Biomechanical Comparison of a Locking Plate with Intraplate Compression Screw Versus Locking Plate with Plantar Interfragmentary Screw for Lapidus Arthrodesis: A Cadaveric Study

Lapidus arthrodesis (first metatarsal cuneiform arthrodesis) has become an accepted procedure for hallux abducto valgus. Several variations of fixation have been described. Earlier weightbearing postoperatively has been one reported benefit of using locking plates for fixation. Additionally, studies have demonstrated that fixation placed on the plantar or tension side of the arthrodesis increases the biomechanical advantage. We performed a biomechanical cadaveric study of the Lapidus procedure, comparing a previously reported technique using a low profile locking plate with an intraplate compression screw versus the same locking plate with a plantar interfragmentary screw (PIFS) placed on the tension side of the arthrodesis in 10 fresh, paired, cadaver limbs. The mean ultimate load of the plate with a PIFS was 383.2 ± 211.5 N, and the mean ultimate load of the plate with an intraplate compression screw was 205.5 ± 97.2 N. The mean ultimate load of the LPS Lapidus plate with a PIFS was statistically greater (p = .027) than that with the plate intraplate compression screw. Our results indicated that changing the orientation of the compression screw to a PIFS significantly increased the stability of the Lapidus arthrodesis fixation construct. The modified construct with the PIFS might decrease the incidence of nonunion and, ultimately, allow patients to bear weight faster postoperatively.     

Biomechanical Comparison of Intramedullary Beaming and Plantar Plating Methods for Stabilizing the Medial Column of the Foot: An In Vitro Study

Charcot neuroarthropathy often results in a rocker-bottom foot deformity, which leads to ulceration, infection, and amputation. Surgical techniques to reconstruct the medial column include intramedullary beaming and plantar plating, with disagreement regarding which approach provides a stronger construct with superior stability and fixation. The objective of the present cadaveric study was to compare the construct rigidity and strength of beaming and plantar plating of the medial column of 5 paired bilateral feet. Cannulated titanium beams and plates were implanted in the right and left feet, respectively. The specimens underwent interval testing to generate load-displacement and load-strain curves, cyclic loading at low loads, and then were loaded to failure. The beamed and plated specimens had statistically similar stiffness (p?=?.80) with a mean of 11.1?±?3.9 N/mm and 11.3?±?5.9 N/mm, respectively. The beamed and plated specimens had a statistically similar mean strain of ?164?±?75.1 µε and ?208?±?87.8 µε on the dorsal (p?=?.45) and 92?±?90.4 µε and 221?±?100.5 µε on the plantar (p?=?.08) surfaces of the first metatarsal. Three beamed specimens failed from talus fracture (60%), and 2 beams plastically deformed (40%). Two plated specimens failed from talus fracture (40%), and 3 experienced screw pullout (60%). The beamed and plated specimens withstood a mean load to failure of 234?±?111.4 N and 140?±?68.9 N, respectively, with the difference statistically significant (p?=?.04). Overall, beaming was more robust than plantar plating, because it was less sensitive to specimen size and bone quality.     

The Lapidus Arthrodesis: Examining the Effect of the Metatarsal Base Transfixion Screw

The modified Lapidus bunionectomy is a useful and highly powerful procedure for correcting hallux abducto valgus. Traditionally reserved for “severe” deformities, this procedure has seen a recent resurgence in the podiatric community for its unique ability to achieve tri-planar correction of this challenging deformity. Although this procedure has been extensively studied in both biomechanical labs and the clinical arenas, no clear consensus has been achieved regarding optimal fixation for this thought-provoking procedure. The current study examined the differences in strength between commercially available 5-hole locking plates with interfragmentary compression vs a crossed-screw with a third “transfixation” screw construct in a controlled setting. Ten fresh-frozen cadaveric match pair limbs (20 total limbs) were used to complete this study. Ten limbs were randomly assigned to a 3-screw construct. The other 10 contralateral limbs were assigned to a commercially available 5-hole locking plate (5 stainless steel and 5 titanium alloy) with an interfragmentary lag screw construct. The first rays were then isolated and potted into a 4-point bending device. The specimens were loaded to failure in a servohydraulic load frame at a controlled rate. Failure was defined as catastrophic or 3 mm of plantar gapping at the arthrodesis site. The mean maximal load to failure was 310.9 ± 109.4 N for the 3-screw construct. The mean maximal load to failure for the locking plate constructs was 264.1 ± 100.9 N. This difference was not statistically significant (p = .328). These results suggest that a 3-screw construct for Lapidus arthrodesis is as strong as commercially available locking plate constructs.     

Fixation of Lapidus Arthrodesis with a Plantar Interfragmentary Screw and Medial Locking Plate: A Report of 88 Cases

Lapidus arthrodesis is a powerful procedure that can be used to correct pathologic features within the forefoot or midfoot. Many different methods of fixation for this procedure have been reported. The use of plating constructs has been shown to provide increased stability compared with screw-only constructs. The technique we have described consists of a plantar to dorsal retrograde lag screw across the arthrodesis site, coupled with a low-profile medial locking plate. A total of 88 consecutive patients were treated with this modification of the Lapidus procedure by 2 surgeons and were retrospectively evaluated. All patients followed an early postoperative weightbearing protocol. Patient age, gender, follow-up duration, interval to weightbearing and radiographic fusion, preoperative and postoperative intermetatarsal angle, hardware removal, preoperative and postoperative American Orthopaedic Foot and Ankle Society midfoot scores, and adjunct procedures were analyzed. The mean follow-up period was 16.76 ± 5.9 (range 12 to 36) months, and all healed fusions demonstrated radiographic union at a mean of 51 ± 19.1 (range 40 to 89) days. The patients were treated with weightbearing starting a mean of 10.90 ± 4.1 (range 5 to 28) days postoperatively. Complications included 15 patients (17%) requiring hardware removal, 2 cases (2%) of hallux varus, 6 cases (7%) of radiographic recurrent hallux valgus, and 2 patients (2%) with first metatarsocuneiform nonunion. The results of the present study have demonstrated that plantar lag screw fixation with medial locking plate augmentation for Lapidus arthrodesis allows for early weightbearing with satisfactory outcomes, improved clinical and radiographic alignment, and improved American Orthopaedic Foot and Ankle Society scores.     

Anatomical study of Lapidus arthrodesis using two different plantar plate systems

BackgroundFirst tarsometatarsal arthrodesis (modified Lapidus procedure) constitutes a sufficient treatment for moderate to severe hallux valgus deformity and first ray instability. The plantar plate arthrodesis was shown to provide superior mechanical stability and less postoperative complications than screw fixation or dorsal plating. Nevertheless, the in-brought hardware may cause irritation of the tibialis anterior or peroneus longus tendon requiring explantation of the material in some cases.The purpose of this study was to investigate the potential of tendon irritation after plantar first tarsometatarsal joint arthrodesis in a cadaver study.MethodsPlantar plate arthrodesis was performed as in real surgery on twelve pairs of fresh frozen cadaveric feet. Two different plate systems were randomly allocated to each pair of feet. After plate fixation careful dissection of the feet followed to analyze potential tendon irritation and to determine a “safe zone” for plantar plate placement.ResultsA “safe zone” between the insertion sties of tibialis anterior and peroneus longus tendon was found and proven to be sufficiently exposed using a standard medio-plantar approach. Both plates were fixed in this zone without compromising central tendon parts. Peripheral tendon parts were irritated in 42% using Darco Plantar Lapidus Plating System® (Wright Medical, Memphis, TN) and in 8% using the Plantar Lapidus Plate® (Arthrex, Naples, FL). Bending of the anatomically preshaped plates is often necessary to ensure optimal fit on the bone surface.ConclusionsModified Lapidus procedure with plantar plating of the first tarsometatarsal joint can be performed safely without compromising central tendon parts via standard medio-plantar approach.Level of clinical evidence5, Cadaver Study.     

Angulated locking plate in periprosthetic proximal femur fractures: biomechanical testing of a new prototype plate

Introduction

To improve proximal plate fixation of periprosthetic femur fractures, a prototype locking plate with proximal posterior angulated screw positioning was developed and biomechanically tested.

Methods

Twelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were fixed proximally with monocortical (LCP) or angulated bicortical (A-LCP) head-locking screws. Biomechanical testing comprised quasi-static axial bending and torsion and cyclic axial loading until catastrophic failure with motion tracking.

Results

Axial bending and torsional stiffness of the A-LCP construct were (1,633?N/mm?±?548 standard deviation (SD); 0.75?Nm/deg?±?0.23?SD) at the beginning and (1,368?N/mm?±?650?SD; 0.67?Nm/deg?±?0.25?SD) after 10,000 cycles compared to the LCP construct (1,402?N/mm?±?272?SD; 0.54?Nm/deg?±?0.19?SD) at the beginning and (1,029?N/mm?±?387?SD; 0.45?Nm/deg?±?0.15) after 10,000 cycles. Relative movements for medial bending and axial translation differed significantly between the constructs after 5,000 cycles (A-LCP 2.09°?±?0.57?SD; LCP 5.02°?±?4.04?SD; p?=?0.02; A-LCP 1.25?mm?±?0.33?SD; LCP 2.81?mm?±?2.32?SD; p?=?0.02) and after 15,000 cycles (A-LCP 2.96°?±?0.70; LCP 6.52°?±?2.31; p?=?0.01; A-LCP 1.68?mm?±?0.32; LCP 3.14?mm?±?0.68; p?=?0.01). Cycles to failure (criterion 2?mm axial translation) differed significantly between A-LCP (15,500?±?2,828?SD) and LCP construct (5,417?±?7,236?SD), p?=?0.03.

Conclusion

Bicortical angulated screw positioning showed less interfragmentary osteotomy movement and improves osteosynthesis in periprosthetic fractures.     

Union Rates With the Use of Structural Allograft in Lapidus Arthrodesis: A Comparison Between Two Fixation Constructs

Although structural allograft has been previously described as acceptable practice for reconstructive foot and ankle surgery, results for an allograft bone wedge in Lapidus arthrodesis are unknown. Additionally, there is no consensus on the superiority of a single fixation construct in Lapidus cases. Our objective was (1) to report union rates for Lapidus arthrodesis with and without the use of an allograft bone wedge and (2) to determine if fixation construct impacts rates of union when using structural allograft. A review was performed for Lapidus cases with fixation constructs of 2 crossed compression screws (CS) and a medial locking plate with single transarticular screw (MPS), both with and without use of an allograft bone wedge. Inclusion required a CT scan to evaluate bony union. There was no significant difference in union rates (p = .41) between the use (90%) and the nonuse (97%) of an allograft bone wedge. Union rates were significantly different (p = .04) when comparing CS fixation (85%) and MPS fixation (98%). The comparative results between the fixation constructs highlight the importance of compression across the arthrodesis site as part of a robust fixation construct. Our findings demonstrate that the use of an allograft bone wedge in Lapidus arthrodesis may mitigate complications due to metatarsal shortening while providing satisfactory rates of union.     

A novel suture anchor constructed of cortical bone for rotator cuff repair: a biomechanical study on sheep humerus specimens

Purpose

The aim of this study was to evaluate biomechanical properties of a new type of suture anchors constructed of human cortical allograft bone and compare it with the similar standard titanium screw anchor for rotator cuff tears in sheep humerus model.

Methods

Twenty-four paired sheep humeri were harvested from 12 male sheep aged 18 months. Specimens were divided into cortical bone anchor group and titanium screw anchor group. The anchors loaded with two sutures were placed at the footprint of infraspinatus tendon. Cyclic loading test was performed from 10 to 60 N at 1 Hz for 500 cycles and followed by a load-to-failure test at 33 mm/sec. A paired t-test was used to compare the biomechanical properties of the anchors of each type.

Results

No anchors failed during the cyclic phase, and the cortical bone anchors were all pulled out intact. The cyclic displacement of the cortical bone anchor was not significantly greater than that of the titanium screw anchor (P?>?0.05). Student’s t test showed no statistically significant difference between anchors in terms of failure load (cortical bone anchor: 304.74?±?64.46 N versus titanium screw anchor: 328.45?±?89.58 N; P?=?0.213), ultimate load (cortical bone anchor: 325.82?±?76.45 N versus titanium screw anchor: 345.61?±?83.56 N; P?=?0.183), yield load (cortical bone anchor: 273.78?±?44.75 N versus titanium screw anchor: 284.72?±?56.37 N; P?=?0.326) or stiffness (cortical bone anchor: 52.97?±?14.28 N/mm versus titanium screw anchor: 62.38?±?18.35 N/mm; P?=?0.112).

Conclusions

In vitro, this experimental study suggested no statistically significant difference in initial fixation stability between the new type anchor and titanium screw anchor at a chosen level of significance (P?<?0.05). The new type of suture anchor constructed of cortical bone provides comparable initial fixation strength to a similar metallic anchor for rotator cuff repair.

     

Stability of Locking Plate and Compression Screws for Lapidus Arthrodesis: A Biomechanical Comparison of Plate Position

Lapidus (first tarsometatarsal joint) arthrodesis is an established and widely used procedure for the management of moderate to severe hallux valgus, especially in cases involving hypermobility of the first tarsometatarsal joint. Multiple fixation methods are available, and several previous investigations have studied the relative strengths of these methods, including dorsomedial and plantar plating comparisons. However, these studies compared plates of varying designs and mechanical properties and used varying modes of compression and interfragmentary screw techniques. The present study mechanically investigated the resulting motion, stiffness, and strength of identical locking plate constructs fixed at various anatomic positions around the first tarsometatarsal joint. In a bench-top study, fourth-generation composite bones were divided into 3 fixation groups, each having identical interfragmentary screw applications, and randomized to 1 of 3 plate positions: dorsal, medial, or plantar. The plates applied in each case were identical locking plates, precontoured to fit the anatomy. Each construct was experimentally tested using a cantilever bending approach. The outcomes obtained were stiffness, yield force, displacement at yield, ultimate force, and displacement at ultimate force. The plantar plate position showed superior initial stiffness and force to ultimate failure. The plantar and medial plate positions exhibited superior force to yield. The medial plate position was superior regarding displacement tolerated before the yield point and catastrophic failure. The dorsal plate position was not superior for any outcome measured. Plantar and medial plating each offered biomechanical benefits. Clinical studies using similarly matched constructs are required to show whether these findings translate into improved clinical outcomes.     

The biomechanical characteristics of arthroscopic tibial inlay techniques for posterior cruciate ligament reconstruction: in vitro comparison of tibial graft tunnel placement

Purpose

The hypothesis of the present study was that the biomechanical properties of arthroscopic tibial inlay procedures depend on tibial graft bone block position.

Methods

Five paired fresh-frozen human cadaveric knee specimens were randomized to a reconstruction with quadriceps tendon placing the replicated footprint either to the more proximal margin of the remnants of the anatomical PCL fibrous attachments (group A) or to the distal margin of the anatomical PCL fibrous attachments at the edge of the posterior tibial facet to the posterior tibial cortex in level with the previous physis line (group B). The relative graft-tibia motions, post cycling pull-out failure load and failure properties of the tibia-graft fixation were measured. Cyclic displacement at 5, 500 and 1,000 cycles, stiffness and yield strength were calculated.

Results

The cyclic displacement at 5, 500 and 1,000 cycles measured consistently more in group A without statistically significant difference (4.11?±?1.37, 7.73?±?2.73 and 8.18?±?2.75 mm versus 2.81?±?1.33, 6.01?±?2.37 and 6.46?±?2.37 mm). Mean ultimate load to failure (564.6?±?212.3) and yield strength (500.2?±?185.9 N) were significantly higher in group B (p?Conclusion Replicating the anatomical PCL footprint at the posterior edge of the posterior tibial facet yields higher pull-out strength and less cycling loading displacement compared to a tunnel position at the centre of the posterior tibial facet.     

Bioabsorbable vs. titanium screws for first tarsometatarsal joint arthrodesis: An in-vitro study

BackgroundThe TMT-1 joint arthrodesis is a common repair for severe hallux valgus. Two crossing interfragmental screws, usually titanium or steel, and a locking plate or a plate with a compression screw are the most common fixation methods for first TMT joint arthrodesis. The qualities of an ideal fixation material include adequate strength and rigidity, biocompatibility, lack of interference with bone healing, lack of visibility and palpability, and a low risk of surgical removal. We sought to determine whether bioabsorbable cannulated screws would perform as well as titanium screws in anatomical models.MethodsIdentical anatomical TMT-1 arthrodesis was created with a saw by making a straight cut in 30 anatomical models (Sawbone®). The bioabsorbable and titanium screws were placed one at a time in exactly the same location in each model according to careful measurements. All 30 models were analyzed with a material testing machine (MTS Insight 30, Eden Prairie, USA). Each model was oriented 15° to the platform to simulate its position to the ground during mid-stance.ResultsIn the single-cycle load-to-failure test, the mean yield load was 61.4 N ± 5.7 N (range, 50.1 N–70.3 N) in the bioabsorbable screw group and 81.2 N ± 12 N (range, 61.7 N–113.4 N) in the titanium screw group (P < .001). The respective values for the stiffness of the fixation were 8.1 N/mm ± 0.8 N/mm (range, 6.7 N/mm to 9.1 N/mm) and 9.7 N/mm ± 1.8 N/mm (range, 6.9 N/mm to 12.6 N/mm) for the bioabsorbable and titanium groups (P = .004). The mean maximum failure loads in the bioabsorbable group were 85.1 N ± 8.5 N (range, 67.1 N–97.2 N) and in the titanium group 120.6 N ± 13.2 N (range, 96.7 N–136.7 N), respectively (P < .001). Analysis of the failure models shows bioabsorbable fixation failures caused by bending occur more often than in the titanium group.ConclusionIn biomechanical testing, titanium screws were stronger than bioabsorbable screws in the TMT-1 arthrodesis model tested, although bioabsorbable cannulated screws may be an alternative to titanium screws in the fixation Lapidus procedure.     

A cadaveric comparison of two methods for isolated talonavicular arthrodesis: Two-screws versus plate with integrated compression screw

BackgroundThis study compared stiffness between two constructs for talonavicular arthrodesis: a dorsomedial plating system and two partially threaded cannulated cancellous screws. We hypothesized that the plate would exhibit greater stiffness and resistance to deformation during cyclic loading.MethodsThe constructs were implanted in eight matched pairs of cadaveric feet and subjected to axial torsion, cantilever bending in two directions, and cyclic loading to failure.ResultsThe two-screw constructs were significantly stiffer in plantar-dorsal bending (p = .025) and trended towards a higher number of cycles before failure than the plate group (p = .087). No significant differences were observed in internal torsion (p = .620), external torsion (p = .165), or medial-lateral bending (p = .686).ConclusionsThis study provided the first biomechanical assessment of a plating system with an integrated compression screw, which was significantly less stiff than a two-screw construct when loaded from plantar to dorsal.     

Screw fixation compared to H-locking plate fixation for first metatarsocuneiform arthrodesis: a biomechanical study

BACKGROUND: Several different techniques have been used for fixation of first metatarsocuneiform (MTC) joint arthrodesis, a standard treatment for arthritis, instability, and deformity of the MTC joint. Improved plating systems using locking designs are now available, but no studies have yet compared this construct with other methods. We compared load to failure with a locking plate design versus standard crossed-screw fixation. METHODS: Ten matched pairs of fresh frozen cadaver feet were used. The bone density of each pair was measured with DEXA scanning. One foot of each pair was randomly assigned to have a dorsomedial Normed H titanium locking plate (Normed Medizin-Technik Vertriebs-GmbH, D-78501 Tuttlingen, Germany) applied to the first MTC joint. On the other foot of the pair, fixation of the first MTC joint was done with crossed ACE DePuy 4.0 (DePuy/Ace, Warsaw, IN) titanium cannulated screws. The first metatarsal and first cuneiform were then isolated and planted in an epoxy resin. The specimens were loaded to failure in a four-point bending configuration using a MTS Mini Bionix test frame (MTS Systems Corp., Eden Prairie, MN). Failure was defined as displacement of more than 3 mm at the arthrodesis site. The Student t-test was used to determine any observed differences, with significance set at p 相似文献   

Medial buttress versus lateral locked plating in a cadaver medial tibial plateau fracture model

OBJECTIVE: To compare the mechanical stability of a medial tibial plateau fracture model secured with a lateral locking periarticular plate versus a medial buttress plate in cyclic testing and load to failure. METHODS: Medial tibial plateau fractures were created in 6 matched pairs of fresh cadaveric tibias. In each pair of tibias, 1 side was randomly selected to be fixed with a lateral locking plate on 1 side and the contralateral limb to be fixed with a medial buttress plate. The fixated tibias then underwent cyclic testing followed by single-cycle failure compressive loading. Displacement of the medial tibial plateau was measured in both cyclic and failure testing. RESULTS: Statistical analyses revealed relevant trends in fixation strength during cyclic testing, but neither the mean maximum displacement during nor mean residual displacement after cyclic testing were statistically different between the 2 fixation techniques. Statistically significant differences were observed for the mean forces to failure however. The medial buttress plate construct provided greater fixation strength with its failure force of 4136 +/- 1469 N compared with the lateral locking plate mean failure force of 2895 +/- 1237 N (P < 0.05). CONCLUSION: In the setting of a vertically oriented fracture in a medial tibial plateau without comminution, the medial buttress plate provides significantly greater stability in static loading, and a trend toward improved stability with cyclic loading. Clinical correlation is necessary to substantiate these findings.     

Tibiale Press-fit-Fixierungen von Beugesehnen zur Rekonstruktion des vorderen Kreuzbandes

Background

Press-fit fixation of hamstring tendon autografts for anterior cruciate ligament reconstruction is an interesting technique because no hardware is necessary. This study compares the biomechanical properties of press-fit fixations to an interference screw fixation.

Methods

Twenty-eight human cadaveric knees were used for hamstring tendon explantation. An additional bone block was harvested from the tibia. We used 28 porcine femora for graft fixation. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclic loading were investigated.

Results

The maximum load to failure was 970±83?N for the press-fit tape fixation (T), 572±151?N for the bone bridge fixation (TS), 544±109?N for the interference screw fixation (I), 402±77?N for the press-fit suture fixation (S) and 290±74?N for the bone block fixation technique (F). The T fixation had a significantly better maximum load to failure compared to all other techniques (p<0.001).

Conclusion

This study demonstrates that a tibial press-fit technique which uses an additional bone block has better maximum load to failure results compared to a simple interference screw fixation.     

Mechanical Comparison of Cortical Screw Fixation Versus Locking Plate Fixation in First Metatarsal Base Osteotomy

The oblique closing base wedge osteotomy has been used for surgical treatment of moderate to severe hallux valgus deformities with an intermetatarsal angle typically greater than 15°. Several postoperative complications have been identified that relate to failure of the fixation construct used to fixate the osteotomy, especially when that construct has been subjected to a vertical load. We performed a mechanical analysis comparing 2 constructs used to fixate oblique osteotomies of the first metatarsal using composite first metatarsals. An oblique base osteotomy was uniformly performed on 40 composite first metatarsals. Of the 40 specimens, 20 were fixated with a locking plate construct and 18 with a cortical screw construct, consisting of an anchor and compression screw (2 specimens from the latter group were excluded because of hinge fracture). Each specimen was loaded in a materials testing machine to measure the maximum load at construct failure when a vertical force was applied to the plantar aspect of the metatarsal head. The mean load to failure for the locking plate construct was significantly greater than the cortical screw construct (190.0 ± 70 N versus 110.3 ± 20.3 N, p < .001). Our study results have demonstrated that the locking plate construct was able to withstand a significantly greater vertical load before failure than was the 2-cortical screw construct in oblique osteotomies performed at the base of composite first metatarsals.     

Progression of Healing on Serial Radiographs Following First Ray Arthrodesis in the Foot Using a Biplanar Plating Technique Without Compression

A review of 195 first ray arthrodeses fixated with a twin-plate biplanar construct, without interfragmentary compression, is presented. This fixation construct was evaluated in a consecutive cohort of patients undergoing first metatarsophalangeal joint (MTP) arthrodesis or the first tarsometatarsal joint (TMT) arthrodesis. Multiple radiographs were used to assess the progression of healing at the following postoperative time frames: 4 to 9 weeks, 10 to 12 weeks, >12 weeks, and the final follow-up. In total, 85 feet underwent first MTP arthrodesis, and 110 feet underwent first TMT arthrodesis. At the final radiographic follow-up, 97.44% of all cases had shown progressive osseous gap filling at the arthrodesis site, stable position of the bone segments, and intact hardware without loosening, 98.24% of the first MTP arthrodesis group and 96.82% of the first TMT arthrodesis group. Five (5.43%) feet had the presence of lucency at the fusion interface at the final follow-up, without positional change or hardware failure. Four (1.8%) feet had a failure of the hardware, loss of position, or frank gapping at the fusion site. Lucency decreased consistently over time in this series of patients (p < .00001). Progressive increase in callus density at the fusion site on serial radiographs was noted to be a consistent finding for both procedures and was the primary indicator of secondary bone healing at the noncompressed, relatively stable arthrodesis site. Our results confirm that biplanar plating construct without interfragmentary compression produces high fusion rates following the first MTP or TMT arthrodesis, with early weightbearing.     

Fixation of the Lapidus arthrodesis with a plantar interfragmentary screw and medial low profile locking plate

The Lapidus arthrodesis can be used to correct pathology within the forefoot or midfoot, and severe hallux valgus deformities as well as hypermobility of the medial column may be amenable to correction with this procedure. Many different skeletal fixation methods have been described for this procedure, and one form that appears to provide enough construct stability to allow patients to bear weight early in the postoperative period is described herein. This construct consists of an interfragmental compression screw oriented from the plantar aspect of the first metatarsal to the superior aspect of the medial cuneiform, with medial locking plate augmentation.     

The Sensitivity of Thresholds by Ground Reaction Force and Postural Stability in Subjects With and Without Navicular Drop

Understanding plantar pressure changes is an important component of the functional evaluation of subjects with flat foot. However, the altered postural control determined by the threshold from the vertical ground reaction force (GRF) requires clarification. The purpose of our study was to investigate the various GRF thresholds in subjects with and without flat foot during 1-leg standing. We included 34 control subjects and 30 subjects with flat foot in the present study. They performed the 1-leg standing test for 30 seconds, with the contralateral hip and knee flexed approximately 90°. The sensitivity of the various GRF thresholds (3, 7, 15, 50, and 100 N) for the postural stability index was analyzed with and without visual input. The standing times for the control and flat foot groups were 23.76?±?4.42 and 21.78?±?6.59 seconds, respectively, with no significant differences (t?=?1.23; p?=?.22). The 2 groups demonstrated a significant interaction between the visual condition and the threshold levels (F?=?11.40; p?=?.001). The postural stability index was significantly different in the eyes-open condition (0.95?±?0.08 for the control group versus 0.84?±?0.23 for the flat foot group; t?=?2.29; p?=?.02). However, no difference was found in the eyes-closed condition (0.94?±?0.10 for the control group versus 0.81?±?0.30 for the flat foot group; t?=?1.45; p?=?.15). These results indicate that GRF thresholds less than the 15N setting are sensitive to detect postural stability between groups, especially in the eyes-open condition. The GRF threshold setting, in addition to the visual condition, could alter the outcomes of sensitive plantar pressure changes in subjects with flat foot.     

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

OBJECTIVE: The objective of this study is to establish the relative strength of fixation of a locking distal femoral plate compared with the condylar blade plate. METHODS: Eight matched pairs of fresh-frozen cadaveric femurs were selected and evaluated for bone density. A gap osteotomy model was used to simulate an OTA/AO A3 comminuted distal femur fracture. One femur of each pair was fixed with the blade plate; the other, with a locking plate. After 100 N preload and 10,000 cycles between 100 N and 1000 N, total displacement of each specimen was assessed. After completion of cyclic loading, maximum load to failure was tested. RESULTS: Significantly greater subsidence (total axial displacement) occurred with the blade plate (1.70 +/- 0.45 mm; range, 1.21-2.48 mm) than with the locking plate fixation (1.04 +/- 0.33 mm; range, 0.67-1.60 mm) after cyclic loading (P = 0.03). In load-to-failure testing, force absorbed by the locking plate before failure (9085 +/- 1585 N; range, 7269-11,850 N) was significantly greater than the load tolerated by the blade plate construct (5591 +/- 945 N; range, 3546-6684 N; P = 0.001). Variability in bone mineral density did not affect the findings (fixed angle distal femoral plate r = 0.1563; condylar blade plate r = 0.0796). CONCLUSIONS: The locking screw-plate construct proved stronger than the blade plate in both cyclic loading and ultimate strength in biomechanical testing of a simulated A3 distal femur fracture. Although differences were small, the biomechanical performance of the locking plate construct over the blade plate may lend credence to use of the locking plate versus the blade plate in the fixation of comminuted distal femur fractures.