Study Of Ultrasound Locating And Clinical Anatomy For Sustentaculum Tali

Objective:Calcaneal fractures are the most common tarsal bone fractures(about 60%),The majority of calcaneal fractures are intra-articular fractures,Up to 20% of patients have complications, such as traumatic arthritis, and left permanently disabled, and poor prognosis.The premise of good prognosis of intra-articular calcaneal fractures is that making subtalar joint smooth and recover the shape of Calcaneus, giving a strong internal fixation, allowing patients early weight-bearing and take functional exercise as soon as possible. The treatment of intra-articular calcaneal fractures has been debated for many years. Non-surgical treatment is the main treatment of calcaneus fracture in very early stage, then developed for surgical treatment gradually. In the nearly 20-30 years, with the rapid development of imaging and internal fixation technology, open reduction and internal fixation with steel plate has been recognized by the vast majority of scholars, and became a standard treatment. Due to the special anatomical structure of the sustentaculum tali, the medial calcaneal fracture block has almost non-displacement in calcaneal fractures. The interior trabecular bone of the sustentaculum tali is dense,So the screw can pass the plate into the sustentaculum tali after reduction will make it more stable.There are many arteriovenous,nerves and tendons in the medial of the calcaneus,so Lateral approach is often adopted in operation.but the sustentaculum tali is located in the medial and can not be exposed directly from lateral approach,wrong enter point and angle may injure the important structural in the medial of calcaneus and traumatic arthritis caused by screw in the inferior articular surface. Exactly locating sustentaculum tali on body surface is of great help to place sustentaculum tali screw exactly whichmany scholars in study of it.This test using protruded sustentaculum tali on the medial of calcaneus to locate exactly with ultrasound technique,and propose new method of placing sustentaculum tail screw exactly.Through the observing the trabecular bone of calcaneus density area, bone cortex and and trabecular bone density area of the sustentaculum tali by section anatomy and measure the angle & length of K-wire which was pulled through the sustentaculum tali to the points which offten used to enter the screw on lateral wall of the calcaneus.It is provided theoretical basis for operation and improve operation accuracy.Methods:1 10 adult lower limbs specimens were chosen to be located sustentaculum tali separately by ultrasound. Find the center of sustentaculum tali, percutaneous inject K-wire, anatomy and verify. 2 Then 40 adult calcaneus dried specimens were chosen,the articular surface of the calcaneus were divided into two parts,Gissane angle is considered as lowest point, and marked Point A(lowest point), Point B(midpoint),Point C(highest point), and make vertical line along Point A,B,C separately and intersected with calcaneus bottom point marked D,E,F. Measure the center of segment AD and marked Point G. Measure quartiles points of the segment CF and marked Point L,H,M. GH and BE is intersected by Point I. Measure center of IB and IE and marked Point J,K.Then K-wire were pulled through the sustentaculum tali center to Point J,H,K,G,I,L,M on calcaneus lateral wall and make the distance between K-wire and subtalar joint surface/calcaneus lateral wall bottom are all more than 5mm. Then measure the angle of K-wire and coronal plane /horizontal plane(accurate to 1°) and the length which can not exceed sustentaculum tali lateral cortex(accurate to1mm). Record test data and photo. The measurement results were registered and all of data were analyzed by SPSS 17.0 statistical software. 3 Dissect wet specimens and observe surrounding structure of sustentaculum tali. Make section anatomy of calcaneus dry specimens and observe trabecular bone density area and structure.Results:1 The location of sustentaculum tail of all the lower limb specimens detected by ultrasound coincide with that of anatomy results completely. 2 Data of each point measured by K-wire which was pulled through the sustentaculum tali to the lateral wall of the calcaneus are as follows:In the back line CF, the downward angle of the sustentaculum tali to three points L、H、M were(1.9 ± 0.83)°、(16.3 ± 3.37)°、(31.9 ± 6.59)°respectively, in the middle line BE, the downward angle of the sustentaculum tali to three points J 、 I 、 K were(12.0 ± 3.78)° 、(23.3± 3.88)° 、(33.4 ± 4.34)°respectively,the downward angle of the sustentaculum tali to G point was(30.4± 4.17)°,The backward angle of the sustentaculum tali to H, I, G points were(20.1 ± 3.23)°、(8.4 ± 3.17)°、(-6.4 ± 3.82) °respectively. The length of K-wire:points J and M to the sustentaculum tali were about 35 mm and 43 mm respectively, other points were between 39-41 mm. 3 The sectional anatomy showed the trabecular bone of calcaneus density area are under the calcaneocuboid articular surface and subtalar articular surface, the tuberosity part of the calcaneus.The sectional anatomy showed the sustentaculum tali had thicker cortical bone and density trabecular which were connected with calcaneal mound department.Conclusions:1 The position of sustentaculum tail in surface could be detected accurately with ultrasound technique. 2 Anatomy observations of sustentaculum tali surrounding structure and internal trabecula bone structure proved that sustentaculum tali was an ideal place for the placement of screw during operation. 3 Measuring the parameters of K-wire angle and length from susentaculum tali to calcaneus lateral wall specified points, which can provide certain guidance for placing sustentaculum tali screw during operation.