Maximum Medical Improvement (MMI) is the point when further recovery and restoration of function after an injury or illness can no longer be anticipated with a reasonable degree of certainty. It implies that the condition is medically permanent and stable because further treatment would probably not result in appreciable improvement. It also means that an individual may or may not have fully recovered, i.e., not necessarily attaining pre-injury functional status or free of all symptoms.
MMI does not preclude additional medical care, but it implies extra care is unlikely to be curative. Any medical care after MMI is, at best, symptomatic and palliative.
Many workers’ compensation jurisdictions have a legal concept of “statutory MMI” based on a statute of limitations following an injury. This interval is usually at least one year. It assumes that the injured person knows whether they have recovered without complications or with permanent impairment within this interval. The injured person can then decide, within the statute of limitations of the injury, whether to bring a lawsuit for damages.
Determination of MMI
The following questions should be helpful to determine if an injured worker has reached MMI:
When did the injury occur?
Did the employee receive all the necessary treatment for the condition?
Does the patient currently report any symptoms?
Is there evidence of functional deficits related to the patient’s symptoms?
Duration of the injury or illness
Many occupational injuries, especially musculoskeletal injuries, are self-limiting or have a predictable recovery course. In such cases, it is relatively easy to determine MMI. For example, acute sprains, strains, and other soft tissue injuries typically heal in 3-6 weeks for mild to moderate injuries and 12 weeks or fewer for more severe injuries.
If the patient has undergone a surgical procedure, enough time must elapse for post-operative recovery and healing before they are considered for MMI. For instance, after arthroscopic surgery of the knee for meniscal repair, the average recovery time is 12 weeks, and about 16 weeks after arthroscopic repair of a partial rotator cuff tear. (Note, these are average recovery times and generally apply to non-occupational musculoskeletal injuries; they vary greatly with workers' compensation injuries).
History of Treatment
Before determining MMI, it is necessary to assure the patient has received all the appropriate and required treatment based on established treatment guidelines for the patient's illness and diagnosis. In addition, a recommendation of additional therapy should provide a clear rationale for how the patient would benefit from the continuation of the treatment or any different treatment under consideration.
Current symptoms
At MMI, the patient may be without symptoms or report residual symptoms after undergoing all the necessary treatment. The residual symptoms are those symptoms that remained unchanged during a reasonable timeframe. Lingering symptoms, such as pain, stiffness, and fatigue, may only be subjective without evidence of the treatable underlying disease process. Presence of merely subjective symptoms is not sufficient reason to delay determining of MMI.
Evidence of dysfunction or disease on physical examination
A thorough physical examination is necessary to verify reported symptoms and their effect on the patient's functional capabilities. The physical findings of the examination should focus on obtaining evidence of the ongoing disease process or dysfunction. Any functional deficit arising from injury or illness needs evaluation for possible improvement with further treatment. If no substantial improvement is possible, the deficit will likely become permanent. At this point, the patient is ready for the certification MMI and impairment rating.
Relationship between MMI and Impairment Rating
In workers’ compensation cases, the assessment of MMI and impairment rating are performed in tandem; impairment rating is followed by MMI certification. Therefore, while determining MMI, the examiner is also assessing the possible permanent functional impairment caused by the injury.
If any functional impairments are noted, the examiner should consider whether these impairments are partially or fully reversible based on reasonable medical probability.
If all or some functional impairment is considered reversible (i.e., further material recovery from or lasting improvement to an injury can reasonably be anticipated), then the employee has not reached MMI. The patient should be recommended additional diagnostic testing or treatment to improve these impairments.
However, if the worker’s condition has been stable for a period and no further treatment will substantially decrease the current impairments of the employee, they have reached MMI and are ready for impairment rating.
Example Case 1: Low back pain after heavy lifting
The patient reported that he developed pain in his low back while lifting an 80-pound box at work several months ago. He heard a pop and felt a burning sensation that radiated from the right side of his back to the toes. An MRI of the lumbar spine revealed a 4-mm extreme right posterolateral disc herniation at L5-S1; his EMG/NCV studies were reported normal. The patient was treated with conservative care, including physical therapy. The patient also underwent lumbar epidural steroid injections and a work-hardening program. There are no pending surgeries currently.
Today, the patient complains of pain in the low back and right leg with occasional numbness, tingling, burning, and pins and needles in the right leg. On examination, he was noted to have mildly decreased range of motion; the Straight Leg Raise test was negative bilaterally. His neurological examination was normal. Has the patient reached MMI?
Yes, the patient has reached MMI due to the following considerations:
The claimant was diagnosed with a lumbar sprain with radicular symptoms eight months ago.
The claimant received all the necessary and appropriate treatment according to the treatment guidelines.
The claimant’s symptoms have been stable and unchanged for the last several weeks.
No additional treatment is planned, which is likely to cause a further functional improvement of the claimant.
Example Case 2: History of severe ankle sprain
The patient reported that he slipped on a wet floor and sprained his left ankle at work. An MRI of the left ankle revealed avulsion of the anterior/inferior tibiofibular ligament. The examinee underwent surgery for ligament repair and ankle stabilization two months ago. He presented today with complaints of pain in the left ankle and foot. The examinee ambulated into the examination room with a slow gait using crutches. He was noted to have a partially healed surgical scar on the left lateral malleolus, with edema and tenderness; he was also noted to have decreased joint range of motion. Has the patient reached MMI?
No; the examinee has not reached MMI due to the following considerations:
The examinee is eight weeks status post left ankle surgery for acute ankle sprain. He was found to have functional limitations, including the inability to walk without the help of crutches.
He has completed 20 physical therapy sessions for post-operative rehabilitation, resulting in gradual improvement.
The treatment guidelines allow up to 34 sessions of PT over 16 weeks for post-surgical treatment of severe ankle ligament injury. Thus, the patient should undergo additional physical therapy for the further improvement of his functional capacity.
Patel AT, Haig AJ, Cook, M: Assessment Tools for Musculoskeletal Impairment
Rating and Disability Assessment. In: Robert Rondinelli and Richard Katz (eds):
Impairment Rating and Disability Evaluation. Philadelphia, W.B. Saunders
Company, 2000; pp. 55-71
Talmage JB. Assessment and Management of Upper and Lower Extremity
Impairment and Disability. Occupational Medicine: State of the Art Reviews. 2000;
15(4): 771- 788
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