Электронный научный журнал

Современные проблемы науки и образования. Хирургия

ISSN 2686-9101

Thus, the groups were similar in terms of acetabular bone defects (p>0.05).

Where there were signs of bone defect in the acetabulum, most patients of the control group (21 of 33) and all the patients of the treatment group underwent computed tomography. Knowing the size and anatomy of the defect helped design the future spacer while preparing for surgery.

In the control group, acetabular bone defects were corrected with different spacers: an articulating spacer, a Tecres officinal spacer, and the bipolar spacer, Patent No. 142311 of May 21, 2014 of the authors' own design, see Figure 1.

Fig. 1. Bipolar hip spacer

Note that the team’s in-house developed surgery tactics pursued excluding the bone from articulation at the first stage of repeated hip replacement. Cement-bone friction pairs are often associated with secondary bone tissue defects, which complicates the second stage of surgery. This is why it is always desirable to implant a truly articulating spacer that would not engage bone structures in articulation. Unfortunately, given the control group’s bone defects, this was sometimes unavoidable, see Table 2.

Table 2

Types of spacers in the control group

Officinal and bipolar spacers are clinically inefficient, resulting in progressing bone defects and bone dislocations before the second stage of surgery. To address that, the research team behind this paper designed a new method for hip spacer implantation to correct acetabular defects, see Patent RU No. 2632525 of October 5, 2017. This device effectively excludes the bone from articulation and helps reduce the prolapse of spacer components in the lesser-pelvic cavity to lower the risk of damaging the anatomical structures.

The designed spacer was implanted as follows. Once X-ray test results were confirmed, patients underwent pelvic CT to collect data from which a special application could retrieve information that would help restore the image of bone structures, while the intensity gradient ratio was set empirically at 0 to 225, see Figure 2.

Fig. 2. Computer 3D model of the acetabulum

Then voxels were filtered that contained data on the patient’s implant, see Figure 3.

Fig. 3. Computer simulation. Acetabular component of the implant removed in the rendering

Based on this data, the research team ran hybrid parametric modeling of the damaged hip. In the case of a bone defect, it was reconstructed using, among other things, a mirror copy of the contralateral acetabulum. A hemisphere of 0.5 to 1 cm in wall thickness was placed at the true center of rotation to place a standard cement-implant cup on bone cement.

To further obtain the volumetric parameters of the modeled acetabular spacer component, the team generated computer models of the mold that would be sent over a remote connection or copied via a hard medium to an FDM 3D printer to make that mold of the Hips material. 3D printing was provided by FDM 3D printers manufactured by Makerbot replicator 2x, USA, and Ultimaker 2+, the Netherlands.

The newly made mold was sterilized, filled with antibiotic-enriched bone cement intraoperatively, and then dismantled once the cement cured, see Figure 4.

Fig. 4. Intraoperatively created acetabular spacer component and the mold for making it

Custom-made acetabular spacers were implanted in the existing defect onto bone cement with an antibiotic, see Figure 5.

Fig. 5. Implanted custom acetabular spacer

A polyethylene acetabular component of the implant was impacted in the placed custom spacer in an appropriate position, and then secured with antibiotic-enriched bone cement, see Figure 6.

Fig. 6. Implanted polyethylene acetabular component of the implant

Further surgery was standard and included placing the femoral component of the implant on the bone cement, adjusting it, doing X-ray scans, and stitching the wound.

Thus, using custom acetabular spacer components attained the main goal of surgery, which was to exclude the bone from articulation in most cases, see Table 3.

Table 3

Types of spacers in the treatment group

Unfortunately, articulating and officinal spacers had to be used in some cases. However, the authors believe there were fewer indications to use them. Today, the authors’ clinic only uses long-legged officinal spacers if there is an accompanying pronounced defect of the proximal femur, Paprosky Type 3, 4, see Figure 7.

Fig. 7. Implanted officinal hip spacer, proximal femur defect, Paprosky Type 4

Bipolar hip spacers were only used in the treatment group in the case of pelvic disjunction or signs of infection in the lesser-pelvic cavity, see Figure 8.

Fig. 8. Implanted bipolar hip spacer: pelvic disjunction

After surgery, both patient groups underwent antibiotic therapy based on their antibiograms, as well as anticoagulant therapy to prevent thromboembolic complications.

Based on the estimated functional status of periarticular tissues, the type of spacer used, and the signs of inflammation (present or not), patients were "activated" on Day 5 to 7 after surgery. The drainage was removed until verticalization. Patients were guided to walk on crutches partially loading the operated limb. Isometric gymnastics was mandatory to preserve periarticular muscle balance.

The follow-up consisted of local status checks, laboratory test assessments, and taking arthrocentesis samples for bacteriological tests. In the case of no signs of inflammatory manifestation, the patient would be directed to Stage II revision hip replacement.

Once the spacer was in place, the patients would be assessed by the Harris hip score in a month and then in three months after spacer placement; they were also asked if they had been taking painkillers, what kind of labor they did, and whether they used walking supports.

STATISTICA for Windows 8.0 was used for statistical processing of the obtained data.

The study protocol followed guidelines for experimental investigation with human subjects in accordance with the Declaration of Helsinki and was approved by the ethics committee. Written informed consent was obtained from each patient (or an official representative) before the study.

RESULTS

It was found out that 2 patients of the treatment group (6.7%) and 4 controls (13.3%) needed repeated post-revision surgery and spacer replacement, with no statistically significant difference (p>0.05). Repeated suppuration of the spacer location as found by bacteriological testing was considered an indication for spacer replacement. Tests were run at 30, 60, and 90 days after surgery.

Harris hip scoring found no statistically significant original difference between the groups, see Table 4. One month later, the treatment group had a somewhat higher score for pain, function, and range of motion; the difference was insignificant. It was only three months after surgery that the total Harris score was significantly higher (p<0.05) in the treatment group than in the controls.

Table 4

Preoperative Harris hip scores

Note: * stands for a significant (p<0.05) Group 2 vs Group 1 difference

Note that 39.4% of the control group and 29.4% of the treatment group were taking painkillers; 42% and 50% (p>0.034) had impaired motility.

DISCUSSION

The medical and social significance of hip pathologies has risen dramatically to date, as many countries currently have ever more elderly and senile patients [3, 5, 13]. Hip replacement is a popular surgery today; it is an efficient method that helps reduce the functional deficiency of limbs in such patients [9]. However, it often fails to perform as expected and is associated with infectious complications developing shortly after surgery, which requires a revision.

Given the ever-greater number of periprosthetic infections in patients, physicians diagnose more and more pronounced acetabular defects that require a nontrivial approach to surgery.

The developed method for implanting an articulating spacer using a custom acetabular component stabilized the implant and enabled bone-free articulation in 29 of 34 patients in the treatment group compared to 17/33 controls.

Full articulation and preservation of motility in the spacer site is the key to a functionally successful second stage of hip replacement as confirmed by the functional testing the patients underwent 3 months after Stage I. Their Harris scores were significantly higher when treated by the approach proposed herein.

Revisiting the frequency of repeated surgeries of the implant that required spacer replacement, the authors found that this was the case for 13.3% of the controls, 6.7% of the treatment group.

CONCLUSIONS

The data generally shows that the proposed treatment strategy that involves finding the exact scope of the bone defect and has an algorithm for the customization of an antibiotic-loaded spacer is an effective method that addresses the chronic purulent inflammatory process while improving the functional outcome.

FINANCIAL SUPPORT AND SPONSORSHIP
Nil.
CONFLICTS OF INTEREST
The authors declare no conflict of interest