The Basic And Clinical Study Of Minimal Invasive Treatment Of Intra-articular Calcaneal Fractures

Part I The anatomic and radiographic study in the minimal invasivetreatment of intra-articular fractures of the calcaneusObjective To carry out anatomic and radiographic study on the detailed skeletal andsoft tissue characters of the lateral hind-foot, the sinus tarsi and the calcaneus in order toprovide the functional morphology for the minimal invasive treatment of intra-articularfractures of the calcaneus．Methods8cadaveric lower leg specimens were used in present study．Based on theanatomic landmark of the tip of lateral malleolus (X), three reference lines were drawn inthe hind-foot．XA was the horizon line measured from the tip of the lateral malleolus to theposterior border of the achilles tendon, XB was a vertical1ine measured from the tip of thelateral malleolus to the plantar floor of the foot, XC was obtained from the tip of the lateralmalleolus to the base of the fifth metatarsal. The peroneal tendons, the sural nerve andlateral calcaneal vessels were identified. The distance was recorded from the intersectionpoint of the soft tissues and the reference lines to the tip of lateral malleolus．The vascularanastomosis was also observed between the various vessels．Then the sinus tarsi wascarefully dissected to explore the anatomical characters.15cases of unilateral Sanders typeII calcaneal fractures were enrolled in this study, bilateral axial and lateral view of thecalcaneus were taken, different angles included the B hler, Gissane, and inclination angelof posterior articular surface were measured, at the same time the height, width and lengthwere also calculated and recorded. The differences in values of the angles and distancesbetween the injured and uninjured (control) foot were compared accordingly for statisticalanalysis.Results The peroneal brevis tendon was intersected with line XA, XB and XC, the distance between the intersection point and point X was2.90±1.16mm,6.09±1.63mmand47.42±12.64mm respectively. The peroneal longus tendon was also intersectedwith line XA and XB, but located below the line XC, the distance from the intersection tothe point X were7.07±2.15mm and10.40±3.04mm. The sural nerve was intersectedwith line XA, XB and XC, the distance to the intersection point X was17.22±6.48mm,17.40±3.77mm and44.48±8.81mm. Rich vascular network and vessel anastomosis existbetween the major lateral calcaneal vessels and their branch. Sinus tarsi takes the shapeoblique from anterolateral to posterior medial, the anterior and middle facet of the subtalarjoint were located in front of the sinus tarsi, and the posterior facet was in the rear. Onthe top there were sinus tarsal artery and vein came from dorsalis pedis vessels, andbranches from the sural nerve also located in the sinus tarsi.15cases of bilateral calcaneallateral and axial views were measured accordingly, the mean calcaneal height was47.34±6.91mm and38.33±7.43mm (t=9.47, P <0.0001), the mean width was32.62±4.52mmand41.72±4.69mm (t=8.07, P <0.0001), and the length was73.67±9.18mm and72.34±9.92mm (t=1.83, P=0.1893), the mean B hler angle was33.53°±4.87°and8.87°±7.57°(t=22.46, P <0.0001), the Gissane angle was122.87°±14.65°and112.87°±17.45°(t=1.77, P=0.1976), the inclination angle of the posterior articular surface was64.33°±8.25°and32.60°±17.46°(t=10.43, P <0.0001).Conclusion There were abundant vascular network in the lateral calcaneal flap, andthere were also a number of vascular anastomosis in the sinus tarsal area, but the sinustarsal incision used in minimal invasive treatment of calcaneal fractures has little damageand effect on the blood supply, which is a safe surgical approach. Lateral and axial viewsof the calcaneus is still the major clinical imaging methods to evaluate the calcanealfractures, the basic anatomical features of intra-articular calcaneal fracture were the loss ofthe height and the width, which provide the anatomical basis for the treatment ofintra-articular calcaneal fractures. Part II Biomechanical and three dimensional finite element study ofminimal invasive treatment of intra-articular fracture of the calcaneusObjective To identify the biomechanical stability of the rafting technique combined withlongitudinal screw fixation in the treatment of intra-articular calcaneal fractures bybiomechanical comparative study．Methods15cadaveric lower leg specimens were prepared to establish the Sanders typeII models and randomly divided into three groups. While the spicemens in the traditionalgroup (group A) were fixed with the3.5mm traditional calcaneal locking plate, theminimal invasive screw fixation group (group B) was fixed with four4.0/6.5mm screws,and the combined group (group C) was used3.5mm mini-plate combined with4.0/6.5mmlongitudinal screws. Cyclic loading tests and the failure load test were carried out, themaximum displacement values and fixation failure load values of two experiments wererecorded, then the results were analyzed statistically. Three dimensional finite elementmodel of calcaneal fractures were also established, and the two minimal invasive fixationgroups were analysised with the three-dimensional finite element method.Results When cyclic loading tests were carried out, the measured values of themaximum displacement of the three groups were differed as3.60±0.14mm in the group A,5.63±0.37mm in group B and3.55±0.18mm in group C. There was no significantdifference between group A and group C (P>0.05), while both of the two groups have thesignificant differences with group B (P<0.05). The fixation failure load values varied in thethree groups as1876.00±162.66N in group A,1140.20±84.85N in group B and1811.80±141.09N in group C, there was also no significant statistical difference between group Aand C (P>0.05). However, there are significant difference between these two groups andgroup B (P<0.05). The mean displacement value of the three groups were8.17±0.78mmin group A,8.31±0.97mm in group B and8.23±0.66mm in group C, there was was nostatistically significant difference (P>0.05). According to the three dimensional finiteelement model of Sanders type II calcaneal fracture, the average maximum shift value under the800N vertical stress test in the screw fixation group was5.10±0.60mm(4.13mm-6.00mm), while the average maximum shift value in the mini-plate group was4.25±0.45mm (3.75mm-5.12mm), the difference has statistically significance (t=3.19, P=0.0065<0.05).Conclusion The biomechanical stability of rafting plate technique under articularsurface combined with longitudinal screws was stronger than traditional screws fixation,and there was no statistically significant difference with traditional locking plate, which isproved to be a safe, biomechanical stable method for the treatment of intra-articularcalcaneal fractures. Part III Locking plate internal fixation for minimally invasive treatmentof intra-articular calcaneal fracturesObjective To summarize and evaluate the surgical technique and clinical outcome oflimited tarsal sinus incision with locking plate internal fixation for minimally invasivetreatment of intra-articular calcaneal fractures.Methods Between February2011and February2012,16cases of intra-articularcalcaneal fractures were treated minimally invasive in our department. All cases wereevaluated carefully with routine X-rays and CT scans pre-operatively to define the type offracture and the involvement of articular surface. Open reduction with locking plateinternal fixation and percutaneous screw fixation was performed via a limited tarsal sinusapproach at the average4th day （3-6days）after injury. X-rays were taken in the regularfollow-up, B hler’s and Gissane angle were recorded. Overall functional evaluation wascarried out according to Visual Analogue Scale (VAS), the Hind-foot score of AmericanOrthopedic Foot and Ankle Society (AOFAS) and SF-36, complications were also beenrecorded.Results13cases got at least1year follow-up, with a mean duration of18months (12to 24months). There were no complications of wound infection, skin and flap necrosis orimplant failure. X-ray demonstrated the bone union at an average10week (8-12weeks)post-operatively. The average B hler’s angle was improved from13.4±3.4°（8-19°）pre-operatively to26.5±4.5（21-38°） post-operatively, which had a significant difference（t=9.781，P<0.001）and the average Gissane angle was improved from88.1±7.6°（77-100°）pre-operatively to116.2±7.5°（100-124°）post-operatively, which had asignificant difference（t=12.934，P<0.001）. The average VAS score was1.5±1.7(0-6), themean post-operative AOFAS Hind-foot score was84.2±5.9(74-95) and average SF-36score was79.5±8.1(64-95) at the final follow-up. There was no post-traumatic arthritisoccurred during the follow-up.Conclusion A minimally invasive open reduction with locking plate and percutaneousscrew fixation via a limited tarsal sinus incision for treatment of intra-articular calcanealfractures has the advantages of direct reduction of articular surface and solid fixation,while avoiding the soft tissue complications, which is proved to be a safe and reliabletechnique. Part IV The clinical evaluation of minimal invasive and traditionalsurgical technique for the treatment of Sanders type II calcanealfracturesObjective To compare and evaluate the clinical outcomes of minimal invasive andtraditional surgical methods for the treatment of Sanders type II calcaneal fractures.Methods Between February2011and February2012, totally30patients were enrolledinto our study and were divided into traditional and minimal invasive group randomized.When soft tissue swelling subsided, the patients of minimal invasive group were performeda limited ORIF via a sinus tarsi incision, while the patients of traditional group were performed ORIF via a classical lateral extensile L-shape approach. Operation time anddrainage were recorded. X-rays were taken in the regular follow-up, B hler’s and Gissaneangle were measured. Overall functional evaluation was carried out according to VisualAnalogue Scale (VAS), the ankle and hind-foot score of American Orthopedic Foot andAnkle Society (AOFAS) and SF-36at the last follow-up, complications were also beenrecorded.Results There was no significant difference in delayed time and operation time. Thedrainage was less in minimal invasive group (t=9.792，P<0.001). There were2cases ofsuperficial skin necrosis in traditional group, while there were no such early complicationsin minimal invasive group. X-ray demonstrated bone union in3months post-operatively inboth groups and no implant failure occurred. The increased B hler’s and Gissane’s anglehad no statistical difference between two groups, and there was no significant difference inAOFAS score and VAS score, either. But SF-36score in minimal invasive group washigher than that in traditional group (t=2.049，P=0.047). Four cases of minimal invasivegroup suffered from varying degrees of subtalar joint stiffness in minimal invasive group,while all cases in traditional group had a subtalar joint stiffness,6of which had an obviousmovement limitation. There was another case of traditional group suffered from apost-traumatic arthritis with persistent pain on the10thmonth post-operatively, which wasrelieved by oral administration of NSAIDs.Conclusion There was no significant difference between the two groups in treatingSanders type II calcaneal fractures. Minimal invasive technique has the advantages oflower soft tissue complication rate and better function of subtalar joint, which is proved tobe a safe and reliable treatment for Sanders type II calcaneal fractures.