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The use and abuse of locking platesAbstractThe concept of locking plates is now more than 15 years old and represents a clear advance in the management of fractures by internal fixation using plate technology. Fractures in osteoporotic bone, fractures with short metaphyseal segments and fractures treated with biological fixation are all better managed with lockable plates. There are, of course, additional and unique problems that arise from their use. Locking plates evolved through the recognition that in order to get a fracture to heal quickly and satisfactorily it was not always necessary to achieve rigid internal fixation and absolute stability. The biology of the fracture would be better preserved by using low contact implants combined with minimally invasive surgical techniques. These implants also offered the ability to confer angular stability to a fixation construct. In this article we use the term locking plates and lockable plates. Locking plates refer to those plates that have holes that will only accommodate locking head screws and are therefore used to bridge across the fracture like an internal splint or fixator e.g. Less Invasive Stabilisation System (LISS). In contrast, lockable plates refer to implants that can accept either standard screws or locking screws. This hybrid implant can, therefore, be used to produce internal splintage with locking screws or the more traditional compression, buttressing and neutralization when standard techniques are employed. Failure to recognize that a lockable plate does not necessarily need to have locking head screws inserted is discussed as one of the pitfalls in using these implants. IntroductionHistorically, internal fixation of fractures was used as a last resort to achieve bony union. This frequently followed prolonged periods of failed non-operative treatment, which resulted in joint stiffness, muscle wasting and disuse osteoporosis: so called ‘fracture disease’. In addition, the techniques of fracture fixation were often poorly understood and poorly executed, resulting in high rates of failure. In the late 1950s the Swiss AO group, led by Maurice Muller, launched a battle against ‘fracture disease’ by promoting early mobilization of injured patients and their limbs. To achieve this, fractures were anatomically reduced and compression fixation was applied in order to achieve sufficient stability to enable patients to mobilize the injured limb free of the constraints of plasters and splints. When successful this technique produced a marked reduction in ‘fracture disease’ and the compression fixation led to direct bone healing with no callus formation by producing absolute stability. However, it required open reduction and anatomical fixation of even the most complex fractures. The price paid for focusing on mechanical stability was slower bone healing and, particularly in less experienced hands, severe damage to the blood supply of the soft tissue envelope and underlying periosteum. Critics often cited examples of increased non-union, infection and re-fractures after premature plate removal. In the late 1980s Stephen Perren and colleagues,1, 2 studied the potential of plates and internal fixators with reduced bone surface contact (LC-DCP and PC-Fix). Animal studies confirmed the reduced damage to periosteal blood supply and the formation of substantial amounts of early solid bridging callus. Infection was also noted to be significantly reduced. A new era was born to respect the biology of the soft tissue envelope, and tools and techniques were developed to reduce damage to the bone blood supply during fracture surgery; so called ‘Biological Fixation’.3, 4 This entailed not only new implants but also new techniques to minimize soft tissue damage. Fracture reduction by closed indirect means using traction and ligamento-taxis (Indirect Reduction), less invasive surgery and minimal disturbance of the fracture hematoma are all important contributors to a successful outcome using these techniques. The need for anatomical reduction and absolutely stable fixation was confined to intra-articular fractures and non-unions. In extra-articular fractures of the metaphyseal and diaphyseal regions, there was a realization that general re-alignment with correction of the overall position, length and rotation would suffice (the radius and ulna being exceptions to this, due to their unique anatomical relationship with each other). This could be achieved using internal and external splints, thus preserving blood supply and accelerating healing by callus formation, indirect bone healing. Locked intra-medullary fixation using nails, and extra-medullary fixation using bridge plating techniques, are both examples of internal splinting, which allows controlled movement at the fracture site, so called relative stability. Providing the blood supply is preserved this will usually lead to reliable callus formation, even in multi-fragmentary fractures, without the need to bone graft. Locking plates are part of this evolution of extra-medullary techniques to preserve biology, allow controlled movement (relative stability), encourage more rapid fracture healing and yet still allow early mobilization of the injured patient and their limb. In order to understand the role of locking plates in modern day fracture surgery we need to consider the following:
Section snippetsWhat are locking plates?Locking plates are surgical tools used to stabilize fractures. They differ from standard plates in that the screw heads lock into the plate, providing a composite unit, or ‘fixed-angle device’. Standard plates are compressed against the underlying bone by the pressure applied using normal screws. This creates friction that abolishes movement but also damages the blood supply to the underlying periosteum. This compression, and hence stability, will reduce with time, particularly in osteoporotic How have they evolved?The first uses of locking plates were reported in Craniomaxillofacial and Spinal surgery.7, 8, 9 In general trauma, various types of experimental plate systems were tested to try and improve bone blood supply and improve fixation in osteoporotic bone (the Schuhli nut10 and PC-Fix1, 2). The main driving force behind these developments was a realization that preserving biology was probably more important than creating absolute stability in every case, no matter what the cost to the bone blood The development of locking head screws (LHS)Unlike conventional screws, which compress against the plate creating friction, locking head screws are locked into the plate giving axial and angular stability. The locking head screws of the internal fixator are actually more like threaded bolts. No compression of the plate onto the bone occurs and the forces from the bone to the fixator occur across the neck of the screws. For this reason the geometry of the LHS is different to a corresponding cortical screw.
Less Invasive Stabilization System (LISS)The AO Less Invasive Stabilization System (LISS) was initially developed for fractures of the distal femur (1995) and proximal tibia (1997). This greatly facilitated fixation and stabilization using all the principles of ‘biological’ fixation, including indirect reduction techniques, minimally invasive surgical exposure and flexible internal splinting to facilitate callus formation. They are 100% locked fixators because only locking head screws are used and the plates are pre-shaped to match Locked Compression Plate (LCP)The LISS system was designed as a device that would provide angular stability and would only accommodate locking head screws (all the holes in the plate are threaded). This made it incompatible with other standard plate systems, usually made of stainless steel. The LISS technology was considered by some to be too restrictive. Thanks to the ingenious work of Professor Michael Wagner (Vienna), Robbie Frigg (AO Institute, Davos) and other colleagues a hybrid system evolved including a combination Clinical indications and examples of useMost common fractures do not require fixation using a locked plate. The majority will heal using either non-operative treatment or conventional methods of internal fixation. The key to correct use of a locked compression plate (LCP) is to understand that it is a versatile implant and not a technique. The surgeon should consider how they would treat a fracture in the absence of a LCP i.e. does the surgeon want to achieve absolute stability or relative stability, since a locked compression plate Conventional plating
A standard LC-DCP or new hybrid LCP using standard screws can achieve the usual plate functions of compression +/? lag screws, buttressing and neutralisation/protection of lag screw fixation (Figure 9). Biological plating
Tips and pitfallsAttention to detail is important:
CostInvariably, because of the newer technology and increased manufacturing costs, these implants are in general much more expensive than the previous non-locking options. Both the locking screws and the pre-shaped anatomical plates command a premium and cost up to 4× as much as corresponding standard implants. The surgeon should therefore, be quite specific about the indications and benefits of using this new technology. Usage should be limited to essential cases then costs can be contained. The SummaryLockable plates have clearly advanced the treatment of certain fractures such as those of the proximal humerus and distal radius, but require careful planning to maximize their benefits. There is no substitute for poor planning or poor surgery. Careful attention to detail is required in pre-op planning and plate insertion to realize these benefits. Fractures involving osteoporotic bone, with short metaphyseal segments and biological fixation are the three situations that lockable plates are of AcknowledgmentThe authors would like to thank the AO Foundation for help in providing the illustrations for this article. No financial inducement has been received by either of the authors in the preparation of this article.
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Shanghai Carefix Medical Instrument Co., Ltd.China
滬ICP備16042301號(hào)-1 (滬）－非經(jīng)營(yíng)性－2016－0122 滬食藥監(jiān)械生產(chǎn)許20101725號(hào)
