The mainstay of the surgical management of malignant osseous tumors is wide en bloc resection.1 In cases where limb function can be preserved, limb salvage has become the standard of care, with amputation reserved for recurrence, extensive tissue involvement with tumor, or inability to preserve neurovascular function distal to the intended resection.2,3 Any attempt at limb salvage will require reconstruction of the surgical defect created during tumor resection. Reconstructive options often involve any one, or a combination, of bulk allografts, modular or custom endoprostheses, arthrodeses, free vascularized autograft, osteosynthesis, or local pasteurized autografts.2,4,5
Many malignant osseous tumors (eg, osteosarcoma) tend to involve metaphyseal areas of long bones.6 However, some tumors (eg, Ewing sarcoma) have been shown to preferentially involve the diaphysis.7 Metaphyseal resections and reconstructions typically involve joint sacrifice, with subsequent arthroplasty or arthrodesis required for the reconstruction.8 However, focal diaphyseal resections (ie, diaphysectomy) and reconstructions offer the unique prospect of joint preservation via intercalary segmental reconstruction.4
Intercalary segmental reconstructions following diaphysectomy offers the advantages of preservation of native joints and/or physeal plates that may allow for normal physiologic growth and better functional outcomes when compared with joint replacement surgery.4 Classically, structural allograft with some form of osteosynthesis has been used for reconstruction of these defects.9 However, these are often fraught with complications, including infection, fixation failure, graft fracture, nonunion, graft resorption, and the potential for disease transmission.9–11 They also may require prolonged periods of immobilization or nonweight bearing during the healing process,1,10 which may obviate the functional advantages of joint preservation surgery.
Recently, modular intercalary endoprosthetics have gained acceptance for reconstructions of diaphysectomies. Long-term studies at multiple centers have shown the utility and longevity of these implants.1,12–19 The available reconstruction systems use conventional cemented or press-fit stems. Such stems require a sufficiently long osseous canal above and below the resection to properly fix the implant to host bone. For additional stability, incorporation of perpendicular transfixation pins or screws that capture holes within the stem can decrease the length of the intramedullary stems required.18 Patients who undergo extended diaphysectomy often require removal of bone into the comparatively wider metaphysis with thin cortices and short canal lengths, precluding use of these implants.
A novel method of stem fixation featuring compressive osseointegration has been developed during the past 2 decades.14,15,20–22 Although this system was originally designed to prevent stress shielding by applying compressive loads to the end of the bone within the diaphysis, this design significantly decreases the amount of bone required for implant fixation. Such short fixation methods may allow metaphyseal fixation for potential sparing of adjacent joints or open physes that might otherwise be sacrificed using traditional fixation methods.
This concept of compressive osseointegration has become commercially available as the Compress implant (Biomet, Inc, Warsaw, Indiana), approved by the Food and Drug Administration in 2003 for reconstruction of the distal femur after resection of bone tumors. This implant features an intramedullary anchor plug secured to the host bone by multiple, bicortical, small-diameter transfixation pins. The anchor plug is then attached to a spindle containing a spring mechanism, which uses stacked Belleville washers to compress a porous-coated collar on the implant body to the host bone cortex. The forces generated by the spring mechanism range from 400 to 800 lb and are selected by the surgeon based on native host bone cortical thickness.23 The resulting rigid fixation between the implant and the bone enhances the ability of the cortical bone to grow into the porous collar via Wolff's law and provides biologic fixation for long-term implant survival.
Potential problems in adapting this system to the metaphyseal portion of the bone can be anticipated due to anatomic differences in the bone surrounding the anchor plug. Cortical thickness is far less in the metaphysis, limiting the amount of force that can be applied before the bone fractures. In addition, the flaring anatomy requires the use of much longer transfixation pins, which are more susceptible to deformation from the compressive forces, again limiting the amount of force that can be applied to the system. Furthermore, widened metaphyseal anatomy can lead to eccentric positioning of the anchor plug, resulting in asymmetric forces that could lead to eccentric loading and failure of the anchor plug stem. Finally, custom shortening of the anchor plug to allow short segment fixation for joint-sparing reconstruction reduces the number of transfixation pins that can be used, increasing the load on each pin and adjoining bone.
Use of poly(methyl methacrylate) bone cement prior to implant insertion has been shown to permit additional implant fixation in bone that would otherwise fail from the applied loads.24–26 Accordingly, this method of augmenting implant fixation may be applicable to the use of the Compress system in metaphyseal bone. To accomplish this, cement must be injected into the metaphyseal bone prior to insertion of the anchor plug system. In addition to providing better support to the long transfixing pins, the cement can help centralize the anchor system, avoiding potential point overloads from asymmetric positioning. Finally, because cement is compressed against the endosteal surface of the bone, the entire cement plug may directly enhance stability by acting as an independent buttress against the compressive forces of the Compress system. This results from both the intrinsic compressive strength of the cement and the conical shape of the metaphyseal zone: the cement plug becomes larger than the opening through which the cement was injected, resisting pullout failure.
Materials and Methods
Combining the 2 concepts of shortening the anchor plug and strengthening the stem fixation with metaphyseal cementation minimizes the amount of bone needed for adequate fixation of a double Compress intercalary implant. Using these methods has permitted intercalary endoprosthetic reconstruction in select cases that would be impossible using conventional implants.
Following a thorough discussion of its risks, benefits, and alternatives, 6 patients were offered double Compress intercalary endoprosthetic reconstruction with custom anchor plug shortening following extended diaphysectomy of weight-bearing long bones of the lower extremity. Five patients with short metaphyseal segments underwent cement augmentation to achieve stable fixation. One patient was offered short-segment fixation for the purposes of sparing both adjacent femoral physeal plates, whereas the remaining 5 implants were designed to spare the adjacent joint(s).
The current study represents a case series reporting the demographics, surgical management, and clinical outcomes of these patients. Following institutional review board approval, retrospective chart review of prospectively collected data for each patient through latest follow-up (2 patients) or death (4 patients) was performed for the analysis. The Musculoskeletal Tumor Society lower extremity functional scores at latest follow-up and the complications of treatment are also reported.
Three men and 3 women were treated with short segment fixation double Compress intercalary endoprosthesis between 2005 and 2009. Five cases followed primary diaphysectomy with en bloc tumor resection and limb salvage for malignant tumors of the long bones of the lower extremities, whereas the other case was a revision implant for multiple failed and infected intercalary allografts originally performed following diaphysectomy for Ewing's sarcoma. Mean patient age at the time of surgery was 35 years (range, 12–86 years). Five cases involved the femoral diaphysis, whereas 1 involved the distal tibial metadiaphysis. Demographics, surgical management, complications, and clinical outcomes of the study patients are presented in the Table.
Cases of Short-Segment Double Compressive Osseointegration Intercalary Endoprosthetic Reconstruction
Fixation was achieved at both ends of the implant in all patients. All patients had additional room to spare in the medullary canal, even when taking into account the thickness of the cement mantle. Measuring from the end of the cement mantle coupled with shortening of the anchor plug, rigid fixation was achieved in an osseous canal segment as short as 3.7 cm (Figure 1). Excellent radiographic results were noted on all patients at latest follow-up, including out to 9 years (Figure 2).
Case 2 index reconstruction with bipolar short segment compressive fixation. Preoperative templating anteroposterior radiograph (A). Intraoperative photograph of the implanted endoprosthesis (B). Close-up intraoperative photograph of proximal fixation (C). Close-up intraoperative photograph of distal fixation (D). Postoperative anteroposterior radiograph denoting the short length of fixation required by the construct (3.7 cm) (E). Postoperative lateral radiograph (F).
Anteroposterior radiograph of intercalary endoprosthetic reconstruction for case 1 showing the index reconstruction with bipolar short segment compressive fixation. Both femoral physes were spared, with cementation and custom shortened anchor plug required distally (A). Follow-up anteroposterior radiograph 8 years after index procedure. Note successful continued normal growth of the limb as a result of the custom component sparing the adjacent physes (B).
Overall functional outcomes were excellent at mean follow-up of 39 months (range, 10–108 months), including a patient who returned to dancing 1 year postoperatively, despite being nonweight bearing for almost 8 years prior to surgery. Mean Musculoskeletal Tumor Society lower extremity functional score was 26.3 (range, 11–30), with 5 of 6 patients achieving scores of 27 or greater. One patient with a score of 11 was the only case in this series to score less than 27. This was likely due to early systemic disease relapse and rapidly fatal metastases precluding adequate rehabilitation time and health status conducive to rehabilitation.
Four patients died from systemic disease progression with no evidence of local recurrence at the site of diaphysectomy at the time of death. All patients were followed for at least 2 years, with the exception of 2 patients who died from systemic disease progression at 10 months and 1.5 years postoperatively. Three of these patients died despite systemic chemotherapy, and case 4 was deemed ineligible for chemotherapy due to advanced age and medical comorbidities. The remaining 2 patients remain alive and free of disease at the time of publication. One patient with a soft tissue sarcoma with secondary bone involvement was the only patient to exhibit local disease recurrence. This occurred in the adjacent soft tissues and was amenable to re-resection with retention of the prosthesis.
Two patients required revision of only a portion of the prosthesis. Both experienced a femoral implant proximal spindle/anchor plug junction fracture 6 months (case 6) and 37 months (case 1) postoperatively. One patient required a return to surgery for dissociation of the Morse taper of the proximal portion of the implant body (Figure 3) that was treated successfully with open reduction and retention of prosthesis. One patient experienced a periprosthetic fracture 25 months postoperatively as a result of trauma that healed uneventfully with closed casting, without the need to return to the operating room. The limb salvage rate was 100%, with no patient requiring revision of the entire implant, revision to a joint-replacing endoprosthesis, or revision to an amputation. No patient exhibited aseptic loosening, and no case was complicated by deep or superficial infection.
Anteroposterior (A) and lateral (B) radiographs showing dissociation of the Morse taper at the proximal compressive spindle 3 weeks postoperatively in case 4. This was successfully treated with open reduction and re-impaction with no further complications seen at 10 months of follow-up when the patient died of metastatic spread of their disease.
In each case, the adjacent joints were preserved, and in case 1 (12-year-old girl), the adjacent open physeal plates could be preserved, allowing for uninterrupted future growth. Because of the high amounts of compression generated by this implant, early bone–implant junction osteonecrosis can occur. Thus, a period of 6 weeks of non-weight bearing following implantation of a Compress implant has been recommended to prevent early failure from loss of fixation in the temporarily necrotic bone before it can recover.27 However, one striking clinical observation during the postoperative period in this series was the lack of pain associated with the compression mechanism. This lack of pain proved challenging because all but 1 patient (case 1) attempted to resume normal activities within the first few weeks postoperatively. However, early failure was not observed as a result.
Follow-up radiographs have demonstrated appositional new-bone formation at each bone–implant junction, which has persisted throughout follow-up beyond 2.5 years for all living patients. This bone growth is thought to indicate successful integration of the implant into the host bone, as demonstrated in study of retrieval specimens.21 Longer-term results in patients with Compress endoprosthetic fixation of the distal femur over a 5- to 10-year period suggest that this bone formation will persist and that this system avoids the complication of stress shielding seen with conventional cemented intramedullary stems.14,15,20,21,27
The intraoperative bone failure from the compression mechanism in case 3 demonstrates the problems associated with compression-loading osteopenic bone. The patient had profound osteopenia, owing to an 8-year history of nonweight bearing and repeated surgeries for multiple failed intercalary reconstruction methods following resection of Ewing's sarcoma. Fortunately, the trans-fixation pins are amenable to easy revision, which in this case was performed during the same operation. Revision of the anchoring system consisted of simple extraction of the pins and re-preparation of the host bone, removing the affected bone, and repositioning the anchor plug more proximally within the metaphysis. Use of cement augmentation initially in this patient's proximal bone–implant junction might have avoided this intraoperative complication. Failure of the osteopenic bone required a revision bone cut, which effectively shortened the limb due to the predetermined custom implant length. Increased modularity would help address this problem and could expand the indications of the system. However, following a contralateral femoral shortening procedure to restore limb-length equality, the patient was able to experience a full functional recovery and was able to return to dancing.
In patients receiving cement augmentation, there were no complications in the critical metaphyseal bone junctions. Patients with diaphyseal resection may not require this modified design and technique, as adequate cortical bone permits the use of standard modular Compress fixation.
One challenge with a modular intercalary prosthesis is mechanical resistance to the effects of rotation.28 Use of Morse tapers, permitting a “cold” welding of individual body segments, can meet this criterion, and they are a design feature of many modular implants. However, for intercalary reconstruction, putting together a Morse taper poses the challenge not only of having to over-distract the limb to engage the male taper into the female socket, but also of impacting the inserted taper sufficiently to ensure a mechanically competent interference fit. One method of avoiding this problem is to use overlapping flanges that can be screwed together.18
The custom intercalary design used with the Compress system features a dual interlocking C-clamp design that is positioned on the main prosthetic body junction between the upper and lower implants to join them. A key placed into a premanufactured slot is used to achieve rotational stability, and screws are placed across the open sections of the clamp to secure the construct. Although this system facilitates easy reduction of the implant, the longevity of this clamp remains unknown. No failures at this junction were seen in the current series. Rotational instability can still occur at the compression spindle/anchor plug junction, but this can be mitigated successfully using the antirotation pins specifically designed for this junction.28
Other challenges with this system are cost and the need for customization in extended partial metaphysealectomy. The customization process adds time to implant availability and may require Food and Drug Administration compassionate use exemption in the United States, which can also be a time-consuming process. In smaller centers, developing countries, or institutions that lack substantial funding, these implants may be cost prohibitive. In such instances, one of the more classic options of allograft, joint replacement, or amputation may be the only viable solution. Alternatively, newer methods such as pasteurized autografts may offer a cost-effective solution in these challenging cases.
Much remains to be learned about the biology and long-term durability of this system. More specifically, questions remain regarding the optimal loading of the bone–implant junction and the number and diameter of the transfixation pins, as well as the design of the porous coating and use of centralizing collars to ensure coaxial loading of the implant. The cases presented here demonstrate the potential of this system, along with some of the design considerations helpful in extending the possibility of a joint-sparing intercalary endoprosthetic reconstruction in patients requiring partial metaphysectomy.
Short segment fixation via compressive osseointegration may serve to extend the benefits of endoprosthetic replacement to patients who previously had limited reconstructive options. Augmentation with metaphyseal cement may help alleviate the issues of eccentric anchor plug placement, over-compression, and high bending stresses seen in uncemented fixation. Because of the obvious functional advantages of joint preservation, this method should be considered over joint replacement arthroplasty whenever at least partial metaphyseal-sparing resections can be accomplished in tumor surgery with a remaining segment of bone of at least 3.7 cm long for adequate fixation.
However, the current series also demonstrated a 50% return to surgery rate for implant-related complications. This should be discussed thoroughly with the patient and taken into consideration when juxtaposed with prognosis, life expectancy, and expectations of the index surgery.
- Hanna SA, Sewell MD, Aston WJ, et al. Femoral diaphyseal endoprosthetic reconstruction after segmental resection of primary bone tumors. J Bone Joint Surg Br. 2010; 92(6):867–874. doi:10.1302/0301-620X.92B6.23449 [CrossRef]
- Rougraff BT, Simon MA, Kneisl JS, Greenberg DB, Mankin HJ. Limb salvage compared with amputation for osteosarcoma of the distal end of the femur: a long-term oncological, functional, and quality-of-life study. J Bone Joint Surg Am. 1994; 76(5):649–656. doi:10.2106/00004623-199405000-00004 [CrossRef]
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- Fuchs B, Ossendorf C, Leerapun T, Sim FH. Intercalary segmental reconstruction after bone tumor resection. Eur J Surg Oncol. 2008; 34(12):1271–1276. doi:10.1016/j.ejso.2007.11.010 [CrossRef]
- Ogura K, Miyamoto S, Sakuraba M, Fujiwara T, Chuman H, Kawai A. Intercalary reconstruction after wide resection of malignant bone tumors of the lower extremity using a composite graft with a devitalized autograft and a vascularized fibula. Sarcoma. 2015; 2015:861575. doi:10.1155/2015/861575 [CrossRef]
- Ottaviani G, Jaffe N. The epidemiology of osteosarcoma. Cancer Treat Res. 2009; 152:3–13. doi:10.1007/978-1-4419-0284-9_1 [CrossRef]
- Maheshwari AV, Cheng EY. Ewing sarcoma family of tumors. J Am Acad Orthop Surg. 2010; 18(2):94–107. doi:10.5435/00124635-201002000-00004 [CrossRef]
- Angelini A, Henderson E, Trovarelli G, Ruggieri P. Is there a role for knee arthrodesis with modular endoprostheses for tumor and revision of failed endoprostheses?Clin Orthop Relat Res. 2013; 471(10):3326–3335. doi:10.1007/s11999-013-3067-7 [CrossRef]
- Ortiz-Cruz E, Gebhardt MC, Jennings LC, Springfield DS, Mankin HJ. The results of transplantation of intercalary allografts after resection of tumors: a long-term follow-up study. J Bone Joint Surg Am. 1997; 79(1):97–106. doi:10.2106/00004623-199701000-00010 [CrossRef]
- Gitelis S, Cole BJ. The use of allografts in orthopaedic surgery. Instr Course Lect. 2002; 51:507–520.
- Gebhardt MC, Flugstad DI, Springfield DS, Mankin HJ. The use of bone allografts for limb salvage in high-grade extremity osteosarcoma. Clin Orthop Relat Res. 1991; (270):181–196.
- Abudu A, Carter SR, Grimer RJ. The outcome and functional results of diaphyseal endoprostheses after tumour excision. J Bone Joint Surg Br. 1996; 78(4):652–657.
- Ahlmann ER, Menendez LR. Intercalary endoprosthetic reconstruction for diaphyseal bone tumours. J Bone Joint Surg Br. 2006; 88(11):1487–1491. doi:10.1302/0301-620X.88B11.18038 [CrossRef]
- Bhangu AA, Kramer MJ, Grimer RJ, O'Donnell RJ. Early distal femoral endoprosthetic survival: cemented stems versus the Compress implant. Int Orthop. 2006; 30(6):465–472. doi:10.1007/s00264-006-0186-8 [CrossRef]
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Cases of Short-Segment Double Compressive Osseointegration Intercalary Endoprosthetic Reconstruction
|Case No.||Diagnosis||Location||Age at Surgery, y||Follow-up||Dead of Disease||Neoadjuvant/Adjuvant Therapy||Cement Augment||Length of Shortest Bone Segment Canal, cm||Complications||MSTS Score|
|1||Ewing's sarcoma||Femur||12||9 y||No||Neoadjuvant/adjuvant chemotherapy||Yes||5.6||Periprosthetic fracture between prosthesis and native joint 25 mo postoperatively treated successfully with closed casting, and proximal anchor plug stem fracture 37 mo postoperatively requiring revision of the anchor plug||30|
|2||Osteosarcoma||Tibia||13||2 y||Yes||Neoadjuvant/adjuvant chemotherapy||Yes||3.7||None||30|
|3||Intercalary allograft septic failure||Femur||21||2.5 y||No||None||Yes||4.6||Bone failure intraoperatively on application of compression mechanism treated successfully with revision bone cut during the same procedure||30|
|4||MFH of bone||Femur||62||10 mo||Yes||Neoadjuvant/adjuvant chemotherapy||No||5.4||Dissociation of implant body Morse taper 3 wk postoperatively treated successfully with open reduction and retention of prosthesis||11|
|5||MFH of soft tissue with bone invasion||Femur||86||1.5 y||Yes||None||Yes||5.6||Soft tissue local recurrence 12 mo postoperatively treated with wide resection and retention of prosthesis||27|
|6||Periosteal osteosarcoma||Femur||17||3.5 y||Yes||Neoadjuvant/adjuvant chemotherapy||Yes||8.2||Proximal anchor plug stem fracture 6 mo postoperatively treated successfully with revision of the anchor plug||30|