Periprosthetic fracture rate after short and long hip nails: Analysis of a regional health database

INTRODUCTION

Intertrochanteric hip fractures are a major socio-economic burden, and a significant source of morbidity and mortality. Treatment is generally surgical, with either a dynamic hip screw or a cephalomedullary hip nail. Recently, there has been a trend toward the use of hip nails. The use of short nails over long nails, which span the length of the femur, remains a source of controversy. Historically, short nails were associated with a higher periprosthetic fracture rate compared with long nails, however newer nail designs, appear to have resolved this issue. Small retrospective studies show a refracture rate similar in both long and short nails. Given the small sample size of current studies, it remains unclear if the refracture rate is indeed the same between treatment arms, or if studies are not sufficiently large to identify a difference between the two. A large database review would provide the practical next step to further explore this question.

METHODS

Intertrochanteric hip fracture cases from our Regional Hip Fracture Registry were reviewed. All patients with an intertrochanteric fracture treated with a cephalomedullary nail from June 2009 to December 2017 were included. Patient demographics were compared using the t-test. Fracture rate was compared using the chi square test.

RESULTS

655 short nails and 315 long nails were reviewed. Patients in the short nail (SN) group were older than in the long nail group (LN) (SN: 81, LN 76 p < 0.001). The periprosthetic fracture rate was 2.1% overall with 1.3% in LN group and 2.4% in SN group (p = 0.34). There was no difference identified in the rate of blood transfusions (SN 38% LN 40% p = 0.5), however the procedure time was shorter in the SN group (SN: 81 min LN: 112 min p < 0.001).

DISCUSSION

This study did not find a statistical difference in periprosthetic fracture rate when comparing short and long cephalomedullary nails for the treatment of intertrochanteric fractures. Procedure time was shorter in the SN group. However, no difference in rate of blood transfusion was noted between patient groups. This study supports use of both nail type for hip fracture fixation, on the basis of periprosthetic fracture rate.

Distal locking of short cephalomedullary nails decreases varus collapse in unstable intertrochanteric fractures - a biomechanical analysis

INTRODUCTION

Peritrochanteric fractures are a growing problem and complications relating to operative fixation of these fracture, including varus collapse and screw cutout, are common in elderly osteoporotic patients. We hypothesize that unlocked nails will demonstrate increased varus collapse and inferior construct stiffness in specimens with increased diaphyseal medullary diameter.

MATERIALS AND METHODS

Sixteen non-cadaveric osteoporotic biomechanical femur specimens were utilized in this study, with eight specimens having an artificially large femoral canal to represent Dorr C femurs. All femurs were instrumented with a short cephalomedullary nail with and without distal cross-lock screw fixation and had an unstable intertrochanteric fracture created in a repeatable pattern. Specimens underwent cyclic compression to a maximal load of 1000N with segmental motion quantified through the use of visual tracking markers. Statistical comparisons were performed using one-way ANOVA with Tukey post-hoc analysis to determine differences between specific groups. Significance was defined as p<0.05.

RESULTS

Unlocked short cephalomedullary nails showed increased varus collapse due to motion of the nail within the femoral canal in capacious femoral canals compared with narrow femoral canals and distally cross-locked nails. The coronal deformation of the wide canal unlocked group (17.9 ^o±2.6^o) was significantly greater in the varus direction than any other fixation under compressive load of 1000N. There was no significant difference in varus angulation between the wide canal or narrow canal locked groups (11.1^o±8.7^o vs. 8.2^o±1.7^o respectively, p=0.267). The narrow canal unlocked group (13.7^o±2.4^o) showed significantly greater varus angulation than the narrow canal locked (p=0.015). The wide canal unlocked group showed significantly greater varus angulation than the wide canal locked group (p=0.003). Motion between the femoral shaft and the cephalomedullary nail (toggling of the nail within the shaft) was significantly greater in narrow or wide canal unlocked specimens, 7.94^o±2.13^o and 10.2^o±1.7^o respectively, than in the narrow or wide canal locked specimens, 2.4^o±0.2^o and 4.2^o±0.5^o respectively (p<0.05) CONCLUSION: Unlocked short intramedullary fixation for unstable peritrochanteric fractures results in increased varus collapse under axial compression. This study supports the use of distal cross-locking of short intramedullary fixation for unstable peritrochanteric fractures in patients with capacious femoral canals secondary to osteoporosis who might otherwise be as risk for varus collapse, device failure, and malunion.

Effect of fracture levels on the strength of bone-implant constructs in subtrochanteric fracture models fixed using short cephalomedullary nails: A finite element analysis

OBJECTIVES

This study was conducted to investigate the stress around nails and cortical bones in subtrochanteric (ST) fractures fixed using short cephalomedullary nails (CMNs) in finite element models (FEMs) and to determine the appropriate short CMN type for different fracture levels.

METHODS

The following three types of short CMNs were used: type A, which is 170 mm in length and has 1 distal locking screw; type B, 200 mm in length and 1 distal screw; and type C, 200 mm in length and 2 distal screws. A total of 24 FEMs were tested on a transverse ST fracture at 8 levels [0, 10, 20, 25, 30, 35, 40 and 50 mm below the lower margin of lesser trochanter (LT)], and were fixed using 3 different CMN types. Finite element analysis was then performed to evaluate the stress around the cortical bones and the CMNs under the assumption of anatomical reduction and fracture gap of 1 mm.

RESULTS

Peak von Mises stress (PVMS) was greatest on the cortical bone around the distal screw hole and was greater than the yield strength at fracture levels ≥ 35 mm below the LT in FEMs fixed with type A and B. In contrast, FEMs fixed with type C showed PVMS less than the yield strength at all fracture levels. The PVMS within the implant was greater than the yield strength at the junction of the nail with the distal screw and distal screw itself at fracture levels ≥ 35 mm below the LT in FEMs fixed using type A. Conversely, in FEMs fixed using type B and C, all PVMSs within the implant were less than the yield strength, regardless of the fracture level.

CONCLUSION

Short CMNs 170 or 200 mm in length with 1 distal screw may be used in a limited manner in high ST transverse fractures under the assumptions of anatomical reduction and fracture gap ≤ 1 mm. Meanwhile, short CMN 200 mm in length with 2 distal screws may be an available treatment option in most of ST transverse fractures regardless of the fracture level under the same set of assumptions.

Femoral intertrochanteric nail (fitn): a new short version design with an anterior curvature and a geometric match study using post-operative radiographs

OBJECTIVE

Femoral intertrochanteric fractures are usually fixed with short, straight cephalomedullary nails. However, mismatches between the nail and the femur frequently occur, such as tip impingement and tail protrusion. The authors designed a new type of short femoral intertrochanteric nail (fitn) with an anterior curvature (length=19.5cm, r=120cm) and herein report the geometric match study for the first of 50 cases.

METHODS

A prospective case series of 50 geriatric patients suffering from unstable intertrochanteric fractures (AO/OTA 31 A2/3) were treated. There were 15 males and 35 females, with an average age of 82.3 years. Post-operatively, the nail entry point position in the sagittal greater trochanter (in three categories, anterior, central and posterior), the nail-tip position in the medullary canal (in 5-grade scale) and the nail-tail level to the greater trochanter (in 3-grade scale) were measured using X-ray films.

RESULTS

For the nail entry point measurement, 5 cases were anterior (10%), 38 cases were central (76%), and 7 cases were posterior (14%). For the distal nail-tip position, 32 cases (64%) were located along the central canal axis, 13 cases (26%) were located anteriorly but did not contact the anterior inner cortex, 2 cases (4%) showed less than one-third anterior cortex thickness contact, and 3 cases (6%) were located posteriorly with no contact. For the proximal nail-tail level, there were no protrusions over the greater trochanter in 15 cases (30%), protrusion of less than 5mm in 29 cases (58%), and protrusion of more than 5mm in 6 cases (12%). The fitness was very high, as 96% cases showed no tip-cortex contact, and 88% cases showed less than 5mm proximal tail protrusion.

CONCLUSION

The newly designed femoral intertrochanteric nail has a good geometric match with the femur medullary canal and the proximal length in the Chinese population.