PFNA-II protrusion over the greater trochanter in the Asian population used in proximal femoral fractures

Abstract

Background: The treatment of proximal femoral fractures in geriatric osteoporotic patients continues to be a challenge in orthopaedic trauma. Various kinds of cephalomedullary nails, such as gamma nail, InterTan and PFNA were used clinically. The latest generation PFNA II, specially designed for Asian population, is commonly used for geriatric per-/intertrochanteric fractures. The aim of this study was to determine whether the current PFNA-II proximal segment length is suitable for the greater trochanter height, as assessed by postoperative radiograph measurements.

Materials and methods: 51 consecutive patients with per-/intertrochanteric fractures treated with the PFNA-II between July 2012 and December 2012 were enrolled in this study. There were 19 males and 32 females, with an average age of 78.6 years (range 66-92 years). According to AO/OTA classification system, there were 4 cases of 31A1 fractures, 35 cases of 31A2 fractures, and 12 cases of 31A3 fractures. The nail protrusion height over the lateral greater trochanter and the Parker ratio of the helical blade tip in the femoral head were measured and compared using pelvic digital anteroposterior radiographs taken within 2 weeks postoperatively. Patients were followed up for a minimum period of 1 year to check whether they had lateral trochanter pain.

Results: Postoperative digital anteroposterior (AP) films were used for assessment and any prominence was recorded as positive. Overall, nail protrusion over the greater trochanter occurred in 87.8% of cases. In 60.8% of the cases, protrusion height was >5 mm. The average protrusion height was 6.25 ± 4.27 mm (male average 4.84 ± 4.38 mm, and female average 7.09 ± 4.70 mm). The average Parker ratio of all cases was 51.0 ± 6.9% (male average 49.8 ± 7.5% and female average 51.7 ± 6.5%). Protrusion height was positively correlated (r = 0.394, P = 0.004) with the helical blade position in the femoral head (Parker ratio). Clinically, a total of 42 patients were followed up at an average of 15.0 ± 2.6 months (range 12-24 months) they were able to walk independently or with a stick. There were 13 patients with lateral trochanter pain on the injured side. Protrusion height of these patients was 11.13 ± 3.75 mm, whereas the protrusion height of the remaining 29 patients was 3.87 ± 3.39 mm.

Conclusions: There was a morphologic mismatch between the proximal segment length of the PFNA-II and the greater trochanter in the Asian population, which may be the cause of postoperative lateral trochanter pain. A modification to shorten the proximal part of the nail is proposed to avoid protrusion over the greater trochanter.

Keywords: Intertrochanteric fractures; asciatic race; intramedullary nail; intramedullary nailing; nail protrusion; pain; proximal femoral nail antirotation-II; soft tissue irritation.

Figure 1

(a-d) Anteroposterior radiographs of hip joint with proximal thigh showing the typical cases with proximal nail end protrusion over the greater trochanter

Figure 2

Measurements on the anteroposterior radiograph. A - lateral proximal tip of intramedullary nail. B - medial proximal tip of intramedullary nail. C - tip of greater trochanter connecting the lateral board of intramedullary nail. O - the center of femoral head. Line I - head-neck axial crossing the center of femoral head. Line M - the helical blade axial line. Line EF - perpendicular to line I crossing the point O. G - intersection point of lines EF and M. E, F - intersection points of line EF and the femoral head circle. NPH: Nail protrusion height. PR: Parker ratio

Figure 3

Radiograph and CT scan of hip joint and proximal femur (a) preoperative showing the intertrochanteric fracture (b and c) immediate postoperative X-rays showing tip of nail at level of great trochanter (d-f) immediate postoperative computed tomography reconstructive images showing relation of tip of implant at greater trochanteric level (g and h) 1-year followup X-rays, anteroposterior view and lateral view showing relation of tip of implant to greater trochanter

Figure 4

X-ray and CT scan of hip joint with proximal femur showing (a) intertrochanteric fracture (b) computed tomography reconstructive images showing fracture anatomy (c) immediate postoperative anteroposterior X-rays showing nail tip at level of greater trochanter (d) Totally healed fracture and nail tip at level of greater trochanter at 1 year followup

Figure 5

X-ray of hip joint with proximal femur (a) Preoperative X-ray showing the fracture (b and c) intraoperative fluoroscopy images showing nail tip positions (d and e) immediate postoperative X-rays, anteroposterior view and lateral view showing nail and trochanter relationship (f and g) 2 years followup X-rays, anteroposterior view and lateral view showing bony union and relation of tip of nail and treater trochanter (h) Clinical photograph of patient showing good functions, but complaints lateral trochanter pain

Figure 6

Schematic diagram of fracture reduction quality and nail protrusion. (a) Anatomical reduction. (b) Slight valgus reduction may cause nail end protrusion. (c) Slight varus reduction