Proximal Humerus Malunion: Evaluation and Surgical Management

Comprehensive Introduction and Patho-Epidemiology

Malunion of a proximal humerus fracture represents one of the most formidable challenges in reconstructive orthopedic surgery. This complex deformity typically arises from either the nonoperative management of a significantly displaced fracture, inadequate primary operative reduction, or secondary loss of fixation following surgical intervention. The proximal humerus relies heavily on a delicate, highly synchronized balance of force couples generated by the surrounding rotator cuff musculature. When a fracture heals in a malaligned position, the profound disruption of the normal anatomical relationships between the articular segment, the greater and lesser tuberosities, and the humeral diaphysis catastrophically alters glenohumeral kinematics. This alteration inevitably leads to a debilitating cascade of chronic pain, severe restriction of motion, and progressive posttraumatic arthropathy.

The specific pathoanatomy of a proximal humerus malunion is inextricably linked to the original fracture pattern and the subsequent unopposed vectors of the attached musculature. In three-part fractures involving the surgical neck and greater tuberosity, the intact lesser tuberosity remains attached to the articular segment. The unopposed pull of the subscapularis drives the articular surface into internal rotation, while the detached greater tuberosity is retracted superiorly and posteriorly by the supraspinatus and infraspinatus. Conversely, when the lesser tuberosity is fractured and the greater tuberosity remains attached to the head, the articular segment is forced into extreme external rotation and abduction. These deformities create massive mechanical blocks to motion, frequently complicated by severe, unyielding contractures of the deforming muscles, inferior glenohumeral subluxation, and rapid degradation of the articular cartilage.

Four-part fractures and complex fracture-dislocations that progress to malunion present an even more devastating clinical scenario. These injuries are characterized by profound articular incongruity, dense intra-articular and extra-articular fibrosis, and a remarkably high incidence of osteonecrosis (avascular necrosis) of the humeral head. The epidemiological profile of these patients is bimodal. One cohort consists of elderly, osteoporotic individuals who suffered low-energy falls and were managed conservatively due to medical comorbidities, eventually developing painful, stiff shoulders. The second cohort comprises younger, high-demand patients who sustained high-energy trauma (e.g., motor vehicle collisions, falls from height) and may have undergone previous, ultimately unsuccessful, internal fixation.

To systematically approach these deformities, the Beredjiklian classification remains the most highly regarded framework in academic orthopedics. Type I malunions involve malposition of the greater or lesser tuberosity by more than 1 cm, which drastically alters the resting length and tension of the rotator cuff, precipitating weakness and severe subacromial impingement. Type II malunions are defined by intra-articular incongruity or an articular step-off exceeding 5 mm, a condition that guarantees the rapid onset of posttraumatic glenohumeral arthropathy. Type III malunions involve rotational malalignment of the articular segment by more than 45 degrees in any plane. Crucially, the Beredjiklian system emphasizes that osseous deformity rarely exists in isolation; concomitant soft tissue contractures, rotator cuff tears, and capsular adhesions are present in nearly 80% of cases, making the soft tissue reconstruction just as critical as the osseous realignment.

Detailed Surgical Anatomy and Biomechanics

A profound understanding of the complex three-dimensional surgical anatomy and biomechanics of the proximal humerus is an absolute prerequisite for attempting any reconstructive intervention. The normal proximal humerus is characterized by a neck-shaft angle of approximately 130 to 140 degrees in the coronal plane and a retroversion angle of 20 to 30 degrees relative to the transepicondylar axis of the distal humerus in the axial plane. The articular surface of the humeral head forms a third of a sphere, oriented medially, superiorly, and posteriorly. The preservation or restoration of the medial calcar—the cortical bone at the inferomedial aspect of the surgical neck—is the linchpin of biomechanical stability. Loss of this medial hinge during the initial fracture or subsequent malunion inevitably leads to varus collapse, which drastically decreases the acromiohumeral distance and severely compromises the mechanical advantage of the abductor musculature.

The biomechanical stability and dynamic function of the glenohumeral joint are governed by intricate transverse and coronal plane force couples. In the transverse plane, the subscapularis anteriorly balances the infraspinatus and teres minor posteriorly, maintaining the humeral head concentrically reduced within the shallow glenoid fossa during rotation. In the coronal plane, the inferior pull of the intact rotator cuff balances the superior sheer force of the deltoid muscle. A malunion of the greater tuberosity that heals in a superiorly migrated position destroys this coronal balance. The superiorly displaced tuberosity physically abuts the acromion and the coracoacromial ligament during abduction, creating a mechanical block. Furthermore, the relative shortening of the supraspinatus and infraspinatus muscle-tendon units leads to active insufficiency, rendering the patient unable to actively elevate the arm despite an anatomically intact nerve supply.

The vascular anatomy of the proximal humerus is famously precarious, and its disruption is the primary driver of posttraumatic osteonecrosis. The arterial supply is derived from the anterior and posterior circumflex humeral arteries, which branch from the axillary artery. The anterior circumflex humeral artery gives rise to the anterolateral ascending branch (the arcuate artery of Laing), which courses parallel to the lateral aspect of the bicipital groove and supplies the majority of the greater tuberosity and the anterolateral humeral head. However, recent microangiographic studies have demonstrated that the posterior circumflex humeral artery provides the dominant blood supply to the inferomedial and posterior aspects of the humeral head. In the setting of a malunion, the dense scar tissue and altered osseous landmarks place these vessels at extreme risk during surgical dissection and osteotomy, frequently necessitating a meticulous, periosteum-sparing technique to prevent iatrogenic devascularization.

Neurological proximity further complicates the surgical management of proximal humeral malunions. The axillary nerve, originating from the posterior cord of the brachial plexus, courses anterior to the subscapularis, passes inferior to the glenohumeral joint capsule, and exits through the quadrangular space to innervate the deltoid and teres minor. In a chronic malunion, particularly those involving inferior subluxation or profound capsular contracture, the axillary nerve is frequently tethered in dense scar tissue directly against the inferior capsule. Similarly, the suprascapular nerve, which supplies the supraspinatus and infraspinatus, can be tethered at the suprascapular or spinoglenoid notch if a massive, chronically retracted greater tuberosity malunion exerts continuous traction on the muscle bellies. Meticulous identification, neurolysis, and protection of these neural structures are mandatory steps before any osseous correction is attempted.

Exhaustive Indications and Contraindications

The decision-making process for surgical intervention in proximal humerus malunions is highly nuanced, requiring the surgeon to synthesize the patient's physiological age, functional demands, rotator cuff integrity, bone stock quality, and the specific morphological characteristics of the deformity. The overarching philosophy is to restore pain-free, functional range of motion while minimizing the risk of catastrophic complications such as osteonecrosis or hardware failure. Nonoperative management is generally reserved for elderly, low-demand patients with minimal pain, or those whose medical comorbidities preclude a major reconstructive procedure. For all other patients experiencing debilitating pain, profound stiffness, or progressive neurological deficit secondary to the malunion, surgical intervention is strongly indicated.

The choice of specific surgical procedure—ranging from joint-preserving corrective osteotomy to anatomic total shoulder arthroplasty (aTSA) or reverse total shoulder arthroplasty (RTSA)—is dictated by the condition of the articular cartilage and the rotator cuff. Corrective osteotomy is strictly indicated for young, active patients (typically under 55 years of age) with a Beredjiklian Type I or Type III malunion, preserved articular cartilage, a functional rotator cuff, and adequate bone stock to support internal fixation. Conversely, arthroplasty is indicated for older patients, those with Beredjiklian Type II malunions (articular step-off >5 mm), established osteonecrosis, or posttraumatic osteoarthritis. If the rotator cuff is intact and functioning, an aTSA may be considered; however, in the presence of an irreparable rotator cuff tear, severe tuberosity malunion, or profound tuberosity resorption, an RTSA is the definitive procedure of choice, as it bypasses the need for a functional rotator cuff by medializing the center of rotation and increasing the deltoid moment arm.

Contraindications to surgical intervention must be rigorously respected to avoid disastrous outcomes. Absolute contraindications include active local or systemic infection, severe medical comorbidities rendering the patient unfit for anesthesia, and a functionally dead arm (e.g., complete, irreparable brachial plexus avulsion). Relative contraindications include profound osteopenia or osteoporosis that would preclude secure hardware fixation in the case of an osteotomy, active substance abuse, uncontrolled psychiatric illness, and severe patient noncompliance, as the postoperative rehabilitation protocol is exceptionally demanding. Furthermore, an isolated corrective osteotomy is relatively contraindicated in patients with a concomitant, irreparable axillary nerve palsy, as the lack of deltoid function will result in a poor functional outcome regardless of osseous realignment.

Pre-Operative Planning, Templating, and Patient Positioning

Preoperative evaluation of a proximal humeral malunion demands a meticulous, multimodal approach, beginning with a comprehensive clinical examination. The surgeon must meticulously document active and passive range of motion in all planes, noting any hard, mechanical blocks that suggest osseous impingement versus soft, rubbery end-points indicative of capsular contracture. A classic clinical sign of a severe greater tuberosity malunion is a profound, unyielding block to external rotation when the arm is abducted to 90 degrees, caused by the malunited tuberosity crashing into the posterior-superior glenoid rim. Rotator cuff integrity must be assessed using specific provocative maneuvers, such as the Hornblower's sign for teres minor incompetence, the belly-press test for subscapularis function, and Jobe's test for supraspinatus integrity. Given the high incidence of concomitant nerve injury in high-energy trauma, a baseline neurological examination is mandatory, frequently supplemented by Electromyography (EMG) and Nerve Conduction Studies (NCS) to map out any subclinical axillary or suprascapular nerve deficits.

Advanced imaging is the cornerstone of preoperative planning, as standard two-dimensional radiographs invariably underestimate the complex, multiplanar nature of the deformity. While a standard trauma series (true AP, scapular Y, and axillary views) provides a baseline assessment of alignment and hardware status, a high-resolution Computed Tomography (CT) scan with three-dimensional surface-rendered reconstructions is the absolute gold standard. The CT scan allows the surgeon to precisely quantify the degree of tuberosity displacement, assess the sphericity of the humeral head, evaluate glenoid version and bone stock, and identify any occult intra-articular fracture lines or step-offs. Furthermore, Magnetic Resonance Imaging (MRI) is highly recommended to evaluate the status of the rotator cuff tendons, quantify the degree of fatty infiltration and muscle atrophy using the Goutallier classification system, and detect early, radiographically silent osteonecrosis of the articular segment.

Digital templating utilizing advanced 3D planning software (e.g., Blueprint, Materialise) has revolutionized the surgical preparation for these complex cases. For corrective osteotomies, the surgeon can virtually separate the malunited fragments, calculate the exact angles of correction required in the coronal, sagittal, and axial planes, and pre-select the appropriate osteotomes and fixation constructs. If an arthroplasty is planned, 3D templating allows for the precise calculation of glenoid version correction, selection of the optimal baseplate size and peg configuration, and determination of the required humeral offset to restore the deltoid resting length. This virtual rehearsal is critical for anticipating intraoperative difficulties, such as severe bone loss that may necessitate structural allografting or custom, patient-specific instrumentation (PSI).

Optimal patient positioning and meticulous operating room setup are critical for the fluid execution of the procedure. The patient is typically placed in a modified beach-chair position, with the head secured in a specialized headrest to ensure neutral cervical spine alignment and clear access to the superior shoulder girdle. The operative arm must be completely free-draped to allow for unrestricted, multiplanar manipulation during the reduction and trialing phases. A mechanical arm positioner (e.g., Spider limb positioner) is highly advantageous, as it provides stable, static holding during complex osteotomies and component implantation. The fluoroscopy unit (C-arm) must be positioned on the contralateral side of the table, coming in perpendicularly to allow for unimpeded orthogonal views of the proximal humerus without disrupting the sterile field or the surgeon's working space.

Step-by-Step Surgical Approach and Fixation Technique

Surgical intervention for proximal humerus malunions is an extraordinarily demanding endeavor that requires a systematic, layered approach to address both the profound soft tissue contractures and the complex osseous deformities. The following sections detail the operative steps for a joint-preserving corrective osteotomy, as well as the management of a concomitant clavicular malunion in the setting of a "floating shoulder" variant.

The Deltopectoral Approach and Soft Tissue Release

The procedure universally begins with an extended deltopectoral approach, which provides the most versatile and expansile access to the proximal humerus. The skin incision is made from the tip of the coracoid process, extending distally and laterally along the deltopectoral groove. The cephalic vein is identified and typically retracted laterally with the deltoid muscle to preserve its venous drainage, minimizing postoperative edema. Upon entering the deep space, the surgeon is immediately confronted by dense, unyielding scar tissue obliterating the normal anatomical planes. A meticulous, systematic tenolysis and capsular release are mandatory. The conjoined tendon is identified and retracted medially. The subdeltoid and subacromial spaces are aggressively cleared of adhesions to mobilize the proximal humerus. The axillary nerve must be identified early in the procedure; it is palpated at the inferior border of the subscapularis and physically protected with a blunt retractor throughout the entirety of the deep dissection and osteotomy.

Corrective Osteotomy for Tuberosity Malunions

Once the soft tissue envelope has been adequately mobilized, the specific osseous deformity is addressed. For a Beredjiklian Type I greater tuberosity malunion, the original fracture line is identified under direct fluoroscopic guidance. Utilizing a fine, curved osteotome or a narrow-bladed oscillating saw, the surgeon carefully recreates the fracture, taking extreme caution to direct the blade away from the underlying articular cartilage of the humeral head. The osteotomy must be complete, allowing the tuberosity fragment—along with its attached supraspinatus and infraspinatus tendons—to be freely mobilized. This mobilization frequently requires an extensive release of the coracohumeral ligament and the superior capsule. Once mobilized, the tuberosity is reduced anatomically to its native footprint, located lateral to the bicipital groove and inferior to the articular margin.

Management of the Articular Segment and Shaft

Following the reduction of the tuberosity, robust fixation is paramount to withstand the immense deforming forces of the rotator cuff during the rehabilitation phase. Depending on the patient's bone quality, fixation is achieved utilizing either a low-profile, anatomically contoured locking plate or a heavy, non-absorbable transosseous suture construct. If a locking plate is utilized, it is positioned lateral to the bicipital groove and distal to the greater tuberosity tip to prevent secondary subacromial impingement. Multiple locking screws are directed into the humeral head to secure the articular segment, while specialized suture holes in the plate are utilized to capture the rotator cuff tendons and the osteotomized tuberosity fragment, neutralizing the superior pull of the supraspinatus. The construct is then rigorously tested under direct visualization by taking the shoulder through a full, passive range of motion to ensure stability and the absence of mechanical impingement.

Intramedullary Correction for Associated Clavicular Malunion

In the complex setting of a "floating shoulder" variant, where a proximal humerus malunion presents concomitantly with a symptomatic clavicular malunion, restoring the superior suspensory complex is critical for optimizing overall shoulder girdle kinematics. For the clavicular component, an intramedullary correction utilizing a Titanium Elastic Nail (TEN) provides excellent stability with minimal soft tissue stripping. A 5 cm incision is made directly over the clavicular deformity. The deltotrapezial fascia is incised and elevated subperiosteally as a single, contiguous sleeve to preserve the vital osseous blood supply. The malunion is osteotomized using a fine oscillating saw. The sclerotic medullary canals of both the medial and lateral fragments are opened using a 2.7-mm drill. A separate 2 cm incision is made over the medial sternoclavicular junction, the anterior cortex is breached, and a 2.5-mm TEN is advanced laterally across the fracture site under continuous fluoroscopic monitoring. The distal fragment, typically displaced caudally and malrotated, is manually reduced, and the nail is driven into the lateral metaphysis. The nail is cut flush medially, and the deltotrapezial fascia is meticulously repaired to ensure a robust soft-tissue envelope over the osteotomy site.

Complications, Incidence Rates, and Salvage Management

Surgical reconstruction of proximal humerus malunions is fraught with a high complication profile, largely attributable to the compromised local biology, the presence of dense scar tissue, and the inherently poor bone stock frequently encountered in these patients. The surgeon must engage in extensive preoperative counseling to manage patient expectations, explicitly detailing the risks of hardware failure, persistent stiffness, and the potential need for secondary salvage procedures. The biological toll of revision surgery on the proximal humerus cannot be overstated; the extensive soft tissue stripping required to mobilize malunited fragments significantly jeopardizes the already tenuous vascular supply to the articular segment.

Osteonecrosis (avascular necrosis) of the humeral head is the most devastating complication following joint-preserving corrective osteotomy, occurring in up to 15-20% of complex cases. The pathogenesis is directly linked to the iatrogenic disruption of the arcuate artery or the posterior circumflex humeral artery during the deep dissection and osteotomy of the tuberosities. Patients typically present with insidious, progressive pain and a rapid decline in range of motion months after an initially successful surgery. Radiographic evaluation will demonstrate subchondral sclerosis, cystic changes, and eventual crescent sign formation leading to catastrophic articular collapse. When symptomatic AVN occurs, salvage management necessitates a conversion to arthroplasty. If the tuberosities have healed and the rotator cuff remains competent, an anatomic total shoulder arthroplasty may be attempted; however, in the setting of tuberosity resorption or cuff failure, a reverse total shoulder arthroplasty is the mandatory salvage procedure.

Nonunion of the osteotomy site and secondary hardware failure represent another major cluster of complications, particularly in the elderly or osteoporotic population. Failure of the greater tuberosity to unite to the humeral shaft results in superior migration of the fragment, profound weakness in abduction, and severe subacromial impingement. This is frequently caused by inadequate initial fixation, excessive tension on the rotator cuff repair, or premature, aggressive active rehabilitation. Hardware impingement is also common, even when union is achieved, as the altered geometry of the reconstructed proximal humerus can cause locking plates or prominent screw heads to abut the acromion during elevation. In cases of isolated hardware impingement with a solidly healed osteotomy, a simple hardware removal procedure often provides dramatic symptomatic relief.

Persistent postoperative stiffness is nearly ubiquitous, to varying degrees, following the surgical management of proximal humeral malunions. Despite meticulous intraoperative capsular release and rigid internal fixation, the profound tendency for these tissues to form dense, restrictive scar tissue during the healing phase is a constant battle. While a functional arc of motion is the primary goal, patients rarely achieve the same kinematic fluidity as a native, uninjured shoulder. Infection, while less common than stiffness or AVN, is a catastrophic event when it occurs, often involving indolent organisms such as Cutibacterium acnes. Deep infections require aggressive surgical debridement, hardware removal, placement of antibiotic-loaded cement spacers, and prolonged intravenous antibiotic therapy before any definitive reconstructive salvage can be entertained.

Phased Post-Operative Rehabilitation Protocols

The postoperative rehabilitation following the surgical correction of a proximal humerus malunion is an arduous, prolonged process that requires a delicate, highly individualized balance between protecting the tenuous osseous fixation and preventing the rapid recurrence of debilitating soft tissue contractures. The protocol must be strictly phased, guided by the specific intraoperative findings, the security of the hardware construct, and the biological quality of the patient's bone and soft tissues. Communication between the operating surgeon and the physical therapy team is absolutely critical; the surgeon must explicitly define the "safe zones" of motion established during the intraoperative testing phase to prevent catastrophic early failure of the reconstruction.

Phase I, the Maximum Protection Phase, spans from postoperative day one to approximately week six. The primary goal during this phase is to protect the osteotomy site and the rotator cuff repair while preventing distal joint stiffness. The shoulder is strictly immobilized in a specialized abduction orthosis or a sling, depending on the tension of the repair. Immediate, aggressive active range of motion of the elbow, wrist, and hand is instituted to prevent complex regional pain syndrome (CRPS) and promote venous return. Passive range of motion (PROM) of the glenohumeral joint is initiated within the strictly defined safe zones. Forward elevation is typically allowed up to 90 degrees in the scapular plane, while external rotation is heavily restricted—often limited to neutral or a maximum of 20 degrees—to prevent excessive tension on the greater tuberosity fixation and the subscapularis repair.

Phase II, the Active Motion and Early Strengthening Phase, encompasses weeks six through twelve. Progression to this phase is strictly contingent upon radiographic evidence of early osseous union at the osteotomy site and clinical signs of stability. Once confirmed, the sling is definitively discontinued. The rehabilitation focus shifts to restoring active-assisted range of motion (AAROM) and progressing to full active range of motion (AROM). Patients begin utilizing pulleys, wands, and wall-walk exercises to regain forward elevation and abduction. Gentle, submaximal isometric strengthening of the rotator cuff and the critical periscapular stabilizers (serratus anterior, rhomboids, trapezius) is initiated to re-establish the dynamic force couples of the shoulder girdle. Aggressive passive stretching remains contraindicated, as the healing bone and tendon interfaces are still susceptible to failure under high tensile loads.

Phase III, the Advanced Strengthening and Functional Return Phase, begins at month three and extends up to one year postoperatively. During this phase, progressive resistive exercises utilizing elastic bands and light free weights are introduced. The rehabilitation program becomes highly functional, focusing on optimizing scapulothoracic rhythm, proprioception, and muscular endurance. The restoration of the transverse and coronal plane force couples is prioritized to ensure concentric rotation of the humeral head during dynamic activities. Return to heavy manual labor, overhead lifting, or high-impact sports is generally delayed until at least six to nine months postoperatively, and is strictly contingent upon complete, robust radiographic union, the absence of pain, and the restoration of near-normal strength compared to the contralateral extremity.

Summary of Landmark Literature and Clinical Guidelines

The evolution of the surgical management of proximal humeral malunions is deeply rooted in a rich history of academic literature and the progressive refinement of clinical guidelines. The foundational understanding of these complex deformities was established by Charles Neer in his seminal works on proximal humeral fractures in the 1970s. Neer was the first to meticulously describe the profound deforming forces of the rotator cuff and the catastrophic functional consequences of allowing a displaced fracture to heal in a malaligned position. His observations laid the groundwork for the modern imperative to achieve anatomic reduction during primary fracture management to prevent the sequelae of malunion.

The modern classification and systematic approach to these deformities were revolutionized by Beredjiklian, Iannotti, and colleagues in their landmark 1998 publication in the Journal of Bone and Joint Surgery. By analyzing a cohort of 39 patients, they developed the comprehensive classification system (Types I, II, and III) that remains the gold standard today. Crucially, their work highlighted that osseous malalignment is almost universally accompanied by profound soft tissue pathology, fundamentally shifting the surgical paradigm to emphasize simultaneous osseous and soft tissue reconstruction. Their study demonstrated that while corrective osteotomy could yield excellent results in carefully selected young patients, the technical demands were immense and the complication rates were not insignificant.

The role of arthroplasty in the management of proximal humeral malunions was definitively shaped by the extensive research of Boileau, Walch, and the French shoulder surgery community in the early 2000s. In their critical analyses of anatomic total shoulder arthroplasty for fracture sequelae, they demonstrated that outcomes were heavily dependent on the integrity of the greater tuberosity