Adult thigh muscle injuries-from diagnosis to treatment: what the radiologist should know

Muscle Healing in Sports Injuries: MRI Findings and Proposed Classification Based on a Single Institutional Experience and Clinical Observation

MRI plays a crucial role in assessment of patients with muscle injuries. The healing process of these injuries has been studied in depth from the pathophysiologic and histologic points of view and divided into destruction, repair, and remodeling phases, but the MRI findings of these phases have not been fully described, to our knowledge. On the basis of results from 310 MRI studies, including both basal and follow-up studies, in 128 athletes with muscle tears including their clinical evolution, the authors review MRI findings in muscle healing and propose a practical imaging classification based on morphology and signal intensity that correlates with histologic changes. The proposed phases, which can overlap, are destruction (phase 1), showing myoconnective tissue discontinuity and featherlike edema; repair (phase 2), showing filling in of the connective tissue gaps by a hypertrophic immature scar; and remodeling (phase 3), showing scar maturation and regression of the edema. A final healed stage can be identified with MRI, which is characterized by persistence of a slight fusiform thickening of the connective tissue. This information can be obtained from a truncated MRI protocol with three acquisitions, preferably performed with a 3-T magnet. During MRI follow-up of muscle injuries, other important features to be assessed are changes in muscle edema and specific warning signs, such as persistent intermuscular edema, new connective tear, and scar rupture. An understanding of the MRI appearance of normal and abnormal muscle healing and warning signs, along with cooperation with a multidisciplinary team, enable optimization of return to play for the injured athlete. ©RSNA, 2024 See the invited commentary by Flores in this issue.

Reinjury Following Return to Play

Radiologists are frequently called on for guidance regarding return to play (RTP) for athletes and active individuals after sustaining a musculoskeletal injury. Avoidance of reinjury is of particular importance throughout the rehabilitative process and following resumption of competitive activity. Understanding reinjury risk estimation, imaging patterns, and correlation of clinical and surgical findings will help prepare the radiologist to identify reinjuries correctly on diagnostic imaging studies and optimize management for a safe RTP.

MRI findings prior to return to play as predictors of reinjury in professional athletes: a novel decision-making tool

BACKGROUND

Because MRI has shown great accuracy in assessing acute muscle injuries, identification of risk factors for reinjury before return to play (RTP) in professional athletes during the healing process could be very relevant. We assessed the value of MRI findings prior to RTP as predictors of reinjury.

METHODS

Retrospective observational study of 59 professional athletes, mean age 26 years, with first-time acute muscle injury and successful rehabilitation ready to RTP. They underwent MRI within 6 days of the injury and within 7 days prior to RTP. The primary outcome was reinjury. Risk of reinjury was assessed using radiological signs in control MRI scans before RTP. The risk was classified as low, medium or high when none, one or two radiological signs were observed, respectively.

RESULTS

Reinjury occurred in 9 participants, with a rate of 15.2%. None of the baseline MRI-related variables was significantly associated with reinjury. In the control MRI scan performed within 7 days prior to RTP, three independent findings were significantly associated with reinjury. These included transversal and/or mixed connective tissue gap (p = 0.002), intermuscular oedema (p = 0.015) and callus gap (p = 0.046). In the predictive model of the risk of reinjury, the presence of two of these radiological signs, together with interstitial feathery oedema, was associated with a high risk of recurrence (OR 29.58, 95% CI 3.86-226.64; p = 0.001).

CONCLUSIONS

In professional athletes with acute muscle injuries of the lower limbs successfully rehabilitated, some radiological signs on MRI performed shortly before RTP were associated with a high risk of reinjury.

Intratendinous hamstring injuries: sequential MRIs as a tool to reduce the risk of reinjury in elite sport

Hamstring injuries are the most common muscle injuries in elite football. Injuries involving the intramuscular tendon are considered more significant, with longer return to play (RTP) times and an increased risk of reinjury. MRI is the gold standard investigation for muscle injuries, but initial findings cannot accurately determine RTP times. The role of MRI in monitoring muscle and tendon healing is not well described. We present three cases of hamstring injuries with intramuscular tendon involvement, illustrating the changes seen on MRI during progressive tendon healing and describing how we utilised this information to inform safe rehabilitation progression. We conclude that intramuscular hamstring tendon healing can be accurately seen on sequential MRI scans and that this information, when combined with traditional rehabilitation markers in and elite sport environment, can be utilised by clinicians to determine the earliest but safe RTP.

Role of ultrasound and magnetic resonance imaging in the prognosis and classification of muscle injuries in professional football players: correlation between imaging and return to sport time

Purpose

To study distractive muscle injuries applying US and MRI specific classifications and to find if any correlation exists between the results and the return to sport (RTS) time. The second purpose is to evaluate which classification has the best prognostic value and if the lesions extension correlates with the RTS time.

Methods

A total of 26 male, professional soccer players (age 21.3 ± 5.6), diagnosed with traumatic muscle injury of the lower limbs, received ultrasound and MRI evaluation within 2 days from the trauma. Concordance between US and MRI findings was investigated. The relationships between MRI and US based injury grading scales and RTS time were evaluated. Correlation between injuries’ longitudinal extension and RTS time was also investigated.

Results

The correlation between US and MRI measurements returned a Spearman value of r_s = 0.61 (p = .001). Peetrons and Mueller-Wohlfahrt grading scales correlations with RTS time were r = 0.43 (p = .02) and r = 0.83 (p =  < .001). The lesion’s extension correlation with RTS time was r = 0.63 (p < .001). The correlation between the site of the lesion and its location with the RTS time were r_s = 0.2 and r_s = 0.25.

Conclusions

Both US and MRI can be used as prognostic indicators along with the Peetrons (US) and the Mueller-Wohlfahrt (MRI) classifications. MRI is more precise and generates more reproducible results. The lesion craniocaudal extension must be considered as a prognostic indicator, while the injury location inside the muscle or along its major axis has doubtful significance.

Sports-related lower limb muscle injuries: pattern recognition approach and MRI review

Muscle injuries of the lower limbs are currently the most common sport-related injuries, the impact of which is particularly significant in elite athletes. MRI is the imaging modality of choice in assessing acute muscle injuries and radiologists play a key role in the current scenario of multidisciplinary health care teams involved in the care of elite athletes with muscle injuries. Despite the frequency and clinical relevance of muscle injuries, there is still a lack of uniformity in the description, diagnosis, and classification of lesions. The characteristics of the connective tissues (distribution and thickness) differ among muscles, being of high variability in the lower limb. This variability is of great clinical importance in determining the prognosis of muscle injuries. Recently, three classification systems, the Munich consensus statement, the British Athletics Muscle Injury classification, and the FC Barcelona-Aspetar-Duke classification, have been proposed to assess the severity of muscle injuries. A protocolized approach to the evaluation of MRI findings is essential to accurately assess the severity of acute lesions and to evaluate the progression of reparative changes. Certain MRI findings which are seen during recovery may suggest muscle overload or adaptative changes and appear to be clinically useful for sport physicians and physiotherapists.