Medical Apparatus: Imaging Guide to Orthopedic Devices
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Orthopedic Devices

Joint Arthroplasty

Conservative Fracture Treatment

Internal Fixation - pins, wires, and screws

Internal Fixation - plates

Internal Fixation - rods and nails

Internal Fixation - bone grafts and bone substitutes

Carbon Fiber Implants

Fracture Fixation References

Joint Arthroplasty References

 

Fracture Fixation continued...


by Tim B Hunter, MD, MSc

 

Internal Fixation continued...

Plates

Most fracture fixation plates are made of stainless steel or titanium and can be used for both flexible and rigid fracture fixation (figure: fracture fixation plates). Flexible fixation means the fracture fragments displace in relation to each other when a load is applied across the fracture site. There is appreciable interfragmentary movement under a functional load. The majority of the fracture fixation methods commonly employed use flexible or "biologic" fixation. Fracture healing under flexible fixation typically occurs by means of callus formation.

Compression fixation techniques, which are less common, produce rigid fixation. Rigid fracture fixation with plates and screws is desirable for fractures that involve an articular surface. Articular fractures require exact anatomic reduction and stable fixation to avoid development of abundant callus. This is important because unevenness of the joint surface and presence of callus formation at the articular surface lead to patient discomfort and often development of early and progressive osteoarthritis (Ruedi, 2007).

Bridging of any fracture with a stiff splint reduces mobility of the fracture fragments, which allows minimal displacement under a functional load. Although rigidity of the fracture fixation contributes to reducing fracture mobility, the only technique that can effectively abolish motion at a fracture site is interfragmentary compression of the fracture fragments. However, with proper placement and use of plates and screws there is often enough stability to diminish the strain at the fracture site to such extent there is direct healing without formation of visible callus.

Terminology commonly used with fracture plating is “compression plating” and “neutralization plating” (figure: neutralization and buttress plates; figure: buttress plate with bone substitute). Compression plating applies compression to the fracture ends. Severely comminuted fractures and/or fractures with bone loss prevent compression plating. In these cases, the fixation plate is applied in neutral mode to hold the fracture fragments in place without compression during healing. No matter the case, frequently not all the screw holes in a fracture fixation plate are filled.

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Six-hole dynamic compression plate (DCP) and syndesmotic screw

Syndesmotic screws and dynamic compression plate (DCP)

Anchor screws (suture anchors)

Acutrak screws and endobuttons

Syndesmotic screw and dynamic compression plate

Syndesmotic screws

Anchor screws

Acutrak screws and endobuttons

Acutrak screws and Endobuttons

The dynamic compression plate and syndesmotic screw are for an acute distal fibular fracture and syndesmotic injury. From Benjamin, 1994

Locking low contact dynamic compression plate and screws with two fully threaded syndesmotic screws. A plaster splint is also present about the bimalleolar fracture. From Taljanovic, 2005 Multiple suture anchors are present along the right shoulder glenoid rim for tacking down the joint capsule in a patient with recurrent shoulder dislocation. From Taljanovic, 2005 64 year-old woman with thumb "tightrope" surgery using Endobuttons and Acutrak screws. The trapezium has been resected.

Endobuttons    
Endobutton Endobutton    
Image © Smith & Nephew. Used with permission.    
Anterior cruciate ligament fixation

Suture anchors (anchor screws) in humeral head

Suture anchor (anchor screw) in calcaneus

ACL intereference screws

ACL intereference screw

Suture anchors in humeral head

Suture anchor in calcaneus

Shown are an "interference screw (Kurosaka screw)" for the anterior cruciate ligament, and fixation staples for the medial collateral ligament and the patellar tendon/tibial tuberosity.

Multiple suture anchors are present in the left shoulder humeral head for tacking down the joint capsule in a patient with recurrent shoulder dislocation.

 

Anterior cruciate ligament (ACL) reconstruction with bioabsorbable tibial interference screw and femoral Endobutton

 

Anterior cruciate ligament repair with bioabsorbable tibial interference screw and femoral Endobutton

Blade spiral (helical) distal locking screw

ACL repair

ACL repair

ACL repair

Spiral distal locking screw

29 year-old man with ACL repair. immediate postoperative images with soft tissue and intra-articular gas from the recent surgery. There is also a fully threaded tibial tuberosity cortical screw.

 

 

There are also two cortical distal locking screws, an intramedullary rod (nail), and skin staples.

Smart Toe implants

Achilles tendon lengthening pin

Interference (Kurosaka) screw

Smart Toe implants

Smart Toe implants

Achilles tendon lengthening pin

Kurosaka screw

71 year-old woman with surgery for recurrent hammertoes. There are Smart Toe implants fusing the right second and third interphalangeal joints. A small cortical screw goes through the second metatarsal neck, and there are K wires in the fourth and fifth toes.

 

50 year-old woman with chronic juvenile arthritis

Interference (Kurosaka) screws are used to anchor anterior cruciate ligament graft in femoral and tibial metaphysis. Note the multiple osteochondromas (familial exostosis). From Benjamin, 1994

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Plates continued...

 

Buttress plates are used more for bony alignment rather than compression. They are indicated for situations in which the fracture fragments are unstable in compression or axial loading. They are most commonly found in the distal radius and in the proximal tibia where they stabilize tibial plateau fractures (figure: buttress plate with bone substitute; figure tibia buttress plate). They are also sometimes found in distal femur intercondylar fractures (figure: femur buttress plate).

Plates are most commonly used for fixation of long bones, but they also are used in the spine and for arthrodesis of the wrist (figure: wrist arthrodesis) (Ruedi, 2007; Benjamin, 1994). When diaphyseal fractures in the long bones are treated with a fixation plate, a minimum of six cortices should be engaged at each fracture site, except for the femur, which requires eight.

Dynamic compression plates (DCPs) were introduced in 1969 and have since been modified for multiple applications. These plates produce axial compression at the fracture site, which is achieved by means of oval holes designed to provide compression of the fracture as eccentrically placed screws are tightened on either side of the fracture line. DCPs are designed to compress fracture fragments together rather than merely hold them in contact. They are typically used for fractures that are stable (figure: fibula dynamic compression plate).

Dynamic compression plates function in different modes: compression, neutralization, tension band, and buttress. They are available in different sizes to accommodate fracture fixation in bones of different sizes. The screw holes in DCPs are oval and are best described as a portion of an inclined and angled cylinder. DCP plates can be used with different types of screws. The areas about the plate holes are less stiff than the areas between them, and during bending the plate tends to bend only at the hole sites (Ruedi, 2007; Benjamin, 1994).

A newer design of DCPs is the low-contact DCP (LCD), which reduces the area of contact “footprint” between the plate and bone. This design produces less compromise to the capillary network of the periosteum, which leads to a relative improvement in cortical perfusion (figure: wrist arthrodesis with LCD). The distribution of the holes and even stiffness of this plate allow gentle and elastic deformation of the entire plate without stress concentration at one of the screw holes, as occurs with the standard DCP. The footprint of the low-contact DCP has a trapezoidal shape, and the screws can be inserted in the plate in different modes: compression, neutral, and buttress (Ruedi, 2007; Benjamin, 1994; Berquist, 1995; Freiberg, 2001; Hunter, 2001).

One-third tubular plates are thinner than DCPs. Tubular plates are called “tubular” because they form part of the circumference of a tube, that is, one-third, one-fourth, and so forth of the circumference of a tube or cylinder. Tubular plates have a radiographic appearance similar to that of DCPs. These plates are only 1 mm thick and are used for fracture fixation in regions with a small amount of overlying soft tissue, such as the distal fibula, distal ulna, and olecranon. The holes in tubular plates are oval and are surrounded by small collars, which allow a certain degree of eccentric screw placement and which prevent screw head penetration of the plate (Benjamin, 1994; Hunter, 2001).

Blade plates are fixed angle plates. They have a sharply angled extension at the end that is placed into the metaphysis. Blade plates have a wide range of angles to accommodate different fixation needs (figure: blade plates) (Ruedi, 2007; Benjamin, 1994; Wiss, 2013; Berquist, 1995; Freiberg, 2001; Hunter, 2001).

Reconstruction plates have deep notches between the holes and allow a considerable amount of bending (figure: uniplanar external fixator; figure: fixation plates; figure pelvis reconstruction plates). These plates are often generically referred to as malleable fixation plates. The screw holes are oval to allow for dynamic compression.

Reconstruction plates are used mainly for fixation of pelvic and acetabular fractures. They can also be used for fixation of distal humeral, clavicular, and finger fractures (figure: clavicle reconstruction plate; figure: finger reconstruction plate) (Ruedi, 2007; Benjamin, 1994; Wiss, 2013; Berquist, 1995; Freiberg, 2001; Hunter, 2001).

Interfragmentary bone compression with a plate can be achieved by compression with a tension device, by compression with a DCP or low- contact DCP, by contouring (over-bending) the plate, and by using additional screws through plate holes. An interfragmentary screw should be used whenever fracture fragments permit it. Placement of the interfragmentary screw through the plate is preferred over a freestanding placement (figure: femur blade plate and interfragmentary screw) (Ruedi, 2007).

In situations where there is a highly comminuted fracture or deficient bone stock a periarticular locking plate and screws may be used. There are locking screw holes combined with the compression plate allowing the plate to be used as both a locking device and a fracture compression device (figure: humerus periarticular locking plate with bone substitute; figure: humerus periarticular locking plate; right femur periarticular plate; figure: tibia periarticular plate and bone substitute.  Periarticular locking plates may also have varying thickness, greater in the diaphysis and thinner in the metaphysis.

Bridge plates are used for fixation of complex diaphyseal fractures to minimize additional soft tissue injury. A bridge plate is applied through minimal soft-tissue exposure. It is designed to span a critical fracture area and is fixed with screws to the bone fragments only near its two ends (Ruedi, 2007).

The point contact fixator (PC-Fix) was initially designed for fixation of forearm bone fractures. It consists of a narrow plate with a specially designed undersurface with small points that come in contact with the bone surface. The plate is fixed to bone with unicortical self-tapping screws. If needed, the PC-Fix plate can be gently contoured to accommodate the shape of the bone.

The LISS (less invasive stabilization system) plate was designed for fracture fixation in the metaphyseal and diaphyseal regions, initially for the distal femur and later for the proximal tibia (figure: femur LISS plate). Its shape conforms to the anatomic contour of a specific area of bone. Therefore separate implants are available for the left and right sides. Additional contouring is not needed because the LISS plate does not need to touch the bone. The plate is fixed to the bone with locked unicortical screws placed by means of a minimally invasive submuscular approach. Before placement of a PC-Fix or LISS plate, the fracture must be adequately reduced.

PC-Fix and LISS plates have several promising advantages over conventional plates, including better preservation of the blood supply to bone and better resistance to infection. They provide a fixed-angle plate screw device that consists of two components for easy application in complex fractures and self-tapping cortical screws that are easily and rapidly applied to a reduced fracture. The additional advantage of a LISS plate is its insertion in a minimally invasive fashion (Collinge, 2000; Kregor, 2001; Frigg, 2001; Kregor, 2002).

A variety of special anatomically shaped plates exists that are dedicated for fracture fixation in a specific location. Some of these are the condylar plate 95° for stabilization of proximal and distal femoral fractures, angled blade plate 120° for valgus osteotomy of the femur, condylar buttress plate for the distal femur, T-plate 4.5 for the proximal humerus and proximal tibia, lateral tibial head buttress plate, tibial head buttress plate (right and left), cobra head plate for arthrodesis of the hip, angled blade plate for the femur, dynamic condylar screw for the proximal and distal femur (combination of side plate and a separate screw), and an oblique angled 3.5 T-plate for fixation of distal radius fractures (figure: wrist T-plate; figure: variable angle volar distal radius locking plate).

The clavicle hook plate is a clavicular plate with a hook engaging below the acromion (figure: clavicle hook plate). It is intended for fixation of both lateral clavicle fractures and acromioclavicular joint injuries (Synthes). The plates are precontoured as left and right plates and are available with 6 or 8 holes, one of which is an anterolateral screw hole for additional options for screw fixation in the lateral clavicle. The dynamic compression screw holes accept 3.5 mm cortex or 4.0 mm cancellous bone screws. The offset hook design is intentional to avoid insertion of the hook into the acromioclavicular ligament. The plate achieves a high percentage of bony unions and a low percentage of complications, but there are concerns about possible long-term complications involving the acromioclavicular joint (Tiren, 2012). A similar hook design is sometimes used in other locations, such as with distal ulnar fractures (figure: distal ulnar hook locking compression plate).

Medial open wedge high tibial osteotomy is a well-established procedure for the treatment of medial knee joint osteoarthritis and symptomatic varus malalignment. Puddu or TomoFix plates systems are specifically designed for use with osteotomies close to the knee, particularly the high tibial osteotomies for treatment of medial compartment knee arthritis or sometimes for opening wedge distal femoral varus osteotomies for treatment of lateral compartment knee arthritis (Puddu, 2007) (figure: tibial osteotomy plate; figure: Puddu titanium plate with hydroxyapatite bone graft wedge).

Total or partial wrist fusion is sometimes performed for severe carpal osteoarthritis. In this regard, a spider plate may be used for partial carpal arthrodesis (figure: spider plate). Modular plate systems are available for four-corner and other limited wrist fusions for osteoarthritis, complex fractures, revision of failed previous wrist fusions, marked carpal instability, or rheumatoid arthritis (figure: Acumed hub cap fusion plates).

The next step in the evolution of biologic plating is percutaneous plating, which results in less surgical trauma to tissues and further improvement in clinical results compared with current methods of open surgical plate insertion. The percutaneous technique was developed in an effort to combine the advantages of intramedullary nailing with the more stable fracture fixation available with plating. In percutaneous plating, a smaller incision is used to place the plate, and the screws are then placed percutaneously. Preliminary reports about the results of percutaneous plating are promising. However, these methods are technically challenging, and long-term results from prospective studies will be needed for definite assessment of their advantages and disadvantages (Ruedi, 2007; Collinge, 2000).

When fracture fixation plates are evaluated radiographically, important considerations are where the plate is located, whether the plate symmetrically spans the fracture, and the degree of fracture reduction. The plate should not impinge on joint motion, and the plate and the screws should not violate the articular surface of a joint. Any malposition or migration of the plate, breakage of the plate or screws, or loosening of the plate should be reported. The major possible complication with conventional plating is potential compromise of cortical blood supply because of a large contact area between the plate and underlying cortex (Ruedi, 2007).

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Fixation plates

Fixation plates

Intramedullary rods and nails

Neutralization and buttress plates

Drawing of fixation plates

Fixation plates

Intramedullary rods and nails

Neutralization and Buttress plates

From Benjamin, 1994

A - one third tubular plate; B - dynamic compression plate (DCP); C- T-plate; D - reconstruction plates. From Benjamin, 1994

Locking femoral intramedullary rods: A - reconstruction rods; B - intramedullary hip screw; C - supracondylar rod. From Benjamin, 1994

From Benjamin, 1994

Wrist arthrodesis with low contact dynamic compression plate

Clavicle hook plate

Spider plate for partial wrist arthrodesis

Wrist arthrodesis with low contact dynamic compression plate

Wrist arthrodesis with low contact dynamic compression plate

Clavicular hooked plate

Spider plate

From Taljanovic, 2005

 

 

The scaphoid has been removed. The spider plate transfixes the lunate, triquetrum, capitate, and hamate which are partially fused. From Taljanovic, 2005
Acumed Hub Cap Fusion Plates Ulnar hook locking compression plate  
Modular hand hub caps Ulnar hook locking plate Ulnar hook locking plate  
These plates are designed for four-corner and other wrist fusions. Image from Acumed 53 year-old woman with distal right radial and ulnar fractures. There is an ulnarly applied hook locking compression plate and screws and a variable angle volar distal radius locking plate and screws.  

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Internal Fixation continued...plates...nails and rods

 


Author contact information

Tim Hunter
Email: hunter@radiology.arizona.edu


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