Results :

In vitro study

                     Among the 15 cadaver tendons tested 5 each were with Modified Kessler, Strickland and Four strand cruciate techniques. The data was collected in the form of Force to produce 2 mm gap formation at repair site; Maximum failure force and Mode of failure.

(Table 1)
 

In Modified Kessler technique, less than 1 kg of mean force produced both 2 mm gap at repair site and failure of repair (Maximum failure force).

 In Strickland method, average 1 kg of force produced failure.

While in four strand cruciate technique, average force to produce 2 mm gap was 1.8 kg and 2.12 kg for repair to fail which was almost double amount of force as compared to other 2 methods.

The average force to produce 2 mm gap and maximum failure force in Modified Kessler and Strickland is almost equal. The paired student’s‘t’ test was used to study the amount of increased force from 2 mm gap formation to maximum failure force. We found that there was no statistical significant increase in force in these 2 groups.

Mod. Kessler – t value = 1.952

                         p value = 0.2662 (p > 0.05)

Strickland -      t value = 1.4142

                        p value = 0.1950 (p > 0.05)

                    But in case of four strand cruciate method, this increase in force between 2 mm gap formation and maximum failure force was 0.3 kg which was statistically significant.

                       t value = 4.003

                       p value = 0.0039 (p < 0.05)

 Among 15 cases, 60% (9/15) repairs failed by pullout of sutures from tendon ends and 40 %( 6/15) failed by breakage of sutures. In four strand cruciate group 80% (4/5) failed by suture breakage while 20% failed by pullout. In other 2 methods, 80% repairs failed by pullout

   (Table 2)  
 

In Vivo study
There were 18 patients with lower limb tendon injuries. Total 19 tendoachilles tendons were repaired (1 patient had B/L TA injury). The age distribution of patients was uniform as shown by kolmogorov test
(Table 3)
 

The ratio of injuries according to occupation was laborers 31.57%, carpenters and sedentary workers as 10.53% each. The other occupations like students, housewives were 47.47%. 36.84% injuries were due to closet injuries (foot slips and traps in Indian closet, repeated attempts to remove foot causes sharp laceration of tendoachilles). Injuries by knife accounted for 26.32% while RTA caused 15.79% injuries. The other modes of injuries like assault, attrition were seen in 21.05% cases.

 (Table 4)

(Table 5)

Seven out of 19 tendoachilles injuries were due to closet injury (36.84%) while it was injured by RTA in 26.31% and by knife in 15.78%.

The sharp cut injuries were seen in 13/19 tendons (68.42%), while 3/19 were frayed (15.79%) and 3 were lacerated (15.79%).All the injuries by knife were sharp while in closet injury 5/7 were sharp (71.43%) and 2/7 were lacerated (28.57%).The 14/19 tendons were right sided (73.68%) while 5/19 were left sided (26.32%).

(Table 6)

The average operative time for tendoachilles repair was 32.81 minutes with S.D. ± 7.52 min. Average operative time for sharply cut tendons was 30 min. S.D. ± 5.77 min while for frayed tendons it was 43.33 min S.D.± 5.77 min. the lacerated tendons required 31.66 minutes with S.D. ± 2.89 minutes. The operative time difference between these groups was statistically not significant.(t = 0.6407, p value = 0.48) 

The plantarflexion movement at ankle > 40° at 3 months was seen in 8/19 cases (42.10%) while planterflexion at 6 months was > 40° in all patients.

At 3 months there were 10 patients with dorsiflexion at ankle < 10° and 9 patients with dorsiflexion > 10°. At 6 months all 19 limbs had dorsiflexion at ankle > 10°.

The average AOFAS score at 3 months was 76.25 with S.D. ± 7.96 and at 6 months was 87.125 with S.D. ± 3.81. The increase in AOFAS score from 3 to 6 months was 11.125

(Table 7)

In patients with age less than 30 years, average AOFAS score at 3 months was 79.2 which improved to 89.8 at 6 months. In age group of 30 – 40 years AOFAS score improved from 77 to 87.4 while in 40 – 50 years group it improved from 77.25 to 86.5. In patients with age > 50 years score of 76.2 improved to 86.2. Patients with < 30 years age had better AOFAS score at 3 and 6 months than others but improvement in score from 3 to 6 months was same in all age groups (10.8).

(Table 8)

Two patients had superficial infection. In one case it was associated with skin dehiscence and slough. Both the cases responded to oral antibiotic course and dressings. Patient with skin dehiscence had AOFAS score 82 which was less than average.

                     Three patients had adhesions in which 2 were unable to use Indian closet and had below average AOFAS score. Only 1 patient in our series had sural nerve paresthesia.

Discussion:

Since 1970 the management of tendon injuries is revolutionized due to immediate tendon repair and post repair motion protocols. Over these years many new suture designs, methods has been developed to increase strength and gap resistance of tendon repair techniques. They have permitted more aggressive post repair motion protocols and hence the global improvement in results. In spite of all these advances, there is no consensus over the gold standard or an ideal tendon repair technique.

A four strand cruciate design for tendon repair as described by McLarney3 and Strickland seems to be the near ideal suture technique. A review of literature shows lack of comprehensive clinical study in tendoachilles repair with this technique. Hence this study was performed.

In our study, 15 cadaver tendons were repaired by 3 methods viz. 1) Modified Kessler, 2) Strickland and 3) Four Strand Cruciate and the tensile strength of repairs was judged by linear force. For four strand cruciate the force to produce 2 mm gap was average 1.9 kg which was double the force required for other 2 methods. The maximum failure force was also double as compared to other methods. The attributed reasons for high tensile strength of four strand cruciate was 4 number of strand while other methods had only 2 strands. Lotz[i] in an analytical model proved that four strand cruciate has more tensile strength. In repairs with same number of strands, design of core repair determines the strength.

The mode of failure depends on core suture design and whether suture is locking or grasping type. The locking configuration is one in which the transverse component is passed superficial to the longitudinal so that suture passes around a bundle of tendon fiber and usually prevents pullout. In grasping type, the transverse component passes deep to longitudinal one so that suture does not pass around or lock and is more prone for pull out.

In our study, all repairs were grasping type so the expected result was pull out of sutures at maximum failure force. Though 80% (4/5) of modified Kessler and Strickland sutures failed by pull out, surprisingly 80% (4/5 repairs) of Four Strand Cruciate failed by suture breakage. Though a grasping type repair four strand cruciate exhibits strong pull out resistance due to 4 strands and cruciate design.

The locking designs are known for more gliding resistance and adhesions than grasping types.  The location of knot in four strand cruciate is away from the repair site. This helps in decreasing bulk at repair site and assuring perfect apposition of tendon ends.  More over 4 grasping sutures on surface may make this design more prone for adhesions. But in our cadaver study we were not able to measure and compare gliding resistance due to lack of costly devices like Load Transducers.  

In lower limb, tendoachilles were the commonest tendon injured. All the patients had minimum arc of movement from 10° dorsiflexion to 40° platarflexion at ankle. Even the AOFAS score showed good improvement between 3 to 6 months with 6 months score being average 87.125 indicating good functional outcome. These good results in tendoachilles were attributable to immobilization of ankle in neutral position. Even the period of immobilization was reduced to just 4 weeks contrary to 8 weeks. Due to this strong repair we were able to mobilize patients early with active motion protocols. Khan et al[ii] in Cochrane review reported rerupture rate of 2.3% to 5% after tendoachilles repairs while in our series there was no case of rerupture. Even the skin dehiscence was seen only in single case and 2 patients had superficial infection without any functional problem. Overall in tendoachilles repair four strand cruciate was found to be a good technique with sustainable persistent good results without any major complication. 

Conclusion: 

The purpose of this study was to compare biomechanical properties of Four Strand Cruciate technique with other established techniques and to evaluate clinical results of this technique.

• Four Strand Cruciate has significant high tensile strength and gap resistance than other two strand techniques which can allow us to use aggressive post repair rehabilitation protocols.

• The Four Strand Cruciate with its peculiarities causes fewer complications like reruptures and adhesions.

• The ease of placement and less time for repair with above properties make it near ideal tendon repair technique.

• There is no significant correlation between tendon ends, operative time and functional outcome of tendons repaired.

• There are significantly good results in patients less than 30 years with respect to functional outcome irrespective of type of tendons involved.

• This technique gives confidence to the surgeon to start with aggressive rehabilitation protocols to achieve good functional results.

• The incidence of complications like reruptures, adhesions, skin dehiscence is very less.