Navigation-assisted implantation of Gamma3 nails – What are the benefits of the ADAPT system?

Abstract

Introduction: Optimal placement of the femoral neck screw is essential during osteosynthesis of pertrochanteric fractures. A low tip-apex distance (TAD) is crucial to avoid a cut-out of the femoral neck screw. Whether the use of a navigation system during osteosynthesis with Gamma3 nails positively influences the TAD, fluoroscopy time and surgery duration has been assessed differently in the initial clinical applications. We tested the ADAPT system for positioning Gamma3 nails as part of a standardised laboratory experiment. Methods: An inexperienced surgeon and an experienced surgeon each implanted 20 Gamma3 nails in artificial bones. Each surgeon performed 10 conventional interventions and 10 using the ADAPT system. Subsequently, TAD, femoral neck screw positioning, fluoroscopy time, number of X-ray images and surgery duration were compared. The experimental set-up also assessed whether the ADAPT system offers advantages over distal freehand locking for long Gamma3 nails. Results: The inexperienced surgeon was able to implant the nail significantly faster when using the ADAPT system (99.10 s/60.20 s; p = 0.005), while the experienced surgeon required more time to implant the femoral neck screws (59.70 s/94.00 s, p < 0.001). The fluoroscopy times of both surgeons were somewhat shorter when using the ADAPT system. All femoral neck screws were placed correctly with a TAD of less than 20 mm. Only the TAD of the inexperienced surgeon was reduced with the use of the ADAPT system (16.30 mm/12.40 mm; p < 0.001). Conclusions: The ADAPT system could reduce TAD and possibly fluoroscopy time, especially in inexperienced surgeons. For experienced surgeons, there was no influence on TAD and only a minimal effect on fluoroscopy time.

Keywords

Femoral trochanteric fracture computer-assisted surgery navigation orthopaedic resident novice surgeon cephalomedullary nail tip-apex distance (TAD)fluoroscopy

Introduction

In Germany, intramedullary nail osteosynthesis is now the standard procedure for the treatment of pertrochanteric femoral fractures. In 2020, 94.3% of pertrochanteric fractures recorded in the AltersTraumaRegister DGU^® (Geriatric Trauma Register) were stabilised using intramedullary nails.¹ While cut-out rates of up to 16.5% were still being reported in 1990,² new insights into the optimal positioning of femoral neck screws have reduced this rate to 1.85%.³ The 1995 study by Baumgaertner et al., which set guidelines for the placement of femoral neck screws and recommended that the tip-apex distance (TAD) remain under 25 mm, was particularly groundbreaking.⁴

The ADAPT system introduced in 2012 by Stryker^® (Stryker^®, Duisburg, Germany) was developed for the implantation of Gamma3 nails and aims to guide the surgeon through the procedure using an adaptive workflow. According to the manufacturer, the system was developed to provide the surgeon with the necessary intraoperative information to achieve the desired placement of the Gamma3 nail. The ADAPT system aims to help visualise and adjust the nail insertion depth before the insertion of the guide wire for the femoral neck screw. Furthermore, it aims to reduce variability, TAD and intraoperative radiation exposure.

Previously, study findings on the application of the ADAPT system have been available from one cadaver study⁵ and several clinical studies with low case numbers.^6–11 These results showed that some surgeons benefit from using the system and demonstrated a general TAD reduction, with less variation.^5,6,10 Furthermore, Regling et al. observed reduced fluoroscopy exposure times.⁵ Some authors observed an increase in surgery duration when using the ADAPT system.^6,7

Kuhl et al. and Takai et al. also compared the intraoperative TAD values displayed by the ADAPT system with the postoperative values determined via X-ray or CT and identified a high level of correlation between the values.^8,12

The aim of this study was for an inexperienced surgeon and an experienced surgeon to perform both conventional and ADAPT system-aided Gamma3 nail implantation using a standardised laboratory model without the influence of soft tissue, different types of fractures, and so on. The precision of the implantation, the fluoroscopy exposure time and the duration of the individual stages of the operation were evaluated.

Methods

Using a standardised trial set-up, an inexperienced surgeon (<5 gamma nail implantations) and an experienced surgeon (>200 gamma nail implantations) each implanted 20 Gamma3 nails (11/180 mm, 125°) into a non-fractured plastic femur (Synbone^®, Zizers, Switzerland).

In the control group, 10 operations were performed by each surgeon in accordance with the standard procedure recommended by the manufacturers (Stryker^®, Duisburg, Germany). Intraoperative position monitoring was carried out using an image converter.

In the trial group, 10 implantations per surgeon were performed using the ADAPT system (Stryker^®, Duisburg, Germany), which provided the surgeons with guidance for implant positioning. The system calculates the current implant position in the bone and provides information as to the optimal insertion depth for the implant, alignment for the insertion of the guide wire for the femoral neck screw and the insertion depth for the femoral neck screw using 2-plane images from the image converter. For this, an ADAPT clip must be installed in the aiming arm of the screw and a FluoroDisc on the image converter to act as a calibration aid. The ADAPT system guides the surgeon through the stages of the surgery, and during the assisted stages, it provides orientation recommendations based on the current images from the image converter.

Execution of the trial

To prevent the surgeons from becoming accustomed to the position of the femur and to make orientation using the bone impossible, it was fitted with a foam covering (Figure 1), and the rotation and axial alignment of the plastic femur were changed before each experimental procedure.¹³ The surgeons also switched every 5 procedures to prevent fatigue.

Figure 1.

Trial set-up comprised of a plastic femur with foam covering (Synbone^®, Zizers, Switzerland), ADAPT clip, FluoroDisc, ADAPT image converter, (Stryker^®, Duisburg, Germany). Set-up for an operation using the ADAPT system. In conventional surgery, the monitor was placed so it was not visible to the surgeon.

The surgeons performed the procedures alone, that is they were not assisted during the surgical stages and received no guidance from the image converter. The image converter was operated by a doctoral candidate on the instructions of the surgeon.

The duration of each surgical stage, the fluoroscopy exposure time and the number of required image converter images were recorded. The number of attempts required during each stage of the surgery was also recorded.

The implant position was recorded and logged for both the trial and for the control group by the ADAPT system. In the control group, the surgeon could not see the ADAPT monitor during surgery.

Statistics

The data were recorded in an Excel^® database (Version 2019, Microsoft^®, Redmondon, USA). Statistical analysis was carried out using t-tests and two-way univariate analysis of variance (UNIANOVA) using SPSS Statistics^® (Version 27, IBM^®, Armonk, USA). The significance level of the applied tests was defined as p < 0.05.

Results

Without the use of the ADAPT system, the experienced surgeon required significantly less surgery duration, fluoroscopy exposure time and X-ray images to insert the guide wire and implants compared to the inexperienced surgeon (Tables 1–3).

Table 1.

Changes in operation duration when using the ADAPT system.

	Guide wire placement for nail insertion	Drilling for nail insertion	Nail insertion	Guide wire placement for femoral neck screw	Drilling for femoral neck screw	Femoral neck screw insertion	Drilling for distal locking	Distal locking screw insertion	Control X-ray
OP duration inexperienced surgeon without ADAPT [s]	103.10	15.70	99.10	260.40	11.80	110.70	7.60	16.40	25.90
OP duration inexperienced surgeon with ADAPT [s]	65.10	15.60	60.20	137.60	8.60	114.00	5.60	15.10	23.60
Change in OP duration inexperienced surgeon [s]	−38.00	−0.10	−38.90	−122.80	−3.20	+3.30	−2.00	−1.30	−2.30
Significance interaction ADAPT* inexperienced surgeon	0.061	0.891	0.005	0.077	0.178	0.746	0.032	0.359	0.413
OP duration experienced surgeon without ADAPT [s]	45.80	11.40	54.90	84.40	8.90	59.70	5.80	12.40	13.80
OP duration experienced surgeon with ADAPT [s]	52.20	11.90	53.60	106.40	9.10	94.00	4.70	11.60	13.80
Change in OP duration experienced surgeon [s]	+6.40	+0.50	−1.30	+22.00	+0.20	+34.30	−1.10	−0.80	±0.00
Significance interaction ADAPT*experienced surgeon	0.475	0.699	0.914	0.344	0.872	<0.001	0.290	0.446	1.000

s: seconds.

Table 2.

Changes in the number of image converter images when using the ADAPT system.

	Guide wire placement for nail insertion	Drilling for nail insertion	Nail insertion	Guide wire placement for femoral neck screw	Drilling for femoral neck screw	Femoral neck screw insertion	Drilling for distal locking	Distal locking screw insertion	Control X-ray
X-ray images inexperienced surgeon without ADAPT [n]	5.70	No X-ray	7.10	26.70	No X-ray	6.10	No X-ray	No X-ray	3.80
X-ray images inexperienced surgeon with ADAPT [n]	3.90		2.90	11.70		4.60			4.30
Change in X-ray images inexperienced surgeon [n]	−1.80		−4.20	−15.00		−1.50			+0.50
Significance interaction ADAPT* inexperienced surgeon	0.014		0.004	0.021		0.072			0.450
X-ray images experienced surgeon without ADAPT [n]	3.30	No X-ray	5.10	12.30	No X-ray	2.70	No X-ray	No X-ray	3.20
X-ray images experienced surgeon with ADAPT [n]	4.20		2.70	8.70		3.60			3.20
Change in X-ray images experienced surgeon [n]	+0.90		−2.40	−3.60		+0.90			±0.00
Significance interaction ADAPT*experienced surgeon	0.213		0.025	0.219		0.027			1.000

n: number.

Table 3.

Changes in fluoroscopy exposure times when using the ADAPT system.

	Guide wire placement for nail insertion	Drilling for nail insertion	Nail insertion	Guide wire placement for femoral neck screw	Drilling for femoral neck screw	Femoral neck screw insertion	Drilling for distal locking	Distal locking screw insertion	Control X-ray
X-ray time inexperienced surgeon without ADAPT [s]	3.00	No X-ray	2.80	10.30	No X-ray	2.50	No X-ray	No X-ray	1.50
X-ray time inexperienced surgeon with ADAPT [s]	2.50		1.20	4.40		2.10			1.70
Change in X-ray time inexperienced surgeon [s]	−0.50		−1.60	−5.90		−0.40			+0.20
Significance interaction ADAPT* inexperienced surgeon	0.121		0.010	0.022		0.276			0.526
X-ray time experienced surgeon without ADAPT [s]	2.20	No X-ray	2.70	4.60	No X-ray	1.50	No X-ray	No X-ray	1.60
X-ray time experienced surgeon with ADAPT [s]	2.50		1.20	3.40		1.30			1.50
Change in X-ray time experienced surgeon [s]	+0.30		−1.50	−1.20		−0.20			−0.10
Significance interaction ADAPT*experienced surgeon	0.268		0.032	0.276		0.470			0.722

s: seconds.

When assisted by the ADAPT system, the inexperienced surgeon was able to carry out 2 of 3 operative stages faster (nail insertion: 99.10 s/60.20 s; p = 0.005; guide wire placement for femoral neck screw: 260.40 s/137.60 s; p = 0.077). The third assisted surgical stage took longer (femoral neck screw insertion: 110.70 s/114.00 s; p = 0.746). In contrast, when using the ADAPT system, the experienced surgeon took longer to place the guide wire for the femoral neck screw (59.70 s/94.00 s, p < 0.001) than during the conventional procedure (Table 1).

For both surgeons, the number of X-ray images required by both surgeons was lower with the ADAPT system compared with the conventional approach, both for nail insertion (inexperienced surgeon: 7.10/2.90; p = 0.004; experienced surgeon: 5.10/2.70; p = 0.025) and placement of the guide wire for the femoral neck screw (inexperienced surgeon: 26.70/11.70; p = 0.021; experienced surgeon: 12.30/8.70; p = 0.219). In contrast, whereas the inexperienced surgeon required fewer X-ray images for the insertion of the femoral neck screw (6.10/4.60; p = 0.072), the experienced surgeon required more X-ray images (2.70/3.60; p = 0.027) to insert the screw when using the ADAPT system (Table 2).

The fluoroscopy exposure times for both surgeons were shorter when using the ADAPT system compared to the conventional approach (Table 3).

The measurements of the final X-ray images by the ADAPT system showed that the TAD values of the inexperienced surgeon were significantly reduced when using the ADAPT system (16.30 mm/12.40 mm; p < 0.001), while those of the experienced surgeon showed a minimal increase (12.70 mm/13.10 mm; p = 0.707). The deviation of the femoral neck screw from the optimal centre-centre position was minimally lower for both surgeons (Table 4).

Table 4.

Precision of femoral neck screw position (target TAD <25 mm, ant.-pos. and sub.-inf. deviation <2 mm).

	Tip-apex distance	Ventral–dorsal deviation of the femoral neck screw	Superior–inferior deviation of the femoral neck screw
Inexperienced surgeon without ADAPT [mm]	16.30	2.10	1.60
Inexperienced surgeon with ADAPT [mm]	12.40	1.00	1.70
Change inexperienced surgeon [mm]	−3.90	1.10	−0.10
Significance interaction ADAPT* inexperienced surgeon	<0.001	0.068	0.866
Experienced surgeon without ADAPT [mm]	12.70	1.50	2.10
Experienced surgeon with ADAPT [mm]	13.10	1.00	1.20
Change experienced surgeon [mm]	+0.40	0.50	0.90
Significance interaction ADAPT*experienced surgeon	0.707	0.258	0.152

Discussion

For patients receiving treatment for hip joint-adjacent fractures with Gamma3 nails, correct fracture repositioning and optimal femoral neck screw placement are crucial. Poor fracture repositioning and a TAD value greater than 25 mm are proven to cause a high femoral neck screw cut-out rate and pseudarthroses.^4,15,16 For inexperienced surgeons, experience shows that correct placement of the guide wire for the nail insertion point, on which the success of the entire osteosynthesis procedure depends, is the most difficult component.

The ADAPT system cannot aid fracture repositioning or guide wire placement for the insertion point. However, it assists in all stages necessary for optimal placement of femoral neck screws. It was shown that the inexperienced surgeon achieved a significantly reduced TAD value of 12.40 mm when using the ADAPT system. However, during conventional surgery, the inexperienced surgeon's TAD never exceeded 18 mm and was therefore within the noncritical range. The experienced surgeon use of the ADAPT system did not lead to any significant change in TAD values. Neither surgeon benefitted significantly from the ADAPT system in ventro/dorsal or superior/inferior wire placement. There is no clinical relevance of a 0.1 or 1.1 mm improvement in placement.

The available literature distinguishes between 9 different trial groups. When the ADAPT system was used, there was a reduction in the average TAD value across all 9 groups. However, this is significant in only 5 of the 9 groups. The variance of the achieved TAD is lower in 8 of the 9 groups with a significant reduction evident in only 3 of these groups. 7 groups reported that conventional procedures led to suboptimal femoral neck screw placement with a TAD of over 25 or 20 mm. However, similar malpositioning also occurred in 4 of the ADAPT system groups. The literature shows that there is at least a trend toward TAD reduction or optimal screw placement in cases where the ADAPT system is used, and this is more prevalent in inexperienced surgeons. However, the ADAPT system cannot completely prevent screw malpositioning (Table 5).

Table 5.

ADAPT system studies, literature review.

Study	Surgeon	Study type	Median TAD	Range TAD	TAD outliers	X-ray time	OP duration
Regling M⁵2014, BMC Musuloselet Disord	Inexperienced surgeon	Exp.	≤	≤	>25 mmconv. YesADAPT No	<^a	≥
Regling M⁵2014, BMC Musuloselet Disord	Experienced surgeon	Exp.	≤	≤	>25 mmconv. YesADAPT No
Lilly R⁷2018, Injury	Group of 3 fellowship-trained surgeons	Clin.	≤	≤	>25 mmconv. NoADAPT No	≥	+^a
Herzog J¹⁰2019, Injury	Group of 5 consultant trauma surgeons	Clin.	<^a	<^a	>25 mmconv. YesADAPT Yes		≤
Takai H⁹2020, Injury	Surgeon Aorthopaedic resident(little experience)	Clin.	<^a	<^a	>20 mmconv. 16.9%ADAPT 0%	<^a	≤
Takai H⁹2020, Injury	Surgeon Borthopaedic resident(little experience)	Clin.	≤	≤	>20 mmconv. 14.0%ADAPT 16.3%	≥	≥
Kuhl M¹¹2020, Clin. Orthop. Rel. Res.	Surgeon on duty	Clin.	<^a	<^a	>25 mmconv. 12.1%ADAPT 1.0%	<^a	≤
Era M⁶2021, Journal of Orthopaedic Science	Young surgeons(2 junior residents)	Clin.	<^a	≤	>20 mmconv. 34.8%ADAPT 5.7%		≥
Era M⁶2021, Journal of Orthopaedic Science	Experienced surgeons(2 orthopaedic residents)	Clin.	≤	≤	>20 mmconv. 0%ADAPT 0%		≥
Murakami T¹⁴2021, SICOT J	Experienced surgeons assisted by a computer operator	Clin.	<^a		>20 mmconv. 0%ADAPT 0%	<^a	<^a
Wilharm et al.Own data	Inexperienced surgeon	Exp.	<^a	≥	>20 mmconv. NoADAPT No	<^a	≤
Wilharm et al.Own data	Experienced surgeon	Exp.	≥	<^a	>20 mmconv. NoADAPT No	≤	≥

clin.: clinical; conv.: conventionally; exp.: experimental.

Changes marked.

A reduction in operation duration is especially desirable for geriatric patients and from an economic perspective. Likewise, a reduction in fluoroscopy exposure times and related radiation exposure is desirable for both the patient and the surgical team. In our study, the ADAPT system led to a significant reduction in fluoroscopy time only in the inexperienced surgeon. This was also the case in 3 of 5 studies that investigated this aspect. In 2 studies, the X-ray duration was slightly shorter when using the ADAPT system, similar to the experienced surgeon in our study (Table 5). The effect of the ADAPT system on surgery duration is even more inconsistent. In none of the 8 studies was a significant reduction in surgery duration reported. 3 of the 8 studies reported either shortening or lengthening of the surgery duration. One study reported significant lengthening of the duration. In our study, the experienced surgeon required slightly longer when using the ADAPT system, while the inexperienced surgeon was slightly faster. No clear correlation with the experience of the surgeon could be confirmed in the available literature (Table 5).

The absence of reference markers is, on the one hand, one of the benefits of the ADAPT system; however, this also means that there is no dynamic display of the instruments and implant position, as is the case with the Brainlab^® system.¹⁷ This also makes navigation-assisted determination of the entry point for the first guide wire and correct guide wire or implant placement impossible at the first attempt or without further X-ray images.

Conclusion

Our study, consisting of an experienced and an inexperienced surgeon, using a standardised trial model, showed that the inexperienced surgeon was able to achieve significantly reduced TAD values and significantly shorter fluoroscopy exposure times. In the case of the experienced surgeon, no relevant impact was observed related to the use of the ADAPT system. Both surgeons were able to achieve optimal femoral neck screw positioning (TAD < 20 mm) when using the conventional technique. When these findings are viewed together with the available literature, there is a trend that the TAD in clinical studies is more often within the optimal range. However, even with the use of the ADAPT system, femoral neck screw malposition with a TAD value of up to 33.7 mm is possible.¹⁰ In this study, in which the ADAPT system was tested on a standardised model, there is no indication that the ADAPT system provides an advantage for experienced surgeons when implanting Gamma III nails.

Footnotes

Acknowledgements

The authors would like to thank Stryker GmbH & Co KG for providing the ADAPT system free of charge for this study. We acknowledge support by the German Research Foundation Projekt-Nr. 512648189 and the Open Access Publication Fund of the Thueringer Universitaets- und Landesbibliothek Jena.

Authors’ contributions

Study design, conception and critical revision were done by AW.

Acquisition of data was done by AG.

Analysis and interpretation of data were done by AG, AW.

Surgery was done by MH, AW.

Literature search and drafting of manuscript were done by AW, AG.

Statistic was done by AG, PS.

Final manuscript review and editing were done by AW, AG, MH, GOH.

Availability of data and material

The datasets used and analysed during the current study are available from the corresponding author on reasonable request.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical approval

An ethical approval was not necessary. The study was performed on artificial bones.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The ADAPT system was provided free of charge by Stryker company. No further financial support was provided.

Informed consent

Informed consent was not necessary. The study was performed on artificial bones.

ORCID iD

Arne Wilharm

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