The purpose of the present investigation was to evaluate muscle damage one year after anterior minimally invasive THA by MRI and to compare these findings with MRI investigations performed in asymptomatic patients one year after THA using a conventional direct lateral approach.

Institutional review board approved this study and patients gave signed informed consent. The minimally invasive group consisted of a consecutive series of 25 patients 1 year after anterior minimally invasive THA. The historic control group consisted of a consecutive series of 25 asymptomatic patients (no pain, no limb, full abduction strength) 1 year after conventional THA. Excluded were patients having prior hip surgery or suffering lumbar spine pathology. Tendon defects and degenerations within the insertion of the Gluteus medius and minimus muscles as well as fatty atrophy within these muscles were recorded according to the protocol of Pfirrmann et al. A Mann-Whitney U Test, two sided t-test and Chi-square test were used for appropriate comparison of quantitative and qualitative variables, respectively.

In terms of gender, age, BMI and side no significant differences were shown between the two groups. When compared to the conventional group, tendon defects, diameter changes and signal alterations of the Gluteus medius and minimus insertion were significantly less frequent in the minimally invasive group (p= 0.001–0.03). Fatty atrophy within the gluteus minimus and gluteus medius musculature was significantly less in the minimally-invasive group (p=0.001–0.04).

In terms of structural damage to muscles and tendons of the hip abductors, the anterior minimally invasive approach proves to be less invasive than the direct lateral approach.

After THR, trochanteric soft tissue abnormalities may be associated with residual trochanteric pain and limping. However, normal MR appearance of the trochanteric region after THR is not known. The aim was to evaluate MR imagings in asymptomatic and symptomatic patients after THR through a transgluteal approach.

Triplanar MR images of 25 asymptomatic (14 men, mean age 60.4 years, 11 women, mean age 60.2) and 49 symptomatic patients (19 men, mean age 62.7 years, 20 women, mean age 64.3) at least 1 year after THR were analyzed by two blinded radiologists. In 14 symptomatic patients MR imaging was correlated to surgical findings.

Tendon defects were uncommon in asymptomatic and significantly more frequent in symptomatic patients (gluteus minimus 8% vs. 56%, p< 0.001; lateral gluteus medius 16% vs 62%, p< 0.001; posterior gluteus medius 0% vs18%, p< 0.025). Signal changes within tendons were very frequent in both groups except for the posterior gluteus medius tendon which demonstrated this finding more frequently in symptomatic patients (20% vs 59%, p=0.002). Changes in tendon diameter were very frequent in both groups but significantly (p=0.001–009) more frequent in symptomatic patients. Fatty atrophy was evident in the anterior two thirds of the gluteus minimus muscle in both asymptomatic and symptomatic patients. In the posterior superior third of the gluteus minimus muscle differences of fatty degeneration were significant. Fatty atrophy of the gluteus medius muscle was only present in symptomatic patients. Bursal fluid collections were more frequent in asymptomatic (32% vs 62%, p=0.021). MR diagnosis was confirmed in all 14 patients undergoing revision surgery.

Although more frequent in symptomatic patients many MR findings are frequently found in asymptomatic patients. However, defects of the abductor tendons and fatty atrophy of the gluteus medius and the posterior part of the gluteus minimus muscle are rare in asymptomatic patients.

Background: It is commonly believed that rotator cuff tears do progress in size over time. Recent reports suggest that tear progression may not be necessarily true. It was the purpose of this study to review non-operatively treated isolated supraspinatus tears especially in terms of tear size progression.

Methods: Inclusion criteria were non-operatively treated isolated full-thickness tears of the supraspinatus, MRI at time of diagnosis available, and patients willing to undergo an additional MRI after more than 2 years after diagnosis. Twenty-four patients (20 men, 4 women) with an average at time diagnosis of 51 years identified and reviewed with MRI and clinically based on the Constant score.

Results: The average follow-up was 46 (27–87) months. The Constant score (not available at time of diagnosis) at follow-up averaged 75 points (relative Constant score 86%). Overall the average tear size did not change significantly over time (366mm2 at follow-up versus 393mm2 at time of diagnosis, p > 0.05). In 2 patients the tear was not detectable any longer on MRI suggesting that it was healed, in 7 patients the tear was smaller, in 10 patients it did not change over time and only in 5 patients it progressed.

Discussion and Conclusion: Non-operatively treated isolated supraspinatus tears were unchanged, smaller or even healed in 79% of the patients after a follow-up period of more than 4 years. This suggests that supra-spinatus tears do not necessarily progress over time and even have a potential to heal.