Nef1204 Intro To Engineering Design: Assessment Answers

"Your project will analyze published data/information to address a specific objective".

The topic is "Advantages and Disadvantages of Locking Compression Plate (LCP) in Fracture Management".

In this assessment you will only focus on small animals (ex. dogs).  compare LCP with other plate such as Dynamic Compression Plate (DCP).

Another randomised prospective cohort study conducted upon 56 patients having disphyseal fractures indicated that the mean period of surgery and time to union were not in support of LCP groups, despite being statistically insignificant. There was lack of any momentous difference between the two groups, in relation to functional assessment (Andersons’ criteria, range of movement, and DASH score) and the associated complications could be easily distinguished. No occurrence of synostosis or refracture was faced in the groups. Thus, the authors suggested that although LCP serves as an actual treatment alternative over LC-DCP, for management of fractures, more research should be done to establish their supremacy (7). Another article tried to draw a comparison between locking plates and conventional bone fixation procedures and found that superior proportion of patients who has long been diagnosed with osteoporosis associated  risk factors were present in the group that was subjected to locking compression of distal fibula plate (27.8% versus 2.3% and 0%). Furthermore, four patients (2.8%) also demonstrated the need of washout for infections. The researchers failed to notice any significant variations between distribution of sex among the groups, reoperation rate and complication rate. This helped them conclude that despite the six times increased cost of locking compression plates, they are more effective for treatment and/or management of unstable fractures that have poor bone quality (8).

Osteoporotic bones with deprived mechanical capacity deliver limited constancy, following fixation of ankle fractures. Additionally, stabilization of such fractures with implants provided an increase in the fixation strength of osteoporotic bone, thereby lowering the rates of failure of fixation, and allowing functional treatment. Another research that evaluated the efficacy of locking contoured plates, in relation to fixation of the distal fibular fractures, when compared to conventional contoured plates suggested that LCP system was directly associated with a greater maximum torque levels and torque-to-failure, in comparison to the traditional plates used in torsional cyclic testing and torque-to-failure experiments. Upon conducting the experiment in 80 osteoporotic bone cylinders, the surrogates were secured to the two plates. The LCP was found to provide an improvement in the osteoporotic bone model fixation strength. Further evidences were also provided by the researchers for the LCP being better effective in distal fibular fracture fixation, in osteoporotic bones that had reduced mechanical capacity (9).

Similar findings were presented by another article that elaborated on the comparison between LCP and conventional plate based fixation for distal fibula fractures in trimalleolar ankle injuries. The researchers used 14leg cadaver specimens that were fresh-frozen, followed by stimulation with the use of OTA 44-B3.3 fracture and its subsequent fixation. Lack of statistically noteworthy differences were established between locking and conventional plate constructs, throughout torque to failure and fatigue testing (p >.05). The fact that the average mineral densities of the failed to represent low bone quality made the authors conclude that distal fibular LCP were not associated with any mechanical benefit for trimalleolar ankle injuries (10). Owing to the fact that ankle fractures are one of the most common fractures that are found among elderly patients who suffer from wrist and hip fractures, researches of another study enrolled 62 patients aged above 64 years who underwent surgery for fractures in osteoporotic distal fibula from 2011-2014. Average time to the AOFAS and union scores were alike in both the groups at 6 and 12 months, respectively for the discrete classes namely, pain, function, alignment and mobility. The partial weight bearing was found to be meaningfully lesser in the LCP group (4.69 ± 2.63 vs 7.77 ± 4.30, p= 0.03). Nonetheless, common complications that originated in both the groups were superficial infection and dehiscence. This helped in establishing the fact that locking plates may were related with more benefits since they took into account concomitant damage of soft tissues and immobilization (11).

Upon testing the biochemical properties of LCP 3.5 fixation to similar LC-DCP fixation in canine cadaveric, distal humeral metaphyseal model, it was found that humeral constructs that were steadied with LCPs were suggestively firmer, in comparison to the LC-DCP plates, during loading in axial compression (p=0.0004). LC-DCP constructs demonstrated momentous firmness than constructs that were steadied with LCPs (P=0.0029), during cyclical loading in axial compression. Similar results were also obtained when the constructs that were plated with LC-DCPs showed increased resistance to torsion, in comparison to constructs that were LCP plated, over 500 cycles (p<0.0001) (12). Parallel findings were represented in another study where LCP group demonstrated increased stiffness in the torsion, in comparison to the LC-DCP groups (p < 0.001), with an average difference of  20.9%. However, there was no major difference between the groups, in terms of load at failure (p<0.07). This was further supported by momentous reduced plate or motion ‘looseness’ in the LCP group (p < 0.017), thus establishing the benefits of LCP in providing increased toughness and reduced deflection, than low-contact dynamic compression plate (13).

Scholarly literature have also elaborated on the fact that extensive exposure of bone is typically necessary to increase access to and deliver good discernibility of the breakage zone to let decrease and plate fixation to be accomplished. This process needs pre-contouring of plates, with the aim of matching the structure of the bone. The screws are tightened to fix the plate onto the bone, which then compresses the plate onto the bone. The actual stability results from the friction between the plate and the bone. The recently developed, locked internal fixators (e.g.PC-Fix and Less Invasive Stabilization System (LISS)) were elaborated upon and were found to comprise of screw and plate systems, at places where the plate locked in the screws. The role of the lock helped to minimise the compressive forces that were exerted on the bone by the plate. Hence, the system of screw-plate fixation does not make it imperative for the plate to touch the bone, thereby providing exacting advantage in Minimal Invasive Percutaneous Osteosynthesis (MIPO) (14).

The biomechanical properties of locking and standard plate, in relation to bending were evaluated in another study that was based on the hypothesis that Titanium constructs are associated with highest deformation, while largest stiffness and strength are related with String of Pearl constructs (SOP). Upon individual evaluation of the plates that were applied to some kind of validated bone models, greater stiffness was demonstrated by the SOP plates, in comparison to all other, while the fixing plates manufactured momentous lessened stiffness compared to others. SOP plates were also associated with increased mean bending strength and stiffness, thereby failing to established the hypothesis (15). Other studies also take into account the fact that locking compression plate has been a recent advancement in the field of AO Technology, and should be examined in order to gain an understanding of the fractured stabilization. The researchers elaborated on the fact that the locking compression plates that were made of pure Titanium had resulted in an increase in the local resistance to all kinds of infection, when compared to the conventional DCP.  This helped in establishing the potential advantages of LCP over traditional fracture management techniques. Further advantages of the LCP were validated owing to its role in improving the safety and anchorage of the fractured bone. Owing to the fact that their role in limiting torque prevents the LCP to get stripped, following insertion in a bone, the requirement for bi-cortical screws gets enhanced. The benefits that LCP offers in fracture management were explained, in relation to the disadvantages of conventional plate designs, where the screws had to be locked with the use of a Morse cone. The cone had subsequently resulted in extreme difficulty in screw removal, due to inadvertent excess tightening and jamming at the places. Hence, the technological shift from compression plating to LCP has been a significant improvement for management of fractures, and all drawbacks of the LCP can be overcome by a combination of LC-DCP (16).

The fact that formulation and implementation of LCP involves a collaborative approach by researchers, developers, clinicians and industrials, the industrial implementation of the compression fracture management technique was assessed to be possible only with the usage of production centres that had state-o- the-art facility with 5 computer controlled access. The researcher celebrated on the innovative facets of LCP that had taken into consideration of combination of two different anchorage concepts in a single implant that reflected the desire of obtaining greatest flexibility in relation to plate osteosynthesis. Advantage of the LCP was also established by the fact that contrary to the conventional fracture management technique, the type of anchorage that needs to be implanted can be decided without changing the system, depending on the fracture type, the insertion technique, the soft tissue prevalence and the quality of the bones. Hence, it was suggested that during the use of an internal fixation, LCP needs a certain facility that will be based on locking the head screw onto the hole of the plate, with adequate axial and angular stability. It was also indicated that LCP takes into account the actual anatomical screw placement sites, with the aim of averting sliding of one screw over another. Hence, the benefit of LCP in integrating two different technologies for treatment into a single implant system, without the need for compromising mechanical properties of anchorage is clearly supported by evidences (17).

The group of authors clearly elucidated on the different biomechanical aspects that affected the constructability of bone and place, with respect to certain essential components such as, stress shielding sharing of load between the plates, and bones anchorage and fracture stability. It was indicated that apart from the basic variations in the plate design and dimensions, there are two principal types of locking plates namely, fixed angle locking plate, and variable angle or poly-axial locking plate. While in the first type, insertion of the locking screws is required in a certain predefined angles that is orthogonal with respect to the plate,  the second kind of plate involves insertion of locking screw in a cone shaped region of angulation that his relative to the hole axis of the place. That has provided adequate evidence for the fact that most of the locking screws are unable to access adequate compression due to presence of head locking mechanism in the hole, thereby suggesting avoidance of locking screw insertion that process the fractured line. Additional evidence provided by the researchers also indicated that placement of the locking place near the vicinity of the bone has chances of increasing the torsional and axial constructability. Hence, locking plates should be fixed at an elevation of 5 minutes from the bone, with the aim of reducing axial failure load, by a range of one-third. Additionally, fracture morphology holds great importance for the locking plate’s fatigue life. This calls for the need of achieving perfect reduction, to lessen the load that is transferred via the plates (18).

These findings were consistent with another study that subjected patients to locking compression plate fixation of fracture. Upon retrospectively evaluating the functional outcome and complications among 72 patients who were subjected to internal fixation of the proximal humerus fractures, it was observed that while two fractures did not unite and three of the patients showed complications of avascular necrosis in the humeral head, technical error also led to implant failures as well. Presence of a constant score in functional outcome among all the patients provided adequate evidence for considering the use of LCP for proximal humeral fracture repair, as a safe and feasible technique among patients who had poor quality of bones (19). The outcome of indirect biological fixation of subtrochanteric fractures with PF-LCP was assessed among 35 patients. The findings suggested that mean operation time among them was 79.5 minutes, followed by an average total blood loss of 233.13ml.  However, all the cases were successful in achieving bone union, with an average time frame of 15.62 weeks. Some of the major complications included two cases each of infection and delayed union, respectively. Therefore, the findings of the study were successful in confirming the fact that biological fixation with the use of PF-LCP of subtrochanteric fractures help in providing stability station with fever complications and increased union rate among the patients (20).

The bio-mechanical properties of locking plates and standard plates were also compared, with respect to torsion and it was found that increased elastic deformation was manifested by ALPS 11 constructs, compared to other constructs. Furthermore, there was lack of any variation in the strength accept ALPS 10. Lack of stiffness in the variation of torsion and greater stiffness among DCP, SS LCD-CP, and ALPS 11 established the fact that the standard constructs and SOP had striking similarity in respect to their by mechanical properties of torsion (21). Other researchers also identified that the failure of most locked plating systems occur due to inappropriate configuration of the device, for the different patterns of fracture that are found among patients. Upon examining the different variables that should be taken into consideration during optimisation of a LCP best fixation device for treatment of fracture, it was suggested that the selection of device is not a straight forward process. This will prevent the plate being too low or high, thus being detrimental to wound healing. Material choice also affects healing rate in distal femur LCP, chiefly till 12 weeks post-operation. The fracture’s anatomical location was also found to change the forces placed on the plates (22). There is mounting evidence for the interfragmentary movement (IFM) present at the fracture site being governed to certain extent by bending of plate bending, thus calling for the need to control plate stiffness (23).

Moreover, it was also suggested that use of plate osteosynthesis for internal fixation of fractures that occurred in the bones is a continuously evolving process, having the primary objective of restoring functional capacity of the bones that have been fractured.  Hence, the major requirements of such fracture management should be to preserve the biology of destruction, reduced anatomical fracture, and increased durability of fixation, promote the healing process, and allow early mobilization of patients. While the traditional approaches for such internal fracture fixation were associated with interface compression and anatomic open reduction, they created extreme biological stress to the fractured surrounding sites. Hence, LCP  based fracture management techniques have been adopted for their role in increased stability in enabling durability of the fixation, while promoting less invasive approaches that are able to preserve the biological tissues at the site of fracture. Considering the fact that the new technique also promotes flexibility that helps in formation of periosteal callus with the use of interfragmentary motion, LCP should be adopted as the primary fracture management approach (24).

These findings were in accordance with another study the primary objective of which was to undergo a bio-mechanical comparison of torsional and axial stiffness of an external LCP. On creating a fracture gap model that simulated mid-shaft tibia, with the use of synthetic composite bones, it was found that significant differences existed in the mean of torsional stiffness between ESS-LCP (0.686 Nm/degree), ET-LCP (0.639 Nm/degree), and UEF (0.512 Nm/degree). Statistically increased torsional stiffness was also found for the ESS-LCP,  in comparison to UEF (0.174 Nm/degree; p = 0.013), which helps in concluding that use of LCP as an external fixator might be an attractive and viable alternative to traditional fracture management methods (25).

Results

Thus, it can be stated that over the last decade orthopaedic plates for breakage management have undergone major changes in their techniques and features. The screw most often locks into machine screws in the plate besides, being inserted into the bone. Union of the screws to the plate helps in keeping the screw fixed at a rigid position at an angle of 90 degrees to the plate. Hence, the locked screw functions in the form of a mini blade plate. While conventional screws most often rely on presence of friction between the screws and the plate, to prevent their movement at the fractured site, lock compression plate do not completely rely on frictional properties (26). Presence of the locking functions in the form of a minute internal fixation and follows the principle that is applied to external fixators as well. In other words, an LCP has a set of rigid screw fragments into the plate and bones and this is completely analogous to the external bar present in external fixator. For management of fractures, the plates in an LCP need not be inside or adjacent to the damaged bone, as is the case with conventional plates. This creates the provision for preservation of all soft tissues that surround the fractured site, which are most often innervated by blood supply to the damaged bone and its associated fragments (27).

The lock plates used for fracture management are often designed by manufacturers in a way that they are specific to the area where the fracture has occurred. The place of insertion varies for different anatomical regions such as, the lateral proximal tibial metaphysis or proximal humerus. While certain designs of the LCP allow the plate to be implanted in a percutaneous manner on to the bone, they also provide guidance to the surgeon to the screw holes that are present underneath (28). Thus, different types of internal fixation platting are utmost imperative in order to prevent any sort of complication, following insertion of the foreign object into the body of the patient. LCP implantation is often challenging in comparison to simple screws and plates, due to the fact that this modality prevents the fractured fragments to be easily pulled towards the plate, which could be easily done with the use of conventional screws. This makes it imperative to use ordinary screws or different techniques namely “whirlybird" screws in the locking plates, in order to obtain proper alignment against the plate. Similarity is obtained in terms of the pull out resistance of cortical screws and locking screws (29).

Single cortex locking screw is associated with 70% strength of the traditional cortical screw, over two different cortices. However, precautions must be taken during the usage of sharp self tapping screw, due to the presence of short points that are intended primarily for unicortical penetration. Failure to insert them in a proper manner might result in possible damage of the surrounding vessels and nerves, present on the other side of the bone fragment (30). Fragility factors also require the use of bi-cortical fixation at anatomical regions that are quite often exposed to high rotational forces. The humeral shaft is one such region that requires the implantation of bi-cortical fixtures of LCP. However, one of the potential disadvantages of LCP over conventional screw is its high expense (31).

Additionally the screws of LCP often do not pull in fragment towards the concerned plate and are capable of causing compression over the major fracture, in comparison to conventional place. A reduction also needs to be obtained prior to insertion of the screw in the plate and LCPs are also associated with extreme rigidity. The LCP becomes so stiff at times that it prevents formation of callous, thereby resulting in delayed union of the bones, or even non-union. Furthermore, at instances where the fractured gets poorly reduced, the alignment is found to persist even after the implementation of the locking plate (32). Consequently, the screws cannot be adequately used in order to pull in the fragments of the bones for achieving reduction, in contrast to those that can be done with traditional plates.

Conclusion

Thus, it can be concluded that locking plate and screws systems have several advantages over the conventional screw based systems. The conventional plate and screws systems are often in need of precise adaptation of the plate, in relation to the bone that underlies it. Without presence of an intimate contact between the two, tightening process of the screws will lead to drawing the bone segments towards the plate, which in turn would result in a variation or modification of the site of osseous segments and their subsequent occlusal relationship. However, the LCP system offers a range of advantages over the former in this regard. One of the most noteworthy advantages is that it often becomes necessary for the plate present in an LCP to from intimate contact with the underlying bones at all specific regions. The screws get stiffened when they lock or secure themselves to the plate, therefore stabilizing the bone fragments, without even calling the need for bone compression to the plate.

Hence, screw insertion for altering reduction becomes impossible in this context. Another probable advantage in the LCP system is that they are not responsible for disruption of cortical bone perfusion, in comparison to the traditional plates that have been found to compress plate under surface to the cortical bones.  A third benefit of the use of LCP is that the screws present in them lead to a reduced likelihood of loosening from the plate.  Therefore, even after insertion of screw in a fracture gap, there are very few chances of the screw getting loosened during healing and/or graft incorporation. This subsequently results in a reduction in inflammatory complication incidence rate, due to loosening of hardware. Loosened implants have a property of propagating inflammatory response and promoting subsequent infection. Furthermore, LCP systems also provide more stable fixation in contrast to the usual ones. Taking into consideration the few drawbacks that LCP system has in management of fractures, they should be used in combination with dynamic compression plates (LC-DCP) for fracture management in canines.

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