AAOS & ABOS Anatomy MCQs (Set 3): Musculoskeletal & Skeletal System Questions | Board Review

At the level of L2, the liver and the vena cava lie to the right. The pancreas and duodenum are anterior to the aorta. The aorta lies in the midline just in front of the vertebral body. Clement CD: Anatomy: A Regional Atlas of Human Anatomy, ed 3. Baltimore, MD, Munich, Germany, Urban and Schwarzberg, 1987, Figure 331.

The radiographs show a posterior knee dislocation. Knee dislocations almost always involve rupture of both the anterior and posterior cruciate ligaments. Collateral ligament injuries also are common. Arterial, nerve, and tendon injuries each occur in less than half of knee dislocations. Schenck RC Jr, Hunter RE, Ostrum RF, et al: Knee dislocations. Instr Course Lect 1999;48:515-522.

Penetrating sharp wounds in proximity to major nerve or vascular structures should always be acutely explored. Because this patient did not seek treatment for a potentially treatable injury, interosseous wasting implies injury to the C8 and T1 nerve roots that contribute to ulnar nerve function. The most likely location for the brachial plexus injury is the location marked L or the inferior trunk. A wrist drop that is the result of radial nerve dysfunction would be expected with an injury at K or O. An upper brachial plexus palsy with loss of elbow flexion and shoulder abduction would be expected with an injury at B. A loss of elbow flexion alone would be expected following an injury at C. Netter F: The Ciba Collection of Medical Illustrations: The Musculoskeletal System. Part 1, Anatomy, Physiology and Metabolic Disorders. West Caldwell, NJ, Ciba-Geigy, 1991, vol 8, pp 28-29. Wolock B, Millesi H: Brachial plexus-applied anatomy and operative exposure, in Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, PA, JB Lippincott, 1991, vol 2, pp 1255-1272.

The iliolumbar vein is a large tributary that sits along the lateral surface of the common iliac vein. It can be quite substantial in size and must be identified prior to mobilizing the common iliac vein toward the midline. The other structures are not of surgical significance in performing this exposure.

Tears of the pectoralis major tendon are frequently missed during examination. MRI provides excellent visualization of the tendon if the study extends low enough down the arm. The pectoralis major tendon inserts on the crest of the greater tubercle of the humerus, just lateral to the long head of the biceps tendon. The latissimus dorsi tendon inserts medial to the long head of the biceps tendon on the lesser tubercle. The subscapularis tendon inserts on the lesser tuberosity more proximally. The deltoid insertion is more distal. Connell DA, Potter HG, Sherman MF, et al: Injuries of the pectoralis major muscle: Evaluation with MR imaging. Radiology 1999;210:785-791. Carrino JA, Chandnanni VP, Mitchell DB, et al: Pectoralis major muscle and tendon tears: Diagnosis and grading using magnetic resonance imaging. Skeletal Radiol 2000;29:305-313.

The arthroscopic views show the lateral side of the ankle as demonstrated by the presence of the tibiofibular articulation. As is typical in chronic anterolateral impingement, synovitis overlies the anteroinferior band of the tibiofibular ligament, the most distal portion of the anterior syndesmosis. Hypertrophic scar formed on or in this ligament can impinge on the lateral margin of the talar dome and has been associated with chronic anterolateral ankle pain. Bassett FH III, Gates HS III, Billys JB, et al: Talar impingement by the anteroinferior tibiofibular ligament: A cause of chronic pain in the ankle after inversion sprain. J Bone Joint Surg Am 1990;72:55-59.

In patients with an osteomyelitic infection, radiographic findings at 1 to 5 days usually show soft-tissue swelling only. Seven to 14 days after symptoms begin, radiographs will most likely show the classic signs of acute osteomyelitis. Reactive bone formation would be expected by 6 months. Kasser JR (ed): Orthopaedic Knowledge Update 5. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1996, pp 149-161.

The scan reveals a bony Bankart lesion. The anterior band of the inferior glenohumeral ligament is the major restraint to anterior translation of the humeral head and is usually injured with anterior shoulder dislocations. It inserts onto the glenoid labrum at the anteroinferior aspect of the glenoid rim. The labrum most frequently avulses from the glenoid (Bankart lesion), but occasionally the bony attachment is avulsed. O'Brien SJ, Neves MC, Arnoczky SP, et al: The anatomy and histology of the inferior glenohumeral ligament complex of the shoulder. Am J Sports Med 1990;18:449-456.

The popliteal artery lies just posterior to the posterior cruciate ligament tibial insertion, separated only by the posterior capsule of the knee. When performing a posterior cruciate ligament reconstruction, this artery is at risk for injury during creation of the tibial tunnel. Jackson DW, Proctor CS, Simon TM: Arthroscopic assisted PCL reconstruction: A technical note on potential neurovascular injury related to drill bit configuration. J Arthroscopy 1993;9:224-227.

The radiographs show a centrally located radiolucent lesion with cortical thinning and mild osseous expansion; these findings are the hallmarks of a simple bone cyst. Whereas this particular lesion does not demonstrate sclerosis, the distinct margin of this lesion with sharp transition to normal bone is common. The MRI scans reveal a purely cystic lesion with bright T2 signal, and the gadolinium image shows the classic rim enhancement of cystic lesions. Fibrous dysplasia with cystic degeneration might have a very similar appearance and should be considered in the differential diagnosis. Parsons TW: Benign bone tumors, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1027-1035. May DA, Good RB, Smith DK, et al: MR imaging of musculoskeletal tumors and tumor mimickers with intravenous gadolinium: Experience with 242 patients. Skeletal Radiol 1997;26:2-15.

The lateral femoral cutaneous nerve pierces the fascia between the tensor fascia lata and the sartorius approximately 2.5 cm distal to the anterosuperior iliac spine and is at risk when the interval is defined. The superior gluteal and femoral nerves define the internervous plane between the tensor fascia lata and the sartorius and are not at risk for injury. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, pp 302-316.

The obturator vessels and nerve pass along the lateral pelvic wall along the true pelvic brim (nerve lies anterior to the vessels and lies on the obturator internus muscle) and descend into the obturator groove at the upper portion of the obturator foramen. Higuchi T: Normal anatomy and magnetic resonance appearance of the pelvis, in Takahashi HE, Morita T, Hotta T, et al (eds): Operative Treatment of Pelvic Tumors. Tokyo, Japan, Springer-Verlag, 2003, pp 4-21.

The plantaris tendon is often harvested to augment a tendon reconstruction. The origin of the plantaris muscle is on the posterolateral aspect of the distal femur, and the muscle lies lateral to the tibial nerve and the posterior tibial artery. The tendon then courses posteriorly between the soleus and the medial head of the gastrocnemius. Clement CD: Anatomy: A Regional Atlas of Human Anatomy, ed 3. Baltimore, MD, Munich, Germany, Urban and Schwarzberg, 1987, Figure 475.

The proximal exposure of the radius is most often used for internal fixation of fractures, resection of tumors, or decompression of the posterior interosseous nerve beneath the supinator muscle. The supinator muscle is exposed through the interval between the extensor carpi radialis brevis and the extensor digitorum comminus muscles. This interval can be more easily palpated further distal in the forearm. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 136-146.

The structure enclosed by the circle is the acetabular labrum. It is visible as the white point of tissue outlined by the darkly radiopaque contrast. The appearance of the contrast surrounding the sharp white point of a normal labrum is called the "rose thorn sign." The limbus is the term reserved for a rounded, infolded labrum seen with arthrography. The pulvinar is the fatty tissue seen in the empty acetabulum when the hip is dislocated. The ligamentum teres is seen as a white stripe outlined by contrast coursing from the central acetabulum to the dislocated femoral head. The transverse acetabular ligament courses across the inferior portion of the acetabulum and is not clearly seen with arthrography. Herring JA: Tachdjian's Pediatric Orthopaedics, ed 3. Philadelphia, PA, WB Saunders, 2002, vol 1, pp 532-533.

The radiographs reveal a geographic, diaphyseal lesion with very subtle cortical expansion, cortical thinning, relatively sharp demarcation, and angular rather than rounded borders, suggesting a fibrous bone lesion. This lesion demonstrates the classic ground glass appearance of fibrous dysplasia. Ewing's sarcoma, metastases, and aneurysmal bone cyst all typically have a more aggressive appearance. Parsons TW: Benign bone tumors, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1027-1035.

The CT scans show large cystic lesions in the talus and calcaneus with complete subluxation of the subtalar joint, allowing the calcaneus to slide laterally until it becomes blocked by the fibula. The cause of this subluxation is severe posterior tibial tendon dysfunction. Although no fibular fracture has yet appeared, it can occur with continued stress from the calcaneus. There is, however, a pathologic fracture in the medial calcaneus through a medial degenerative cyst. The joint space is irregular and not symmetrical as would be seen in an inflammatory arthropathy. Cystic lesions are not present in the tibia. No stress fracture is seen in the talus. Coughlin MJ: Sesamoids and accessory bones of the foot, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 437-499.

The lunotriquetral interosseous ligament stabilizes the lunotriquetral joint. The scapholunate interosseous ligament stabilizes the scapholunate joint. The ulnolunate ligament originates from the base of the ulnar styloid and inserts in the lunate. The ulnotriquetral ligament originates from the base of the ulnar styloid and inserts on the triquetrum. The ulnolunate and the ulnotriquetral ligaments are important stabilizers to the ulnar side of the wrist. The short radiolunate ligament originates on the volar ulnar margin of the distal radius and inserts in the ulnar margin of the lunate. Berger RA: Ligament anatomy, in Cooney WP, Linscheid RL, Dobyns JH (eds): The Wrist, Diagnosis and Operative Management. St Louis, MO, Mosby, 1998, pp 73-105.

The medial collateral ligament complex of the elbow consists of three portions: the anterior bundle, the posterior bundle, and a transverse component that has little biomechanic significance. The origin of the ligament is from the central two thirds of the anteroinferior undersurface of the medial epicondyle.

To improve hip biomechanics and secure more suitable bone for acetabular fixation, the true acetabulum is often resurfaced in patients who have developmental dysplasia of the hip, thus lowering the hip center and lengthening the leg. Acute lengthening of more than 3 cm will place excessive tension on the sciatic nerve and require a femoral shortening to avoid sciatic nerve injury. The other maneuvers will not relieve sciatic nerve tension because of limb lengthening. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 430-431.

The radiograph shows a diastasis of the scapholunate interval, caused by certain failure of the scapholunate interosseous ligament. The lunotriquetral interosseous ligament stabilizes the lunotriquetral joint. The long radiolunate ligament originates in the volar radius and inserts in the lunate. The short radiolunate ligament originates on the ulnar margin of the radius and inserts on the ulnar margin of the lunate. The ulnolunate ligament originates at the ulnar styloid base and inserts on the volar aspect of the lunate. Linscheid RL, Dobyns JH, Beabout JW, et al: Traumatic instability of the wrist: Diagnosis, classification, and pathomechanics. J Bone Joint Surg Am 1972;54:1612-1632. Mayfield JK, Johnson RP, Kilcoyne RK: Carpal dislocations: Pathomechanics and progressive perilunar instability. J Hand Surg Am 1980;5:226-241.

The extensor digiti mini quinti is most typically a tendon with two slips. The abductor pollicis longus has multiple slips that insert in order of frequency on the base of the first metacarpal, trapezium, and thenar muscles. The extensor pollicis longus, extensor carpi radialis brevis, and extensor indicis proprius consistantly have only one slip. von Schroeder HP, Botte MJ: Anatomy of the extensor tendons of the fingers: Variations and multiplicity. J Hand Surg Am 1995;20:27-34.

The nerve to the abductor digiti quinti is the first branch of the lateral plantar nerve. It branches off while the nerve is still on the medial side of the foot and also innervates a portion of the plantar fascia. It can become entrapped beneath the deep fascia of the abductor hallucis muscle and has been associated with some forms of chronic heel pain. Baxter DE, Pfeffer GB: Treatment of chronic heel pain by surgical release of the first branch of the lateral plantar nerve. Clin Orthop 1992;279:229-236.

The MRI scan reveals disruption of the lateral capsule and ligaments with fluid in the soft tissues laterally. Additionally, there is a large bone bruise on the medial femoral condyle. This combination indicates injury to the posterolateral complex. These injuries often have coexisting anterior and/or posterior cruciate ligament injuries. Failure to recognize the posterolateral corner injury can lead to failure of anterior or posterior cruciate ligament reconstructions. LaPrade RF, Gilbert TJ, Bollom TS, et al: The magnetic resonance imaging appearance of individual structures of the posterolateral knee: A prospective study of normal knees and knees with surgically verified grade III injuries. Am J Sports Med 2000;28:191-199.

The axillary nerve courses from anterior to posterior just below the inferior shoulder capsule. Thermal energy applied to the inferior aspect of the shoulder capsule can result in injury to this nerve. Wong KL, Williams GR: Complications of thermal capsulorrhaphy of the shoulder. J Bone Joint Surg Am 2001;83:151-155.