Digital Flexor Tenotomy: An Emerging Answer For Surgical Offloading

Given the potential for forefoot complications in patients with diabetic neuropathy, can the digital flexor tenotomy be an effective method of offloading? Noting the low risks of tenotomy, these authors explore the literature and offer pearls on the minimally invasive surgical technique.

Patients with diabetes present unique and often complex challenges. As part of the natural history of the disease process, diabetic peripheral neuropathy, vasculopathy, tendinopathies, myopathies and skin manifestations are the main culprits in the progression of diabetic foot issues. In particular when neuropathy is present, the clinical approach must become more rigorous and comprehensive. Though any part of the foot can be affected, the most common area is the forefoot.

It is essential to realize that with any foot deformity related or unrelated to diabetes, it becomes increasingly important to address deformity when there is coexisting neuropathy. Toe deformities are the most common and usually present as hammertoe(s). Though many individuals can tolerate various degrees of deformity, the patient with diabetic neuropathy is far more prone to skin breakdown and the sequela of ulceration. With the hammertoe deformity, ulcerations can occur at the distal aspect and/or dorsal aspect of the toe, or under the respective metatarsal head. One must assess these areas regularly when the patient has a neuropathic hammertoe.

After deciding to address a hammertoe deformity in any patient with diabetes, surgeons must take many factors into consideration. Primarily, one must scrutinize the patient’s overall health and past medical history. Diabetes in the presence of concomitant chronic disease compounds the risks associated with surgical intervention. Thus, when enlisting the digital flexor tenotomy as a prophylactic offloading procedure, one should strive to ensure patient optimization to improve postsurgical outcomes.

In the lower extremity literature, various authors have described tendon-based procedures that can correct a multitude of deformities. All tendons have a specific action, defined by their origin, insertion and course. Additionally, each tendon functions in concert with its antagonist during very specific segments of the gait cycle. When performing a tendon transfer or lengthening, a careful assessment of range of motion and strength of the associated muscle is essential. Since one does not completely transect the tendon, assessing the muscle strength of the flexor digitorum longus is not required.
The flexor tenotomy, however, is contraindicated as the sole procedure for rigid hammertoe deformities. A non-reducible, rigid hammertoe deformity is an osseous problem that requires more than just a tenotomy. A tenotomy will fail in offloading and reducing pressure in this instance.

Given that patients with diabetes are at high risk for amputations, prophylactic surgery aims at mitigating the risk of ulceration in areas associated with increased pressures and osseous deformity. All surgical procedures carry inherent risks that one must balance with the benefits the procedures confer. It is this point that makes the flexor tenotomy an important limb salvage procedure as it is both minimally invasive and has minimal postoperative risks and complications.

A Guide To Surgical Planning And Technique
The physical examination is the single most important guide to surgical planning. The assessment of the skin and soft tissues, joint and joint range of motion, presence of neuropathy, and the vascular exam aid in defining the extent of present pathology and give insight on the urgency toward surgical intervention. Obtain a radiographic evaluation, particularly if an open lesion is present. Advanced imaging can further rule out osteomyelitis, which if positive, changes the management algorithm.

For the patient without evidence of an overt clinical infection, the most vital laboratory test to obtain is the HbA1c. Multiple authors have emphasized the importance of preoperative screening in the literature.¹ Patients with suboptimal HbA1c levels are at much higher risk for postoperative complications. The greatest complications that patients should be aware of in the postoperative period include surgical site infection and sepsis, dehiscence, prolonged healing, and a perpetual risk for future amputation. Though there is no current consensus for a definitive cutoff for HbA1c levels, it is generally accepted that an HbA1c of 7.5% or less is appropriate.

In a 2014 paper, Wukich and colleagues published a level 1 prospective study identifying neuropathy and HbA1c ≥8% as independent risk factors for postoperative surgical site infection.1 Although getting under this HbA1c level can be a challenge in many instances to achieve for a prophylactic procedure, there should be little leeway in this regard. There is a direct relationship between high HbA1c levels and postoperative complications. Decreasing this risk by timing surgery when HbA1c levels are optimal lessens the chance for infection, dehiscence and impaired healing. However, it is worth noting that on the scale of invasiveness, toe procedures are relatively safe. The risks involved relate more to the patient’s comorbidities and glycemic control than the flexor tenotomy and associated procedure(s).  

It is important to discuss all relevant clinical findings with patients and educate them in layman’s terms during the consent process. Facilitate a two-way discussion to uncover any misconceptions, unrealistic expectations or gray areas. Finally, the consent should always include the possibility to require additional osseous work in order to achieve a maximal result. Hammertoe deformities that have adequate range of motion at the distal and proximal interphalangeal joints are the most amiable for pressure reduction. In these cases, a tenotomy is generally all that is required. As the deformity becomes more rigid, the more likely an arthroplasty of the affected joint(s) is needed.

Although a perfectly rectus toe may be an optimal aesthetic goal, the main reasons to perform such a procedure are to decrease pressures (thus decreasing the likelihood of future ulceration) and heal existing ulcers. We should ultimately view the digital flexor tenotomy as a surgical offloading procedure rather than a procedure for hammertoe correction.

There should not be a need to use Kirschner wires to facilitate a more rectus toe position. If the clinical exam reveals an irreducible joint, then an arthroplasty should be the primary surgical intervention. Avoid the use of Kirschner wires if at all possible when performing arthroplasties. Patients with such deformities, who have diabetes and/or loss of protective sensation, should not have an arthrodesis procedure. An arthrodesis makes the toe less mobile and thus more prone to increased pressures as the toe will not yield when pressures are exerted upon it. In short, an arthrodesis could potentiate pressures rather than decrease them.

When performing the flexor tenotomy, take care to ensure that the incision is minimal and that the blade or needle remains central so as not to inadvertently violate the small medial and lateral vessels in the toe. One should completely tenotomize the flexor digitorum longus tendon of the involved toe(s). If the deformity remains, one can perform an additional tenotomy on the flexor digitorum brevis. It is for this reason that performing the open technique at the base of the toe plantarly is a viable approach. After making a small incision, blunt dissection quickly reveals the tendon complex as both the flexor digitorum brevis tendon and flexor digitorum longus tendon traverse this area. Employing direct visualization, targeted sequential release can provide a much more controlled reduction. Due to the dorsal contracture at the proximal interphalangeal joint, the extensor tendons are usually elongated, which compensates for the loss of flexor antagonism. It is this key point that allows the toe to remain flexible, balanced and rectus.

An alternate incisional approach focuses on the distal plantar sulcus, just proximal to the distal pulp of the toe. At this level, only the flexor digitorum longus is available for tenotomy. This is a common approach and provides effective offloading for distal toe ulcerations. In this case, since there are no other structures to be wary of violating, a percutaneous blind approach is acceptable. One can always extend the incision for direct visualization if the blind approach fails. To ensure complete release, the toe should be hyperextended to place tension on the flexor digitorum longus. Repeat this for all of the lesser digits irrespective of the presence of hammertoe deformity. This prevents the inevitable “transfer” lesion, which will develop under the adjacent metatarsophalangeal joint (MPJ). Since this is a prophylaxis against ulceration, it is fitting to be proactive in the tenotomies of the second through fifth toes.

For longstanding deformities, a separate incision dorsal to the respective metatarsal head may be required to release contracture and adhesions to the plantar apparatus. The reduction of pressure under the MPJ when callus or ulceration is present requires reducing the toe at the proximal interphalangeal joint. A hammertoe exerts retrograde pressure, which increases submetatarsal head pressure. Contractures and adhesions to the plantar apparatus can prevent the toe from relaxing after completion of the tenotomy. However, this is rarely required and usually occurs as an adjunct with arthroplasties.

The use of the percutaneous needle method for a flexor tenotomy offers several advantages. There is no need for any suture and the patient can bathe the next day. Although this procedure should ideally occur in an operating theater, many opt to perform this sterilely in the clinic setting. We recommend post-procedural antibiosis in this scenario and especially when there is a suboptimal HbA1c.

In regard to the closure of the stab incision, simple interrupted sutures, an apical horizontal suture or a horizontal mattress suture are optimal. One should avoid utilizing a vertical mattress suture, which may create plantar tension and recreate the deformity.

What Does The Literature Say About Digital Flexor Tenotomy?
The International Working Group on the Diabetic Foot in 2015 published guidelines on the prevention of foot ulcers in “at-risk” patients with diabetes.² They define the key risk factors of the at-risk patient as the presence of peripheral neuropathy, foot deformity, peripheral vascular disease or a history of foot ulceration or amputation of (a part of) the foot or leg. As part of the guidance, a grade/quality score reflecting strength of recommendation and level of evidence respectively is provided to each recommendation. Flexor tenotomy, according to their consensus (weak; moderate) should be a consideration to prevent a toe ulcer when conservative treatment fails in a high-risk patient with diabetes, hammertoes and either a pre-ulcerative sign or an ulcer on the distal toe.

In 2009, Roukis and Schade published a systematic review on percutaneous flexor tenotomy for neuropathic toe ulceration secondary to toe contracture in patients with diabetes.³ They state “… it appears that percutaneous flexor tenotomy for the treatment of neuropathic toe ulceration secondary to toe contracture in persons with diabetes might provide structural realignment and ulcer healing comparable with traditional open surgical approaches and could offer some advantages. However, it is still necessary to have more evidence to be able to make solid recommendations regarding use of percutaneous flexor tenotomy for the treatment of neuropathic toe ulceration secondary to toe contracture in persons with diabetes.”

It is perhaps the paucity of well-designed, high-powered studies that have driven the International Working Group on the Diabetic Foot to reach its conclusions.² Suffice it to say, as more research in this area develops, guidelines will reflect the true nature of the utility of the digital flexor tenotomy. Anecdotally, the potential benefits far outweigh the procedure’s risks. Until more evidence elucidates specific questions such as rate of ulcerations, amputations, wound complications and cost effectiveness related to the procedure, tenotomy still serves as a desirable and likely underutilized tool.

Most of the current literature on this subject is level 4 evidence. Tamir and colleagues did a study on 160 toes with tenotomies of the flexor digitorum longus tendon, extensor digitorum longus tendon, and combined tenotomy of the flexor digitorum longus and extensor digitorum longus tendons based on ulcer location.⁴ They found that the tenotomy of the flexor digitorum longus tendon for distal toe ulceration had the highest healing rates (98 percent at four weeks) in comparison to the other tenotomy procedures. The complication rate was very low with the exception of “transfer lesions,” in which an adjacent toe became involved and needed subsequent tenotomy in 8 percent of tip-of-toe ulcers.  

Rasmussen and coworkers published a retrospective study that assessed the percutaneous tenotomy on 65 toes in 38 patients.⁵ In this study, the surgeons had performed the procedure on the flexor digitorum longus and flexor digitorum brevis through a small transverse plantar stab incision just proximal to the web level. Rasmussen and colleagues noted that patients had no postoperative infections and experienced healing of all ulcerations including neuroischemic toes.  

Van Netten and colleagues studied flexor digitorum longus tenotomies for 38 distal toe ulcerations.⁶ Thirty-five ulcers healed with a mean time to healing of 22 ± 26 days. There were nine additional cases without ulceration and the surgeons performed prophylactic flexor tenotomies. None of these cases resulted in any ulcer or other complications during the time to healing.

In Conclusion
The flexor tenotomy is a simple and very effective procedure that carries minimal risk when surgeons ensure appropriate patient selection. One may perform this procedure with the patient having straight local anesthesia if he or she has residual sensation. The flexor tenotomy is minimally invasive. There are two approaches: an open approach offering direct visualization and a percutaneous approach. The preferred percutaneous method is via a small stab incision with a #11, #15 or beaver blade. However, using an 18-gauge needle can also be effective and offers the advantage of not needing any sutures for skin repair. Due to the relative ease and quickness of the procedure, and its utility in the patient with a complex medical and social history, the flexor tenotomy becomes an attractive procedure.

Consider the flexor tenotomy as an adjunctive procedure for ulcer healing and prevention. It is primarily an offloading procedure with a secondary benefit of some hammertoe reduction. Ulcerations that occur as a result of hammertoe deformities are preventable. Moreover, once an ulcer has formed, the risk of an ascending infection or infection of bone leads to a protracted cycle of hospitalization, intravenous antibiotics, prolonged wound healing and amputation. The utility of the flexor tenotomy is a valuable adjunctive procedure that carries minimal risk. One can mitigate the risk of infection by preoperative HbA1c and patient optimization. Postoperative antibiotics can be an option in specific situations.

The utility of the digital flexor tenotomy in the patient with diabetes and neuropathy is respectable. The literature remains inconclusive regarding long-term effects related to ulcer recidivism and amputation rates. Further studies aimed at these points would be beneficial. However, the overall risks are low and the benefits of the procedure are tangible.

Dr. Elmarsafi is a Diabetic Limb Salvage Fellow at Medstar Georgetown University Hospital in the Center for Wound Healing in Washington, DC.

Dr. Kim is an Associate Professor at the Georgetown University School of Medicine. He is a Fellow of the American College of Foot and Ankle Surgeons.    

References

1.     Wukich DK, Crim BE, Frykberg RG, Rosario BL. Neuropathy and poorly controlled diabetes increase the rate of surgical site infection after foot and ankle surgery. J Bone Joint Surg Am. 2014;96(10):832–9.
2.     International Working Group on the Diabetic foot. International consensus on the diabetic foot and practical guidelines on the management and the prevention of the diabetic foot, 2015. Available at https://iwgdf.org/guidelines/ .
3.     Roukis TS, Schade VL. Percutaneous flexor tenotomy for treatment of neuropathic toe ulceration secondary to toe contracture in persons with diabetes: a systematic review. J Foot Ankle Surg. 2009; 48(6):684–9.
4.     Tamir E, Vigler M, Avisar E, Finestone AS. Percutaneous tenotomy for the treatment of diabetic toe ulcers. Foot Ankle Int. 2014;35(1):38-43.
5.     Rasmussen A, Bjerre-Christensen U, Almdal TP, Holstein P. Percutaneous flexor tenotomy for preventing and treating toe ulcers in people with diabetes mellitus. J Tissue Viability. 2013;22(3):68-73.
6.     Van Netten J, Bril A, van Baal JG. The effect of flexor tenotomy on healing and prevention of neuropathic diabetic foot ulcers on the distal end of the toe. J Foot Ankle Res. 2013 24;6(1):3.
7.     Bus S, van Netten J, Lavery L, et al. IWGDF guidance on the prevention of foot ulcers in at-risk patients with diabetes. Diabetes Metab Res Rev. 2016; 32(Suppl 1):16-24.
8.     Lavery LA, Armstrong DG, Vela SA, Quebedeaux TL, Fleischli JG. Practical criteria for screening patients at high risk for diabetic foot ulceration. Arch Intern Med. 1998; 158(2):157–162.