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FOUR POINTS OF LEVERAGE STORY
FOUR POINTS OF LEVERAGE STORY
The Four Points of Leverage system is a patented, dynamic bracing system. Simply, it puts a posterior pre-load on the tibia. But what exactly are the four points and how do they work?
To understand that, we should first take a look at the ACL, or the anterior cruciate ligament that helps support the knee. Working in conjunction with the PCL, or posterior cruciate ligament (cruciate meaning crossed) these two ligaments join the femur (thigh bone) to the tibia (shin bone) and along with collateral ligaments on either side of the knee, provide stability and functionality. Simply standing still will apply load or pressure on the ligaments and bring them to a level of tautness. A forceful blow or sudden shifting of the leg can cause any of these ligaments to sprain via a stretch or tear.
Four point knee braces are used prophylactically to prevent an injury, post-injury to stabilize an unstable knee and post-surgically to protect the soft tissue repair. If ACL replacement surgery is performed, there is a need to protect the healing soft tissue graft used to replace the native ACL. The need to protect the graft during the healing is confirmed by research being done at the University of Vermont. In their study, patients with an aggressive rehabilitation program developed looser knees than those in a conservative program. The difference in the two programs was at what point in the rehabilitation period specific exercises were done: the aggressive group doing the exercises earlier in the healing process than the conservative group. The Vermont work confirms that exposure to excessive loading during rehabilitation can damage a graft if this is done too early in the rehabilitation period. The concept of beneficial load and detrimental load has been discussed by other researchers over the years. Dr. Woo hypothesized that ligaments will get stronger when exposed to loads seen during normal activities, but may get weaker if overloaded during exercise. If overloading the healing tissue while it is remodeling and maturing can damage the graft and degrade the surgical outcome, it follows that reducing the strain in the ACL graft can protect the graft and improve the surgical result.
The four-point system was developed to reduce the strain in the ACL. The system accomplishes this by pre-loading the tibia posteriorly (backwards). The first point anchors the femur with a cuff placed at the anterior thigh. Point two anchors the tibia with a cuff placed at the posterior or bottom of the calf. Using a strap in point number three on the posterior thigh, the femur is pushed to the anterior, thereby pushing the hinges back on the knee. Finally, point number four brings the hinges back to midline using a strap on the anterior tibia creating a posterior pre-load on the tibia, reducing the strain on the ACL.
A 1997 paper discusses a study on functional bracing such as the Four Points system. It was conducted at the University of Vermont. It confirms that the Four Points system works during in-vivo testing, as our surrogate testing attests. Using live subjects, ACL strain (stretch) was tested in both seated and standing positions. By implanting a small device on the ACL, the actual strain was measured in both positions. The results showed that the strain values were less in both weightbearing and non-weightbearing conditions, when compared to unbraced knees.
We stand by the efficacy of our braces in all phases of the injury process. Before injuries even happen, bracing protects the knee during sport activities. Before surgery, the four points brace stabilizes the joint, reducing the risk of additional soft tissue damage. After surgery, the four points brace protects the healing graft. And during rehabilitation, the bracing system may allow for more aggressive treatments while providing some strain shielding of the ligament or its replacement, thereby preventing over-assertion on the weak area.
In any and all of these stages, we want the patient to Never Stop Getting Better and our Four Points of Leverage system makes that possible.