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<article article-type="case-report" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" dtd-version="1.3" xml:lang="EN">
<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Surg.</journal-id><journal-title-group>
<journal-title>Frontiers in Surgery</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Surg.</abbrev-journal-title></journal-title-group>
<issn pub-type="epub">2296-875X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fsurg.2026.1788560</article-id>
<article-version article-version-type="Version of Record" vocab="NISO-RP-8-2008"/>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Case Report</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>Application of a humeral intramedullary nail for subtrochanteric fracture in a patient with poliomyelitis sequelae: a case report</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Yu</surname><given-names>Xiang</given-names></name>
<xref ref-type="aff" rid="aff1"/>
<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref><uri xlink:href="https://loop.frontiersin.org/people/2844631/overview"/><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="methodology" vocab-term-identifier="https://credit.niso.org/contributor-roles/methodology/">Methodology</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; review &#x0026; editing" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-review-editing/">Writing &#x2013; review &#x0026; editing</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; original draft" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-original-draft/">Writing &#x2013; original draft</role></contrib>
<contrib contrib-type="author" equal-contrib="yes"><name><surname>Sheng</surname><given-names>Wen-Bo</given-names></name>
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<xref ref-type="author-notes" rid="an1"><sup>&#x2020;</sup></xref><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="methodology" vocab-term-identifier="https://credit.niso.org/contributor-roles/methodology/">Methodology</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; review &#x0026; editing" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-review-editing/">Writing &#x2013; review &#x0026; editing</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; original draft" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-original-draft/">Writing &#x2013; original draft</role></contrib>
<contrib contrib-type="author"><name><surname>Ao</surname><given-names>Rong-Guang</given-names></name>
<xref ref-type="aff" rid="aff1"/><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Project administration" vocab-term-identifier="https://credit.niso.org/contributor-roles/project-administration/">Project administration</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Funding acquisition" vocab-term-identifier="https://credit.niso.org/contributor-roles/funding-acquisition/">Funding acquisition</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; review &#x0026; editing" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-review-editing/">Writing &#x2013; review &#x0026; editing</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="supervision" vocab-term-identifier="https://credit.niso.org/contributor-roles/supervision/">Supervision</role></contrib>
<contrib contrib-type="author"><name><surname>Liu</surname><given-names>Bing-Li</given-names></name>
<xref ref-type="aff" rid="aff1"/><uri xlink:href="https://loop.frontiersin.org/people/3108964/overview" /><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Funding acquisition" vocab-term-identifier="https://credit.niso.org/contributor-roles/funding-acquisition/">Funding acquisition</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Project administration" vocab-term-identifier="https://credit.niso.org/contributor-roles/project-administration/">Project administration</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; review &#x0026; editing" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-review-editing/">Writing &#x2013; review &#x0026; editing</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="methodology" vocab-term-identifier="https://credit.niso.org/contributor-roles/methodology/">Methodology</role></contrib>
<contrib contrib-type="author" corresp="yes"><name><surname>Zhang</surname><given-names>Jun</given-names></name>
<xref ref-type="aff" rid="aff1"/>
<xref ref-type="corresp" rid="cor1">&#x002A;</xref><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="Writing &#x2013; review &#x0026; editing" vocab-term-identifier="https://credit.niso.org/contributor-roles/writing-review-editing/">Writing &#x2013; review &#x0026; editing</role><role vocab="credit" vocab-identifier="https://credit.niso.org/" vocab-term="resources" vocab-term-identifier="https://credit.niso.org/contributor-roles/resources/">Resources</role></contrib>
</contrib-group>
<aff id="aff1"><institution>Department of Orthopedics, The Seventh People&#x2019;s Hospital Affiliated to Shanghai University of Traditional Chinese Medicine</institution>, <city>Shanghai</city>, <country country="cn">China</country></aff>
<author-notes>
<corresp id="cor1"><label>&#x002A;</label><bold>Correspondence:</bold> Jun Zhang <email xlink:href="mailto:adesso@163.com">adesso@163.com</email></corresp>
<fn fn-type="equal" id="an1"><label>&#x2020;</label><p>These authors have contributed equally to this work and share first authorship</p></fn>
</author-notes>
<pub-date publication-format="electronic" date-type="pub" iso-8601-date="2026-02-26"><day>26</day><month>02</month><year>2026</year></pub-date>
<pub-date publication-format="electronic" date-type="collection"><year>2026</year></pub-date>
<volume>13</volume><elocation-id>1788560</elocation-id>
<history>
<date date-type="received"><day>15</day><month>01</month><year>2026</year></date>
<date date-type="rev-recd"><day>01</day><month>02</month><year>2026</year></date>
<date date-type="accepted"><day>06</day><month>02</month><year>2026</year></date>
</history>
<permissions>
<copyright-statement>&#x00A9; 2026 Yu, Sheng, Ao, Liu and Zhang.</copyright-statement>
<copyright-year>2026</copyright-year><copyright-holder>Yu, Sheng, Ao, Liu and Zhang</copyright-holder><license><ali:license_ref start_date="2026-02-26">https://creativecommons.org/licenses/by/4.0/</ali:license_ref><license-p>This is an open-access article distributed under the terms of the <ext-link ext-link-type="uri" xlink:href="https://creativecommons.org/licenses/by/4.0/">Creative Commons Attribution License (CC BY)</ext-link>. The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</license-p></license>
</permissions>
<abstract><sec><title>Objective</title>
<p>To investigate the clinical feasibility and efficacy of using a humeral intramedullary nail for the treatment of subtrochanteric fracture in a patient with ipsilateral poliomyelitis sequelae.</p>
</sec><sec><title>Methods</title>
<p>A case of a 54-year-old female patient with a left subtrochanteric fracture caused by a traffic accident was reported. The patient had a 50-year history of ipsilateral poliomyelitis, leading to developmental deformity and severe stenosis of the femoral medullary canal in the affected limb, which could not accommodate a conventional femoral intramedullary nail. Therefore, we innovatively used a 7&#x2005;mm diameter humeral interlocking intramedullary nail for internal fixation. Limited open reduction was performed during surgery, supplemented with cerclage wiring to enhance fracture stability. The medullary canal was reamed to 8&#x2005;mm, after which the nail was successfully inserted.</p>
</sec><sec><title>Results</title>
<p>The surgical procedure was smooth. Intraoperative fluoroscopy and postoperative x-rays showed satisfactory fracture reduction and good positioning of the internal fixation. The patient was followed up for 30 months. Imaging examinations confirmed bony union of the fracture without complications such as failure of internal fixation. Ultimately, the walking and flexion functions of the left lower limb recovered to the pre-injury level.</p>
</sec><sec><title>Conclusion</title>
<p>For special types of subtrochanteric fractures with severe femoral medullary canal stenosis due to conditions like poliomyelitis sequelae, the application of a humeral intramedullary nail is a safe and effective innovative treatment strategy. This approach provides reliable intramedullary fixation. This experience offers a valuable reference for managing similar complex orthopedic problems.</p>
</sec>
</abstract>
<kwd-group>
<kwd>case report</kwd>
<kwd>fracture fixation</kwd>
<kwd>humeral intramedullary nail</kwd>
<kwd>poliomyelitis sequelae</kwd>
<kwd>subtrochanteric fracture</kwd>
</kwd-group><funding-group><funding-statement>The author(s) declared that financial support was received for this work and/or its publication. The Scientific Research Program of Shanghai Pudong New Area Health Commission (the Joint Research and Development Program) (PW2025D-09), Special project of Cross Medical Engineering Innovation of The Seventh People&#x0027;s Hospital (XKB00004).</funding-statement></funding-group><counts>
<fig-count count="4"/>
<table-count count="1"/><equation-count count="0"/><ref-count count="5"/><page-count count="7"/><word-count count="0"/></counts><custom-meta-group><custom-meta><meta-name>section-at-acceptance</meta-name><meta-value>Orthopedic Surgery</meta-value></custom-meta></custom-meta-group>
</article-meta>
</front>
<body><sec id="s1" sec-type="intro"><title>Introduction</title>
<p>The treatment of subtrochanteric fractures is particularly challenging when combined with poliomyelitis sequelae, as the affected limb often presents anatomical abnormalities such as severe medullary canal stenosis, osteoporosis, and deformity, making standard femoral intramedullary nails inapplicable. To address this challenge, this study reports a case of a 54-year-old female with ipsilateral poliomyelitis sequelae and a subtrochanteric fracture, where a thinner humeral intramedullary nail was innovatively used for internal fixation. By detailing the preoperative planning, surgical technique, and follow-up results, this study aims to explore the feasibility and efficacy of this alternative method for special types of subtrochanteric fractures, providing a reference for the clinical management of similar complex situations.</p>
</sec>
<sec id="s2"><title>Case presentation</title>
<sec id="s2a"><title>Chief complaints</title>
<p>Left hip pain and limited mobility for 2&#x2005;h after a traffic accident.</p>
</sec>
<sec id="s2b"><title>History of present illness</title>
<p>The patient, a 54-year-old female, was injured in a traffic accident while cycling 2&#x2005;h prior, resulting in left hip pain and limited mobility. She was sent to our emergency department, where x-rays indicated a &#x201C;left subtrochanteric fracture&#x201D;. She was admitted for further treatment.</p>
</sec>
<sec id="s2c"><title>History of past illness</title>
<p>The patient has a 50-year history of poliomyelitis.</p>
</sec>
<sec id="s2d"><title>Personal and family history</title>
<p>The patient declared no family history of genetic diseases.</p>
</sec>
<sec id="s2e"><title>Physical examination</title>
<p>The patient was lying supine with a pained expression. Generalized muscle atrophy was observed in the left lower limb, with surgical scars visible on the left proximal thigh and knee. Significant swelling and subcutaneous ecchymosis were present in the left hip and upper thigh, with the limb exhibiting shortening and external rotation deformity. Obvious tenderness was noted in the left upper thigh, with palpable bone crepitus and abnormal movement; axial percussion pain was positive. Due to pain protection, all ranges of motion in the affected limb were severely limited, and muscle strength could not be assessed cooperatively. Dorsalis pedis artery pulses were palpable bilaterally, with normal capillary refill time; active toe movement was present, and no significant decrease in superficial sensation on the dorsum and sole of the foot was noted. Limb length measurement indicated structural shortening of the left lower limb.</p>
</sec>
<sec id="s2f"><title>Laboratory examinations</title>
<p>The patient&#x0027;s vital signs were as follows: temperature, 37.2&#x2005;&#x00B0;C; pulse rate, 102 beats/min; respiration rate, 35 breaths/min; and blood pressure, 112/52 mmHg. A blood test revealed that the white blood cell count was 9.6&#x2009;&#x00D7;&#x2009;109/L, the neutrophil count was 71&#x0025;, the haemoglobin level was 101&#x2005;g/L, and the C-reactive protein level was 22&#x2005;mg/L. The rest of the laboratory tests were unremarkable.</p>
</sec>
<sec id="s2g"><title>Imaging examinations</title>
<p>x-ray showed a left subtrochanteric fracture (<xref ref-type="fig" rid="F1">Figure&#x00A0;1</xref>).</p>
<fig id="F1" position="float"><label>Figure&#x00A0;1</label>
<caption><p>Preoperative anteroposterior x-ray of the left hip showed a left subtrochanteric femoral fracture AO/OTA type A3.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-13-1788560-g001.tif"><alt-text content-type="machine-generated">X-ray of a left upper leg shows a displaced fracture of the femoral shaft just below the femoral head, with clear separation of bone fragments and misalignment.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s2h"><title>Final diagnosis</title>
<list list-type="order">
<list-item>
<p>Left subtrochanteric fracture, AO/OTA A3 type.</p></list-item>
<list-item>
<p>Poliomyelitis sequelae.</p></list-item>
</list>
</sec>
<sec id="s2i"><title>Treatment</title>
<sec id="s2i1"><title>Perioperative management</title>
<p>A comprehensive perioperative management protocol was implemented to ensure patient safety and optimize outcomes. Upon admission, the patient&#x0027;s general condition was thoroughly evaluated. Given the trauma and pre-existing disability, nutritional status was assessed, and nutritional support was initiated to address the mild anemia (haemoglobin 101&#x2005;g/L). Multimodal analgesia was employed to effectively control pain. Pharmacological thromboprophylaxis with low-molecular-weight heparin was administered preoperatively and continued postoperatively, considering the high risk of deep vein thrombosis associated with lower limb fractures and anticipated reduced mobility. The anesthesia team conducted a preoperative assessment, and general anesthesia was selected. Intraoperative measures included antibiotic prophylaxis administered 30&#x2005;min before incision and careful monitoring of hemodynamic status and fluid balance. This holistic approach aimed to mitigate systemic risks and create optimal conditions for surgery and recovery.</p>
</sec>
<sec id="s2i2"><title>Preoperative preparation</title>
<p>Following the general perioperative optimization, the specific surgical plan was determined to be open reduction and internal fixation with an intramedullary nail. Preoperative measurements revealed a critical anatomical constraint: the narrowest diameter of the femoral medullary canal was only 4.5&#x2005;mm, rendering commonly used femoral intramedullary nails unsuitable. Consequently, a humeral intramedullary nail (Smith &#x0026; Nephew, TRIGEN, proximal bend humeral long nail, 8/7&#x2005;mm, 28&#x2005;cm) was selected as a viable alternative to achieve stable intramedullary fixation. Although a plate-screw system was considered as it could circumvent the issue of medullary canal stenosis, this option was ultimately rejected. The decision was based on the high risk of mechanical failure (such as screw loosening or plate breakage) associated with plates due to stress concentration in the high-stress subtrochanteric region, a risk exacerbated by the patient&#x0027;s osteoporotic bone quality resulting from long-term disuse.</p>
</sec>
<sec id="s2i3"><title>Surgical procedure</title>
<p>After satisfactory anesthesia, the patient was placed in the supine position. Routine disinfection and draping were performed. A straight lateral incision approximately 15&#x2005;cm long was made over the left hip, and layers were incised to expose the tip of the greater trochanter and the subtrochanteric fracture line. Under direct vision, the fracture was reduced using reduction forceps and then stabilized with cerclage wiring. The entry point was selected slightly medial to the tip of the greater trochanter. A guide wire was inserted, and its position within the medullary canal was confirmed as satisfactory by C-arm fluoroscopy. Subsequently, flexible reamers were used starting from 5&#x2005;mm, progressively reaming the medullary canal until the proximal femoral canal was enlarged to 8&#x2005;mm, with the cortical bone remaining intact. A 7&#x2005;mm diameter, 28&#x2005;cm long humeral interlocking intramedullary nail was selected and smoothly inserted along the guide wire into the medullary canal. Fluoroscopy confirmed good fracture alignment and appropriate depth of the nail. The proximal aiming device was installed, and two proximal locking screws were successfully inserted. Distal locking was not performed. Repeat anteroposterior and lateral fluoroscopy confirmed satisfactory fracture reduction, good position of the intramedullary nail and proximal locking screws, and stability of the fracture site. The surgical field was irrigated, hemostasis was thoroughly achieved, and the incision was closed in layers. The surgery proceeded smoothly with an estimated blood loss of about 200&#x2005;mL; no blood transfusion was required, and the patient returned to the ward safely after surgery (<xref ref-type="fig" rid="F2">Figure&#x00A0;2</xref>).</p>
<fig id="F2" position="float"><label>Figure&#x00A0;2</label>
<caption><p>Intraoperative imaging: <bold>(A)</bold> insertion of intramedullary nail. <bold>(B)</bold> The intramedullary nail is of appropriate length and well-matched in diameter. <bold>(C)</bold> Insert the proximal locking screw. <bold>(D)</bold> Intraoperative fluoroscopy showed satisfactory positioning of the intramedullary nail and wires with good fracture reduction.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-13-1788560-g002.tif"><alt-text content-type="machine-generated">Panel A shows a fluoroscopic image of a hip joint with a guidewire placed in the femur. Panel B displays an intramedullary nail being inserted into the femoral canal. Panel C depicts orthopedic tools used for intramedullary fixation during surgery. Panel D presents the final fixation of a femoral fracture using an intramedullary nail and screws.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s2i4"><title>Postoperative rehabilitation and follow-up</title>
<p>x-ray review three days postoperatively showed satisfactory fracture reduction and well-matched internal fixation.</p>
<p>The postoperative rehabilitation plan followed the principles of &#x201C;individualization, safety, and progression&#x201D;, tailored according to the patient&#x0027;s ipsilateral limb muscle weakness, slender bone structure, and internal fixation characteristics. In the early postoperative period (0&#x2013;4 weeks), the focus was on bed rest with strict non-weight-bearing, emphasizing ankle pump exercises, isometric contractions of the affected limb muscles, and passive range of motion exercises for the hip and knee joints to reduce swelling, alleviate pain, and prevent complications. In the mid-term (starting 5&#x2013;8 weeks postoperatively), after x-ray confirmation of callus formation, gradual partial weight-bearing with the assistance of crutches was initiated, along with enhanced range of motion and muscle strength training for the hip and knee. In the later stage (approximately 3 months postoperatively), based on fracture healing progress, a gradual transition to full weight-bearing was made, focusing on strengthening stabilizing muscle groups like the gluteus medius, gait training, and functional exercises to restore daily activity capacity. Fall prevention was strictly emphasized throughout the process. Regular follow-up examinations were conducted, and the rehabilitation progress was dynamically adjusted based on imaging results and functional recovery.</p>
<p>The patient returned for follow-up examinations at 1 month, 5 months, and 30 months postoperatively. Follow-up x-rays showed good fracture recovery and satisfactory position of the internal fixation (<xref ref-type="fig" rid="F3">Figure&#x00A0;3</xref>). The patient essentially recovered limb function to the pre-injury level (<xref ref-type="fig" rid="F4">Figure&#x00A0;4</xref>).</p>
<fig id="F3" position="float"><label>Figure&#x00A0;3</label>
<caption><p>Postoperative follow-up: <bold>(A)</bold> anteroposterior x-ray on the third postoperative day. <bold>(B)</bold> Lateral x-ray film 3 days postoperatively. <bold>(C)</bold> Anteroposterior x-ray at 1 month postoperatively. <bold>(D)</bold> Anteroposterior x-ray at 5 months postoperatively. <bold>(E)</bold> Anteroposterior x-ray at 30 months postoperatively. F. Lateral x-ray at 30 months postoperatively.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-13-1788560-g003.tif"><alt-text content-type="machine-generated">Panel A shows anteroposterior pelvic X-ray with a left femoral shaft fracture fixed with an intramedullary rod and screws. Panel B presents a lateral view of the same fixation. Panel C displays anteroposterior hip X-ray with proximal femoral fracture and intramedullary nail fixation. Panel D illustrates a lateral view demonstrating femoral fixation hardware alignment. Panel E shows a frontal view of the left femur with visible intramedullary rod fixation. Panel F shows a lateral femur view highlighting the fixation device and fracture healing.</alt-text>
</graphic>
</fig>
<fig id="F4" position="float"><label>Figure&#x00A0;4</label>
<caption><p>At 30 months post-operation, the patient&#x0027;s walking and squatting functions have recovered to the pre-injury state.</p></caption>
<graphic mimetype="image" mime-subtype="tiff" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="fsurg-13-1788560-g004.tif"><alt-text content-type="machine-generated">Two side-by-side photographs show a person indoors wearing a light-colored padded jacket, dark pants, and pink sneakers; in the left image, the person is walking forward, while in the right image, the person is bent forward with hands on knees, head lowered.</alt-text>
</graphic>
</fig>
</sec>
<sec id="s2i5"><title>Timeline</title>
<p>See <xref ref-type="table" rid="T1">Table&#x00A0;1</xref>.</p>
<table-wrap id="T1" position="float"><label>Table&#x00A0;1</label>
<caption><p>Timeline.</p></caption>
<table>
<colgroup>
<col align="left"/>
<col align="left"/>
<col align="left"/>
</colgroup>
<thead>
<tr>
<th valign="top" align="left">Timepoint</th>
<th valign="top" align="center">Key event</th>
<th valign="top" align="center">Main findings and decisions</th>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">Day of Injury</td>
<td valign="top" align="left">Traffic accident injury, Emergency visit</td>
<td valign="top" align="left">x-ray confirmed left subtrochanteric fracture (AO/OTA A3 type)</td>
</tr>
<tr>
<td valign="top" align="left">Preoperative Preparation</td>
<td valign="top" align="left">Post-admission completion of examinations</td>
<td valign="top" align="left">Imaging measurements revealed medullary canal stenosis (narrowest 4.5&#x2005;mm), decision to use humeral intramedullary nail</td>
</tr>
<tr>
<td valign="top" align="left">Surgery Day</td>
<td valign="top" align="left">Open reduction and internal fixation surgery</td>
<td valign="top" align="left">Successful insertion of 7&#x2005;mm humeral intramedullary nail, assisted by cerclage wiring, no distal locking performed</td>
</tr>
<tr>
<td valign="top" align="left">Postoperative Day 3</td>
<td valign="top" align="left">First postoperative x-ray review</td>
<td valign="top" align="left">Confirmed good position of internal fixation, satisfactory fracture reduction</td>
</tr>
<tr>
<td valign="top" align="left">Postoperative 1 Month</td>
<td valign="top" align="left">Outpatient follow-up</td>
<td valign="top" align="left">x-ray showed early callus formation, guidance for non-weight-bearing rehabilitation</td>
</tr>
<tr>
<td valign="top" align="left">Postoperative 5 Months</td>
<td valign="top" align="left">Outpatient follow-up</td>
<td valign="top" align="left">x-ray showed blurred fracture line, continuous callus, guidance for gradual weight-bearing</td>
</tr>
<tr>
<td valign="top" align="left">Postoperative 30 Months</td>
<td valign="top" align="left">Outpatient follow-up</td>
<td valign="top" align="left">Clinical assessment indicated recovery of walking and squatting functions to pre-injury leve</td>
</tr>
</tbody>
</table>
</table-wrap>
</sec>
</sec>
</sec>
<sec id="s3" sec-type="discussion"><title>Discussion</title>
<p>This case report presents a challenging case of subtrochanteric fracture, its particularity lying in the patient&#x0027;s concomitant ipsilateral limb poliomyelitis sequelae. The core challenge and innovation of this case lie in the successful application of a humeral intramedullary nail to address the internal fixation problem posed by femoral developmental deformity and severe medullary canal stenosis resulting from poliomyelitis sequelae.</p>
<p>Poliomyelitis sequelae lead to muscle atrophy, muscle imbalance, and long-term disuse in the affected limb, subsequently causing skeletal hypoplasia, manifesting as a slender femur, thin cortex, and narrow medullary canal (<xref ref-type="bibr" rid="B1">1</xref>). These anatomical abnormalities make patients more susceptible to fractures during daily activities, and once a fracture occurs, its internal fixation treatment faces significant challenges (<xref ref-type="bibr" rid="B2">2</xref>). In this case, preoperative measurement revealed the narrowest diameter of the femoral medullary canal was only 4.5&#x2005;mm, far below the minimum diameter required for conventional proximal femoral intramedullary nails. This anatomical abnormality rendered standard femoral intramedullary nail systems completely inapplicable. While plate and screw systems could avoid the medullary canal issue, their biomechanical disadvantages pose a high risk of failure for extramedullary fixation in the high-stress subtrochanteric region (<xref ref-type="bibr" rid="B3">3</xref>). Plate fixation, as a load-bearing device, is susceptible to failure due to stress concentration at the screw-bone interface, particularly in osteoporotic bone. Given the patient&#x0027;s long-term limb disuse and associated osteopenia secondary to poliomyelitis, the risk of implant failure with a plate construct was deemed unacceptably high. Therefore, selecting a device that can both adapt to the narrow medullary canal and provide strong intramedullary fixation is crucial for such patients.</p>
<p>In this case, we innovatively selected a thinner humeral intramedullary nail (7&#x2005;mm) as the main internal fixation device. The fundamental premise for applying a humeral nail to the femur lies in anatomical feasibility. Although the humerus and femur differ in length and curvature, as long tubular bones, their medullary canal structures share similarities in the diaphyseal portion. The key to success in this case was precise preoperative measurement. We confirmed the narrowest diameter of the patient&#x0027;s femoral medullary canal was 4.5&#x2005;mm, while the selected humeral nail diameter was 7&#x2005;mm, leaving a safe margin for reaming. By using flexible reamers starting from 5&#x2005;mm and progressively reaming to 8&#x2005;mm, we successfully created a channel in a physiologically narrow femur that could accommodate the 7&#x2005;mm nail while preserving cortical integrity. Intraoperative and postoperative imaging showed a tight fit between the nail and the medullary canal, achieving satisfactory axial and rotational stability even without distal locking.</p>
<p>Buseck et al (<xref ref-type="bibr" rid="B4">4</xref>). reported a case of a patient with congenital hip dysplasia who had undergone a proximal femoral varus osteotomy, resulting in a neck-shaft angle of only 98&#x00B0; and a narrow medullary canal (diameter 6&#x2005;mm), preventing the use of a traditional femoral nail. The authors also chose a humeral intramedullary nail for fixation, pre-bending the nail to adapt to the femoral anterior bow, ultimately achieving stable fracture healing. That study emphasized that for patients with significantly abnormal neck-shaft angles or narrow medullary canals, the humeral nail, due to its smaller diameter and adjustable proximal locking angles, offers a biomechanically superior intramedullary fixation option compared to traditional plates.</p>
<p>Furthermore, Sa-ngasoongsong et al (<xref ref-type="bibr" rid="B5">5</xref>). reported the successful application of humeral nails in femoral reconstruction in adolescent patients with osteogenesis imperfecta. Patients with osteogenesis imperfecta often have femoral deformities and narrow medullary canals, sharing similarities with the anatomical characteristics of this case. The authors noted that the humeral nail not only adapts to the narrow canal but also, via a lateral trochanteric entry approach, can avoid iatrogenic injury to the femoral head blood supply while providing better rotational stability than Rush rods.</p>
<p>Of course, the humeral intramedullary nail is not designed for the anatomical morphology of the proximal femur, and its application has certain limitations. For instance, its proximal locking screw angles are typically 90&#x00B0;-100&#x00B0;, which might not be suitable for patients with a normal femoral neck-shaft angle; additionally, distal locking might require longer screws due to the greater width of the distal femur. In this case, the decision to forgo distal locking was based on the fracture type and intraoperative stability assessment, but for more complex fracture types, full locking might be necessary to enhance stability.</p>
<p>To mitigate the risk of nonunion or delayed union resulting from the aforementioned limitations, we enhanced fracture stability intraoperatively through limited open reduction combined with cerclage wiring, thereby compensating for the insufficient angular stability of the humeral intramedullary nail. Postoperative rehabilitation was strictly guided by the principles of individualization, safety, and gradual progression. During the early stage (0&#x2013;4 weeks), absolute non-weight bearing bed rest was emphasized, supplemented with ankle pump exercises and passive joint mobilization to minimize mechanical stress. In the intermediate stage (5&#x2013;8 weeks), partial weight bearing was initiated only after radiographic confirmation of callus formation. A gradual transition to full weight bearing was implemented in the later stage (beyond 3 months). This conservative regimen aimed to reduce the risk associated with angular stability deficiency by carefully controlling mechanical load. Follow-up at 30 months confirmed fracture union without complications, validating the effectiveness of this strategy.</p>
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<sec id="s4" sec-type="conclusions"><title>Conclusion</title>
<p>In summary, for special types of subtrochanteric fractures with severe femoral medullary canal stenosis or abnormal neck-shaft angles due to conditions such as poliomyelitis sequelae, osteogenesis imperfecta, or previous osteotomy history, the application of a humeral intramedullary nail is a safe and effective innovative treatment strategy. This approach provides reliable intramedullary fixation and can achieve good fracture healing and functional recovery outcomes. This experience offers new insights for managing similar rare and complex orthopedic problems, but its general applicability still requires further validation with more cases and long-term follow-up.</p>
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</body>
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<sec id="s5" sec-type="data-availability"><title>Data availability statement</title>
<p>The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.</p>
</sec>
<sec id="s6" sec-type="ethics-statement"><title>Ethics statement</title>
<p>The studies involving humans were approved by the Medical Ethics Committee of Shanghai Seventh People&#x0027;s Hospital (SSJW-20220505). The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.</p>
</sec>
<sec id="s7" sec-type="author-contributions"><title>Author contributions</title>
<p>XY: Methodology, Writing &#x2013; review &#x0026; editing, Writing &#x2013; original draft. W-BS: Methodology, Writing &#x2013; review &#x0026; editing, Writing &#x2013; original draft. R-GA: Project administration, Funding acquisition, Writing &#x2013; review &#x0026; editing, Supervision. B-LL: Funding acquisition, Project administration, Writing &#x2013; review &#x0026; editing, Methodology. JZ: Writing &#x2013; review &#x0026; editing, Resources.</p>
</sec>
<sec id="s9" sec-type="COI-statement"><title>Conflict of interest</title>
<p>The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
<sec id="s10" sec-type="ai-statement"><title>Generative AI statement</title>
<p>The author(s) declared that generative AI was not used in the creation of this manuscript.</p>
<p>Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.</p>
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<sec id="s11" sec-type="disclaimer"><title>Publisher&#x0027;s note</title>
<p>All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.</p>
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<fn-group>
<fn id="n1" fn-type="custom" custom-type="edited-by"><p>Edited by: <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/470559/overview">Gergo Jozsa</ext-link>, University of P&#x00E9;cs, Hungary</p></fn>
<fn id="n2" fn-type="custom" custom-type="reviewed-by"><p>Reviewed by: <ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/2053598/overview">Shuai Liu</ext-link>, Soochow University, China</p>
<p><ext-link ext-link-type="uri" xlink:href="https://loop.frontiersin.org/people/3115758/overview">Adrian Surd</ext-link>, University of Medicine &#x0026; PHarmacy &#x0022;Iuliu Ha&#x021B;ieganu&#x0022;, Romania</p></fn>
</fn-group>
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</article>