Suprapatellar versus infrapatellar nailing for tibial shaft fractures: A comparison of surgical and clinical outcomes between two approaches

Abstract

Background

Tibial shaft fractures are a relatively common injury and contemporary treatment includes on-axis fixation with a locked intramedullary nail in the majority of cases. The conventional technique is via an infrapatellar approach but currently there is a trend towards the use of a suprapatellar approach. We compared key variables including operative time, radiation exposure and early patient reported outcomes when adopting a suprapatellar approach to tibial nailing in our unit versus our previous experience of infrapatellar tibial nailing.

Method

Twenty-eight consecutive patients with tibial fracture underwent tibial nailing via the suprapatellar (SPN) approach. Six patients in the study group were excluded due polytrauma and need for dual orthopaedic and plastic surgery management. We compared outcomes with our most recent 20 consecutive patients who had undergone tibial nailing via an infrapatellar (IPN) approach. Primary surgical outcomes were: operative time, radiation exposure and accuracy of entry point of the nail on both anteroposterior and lateral radiographs. Clinical outcomes included time to weightbearing, time to radiographic union and patient-reported outcome score (Lysholm score).

Results

Forty-eight consecutive patients underwent intramedullary nail fixation for tibial shaft fractures and 42 were eligible for inclusion in our study (22 SPN vs 20 IPN). There were no significant differences in patient demographics or injury patterns between the two groups. Operative time and radiation exposure were significantly lower in the SPN group when compared to the IPN group (115 min vs 139 min ± 12.5) (36 cGY/cm² vs 76.33 cGY/cm² +/- 20.1). Furthermore, patients in the SPN group reported superior outcome scores at a mean follow up of 3 months (8–24 weeks) There were no observed differences in complication rate between groups and time of final clinical follow up at a minimum of 6 months.

Conclusion

Our study shows that adoption of the SPN approach requires minimal learning curve, and has the potential benefits of reduced operative time, radiation exposure and superior patient reported outcomes when compared to the conventional infrapatellar approach.

1. Introduction

Tibial shaft fractures are common representing 2% of the workload for all fractures in adults.¹ Contemporary treatment includes an on-axis fixation with a locked intramedullary nail. Traditionally, an infrapatellar approach has been used for this operation however, a suprapatellar approach with the knee in a semi-extended position is gaining popularity due to its benefits, including easier fracture reduction, accurate nail entry point, a shorter operating time and a lower radiation dose exposure.2, 3, 4 As a department we have adopted the suprapatellar approach for tibial nailing and wanted to compare this to our previous experience using the infrapatellar approach.

Accurate nail entry point will allow the tibial nail to be inserted within an anatomical safe zone or “sweetspot” as described by Tornetta et al. in cadaveric studies located 5 mm lateral to the midline of the tibial plateau⁵ and immediately adjacent and anterior to the articular margin of medial tibial plateau.⁶ Aiming for an accurate nail entry point will also help in the fracture reduction by reducing iatrogenic varus and valgus alignment via excessive lateral or medial entry points.⁷

Fluoroscopy plays an essential role in fracture reduction and helps with ensuring precise positioning of the intramedullary nail, however, excessive use of radiation in the operating theatre can lead to significant biological consequences to the surrounding patient and staff, therefore reducing the radiation dose and time exposure is encouraged as good practice.^8,9

We aimed to achieve the above by adopting this new surgical approach to tibial nailing and the aim of this paper is to offer a comparison of surgical and clinical outcomes between the two approaches.

2. Methods

Our study includes 42 consecutive intramedullary tibial nail fixations performed at our central London Teaching Hospital and Trauma Unit. We included all adult (18 years and older) tibial shaft fractures for intramedullary nailing. Exclusion criteria included polytrauma and/or combined plastic surgery management, previous tibial surgery, deformity or pathology such as metastatic disease. All consecutive patients in the study period of 18 months underwent SPN intramedullary nailing (22 patients) and these were compared with our most recently performed IPN intramedullary tibial nailing cases (20 patients).

The fracture pattern, classified using the AO classification¹⁰ for tibial diaphyseal fractures, was recorded from imaging and operative notes. Patient demographics were recorded from admission paper notes and electronic records.

All operations were performed by consultants or senior trainees (ST7 or above) on a planned day time Consultant supervised trauma list. The implants used were the DePuy Synthes Expert Tibial Nail and in the suprapatellar cases the DePuy Synthes Suprapatellar Instrumentation for Expert Tibial Nail was used (DePuy Synthes, Warsaw, IN., USA). In all cases the operative standard was general and local anaesthetic. At time of induction all patients received antibiotic prophylaxis. Patients were positioned supine on a radiolucent operating table; a side support and leg holder were used for the infrapatellar approach setup and a foam wedge in a semi-extended leg position was used for the suprapatellar approach.

Intraoperative time including the initial positioning and fracture reduction were recorded separately for both techniques. Radiation time and dose exposure were recorded using a PACS system report generated by the image intensifier intraoperatively. Radiation dose data were measured as Dose Area Product (DAP), defined as the dose of radiation absorbed multiplied by the area irradiated the unit measurements for DAP is expressed as Grey per centimetre squared (GYcm²).¹¹ The nail entry point was also assessed for both groups using intraoperative and/or immediate post-operative radiographs. The measurements were assessed on both the anteroposterior and lateral view. The optimum nail entry point was selected as 2 mm medial to the lateral tibial spine on the anteroposterior view. On the lateral view, the entry point used was immediately adjacent to and anterior to the articular margin of the medial tibial plateau consistent with previous literature descriptions.¹² In non-calibrated radiographs we used the core diameter of the proximal locking screw as a 5 mm reference point for the measurements. The nail entry point was measured for both groups by a blinded observer and compared to the optimum entry point images with measurements saved and reviewed by a second observer. All results were subject to statistical analysis using the Shapiro Wilk test for sample characteristics and a P-value of <0.05 was considered significant throughout the study. Patients were contacted postoperatively and asked to complete a knee trauma specific outcome score (Lysholm score)¹³

3. Results

A total of 48 operations were identified over the selected time period, 6 cases were excluded due to being multiple injuries or having plastics involvement. The infrapatellar nail group (IPN) comprised 20 patients with a mean age of 32 years (28–80 years). The suprapatellar nail group (SPN) comprised 22 patients with a mean age of 38 years (26–78 years). The majority of patients had tibial nail fixation for acute trauma 97.5% (41) while 2.5% (1) had tibial nail for non-union. There was no significant difference between the IPN and SPN groups for age, gender and open versus closed injury (Table 1). However, on review, we noted an incidental finding that fracture patterns were more complex in the SPN group (Table 2). The most common modes of injury were: fall from a height 52% (19) and sports injury 25% (9). The majority of patients were American Society of Anaesthesiologists (ASA) grade 1 (96%).

Table 1.

Demographics of patients and type of injury between groups.

	Infrapatellar Group	Suprapatellar Group	P Value
Median age (yrs)	32 (19–76)	38 (22–65)	0.003
Male: Female ratio	10:6	16:4	0.342
Closed fracture: open	14:2	17:3	0.001

Table 2.

Fracture pattern.

Fracture Pattern	Simple	Wedge	Complex
IPN	10	4	6
SPN	4	8	10

There was a statistically significant difference between the two groups for both total operative time and radiation dose exposure. The mean operative time in the IPN group was 139 ( ±24.5) minutes compared to 110 ( ±34.2) minutes for the SPN group (p < 0.05). The IPN group had a mean radiation dose (Dose Area Product) of 76.33 ( ±33.4) cGY cm² compared to 36 ( ±28.6) cGY cm² for the SPN group (p < 0.05) (Table 3). Comparing the nail entry point between the two groups we observed a superior accuracy of nail entry point relative to the described ideal point of entry using the SPN approach. In the IPN group the mean entry point on the AP radiograph was±3.5 mm ( ±1.8 mm) while in the SPN group on AP radiograph was±2.1 mm ( ±0.9 mm) (P < 0.01) from the entry point. Similarly, on the lateral radiograph the mean entry point was±7.6 mm ( ±2.1 mm) and +-5.2 mm ( ±1.6 mm) (P < 0.04) from the entry point for IPN and SPN respectively (Fig. 1, Fig. 2).

Table 3.

Primary operative outcome measures between groups.

Outcome (Mean)	IPN	SPN
Operative Time	139	110
Radiation dose (cGY/cm2)	76.3	46.5
Lysholm score	75	90

Fig. 1.

Infrapatellar technique: measurement of the nail entry point on AP/Lateral radiographs.

Fig. 2.

Suprapatellar technique: measuremnt of the nail entry point on AP/Lateral radiographs.

At outpatient clinical follow up all patients were asked to complete a Lysholm score questionnaire with a focus on anterior knee pain and return to normal function level. The SPN showed superior results compared to the IPN group at mean follow up duration of 6 weeks despite the SPN group having more complex fracture patterns. The mean Lysholm score was 90 (84–100) in the SPN group compared to 75 (62–95) to the IPN group.

4. Discussion

Our study suggests improved nail entry-point, reduced operative time and radiation exposure and higher patient satisfaction scores in the early post-operative period may be achieved with SPN versus IPN tibial nailing. The SPN approach makes identification of the ideal entry point easier due to the advantageous anatomy of the trochlear notch of the femur acting as a stabilising guide. We found nail entry point in the SPN approach was more accurate on both AP and lateral radiographs which is consistent with a similar study by Jones et al.¹⁴ The importance of a more accurate nail entry point is demonstrated by improved fracture reduction and less risk of damage to the intra-articular surface thus leading to reduced pain, better function and potential to minimise post-traumatic osteoarthritis.

In our study we have focused on the important effect of the SPN approach on the radiation time and exposure which may be due to the table setup with the knee in a semi-extended position. This more accurate nail entry point gives the C-arm of the image intensifier better access to the limb intra-operatively, thus fewer radiographs are required to check nail positioning and maintenance of fracture reduction, as well as this reducing the time between anteroposterior and lateral radiographs without the need for limb repositioning.¹⁵ On the contrary the IPN approach, due to the use of blocks and the need to change limb position between radiographs for different views increases the number of radiographs taken in order to obtain proper images therefore increasing radiation time and exposure. The radiation exposure is important for both patients and staff. Despite wearing lead protection, regular operating in trauma theatres will undoubtedly lead to additional radiation exposure and thus being able to minimise this is desirable. Two previous studies compared radiation time and exposure between the two techniques. Sun et al. demonstrated that radiation time was reduced in the SPN compared to IPN approach in 162 tibial nails¹⁶ and another supporting study by Williamson et al., who also compared radiation time and exposure between the two techniques in 90 tibial nails¹⁷ also demonstrated this. However, in the first study didn’t look at the radiation dose and the later study compared only the fluoroscopy difference between the two techniques unlike our study where we compared multiple factors. Furthermore, due to the fact that this is a new technique there may be some concerns over the effect of the learning curve on outcomes such as radiation exposure (DAP) and fluoroscopy time while surgeons learn this technique. However, this has been studied by Valsamis et al.¹⁸ and they demonstrated that in the hands of experienced trauma surgeons there is no significant impact of the learning curve and thus no increased radiation dose exposure as compared to the more traditional technique of the Infrapatellar tibial nail approach.

Anterior knee pain is one of the most common presentations following tibial nail insertion as described in the literature.¹⁹ The outcome of anterior knee pain in our study was assessed using a validated patient questionnaire, the Lysholm scale.¹³ This specifically asks about anterior knee pain, pain on squatting, pain on climbing the stairs and whether a walking stick is required, any swelling and locking sensation. This attributes a score depending on answers where >90 is good and <65 is poor. In our study fewer patients reported anterior knee pain in the SPN group compared to the IPN group which may be due to the accuracy of the femoral trocar protection sleeve which helps with the positioning of the guide wire, reducing iatrogenic soft tissue trauma or could be a by-product of a distant entry incision from the proximal tibia, this is consistent with findings from a study by Courtney et al. who reasoned that during the SPN approach the infrapatellar nerve is distant from the incision compared to the IPN.²⁰ A further meta-analysis by Xu et al. supports our finding of lower incidence of anterior knee pain following SPN tibial nailing.²¹

However, it is important to bear in mind that this new approach is not free from complications. A recent study evaluated 139 open tibial shaft fractures which were managed by an SPN approach²² and demonstrated, in a single case, that septic arthritis of the knee joint may occur following SPN tibial nailing.

Longer term sequelae of SPN tibial nailing have been an ongoing concern and well discussed in the literature. Various studies have compared intra-articular injuries between the two techniques²³ looking at secondary iatrogenic damage to the cartilage surface of the patellofemoral joint or other intra-articular structures such as the footprint of the anterior cruciate ligament, the meniscus and the intermeniscal ligament.²⁴ While we acknowledge this concern, as demonstrated by Tornetta et al. on cadaveric knees, this can be avoided by following simple steps to aim for the ‘safe zone’ in the nail entry point which, as described above, is slightly lateral to the centre of the tibial tubercle⁵ and by using the specifically designed silicone protection sleeve which is a standard part of the SPN instruments. Indeed, Leary et al. found there is no evidence of damage to the knee structures on both insertion and extraction of the suprapatellar tibial nail in a cadaveric knee study using a standard SPN technique and instruments.²⁵ Further evidence comes from a study to assess for chondral damage by Gelbke et al.²⁶ They demonstrated that following SPN tibial nailing there was not only no increase in the macroscopic chondral damage compared with IPN tibial nailing but that the increased intra-articualr pressure generated was well below the threshold to cause chondrocyte death at a microscopic level.

We acknowledge some limitations of our study. This is a cohort study design utilised to establish initial outcomes with utilisation of this new approach in our department. We found a wide variation in patient reported outcome scores at follow-up and had a relatively small sample size therefore we acknowledge greater margins for error in interpreting clinical outcomes specifically. Duration of follow up was limited to 4 months and therefore longer-term benefits or risks have not been reported in this study. We believe 4 months is a satisfactory, pragmatic time period for typical follow up after routine, uncomplicated tibial nailing. Our outcomes are based on clinical examination and patient’s satisfaction scores, perhaps a more objective method to assess healing and damaged articular surface would add validity to our study for example post-operative knee arthroscopy or MRI scan.

5. Conclusion

In our study, adoption of the SPN approach reduced operative time and radiation exposure and achieved greater accuracy of nail entry point compared to IPN approach. Clinical follow up of patients demonstrated higher patient satisfaction scores after SPN tibial nailing when compared to the conventional approach with no change in complication rate at four months follow-up. Our findings have led to the adoption of the SPN approach as standard for tibial nailing in our trauma unit.

In the current climate of COVID-19 minimising operative time and exposure is particularly important in order to provide safe, effective trauma care for both patients and staff. We recommend further prospective randomised controlled trials comparing techniques to further evaluate the superiority of the SPN tibial nailing versus IPN tibial nailing.

Contributor statement

MA, DD; data collection, analysis, manuscript preparation, submission and revision, ZS, RK; manuscript preparation, AA; data collection, analysis, manuscript preparation.

Declaration of competing interest

None.