Mechanical comparative analysis of three different types of sutures in different dimensions tendons: experimental study

Análise mecânica comparativa de três tipos de sutura entre tendões de dimensões diferentes: estudo experimental

Mechanical comparative analysis of three different types of sutures in different dimensions tendons - experimental study

Análise mecânica comparativa de três tipos de sutura entre tendões de dimensões diferentes- estudo experimental

Trajano Sardenberg^I; Sérgio Swain Müller^II; Chafi Facuri Neto^III; Gustavo Colani Barbosa^III; José Fernando El Murr^III; Hamilton da Rosa Pereira^II

^IAssistant Professor

^IIPhD Assistant Professor

^IIIEx-Resident Doctor

^{Address for correspondence}

SUMMARY

The aim of this experimental investigation was study of mechanical profile of three kinds of suture, between tendons with different dimensions. Were utilized 21 mongrel dogs ( 11males, 10 females) of wich were obtained the tendon comum flexor and tendon tibial cranial of both pelvic limbs. After the dissection of the tendons, suture was done, seven animal per group. The tendons utilized allways were from the right limb and from the left limb side utilized as control. After the suture, we performed axial traction tests, rate level of 30mm /min, using special jaws. After the test the machine's program informed the values of ultimate load, elongation and strain, and load elongation diagram. The results were submite to statistical study, that showed no difference between the technics utilized. The values of suture groups were smaller than the control, for ultimate load, and higher for elongation and strain.

Key Words: Tendon; suture; biomechanical

RESUMO

O objetivo da presente investigação experimental foi avaliar o perfil mecânico de três tipos de técnicas de sutura entre tendões de dimensões diferentes. Foram utilizados 21 cães sem raça definida (11machos/10 fêmeas), dos quais foram obtidos os tendões flexor comum dos dedos - t.c. (maior dimensão) e tibial cranial - t.cr. (menor dimensão), de ambos os membros pélvicos. Logo após a obtenção das peças foi realizada sutura, segundo cada tipo de técnica, porém sempre com o mesmo número de pontos. Os tendões utilizados para sutura foram sempre do lado direito e o controle do lado esquerdo (t.cr.). Após a sutura, os corpos de prova foram fixados em garras especialmente desenvolvidas e submetidos a ensaio de tração axial à velocidade de 30mm/minuto. Após o ensaio o programa da máquina forneceu os valores da carga máxima ( na ruptura) e deformação absoluta (mm) e relativa (%), além do diagrama carga-deformação. Os resultados foram submetidos a estudo estatístico pela análise de medidas repetidas no nível de 5% de significância. Não foi constatada diferença estatisticamente significativa nos parâmetros mecânicos avaliados nos três grupos de técnicas de suturas. Em relação ao controle (tendão de menos diâmetro contra-lateral), observou-se que a sutura apresenta resistência máxima a tração significativamente menor que o controle e maior deformação.

Descritores: Tendão; sutura e biomecânica

INTRODUCTION

Direct and primary repair of flexor tendon injuries in hands is considered as the best option for treatment of isolated lesions of tendons or associated to injuries of peripheral nerves⁽¹²⁾. Other situations, such as complex injuries involving other anatomical structures (bone, joints, blood vessels, etc) or the impossibility of performing a primary repair (diagnosis failure, priority for treatment of other systems, lack of an specialized team, etc) make impossible to bring near the stomps of tendons for a direct repair. In these cases there is indication for using grafting techniques of free flexor tendon^(10,12).

Tendon dimensions, mostly width and diameter, to be used as free graft are important factors in choice, being advantageous to use small dimension tendons to make easier to pass through the osteofibrous channel of the fingers, the sliding, the revascularization and, consequently, reduction of adherence to surrounding tissues^(3,10,12,15). Superficial and deep flexor tendons, normally used as motors in tendon grafting, are larger than the tendons used as graft (palmaris longus, plantaris delgadus, extensor tendons of the toes) and so, proximal anastomosis are performed between tendons of different dimensions.

Direct repair techniques between different dimension tendons may bring the so called phenomenon of "dissatisfied tendon", increasing the risk of adherence to surrounding tissues^(2,3,8). Many suture techniques for the tendons were developed for solving this problem, being currently most used Pulvertaft's⁽⁸⁾ technique or its variations^{(2,8,9,10,12)}.

The use of post operative protocols involving a degree of joint mobilization intensified the request for suture techniques with a high degree of endurance to traction, allowing early mobilization^{(1,5,6,7,11,13,14)}. However, the majority of these studies are related to direct repair techniques of tendons with similar dimensions. Gabuzda et al⁽⁴⁾ performed a biomechanical study of a lateral suture technique, however using similar size tendons.

The aim of this study was to perform a biomechanical evaluation of the suture between different dimension tendons.

MATERIAL AND METHODS

Pelvian members of 21 adult dogs, of no specified race, both genders, weighting between 12.0 kg and 15.0 kg, clinically healthy, used for other purposes, were amputated at the hip and kept in a freezer at a -20° C for 3 to 6 weeks.

On the day of the test, the anatomical specimens were defrosted at room temperature and dissected removing the comum tendon ¾ c.t. (deep digital flexor muscle and long flexor of halux) and the cranial tibial ¾ t.cr. ¾ muscle tendon.

After assessment of the width of the extremities of the tendons, sutures were performed in three groups, G1, G2 and G3 (Figure 1).

The stitches were in "U", with three knots and in a number of six in all techniques, with monofilamentar nylon line 4-0*, with a triangular needle. The distance between the orifices performed in the common tendon in group G1 were of 1.0 cm, and in group G3 the distance between the orifice and the distal extremity of the tendon was of 1.5 cm. The procedures were performed on the right pelvian limb and the tibial cranial muscle tendon of the left limb was used as a control.

The tendons sutured were fixed to specially developed claws, with the c.t. placed proximally. The tendons were kept moist with saline solution.

It was used an Universal Mechanical Test Machine, brand EMIC, model DL 10.000. The method included a load cell of 5000N, and traction and speed applied at a load of 30 mm/min.

Were performed 7 tests for each group (G1, G2, G3), being tested 21 tendons.

Data obtained for analysis were: maximum load, absolute and relative deformation at maximum load.

The results were statistically analyzed by means of repeated measures for independent groups ⁽¹⁷⁾, and the conclusions discussed at a 5% significance level.

RESULTS

Results are presented in the (Tables 1, 2 and 3 and the Figures 2, 3 and 4). The average width of the common tendon was 6.1 mm and of the cranial tendon 4.2 mm.

DISCUSSION

Flexor tendon grafting is performed by means of a proximal and a distal junction. The proximal involves suture of different dimension tendons and distally the tendon is inserted in bone. The present study is limited to the biomechanical evaluation of the proximal junction.

The endurance of suture procedures, such as the ones used in this work, depends on several factors: arrangement between the tendons of different dimensions, number of applied stitches, diameter of the suture line, kind and number of knots. The central aim of the investigation was to evaluate eventual differences in mechanical behavior of the distinct arrangements. The technique used in group G1 was selected due to its large use in clinical practice⁽¹²⁾; the technique for group G2 was chosen for its simplicity and possible clinical use and technique for group G3, even not normally used in clinical practice due to possible problems related to "dissatisfied tendon"^(2,3,8) was selected to evaluate the mechanical efficiency of tendon adaptation without a "complete closing" between different dimension tendons. The statistical analysis showed not to exist a significant difference between the studied groups: group G1 (56,5 ± 17,9 N), group G2 ( 42 ± 3,6N) and group G3 ( 48,5 ± 9,3N). Nevertheless the mean values for each group were not identical, group 1 presenting a slightly superior value, this difference was not significant. These results also present in group G1 an standard deviation that is larger than the observed in the other groups, suggesting a less homogeneous behavior explainable by the more difficult technique, thus, with more variable and less predictable results. In the other groups (G2 and G3) the standard deviation was smaller, looking to indicate more uniform results.

In relation to absolute deformation, expressed in millimeters, it is observed the same: a similar mean, and in this case a similar standard deviation as well. Relative deformation, in relation to length at start, also did not show significant differences. So, independently of the arrangement between the tendons, with variation of the contact area between the parts, maximum load and deformation were similar.

What would be the explanation for this behavior, since in the beginning it was supposed that the techniques increasing the contact surfaces between the sutured parts should, theoretically, bring more endurance to traction? For attending the aims of the investigation it was programmed that all techniques would use the same kind of suture line, knot and specially the same number of stitches. The results bring to consideration that the similitude of behavior found is probably a consequence of the sum of the resistance of each stitch and, as the number of stitches was the same, the results were similar.

The differences in the arrangements of the three types of technique were not, so, enough to differentiate the mechanical performance, what was proven by the rupture pattern found in all assays of suture rupture. The "complete closing" of the transition between the tendons did not show to have a mechanical importance. It is necessary to remember that these results were found in vitro: and that an evaluation keeping the animals alive for observation after a given time of the evolution of the reparation process and its mechanical features could bring different results.

The reason for testing the specimens just after the suture was exactly to know how much of immediate endurance can be expected, without any reparation process, and in consequence to speculate on the possibility of the suture to endure an immediate mobilization after surgery. For this, it was used a paired control (the thinner contralateral tendon, from the same dog) for comparison of the suture performed. The analysis of this comparison shows that the control (intact tendon) had higher values for the maximum load endured than the suture, in all groups, and that this difference was significant. In relation to deformation, absolute or relative, the controls had significantly lower values in all groups, that is, were less deformed than the sutured ones.

The mean maximum load values in the sutured groups were approximately 25% to 30% of the controls. The question that so arises is if the initial endurance could be considered enough to allow a passive assisted or even active (without resistance) movement in immediate post-operative period.

The phenomenon of reduction of the initial endurance of the reparation in the first five to seven post operative days in about 20% to 25% and the recovery at the end of the third week in about 75% was demonstrated by URBANIACK et al ⁽¹⁶⁾ in an in vivo study using a suture technique between tendons of similar dimensions in dogs. In this study, URBANIACK et al⁽¹⁶⁾ showed that in humans, active flexion of the finger against a moderate load produces a force of 1.500 g, approximately 15 N. The biomechanical values found in the present groups would allow, in theory, an early post operative mobilization, not taking into consideration the distal tendon-bone junction.

On the other hand, alternatives for improving the mechanical profile of tendon suture techniques aiming an active loaded mobilization, as earliest as possible post operatively should be sought for improving healing and sliding of the tendons.

The results observed in this study look to express the sum of the endurance of each stitch. So, in order to improve the endurance it would be necessary technical modifications. These modifications could be on the diameter of the used line, or increasing in the number of stitches, certainly improving the mechanical performance of the suture independently of the tendons arrangement. It should be highlighted that these changes have their potential for increasing the morbidity of the procedure and eventually lead to other complications such as increase in tendon tissue necrosis and adherence to surrounding tissues.

CONCLUSIONS

The mechanical profile of the three types of sutures analyzed was similar, depending on the number of stitches, the type and number of knots and the kind of line used.

Trabalho recebido em 01/11/2001. Aprovado em 15/05/2002

Work performed at Department of Surgery and Orthopedics from Faculdade de Medicina de Botucatu - UNESP

• 1. Barmakian, J.T., Lin, H., Green, S.M., Posner, M.A., Casar, R.S.: Comparison of a suture technique with the modified Kessler method: resistence to gap formation. J Hand Surg 19 A: 777-781, 1994.
• 2. Boyers, J.H.: Problems of tendon surgery. Am J Surg 109: 269-271, 1965.
• 3. Bunnell, S., Boyes, J. H.: Tendones; in Cirurgia de la mano, Buenos Aires, Editorial Intermédica, 1967, p. 400-476.
• 4. Gabuzda, G.W., Lovallo, J. L., Nowak, M.D.: Tensile strength of the end-weave flexor tendon repair. J Hand Surg 19 B: 397-400, 1994.
• 5. Gordon, L., Garrison, J.L., Chang, J.C., Lin, Y.K., Nathan, R.P., Levinsohn, D. G.: Biomechanical analysis of a step-cut technique for flexor tendon repair. J Hand Surg 17 B: 282-285, 1992.
• 6. Haddad, R.J., Kester, M.A., McCluskey, G.M., Brunet, M.E., Cook S. D.: Comparative mechanical analysis of a looped-suture tendon repair. J Hand Surg 13 A: 709-713, 1988.
• 7. Komanduri, M., Phillips, C.S., Mass, D.P.: Tensile strength of flexor tendon repairs in a dynamic cadaver model. J Hand Surg 21 A: 605-611, 1996.
• 8. Pulvertaft, R.G.: Suture materials and tendon junctures. Am J Surg 109: 346-352, 1965.
• 9. Robertson, D.C.: The place of flexor tendon grafts in the repair of flexor tendons injuries to the hand. Clin Orthop 15: 16-21, 1959.
• 10. Shneider, L.H.: Flexor tendons ¾ Late reconstruction; in Green, D.P., Hotshkiss, R.N., Pederson, W.C. (ed.), Green's operative hand surgery, Philadelphia, Churchill Livingstone, p.p. 1999, p. 1898-1949.
• 11. Silfverskiöld, K.L., Anderson, C.H.: Two new methods of tendon repair: an in vitro evaluation of tensile strength and gap formation. J Hand Surg 18 A: 58-65, 1993.
• 12. Sobania, L.C., Santos, P.S.: Lesões dos tendões flexores; in Pardini, A.G. (ed.), Traumatismos da mão, Rio de Janeiro, Medsi, 2000, p. 317-350.
• 13. Strickland, J.W.: Flexor tendons- acute injuries; in Green, D.P., Hotshkiss, R.N., Pederson, W.C. (ed.), Green's operative hand surgery, Philadelphia, Churchill Livingstone, 1999, p. 1851-1897.
• 14. Thurmam. R.T., Thumble. T.E., Hamel. D.P., Tencer. A.F., Kiser. P.K.: Two- four-, and six- strand zone II flexor tendon repairs: an in situ biomechanical comparison using a cadaver model. J Hand Surg 23 A: 261-265, 1998.
• 15. Tubiana, R.: Incisions and technics in tendon grafting. Am J Surg 109: 339-345, 1965.
• 16. Urbaniak, J.R., Cahill, J.D., Mortensen, R.A.: Tendon suturing methodo: analysis of tensile strengths; in American academy of orthopedic surgeons-symposium on tendon surgery in the hand, St louis, Morby, 1975, p.70-80.
• 17. Wichern, D.W., Johnson, R.A.: Applied multivariate statistical analysis; New Jersey, Prentice Hall, 1992, p. 642.
• 18. Winters, S.C., Gelberman, R.H., Woo, S.L.Y., Chan, S.S., Grewal, R., Seiler III, J.G.: The effects of multiple- strand suture methods on the strength and excursion of repaired intrasynovial flexor tendons: a biomechanical study in dogs. J Hand Surg 23 A: 97-104, 1998.

Publication Dates

• Publication in this collection
  25 Feb 2003
• Date of issue
  Sept 2002

History

• Accepted
  15 May 2002
• Received
  01 Nov 2001