The purpose of this study was to compare clinical outcomes (as judged by the Lysholm score and the International Knee Documentation Committee [IKDC] scores) and objective results (as judged by KT-2000 arthrometer testing, Lachman examination, and pivot-shift examination) of anterior cruciate ligament reconstructions in which two different grafts were used: bone-patellar tendon-bone and four-strand hamstring autograft. Patients were divided into two groups: those with excessive joint laxity and those without. Joint laxity was defined as having four of five positive findings, including, at a minimum, hyperextension of the contralateral knee, in accordance with the Beighton and Horan criteria1. The authors concluded that patients who had excessive joint laxity, regardless of gender, had a better two-year outcome after anterior cruciate ligament reconstruction when bone-patellar tendon-bone autograft was used rather than four-bundle hamstring autograft. The main determining criteria for this conclusion involved side-to-side difference in anterior laxity and clinical results.
In this commentary, I will discuss this paper and its findings in the context of its potential relevance to the treatment of anterior cruciate ligament injuries and the selection of anterior cruciate ligament grafts.
The literature currently has a number of studies that suggest that, in comparison with men, women have greater tibiofemoral joint laxity (as defined by anterior knee laxity and genu recurvatum) and less joint resistance to translation and rotation2-4. Additional literature supports the concept that there are gender differences in knee laxity, and that these differences are menstrual-cycle dependent5. In the study by Kim et al., female patients were overrepresented in the group of patients with hyperlaxity (twenty-one of thirty-one patients, or 68%). Female patients were also overrepresented in the subgroup of hyperlaxity patients that received hamstring grafts (eight of eleven patients, or 73% of that subgroup), as compared with the percentage of female patients in the entire study group (fifty of 117, or 43%).
Progressive laxity, as judged with use of KT-2000 arthrometer testing and Lachman examination, has been reported over the course of several years in patients with anterior cruciate ligament reconstruction. This laxity is most obvious for female sex and for patients in whom four-strand hamstring grafts have been used6. In the study by Kim et al., however, gender did not appear to be a factor in progressive joint laxity—in patients of either sex, the results of anterior cruciate ligament reconstruction with a hamstring autograft were inferior to those associated with the use of a bone-patellar tendon-bone construct.
From the work of Rodeo et al.7, we understand that soft-tissue healing within a bone tunnel takes longer than healing of autogenous bone-patellar tendon-bone grafts. This study, as well as others, supports the assumption that tendinous grafts within a bone tunnel heal through a fibrous tissue envelope rather than through a firm osseous attachment. This finding has been implicated as a possible reason for the increased laxity seen in four-strand hamstring anterior cruciate ligament grafts. The study by Kim et al., however, suggests that, for the subgroup of patients with hyperlaxity, another factor may be responsible for this increased laxity.
The findings of this paper suggest that knee-joint laxity and hypermobility are related and that knees with hypermobility may have certain healing-phase characteristics that promote laxity of the hamstring graft tissue, resulting in increased anterior laxity at the fixation level, the graft incorporation level, or both.
Certainly, hormones have been implicated as a factor. We recognize that graft incorporation and healing may be influenced by a number of factors, including hormonal control, collagen turnover, and muscle-tendon anatomy, architecture, and matrix, which may explain differences both with and without regard to gender difference. The fact that increased graft laxity is more common in individuals with hyperlaxity, regardless of sex, suggests that some characteristics of collagen-structure healing in individuals with hyperlaxity may be altered. In those individuals, there may be a predisposition to slower healing times or less robust collagen-matrix incorporation to the degree that laxity of the ultimate incorporated tendon structure is the end result.
The major limitations of this paper are that the selection process was not randomized with regard to the type of graft to be used, the authors did not state their criteria for determination of graft choice, and there were unequal numbers of men and women represented in each group. In addition, the hamstring grafts were underrepresented in each group. This fact notwithstanding, this study suggests a fruitful area of potential research with regard to the healing characteristics of grafts when placed into different joint environments. This paper explores the concept that certain anatomic characteristics might factor into the equation that will supply the answer as to which anterior cruciate ligament graft type will be best for individual patients.
*The author did not receive any outside funding or grants in support of her research for or preparation of this work. Neither she nor a member of her immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of her immediate family, is affiliated or associated.
1. Beighton P, Horan F. Orthopaedic aspects of the Ehlers-Danlos syndrome. J Bone Joint Surg Br. 1969;51:444-53.
2. Chandrashekar N, Mansouri M, Slauterbeck J, Hashemi J. Sex-based differences in the tensile properties of the human anterior cruciate ligament. J Biomech. 2006;39:2943-50.
3. Onambélé GN, Burgess K, Pearson SJ. Gender-specific in vivo measurement of the structural and mechanical properties of the human patellar tendon. J Orthop Res. 2007;25:1635-42.
4. Shultz SJ, Shimokochi Y, Nguyen AD, Schmitz RJ, Beynnon BD, Perrin DH. Measurement of varus-valgus and internal-external rotational knee laxities in vivo--Part I: assessment of measurement reliability and bilateral asymmetry. J Orthop Res. 2007;25:981-8.
5. Shultz SJ, Sandler TC, Kirk SE, Perrin DH. Sex differences in knee joint laxity change across the female menstrual cycle. J Sports Med Phys Fitness. 2005;45:594-603.
6. Noojin FK, Barrett GR, Hartzog CW, Nash CR. Clinical comparison of intraarticular anterior cruciate ligament reconstruction using autogenous semitendinosus and gracilis tendons in men versus women. Am J Sports Med. 2000;28:783-9.
7. Rodeo SA, Arnoczky SP, Torzilli PA, Hidaka C, Warren RF. Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am. 1993;75:1795-803.