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Controversies in Intramedullary Fixation for Intertrochanteric Hip Fractures

Baldwin, Paul C. III MD; Lavender, Randy C. MD; Sanders, Roy MD; Koval, Kenneth J. MD

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doi: 10.1097/BOT.0000000000000652
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Abstract

INTRODUCTION

Intertrochanteric fractures are among the most commonly encountered injuries in orthopaedic practice. Successful management of these fractures is critical not only in achieving optimal long-term patient outcomes but also to decrease the economic burden these injuries exert on global health care systems. The preferred treatment for these injuries has evolved over time, with the cephalomedullary nail (CMN) now becoming a more commonly used implant for stabilization. However, the introduction of newer implants and techniques has resulted in several debates regarding the best management for these fractures. This review attempts to provide an evidence-based discussion about some of the implant-related controversies surrounding intramedullary fixation of intertrochanteric hip fractures including long versus short CMN, need to distally interlock, and proximal lag screw designs. Through discussion of these controversies, this review aims to provide improved insight into intramedullary fixation techniques and options, in turn allowing surgeons to optimize the treatment of intertrochanteric hip fractures.

LONG VERSUS SHORT CMN

Originally, all CMNs were short; however, concern over creating a stress riser and resultant fracture at the tip of the nail led to the development of a full-length nail. Currently, short and long CMNs are used for the stabilization of intertrochanteric fractures, both of which have positive reported clinical results. Although short nails are often universal, long nails require a left and right version to take into account femoral bow and version.

Postoperative femoral shaft fractures were commonly reported with the use of early CMNs. The original Gamma nail (Stryker, Mahwah, NJ) had a rate of postoperative femoral shaft fracture as high as 6%–17%.1–5 However, in a 2009 meta-analysis, Bhandari et al6 reported that newer designs (Gamma 2) and improved surgical techniques significantly lowered the rate of these serious complications. These findings have been supported by additional studies. In a retrospective review of 3066 consecutive Gamma nails for intertrochanteric hip fractures over a 12-year period at a single center, Bojan et al7 reported 19 postoperative femoral shaft fractures for a rate of 0.6% Subanalysis of long and short Gamma nails did not demonstrate a statistically significant difference in femoral shaft fracture rates. The authors concluded that the substantial reduction in the incidence of femoral shaft fractures over time when using the Gamma nail was attributed to improvements in implant design and strict adherence to the surgical technique described in the product manual.7

The proposed advantages of short CMNs include ease of use, decreased operative time and blood loss, decreased implant cost, and targeted locking bolts through the insertion jig. Disadvantages include placement of a stress riser in the mid femur in a patient who has a history of falling and osteopenia at a minimum. The theoretical advantage of a full-length nail therefore is protection of the entire femoral shaft in a patient with probable osteoporosis and a history of falling. Disadvantages include increased cost, need for free-hand distal locking, and mismatch of nail bow to femur with the risk for distal anterior cortical penetration with certain implants. The average femoral radius of curvature has been reported to be 120 ± 36 cm; given the mismatch between patient and most implants' radii of curvature [ie, Stryker Gamma 3 (Stryker, Mahwah, NJ), radius of curvature 150 cm; Smith & Nephew Intertan and trochanteric antegrade nail (TAN) (Smith & Nephew, Memphis, TN), radius of curvature 150 cm or 200 cm; Synthes trochanteric fixation nail, radius of curvature 150 cm; Synthes trochanteric fixation nail-advanced, radius of curvature 100 cm], anterior cortical impingement and perforation can occur with long CMNs8 (Figure 1).

FIGURE 1
FIGURE 1:
Intraoperative anterior femoral cortical perforation from implant/femur radius of curvature mismatch.

Multiple clinical studies have compared the outcomes of short versus long nail CMNs for the stabilization of intertrochanteric fractures. Kleweno et al9 retrospectively evaluated 559 patients older than 65 years who sustained an intertrochanteric fracture and were treated with either a short (n = 219) or long (n = 340) CMN. In this study, the rate of periprosthetic fracture (2.7% and 1.5% in short and long nails, respectively; P = 0.35) and the need for revision surgery (3.2% and 3.5%; P = 0.81) was comparable between the 2 groups. The most commonly reported reason for revision surgery was lag screw/blade cut out of the head/neck segment. On average, operative time was longer for long CMNs when compared with short nails (70 ± 35 minutes vs. 51 ± 22 minutes; P < 0.001). The difference in operative time remained statistically significant even when comparing the short nail with long nails without the use of distal interlocking screws (51 ± 22 minutes vs. 59 ± 41 minutes; P = 0.01).9

Hou et al10 retrospectively compared the clinical outcomes of patients treated for intertrochanteric fractures, without subtrochanteric extension, using either a short or long CMN. Patients treated with a long nail (n = 183) had higher blood loss (135 mL vs. 100 mL; P = 0.031) and operative time (61 minutes vs. 41 minutes; P = 0.000) when compared with those treated with a short nail (n = 100). Comparable rates of intraoperative and postoperative complications, and union, were observed between the 2 nail groups. These findings remained consistent even within a subanalysis of stable versus unstable fracture patterns. The authors concluded that there was no clinical benefit to the use of long nails for the stabilization of either stable or unstable intertrochanteric fractures.

Finally, these results were confirmed in 2 clinical studies from 2016. In a retrospective cohort study by Lindvall et al, the rate of ipsilateral fracture and implant costs were evaluated with the use of short and long CMNs for the treatment of intertrochanteric hip fractures (N = 609 patients). Over the 5-year follow-up period, the rates of union were equivalent for the short CMN and long CMN cohorts. Although the rate of ipsilateral femoral shaft fractures in both groups steadily increased with greater follow-up time, there were no significant differences between the groups at any time point. Of the periprosthetic femoral shaft fractures that did occur, 15 of 16 fractures occurred in nails that were not locked distally. Cost analysis revealed that the overall cost was equivalent at 1, 2, or 5 years of follow-up between the short CMN and long CMN groups (P = 0.76).11

Krigbaum et al12 performed a retrospective study of costs and complications in the treatment of intertrochanteric fractures using short and long CMNs in US military veterans. Across the 262 patients included in this study (short CMN, n = 125; long CMN, n = 137), similar rates of complications, readmissions, and reoperations were reported. However, there was a significant difference in the cost of care associated with the use of a long CMN when compared with a short CMN. The $7579 (2010 US dollars) increased cost of care associated with the use of long CMNs was related to a longer duration of stay. On average, patients treated with a long CMN had a postoperative stay of 9.1 ± 8.9 days compared with 6.9 ± 4.8 days for those treated with a short CMN (P = 0.018). The increased duration of stay for patients treated with long nails was partially explained by the higher rate of preoperative morbidities, such as diabetes, congestive heart failure, and chronic obstructive pulmonary disease in this cohort.

In conclusion, when used appropriately, both short and long nails are effective implant options for the treatment of intertrochanteric fractures. Without definitive evidence identifying superiority of a long versus short nail, the decision to use a short or long nail should be based on fracture characteristics, patient factors, and cost, as well as surgeon preference and experience.

IS DISTAL INTERLOCKING NECESSARY?

Current biomechanical and clinical research supports the use of both locked and unlocked CMNs for the treatment of intertrochanteric hip fractures, dependent on the fracture pattern and stability. Although the use of distal interlocking screws confers additional biomechanical stability, it also adds radiation exposure, operative time, and cost to the procedure.

Stable Fracture Patterns

In stable intertrochanteric fracture patterns, axial and rotational stability are probably adequate without the use of distal locking due to interdigitation of metaphyseal cancellous bone, cortical contact, and an intact posteromedial cortex.13 In a cadaver study by Kane et al14, the addition of a single distal interlocking screw to a long CMN for the treatment of stable intertrochanteric hip fractures increased the rotational stiffness of the bone–implant construct. In a retrospective clinical study by Vopat et al15 comparing the use of a locked versus unlocked long CMN for the stabilization of stable intertrochanteric fractures, no significant differences in failure or complication rates were found between patients treated with either construct (N = 107 fractures; locked long CMN failure rate = 0.0%; unlocked long CMN failure rate = 3.9%; P = 0.224).

With respect to short CMNs, Kleweno et al reported a small subset of patients who were treated with both locked and unlocked short CMNs in the setting of a stable intertrochanteric fracture. Although not specifically aimed at evaluating the need for distal interlocking screws in short nails, there was no difference in outcome or complication rates between locked and unlocked implants.9 Skála-Rosenbaum et al,16 retrospectively evaluated the need for distal locking screws in the treatment of 118 intertrochanteric fractures using a short CMN. Indications for the use of distal locking included greater trochanter lateral wall comminution, secondary diaphyseal fracture lines, large posterior medial fracture fragments with extension below the level of the lesser trochanter, and a capacious intramedullary canal. No significant differences were noted between distally locked and unlocked nails with respect to fracture healing, radiographic and functional outcomes (P = 0.92), and frequency of complications. Given the evidence listed above, the use of distal interlocking screws in the treatment of stable intertrochanteric fracture patterns is not a required fixation adjunct.

Unstable Fracture Patterns

Unstable intertrochanteric fracture patterns include those with posteromedial comminution, reverse obliquity, and subtrochanteric extension. For unstable patterns, the use of distal interlocking screws has been advocated based on biomechanical studies. In a cadaver study of 4-part intertrochanteric hip fractures, Gallagher et al reported that a distally locked long CMN had a mean maximal torsional load-to-failure of 57.9 ± 19.0 N·m and mean rotational stiffness of 119.4 ± 35.7 N·m/rad.17 The mean torsional load-to-failure and mean rotational stiffness for an unlocked nail was 29.1 ± 12.2 N·m and 77.2 ± 31.3 N·m/rad, respectively; these differences were statistically significant (P = 0.001 and P = 0.004, respectively). The authors attempted to correlate the biomechanical profiles of the locked and unlocked constructs with the values placed upon the proximal femur during activities of daily living. The rotational hip torque for a healthy individual during an unrestricted squat with a load equal to body weight has been shown to be 28.2 N·m.18 This value approached that of the mean torsional load-to-failure seen in the unlocked nail group (29.1 ± 12.2 N·m). Based on these findings, the authors recommended that unstable intertrochanteric hip fractures be treated with distal locking screws.

HELICAL BLADE VERSUS LAG SCREW FOR PROXIMAL LOCKING OF CMNs

Accurate placement and positioning of the proximal locking option of a sliding hip screw (SHS) or intramedullary nail is a critical component of intertrochanteric fracture fixation. The most common mode of fixation failure after stabilization is lag screw cut out from the femoral head.19 As surgical techniques improved and the importance of obtaining a tip–apex distance (TAD) of <25 mm became more apparent, the failure rates from lag screw cutout has decreased across all implant types.20,21 In an attempt to further reduce the rate of fixation failure, implant manufacturers have developed various proximal locking designs. Currently, the most commonly used proximal locking implant designs are the standard lag screw and the helical blade.

Multiple biomechanical studies have evaluated these 2 designs, but limited clinical data exist comparing the use of a lag screw versus helical blade. The advantages of a lag screw include surgeon familiarity with the technique and relatively atraumatic insertion, particularly if a tap is used before lag screw placement. Disadvantages of a lag screw include the possibility of femoral head rotation during insertion, poor rotational control once implanted, and the fact that bone is removed by the reamer before insertion. The advantages of the helical blade include impaction of the surrounding bone as the blade is impacted into place and excellent rotation control, based on the blade design. Disadvantages of the helical blade include the possibility of fracture distraction during blade impaction, central perforation of the blade through the femoral head (“cut through”) during fracture settling, and inferior compression at the fracture site22 (Figure 2).

FIGURE 2
FIGURE 2:
Femoral head helical blade “cut through.”

A leading theory in the observed decreased rate of cutout with the use of helical implants is that local bone compaction around the blade improves implant fixation. The insertion of a helical implant without reaming leads results in bone compaction around the blade, which increases local bone density. This increased local bone density was quantified by an imaging study that demonstrated a 30% increase in the density of trabecular bone surrounding the helical implant compared with an intact femoral neck and head.23

Although biomechanical studies may support the use of a helical blade over that of the conventional lag screw, limited clinical data exist comparing these 2 implant designs. A prospective randomized study by Yaozeng et al24 compared the use of a CMN with a helical blade versus that with a conventional lag screw in 107 patients aged 60 years or older who sustained a intertrochanteric fracture. At the final follow-up (mean follow-up of 17.5 months), all fractures were radiographically healed. Comparison of the 2 patient treatment groups demonstrated equivocal outcomes with respect to functional outcomes, hospital stay, intraoperative, or postoperative complications.24 These findings were supported in a prospective randomized study by Stern et al25; 335 patients who sustained an intertrochanteric fracture were stabilized using either a helical blade or a lag screw implant. Of the 335 patients enrolled, 269 patients were available for the final follow-up (137 lag screw, 132 helical blade). Comparison of the 2 treatment groups demonstrated no significant differences in the rates of cephalic implant cutout (blade = 1.5% vs. lag screw = 2.9%; RR = 1.9; 95% confidence interval, 0.4–10.3) or the need for revision surgery (blade = 4.5% vs. lag screw = 5.1%). The authors noted that in all patients in whom cutout occurred, the TAD was greater than 25 mm (mean, 29.4 ± 2.0 mm). Based on the results of this study, the authors concluded that both a helical blade and single lag screw perform equally well for the stabilization of low-energy intertrochanteric hip fractures in elderly patients. The authors stated that the most important factor in reducing the rate of implant cutout was not the implant type but rather achieving a TAD of <25 mm.

In conclusion, with the lack of definitive evidence identifying the superiority of a helical blade or lag screw implant, surgeon experience and familiarity should dictate implant selection.

SINGLE VERSUS DOUBLE LAG SCREW DESIGN

Advantages of a single lag screw design include easier and faster insertion technique and known parameters for ideal lag screw location (TAD). Common complications associated with implants using a single lag screw (and therefore a single point of cephalic fixation) include rotational malalignment during insertion and rotational instability; postoperative rotational instability can lead to flexion and extension of the proximal fragment, loosening of the cephalic implant, uncontrolled fracture collapse, and implant failure.26 To improve rotational stability, implants have been designed, which feature 2 separate cephalic lag screws that are not locked to the nail or to each other and therefore slide independently (Figure 3). The primary advantage of the double lag screw design is improved rotational control of the proximal fragment. However, a Z-effect deformity has been described using a double lag screw design in which neither lag screw is locked to the nail or telescopes within a barrel (Figure 4). The Z-effect occurs as the proximal cephalic lag screw bears a higher proportion of the load with weight bearing than the more distal lag screw. With cyclic loading and varus force, the proximal lag screw jams in the nail and the lower screw begins to toggle and back out of the nail laterally. As these progresses, the proximal fragment further collapses and the superior screw migrates proximally through the femoral head.27 Although the collapse seems to be one of varus on the anteroposterior radiograph, if both this and the lateral are carefully evaluated, it becomes clear that the unstable head–neck fragment has rotated off the shaft, giving the appearance of varus on the anteroposterior radiograph.

FIGURE 3
FIGURE 3:
Nonintegrated dual lag screw CMN.
FIGURE 4
FIGURE 4:
The “Z-effect” as seen with proximal lag screw superior migration/cutout and lateral migration of the inferior lag screw.

Cadaveric studies have evaluated the biomechanical advantages of single versus double lag screw implant designs. Kubiak et al performed a biomechanical analysis of a single lag screw implant [the intramedullary hip screw (IMHS); Smith & Nephew] and a double lag screw implant (the TAN; Smith & Nephew).28 In this study, paired, cadaveric, unstable, 4-part intertrochanteric fracture models were instrumented with the IMHS and TAN and then evaluated for screw sliding, inferior and lateral femoral head displacement, and ultimate load to failure. The 2 constructs demonstrated equivalent resistance to screw sliding and proximal fragment migration. However, the TAN construct was found to have a statistically significantly higher load to failure than the IMHS construct (TAN = 3238 ± 829 N; IMHS = 2162 ± 829 N; P = 0.01).28 Kouvidis et al29 evaluated resistance to cutout in dual and single lag screw implants. Using simulated osteoporotic specimens with unstable intertrochanteric fracture patterns, 5 dual lag screw implants and 5 single lag screw implants were analyzed using biaxial rocking motion representative of hip loading during normal gait. The dual lag screw implant demonstrated significantly less lag screw migration and survived more loading cycles before failure than a single lag screw implant. In addition, decreased varus collapse and neck rotation were observed with the dual lag screw implant.

In conclusion, based on the current available evidence, equivocal outcomes can be obtained with the use of both single and double lag screw design implants in the treatment of low-energy intertrochanteric femur fractures.

INTEGRATED SLIDING LAG SCREWS

To provide improved rotational control of the proximal fragment yet minimize the risk of the Z-effect, certain implant designs have integrated the 2 cephalic lag screws so that they slide as a unit. The Trigen Intertan nail (Smith & Nephew) integrates the 2 cephalic lag screws through a worm gear mechanism (Figure 5). This integration provides rotational stability and linear compression.30,31 The Intertan nail has been shown to be biomechanically superior to a single lag screw CMN. In a cadaveric study with an unstable intertrochanteric fracture model by Hoffmann et al, the Intertan nail was found to have an initial stiffness almost 40% greater than that of the Gamma 3 nail (Stryker) (P = 0.005). In addition, the Intertan nail demonstrated a 13% higher load to failure (P = 0.02) and 18% increase in cycles to failure (P = 0.02) when compared with the Gamma 3 nail. Varus collapse and rotational loss of reduction were also decreased by 84% with the Intertan nail in comparison to the Gamma 3 nail (P < 0.013).31

FIGURE 5
FIGURE 5:
Smith & Nephew Trigen Intertan nail with dual integrated lag screw design.

Santoni et al32 evaluated the biomechanical properties of the Intertan nail and Gamma 3 nail using a novel sit-to-stand biomechanical model. In this study, an unstable intertrochanteric femur fracture pattern was created in 22 female hemipelvises and instrumented with a short, distally interlocked Intertan or Gamma 3 nail. The hemipelvises then underwent simulated 3-month sit-to-stand testing of 13,500 cycles with controlled pelvic rotation (0–90 degrees) and axial loading of the distal femur of 2:1 body weight ratio. Femoral head rotation and varus collapse were monitored by optoelectronic methods. After 13,500 cycles, observed femoral head rotation was significantly less in the Intertan nail group when compared with the Gamma 3 group (Intertan, 3.2 degrees vs. Gamma 3, 24.5 degrees; P = 0.016). At 4 times body weight loading, specimens treated with the Intertan nail demonstrated a 7-fold reduction in maximum femoral head rotation over specimens treated with Gamma 3 nail (P = 0.006). Throughout all loading cycles, femoral neck varus collapse was significantly lower in the Intertan nail group than in the Gamma 3 nail group (P = 0.021).32 Based on this study, the authors concluded that the larger surface area, noncylindrical profile, and ability for fracture compression of an integrated dual lag screw provides significantly greater resistance to multiplanar femoral head rotation and varus collapse than a single lag screw implant.

The clinical efficacy of the Intertan was evaluated in a prospective, randomized, multicenter trial by Matre et al. This study compared the Trigen Intertan versus a SHS for the stabilization of intertrochanteric hip fractures.33 A total of 684 patients were enrolled in the study with 341 patients and 343 patients allocated to the Intertan and SHS groups, respectively. At 12-month follow-up, 204 patients in the Intertan group and 202 patients in the SHS group were available for evaluation. Patients stabilized using the Intertan reported slightly less pain during early postoperative mobilization compared with those stabilized using an SHS (Visual Analogue Scale 48 vs. 52; P = 0.042). This early difference in pain levels did not affect hospital length of stay and was not statistically different at 3-month and 12-month follow-ups. In addition, there was no difference between the 2 groups with respect to functional mobility, hip function, patient satisfaction, or quality-of-life measurements at 3 and 12 months. There was also no difference between the groups when comparing the rates of complications or revision surgery.33

In a more recent multicenter, prospective, randomized, control trial, Sanders et al compared the differences in functional and radiographic outcomes, as well as the rate of complications, of geriatric hip fracture patients treated with either the Intertan or SHS. The 249 patients enrolled in this study (123 Intertan, 126 SHS) were followed for 12 months with radiographic and functional outcome evaluations. The patients treated with the SHS demonstrated significantly higher rates of limb shortening greater than 2 cm than did those treated with the Intertan (42.9% vs. 17.2%; P < 0.001). Subgroups analysis also showed that patients with higher preinjury functional scores and more unstable fracture patterns (3 and 4 part fractures) who were treated with the SHS had inferior functional outcomes when compared with those treated with the Intertan. A similar complication rate and rate of reoperation was reported for both implants. When all patients (stable and unstable fracture patterns) from both the groups were compared, the functional outcome benefit of the Intertan became less evident and functional outcomes between the Intertan and SHS were reported as equivocal.34

Serrano-Riera et al analyzed the radiographic changes in intertrochanteric femur fracture alignment after treatment with either a single or double integrated lag screw CMN construct. In this study, the radiographs of 108 patients with 12-month follow-up were evaluated (54 patients treated with the Gamma 3 and 54 patients treated with the Intertan). The Gamma 3–treated cohort included 32 stable and 22 unstable fracture patterns, whereas the Intertan-treated cohort included 23 and 31 unstable fracture patterns. At 12 months, the Gamma 3 cohort demonstrated 2.5 times greater varus collapse and 2 times greater neck shortening compared with the Intertan cohort regardless of fracture pattern and stability (P < 0.001). Although this study did not include clinical or functional outcomes, the dual integrated lag screw design of the Intertan provided enhanced fracture stability at 12 months when compared with a single lag screw design based on radiographic analysis.35

With the more recent identification that rotational instability contributes to malunion and implant–bone construct failure, the use of an integrated-slide implant should be considered to provide added rotational stability in unstable fracture patterns.

CONCLUSIONS

Newer developments and designs will continue to become available for the treatment of intertrochanteric hip fractures. Although some implant designs may prove more advantageous in specific fracture patterns, the basic principles of stable fracture reduction and proper implant positioning must be applied to all fractures to optimize patient outcomes. Further evaluation of newly innovated implants in clinical trials is necessary to determine if a superior implant exists.

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Keywords:

hip fracture; pertrochanteric femur fracture; intertrochanteric hip fracture; pertrochanteric hip fracture; cephalomedullary nail; intramedullary nail

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