Mechanical Testing of Maximal Shift Scarf Osteotomy with Inside-Out Plating Compared to Classic Scarf Osteotomy With Double Screw Fixation

The purpose of the present study was to biomechanically compare the primary stability of our formerly described inside-out plate fixation to the classic double screw fixation for scarf osteotomy in the treatment of hallux valgus. We performed 20 scarf osteotomies on first metatarsal composite bone models. One half were fixed using a double screw technique and the other half using a locking plate inside-out technique. Using a testing device to simulate the physiologic load, the specimen was loaded until failure, and the load at failure, displacement at failure, and work at failure were recorded. The results were compared between the 2 groups and against the findings from intact sawbones. Compared with the intact bone models, the energy absorption was low for both types of osteotomy fixation. Between the 2 fixation groups, the load at failure was greater for plate fixation, although the difference was not statistically significant (p?=?.051). However, a statistically significant difference was found between both groups comparing work and displacement at failure (p?<?.001). In conclusion, the formerly described inside-out plating technique is a biomechanically reasonable alternative to screw fixation because of its primary stability after scarf osteotomy for hallux valgus.     

Biomechanical analysis of two fixation methods for proximal chevron osteotomy of the first metatarsal

Purpose

The proximal chevron osteotomy provides high correctional power. However, relatively high rates of dorsiflexion malunion of up to 17 % are reported for this procedure. This leads to insufficient weight bearing of the first ray and therefore to metatarsalgia. Recent biomechanical and clinical studies pointed out the importance of rigid fixation of proximal metatarsal osteotomies. Therefore, the aim of the present study was to compare biomechanical properties of fixation of proximal chevron osteotomies with variable locking plate and cancellous screw respectively.

Methods

Ten matched pairs of human fresh frozen cadaveric first metatarsals underwent proximal chevron osteotomy with either variable locking plate or cancellous screw fixation after obtaining bone mineral density. Biomechanical testing included repetitive plantar to dorsal loading from 0 to 31 N with the 858 Mini Bionix^® (MTS^® Systems Corporation, Eden Prairie, MN, USA). Dorsal angulation of the distal fragment was recorded.

Results

The variable locking plate construct reveals statistically superior results in terms of bending stiffness and dorsal angulation compared to the cancellous screw construct. There was a statistically significant correlation between bone mineral density and maximum tolerated load until construct failure occurred for the screw construct (r = 0.640, p = 0.406).

Conclusion

The results of the present study indicate that variable locking plate fixation shows superior biomechanical results to cancellous screw fixation for proximal chevron osteotomy. Additionally, screw construct failure was related to levels of low bone mineral density. Based on the results of the present study we recommend variable locking plate fixation for proximal chevron osteotomy, especially in osteoporotic bone.     

Comparison of Fixation Techniques in Oblique and Biplanar Chevron Medial Malleolar Osteotomies; a Finite Element Analysis

This study aimed to evaluate different fixation techniques and implants in oblique and biplanar chevron medial malleolar osteotomies using finite element analysis. Both oblique and biplanar chevron osteotomy models were created, and each osteotomy was fixed with 2 different screws (3.5 mm cortical screw and 4.0 mm malleolar screw) in 2 different configurations; (1) 2 perpendicular screws, and (2) an additional third transverse screw. Nine simulation scenarios were set up, including 8 osteotomy fixations and the intact ankle. A bodyweight of 810.44 N vertical loading was applied to simulate a single leg stand on a fixed ankle. Sliding, separation, frictional stress, contact pressures between the fragments were analyzed. Maximum sliding (58.347µm) was seen in oblique osteotomy fixed with 2 malleolar screws, and the minimum sliding (17.272 µm) was seen in chevron osteotomy fixed with 3 cortical screws. The maximum separation was seen in chevron osteotomy fixed with 2 malleolar screws, and the minimum separation was seen in oblique osteotomy fixed with 3 cortical screws. Maximum contact pressure and the frictional stress at the osteotomy plane were obtained in chevron osteotomy fixed with 3 cortical screws. The closest value to normal tibiotalar contact pressures was obtained in chevron osteotomy fixed with 3 cortical screws. This study revealed that cortical screws provided better stability compared to malleolar screws in each tested osteotomy and fixation configuration. The insertion of the third transverse screw decreased both sliding and separation. Biplanar chevron osteotomy fixed with 3 cortical screws was the most stable model.     

The effect of screw type on the biomechanical properties of SCARF and crescentic osteotomies of the first metatarsal

The basilar crescentic osteotomy is a popular method for correcting moderate to severe hallux valgus. However, inadvertent dorsiflexion of the osteotomy can result from intraoperative malposition or from malunion after fixation failure. The mechanical properties of osteotomies are dependent on the nature of the osteotomy and the type of fixation. This study examines the mechanical properties of the SCARF and crescentic osteotomies of the first metatarsal by using a cannulated asymmetric pitched screw or AO cancellous screws. Sixteen human cadaveric first metatarsal specimens were tested in plantar to dorsiflexion cantilever bending by using a mechanical testing machine. The data was compared with our recent work on the mechanical properties of the SCARF and crescentic osteotomies. Ultimate load and stiffness of the SCARF osteotomy were superior to the crescentic osteotomy but were not dependent on screw type. Screw type was a prominent factor in the stiffness but not in the strength of the crescentic osteotomy. The ultimate load and the stiffness of SCARF osteotomy fixed with the cannulated asymmetric pitched screws were not significantly different compared with AO screws (ultimate load, 124.6 N [SD = 56.8] v 105.3 N [SD = 57.0]; stiffness, 52.0 N/mm [SD = 48.0] v 31.8 N/mm [SD = 19.0]). Modes of failure were fracture of the cortical bone bridge between the screw hole and the osteotomy in all crescentic osteotomies and fracture of the proximal dorsal bridge in all SCARF osteotomies. The superior mechanical properties of the SCARF osteotomy, fixed with cannulated asymmetric pitched screws, make this a more secure construct, with less risk of malunion than the crescentic osteotomy. Stiffness is an important mechanical factor that helps distinguish the mechanical performance of different osteotomy techniques.     

Comparison of lateral locking plate and antiglide plate for fixation of distal fibular fractures in osteoporotic bone: a biomechanical study

OBJECTIVES: The purpose of this study was to compare the biomechanical properties of posterolateral antiglide plating and lateral locked plating for fixation of displaced short oblique fractures of the fibula in osteoporotic bone. METHODS: Short oblique fractures of the distal fibula at the level of the syndesmosis were simulated with a fibular osteotomy and ligamentous sectioning in 18 paired fresh frozen ankles. The fractures were fixed with either a lateral locking plate with an independent lag screw or a posterolateral antiglide plate with a lag screw through the plate. The specimens were tested under a torsional load to failure. The torque to failure, angular rotation at failure, and construct stiffness of the two groups were compared. RESULTS: The torque to failure and construct stiffness were significantly greater on the side with the posterolateral antiglide plate than on the side with the the lateral locking plate (P = 0.01 and 0.005, respectively). CONCLUSIONS: The posterolateral antiglide plate demonstrated improved biomechanical stability as compared to the lateral locking plate in osteoporotic bone. In situations where fixation needs to be optimized, use of an antiglide plate may be favored over a lateral locking plate construct.     

Biomechanical analysis of stability of joint depression calcaneal fractures: Fixation with locking compression plate alone compared with addition of supplemental oblique screw

PurposeThe standard treatment of calcaneus fractures is a lateral plate and screw construct. Patients at our institution have been treated with a lateral locking plate combined with one retrograde screw inserted in the oblique plane to allow immediate weight bearing. The purpose of this study was to determine whether addition of a oblique screw to a lateral plate construct increases stability.MethodsA Sanders 2B fracture (AO/OTA 83-C2) was created in 8 pairs (16 total specimens) of cadaveric feet. All were repaired using a lateral locking plate/screws construct. One specimen in each pair was chosen randomly to receive an additional oblique screw. The specimens were tested with cyclic load of up to 800 N. Movement at the fracture sites and subsidence of the talus were tracked with a three-dimensional video analysis system.ResultsTalar subsidence was not significantly affected by the presence of the additional oblique screw (p = 0.22). The sustentaculum fragment in the case of the screw repair moved 0.39 mm while the same fragment without the additional screw repair displaced 0.12 mm (p < 0.01). Two repairs with and one repair without the additional screw failed during longer-term cyclic loading.ConclusionThe two repair types were not statistically different in regards to talar subsidence. While statistical significance resulted in the comparison of sustentaculum fragment movement, the amount of movement did not reach a level of clinical relevance. This study demonstrated immediate stability and durability of the additional screw construct with high volume weight bearing loads.     

Locking Compression Plate Distal Ulna Hook Plate as Alternative Fixation for Fifth Metatarsal Base Fracture

Intramedullary screw fixation has been the most common treatment for fifth metatarsal base fractures. However, screw application will not achieve accurate reduction in fractures with small fragments, osteoporotic bone, or Lawrence zone 1 fractures. Because of the similar anatomic architecture between the distal ulna and the fifth metatarsal base, the purpose of the present study was to assess the results of a locking compression plate distal ulna hook plate in stabilizing displaced zone 1 or 2 fifth metatarsal base fractures. A total of 19 patients with Lawrence zone 1 (n = 12) or 2 (n = 7) fractures of the fifth metatarsal base were treated surgically with a locking compression plate distal ulna hook plate. The patients were evaluated clinically and radiographically, and the functional outcomes were graded using the American Orthopaedic Foot and Ankle Society midfoot scoring system. Radiographic bony union was obtained in all patients, at an average of 7.4 weeks. The mean American Orthopaedic Foot and Ankle Society midfoot score improved from 26 (range 0 to 45) points preoperatively to 94 (range 72 to 100) points at the final follow-up visit. Three patients developed post-traumatic cubometatarsal arthrosis, and 1 patient developed sural nerve neurapraxia. In our experience, the distal ulna hook plate achieved a high rate of bony consolidation and anatomically suitable fixation in zone 1 or 2 fifth metatarsal base fractures. We suggest that the locking compression plate distal ulna hook plate should be considered as an alternative treatment of multifragmentary, osteoporotic, and tuberosity avulsion (zone 1) fifth metatarsal base fractures.     

Biomechanical Comparison of Fixation With a Single Screw Versus Two Kirschner Wires in Distal Chevron Osteotomies of the First Metatarsal: A Cadaver Study

Distal chevron osteotomy is a common procedure for surgical correction of hallux valgus. Osteosynthesis with 1 screw or 2 Kirschner wires has been commonly used. We compared the stability of the 2 techniques in distal chevron osteotomy. Sixteen first metatarsals from fresh-frozen human cadaver feet (9 different cadaveric specimens) were used. A standardized distal chevron osteotomy was performed. One first metatarsal from each pair was assigned to group 1 (3.5-mm cortical screw; n?=?8) and one to group 2 (two 1.6-mm Kirschner wires; n?=?8). Using a materials testing machine, the head of the first metatarsals was loaded in 2 different configurations (cantilever and physiologic) in succession. In the cantilever configuration, the relative stiffness of the osteosynthesis compared with intact bone was 59% ± 27% in group 1 and 68% ± 18% in group 2 (p?=?.50). In the physiologic configuration, it was 38% ± 25% in group 1 and 35% ± 7% in group 2 (p?=?.75). The failure strength in the cantilever configuration was 187 ± 105 N in group 1 and 259 ± 71 N in group 2 (p?=?.21). No statistically significant differences were found in stability between the 2 techniques. The use of 1 screw or 2 Kirschner wires had no significant differences in their biomechanical loading capacity for osteosynthesis in distal chevron osteotomies for treatment of hallux valgus.     

Crossed screws versus dorsomedial locking plate with compression screw for first metatarsocuneiform arthrodesis: a cadaver study

BACKGROUND: We hypothesized that a dorsomedial locking plate with adjunct screw compression would provide superior rigidity compared to crossed screws for first metatarsocuneiform (MTC) arthrodesis. MATERIALS AND METHODS: In ten matched lower extremity pairs, specimens in each pair were randomly assigned to receive screw fixation or plate with screw fixation. Bone mineral density (BMD) was measured. For the crossed-screw construct, two 4.0-mm cannulated screws were used. One screw was inserted dorsal to plantar beginning from the first metatarsal 10 to 15 mm distal to the joint, and the second was inserted from the cuneiform 8 to10 mm proximal to the joint, medial to the first screw, into the first metatarsal. For the plate construct, a 4.0-mm cannulated compression screw was inserted from the dorsal cortex of the first metatarsal to the plantar aspect of the medial cuneiform. A locking plate was inserted dorsomedially across the MTC joint. Specimens were loaded in four-point bend configuration (displacement rate, 5 mm/min) until failure of the fixation or 3-mm deformation. An extensometer was used to measure deformation. RESULTS: There was no difference in load to failure or stiffness between the two groups. BMD was positively correlated with load to failure in the screw (r = 0.893, p = 0.001) and the plate (r = 0.858, p = 0.001) construct. CONCLUSION: The plate construct with compression screw did not show different rigidity as compared with the screw construct with the numbers available. CLINICAL RELEVANCE: Further investigation of a dorsomedial plate with adjunct screw compression may be warranted for first MTC arthrodesis.     

Biomechanical Comparison of Internal Fixation Techniques for the Akin Osteotomy of the Proximal Phalanx

The Akin osteotomy is performed at the proximal phalanx for correction of an abducted great toe in a hallux abducto valgus deformity. Several internal fixation techniques have been widely advocated; however, their respective stabilities have not been compared. A biomechanical analysis was performed comparing 5 commonly used fixation techniques for the Akin osteotomy to determine the strongest method in simulated weightbearing in sawbone models. An Akin osteotomy was uniformly performed on 25 sawbones and fixated with 5 different internal fixation types, including a 2-hole locking plate and locking screws, a heat-sensitive memory staple (8 mm × 8 mm), a 28-gauge monofilament wire, 2.7-mm bicortical screws, and crossed 0.062-in. Kirschner wires. The results of simulated weightbearing load to failure rates with an Instron compression device demonstrated the following mean load to failures: crossed Kirschner wire, 57.05 N; 2-hole locking plate, 36.49 N; monofilament wire, 35.69 N; heat-sensitive memory staple, 34.32 N; and 2.7-mm bicortical screw, 13.66 N. Statistical analysis demonstrated the crossed Kirschner wire technique performed significantly better than the other fixation techniques (p < .007); the 4 other techniques were found not to be significantly different statistically (p = .041) from each another. Our study results suggest a crossing Kirschner wire construct significantly increases the stability of the Akin osteotomy in a sawbone model. This might be clinically extrapolated in an effort to improve patient outcomes because these osteotomies can undergo nonunion and malunion, resulting in postoperative pain and swelling.     

Relative Strength of Tailor’s Bunion Osteotomies and Fixation Techniques

A paucity of data is available on the mechanical strength of fifth metatarsal osteotomies. The present study was designed to provide that information. Five osteotomies were mechanically tested to failure using a materials testing machine and compared with an intact fifth metatarsal using a hollow saw bone model with a sample size of 10 for each construct. The osteotomies tested were the distal reverse chevron fixated with a Kirschner wire, the long plantar reverse chevron osteotomy fixated with 2 screws, a mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, the mid-diaphyseal sagittal plane osteotomy fixated with 2 screws, and an additional cerclage wire and a transverse closing wedge osteotomy fixated with a box wire technique. Analysis of variance was performed, resulting in a statistically significant difference among the data at p <.0001. The Tukey-Kramer honestly significant difference with least significant differences was performed post hoc to separate out the pairs at a minimum α of 0.05. The chevron was statistically the strongest construct at 130 N, followed by the long plantar osteotomy at 78 N. The chevron compared well with the control at 114 N, and they both fractured at the proximal model to fixture interface. The other osteotomies were statistically and significantly weaker than both the chevron and the long plantar constructs, with no statistically significant difference among them at 36, 39, and 48 N. In conclusion, the chevron osteotomy was superior in strength to the sagittal and transverse plane osteotomies and similar in strength and failure to the intact model.     

Beaming in Charcot Arthropathy—Intramedullary Fixation for Complicated Reconstructions: A Cadaveric Study

In the modern treatment of Charcot neuroarthropathy, beam screw fixation is an alternative to plate and screw fixation. Exposure is minimized for implantation, and this technique supports the longitudinal columns of the foot as a rigid load-sharing construct. A published data review identified a paucity of data regarding metatarsal intramedullary canal morphology relevant to beam screw fixation. The purpose of the present study was to describe metatarsal diaphyseal morphology qualitatively and quantitatively in an effort to provide data that can be used by surgeons when selecting axially based intramedullary fixation. Twenty fresh-frozen cadaveric below-the-knee specimens were obtained. The metatarsals were exposed, cleaned of soft tissue, and axially transected at the point of the narrowest external diameter. Next, a digital caliper was used to measure the size and shape of the diaphysis of the first through fourth metatarsals. The diaphyseal canal shape was categorized as round, oval, triangular, or pear. The widest distance between the endosteal cortical surfaces was measured. Triangular endosteal canals were only found in the first metatarsal, and the remainder of the metatarsal canals were largely round or oval. These data help to approximate the size of fixation needed to achieve maximal screw–endosteal purchase.     

Biomechanical Comparison of Two Pediatric Blade Plate Designs in Proximal Femoral Osteotomies

Background

Blade plates are frequently used for internal fixation following proximal femoral varus rotational osteotomy to treat hip dysplasia in children with cerebral palsy. Recently, cannulated blade plates with the option for a proximal locking screw have demonstrated ease of insertion and low complication rates. Although there are two commonly used blade plates with a proximal screw option, no comparison of their biomechanical profiles has been undertaken.

Questions/Purposes

Our study sought to compare the structural properties under axial loading, as well as the biomechanical contribution of a proximal screw, of two different 90° cannulated blade plates designed for pediatric proximal femurs. Plate A has a hole distal to the blade designed to attach a plate inserter, through which a 3.5-mm non-locking cortical screw could be placed. Plate B has a threaded hole distal to the blade designed to accept a 3.5-mm locking screw.

Methods

Plate A and plate B were inserted into 33 left pediatric synthetic proximal femurs. Axial loading to failure of plate A with and without a proximal screw was compared to that of plate B with and without a proximal screw. An additional 10 samples using plate B, with and without a proximal locking screw, were tested in tension to quantify the effect of the proximal screw on pullout strength.

Results

Plate B failed at a higher axial load than plate A. The addition of a proximal screw did not affect the axial load to failure for either plate. Pullout testing revealed that blade plates fixed with the proximal screw failed in tension at a significantly higher load (856.3?±?120.9 N) than those without proximal fixation (68.1?±?9.3 N, p?<?0.001).

Conclusions

Plate B failed at a higher axial load in biomechanical testing, likely related to differences in its design. The addition of a proximal screw did not increase the axial loading properties of the blade plate construct but did increase the pullout strength by a factor of 12. These results may be used to influence implant selection and post-operative rehabilitation following proximal femoral osteotomies in children.

     

Analysis of Three Types of Fixation of the Weil Osteotomy

This study assessed 3 methods of fixation for the Weil osteotomy. A total of 40 bone models were divided equally into 4 groups: a control group consisting of intact lesser rays; and Weil osteotomies that were fixated with 2 crossed Kirschner wires (0.045-in K-wires), 2.0-mm cortical screws, or cannulated 2.4-mm cortical screws. Each specimen was stressed in a computer-controlled hydraulic tensile testing machine, and maximum load, energy to failure, and stiffness were recorded. The following mean load to failure measurements were found: control, 62.9 Newtons (N); K-wire, 22.9 N; cannulated screw, 31.3 N; and noncannulated screw, 19.9 N. There was no statistical difference among the 3 groups of fixation methods in terms of the maximum load. The mean energy to failure of the control group was 326 joule (J); K-wire, 79 J; cannulated screw, 163 J; and noncannulated screw, 66 J. The cannulated screw generated a statistically greater amount of energy at failure than the noncannulated screw (P < .05). The mean structural stiffness of the control group was 7.3 N/mm; K-wire, 2.8 N/mm; cannulated screw 3.3 N/mm; and noncannulated screw, 3.2 N/mm. There was no statistical difference in structural stiffness among the 3 groups of fixation methods. The results indicated a trend toward better biomechanical stability with the 2.4-mm cannulated screw than the 2.0-mm noncannulated screw for fixation of the Weil osteotomy.     

Strength of fixation of Ludloff metatarsal osteotomy utilizing three different types of Kirschner wires: a biomechanical study

Static biomechanical studies have demonstrated that the Ludloff shaft metatarsal osteotomy is significantly more stable than other commonly used proximal (basilar) osteotomies, such as the proximal crescentic and the proximal chevron. High average static bending failure moments have been recorded for the screw fixation Ludloff osteotomy construct. The objective of the current study was to find a reasonable alternative method of fixation in cases where a short osteotomy may not be amenable to adequate screw fixation and in cases where an inadvertent intraoperative fracture of the metatarsal occurs and subsequent screw fixation is precarious due to inadequate bone stock. A Ludloff osteotomy was performed on 24 matched pairs of cadaveric specimens to compare the strength of fixation of three different types of Kirschner wires (smooth, threaded, and SOC threaded). Biomechanical testing with plantar force was carried out, and failure load and stiffness were measured for each specimen. The current results indicate that the threaded pin construct provides adequate strength for fixation of the Ludloff osteotomy in the clinical setting.     

Plantar-to-dorsal compared to dorsal-to-plantar screw fixation for proximal chevron osteotomy: a biomechanical analysis

BACKGROUND: A change in screw orientation in fixing the chevron proximal first metatarsal osteotomy was noted anecdotally to improve fixation strength. The authors hypothesized that plantar-to-dorsal screw orientation would be more stable than the conventional dorsal-to-plantar screw orientation for fixation of the chevron osteotomy. The purpose of this study was to determine if the load-to-failure and stiffness of the chevron type proximal first metatarsal osteotomy stabilized using plantar-to-dorsal screw fixation were greater than with the more conventional dorsal-to-plantar screw fixation method. METHODS: One foot from each of eight matched cadaver pairs was randomly assigned to one of two groups: 1) fixation with a dorsal-to-plantar lag screw or 2) fixation with a plantar-to-dorsal lag screw. A proximal chevron osteotomy was then created using standard technique and the metatarsal was fixed according to previously established method. The bone was potted in polyester resin, and the construct was fitted into a materials testing system machine in which load was applied to the plantar aspect of the metatarsal until failure. The two groups were compared using a two-tailed Student t test. RESULTS: The average load-to-failure and stiffness of the chevron osteotomy fixed with the plantar-to-dorsal lag screw were significantly greater (p < 0.05) than the group fixed with more conventional dorsal-to-plantar lag screws. CONCLUSION: Plantar-to-dorsal screw orientation was more stable than the conventional dorsal-to-plantar screw orientation for fixation of the proximal chevron osteotomy. Plantar-to-dorsal screw orientation should be considered when using the chevron proximal first metatarsal osteotomy.     

Minifragment Screw Fixation of Oblique Metacarpal Fractures: A Biomechanical Analysis of Screw Types and Techniques

The lag screw technique has historically been a successful and accepted way to treat oblique metacarpal fractures. However, it does take additional time and involve multiple steps that can increase the risk of fracture propagation or comminution in the small hand bones of the hand. An alternate fixation technique uses bicortical interfragmentary screws. Other studies support the clinical effectiveness and ease of this technique. The purpose of this study is to biomechanically assess the strength of the bicortical interfragmentary screw versus that of the traditional lag screw. Using 48 cadaver metacarpals, oblique osteotomies were created and stabilized using one of four methods: 1.5 mm bicortical interfragmentary (IF) screw, 1.5 mm lag technique screw, 2.0 mm bicortical IF screw, or 2.0 mm lag technique screw. Biomechanical testing was performed to measure post cyclic displacement and load to failure. Data was analyzed using one-way analysis of variance (ANOVA). There was no significant difference among the fixation techniques with regard to both displacement and ultimate failure strength. There was a slight trend for a higher load to failure with the 2.0 mm IF screw and 2.0 mm lag screw compared to the 1.5 mm IF and 1.5 mm lag screws, but this was not significant. Our results support previously established clinical data that bicortical interfragmentary screw fixation is an effective treatment option for oblique metacarpal fractures. This technique has clinical importance because it is an option to appropriately stabilize the often small and difficult to control fracture fragments encountered in metacarpal fractures.     

Mechanical Comparison of the Youngswick, Sagittal V, and Modified Weil Osteotomies for Hallux Rigidus in a Sawbone Model

The purpose of this study was to compare the mechanical properties of 3 osteotomies often used for hallux rigidus. Maximum load, failure energy, stiffness, and fracture pattern were determined for 3 different test models as well as a control group. Twenty-eight first metatarsal polyurethane sawbone models were equally divided into 4 groups. The osteotomy groups tested consisted of a Youngswick, sagittal V, and modified Weil-type osteotomy of the first metatarsal. Each osteotomy was fixated with a 2.7-mm cortical screw, all 16 mm in length, and a small diameter smooth wire, both placed perpendicular to the osteotomy. Each model was then loaded to failure in a servo-hydraulic material testing machine. Results for maximum load to failure for all 4 constructs showed a mean range of 15.1 to 33.7 N, a mean energy to failure ranging from 0.04 to 0.8 J, and stiffness from 1.5 to 3.4 N/mm. Significant differences in peak load and stiffness (P = .015 for peak load, P = .025 for stiffness) were found between the sagittal V group versus the control and between the modified Weil and sagittal V group (P = .037 for peak load, P = .017 for stiffness). There were no significant differences in the energy to failure between the 4 groups (P > .083). These findings suggest that the sagittal V osteotomy construct was significantly weaker and less stiff than the modified Weil.     

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.     

Midshaft metatarsal segmental osteotomy with open reduction and internal fixation

BACKGROUND: Metatarsalgia is a common source of patient discomfort and has multiple etiologies. Lesser metatarsal osteotomy is a recognized treatment modality for persistent symptoms after conservative care, yet the location and type of osteotomy remain highly debated topics. The current investigation reports the initial results regarding midshaft, segmental osteotomy of the lesser metatarsals with open reduction and internal fixation. METHODS: Ninety-five consecutive patients had lesser metatarsal midshaft, segmental osteotomy with open reduction and internal fixation from June, 1999, to October, 2001, representing 102 feet and 126 osteotomies. Patient records were retrospectively reviewed for osteotomy union, symptomatic relief, and complications associated with this procedure. Followup ranged from 5 months to 18 months with an average of 8.8 months. Fixation was achieved with a four-hole, 1/4-tubular, minifragment, plate and four 2.7-mm cortical screws. RESULTS: Five patients had transfer lesions, (five feet, five osteotomies) within the followup period. One patient (one foot, one osteotomy, 0.8%) developed a nonunion. After hardware removal this patient's osteotomy united. This technique produced excellent metatarsal union rates (125 of 126 osteotomies, 99.2%). CONCLUSIONS: Although further clinical investigation regarding patient outcome from this procedure needs to be carried out, the data from this preliminary study indicate that midshaft segmental osteotomy of a lesser metatarsal is a useful technique for metatarsal shortening with a high rate of bony union.