anatomic approach to preparation and fusion of the interphalangeal ...

52CHAPTER 12Figure 2. Representation of the base of the middlephalanx. Lateral depressions with central crista forcentering the phalanx at the articulation.Figure 3A. Collateral ligaments assist in maintainingtransverse plane alignment and normal sagittal planejoint tracking.Figure 3B. Collateral ligaments help maintain transverse plane alignment.central projection that tracks within the groove formedby the proximal phalangeal condyles (Figure 2). Thisarrangement, along with the presence of a pair of collateralligaments that run on either side of the joint restrictsmovement to just the sagittal plane (Figure 3).Anatomic access to the joint begins with transversesectioning of the extensor tendon and capsule over thedorsum of the joint. This palpable landmark translates to theproximal ridge of the bone-cartilage junction on the head ofthe proximal phalanx. The medial and lateral collateralligaments are then divided, completing the disarticulationand exposing the head of the proximal phalanx. A smallamount of further dissection of the capsular attachments andadjacent periosteum may be required for full degloving inpreparation for joint ressection. This leaves a small flap oftissue over both the head of the proximal phalanx and baseof the middle phalanx. These are usually clamped andretracted with a mosquito hemostat.Arthrodesis requires cartilage removal from adjacentsides of the joint, removal of the subchondral bone plate,and approximation and rigid fixation throughout the phasesof bone healing. When performing an arthrodesis there area few general principles to follow. First, exposure of thecancellous bone material is critical to fusion. Incompletetissue removal during the operation is possibly the leadingcause of nonunion. However, aggressive bone resection canFigure 4. The typical resection includes the entiretyof articular cartilage back to the flare of themetaphysis on the respective sides of the proximaland middle phalanges as depicted by the red lines.leave a digit short or render the tendinous structures unableto move the toe, resulting in a flail toe. The digital lengthshould represent a parabola, or unbroken arc with respectto adjacent digits. Second, joint apposition is critical tosuccessful osseous bridging. The prepared joint ends must bein contact, preferably along the entire surface of the boneends, to achieve fusion. Third, anatomic alignment isimportant for both function and cosmesis. The fusion shouldleave the toe neutral on the frontal plane, neutral to slightlyflexed on the sagittal plane, and parallel with adjacent digitson the transverse plane. Finally, the choice of fixation mustmake sound biomechanical sense, maintaining the bone endsin alignment against the two main deleterious forces:distraction and plantarflexion. Use of poor fixation methodsor failure to maintain bone apposition for long enough willlikely result in postoperative complications.