(Golden Oldie) Connective tissue injury in calf muscle tears and return to play: MRI correlation

Key points

1. 01The researchers proposed a new MRI grading system (grade 0 to 3) based on how badly the muscle's connective tissue scaffold is injured, not just the muscle fibres.
2. 02Higher injury grades were strongly linked to longer time to return to play, with grade 0 averaging 8 days and grade 3 averaging 48 days.
3. 03Connective tissue was involved in 63 of 100 patients, and complete failure (grade 3) in 18.
4. 04The soleus muscle was the most commonly injured calf muscle, though gastrocnemius injuries were more likely to be the severe grade 3 type.
5. 05Findings come mostly from elite and professional athletes, so they may not transfer directly to recreational exercisers.

How it was conducted

Design

Retrospective MRI evaluation of consecutive patients, with a newly proposed grading system

Participants

100 patients aged 20 to 49 (mean 30.5 years), 89 men and 11 women, mostly professional or elite athletes, with acute calf tear within the prior 2 weeks

Imaging

3T MRI with a surface coil, read by consensus of three musculoskeletal radiologists blinded to clinical history and outcome

Grading

Each tear graded 0 to 3 by degree of myofibril and connective tissue (epimysium, aponeurosis, intramuscular tendon) injury

Primary outcome

Time to return to play, defined as days from injury to return to full competition

Analysis

Analysis of variance comparing mean return to play across injury grades (SPSS V.23)

What they found

• In 100 patients, 114 injuries were detected; connective tissue involvement was seen in 63 of 100 patients and failure (grade 3) in 18.
• Mean time to return to play was 8.1 days (SD 7.45) for grade 0, 17.17 days (SD 8.84) for grade 1, 24.69 days (SD 9.71) for grade 2 and 48 days (SD 15.95) for grade 3 (p<0.001).
• Across all calf muscles there were 8 grade 0, 29 grade 1, 45 grade 2 and 18 grade 3 injuries.
• Of 114 muscle tears, 79 (69.3%) were in the soleus, 31 (27.2%) in the medial gastrocnemius and 4 (3.5%) in the lateral gastrocnemius.
• Of 79 soleus tears, 43 (54.4%) involved the proximal soleus and 36 (45.6%) the distal soleus.
• For soleus-only injuries (n=66), mean return to play was 9 days (SD 7.58) for grade 0, 16 days (SD 6.61) for grade 1, 23.2 days (SD 10.66) for grade 2 and 52 days (SD 15.19) for grade 3.

Limitations

• Most patients were professional or elite athletes, so the findings may not apply to the general population.
• Higher grade injuries may be over-represented because more severe clinical cases were more likely to be referred for MRI.
• MRI was graded by consensus of three radiologists, so intraobserver and interobserver reliability is unknown.
• Doctors deciding return to play were not blinded to the MRI findings, and patients were not followed for reinjury.

Why it matters

For patients

If you tear a calf muscle, an MRI can give your medical team a clearer estimate of how many days or weeks you may need before returning to sport.

For clinicians

Grading the integrity of the calf connective tissue on MRI, rather than just measuring oedema or tear size, may better predict rehabilitation duration in athletes.

For readers

This introduces a connective-tissue-based MRI grading scheme for calf tears, but it rests on one retrospective athlete cohort and needs prospective validation.