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Medical Articles »Martin Trieb, M.D.
Meniscal and Anterior Cruciate Ligament Injuries in Industrial Workers
Martin Trieb, M.D.
Orthopedic Surgery
As workers’ compensation or disability specialists, the knowledge and skills you develop can influence the outcome of an orthopedic claim and your overall goal of providing timely, quality medical treatment to injured workers.
In this article two of the most common knee conditions, Meniscal and Anterior Cruciate Ligament Injuries, are presented.
The intent of this article is to assist you in understanding these common knee injuries, their treatment, and the general expected outcomes. This will allow you to make a more informed decision about specific knee injury claims.
Part 1: Meniscal Ligament Injuries
Part 2: Anterior Cruciate Ligament Injuries
Part 1: Meniscal Ligament Injuries
Meniscal tears are much more common than cruciate ligament injuries, with more options for treatment. It is important to understand the biomechanics of the meniscus, because even a partial meniscectomy does not leave the knee normal. There are four main contributions the meniscus makes to maintaining normal knee function:
1. Each meniscus is responsible for absorbing approximately 20% or more of the impaction forces across the joint surface throughout its range of motion.
2. Because of the wedge shape configuration it assists the ligaments in stabilizing the knee, especially in preventing anterior translation of the tibia on the femur.
3. Since there is no blood supply to the articular cartilage, nourishment is through diffusion from the pressure of contact between the articular surfaces. On the periphery of the articular surfaces, the meniscus supplies the contact.
4. The meniscus acts like ball-bearings to propagate the nourishing synovial fluid, keeping all the articular surfaces lubricated throughout the full range of motion (along with the fat pad which similarly functions to do this).
Therefore, if the symptoms indicate meniscal damage (the MRI may or may not support the diagnosis) it doesn’t mean that the meniscus has to be removed. A partially torn, stable meniscus continues to function and can actually prevent further deterioration in the knee. On the other hand if the meniscus tears and forms a flap or if it completely displaces, such as with a bucket-handle tear, then the offending meniscal tissue has to be sacrificed in order to allow the individual to continue to perform. So, when is the surgical excision of a meniscal tear appropriate?
Arthroscopic partial meniscectomy is indicated when there is persistent catching, locking and giving way with effusion. This is frequently associated with some quadricep disuse atrophy. Nocturnal pain can be significant and is usually associated with a horizontal cleavage type of tear. This type of degenerative tear is usually seen in older individuals, although its degenerative changes can be detected as early as the teen ages years by MRI.
If a partial meniscectomy is performed in the presence of some previous degenerative arthritis of the adjacent articular surfaces, to remove the meniscus can accelerate the degenerative process and should, therefore, be approached with reservation and understanding of the limitations.
Meniscal repair has gained favor in order to preserve the functions of the meniscus that we now acknowledge. However, repair is fraught with failure if it is attempted in area where there is no blood supply. The meniscus cartilage is different from the articular cartilage in that it does have blood supply at its peripheral attachment to the capsule extending into the meniscal tissue itself for approximately 3-4 mm. Then, it gradually decreases to the point that the most interior portion of the meniscus, the free border, is avascular. An attempt to repair a meniscus tear that enters what is referred to as the white zone, which is the inner third, is going to fail.
Many of the meniscal tears are combined with a tear from the red zone, through the transitional red / white zone, and into the white zone itself. Unfortunately, in the more mature individual, as middle age is reached, the chances of there being a pure red zone tear is rare. Therefore, most of the meniscal repairs are reserved for younger individuals and definitely ones who have associated anterior cruciate ligament tears, as well. The bleeding that occurs with an anterior cruciate ligament tear seems to assist the repair process of the meniscus. Meniscal repair should never be performed in the presence of an unstable knee, as it will fail.
An MRI may give you some information about the type of tear and whether it is repairable in order to prepare the patient for the likelihood that a repair may be performed and, therefore, crutches and partial weightbearing will be necessary for four weeks postoperatively.
Most meniscal injuries are associated with recurrent and increasing symptoms. If it becomes a disabling condition, then the axiom of early, accurate diagnosis so that partial excision can be performed prevails.
As mentioned, menisci have a very poor blood supply and so very few of them actually heal spontaneously. Occasionally, there may even be one or two years between episodes of pain and swelling, but usually the recurrences are frequent. If it is necessary to have temporary total disability because of the pain and swelling in the knee, it is time to proceed with the surgical intervention.
Part 2: Anterior Cruciate Ligament Injuries
1. Forceful hyperextension, usually with associated twisting.
2. Forceful varus or valgus stress, with or without the knee in full extension but usually when weight-bearing and knee is flexed slightly.
3. There does not have to be an external force against the knee such as a blow for the injury to occur.
4. Frequently, the foot is fixed while the femur rotates either internally or externally.
5. Spending time to ascertain the exact mechanism of injury is probably the most important portion of the history. With an understanding of the anatomy and the severity and direction of the forces applied to the knee the diagnosis is almost made for you.
Pertinent Findings on History
1. Sudden onset of swelling, at least within twelve hours from acute bleeding.
2. Pain posterolaterally.
3. A sense of instability and giving way.
4. Pain with hyperextension in the posterolateral aspect of the knee.
Physical Findings
1. Grade I sprain. Incomplete with sufficient ligament intact to maintain good stability. The ligament is weakened and possibly more easily injured in the future. The diagnosis is difficult because all diagnostic studies and the examination are normal. High index of suspicion based on the mechanism of injury. Disability may last 2-3 weeks during which time light duty is appropriate, avoiding twisting, squatting, jumping, crawling and running. Full recovery is anticipated.
2. Grade II sprain. This is a partial tear as described on MRI. There may be slight laxity on drawer and Lachman’s tests, but a negative pivot shift test. There is usually some swelling but not massive since there is less bleeding. There is associated deep-seated pain which is difficult to localize. There can be a sense of instability on vigorous motions, e.g., twisting and jumping. Recovery takes approximately 3-6 weeks, during which time light duty is appropriate, minimizing weight bearing activities as much as possible. As with a Grade I sprain, susceptibility for further stretching or completely tearing the ligament is even greater. This susceptibility, however, does not represent significant enough danger to require any restrictions once the person has recovered from the acute phase. Disability is the same as Grade I, but for approximately six weeks, with a full recovery if there is no associated meniscal or artilage damage.
3. Grade III or complete tear of the anterior cruciate ligament. There nearly always is significant immediate swelling, with the historical findings as mentioned above. The significant guarding and muscle spasm prevent pivot shift tests or even the more sensitive Lachman’s test. It is necessary to have complete relaxation of the hamstring muscles in order for there to be a positive drawer or Lachman’s test. Therefore, on examination, a bolster placed under the hamstrings allows the necessary relaxation and increases the accuracy of the Lachman’s test tremendously. There are arthrometer tests available, as well, but examination with a bolster under the hamstrings correlates well with the arthrometric examinations.
Complete tears of the anterior cruciate ligament can also occur without the associated acute symptoms if there has been previous partial disruption of the ligamentous tissue. Then, further tearing is not associated with a sudden pop and swelling, and takes much less force to create the instability. The first awareness that there is looseness in the knee may, unfortunately, be associated with a tear of the meniscus which is painful and is the presenting complaint. 80% of complete anterior cruciate ligament tears have associated meniscal injury. Whether it is severe enough to be seen at the time of arthroscopy or on MRI, there are still compressive forces that damage the meniscus enough to make is susceptible to further tearing later.
Treatment for complete tears of the anterior cruciate ligament in an active individual requires reconstruction.
In the natural history of an anterior cruciate deficient knee, the younger the person is who has the injury, the more likely that he will develop degenerative changes in the knee later, especially if there is an associated meniscal injury or subchondral bone contusion that can be seen on MRI.
As mentioned, an unstable knee frequently results in significant tearing of the meniscus, requiring subsequent surgery. The best results following a surgical repair of the anterior cruciate ligament are associated with intact or repaired menisci. If the meniscus has to be removed, there is always the 2-3 mm of anterior drawer indicating some loss of the stabilizing influence of the meniscus.
Following anterior cruciate ligament reconstruction, whether done with an autograft or allograft (cadaver tissue), temporary total disability will average 6-8 weeks with the individual using crutches for the first 2-3 weeks. If the meniscus is repaired, partial weightbearing on crutches will be for approximately 4-5 weeks. At between 6-8 weeks, light duty of a sedentary nature can be performed well, usually with the patient being able to drive a car and be off medications. If the work originally is of a sedentary nature, then the person could return to full, modified duty at that time; however, most injuries of this type do not occur in a sedentary worker and, therefore, the anticipated return to full duty without restrictions could be between 6-8 months or as early as 4 months if there is no prolonged weightbearing, climbing, squatting, twisting, crawling or heavy lifting.
Often in industrial injuries to the anterior cruciate ligament, the diagnosis is not made early enough and the treatment, therefore unfairly delayed. However, to operate on an anterior cruciate ligament tear immediately is not necessary. In fact, it is preferable to wait 2-3 weeks while the acute injury subsides and the patient regains full extension in the knee. It has been shown that, with this 2-3 week delay and using accelerated rehabilitation, recovery is more rapid after surgery than if the surgery is performed immediately after the injury.
Rehabilitation
The above-predicted time to return to duty depends on appropriate rehabilitation.
Following anterior cruciate ligament reconstruction, we are now following an accelerated rehab program, using a shuttle machine to regain motion and strength starting within several days post-op, progressing to a stationary bike at 2-3 weeks post-op, and a progressive resistive exercise program, concentrating on a hamstring strengthening and a closed chain kinetic program. Formal physical therapy can vary from individual to individual, depending upon the response, but the patient usually can be moved gradually into a supervised exercise program at a fitness facility by 10-12 weeks. Running is allowed when 60% of normal strength returns, usually by 3 months. A brace is the surgeon's choice but usually it gives the patient confidence he can procede to normal activities.
Quadriceps atrophy is very common, and it may take up to one year to get the quadriceps fully rehabilitated to where there is no longer any measurable atrophy. This does not mean that there are associated work restrictions during the last several months.
Following arthroscopic partial meniscectomy, rapid return to function is also indicated. The key to a speedy recovery starts with the control of swelling using ice elevation and compression dressings immediately post-op. People certainly vary as to their degree of post-op swelling that occurs and their rehab program has to be adjusted accordingly, which requires visits to a physician on a regular basis as well as the oversight of a physical therapist. This means that, during the first few weeks, the visits to the therapist should be 2-3 times per week. After approximately eight weeks, the visits can be reduced as the patient transitions into the fitness facility.
Following partial menisectomy, crutches are not usually necessary. It is an outpatient procedure, frequently done under a local anesthetic with supplemental sedation. The temporary total disability postoperatively lasts from 2-3 weeks, with a temporary partial disability for the next 3-4 weeks, during which time sedentary light duty is appropriate. In the absence of any associated arthritic changes, it is anticipated that an individual could return to full duty between 6-8 weeks.
Diagnostic Testing
X-rays should always be taken of the knee. Ideally, these should include a PA standing view with a comparison of the opposite knee to determine any degree of narrowing of the joint space which would indicate some articular surface degenerative changes that could have preceded the injury and be aggravated by it. If they are normal X-rays, this is a good baseline for comparison should there be future deterioration. Lateral and tunnel views are also obtained to look for the presence of degenerative arthritis loose bodies, or subchondral bone defects. Merchant (tangential) views of both patellae are also useful to look for loose bodies or marginal fractures of the patella. There is often associated lateral subluxation of the patella, especially it the medial collateral ligament is involved as well as the anterior cruciate ligament and valgus stress had occurred.
MRI is a proper diagnostic study which has received a lot of hype due to its use in professional athletes. However, a thorough history and physical examination offers a more accurate diagnosis than the MRI. The MRI is about 80% accurate and should not be the determining factor in the care to be given or even the prognosis. Most of the 20% inaccuracies are false negatives. It does not show articular surface damage well. However, an MRI will reveal a subchondral bone contusion, this can be seen from trabecular disruption which is too subtle to be seen on the plain X-rays. The location of this contusion also gives an indication as to the mechanism of injury, whether there were varus, valgus or hyperextensive forces.
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