Joint & Connective Tissue

Question 1

A 72-year-old woman underwent right total knee arthroplasty 2 days ago. When you see her in consultation, she tells you that she has numbness along the lateral portion of the incision site. What is the most likely cause?

(a) Femoral or peroneal nerve injury
(b) Deep vein thrombosis
(c) Cutaneous nerve injury
(d) Temporary side effect from anesthesia

Answer 1

Answer: (c)
Commentary: Cutaneous sensory loss is a very common complication following primary total knee arthroplasty. One study from 1995 found that 100% of patients had lateral skin flap numbness, and more recent studies in 2004 and 2009 found 81%-86% of patients had lateral skin flap numbness. In most cases, the numbness does improve with time (50% recovered in 2 years in the 2009 study). Deep vein thrombosis (DVT) and common peroneal nerve palsy are other known complications of total knee arthroplasty.

References: (a) Borley NR, Edwards D, Villar RN. Lateral skin flap numbness after total knee arthroplasty. J Arthroplasty. 1995Feb;10(1):13-4. (b) Hopton BP, Tommichan MC, Howell FR. Reducing lateral skin flap numbness after total knee arthroplasty. Knee. 2004 Aug;11(4):289-91. (c) Subramanian S, Lateef H, Massraf A. Cutaneous sensory loss following primary total knee arthroplasty: a two years follow-up study. Acta Orthop Belg. 2009 Oct; 75(5):649-53.

Question 2

A 70-year-old woman complains of acute localized mid back pain. She has a non-focal neurologic examination. An anteroposterior and lateral thoracic spine x-ray confirms your clinical suspicion of an acute T8 compression fracture. Which recommendation would best help her to reduce her risk of
future fractures?

(a) Swimming laps 20-30 minutes daily
(b) Isotonic abdominal strengthening program
(c) A weight reduction diet
(d) Avoidance of tobacco use

Answer 2

(d) The National Osteoporosis Foundation (NOF) established guidelines to reduce risk of osteoporotic
fractures. These recommendations include, participating in weight bearing exercise, ingesting adequate calcium (1200mg/day) and vitamin D (400-800IU), and avoiding tobacco use.

Heinemann DF. Osteoporosis: an overview of the National Osteoporosis Foundation clinical practice
guide. Geriatrics 2000;55:31-6.

Question 3

What is the most common reason for revision of a total hip arthroplasty?

(a) Recurrent dislocation
(b) Peri-prosthetic fracture
(c) Aseptic loosening from polyethylene wear
(d) Infection

Answer 3

(c) Aseptic loosening caused by polyethylene wear is is the most common reason for hip arthroplasty
revision surgery.

Question 4

113. Which factor is associated with the highest risk for postoperative dislocation after a total hip
     arthroplasty?

(a) Femoral anteversion
(b) Anterior approach for hip replacement
(c) Long femoral component
(d) Previous hip replacement

Answer 4

(d) Patients with history of previous hip replacement and posterior approach are at greater risk for postoperative
dislocation. Posterior surgical approach has a higher risk of dislocation than anterior
approach.

Question 5

How much knee flexion is required to descend stairs step over step after a total knee replacement?

(a) 45°
(b) 70°
(c) 90°
(d) 110°

Answer 5

(d) Descending stairs requires 110° knee flexion.

Question 6

Painful, arthritic hip disease is associated with the following gait abnormality.

(a) Prolonged stance phase of the affected limb
(b) Limb circumduction during swing
(c) Lateral trunk shift over the affected joint during stance
(d) Shortest step length of the affected limb

Answer 6

(c) The patient will lean over the affected hip (compensated Trendelenburg gait) in an attempt to
minimize painful contractions of the hip abductors. In addition, the characteristics of an antalgic
gait include shorter stance phase on the affected leg (as the patient attempts to remove weight
quickly from the affected leg), decreased swing phase of the uninvolved leg, and a shorter step
length on the uninvolved side. Limb circumduction is characteristic of increased limb length or
abductor muscle shortening.

Question 7

In patients with osteoporosis, which treatment reduces incidence of vertebral compression
fracture?

(a) Weight reduction
(b) Cash brace
(c) Strengthening of spinal extensors
(d) Strengthening quadriceps

Answer 7

(c) Weak extensor muscles increase risk of compression fracture. Risk increases with immobilization
longer than 2 days. There is no association between osteoporotic compression fractures and weight
or family history.