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Background: Female athletes who participate in sports involving jumping and cutting maneuvers are up to eight times more likely to sustain a rupture of the anterior cruciate ligament than are men participating in the same sports. We tested the hypothesis that healthy young women are able to volitionally increase the apparent torsional stiffness of the knee, by maximally activating the knee muscles, significantly less than are size-matched men participating in the same type of sport. Methods: Twenty-four NCAA (National Collegiate Athletic Association) Division-I athletes (twelve men and twelve women) competing in sports associated with a high risk of injury to the anterior cruciate ligament (basketball, volleyball, and soccer) were compared with twenty-eight collegiate endurance athletes (fourteen men and fourteen women) participating in sports associated with a low risk of such injuries (bicycling, crew, and running). Male and female pairs were matched for age, height, weight, body mass index, shoe size, and activity level. Testing was performed with a weighted pendulum that applied a medially directed 80-N impulse force to the lateral aspect of the right forefoot. The resulting internal rotation of the leg was measured optically, to the nearest 0.25°, at 30° and 60° of knee flexion, both with and without maximal activation of the knee muscles. Results: Maximal rotations of the leg were greater in women than in men in both the passive and the active muscle state (16% and 27% greater [p = 0.01 and p = 0.02], respectively). Moreover, female athletes exhibited a significantly (18%) smaller volitional increase in apparent torsional stiffness of the knee under internal rotation loading than did the matched male athletes (p = 0.014); this was particularly the case for those who participated in sports involving jumping and pivoting maneuvers (42% difference between genders, p = 0.001). Conclusions: The collegiate female athletes involved in high-risk sports exhibited less muscular protection of the knee ligaments during external loading of the knee than did size and sport-matched male athletes. Clinical Relevance: Improving active muscle protection of the knee during training and rehabilitation might help to decrease rates of knee injury.

Purpose: The goal of the study was to determine which position of the throwing motion, late-cocking or early deceleration, was more likely to produce lesions of the biceps superior labral complex. Type of Study: Cadaveric biomechanical model. Methods: Ten paired cadaver shoulders were prepared and mounted on a custom testing apparatus in 60° glenohumeral abduction with the humerus in the plane of the scapula. All specimens were loaded with 100 cycles of subfailure external rotation torque (7.9 N-m) with 22 N applied to the rotator cuff tendons and long head of the biceps tendon. One of each pair of specimens was randomly tested in a late cocking position for throwing (>125° external rotation, 60° glenohumeral abduction, in the plane of the scapula). The other was tested in a position of early deceleration (80° external rotation, 60° glenohumeral abduction, 16° horizontal adduction). The biceps was loaded to failure with the shoulder fixed in these positions. The specimens were then examined by 2 experienced shoulder surgeons, blinded to the test protocol, to assess for the presence of a type II SLAP lesion. Results: Failure of the biceps superior labral complex occurred at the superior glenoid in 9 of 10 specimens in the late cocking position and in 2 of 10 specimens in the early deceleration position ( P =.055). Five specimens developed type II SLAP lesions, with more in the late cocking position (4 of 10) than in the early deceleration position (1 of 10; P =.12). Load to failure was significantly less for the late cocking position (289 ± 39 N) than for the early deceleration position (346 ± 40 N; P =.004). Conclusions: These results suggest that the late cocking position may contribute to biceps-superolabral complex injuries in the thrower's shoulder. Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 19, No 4 (April), 2003: pp 373–379

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.

This experiment was conducted to determine the primary ligamentous restraints to anterior and posterior translation of the sternoclavicular joint. Twenty-four unpaired cadaver specimens were mounted in a custom fixture. Anterior and posterior translations were measured under a sub-failure load in the intact specimen and again after transecting one randomly chosen ligament (anterior capsule, posterior capsule, interclavicular ligament, and costoclavicular ligament; n = 6 for each group). Cutting the posterior capsule resulted in significant increases in anterior translation and posterior translation. Cutting the anterior capsule produced significant increases in anterior translation. Cutting the costoclavicular and interclavicular ligaments had little effect on sternoclavicular joint translation. The posterior capsule is the most important restraint for anterior and posterior translation of the sternoclavicular joint. The anterior capsule is another important restraint for anterior translation. The costoclavicular and interclavicular ligaments have little effect on anterior or posterior translation of the sternoclavicular joint.

Background: Women’s susceptibility to injuries involving the anterior cruciate ligament remains unexplained. Volitional contraction of the knee musculature is known to increase the resistance of the knee to shear deformation, raising the possibility that muscles play a part in protecting the anterior cruciate ligament during hazardous activities. We therefore tested the hypothesis that a volitional co-contraction of the knee muscles increases the sagittal-plane shear stiffness (or resistance to anterior tibial translation) of the knee more in men than in women. Methods: Twenty-three volunteers (ten men and thirteen women; mean age, 24.7 ± 5.4 years), all with anterior tibial translation of 6 mm, agreed to participate in the study. Each subject underwent a subjective evaluation of knee function and activity level, an arthrometric measurement of passive anterior tibial translation, and an isokinetic dynamometer strength test at 60°/sec. A dynamic stress test was then performed to measure anterior tibial translation while simultaneously monitoring lower-extremity muscle response. Results: Maximum co-contraction of the knee musculature significantly decreased mean anterior tibial translation in both men and women (from 7.8 mm to 2.2 mm in men and from 6.5 mm to 3.1 mm in women). The corresponding percentage increase in shear stiffness of the knee was significantly greater (p = 0.003) in men (379%) than in women (212%). Conclusions: The results suggested that women have a diminished potential for muscular protection of passive structures of the knee in anterior tibial translation. Clinical Relevance: Maximal muscular protection of the anterior cruciate ligament in women may be less than that in men. This may be one factor explaining why more women than men are apt to sustain injuries to the anterior cruciate ligament.

Objectives: Retear of an ACL after an ACL reconstruction (ACLR) is devastating for all involved. Understanding risk factors and predictors of subsequent ACL tear after an ACLR is vital for patient education of subsequent risk of injury and if a predictor is modifiable, to make adjustments to minimize the risk of repeat ACL tear. The objectives of this study were 1) to identify the risk factors and predictors for ispilateral and contralateral ACL tears after primary ACLR and 2) to compare retear risk between the 2002/03 and 2007/08 cohorts. This is the largest and most comprehensive prospective analysis of this kind in the literature. Methods: Data from the 2002-2008 MOON database was used to identify risk factors for ACL retear. Subjects who had a primary ACLR with no history of contralateral knee surgery and had 2 year follow-up data were included. Subjects who had multiligament surgery were excluded. Graft type (auto-BTB, auto-hamstring, allograft), age, Marx score at time of index surgery, sport played post ACLR, sex, smoking status, lateral meniscus tear at the time of ACLR, medial meniscus tear at the time of ACLR, BMI, and MOON site were evaluated to determine their contribution to both ipsilateral retear and contralateral ACL tear. The analysis was repeated using the 2002/3 and 2007/8 cohort and included age, graft, sex, and Marx. An ANOVA with post-hoc analysis was performed to detect significant differences in age and Marx score by graft type over time. Results: A total of 2801 subjects met all inclusion/exclusion criteria. There were 165/2801 (5.89%) ipsilateral and 177/2801 (6.32%) contralateral ACL tears identified in the cohort at the two year follow-up. The odds of ipsilateral retear are 1.68 times greater for hamstring autograft (p=0.04) and 4.67 times greater for an allograft (pConclusion: Age, activity, and graft type were predictors of increased risk of ipsilateral graft failure after ACLR. Higher activity and lower BMI were found to be risk factors in contralateral ACL tears. Allograft use in young active patients was shown to be a risk factor for graft retear in the 02/03 group, subsequent to this, graft choice changed to using allografts in older and less active patients with an associated decrease in graft retear risk in the 07/08 group. The contralateral ACL injury risk did not change from the early group to the later group. The risk of ACL graft retear was lower for all graft types in the 07/08 group compared to the 02/03 group. The relative decrease risk in hamstring autografts compared to BTB in 07/08 compared to 02/03 may be due to improved surgical techniques, rehabilitation, and/or slower return to play guidelines, and bears further investigation.

Lesions of the superior glenoid labrum are a source of shoulder disease. However, the mechanisms of injury to this region are unknown, and controversy exists regarding the role of shoulder instability in creation of this lesion. With a cadaver model that simulates physiologic rotator cuff forces and produces traction on the biceps tendon, the creation of type II superior labrum, anterior, and posterior (SLAP) lesions and the role of glenohumeral subluxation were investigated: Left and right shoulders from each of 8 paired cadavers (age 62 +/- 7.2 years, 5 male and 3 female) were randomized to be tested in either a 20 mm inferiorly subluxed position or in a reduced position. The long head of the biceps tendon was held near the musculotendinous junction with a novel cryogenic clamp. Traction on the long head of the biceps tendon was applied at a fast rate of 12.7 cm/sec with a servohydraulic testing machine. A load cell was used to monitor the biceps tendon load. After testing to failure, the presence or absence of a type II SLAP lesion was determined by 2 experienced shoulder surgeons masked to the test group. The production of type II SLAP lesions differed significantly (P = .03) between reduced shoulders (2 SLAP lesions out of 8 tests) and the shoulders with inferior subluxation (7 SLAP lesions out of 8 tests). This experiment has shown that traction on the biceps tendon in this biomechanical model can reproducibly create type II SLAP lesions, and inferior subluxation facilitates the generation of such lesions.

Five commercially available suture anchor devices were tested to failure in human cadaveric proximal tibiae. A total of 198 trials were completed. Insertion was uncomplicated for all anchors, with the exception of the Acufex Rod TAG device, with five of 22 (23%) of these breaking upon insertion into thicker cortical bone. Overall, the anchors performed significantly (p < 0.05) better when placed in thicker cortical bone, further away from the joint surface, and when loaded in a direction parallel to the bone surface. The Mitek GII anchor failed (pulled out of bone) less often than the other anchors (19% vs. 46%). In loading perpendicular to the bone surface, the Mitek GII and Statak were the strongest (p < 0.05), with mean loads at failure of 82.5 and 90.2 N, respectively. The Acufex Rod TAG, Acufex Wedge TAG, and Mitek GI failed at 67.2, 65.5, and 49.4 N respectively.

An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States. The highest incidence is in individuals 15 to 25 years old who participate in pivoting sports. With an estimated cost for these injuries of almost a billion dollars per year, the ability to identify risk factors and develop prevention strategies has widespread health and fiscal importance. Seventy percent of ACL injuries occur in noncontact situations. The risk factors for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical. Early data on existing neuromuscular training programs suggest that enhancing body control may decrease ACL injuries in women. Further investigation is needed prior to instituting prevention programs related to the other risk factors.