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Clin Orthop Relat Res. 2012 April; 470(4): 1194–1203.
Published online 2011 November 29. doi:  10.1007/s11999-011-2186-2
PMCID: PMC3293973

What are Estimated Reimbursements for Lower Extremity Prostheses Capable of Surgical and Nonsurgical Lengthening?

Abstract

Background

Growing prostheses accommodate skeletally immature patients with bone tumors undergoing limb-preserving surgery. Early devices required surgical procedures for lengthening; recent devices lengthen without surgery. Expenses for newer expandable devices that lengthen without surgery are more than for their predecessors but overall reimbursement amounts are not known.

Questions/purposes

We sought to determine reimbursement amounts associated with lengthening of growing prostheses requiring surgical and nonsurgical lengthening.

Methods

We retrospectively reviewed 17 patients with growing prostheses requiring surgical expansion and eight patients with prostheses capable of nonsurgical expansion. Insurance documents were reviewed to determine the reimbursement for implantation, lengthening, and complications. Growth data were obtained from the literature.

Results

Mean reimbursement amounts of surgical and nonsurgical lengthenings were $9950 and $272, respectively. Estimated reimbursements associated with implantation of a growing prosthesis varied depending on age, sex, and location. The largest difference was found for 4-year-old boys with distal femoral replacement where reimbursement for expansion to maturity for surgical and nonsurgical lengthening prostheses would be $379,000 and $208,000, respectively. For children requiring more than one surgical expansion, net reimbursements were lower when a noninvasive lengthening device was used. Annual per-prosthesis maintenance reimbursements to address complications for surgical and nonsurgical lengthening prostheses were $3386 and $1856, respectively.

Conclusions

This study showed that reimbursements for lengthening of growing endoprostheses capable of nonsurgical expansion may be less expensive in younger patients, particularly male patients undergoing distal femur replacement, than endoprostheses requiring surgical lengthening. Longer outcomes studies are required to see if reimbursements for complications differ between devices.

Level of Evidence

Level III, economic and decision analysis. See the Guidelines for Authors for a complete description of levels of evidence.

Introduction

Neoadjuvant and adjuvant treatment of bone sarcomas have allowed successful limb preservation surgery in pediatric patients [30, 34]. Median Musculoskeletal Tumor Society (MSTS) functional scores of 80 have been reported in this population [1, 13]. Mean patient satisfaction, measured with the Pediatric Outcomes Data Collection Instrument (PODCI), has been reported to range from 80 to 90 [11, 20].

Expandable endoprostheses accommodate growth of skeletally immature patients [24, 25, 28, 31]. Over four decades these devices evolved with changes in the lengthening mechanisms. Early devices required the addition of metallic spacers or exchange of modular components to facilitate expansion and required additional surgery for lengthening [8, 23]. Recent devices have used a worm drive actuated by a screw accessible by percutaneous dissection (Fig. 1) [18]; these devices allow fine adjustment and are associated with reduced hospital stay [5].

Fig. 1
A second-generation expandable endoprosthesis requiring surgical lengthening is shown.

The most recent generation of expandable devices incorporates nonsurgical lengthening. One implant uses a telescoping wheel powered by an internal motor driven by an external electrical coil (Fig. 2). Early reports suggest this technology provides reliable lengthening with minimal complications [16, 17].

Fig. 2
A third-generation expandable endoprosthesis capable of nonsurgical lengthening is shown.

The financial expense of all expandable devices is considerable. Manufacturer charges for newer extendible prostheses capable of nonsurgical lengthening are increased over those of their predecessors, however, overall reimbursements for longitudinal care are unclear.

We compared reimbursements of lengthening endoprostheses capable of surgical and nonsurgical lengthening to answer the following questions: (1) What are reimbursement amounts for a single surgical and nonsurgical lengthening of an expandable prosthesis? (2) What are predicted healthcare cost provider reimbursements for lengthening a child’s limb from implantation to skeletal maturity? (3) How much lengthening is required to reach an equivalence point where the cost provider’s reimbursements for the two devices are equivalent and at what age does this occur? (4) What additional reimbursements are required for device complications and failures?

Patients and Methods

We queried our database for patients with adequate followup who had received an extendible endoprosthesis. From July 2001 to May, 2007, 18 patients (Group 1) received an extendible endoprosthesis requiring minimally invasive surgical lengthening (Stryker Orthopaedics, Mahwah, NJ, USA); one was excluded owing to insufficient data. From December 2004 to May 2009, eight patients (Group 2) received an endoprosthesis capable of nonsurgical lengthening (Stanmore Implants, Elstree, UK) at our institution (Table 1). Both implants have FDA approval. The mean age of patients in Group 1 was 10.9 years (range, 4–14 years) and in Group 2 was 10.6 years (range, 6–15 years); there was no significant difference in age between groups with the Student’s t-test (p = 0.84). Although no attempt was made to assign prosthesis type by sex, there was a significant difference in sex ratios between groups with Fisher’s exact test (p = 0.03). There was no significant difference between Group 1, which had 14 patients with a diagnosis of osteosarcoma and three with Ewing sarcoma, and Group 2, which had four patients with a diagnosis of osteosarcoma and four with Ewing sarcoma by Fisher’s exact test (p = 0.16). We had prior Institutional Review Board approval.

Table 1
Patient demographics

After discharge from the hospital, patients returned to clinic 1 to 2 weeks after surgery and then 6 weeks after implantation. Skeletally immature patients then were seen every 3 months and radiographs were obtained. Surgical lengthening was offered when the patient’s operative leg had a discrepancy of 1 cm or greater compared with the nonoperative leg; all lengthening procedures were performed as outpatient procedures and the mean operative time was 17 minutes. Nonsurgical lengthening was offered when the operative leg had a discrepancy of 4 mm or greater.

Failures experienced by patients in this series included two Type 1 failures, two Type 2 failures, one Type 3 failure, one Type 4 failure, and no Type 5 failures (Table 2) [19]. One physeal arrest and two patients with maximal extension of their growing prosthesis who required additional growth had failures not accounted for by this classification system. Four patients with superficial wound infections and one patient with flexion contracture had Grade I complications and one patient with seroma and one with wound dehiscence had Grade III complications. One failure for deep infection (Patient 3) and one superficial infection (Patient 14) followed surgical lengthening procedures. No patients receiving nonsurgical lengthenings had complications related to a lengthening or required admission to the hospital for any reason.

Table 2
Adverse events of subjects receiving expandable endoprostheses

Insurance records for patients receiving lengthening procedures between January 1, 2006 and December 31, 2009 were used to determine the reimbursement amounts for initial implantation surgeries, lengthening procedures, and treatment of complications. Amounts of the expandable endoprostheses requiring surgical lengthening were $20,000 (US dollars) for the proximal and distal femur replacement models and $25,000 for the proximal tibia replacement model; amounts of comparable nonsurgical lengthening devices were $34,200 per device. Reimbursement for a primary implantation surgery was $30,155. Reimbursement for a single lengthening procedure for each device was determined.

Total reimbursement for lengthening a prosthesis from implantation to skeletal maturity was calculated using reimbursements for the implant, implantation surgery, total expansion procedures (determined by anticipated growth), and the maximum growth allowed by the individual prosthesis (dictating whether revision for lengthening mechanism completion was required). Revision surgery was deemed necessary if more than 2 cm of anticipated growth remained after maximal prosthesis expansion. In the event that a revision surgery was included in the calculation, the reimbursement of one lengthening procedure or 1 cm of lengthening, whichever was greater, was subtracted because it is our practice to perform intraoperative lengthening during the revision process through implant length selection. The external power source for facilitating nonsurgical lengthenings is provided at no charge and no reimbursement for its use was sought.

Annual physeal growth rates were obtained from the literature and a multiplier of 1.243 was used based on the finding of contralateral limb overgrowth in this population [2, 3, 7]. Based on our practice, surgical expansions were assumed to be 1 cm per lengthening procedure and noninvasive expansions were 0.40 cm each; 2-cm surgical lengthening procedures were included in the analysis for completeness although lengthening of this amount is not performed at our institution (Tables 3 and and4).4). The maximum lengthening potentials of the implants were obtained from the manufacturers and were 90 mm and 85 mm for the surgical and nonsurgical lengthening devices, respectively.

Table 3
Growth and expansion requirements by location in boys
Table 4
Growth and expansion requirements by location in girls

Results

What are reimbursements for a single surgical and nonsurgical lengthening of an expandable prosthesis? Mean provider reimbursement for a surgical lengthening, adjusted to 2010 inflation, was $9947.54 (range, $4897.29–$12,166.39). This amount included two fixed-amount expansions for which itemized reimbursements were unavailable. Exclusion of these procedures raised the mean reimbursement to $10,587.49 (Table 5). Reimbursement for an in-clinic expansion of the Stanmore device, including clinic fees and radiographs, was $272.44.

Table 5
Hospital and operative costs associated with surgical expansion procedure

What are predicted total healthcare cost provider reimbursements for lengthening a child’s limb from implantation to skeletal maturity? Substantial differences existed in the reimbursements associated with lengthening an expandable prosthesis to achieve equivalent leg lengths for boys (Table 6) and girls (Table 7) from age 4 years to skeletal maturity. Larger differences were seen in boys, who reach skeletal maturity later than girls. The distal femoral physis has the greatest growth potential and therefore its replacement requires more lengthening procedures than the other locations; the proximal femoral physis showed the smallest reimbursement difference. The implants in consideration had expansion capabilities within 5 mm of each other, therefore the number of anticipated revisions did not differ between prostheses.

Table 6
Estimated reimbursements of expandable endoprosthesis use in boys
Table 7
Estimated reimbursements of expandable endoprosthesis use in girls

How much lengthening is required to reach an equivalence point where the cost provider reimbursements for the two devices are equivalent and at what age does this occur? The equivalence point for the proximal and distal femur prostheses was reached with 1.6 surgical lengthening procedures; the equivalence point for proximal tibial prostheses was reached with a single surgical lengthening. In boys when 1-cm surgical lengthenings were considered, equivalence for proximal femur replacement occurred at approximately 14 years. For distal femur replacement and proximal tibia replacement, equivalence occurred between ages 15 and 16 years (Fig. 3A). Use of 2-cm lengthenings lowered the equivalence age (Fig. 3B). For girls, when 1-cm surgical lengthenings were considered, equivalence for proximal femur replacement occurred at approximately 12 years and for proximal tibia and distal femur replacement between 13 and 14 years (Fig. 3C). Use of 2-cm lengthenings in girls also lowered the equivalence age (Fig. 3D).

Fig. 3A D
Estimated expansion costs for surgical and nonsurgical lengthenings of expandable endoprostheses for proximal femoral replacement (PFR), distal femoral replacement (DFR), and proximal tibial replacement (PTR) are shown for: (A) boys receiving 1-cm surgical ...

What additional reimbursements occur from device complications and failures? Adverse events contributed to increased payments from healthcare cost providers (Table 8). The least expensive complication we treated was a superficial wound infection, for which we prescribed enteral vancomycin and checked laboratory values. The most expensive complication was staged revision attributable to deep infection, which required removal of the infected device, parenteral antibiotics, and revision surgery. When maintenance reimbursements by group were divided by total implant service years for all patients in the group, mean reimbursements for Group 1 and Group 2 were $3386 and $1856, respectively.

Table 8
Treatment costs for adverse events

Discussion

Advances in medical oncology have made limb preservation a viable option for many children with malignant extremity tumors [30, 34]. Substantial financial expenses associated with these procedures require that their use be coupled with justification of their functional and fiscal viability.

We acknowledge limitations to this study. We did not include costs to the patient’s family, including travel and lost work productivity. Although these costs are relevant, they would vary substantially for patients treated at a tertiary center and would be influenced by the family’s financial situation and lifestyle. Our intention was to address only the reimbursements associated with expansion of these devices from the cost provider’s standpoint. Second, our analysis was based on mean surgical expansions of 1 cm or 2 cm and mean nonsurgical expansions of 0.40 cm. Altering these amounts would change the results of this analysis. Third, our analysis was based on average growth patterns at the remaining physes and contralateral limb with a compensatory multiplier because physeal growth has been shown, on average, to accelerate after limb preservation [7]. Physeal activity may be affected by factors specific to an individual patient’s diagnosis and treatment and individual growth rates may vary considerably [7]. Fourth, reimbursements for oral analgesia after discharge from the hospital after surgical lengthenings were minimal and were not included in the analysis. Fifth, other endoprostheses are capable of noninvasive expansion and were not included in this study. Sixth, the reimbursements reported here were from private insurance and may not reflect the payments associated with a government-subsidized health plan.

Our review of financial records showed a mean reimbursement difference between surgical and nonsurgical lengthening procedures of almost 40-fold. This substantial difference is offset somewhat by a higher device reimbursement for the nonsurgical lengthening implants. Complete analysis of reimbursements associated with use of these devices, however, requires consideration of the number of anticipated lengthenings and reimbursement for the index surgery, planned revisions, and incidence of complications [14].

The results of our study showed that total expansion reimbursements for the youngest patients receiving extendible endoprostheses may approach $400,000 even in the absence of complications, which are common. Endoprosthesis alternatives must be considered. Amputation and rotationplasty are alternatives to limb-preservation surgery [4, 12, 22, 30]. These surgeries require the patient to use an external prosthesis for ambulation. Longitudinal reimbursements for these surgeries in children have not been studied. Grimer et al. [14] investigated long-term reimbursements of amputation with prosthetic limb use compared with nonexpandable limb preservation and reported substantially lower reimbursements with limb preservation. The reimbursement associated with amputation with private insurance was $9442, with additional amounts for prosthesis fitting and maintenance of $16,033 per year. Adjusted for 2010 inflation, these amounts would be $12,778 and $21,698, respectively. Their 20-year projections for amputation and prosthesis use showed an eightfold reimbursement increase over use of a nonexpandable endoprosthesis [14]. When applied to a four-year-old male patient, their model shows total surgical and prosthetic reimbursement at skeletal maturity would be $273,154. By contrast, our model yielded total expansion reimbursements for the same patient from $70,076 to $379,000, depending on the anatomic location and choice of prosthesis. The early, multifold cost-effectiveness of endoprostheses reported by the authors for nonexpandable devices is not seen with the more expensive expandable devices [14]. If a child achieves skeletal maturity with the endoprosthesis intact, even with a revision, continued external prosthesis maintenance reimbursement amounts associated with amputation would overtake net reimbursements for expandable device use within a decade even for distal femoral devices requiring surgical lengthening.

Results from our study suggest that the initial, increased reimbursements for an expandable endoprosthesis capable of nonsurgical lengthening compared with one requiring surgical lengthening are negated if more than one surgical procedure is performed. This indicates that reimbursements for prostheses requiring surgical expansion are less than for nonsurgical expanding devices only in patients who are approaching skeletal maturity. These findings also were reflected in the late ages at which equivalence was reached. Given that limb-length discrepancies of 1 to 2 cm are treated effectively with a shoe lift and discrepancies of 4 cm may be treated with contralateral epiphysiodesis [35], these treatments combined with a conventional endoprosthesis may be considered in lieu of a growing prosthesis. When future shoe lift use is planned, careful assessment of skeletal age and predicted growth should be performed given the substantial variability of contralateral physeal growth rates [7]. Even with strict attention to growth potential, unanticipated limb length discrepancies may result, leaving the surgeon without an uncomplicated solution [7].

Although our goal was to create a model for comparing the reimbursements for lengthening these devices, complications will affect their ultimate financial impact. When reporting on tumor endoprosthesis reimbursements, Grimer et al. [14] reported an average of $1419 per year for maintenance or replacement of nonexpandable implants ($1920 in 2010 US dollars). Their analysis did not consider expandable implants and therefore the reported maintenance reimbursements reflected only the incidence of complications averaged over all implant recipients. Failure rates for extendible tumor endoprostheses are high and revision surgery is not uncommon for complications including infection, tumor recurrence, and prosthesis fracture [28, 3133]. Higher reimbursements for growing prostheses are explained partially by the added complexity of their lengthening mechanisms and their use in children [8, 16, 31], therefore opening them to modes of failure in addition to those described [19]. A high rate of prosthesis fracture is attributed to reduced structural integrity owing to the lengthening mechanism [28]. In the current study, premature physeal closure resulted in one patient. Flexion contractures may be more common in this population owing to repetitive lengthening without soft tissue stretching [16]. Maximum extension of the prostheses before skeletal maturity also may occur and require revision [28]. In addition, children tend to be more active than adults and may be less compliant with activity restrictions [26]. Overall we observed fewer complications with the nonsurgical lengthening prostheses, however, this limited series and those in the literature cannot provide statistical justification of one device over another [8, 9, 15, 16, 18, 20, 24, 25, 28, 31]. When considering inflation, the maintenance reimbursements for our noninvasive lengthening devices were similar to that reported by Grimer et al., albeit with less followup [14].

Expandable prostheses continue to evolve but their role remains ill-defined. Numerous small series have compared patient function, quality of life, and reconstruction longevity after expandable endoprosthesis and amputation or rotationplasty with external prosthesis; no one option has presented as a clear winner [4, 12, 21, 27, 29]. Lacking from these analyses has been any mention of the expense of these implants. Our findings showed that expandable prosthesis use requires continued financial investment on the part of the healthcare cost provider and the magnitude of that investment is correlated to the patient’s age, sex, tumor location, and complication incidence. Prosthesis selection or, more appropriately, lengthening mechanism selection also appears to have a considerable effect on the net reimbursements associated with these implants. Additional study is needed, but given similar or perhaps higher complication rates for the surgical lengthening devices, the smallness of the lengthening required to exceed the equivalence point allowing these implants a financial edge calls into question whether these devices should be used. The prosthesis is not at fault, but rather it is the substantial expense of taking a patient to the operating room. Unfortunately percutaneous lengthening procedures are performed more easily with fluoroscopy and to attempt surgical lengthening in the office setting precludes many techniques that decrease surgical site infection [10]. Our practice is to use nonsurgical lengthening endoprostheses when pediatric limb preservation is required.

Acknowledgments

We thank David Johnson, PA-C for his continued dedication and care for our pediatric patients.

Footnotes

Each author certifies that he or she has no commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. One of the authors (GDL) is a design consultant for Stryker Corp (Mahwah, NJ, USA) but does not receive royalties of any kind for the devices that are the subject of this manuscript.

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.

Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.

Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.

This work was performed at Moffitt Cancer Center, Tampa, FL, and All Children’s Hospital, St Petersburg, FL.

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