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Periprosthetic hip infection treated with two-stage stage-one Select Spacer– complication rate and restoration of anatomy
∗Corresponding author: Josephine Olsen Kipp. josephine.olsen@clin.au.dk
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
Two-stage revision with ‘StageOne™ Select Hip Cement Spacer’ is used as treatment of periprosthetic hip joint infection.
The aim is to evaluate complications and restoration the joint with the StageOne Select Spacer.
From 2013 to 2018 twenty-nine StageOne Select Spacers was inserted. Data was obtained through medical records and radiographs.
3.5% dislocated the spacer, 6.9% sustained a femoral fracture, 6.9% got reinfected and 6.9% failed to control the infection. Leg length discrepancy was 1.5 mm (−4,25-5.25) and offset discrepancy was 4 mm (−0.5-9).
The spacer shows promising results with a low reinfection and dislocation rate and allowance of restoration of the joint.
Keywords
Cement spacer
Periprosthetic infection
Surgical complication
Total hip arthroplasty
1 Introduction
Periprosthetic hip joint infection (PHJI)11Periprosthetic hip joint infection (PHJI). is a severe complication to total hip arthroplasty with serious consequences to affected patients. Approximately 1% of hip arthroplasties become infected.1,2 The incidence of hip revision arthroplasty due to deep infection in Denmark has increased from 9% in the period 1995–2014 to 15% percent in 2015 and 2016.3 Furthermore, PHJI is the most frequent indication for second revision surgery. It is a painful, disabling and costly condition with a high mortality.4
Diagnosing a PHJI can be challenging. Parvizi, Javad et al., in 2018, on behalf of a workgroup in Musculoskeletal Infection Society, published a definition for periprosthetic joint infections. Two conditions are seen as pathognomic: 1) two positive cultures or 2) presence of a sinus tract. However, in some cases the diagnosis is based on a collection of other signs of infection, such as serological markers (C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate), elevated synovial white blood cell count, purulence in the joint or periprosthetic fluid with isolation of a microorganism or highly elevated neutrophils.5
One of the key pillars in treatment of PHJI is surgery. This can be done in either one or two stages. Two-stage surgery is currently regarded as the surgical gold standard,6,7 and a new temporary modular joint replacement ‘StageOne™ Select Hip Cement Spacer’ has been developed by ZimmerBiomet. The spacer has a core of titanium covered by Gentamycin loaded bone cement of the surgeon's choice. The geometric design potentially preserves more bonestock and creates a stable environment for the femoral prosthesis. The spacer is modular, with separate head and femoral stem, adapters between these allowing for adjustment of leg length and offset. This in theory results in a relatively functional and stable hip joint in the intervening period, and an easier secondary revision procedure. Furthermore, weight bearing on the spacer after the surgery with assistive technology can be allowed and after six weeks full weightbearing.
The aim of this retrospective study is to evaluate the clinical results concerning the rate of complications, level of bone destruction, level of mobilization and the restoration of natural joint anatomy with the StageOne Select Spacer used for two-stage revisions.
2 Patients and methods
From 2013 the StageOne Select Spacer has been used for two-stage revisions in patients with PHJI treated at our institution. The indication for two stage revision in PHJI, was a chronic infected total hip arthroplasty, as described previously, which did not fulfill the inclusion criteria or had one or more exclusion criteria for a one-stage revision.8 Patients not found suitable for two-stage revision was treated with either a one-stage revision, debridement and implant retention or a Girdlestone resection, see Fig. 1. The procedures were performed by three specialized hip arthroplasty surgeons. It was performed through a posteriolateral approach. All the components of the infected arthroplasty, including bonecement, cables, screws, plates etc. were removed, followed by a thorough debridement and irrigation.9 After insertion of the cement spacer, the posterior capsule was reconstructed, if possible, and reattached to the trochanter through drillholes.
Patients included in this study were identified through a review of our institutional records. From 2013 to 2018 a total of 27 patients was treated with a StageOne Select Spacer. One patient received three StageOne Select Spacers, therefore in total 29 spacers were inserted. No one were excluded from this study. Through a retrospective review of the patients' medical records we obtained data about the patients’ demographics, lifestyle markers (Table 1), pre and postoperative serology, medication, indication for two-stage revision, perioperative data and the postoperative regime and complications (Table 2). A retrospective evaluation radiographs was performed (Table 3). The static analyses were performed by using JASP Team (2019). JASP(Version 0.8.4). Data was normal distributed. ANOVA and T-test was used to compare if the patients with complications differed at any parameters.
| Age, year Mean [SD] | 72.48 [10.98] |
| Weight, kg Mean [SD] | 76.75 [13.55] |
| Height, cm Mean [SD] | 172.1 [10.09] |
| BMI Mean [SD] | 25.89 [3.63] |
| ASA score Mean [SD] | 2.37 [0.63] |
| Sex N [%] | |
| Female | 12 [44.4] |
| Male | 15 [55.6] |
| Smoker N [%] | |
| Current | 4 [14.8] |
| Previous | 10 [37.0] |
| Never | 13 [48.1] |
| Alcohol N [%] | |
| <7/14 | 26 [96.3] |
| >7/14 | 1 [3.7] |
| Dislocation N [%] | 1 [3.5] |
| Fracture N [%] | 2 [6.9]a |
| Mortality N [%] | 4 [13,79]b |
| Reinfection after second prosthesis N [%] | 2 [6.9]c |
| Removal of spacer due to ongoing infection N [%] | 2 [6.9] |
| Change to Girdlestone resection arthroplasty N [%] | 2 [6.9] |
| Hematoma | 1 [3.5] |
| Neurovascular lesion | 0 |
| Thrombosis and embolus | 0 |
| Failure of material | 0 |
| Spacer removal because of pain | 0 |
| Time from previous arthroplasty to spacer implantation in monthsMean [SD] | 81.9 [72.37] |
| Spacer stem subsidence mmaMedian [25%IQR-75%IQR] | 3 [(-7.5)-0] |
| Spacer head cranial migration mmaMedian [25%IQR-75%IQR] | 1 [0–2] |
| Femoral offset difference, mmbMedian [25%IQR-75%IQR] | 4 [(-0.5)-9] |
| Femoral length difference, mmbMedian [25%IQR-75%IQR] | 1.5 [(-4.25)-5.25] |
| Spacer head acetabular offset difference, mmbMedian [25%IQR-75%IQR] | 6 [(-1.75)-9] |
| Spacer head acetabular height difference, mmbMedian [25%IQR-75%IQR] | −7 [(-12)-(-3.75)] |
| Estimated leg length discrepancy, mmcMedian [25%IQR-75%IQR] | −7.5 [(-16)-1] |
| Gruen zones Median [25%IQR-75%IQR]d | |
| 1 | 1 [1–1.75] |
| 2 | 2 [1–2] |
| 3 | 1 [0–2] |
| 4 | 0 [0-0] |
| 5 | 1 [0–2] |
| 6 | 1 [0.25–2] |
| 7 | 1 [1–2] |
| Caput zones Median [25%IQR-75%IQR] | |
| 1 | 2 [1–2] |
| 2 | 2 [1–2] |
| 3 | 1 [0–2] |
| Paprosky N [%] | |
| I | 13 [46.3] |
| IIa | 3 [10.71] |
| IIb | 6 [21.43] |
| IIc | 6 [21.43] |
| Weight bearing regime 1st week N [%] | |
| 5–10 kg | 11 [37.93] |
| 10–20 kg | 12 [41.38] |
| Full weight | 4 [17.24] |
| Missing | 1 [3.44] |
To evaluate the restoration of hip joint anatomy after the spacer, we compared the first postoperative pelvic radiograph after spacer insertion, with radiographs before the primary arthroplasty if available. The first line choice was to compare radiographs from the ipsilateral side before the primary arthroplasty. In cases where pre arthroplasty radiographs were not available, we compared with the contralateral side. We measured the placement of the spacer components; spacer head acetabular offset, femoral offset, femoral leg length and spacer head acetabular height. It was assessed by the techniques described by Nunn et al.10 and Jolles et al.11 (Fig. 2). To evaluate the spacer head cranial migration and spacer stem subsidence, the difference in leg length and spacer head acetabular height were measured from the first radiographs after the spacer implantation, to the last radiographs with the spacer present, before second stage surgery.
The interface between the prosthesis and surrounding bone was evaluated on the last radiographs with the spacer present before second stage surgery. The femoral bone around the spacer stem was divided into seven zones as described by Gruen et al.12 and the acetabular bone around the spacer head was divided into three zones described by DeLee and Charnley.13 The degree of contact between spacer and bone was categorized in three categories: no contact, intermediary contact or full contact. At the last radiographs with the spacer before second surgery, the acetabular deficit was classified by the system developed by Paprosky et al.14
3 Results
The median follow-up with the spacer implant in situ was 24 weeks (17–40). Four patients are still having the spacer in situ after respectively 220, 165, 61 and 17 weeks. Out of twenty-nine spacers in twenty-seven patients, fourteen complications have occurred in eight patients. Two have undergone additional surgery after the second stage surgery.
3.1 Mechanical complications
Two mechanical complications have been reported: one spacer head dislocation (3.5%) and two femoral fractures (6.9%). The dislocation of the spacer head occurred three times in the same patient within ten days. This patient had a lower BMI (20.2) than average (95%CI = 24.0–27.1). The patient was never mobilized during the first post-operative week as the only one in this study (p = 0.021), but due to dislocations which occurred while lying in bed, he was never allowed to mobilize. The patient did not differ at any other parameter (age: 76y 95%CI:[69.0–76.8], smoking (p = 044), weight bearing regime (p = 0.80), range of motion (p = 0.26), paprosky type (p = 0.45)). Regarding the spacer stem/bone interface, there were three Gruen zones in which there was no contact and two zones with respectively intermediate and full contact. There was full bone contact of the spacer head.
There was one case of perioperative fracture, and one case of traumatic postoperative periprosthetic femoral fracture which lead to a subsidence of the spacer stem. The traumatic fracture could be classified as a type B2/B3 fracture using the Vancouver classification system.15 The perioperative fracture occurred in a patient where an extended osteotomy was used for removal of femoral stem. Postoperative radiographs showed a fracture of the medial femoral cortical bone at the site of the transverse distal osteotomy of the extended osteotomy. The spacer was removed four days after insertion because of the fracture, which needed internal fixation. The fracture patients did not differ at any measured parameters (smoking (p = 0.25), weightbearing regime (p = 0.37), high speed burr (p = 0.17), assistive technology (0.43)).
3.2 Complications with the infection
Two patients (6.9%) had the spacer removed due to ongoing infection. One patient continued to have a fistula more than five weeks postoperative and was treated with a Girdlestone resection arthroplasty. The other patient had a recurrence of all the symptoms shortly after the end of the antibiotic treatment. Two patients (6.9%) were re-infected after implantation of the secondary prosthesis. In both cases there were negative tissue cultures obtained during second stage arthroplasty implantation. In one case the same microbiological agent was found, and in the other case a new microbial agent was found. A weak association was seen at CRP after one week (0.052). They did not differ at any other measured parameters (age (p = 0.449), BMI (P = 0.75), ASA (p = 0.92), smoking (0.83), CRP preoperative (p = 0.998), CRP at 6 weeks (p = 0.31), CRP at 3 months (p = 0.72), time from spacer implantation in weeks (p = 0.64), duration of the previous arthroplasty in months (p = 0.66), indication for primary surgery (p = 0.467). A third possible re-infected patient died of sepsis and control of the infection was never obtained, with either the spacer in situ or a Girdlestone resection arthroplasty before she died.
3.3 Mortality and other complications
Four patients (13.8%) died in the follow up period and of these, three unrelated to the infected hip. One patient died due to an acute aorta dissection, one due to sepsis due to an UTI because the patient refused treatment, one died due to heart attack and one due to sepsis (mentioned above).
The last complication reported was a spontaneous hematoma in one out of 27 patients (3.5%). It was located in vastus lateralis with an estimated size of 11 × 6 × 8 cm and was treated non operatively.
3.4 Anatomy and bone healing
All the anatomic results are shown as a median of our patient group. When looking at restoration of the anatomy, the femoral offset was increased 4 mm ((-0.5)-9). The femoral length was increased with 1.5 mm ((-4.25)-5.25). The spacer head acetabular offset was increased with 6 mm ((-1.75)-9). The spacer head acetabular height was decreased with 7 mm ((-12)-(-3.75)). The spacer stem subsided by 3 mm ((-7.5)-0) and the spacer head had migrated in the cranial direction with 1 mm (0–2). The estimated leg length discrepancy before vs after the spacer was 7.5 mm ((-16)-1). 46.3% of the patients were unaffected before second stage surgery, regarding acetabular defect classification according to Paprosky, and thus classified with a type I defect, 10.7% could be classified with a type IIa, 21.4% with a type IIb defect and 21.4% with a type IIc defect. The first two zones of the spacer head had a median of two, which we defined as full contact. The average median contact in the seven Gruen zones was one, which we defined as intermediary contact.
4 Discussion
The purpose of this study was to evaluate the clinical results concerning the rate of complications, level of bone destruction, level of mobilization and the restoration of natural joint anatomy with the StageOne Select spacer used for two-stage revisions.
We enrolled 29 StageOne Select surgeries in 27 patients, in which we found fourteen complications occurring in eight patients. Three with mechanical complications, four with infection complications, one with a hematoma and four patients died, three of courses unrelated to the PHJI. The anatomy must be considered as restored when comparing with the preoperative anatomy measurements. In only seven patients a modular revision femoral component was used in the secondary surgery, which supports this fact.
4.1 Limitations
The sample size is a weakness of this study, though it reflects the fact that this is a rare patient category. We have not collected and compared our data with the conventional spacer or made a randomization of our patients. When commenting on the outcome of the spacer, we have only focused on quantitative outcomes and not asked the patients about their functional outcome, which also is a limitation of the study. Despite these limitations we consider the obtained results important and reliable.
4.2 Mechanical complications
In our study we only found a dislocation rate of 3.5%. The dislocation was in a multimorbid patient and who was not mobilized in the postoperative period. Three studies have examined the mechanical complications with preformed antibiotic-loaded spacers for two-stage revisions of PHJI. When looking at the rate of dislocation, Pattyn, C., et al. and Romano, C. L., et al. both reported a dislocation rate at 16.4%. D'Angelo, F., et al. reported a lower dislocation rate at 10.7%.
Concerning femoral fractures, we had two fractures (6.9%); one traumatic and one perioperative when removing the previous infected prosthesis. Pattyn, C., et al. reported seven intraoperative femoral fractures (11.4%). Romano, C. L. et al. only had one perioperative fracture (2.7%). D'Angelo, F., et al. only reported one fracture (3.5%), which happened at stem removal.
4.3 Complications with the infection and mortality
Two patients (6.9%) were reinfected. Lange, J., et al.16 have made a systematic review concerning reinfection after two-stage surgery. They found an estimated absolute risk of reinfection after two-stage at 13.1% (95%CI: 10.0%–17.1%), which is significantly higher than what we found.
Two patients (6.9%) in our study had a persistent infection. One was treated with a Girdlestone resection arthroplasty, the other successfully with a new Stage One Select spacer. Regarding persistent infection D'Angelo, F., et al. reported one case (3.5%). Romano, C. L., et al. reported three patients (1.6%) with ongoing infection after the spacer implantation.
Concerning the mortality rate, there is no reason to believe that the spacer is a course in any of the deaths in our study which happened minimum one year after second stage surgery.
4.4 Anatomy and bone healing
Three studies compared the biomechanical nature of hip joint reconstruction in conventional total hip arthroplasty (THA).17–19 When looking at the femoral offset the studies ranged from −0.2 mm to 5.1 mm, with the majority reporting an increased femoral offset. In our study we measured an almost balanced femoral offset with a median increase of 4 mm. This is a satisfying result, knowing that a balanced or even moderately increased femoral offset seems to offer a favorable outcome due to a better range of motion20 and reduced risk of dislocation.21 Concerning the femoral length, which is an important goal in hip arthroplasty, the three studies, which compared the biomechanical nature of hip joint reconstruction, ranged between 1.3 and 3.7 mm. Our leg length increased with a median of 1.5 mm ((-4.75)-6.25), which is fully satisfying especially when taking into account that a study found that discrepancies <5 mm generally are well perceived.22
On the acetabular side the StageOne Select Spacer head differed compared to the above-mentioned studies with conventional THA. The spacer head acetabular offset was increased with a median of 6 mm contrary to a decrease between 1.1 mm and 3.5 mm at the conventional THA. The spacer head acetabular height was decreased with median of 7 mm contrary to an increase at 1.4 mm–3.9 mm at the conventional THA.
Full weight bearing was allowed in most cases, which made the mobilization of the patients possible far sooner. This is a huge advantage compared to conventional cement spacers without metal core reinforcement.
In summary, the findings of the StageOne Select Spacer show promising results in treatment of PHJI with two-stage surgery. Especially the reinfection and dislocation complication rate show promising results with a lower rate compared to other preformed spacer studies. Likewise, the spacer seems to be able to restore the natural anatomy of joint, especially on the femoral side. This is a subject, which needs further investigation. A prospective follow-up study with functional outcome scores and a larger patient group could provide more evidence on this interesting research area.
Declarations of interest
None.
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