Thin lateral wall cortex intertrochanteric proximal femur fractures: a comparative study between past and present

INTRODUCTION

Traditionally, orthopedic surgeons used to focus on Calcar involvement (posteromedial portion of the proximal femur) being the most alarming prognostic indicator for fracture stability.^1-6 Recently, all the concern has been changed towards identifying the significance of integrity of lateral wall, and how implant selection is important to have much better outcomes.^7-11 Therefore, understanding various fracture patterns is critical in order to select the appropriate surgical technique and implant applied.

How to assess lateral femoral wall thickness?

It is commonly measured through an AP radiograph, through drawing a line from the greater trochanter's innominate tubercle on the lateral aspect of the proximal femur, making an angle at 135° going toward fracture line.

Thickness less than 20.5 mm is defined as thin lateral wall.^12,13

The aim of this study was to retrospectively review 225 cases of treated thin lateral wall intertrochanteric fractures to assess outcomes associated with different implant choices and compare various surgical options in terms of complications and healing time. The findings will tailor the surgical decision regarding fracture fixation techniques and best implant to choose then.

METHODS

This is a retrospective study performed through clinical and radiological evaluation for patients’ records, emphasizing on patients managed for thin lateral wall cortex intertrochanteric proximal femur fractures between January 2017 and December 2023. Data analysis was performed through retrospective review of patients records managed in military hospitals within the Royal Medical Services in Jordan (Royal rehabilitation center-King Hussein Medical City and Queen Alia Military Hospital). Out of 974 intertrochanteric fractures evaluated, 300 were classified as thin lateral cortex pattern. Inclusion criteria include isolated intertrochanteric femur fractures with thin lateral wall cortex managed by fixation techniques either (PFN, DHS or DCS). Exclusion criteria include insufficiency and pathological fractures, stress fractures, fractures managed by hemiarthroplasty rather than fixation techniques, incomplete data. 75 patients were excluded according the exclusion criteria ending in assessing 225 patients. Sampling technique we applied was nonprobability convenient sampling. Fractures were assessed based on fixation technique and implant choice, with radiological follow-ups conducted at intervals to evaluate outcomes and complications associated with each implant choice.

Follow-up period groups were as the following: immediate post-fixation, early-stage follow-up (up to three months), and subsequent intervals. X-rays were analyzed for multiple parameters including: reduction quality, technique of fixation, related complications (such as varus collapse, medialization of the shaft, cut-out, Z-effect [Figure 2], malunion, nonunion, metal failure and per-prosthetic fractures), and healing process. Accepted degree of fracture healing was evaluated radiologically by the presence of callus on AP and lateral views.

Ethical approval was obtained from the ethical committee of directorate of professional training and planning in Royal Medical Services under the IRB number 19/9/2024.

Statistical analysis

Includes descriptive analysis, employing mean and standard deviation for continuous variables, and frequency along with percentages for categorical variables. To assess associations between categorical variables, the chi-squared test of independence (χ2-test) and Fisher exact test were utilized. Additionally, the One-way ANOVA test was employed to compare mean age and healing time among different treatment modalities for any significant disparities. Time-to-event data was analyzed using the Kaplan-Meier (KM) method. The Statistical Package for the Social Sciences (SPSS) IBM Version 21 Chicago facilitated the statistical analysis, with a significance level set at α = 0.050.

RESULTS

Starting with demographic analysis, we started analysis for seventy-five patients with intertrochanteric proximal femoral fractures characterized by a thin lateral cortex over a span of six years. Table 1 demonstrates the demographic characteristics of the above-mentioned category of patients. The majority of patients were females, making about 69.3% of the population. The mean age of the patients was 79.75±11.37 years. Left femur was predominantly affected in about 60% of cases. Comorbidities such as diabetes, hypertension, previous cerebrovascular accidents and ischemic heart diseases were noticed to be found in about 61.3% of patients.

After demographic analysis we moved forward to compare between the three treatment options used. This was summarized clearly in Table 2. PFN was the implant applied in 50% of the fractures. There were no discernible differences observed in terms of age, gender, or the affected extremity among the three treatment modalities. Statistical analysis revealed no significant difference in healing time across the three options (p=0.242). Additionally, there were no disparities noted in the one-year mortality rate or the need for revision surgery among the different treatment modalities (p=0.626, p=0.841 respectively). However, among the three fixation modalities, DHS was significantly associated with nonunion (p=0.042). The overall mortality rate within the first year stood at 26%.

Regarding outcomes and complications associated with the three treatment modalities, comparison between the 3 implants used was discussed through Table 3. Patient X-rays were assessed at various intervals, including immediately after surgery, early follow up carried within first three months, between three and six months, and finally between six and twelve months. The sample size decreased over time due to mortality and loss to follow-up, leading to independent statistical analyses for each follow up interval.

In the immediate follow up radiographs comprising 225 patients, DHS and PFN exhibited superior reduction results compared to DCS. However, 34 patients treated with DHS (15.4%) experienced intraoperative lateral wall fractures explained due to having thin lateral wall.^13-15 Despite this, Fisher exact test results showed no statistically significant association between treatment methods and complications (X2(4) = 6.237, p = 0.088).

During the follow-up radiographs within the first three months, 18 patients' X-rays were missing, leaving 207 patients for analysis. Although 96.2% of initial DHS radiographs post-op displayed an acceptable reduction, only 44% maintained this accepted position on follow-up x-rays, and this is related to shaft medialization effect (11 cases, 32%) and varus collapse in other patients (8 cases, 24%).¹⁶ Varus collapse was more pronounced and progressive in DCS treatment (initial radiograph: 18.2%, first follow-up: 55.6%). PFN exhibited greater resistance to varus collapse, but three cases showed Z-effect, a PFN-specific complication (X2(8) = 22.213, p = 0.001).

Similarly, the sample size reduced to 200 radiographs during the three to six-month follow-up period. PFN maintained a superior position, although varus collapse occurred in five patients (14.7%), with an additional three patients (8.8%) experiencing the Z-effect. Shaft medialization was more evident in DHS, and varus collapse in DCS (X2(10) = 25.279, p≤0.001).

Findings during the six to twelve-month interval were very similar to those of the previous period, but this was not statistically significant (X2(8) = 9.501, p = 0.224). This could be attributed to the progressive loss of patients from follow-up.

DISCUSSION

In this retrospective study, we aimed to evaluate the effectiveness of treatment modalities-DHS, DCS, and PFN-regarding intertrochanteric fractures with thin lateral cortex. One of our main challenges arose was due to patients being lost to follow-up, due to mortality, seeking follow-up care elsewhere, or missing their appointments.

We initiated our cohort study having 225 patients, yet by the six to twelve-month follow-up interval, the sample size had dwindled to 180 patients, leading to a statistical analysis discrepancy.

In our study, PFN emerged as the superior treatment in maintaining reduction position during follow-up despite the fact that there were no significant differences observed among the three modalities concerning healing duration, mortality rates, or the necessity for revision surgery. And this superiority goes back to the factor of PFN implant being more biomechanically stable than DHS and DCS due to the fact that PFN being an intramedullary device in comparison to DHS and DCS which extramedullary implants have a better lateral wall buttress and shorter lever arm leading to lower shearing force and moment over intertrochanteric fracture line. Furthermore, PFN showed to have a lower propensity for varus collapse, shaft medialization due to the same discussed biomechanical issue, and lower intraoperative lateral wall fractures due to lower need to ream lateral wall except for lag screw in comparison to DHS and DCS which need lateral wall reaming for both lag and side plate screws. Pradeep et al, stated similar results to our study results.

On the other hand, occurrence of Z-effect deformity was noted uniquely in PFN treatment. Conversely, although DHS demonstrated favorable initial reduction, over 50% of the fractures experienced reduction loss within the initial three months due to the fact that varus collapse and shaft medialization occurred later on during months of follow up.¹⁶ This loss of maintenance of reduction goes to posteromedial calcar involvement, in which it can’t stand the biomechanical shearing force through using DHS over such fracture.

DHS also exhibited a significant risk of lateral wall fractures and a higher incidence of nonunion in thin lateral cortex intertrochanteric fractures, putting it in inferior to PFN in managing such type of fractures with thin lateral wall.^14,15 Guerra et al stated that in his study confirming that PFN is still superior to DHS in thin lateral wall cortex fractures due to the fact that PFN being biomechanically more stable than both DHS and DCS.¹⁵

Conversely, DCS was associated with a higher incidence of varus positioning from the outset, a trend that escalated markedly during the initial three-month follow-up period.

And by having a look over the literature and the effect of thin lateral wall cortex is so important, Gotfried analyzed twenty-four patients with documented postoperative fracture collapse, they highlighted the importance of the lateral wall's presence on preoperative radiographs prior to selecting the appropriate implant for stabilization of such a fracture.^17,18 Palm et al. in the same way recognized postoperative fracture of the lateral femoral wall after DHS usage as a primary predictor for reoperation following an intertrochanteric fracture, with a fracture incidence of 21%.^10,16

In our study, lateral wall fractures occurred in 15.4% of DHS-fixed fractures, which advocates for their avoidance for thin lateral wall fractures. This result was comparable to the international results which show higher incidence of lateral wall fracture occurring in DHS managed fractures, Sharma et al stated that as well.¹⁵

The limitations we faced in our study were sample size which was affected by covid crises since that the study analysis were held over January 2017 and December 2023, during which covid crises has an effect over the sample size. Also, being a retrospective study is another limitation in analysis some factors like comorbidities. Moreover, some factors were not studies like the BMI factor and its effect on each modality of treatment.

CONCLUSION

Awareness of the importance of lateral wall integrity in intertrochanteric fractures is highly increasing among orthopedic surgeons. Higher complications and reoperation rates are being associated when improper implant is used in thin lateral wall fractures. Despite no significant differences were obtained in mortality. healing time, or reoperation rates among DHS, DCS, and PFN, PFN showed much better results in reduction maintenance and lower complication rates. Therefore, PFN should be preferred over DHS and DCS for treating thin lateral wall intertrochanteric fractures.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee of of directorate of professional training and planning in Royal Medical Services under the IRB number 19/9/2024

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