Introduction to Radial Longitudinal Deficiency and Centralization

Radial longitudinal deficiency (RLD), historically referred to as radial clubhand, represents a complex spectrum of congenital upper extremity anomalies characterized by hypoplasia or complete aplasia of the radius and preaxial carpal bones. This deficiency results in a severe radial deviation of the hand, a shortened and often bowed ulna, and profound functional impairment of the upper limb. The primary goal of surgical intervention is to realign the hand and carpus over the distal ulna, thereby improving the biomechanical axis of the forearm, enhancing grip strength, and optimizing the aesthetic appearance of the limb.

The centralization of the hand with the removal of the distal radial anlage, as described by Watson, Beebe, and Cruz, remains a cornerstone technique in the operative management of RLD. The "anlage" is a fibrotic, non-yielding cartilaginous or fibrous band that represents the embryological remnant of the absent radius. If left in situ, this anlage acts as a restrictive tether, exacerbating the radial deviation of the hand and contributing to the progressive bowing of the ulna as the child grows.

This comprehensive guide details the advanced surgical technique for hand centralization, emphasizing the critical steps of soft tissue balancing, neurovascular preservation, anlage resection, and skeletal stabilization.

Pathoanatomy and Biomechanical Considerations

Understanding the pathoanatomy of RLD is paramount for successful surgical correction. The deformity is not merely a skeletal absence; it involves a global hypoplasia of the preaxial soft tissues, including muscles, tendons, ligaments, and neurovascular structures.

The Fibrotic Radial Anlage

In cases of partial radial aplasia (Bayne and Klug Type II or III), the distal radius is replaced by a dense fibrotic band—the radial anlage. This structure originates from the proximal radial remnant or the lateral epicondyle and inserts into the radial carpus. Because the anlage lacks growth potential, it creates a bowstring effect across the radial aspect of the forearm. As the ulna continues to grow, the anlage tethers the carpus, forcing the hand into severe radial deviation and volar flexion, while simultaneously inducing a secondary bowing deformity in the ulna.

Neurovascular Anomalies

The vascular and neural anatomy in RLD is highly aberrant. The radial artery is frequently absent or severely hypoplastic, rendering the hand entirely dependent on the ulnar artery and the anterior interosseous artery for perfusion.

Surgical Warning: The median nerve in RLD does not follow its typical anatomic course. It frequently assumes a superficial, radialized position just beneath the dermis on the preaxial border of the forearm. This anomalous "radialmedian" nerve is at extreme risk during the initial radial skin incision.

Preoperative Evaluation and Optimization

Patient Selection and Timing

The optimal timing for centralization is typically between 6 and 12 months of age. Intervening before the age of one year capitalizes on the plasticity of the infant's soft tissues and prevents the progression of severe ulnar bowing.

Contraindications to centralization include:
* Severe elbow extension contractures: If the elbow lacks passive flexion, centralizing the hand will severely impair the child's ability to bring the hand to the mouth for feeding and facial hygiene.
* Mild deformities: Bayne and Klug Type I deficiencies may be managed with soft tissue releases or lengthening alone.
* Older patients with stiff, unyielding deformities: In neglected cases, preliminary soft tissue distraction (e.g., Ilizarov or Taylor Spatial Frame) may be required prior to formal centralization.

Preoperative Soft Tissue Management

Surgical centralization must be preceded by rigorous conservative management. Immediately after birth, a regimen of serial casting and passive stretching is initiated to stretch the contracted radial soft tissues and elongate the radial neurovascular bundle. Adequate preoperative soft tissue laxity is the most critical predictor of a tension-free surgical centralization.

Surgical Technique: Watson, Beebe, and Cruz Centralization

The following technique outlines the meticulous step-by-step approach to centralizing the carpus over the distal ulna while resecting the deforming radial anlage.

1. Anesthesia, Positioning, and Preparation

The procedure is performed under general anesthesia. The patient is positioned supine with the affected upper extremity extended on a radiolucent hand table. A well-padded pneumatic tourniquet is applied to the proximal arm.

Prior to inflation, the limb is exsanguinated using an Esmarch bandage. Tourniquet pressure is typically set based on the patient's systolic blood pressure and age, ensuring a bloodless surgical field which is absolutely critical for identifying anomalous neurovascular structures.

2. Incision Design and Skin Flaps

The soft tissue envelope in RLD is characterized by a severe deficiency of skin on the radial (concave) aspect and a redundancy of skin on the ulnar (convex) aspect. The Watson, Beebe, and Cruz technique utilizes a dual Z-plasty approach to address this discrepancy.

• Radial Incision: Make a standard 60-degree Z-plasty on the radial aspect of the distal forearm and wrist. The central limb of this Z-plasty must be oriented longitudinally. This configuration allows for the recruitment of transverse skin laxity to achieve lengthening along the longitudinal axis of the forearm, directly addressing the radial skin shortage.
• Ulnar Incision: On the ulnar aspect of the wrist, design a second 60-degree Z-plasty. However, the central limb of this ulnar Z-plasty must be oriented transversely. This design takes up the redundant skin on the ulnar side and allows the excess tissue to be transposed toward the deficient radial wrist area during closure.

3. Radial Dissection and Nerve Preservation

Once the radial skin flaps are elevated, extreme caution must be exercised. The dissection is carried out along the radial side of the forearm.

Clinical Pearl: Assume the median nerve is immediately deep to the dermis on the radial side. Do not use deep, sweeping scalpel strokes. Use blunt dissection and tenotomy scissors to carefully spread the subcutaneous tissues until the nerve is identified.

Identify the anomalous "radialmedian" nerve. It is often the most superficial structure encountered and may be thickened or flattened. Gently mobilize the nerve and retract it with a vessel loop. Identification, mobilization, and absolute preservation of this nerve are vital to maintaining the functional capacity, sensation, and intrinsic muscle innervation of the hand.

4. Resection of the Distal Radial Anlage

With the median nerve protected, continue the dissection ulnarward and deep into the forearm to identify the distal radial anlage. The anlage will appear as a dense, avascular, fibrotic band extending from the proximal forearm down to the radial carpal bones (typically the scaphoid or trapezium equivalents).

Carefully dissect the anlage free from the surrounding flexor and extensor muscle bellies. Excise the fibrotic anlage completely. Its removal instantly eliminates the primary restricting band that maintains the hand in radial deviation. You will immediately notice an improvement in the passive mobility of the carpus.

5. Ulnar Dissection and Neurovascular Protection

Attention is then turned to the ulnar incision. Elevate the ulnar Z-plasty flaps.

Identify the ulnar nerve and the ulnar artery. In RLD, the ulnar artery is often the dominant or sole blood supply to the hand. Both structures must be meticulously dissected, mobilized, and protected with vessel loops. This mobilization allows for complete, circumferential dissection around the distal ulna without placing tension on these crucial structures during the subsequent centralization maneuver.

6. Ulnocarpal Capsular Release

To centralize the hand, the tethering joint capsule must be completely released. Perform a radical, 360-degree capsular release of the ulnocarpal joint.

Pitfall: The distal ulnar physis is the only remaining growth plate for the forearm. Any iatrogenic injury to this physis during the capsular release or subsequent pin fixation will result in premature growth arrest, leading to a severely stunted forearm. Dissect strictly within the joint space and avoid elevating the periosteum over the physis.

Following the complete capsular release, the hand should be fully mobile. At this stage, the hand is attached to the forearm exclusively by the skin envelope, the dorsal and palmar tendons, and the preserved neurovascular bundles.

7. Preparation of the Centralization Site

Remove all fibrotic material, remnants of the joint capsule, and anomalous fibrous septa in the "center" of the wrist and distal forearm area.

A critical checkpoint at this stage is visual continuity: the distal ulna and the ulnar incision should be clearly visible through the radial incision, and vice versa. This confirms that all central tethering structures have been eradicated.

Surgical Warning: Historically, some techniques advocated for the excision of carpal bones (e.g., lunate or capitate) or the shaving/remodeling of the distal ulnar epiphysis to create a "notch" for the carpus. The Watson, Beebe, and Cruz technique strictly advises against this. It should not be necessary to remove any carpal bones or remodel the distal ulna. Preserving the cartilaginous architecture of the ulnar head and the carpus is essential for maintaining future growth potential and joint mobility.

8. Skeletal Fixation and Alignment

With the soft tissues completely released, the hand is manually centralized over the distal ulna. The alignment should place the third metacarpal in direct longitudinal alignment with the shaft of the ulna.

• Pin Placement: Select a 0.045-inch (1.14 mm) smooth Kirschner wire (K-wire).
• Antegrade Pass: Drive the K-wire antegrade through the center of the carpus—specifically targeting the lunate and the capitate—and advance it down the medullary canal of the long finger (third) metacarpal until it exits through the metacarpophalangeal (MCP) joint.
• Retrograde Pass: Centralize the hand perfectly over the distal ulna. Ensure there is no volar or dorsal subluxation. Once aligned, drive the K-wire in a retrograde fashion out of the carpus, directly across the center of the distal ulnar epiphysis, through the ulnar physis, and into the medullary canal of the ulnar shaft.

The K-wire must sit centrally within the narrow ulnar canal to maintain the precise longitudinal axis of the hand and forearm. Cut the distal end of the K-wire beneath the skin at the MCP joint, or leave it protruding slightly with a protective cap, depending on surgeon preference and institutional protocol.

9. Hemostasis and Closure

Before skin closure, it is imperative to assess the perfusion of the hand. Deflate the pneumatic tourniquet.

Obtain meticulous hemostasis using bipolar electrocautery. Observe the capillary refill in the digits. Because the hand has been repositioned from a severely deviated posture to a straight alignment, the neurovascular bundles are now under a new tension vector.

Clinical Pearl: If the hand appears ischemic after tourniquet deflation and centralization, the skeletal fixation must be removed, and the hand allowed to fall back into slight radial deviation until perfusion is restored. A viable, slightly deviated hand is infinitely preferable to a centralized, ischemic hand. Shortening of the ulna is rarely indicated but may be considered in extreme cases of vascular tethering.

Once satisfactory circulation is confirmed, close the radial and ulnar Z-plasties. The transposition of the ulnar skin flaps to the radial side should allow for a tension-free closure. Use fine absorbable sutures (e.g., 5-0 or 6-0 chromic gut or fast-absorbing plain gut) to avoid the need for suture removal in an awake infant.

10. Dressing and Splinting

Apply a sterile, non-adherent dressing over the incisions. Pad the forearm and hand generously with cast padding, paying special attention to bony prominences.

Apply a bulky hand dressing reinforced with a rigid dorsal plaster splint. The splint must extend above the elbow (long-arm configuration) with the elbow flexed at 90 degrees to prevent the infant from slipping out of the dressing. The wrist is immobilized in the neutral, centralized position.

Before the patient is awakened and anesthesia is discontinued, perform a final check to ensure that the circulation in the digits remains brisk and satisfactory.

Postoperative Care and Rehabilitation Protocol

The postoperative management is as critical as the surgical execution in preventing the recurrence of the deformity.

Immediate Postoperative Phase (0 to 2 Weeks)

• Elevation: The operated limb must be strictly elevated for the first 24 to 48 hours to minimize postoperative edema and protect the delicate vascular supply.
• Monitoring: Frequent neurovascular checks of the exposed digits are mandatory.
• First Clinic Visit: At 2 weeks post-surgery, the initial bulky dressing and splint are removed in the clinic. The incisions are inspected. If non-absorbable sutures were used, they are removed at this time.

Intermediate Phase (2 to 6 Weeks)

• Long-Arm Cast: Following the 2-week wound check, a well-molded, fiberglass long-arm cast is applied. This cast is worn for an additional 4 weeks (totaling 6 weeks of long-arm immobilization). The cast protects the K-wire fixation and allows the soft tissues to heal in their new, lengthened positions.

Pin Removal and Short-Arm Casting (6 to 9 Weeks)

• K-wire Removal: At 6 weeks postoperatively, the intramedullary Kirschner wire is removed. This is typically done in the clinic if the pin was left proud, or under brief sedation if it was buried.
• Short-Arm Cast: After pin removal, a short-arm cast is applied to protect the ulnocarpal articulation as it continues to stabilize. This short-arm cast is worn for an additional 3 weeks.

Long-Term Management and Splinting

• Night Splinting: At 9 weeks postoperatively, all casts are discontinued. However, the tendency for the radial deviation to recur is exceptionally high due to the lack of radial skeletal support and the persistent imbalance of the forearm musculature.
• Protocol: A custom-molded thermoplastic resting splint must be fabricated. The patient is required to wear this splint every night. Night splinting is strictly continued until the child reaches skeletal maturity and physeal closure occurs.

Complications and Pitfalls

Despite meticulous surgical technique, centralization carries a high risk of complications, primarily due to the severe inherent biology of the congenital defect.

1. Recurrence of Deformity: This is the most common complication. Recurrence is driven by the natural growth of the ulna without a radial counterpart, inadequate initial soft tissue release, or failure of the patient to adhere to the strict night-splinting regimen.
2. Physeal Arrest: The distal ulnar physis is highly sensitive. Repeated passes of the K-wire, thermal necrosis during drilling, or aggressive capsular dissection can cause premature closure of the physis, resulting in a severely shortened forearm.
3. Neurovascular Compromise: Over-stretching the ulnar artery or the anomalous radialmedian nerve during the centralization maneuver can lead to ischemia or permanent neuropathy.
4. Pin Tract Infection: If the K-wire is left protruding through the skin, superficial pin tract infections can occur. These are usually managed effectively with oral antibiotics and local wound care, but deep infections may necessitate premature pin removal.

Conclusion

The centralization of the hand with the removal of the distal radial anlage is a demanding but highly rewarding procedure that fundamentally alters the trajectory of a child born with radial longitudinal deficiency. By adhering to the principles of the Watson, Beebe, and Cruz technique—specifically the utilization of dual Z-plasties, the meticulous preservation of the anomalous median nerve, the complete resection of the fibrotic anlage, and the careful, non-destructive centralization of the carpus over the distal ulna—orthopaedic surgeons can achieve a stable, functional, and cosmetically improved upper extremity. Long-term success, however, relies heavily on rigorous postoperative splinting and continuous monitoring throughout the child's growing years.