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Title: Biomechanical investigation of a new core suture configuration and a new peripheral repair method for zone II flexor tendon injuries : an experimental ex vivo study
Author: Zetlitz, Elisabeth
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2013
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Flexor tendon repair continues to provide surgeons with a challenge. Injuries occurring in zone II are a particular challenge due to the complex arrangement of the anatomy in this area. Poor results postoperatively are costly and lead to even more complex second operations, resulting in long time periods where patients are unable to use their hands fully. The repair techniques are numerous, as are the materials available for such repairs, and the training for surgeons in this field is largely based on practice on simulation models and the apprenticeship method. The literature review in this dissertation highlights the numerous repair variables, the type of repair, suture size and material, number of strands of suture crossing the repair site, as well as testing models. The use of a non-absorbable suture like braided polyester (Ticron) and a monofilament of polypropylene (Prolene) are commonly used in clinical practice, and these are both investigated for effect on tensile properties of the repair, as is the learning curve of one of the investigators. One aim of this research was to develop a realistic, low cost bench-top model for tensile testing of tendon repairs, to enable the primary of the study; an investigation of a new core suture and a new peripheral repair method. A porcine model is investigated for anatomical similarity with human flexor tendons, and a mechanical testing protocol established, that allows investigation of tendon repairs for tensile tests as well as internal work of friction. A comparison of the well-known and tested Pennington Modification of the Modified Kessler (MK) technique is performed with a new repair type that incorporates a ventral locking loop to the standard Modified Kessler (LMK). In addition the work introduces a PolyCaprolactone (PCL) sheet to the repair, as a new peripheral repair method. Early findings showed higher values for the Ticron repairs and a clear learning curve with regards to mechanical properties of the repairs. The importance of conditioning of the tendons was also investigated in the preliminary studies and a clear effect on the work of flexion was found for each cycle tested. No difference was seen in the tensile properties between the repairs, but for the two strand core suture repairs the LMK had lower work of flexion values. This was investigated further by measuring the cross sectional diameters of the two repair types to see if the change in repair technique had influenced the size of the repair. No difference was found. The four strand core suture repairs showed a higher force to gap formation of the LMK repair compared to the MK. The addition of the PCL sheet resulted in lower force to gap formation values. With regards to the work of flexion the PCL resulted in an almost doubling of the values seen with MK or LMK repairs, however no statistical difference was seen with regards to work of flexion between the MK and LMK. This work has shown that the porcine model is similar to human and provides a good model for tendon repair. A mechanical testing procedure for tensile testing as well as work of flexion has been established that allows for testing of tendon repairs. The model would also allow for trainees to practice and get qualitative feedback on their repairs. No clear biomechanical advantage was seen with the addition of the ventral locking loop when compared to the MK, however the MK configuration used had an increased locking loop diameter than those presented in the literature which means that the LMK may provide a biomechanical advantage. Further studies are warranted to investigate how the LMK compares to MK with smaller locking loop areas, and other commonly used repair techniques. The addition of the PCL sheet to the repair, caused a large increase in the work of flexion of the repairs, and the PCL sheets showed large deformation after low loads during tensile testing which means that they would not have any clinical application for zone 2 tendon repairs. The possibility of using the PCL sheet as a tissue engineering scaffold/matrix for tendon repairs out with the hand could be investigated in further studies, however it is likely that modifications need to be done to the PCL before it proves useful in clinical practice.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available