Medial Meniscus Tear and Comminuted Fibula Fracture
It is well known that traumatic injuries occur together in pedestrian-vehicle accidents. Being aware of the pattern of these injuries can enable physicians to assess the extent of injuries more accurately. Common patterns of injury to the knee include knee avulsion fractures. The Segond fracture (a lateral tibial plateau avulsion) often pairs with an ACL injury and meniscal tear (1). The arcuate sign, which is an avulsion fracture of the fibular head, often occurs with ACL, PCL, and popliteal nerve injury (1, 2). While reports of tibial plateau fractures associated with acute meniscal tears are well documented, there are no reports citing comminuted fibula fractures in association with meniscal tears.
The menisci of the knee are responsible for stability, lubrication, load distribution, and proprioception at the joint (3). Each meniscus is a C-shaped pad of cartilage that fits between each rounded femoral condyle and flat tibial plateau; each knee has a medial and lateral condyle-plateau pairing (3). The larger arc of the meniscus is thicker than the smaller arc, making menisci appear wedge-shaped on the sagittal plane of the knee (4). The purpose of this is to redistribute the force evenly across the femoral-tibial articulation (5).
Meniscal tears are commonly a result of flexion or extension and rotation of the femur relative to the tibia; they can occur abruptly from trauma or as a result of chronic degeneration and repetitive twisting (4, 5). Tears are further organized into several characteristics; partial versus complex, anterior, lateral, or posterior in location of the tear, torn horizontally (medial-lateral), vertically (superior-inferior), radially, like a parrot beak, or like a bucket handle (4).
There are certain aspects of the menisci that make them susceptible to particular types of damage. The geniculate arteries supply the menisci but inner regions receive a lesser amount of blood flow relative to the peripheral portions, leaving the inner region unable to heal from tears left untreated (4). It is estimated that 80% of meniscal tears occur in the inner region (5). Meniscal tears can occur by themselves or with damage to collateral and/or cruciate ligaments (4). The medial menisicus is more prone to injury than the lateral because the medial meniscus is rigidly bound to the medial collateral ligament while the lateral meniscus is more loosely attached to the lateral collateral ligament (4). In particular, the posterior horn of the medial meniscus make up 28% of medial meniscal tears (3). Medial menisci commonly tear longitudinally along the anterior-posterior direction (5). Medial meniscal tears are also associated with extrusion (3mm past the outer margin of the meniscus) 50-79% of the time (3).
Acute meniscal injuries typically occur during participation in contact sports. They occur in both genders and across all age groups, however, they are less frequent in individuals younger than the age of ten. Patients may report a tearing or popping sensation at onset. The severity of pain varies with the degree of the tear, but most patients can continuously ambulate. Pain and swelling gradually develop within 24 hrs (4).
Reported symptoms correlate with the abnormal interactions between the menisci and bones. If the torn cartilage catches between the bones inappropriately, the position of the bones relative to each other may be misaligned, causing a change of proprioception at the joint (4). Untreated large complex tears of the menisci expose the femoral condyles and tibial plateaus to each other, allowing them to directly rub against each other and â€ślockâ€ť the motion of the knee, preventing smooth extension (4). The direct contact also causes inflammation and effusion in the joint space, causing a feeling of stiffness (4). Inflammation caused by direct articulation can lead to osteoarthritis. The grinding of the femur and tibia is also responsible for the exacerbation of pain that a patient experiences when they twist or pivot along the knee (4).
Diagnosis is based on mechanism of the injury, symptoms, and positive signs on physical exam. Plain radiographs, ultrasound, CT, MRI and arthroscopy can aid differentiating the diagnosis. MRI has been reported to have 88% sensitivity and 90% specificity (6) in diagnosing meniscal tears. MRI is often used to assess extent of meniscal tearing prior to surgery (6). Arthroscopy has two roles regarding meniscal tears. These include diagnosis and management. Such diagnostically, evaluates the degree of injury to the menisci, along with evaluating the integrity of associated structures, (ie. cruciate ligaments and articular cartilage). Regarding management such procedure is utilized to correct meniscal injury (2, 4).
Physical exam should include assessment of gait, passive and active flexion, extension of the knee, and the ability to squat. While small tears may not elicit positive findings, typical positive findings on physical exam include joint line tenderness or effusion, inability to fully extend the knee, inability to squat, positive McMurray maneuver, and pain elicited on Thessaly testing (4). Positive McMurray sign is reported to have about 50% sensitivity while Thessaly testing is reported to have 61-96% sensitivity for meniscal tears; negative tests on either do not rule tears out (4). Definitive diagnosis of effusion is by joint aspiration, which can differentiate hemarthrosis (associated with ACL tears and intraarticular fractures) and septic arthritis (4).
Treatment of a meniscal tear initially includes resting the knee from pressure and weight, avoiding repetitive squatting, kneeling, and twisting (4). The knee should be elevated and compressed with ice to minimize swelling. If the pain is severe, crutches or a patellar restraining brace (in the case of weak quadriceps muscles) can be prescribed (4). Early evaluation involves determining the extent of the tear, and evaluating the need for surgery (4). Long term treatment would encompass rehabilitation of the injured or post-surgical knee, inclusive of strengthening associated musculature, forms of conservative management and evaluating the need for any further orthopedic surgery.
Conservative management is indicated for small tears with minimal pain that do not hinder knee function or chronic degenerative tears. Physical therapy rehabilitation has been associated with better outcomes than surgery for chronic degenerative tears (4). Physical therapy exercises should focus on strengthening quadricep and hamstring muscles to support the knee. A typical exercise regimen would begin with 10 repetitions of straight leg raising with a goal of 25 reps while progressively adding resistance through ankle weights (2lbs increased to up to 10lbs) (4). Friction massage along the femorotibial joint line and repetitions of internally rotating the tibia during knee extension can reduce meniscal-bone articulation scarring (5). Walking, light jogging, and water aerobics is recommended, stair-stepping, cycling, rowing and other forms of exercise that require sharp knee flexion should be avoided while the patient is symptomatic (4).
Referral for orthopedic surgical evaluation would be appropriate in cases of: large, complex tears that extend to the articular surface, chronic knee effusion, limited the range of motion of the knee or inability to squat, or in patients that have no improvement of symptoms after 3-6 weeks of conservative care (4). With arthroscopy, a physician is able to clear debris and hematomas that surround the tear, perform a meniscectomy, and suture tears (2). Partial meniscectomy is preferable over a total meniscectomy due to the risk of osteoarthritis associated with the latter procedure (4). Studies have shown that complete meniscectomies result in 50-200% increases in medial contact pressure between the femoral condyle and tibial plateau and correlate with the onset and severity of osteoarthritis (3). Degenerative meniscal tearing accompanied by the comorbidity of joint osteoarthrosis singly benefits from glucocorticoid injections (4).
Many studies report acute meniscal tears with fractures to the tibial plateau. One study reported 41% of patients with tibial plateau fractures also have meniscal tearing (6). However, there are few reports of proximal fibula fracture in association with meniscal tearing. While fibular fractures make up 25% of all stress fractures in athletes, they are limited to the middle and distal third of fibula (7). When proximal fibula fractures do occur in trauma, they are rarely isolated injuries; they commonly occur with damage of ligaments of the knee, fractures of the lateral tibial plateau or ankle, and comminuted fractures of the femoral condyles (8). The most widely reported proximal fibula fracture is an avulsion of the fibular head commonly known as the â€śarcuate sign.â€ť The arcuate sign is often caused by motor vehicle accidents, in which a force is applied against the anteromedial tibia while the knee is extended (9). In one study, fracture to the fibular head was associated with injury to the posterior cruciate ligament as well as the lateral and medial collateral ligaments. There was an equal prevalence of medial and lateral mensical tearing in this study, although the tears were exclusively in the posterior body or horn of either menisci (9). When meniscal tears are suspected or seen in images, it is important to assess for additional injuries to the tibial, femoral, and fibular structures and their associated ligaments.