The first bilateral simultaneous quadriceps rupture was reported by Steiner and Plamer in 1949. Since then, just over 100 such cases with different etiopathologies have been reported in the English and German literature [2
]. Diagnostic delay is quite common especially in bilateral ruptures, as they can be mistaken for stroke, rheumatoid arthritis, disc prolapse, neuropathy or even a psychiatric disorder [2
The quadriceps tendon is an inherently very strong structure that is extremely resistant to heavy load. McMaster, in his animal studies, postulated that about 50-75% of the fibres of the quadriceps need to be severed before it will rupture totally under a physiological load [1
]. The common mechanisms of trauma include a stumble, a simple fall, falling from the stairs or from a height. The ratio of ligamentum patellae and quadriceps tendon forces is a function of the knee flexion [3
], hence quadriceps ruptures tend to occur commonly when the knee is flexed more than 60 degrees. At about 30 degrees of knee flexion, the force through the extensor mechanism reached an average of 3000 N, along with the highest lateral forces on the patella [4
]. Most of the injuries occur during an eccentric contraction of the quadriceps against the body weight, when a significantly higher force is generated [1
Degenerative changes commonly occur in the tendons as the ageing process causes their architecture to change. However, quadriceps tendon rupture is rare even among older people [1
]. Thus, other underlying factors, and not age, predispose the tendon to rupture.
An array of conditions has been reported to predispose the rupture by either changing the tendon ultrastructure or affecting the vascularity to the tendon [5
]. Thirty percent of bilateral ruptures are spontaneous [2
]. Pre-existing degeneration has been implicated as a risk factor in acute tendon rupture.
The tensile strength of a tendon is related to its thickness and collagen content. An objective measure quoted in one study shows that a quadriceps tendon with a cross-sectional area of 65 mm2
has a tensile stress value of 37 N/mm2
]. Degeneration as a common histological finding in spontaneous tendon ruptures has been reported commonly in the achilles tendon. Tendons respond to repetitive overload with either inflammation of their sheath or degeneration, or even both. Mucoid degeneration is more common in quadriceps and patellar tendons. Tendinosis can be more often clinically silent. Its manifestation may be a rupture, although it may also co-exist with symptomatic paratendinopathy [5
Ultrasound examination, rather than plain radiograph, is more sensitive in demonstrating the full extent of the tendinopathy. It is also a cheap, easy and reliable way to diagnose tendon ruptures, whether partial or complete. However, ultrasound examination is still operator dependent.
A quadriceps tendon thickness of >6.1 mm, a superior pole of patella erosion, the patellar enthesophytes and intratendinous calcification are all signs of chronic tendinopathy [7
]. Hardy et al.
reported that 79% of patients diagnosed with quadriceps rupture had a patellar spur on lateral knee radiographs [8
]. A report of consequent bilateral quadriceps rupture following trivial trauma was reported in a middle-aged man who had a chronic patellar maltracking postulating patellofemoral arthritis as the predisposition [9
]. Calcific tendonitis of the quadriceps was reported along with a quadriceps tear with liquefied calcific collection in the tendon on exploration [10
Our patient had established changes such as the thickening of his quadriceps tendon, patellar spurs and intratendinous calcifications on both sides of his knee, about two to three years before complete rupture occurred. His farming occupation was attributed as the cause of the pathology due to his frequent squatting and prolonged knee flexion. This could have contributed to the rupture due to the local ischemic changes produced in the tendon.
Our patient did not undergo ultrasonography and hence we did not know the extent of the degeneration of the soft tissue. The rupture was at the intratendinous part of the quadriceps on both sides. His quadriceps was ruptured at the same level, which is an uncommon occurrence.
In a meta-analysis of 52 quadriceps ruptures, osteotendinous junction was the most common site of failure [2
]. A range of medical conditions have been associated with quadriceps ruptures, especially those that are bilateral [2
]. Bilateral complete quadriceps ruptures that are simultaneous and intratendinous in patients with previous chronic symptomatic tendinopathy are rare. Although chronic enthesopathy cannot be cited as the only cause in our patient, a combination of tendinosis, ischaemia and trauma might have caused the final injury.
We think an objective assessment (bony and soft tissue changes) of the degree of degeneration or even histopathological status of the tendon needs to be developed in order to identify patients most at risk of ruptures or at least warn them of this possibly disabling complication.