Research Of Anatomy And Repairing Methods Of Rupture Of Extensor Tendon Hood

BackgroundExtensor hood maintains the extensor digitorum at normal position, it consist of sagittal band ?transverse fiber and oblique fiber which was sended from extensor digitorum.Sagittal band is the most important structure of the extensor hood to maintain the extensor digitorum.The current anatomic studies about extensor hood are all gross anatomy, none of them described the accurate length and accurate thickness of extensor hood and metacarpo-phalangeal capsule. The gross anatomic dates can not be used for current clinical researchs.Rupture of extensor hood will result in extended limitation and dislocation of extensor digitorum. Recent rupture of extensor hood can be suture at once.Nevertheless,old rupture of hood which lasting more than 3 weeks can be recovered difficultly for old rupture sites retraction and scar formation of it. Thus,the rupture of hood will cause the unbalance strength of two sides of extensor digitorum which result in dislocation of extensor digitorum time and again. At present, “transpositon of tendon” surgical method is commonly used of all operative treatments for old extensor hood rupture,such as Mccoy?Weeldon?Carroll methods. Mccoy method is the most commonly used. Although all of three surgical methods mentioned above can treatment rupture of hood,there are shortcomings of them, such as:causeing big injuries?strength control is difficult?complicated to operate?long learning cycle and high relapse rate. By referring to plenty of Anatomical dates of metacarpo-phalangeal joints, we found that the metacarpo-phalangeal capsule is similar to extensor hood in anatomical position?character?running direction?area and so on.anatomy.Objective 1. Measure the accurate length, ?thickness of extensor hood and the accurate thickness of metacarpo-phalangeal capsule by anatomy experiment. 2.Compare the toughness and max displacement-strength of extensor hood and the metacarpo-phalangeal capsule by means of biomechanical tests. 3.Understand immediate surgery effects of repairing extensor hood rupture by metacarpo-phalangeal capsule to provide reference date for clinical study sequentially.MethodsPart one :Anatomy of Extensor Hood andImmediate Surgery Effects of RepairingObtain 48 specimens of index finger?middle finger?digitus annularis?little finger from right and left hands of six fresh cadavers for test. 48 fingers were equally randomized into two group, 24 cases of one groups: group A and group B. Measure the length and thickness of extensor hoods of 48 fingers. Measure preoperative max unlar offset of 48 extensor digitorum when metacarpo-phalangeal joints flex 0°~90°.(unlar offset of extensor digitorum : the length between mid-point of extensor digitorum and mid-point of digital dorsum). Cutting radial sagittal band of hoods 5mm away from extensor digitorum to making ruptured extensor hood model. Measure the thickness of metacarpo-phalangeal capsules of 48 fingers at the gap of the broken extensor hood.Repairing all the ruptured hoods of group A by metacarpo-phalangeal capsule. At the same time,repair all the ruptured hoods of group B by operation Mccoy. Measure postoperative max unlar offset of 48 extensor digitorum when metacarpo-phalangeal joints flex 0°~90°. Calculate the absolute D-value between postoperative max unlar offset and preoperative max unlar offset.Compare the length of radial and unlar extensor hoods by single factor analysis of variance, then operate LSD- t-test in Pairwise comparison. P < 0.05 is considered statistically significance. Compare the thickness of radial extensor hoods ? unlar extensor hoods and metacarpo-phalangeal capsules by the same method.Compare absolute D-value of unlar offset of extensor digitorum of group A and group B by single factor analysis of variance, then operate LSD- t-test in Pairwise comparison. P <0.05 is considered statistically significance.Part two :Study About Biomechanics Quality of Eextensor HoodsTaking the unbroken unlar extensor hoods and metacarpo-phalangeal capsules of 24 fingers of group B as specimen,then divide them into group A(extensor hood group) and group B(metacarpo-phalangeal capsule).Making all the hoods and capsules into equal area tissues. All the tissues were placed on biomechanical testing machine immediately, the computer automatically recorded the displacement of max displacement(mm)and max load(N),then make displacement-load curve. Calculate toughness(N/mm)?max displacement-strength(N/mm2). Compare toughness and max displacement-strength by single-factor variance analysis. Then operate LSD- t-test in Pairwise comparison. P < 0.05 is considered statistically significance.Results1. D-value of unlar offset results:D-value of unlar offset of index finger?middle finger?digitus annularis?little finger of Group A is obviously shorter than them of Group B,differences between groups were statistically significant(P < 0.05). Standard deviation of group A is smaller than it of group B,it proves that D-value of unlar offset of Group A is much more centralized than group B.Therefore effectiveness of ours is more stable than Mccoy operation.2.Of all the index finger?middle finger?digitus annularis?little finger specimen,radial extensor hoods are langer than unlar ones(P < 0.05); Radial hoods are as thick as unlar ones,but both of them are obviously are thinner than metacarpo-phalangeal capsules(P <0.05).3.We found that through Biomechanic test,toughness of hoods(24.46±0.392 N/mm)is much similar to that of metacarpo-phalangeal capsulequality( 24.85±1.042 N/mm),differences between them have no statistically significant(P < 0.05)results;Differences of max displacement-strength between hoods( 12.21±0.191 N/mm2) and metacarpo-phalangeal(12.33±0.302 N/mm2) have no statistically significant(P < 0.05)results.ConclusionsThrough experiment, it proved that repairing the extensor hood by metacarpo-phalangeal capsule will reduce D-value of unlar offset compared to Mccoy operation. Consequently, we consider that repair the extensor hood rupture by metacarpo-phalangeal capsule will receive better immediate surgery effects than Mccoy operation.We found that metacarpo-phalangeal capsules are thicker than extensor hoods,repairing the broken hoods by metacarpo-phalangeal capsule will not change stability of metacarpo-phalangeal joint. Also,it is proved that biomechanics quality between extensor hood and metacarpo-phalangeal capsule such as toughness ? max displacement-strength is similar through experiments. We can think of that metacarpo-phalangeal capsule can be used as substitution to recover ruptured extensor hood.