ABSTRACT
BACKGROUND: Lateral meniscus transplantation is a proven treatment option for the meniscus-deficient knee, yet little is known about meniscal kinematics, strain, and tibiofemoral contact pressure changes after transplantation or the effect of altered root position in lateral meniscus transplantation. PURPOSE: To compare the native lateral meniscal kinematics, strain, and tibiofemoral contact pressures to a best-case scenario meniscus transplant with perfectly matched size and position and to determine how sensitive these factors are to subtle changes in shape and position by using a nonanatomic meniscus transplant position. STUDY DESIGN: Controlled laboratory study. METHODS: The lateral menisci of 8 cadaveric knees were circumferentially implanted with radiopaque spherical markers. They were mounted to a testing apparatus applying muscle and ground-reaction forces. The meniscus was evaluated at 0°, 30°, 90°, and 115° of knee flexion using Roentgen stereophotogrammetric analysis (RSA), with a pressure sensor affixed to the lateral tibial plateau. Measurements were recorded for 3 states: the native lateral meniscus, an anatomic autograft transplant, and a nonanatomic autograft transplant with an anteriorized posterior root position. RESULTS: After transplantation, there was less posterior displacement in both the anatomic and nonanatomic transplant states compared with the native meniscus, but this was not significant. The largest lateral translation in the native state was 2.38 ± 1.58 mm at the anterolateral region from 0° to 90°, which was increased to 3.28 ± 1.39 mm (P = .25) and 3.12 ± 1.18 mm (P = .30) in the anatomic and nonanatomic transplant states, respectively. Internal deformations of the transplant states were more constrained, suggesting less compliance. The native meniscus distributed load over 223 mm2, while both the anatomic (160 mm2) and nonanatomic (102 mm2) states concentrated pressure anteriorly to the tibial plateau centroid. CONCLUSION: This study is the first to characterize kinematics in the native lateral meniscus compared with a transplanted state utilizing RSA. Results demonstrate increased meniscal constraint and pressure concentrations even after an ideal size and position matched transplantation, which further increased with a nonanatomic posterior root position. CLINICAL RELEVANCE: The results show that kinematics are similar in both transplanted states when compared with the native meniscus at various flexion angles. Because both transplanted states were more constrained with less deformation compared with the native state, this should allow for relatively safe postoperative range of motion. However, in the transplanted states, peak pressures were distributed over a smaller area and shifted anteriorly. This pattern was exacerbated in the nonanatomic state compared with anatomic. This could have detrimental effects with regard to articular cartilage degeneration, and ultimately result in a failed transplantation.
ABSTRACT
BACKGROUND: Early cocking phase pitching mechanics may affect risk of upper extremity injury requiring surgery in professional baseball players. PURPOSE: To assess the occurrence of inverted-W arm positioning and early trunk rotation in Major League Baseball (MLB) pitchers and to determine whether this throwing position is associated with upper extremity injury requiring surgery. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: For 250 MLB pitchers in the 2010 season, 15 to 20 pitches from the start and end of an outing were reviewed using slow-motion game video for presence of an inverted-W position and early trunk rotation. Previous or current incidence of upper extremity injury requiring surgery for each player was determined using the MLB injury database, minor league injury records, available collegiate data, and publicly available online injury databases. Upper extremity surgery associated with an injury was considered to result from pitching. RESULTS: Consensus between investigators was achieved for 99% of players for inverted-W positioning (248 players) and in 97% of players for early trunk rotation (243 players) for videos reviewed independently. Rate of surgery with and without inverted-W position was 28 of 93 (30%) and 42 of 155 (27%), respectively. Rate of surgery with and without early trunk rotation was 37 of 111 (33%) and 30 of 132 (23%), respectively. Using a Cox proportional hazards model for risk analysis using the measured number of innings pitched at time of surgery as an approximate index of exposure and adjusting for age and fastball speed at time of surgery, early trunk rotation was associated with significantly increased risk of shoulder and/or elbow surgery with hazard ratio estimate of 1.69 (95% CI, 1.02-2.80). Presence of the inverted-W position was not associated with significantly increased risk (hazard ratio, 1.30; 95% CI, 0.79-2.14). CONCLUSION: The inverted-W throwing position was not associated with significantly greater risk of upper extremity injury requiring surgery in MLB pitchers. Early trunk rotation was associated with significantly elevated risk of injury requiring surgery.
ABSTRACT
BACKGROUND: The irregular nature of the dorsal surface of the distal radius makes it difficult to detect prominent screws with volar plate fixation for distal radius fractures using standard fluoroscopic images. This study evaluates the accuracy of a new radiographic method, the Hoya view, for the assessment of dorsal cortical screw penetration with volar plate fixation. METHODS: Eight cadaveric upper extremities underwent application of a volar distal radius plate with polyaxial locking screws placed distally. Utilizing a mini C-arm, lateral and Hoya views were obtained with notation of any dorsal cortical screw prominence. Dissection of the cadavers was then performed for direct visualization of screw prominence. The screws were then exchanged sequentially for screws 2-mm longer than their initial measurements with repeated imaging and direct visualization. RESULTS: The Hoya view revealed that 9.4 % of the screws penetrated the dorsal cortex with an average screw prominence of 1.08 mm (range 0.5-2 mm). None of the six prominent screws were detected with lateral views. With the Hoya view, six of six prominent screws were identified. With locking screws exchanged for screws 2-mm longer, 76.6 % of the screws had violated the dorsal cortex; of these, 24.5 % were detected with lateral imaging versus 100 % with the Hoya view. CONCLUSIONS: This study supports the intraoperative use of the Hoya view to evaluate screw length and dorsal cortical screw penetration in volar plate fixation of distal radius fractures. However, this view may be difficult to obtain in patients with limitations in elbow or shoulder range of motion.
