髋臼杯内螺钉孔簇:螺钉孔最佳定位的形态学研究

髋臼杯内螺钉孔簇:螺钉孔最佳定位的形态学研究Screw-hole clusters in acetabular cups: a morphological study of optimal positioning of screw-holes

Yin X, Zhou Y, Tang Q, Yang D, Tang H, Huang X. Screw-hole clusters in acetabular cups: a morphological study of optimal positioning of screw-holes[J]. Hip Int, 2017,27(4): 382-388.

转载文章的原链接1：

https://pubmed.ncbi.nlm.nih.gov/28218378/

转载文章的原链接2：

https://sage-cnpereading-com.vpnm.ccmu.edu.cn/paragraph/download/?doi=10.5301/hipint.5000471

Abstract

Background: Rigid and safe transacetabular screw fixation in total hip arthroplasty (THA) is achieved by pursuing deeper bone stock and avoiding injuries to the neurovascular structures, but these efforts can be restricted by the distribution of screw-holes on cups by the manufacturer. We therefore tried to determine: (i) optimal screw-hole positions on cups to allow anatomical placement of screws; (ii) rationality of the basic 3-screw-hole cluster on commercial cups; and (iii) the optimum method for placing commercial cups in accordance with acetabular anatomy.

Methods: Periacetabular osseous structure of 64 hips and arterial structures of 50 hips were three-dimensionally reconstructed. Simulated transacetabular screw fixation during THA was performed in these hips with 3 different screw lengths (15, 25, and 35 mm) to define deeper and safer screw trajectories. Screw-hole locations of 7 commercially available cups were measured and matched with the periacetabular anatomy.

Results: When the cup was placed into the acetabulum at 45° of abduction and 20° of anteversion, the optimal locations of 2 screw-holes on the cups were at 30° and 64° of latitude, with a 35° separation angle. The inverse triangle distribution pattern was safer than the triangle pattern in basic 3-screw-hole-cluster cups. When placing the commercial cups, 5°-10° of anterior rotation can be added to allow better screw trajectories.

Conclusions: Our study determined optimal screw-hole positions and their distribution pattern on cups. We describe methods to place the commercial cups that are not designed according to acetabular anatomy.

Keywords: Acetabular cup, Screw-hole, Total hip arthroplasty, Transacetabular screw fixation

Fig. 1 - Simulated surgery was performed with the measurement of periacetabular bone stock and checking for safe zones for screw fixation.

(A) The Lats (latitudes) of screws that were about to pierce bone cortex. RC = rotation centre.

(B) There were 36 half-planes positioned at 10° intervals. We defined the plane passing through the ASIS (anterior superior iliac spine) as 0° Lon (longitude). The Lon value increased counterclockwise.

(C) Using 30° and 60° latitude lines and longitude lines at 10° intervals, we divided screw placement direction into 108spatial areas (3 × 36). In the posterosuperior and posteroinferior quadrants, we subdivided the pole region with a 75° latitude line. We obtained a total of 126 spatial areas (3 × 36 + 18).

Fig. 2 - 2-D topographical map according to the 3-D depth of bone stock.

In Panel A, rotatable angles (RA) and centre longitudes (CL)of 35-mm screws in different latitudes were measured. The grey area is 35-mm bone stock area.

In Panels B and C, different depth of bone stock was delineated and 2 optimal screw-hole locations were demonstrated, and 2 possible ways to locate the 3rd screw-hole are shown. In Panel B, the rim-hole, pole-hole, and 3rd hole together form the inverse triangle pattern.

In Panel C, the midpoint of the 2 optimal holes is first located; the latitude and longitude degrees of the midpoint are the average value of the 2 holes. Mirror imaging of the mid-point is then done to determine the 3rd hole through which the screw can pursue much deeper bone stock. ASIS = anteriorsuperior iliac spine.

Fig. 3 - Rotatable angles changed along with the latitude in 35-mm bone stock. 4 curves of different colours represent different groups: blue = male group; red =female group; green = large acetabulum group (from 52 mm to 58 mm); purple =small acetabulum group (from 44 mm to50 mm). The curves in each group represent a 2-peak trend.

TABLE I - Case numbers of peak rotatable angles in different latitudes

All cases are included in 2 boxes (Near Rim Box and Near Pole Box). The 2 boxes are independent.

*Central latitude in the grey range near rim.

**Central latitude in the grey range near pole. The grey range in each group represents the centralised tendency of latitudes that had the most peak values of rotatable angles.

Fig. 4 - Screw-hole distribution patterns (A) and anatomy-based placement of the screw-holes in the commercial cups (B).

In Panel A, the triangle pattern (A-1) and the inverse triangle-pattern (A-2) are shown.

In Panel B-1 and B-2, 3 screw-holes represent triangle-pattern cups, and a Pinnacle cup was used as an example to demonstrate this pattern.

In Panel B-1, the rim-hole and posterior pole-hole (2 small circles)are used and the midpoint of the 2 (the small triangle) sits on the centre longitude line of 35 mm bone stock. Thus, the deepest bone stock was pursued by 2 screws. The anterior pole-hole (the circle with cross) should not be used.

In Panel B-2, when all 3 holes are to be used, the cup can be rotated backward to allow all holes avoid the dangerous anterior-superior quadrant.

In Panel B-3, 3 holes represent inverse triangular-pattern cups and an Option cup was used as an example. The pole-hole and anterior rim-hole (2 small circles) are used, and the cup was rotated to locate these 2 holes like in Panel B-1. When all 3 holes are used, the posterior pole-hole (the circle with a cross) may also be used safely in this rotating position of the cup. The α angle in B-1 and B-3 represents the anterior rotation angle of the midpoint from the superior direction of the cup. ASIS = anterior superior iliac spine.

TABLE II - Placement of the commercial cups in the acetabulum making 2 screw-holes pursue deepest bone stock

*When 1 of the 2 selected screw-holes sits on the centre longitude line of the deepest bone stock, longitudinal distance from the other screw-hole to the centre longitude line is measured.

**Midpoint of 2 selected screw-holes that can sit on the deepest bone stock simultaneously.

***When the midpoint of 2 selected screw-holes sits on the centre longitude line of the deepest bone stock.

Our study defined optimal screw-hole positions and their distribution pattern on cups. Screw-holes in commercial cups are not currently designed according to acetabular anatomy. Our findings may provide a reference for the design screw holes in new cups in the future.