Copyright © 2008 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Elizabeth A. Arendt, MD*,
University of Minnesota, Minneapolis, Minnesota
Posted April 2008
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.
References
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.
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