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The Use of Locking Plates in Fracture Care S ince the advent of surgical fracture care, orthopaedic surgery has seen many great advances. The invention of intramedullary nailing by Kuntscher in the 1940s marked the beginning of a new approach to the treatment of long bone fractures. The circular external fixator developed by Ilizarov in the 1950s added greatly to fracture care and limb lengthening. The dynamic compression plate developed by Perren allowed for rigid fixation of both extra- and intra-articular fractures, permitting early joint motion and re- turn of function. The concept of rigid and anatomic fracture reduction became the goal for many surgeons. This approach, however, sometimes sacrificed the biology of the fracture and failed to protect the blood sup- ply of the bone in an effort to pre- cisely reduce and fix each fracture fragment. 1,2 The technique of locked plating, developed in Davos, Swit- zerland, in the 1990s, 1 has been de- scribed as a “revolution” in fracture care. 3 Locked plating refers to the fact that the screw heads are threaded and, when tightened, lock into threads in the plate. By locking the screws into the plate, a fixed-angle construct is created that is much less prone to loosening or toggle than traditional nonlocked plates ( videos 1, 2, and 3). Recent terms such as percutaneous plating, submuscular plating, minimally invasive plate osteosynthesis, and bridge plating refer to techniques of plate placement; although they are commonly used with locked plates, these terms are not synonymous. Percutaneous plating, submuscular plating, and minimally invasive plate osteosynthesis mean that the plate is placed through small incisions with as little dissection and stripping of the soft-tissue envelope as possible. Bridge plating refers to a plate in which several screw holes are left open at the level of the fracture (Figure 1). Locked plating simply means that the screws lock into the plate regardless how the plate is inserted. An unlocked plate means that the screw is not firmly attached to the plate, and toggling of the screw can occur through bone ( video 4). Indications and Contraindications The indications for use of locking plates include the following: (1) metaphyseal and intra-articular fractures; (2) highly comminuted fractures, par ticularly those involving diaphyseal and metaphyseal bone; (3) osteoporotic bone; (4) proximal tibia and distal femur fractures; and (5) periprosthetic fractures. 4 Theoret- ically a locking plate could be used anywhere a traditional plate is applied. Locking plates have an advantage with fractures in osteoporotic bone, where loss of fixation is a con- cern. 5 Highly comminuted diaphyseal or metaphyseal fractures often can be spanned or bridged by a locked submuscular plate (Figure 1). Locked plates offer an advantage in unstable fracture patterns that tradi- tionally required dual plating, such as bicondylar tibial plateau fractures. 4,6 Proximal third tibia fractures have a high malunion rate with intramedullary nailing; locked plating may be advantageous with these fractures, as well. 7,8 Locked plates have been designed for the treatment of most periarticu- lar fractures and are precontoured to fit. Less Invasive Surgical Stabiliza- Robert V. Cantu, MD Kenneth J. Koval, MD Dr. Cantu is Assist ant Professor, Orthopaedic Surgery, Dartmouth- Hitchcock Medical Center, Lebanon, NH. Dr. Koval is Professor, Orthopaedic Surgery, Dartmouth-Hitchcock Medical Center. None of the following authors or the departments with which they are affiliated has received anything of value from or owns stock in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Cantu and Dr. Koval. Reprint requests: Dr. Cantu, Dartmouth- Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756. J Am Acad Orthop Surg 2006;14:183- 190 Copyright 2006 by the American Academy of Orthopaedic Surgeons. The video that accompanies this article is “The Use of Lock- ing Plates in Fracture Care,” available on the Orthopaedic Knowledge Online Website, at http:// www5.aaos.org/oko/jaaos/surgical.cfm Surgical Techniques Volume 14, Number 3, March 2006 183 tion (LISS) plates (Synthes, West Chester, PA) and Locking Compres- sion Plates (Synthes) are locked plates designed specifically for peri- articular fractures 9 (Figure 2). Used for malunions, locking plates act as a fixed-angle construct to hold alignment as well as to provide increased stability. Combination plates (plates with holes for both locked and nonlocked screws) can be used for cer- tain nonunions, such as hyper- trophic nonunions, both to compress the fracture and provide increased stability ( videos 5 and 6). There are few absolute contraindications to the use of locked plates. Relative contraindications include the following: (1) fractures best served with fixation other than plates (eg, patella fracture); (2) fractures in which the soft-tissue injury pre- cludes immediate plating (eg, Gustilo grade IIIB or IIIC tibia fracture); (3) simple fracture patterns that do not require either unlocked or locked plates; and (4) fractures that would require bending of precontoured locked plates. Because of the increased cost of locked plates compared with traditional nonlocked ones, use of locking plates should be reserved for instances in which they are clearly advantageous. Surgical Techniques Traditional open approaches can be used with locking plates ( video 7). The technique of fracture exposure and reduction is similar to that used with nonlocked plates. Tempo- rary fracture reduction with clamps or Kirschner wires (K-wires) is fol- lowed by application of the plate. The primary difference with a locking plate is the technique of screw insertion. With nonlocked screws, the surgeon has tactile recognition when the screw purchases the far cortex and pulls the plate against the bone. This sensation helps the surgeon know the quality of the bone and ensures that the screw is of ap- propriate length. This sensation is lost with locking screws because the screw is inserted until it locks into the plate. Screw length must be care- fully determined before insertion. Another difference is that the locked screw can be inserted only in a fixed angle. Proper plate position and location are important to ensure that the screws do not engage any neurovas- cular structures. The insertion techniques for many locked plates, such as the LISS plate, are an important advance in fracture treatment. By placing the plates in a minimally invasive manner, the soft-tissue envelope around the fracture is preserved. Fracture reduction can be difficult when using minimally invasive techniques and a locking plate. Articular fragments still require direct visualization and rigid fixation before plate placement. Figure 1 A locked plate bridging a highly comminuted femur fracture. Several screw holes are left open over the comminuted portion of the fracture site. (Adapted with permission from Synthes, USA, West Chester, PA.) Figure 2 A, Less Invasive Surgical Stabilization (LISS) plate. B, Locking Compression Plate. (Reproduced with permission from Synthes, USA, West Chester, PA.) Use of Locking Plates in Fracture Care 184 Journal of the American Academy of Orthopaedic Surgeons An example is a distal femur fracture with an intra-articular exten- sion. 9,10 A parapatellar incision is required to reduce and fix the articular fragments. Following articular fracture reduction, the locked plate can be placed in a submuscular fashion along the lateral cortex, avoiding dis- ruption of the fracture biology in the metaphyseal region (Figure 1). For extra-articular metaphyseal or diaphyseal fractures, locked plates can be placed through minimal incisions. An example is a periprosthetic metaphyseal femur fracture (Figure 3). A 5- to 7-cm lateral incision is made over the distal femur and car- ried down through the tensor fascia (Figure 4). The periosteum is elevated off the lateral epicondyle of the distal femur. The fracture itself is not exposed; rather , an indirect reduction is performed. Manual traction com- bined with use of appropriately placed bumps can restore proper length, rotation, and alignment of the fracture. Additionally, an external fixator or the universal distractor can be applied to hold the reduction (Fig- ure 5). Next the locked plate is slid along the lateral cortex of the femur in a submuscular fashion. A separate 2- to 3-cm incision can be made at the proximal extent of the plate. This allows insertion of an elevator or a finger to ensure that the plate is properly positioned on the lateral cortex in the anteroposterior dimension. Most locked plates have a targeting arm that allows for temporary fixation of the plate using K-wires both proximal and distal to the fracture (Figure 6). Some targeting arms allow insertion of a K-wire just proximal to the plate (Figure 7, A and B). This wire Figure 3 Preoperative anteroposterior (A) and lateral (B) radiographs of a comminuted, periprosthetic distal femur fracture. Figure 4 Intraoperative view of a lateral incision of the distal femur. The soft-tissue envelope at the level of the fracture is not violated. Because the fracture is extra-articular, no parapatellar arthrotomy is required. Spanning external fixator before plating. The fixator was used for temporary stabilization while soft-tissue swelling decreased. The fixator can be left in place or adjusted to aid in fracture reduction during definitive internal fixation. Figure 5 Robert V. Cantu, MD, and Kenneth J. Koval, MD Volume 14, Number 3, March 2006 185 should be placed parallel to the joint surface to ensure proper varus- valgus orientation (Figure 7, C). Intraoperative fluoroscopy is es- sential to judge fracture reduction and hardware placement (Figure 8). With the LISS system, the whirlybird, or push-pull device, can be inserted to improve fracture reduction and pull the bone closer to the plate (Figure 9). Because locked plates do not rely on bone contact for fixation, it is not necessary to pull the bone tightly against the plate (Figure 10). For this reason, locked plates have been called internal external fixators. Once provisional reduction and fixation have been achieved, placement of locked screws can be performed. Several systems employ self- drilling and self-tapping screws, which can be placed using a power Figure 6 Placement of proximal K-wire in the proximal femur. The index finger of the right hand placed in the incision helps to ensure that the plate is properly positioned on the femur. Outside of view, traction is being maintained to hold the length and alignment. Figure 7 A, Placement of provisional distal K-wire. The plate is centered on the lateral cortex of the distal femur. The K-wire is placed parallel to the joint surface. B, Submuscular placement of a LISS plate. A targeting device can be used as a handle to help position the plate on the lateral cortex of the femur. The soft-tissue envelope at the fracture level is intact. C, Intraoperative fluoroscopic view demonstrating the provisional K-wire. The K-wire is placed parallel to the joint surface. Use of Locking Plates in Fracture Care 186 Journal of the American Academy of Orthopaedic Surgeons Figure 8 Intraoperative fluoroscopic view showing the plate off the femur bone with the provisional K-wire. External fixation pins are visible to the left of the K-wire. Figure 9 Use of the whirlybird, or push-pull device. The whirlybird pulls the bone toward the plate, decreasing the distance between the plate and the bone, improving fracture reduction. Figure 10 Intraoperative fluoroscopic view after the whirlybird tightening. Figure 11 A power drill is used to place the self-drilling, self-tapping screws. Note the K-wires holding the length and the bump of folded towels under the thigh to maintain alignment. Figure 12 Postoperative anteroposterior (A) and lateral (B) radiographs demonstrating overall restoration of length, alignment, and rotation. Rather than expose and reduce each fracture fragment, the construct was used to bridge the fracture comminution. Robert V. Cantu, MD, and Kenneth J. Koval, MD Volume 14, Number 3, March 2006 187 drill (Figure 11). It is important that proper plate position and screw length be determined before the screws are inserted. W ith a distal femur fracture, multiple screws can be placed proximal and distal to the fracture using the targeting device (Figure 12). As mentioned, several screw holes typ- ically are left open at the level of the fracture to create a bridging construct. If every screw were to be inserted, the fixation would be overly rigid, and only primary bone healing would occur. A minimum of three unicortical screws should be placed distal to the fracture. The unicortical screws are placed through small stab incisions. The soft-tissue sleeve can be placed through the targeting arm to deter- mine the exact location of these incisions. Once definitive fixation is achieved, the incisions are irrigated and closed. Early range of motion can be started, but weight bearing typi- cally is delayed a minimum of 4 to 6 weeks or until radiographic evidence of healing. Outcomes Locking Plates Some of the earliest studies on locking constructs looked at infection rates. Of 1,229 applications of the PC-Fix in one prospective, mul- ticenter trial, the overall infection rate was only 1.1%. 7 The infection rate for open fractures was 1.6%. These results correspond with those of animal studies. 7 The same authors compared the PC-Fix to a dynamic compression plate on tibia fractures in rabbits. After plate application, an inoculum of bacteria was injected around the plate. The PC-Fix constructs required 10 times as many bacteria to create clinical infection. 7 Biomechanical testing of locking plates has shown favorable outcomes compared with nonlocking plates. One of the earliest biomechanical studies for fixation of distal femur fractures compared a standard condylar buttress plate and a 95° blade plate with a locked condylar Pearls and Pitfalls Soft-Tissue Dissection and Fracture Exposure • Articular fractures require open exposure to permit anatomic reduction. With metaphyseal and diaphyseal fractures, however, the goal is to minimize soft-tissue dissection at the level of the fracture. Ca- daveric studies have shown a significant improvement in maintain- ing the perforating arteries of the distal femur when percutaneous plate insertion was compared with traditional open placement. 11 Fracture Reduction • Locked plates are not a justification for inadequate fracture reduction. Newer locking plates allow for placement of either a locked or nonlocked screw through so-called combination holes. With these plates, a nonlocked screw can be placed in a lag fashion to help with fracture reduction. With plates that provide only locked holes, fracture reduction must be achieved before screw placement. • Reduction aids include using various-sized bumps, manual or mechanical traction, or a temporary external fixator or the universal distractor. Schanz pins can be used to manipulate fragments, and the self-drilling, self-tapping whirlybird can be used. 12 Universal T-handle chucks (Synthes) placed over the provisional K-wires and tightened against the stabilization bolt sleeves also obtain provisional reduction. 12 Locking Plate Application • Once adequate anatomic reduction has been achieved, locking plate fixation can be applied. Most locked plates are designed to be placed in a submuscular fashion. If the plate has a targeting device, this can be used to help manipulate the plate into proper position. Fluoros- copy is also helpful in judging proper plate position (Figure 7, A). • A 2- to 3-cm incision at the end of the plate allows a finger to be placed, ensuring that the plate is centered on the bone. • When using combination plates, any nonlocked screws should be placed before locked screws. Once a locked screw has been placed, the distance between the bone and the plate is fixed and cannot be changed with a nonlocked screw. The LISS System • LISS system screws are self-drilling and self-tapping. They are placed in a unicortical manner , eliminating the need to measure screw depth. In the metaphyseal region, screw length is based on the size of the patient’s condyles as measured on preoperative radiographs or by placing K-wires and measuring their depth. In the diaphyseal region, screw length should be shorter than the width of the medullary canal; oth- erwise, the screw will not completely seat in the plate if the screw tip contacts the opposite cortex. • The whirlybird is used before placing locked screws (Figures 8 and 9). • When using the 13-hole tibial LISS plate, the superficial peroneal nerve is at risk with percutaneous insertion of screws 11 through 13. 13 It is recommended that a larger incision be used at this level and careful dissection be performed to protect the superficial peroneal nerve. Use of Locking Plates in Fracture Care 188 Journal of the American Academy of Orthopaedic Surgeons buttress plate. The locked plate showed greater fixation stability in axial loading both before and after cyclic loading. 16 Biomechanical tests have shown that many of the factors that influence stability of an external fixator apply to locked plates. Factors such as bone contact, work- ing length or distance of the first screw to the fracture, number of screws, and distance of the plate to the bone all contribute to rigidity of the construct. In one biomechanical test, leaving one screw hole open on either side of a fracture resulted in a doubling of the flexibility of the construct in both compression and tor- sion. 17 As mentioned, in many applications, some flexibility is desirable to stimulate callus formation and secondary bone healing. LISS Plates Most outcome studies on LISS plates have shown favorable results. In one retrospective review of 123 distal femur fractures treated with the LISS system, 93% healed without bone graft, the infection rate was 3%, and there was no loss of distal fixation. 18 In a prospective study of 38 complex proximal tibia fractures treated with the LISS system, 37 (97%) healed with satisfactory alignment, there were no infections, and the average lower extremity measure score was 88. 19 Another review of 77 proximal tibia fractures treated with the LISS system showed that 70 (91%) healed without complica- tion. 20 The overall union rate was 97%, with an average time to full weight bearing of 12.6 weeks. The infection rate was 4%. 20 LISS plates also have shown favorable results in biomechanical tests. One cadaveric study compared the LISS plate with a condylar buttress plate and a dynamic condylar screw for supracondylar femur fractures. Under physiologic loading conditions, the LISS construct con- sistently showed less irreversible de- formation than did the other two. 21 Another biomechanical study compared the tibial LISS plate with dual plating of simulated Schatzker type VI tibial plateau fractures. After re- petitive loading, no statistical differ- ences between the two constructs were found. 22 Summary Locked plating represents a major advance in fracture care. Advantages over traditional plating include im- proved construct stability, targeting devices that permit percutaneous insertion of screws and preservation of fracture biology, and, in some studies, higher union rates with lower infection rates. 18-20 As with any new technique, there is a learning curve for fracture reduction and implant insertion. When using percutaneous techniques, fracture reduction may prove to be more challenging than with traditional open incisions. A locked construct is not a justification for im- proper fracture reduction. Compared with nonlocked plates, removal of locked plates may be more difficult and often requires larger incisions and special extraction devices. References Citation numbers printed in bold type indicate references published within the past 5 years. Pearls and Pitfalls Plate and Screw Removal • Although LISS plates can be inserted percutaneously, removal may require a larger incision. Stripping of the screw heads is a common occurrence when removal is attempted percutaneously. 14 • One technical trick is to interpose the foil from a suture pack between the screw driver and the screw head in an attempt to improve the connection. 15 If this does not work, the conical extraction screws for the 4.9-mm locking bolts in the Synthes Screw Removal Set (no. 309.530) can be used to remove the stripped screws. • Multiple extraction screws may be required because they often cannot be easily removed from the LISS locking bolts after extraction. • Sometimes the conical extraction screw may fail to engage the stripped screw. When this happens, a high-speed burr can be used to cut the plate around the screw head. • Once the plate is removed, the stripped screws can be removed using the extraction forceps in the Synthes Screw Removal Set. 14 Locking Plate Position • When using precontoured plates on the distal femur, it is necessary to place the plate on the lateral aspect of the condyles. If the plate is placed too anterior, the fixed-angle screws may aim too far poste- rior. Also, if the plate is placed too anterior, the plate may sit ante- riorly off the proximal femur. Matching the precontoured plates to the curve of the condyles is important to restore proper varus-valgus alignment. Bridging Plates • A potential pitfall when treating highly comminuted fractures is placing too many screws. To achieve a bridging construct and secondary bone healing, a plate of sufficient length is needed and a minimum of 2 to 3 screw holes must be left open at the level of the fracture. If part of the plate is not left open, the plate will not have sufficient flexibility to permit micromotion and subsequent callus formation. Robert V. Cantu, MD, and Kenneth J. Koval, MD Volume 14, Number 3, March 2006 189 1. Perren SM: Evolution of the internal fixation of long bone fractures: The scientific basis of biological inter nal fixation. Choosing a new balance between stability and biology. J Bone Joint Surg Br 2002;84:1093-1110. 2. Perren SM, Cordey J, Rahn BA, Gauti- er E, Schneider E: Early temporary po- rosis of bone induced by internal fixation implants:A reactionto necrosis, not to stress protection? Clin Orthop Relat Res 1988;232:139-151. 3. Sanders R: When evolution begets revolution. J Orthop Trauma 2004; 18:481-482. 4. Perren SM: Evolution and rationale of locked internal fixator technology: In- troductory remarks. Injury 2001; 32(suppl 2):B3-B9. 5. Cordey J, Borgeaud M, Perren SM: Force transfer between the plate and the bone: Relative importance of the bending stiffness of the screws fric- tion between plate and bone. Injury 2000;31(suppl 3):C21-C28. 6. Hertel R, Eijer H, Meisser A, Hauke C, Perren SM: Biomechanical and biological considerations relating to the clinical use of the Point Contact-Fix- ator: Evaluation of the device han- dling test in the treatment of diaphyseal fractures of the radius and/or ulna. Injury 2001;32(suppl 2):B10- B14. 7. Eijer H, Hauke C, Arens S, Printzen G, Schlegel U, Perren SM: PC-Fix and local infection resistance: Influence of implant design on postoperative infection development, clinical and experimental results. Injury 2001; 32(suppl 2):B38-B43. 8. Hofer HP, Wildburger R, Szyszkowitz R: Observations concerning different patterns of bone healing using the Point Contact Fixator (PC-Fix) as a new technique for fracture fixation. Injury 2001;32(suppl 2):B15-B25. 9. Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ: Biomechanics of locked plates and screws. J Orthop Trauma 2004;18:488-493. 10. Frigg R: Locking Compression Plate (LCP): An osteosynthesis plate based on the Dynamic Compression Plate and the Point Contact Fixator (PC- Fix). Injury 2001;32(suppl 2):63-66. 11. Farouk O, Krettek C, Miclau T, Schandelmaier P, Tscherne H: Effects of percutaneous and conventional plating techniques on the blood sup- ply to the femur. Arch Orthop Trauma Surg 1998;117:438-441. 12. Hak DJ, Stewart RL, Lee M: Prelimi- nary stabilization of the Less Invasive Stabilization System. J Orthop Trauma 2004;18:559-561. 13. Deangelis JP, Deangelis NA, Ander- son R: Anatomy of the superficial peroneal nerve in relation to fixation of tibia fractures with the less invasive stabilization system. J Orthop Trauma 2004;18:536-539. 14. Georgiadis GM, Gove NK, Smith AD, Rodway IP: Removal of the less invasive stabilization system. J Orthop Trauma 2004;18:562-564. 15. Pattison G, Reynolds J, Hardy J: Sal- vaging a stripped drive connection when removing screws. Injury 1999; 30:74-75. 16. Koval KJ, Hoehl JJ, Kummer FJ, Simon JA: Distal femoral fixation: A biomechanical comparison of the standard condylar buttress plate, a locked buttress, and the 95-degree blade plate. J Orthop Trauma 1997;11:521-524. 17. Stoffel K, Dieter U, Stachowiak G, Gachter A, Kuster MS: Biomechanical testing of the LCP: How can stability in locked internal fixators be con- trolled? Injury 2003;34(suppl 2):B11- B19. 18. Kregor PJ, Stannard JA, Zlowodzki M, Cole PA: Treatment of distal femur fractures using the less invasive stabilization system: Surgical experience and early clinical results in 103 fractures. J Orthop Trauma 2004;18:509- 520. 19. Ricci WM, Rudzki JR, Borrelli J Jr: Treatment of complex proximal tibia fractures with the less invasive skele- tal stabilization system. J Orthop Trauma 2004;18:521-527. 20. Cole PA, Zlowodzki M, Kregor PJ: Treatment of proximal tibia fractures using the less invasive stabilization system: Surgical experience and early clinical results in 77 fractures. J Orthop Trauma 2004;18:528-535. 21. Marti A, Fankhauser C, Frenk A, Cordey J, Gasser B: Biomechanical evaluation of the less invasive stabilization system for the internal fixation of distal femur fractures. J Orthop Trauma 2001;15:482-487. 22. Goesling T, Frenk A, Appenzeller A, Garapati R, Marti A, Krettek C: LISS PLT: Design, mechanical and biomechanical characteristics. Injury 2003; 34(suppl 1):A11-A15. Use of Locking Plates in Fracture Care 190 Journal of the American Academy of Orthopaedic Surgeons