Faculty Bibliography

BACKGROUND:Biomechanical studies on retrograde intramedullary fixation for tibiotalocalcaneal fusion have been reported, but no studies have investigated dorsiflexion stiffness, load-to-failure, fatigue endurance, and plastic deformation using different distal screw orientations. Also, no studies have examined the effect of bone density on different distal screw orientations while using a fatigue loading mode. METHODS:Eight matched pairs of cadaver legs were used. In one leg from each pair an intramedullary nail was inserted with lateral-to-medial distal screws and in the other with posterior-to-anterior screws. These samples underwent dorsiflexion fatigue testing with determination of initial and final stiffness, load-to-failure, and degree of plastic deformation at failure. DEXA scanning was done of each cadaver specimen to determine bone mineral density. Statistical analysis was performed using the Student t-test and a Pearson correlation. Significance level was set at p < 0.05. RESULTS:The specimens with posterior-to-anterior screws had a significantly higher fatigue endurance load-to-failure (1130.0 +/- 362.0 N compared to 801.0 +/- 227 N, p = 0.01). They also had significantly higher final stiffness (203.1 +/- 23.1 N/mm compared to 146.6 +/- 46.2 N/mm, p = 0.05) and lower plastic deformation (2.4 +/- 1.5 mm compared to 3.8 +/- 2.3 mm, p = 0.04). There was a statistically significant correlation between bone mineral density and the difference in construct deformation with posterior-to-anterior and lateral-to-medial screw orientation (r = 0.76, p = 0.03). CONCLUSIONS:In this biomechanical investigation of tibiotalocalcaneal arthrodesis with intramedullary nail fixation, posterior-to-anterior distal screw orientation provided more stable fixation than lateral-to-medial screw orientation.

BACKGROUND:Charcot arthropathy is a chronic, progressive destructive process affecting bone architecture and joint alignment in people lacking protective sensation. The etiologic factors leading to progressive bone resorption have not been elucidated. The purpose of this study was to histologically examine surgical specimens with Charcot arthropathy for cell type and immunoreactivity of known cytokine mediators of bone resorption. METHODS:Tissue samples of 20 specimens with known Charcot arthropathy were stained for Hematoxylin and Eosin (H&E) to quantify cell type. Nine of the specimens were stained with interleukin-1 (IL-1) antibody, nine with tumor necrosis factor (TNF) alpha antibody, and nine with interleukin-6 (IL-6) antibody. Distribution of staining was graded as focal (less than 10% of cells), moderate (10% to 50% of cells), and diffuse (more than 50% of cells) by two independent investigators. Inflammatory cells in tissue sections of rheumatoid synovium served as a positive control. RESULTS:Osteoclasts were seen in excessive numbers lining the resorptive bone lacunae. There was a disproportionate increase in osteoclasts to osteoblasts in the Charcot-reactive bone. In each case, osteoclasts demonstrated immunoreactivity for IL-1, IL-6 and TNF-alpha with a grade of moderate or diffuse reactivity. CONCLUSION/CONCLUSIONS:The findings of excessive osteoclastic activity in the environment of cytokine mediators of bone resorption (IL-1, IL-6, and TNF-alpha) suggest enhanced bone resorption through the stimulation of osteoclastic progenitor cells as well as mature osteoclasts. Alteration in the synthesis, secretion, or activity of these important regulatory molecules through the use of pharmacologic agents may, in turn, alter bone remodeling and loss and lead to accelerated healing without collapse or malalignment.

BACKGROUND:Acquired flexible flatfoot encompasses a wide spectrum of disease, and there is no validated treatment protocol. We hypothesized that a medializing calcaneal osteotomy with a flexor digitorum longus transfer is adequate to correct a less severe acquired flexible flatfoot but not a more severe flatfoot. We also hypothesized that use of an additional procedure would further correct the flatfoot. METHODS:The study included seven pairs of cadaver specimens, with one side randomly selected for the creation of a mild flatfoot deformity and the other, for the creation of a severe flatfoot deformity. Cyclic axial load was applied to the intact foot, to the flatfoot, after correction with a medializing calcaneal osteotomy and a flexor digitorum longus transfer, and after the addition of a subtalar arthroereisis. Radiographic and pedobarographic data were obtained at each stage. A repeated-measures analysis of variance with post hoc analysis was used to compare all parameters in the intact foot with those in the flatfoot and corrected specimens. A Student t test was used to compare flatfoot severity between the mild and severe models. RESULTS:Compared with the intact foot, the mild and severe flatfoot models showed a significant change in the talar-first metatarsal angle (p = 0.01 and 0.03, respectively), talonavicular angle (p = 0.04 and 0.04), and medial cuneiform height (p = 0.03 and 0.05). The mild and severe models were significantly different from each other with regard to the talar-first metatarsal angle (p = 0.003) and talonavicular angle (p = 0.002). After the osteotomy and tendon transfer in the mild-flatfoot model, the talar-first metatarsal angle and talonavicular angle were not significantly different from those in the intact state. In the severe-flatfoot model, the talar-first metatarsal angle, talonavicular angle, and medial cuneiform height remained significantly undercorrected after the osteotomy and tendon transfer. After the arthroereisis, the talonavicular angle and medial cuneiform height were not significantly different from the values for the intact foot. CONCLUSIONS:In a cadaver model, the effectiveness of different procedures on radiographic and pedobarographic parameters varies with the severity of an acquired flatfoot deformity.

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 <or= 0.05. RESULTS:The mean maximal load to failure was 140.08 N (SD +/- 77.1) for screw fixation alone and 58.09 N (SD +/- 11.86) for the H-locking plate. This difference was statistically significant (p = 0.008). The mean stiffness of the construct for screw fixation alone was 83.10 N/mm (SD +/- 49.8) and 19.96 N/mm for the H-locking plate. This difference also was statistically significant (p = 0.004). CONCLUSION/CONCLUSIONS:Screw fixation for first MTC arthrodesis created a stronger and stiffer construct than did the H-locking plate. This was likely due to the mechanical design of the implants. Compression across the MTC joint could be applied with the screws, but the plate relied on a fixed angle design with no compression.

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/CONCLUSIONS: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.

BACKGROUND:Metatarsalgia of the second ray is a common problem associated with disorders of the first metatarsal. It also occurs after the operative treatment of those disorders. Plantar pressure changes from alteration of the static and dynamic structure of the forefoot may be associated with this condition. This study evaluated changes in plantar forefoot pressure especially under the second metatarsal head after three operative procedures on the first ray. METHODS:Each of 12 cadaver foot specimens was cyclically loaded on the servohydraulic MTS Mini Bionix test frame (MTS Systems Corp., Eden Prairie, MN) with traction on the Achilles tendon. Plantar forefoot pressure was measured by the F-scan system (Tekscan, Inc., S. Boston, MA) with the foot intact, after a first metatarsal base dorsal closing-wedge osteotomy with 5-mm base length to simulate dorsal malunion, and after 5-mm and 10-mm metatarsal shortening procedures. Paired Student t-test analysis was used to compare data for the intact foot with data after each intervention. One form of Bonferroni's correction was done to establish a new alpha level to tighten the analysis and to compensate for multiple paired Student t-tests. The significance level was calculated to be 0.016 based on an original alpha level of 0.05. RESULTS:As compared with the intact foot, all three procedures on the first metatarsal resulted in significant decreases in plantar pressure under the first metatarsal head (p < 0.016). Plantar pressure under the second metatarsal head increased significantly as compared with the intact foot (p < 0.016) after all three procedures. Pressures under the third-fourth metatarsal heads increased significantly compared with the intact foot after the 5-mm and 10-mm shortenings (p < 0.016). Plantar pressure under the fifth metatarsal did not change significantly after any of the three procedures. CONCLUSIONS:Dorsiflexion osteotomy and shortening of the first metatarsal are associated with significant forefoot plantar pressure changes in a cadaver model.

Despite reports of high nonunion rates for isolated talonavicular fusion, this procedure may be indicated for some patients, including those for whom increased stability of the talonavicular joint in triple arthrodesis is needed. In the biomechanical cadaveric study reported here, we evaluated fixation methods used to provide optimal stability of talonavicular arthrodesis. A physiologic 3-point loading model was used to measure dorsal displacement of the navicular on the talus with 1 or 2 cannulated 4.5-mm screws across the talonavicular joint both with and without one 7.3-mm cannulated screw across the subtalar joint. Statistically significant differences in displacement under cyclic loading to one-half body weight were found. Use of 2 talonavicular screws and no subtalar screw or 1 talonavicular screw plus 1 subtalar screw decreased the motion, as compared with use of 1 talonavicular screw and no subtalar screw.

BACKGROUND:Loss of reduction of proximal metatarsal osteotomies may result from poor bone quality, suboptimal fixation, and limitations inherent in the bony geometry of the osteotomy. This study evaluated the mechanical benefit of adding two supplementary Kirschner wires to the crescentic and Ludloff osteotomies. METHODS:Eleven and 10 matched pairs of cadaver foot specimens were used for the Ludloff and the proximal crescentic metatarsal osteotomies, respectively. Each metatarsal head specimen was then loaded to failure using a servohydraulic MTS Mini Bionix test frame (MTS Systems Corp, Eden Prairie, MN), and the failure gap was measured with an extensometer. To account for variable bone quality in the study specimens, the failure loads were normalized with the measured bone mineral density (BMD) values of the metatarsal specimens. A paired Student's t-test analysis was used to compare the failure loads between the specimens with the conventional osteotomies and the osteotomies supplemented with two axial Kirschner wires. RESULTS:The load-to-failure of the Ludloff osteotomy with two screws and with one proximal screw and two Kirschner wires was 858.5 N cm(2)/gm and 692.3 N cm(2)/gm, respectively (p > 0.05). The average load-to-failure of crescentic osteotomy with one screw and two axial Kirschner wires (458.8 N cm(2)/gm) was significantly higher than the strength of crescentic osteotomy fixed with one screw only (367.5 N cm(2)/gm) (p = 0.05). For the Ludloff osteotomy, 16 specimens (72.7%) failed by more than 2 mm of gapping. The crescentic osteotomy failures included 16 2-mm gap failures (80%). The Ludloff osteotomy showed a trend toward increased fixation stability as compared with both crescentic osteotomy constructs. CONCLUSION/CONCLUSIONS:The use of two supplemental axial Kirschner wires offers a simple and effective means to improve the initial mechanical stability of the proximal crescentic osteotomy and can be used in the standard Ludloff osteotomy to replace the second screw when screw purchase is poor without significant loss of fixation strength. The possible advantage of Kirschner wire flexibility in restoring position after gapping of the osteotomy site should be investigated.