Orthopedics

Feature Article 

The Use of Triphasic Bone Graft for the Treatment of Pediatric Bone Cysts: Experience at 2 Institutions

Ting Zhang, MD; Charles T. Price, MD; James J. McCarthy, MD; Jie Nguyen, MD, MS; Kenneth J. Noonan, MD

Abstract

Unicameral/aneurysmal bone cysts can lead to pain, fracture, and limb deformity. In this study, the authors evaluated the outcome of triphasic bone graft to treat unicameral/aneurysmal bone cysts. They retrospectively evaluated 41 immature patients from a prospectively enrolled cohort from 2 institutions treated from May 9, 2007, to November 1, 2014. Medical record review and evaluation of radiographs and computed tomography scans were performed. The authors characterized replacement of the material by normal bone or recurrent cyst at final follow-up. They recorded rates of fractures and complications after treatment. Twenty-nine patients were treated in Wisconsin, and 12 patients were treated in Florida. Average follow-up was 2.8 years. At follow-up, 13 of 41 patients had cyst recurrence. Three patients had fracture after initial treatment; 2 were treated surgically. Two of 9 patients with extraosseous bone graft had soft tissue swelling, and 1 required debridement. Complications did not differ by cyst type, location, sex, age, or use of internal fixation. For 27 patients with at least 2-year follow-up, percent fill of triphasic bone graft at initial surgery correlated with rate of recurrence at final follow-up: 15 of 27 patients with no cyst recurrence at final follow-up had a mean of 100% initial fill, and 12 of 27 with cyst recurrence at final follow-up had a mean of 90% initial fill (P=.048). Using triphasic bone graft for the treatment of unicameral/aneurysmal bone cysts, the authors observed a 7% rate of clinical recurrence (3 of 41 had fracture). Because this material has the potential to be locally inflammatory, efforts are needed to keep it within the bone. [Orthopedics. 201x; xx(x):xx–xx.]

Abstract

Unicameral/aneurysmal bone cysts can lead to pain, fracture, and limb deformity. In this study, the authors evaluated the outcome of triphasic bone graft to treat unicameral/aneurysmal bone cysts. They retrospectively evaluated 41 immature patients from a prospectively enrolled cohort from 2 institutions treated from May 9, 2007, to November 1, 2014. Medical record review and evaluation of radiographs and computed tomography scans were performed. The authors characterized replacement of the material by normal bone or recurrent cyst at final follow-up. They recorded rates of fractures and complications after treatment. Twenty-nine patients were treated in Wisconsin, and 12 patients were treated in Florida. Average follow-up was 2.8 years. At follow-up, 13 of 41 patients had cyst recurrence. Three patients had fracture after initial treatment; 2 were treated surgically. Two of 9 patients with extraosseous bone graft had soft tissue swelling, and 1 required debridement. Complications did not differ by cyst type, location, sex, age, or use of internal fixation. For 27 patients with at least 2-year follow-up, percent fill of triphasic bone graft at initial surgery correlated with rate of recurrence at final follow-up: 15 of 27 patients with no cyst recurrence at final follow-up had a mean of 100% initial fill, and 12 of 27 with cyst recurrence at final follow-up had a mean of 90% initial fill (P=.048). Using triphasic bone graft for the treatment of unicameral/aneurysmal bone cysts, the authors observed a 7% rate of clinical recurrence (3 of 41 had fracture). Because this material has the potential to be locally inflammatory, efforts are needed to keep it within the bone. [Orthopedics. 201x; xx(x):xx–xx.]

Unicameral bone cysts (UBCs) and aneurysmal bone cysts (ABCs) are the most common benign intraosseous lesions found in skeletally immature individuals. The annual incidence is approximately 1 per 10,000 children, with a male predominance of 2:1.1 Although diagnosis is frequently straightforward, management remains controversial, and no single method has emerged as the standard of care.2

Current treatment includes, but is not limited to, open curettage and bone grafting with either autogenous or allogeneic bone, decompression, and internal fixation.3 After curettage of a UBC/ABC, the large remaining defect and small patient size often make autogenous bone graft an impractical solution. Percutaneous injection of methylprednisolone acetate has shown success rates ranging from 50% to 80%, with downsides of repeated injections and prolonged limitations of physical activities.4 Despite osteogenic potential, autologous bone marrow aspirate injection has not shown advantage compared with steroid.5 Di Bella et al6 found a favorable result by combining demineralized bone matrix and autologous bone marrow, compared with steroid injection.

Triphasic bone graft that has 75% calcium sulfate, 25% calcium phosphate, and beta-tricalcium phosphate granules is a bone graft substitute that can be injected or manually packed into open bone voids (PRO-DENSE; Wright Medical, Memphis, Tennessee). The paste is essentially a bone graft substitute that resorbs and is replaced with bone during the healing process. Calcium sulfate, which resorbs first, is the primary osteoconductive filler, and calcium phosphate provides a secondary porous scaffold that is resorbed after the primary filler. Beta-tricalcium phosphate granules are resorbed in the third and final phase. The triphasic nature of this bone graft has shown a favorable resorption pattern in animal studies.7

This retrospective review study was performed to evaluate the clinical results, complications, and radiographic healing rates of this material in children who underwent treatment of UBCs/ABCs.

Materials and Methods

The authors retrospectively reviewed a prospectively enrolled cohort of 41 immature patients (<18 years old) from 2 institutions who were treated for a UBC/ABC with triphasic bone graft from May 9, 2007, to November 1, 2014. The diagnosis was confirmed from biopsy (ABC) or the presence of straw-colored fluid aspiration indicative of UBC. Primary or recurring, with recurrence defined as a previously treated lesion, bone cysts requiring surgery with or without instrumentation were included in this study.

Patients' electronic medical records were reviewed in a retrospective fashion once institutional review board approval had been obtained. The authors recorded demographic information, presenting symptoms, surgical methodology, and patients' course after treatment. At surgery, the cyst could be filled with triphasic bone graft after open curettage and packing or via injection with the material after the cyst was aspirated.

Standard radiographs were evaluated to characterize the size of the initial cyst, the degree of fill after surgery, and the presence of recurrent cyst at most recent follow-up radiograph (Figure 1). The authors attempted to confirm their radiographic methodology at these time points through comparison with available computed tomography data. A subgroup of patients had a computed tomography scan of the lesion after treatment (n=14). Eight of these patients had recurrence; thus, the authors compared their radiograph-based method of calculating cyst size recurrence percentage (maximum anteroposterior width × height [Figure 1]) with computed tomography–documented recurrence. Computed tomography volume was calculated with standard software (Volume Viewer; General Electric Company, Boston, Massachusetts). Initial computed tomography scans were acquired in 0.625- or 1.25-mm thick slices depending on the size of the structure imaged (ie, humerus, 1.25 mm; foot, 0.625 mm). This measurement was performed by 1 of the authors who is a fellowship-trained pediatric radiologist (J.N.). In these 8 cases where a recurrence was noted on both the computed tomography scan and the radiographs, the authors' method of estimating recurrent cyst size from 2-dimensional radiographic studies differed from computed tomography data by only 3% to 7% (Table 1).

Preoperative anteroposterior (A) and lateral (B) radiographs of a distal femoral metaphyseal unicameral bone cyst. Ten months later, the anteroposterior (C) and lateral (D) radiographs of the lesion show no recurrence. Measures of the healed cyst consist of the maximum width and height.

Figure 1:

Preoperative anteroposterior (A) and lateral (B) radiographs of a distal femoral metaphyseal unicameral bone cyst. Ten months later, the anteroposterior (C) and lateral (D) radiographs of the lesion show no recurrence. Measures of the healed cyst consist of the maximum width and height.

Percentage of Cyst Recurrence: Comparison Between Radiograph and Computed Tomography Scan Measurements for Recurrence in 8 Patients Who Had Both Studies

Table 1:

Percentage of Cyst Recurrence: Comparison Between Radiograph and Computed Tomography Scan Measurements for Recurrence in 8 Patients Who Had Both Studies

In terms of the clinical outcome of pediatric ABCs/UBCs treated with triphasic bone graft, within this multicenter chart review study, the authors documented patients' pain level per subjective report on a pain scale of 0 to 10 and their postoperative activity level. The authors additionally documented the rate of fractures after treatment and any complications that occurred from treatment. Statistical analyses were performed with Fisher's exact test and the Wilcoxon signed rank sum test, and significance was set at P<.05.

Results

Twenty-nine patients were treated in Wisconsin and 12 were treated in Florida. There were 35 UBCs and 6 ABCs (Table 2). Eighteen patients presented with fracture, 3 patients presented with incidental radiographic finding, and 20 presented with pain without obvious fracture. The average age when the lesion was first identified was 8.6 years (range, 9 months to 14 years). The average duration from diagnosis to treatment with triphasic bone graft was 5 months (range, 0–52 months). The diagnosis of UBC/ABC was made by variable combinations of biopsy, cyst aspiration, and cystogram. Eight of the 41 patients had the diagnosis of UBC confirmed via aspiration of characteristic straw-colored fluid and complete filling via cystogram. Thirty-three of the 41 patients had the diagnosis confirmed from biopsy. Eleven of these patients had bloody aspirates and underwent open biopsy even if a cystogram was suggestive of a UBC. Twenty-three patients underwent open triphasic bone graft placement, and 18 patients underwent injection of the material. Nine of the 41 patients had concomitant internal fixation, mostly in the lower extremity. Five patients had the proximal femur stabilized with a femoral hip device, and 2 patients had their femoral shaft lesion stabilized with flexible nails. One humerus and 1 tibia were similarly stabilized with flexible nails in addition to the triphasic bone graft.

Cyst Location

Table 2:

Cyst Location

Radiographs and computed tomography scans were available to document cyst recurrence. Fourteen of 41 patients had a computed tomography scan between 12- and 18-month follow-up visits. On the basis of these studies, 8 patients had recurrent cysts and 6 did not. At the most recent follow-up, radiographs were analyzed in all patients. On the basis of these studies, 13 patients had recurrent cysts with an average total follow-up time of 43 months, and 28 patients did not have recurrence with an average total follow-up time of 28 months. Those patients with cyst recurrence had an average recurrence of 17% (range, 3%–68%) of the original cyst size. In the 13 patients with a recurrent cyst, the average time to cyst recurrence was 21 months (range, 2–60 months). Cyst enlargement greater than the original cyst size was not observed at the latest follow-up.

There were no differences in recurrence rate or fracture rate by cyst type, location, sex, age, or use of internal fixation. At the 2-year follow-up, those cysts with 100% fill had a lower rate of recurrence than those with 90% or less fill (P=.048). In terms of complications, 3 of 41 patients had recurrent fractures. For these 3 patients, times from initial treatment to fracture were 12, 16, and 38 months and they received internal fixation, triphasic bone graft refill, and conservative treatment with a sling, respectively. Radiographic fill, radiographic healing, and clinical outcomes of patients with cyst recurrence and fracture complication are presented in Table 3. Nine of 41 patients were noted to have triphasic bone graft outside of the confines of the cyst on the immediate postoperative radiograph (Table 4). For these patients, the average time for resolution was 5 months (range, 3–6 months).

Different Percent Fills and the Radiographic and Clinical Outcomes in Patients With Cyst Recurrence and FractureDifferent Percent Fills and the Radiographic and Clinical Outcomes in Patients With Cyst Recurrence and Fracture

Table 3:

Different Percent Fills and the Radiographic and Clinical Outcomes in Patients With Cyst Recurrence and Fracture

Triphasic Bone Graft Extravasation, Soft Tissue Inflammation, and Resolution Time

Table 4:

Triphasic Bone Graft Extravasation, Soft Tissue Inflammation, and Resolution Time

The presence of the material outside of the cyst and in the soft tissues was occasionally problematic. One patient had injection of a calcaneal cyst, and a portion of the material was extruded into the peroneal tendon sheath and tracked proximally in the sheath. She had moderately severe pain and inflammation in the sheath and underwent an additional surgery for peroneal tendon and tendon sheath debridement (Figure 2). Even when the material was confined to the cyst, there were a few instances of inflammation and pain and swelling within the foot. One boy had pain and local swelling after a calcaneal cyst injection. Another patient had superficial cellulitis, empirically treated with cephalexin, which resolved with oral antibiotics.

Preoperative anteroposterior (A) and lateral (B) radiographs of a presumed calcaneal unicameral bone cyst. The diagnosis was confirmed with aspiration and cystogram. Treatment consisted of percutaneous injection of triphasic bone graft. Initial postoperative radiographs showed excellent filling, yet leakage of the material was noted to be lateral and proximal and presumably within the peroneal sheath. The child had significant pain and tenderness in the peroneal tendons, and she underwent debridement of the tendon sheath (C, D). Final follow-up radiographs showed slight recurrence with resolution of the peroneal material (E, F).

Figure 2:

Preoperative anteroposterior (A) and lateral (B) radiographs of a presumed calcaneal unicameral bone cyst. The diagnosis was confirmed with aspiration and cystogram. Treatment consisted of percutaneous injection of triphasic bone graft. Initial postoperative radiographs showed excellent filling, yet leakage of the material was noted to be lateral and proximal and presumably within the peroneal sheath. The child had significant pain and tenderness in the peroneal tendons, and she underwent debridement of the tendon sheath (C, D). Final follow-up radiographs showed slight recurrence with resolution of the peroneal material (E, F).

One patient developed laryngospasm during the injection of the material and required admission overnight to monitor pulmonary function.

Discussion

Preliminary biomechanical studies have shown that calcium sulfate/calcium phosphate composite graft has an initial compressive strength of 50 to 70 MPa and thus appears to be a solid filling agent for cystic structures.7 After injection in animals, there has been a remarkable increase in the amount and strength of bone regeneration using calcium sulfate/calcium phosphate composite graft.7 In an in vitro study, 90% of the implant material was resorbed after 7 days for the pure calcium sulfate controls and after 24 days for the calcium sulfate/calcium phosphate composite.7

In a recent pilot study, 16 pediatric patients with bone cysts were treated with curettage, decompression, and injection of a calcium sulfate/calcium phosphate composite.8 A 93.7% radiographic healing rate and return to full activity, including sports, at an average of 3.1 months after treatment, with follow-up occurring at an average of 16 months after treatment, were documented.

The current study involved a retrospective evaluation of triphasic bone graft as a treatment for UBCs/ABCs in growing children with longitudinal follow-up averaging 2.8 years. Using triphasic bone graft for UBC/ABC treatment, the authors had a 7% rate of clinical recurrence (3 of 41 had pain/fracture). Despite lack of clinical problems, the authors noted radiographic recurrence in 12 of 27 patients who were followed for greater than 2 years. In this study with longer follow-up, those patients followed longer were more likely to have mild recurrence. In this study, the longest time observed for a cyst to recur was 52 months. Those cysts that were fully filled fared much better regarding these findings.

The authors also compared their results with those of multiple treatment studies (Table 5).5,9–13 In summary, decompression alone, decompression with intramedullary nail, and percutaneous injection of apatitic calcium phosphate had clinical cyst recurrence comparable to that of the current study. Demineralized bone matrix, autogenous bone marrow, steroid injection, and a combination of steroid and autogenous bone marrow aspirate injection showed higher clinical recurrence, which required a secondary procedure in all cases. Many studies have gauged radiographic healing and recurrence with the Neer classification with various modifications, the criteria of Capanna, or predefined parameters. In contrast, the authors used standard software to compare their radiographic quantification estimation with computed tomography volume computation. On the basis of these differences, the authors judge the rate of at least partial recurrence from their study to be 32% and the range of partial recurrence from the other studies to be 16% to 58%.

Outcomes of Treatment of Unicameral/Aneurysmal Bone Cysts Reported in the Literature

Table 5:

Outcomes of Treatment of Unicameral/Aneurysmal Bone Cysts Reported in the Literature

In the authors' experience, a triphasic bone graft may have a local inflammatory effect on soft tissues, with this happening predominately in the foot. Since the completion of this study, the authors have had another patient who had moderately severe inflammation of the foot and leg after injection into the first metatarsal bone (Figure 3). Currently and as a result of this study, the authors take great pains to make sure the triphasic bone graft is contained within the cyst wall and is completely removed from soft tissues. It would seem to be prudent to avoid spread into an adjacent joint to avoid the possibility of chondrolysis. The authors have also chosen to use more inert material such as allograft for subcutaneous bones (distal fibula) that, if inflamed, could lead to wound breakdown.

Although not included in the original cohort, this child had a unicameral bone cyst of the first metatarsal and underwent open biopsy and packing of the lesion with triphasic bone graft. She developed severe pain and global inflammation of the lower leg.

Figure 3:

Although not included in the original cohort, this child had a unicameral bone cyst of the first metatarsal and underwent open biopsy and packing of the lesion with triphasic bone graft. She developed severe pain and global inflammation of the lower leg.

The authors and others have noted laryngospasm in a few patients when the material is pressurized into the cyst. This is presumably due to electrolyte imbalances at the moment.14 As a result, the authors recommend intubation for these procedures.

Although their sample was small, the authors hope that, in the long run, this study will lead to larger, confirmatory studies drawing more confidence in their conclusions. Triphasic bone graft appears to be a viable treatment option for UBCs/ABCs, and improved radiographic appearance at follow-up is noted when the cyst is filled completely. There appears to be good clinical healing (low rates of fracture and pain) and some radiographic recurrence that is small and subclinical. Longer-term follow-up seems to correlate with development of these small recurrences. Although the incidence is low, triphasic bone graft has the potential to be locally inflammatory. Thus, efforts are needed to keep it within the cyst wall and to consider carefully the effect of severe inflammation on articular cartilage and soft tissues with potential wound issues.

References

  1. Cha SM, Shin HD, Kim KC, Park JW. Does fracture affect the healing time or frequency of recurrence in a simple bone cyst of the proximal femur?Clin Orthop Relat Res. 2014; 472(10):3166–3176. doi:10.1007/s11999-014-3768-6 [CrossRef]
  2. Wilkins RM. Unicameral bone cysts. J Am Acad Orthop Surg. 2000; 8(4):217–224. doi:10.5435/00124635-200007000-00002 [CrossRef]
  3. Boseker EH, Bickel WH, Dahlin DC. A clinicopathologic study of simple unicameral bone cysts. Surg Gynecol Obstet. 1968; 127(3):550–560.
  4. Scaglietti O, Marchetti PG, Bartolozzi P. Final results obtained in the treatment of bone cysts with methylprednisolone acetate (depomedrol) and a discussion of results achieved in other bone lesions. Clin Orthop Relat Res. 1982; 165:33–42.
  5. Chang CH, Stanton RP, Glutting J. Unicameral bone cysts treated by injection of bone marrow or methylprednisolone. J Bone Joint Surg Br. 2002; 84(3):407–412. doi:10.1302/0301-620X.84B3.12115 [CrossRef]
  6. Di Bella C, Dozza B, Frisoni T, Cevolani L, Donati D. Injection of demineralized bone matrix with bone marrow concentrate improves healing in unicameral bone cyst. Clin Orthop Relat Res. 2010; 468(11):3047–3055. doi:10.1007/s11999-010-1430-5 [CrossRef]
  7. Urban RM, Turner TM, Hall DJ, Inoue N, Gitelis S. Increased bone formation using calcium sulfate-calcium phosphate composite graft. Clin Orthop Relat Res. 2007; 459:110–117. doi:10.1097/BLO.0b013e318059b902 [CrossRef]
  8. Gentile JV, Weinert CR, Schlechter JA. Treatment of unicameral bone cysts in pediatric patients with an injectable regenerative graft: a preliminary report. J Pediatr Orthop. 2013; 33(3):254–261. doi:10.1097/BPO.0b013e318285c56c [CrossRef]
  9. Masquijo JJ, Baroni E, Miscione H. Continuous decompression with intramedullary nailing for the treatment of unicameral bone cysts. J Child Orthop. 2008; 2(4):279–283. doi:10.1007/s11832-008-0114-0 [CrossRef]
  10. Canavese F, Wright JG, Cole WG, Hopyan S. Unicameral bone cysts: comparison of percutaneous curettage, steroid, and autologous bone marrow injections. J Pediatr Orthop.2011; 31(1):50–55. doi:10.1097/BPO.0b013e3181ff7510 [CrossRef]
  11. Cho HS, Seo SH, Park SH, Park JH, Shin DS, Park IH. Minimal invasive surgery for unicameral bone cyst using demineralized bone matrix: a case series. BMC Musculoskelet Disord. 2012; 13:134. doi:10.1186/1471-2474-13-134 [CrossRef]
  12. Thawrani D, Thai CC, Welch RD, Copley L, Johnston CE. Successful treatment of unicameral bone cyst by single percutaneous injection of alpha-BSM. J Pediatr Orthop. 2009; 29(5):511–517. doi:10.1097/BPO.0b013e3181aad704 [CrossRef]
  13. Rougraff BT, Kling TJ. Treatment of active unicameral bone cysts with percutaneous injection of demineralized bone matrix and autogenous bone marrow. J Bone Joint Surg Am. 2002; 84(6):921–929. doi:10.2106/00004623-200206000-00005 [CrossRef]
  14. Nystrom L, Raw R, Buckwalter J, Morcuende JA. Acute intraoperative reactions during the injection of calcium sulfate bone cement for the treatment of unicameral bone cysts: a review of four cases. Iowa Orthop J. 2008; 28:81–84.

Percentage of Cyst Recurrence: Comparison Between Radiograph and Computed Tomography Scan Measurements for Recurrence in 8 Patients Who Had Both Studies

Patient No.Radiographic Fill at SurgeryRadiographic HealingComputed Tomography Healing
490%82%89%
590%49%49%
790%81%74%
860%61%57%
1080%77%80%
12100%38%32%
1490%80%77%
O5 (5th patient from Orlando)80%65%61%

Cyst Location

LocationNo.
Proximal femur9
Distal femur3
Proximal humerus20
Calcaneus4
Proximal tibia2
Distal tibia2
Fibula1

Different Percent Fills and the Radiographic and Clinical Outcomes in Patients With Cyst Recurrence and Fracture

Patient No.DiagnosisaLocation of CystRadiographic Fill at SurgeryRadiographic HealingTime After Surgery Until Return to Full Activity, moFracturebFracture Management
10Femur100%100%2.50
20Femur100%100%0.80
30Humerus100%100%2.80
40Humerus90%82%1.40
50Humerus90%49%2.50
60Humerus90%100%2.00
71Humerus90%81%0.80
80Humerus60%61%1.50
90Humerus90%100%1.40
100Calcaneus80%77%2.00
110Humerus100%100%2.50
121Humerus100%38%2.91Refill
130Humerus100%100%3.40
141Tibia90%80%2.00
150Humerus100%100%1.00
160Tibia100%100%1.50
170Humerus100%100%1.60
180Humerus100%86%3.50
190Humerus100%100%0.40
200Calcaneus100%100%0.30
210Humerus90%100%2.21Sling
220Fibula100%100%1.50
230Humerus80%100%1.00
240Humerus100%100%1.70
250Calcaneus100%100%2.10
260Femur100%100%1.50
271Tibia100%100%2.80
280Calcaneus100%100%1.40
290Femur100%100%1.40
300Femur100%48%2.70
310Femur100%100%4.40
320Humerus80%100%2.50
330Femur80%65%6.21Dynamic hip screw
340Femur100%100%3.80
350Femur100%87%2.00
360Humerus100%100%0.50
371Femur100%100%2.60
380Femur100%100%8.70
390Humerus90%65%1.20
401Tibia80%94%6.20
410Femur100%100%2.50

Triphasic Bone Graft Extravasation, Soft Tissue Inflammation, and Resolution Time

Cyst LocationDistance Outside of Bone, mmTime of Extraosseous Resolution, moSoft Tissue Inflammation/Wound Complicationa
Tibia160
Humerus261
Femur1540
Calcaneus69.741
Femur160
Humerus260
Humerus240
Humerus1.5630
Humerus260

Outcomes of Treatment of Unicameral/Aneurysmal Bone Cysts Reported in the Literature

Study (Year)TreatmentMean Follow-upClinic RecurrenceRadiographic Recurrence
Cho et al11 (2012)Demineralized bone matrix24 mo8%16%
Canavese et al10 (2011)Autogenous bone marrow81 mo17%58%
Canavese et al10 (2011)Decompression31 mo0%30%
Canavese et al10 (2011)Steroid82 mo23.5%58%
Thawrani et al12 (2009)Apatitic calcium phosphate36 mo0%46%
Masquijo et al9 (2008)Decompression with intramedullary nail9.8 y8%35%
Rougraff et al13 (2002)Autogenous bone marrow + demineralized bone matrix50 mo22%30%
Chang et al5 (2002)Steroid44 mo49%
Chang et al5 (2002)Autogenous bone marrow44 mo57%
CurrentTriphasic bone graft33 mo7%32%
Authors

The authors are from American Family Children's Hospital (TZ, JN, KJN), University of Wisconsin School of Medicine and Public Health, Madison, Madison, Wisconsin; The Center for Pediatric Orthopedics at Arnold Palmer Hospital for Children (CTP), Orlando, Florida; and the Department of Orthopaedics (JJM), Cincinnati Children's Hospital, Cincinnati, Ohio.

Dr Zhang, Dr Price, Dr Nguyen, and Dr Noonan have no relevant financial relationships to disclose. Dr McCarthy is a paid consultant for Orthopediatrics, is a paid presenter for Synthes, is on the speaker's bureau of Johnson & Johnson, and has received grants from Nuvasive.

Correspondence should be addressed to: Kenneth J. Noonan, MD, American Family Children's Hospital, University of Wisconsin School of Medicine and Public Health, Madison, 1675 Highland Ave, Madison, WI 53792 ( noonan@ortho.wisc.edu).

Received: January 27, 2018
Accepted: April 23, 2018

10.3928/01477447-20180806-02

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