Novel endoscopic sacroiliac screw removal technique: reduction of intraoperative radiation exposure

Advanced topology of triply periodic minimal surface structure for osteogenic improvement within orthopedic metallic screw

Metallic screws are one of the most common implants in orthopedics. However, the solid design of the screw has often resulted in stress shielding and postoperative loosening, substantially impacting its long-term fixation effect after surgery. Four additive manufacturing porous structures (Fischer-Koch S, Octet, Diamond, and Double Gyroid) are now introduced into the screw to fix those issues. Upon applying the four porous structures, elastic modulus in the screw decreased about 2∼15 times to reduce the occurrence of stress shielding, and bone regeneration effect on the screw surface increased about 1∼50 times to improve bone tissue regrowing. With more bone tissue regrowing on the inner surface of porous screw, a stiffer integration between screw and bone tissue will be achieved, which improves the long-term fixation of the screw tremendously. The biofunctions of the four topologies on osteogenesis have been fully explored, which provides an advanced topology optimization scheme for the screw utilized in orthopedic fixation.

Is a Washer a Mandatory Component in Young Trauma Patients with S1-S2 Iliosacral Screw Fixation of Posterior Pelvis Ring Injuries? A Biomechanical Study

Background and purpose: Cannulated screws are standard implants for percutaneous fixa-tion of posterior pelvis ring injuries. The choice of whether to use these screws in combination with a washer is still undecided. The aim of this study was to evaluate the biomechanical competence of S1-S2 sacroiliac (SI) screw fixation with and without using a washer across three different screw designs. Material and Methods: Twenty-four composite pelvises were used and an SI joint injury type APC III according to the Young and Burgess classification was simulated. Fixation of the posterior pelvis ring was performed using either partially threaded short screws, fully threaded short screws, or fully threaded long transsacral screws. Biomechanical testing was performed under progressively increasing cyclic loading until failure, with monitoring of the intersegmental and bone-implant movements via motion tracking. Results: The number of cycles to failure and the corresponding load at failure (N) were significantly higher for the fully threaded short screws with a washer (3972 ± 600/398.6 ± 30.0) versus its counterpart without a washer (2993 ± 527/349.7 ± 26.4), p = 0.026. In contrast, these two parameters did not reveal any significant differences when comparing fixations with and without a washer using either partially threaded short of fully threaded long transsacral screws, p ≥ 0.359. Conclusions: From a biomechanical perspective, a washer could be optional when using partially threaded short or fully threaded long transsacral S1-S2 screws for treatment of posterior pelvis ring injuries in young trauma patients. Yet, the omission of the washer in fully threaded short screws could lead to a significant diminished biomechanical stability.

Evaluation of Cannulated Compression Headless Screw (CCHS) as an alternative implant in comparison to standard S1-S2 screw fixation of the posterior pelvis ring: a biomechanical study

BACKGROUND/PURPOSE

Posterior pelvis ring injuries represent typical high-energy trauma injuries in young adults. Joint stabilization with two cannulated sacroiliac (SI) screws at the level of sacral vertebrae S1 and S2 is a well-established procedure. However, high failure- and implant removal (IR) rates have been reported. Especially, the washer recovery can pose the most difficult part of the IR surgery, which is often associated with complications. The aim of this biomechanical study was to evaluate the stability of S1-S2 fixation of the SI joint using three different screw designs.

METHODS

Eighteen artificial hemi-pelvises were assigned to three groups (n = 6) for SI joint stabilization through S1 and S2 corridors using either two 7.5 mm cannulated compression headless screws (group CCH), two 7.3 mm partially threaded SI screws (group PT), or two 7.3 mm fully threaded SI screws (group FT). An SI joint dislocation injury type III APC according to the Young and Burgess classification was simulated before implantation. All specimens were biomechanically tested to failure in upright standing position under progressively increasing cyclic loading. Interfragmentary and bone-implant movements were captured via motion tracking and evaluated at four time points between 4000 and 7000 cycles.

RESULTS

Combined interfragmentary angular displacement movements in coronal and transverse plane between ilium and sacrum, evaluated over the measured four time points, were significantly bigger in group FT versus both groups CCH and PT, p ≤ 0.047. In addition, angular displacement of the screw axis within the ilium under consideration of both these planes was significantly bigger in group FT versus group PT, p = 0.038. However, no significant differences were observed among the groups for screw tip cutout movements in the sacrum, p = 0.321. Cycles to failure were highest in group PT (9885 ± 1712), followed by group CCH (9820 ± 597), and group FT (7202 ± 1087), being significantly lower in group FT compared to both groups CCH and PT, p ≤ 0.027.

CONCLUSION

From a biomechanical perspective, S1-S2 SI joint fixation using two cannulated compression headless screws or two partially threaded SI screws exhibited better interfragmentary stability compared to two fully threaded SI screws. The former can therefore be considered as a valid alternative to standard SI screw fixation in posterior pelvis ring injuries. In addition, partially threaded screw fixation was associated with less bone-implant movements versus fully threaded screw fixation. Further human cadaveric biomechanical studies with larger sample size should be initiated to understand better the potential of cannulated compression headless screw fixation for the therapy of the injured posterior pelvis ring in young trauma patients.

Removal of iliosacral screws: the washer problem

Iliosacral screw removal is an infrequent surgery, and when needed, removal of the washer can be surprisingly difficult. Different forceps, clamps and other non-specific instruments are frequently used to this end, many a time without success, or at the expense of tissue damage, blood loss and radiation exposure. After trying all the tricks in the book, we devised this neat little surgical tactic that ensures easy and reliable retrieval of the washer when removing iliosacral screws percutaneously, with no increased morbidity.

Technique for Removal of Entrapped Screw and Washer Fixation of the Posterior Pelvic Ring

Removal of internal fixation implants previously placed to stabilize posterior pelvic ring injuries may be technically challenging. Described techniques for extraction require specialized equipment, extensile measures, or purchase of additional implants. We describe a technique for removal of large diameter cannulated screws and washers from the posterior pelvic ring, which requires no additional equipment or implants beyond the instrumentation used for implant insertion, as well as a series of 15 cases in which the technique was applied.

Rate of intraoperative problems during sacroiliac screw removal: expect the unexpected

BACKGROUND

The indications for sacroiliac screw (SI) removal have been under debate. Data on complication rates of SI screw removal is missing in the current literature. The objective of this study was to compare the rate of intra- and perioperative problems and complications during SI screw removal to those with SI screw fixation.

METHODS

A retrospective observational study with two interventions in the same cohort was performed. Consecutive patients who underwent both sacroiliac screw fixation for an isolated fracture of the pelvic ring and removal of the same implants between November 2008 and September 2015 (n = 19; age 57.3, SD 16.1 years) were included. Intraoperative technical problems, postoperative complications, duration of surgery, and radiation dose were analysed.

RESULTS

Intraoperative technical problems occurred in 1/19 patients (5%) during SI screw fixation and in 7/19 cases (37%) during SI screw removal (p = .021). Postoperative complications were seen in 3/19 patients after SI screw fixation and in 1/19 patients after SI screw removal (p = 0.128). The surgical time needed per screw was longer for screw removal than for implantation (p = .005). The amount of radiation used for the whole intervention (p = .845) and per screw (p = .845) did not differ among the two interventions.

CONCLUSIONS

Intraoperative technical problems were more frequent with SI screw removal than with SI screw fixation. Most of the intraoperative technical problems in this study were implant-related. They resulted in more surgical time needed per screw removed but similar radiation time.

Minimally Invasive Endoscopic-Assisted Technique for Implant Removal After Pelvic Bridge Plating

Subcutaneous internal plate fixation for anterior pelvic ring injuries has become more common, but implants require removal, usually by 12 weeks. The purpose of this article is to report a novel, minimally invasive, endoscopic-assisted technique for the removal of subcutaneous anterior pelvic plates safely and atraumatically without violating the underlying fascia.

Standalone percutaneous transiliac plating of vertically unstable sacral fractures: outcomes, complications, and recommendations

PURPOSE

The aim of this study is to evaluate results of a standalone percutaneous posterior plating of the vertically unstable sacral fractures, to analyze the influencing factors, to discuss encountered complications, and to express the related recommendations.

METHODS

Forty two cases were included; all of them had type C vertical sacral fractures; and 16 cases had associated nerve roots injury. Subcutaneous 3.5-mm reconstruction plate was used in all cases, through vertical incisions in 28 cases and transverse incisions in 14 cases. Hannover pelvic outcome scoring system was implemented for results evaluation.

RESULTS

The mean follow-up period was 22.1 ± 7.5 months; the mean operative time was 43.3 ± 7 min; the mean surgical incision length was 4.6 ± 1.1 cm. 14 cases had excellent scores, 16 cases had good scores, 6 cases had fair scores, and 6 cases had poor scores. Younger age groups had significantly better outcome (P = 0.015), whereas the comminuted sacrum had significantly worse score (P = 0.041). Final residual posterior displacements significantly improved (P = 0.001) in comparison to the initial displacement. The nerve roots injury had final significant recovery (P = 0.012). Transverse skin incisions had subjectively significant satisfaction (P = 0.017).

CONCLUSIONS

Percutaneous 3.5-mm reconstruction plate is a good alternative to percutaneous iliosacral screws in vertically unstable sacral fractures; especially in the presence of contraindication to the latter. It is simple procedure with minimal incisions; short operative time; less radiological exposure; good mechanical stability; and less iatrogenic injuries.