Kaplan’s Lesion: Why a Wrist Block Alone Is InadequateIntroduction

Kaplan’s lesion is a rare but surgically complex traumatic injury involving disruption of digital neurovascular bundles and flexor tendons, often on the volar aspect of the index finger or hand. Because repair requires precise exposure and neurovascular reconstruction, the anesthetic plan must be comprehensive. A wrist block alone fails to provide complete surgical anesthesia, compromising exposure, pain control, and hemostasis.

This article explains the limitations of a wrist block in this context and highlights preferred anesthesia options.

Kaplan’s Lesion: Surgical Anatomy and Clinical SignificanceDefinition and Mechanism

• Involves simultaneous injury to flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), digital nerves, and arteries.
• Typically occurs at the MCP joint or proximal phalanx.
• Mechanism: lacerations from sharp objects (knives, glass) or crush injuries.
• Classified within flexor tendon Zone II or III, which are challenging areas for tendon repair and functional recovery.

Surgical Implications

• Requires magnification for neurovascular repair.
• Demands deep field exposure and tendon retraction.
• Commonly performed under an arm tourniquet for hemostasis.

References: Doyle JR (1988); Tang JB (2019); Green DP et al. (2010).

Wrist Block: Technique and CoverageOverview

• Targets median, ulnar, and superficial radial nerves at or distal to the wrist crease.
• Provides cutaneous anesthesia but has limited motor and autonomic blockade.
• Commonly chosen for minor hand procedures because of technical simplicity and safety.

Limitations

• Does not provide tolerance to an arm tourniquet.
• Produces incomplete motor block.
• Fails to anesthetize the palmar cutaneous branch of the median nerve.

References: Hadzic A (2017); Neal JM et al. (2009).

Why Wrist Block Alone Is Inadequate1. Inadequate Proximal Coverage

• The palmar cutaneous branch of the median nerve arises ~5 cm proximal to the wrist, escaping wrist-level blockade.
• Kaplan’s lesion repair may require incisions extending proximally beyond wrist block coverage.

References: Fabregas N et al. (1996); Sunderland S (1978).

2. Inability to Control Tourniquet Pain

• Tourniquet pain arises from unmyelinated C fibers and A-delta fibers.
• Involves proximal nerves such as the medial cutaneous nerve of the arm and intercostobrachial nerve.
• Wrist block does not anesthetize these fibers, making it inadequate when a tourniquet is required.

References: Flamer D, Peng PWH (2011); McCartney CJ et al. (2007).

3. Lack of Motor Block

• Wrist block does not cover anterior interosseous nerve fibers, which supply FDP and FDS.
• Preserved motor activity may hinder tendon exposure and surgical manipulation.

References: Tubbs RS et al. (2007); Franco CD, Vieira ZE (2000).

4. Anatomical Variations and Incomplete Anesthesia

• Variations such as Martin-Gruber anastomosis (median–ulnar crossover) and Berrettini anastomosis (ulnar–median digital communication) compromise the predictability of wrist block.
• Such cross-innervations may leave unblocked sensory zones.

References: Roy J et al. (2016); Cannie M et al. (2006).

Preferred Anesthesia OptionsSupraclavicular Brachial Plexus Block

• Provides dense anesthesia of median, ulnar, radial, and musculocutaneous nerves.
• Offers reliable tourniquet tolerance and motor relaxation.
• Suitable for surgeries below the mid-humerus.

References: Neal JM et al. (2002); Delaunay L et al. (2008).

Infraclavicular Block

• Particularly effective in obese patients or trauma cases.
• Produces dense plexus anesthesia while minimizing risk of phrenic nerve palsy.

References: Kilka HG et al. (1995); Tran DQH et al. (2015).

Axillary Block with Musculocutaneous Supplementation

• Can be used for distal surgeries but is less reliable due to variation in musculocutaneous nerve location.
• Inadequate for controlling proximal tourniquet pain.

References: Urban MK, Urquhart B (1994).

Intraoperative Anesthetic ManagementTourniquet Use

• Pressure: 100–150 mmHg above systolic blood pressure.
• Maximum recommended time: 90 minutes.
• Block choice must account for deep ischemic pain pathways.

Sedation

• Light sedation with agents such as dexmedetomidine can improve comfort.
• Over-sedation should be avoided to allow neurological monitoring.

References: Brull R et al. (2007); Marhofer P et al. (2010).

Postoperative AnalgesiaProlonged Analgesia

• Long-acting local anesthetics such as bupivacaine or ropivacaine provide 12–18 hours of relief.
• Adjuvants such as dexamethasone or clonidine can further extend duration.

Multimodal Pain Control

• Paracetamol, NSAIDs, and rescue opioids as required.
• Cryotherapy and limb elevation aid in pain and edema reduction.

References: Ilfeld BM (2011); Mariano ER et al. (2010).

Conclusion

Wrist block alone is insufficient for Kaplan’s lesion repair because it does not address proximal innervation, tourniquet pain, or motor requirements and is subject to anatomical variability. Supraclavicular or infraclavicular brachial plexus blocks provide superior anesthesia and surgical conditions. The anesthesiologist must individualize the regional anesthesia plan to surgical field, expected duration, and tourniquet use, ensuring optimal outcomes through a combination of anatomical knowledge and pharmacologic expertise.