Biomechanical analysis of distal femur fracture fixation: fixed-angle screw-plate construct versus condylar blade plate

A novel anatomical locked medial femoral condyle plate: a biomechanical study

BACKGROUND

Fixation with a distal lateral femoral plate is a standard approach in treating osteoporotic or comminuted supracondylar femur fractures. However, in clinical practice, this method may prove inadequate, necessitating the application of a plate on the medial side of the distal femur. The aim of this study is to perform a biomechanical evaluation of the newly manufactured anatomically locked plate applied to the distal medial femoral condyle.

MATERIALS AND METHODS

The plate underwent 2 biomechanical tests by simulating an AO/OTA 33A3 type supracondylar fracture model on synthetic femur bones. The samples were divided into three groups. Fracture fixations were carried out on the medial side using the distal femur medial anatomical locking plate (DFMALP) in group A samples, on the lateral side using the distal femur lateral anatomical locking plate in group B samples, and on both sides in group C samples.

RESULTS

In the axial compression test, stability was preserved 23% more in group C than in group B. During the cyclic axial compression test, total displacement was 21% less in group C than in group B. Group A was collapsed at early cycle degrees.

CONCLUSION

In our study, it was observed that the application of DFMALP in conjunction with the lateral plate in AO/OTA 33A3 fragmented supracondylar femur fractures significantly enhanced biomechanical fracture stability.

LEVEL OF EVIDENCE

This is a Level 2 prospective, randomized controlled study.

Wire Osteosynthesis in the Treatment of Mandible Fractures in Low Resource Settings: A Force Study

Study Design

Cadaveric investigation.

Objective

Rigid internal fixation (RIF) using plates and screws is often not feasible in low and middle-income countries due to limited resources. Interosseous wiring to achieve semi-rigid fixation is often used, but lacks biomechanical force data. Herein we aim to quantitatively compare interosseous wiring to RIF.

Methods

Cadaveric mandibles were fractured at the parasymphysis and angle. Fixation was achieved using interosseous wiring in both single wire loop and figure-of-eight formations, as well as plate and screw fixation (n = 5 for each fixation type at each fracture site). A force gauge was used to measure the number of Newtons (N) required to achieve diastasis and complete failure at the fixation site.

Results

For angle fractures, the mean force required for initial diastasis was 4.1, 5.9, and 10.9 N for single wire, figure-of-eight wiring, and plating respectively (P < .001). Complete failure was achieved with 152.9, 168.9, and 237.6 N of force for the three methods, respectively (P < .001). Complete failure was achieved for parasymphyseal fractures with 197.7, 263.0, and 262.8 N of force for single wire, figure-of-eight wiring, and plating respectively (P = .002). Forces to achieve initial diastasis for parasymphyseal fractures were not statistically significant among the three fixation methods (P = .29).

Conclusions

Figure-of-eight interosseous wiring resists comparable forces across mandibular fractures compared to the gold standard of plating. In resource-limited settings when plates and screws are not available, this technique can be considered to achieve semi-rigid fixation of mandibular fractures.

Outcome of the Masquelet Technique for Complex Bilateral Distal Femoral Bone Defects

Bone defects are severe conditions caused by various etiologies, including trauma, tumor resection, or chronic osteomyelitis. Different surgical interventions can be utilized to manage such cases, including autologous graft or allograft implantation, distraction osteogenesis, acute shortening, amputation, or the induced membrane technique. Herein, the case of a 39-year-old woman with complex bilateral distal femoral fractures with intra-articular extension is presented. The fractures were accompanied by a significant metaphyseal bone defect, which was managed successfully using the induced membrane Masquelet technique. The patient fully healed despite residual knee joint contractures that did not inhibit her mobility. In conclusion, the Masquelet technique successfully manages complex bone defects and restores functionality even in bilateral simultaneous open bone defects.

Orthogonal plating of distal femur fractures: A biomechanical comparison with plate-nail and parallel plating constructs

Purpose

This study compared the biomechanical properties of orthogonal plating with plate-nail and parallel plating constructs for supracondylar distal femur fractures.

Methods

A supracondylar distal femur fracture was simulated using 15 synthetic osteoporotic femurs. Constructs included: (1) plate-nail (lateral locked distal femoral plate + retrograde intramedullary nail); (2) parallel plating (lateral locked distal femoral plate + medial 4.0 mm compression plate); and (3) orthogonal plating (lateral locked distal femoral plate + posterior one-third tubular plate). Specimens underwent nondestructive loading, fatigue loading, and loading to failure. Gapping at the fracture was measured using a three-dimensional motion capture system. Baseline torsional and axial stiffness, stiffness and strain after fatigue loading, and load to failure were determined. A case example of orthogonal plating is also presented.

Results

There was no difference in baseline torsional (p = 0.51) and axial stiffness (p = 0.53). Stiffness after fatigue loading was highest with parallel plating, with no difference between the plate-nail and orthogonal plating constructs (p = 0.84). Strain after fatigue loading was lowest in the parallel plating group (0.54 ± 0.19%), followed by the plate-nail (2.89 ± 0.83%) and orthogonal plating groups (3.04 ± 0.51%).

Conclusion

Orthogonal plating demonstrated comparable baseline stiffness to plate-nail and parallel plating constructs, and similar biomechanical performance in fatigue loading to plate-nail constructs. All specimens had ≤3% strain after fatigue loading, suggesting sufficient stability for fracture healing. The benefits of enhanced stability from dual-implant fixation may be achieved through orthogonal plating while avoiding an additional medial surgical approach, and therefore warrants further investigation as a novel alternative for distal femur fracture fixation.

Outcome Evaluation of Distal Femoral Fractures Following Surgical Management: A Retrospective Cohort Study

BACKGROUND

Distal femur fractures are challenging in surgical management as the outcome is crucial for restoring the biomechanical stability and longitudinal axis of the leg and function of the knee joint.

METHODS

A retrospective review of all distal femoral fractures treated in a level I trauma center over a decade was performed. The radiographs were reviewed for fracture entity, osseous healing, implant failure, mechanical axis, and degenerative joint changes. Clinical outcome was reviewed regarding postoperative complications and postoperative range of motion of the knee joint.

RESULTS

130 patients who were managed with screw fixation (n = 35), plating systems (n = 92) or intramedullary nailing systems (n = 3) remained for evaluation. Mean follow up was 26 months. Clinical outcome was significantly better for flexion degrees following screw fixation (p = 0.009). Delayed fracture union (p = 0.002) or non-union (p = 0.006) rates were significantly higher in plate osteosynthesis. Mild pathologic deformity for varus and valgus collapse was found following plate osteosynthesis.

CONCLUSIONS

Screw fixation shows fewer postoperative complications than plate fixation and is favored for extra and partial intraarticular distal femur fractures. Plating constructs remain the superior fixation method in complex distal femur fractures but are associated with higher rates of non-union and leg axis deviation.

Rethinking the 10% strain rule in fracture healing: A distal femur fracture case series

Since the 1970s, the 2%-10% rule has been used to describe the range of interfragmentary gap closure strains that are conducive for secondary bone healing. Interpreting the available evidence for the association between strain and bone healing remains challenging because interfragmentary strain is impossible to directly measure in vivo. The question of how much strain occurs within and around the fracture gap is also difficult to resolve using bench tests with osteotomy models because these do not reflect the complexity of injury patterns seen in the clinic. To account for these challenges, we used finite element modeling to assess the three-dimensional interfragmentary strain in a case series of naturally occurring distal femur fractures treated with lateral plating under load conditions representative of the early postoperative period. Preoperative computed tomography scans were used to construct patient-specific finite element models and plate fixation constructs to match the operative management of each patient. The simulations showed that gap strains were within 2%-10% only for the lowest load application level, 20% static body weight (BW). Moderate loading of 60% static BW and above caused gap strains that far exceeded 10%, but in all cases, strains in the periosteal region external to the fracture line remained low. Comparing these findings with postoperative radiographs suggests that in vivo secondary healing of distal femur fractures may be robust to early gap strains much greater than 10% because formation of new bone is initiated outside the gap where strains are lower, followed by later consolidation within the gap.

Fixed-angle plate fixation and autogenous iliac crest graft for repair of distal metaphyseal femoral nonunion

PURPOSE

To analyze clinical, radiographic and patient-reported outcomes of distal metaphyseal femoral nonunions treated with fixed-angle plates and screws.

METHODS

All patients presenting with a distal metaphyseal femoral fracture nonunion repaired with fixed-angle plating from one urban level 1 trauma center and an orthopedic specialty hospital were identified. Baseline demographic, injury information, and outcomes (healing rates, Short Musculoskeletal Function Assessment, range of motion, and post-operative pain levels) at 12 months following nonunion repair were collected. Outcomes were evaluated between patients fixed with a blade plate and with a locking plate.

RESULTS

Of these 31 patients, 27 (87.1%) healed after their index nonunion surgery, 2 (6.5%) healed after one reoperation, 1 (3.2%) healed after 2 reoperations, and 1 (3.2%) had a persistent nonunion but did not want further treatment. At one-year follow-up, the group demonstrated a significant improvement in functional recovery with a mean difference of 14.5 points (p = 0.007) when compared to status before fixed-angle fixation of the nonunion. There was also a significant change in patient-reported pain levels using the VAS scale with a mean difference of 2.0 points (p = 0.009). At one-year follow-up, 11 (39.3%) had full knee range of motion (0-130), 11 (39.3%) had flexion greater than 90 and less than 120°, and 6 (21.4%) had range of motion less than 90°.

CONCLUSION

Patients who undergo fixed angle plating and autogenous bone grafting for distal femoral metapyseal nonunions demonstrate improved functional outcomes and VAS pain score at one year follow up.

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.

New versus old: 95 degree angled blade plate versus distal femoral locking plate. A randomized clinical trial

INTRODUCTION

The purpose was to compare the locking condylar plate (LCP) with the 95° angled blade plate (ABP) for distal femoral fracture patterns amenable to either device. Our hypothesis was that LCP would outperform ABP with primary outcome of nonunion and secondary outcomes of reoperation and malunion.

METHODS

78 adult patients with 79 eligible fractures and mean age of 60 years were prospectively randomized to LCP (n = 45) or ABP (n = 34). Mean ISS was 16. 22% fractures were open. Patient-reported functional outcomes were assessed with the Musculoskeletal Function Assessment (MFA).

RESULTS

All patients were followed to union, and mean follow-up was 25 months. There were no differences in age, sex, fracture pattern, co-morbidities or mechanism for the two groups. Three patients had infections, one superficial after LCP and one deep infection each after ABP and LCP. Three patients developed nonunion after LCP versus none after ABP (p = 0.06). Nine patients healed with minor deformity after LCP versus 5 following ABP. One fracture had major deformity after ABP versus two after LCP. Eight patients had a secondary procedure following LCP versus two after ABP (p = 0.05).

CONCLUSIONS

The investigation failed to support newer technology being better. Evidence did not indicate the LCP was superior to the ABP. Trends for primary union and fewer secondary procedures suggest that ABP may have superior performance to LCP for fracture patterns which may be treated with either implant.

Comparing Intramedullary Nailing Versus Locked Plating in the Treatment of Native Distal Femur Fractures: Is One Superior to the Other?

INTRODUCTION

Distal femur fractures make up < 1% of all fractures and 3-6% of all femur fractures. In the literature, both intramedullary nailing (IMN) and locked plating (LP) have shown favorable results, but there is no consensus on a gold standard. The purpose of this systematic review is to compare outcomes of native distal femur fractures treated via IMN versus LP in an effort to determine if one is superior to the other.

METHODS

Systematic review of MEDLINE, EMBASE, and Cochrane Library databases was conducted according to PRISMA guidelines. Only articles published within the last ten years were included. Evidence and study quality were evaluated with the MQOE and Oxford Criteria.

RESULTS

Forty-six articles were included in the review. Fractures treated with IMN were found to have a 93.9% union rate, an average time to union of 19.2 weeks, an average arc of motion of 105.1 degrees, with an average of 14.4 degrees of malalignment. Fractures treated with LP were found to have a 90.2% union rate, an average time to union of 20.5 weeks, an average arc of motion of 104 degrees, with an average of 12.6 degrees of malalignment.

CONCLUSION

Compiled data comparisons revealed no differences in union rate, malalignment, time to union, average arc of motion, or complication rates requiring a return to the operating room. Until higher level randomized data is available, either IMN or LP are acceptable methods of treatment for native distal femur fractures.

Effect of cyclic loading on the stability of screws placed in the locking plates used to bridge segmental bone defects

The objective of this study was to evaluate the ex vivo effect of cyclic loading on the stability of screws placed in locking plates used to bridge segmental bone defects. The primary interface stability was assessed using peak reverse torque. Eighteen, 8-hole stainless-steel 4.5 mm locking plates and 4.0-mm self-tapping locking-head screws were used to stabilize 40-mm segmental defects in goat tibiae. Treatment groups included control constructs without cyclic loading (n = 6) and constructs tested to 5000 (n = 6) and 10,000 cycles (n = 6) of 600 N compressive axial loading. The insertion of all screws was standardized to 400 N-cm insertion torque. Peak reverse torque was measured immediately after screw placement (control), or after the completion of the respective loading cycles. The difference between treatment groups was compared using univariate analysis of variance. The analysis revealed a significant difference in peak reverse torque of the screws among the treatment groups (p = .000). The mean reverse torque values equaled 343.5 ± 18.3 N-cm for non-cycled controls, 303.3 ± 25.9 and 296.0 ± 42.9 N-cm after 5000 and 10,000 cycles, respectively. Among all treatment groups, screws placed in the distal bone segment tended to have lesser peak reverse torque reduction than those placed in the proximal segment and the difference was proportional to the number of cycles (p = .562; p = .255; p = .013 in control, and after 5000 and 10,000 cycles, respectively). Cyclic loading may have a negative effect on the primary stability of screws placed in locking plate constructs used to bridge segmental bone defects and could contribute to the risk of screw loosening.

Supplementation of Lateral Locked Plating for Distal Femur Fractures: A Biomechanical Study

OBJECTIVES

To investigate the biomechanical properties of a lateral locked plate alone or in combination with a supplemental medial plate or an intramedullary nail (IMN).

METHODS

Intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C) were simulated with a standardized model in 28 synthetic femora and divided into 4 groups. Group I was instrumented with a 4.5-mm lateral locked distal femoral plate alone, group II with a lateral locked plate plus a low-profile precontoured 3.5-mm medial distal tibial plate, group III with a lateral locked plate plus a medial 3.5-mm reconstruction plate, and group IV with a lateral locked plate plus a retrograde IMN. Specimens were then axially loaded and cycled to failure or runout. Outcomes of interest were baseline stiffness, survivability, and cycles to failure.

RESULTS

Groups III and IV have a significantly higher baseline stiffness (P < 0.001) when compared with groups I and II. Furthermore, groups III and IV had a higher max load to failure (P < 0.01) when compared with groups I and II. The survivability in groups III and IV was 71% and 100%, respectively, while no specimens in group I or II survived maximum loading. There was no significant difference between group III and IV regarding stiffness, survivability, and cycles to failure.

CONCLUSION

When considering fixation for intra-articular distal femur fractures with metaphyseal comminution (OTA/AO 33-C), we found that supplementation of a lateral locked plate with a medial plate or an IMN to be biomechanically superior to lateral locked plating alone regarding stiffness, survivability, and cycles to failure. A low-profile precontoured plate did not add significantly to the construct stiffness in this study.

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.

Comparação biomecânica de CRIF e placa de reconstrução na estabilização de fraturas distais de fêmur em cães

RESUMO O presente estudo objetivou comparar, biomecanicamente, por meio do ensaio de compressão excêntrica, a resistência dos implantes Clamp and Rod Internal Fixation (CRIF) 5,0mm e placa de reconstrução 3,5mm na fixação de fraturas distais de fêmur de cão. Foram utilizados 22 fêmures de 11 cadáveres de cão entre 2 e 7 anos de idade e peso corporal entre 20 e 40kg e subdivididos em dois grupos, denominados grupo CRIF (GC - 11 fêmures) e grupo placa (GP - 11 fêmures).Para realização dos testes, foi simulada falha que mimetizasse uma fratura distal nos corpos de prova, por meio de uma osteotomia de até 0,5cm, realizada com auxílio de serra oscilatória, imediatamente proximal ao início da tróclea. Os implantes foram fixados segundo os padrões AOSIF, lateralmente ao fêmur, sendo utilizados três parafusos distais e cinco proximais ao foco de fratura. Foi empregado o programa de computador PMI para calcular o ponto máximo de resistência antes da falha e avaliaram-se as variáveis força máxima, deformação máxima real, rigidez, força intermediária e deformação intermediária real. Não foram encontradas diferenças estatisticamente significativas entre os GC e GP quanto às variáveis avaliadas, sugerindo que ambos os implantes são boas opções de fixações para tais fraturas.

A Preliminary Comparison Suggests Poor Performance of Carbon Fiber Reinforced Versus Titanium Plates in Distal Femoral Osteotomy

BACKGROUND

Carbon fiber-reinforced (CFR) polymer implants have theoretical advantages over titanium plates.

QUESTIONS/PURPOSES

The aim of the present study was to assess our early outcomes with CFR plates in lateral opening-wedge distal femoral osteotomy to correct valgus lower limb malalignment. We asked the following: (1) Did the CFR polymer implant change time to union when compared with the titanium implant? (2) Did the incidence of displacement of medial cortical fractures differ between the implants? (3) Did the incidence of complications differ between the two techniques, and did other factors, such as bone graft material used, affect healing?

METHODS

A retrospective review of 16 limbs treated with an opening-wedge distal femoral osteotomy for genu valgum using either titanium (n = 10) or CFR plates (n = 6) was performed. Patient and clinical covariates as well as the primary outcome of time to union and secondary outcome of fracture displacement were collected and analyzed.

RESULTS

Those treated with CFR plates had longer times to union than did those in the titanium-treated group (median, 121.5 vs 81.5 days, respectively). The incidence of fracture displacement was higher in the CFR plate-treated group (CFR, n = 5/6; titanium, n = 1/10). Although the CFR plate-treated group had a 33% nonunion incidence while the titanium group had no nonunions, the study lacked the power to show significance. Bone graft material used did not affect outcome. Complication rates were higher in the CFR plate-treated patients.

CONCLUSION

The CFR plate was associated with a longer time to unite and higher fracture displacement rate than the titanium plate. As this is a retrospective case series, further research is required to confirm these results and clarify best practices in plating of distal femoral osteotomy for deformity correction.

Distal femur: dynamization of plating

With advances in osteosynthesis technology providing improved stability of fixation and better outcomes, surgical treatment has become the standard of care for distal femur fractures. Pre-contoured distal femoral locking plates are the most commonly used implants for fixation. However, healing problems such as delayed union, failure of fixation, and /or nonunion are not uncommon. The fixation construct being "too stiff" is a commonly quoted reason when nonunion/failure of fixation occurs on distal femur fractures fixed with a plate. A flexible fixation construct allowing controlled axial micromotion could help stimulate the bone healing. In order to achieve this goal, plating construct stiffness can be modified by several methods.

The Epidemiology of Adult Distal Femoral Shaft Fractures in a Central London Major Trauma Centre Over Five Years

Background:

Distal femoral fractures account for 3-6% of adult femoral fractures and 0.4% of all fractures and are associated with significant morbidity and mortality rates. As countries develop inter-hospital trauma networks and adapt healthcare policy for an aging population there is growing importance for research within this field.

Methods:

Hospital coding and registry records at the central London Major Trauma Center identified 219 patients with distal femoral shaft fractures that occurred between December 2010 and January 2016. CT-Scans were reviewed resulting in exclusion of 73 inappropriately coded, 10 pediatric and 12 periprosthetic cases. Demographics, mechanism of injury, AO/OTA fracture classification and management were analyzed for the remaining 124 patients with 125 fractures. Mann Whitney U and Chi Squared tests were used during analyses.

Results:

The cases show bimodal distribution with younger patients being male (median age 65.6) compared to female (median age 71). Injury caused through high-energy mechanisms were more common in men (70.5%) whilst women sustained injuries mainly from low-energy mechanisms (82.7%) (p<0.0001). Majority of fractures were 33-A (52.0%) followed by 33-B (30.4%) and 33-C (17.6%). Ninety-two (73.6%) underwent operative management. The most common operation was locking plates (64.1%) followed by intramedullary nailing (19.6%).

Interpretation:

The epidemiology of a rare fracture pattern with variable degrees of complexity is described. A significant correlation between biological sex and mechanism of injury was identified. The fixation technique favored was multidirectional locking plates. Technical requirements for fixation and low prevalence of 33-C fractures warrant consideration of locating treatment at centers with high caseloads and experience.

Working length and proximal screw constructs in plate osteosynthesis of distal femur fractures

BACKGROUND

The study purpose is to evaluate the working length, proximal screw density, and diaphyseal fixation mode and the correlation to fracture union after locking plate osteosynthesis of distal femoral fractures using bridge-plating technique.

METHODS

A four-year retrospective review was performed to identify patients undergoing operative fixation of distal femur fractures with a distal femoral locking plate using bridge-plating technique for the metadiaphyseal region. Primary variables included fracture union, secondary surgery for union, plate working length, and diaphyseal screw technique and configuration. Multiple secondary variables including plate metallurgy and coronal plane fracture alignment were also collected.

RESULTS

Ninety-six patients with distal femur fractures with a mean age 60 years met inclusion criteria. None of the clinical parameters were statistically significant indicators of union. Likewise, none of the following surgical technique parameters were associated with fracture union: plate metallurgy, the mean working length, screw density and number of proximal screws and screw cortices. However, diaphyseal screw technique did show statistical significance. Hybrid technique had a statistically significant higher chance of union when compared to locking (p=0.02). All proximal locking screw constructs were 2.9 times more likely to lead to nonunion.

CONCLUSIONS

Plating constructs with all locking screws used in the diaphysis when bridge-plating distal femur locking plates were 2.9 times more likely to incur a nonunion. However, other factors associated with more flexible fixation constructs such as increased working length, decreased proximal screw number, and decreased proximal screw density were not significantly associated with union in this study.

Implant Material, Type of Fixation at the Shaft, and Position of Plate Modify Biomechanics of Distal Femur Plate Osteosynthesis

OBJECTIVES

To investigate whether (1) the type of fixation at the shaft (hybrid vs. locking), (2) the position of the plate (offset vs. contact) and (3) the implant material has a significant effect on (a) construct stiffness and (b) fatigue life in a distal femur extraarticular comminuted fracture model using the same design of distal femur periarticular locking plate.

METHODS

An extraarticular severely comminuted distal femoral fracture pattern (OTA/AO 33-A3) was simulated using artificial bone substitutes. Ten-hole distal lateral femur locking plates were used for fixation per the recommended surgical technique. At the distal metaphyseal fragment, all possible locking screws were placed. For the proximal diaphyseal fragment, different types of screws were used to create 4 different fixation constructs: (1) stainless steel hybrid (SSH), (2) stainless steel locked (SSL), (3) titanium locked (TiL), and (4) stainless steel locked with 5-mm offset at the diaphysis (SSLO). Six specimens of each construct configuration were tested. First, each specimen was nondestructively loaded axially to determine the stiffness. Then, each specimen was cyclically loaded with increasing load levels until failure.

RESULTS

Construct Stiffness: The fixation construct with a stainless steel plate and hybrid fixation (SSH) had the highest stiffness followed by the construct with a stainless steel plate and locking screws (SSL) and were not statistically different from each other. Offset placement (SSLO) and using a titanium implant (TiL) significantly reduced construct stiffness. Fatigue Failure: The stainless steel with hybrid fixation group (SSH) withstood the most number of cycles to failure and higher loads, followed by the stainless steel plate and locking screw group (SSL), stainless steel plate with locking screws and offset group (SSLO), and the titanium plate and locking screws group (TiL) consecutively. Offset placement (SSLO) as well as using a titanium implant (TiL) reduced cycles to failure.

CONCLUSIONS

Using the same plate design, the study showed that implant material, screw type, and position of the plate affect the construct stiffness and fatigue life of the fixation construct. With this knowledge, the surgeon can decide the optimal construct based on a given fracture pattern, bone strength, and reduction quality.

Impact of cement-augmented condylar screws in locking plate osteosynthesis for distal femoral fractures - A biomechanical analysis

INTRODUCTION

Compromised bone quality and the need for early mobilization continue to lead to implant failure in elderly patients with distal femoral fractures. The cement augmentation of screws might facilitate improving implant anchorage. The aim of this study was to analyse the impact of cement augmentation of the condylar screws on implant fixation in a human cadaveric bone model.

MATERIAL AND METHODS

Ten pairs of osteoporotic femora (mean age: 90 years, range: 84-99 years) were used. A 2-cm gap osteotomy was created in the metaphyseal region to simulate an unstable AO/OTA 33-A3 fracture. All specimens were treated with a polyaxial locking plate. Specimens randomly assigned to the augmented group received an additional cement augmentation of the condylar screws using bone cement. A servohydraulic testing machine was used to perform incremental cyclic axial loading using a load-to-failure mode.

RESULTS

All specimens survived at least 800N of axial compressive force. The mean compressive forces leading to failure were 1620N (95% CI: 1382-1858N) in the non-augmented group and 2420N (95% CI: 2054-2786N) in the group with cement-augmented condylar screws (p=0.005). Deformation with cutting out of the condylar screws and condylar fracture were the most common reasons for failure in both groups. Whereas axial stiffness was comparable between both osteosyntheses (p=0.508), significant differences were observed for the plastic deformation of the constructs (p=0.014).

CONCLUSION

The results of the present study showed that the cement augmentation of the condylar screws might be a promising technique for the fixation of distal femoral fractures in elderly patients with osteoporotic bones.

Retrospective analysis of extra-articular distal humerus shaft fractures treated with the use of pre-contoured lateral column metaphyseal LCP by triceps-sparing posterolateral approach

Management of extra-articular distal humerus fractures presents a challenge to the treating surgeon due to the complex anatomy of the distal part of the humerus and complicated fracture morphology. Although surgical treatment has shown to provide a more stable reduction and alignment and predictable return to function, it has been associated with complications like iatrogenic radial nerve palsy, infection, non-union and Implant failure. We in the present series retrospectively analysed 20 patients with extra-articular distal humerus shaft fractures surgically treated using the extra-articular distal humeral locking plate approached by the triceps-sparing posterolateral approach. The outcome was assessed using the DASH score, range of motion at the elbow and the time to union. The mean time to radiographic fracture union was 12 weeks.

Comminuted supracondylar femoral fractures: a biomechanical analysis comparing the stability of medial versus lateral plating in axial loading

The aim of this study was to compare the biomechanical properties of medial and lateral plating of a medially comminuted supracondylar femoral fracture. A supracondylar femoral fracture model comparing two fixation methods was tested cyclically in axial loading. One-centimetre supracondylar gap osteotomies were created in six synthetic femurs approximately 6 cm proximal to the knee joint. There were two constructs investigated: group 1 and group 2 were stabilized with an 8-hole LC-DCP, medially and laterally, respectively. Both construct groups were axially loaded. Global displacement (total length), wedge displacement, bending moment and strain were measured. Medial plating showed a significantly decreased displacement, bending moment and strain at the fracture site in axial loading. Medial plating of a comminuted supracondylar femur fracture is more stable than lateral plating.

Biomechanical Evaluation of Four Methods for Internal Fixation of Comminuted Subtrochanteric Fractures

Subtrochanteric fractures are common and result in significant morbidity and mortality. Various kinds of implants have been used to fix it. The aim of this study was to compare the biomechanical performance of PFN, DHS, DCS, and the PFLP in the treatment of subtrochanteric comminuted fractures.A total of 32 antiseptic human femurs from 16 donors were randomly allocated to 4 groups for fixation with PFN, DHS, DCS, and PFLP. A 2-cm cylindrical bone fragment was removed 1 cm below the lesser trochanter to simulate OTA/AO 32-C3.2 post instrumentation fracture. All specimens in single-leg stance situation were preloaded 5 times at 100 N in the axial direction to eliminate the time effect of relaxation and settling, followed by cyclic testing at a rate of 1 Hz with stepwise increasing load. Keeping the valley load at a constant level of 100 N during the entire cyclic test, the peak load, starting at 200 N, was increased by 100 N at 300-cycle steps until a maximum of 1500 cycles or until failure of the bone-implant construct occurred. Each specimen was kept unloaded under 100 N compression for 30 minutes between the 300-cycle steps.Femoral head displacement after 1500 cycles was 1.09 mm ± 0.13 for PFN, 1.78 mm ± 0.25 for DHS, 2.63 mm ± 0.46 for DCS, and 2.26 mm ± 0.16 for PFLP, with significant difference between any 2 implants (P < 0.01). The required load to reach 1-mm femoral head displacement was 563.04 N ± 158.34 for PFN, 485.73 N ± 147.27 for DHS, 258.44 N ± 97.23 for DCS, and 332.68 N ± 100.34 for PFLP. Significant differences were detected between any 2 implants (P < 0.001), except between DCS and PFLP and between DHS and PFN. The number of cycles until 1-mm femoral head displacement was 1458 ± 277 for PFN, 908 ± 184 for DHS, 369 ± 116 for DCS, and 603 ± 162 for PFLP. Significant differences were detected between any 2 implants (P < 0.01), except between DCS and PFLP.From biomechanical point of view, comminuted subtrochanteric fractures OTA/AO 32-C3.2 revealed in the current test setup highest fixation strength with PFN, followed by DHS, PFLP, and DCS.

Management of Distal Femur Fractures in Adults: An Overview of Options

Surgical treatment of periarticular and intra-articular fractures of the distal femur pose a significant challenge to the orthopedic surgeon. The primary goal of surgical treatment remains: restoration of the articular surface to the femoral shaft, while maintaining enough stability and alignment to enable early range of motion and rehabilitation. With appropriate surgical planning, these injuries can be managed with a variety of methods and techniques, while taking into account patients' functional goals, fracture characteristics, health comorbidities, bone quality, and risk of malunion and nonunion.

Preliminary testing of a novel bilateral plating technique for treating periprosthetic fractures of the distal femur

BACKGROUND

Current stabilization methods for periprosthetic fractures of the distal femur are inadequate in achieving fracture fixation, with complication rates as high as 29%. A major contributor to poor outcomes is that these methods rely only on screw purchase in the bone to maintain fracture reduction. We designed, manufactured and evaluated a novel plating method that utilizes the femoral prosthesis to enhance stability for treatment of distal femoral periprosthetic fractures.

METHODS

Medial and lateral plates were designed and manufactured based on geometry of a synthetic femur and femoral prosthesis. The two plates were linked via a compression screw and a small tab on each plate that inserted into pre-existing slots on the prosthesis. Mechanical tests (500N compression or 250N anterior directed cantilever bending), were performed on synthetic femurs with simple transverse fractures (3mm gap) just superior to the distal femoral prosthesis that were stabilized using either the prototype plates or a single lateral plate. Translational movements of the fracture site during loading were measured using 3D motion tracking.

FINDINGS

With the single lateral plate, the distal fragment experienced a resultant displacement of 0.40mm under cantilever bending and 0.61mm under compression (13% and 20% respectively of fracture gap width). With the bilateral plates, fracture gap motion was significantly reduced to 0.13mm under bending and compression (4.3% of the fracture gap).

INTERPRETATION

Our results indicate that a bilateral plating method is capable of improving stabilization of periprosthetic fractures compared to the traditional lateral plating technique.

Internal fixators: a safe option for managing distal femur fractures?

OBJECTIVE:

Evaluate safety and reliability of internal fixator for the treatment of intra-articular and periarticular distal femur fractures.

METHODS:

Retrospective data evaluation of 28 patients with 29 fractures fixed with internal fixator was performed. There was a predominance of male patients (53.5%), with 52% of open wound fractures, 76% of AO33C type fractures, and a mean follow up of 21.3 months. Time of fracture healing, mechanical axis deviation, rate of infection and postoperative complications were registered.

RESULTS:

Healing rate was 93% in this sample, with an average time of 5.5 months. Twenty-seven percent of patients ended up with mechanical axis deviation, mostly resulting from poor primary intra-operative reduction. There were two cases of implant loosening; two implant breakage, and three patients presented stiff knee. No case of infection was observed. Healing rate in this study was comparable with current literature; there was a high degree of angular deviation, especially in the coronal plane.

CONCLUSION:

Internal fixators are a breakthrough in the treatment of knee fractures, but its use does not preclude application of principles of anatomical articular reduction and mechanical axis restoration.

Level of Evidence II, Retrospective Study.

Delayed bone healing following high tibial osteotomy related to increased implant stiffness in locked plating

INTRODUCTION

Asymmetrical callus formation and incomplete bone formation underneath stiff locking plates have been reported recently in clinical and experimental fracture healing studies. After similar effects were observed in the outcome of high tibial osteotomy (HTO) patients, a retrospective study was performed to quantify the frequency and level of such incomplete healing cases.

MATERIAL AND METHODS

Twenty-three patients treated with medial open wedge HTO and locking plate (Tomofix™) for posttraumatic or congenital genu varum were investigated. No bone grafts were applied to fill the osteotomy gap. The median correction angle was 8° (5-18°). Elective hardware removal was performed after a median of 19.5 months (12-58 months) following an uneventful clinical course. The most recent postoperative X-ray available (median 21 months; 13-56 months) was evaluated for consolidation of the osteotomy. We performed an in vitro biomechanical experiment using the same HTO on a loaded cadaver knee joint to compare interfragmentary movements (IFMs) when using regular locking screws with the Tomofix™ plate and screws that enabled dynamic stabilisation of this plate.

RESULTS

Fifteen patients (65%) displayed incomplete consolidation of the osteotomy underneath the locking plate (10.9% of the osteotomy length) and cortical deficiency. The time to implant removal for these patients of 27 months was longer than the 21 months for the patients with a complete osteotomy gap healing. The biomechanical experiment demonstrated that very low IFMs and corresponding interfragmentary strain occur underneath the plate when using regular locking screws. Replacement with dynamic screws resulted in an increased IFM.

DISCUSSION AND CONCLUSIONS

These results support the hypothesis that low bone formation underneath locking plates is induced by increased stiffness. This high stiffness situation could be altered by replacing the standard screws with dynamic screws which allow for a movement of 0.35mm perpendicular to the screw axis. This resulted in an approximately threefold increase in the IFM and may be a potential concept to avoid incomplete bone healing under stiff plate fixations.

Biomechanical analysis of distal femoral fracture fixation: dynamic condylar screw versus locked compression plate

BACKGROUND

This human cadaveric study i ntroduces a laboratory model to establish and compare the fixation stability of the distal femoral locking plate (DFLP) and dynamic condylar screw (DCS) in distal femoral fracture fixation.

MATERIALS AND METHODS

The study was conducted on 16 fresh cadaveric femoral specimens, 8 implanted with the DCS and the other 8 with the DFLP. The construct was made unstable by removing a standard-sized medial wedge with a 1-cm base (gap osteotomy) beginning 6 cm proximal to the lateral joint line in the distal metaphyseal region with loss of the medial buttress. Each specimen underwent axial and torsional stiffness testing along with cyclic axial loading to failure. The mean DEXA value for the DFLP group was 0.82 g/cm(2) and in the DCS group was 0.79 g/cm(2).

RESULTS

Axial stiffness in the DFLP group was significantly higher than in the DCS group, but no significant difference was found in torsional stiffness between the groups. A significant difference was found in the load-to-failure results between the groups. Plastic and total deformation was significantly higher in constructs in the DCS group than in those in the DFLP group. Total energy absorbed before construct failure was also significantly higher in the DFLP group than in the DCS group.

CONCLUSIONS

The DFLP construct proved stronger than the DCS in both axial stiffness and cyclic loading, but similar in torsional stiffness in biomechanical testing in a simulated A3 distal femoral fracture.

Blade-plate fixation for distal femoral fractures: a case-control study

BACKGROUND

The blade-plate is the earliest of the contemporary internal fixation devices introduced for distal femoral fractures. The recent development of dedicated, fixation devices has considerably limited its use. The objective of this study was to evaluate outcomes after blade-plate fixation and after fixation using other devices.

HYPOTHESIS

Outcomes after blade-plate fixation are similar to those after condylar screw-plate, distal femoral nail, or locking condylar plate fixation.

MATERIAL AND METHODS

We reviewed outcomes after 62 patients managed with blade-plate fixation and included in a multicentre retrospective study (n=57) or a multicentre prospective study (n=5) and we compared them to outcomes after fixation using condylar screw-plates (n=82), distal femoral nail (n=219), or locking condylar plates (n=301). The four groups were comparable for age, gender distribution, occupational status, prevalence of skin wounds, patient-related factors, type of accident, and type of fracture. The evaluation relied on the clinical International Knee Society (IKS) score and on radiographs.

RESULTS

No significant differences existed across the four groups for operative time, blood transfusion use, complications, need for bone grafting, non-union rate, or IKS score values. The early surgical revision rate for removal of the fixation material was 4% with the blade-plate and 16% with the other three fixation devices (P=0.02). Post-operative fracture deformity was similar in the four groups with, however, a higher proportion of residual malalignment in the screw-fixation group. The final anatomic axis was 3.3±1.4° with the blade-plate versus 2.3±3.7° with the other three fixation devices. The blade-plate group had few patients with axial malalignment, and the degree of malalignment was limited to 3° of varus and 10° of valgus at the most, compared to 10° and 18° respectively, with the other three fixation devices.

CONCLUSION

Despite the now extremely limited use and teaching of blade-plate fixation, as well as the undeniable technical challenges raised by the implantation of this device, the blade-plate is a simple, strong, and inexpensive fixation method. It remains reliable for the fixation of distal femoral fractures. The disfavour into which the blade-plate is currently falling is not warranted.

LEVEL OF EVIDENCE

III, case-control study.

Biomechanical comparison of locked plating and spiral blade retrograde nailing of supracondylar femur fractures

OBJECTIVE

Biomechanical comparison between locked plating and retrograde nailing of supracondylar femur fractures with simulated postoperative weight-bearing.

METHODS

The Locking Condylar Plate (LCP) and Retrograde/Antegrade EX Femoral Nail (RAFN) were tested using 10 paired elderly cadaveric femurs, divided into Normal and Low Bone Mineral Density (BMD) groups, with a simulated AO/OTA type 33-A3 supracondylar femur fracture. Each specimen was subjected to 200,000 loading cycles in an attempt to simulate six weeks of postoperative recovery with full weight-bearing for an average individual. The construct's subsidence due to cyclic loading, and axial stiffness before and after the cyclic loading were measured and their correlation with BMD was studied. The two implants were compared in a paired study within each BMD group.

RESULTS

LCP constructs showed higher axial stiffness compared to RAFN for both Normal and Low BMD groups (80% and 57%, respectively). After cyclic loading, axial stiffness of both constructs decreased by 20% and RAFN constructs resulted in twice as much subsidence (1.9 ± 0.6mm). Two RAFN constructs with Low BMD failed after a few cycles whereas the matched pairs fixed with LCP failed after 70,000 cycles.

CONCLUSIONS

The RAFN constructs experienced greater subsidence and reduced axial stiffness compared to the LCP constructs. In Low BMD specimens, the RAFN constructs had a higher risk of failure.

Implant material and design alter construct stiffness in distal femur locking plate fixation: a pilot study

BACKGROUND

Construct stiffness affects healing of bones fixed with locking plates. However, variable construct stiffness reported in the literature may be attributable to differing test configurations and direct comparisons may clarify these differences.

QUESTIONS/PURPOSES

We therefore asked whether different distal femur locking plate systems and constructs will lead to different (1) axial and rotational stiffness and (2) fatigue under cyclic loading.

METHODS

We investigated four plate systems for distal femur fixation (AxSOS, LCP, PERI-LOC, POLYAX) of differing designs and materials using bone substitutes in a distal femur fracture model (OTA/AO 33-A3). We created six constructs of each of the four plating systems. Stiffness under static and cyclic loading and fatigue under cyclic loading were measured.

RESULTS

Mean construct stiffness under axial loading was highest for AxSOS (100.8 N/mm) followed by PERI-LOC (80.8 N/mm) and LCP (62.6 N/mm). POLYAX construct stiffness testing showed the lowest stiffness (51.7 N/mm) with 50% stiffness of AxSOS construct testing. Mean construct stiffness under torsional loading was similar in the group of AxSOS and PERI-LOC (3.40 Nm/degree versus 3.15 Nm/degree) and in the group of LCP and POLYAX (2.63 Nm/degree versus 2.56 Nm/degree). The fourth load level of > 75,000 cycles was reached by three of six AxSOS, three of six POLYAX, and two of six PERI-LOC constructs. All others including all LCP constructs failed earlier.

CONCLUSIONS

Implant design and material of new-generation distal femur locking plate systems leads to a wide range of differences in construct stiffness.

CLINICAL RELEVANCE

Assuming construct stiffness affects fracture healing, these data may influence surgical decision-making in choosing an implant system.

Primary total knee arthroplasty for simple distal femoral fractures in elderly patients with knee osteoarthritis

Purpose

Primary total knee arthroplasty (TKA) can be an alternative method for treating distal femoral fractures in elderly patients with knee osteoarthritis. The purpose of this study was to evaluate the clinical and radiographic results in patients with knee osteoarthritis who underwent TKA with the Medial Pivot prosthesis for distal femoral fractures.

Materials and Methods

Eight displaced distal femoral fractures in 8 patients were treated with TKA using the Medial Pivot prosthesis and internal fixation. The radiographic and clinical evaluations were performed using simple radiographs and Hospital for Special Surgery (HSS) knee scores during a mean follow-up period of 49 months.

Results

All fractures united and the mean time to radiographic union was 15 weeks. The mean range of motion of the knee joint was 114.3° and the mean HSS knee score was 85.1 at the final follow-up.

Conclusions

Based on the radiographic and clinical results, TKA with internal fixation can be considered as an option for the treatment of simple distal femoral fractures in elderly patients who have advanced osteoarthritis of the knee with appropriate bone stock.

Biomechanical comparison of dynamic condylar screw and locking compression plate fixation in unstable distal femoral fractures: An in vitro study

BACKGROUND

Distal femur fractures are difficult to manage and the selection of implant for internal fixation remains controversial. The objective of this study is to establish the relative strength of fixation of a distal femoral locking plate (DFLP) compared with the dynamic condylar screw (DCS) in the distal femur fractures.

MATERIALS AND METHODS

Study was conducted on 16 freshly harvested cadaveric distal femoral specimens, eight implanted with DCS and other eight with DFLP. The construct was made unstable by removing a standard sized medial wedge of 1 cm base (gap-osteotomy) beginning 6 cm proximal to the lateral joint line in distal metaphyseal region with the loss of medial buttress. Fatigue test was conducted under load control mode at the frequency of I Hz. Specimens were subjected to cyclic loading of 2 kN, under observation for 50,000 cycles or until failure/cutout, which ever occurred earlier.

RESULTS

In DFLP group, there was no implant failure and the average number of cycles sustained was 50,000. Six out of eight specimens completed 50,000 cycles and two failed in DCS group. The average number of cycles sustained by DCS was 46150. Though the bone quality as assessed by dual energy X-ray absorptiometry DEXA was comparable in both DFLP and DCS group (P = 0.06), none failed in DFLP group and subsidence was 1.02 ± 0.34 mm (range: 0.60-1.32 mm), which was significantly 43% lower (P = 0.006) than subsidence in DCS group (1.82 ± 0.58; range: 1.20-3.08 mm). The average stiffness of DCS group was 52.8 ± 4.2 N/mm, which was significantly lower than average stiffness of locked condylar plate group (71.2 ± 5.1 N/mm) (P = 0.02).

CONCLUSIONS

DFLP fixation of the distal femur fractures resulted in stronger construct than the DCS fixation in both cyclic loading and ultimate strength in biomechanical testing of a simulated A3 distal femur fracture.

Biomechanical analysis of a volar variable-angle locking plate: the effect of capturing a distal radial styloid fragment

PURPOSE

Variable-angle volar locked constructs for distal radius fractures are a recent treatment addition. This study sought to biomechanically evaluate a variable-angle volar locking plate as compared with a fixed-angle construct.

METHODS

We created 2 different AO-C3 osteotomies in fourth-generation synthetic composite distal radiuses and labeled them proximal and distal. The distal osteotomy consisted of a smaller radial styloid fragment. We then fixed both sets of specimens with either a fixed-angle or variable-angle volar locking construct. We tested samples in axial compression with regard to cyclical loading and load to failure. Articular stepoff, stiffness, and load to failure data were then analyzed.

RESULTS

Neither the proximal nor the distal osteotomy groups showed articular failure after cyclic loading, significant loss of stiffness over cycling, or superior stiffness compared with the other. After load to failure in the proximal osteotomy, 1 of 8 fixed-angle and none of 8 variable-angle constructs had articular failure, whereas in the distal osteotomy, all 8 fixed-angle and none of 8 variable-angle constructs had articular failure.

CONCLUSIONS

Variable-angle and fixed-angle volar locked fixation of unstable intra-articular distal radius fractures in fourth-generation composite radii provide mechanically sound constructs with high load to failure values and no loss of stiffness over testing. The variable-angle construct exhibited excellent resistance to articular stepoff at load to failure and no loss of stiffness throughout cyclic loading, and did not exhibit significantly less overall stiffness compared with fixed-angle constructs. The variable-angle fixation exhibited a distinct mechanical advantage over fixed-angle fixation in the setting of a smaller radial styloid fragment.

CLINICAL RELEVANCE

Variable-angle constructs could be expected to hold up to standard loads in the postoperative period as well as traditional fixed-angle devices. The additional cost associated with variable-angle constructs may be warranted when treating distal radius fractures with radial styloid fragments, owing to the fragment-specific fixation allowed by customized screw placement.

Immediate weight bearing of comminuted supracondylar femur fractures using locked plate fixation

Comminuted supracondylar femur fractures (AO-OTA 33A3) are commonly treated with locked plates. Weight bearing is generally restricted for 6 to 12 weeks until radiologic evidence exists of sufficient callous to support weight bearing. Recent clinical studies have reported high nonunion rates with distal femur locked plates. In an attempt to induce beneficial motion across the fracture site, some studies have recommended earlier weight bearing. The purpose of the current study was to determine the biomechanical feasibility of an immediate weight-bearing rehabilitation protocol to encourage healing of distal femur fractures treated with lateral locked plate fixation.Sixteen fresh-frozen cadaveric femora were used for this study. A 2.5-cm supracondylar gap osteotomy was made. Ten-hole, 4.5-mm distal femur locking plates were used with a standardized screw configuration that maximized the working length. The specimens were placed in a servohydraulic testing machine and axially loaded (unidirectional) at 1 Hz for up to 200,000 cycles. Failure was defined as 1 cm of deformation of the construct. The staircase method was used to determine the fatigue limit of the construct. The fatigue limit was calculated to be 1329±106 N. No specimen failed through the non-locking diaphyseal screws. Plastic deformation, when present, occurred at the metaphyseal flare of the plate. The fatigue limit of the locked plate constructs equaled 1.9 times body weight for an average 70-kg patient over a simulated 10-week postoperative course. Given that distal femoral loads during gait have been estimated to be more than 2 times body weight, the data from this study do not support immediate full weight bearing.

Comparison of the 95-degree angled blade plate and the locking condylar plate for the treatment of distal femoral fractures

OBJECTIVES

In the distal femur, locked plating is efficacious when coronal fractures preclude the use of a conventional fixed-angle device. However, minimal comparative data exist for supracondylar fracture patterns, which could be treated with other devices. The purpose of this study was to compare the 95-degree angled blade plate (ABP) versus the Locking Condylar Plate (LCP) by assessing complications and secondary procedures in fractures amenable to treatment with either implant.

DESIGN

Retrospective review.

SETTING

Level 1 trauma center.

PATIENTS/PARTICIPANTS

Seventy patients with 71 distal femoral fractures (OTA 33-A, 33-C1, 33-C2) amenable to either ABP or LCP with a mean age of 59.5 years (range, 20-92 years) were included. Seventeen fractures (24%) occurred adjacent to a previous knee arthroplasty (10 ABP and 7 LCP). The 2 groups were similar with respect to age, fracture pattern, and the presence of open fracture. Most injuries were the result of high-energy trauma, and 21% were open fractures.

INTERVENTION

Thirty-two fractures (45%) were treated with an ABP, and 39 (55%) were treated with the LCP.

MAIN OUTCOME MEASURES

Complications, including infection, nonunion, and malunion, and secondary operations were determined.

RESULTS

After a mean of 26-month follow-up, 4 patients (6.0%) were treated for infections. Malunions occurred in 11% of LCP patients and in 1 ABP patient (3.4%, P = 0.14). All patients with malunions were older than 55 years. Seven patients (11%) were treated for nonunions. Six of the nonunions occurred after LCP (16% vs. 3.4%, P = 0.11) Complications were more frequent in LCP patients (35%) versus ABP patients (10%, P = 0.001). Complications were not related to fracture pattern, periprosthetic fracture, or open fracture. Mean age of patients with complications was 64 years (vs. 53 years, P = 0.01), and they were more likely to have lower energy mechanisms (P = 0.017). Overall, 18 patients (27%) underwent secondary procedures, including treatment of infection, nonunion, malunion, or prominent implant removal. Secondary procedures were more common after LCP (43%) versus ABP (6.9%, P = 0.0008) patients. Painful prominent implants were removed from 7 LCP patients (18%) and no ABP patients (P = 0.01).

CONCLUSIONS

Distal femur fractures are often associated with prolonged healing and rehabilitation times, which increase substantially when complications occur. Internal fixation of these fractures may be performed successfully with ABP or LCP. In our review of fractures that could be treated with either implant, patients treated with locking plates had more complications and nonunions, requiring more secondary procedures to treat complications and to remove prominent implants. Furthermore, locking plates are substantially more expensive than conventional fixed-angle devices. Future investigation is needed in the form of a large randomized prospective study to clearly define clinical differences, functional outcomes, and costs of care.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

A distal femoral supra-condylar plate: biomechanical comparison with condylar plate and first clinical application for treatment of supracondylar fracture

PURPOSE

An anatomical supra-condylar plate is designed and analysed by biomechanical testing.

METHODS

The biomechanical properties of the supra-condylar and condylar plate were compared in six matched pairs of cadaveric femurs. A transverse osteotomy gap was created to simulate an OTA/AO type A3 supracondylar fracture. The left and right specimens were fitted with supra-condylar and condylar plate, respectively. Nondestructive axial compression, three-point bending and torsion tests were performed, and the peak load of the bone-implant construction was measured. The fracture site suitable for supra-condylar plate application and its correlation with femoral length were calculated. The gender influence on it was also discussed.

RESULTS

The difference of stiffness between the supra-condylar and condyle groups were not significant (P > 0.05) at 363.4 and 362.5 N/mm for compression, 229.5 and 237.6 N/mm in the sagittal plane and 195.5 and 188.4 N/mm in the coronal plane for three-point bending, and 7.5 and 7.9 Nm/deg for axial torsion, respectively. The peak load was 4438 ± 136.15 N and 5215 ± 174.33 N, respectively, for the two groups. The average extent of the fracture site suitable for the application of the supra-condylar plate was 70.86 ± 4.61 mm. The femoral length and gender showed no influence on it.

CONCLUSION

Despite the limited bone contact area provided by the supra-condylar plate, its construct stiffness is comparable to the condylar plate. The supra-condylar plate can be used to treat carefully-selected extra-articular supracondylar fractures.

Finite element analysis of osteosynthesis screw fixation in the bone stock: an appropriate method for automatic screw modelling

The use of finite element analysis (FEA) has grown to a more and more important method in the field of biomedical engineering and biomechanics. Although increased computational performance allows new ways to generate more complex biomechanical models, in the area of orthopaedic surgery, solid modelling of screws and drill holes represent a limitation of their use for individual cases and an increase of computational costs. To cope with these requirements, different methods for numerical screw modelling have therefore been investigated to improve its application diversity. Exemplarily, fixation was performed for stabilization of a large segmental femoral bone defect by an osteosynthesis plate. Three different numerical modelling techniques for implant fixation were used in this study, i.e. without screw modelling, screws as solid elements as well as screws as structural elements. The latter one offers the possibility to implement automatically generated screws with variable geometry on arbitrary FE models. Structural screws were parametrically generated by a Python script for the automatic generation in the FE-software Abaqus/CAE on both a tetrahedral and a hexahedral meshed femur. Accuracy of the FE models was confirmed by experimental testing using a composite femur with a segmental defect and an identical osteosynthesis plate for primary stabilisation with titanium screws. Both deflection of the femoral head and the gap alteration were measured with an optical measuring system with an accuracy of approximately 3 µm. For both screw modelling techniques a sufficient correlation of approximately 95% between numerical and experimental analysis was found. Furthermore, using structural elements for screw modelling the computational time could be reduced by 85% using hexahedral elements instead of tetrahedral elements for femur meshing. The automatically generated screw modelling offers a realistic simulation of the osteosynthesis fixation with screws in the adjacent bone stock and can be used for further investigations.

Biomechanical measurements of axial crush injury to the distal condyles of human and synthetic femurs

Few studies have evaluated the ‘bulk’ mechanical properties of human longbones and even fewer have compared human tissue to the synthetic longbones increasingly being used by researchers. Distal femur fractures, for example, comprise about 6% of all femur fractures, but the mechanical properties of the distal condyles of intact human and synthetic femurs have not been well quantified in the literature. To this end, the distal portions of a series of 16 human fresh-frozen femurs and six synthetic femurs were prepared identically for mechanical testing. Using a flat metal plate, an axial ‘crush’ force was applied in-line with the long axis of the femurs. The two femur groups were statistically compared and values correlated to age, size, and bone quality. Results yielded the following: crush stiffness (human, 1545 ± 728 N/mm; synthetic, 3063 ± 1243 N/mm; p = 0.002); crush strength (human, 10.3 ± 3.1 kN; synthetic, 12.9 ± 1.7 kN; p = 0.074); crush displacement (human, 6.1 ± 1.8 mm; synthetic, 2.8 ± 0.3 mm; p = 0.000); and crush energy (human, 34.8 ± 15.9 J; synthetic, 18.1 ± 5.7 J; p = 0.023). For the human femurs, there were poor correlations between mechanical properties versus age, size, and bone quality (R2 ≤ 0.18), with the exception of crush strength versus bone mineral density (R2 = 0.33) and T-score (R2 = 0.25). Human femurs failed mostly by condyle ‘roll back’ buckling (15 of 16 cases) and/or unicondylar or bicondylar fracture (7 of 16 cases), while synthetic femurs all failed by wedging apart of the condyles resulting in either fully or partially displaced condylar fractures (6 of 6 cases). These findings have practical implications on the use of a flat plate load applicator to reproduce real-life clinical failure modes of human femurs and the appropriate use of synthetic femurs. To the authors’ knowledge, this is the first study to have done such an assessment on human and synthetic femurs.

Treatment of periprosthetic femoral fractures of the knee

PURPOSE

We report a continuous series of periprosthetic femoral fractures after knee arthroplasty treated with a locking plate. We hypothesize that minimally invasive surgery and immediate weight-bearing improve functional recovery.

METHODS

From June 2002 to December 2008, 15 patients with 16 fractures were treated. Median age was 81 years. The autonomy level according to the mobility score of Parker and Palmer showed a median of 5 (0-9). Osteosynthesis was performed mainly through a minimally invasive approach using a locking compression plate. The rehabilitation protocol consisted of immediate mobilization and, whenever possible, immediate unrestricted weight-bearing.

RESULTS

Five patients died during follow-up, more than 1 year after osteosynthesis. Their results were included. Autonomy and mobility were preserved with a median postoperative score of 4 (0-9) according to Parker and Palmer. The consolidation rate was 93.8%, which was obtained within 10 weeks. There were no mechanical or infectious complications. Fourteen cases were treated with minimally invasive surgery without fracture exposition; the remaining 2 required a slightly more extended approach. Full weight-bearing occurred 10 times; 20-kg partial weight-bearing was advised twice; and on 4 occasions, no weight-bearing was allowed for 6 weeks.

CONCLUSION

Osteosynthesis with a minimally invasive bridge-plating technique is effective in the treatment of periprosthetic, distal femoral fractures without component loosening. Immediate full weight-bearing is possible if certain rules are respected. The surgical management presented herein is beneficial for these challenging fractures, and it may help reduce the complication rate and improve functional outcome.

Minimally invasive plate osteosynthesis using a locking compression plate for distal femoral fractures

PURPOSE

To evaluate treatment outcomes of minimally invasive plate osteosynthesis (MIPO) for distal femoral fractures in 31 patients.

METHODS

22 male and 9 female consecutive patients aged 21 to 65 (mean, 42) years underwent minimally invasive plate osteosynthesis using a locking compression plate (LCP) for distal femoral fractures. The causes of injury were vehicular accidents (n=24), falls (n=6), and assault (n=1). According to the AO classification, the fractures were classified as types A1 (n=10), A2 (n=7), and A3 (n=14). Most fractures were closed; 3 were Gustilo type-II fractures. Clinical and functional outcomes were assessed using the Knee Society Scores.

RESULTS

The mean operating time was 70 (range, 60-100) minutes. The mean length of hospital stay was 9 (6-14) days. The mean time to union was 3.7 (range, 2.8-4.6) months. The mean follow-up period was 18 (14-26) months. At the one-year follow-up, 29 of the patients had good or excellent outcomes. No patient had angular or rotational deformity of >10º. One osteoporotic woman with a type-A1 fracture had implant failure at 10 weeks and underwent revision surgery. Another patient with a type-A1 fracture had persistent pain on the lateral aspect of the distal thigh and underwent implant removal at 22 months. No patient developed deep infection, malunion or nonunion.

CONCLUSION

MIPO using a LCP achieves favourable biological fixation for distal femoral fractures with few complications. Bone grafting is not needed even in cases of metaphyseal comminution. Proper patient selection and preoperative planning are essential to prevent complications.

Distal femoral fractures: current concepts

The diversity of surgical options for the management of distal femoral fractures reflects the challenges inherent in these injuries. These fractures are frequently comminuted and intra-articular, and they often involve osteoporotic bone, which makes it difficult to reduce and hold them while maintaining joint function and overall limb alignment. Surgery has become the standard of care for displaced fractures and for patients who must obtain rapid return of knee function. The goal of surgical management is to promote early knee motion while restoring the articular surface, maintaining limb length and alignment, and preserving the soft-tissue envelope with a durable fixation that allows functional recovery during bone healing. A variety of surgical exposures, techniques, and implants has been developed to meet these objectives, including intramedullary nailing, screw fixation, and periarticular locked plating, possibly augmented with bone fillers. Recognition of the indications and applications of the principles of modern implants and techniques is fundamental in achieving optimal outcomes.

Pathological fractures of the proximal humerus treated with a proximal humeral locking plate and bone cement

Bone loss secondary to primary or metastatic lesions of the proximal humerus remains a challenging surgical problem. Options include preservation of the joint with stabilisation using internal fixation or resection of the tumour with prosthetic replacement. Resection of the proximal humerus often includes the greater tuberosity and adjacent diaphysis, which may result in poor function secondary to loss of the rotator cuff and/or deltoid function. Preservation of the joint with internal fixation may reduce the time in hospital and peri-operative morbidity compared with joint replacement, and result in a better functional outcome. We included 32 patients with pathological fractures of the proximal humerus in this study. Functional and radiological assessments were performed. At a mean follow-up of 17.6 months (8 to 61) there was no radiological evidence of failure of fixation. The mean revised musculoskeletal Tumour Society functional score was 94.6% (86% to 99%). There was recurrent tumour requiring further surgery in four patients (12.5%). Of the 22 patients who were employed prior to presentation all returned to work without restrictions.

The use of a locking plate combined with augmentation with cement extends the indications for salvage of the proximal humerus with good function in patients with pathological and impending pathological fractures.