Glenoid neck length in a healthy population and its association with scapular notching.

BACKGROUND: Scapular notching is a radiographic finding associated with the use of a reverse shoulder prosthesis. The morphological characteristics of the glenoid neck have been scarcely explored as a relevant factor in relation to scapular notching. The objective of this study is to measure the length of the glenoid neck in a three-dimensional CT reconstruction of a healthy population and to simulate the scapular notching free range of motion for the "long neck" and for the "short neck" groups. METHODS: CT scans of 214 shoulders were reviewed, excluding incomplete, poor quality, or altered studies. 100 CT scans were finally processed. The mean age was 51.7 years (SD 19.4; range, 15-84 years), with 49 female and 51 male patients. For each of the scapulae, four morphometric measurements were obtained: anterior glenoid neck (AGN), middle glenoid neck (MGN), posterior glenoid neck (PGN) and alternative posterior glenoid neck (aPGN). Using 3D software, we simulated a reverse shoulder prosthesis, and the scapular notching free range of motion was registered. Differences between measurements were evaluated with an unpaired t-test using StataIC16®. P-values < 0.05 were considered significant. The intraobserver and interobserver correlation was evaluated with the intraclass correlation coefficient. RESULTS: The AGN measured 7.43 ± 2.52 mm (range, 1.72-13.3 mm); MGN measured 8.05 mm ± 1.93 (range, 2.92-13.2 mm); PGN measured 7.26 ± 2.6 mm (range, 2-13.4 mm); and aPGN measured 8.97 ± 2.3 mm (range, 4.08-15.4 mm). The scapular notching free range of motion for the "long neck" group was 74.98° ± 7.35 (range, 55-83°) and for the "short neck" group, it was 62.93° ± 6.84 (range, 45-70°) (p = 0.0004). CONCLUSIONS: Measurement of posterior glenoid neck length exhibits excellent reliability and reproducibility, as well as being associated to the scapular notching free range of motion. STUDY DESIGN: Basic, retrospective, CT images research.

Estimating glenoid fossa width for instability - related bone loss with CT scan in a Chilean sample / Estimación del ancho de la fosa glenoidea para la pérdida ósea relacionada con inestabilidad con tomografía computarizada en una muestra chilena

SUMMARY: Glenoid fossa bone loss has been associated with recurrence and failure after glenoid labrum repair for shoulder instability. Quantification of glenoid fossa bone loss is critical for the successful treatment of glenohumeral instability. The aim of this paper was to estimate a linear regression model based on glenoid height in CT scan adjusted for age and sex to calculate glenoid fossa width in a healthy Chilean sample. CT scans of 101 shoulders were reviewed. The mean age was 51.96 years (SD 19.16; range, 15-88 years) with 53 females and 48 male patients. Studies with signs of bone loss, instability, fracture, or arthritis were excluded. After 3D-CT reconstruction, the height and width of each glenoid fossa was measured using the Owens methodology. All landmarks for the 2 measurements were placed on the most lateral surface of the glenoid fossa margin. Measurements for all shoulders were recorded by 3 observers and repeated on a subset (n = 20) of shoulders, under blinded conditions, by the same observer, at least 2 weeks after the initial measurements. Descriptive statistics, intraclass correlation and regression coefficients were calculated with Stata BE 17® software. A p- value of 0.05 was considered significant. A linear regression model was estimated resulting in the formula "Width = 10.97 + 0.02 * Age + 0.41 * Height - 1.95 * Sex (1=Female, 0=Male)". This model presented all coefficients with p <0.05 and an adjusted R2 of 0.73. Furthermore, it fulfilled the assumption of linearity, normal distribution of errors, independence of errors, and homoscedasticity. Regarding the intraobserver correlation, ICC was 0.76 for height and 0.91 for width; the interobserver ICC was 0.93 for height and 0.86 for width. A 3D-CT specific formula was developed to predict glenoid fossa width based on height with sufficient accuracy to be clinically valuable.

RESUMEN: La pérdida de hueso de la fosa glenoidea se ha asociado con recurrencia y falla después de la reparación del labrum glenoideo por inestabilidad del hombro. La cuantificación de la pérdida ósea glenoidea es fundamental para el tratamiento exitoso de la inestabilidad glenohumeral. El objetivo de este trabajo fue estimar un modelo de regresión lineal basado en la altura glenoidea en una tomografía computarizada ajustada por edad y sexo para calcular el ancho de la fosa glenoidea en una muestra chilena sana. Se revisaron las tomografías computarizadas de 101 hombros. La edad media fue de 51,96 años (DE 19,16; rango, 15- 88 años) con 53 mujeres y 48 hombres. Se excluyeron los estudios con signos de pérdida ósea, inestabilidad, fractura o artritis. Después de la reconstrucción 3D-CT, se midió la altura y el ancho de cada fosa glenoidea utilizando la metodología de Owens. Todos los puntos de referencia para las 2 mediciones se colocaron en la superficie más lateral del margen glenoideo. Las mediciones de todos los hombros fueron registradas por 3 observadores y repetidas en un subconjunto (n = 20) de hombros, en condiciones ciegas, por el mismo observador, al menos 2 semanas después de las mediciones iniciales. La estadística descriptiva, la correlación intraclase y los coeficientes de regresión se calcularon con el software Stata BE 17®. Se consideró significativo un valor de p de 0,05. Se estimó un modelo de regresión lineal que resultó en la fórmula "Ancho = 10,97 + 0,02 * Edad + 0,41 * Altura - 1,95 * Sexo (1 = Mujer, 0 = Hombre)". Este modelo presentó todos los coeficientes con p <0.05 y un R2 ajustado de 0.73. Además, cumplió con los supuestos de linealidad, distribución normal de errores, independencia de errores y homocedasticidad. En cuanto a la correlación intraobservador, el CCI fue de 0,76 para la altura y 0,91 para la anchura; el ICC interobservador fue de 0,93 para la altura y 0,86 para la anchura. Se desarrolló una fórmula específica de 3D-CT para predecir el ancho glenoideo en función de la altura con suficiente precisión para ser clínicamente valiosa.