The anterior cruciate ligament (ACL) is one of the main stabilizers of the knee. In the previous article, the basic anatomy of the ACL and injuries to it were described. Playing sports on an unstable knee can lead to further injury. Therefore, a young athlete with an unstable knee will generally be recommended for surgery to achieve a more optimum outcome. Many different surgeries have been used to treat an ACL injured knee. Techniques have evolved and knowledge has been gained as orthopedists study the knee and the results of surgery.
Options for Treatment
The ACL is a ligament that resembles a “rope” on initial inspection. Its fibers consist of strands of collagen. Some of the earliest surgeries to restore the ACL involved repairing the ligament. This was done using sutures to stitch (or sew) together the torn ends of the ligament. It has been discovered that the sutured ligament tends to stretch out over time and the knee once again becomes unstable; repairs are rarely successful.
Hence, a method to create a totally new ligament was created. This is called reconstruction of the ACL. This is an important distinction from simply repairing the torn ACL. Reconstruction means building a new ACL out of tissue. The tissue used to make a new ligament is called the graft. The details of the surgical technique as well as choices of graft will differ among surgeons, but this article will concentrate on discussing the main philosophy of our practice with athletes.
For the most part, the surgery is done with the aid of arthroscopy. This is the small lens attached to a camera that allows the surgeon to look throughout the knee through tiny incisions in the skin. During this part of the procedure, any tears of the meniscus are addressed by either repairing the meniscus or trimming away the torn tissue (see previous article for details). The torn ACL is confirmed and the remnants of the old ACL are removed since they have no ability to heal further.
The graft used may come from several different sources. Artificial ligaments had been used in the past and the results were very disappointing. They are no longer used.
After the chosen graft is obtained, the knee is prepared for the placement of the graft. Small holes are drilled through the tibia (shin bone) and femur (thigh bone) to make “tunnels” that the graft will be passed through. The graft is passed by pulling it through with sutures at either end. The graft is anchored within the tunnels at either end. The most common means of doing this is a small titanium screw that wedges against the graft providing firm fixation. These screws remain deep within the bone and do not need to be removed. They do not corrode and will not set off airport alarms.
After surgery, the patient goes to the recovery room. If all progresses well, they may often be discharged home that night and be able to sleep in their own bed. Over time, the new graft begins to gain its own blood supply. The patient’s own cells generally populate the graft and begin laying down new collagen that anchors the newly created ligament at each end.
Crutches and a brace are used for a short time after surgery until the appropriate motion and control of the leg are regained. Pain and swelling lessen rapidly after the first few days. The ability to walk is progressed until the brace and crutches may be discarded (usually several weeks after surgery). The rehabilitation after surgery requires time and hard work. Younger patients can generally return to school within a few days to a week. The return to sports is based upon motion, strength, balance, and the amount of time since surgery. The graft is continually strengthening during the time after surgery and it needs to gain a large portion of its strength before being stressed during sports. This generally takes several months (four to six months in our practice) depending upon the type of sports played.
Overall, the success rate after reconstruction is quite good. Our results and several other studies have shown that about 90% of patients may return to activity without instability. It is conceivable that one could tear the ligament again, just like they tore the one that they were born with, but the rate of reinjury is quite low. The incisions are currently very acceptable cosmetically and the occasional aches and stiffness that can follow some surgery has been improved with advances in surgical technique. We currently use a specific rehabilitation program to maximize the potential of the knee in a short period of time.