MRI: Not the Whole Story
William P. Rix, MD
MRI is an imaging tool commonly used by orthopedists in making a diagnosis in patients with musculoskeletal complaints. It is frequently mentioned in the media when professional athletes are injured:
“Major League Baseball pitcher John Smith’s production has fallen over the past few games. MRI of his sore shoulder reveals no structural damage and rest is indicated.”
“National Football League lineman Jim White’s episodes of low back pain have limited his starts this season. An MRI showed he will need surgery and will be out for the rest of the season”.
The implication of these common references in the sports media is that an MRI offers the definitive answer for musculoskeletal problems. MRI is a state-of-the-art imaging technique that depicts the anatomy of our musculoskeletal system in astonishing detail. Despite its unquestionable value, however, it can be confusing and in some cases, downright misleading. This is because the abnormality seen on the scan may not be the cause of the patient’s problem. Remarkable as the technology is, it is no substitute for a good history and physical examination.
To illustrate, let’s look at some actual cases:
- A 50-year-old man was referred to the orthopedist for possible surgery after an MRI revealed a small rotator cuff tear in his shoulder. The patient told the orthopedist that he had experienced sudden onset of severe shoulder pain without injury in a previously normal shoulder. His pain had subsided after 2 weeks, but left him with profound shoulder weakness. The physical examination revealed severe wasting of the supraspinatus and infraspinatus muscles, two important components of the rotator cuff. Because rotator cuff patients usually do not present with such extremes on history or examination, the orthopedist suspected something else was going on. Further muscle testing revealed subtle weakness of the Serratus Anterior, a muscle that holds the scapula (wing-bone) tight to the chest wall, a finding inconsistent with a primary diagnosisof rotator cuff tear. Electrical nerve studies confirmed that this man had inflammation of his brachial plexus, the network of nerves that runs from collarbone to armpit and sends nerves to the shoulder girdle and arm. Though the exact cause of this condition is unknown, the treatment is non-surgical. This man was instructed in an exercise program and his weakness resolved over the next 12 months. The cuff tear was not addressed because it was an incidental finding on MRI and did not contribute to the man`s symptoms.
- A 75-year-old woman experienced severe knee pain when she twisted her leg getting up from the toilet. She arrived at her primary care physician’s office using a walker and unable to bear weight on that leg. A knee x-ray showed no fracture, but an MRI of the knee revealed a torn meniscus (cartilage) and mild-to-moderate arthritis. She was referred to the orthopedist for possible arthroscopic surgery. During thehistory, the orthopedist noted that the woman was very thin, her diet tended toward “tea and toast” rather than three nutritional meals per day and she smoked, all high risk factors for osteoporosis. The physical examination revealed the knee was non-tender over the torn cartilage area and there was no effusion (water in the knee). These negative findings were unusualfor symptoms coming from a torn meniscus as seen on her MRI. Bending and straightening her knee while sitting (hip stationary) caused no pain, but doing the same maneuver in a supine position (hip free to move) reproduced her severe knee pain. The orthopedist became concerned about a hip fracture because hip bone and hip joint conditions sometimes refer pain only to the knee rather than the more common areas of groin and buttocks. An x-ray of her pelvis revealed a non-displaced fragility fracture of the hip, a break that occurs in osteoporotic bone after minor trauma. The danger was that the hip fracture might displace at any time causing pain, blood loss and even death. She underwent same day hip pinning surgery with complete resolution of her pain. She was also counseled on the proper treatment of her osteoporosis. The torn meniscus was not the root cause of this woman`s pain and therefore was ignored.
- Our last example is a 65-year-old man with a six month history of increasing buttocks pain, right greater than left. His pain was worse on walking and better with rest. He had undergone low back (lumbar) surgery 10 years prior and experienced intermittent episodes of backache ever since. An MRI of his lumbar spine showed lumbar stenosis (narrowing) at the site of the old surgery. Spine physical therapy had been ineffective in reducing his pain significantly. He was referred to the orthopedic spine surgeon for possible decompressive surgery at the area of stenosis. The history revealed that the man’s father was “loaded with arthritis” and his brother had undergone both total knee and total hip surgery for debilitating arthritis. The surgeon also noted that the patient, when getting onto the exam table, used his hand to assist in lifting his right leg from the vertical to the horizontal, a move more typical of hip problems than back problems. Physical examination of the hip revealed stiffness, and stressing the hips in rotation reproduced his buttock pain. Dedicated X-rays of his hips revealed bilateral osteoarthritis, right greater than left. Since both lumbar stenosis and hip arthritis can cause buttocks symptoms, further testing were needed to identify which condition was the primary pain generator. An injection into both hip joints with steroid and Xylocaine completely relieved this man’s pain, thus confirming that his buttocks pain was coming from his hips and not from his low back. This man eventually underwent total hip replacement on both sides, as the steroid`s benefit was only temporary. The coexisting lumbar stenosis was not the root cause of this patient’s problem and was left alone.
In all three cases, the MRI showed a true structural abnormality that could be corrected surgically. However, one does not operate on an abnormality just because it`s there. It has to be the cause of the patient`s problem. The MRI did not tell the physician if the findings seen on film were actually causing the patient’s symptoms. An MRI cannot stand by itself. It must be ordered and interpreted in the context of a proper history and exam. In these patients, the MRI findings were age-related or post-surgical and not contributing to their complaints.
The proper sequence in arriving at the root of a patient’s orthopedic problem is a thorough history, a proper examination and, usually, an x-ray. If further investigation is needed to come to a specific diagnosis, further testing, including MRI is then employed.
Since the time of Hippocrates, the backbone of delivering good patient care has been the history and physical. It still is.