Anatomy Board Review MCQs (Set 4): Peripheral Nerve & Musculoskeletal Systems | AAOS ABOS OITE

The normal fascial components that become diseased and compose the spiral cord include the pretendinous band, spiral band, lateral digital sheet, and Grayson's ligament. Cleland's ligament lies dorsal and is not involved with spiral cord formation. The intrinsic muscle and tendon, the natatory ligament, and the intermetacarpal ligament are well proximal to the digit and are not involved in spiral cord formation. McGrouther D: Dupuytren's contracture, in Green DP, Hotchkiss RN, Pederson WC (eds): Green's Operative Hand Surgery, ed 4. New York, NY, Churchill Livingstone, 1999, vol 1, pp 565-569.

Passing the 70-degree arthroscope through the intercondylar notch provides excellent visualization of the posteromedial corner of the knee. This view should be part of every knee arthroscopy because these structures are often not well visualized from the anterior portals. If this view is omitted, tears of the peripheral posterior horn of the medial meniscus can be overlooked. The arrow points to the peripheral aspect of the posterior horn of the medial meniscus. With an intact medial meniscus, the medial tibial plateau should not be seen from this view. The semimembranosus and gastrocnemius tendons are extra-articular and not visualized. Miller MD: Basic arthroscopic principles, in DeLee JC, Drez D Jr, Miller MD (eds): Orthopaedic Sports Medicine, ed 2. Philadelphia, PA, Saunders, 2003, pp 224-237.

The sural nerve lies lateral to the Achilles tendon at the level of the foot but follows an oblique course proximally to lie directly over the tendon as it heads to the popliteal fossa. It is at risk with any proximal dissection from a direct posterior approach and in particular with procedures done at the musculotendinous junction. The nerve crosses over the lateral border of the Achilles tendon at an average of 9.8 cm above its insertion. Webb J, Moorjani N, Radford M: Anatomy of the sural nerve and its relation to the Achilles tendon. Foot Ankle Int 2000;21:475-477.

The radiograph reveals bilateral patchy sclerosis of the femoral heads without evidence of collapse. The MRI scan shows bilateral head involvement with a common serpentine-like low-intensity signal of the superior femoral head that is common to osteonecrosis. Changes confined to the femoral head effectively exclude rheumatoid arthritis and osteoarthritis. Resnick D (ed): Diagnosis of Bone and Joint Disorders, ed 4. Philadelphia, PA, WB Saunders, 2002, vol 4, pp 3160-3162.

The elongated anterior process of the calcaneus reaching distally toward the navicular is an abnormal finding. Instead of viewing the rounded, blunt distal anterior process of the calcaneus, a bridge extends to the navicular, albeit incomplete. These findings are consistent with a fibrous coalition. CT can reveal a stress fracture of the calcaneus, arthritis of the subtalar joint with subchondral cysts, or an os peroneal bone disruption in the peroneus longus, but those entities are not shown here. The plantar fascia is intact. Richardson EG: 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 702-732.

MRI findings of acute osteomyelitis include a decrease in the normally high signal intensity of bone marrow on T1-weighted imaging; however, a postgadolinium T1-weighted image with fat suppression will show osteomyelitis as a bright marrow signal compared to the surrounding fat. Osteomyelitis is also brighter than normal fat on T2-weighted imaging. There is no rim-enhancing lesion suggesting an abscess, although myositis is seen in the obturator internus and short external rotators. The clinical scenario and imaging studies do not support the diagnosis of septic hip, eosinophilic granuloma, or pelvic fracture. Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994;2:333-341.

The PCBMN originates from the median nerve proper between 3 and 21 cm proximal to the wrist with moderate variation. It virtually always originates from the radial side of the nerve and travels distally with the median nerve, radial to the palmaris longus, and ulnar to the flexor carpi radialis. Hobbs RA, Magnussen PA, Tonkin MA: Palmar cutaneous branch of the median nerve. J Hand Surg Am 1990;15:38-43.

Microvascular studies have shown that the majority of the blood supply to the cruciate ligaments comes from the middle geniculate artery, although there is collateral flow through the other geniculates and from bone. Arnoczky SP: Blood supply to the anterior cruciate ligament and supporting structures. Orthop Clin North Am 1985;16:15-28.

The bifurcate ligament bifurcates to connect the dorsal aspect of the anterior process of the calcaneus to both the cuboid and the navicular. Inversion injuries on the side of the foot can result in avulsion fractures (arrow) of the anterior process of the calcaneus. Sarrafian SK: Anatomy of the Foot and Ankle: Descriptive, Topographic, Functional, ed 2. New York, NY, Lippincott, 1993, p 192.

The arrow points to the biceps femoris, which is inserted onto the fibula. The biceps femoris lies at the posterolateral aspect of the thigh. The semimembranosus and the semitendinous lie at the posterior medial aspect of the thigh. Gray H: Anatomy of the Human Body. Philadelphia, PA, Lea and Febiger, 1918, 2000.

The ratio of displacement from CD to AB normally equals 1.0. If the ratio is greater than 1.0, an anterior atlanto-occipital dislocation may exist. Ratios slightly less than 1.0 are normal except in posterior dislocations, fractures of the odontoid process or ring of the atlas, or congenital abnormalities of the foramen magnum. In these conditions, the ratio may approach 0.7. Powers B, Miller MD, Kramer RS, et al: Traumatic anterior atlanto-occipital dislocation. Neurosurgery 1979;4:12-17.

Pelvic osteolysis in the presence of a well-fixed porous-coated socket is a recognized complication in total hip arthroplasty. The radiograph shows large lytic lesions superiorly adjacent to an acetabular screw and inferiorly extending into the ischium. It also reveals eccentricity of the femoral head with respect to the acetabular component, consistent with polyethylene wear. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 440.

The MRI scan shows a far lateral disk herniation. With the L4-5 disk, a far lateral herniation abuts the left L4 nerve root. The findings would be consistent with those of a left L4 radiculopathy and would include pain or a sensory deficit on the anteromedial aspect of the knee, diminished patellar tendon reflex, and quadriceps weakness, perhaps making it difficult to walk up and down stairs. Fardin DF, Garfin SR (eds): Orthopaedic Knowledge Update: Spine 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 329.

A ganglion cyst compressing the suprascapular nerve results in poorly localized pain in the shoulder girdle. Sensation is intact, with weakness of external rotation and abduction. Supraspinatus and infraspinatus atrophy is often noted when viewed from behind. These cysts are typically associated with labral tears. Deltoid weakness is associated with an axillary nerve injury, and scapular winging results from injury to the long thoracic nerve. Piatt BE, Hawkins RJ, Fritz RC, et al: Clinical evaluation and treatment of spinoglenoid notch ganglion cysts. J Shoulder Elbow Surg 2002;11:600-604.

The imaging studies reveal an expansile lesion with the classic soap bubble appearance that involves most of the calcaneus. The bone scan reveals a very active lesion with intense uptake, and the MRI scans show the classic, loculated appearance of the lesion with multiple fluid-fluid levels. While it is important to rule out telangiectatic osteosarcoma, the most likely diagnosis is an aneurysmal bone cyst. While giant cell tumor might have a similar appearance, the multiple fluid levels in a expansile lesion strongly favor an aneurysmal bone cyst. Parsons TW: Benign bone tumors, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1027-1035.

The Merchant radiograph shows a lateral patellar shift with total polyethylene failure, resulting in a metal-on-metal bearing. This problem is associated with metal-backed patellar components. Component fixation appears solid, and no osteolysis is evident. Poss R (ed): Orthopaedic Knowledge Update 3. Park Ridge, IL, American Academy of Orthopaedic Surgeons, 1990, pp 590-593. Leopold SS, Berger RA, Patterson L, et al: Serum titanium level for diagnosis of a failed metal-backed patellar component. J Arthroplasty 2000;15:938-943.

The MRI scans reveal a chronic distal biceps tendinitis. The T1-weighted scan shows the anatomic detail of the biceps tendon, and the T2-weighted scan shows increased signal caused by edema surrounding the tendon. The T1-weighted scan is not consistent with an antecubital lipoma. The chronicity of the lesion makes hematoma unlikely. An aneurysm usually appears with blood flow through the region and is dark on T1- and T2-weighted scans. Morrey BF: Tendon injuries about the elbow, in Morrey BF (ed): The Elbow and Its Disorders, ed 2. Philadelphia, PA, WB Saunders, 1993, pp 492-504.

The carpal tunnel canal has an hourglass shape in the coronal plane and is narrowest at the level of the hook of the hamate. Cobb TK, Dalley BK, Posteraro RH, et al: Anatomy of the flexor retinaculum. J Hand Surg Am 1993;18:91-99.

The superior cluneal nerves (L1, L2, and L3) are at greatest risk when harvesting iliac crest bone graft during a posterior decompression and fusion. The nerves pierce the lumbodorsal fascia and cross the posterior iliac crest beginning at 8 cm lateral to the posterior superior iliac spine. The ilioinguinal and iliohypogastric nerves innervate anterior structures, and the lateral femoral cutaneous nerve lies in proximity to the anterior superior iliac spine and is at risk with anterior iliac crest bone graft harvesting. The superior gluteal nerve courses through the sciatic notch and supplies motor branches to the gluteus medius, minimus, and tensor fascia lata muscles. An HS: Principles and Techniques of Spine Surgery. Baltimore, MD, Williams and Wilkins, 1998, pp 770-773.

The right syndesmosis appears disrupted on the CT scan when compared to the normal left side. CT can be helpful in determining injury to the syndesmosis, especially with occult clinical findings. Ebraheim NA, Lu J, Yang H, et al: The fibular incisure of the tibia on CT scan: A cadaver study. Foot Ankle Int 1998;19:318-321. Ebraheim NA, Lu J, Yang H, et al: Radiographic and CT evaluation of tibiofibular syndesmotic diastasis: A cadaver study. Foot Ankle Int 1997;18:693-698.

The most likely diagnosis is acute osteomyelitis. She may also have a septic wrist; however, the lytic lesion in the distal radius has the typical presentation and radiographic appearance of metaphyseal osteomyelitis. In this area of sluggish vascular flow, low oxygen tension, and low pH, bacterial seeding is common and is the usual origin of metaphyseal osteomyelitis. Leukemia and Ewing's sarcoma can present as a lytic lesion with an elevated erythrocyte sedimentation rate, but they are much less common than osteomyelitis and are less focal and more destructive in appearance. Nonossifying fibroma is typically metaphyseal and eccentric; however, it is well circumscribed and uncommon in the upper extremity. Eosinophilic granuloma does not typically present with inflammatory indicies. Dormans JP, Drummond DS: Pediatric hematogenous osteomyelitis: New trends in presentation, diagnosis and treatment. J Am Acad Orthop Surg 1994;2:333-341.

At least 8 cm of the posterior aspect of the proximal region of the humeral diaphyseal cortex can be exposed through the interval between the lateral head of the triceps and the deltoid muscle. No nerves or blood vessels need to be exposed in the dissection. The deltoid muscle is innervated by the axillary nerve and the triceps muscle by the radial nerve. This is a true internervous plane.

The main blood supply to the lateral two thirds of the talar body is derived from the artery of the tarsal canal, a branch of the posterior tibial artery. The peroneal artery helps form a vascular plexis over the posterior tubercle and combines with other arteries to form the artery of the sinus tarsi, which is the principal blood supply of the intrasinus structures of the talus. The anterior tibial arteries send branches to the superior surface of the talar head and give rise to the anterolateral malleolar artery, which may anastomose with other vessels to form the artery of the tarsal sinus. Sanders R: Fractures and fracture-dislocations of the talus, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 1465-1518.

The acromial branch of the thoracoacromial trunk courses along the coracoacromial ligament. This artery enters the ligament approximately 5 mm below the acromial edge. Division of the ligament at its insertion on the acromion minimizes the risk of bleeding. Esch JC, Baker CL: Arthroscopic anatomy and normal variations, in Whipple TL (ed): Surgical Arthroscopy: The Shoulder and Elbow. Philadelphia, PA, JB Lippincott, 1993, pp 63-76.

Though anatomic variations exist, both divisions of the sciatic nerve most commonly pass between the piriformis and superior gemellus. This anatomic consideration is relevant during the posterior approach to the hip, where careful retraction of the rotators avoids sciatic nerve injury. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, pp 335-348.