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The Cobb angle measurement is well established for the measurement of coronal deformity aspect of scoliotic curves. The effect of positional differences in relation to the apex side of the scoliosis is not yet fully quantified. While theoretically plausible that positioning error with rotation toward the apex of the scoliosis would decrease the Cobb angle, the relations are not investigated yet and were object of this study. Multiple measurements of the Cobb angle were performed, while turning a spine-pelvic cadaveric specimen with a right-sided thoracic scoliosis of 47° (in neutral position) from 45° to −45° in steps of 5° using biplanar radiography. Statistical methods were applied to find the critical position, in which measurement errors potentially become clinically relevant (Cobb angle deviation >5°). Turning the specimen to the right (toward the apex of the scoliosis) produced during the first −15° of rotation, a Cobb angle ranging from 47° to 45°. At −20°, the Cobb angle was 42°, at −25° rotation 37° and at −30° rotation 36°. Above −30° rotation, the measured Cobb angle decreased to 36° (77 % of the original Cobb angle). No relevant differences were found by rotating the specimen to the left (away from the apex) (47° at neutral rotation and 44° at maximal error rotation of +45°). The influence of rotational misplacement of the patient at the time of image acquisition on Cobb angle measurements is negligible for a rotational misplacement of ±20° of rotation for a idiopathic right-sided thoracic scoliosis of 47°. Over 20° of rotational misplacement of the patient toward the apex of the scoliosis falsely decreases the Cobb angle.

Background: Recurrence of anterior shoulder instability after operative repair is an uncommon but disabling condition for which treatment options have been insufficiently studied. Coracoid transfer as described by Latarjet is a highly successful primary operation for recurrent anterior shoulder instability. The purpose of this study was to verify the hypothesis that this procedure is also effective for treating recurrent glenohumeral instability after previous operative repair. Methods: Forty-nine consecutive patients with either one (n = 32), two (n = 12), or at least three (n = 5) previous stabilizations other than a Latarjet procedure and recurrence of anterior glenohumeral instability associated with a lesion of the anterior aspect of the glenoid rim had revision with a coracoid transfer as described by Latarjet. Clinical outcomes at a mean of thirty-eight months postoperatively included the subjective shoulder value, the Constant-Murley score, and glenohumeral stability. Standardized anteroposterior and axial radiographs before and after the Latarjet revision were used to grade the degree of glenohumeral osteoarthritis. Results: The results in all forty-nine patients were reviewed. No shoulder redislocated, subluxations recurred in two patients, and five patients reported slight, unspecified shoulder symptoms. No revision surgery was needed. Forty-three shoulders (88%) were subjectively graded as excellent or good; three, fair; and three, poor. Dissatisfaction was associated with persistent pain, and patients with preoperative pain had a twentyfold higher probability of having postoperative pain. The mean subjective shoulder value increased from 53% preoperatively to 79% at the time of follow-up (p < 0.001), and the Constant-Murley score remained high (80% preoperatively and 85% at the time of follow-up; p = 0.061). Optimal graft placement was obtained in thirty cases and was related to better clinical outcome and less progression of osteoarthritis than was suboptimal graft placement. Conclusions: Coracoid transfer as described by Latarjet can effectively restore anterior glenohumeral shoulder stability if previous operation(s) have failed to do so. If recurrence is associated with chronic pain, the pain is likely to persist and compromise the subjective outcome. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.