Is augmented LISS plating biomechanically advantageous over conventional LISS plating in unstable osteoporotic distal femoral fractures?

Biomechanical analysis of titanium-alloy and biodegradable implants in dual plate osteosynthesis for AO/ASIF type 33-C2 fractures

Background and objective

Treating geriatric osteoporotic distal femur fractures has always presented challenges, but developing biodegradable materials has brought new opportunities for therapeutic intervention. Despite this progress, there currently needs to be more evidence-based biomechanical guidelines for using dual plate fixation and biodegradable materials in treating osteoporotic comminuted distal femoral fractures.In this study, finite element analysis was conducted to evaluate the mechanical effectiveness of different implant materials (titanium alloys, biodegradable materials, and combinations of both) in the fixation of physiological and osteoporotic distal femoral fractures.

Methods

We constructed finite element models of 33-C2 fractures and three types of plates: the Lateral Less Invasive Stabilization System (LISS) plate, the titanium-alloy medial plate (TAP), and the biodegradable plate (BP). To evaluate the biomechanical advantages in both physiological femur (PF) and osteoporotic femur (OF) conditions, three scenarios were developed: LISS + TAP, LISS + BP, and double biodegradable plates (DBPs). Five loading conditions were applied to measure structural stiffness, fracture micromotion, and implant stress: medio-lateral four-point bending, antero-posterior four-point bending, axial loading, torsional loading, and sideways falling. Several parameters were examined, including peak Von Mises Stress (VMS) of the femur and lateral plate, maximum displacement, bending angle, torsional angle of fracture, and risk of fracture.

Results

In four-point bending tests, the lateral plate of the DBPs group exhibited a slightly lower peak VMS compared to the LISS + TAP and LISS + BP groups. When subjected to axial loading, the stiffness values of the LISS + TAP (OF) were 1.42 times and 1.86 times higher than LISS + BP (OF) and DBPs (OF) groups, and the peak VMS of lateral plate of DBPs (OF) construct was approximately 2% and 16% lower than that of the LISS + TAP (OF) and LISS + BP (OF) constructs. Under torsional loading, DBPs (OF) demonstrated rotational stiffness that was respectively 2% and 52% greater than that of LISS + TAP (OF) and LISS + BP (OF). Regarding the peak VMS of femur, the values of DBPs (OF) were almost 8% and 15% lower than those of LISS + TAP (OF) and LISS + BP (OF).

Conclusions

The use of DBPs at 11.33 GPa facilitated early mobilization of load-bearing joints but exhibited limited ability to support full weight-bearing activities. Though LISS + TAP met practical strength requirements, one should consider the potential biological irritation and stress shielding. Thus, employing a combination of biodegradable and metal internal fixation is a valid approach to effectively treat weight-bearing joint fractures in clinical practice.

Does the type of medial plate fixation matter for supplemental fixation of distal femur fractures manage with a lateral pre-contoured locked plate? A Biomechanical study

INTRODUCTION

Fixation of distal femur fractures with a lateral pre-contoured locking plate provides stable fixation and is the standard treatment in most cases, allowing early range of motion with a high rate of union. However, in situations, the stability achieved with the lateral plate alone may be insufficient, predisposing to fixation failure. The objective of the study was to compare, in synthetic bone models, the biomechanical behaviour of the fixation with a distal femur lateral pre-contoured locking plate solely and associated with a 3.5 mm proximal humeral locking plate applied upside down or a 4.5 mm helical locking compression plate on the medial side.

MATERIAL AND METHODS

A total of 15 solid synthetic left femur samples were used. A metaphysical defect at the level of the medial cortex was simulated. The samples were randomly distributed into three groups equally. All groups received a 4.5/5.0 mm single lateral 9-hole distal femur lateral pre-contoured locking plate. Group 1 had no supplementary plate. Group 2 received a supplementary 6-hole 3.5 mm proximal humeral locking plate and Group 3 received a supplementary 4.5/5.0 mm helical 14-hole narrow locking compression plate.

RESULTS

Both supplementary plate types used in groups 2 and 3 contributed to increase the apparent stiffness of the construct, but pairwise comparison showed statically significant difference only between group 1 and 3. No significant difference was observed between groups 2 and 3.

CONCLUSION

Both supplementary plates might be considered for improving the fixation in distal femur fracture in selected cases.

Biomechanical design optimization of distal femur locked plates: A review

Clinical findings, manufacturer instructions, and surgeon's preferences often dictate the implantation of distal femur locked plates (DFLPs), but healing problems and implant failures still persist. Also, most biomechanical researchers compare a particular DFLP configuration to implants like plates and nails. However, this begs the question: Is this specific DFLP configuration biomechanically optimal to encourage early callus formation, reduce bone and implant failure, and minimize bone "stress shielding"? Consequently, it is crucial to optimize, or characterize, the biomechanical performance (stiffness, strength, fracture micro-motion, bone stress, plate stress) of DFLPs influenced by plate variables (geometry, position, material) and screw variables (distribution, size, number, angle, material). Thus, this article reviews 20 years of biomechanical design optimization studies on DFLPs. As such, Google Scholar and PubMed websites were searched for articles in English published since 2000 using the terms "distal femur plates" or "supracondylar femur plates" plus "biomechanics/biomechanical" and "locked/locking," followed by searching article reference lists. Key numerical outcomes and common trends were identified, such as: (a) plate cross-sectional area moment of inertia can be enlarged to lower plate stress at the fracture; (b) plate material has a larger influence on plate stress than plate thickness, buttress screws, and inserts for empty plate holes; (c) screw distribution has a major influence on fracture micro-motion, etc. Recommendations for future work and clinical implications are then provided, such as: (a) simultaneously optimizing fracture micro-motion for early healing, reducing bone and implant stresses to prevent re-injury, lowering "stress shielding" to avoid bone resorption, and ensuring adequate fatigue life; (b) examining alternate non-metallic materials for plates and screws; (c) assessing the influence of condylar screw number, distribution, and angulation, etc. This information can benefit biomedical engineers in designing or evaluating DFLPs, as well as orthopedic surgeons in choosing the best DFLPs for their patients.

Effect of Implant Linkage on Axial and Rotational Stiffness of Nail-Plate Constructs for Comminuted Distal Femoral Fractures

OBJECTIVES

To determine the effect of linking the intramedullary nail and the laterally applied locking plate to treat comminuted distal femur fractures and allow for immediate weight bearing.

METHODS

Comminuted extra-articular distal femur fractures were created in 16 synthetic osteoporotic femurs and split into 2 groups: linked versus unlinked. In the linked construct, in addition to standard plate fixation and proximal locking of the nail, 2 nonthreaded locking bolts (prototypes) were placed through both the plate and the nail. In the unlinked construct, the same number of screws affixed the plate to the bone but were directed around the nail, and separate distal interlocking screws were placed for nail fixation. Each specimen underwent sequential axial and torsional loading, and axial and torsional stiffness were calculated and compared.

RESULTS

On average, the unlinked constructs demonstrated a greater axial stiffness at all levels of axial loading, and linked constructs demonstrated greater average rotational stiffness. However, there were no statistically significant differences ( P > 0.189) between the linked and unlinked groups at any axial or torsional load.

CONCLUSION

In distal femur fractures with metaphyseal comminution, there were no significant differences in axial or torsional stiffness when linking the plate to the nail. Linking the construct seems to provide no significant mechanical advantage compared with the unlinked environment, but it may be a useful strategy to reduce nail "traffic" in the distal segment with no significant disadvantage.

Medial and lateral dual plating of native distal femur fractures: a systematic literature review

Introduction

Lateral locked plating (LLP) development has improved outcomes for distal femur fractures. However, there is still a modest rate of nonunion in fractures treated with LLP alone, with higher nonunion risk in high-energy fractures, intra-articular involvement, poor bone quality, severe comminution, or bone loss. Several recent studies have demonstrated both the safety and the biomechanical advantage of dual medial and lateral plating (DP). The purpose of this study was to evaluate the clinical outcomes of DP for native distal femoral fractures by performing a systematic review of the literature.

Methods

Studies reporting clinical outcomes for DP of native distal femur fractures were identified and systematically reviewed. Publications without full-text manuscripts, those solely involving periprosthetic fractures, or fractures other than distal femur fractures were excluded. Fracture type, mean follow-up, open versus closed fracture, number of bone grafting procedures, nonunion, reoperation rates, and complication data were collected. Methodologic study quality was assessed using the Coleman methodology score.

Results

The initial electronic review and reverse inclusion protocol identified 1484 publications. After removal of duplicates and abstract review to exclude studies that did not discuss clinical treatment of femur fractures with dual plating, 101 potential manuscripts were identified and manually reviewed. After final review, 12 studies were included in this study. There were 199 fractures with average follow-up time of 13.72 months. Unplanned reoperations and nonunion occurred in 19 (8.5%) and 9 (4.5%) cases, respectively. The most frequently reported complications were superficial infection (n = 6, 3%) and deep infection (n = 5, 2.5%) postoperatively. Other complications included delayed union (n = 6, 3%) not requiring additional surgical treatment and knee stiffness in four patients (2%) necessitating manipulation under anesthesia or lysis of adhesions. The average Coleman score was 50.5 (range 13.5-72), suggesting that included studies were of moderate-to-poor quality.

Conclusions

Clinical research interest in DP of distal femoral fractures has markedly increased in the past few decades. The current data suggest that DP of native distal femoral fractures is associated with favorable nonunion and reoperation rates compared with previously published rates associated with LLP alone. In the current review, DP of distal femoral fractures was associated with acceptable rates of complications and generally good functional outcomes. More high-quality, directly comparable research is necessary to validate the conclusions of this review.

Biomechanical and anatomical considerations for dual plating of distal femur fractures: a systematic literature review

INTRODUCTION

Distal femur fractures are challenging injuries historically associated with high rates of nonunion and varus collapse with operative management. As a result, clinical and research interest in dual plating (DP) of distal femur fractures has seen a dramatic increase in recent years. The purpose of this study was to systematically review the literature regarding vascular anatomy and biomechanics of distal femur fractures treated with DP constructs.

MATERIALS AND METHODS

A systematic literature review of two medical databases (PubMed & Scopus) was performed to identify peer-reviewed studies on the anatomy and biomechanics regarding DP of distal femur fractures. A total of 1,001 papers were evaluated and 14 papers met inclusion criteria (6 anatomy and 8 biomechanics). Methodological quality scores were used to assess quality and potential bias in the included studies.

RESULTS

In the biomechanical studies, DP constructs demonstrated greater axial and rotational stiffness, as well as less displacement and fewer incidences of failure compared to all other constructs. Vascular studies showed that the femoral artery crosses the mid-shaft femur approximately 16.0-18.8 cm proximal to the adductor tubercle and it is located on average 16.6-31.1 mm from the femoral shaft at this location, suggesting that medial plate application can be achieved safely in the distal femur. The methodological quality of the included studies was good for biomechanical studies (Traa score 79.1; range 53-92.5) and excellent for anatomical studies (QUACs score 81.9; range 69.0-88.5).

CONCLUSIONS

Existing biomechanics literature suggests that DP constructs are mechanically stronger than other constructs commonly used in the treatment of distal femur fractures. Furthermore, medial distal femoral anatomy allows for safe application of DP constructs, even in a minimally invasive fashion. Dual plating should be considered for patients with distal femur fractures that have risk factors for instability, varus collapse, or nonunion.

Anatomical analysis of different helical plate designs for distal femoral fracture fixation

PURPOSE

Helical plates potentially avoid the medial neurovascular structures of the thigh. Two implant designs for additional medial 90° helical plate in double plate constructs for geriatric patients and 180° helical plate for single plating in young patients are potential alternatives to widely used standard straight plates.

AIMS

(1) assess the distances to adjacent anatomical structures being at risk when applying medial 90° and 180° helical plates with MIPO technique to the femur, (2) compare these distances with medial straight plates, and (3) correlate measurements performed during surgical dissection with CT angiography.

METHODS

MIPO was performed in ten human cadaveric femoral pairs using either a 90° helical 14-hole LCP (Group 1) or a 180° helical 15-hole LCP-DF (Group 2). Using CT angiography, distances between femoral arteries and plates as well as distances between plates and perforating vessels were evaluated. Following, specimens were dissected and distances determined again. All plates were removed and measurements were repeated with straight medial plates (Group 3).

RESULTS

Overall closest distances between plates and femoral arteries were 14.5 mm (11-19 mm) in Group 1, 21.6 mm (15-24 mm) in Group 2 and 6.5 mm (5-8 mm) in Group 3, with significant differences between Group 3 and both other groups (p < 0.001). Distances to the nearest perforating vessels were 22.4 mm (15-30 mm) in Group 1 and 1.2 mm (1-2 mm) in Group 2. Measurement techniques (visual after surgical disection and CT angiography) demonstrated a strong correlation (p < 0.010).

CONCLUSIONS

Inserting 90° and 180° helical plates with MIPO technique is safe, however, attention must be paid to the medial neurovascular structures with 90° helical plates and to the proximal perforating vessels with 180° helical plates. Helical plates can avoid irritation of medial neurovascular structures - compared with straight plates - although care must be taken during their distal insertion. Measurements during surgical dissection correlate with CT angiography.

Practical approach to the native distal femur fractures in the elderly: A rapid review over the recent trends

Significant work has been done in recent years on treatment strategies for distal femur fractures. Inclusive reviews on periprosthetic fractures of distal femur have been carried out recently, but there is a lack of such reviews on the subject of native distal femur fractures in the recent literature. In this narrative review, we are set out to address the latest updates on geriatric non-periprosthetic distal femur fractures, and perform a rapid review over different treatment options, arriving at a summarized proposed treatment algorithm.

Primary fibular grafting combined with double plating in distal femur fractures in elderly patients

PURPOSE

To report functional and radiological outcomes of using primary fibular graft together with double plating in distal femoral fractures in the elderly.

METHODS

A retrospective study on 30 elderly patients with comminuted distal femoral fractures managed by primary fibular grafting and double plating through an anterior midline approach has been conducted. Only isolated distal femoral fractures type 33-A3, 33-C2, and 33-C3 were included. The patient's mean age was 75.3 years. Evaluation included operative time, blood loss, time to union, knee range of motion, Sanders scoring, and presence of complications.

RESULTS

The average follow-up period was 26.6 months. Mean intraoperative blood loss was 401 ml, and mean operative time was 216 min. All patients had a knee range of motion (90-120°) during follow-up. Time for union ranged from 16 to 23 weeks with a mean of 18.4 weeks, with no cases of non-union. A total of 22 patients (73.3%) showed excellent functional outcomes, and the remaining eight (26.7%) showed good functional outcomes according to the Sanders scoring system. Only two cases (6.6%) had superficial wound infections managed conservatively. No post-operative deformity, loss of reduction, or implant failure was observed until the end of follow-up period.

CONCLUSION

Primary fibular grafting combined with double plating of comminuted distal femur fractures in patients above 70 years is an effective technique with higher rates of union and lower re-operation rates compared to other fixation modalities.

Boundary Conditions Matter - Impact of Test Setup On Inferred Construct Mechanics in Plated Distal Femur Osteotomies

The mechanics of distal femur fracture fixation has been widely studied in bench tests that employ a variety of approaches for holding and constraining femurs to apply loads. No standard test methods have been adopted for these tests and the impact of test setup on inferred construct mechanics has not been reported. Accordingly, the purpose of this study was to use finite element models to compare the mechanical performance of a supracondylar osteotomy with lateral plating under conditions that replicate several common bench test methods. A literature review was used to define a parameterized virtual model of a plated distal femur osteotomy in axial compression loading with four boundary condition sets ranging from minimally to highly constrained. Axial stiffness, longitudinal motion, and shear motion at the fracture line were recorded for a range of applied loads and bridge spans. The results showed that construct mechanical performance was highly sensitive to boundary conditions imposed by the mechanical test fixtures. Increasing the degrees of constraint, for example by potting and rigidly clamping one or more ends of the specimen, caused up to a 25x increase in axial stiffness of the construct. Shear motion and longitudinal motion at the fracture line, which is an important driver of interfragmentary strain, was also largely influenced by the constraint test setup. These results suggest that caution should be used when comparing reported results between bench tests that use different fixtures and that standardization of testing methods is needed in this field.

Supplemental medial small fragment fixation adds stability to distal femur fixation: A biomechanical study

INTRODUCTION

Bridge plating of distal femur fractures with lateral locking plates is susceptible to varus collapse, fixation failure, and nonunion. While medial and lateral dual plating has been described in clinical series, the biomechanical effects of dual plating of distal femur fractures have yet to be clearly defined. The purpose of this study was to compare dual plating to lateral locked bridge plating alone in a cadaveric distal femur gap osteotomy model.

MATERIALS AND METHODS

Gap osteotomies were created in eight matched pairs of cadaveric female distal femurs (average age: 64 yrs (standard deviation ± 4.4 yrs); age range: 57-68 yrs;) to simulate comminuted extraarticular distal femur fractures (AO/OTA 33A). Eight femurs underwent fixation with lateral locked plates alone and were matched with eight femurs treated with dual plating: lateral locked plates with supplemental medial small fragment non-locking fixation. Mechanical testing was performed on an ElectroPuls E10000 materials testing system using a 10 kN/100 Nm biaxial load cell. Specimens were subject to 25,000 cycles of cyclic loading from 100-1000 N at 2 Hz.

RESULTS

Two (2/8) specimens in the lateral only group failed catastrophically prior to completion of testing. All dual plated specimens survived the testing regimen. Dual plated specimens demonstrated significantly less coronal plane displacement (median 0.2 degrees, interquartile range [IQR], 0.0-0.5 degrees) compared to 2.0 degrees (IQR 1.9-3.3, p = 0.02) in the lateral plate only group. Dual plated specimens demonstrated greater bending stiffness compared to the lateral plated group (median 29.0 kN/degree, IQR 1.5-68.2 kN/degree vs median 0.50 kN/degree, IQR 0.23-2.28 kN/degree, p = 0.03).

CONCLUSION

Contemporary fixation methods with a distal femur fractures are susceptible to mechanical failure and nonunion with lateral plates alone. Dual plate fixation in a cadaveric model of distal femur fractures underwent significantly less displacement under simulated weight bearing conditions and demonstrated greater stiffness than lateral plating alone. Given the significant clinical failure rates of lateral bridge plating in distal femur fractures, supplemental fixation should be considered, and dual plating of distal femurs augments mechanical stability in a clinically relevant magnitude.

Supplemental Fixation of Supracondylar Distal Femur Fractures: A Biomechanical Comparison of Dual-Plate and Plate-Nail Constructs

OBJECTIVES

This biomechanical study compares the effectiveness of dual-plate (DP) and plate-nail (PN) constructs for fixation of supracondylar distal femur fractures in synthetic and cadaveric specimens.

METHODS

Twenty-four synthetic osteoporotic femurs were used to compare 4 constructs in an extra-articular, supracondylar fracture gap model (OTA/AO type 33-A3). Constructs included: (1) distal lateral femoral locking plate (DLFLP), (2) retrograde intramedullary nail (rIMN), (3) DLFLP + medial locking compression plate (DP construct), and (4) DLFLP + rIMN (PN construct). DP and PN constructs were then directly compared using 7 matched pairs of cadaveric femurs. Specimens underwent cyclic loading in torsion and compression. Biomechanical effectiveness was measured by quantifying the load-dependent stiffness of each construct.

RESULTS

In synthetic osteoporotic femurs, the DP construct had the greatest torsional stiffness (1.76 ± 0.33 Nm/deg) followed by the rIMN (1.67 ± 0.14 Nm/deg), PN construct (1.44 ± 0.17 Nm/deg), and DLFLP (0.68 ± 0.10 Nm/deg) (P < 0.01). The DP construct also had the greatest axial stiffness (507.9 ± 83.1 N/mm) followed by the PN construct (371.4 ± 41.9 N/mm), DLFLP (255.0 ± 45.3 N/mm), and rIMN (109.2 ± 47.6 N/mm) (P < 0.05). In cadaveric specimens, the DP construct was nearly twice as stiff as the PN construct in torsion (8.41 ± 0.58 Nm/deg vs. 4.24 ± 0.41 Nm/deg, P < 0.001), and over one-and-a-half times stiffer in compression (2148.1 ± 820.4 vs. 1387.7 ± 467.9 N/mm, P = 0.02).

CONCLUSIONS

DP constructs provided stiffer fixation than PN constructs in this biomechanical study of extra-articular distal femur fractures. In the clinical setting, fracture morphology, desired healing mode, surgical approach, and implant cost should be considered when implementing these fixation strategies.

Dual Plating of the Distal Femur: Indications and Surgical Techniques

Dual-plating of the distal femur is required in some cases to achieve stable fixation. The indications of a medial plate in addition to the lateral plate are medial supracondylar bone loss, low trans-condylar bicondylar fractures, medial Hoffa fracture, peri-prosthetic distal femur fractures, non-union after failed fixation with single lateral plate, poor bone quality and comminuted distal femur fractures (AO type C3). We recommend orthogonal plate configuration with locked plates by a single incision or dual incision approach as per surgeon choice.

Augmented Fixation for Fractures of the Appendicular Skeleton

Despite advances in technology such as locked plating, osteoporotic bone and bone defects remain challenging complications for orthopaedic surgeons. The concept of augmented fixation is useful in these settings. Augmented fixation can be described as improving construct strength and stability by enhancing the surrounding environment. By understanding and using the techniques of alternative fixation strategies, endosteal or medullary support, structural grafting, or the use of bone graft substitutes in combination with standard or integrated fixation, surgeons can improve the chances of success when treating difficult fractures. The purpose of this article is to introduce the reader to the concept of augmented fixation, review strategies for its application, and review applicable published results.

Additional fixation of medial plate over the unstable lateral locked plating of distal femur fractures: A biomechanical study

INTRODUCTION

Lateral locked plating is a standard treatment option for distal femur fractures. However, the unstable conditions after lateral locked plating are increasing. The objective of this study was to investigate the biomechanical strength of additional medial plate fixation over the unstable lateral locked plating of distal femur fractures.

MATERIALS AND METHODS

A distal femur fracture model (AO/OTA 33-A3) was created with osteotomies in the composite femur. Three study groups consisting of 6 specimens each were created for single-side lateral locked plating with 6 distal locking screws (LP-6), single-side lateral locked plating with 4 distal locking screws (LP-4), and additional medial locked plating on LP-4 construct (DP-4). A compressive axial load (10 mm/min) was applied in the failure test. Mode of failure, load to failure, and ultimate displacement were documented.

RESULTS

All single-side lateral locked plating (LP-4 and LP-6) showed plate bending at the fracture gap, while none of the DP-4 showed plate bending at the fracture gap. Load to failure of DP-4 (mean 5522 N) was 17.1% greater than that of LP-6 (mean 4713.3 N, p < 0.05) and 29.2% greater than that of LP-4 (mean 4273.2 N, p < 0.05). Ultimate displacement of DP-4 (mean 5.6 mm) was significantly lower than that of LP-6 (mean 8.8 mm, p < 0.05) and LP-4 (mean 9.1 mm, p < 0.05).

CONCLUSIONS

Additional fixation of medial plate significantly increased the fracture stability in distal femur fractures fixed with the lateral locked plating. Especially in the clinical situations where sufficient stability cannot be provided at the distal segment, the medial plate may be considered as a useful biomechanical solution to obtain adequate stability for fracture healing.

Comparison of Less Invasive Stabilization System Plate and Retrograde Intramedullary Nail in the Fixation of Femoral Supracondylar Fractures in the Elderly: A Biomechanical Study

Objective

To compare the biomechanical stabilities of less invasive stabilization system (LISS) plate and retrograde intramedullary nail (IMN) for the comminuted femoral supracondylar fracture fractures in the elderly.

Methods

Sixteen pairs of embalmed cadaver femurs were obtained to simulate a comminuted supracondylar femur fracture (AO/OTA33‐A3) gap model. All left‐side specimens were fixed with LISS plate, and retrograde IMN were applied to the right‐side specimens. All specimens were tested in torsional, axial and cyclic load mode on an Instron testing machine.

Results

The mean torsional stiffness for LISS plate group was 34.1% greater than retrograde IMN group (2.90 vs. 1.91 Nm/degree, P = 0.002), but the mean axial stiffness was greater for the retrograde IMN (199.16 vs. 303.93 N/mm, P < 0.001). The total deformation of LISS plate caused by cyclic axial loading was greater than retrograde IMN (4.17 vs. 3.57 mm, P = 0.014). Significantly less mean irreversible deformation was detected in LISS plate than in retrograde IMN (1.64 vs. 1.69 mm, P = 0.699). Failure loads of the constructs were significantly different between the two groups (LISS plate: 2941±128 N; retrograde IMN: 4022±176 N, P < 0.001).

Conclusion

For comminuted femoral supracondylar fractures in the elderly, the tested instruments can both maintain sufficient biomechanical stabilities, but retrograde IMN is superior to LISS plate in deformation of fracture site.

Does Supplemental Intramedullary Grafting Increase Stability of Plated Proximal Humerus Fractures?

OBJECTIVES

To investigate the biomechanical competence of locked plating augmented with supplemental intramedullary graft in comparison to conventional locked plate fixation in proximal humerus fractures (PHF).

METHODS

Complex four-part PHFs were set in 30 artificial humeri assigned to 3 study groups (n = 10 in each group). Group 1 was characterized by loss of medial support, group 2 by simulated severe cancellous bone damage due to osteoporosis, and group 3 by combination of the 2 features. After locked plating, each specimen underwent nondestructive quasi-static mechanical testing in 25 degrees lateral angulation under axial loading between 150 and 400 N in 50-N increments, accompanied by consecutive anteroposterior x-ray imaging. Subsequently, an additional 3D-printed intramedullary graft was inserted into each specimen and all tests were repeated.

RESULTS

Grafting resulted in significantly higher axial stiffness compared with no graft in groups 1 and 3 (P < 0.01) but not in group 2 (P = 0.12). Nongrafted specimens represented significantly higher stiffness in group 2 compared with groups 1 and 3 (P < 0.01), whereas no significant differences were detected among the 3 groups in the grafted state (P > 0.99). Varus deformation decreased significantly in each group after graft insertion (P ≤ 0.04). Nongrafted specimens in group 2 showed significantly lower varus deformation compared with groups 1 and 3 (P ≤ 0.04). No significant differences were registered among the 3 groups after grafting (P ≥ 0.65).

CONCLUSIONS

From a biomechanical perspective, locked plating augmented with intramedullary graft has the potential to increase significantly the stability against varus collapse in unstable PHFs when compared with conventional locked plate fixation.