Periprosthetic Fractures Around the Acetabulum

Abstract

Peri-Prosthetic acetabular fractures are rare but challenging Complications related to total hip arthroplasty (THA), especially during revision procedures. Factors contributing to these fractures include poor bone quality, prior implant placement, and increased mechanical stress. Several systems classify these fractures and management strategies differ based on whether the fracture occurs intraoperatively or postoperatively and whether the prosthesis is stable/unstable. Undisplaced fractures may be managed conservatively, while displaced fractures often require surgical intervention, such as open reduction and internal fixation (ORIF), alongside implant revision. The modern porous coated cups along with other reconstruction techniques have improved the outcomes. The complications include non-union, implant loosening, deep infection, dislocation.

Introduction

Periprosthetic acetabular fractures occur around a prosthetic acetabular component following a total hip arthroplasty (THA). These fractures can arise during or after the procedure and are considered as a challenging due to the complexity of management, which involves both the fracture and the stability of the prosthetic implant. With rise in THAs, it is expected that periprosthetic acetabular fractures will increase [1]. Currently the incidence rate is 0.07%, making these fractures most difficult to treat [2]. Moreover, most surgeons have minimal experience in dealing with these fractures [3]. Incidence of these fractures is even more in revision THRs ranging from 2 to 10% [4, 5].

Risk Factors for Periprosthetic Acetabular Fractures [4, 6–9]

• (A)
  Decreased bone quality:

  • Older age
  • Osteoporosis
  • Use of steroids
  • Seronegative arthritis (rheumatoid arthritis)
  • Paget disease
  • Bone resorption secondary to stress shielding (implant in situ from previous hip surgery)
• (B)
  Mechanical stress riser

  • Prosthesis associated stress risers
  • Loose implant due to prior implant in situ
  • Local osteolysis
  • Stiff hip: during surgery, forced mobilization might cause fracture
  • Menopausal women: small acetabular dimension and low bone density
• (C)
  Increased fall risk (neurological disorders)

  • Epilepsy
  • Parkinson’s disease
  • Cerebellar ataxia
  • Myasthenia gravis
  • Polio
  • Cerebral palsy
• (D)Infection

Classification of Periprosthetic Acetabular Fractures

Several classification systems have been devised till date, but only a few are widely used these days. The first classification for these fractures was given by Peterson and Lewallen [3].

Type 1: Clinically and radiologically stable acetabular component.

Type 2: Unstable acetabular component.

This classification was based on postoperative radiograph determining the stability of the cup but does not take into account timing of fracture. The classification system by Paprosky and Della was one of the most commonly used till now and had included all the parameters [10] (Table 1). However, Paprosky and Della classification system was difficult and cumbersome to use. Unified Classification System (UCS) was published in the year 2014 and was popularized by AO group, and was based on relationship between implant stability and bone but was not able to guide the treatment algorithm [11]. A novel classification system was developed by Pascarella [12] which included two parameters—time since fracture (intraoperative vs postoperative) and stability of the component, and also defines treatment algorithm (Table 2).

Table 1.

Modified 2003 Paprosky and Della Valle classification for periprosthetic acetabular fractures [5]

S. No.	Type of fracture	Description
Type 1	Intraoperative during component insertion	A: Recognized, stable component, undisplaced fracture B: Recognized, unstable component, displaced fracture C: Unrecognized at the time of surgery
Type 2	Intraoperative during component removal	A: Less than 50% bone stock loss B: More than 50% bone stock loss
Type 3	Traumatic	A: Component stable B: Component unstable
Type 4	Spontaneous	A: Less than 50% bone stock loss B: More than 50% bone stock loss
Type 5	Pelvic discontinuity	A: Less than 50% bone stock loss B: More than 50% bone stock loss C: Associated with pelvic radiation

Table 2.

Acetabular periprosthetic fractures by Pascarella 2018

S. No.	Timing	Prosthetic stability
1	Intraoperative fracture	Stable prosthesis
		Unstable prosthesis
2	Postoperative/traumatic fracture	Stable prosthesis
		Unstable prosthesis, mobilized simultaneously with trauma
		Unstable prosthesis, mobilized before trauma (osteolysis/bone loss)

Clinical Presentation

History

Acute onset groin pain following trauma in operated case of THA associated with difficult weight bearing indicates fresh acetabular periprosthetic fracture, whereas chronic pain in case of primary THA indicates pre-existing mechanical loosening or prosthetic joint infection (PJI).

Mechanical loosening causes startup pain—as the patient, when starts taking steps, experiences pain, whereas on the other hand, PJI causes continuous pain.

Investigation

Radiological investigations include radiograph of pelvis with lateral radiograph of affected hip with thigh. Judet views (iliac and obturator) along with inlet and outlet radiographs of affected acetabulum should also be ordered in case of suspicious fracture lines. Old radiographs before injury should be assessed to gather more information about pre-existing implant loosening and osteolysis or any other sign of prosthetic joint infection.

For postoperative fractures, a metal-suppressed CT scan is preferred modality to assess stability of implant (osteolysis), fracture pattern, and bone quality/resorption. Preoperative assessment of vascular anatomy by CT angiography is of utmost importance in patients with medial migration of the cup or suspected vascular injury or arteriovenous (AV) malformations to prevent potential catastrophic complications (Fig. 1).

Fig. 1.

Proximity of vessels in cases of intra-pelvic cup migration

In cases of prosthetic joint infection, aspiration with analysis of synovial fluid (cell counts with cytology, and microbiological culture) should also be done.

Management

Pascarella classification defines treatment algorithm based upon different groups and subgroups. In a case of traumatic event based upon timing, periprosthetic acetabular fractures are divided into two categories (Table 2):

1. Intraoperative fractures

2. Postoperative fractures due to trauma

• (A)Intraoperative fractures are more difficult to detect; suspicion of periprosthetic acetabulum fracture should arise in the mind of operating surgeon when press fit fixation is not achieved with the acetabular component. These fractures are more common with cementless acetabular components due to impaction/line to line reaming. Treatment, therefore, depends upon the degree of displacement of fractured fragments and the acetabular component stability (Figs. 2 and 3).

Fig. 2.

Pascarella type 1a fracture (missed intraoperative fracture with stable implant)

Fig. 3.

Pascarella type 1a fracture (healed fracture at 1-year follow-up)

Stable acetabular component along with undisplaced intraoperative fractures (Paprosky and Della Valle IA and Pascarella type 1a) can be managed conservatively in 6–10 weeks using toe-touch or non-weight bearing mobilization. If the fracture is detected during surgery, supplemental screw fixation should be advocated and in such cases, a multi-hole cup is inserted and fixation is achieved in both posterosuperior (ilium) and posteroinferior (ischium) zones with bicortical screws. Bone grafting from the iliac crest is also suggested by some authors to hasten healing process [13]. Studies have shown that these fractures have outcomes comparable to non-complicated THA without additional treatment [14]. On the contrary, some authors believe that these fractures will lead to acetabular loosening in all the cases [13].

Unstable acetabular component along with displaced intraoperative fractures (Paprosky and Della Valle type IB and Pascarella type 1b) impose greater challenge and even more difficult situation. In all these cases, the first step is to remove the component and visualize the fracture line and obtain intraoperative radiographs. Anterior and posterior column integrity should be assessed. The major concern in the fixation of these fractures is the surgical approach, whether same or additional approach is required. For transverse, posterior column and posterior wall fractures, Kocher-Langenbeck approach would suffice and will easily cater to both acetabular and femoral components. Anterior column fractures will require either ilioinguinal, iliofemoral or modified Stoppa depending upon surgeon expertise and fracture pattern [15]. The most common fracture pattern seen is of posterior wall which usually requires fixation [16]. Fixation of fracture is achieved using standard plates prior to insertion of acetabular component.

• B.Postoperative fractures

Stable acetabular component along with undisplaced fractures (Paprosky and Della Valle type IIIA and Pascarella type 2a) can be managed conservatively with non-weight bearing mobilization of 6–8 weeks. Peterson and Lewallen [3] in their series of eight patients treated conservatively for undisplaced fractures reported that six patients went for surgery at 20 weeks. In two cases, it was done for non-union at fracture site and there was loosening of acetabular component in four cases. Even authors have recommended open reduction and internal fixation (ORIF) for acute non-displaced fractures [12].

Unstable acetabular component along with displaced fractures (Paprosky and Della Valle type IIIB and Pascarella type 2b) operative management is the key. The principle remains the same, i.e., fixation of fracture using reconstruction plates followed by revision component fixed using multiple screws in ilium, ischium, and pubis (if required). Bony gap at fracture site might require bone grafting to fill the gap. If the stability is deemed inadequate, reinforcement rings, antiprotrusio cages or cup-cage constructs can be used with cemented dual-mobility cups to prevent dislocation [12, 17] (Figs. 4, 5, 6, 7 and 8).

Fig. 4.

45-year-old female with bilateral arthritic hips due to ankylosing spondylitis

Fig. 5.

Stiff spine

Fig. 6.

Cementless dual mobility bilateral THA

Fig. 7.

Sustained periprosthetic acetabular fracture after 3 months of index THA surgery (Pascarella Type 2B)

Fig. 8.

TMRS (trabecular metal shell) and cemented dual-mobility cup with use of allograft and CERAMENT at the floor (2-year follow-up X-ray)

Type 2C fracture (implant mobilization prior to trauma): These cases will require implant revision along with restoration of bone stock if needed. Usually such cases require cup cage or antiprotrusio cage. Bone defect needs to be reconstructed either using impaction bone grafting (for contained defects) or metallic augments (when acetabular rim is involved).

In cases where fracture will not unite due to poor local conditions and there is unstable prosthesis accompanying, explant of prosthesis can be done, and after fracture consolidation, re-implantation of the component can be done (Fig. 9).

Fig. 9.

Management algorithm for periprosthetic acetabulum fractures as per Pascarella 2018 classification

(Adapted from: R. Pascarella et al./Injury, Int. J. Care Injured 49S3 (2018) S65–S73)

Pelvic Discontinuity (PD)

Pelvic discontinuity is seen in 0.9–2.1% of acetabular revisions and defined as bone loss where the superior hemi-pelvis is separated from the inferior hemi-pelvis, either due to bone loss or acetabular fracture [18, 19].

There are two types of PD—acute and chronic, both differing in potential to heal which determines the treatment plans. The amount of bone loss also needs to be considered while deciding management plan, since it will affect final outcomes.

Acute pelvic discontinuity occurs secondary to trauma (due to fall) or iatrogenic (over-reaming or implant impaction) [20]. Management of acute PD depends upon fracture pattern. Posterior column plating usually provides extra-acetabular compression in the acute cases followed by placement of acetabular component in achieving stability. Rogers et al. reported no complication with nine patients in terms of no need of revision surgery, no reported case of infection or dislocation using this technique at a mean follow-up of 34 months [18]. In very unstable fracture patterns like associated both column fracture or T type fracture, stable rigid fixation can be achieved via supplemental fixation with a pelvic reconstruction plate.

In chronic PD, pelvis is stiff, and achieving implant stability is difficult and requires specific techniques as there is frequent component of bone loss. Posterior compression plating along with bone grafting and revision shell will be sufficient to achieve stable construct in cases of moderate bone loss. Cemented cup can also be used along with Kerboull reinforcement device and bulk allograft.

In the cases of severe bone defect (Paprosky and Della Valle type VB and VC), if cage alone is used, it will be associated with unfavorable outcomes and complications like early loosening and implant failure [12, 21]; therefore, following techniques have been described for these situations:

Hanssen and Lewallen described the “Cup-cage construct” technique which consists of an ilio-ischial cage, placed over cementless trabecular metal cup which is highly porous [22]. Jumbo cups is used to restore center of rotation of hip and is defined as acetabular component with an outside diameter ≥ 66 mm in men and ≥ 62 mm in women [23]. Bone defect should be filled with reaming material along with allograft and augments. Initial stability is offered by cage and polyethylene liner/dual mobility can be cemented in the cage to achieve desired version. This technique is associated with survival rate of 75–100% and the complications which can occur are dislocation (7–8%), infection (4–7%), and aseptic loosening (4–15%) [24, 25] (Fig. 10a, b).

Fig. 10.

a Preoperative radiograph of 72-year-old male with acute acetabular fracture. b Postoperative radiograph of 72-year-old male with acute acetabular fracture treated with cup-cage construct

Sporer et al. described the acetabular distraction technique where the acetabulum is reamed until the anterosuperior and posteroinferior margins are captured. Bone defects can be filled up using porous tantalum augments. Usually, an acetabular component 6–8 mm larger than the last reamer is impacted and press fit is achieved as a result of ligamentotaxis. The component is inserted along with multiple screws in ilium and ischium so that primary stable fixation is attained and then the poly liner or a dual-mobility cup is placed into the shell. Excellent results with lesser complication rates have been reported with this technique with 3–5% rate of aseptic loosening at a mean follow-up of 2–7 years [26]. Dislocation has been reported as the major cause of failure in PD cases followed by infection [27].

Custom-made triflange components can also be used. Based upon 3D printing, custom-made hydroxyapatite-coated triflange cups are developed. Through these flanges, initial stability is achieved via fixation at ilium, ischium, and pubis and hip center of rotation is restored at its anatomic position. Excellent results are achieved with this technique although cost is a disadvantage with this technique and high dislocation rates are known complication (upto 21%) [28, 29].

The major limitation in the management of periprosthetic acetabular fractures (PAFs) is due to presence of retrospective study design, single-center, or case series, limiting the generalizability of findings. The lack of randomized controlled trials (RCTs) makes it difficult to establish standardized treatment protocols. Various classification systems (e.g., UCS, Paprosky) lack uniformity in guiding management decisions. Most studies report short- to mid-term outcomes, making it difficult to assess long-term survivorship and functional recovery. Limited studies address frailty, preoperative optimization, and rehabilitation strategies.

The future studies should be directed to establish evidence-based protocols for fracture classification, surgical techniques, and postoperative management and long-term follow-up studies to assess functional outcomes and implant longevity, such as use of Artificial Intelligence for predicting fracture risk, personalized surgical planning, and outcome optimization.

Conclusion

Periprosthetic acetabular fractures are rare but pose a challenging complication following total hip arthroplasty (THA), especially during revision procedures. These fractures occur either intraoperatively or postoperatively and have an incidence of around 0.07% in primary THA but increase significantly up to 2–10% in revision cases. Factors contributing to these fractures include poor bone quality, prior implant placement, and increased mechanical stress. Several systems classify these fractures, including the Paprosky and Della Valle classification (2003) and the more recent Pascarella classification (2018), which emphasizes timing of fracture (intraoperative or postoperative) and prosthetic stability. Management strategies differ based on whether the fracture occurs intraoperatively or postoperatively and whether the prosthesis is stable/unstable. Undisplaced fractures may be managed conservatively, while displaced fractures often require surgical intervention, such as open reduction and internal fixation (ORIF), alongside implant revision. The complications include non-union, implant loosening, deep infection, dislocation. The functional outcomes are worse in elderly patients with poor bone stock which have been improved with modern reconstruction techniques.

Declarations

Conflict of Interest

On behalf of corresponding author, the authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

All images included, if any, were original and not published elsewhere except Fig. 9 which has been adapted from: R. Pascarella et al./Injury, Int. J. Care Injured 49S3 (2018) S65–S73.

Ethical standard statement and Informed consent

This article contains cases/ X rays of the patients which have been operated upon by one of the authors