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American and Norwegian Surgeons Combine Forces to Study Knee Surgery
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Posted on: 01/27/2010
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There are plenty of studies looking at the results of anterior cruciate ligament (ACL) repairs. But this may be the first to report outcomes for posterolateral knee reconstruction. Whereas the anterior and posterior cruciate ligaments hold the knee stable from inside the joint, there are other ligaments that hold it together from the outside. Three ligaments that provide posterior (to the back) and lateral (to the side) support and stability to the knee are the focus of this study.
Those three ligaments are: fibular collateral ligament (FCL), popliteus tendon (PLT), and popliteofibular ligament (PFL). The fibular collateral ligament connects the top of the fibula (bone along the outside of the lower leg) to the bottom of the femur (thigh bone). It gives lateral (side) support to the knee to keep it from bowing out too far. The popliteus tendon starts midway along the bottom portion of the femur and angles back to connect to the back of the upper tibia (shin bone in the lower leg). This tendon supports the knee and keeps it from rotating too far in one direction. And the popliteofibular ligament connects the back of the tibia to the back and side of the fibula. The fibula and tibia sit side by side as the two bones in the lower leg.
A previous study by these surgeons (one group from the U.S., the second group from Norway) reported on their success anatomically reconstructing these three support structures. Many other surgical procedures have been used to repair damage in this area. They believe theirs is the first to actually restore the natural anatomy by using Achilles tendon grafts taken from a donor bank. The surgical procedure was described in detail -- how the Achilles tendon was prepared for use as a graft, preparation of the bone with tunnels for the grafts, and anchors used to keep the grafts in place.
Everything was done with the idea in mind of stabilizing the knee in the most optimal way possible -- by mimicking the original, natural anatomy. In this way, patients can get full function back without fear that the knee is going to give way from underneath them or get reinjured. They should get the same kind of good results other knee patients get when the anterior or posterior cruciate ligaments are reconstructed. But instead of keeping the bones in the knee from sliding too far forward or too far backward (the job of the cruciate ligaments), these posterolateral structures protect the knee from bowing out to the side too far or externally rotating too far.
Patients came from two separate centers but with everything done in the same way so that all the data could be combined. Everyone in the study had been diagnosed with a grade-3 chronic posterolateral knee instability. The term chronic is a key factor in this study. These are people who had a significant delay between the time the knee was injured and the surgery was performed. The time interval ranged anywhere from two months up to 12 years. The patients ranged in age from 18 to 58, so it wasn't just young, athletes who were involved in the study. And quite a few of the subjects had other knee injuries (e.g., nerve damage, previous failed knee surgery) that added to the complexity of surgery and recovery.
Clinical tests used to make the diagnosis showed a widening of the joint space along the outside (lateral edge) of the knee when pressure was applied in that direction. Likewise, there was an increase in external rotation of the tibia under the femur and a positive posterolateral drawer test. The drawer test is done by applying pressure to the lower leg (tibia) and seeing or feeling too much backward movement of the tibia under the femur. Sometimes there is even a clunk as the bone shift too far back. This occurs because the ligaments are damaged and don't hold the tibia in place as they should.
Before the surgery was done, patients were tested using X-rays, MRIs, and rating scales to measure pain, knee range-of-motion, and function. Patient ratings of their symptoms and disability were measured using the Cincinnati scores. Function was measured using the International Knee Documentation Committee (IKDC) score.
Results of the clinical tests were also recorded. All of these tests were repeated after surgery and during the follow-up period to compare before and after results. Everyone was followed for at least two years. Some of the patients had been treated and reassessed over a longer period of time (up to seven years total). And the authors intend to continue following as many people in the study they can keep in touch with in order to gather data to judge intermediate and long-term results.
A postoperative rehab program was part of the post-surgical plan. No one was allowed to put weight on the involved leg for six weeks. They were allowed to do some specific range-of-motion and strengthening exercises supervised by a physical therapist. A knee immobilizer (splint) was used to protect the knee until they could lift the leg off the table (straight leg raise) without an extension lag. Extension lag refers to a lack of full extension of the knee when trying to straighten it all the way or while doing a straight-leg raise.
The surgeons set certain milestones to be reached during rehab such as 90 degrees of knee flexion by the end of two weeks, full knee motion at the end of six weeks, and resume weight bearing by the end of 10 weeks. It was expected that the patients would walk normally again (without a limp) by the end of four months. Athletes could return to full competitive sports action when they had full motion, strength, endurance, and proprioception (sense of joint position).
The length of time for complete recovery varied depending on the extent of surgery. Some patients only had one ligament reconstruction whereas others had all three restored. And in some cases, the surgeon had to perform a two-part procedure, first realigning the knee and then reconstructing the damaged soft tissues. Realignment was necessary for those patients who had too much varus contributing to the problem. Varus is a natural bow-legged position of the knee. Without reducing the pressure along the outside of the knee by putting it in a more neutral position, the reconstructed ligaments would be under abnormal stretch, stress, and strain again. The realigning procedure is called an opening-wedge tibial osteotomy.
So for a quick recap: we've got patients with posterolateral knee instability. It's a complex instability pattern affecting two ligaments, one tendon, and two areas of the joint (side and back). It's been there a long time, so it's considered chronic. The surgeons have come up with a way to reconstruct the knee stability (not just repair the torn tissues). Because the procedure is meant to recreate the normal anatomy, they are calling the procedure an anatomic posterolateral knee reconstruction.
And the results? All patients in the study had a good result. This included those with only one soft tissue structure involved, patients with all three tissue structures damaged, and people with varus deformities creating alignment problems requiring additional surgery. Test results from before to after showed significant improvement in all areas measured.
The test measures used are standard in the treatment of knee injuries and can be repeated by others interested in studying results of surgery for chronic posterolateral instability. In this way, evidence can be gathered and reported to help determine the long-term results of this particular operation. And surgeons using other procedures can report their data in the same way. The comparisons will help surgeons find the best way to treat this problem.
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References:
Robert F. LaPrade, MD, PhD, et al. Outcomes of an Anatomic Posterolateral Knee Reconstruction. In The Journal of Bone and Joint Surgery. January 2010. Vol. 91-A. No. 1. Pp. 16-22.
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