[Hardware removal after pelvic ring injury]

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.

Endoscopically assisted implant removal of a symphyseal pelvic plate - A case report

Introduction

The approach-related morbidity rate in the care of pelvic fractures is still high. Endoscopic procedures are known to significantly reduce access-related complications. Recently, a new endoscopically assisted implantation technique for plate osteosynthesis on the anterior pelvic ring has been described as the “Endoscopic Approach to the Symphysis”.

Case report

We present a case of a 29-year old male with a pelvic injury (AO type 61B2.3a) initially treated with a supraacetabular external fixator. After one week the definitive stabilization was performed by an endoscopically assisted symphyseal plating as well as a percutaneous iliosacral screw on the right side. One year after primary surgery, we performed an endoscopically assisted removal of the symphyseal plate using standard laparoscopic instruments.

Results

We demonstrate the feasibility of an endoscopically assisted implant removal at the anterior pelvic ring. No complications occurred during the procedure. The patient was discharged after a regular time of surveillance and with an adequate decline of pain.

Discussion

While we were able to show that the endoscopically assisted implantation as well as the removal of a plate osteosynthesis on the anterior pelvic ring is possible, there is still further research necessary, especially regarding the development of specific endoscopic instruments. This should enable operating times similar to the standard open procedures.

Does Implant Removal Across the Sacroiliac Joint Improve Pain and Outcomes?

OBJECTIVES

To determine if removal of previously inserted iliosacral screws improved posterior pelvic pain and Short Musculoskeletal Form Assessment (SMFA) scores.

DESIGN

Retrospective database review.

SETTING

Level-1 trauma center.

PATIENTS/INTERVENTION

Twenty-five patients who underwent iliosacral screw removal.

MAIN OUTCOME MEASURE

SMFA score.

RESULTS

Eighty-eight percent of patients stated that they were satisfied with the procedure and would undergo screw removal again. SMFA functional and bothersome scores decreased (improved) after the screw removal procedure, both at 3 months and at the final follow-up. Two-eight percent of the patients required narcotics before surgery compared with 8% after screw removal. No surgical complications occurred during screw removal.

CONCLUSION

A select group of patients who have symptomatic screws across the sacroiliac joint may benefit from elective screw removal.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Development of magnesium implants by application of conjoint-based quality function deployment

Biodegradable magnesium-based implants are the subject of a great deal of research for different orthopedic and vascular applications. The targeted design and properties depend on the specific medical function and location in the body. Development of the biomaterial requires a comprehensive understanding of the biological interaction between the implant and the host tissue, as well as of the behavior in the physiological environment in vivo. Research into and the development of innovative magnesium implants entails interdisciplinary research efforts and communication between materials science, bioscience, and medical experts. The present study provides a transparent planning and communication tool for market-oriented implant development processes. The objective was to identify medical needs at an early stage of the development process and to quantify the importance of the engineering characteristics of different research fields that cater to specific implant requirements. The method is demonstrated by the performance of a survey-based conjoint analysis, which was integrated into a quality function deployment approach. Twenty-seven medical professionals and 29 biomaterial scientists assessed the importance of identified medical requirements, whereby the control of mechanical integrity and degradation along with nontoxicity and nonimmunogenicity showed the highest number of preferences. The evaluation of implant options by 31 experts indicated that the engineering characteristic with the highest importance was the condition and sterilization of the surface. These values can be used to set priorities in strategic decisions. Research trials can be aligned to medical preferences, ensuring high product quality and an effective development process. This is the first paper to report on the application of conjoint-based quality function deployment in biomaterial research.

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.

EASY (endoscopic approach to the symphysis): a new minimally invasive approach for the plate osteosynthesis of the symphysis and the anterior pelvic ring-a cadaver study and first clinical results

BACKGROUND

Minimally invasive surgical approaches to reduce approach-associated morbidity are an interdisciplinary goal in surgery. In principle, the endoscopic approach for the extraperitoneal repair of groin hernias is the minimally invasive variant of the modified Stoppa-approach, which is used for the treatment of pelvic ring injuries in traumatology.

METHOD

Anatomical feasibility study regarding the plate osteosynthesis of the anterior pelvic ring via a minimally invasive variant of the modified Stoppa-approach.

RESULTS

We present the minimally invasive variant of the modified Stoppa-approach in a human cadaver step by step, both photographically and radiologically. Feasibility of the plate osteosynthesis of the symphysis is presented in a patient with open book injury via the minimally invasive approach using standard laparoscopic instruments.

CONCLUSION

The plate osteosynthesis of the anterior pelvic ring via the minimally invasive variant of the modified Stoppa-approach is feasible with existing standard laparoscopic instruments.

Metal implant removal: benefits and drawbacks--a patient survey

BACKGROUND

Hardware removals are among the most commonly performed surgical procedures worldwide. Current literature offers little data concerning postoperative patient satisfaction. The purpose of our study was to evaluate the patients' point of view on implant removal.

METHODS

We surveyed patients of a German level one trauma center, who underwent hardware removal in 2009 and 2010, with regard to their personal experiences on implant removal. Exclusively, data obtained out of the survey were analyzed.

RESULTS

In 332 patients surveyed, most hardware removals were performed at the ankle joint (21%) followed by the wrist (15%). The most frequent indication was a doctor's recommendation (68%), followed by pain (31%) and impaired function (31%). Patient reported complication rate of implant removal was 10%. Importantly, after implant removal because of pain or impaired function patients reported an improvement in function (72%) as well as decreased pain (96%). 96% of all responding patients and 66% of the patients who suffered from subsequent complications would opt for surgical implant removal again.

CONCLUSION

In summary, despite the challenging and frequently troublesome nature of surgical hardware removal our data contradicts the widely held view that implant removal is often without a positive effect on the patients. These findings may influence the surgeons' attitude towards implant removal and their day-to-day routine in patient counseling.

Influence of flexible fixation for open book injury after pelvic trauma--a biomechanical study

BACKGROUND

Implant loosening is frequently detected after fixation of open book injuries. Though many authors do not see this as a complication, it is often the reason for hardware removal or reinstrumentation in the case of remaining instability. We hypothesized that the flexibility of the implant has an influence on loosening and thus on failure of the construct.

METHODS

We used 6 fresh-frozen pelvic specimens and tested them with our recently introduced test setup for two-leg alternate loading. We subjected them to a non-destructive quasi-static test in the intact condition followed by a non-destructive cyclic test under axial sinusoidal loading with progressive amplitude. Afterwards we simulated an open book injury and performed fixation with three different configurations of a modular fixation system (1-, 2- or 4-rod configuration) in randomized order. Subsequently, the specimens were subjected to 3 cyclic tests with the same loading protocol as previously defined. Finally, each construct was cyclically tested to failure keeping the final rod configuration.

FINDINGS

We detected significantly greater mobility after 1-rod-fixation and no significant differences after 2-rod or 4-rod-fixation compared to the intact symphysis condition. In the destructive test series the 4-rod-fixation failed first followed by the 1-rod-fixation. The 2-rod-fixation sustained almost 3 times as many load cycles prior to failure as the 4-rod-fixation, whereas the 1-rod-fixation sustained twice as many cycles as the 4-rod-fixation.

INTERPRETATION

In conclusion, flexible fixation of the ruptured pubic symphysis in human specimens shows superior behavior with respect to load bearing capacity and ability to withstand cyclic loading compared to stiff constructs.