Nuts and bolts: dimensions of commonly utilized screws in upper extremity surgery

Fracture Gap Closure and Reduction Are Affected by the Orientation of the Headless Compression Screw

BACKGROUND

We evaluated the impact of a variable-pitch headless screw's angle of insertion relative to the fracture plane on fracture gap closure and reduction.

METHODS

Variable-pitch, fully threaded headless screws were inserted into polyurethane blocks of "normal" bone model density using a custom jig. Separate trials were completed with a 28-mm screw placed perpendicular and oblique/longitudinal to varying fracture planes (0°, 15°, 30°, 45°, and 60°). Fluoroscopic images were taken after each turn during screw insertion and analyzed. Initial screw push-off, residual fracture gap at optimal fracture gap reduction, and malreduction were determined in each trial. Statistical analysis was performed via a 1-way analysis of variance followed by Student t tests.

RESULTS

Malreduction was found to be significantly different between the perpendicular (1.88 mm ± 1.38) and the oblique/longitudinal (0.58 mm ± 0.23) screws. The malreduction increased for the perpendicular screw as the fracture angle increased (60° > 45°=30° > 15° > 0°). Residual fracture gap at optimal fracture gap reduction was also found to be significantly different between the perpendicular (0.97 ± 0.42) and oblique/longitudinal (1.43 ± 1.14) screws. The residual fracture gap increased for the oblique/longitudinal screw as the fracture angle increased, although the oblique/longitudinal screw with a 60° fracture angle was the only configuration significantly larger than all the other configurations. Screw push-off was not found to be significantly different between the oblique/longitudinal screw and perpendicular screw trials.

CONCLUSIONS

The perpendicular screw had a larger malreduction that increased with fracture angle, whereas the oblique/longitudinal screw had a larger residual fracture gap that increased with fracture angle.

The Effect of Derotational Kirschner Wires on Fracture Gap Reduction With Variable-Pitch Headless Screws

PURPOSE

We evaluated the impact of angled derotational Kirschner wires (K-wires) on fracture gap reduction with variable-pitch headless screws.

METHODS

Fully threaded variable-pitch headless screws (20 and 28 mm) were inserted into "normal" bone models of polyurethane blocks. In separate trials, derotational K-wires were inserted at predetermined angles of 0°, 15°, 30°, and 40° and compared with each other, with no K-wire as a control. Fluoroscopic images taken after each screw turn were analyzed. The optimal fracture gap closure, initial screw push-off, and screw back-out gap creation were determined and compared at various derotational K-wire angles.

RESULTS

Initial screw push-off due to screw insertion and screw back-out gap creation were not significantly affected by the angle of the derotational K-wire. With a 20-mm screw, only a 40° derotational K-wire led to significantly less gap closure compared with control and with 0°, 15°, and 30° derotational K-wires. It led to an approximately 60% decrease in gap closure compared with no K-wire. With the 28-mm screw, compared with no K-wire, 15° and 30° derotational K-wires led to statistically significant decreases in gap closure (approximately 25%), whereas a 40° derotational K-wire led to an approximately 60% decrease. With the 28-mm screw, the 40° derotational K-wire also led to a statistically significant smaller gap closure when compared with 0°, 15°, and 30° derotational K-wires.

CONCLUSIONS

A derotational K-wire placed in parallel to the planned trajectory of a headless compression screw does not affect fracture gap closure. With greater angulation of the derotational K-wire, the fracture gap is still closed, but less tightly.

CLINICAL RELEVANCE

Derotational K-wires can help prevent fracture fragment rotation during headless compression screw insertion. At small deviations from parallel (≤30°), fracture gap closure achieved by the screw is minimally affected. At greater angles (ie, 40°), fracture gap closure may be substantially reduced, preventing fracture compression.

Which Headless Compression Screw Produces the Highest Interfragmentary Compression Force in Scaphoid Fracture?

BACKGROUND

Interfragmentary compression at the fracture site facilitates healing. Headless compression screws used to treat scaphoid fractures can be grouped as shank screws, conical tapered screws and double component screws. There has been no meta-analysis of biomechanical studies to compare interfragmentary compression produced by the above screws.

METHODS

A computerised search of Pubmed, Embase and OVID database was undertaken to identify the studies. We estimated the weighted mean difference of interfragmentary compression (in Newton) with 95% confidence intervals. Random effects model was selected for meta-analysis.

RESULTS

The pooled estimate of nine studies demonstrated that conical tapered screw produced significantly higher interfragmentary compression force compared to the shank screw (WMD 19.96, 95% CI 11.2-28.8, p < 0.0001, I ² = 99%). The pooled estimate of four studies demonstrated that dual component screw produced significantly higher interfragmentary compression force compared to the shank screw (WMD 16.93, 95% CI 12.3-21.6, p < 0.0001, I ² = 97.7%). The pooled estimate of four studies showed that there was no significant difference in the interfragmentary compression force generated by either conical tapered screw or dual component screw (WMD 3.93, 95% CI - 8.3 to 16.2, p = 0.53, I ² = 99.7%). There was evidence of minimal publication bias.

CONCLUSION

Conical tapered screws and dual component screws produced statistically significant higher interfragmentary compression force at the scaphoid fracture site compared to shank screws. There was no difference in the compression force generated by either conical tapered screw or dual component screw.

Distal Radius Fracture Fixation Devices and Their Radiographs

Background: Distal radius fractures are among the most common fractures encountered in orthopedic practices. If treated operatively, most implants are retained after the fracture heals unless there is hardware failure, limitation of wrist motion, pain, infection, tendon rupture, or tenosynovitis. Complications have been reported during hardware removal, including not knowing the exact implant prior to its removal. If a patient presents for plate removal to a surgeon who did not perform the initial fracture fixation, having a preoperative visual aid can help the treating surgeon choose the right instruments for their removal. Methods: To identify many of the available distal radius fixation devices, we searched the Internet and contacted local industry representatives. We also approached industry personnel at the commercial exhibit of a national hand society meeting to provide us with implants they manufacture. The implants were placed on the volar and dorsal aspects of sawbone models of the distal radius and in one case the radial styloid, using the screws, screwdrivers and accessories in the standard implant set and then posteroanterior and lateral x-rays of the implants were obtained. We created an atlas and a list of the screwdriver(s) used for each. Results: We obtained radiographs and photographs for 28 implants that were manufactured by 14 different companies. Two companies sent us radiographs and photographs placed on either a sawbone or cadaveric model. We found that 7 of the implants were outliers and could be identified easily on the x-rays, whereas 21 implants had similar design of shaft and distal components. Conclusions: To aid the orthopedic surgeon in their removal, we compiled a comprehensive list of most distal radius fixation devices on the market including plates and their corresponding screws and screwdrivers. The goal was to help the surgeon when removing the plate to identify the implant on radiographs.

The effect of screw trajectory for the reduction and association of the scaphoid and lunate (RASL) procedure: a biomechanical analysis

The purpose of this study was to determine if screw placement in the reduction and association of the scaphoid and the lunate (RASL) procedure affected the ability of the scapholunate joint to withstand force. After completely disrupting of the scapholunate ligament in 29 fresh-frozen cadaveric wrists, we placed the RASL screw either distal or proximal to the lateral aspect of the dorsal ridge of the scaphoid and into the dorsal or volar aspect of the lunate. Specimens were subjected to repeated cycles of transcarpal axial force, mimicking clenched-fist loading, until failure. Screw placement distal to the lateral aspect of the dorsal scaphoid ridge was significantly associated with failure when examined manually, radiographically (1.8 vs. 0.5 mm) and using real-time motion capture (diastasis: 1.6 vs. 0.4 mm; Euler angle: 4.5 ° vs. 0.8 °). The lateral aspect of the dorsal ridge is a reliable radiographic landmark on the scaphoid and provides surgeons with a convenient starting point to achieve the most biomechanically stable RASL construct, and, therefore, enhances the potential for an optimal clinical outcome.

Current Trends in the Management of Distal Radius Fractures

This article discusses recent reports on distal radius fractures. The keyword "distal radius fracture" was used to query the PubMed database of the US National Library of Medicine. From the resulting list, articles published in the Journal of Hand Surgery (American Volume), the Journal of Hand Surgery (European Volume), and the Journal of Orthopaedic Trauma from April 2014 through December 2015 were reviewed. Related commentaries were also evaluated. Case series of fewer than 5 patients were excluded. The 65 studies and commentaries identified are categorized and summarized. [Orthopedics. 2017; 40(3):145-152.].

Skeletal Fixation in a Mutilated Hand

Hand fracture fixation in mutilating injuries is characterized by multiple challenges due to possible skeletal disorganization and concomitant severe injury of soft tissue structures. The effects of skeletal disruption are best analyzed as divided into specific locales in the hand: radial, ulnar, proximal, and distal. Functional consequences of injuries in each of these regions are discussed. Although a variety of implants are now in vogue, K-wire fixation has stood the test of time and is especially useful in multiple fracture situations. Segmental bone loss is quite common in such injuries, which can be safely reconstructed in a staged manner.

Hand Fractures: Indications, the Tried and True and New Innovations

Hand fractures are the second most common fracture of the upper extremity, and management of patients with these injuries is common for most hand surgery practices. In this article, we outline the principles of management of these injuries with a special focus on those that are common or complex. We also highlight recent innovations in the context of these injuries. From this cross-section of contemporary evidence on phalangeal and metacarpal fracture treatment, we have noted a trend toward minimally invasive surgery with immediate postoperative mobilization, the use of wide-awake anesthesia, as well as sustained investigation and innovation in the biomechanics and treatment of proximal interphalangeal joint fracture dislocations.