➢ Locking plate constructs can be used to avoid secondary collapse of comminuted metaphyseal fractures.
➢ Locking constructs provide improved fixation compared with nonlocking constructs in osteoporotic bone.
➢ Locking screws have little or no advantage over nonlocking screws in good-quality diaphyseal bone.
➢ Contrary to popular belief, locking constructs are not necessarily stiffer than similar nonlocking constructs.
➢ Construct working distance (the distance between screws on either side of a fracture) modulates construct stiffness more effectively than does the choice of locking or nonlocking screws.
Overview of Locked Plating
Locking plate constructs have a potential role whenever plating is considered for the treatment of fractures. Deciding when locked plating provides advantages that justify its increased costs over conventional nonlocking constructs remains a challenge. When locked plating is utilized, optimizing the precise number and location of locking screws and the utility of combining nonlocking screws with locking screws are additional considerations.
Locking plate constructs offer advantages over nonlocking constructs for the treatment of comminuted metaphyseal fractures. These fractures demand a fixed-angle construct to avoid loss of reduction1. Partially because of their ease of application, locking plates have essentially supplanted other fixed-angle constructs such as the blade plate and dynamic condylar screw. The application of locking constructs to other metaphyseal fractures for which satisfactory fixed-angle alternatives do not exist, such as the proximal and distal parts of the tibia, proximal part of the humerus, and distal part of the radius (the latter of which are beyond the scope of this review), are rational extensions of locking plate technology.
The primary advantage of locking plates is that they can be effectively used in situations in which bone quality precludes satisfactory fixation with nonlocking screws. Nonlocking screw constructs require good bone quality in order to be effective. The stability of nonlocking constructs depends on the degree of compression between plate and bone. Without such compression, the bone is free to move relative to the plate and construct stability is absent. Resistance to motion between plate and bone is determined by the frictional force between the two. The frictional force is related to the degree of compression, the degree of compression is related to the insertional torque generated by the nonlocking screw, and the ability to generate such torque is determined by bone quality. In poor-quality bone, nonlocking screws may strip prior to generating sufficient compressive force between plate and bone. Locking constructs are not as dependent on bone quality to provide stability2, and they have been shown to maintain stability in osteoporotic bone better than nonlocking constructs1.
A complete understanding of the role of locked plating requires knowledge of its limitations. Locking screws do not generate compression; they hold bone fragments at a fixed distance from one another and hold bone at a fixed distance relative to the plate. As a consequence, compression across bone fragments (e.g., lag fixation) is not accomplished, and, once a locking screw is applied across a fracture, secondary application of lag screws will be ineffective. Similarly, when placed through a plate, locking screws cannot be used to effect reduction the way nonlocking screws can. Another limitation is the threefold to fivefold increased cost of locking constructs compared with similar nonlocking constructs. For example, fixation of a lateral malleolar fracture with one plate and six screws costs between $800 and $1500 for a locking construct and between $190 and $310 for a nonlocking construct. In the current era of cost containment, it is prudent to avoid locking constructs when advantages over nonlocking constructs are not evident. Combining locking and nonlocking screws in the same construct (i.e., the use of a so-called hybrid locking plate construct) is often a valid strategy. The advantages of both screw types can be leveraged when needed, with nonlocking screws being used to effect reduction and to control costs and with locking screws being used to provide improved fixation in poor-quality bone. In a hybrid construct, nonlocking screws, in general, should be placed in any given fragment prior to locking screws. The placement of locking screws prior to nonlocking screws will not allow the nonlocking screws to compress bone to plate. Also, nonlocking screws should be used in regions of good-quality diaphyseal bone as locking screws provide little advantage in such regions.
Biomechanical Properties and Fallacies Related to the Use of Locking Plate Constructs
The biomechanical properties of locking plate constructs are often misrepresented. Although it may be true that locking constructs are stiffer than similar nonlocking constructs under certain conditions, this is not necessarily true under all conditions.
Many biomechanical studies have served to confuse rather than clarify the relationships between locking and nonlocking constructs. A study that compared locking and nonlocking constructs in a distal ulnar fracture model is an example3. In that study, the working length (defined as the distance between nearest points of fixation on either side of the fracture) (Fig. 1) was shorter in the locking construct than in the nonlocking construct because of the use of so-called combi-holes. As working length is the primary determinant of construct stiffness, the reduced working length, rather than the use of locking screws, may explain the increased stiffness in the locking group. The results also showed that nonlocking constructs were actually stiffer than locking constructs under certain loading conditions. Biomechanical studies also can yield misleading results because of the use of sawbones or other poor methodologies. Sawbones do not approximate the bone quality encountered in human bone, especially not the bone quality seen in metaphyseal regions or in osteoporotic patients. Applying the results of biomechanical tests performed under highly controlled conditions to uncontrolled clinical situations is not valid.
The attribution of clinical problems to locking-construct stiffness often is based on the inaccurate notion that locking constructs are inherently stiffer than nonlocking constructs. The fact that such reports pass the peer-review process represents a potential inherent bias of the orthopaedic trauma community toward the fallacy that locking constructs are stiffer than nonlocking constructs. Röderer et al. were the authors of an article entitled “Delayed Bone Healing Following High Tibial Osteotomy Related to Increased Implant Stiffness in Locked Plating.”4 The reference to “increased implant stiffness” was without basis as the study did not provide any direct comparison of stiffness between locking and nonlocking constructs. Cui et al. also assumed that locking constructs are stiffer than nonlocking constructs5. The first sentence of that report reads “Locked plates provide greater stiffness, possibly at the expense of fracture healing.” Contrary to that statement, the results showed no difference in axial stiffness between locking and nonlocking diaphyseal fixation.
Several studies involving human bone have directly contradicted the notion that locking constructs are stiffer than nonlocking constructs. Ricci et al. compared locking and nonlocking constructs for diaphyseal fixation in non-osteoporotic bone with use of cyclic loading in a cadaveric distal femoral fracture model6. The nonlocking constructs showed either similar or higher average stiffness when compared with the locking constructs. White et al. compared locking and nonlocking constructs in a comminuted distal fibular fracture model and found no differences in stiffness7. Zlowodzki et al. found that a locked plating construct with unicortical locking screws was less stiff than a 95° blade plate when tested in a cadaveric distal femoral fracture model8. Gardner et al., in a cadaveric radial fracture model, found only subtle biomechanical differences between locking and nonlocking constructs9. In summary, there is little evidence that locking constructs are stiffer than nonlocking constructs in good-quality bone. Under these conditions, the stiffness of a construct is less related to whether locking or nonlocking screws are used and is more related to other construct-related properties such as plate geometry, plate material, and working length.
Locking constructs can be stiffer than nonlocking constructs under certain conditions. When bone quality is poor and nonlocking screws are unable to rigidly compress plate to bone, locking constructs will be stiffer than nonlocking constructs immediately after fixation. A more clinically relevant scenario in which locking constructs are stiffer is after cyclic loading in the presence of poor-quality bone. Ricci et al. directly compared locking and nonlocking constructs in osteoporotic bone with use of cyclic loading in a cadaveric distal femoral fracture model and found that locking constructs were stiffer than nonlocking constructs10. When used in poor-quality bone, nonlocking screws loosen with repetitive stress, and this failure leads to a reduction in stiffness. It is worth identifying stiffness differences between locking and nonlocking constructs that are due to the failure of nonlocking fixation as such differences are distinctly different from stiffness differences that are inherent to the initial constructs. Several biomechanical studies have indicated that mechanical differences between locking and nonlocking may be related to differences in failure rates and failure modes. In a study of paired osteoporotic humeri with proximal fractures, Röderer et al. compared interfragmentary motion between locking and nonlocking constructs after cyclic loading1. The locking constructs had lower interfragmentary motion in all axes and had higher cumulative survival rates. Higgins et al. found that locking constructs resisted subsidence better than blade plate constructs in a distal femoral fracture model involving cadaveric femora with varying bone densities11. Gardner et al. found that locking constructs initially were stiffer and retained stability better than nonlocking constructs when tested in a Sawbones model designed to simulate purchase in osteoporotic bone in which all screw holes were drilled to 0.3 mm less than the diameter of the screw used12.
For every fracture that is treated with plate fixation, the surgeon should align the fracture pattern, construct biomechanics, and expected mode of fracture-healing. A simple fracture pattern that is treated with compression plating will reliably heal by means of primary bone-healing (without callus), provided that the fragments are anatomically aligned, the fragments are compressed (with lag screws and/or dynamic compression), and the fixation is relatively rigid (short working length) (Fig. 2). When fixation is rigid (short working length) and the fracture is not compressed, healing problems may occur (Fig. 3). A plated comminuted fracture pattern is best treated with a less-rigid bridge construct (large working length) that promotes secondary fracture-healing (Fig. 1). These decisions are independent of the choice of locking or nonlocking screws.
Dynamic Locked Plating
Bottlang and colleagues introduced the concept of far cortical locking (also referred to as dynamic locked plating)13-16. The initial goal of this methodology was to reduce stiffness of locking plate constructs by overdrilling the near cortex. With this method, the locking screw is anchored to the plate on the near side and is anchored in the far cortex. Controlled bending of the screw and toggle within the overdrilled near cortex provide reduced stiffness. Far cortical locking also has the benefit of making the stiffness and motion at the fracture site more symmetric than is the case with traditional locking constructs13, potentially leading to more symmetric callus formation15,17. Several animal15,17 and clinical18,19 reports have supported the concept of dynamic locked plating.
Clinical Outcomes of Locked Plating
Locked Plating of Upper Extremity Fractures
There has been a recent resurgence of interest in the fixation of clavicular fractures20,21. Given the complex and variable contour of the clavicle, precontoured plates provide convenience. As is the case in other anatomic areas, most manufacturers only offer highly precontoured plates as locking plates. The advantages of locked plating of clavicular fractures remain unclear as diaphyseal clavicular fractures are rarely associated with poor bone quality. Lai et al. compared nonlocking dynamic compression plates with locking plates and found no difference in terms of fracture union but noted a higher need for plate removal in the nonlocking plate group, likely related to the bulk of these implants22. Cho et al. found no difference in outcomes between nonlocking and locking reconstruction plates in a study of forty-one patients with midshaft clavicular fractures23. The advantages of locking plates may be greater for lateral clavicular fractures as the small fragment size combined with metaphyseal bone quality lends itself to the advantages of locked plating. Several studies have shown good results with this strategy24-26, and one showed improved results in association with locked plating as compared with hook plating27.
Proximal Humeral Fractures
Locking plates designed specifically for the proximal part of the humerus have in common multiple fixed-angle points of fixation into the humeral head. In theory, these devices should reduce the risk of varus collapse of osteoporotic proximal humeral fractures in comparison with nonlocking fixation. However, the failure of locking plate constructs has been reported to occur via other mechanisms. Collapse of the osteoporotic humeral head around fixed-angle locking screws and mechanical failure of the locking mechanism have been reported28-30. In the series of Fankhauser et al., such failures occurred in association with three of twenty-nine displaced and unstable proximal humeral fractures that were treated with a locking plate28. Three fractures, each of which had been treated with four locking screws in the humeral head, fell into varus malalignment. These failures were due to either loss of fixation of the locking screws (seven of twenty-one screws) or the cutting of the locking screws through bone in the humeral head. Hente et al.29, in a prospective series of thirty-one patients with three and four-part fractures that were classified according to the Neer system31, reported loosening of the locking-screw mechanism one patient, secondary displacement of the greater tuberosity in two patients, and a fracture below the plate in one patient.
When satisfactory fixation of the locking screws in the humeral head is achieved, stresses can become concentrated at other areas of the construct. Locking screws can fracture at the plate interface or stresses can become concentrated over the working length of the plate in the zone of the surgical neck, where fracture comminution often prevents screw fixation. Plate failure in this zone occurred in association with one of the twenty-nine unstable fractures in the previously mentioned study by Fankhauser et al.28 as well as in one of thirty-six patients with two, three, and four-part fractures in the retrospective study by Plecko and Kraus30.
Union rates of proximal humeral fractures treated with locking plates have been high. Björkenheim et al.32 reported nonunion in two of seventy-two patients with Neer Type-2, 3, and 4 fractures that were treated with a locking plate construct. Moonot et al. reported one nonunion in a series of thirty-two patients with three and four-part fractures33.
Other complications after locked plating of proximal humeral fractures have been infrequent. Impingement has been rarely reported, occurring in three of twenty-six patients in the series of Fankhauser et al.28 and in none of the seventy-two patients in the series of Björkenheim et al.32. Although not specifically associated with impingement, reoperation for the treatment of pain at the site of the implant was required in one of twenty patients in the series of Koukakis et al.34 that included patients with Neer Type-2, 3, and 4 fractures with and without associated glenohumeral dislocation. Infection rates also have been low, ranging from 0% to 8%28-30,32,34,35.
The relatively low rates of fixation failure, nonunion, and other complications that have been reported in association with locked plating of proximal humeral fractures would be of little benefit if not also associated with satisfactory clinical outcomes. Average shoulder outcome scores generally have been good as well as remarkably consistent after locked plating. Björkenheim et al.32, Hente et al.29, Fankhauser et al.28, and Koukakis et al.34 all reported average Constant scores36 of between 72 and 77 for their entire cohorts. Moonot et al. reported an average Constant score of 66.5 in patients with three and four-part fractures33. Lungershausen et al.35 used the Neer score31, and their results with use of this score were similar to those in the aforementioned studies involving the Constant score.
Direct comparisons of locked plating with other methods for the treatment of proximal humeral fractures are generally lacking. As an exception, in 2003, Lungershausen et al.35 retrospectively reviewed the records for twenty-four patients (with adequate follow-up) with Neer Type-2, 3, and 4 fractures and compared them with fifteen patients who had been managed with conventional open reduction and internal fixation (ORIF) without locking. The average Neer outcome score was 72 for the patients who had been managed with locking plates, compared with 66 for those who had been managed with conventional methods. The only difference was a better Neer score for patients with three-part fractures who were managed with locking plates. Secondary displacement occurred in two patients in the locking plate group and seven patients in the conventional treatment group.
We are not aware of any studies in which locked plating has been directly compared with hemiarthroplasty; however, indirect comparisons have revealed favorable results for locked plating. Despite moderately high rates of osteonecrosis (with reported rates as high as 16%29,30), the functional results after locked plating of three and four-part fractures have compared favorably with the results of hemiarthroplasty in this patient population. The average Constant scores after hemiarthroplasty for the treatment of three and four-part proximal humeral fractures have been reported to be between 46 and 6837-42. The results of locked plating for this subset of patients have been better, with average Constant scores of between 57 and 7828-30,32.
Humeral Shaft Fractures
The use of locking plates for the treatment of fractures of the humeral shaft has been reported primarily for fractures that have progressed to nonunion43-45. Osteopenic bone, the failure of prior fixation devices, and multiple bone defects from prior screws make locking fixation attractive in this setting.
Distal Humeral Fractures
We are aware of only a few reports on the use of locking plate technology for the treatment of fractures of the distal part of the humerus. The highly contoured nature of plates designed for this region is a clear advantage, but the benefits of locking technology for other fractures remains unproven. The theoretical advantages of locking constructs, improved end-segment stability thereby allowing early motion and better function for patients with osteoporotic distal humeral fractures, have not been substantiated by published clinical data. Ducrot et al. reviewed the outcomes for forty-three patients who were more than sixty-five years old in whom distal humeral fractures were treated with locking plates46. Function was good (with 95% of the patients having a result that was good or better) and the union rate was high (95%), but there were a number of complications that did not appear to be related to the choice of a locking plate (infection, ulnar nerve injury, and heterotopic ossification). Greiner et al. also noted good results in a small cohort of fourteen younger patients (mean age, 55.2 years; range, twenty-one to eighty-three years), reporting a 100% rate of union and a 0% rate of loss of reduction47. Schmidt-Horlohé et al. reported less-promising results in their series of forty-five patients with extra-articular distal humeral fractures that were treated with locking plates48. Only thirty-four fractures were considered stable enough to allow early physical therapy, and the rates of implant failure, nonunion, and revision were 13%, 7%, and 36%, respectively.
Some of the earliest modern published reports on locked plating included diaphyseal radial and ulnar fractures that were treated with a construct involving unicortical locking screws49,50. Good results were reported, but the use of unicortical locking screws in this anatomic location has been largely abandoned. Saikia et al., in a more recent prospective study involving seventy-two fractures of the forearm, reported no differences between a locking compression plate (with bicortical locking screws) and a nonlocking compression plate in terms of motion, grip strength, and complications51. Similarly, the retrospective studies by Azboy et al.52 and Stevens and ten Duis53 demonstrated no differences in outcomes between locking and nonlocking plates that were used for the treatment of forearm shaft fractures.
Locked Plating of Lower Extremity Fractures
Pelvic and Acetabular Fractures
Locked plating systems are available for the treatment of fractures of the pelvis and acetabulum. We are not aware of any clinical or biomechanical data to support the widespread use of these devices for the treatment of these fractures. Multiple studies have demonstrated a high rate of implant loosening and loss of reduction when nonlocking constructs have been used to stabilize pubic symphysis disruptions54,55. The use of locking plates for the treatment of this type of injury also has resulted in failures. The mode of failure associated with locking plate constructs is distinctly different from that associated with nonlocking plate constructs. With nonlocking constructs, the inherent and persistent motion at the symphysis leads to screw loosening (Fig. 4, A and B). With locking constructs, the plate-screw-bone interfaces remain intact and the plate over the motion segment is subjected to increased stress, resulting in plate fracture (Fig. 4, C and D).
Proximal Femoral Fractures
Locking plates may have a role in the treatment of very proximal subtrochanteric, reverse-oblique, or transtrochanteric fractures that are difficult to stabilize with intramedullary techniques or when sliding hip screws are not indicated. The initial reports on locked plating for the treatment of subtrochanteric femoral fractures involved the use of plates that were designed for the distal part of the femur56,57. Newer devices designed specifically for the proximal part of the femur are now available and have yielded satisfactory results58-60; however, the vast majority of these fractures typically are treated with intramedullary devices. The use of locked plating for the treatment of femoral neck fractures has been associated with poor results. Berkes et al. found that 36.8% of patients had catastrophic failure and that only 61.1% achieved union after the treatment of a femoral neck fracture with a locking plate61.
Femoral Shaft Fractures
In the femoral shaft, plate fixation is most often reserved for periprosthetic fractures. For periprosthetic fractures that have occurred distal to a total hip implant, some combination of screws and cerclage cables is typically preferred62. The use of unicortical or bicortical locking screws around the stem as adjuvants to cable fixation has been associated with good results63. This ability to optimize fixation by using cables and locking screws in the stem zone may obviate the need for orthogonally placed allograft struts in many cases63. The use of unicortical locking screws as the sole method of proximal fixation is not recommended.
Distal Femoral Fractures
Fractures of the distal part of the femur are the best-studied of all of the fractures that are treated with locked plating (Table I)64-74. Problems encountered with first-generation locking plates included valgus malalignment of the distal fragment, plate malposition on the femoral shaft, and proximal fixation failure due to unicortical shaft fixation. These complications have been minimized with the introduction of more modern implant designs and reduction instruments as well as increased surgeon experience with these implants64,75,76. In most centers, locked plating has become the procedure of choice for the treatment of intra-articular and extra-articular fractures of the distal part of the femur.
Despite the popularity of locked plating for the treatment of distal femoral fractures, complication rates remain modestly high. Vallier et al.77 recently reported a 15% rate of nonunion or plate failure. Two recent large cohort studies evaluated risk factors for complications after the use of locked plating for the treatment of distal femoral fractures70,71. Rodriguez et al. retrospectively reviewed the records on 283 distal femoral fractures that had been treated with locked plating at three institutions71. After the exclusion of thirteen patients who had been referred for the treatment of nonunion, the rate of nonunion among fractures that had been treated primarily at the institutions was 10%. Independent risk factors for surgical intervention to promote healing were open fracture (present in 18% of patients) and infection. An interesting subanalysis implicated differences in practice patterns as being a determinant of reoperation. The time to intervention was longest at the institution with the lowest nonunion rate, suggesting that the management approach at that hospital tended toward longer waiting times and late intervention. Ricci et al. reviewed the records for 335 patients with distal femoral fractures that had been treated with locking plates at three trauma centers70. The severity of injury in this cohort was high: 33% of the fractures were open, and 9% were associated with metaphyseal bone voids after debridement. Among the entire cohort, 19% of patients required reoperation to promote union. Diabetes and open fracture were independent risk factors for reoperation to promote union. The rate of reoperation was 67% when both diabetes and open fracture were present, compared with 8% when neither risk factor was present. The study also critically analyzed locking construct parameters such as working length, plate length, and number of screws as potential risk factors for failure. Shorter plate length was identified as an independent risk factor for failure, and the use of a plate with more than eight holes covering the proximal fragment was recommended.
A novel study by Lujan et al. critically examined callus formation in patients with distal femoral fractures that were treated with locking plates78. The authors reported asymmetric callus formation (with more callus medially) and found more callus in association with titanium plates as compared with stainless steel plates. Working length only weakly correlated with callus size. A potential limitation of the study that was not addressed was the absence of control for constructs designed to provide rigid fixation. These constructs, by design, would promote primary bone-healing without substantial callus. As the cohort included a high number of simple fractures (thirty-one of sixty-six), it is conceivable that many constructs were inserted with lag-screw fixation, designed for primary bone-healing.
The clinical results of far cortical locking have been evaluated in two published studies18,19. Ries et al. found an 11.1% rate of nonunion in a preliminary series of twenty patients who were managed with far cortical locking19. Bottlang et al. reported on thirty-one patients with distal femoral fractures who were managed with specialized far cortical locking screws. Only one patient (3%) went on to have nonunion18. These data indicate that far cortical locking appears to offer similar or better union rates than standard locked plating for the treatment of distal femoral fractures. Direct comparisons in similar patient populations are needed to substantiate these preliminary results.
Multiple series have emerged regarding the utility of locking plates for the treatment of periprosthetic fractures proximal to the site of a total knee arthroplasty79-81. It is intuitive that the ability to obtain multiple points of fixation around the prosthesis and cement mantle at the site of a total knee arthroplasty would improve fixation, and such fixation methods, in fact, have led to higher rates of union and lower rates of secondary surgery as compared with historical controls79-81.
Proximal Tibial Fractures
Similar to the situation in the distal part of the femur, locked plating is rapidly replacing traditional plating for the treatment of complex fractures of the proximal part of the tibia and the tibial plateau. High-energy unstable bicondylar fractures theoretically benefit from the application of locking plates in this anatomic area. These fractures often have metaphyseal comminution and are prone to varus collapse without an angle-stable construct. Locking plates theoretically provide such support; however, controversy remains with regard to how effective a laterally based locking plate can support the medial side and how well a lateral plate can capture a posterior medial fragment. Gosling et al. reported secondary loss of reduction in 15% (nine) of sixty-two fractures, with subsidence on the medial side occurring most frequently82. Spagnolo and Pace recommended that comminuted fractures should not be stabilized just with lateral angular stable plates but rather that fixation of the medial plateau should be performed separately83. In contrast, Ehlinger et al., in a small series of thirteen patients with Schatzker Type-IV, V, or VI tibial plateau fractures with a medial component, reported no loss of reduction and reported that they favored the use of a single lateral locking plate for the treatment of such fractures84. Weaver et al. attempted to identify associations between fracture pattern, fixation method, and loss of reduction in a study of 140 bicondylar tibial plateau fractures85. Although most patients did well when treated with lateral locked plates, those with a medial coronal fracture line tended to have a higher rate of reduction loss with lateral locked plating alone compared to those with dual plating. There is little dispute that a dual plating construct applied through dual incisions is safe86 and provides more support for the medial side than a single lateral locking plate does87; however, the precise clinical indications for dual plating of proximal tibial fractures remains unclear. The exception is the bicondylar fracture with the characteristic posterior medial fragment, for which most surgeons advocate lateral and posterior medial plates.
Locked plating probably offers little advantage for the treatment of lower-energy unicondylar fractures (Schatzker Type-I, II, and III fractures) in all but the most osteopenic patients. These fractures can be treated effectively with traditional plates and nonlocking raft screws to support depressed articular fragments in conjunction with an appropriate bone void filler. However, most modern low-profile precontoured periarticular plates are manufactured only as locking plates. Much of the cost of locking constructs is due to the locking screws; therefore, appropriate use of nonlocking screws through anatomically contoured locking plates is prudent.
Distal Tibial Fractures
Several reports have described successful results after locked plating for the treatment of distal tibial fractures88-91. Bastias et al., in a retrospective study of twenty-eight patients who had been managed with nonlocking plates and forty patients who had been managed with locking plates for the treatment of distal tibial fractures, reported that the groups had similar rates of union and infection as well as similar AOFAS (American Orthopaedic Foot & Ankle Society) scores92. Differences that were noted in terms of alignment and implant removal favored the use of locked plating, but these outcomes likely were related more to surgeon than to plate type.
Locking plates are available for the treatment of fractures of the calcaneus. These plates theoretically provide better coronal plane stability of the tuberosity and may provide more robust support of the reconstructed articular surface, factors that prompted a study of early weight-bearing after locked plating. In the study by Kienast et al., patients started weight-bearing to 20 kg after six weeks and gradually increased to full weight-bearing by ten weeks93. No secondary loss of reduction occurred. Hyer et al. accelerated weight-bearing further, with weight-bearing being initiated at an average of 4.8 weeks94. In that retrospective review of seventeen patients who had been managed with locking plate fixation of calcaneal fractures, no clinically important subsidence occurred.
Conclusions and Clinical Recommendations
Every internally fixed fracture represents a race between fracture-healing and implant failure. Biologic as well as mechanical factors influence the ultimate outcome Locking plates are more effective than nonlocking constructs for maintaining mechanical integrity at the sites of end-segment fractures and in poor-quality bone. Locking constructs appear to maintain stiffness better than similar nonlocking constructs after cyclic loading in osteoporotic bone. Modulating construct stiffness can influence the biologic response; however, the choice of locking or nonlocking screws will not substantially influence construct stiffness, especially when good bone quality is present. Construct working length, plate properties (e.g., thickness, width, material), and use of dynamic locking screws are much more effective methods to affect construct stiffness than the choice of locking screws.
The clinical results of locked plating are generally good. However, few comparative studies have clearly demonstrated that locking constructs are superior to nonlocking constructs. Therefore, it is prudent for surgeons to use locked plating on the basis of a clear understanding of its potential benefits. Clinical scenarios in which bone quality is poor, in which there are short end segments of bone, or in which fractures are at high risk for secondary collapse are logically suited for locked plating.
Source of Funding: No direct funding was provided for preparation of this manuscript.
Investigation performed at the Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, Missouri
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. One or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. In addition, one or more of the authors has a patent or patents, planned, pending, or issued, that is broadly relevant to the work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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