Feasibility of the Inner-Side-Out Use of the LC-DCP for Periprosthetic Femoral Fracture in Total Hip Arthroplasty

Abstract

Background

The optimal technique for plate fixation to treat type B and C periprosthetic femoral fractures (PFFs) is unclear. The purpose of this study is to evaluate the radiographic results of inner-side-out limited contact dynamic compression plate (LC-DCP) to treat PFFs during or after total hip arthroplasty (THA).

Methods

This retrospective study comprised of four men and six women with an average age of 64.7 years who underwent open reduction and internal fixation with an inner-side-out LC-DCP technique to treat PFFs; the reduction was maintained preliminary with the use of contoured plate and cables, and the grooves on the undersurface of LC-DCP for limited contact was used to hold and prevent the cables from slippage during tightening the cables. There were five intraoperative and five postoperative PFFs after THA. According to the Vancouver classification, the intraoperative PFFs included type B2 in two, B3 in one and C3 in two patients while postoperative PFFs were categorized into type B1 in one, type B2 in two and type C in two patients. The mean follow-up duration was 5.9 years (range 1–10.4). We evaluated radiographic union and complications after index operation.

Results

All patients demonstrated radiographic bone union at an average follow-up duration of 4.4 months (range 3–8). Two patients showed stem subsidence after revision THA and one patient demonstrated a subsequent peri-implant fracture around the distal end of plate after union of the initial PPF; one patient underwent re-revision THA for stem loosening while another patient went through refixation for the peri-implant fracture. There was no nonunion, infection, nerve injury, or dislocation.

Conclusion

The inner-side-out LC-DCP technique showed satisfactory radiographic outcome. In certain situations where locking plates are not available, this technique might be a useful alternative for treating type B and C PFFs.

Electronic supplementary material

The online version of this article (10.1007/s43465-020-00200-9) contains supplementary material, which is available to authorized users.

Introduction

The incidence of periprosthetic femoral fractures (PFFs) during or after total hip arthroplasty (THA) is increasing as a result of the increased prevalence of THA, the aging of the population and popularity with the use of cementless stem, ranging from 1 to 2.3% after primary THA and from 1.5 to 7.8% after revision THA [1–3] Significant morbidity and mortality are associated with PFF, and treatment of PFF continues to challenge orthopedic surgeons. According to Vancouver classification, recommended treatment for type B2 and B3 PFF is to revise the prosthesis with or without combination of plate fixation while type B1 and C PPF with a stable prosthesis should be fixed [1, 4–7] However, the optimum fixation technique is still unclear [5].

A limited contact dynamic compression plate® (LC-DCP, Synthes®, Oberdorf, Switzerland) or cable-ready bone plate® (Zimmer®, Warsaw, USA) is one of option for the fixation of PFF. A cable-ready bone plate is made of stainless steel and is difficult to bend, as its thickness is about 5 mm for the cable hole that passes through the plate [8]. On the meanwhile, the LC-DCP is made of titanium and has a thickness of about 1.5–3.5 mm which makes it to bend easily [9, 10]. Fundamentally, the LC-DCP has grooves on the undersurface that promotes periosteal callus formation at the fracture site by providing limited contact between the plate and bone [10].

Our idea introducing inner-side-out use of the LC-DCP to PFF treatment was, first, that the grooves on the undersurface of the LC-DCP could be used to hold the cable to avoid slippage and, second, that it was convenient for bending. The fracture location, anatomical bowing, and deformity of the femur from stress concentration by the prosthesis often require the bending or contouring of the plate to enable appropriate fixation of the plate and cables and/or screws. The purpose of this study was to evaluate the radiographic results of inner-side-out use of the LC-DCP to treat PFFs during or after THA.

Materials and Methods

This retrospective study obtained approval from institutional review board in our hospital (KNUH 2014-09-048). From July 2000 to December 2011, ten patients with intra- or post-operative PFFs underwent open reduction and internal fixation (OR/IF) with the inner-side-out use of the LC-DCP to treat PPFs (Fig. 1). Before introducing this technique into the clinical practice in the year of 2000, there has been no clinical and biomechanical study related to this subject. Since this technique was an ‘off-label use’ of the implant, we obtained the informed consent before surgery regarding the potential risk, benefits, and alternatives, and took all responsibilities possibly caused from 'off-label use' of plate.

Fig. 1.

The undersurface for limited contact was facing outward and not used for its original purpose. Instead, the groove on the undersurface for limited contact can be used to hold cables and avoid slippage. a Unturned LC-DCP. b Inner-side-out LC-DCP

This study comprised four men and six women with an average age of 64.7 years (range 40–78) and included five intraoperative and five postoperative PFFs after THA (Table 1). According to the Vancouver classification [11], the intraoperative PFFs included type B2 in two, B3 in one and C3 in two patients while postoperative PFFs were categorized into type B1 in one, type B2 in two and type C in two patients. Type of arthroplasty and prosthesis, and reason for arthroplasty were described in detail in Table 1. The average time from THA and postoperative PFF was 7.0 years (range 1–13.1) and all postoperative PFFs were associated with low-energy injury, such as a fall from a height. The mean follow-up duration was 5.9 years (range 1–10.4).

Table 1.

Demographics and radiographic result of periprosthetic femoral fractures

Case	Sex/age	Reason for arthroplasty	Type of arthroplasty	Cause of fracture	Vancouver classification	Type of stem	Follow-up, years	Time to Union, months
1	F/40	RA	THA	Intraoperative fracture	B2	Cemented	7.6	3
2	F/73	OA	THA	Intraoperative fracture	C3	Cementless	1.0	3
3	F/71	Stem loosening	Revision THA	Intraoperative fracture	B3	Cementless	3.0	5
4	F/74	Stem loosening	Revision THA	Intraoperative fracture	B2	Cementless	8.0	3
5	F/78	Stem loosening	Revision THA	Intraoperative fracture	C3	Cementless	9.2	6
6	M/54	Femur neck fracture	THA	Slip down	C	Cementless	5.2	7
7	F/72	ONFH	THA	Slip down	B1	Cementless	10.4	3
8	M/62	Stem loosening	Revision THA	Slip down	B2	Cementless	5.0	3
9	M/58	Stem loosening	Revision THA	Fall down	B2	Cementless	6.6	3
10	M/65	ONFH	THA	Slip down	C	Cementless	3.5	8

RA rheumatoid arthritis, OA osteoarthritis, ONFH osteonecrosis of the femoral head, THA total hip arthroplasty

The inner-side-out LC-DCP was bent along the contour of the femur during operation under fluoroscopic guidance. The fracture site was reduced and reduction was maintained preliminary with the use of contoured-plate and cables; the grooves on the undersurface of LC-DCP for limited contact were used to hold and prevent the cables from slippage during tightening the cables (Fig. 1). An allogeneic cancellous bone chip was grafted in six patients.

Radiographs were taken at 1, 3, 6, 9, 12 months and every year thereafter. We evaluated radiographic union of the fracture site and complications after index operation including nonunion, refracture, infection, nerve injury, dislocation, stem subsidence, and loosening.

Results

All patients demonstrated radiographic bone union at an average follow-up duration of 4.4 months (range 3–8) and were able to ambulate independently at the final follow-up (Table 1). Two patients showed stem subsidence after revision THA; among these, one patient with stem loosening after revision THA for postoperative type B2 PFF underwent re-revision using an extensively porous-coated cylinderical stem with thicker diameter at 28 months after index operation.

One patient demonstrated a subsequent peri-implant fracture around the distal end of plate after union of the initial PPF (Fig. 2). The patient went through refixation using the locking plate available at that time and less invasive plating technique. There was no nonunion, infection, nerve injury, or dislocation.

Fig. 2.

The radiograph taken at 3 years after THA in a 72 year-old female showed Vancouver type B1 fracture in her right femur (a), which was fixed with the combination of inner-side-out LC-DCP and screw/cable combination (b). At 8 years after index operation and bone union, a type C peri-implant fracture around the distal end of plate developed (c). Since locking plate was introduced and

available at the time, it was refixed with a antomical pre-shaped locking plate using less invasive plate-osteosynthesis technique. At the final follow-up, bone union was shown on the anteroposterior view of right femur (d)

Discussion

Treatment of PFFs during or after THA is still challenging and plate fixation is performed to treat not only Vancouver type C, but also type B PFFs to obtain additional stability [1, 4–6]. Several options for plate fixation have been described without any single method gaining universal acceptance [12, 13]. In this study, we performed a combination of screw and cable fixation with an easy-to-bend and grooved inner-side-out LC-DCP for treating type B or C PFFs. Bone union was obtained in all ten patients. However, one patient with stem loosening lack of scratch fit after revision THA underwent re-revision THA and another patient underwent refixation due to subsequent peri-implant fracture after bone union.

Plate fixation has evolved from the Ogden plate, which is fixed distally with screws and proximally with Parham bands, to cable-plate systems such as the Dall-Miles plate, which used incorporated sites for cable attachment proximally and screws distally. Subsequently, plates have evolved to the dynamic compression plate (DCP), LC-DCP, and locking plate, respectively. Eleftherios et al. [14] studied 18 cases of Vancouver type B PFFs using the DCP and reported that only 11 cases showed radiographic bone union at an average 13 months. An in vitro mechanical study comparing the LC-DCP with the DCP reported that the structural stiffness and strength on bending of the LC-DCP is greater than that of the DCP and the LC-DCP was better to bend and contour for anatomical bowing of the femur [15].

The LC-DCP has a grooved undersurface, even stiffness, longitudinally undercut screw holes, uniform spacing of screw holes, and symmetric plate holes, among other features [10]. In the present study, we reversed the LC-DCP. The undersurface for limited contact was out-surfaced and not used for its original purpose. Instead, the groove on the undersurface for limited contact was used as a cavity for facing outward to hold the cable fixation (Fig. 1). Moreover, it had a distance of 16 mm from between the deepest portion of the neighboring grooves, which is was closer than other devices such cable-ready bone plate® (Zimmer®, Warsaw, USA), which has with a distance of 29 mm between the neighboring holes [8] (Fig. 3). Therefore, we were able to use more cables and wires to ensure solid better fixation, especially useful in cases of PFF with short proximal fragment.

Fig. 3.

The LC-DCP has a distance of 16 mm between the deepest portion of the neighboring grooves, which is closer than a distance of 29 mm of the cable-ready bone plate® (Zimmer, Warsaw, USA). In addition, the LC-DCP is thinner than cable-ready bone plate®. a LC-DCP. b Cable-ready bone plate® (Zimmer, Warsaw, USA)

Regarding screws or cables/wires fixation, not only age-related osteoporosis but also stress shielding due to implant can lead to poor bone quality in which purchasing cortex even with the use of locking screw is not easy, particularly in the revision THA setting [16]. Moreover, the stem preoccupying in the femoral canal makes it difficult to use screw (fixed angle locking plate in particular). Although screw fixation has advantages such as firm fixation (especially rotation control), it is also not easy for screws to achieve stable fixation in osteoporotic bone and the use of cables has some advantages over screws such as less chance to tamper the cement mantle, less pull-out potential during approximation of plate to the osteoporotic bone and convenience to modify and place the plate along the bone contour. Thus, use of cables and screws might be an effective combination for plate fixation to treat type B and C PPFs.

The screw head in the inner-side-out LC-DCP could not be seated deep into the hole (Fig. 4). In comparing the unturned and inner-side-out LC-DCP, we found that the screw head protruded from the plate by 1 and 3 mm, respectively. However, none of the patients complained of symptoms related to screw protrusion such as soft tissue irritation or occurrence of the screw pulling out from the hole at the final follow-up. Although the plate was reversed, we were able to take the original advantage of smooth contouring of the plate allowing firm fixation with less irritation to the soft tissues.

Fig. 4.

The length of the screw head protrusion from the unturned and inner-side-out LC-DCP was 1 and 3 mm, respectively. a Unturned LC-DCP. b Inner-side-out LC-DCP

In our study, one patient underwent refixation due to subsequent peri-implant fracture after bone union (Fig. 2c). Although LC-DCP was relatively better to bend, it was difficult to use longer plate enough to span the whole femur length because of time elapsed for bending and insufficient contouring due to the three-dimensional structure of the femur [3, 17]. Moreover, because we performed OR/IF for all PPFs, it was also difficult to use longer plate with larger incision. We hypothesized that all of these contributed to peri-implant fracture occurred at 8 years after index surgery [18]. Recently, pre-shaped anatomical locking plate to cover sufficient length of the femur combined with minimally invasive plate osteosynthesis (MIPO) technique has shown good clinical results [19, 20]; this patient also underwent refixation using pre-shaped anatomical locking plate and less invasive plate osteosynthesis (Fig. 2d).

Care should be taken in interpreting the results of our study. First, this inner-side-out technique was ‘off-label use’. According to the American Academy of Orthopaedic Surgeons off-label recommendations [21], surgeons should counsel patients appropriately regarding the risks, benefits, and alternatives that might be available. When we introduced our technique into clinical practice in the year of 2000, there have been no previous studies on biomechanical or clinical outcomes related to this. Therefore, we obtained the full informed consents before surgery regarding the potential risk and took all responsibilities possibly caused from 'off-label use' of plate by all patients Second, most of our surgeries were performed in early 2000s when locking plates were not available in our country and the locking plate gained world-wide popularity in late 2000s [22]. Because locking plate showed superior stiffness, less strain and longer survival under torsional stress than LC-DCP in biomechanical study [23–25] and satisfactory clinical outcome in patients with PFF [5, 26], it has gained recent popularity in the treatment for type B and C PFF. Also, the problem of wire slippage can be avoided by passing the wires through the vacant portion of the hole in the locking plate before tightening screws. Thus, locking plate may have advantages to avoid wire slippage as well as provide better stability over inner-side-out LC-DCP. However, there has been no study comparing LC-DCP and locking plate in the setting of PFF. In some studies comparing the outcomes of LC-DCP and locking plate in the shaft fracture of humerus and forearm both bone [27, 28], the clinical outcome of both plate were not significantly different. Moreover, LCPs are more expensive than LC-DCPs ($420 and $180 for 4.5 mm narrow plate in United States, respectively), and there are still some countries where LCPs are not available. Our study is also limited because this is a retrospective study with heterogenous cohort including intra- and post-operative PFFs in primary and revision THA.

To the best of our knowledge, there has been no report with the use of the inner-side-out LC-DCP technique for treating PFFs. Although the inner-side-out LC-DCP technique worked in our cases, it might be difficult to justify its routine use for type B and C PPFs if locking plates are available, and this technique could be a useful surgical option as an alternative for treating PFFs in certain situations or countries where locking plates are not available. Recently, NCB® plate system (Zimmer®, Warsaw, USA), which was made of titanium alloy was introduced and provides angular stability with locking caps (Fig. 5). It has also grooves on the surface, which can play a role to hold cable or wire for fixation similarly to the concept of inner-side-out LC-DCP technique. Molinari et al. [29] performed OR/IF with this plate in 52 patients with PFF and reported excellent outcome without mechanical failure or complications such as soft tissue irritation or cable slippage after an average follow-up duration of 2 years.

Fig. 5.

The recently introduced NCB® plate system (Zimmer, Warsaw, USA) can provide angular stability with locking caps and also has grooves that can be used to hold cables and avoid slippage for treating PFFs, similar to the inner-side-out LC-DCP

In conclusion, the inner-side-out LC-DCP technique showed stable fixation with satisfactory radiographic outcome by providing grooves to hold cable or wire fixation and better adjustments along the contour of femur. If used in certain situations where locking plates are not available, this technique might be a useful alternative for treating Vancouver type B and C PFFs.

Electronic supplementary material

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Author Contributions

All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by HW, J-YK, S-HB, WH, J-WY, and S-YK. The first draft of the manuscript was written by HW, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Compliance with Ethical Standards

Conflict of interest

All authors declare that they have no conflict of interest.

Ethical standard statement

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).

Informed consent

Informed consent for study inclusion was obtained from all patients.