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

IntroductionLateral 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 methodsA 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.ResultsAll 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).ConclusionsAdditional 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.     

Influence of fragment volume on stability of 3-part intertrochanteric fracture of the femur: a biomechanical study

Complex unstable fracture can complicate the treatment outcome of intertrochanteric fracture of the femur, and fixation failure after surgery is a significant problem in elderly patients. This study aimed to evaluate the effect of fracture geometry on the stability of 3-part intertrochanteric fracture by assessing the fragment size. Four categories (group I: large greater trochanter, small lesser trochanter; group II: large greater trochanter, large lesser trochanter; group III: small greater trochanter, small lesser trochanter; and group IV: small greater trochanter, large lesser trochanter) of a 3-part intertrochanteric fracture model were designed. Three-dimensional computer tomography scanning was performed to measure the volume of each fragment. After fixation with a dynamic hip screw, a cyclic loading study was conducted using a servohydraulic machine. There was a significant difference in fatigue failure between each group. After all specimens had endured 10,000 cycles with a range of loads (100–1,000 N), the mean number of cycles until fixation failure with a load range of 200–2,000 N was 1,467.67 ± 199.92 in group I; 579 ± 93.48, group II; 398.17 ± 37.92, group III; and 268.67 ± 19.92, group IV. Fixation strength was approximately 5 times greater in group I than in group IV. In 3-part intertrochanteric fracture, the sizes of the greater and lesser trochanteric fragments are important factors for determining stability after dynamic compression screw fixation. This study supports our hypothesis that the volumetric ratio of ?lesser trochanter/?greater trochanter can be used to predict stability of intertrochanteric femoral fracture.     

Hybrid locked medial plating in dual plate fixation optimizes the healing of comminuted distal femur fractures: A retrospective cohort study

ObjectivesDual plate fixation has been reported to be effective in the treatment of comminuted distal femur fractures (DFFs). However, optimized use of the medial plate and screws is less studied. This study aimed to evaluate the effect of a hybrid configuration of the medial plate in dual plate fixation of comminuted DFFs in promoting fracture healing.Materials and methodsWe retrospectively analyzed 62 patients with comminuted DFFs (AO/OTA 33-A3/33-C2/33-C3) from January 2015 to March 2020, who were either fixed with lateral locked plating augmented with hybrid locked medial plating (LP-HLMP, n = 32) or lateral locked plating (LLP, n = 30) alone. Specifically, compression screws were applied in the middle of the medial plate and flanked by locking ones at both ends. Baseline characteristics, radiological and clinical outcomes were reviewed and analyzed. Multivariate logistic regression analysis was used to identify predictive factors for early fracture healing, and risk factors for delayed union/nonunion.ResultsDemographics including age, gender, smoking, diabetes, and injury mechanism were comparable between the two groups. Reduction quality was better in the LP-HLMP group (p < 0.001). Although the LP-HLMP group experienced longer duration of surgery (125 min vs. 100 min, p < 0.001), sign of healing at 3 months was more obvious in this group (75%, 24/32 vs. 30%, 9/30; p < 0.001). The LP-HLMP group also presented with higher union rate (93.8%, 30/32 vs. 56.7%, 17/30; p = 0.001) and lower reoperation rate (0%, 0/32 vs. 13.3%, 4/30; p = 0.049). Kolment score showed no statistical significance between the two groups. Multivariate analysis revealed that younger age (< 60 years) (OR 5.99, 95%CI 1.16 – 31.03; p = 0.001) and LP-HLMP fixation (OR 45.90, 95% CI 4.78 – 440.56; p = 0.001) predict early healing; while smoking (OR 17.80, 95% CI 2.41 – 131.49; p = 0.01) and fracture translation (OR 3.49, 95% CI 1.46 – 8.32; p = 0.01) were identified as risk factors for delayed union/nonunion.ConclusionHybrid locked medial plating in this study favors the healing of comminuted DFFs and reduces reoperation. Additionally, smoking and suboptimal reduction (translation) predict delayed union/nonunion.     

Effect of wrist position on distal radioulnar joint stability: A biomechanical study

We investigated distal radioulnar joint (DRUJ) stability in different wrist positions and examined the relative contribution of each ligamentous component of the triangular fibrocartilage complex (TFCC) to DRUJ stability. We used nine fresh‐frozen cadavers. The humerus and ulna were fixed at 90° elbow flexion. The radiocarpal unit was translated relative to the ulna in dorsopalmar directions with the wrist in five positions. Displacement of the unit was measured by an electromagnetic tracking device. Magnitudes of displacement were compared between different wrist positions in various sectioning stages: ulnocarpal ligament (UCL) sectioning, radioulnar ligaments (RUL) sectioning, and extensor carpi ulnaris (ECU) floor sectioning. Wrist position and sectioning stage significantly influenced the displacement. In intact wrists, the displacement in wrist extension was significantly lower than that in neutral. However, after UCL sectioning, there were no longer any significant differences. After RUL sectioning, the displacement in radial deviation was significantly lower than that in neutral. Following ECU floor sectioning, there were no longer any significant differences. Thus, in intact wrists, DRUJ stability in wrist extension is likely due to tightening of the UCL. After complete RUL sectioning, DRUJ is stabilized in radial deviation due to tightening of the ECU floor. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1247–1251, 2014.     

Locked plate fixation of the comminuted distal fibula: a biomechanical study

Background

The purpose of this study was to compare the biomechanical properties of locked versus nonlocked lateral fibular bridge plating of comminuted, unstable ankle fractures in a mode of catastrophic failure.

Methods

We created comminuted Weber C fractures in 8 paired limbs from fresh cadavers. Fractures were plated with either standard or locked one-third tubular bridge plating techniques. Specimens were biomechanically evaluated by external rotation to failure while subjected to a compressive load approximating body weight. We measured the angle to failure, torque to failure, energy to failure and construct stiffness.

Results

There was no significant difference in construct stiffness or other biomechanical properties between locked and standard one-third tubular plating techniques.

Conclusion

We found no difference in biomechanical properties between locked and standard bridge plating of a comminuted Weber C fibular fracture in a model of catastrophic failure. It is likely that augmentation of fixation with K-wires or trans-tibial screws provides a construct superior to locked bridge plating alone. Further biomechanical and clinical analysis is required to improve understanding of the role of locked plating in ankle fractures and in osteoporotic bone.     

A double-plating approach to distal femur fracture: A clinical study

BackgroundLocked plating is one of the latest innovative options for treating supracondylar femur fractures with relatively low failure rates. Single lateral plating was often found to have a relative higher failure rate. No clinical studies of double-plating distal femur fixation have thus far been reported. The aim of this study is to present our clinical experience with this surgical approach.Patients and methodsThirty-two patients (26 females and 6 males, mean age 76 years, range 44–101) were included in the study. Eight of them patients had a periprosthetic stable implant fracture and two patients were treated for a nonunion.ResultsAll fractures, excluding one that needed bone grafting and one refracture, healed within 12 weeks. One patient needed bone grafting for delayed union and one patient needed fixation exchange due to femur re-fracture at the site of the most proximal screw. Two patients developed superficial wound infection and one patient required medial plate removal after union due to deep infection.ConclusionsBased on these promising results, we propose that the double-plating technique should be considered in the surgeon’s armamentarium for the treatment of supracondylar femur fractures, particularly in patients with poor bone quality, comminuted fractures and very low periprosthetic fractures.     

A biomechanical study comparing proximal femur nail and proximal femur locking compression plate in fixation of reverse oblique proximal femur fractures

BackgroundThe reverse oblique trochanteric fractures are common fractures and its treatment poses a challenge. The purpose of this study was to compare the biomechanical parameters of the construct using proximal femoral nail (PFN) and proximal femoral locking compression plates (PFLCP) in these fractures using cadaveric specimens.Materials and MethodsTwenty freshly harvested cadaveric femoral specimens were randomly assigned to two groups after measuring bone mineral density, ten of which were implanted with PFN and the other ten with PFLCP. The constructs were made unstable to simulate reverse oblique trochanteric fracture (AO type 31A3.3) by removing a standard size posteromedial wedge. These constructs were tested in a computer controlled cyclic compressive loading with 200 kg at a frequency of 1 cycle/s (1 Hz) and test was observed for 50,000 cycles or until implant failure, whichever occurred earlier. Peak displacements were measured and analysis was done to determine axial stiffness and subsidence in axial loading.ResultsAll the specimens in PFN group completed 50,000 cycles and in PFLCP group, seven specimens completed 50,000 cycles. Average subsidence in PFN group was 1.24 ± 0.22 mm and in PFLCP group was 1.48 ± 0.38 mm. The average stiffness of PFN group (72.6 ± 6.8 N/mm) was significantly higher than of PFLCP group (62.4 ± 4.9 N/mm) (P = 0.04). The average number of cycles sustained by PFLCP was 46634 and for PFN group was 50,000 (P = 0.06).ConclusionThe PFN is biomechanically superior to PFLCP in terms of axial stiffness, subsidence and number of specimens failed for the fixation of reverse oblique trochanteric fractures of femur.     

Ulnar shortening effect on distal radioulnar joint stability: a biomechanical study

PURPOSE: The ulnar-shortening procedure has been adopted widely to reduce pressure between the ulna and ulnar carpus in ulnocarpal abutment syndrome. The hammock-like structure of the triangular fibrocartilage complex (TFCC), which supports and connects the ulnocarpal and distal radioulnar joint (DRUJ), variably is torn in this condition. The degree to which the torn TFCC may be tensioned to restabilize the DRUJ with ulnar recession is uncertain. This study examined changes in the stabilizing effect of the ulnar-shortening procedure in several TFCC tear conditions. METHODS: Six fresh-frozen cadaver arms amputated at the midportion of the humerus were used. The skin, muscles, and capsuloligamentous structures below the elbow all were preserved. The ulna and humerus were affixed firmly to a custom mount that allowed 60 degrees of forearm rotation. An external fixator was attached to the distal ulna leaving space for a 10-mm resection of the ulna to allow progressive shortening. The radius was attached to a materials testing machine. The load-displacement curves were obtained while translating the distal radius dorsally or palmarly with respect to the ulna at 1.25 mm/s. Stiffness in dorsopalmar displacement was recorded at 1-mm intervals through 6 mm of length. These measurements then were compared with controls (0 mm shortening of the intact specimens) at 60 degrees pronation, neutral position, and 60 degrees supination. The tests then were repeated after sectioning either the dorsal or palmar portion of the radioulnar ligament (RUL) and then after complete sectioning of the RUL. Each portion was sectioned at its attachment to the ulnar fovea. RESULTS: The stiffness of the DRUJ increased significantly in all 3 rotatory positions after shortening the ulna. A shortening of 6 mm resulted in a 26% to 44% increase in DRUJ stiffness. The stiffness decreased after partial sectioning of the RUL but increased with further ulnar shortening in all 3 positions. The DRUJ stiffness with the partially sectioned RUL after a shortening of 3 to 6 mm was as large as that of the intact specimens. The stiffness of the DRUJ after the complete section of the RUL was significantly smaller than that of the intact specimens even after shortening of 6 mm. CONCLUSIONS: The ulnar-shortening procedure can stabilize the DRUJ by increasing intrastructural tension of the TFCC, only when the RUL is attached totally or partially to the ulnar fovea. If the RUL is avulsed completely then stability of the DRUJ no longer is obtained by the ulnar-shortening procedure.     

Enhancing fixation strength in periprosthetic femur fractures by orthogonal plating—A biomechanical study

Orthogonal plate osteosynthesis enhances fixation stability in periprosthetic femur fractures. Another option are locking attachment plates (LAP) allowing bicortical locking screw placement lateral to the prosthesis stem. Stability of lateral plate osteosynthesis with two LAP (2LAP) was compared to anterolateral orthogonal plate osteosynthesis (OP) with one LAP in a periprosthetic femur fracture model. In six pairs of fresh frozen human femora with cemented Charnley hip prosthesis, a transverse osteotomy was set distal to the tip of the prosthesis simulating a Vancouver type B1 fracture. Each pair was instrumented using a plate tensioner with either one lateral plate and two LAP, or two orthogonal anterolateral plates and one LAP. Stiffness was determined in a four‐point‐bending test prior to cyclic testing (2Hz) with physiologic profile and progressively increasing load up to catastrophic construct failure. Paired t‐test and Wilcoxon‐signed‐rank test were used for statistical evaluation at a level of significance p = 0.05. The OP construct exhibited a significantly higher number of cycles and load to failure (39,627 cycles ± 4,056; 4,463 N ± 906) compared to the 2LAP construct (32,927 cycles ± 3,487; 3,793 N ± 849), p < 0.01. Mediolateral bending and torsional stiffness of the OP (1610 N/mm ± 249; 16.9 Nm/mm ± 6.3) were significantly higher compared to 2 LAP (1077 N/mm ± 189; 12.1 Nm/mm ± 3.9), p = 0.03 for both comparisons. Orthogonal plate osteosynthesis is a valuable option in periprosthetic fracture surgery, offering increased stability compared to a single lateral plate fixed with two LAP. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:591–596, 2016.     

A biomechanical study of wire fixation

A biomechanical study of wire fixation was performed using 18-gauge stainless steel wire on an Instron universal testing machine. Six groups of wires were tested--an intact piece of wire (control), a wire bent to a right angle five times, a simple knot, a square knot, a loop knot and a twist knot. The tensile load-to-failure value for each wire was recorded. The intact wire broke at a mean load of 67 kg. The wires with the bend, the simple knot and the square knot all broke at similar loads. Those wires with a knot broke at the knot. The loop and the twist knots pulled apart at much lower loads. These results indicate that bending the wire does not weaken it substantially, but kinking may initiate the site of breakage. The square knot is the strongest knot; the loop and twist knots are not recommended if the wire is to be under tension.     

Differences in biomechanical stability of femur fracture fixation when using titanium nails of increasing diameter

Purpose The purpose of this study was to compare the biomechanical stability generated when utilizing increasing sizes of titanium (Ti) flexible nails for fixation of simulated comminuted femur fractures. Methods Five synthetic adolescent-sized femur models were reamed to create a 9-mm canal. A 2-cm section was removed in the mid-diaphysis to simulate comminution. Each femur was first stabilized with bilateral, retrograde 3.0-mm titanium elastic nails. Femurs were tested in axial rotation and axial compression. The constructs were removed, and femurs were re-nailed with 3.5-mm nails. Identical testing was conducted. These nails were then removed, and femurs were re-nailed with 4.0-mm nails. This provided data on “canal fill” representing 67, 78 and 89% of the reamed canal diameter. Data for axial rotation (degrees) and failure load (N) required to produce 5 mm of fracture shortening were analyzed with a one-way ANOVA (P < 0.05) and a Tukey’s post-hoc test for multiple comparisons. Results For axial rotation, there were statistically significant improvements in rotational control for each increase in nail size. For axial stability, each increase in nail size resulted in increased axial failure loads to 5 mm, although these data were not statistically different. A specific comparison between 3.0- and 3.5-mm nails for compressive stability found significantly greater stability afforded by using 3.5-mm nails. Conclusions Data from this study demonstrate that increasing the amount of canal fill provides significant improvements in rotational control. The largest improvement was seen when increasing from 3.0- to 3.5-mm nails. While increasing the nail size from 3.5 to 4.0 mm again provided greater stability, larger nails may be more difficult to insert. Thus, increasing the nail size for femoral fracture fixation should be considered after measuring the diameter of the canal and evaluating the potential difficulty of insertion as well as specific demands of the fracture pattern.     

Temporary hemiepiphysiodesis of the distal medial femur: MPFL in danger

Introduction

Temporary hemiepiphysiodesis (TH) with plate fixation is a well-accepted and common treatment for correcting leg malalignment in skeletally immature patients. The purpose of this study was to investigate any soft tissue damage caused during TH at the distal medial femur with a plate and two screws. We hypothesized that correct plate placement can affect the integrity of the medial stabilizing structures of the knee, especially the medial patellofemoral ligament (MPFL), the medial collateral ligament (MCL) or result in arthrotomy of the knee joint itself.

Materials and methods

In eight cadaveric knees of five adult humans a TH was performed with a plate and two cancellous screws at the distal medial femur using a standardized surgical technique. Subsequently the medial capsular and ligamentous structures were systematically exposed and assessed. Capsular and synovial tissue was also inspected for impingement by the plate or screws.

Results

In all knees the MPFL was present. In two specimens the MPFL was intact and the plate was lying over the dorsal part of the MPFL close to the MCL. The MPFL was completely cut in two cases in the central part of the ligament. In four cases the MPFL was partially dissected or perforated by a screw and fixed to the femur by the plate. The MCL was intact and not impinged by the implant in any case. In total four of eight knees the capsule was transected or perforated by a screw or by a part of the plate, resulting in intraarticular implant placement.

Conclusions

Standard plate placement during TH on the distal medial femur frequently leads to damage to the MPFL, impingement of the MPFL, the capsular and synovial tissues or exposure of the knee joint.     

A biomechanical study of distal radial fractures

In an attempt to explain disability in dorsally angulated malunited distal radius fractures, an experiment was designed to evaluate load patterns about the wrist with varying degrees of dorsal angulation of the distal radius. Osteotomies were made in the distal radius of fresh cadaver arms after a modified external fixator was applied to the radius and load cells applied to the proximal radius and ulna. Pressure-sensitive film was inserted into the radioulnar carpal joint. After a predetermined load was applied to the wrist it was found that the load through the ulna increased from 21% to 67% of the total load as the angulation of the distal radial fragment increased from 10 degrees of palmar tilt to 45 degrees of dorsal tilt. The pressure distribution on the ulnar and radial articular surfaces changed in position and became more concentrated as dorsal angulation increased.     

Plate fixation adds stability to two-level anterior fusion in the cervical spine: a randomized study using radiostereometry

This study evaluated whether addition of a cervical spine locking plate (CSLP) in two-level disc fusions improved the postoperative stability and reduced the time to healing. Radiostereometric analysis was used to obtain precise recordings of the three-dimensional motion between the fused vertebrae. Eighteen consecutive patients were operated on with excision of two adjacent cervical discs and anterior horseshoe grafting with autologous bone (Smith Robinson technique). Nine patients were randomized to stabilization with autologous bone grafting and CSLP plate fixation and nine patients to grafting without fixation. Clinical symptoms in terms of pain in the neck and the arm were analysed preoperatively and after 1 year using a visual analogue scale (VAS). The patients operated without a plate displayed increased rotations around the transverse axis, corresponding to the development of a kyphosis [mean value no plate/plate 14.4°/0.8° (repeated measure ANOVA: P < 0.01)]. The mean compression was 3.2 mm larger in patients operated without a plate (repeated measure ANOVA: P < 0.01). Patients operated without a plate had more arm pain at the 1-year follow up (P < 0.05, Mann-Whitney U test). The VAS score for neck pain did not differ significantly between the two groups. Plate fixation could not be demonstrated to increase the healing rate, promote more rapid fusion or influence the frequency of graft complications. Received: 17 September 1997 Revised: 21 February 1998 Accepted: 2 March 1998     

Volar fixation for dorsally angulated extra-articular fractures of the distal radius: a biomechanical study

PURPOSE: To compare the biomechanical properties of 10 volar plate-fixation designs in 2 fracture models (dorsal wedge osteotomy, segmental resection osteotomy models). METHODS: Forty-eight radiuses were used in this study including 8 pairs. In 40 specimens a 15-mm dorsally based wedge osteotomy was performed and the volar cortex was fractured manually. They were arranged into 10 fixation groups with 5 different fixation designs (test 1). In the contralateral specimens of 8 paired radiuses a 10-mm segment of bone was excised (test 2). Four of the 10 fixation systems were chosen for these specimens. Cadaver hands and the proximal radiuses were potted in polymethylmethacrylate and tested with a servohydraulic materials testing machine with 300 N of axial compression load at 1 N/s initially and after each 1,000 cycles up to 5,000 cycles. After cyclic loading the specimens were loaded to failure in axial compression at 2 mm/min. The stiffness, failure peak load, and failure mode of each specimen were recorded. RESULTS: In test 1 in the wedge osteotomy specimens the T plate was the stiffest and the Synthes titanium plate was the least stiff; however, all specimens completed the 5,000 cycles of loading with no failures. There was no significant difference between the 10 fixation groups in failure peak load and only 7 of 40 failed at the distal portion of the hardware in the final load to failure testing. In test 2 the resection osteotomy specimens were less stiff and failed at a lower failure peak load compared with the wedge osteotomy specimens. Failure at the distal portion of the fixation system was seen in 7 of 8 specimens; nonlocking screws loosened and tines compressed the surrounding bone, resulting in tine-hole enlargement. CONCLUSIONS: All of the plate-fixation systems delivered sufficient stability to permit the simulated postoperative regimen of 1 week of immobilization followed by 5 weeks of early mobilization until expected union at 6 weeks after surgery. Based on these results a preferable volar fixation system would appear to benefit from the following: (1) sufficient plate strength to support the distal fragment from the volar side, (2) a locking system with sufficient strength to remain locked during the healing process, and (3) a distal design that does not affect the bone adversely. The anatomic reduction of the volar cortex in the wedge osteotomy specimens added stability to the construct.