MORPHOMETRIC PARAMETERS OF THE GLENOID FOSSA WITH THE LABRUM ATTACHED

La altura y la anchura de la cavidad glenoidea es importante en el reemplazo total de hombro. Estudios previos, utilizando diferentes métodos, han presentado diferencias respecto a la altura y a la anchura de la cavidad glenoidea. El presente estudio tiene como objetivo proporcionar los parámetros morfométricos de la fosa glenoidea con el labrum incluido. Materiales y métodos: Se disecaron y tomaron medidas de ciento cuarenta hombros pertenecientes a 30 varones y 40 mujeres. La cavidad glenoidea se expuso con el labrum incluido y seguido de la medición directa de la altura de la cavidad glenoidea, la anchura y el nivel de máxima anchura usando calibres digitales. Los datos tuvieron doble entrada en el Paquete Estadístico para Ciencias Sociales (SPSS, versión 21). Se utilizaron Kruskal Wallis y análisis de varianza de una sola vía en las pruebas de filas. La significancia estadística se definió como p<0,05. Resultados: Los valores de la altura, anchura y altura a la anchura máxima media para ambos sexos fueron: 38,94 mm, 30,50 mm y 17,14 mm, respectivamente. Sin embargo, la altura media, anchura y nivel de anchura máxima fueron significativamente mayores en los hombres que en las mujeres (p< 0,001 para cada uno). Conclusiones: La altura media, anchura y el nivel de máxima anchura con el labrum glenoideo incluido fueron significativamente mayores en hombres que en mujeres. Esto sugiere que el aumento de la altura y la anchura se debe a que el labrum glenoideo es proporcional a la altura y la anchura de la cavidad glenoidea, teniendo en cuenta la diferencia de los resultados tomados entre varones y mujeres, con o sin el labrum glenoideo incluido.


INTRODUCTION
Glenoid height is the distance between the most superior and inferior points on the glenoid fossa.Based on gender, side and the methodology used mean glenoid height is variable (Table 1).Nevertheless, glenoid height is reported to be greater in males than females, with the difference being significant in some studies (Mallon et al, 1992;Churchill et al, 2001;Checroun et al, 2002;Merrill et al, 2009), but not in others (Iannotti et al, 1992).No difference in glenoid height has been reported between different races (Churchill et al, 2001;Merrill et al, 2009).Kwon et al (2005) reported that measurements taken directly from bone compared to those taken from 3computed tomography scans (3D CT scans) were smaller and concluded that measurements from 3D CT scans were accurate and could be used in the preoperative evaluation of the glenoid fossa.Glenoid width is the distance between the most anterior and posterior points on the glenoid fossa.
Based on gender, side and the methodology used mean glenoid width also appears to be variable (Table 1).Not surprisingly the mean width of the lower half of the glenoid fossa is greater than the upper half with a ratio of 1:0.80±0.01(Iannotti et al, 1992).Significant differences in width between genders have been reported by Mallon et al (1992), Churchill et al (2001), Checroun et al (2002) and Merrill et al (2009), but not between races (Churchill et al 2001;Merrill et al, 2009).De Wilde et al (2004) reported a correlation between glenoid height and width (r=0.77).Previous studies have tended to measure glenoid height and width directly from the scapula or from CT scans.Accurate measurement of the glenoid fossa is critical in glenohumeral joint arthroplasty; furthermore, the glenoid labrum plays an important role in glenohumeral joint stability by increasing the surface area of the articular surface.The current study aims to provide morphometric parameters of the glenoid fossa with the labrum attached.

MATERIAL AND METHODS
One hundred and forty shoulders from 30 males and 40 females Caucasian cadavers (average age 81.5 years: range 53-101 years) were dissected and examined.All muscles and blood vessels surrounding the glenohumeral joint, as well as the fibrous joint capsule, were removed allowing full exposure of the glenoid fossa with the glenoid labrum still attached.
Using a digital caliper, the maximum distance between the most superior and inferior aspects of the glenoid labrum was considered as glenoid height; while the maximum distance between the most anterior and posterior points of the glenoid labrum was considered as glenoid width.
Maximum width was determined by measuring the distance between the mid-point of the maximum width and the most inferior point of the glenoid labrum (Figure 1).

RESULTS
One Way Analysis of Variance on Ranks showed there were no intra or inter-observer differences in measurements taken, suggesting that the measurement methodology used was reliable and repeatable.
The overall mean height, width and level of maximum width were 38.94 mm, 30.50 mm and 17.14 mm, respectively.However, when considered separately the mean height, width and level of maximum width were all significantly greater in males than females (P<0.001 for each).In both genders there was no significant side to side difference in all measured parameters (Table 2).

DISCUSSION
The height of the glenoid fossa reported in the literature varies.While the current observations respect to glenoid height in males is similar to previous reports, it is distinctly different in females (Mallon et al, 1992;Churchill et al, 2001;Checroun et al, 2002;Merrill et al, 2009).The current study also supports earlier observations that glenoid height is greater in males than females (Mallon et al, 1992;Churchill et al, 2001;Merrill et al, 2009), with the glenoid labrum attacged being 42.21 mm and 36.63 mm respectively.The glenoid labrum therefore increases glenoid height and as such increases the articular surface area thus enhancing joint stability.The significant difference in glenoid height between males and females with the labrum attached suggests that the thickness of the labrum is proportionate to the height of the glenoid fossa.
It can be argued that glenoid height could be affected by degenerative diseases; however, Bicknell et al (2007) found that mean glenoid height showed no difference with respect to osteoarthritis or gender.One criticism concerns the potential difference in the measurement of  (Mallon et al, 1992;Churchill et al, 2001;Checroun et al, 2002;Merrill et al, 2009).
According to Iannotti et al (1992)   In summary the mean height, width and level of maximum width of the glenoid fossa with the labrum attached were 38.94 mm, 30.50 mm and 17.14 mm respectively, being significantly greater in males than females (P<0.001 for each).
Compared to previous studies, the current study suggests that the increase in height and width provided by the glenoid labrum is proportionate to its height and width, thus accounting for why the difference between males and females remains irrespective of whether the glenoid labrum is present or not.The current study also supports the concept that the glenoid labrum provides stability to the glenohumeral joint by increasing the articular surface area.It is suggested that further research should be conducted to improve prosthetic glenoid design and fixation in total shoulder arthroplasty.
repeatability and reliability of the taken measurement was determined by randomly selecting shoulders from the study cohort.Three measurements were taken on a three separate occasions by the researcher and by two other individuals on two separate occasions.

Figure 1 -
Figure 1-Measurement of the glenoid fossa with the glenoid labrum attached.

Table 1 -
Comparison of glenoid height and width (mm) in different studies; M: males; F: females; Nº: number.

Table 2 -
Measurements of the glenoid fossa parameters in both genders; H: height; W: width; LW: Level at maximum width.Measured parameters are significantly different.