Biomechanical analysis of operative methods in the treatment of extra-articular fracture of the proximal tibia

Stable elastic nail application with poller K-wire for Irreducible distal radius metaphyseal-diaphyseal Junction fractures in preadolescents: a new operative technique

BACKGROUND

Surgical treatment of irreducible distal radius diaphyseal- metaphyseal junction fractures involves difficulties as the fracture remains too proximal for K-wire fixation and too distal for the elastic stable intramedullary nail. Our study aims to present the clinical results of applying an elastic stable intramedullary nail with a poller K-wire to achieve both reduction and stable fixation.

PATIENTS AND METHODS

A retrospective analysis was performed on 26 patients who underwent ESIN with a poller K-wire for distal radius diaphyseal-metaphyseal region fracture. Reduction parameters such as residual angulation and alignment were evaluated on postoperative follow-up radiographs. Changes in angular and alignment parameters on follow-up radiographs were recorded. Wrist and forearm functions were evaluated at the last follow-up.

RESULT

There were 17 male and nine female patients with an average age of 10.9. The residual angulation in coronal and sagittal planes on immediate postoperative radiographs was 4.0 ± 1.62° and 3.0 ± 1.26°, respectively. The mean translation rate on immediate postoperative radiographs was 6.0 ± 1.98% and 5.0 ± 2.02% in the coronal and sagittal planes, respectively. No change was observed in translation rates in the last follow-ups. The mean angulation in the coronal and sagittal planes measured on 6th-week radiographs was 4.0 ± 1.72°and 3.0 ± 1.16°, respectively. No significant difference was observed in angular changes in the sagittal and coronal planes at the last follow-up (p > 0.05). No tendon injury or neurovascular injury was observed in any of the patients.

CONCLUSION

In the surgical treatment of pediatric DRDMJ fractures, applying ESIN with poller K-wire is an effective, safe, and novel method for achieving reduction and stable fixation.

Do Long-Segment Blocking Screws Increase the Stability of Intramedullary Nail Fixation in Proximal Tibia Fractures, Eliminating the "Bell-Clapper Effect?"

OBJECTIVES

To determine change in stiffness and horizontal translation of a geriatric extra-articular proximal tibia fracture model after intramedullary nailing with distal (long)-segment blocking screws versus proximal (short)-segment blocking screws.

METHODS

Unstable extra-articular proximal tibia fractures (OTA/AO 41-A3) were created in 12 geriatric cadaveric tibias. Intramedullary nails were locked with a standard construct (4 proximal screws and 2 distal screws). Specimens were then divided into 2 groups (6 matched pairs per group). Group 1 had a blocking screw placed lateral to the nail in the proximal segment (short segment). Group 2 had a blocking screw placed 1 cm distal to the fracture and medial to the nail (long segment). Specimens were then axially loaded and cycled to failure or cycle completion (50,000 cycles).

RESULTS

Long-segment blocking screws significantly decreased the amount of horizontal translation at the fracture site compared with short-segment screws (0.77 vs. 2.0 mm, P = 0.039). They also resulted in a greater trend towards greater baseline stiffness, (807.32 ± 216.95 N/mm vs. 583.12 ± 130.1 N/mm, P = 0.072). There was no difference in stiffness after cyclic loading or survival through 50,000 cycles between the long-segment and short-segment groups.

CONCLUSION

Long-segment blocking screws added to an intramedullary nail construct resulted in decreased horizontal translation at the fracture site compared with short-segment screws in this model of a geriatric proximal tibia fracture.

CLINICAL RELEVANCE

Blocking screws are commonly used to aid in fracture alignment during intramedullary nailing of proximal tibia fractures. Even when not required to attain or maintain alignment, the addition of a blocking screw in either the proximal or the distal (long) segment may help mitigate the "Bell-Clapper Effect" in geriatric patients.

Comparison of suprapatellar intramedullary nailing versus minimal invasive locked plating for proximal tibia fractures

PURPOSE

To compare the radiological alignment, union time, union rate, and complication rate between suprapatellar intramedullary nails and minimally invasive locking plate fixation in the treatment of proximal tibial fractures.

MATERIALS AND METHODS

We retrospectively analyzed 103 patients who underwent plate fixation (n = 50) or suprapatellar intramedullary nailing (n = 53) for proximal tibial fractures involving the meta-diaphyseal junction between November 2015 and October 2020 at our institution. The union rate, union time, radiologic alignments, and complications, such as malalignment, nonunion, and deep infection, were investigated.

RESULTS

The demographic data did not differ between the plate and suprapatellar intramedullary nail groups. The alignment of the coronal plane was 0.24 ± 3.19 in the plate group and - 0.49 ± 2.22 in the intramedullary nail group (p = 0.196). Sagittal plane alignment was - 0.29 ± 4.97 in the plate group and 0.24 ± 4.12 in the intramedullary nail group (p = 0.571), and coronal malalignment (p = 0.196), sagittal malalignment (p = 0.57), deep infection (p = 0.264), nonunion (p = 0.695), union time (p = 0.329), and final union rate (p = 0.699) were not significantly different between groups.

CONCLUSION

Compared with the minimally invasive locking compression plate group, the suprapatellar intramedullary nail group yielded comparable results in terms of radiological alignment and complications. Considering that proximal tibial fractures are associated with high-energy trauma and severe soft tissue damage, we believe that a suprapatellar intramedullary nail may be a good alternative.

LEVEL OF EVIDENCE

Level III.

In silico biomechanical analysis of poller screw-assisted small-diameter intramedullary nail in the treatment of distal tibial fractures

Objective: To evaluate the biomechanical effects of Poller screws (PS) combined with small-diameter intramedullary nails in the treatment of distal tibial fractures at different locations and on different planes. Methods: Nine finite element (FE) models were used to simulate the placement of the intramedullary nail (IMN) and the PS for distal tibial fractures. Structural stiffness and interfragmentary motion (IFM) through the fracture were investigated to assess the biomechanical effects of the PS. The allowable stress method was used to evaluate the safety of the construct. Results: With the axial load of 500 N, the mean axial stiffness of IMN group was 973.38 ± 95.65 N/mm, which was smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). The shear IFM of the IMN group was 2.10 ± 0.02 mm, which were smaller than that at positions A and B of the coronal group and sagittal group (p < 0.05). Under physiological load, the stresses of all internal fixation devices and the nail-bone interface were within a safe range. Conclusion: In the treatment of distal tibial fractures, placing the PS in the proximal fracture block can obtain better biomechanical performance. The IMN fixation system can obtain higher structural stiffness and reduce the IFM of the fracture end by adding PS.

Biomechanical comparison of intramedullary nail and plate osteosynthesis for extra-articular proximal tibial fractures with segmental bone defect

Purpose: Proximal tibial fractures are common, but the current available internal fixation strategies remain debatable, especially for comminuted fractures. This study aimed to compare the biomechanical stability of three internal fixation strategies for extra-articular comminuted proximal tibial fractures. Methods: A total of 90 synthetic tibiae models of simulated proximal tibial fractures with segmental bone defects were randomly divided into three groups: Single lateral plating (LP), double plating (DP) and intramedullary nailing (IN). Based on the different number of fixed screws, the above three groups were further divided into nine subgroups and subjected to axial compression, cyclic loading and static torsional testing. Results: The subgroup of intramedullary nailing with five proximal interlocking screws showed the highest axial stiffness of 384.36 ± 35.00 N/mm. The LP group obtained the lowest axial stiffness performance with a value of 96.59 ± 16.14 N/mm. As expected, the DP group offered significantly greater biomechanical stability than the LP group, with mean static axial stiffness and mean torque increasing by approximately 200% and 50%, respectively. According to static torsional experiments, the maximum torque of the DP subgroup was 3,308.32 ± 286.21 N mm, which outperformed all other groups in terms of torsional characteristics. Conclusion: Utilizing more than four distal screws did not provide improved biomechanical stability in the LP or DP groups, while a substantial increase in the biomechanical stability of DP was obtained when an additional medial plate was used. For the intramedullary nailing group, increasing the number of proximal interlocking screws could significantly improve biomechanical stability, and the intramedullary nailing with three proximal interlocking screws had similar static and cyclic stiffness as the DP group. The intramedullary nailing with five proximal screws had better axial stability, whereas DP had better torsional stability.

Fixation of Extra-articular Proximal Tibia Fractures: Biomechanical Comparison of Single and Dual Implant Constructs

OBJECTIVES

This biomechanical study seeks to define the relative effectiveness of contemporary single and dual implant constructs for fixation of an extra-articular proximal tibia fracture model.

METHODS

An extra-articular proximal tibia fracture model was created using synthetic tibias. Four constructs were tested. Constructs included (1) lateral locked plate (LLP), (2) intramedullary nail (IMN), (3) combined LLP and IMN (PN), and (4) LLP and medial locked plate. Specimens were axially loaded through the medial plateau to evaluate construct stiffness and the ability to resist varus collapse.

RESULTS

Dual implant constructs were stiffer than single implant constructs in this model. Although DP and PN were stiffer than IMN at all loads tested, the difference was notable only for DP at higher loads. Isolated LLP provided insufficient stability to be tested at higher loads.

CONCLUSION

Dual plate fixation provides the greatest resistance to varus collapse. In the clinical setting, consideration must be given to the fracture morphology, desired construct stiffness, and soft-tissue envelope in selecting the optimal construct to be used.

Combined Medial Plate and Intramedullary Nailing for the Fixation of Extra-Articular Proximal Tibial Fractures: a Biomechanics Study

Purpose: The extra-articular proximal tibial fractures continue to have high malunion rates despite development in intramedullary nailing (IMN) technology. Combined plate and IMN fixation can increase mechanical stability. The purpose of this study was to investigate combined plate and IMN for the treatment of extra-articular proximal tibial fracture using a biomechanical model.

Methods: A 10-mm defective osteotomy was created in the fourth-generation composite tibia to simulate extra-articular proximal tibial fractures (AO/OTA 41A2). The fractures were stabilized with IMN alone (IMN group), IMN with supplementary medial plate (M-IMN group), and IMN with supplementary lateral plate (L-IMN group). The biomechanical properties of each specimen were tested under axial compression loading, bending stress, and cyclic loading. The maximum displacement of the fragments and implant-bone construct failure was recorded.

Results: The maximum displacement of the M-IMN group was significantly less than either the L-IMN or IMN group in both axial compression loading and bending stress (p < 0.05 for both comparisons). All specimens in the three groups survived in 10,000 cyclic loading without hardware deformation. The maximum stiffness of failure was similar between the M-IMN and L-IMN groups, but the IMN group was statistically lower than either the L-IMN or the IMN group (p < 0.05).

Conclusion: The results indicated that combined medial plate and IMN fixation could effectively increase the mechanical stability of proximal tibial fractures.

Management of Pathologic Fractures around the Knee: Part 2-Proximal Tibia

Metastatic disease affecting the proximal tibia is rarer than disease affecting the femur; however, it presents unique challenges that the orthopaedic surgeon must address to ensure successful outcomes and return the patient to an ambulatory status. The essential workup for evaluating and treating these patients is addressed briefly in this review as a summary of the information is provided in part 1 of this series. Part 2 of this series will focus on the surgical treatment of these lesions, which can be complex and is not as well described in the literature. Procedures ranging from open reduction internal fixation with cement augmentation to complex endoprosthetic reconstruction can be employed to address proximal tibia metastatic disease. An awareness of these various treatment modalities allows the orthopaedic surgeon to plan the most effective operation for the patients under their care.

Excellent outcomes after double-locked plating in very low periprosthetic distal femoral fractures

INTRODUCTION

Very low periprosthetic distal femur fractures (PPDFFs) are rare injuries and often have a relatively high failure rate after single lateral locked plating. The double plating technique yields good outcomes in osteoporotic fractures of the distal femur. To date, there is limited information on double-locked plate fixation of very low PPDFFs. This study aimed to evaluate the outcomes and complications of surgically treated very low PPDFFs using double-locked plate fixation.

MATERIALS AND METHODS

Between January 2013 and December 2018, sixty-one consecutive patients with PPDFFs have been conducted. Only Su type III PPDFFs with double-locked plate fixation through a lateral minimally invasive approach and a medial subvastus approach to the distal femur were analyzed. Patients were encouraged to perform straight leg raising exercises and active knee motion on the second postoperative day. Assisted weight bearing from the early postoperative days was supported, and full weight-bearing was allowed after healing the fracture site. All patients were evaluated according to the time to union, limb alignment, range of knee motion, Knee Society Score, and presence of complications.

RESULTS

Twenty one patients (17 females and 4 males, mean age 76 years, range 56-90) were included in the study. There were 10 of 33-A1, 6 of 33-A2 and 5 of 33 A3 fractures, according to the AO classification. Of 21 patients, 20 achieved union at an average of 14 weeks postoperatively. Postoperative limb alignment was satisfactory in all cases, with an average mechanical distal lateral femur angle of 89° and average mechanical posterior distal femur angle of 86°. All patients recovered the knee joint motion similar to that of the contralateral side, and daily life pre-injury. The average knee and function scores were 94 and 89, respectively. There were one case of non-union and three cases of superficial wound infection, which resolved after intravenous antibiotic therapy.

CONCLUSIONS

Double locked plating showed excellent radiographic and functional outcomes with few complications in patients with very low PPDFFs. Based on these promising results, we propose the consideration of double-locked plate fixation in the treatment of very low PPDFFs.

Management and results in periprosthetic tibial fracture after total knee arthroplasty: Two-center 15-case retrospective series at 2 years' follow-up

INTRODUCTION

Periprosthetic tibial fracture after total knee arthroplasty (TKA) is rare, but jeopardizes implant survival. The main objective of the present study was to assess treatment efficacy, on the hypothesis that surgery provides good long-term results.

MATERIAL AND METHODS

A two-center retrospective study included 15 patients (6 male, 9 female: mean age, 71.8±10.2 years), managed between 1997 and 2017 for isolated tibial fracture after TKA. Patients were assessed clinically (IKS, inverted Oxford, Parker and SF-12 scores) and radiologically. Complications and revision surgeries were collated. Fractures were classified on the SoFCOT classification: 9 stable implants (4 type B1, 5 type C1), 4 periprosthetic osteolyses (1 type A3, 2 type B3, 1 type C3), and 2 loosenings (type A2). Treatments comprised: non-operative treatment (1 bed-ridden patient), 11 osteosyntheses for fracture on stable implant (2 standard plates, 7 locking plates, 2 intramedullary nailings), and 3 implant replacements by cemented long stem models for loosening.

RESULTS

Mean follow-up was 28 months (range, 12-120 months). Consolidation was achieved in 13 cases, at a mean 15 weeks. Complications comprised: 4 infections, 2 cases of secondary displacement, and 2 of non-union. Surgical revision was required in 8 cases, including 2 secondary implant revision procedures. Functional results were good in 10 cases. At last follow-up, mean Parker score was 7 (range, 4-8.5), Oxford score 32 (range, 16-39), and IKS score 150 (range, 85-167) with knee and function scores respectively 78 (range, 55-86) and 75 (range, 30-85).

CONCLUSION

Radiologic and clinical results were encouraging, but with impaired quality of life and a high rate of complications.

LEVEL OF EVIDENCE

IV, retrospective cohort 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.

Efficacy of a Modified Scoring System to Facilitate Surgical Decision-making for Diaphyseal Malignancies: When is Devitalized Tumor-bearing Autograft of Value?

Objectives

To evaluate the validity of a modified scoring system (MSS) for inferring the bony quality of tumor‐bearing diaphyses and predicting the risk of reconstructive failure after devitalized bone replantation (DBR).

Methods

In this retrospective cohort study, we reviewed the records of 30 patients surgically treated for diaphyseal malignancies between 1996 and 2015. There were 18 male and 12 female subjects; the average age was 34.0 ± 24.5 years (8–82 years). Tumor locations comprised the femur (21), the humerus (4), the tibia (3), the radius (1), and the fibula (1). Histological diagnoses included osteosarcoma (13), metastases (4), Ewing sarcoma (3), chondrosarcoma (3), malignant fibrohistiocytoma (2), periosteal osteosarcoma (1), Langerhans cell sarcoma (1), lymphoma (1), rhabdomyosarcoma (1), and malignant giant cell tumor (1). All primary tumors were rated as stage IIB. Twenty patients underwent DBR. Prosthetic procedures and segmental autografting/allografting were performed in 7 and 3 cases, respectively. MSS (comprising 5 elements: pain, tumor location, bone destruction, localized dimension, and longitudinal dimension) for each patient was calculated in accordance with their preoperative presentations. Outcome measurements included oncological results, outcomes of reconstructions, complications, and functional preservation, presented using the musculoskeletal tumor society (MSTS) scale.

Results

Follow up was available in 29 cases for an average duration of 61.0 ± 49.9 months (12–152 months). Infection occurred in 2 patients (6.9%), primary nonunion in 6 (27.3%), metastases in 9 (31.9%), recurrences in 4 (13.8%), and deaths in 7 (24.1%); 1 subject underwent amputation due to recurrence following endoprosthetic replacement (3.4%). In the DBR group, fractures occurred in 4 cases (21.1%) and nonunion in 5 (25%); internal fixation was related to nonunion (nails, 44.4% vs plates, 9.1%, P = 0.02). MSS was associated with fractures of devitalized autografts (11.0 ± 1.2 vs 8.3 ± 1.8, P = 0.01); the system was efficacious in predicting chances of fractures of these grafts (P = 0.02). MSS ≥ 10 (with false positive rate ≤ 6.7%) suggested increased fracture probability (≥22.7%) after DBR; therefore, 10 was considered a cutoff value.

Conclusions

Diaphyseal malignancies with MSS ≥10 may contraindicate DBR for increased chances of reconstructive failure. In this situation, alternative procedures are advisable. Further investigations are warranted to assess the efficacy of MSS in implying the validity of DBR for diaphyseal malignancies.

Novel implant for peri-prosthetic proximal tibia fractures

BACKGROUND

Repair of peri-prosthetic proximal tibia fractures is very challenging in patients with a total knee replacement or arthroplasty. The tibial component of the knee implant severely restricts the fixation points of the tibial implant to repair peri-prosthetic fractures. A novel implant has been designed with an extended flange over the anterior of tibial condyle to provide additional points of fixation, overcoming limitations of existing generic locking plates used for proximal tibia fractures. Furthermore, the screws fixed through the extended flange provide additional support to prevent the problem of subsidence of tibial component of knee implant.

METHODS

The design methodology involved extraction of bone data from CT scans into a flexible CAD format, implant design and structural evaluation and optimisation using FEM as well as prototype development and manufacture by selective laser melting 3D printing technology with Ti6Al4 V powder.

RESULTS

A prototype tibia implant was developed based on a patient-specific bone structure, which was regenerated from the CT images of patient's tibia. The design is described in detail and being applied to fit up to 80% of patients, for both left and right sides based on the average dimensions and shape of the bone structure from a wide range of CT images.

CONCLUSION

A novel tibial implant has been developed to repair peri-prosthetic proximal tibia fractures which overcomes significant constraints from the tibial component of existing knee implant.

Finite element analysis of intramedullary nailing and double locking plate for treating extra-articular proximal tibial fractures

Background

Proximal tibia fractures are one of the most familiar fractures. Surgical approaches are usually needed for anatomical reduction. However, no single treatment method has been widely established as the standard care. Our present study aims to compare the stress and stability of intramedullary nails (IMN) fixation and double locking plate (DLP) fixation in the treatment of extra-articular proximal tibial fractures.

Methods

A three-dimensional (3D) finite element model of the extra-articular proximal tibial fracture, whose 2-cm bone gap began 7 cm from the tibial plateau articular surface, was created fixed by different fixation implants. The axial compressive load on an adult knee during single-limb stance was imitated by an axial force of 2500 N with a distribution of 60% to the medial compartment, while the distal end was fixed effectively. The equivalent von Mises stress and displacement of the model was used as the output measures for analysis.

Results

The maximal equivalent von Mises stress value of the system in the IMN model was 293.23 MPa, which was higher comparing against that in the DLP fixation model (147.04 MPa). And the mean stress of the model in the IMN model (9.25 MPa) was higher than that of the DLP fixation system in terms of equivalent von Mises stress (EVMS) (P < 0.0001). The maximal value of displacement (sum) in the IMN system was 8.82 mm, which was lower than that in the DLP fixation system (9.48 mm).

Conclusions

This study demonstrated that the stability provided by the locking plate fixation system was superior to the intramedullary nails fixation system and served as an alternative fixation for the extra-articular proximal tibial fractures of young patients.

Intramedullary Nailing with a Suprapatellar Approach and Condylar Bolts for the Treatment of Bicondylar Fractures of the Tibial Plateau

Background

Bicondylar tibial plateau fractures have been treated with either plating or external fixation techniques, with conflicting results. A recently introduced technique involving the combined use of intramedullary nailing via a suprapatellar approach and condylar bolts could represent a new pathway toward better treatment of this severe injury.

Methods

The present report describes a retrospective and prospective study of all 17 patients (age range, 25 to 75 years) who were admitted under the author's care for the treatment of a closed, bicondylar tibial plateau fracture between 2013 and 2015. All patients consented to undergo fixation of the fracture with intramedullary nailing through a suprapatellar approach and with use of condylar bolts. The reconstructed articular surface was supported with freeze-dried allograft that had been previously soaked in concentrated bone marrow. The patients were followed at regular intervals, and the results were assessed with the Knee injury and Osteoarthritis Outcome Score (KOOS).

Results

All patients were followed for at least 1 year (average and standard deviation, 25.23 ± 8.95 months; range, 12 to 46 months). All fractures united clinically and radiographically between 10 and 22 weeks (average, 15.1 ± 2.91 weeks), with no instances of neurovascular complication, infection, or implant failure. One patient underwent early revision of the fixation because of unsatisfactory reduction of the articular surface, and 1 patient had secondary fracture displacement. One condylar bolt was removed after fracture healing because of irritation at the insertion site. However, all patients regained knee motion without physiotherapy and all were fully weight-bearing by the fifth postoperative month.

Conclusions

The short and intermediate-term results associated with the use of the proposed technique appear to be satisfactory. However, the effectiveness of the technique should be reassessed with long-term studies as well as comparative studies involving other fixation techniques.

Level of Evidence

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

Successful outcome with minimally invasive plate osteosynthesis for periprosthetic tibial fracture after total knee arthroplasty

INTRODUCTION

The incidence of periprosthetic fractures after total knee arthroplasty (TKA) is increasing, and treatment is becoming more necessary. In periprosthetic tibial fractures, the stem of the tibial component largely occupies the medullary canal of the proximal tibia, which limits the selection of implants. The purpose of this study was to evaluate the effectiveness of the minimally invasive plate osteosynthesis (MIPO) technique with locking plates for periprosthetic tibial fractures after TKA.

MATERIALS AND METHODS

Sixteen patients with periprosthetic tibial fracture after TKA were included. There were 6 type II and 10 type III fractures according to the Felix classification. Ten patients had fractures in the proximal metaphysis, and 6 in the diaphysis. MIPO using locking plates was performed on the medial side in 4 cases, the lateral side in 2 cases, and both in 10 cases. Radiographic results included time to union, alignment, and malunion. Clinical results included range of motion (ROM), functional activity data, Knee Society scores, and complications.

RESULTS

Fourteen of 16 fractures achieved union at 17.1 weeks (range, 14-24) postoperatively. There were 2 failures that required a secondary procedure. Except one for 1 case with varus malunion, all had acceptable alignment. Mean ROM at the final follow-up was 108.8° (range, 15-135°), and 15 patients recovered pre-injury knee joint activity. Mean knee and function scores were 88.9 (range, 77-100) and 83.3 (range, 60-100), respectively. Knees with fewer than 8 cortices giving purchase to screws in the proximal segment showed higher failure rates (P=0.025).

DISCUSSION

MIPO with locking plates can achieve satisfactory results for periprosthetic tibial fractures after TKA. Rigid fixation of the proximal segment may be necessary for successful outcome.

LEVEL OF EVIDENCE

IV.

Peri-implant failure in dual plating of the distal humerus-A biomechanical analysis with regard to screw and plate positioning

PURPOSE

The aim of this biomechanical study was to analyse the influence of plate and screw positioning on peri-implant failure in dual plate osteosynthesis. We hypothesized that screw positioning rather than plate configuration influences the risk of peri-implant fractures.

METHODS

Twenty macerated humerus specimens were available. 5 groups of 4 were built according to specimen size. Locking dual plates (Medartis, Switzerland) were randomly applied to the distal humerus of the specimens in 4 types of configuration: Bending forces were applied using a universal testing machine until peri-implant fracture occurred.

RESULTS

Mean failure loads for respective configuration types were as follows: P1: 428.7 (±84.2) N, A1: 410.0 (±54.7) N, A0: 297.8 (±48.3) N, P0: 261.0 (±65.0) N. Configurations with positioning of the most proximal screws at different levels (P1, A1) reached significantly higher failure loads when compared to screw placement at the same level (P0, A0) (0.01≤p≤0.03). Altering the plate configuration did not significantly influence failure loads (0.34≤p≤0.58).

CONCLUSIONS

The results of this study suggest that placement of the most proximal screws rather than the configuration of the plates is critical regarding the predetermined risk of peri-implant failure in dual plate osteosynthesis of the distal humerus. Varying levels of the outermost screws of corresponding double plates seem to be crucial to avoid complications related to the osteosynthesis.