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Countersinking the Lag Screw or Blade During Cephalomedullary Nailing of Geriatric Intertrochanteric Femur Fractures: Less Collapse and Implant Prominence Without Increased Cutout Rates

Henry Goodnough, L. MD, PhD; Wadhwa, Harsh BS; Tigchelaar, Seth S. PhD; Pfaff, Kayla BS; Heffner, Michael MD; van Rysselberghe, Noelle MD; DeBaun, Malcolm R. MD; Gardner, Michael J. MD; Bishop, Julius A. MD

Author Information
Journal of the American Academy of Orthopaedic Surgeons: January 1, 2022 - Volume 30 - Issue 1 - p e83-e90
doi: 10.5435/JAAOS-D-20-01029

Abstract

Cephalomedullary nails are increasingly used in the treatment of intertrochanteric femur fractures1-3 and are designed to allow controlled collapse at the fracture site to optimize fracture union.4 However, lateral prominence of the blade or lag screw after controlled collapse is a common source of patient disability.5,6 Moreover, excessive collapse at the fracture site is associated with decreased hip offset and compromised functional outcomes, likely related to compromised abductor function.7

Some surgeons countersink the cephalomedullary lag screw or blade past the lateral cortex of the proximal femur in an effort to minimize subsequent lateral implant prominence. However, the collapse of a countersunk blade or screw may theoretically be inhibited by the lateral cortex, preventing controlled collapse and increasing the risk of cutout.5 The purpose of this study was to evaluate the consequences of countersinking the lag screw or blade of a cephalomedullary nail past the lateral cortex of the proximal femur. We hypothesized that countersinking would not be associated with increased cutout rates and that initially countersunk implants would be less prominent at the final radiographic follow-up.

Methods

We designed a retrospective review at a single tertiary care level I trauma center in the United States. Our cohort consisted of patients with intertrochanteric proximal femur fracture (AO/OTA 31A1-3) treated with a cephalomedullary nail over a 6-year period (2014 to 2020) identified by chart review using Current Procedural Terminology code 27245 (open treatment of intertrochanteric, pertrochanteric, or subtrochanteric femoral fracture; with intramedullary implant, with or without interlocking screws and/or cerclage).

Review of surgical reports and analysis of radiographs confirmed the diagnosis of intertrochanteric femur fracture. Treatment details and complications were identified by review of the electronic medical record. Fractures were classified according to the AO/Orthopaedic Trauma Association Classification for proximal femur fractures.8-10

The details of the surgical technique were per surgeon preference. In general, closed reduction maneuvers were attempted on an orthopaedic fracture table, followed by percutaneous or open reduction maneuvers as needed to obtain an appropriate reduction. The cephalomedullary nails were all trochanteric fixation nail (TFN), trochanteric fixation nail advanced (TFNA) (Synthes), or Gamma (Stryker) devices and were inserted according to the manufacturer's guidelines. For all implants, proximal set screws were inserted to control rotation but allow sliding. The nail length was selected based on the surgeon's preference, and all nails were distally locked statically.

Cephalomedullary screw/blade countersinking was defined by the insertion of the lag screw or blade to a depth beyond the lateral cortex at the inferior aspect of the screw (Figure 1, A) such that screw or blade collapse could theoretically be prevented by this lateral cortical bone. This was identified on intraoperative fluoroscopy.

Figure 1
Figure 1:
A, Fluoroscopic AP hip radiograph demonstrating a short cephalomedullary nail with lag screw countersunk into the lateral femoral cortex (yellow asterisk). B, Plain AP radiograph 3 months postoperatively. Line “a” (red) is the length of the screw, line “b” (yellow) measures the lateral protrusion of the screw, which is expressed as a ratio of line b/a, multiplied by the known screw length. The amount of collapse is quantified as the difference between these measurements over time from immediate postoperatively to 6 weeks and 3 months. C, Fluoroscopic AP radiograph of the left hip demonstrating the cephalomedullary nail with “noncountersunk” lag screw (red asterisk) and D, the same patient at 3 months postoperatively.

Cephalomedullary screw/blade prominence and collapse were measured using a previously established technique.11,12 Briefly, radiographs were calibrated with the screw/blade diameter, which is round and therefore constant in every plane. Screw/blade prominence was measured as a percentage of the superior border of the screw projecting beyond the lateral surface of the nail (Figure 1, B) and multiplied by the known screw length from the implant record. Collapse was quantified as the difference in screw prominence between immediate and 6-week or 3-month postoperative intervals (Figure 1, C and D).

Our search strategy yielded 519 patients. Of these, 37 patients were excluded for subtrochanteric femur fractures, 39 patients were excluded for reconstruction nail fixation, and 26 patients were excluded because of pathologic fracture. One hundred seven patients were excluded for an insufficient follow-up. In total, 254 patients with a minimum 6-week follow-up were available for analysis of collapse, and 172 patients with a minimum 3 month follow-up were available for analysis of cutout and revision surgery. In addition, 3 patients experienced radiographic cutout at the 6-week mark but did not follow up at 3 months, and these patients were included in the analysis of radiographic cutout (n = 175).

Normality was assessed with histograms. The Student t-test was done for normally distributed continuous variables and reported as mean and SD. The Mann-Whitney U test was done for non-normally distributed continuous variables and was reported as median and interquartile range. For categorical variables, the Fisher exact test was done and reported as odds ratio and 95% confidence interval. The variables included in the multivariate analysis were the variable of interest (countersinking) and any variable with P < 0.10 significance in univariate analysis.13-15 For collapse, categorical variables were compared with the Mann-Whitney U test and reported as median difference, 95% confidence interval of the median, and P values while continuous variables were compared using linear regressions, R2 values, and P values, as described previously.12 Logistic and linear regression analyses were done in R studio (version 1.2.1335 for Mac OS16). All other calculations were done in Prism (version 8.0.2 for macOS, GraphPad Software).

Results

No differences were observed in patient age, sex, American Society of Anesthesiologists Class, body mass index, or comorbidities between patients with countersunk and noncountersunk screws/blades. No notable differences were observed in fracture pattern or injury characteristics between groups. No difference was observed between groups in postoperative reduction quality (Table 1). However, significantly more patients with countersunk screw/blade were treated with a lag screw (31/45, 69.9%) than patients with noncountersunk screws/blades (29/209, 13.9%, P < 0.0001).

Table 1 - Patient Demographics, Fracture Characteristics, and Surgical Details
Factor Countersunk Noncountersunk P value
Median IQR Median IQR
Age 87.0 76.5-91.0 82.0 73.0-90.0 0.08
ASA 3.0 3.0-3.0 3.0 2.0-3.0 0.11
Factor Countersunk Noncountersunk P value
Mean St. Dev. Mean St. Dev
BMI 24.0 4.9 24.2 4.5 0.77
Factor Countersunk Noncountersunk OR (95% CI) P value
% Proportion % Proportion
Female 64.4 29/45 73.7 154/209 0.6 (0.3-1.2) 0.27
Smoking 33.3 15/45 32.5 68/209 1.0 (0.5-2.1) 0.99
Diabetes 17.8 8/45 13.0 33/254 1.4 (0.7-32) 0.36
Injury characteristics
 AO/OTA 31A1/312 75.6 34/45 79.9 167/209 0.8 (0.4-1.7) 0.54
 AO/OTA 31A3 24.4 11/45 20.1 42/209 1.3 (0.6-2.7) 0.54
 Low energy 91.1 41/45 90.0 188/209 1.1 (0.4-3.2) 0.99
Treatment variables
 CM implant
  Helical blade 31.1 14/45 86.1 180/209 0.1 (0.01-0.2) <0.0001
  Lag screw 69.9 31/45 13.9 29/209 13.7 (6.6-27.7) <0.0001
Factor Countersunk Noncountersunk P value
Mean (°) St. Dev Mean (°) St. Dev
Neck-shaft angle 129.9 3.5 129.4 3.7 0.39
95% CI = 95% confidence interval, ASA = American Society of Anesthesiologists Class, BMI = body mass index, CM = cephalomedullary, IQR = interquartile range, NSA = neck-shaft angle, OR = odds ratio, OTA = Orthopaedic Trauma Association

Outcome analysis revealed no difference in cutout rates between groups (1/34 of patients [2.9%] with countersunk nails versus 7/138 [5.1%] of patients with noncountersunk nails). No patients with countersunk nails underwent revision surgery for symptomatic implants, whereas 4/138 (2.9%) of patients with noncountersunk nails underwent a revision surgery for symptomatic lateral implants (Table 2). This difference was also not statistically significant (P = 0.59).

Table 2 - Cutout, Symptomatic Implant Exchange, and Revision Surgery Rates
Factor Countersunk Noncountersunk OR 95% CI P value
Min. 3 mo % Proportion % Proportion
Radiographic cutout 2.9 1/34 7.8 11/141 0.4 0.04-2.2 0.47
Revision surgery for cutout 1/34 5.1 7/138 0.6 0.05-3.3 0.99
Revision surgery for symptomatic implant 0 0/34 2.9 4/138 0.0 0-4.2 0.59
Any revision surgery 2.9 1/34 11.6 16/138 0.2 0.23-1.4 0.2
95% CI = 95% confidence interval, OR = odds ratio

Univariate logistic analysis was done to determine risk factors for radiographic cutout, revision surgery for cutout, or revision surgery for symptomatic lateral implants. Patient age was a significant independent risk factor for radiographic cutout (P < 0.05), and varus angulation was an independent risk factor for revision surgery for cutout (P < 0.05). No risk factors were associated with revision surgery for lateral implant prominence (Table 3).

Table 3 - Univariate and Multivariate Analysis of Variables Associated With Radiographic Cutout, Revision for Cutout, or Symptomatic Implant Exchange
Variable Univariate Multivariate
OR CI P value OR CI P value
Outcome
 Radiographic cutout
  Age 1.0 1.0-1.2 0.06 1.1 1.0–1 0.05
  Female 1.1 0.3-5.0 0.91
  Blade 1.6 0.4-10.9 0.5
  Stryker N/A N/A 0.99
  AO/OTA 31A1/312 0.6 0.2-2.4 0.4
  NSA 0.9 0.8-1.1 0.28
  Countersink 0.4 0.02-1.9 0.3 0.03 0.02-1.6 0.2
 Revision surgery cutout
  Age 1.1 0.99-1.2 0.2
  Female 1.1 0.2-7.5 0.9
  Blade 0.9 0.2-6.6 0.9
  AO/OTA 31A1/312 2.3 0.4-43.2 0.4
  NSA 0.8 0.7-0.9 0.02 0.8 0.7-0.97 (fit 0.02
  Countersunk 0.6 0.03-3.4 0.6 0.6 0.03-3.7 0.6
 Revision surgery implant prominence
  Age 0.99 0.9-1.1 0.8
  Female N/A N/A 0.99
  BMI 0.77 0.55-1.00 0.08
  Blade 0.94 0.1-19.4 0.96
  Implant prominence 0.99 0.74-1.25 0.95
  Countersunk N/A N/A 0.99
  Collapse (6 wk) 1.1 0.9-1.3 0.4
  Collapse (3 mo) 1.1 0.9-1.1 0.3
95% CI = 95% confidence interval, NSA = neck-shaft angle, OR = odds ratio
P < 0.05 significant (bold).

When comparing lateral implant prominence and collapse between groups, we found that the countersunk group had significantly less screw/blade prominence (median 7.8 mm, interquartile range [IQR] 6.4 to 10.1) compared with the noncountersunk group on intraoperative fluoroscopy (median 10.2 mm, IQR 7.9 to 12.6, P < 0.0001) and at the 6-week follow-up (median 13.4 versus 15.7 mm, IQR 10.1 to 18.3 versus 12.1 to 20.4, P < 0.05, Table 4).

Table 4 - Comparison of Screw/Blade Prominence and Collapse Between Groups
Factor Countersunk Noncountersunk P value
(Min 6-wk f/u) Median (mm) IQR (mm) Median IQR
Immediate postoperative
 Screw/blade prominence 7.8 6.4-10.1 10.2 7.9-12.6 0.0001
6 wk
 Screw prominence 13.4 10.1-18.3 15.7 12.1-20.4 0.03
 Collapse 4.5 1.9-7.4 5.2 2.3-8.1 0.72
3 mo
 Screw prominence 12.8 10.7-18.6 15.3 12.0-19.7 0.11
 Collapse 4.5 1.7-9.0 5.0 2.5-8.2 0.82
f/u = follow-up, IQR = interquartile range

Next, to assess whether countersunk screws were associated with less symptomatic lateral implant prominence, we queried patients by telephone survey about lateral hip pain on the surgical side using a numerical rating scale. Thirty percent (52/175) of the original study population responded, and in these patients, laterally based hip symptoms were minimal in both groups and overall similar (Supplemental Data Table 1, https://links.lww.com/JAAOS/A700). At the time of survey, 34% (59/175) of patients were deceased, and an additional 27% (47/175) could not be contacted (Supplemental Data Table 2, https://links.lww.com/JAAOS/A700).

Finally, we analyzed variables that predicted collapse at 6 weeks and 3 months. Not countersinking was a significant independent predictor of collapse at 6 weeks (P < 0.01, Table 5). Use of a helical blade also independently predicted less collapse at 6 weeks and 3 months (P < 0.0001, Table 5). Increasing age was linearly associated with increased collapse at 6 weeks (P < 0.01) and 3 months (P < 0.05, Table 5).

Table 5 - Univariate, Multivariate Linear Regression, and Mann-Whitney U of Variables Contributing to Collapse Screw/Blade at 6 Week and 3 Months
Outcome Univariate Multivariate
Variable R2 P R2 P
Collapse 6 wk
 Linear regression
  Age 0.04 0.002 0.12 0.002
  NSA 0.0002 0.8
  Initial prominence 0.006 0.2
 Mann-Whitney U
Median difference (mm) 95% CI P
  Female 0.9 −0.8 to 1.4 0.6
  AO/OTA 31A1/312 −2.0 −0.14 to (−3.0) 0.02 0.12 0.2
  Blade −2.8 −1.0 to (-3.6) 0.0007 0.12 4 × 10 −5
  Countersunk −0.7 −1.7 to 1.1 0.7 0.12 0.003
Outcome Univariate Multivariate
Variable R2 P R2 P
Collapse 3 mo
 Linear regression
   Age 0.05 0.005 0.14 0.02
   NSA 0.001 0.7
   Initial prominence 0.01 0.13 0.14 0.2
 Mann-Whitney U
Median diff 95% CI P
   Female 1.8 −0.3 to 2.6 0.11 0.14 0.5
   AO/OTA 31A1/312 −1.9 −0.1 to 3.8 0.03 0.14 0.09
   Blade −3.7 −0.7 to (−4.5) 0.006 0.14 0.004
  Countersunk −0.4 −1.7 to 1.7 0.9 0.14 0.22
95% CI = 95% confidence interval of median difference, OTA = Orthopaedic Trauma Association
R2, from linear regression. Boldface indicates that p < 0.05 is significant.

Discussion

Cephalomedullary implants are used to treat intertrochanteric hip fractures and rely, in part, on controlled collapse, the consequences of which can include lateral implant prominence and malunion associated with excessive collapse. Deep insertion of the lag screw or blade can mitigate lateral prominence, but some surgeons are concerned that this could prevent collapse and increase the risk of nonunion and implant cutout. Previous research has revealed that treating an intertrochanteric fracture with a device that does not allow controlled collapse seems to increase the risk of treatment failure.4 However, we found that countersinking the lag screw or blade during cephalomedullary nailing of intertrochanteric fractures did not prevent controlled collapse and was not associated with increased cutout rates and was associated with less collapse and implant prominence. Countersinking the screw or blade seems to be safe and is associated with improved radiographic parameters that are known to be important to patient outcome.7,17

The remainder of our findings is consistent with previous research. Overall cutout rates in our study were similar to those previously published in the literature.5,17-19 Like several previous studies, our study identified malreduction as a risk factor for failure.5,18,19 Whether helical blades are associated with increased cutout rates are controversial because one previous study found a notable association,18 whereas another did not.19 In this study, there was no association between blade or screw usage and cutout. No difference was observed in sliding between two single-screw implants from different manufacturers in this study, although a previous study reported that two-screw implants may slide less than single-screw implants.11 The authors hypothesized that countersinking may also mitigate sliding in two-screw implants. This consistency suggests that our findings are generalizable to a large number of patients with intertrochanteric femur fractures.

We observed decreased collapse and lateral implant prominence when the blade or lag screw was countersunk. To our knowledge, this has not been previously reported in the literature. Collapse at the fracture site was measured using previously validated methods, and the overall degree of collapse was similar to that seen in previous studies.11,12,20,21 Although it is intuitive that countersunk lag screws would be less prominent after controlled collapse, it is not entirely clear why there was less collapse in the countersunk group. Because some surgeons have suggested, it is possible that countersunk blades or screws catch on the residual lateral cortex during the process of controlled collapse and result in less sliding. Countersinking may have the dual advantages of minimizing lateral symptoms and modulating controlled collapse so as to better preserve length and offset.

Our study had several limitations. This was a retrospective in nature and therefore subject to bias. Groups were not randomized to any specific intervention but were instead treated according to surgeon preferences. To limit this bias, we controlled for confounders with multivariate analysis and determined that the cohorts were similar for demographics and injury pattern. Although we did not have a 1-year follow-up on all patients, previous studies have revealed that all collapse occurs within the first 4 to 6 weeks after surgery, and we, therefore, chose to measure collapse on the 6-week follow-up radiographs.21,22 Similarly, previous research had demonstrated that 3 months is the sufficient follow-up time to identify such key variables as cutout.18,23-25 The minimum clinically important difference has not been established for lateral implant prominence and sliding. By way of comparison, the difference in sliding with cephalomedullary devices between stable and unstable fracture patterns is approximately 2 mm.12 When we queried patients about laterally based hip symptoms postoperatively, a substantial number of patients were lost to follow-up or deceased, both of which are known limitations of collecting patient-reported outcomes in the geriatric hip fracture population.26 Although our study may also have been underpowered to detect differences in the cutout rates, there were actually fewer cutouts in our countersunk patient group. Finally, we measured collapse and implant prominence on plain radiographs, which are sensitive to the limb position. Although our radiograph technicians follow a standardized technique when obtaining such radiographs, differences in hip rotation may have affected the measurements.

In conclusion, surgeons can countersink the cephalomedullary blade or lag screw when treating intertrochanteric proximal femur fractures in an effort to decrease implant prominence and mitigate collapse. This technique does not prevent collapse altogether or increase the risk of cutout. Additional research is warranted to evaluate the clinical benefits of better maintenance of reduction and less lateral prominence provided by this technique.

References

References printed in bold type are those published within the past 5 years.

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