Imaging Quiz Answer: Calf Pain in a Recreational Basketball Player
Bryan D. Caldwell, DPM, MSTHE PHYSICIAN AND SPORTSMEDICINE - VOL 25 - NO. 1 - JANUARY 1997
The STIR sequence in the axial plane (figure 2) revealed high signal fluid in the soleus muscle with no such increase in the medial or lateral heads of the gastrocnemius. In the sagittal STIR image (figure 3), patchy abnormal signal was seen in the patient's soleus muscle from its origin to the distal calf. In the coronal plane (figure 4), high-signal fluid is seen tracking along the fascial plane between the gastrocnemius and soleus, a sign consistent with hematoma. The patient was diagnosed with a diffuse tear of the soleus muscle with hemorrhage and hematoma.
Pathology and Detection
According to an extensive literature search, isolated ruptures of the soleus muscle are very rare. Medial gastrocnemius tears are far more common, and recent advances in MRI have shown that plantaris ruptures, although not confirmed surgically, do occur (1,2). It is reasonable to conclude that the gastrocnemius and plantaris muscles are more prone to injury, because they stretch and change length over two joints, while the soleus muscle spans only one joint (3,4).
MRI studies of the physiologic cross-sectional area of the soleus have shown that the muscle accounts for approximately 70% of the total area of the triceps surae, which optimizes the production of force by the muscle. The mean fiber length is unusually short relative to muscle volume, boosting its force potential at the expense of velocity (5). These characteristics are typical of a pennate muscle. Since stress is inversely proportional to cross-sectional area, soleus rupture is less common. Rupture of the gastrocnemius, which accounts for 30% of the cross-sectional area of the triceps surae, may be more likely for this reason.
This patient's injury was initially diagnosed as a plantaris rupture or a medial gastrocnemius tear because of the initial presentation. A soleus rupture was not suspected because dorsiflexion of the foot with knee flexion was not painful. This maneuver, known as the Silfverskiöld test, eliminates tension on the gastrocnemius and plantaris muscles, but leaves the soleus under traction. Hence, if a soleus rupture is present, this maneuver should not reduce or eliminate pain, as happened in this patient. It is possible that most of his initial pain was from hematoma formation within a confined space rather than the actual muscle tear. Flexing the knee may have decreased motion between the two muscles (since the gastrocnemius was no longer under traction), but this is speculative.
One would also expect significant ecchymosis after a gastrocnemius or soleus rupture because of the size and blood supply of these muscles relative to other calf muscles such as the plantaris. But the patient presented only 1 day after the injury, which apparently was too soon for ecchymosis to develop.
The same MRI advances that allow diagnosis of plantaris muscle ruptures (1,2) allow for definitive diagnosis of soleus ruptures. Typically, collections of high-signal fluid are observed at the site of disruption and throughout the belly of the strained muscle.6 Partial muscle tears show characteristic stellate areas of intermediate intensity on proton-density images, particularly within the muscle belly. Complete tears show a true gap with associated edema and hemorrhage (7). This patient's partially ruptured soleus demonstrated increased T2 and STIR signal throughout the muscle (figure 3).
The physician may need to immobilize the extremity in the acute phase of soleus muscle injury, but it is important to choose a position that does not lead to soleus muscle atrophy. Research (8) has shown that immobilization of the feline soleus muscle in a shortened position (rather than the neutral or lengthened position) results in significant atrophy of the muscle and marked loss of myofibril protein concentration. Furthermore, a reduction in contractile force of a soleus muscle held in a shortened position may negatively alter the contractile properties of the myofibrillar protein (8). This results in increased total muscle atrophy. Therefore, the patient's foot was splinted in neutral to prevent marked disuse atrophy.
Treatment of these injuries should probably be similar to that of other gastrocnemius-soleus injuries, which consists of non-weight-bearing crutch walking for the first few days with a posterior splint on the affected limb. This is followed by an early return to weight bearing as tolerated (9).
Other treatment components for soleus muscle tear are similar to those for soleus muscle strain, including electrotherapeutic modalities, stretching, and strengthening exercises (10). For this patient, electrical stimulation, ultrasound, massage, and passive muscle stretching were used. After prescribing non-weight bearing on the affected limb in the acute phase of injury, we encouraged early mobilization and weight bearing to tolerance.
Following extensive physical therapy, the patient's only symptom at 10 weeks postinjury was mild nonpitting edema over his medial and lateral malleoli.
Dr Caldwell is an assistant professor in the department of medicine at the Ohio College of Podiatric Medicine, a podiatric physician in the department of orthopaedic surgery at The Cleveland Clinic Foundation, and director of podiatric primary care residency training at Richmond Heights General Hospital, all in Cleveland. Address correspondence to Bryan D. Caldwell, DPM, MS, Dept of Medicine, Ohio College of Podiatric Medicine, 10515 Carnegie Ave, Cleveland, OH 44106.
The author thanks James Lichniak, DPM, and Bernice Krumhansl, PT, for their expert participation in the care of this patient.