Humeral Shaft Fractures

Humeral shaft fractures are unique in that non-operative management achieves excellent outcomes in the majority of cases. The shoulder and elbow joints compensate well for residual angulation and shortening, making functional bracing the gold standard treatment.

The radial nerve supplies the triceps before entering the spiral groove. Therefore, triceps function may be preserved despite radial nerve injury at the spiral groove level. Always test wrist and finger extension - these are the key clinical findings for radial nerve palsy.

Look specifically for distal third spiral oblique fracture pattern on radiographs. This is the Holstein-Lewis fracture with high radial nerve palsy risk. Even with intact nerve function, consider lower threshold for surgical intervention.

The humerus is the second most common long bone for skeletal metastases (after the femur), so "pathological fracture" appears in the indication list - but the examinable decision-making behind it is distinct from a normal trauma fracture.

Impending fracture (still intact bone with a destructive lesion) - quantify the risk with the Mirels score (1 to 3 points each for: site, pain, lesion type lytic/blastic/mixed, and size as a fraction of cortical diameter):

• Score 9 or more = prophylactic fixation before it breaks (a fixed bone is far easier than a pathological fracture, and avoids the morbidity of a sudden break).
• Score 7 or less = radiotherapy and surveillance; 8 is borderline and individualised.
• Functional bracing's usual forgiveness does not apply: tumour bone will not unite, so the goal is durable mechanical stability for the patient's remaining life, not union.

Implant choice for diaphyseal disease differs from trauma:

• A long intramedullary nail spanning the whole bone is often preferred for diaphyseal metastases - it protects the entire humerus against further lesions and allows immediate load-bearing, unlike a plate that protects only the fracture.
• Plate plus cement (PMMA) is an alternative where a nail is unsuitable or for periarticular lesions, filling the defect for immediate stability.
• Always biopsy/confirm the diagnosis before fixing an unknown solitary lesion (it may be a primary sarcoma where a nail would contaminate the whole bone), and give postoperative radiotherapy to the construct to control local tumour.

Exam point: for a humeral lesion, score the impending fracture with Mirels (fix if 9 or more, irradiate if 7 or less); for diaphyseal metastatic disease favour a long IMN spanning the whole bone plus postoperative radiotherapy, and biopsy an unknown solitary lesion before fixation to avoid seeding a primary sarcoma.

Meta-analyses show similar union rates for plate vs nail (both over 95%). However, plating has lower reoperation rates and less shoulder problems. Nailing is faster but associated with more shoulder pain (antegrade) or elbow issues (retrograde).

The Swedish Fracture Register (Bergdahl et al, BMC Musculoskelet Disord 2016) provides the cleanest contemporary denominator: humeral shaft fractures occur at 13.4 per 100,000 person-years, are predominantly low-energy falls in older women (F:M 2.4:1), and make up about 13% of all humeral fractures. Only ~1% are open.

There is genuine international practice variation: the historical Sarmiento data and Shao systematic review underpin a non-operative-first culture in many UK/European and Australian units, whereas the Matsunaga RCT and lower nonunion rates with fixation have driven a trend toward earlier operative management in some centres. No registry or guideline currently mandates routine surgery for the typical closed isolated fracture.

Specific risks to discuss: Radial nerve injury (iatrogenic 2-5%), infection, nonunion, hardware failure/irritation, need for bone grafting, shoulder stiffness. For IMN: add rotator cuff injury and shoulder pain (15-30%).