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Category: Hindfoot; Basic Sciences/Biologics; Other Introduction/Purpose: Minimally Invasive (MIS) calcaneal osteotomy has grown in popularity in recent years to address hindfoot deformity. A potential complication is thermal bone necrosis secondary to heat generation from the burr, leading to nonunion of the osteotomy. Irrigation is commonly employed to reduce this risk. The effect of irrigation on reducing this risk remains an understudied area. The purpose of this study was to evaluate the effect of cooled versus room-temperature irrigation on thermal energy dissipation on a temperature curve during calcaneal osteotomy using a Shannon burr. Methods: Ten cadaveric limbs (5 pairs) at room temperature (68 0F) were randomized to receive either cooled saline or room temperature irrigation during MIS calcaneal osteotomy. Two thermocouple probes (EL-USB-TC-LCD, Lascar Electronics) were inserted 5mm away from the plane of the osteotomy, on proximal and distal sides respectively (Fig. 1). The probes were inserted to a depth of 2cm. A 3 x 30mm Shannon burr was used to perform the osteotomy. The burr was run continuously under continuous irrigation using either room temperature (680F) and chilled (370F) irrigation, until the osteotomy was completed. All osteotomies were performed in approximately 60 seconds. Temperature was recorded at 15sec, 30sec, 45 sec and 60 sec for the two groups and used as a measure of thermal energy generation. Results: Both room temperature and chilled irrigation were effective in minimizing temperature change. On the proximal side, an overall mean increase of 2.60F (70.60F) with room temperature irrigation and a mean increase of 0.70F (68.70F) with chilled irrigation were observed at the 60 sec interval (p=0.09). On the distal side both irrigation methods were more effective in heat control (70.20F vs 67.10F; p=0.17). Conclusion: For the duration of a MIS calcaneal osteotomy, both continuous room temperature and chilled irrigation can reduce thermal energy generation. Use of chilled irrigation can be considered for osteotomies of denser bone that may take longer to perform and generate higher temperatures.

Background: Minimally invasive (MIS) calcaneal osteotomy has grown in popularity in recent years to address hindfoot deformity. A potential complication is thermal bone necrosis secondary to heat generation from the burr that may lead to osteotomy nonunion. Irrigation is commonly employed to reduce this risk. The effect of irrigation on reducing heat accumulation remains an understudied area. The purpose of this study was to evaluate the effect of cooled vs room-temperature irrigation on thermal energy dissipation during calcaneal osteotomy using a Shannon burr. Methods: Fourteen cadaveric limbs at room temperature (68 °F) were randomized to receive either cooled saline (7 limbs) or room-temperature (7 limbs) irrigation during MIS calcaneal osteotomy. Two thermocouple probes were inserted 5 mm away from the plane of the osteotomy, on the proximal and distal sides, respectively. A 3 × 30-mm Shannon burr was used to perform the osteotomy. The burr was run continuously with continuous irrigation using either room-temperature (68 °F) or chilled (37 °F) irrigation, until the osteotomy was completed. Temperature was recorded at 0, 15, 30, 45, and 60 seconds for the 2 groups and used as a measure of thermal energy accumulation. Results: Both room-temperature and chilled irrigation were effective in minimizing temperature change. On the proximal side, an overall mean increase of 2.5 °F with room-temperature irrigation and a mean decrease of 1.0 °F with chilled irrigation were observed at the 60-second interval ( P = .004). On the distal side, there was a mean increase of 1.3 °F with room-temperature irrigation and a mean increase of 0.5 °F with chilled irrigation ( P = .05). Conclusion: For the duration of an MIS calcaneal osteotomy, both continuous room-temperature and chilled irrigation can minimize temperature increases and potentially reduce the risk of an osteotomy nonunion. Clinical Relevance: Both room-temperature and chilled irrigation can minimize bone temperature increases during MIS calcaneal osteotomy.

Category: Bunion Introduction/Purpose: Proximal metatarsal osteotomies are commonly employed to treat moderate to severe hallux valgus deformities. An understudied area with respect to these procedures is the effect on articular contact properties following the surgeries. Potential long-term risks include altered joint mechanics and possible arthritic progression. A biomechanical comparison of articular characteristics of the proximal opening wedge and Ludloff osteotomies was performed in this study. It is hypothesized that the proximal opening wedge osteotomy (POWO) would lead to greater alterations in articular contact properties along the first ray. Methods: Seven paired fresh-frozen below-knee cadaveric limbs with hallux valgus deformity were selected. The first ray inclusive of the navicular-medial cuneiform articulation was dissected and potted in resin. Specimens in each pair were tested in the intact state and then randomized to receive either a Ludloff or POWO. A 4 mm opening wedge osteotomy was used in all cases. The FHL was dissected and isolated. Testing was conducted in a customized apparatus with the cuneiform pinned to the apparatus and positioned at 10 degrees of declination. Loading of the FHL was conducted to 100 N utilizing an instrumented tensioner. A 28 N load was added at the distal phalanx to simulate the ground reaction force(Fig.1). First MTP and TMT articular properties were recorded simultaneously using two pressure sensors. For each state, a pressure map was generated and contact area, peak pressure and center of pressure were calculated. Results: Average peak pressure was noted to be elevated at the MTP (4.6 mPa vs 6.9 mPa, P = 0.08) and TMT (3.3 mPa vs 5.1 mPa, P = 0.16) joints when comparing the Ludloff and the POWO respectively, but was not significant. Contact area was also noted to be lower in the POWO vs Ludloff states for the MTP (86. 6mm2 vs 69.1mm2, P = 0.15) but not the TMT joints (89.1 mm2 vs 88.5mm2, P = 0.96). A trend towards decreased contact force within the TMT joint was noted following opening wedge osteotomy relative to the intact state (103.8 N vs 113.9 N, P = 0.31), while forces were elevated at the MTP joint (104.3 N vs. 96.0 N, P = 0.63), although not statistically significant. Conclusion: POWO can potentially change articular contact characteristics along the TMT and MTP articulations of the first ray. This could possibly lead to altered loading patterns and possible long-term arthritic progression versus other osteotomies. However, it is unlikely that the changes observed with the sizes of the osteotomy commonly used would lead to long term significant consequences.

Background: An understudied area of proximal first metatarsal osteotomies is the effect on articular contact properties following the surgeries. Potential long-term risks include altered joint mechanics and possible arthritic progression. A biomechanical comparison of articular characteristics of the proximal opening wedge and Ludloff osteotomies was performed in this study. It was hypothesized that the proximal opening wedge osteotomy (POWO) would lead to greater alterations in articular contact properties along the first ray. Methods: Seven paired fresh-frozen below-knee cadaveric limbs with hallux valgus were selected. Specimens in each pair were tested in the intact state and then randomized to receive either a Ludloff or POWO. A 4-mm opening wedge osteotomy was used in all cases. Loading of the flexor hallucis longus was to 100 N using an instrumented tensioner. A 28-N load was added at the distal phalanx to simulate the ground reaction force. First metatarsophalangeal (MTP) and tarsometatarsal (TMT) articular properties were recorded simultaneously using 2 pressure sensors. For each state, a pressure map was generated and contact area, peak pressure, and center of pressure were calculated. Wilcoxon signed-rank test was used to assess statistical significance. Results: Average peak pressure was noted to be elevated at the MTP (4.6 vs 6.9 mPa, P = .04) and TMT (3.3 mPa vs 5.1 mPa, P = .30) joints when comparing the Ludloff and the POWO, respectively. Contact area was also noted to be lower in the POWO relative to the Ludloff for the MTP (86.6 vs 69.1 mm 2 , P = .30) but not the TMT joints (89.1 vs 88.5 mm 2 , P = .97). There was a slight plantar-lateral and dorsomedial shift in pressure at the MTP and TMT articulations, respectively, of the POWO relative to the Ludloff. A trend toward decreased contact force within the TMT joint was noted following opening wedge osteotomy relative to the intact state (103.8 vs 113.9 N, P = .31), while forces were elevated at the MTP joint (104.3 vs 96.0 N, P = .63), although not statistically significant. Smaller increases in TMT and MTP joint forces were noted following the Ludloff when compared to the intact state (95.6 vs 93.3 N at TMT and 109.2 vs 103.2 N at MTP). Conclusion: POWO can potentially change articular contact characteristics along the TMT and MTP articulations of the first ray. This could possibly lead to altered loading patterns and possible long-term damage vs other osteotomies. Clinical Relevance: While it is unlikely that the changes observed with the sizes of the osteotomy commonly used would lead to long-term significant clinical consequences, further study with larger group sizes would be beneficial.