Knee and hip loading patterns at different phases in the menstrual cycle: implications for the gender difference in anterior cruciate ligament injury rates.

BACKGROUND: Menstrual cycle phase has been correlated with risk of noncontact anterior cruciate ligament injury in women. The mechanism by which hormonal cycling may affect injury rate is unknown. HYPOTHESES: Jumping and landing activities performed during different phases of the menstrual cycle lead to differences in foot strike knee flexion, as well as peak knee and hip loads, in women not taking an oral contraceptive but not in women taking an oral contraceptive. Women will experience greater normalized joint loads than men during these activities. STUDY DESIGN: Controlled laboratory study. METHODS: Twenty-five women (13 using oral contraceptives) and 12 men performed repeated trials of a horizontal jump, vertical jump, and drop from a 30-cm box on the left leg. Lower limb kinematics (foot strike knee flexion) and peak externally applied moments were calculated (hip adduction moment, hip internal rotation moment, knee flexion moment, knee abduction moment). Men were tested once. Women were tested twice for each phase of the menstrual cycle (follicular, luteal, ovulatory), as determined from serum analysis. An analysis of variance was used to examine differences between phases of the menstrual cycle and between groups (alpha = .05). RESULTS: No significant differences in moments or knee angle were observed between phases in either female group or between the 2 female groups or between either female group and the male controls. CONCLUSIONS: Variations of the menstrual cycle and the use of an oral contraceptive do not affect knee or hip joint loading during jumping and landing tasks. CLINICAL RELEVANCE: Because knee and hip joint loading is unaffected by cyclic variations in hormone levels, the observed difference in injury rates is more likely attributable to persistent differences in strength, neuromuscular coordination, or ligament properties.

Reliability of a New Clinical Instrument for Measuring Internal and External Glenohumeral Rotation.

BACKGROUND: The shoulder plays a critical role in many overhead athletic activities. Several studies have shown alterations in shoulder range of motion (ROM) in the dominant shoulder of overhead athletes and correlation with significantly increased risk of injury to the shoulder and elbow. The purpose of this study was to measure isolated glenohumeral joint internal/external rotation (IR/ER) to determine inter- and intraobserver reliability of a new clinical device. HYPOTHESIS: (1) Inter- and intraobserver reliability would exceed 90% for measures of glenohumeral joint IR, ER, and total arc of motion; (2) the dominant arm would exhibit significantly increased ER, significantly decreased IR, and no difference in total arc of motion compared with the nondominant shoulder; and (3) a significant difference exists in total arc between male and female patients. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: Thirty-seven subjects (mean age, 23 years; range, 13-54 years) were tested by 2 orthopaedic surgeons. A single test consisted of 1 arc of motion from neutral to external rotation to internal rotation and back to neutral within preset torque limits. Each examiner performed 3 tests on the dominant and nondominant shoulders. Each examiner completed 2 installations. RESULTS: Testing reliability demonstrated that neither trial, installation, nor observer were significant sources of variation. The maximum standard deviation was 1.3° for total arc of motion and less than 2° for most other measurements. Dominant arm ER was significantly greater than nondominant arm ER (P = 0.02), and dominant arm IR was significantly less than nondominant arm IR (P = 0.00). Mean total rotation was 162°, with no significant differences in total rotation between dominant and nondominant arms (P = 0.34). Mean total arc of motion was 45° greater in female subjects. Differences in total arc of motion between male and female subjects was statistically significant (P < 0.00). CONCLUSION: This simple, clinical device allows for both inter- and intraobserver reliability measurements of glenohumeral internal and external rotation.

The effect of the menstrual cycle on anterior cruciate ligament injuries in women as determined by hormone levels.

Anterior cruciate ligament injury rates are reported to be two to eight times higher in women than in men within the same sport. Because the menstrual cycle with its monthly hormonal fluctuations is one of the most basic differences between men and women, we investigated the association between the distribution of confirmed anterior cruciate ligament tears and menstrual cycle phase. Sixty-nine female athletes who sustained an acute anterior cruciate ligament injury were studied within 24 hours of injury at four centers. The mechanism of injury, menstrual cycle details, use of oral contraceptives, and history of previous injury were recorded. Urine samples were collected to validate menstrual cycle phase by measurement of estrogen, progesterone, and luteinizing hormone metabolites and creatinine levels at the time of the anterior cruciate ligament tear. Results from the hormone assays indicate that the women had a significantly greater than expected percentage of anterior cruciate ligament injuries during midcycle (ovulatory phase) and a less than expected percentage of those injuries during the luteal phase of the menstrual cycle. Oral contraceptive use diminished the significant association between anterior cruciate ligament tear distribution and the ovulatory phase.

Peri-epiphyseal and Overuse Injuries in Adolescent Athletes.

CONTEXT: Overuse injuries of the musculoskeletal system in immature athletes are commonly seen in medical practice. EVIDENCE ACQUISITION: An analysis of published clinical, outcome, and biomechanical studies of adolescent epiphyseal and overuse injuries was performed through 2008 to increase recognition and provide treatment recommendations. RESULTS: Adolescent athletes can sustain physeal and bony stress injuries. Recovery and return to play occur more swiftly if such injuries are diagnosed early and immobilized until the patient is pain-free, typically about 4 weeks for apophyseal and epiphyseal overuse injuries. Certain epiphyseal injuries have prolonged symptoms with delayed treatment, including those involving the bones in the hand, elbow, and foot. If such injuries are missed, prolonged healing and significant restrictions in athletic pursuits may occur. CONCLUSION: Some of these injuries are common to all weightbearing sports and are therefore widely recognized. Several are common in gymnastics but are rarely seen in other athletes. Early recognition and treatment of these conditions lead to quicker recovery and so may prevent season-ending, even career-ending, events from occurring.

Structural and mechanical properties of the glenohumeral joint posterior capsule.

The purpose of this study was to quantify regional variations in material properties of the glenohumeral joint posterior capsule and to compare these data with the anterior band of the inferior glenohumeral ligament (AB-IGHL). Mechanical properties were determined for individual bands of the AB-IGHL, superior posterior capsule (SUP-PC), middle posterior capsule (MID-PC), and inferior posterior capsule (INF-PC). Significant differences in tissue thickness were found among the 3 posterior capsular regions and the AB-IGHL. The AB-IGHL was thicker than the MID-PC (P=.03) and INF-PC (P=.01), and the SUP-PC was thicker than the INF-PC (P=.02). Except for significant differences in failure strains, material properties were not significantly different among the 4 tissue regions. There were no significant differences between tissue bands in modulus (P=.2), maximum stress (P=.46), or strain energy density (P=.62). Specimens failed primarily near the glenoid insertion (75%), with 4 specimens failing at the humeral insertion and 2 others failing in the tissue's mid substance.