Comprehensive Clinical Guide: Kienbock’s Disease and Radial Shortening Osteotomy

Kienbock’s disease, or osteonecrosis of the lunate bone, remains one of the most complex clinical challenges in upper extremity orthopedics. Characterized by the progressive collapse of the lunate due to interrupted vascular supply, it typically affects young, active adults. When conservative measures fail, surgical intervention becomes mandatory to halt disease progression and preserve wrist function. Among these interventions, the Radial Shortening Osteotomy (RSO) stands as a gold-standard procedure for patients presenting with ulnar negative variance.

1. Introduction and Overview

Kienbock’s disease (lunate malacia) is a debilitating condition where the lunate bone loses its blood supply, leading to necrosis, fragmentation, and eventual collapse. This process results in chronic wrist pain, stiffness, and loss of grip strength.

Pathophysiology

The etiology is likely multifactorial, involving mechanical, vascular, and anatomical factors. A critical mechanical factor is ulnar negative variance, where the ulna is shorter than the radius. This anatomical discrepancy shifts the mechanical load disproportionately onto the lunate, leading to chronic microtrauma and vascular compromise.

The RSO Philosophy

The Radial Shortening Osteotomy aims to restore the biomechanical equilibrium of the radiocarpal joint. By shortening the radius, the load-bearing characteristics of the wrist are altered, shifting the pressure away from the lunate and toward the ulnar head, thereby facilitating revascularization and preventing further collapse.

2. Technical Specifications and Mechanisms

The RSO is a structural procedure designed to modify the distal radius length.

Biomechanical Mechanism

The distal radius typically bears approximately 80% of the axial load of the forearm, with the remaining 20% distributed through the triangular fibrocartilage complex (TFCC) to the ulna. In patients with ulnar negative variance, the lunate bears a higher-than-normal percentage of this force.

• Load Redistribution: By shortening the radius by 2–4 mm, the ulnar abutment is increased, effectively offloading the lunate.
• Intraosseous Pressure: Studies indicate that RSO significantly reduces the intraosseous pressure within the lunate, creating a biological environment conducive to bone healing.

Surgical Instrumentation

• Fixed-angle locking plate: Essential for stable fixation.
• Oscillating saw: For precise osteotomy cuts.
• Compression device: To ensure accurate shortening and bone apposition.
• Fluoroscopy: Mandatory for intraoperative verification of radial length and hardware placement.

3. Clinical Indications & Patient Selection

Not every patient with Kienbock’s is a candidate for RSO. Patient selection is governed by the Lichtman Classification system.

The Lichtman Classification

Indications for Radial Shortening

1. Ulnar Negative Variance: The primary anatomical prerequisite.
2. Lichtman Stage II or IIIa: Where the lunate is fragmented but the carpal architecture is still intact.
3. Failure of Conservative Management: Continued pain despite 3–6 months of immobilization or activity modification.
4. Active, Working-Age Patients: Those who require high-demand wrist function.

4. Pre-operative Preparation

Preparation is critical to ensure a successful outcome and minimize complications.

• Imaging Protocol:
  • Standard X-rays: PA and lateral views to measure ulnar variance.
  • MRI: To confirm the extent of necrosis and assess the viability of the lunate (T1/T2 signal intensity).
  • CT Scan: To evaluate the degree of lunate fragmentation.
• Patient Optimization:
  • Smoking Cessation: Mandatory for at least 6 weeks pre- and post-operatively to ensure bone union.
  • Co-morbidity Management: Optimization of diabetes or other systemic conditions that impair bone healing.
• Informed Consent: Detailed discussion regarding the potential for non-union, hardware irritation, and the possibility that the disease may progress despite surgery.

5. The Procedure: Step-by-Step

The RSO procedure is typically performed under regional or general anesthesia with a pneumatic tourniquet.

1. Incision: A longitudinal volar or dorsal approach (depending on surgeon preference and plate design) to the distal radius.
2. Exposure: Subperiosteal dissection of the distal radial shaft.
3. Osteotomy Planning: Measurement of the required shortening (typically 2–3 mm) using pre-operative templating.
4. The Cut: Two parallel osteotomy cuts are made using an oscillating saw with copious saline irrigation to prevent thermal necrosis.
5. Compression and Fixation: The radial segments are compressed together. A low-profile locking plate is applied to the radial shaft, providing rigid fixation.
6. Closure: Layered closure of the subcutaneous tissue and skin.
7. Dressing: A bulky, compressive dressing with a volar splint is applied.

6. Post-operative Recovery Protocol

Recovery is a staged process requiring patient compliance.

• Phase I (Weeks 0–2): Immobilization in a splint. Focus on elevation to reduce edema.
• Phase II (Weeks 2–6): Transition to a removable wrist brace. Initiation of gentle active range of motion (AROM) of the fingers and thumb.
• Phase III (Weeks 6–12): Radiographic assessment for bone union. If union is confirmed, gradual increase in wrist ROM exercises and initiation of light strengthening.
• Phase IV (3–6 Months): Progressive return to heavy lifting and high-impact activities.

7. Risks and Complications

While highly effective, RSO carries inherent surgical risks:

• Non-union: Failure of the osteotomy site to heal (risk increased in smokers).
• Hardware Irritation: Tendon irritation or skin discomfort caused by the plate, often requiring secondary hardware removal.
• Infection: Standard surgical site infection risks.
• Delayed Revascularization: The lunate may fail to revascularize despite mechanical unloading, leading to disease progression to Stage IV.
• Complex Regional Pain Syndrome (CRPS): A rare but severe neurological complication.

8. Alternative Treatments

When RSO is not indicated, other options must be considered:

• Core Decompression: Drilling into the lunate to encourage revascularization (best for Stage I/early Stage II).
• Capitate Shortening with Pyrocarbon Implant: Used when ulnar variance is neutral or positive.
• Proximal Row Carpectomy (PRC): A salvage procedure for Stage IV disease where the proximal carpal row is removed.
• Wrist Fusion (Arthrodesis): The final resort for end-stage, painful degenerative arthritis.

9. Massive FAQ Section

1. Does the RSO procedure guarantee that my lunate will return to normal?
No. RSO is a joint-preserving procedure intended to halt progression. While many patients experience pain relief and improved function, the lunate may remain structurally altered.

2. How long do I have to stay off work?
This depends on your occupation. Sedentary workers may return in 2–3 weeks; manual laborers may require 3–6 months.

3. Will I have a permanent scar?
Yes, there will be a surgical scar on the forearm. Over time, it typically fades, but the length is determined by the plate size.

4. What happens if the bone doesn't heal at the osteotomy site?
Non-union is rare but requires secondary surgery, such as bone grafting or plate revision.

5. Can I still play sports after this surgery?
Yes. Once the radial osteotomy is fully healed and strength is regained, most patients return to their previous level of sporting activity.

6. Is RSO performed on both wrists?
Kienbock’s is rarely bilateral. If it is, the procedure is typically performed on one side at a time.

7. Does the plate stay in forever?
Not necessarily. If the plate causes irritation under the skin, it can be removed once the bone is fully consolidated, usually after 12–18 months.

8. What is "ulnar negative variance"?
It is a condition where the ulna bone is shorter than the radius, which is the primary mechanical culprit in many Kienbock’s cases.

9. How successful is this surgery?
Success rates for pain relief and preventing progression in early-stage Kienbock's are generally reported between 75% and 90% in clinical literature.

10. Do I need physical therapy?
Yes. Professional hand therapy is essential to regain wrist mobility and strength safely without overstressing the healing bone.

10. Conclusion

Radial Shortening Osteotomy remains a cornerstone of orthopedic hand surgery for the management of Kienbock’s disease. By addressing the underlying mechanical etiology of ulnar negative variance, it provides a logical, effective path to preserving wrist longevity. Success is predicated on rigorous patient selection, meticulous surgical technique, and a structured, patient-led rehabilitation program. For the active patient, RSO offers the best chance of avoiding the long-term morbidity associated with salvage procedures like wrist fusion.

Disclaimer: This guide is for educational purposes only and does not constitute medical advice. Always consult with a board-certified orthopedic surgeon specializing in hand and upper extremity surgery for clinical diagnosis and treatment planning.