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The following article provides in-depth information about treatment for anterior cruciate ligament injuries. The general article,, provides a good introduction to the topic and is recommended reading prior to this article.
The information that follows includes the details of anterior cruciate ligament (ACL) anatomy and the pathophysiology of an ACL tear, treatment options for ACL injuries along with a description of ACL surgical techniques and rehabilitation, potential complications, and outcomes. The information is intended to assist the patient in making the best-informed decision possible regarding the management of ACL injury.
The bone structure of the knee joint is formed by the femur, the tibia, and the patella. The ACL is one of the four main ligaments within the knee that connect the femur to the tibia.
The knee is essentially a hinged joint that is held together by the medial collateral (MCL), lateral collateral (LCL), anterior cruciate (ACL) and posterior cruciate (PCL) ligaments. The ACL runs diagonally in the middle of the knee, preventing the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee.
The weight-bearing surface of the knee is covered by a layer of articular cartilage. On either side of the joint, between the cartilage surfaces of the femur and tibia, are the medial meniscus and lateral meniscus. The menisci act as shock absorbers and work with the cartilage to reduce the stresses between the tibia and the femur.
The anterior cruciate ligament (ACL) is one of the most commonly injured ligaments of the knee. The incidence of ACL injuries is currently estimated at approximately 200,000 annually, with 100,000 ACL reconstructions performed each year.1, 2 In general, the incidence of ACL injury is higher in people who participate in high-risk sports, such as basketball, football, skiing, and soccer.3, 4, 5
Approximately 50 percent of ACL injuries occur in combination with damage to the meniscus, articular cartilage, or other ligaments. Additionally, patients may have bruises of the bone beneath the cartilage surface. These may be seen on a magnetic resonance imaging (MRI) scan and may indicate injury to the overlying articular cartilage.20, 21
It is estimated that 70 percent of ACL injuries occur through non-contact mechanisms while 30 percent result from direct contact with another player or object.4
Several studies have shown that female athletes have a higher incidence of ACL injury than male athletes in certain sports.3, 10 It has been proposed that this is due to differences in physical conditioning, muscular strength, and neuromuscular control. Other hypothesized causes of this gender-related difference in ACL injury rates include pelvis and lower extremity (leg) alignment, increased ligamentous laxity, and the effects of estrogen on ligament properties.4, 11, 12, 13, 14, 15, 16, 17, 18, 19
Immediately after the injury, patients usually experience pain and swelling and the knee feels unstable. Within a few hours after a new ACL injury, patients often have a large amount of knee swelling, a loss of full range of motion, pain or tenderness along the joint line and discomfort while walking.
When a patient with an ACL injury is initially seen for evaluation in the clinic, the doctor may order X-rays to look for any possible fractures. He or she may also order a magnetic resonance imaging (MRI) scan to evaluate the ACL and to check for evidence of injury to other knee ligaments, meniscus cartilage, or articular cartilage.
In addition to performing special tests for identifying meniscus tears and injury to other ligaments of the knee, the physician will often perform the Lachman's test to see if the ACL is intact.
If the ACL is torn, the examiner will feel increased forward (upward or anterior) movement of the tibia in relation to the femur (especially when compared to the normal leg) and a soft, mushy endpoint (because the ACL is torn) when this movement ends.
Another test for ACL injury is the pivot shift test. 22In this test, if the ACL is torn, the tibia will start forward when the knee is fully straight and then will shift back into the correct position in relation to the femur when the knee is bent past 30 degrees.
The natural history of an ACL injury without surgical intervention varies from patient to patient and depends on the patient's activity level, degree of injury and instability symptoms.
The prognosis for a partially torn ACL is often favorable, with the recovery and rehabilitation period usually at least three months. However, some patients with partial ACL tears may still have instability symptoms. Close clinical follow-up and a complete course of physical therapy helps identify those patients with unstable knees due to partial ACL tears.
Complete ACL ruptures have a much less favorable outcome. After a complete ACL tear, some patients are unable to participate in cutting or pivoting-type sports, while others have instability during even normal activities, such as walking. There are some rare individuals who can participate in sports without any symptoms of instability. This variability is related to the severity of the original knee injury, as well as the physical demands of the patient.
About half of ACL injuries occur in combination with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to ACL injury. With chronic instability, up to 90 percent of patients will have meniscus damage when reassessed 10 or more years after the initial injury. Similarly, the prevalence of articular cartilage lesions increases up to 70 percent in patients who have a 10-year-old ACL deficiency.23, 24, 25, 26, 27, 28, 29, 30, 31, 32
In nonsurgical treatment, progressive physical therapy and rehabilitation can restore the knee to a condition close to its pre-injury state and educate the patient on how to prevent instability.37, 38 This may be supplemented with the use of a hinged knee brace. However, many people who choose not to have surgery may experience secondary injury to the knee due to repetitive instability episodes.
Surgical treatment is usually advised in dealing with combined injuries (ACL tears in combination with other injuries in the knee). However, deciding against surgery is reasonable for select patients. Nonsurgical management of isolated ACL tears is likely to be successful or may be indicated in patients:
- With partial tears and no instability symptoms39
- With complete tears and no symptoms of knee instability during low-demand sports who are willing to give up high-demand sports
- Who do light manual work or live sedentary lifestyles
- Whose growth plates are still open (children)
ACL tears are not usually repaired using suture to sew it back together, because repaired ACLs have generally been shown to fail over time.31, 33, 34, 35, 36 Therefore, the torn ACL is generally replaced by a substitute graft made of tendon.
Animation courtesy Visual Health Solutions, Inc.
The grafts commonly used to replace the ACL include:
- Patellar tendon autograft (autograft comes from the patient)
- Hamstring tendon autograft
- Quadriceps tendon autograft
- Allograft (taken from a cadaver) patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibialis tendon
Patients treated with surgical reconstruction of the ACL have long-term success rates of 82 percent to 95 percent. Recurrent instability and graft failure are seen in approximately 8 percent of patients.
The goal of the ACL reconstruction surgery is to prevent instability and restore the function of the torn ligament, creating a stable knee. This allows the patient to return to sports. There are certain factors that the patient must consider when deciding for or against ACL surgery.
Active adult patients involved in sports or jobs that require pivoting, turning or hard-cutting as well as heavy manual work are encouraged to consider surgical treatment.40, 41, 42, 43, 44 This includes older patients who have previously been excluded from consideration for ACL surgery. Activity, not age, should determine if surgical intervention should be considered.
In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems. The surgeon can delay ACL surgery until the child is closer to skeletal maturity or the surgeon may modify the ACL surgery technique to decrease the risk of growth plate injury.45, 46
A patient with a torn ACL and significant functional instability has a high risk of developing secondary knee damage and should therefore consider ACL reconstruction.
It is common to see ACL injuries combined with damage to the menisci (50 percent), articular cartilage (30 percent), collateral ligaments (30 percent), joint capsule, or a combination of the above. The "unhappy triad," frequently seen in football players and skiers, consists of injuries to the ACL, the MCL, and the medial meniscus.23, 24, 25, 26, 27, 28, 29, 30, 31, 32
In cases of combined injuries, surgical treatment may be warranted and generally produces better outcomes.47, 48, 49, 50, 51, 52, 53, 54 As many as 50 percent of meniscus tears may be repairable and may heal better if the repair is done in combination with the ACL reconstruction.42, 55, 56
Patellar tendon autograft. The middle third of the patellar tendon of the patient, along with a bone plug from the shin and the kneecap is used in the patellar tendon autograft. Occasionally referred to by some surgeons as the "gold standard" for ACL reconstruction, it is often recommended for high-demand athletes and patients whose jobs do not require a significant amount of kneeling.57
In studies comparing outcomes of patellar tendon and hamstring autograft ACL reconstruction, the rate of graft failure was lower in the patellar tendon group (1.9 percent versus 4.9 percent).58 In addition, most studies show equal or better outcomes in terms of postoperative tests for knee laxity (Lachman's, anterior drawer and instrumented tests) when this graft is compared to others. However, patellar tendon autografts have a greater incidence of postoperative patellofemoral pain (pain behind the kneecap) complaints and other problems.58, 59
The pitfalls of the patellar tendon autograft are:
- Postoperative pain behind the kneecap
- Pain with kneeling
- Slightly increased risk of postoperative stiffness
- Low risk of patella fracture
Hamstring tendon autograft. The semitendinosus hamstring tendon on the inner side of the knee is used in creating the hamstring tendon autograft for ACL reconstruction. Some surgeons use an additional tendon, the gracilis, which is attached below the knee in the same area. This creates a two- or four-strand tendon graft. Hamstring graft proponents claim there are fewer problems associated with harvesting of the graft compared to the patellar tendon autograft including:
- Fewer problems with anterior knee pain or kneecap pain after surgery
- Less postoperative stiffness problems
- Smaller incision
- Faster recovery60, 61
The graft function may be limited by the strength and type of fixation in the bone tunnels, as the graft does not have bone plugs.62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73 There have been conflicting results in research studies as to whether hamstring grafts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during objective testing.57, 58, 60, 61, 74, 75, 76, 77, 78 Recently, some studies have demonstrated decreased hamstring strength in patients after surgery.79, 80, 81
There are some indications that patients who have intrinsic ligamentous laxity and knee hyperextension of 10 degrees or more may have increased risk of postoperative hamstring graft laxity on clinical exam. Therefore, some clinicians recommend the use of patellar tendon autografts in these hypermobile patients.130
Additionally, since the medial hamstrings often provide dynamic support against valgus stress and instability, some surgeons feel that chronic or residual medial collateral ligament laxity (grade 2 or more) at the time of ACL reconstruction may be a contra-indication for use of the patient's own semitendinosus and gracilis tendons as an ACL graft.
Quadriceps tendon autograft. The quadriceps tendon autograft is often used for patients who have already failed ACL reconstruction.43, 82, 83 The middle third of the patient's quadriceps tendon and a bone plug from the upper end of the knee cap are used. This yields a larger graft for taller and heavier patients. Because there is a bone plug on one side only, the fixation is not as solid as for the patellar tendon graft. There is a high association with postoperative anterior knee pain and a low risk of patella fracture. Patients may find the incision is not cosmetically appealing.
Allografts. Allografts are grafts taken from cadavers and are becoming increasingly popular.84, 85 These grafts are also used for patients who have failed ACL reconstruction before and in surgery to repair or reconstruct more than one knee ligament. Advantages of using allograft tissue include elimination of pain caused by obtaining the graft from the patient, decreased surgery time and smaller incisions. The patellar tendon allograft allows for strong bony fixation in the tibial and femoral bone tunnels with screws.
However, allografts are associated with a risk of infection, including viral transmission (HIV and Hepatitis C), despite careful screening and processing.86, 87, 88, 89 Several deaths linked to bacterial infection from allograft tissue (due to improper procurement and sterilization techniques) have led to improvements in allograft tissue testing and processing techniques.90 There have also been conflicting results in research studies as to whether allografts are slightly more susceptible to graft elongation (stretching), which may lead to increased laxity during testing.84, 91, 92, 93, 94
Recently published literature may point to a higher failure rate with the use of allografts for ACL reconstruction. Failure rates ranging from 23% to 34.4% have been reported in young, active patients returning to high-demand sporting activities after ACL reconstruction with allografts. This is compared to autograft failure rates ranging from 5% to 10%.131, 132, 133
The reason for this higher failure rate is unclear. It could be due to graft material properties (sterilization processes used, graft donor age, storage of the graft). It could possibly be due to an ill-advised earlier return to sport by the athlete because of a faster perceived physiologic recovery, when the graft is not biologically ready to be loaded and stressed during sporting activities. Further research in this area is indicated and is ongoing.
Before any surgical treatment, the patient is usually sent to physical therapy. Patients who have a stiff, swollen knee lacking full range of motion at the time of ACL surgery may have significant problems regaining motion after surgery.95, 96, 97 It usually takes three or more weeks from the time of injury to achieve full range of motion. It is also recommended that some ligament injuries be braced and allowed to heal prior to ACL surgery.52, 53, 54, 98
The patient, the surgeon, and the anesthesiologist select the anesthesia used for surgery. Patients may benefit from an anesthetic block of the nerves of the leg to decrease postoperative pain.
The surgery usually begins with an examination of the patient's knee while the patient is relaxed due the effects of anesthesia. This final examination is used to verify that the ACL is torn and also to check for looseness of other knee ligaments that may need to be repaired during surgery or addressed postoperatively.
If the physical exam strongly suggests the ACL is torn, the selected tendon is harvested (for an autograft) or thawed (for an allograft) and the graft is prepared to the correct size for the patient.
After the graft has been prepared, the surgeon places an arthroscope into the joint. Small (one-centimeter) incisions called portals are made in the front of the knee to insert the arthroscope and instruments and the surgeon examines the condition of the knee. Meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed.
In the most common ACL reconstruction technique, bone tunnels are drilled into the tibia and the femur to place the ACL graft in almost the same position as the torn ACL. A long needle is then passed through the tunnel of the tibia, up through the femoral tunnel, and then out through the skin of the thigh. The sutures of the graft are placed through the eye of the needle and the graft is pulled into position up through the tibial tunnel and then up into the femoral tunnel. The graft is held under tension as it is fixed in place using interference screws, spiked washers, posts, or staples. The devices used to hold the graft in place are generally not removed.
Variations on this surgical technique include the "two-incision," "over-the-top," and "double-bundle" types of ACL reconstructions, which may be used because of the preference of the surgeon or special circumstances (revision ACL reconstruction, open growth plates).45, 99, 100
Before the surgery is complete, the surgeon will probe the graft to make sure it has good tension, verify that the knee has full range of motion and perform tests such as the Lachman's test to assess graft stability. The skin is closed and dressings (and perhaps a postoperative brace and cold therapy device, depending on surgeon preference) are applied. The patient will usually go home on the same day of the surgery.
Infection. The incidence of infection after arthroscopic ACL reconstruction has a reported range of 0.2 percent to 0.48 percent.101, 102, 103, 104 There have also been several reported deaths linked to bacterial infection from allograft tissue due to improper procurement and sterilization techniques.90
Viral transmission. Allografts specifically are associated with risk of viral transmission, including HIV and Hepatitis C, despite careful screening and processing.86, 87, 88, 89 The chance of obtaining a bone allograft from an HIV-infected donor is calculated to be less than 1 in a million.87
Bleeding, numbness. Rare risks include bleeding from acute injury to the popliteal artery (overall incidence is 0.01 percent) 105 and weakness or paralysis of the leg or foot. It is not uncommon to have numbness of the outer part of the upper leg next to the incision, which may be temporary or permanent.106, 107
Blood clot. A blood clot in the veins of the calf or thigh is a potentially life-threatening complication. A blood clot may break off in the bloodstream and travel to the lungs, causing pulmonary embolism or to the brain, causing stroke. This risk ofis reported to be approximately 0.12 percent.
Instability. Recurrent instability due to rupture or stretching of the reconstructed ligament or poor surgical technique (reported to be as low as 2.5 percent and as high as 34 percent) is possible.2, 25, 58, 108, 131, 132, 133
Extensor mechanism failure. Rupture of the patellar tendon (patellar tendon autograft) or patella fracture (patellar tendon or quadriceps tendon autografts) may occur due to weakening at the site of graft harvest.114, 115, 116, 117, 118, 119, 120
Growth plate injury. In young children or adolescents with ACL tears, early ACL reconstruction creates a possible risk of growth plate injury, leading to bone growth problems.45, 46, 121, 122, 123 The ACL surgery can be delayed until the child is closer to reaching skeletal maturity. Alternatively, the surgeon may be able to modify the technique of ACL reconstruction to decrease the risk of growth plate injury.
Kneecap pain. Postoperative anterior knee pain is especially common after patellar tendon autograft ACL reconstruction. The incidence of pain behind the kneecap varies between 4 percent and 56 percent in studies, whereas the incidence of kneeling pain may be as high as 42 percent after patellar tendon autograft ACL reconstruction.58
Physical therapy is a crucial part of successful ACL surgery, with exercises beginning immediately after the surgery. Much of the success of ACL reconstructive surgery depends on the patient's dedication to rigorous physical therapy. With new surgical techniques and stronger graft fixation, current physical therapy uses an accelerated course of rehabilitation.95, 96, 109
Postoperative Course. In the first 10 to 14 days after surgery, the wound is kept clean and dry, and early emphasis is placed on regaining the ability to fully straighten the knee and restore quadriceps control.
The knee is iced regularly to reduce swelling and pain. The surgeon may dictate the use of a postoperative brace and the use of a machine to move the knee through its range of motion.124, 125 Weight-bearing status (use of crutches to keep some or all of the patient's weight off of the surgical leg) is also determined by physician preference, as well as other injuries addressed at the time of surgery.
Rehabilitation. The goals for rehabilitation of ACL reconstruction include reducing knee swelling, maintaining mobility of the kneecap to prevent anterior knee pain problems, regaining full range of motion of the knee, as well as strengthening the quadriceps and hamstring muscles.
The patient may return to sports when there is no longer pain or swelling, when full knee range of motion has been achieved, and when muscle strength, endurance and functional use of the leg have been fully restored.
The patient's sense of balance and control of the leg must also be restored through exercises designed to improve neuromuscular control.4 This usually takes four to six months. The use of a functional brace when returning to sports is ideally not needed after a successful ACL reconstruction, but some patients may feel a greater sense of security by wearing one.126, 127, 128, 129
To learn more about the full value of ACL surgery:
|1.||Miyasaka KC, Daniel DM, Stone ML. The incidence of knee ligament injuries in the general population. Am J Knee Surg 1991;4:43-48.|
|2.||Brown CH, Carson EW. Revision anterior cruciate ligament surgery. Clin Sports Med 1999;18:109-171.|
|3.||Arendt E, Dick R. Knee Injury Patterns Among Men and Women in Collegiate Basketball and Soccer: NCAA Data and Review of Literature. Am J Sports Med 1995;23(6):694-701.|
|4.||Griffin LY. Noncontact Anterior Cruciate Ligament Injuries: Risk Factors and Prevention Strategies. J Am Acad Orthop Surg 2000;8:141-150.|
|5.||Viola RW, Steadman JR, Mair SD, et al. Anterior Cruciate Ligament Injury Incidence Among Male and Female Professional Alpine Skiers. Am J Sports Med 1999;27:792-795.|
|6.||Gwinn DE, Wilckens JH, McDevitt ER, et al. The Relative Incidence of Anterior Cruciate Ligament Injury in Men and Women at the United States Naval Academy. Am J Sports Med 2000;28(1):98-102.|
|7.||Kirkendall DT, Garrett WE. The anterior cruciate ligament enigma. Injury mechanisms and prevention. Clin Orthop 2000;372:64-68.|
|8.||Yu B, Kirkendall DT, Taft TN, et al. Lower extremity motor control-related and other risk factors for noncontact anterior cruciate ligament injuries. Inst Course Lect 2002;51:315-324.|
|9.||Colby S, Francisco A, Yu B, et al. Electromyographic and Kinematic Analysis of Cutting Maneuvers: Implications for Anterior Cruciate Ligament Injury. Am J Sports Med 2000;28(2):234-240.|
|10.||Ireland ML. Anterior Cruciate Ligament Injury in Female Athletes: Epidemiology. Journal of Athletic Training 1999;34(2):150-154.|
|11.||Anderson AF, Dome DC, Gautam S, et al. Correlation of Anthropometric Measurements, Strength, Anterior Cruciate Ligament Size, and Intercondylar Notch Characteristics to Sex Differences in Anterior Cruciate Ligament Tear Rates. Am J Sports Med 2001;29(1):58-66.|
|12.||Wojtys EM, Huston LJ, Lindenfeld TN, et al. Association Between the Menstrual Cycle and Anterior Cruciate Ligament Injuries in Female Athletes. Am J Sports Med 1998;26(5):614-619.|
|13.||Wojtys EM, Huston LJ, Boynton MD, et al. The Effect of the Menstrual Cycle on Anterior Cruciate Ligament Injuries in Women as Determined by Hormone Levels. Am J Sports Med 2002;30(2):182-188.|
|14.||Wojtys EM, Ashton-Miller JA, Huston LJ. A Gender-Related Difference in the Contribution of the Knee Musculature to Sagittal-Plane Shear Stiffness in Subjects with Similar Knee Laxity. J Bone Joint Surg Am 2002;84(1):10-16.|
|15.||Wojtys EM, Huston LJ, Schock HJ, et al. Gender Differences in Muscular Protection of the Knee in Torsion in Size-Matched Athletes. J Bone Joint Surg Am 2003;85(5):782-789.|
|16.||Liu S, Al-Shaikh R, Panossian V, et al. Estrogen affects the cellular metabolism of the anterior cruciate ligament. A potential explanation for female athletic injury. Am J Sports Med 1997;25(5):704-709.|
|17.||Hewett TE, Myer GD, Ford KR. Decrease in Neuromuscular Control About the Knee with Maturation in Female Athletes. J Bone Joint Surg Am 2004;86(8):1601-1608.|
|18.||Huston LJ, Wojtys EM. Neuromuscular performance characteristics in elite female athletes. Am J Sports Med 1996;24:427-436.|
|19.||Huston LJ, Greenfield ML, Wojtys EM. Anterior Cruciate Ligament Injuries in the Female Athlete: Potential Risk Factors. Clin Orthop 2000;372:50-63.|
|20.||Graf B, Cook D, De Smet A, et al. "Bone bruises" on Magnetic Resonance Imaging Evaluation of Anterior Cruciate Ligament Injuries. Am J Sports Med 1993;21(2):220-223.|
|21.||Johnson DL, Urban WP, Jr, Caborn DNM, et al. Articular Cartilage Changes Seen With Magnetic Resonance Imaging-Detected Bone Bruises Associated With Acute Anterior Cruciate Ligament Rupture. Am J Sports Med 1998;26(3):409-414.|
|22.||Bach B, Jr, Warren R, Wickiewicz T. The Pivot Shift Phenomenon: Results and Description of a Modified Clinical Test for Anterior Cruciate Ligament Insufficiency. Am J Sports Med 1988;16(6):571-576.|
|23.||Uribe JW, Hechtman KS, Zvijac JE, et al. Revision anterior cruciate ligament surgery: Experience from Miami. Clin Orthop 1996;325:91-99.|
|24.||Johnson DL, Swenson TM, Irrgang JJ, et al. Revision anterior cruciate ligament surgery: Experience from Pittsburgh. Clin Orthop 1996;325:100-109.|
|25.||Noyes FR, Barber-Westin SD. Revision anterior cruciate ligament surgery: Experience from Cincinnati. Clin Orthop 1996;325:116-129.|
|26.||Smith JP, III, Barrett GR. Medial and Lateral Meniscal Tear Patterns in Anterior Cruciate Ligament-Deficient Knees: A Prospective Analysis of 575 Tears. Am J Sports Med 2001;29(4):415-419.|
|27.||Shelbourne K, Johnson G. Locked Bucket-Handle Meniscal Tears in Knees with Chronic Anterior Cruciate Ligament Deficiency. Am J Sports Med 1993;21(6):779-782.|
|28.||Keene G, Bickerstaff D, Rae P, et al. The Natural History of Meniscal Tears in Anterior Cruciate Ligament Insufficiency. Am J Sports Med 1993;21(5):672-679.|
|29.||Casteleyn PP, Handelberg F. Non-operative management of anterior cruciate ligament injuries in the general population. J Bone Joint Surg Br 1996;78(3):446-451.|
|30.||Finsterbush A, Frankl U, Matan Y, et al. Secondary Damage to the Knee After Isolated Injury of the Anterior Cruciate Ligament. Am J Sports Med 1990;18(5):475-479.|
|31.||Maletius W, Messner K. Eighteen- to Twenty-four-Year Follow-up After Complete Rupture of the Anterior Cruciate Ligament. Am J Sports Med 1999;27(6):711-717.|
|32.||Murrell GAC, Maddali S, Horovitz L, et al. The Effects of Time Course after Anterior Cruciate Ligament Injury in Correlation with Meniscal and Cartilage Loss. Am J Sports Med 2001;29:9-14.|
|33.||Clancy WG, Ray JM, Zoltan DJ. Acute tears of anterior cruciate ligament. Surgical versus conservative treatment. J Bone Joint Surg [Am] 1988;70:1483-1488.|
|34.||Andersson C, Odensten M, Good L, et al. Surgical or non-surgical treatment of acute rupture of the anterior cruciate ligament. A randomized study with long-term follow-up. J Bone Joint Surg [Am] 1989;71:965-974.|
|35.||Aho AJ, Lehto MUK, Kujala UM. Repair of the anterior cruciate ligament: Augmentation versus conventional suture of fresh rupture. Acta Orthop Scand 1986;57:345-357.|
|36.||Kaplan N, Wickiewicz T, Warren R. Primary surgical treatment of anterior cruciate ligament ruptures. A long-term follow-up study. Am J Sports Med 1990;18(4):354-358.|
|37.||Buss D, Min R, Skyhar M, et al. Nonoperative Treatment of Acute Anterior Cruciate Ligament Injuries in a Selected Group of Patients. Am J Sports Med 1995;23(2):160-165.|
|38.||Noyes FR, McGinniss GH, Grood ES. The variable functional disability of the anterior cruciate ligament-deficient knee. Orthop Clin North America 1985;16:47-67.|
|39.||Messner K, Maletius W. Eighteen- to Twenty-Five-Year Follow-up After Acute Partial Anterior Cruciate Ligament Rupture. Am J Sports Med 1999;27(4):455-459.|
|40.||Johnson RJ, Beynnon BD, Nichols CE, et al. Current concepts review. The treatment of injuries of the anterior cruciate ligament. J Bone Joint Surg Am 1992;74A:140-151.|
|41.||Roos H, Ornell M, Gardsell P, et al. Soccer after anterior cruciate ligament injury-an incompatible combination? A national survey of incidence and risk factors and a 7-year follow-up of 310 players. Acta Orthop Scandinavica 1995;66:107-112.|
|42.||Buckley S, Barrack R, Alexander A. The Natural History of Conservatively Treated Partial Anterior Cruciate Ligament Ttears. Am J Sports Med 1989;17(2):221-225.|
|43.||Howe J, Johnson R, Kaplan M, et al. Anterior Cruciate Ligament Reconstruction Using Quadriceps Patellar Tendon Graft. Part I. Long-term followup. Am J Sports Med 1991;19(5):447-457.|
|44.||Noyes FR, Mooar LA, Moorman CT, et al. Partial tears of the anterior cruciate ligament. Progression to complete ligament deficiency. J Bone Joint Surg Br 1989;71B(5):825-833.|
|45.||Bales CP, Guettler JH, Moorman CT III. Anterior Cruciate Ligament Injuries in Children With Open Physes: Evolving Strategies of Treatment. Am J Sports Med 2004;32(8):1978-1985.|
|46.||Stanitski C. Anterior Cruciate Ligament Injuries in the Young Athlete with Open Physes. Am J Sports Med 1988;16(4):424-.|
|47.||Hefzy MS, Grood ES. Ligament restraints in anterior cruciate ligament-deficient knees. In: Jackson DW, Arnoczky SP, Woo SL-Y, Frank CB, Simon TM, eds. The Anterior Cruciate Ligament. Current and Future Concepts. New York: Raven Press, 1993;141-151.|
|48.||Levy IM, Torzilli PA, Warren RF. The effect of medial meniscectomy on anterior-posterior motion of the knee. J Bone Joint Surg Am 1982;64A:883-888.|
|49.||LaPrade RF, Resig S, Wentorf F, et al. The Effects of Grade III Posterolateral Knee Complex Injuries on Anterior Cruciate Ligament Graft Force: A Biomechanical Analysis. Am J Sports Med 1999;27(4):469-475.|
|50.||Hillard-Sembell D, Daniel DM, Stone ML, et al. Combined Injuries of the Anterior Cruciate and Medial Collateral Ligaments of the Knee. Effect of Treatment on Stability and Function of the Joint. J Bone Joint Surg Am 1996;78(2):169-76.|
|51.||Haimes J, Wroble R, Grood E, et al. Role of the Medial Structures in the Intact and Anterior Cruciate Ligament-Deficient Knee. Limits of Motion in the Human Knee. Am J Sports Med 1994;22(3):402-409.|
|52.||Nakamura N, Horibe S, Toritsuka Y, et al. Acute Grade III Medial Collateral Ligament Injury of the Knee Associated with Anterior Cruciate Ligament Tear: The Usefulness of Magnetic Resonance Imaging in Determining a Treatment Regimen. Am J Sports Med 2003;31(2):261-267.|
|53.||Shelbourne K, Nitz P. The O'Donoghue Triad Revisited. Combined Knee Injuries Involving Anterior Cruciate and Medial Collateral Ligament Tears. Am J Sports Med 1991;19(5):474-477.|
|54.||Shelbourne K, Porter D. Anterior cruciate ligament-medial collateral ligament injury: nonoperative management of medial collateral ligament tears with anterior cruciate ligament reconstruction. A preliminary report. Am J Sports Med 1992;20(3):283-286.|
|55.||Cannon W, Jr, Vittori J. The incidence of healing in arthroscopic meniscal repairs in anterior cruciate ligament-reconstructed knees versus stable knees. Am J Sports Med 1992;20(2):176-181.|
|56.||Warren RF. Meniscectomy and repair in the anterior cruciate ligament-deficient patient. Clin Orthop 1990;252:55-63.|
|57.||Spindler KP, Kuhn JE, Freedman KB, et al. Anterior Cruciate Ligament Reconstruction Autograft Choice: Bone-Tendon-Bone Versus Hamstring: Does It Really Matter? A Systematic Review. Am J Sports Med 2004;32(8):1986-1995.|
|58.||Freedman KB, D'Amato MJ, Nedeff DD, et al. Arthroscopic Anterior Cruciate Ligament Reconstruction: A Metaanalysis Comparing Patellar Tendon and Hamstring Tendon Autografts. Am J Sports Med 2003;31(1):2-11.|
|59.||Sachs R, Daniel D, Stone M, et al. Patellofemoral problems after anterior cruciate ligament reconstruction. Am J Sports Med 1989;17(6):760-765.|
|60.||Pinczewski LA, Deehan DJ, Salmon LJ, et al. A Five-Year Comparison of Patellar Tendon Versus Four-Strand Hamstring Tendon Autograft for Arthroscopic Reconstruction of the Anterior Cruciate Ligament. Am J Sports Med 2002;30(4):523-536.|
|61.||Shaieb MD, Kan DM, Chang SK, et al. A Prospective Randomized Comparison of Patellar Tendon Versus Semitendinosus and Gracilis Tendon Autografts for Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2002;30(2):214-220.|
|62.||Starch DW, Alexander JW, Noble PC, et al. Multistranded Hamstring Tendon Graft Fixation with a Central Four-Quadrant or a Standard Tibial Interference Screw for Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2003;31(3):338-344.|
|63.||Nurmi JT, Kannus P, Sievanen H, et al. Interference Screw Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction: Part 1: Effect of Tunnel Compaction by Serial Dilators Versus Extraction Drilling on the Initial Fixation Strength. Am J Sports Med 2004;32(2):411-417.|
|64.||Nurmi JT, Kannus P, Sievanen H, et al. Interference Screw Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction: Part 2: Effect of Preconditioning on Graft Tension During and After Screw Insertion. Am J Sports Med 2004;32(2):418-424.|
|65.||Nurmi JT, Kannus P, Sievanen H, et al. Compaction Drilling Does Not Increase the Initial Fixation Strength of the Hamstring Tendon Graft in Anterior Cruciate Ligament Reconstruction in a Cadaver Model. Am J Sports Med 2003;31(3):353-358.|
|66.||Nurmi JT, Jarvinen TLN, Kannus P, et al. Compaction Versus Extraction Drilling for Fixation of the Hamstring Tendon Graft in Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2002;30(2):167-173.|
|67.||Nagarkatti DG, McKeon BP, Donahue BS, et al. Mechanical Evaluation of a Soft Tissue Interference Screw in Free Tendon Anterior Cruciate Ligament Graft Fixation. Am J Sports Med 2001;29(1):67-71.|
|68.||Magen HE, Howell SM, Hull ML. Structural Properties of Six Tibial Fixation Methods for Anterior Cruciate Ligament Soft Tissue Grafts. Am J Sports Med 1999;27(1):35-43.|
|69.||Kousa P, Jarvinen TLN, Vihavainen M, et al. The Fixation Strength of Six Hamstring Tendon Graft Fixation Devices in Anterior Cruciate Ligament Reconstruction: Part I: Femoral Site. Am J Sports Med 2003;31(2):174-181.|
|70.||Kousa P, Jarvinen TLN, Vihavainen M, et al. The Fixation Strength of Six Hamstring Tendon Graft Fixation Devices in Anterior Cruciate Ligament Reconstruction: Part II: Tibial Site. Am J Sports Med 2003;31(2):182-188.|
|71.||Giurea M, Zorilla P, Amis AA, et al. Comparative Pull-Out and Cyclic-Loading Strength Tests of Anchorage of Hamstring Tendon Grafts in Anterior Cruciate Ligament Reconstruction. Am J Sports Med 1999;27(5):621-625.|
|72.||Ahmad CS, Gardner TR, Groh M, et al. Mechanical Properties of Soft Tissue Femoral Fixation Devices for Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2004;32(3):635-640.|
|73.||Rodeo SA, Arnoczky SP, Torzilli PA, et al. Tendon healing in a bone tunnel. A biomechanical and histological study in the dog. J Bone Joint Surg Am 1993;75A:1795-1803.|
|74.||Steiner M, Hecker A, Brown C, Jr, et al. Anterior cruciate ligament graft fixation. Comparison of hamstring and patellar tendon grafts. Am J Sports Med 1994;22(2):240-246.|
|75.||Adam F, Pape D, Schiel K, et al. Biomechanical Properties of Patellar and Hamstring Graft Tibial Fixation Techniques in Anterior Cruciate Ligament Reconstruction: Experimental Study With Roentgen Stereometric Analysis. Am J Sports Med 2004;32(1):71-78.|
|76.||Ejerhed L, Kartus J, Sernert N, et al. Patellar Tendon or Semitendinosus Tendon Autografts for Anterior Cruciate Ligament Reconstruction?: A Prospective Randomized Study with a Two-Year Follow-up. Am J Sports Med 2003;31(1):19-25.|
|77.||Rowden N, Sher D, Rogers G, et al. Anterior cruciate ligament graft fixation. Initial comparison of patellar tendon and semitendinosus autografts in young fresh cadavers. Am J Sports Med 1997;25(4):472-478.|
|78.||Otsuka H, Ishibashi Y, Tsuda E, et al. Comparison of Three Techniques of Anterior Cruciate Ligament Reconstruction with Bone-Patellar Tendon-Bone Graft: Differences in Anterior Tibial Translation and Tunnel Enlargement with Each Technique. Am J Sports Med 2003;31(2):282-288.|
|79.||Tashiro T, Kurosawa H, Kawakami A, et al. Influence of Medial Hamstring Tendon Harvest on Knee Flexor Strength after Anterior Cruciate Ligament Reconstruction: A Detailed Evaluation with Comparison of Single- and Double-Tendon Harvest. Am J Sports Med 2003;31(4):522-529.|
|80.||Tadokoro K, Matsui N, Yagi M, et al. Evaluation of Hamstring Strength and Tendon Regrowth After Harvesting for Anterior Cruciate Ligament Reconstruction. Am J Sports Med 2004;32(7):1644-1650.|
|81.||Marder RA, Raskind JR, Carroll M. Prospective evaluation of arthroscopically-assisted anterior cruciate ligament reconstruction. Patellar tendon versus semitendinosus and gracilis tendons. Am J Sports Med 1991;19:478-484.|
|82.||Kornblatt I, Warren R, Wickiewicz T. Long-term followup of anterior cruciate ligament reconstruction using the quadriceps tendon substitution for chronic anterior cruciate ligament insufficiency. Am J Sports Med 1988;16(5):444-448.|
|83.||Harris N, Smith D, Lamoreaux L, et al. Central quadriceps tendon for anterior cruciate ligament reconstruction. Part I: Morphometric and biomechanical evaluation. Am J Sports Med 1997;25(1):23-28.|
|84.||Noyes FR, Barber-Westin SD. Reconstruction of the anterior cruciate ligament with human allograft. Comparison of early and later results. J Bone Joint Surg Am 1996;78A:524-537.|
|85.||Fu FH, Jackson DW, Jamison J, et al. Allograft reconstruction of the anterior cruciate ligament. In: Jackson DW, Arnoczky SP, Woo SL-Y, Frank CB, Simon TM, eds. The Anterior Cruciate Ligament. Current and Future Concepts. New York: Raven Press, 1993;325-338.|
|86.||Tomford WW. Current concepts review: Transmission of disease through transplantation of musculoskeletal allografts. J Bone Joint Surg Am 1995;77A:1742-1754.|
|87.||Buck BE, Malinin TI, Brown MD. Bone transplantation and human immunodeficiency virus. An estimate of risk of acquired immunodeficiency syndrome (AIDS). Clin Orthop 1989;240:129-136.|
|88.||Tomford WW. Transmission of disease through musculoskeletal transplantation. Portland Bone Symposium. Portland OR: Oregon Health Sciences University, 1997:410-420.|
|89.||Conrad EU, Gretch DR, Obermeyer KR. Transmission of the hepatitis-C virus by tissue transplantation. J Bone Joint Surg Am 1995;77A:214-224.|
|90.||Update: Allograft associated bacterial infections-United States, 2002. MMWR Morb Mortal Wkly Rep 2002;51:207-210.|
|91.||Nikolaou P, Seaber A, Glisson R, et al. Anterior cruciate ligament allograft transplantation. Long-term function, histology, revascularization, and operative technique. Am J Sports Med 1986;14(5):348-360.|
|92.||Linn R, Fischer D, Smith J, et al. Achilles tendon allograft reconstruction of the anterior cruciate ligament-deficient knee. Am J Sports Med 1993;21(6):825-831.|
|93.||Jackson D, Grood E, Goldstein J, et al. A comparison of patellar tendon autograft and allograft used for anterior cruciate ligament reconstruction in the goat model. Am J Sports Med 1993;21(2):176-185.|
|94.||Indelicato P, Linton R, Huegel M. The results of fresh-frozen patellar tendon allografts for chronic anterior cruciate ligament deficiency of the knee. Am J Sports Med 1992;20(2):118-121.|
|95.||Shelbourne K, Gray T. Anterior cruciate ligament reconstruction with autogenous patellar tendon graft followed by accelerated rehabilitation. A two- to nine-year followup. Am J Sports Med 1997;25(6):786-795.|
|96.||Shelbourne K, Nitz P. Accelerated rehabilitation after anterior cruciate ligament reconstruction. Am J Sports Med 1990;18(3):292-299.|
|97.||Wasilewski S, Covall D, Cohen S. Effect of surgical timing on recovery and associated injuries after anterior cruciate ligament reconstruction. Am J Sports Med 1993;21(3):338-342.|
|98.||Inoue M, McGurk-Burleson E, Hollis J, et al. Treatment of the medial collateral ligament injury. I: The importance of anterior cruciate ligament on the varus-valgus knee laxity. Am J Sports Med 1987;15(1):15-21.|
|99.||Stapleton TR, Waldrop JI, Ruder CR, et al. Graft Fixation Strength with Arthroscopic Anterior Cruciate Ligament Reconstruction: Two-Incision Rear Entry Technique Compared With One-Incision Technique. Am J Sports Med 1998;26(3):442-445.|
|100.||Hess T, Duchow J, Roland S, et al. Single- versus Two-Incision Technique in Anterior Cruciate Ligament Replacement: Influence on Postoperative Muscle Function. Am J Sports Med 2002;30(1):27-31.|
|101.||Matava M, Evans T, Wright R. Septic arthritis of the knee following anterior cruciate ligament reconstruction: Results of a survey of sports medicine fellowship directors. Arthroscopy 1998;14:717-725.|
|102.||McAllister DR, Parker RD, Cooper AE, et al. Outcomes of Postoperative Septic Arthritis After Anterior Cruciate Ligament Reconstruction. Am J Sports Med 1999;27(5):562-570.|
|103.||Burks RT, Friederichs MG, Fink B, et al. Treatment of Postoperative Anterior Cruciate Ligament Infections with Graft Removal and Early Reimplantation. Am J Sports Med 2003;31(3):414-418.|
|104.||Williams R, 3rd, Laurencin C, Warren R, et al. Septic arthritis after arthroscopic anterior cruciate ligament reconstruction. Diagnosis and management. Am J Sports Med 1997;25(2):261-267.|
|105.||Sachs RA, Reznik A, Daniel DM. Complications of knee surgery. In: Daniel DM, Akeson WH, O'Connor JJ, eds. Knee Ligaments: Structure, Function, Injury, and Repair. New York: Raven Press, 1990;505-520.|
|106.||Kartus J, Ejerhed L, Sernert N, et al. Comparison of Traditional and Subcutaneous Patellar Tendon Harvest: A Prospective Study of Donor Site-Related Problems After Anterior Cruciate Ligament Reconstruction Using Different Graft Harvesting Techniques. Am J Sports Med 2000;28:328-335.|
|107.||Tifford CD, Spero L, Luke T, et al. The Relationship of the Infrapatellar Branches of the Saphenous Nerve to Arthroscopy Portals and Incisions for Anterior Cruciate Ligament Surgery: An Anatomic Study. Am J Sports Med 2000;28(4):562-567.|
|108.||Bach BR, Jr, Tradonsky S, Bojchuk J, et al. Arthroscopically Assisted Anterior Cruciate Ligament Reconstruction Using Patellar Tendon Autograft: Five- to Nine-Year Follow-up Evaluation. Am J Sports Med 1998;26(1):20-29.|
|109.||Shelbourne K, Wilckens J, Mollabashy A, et al. Arthrofibrosis in acute anterior cruciate ligament reconstruction. The effect of timing of reconstruction and rehabilitation. Am J Sports Med 1991;19(4):332-336.|
|110.||Cosgarea A, Sebastianelli W, DeHaven K. Prevention of arthrofibrosis after anterior cruciate ligament reconstruction using the central third patellar tendon autograft. Am J Sports Med 1995;23(1):87-92.|
|111.||Harner C, Irrgang J, Paul J, et al. Loss of motion after anterior cruciate ligament reconstruction. Am J Sports Med 1992;20(5):499-506.|
|112.||Marzo JM, Bowen MK, Warren RF. Intraarticular fibrous nodule as a cause of loss of extension following anterior cruciate ligament reconstruction. Arthroscopy 1992;8:10-18.|
|113.||Irrgang JJ, Harner CD, Fu FH, et al. Loss of Motion Following ACL Reconstruction: A Second Look. Jour Sports Rehab 1997;6:213-225.|
|114.||Christen B, Jakob RP. Fractures associated with patellar ligament grafts in cruciate ligament surgery. J Bone Joint Surg Br 1992;74B:617-619.|
|115.||McCarroll J. Fracture of the patella during a golf swing following reconstruction of the anterior cruciate ligament. A case report. Am J Sports Med 1983;11(1):26-27.|
|116.||Hughston JC. Complications of anterior cruciate ligament surgery. Orthop Clin North America 1985;16:237-240.|
|117.||Marumoto J, Mitsunaga M, Richardson A, et al. Late patellar tendon ruptures after removal of the central third for anterior cruciate ligament reconstruction. A report of two cases. Am J Sports Med 1996;24(5):698-701.|
|118.||Bonamo JJ, Krinick RM, Sporn AA. Rupture of the patella ligament after use of its central third for anterior cruciate ligament reconstruction. A report of two cases. J Bone Joint Surg Am 1984;66A:1294-1297.|
|119.||Viola R, Vianello R. Three cases of patella fracture in 1,320 anterior cruciate ligament reconstructions with bone-patellar tendon-bone autograft. Arthroscopy 1999;15(1):93-97.|
|120.||Stein DA, Hunt SA, Rosen JE, et al. The Incidence and Outcome of Patella Fractures after Anterior Cruciate Ligament Reconstruction. Arthroscopy 2002;18(6):578-583.|
|121.||Lipscomb AB, Anderson AF. Tears of the anterior cruciate ligament in adolescents. J Bone Joint Surg Am 1986;68A:19-28.|
|122.||Kocher MS, Saxon HS, Hovis WD, et al. Management and complications of anterior cruciate ligament injuries in skeletally immature patients: survey of the Herodicus Society and the ACL Study Group. J Pediatr Orthop 2002;22:452-457.|
|123.||Koman JD, Sanders JO. Valgus Deformity After Reconstruction of the Anterior Cruciate Ligament in a Skeletally Immature Patient. A Case Report. J Bone Joint Surg Am 1999;81(5):711-5.|
|124.||Burks R, Daniel D, Losse G. The effect of continuous passive motion on anterior cruciate ligament reconstruction stability. Am J Sports Med 1984;12(4):323-327.|
|125.||Rosen M, Jackson D, Atwell E. The efficacy of continuous passive motion in the rehabilitation of anterior cruciate ligament reconstructions. Am J Sports Med 1992;20(2):122-127.|
|126.||Beynnon B, Pope M, Wertheimer C, et al. The effect of functional knee-braces on strain on the anterior cruciate ligament in vivo. J Bone Joint Surg Am 1992;74(9):1298-1312.|
|127.||McDevitt ER, Taylor DC, Miller MD, et al. Functional Bracing After Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized, Multicenter Study. Am J Sports Med 2004;32(8):1887-1892.|
|128.||Risberg MA, Holm I, Steen H, et al. The Effect of Knee Bracing After Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized Study with Two Years' Follow-up. Am J Sports Med 1999;27(1):76-83.|
|129.||Wojtys E, Kothari S, Huston L. Anterior cruciate ligament functional brace use in sports. Am J Sports Med 1996;24(4):539-546.|
|130.||Kim S-J, Moon H-K, Kim S-G et al. Does Severity or Specific Joint Laxity Influence Clinical Outcomes of Anterior Cruciate Ligament Reconstruction? Clin Orthop Relat Res July 2009 publication visible on line (volume and page number pending)|
|131.||Sun K, Tian S, Zhang J, Xia C, Zhang C, Yu T. Anterior cruciate ligament reconstruction with BPTB autograft, irradiated versus non-irradiated allograft: a prospective randomized clinical study. Knee Surg Sports Traumatol Arthrosc 2009;17(5):464-74.|
|132.||Singhal MC, Gardiner JR, Johnson DL. Failure of primary anterior cruciate ligament surgery using anterior tibialis allograft. Arthroscopy 2007; 23(5):469-75.|
|133.||Luber KT, Greene PY, Barrett GR. Allograft Anterior Cruciate Ligament Reconstruction in the Young, Active Patient (Tegner Activity Level and Failure Rate). AOSSM Annual Meeting Podium presentation July 10-13 2008, Orlando Florida|
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