A Mechanical Comparison of the Compressive Force Generated by Various Headless Compression Screws and the Impact of Fracture Gap Size

Background: There is evidence that interfragmentary fracture gap size may affect the compression achievable with a modern headless compression screw (HCS). This mechanical study compared the compression achieved by 3 commercial HCS systems through various fracture gaps: CAPTIVATE Headless (Globus Medical, Inc, Audubon, Pennsylvania), Synthes (DePuy Synthes, Westchester, Pennsylvania), and Acumed Acutrak 2 (Acumed LLC, Hillsboro, Oregon). Methods: Screws were inserted into a custom test fixture composed of polyurethane synthetic bone foam fragments, separated by a layer of easily compressible polyurethane foam simulating a fracture gap. Compression was measured after final insertion and countersinking. The effect of the interfragmentary fracture gap size on the compression generated was also investigated. Results: The CAPTIVATE Headless 3.0 mm screw (70.1 ± 5.7 N) and the Synthes 3.0 mm screw (64.9 ± 7.3 N) achieved similar compressive forces after final countersink. Similar comparisons were found for the CAPTIVATE Headless 2.5 mm and Synthes 2.4 mm screws, and the CAPTIVATE Headless 4.0 mm and Acutrak 2 Standard screws. The final compression of the CAPTIVATE Headless 2.5 mm and Synthes 2.4 mm screws was not significantly affected when the fracture gap was doubled from 2 to 4 mm, but was reduced significantly by 95.9% with the Acutrak 2 Micro screw. Conclusion: When comparing like-sized screws, the CAPTIVATE, Synthes, and Acutrak 2 HCS systems demonstrated similar potential compressive forces. However, compared with the CAPTIVATE Headless and Synthes HCS systems, which are inserted with a compression sleeve that is not gap distance–dependent, the Acutrak 2 HCS system demonstrated less compression when the simulated fracture gap size was increased to 4 mm.     

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.     

Locking Plate Alone or in Combination with Cannulated Screws for Hoffa Fractures: A Retrospective Study

ObjectiveTo determine the efficacy of distal femur condyle locking plate (DFCLP) alone or in combination with cannulated screws for Hoffa fractures.MethodsIn this study, between May 2014 and February 2019, 13 patients between 26 and 64 years with isolated Hoffa fractures were enrolled during the study period and retrospectively analyzed. All patients underwent open reduction and internal fixation by DFCLP alone or in combination with cannulated screws followed by early active rehabilitation postoperatively. The primary outcome was evaluated using range of movement (ROM), Knee Society Score (KSS), International Knee Documentation Committee (IKDC) scoring system, and the fracture healing time of the patients during the 24‐month follow‐up period. Postoperative complications were also used to assess the patients’ conditions.ResultsA total of 13 patients completed the 24‐month follow‐up assessment and achieved bone re‐union at Hoffa fracture sites. The average follow‐up period was 24.5 months (ranging from 24 to 28 months). Six patients were treated by DFCLP in combination with cannulated screws and the remaining seven patients were treated by DFCLP alone. The mean ROM was determined as 119° (ranging from 100° to 130°). The mean KSS score was 87.9 (ranging from 80 to 92 points), with 11 patients evaluated as excellent, two as good, and zero bad cases. The mean IKDC score was 84.2 (ranging from 74.7 to 89.7 points), with 10 evaluated as excellent, three as good, and zero bad cases. The mean IKDC score was 83.3 for patients with medial Hoffa fractures and 84.4 for those with lateral Hoffa fractures. The average time to healing was 3.5 months (ranging from 3 to 4 months), and at month 3, the fracture healing was evident in seven patients (54%), and at month 4, fracture healing was seen in six patients (46%). It is worth mentioning that two patients suffered from knee joint stiffness and osteoarthritis during the 24 months follow‐up. Eleven patients (84.6%) achieved satisfactory knee joint function through early postoperative rehabilitation.ConclusionIn patients with Hoffa fractures, treatment with DFCLP alone or in combination with cannulated screws followed by early active rehabilitation resulted in great stability and satisfactory functional outcomes after 24 months. Our findings may provide surgeons with a new way to treat Hoffa fractures.