Examination of the acutely lacerated hand

1. After isolated division of flexor digitorum profundus, the resting flexion cascade of the fingers is disrupted, although the injured finger may still flex at the proximal interphalangeal and metacarpophalangeal joints.

True

Murphy and Mass's review of zone I injuries notes that these involve the profundus tendon alone, distal to the superficialis insertion. On examination the cascade of the fingers is disrupted, and active distal interphalangeal flexion must be isolated to confirm that the profundus is continuous, because other structures can still flex the more proximal joints.

• Murphy BA, Mass DP. Zone I flexor tendon injuries. Hand Clin. 2005;21(2):167-71. PMID 15882595

2. In uninjured hands, extending the wrist produces synergistic flexion of the finger joints through passive tension in the muscle–tendon units (the tenodesis effect).

True

Su and colleagues measured 50 normal subjects with three-dimensional motion analysis. Moving the wrist from flexion into extension flexed the metacarpophalangeal, proximal and distal interphalangeal joints through passive muscle tension, in an approximately linear relationship (the proximal interphalangeal joint, for example, from about 19° to 70° of flexion), and the authors suggest that this relationship can help in diagnosing problems with the integrity of the flexor and extensor mechanisms.

• Su FC, Chou YL, Yang CS, Lin GT, An KN. Movement of finger joints induced by synergistic wrist motion. Clin Biomech (Bristol). 2005;20(5):491-7. PMID 15836936

3. Examination by a hand surgeon reliably predicts a complete digital nerve laceration: in a multicentre trial, nearly all patients explored for a suspected complete laceration needed nerve repair.

False

In a study embedded in a multicentre randomised trial, hand surgeons examined adults with a suspected complete digital nerve injury in flexor zone 2, with surgical exploration as the reference standard. Of 242 patients explored, 137 had a complete laceration and 105 had a partial or no visible laceration, a positive predictive value of 57%. The authors conclude that examination could not reliably predict complete injury, although exploration remains necessary because no bedside test is accurate enough.

• O'Hanlon C, Gardiner MD, Davies L, Power D, Jain A, Cook JA, et al.. Investigating the diagnostic accuracy of physical examination in digital nerve injury: a study within a trial. J Hand Surg Eur Vol. 2026;51(7):876-880. PMID 41674037

4. Squeezing the distal forearm normally flexes the fingers passively; a digit that flexes little or not at all suggests division of its flexor tendons.

True

Zhi and colleagues describe the distal forearm squeeze test in two patients with flexor tendon ruptures, 50 outpatients with intact digital tendons and a chicken model. All 50 of these subjects responded with a clenched or half-clenched hand, whereas the injured digit flexed only slightly; to test the profundus alone, the proximal interphalangeal joint is held in extension during the squeeze. The clinical evidence for the test is limited to these two patients.

• Zhi Y, Wu C, Li M. Distal forearm squeeze test for the diagnosis of digital flexor tendon injuries. BMC Musculoskelet Disord. 2023;24(1):975. PMID 38104094

5. When a hand wound has a normal clinical examination, injury to a deep structure is rarely found at surgical exploration.

False

Amsallem and colleagues explored 145 hand wounds deeper than the dermis that showed no clinical deficit and found damage to a major structure in 58.6%. In a prospective series of 80 volar hand and wrist wounds, 28% of wounds with a normal examination had tendon, vascular or nerve damage at surgery, and an earlier review of 101 patients whose hand lacerations were explored found that emergency doctors and hand surgeons each missed about 30% of injuries. These authors therefore recommend exploring such wounds rather than relying on examination alone.

• Amsallem L, Pierrart J, Werthel JD, Delgrande D, Bihel T, Sekri J, et al.. Hand injury without any deficit: Is systematic surgical exploration justified?. Hand Surg Rehabil. 2019;38(1):20-23. PMID 30249493
• Baron-Trocellier T, Rongières M, Mericq O, Lupon E, Mansat P. Prospective study of 80 volar wounds of the hand and wrist: Correlations between clinical examination and intraoperative findings. Hand Surg Rehabil. 2020;39(5):389-392. PMID 32376508
• Nassab R, Kok K, Constantinides J, Rajaratnam V. The diagnostic accuracy of clinical examination in hand lacerations. Int J Surg. 2007;5(2):105-8. PMID 17448974