喙突血运支配特点及Latarjet手术截骨后骨块血运变化的研究

目的研究喙突的血运支配特点，明确Latarjet喙突截骨转位术后喙突移植骨块的血运剩余情况。 方法解剖5例防腐上肢标本，观察营养喙突的穿支血管来源及其支配情况；16例新鲜冷冻肩关节标本用于Micro-CT血管造影及三维重建。其中，8例新鲜标本为完整组进行血管造影扫描，统计喙突各侧面滋养孔的数目、直径。8例配对的肩关节标本按标准Latarjet手术进行喙突根部截骨，仅保留联合腱为截骨组，用于研究截骨喙突的剩余血运状态并与完整组进行对比。 结果胸肩峰动脉分支以及腋动脉第二段发出的分支为喙突较为恒定的穿支营养动脉；完整喙突的内侧面、下表面的滋养孔数目、直径分别大于外侧面、上表面的对应指标，差异有统计学意义（P<0.05）。1例截骨组的移植骨块可见残余的联合腱来源血管从下壁穿入骨块，余例数均未见造影成功的、从喙突尖（联合腱附着点）穿入的动脉。截骨后骨块的血管体积密度与完整组的血管体积密度差异有统计学意义。 结论喙突作为一个血运丰富的结构，胸肩峰动脉分支以及腋动脉第二段的分支较为恒定的营养支，其内侧面、下表面的血运分别比外侧面、上表面的丰富。在所能达到的灌注条件下，当行Latarjet手术截骨转位后，传统Latarjet术后固定的移植骨块为无血运结构。

Study on the characteristics of coracoid blood supply and its changes after Latarjet osteotomy

BackgroundThe shoulder joint has the largest range of motion among all joints. Due to the anatomical and physiological characteristics of shoulder joint, shoulder dislocation accounts for about 50% of all joint dislocations, which is the most common dislocation. It has been reported in literature that the incidence of shoulder dislocation every year reaches 23.1/100 000. Currently, there are various treatment methods for the anterior dislocation of shoulder joint. However, for young patients with high exercise requirement or with defect area over 25%, Latarjet surgery is an effective procedure for treatment of the recurrent anterior dislocation of shoulder joint. The surgery was firstly proposed by French physician Latarjet in 1954. The main concept of operation is to cut off the apex of coracoid process adjacent to the glenoid, and then the bone graft is transferred to the anterior and inferior aspects of the defect to repair the defect of glenoid, which helps to stabilize the humeral head. Many patients have been benefited from the invention of this surgery. With the development of arthroscopic technique, the operation can be completed under arthroscopy. Meanwhile, Latarjet surgery takes less time, and its incision is smaller. Currently, there are many literature reports, and some patients have serious complications such as bone graft absorption and nonunion during the follow-up period of Latarjet, which obviously affects its surgical results. The orthopaedic community has reached a consensus that the blood supply is an important factor affecting tissue healing and growth. Therefore, it is clear that the study of the blood supply characteristics before coracoid osteotomy and its changes after osteotomy may provide a reasonable anatomical basis for the improvement of surgical procedure, which helps to reduce the nonunion, the bone resorption and the occurrence of disease mentioned above and finally improves the efficacy of surgery. This study intends to comprehensively understand the source and direction characteristics of the perforating artery of the coracoid process and to describe the blood supply characteristics of coracoid through the anatomical observation of anti-corrosion shoulder joint specimen and the micro-CT angiography scan of fresh frozen shoulder joint specimen. In the meanwhile, the specific conditions of the blood vessel destruction of coracoid graft by Latarjet surgery are clarified, which provide a reasonable anatomical explanation for the absorption of bone and the occurrence of nonunion after Latarjet operation. Furthermore, this study intends to improve the surgical procedure and transplant protection, and to provide a reasonable anatomical basis for the residual bone blood supply protection. Methods1. Experimental method: Anatomical observation and section observation of anti-corrosion specimens: Five specimens of anti-corrosion upper limb were from the Department of Anatomy of Southern Medical University. The specimens were filled with red latex into the subclavian artery, and then 2 ml of acetic acid was injected to harden the latex; the upper limb specimen was carefully dissected, and the source and characteristic of all visible extra-orbital arteries with a nutritional effect on the coracoid process were observed and recorded. After dissection, a small portion of tissue (about 15 mm) at the interface between conjoint tendon and coracoid was removed, and then soaked in 10% neutral formalin. The interfacial specimen of tendon and bone was decalcified with 7.0% concentrated hydrochloric acid. 48 hours later, it was dehydrated by 70% alcohol for 2 hours and then embedded in paraffin. Finally, a 5 μm thick section was cut along the sagittal plane of the coracoid and then stained with HE. The presence of nutritional artery on the coracoid process was observed under optical microscope. Fresh specimen processing method: (1) Fresh specimen preparation: Eight pairs of fresh frozen shoulder joint specimen (16 in total) were purchased from Southern Medical University's body donation center. This study was approved by the ethics approval committee of the hospital. None of the known shoulder-related disease, congenital shoulder abnormality or shoulder trauma history were found in each shoulder joint specimen. Once obtained, the specimens were disconnected from the junction between ribs and spine so as to keep the ribs on the shoulder joint specimens, and to minimize the damage of arteries and muscles. The forearm was cut at the lower third of humerus completely. (2) Contrast agent preparation: According to the study by Qiu et al, a suspension of 30% nano-scale barium sulfate with 5% gelatin was selected as our arterial contrast agent. The preparation procedure of contrast agent was as follows: 800ml of water was added into a clean beaker container, and heated to 80 Celsius degrees in constant temperature water bath; 40g gelatin (Sigma, V900863) was added in it with continuous stir until dissolved. The solution was pale yellow and transparent; the temperature of water bath was adjusted to 37 ℃. 240 g of nano-sized barium sulfate (Sachtleben, particle size of 700 nm) was added when the temperature of gelatin solution dropped to 37℃. The solution was stirred till the barium sulfate completely dissolved. The final contrast agent suspension was milky white. Fresh specimen perfusion method: (1) Intact group perfusion method: Eight fresh frozen shoulder joint specimens were immersed in the thermostatic waterbath of 37 ℃ for 2 hours to thaw, and to find the exposed end of subclavian artery. A special arterial infusion tube (3 mm in diameter) was placed in the exposed end of the subclavian artery, which was ligated and fixed, and then the tourmaker was ligated with the tourniquet in the middle and lower third of the upper arm; the prepared contrast agent was perfused into the tube at the constant pressure (about 100-110 mmHg) . During the perfusion process, the other arterial stumps should be carefully ligated. Due to the presence of a small amount of muscle stump on the inner side of the specimen, the microvascular stumps leaking in the muscles were heat-seal by thermocoagulation, and thus the perfusion could achieve sufficient pressure in the closed vascular system. The intention was to infuse as much of the tiny arteries in the bone as possible; this perfusion pressure was maintained for approximately 15 minutes. In the end of the perfusion, the special perfusion tube was clamped with hemostat, and the perfused sample was immersed in the thermostatic waterbath of 0℃ for at least 4 hours to fully condense the contrast agent into jelly. (2) Osteotomy group perfusion method: Eight fresh frozen shoulder joint specimens paired with those of the intact group were immersed in the thermostatic waterbath of 37 ℃ for 2 hours to unfreeze. A 5 cm vertical incision was made under the coracoid process, and the subcutaneous fascia and the connective tissue were cut layer by layer. After the exposure to the pectoralis major-delta muscle gap, attention should be paid to the protection of cephalic vein, and then the coracoid tip was found through the pectoralis major-deltoid gap. The acromiocoracoid ligament was exposed in the position of shoulder joint abduction, and then cut off as the insertion in the coracoid side was retained at about 5 mm; then the shoulder joint specimen was placed at adduction and internal rotation to expose the inner structure of the coracoid process. The pectoralis minor muscle was also cut off as its insertion was retained at 5 mm in the coracoid side as well. A micro oscillating saw was used to cut a 2-2.5 cm long coracoid bone in the anterior aspect of the coracoclavicular ligament insertion (depending on the size of the coracoid) , and then the soft tissue (about 2-3 cm outward from the coracoid insertion of conjoint tendon) between conjoint tendon and subscapularis was carefully dissociated, allowing the coracoid graft to be transposed to the corresponding position below the equator in front of the glenoid (3 to 5 o'clock of the right glenoid plane and 7 to 9 o'clock of the left glenoid plane) . During the exposure and dissociation of the coracoid, attention should be paid to ligate the blood vessels visible to naked eye and the broken tissue points as well. Perfusion and freezing treatment were then carried out based on the above-mentioned contrast agent infusion method in the intact group. Specimen acquisition: (1) Specimens acquisition in the intact group: According to the surgical approach described in the osteotomy group, the fresh shoulder joint specimens were dissected and perfused, and the coracoid process was exposed via a vertical small incision below it. The structures (including the acromiocoracoid ligament, pectoralis minor muscle, combined sputum) attached to the coracoid were carefully retained for about 5-10 mm while dissociating the coracoid, as well as a small amount of soft tissue containing blood vessels covered on the surface of the coracoid process. The procedure should be gentle and rapid. The 3-0 silk suture was used to ligate the visible, milky white blood vessels on the coracoid to prevent the contrast agent leakage during dissociation. Finally, the oscillating saw was used to cut the junction between the coracoid and the scapula (About the level of the superior transverse scapular ligament) to obtain the intact coracoid process. (2) Specimen acquisition in the osteotomy group: The conjoint tendon attached to the coracoid was retained for only 3 cm, and then it was cut off to remove the bone graft. Micro-CT scanning and image reconstruction: All the removed bone grafts were scanned in the coronal plane using a small animal Micro-CT (Skyscan 1176, Bruker) with the resolution set to 18 μm. All the scanned BMP format images were imported into NRecon software (Skyscan, Version 1.6.10.1) for reconstruction. The reconstructed TIFF format images were imported into CT-Vox software (supplied by Skyscan) for 3D reconstruction, and the observed perforating vessels were matched for recognition with anti-corrosion specimens; the reconstructed images of the intact group and the osteotomy group were compared to find the changes of angiogenic artery volume. 2. Data collection and statistical analysis: (1) Data collection: The images of sagittal, coronal, and cross-section of the scanned specimen were reconstructed using Data-Viewer software. For the scanned images in the intact group, the coracoid process was approximately divided it into inner, outer, upper and lower surfaces in the two-dimensional coronal section since it was an irregularly shaped bone structure. The number of nutrient foramen on the inner, outer, upper and lower surfaces of the intact coracoid was viewed layer by layer using Data-Viewer software in three directions, and the diameter was measured with CT-analyser software; The complete coracoid process was recorded to analyze the characteristics and differences of blood supply on each surface. The left and right sides of the same fresh specimens was paired with one side in the intact group and the other in the osteotomy group. The CT-analyser software was used to calculate bone volume, arterial volume and arterial volume density (contrast agent volume/bone volume) of the 20 mm long bone from the tip of coracoid process in the coronal plane. A numerical analogy of the blood supply before osteotomy in the intact group of samples from the same pair. The value of the same sample in the intact group was analogous to the blood supply before osteotomy, and the value in the osteotomy group was analogous to the blood supply after osteotomy. The specific changes of bone graft blood supply were compared before and after Latarjet surgery. (2) Statistical methods: The statistical analysis was conducted using SPSS 21.0 software (IBM, Rochester, MN) . The Shapiro-Wilk test was firstly used to check whether the data conformed to the normal distribution; the normal distribution results were expressed as mean ± standard deviation, and the skewed distribution results were expressed as median. The homogeneity test of variance was performed before the statistical test. For paired samples, the paired t test was adopted if the data between the two groups was continuous which conformed to the normal distribution. If the data was discrete or small sample size, then the Wilcoxon signed rank sum test was used. The comparison of two independent samples was performed using two independent sample t-tests. A P value of <0.05 were regarded as statistical significance. Results1. General observation results of anti-corrosion specimens: In the five antiseptic shoulder joint specimens, it was found that the blood supply of the coracoid process was mainly from the thoracoacromial artery and the second branch of the axillary artery. The thoracodorsal artery usually originated from the first segment of axillary artery and travelled outward through the medial side of pectoralis minor muscle. It was then divided into pectoral muscle branch, deltoid muscle branch and acromial branch. Among them, while the acromial branch in 4 specimens traveled through the upper surface of the coracoid, the perforating vessels were inserted to nourish the upper surface of its horizontal portion. No nutritional effect of the acromial branch was seen on the coracoid of 1 specimen. In 2 antiseptic specimens (2/5) , the second segment of the axillary artery emitted a branch vessel, which travelled in the superolateral direction and penetrated into the coracoid from its inferior wall through the gap between the subscapularis and the lower surface of the coracoid. 2. Results of anti-corrosion specimen section: The histopathological sections made of the conjoint tendon-coracoid process interface were removed from the 5 antiseptic specimens, and showed that there were abundant vascular lumen-like structures in the conjoint tendon. However, the cortical bones were intact in all the coracoid tip sections, and no vascular lumen-like structure was found to penetrate into the coracoid for nourishment. 3. Analysis of Micro-CT image and 3D reconstruction: (1) Micro-CT image performance of coracoid blood supply in the intact group: Through contrast infusion and micro-CT scan on the fresh shoulder joint specimens, the reconstructed images and three-dimensional reconstructions could clearly show that the coracoid process bone structures and the distribution of the related nutrient vessels into the cortex. In the three-dimensional reconstruction images, the specific sources of the nutritive branches were determined through the matches of the vessel distribution observed in the anatomy of anti-corrosion specimens. Intact group: According to the results of angiography, the right specimen showed good microvascular perfusion inside the bone of coracoid process, and the part of the extra-osseous perforating branches penetrated into the bone was clearly revealed; The comparison of contrast agent and bone was obvious; The branch of the suprascapular artery and the second branch of axillary artery were connected with each other and penetrated into the coracoid cortexes respectively. However, the branches of thoracoacromial artery was not found in this specimen. Interestingly, this specimen showed a group of perforating arteries of unknown origin penetrating through the coracoid from the lateral side of the coracoid vertical portion. This artery was not found in the micro-CT images of the other seven fresh specimens, and it had not been reported in the embalmed specimens of previous studies as well. The perforator vessels with contrast agent were not found in the corresponding spatial positions of acromiocoracoid ligament or coracohumeral ligament. Rich vascular network was seen in the corresponding insertions of conjoint tendon and pectoralis minor muscle, but the vascular network in the conjoint tendon did not penetrate through the coracoid cortex. (2) Micro-CT images of coracoid blood supply in the osteotomy group: Eight specimens in the osteotomy group were paired with those in the intact group. Despite the poor imaging quality due to vascular rupture during perfusion in one left specimen in the osteotomy group, it was still found that the vascular network of graft and conjoint tendon was abundant after osteotomy and translocation, and that one branch originated from the conjoint tendon penetrated through the coracoid in the inferior aspect. For the micro-CT reconstructed images of the other seven specimens, despite the observation of the profuse vascularity in the conjoint tendon, it was never found that the angiographic arterioles travelled from the conjoint tendon and penetrated through the bone graft of coracoid at the insertion of conjoint tendon. (3) Distribution characteristics of intact coracoid nutrient foramen:The sagittal, coronal and cross-sectional images of 8 intact coracoids were reconstructed with DataViewer software to measure the related data of nutrient foramen. It was clearly observed that the capillaries penetrated into the coracoid cortex on the coronal view, and the CTAn (Skyscan) software was used to measure the number, diameter and area of the nourishing foramen on each side. The Wilcoxon rank sum test was used to compare the difference of nutrient foramen between the medial and lateral aspects as well as the superior and inferior aspects due to the small sample size. The characteristics of nutrient foramen in the 8 specimens were as follows: the number of nutrient foramen was (3.50±0.93) on the medial aspect, and (2.10±0.64) on the lateral aspect. The Wilcoxon signed-rank test showed that Z=-2.414 and P<0.05, and the difference was statistically significant. The difference of nutrient foramen on the superior and inferior aspects were analyzed using Wilcoxon signed-rank test as well. As the number of nutrient foramen on both superior and inferior aspects were obtained through Shapiro-Wilk normality test, and the data of this group did not conform to normal distribution, the median was used to describe the number of nutrient foramen. The results revealed that the median number of nutrient foramen was 2.00 on the superior aspect and 4.50 on the inferior aspect. The median number difference was -2.00 with a P value of <0.05, and the difference was statistically significant, indicating that number of nutrient foramen on the superior aspect was less than that on the inferior aspect. For the diameter of the nutrient foramen, the data of medial, lateral, superior and inferior conformed to the normal distribution, and thus the independent sample t test was used to compare the difference of nutrient foramen diameter on the medial and lateral aspects as well as superior and inferior aspects. The diameter of the nutrient foramen on the medial aspect was (229±50) μm, and the diameter on the lateral aspect was (187±32) μm. The homogeneity test for variance showed that the variance of the two groups of data was not even. Therefore, the corrected t' test was used with t'=3.435 and P=0.001, indicating that the difference of the nutrient foramen diameter was statistically significant. For the comparison of the superior and inferior aspects, the diameter of the nutrient foramen aspect was (201±21) μm, and the diameter on the inferior aspect was (261±58) μm. The homogeneity test for variance showed that the variance of the two groups of data was not even. The t' value was -5.256 using t' test with a P value of <0.05. Therefore, the difference of the nutrient foramen diameter was statistically significant on the superior and inferior aspects. The diameter on the inferior aspect was larger than that on the superior aspect. In the end, the difference of vascular volume density was analyzed and compared among the paired shoulder joint specimens with one side as the intact group and the other as the osteotomy group, respectively corresponding to the vascular volume density (vascular volume/bone volume) before and after osteotomy. The paired data was in accordance with the normal distribution. The volume density in the intact group was 0.0098±0.0012, and the volume density in the osteotomy group was 0.00037±0.0011. The Wilcoxon signed-rank test showed a Z value of -2.521 with P<0.05, and the difference was statistically significant. It was considered that the blood volume density after osteotomy was lower than that before osteotomy. ConclusionsAs a vascularized structure, the branches of the thoracoacromial artery and the branches of the second segment of axillary artery are both relatively constant nutritive branches. The blood supply to the medial and inferior aspects was more abundant than that on the lateral and superior aspects. Mastering this anatomical features has certain clinical value for the protection of coracoid blood supply intraoperatively. After the osteotomy and transposition duiring the Latarjet procedure, the conjoined tendon still has rich blood supply, while the vast majority of bone graft blood supply was damaged. However, part of the vessels in the residual conjoint tendon were found in 1case, and it was possible to preserve theses retained vessels with the bone graft fixed in 90° of rotation. Though, under all available perfusion conditions, the author believed that the bone graft was a structure without blood supply after traditional Latarjet operaion.