The quadriga effect revisited: designing a "safety incision" to prevent tendon repair rupture and gap formation in a canine model in vitro

Concomitant injuries affect prognosis in patients with central slip tear

Central slip tears often occur with concomitant hand injuries. However, the outcome of a central slip tear and the effect of concomitant injuries are rarely reported. We evaluated 67 fingers in 63 patients with central slip tears who underwent primary surgery in our hospital between April 2009 and June 2017. We performed multivariate analyses, with proximal interphalangeal (PIP) joint active range of motion (AROM) and existing extension lag greater than 10° as dependent variables and age, existence of concomitant fractures, skin defects, collateral ligament injuries, ruptured lateral bands, ruptured flexor tendons or vascular injury in the injured finger as independent variables. Concomitant injuries of tendons in the adjacent fingers were also independent variables. The average AROM of the PIP joint was 62°, and extension lag occurred in 34 fingers (51%). Patients aged > 40 years with fractures of the injured finger or flexor tendon injuries in an adjacent finger had low decreases in AROM (partial regression coefficient [95% confidence interval, CI]: -13.7 [43-66], -31.6 [30-57], -34.5 [32-60] and -33.5 [10-43]). Extensor tendon injuries in an adjacent finger caused significantly more extension lag in the PIP joint (odds ratio [95% CI]: 3.2 [1.0-9.6]). The present study indicated the negative impact of a tendon injury on adjacent fingers, a circumstance widely known as the quadriga phenomenon. Ultimately, we can use these prognostic factors in surgical repair planning, particularly when comparing treatments such as central slip reconstruction and primary arthrodesis.

The quadriga phenomenon: a review and clinical relevance

The flexor digitorum profundus tendons are markedly interconnected, making them less able to move independently than the tendons of the flexor digitorum superficialis. This difference is often attributed to the common muscle belly of the profundus, but also, more importantly, to cross-connections between the tendons of the profundus. The effect of this quadriga phenomenon is important in several clinical situations, including testing for strength, assessing movement of the tendons, and when deciding which exercises to teach the patient after a tendon injury. The anatomy and biomechanics of this phenomenon are reviewed in this article to help explain why certain conditions occur, and to improve the diagnosis and treatment of some conditions in rehabilitation medicine.