Transfer of the Sublimis Tendon: Brand's Technique for Thumb Opposition

INTRODUCTION TO OPPONENSPLASTY AND THE BRAND TECHNIQUE

The restoration of thumb opposition is one of the most critical reconstructive endeavors in hand surgery. Opposition is a complex, multi-planar movement comprising palmar abduction, flexion, and pronation of the first metacarpal, coupled with flexion and slight radial deviation of the metacarpophalangeal (MCP) and interphalangeal (IP) joints. This composite motion is primarily driven by the median nerve-innervated thenar musculature: the abductor pollicis brevis (APB), the opponens pollicis, and the superficial head of the flexor pollicis brevis (FPB).

In the setting of isolated low median nerve palsy, severe carpal tunnel syndrome, poliomyelitis, or traumatic thenar muscle loss, the thumb rests in a supinated, adducted posture, severely compromising pinch strength and global hand function. To restore this vital mechanic, Paul Brand popularized the transfer of the flexor digitorum superficialis (FDS)—historically referred to as the sublimis tendon—of the ring finger.

Brand’s sublimis tendon transfer is distinguished by its ingenious use of the local fascial anatomy at the ulnar aspect of the wrist to create a natural pulley, and a meticulously designed dual-insertion at the thumb MCP joint to prevent biomechanical shifting. This comprehensive guide details the indications, biomechanical principles, step-by-step surgical execution, and postoperative management of this masterclass technique.

PREOPERATIVE EVALUATION AND BIOMECHANICS

Biomechanical Prerequisites for Opposition

For an opponensplasty to be successful, the vector of pull must accurately replicate the function of the APB, which is the primary driver of opposition. The ideal vector originates from the region of the pisiform and the distal flexor carpi ulnaris (FCU). By routing the donor tendon from this ulnar-volar position toward the radial-dorsal aspect of the thumb MCP joint, the transfer effectively pronates and palmar-abducts the first ray.

Clinical Pearl: The Supple Web Space
No tendon transfer can overcome a fixed joint contracture. Prior to any opponensplasty, the first web space must be completely supple. If a first web space contracture exists, it must be addressed preoperatively or concomitantly via a Z-plasty, release of the adductor pollicis fascia, or even a trapeziometacarpal joint capsulotomy.

Donor Tendon Selection

The FDS of the ring finger is the preferred donor for several reasons:
* Excursion and Power: The FDS possesses an amplitude of excursion (approximately 7 cm) and a cross-sectional area that perfectly matches the requirements of the thenar musculature.
* Independence: The ring finger FDS has an independent muscle belly, facilitating easier postoperative motor re-education compared to the tethered profundus system.
* Acceptable Morbidity: Harvest of the ring FDS leaves the flexor digitorum profundus (FDP) intact to flex the digit, with minimal loss of grip strength.

INDICATIONS AND CONTRAINDICATIONS

Indications

• Isolated low median nerve palsy (e.g., neglected carpal tunnel syndrome, lacerations at the wrist).
• Poliomyelitis affecting the thenar musculature.
• Charcot-Marie-Tooth disease (in specific presentations with preserved FDS function).
• Traumatic loss of the thenar eminence with intact overlying soft tissue coverage.

Contraindications

• Fixed contracture of the first web space (absolute contraindication until corrected).
• Absence of a functional FDP in the donor ring finger.
• Severe joint stiffness or arthrosis of the thumb carpometacarpal (CMC) or MCP joints.
• High median nerve palsy where the FDS muscle bellies are denervated (necessitating alternative transfers, discussed below).

SURGICAL TECHNIQUE: BRAND'S SUBLIMIS TENDON TRANSFER

The procedure is performed under regional anesthesia (brachial plexus block) or general anesthesia, with the patient supine and the arm extended on a radiolucent hand table. A well-padded pneumatic tourniquet is applied to the proximal arm and inflated to 250 mm Hg after exsanguination.

Step 1: Exposure and Harvest of the Donor Tendon

1. Incision: Make a Bruner zig-zag or mid-lateral incision over the volar aspect of the ring finger, extending from the proximal phalanx to the distal palmar crease.
2. Tendon Identification: Identify the flexor tendon sheath. Open the A1 and A2 pulleys carefully, preserving the A2 pulley if possible to prevent bowstringing of the remaining FDP.
3. Division: Identify the FDS tendon where it bifurcates (Camper's chiasm) to insert into the middle phalanx. Divide the slips of the FDS as distally as possible to maximize tendon length.
4. Withdrawal: Make a small transverse incision in the distal forearm, approximately 5 cm proximal to the flexor crease of the wrist. Identify the ring FDS tendon at this level and gently withdraw it into the forearm wound.

Surgical Warning: Donor Digit Morbidity
When dividing the FDS slips, take meticulous care not to injure the underlying FDP tendon or the vincula. Excessive traction during withdrawal can damage the muscle belly in the proximal forearm.

Step 2: Creation of the Fascial Pulley

The creation of the pulley is the most anatomically nuanced step of the Brand technique. The pulley must be strong enough to withstand the tension of opposition without migrating.

1. Incision: Make a small longitudinal incision just to the radial side of, and approximately 6 mm distal to, the pisiform bone.
2. Dissection: Deepen this incision through the subcutaneous tissue. You will observe a distinct transition in the adipose tissue: the fat changes from a dense, fibrous, superficial type to a soft, loose, free type that bulges into the wound.
3. Anatomical Landmarks: This change in fat consistency marks the entry into a natural anatomical tunnel that runs proximally. This tunnel contains a branch of the ulnar nerve and lies superficial to the hook of the hamate.
4. Pulley Formation: The fibrous septa within this fat pad, extending from the flexor retinaculum and the hypothenar fascia, compose the natural pulley.

Step 3: Tendon Routing

1. Passage to the Wrist: Using a tendon passer or a curved hemostat, navigate through the loose fat in a proximal direction toward the forearm incision.
2. Tendon Retrieval: Grasp the distal end of the harvested FDS tendon in the forearm and pull it distally through this newly identified tunnel into the palmar incision near the pisiform. The tendon now exits the ulnar aspect of the hand, providing the perfect vector for opposition.
3. Subcutaneous Tunneling to the Thumb: Create a wide subcutaneous tunnel across the palm from the pisiform incision to the MCP joint of the thumb. The tunnel must be superficial to the palmar fascia to avoid tethering. Pass the FDS tendon through this tunnel to the thumb.

Step 4: The Dual Insertion Technique

The insertion of the transferred tendon is critical. A single-point insertion is prone to subluxation, which drastically alters the biomechanics of the thumb MCP joint. Brand’s dual-insertion technique mitigates this risk.

1. Thumb Incision: Make a curved or lazy-S incision over the radial and dorsal aspect of the thumb MCP joint, exposing the extensor mechanism, the APB insertion, and the joint capsule.
2. Splitting the Tendon: Split the distal end of the FDS tendon longitudinally into two equal slips for approximately 2 to 3 cm.
3. Proximal Slip Insertion: Route the proximal slip to the ulnar side of the MCP joint. Suture it securely to the ulnar collateral ligament or the ulnar aspect of the joint capsule.
4. Distal Slip Insertion: Route the distal slip radially and dorsally. Interweave and suture it into the tendinous insertions of the abductor pollicis brevis (APB) and the extensor pollicis longus (EPL).

Biomechanical Pitfall: Tendon Shifting
The dual insertion is explicitly designed to prevent the tendon from shifting position as it crosses the MCP joint.
* If an unsplit tendon shifts dorsally over the MCP joint, the vector changes, and the transfer will paradoxically hyperextend the joint.
* If the tendon shifts anteriorly (volarly) from the radial side of the joint, it will excessively flex the joint, failing to provide adequate palmar abduction.

Step 5: Tensioning and Closure

1. Setting the Tension: Tensioning is performed with the wrist in a neutral position. The thumb should be held in maximum palmar abduction and opposition (the pulp of the thumb facing the pulp of the middle finger).
2. Suturing: Suture the slips under moderate tension using non-absorbable braided sutures (e.g., 3-0 or 4-0 Ethibond or Ticron). The resting posture of the hand on the table should demonstrate the thumb sitting proudly in opposition without external support.
3. Closure: Deflate the tourniquet, achieve meticulous hemostasis, and close the skin incisions with non-absorbable monofilament sutures.

ALTERNATIVE TECHNIQUES FOR COMPLEX PALSIES

While the Brand FDS transfer is the gold standard for isolated low median nerve palsy, alternative donor motors must be utilized when the FDS is unavailable or paralyzed.

The Burkhalter Extensor Indicis Proprius (EIP) Transfer

If the ring or long finger sublimis is unsuitable for transfer (e.g., due to prior trauma, congenital absence, or specific patterns of weakness), the extensor indicis proprius (EIP) can be utilized, as described by Burkhalter et al.
* Technique: The EIP is harvested at the level of the index MCP joint, withdrawn to the distal forearm, and rerouted around the ulnar aspect of the wrist.
* Advantage: This transfer does not require a fascial pulley, as the ulnar border of the forearm acts as a natural fulcrum. It is particularly useful in patients who require preservation of all flexor power.

The Groves and Goldner FCU to FDS Transfer

In cases of high median nerve palsy or severe brachial plexus paralysis, the FDS muscle bellies are denervated, rendering them useless as primary motors.
* Technique: Groves and Goldner described a salvage technique employing the flexor carpi ulnaris (FCU)—which is innervated by the ulnar nerve and thus spared in isolated median nerve injuries—as a motor. The FCU is transected distally and woven into the paralyzed FDS tendon unit in the forearm. The distal FDS is then routed to the thumb as described in the Brand technique.
* Advantage: This restores opposition by utilizing an expendable, powerful ulnar-innervated muscle to drive the anatomically ideal FDS tendon.

POSTOPERATIVE CARE AND REHABILITATION

The success of an opponensplasty relies as much on meticulous postoperative rehabilitation as it does on surgical execution. The protocol closely mirrors that described for the Riordan technique.

Phase I: Immobilization (Weeks 0-3)

• Immediately postoperatively, the hand and forearm are immobilized in a custom-molded thermoplastic thumb spica splint or a well-padded fiberglass cast.
• Positioning: The wrist is positioned in neutral to 10 degrees of flexion. The thumb is immobilized in maximum palmar abduction and opposition. The thumb IP joint is left free to prevent stiffness.
• Strict elevation and digital range of motion (ROM) of the uninvolved fingers are encouraged to minimize edema.

Phase II: Early Mobilization (Weeks 3-6)

• The rigid cast is removed at 3 to 4 weeks.
• A removable thumb spica splint is fabricated. The patient wears this splint at all times, removing it only for structured, therapist-supervised exercise sessions.
• Exercises: Active ROM exercises are initiated. The patient is instructed to actively oppose the thumb to the digits. Cortical re-education is crucial here; if the FDS was used, the patient is taught to "flex the ring finger" to initiate thumb opposition until the brain remaps the motor pathway.
• Passive stretching of the transfer is strictly prohibited during this phase.

Phase III: Strengthening (Weeks 6-12)

• At 6 weeks, the splint is gradually weaned during the day but maintained at night.
• Progressive resistance exercises are introduced, focusing on pinch strength and grasp.
• Unrestricted activity and heavy lifting are generally permitted after 10 to 12 weeks, provided that the tendon transfer demonstrates adequate strength and the patient has achieved independent cortical control of the new motor unit.

COMPLICATIONS AND MANAGEMENT

1. Loss of Opposition (Stretching of the Transfer): Usually results from inadequate initial tensioning, failure of the pulley, or premature aggressive passive stretching. Management may require surgical revision and retensioning.
2. MCP Joint Hyperextension: As noted in the biomechanical pitfalls, this occurs if the tendon shifts dorsally. It can also occur if the EPL is over-tensioned during the distal slip insertion. Treatment may require capsulodesis of the MCP joint or revision of the insertion.
3. Donor Digit Swan Neck Deformity: Resection of the FDS can destabilize the PIP joint of the ring finger, leading to a swan neck deformity, particularly in hypermobile patients. Preserving the Camper's chiasm or performing a concomitant PIP joint volar dermodesis can prevent this.
4. Adhesions: Subcutaneous adhesions along the palmar tunnel can restrict excursion. Meticulous hemostasis, gentle tissue handling, and adherence to the early active mobilization protocol are the best preventative measures. Tenolysis is rarely required but may be considered after 6 months if progress plateaus.

CONCLUSION

Brand’s transfer of the sublimis tendon remains a cornerstone procedure in reconstructive hand surgery. By respecting the intricate biomechanics of the thumb ray, utilizing the native fascial anatomy for a secure pulley, and employing a dual-insertion technique to stabilize the MCP joint, the orthopedic surgeon can reliably restore the critical function of opposition, profoundly improving the patient's quality of life and functional independence.