The Use of Locking Plates in Orthopedic Oncology Reconstructions

Abstract

Locking-plate systems are believed to provide better purchase in poor quality bone and equivalent purchase with fewer screws, and also to limit screw pullout by functioning as fixed-angle devices. This retrospective study examined 25 oncologic reconstructions involving locking plates. There were 8 cases of open reduction and internal fixation for pathologic fracture or nonunion and 17 limb-salvage reconstructions. Mean follow-up was 18.2 months with 92% of constructs intact (there were 2 implant-related failures). Locking plates offer advantages that can be useful in orthopedic oncology reconstructions. The long-term performance and mechanisms of failure of these implants remains to be defined.

Many oncologic reconstructions require osteosynthesis. These include fixation of pathologic fractures, allograft-prosthetic composites, intercalary allograft reconstructions, arthrodeses, and prophylactic fixation of impending fractures.

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There are numerous biologic and mechanical obstacles that are present in oncology patients that make osteosynthesis more challenging than in most fracture patients.^1-7 Biologic obstacles include chemotherapy, radiation therapy, bulk allograft bone grafts, and pathologic host bone. Mechanical obstacles include long pathologic segments, short residual host segments, multiple implants, and the presence of polymethylmethacrylate.

Locking plates are a recent addition to the implants available for internal fixation. These plates have threads on the screw head matching threads in the plate hole, allowing the screw to be fixed directly into the plate. This provides numerous potential advantages to standard plates.^8-12 Because the screws do not toggle in the plate, these constructs function as multiple fixed-angle devices, similar to a blade plate, providing additional stability. Moreover, the construct stability is based on the screw purchase in the plate rather than on the screw purchase in the bone; therefore, the stability is less affected by poor quality bone.¹²

Improved purchase also can be obtained with locking plates using a unicortical screw compared to a unicortical standard screw. This can be advantageous in reconstructions involving bulk allografts, as it has been shown that holes in the allograft from screws can lead to late fracture.^13,14 Finally, because each screw provides more stability than a standard screw, additional purchase can be obtained in short osseous segments. These advantages have many beneficial applications in oncologic reconstructions.

This study assessed the use of locking plates in orthopedic oncologic reconstructions and reports the preliminary results of this new type of fixation.

Materials and Methods

This study received institutional review board approval. A review of our orthopedic oncology database identified 28 patients who underwent oncologic reconstruction using a locking plate. The charts of these patients then were reviewed for the following data: oncologic diagnosis, type of surgical reconstruction, type of locking plate, length of follow-up, and use of chemotherapy or radiation. Any failure of the reconstruction or fixation was noted.

Figure 1: Preoperative radiograph shows a pathologic fracture of the distal femur secondary to multiple myeloma (A). Postoperative radiograph shows fixation with a distal femoral locking plate (B). Figure 2: Preoperative radiograph shows an osteosarcoma (A). Postoperative AP (B) and lateral (C) radiographs show locking-plate fixation of an intercalary allograft construct. Follow-up radiograph shows union (D).

Patients underwent follow-up until death, union, or reconstruction failure. In many patients, follow-up extended beyond radiographic and clinical union because of their underlying oncologic condition. Because of the palliative nature of many of these procedures, minimum follow-up for study inclusion was 3 months. Of the 28 patients identified, 4 patients died with intact constructs with <3 months of follow-up, leaving 24 patients in the study.

A total of 25 reconstructions were performed in these 24 patients (8 males and 16 females). Mean patient age was 42.4 years (range, 15-73 years). There were 8 cases of open reduction and internal fixation (ORIF) for pathologic fracture (Figure 1), 7 intercalary allograft reconstructions (Figure 2), 5 allograft arthrodeses, 3 allograft-prosthetic composites, and 2 prophylactic ORIFs. The sites of the reconstructions are listed in Table 1.

Locking plates were used in all cases and consisted of a distal femoral locking plate in 9 cases, a locking 3.5-mm (small fragment) plate in 9 cases, a proximal tibial locking plate in 3 cases, a locking 4.5-mm (large fragment) plate in 2 cases, a proximal humeral locking plate in 1 case, and a distal humeral locking plate in 1 case. Two locking large fragment plates were used in 1 case, and in 3 cases, the locking plate was used in conjunction with an intramedullary nail.

Ten patients received radiation either before or after reconstruction. Table 2 lists histologic diagnoses. One patient without an oncologic diagnosis was included. She had bilateral allograft-prosthetic composites reconstructions of nearly the entire femur after multiple hip reconstructions for developmental dysplasia of the hip (Figure 3).

Six patients had supplemental local or iliac crest bone graft. Two patients had a vascularized fibula as an augmentation to fixation. Five patients had chemotherapy postoperatively, 3 patients had radiation postoperatively, 4 patients had chemotherapy and radiation postoperatively, and 3 patients had a remote history of prior radiation with subsequent radiation-related fracture.

Three patients died at 3, 5, and 6 months of follow-up without failure of the reconstruction. In 5 patients, the most recent clinical follow-up was obtained by telephone and did not include radiographs; none of these 5 patients had pain or other complaints related to their procedure. Four of these 5 patients had previous radiographic follow-up demonstrating union of their reconstruction.

Results

Overall, 23 of 25 reconstructions (92%) were intact at mean follow-up of 18.2 months. Three implant-related complications occurred. One was in a patient who had a distal femoral locking plate for treatment of a radiation-induced pathologic periprosthetic fracture. The plate broke at the fracture site 6 months after implantation. An enlarging mass was noted at the area of the nonunion site; a biopsy showed the mass to be a postradiation sarcoma, and the patient subsequently underwent an above-knee amputation.

The second complication was plate breakage in a patient treated with a resection and intercalary allograft of the proximal tibia for Ewing sarcoma. Plate breakage occurred 28 months postoperatively, and a nonunion of the metaphyseal-metaphyseal host-allograft junction was identified. This patient had been treated with preoperative and postoperative chemotherapy and radiation to the area of the reconstruction. Revision reconstruction included plate removal, iliac crest bone grafting, and a revision with another proximal tibial locking plate.

The third complication was soft-tissue irritation at the anterior distal corner of a distal femur locking plate. This was treated by cutting off the anterior corner of the plate with subsequent pain relief.

There were no additional cases of plate breakage, screw pullout, or loss of fixation. Complications not related to the nature of the implant included residual knee stiffness in 3 patients, local recurrence in 2 patients (1 osteosarcoma and 1 metastatic renal cell carcinoma), and distant metastasis of a dedifferentiated chondrosarcoma in 1 patient. Fourteen of 15 limb salvage reconstructions had successful osteosynthesis with an average time to union of 8.2 months (range, 2-20 months).

Discussion

This is one of the first reports of the use of locking plates in orthopedic oncology reconstructions. In this study, 24 patients with 25 reconstructions were treated using locking plates as either primary or supplemental fixation. Reconstructions were intact in 23 of 25 cases (92%) at a mean follow-up of 18.2 months. The 2 failures were caused by plate breakage resulting from nonunion; the first failure occurred in a radiation-induced pathologic fracture of the distal femur and the second failure occurred in an allograft reconstruction of the proximal tibia. There were no screw fractures or loss of fixation from the bone (screw pullout).

At patients’ last clinical evaluation, all of the surviving pathologic fractures, apart from the 1 plate breakage, had no radiographic evidence of implant failure and were asymptomatic at the fracture site. The remaining 14 limb-salvage operations all had evidence of successful osteosynthesis, with no indication of plate or screw failure.

Figure 3: Postoperative AP (A) and lateral (B, C) radiographs show locking-plate fixation of a proximal femoral allograft-prosthetic composite in a patient with a history of developmental dysplasia of the hip and multiple hip reconstructions.

Locking-plate technology has gained popularity in recent years as an attractive option for fracture stabilization. Many clinical and biomechanical advantages of locking plates over traditional compression plating have been identified.^8,11,12 These include superior fixation in pathologically osteoporotic bone, improved purchase using unicortical screws, and equivalent strength with a lesser number of locking screws.

In the field of orthopedic oncology, there are 2 main areas in which successful internal fixation are critical to surgical success. These are stabilization of pathologic fractures and allograft fixation after resection of an osseous tumor. Pathologic bone presents many challenges to the surgeon, as the quality of the bone is compromised from a destructive oncologic process, irradiation, or chemotherapy.^1-7 This creates significant biological barriers for cellular response and tissue repair, and can prolong the time to union. As long as the patient’s life expectancy and overall health are adequate, surgical intervention often is necessary to treat these fractures.

Classically, operative stabilization in pathologic bone has ranged from ORIF with traditional compression plating to intramedullary fixation, with variations on use of cement and bone graft. The mechanically compromised pathologic bone often makes it challenging to obtain a satisfactory amount of fixation for stabilization. Osteoporotic and pathologic bone both possess decreased strength and ability to hold fixation compared to healthy bone. Although no biomechanical studies using locking plates have specifically included treatment of pathologic fracture, it is theoretically reasonable to advocate their use in a manner similar to severely osteoporotic bone.¹² While the biological hindrances to healing exist independent of implant choice, the increased stability and screw purchase offered by locking plates may lessen the mechanical impediments to union in pathologic fractures.

Allograft reconstructions also present a challenge to osteosynthesis. Allograft bone does not have a native blood supply and almost always demonstrates a delayed time to union. The biologic inertness of allograft bone combined with attenuated host bone secondary to malignancy, periosteal stripping, chemotherapy, or irradiation creates a challenging environment for healing. Mechanical obstacles, including long or short segments, multiple implants, and proximity to cement, also negatively impact bone healing and place unique demands on the implant chosen for fixation. Locking plates effectively address the problem of short allograft segments by providing a substantial amount of stability over a small surface area by giving multiple fixed angle points of fixation.

The 2 major complications that occur with the use of allograft in the form of intercalary segments, allograft-prosthetic composite, or arthrodesis are nonunion and allograft fracture. Healing rates reported in the literature have ranged from 78% to 92%, with significant variance between method of reconstruction, length of allograft, and time to union.^14-22 Even when an allograft heals without incident, there are a significant number of complications caused by fracture through the allograft itself, with many of these fractures occurring at 1 to 3 years or later postoperatively.^13,23,24

Nonunion at the site of the allograft-host interface often can be addressed with revision surgery and bone grafting with acceptable results, but allograft fracture, especially through long intercalary segments, is a problem for which a consistently successful long-term solution is difficult. The use of unicortical screws in the allograft segments, an advantage of locking plates, decrease the stress risers in the allograft itself and may minimize the risk of subsequent fracture.

Weaknesses of this study include its retrospective nature, length of follow-up, variations in constructs, and size of the cohort. For allograft reconstructions, many failures are observed several years after the initial procedure, even when there is no evidence of immediate complications. It is inevitable that fixation of pathologic fractures will be subject to inadequate time of follow-up, as there is a high early mortality rate due to the underlying condition. As this is an initial study describing a novel form of treatment, the scope is understandably limited.

This short-term retrospective analysis on locking-plate technology as the method of fixation in various oncologic conditions reveals good early results with minimal complications when used in ORIF of pathologic fractures as well as limb-sparing allograft reconstruction. The theoretical benefits in allograft reconstruction include adequate fixation into short segments and the use of unicortical screws to decrease stress risers, with healing rates comparable to current treatment modalities. Studies with long-term follow-up and a larger series are needed to further assess the utility of these implants. However, the advantages of locking plates with respect to ease of surgical technique and fixation into compromised bone show this to be a viable and attractive option in the field of orthopedic oncology.

References

1. Habermann ET, Lopez RA. Metastatic disease of bone and treatment of pathological fractures. Orthop Clin North Am. 1989; 20(3):469-486.
2. Springfield DS, Pagliarulo C. Fractures of long bones previously treated for Ewing’s sarcoma. J Bone Joint Surg Am. 1985; 67(3):477-481.
3. Gainor BJ, Buchert P. Fracture healing in metastatic bone disease. Clin Orthop Relat Res. 1983; (178):297-302.
4. Damron TA, Sim FH, O’Connor MI, Pritchard DJ, Smithson WA. Ewing’s sarcoma of the proximal femur. Clin Orthop Relat Res. 1996; (322):232-244.
5. Bragg DG, Shidnia H, Chu FC, Higinbotham NL. The clinical and radiographic aspects of radiation osteitis. Radiology. 1970; 97(1):103-111.
6. Howland WJ, Loeffler RK, Starchman DE, Johnson RG. Postirradiation atrophic changes of bone and related complications. Radiology. 1975; 117(3 pt 1):677-685.
7. Holt GE, Griffin AM, Pintilie M, et al. Fractures following radiotherapy and limb-salvage surgery for lower extremity soft-tissue sarcomas: a comparison of high-dose and low-dose radiotherapy. J Bone Joint Surg Am. 2005; 87(2):315-319.
8. Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004; 18(8):488-493.
9. Gautier E, Sommer C. Guidelines for the clinical application of the LCP. Injury. 2003; 34(suppl 2):B63-B76.
10. Haidukewych GJ. Innovations in locking plate technology. J Am Acad Orthop Surg. 2004; 12(4):205-212.
11. Stoffel K, Dieter U, Stachowiak G, Gachter A, Kuster MS. Biomechanical testing of the LCP—how can stability in locked internal fixators be controlled? Injury. 2003; 34(suppl 2):B11-B19.
12. Wagner M. General principles for the clinical use of the LCP. Injury. 2003; 34(suppl 2):B31-B42.
13. Sorger JI, Hornicek FJ, Zavatta M, et al. Allograft fractures revisited. Clin Orthop Relat Res. 2001; (382):66-74.
14. Vander Griend RA. The effect of internal fixation on the healing of large allografts. J Bone Joint Surg Am. 1994; 76(5):657-663.
15. Weiner SD, Scarborough M, Vander Griend RA. Resection arthrodesis of the knee with an intercalary allograft. J Bone Joint Surg Am. 1996; 78(2):185-192.
16. Benevenia J, Makley JT, Locke M, Gentili A, Heiner J. Resection arthrodesis of the knee for tumor: large intercalary allograft and long intramedullary nail technique. Semin Arthroplasty. 1994; 5(2):76-84.
17. Gitelis S, Heligman D, Quill G, Piasecki P. The use of large allografts for tumor reconstruction and salvage of the failed total hip arthroplasty. Clin Orthop Relat Res. 1988; (231):62-70.
18. Gitelis S, Piasecki P. Allograft prosthetic composite arthroplasty for osteosarcoma and other aggressive bone tumors. Clin Orthop Relat Res. 1991; (270):197-201.
19. Muscolo DL, Ayerza MA, Aponte-Tinao LA, Ranalletta M. Partial epiphyseal preservation and intercalary allograft reconstruction in high-grade metaphyseal osteosarcoma of the knee. J Bone Joint Surg Am. 2004; 86(12):2686-2693.
20. Wang JW, Shih CH. Allograft transplantation in aggressive or malignant bone tumors. Clin Orthop Relat Res. 1993; (297):203-209.
21. DeGroot H, Donati D, Di Liddo M, Gozzi E, Mercuri M. The use of cement in osteoarticular allografts for proximal humeral bone tumors. Clin Orthop Relat Res. 2004; (427):190-197.
22. Makley JT. The use of allografts to reconstruct intercalary defects of long bones. Clin Orthop Relat Res. 1985; (197):58-75.
23. Mnaymneh W, Malinin TI, Lackman RD, Hornicek FJ, Ghandur-Mnaymneh L. Massive distal femoral osteoarticular allografts after resection of bone tumors. Clin Orthop Relat Res. 1994; (303):103-115.
24. Fuchs B, Valenzuela RG, Sim FH. Pathologic fracture as a complication in the treatment of Ewing’s sarcoma. Clin Orthop Relat Res. 2003; (415):25-30.

Authors

Drs Virkus, Miller, and Gitelis are from Rush University Medical Center, Rush Orthopedic Oncology, Chicago, Illinois; and Dr Chye is from the Unit of Musculoskeletal Tumor and Limb Reconstruction Surgery, Department of Orthopedic Surgery, Hospital Kuala Lumpur, Kuala Lumpur, Malaysia.

Dr Virkus is a consultant for Stryker Orthopedics; Drs Miller, Chye, and Gitelis have no relevant financial relationships to disclose.

Correspondence should be addressed to: Walter W. Virkus, MD, Rush Orthopedic Oncology, 1725 W Harrison, Ste 440, Chicago, IL 60612.