Abstract
Background:
Hand zone II flexor tendon repair had been associated with many complications thereby it was previously called no man’s land. Although there is some agreement on the primary repair of flexor tendons in this area, it is challenging due to certain complications.
We compared the six and four-strand techniques in the repair of flexor digitorum profundus (FDP) tendons of zone II.
Methods:
This randomized controlled clinical trial was registered with the Iranian Registry of Clinical Trials (IRCT20130812014333N139). Fifty patients with damaged FDP in zone II of the hand who were referred to Taleghani Hospital, Kermanshah, Iran in 2020 were included and divided into two groups (n=25). In group 1, the damaged tendons were repaired using the four-strand technique and prolene suture while in group 2, the six-strand technique was used. Postoperatively, the patients were examined every week for the first three weeks. In the second and third weeks, sutures were removed. At the end of 3rd month, the outcomes of surgery were compared in the groups.
Results:
Fifty patients (74% male) with 85 damaged fingers were investigated. Based on Buck-Gramcko criteria, the outcomes of surgery were excellent in 78%, good in 16%, fair in 4%, and bad in 2%. Complications after surgery were adhesion (8%) and 2 cases of rupture. There was no significant difference between 4 and 6-strand sutures regarding tendon adhesion and range of motion.
Conclusion:
Both 4 and 6-strand sutures were associated with favorable outcomes in patients with damaged FDP in zone II of the hand.
Key Words: Hand Injury, Tendon, Tendon Injury, Plastic Surgery Procedure
INTRODUCTION
The hand has been divided into five anatomic zones in order to diversify the therapeutic approach based on the site of flexor tendon injury 1, 2. Among these 5 zones, zone II has particular importance as it contains both flexor digitorum superficialis and flexor digitorum profundus (FDP) 3. Zone II is located between the middle part of the middle phalanx and the distal palmar fold. This zone has been historically named “no man’s land” by Bunnell 4 as the surgical intervention in this area is associated with a high risk of complications including tendon rupture, because of an insufficient vascular supply, and adhesion formation due to the tightness of the tunnel that encompasses the two tendons 5.
Recovering sufficient digital function following flexor tendon injury is among the most challenging topics in hand surgery. Although many techniques have been introduced to optimize the outcomes of surgical intervention, numerous controversies still remain in this field 3. The strength of the repair is the most crucial factor that preserves the physiological function of tendons. More strands in sutures cause more strength but bulking the area like six-strand sutures. Four stand sutures maintain the balance between strength and bulking 6, 7. Overall, the existing evidence suggests the use of a four-strand repair using braided nonabsorbable sutures 8. To reduce the risk of tendon adhesion, the surgical procedure should be performed within the first 6 to 12 hours after damage. If the diagnosis is delayed for only a week, the tendon repair may become impossible 9.
Due to the inconsistency of the results of previous studies and the lack of agreement on the methods used to repair flexor tendons in zone II and also the importance of these tendons in hand function, we conducted the present study to evaluate the results of FDP repair with four-strand proline suture compared with the six-strand technique.
METHODS
Study design and participants
This randomized controlled clinical trial was conducted at Taleghani Hospital, Kermanshah, Iran in 2020. The inclusion criteria were damaged FDP in zone II of the hand. Patients who did not consent to participate in the study, had severe bone or finger damage, and crushed injury were excluded. Randomization was done with random allocation software. A total of 50 patients were included in the study and randomly divided into two groups of 25.
Data collection
Demographic information and subjective data related to the injury were collected by interviewing with patients. The severity of damage was assessed by exploring by the surgeon. Patients in the two groups underwent surgical procedure by the same surgeon. The procedure was performed under local anesthesia and within the first 24 hours after injury if possible. Various core suture techniques have been described in the literature. Modified Kessler is a popular technique chosen by 65% of surgeons 10. In the present study, in group 1, the damaged tendons were repaired using modified Kessler four-strand suture while in group 2, modified Kessler six-strand suture were used. After surgery, the limb’s immobility was achieved by casting in dorsal of the limb with 40 to 45-degree flexion of the wrist, 50 to 60-degree flexion of the metacarpophalangeal joint, and interdigital joints extension. Finger mobility started on the second day after surgery based on the modified Kleinert technique. All patients were examined every week for the first three weeks. The first examination of the fingers was performed by measuring the total range of motion of the JAMAR fingers and Total Active Motion 11 was compared recorded with the healthy finger of the opposite hand. In the second and third weeks, sutures were removed. After removing sutures and casting, patients were referred for physiotherapy. At the of the third month, all the limitations in the motility were eliminated. 3 months after the surgery, the results were compared in two groups based on the Buck-Gramcko criteria 12. The healing process, digital range of motion, and complications such as adhesion and rupture of tendons were investigated. Primary repair (within the first 24 hours) and delayed repair (24 hours to 10 days) were also compared.
Statistical analysis
SPSS software version 16 (Chicago, IL, USA) was used for statistical analysis. Kolmogorov-Smirnov test was used to determine the normality of quantitative variables. For comparison of quantitative variables in two groups, independent t-test or Mann Whitney U test were used. The chi-square test or Fisher’s exact test were used to analyze the qualitative variables. The statistical significance was set at 0.05 for all tests.
Ethical considerations
This randomized controlled clinical trial was registered with the Iranian Registry of Clinical Trials (IRCT20130812014333N139). The study was also approved by the Research Ethics Committee of Kermanshah University of Medical Sciences (IR.KUMS.REC.1398.942). Written informed consent was obtained from all of the participants in this study. The patients were assured that they could withdraw from the study at any time. The principles of ethics Medicine, The Helsinki Declaration, was observed.
RESULTS
Baseline characteristics of the participants
Overall, 25 patients (20 men and 5 women) were in the four-strand suture group and 25 patients (17 men and 8 women) were in the six-strand suture group. The mean age was 27.08 in four-strand group and 34.4 in six-strand suture group. In the four-strand group, the minimum age was 2 years and the maximum was 57 years, and in the six-strand suture group, it was 8 and 50 years, respectively. In the four-strand group, 18 were married and 7 were single while in the six-strand suture group, 11 were married and 14 married single (Table 2).
Table 2.
Baseline characteristics of the participants in the two groups
| Variable | Six-strand group Number (%) |
Four-strand group Number (%) |
|
|---|---|---|---|
| Age group (years) | 1-10 | 1 (4) | 1 (4) |
| 11-20 | 5 (20) | 2 (8) | |
| 21-30 | 13 (52) | 7 (28) | |
| 31-40 | 2 (8) | 5 (20) | |
| 41-50 | 3 (12) | 10 (40) | |
| 51-60 | 1 (4) | 0 | |
| Number of damaged digits | One | 13 (52) | 7 (28) |
| Two | 10 (40) | 15 (60) | |
| Three | 2 (8) | 3 (12) | |
| Involved side | Dominant | 18 (72) | 15 (60) |
| Non-dominant | 7 (28) | 10 (40) | |
Surgical outcomes
Postoperatively, digital range of motion was excellent in 39 patients (78%), good in 8 patients (16%), fair in 2 patients (4%), and bad in 1 patient (2 %). In the four-strand group, there were 20 patients with excellent range of motion, 3 with good range of motion, 2 with fair range of motion, and 0 with bad range of motion. In the six-strand suture group, there were 19, 5, 0, and 1 patient/patients with excellent, good, fair, and bad range of motion, respectively. In each group one case had rupture. Two cases of adhesion occurred in in each group (8%). There was no significant difference between the two groups in terms of range of motion (0.317), and tendon adhesion. There was no significant difference between men and women in terms number of damaged digits, range of motion, and adhesion (Table 3). However, there was a remarkable association between gender and involved side.
Table 3.
Clinical characteristics of the study population by gender
| Variable | Gender | P-value | ||
|---|---|---|---|---|
| Male | Female | |||
| Digital range of motion | Excellent | 29 | 10 | .657 |
| Good | 5 | 3 | ||
| Fair | 2 | 0 | ||
| Poor | 1 | 0 | ||
| Tendon adhesion | Yes | 2 | 2 | .253 |
| No | 35 | 11 | ||
| Number of damaged digits | One | 13 | 7 | .265 |
| Two | 19 | 6 | ||
| Three | 5 | 0 | ||
| Involved side | Dominant | 21 | 12 | .01 |
| Non-dominant | 16 | 1 | ||
There was no significant association between involved side and range of motion, or tendon adhesion (Table 4).
Table 4.
Surgical outcomes of the study population by involved side
| Variable | Involved side | P-value | ||
|---|---|---|---|---|
| Dominant | Non-dominant | |||
| Digital range of motion | Excellent | 25 | 14 | .778 |
| Good | 6 | 2 | ||
| Fair | 1 | 1 | ||
| Poor | 1 | 0 | ||
| Tendon adhesion | Yes | 3 | 1 | .692 |
| No | 30 | 16 | ||
There was a significant association between number of damaged digits with range of motion and tendon adhesion (Table 5).
Table 5.
Surgical outcomes of the study population by number of damaged digits
| Variable | Number of damaged digits | P-value | |||
| One | Two | Three | |||
| Digital range of motion | Excellent | 20 | 17 | 2 | .03 |
| Good | 0 | 6 | 2 | ||
| Fair | 0 | 1 | 1 | ||
| Poor | 0 | 1 | 0 | ||
| Tendon adhesion | Yes | 0 | 2 | 2 | .01 |
| No | 20 | 23 | 3 | ||
DISCUSSION
Superficial position of flexor tendons, vessels, and nerves of the hand and forearm dispose them to rupture and damage. Despite the development of novel techniques, repairing the zone II flexor tendons is still a challenging field in hand surgery due to the high risk of rupture and adhesion 13.
Demographic characteristics
The number of damaged digits was 1.7 in males and 1.4 in females. In other studies, this ranged from 1.2 to 2 14, 15. Similar to our findings, Güntürk et al. observed no difference between men and women in terms of surgical outcomes 16. In this study, the prevalence of injury was higher in the age group of 21-30, which is consistent with a previous study, where an average age of 28.9 was reported 16. Behdaneh et al., in contrast to the present study, showed that excellent and good results were more in non-dominant hands 14.
Functional outcomes
In the present study, the application of four-strand and six-strand suture techniques was associated with good or excellent postoperative results in 94% of the cases with damaged FDP in zone II of the hand. Previous studies have shown different surgical outcomes. Zhou et al. reported a 83% chance of excellent and good healing after surgery of ruptured tendons 17. In a study performed by Moriya et al., a good or excellent outcome was observed in 82% of the cases 18. Another study also demonstrated 87% of good and excellent range of motion achievement after surgery 19. These results are mainly consistent with the outcomes of our study, however, some discrepancy is noted in results of different studies that could be because of non-referral to physiotherapist, early removing of cast, and damage to the nerve and vessels. Some patients are scared of secondary rupture due to physiotherapy and avoid referring because of pain and hardness of joint while physiotherapy is recommended 20, 21.
Surgical complications
In this study, the risk of complications was similar in both groups (12%). We observed a 4% risk of rupture which is lower than the 5.4% risk reported by Moriya et al. 18. Venting the pulley has been suggested as the major strategy in reducing the risk of rupture 19. Four stand and six-strand sutures were not different in the present study regarding digital motions and adhesion. Previous studies noted that 4 strand suture was associated with higher strength and lower risk of rupture, as well as reduced need for a second surgery 11, 22.
Postoperative care
Tendon repair happens in three-stage of inflammation, fibroblasts proliferation, and remodeling. Tendon strength increases 21 days after repair and inserted stresses, and movement is so important in the reorganization of collagen 23. These facts prove the importance of early movements in strength increase and adhesion reduction after surgery. So, after surgery, rehabilitation is necessary for achieving social and occupational activities. Immobility for a period, and then physiotherapy is suitable for this purpose 24, 25. In the present study, limb immobilization was performed after surgery by placing a plaster splint on the dorsal surface of the limb. The modified Kleinert method trained and performed starting movements from the second day after surgery. In this study, immobility after surgery casting on the dorsal surface was done. Moreover, on the second day after surgery, the movement by the modified Kleinert method was started.
The results of flexor tendon repair procedures are strongly influenced by a wide range of factors, including the patient’s age and motivation, preoperative condition, surgical technique, and postoperative management 26. Tendon repair, when accompanied by full observance of technical principles such as minimal damage to the tendon sheath during dissection to find the two ends of tendons, tendon sheath repair after tendon repair, avoiding lumps at the repair site, and maintaining proper rotation of tendons power, leads to excellent results 27. Overall, multi-stranded repair is undoubtedly stronger, but regarding the time of surgery and tissue damage, which may have biological consequences for tendon healing. It is also essential to maintain friction between the tendon and the sheath. As the extra suture fibers are repaired, the repair volume must be increased to elevate the resistance to further shear of the tendon. After each repair, a slight increase in friction resistance is observed. However, there is no significant difference between the techniques, which may lead to controversies on the selection of repair techniques 28-30. The limitation of this study was the relatively short length of follow-up. A long-term follow-up might affect the results of the surgical techniques evaluated in this study.
Figure 1.
Surgical techniques used in this study: A= modified Kessler six-strand suture, B= modified Kessler four-strand suture
Table 1.
Assessment of FDP recovery according to Buck-Gramcko criteria
| Variable | Degrees | Points | |
|---|---|---|---|
| Flexion of interphalangeal joint | 50-90 | 6 | |
| 30-49 | 4 | ||
| 10-29 | 2 | ||
| <10 | 0 | ||
| Extension deficit | 0-10 | 3 | |
| 11-20 | 2 | ||
| 21-30 | 1 | ||
| 30< | 0 | ||
| Total active movement | 40< | 6 | |
| 30-39 | 4 | ||
| 20-29 | 2 | ||
| <20 | 0 | ||
| Evaluation | Excellent | 14-15 | |
| Good | 11-13 | ||
| Fair | 7-10 | ||
| Poor | 0-6 | ||
CONCLUSION
Despite significant advances in hand zone II flexor tendon surgical repair, adhesion between the tendon and its sheath is still problematic. This study compared the results of four-strand suture and six-strand suture in patients with damaged FDP in zone II of the hand. Overall, surgical intervention showed favorable outcomes in patients and no significant difference was found between the two techniques in terms of range of motion and tendon adhesion. Zone II flexor tendon rehabilitation protocols are evolving toward the use of early active movement, and the search for stronger repair techniques continues.
FUNDING
This study was supported by Kermanshah University of Medical Sciences.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests.
ACKNOWLEDGMENTS
Not applicable.
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