Orthopaedic Implants - Basic Science

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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 an identical construct with bicortical unlocked proximal screw fixation, the periarticular locking plate with unicortical locking screws has which biomechanical properties? Review Topic

QID: 3121

FIGURES:

A

1

Greater torsional and axial fixation strength

13%

(382/2842)

2

Less torsional but greater axial fixation strength

47%

(1345/2842)

3

Equal torsional and axial fixation strength

4%

(110/2842)

4

Greater torsional but less axial fixation strength

19%

(526/2842)

5

Less torsional and axial fixation strength

16%

(468/2842)

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

QID: 3276

1

Locking plates always enhance fracture healing more than non-locking plating

1%

(17/1465)

2

Locking plates reduce interfragmentary strain more than non-locking plating

75%

(1099/1465)

3

Locking plates are best utilized in diaphyseal fractures

2%

(33/1465)

4

Locking plates are contraindicated in patients with osteoporosis

0%

(4/1465)

5

Fractures treated with anatomic reduction and locked plate fixation demonstrate more strain than fractures treated with intramedullary fixation

21%

(305/1465)

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

QID: 248

1

standard plating results in greater compromise to both medullary and periosteal bloodflow

22%

(82/381)

2

standard plating results in greater compromise to periosteal bloodflow only

67%

(257/381)

3

standard plating results in greater compromise to medullary bloodflow only

2%

(8/381)

4

standard plating results in less compromise to both medullary and periosteal bloodflow

3%

(12/381)

5

there is no difference between the two techniques with respect to periosteal and medullary bloodflow

6%

(22/381)

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

QID: 358

1

Eccentric placement of a cortical screw into a hole in the plate

92%

(392/428)

2

Placing a cortical screw in lag fashion by overdrilling the near cortex

3%

(11/428)

3

Locking of the head of the screw into a threaded hole in the plate

2%

(7/428)

4

Concentric placement of a cortical screw into the center of the hole in the plate

3%

(11/428)

5

The plate allows secondary healing of bone and does not acheive compression at the fracture site

1%

(4/428)

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(SBQ12TR.28) After application of a unilateral tibial external fixator, it is observed that the frame does not provide sufficient rigidity across the fracture site. Altering the external fixator in which of the following ways will have the greatest impact on frame stiffness? Review Topic

QID: 3943

1

Increasing the distance between pins in each fragment

7%

(248/3458)

2

Increasing the pin diameter

53%

(1846/3458)

3

Reducing the distance between bone and connecting bar

28%

(960/3458)

4

Increasing the connecting bar diameter

2%

(55/3458)

5

Adding one stacked connecting bar

10%

(332/3458)

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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? Review Topic

QID: 3325

1

Lag screw

0%

(6/1469)

2

Lag screw plus non-locked neutralization plate

2%

(25/1469)

3

External fixator without compression

92%

(1353/1469)

4

Lag screw plus locked neutralization plate

1%

(16/1469)

5

External fixator used in compression mode

4%

(61/1469)

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

QID: 3333

1

The length of the interfragmentary lag screw

0%

(8/2385)

2

The length between the 2 screws closest to the fracture on each end of the fracture

69%

(1651/2385)

3

The distance from the bone to the plate

3%

(67/2385)

4

The length from the screw closest to the fracture to the screw furthest from the fracture on the same end of the plate

8%

(200/2385)

5

The length between the 2 screws furthest from the fracture on each end of the plate

18%

(439/2385)

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(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? Review Topic

QID: 3262

1

Compression plate with concave bend (ends bowed towards bone)

78%

(1413/1815)

2

Large fragment locking plate with 3 bicortical locking screws proximal and distal to the fracture

3%

(51/1815)

3

Intramedullary nail

2%

(43/1815)

4

Compression plate with convex bend (ends bowed away from the bone)

16%

(293/1815)

5

Sarmiento style fracture brace

0%

(8/1815)

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

QID: 484

FIGURES:

A

1

Neutralization

1%

(16/1485)

2

Locking

1%

(14/1485)

3

Compression

2%

(35/1485)

4

Bridging

95%

(1417/1485)

5

Antiglide

0%

(0/1485)

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

QID: 275

1

Unicortical locking screws compared to bicortical locking screws

1%

(5/493)

2

Angular cross-threading screws into a plate

5%

(27/493)

3

Overdrilling the near cortex for the screw holes

5%

(27/493)

4

Far cortical locking screws

19%

(92/493)

5

Increased number of screws in the plate

69%

(340/493)

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

QID: 2982

1

Compression

5%

(28/523)

2

Torsion

74%

(388/523)

3

Distraction

4%

(19/523)

4

Bending on the side of the plate

7%

(36/523)

5

Bending on the surface perpendicular to the plate

10%

(50/523)

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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? Review Topic

QID: 512

FIGURES:

A

1

Screw A can assist in fracture reduction while screw B provides a fixed angle support

20%

(111/556)

2

Screw A provides improved axial stiffness while screw B provides a fixed angle support

10%

(56/556)

3

Screw A can be used to reduce the plate to bone while screw B can be used to lag fracture fragments together

3%

(14/556)

4

Screw A provides a fixed angle support while screw B can be used to reduce the plate to the bone

64%

(357/556)

5

Screw A can be used to lag fracture fragments together and screw B increases the plate bone frictional stability

3%

(15/556)

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(OBQ09.109) Which of the following fracture patterns (Figures A through E) has the least amount of evidence-based support for use of locking or hybrid plating techniques? Review Topic

QID: 2922

FIGURES:

A
B
C
D
E

1

Figure A

5%

(30/641)

2

Figure B

4%

(24/641)

3

Figure C

22%

(140/641)

4

Figure D

7%

(46/641)

5

Figure E

62%

(395/641)

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

QID: 377

1

Greater interfragmental strain

60%

(280/467)

2

Greater ductility

2%

(10/467)

3

Greater primary Haversian remodeling

31%

(146/467)

4

Greater union rate

2%

(10/467)

5

Greater callus volume formation

4%

(19/467)

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

QID: 269

1

Pitch

16%

(69/445)

2

Working length

67%

(300/445)

3

Screw lead

13%

(60/445)

4

Core diameter

1%

(4/445)

5

Area moment of inertia

2%

(10/445)

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(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? Review Topic

QID: 3148

1

Functional bracing of a transverse midshaft fracture

1%

(5/526)

2

Comminuted midshaft fracture with locked bridge plating

19%

(98/526)

3

Short oblique fracture with interfragmentary lag screw and locked neutralization plate

76%

(398/526)

4

Uniplane external fixation of a spiral open fracture

0%

(2/526)

5

Oblique fracture with intramedullary nail fixation

3%

(18/526)

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(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? Review Topic

QID: 1161

1

The radius of curvature of an intramedullary nail is generally greater than the radius of curvature of the femur

66%

(675/1026)

2

Closed section nails have less stiffness than slotted nails

3%

(33/1026)

3

The medial/lateral nail starting point relative to the greater trochanter does not affect varus/valgus position in the fracture

2%

(24/1026)

4

The bending stiffness of your nail is proportional to the second power of the radius

23%

(241/1026)

5

Intramedullary nails allow for mostly direct intramembranous bone healing

5%

(49/1026)

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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: Review Topic

QID: 455

1

1/2 the torsional rigidity

4%

(17/457)

2

1/4 the torsional rigidity

14%

(62/457)

3

1/16 the torsional rigidity

62%

(283/457)

4

1/8 the torsional rigidity

17%

(78/457)

5

the same torsional rigidity

3%

(15/457)

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

QID: 255

1

Less implant-bone and fracture gap micromotion

3%

(14/475)

2

More fracture site compression

0%

(2/475)

3

Less implant-bone contact induced osteopenia

93%

(442/475)

4

Stiffer fracture fixation construct

0%

(2/475)

5

More stress shielding

3%

(12/475)

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

QID: 849

1

Placement parallel to the trabecular pattern

42%

(193/465)

2

Purchase in cortical bone

1%

(5/465)

3

Use of a fixed angle (locking screw construct)

3%

(12/465)

4

Tapping prior to screw placement

47%

(220/465)

5

Augmentation with polymethylmethacrylate

7%

(32/465)

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

QID: 1000

1

The decrease in physiologic stress in bone due to a stiffer structure sharing load

94%

(472/504)

2

Electrochemical potential created between two metals in physical contact and immersed in a conductive medium

1%

(6/504)

3

Degradation from exposure to a harsh environment

0%

(2/504)

4

Physical movement of two plates against each other leading to mechanical wear and material transfer at the surface

4%

(21/504)

5

Bone death secondary to compromise in blood supply

0%

(0/504)

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

QID: 3430

1

Unicortical pin fixation

0%

(4/2553)

2

Decreasing total pin separation distance

3%

(83/2553)

3

Increased working distance from the pin to fracture site

2%

(48/2553)

4

Decreasing the distance between the bone and the construct

94%

(2399/2553)

5

Using smaller diameter pins

0%

(5/2553)

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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? Review Topic

QID: 3482

FIGURES:

A

1

A only

74%

(1148/1551)

2

C only

1%

(10/1551)

3

B only

21%

(328/1551)

4

A and C

1%

(23/1551)

5

C and B

2%

(30/1551)

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

QID: 674

1

As a bridge for severely comminuted fractures

3%

(11/375)

2

Osteoporotic metaphyseal fractures

2%

(7/375)

3

Short fracture segments

18%

(68/375)

4

Oligotrophic diaphyseal nonunions

58%

(218/375)

5

Indirect fracture reduction techniques

18%

(69/375)

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

QID: 2990

FIGURES:

A
B
C
D
E

1

Figure A

1%

(6/1066)

2

Figure B

5%

(51/1066)

3

Figure C

5%

(48/1066)

4

Figure D

89%

(948/1066)

5

Figure E

1%

(9/1066)

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

QID: 371

1

Periarticular fracture with metaphyseal comminution

1%

(6/460)

2

Fracture in osteoporotic bone

4%

(20/460)

3

Bridge plating for severely comminuted fractures

5%

(21/460)

4

Compression plating of transverse fracture

85%

(391/460)

5

Plating of fractures where anatomical constraints prevent plating on the tension side of the bone

5%

(22/460)

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