Orthopedics

Feature Article 

Hospital Resource Utilization Associated With Endoprosthetic Reconstruction Versus Primary Arthroplasty

Christopher W. Hoedt, MD; Alec S. Kellish, BS; Justin C. Frisby, BS; Christopher Rivera-Pintado, MD; Tae Won Kim, MD; Christina J. Gutowski, MD, MPH

Abstract

Endoprosthetic reconstructions of the hip and knee are currently reimbursed as primary hip and knee arthroplasty according to Current Procedural Terminology (CPT) coding guidelines. The purpose of this study was to compare hospital resources consumed by patients undergoing endoprosthetic reconstruction with those consumed by patients undergoing primary arthroplasty. The authors' hypothesis was that the former group carries more comorbidities, experiences longer length of stay (LOS), and has greater resource consumption. A retrospective review was performed of 61 patients undergoing endoprosthetic reconstruction and 745 patients undergoing primary hip or knee arthroplasty between 2015 and 2018 at a single institution. Demographic, clinical, and financial data were compared. The Charlson Comorbidity Index (CCI) was used to measure patients' health status and identify comorbidities associated with prolonged LOS through linear regression analysis. Patients who underwent endoprosthetic reconstruction had a greater than 3.5 times average LOS compared with primary arthroplasty patients: 10.81 days vs 2.94 days (P<.01). They demonstrated a higher mean CCI, higher rates of malignancy and pulmonary disease, and a wider age range. Their mean cost of care totaled $73,730.29, compared with $24,940.84 imposed by primary arthroplasty patients (P<.01). Significant predictors of LOS were malignancy status (metastatic or localized) and age younger than 50 years, with increased LOS being associated with increased cost. Patients undergoing endoprosthetic reconstruction of the hip and knee represent a fundamentally different patient population than primary arthroplasty patients based on comorbidities, variability in health status, and surgical indications. They have higher comorbidity scores and longer hospitalizations and consume more financial resources than primary arthroplasty patients. [Orthopedics. 2021;44(1):e73–e79.]

Abstract

Endoprosthetic reconstructions of the hip and knee are currently reimbursed as primary hip and knee arthroplasty according to Current Procedural Terminology (CPT) coding guidelines. The purpose of this study was to compare hospital resources consumed by patients undergoing endoprosthetic reconstruction with those consumed by patients undergoing primary arthroplasty. The authors' hypothesis was that the former group carries more comorbidities, experiences longer length of stay (LOS), and has greater resource consumption. A retrospective review was performed of 61 patients undergoing endoprosthetic reconstruction and 745 patients undergoing primary hip or knee arthroplasty between 2015 and 2018 at a single institution. Demographic, clinical, and financial data were compared. The Charlson Comorbidity Index (CCI) was used to measure patients' health status and identify comorbidities associated with prolonged LOS through linear regression analysis. Patients who underwent endoprosthetic reconstruction had a greater than 3.5 times average LOS compared with primary arthroplasty patients: 10.81 days vs 2.94 days (P<.01). They demonstrated a higher mean CCI, higher rates of malignancy and pulmonary disease, and a wider age range. Their mean cost of care totaled $73,730.29, compared with $24,940.84 imposed by primary arthroplasty patients (P<.01). Significant predictors of LOS were malignancy status (metastatic or localized) and age younger than 50 years, with increased LOS being associated with increased cost. Patients undergoing endoprosthetic reconstruction of the hip and knee represent a fundamentally different patient population than primary arthroplasty patients based on comorbidities, variability in health status, and surgical indications. They have higher comorbidity scores and longer hospitalizations and consume more financial resources than primary arthroplasty patients. [Orthopedics. 2021;44(1):e73–e79.]

Segmental endoprosthetic reconstructions of the proximal and distal femur were introduced to the orthopedic oncology patient population several decades ago, offering those with malignant bone tumors the opportunity for reliable and durable limb salvage.1–4 The use of these implants has recently been expanded to indications such as periarticular/periprosthetic trauma and reimplantation arthroplasty after periprosthetic joint infection.5–8 Neoplasms, complex trauma, and infection starkly contrast the most common indication for primary total hip arthroplasty (THA) or total knee arthroplasty (TKA): degenerative joint disease (DJD).9

Proximal femoral replacement (PFR) and distal femoral replacement (DFR) surgeries involve wide exposures, often with dissection of major neurovascular structures about the knee or detachment/reattachment of the abductor complex about the hip. They involve intraoperative variability and require surgical expertise with a modular implant system; the technical aspects of the surgery are vastly different from those of traditional THA or TKA.10 They are associated with higher blood loss and longer operative time: the average operative time for a primary THA is approximately 102 minutes, significantly shorter than a PFR, with an average time of 119 minutes.11,12 In 2013, Bohl et al13 demonstrated that with an average operative time of 92 minutes for THA and TKA, every 15-minute increase in operative time increased the risk of complications as such: readmission by 5%, anemia requiring transfusion by 9%, renal insufficiency by 9%, surgical site infection by 9%, extended stay by 9%, sepsis by 10%, and wound dehiscence by 13%.13 These data are consistent with studies showing the risk of postoperative infection in patients with DFRs ranges from 5% to 37%, compared with infection rates of 0.6% to 1.9% in patients with primary TKA.14–16 Furthermore, the incidence of a secondary surgery resulting in amputation of the extremity has been shown to exceed 25%, in comparison with a rate of 0.36% in primary TKA.14,17,18 In summation, proximal and distal endoprosthetic replacements carry increased risk of complication, compounding the risk borne by the surgeon, hospital, and patient. Segmental replacement implants are also more expensive than those used in primary arthroplasty.19–22

The demographics and clinical characteristics of these patients also differ. Patients undergoing primary arthroplasty for DJD are more homogeneous in nature, following a more predictable postoperative course with more reliable length of stay (LOS) in the hospital.23 In endoprosthetic reconstruction, especially when indicated for a malignant bone tumor, many patients are deconditioned and immunosuppressed after extensive neoadjuvant treatment and suffer a higher perioperative complication rate.24 These patients often require longer hospitalizations, in part due to their complex medical comorbidities, but also due to the longer, more morbid periarticular surgery they undergo.

Current Procedural Terminology (CPT) codes were developed by the American Medical Association in 1966, years before endoprosthetic reconstruction was introduced and accepted by orthopedic surgeons. The Medicare Fee Schedule was implemented in 1992, which attempted to standardize billing for services and procedures for the “typical patient.”25,26 Despite the clinical, financial, and patient-related differences between endoprosthetic hip/knee reconstruction and primary total joint arthroplasty using standard components, CPT coding guidelines do not distinguish between these classes of reconstructions. A DFR is coded as 27447, the code used by millions of surgeons annually to represent primary TKA. A PFR with hemiarthroplasty of the hip is coded as 27125, the code used to describe hemiarthroplasty with standard primary components. Prior studies have demonstrated that surgery with an endoprosthesis is expensive, yet cost-effective when well-indicated, but in countries where payment mechanisms may at least in part be based on CPT coding (such as in calculation of surgeons' fees in the United States), the current paradigm is prone to inappropriately low reimbursement relative to the costs of the procedure.20 Currently, the codes used to describe endoprosthetic hip and knee reconstruction do not accurately reflect the work performed and risks borne. Miscoding of these procedures also introduces systematic bias into database research tied to CPT codes. It results in inefficiency in an institution's internal audits into LOS, duration of surgery, and resource utilization when data are stratified by CPT code. These inefficiencies could be reconciled by a unique, more precise code for endoprosthetic.

The authors hypothesize that the hospital resources consumed in caring for a patient undergoing segmental endoprosthetic reconstruction of the hip or knee are considerably greater than resources associated with primary joint arthroplasty. They believe this difference is due to the medical complexity of the former cohort, complicated nature and duration of their surgery, and extensive postoperative recovery process required prior to discharge. The purpose of this study was to therefore investigate the differences in cost of inpatient care between these 2 groups, as well as to identify the drivers of any difference found. If future hospital reimbursement practices are designed to reflect the CPT code associated with the patient's admission, as many systems move away from a fee-for-service model, a great disconnect will exist between hospital resource utilization and reimbursement in cases involving endo-prosthetic reconstruction. This will pose an unsustainable paradigm for tertiary care centers performing these complex procedures on medically complex patients.

Materials and Methods

No informed consent was needed for this retrospective analysis, which was approved by the institutional review board of the authors' tertiary care hospital and conducted in accordance with all appropriate guidelines. The authors performed a retrospective review of longitudinally collected data within the institution's orthopedic oncology database from the years 2015 to 2018 by querying for CPT codes 27447 (TKA), 27130 (THA), and 27125 (hip hemiarthroplasty). This query yielded an initial patient sample size of 1465 inpatient encounters. From these 1465 encounters, 806 met inclusion with (1) the relevant surgical procedure performed, and (2) available cost data. These were composed of 745 primary arthroplasties and 61 endoprostheses. The 745 primary arthroplasties included 252 primary THAs, 489 primary TKAs, and 4 hip hemiarthroplasties performed for reasons other than hip fracture. The 61 endoprostheses included 28 PFRs with/without acetabular resurfacing and 33 DFRs (Figure 1).

Procedure counts showing the initial number of patients included in the study (1465), the exclusion of 659 patients who either were nonsurgical encounters erroneously included or lacked financial data, and the inclusion of 806 patients. The 806 patients were divided in primary arthroplasty (745: 4 hip hemiarthroplasties, 252 primary total hip arthroplasties [THA], and 489 primary total knee arthroplasties [TKA]) and endoprosthesis reconstruction (61: 28 proximal femoral replacements [PFR] and 33 distal femoral replacements [DFR]).

Figure 1:

Procedure counts showing the initial number of patients included in the study (1465), the exclusion of 659 patients who either were nonsurgical encounters erroneously included or lacked financial data, and the inclusion of 806 patients. The 806 patients were divided in primary arthroplasty (745: 4 hip hemiarthroplasties, 252 primary total hip arthroplasties [THA], and 489 primary total knee arthroplasties [TKA]) and endoprosthesis reconstruction (61: 28 proximal femoral replacements [PFR] and 33 distal femoral replacements [DFR]).

For each of the 806 patients, demographic information including sex, age, height, weight, and body mass index (BMI) were collected, in addition to medical comorbidities. The Charlson Comorbidity Index (CCI) was used to objectively assess patient health status, due to its evidence-based ability to predict LOS and increased hospital cost in THA patients (Table 1).27,28 A CCI score was calculated for all 61 endoprosthesis patients. For the primary arthroplasty cohort, the CCI score was calculated for 183 patients randomly selected via a random-number generator, representing a 3:1 ratio with endoprosthesis patients. The demographics of these 183 patients were compared with the 745 primary arthroplasty patients and showed no statistically significant difference.

Charlson Comorbidity Indexa

Table 1:

Charlson Comorbidity Index

For normally distributed continuous variables, Student's t test were used to evaluate differences between the 2 cohorts. For non-normal distributions of continuous variables, Mann–Whitney U test was used. Categorical variables were evaluated using Pearson's chi-square test or Fisher's exact test. The effect of any difference in their scores on LOS was examined using linear regression analysis with statistical selection.

The institution's financial department provided each encounter's inpatient costs, categorized by cost center and designated as direct or indirect cost. Financial data were available for only 58 of the 61 endoprosthesis patients. The direct cost sub-categories included implant, labor, medication, and medical supply, and the direct costs are the focus of the remainder of this study. The authors' institution does not designate a specific cost center associated exclusively with room and board; instead, these costs are distributed across the LOS based on resource utilization each day, largely being reflected in the direct cost centers. P<.05 was considered to represent a statistically significant finding.

Results

Demographic Data

The demographic characteristics of the 745 patients who underwent primary joint arthroplasty and the 61 patients who underwent endoprosthetic reconstruction are displayed in Table 2. For the primary arthroplasty group, surgical indication was DJD, avascular necrosis, or fracture. Indications for the 61 endoprosthetic reconstruction patients were neoplastic disease (n=38), fracture (n=20), and infection (n=3). A statistically significant difference was found in the weight and average BMI of the primary arthroplasty group (Table 2).

Comparison of Demographics Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

Table 2:

Comparison of Demographics Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

Charlson Comorbidity Index

A significant difference was found in the overall CCI score of the 2 groups: endoprosthesis patients exhibited an average score of 5.62, whereas primary arthroplasty patients scored 3.26 (P<.001). Women undergoing endoprosthetic replacement were notably more ill, with an average CCI of 6.31. More than 72% of endoprosthesis patients had malignancy, compared with only 19.67% of the primary arthroplasty patients. Endoprosthetic patients had a higher incidence of chronic obstructive pulmonary disease (Table 3).

Charlson Comorbidity Index for Endoprosthesis and Primary Arthroplasty Patients

Table 3:

Charlson Comorbidity Index for Endoprosthesis and Primary Arthroplasty Patients

The age distribution of patients undergoing the 2 procedures was also significantly different, despite a similar average age. The endoprosthesis group demonstrated a wider range and a higher proportion of patients at the extremes (12–96 years, with 4 patients younger than 20 years and 5 patients older than 90 years). The age of the arthroplasty patient group was more predictable, as the age range was much narrower: 46–90 years. Approximately 21% of the endoprosthetic cohort were younger than 50 years, compared with only 4.92% of those undergoing primary arthroplasty.

Length of Stay

Patients who underwent endoprosthetic reconstruction had an average LOS greater than 3.5 times that of primary arthroplasty patients (10.81 days vs 2.94 days, P<.01). A linear regression analysis using forward selection was performed to identify CCI domains most predictive of LOS. The greatest predictors were meta-static cancer status (P<.01; 95% CI, 4.53–9.16), leukemia/lymphoma/nonmetastatic cancer (P<.028; 95% CI, 0.19–3.27), and age younger than 50 years (P<.045; 95% CI, 0.053–4.55).

Financial Analysis

Total average cost of care provided to an endoprosthetic patient totaled $73,730.29, compared with $24,940.84 imposed by the average primary arthroplasty patient (P<.01). Total average cost can be compartmentalized into direct and indirect costs: average indirect cost incurred by the hospital for endoprosthesis patients was significantly higher than it was for the primary arthroplasty patients ($31,191.51 vs $10,409.31, P<.01). Total direct cost for endoprosthesis patients was significantly higher than primary arthroplasty ($42,538.77 vs $14,531.53, P<.01). Cost of the segmental endoprosthetic implant itself was more than 3 times the cost of a standard arthroplasty implant ($20,826.10 vs $6749.50, P<.01). Additionally, all other direct cost subcategories, including medical supplies, drugs, intern/resident, labor, benefits, and “other,” were all significantly greater for endoprosthesis patients when compared with primary arthroplasty patients (Table 4).

Financial Comparison Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

Table 4:

Financial Comparison Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

Discussion

There are few reports on costs incurred by an institution caring for a patient undergoing limb salvage.29 Available data in the literature are reported in international currencies and are not necessarily generalizable to the United States. These procedures share a CPT code with primary THA and TKA; however, the medical community has not examined the financial burden of these surgeries, the suitability of coding them in this way, or the appropriateness of CPT-based physician reimbursement in these cases. Primary arthroplasty previously shared the same CPT code as revision arthroplasty until approximately a decade ago, when Bozic et al30 demonstrated the difference in resources required to care for patients undergoing each of these procedures and brought about creation of a new revision TKA CPT code. This study attempted to provide a detailed and accurate report of hospital resource utilization associated with endoprosthetic reconstruction of the hip and knee.

This study established that patients undergoing endoprosthetic reconstruction are fundamentally different patients, in terms of clinical characteristics, from those undergoing primary arthroplasty. They have increased heterogeneity and complexity in their comorbidities, with these comorbidities driving longer hospitalizations. Their surgical indications were extremely variable (eg, malignant tumor vs traumatic fracture), and their age range was wider, introducing unpredictability into their perioperative course. The incidence of malignancy in patients undergoing endoprosthetic reconstruction was 72.13%, compared with 19.67% in primary arthroplasty patients. In a multivariate analysis of orthopedic surgery patients, patients with malignancy had odds ratios of 8.72 and 4.83 for having major perioperative bleeding and developing perioperative myocardial necrosis, respectively.31 One of the most influential CCI domains on LOS was age younger than 50 years, and those who undergo these procedures at this young age are sarcoma patients whose comorbidities introduce increased rates of referral to tertiary care institutes, perioperative complications, and resource consumption.

This study presents important findings about the categorical drivers of total cost. The comparison of implant cost demonstrated that endoprostheses were greater than 3 times more expensive than primary THA and TKA components. All major cost centers contributing to direct and indirect cost of care were also significantly greater for the endoprosthetic group. The greatest drivers of LOS among the current patients were malignancy status and age younger than 50 years; these factors were most prevalent in the endoprosthetic cohort. These findings support the establishment of new CPT codes to better identify and differentiate patients who undergo endoprosthetic reconstruction, so as to generate reimbursement that is commensurate with hospital and surgeon resource use. The intended purpose of establishing the CPT coding system was to provide a code representing the typical patient, and the authors argue that patients requiring endoprosthetic reconstruction of the hip or knee are not consistent with the typical patient falling into these arthroplasty coding categories. On a national level, reconciling accurate cost of individualized care with appropriate risk-adjusted reimbursement will play a critical role in developing a sustainable health care delivery system. Although the volume of endoprosthetic reconstructions performed each year is small in comparison with the number of standard primary total joint arthroplasties, these procedures comprise a significant portion of the practice for the small number of surgeons across the country. As new codes are created across other subspecialties of orthopedics to distinguish nuanced differences between procedures, the authors argue that it is fair and in keeping with the intentions of the CPT coding system to establish new codes for these segmental endoprosthetic reconstructions.

A retrospective, nonrandomized study design was appropriate, because this was a study of 2 dissimilar patient groups and procedures. This study had several limitations. First, the authors did not assess costs associated with rehabilitation after hospitalization and readmissions. Patients undergoing large reconstructions may carry a higher risk of postoperative complications, inpatient rehabilitation facility admission, and hospital readmissions.32 Therefore, the total burden to the health care system associated with treating endoprosthetic patients may be underestimated.

Second, this study reflects data collected at a single institution, which may limit the generalizability of the results. For example, the authors found that patients undergoing primary arthroplasty at their institution have more comorbidities than the national average, according to National Inpatient Sample data from recent years; this may cause the 2 groups to artificially appear more similar in baseline comorbidities and cost.33 Finally, this study was plagued by a small sample, which may have led to higher variability in the data and affected the reliability of the results.

Conclusion

The authors' primary aim was to investigate hospital resource utilization associated with endoprosthetic reconstruction of the hip and knee and compare these costs to those associated with primary THA and TKA. They have found that the patient populations undergoing these 2 interventions are vastly different, and both the clinical and financial aspects of their inpatient episodes of care contrast starkly. The authors hope that their findings will provide a better understanding of the financial burden borne by surgeons and hospitals caring for these patients and that more accurately matched hospital reimbursement policy will be created to reflect the resource-intense nature of this field.

References

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Charlson Comorbidity Indexa

ScoreCondition
1Age 50–59 y
Myocardial infarction
Congestive heart failure
Peripheral vascular disease
CVA or TIA
COPD
Diabetes mellitus (requiring medications)
Moderate to severe renal disease
Chronic mild liver disease
Peptic ulcer disease
Alzheimer's disease or dementia
Connective tissue disease
2Age 60–69 y
Hemiplegia
End-organ damage from diabetes mellitus
Leukemia/lymphoma/solid tumor
3Age 70–79 y
Moderate to severe liver disease
4Age 80+ y
6Metastatic solid tumor
HIV/AIDS

Comparison of Demographics Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

CharacteristicPrimary arthroplastyEndoprosthetic reconstructionP
Patients, No.74561
Male37.60%37.70%.958
Height, average, cm
  Female162.6160.6.444
  Male178.6179.27.408
  Total167.62167.51.781
Weight, average, kg
  Female86.880.4.005
  Male100.587.6.002
  Total91.9283.22<.001
Body mass index, average, kg/m232.7129.66<.001
Age, average, y62.5562.67.693

Charlson Comorbidity Index for Endoprosthesis and Primary Arthroplasty Patients

Charlson Comorbidity Index DomainNo. of patientsP

EndoprosthesisPrimary arthroplasty
No.61183
Age <50 y13 (21.31%)9 (4.92%)<.001a
Age 50–59 y12 (19.67%)60 (32.79%).052
Age 60–69 y9 (14.75%)70 (38.25%)<.001a
Age 70–79 y17 (27.87%)27 (14.75%).078
Age ≥80 y10 (16.39%)17 (9.29%).126
Diabetes—uncomplicated8 (13.11%)39 (21.31%).160
Diabetes—end-organ damage1 (1.64%)6 (3.28%).684
Liver disease—mild1 (1.64%)12 (6.56%).194
Liver disease—moderate to severe1 (1.64%)0 (0.00%)
Malignancy—leukemia/lymphoma/localized24 (39.34%)33 (18.03%)<.001a
Malignancy—metastatic20 (32.79%)3 (1.64%)<.001a
Myocardial infarction3 (4.92%)13 (7.10%).767
Peripheral vascular disease2 (3.28%)8 (4.37%)1.000
CVA/TIA3 (4.92%)14 (7.65%).574
Dementia3 (4.92%)4 (2.19%).371
Peptic ulcer disease2 (3.28%)3 (1.64%).601
Congestive heart failure6 (9.84%)10 (5.46%).240
Chronic pulmonary disease12 (19.67%)13 (7.10%).005a
HIV/AIDS0 (0.00%)1 (0.55%)
Connective tissue disorders3 (4.92%)13 (7.10%).767
Moderate to severe chronic kidney disease6 (9.84%)10 (5.46%).240

Financial Comparison Between Patients Undergoing Primary Arthroplasty With Standard Components and Patients Undergoing Endoprosthetic Reconstruction

Cost centerPrimary arthroplastyEndoprosthetic reconstructionP
No.74558
Length of stay, average (SD), d2.74 (1.18)10.81 (7.99)<.01
Total cost, average (SD)$24,940.84 ($11,168.90)$73,730.29 ($30,785.03)<.01
Total indirect cost, average (SD)$14,531.53 ($6840.49)$31,191.51 ($13,244.72)<.01
Total direct cost, average (SD)$10,409.32 ($4592.86)$42,538.77 ($18,280.72)<.01
Direct cost subcategories
  Direct supply cost, average (SD)$2484.77 ($1627.63)$6309.25 ($3779.30)<.01
  Direct pharmaceutical cost, average (SD)$540.55 ($335.83)$1471.83 ($1881.14)<.01
  Other direct cost, average (SD)$410.96 ($181.37)$1273.71 ($687.14)<.01
  Direct implant cost, average (SD)$6730.60 ($3785.89)$20,826.10 ($9785.83)<.01
  Direct intern/resident cost, average (SD)$139.65 ($93.05)$670.80 ($594.68)<.01
  Direct benefits cost, average (SD)$728.64 ($345.79)$2161.88 ($1302.36)<.01
  Direct labor cost, average (SD)$3496.35 ($1548.76)$9825.21 ($5418.95)<.01
Authors

The authors are from the Department of Orthopaedics (CWH, JCF, CR-P, TWK, CJG), Cooper University Hospital, and Cooper Medical School of Rowan University (ASK), Camden, New Jersey.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Christina J. Gutowski, MD, MPH, Department of Orthopaedics, Cooper University Hospital, 3 Cooper Plaza, Ste 400, Camden, NJ 08103 ( gutowski-christina@cooperhealth.edu).

Received: July 04, 2019
Accepted: November 06, 2019
Posted Online: November 03, 2020

10.3928/01477447-20201012-02

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