| Background and Purpose:Anterior spina l fixa tion is an effective interna l fixa tion for spina l diseases such asspina l tumors, tuberculosis, vertebra l fractures and spina l disc disease . In various anteriorspina l fixa tion devices, PACH designed and ma nufactured by French SCIENT'X Companyis a widely used interna l fixa tion device in the field of spine surgery in recent years. Thisdevice is used for anterior fixa tion after anterior Lumbosacra l intervertebra l fusion. It hasthe following features : 1. Proper shape to agree with the horizontal curvature of anteriorvertebra l body can help to improve the stability of level pla ne and sagittal pla ne; 2. bila tera lfixa tion provide s three-dimensiona l stability; 3. with a screw security system: elastictitanium bar welded on the steel pla te can bent to allow screw restored after crossingthrough and avoid the screw's exit; 4. the surface notch allows the pla te attached in thevertebra l body perfectly. However, we gradua lly find some shortcomings of the pla te inclinica l applica tion: 1. This pla te is a single steel pla te with two holes . It needs to impla nttwo steel sheets in the surgica l operation, which makes the process become complica ted. Ifonly one steel sheet is impla nted, the fastness of fixa tion ma y be inadeq uate; 2. the pla te isdesigned on the basis of anatomica l characteristics of foreign race's spine, and it could notfully conform to the anatomica l characteristics of Chinese spine; 3. no definite standard sare given for the spacing and angle between two impla nted steel sheets, which mea ns thatthe biomecha nica l stability could not be guaranteed. The purpose of this study is to improvethe pla te into an integrated composite pla te with four hole s on the basis of present PACHinterna l fixa tion pla te after statistica l ana lysis of the anatomica l structure of ChineseLumbosacra l vertebrae. Curva ture, length and angle of the improved/mod ified pla te willagree with the anatomica l structure of Chinese Lumbosacra l vertebrae. Biomecha nica l testwill be performed on spine specimens and the biomecha nica l properties sha ll achieve the desired results.MethodMethods1. Measure lumbosacra l angle and the heights of L5 and S1 vertebra l bodies andintervertebra l discs on latera l X-rays of 350 cases of norma l adults'Lumbosacra l vertebrae.Perform statistica l ana lysis upon results of the measurement and obtain usua l numerica lrange of Chinese lumbosacra l structure.2. Design parameters such as height, width, angle and curvature of improved/mod ifiedPACH pla te accord ing to vascular distribution of anterior L5 and S1 vertebra l bodies , so asto have the pla te conform to anatomica l characteristics of Chinese Lumbosacra l vertebrae.3. Manufacture pla te samples and do biomecha nica l tests on huma n spine specimens .Compare biomecha nica l characteristics of improved/mod ified pla te group, PACH pla tegroup and the control group.Results1. After measuring lumbosacra l angle and the heights of L5 and S1 vertebra l bodiesand intervertebra l discs on anteroposterior and latera l films of 350 cases of norma l adults'Lumbosacra l vertebrae, the researchers obtained usua l numerica l range of Chineselumbosacra l structure: height of L5 vertebra l body - (27.06±2.30) mm, height of S1vertebra l body - (22.3±2.8) mm, height of L5 S1 disc - (8.2±0.3) mm, lumbosacra l angle -(129°±5.9°).2. Based on the find ings of anatomica l structure of Chinese Lumbosacra l vertebrae, theresearchers developed optiona l parameters for mod ified PACH interna l fixa tion system:pla te height - 28/32 mm, pla te width - 30 mm, pla te angle - 125°/130°/135°, pla te curvature- arc length 22 mm and chord length 20 mm, screw length - 30/32.5/35/37.5/40/42.5/45 mm,screw dia meter - 5 mm. Ballhead full thread tapping screws are used. And screws tend tohead and tail sides in natural state, with an angle of 18°between the side s.3. The researchers performed bend ing test before testing the specimens : continuingload ing till the set deflection, record ing load - shift curve, and determining shift cha nge ofcontrol group and experimental group under cond itions of anteflexion, postextension andlatera l flexion with 500N load . The results ind ica ted that resista nce to bend ing of mod ified pla te group was superior to the PACH group (P <0.05). Then compression experiment wasperformed. The researchers calcula ted stiffness mea ns of each group under 400N load :PACH group - (87.4±4.2) N/mm, mod ified pla te group - (105.8±7.6) N/mm. The differenceof 20% was statistica lly significa nt (P<0.05). Torsion test was performed in the end. Whenthe turn angle reached 5°, the required torque of spine specimens of mod ified pla te groupand PACH group increased 54.6% and 53.7% respectively compared to control group. Andtorsiona l stiffness of the two was simila r, which mea nt no statistica l difference (P>0.05).ConclusionThe improved/mod ified pla te applies to fusing and fixa tion of tumor, tuberculosis anddisc diseases at L5S1, especia lly suitable for dama ged disc structure and slightly dama ge dsclerotin of vertebra l body. Compared to PACH pla te under the same cond itions, thismod ified pla te has obviously increased resista nce to bend ing and compress ion. In addition,flexion shift and vertica l compression stiffness in all directions of the two groups underlinear load also ind ica tes significa ntly differen ce (P<0.05). This pla te has a reliablebiomecha nica l stability, provid ing an idea l mecha nica l environment for lumbosacra l area .So it is very ind ica ted for fusing and fixa tion at this site.
|
PDF Full Text Request