Femoral allograft augmentation in addition to locking plate fixation in displaced proximal humerus fractures: a retrospective case-series

Abstract

Background:

Proximal humerus fractures (PHFs) rank among the most prevalent fractures in adults and the elderly, with approximately 20% of them displaced and requiring surgery. Despite various operative strategies, no consensus exists on the optimal treatment for displaced PHFs. Locking plate (LCP) fixation is widely used but has high complication rates, especially in the elderly. To mitigate these risks, cortical allografts have been utilized, however, complications and challenges persist. Cancellous allografts, proven effective in other fractures, may reduce complications and improve outcomes. This study retrospectively evaluated femoral allograft augmentation with LCP fixation in displaced PHFs.

Methods:

This single-center retrospective case-series reviewed patients with displaced 2-, 3- or 4-part PHFs treated with femoral allograft augmentation and LCP fixation. Follow-ups were at 2 to 4 weeks, 6 weeks to 3 months, 4 to 7 months, and 10 to 14 months. Functional, radiological, and clinical outcomes were assessed by reviewing patients' records.

Results:

Fourteen patients were included with a mean follow-up of 9.6 ± 4.4 months (range, 1–14). At the last follow-up, mean range of motion was 138.9 ± 35.5° anteflexion, 46.7 ± 24.4° external rotation, internal rotation 50.0 ± 11.0°, and 122.8 ± 36.0° of abduction. Mean humeral head height was 17.2 ± 3.0 mm at the first follow-up and 17.3 ± 3.6 mm at the last follow-up. The mean humeral neck shaft angle was 135.7 ± 10.1° at the post-operative x-ray and 135.4 ± 11.1° at the final follow-up. Three major complications were reported: 2 infections and one avascular necrosis.

Conclusion:

Femoral allograft augmentation with LCP fixation for displaced PHFs demonstrated favorable clinical and radiological outcomes in this retrospective case-series. This technique may provide increased construct stability in displaced PHFs. Further prospective comparative studies are needed to confirm these findings.

Level of Evidence:

Level IV; Case series with no comparison group; Treatment study.

Introduction

Proximal humerus fractures (PHFs) are one of the top 10 most prevalent bone fractures in adults, representing 4% to 10% of all bone fractures among adults.¹ They are frequently reported in the elderly, particularly women, often associated with low-energy trauma and osteoporosis.^2,3 PHFs also occur in younger adults after high-energy trauma.⁴ These fractures significantly correlate with disability, loss of independence, and have a negative influence on quality of life.⁵

The treatment options for PHF can be either non-surgical or surgical and are determined by various factors, including activity level, patient's age, patient's demands, the pattern of the fracture, and comorbidity including osteoporosis.⁶ PHFs can be classified using the Neer⁷-system established in 1970. This classification is based on 2, 3, or 4 parts, based on the degree of angulation, displacement of the humeral head, and the position of the greater and lesser tuberosities. Most PHFs (80%) are non-displaced and can be managed non-surgically,⁸ whereas displaced 2-part, 3-part, and 4-part fractures (20%) require surgical management, with the aim of improving quality of life.^9–11 Surgical options include locking plate (LCP) fixation, percutaneous fixation, hemiarthroplasty, or reverse shoulder arthroplasty (RSA).¹² Regardless of the surgical options, stable LCP fixation of the displaced fractures remains challenging, especially in elderly patients with poor bone quality.^13–15

Despite the increasing incidence of PHFs,¹⁶ a consensus on the treatment algorithm is lacking.^11,17,18 Surgical treatment is largely dependent upon the surgeon's experience and preference. In addition, the absence of evidence-based guidelines for displaced PHFs has prompted surgeons to explore optimal surgical solutions.² A potential surgical treatment strategy is LCP fixation, which has emerged as the predominant surgical technique for displaced PHFs in recent years.¹⁹ However, LCP fixation is associated with relatively high complication rates, ranging from 13.4% to 36%.^20–22 Reported complications include secondary displacement and avascular necrosis of the fracture parts, resulting in collapse of the humeral head, leading to intra-articular protrusion of the screws.^20–22 Complication rates also increase with age.^1,3 To reduce these complications, innovative techniques such as cement augmentation, inferomedial screws, medial calcar plate, and allograft augmentation, have been introduced for the surgical treatment of displaced PHFs.^23,24 One of the more recent treatment options is LCP fixation combined with an intramedullary fibular allograft.^15,25–27 In 2008, Gardner et al²⁶ presented promising results of the fibular allograft in combination with LCP fixation, resulting in complete fracture healing without reduction loss.

Several studies have explored the use of this intramedullary cortical graft technique and reported improved radiographic outcomes, improved functional outcomes, and a reduced rate of complications compared with LCP fixation.^{10,15,24,28–30} Despite its clinical successes, a few concerns remain, particularly regarding challenges for future RSA conversion^31,32 due to the need to remove an extra 6 to 8 cm of ingrown endosteal fibular allograft.³³ Considering these challenges, a cancellous allograft may serve as an alternative for this fibular graft aiming to improve outcomes of LCP fixation of 3- and 4-part PHFs. Hypothesized benefits include a reduced risk of complications and revision surgery compared to regular LCP fixation. In addition, femoral head allografts may be more available and have potentially lower costs compared to fibular allografts, depending on the local health care setting.^26,34,35

Cancellous bone grafts showed promising results in extremity fractures, for example, distal radius fractures, calcaneal fractures, and tibial plateau fractures.^36,37 In a study by Euler et al,³⁸ 2-part fractures in high-risk patients treated with LCP in combination with a femoral allograft were retrospectively assessed. After a mean follow-up of 28.5 months, all fractures healed without loss of reduction, demonstrating good stability and fracture healing with a satisfactory functional outcome. However, biomechanical testing of the graft was recommended. Dank et al³⁹ biomechanically tested the femoral allograft in combination with LCP fixation compared to only LCP fixation in 3-part fractures, noting an increased load of failure and stiffness in the femoral graft.

Despite positive results from different studies of femoral allograft augmentation combined with LCP fixation,^33,38–43 there is currently limited biomechanical or clinical evidence-based data available on the use of femoral allografts in displaced PHFs. Therefore, the aim of the present study was to report outcomes of this novel and promising surgical treatment.

Methods

Study design

A retrospective single-center case series was conducted including all patients who underwent treatment LCP fixation with femoral allograft augmentation for displaced PHFs at the orthopaedic and trauma department of Tergooi MC, the Netherlands. The decision to add an allograft to LCP fixation was multifactorial and based on both patient- and fracture-related characteristics, including preoperative bone impaction, poor bone quality, calcar comminution, fracture displacement, and medial hinge insufficiency, when additional intramedullary support was considered beneficial.

Patients were contacted and provided with information about the study. Informed consent was obtained from all patients. The present study was approved and reviewed by the Tergooi MC Institutional Review Board (CTS 23.36).

Patients and data-extraction

Patients were eligible for this study, if they (1) had a displaced 2-part, 3-part, or 4-part PHF; (2) underwent surgical treatment using LCP fixation combined with augmentation constructed from a femoral allograft; and (3) underwent surgery between January 2019 and December 2022 at Tergooi MC.

The exclusion criteria were (1) PHFs non-surgically treated; (2) PHFs exclusively managed with LCP fixation, arthroplasty, or percutaneous fixation; (3) patients with pathological fractures; (4) patients with non-displaced fractures; or (5) patients with revision surgery of fractures.

Routine follow-up appointments for radiological and clinical examination were at 2 to 4 weeks, 6 weeks to 3 months, 4 to 7 months, and 10 to 14 months post-operatively. The post-operative radiological assessments involved anteroposterior (AP) and lateral radiographs. Data extraction and analysis for this retrospective study was performed by reviewing patient records, assessing previous x-rays, and physical examinations from December 2023 to March 2024.

Surgical technique

Pre-operatively, all patients received an interscalene plexus brachialis block and 2.0-g intravenous dose of cefazolin. Under general anesthesia, patients were placed in the beach-chair position. After sterile preparation, the arm was placed in a pneumatic arm holder. This surgical procedure was performed by a single orthopaedic surgeon. A deltopectoral or anterolateral approach was used, depending on the fracture pattern and pre-operative estimated anticipation on conversion to reverse shoulder arthroplasty.

After systematic dissection of the subcutaneous tissue, the deltopectoral approach involved lateral positioning of the cephalic vein. In the anterolateral approach, the deltoid is opened to a maximum of 5 cm distally from the acromion without osteotomy, followed by creation of a second window to protect the axillary nerve. Biceps tenotomy was performed in fracture patterns involving the biceps sulcus or biceps tendon pathologies. Non-resorbable sutures were used to secure the supraspinatus, subscapularis, and infraspinatus tendons, allowing control and traction over the fracture fragments. Using the sutures, K-wires and manipulation, preliminary reduction was achieved and verified using x-ray imaging.

A thawed allograft femoral head is prepared on the back table to an appropriate form and length. After removal of the cartilage, the cancellous graft was shaped into a mushroom configuration and adjusted to the patient's anatomy and fracture pattern, with a diameter of approximately 12 to 14 mm at its inferior aspect and 20 to 30 mm at its superior aspect (Fig. 1A and B).^33,39 After preliminary reduction of the humeral head and the tuberosities, the allograft was inserted intramedullary into the humeral shaft to restore support of the humeral head (Fig. 1C). The tuberosities were then provisionally reduced and secured around the graft, after which reduction and graft position are confirmed with x-ray.

Figure 1.

(A) and (B) Photographs showing preparation of the femoral head allograft and (C) schematic illustration of graft positioning.

After inserting the allograft, the LCP (PHILOS—Proximal Humeral Plate 3.5, Stainless Steel, DePuy Synthes, Oberdorf, Switzerland) was positioned and cortically fixated with a first cortical screw into the humeral shaft. This is followed by locking screw fixation in the head. The number of screws in the head is chosen depending on fracture characteristics. The rotator cuff is again sutured and attached to the plate with non-resorbable sutures. Finally, the shaft is fixated with 2 additional bicortical locking screws into the humeral shaft. X-ray confirmations were obtained at this point, verifying the location of the plate, the screws, and anatomical reduction. Sequential closure in layers is performed, and the skin was closed in an intracutaneous fashion.

Postoperatively, the arm was immobilized in a shoulder immobilizer for 6 weeks. Circumduction exercises were initiated during the first 2 weeks, followed by active exercises with a maximum of 20° of external rotation, supervised by a specialized shoulder physiotherapist. From week 7 onward, the rehabilitation protocol incorporates exercise therapy encompassing the entire range of motion, along with scapulothoracic and rotator cuff strength exercises.

Outcome measurements

The primary outcome of this analysis was the complication rate. Complications were categorized as major or minor. Major complications included deep infection, avascular necrosis (AVN), fixation failure, screw cut-out, non-union, and varus collapse. Minor complications included symptomatic hardware irritation and elective implant removal. Secondary outcomes included functional outcomes and radiological assessment of secondary displacement using humeral head height (HHH) and humeral neck-shaft angle (HNSA).

Functional outcomes

Functional outcomes were assessed using a range of motion (ROM), including anteflexion, abduction, internal rotation, and external rotation, as documented by the orthopaedic surgeon at 6 weeks to 3 months, 4 to 7 months, and 10 to 14 months postoperatively.

Radiological outcomes

Radiological outcomes, including comminuted fracture, fracture healing, and AVN classified according to the Cruess classification,⁴⁴ were assessed on pre-operative and post-operative radiographs. Additional parameters, such as HHH in mm and HNSA in degrees, were independently scored by 2 researchers. Each observer was blinded to the assessments of the other.

HHH was calculated by drawing 2 lines perpendicular to the humerus shaft. One line was positioned at the superior top of the humeral head, while the other was placed at the top of the plate. The vertical distance in mm between these lines was defined as the HHH (Fig. 2A).⁴⁵ A discrepancy exceeding 5 mm in HHH between the first and final follow-up was considered as loss of fixation.⁴⁶ The HNSA was assessed to determine varus deformity in the humerus. HNSA was defined as the angle between the line perpendicular to the articular surface and the line bisecting the humeral shaft (Fig. 2B).⁴⁷ Varus deformity was identified if the change in HNSA between the first and final follow-ups exceeded 10°.⁴⁶

Figure 2.

(A) HHH was defined as the vertical distance (in mm) between the uppermost lines of the head and plate.⁴⁵ (B) HNSA was defined as the angle between the line perpendicular to the articular surface and the line bisecting the humeral shaft.⁴⁷

Medial hinge integrity was documented, as disruption of the medial hinge may indicate compromised humeral head vascularization.⁴⁸ Deltoid tuberosity index (DTI) was employed to assess bone quality, involving the division of the outer cortex by the inner cortex of the humeral shaft. A DTI-ratio <1.44 was considered indicative of increased osteoporosis risk.⁴⁹

Statistical analyses

Statistical analysis was performed using SPSS software version 27.0 (SPSS Inc). As there was no comparison group, baseline characteristics, functional outcomes, and radiological outcomes (comminuted fracture, fracture healing, and AVN) were presented as descriptive statistics. The data were normally distributed. Nominal and ordinal data, for example, classifications, pain score, injury mechanism (high-energetic trauma [HET]/low-energetic trauma [LET]), ASA-score, and complications, were presented as numbers with corresponding percentages. Interval and ratio levels, for example, ROM-measurements, operation time, age, time between injury and surgery, bleeding volume, and body mass index (BMI), were described as means with standard deviations (SD). The independently scored radiological outcomes (HHH and HNSA) were reported as means with SDs. Furthermore, corresponding intra-correlation coefficients (ICC) were presented. This coefficient assesses the overall concordance of the inter-rater reliability among independently scored values. These ICCs, along with their 95% confidence intervals (CIs), were calculated based on absolute-agreement and the 2-way mixed-effects model. The ICC ranges from 0 to 1, with <0.5 poor agreement, 0.5 to 0.75 moderate agreement, 0.75 to 0.9 good agreement, and 0.9 to 1.0 excellent agreement.⁵⁰

Results

Baseline characteristics

Fourteen patients were included, 9 female and 5 male patients. The mean age of the patients at the time of surgery was 55.1 ± 12.3 years (range, 22–68). The right arm was injured in 7 patients and the left arm in 7 patients, and the dominant arm in 6. Average follow-up time was 9.6 ± 4.4 months (range, 1–14). Two patients had limited follow-up (1 and 3 months, respectively) because of favorable clinical recovery and subsequent discharge from routine follow-up. The most common injury mechanism was a LET, reported in 11 patients. One fracture was classified as displaced 2-part fracture, 4 fractures were classified as 3-part, and 9 as 4-part according to the Neer classification.³¹ The medial hinge was displaced in 10 fractures (Table 1). Representative pre- and postoperative radiographs of the fracture patterns included in this study are shown in Figure 3.

Table 1.

Baseline clinical characteristics of the study population.

Baseline clinical characteristics	n = 14
Age at time of injury, y, (M ± SD, R)	55.1 ± 12.3, 22-68
Gender, n (%)
Female	9 (64.3)
Male	5 (35.7)
BMI, kg/m2, n (%)
Underweight <18.5 kg/m2	0 (0)
Normal 18.5–25 kg/m2	4 (28.6)
Overweight 25–30 kg/m2	6 (42.9)
Obese >30 kg/m2	4 (28.6)
Bone mineral density, n (%)
Osteopenia	3 (21.4)
Osteoporosis	2 (14.3)
Pre-operative DTI, (M ± SD)	1.4 (0.1)
Mechanism of injury, n (%)
LET	11 (78.6)
HET	3 (21.4)
Side of injury, n (%)
Right side	7 (50.0)
Left side	7 (50.0)
Dominant side	6 (42.9)
Neer fracture classification, n (%)
2-part	1 (7.1)
3-part	4 (28.6)
4-part	9 (64.3)
Headsplit fracture, n (%)	1 (7.1)
Medial hinge, n (%)
Intact	4 (28.6)
Displaced	10 (71.4)

M, mean; R, range.

Figure 3.

Representative pre-operative and post-operative radiographs of displaced proximal humerus fractures treated with femoral head allograft augmentation and locking plate fixation: (A and B) 3-part fracture; (C and D) 4-part fracture.

Surgery characteristics

The surgery characteristics are presented in Table 2. The average time between injury and surgery was 9.7 ± 7.0 days. The mean operation time was 1 hour and 54 minutes (range, 01:24–02:26), and the mean blood loss was 285 mL (range, 150–500). No cases required conversion to arthroplasty.

Table 2.

Surgery characteristics of the study population.

Surgery characteristics
Interval trauma-surgery, d, (M ± SD)	9.7 ± 7.0
ASA-score, n (%)
1	4 (28.6)
2	8 (57.1)
3	2 (14.3)
Operation time, hour:min, (M, range)	01:54 (01:24–02:26)
Approach, n (%)
Anterolateral approach	9 (64.3)
Deltopectoral approach	5 (35.7)
Brachial plexus analgesia in combination with general anesthesia, n (%)	14 (100)
Blood loss, ml, (M, range)	285 ± 150-500
Screws humeral shaft, (M ± SD)	2.9 ± 0.4
Screws humeral head, (M ± SD)	6.9 ± 1.0
Fracture consolidated, n (%)	14 (100)

ASA-score, American Society of Anesthesiologist classification system; M, mean; R, range.

Functional outcomes

On average, patients had 73.9 ± 18.5° of anteflexion, 19.0 ± 9.9° of external rotation, and 67.3 ± 22.0° of abduction on the injured side at 6 weeks to 3 months. At the last follow-up, patients had 138.9 ± 35.5° of anteflexion, 46.7 ± 24.4° of external rotation, internal rotation of 50.0° and 122.8 ± 36.0° of abduction on the injured side (Table 3).

Table 3.

Functional outcomes of the study population.

ROM
FU 2 at 6 wk–3 mo
Abduction, degrees, (M ± SD)	67.3 ± 22.0
Anteflexion, degrees, (M ± SD)	73.9 ± 18.5
Exo-rotation, degrees, (M ± SD)	19.0 ± 9.9
Endo-rotation, degrees, (M ± SD)	42.5 ± 2.9
FU 3 at 4–7 mo
Abduction, degrees, (M ± SD)	108 ± 41.0
Anteflexion, degrees, (M ± SD)	118.0 ± 41.8
Exo-rotation, degrees, (M ± SD)	36.0 ± 15.6
Endo-rotation, degrees, (M ± SD)	51.9 ± 8.8
FU 4 at 10–14 mo
Abduction, degrees, (M ± SD)	122.8 ± 36.0
Anteflexion, degrees, (M ± SD)	138.9 ± 35.5
Exo-rotation, degrees, (M ± SD)	46.7 ± 24.4
Endo-rotation, degrees, (M ± SD)	50.0 ± 11.0

FU 2, follow-up 2; FU, 3 follow-up 3; FU, 4 follow-up 4; M, mean.

In Figure 4 and 5, boxplots are presented for the ROM: anteflexion and external rotation. The range of anteflexion at FU-2 was 40 to 90, with a 25th percentile score of 60.0° and 75th percentile score of 90.0°. FU-3 showed a range of 70 to 170 of the anteflexion, with a 25th percentile score of 80.0° and 75th percentile score of 162.5°. FU-4 illustrated the anteflexion with a range of 90 to 170, with a 25th percentile score of 95.0° and 75th percentile score of 170.0° (Fig. 4).

Figure 4.

Boxplots of range of motion anteflexion at follow-up moments 2, 3, and 4.

Figure 5.

Boxplots of range of motion external rotation at follow-up moments 2, 3, and 4.

In Figure 5, the range of external rotation at the FU-2 was 10 to 40, with a 25th percentile score of 10.0° and 75th percentile score of 22.5°. At FU-3, a range of 20 to 60 was reported, with a 25th percentile score of 20.0° and 75th percentile score of 48.8°. External rotation at the FU-4 showed a range of 20 to 90, with a 25th percentile score of 25.0° and 75th percentile score of 65.0° (Fig. 5).

Radiological outcomes

The HHH and HNSA were independently scored by 2 researchers. The inter-reliability of these measurements is summarized in Table 4. The mean HHH was 17.2 ± 3.0 at the first post-operative x-ray and 17.3 ± 3.6 at the last follow-up (Table 5). The mean HNSA was 135.7 ± 10.1° at the first post-operative x-ray and 135.4 ± 11.1° at the last follow-up (Table 5).

Table 4.

ICC values for HHH and HNSA of the study population, scored independently by 2 researchers.

	FU2		FU3		FU4
	ICC	95% CI	ICC	95% CI	ICC	95% CI
HHH	0.71	0.33–0.90	0.93	0.67–0.98	0.85	0.28 to 0.97
HNSA	0.73	0.35–0.91	0.90	0.55–0.87	0.53	−0.29 to 0.89

FU2 follow-up at 6 weeks to 3 months; FU3 follow-up at 4 to 7 months; FU4 follow-up at 10 to 14 months; ICC intra-correlation coefficient; ICC <0.5 poor agreement; ICC 0.5–0.75 moderate agreement; ICC 0.75–0.9 good agreement; ICC 0.9–1.0 excellent agreement. FU2 follow-up at 6 weeks to 3 months; FU3 follow-up at 4 to 7 months; FU4 follow-up at 10 to 14 months.

M, mean.

Table 5.

Radiological outcomes—mean of the independently scored HHH and HNSA.

	FU2	FU3	FU4
HHH, mm, (M ± SD)	17.2 ± 3.0	17.3 ± 3.9	17.3 ± 3.6
HNSA, degrees, (M ± SD)	135.7 ± 10.1	137.3 ± 11.5	135.4 ± 11.1

Complications

Two major complications were documented: infection and AVN. A total of 2 patients had a deep infection, with microbiological analysis confirming the presence of Cutibacterium acnes. One of these cases occurred 3 months post-operatively in a patient with a complex displaced 4-part fracture and comorbidities including hypertension, smoking, and BMI of 39.51 kg/m². The other infection occurred 1 year post-operatively; this patient had a challenging displaced 4-part fracture, leading to an operation time of 2 hours and 26 minutes. Both infections were managed with antibiotic therapy and surgical debridement.

One patient was radiologically diagnosed with stage 2 AVN according to the Cruess classification.⁴⁴ The patient’s medial hinge was not intact pre-operatively. The diagnosis was confirmed by sclerosis evident on x-ray images after 7 months post-operative, which remained stable. Therefore, conservative treatment was suggested with watchful waiting. Of the minor complications, plate irritation occurred in 3 patients and 2 patients underwent re-operation for this reason with removal of osteosynthesis material (Table 6).

Table 6.

Complication rates of the study population, n = 14.

Complication type	No. of patients	Percentage
Infection
Deep infection	2	14.3
Avascular necrosis
Stage II	1	7.1
Secondary displacement	0	0
Screw protrusion	0	0
Plate irritation	3	21.4
Re-operation: removal of osteosynthesis material	4	28.6

No. number.

Discussion

In this retrospective study, the clinical, functional, and radiological outcomes in 14 patients with displaced 2-part, 3-part, and 4-part PHFs treated with femoral allograft in addition to LCP were evaluated. The key findings of this study were as follows: (1) radiographic evaluation demonstrated no evidence for secondary displacement, indicating the effectiveness in maintaining fracture reduction; (2) evaluation of the mean ROMs showed favorable functional outcomes.

One of the most important findings was the absence of radiographic evidence of secondary displacement, head collapse, or progressive varus deformity during the follow-up period. In addition, no screw protrusion occurred, and measurements of secondary displacement using HHH and HNSA scored by 2 independent researchers showing high inter-reliability agreement. These results support the hypothesis that a femoral head allograft contributes to a stable fixation when combined with LCP fixation. Therefore, these findings suggest that the addition of a femoral allograft may contribute to improved construct stability compared to previously reported outcomes of LCP fixation alone.

Previous studies reported high rates of secondary displacement in LCP fixation alone, including head collapse or screw protrusion,^{10,15,30,47,51} in contrast to the absence of secondary displacement observed in our study. For instance, Sproul et al⁵² reported an overall complication rate of 48.8% in LCP fixation alone, with varus malunion occurring in 16.3% and intra-articular screw protrusion in 7.5% of cases. Similarly, in the study by Zhang et al,³⁰ 8 out of 42 patients had varus malunions and screw protrusion was observed in 6 patients. These findings may indicate that femoral allograft augmentation compared to LCP fixation alone may reduce reduction loss, reducing major post-operative complication rates of PHFs.

In comparison with studies evaluating fibula allografts augmentation, complications such as AVN, screw-protrusion, secondary displacement, infection, and varus malunion have been reported.^{10,13,15,25,30,47,51,53} Dasari et al²⁵ reported 32 complications in 296 patients treated with fibula allograft augmentation in 10 reviewed studies. Other studies on fibula grafts showed screw protrusion, which is contrasting with the femoral allograft.^{10,13,15,25,30,47,51,53} In addition, the mushroom-shaped design of the graft contributes to enhancing stability by effectively filling and supporting the hollow humeral head. The graft is prepared to the appropriate form and length during surgery, providing an advantage over fibula allografts, as noted in the studies by Parada et al³³ and Skura et al.³² The fibula graft may have limitations in achieving a precise fit because of uniform shape and dense cortical structure.

In the present study, no cases of fixation failure, screw cut-out, non-union, or varus collapse were observed during follow-up, which may be attributable to structural support provided by the graft. Cancellous allografts (e.g., femoral allograft) are known to promote fracture healing due to their large trabecular surface, which encourages revascularization and incorporation at the implantation site.⁵⁴ Thus, femoral allograft augmentation may contribute to the overall structural integrity of the construct and minimize the risk of reduction failure.

Regarding the post-operative functionality, we observed a mean anteflexion of 138.9°, external rotation of 46.7°, abduction of 122.8°, and internal rotation of 50.0° at the last follow-up. In comparison with prior studies of the fibula allograft, slight differences are noted.^13,51 Matassi et al¹³ reported a mean anteflexion of 149°, external rotation of 65°, internal rotation of 40°, and abduction of 135° in fibular allograft augmentation. Davids et al⁵¹ documented mean ROMs for fibula allografts, including anteflexion of 142.3°, external rotation of 54.2°, and abduction of 125°. Our findings indicate a lower mean ROM in patients treated with the femoral allografts. However, these lower scores may be attributed to the loss of data from 2 patients with favorable recovery and subsequent discharge before the last follow-up of 10 to 14 months. If these measurements had been obtained at the last follow-up at 10 to 14 months, the mean ROMs would have been higher. Consequently, there is an underestimation of the true mean ROM in our study.

The use of an allograft has several downsides, such as disease transmission, infection, and immune reaction. However, these risks can be reduced by careful donor selection.⁵⁵ In our study, 2 patients experienced deep infections, resulting in an infection rate of 14.3%. Although this rate may seem relatively high, it necessitates further exploration within the context of patients-specific variables.

In the 2 infection cases, C. acnes was identified as the pathogen, a bacterium commonly present in the skin and subcutis in the shoulder region. Therefore, it is unlikely that the infection is the result of the allograft itself. Moreover, both patients presented with risk factors for post-operative infection, which could have contributed to the development of this complication. In addition, 1 patient had a complex 4-part fracture, resulting in a prolonged operation time exceeding the mean operation time of 1 hour and 54 minutes. Nevertheless, both cases were effectively managed with antibiotic therapy and surgical debridement, followed by plate-removal after consolidation of the fracture.

A frequent complication in displaced proximal humeral fractures is AVN, primarily attributing to the displacement of the segments. This displacement can potentially damage the circumflex arteries and disrupt arterial blood supply, even after reduction and surgical fixation, resulting in AVN.⁵³ The patient diagnosed with AVN stage II had a displaced medial-hinge pre-operatively, heightening the risk of AVN.⁵³ The AVN remained stable and was managed with conservative management with clinical and radiographic surveillance. Despite this relevant complication, compared to recent studies, the overall complication rates remain comparable with the fibula allograft and superior to LCP fixation.^{10,15,30,47,51} Notably, when assessing the most prevalent complication, secondary displacement, our study showed no cases of secondary displacement.

Due to its retrospective design, our study has several limitations. First, it poses a risk of introducing selection bias and confounding variables, potentially influencing the reliability of the findings. Second, the small sample size and absence of a control group reduced the study statistical power and limited its generalizability. A direct retrospective comparison with patients treated using LCP fixation alone was not performed, as femoral head allograft augmentation is selectively used in more complex fracture patterns at our institution, making such comparisons highly susceptible to selection bias and confounding by indication. Finally, the loss of patients' data leads to an underestimation of the mean ROM scores. Despite these limitations, this study provides preliminary clinical and radiological data supporting the potential use of femoral allograft augmentation in displaced PHFs. Both the acknowledged limitations and favorable outcomes collectively highlight the need for future research to address these constraints and strengthen the validity of our findings.

To validate our findings and provide further evidence for the use of femoral allograft augmentation, a prospective randomized controlled trial is necessary. This randomized controlled trial should compare femoral allograft augmentation combined with LCP fixation or LCP fixation alone. In addition, considering the biomechanical aspects, a study comparing femoral allograft and fibula allograft augmentation could provide valuable insight into their biomechanical stability. These future investigations are essential to optimize the treatment strategies and enhance patient outcomes in the management of displaced PHFs.

Conclusions

In conclusion, patients with displaced PHFs treated with a femoral allograft in addition to LCP demonstrated favorable clinical and radiological results in this retrospective case series. Femoral allograft augmentation may provide increased construct stability, contributing to potentially lower complication and secondary displacement rates compared to previously reported outcomes in the literature on LCP fixation with or without fibular graft. In addition, the high availability and relatively low cost of the graft make it a feasible option for surgeons and patients as treatment for displaced PHFs. Further prospective comparative studies are needed to confirm these findings.

Data availability statement

The datasets generated and analyzed during the current study are not publicly available but are available from the corresponding author on reasonable request.