The flexor sheaths originate just distal to the distal interphalangeal joint and extend to the palmar flexion crease. The sheath of the flexor pollicis longus continues to the radial bursa and the flexor sheath of the little finger is confluent with the ulnar bursa (Figure 8). For early infections (less than 24 hours) without evidence of abscess, conservative treatment with broad-spectrum intravenous antibiotics, splinting, elevation, and frequent physical examination can be performed. If moderate infection is present, drainage can be performed with a limited incision approach proximally and distally in the sheath to allow for an indwelling irrigation catheter. The proximal incision is transversely oriented at the distal palmar flexion crease and the distal incision is obliquely oriented over the middle phalanx or along with midlateral line to expose the flexor tendon sheaths (Figure 9). Care is taken to prevent injury to the neurovascular bundles. Extensive infection should be approached through lateral midaxial incisions placed ulnar on digits 2, 3, and 4 and radial on the thumb and small finger (Figure 10). For all infections, cultures and sensitivities should be performed with directed antibiotic coverage performed.
Dry dressings and early return of motion, usually on the following day, with gradual increase in range of motion, are indicated in uncomplicated felon and paronychia. In tendon sheath infections, antibiotics are continued for a week. Gentle movements are encouraged and increased as tolerated. Elevation of the extremity to heart level will lessen discomfort during the period of immobilization until swelling has cleared. The rehabilitation of the infected hand requires careful supervision.