| Background:There is still no uniform standard for the surgical treatment of the calcaneus,and the surgical treatment of calcaneal fractures is still a challenge for orthopaedic specialists.At present,the most common surgical method is still " extended lateral approach in the operative treatment of displaced intraarticular calcaneal fractures".This incision is used to separate the lateral calcaneus flap along the lateral surface of the calcaneus,which has certain advantages in the reduction and fixation of the calcaneus.However,the incidence of complications such as incision skin necrosis,infection,and delayed incision healing is high.In addition,the plate is eccentrically fixed,and the surrounding stress concentration leads to failure of internal fixation and osteoporosis around the plate.Current trends in the treatment of calcaneal fractures tend to be minimally invasive.The percutaneous screw technique for the treatment of calcaneal fractures can be implanted minimally,is not limited by the timing of the operation,and is relatively simple to operate,making it an excellent choice for minimally invasive calcaneal surgery.Various minimally invasive techniques can reduce the above complications,but there are also some controversies: the mechanical strength of minimally invasive implants is not as good as that of lateral calcaneal plate implants,whether it can provide strong internal fixation suitable for calcaneus,the indications are narrow,and there are still dispute.In response to the above problems,this study will try to weave an orderly system of calcaneal internal fixation according to the type of fracture,aiming to improve the biomechanical stability of screws in calcaneal fixation and reduce related problems such as insufficient mechanical strength;On the basis of "spatial weaving technology",an intraosseous "central fixation" of calcaneal fractures was preliminarily designed with a " spatial weaving fixation frame" that could provide sufficient biomechanical stability.And further verify its biomechanical stability and compare it with the biomechanical study of conventional steel plate fixation.Methods:1.Research on the safe screw placement range of the lateral calcaneus anatomy:take the apex of the fibula(the lowest point)as the origin on the lateral side of the calcaneus,establish a coordinate system,and measure the lateral calcaneal artery and lateral calcaneus of the four important anatomical structures on the lateral side of the calcaneus.Cutaneous nerve,lateral calcaneal ligament of calcaneus,tendon of peroneus longus brevis.After quantifying and summarizing the range relationship.Identify the surgical incision and pin placement range with the least probability of damaging the lateral calcaneal vital structures.2.Through the concept of "trabecular bone shelf",the space range of the loadcarrying protrusion is re-divided: a: 17.00±2.50,b: 34.21±3.13,c: 21.83±6.10,d:17.10±2.98,e: 16.22±2.36,f: 33.72±2.78,g: 12.51±3.06,h: 26.44±3.06.For the two kinds of clinically common calcar protruding screws(transverse group and oblique group),for screw implantation in the peak area,the screw bearing capacity of the calcar protruding transverse group is better than that of the calcar protruding oblique group,about 15.15%;for the lumbar and valley areas for screw implantation,the screw bearing capacity of the oblique group was better than that of the transverse group,about 14.13%and 5.59%,respectively.3.The results of the biomechanical experiment of the space braided screw: under the load of 20-200 N,the model gap of the 7 absorbable screw group is larger than that of the steel plate group.3500 N static test,7 can absorb the compression displacement of the screw group is greater than the steel plate group.Finite element analysis results:In the state of standing on one foot of the human body: the stress concentration of the steel plate and the screw is mainly distributed at the junction of the screw and the steel plate,as well as the rear and upper part of the outer steel plate.Stress distribution of the braided screw group: The stress concentration of the screw is mainly distributed in the middle and upper parts of the calcaneus.4.Two kinds of braided internal fixation frame systems are designed: "triangular braided fixed frame" for simple fractures;"spatial weaving fixation frame" for complex fractures.Finite element experiment: In the state of standing on one foot of the human body,the structural strength requirements are met.The braided triangle group and the space braided group are superior to the steel plate screw group in terms of structural strength and bearing capacity.From the perspective of structural stability,the structural displacement of the steel plate screw group is the largest.The maximum displacement of the braided triangle group and the space braided group is lower than that of the steel plate and screw group,especially the maximum displacement of the spatial braided group is the smallest.5.Compared with the conventional calcaneal plate group,the clinical indexes of the space braided screw group were significantly decreased.The last follow-up AOFAS score in the spatial braiding group was significantly higher than that in the ORIF group.The Gissane’s Angle(GA)at one year after surgery in both groups was significantly higher in the 3D-SWSF group than in the ORIF group.Results:1.The ranges of lateral calcaneal artery,lateral calcaneal cutaneous nerve,and peroneal longus brevis tendon on X,Y,and Z axes are(unit mm)Og: 21.4±3.38,Oh:18.46±3.91,Oi: 25.06±3.45,Od: 16.5±4.77,Oe: 16.3±3.67,Of: 23.1±4.00,Oa:9.7±1.73,Ob: 11.5±2.12,Oc: 10.9±1.56;Lateral calcaneal calcaneal ligament: 22.3±2.8.2.Through the concept of "trabecular bone shelf",re-divide the space range of the saccade: a: 17.00±2.50,b: 34.21±3.13,c: 21.83±6.10,d: 17.10±2.98,e: 16.22±2.36,f:33.72±2.78,g: 12.51±3.06,h: 26.44±3.06.For the two kinds of clinically common calcar protruding screws(transverse group and oblique group),for screw implantation in the peak area,the screw bearing capacity of the calcar protruding transverse group is better than that of the calcar protruding oblique group,about 15.15%.For the lumbar and valley areas,screw implantation,the screw bearing capacity of the oblique group was better than that of the transverse group,about 14.13% and 5.59%,respectively.3.The results of the biomechanical experiment of the space braided screw: under the load of 20-200 N,the model gap of the 7 absorbable screw group is larger than that of the steel plate group.3500 N static test,7 can absorb the compression displacement of the screw group is greater than the steel plate group.Finite element analysis results:In the state of standing on one foot of the human body: the stress concentration of the steel plate and the screw is mainly distributed at the junction of the screw and the steel plate,as well as the rear and upper part of the outer steel plate.Stress distribution of the braided screw group: The stress concentration of the screw is mainly distributed in the middle and upper parts of the calcaneus.4.Two kinds of braided internal fixation frame systems are designed: "triangular braided fixed frame" for simple fractures;"spatial braided fixed frame" for complex fractures.Finite element experiment: In the state of standing on one foot of the human body,the structural strength requirements are met.The braided triangle group and the space braided group are superior to the steel plate screw group in terms of structural strength and bearing capacity.From the perspective of structural stability,the structural displacement of the steel plate screw group is the largest.The maximum displacement of the braided triangle group and the space braided group is lower than that of the steel plate screw group,especially the spatial braided group has the smallest maximum displacement.5.Compared with the conventional calcaneal plate group,the clinical indexes of the space braided screw group were significantly decreased.The last follow-up AOFAS score in the spatial braiding group was significantly higher than that in the ORIF group.The GA at one year after surgery in both groups was significantly higher in the 3DSWSF group than in the ORIF group.Conclusion:1.The lateral calcaneal ligament(LAL)of the calcaneus falls within the middle range of the above three structures(LCA,LCN,PS).The safe range of internal fixation implantation is about the posterior 2/3 of the posterior border of the calcaneus of the fibula.The arc incision > 3 cm below the tip of the fibula and > 2.1 cm at the posterior side was designed as a safety incision.2.Enlarged the range of load-carrying protrusion through the concept of "trabecular bone shelf".The finite element method is used to prove that the mechanical advantages of the two types of load-bearing protruding screws(horizontal and oblique type)are similar in the load-distance trough peak,and gradually decrease in the waist and valley areas,but the waist and valley areas can still achieve relatively stable fixation Effect.3.It is proved by biomechanics and finite element research: from the perspective of structural strength,the braided screw group is superior to the steel plate screw group in terms of structural strength and bearing capacity,and the braided screw group is slightly superior to the steel plate screw group in terms of structural stability.Braided screws can provide a sufficiently stable biomechanical healing environment for conventional calcaneal plate locks.4.The braided triangle group and the space braided group are superior to the steel plate screw group in terms of structural strength and bearing capacity.In terms of structural stability,the braided triangle group and the space braided group are superior to the steel plate screw group,the spatial braided group has the best stability,and the structural stability of each group presents the phenomenon of " spatial weaving >>braided triangle > steel plate screw".5.Minimally open the lateral wall of the calcaneus and reduce the collapsed articular surface through the lateral safety zone of the calcaneus to avoid damage to the lateral calcaneal structure;compared with the ORIF group,the 3D-SWSF group treated DIAF patients with the risk of wound complications lower,shorter operative time,shorter hospital stays,and better postoperative recovery. |
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