Lintz François, Grün Wolfram, Pozzessere Enrico, Luo Emily, Huanuco Casas Erik Jesus, Vermorel Pierre-Henri, Acker Antoine, de Cesar Netto Cesar
Ramsay Healthcare, Clinique de l'Union, Department of Foot and Ankle Surgery, Saint Jean, France.
Department of Foot and Ankle Surgery, Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC, USA.
Clin Orthop Relat Res. 2025 Jul 10. doi: 10.1097/CORR.0000000000003613.
Stress fractures of the fifth metatarsal (M5) are common among individuals engaging in repetitive impact activities or patients with preexisting deformities. Compared with patients who have traumatic fractures, those with stress fractures often develop delayed union, nonunions, or recurrence. Risk factors such as hindfoot varus and foot adduction have been implicated. The recent advent of weightbearing CT enables the study of specific bone density and orientation characteristics that have not, to our knowledge, previously been explored. Such tools could detect higher risk patients and help trigger potential preventive measures.
QUESTIONS/PURPOSES: Do patients with an M5 stress fracture present altered three-dimensional orientation and alignment parameters compared with an age- and sex-matched control group? (2) Do the feet and M5s of patients with an M5 stress fracture present different foot ankle offset (FAO) parameters compared with the control group? (3) Do the M5s of patients with an M5 stress fracture present with altered bone density patterns compared with the control group, and is a clinically relevant threshold identifiable?
This institutional review board-approved retrospective case-control study analyzed 15 feet of patients with M5 stress fractures and 15 feet of a control group using weightbearing CT. Between February 2022 and May 2024, a total of 74 patients with available weightbearing CT scans were treated for an M5 fracture. Among those patients, we considered 77% (57) of proximal fractures as potentially eligible. Of those patients, 39% (22 of 57) were included; a further 32% (7 of 22) were later excluded because of metal artifact conflicting with M5 bone density assessment, leaving 68% (15 of 22) for analysis here. Controls were selected from our weightbearing CT archive, matched for age and sex and excluded if any foot disorder or prior intervention was identified. Accordingly, there were seven males and eight females in each group, and five and nine left sides, respectively, in the stress fractures and control groups. The mean ± SD age was 53 ± 13 years for the stress fractures group versus 51 ± 12 years for controls. Mean ± SD BMI was 34.4 ± 10.2 kg/m2 for the stress fractures group and 36.8 ± 8.2 kg/m2 for controls. For the first study question, M5 orientations and baseline foot alignment parameters were evaluated based on Digital Imaging and Communications in Medicine (DICOM) data sets using weightbearing CT software. For the second study question, weightbearing CT software was used to measure the FAO and assess the spatial relationship of the M5 with the foot tripod. For the third study question, segmentation and bone density measurements, using Hounsfield units (HUs), were performed with commercially available and open-source software. Receiver operating characteristic analysis with the Youden index was performed to determine the sensitivity and specificity of the HU M5/HU talus density ratio for identifying stress fractures.
The stress fractures group exhibited a lower M5 base height at mean ± SD 9 ± 3 mm versus 12 ± 3 mm (p = 0.045), greater ground contact frequency (11 of 15 versus 0 of 15 for the control group; p < 0.001), and an increased median (range) M5/M4 length ratio of 1.06 (0.95 to 1.14) versus 1.01 (0.97 to 1.10) for controls (p = 0.04). Hindfoot varus and foot adduction were associated with stress fractures, as indicated by altered hindfoot alignment and tarsometatarsal angles. The stress fractures group demonstrated a mean 50% increase in the HU M5/HU talus density ratio, at a median (range) of 1.52 (0.9 to 2.3) versus 1.02 (0.97 to 1.1) (p < 0.001). A relative increase by a factor of 1.2 in the HU M5/HU talus density ratio was associated with the stress fractures group with 80% sensitivity and 94% specificity.
Stress fractures of the M5 are known to be associated with hindfoot varus and forefoot adductus. The present study adds that these injuries may also be associated with reduced base height, increased plantarflexion, a longer M5, and higher bone density. Future prospective studies could investigate whether using a threshold of 1.2 for the HU M5/HU talus density ratio to trigger early preventive measures could help decrease the occurrence of stress fractures.
Level III, prognostic study.
第五跖骨（M5）应力性骨折在从事重复性冲击活动的个体或存在既往畸形的患者中很常见。与创伤性骨折患者相比，应力性骨折患者常出现愈合延迟、不愈合或复发。后足内翻和前足内收等危险因素已被提及。负重CT的出现使得能够研究特定的骨密度和方向特征，据我们所知，此前尚未对此进行过探索。此类工具可以检测出高风险患者，并有助于触发潜在的预防措施。
问题/目的：（1）与年龄和性别匹配的对照组相比，M5应力性骨折患者的三维方向和对线参数是否发生改变？（2）与对照组相比，M5应力性骨折患者的足部和M5的足踝偏移（FAO）参数是否不同？（3）与对照组相比，M5应力性骨折患者的M5骨密度模式是否改变，是否存在临床相关阈值？
这项经机构审查委员会批准的回顾性病例对照研究，使用负重CT分析了15例M5应力性骨折患者的足部和15例对照组的足部。在2022年2月至2024年5月期间，共有74例有可用负重CT扫描的患者接受了M5骨折治疗。在这些患者中，我们认为77%（57例）近端骨折患者可能符合条件。其中，39%（57例中的22例）被纳入研究；由于金属伪影与M5骨密度评估冲突，另外32%（22例中的7例）后来被排除，最终留下68%（22例中的15例）用于本分析。对照组从我们的负重CT存档中选取，根据年龄和性别进行匹配，若发现任何足部疾病或既往干预则排除。因此，每组有7名男性和8名女性，应力性骨折组和对照组分别有5例和9例左侧足部。应力性骨折组的平均±标准差年龄为53±13岁，对照组为51±12岁。应力性骨折组的平均±标准差体重指数为34.4±10.2kg/m²，对照组为
