Radial head arthroplasty: A pillar of stability in complex elbow fractures

Abstract

Radial head (RH) arthroplasty (RHA) has emerged as a critical intervention in the management of complex elbow fractures, particularly Mason type III and IV injuries where the native RH is irreparable. Beyond its role in pain relief and joint congruity, RHA serves as a biomechanical cornerstone for restoring the lateral column and ensuring elbow stability, especially in the presence of associated ligamentous injuries or fracture-dislocations. This editorial synthesizes current evidence on RHA in Mason type III and IV RH fractures, with attention to biomechanical rationale, implant design, and complication trends. Aiming to reaffirm RHA’s position as a vital tool in contemporary elbow trauma care, a simplified treatment algorithm is presented to support individualized surgical decision-making.

Key Words: Radial head arthroplasty; Mason classification; Comminuted radial head fractures; Modular prosthesis; Aseptic loosening; Overstuffing; Cost-effectiveness

Core Tip: Radial head (RH) arthroplasty has become a preferred treatment option for non-reconstructable Mason type III and IV RH fractures, particularly when associated with elbow instability. This editorial examines the anatomical and biomechanical rationale for RH arthroplasty, evaluates prosthetic design evolution, and critically reviews clinical outcomes and complication patterns. Special emphasis is placed on common failure modes such as aseptic loosening, overstuffing, and stiffness, as well as its cost-effectiveness in comparison to alternative surgical strategies. The aim is to provide a comprehensive, evidence-based perspective to guide surgical decision-making in complex elbow trauma. A treatment algorithm is provided to aid surgical decision-making in Mason type III and IV RH fractures, based on fracture morphology and elbow stability.

INTRODUCTION

The radial head (RH) plays a critical biomechanical role in the stability and function of the elbow joint. Beyond its contribution to forearm rotation, it serves as a secondary stabilizer against valgus stress and helps resist axial and posterolateral forces, particularly in the setting of ligamentous injury[1]. This function renders the RH a true “pillar of stability” within the elbow against these forces. RH fractures (RHFs) are among the most common injuries around the elbow, with Mason type III and IV fractures representing the more severe grades, often associated with elbow instability, comminution, and complex soft tissue involvement[2]. Management options for complex RHFs have evolved from excision to internal fixation and, more recently, RH arthroplasty (RHA). While excision may have a limited role in low-demand patients or in isolated injuries with preserved stability, it has shown long-term drawbacks including valgus deformity, proximal migration of the radius, and elbow instability particularly with concomitant ligamentous injury. Internal fixation is technically demanding and often unreliable with comminuted Mason III and IV RHFs[3,4].

RHA has emerged as a valuable option in such challenging scenarios, restoring lateral column integrity, preserving joint biomechanics, and allowing early motion. Nonetheless, its use remains debated due to concerns about implant selection, longevity, and complication rates[4-6]. This editorial expands upon the findings of Bindal et al[7], which reported favorable short-term functional outcomes of RHA in Mason type III and IV fractures. Building on their insights, we critically examine the role of RHA, assessing its anatomical and biomechanical justification, functional performance, complication spectrum, and cost-effectiveness, to determine whether it serves as a dependable cornerstone in elbow reconstruction or a more selective alternative. This editorial specifically focuses on the management of acute type III and IV RHFs, where timely surgical decision-making directly impacts elbow stability and function.

RH ANATOMY AND BIOMECHANICS: FOUNDATIONAL INSIGHTS FOR UNDERSTANDING FRACTURE MANAGEMENT

RH plays a crucial role in elbow stability and kinematics, particularly under conditions of ligamentous compromise or joint disruption[8]. Anatomically, it is elliptical rather than circular, with its long axis perpendicular to the lesser sigmoid notch when the forearm is in neutral rotation[9,10]. This configuration, combined with a natural offset and tilt from the radial neck axis (average inclination of 15°), contributes to the unique articulation dynamics during pronation and supination[11]. These features are essential for preserving radio-capitellar (RC) congruity and for distributing axial loads during functional activities[12]. From a biomechanical perspective, RH serves as a secondary stabilizer to valgus stress and axial compression, especially when the medial collateral ligament (MCL) is deficient. It also contributes to posterolateral rotatory stability in conjunction with the lateral ulnar collateral ligament[13]. During forearm rotation, the RH undergoes a “windshield-wiper” motion against the capitellum, which depends on both bony architecture and ligamentous tensioning[10].

Morphometric studies further emphasize the anatomical variability of RH and its surgical implications. King et al[14] demonstrated a diameter range of 22-25 mm and an average offset of 4.2 mm between the head and neck axes. Swieszkowski et al[15] confirmed similar variability using coordinate measuring systems, reporting an average head diameter of 23.36 mm, height of 10.14 mm, and articular surface depth of 1.92 mm. While some studies found no significant side-to-side differences[15], others - including Gupta et al[16], MacIntyre et al[17], and Hiramoto[18] - highlighted variability based on sex or arm dominance. These inconsistencies make standardized replication of RH anatomy challenging, supporting the evolution of modular RHA systems that allow intraoperative customization of size, shape, and offset[16-18]. Taken together, these anatomical and biomechanical insights underscore the need for individualized surgical strategies in managing complex RHFs. Whether through reconstruction or prosthetic replacement, the goal remains to replicate native mechanics and restore stability to the compromised elbow joint.

REVISITING THE CLASSIFICATION SYSTEMS FOR RHFs

The classification of RHFs has evolved over time to reflect the growing understanding of their complexity and associated injuries. The most widely used system remains the Mason classification, initially introduced by Mason[19] and later modified by Johnston[20]. This system categorizes fractures based on displacement and comminution: (1) Type I fractures are non-displaced or minimally displaced injuries of the RH (less than 2 mm) without mechanical block to motion; (2) Type II fractures are displaced by more than 2 mm, with potential blocking effect, but lack comminution; (3) Type III injuries are both comminuted and displaced; and (4) Type IV refers to RHFs occurring in the setting of elbow instability. An illustrated summary of the Mason-Johnston classification is presented in Figure 1, emphasizing the structural severity and instability potential of types III and IV. Hotchkiss[21] later refined this classification by introducing a more quantifiable threshold for displacement, enhancing its clinical applicability. Building further on this, van Riet and Morrey[22] proposed an extended system that incorporates associated soft tissue and bony injuries by appending suffixes to the Mason types (I, II, and III). These include “c” for coronoid fracture, “o” for olecranon fracture, “m” for MCL injury, “l” for lateral collateral ligament injury, and “d” for distal radioulnar joint disruption. This comprehensive approach acknowledges the frequent complexity of RHFs and highlights the importance of evaluating both osseous and ligamentous elements when formulating a treatment strategy.

Figure 1 Mason-Johnston classification of radial head fractures. Type I fractures are non-displaced or minimally displaced injuries of radial head (less than 2 mm) without mechanical block to motion; type II fractures are displaced by more than 2 mm, with potential blocking effect, but lack comminution; type III injuries are both comminuted and displaced; and type IV refers to radial head fractures occurring in the setting of elbow instability.

MASON TYPE III AND IV FRACTURES: A NEXUS OF INSTABILITY AND SURGICAL CONSEQUENCES

Mason type III and IV RHFs are often present as complex, destabilizing injuries of the elbow due to their frequent association with comminution, displacement, and elbow instability in type IV. These patterns are rarely isolated and typically signal a more extensive disruption of the elbow’s stabilizing structures[23,24]. While the biomechanical importance of the RH in resisting valgus and axial forces has been well established, its clinical relevance becomes especially apparent when evaluating high-grade injuries. In these fracture types, the inability to preserve or reconstruct the native RH significantly alters elbow kinematics and challenges joint stability, particularly in the setting of ligamentous disruptions[22]. This risk of instability is markedly heightened in complex patterns, such as the “terrible triad”, where concomitant coronoid fractures and soft tissue injury coexist[25,26]. In such cases, failing to restore lateral column support, whether through excision, mal-reduction, or inadequate implant selection, may lead to persistent subluxation, limited motion, and early joint degeneration[24,27].

RH resection (RHR), although historically common, should be cautiously considered in this context. Its use in the presence of ligament insufficiency can lead to medial joint gapping, increased valgus loading on the MCL, and progressive arthrosis[28]. Similarly, implant mal-positioning or improper sizing may compound joint incongruity, provoking further instability rather than resolving it. In unreconstructible fractures, RHA offers a reliable surgical solution that restores lateral column integrity, preserves joint articulation, and provides a stable platform for ligamentous healing. Importantly, RHA should be viewed as part of a broader strategy to restore elbow function in the face of combined osseous and soft tissue trauma. Patient-specific factors, including activity level, joint laxity, and ligament integrity, should guide the decision-making process to optimize both mechanical and functional outcomes.

RECONSTRUCT, RESECT, OR REPLACE? NAVIGATING SURGICAL DECISION-MAKING IN MASON III/IV FRACTURES

The optimal surgical approach for Mason type III and IV RHFs remains a subject of ongoing debate. Numerous studies have explored outcomes for each technique whether in isolation or through direct comparisons. Yet, a universally accepted treatment algorithm remains elusive. Several authors have advocated for open reduction and internal fixation (ORIF) when anatomical reduction, restoration of joint congruity, and early mobilization can be achieved[29,30]. Helmstetter et al[31] reported favorable outcomes using ORIF in Mason type III and IV RHFs involving more than three fragments, with all patients achieving radiographic healing within an average of 9 weeks. Their findings were consistent with prior studies supporting ORIF in similarly complex fracture patterns[32-34]. However, other investigations by Ring et al[35], Ruan et al[36], and Chen et al[37] reported lower patient satisfaction and suboptimal clinical results with ORIF.

More recent evidence, including meta-analyses by Sun et al[38] and De Mauro et al[4], suggest that ORIF for Mason type III fractures yields inferior satisfaction and functional scores compared to RHA, along with longer operative times and a higher incidence of complications and reoperations. Comparative analyses of all three surgical strategies - ORIF, RHR, and RHA have also been reported. Zwingmann et al[39] found ORIF to be marginally superior in Mason III fractures, though without statistical significance. Likewise, Scoscina et al[40] found no significant differences in functional outcomes among the three techniques, although ORIF was associated with a more limited range of motion (ROM). In contrast, Pogliacomi et al[41] demonstrated equivalent outcomes for Mason III fractures with all surgical options but reported superior results with RHA for Mason IV fractures.

Historically, RHR showed favorable long-term results in selected patients[28,42]. Supporting this, Lópiz et al[43] found better functional outcomes and fewer complications with RHR compared to RHA in Mason III fractures. However, none of these studies were free from complications. Ikeda and Oka[44] recommended reserving RHR for low demand patients. In a recent systematic review and meta-analysis, Bianco Prevot et al[24] compared RHR and RHA in the treatment of Mason III and IV fractures. Both interventions yielded satisfactory functional outcomes with no significant differences in ROM or functional scores. However, RHR was associated with a higher rate of post-traumatic osteoarthritis. In alignment with Scoscina et al[40], the authors suggested RHR may be more appropriate for elderly patients with limited functional demands, while RHA should be considered in patients with a higher risk of joint instability.

Each surgical approach carries a distinct complication profile. ORIF is associated with risks of nonunion, hardware failure, secondary displacement, stiffness, and osteoarthritis[23]. Multiple comparative studies noted increased complication and revision rates when ORIF was used for comminuted RHFs[39-41]. Similarly, RHR has not been complication-free, with reports of longitudinal instability, proximal radial migration, valgus deformity, elbow osteoarthritis, reduced grip strength, and ulnar neuropathy[42,45]. Additionally, Scoscina et al[40] documented cases of heterotopic ossification (HO) and valgus instability following RHR that necessitated conversion to RHA. Given the multifactorial decision-making required in RHFs, Table 1 offers a comparative summary of the main surgical strategies including ORIF, RHA, and RHR to highlight their respective indications, advantages, limitations, and complication profiles. To further support intraoperative decision-making, a practical treatment algorithm is provided (Figure 2) to guide appropriate selection between RHA, ORIF, and RHR in Mason type III and IV RHFs.

Figure 2 Simplified decision-making algorithm for Mason type III and IV radial head fractures. Illustrating surgical selection among radial head arthroplasty, open reduction and internal fixation, and radial head resection based on fracture characteristics, reconstructability, ligament integrity, and patient demand level. ORIF: Open reduction and internal fixation; RHA: Radial head arthroplasty; RHR: Radial head resection.

Table 1 Indications, advantages and disadvantages of surgical management options of radial head fractures.

Surgical option	ORIF	RHA	RHR
Indications	Type II RHFs with mechanical block; and reconstructible type III and IV RHFs with simple fracture patterns	Unreconstructible RHFs, especially comminuted patterns; unreconstructible RHFs associated with ligamentous injury or elbow dislocation; instability following RHR; and failure of ORIF	Low-demand patients with stable elbows; salvage procedure following failed fixation or failed arthroplasty, in patients with stable elbow and low functional demand
Advantages	Restores native anatomy; and good for simple patterns	Good functional outcomes; maintains elbow stability; prevents proximal radial migration; and reduces early arthritis	Tolerated in low-demand patients despite mild instability
Limitations	Difficult in comminuted fractures; poorer outcomes in complex cases; and risk of nonunion and hardware failure	Complications are not rare; requires precise technique; small studies limit evidence; long-term data limited for young patients; and delayed RHA yields poorer outcomes	Alters elbow biomechanics; loss of RH’s stabilizing role, loss of support against valgus and axial forces; loss of PRUJ or DRUJ stability and proximal radial migration; and increases load on humero-ulnar joint, accelerate degenerative changes
Complication profiles	Nonunion; hardware failure; limited pronation/supination; and may require conversion to RHA	Painful loosening, radiolucency, overstuffing, osteoarthritis, HO, erosion, stiffness; PIN injury, dislocation, infection; reoperation rate: 12%-26%; and revision rate: 0%-45%	Early elbow instability; delayed: Cubitus valgus, proximal radial migration, arthritis, grip weakness, ulnar nerve irritation secondary to valgus overload or instability; and chronic elbow instability

ORIF: Open reduction and internal fixation; RHF: Radial head fracture; RHA: Radial head arthroplasty; RHR: Radial head resection; HO: Heterotopic ossification; PIN: Posterior interosseous nerve; PRUJ: Proximal radioulnar joint; DRUJ: Distal radioulnar joint.

ASSESSING THE RELIABILITY OF RHA IN MASON III AND IV FRACTURES

RHA has emerged as a competent solution and a cornerstone in the management of unreconstructible RHFs, particularly Mason type III and IV. Its role extends beyond mere replacement of bone stock. It contributes meaningfully to elbow stability, kinematic restoration, and load transmission[46]. RHA is indicated in cases where ORIF is unfeasible due to extensive comminution or poor bone quality, especially when more than three articular fragments are present. It is also preferred when associated with soft tissue injuries such as MCL injuries or coronoid fractures that raise concerns about elbow stability. In Mason type IV fractures, RHA is often selected to restore joint congruence and prevent recurrent instability[47].

EVOLUTION AND DESIGN PRINCIPLES OF RH PROSTHESES

RH prostheses (RHP) designs have evolved considerably in response to anatomical complexity, variable fracture patterns, and the biomechanical demands of the elbow. Modern systems are shaped by three key variables: Stem fixation method, articulation, and design implant modularity. These elements collectively aim to replicate the stabilizing role of the native RH while minimizing complications[6,48]. In terms of fixation, three main strategies are demonstrated in literature: Cemented stems provide immediate stability; however, they can complicate revision procedures and may increase stiffness in younger patients[49]. Press-fit stems aim for both primary and secondary stability through bone ingrowth, but are susceptible to proximal osteolysis due to stress shielding, particularly in rigid designs[50]. Loose-fit stems, typically smooth and undersized, allow for micromotion within the canal. This “floating” design facilitates self-centering of the head during elbow movement and forearm rotation, enhancing articulation with the capitellum and sigmoid notch[51,52].

The choice between monopolar and bipolar heads also influences prosthetic behavior. Monopolar implants offer greater inherent stability and reduced risk of dissociation or polyethylene debris, but may struggle with tracking in mal-aligned RC joint[53]. Bipolar prostheses, with an internal articulation between the head and stem, permit adaptive motion and are often favored in chronic or incongruent joints[54]. However, they may be less stable in ligament-deficient elbows and are linked to wear-related complications[55]. Moreover, modular implants have largely replaced monobloc designs, offering intraoperative flexibility to adjust head size, neck height, and offset to match patient anatomy. This modularity can address the well-documented anatomical variability seen in morphometric studies and enhances the likelihood of restoring native joint kinematics[48].

More recently, anatomic prostheses have been developed to closely mimic the shape and offset of the native RH. These designs aim to improve RC tracking, reduce overstuffing, and better distribute joint forces[49,56,57]. Material innovation has paralleled this evolution. Early RHPs were composed of acrylic, glass, or silicone rubber, which were prone to failure. In contrast, current prostheses utilize biocompatible metals such as titanium, cobalt-chromium, and vitallium[58]. Pyrocarbon has also been introduced as a bearing material due to its elasticity, which more closely approximates natural cartilage and may reduce capitellar wear[59]. Despite these advancements, no single design has emerged as universally superior. Emerging technologies, including three-dimensional-printed RHP components and customizable modular systems with variable offset and curvature, offer promise for improved anatomic conformity and long-term performance.

RESTORING NATIVE BIOMECHANICS: INSIGHTS FROM DYNAMIC CONTACT ANALYSIS OF ANATOMIC RHP

An essential goal of modern RHA is to replicate the native joint’s biomechanics, particularly in the RC articulation. While early prosthetic designs prioritized mechanical stability, more recent developments have shifted toward anatomically contoured implants intended to restore normal motion and load transmission. However, questions remain about how well these implants reproduce native contact mechanics under physiological conditions. In a dynamic cadaveric study, Sun et al[60] assessed the contact characteristics of an anatomic RHP during elbow flexion from 0° to 130°, comparing it directly with the native RH. The study analyzed three primary metrics at the RC joint: Contact area, mean contact pressure, and peak contact pressure. Their findings showed that anatomic prostheses closely approximated the mean contact area and pressure observed in native specimens. However, notable differences were found in the pattern of pressure distribution.

While native RH exhibited a linear shift in contact pressures during flexion, the prostheses demonstrated a parabolic, nonlinear pressure curve. This discrepancy reflects altered kinematic behavior of the prosthesis during motion and was attributed to the material stiffness of the implant and morphologic incongruity with the ellipsoidal capitellum. The prostheses also generated higher focal pressures, which could contribute to capitellar cartilage degeneration and subchondral erosion over time[60]. These observations highlight that achieving a successful prosthetic outcome depends not only on replicating anatomical shape, but also on ensuring proper joint surface compatibility and material properties. Even when geometric accuracy is achieved, prostheses may still fall short in reproducing the natural pressure distribution patterns that occur during joint movement. Thus, future innovations in RHA should integrate improved materials, modularity, and articulation profiles to minimize RC stress and optimize long-term outcomes[60].

RHA IN MASON III AND IV FRACTURES: FUNCTIONAL OUTCOMES AND COMPLICATION PROFILES

RHA has consistently demonstrated favorable outcomes in managing type III and IV RHFs, particularly when reconstruction is unfeasible and elbow stability is compromised. Across numerous cohort studies and systematic reviews, short- to mid-term results typically report good to excellent functional scores, preserved motion arcs, and high patient satisfaction rates[37,40,61-64]. Outcomes appear to vary modestly with implant design and material. Metallic prostheses, particularly those utilizing modular, press-fit titanium or cobalt-chromium components, have shown reliable results, with early functional restoration and low early revision rates in most studies[7,65]. Anatomic designs, aiming to replicate native morphology, may offer advantages in tracking and load distribution[59,66]. Pyrocarbon implants, with their bone - like elasticity, have been associated with lower contact pressure and reduced capitellar wear, although radiographic findings such as proximal osteolysis and radiolucency remain common[59,67-70]. Despite generally positive outcomes, complications are not uncommon. Aseptic loosening, stiffness, HO, and RC arthritis have been reported across all prosthetic systems[71]. While no clear consensus exists as to whether implant material, stem fixation, or modularity independently contributes to these complications, certain patterns have emerged in the literature.

Systematic reviews comparing prosthesis types (modularity, stem fixation, implant material) have not conclusively favored one design over another, though silicone prostheses were biomechanically inferior[54,61,72]. Similarly, long-term studies suggest that while implant survival generally exceeds 80% at 10 years, complications may increase over time[69,70]. In a systematic analysis by Davey et al[73], the overall revision rate after RHA was 20%, with most reoperations related to implant malposition, stiffness, or mechanical failure. Importantly, several high-quality meta-analyses, including those by Sun et al[38] and De Mauro et al[4], reported that more than 80%-85% of patients achieve satisfactory functional outcomes and implant survivorship beyond 10 years following RHA for Mason III and IV fractures, reinforcing its clinical durability in appropriately selected cases. A comparative summary of clinical outcomes and complication rates associated with different RHP designs is provided in Table 2, offering a consolidated view of key studies evaluating monopolar and bipolar heads, as well as various stem fixation strategies. Although RHA offers reliable functional outcomes in complex RHFs as reported, the heterogeneity of these studies underscores the need for standardized outcome measures and longer-term follow-up across diverse patient populations and prosthesis designs.

Table 2 Comparative clinical outcomes and complication rates across radial head arthroplasty designs.

Ref.	Implant comparison	Follow-up/ demographics	Clinical outcome	Complications
Rotini et al[78]	Bipolar vs monopolar cementless modular RHPs	Follow-up: 24 months; bipolar: n = 19, age: 42.4, M/F: 13/6; monopolar: n = 12, age: 47.5, M/F: 7/5	MEPS: Bipolar 90, monopolar 89.5; flexion: 131.5° vs 132.5°; extension: 16.8° vs 17.9°; pronation: 56.8° vs 70.4°; supination: 55.7° vs 75.4°	Bipolar: Arthrosis (n = 6), radiolucency (n = 7), HO (n = 9), resorption (n = 7); monopolar: Arthrosis (n = 6), radiolucency (n = 4), HO (n = 5), resorption (n = 2)
Gramlich et al[64]	Bipolar short-stem (22 mm) vs monopolar long-stem (50 mm) RHPs	Follow-up: 42.2 months; bipolar: n = 31, age: 37, M/F: 12/19; monopolar: n = 35, age: 48, M/F: 13/22	Not reported	Bipolar: Major complication required revision (22.6%), loosening (38.7%), prosthesis removal (n = 5); monopolar: Major complication required revision (17.1%), loosening (14.3%, P = 0.023), prosthesis removal (n = 1); the most frequent reason for revision was painful loosening: 9.1%, followed by arthrofibrosis (joint stiffness): 4.5%
Laumonerie et al[50]	Short stem (16 mm to 22 mm) vs long stem (30 mm) tight-fitting RHPs	Follow-up: 76.78 months; long-stem: n = 50, age: 52.2, M/F: 35/15; short-stem: n = 15, age: 53.3, M/F: 9/6	No significant difference between both groups; MEPS: Long-stem 86.8, short-stem 92; Quick-DASH: 17.7 vs 12.8; subjective elbow: 75.5% vs 80%; flexion: 133.6° vs 123°; extension: -16.8° vs -11°; supination: 66.3° vs 67.5°; pronation: 74.5° vs 81°	No significant difference between both groups; long-stem: Painful loosening (16%), osteolysis (46%), overstuffing (46%), capitellar wear (36%); short-stem: Painful loosening (40%), osteolysis (80%), overstuffing (47%), capitellar wear (64%)
Laflamme et al[65]	Smooth vs porous stemmed RHP	Follow-up: 6.3 years; porous stemmed: n = 36, age: 52.8, M/F: 19/17; smooth stemmed: n = 21, age: 45.6, M/F: 10/11	No significant difference between both groups; MEPS: Porous stemmed 96.5, smooth stemmed 97.1; VAS: 1.36 vs 0.67; extension improvement: 15° vs 12°; flexion improvement: 6° vs 1°; pronation improvement: 9° vs 5°; supination improvement: 15° vs 14°	No significant difference between both groups; porous stemmed: Osteolysis (n = 18), overstuffing (n = 4), HO (n = 13), reoperation (n = 2); smooth stemmed: Osteolysis (n = 5), overstuffing (n = 0), HO (n = 8)
Shimura et al[89]	Loose-fit vs press-fit stems in monopolar RHPs	Follow-up: 40.1 months; loose-fit: n = 17, age: 63, M/F: 5/12; press-fit: n = 15, age: 64, M/F: 4/11	Elbow flexion: Loose-fit 128°, press-fit 133°; extension: -12° vs -9°; pronation: 63° vs 78°; supination: 79° vs 83°	Loose-fit: Stiffness (n = 2), infection (n = 2), HO (n = 1), reoperation (n = 4); press-fit: Ulnar neuropathy (n = 1), painful loosening (n = 1), HO (n = 1), reoperation (n = 2)
Agyeman et al[72]	Cemented vs cementless RHPs	Follow-up; 45.2 months; cemented: n = 522, age: 49.3, M/F: 272/278; cementless: n = 356, age: 48.7, M/F: 189/34	No significant difference between both groups; MEPS: Cemented: 85.9 ± 6.1, cementless: 88.2 ± 3.4; flexion/extension: 119.1° ± 14.8° vs 115.8° ± 8.2°	Cemented: Complication rate (25.5%), implant loosening (8.6%), elbow stiffness/HO (8%), ulnar nerve palsy (4.3%); revision rate (7.9%); cementless: Complication rate (13.2%), elbow stiffness (9.8%), ulnar neuropathy (3.6%), loosening (2.1%), revision rate (3.1%)

RHP: Radial head prostheses; M/F: Male to female; MEPS: Mayo Elbow Performance Score; DASH: Disabilities of the Arm, Shoulder and Hand; VAS: Visual analogue scale; HO: Heterotopic ossification.

UNDERSTANDING COMPLICATIONS OF RHA: MECHANISMS AND PATTERNS

While RHA can restore elbow stability in complex fractures, it is not without potential complications. Understanding their etiology and prevention is essential to optimize patient outcomes and avoid early implant failure.

Aseptic loosening

It is among the most frequently reported failure modes[71]. Peri-stem radiolucent lines can be observed in both cemented and uncemented designs. That radiolucency is more linked to press-fit and loose-fit stems[57,74]. Various hypotheses have been proposed. The floating mechanism achieved by the smooth loose fit stems, with minimal micromotion, permits the stem to self-center during elbow motion, accommodating minor incongruities with the capitellum and the lesser sigmoid notch[75]. As a result, radiolucent lines commonly develop at the bone - implant interface, reflecting a benign adaptive process rather than pathological loosening[57,74]. These lines are typically non-progressive and do not necessitate revision unless associated with clinical symptoms. In fact, this controlled motion may reduce the incidence of stress shielding by promoting more physiological load distribution. Conversely, for press-fit stems, inadequate bone in-growth has been implicated, leading to increased micromotion and loosening. Stress shielding due to stiff stem - bone contact may also contribute to proximal osteolysis[74,76]. In cemented stems, poor cementing technique, particularly in the setting of a narrow medullary canal, can predispose loosening; the use of a cement restrictor and low-viscosity cement has been recommended to optimize fixation[77].

True loosening is often painful and presents radiographic signs of progressive osteolysis and implant migration. It often requires intervention[57,74]. On contrary, a positive periosteal bone reaction on the anterolateral neck cortex, described by Rotini et al[78], may represent good stem - bone integration in some press-fit designs. Still, given the multifactorial nature of aseptic loosening, careful radiographic surveillance is recommended even in asymptomatic cases to differentiate between benign radiolucency and progressive loosening avoiding unnecessary revision and to ensure timely intervention when clinically warranted.

Overstuffing

Prosthesis overlengthening or overstuffing remains a technical complication with biomechanical consequences. It disrupts humeroulnar joint symmetry, increases RC contact pressure, and limits ROM. Radiographically, overstuffing may be identified by the “delta river sign”, a widened lateral humeroulnar joint space, on anteroposterior radiographs, this sign was described by Gauci et al[59]. Computed tomography evaluation can confirm excessive head height by comparing the prosthesis to the lesser sigmoid notch and assessing capitellum - olecranon alignment. Overlengthening exceeding 2 mm in height can measurably alter elbow kinematics and cause progressive capitellar erosion[67,79,80]. Intraoperative fluoroscopic techniques are essential for preventing prosthetic overlengthening. A key radiographic clue is the “sauce sign”, characterized by visible capitellar clearance on the lateral view, which indicates appropriate tension and prosthetic height. Additionally, referencing the lesser sigmoid notch of the ulna is a reproducible method for estimating the correct level of the native RH. The prosthesis should align flush with this notch without exceeding it[81]. On anteroposterior radiographs, symmetry between the medial and lateral humeroulnar joint lines should also be confirmed to avoid asymmetric loading. An asymmetrical appearance is strongly associated with prosthetic overlengthening of 4 mm or more[74]. In cases of confirmed overstuffing, particularly when symptomatic or associated with loss of motion, prosthesis removal or revision is often required. Prevention remains the optimal strategy, emphasizing the need for meticulous intraoperative assessment, appropriate prosthetic sizing, and awareness of radiographic indicators of overlengthening.

Elbow stiffness

Post-RHA elbow stiffness is multifactorial, resulting from improper implant sizing, prosthetic migration, soft tissue contracture, aseptic loosening, or biological responses such as HO. HO often follows RHA, with rates reported between 30% and 38%[82,83]. It may be presented as extrinsic mechanical block or progressive contracture. Management includes nonsteroidal anti-inflammatory drugs or radiotherapy for prophylaxis, though the supporting evidence remains variable. When clinically significant, capsular release or implant revision may be necessary[84]. Press-fit stems have been associated with lower revision rates for stiffness compared to loose-fit systems, though outcomes also depend on design type and soft tissue balance[71].

In terms of treatment, Amaro et al[85] proposed a structured algorithm for managing post-RHA elbow stiffness. Management is guided by the degree of motion restriction, underlying cause, and the presence or absence of joint degeneration. For cases involving soft tissue contractures without arthritis, HO, or implant-related mechanical issues, open or arthroscopic capsular release may restore mobility. In elbows with mild to moderate HO or arthritis, selective bony debridement can be combined with soft tissue release. In contrast, advanced arthritis often necessitates conversion to interposition arthroplasty or total elbow arthroplasty. When stiffness stems from the prosthesis itself, due to loosening, malposition, oversizing, or secondary arthritis, treatment options include implant revision or removal, depending on patient demand and the stability of surrounding structures[85].

IS RHA COST-EFFECTIVE?

The long-term value of RHA in the treatment of complex RHFs must be considered not only in terms of clinical outcomes, but also through the lens of cost-effectiveness and implant durability. Revision and reoperation rates serve as key metrics in evaluating the procedure’s reliability and its potential burden on healthcare systems. In a comprehensive systematic review, Davey et al[73] reported an overall reoperation rate of 20% after an average follow-up of eight years. Of these, 3% underwent RHA implant revision, 15% required implant or hardware removal, and 5% required arthrolysis. Similarly, Duckworth et al[86] in a series of 105 RHA cases, observed a reoperation rate of 28% within a mean follow-up of 6.7 years. Comparable findings were reported by Schnetzke et al[67], who documented a 28% revision rate following monopolar RHA, with an implant survival rate of 75.1% at 18 years. Cristofaro et al[87] corroborated these results, noting a 25% reoperation rate at eight years. Independent risk factors for revision included younger patient age and the use of silastic implants, as also reported by Duckworth et al[86]. Laumonerie et al[6], through a broad literature review, demonstrated a wide range of reoperation rates following RHA, from 0% to as high as 45%, depending on implant type and patient selection. In a separate study, the same group reported a reoperation rate of 38.9% after 74 months with modular bipolar designs, with implant survival dropping to 60.8% at 10 years[88]. A more recent comparative study by Shimura et al[89], examining press-fit vs loose-fit stems in monopolar RHA for comminuted fractures, found reoperation rates of 15.2% and 23.5%, respectively, with no statistically significant difference between the two groups.

On the other hand, several studies have reported more favorable long-term results. Viswanath and Watts[68] and Gauci et al[59] reported reoperation rates of just 11% and 12.3%, respectively, following the use of anatomical press-fit pyrocarbon prostheses. Similarly, Heijink et al[61], in a systematic review of 30 studies, found a revision rate of only 8% across various implant designs. Long-term follow-up data from Marsh et al[90], Chen et al[91], and Popovic et al[92] further demonstrated excellent implant survival, with no reported revisions after eight years. In the long term, RHA may offer superior cost-effectiveness compared to ORIF in the treatment of complex RHFs particularly unstable, comminuted Mason type III and IV injuries, and in older or functionally active patients. While RHA entails higher upfront implant and surgical costs, it may offset these through reduced reoperation rates, faster return to function, and lower long-term rehabilitation demands. Conversely, ORIF may appear less costly initially, but carries increased risk of complications such as malunion, nonunion, or secondary osteoarthritis, which often necessitate further interventions and extended care. Reinhardt et al[5] confirmed this economic discrepancy in a comparative study, showing that ORIF patients incurred significantly higher overall costs due to increased revision procedures and prolonged rehabilitation. These findings were consistent regardless of the presence of elbow dislocation, highlighting RHA’s potential as a cost-effective option in appropriately selected cases.

CONCLUSION

RHA is an effective solution for Mason type III and IV RHFs when reconstruction is not feasible, offering biomechanical stability and enabling early mobilization. While promising short- and mid-term outcomes support its use, surgical decisions must remain individualized, considering fracture pattern, patient factors, and elbow stability. Alternative treatments like ORIF or RHR remain valid in selected cases. Long-term data on modern implants is still evolving, and further comparative research is needed to optimize technique and implant selection.