Current state of unloading braces for knee osteoarthritis

PURPOSE

Unicompartmental knee osteoarthritis (OA) is often treated with the prescription of an unloading knee brace to decrease pain and stiffness. Braces have been shown to improve the quality of life by applying an external moment to offset increased compressive tibiofemoral contact loads, but evidence regarding mechanical efficacy at the joint is controversial. Thus, the purpose of this study was to review the current state of unloading braces on knee mechanics, clinical impact, and long-term disease progression.

METHODS

A literature search was performed through the PubMed MEDLINE database for the search terms "osteoarthritis," "knee," "brace," and derivatives of the keyword "unload." Articles published since January 1, 1980 were reviewed for their relevance. Evidence for the effectiveness of unloading braces for disease management both biomechanically and clinically was considered.

RESULTS

While significant research has been done to show improvement in OA symptoms with the use of an unloading brace, current literature suggests a debate regarding the effectiveness of these braces for biomechanical change. Clinical findings reveal overall improvements in parameters such as pain, instability, and quality of life.

CONCLUSION

Although clinical evidence supports brace use to improve pain and functional ability, current biomechanical evidence suggests that unloading of the affected knee compartment does not significantly hinder disease progression.

LEVEL OF EVIDENCE

III.

Measurements of bone tunnel size in anterior cruciate ligament reconstruction: 2D versus 3D computed tomography model

BACKGROUND

Revision anterior cruciate ligament (ACL) reconstruction requires a precise evaluation of previous tunnel locations and diameters. Enlargement of the tunnels, despite not usually affecting primary reconstruction outcomes, plays an important role in revision ACL management. Three dimensional (3D) computed tomography (CT) models are reported to be the most accurate method for identifying the tunnel position and possible conflicts with a revision tunnel placement. However, the ability of 3D CT to measure the tunnel size is still not proven. The goal of this study was to evaluate the ability of measuring the size of the bone tunnels in ACL reconstructed knees with 3D CT compared to the traditional two dimensional (2D) CT method.

METHODS

Twenty-four patients had CT scans performed immediately following ACL reconstruction surgery. Their femoral tunnels size were measured by a standard 2D CT measurement and then compared with three novel 3D CT measuring methods: the best transverse section method, the best fit cylinder method and the wall thickness method. The drill size used during surgery was used as a control measure for the tunnel width. Intra-class correlation coefficients were obtained.

RESULTS

The intra-class correlation coefficient and respective 95% confidence interval range (ICC [95%CI]) for the three methods compared with the drill sizes were 0.899 [0.811-0.947] for the best transverse section method, 0.745 [0.553-0.862] for the best fit cylinder method, -0.004 [-0.081 to -0.12] for the wall thickness method and 0.922 [0.713-0.97] for the 2D CT method. The mean differences compared to the drill size were 0.02 mm for the best fit transverse section method, 0.01 mm for the best fit cylinder diameter method, 3.34 mm for the wall thickness method and 0.29 mm for the 2D CT method. The intra-rater agreement (ICC [95%CI]) was excellent for the best transverse section method 0.999 [0.998-0.999] and the 2D CT method 0.969 [0.941-0.984].

CONCLUSIONS

The 3D best transverse section method presented a high correlation to the drill sizes and high intra-rater agreement, and was the best method for ACL tunnel evaluation in a 3D CT based model.

Position-Specific Hip and Knee Kinematics in NCAA Football Athletes

BACKGROUND

Femoroacetabular impingement is a debilitating hip condition commonly affecting athletes playing American football. The condition is associated with reduced hip range of motion; however, little is known about the range-of-motion demands of football athletes. This knowledge is critical to effective management of this condition.

PURPOSE

To (1) develop a normative database of game-like hip and knee kinematics used by football athletes and (2) analyze kinematic data by playing position. The hypothesis was that kinematics would be similar between running backs and defensive backs and between wide receivers and quarterbacks, and that linemen would perform the activities with the most erect lower limb posture.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Forty National Collegiate Athletic Association (NCAA) football athletes, representing 5 playing positions (quarterback, defensive back, running back, wide receiver, offensive lineman), executed game-like maneuvers while lower body kinematics were recorded via optical motion capture. Passive hip range of motion at 90° of hip flexion was assessed using a goniometer. Passive range of motion, athlete physical dimensions, hip function, and hip and knee rotations were submitted to 1-way analysis of variance to test for differences between playing positions. Correlations between maximal hip and knee kinematics and maximal hip kinematics and passive range of motion were also computed.

RESULTS

Hip and knee kinematics were similar across positions. Significant differences arose with linemen, who used lower maximal knee flexion (mean ± SD, 45.04° ± 7.27°) compared with running backs (61.20° ± 6.07°; P < .001) and wide receivers (54.67° ± 6.97°; P = .048) during the cut. No significant differences were found among positions for hip passive range of motion (overall means: 102° ± 15° [flexion]; 25° ± 9° [internal rotation]; 25° ± 8° [external rotation]). Several maximal hip measures were found to negatively correlate with maximal knee kinematics.

CONCLUSION

A normative database of hip and knee kinematics utilized by football athletes was developed. Position-specific analyses revealed that linemen use smaller joint motions when executing dynamic tasks but do not demonstrate passive range of motion deficits compared with other positions.

CLINICAL RELEVANCE

Knowledge of requisite game-like hip and knee ranges of motion is critical for developing goals for nonoperative or surgical recovery of hip and knee range of motion in the symptomatic athlete. These data help to identify playing positions that require remedial hip-related strength and conditioning protocols. Negative correlations between hip and knee kinematics indicated that constrained hip motion, as seen in linemen, could promote injurious motions at the knee.

Neuroglial-specific factors and the regulation of retrovirus transcription

Retroviruses have been implicated as causative agents of a variety of human diseases including malignancy, immune system dysfunction, and neurologic disorders. Despite the isolation of various retroviral agents from patients suffering from malignant neoplasias and neurologic disorders, only the human T-cell lymphotropic virus type I (HTLV-I) and the human immunodeficiency virus (HIV) have been definitively accepted as etiologic agents of human disease (Hjelle, 1991; Gessain and Gout, 1992; Rosenblatt, 1993). Because of their increasingly defined roles in disease progression, the replication of HTLV-I and HIV is an important focus for understanding the pathogenic processes resulting from viral infection. Of particular interest are the molecular mechanisms by which expression of retroviral genomes is regulated by their regulatory units, the long terminal repeats (LTR), in a manner specific to the cellular targets which they infect.

Persistence of multiple maternal genotypes of human immunodeficiency virus type I in infants infected by vertical transmission

The extent of nucleotide variation within the HIV-1 env hypervariable domains serves as a marker of virus genotypes within infected individuals and as a means to track transmission of the virus between individuals. We analyzed env V1 and V2 sequences in longitudinal samples from two HIV-1-infected mothers, each with three children infected by maternal transmission of the virus. Sequences in samples that were obtained from two infants at 2 d and 4 wk after birth displayed more variation in V1 and V2 than maternal samples obtained at the same times. Multiple HIV-1 genotypes were identified in each mother. In each family, multiple maternal HIV-1 genotypes were transmitted to the infants. Specific amino acid residues in the hypervariable domains were conserved within sequences from each family producing a family-specific amino acid signature pattern in V1 and V2. Viruses that were highly related to maternal viruses in signature pattern persisted for as long as 4 yr in the older children. Results support a model of transmission involving multiple HIV-1 genotypes with development of genetic variation from differential outgrowth and accumulation of genetic changes within each individual.

Independent variation and positive selection in env V1 and V2 domains within maternal-infant strains of human immunodeficiency virus type 1 in vivo

Multiple targets for immune recognition and cellular tropism are localized to the V1 and V2 hypervariable regions in the amino portion of human immunodeficiency virus type 1 (HIV-1) gp120env. We have assessed genetic diversity in env V1 and V2 hypervariable domains in vivo within epidemiologically related strains of HIV-1. Our strategy was to analyze longitudinal samples from two seropositive mothers and multiple children infected by perinatal transmission. Although the V1 and V2 domains are closely linked in the HIV-1 genome, nucleotide sequences in V1 and in V2 evolved independently in maternal-infant viruses in vivo. A high proportion of the nucleotide substitutions would introduce amino acid diversity in V1 and in V2. A significant excess of nonsynonymous over synonymous substitutions was identified in HIV-1 env V1 and V2 peptides in the mothers and in two older children but was not generally apparent in HIV-1 sequences in infants. An excess of nonsynonymous over synonymous substitutions indicated that there is positive selection for independent genetic variation in the V1 and V2 domains in vivo. It is likely that there are host responses to complex determinants in the V1 or V2 hypervariable domain of HIV-1 gp120.