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Clavicle (collarbone) fractures make up 44% to 66% of all fractures of shoulder. A doctor can often diagnose a clavicle fracture during a physical evaluation, but X-rays and other tests are often recommended. The fracture may also require surgical intervention when Orthopaedic or trauma Implant may be used to fix the fracture.
Diagnosing Clavicle Fractures
X-rays can help determine the extent and location of the injury. At times it is essential to distinguish between a clavicle fracture and an injury to the joint at the top of the shoulder, called the acromioclavicular joint. A CT scan may also be required for more detailed images.
During the physical examination, the physician may do the following tasks:
- Note areas of tenderness
- Observe skin discoloration
- Look for deformities
- Address any open wounds
- Palpate or touch the shoulder blade and ribs to determine if there is an accompanying injury
- Listen to the lungs with a stethoscope, and observe differences in breathing
- Evaluate the shoulder’s range of motion
A doctor may conduct a neurological examination to make sure that motor functions and sensation are normal. The clavicle is located near a series of nerves found based in the shoulder and neck called the brachial plexus. Injury to the brachial plexus is uncommon but can happen with a clavicle break.
The physician will also ask about the medical history of patient, how the injury occurred, and any symptoms associated with it.
Common Causes and Risk Factors of Clavicle Breaks
They may be caused by:
- An athletic event resulting in a fall or direct hit. Clavicle fractures related to sports are commonly seen in children and young adults. Caution is advised when playing contact sports- including rugby, football, and hockey- and when participating in “extreme” sports where falls can happen- such as skateboarding and biking.
- A fall on the shoulder or an extended arm.
- A direct hit to the shoulder in a collision of motor vehicle.
Falling on the shoulder is the common cause of clavicle fractures.
Risk factors for clavicle breaks include:
- Young age, reaching a high point between the ages of 10 and 19. The clavicle is not entirely developed until about 20 years of age.
- Advanced age in both females and males over the age of 70.
- The onset of osteopenia, which is the early stage of reduced bone maps that can eventually lead to osteoporosis.
While certain people are at greater risk for a clavicle fracture, they can affect any person.
Nonsurgical Treatment for a Clavicle Fracture
Nonsurgical treatment for a broken clavicle can include the following:
- A wrap or arm sling is typically worn after the break occurs. This helps to prevent arm movement as the collarbone recovers.
- Pain medication, typically nonsteroidal anti-inti-inflammatory drugs such as ibuprofen or naproxen, can be taken to reduce pain.
- Physical therapy exercises will be recommended once the collarbone starts to mend. The patient will start with mild movements to ease stiffness. More intense exercises will be added after the recovery of bone.
Surgical Treatment for a Clavicle Fracture
Clavicle surgery may be required if the fractured pieces of bone are not in their anatomical and correct location. (The medical term for this is a displaced fracture). In these cases, the bones need to be secured and moved to heal properly. Bone plates, bone screws, and pins are often used during the surgical process. Rehabilitation after surgery includes exercises that can be done at home or with a physical therapist.
Stress fractures are a type of overuse injury characterized by small cracks in the bone. When muscles are fatigued and can’t absorb repeated impact, the shock is transferred to the bones. Weak bones caused by Osteoporosis may also be more vulnerable to stress fractures. These fractures can occur from sports or normal daily activities.
Stress fractures mostly occur in the bones of the lower leg and foot. The second or third long bones between the mid-foot and toes are the most often effected. Stress fractures sometimes appear in the heel, on the top of the foot, the outer bone of the lower and the navicular.
One of the most common occurrences of stress fractures occurs in runners who have been confined indoors during an off season and then, return to running without proper conditioning.
Improper foot gear is another reason due to which athletes get stress fractures. A well-known and old shoe can alter the dynamics of the foot and contribute to stress fractures. Athletes that change surfaces, like going from a grass tennis court to a hard court, can increase their risk for stress fractures, or from an outdoor running track to an indoor track. Other conditions, such as flatfoot or bunions, can alter the mechanics of the foot making it more vulnerable to stress fractures.
Symptoms of Stress Fractures
- Pain that develops slowly and is relieved with rest
- Swelling on top of the outside the ankle or foot
- Possible bruising
Treatment of stress fractures
Most stress fractures will heal if activity level is decreased and protective footwear is worn for two to four weeks. A stiff-soled shoe, a removable leg brace shoe, or sandal may be needed to provide support. Athletes are often advised to switch to a sport that puts less stress on the leg and foot while the bone heals, such as bicycle riding and swimming.
For stress fractures in the outer side of the foot or in the talus or navicular bones that take longer to heal, a cast may be applied to the foot or the use of crutches may be recommended until the bone heals. In some cases, surgery may be essential. The orthopedist may insert a bone screw into the bone to ensure proper healing. The orthopedic implants such as bone screws, etc. can be accessible from the orthopaedic implant manufacturer.
A fibula fracture occurs when there is an injury in the leg to one of the two bones of the leg. The leg (the segment between the ankle and knee) is made up of two bones. The larger bone, the tibia, carries most of the weight of the body). The smaller bone, the fibula, is located on the outside part of the leg.
The fibular bone starts just below the knee joint on the outside of the leg and extends all the way down to the ankle joint. The bone is a thin, long bone, hollow in its center. While the bone does little to support the body weight, it is a critical site of attachment for ligaments at both the ankle and knee joint and is also connected to the tibia by a thick ligament called the syndesmosis.
While the fibula is a significant bone, it is possible to extract much of the bone for surgical procedures where the bone is needed elsewhere in the body. When these grafting procedures are performed, people can function very normally, despite missing a large part of the fibula bone.
Types of Fibula Fractures
There are several types of injury to the fibula bone. For this discussion, I will divide them into more manageable topics:
- Fibula fractures that occur due to injury to the ankle joint
- Fibula fractures that occur in conjunction with tibia fractures
- Stress fractures of the fibula
These are not the only types of injury that can occur to the fibula but account for the majority of cases of injury to the fibula bone. By far the most common are injuries that occur when the ankle joint is damaged. Typically, the ankle buckles or is twisted and the fibula is injured as part of the injury.
As mentioned, fibula fractures can occur in association with injuries to the ligaments, other bones, tendons, and tendons around the knee and ankle. The most common symptoms related to the fibula fracture include:
- Pain directly over the fibula bone (outside of the leg)
- Swelling in the fracture part
- Bruising over the injury site
Diagnosis of a fibular fracture can typically be done with an x-ray image. Other imaging studies such as CT scan or MRI are typically not necessary, but there are some situations where a fibular fracture may not show up on a regular x-ray. These conditions include injuries such as stress fractures. Your physician will examine the injury site, the ankle and knee joints for associated injuries which may impact the treatment of the fibular fracture.
Fibula fractures typically occur as part of an ankle injury. Whenever a fibula fracture is found, the ankle joint should be examined for an injury that can be possible.
The most common kind of fracture to occur to the fibula bone is an isolated injury to the end of the fibula bone at the level of the ankle joint. These injuries occur in a similar manner to a badly sprained ankle, and mostly the injury can be treated similarly to a badly sprained ankle.
The components of a ring fixator system are categorized into 2 categories: main and secondary. The main parts are the standard elements utilized to correct skeletal deformities: rings, wire-fixation bolts, wires, and buckles, pin clamps, and pins.
The secondary parts of the system comprised of the elements essential for the assembly of the fixator: rods, plates, posts, supports, hinges, washers, bushings, sockets, nuts and bolts. To assemble the several pieces of equipment various kinds of wrenches and wire tensioner are required. There are no screws in this system and screwdrivers aren’t required.
A ring with multiple holes and a flat surface is the main component of a circular external fixator (Ilizarov).
The ring encloses a limb segment: 2 or more rings are connected to make a frame. The ring’s flat surface supports the heads of the nuts and bolts. The surface-nut interface or surface -bolt guarantees firm fixation of the wires, threaded rods, and bolts while treatment. The flat surface of the rings is essential for attaining a secure wire inclination and plane orientation. All rings in a frame are aligned perpendicular to bone’s long axis. A ring is made of carbon fiber or stainless steel provides strong support for the frame and is intended to bear high stresses of the tensioned wire, up to 150 kg. The ring’s internal diameter measures from 80 to 240 mm. A whole set has rings of 12 different diameters to suit several limb thicknesses.
A ring fixator set has several half and full rings. A full ring is lighter, has more holes than 2 connected half-rings, and doesn’t need connecting bolts and nuts. The holes in the ring are utilized for introduction of a threaded rod, a connector plate or a hinge. On the negative side, a full ring must be placed before the introduction of wires. If clinical state demands the removal of a full ring during the treatment tenure, then it must be cut with specific instruments.
Every half-ring, depending on its size, has eighteen to twenty-eight holes in the mid-segment of the flat surface. The standard holes are equally distance threaded (4 mm apart) and are of same size (8 mm in diameter). Threaded rods or bolts are affixed in the holes. 2 half-rings are joined by bolts and nuts to make a full ring. The ends of the plate don’t have standard-sized hole, are offset as well as ledged to fit together on an even plane to form a full ring.
The half-rings may also be connected to make an oval ring, three- and four-leaf clover rings and another specialized construct with the help of additional devices to make more space between the ring and the limb.
A five-eighths ring enables joint motion and is usually deployed near knee and elbow joints. Besides motion, these rings enable the introduction of cross wires, a distinct benefit near these joints. This ring can be used in the middle of a regular frame to offer access for management of soft tissue. Though, 5/8 ring is weaker than a full ring; a three-point connection to a full ring reinforces as well as strengthen it. Wires attached to a 5/8 rings are tensioned only after such stable connection is established. These rings can be accessible in three sizes from 130 to 160 mm.
From the mechanical viewpoint, it’s not essential to remove an orthopaedic nail in a weight-bearing limb and dissimilar from a plate, it can be left indefinitely in the body. Removal initiated by the request of the patient should be delayed for eighteen months. Intramedullary devices sometimes induce local changes that can be irritative either to the bone or to the patient and require removal. Swelling and local pain secondary to backing out of the implant is another indication for removal; confirmed bone union on radiological examination is a prerequisite for such removal.
A sharp-angled deformation seeming in the follow-up roentgenogram is an indication of appliance failure. A sharply bent device is necessary to be removed and replaced as it has undertaken plastic deformation and is expected to fail with further weight-bearing. Bent nails may be removed forcefully straightening and extraction.
Nail removal shouldn’t be undertaken lightly. Specialized extraction equipment fitting the exact nail must be available. Although removal is often a straightforward process, mismatching equipment, nail breakage, damage to the threads in the proximal end of the nail and distortion in the bony anatomy preventing removal are common causes of difficulty.
Difficult situations in nail removal
- The extraction hook fails to grasp.
- Stack the canal round the hook with ball-tipped guide wires. Hold the bunch in a vice grip and hammer out to remove the nail.
- Bone growth along the track of the locking bone screws removed some time ago.
- Re-drill the holes with an appropriately large drill bit.
- The broken nail in a united fracture; the extraction hook fails to regulate the alignment as well as pulls the nail tight against the opposite cortex rather than out of the canal.
- Take away the proximal half of the nail. Pass a guidewire that is ball-tipped into the proximal canal till the ball is near the broken end of the nail. Ream the proximal canal up to the nail’s broken end to facilitate easy removal. Pass 2 or more guidewires into the distal nail fragment and impact them with a hammer. Grasp the bunch in a vice grip as well as hammer out to remove the nail.
- The broken solid nail in an ununited fracture.
- Take away the proximal half. Create a window in the bone distal to the tip of the nail as well as hammer the nail out. In the femur, arthrotomy of the knee joint can be needed. In the tibia, if the nail is short, make an opening in the medial malleolus to arrive till the nail.
- The protruding nail in a healed fracture and nail doesn’t move.
- Use specialized metal cutting equipment to remove the offending nail length.
- Impacted nail.
- Find the point of maximum hold under fluoroscopy. Create a longitudinal cut in the bone with the help of an oscillating saw or an osteotome at that point. Extend the cut either way till the bone springs open enough to allow removal of the nail. The method is suited best for a tibial nail and is employed only as a final resort.
Full weight-bearing may start immediately after the removal of an intramedullary nail, but a coming back to vigorous sporting activity should be delayed until rehabilitation is attained.
Pins are versatile and are usually helpful for internal fixation. A pin has a comparatively small diameter and is inserted through the soft tissue and bone with comparatively little trauma. A Kirschner wire is inserted with a power drill as well as a guidance system. The soft tissues tend to wind round the Kirschner wire at the time of insertion and must always be protected. Several types of guides are in use: a telescoping guide linked to the drill, or an external guide with a handle are common orthopedic Instruments. A power drill with a quick locking and release mechanism save considerable time and is also suitable for insertion of Kirschner wire from the barrel of the drill, that doubles as a guide.
Kirschner wire insertion
- Always deploy a power drill to insert a Kirschner wire.
The wire bends once it’s inserted on a hand drill.
- To protect soft tissues during insertion, always use a guide to direct the pin.
- Support the wire.
- Place the cutter jaws at right angles to the wire.
- Bend the wire up after cutting.
- Tip of wire must not touch the plaster cast.
Fashion a point- 2 oblique cuts to fabricate a sharp tip
Kirschner wires are helpful for provisional fixation of a comminuted fracture. They help in accurate placement of the fragments and orthopedic implants, especially the plates and the bone screws. Multiple wires are inserted without any added trauma. When provisional stability has been attained, X-ray pictures can be made to visualize the strength as well as weakness of the construct.
Planning is necessary while inserting Kirschner wires for provisional fixation. Pins are introduced in such a way that they don’t obstruct the final placement of the definitive implants. For instance, wires are passed parallel to each other in the same direction in which the lag screw is to be introduced in order that there’s no obstruction to compression of the fracture with the lag screw.
Whenever a Kirschner wire is used for definitive fixation, the pin’s end should be cut a centimeter under the skin and may be bent; a long wire end will protrude through the skin, either because of the pressure from within or from outside. If a wire is cut too near the bone, it’s difficult to locate it at the time of removal. The jaws of a wire cutter are always positioned at right angles to the wire. If they’re positioned at any other angle, a twisting force develops whereas snapping the wire. This force is transferred to the bone and due to this unintentional fracture may occur in a small bone, specifically in the cancellous area. A sharp point at the pin trip may be fabricated by making an oblique cut and then rotating the pin to make the 2nd oblique cut. The free end of the wire must always be bent with an orthopedic instrument. The bending force, if transmitted to the bone, may cause an inadvertent fracture; this complication is avoided by gripping and stabilizing the pin at the time of bending. There’s a genuine danger of migration of a straight pin into the soft tissues or into the bone; a pin is known to travel a long distance across the planes of soft tissue. When using a pin around the shoulder, it’s imperative that the trip be bent.
A pin enclosed in a plaster cast shouldn’t touch the cast but move freely inside. There’s considerable movement between the cast and the bone because of the presence and the thickness of the soft tissues. If any pin touches the plaster, forces are transferred to the bone, resulting in pin loosening as well as loss of fixation. A pin must be removed after it has served its purpose.
The orthopedic implants manufacturers deploy many of the metal-working methods. A brief account of the fabrication process of some implants follows.
An orthopedic bone screw is manufactured by very precise procedures from titanium or steel rod with a diameter of at least the width of a cannulation at this step, which is added by gun drilling. Gun drilling is an exact process with minimum variation from the required dimensions. The special drill contains a central channel for cooling fluid delivery as well as for removal of metallic debris. The next step in screw production includes machining of the threads. The cutting flutes are cut on a Lathe/ CNC Turning Centre or a SPM. In the bone head drilling and punching with a hexagonal tool is done to make recess for Screw Driver.
Electropolishing as well as passivation are done on the screw to clean the material after machining and increase the resistance of material to the corrosion.
A bone plate is produced from a sheet from which its profile is cut by laser Cutting. Different variety of plates, shaped to suit the bone profile on which it must be fitted, are cut out of steel or titanium sheets. After facing, holes are drilled or milled according to the design (self-compressing or round).
The plate for a sliding hip screw is produced from a bar which is forged and bent to the desired angle (e.g. 135⁰, 140⁰, 145⁰, 150⁰). The plate’s barrel segment is turned on a lathe and the barrel hole is drilled as well as broached. The plate is than milled to attain the correct profile. The holes of plate are milled to obtain the correct profile. The counter on the holes of plate are milled and the product is finally finished. Finishing is labour intensive job, which needs advanced manual skills.
AO/ASIF nail is an example of combined metal working techniques. This is made from a tube which is cold drawn as well as annealed several times to decrease the wall thickness and diameter of the tube.
Then the longitudinal slot is cut into the tube, and the drive is threaded. The locked Universal nail isn’t made from a sheet of stainless steel but from a stainless-steel tube which is cold drawn and annealed many times to decrease the wall thickness and diameter. A longitudinal slot is then cut into the tube and, finally, the threads are cut in the drive. A non-slotted nail is manufactured from a solid bar of stainless steel. The central cannulation is produced through the method of gun drilling.
It is evident from above that machining of implants utilizes many machining and metal working techniques, which are essentially in ‘cold condition’ i.e. at a temperature at which its microstructure is not affected.
An ideal trauma implant material should be inert, non-toxic to the body, and completely corrosion-proof. It should be inexpensive, simply worked, and mouldable in various shapes without expensive manufacturing techniques. It should have high resistance to fatigue and great strength too. Such a material isn’t available at present.
There are at least fifty alloys and grades of alloys known as commercial stainless steel. Only a few are helpful as implant biomaterial in fracture surgery.
Stainless steel designated as ASTM F-55, -56 (grades 316 and 316L) is utilized extensively for fracture fixation implants. Stainless steel of type 316L is an iron-based alloy. Alloying with chromium generates a self-regenerating, protective chromium oxide layer which offers a major protection against corrosion.
The addition of molybdenum reduces the rate of slow, passive dissolution of the chromium oxide layer by up to thousand times. Molybdenum further protects against pitting corrosion. Nickel imparts any further corrosion resistance and enables the production process, while limited quantities of silicon and manganese are added to control some problems related to manufacturing.
The carbon component raises the strength, but its existence in the alloy is undesirable. Under certain conditions created as a results of improper heat treatment, the carbon segregates from the main elements of the alloy, taking with it a considerable amount of chromium in the form of chromium carbide precipitates. Carbides formed at grain boundaries, whereas corrosion selectively happens. Moreover, the carbides degrade the material’s mechanical properties. Mixing of small quantities of titanium or niobium lessens the creation of intergranular carbides by competing for carbon.
Stainless steel of type 316L has a very low permissible level of carbon to diminish this problem. To rise the resistance to fatigue failure, 316L stainless steel can be accessible in a special grade with smaller as well as more widely spaced inclusions. This grade, designated as AISI 316LVM and specified by ASTM F-138, is made by a special method known as ‘vacuum-melting’, which results in a cleaner metal. The strength of 316L may be greatly altered by the method of production, and it may be made extremely ductile (up to 55 percent strain to failure). The alloy selected F-745 is a high strength casting material, whereas 22-13-5 has much more yield strength than 316L for the same treatment method.
Though it is a stiff, strong, and biocompatible material, 316L stainless steel has a slow nevertheless finite corrosion rate. Concerns regarding the long-term effects of nickel ions, still, prevail. Stainless steel is best fitted for short-term implantation within the body as in fracture fixation. Stainless steel is often used because the base materials are cheap, the alloy may be formed using common techniques, as well as its mechanical properties may be controlled over a wide range for ductility and strength. The elastic modulus of stainless steel is approx. 12 times higher than the elastic modulus of cortical bone.
Titanium is the 9th most common element in the crust of earth, where it forms oxidic minerals (ilmenite, rutile). The pure element is very reactive; it’s the sole element that burns in nitrogen. Though, the metal quickly becomes coated with an oxide layer, making it resistant to most chemicals and physiologically inert. Titanium is utilized for making orthopaedic implants in 2 forms: commercially pure and a range of alloys.
Titanium-aluminum-vanadium alloy (ASTM F-136) is generally known as Ti6A14V. This alloy is broadly used to manufacture implants. Impurities such as hydrogen, oxygen and nitrogen tend to make it brittle, which describes why only minimal amounts are acceptable in titanium alloys utilized in surgical implants. ASTM F-136 limits the oxygen concentration to a particularly low level of 0.13%, referred as the ELI (extra low interstitial) grade. Limiting the extent of dissolved oxygen improves the material’s mechanical properties, mainly increasing its fatigue life. Aluminium stabilizes the alpha material’s form while vanadium stabilizes the beta form. Combination of both components forms a two-phase alloy with good strength properties and one that may be heat treated. Ti6A14V ELI is often used for making orthopedic implants.
Commercially pure titanium isn’t a single chemical element however is alloyed by a level of oxygen dissolved into the metal. It also has traces of nitrogen, iron, hydrogen and carbon. The presence of these trace elements effects the mechanical properties of the titanium. International standard ISO 5832/2 defines the extent of permissible impurities.
Titanium has an elastic modulus approx. half that of the cobalt-chromium alloys and stainless steel. The lower stiffness of bone plate made of titanium decreases the severity of stress shielding and cortical osteoporosis. Another benefit of lower stiffness is that a titanium plate is less susceptible to fatigue failure than a stainless-steel plate. The elastic properties of titanium need that contouring be attained by slight over bending; it’s important however, that no metal should be twisted or bent repeatedly at the same location. The titanium’s modulus of elasticity is still roughly 6 times that of cortical bone. The ductility of titanium alloy is considerably less than that of most stainless steels. Because of this difference a surgeon needs some adaptation of his feel when knowing the optimal amount of torque to be applied to the bone screws. The feel should be acquired prior starting to use these bone screws in clinical practice.
The corrosion resistance of pure titanium is outstanding as a very dense and stable layer can be destroyed mechanically at the time of implantation by instruments such as bending pliers. The passive layer is restored spontaneously, quickly and effectively (re-passivation). In the presence of unstable fixation, the components of titanium of an internal fixation system are exposed to fretting conditions and make metal debris. Such debris causes black or grey coloration of the surrounding tissues. This discoloration, which isn’t a result of corrosion, is harmless. Special surface treatment of the ortho implant lessens such discoloration.
Forging is basically the art of the blacksmith. The metal is heated as well as hammered or squeezed into shape. A die is occasionally used; this is a mold to guide the flow of the metal. Drop forging, the most commonly utilized forging method, means that the piece is formed in a mould comprising of two or more parts in an eccentric press. Forging produces an orientation of the grain flow which makes the metal stronger than before. Many orthopedic implants use this technique for shaping the raw material.
Casting involves heating the metal to a molten state and pouring it into a mould. In comparison to Forging, the strength of processed product is less and there may be cracks/ blow holes inside if metal flow is improper during casting. Few fracture fixation orthopedic implants, if any, are presently fabricated in this way.
Rolling & Drawing
Rolling (between rollers) as well as drawing (through a hole in a hardened plate) are utilized to form bar and wire.
The material is plastically deformed in the procedure and the grains turn out to be elongated in the direction of deformation. Most of the raw material in form of wire/ rod or Sheet is processed in this way.
Milling is a basic machining procedure in which material is removed by feeding the work or the workpiece (the core material from which a portion of specified geometry and surface finish is to be fabricated) into a rotating cutter or by means of having the rotating cutter advance into a stationary workpiece. The cutter usually consists of multiple cutting teeth and material may thereby be removed at high rates. Milling offers good surface finish characteristics. This method is abundantly used for manufacturing Plating Systems.
Cold working is a finishing procedure employed after the metal has been shaped by hot forging and is somewhat like it, but the work is performed below the recrystallization temperature. The benefits of cold working are a smoother surface finish, uniform grain structure, higher tensile strength, and superior dimension control. Cold working needs more energy compared to hot forging to deform the metal below its recrystallization temperature.
Many Anatomical plates are bent in this manner, particularly which are having low plate thickness.
After forming, metal parts may undergo heat treatment to alter their structure as well as properties. Heat treatment methods used are:
Annealing is heating to approximately half the melting point, followed by controlled cooling. The procedure reverses the consequences of work hardening as well as restores ductility and toughness to the metal. Annealing (heat treatment) of a forged piece decreases its internal stresses.
Some products are also treated to cause the outside surface of the rod to be stiffer than the inner core. The benefit is that the harder outer surface will resist indentation while the core is able to absorb more energy.
Geometric features such as holes and grooves require machining. This can work harden the material surface, but its grain structure remains without any change.
Bone Screws manufacturing is carried out by machining on Lathe/ CNC Lathe.
Successful use of a bone plate relies on the properties of the plate, the bone screws, the bone and on the accurate application of biomechanical principles.
Plate related factors
The strength of a plate relies on its cross-sections; thickness is the most significant contributing factor. The strength differs with the cube of the thickness. The plate should be made from a material of suitable strength and stiffness of the plate should be close to that of the bone. The titanium’s stiffness is closer to that of bone, while stainless steel is stiffer than titanium. Very stiff bone plates can weaken the bone after fracture healing is done. The plate’s contact surface is also a significant factor. The conventional plate’s surface causes reduction of blood supply under the plate, resulting in immediate post-fixation osteoporosis.
In the new design featuring decreased contact self-compressing plate to lessen contact surface, substantial material is removed from the plate’s undersurface between the holes, giving it an arched appearance. A conventional orthopedic plate is weak at the screw holes. The excavation lessens the stiffness of the plate to the similar level as of the screw hole area. The bone plate with this design now has even stiffness in both the areas. Such a plate may be bent in a constant curvature with a good fit of the screw head in the plate hole and still preserve the mechanical features that consistently distribute bending as well as torsional stresses over a long distance along the plate. The fatigue life of plate is prolonged because its holes are protected from localized high stresses. The holes of plate are symmetrical, consistently distributed along the plate, and have oblique undercuts on the plate’s lower side. This undercut enables unhindered inclination of a lag screw up to 40⁰ longitudinally, as well as 7⁰ in the transverse plane, in both directions through the plate. Usage of a shaft screw as a lag screw through the plate in position of a fully threaded cortical screw provides superior static compression force. The plate’s even distribution holes allow the place of the plate to be adjusted or for the plate to be replaced for a longer plate without conflicting with any previously drilled holes.
The plate’s length is another important factor. A too short plate can make a construct unstable, while application of a very long plate can cause needless damage to the soft tissue.
Screw related factors
The bone screws fasten a plate to the bone. The effectiveness of a screw largely depends on the design of its head. Well-made threads are easy to insert and hold well in all conditions. A well-designed slot for the screwdriver’s placement ensures ease of screw insertion. Suitable number of screws is necessary to hold the plate. A minimum of 2 in each fragment are essential to prevent rotation. The total number of screws required for a fixation relies on the site and kind of fracture. The ratio of the pilot hole to screw’s depth depends on this ratio. Strength of the plate fixation relies on turn on the holding power of the bone screws. The screws should be made of strong material which may withstand heavy loads. Plates and screws should be of the same material to diminish corrosion.
The success of bone plate fixation relies on:
- Plate thickness, geometry, dimensions, material used
- Screw design, number, material, and hold in the bone
- Bone-mechanical properties as well as the health of the bone
- Construct- direction of load and placement of plate
- Compression between the fragments
Bone related factors
The health of the bone is a factor which is often overlooked while fixing a fracture. A young bone is dense in consistency and a screw holds good in such a bone. As the holding power of a screw is dependent on the elastic force offered by the bone, it’s obvious that the denser the bone, the stronger the hold. In the elderly people, the bone is porotic, being less dense than young bone. The holding elasticity of porotic bone is a lower magnitude as well as leads to inferior screw hold. Therefore, the mechanical properties of bone and health are of importance in this context.
The bone’s interaction and the plate are important, since the 2 are combined in a composite structure that becomes a vital entity in the strength of a fixation. The strength of a plate-bone construct is its capability to withstand load without structural failure. This entity may be described as a torsional strength or a bending strength, depending on the load application. An orthopedic plate is a load sharing device. Loads may be transmitted between plate as well as bone through the bone screws and through friction kind of forces between the plate surface and the bone. Some of the load is supported by the plate and some load passes between the fragments of bone. The reconstructed bone must support a certain load.