A New Classification Scheme for Closed Avulsion Injuries of the Flexor Digitorum Profundus Tendon

Background: Closed avulsion injury of the flexor digitorum profundus (FDP) tendon is a relatively common condition of the hand. Its present classification system seems to be deficient in including all possible patterns of injury, leading to improper selection of the best treatment method for the injury. We aim to provide a new classification scheme for this injury.

Methods: We developed a new classification scheme based on the possible pattern of FDP tendon injury. It consisted of three main types, and 10 sub-types. This was used to classify the injury of 34 patients, and help in choosing the best management approach. All patients underwent surgical treatment of their injury. The distal interphalangeal (DIP) joint extension deficit and total active motion (TAM) of the proximal interphalangeal (PIP) and DIP joints were considered as the main outcomes. Five orthopaedic surgeons used the new classification system for our cases, and the inter-rater reproducibility was tested with Fleiss' kappa.

Results: The multi-rater kappa for the classification was excellent. At the final follow-up visit 24 months following surgery, the mean loss of extension of the DIP joint was 13.76° ± 13.53° (range 0° to 45°), while the mean TAM was 148.88° ± 22.64° (range 94° to 172°). Based on the TAM score, 21 (61.76%), 8 (23.53%) and 5 (14.71%) patients had excellent, good and fair results, respectively. None of our patients had poor results.

Conclusions: Our new classification scheme of FDP tendon avulsion appeared to be comprehensive and useful in guiding the surgeon for the best treatment option. Nevertheless, this should be confirmed by using it for larger number of patients with different patterns of injury.