Residency · Residency · Orthopedic Surgery
Diaphyseal Humerus Fractures and Radial Nerve Palsy
Overview
Humeral shaft fractures account for approximately 3-5% of all fractures and display a bimodal age distribution, affecting young males in high-energy trauma and elderly females in low-energy falls. The humerus tolerates significant malunion compared to the lower extremity because compensatory range of motion at the shoulder and elbow masks angular deformity. Acceptable alignment parameters include less than 20 degrees of anterior angulation, less than 30 degrees of varus/valgus, less than 3 cm of shortening, and less than 15 degrees of rotational malalignment.
Anatomy
Deforming Forces by Fracture Level
In proximal third fractures (above the pectoralis major insertion), the proximal fragment is abducted and externally rotated by the supraspinatus and infraspinatus, while the distal fragment is pulled medially by the pectoralis major and deltoid. In middle third fractures (between the pectoralis major and deltoid insertions), the proximal fragment is adducted by the pectoralis and the distal fragment is abducted by the deltoid. In distal third fractures, the distal fragment is pulled proximally by the biceps, triceps, and brachialis.
Radial Nerve Course
The radial nerve lies posterior to the humerus in the spiral groove at the middle third. It pierces the lateral intermuscular septum approximately 10 cm proximal to the lateral epicondyle, making it most vulnerable at the junction of the middle and distal thirds. At the lateral intermuscular septum, the nerve transitions from the posterior compartment to the anterior compartment, creating a tethering point that increases susceptibility to injury.
<image>Anatomy of the radial nerve in relation to the humeral shaft showing the spiral groove and lateral intermuscular septum</image>
Classification
The AO/OTA classification categorizes humeral shaft fractures as 12A (simple), 12B (wedge), or 12C (complex/comminuted). A descriptive classification by location (proximal, middle, or distal third), fracture pattern (transverse, oblique, spiral, comminuted, segmental), and soft tissue status is also used.
Nonoperative Management
Functional Bracing (Sarmiento)
Functional bracing is the workhorse of humeral shaft fracture management. It is indicated for isolated, closed humeral shaft fractures with acceptable alignment. The technique begins with an initial coaptation splint or hanging arm cast for 1-2 weeks until acute pain subsides, followed by transition to a prefabricated humeral fracture brace (circumferential clamshell). The brace works through gravity alignment combined with hydrostatic compression. Results show union rates of 90-98% with a mean time to union of 10-16 weeks, and acceptable functional outcomes despite some angular and shortening deformity.
Relative Contraindications to Nonoperative Treatment
Relative contraindications include inability to comply with bracing (cognitively impaired or polytrauma patients), bilateral humeral fractures, associated vascular injury requiring repair, floating elbow (ipsilateral forearm and humerus fractures), pathologic fractures, open fractures, obesity (brace poorly tolerated), and transverse fracture patterns at midshaft (higher nonunion risk with bracing).
Operative Management
Indications
Operative management is indicated for failed nonoperative treatment (unacceptable alignment or nonunion), polytrauma or floating elbow, open fractures, associated vascular injury, pathologic fractures, and patient factors such as obesity, inability to brace, or bilateral injuries.
Open Reduction and Internal Fixation (Plate)
Plate fixation is the gold standard surgical treatment. The posterior approach (triceps-splitting or paratricipital) provides excellent exposure of the radial nerve and humeral shaft. The anterolateral approach is used for proximal and middle third fractures, allowing direct visualization of the radial nerve. A 4.5 mm broad or narrow LCP/DCP plate with a minimum of 6 cortices (3 screws) above and below the fracture is used. Lag screws through the plate are applied for oblique or spiral patterns. MIPO (minimally invasive plate osteosynthesis) uses anterior bridge plating through proximal and distal incisions and is gaining popularity, but requires careful identification and protection of the radial nerve.
Intramedullary Nailing
Intramedullary nailing may be antegrade (shoulder entry) or retrograde (elbow entry). Advantages include load-sharing mechanics, alignment maintenance, and percutaneous insertion. Disadvantages of antegrade nailing include rotator cuff damage from the shoulder entry, shoulder pain (10-20%), and risk of shoulder stiffness. Retrograde nailing risks supracondylar fracture at the entry point and elbow stiffness. Nailing is generally less favored than plating for humeral shaft fractures due to shoulder and elbow morbidity but may be preferred in polytrauma (damage control) or pathologic fractures (supports the entire bone).
External Fixation
External fixation provides temporary stabilization in open fractures, polytrauma, or soft tissue compromise. Definitive treatment with external fixation is rarely indicated.
<image>Anteroposterior and lateral radiographs showing humeral shaft fracture fixation with plate and screw construct</image>
Radial Nerve Palsy
Epidemiology
Radial nerve palsy occurs in 2-17% of humeral shaft fractures and represents the most common peripheral nerve injury associated with any long bone fracture. It is most frequently associated with middle-third and distal-third junction fractures, spiral or oblique fracture patterns (Holstein-Lewis fracture), and high-energy mechanisms.
Holstein-Lewis Fracture
The Holstein-Lewis fracture is a distal-third spiral fracture with proximal extension. The radial nerve is at particular risk of entrapment at the lateral intermuscular septum. This fracture was historically cited as an indication for early exploration, though this recommendation is now debated.
Presentation
Radial nerve palsy presents with wrist drop (inability to extend the wrist and MCP joints), loss of thumb extension and abduction, and a sensory deficit over the dorsal first web space (superficial branch of the radial nerve). Notably, finger IP extension is preserved because the lumbricals and interossei are innervated by the ulnar and median nerves.
| Scenario | Management | Rationale |
|---|---|---|
| Primary palsy (closed fracture) | Observation; splint in extension; EMG at 6-8 weeks | 70-90% recover spontaneously (neurapraxia) |
| Palsy after closed manipulation | Early exploration strongly considered | Concern for nerve entrapment |
| Open fracture with nerve in zone | Early exploration | Direct assessment needed |
| No recovery by 3-4 months | Late exploration (6-9 months) | Possible neurotmesis requiring grafting |
| Irreversible palsy | Tendon transfers | PT→ECRB, FCR→EDC, PL→EPL |
Management Algorithm
Primary Radial Nerve Palsy (Present at Injury)
Observation is the standard of care. Seventy to ninety percent of primary palsies recover spontaneously because the injury is typically neurapraxia or axonotmesis. A wrist splint in extension prevents contracture. Serial clinical examination with EMG/NCS at 6-8 weeks post-injury monitors recovery (EMG before 3 weeks is not useful because Wallerian degeneration takes 2-3 weeks). Expected recovery shows an advancing Tinel sign distally with clinical recovery at 3-6 months. Indications for early surgical exploration include open fractures with the nerve in the zone of injury, penetrating trauma, associated vascular injury requiring surgical repair, and nerve palsy developing after closed manipulation or reduction (suggesting iatrogenic entrapment). Late exploration at 6-9 months is indicated if no clinical or electrodiagnostic recovery occurs by 3-4 months.
Secondary Radial Nerve Palsy (After Manipulation or Surgery)
Secondary palsies carry higher concern for nerve entrapment or laceration, and many surgeons advocate early exploration. If palsy develops after closed reduction, surgical exploration is strongly considered.
Surgical Findings at Exploration
In approximately 70% of cases, the nerve is intact but contused or stretched. In 15-25%, the nerve is entrapped in the fracture. In 5-10%, the nerve is lacerated. When intact, neurolysis alone is performed. When lacerated, direct repair is performed if the ends approximate without tension; nerve grafting with sural nerve autograft is used when a gap exists.
Tendon Transfers for Irreversible Palsy
Tendon transfers are performed when nerve recovery is not expected or has failed. Classic transfers include pronator teres to ECRB (wrist extension), FCR or FCU to EDC (finger extension), and palmaris longus rerouted to EPL (thumb extension). Results are generally excellent with reliable functional recovery.
<image>Clinical photograph of wrist drop from radial nerve palsy with diagram of tendon transfer options</image>
Nonunion
Risk Factors
Risk factors for nonunion include transverse fracture pattern, distraction at the fracture site, soft tissue interposition, smoking, inadequate immobilization, and open fractures.
Treatment
Treatment involves compression plating with autologous bone grafting (iliac crest), decortication of fracture ends, and addressing any infection. Union rates after revision fixation with bone grafting exceed 90%.
Clinical Pearls
Functional bracing remains a highly effective treatment, and patients should be counseled about the expected healing timeline and the tolerance for angular deformity in the humerus. If performing ORIF through a posterior approach, the radial nerve must be identified first before any retraction or plating. A new radial nerve palsy after closed manipulation is a relative surgical emergency and exploration should be considered. In the MIPO technique, the radial nerve is at risk at the distal wound because the nerve can lie directly on the lateral cortex and be compressed by the plate. Radial nerve function must always be documented before and after any intervention including manipulation, splinting, or surgery. The deltoid splitting approach for very proximal shaft fractures risks axillary nerve injury, as the nerve is approximately 5-7 cm distal to the lateral acromion.
References
- Sarmiento A, et al. Functional bracing for the treatment of fractures of the humeral diaphysis. JBJS Am. 2000;82(4):478-486.
- Holstein A, Lewis GB. Fractures of the humerus with radial-nerve paralysis. JBJS Am. 1963;45(7):1382-1388.
- Shao YC, et al. Radial nerve palsy associated with fractures of the shaft of the humerus: a systematic review. JBJS Br. 2005;87(12):1647-1652.
- Ekholm R, et al. Fractures of the shaft of the humerus: an epidemiological study of 401 fractures. J Bone Joint Surg Br. 2006;88(11):1469-1473.
- Denard A Jr, et al. Outcome of nonoperative vs operative treatment of humeral shaft fractures: a retrospective study of 213 patients. Orthopedics. 2010;33(8).
