Estrogen affects the cellular metabolism of the anterior cruciate ligament: a potential explanation for female athletic injury. Liu SH, Al-Shaikh RA, Panossian V, et al. Am J Sports Med Vol. 25, No. 5, 1997.
This study measured the degree of fibroblast proliferation and collagen synthesis in rabbit ACLs with various concentrations of estradiol. At normal physiologic levels of estradiol, collagen synthesis was reduced by more than 40% compared to the control ACLs. Increasing the levels of estradiol to pharmacologic levels decreased collagen synthesis by 50% compared to controls. It is suggested that fluctuations in estrogen levels associated with the menstrual cycle or exogenous estrogen effects from contraceptive pills, may change the structure of the ACL and predispose the individual to ACL injury during those times. More studies must be performed on humans before extrapolating these findings from rats to humans, but other studies indirectly support this study.
Symmetry of the femoral notch width index. Teitz CC, Lind BK, Sacks BM. Am J Sports Med Vol. 25, No. 5, 1997.
Last month, I mentioned the theory that in women it has been suggested that a small femoral intercondylar notch may represent a smaller ACL, and therefore indicate a knee with less stability. This study challenges that concept.
The notch width index is radiographically measured as the ratio of intercondylar notch width to the distal femur width. This allows an adjustment of the size of the intercondylar notch to the size of the knee so that women would not artificially have a smaller notch width by virtue of a smaller knee. This study indicates that although women have smaller notch width indexes as compared to men, it is not statistically significant. Further, they found that the ranges of indexes in males and females overlapped. Most importantly, there was no difference in the notch width index between patients with and without ACL tears.
The authors suggest that although it may be a factor, it cannot entirely account for the difference in ACL tear patterns between males and females. I would like to note that even if it were, the notch width is a non-modifiable factor and that the focus should be on functional considerations such as training and sport modification (see "Anterior Cruciate Ligament Deficiency in Women" in the October 20, 1997 issue).
Early season anterior cruciate ligament tears: a treatment dilemma. Shelton WR, Barett GR, Dukes A. Am J Sports Med Vol. 25, No. 5, 1997.
One of the most common questions I am asked is whether an athlete who tears the ACL before or early in the season can return to play without surgery. This small study supports my general belief that just like all things in life, it depends. It depends on whether there is an isolated ACL tear versus one that has meniscal or other damage, and it depends on whether there is recurrent buckling of the knee during the sport activity.
This was a prospective study using 43 athletes with an acute injury to a knee with no prior ACL damage. The positives included a Lachman test, ligament abnormalities measured with the KT-1000, and MRI evidence of an ACL tear with no meniscal tear. (Of course, it is possible that a meniscus tear was present, but not evident on MRI, as was later found on some of the knees treated surgically). Thirty-one of the 43 athletes returned to play in an average of six weeks post-injury with rehabilitation and a brace. Out of this group, 12 athletes returned with no report of repeated buckling of the knee, 18 patients returned with repeated buckling, and 13 athletes could not return to play.
Patients were followed until they either had surgery, gave up the sport, or continued playing with a brace without having surgery (follow-up period of 44 months). Twenty-nine patients had reconstructive surgery (all of these patients were those that had recurrent buckling), three patients gave up the sport; and 11 patients continued with rehab and bracing. Therefore, out of a total of 43 athletes, 11 (26%) were able to continue with conservative treatment only. One of the strongest indicators of failure of conservative care was repeated buckling.
Electromyographic activity in expert downhill skiers using functional knee braces after anterior cruciate ligament injuries. Nemeth G, Lamontagne M, Thos KS, Eriksson E. Am J Sports Med Vol. 25, No. 5, 1997.
Only recently have studies appeared that attempt to determine the effectiveness of knee braces in humans (as compared to cadaveric studies). Even the human studies are deficient, in that large loads cannot be safely applied to the knee experimentally. An indirect measure of effectiveness, then, would not be a measure of strain at the ACL but a measure of the difference in knee function with and without brace application.
Obviously braces differ and extrapolation cannot occur for all braces. This study used surface electrodes to measure activity of the vastus medialis, biceps femoris, semitendinosus and membrinosus, and gastrocnemius activity for both legs. Six skiers were used (3 men; 3 women). Three had had surgical reconstruction; all had confirmed ACL tears with arthroscopic or open surgery. The brace that was used was the Defiance (made by Smith & Nephew DonJoy, Inc.).
Generally, it was found that the more unstable knees demonstrated significant increases in biceps femoris activity with bracing. Those without bracing had increases in semimembranosus activity as compared to the good leg. It is proposed that this increase in biceps femoris activity is directly related to the degree of instability and, most importantly, that the brace provides an afferent proprioceptive impulse generator resulting in the increased activity. It is believed that this is a centrally controlled process. The increase in biceps femoris activity prevents the anterolateral pivot shift seen with ACL deficient knees.
Epidemiology of anterior cruciate ligament injuries in soccer. Bjordal JM, Arnoy F, Hannestad B, Strand T. Am J Sports Med Vol. 25, No. 3, 1997.
Soccer is certainly one of the common ACL injury sports. This study was based on questionnaires to almost a thousand ACL injured surgical patients over a nine year period. Out of the patients who answered the questionnaire, 176 patients had participated in soccer.
The incidence rate was higher for women than men. The incidence rate was higher for men in the top three divisions as compared to the lower divisions. Tackling injuries accounted for almost half of all ACL injuries. Approximately 70% of injuries occurred when players were on the offensive team. Most injuries occurred during games versus practice. Over half of the patients returned to play (with surgical reconstruction); almost 90% of those who did return to play were high-level players.
Thomas Souza, DC, DACBSP
San Jose, California