Aynardi Michael C, Atwater Lara C, Melvani Roshan, Parks Brent G, Paez Adrian G, Miller Stuart D
Department of Orthopaedic Surgery, MedStar Union Memorial Hospital, 3333 North Calvert Street, Suite 400, Baltimore, MD, 21218, USA.
Clin Orthop Relat Res. 2017 Oct;475(10):2588-2596. doi: 10.1007/s11999-017-5410-x. Epub 2017 Jun 14.
Large Achilles tendon defects pose a treatment challenge. The standard treatment with a turndown flap requires a large extensile incision, puts the sural nerve at risk, and demands slow, careful rehabilitation. Dual allograft semitendinosus reconstruction is a new clinical alternative that has the theoretical advantages of a smaller incision, less dissection, and a stronger construct that may allow for faster rehabilitation.
QUESTIONS/PURPOSES: In a cadaver biomechanical model, we compared the dual allograft semitendinosus reconstruction with the myofascial turndown in terms of (1) mechanical strength and resistance to deformation and (2) failure mechanisms in reconstruction of large segmental Achilles defects.
An 8-cm segmental Achilles defect was created in 18 cadaveric lower extremities, nine matched pairs without defect or previous surgery (mean age, 78.4 years; range, 60-97 years; three female and six male pairs). Femoral neck densitometry to determine bone mineral density found that all specimens except two were osteopenic or osteoporotic. Specimens in each pair were assigned to allograft or turndown reconstruction. The constructs were mounted on a load frame and differential variable reluctance transducers were applied to measure deformation. Specimens were preconditioned and then loaded axially. Tensile force and proximal and distal construct deformation were measured at clinical failure, defined as 10 mm of displacement, and at ultimate failure, defined as failure of the reconstruction. Failure mechanism was recorded.
Tensile strength at time zero was higher in the allograft versus the turndown construct at clinical failure (156.9 ± 29.7 N versus 107.2 ± 20.0 N, respectively; mean difference, -49.7 N; 95% CI, -66.3 to -33.0 N; p < 0.001) and at ultimate failure (290.9 ± 83.2 N versus 140.7 ± 43.5 N, respectively; mean difference, -150.2 N; 95% CI, -202.9 to -97.6 N; p < 0.001). Distal construct deformation was lower in the turndown versus the allograft construct at clinical failure (1.6 ± 1.0 mm versus 4.7 ± 0.7 mm medially and 2.2 ± 1.0 mm versus 4.8 ± 1.1 mm laterally; p < 0.001). Semitendinosus allograft failure occurred via calcaneal bone bridge fracture in eight of nine specimens. All myofascial turndowns failed via suture pullout through the fascial tissue at its insertion.
In this comparative biomechanical study, dual semitendinosus allograft reconstruction showed greater tensile strength and construct deformation compared with myofascial turndown in a cadaveric model of large Achilles tendon defects.
Further study of dual semitendinosus allograft for treatment of severe Achilles tendon defects with cyclic loading and investigation of clinical results will better elucidate the clinical utility and indications for this technique.
巨大的跟腱缺损带来了治疗挑战。传统的带蒂皮瓣治疗需要一个大的扩展性切口，使腓肠神经面临风险，且需要缓慢、谨慎的康复过程。同种异体半腱肌双束重建是一种新的临床选择，理论上具有切口更小、解剖操作更少以及重建结构更强等优点，可能允许更快的康复。
问题/目的：在尸体生物力学模型中，我们比较了同种异体半腱肌双束重建和肌筋膜翻转皮瓣重建在以下方面的差异：（1）力学强度和抗变形能力；（2）在重建大段跟腱缺损时的失效机制。
在18具尸体下肢上制造一个8厘米的节段性跟腱缺损，其中9对为无缺损或既往无手术史的匹配下肢（平均年龄78.4岁；范围60 - 97岁；3对女性和6对男性）。通过股骨颈骨密度测定法确定骨矿物质密度，发现除2个标本外，所有标本均为骨质减少或骨质疏松。每对标本分别进行同种异体移植或翻转皮瓣重建。将构建物安装在加载框架上，并使用差动可变磁阻传感器测量变形。对标本进行预处理，然后轴向加载。在临床失效（定义为位移10毫米）和最终失效（定义为重建失败）时测量拉伸力以及近端和远端构建物的变形。记录失效机制。
在临床失效时，同种异体移植构建物的初始拉伸强度高于翻转皮瓣构建物（分别为156.9 ± 29.7牛和107.2 ± 20.0牛；平均差异 - 49.7牛；95%可信区间， - 66.3至 - 33.0牛；p < 0.001），在最终失效时也是如此（分别为290.9 ± 83.2牛和140.7 ± 43.5牛；平均差异 - 150.2牛；95%可信区间， - 202.9至 - 97.6牛；p < 0.001）。在临床失效时，翻转皮瓣构建物的远端构建物变形低于同种异体移植构建物（内侧分别为1.6 ± 1.0毫米和4.7 ± 0.7毫米，外侧分别为2.2 ± 1.0毫米和4.8 ± 1.1毫米；p < 0.001）。9个同种异体半腱肌移植标本中有8个通过跟骨骨桥骨折而失效。所有肌筋膜翻转皮瓣均通过筋膜组织在其附着处的缝线拔出而失效。
在这项比较生物力学研究中，在大跟腱缺损的尸体模型中，同种异体半腱肌双束重建与肌筋膜翻转皮瓣相比显示出更大的拉伸强度和构建物变形。
进一步研究同种异体半腱肌双束重建在循环加载下治疗严重跟腱缺损的情况以及临床结果，将更好地阐明该技术的临床实用性和适应证。
