Outcomes of Reduction and Fixation versus In-situ Fixation for Valgus-impacted Femoral Neck Fractures: A Systematic Review

Abstract

Due to the presumed inherent stability of valgus-impacted femoral neck fractures (VIFNF), in-situ fixation has traditionally been the preferred surgical treatment. However, regarding the particular need for reduction before fixation, the optimal surgical strategy for this type of injury remains controversial. A comprehensive literature search was performed using PubMed, Embase, and Cochrane Library databases. Studies comparing outcomes between in-situ fixation and reduction with fixation for VIFNF published between 2014 and 2024 were included. Utilizing the Modified Coleman Methodology Score, study quality was assessed by two independent reviewers. Eleven studies published during the selected timeframe met the inclusion criteria. Studies on in-situ fixation reported significant femoral neck (FN) shortening regardless of screw configuration. Two of three comparative studies between in-situ and reduction demonstrated significantly less FN shortening in the in-situ group at the postoperative one year follow-up. Furthermore, all three comparative studies reported significantly higher postoperative 1-year Harris hip scores in the reduction group. For VIFNF, anatomical reduction prior to fixation may improve functional outcomes and reduce FN shortening compared to in-situ fixation. However, reduction techniques may offer better long-term stability and lower complication rates although they require additional surgical steps. Nevertheless, patient selection remains crucial, particularly in elderly or osteoporotic patients where in-situ fixation may still be a viable option. Further prospective randomized controlled trials are needed to confirm these findings.

INTRODUCTION

With our aging population, the incidence of hip fractures continues to rise globally. Valgus-impacted femoral neck fractures (VIFNF) represent approximately 15%-20% of all femoral neck fractures worldwide¹⁾. Due to their impacted nature, these fractures, classified as AO/OTA 31-B1.1, have traditionally been considered inherently stable, thus leading many surgeons to favor in-situ fixation^1-3).

However, recent studies have raised significant concerns about in-situ fixation outcomes. Goodnough et al.³⁾ reported a 15.5% failure rate requiring subsequent operations with in-situ fixation, while Gaski et al.⁴⁾ found a 17.3% rate of major complications including avascular necrosis (AVN), varus collapse, and nonunion. Challenging the traditional assumption of reliable outcomes with in-situ fixation, Moon et al.⁵⁾ similarly reported a 19.2% reoperation rate. Perhaps most notably, femoral neck (FN) shortening has emerged as a critical concern, with DeClouette et al.⁶⁾ reporting that, regardless of screw configuration, approximately 31% of patients experience more than 2 mm of shortening^6-8).

The potential benefits of anatomical reduction before fixation have garnered increasing attention^9-12). Park et al.⁹⁾ demonstrated significantly lower FN shortening rates and superior Harris hip scores (HHS) in patients treated with reduction before fixation compared to in-situ fixation. Kweon et al.¹⁰⁾ further supported these findings by showing improved radiological and functional outcomes compared to in-situ fixation through the introduction of a minimally invasive reduction technique using threaded Steinmann pins.

Despite these emerging data, the optimal surgical management strategy remains controversial. While in-situ fixation offers technical simplicity and, theoretically, minimizes disruption of the remaining blood supply, the risk of FN shortening and its associated functional implications cannot be ignored. Age and posterior tilt angle were identified by Moon et al.⁵⁾ as independent predictors of failure, suggesting that patient selection may be crucial in determining the most appropriate treatment strategy.

This systematic review aims to comprehensively compare the outcomes of in-situ fixation versus reduction and fixation in VIFNF, with particular focus on FN shortening, functional outcomes, and complication rates.

MATERIALS AND METHODS

1. Search Strategy

A comprehensive literature search was performed on October 18, 2024, using PubMed, Embase, and Cochrane Library databases for articles published through October 18, 2024. Search terms included both MeSH (Medical Subject Headings) and free text terms related to “femoral neck fracture,” “hip fracture,” “valgus-impacted,” “valgus,” and “subcapital.” Boolean operators “AND” and “OR” were used to combine these terms (Supplementary Table 1). Studies with English abstracts were included regardless of the publication language.

2. Study Selection

The initial database search identified 2,051 studies (883 from PubMed, 1,104 from Embase, and 64 from Cochrane Library). After removing 704 duplicates, 1,347 articles remained for screening. Two independent investigators (S.W.L. and J.Y.K.) screened titles and abstracts according to predetermined inclusion and exclusion criteria. Inclusion criteria for the studies were: (1) reported outcomes of in-situ fixation or reduction with fixation for VIFNF, this allowed for studies that examined different fixation methods within in-situ fixation as well as those that reported outcomes without direct comparisons (e.g., case series), (2) a minimum 6-month follow-up period, (3) human studies with clinical data, (4) published from 2014 onwards, and (5) the availability of English language abstracts (Fig. 1). The exclusion criteria are detailed in Fig. 1.

Fig. 1.

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow diagram.

After screening, 11 studies met all inclusion criteria and were included in the final analysis. To ensure comprehensive and transparent reporting of the review process, this systematic review was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines¹³⁾.

3. Data Extraction

Using a standardized form, the same two investigators independently extracted the following information: (1) study characteristics including first author, publication year, study design, and level of evidence; (2) patient demographics including sample size, age, gender distribution, and time to operation; (3) surgical details including approach and fixation method; (4) clinical outcomes including union rates, FN shortening, AVN rates, and functional scores; and (5) complications.

Any disputes were resolved through discussion until consensus was reached.

4. Quality Assessment

The methodological quality of the included studies was evaluated using the Modified Coleman Methodology Score, with scores ranging from 0 to 100¹⁴⁾. To determine the quality of the studies, this scoring system assessed ten criteria: study size, mean follow-up duration, number of surgical procedures, study design, diagnostic certainty, surgical technique description, rehabilitation description, outcome criteria, outcome assessment, and selection process¹⁴⁾.

RESULTS

1. Study Characteristics

After screening, 11 studies from the initial database search of 2,051 articles met the final inclusion criteria. Of these 11 studies, seven studies focused on in-situ fixation outcomes, while four studies evaluated various reduction techniques with fixation. Three out of the four studies directly compared in-situ fixation with reduction and fixation. The search included studies published between 2014 and 2024, with most being Level III or IV evidence (except for one prospective study by Wang et al.¹¹⁾). Five studies were conducted in South Korea, three in the USA, two in China, and one in France (Table 1). Among the studies, mean follow-up duration varied considerably, ranging from 11.7 to 36.2 months.

Table 1.

Study Characteristics

Study	Location	Study type	Level of evidence	Critical appraisal
Kim et al.2) (2014)	South Korea	Retrospective	IV	Focus on elderly patients
Sung et al.7) (2017)	South Korea	Retrospective	IV	Risk factors for FN shortening
Moon et al.5) (2019)	South Korea	Retrospective	IV	Multicenter study
Nanty et al.8) (2019)	France	Retrospective	IV	Focus on FN shortening and AVN
Goodnough et al.3) (2021)	USA	Retrospective	III	Comparison with non-operative treatment
Gaski et al.4) (2023)	USA	Retrospective	IV	Large cohort study
DeClouette et al.6) (2024)	USA	Retrospective	III	Comparison of screw configurations
Wang et al.11) (2023)	China	Prospective	IV	Novel reduction technique
Park et al.9) (2021)	South Korea	Retrospective comparative	III	Comparing reduction vs. in-situ
Kweon et al.10) (2023)	South Korea	Retrospective comparative	III	Comparing reduction vs. in-situ
Yu et al.12) (2023)	China	Retrospective comparative	III	Comparing reduction vs. in-situ

FN: femoral neck, AVN: avascular necrosis.

2. Patient Demographics and Surgical Techniques

A total of 821 patients were included across all studies, with individual study populations ranging from 12 to 207 patients. The mean age of patients widely varied and ranged from 40 to 77 years. Mean time to operation was reported in only six studies, and ranged from 24 hours to 5.5 days. Various surgical techniques were employed across the studies. Multiple screw configurations were utilized in the in-situ fixation group, including two parallel screws, three parallel screws in an inverted triangle configuration, and three to four cannulated screws (Table 2). DeClouette et al.⁶⁾ compared different screw configurations, but found no significant differences in outcomes between the use of two parallel screws and three screws in an inverted triangle configuration.

Table 2.

Patients’ Demographic Information and Surgical Procedure

Study	No. of patients	Sex, M/F	Mean age (yr)	Mean time to operation (day)	Reduction methods	Fixation device	Mean follow-up (mo)
Kim et al.2) (2014)	33	12/21	77 (70-100)	3.5	In-situ	3-4 Cannulated screws	12
Sung et al.7) (2017)	83	13/70	69.1 (28-94)	24 hr	In-situ	Three parallel screws (inverted triangle)	29.1 (12-98)
Moon et al.5) (2019)	104	29/75	67.1 (26-85)	N/A	In-situ	Multiple screws (inverted triangle)	16.3 (12-36)
Nanty et al.8) (2019)	75	19/56	66.0±15.4	N/A	In-situ	Triple cannulated screws	12
Goodnough et al.3) (2021)	97	N/A	40-95	N/A	In-situ	Three cannulated screws (inverted triangle)	13.8 (3.1-154.3)
Gaski et al.4) (2023)	207	45/162	77±11	N/A	In-situ	Large diameter cancellous screws	22 (1-79)
DeClouette et al.6) (2024)	61	8/53	72 (65-83)	N/A	In-situ	2 Parallel or 3 inverted triangle screws	12 (7.2-21.6)
Wang et al.11) (2023)	12	6/6	52.5 (21-63)	5.5 (1-11)	Screwdriver rod reduction	FNS (femoral neck system)	11.7 (6-18)
Park et al.9) (2021)	55 -In situ: 28 -Reduction: 27	-In situ: 6/22 -Reduction: 5/22	-In situ: 52.6 -Reduction: 51.3	-In situ: 35.5 hr -Reduction: 29.4 hr	Schanz pin reduction	Three cannulated screws	36.2 (13-120)
Kweon et al.10) (2023)	46 -In situ: 23 -Reduction: 23	-In situ: 8/15 -Reduction: 10/13	-In situ: 66.4 -Reduction: 69.7	-In situ: 25.0 hr -Reduction: 25.4 hr	Steinmann pin reduction	FNS (femoral neck system)	17.0±4.7
Yu et al.12) (2023)	48 -In situ: 24 -Reduction: 24	-In situ: 10/14 -Reduction: 7/17	-In situ: 52.1 -Reduction: 54.4	-In situ: 40.2 hr -Reduction: 37.6 hr	“In-out-in” technique	Three cannulated screws	24-42

Values are presented as number only, mean (range), or mean±standard deviation.

M: male, F: female, N/A: not available.

Reduction techniques have demonstrated distinct characteristics and evolution over time. Park et al.⁹⁾ introduced a technique using lateral traction with a Schanz pin inserted transversely into the middle one-third of the trochanter, showing promising results in anatomical reduction. Kweon et al.¹⁰⁾ employed a threaded Steinmann pin technique with a pull-out method, while Wang et al.¹¹⁾ developed a screwdriver rod-assisted reduction technique performed percutaneously. Yu et al.¹²⁾ described a novel “in-out-in” percutaneous technique using sequential pin placement for controlled reduction.

3. Clinical Outcomes

Rates were consistently high across studies reporting on successful union, with several studies demonstrating 100% union rates^6,9-12). In comparative studies, AVN rates varied from 0% to 13.0%, with no significant difference between in-situ and reduction groups. However, FN shortening showed significant variations between techniques. DeClouette et al.⁶⁾ reported 31.1% of patients experiencing more than 2 mm shortening in their in-situ fixation group, regardless of screw configuration. In contrast, Park et al.⁹⁾ demonstrated significantly lower rates of shortening greater than 5 mm in their reduction group compared to in-situ fixation (11% vs. 75%). Wang et al.¹¹⁾ reported particularly favorable results with their reduction technique, with mean shortening value of only 2.1 mm (range, 1-4 mm) (Table 3).

Table 3.

Overall Clinical Outcomes

Study	Union rate (%)	FN shortening (%)	AVN rate (%)	HHS	Complications
Kim et al.2) (2014)	81.8	N/A	3.0	N/A	Reoperation rate of 24% (failure rate 18.2%, subtrochanteric fracture at the screw insertion site 6%)
Sung et al.7) (2017)	N/A	Significant FN shortening (38.5%)	N/A	N/A	Complications occurred in 13 of 83 (AVN 11 cases, nonunion 4 cases)
Moon et al.5) (2019)	89.4	N/A	8.7	In-situ*: -Posterior tilt angle <13°: 90.4 -Posterior tilt angle >13°: 82.5	Nonunion 10.6%, reoperation 19.2%
Nanty et al.8) (2019)	Not detailed but successful initial healing for most cases.	N/A	12.0	N/A	26% of impaction cases had complications
Goodnough et al.3) (2021)	N/A	N/A	N/A	N/A	Reoperation 15.5%
Gaski et al.4) (2023)	N/A	N/A	5.3	N/A	Major complications (included AVN, nonunion, and varus collapse) 17.3%, reoperation 15.0%
DeClouette et al.6) (2024)	100	31.1% exceeding 2 mm of FN shortening	5.0	N/A	AVN more common in inverted triangle group
Wang et al.11) (2023)	100	Mean 2.1 mm (range, 1-4 mm)	0	In-situ: 92.4 (85-96)	No major complications
Park et al.9) (2021)	100	In-situ: 75%, reduction: 11%, exceeding 5 mm of FN shortening	7.3	-In-situ: 82.7 -Reduction: 89.9	AVN 2 cases in each group
Kweon et al.10) (2023)	100	Less in reduction group (1 yr postoperative z-axis value; in-situ: 6.9 mm, reduction: 3.5 mm)	13.0 (in situ) vs. 8.7 (reduction)	-In-situ: 79.7 -Reduction: 87.9	AVN: 3/23 vs. 2/23 cases (in situ vs. reduction)
Yu et al.12) (2023)	100	Reduction group only (preooperative FN shortening: 8.93 mm, 2 yr postoperative FN shortening: 2.54 mm)	8.3	-In-situ: 84.1 -Reduction: 90.5	Fixation failure 1, AVN 3 cases

FN: femoral neck, AVN: avascular necrosis, HHS: Harris hip score, N/A: not available.

*HHS values in Moon et al.’s study⁵⁾ represent comparison between groups with posterior tilt angle <13° vs. >13°.

Functional outcomes, primarily measured using the HHS, consistently favored reduction techniques¹⁵⁾. Park et al.⁹⁾ reported significantly higher HHS at one year follow-up in their reduction group compared to in-situ fixation (89.9 vs. 82.7). Similar findings were reported by Kweon et al.¹⁰⁾ (87.9 vs. 79.7) and Yu et al.¹²⁾ (90.5 vs. 84.1 at 24 months), while Wang et al.¹¹⁾ achieved excellent results with their reduction technique (mean HHS, 92.4 [range, 85-96]).

4. Complications

While complications varied among studies, some showed consistent patterns. In the in-situ fixation group, Gaski et al.⁴⁾ reported a 17.3% major complication rate, including AVN, nonunion, and varus collapse, in their large series of 207 patients. Kim et al.²⁾ noted an 18.2% failure rate plus 6% incidence of subtrochanteric fracture at screw insertion sites. Reduction techniques generally showed lower complication rates, with Wang et al.¹¹⁾ reporting no major complications in their series. Reoperation rates ranged from 15.0% to 24% in the in-situ fixation groups, while reduction groups demonstrated lower reoperation rates overall.

5. Quality Assessment

The Modified Coleman Methodology Score showed a mean score of 71.9 (range, 62-85). Comparative studies achieved the highest scores (Park et al.⁹⁾ and Yu et al.¹²⁾: 85; Kweon et al.¹⁰⁾: 82), reflecting their more rigorous methodology and comprehensive outcome reporting. Among non-comparative studies, Gaski et al.⁴⁾ achieved the highest score of 76 points, while most in-situ fixation studies scored between 62 points and 76 points (Table 4).

Table 4.

Modified Coleman Methodology Score

Study	Study size (10)	Mean follow-up (5)	No. of procedures (10)	Type of study (15)	Diagnostic certainty (5)	Surgery description (5)	Rehabilitation description (10)	Outcome criteria (10)	Procedure for outcomes (15)	Selection process (15)	Total score (100)
Kim et al.2) (2014)	4	2	10	0	5	5	10	10	6	10	62
Sung et al.7) (2017)	7	0	10	0	5	5	10	10	11	10	68
Moon et al.5) (2019)	7	0	10	0	5	5	10	10	11	10	68
Nanty et al.8) (2019)	4	0	10	0	5	5	10	10	11	10	65
Goodnough et al.3) (2021)	7	2	10	0	5	5	10	10	11	10	70
Gaski et al.4) (2023)	10	5	10	0	5	5	10	10	11	10	76
DeClouette et al.6) (2024)	4	2	10	0	5	5	10	10	11	10	67
Wang et al.11) (2023)	0	2	10	0	5	5	10	10	11	10	63
Park et al.9) (2021)	4	5	10	10	5	5	10	10	11	15	85
Kweon et al.10) (2023)	4	2	10	10	5	5	10	10	11	15	82
Yu et al.12) (2023)	4	5	10	10	5	5	10	10	11	15	85

DISCUSSION

In-situ fixation remains the mainstream treatment for VIFNF, based on the perceived inherent stability of the impacted fracture pattern^1,2,5,16). The traditional concern has been that reduction might destabilize this naturally stable configuration by causing fracture disimpaction, thus potentially creating bone voids and compromising stability^9,10,17). However, our systematic review of recent literature reveals several important findings that challenge this conventional approach.

Studies have shown that traditional in-situ fixation with multiple cannulated screws has shown significant limitations^7,18-20). Park et al.⁹⁾ reported that 75% of patients experienced more than 5 mm shortening in their in-situ fixation group, and DeClouette et al.⁶⁾ found 31.1% of patients had more than 2 mm shortening regardless of screw configuration. Reflected in lower HHS, the clinical importance of this shortening is demonstrated by consistently poorer functional outcomes.

Recent developments in both reduction techniques and fixation devices have provided potential solutions to these concerns. Various studies have described minimally invasive reduction methods such as: Park et al.⁹⁾ using Schanz pin lateral traction, Kweon et al.¹⁰⁾ employing a threaded Steinmann pin pull-out method, Wang et al.¹¹⁾ developing a screwdriver rod-assisted reduction, and Yu et al.¹²⁾ describing an “in-out-in” technique. These techniques, when combined with modern fixation devices such as the femoral neck system (FNS) or strategic placement of fully threaded posterior screws to prevent anterior angulation, have demonstrated promising results in maintaining reduction and preventing shortening^11,21,22). Of particular note is Wang et al.’s technique¹¹⁾ with FNS fixation in which a mean shortening of only 2.1 mm with no major complications was achieved.

Patient selection has emerged as crucial in determining optimal treatment strategy. Moon et al.⁵⁾ identified age (>72.5 years) and posterior tilt angle (>13°) as independent predictors of failure, reinforcing the importance of patient selection in treatment decision-making. Furthermore, Gaski et al.⁴⁾ reported a 17.3% major complication rate in their large in-situ fixation series, despite careful selection of patients without sagittal malalignment.

Moreover, as reduction and fixation generally require a longer operative time than in-situ fixation due to additional surgical steps, such as anatomical reduction and fixation verification, it should be considered when determining the optimal treatment approach.

The correlation between FN shortening and complications merits special attention. FN shortening is recognized as a significant complication following fixation. Studies indicate that excessive shortening is associated with impaired functional outcomes and increased risk of nonunion. Nanty et al.⁸⁾ demonstrated that FN shortening during healing significantly correlates with the development of AVN. This finding suggests that achieving and maintaining anatomical reduction through improved fixation techniques might offer benefits beyond just maintaining length⁸⁾. In our review, AVN rates ranged from 0% to 13%, with several studies showing comparable rates between reduction and in-situ fixation groups when using appropriate fixation devices. In summary, Fig. 2 presents the advantages and disadvantages of in-situ fixation and reduction & fixation.

Fig. 2.

Summarized comparison of in-situ fixation and reduction & fixation: advantages and disadvantages. AVN: avascular necrosis.

This study has several limitations. First, only a few direct comparative studies were available as most included studies were retrospective in nature. Included articles were predominantly observational studies. As such, there remains a need for prospective randomized studies to confirm the observed associations and further strengthen the evidence base. Second, the included studies showed considerable heterogeneity in their methodology, making direct comparison challenging. Third, there was significant variation in follow-up periods among studies, potentially affecting the detection of late complications such as AVN. Fourth, the strength of our conclusions was limited since the number of included studies was relatively small. Fifth, there was a geographical bias in the included studies, with nearly half of the studies being conducted in South Korea, potentially limiting the applicability of our findings to other populations. Sixth, the statistical analysis and interpretation in some studies were limited, with varying levels of depth and rigor. This limitation may impact the overall strength of the conclusions drawn and highlights the need for further studies with robust statistical methodologies. Seventh, the retrospective design of most of the included studies introduces potential biases and limits the ability to establish causation.

CONCLUSION

Anatomical reduction with fixation leads to better functional outcomes and less FN shortening than in-situ fixation for VIFNF. While in-situ fixation is simpler and traditionally favored, it is associated with significant shortening, which may impair long-term function. Reduction results in higher HHS and reduced shortening, with lower complication and reoperation rates, though AVN incidence is similar between techniques. In-situ fixation may be more suitable for older or osteoporotic patients, whereas reduction is preferable for younger, active individuals.

Supplemental Materials

Supplementary data is available at https://hipandpelvis.or.kr/.

Funding Statement

Funding This study was supported by the 2022 Hip & Pelvis Research Grant from the Korean Hip Society.