Defining the proximity of the axillary nerve from defined anatomic landmarks: an in vivo magnetic resonance imaging study.

BACKGROUND: The location of the axillary nerve in the shoulder makes it vulnerable to traumatic or iatrogenic injury. Cadaveric studies have reported the location of the axillary nerve but are limited because of tissue compression, dehydration, and decay. Three-Tesla (T) magnetic resonance imaging (MRI) allows high anatomic resolution of neural structures. The aim of our study was to better define the location of the axillary nerve from defined bony surgical landmarks in vivo, using MRI scan. METHODS: Using MRI, we defined a number of anatomic points and measured the distance from these to the perineural fat surrounding the axillary nerve using simultaneous tracker lines on both images. Two observers were used. RESULTS: A total of 187 consecutive 3-T MRI shoulder scans were included. Mean age was 57.9 years (range 18-86). The axillary nerve was located at a mean of 14.1 mm inferior from the bony glenoid at the anterior border, 11.9 mm from the midpoint, and 12.0 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P < .001), and between the anterior and posterior borders (P < .001). The axillary nerve was located at a mean of 12.6 mm medial to the humeral shaft at the anterior border, 9.9 mm at the midpoint, and 8.6 mm from the posterior border. There was a significant difference between distance at the anterior border and midpoint (P = .008) and between the anterior and posterior borders (P = .002). The mean distance of the axillary nerve from the anterolateral edge of the acromion was 53.3 mm (95% confidence interval [CI] 52.3, 54.2; range 33.9-76.3). The mean distance of the axillary nerve from the inferior edge of the capsule was 2.7 mm (95% CI 2.9, 3.1; range 0.3-9.9). There was a positive correlation between humeral head diameter and axillary nerve distance from the inferior glenoid (R2 = 0.061, P < .001). There was a positive correlation between humeral head diameter and distance from the anterolateral edge of the acromion (R2 = 0.140, P < .001). CONCLUSION: Our study has defined the proximity of the axillary nerve from defined anatomic landmarks. The proximity of the axillary nerve to the inferior glenoid and medial humeral shaft changes as the axillary nerve passes from anterior to posterior. The distance of the axillary nerve from the anterolateral edge of the acromion remains relatively constant. Both sets of distances may be affected by humeral head size. The study has relevance to the shoulder surgeon when considering "safe zones" during arthroscopic or open surgery.

Anatomic study of the superior glenoid labrum.

The purpose of the study was to describe the normal anatomy of the glenoid labrum to help identification of pathology and guide surgical repair. Twenty dry bone scapulae and 19 cadaveric shoulders were examined. Light microscopy was performed on 12 radial slices through the glenoid. An external capsular circumferential ridge, 7-8 mm medial to the glenoid rim marks the attachment of the capsule. A separate internal labral circumferential ridge 4 mm central to the glenoid rim marks the interface between the labrum and articular cartilage. A superior-posterior facet was found consistently on the glenoid. Two thirds of the long head of biceps arises from the supraglenoid tubercle, 6.6 mm from the glenoid face, the remainder from the labrum. The superior labrum is concave and is loosely attached to the articular cartilage and glenoid rim. Clefts and foramens are common superiorly. In contrast the anterior-inferior labrum is convex, attaches 4 mm central to the glenoid rim and has a strong attachment to articular cartilage and bone. Sublabral clefts, recesses, and holes are common, but only in the superior-anterior labrum. Lesions in other regions of the labrum are potentially pathological. A complex superior labrum tear that extends to involve the biceps anchor, should have the biceps anchor repaired to the supraglenoid tubercle (mean 6.6 mm off the glenoid face) and the labrum be repaired to the glenoid rim. The anteroinferior labrum should be repaired 4 mm onto the glenoid face. This study will aid in identifying pathological labral lesions and guide anatomic repairs.

Axillary artery pseudoaneurysm after plate osteosynthesis for a clavicle nonunion: A case report and literature review.

Neurovascular complications have been reported from both plate osteosynthesis and intramedullary fixation of midshaft clavicle fractures. We wish to report a case of limb threatening ischemia from screw penetration of the axillary artery after plate osteosynthesis for a clavicle nonunion. A literature review of vascular trauma from midshaft clavicle fractures is presented.

Influence of lunate type on scaphoid kinematics.

PURPOSE: To assess the influence of lunate type on scaphoid kinematics. METHODS: One hundred normal wrists had fluoroscopic assessment of the wrist in maximal radial, neutral, and ulnar deviation. The shortest distance in a neutral position between the capitate and triquetrum, C-T distance, determined lunate type. A type I lunate had a C-T distance of < or =2 mm, a type II lunate > or =4 mm, and an intermediate group lay between these values. Scaphoid flexion and translation in radial and ulna deviation was measured. RESULTS: There were 18 subjects with a type I lunate, 19 with an intermediate lunate, and 63 with a type II lunate. There was no statistically significant difference between lunate type, subject age, or hand dominance. There was a statistically significant higher proportion of women with a type I lunate. Subjects with a type II lunate had a statistically greater amount of flexion during radioulnar deviation as determined by CR index (0.79 vs 0.91) and scaphoid flexion index (0.21 vs 0.09). Subjects with a type II lunate had statistically less translation during radioulnar deviation as determined by translation ratio (0.22 vs 0.31) and scaphoid inclination index (0.18 vs 0.23). The average scaphoid kinematic index in subjects with a type II lunate was 1.24, intermediate 0.86, and type I 0.42. A scaphoid kinematic index of greater than 1 indicates the scaphoid has more flexion during radioulnar deviation than translation. CONCLUSIONS: Wrists with a type I lunate show statistically greater scaphoid translation with radial deviation. Wrists with a type II lunate show statistically greater scaphoid flexion with radial deviation. Intermediate lunates have intermediate scaphoid mechanics. This allows the surgeon to determine the likely wrist scaphoid mechanics based on the lunate type determined from a single posterior-anterior x-ray.

Brachialis muscle anatomy. A study in cadavers.

BACKGROUND: There have been conflicting descriptions of brachialis muscle anatomy in the literature. The purpose of the present study was to clarify brachialis muscle anatomy in order to refine surgical techniques around the elbow. METHODS: Eleven cadaveric upper limbs were dissected under loupe magnification. The gross morphological characteristics, relationships, and nerve supply of the brachialis muscle were recorded. The nerve supply was examined histologically to confirm the gross findings. RESULTS: In all specimens, the brachialis muscle had two heads. The larger, superficial head originated from the anterolateral aspect of the humerus, proximal to the smaller, deep head. The superficial head contained longitudinal fibers, which inserted by means of a thick round tendon onto the ulnar tuberosity. The deep head fibers were fan-shaped and converged to insert by means of an aponeurosis onto the coronoid process. In all specimens, a branch of the radial nerve supplied the inferolateral fibers of the deep head. CONCLUSIONS: Our observations of brachialis muscle anatomy differ considerably from the descriptions in the current literature. The larger, superficial head has the mechanical advantage of a more proximal origin and a more distal insertion, which may enable it to provide the bulk of flexion strength. The smaller, oblique, deep head has a more anterior insertion on the coronoid, which may facilitate the initiation of elbow flexion from full extension. The radial nerve-innervated inferolateral fibers of the deep head run in a direction similar to the anconeus muscle, forming a muscular sling around the elbow. This complex may act to dynamically stabilize the ulnohumeral joint. CLINICAL RELEVANCE: This information may enhance surgical techniques about the elbow. The identification of an internervous plane may allow for improvement in the current anterior and anterolateral surgical approaches to the humerus. The tendon of the superficial head is well positioned to allow its transfer to the radial tuberosity, potentially improving supination strength in the absence of a distal biceps tendon. It is possible that the tendon of the superficial head might also be used to reconstruct the anular ligament or the medial collateral ligament of the elbow.

External fixation for the foot and ankle in children.

During the last decade, external fixation for the pediatric foot and ankle has evolved as a result of advances in technology (eg, Taylor spatial frame, hydroxyapatite-coated external fixator pins) and preoperative deformity planning. Although complications are common, most are minor and can be addressed nonoperatively while treatment continues. This article reviews the indications and applications of external fixation for soft tissue contractures, idiopathic and teratologic clubfoot, osteotomies, metatarsal lengthening, tibial lengthening, and foot and ankle trauma.

The reliability and validity of assessment of sagittal plane deviations in children who have spastic diplegia.

OBJECTIVE: To assess the reliability and validity of a newly described classification of sagittal plane alignment in spastic diplegic gait. DESIGN: Twenty split-screen videos of children with spastic diplegia, Gross Motor Function Classification System levels I to III, were viewed on 2 occasions, 6 weeks apart, by 5 raters. The sagittal plane alignments of the right and left lower limbs in gait were classified separately as true equinus, jump knee, apparent equinus, or crouch, based on the published classification. A fifth category, nonclassifiable, was used if classification was not possible. We then used sagittal plane kinematic data to confirm the classification for each subject and these were compared with rater classification scores, which used the video information only. SETTING: Tertiary-level children's hospital. PARTICIPANTS: Three pediatric orthopedic surgeons and 2 pediatric orthopedic residents. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Gait classification scores derived from visual observation were compared among and within raters. The gait classification scores derived from visual observation were compared with the scores derived from sagittal plane kinematic data to assess validity. RESULTS: A moderate correlation was found among the 5 raters within each session, with an interrater weighted kappa score of .45 in session 1 and .49 in session 2. The intrarater, weighted kappa scores showed a moderate to substantial level of agreement between sessions, ranging from .50 to .68. The classification scores of individual raters had moderate validity when compared with classifications derived from the sagittal plane kinematic data. However, there was a substantial level of agreement between the consensus opinion and the classification obtained using the kinematic data as well as the video recordings (weighted kappa=0.8). CONCLUSIONS: This classification has only moderate reliability and validity when a single experienced rater views the 2-dimensional gait videos. However, the consensus opinion derived from the scores of 5 raters considerably improves the validity of the assessment.