Flexor Tendon Injuries- A Decade for Change

The quality of the outcome following flexor tendon repair is highly dependent on the rehabilitation received. Published research into flexor tendon injuries has spanned almost half a century. Yet rupture rates continue to be cited at an incidence of 5%-11% and complications still occur. Clinical results of early active mobilisation protocols are not reliably better than passive protocols (Harris et al 1999, Cetan et al 2001, Saldana 1991).

Early active motion protocols have found to be either be too passive where tendon glide and excursion are ineffective, too aggressive resulting in tendon gap or rupture or implemented too soon when the Worl Of Flexion (WOF) is high resulting in bleeding and adhesion formation. Over the past decade, the literature presented new variables for change in the therapeutic management of flexor tendon injuries. These include synergistic wrist motion combined with early active movement, Metacarpophalangeal joint positioning within the splint, splint design (Manchester short splint), the timing of treatment (from 24 hours to 3-5 days) and more recently a move away from place and hold exercise as observations made during WALANT surgery by Dr Lalonde indicate that this exercise causes the tendon to ‘buckle and jerk’. Even though we were cautioned against this exercise by Savage in 1998, it was only in 2016 that we implemented this change in our practice following the publication of the Saint John Protocol. Research and clinical findings lead to a change in practice, but it also leads to confusion as tendon surgery and rehabilitation protocols develop in response to the literature. For example, prior to WALANT & Jin Bo Tang’s work on the value in venting pulley’s, surgeons and therapists were cautioned against a bulky repair for fear of restricting tendon glide beneath the pulley’s. Pulley’s were repaired or salvaged at all costs for fear of bowstringing. These two factors significantly impacted on our failure rates.

In response to this literature, surgeon’s developed the 2 strand Modified Kessler technique but in accordance with the Strickland Force Threshold Model, therapists and surgeons were cautioned against implementing early active motion with these repairs. Even though this model was outdated in a sense and did not recognise that a 2 strand repair can permit a range of low force exercises, provided the patient works within the safe zone. A zone where tendon loads are large enough to induce tendon motion yet small enough to avoid tendon gapping or rupture. This concept was the basis for where we are today where we understand that patients do not need to work towards a full fist immediately and should, in fact, take up to 6 weeks to achieve a full fist as described by the St John’s protocol. Patients can work in a safe zone. We also know that pulleys can be vented and repairs should be bulky. Furthermore, we also know that although the introduction of synergistic wrist motion into our practice has been extremely valuable, a change of wrist position alone does not influence differential glide in Zone II. We needed to do more to get better results.

The influence of wrist position and synergistic wrist motion on the forces exerted on the flexor tendon was documented between 1989 and 2002, emphasizing that synergistic wrist motion is a vital component of flexor tendon rehabilitation. It decreases active and passive tension on the healing flexor tendon, increases differential excursion and facilitates proximal glide in Zone V.

In 1998, Savage evaluated the influence of wrist position on ‘minimal active tension’ in the flexor tendons. The study showed that by positioning the wrist in extension, active tension in the flexors was minimal. He recommended that this be the position for post-operative protection of a flexor tendon repair, with active mobilisation being used cautiously. A positive move away from Kleinert splinting where the wrist was positioned in flexion.

Savage also reported that when the MP joints are flexed to 45°, passive tension in the extensors (‘Flexion Force’) is less than when the MP joints are flexed to 90°. Therefore during Early Active Motion (EAM) regimes, the wrist and MP joints should not be positioned in maximum flexion and early active place and hold exercises must not be performed against resistance. Positioning the MCP joints in 0-30 degrees to place the tendons at a biomechanical advantage was not considered at this stage for the fear of causing tendon gapping or rupture.

In summary, we understand that synergistic motion creates the greatest amount of excursion of both FDS & FDP tendons as well as differential excursion. Synergistic motion results in low forces with high excursion and it facilitates the length/tension relationship, with the minimal force generated in the flexor tendons. In addition, we know that wrist extension has an effective pulling force to create proximal glide.

Cadaver studies performed by Judy Colditz, OT/L, CHT, FAOTA and described in the Under the Skin DVD series demonstrate that the intrinsic plus position combined with the wrist in different positions does not facilitate proximal glide in Zone II. The joint distal to the repair site must be moved in order to achieve proximal glide beyond the sheath in Zone II.

This is a critical concept in flexor tendon rehabilitation. It also makes perfect sense as we cannot achieve adequate FDP pull through or differential glide with the MCP joints in a flexed position as the tendons are placed at a biomechanical disadvantage. We need to bring the MCP joints into neutral or at least 20-30 degrees in order to facilitate FDP glide within Zone 2. This concept must be applied to rehabilitation protocols in combination with wrist position and synergistic motion and applied now that we have the WALANT and other advancements in surgical techniques which assures us that the tendons will not gap or rupture.

Although we need a splint to protect the hand post-op, we do not need the splint to exercise the hand. Jin Bo Tang, MD, PHD states that the position of the MCP joints is, in fact, irrelevant and the patient should, in fact, mobilize out of the splint and wear it only as a reminder and for protection. But education is key and must begin in the operating room, with the mantra reinforced that they can 'move it but not use it'.

As we have entered a new decade, we need to take advantage of advancements in surgical techniques and therapeutic protocols and implement these key concepts in our practice:

• Educate our patients adequately.
• Adopt the WALANT technique.
• Delay our rehab to 3-5 days postoperatively.
• Use passive motion as a warm-up exercise.
• Combine synergistic motion with early active movement.
• Position the MCP joints between 0-30 degrees of flexion
• Encourage a hook fist position out of the splint, without aiming for full range of motion.
• Avoid place and hold exercises.
• Take 6 weeks to achieve full AROM
• Encourage functional hand use in the early stages of rehab.
• Act fast if rehab is failing & implement the CMMS technique

Most importantly we need to work as a team to improve functional outcomes. This includes being consistent with patient education & ensuring compliance through implementing evidence-based treatment regimes, reducing and managing complications and changing our approach if traditional therapy is failing.

When considering a successful outcome, we must take into account that the need for a Tenolysis or inadequate AROM on discharge is considered a failed outcome. We need to strive for excellent results. If we begin educating the patient on the operating table whilst having WALANT, if they are able to witness their fingers flexing actively into full flexion and extension intraoperatively and if we encourage the mantra 'I can move it but I can't use it' and then position the MCP joints into extension to facilitate differential glide combined with synergistic wrist motion, then we stand a good chance of achieving a good, functional result.