Effect of gender and maturity on quadriceps-to-hamstring strength ratio and anterior cruciate ligament laxity.

BACKGROUND: Exercise programs have been introduced to reduce the ACL injury risk in female athletes. The most effective age at which to start these programs is not known. HYPOTHESIS: Age and gender affect ligament laxity and quadriceps-to-hamstring strength ratio. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Fifty-three female and 70 male recreational soccer players, 10 to 18 years of age, were studied with physical examination, KT-1000 arthrometry, and manual maximum quadriceps and hamstring strength using a handheld dynamometer. The subjects were separated into 4 groups to examine maturity-related intergender differences: group G1, premenarchal girls (n = 24); group B1, boys 13 years and younger (n = 38); group G2, girls 2 or more years after menarche (n = 29); and group B2, boys 14 years and older (n = 32). RESULTS: Both knees of 123 soccer players were evaluated. The mean ages for groups G1, B1, G2, and B2 were 11.50 +/- 1.69, 10.63 +/- 1.85, 15.5 +/- 1.43, and 15.59 +/- 1.24 years, respectively, and the mean laxity measurements were 8.84 +/- 2.12, 8.51 +/- 1.61, 8.85 +/- 1.86, and 7.33 +/- 1.27 mm, respectively. Laxity was significantly less for the mature boys (P = .0015) than for the immature boys, mature girls, and immature girls. With increasing maturity, significant increases in both quadriceps and hamstring muscle strength were observed for both boys and girls (P < .05). Boys demonstrated a greater percentage increase in hamstring strength with maturity (179%) compared with girls (27%) (P < .05). Mature girls (2.06) had significantly greater quadriceps-to-hamstring ratio when compared with immature girls (1.74), immature boys (1.58), and mature boys (1.48) (P < .05). CONCLUSION: Female athletes after menarche increase their quadriceps strength greater than their hamstring strength, putting them at risk for anterior cruciate ligament injury. Anterior cruciate ligament-prevention programs based on improving dynamic control of the knee by emphasizing hamstring strengthening should be instituted for girls after menarche.

Operative lengthening of the humerus: indications, benefits, and complications.

The purpose of this study was to determine the benefits and risks of humeral lengthening procedures. Distraction osteogenesis was performed in 19 humeri on 16 patients (9 males, 7 females). The mean age at the time of lengthening was 11.5 years (range 3-24 years) and average follow-up was 8.7 years (range 2-21 years). Etiologies for short humeri included infection in six patients, congenital anomaly in six patients, unicameral bone cysts involving the physis in five patients, and posttraumatic growth disturbance in two patients. The average lengthening was 5 cm. The benefits from humeral lengthening include increased performance in daily activities, improved sports performance, and significantly better self-image. Complications included temporary radial nerve palsy in three cases, drainage from the pin tracts in two cases, elbow flexion contracture in three cases, and late humerus fracture in two cases. All the complications resolved over time and did not affect the outcome. Eleven lengthening procedures were not associated with any complications. Although the humerus is surrounded by complex neurovascular structures and muscles, humerus lengthening provided satisfactory results with temporary minor complications.