Peritendinous adhesions that form after the repair of lacerated digital flexor tendons cause stiffness and functional impairment. In the healing process, tendon regeneration and scarring are, probably, the two sides of the same coin. Surgeons, physical therapists, and basic scientists have explored new surgical and rehabilitation methods, pharmacological modalities, and nonpharmacological modalities (including ultrasound and pulsed electromagnetic field stimulation) to allow unrestricted gliding of the digital tendons. Pharmacological adjuvants fall into two main categories, namely, drugs (e.g., nonsteroidal anti-inflammatory drugs, hyaluronic acid, and 5-fluorouracil) and barriers1,2.
The authors explored a novel management modality that potentially could be applied for the prevention of adhesion formation after tendon repair. Using a rat Achilles tendon model and a rabbit flexor digitorum profundus tendon model, they injected an aqueous solution of a biocompatible phospholipid polymer around the repaired tendons. This material, which possibly can act as a "barrier," was biocompatible (that is, it did not cause adverse tissue reactions), and its higher concentration reduced adhesions without impairing the strength of the tendon repair. These findings are important because a biocompatible material potentially has clinical applications.
However, several questions remain unanswered regarding the efficacy of such a modality in clinical practice. As shown in numerous studies, adhesion formation is multifactorial. What is the balance between early mobilization and adequate immobilization to allow tendon healing in humans? What is the role of the tendon sheath and that of pulleys? We know that there are conflicting views on the advantages of different surgical and rehabilitation management strategies.
Furthermore, can the results from animal studies be extrapolated in humans? What is the equivalent of three or six weeks of immobilization in the rat and rabbit as compared with immobilization in a human? The prevention of adhesion formation would be extremely important in hand surgery. However, because the human hand is unique in terms of function as it allows fine movements that no other species can produce, is there comparability? Primates have the closest resemblance to humans in terms of both the application of surgical techniques and physical attributes. The use of rats, rabbits, dogs, and chickens, although interesting, may not be directly translatable to human hand surgery as the functional and anatomical features of these species do not match those of humans.
By raising the issues delineated above, however, we do not aim to criticize the article by Ishiyama et al. What we are saying is that proposed modifications in surgical techniques and novel pharmacological and nonpharmacological modalities need to withstand the test of adequately powered human trials before their potential benefit is accepted in routine clinical practice.