Humeral retroversion and shoulder muscle changes in infants with internal rotation contractures following brachial plexus birth palsy

AIM To examine humeral retroversion in infants who sustained brachial plexus birth palsy(BPBI) and suffered from an internal rotation contracture. Additionally, the role of the infraspinatus(IS) and subscapularis(SSc) muscles in the genesis of this bony deformation is explored.METHODS Bilateral magnetic resonance imaging(MRI) scans of 35 infants(age range: 2-7 mo old) with BPBI were retrospectively analyzed. Retroversion was measured according to two proximal axes and one distal axis(transepicondylar axis). The proximal axes were:(1) the perpendicular line to the borders of the articular surface(humeral centerline); and(2) the longest diameter through the humeral head. Muscle cross-sectional areas of the IS and SSc muscles were measured on the MRI-slides representing the largest muscle belly. The difference in retroversion was correlated with the ratio of muscle-sizes and passive external rotation measurements.RESULTS Retroversion on the involved side was significantly decreased, 1.0° vs 27.6°(1) and 8.5° vs 27.2°(2),(P < 0.01), as compared to the uninvolved side. The size of the SSc and IS muscles on the involved side was significantly decreased, 2.26 cm2 vs 2.79 cm2 and 1.53 cm2 vs 2.19 cm2, respectively(P < 0.05). Furthermore, the muscle ratio(SSc/IS) at the involved side was significantly smaller compared to the uninvolved side(P = 0.007).CONCLUSION Even in our youngest patient population, humeral retroversion has a high likelihood of being decreased. Altered humeral retroversion warrants attention as a structural change in any child being evaluated for the treatment of an internal rotation contracture.

Acetabular cup version modelling and its clinical applying on plain radiograms

AIM To measure the sensitivity and specificity of the cup version assessment by using only anteroposterior hip and pelvis views, evaluate the incidence of inadequate cup version in patients with repeated dislocations after total hip arthroplasty(THA). METHODS Radiographic retrospective analysis of 2 groups of patients, with follow up of 6-60 mo, after undergoing primary THA. First group of 32 patients(20 female, 12 male) with unilateral THA(32 hips) required early revision arthroplasty for reasons of dislocation. The mean age and mode were 59(from 38 to 83) and 66 ages respectively. The average body mass index(BMI) was 24.2(from 17.7 to 36.3), mode 23.9. Second group was consisted of 164 patients(101 female, 63 male) without dislocations during the follow-up period(170 hips). Among them 6 patients required bilateral THA. The mean age was 60(from 38 to 84) and mode 59. BMI was 24.8(17.2-36.8), mode 25.2. Clinical significance of the cup anteversion sign was estimated with cross tabulation 2 × 2. RESULTS The value of the χ~2 yates was 10.668(P < 0.01).Sensitivity of SAI(sign of anteversion insufficiency) was 29%(95%CI: 9%-46%), and specificity was 92%(95%CI: 88%-96%). Relative risk of dislocation in patients with SAI was 3.4(95%CI: 1.8-6.3). CONCLUSION This method provides the surgeons with the ability to perform a reliable and simple qualitative assessment of the acetabular component version. It can be useful during patient examination with early loosening of the implant, dislocations, and impingement. Additionally, it can provide necessary information during planning of revision surgery, especially when considering question about cup replacement, although final assessment of the cup position should be done with a computed tomography scan.