Use of the "Two-Three Click" Protocol in Screw Stabilization of a Patient With Loosened Nuts and Dislocation of Rods - A Case Report

Vertebral fixation, utilizing titanium screws, is a highly prevalent technique employed to address spinal instability. Screw stabilization malfunction due to pedicle screw nuts loosening is rare. Under tightening the internal nut in the pedicle screw head may increase the likelihood of rod movement within the system resulting in severe pain when moving. Our goal is to raise the attention of surgeons when tightening the screws nuts of the screw stabilization because the consequences for the patient can be subsequent additional operations and complications. This report describes a clinical case of a 40-year-old man who underwent three surgeries at different clinics several years ago for disc herniation at the L4-L5 level and screw stabilization at the same level. The patient presents to the neurosurgery clinic of Saint Marina University Hospital with a clinical manifestation of low back pain escalating with movement, with a pain intensity rating of six on the Visual Analogue Scale (VAS). From the CT scan, it was revealed a malfunction in the screw stabilization with loosening of the screw nuts and dislodgement of the rods. Screw stabilization was restored using intraoperative X-ray guidance and following the "two-three click" protocol. The patient was mobilized on the first day after surgery and discharged on the fifth day with neurological improvement (VAS=1). The patient was followed up for a period of six months, and no further complications were observed. Surgeons must use caution while tightening the screw nuts, as not doing so may result in additional surgeries and complications for the patient in the future. The "two-three click" protocol for screw stabilization is an effective method for minimizing the issues associated with inner loosening and rod migration.


Introduction
Pedicle screw fixation is a commonly employed technique in spine surgery.The device restricts the movement of the stabilized spine, enhances the rate at which fusion occurs, and is generally regarded as safe with a relatively low rate of complications [1,2].However, in certain instances, the pedicle screw nut may develop, resulting in the migration of the rod and malfunctioning of the system [3,4].There is a limited amount of research on this complication, with the majority of studies being in the form of individual case reports [2,[5][6][7].
Our goal is to raise the attention of surgeons when tightening the screw nuts because the consequences for the patient can be subsequent additional operations and complications.

Patient history
This report describes a clinical case of a 40-year-old patient who underwent three surgeries at different hospitals several years ago for disc herniation at the L4-L5 level and screw stabilization at the same level.

Clinical examination
The patient presents to the neurosurgery clinic of Saint Marina University Hospital with clinical manifestation of low back pain increasing with movement with a pain intensity rating of six on the Visual Analogue Scale (VAS).

Imaging findings
From a CT scan, it was revealed a malfunction in the screw stabilization with loosening of the nuts and movement of the rods (Figure 1).

FIGURE 1: Preoperative 3D scan; the screw stabilization experienced a malfunction due to titanium rod migration and screw nut loosening
A -sagittal plane, B -coronal plane

Patient outcome
Radiographically the screw stabilization was restored by retightening the nuts using standard tools; afterward, with a torque tool up to the "two-three clicks" protocol, all inner nuts were retightened (Figure 2).Surgery-related complications were not observed.The patient was verticalized on the first day after intervention and discharged on the fifth day with neurological improvement (VAS=1).The patient was followed up for a period of six months, and no further complications were observed.

Discussion
Although transpedicular fixations offer certain benefits, they also include the potential dangers of nut loosening, screw loosening, screw breakage, screw/rod disconnection, pseudo-arthrosis, and nerve root injury, which can occur due to dural laceration and pedicle fracture during screw insertions.The occurrence of implant disassembly resulting from the loosening of the pedicle screw nut is extremely uncommon.If the inner nut is not adequately tightened into the pedicle screw head or the surgical team forgets to tighten the nuts additionally with the torque screwdriver, it can increase the likelihood of rod migration in the system [2][3][4].Most of the time, only one of the inner components is developed.In our case, all four inners were developed.
We present a concise review of screw malfunction due to nut loosening cases reported in the literature (Table 1).

Conclusions
Surgeons should be careful when tightening the screw nuts since this could result in later additional surgeries and complications for the patient.Patients who have had screw stabilization and experience worsening symptoms during movement should undergo a CT scan.The "two-three click" protocol in screw stabilization is a dependable method for minimizing the complications associated with nut loosening and rod migration.Аlthough in some individual cases, it would be inapplicable.

FIGURE 3 :
FIGURE 3: "Two-three click" clinical protocol for tightening the screw nuts This image was created with Canva by the author Plamen Penchev.