Magnetically controlled growing rods (MCGRs) allow non-invasive
correction of the spinal deformity in the treatment of early-onset
scoliosis. Conventional growing rod systems (CGRS) need repeated
surgical distractions: these are associated with the effect of the
‘law of diminishing returns’. The primary aim of this study was to quantify this effect in
MCGRs over sequential distractions. A total of 35 patients with a maximum follow-up of 57 months
were included in the study. There were 17 boys and 18 girls with
a mean age of 7.4 years (2 to 14). True Distraction (TD) was determined
by measuring the expansion gap on fluoroscopy. This was compared
with Intended Distraction (ID) and expressed as the ‘T/I’ ratio.
The T/I ratio and the Cobb angle were calculated at several time
points during follow-up.Aims
Patients and Methods
We hypothesised that a large acromial cover with
an upwardly tilted glenoid fossa would be associated with degenerative
rotator cuff tears (RCTs), and conversely, that a short acromion
with an inferiorly inclined glenoid would be associated with glenohumeral
osteoarthritis (OA). This hypothesis was tested using a new radiological parameter,
the critical shoulder angle (CSA), which combines the measurements
of inclination of the glenoid and the lateral extension of the acromion
(the acromion index). The CSA was measured on standardised radiographs of three groups:
1) a control group of 94 asymptomatic shoulders with normal rotator
cuffs and no OA; 2) a group of 102 shoulders with MRI-documented
full-thickness RCTs without OA; and 3) a group of 102 shoulders
with primary OA and no RCTs noted during total shoulder replacement.
The mean CSA was 33.1° (26.8° to 38.6°) in the control group, 38.0°
(29.5° to 43.5°) in the RCT group and 28.1° (18.6° to 35.8°) in
the OA group. Of patients with a CSA >
35°, 84% were in the RCT
group and of those with a CSA <
30°, 93% were in the OA group. We therefore concluded that primary glenohumeral OA is associated
with significantly smaller degenerative RCTs with significantly
larger CSAs than asymptomatic shoulders without these pathologies.
These findings suggest that individual quantitative anatomy may
imply biomechanics that are likely to induce specific types of degenerative
joint disorders. Cite this article:
