Proximal Humerus Nonunion & Malunion

The proximal humerus most commonly fails to unite at the surgical neck. The classic lesion is the two-part surgical-neck nonunion, designated a Boileau type-3 fracture sequela, and the typical patient is elderly and osteoporotic.

Boileau's sequelae. Boileau grouped the sequelae of proximal humeral fracture into four types, and the type informs both the arthroplasty technique and the patient's expectations.

• Type 1: impacted cephalic collapse or necrosis
• Type 2: locked dislocation or fracture-dislocation
• Type 3: surgical-neck nonunion
• Type 4: severe tuberosity malunion

In type 1 a prosthesis is usually possible without tuberosity osteotomy, and it does well. Types 3 and 4 require a tuberosity osteotomy and have worse arthroplasty outcomes.

Why the neck fails to unite. Displacement and comminution, especially metaphyseal comminution, contribute, as do osteoporosis, inadequate fixation or stability and soft-tissue interposition. So do the deforming muscle forces that distract the fracture, with pectoralis major pulling the shaft medially and the cuff abducting and rotating the head.

Presentation. Months after the fracture the patient has pain, weakness or pseudoparalysis, and a mobile, painful nonunion.

Bone graft, a fibular strut and inadequate stability all make sense through the hypertrophic-versus-atrophic framework of nonunion, developed in full in Nonunion Management.

Hypertrophic nonunion. Abundant "elephant-foot" callus signals adequate biology but inadequate mechanical stability. It is a stability problem, and it usually unites with stable fixation alone, with no graft needed.

Atrophic or oligotrophic nonunion. Little or no callus signals failed biology. It needs biological augmentation (graft, and correction of any instability), not just more metalwork.

Where the surgical neck sits. The proximal-humeral surgical-neck nonunion is typically atrophic or oligotrophic. It arises in osteoporotic bone with metaphyseal comminution, poor metaphyseal vascularity and deforming muscle pull, so simply re-fixing it with revision plating alone tends to fail. A head-preserving reconstruction has to supply stability and biological and structural augmentation together; address only one and the nonunion recurs.

The work-up gathers what the choice between preserving and replacing the head depends on, and it excludes infection before any reconstruction.

• Radiographs, with or without CT, to confirm the nonunion, characterise the fragments and assess bone stock
• Head viability (AVN or cephalic collapse) and the size of the head fragment
• Rotator cuff integrity, clinically with or without imaging, which is central to the ORIF-versus-RSA decision
• The patient's age, demand and comorbidities
• Infection, which must be excluded before reconstruction (below)

An unrecognised low-grade (septic) nonunion will defeat both ORIF and arthroplasty, so infection must be excluded before reconstruction. The infection work-up belongs in the reconstruction decision itself, not after it.

The organism. In the shoulder, "exclude infection" specifically means think of Cutibacterium (formerly Propionibacterium) acnes, the predominant indolent shoulder pathogen. It characteristically produces few clinical signs and normal or only mildly raised CRP/ESR, so a "clean" blood panel does not exclude infection. Maintain a high index of suspicion in any failed fixation or recurrent nonunion.

The work-up. Sample properly rather than relying on the bloods.

• Screen with the history (rest or night pain, prior surgery, wound-healing problems), examination and inflammatory markers; CRP/ESR are useful when raised but unreliable when normal for C. acnes.
• Consider pre-operative aspiration.
• At surgery take multiple separate deep tissue samples for microbiology and histology, not a single swab, and have them held for prolonged culture of around two weeks to capture the slow-growing C. acnes.
• If the nonunion is infected, treat it as a septic nonunion, with debridement, organism-directed antibiotics and a staged reconstruction rather than a one-stage definitive procedure.

The C. acnes microbiology and management are developed in Cutibacterium acnes Shoulder Infection, and the general principles in Nonunion Management.

The elderly, osteoporotic patient explains why the fracture failed, and the same features are a list of things to correct before and after reconstruction. Re-operating on an unoptimised host repeats the conditions that produced the nonunion.

These thresholds and the wider work-up follow Nonunion Management, so they apply whichever bone has failed to unite. What is specific to the proximal humerus is the demographic, which makes every item on the list more likely to be abnormal, not less.

The decision: preserve the head or replace it. Treatment is driven by age, head viability, bone stock and the rotator cuff. A younger patient with good bone stock, a viable head and an intact cuff favours head-preserving ORIF. An elderly patient, poor bone stock, a non-viable or small head fragment, a deficient cuff or a failed ORIF favours reverse total shoulder arthroplasty.

Head-preserving ORIF. A fixed-angle locked plate (or blade plate) provides the stability and bone graft provides the biology, most commonly an intramedullary fibular strut and/or cancellous autograft at the nonunion. The strut restores the medial calcar buttress and improves the grip of fixation in the osteoporotic, comminuted metaphysis. ORIF needs a viable head with a fragment large enough to hold fixation, and adequate bone stock; given those, it achieves reliable union and preserves the native joint. Graft choice is covered in Bone Grafts.

Reverse total shoulder arthroplasty. For the elderly, the non-viable head, the deficient cuff and the failed ORIF, reverse TSA is the workhorse: it is cuff-independent and gives reliable pain relief and function. When the nonunion extends into the metadiaphysis, a long-stem implant, often cementless, is used to bypass it.

Consent with the complication figures, not just the gains. In the largest series of reverse arthroplasty for surgical-neck nonunion (32 patients), the Constant score rose from 14 to 47 and flexion from 43 to 110 degrees, which is genuinely transformative. There were also complications in 41%, revision in 28% and dislocation in 34%, the commonest problem. Those are not the figures of a routine reverse for cuff arthropathy, because a nonunion shoulder is a harder operation on worse bone with disturbed anatomy.

The honest framing is a high-yield operation with a high complication rate, chosen because the alternatives are worse. The numbers come from a single series of 32, so they indicate the scale of the risk rather than a precise probability.

Preserve the tuberosities. This is the pivotal technical lesson of reverse arthroplasty for nonunion. Intra-operative resection of the tuberosities significantly increases the dislocation rate, which is already the leading complication, so the tuberosities and their attached rotator cuff are retained and repaired whenever possible.

Malunion. Management of a malunited proximal humerus depends on the site, the severity and the condition of the joint.

• A prominent, superiorly or posteriorly malunited greater tuberosity causes subacromial or internal impingement and lost motion, and is treated by tuberosity osteotomy/reduction, excision of the prominent portion, or acromioplasty.
• Surgical-neck malunion (angulation) may need a corrective osteotomy.
• Severe malunion with joint damage is treated by arthroplasty, as a Boileau type-4 sequela with tuberosity osteotomy.