Normal Parameters of the Skeletally Immature Knee: Developmental Changes on Magnetic Resonance Imaging.

BACKGROUND: A child's knee undergoes significant morphologic changes during development. Age-specific normal parameters have not been previously described. The purpose of this study was to delineate knee morphology changes that occur with maturation utilizing magnetic resonance imaging (MRI). METHODS: A retrospective review of knee MRIs, ages 4 to 18 years, was performed using "normal" diagnosis codes, including: knee pain, plicae, septic arthritis, jumper's knee, growing pains, benign neoplasm, and osteomyelitis. Seventeen osseous parameters were measured, plus their cartilaginous counterparts, if different. Spearman ρ correlations were calculated between age and MRI measures. RESULTS: A total of 132 MR images were reviewed. Significant correlation with age was observed in all osseous measurements, except medial patellofemoral ligament (MPFL) insertion (P<0.05). Similarly, the cartilage measures demonstrated significant correlation with age, except the notch width index, MPFL insertion, and trochlear morphology. The magnitude of correlation was significantly different between the osseous and cartilage measures for all but 4 of the variables: anterior cruciate ligament (ACL) length and width, intercondylar width and tibial tubercle-trochlear groove (TT-TG) interval. Sex seems to affect ACL length, Insall-Salvati ratio, intercondylar width, and sulcus angle.The MPFL origin starts distal to the physis and moves proximal with age (ρ=0.33, P<0.001), when at age 7 years, it is located at or above the femoral physis. The mean ACL diameter grows from 6.5 to 9.8 mm. Cartilage sulcus angle remains consistently 150 degrees, and the TT-TG interval shifts from 6 to 12 mm with maturity. CONCLUSIONS: The normative data presented here demonstrates that maturity correlates well with the morphologic changes seen in most of the studied parameters. These data not only aid in the identification of the abnormal findings by sex and age, but also provides normal sizes of the ACL and location of insertion for the MPFL which can benefit surgical planning.

Chronic nerve compression alters Schwann cell myelin architecture in a murine model.

INTRODUCTION: Myelinating Schwann cells compartmentalize their outermost layer to form actin-rich channels known as Cajal bands. Herein we investigate changes in Schwann cell architecture and cytoplasmic morphology in a novel mouse model of carpal tunnel syndrome. METHODS: Chronic nerve compression (CNC) injury was created in wild-type and slow-Wallerian degeneration (Wld(S) ) mice. Over 12 weeks, nerves were electrodiagnostically assessed, and Schwann cell morphology was thoroughly evaluated. RESULTS: A decline in nerve conduction velocity and increase in g-ratio is observed without early axonal damage. Schwann cells display shortened internodal lengths and severely disrupted Cajal bands. Quite surprisingly, the latter is reconstituted without improvements to nerve conduction velocity. CONCLUSIONS: Chronic entrapment injuries like carpal tunnel syndrome are primarily mediated by the Schwann cell response, where decreases in internodal length and myelin thickness disrupt the efficiency of impulse propagation. Restitution of Cajal bands is not sufficient for remyelination after CNC injury.

Advances in the management of spinal cord injury.

Historically, clinical outcomes following spinal cord injury have been dismal. Over the past 20 years, the survival rate and long-term outcome of patients with spinal cord injury have improved with advances in both medical and surgical treatment. However, the efficacy and timing of these adjuvant treatments remain controversial. There has been a tremendous increase in the number of basic science and clinical studies on spinal cord injury. Current areas of investigation include early acute management, including early surgical intervention, as well as new pharmacotherapy and cellular transplantation strategies. It is unlikely that a single approach can uniformly address all of the issues associated with spinal cord injury. Thus, a multidisciplinary approach will be needed.