

of selection bias as there was no prospective treatment randomization and it is possible that older and

263

frailer patients with more comorbidities were selected for the cemented hemiarthroplasty group.

264

Langslet et al. performed a randomized clinical trial of displaced femoral neck fractures treated with

265

either cemented or cementless hemiarthroplasty with 5-year follow-up that yielded higher Harris Hip

266

Scores in the cementless group[44]. However, they also demonstrated a significantly higher rate of

267

periprosthetic femur fracture in the cementless group with similar rates of infection, instability, and

268

mortality. Other studies have proposed that cementless fixation is safer with regards to

269

cardiopulmonary and thromboembolic problems as well as all-cause mortality[6–12], and have been

270

refuted by other studies in turn[13–22]. While some studies suggest lower perioperative mortality with

271

cementless fixation, mortality at one year has not been different and this may relate to the morbidity

272

and mortality related to failed cementless fixation and its treatment[12,20,44].

273

We acknowledge several limitations to our study. Firstly, this study was designed primarily to leverage

274

30-day and 90-day cost data provided by the BPCI and CJR initiatives, respectively, to determine the

275

effect of fixation strategy on costs, resource utilization and complications. Therefore, clinical data were

276

recorded only through the same early postoperative periods. Patient-reported outcome scores, as well

277

as mid-term and long-term follow-up studies, are necessary to fully assess the performance of cemented

278

versus cementless femoral fixation over time. These longer-term outcomes have been studied

279

extensively by others but remain a focus for further inquiry. Deeper investigation into specific medical

280

complications such as fat embolism syndrome has been performed by others[19,45] but may also be a

281

useful direction of future study, as modern techniques may influence the incidence of these events.

282

Secondly, as a retrospective database analysis spanning across multiple hospitals, there were significant

283

differences between the cemented and uncemented cohorts with regards to multiple demographic

284

factors: age, gender, comorbidities, frequency of emergency room visits, and presenting diagnosis. The

285

correlation between surgical indication and cemented status was particularly strong. It has been well-

286

described in the literature that patients undergoing hip arthroplasty for fracture have significantly 9

287

poorer outcomes across all clinical and cost parameters than patients undergoing elective

288

arthroplasty[46–48]. However, we did adjust for these known confounding factors with the use of

289

inferential statistics. Although there may be additional unrecognized and potentially confounding

290

variables associated with institutional participation in the bundled payment systems, it should be noted

291

that all patients, whether cemented or cementless, were in one of the two bundled payment programs.

292

There may have been selection bias based upon surgeon training and experience, which we were not

293

able to control given the available database information. For example, older surgeons, those with

294

foreign training, and/or those with arthroplasty fellowship training may have been more likely to use

295

cemented femoral fixation. Based upon our own practice patterns, we suspect there may have been bias

296

towards use of cemented fixation in cases of patient frailty, osteoporosis, Dorr C femoral morphology,

297

higher fall risk, and other patient characteristics that lend themselves to higher risk of hip and

298

periprosthetic fracture. Alternatively, surgeons may have steered away from cemented fixation when

299

treating patients with known cardiopulmonary disease. Individual hospital norms and culture may also

300

have played some role in femoral fixation preference, but the majority of surgeries were performed

301

using cementless fixation at all hospitals. Furthermore, we were not able to standardize specific aspects

302

of surgical technique with regards to surgical approach, implant selection, cementation protocol,

303

cement brand and type, and other factors. Surgical approach may be particularly salient given that

304

previous literature have suggested differences in perioperative complications between approaches, such

305

as increased rates of intraoperative femoral fracture with the anterior approach and lower rates of

306

instability with the direct lateral approach[49–52]. Our institutional databases did not track surgical

307

approach. The nature of the CMS database also precluded us from capturing cost data past the 30 day

308

post-discharge period for BPCI and the 90 day post-discharge period for CJR. We lacked data on

309

osteoporosis or bone morphology and our study population was not large enough to meaningfully

310

stratify our analysis by age, gender, diagnosis or other factors that might define subpopulations that

311

would most or least benefit from cement fixation. Our study size was also insufficient to power certain

312

findings that we feel should have been reproducible from the existing literature, particularly the

313

increased likelihood of early implant-based complications such as PFF and subsidence with cementless

314

fixation. Power analysis regarding early reoperations revealed that we would have required at least 932

315

patients in each cohort to achieve a power of 80% at an alpha error of 0.05. Another limitation is our

316

study is that although CMS data comprehensively covered perioperative costs and readmissions, we

317

were not able to capture reoperation data at facilities outside of our hospital network. This will be a

318

direction of future study. We expect that with greater power, statistical significance may be achieved 10

319

with regards to the observed trends towards improved cost, readmissions, and LOS among cemented

320

patients. Greater power would also allow us to investigate possible effects on mortality, which was not

321

included in this study for the same reason. Conversely, we acknowledge that a larger data set may

322

reveal some of the observed trends to be statistical anomalies related to chance, rather than reflecting

323

true differences between groups.

324 325

Conclusion

326

Although there has been a strong movement in the United States and globally in favor of cementless

327

femoral fixation, historical and current evidence both demonstrate that cemented technique produces

328

equivalent or superior outcomes for hip arthroplasty patients, particularly in older adults such as the

329

Medicare population studied here. Nevertheless, any short term economic advantage of cemented

330

femoral fixation was too small for us to measure as total costs were equivalent in our cohorts. We

331

continue to favor cemented fixation for frail older patients with osteopenic bone who are at risk for

332

implant subsidence and periprosthetic fracture. Our data do not support any need for wholesale change

333

in practice pattern with return to cemented femoral fixation as the standard for all older or Medicare

334

patients, nor do our data suggest that any such change would be associated with unanticipated

335

increased risk or cost.

336

Prior studies have identified risk factors such as advanced age, malnutrition, osteoporosis, female

337

gender, and low socioeconomic status for periprosthetic fracture or cementless fixation failure and

338

these criteria may be useful to identify selected patients most likely to obtain benefit from cemented

339

fixation. Because some patients clearly can benefit from cemented fixation and most patients over age

340

65 get results from cemented fixation equal or better to what they would achieve with cementless

341

fixation, there may be a role for practicing surgeons to use cemented fixation routinely enough that the

342

knowledge and skills necessary are maintained and transmitted to surgeons in training.

11

343

References

344 345

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https://doi.org/10.2106/JBJS.F.00222.

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16

Tables

Table 1. Baseline demographic and clinical characteristics, split by payment model and cemented status BPCI Cemented

Cementless

Age (mean,

80.06

73.70

sd)

(7.71)

(8.58)

28

CJR p value

Cemented

Cementless

82.90

75.06

(8.64)

(9.08)

238

48

272

(15.1%)

(43.4%)

(27.6%)

(35.6%)

157

311

126

491

(84.9%)

(56.6%)

(72.4%)

(64.4%)

<0.001 Ɨ

Total p value <0.001 Ɨ

Cemented 81.44 (8.28)

Cementless

p value

74.49 (8.90)

<0.001 Ɨ

Gender (n, %) Male

Female CCI score

4.41

(mean, sd)

(1.87)

<0.001 Ɨ

3.63 (1.69)

<0.001 Ɨ

0.38 (0.92)

<0.001 Ɨ

5.43 (2.35)

76 (21.2%)

0.0511

283 (78.8%)

510 (38.9%)

802 (61.1%)

<0.001 Ɨ

3.82 (1.93)

<0.001 Ɨ

4.90 (2.17)

3.74 (1.84)

<0.001 Ɨ

0.60 (1.07)

<0.001 Ɨ

1.05 (1.41)

0.50 (1.02)

<0.001 Ɨ

ED visits in prior 6

0.83

months

(1.29)

1.28 (1.49)

(mean, sd) Indication (n, %) 59 Fracture

Elective

(31.9%)

81 (14.8%)

126

468

(68.1%)

(85.2%)

<0.001 Ɨ

132

122

191

(75.9%)

(16.0%)

(53.1%)

42

641

(24.1%)

(84.0%)

<0.001 Ɨ

168 (46.8%)

203 (15.5%)

1109 (84.5%)

<0.001 Ɨ

Cohort (n, %) 185 BPCI

(51.5%) 174

CJR

(48.5%)

549 (41.8%)

763 (58.2%)

0.001 Ɨ

Ɨ Statistically significant.

Table 2: Univariate analysis of total costs, readmissions, and reoperations; split by payment model BPCI Cemented

Cementless

Total costs

27,603.15

24,588.59

(mean, sd)

(9,505.25)

(9,520.29)

9 (4.9%)

27 (4.9%)

CJR p value <0.001 Ɨ

Cemented

Cementless

37,016.52

26,289.06

(16,300.03)

(13,422.14)

21 (12.1%)

59 (7.7%)

Total p value <0.001 Ɨ

Cemented

Cementless

32,165.62

25,577.51

(14,036.49)

(11,970.87)

30 (8.4%)

86 (6.6%)

p value <0.001 Ɨ

Readmission (n, %) Yes No

176

522

(95.1%)

(95.1%)

1.00

153

704

(87.9%)

(92.3%)

0.07

329

1226

(91.6%)

(93.4%)

0.24

Reoperation (n, %) Yes No

Total

0 (0%)

3 (0.55%)

0 (0%)

8 (1.05%)

11 (0.84%)

185

546

(100%)

(99.45%)

185

549

174

763

359

1312

(25.2%)

(74.8%)

(18.6%)

(81.4%)

(21.5%)

(78.5%)

0.576

174 (100%)

755

0 (0%)

(98.95%)

0.364

359 (100%)

1301

0.135

(99.16%)

Ɨ Statistically significant.

Table 3: Univariate analysis of LOS and discharge disposition with aggregated data Cemented

Cementless

p value

4.88 (2.89)

3.76 (2.35)

<0.001 Ɨ

Home

138 (38.4%)

755 (57.9%)

Other

221 (61.6%)

550 (42.1%)

LOS (mean, sd) Discharge disposition (n, %)

<0.001 Ɨ

LOS: length of stay. Ɨ Statistically significant.

Table 4. Surgical site reoperations Case

Indication for reoperation

Management

1

Periprosthetic femur fracture (Vancouver B)

Open reduction internal fixation and femoral revision

2

Periprosthetic femur fracture (Vancouver B)

Open reduction internal fixation and femoral revision

3

Periprosthetic femur fracture (Vancouver B)

Open reduction internal fixation and femoral revision

4

Periprosthetic femur fracture (Vancouver AG)

Open reduction internal fixation

5

Recurrent dislocation

Head and liner exchange

6

Recurrent dislocation

Resection arthroplasty

7

Recurrent dislocation

Acetabular component revision

8

Femoral subsidence

Femoral revision

9

Femoral subsidence

Femoral revision

10

Acute periprosthetic joint infection

Irrigation and debridement, head and liner exchange

11

Acute periprosthetic joint infection

Two-stage revision

Table 5: Impact of covariates upon total cost of care CJR Cost*

p Value

BPCI Cost*

p Value

-$671 (-$3005 to $1664)

0.573

-$570 (-$2067 to $947)

0.461

Age (per year)

$179 ($76 to $281)

0.001 Ɨ

$203 ($114 to $293)

<0.001 Ɨ

Female Gender

$2233 ($598 to $3867)

0.007 Ɨ

$327 (-$978 to $1632)

0.623

$54 (-$405 to $514)

0.816

$858 ($440 to $1275)

<0.001 Ɨ

$2938 ($2241 to $3635)

<0.001 Ɨ

$1392 ($772 to $2011)

<0.001 Ɨ

$12,887 ($10,706 to $15,068)

<0.001 Ɨ

$5262 ($3508 to $7016)

<0.001 Ɨ

Cemented Fixation

CCI (per unit) ED visits in prior 6 months (per visit) Fracture Diagnosis

*The values given represent amount of change in cost of care with the 95% confidence interval given in parentheses; all amounts rounded to the nearest full dollar. Ɨ Statistically significant.

Table 6: Impact of covariates upon readmissions CJR Readmissions*

p Value

BPCI Readmissions*

p Value

Cemented Fixation

0.559 (0.286 to 1.092)

0.089

0.728 (0.310 to 1.706)

0.464

Age (per year)

1.016 (0.985 to 1.049)

0.317

1.010 (0.962 to 1.061)

0.681

Female Gender

1.324 (0.754 to 2.325)

0.328

0.850 (0.416 to 1.738)

0.656

CCI (per unit)

1.019 (0.895 to 1.160)

0.778

1.258 (1.074 to 1.472)

0.004 Ɨ

ED visits in prior 6 months (per visit)

2.049 (1.723 to 2.436)

<0.001 Ɨ

1.179 (0.880 to 1.580)

0.269

Fracture Diagnosis

1.642 (0.876 to 3.080)

0.122

0.952 (0.375 to 2.417)

0.917

*The values given represent the odds ratio of readmission with the 95% confidence interval given in parentheses. Ɨ Statistically significant.

Table 7: Impact of covariates upon LOS LOS*

p Value

-0.179 (-0.456 to 0.099)

0.207

Age (per year)

0.019 (0.005 to 0.034)

0.009 Ɨ

Female Gender

-0.022 (-0.243 to 0.199)

0.845

CCI (per unit)

0.164 (0.098 to 0.229)

<0.001 Ɨ

ED visits in prior 6 months (per visit)

0.347 (0.249 to 0.445)

<0.001 Ɨ

Fracture Diagnosis

2.096 (1.807 to 2.384)

<0.001 Ɨ

Cemented Fixation

*The values given represent additional days of LOS with the 95% confidence interval given in parentheses. Ɨ Statistically significant.

Table 8: Impact of covariates upon likelihood of discharge to home Home Discharge OR*

p Value

Cemented Fixation

1.441 (1.061 to 1.958)

0.019 Ɨ

Age (per year)

0.935 (0.919 to 0.950)

<0.001 Ɨ

Female Gender

0.651 (0.514 to 0.825)

<0.001 Ɨ

CCI (per unit)

0.944 (0.878 to 1.015)

0.120

ED visits in prior 6 months (per visit)

0.789 (0.706 to 0.882)

<0.001 Ɨ

Fracture Diagnosis

0.213 (0.154 to 0.294)

<0.001 Ɨ

* The values given represent the odds ratio of discharge to home with the 95% confidence interval given in parentheses. Ɨ Statistically significant.

Appendices

Appendix A: Multiple linear regression analysis for sum costs

Multiple linear regression analysis split by payment model (CJR vs. BPCI). Model 1 contains univariate analysis of cemented vs. cementless fixation and Model 2 includes multivariate analysis accounting for confounding variables: age, gender, Charlson Comorbidity Index, number of emergency department visits in the 6 months prior to index surgery, and indication for surgery (fracture vs. elective). Model Summary Change Statistics R Cohort Model CJR

BPCI

R

Adjusted Std. Error of

R Square

F

Sig. F

Square R Square the Estimate

Change

Change

df1

df2

Change

1

.286a

.082

.081 13999.30845

.082 83.110

1

934

.000

2

.583b

.340

.335 11904.55315

.258 72.523

5

929

.000

1

.136a

.019

.017

9516.51678

.019 13.866

1

731

.000

2

.505c

.255

.248

8322.44541

.236 45.962

5

726

.000

a. Predictors: (Constant), Final Cement b. Predictors: (Constant), Final Cement, Gender_bi, E, Age of Surg, CCI, Fix_bi c. Predictors: (Constant), Final Cement, Fix_bi, Gender_bi, CCI, E, Age of Surg

Coefficientsa Unstandardized

Standardized

95.0% Confidence

Coefficients

Coefficients

Interval for B

Std. Cohort Model CJR

1

B

(Constant) 26289.058

Error

Beta

507.080

t 51.844

Sig.

Lower

Upper

Bound

Bound

.000 25293.911 27284.206

Final 10727.462 1176.716

.286

9.116

.000

8418.149 13036.776

2.099

.036

482.990 14386.581

Cement 2

(Constant)

7434.785 3542.279

Final -670.715 1189.518

-.018

-.564

.573 -3005.169

1663.738

Cement Age of 178.513

52.064

.116

3.429

.001

76.337

280.689

2232.520

832.644

.073

2.681

.007

598.438

3866.602

54.373

234.113

.008

.232

.816

-405.079

513.825

2937.750

355.168

.239

8.271

.000

2240.725

3634.774

Surg Gender_bi CCI E Fix_bi BPCI

1

12886.905 1111.313

(Constant) 24588.591

.393 11.596

.000 10705.930 15067.879

60.499

.000 23790.678 25386.504

406.432

Final 3014.562

809.563

.136

3.724

.000

1425.217

4603.907

1.644

.101

-970.855 10987.866

Cement 2

(Constant)

5008.505 3045.664

Final -569.845

772.642

-.026

-.738

.461 -2086.724

947.035

203.234

45.662

.186

4.451

.000

113.589

292.878

Gender_bi

327.077

664.719

.016

.492

.623

-977.923

1632.078

CCI

857.851

212.590

.158

4.035

.000

440.485

1275.216

E

1391.731

315.492

.152

4.411

.000

772.346

2011.117

Fix_bi

5262.178

893.330

.216

5.891

.000

3508.359

7015.997

Cement Age of Surg

a. Dependent Variable: Sum Cost CJR = Comprehensive Care for Joint Replacement; BPCI = Bundled Payment for Care Improvement; Final Cement = cemented fixation; Age of Surg = patient age in years; Gender_bi = female gender; CCI = Charlson Comorbidity Index; E = number of emergency department visits in 6 months prior to surgery; Fix_bi = fracture diagnosis

Appendix B: Multiple linear regression analysis for length-of-stay (LOS)

Multiple linear regression analysis with cumulative data. Model 1 contains univariate analysis of cemented vs. cementless fixation and Model 2 includes multivariate analysis accounting for confounding

variables: age, gender, Charlson Comorbidity Index, number of emergency department visits in the 6 months prior to index surgery, and indication for surgery (fracture vs. elective).

Model Summary Change Statistics

Std. Error

Model

R

R

Adjusted R

of the

R Square

F

Sig. F

Square

Square

Estimate

Change

Change

df1

df2

Change

1

.183a

.033

.033

2.477

.033

57.619

1

1667

.000

2

.522b

.273

.270

2.152

.239 109.428

5

1662

.000

a. Predictors: (Constant), Final Cement b. Predictors: (Constant), Final Cement, Gender_bi, E, CCI, Fix_bi, Age of Surg

Coefficientsa Unstandardized

Standardized

95.0% Confidence

Coefficients

Coefficients

Interval for B

Model

B

1

3.757

.068

1.121

.148

1.222

.495

-.179

.141

Age of Surg

.019

Gender_bi

(Constant)

Std. Error

Beta

t

Sig.

Lower

Upper

Bound

Bound

54.905

.000

3.623

3.891

7.591

.000

.831

1.410

2.469

.014

.251

2.192

-.029

-1.262

.207

-.456

.099

.007

.071

2.631

.009

.005

.034

-.022

.113

-.004

-.196

.845

-.243

.199

CCI

.164

.033

.128

4.906

.000

.098

.229

E

.347

.050

.156

6.919

.000

.249

.445

2.096

.147

.353

14.262

.000

1.807

2.384

Final .183

Cement 2

(Constant) Final Cement

Fix_bi

a. Dependent Variable: LOS (inclusive)

CJR = Comprehensive Care for Joint Replacement; BPCI = Bundled Payment for Care Improvement; Final Cement = cemented fixation; Age of Surg = patient age in years; Gender_bi = female gender; CCI = Charlson Comorbidity Index; E = number of emergency department visits in 6 months prior to surgery; Fix_bi = fracture diagnosis

Appendix C: Multiple logistic regression analysis for discharge disposition

Multiple logistic regression analysis with cumulative data. Model 1 contains univariate analysis of cemented vs. cementless fixation and Model 2 includes multivariate analysis accounting for confounding variables: age, gender, Charlson Comorbidity Index, number of emergency department visits in the 6 months prior to index surgery, and indication for surgery (fracture vs. elective).

Model 1: Variables in the Equation 95% C.I.for EXP(B) B Step 1a FinalCement(1) Constant

S.E.

Wald

df

Sig.

Exp(B)

-.782

.122

40.926

1

.000

.458

.315

.056

31.651

1

.000

1.371

Lower

Upper

.360

.581

a. Variable(s) entered on step 1: FinalCement.

Model 2: Variables in the Equation 95% C.I.for EXP(B) B Step 1a FinalCement(1)

S.E.

Wald

df

Sig.

Exp(B)

Lower

Upper

.366

.156

5.466

1

.019

1.441

1.061

1.958

AgeofSurg

-.068

.008

65.083

1

.000

.935

.919

.950

Gender_bi(1)

-.429

.121

12.627

1

.000

.651

.514

.825

CCI_sum

-.058

.037

2.411

1

.120

.944

.878

1.015

E

-.237

.057

17.541

1

.000

.789

.706

.882

Fx_bi(1)

-1.546

Constant

6.185

.164

88.599

1

.000

.213

.582 113.102

1

.000 485.335

.154

.294

a. Variable(s) entered on step 1: AgeofSurg, Gender_bi, CCI_sum, E, Fx_bi. CJR = Comprehensive Care for Joint Replacement; BPCI = Bundled Payment for Care Improvement; Final Cement = cemented fixation; Age of Surg = patient age in years; Gender_bi = female gender; CCI = Charlson Comorbidity Index; E = number of emergency department visits in 6 months prior to surgery; Fix_bi = fracture diagnosis

Appendix D: Multiple logistic regression analysis for readmissions

Multiple logistic regression analysis, split by payment model (CJR vs. BPCI). Model 1 contains univariate analysis of cemented vs. cementless fixation and Model 2 includes multivariate analysis accounting for confounding variables: age, gender, Charlson Comorbidity Index, number of emergency department visits in the 6 months prior to index surgery, and indication for surgery (fracture vs. elective).

Variables in the Equation 95% C.I.for EXP(B) Cohort CJR

B

Step 1

a

BPCI Step 1a

FinalCement(1) Constant FinalCement(1) Constant

S.E.

.500 -2.479 -.013 -2.960

.269

Wald

df

Sig.

Exp(B)

Lower

Upper

.972

2.795

.455

2.139

3.443

1

.064

1.649

.136 334.609

1

.000

.084

.395

.001

1

.973

.987

.197 224.895

1

.000

.052

a. Variable(s) entered on step 1: FinalCement.

Variables in the Equation 95% C.I.for EXP(B) Cohort

B

S.E.

Wald

df

Sig.

Exp(B)

Lower

Upper

CJR

Step

FinalCement(1)

-.581

.341

2.899

1

.089

.559

.286

1.092

1a

AgeofSurg

.016

.016

1.001

1

.317

1.016

.985

1.049

Gender_bi(1)

.281

.287

.957

1

.328

1.324

.754

2.325

CCI_sum

.019

.066

.080

1

.778

1.019

.895

1.160

E

.717

.088 65.815

1

.000

2.049

1.723

2.436

Fx_bi(1)

.496

.321

2.391

1

.122

1.642

.876

3.080

1.155 17.726

1

.000

.008

Constant BPCI Step 1a

FinalCement(1)

-4.865 -.318

.435

.535

1

.464

.728

.310

1.706

.010

.025

.169

1

.681

1.010

.962

1.061

-.163

.365

.199

1

.656

.850

.416

1.738

CCI_sum

.229

.080

8.132

1

.004

1.258

1.074

1.472

E

.165

.149

1.224

1

.269

1.179

.880

1.580

Fx_bi(1)

-.050

.476

.011

1

.917

.952

.375

2.417

Constant

-4.636

1.768

6.877

1

.009

.010

AgeofSurg Gender_bi(1)

a. Variable(s) entered on step 1: AgeofSurg, Gender_bi, CCI_sum, E, Fx_bi. CJR = Comprehensive Care for Joint Replacement; BPCI = Bundled Payment for Care Improvement; Final Cement = cemented fixation; Age of Surg = patient age in years; Gender_bi = female gender; CCI = Charlson Comorbidity Index; E = number of emergency department visits in 6 months prior to surgery; Fix_bi = fracture diagnosis