Scaphoid Bone

A detailed explanation of the exam was preliminarily provided to each subject. In preparation for placement of the recording electrodes and to decrease cutaneous impedances, the skin was gently abraded with fine-grade sandpaper and cleaned with an isopropyl alcohol pad. MEPs were recorded via standard surface EMG silver/silver chloride cup electrodes (9 mm diameter), filled with electrode jelly and applied on FDI and TA contralaterally to the side of stimulation, in a conventional belly tendon montage. For upper limbs, the recording (active) electrode was placed over the mid-point of the FDI belly, the reference electrode distally at the metacarpal-phalangeal joint of the index finger, and the ground electrode on the radial surface of wrist; for lower limbs, the recording (active) electrode was placed over the mid-point of TA belly, the reference electrode 3–4 cm distally over the muscle tendon, and the ground electrode over the patella. The FDI muscle, commonly examined using TMS, was selected because it can be easily contracted and recorded compared to other hand muscles. Based on the fact that evoking MEPs in the lower limbs is usually more difficult than in the upper limbs, we used the TA muscle for a number of reasons: it has a more pronounced representation than most of the other leg muscles; it has a relatively low excitation threshold; its MEPs have a larger amplitude compared to other leg muscles (Petersen et al., 2003 (link)); differently from the foot muscles, it is usually not wasted in elderly patients (Claus, 1990 (link)). Electrode impedance was constantly kept <10 KOhms, as recommended (Groppa et al., 2012 (link)).
Side-to-side difference was also considered, with “right” and “left” referred to the recording side of the target muscle. Trials containing any type of artifact were removed. Similarly, we have excluded trials contaminated by EMG activity at rest (indicating a non-relaxed muscle), as well as the “active” trials (during contraction) with excessive EMG voluntary activity that made a reliable recognition of the onset of MEP cortical latency difficult or doubtful.
All data were collected on a dedicated PC and stored for off-line analysis. Subjects were seated in a comfortable armchair, in a quiet environment, and asked to keep their hands and legs as relaxed as possible. All exams were conducted in the same laboratory and experimental conditions (including room temperature), at the same time of the day (approximately 9:00–11:30 am) and by the same trained operators. All measurements were made by a senior operator (GL) and finally checked and approved by the Lab head (GP).

The operation was performed under brachial plexus block anesthesia using an upper arm tourniquet. A straight incision was made in the distal forearm between the distal portion of the flexor carpi radialis (FCR) and the radial artery and was carried across the distal wrist crease using a hockey-stick incision that angles toward the base of the thumb. The FCR tendon was retracted ulnarly, and the radial artery was retracted radially. The wrist capsule was entered through a longitudinal incision from the volar lip of the radius to the proximal tubercle of the trapezium. The capsule and intracapsular ligaments were carefully divided and reflected sharply off the scaphoid with a scalpel. Fibrous tissue or pseudarthrosis of opposing bone surfaces of the proximal and distal fragments were thoroughly debrided by using a high-speed burr with constant irrigation, leaving a shell of intact cartilage (Figure 2A). We used Kirschner wires as joysticks to distract across the nonunion site. A cancellous graft obtained from the patient’s iliac crest was impacted into the shell, and a wedge-shaped cortico-cancellous graft was shaped to fit the gap between distal and proximal fragments and then inserted into the defect to maintain the reduction (Figure 2B).
The first guide wire was inserted along the long axis and was approximately 2 mm distant from the medial cortex of the scaphoid. Usually, two or three attempts were needed for guide wire insertion until the position of the first guide wire was ideal. Then, we inserted the second guide wire adjacent to the first, but separated in the radioulnar plane by the distance of the diameter of the planned screws. Usually, one or two attempts were needed for second screw guide wire insertion.
After the positions of the guide wires were verified by the C-arm, two cannulated screws (one Acutrak Mini and one Acutrack Mirco Hillsboro, OR, USA) were inserted into the scaphoid by the palmar approach. For most cases, we inserted the 2.5 mm-diameter screw through the radial guide wire first and then the 3.5 mm-diameter screw through the ulnar guide because the bone quality of the ulnar side of the scaphoid waist was the highest. Only in one female patient, we used two 2.5 mm-diameter screws, while in two male patients, we inserted two 3.5 mm-diameter screws into the scaphoid. The length and position of the screws were confirmed by C-arm (Figures 2C,D). Finally, the wires were removed, and the capsule and radioscaphocapitate ligament were repaired. All procedures were performed by one senior surgeon.

This retrospective study was approved by the ethics committee of our hospital prior to the commencement of any data collection. Medical records of scaphoid fracture nonunions with humpback deformities treated with open debridement, autologous iliac crest bone grafting, and internal fixation with two headless compression screws between January 2018 and December 2019 by a single surgeon were retrospectively reviewed. Inclusion criteria required an established scaphoid waist nonunion with humpback deformity suggested by preoperative computed tomography (CT) (Figure 1), without evidence of healing more than 6 months after injury and a minimum follow-up of 1 year. The lateral intrascaphoid angle (LISA), scapholunate angle (SLA), and height-to-length ratio (HLR) were examined as an index of displaced scaphoid nonunions (12 (link)). Exclusion criteria were (1) younger than 18 years of age, (2) additional injuries to the hand, (3) pregnancy, and (4) less than 1 year of follow-up.
Pertinent patient demographics (age, sex, smoking status) and injury specifics were included in the medical record review. Both preoperative and postoperative sagittal LISA and SLA were assessed and compared based on CT scans. 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. Grip strength was measured by using a Jamar hand dynamometer and compared with the contralateral hand. AROM was measured before and after surgery using a goniometer. Available computed tomography scans were also carefully analyzed for cortical penetration of either screw. All complications were recorded. Whether the patient was able to perform previous work and sports activities comfortably was documented.