CASE REPORT Open Access

A three-dimensional printed porousimplant combined with bone graftingfollowing curettage of a subchondral giantcell tumour of the proximal tibia: a casereportMinxun Lu, Jie Wang, Fan Tang, Li Min, Yong Zhou, Wenli Zhang and Chongqi Tu*

Abstract

Background: Subchondral bone is commonly affected in cases of giant cell tumour (GCT) of the proximal tibia.Numerous studies have stated that retaining a sufficient subchondral bone layer could decrease the possibilities ofpostoperative degenerative changes and mechanical failure of the knee joint. However, the most commonly usedmethods of cement packing only or cement packing combined bone grafting have some limitations regarding theprotection of subchondral bone after surgery. Our paper describes our attempt to reconstruct a tumorous defectassociated with the subchondral area in the proximal tibia with a three-dimensional (3D)-printed porous implantcombined with bone grafting and our evaluation of the short-term outcomes.

Case presentation: A 42-year-old man with a Campanacci grade II GCT visited our institution for initial assessment.Radiographs showed a tumour located at the epiphyseal part of the proximal tibia, and had invaded the subchondralarea. Considering that the residual subchondral bone had to be protected, we used an autograft to ensure a highintegration rate between the graft and host subchondral bone. We also used three-dimensional (3D) printingtechnology to design and fabricate a personalized porous implant to mechanically support the graft andsubchondral area and help avoid degenerative changes and mechanical failure. At the last follow-up at 29months postoperatively, the patient had satisfactory limb function and no further damage was seen to thesubchondral area and articular surface.

Conclusions: The 3D-printed porous implant combined bone grafting may be a feasible option in the reconstructionof defects that are close to the subchondral area following extensive intracurettage of GCTs. Moreover, it can result ingood postoperative function and low complication rates. However, consistent follow-up is required to clarifyits long-term outcomes.

Keywords: Proximal tibia, Giant cell tumour, Epiphysis, Subchondral bone, Three-dimensional printed implant,Porous, Bone graft, Case report

* Correspondence: Tuchongqi@yeah.netDepartment of Orthopedics, West China Hospital, Sichuan University, No. 37Guoxue Street, Chengdu 610041, People’s Republic of China

© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Lu et al. BMC Surgery (2019) 19:29 https://doi.org/10.1186/s12893-019-0491-y

BackgroundGiant cell tumour (GCT) of the bone is a benign but lo-cally aggressive tumour with a relatively high recurrencerate after primary treatment [1]. GCTs mainly occur be-tween the age of 20 and 40 years [2]. Epiphyseal regionsof the long bones are the most commonly affected, espe-cially the distal femur and proximal tibia [3]. Further-more, subchondral bone around the knee is commonlyinvaded and/or destroyed by Campanacci Grade I and IIGCTs of the epiphyseal region. Previous studies havestated that a lower quantity of subchondral boneremaining can result in postoperative mechanical failure,including deformity, fracture, and even collapse of thearticular surface [4], which may result in discomfort andpoor joint function of the knee [4, 5]. Therefore, protect-ing the retained subchondral bone after extensive intra-curettage and postoperatively promoting the ingrowth ofsubchondral bone are the most crucial principles for thetreatment of GCTs with Campanacci Grade I and II thatoccur around the knee. Currently, cement packing [6],bone grafting [7], and a combination of cement packingand bone grafting [5] are the most common and accept-able choices for reconstruction. Cement packing was ini-tially the most popular method, the lack of boneinducibility and conductibility is the major disadvantageof the method. In contrast, bone grafting provides excel-lent biocompatibility and enables biological reconstruc-tion. However, mechanical strength is often lacking inbone grafts [8]. Therefore, combined bone grafting andcement packing seems to be the best option. Subchon-dral bone is protected from cement deconstruction bythe bone graft that is placed between the subchondralbone and cement [9], but the problems related to thegraft-cement interface still exist in this combination. Weproposed the use of a three-dimensional (3D)-printedporous implant with scaffold structure combined withbone grafting, which would ideally enable a high level ofosseointegration, therefore resulting in an improved bio-logical interface between the graft and implant after re-construction when compared to cement packingcombined bone grafting. To the best of our knowledge,no studies have been performed on this subject. Ourpaper describes a case wherein reconstruction was per-formed with a combined bone grafting and 3D-printedporous implant for a tumour-induced defect of the prox-imal tibia in a patient with Campanacci grade II GCT.

Case presentationHistoryA 42-year-old man complained of progressive pain inthe left knee region without any limitation in dailyactivity for 3 months. He visited our institution forinitial assessment and underwent radiographic investi-gation in January 2016. A large radiolucent area

caused by osteolytic deconstruction in the epiphysealpart of the left proximal tibia was observed. Com-puted tomography (CT), magnetic resonance imaging,Tomosynthesis-Shimadzu metal artefact reductiontechnology (T-SMART), bone scan, and biopsy werethen performed to assess the precise diagnosis, safeborder of the lesion, condition of the surroundingbone, and lung condition. The lesion was finally diag-nosed as Campanacci Grade II GCT with no pulmon-ary metastasis. No fracture of the subchondral bonewas detected on the CT scan.Before surgery, the pain, knee joint function, percent-

age of affected area of the subchondral bone, and thick-ness of the residual subchondral bone layer wereprecisely evaluated. The pain at rest was evaluated ac-cording to the Visual Analog Scale (VAS) in which 0represents no pain and 10 represents the worst pain im-aginable. The range of knee joint motion was also re-corded. The percentage of affected area of thesubchondral bone was calculated as described by Chen[10]. The shortest distance from the articular surface tothe nearest margin of the tumour on radiographs wasdefined as the thickness of the residual pre-operativesubchondral bone layer. This distance was measuredwith imaging generated using the 3D-CT scan andTomosynthesis-Shimadzu metal artefact reduction tech-nology (T-SMART). Considering the poor condition ofthe retained subchondral bone, implantation using a3D-printed scaffold structure and supplemental bonegraft were performed to prevent further damage on thesubchondral bone that could potentially be caused bythe friction between the cement and subchondral bonewhen cement packing and to avoid formation ofnon-biological and rigid graft-cement interface that oc-curs after cement packing combined bone grafting. Thisstudy was approved and monitored by the local EthicalCommittee. The patient was informed about the risksand benefits of the treatment, after which he providedwritten informed consent.

Implant design and fabricationThe implant was fabricated by Chunli Co, Ltd., Tongz-hou, Beijing, China. The primary aims when designingthe implant were: maintaining the articular surface inthe proper position, preventing collapse of the subchon-dral bone and joint surface, and promoting healing be-tween the subchondral bone and graft. Therefore, theimplant needed a porous bearing surface with a greatability of osseointegration and a porous strut providingeffective axial support as per the appropriate length. Toanalyse and evaluate the size and shape of cavity causedby tumorous deconstruction, importing 3D CT scan datainto the Mimics V17.0 software (Materialise Corp.Belgium) was initially performed. The possible size and

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shape of the implant was preliminarily calculated withthe Mimics software using the sagittal, coronal, andtransverse images obtained via the CT scan. The implantprototype using the initial data was created by Solid-works 2016 (Dassault Systemes, France). To ensure sat-isfactory fitting in the tumorous cavity of the proximaltibia, the size and shape of the implant was optimizedvia computer simulation of implantation. Consideringthe convenience of implantation, the final implant con-sisted of two parts that could be assembled, including atruncated ellipsoid cone-shaped plate with 10mm thick-ness (Fig. 1), and a square frustum-shaped strut with 45mm axial length (Fig. 2). To assemble the two partstightly, a specialized slideway, which can mechanicallyprevent dropping and slipping of the strut, was createdon the bearing plate; the appropriate slider was requiredto be located on the strut. Three screw holes were de-signed to thoroughly affix the strut to the unaffectedcortex of the proximal tibia. Except for the specializedslideway and slider, the whole implant was designedusing a scaffold structure. For fabricating the implant,

Electron Beam Melting technology (ARCAM Q10,Sweden) was applied (Fig. 3).

SurgeryThe surgery was performed by a senior surgeon(Chongqi Tu). With the patient under general anaesthe-sia, the GCT of proximal tibia was exposed through alateral approach. Before intracurettage, mini drill biteswere used to minimize the bone loss caused by the drill.To reduce the rate of local recurrence, the invaded softtissue over the tumour cortex was removed. Then, ex-tensive intracurettage was performed with a high-speedburr and electrocauterization repeatedly to completelyremove the tumour. After the curettage was completed,phenol, hydrogen peroxide solution, and distilled waterpulse irrigation was used to rinse the cavity. The bonegraft obtained from the patient’s iliac bone was placeddirectly under the residual subchondral bone to providebiomechanical support. Then, a bearing plate with a por-ous surface was implanted into the cavity just under thegraft and the strut was inserted into the cavity throughthe slideway on the porous plate (Fig. 4). After confirm-ing both locations of the plate and strut of the implant,the three screws were fixed to the contralateral side ofthe proximal tibia cortex to enhance the primary stabil-ity of the implant (Fig. 5).

Postoperative managementConsidering insufficient primary stability in the earlypostoperative period, the patient was allowednon-weight-bearing standing and walking with twocrutches 3 weeks after surgery. However, range of motionexercises of the knee were performed from postoperativeweek 4. Partial weight-bearing with crutches was encour-aged from 6weeks postoperatively, followed by gradualfull weight-bearing. The patient was followed up everymonth for the first 3 months, then every 3months there-after. The postoperative pain, range of motion, degenera-tive changes, thickness of subchondral bone layer,oncology outcomes, and radiographs were assessed ateach follow-up visit to verify the outcomes of the3D-printed implant reconstruction.

OutcomeThe patient was followed up over a duration of 29months. The preoperative VAS score was 7, which de-creased to 0 after the surgery. There was no detectabledifference in the range of knee motion, which was satis-factory in the preoperative and postoperative period,with a normal range. Before the surgery, the percentageof the affected subchondral area was 48.2% (Fig. 6) andthe thickness of the subchondral bone layer was lessthan 3 mm. However, because of the excellent integra-tion between the graft and retained subchondral bone,

Fig. 1 a-d. 3D model of bearing plate: (a) top-bottom view; (b)anterior-posterior view; (c) lateral view; (d) plate with scaffold structure

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the subchondral bone layer was noticeably thicker at thelast follow-up, which is 10.9 mm. Furthermore, no de-generative changes were observed during the follow-upperiod. No fracture or collapse of articular surface wasdetected. No local recurrence or lung metastasis oc-curred. Radiography indicated that the implant fittedwell with the tibia and no signs of complications, includ-ing breakage and displacement, were found (Fig. 7).

Discussion and conclusionCampanacci grade I or II GCTs have a lower recurrencerate and are less aggressive than grade III GCTs. How-ever, the subchondral bone or even articular surfacemight be affected when grade I or II GCTs are located atthe epiphyseal part of the proximal tibia. Several studieshave indicated that insufficient postoperative subchon-dral bone thickness would increase the risk for degen-erative changes, deformity, fracture, and even collapse ofthe knee joint [11–13]. According to a study by Abdel-rahman [4], the probability of degeneration in the groupwhere the thickness was less than 10 mm was 2.5 timesthat of the group where the thickness was more than 10mm. The most acceptable explanation related to theinteraction between mechanical failure and thickness of

the subchondral bone layer might be that the thinnersubchondral layer has a lower shock-absorbing capacity[7, 14–16]. Considering the ages of the patients withGCTs, maintaining a normal articular surface and pre-venting further damage to the subchondral bone arevery crucial. Although extensive intracurettage might bea potential risk factor for operative damage on the sub-chondral bone, this procedure was necessary to maintaina lower recurrence rate after treatment of GCTs. How-ever, the best reconstruction option was still controver-sial, especially regarding the aspect of subchondral boneand articular surface protection. Three methods for fill-ing the cavity have been reported and discussed [4–7,17, 18]. Among these, cement packing is the most fre-quently used method. However, cement has no ability toinduce the growth of surrounding bone, and could in-stead result in the absorption of the surrounding bonebecause of the significant difference in the materialproperties between cement and bone. Consequently, asclerotic rim would be inevitably apparent, separatingthe cement from the surrounding bone and subchondralbone layer [18]. Welch et al. [16] described that this rimcould decrease the shock-absorbing capacity of the sub-chondral bone layer. Furthermore, the sclerotic rim

Fig. 2 a-e. 3D model of strut: (a) anterior-posterior view; (b) lateral view; (c) top-bottom view; (d) bottom-top view; (e) strut with scaffold structure

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Fig. 3 a-e. Components of implant: (a) top-bottom view of plate; (b)bottom-top view of plate; (c) anterior-posterior view of strut; (d)lateral view of strut; (e) Assembled implant with screws

Fig. 4 a-c. Intraoperative pictures: (a) indicating graft transplantation; (b) indicating implantation of plate; (c) indicating implantationof strut

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could increase the micro-movement between the cementand bone, resulting in further damage to the surround-ing bone such as subchondral bone. In contrast, an auto-graft or allograft is a better choice for protection of thesubchondral bone. In a study by Benevenia et al. [19],nononcologic complications in patients of GCTs wereclearly reduced after bone grafting in the subchondralbone area. However, the mechanical strength was a con-cern when packing alone. Therefore, degenerativechanges and/or mechanical failure of the knee joint werealso seen to occur with this approach. Furthermore, ahigher rate of mechanical failure was seen when the cav-ity was filled using only bone graft when compared to

when it was filled using cement packing only. In an ani-mal model experiment [8], it was seen that the strengthof the subchondral defect filled with cancellous bonewas only slightly greater than that of the empty cavity.Therefore, the combination packing using graft and ce-ment, which provides both mechanical strength and bio-logical reconstruction, has been accepted by severalresearchers. It was seen that the sufficient supportstrength generated by cement packing and great boneconduction and induction provided by autograft/allograftwould ensure a low incidence of postoperative degenera-tive changes and mechanical failure. This was also seenin the study by Teng et al. [5]. However, the complica-tions related to non-biological bone-cement interfacehave still not been solved. We believe that 3D-printedporous implant reconstruction combined with bone graftwould provide adequate support strength and excellentosseointegration and would therefore be a bettermethod. In our case, we observed integration betweenthe residual subchondral bone and graft, resulting in suf-ficient thickness of the postoperative subchondral bonelayer to support the articular surface. This indicated arelatively low possibility of degenerative changes, frac-ture, or collapse of the knee joint in the future. Further-more, no radiolucent area was detected in thegraft-implant interface, indicating that the interface waswell integrated. No degenerative changes or mechanicalfailure were seen during the follow-up period of 29months.In addition to the shape and thickness of the bearing

plate, suitable strut length and appropriate settings withpore size and porosity to each part would be the mainfactors that enable good function with a low complica-tion rate. The main principle of shape design of thebearing plate is enlarging the contact area between theplate and surrounding bone to provide strong primarystability and to induce bone growth more easily. Whendesigning the bearing plate, osseointegration was themain priority. Thus, all settings related to scaffold struc-ture were intended to increase and enhance the bone in-growth by simulating the properties of trabecular bone.Torres-Sanchez [20] reported that a combination of poresize with a diameter of 500 μm and nearly 70% porositywould be a better option to simulate trabecular boneand to improve osseointegration. Therefore, the porousplate was designed with these parameters to provide anincreased osseointegration ability. Regarding the plate,the location of the edges and the plate thickness are im-portant factors. Although the edges of the plate insertedinto the surrounding bone could generate supplementalprimary stability, this edge design should be avoided insites that have no cortex or insufficient cortical thick-ness. In our case, plate thickness was an important partof the design. It is obvious that the thinner plate would

Fig. 5 a-b. Intraoperative pictures: (a) confirming the location ofimplant by the X-ray; (b) indicating screws fixation after theconfirmation of implant position

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have weaker mechanical strength. However, a relativelythick plate with adequate support strength might be anobstacle for strut implantation, which would generatethe major strength required to support the graft, sub-chondral bone, and articular surface. Therefore, we be-lieve that a thickness of 10 mm would be a better choice.Furthermore, some designing points of the strut were

also crucial, including the length, screw hole, pore size,and porosity. Because the major function of the strut isto provide mechanical support, a suitable length shouldbe precisely calculated and designed. If the strut is notlong enough, the plate, graft, subchondral bone, and ar-ticular surface would collapse due to the lack of mech-anical support. If the strut is longer than we needed, agreater amount of cortex will need to be removed to en-large the potential window of implantation, which wouldcause meaningless bone loss. Compared to the plate, thesettings with pore size and porosity of the strut weremore likely to require focus on the mechanical strengthto provide enough support. Therefore, the porous strutwe used was designed with a pore size of 400 μm and55% porosity, based on the design provided byTorres-Sanchez [20] to simulate the cortex.Appropriate bone graft obtained from the patient’s

iliac bone, placing the bearing plate with proper position,ensuring a stable connection between the plate andstrut, and effective fixation of screws were the key proce-dures during the surgery. The removal of the graft cor-tex obtained from the iliac bone was necessary toachieve a well-integrated interface between the subchon-dral bone and graft. Furthermore, ensuring a propershape of bone graft was also required to enlarge the con-tact area and to distribute the stress loaded on the

Fig. 6 A-B. Method used to measure the area of the subchondral bone affected by the giant cell tumor of the bone: (A) The width of epicondyleto middle of joint (A) and the width of affected subchondral area (a) were measured in the anteroposterior plane; (B) The whole width of joint (B)and the width of affected subchondral area (b) were measured in the lateral plane; (a × b/A × B) × 100 =% of the subchondral bonearea affected by tumor

Fig. 7 Anteroposterior radiograph of left tibia 29 months after 3D-printed implant reconstruction

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subchondral bone more evenly. When placing the plate,we should ensure there is no gap between both inter-faces, including subchondral bone-graft interface andgraft-plate interface, because the bone ingrowth wouldbe affected by the gap. After the plate was satisfactorilyplaced, the strut could be tightly assembled with theplate using a specialized slideway. Finally, we fixed thestrut using three screws to the cortex of the proximaltibia to achieve increased primary stability.We recognize the following limitations of this case re-

port. The duration of follow-up is not yet sufficient toverify the long-term efficacy of this alternative design ofimplant and surgical techniques. More complications orproblems might become apparent once these patientsare followed up for a longer time. One case is insuffi-cient to verify the advantages of the 3D-printed implantwith porous structure. However, the patients with sub-chondral bone affected by GCTs in the proximal tibia isextremely rare. Moreover, recruiting a large number ofpatients in one institution is difficult, because there arefew standard indications for 3D-printed prostheses atpresent. The complicated approval process and the highcost of 3D printing are some of the reasons why thismodality is not widely used. Therefore, a largermulti-institutional study is needed to adequately com-pare this approach with other types of reconstruction.Despite these shortcomings, this case study may providevaluable direction for further studies.Use of combination of 3D-printed porous implant and

bone grafting can be a treatment option for Campanaccigrade I or II GCTs of the proximal tibia with affectedsubchondral area after intracurettage. The appropriateshape of iliac graft, porous design setting of plate andstrut, tight and stable connection between plate andstrut, and use of three screws for fixation could lead tosatisfactory biomechanical support with biological inte-gration and prevent further damage to the subchondralarea and joint. As we have collected only short-termfollow-up results, the long-term efficacy of local controlsfor GCT and postoperative complications are yet to beobserved.

Abbreviations3D: Three-dimensional; CT: Computed tomography; GCT: Giant cell tumor;; T-SMART: Tomosynthesis-Shimadzu metal artefact reduction technology;VAS: Visual Analog Scale

AcknowledgementsNot Applicable.

FundingThe manufacturing of prosthesis was funded by National key research anddevelopment plan (2016YFC1102003).

Availability of data and materialsThe data of this article was available on request. Please feel free to contactMX Lu if someone wants to request the data.

DisclosureThe authors declare that there are no conflicts of interest.

Authors’ contributionsMXL and CQT were involved with the concept and design of this manuscript.JW, WLZ and LM was involved with the acquisition of subjects and data. MXLand CQT were involved in the design of the prosthesis. FT, YZ and CQT wereinvolved in postsurgical evaluation of the patients. All authors contributedtoward data analysis, drafting and critically revising the paper, gave finalapproval of the version to be published, and agree to be accountablefor all aspects of the work.

Ethics approval and consent to participateThis study was approved by the ethical committee of West China Hospital,Sichuan University (Chengdu, China) and performed in accordance with theethical standards of the 1964 Declaration of Helsinki. Written informedconsent of the patient t in this study was obtained.

Consent for publicationThe written consent to publish images or other personal or clinical details ofparticipants was obtained from study participants.

Competing interestsThe authors declare that they have no competing interests.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims in publishedmaps and institutional affiliations.

Received: 13 November 2018 Accepted: 19 February 2019

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