Flexor Tendon Injuries in the Hand : A UK Survey of Repair Techniques and Suture Materials — Are We Following the Evidence ?

Introduction. Injuries to the hand are common, and poor functional outcomes can have significant long-term consequences affecting both work and social activities. Good outcomes following flexor tendon lacerations in the hand are dependent on a sound surgical repair allowing early active mobilisation.Materials andMethods. We reviewed the literature regarding the choice of suture material and repair technique. We then carried out a nationwide postal survey of plastic surgery hand units to assess the level of compliance with the evidence. Results. Fifty-four units were surveyed. The response rate was 72%, with the most popular core suture being Prolene (64%) and themost popular technique being theKessler repair (36%).Discussion. Current evidence advocates amultistrand repair using Ethibond. We found that the majority of units are not following the evidence. We suggest the use of evidence-based departmental guidelines to improve the practice and outcomes following these common injuries.


Introduction
Injuries to the hand are common, accounting for around one-fifth of all presentations to the emergency department in most hospitals and costing over £100,000,000 per year in the United Kingdom to treat [1].Of these patients around 1-2% have tendon lacerations [2], more commonly on the flexor aspect.Strickland [3] described the characteristics of an ideal primary flexor tendon repair: (i) easily placed in tendon; (ii) secure knots; (iii) smooth junctions; (iv) minimal gapping; (v) minimal interference with tendon vascularity; (vi) sufficient strength throughout healing to permit application of early motion stress.
Early active mobilisation has been shown to be important in terms of preventing the formation of adhesions [4], stimulating tendon healing [5], and improving functional outcome [6,7].Immediately after a tendon repair, the tendon itself will contribute nothing to the strength of the repair, which is therefore entirely dependent on the suture material and the technique used, as well as meticulous surgical technique and careful tissue handling.Suture material and technique are thus crucial to the survival of the repair.We have examined the evidence related to different suture materials and the different techniques for tendon repair and compared this with current practice in plastic surgery hand units within the United Kingdom and the Republic of Ireland.

Current Evidence
2.1.Suture.The ideal core suture material should have high tensile strength, be inextensible, cause no tissue reaction, and be easy to handle and knot [8].Stainless steel fulfils the first 3 of these criteria and was historically the recommended choice [9].However, this has now fallen out of favour due to poor handling characteristics, problems with kinking, and bulky knot formation.The sutures used most commonly in the UK are Prolene (Ethicon, Edinburgh, UK), a monofilament polypropylene suture; Ethibond (Ethicon), braided polyethylene terephthalate coated with polybutilate; and Ticron (Tyco Healthcare, Gosport, UK), braided polyester coated with silicon.Also gaining popularity is Fiberwire (Arthrex, Naples, FL), a multistranded long chain polyethylene core with a polyester braided jacket.These have all been evaluated in purely material terms and also their biomechanical properties when used in tendon repairs.
Despite its poor handling stainless steel has been shown to be stiffer and have a higher tensile strength than its competitors [8,10], Fiberwire has similar biomechanical properties, but improved handling [10].However, there are still concerns with regard to the knotting of Fiberwire, and the multiple knots required for a secure hold result in a bulky repair [11].Ethibond is next stiffest, with increased stiffness and reduced gapping relative to Prolene [10,12].In addition Ethibond is stiffer than Nylon [13], PDS, Maxon, Dexon, and Vicryl and does not show significant deterioration in its mechanical properties following in vivo incubation after 6 weeks [12].Ethibond therefore has a good balance of mechanical properties and handling/knotting characteristics.
Increasing the size of the core suture increases the strength of the repair [14].Using a 2-0 core suture significantly increases the maximum tensile strength of the repair when compared with 3-0 or 4-0 sutures but also increases the resistance to gliding of the tendon, measured as work of flexion [15].The same study showed no significant difference between 3-0 and 4-0 sutures for either tensile strength or work of flexion.

Repair Technique.
There have been many different techniques described for the repair of digital flexor tendons, including the Kessler repair [16], which was modified in 1979 [17], Strickland repair [3], and Savage repair [18], all of which are in common usage.Many studies have demonstrated that the strength of a flexor tendon repair is roughly proportional to the number of suture strands crossing the site of the repair [19][20][21].However, increasing the number of strands may lead to a bulkier repair [22] and increased work of flexion [23].Four strand repairs are therefore gaining in popularity, with a reasonable balance between strength and size of repair.The 4-Strand Cruciate repair shows good biomechanical properties when compared with a variety of other options [24][25][26].It has been shown that there is no increase in operative time for this repair, and it is no more technically challenging to a trainee surgeon [27].

Method
We sent a postal survey questionnaire to the hand unit of all plastic surgery departments within the UK and Ireland (from a list taken from the website of the British Association of Plastic, Reconstructive and Aesthetic Surgeons), excluding children's hospitals and those performing elective surgery only.We asked if there was a departmental protocol or guidelines for the repair of zone II flexor tendon lacerations, and if so what was the choice of repair technique, core suture, and peripheral suture.We also asked for the personal preference of the lead consultant of the hand unit in each of these same categories.

Results
From the 54 units surveyed we had 39 replies-a response rate of 72%.Of these 39, 18 (46%) had departmental protocols.The protocols were identical to the personal preference of the lead consultant in all except 2 departments, showing that for the purposes of this study the personal preference of the lead consultant could be used as a standard to allow for comparison between those departments with guidelines and those without.
The results for repair techniques are shown in Table 1.The Kessler repair was by far the most commonly used, being the technique of choice in 25 units (64%).Fourteen units (36%) used a standard Kessler repair (2 strands), and 11 units (28%) used a modified Kessler repair (4 or more strands).The other techniques used were the Strickland repair (7 units, 18%), the Modified Savage repair (5 units, 13%), and the 4-Strand Cruciate repair (2 units, 5%).
The results for the preipheral suture are shown in Table 3.By far the most commonly used material for the peripheral suture was Prolene, used in 32 units (82%), with the remaining 7 units (18%) using Nylon.Twenty-eight units (72%) used 6-0 peripheral sutures, with the remaining 11 units (28%) choosing a 5-0 peripheral suture.

Discussion
Flexor tendon injuries are common, and a good functional outcome relies on a strong low friction repair to allow early mobilisation, without compromising the vascularity of the tendon and without the formation of adhesions.The choice of suture material and repair technique is a complex one and involves a balance between tensile strength, ease of handling and knotting, technical difficulty, and work of flexion following repair.
There is no single core suture material which meets perfectly all of the requirements as described by Trail [8].However, there is an increasing weight of evidence to support Ethibond as the best compromise.In our study only 26% of units were using Ethibond.The majority (64%) were using Prolene, which is biomechanically inferior to Ethibond [10,12].
The size of the core suture has an impact on tensile strength and work of flexion of the repair, with 2-0 sutures being stronger-but causing more friction-than 3-0 or 4-0 sutures [15].The balance between tensile strength and work of flexion therefore remains a choice for the surgeon.In our study all units were using either 3-0 or 4-0 sutures, which show no statistically significant difference in tensile strength or work of flexion.
There are many different options for the repair technique, but it is now clear that a two-strand repair is biomechanically inferior to a repair with 4 or more strands.Despite this we found that a two strand Kessler repair remains the most popular choice, being the preferred technique in 36% of respondents.These findings are similar to those of an earlier survey [28].

Conclusions
The majority of studies comparing strengths of tendon repairs are based on cadaveric, nonhuman, and purely biomechanical data.There is a need for large scale randomised control trials to evaluate clinical outcomes for different suture choices and repair techniques.Our study shows that there is a wide range of suture materials and repair techniques in use.Even despite the limitations of current evidence, it would appear that many units are carrying out tendon repairs based on historical preferences rather than making evidencebased choices.There needs to be improved awareness of the evidence, and we would suggest that departmental guidelines should be drawn up or updated based on current evidence in order to encourage best practice.

Table 1 :
Choice of repair technique.

Table 2 :
Choice of core suture.

Table 3 :
Choice of peripheral suture.