The Related Researches Of Applied Anatomy And Biomechanics Of Soft Tissues Balancing In Total Knee Arthroplasty

Background:Knee is the biggest joint of the human kind.Knee disorders are common, especially the knee osteoarthritis affecting the old victims seriously.It is a leading cause of disability and has a formidable societal and public health impact.Total knee arthroplasty(TKA) has been documented to be the most beneficial management for these advanced stage sufferers.In TKA,achieving appropriate alignment in the coronal and sagittal planes by correctly cutting bone and soft tissues balancing is the keystone to success.In summery,correcting deformity,relieving pain and normal dynamic knee kinematics restoration were dependent on accurate soft tissue balancing (STB).The therapeutic effect was correlated closely to the management of blood vesseles,nerves and ligaments of knee.A great quantity of studies about these issues had been executed.Even though the advanced prothesis was companied with skilled operation technique now,soft tissue balancing was viewed generally as the most difficult procedure in TKA.There were considerable disputes about incision and technique of STB in clinic.Most of the orthopedist executed TKA with oneself experience and "feel".Therefore,diversity complications shown up in some victims were reasonable.Our clinical practice and literatures review suggested that these disagreements fundamentally impute to the insufficient of relational clinical anatomy documents about TKA,especially in our country.Although the morphological features of distal femur and proximal tibia had been clear,the documents about soft tissues were insufficient now.First,the basic purpose of TKA was relievate pain.But because of the innervation of knee joint was unclearly,the cause and mechanism of the complex arthronalgia was unclear.Therefore,some patients were executed TKA early to relievate pain,some ones remained different extent functional impairment of nerves postoperation.Second,approaches of TKA were related to the morphological features and distribution of nerves and blood vessel closely.It was benefit to diminish unnecessary hurt of never and blood vessel with appropriate approach.Third,and the capital,many issues about soft tissue balancing of TKA puzzled us today:(1)The concept of soft tissue balancing or soft tissue balance was ambiguity and inconsistent. What was it to balance? What the tissues were? No clearly answer to them.(2)How to achieve soft tissue balance? Kinds of Ligament releasing skill relation to soft tissue balancing were not reported with standard anatomy technical terms.These presentations were difficult to understand,even leaded to mistake sometimes.(3)Why and where to release these ligament?The function and morphological characters of these ligament complexs of knee were not clear.No sufficiency evidence was provide to answer which one should to be release and where should to do.(4)What the impact on dynamic knee kinematics after ligament released? Several studies suggested that influenced not only on the varus-valgus stability and internal-external rotation stability of knee,but also on the wide of joint gap.Furthermore,the effect was related intimately to the flexion angle of knee joint.It was known to all that over-released ligament should change the joint line and result in malfunction.Objectives:Our study had done some research to aim directly at above- mentioned.(1)To provide anatomical basis of the approach,nevers and blood vessels protection of TKA.(2) To provide anatomical and biomechanic basis of soft tissues balancing in TKA.(3)To explore a useful and practical method for three-dimensional reconstruction of the blood vessels,ligaments,articular cartilage and menisci of knee. Methods:1.Macromicrodissection:8 fresh adult human cadaveric knees and 80 formal-dehyde-fixed ones were executed with microsurgical techniques.①The innervation morphological features in knee joint and the relations between the nerves and surrounding tissues were observed and measured.The possibility of neurotomy to treat the arthronalgia of knee joint was observed.The relations of innervation to the exposures in TKA were explored.②2 fresh adult human cadaveric knees had taken TKA,to observe the risk factors of peroneal nerve palsy in operation.③The distribution morphological features and the relation to the approach and operation techniques in TKA of knee joint bloodes were observed.④Anterior region of knee: Morphological features were observed,and the data were measured for realignment of the extensor mechanism of the knee joint in total knee arthroplasty (TKA).⑤Medial area of knee:The morphological features of the structures and each part of them were observed,and the relation to the soft tissue balancing techniques in TKA had been explored.⑥Lateral region and angulus posteriolateralis of knee:The morphological features of each part of the structures were observed,and the relation to the soft tissue balancing techniques in TKA had been explored.2.Three-dimensional reconstruction of the blood vessels:CT data of 1 adult knee joint specimen which the artery had been perfused by contrast medium were harvested.The bone and artery structures of knee were 3D reconstructed using Mimics10.01.3.Three-dimensional reconstructions of the bone and ligaments,articular cartilage and menisci:387 slices of CT data(0.299 mm interval) and 64 slices of MRI data (1.497mm interval) of an adult knee joint specimen were harvested.The structures such as bone,articular cartilage,meniscus and ACL/PCL of knee joint were reconstructed using 3D reconstruction software Mimics and reverse-engineering software Geomagic 8.4.Biomechanics study of the medial supporting structures:6 fresh knee specimens were embedded by Polymethylmethacrylate(PMMA) both the superior and inferior ends,and reconstructed 3D reconstruction.The positions of them in test were got by a 3D laser scan.The movement parameters of knee joint were calculated(precision 0.01mm and 0.01°) with Geomagic 8 through 3D laser scan and CT 3D reconstruction. The valgus and rotation laxity and width of joint gap were calculated.Result:1.Innervation of knee:The innervation pattern of the study was similar to that of Horner's.But our study suggested that the innervation of knee joint had two layer groups:the superficial layer group and the profunda layer group.The superficial layer were composed of the cutaneous nerves which may form nerve tumor easily.The profunda layer group could be divided into 4 groups which comprised different articular branches respectively.Although them had some extent superimpose innervation outside the articular capsule,each one had its special distribution area. With the coverage and extension of synovial membranes,an extensive network of somatic nerve and autonomic nerve formed inside knee joint.The articular branches of saphenous nerve,common peroneal nerve and the muscular branches of quadriceps muscle never were mostly about 1mm thickness,so could be located easily.2.Risk factors for common peroneal nerve in TKA:Cadaver knees TKA suggested the dangerous handlings include the belows in turn.①Lifting distal femur by encircle dragging could rise risk of common peroneal nerve.②It was risk for common peroneal nerve to set Hoffman crook not paralleling longitudinal axis of tibia or posterior the lateral collateral ligament.③Excessive extened knee joint when the prosthesis had been fixed.3.Arteriovenous of knee:①Branches of femoral artery and popliteal artery and anterior tibial artery,also of deep femoral artery formed blood vessel strainer.As a safe marker for femoral artery in total knee arthroplasty,the musculoarticular branch should be preserved wherever possible if the subvastus approach was used.The lateral inferior genicular artery should be preserved carefully.②3D models of bone-blood vessel structures were constructed using angiography-irrigated CT scanning data.The transparence demonstrations were carried out using both Mimics and 3ds max methods.It demonstrated the position relations and 3D morphology clearly.And it displayed the regional blood supply clearly.③Risk of thrombogenic:The popliteal AtV was fixed by its branches.The endomembran of these veins was prone to be teared by hyperextension while the tibia dislocating forwards and backwards in TKA. Such kind of endomembran hurts leads to popliteal vascular plexus thrombogenic.The risk of thrombogenic was highlighted when the insertion of caput laterale musculi gastrocnemii tendon has variation.4.The extensor mechanisim were wraped up by trilaminar prepatellar fibrous soft tissues of different arrangement.The angles of the vastus lateralis tendon and the vastus medialis obliquus muscle(VMO) fibers to the rectus tendon were 33.5 and 78.6,respectively.The pavilion of quadriceps tendon spreaded downward and formed the lateral and medial patellar retinaculum.The medial patellofemoral ligament (MPFL)was about 47.6 mm long and 12mm(8-26 mm) wide.The subcrureus was an independent muscle which acted as a frift structure and a medial stabilizer of patellar.5.The medial area supporting structures of knee were composed of the medial collateral ligament complex and semimembranous muscle complex which could be divided into three layers.Anterior portions of the medial collateral ligament stopped anterior-medial tibia,inferior to the tibial plateau 50-60mm.The posterior oblique portions one mixed the third layer together,and fixed by medial meniscus and coronary ligament.The tendinous sheath and tendon of semimembranous muscle strengthened post-medial area of knee,and could be divided into 9 parts.Furthermore, the tendon intervened the superficial layer and deep layer of MCL.The third layer (articular capsule)stopped inferior to tibial plateau 0.8-1.5cm.6.The posterolateral comer complex was consisted of 3 layers of structure. Superficial layer included iliotibial tract,lateral collateral ligament,popliteofibular ligament and arcuate ligament.Stratum medium had popliteus-tendon complex, popliteus-tibia fascia and popliteus-niscus fascia.Deep layer was consisted of lateral capsule ligament,posterior hom of lateral meniscus,lateral coronary ligament and lateral articular capsule.7.Release of the anterior portion of MCL and ACL produced valgus and rotation laxity at 60°and 90°(11.19°±2.05°,P=0.045)flexion.Release of the posterior oblique portion and posterior capsule produced moderate laxity at from full extension to 30°flexion.Complete medial collateral ligament release increased laxity significantly in flexion and extension both.8.With the merit of CT to demonstrate the bone structure well,segmentation and 3D reconstruction of bone were performed using Mimics 10.01 in CT data.Documents of bone was saved.The registration was performed after the 3d models which reconstructed by MRI and CT separately were imported in the software Geomagic to transform the coordinate of CT data which enabled the CT model be fit for the MRI image.With the merit of MRI to demonstrate the soft tissue structure well, segmentation and 3D reconstruction of meniscus,atricular cartilage and ACL/PCL were performed using Mimics 10.01 in MRI data.The 3D models of these structures were imported to Geomagic software to 3D modification to let the structure smooth. The articular cartilage models were imported into CT image again to testify the region of the segmentation.Finally,the 3D knee joint model with bone,meniscus, ACL/PCL and articular cartilage was reconstructed.Conclusion:1.The extrinsic innervation of knee joint could be divided into different groups. Oppositly,reticulate innervation inside joint.Arthronalgia could be relieved by resecting the membrane synovialis and articular braches through total knee arthroplasty or arthroscopy.Denervation have the rational anatomical foundation to relieve the pain in patellofemoral joint.Selective denervation technique may be effective to some extrinsic source pain due to the regional cutaneous nerve neoplasia or nerve branch compression.2.Lifting distal femur by encircle dragging should be avoid while peeling posterolateral joint caps and caput laterale musculi gastrocnemii.The location, inserting orientation and depth of Hoffman crook should be taken care of.Avoid hyperextension of the knee.3.Combining the image technology such as CT,MRI with computer image processing and 3D reconstruction and registration technologies,the direct-viewing bone and arteries of knee joint could be achieved to benefit surgery approach choice. The deep venous thrombosis after TKA was related to vessels injury by excess drag.4.The key procedure of soft tissue balancing in TKA was to suture the VMO and MPFL accurately,and loosen the vastus lateralis tendon or the lateral patellar retinaculum if necessary.Protection of the subcrureus is significant in TKA.5.It was benefit to achieve soft tissue balancing of medial structure in TKA with "spreader" skill.The key to correct yams deformity was to release the MCL complex at the tibia.To correct flexion deformity should be concentrate on medial-posterior articular capsule at the femoral and the lateropusion tendon branch of the semimembranous muscle at the tibia.If the medial joint gap tension happened at flexion＜30°,release of the anterior part of MCL.At flexion 30°～60°,release of the posterior oblique part of MCL and the lateropusion tendon branch of the semimembranous muscle.At flexion＞60°,increase release of the posterior articular capsule.6.The fundamental stabilizer of posterolateral corner of knee was lateral collateral ligament complex and popliteus-tendon complex.To achieve soft tissue balancing of medial structure in TKA,when the valgus deformity＜20°,sequence release of lateral capsule ligament,lateral articular capsule,iliotibial tract,popliteofibular ligament and arcuate ligament.7.With the merit of CT and MRI,it is realizable to reconstructe 3D knee joint model with bone,meniscus,ACL/PCL,articular cartilage and blood vessel.