A Serial Study Of Internal Fixation Of Olecranon Fracture

Olecranon fracture is one of the most common elbow injuries in adult patients,and the incidence is about 1% of all fractures.The fracture can be the result of a number of different mechanisms,including avulsion, a direct blow,a fall on the outstretched hand with the elbow in flexion.A displaced fracture of the olecranon represents a disruption of the triceps mechanism and, as a consequence, the loss of active extension of the injuried elbow.Because immobilization of the elbow in extension lead to displacement of the fragments and weak extension,innovative surgeons, starting with Lord Lister who attempted an open reduction and suture of the olecranon,began to use a variety of technigues and materials to securely stabilize the olecranon to permit early functional motion and avoid displacement including screws,nails,plates and etc.Then the necessity for surgical treatment has been appreciated and the goals of treatment of olecranon fractures were widely accepted:articular restoration,preservation of motor power of extension,stability,avoidance of stiffness,and limitation of possible associated complications.In 1960s,Weber and the AO group introduced tension band wiring as the most effective method of internal fixation of olecranon fractures.With a widely clinical application of the K-wire tension band skill,however,complications were observed and reported mainly about the retreating of K-wires and hardware impingement.Some researchers found that the plate system was more stable biomechanically and much reliable clinically nearly for all types of olecranon fractures.But we observed clinically that the tip of commom hook plate is blunt round,and the triceps brachii tendon must be partially cut off in order to implant it.What`s more,the common hook plate is flat and must to be placed on the facies medialis or lateralis of proximal ulna,which don`t conform to the principle of tension band and then lead to instability.For these reasons,we developed the sharp-pointed central tension-band hook plate which is more stable and minimal invasive. In this paper we reported our series research,biomechanically and clinically,about the sharp-pointed central tension-band hook plate system.Part 1 The experimental study of the effect of injured tendon on the skeletal muscleTriceps brachii,triceps brachii tendon and aponeurosis are the most important posterior stabilizing and motive mechanism of elbow.The triceps brachii tendon attaches to the olecranon,and the fracture of olecranon may cause the injury and even partially disruption of the tendon and aponeurosis.In the surgical procedure of olecranon fracture treatment, triceps brachii tendon usually need to be cut off partially in order to implanting the traditional anatomical plate because of its blunt tip.We designed the experiment to study the changes of the contractive property of tendon-injured skeletal muscle in animals and then to discuss the effect of injured triceps brachii tendon on the patients with olecranon fracture.Objective To study the changes of the contractive property of tendon-injured skeletal muscle in animals,and then discuss the effect of injured triceps brachii tendon on the patients with olecranon fracture.Methods Take seven normal Japanese White rabbits as study participants and establish sciatic nerve-gastrocnemius muscle specimen in vivo.Each specimen was intervened successively in five levels:the gastrocnemius muscle tendon was kept intact,the tendon was transversly cut off by 20% at the central section,the tendon was transversly cut off by 40% at the central section,the tendon was transversly cut off by 60% at the central section,and the tendon was transversly cut off by 80% at the central section.In every level the maximum strength of the muscle and the mean were measured by digital force gauge when the sciatic nerves were excited by impulse current of 3v and 50Hz. Input data of the five levels and carry on statistics analysis with SAS the v9 (two way ANOVA).Result Eeleven specimens were successfully established and measured in all.There were significant differences for muscle strength(both the maximum and the mean) of the five levels(P<0.05).With the initial specimens,the maximum muscle strength was 22.19±7.20N and the mean was 17.72±6.61N;With the gastrocnemius muscle tendons 20% cut off,the maximum muscle strength was 16.98±4.91N and the mean was 13.43±3.94N;With the tendons 40% cut off,the maximum was 10.94±4.00N and the mean was 8.75±2.89N;With the tendons 60% cut off,the maximum was 9.72±2.31N and the mean was 7.63±2.13N;With the tendons 80% cut off,the maximum was 5.94±2.15N and the mean was 4.70±1.55N;In multiple comparison,significant differences were found among these five level(sP<0.05),except that there was no significant difference in the muscle strength(both the maximum and the mean) between the 40% group(maximum 10.94±4.00N and mean 8.75±2.89N) and the 60% group(maximum 9.72±2.31N and the mean 7.63±2.13N).In linear correlation analysis,there was a significant negative correlation (P <0.05) between the muscle strength and the cut off percentage ( per_cut ) of the tendon.The correlation coefficient between the maximum muscle strength and the cut off percentage of the tendon is -0.7833,and the correlation coefficient between the mean muscle strength and the cut percentage of the tendon is -0.7649.The linear regression eqations were found: Strength_max=21.1073-19.8864per_cut, Strength_mean=16.8117-15.9141 per_cut.Conclusion The skeletal muscle strength is inversely proportional to the severing percentage of its tendon in the experimental rabbits.That is,the severing percentage of the skeletal muscle tendon increased while the muscle strength significantly reduced gradually.Therefore,triceps brachii tendon injury should be avoided as much as possible in the patients with olecranon fracture,which will be contributive to the functional rehabilitation of the elbow.Part 2 Surgical treatment of olecranon fractures with a central tension-band sharp-pointed hook plate : a biomechanical studyThe traditional plate for olecranon is flat and must to be placed on the facies medialis or facies lateralis of proximal ulna,which don`t conform to the principle of tension band and lead to instability.So our group reformed the traditional plate and developed the sharp-pointed central tension-band hook plate.First,the tip of the plate is designed sharp ,which allows the tip can be thrust into the triceps brachii tendon keeping it from being partially cut off.Second,the cross section of the plate stem,contouring to the posterior border of upper ulna,is angularly bended gradually changing from 80°distally to 110°proximally.So the sharp-pointed central tension-band hook plate is more rigid and can be implanted anatomically onto the posterior border of the proximal ulna where the tension load locates.This conform to the AO principle of tension band.This study discusses biomechanical properties of central tension-band sharp-pointed hook plate in order to provide laboratory evidence for its clinical use.Objective This study discusses biomechanical properties of central tension-band sharp-pointed hook plate by comparing its biomechanical stability with the traditional anatomic plate,in order to explore the better internal fixation of olecranon fractures and provide laboratory evidence for its clinical use.Methods Twelve cadaveric elbow specimens from six cadavers were studied.There was no evidence of previous trauma or arthrosisin any of the specimens.Desecteding the humerus and the forearm from the middle part,and reject the skin,muscle and other soft tissue carefully but maintaining the joint capsule, triceps brachii tendon and part of the triceps.The proximal humerus of the dissected elbow were then potted in the custom jig vertically to the test-bed.Suture and tie the triceps brachii tendon and the triceps tightly with wire,then link the wire via a pulley set to the clamping apparatus of the the vitodynamics machine.Hold the elbow in 90 degrees by adjusting the external fixation device which is fixed on the jig,and then simulate the transverse fracture by cutting in the middle of the olecranon trochlear notch.This study adopt paired design,each specimen was fixed and tested successively by traditional anatomic plate and then central tension-band sharp-pointed hook plate.The former is control group group,and the latter is test group.Mechanical testing was performed with the CSS-44020 vitodynamics machine.The triceps brachii tendon was loaded with extension force through the wire via pulley set,the load were applied at a rate of 20N/s to a maximum load of 200N,the load was maintained for five seconds and then was released.The displacements of the fracture site were measured using linear variable differential transducers,which was set 1cm to the fracture site,and the data recorded by computer.Input the two groups data and carry on statistics analysis with sas the v9 (matched t-test).Result In control group(the fractures were fixed with traditional anatomic plate),under the extension load of 200N, the displacement of the fracture site is 2.8783±0.9031mm.And it is 2.1025±0.6701mm in the test group(fixed with central tension-band sharp-pointed hook plate).The statistics analysis shows that there are significant difference between the test group and the control group(P<0.05).The displacement of the fracture site in the control group is greater than the test group.Conclusion Compared to the traditional anatomic plate,the central tension-band sharp-pointed hook plate is more stable biomechanically,and is a better choice for internal fixation of olecranon fractures.Part 3 Surgical treatment of olecranon fractures with a sharp-pointed hook plate:a central tension-band plating system of minimal invasiveOur newly developed sharp-pointed central tension-band hook plating system is more stable and minimal invasive for the treatment of olecranon fractures.With the evidences of series of laboratory experiment and permission of the Ethics Committee,we carried out clinical research to discuss the clinical efficacy of sharp-pointed central tension-band hook plating system as internal fixation for olecranon fractures.Objective Most fractures of the olecranon need to be treated by surgical means.We used a new developed fixative implant,sharp-pointed central tension-band hook plating system, for treatment of olecranon fractures.This study describes the operative procedure and the clinical results obtained, as well as discussion of the advantages and problems encountered.Method Twelve patients with fractures of olecranon were treated using sharp-pointed central tension-band hook plating system. There were 8 males and 4 females and the average age of patients was 36 years. The mean follow-up period was 6.5 months. Plain and lateral radiographs of the injured elbow were used to assess bony union. Functional recovery of the elbow joint was assessed using the Broberg & Morrey score system.Results All fractures eventually achieved solid bony union within 4 months after surgery.Clinical results were excellent with a mean Broberg & Morrey score of 90.17±6.25 points at final follow-up.Conclusion This study shows that,in a representative number of cases,the newly developed sharp-pointed central tension-band hook plating system for olecranon fractures is a safe and effective treatment modality.The sharp-pointed central tension-band hook plating system are useful fixative implants,stable fixation was achieved,and physiotherapy can be started immediately after surgery.Early surgical treatment results in optimal outcome regarding patient's quality of life.