Treatment of chronic achilles tendon ruptures with an acellular dermal matrix augmentation
Although Achilles tendon repairs have been augmented using fascia lata, gastrocnemius flaps, plantaris tendon grafts, the palmaris longus, the flexor hallucis longus, and synthetic grafts, the implementation of a single surgical model has not been universally accepted. Some studies reporting marginal improvement or equivalent results between direct repair and augmentation concluded that any advantages with augmentation did not merit the additional surgical risks in acute Achilles tendon repair. In chronic Achilles tendon tears, however, the use of augmentation with primary repair or transfers has received greater acceptance. The reinforcement of chronic or neglected Achilles tear repairs is logically advantageous due to the poor tendon tissue quality present, the gap that remains following excision of the fibrous pseudotendon, and the tendon retraction or fatty infiltration resulting from delayed treatment. Patients with chronic Achilles tendon ruptures are more technically challenging than those with acute ruptures; they have slower return to activity, higher complication rates, and greater functional deficits than their acute counterparts. Although the idea of reinforcing chronic tears is generally accepted, the method for supporting the primary repair is not standardized. Unfortunately, many of the augmentation techniques in current use require the harvest of a healthy, autogenous tendon. Although these techniques have been shown to benefit the patient, the sacrifice of autologous tendons can be of concern since these tendons may be inadequate in length or diameter for Achilles repair. If local tendons are rerouted or removed, the biomechanical and soft tissue effects on the foot should also be taken into consideration. Misgivings regarding the use of local tendons or a lack of suitable tendons in specific patients has spurred the investigation of allografts and synthetic materials as a means of Achilles augmentation. Synthetic materials have offered good results; however, since such materials do not incorporate or facilitate tendon regeneration over time, they merely offer interim strength, which may ultimately cause problems. Recently, the use of an acellular human dermal matrix has received attention as a material for augmenting chronic Achilles tendon injuries. An allograft in sheet form allows the surgeon to reinforce a tendon repair without sacrificing local tissues. Ideally, the reinforcing material offers additional stability to the repair, facilitates cellular infiltration without inflammation, and incorporates into the tendon over time. In a study by Lee, nine neglected Achilles tendon ruptures were augmented with an acellular tissue graft and followed for a minimum of 20 months. There were no reruptures or instances of recurrent pain within this group. The patients had an average return-to-activity time of 15.2 weeks and an average American Orthopedic Association of Foot and Ankle Surgeons (AOFAS) ankle hindfoot score of 86.2 at 12 months. The return to activity time in this series was markedly faster than previous reports in chronic ruptures treated with primary repair alone or with turndown flaps. These positive results were particularly interesting since the majority of the treated patients had comorbidities of smoking or diabetes. In a technique study by Brigido et al., 21 Achilles tendons were treated with the acellular dermal matrix for chronic Achilles tendinosis when greater than 50% of the tendon was excised due to disease. In that population, patients returned to activity at an average of 12.1 weeks after surgery. Collectively, these clinical results correspond to the preclinical performance of this extracellular matrix in cellular studies, animal models, and biomechanical testing. Mechanical testing of a variety of extracellular matrices by Barber et al. showed that the suture pullout strength was higher (157 to 229 N) for this type of material than all other materials tested. The inherent mechanical properties and suture purchase offered by the matrix should aid in the intraoperative and preliminary postoperative reinforcement of the primary repair prior to graft incorporation. The initial strength properties of an acellular dermal matrix construct were also statistically equivalent to palmaris longus tendon grafts in a biomechanical study of medial collateral ligament elbow reconstruction. This acellular human dermal graft has repeatedly reflected regenerative tissue properties, a lack of inflammation, and cellular incorporation in a variety of canine, porcine, and rat models as well as in vitro cellular testing. The incorporation and regenerative nature of the acellular human dermal matrix is attributed to processing methods maintaining an intact native connective tissue structure rather than damaging or cross-linking the matrix. The augmentation of rotator cuff tendinous tissue with this material has been accomplished successfully and provided reduced re-tear rates and good functional outcomes clinically using a number of different techniques. Anecdotal evidence indicates that the positive histology reports with this material in preclinical models correspond to the clinical cellular response seen in patients. In postoperative graft biopsies of the rotator cuff, there was notable formation of a neotendon populated by healthy cells and blood vessels. © Springer Science+Business Media, LLC 2009.
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