AAOS & ABOS Anatomy MCQs (Set 3): Skeletal, Joint, and Muscle Anatomy | Orthopedic Board Prep

A winged scapula is most often associated with Parsonage-Turner syndrome, a condition thought to be due to an inflammatory or immune-mediated mechanism. Certain muscles are predisposed, particularly the serratus anterior muscle innervated by the long thoracic nerve. Other less common nerve lesions (eg, the spinal accessory and dorsal scapular nerves) may also cause winged scapulae. Kline DG, Hudson AR: Nerve Injuries: Operative Results for Major Nerve Injuries, Entrapments and Tumors. Philadelphia, PA, WB Saunders, 1995.

The radiographs reveal a blastic lesion of the proximal tibial metaphysis with cortical destruction, mineralization extending into the soft tissue laterally, indistinct margins, and destruction of the normal trabecular pattern. In this age group, with this aggressive appearance, osteosarcoma is the most likely diagnosis. Chondroblastoma and giant cell tumor are generally geographic and lytic. Chondrosarcoma is rare in this age group and would likely be a secondary lesion from an underlying chondroid tumor that is not present here. Whereas infection can have a wide variety of appearances, it tends to be more lytic in the acute presentation. Sanders TG, Parsons TW: Radiographic imaging of musculoskeletal neoplasia. Cancer Control 2001;8:221-231.

The radiograph reveals a subchondral lesion in the metacarpophalangeal joint that is lytic and expansile. The MRI scans show a mass that is moderate in intensity on the T2-weighted image and has some gadolinium uptake. There are no cystic components in this lesion. The subchondral location and expansile nature are highly suggestive of giant cell tumor of bone. A lesion with this appearance might also represent an aneurysmal bone cyst, given the amount of expansion present. Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 113-118.

The median nerve has an intimate association with the palmaris longus and the flexor carpi radialis at the proximal aspect of the carpal canal. The median nerve lies just ulnar and dorsal to the flexor carpi radialis tendon. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 118-131.

The brachialis muscle typically receives dual innervation. The major portion is innervated by the musculocutaneous nerve. Its inferolateral portion is innervated by the radial nerve. The others listed have single innervation. The anterior approach to the humerus, which requires splitting of the brachialis, capitalizes on this dual innervation.

In a normal AP pelvis radiograph, the anterior rim of the acetabulum runs medially and distally, diverging from the posterior rim which runs much more vertically. In excessive acetabular retroversion, the anterior rim (bold line in Figure 33b) and posterior rim start laterally, and as these lines progress medially and distally, the anterior line crosses the posterior line. This predisposes to femoral acetabular impingement. Reynolds D, Lucas J, Klaue K: Retroversion of the acetabulum: A cause of hip pain. J Bone Joint Surg Br 1999;81:281-288.

The plantar-medial cutaneous nerve is at risk with the surgical approach to the medial sesamoid. It is found directly underlying an incision made at the junction of the glabrous skin of the hallux and must be identified before the approach can proceed. Transection will result in a painful neuroma that impinges on the plantar-medial surface of the toe and cause problems with shoe wear. The only other structure that lies near the surgical field is the abductor hallucis tendon which lies dorsal to the incision.

Although any of these structures can be injured by pressure from the medial blade of a self-retaining retractor, the recurrent laryngeal nerve runs cephalad in the interval between the esophagus and trachea and is vulnerable to pressure if caught between the retractor and an inflated endotracheal tube balloon. Ebraheim NA, Lu J, Skie M, et al: Vulnerability of the recurrent laryngeal nerve in the anterior approach to the lower cervical spine. Spine 1997;22:2664-2667.

Femoral acetabular impingement (FAI) is a pathologic entity leading to pain, reduced range of motion in flexion and internal rotation, and development of secondary arthritis of the hip. There are two types of FAI: cam impingement and pincher impingement. Cam impingement is seen when a nonspherical femoral head produces a cam effect when the prominent portion to the femoral head rotates into the joint. This mechanism produces shear forces that damage articular cartilage. Radiographs reveal early joint degeneration and flattening of the head neck junction (the so-called "pistol grip deformity") as seen in this image. The pincher type of impingement involves abnormal contact between the femoral head neck junction and the acetabulum, in the presence of a spherical femoral head. Beall DP, Sweet CF, Martin HD, et al: Imaging findings of femoraoacetabular impingement syndrome. Skeletal Radiol 2005;34:691-701.

The posterior atlanto-dens interval represents the space available for the spinal cord and a distance of less than 14 mm is predictive of neurologic progression, thus warranting consideration for fusion, even in the absence of symptoms.

While the most prominent functional deficit from axillary nerve lesions occurs from denervation of the deltoid, denervation of the teres minor also occurs.

The AP radiograph demonstrates extensive periacetabular osteolysis. The central hole eliminator has dissociated from the shell and migrated into a lytic defect in the ischium. In a retrieval study, most periacetabular osteolytic lesions had a clear communication pathway with the joint space. Lesions with communication to the joint via several pathways or through a central dome hole (as in this patient) were larger and more likely to be associated with cortical erosion. Although periprosthetic tumors have been described, they are rare and particle-induced inflammation around a prosthesis does not seem to increase the risk for carcinogenesis. Visuri T, Pulkkinen P, Paavolainen P: Malignant tumors at the site of total hip prosthesis: Analytic review of 46 cases. J Arthroplasty 2006;21:311-323. Bezwada HP, Shah AR, Zambito K, et al: Distal femoral allograft reconstruction for massive osteolytic bone loss in revision total knee arthroplasty. J Arthroplasty 2006;21:242-248.

The coronal MRI scan of the wrist shows the scaphoid. There is a subtle fracture line with a step-off at the radial surface consistent with a nonunion. The signal intensity is markedly different between the two fragments of the scaphoid. This strongly suggests osteonecrosis. Preiser's disease is osteonecrosis typically involving most or all of the scaphoid. Kienbock's disease involves the lunate. Intraosseous ganglia are easily diagnosed on MRI but typically have a fluid-filled area surrounded by denser bone in the periphery. Scapholunate dissociation can be seen on MRI as an injury to the scapholunate ligament and widening of the scapholunate interval, neither of which is seen on this image.

The radiographs reveal a large femoral metaphyseal lytic lesion with well-defined borders. Joint space narrowing medially is consistent with polyethylene wear. The most likely diagnosis is particle-mediated osteolysis. Metastatic tumors and primary sarcomas adjacent to an arthroplasty are extremely rare. In addition, malignant tumors and infection would more likely reveal a destructive lesion with poorly defined borders and increased uptake on a bone scan. Stress shielding with massive bone loss has not been described in knee arthroplasty literature, although this entity has been observed in fully porous-coated femoral implants in total hip arthroplasty. Robinson EJ, Mulliken BD, Bourne RB, et al: Catastrophic osteolysis in total knee replacement: A report of 17 cases. Clin Orthop Relat Res 1995;321:98-105. Archibeck MJ, Jacobs JJ, Roebuck KA, et al: The basic science of periprosthetic osteolysis. Instr Course Lect 2001;50:185-195.

The terminal branch of the posterior interosseous nerve is contained in the fourth dorsal compartment. The contents of the various dorsal wrist compartments are as follows: 1st Compartment: Abductor pollicis longus, extensor pollis brevis; 2nd Compartment: Extensor carpi radialis brevis, extensor carpi radialis longus; 3rd Compartment: Extensor pollicis longus; 4th Compartment: Extensor digitorum comminus, extensor indicus proprius, posterior interosseous nerve; 5th Compartment: Extensor digiti minimi; 6th Compartment: Extensor carpi ulnaris. The extensor indicis proprius is also contained in the fourth dorsal compartment. The extensor digiti minimi is located in the fifth dorsal compartment. The extensor carpi radialis brevis is located in the second dorsal compartment. The extensor pollicis longus is located in the third dorsal compartment, and the abductor pollicis longus is located in the first dorsal compartment. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 150-151.

The MRI scans show coronal oblique and sagittal oblique views of a partial articular surface supraspinatus tear or tendon avulsion (PASTA lesion). The arthroscopic view is a posterior portal of the glenohumeral joint viewing the articular surface of the supraspinatus. These tears are a common source of shoulder pain and are often amenable to transtendon arthroscopic repair without detachment of the intact bursal surface. Sanders TG, Miller MD: A systematic approach to magnetic resonance imaging interpretation of sports medicine injuries of the shoulder. Am J Sports Med 2005;33:1088-1105. McConville OR, Iannotti JP: Partial-thickness tears of the rotator cuff: Evaluation and management. J Am Acad Orthop Surg 1999;7:32-43.

The middle genicular artery supplies the posterior capsule and intracapsular structures (anterior cruciate ligament, posterior cruciate ligament, posterior horns of the meniscus). The medial and lateral inferior geniculates anastomose anteriorly to form a capillary network to supply the fat pad, synovial cavity, and patellar tendon. The lateral superior and inferior genicular arteries supply the lateral retinaculum. Insall J, Scott WN: Anatomy, in Surgery of the Knee, ed 3. Philadelphia, PA, Churchill Livingstone, 2001, pp 64-70.

Using an infraspinatus-splitting incision allows for excellent exposure of the posterior capsule and minimizes the risk of injury to the axillary nerve which lies inferior to the teres minor in the quadrilateral space. Dreese J, D'Alessandro D: Posterior capsulorrhaphy through infraspinatus split for posterior instability. Tech Shoulder Elbow Surg 2005;6:199-207. Shaffer BS, Conway J, Jobe FW, et al: Infraspinatus muscle-splitting incision in posterior shoulder surgery: An anatomic and electromyographic study. Am J Sports Med 1994;22:113-120.

The lateral calcaneal nerve is a branch of the sural nerve that runs along the lateral border of the Achilles tendon to innervate the lateral heel pad. Ankle arthroscopy involves posterior portals that hug the Achilles tendon to avoid the main trunks of the sural nerve and tibial nerve; however, the lateral calcaneal branch remains potentially vulnerable. The first branch of the lateral plantar nerve is actually a medial structure that partially innervates the plantar fascia and the abductor digiti quinti. The deep peroneal nerve is anterior to the ankle. Sitler DF, Amendola A, Bailey CS, et al: Posterior ankle arthroscopy: An anatomic study. J Bone Joint Surg Am 2002;84:763-769.

The MRI scan shows an ALPSA lesion. This is also known as a medialized Bankart with medial displacement of the torn anterior labrum. During surgical stabilization, the labrum and periosteal sleeve must be mobilized and repaired laterally to reduce recurrent instability. A Perthes lesion is a nondisplaced labral tear. A GLAD lesion represents a nondisplaced anterior labral tear with an associated articular cartilage injury. Neviaser TJ: The anterior labroligamentous periosteal sleeve avulsion lesion: A cause of anterior instability of the shoulder. Arthroscopy 1993;9:17-21.

Pectoralis major ruptures typically occur in avid weightlifters (often on supplements) and typically while bench-pressing. Clinically there is significant discoloration/bruising over the pectoralis and into the axilla. MRI helps confirm the diagnosis and may help determine if the tear is in the muscle belly or at the bone-tendon junction. Bal GK, Basamania CJ: Pectoralis major tendon ruptures: Diagnosis and treatment. Tech Shoulder Elbow Surg 2005;6:128-134.

The correct progression of the annular and cruciform pulley in the digits is A1, A2, C1, A3, C2, A4, C3. The two cruciform pulleys are collapsible elements adjacent to the more rigid annular pulleys of the flexor tendon sheath. This arrangement enables unrestricted flexion of the proximal interphalangeal joint. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics, ed 2. Philadelphia, PA, Lippincott-Raven, 1994, pp 176-186.

It is often tempting to assign a diagnosis of plantar fasciitis in patients with hindfoot pain. In this patient, the radiographs confirm a diagnosis of a calcaneal insufficiency fracture. The dense condensation of bone on the lateral view confirms the diagnosis. There is no radiographic evidence of a heel spur, osteochondral lesions, or chondrocalinosis. Resnick D: Diagnosis of Bone and Joint Disorders, ed 3. Philadelphia, PA, WB Saunders, 1995, p 2591. Kearon C: Natural history of venous thromboembolism. Semin Vasc Med 2001;1:27-37.

This view from the lateral portal shows a full-thickness rotator cuff tear. The glenohumeral joint can be visualized through this tear. The glenoid, labrum, and biceps tendon attaching to the superior aspect of the glenoid are easily viewed from this portal, and the arrow is pointing to the biceps tendon. Arthroscopic rotator cuff repair can be performed while visualizing from this portal and using anterior and posterior working portals. Mazzocca AD, Noerdlinger M, Cole B, et al: Arthroscopy of the shoulder: Indications and general principles of techniques, in McGinty JB (ed): Operative Arthroscopy, ed 3. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 412-427.

In Charcot-Marie-Tooth disease, the posterior tibialis and peroneus longus tendons remain strong, serving to invert the hindfoot and depress the first metatarsal head thus causing the cavovarus foot associated with this disease. In contrast, the tibialis anterior and peroneus brevis are less functional and therefore cannot dorsiflex the ankle, elevate the first metatarsal, or evert the foot, contributing to the deformity.