Introduction

Periprosthetic femur fracture (PPFF) is an acute complication that often occurs after hip arthroplasty. Due to the increasing use of arthroplasty surgery and the aging population, the incidence of PPFF is increasing1,2,3,4.

The Vancouver Classification System (VCS)5 and subsequent Unified Classification System (UCS)6 were intended as simple systems for classifying fractures and guiding management. However, these two classifications do not include some special types of fracture. For example, Van Houwelingen and Duncan7 reported a type of periprosthetic fracture of the lesser trochanter that involved a segment of the proximal medial femoral cortex. This fracture is easily misidentified as an ALT fracture, but is actually type B2. Consequently, it is called a “pseudo ALT” or “new B2” fracture. Pseudo ALT fractures often occur in non-cemented stems7,8,9,10,11; the mechanism may involve an occult fracture resulting from surgical insertion, and the fractures occur during early weight-bearing rehabilitation.

To assess the importance to this type of fracture and improve the surgical outcome, we hypothesized pseudo ALT fractures occur only with non-cemented stems and examined how different surgical treatments of pseudo ALT fractures affect the clinical outcome.

Materials and methods

This study was approved by the Hospital Ethics Committee. All methods were carried out in accordance with relevant guidelines and regulations. All X-rays were preoperatively evaluated by two senior doctors to confirm the type of fracture. Any disagreement between two doctors was resolved by a third doctor. The final determination of whether the prosthesis was loose was made during the operation.

Inclusion and exclusion criteria

The inclusion criteria were confirmed pseudo ALT fractures on X-ray, surgical treatment, and complete clinical records and follow-up. Exclusion criteria were a combined (or suspected) infection, ipsilateral lower-extremity neurovascular injury, conservative (non-surgical) treatment, and incomplete follow-up.

Patient-related information

A search of the hospital database from January 2010 to July 2020 identified 28 patients. The patients’ basic data were collected, including gender, age, preoperative physical condition, surgical index, and type of stem.

Treatment methods

Two treatment methods were adopted. Longer stem revision and internal fixation (LSRIF) with cables was applied in 24 cases (Figs. 1 and 2). Open reduction and internal fixation (ORIF) with cables was done in four cases (Fig. 3). The choice of surgical treatment was based on the patient’s physical condition. The standard treatment was LSRIF, while ORIF was chosen if the patient was in poor condition and could not tolerate LSRIF.

Figure 1
figure 1

Case 2, a 60-year-old woman with a left femoral neck fracture due to a fall. (A) Preoperative lateral radiograph. (B) Postoperative anterior–posterior radiograph after longer stem revision and internal fixation with cables.

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Figure 2
figure 2

Case 8, an 81-year-old woman. (A) Anterior–posterior radiograph after hemi-arthroplasty. (B) After a fall in the ward, the continuity of the left medial femoral cortex was disrupted on anterior–posterior and lateral radiographs. (C) Postoperative anterior–posterior radiograph shows the patient with a longer stem revision and internal fixation with cables.

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Figure 3
figure 3

Case 19, an 88-year-old woman. (A) Anterior–posterior radiograph after hemi-arthroplasty. (B–C) Two coronal CT images show the periprosthetic fracture. (D) Anterior–posterior radiograph shows the surgical treatment of open reduction and internal fixation with cables.

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Anticoagulant therapy with low-molecular-weight heparin was given postoperatively. Rehabilitation was based on the patient’s physical condition. Patients were allowed early weight bearing when the circumstances permitted; otherwise, they exercised in bed.

Follow-up

All patients were followed as outpatients at 1, 3, 6, 12, and 24 months and yearly thereafter. All surviving patients with complete follow-up were analysed. Fracture healing and the position of the prosthesis loosening were evaluated by X-rays at each visit. The Harris Hip Score (HHS)12 and Short Form Health Survey questionnaire (SF-36) quality of life score13 were also recorded. Fracture healing was assessed in terms of local tenderness, longitudinal percussion pain on the injured leg, local abnormalities, and blurred fracture lines with continuous callus passing through the fracture line on X-ray at the last follow-up. The fracture healing time was defined as the time from the second postoperative day to the end of follow-up if there were no special circumstances.

Statistical analysis

The data were analysed using SPSS software (ver. 22.0; SPSS Inc., Chicago, IL, USA). Data are expressed as mean ± standard deviation (SD). The groups were compared using t-tests. Count data are expressed as numbers or percentages. P-values < 0.05 were considered significant.

Ethical approval

Approved by the Ethics Committee of the First Affiliated Hospital of Zhejiang Chinese Medicine University, Ethics No. 2016-K-143-01.

Informed consent

Informed consent was obtained from all participants.

Results

Postoperative pseudo ALT fractures were seen in 28 patients (7 males [25% and 21 females [75%]). The age of the patients at surgery was 73.7 (range: 52–92) years. Of the cases, 27 (96.43%) occurred with non-cemented stems, and 1 (3.57%) with cemented stems (Fig. 4). The basic patient data are summarised in Table 1.

Figure 4
figure 4

Case 1, an 82-year-old man underwent left hemi-arthroplasty with a cemented stem because of a left femoral neck fracture. (A–B) Two intraoperative radiographs taken with a C-arm machine. (C) After a fall, the continuity of the left medial femoral cortex was interrupted on an anterior–posterior radiograph. (D) Postoperative anterior–posterior radiograph after longer stem revision and internal fixation with cables.

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Table 1 Basic patient data.
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At the time of the last follow-up, three patients were lost to contact, two died, and two were hospitalised elsewhere. The remaining 21 patients were followed for 49.3 ± 15.4 (24–74.4) months. These patients had a fracture healing time of 13.5 ± 1.1 (12–15.4) weeks.

Postoperative complications included thrombus in three cases (10.71%) and heart failure and pulmonary infection in one case each (both 3.57%). The patients with postoperative thrombosis all recovered on treatment with low-molecular-weight heparin. There were no revisions for prosthesis loosening, subsidence, or infection. The HHS and SF-36 scores were obtained scores those with complete follow-up (Table 2).

Table 2 Patient demographic and medical data.
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Of the 21 patients who completed follow-up, 18 (85.71%) underwent LSRIF and 3 (14.29%) underwent ORIF. At the last follow-up, the LSRIF and ORIF groups had an HHS of 82.9 ± 6.6 (range: 68–92) and 74.7 ± 3.9 (range: 71–80) (p = 0.059), SF-36 mental scores of 50.9 ± 7.6 (range: 38–64) and 38 ± 1.4 (range: 37–40) (p = 0.012), and SF-36-physical scores of 51.7 ± 8.4 (range: 36–67) and 39.7 ± 3.4 (range: 35–43), respectively (p = 0.032) (Table 3).

Table 3 Comparison of the characteristics and outcomes of the two groups.
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Discussion

The VCS divides fractures into three subtypes. Type A consists of fractures in the greater (AGT) and lesser (ALT) trochanteric areas. Type B fractures involve the metaphyseal or diaphyseal femur around the prosthetic stem: type B1 fractures occur around a stable stem; B2 fractures involve a loose stem with good bone quality; and B3 fractures involve bone loss. Type C fractures occur distal to the stem.

The UCS expanded and updated the VCS by adding three types. Type D is a femoral fracture occurring after hip or knee arthroplasty. Type E is a fracture of both the acetabulum and femur after hip arthroplasty. Type F is a fracture of the acetabulum after hemi-arthroplasty of the hip4,6 (Table 4).

Table 4 Summary of the Unified Classification System.
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However, some special fractures are not included. For example, a pseudo ALT/new B2 fracture occurs at the lesser trochanter extending into the medial cortex of the proximal femur7,8, 14,15,16,17,18 (Table 5). Consequently, modified classifications based on the VCS and UCS were proposed. Capello et al. proposed “A1 and A2” for well-fixed or loose stems in category A8. Huang et al. classified type B2 as B2PAGT and B2PALT, representing greater trochanter fractures including a segment of the proximal lateral femoral cortex and lesser trochanter fractures including a segment of the proximal medial femoral cortex, respectively15. Egrise et al. subdivided Vancouver B-lesser trochanter fractures (VB-LT) into stable (VB-LT1) and unstable (VB-LT2) fractures9. These are all actually B2/pseudo ALT fractures.

Table 5 Related reports on pseudo ALT fractures.
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Pseudo ALT fractures often occur with non-cemented stems, especially tapered stems7,10,11. This may be due to an unrecognised intraoperative fracture that is subsequently displaced under load or during rehabilitation7,8,9,15, 16. Capello et al. reported nine newly described “clamshell” fractures that might be related to unrecognised fractures during operation and believed that they were directly related to the geometry of the tapered stem used8. Huang et al. mentioned that this type of fracture occurred at the lesser trochanter, including a segment of the proximal medial femoral cortex, and was associated with destabilisation of the stem15. Karam et al. showed that such fractures were significantly associated with non-cemented supports with an anatomical wedge-shaped design16. Egrise et al. thought this type of fracture can occur intraoperatively or in the early postoperative period with non-cemented implants, and is an occult intraoperative fracture9.

In our series, 27 patients with non-cemented stems (96.43%) sustained a PPFF. The mechanism was as described above. One fracture involved a cemented stem (3.57%); this patient had osteoporosis and it might have been an occult fracture that was not found intraoperatively.

There are three common treatments for new B2 fractures in PPFF: LSRIF, ORIF, and conservative treatment. When Van Houwelingen and Duncan recognised an undisplaced cortical crack, they performed cerclage cable fixation and revision with a longer stem, with protected weight-bearing for 6 weeks7. Capello et al. reported nine cases of pseudo ALT fracture caused by non-cemented femoral stems. They treated three cases conservatively without surgery because the stem subsidence stabilised during rehabilitation; the remaining six were treated by removing the loose stems and fixing the fracture and all healed well8; the remaining six were treated by removing the loose stems and fixing the fracture and all healed well8. Karam et al. adopted wedge-shaped (10 cases) and straight (20 cases) fixation treatments16. Egrise et al. treated nine VB-LT1 and six VB-LT2 in patients in poor health nonoperatively, 13 VB-T2 stems with exchange and cerclage, three with isolated stem exchange, and two with internal fixation by cerclage9. Huang et al.15 and González-Martín et al.17 treated this type with LSRIF.

In this study, of the 21 patients with complete follow-up, 18 underwent LSRIF and ORIF was used in 3 cases. The patient outcomes were determined by postoperative fracture-healing and functional assessment scores (HHS and SF-36). LSRIF had the better curative effect, not only in terms of the above but also from the average healing time of 13.4 ± 1.1 weeks. The LSRIF patients were aged 71.8 ± 10.9 (52–86) years and were younger than the ORIF patients (88 [range: 85–91] years). The mental and physical SF-36 scores were better with LSRIF (50.9 ± 7.6 and 51.7 ± 8.4, respectively) than with ORIF (38 ± 1.4 and 39.7 ± 3.4, respectively); we attributed this to the patients’ age and clinical condition. The HHS exceed 70 in all patients except case 1 (Table 2), indicating good functional recovery after surgery. The HHS of case 1 was 68, which we attributed to the patient’s poor basic condition and severe osteoporosis. Moreover, revision surgery with a cemented stem was more difficult than conventional LSRIF. Compared with LSRIF, ORIF is less invasive and is a suitable choice for the elderly with poor physical condition and low living needs3. Smitham et al. confirmed that the anatomical reduction and ORIF of type B2 fractures should be considered an appropriate treatment for frail elderly patients with a PPFF around cemented polished double-tapered stems14.

This study has some limitations. The patients were from a single hospital, limiting the generalisability of the results. Given the retrospective nature of the study, multicentre prospective research is needed.

Conclusion

Pseudo ALT fractures result mainly from unrecognised occult fractures intraoperatively and improper exercise postoperatively. They involve a posteromedial cortical fragment around the lesser trochanter and mainly occur with non-cemented stems. While the main treatment is LSRIF with cables/plates, simple ORIF can achieve good healing, especially for elderly patients in poor general condition.