Self-test - Orthopaedic Biomaterials in Research and Practice - page 419

11. Cortical bone ( true or false )

Is stiffer if more highly mineralized ____

Is weaker if more highly mineralized ____

Is weaker in older individuals ____

Is elastic-plastic ____

Contains no important stress risers ____

(5)

12. Articular cartilage (select the best answer[s])

A. Is viscoelastic ___

B. Has almost identical relaxed and unrelaxed moduli ___

C. Is a uniform material ___

D. May be represented by a standard linear model (for small
deformations)

___

E. Displays creep for times less than t min ___

(5)

Questions 13-16 refer to the following paragraph

A 19-year-old male pedestrian was struck by a car, sustaining a tibial
fracture at the junction of the mid and distal third. The fibula was intact;
the tibia had an incomplete “butterfly” on the medial aspect (as seen in
an anteroposterior [AP] view). The fracture was fixed with a stainless-
steel eight-hole compression plate, placed laterally. The patient was dis-
charged fully weight bearing.
The following clinical observations were made:

1 month postoperation (PO): Patient complains of pain over distal
aspect of plate.
2 months PO: Continued complaint of pain, localized erythema.
6 months PO: Fracture nonunited in AP radiograph.
9 months PO: Patient presents with acute onset of pain “in leg”; AP
radiograph reveals broken plate, nonunited fracture.

13. On surgical exploration, which is (are) the most likely finding(s)?

A. Plate broken between two screw holes ___

B. Plate broken at level of screw hole ___

C. Soft tissue discoloration over most distal screwhead ___

D. Soft tissue discoloration over most screwheads ___

E. None of the above ___

(5)