Comparison of percutaneous dorsal versus volar fixation of scaphoid waist fractures using a computer model in cadavers

Clinical outcomes of double-screw fixation with bone grafting for displaced scaphoid nonunions: A series of 21 cases

Purpose

This study reports the clinical outcomes of double-screw fixation with bone grafting for displaced scaphoid nonunions.

Patients and methods

This study was a retrospective survey. From January 2018 to December 2019, 21 patients with displaced scaphoid fractures underwent open debridement and two headless compression screw fixation with bone grafting. The preoperative and postoperative lateral intrascaphoid angle (LISA) and scapholunate angle (SLA) were recorded. Preoperative and postoperative grip strength (% of the healthy side), active range of motion (AROM), visual analogue scale (VAS), and patient-rated wrist evaluation (PRWE) scores at the final follow-up were obtained for all patients for comparison.

Results

Patients were treated for an average of 38.3 months (range 12-250) after the injury. The average time of postoperative follow-up was 30.5 months (range 24-48). All fractures achieved union at a mean of 2.7 months (range 2-4) after surgery, and 14 scaphoids of 21 patients (66.7%) healed by 8 weeks. CT scans showed no evidence of cortical penetration of either screw in all patients. There was a statistically significant improvement in AROM, grip strength, and PRWE. No complications occurred in this study, and all patients returned to work.

Conclusion

This study indicates that double-screw fixation with bone grafting is an effective technique for treating displaced scaphoid nonunions.

[Fractures and Non-Unions of the Scaphoid: Our preferred surgical Approaches]

This article describes our algorithm for approaching and fixing scaphoid fractures and non-unions.

A Study on Sexual Dimorphism of Adult Wet Scaphoid Specimens

Background

Sexual dimorphism in human bones has mostly been confined to the study of the bony pelvis. However, considerable changes also exist in the other parts of the skeletal system. This study focuses on the differences in the morphometry of male and female adult scaphoids.

Aims and objectives

We aim to study the morphometry of male and female adult human scaphoids and determine the differences between the same.

Materials and methods

A total of 100 scaphoids were freshly dissected from both hands of 25 male and 25 female cadavers in Saveetha Medical College, Chennai, India. The soft tissues were loosened using 5% potassium hydroxide (KOH) solution. Further, the soft tissues were removed by meticulous dissection. For the measurements, vernier calipers and threads for circumference measurement were used.

Results

The morphometric parameters included length, proximal width, width of the middle part (waist), distal width and circumference of the waist, and circumference of the tubercle in scaphoids. Statistical differences were found in most of the parameters.

Conclusion

A statistically significant difference exists between the morphometric measurements of male and female adult scaphoids, which may prove helpful in the fracture fixation of the scaphoid, as scaphoid fracture has a risk of avascular necrosis.

Mixed Reality Assisted Percutaneous Scaphoid Fixation: A Proposed New Surgical Technique

The success of percutaneous fixation of non or minimally displaced scaphoid waist fractures is reliant on optimal placement of the screw. This can be challenging for surgeons to achieve, potentially involving a large volume of intraoperative imaging, and surgical time. Mixed reality (MR) is a new technology that allows the projection of holographic imagery within the surgeon's field of vision intraoperatively. This imagery can include surgical planning data and 3D reconstructions of a patient's anatomy that can be used in order to aid the surgeon in achieving accuracy. We describe a technique for how this novel technology might be used in the future to fix scaphoid fractures-MR assisted percutaneous scaphoid fixation. This is done using cadaveric modeling. MR assisted percutaneous scaphoid fixation may have the potential to aid surgeons in achieving an optimal guidewire placement with the ability to reduce surgical time and radiation exposure.

Two-Screw Fixation of Scaphoid Waist Fractures

Optimal fixation strategy for scaphoid waist fractures remains a contentious topic with options including using a single screw, 2 screws, or a scaphoid plate. Biomechanical studies favor 2-screw fixation with regards to higher load to failure, load to 2-mm displacement, energy absorbed, rotational stability, and stiffness. Furthermore, recent retrospective studies found increased union rate with 2 screws. Although conclusive clinical data are lacking, 2-screw fixation of a scaphoid waist fracture may theoretically allow the patient to start earlier range of motion and strengthening with greater confidence. Our experience with 2-screw fixation has been promising with all acute waist fractures healing and nonunions treated with 2 screws having high union and low reoperation rates.

Computer-assisted Surgery for Scaphoid Fracture

The computer-assisted surgery (CAS) has significantly improved the accuracy, reliability and outcomes of traumatic, spinal, nerve surgery and many other operations with a less invasive way. The application of CAS for scaphoid fractures remains experimental. The related studies are scanty and most of them are cadaver researches. Some intrinsic defects from the registration procedure, scan and immobilization of limbs may inevitably result in deviations. Some deviations become more obvious with operations of small bones (such as scaphoid) although they are acceptable for spine and other orthopedic surgeries. We reviewed the current literatures on the applications of CAS for scaphoid operation and summarized technical principles, scan and registration methods, immobilization of limbs and their outcomes. On the basis of the data, we analyzed the limitations of this technique and envisioned its future development.

Comparison of volar versus dorsal screw fixation for scaphoid waist fractures: A finite element analysis

PURPOSE

Scaphoid waist fractures may be fixed through volar or dorsal screw fixation. However, there is no consensus on which surgical fixation method should be performed. The purpose of this study was to compare volar versus dorsal screw fixation of scaphoid waist fractures under physiological loading conditions utilizing finite element analysis.

METHODS

A transverse scaphoid waist fracture (Herbert type B2) model was fixed with a headless cannulated compression screw using either a volar or dorsal approach. Displacement and rotation of the fragments and stress analysis on the scaphoid bone and screw were analyzed in the models using 3-D finite element analysis in three different wrist positions; total extension (TE), neutral (N) and total flexion (TF).

RESULTS

Displacement of the fracture gap in volar fixation in all planes (x, y, z) was less than in dorsal fixation in the TF and N positions. Furthermore, rotational stability was stronger in volar fixation in all planes and wrist positions. von Mises stress values were concentrated on the proximal fragment in all wrist positions.

CONCLUSIONS

Although both volar and dorsal fixation techniques can be preferred in Herbert type B2 fractures, results of this finite element analysis suggest that centrally placed volar compression screw fixation may be biomechanically advantageous over dorsal screw fixation.

LEVEL OF EVIDENCE

I.

Scaphoid screw fixation perpendicular to the fracture plane: Comparing volar and dorsal approaches

INTRODUCTION

To percutaneously fixate a midwaist scaphoid fracture, both volar and dorsal approaches are considered valid options although they may have different screw insertion angles relative to the scaphoid fracture plane influencing fixation stability. In this virtual simulation study, we investigated the accessibility of placing a screw perpendicularly to the fracture plane in transverse and horizontal oblique scaphoid midwaist fracture models and compared standard volar and dorsal approaches.

MATERIAL AND METHODS

Computed tomography scans of 38 healthy wrists were used to obtain virtual 3-dimensional wrist models in flexion and extension. In case the trapezium in volar approach or the distal radius in dorsal approach obstructed the screw axis perpendicular to the fracture plane, an alternative non-obstructed screw axis was chosen as close as possible to the perpendicular axis. The deviation angle between the best possible non-obstructed screw placement and true perpendicular screw placement was quantified.

RESULTS

For transverse fractures, the average deviation angle (±standard deviation) was 8° (±5°) in volar approach, and 0° (±0°) in dorsal approach. For horizontal oblique fractures, these angles were 40° (±6°) and 14° (±8°), respectively.

DISCUSSION

In our simulations, compared to the volar approach, the dorsal approach provided the most precise screw placement perpendicular to the fracture plane, with the largest differences for horizontal oblique fractures. When taken in addition to screw purchase, thread engagement and protrusion risk, information about screw orientation may help surgeons in deciding between percutaneous approaches in scaphoid surgery on which there is currently no consensus.

LEVEL OF EVIDENCE

N/A.

Scaphoid screw placement under minimal radiation exposure

BACKGROUND

Percutaneous scaphoid fixation through either a volar or dorsal approach has the advantage of minor soft tissue damage compared with ORIF, and faster fracture union compared with conservative treatment. However, this technique demands highly intraoperative reliance on X-ray control, including increased radiation exposure and all associated side effects.

PURPOSE

To test the possibility and efficacy of volar percutaneous scaphoid screw placement under minimalradiation exposure.

METHODS

The sample included 20 hands (seven left, 13 right) from human adult cadavers. For this study, the utilised wrists were assumed to have non-displaced scaphoid fractures. Using a percutaneous approach, a 2-mm Kirschner wire (K-wire) was advanced to the distal pole of the scaphoid and placed in a 45° horizontal and vertical angle under monitoring with the C-arm. The K-wire was inserted blindly alongside the estimated length of the scaphoid. Following K-wire insertion, four X-rays were taken to depict K-wire positioning and to assess positioning alongside the axis of the scaphoid and K-wire protrusion. The rating scale comprised 1 (good), 2 (moderate) or 3 (poor).

RESULTS

All tested radiographic views were evaluated with a median of 2 points (moderate position) regardingplacement alongside the scaphoid axis.

CONCLUSION

Our results indicate that percutaneous scaphoid fixation with the guide wire placed in a 45° horizontal and vertical angle enables primary moderate positioning, which may lead to quicker adjustment to the ideal position and a decrease of radiation exposure.

Percutaneous Treatment of Unstable Scaphoid Waist Fractures

BACKGROUND

Percutaneous techniques have been described for the treatment of nondisplaced scaphoid fractures, although less information has been reported about outcomes for unstable, displaced fractures. The aim of this study was to evaluate the union and complication rates following manual closed reduction and percutaneous screw placement for a consecutive series of unstable, displaced scaphoid fractures.

METHODS

A total of 28 patients (average age, 27 years; 22 male/6 female) were treated for isolated unstable displaced scaphoid waist fractures. Closed reduction and percutaneous headless, compression screw fixation was successfully performed in 14 patients (average age, 32 years; 10 male/4 female), and the remaining 14 patients required open reduction. Patients who underwent percutaneous treatment were followed for radiographic fracture union and clinical outcomes.

RESULTS

Thirteen of 14 fractures (93%) had clinical and radiographic evidence of bone union at an average of 2.8 months postoperatively. Average visual analog pain score at the time of union was 0.9. The average Quick Disability of the Arm, Shoulder, and Hand score at 2.5 years follow-up (range, 1.5-8.3 years) was 9.6 (range, 0.0-27.3). Complications included 1 case of nonunion and 1 case of intraoperative Kirschner wire breakage.

CONCLUSIONS

Manual closed reduction followed by percutaneous headless, compression screw fixation was possible in 50% of patients who presented with acute unstable, displaced scaphoid fractures. This technique appears to be a safe and effective method when a manual reduction is possible, and it may offer a less invasive option when compared with a standard open technique.

3-Dimensional Printing-Assisted Percutaneous Fixation for Acute Scaphoid Fracture: 1-Shot Procedure

Scaphoid fractures are the most common carpal fractures. Percutaneous fixation is a popular treatment option for nondisplaced or minimally displaced scaphoid fractures. Placement of the guidewire in the percutaneous fixation procedure often requires several attempts and adjustments with the help of intraoperative fluoroscopy. This article describes a 1-shot procedure of percutaneous fixation for acute scaphoid fracture with patient-specific guiding templates made by computer reconstructions and 3-dimensional printing technique.

Rotational stability in screw-fixed scaphoid fractures compared to plate-fixed scaphoid fractures

BACKGROUND

The literature describes the treatment of scaphoid fractures comparing the volar and dorsal approaches, the advantages and disadvantages of percutaneous screw fixation, as well as the treatment of scaphoid nonunions using different types of cancellous or corticocancellous bone grafts. Yet, to date no studies are available comparing the outcome of rotational stability in screw-fixed scaphoid fractures to angular stable systems. The purpose of this study is to provide reliable data about rotational stability in stabilised scaphoid fractures and to gain information about the rigidity and the stability of the different types of fixation.

METHODS

Three groups of different stabilisation methods on standardised scaphoid B2 fractures were tested for rotational stability. Stabilisation was achieved using one or two cannulated compression screws (CCS) or angular stable plating. We performed ten repetitive cycles up to 10°, 20° and 30° rotation, measuring the maximum torque and the average dissipated work at angle level.

RESULTS

Our study showed that rotational stability using a two CCS fixation is significantly (p < 0.05) higher than single CCS fixation. Using the angular stable plate system was also superior to the single CCS (p < 0.05). There was, however, no significant difference between two CCS fixation and angular stable plate fixation.

CONCLUSION

Even though indications of using screws or plate systems might be different and plate osteosynthesis may be preferable in treatment of dislocated or comminuted fractures as well as for nonunions, our study showed a better rotational stability by choosing more than just one screw for osteosynthesis. Angular stable plating of scaphoid fractures also provides more rotational stability than single CCS fixation. The authors therefore hypothesise higher union rates in scaphoid fractures using more stable fixation systems.

Acute Scaphoid Fractures: A Critical Analysis Review

Nondisplaced scaphoid fractures can be effectively treated nonoperatively, with union rates approaching or, in some series, exceeding the rates attained with operative intervention. The evidence supports equal outcomes when using a short arm or long arm cast for the closed treatment of nondisplaced scaphoid fractures. Also, equivalent outcomes have been demonstrated with or without a thumb spica component to the cast. Operative intervention is the recommended treatment for displaced scaphoid fractures. Advanced imaging should be obtained if clinical suspicion is present for a scaphoid fracture with negative radiographs more than 2 weeks after the injury. In some settings, it may even be more cost-effective to obtain advanced imaging sooner.

Comparison of Dorsal and Volar Percutaneous Approaches in Acute Scaphoid Fractures: A Meta-Analysis

The dorsal approach allows better central screw placement along the long axis of the scaphoid compared with the volar approach in managing acute scaphoid fractures. However, it is unclear whether the dorsal approach leads to better clinical outcomes than the volar approach. This meta-analysis compared clinical outcomes, including the incidence of nonunion, postoperative complications, overall functional outcome, postoperative pain, grip strength, and range of wrist motion, between the dorsal and volar percutaneous approaches for the management of acute scaphoid fractures. Seven studies met the criteria for inclusion in the meta-analysis. The proportion of patients who developed nonunion (OR 0.74, 95% CI: 0.21 to 2.54; P = 0.63) and postoperative complications (OR 1.05, 95% CI: 0.45 to 2.44; P = 0.91) did not differ significantly between the dorsal and volar approaches. Both approaches also led to similar results in terms of overall functional outcome (95% CI: -0.39 to 0.22; P = 0.57), postoperative pain (95% CI: -0.52 to 0.46; P = 0.92), grip strength (95% CI: -4.56 to 1.02; P = 0.21), flexion (95% CI: -2.86 to 1.13; P = 0.40), extension (95% CI: -1.17 to 2.67; P = 0.44), and radial deviation (95% CI: -1.94 to 2.58; P = 0.78). However, ulnar deviation (95% CI: -7.48 to 0.05; P = 0.05) was significantly greater with the volar approach. Thus, orthopedic surgeons need to master both the dorsal and volar percutaneous approaches because not all acute scaphoid fractures can be dealt with completely with one approach.

Radiographic Parameters to Predict Union After Volar Percutaneous Fixation of Herbert Type B1 and B2 Scaphoid Fractures

PURPOSE

To study the angle of screw placement in relation to the scaphoid fracture plane and its effect on union after percutaneous fixation of scaphoid waist fractures.

METHODS

Twenty-four consecutive scaphoid waist fractures were retrospectively evaluated for the orientation of screws in relation to the fracture plane using a method in which the sum-of-smaller angles (SSA) in 3 different radiographs were used to correlate with time to fracture union.

RESULTS

All but one patient achieved union after percutaneous fixation of the scaphoid. Another patient required revision surgery within the study period for inadequate fixation. A shortened time to union was significantly correlated to larger SSA.

CONCLUSIONS

SSA may be a reasonable predictor of union after percutaneous fixation of scaphoid waist fracture. It can be reliably calculated using plain radiographs. An SSA of 190° or more correlated with union by 8 weeks postoperatively.

Transtrapezial Approach for Fixation of Acute Scaphoid Fractures: Rationale, Surgical Techniques, and Results: AAOS Exhibit Selection

The ideal position for a screw used for scaphoid fixation is central. The purpose of this study was to compare the current volar percutaneous approaches used for scaphoid fracture fixation, explore different options to improve central screw placement, and describe our experience with the transtrapezial approach.

Management of complications of wrist fractures

This article reviews the most common complications associated with the management of carpal fractures. Discussion focuses on the recognition of commonly "missed" fractures and fracture patterns and the negative sequelae that can result from these delayed diagnoses. The pitfalls of conservative treatment of specific carpal fractures are reviewed, and the most common complications resulting from the operative management of carpal injuries are described.

Comparison of two percutaneous volar approaches for screw fixation of scaphoid waist fractures: radiographic and biomechanical study of an osteotomy-simulated model

BACKGROUND

When a surgeon uses a percutaneous volar approach to treat scaphoid waist fractures, central screw placement is complicated by the shape of the scaphoid and by obstruction by the trapezium. In this study, we used radiographs and biomechanical tests to compare the standard volar percutaneous approach with the transtrapezial approach, with regard to central screw placement at the distal pole of the scaphoid.

METHODS

Fourteen matched pairs of cadaveric wrists were randomly assigned to two treatment groups. Under fluoroscopic control, a guidewire was drilled into the scaphoid, either through a transtrapezial approach or through a standard volar approach that avoided the trapezium. Guidewire position was measured in the coronal and sagittal planes. A transverse osteotomy was performed along the scaphoid waist, and this was followed by the insertion of the longest possible cannulated headless bone screw. Each specimen was placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. Load was applied by using a load-controlled test protocol in a hydraulic testing machine.

RESULTS

All guidewires were inside the central one-third of the proximal pole. The guidewire positions at the distal pole differed significantly between the transtrapezial and standard volar approach groups (p < 0.001). The load to 2 mm of displacement and the load to failure averaged, respectively, 324.4 N (standard error of the mean [SEM] = 73.5 N) and 386.4 N (SEM = 65.6 N) for the transtrapezial approach group compared with 125.7 N (SEM = 22.6 N) (p = 0.002) and 191.4 N (SEM = 36.30 N) (p = 0.005) for the standard volar approach group.

CONCLUSIONS

The data suggest that, in a cadaveric osteotomy-simulated scaphoid waist fracture model, the transtrapezial approach reliably achieves central positioning of a screw in the proximal and distal poles. This position offers a biomechanical advantage compared with central placement in only the proximal pole.

Radiographic clues for determining carpal instability and treatment protocol for scaphoid fractures

The magnitude of carpal instability following scaphoid fracture is closely related to the fracture location. Middle-third fractures of the scaphoid are classified into B1 (distal oblique fractures) and B2 (complete waist fractures). Deciding preoperatively whether a fracture is B1 or B2 is clinically important, because several studies have revealed that B1 is more stable than B2. Dorsal intercalated segment instability deformity often develops in B2, creating a large, wedge-shaped bone defect, while minimal humpback deformity develops in B1, and the bone defect is much smaller, even after long-standing nonunions. However, determination of the fracture types using X-rays may be less accurate than using three dimensional computed tomography. This article suggests two radiographic clues for estimation of post-fracture carpal instability along with a treatment protocol for each fracture type.

Volar percutaneous screw fixation of the scaphoid: a cadaveric study

PURPOSE

To test the efficacy of a previously described technique of angiocatheter-assisted instrument positioning in achieving a central screw position in a cadaveric model for volar percutaneous screw fixation (PSF) of the scaphoid and to quantify the damage to surrounding soft tissue and articular cartilage associated with the procedure.

METHODS

We performed fluoroscopically guided volar PSF of the scaphoid on 10 fresh cadaveric wrists. We then dissected the specimens, analyzed screw position in cross sections of the scaphoid, and described injury to nearby soft tissue structures as well as articular cartilage of the scaphotrapezial joint.

RESULTS

All 10 screws were positioned within the central third of the scaphoid on at least 2 of 3 cross sections, and 8 of 10 screws were positioned within the central third of the proximal pole. Two wrists required a transtrapezial trajectory for satisfactory screw positioning. None of the specimens sustained visible neurovascular damage, and 2 wrists revealed minor tendon damage. Trajectories involving the scaphotrapezial joint violated, on average, 7% of the scaphoid articular cartilage. With a transtrapezial trajectory, 11% of the trapezial cartilage was violated

CONCLUSIONS

Central positioning of the screw is biomechanically superior, and screw position within the central one third of the proximal pole has been associated with faster time to union. Volar PSF achieved satisfactory screw position in the scaphoid. The majority of wrists were amenable to PSF via the scaphotrapezial joint, though a transtrapezial approach was a viable alternative for wrists with restrictive anatomy. Both approaches minimally disrupted the scaphotrapezial joint and surrounding soft tissues.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Establishing a central zone in scaphoid surgery: a computational approach

PURPOSE

Scaphoid fractures are commonly fixed with headless cannulated screws positioned centrally in the scaphoid. Judgement of central placement of the screw may be difficult. We generated a central zone using computer analysis of 3D reconstructions of computed tomography (CT) images. As long as the screw axis is completely contained within this central zone, the screw would be considered as centrally placed.

METHODS

Thirty cases of 3D CT reconstructions of normal scaphoids in a computerised operation planning and simulation system (Vxwork software) were obtained. The central zone was established after some distance shrinkage of the original scaphoid surface reconstruction model using the function "erode" in the software. The shape of the central zone was evaluated, and the width of the central zone in the proximal pole, waist portion and distal pole was measured. We also established the long axis of the scaphoid to see whether it stays in the central zone.

RESULTS

All central zones could be divided into distal, waist and proximal portions according to the corresponding irregular shape of the scaphoid. As the geometry of the central zone was so irregular and its width very narrow, it was possible to completely contain the screw axis either in the proximal portion alone, waist alone or distal central zone alone.

CONCLUSIONS

Establishing the central zone of scaphoid 3D CT images provided a baseline for discussion of central placement of a scaphoid screw. The geometry of the scaphoid central zone determined that the screw could hardly be inserted through entire scaphoid central area during surgery.

Optimal fixation of oblique scaphoid fractures: a cadaver model

PURPOSE

Acute scaphoid fractures are commonly fixed with headless cannulated screws positioned in the center of the proximal fragment. Central placement of the screw may be difficult and may violate the scaphotrapezial joint. We hypothesize that placement of the screw through the scaphoid tuberosity will achieve perpendicular fixation of an oblique waist fracture and result in more stable fixation than a screw in the center of the proximal fragment.

METHODS

We designed oblique osteotomies for 8 matched pairs of cadaver scaphoids and fixed each specimen with a headless cannulated screw. In 1 specimen, we positioned the screw at the center of the proximal fragment; we placed its matched pair perpendicular to the fracture. The perpendicular screw was directed through the scaphoid tuberosity. We placed the specimen under the increasing load of a pneumatically driven plunger. We compared stiffness, load, distance at failure, and mechanism of failure between the central and perpendicular screw groups.

RESULTS

We found no difference between groups. Stiffness was identical in both groups (131 N/mm) and load to failure was similar (central screw, 137 N vs perpendicular screw, 148 N).

CONCLUSIONS

In this biomechanical model of an unstable scaphoid fracture, we found that similar stability of fixation had been achieved with a screw perpendicular to the fracture plane with entry through the tuberosity, compared with a screw in a central position in the proximal fragment. This study suggests that placing the screw through the tuberosity, perpendicular to a short oblique fracture, will not impair fixation stability.

CLINICAL RELEVANCE

Percutaneous fixation of scaphoid fractures has become popular although it is technically challenging. An easier distal approach through the tuberosity, without violating the scaphotrapezial joint, may not impair the fixation stability of an oblique fracture.

Influence of screw design, sex, and approach in scaphoid fracture fixation

BACKGROUND

Screw fixation of scaphoid fractures has gained popularity. A long central screw has been shown to be biomechanically advantageous.

QUESTIONS/PURPOSES

We compared the ability of different screw designs to obtain this goal and determined the influence of sex and approach on screw length.

METHODS

We performed all measurements on three-dimensional reconstructions of 20 CT scans of normal scaphoids (10 men and 10 women) with the use of software. The three-dimensional computer models were analyzed, the central axis was defined, and the screws were placed along this axis. We compared 15 different available screw designs and volar and dorsal screw placement.

RESULTS

The length of the scaphoid along its central axis was longer in men (mean, 27.14 mm; standard error of the mean, 0.97 mm) than in women (mean, 23.86 mm; standard error of the mean, 0.37 mm). The screw length that can be used was longer in the volar approach (mean, 23.72 mm; standard error of the mean, 0.19 mm) than in the dorsal approach (mean, 23.31 mm; standard error of the mean, 0.19 mm) regardless of the screw design. Screws with a trailing thread diameter greater than 3.9 mm and leading thread diameter greater than 3.0 mm were shorter.

CONCLUSIONS

Scaphoids in women are smaller than in men. Theoretically, fixation of scaphoid fractures through a volar approach will allow the surgeon to use longer screws. The screw design has a significant influence on the screw length that can be used in scaphoid fracture fixation. We recommend using a differential pitch screw with a thread diameter of 3.9 mm or less.

A comparison of 2 methods for scaphoid central screw placement from a volar approach

PURPOSE

We studied 2 methods used for screw placement through a volar approach for fixation of scaphoid fractures.

METHODS

We performed measurements on 20 computed tomography scans of unfractured scaphoids. A central virtual guidewire was computed in 10 scaphoids with the wrist in neutral or in extension and ulnar deviation. Second, we compared the central guidewire and a guidewire representing a volar approach to the scaphoid avoiding the trapezium.

RESULTS

The central guidewire passed through the trapezium in all cases with the wrist either in neutral or in extension and ulnar deviation. There was a statistically significant difference only in the sagittal plane. When the central guidewire was compared with a guidewire placed through a standard volar approach, the latter was more eccentric in the distal and waist portions.

CONCLUSIONS

We showed that central placement throughout the scaphoid with a standard volar approach is not feasible without partially resecting, manipulating, or drilling through the trapezium.

CLINICAL RELEVANCE

Our data suggest that a volar transtrapezial approach can be an alternative for optimum central placement in volar percutaneous fixation of scaphoid fractures.

Volume slicing of cone-beam computed tomography images for navigation of percutaneous scaphoid fixation

PURPOSE

Percutaneous scaphoid fixation (PSF) is growing in popularity as a treatment option for non-displaced fractures. Success of this procedure demands high-precision screw placement, which can be difficult to achieve with standard 2D imaging. This study aimed to develop and test a system for computer-assisted navigation using volume slicing of 3D cone-beam computed tomography (CBCT).

METHODS

The navigated technique involved a distinctive workflow in which a 3D CBCT imager was calibrated preoperatively, circumventing the need for intraoperative patient-based registration. Intraoperatively, a 3D CBCT image was acquired for both preoperative planning and direct navigation using volume-rendered slices. An in vitro study was conducted to compare the navigated approach to two conventional fluoroscopic methods for volar PSF. The surgical goal was to insert a guide wire to maximize both length and central placement.

RESULTS

There was no significant difference in the mean central placement of guide wire, although the variance in central placement was significantly lower using VS navigation (P < 0.01). The lengths of the drill paths were significantly longer for the VS-navigated group compared with one 2D group (P < 0.1). Each navigated trial required only one drilling attempt and resulted in less radiation exposure than conventional C-arm (P < 0.01).

CONCLUSIONS

Volume-sliced navigation achieved a more repeatable and reliable central pin placement, with fewer drilling attempts than conventional 2D techniques. Volume-sliced navigation had a higher number of drill paths within the optimal zone maximizing both length of the path and depth from the surface.

Optimization of volar percutaneous screw fixation for scaphoid waist fractures using traction, positioning, imaging, and an angiocatheter guide

Percutaneous screw fixation of nondisplaced or reducible scaphoid fractures has become more popular as techniques and implants have improved. Many authors have advocated for the dorsal approach, citing difficulties with adequate screw placement from the volar approach. We have developed a straightforward and reproducible technique for volar percutaneous scaphoid screw fixation that mitigates most of the drawbacks of the approach. The wrist is held in extension and ulnar deviation with traction through the thumb. A 14-gauge angiocatheter needle is then used to localize the starting point and as a cannula for the guide wire. Specific fluoroscopic views help to confirm optimal guide wire placement.

Headless compression screw fixation of scaphoid fractures

Scaphoid fractures carry significant long-term morbidity and short-term socioeconomic difficulty in the young and active patient population in which they most commonly occur. While cast immobilization results in high rates of radiographic union in nondisplaced scaphoid fractures, internal fixation with headless compression screws has been recommended in cases of displaced fractures. Internal fixation has led to high rates of union in both nondisplaced and displaced fractures with the added benefits of earlier mobilization and return to work and sports. Multiple manufacturers are now offering "second generation" headless compression screws for the internal fixation of scaphoid fractures. The few biomechanical studies that exist demonstrate improved compression forces and load to failure for the newer generation of headless compression screws when compared with the first generation headless compression screw, although it is unclear if these differences are clinically significant.