Quantifying the 'law of diminishing returns' in magnetically controlled growing rods.

AIMS: 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. PATIENTS AND METHODS: 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. RESULTS: The mean follow-up was 30 months (6 to 57). There was a significant decrease in the mean T/I ratio over time (convex rod at 3 months 0.81, sd 0.58 vs 51 months 0.17, sd 0.16, p = 0.0001; concave rod at 3 months 0.93, sd 0.67 vs 51 months 0.18, sd 0.15, p = 0.0001). A linear decline of the mean T/I ratios was noted for both convex rods (r2 = 0.90, p = 0.004) and concave rods (r2 = 0.81, p = 0.015) over 51 months. At the 24-month follow-up stage, there was a significant negative correlation between the mean T/I ratio of the concave rod with weight (r = -0.59, p = 0.01), age (r = -0.59, p = 0.01), and BMI of the child (r = -0.54, p = 0.01). CONCLUSIONS: The 'law of diminishing returns' is also seen after serial distraction using MCGR. Compared to previously published data for CGRS, there is a gradual linear decline rather than a rapid initial decline in lengthening. In older, heavier children a reduced distraction ratio in the concave rod of the MCGR device is noted over time. Cite this article: Bone Joint J 2017;99-B:1658-64.

Is there an association between the individual anatomy of the scapula and the development of rotator cuff tears or osteoarthritis of the glenohumeral joint?: A radiological study of the critical shoulder angle.

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.

Construct validity of a 12-item WOMAC for assessment of femoro-acetabular impingement and osteoarthritis of the hip.

OBJECTIVE: Evaluation of the internal construct validity of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index adapted for use in patients with femoro-acetabular impingement (FAI) and osteoarthritis (OA) of the hip. METHODS: Distribution of a German version of WOMAC to patients upon first consultation. Patients with FAI [n=100, mean age 31.7 years, standard deviation (SD) 9.7] and OA (n=57, mean age 60.3 years, SD 11.7) and without comorbidities or prior hip surgery were included and compared to age- and gender-matched control population to FAI (n=200, mean age 32.6 years, SD 5.6). WOMAC data of 157 questionnaires were evaluated by Rasch analysis using RUMM2020 software. RESULTS: Summation of total WOMAC shows misfit to the Rasch model as well as multidimensionality. While the pain subset shows adequate fit and is unidimensional, item reduction is required to fit a unidimensional subset of functional items to the Rasch model. Summating the two fitting subsets yields again slight model misfit and multidimensionality requiring further item reduction. Finally, a 12-item version of the total WOMAC shows good model fit and unidimensionality, i.e., internal construct validity, for assessment of patients with FAI and OA without differential item functioning (DIF). A person separation index (PSI)=0.93 indicates a high internal consistency reliability for the 12-item subscale. Scores for FAI are significantly higher than control (P<0.001, effect size 0.71) and lower than OA group (P<0.001, effect size 0.45). Adequate statistical power is shown discriminating the three groups, therefore indicating some evidence also for external construct validity. CONCLUSIONS: The WOMAC as a total construct is multidimensional and summating the subsets into a total score is not valid. The reduced 12-item WOMAC is demonstrated to have internal construct validity for assessing patients with FAI and OA on the same scale and high internal consistency reliability. Discrimination of the groups with adequate statistical power also indicates external construct validity.

Radical sternectomy and primary musculocutaneous flap reconstruction to control sternal osteitis.

OBJECTIVE: Sternal osteitis after median sternotomy is associated with considerable morbidity and mortality. The use of muscle and omentum flaps has been proved as valid adjunct to combat these severe infections. In this study we present our experience with a more radical approach. METHODS: Sternectomy consisted of the resection of the entire sternum, including the costochondral arches and the sternoclavicular joints, and was followed by the repair of the defect with musculocutaneous flaps without any restabilization of the thoracic wall. Thirteen patients received a vertical rectus abdominis musculocutaneous flap, 14 patients received a pedicled latissimus dorsi musculocutaneous flap, and 12 patients received a free latissimus dorsi musculocutaneous flap (total of 40 flaps in 39 patients of 66 patients who required surgical revision for sternal osteitis of 6078 total patients with sternotomies). RESULTS: Two patients died within 30 days after the operation (early mortality of 5.1%); however, they did not die of sternal infection, which was cured without any recurrence in all cases. Seventeen patients (44%) required secondary, mostly minor operations for local complications. Despite some paradoxic chest movements, the patient satisfaction rating was unanimously high at the long-term follow-up (0.4 to 8.5 years, median 2.3 years). The short- and long-term complication rates were similar in the three groups. CONCLUSION: We conclude that radical sternectomy and immediate musculocutaneous flap repair provided definitive control of sternal infection in even the most severe cases, thus reducing infection-related mortality. The trade-off was a substantial rate of local complications; however, these did not cause any relevant morbidity.

Entry point soft tissue damage in antegrade femoral nailing: a cadaver study.

INTRODUCTION: Little attention is paid to insertion site morbidity associated with antegrade femoral nailing. However, residual peritrochanteric pain after nailing is not uncommon. Additionally, the end branches of the medial femoral circumflex artery (m.f.c.a.) supplying the femoral head are in close proximity to the insertion site of the nail, and the occurrence of avascular necrosis of the femoral epiphysis after nailing in adolescents is rather frequent. OBJECTIVE: The aim of this study was to assess iatrogenic soft tissue injuries at the site of nail insertion. MATERIALS AND METHODS: Nailing with a reamed AO universal femoral nail was performed on sixteen adult cadavers followed by dissection of the proximal part of the femur to assess possible damage to the soft tissues. Three entry portals were defined. (A) entry portal lateral to the junction of the neck and the greater trochanter; (B) entry portal at the base of the greater trochanter anterior to a line along the longitudinal axis of the femoral neck; and (C) entry portal at the base of the greater trochanter posterior to a line along the axis of the femoral neck (at the piriformis fossa). RESULTS: In Group A, partial avulsion of the piriformis and the obturator internus tendon were present in four and in one of five specimens, respectively. Group B showed injuries to the piriformis tendon in two and to the gluteus minimus tendon in one of four cases. In Group C, partial avulsion of the piriformis, obturator internus, and obturator externus tendon were encountered in five, six, and two of seven specimens, respectively. Anterior branches of the ramus profundus of the m.f.c.a. within the synovial fold were damaged in all of these cases. CONCLUSION: To select the best nail entry portal, the ease of nail insertion must be weighed against the resulting soft tissue damage at the site of insertion. The nail entry portal at the piriformis fossa, although geometrically ideal and most recommended, causes the most significant damage to muscle and tendons as well as to the blood supply to the femoral head. Therefore, even if reported only once, the occurrence of avascular necrosis of the femoral head after nailing in adults is a possible complication of this nail entry portal. The authors therefore prefer to avoid this entry portal in every case. The nail entry portal anterior to the longitudinal axis of the femoral neck, as in group B, although better with respect to the soft tissue damage, has the worst geometric and biomechanical disadvantages. The results of the current study favor the nail entry portal lateral at the greater trochanter as in Group A, which is equal to the entry portal B with respect to the soft tissue damage but allows introduction of the nail into the medullar cavity without difficulties.