Scot E. Campbell

Pathoanatomy of first-time, traumatic, anterior glenohumeral subluxation events.

BACKGROUND Relative to dislocations, glenohumeral subluxation events have received little attention in the literature, despite a high incidence in young athletes. The pathoanatomy of first-time, traumatic, anterior subluxation events has not been defined, to our knowledge. METHODS As part of a prospective evaluation of all cases of shoulder instability sustained during one academic year in a closed cohort of military academy cadets, a total of thirty-eight first-time, traumatic, anterior glenohumeral subluxation events were documented. Clinical subluxation events were defined as incomplete instability events that did not require a manual reduction maneuver. Twenty-seven of those events were evaluated with plain radiographs and magnetic resonance imaging within two weeks after the injury and constitute the cohort studied. Magnetic resonance imaging studies were independently evaluated by a musculoskeletal radiologist blinded to the clinical history. Arthroscopic findings were available for the fourteen patients who underwent arthroscopic surgery. RESULTS Of the twenty-seven patients who sustained a first-time, traumatic, anterior subluxation, twenty-two were male and five were female, and their mean age was twenty years. Plain radiographs revealed three osseous Bankart lesions and two Hill-Sachs lesions. Magnetic resonance imaging revealed a Bankart lesion in twenty-six of the twenty-seven patients and a Hill-Sachs lesion in twenty-five of the twenty-seven patients. Of the fourteen patients who underwent surgery, thirteen had a Bankart lesion noted during the procedure. Of the thirteen patients who chose nonoperative management, four experienced recurrent instability. Two of the thirteen patients left the academy for nonmedical reasons and were lost to follow-up. The remaining seven patients continued on active-duty service and had not sought care for a recurrent instability event at the time of writing. CONCLUSIONS First-time, traumatic, anterior subluxation events result in a high rate of labral and Hill-Sachs lesions. These findings suggest that clinical subluxation events encompass a broad spectrum of incomplete events, including complete separations of the articular surfaces with spontaneous reduction. A high index of suspicion for this injury in young athletes is warranted, and magnetic resonance imaging may reveal a high rate of pathologic changes, suggesting that a complete, transient luxation of the glenohumeral joint has occurred.

Risk Factors for Posterior Shoulder Instability in Young Athletes

Background: While posterior glenohumeral instability is becoming increasingly common among young athletes, little is known of the risk factors for injury. Purpose: To determine the modifiable and nonmodifiable risk factors for posterior shoulder instability in a high-risk cohort. Study Design: Case-control study (prognosis); Level of evidence, 2. Methods: A prospective cohort study in which 714 young athletes were followed from June 2006 through May 2010 was conducted. Baseline testing included a subjective history of instability, instability testing by a sports medicine fellowship–trained orthopaedic surgeon, range of motion, strength measurement with a handheld dynamometer, and bilateral noncontrast magnetic resonance imaging of the shoulder. A musculoskeletal radiologist measured glenoid version, height, depth, rotator interval (RI) height, RI width, RI area, and RI index. Participants were followed to document all acute posterior shoulder instability events during the 4-year follow-up period. The time to the posterior shoulder instability event during the follow-up period was the primary outcome of interest. Univariate and multivariable Cox proportional hazards regression models were used to analyze the data. Results: Complete data on 714 participants were obtained. During the 4-year surveillance period, 46 shoulders sustained documented glenohumeral instability events, of which only 7 were posterior in direction. The baseline factors that were associated with subsequent posterior instability during follow-up were increased glenoid retroversion (P < .0001), increased external rotation strength in adduction (P = .029) and at 45° of abduction (P = .015), and increased internal rotation strength in adduction (P = .038). Conclusion: This is the largest known prospective study to follow healthy participants in the development of posterior shoulder instability. Posterior instability represents 10% of all instability events. The most significant risk factor was increased glenoid retroversion. While increased internal/external strength was also associated with subsequent instability, it is unclear whether these strength differences are causative or reactive to the difference in glenoid anatomy. This work confirms that increased glenoid retroversion is a significant prospective risk factor for posterior instability.

Atlanto-occipital dislocation with traumatic pseudomeningocele formation and post-traumatic syringomyelia.

Study Design. A case report of traumatic atlanto-occipital dislocation complicated by the development of anterior and posterolateral pseudomeningoceles and the late development of syringohydromyelia is presented. Objective. To describe a unique post-traumatic and postsurgical course following atlanto-occipital dislocation. Summary of Background Data. Syringomyelia is a significant potential long-term complication in patients recovering from traumatic atlanto-occipital dislocation. Cord enlargement and increased T2 signal can be a marker of abnormal cerebrospinal fluid flow dynamics. This “presyrinx state” can be seen before clinical evidence of neurologic compromise. Pseudomeningocele formation after atlanto-occipital dislocation is rare, with only 3 reported cases. To our knowledge, all reported cases describe retropharyngeal pseudomeningoceles, and posterolateral pseudomeningocele as seen in this case has not previously been described. Methods. A single case is reported with an emphasis on the imaging findings related to the patient’s subsequent neurologic deterioration. Results. Following a pedestrian-motor vehicle collision, the patient received initial evaluation and treatment at a local foreign medical facility, where his cervical spine was cleared. Several days following stabilizing treatment and surgery, the patient was transferred to a foreign-based United States military medical facility and ultimately to our institution, where magnetic resonance imaging demonstrated occipitocervical dissociation. The patient was taken to the operating room for surgical stabilization. Four months after his index operation, the patient underwent halo removal. Follow-up magnetic resonance imaging revealed thickening of the cervical spinal cord in conjunction with diffuse high cord T2 signal and a small low cervical segment of syringomyelia. The patient was observed with follow-up magnetic resonance imaging obtained after 1 month. At this time, the low cervical syrinx had enlarged slightly, a small thoracic syrinx was observed, and cine imaging of cerebrospinal fluid flow demonstrated obstruction at the level of the foramen magnum. The patient was taken to the operating room fordecompression of the foramen magnum and posterior fossa and duraplasty. One month later, the patient’s clinical condition began to deteriorate, and repeat imaging showed continued enlargement of the patient’s syrinx and hydrocephalus. He was admitted for an urgent shunt procedure but unfortunately sustained cardiorespiratory arrest while on the ward awaiting surgery. Conclusions. Atlanto-occipital dislocation is rarely survivable, and delayed diagnosis can negatively affect long-term clinical outcome. This case illustrates how, despite early signs of improvement, post-traumatic syringomyelia may occur months or even years after spinal trauma and should always be considered in patients who experience late neurologic deterioration after atlanto-occipital dislocation.

MR Imaging of Ankle Inversion Injuries

Ankle inversions are common in the general population and in athletes. Multiple concurrent injuries are a common result of an ankle-inversion injury. Syndesmosis injury, lateral ankle ligament tears, peroneal retinaculum or tendon injury, osteochondral lesion, or fracture may occur. Chronic pain or instability may result from one or more of these injuries. MR imaging provides superior soft tissue resolution, high sensitivity for occult fractures, and the ability to image the articular cartilage and ankle ligaments directly. This article discusses the MR imaging evaluation of acute and chronic ankle inversion injuries.

Simple Method of Glenoid Bone Loss Calculation Using Ipsilateral Magnetic Resonance Imaging

Background: Current methods for estimating glenoid bone loss in patients with chronic shoulder instability include computed tomography imaging with 3-dimensional reconstruction, specialized computer software, and imaging of the contralateral shoulder. An ideal method of glenoid measurement would require only magnetic resonance imaging (MRI) of the injured shoulder. Purpose: To determine whether MRI measurement of glenoid height, as well as sex, could be used to estimate glenoid width in healthy subjects with no history of shoulder instability. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Bilateral shoulder MRIs were obtained in a healthy cohort of young athletes as part of the baseline assessment in a prospective cohort study. A musculoskeletal radiologist measured glenoid height and width using the sagittal MRI cuts. Univariate and multivariate regression analyses were performed to determine whether demographic and MRI measurements of the glenoid could be used to estimate glenoid width. Results: Of the 1264 shoulder MRIs evaluated, the mean glenoid width was 26.67 mm (±2.49 mm), and the mean glenoid height was 42.15 mm (±3.00 mm). There were significant differences between the 129 female glenoids and the 1035 male glenoids for both width (23.1 mm, 27.1 mm, respectively, P < .0001) and height (37.9 mm, 42.7 mm, respectively, P < .0001); however, the relationship between glenoid height and width was similar for both men and women. The glenoid width was found to correlate with the height measurement (r = 0.56) for the entire cohort. Based on the results of linear regression analysis, controlling for the influence of sex, a formula was created that represents the relationship between these variables for male subjects: Glenoid Width = (1/3 Height) + 15 mm. Female patients are estimated with a formula that represents the same slope but a different intercept: W = 1/3 H + 13 mm. Conclusion: Significant differences in glenoid height and width were found by sex; however, the relationship between height and width was similar. These variables are correlated, and the resultant formula can be used to estimate the expected glenoid width in a patient with bone loss. This formula allows for easy calculation of the amount of glenoid bone loss with only a ruler and an MRI of the injured shoulder.

Imaging of stress injuries of the pelvis.

Stress fractures are common, representing the final stage in a continuum of bone response to continued mechanical damage. Encompassing fatigue- and insufficiency-type fractures, stress fractures of the pelvis are likely underreported. Radiographs are insensitive to stress injuries, particularly those in the pelvis, whereas scintigraphy and magnetic resonance imaging are exquisitely sensitive. In this article we discuss the pathophysiology and imaging appearances of stress injuries of the pelvis and sacrum. Relevant literature regarding risk factors, problem-solving issues, and an imaging algorithm are discussed, with the goal of improving accuracy in the diagnosis of these common injuries.

Risk Factors for Anterior Glenohumeral Instability

Objectives: While anterior glenohumeral instability has been shown to be common in young athletes, the risk factors for injury are poorly understood. The elucidation of risk factors is critical to help develop prevention strategies. We hypothesized that specific modifiable and non-modifiable factors at baseline would be associated with the subsequent risk of injury in a cohort of young athletes. Methods: We conducted a prospective cohort study in which 714 young athletes were followed from June 2006 through May 2010. Baseline assessments included a subjective history of instability, physical examination by a sports-trained orthopaedic surgeon, range-of-motion, strength with a hand-held dynamometer, and bilateral noncontrast shoulder MRI. A musculoskeletal radiologist measured glenoid version, glenoid height, glenoid width, glenoid index (height-to-width ratio), glenoid depth, rotator interval (RI) height, RI width, RI area, RI index, and the coracohumeral interval. Subjects were followed to document all acute anterior shoulder instability events during the 4 year follow-up period. The time to shoulder instability event during the follow-up period was the primary outcome of interest. Univariate and multivariable Cox proportional hazards regression models were used to analyze the data. Results: We obtained complete data on 714 subjects. During our 4 year surveillance period, there were 38 anterior instability events documented. While controlling for covariates, significant risk factors of physical exam were: apprehension sign HR=2.96 (1.48, 5.90, p=0.002) and relocation sign HR=4.83 (1.75, 13.33, p=0.002). Baseline range-of-motion and strength measures were not associated with subsequent injury. Significant anatomic risk factors on MRI measurement were glenoid index HR=8.12 (1.07, 61.72) p=0.043 and the coracohumeral interval HR=1.20 (1.08, 1.34, p=0.001). Conclusion: This prospective cohort study revealed significant risk factors for shoulder instability in this high-risk population. While modifiable risk factors such as strength and range-of-motion were not associated with subsequent instability, some non-modifiable risk factors were. That the exam findings of apprehension and relocation were significant while controlling for prior history of injury suggests that patients may be unaware of prior instability episodes. The anatomic variables of significance are also not surprising - tall and thin glenoids were at higher risk compared to short and wide glenoids; and the risk of instability increased by 20% for every 1mm increase in coracohumeral distance.

MR Imaging of Neuropathies of the Leg, Ankle, and Foot

Neuropathies of the lower extremity may occur from traumatic injury, surgery, tumor, entrapment by adjacent structures, and a variety of other causes. At times, the clinical presentation can be confusing. Because of its superior soft tissue contrast and the ability to image in any plane, MR imaging is the modality of choice for visualization of peripheral nerve pathology. This article discusses the anatomy and pathology of the nerves of the leg, ankle, and foot, with an emphasis on MR imaging.

Primary periosteal lymphoma: an unusual presentation of non-Hodgkin's lymphoma with radiographic, MR imaging, and pathologic correlation

This report describes a primary periosteal location of non-Hodgkins lymphoma, without nodal disease, and without adjacent intramedullary disease at presentation. The clinical and imaging appearance of periosteal lymphoma simulates other neoplastic osseous surface tumors more than that of lymphoma in other locations. Consideration of this rare presentation of non-Hodgkins lymphoma in the differential diagnosis of periosteal bone lesions can be helpful to ensure proper diagnosis and treatment.

Magnetic resonance imaging appearance of the flexor carpi radialis tendon after harvest in ligamentous reconstruction tendon interposition arthroplasty

ObjectiveTo determine whether the post-harvest magnetic resonance (MR) imaging appearance of flexor carpi radialis (FCR) tendons, harvested during ligamentous reconstruction tendon interposition (LRTI) of the thumb carpometacarpal (CMC) joint arthroplasty, is consistent with tendon regeneration.DesignOperative reports and patient medical records for all patients undergoing LRTI arthroplasty between 1995 and 2003 at our institution were reviewed. MR images of the patients’ forearms and wrists were obtained and interpreted by two musculoskeletal radiologists. Using the flexor carpi ulnaris (FCU) tendon as an internal standard, the extent of FCR tendon regeneration was expressed as a percentage by dividing the volume of regenerated FCR tendon by the volume of the FCU tendon.PatientsFourteen patients who had the full thickness of the FCR tendon harvested and who were available for MR imaging were identified and included in the study.Results and ConclusionsAt least partial regeneration of the FCR tendon occurred in 11 of the 14 patients (79%). Of these, 2 patients (14%), demonstrated complete, or nearly complete regeneration. Partial regeneration of the FCR tendon was seen in 9 of the 14 patients (64%). In 3 patients (21%), there was no appreciable regeneration of the FCR tendon. Among patients who underwent full-thickness harvest of the FCR tendon for LRTI arthroplasty of the first CMC joint, the follow-up MR imaging appearance of the flexor carpi radialis tendon was consistent with tendon regeneration in 79% of those examined.