AAOS Orthopedic Anatomy Board Review (Set 4): Hip & Pelvic Girdle MCQs | ABOS, SMLE

The figure shows an axial image of the shoulder immediately inferior to the coracoid process. The subscapularis tendon, which can be traced from the myotendinous junction, is torn and detached from its lesser tuberosity attachment on the humerus. Lateral to the lesser tuberosity, the bicipital groove is empty. The arrow points to the subluxated biceps tendon. Superficial fibers of the subscapularis tendon are contiguous with the biceps retinaculum, which covers the bicipital groove and hold the biceps tendon in place. The vast majority of subscapularis tendon tears result in disruption of the biceps retinaculum with resultant subluxation of the tendon. Resnick D, Kang HS (eds): Internal Derangement of Joints: Emphasis on MR Imaging. Philadelphia, PA, WB Saunders, 1997, pp 308-317.

The majority of large collagen fibers within the menisci are oriented circumferentially. It is these fibers that develop the hoop stress with compressive loading of the menisci. Most meniscal tears are longitudinal and occur between these circumferential fibers. Mow VC, et al: Structure and function relationships of the menisci of the knee, in Mow VC, Arnoczky SP, Jackson DW (eds): Knee Meniscus: Basic and Clinical Foundations. New York, NY, Raven Press, 1992, pp 37-57.

The safe zone for anterior halo pin insertion is marked laterally by the anterior border of the temporalis muscle (to avoid penetration of this muscle and relative thin cortex of the skull). Medially, the pin should be placed 4.5 cm lateral to the midline to avoid injury to the supraorbital nerve or the frontal sinus. The safe area is marked superiorly by the head equator to avoid cephalad migration of the pin and inferiorly by the supraorbital ridge to prevent displacement or penetration into the orbit.

The axial views show fusion of the talus and calcaneus at the medial facet (talocalcaneal coalition). Peroneal spastic flatfoot is a descriptive term applying to the symptoms of painful flatfoot associated with apparent peroneal spasm and is sometimes caused by tarsal coalition; however, this is not the most appropriate diagnosis for this patient. Flexible flatfoot with a short Achilles tendon often causes symptoms similar to the ones listed above, but subtalar motion should be normal. A diagnosis of calcaneonavicular coalition can be made based on plain oblique views of the foot but is not seen in these views. Posterior tibial tendon dysfunction in the absence of other pathology is uncommon in children. Vincent KA: Tarsal coalition and painful flatfoot. J Am Acad Orthop Surg 1998;6:274-281.

The superficial branch of the peroneal nerve travels subcutaneously anterior to the lateral malleolus at the ankle. It can be easily damaged by deep penetration of the knife blade when making this portal or when passing shavers in and out of the portal. Anesthesia or dysesthesia from laceration or neuroma formation can cause significant postoperative morbidity. The anterior tibialis tendon, anterior tibial artery, and the deep peroneal nerve are located much more anterior and central on the ankle. The sural nerve is posterior lateral to the ankle and is not at risk from this portal. Ferkel RD, Heath DD, Guhl JF: Neurological complications of ankle arthroscopy. Arthroscopy 1996;12:200-208.

Acetabular screws are inserted to supplement fixation. The acetabular component can be divided into four quadrants. Anatomic studies have shown that screws placed in the anterior superior and anterior inferior quadrants of the cup may injure the external iliac vein and obturator artery, respectively. Posterior superior and posterior inferior placement (in screws greater than 25 mm) may injure the sciatic nerve or the superior gluteal artery. The common iliac artery is proximal to the acetabulum and is at least risk for injury from acetabular screw placement.

The patient has a pars interarticularis defect of L5 without apparent listhesis. The other diagnoses are not present. Papanicolaou N, Wilkinson RH, Emmans JB, Treves S, Micheli LJ: Bone scintigraphy and radiography in young athletes with low back pain. Am J Roentgenol 1985;145:1039-1044.

Posttraumatic osteolysis of the distal portion of the clavicle is a condition that can be a complication of acute or repetitive trauma. The distal end of the clavicle is frayed and resorbed. Resorption may occur after weeks or months. The end of the clavicle may reconstitute over a period of months, or the acromioclavicular joint may remain widened. The differential diagnosis for distal clavicular erosion also includes rheumatoid arthritis, hyperparathyroidism, neoplastic destruction, cleidocranial dysplasia, and pyknodysostosis. Acutely, a type 2 acromioclavicular joint injury does not result in erosion or resorption of the clavicle. Periosteal sleeve injuries radiographically mimic acromioclavicular joint dislocation. Rickets occurs only in childhood.

The main arterial supply to the humeral head is provided by the ascending branch of the anterior humeral circumflex artery and its intraosseous continuation, the arcuate artery. There are significant intraosseous anastomoses between the arcuate artery, the posterior humeral circumflex artery through vessels entering the posteromedial aspect of the proximal humerus, the metaphyseal vessels, and the vessels of the greater and lesser tuberosities. Four-part fractures and dissection during exposure affect perfusion of the humeral head. Brooks CH, Revell WJ, Heatley FW: Vascularity of the humeral head after proximal humeral fractures: An anatomical cadaver study. J Bone Joint Surg Br 1993;75:132-136.

The MRI scan shows a defect in the posterior aspect of the humeral head, commonly referred to as a Hill-Sachs lesion. This is an impaction fracture of the humeral head that occurs during anterior shoulder dislocation. The abnormality on this image is an irregularity of the posterior humeral head; the humeral head otherwise has a homogenous appearance. The coracoid, subscapularis, and posterior labrum are normal. Griffin LY (ed): Orthopaedic Knowledge Update: Sports Medicine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 47-63.

The rhomboideus major and minor muscles are innervated by the dorsal scapular nerve, which is supplied entirely by the C5 nerve root. The dorsal scapular nerve arises just distal to the dorsal root ganglion of the C5 nerve root. A functioning rhomboid muscle indicates that an injury involving C5 nerve root fibers must be postganglionic or distal to the C5 dorsal root ganglion. Woodburne RT, Crelin ES, Kaplan FS, Dingle RV (eds): The Ciba Collection of Medical Illustrations. Summit, NJ, Ciba-Geigy Corporation, 1987, vol 8, pp 23-28.

Radiographic abnormalities such as coxa magna, coxa breva secondary to growth arrest, and coxa plana and acetabular deformities are associated with healed Legg-Calve-Perthes disease. Femoral heads that were flat yet congruent with the acetabulum are at risk for disabling arthritis in the sixth decade of life in 50% of these untreated patients. As the normal ball-and-socket joint deforms to a flattened cylinder, the hip loses abduction and rotation capability, while retaining flexion and extension potential. If the femoral head is flat and is not concentric with the acetabulum, early severe arthritis occurs. Hinge abduction and anterior impingement are known sequelae of a flat, incongruent femoral head.

The median nerve passes through the pronator teres and deep to the flexor digitorum superficialis. The ulnar artery passes deep to both. Anderson JE (ed): Grant's Atlas of Anatomy, ed 7. Baltimore, MD, Williams and Wilkins, 1978, pp 6-55.

The vascularity of the dorsal portion of the digital flexor tendons is considerably richer than the volar portion. The other regions are not preferentially more vascular. Hunter JM, Scheider LH, Makin EJ (eds): Tendon Surgery in the Hand. St Louis, MO, Mosby, 1987, pp 91-99.

The supraspinatus tendon shows clear detachment and retraction from its greater tuberosity attachment by the absence of the normal dark subacromial signal extending to the attachment on the greater tuberosity. There is no anterior inferior glenoid labral detachment that usually is seen in a Bankart lesion. The acromioclavicular joint shows no evidence of separation. The humeral head is migrated cranially, indicating a chronic rotator cuff tear. Iannotti JP, Zlatkin MB, Esterhai JL, Kressel HY, Dalinka MK, Spindler KP: Magnetic resonance imaging of the shoulder: Sensitivity, specificity, and predictive value. J Bone Joint Surg Am 1991;73:17-29. Seeger LL, Gold RH, Bassett LW, Ellman H: Shoulder impingement syndrome: MR findings in 53 shoulders. Am J Roentgenol 1988;150:343-347.

As long as the dissection stays proximal to the annular ligament, the posterior interosseous nerve is not at risk for injury. However, to ensure that the nerve is as far removed from the surgical field as possible, the forearm should be placed in pronation. Forearm supination of any degree will bring the nerve toward the surgical field. A neutral position of the forearm or elbow extension with wrist extension will not protect the posterior interosseous nerve. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach, ed 2. Philadelphia, PA, Lippincott-Raven, 1992, p 100.

The MRI scan shows an acute complete tear of the posterior cruciate ligament. No evidence is seen of a quadriceps tendon rupture, a tibia fracture, or a bone contusion. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 533-557.

The tibiofibular overlap is measured between the medial border of the fibula and the lateral border of the anterior tibial tubercle. Plain radiographic assessment of the distal tibiofibular syndesmosis requires AP and mortise views. The following criteria have been used as the normal limits in adults: a talocrural angle of + or - 83 degrees with up to 5 degrees of normal difference between both sides, a medial clear space of less than 4 mm, a talar tilt of less than 2 mm, a tibiofibular clear space of less than 5 mm, a tibiofibular overlap of greater than or equal to 0 mm, and a talar subluxation that is a subjective assessment of congruity of the tibial articular surface and the talar dome; any incongruity is abnormal. It has been recommended to obtain the first three measurements on the mortise view and the other three on the AP view. Wuest TK: Injuries to the distal lower extremity syndesmosis. J Am Acad Orthop Surg 1997;5:172-181.

The extensor carpi ulnaris tendon is shown subluxated from its tunnel at the ulnar head; this requires disruption of the tendon's subsheath. Rowland SA: Acute traumatic subluxation of the extensor carpi ulnaris tendon at the wrist. J Hand Surg Am 1986;11:809-811.

Ankle sprains most commonly involve injury to the lateral collateral ligaments of the ankle (anterior talofibular, posterior talofibular, and calcaneofibular) from an inversion mechanism of injury. A different entity has been more recently described that involves an external rotation mechanism of injury that widens the ankle mortise and disrupts the anterior inferior tibiofibular ligament. Deltoid ligament and extensor retinaculum injuries do occur, although infrequently, and involve eversion and extreme plantar flexion mechanisms, respectively. Last RJ: Anatomy: Regional and Applied, ed 6. London, England, Churchill Livingstone, 1978, p 182. Kaye RA: Stabilization of ankle syndesmosis injuries with a syndesmosis screw. Foot Ankle 1989;9:290-293. Baxter DE: The Foot and Ankle in Sports. St Louis, MO, Mosby-Year Book, 1995, p 30.

The first extensor compartment of the wrist typically contains a single extensor pollicis brevis tendon and the abductor pollicis longus tendon that nearly always has multiple tendon slips. The extensor pollicis brevis tendon is frequently found to be separated from the slips of the abductor pollicis longus tendon by an intracompartmental septum. During surgery, this septum must be divided to complete the release of the compartment. Jackson WT, Viegas SF, Coon TM, Stimpson KD, Frogameni AD, Simpson JM: Anatomical variations in the first extensor compartment of the wrist: A clinical and anatomical study. J Bone Joint Surg Am 1986;68:923-926.

In a type III supracondylar distal humerus fracture of the elbow, the brachial artery can become incarcerated, yielding a pulseless extremity. In this situation, closed reduction may not be effective; therefore, open management is often necessary. The preferred surgical approach to the brachial artery and to this fracture is the anterior approach to the cubital fossa. The lacertus fibrosis is incised, and the dissection is carried out between the brachialis (musculocutaneous nerve) and the pronator teres (median nerve), mobilizing the brachial artery. Once the brachial artery is mobilized, the anterior elbow joint capsule may be exposed. The interval between the brachialis and the biceps describes the anterolateral approach to the elbow more commonly used for exposure of the proximal aspect of the posterior interosseous nerve. The dissection interval between the brachioradialis and the pronator teres describes the proximal extent of the anterior approach to the radius. Tubiana R, McCullough CJ, Masquelet AC: An Atlas of Surgical Exposures of the Upper Extremity. Philadelphia, PA, JB Lippincott, 1990, p 115.

Meniscal tears have many configurations and locations. The normal medial meniscus has a bow-tie configuration on the two most medial consecutive sagittal views. Toward the center of the joint the anterior and posterior horns have a triangular shape. These images show an abnormal intra-articular low-signal structure located anterior to the intact posterior cruciate ligament. This most likely represents a torn and displaced posterior horn of the medial meniscus, sometimes called "double PCL sign". A popliteal cyst and ligaments of Wrisberg and Humphry are not visible on these figures. Helms CA: MR image of the knee, in Fundamentals of Skeletal Radiology, ed 2. Philadelphia, PA, WB Saunders, 1995, pp 172-191.

The string passes under the ligamentum flavum as it runs from the posterior aspect of the vertebra above to the inferior aspect of the vertebra below in the sagittal midline. This is an important structure in diskectomy and in posterior approaches to the thoracolumbar spine and neural elements. It is rarely visualized in its entirety because typical exposures provide only a limited view.

Mapping of a physeal bar from biplane polytomography or CT helps to identify lesions that should be treated surgically and aids in planning the surgical approach and resection. Criteria for surgical excision are at least 2 years of longitudinal growth remaining and involvement of no more than 50% of the physis. Osteotomy is required if angular deformity is greater than 20 degrees. Although this physeal bar is large, it is slightly less than 50% of the total area of the physis. Limb lengthening in this case should be reserved for failure of bar resection. Physiodesis of the opposite distal tibia at this age would result in disproportionate shortening of both tibiae. Carlson WO, Wenger DR: A mapping method to prepare for surgical excision of a partial physeal arrest. J Pediatr Orthop 1984;4:232-238.