Orthopaedic Implants

Author: David Abbasi

Topic updated on 05/20/13 10:38pm

Introduction

Characteristics of orthopaedic implants depends on
- material properties
- structural properties

Screws

Definitions
- pitch
  - distance between threads
- lead
  - distance advanced with one revolution
- screw working distance (length)
  - defined as the length of bone traversed by the screw
- outer diameter
- root (inner) diameter
- pullout strength
  - maximized by
    - large inner outer diameter difference
    - fine pitch
  - pedicle screw pullout most affected by degree of osteoporosis
Types of screws
- cortical screws
- cancellous screws
- locking screws

Plates Properties

Overview & definitions
- a load-bearing device that is most effective when placed on the tension side
- plate working distance
  - defined as the length from the fracture to the closest screw on either side of the fracture
  - decreasing the working distance increases the stiffness of the fixation construct
Material Properties
- bending rigidity proportional to thickness to the 3rd power
Biomechanics
- absolute stability
  - constructs heal with primary (Haversian) healing
  - must eliminate micromotion with lag screw fixation
  - must be low strain at fracture site with high fixation stiffness
- relative stability
  - constructs heal with enchondral healing
  - strain rates must be <15%, or fibrous union will predominate

Plate Variations

Concave plates
- placing a concave bend on a plate is useful in transverse fractures to ensure compressive forces occur on both the far and near cortices of the fracture
Compression plates
- compression plates work by placing a cortical screw eccentrically into an oval hole in the plate
Locking plates
- advantages of locking plates
  - locked plate/screw constructs compared to non-locked plate/screw constructs result in less angulation in comminuted metaphyseal fractures
- indications for locking plate technology
  - indirect fracture reduction
  - diaphyseal/metaphyseal fractures in osteoporotic bone
  - bridging severely comminuted fractures
  - plating of fractures where anatomical constraints prevent plating on the tension side of the bone (e.g. short segment fixation).
- locking plate screw biomechanics
  - bicortical locking screws have significantly more resistance to all applied forces, with resistance to torsion increased the most (versus unicortical)
  - unicortical locking screws have less torsion fixation strength than non-locking bicortical constructs
- percutaneous locking plates
  - application has less soft-tissue stripping but higher chance malunion
- hybrid locked plates
  - utilize locking and nonlocking screws in order to assist with fracture reduction (nonlocking screws) as well as provide a fixed angle construct (locking screws).
- locking plate construct stability increases with:
  - bicortical locking screws
  - increased number of screws
  - screw divergence from screw hole < 5 degrees
  - longer plate
Bridging plates
- provides relative stability, relative length and alignment
- preserves the blood supply to the fracture fragments as the fracture site is undisturbed during the operative procedure
  - this theoretically improves secondary bone healing
- allows some motion at fracture site; relative stability leads to callus formation

Intramedullary nails

Overview
- a load-sharing device
Material Properties
- stiffness
  - torsional rigidity
    - defined as amount of torque needed to produce torsional (rotational) deformation
    - proportional to the radius to the 4th power
    - depends on
      - shear modulus
      - polar moment of inertia
    - increased by reaming
    - decreased by slotting of nail
  - bending rigidity
    - proportional to the radius to the 4th power for a nail
    - depends on
      - material properties
        
        Young modulus of elasticity of material
      - structural properties
        
        area moment of inertia
        
        length
Radius of curvature
- intramedullary nail radius of curvature is greater (straighter) than the radius of curvature of the femur
Interlocking options
- dynamic locking-->axially and rotationally stable fractures
- static locking-->axially and rotationally unstable fractures
- secondary dynamization for nonunion
  - remove proximal interlocking screw or move proximal interlocking screw from the static to dynamic slot

External fixators

Factors that increase stability of conventional external fixators
- contact of ends of fracture (most important)
- larger diameter pins (second most important)
- additional pins
- decreased bone to rod distance
- pins in different planes
- increasing size or stacking rods
- rods in different planes
- increased spacing between pins
Factors that increase stability of circular (Ilizarov) external fixators
- larger diameter wires
- decreased ring diameter
- olive wires
- extra wires
- wires cross perpendicular to each other
- increased wire tension
- placement of two central rings close to fracture
- increased number of rings

Total Hip Implants

Material Properties
- rigidity depends on length and radius of femoral stem
Biomechanics
- place femoral component in neutral or slight valgus to reduce moment arm and stress on cement
- increasing femoral offset does the following
  - advantages
    - moves abductor moment away from center of rotation
    - increase abductor moment arm
    - reduces abductor force required for normal gait
  - disadvantages
    - increased strain on implant
    - increases strain on medial cement mantle

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Qbank (26 Questions)

TAG

(OBQ11.7) Which of the following techniques increases strength and stability to an external fixation construct? Topic

Review Topic

1. Unicortical pin fixation
2. Decreasing total pin separation distance
3. Increased working distance from the pin to fracture site
4. Decreasing the distance between the bone and the construct
5. Using smaller diameter pins

PREFERRED RESPONSE ▶

DISCUSSION: There are several methods that can be used to increase the strength of an external fixation construct. Decreasing the distance from the bar to the bone increases stability and strengthens the construct. Some other methods to increase stability include: good bone-to-bone fracture end apposition, using an increased number of pins, using larger pins, small distance from the near pins to the fracture site (smaller working distance), increased spacing between the near and far pins, and bicortical pin fixation.

Tencer et al looked at biomechanical aspects of external fixation systems. They demonstrated that system rigidity could be increased by maximizing pin separation distance in the fracture component and the number of pins used while minimizing pin separation distance across the fracture site and the sidebar offset distance from bone.

Incorrect Answers: Answer choices 1,2,3, and 5 all act to decrease external fixation construct strength.

REFERENCES:

1. Tencer AF, Claudi B, Pearce S, Bucholz RW, Johnson KD. Development of a variable stiffness external fixation system for stabilization of segmental defects of the tibia. J Orthop Res. 1984;1(4):395-404. PMID:6491789 (Link to Abstract)

2. Tencer AF, Johnson KD, eds. Biomechanics in Orthopaedic Trauma. Philadelphia, PA: JB Lippincott; 1994:249-304.

Question Authors:

David Abbasi MD, Ben Taylor MD, Patrick McCulloch MD,

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(OBQ11.59) A 27-year-old male undergoes intramedullary nailing of a midshaft tibia fracture with static locking proximally and distally. There is minimal healing noted 3 months postoperatively and the decision is made to dynamize the nail. For intramedullary nail dynamization, an interlocking screw should be placed in which of the holes shown in Figure A? Topic

Review Topic

FIGURES: A

1. A only
2. C only
3. B only
4. A and C
5. C and B

PREFERRED RESPONSE ▶

DISCUSSION: The portion of the long slot hole labeled A is the dynamic interlocking site because it allows the proximal tibia to collapse with weight bearing. Placement of an interlocking screw in holes B or C would lead to static locking of the nail.

In general, axially and rotationally stable fractures can be locked dynamically in the long slot at the time of initial fracture fixation. This is referred to as primary dynamization. Axially and rotationally unstable fractures should be locked statically both proximally and distally. In the setting of a long bone nonunion where it is felt that further fracture site compression may aid in healing, the nail can undergo secondary dynamization by either removing the proximal interlocking screw, or by moving the proximal interlocking screw from the static to dynamic slot in the nail.

Illustration A shows the static and dynamic slots of the tibial nail.

Illustrations: A

REFERENCES:

1. Schutz M, Rüedi T. Principles of internal fixation. In: Bucholz RW, Heckman JD, Court-Brown CM, Tornetta P III, McQueen MM, Ricci WM, eds. Rockwood and Green's Fractures in Adults. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins 2010:162-190.

2. Rüedi TP, Murray AM. AO Principles of Fracture Management. New York, NY: AO Publishing; 2000.

Question Authors:

Joshua Blomberg MD, Jan Szatkowski MD, Ben Taylor MD,

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(OBQ10.33) A surgeon chooses a periarticular locking plate with unicortical proximal locking screws for an extra-articular distal femur fracture as seen in Figure A. Compared to a fixed-angle blade plate construct with bicortical unlocked proximal screw fixation, the periarticular locking plate with unicortical locking screws has which biomechanical advantages? Topic

Review Topic

FIGURES: A

1. Greater torsional and axial fixation strength
2. Less torsional but greater axial fixation strength
3. Equal torsional and axial fixation strength
4. Greater torsional but less axial fixation strength
5. Less torsional and axial fixation strength

PREFERRED RESPONSE ▶

DISCUSSION: Unicortical locking plates have characteristically less torsional strength than bicortical locking plates and bicortical non-locking plates. Axial strength is improved with locking plate fixation.

Zlowodzki et al studied the LISS periarticular locking plate with unicortical proximal fixation in a distal femur model and found superior axial fixation strength (134%) but worse torsional strength (68%) compared to a fixed angle blade plate with non-locking bicortical screw fixation.

Locked plating was reviewed by Haidukewych and Ricci which highlighted the added cost, unique complications, and they recommended the use of locked plating only in situations when unlocked constructs have demonstrated poor outcomes.

REFERENCES:

1. Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)

2. Zlowodzki M, Williamson S, Zardiackas LD, Kregor PJ. Biomechanical evaluation of the less invasive stabilization system and the 95-degree angled blade plate for the internal fixation of distal femur fractures in human cadaveric bones with high bone mineral density. J Trauma. 2006 Apr;60(4):836-40. PMID:16612305 (Link to Abstract)

3. Zlowodzki M, Williamson S, Cole PA, Zardiackas LD, Kregor PJ. Biomechanical evaluation of the less invasive stabilization system, angled blade plate, and retrograde intramedullary nail for the internal fixation of distal femur fractures. J Orthop Trauma. 2004 Sep;18(8):494-502. PMID:15475844 (Link to Abstract)

Question Authors:

Charles Jobin MD, Patrick McCulloch MD, Michael Hughes MD,

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TAG

(OBQ10.60) Which of the following scenarios of treatment of a humerus fracture best achieves low strain at the fracture site and high stiffness of the treatment construct? Topic

Review Topic

1. Functional bracing of a transverse midshaft fracture
2. Comminuted midshaft fracture with locked bridge plating
3. Short oblique fracture with interfragmentary lag screw and locked neutralization plate
4. Uniplane external fixation of a spiral open fracture
5. Oblique fracture with intramedullary nail fixation

PREFERRED RESPONSE ▶

DISCUSSION: Strain in fractures is calculated by dividing the interfragmentary movement by the size of the fracture gap. Strain must be very low (2%) for primary bone healing to occur, and should be between 10-30% for secondary bone healing to occur. Stiffness refers the ability of the construct to resist movement under applied loads. Answer 3 describes a situation where primary bone healing is the goal. For this to occur, there must be no significant gapping at the fracture site, there must be low strain between fracture fragments, and the construct must be stiff. None of the other answers would accomplish this. Functional bracing and intramedullary fixation both accomplish healing through formation of fracture callus, or secondary healing. A comminuted fracture treated with locked bridge plating relies on less stiffness to allow for secondary healing between fragments. However, since there are many fracture fragments, the strain is distributed among them and therefore remains low. A uniplane external fixator is very unlikely to accomplish low strain and high stiffness in this setting.

REFERENCES:

1. Hipp JA, Hayes WB. Biomechanics of fractures. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4th ed. Philadelphia, PA: WB Saunders; 2009:51-82.

2. Mazzoca AD, DeAngelis JP, Caputo AE, et al. Principles of internal fixation. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4th ed. Philadelphia, PA: WB Saunders; 2009:83-142.

Question Authors:

Aaron Bott MD, Patrick McCulloch MD, Ben Taylor MD,

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TAG

(OBQ10.169) A 24-year-old female presents with a transverse midshaft humerus fracture. Which of the following implants would create the most compression on both the far and near cortices? Topic

Review Topic

1. Compression plate with concave bend (ends bowed towards bone)
2. Large fragment locking plate with 3 bicortical locking screws proximal and distal to the fracture
3. Intramedullary nail
4. External fixator
5. Sarmiento style fracture brace

PREFERRED RESPONSE ▶

DISCUSSION: Placing a concave bend in the plate during compressive plating results in compressive forces at both the near and far cortices (Illustration A). As described in the AO manual of fracture fixation, this technical pearl helps to ensure that osteosynthetic forces occur on both sides of the fracture. This technique is most useful in transverse fractures and can be used in any transverse fracture, not just humeral shaft fractures.

Illustrations: A

REFERENCES:

1. Wittner B, Holtz U. Plates. In: Ruedi TP, Murphy WM, eds. AO Principles of Fracture Management. Stuttgart, New York, NY: AO Publishing-Thieme Publishers; 2001:169-184.

2. Mazzocca AD, Caputo AE, Browner BD, Mast JW, Mendes MW: Principles of internal fixation. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, eds. Skeletal Trauma: Fractures, Dislocations, Ligamentous Injuries, 2nd ed. Philadelphia, PA: WB Saunders; 1998:287-348.

Question Authors:

Patrick O'Donnell MD/PhD, Patrick McCulloch MD,

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(OBQ10.183) Which of the following is true regarding rigid locking plate constructs in fracture fixation? Topic

Review Topic

1. Locking plates always enhance fracture healing more than conventional plating
2. Locking plates reduce interfragmentary strain more than conventional plating
3. Locking plates are best utilized in diaphyseal fractures
4. Locking plates are contraindicated in patients with osteoporosis
5. Fractures treated with anatomic reduction and locked plate fixation demonstrate more strain than fractures treated with intramedullary fixation

PREFERRED RESPONSE ▶

DISCUSSION: Locking plate technology functions through the threaded locking of the screw heads into the plate to create a fixed angle construct. Illustrations A and B show the locking threads of a locking screw and locking plate. This results in less screw toggle and resistance to screws backing out. Locked plates provide stiffer constructs than conventional plates and intramedullary nails and thus reduce interfragmentary strain.

Egol et al reviews the principles of locked plating and the advantages and disadvantages as compared to conventional plating. Locked plates are especially useful in severely comminuted fractures, osteoporotic bone, and fractures of metaphyseal bone.

Stoffel et al performed in vivo plating of sheep tibia following osteotomy. Overbending the plate and augmenting with a lag screw resulted in decreased strain at the osteotomy site.

Claes et al use a biomechanical model to hypothesize the magnitude of strain necessary at a fracture site to determine the differentiation of callus tissue. Primary bone healing occurs with anatomic fracture reduction and absolute stability as seen with lag screw compression of an oblique fracture. Secondary healing occurs through enchondral ossification when fractures are fixed with relative stability as seen with intramedullary nail constructs.

Illustrations: A

REFERENCES:

1. Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004 Sep;18(8):488-93. PMID:15475843 (Link to Abstract)

2. Stoffel K, Klaue K, Perren SM. Functional load of plates in fracture fixation in vivo and its correlate in bone healing. Injury. 2000 May;31 Suppl 2:S-B37-50. PMID:10853760 (Link to Abstract)

3. Claes LE, Heigele CA. Magnitudes of local stress and strain along bony surfaces predict the course and type of fracture healing. J Biomech. 1999 Mar;32(3):255-66. PMID:10093025 (Link to Abstract)

Question Authors:

John Badylak MD, Patrick McCulloch MD, Ben Taylor MD,

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(OBQ10.226) A locked plate used in a bridge plate fashion is biomechanically most similar to which of the following fixation methods? Topic

Review Topic

1. Lag screw
2. Lag screw plus non-locked neutralization plate
3. External fixator without compression
4. Lag screw plus locked neutralization plate
5. External fixator used in compression mode

PREFERRED RESPONSE ▶

DISCUSSION: The definition of a bridge plate is one where (1) there is no direct compression between the bone ends at the fracture site and (2) the screws are placed far from the fracture site (thus increasing the working length of the construct). Keeping the screws remote from the fracture site prevents disturbance of the blood supply and allows more motion of the construct. This is ideal for spanning comminuted segments, not for simple fracture patterns. A bridge plate with locking screws functions the same as an external fixator, except that it is placed internally. Like plates, external fixators can be designed to compress across a fracture or osteotomy site.

REFERENCES:

1. Hipp J & Hayes W. Biomechanics of fractures. In: Browner BD, Levine AM, Jupiter JB, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4 th ed. Philadelphia, PA: WB Saunders; 2009:51-82.

2. Mazzocca A, DeAngelis J, Caputo A, Browner B, Mast J, Mendes M. Principles of internal fixation, In: Browner BD, Levine AM, Jupiter JB, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4 th ed. Philadelphia, PA: WB Saunders; 2009:83-142

Question Authors:

Dave Marcu MD, Patrick McCulloch MD,

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(OBQ10.234) Which of the following defines the working distance of a plate in a plate/screw fracture fixation construct? Topic

Review Topic

1. The length of the interfragmentary lag screw
2. The length between the 2 screws closest to the fracture
3. The distance from the bone to the plate
4. The length from the screw closest to the fracture to the screw furthest from the fracture on the same side of the plate
5. The length between the 2 screws furthest from the fracture on each side of the plate

PREFERRED RESPONSE ▶

DISCUSSION: The working distance is defined as the distance between the 2 screws closest to the fracture. Decreasing the working distance increases the stiffness of the plate fixation construct. An example of the working distance is provided in Illustrations A and B from Hak's review article. Changing the screw position from A to B results in a less rigid construct that is more suitable for secondary bone healing. Stoffel et al review the biomechanics of locking bridge plate constructs. The working distance is the most important determinant of axial stiffness and torsional rigidity. Decreasing the distance from the plate to the bone, using a longer plate, and increasing the number of screws used also increased stiffness. Egol et al reviews and compares the biomechanics of locked plates and conventional nonlocked plates. Locked plates are most indicated for diaphyseal-metaphyseal junction fractures in osteoporotic bone, severely comminuted fractures, indirect fracture reduction, and fractures where anatomical constraints prevent plating on the tension side of the bone. Conventional nonlocked plates are the fixation of choice for periarticular fractures that require anatomic reduction, and nonunions that require compression to enhance healing.

Illustrations: A

REFERENCES:

1. Stoffel K, Dieter U, Stachowiak G, Gächter A, Kuster MS. Biomechanical testing of the LCP-- how can stability in locked internal fixators be controlled? Injury. 2003 Nov;34 Suppl 2:B11-9. PMID:14580982 (Link to Abstract)

2. Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004 Sep;18(8):488-93. PMID:15475843 (Link to Abstract)

3. Hak DJ, Toker S, Yi C, Toreson J. The influence of fracture fixation biomechanics on fracture healing. Orthopedics. 2010 Oct;33(10):752-5. PMID:20954622 (Link to Abstract)

Question Authors:

John Badylak MD, Patrick McCulloch MD,

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TAG

(OBQ09.109) The use of locked plating techniques has limited support in the literature in the treatment of which of the following fracture patterns (Figures A-E)? Topic

Review Topic

FIGURES: A

1. Figure A
2. Figure B
3. Figure C
4. Figure D
5. Figure E

PREFERRED RESPONSE ▶

DISCUSSION: Figure E shows an infraisthmal femur fracture for which a intramedullary nail remains the gold standard treatment option.

Fractures that have historically been treated successfully with traditional non-locking plates (eg, humeral shaft, both-bone forearm, lateral malleolus) require locked fixation in osteoporotic bone or fractures with segmental loss or short-end segments as a result of comminution. Fractures that have demonstrated an increased risk of mechanical failure with unlocked plates include proximal humerus, distal radius, distal femur, and proximal tibia.

Haidukewych et al, in their review article, state that locked plates may prove to be ideal for: 1) indirect fracture reduction, as they can tolerate imperfect reduction and need not be placed on the tension side of the bone; 2) diaphyseal/metaphyseal fractures in osteoporotic bone; 3) the bridging of severely comminuted fractures to minimize soft tissue damage; and 4) the plating of fractures where, due to anatomic constraints, a compression plate may not be placed on the tension side of the fracture.

Incorrect Answers:
Answer 1: Proximal humerus fractures are commonly treated with proximal humeral locking plates.
Answer 2: Periprosthetic distal femur fractures are typically treated with locking or hybrid technology due to osteopenia and short-segment fixation.
Answer 3: A comminuted tibial plateau fracture can be treated with locking technology to serve as rafting-type screws to provide fixed angle support for the articular surface.
Answer 4: Distal radius fractures are often treated with locking technology due to osteopenia and fixed angle support of the smaller distal fragment(s).

REFERENCES:

1. Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)

Question Authors:

Ben Taylor MD, Ben Taylor MD, Ben Taylor MD,

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(OBQ09.169) The greatest biomechanical difference between unicortical and bicortical locking screws is seen when what force is applied? Topic

Review Topic

1. Compression
2. Torsion
3. Distraction
4. Bending on the side of the plate
5. Bending on the surface perpendicular to the plate

PREFERRED RESPONSE ▶

DISCUSSION: Torsion force has the largest biomechanical difference between unicortical locked screws and bicortical locked screws.

The first referenced article by Roberts et al noted that by replacing the farthest unicortical screws (3 per side of the fracture) with bicortical locking screws, torsion resistance was increased by over 50%.

The second referenced article by Fulkerson et al noted decreased resistance to all applied forces with unicortical screws in a comminuted fracture model, and recommended against their use in such a fracture.

REFERENCES:

1. Roberts JW, Grindel SI, Rebholz B, Wang M. Biomechanical evaluation of locking plate radial shaft fixation: unicortical locking fixation versus mixed bicortical and unicortical fixation in a sawbone model. J Hand Surg Am. 2007 Sep;32(7):971-5. PMID:17826548 (Link to Abstract)

2. Fulkerson E, Egol KA, Kubiak EN, Liporace F, Kummer FJ, Koval KJ. Fixation of diaphyseal fractures with a segmental defect: a biomechanical comparison of locked and conventional plating techniques. J Trauma. 2006 Apr;60(4):830-5. PMID:16612304 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, Michael Hughes MD,

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(OBQ09.177) Which of the following Figures shows a fixation construct achieving absolute stability? Topic

Review Topic

FIGURES: A

1. Figure A
2. Figure B
3. Figure C
4. Figure D
5. Figure E

PREFERRED RESPONSE ▶

DISCUSSION: Figure A shows percutaneous pinning, Figure B shows locked bridge plating, Figure C shows intramedullary nailing, Figure D shows lag fixation and neutralization plating, and Figure E shows external fixation. All except Figure D show relative stability constructs.

Absolute stability is a construct seen in Figure D, where lag screws and a neutralization plate are shown in a postoperative clavicle. No micromotion is seen with this technique, and healing is by primary (Haversian) healing, as opposed to the other four constructs, which have relative stability and heal via callus formation. The first reference, the AO Principles textbook, covers this in depth.

The second reference by Claes et al notes that bone can still heal with bone (as opposed to fibrous union) with strain rates up to 15%.

REFERENCES:

1. Ito K, Perren SM: Biology and biomechanics in bone healing, in Rüedi TP, Buckley RE, Moran CG (eds): AO Principles of Fracture Management, ed 2. Boston, MA, AO Publishing, 2007, pp 9-31

2. Claes LE, Heigele CA: Magnitudes of local stress and strain along bone surfaces predict the course and type of fracture healing. J Biomech 1999;32:255-266 PMID:10093025 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, John Badylak MD,

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(OBQ08.69) An adolescent patient is treated with a 6mm solid intramedullary nail. Compared to a 12mm solid nail of the same material, the 6mm nail has: Topic

Review Topic

1. 1/2 the torsional rigidity
2. 1/4 the torsional rigidity
3. 1/16 the torsional rigidity
4. 1/8 the torsional rigidity
5. the same torsional rigidity

PREFERRED RESPONSE ▶

DISCUSSION: Nail radius affects nail bending and torsional rigidity. For a solid circular nail, the torsional rigidity is proportional to the fourth power of the radius. Thus a nail with 1/2 the diameter (6mm compared to 12mm) and therefore 1/2 the radius (3mm compared to 6mm) would have(1/2)^4 = 1/16 the torsional rigidity (answer 3). Bong et al. performed a great review of the biomechanics and biology of intramedullary nailing of the lower extremity.

REFERENCES:

1. Bong MR, Kummer FJ, Koval KJ, Egol KA. Intramedullary nailing of the lower extremity: biomechanics and biology. J Am Acad Orthop Surg. 2007 Feb;15(2):97-106. PMID:17277256 (Link to Abstract)

Question Authors:

Charles Jobin MD, Patrick McCulloch MD, Ben Taylor MD,

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(OBQ08.98) A 25 year-old male sustained the fracture seen in Figure A and undergoes open reduction internal fixation. What type of plating technique is used for the ulna? Topic

Review Topic

FIGURES: A

1. Neutralization
2. Locking
3. Compression
4. Bridging
5. Minimally invasive

PREFERRED RESPONSE ▶

DISCUSSION: This is bridge plating as the fracture site is bridged by the plate and fixation is achieved proximal and distal to the zone of the fracture and thus provides relative stability, relative length and alignment. Bridge plating preserves the blood supply to the fracture fragments as the fracture site is undisturbed during the operative procedure. This theoretically makes less dead bone fragments and lets the whole thing heal by secondary bone healing.

REFERENCES:

1. Ruedi TP, Buckley RE, Moran CG (eds): AO Principles of Fracture Management, ed 2. Stuttgart, Germany, Thieme, 2007

2. Rockwood and Green’s Fractures in Adults, ed 6. Philadelphia, PA, Lippincott Williams & Wilkins, 2006

Question Authors:

Sam Cho MD, Patrick McCulloch MD,

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(OBQ08.126) Figure A is a radiograph taken after an open reduction and internal fixation of a periprosthetic distal femur fracture. With this type of hybrid locked plate fixation, what is the difference between screw A and screw B? Topic

Review Topic

FIGURES: A

1. Screw A can assist in fracture reduction while screw B provides a fixed angle support
2. Screw A provides improved axial stiffness while screw B provides a fixed angle support
3. Screw A can be used to reduce the plate to bone while screw B can be used to lag fracture fragments together
4. Screw A provides a fixed angle support while screw B can be used to reduce the plate to the bone
5. Screw A can be used to lag fracture fragments together and screw B increases the plate bone frictional stability

PREFERRED RESPONSE ▶

DISCUSSION: Locking screws provide a fixed angle support and can improve fixation in osteoporotic bone while nonlocking screws can be used to reduce the plate to the bone, lag fracture fragments together and increase the plate bone frictional stability. "Hybrid" locked plate fixation utilizes both screw types in order to assist with difficult fracture fixation such as when there is a short metaphyseal segment and osteoporotic bone.

Zura et al discusses the biomechanical and biological advantages offered by locked plate fixation.

REFERENCES:

1. Zura RD, Browne JA. Current concepts in locked plating. J Surg Orthop Adv. 2006 Fall;15(3):173-6. Review. PMID:17087887 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, Michael Hughes MD,

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(OBQ07.13) Locking plate technology has relative indications for use in all of the following, EXCEPT: Topic

Review Topic

1. As a bridge for severely comminuted fractures
2. Osteoporotic metaphyseal fractures
3. Short fracture segments
4. Oligotrophic diaphyseal nonunions
5. Indirect fracture reduction techniques

PREFERRED RESPONSE ▶

DISCUSSION: Locked plating technology can be thought of as a stiff construct used as an internal fixator, similar to the fixed angle design of an external fixator (with more of a biomechanical advantage). Locking plates utilize the fixed angle to ensure stability of the construct, whereas conventional plates utilize the plate/bone friction, as well as fracture end contact to ensure stability. A combination of both screw types offers the possibility to achieve a synergy of both internal fixation methods.

According to Egol et al's excellent review of locked vs. nonlocked plates, locked plating technology may increasingly be indicated for indirect fracture reduction, diaphyseal/metaphyseal fractures in osteoporotic bone, bridging severely comminuted fractures, and the plating of fractures where anatomical constraints prevent plating on the tension side of the bone.

REFERENCES:

1. Egol KA. Biomechanics of locked plates and screws. J Orthop Trauma 2004;18:488-493 PMID:15475843 (Link to Abstract)

2. Wagner M. General principles for the clinical use of the LCP. Injury 2003;34:B31-42 PMID:14580984 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, John Badylak MD,

Please Rate Educational Value!

2.0

Average 2.0 of 11 Ratings

TAG

(OBQ07.188) The resistance to pullout of a screw in osteoporotic bone is increased by all of the following EXCEPT? Topic

Review Topic

1. Placement parallel to the trabecular pattern
2. Purchase in cortical bone
3. Use of a fixed angle (locking screw construct)
4. Tapping prior to screw placement
5. Augmentation with polymethylmethacrylate

PREFERRED RESPONSE ▶

DISCUSSION: Of the options listed, tapping prior to screw placement is the only variable that does not increase the pullout strength of a screw in osteoporotic bone.

Cornell reviews internal fixation in osteoporotic bone. According to this article, the quality of the bone is the primary determinant of the holding power of an individual screw. Other factors that increase the pullout strength include fixation in cortical bone (cortical bone has greater mineral density and, therefore, greater resistance to screw pullout than trabecular bone), screws placed parallel to the trabecular pattern, and screw fixation augmented with PMMA. The addition of a locking plate will also increase the resistance to pullout of a screw by creating a fixed angle construct. Tapping prior to placement of the screw has not been shown to increase resistance to pullout, on the contrary studies have shown this decreases resistance to pullout.

Turner et al examined the holding strength of small and large diameter screws in healthy bovine and diseased human bone. They found the screw diameter, trabecular orientation of the bone, and mineral content of the bone all affect the hoding strength. A larger diameter screw, parallel placement to the trabecular pattent, and purchase in bone with a higher density all increase the holding strength.

REFERENCES:

1. Cornell CN. Internal fracture fixation in patients with osteoporosis. J Am Acad Orthop Surg. 2003 Mar-Apr;11(2):109-19. PMID:12670137 (Link to Abstract)

2. Turner IG, Rice GN. Comparison of bone screw holding strength in healthy bovine and osteoporotic human cancellous bone. Clin Mater. 1992;9(2):105-7. PMID:10149962 (Link to Abstract)

Question Authors:

Robert Boykin MD, Patrick McCulloch MD, Ben Taylor MD,

Please Rate Educational Value!

3.0

Average 3.0 of 12 Ratings

TAG

(OBQ06.172) How does a dynamic compression plate achieve compression at the fracture of a long bone? Topic

Review Topic

1. Eccentric placement of a cortical screw into a hole in the plate
2. Placing a cortical screw in lag fashion by overdrilling the near cortex
3. Locking of the head of the screw into a threaded hole in the plate
4. Concentric placement of a cortical screw into the center of the hole in the plate
5. The plate allows secondary healing of bone and does not acheive compression at the fracture site

PREFERRED RESPONSE ▶

DISCUSSION: Dynamic compression plates achieve compression through eccentric placement of a cortical screw into an oval hole in the plate. During the final tightening of the screw, the screw head will be forced into the center of the hole squeezing the fracture together beneath the plate. This creates compression at the fracture site. Dynamic compression is ideal for transverse fractures that are not suitable for lag screw compression.

Incorrect Answers:
Answer 2: describes lag screw fixation
Answer 3: describes locking screw fixation
Answer 4: describes a screw placed into a neutralization plate
Answer5: incorrect statement

Illustration A is a photo of a dynamic compression plate. Compression is acheived by placing the screw eccentrically into the far side of the plate hole away from the fracture.

Illustrations: A

REFERENCES:

1. Browner BD. “Principles of Internal Fixation”. Skeletal Trauma. 2003: 195-249.

Question Authors:

John Badylak MD, Patrick McCulloch MD,

Please Rate Educational Value!

4.0

Average 4.0 of 9 Ratings

TAG

(OBQ06.185) All of the following are indications for locked plating technology EXCEPT: Topic

Review Topic

1. Periarticular fracture with metaphyseal comminution
2. Fracture in osteoporotic bone
3. Bridge plating for severely comminuted fractures
4. Compression plating of transverse fracture
5. Plating of fractures where anatomical constraints prevent plating on the tension side of the bone

PREFERRED RESPONSE ▶

DISCUSSION: Locked plates are indicated for indirect fracture reduction, diaphyseal/metaphyseal fractures in osteoporotic bone, bridging severely comminuted fractures, and the plating of fractures where anatomical constraints prevent plating on the tension side of the bone. Locked plates and conventional plates rely on completely different mechanical principles to provide fracture fixation and in so doing they provide different biological environments for healing. Approaches to internal fixation have become more biologic. Greater emphasis is placed on vascularity and soft tissue integrity. Locked plates, analogous to rigid internal fixators, can provide relative stability favorable to secondary fracture healing. If applied appropriately, they can avoid soft tissue compromise. The key to this new generation of plates is the locking mechanism of the screw to the plate, which provides angular stability and avoids compression of the plate to the periosteum. Favorable biomechanical and clinical results continue to expand the number of appropriate indications for use of locked plating devices, although exact indications for their use have yet to be precisely defined.

The referenced articles by Haidukewych and Egol et al are reviews of the biomechanical characteristics of locked plating technology.

REFERENCES:

1. Haidukewych GJ. Innovations in locking plate technology. J Am Acad Orthop Surg. 2004 Jul-Aug;12(4):205-12. PMID:15473672 (Link to Abstract)

2. Egol KA, Kubiak EN, Fulkerson Em: Biomechanics of locked plates and screws. J Orthop Trauma 2004;18:488-493. PMID:15475843 (Link to Abstract)

Question Authors:

Ben Taylor MD, John Badylak MD, Patrick McCulloch MD,

Please Rate Educational Value!

3.0

Average 3.0 of 6 Ratings

TAG

(OBQ06.191) A long oblique diaphyseal fracture is internally fixed with 2 lag screws. There is 2 mm of residual fracture fragment displacement following screw fixation. This construct has which of the following compared to a comminuted diaphyseal fracture internally fixed with a long bridge plating technique? Topic

Review Topic

1. Greater interfragmental strain
2. Greater ductility
3. Greater primary Haversian remodeling
4. Greater union rate
5. Greater callus volume formation

PREFERRED RESPONSE ▶

DISCUSSION: A long oblique diaphyseal fracture with 2 mm of residual displacement after being internally fixed with lag screws has greater interfragmental strain than comminuted fractures treated with bridge plating or fractures that are anatomically reduced and internally fixed.

Perrens’ theory of strain states that there is a relationship between decreasing strain and increasing the potential for osteogenesis across a fracture or fusion site. The strain theory states that for two given fracture segments, the healing interface will possess a force-generated motion potential that is contingent on the stability of the original fixation construct. Mathematically, the strain for any given force is equal to the change in the interface length divided by the original interface length. Therefore, with an unstable construct, the healing gap may undergo excessive motion with resultant increasing strain. It has been shown that strain of less than 2% will yield absolute stability and subsequent primary bone healing. Comminuted fractures have multiple fracture lines therefore the force is dissipated over multiple fracture lines and interfragmentary strain is decreased.

REFERENCES:

1. Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002 Nov;84(8):1093-110. Review: PMID:12463652 (Link to Abstract)

Question Authors:

Michael Hughes MD, Jan Szatkowski MD, Ben Taylor MD,

Please Rate Educational Value!

2.0

Average 2.0 of 9 Ratings

TAG

(OBQ06.237) Which statement is true regarding standard open plating techniques compared to minimally invasive submuscular plating techniques? Topic

Review Topic

1. standard plating results in greater compromise to both medullary and periosteal bloodflow
2. standard plating results in greater compromise to periosteal bloodflow only
3. standard plating results in greater compromise to medullary bloodflow only
4. standard plating results in less compromise to both medullary and periosteal bloodflow
5. there is no difference between the two techniques with respect to periosteal and medullary bloodflow

PREFERRED RESPONSE ▶

DISCUSSION: Using silicone arterial dye injection in a cadaveric femur model, Farouk et al. studied the vascular disruption of conventional plate osteosynthesis (CPO) with minimally invasive plate osteosynthesis (MIPO). All MIPO specimens showed intact perforating and nutrient arteries, whereas the CPO specimens had a variable incidence of vessel disruption. Based on this evidence, they concluded that MIPO may be more advantageous biologically than the traditional method.

REFERENCES:

1. Farouk O, Krettek C. Miclau T, et al: Minimally invasive plate osteosynthesis: Does percutaneous plating disrupt femoral blood supply less than the traditional technique? J Orthop Trauma 1999; 13:401-406. PMID:10459598 (Link to Abstract)

2. Farouk O, Krettek C, Miclau T, et al: Minimally invasive plate osteosynthesis and vascularity: Preliminary results of a cadaver injection study. Injury 1997;28:A7-A12. PMID:10897282 (Link to Abstract)

Question Authors:

Greg Galano MD, Derek Moore,

Please Rate Educational Value!

4.0

Average 4.0 of 11 Ratings

TAG

(OBQ06.244) Limited contact dynamic compression (LCDC) plates have what advantage over standard dynamic compression plates? Topic

Review Topic

1. less micromotion
2. more compression
3. less implant-bone contact induced osteopenia
4. stiffer construct
5. less stress shielding

PREFERRED RESPONSE ▶

DISCUSSION: LCDC plates have less contact with the bone as compared to the standard dynamic compression plates. The decreased surface area leads to less contact-induced osteopenia.

The Perren article describes the advantages of locked plating when viewed as an internal fixator. In other words, the locked plate functions like an external fixator yet it is close to the bone and in situ, i.e. an internal fixator. The negatives of dynamic compression plating include the osteopenia that can develop because dynamic plating relies on bone plate friction whereas the locking plate relies on the screws and screw placement. Perren states that “The biological aspects of damage to the blood supply, necrosis and temporary porosity explain the importance of avoiding extensive contact of the implant with bone.”

REFERENCES:

1. Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002, Nov;84(8):1093-110. PMID:12463652 (Link to Abstract)

Question Authors:

Ben Taylor MD, Ben Taylor MD, Patrick McCulloch MD,

Please Rate Educational Value!

4.0

Average 4.0 of 8 Ratings

TAG

(OBQ06.258) The distance of bone traversed by a screw is defined as which of the following terms? Topic

Review Topic

1. Pitch
2. Working length
3. Screw lead
4. Core diameter
5. Area moment of inertia

PREFERRED RESPONSE ▶

DISCUSSION: The distance a screw traverses in a bone during fracture fixation is defined as the working length (or less commonly "working distance") of that screw.

The referenced article is a good review of the biomechanics of plate and screw fixation, and covers important topics such as creating a high plate:span ratio and a low plate screw density.

Incorrect Answers:
1: Pitch: Distance between adjacent threads
3: Screw Lead: Distance screw advances with each turn
4: Core Diameter: narrowest diameter of screw
5: Area moment of Inertia: resistance to torsional force related to cube of radius

REFERENCES:

1. Gautier E, Sommer C. Guidelines for the clinical application of the LCP. Injury. 2003 Nov;34 Suppl 2:B63-76. PMID:14580987 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, Michael Hughes MD,

Please Rate Educational Value!

2.0

Average 2.0 of 21 Ratings

TAG

(OBQ06.264) Assuming all other variables are the same, which of the following increases fixation construct stiffness in a locking plate model? Topic

Review Topic

1. Unicortical locking screws compared to bicortical locking screws
2. Angular cross-threading screws into a plate
3. Overdrilling the near cortex for the screw holes
4. Far cortical locking screws
5. Increased plate length

PREFERRED RESPONSE ▶

DISCUSSION: In a locking plate fixation model, use of bicortical screws, parallel screw placement, increased plate length, increased number of screws, and screws placed at appropriate angles into the screw hole all serve to increase fixation construct stability. Far cortical locking screws lock into the plate as well as gain thread purchase on the far cortex, with a near cortex that does not touch the screw (whether via lack of threads or overdrilling of the near cortex).

The referenced article by Haidukewych and Ricci reviews the concepts of locking plates, including biomechanics and technique.

The referenced article by Kaab et al is a biomechanical study of locking plates that found significantly decreased construct stability if screw trajectory varied > 5 degrees from the screw hole orientation.

The referenced article by Sommer et al is a case series of locking plate failures and review of the concepts important to create a successful construct with these devices. They warn against inappropriate use of locking plates when standard plates can be used.

REFERENCES:

1. Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)

2. Kaab MJ, Frenk A, Schmeling A: Locked internal fixator: Sensitivity of screw/plate stability to the correct insertion angle of the screw. J Orthop Trauma 2004;18:483-487. PMID:15475842 (Link to Abstract)

3. Sommer C, Babst R, Muller M: Locking compression plate loosening and plate breakage: A report of four cases. J Orthop Trauma;18:571-577. PMID:15475856 (Link to Abstract)

Question Authors:

Ben Taylor MD, Patrick McCulloch MD, Jan Szatkowski MD,

Please Rate Educational Value!

1.0

Average 1.0 of 29 Ratings

TAG

(OBQ05.114) Which of the following is the most accurate definition of stress shielding? Topic

Review Topic

1. The decrease in physiologic stress in bone due to a stiffer structure sharing load
2. Electrochemical potential created between two metals in physical contact and immersed in a conductive medium
3. Degradation from exposure to a harsh environment
4. Physical movement of two plates against each other leading to mechanical wear and material transfer at the surface
5. Bone death secondary to compromise in blood supply

PREFERRED RESPONSE ▶

DISCUSSION: Based on Wolff’s Law, bone in a healthy person will remodel in response to applied load. Orthopedic implants often reduce applied load, resulting in bone resorption, leading to decreased bone mineral density or osteopenia. This will be apparent on plain radiographs, and can be seen with arthroplasty implants or with fracture fixation implants.

Incorrect answers:
2: This is the definition of galvanic corrosion.
3: This is a generic corrosion definition.
4: This is a definition of fretting.
5: This is a definition of avascular necrosis.

REFERENCES:

Question Authors:

Ben Taylor MD, Derek Moore, Ben Taylor MD,

Please Rate Educational Value!

3.0

Average 3.0 of 6 Ratings

TAG

(OBQ05.275) You are planning an intramedullary nail to treat a geriatric patient with a peritrochanteric femur fracture. Which of the following preoperative considerations is correct regarding your implant? Topic

Review Topic

1. The radius of curvature of an intramedullary nail is generally greater than the radius of curvature of the femur
2. Closed section nails have less stiffness than slotted nails
3. The medial/lateral nail starting point relative to the greater trochanter does not affect varus/valgus position in the fracture
4. The bending stiffness of your nail is proportional to the second power of the radius
5. Intramedullary nails allow for mostly direct intramembranous bone healing

PREFERRED RESPONSE ▶

DISCUSSION: The radius of curvature of an intramedullary nail is generally greater than the radius of curvature of the femur, which is why anterior distal femur penetration is a known complication of intramedullary nailing procedures.

Egol et al. evaluated the radius of curvature of 948 femurs (474 matched pairs) and compared those data with current intramedullary nails. He found the average femoral anterior radius of curvature was 120 cm (± 36 cm) whereas the radius of curvature of the intramedullary nails ranged from 186 to 300 cm.

The other answers are incorrect because closed section nails have more stiffness than slotted nails. The starting position on the greater trochanter greatly affects the post-operative varus/valgus of the fracture. The bending stiffness of a hollow cylinder is proportional to the third power of the radius. Intramedullary nails allow for mostly indirect enchondral bone healing due to relative motion at the fracture site.

REFERENCES:

1. Buckwalter J, O'Keefe R, Einhorn T (EDS). Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 277-323

2. Tencer AF, Johnson KD (EDS). Lower extremity fixation. Orthopaedic Trauma: Bone Fracture and Fixation. Philadelphia, PA, Lippincott Williams & Wilkins, 1994, pp 249-304

3. Egol KA, Chang EY, Cvitkovic J, Kummer FJ, Koval KJ. Mismatch of current intramedullary nails with the anterior bow of the femur. J Orthop Trauma. 2004 Aug;18(7):410-5. PMID:15289685 (Link to Abstract)

Question Authors:

Patrick O'Donnell MD/PhD, Patrick McCulloch MD, Ben Taylor MD,

Please Rate Educational Value!

2.0

Average 2.0 of 13 Ratings

Evidence & References Show References

Level of Evidence 4 (Case Series)

Zlowodzki M, Williamson S, Cole PA, Zardiackas LD, Kregor PJ. Biomechanical evaluation of the less invasive stabilization system, angled blade plate, and retrograde intramedullary nail for the internal fixation of distal femur fractures. J Orthop Trauma. 2004 Sep;18(8):494-502. PMID:15475844 (Link to Abstract)
Kaab MJ, Frenk A, Schmeling A: Locked internal fixator: Sensitivity of screw/plate stability to the correct insertion angle of the screw. J Orthop Trauma 2004;18:483-487. PMID:15475842 (Link to Abstract)
Sommer C, Babst R, Muller M: Locking compression plate loosening and plate breakage: A report of four cases. J Orthop Trauma;18:571-577. PMID:15475856 (Link to Abstract)

Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions, Personal Observations, and Biomechanic Studies)

Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)
Zlowodzki M, Williamson S, Zardiackas LD, Kregor PJ. Biomechanical evaluation of the less invasive stabilization system and the 95-degree angled blade plate for the internal fixation of distal femur fractures in human cadaveric bones with high bone mineral density. J Trauma. 2006 Apr;60(4):836-40. PMID:16612305 (Link to Abstract)
Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004 Sep;18(8):488-93. PMID:15475843 (Link to Abstract)
Stoffel K, Dieter U, Stachowiak G, Gächter A, Kuster MS. Biomechanical testing of the LCP-- how can stability in locked internal fixators be controlled? Injury. 2003 Nov;34 Suppl 2:B11-9. PMID:14580982 (Link to Abstract)
Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004 Sep;18(8):488-93. PMID:15475843 (Link to Abstract)
Hak DJ, Toker S, Yi C, Toreson J. The influence of fracture fixation biomechanics on fracture healing. Orthopedics. 2010 Oct;33(10):752-5. PMID:20954622 (Link to Abstract)
Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)
Roberts JW, Grindel SI, Rebholz B, Wang M. Biomechanical evaluation of locking plate radial shaft fixation: unicortical locking fixation versus mixed bicortical and unicortical fixation in a sawbone model. J Hand Surg Am. 2007 Sep;32(7):971-5. PMID:17826548 (Link to Abstract)
Fulkerson E, Egol KA, Kubiak EN, Liporace F, Kummer FJ, Koval KJ. Fixation of diaphyseal fractures with a segmental defect: a biomechanical comparison of locked and conventional plating techniques. J Trauma. 2006 Apr;60(4):830-5. PMID:16612304 (Link to Abstract)
Bong MR, Kummer FJ, Koval KJ, Egol KA. Intramedullary nailing of the lower extremity: biomechanics and biology. J Am Acad Orthop Surg. 2007 Feb;15(2):97-106. PMID:17277256 (Link to Abstract)
Zura RD, Browne JA. Current concepts in locked plating. J Surg Orthop Adv. 2006 Fall;15(3):173-6. Review. PMID:17087887 (Link to Abstract)
Haidukewych GJ. Innovations in locking plate technology. J Am Acad Orthop Surg. 2004 Jul-Aug;12(4):205-12. PMID:15473672 (Link to Abstract)
Egol KA, Kubiak EN, Fulkerson Em: Biomechanics of locked plates and screws. J Orthop Trauma 2004;18:488-493. PMID:15475843 (Link to Abstract)
Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002 Nov;84(8):1093-110. Review: PMID:12463652 (Link to Abstract)
Haidukewych GJ, Ricci W. Locked plating in orthopaedic trauma: a clinical update. J Am Acad Orthop Surg. 2008 Jun;16(6):347-55. PMID:18524986 (Link to Abstract)
Egol KA, Chang EY, Cvitkovic J, Kummer FJ, Koval KJ. Mismatch of current intramedullary nails with the anterior bow of the femur. J Orthop Trauma. 2004 Aug;18(7):410-5. PMID:15289685 (Link to Abstract)

Textbooks

Review of Orthopaedics, 6th Edition, Mark D. Miller MD, Stephen R. Thompson MBBS MEd FRCSC, Jennifer Hart MPAS PA-C ATC, an imprint of Elsevier, Philadelphia, Copyright 2012
AAOS Comprehensive Orthopaedic Review, Jay R. Leiberman. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2009
Orthopaedic Knowledge Update 10, John M Flyn. Published by American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2011
Hoppenfeld SP. Surgical Exposures in Orthopaedics: The Anatomic Approach. Lipponcott, Williams, and Wilkins, Philadelphia, PA, Copyright 2009
Orthopaedic In-training Examination (OITE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Self-Assessment Examination (SAE) Questions 2004-2012, American Academy of Orthopaedic Surgeons, Rosemont IL. Copyright 2004-2012
Hipp JA, Hayes WB. Biomechanics of fractures. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4th ed. Philadelphia, PA: WB Saunders; 2009:51-82.
Mazzoca AD, DeAngelis JP, Caputo AE, et al. Principles of internal fixation. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4th ed. Philadelphia, PA: WB Saunders; 2009:83-142.
Wittner B, Holtz U. Plates. In: Ruedi TP, Murphy WM, eds. AO Principles of Fracture Management. Stuttgart, New York, NY: AO Publishing-Thieme Publishers; 2001:169-184.
Mazzocca AD, Caputo AE, Browner BD, Mast JW, Mendes MW: Principles of internal fixation. In: Browner BD, Jupiter JB, Levine AM, Trafton PG, eds. Skeletal Trauma: Fractures, Dislocations, Ligamentous Injuries, 2nd ed. Philadelphia, PA: WB Saunders; 1998:287-348.
Browner BD. “Principles of Internal Fixation”. Skeletal Trauma. 2003: 195-249.
Buckwalter J, O'Keefe R, Einhorn T (EDS). Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 277-323
Tencer AF, Johnson KD (EDS). Lower extremity fixation. Orthopaedic Trauma: Bone Fracture and Fixation. Philadelphia, PA, Lippincott Williams & Wilkins, 1994, pp 249-304

Undefined

Tencer AF, Claudi B, Pearce S, Bucholz RW, Johnson KD. Development of a variable stiffness external fixation system for stabilization of segmental defects of the tibia. J Orthop Res. 1984;1(4):395-404. PMID:6491789 (Link to Abstract)
Tencer AF, Johnson KD, eds. Biomechanics in Orthopaedic Trauma. Philadelphia, PA: JB Lippincott; 1994:249-304.
Schutz M, Rüedi T. Principles of internal fixation. In: Bucholz RW, Heckman JD, Court-Brown CM, Tornetta P III, McQueen MM, Ricci WM, eds. Rockwood and Green's Fractures in Adults. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins 2010:162-190.
Rüedi TP, Murray AM. AO Principles of Fracture Management. New York, NY: AO Publishing; 2000.
Stoffel K, Klaue K, Perren SM. Functional load of plates in fracture fixation in vivo and its correlate in bone healing. Injury. 2000 May;31 Suppl 2:S-B37-50. PMID:10853760 (Link to Abstract)
Claes LE, Heigele CA. Magnitudes of local stress and strain along bony surfaces predict the course and type of fracture healing. J Biomech. 1999 Mar;32(3):255-66. PMID:10093025 (Link to Abstract)
Hipp J & Hayes W. Biomechanics of fractures. In: Browner BD, Levine AM, Jupiter JB, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4 th ed. Philadelphia, PA: WB Saunders; 2009:51-82.
Mazzocca A, DeAngelis J, Caputo A, Browner B, Mast J, Mendes M. Principles of internal fixation, In: Browner BD, Levine AM, Jupiter JB, Trafton PG, Krettek C, eds. Skeletal Trauma: Basic Science, Management, and Reconstruction, 4 th ed. Philadelphia, PA: WB Saunders; 2009:83-142
Ito K, Perren SM: Biology and biomechanics in bone healing, in Rüedi TP, Buckley RE, Moran CG (eds): AO Principles of Fracture Management, ed 2. Boston, MA, AO Publishing, 2007, pp 9-31
Claes LE, Heigele CA: Magnitudes of local stress and strain along bone surfaces predict the course and type of fracture healing. J Biomech 1999;32:255-266 PMID:10093025 (Link to Abstract)
Ruedi TP, Buckley RE, Moran CG (eds): AO Principles of Fracture Management, ed 2. Stuttgart, Germany, Thieme, 2007
Rockwood and Green’s Fractures in Adults, ed 6. Philadelphia, PA, Lippincott Williams & Wilkins, 2006
Egol KA. Biomechanics of locked plates and screws. J Orthop Trauma 2004;18:488-493 PMID:15475843 (Link to Abstract)
Wagner M. General principles for the clinical use of the LCP. Injury 2003;34:B31-42 PMID:14580984 (Link to Abstract)
Cornell CN. Internal fracture fixation in patients with osteoporosis. J Am Acad Orthop Surg. 2003 Mar-Apr;11(2):109-19. PMID:12670137 (Link to Abstract)
Turner IG, Rice GN. Comparison of bone screw holding strength in healthy bovine and osteoporotic human cancellous bone. Clin Mater. 1992;9(2):105-7. PMID:10149962 (Link to Abstract)
Farouk O, Krettek C. Miclau T, et al: Minimally invasive plate osteosynthesis: Does percutaneous plating disrupt femoral blood supply less than the traditional technique? J Orthop Trauma 1999; 13:401-406. PMID:10459598 (Link to Abstract)
Farouk O, Krettek C, Miclau T, et al: Minimally invasive plate osteosynthesis and vascularity: Preliminary results of a cadaver injection study. Injury 1997;28:A7-A12. PMID:10897282 (Link to Abstract)
Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br. 2002, Nov;84(8):1093-110. PMID:12463652 (Link to Abstract)
Gautier E, Sommer C. Guidelines for the clinical application of the LCP. Injury. 2003 Nov;34 Suppl 2:B63-76. PMID:14580987 (Link to Abstract)
Egol KA, Kubiak EN, Fulkerson E, Kummer FJ, Koval KJ. Biomechanics of locked plates and screws. J Orthop Trauma. 2004 Sep;18(8):488-93. Review. PMID:15475843 (Link to Abstract)
Haidukewych GJ. Innovations in locking plate technology. J Am Acad Orthop Surg. 2004 Jul-Aug;12(4):205-12. Review. PMID:15473672 (Link to Abstract)

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Orthopaedic Implants

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Evidence & References Show References

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