Deltoid ligament integrity in lateral malleolar fractures: a comparative analysis of arthroscopic and radiographic assessments

Foot and ankle surgeons often rely on the medial clear space to evaluate competency of the deep deltoid ligament when evaluating ankle fractures. This investigation assesses the integrity of the deep deltoid ligament after lateral malleolar fracture by using direct arthroscopic visualization and medial clear-space separation on plain film radiographs. The objectives of this study were to test the reliability of medial clear-space separation and the Lauge-Hansen classification scheme in predicting deep deltoid rupture in displaced lateral malleolar fractures. The medial clear space was measured on injury radiographs of 40 patients with an isolated displaced lateral malleolar fracture who underwent open reduction and internal fixation. Injury radiographs were classified according to the Lauge-Hansen scheme. Direct arthroscopic visualization was used to evaluate the deep deltoid ligament under manual stress before fracture reduction. The mean preoperative medial clear space in patients with a deep deltoid rupture (n = 13) was 6.6 +/- 2.4 mm (range, 4 to 12 mm), and in patients without a deep deltoid rupture (n = 26), it was 4.0 +/- 1.0 mm (range, 2.5 to 6 mm) (P =.002, 2-sample t test). At an injury medial clear space > or =3 mm, the false positive rate for deltoid rupture was 88.5% (P =.54, Fisher's exact test). At > or =4 mm, the false positive rate was 53.6% (P =.007). All fractures were rotational injuries according to the Lauge-Hansen system. Three fractures were not classifiable; another 3 fractures showed deltoid ligament integrity opposite the expected finding. The results indicate that, in isolated displaced fractures of the lateral malleolus, radiographic widening of the medial clear space is not a reliable indicator for deep deltoid rupture. Some fractures considered stable by the Lauge-Hansen classification may require careful scrutiny to rule out deep deltoid injury.     

旋后-外旋型踝关节骨折中三角韧带断裂的诊断与治疗

旋后-外旋型或Weber B型踝关节骨折存在稳定型和不稳定型骨折。不稳定性骨折通常在腓骨骨折的同时存在内踝的骨折或三角韧带的撕裂。现在的共识是对于不稳定型的踝关节骨折,采取切开复位内固定的方式能达到较好的临床疗效。对于内侧韧带撕裂的诊断有很多研究,但对于评估内侧韧带撕裂的最合适方法仍未达成共识。由于外旋引起的三角韧带断裂的患者数量要远比过去想象中的多。在Lauge-Hansen分型中,根据损伤的机制可以提供可能的韧带损伤的信息。通过X线的表现,运用Lauge-Hansen分型系统在评估三角韧带是否损伤具有重要的价值,但其敏感性和特异性有待考究。体格检查、应力位X线片、MRI、关节镜、B超现在已用于踝关节骨折中内侧副韧带的完整的评估,但是这些方法没有一种是便宜、简便、可靠的。现在临床医师习惯使用重力应力试验进行评估,对于可疑的病例,行关节镜探查是非常有价值的。最新的观点认为单纯腓骨骨折,可仅行腓骨骨折切开复位内固定术,对合并外踝骨折的三角韧带撕裂进行修复是没有意义的,也没有证据证明暴露并修复三角韧带对内踝结构有影响。     

Biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation: A finite element analysis

ObjectiveTo determine the biomechanical effect of anterior talofibular ligament injury in Weber B lateral malleolus fractures after lateral plate fixation.MethodA three-dimensional model was established based on CT images from a healthy volunteer. The simulation of lateral malleolus fracture, and the modeling and assembly of plate were completed by referring to characteristics of Weber B lateral malleolus fractures, as well as the technical characteristics of open reduction and internal fixation of lateral plate. Operating conditions were set up for groups A−D. The proximal end of the model was restrained in all four groups, 200 N of upward force and 100 N of backward force were applied at anterior of talus head in order to simulate the dorsiflexion of ankle joint. Biomechanical differences of the lateral plate were observed under various conditions of different ligament ruptures.ResultsThe maximum stress value of group A was the smallest, approximately 78.47 N, while that of group C was the largest, approximately 238.83 N. The maximum stress value of group B was about 91.69 N; and that of group D was about 184.08N. Importantly, location of the maximum stress in group D (CUT ATaF) was displaced from the posterior edge to the anterior edge of the plate, which was different from those of the other three groups.ConclusionsThe anterior talofibular ligament injury may be a major contributing factor to the stress of lateral plate fixation following Weber B lateral malleolus fracture. It should be considered as an essential risk factor for evaluation of the stability in these fractures.     

Posterior Malleolus Fracture Displacement Is Associated with Rotational Ankle Fracture Stability in Patients Without Medial Malleolar Fractures

Background

The optimal method for the determination of ankle stability remains controversial in rotational ankle fractures without medial bony injury.

Questions/Purposes

The purposes of this study were to (1) evaluate whether posterior malleolar (PM) fracture displacement is associated with deltoid ligament injury in supination-external rotation (SER) ankle fractures and (2) compare the diagnostic accuracy of PM displacement and magnetic resonance imaging (MRI) evaluation of the deep deltoid ligament in identifying fractures with deltoid ligament incompetence.

Methods

Patients with rotational bimalleolar injuries containing lateral malleolar and PM fractures without bony medial injury were included. After operative lateral and PM fixation, an external rotation stress test was performed to evaluate deltoid ligament stability. Operative dictations were reviewed to confirm injury pattern, stability on stress test, and visual inspection of the deltoid ligament. Maximum PM displacement was assessed on lateral X-ray. Pre-operative MRI of the ankle was performed following closed reduction and splinting.

Results

The final cohort consisted of 13 trimalleolar equivalent fractures (torn deltoid ligament) and 20 bimalleolar fractures (medial malleolus and deltoid ligament intact). Average PM displacement was significantly higher for SER trimalleolar equivalent patterns when measured on lateral X-ray. The sensitivity of detecting trimalleolar equivalent fracture was higher on all reported X-ray findings than the sensitivity obtained by the reported MRI findings of deltoid ligament injury.

Conclusion

PM displacement on X-ray is a useful adjuvant along with external rotation stress radiography and MRI evaluation of deep deltoid integrity to distinguish between stable and unstable fracture patterns and thus helps facilitate treatment decisions.

     

Syndesmotic instability in Weber B ankle fractures: a clinical evaluation

OBJECTIVE: Syndesmotic instability may coexist with unstable Weber B supination-external rotation (SE) lateral malleolar fractures. Current recommendations suggest that Weber B injuries should not have associated syndesmotic instability after open reduction and internal fixation of the lateral malleolus. The purpose of this study was to evaluate syndesmotic stability with respect to the current recommendations for syndesmotic fixation in Weber B SE pattern lateral malleolar fractures. DESIGN: Retrospective cohort, consecutive series. SETTING: Academic Level I trauma center. PATIENTS/PARTICIPANTS: Over a 7-year period, 238 skeletally mature patients with unstable SE pattern Weber B lateral malleolus fractures with deltoid ligament incompetence were evaluated. INTERVENTION: After lateral malleolar fixation, syndesmotic stability was evaluated by an external rotation stress examination under direct vision and fluoroscopy. MAIN OUTCOME MEASURES: The incidence of syndesmotic instability as defined by previously reported criteria. RESULTS: Syndesmotic instability was found in 93 of the 238 (39%) fractures after fixation. Instability was identified in the operating room in 92 of the 93 ankles. One case of instability was missed intraoperatively and diagnosed 2 weeks after surgery. All other patients were followed to union without displacement. CONCLUSIONS: We found syndesmotic instability to be common after anatomic and stable bony fixation in unstable Weber B SE pattern lateral malleolar fractures. Previously published criteria for syndesmotic instability based on cadaveric studies are not representative of the clinical situation. Syndesmotic instability in conjunction with unstable Weber B SE pattern lateral malleolar fractures must be sought out in the operating room with an intraoperative stress examination.     

Ultrasonographic examination of the deltoid ligament in bimalleolar equivalent fractures

BACKGROUND: Lauge-Hansen supination-external rotation Stage IV ankle injuries may simulate a Stage II or Stage III injury radiographically if the medial disruption occurred through the deltoid ligament instead of the medial malleolus, making it difficult to determine whether an operation is indicated. MATERIALS AND METHODS: Seventeen patients presented with radiographically isolated lateral malleolar fractures at the syndesmotic level. They were examined with ultrasonography for evaluation of the integrity of the deltoid ligament. Patients in whom ultrasonography showed complete rupture of the deltoid ligament received operative fixation of the ankle fracture, with exploration and repair of the deltoid ligament at the same time. Patients without complete rupture of the deltoid ligament were treated conservatively with a short leg cast for 6 weeks followed by an ankle brace for another 6 weeks. Nine male and six female patients completed the final clinical and radiographic evaluations. RESULTS: Ultrasonography showed complete rupture of the deltoid ligament in six patients. Exploration of the deltoid ligaments confirmed the sonographic findings in all these patients. In the remaining nine patients, the deltoid ligaments were not completely ruptured on ultrasound. These fractures were treated conservatively, and all healed uneventfully. All the 15 patients had good or fair results on the final evaluation. CONCLUSION: Ultrasonography is a convenient and accurate diagnostic tool to differentiate unstable bimalleolar-equivalent ankle fractures from an isolated lateral malleolar fracture. Thus, it can be helpful in the decision process for the treatment of choice for different fracture patterns.     

三角韧带损伤在旋后一外旋型踝关节骨折治疗中的意义

背景：旋后-外旋型踝关节骨折临床常见,三角韧带是否损伤是判定损伤严重程度与影响预后的重要因素。同时三角韧带是否修补与如何修补一直是大家争论的问题。目的：探讨三角韧带的解剖与组织特性,探讨损伤之后的诊断与治疗方法。方法：新鲜尸体标本10具,将内踝与距骨内侧结节之间的软组织由浅至深逐层解剖,胫后肌腱深层部分送检,HE染色后显微镜观察。记录2007年1月至2008年12月,旋后-外旋踝关节损伤患者40例的临床资料。结果：位于胫后肌腱深层的软组织,无论大体解剖还是显微结构,均分为两层、表面是胫后肌腱腱鞘鞘膜,深层是位于内踝后丘与距骨结节之间的三角韧带,宽10．8±1．5mm,长10．4±1．9mm,厚6．4±0．5mm。40例患者没有内侧切开处理三角韧带,随访终点结果良好。结论：三角韧带损伤临床常见,建议必要的辅助检查,分清内踝前丘、后丘与三角韧带的损伤情况。选择合适的手术方式,恢复踝关节的稳定性与关节面平整。     

The diagnosis and treatment of deltoid ligament lesions in supination–external rotation ankle fractures: a review

The supination-external rotation or Weber B type fracture exists as a stable and an unstable type. The unstable type has a medial malleolus fracture or deltoid ligament lesion in addition to a fibular fracture. The consensus is the unstable type and best treated by open reduction and internal fixation. The diagnostic process for a medial ligament lesion has been well investigated but there is no consensus as to the best method of assessment. The number of deltoid ruptures as a result of an external rotation mechanism is higher than previously believed. The derivation of the injury mechanism could provide information of the likely ligamentous lesion in several fracture patterns. The use of the Lauge-Hansen classification system in the assessment of the initial X-ray images can be helpful in predicting the involvement of the deltoid ligament but the reliability in terms of sensitivity and specificity is unknown. Clinical examination, stress radiography, magnetic resonance imaging, arthroscopy, and ultrasonography have been used to investigate medial collateral integrity in cases of ankle fractures. None of these has shown to possess the combination of being cost-effective, reliable and easy to use; currently gravity stress radiography is favoured and, in cases of doubt, arthroscopy could be of value. There is a disagreement as to the benefit of repair by suture of the deltoid ligament in cases of an acute rupture in combination with a lateral malleolar fracture. There is no evidence found for suturing but exploration is thought to be beneficial in case of interposition of medial structures.     

Competence of the deltoid ligament in bimalleolar ankle fractures after medial malleolar fixation

BACKGROUND: The stability of the ankle joint is provided by the medial and lateral malleoli and ligaments. Recent studies of cadaveric ankles have demonstrated that injury to the medial structures of the ankle is necessary to allow lateral subluxation of the talus after fracture. However, cadaveric models are limited by the fracture pattern chosen for the model. We sought to investigate the competency of the deltoid ligament in vivo in patients with an operatively treated bimalleolar ankle fracture. METHODS: Twenty-seven patients with a bimalleolar ankle fracture were evaluated. In each patient, the medial malleolus was anatomically reduced and fixed. A radiograph of the ankle was then made with application of an external rotation load to the joint. All lateral malleolar injuries were then reduced and fixed. The radiographs were evaluated for restoration of the competence of the deltoid ligament according to established criteria. RESULTS: Seven (26 percent) of the twenty-seven patients had radiographically evident incompetence of the deltoid ligament after medial malleolar fixation. This finding was associated with a small medial malleolar fragment. CONCLUSIONS: In bimalleolar fractures, the medial injury may be an osseous avulsion, leaving the deltoid intact on the displaced fragment, or it may be a combination of ligamentous and osseous injury with disruption of the deep portion of the deltoid ligament.     

Clinical outcome of primary medial collateral ligament-posteromedial corner repair with or without staged anterior cruciate ligament reconstruction

IntroductionMedial collateral ligament (MCL) is a prime valgus stabilizer of the knee, and MCL tears are currently managed conservatively. However, posteromedial corner (PMC) injury along with MCL tear is not same as isolated MCL tear and the former is more serious injury and requires operative attention. However, literature is scarce about the management and outcome of PMC-MCL tear alongside anterior cruciate ligament (ACL) tear. The purpose of this study is to report the clinical outcome of primary repair of MCL and PMC with or without staged ACL reconstruction.MethodsA retrospective evaluation was performed on patients with MCL-PMC complex injury with ACL tear who underwent primary repair of MCL-PMC tear followed by rehabilitation. Further, several of them chose to undergo ACL reconstruction whereas rest opted conservative treatment for the ACL tear. A total of 35 patients of two groups [Group 1 (n = 15): MCL-PMC repaired and ACL conserved; Group 2 (n = 20): MCL-PMC repaired and ACL reconstructed] met the inclusion criteria with a minimum follow-up of two years. Clinical outcome measures included grade of valgus medial opening (0° extension and 30° flexion), Lysholm and International knee documentation committee (IKDC) scores, KT-1000 measurement, subjective feeling of instability, range of motion (ROM) assessment and complications.ResultsWhile comparing group 2 versus group 1, mean Lysholm (94.6 vs. 91.06; p = 0.017) and IKDC scores (86.3 vs. 77.6; p = 0.011) of group 2 were significantly higher than group 1. 60% patients of group 1 complained of instability against none in the group 2 (p < 0.0001). All the knees of both the groups were valgus stable with none requiring late reconstruction. The mean loss of flexion ROM in group 1 and 2 was 12° and 9° respectively which was not statistically different (p = 0.41). However while considering the loss of motion, two groups did not show any significant difference in clinical scores.ConclusionsPrimary MCL-PMC repair renders the knee stable in coronal plane in both the groups and further ACL reconstruction adds on to the stability of the knee providing a superior clinical outcome. Minor knee stiffness remains a concern after primary MCL-PMC repair but without any unfavorable clinical effect.     

踝关节骨折伴下胫腓联合分离的手术治疗及临床意义

目的探讨治疗踝关节骨折伴下胫腓联合分离的手术方法及临床意义。方法自2002年1月～2005年12月对112例伴踝关节骨折下胫腓联合分离行腓骨内固定或不固定,内踝内固定,三角韧带探查修复术。未固定下胫腓联合。术后随访6～36个月,平均20.8个月。结果用Mazur评分系统评估手术疗效:优98例,良14例。未见骨折不愈合、关节不稳及创伤性关节炎等并发症。结论对伴下胫腓联合分离的踝关节骨折行手术治疗时,除了固定内、外踝,还要修复三角韧带损伤。恢复了内、外侧所有结构的完整性后才能真正恢复下胫腓联合及踝关节的正常生物力学环境和稳定性,这时即使不固定下胫腓联合,也可以获得下胫腓联合的稳定。固定内、外踝和下胫腓联合,而三角韧带的损伤不修复,虽然下胫腓韧带可以获得愈合,但三角韧带会愈合不佳、韧带松弛及功能不良,最终仍会导致创伤性关节炎。     

MRI与术中外旋应力试验在旋后-外旋踝关节骨折中的应用价值比较

背景：旋后-外旋骨折占所有踝关节骨折的40%~75%。其治疗方式的选择主要依赖对内侧结构损伤程度的判断,特别是内侧三角韧带是否有损伤。循证医学的资料表明,术前MR扫描与术中外旋应力试验是判断三角韧带损伤的方法。那么,术前MR扫描是否可以替代术中应力试验,明确三角韧带损伤的情况并指导踝骨折采用保守治疗或手术治疗。本文试图通过手术验证两者的敏感性是否一致。目的：探讨MRI与术中外旋应力试验在判断踝关节旋后-外旋型损伤程度中的应用价值。方法：2008年1月至2012年12月,我院收治的Lauge-Hansen分型旋后-外旋型踝关节骨折患者,共计30例,术前常规行X线、MR扫描,记录踝关节内侧三角韧带损伤情况。麻醉后行踝关节外旋应力位摄片,依据踝关节内侧间隙是否正常判定三角韧带损伤情况。再比较外旋应力试验与MR结果。结果：MR扫描对三角韧带损伤情况判定,等同于术中外旋应力试验。结论：MRI对于判断三角韧带是否损伤有一定价值,可以指导旋后-外旋型踝关节骨折不同程度损伤的鉴别与治疗方法的选择。     

Compatibility of Lauge-Hansen Classification Between Plain Radiographs and Magnetic Resonance Imaging in Ankle Fractures

We evaluated the accuracy of the predictive injury sequences of the Lauge-Hansen (L-H) classification using magnetic resonance imaging (MRI) in patients with ankle fractures and determined the possible causes of mismatch. Sixty-five patients with ankle fractures who had a complete series of anteroposterior, lateral, and oblique radiographs and ankle MRI studies available were included. The fracture pattern was assigned by 2 senior orthopedic surgeons according to the L-H classification system. The syndesmotic ligaments, lateral collateral ligaments, and medial deltoid complex ligaments were evaluated on the preoperative MRI scans. Comparisons were performed between the predicted ankle ligamentous injury based on the radiographic L-H classification and preoperative MRI analysis. Of the 65 feet in 65 patients, 50 feet (76.9%) were classified as having a supination-external rotation (SER) fracture, 6 feet (9.2%) as having a pronation-external rotation fracture, 4 feet (6.2%) as having a supination adduction fracture, and 2 feet (3.1%) as having a pronation abduction fracture. The overall compatibility of the radiologic classification with the MRI classification was 66.1%. In the evaluation of 50 feet with the MRI SER designation, maximum compatibility was found for stage 4 (77.3%). The main cause for the discrepancy in the SER designation was missing the presence of deltoid ligament disruption on the plain radiographs, especially in the stage 2 and 3 SER fracture pattern. In the evaluation of deltoid complex injuries, all injuries were localized to the anterior part of the medial deltoid complex. The validity of the L-H classification system was low. A new classification system is needed to address the medial malleolus fracture or deltoid complex injuries without posterior injury. Also, stress radiographs could be added to standard radiographs for the classification to address deltoid complex injuries.     

三角韧带损伤的手术治疗

[目的]探讨踝关节三角韧带损伤的手术治疗及效果。[方法]2002年4月-2005年4月治疗伴有三角韧带损伤的踝关节骨折40例，均采用切开复位和坚强内固定，并修复重建三角韧带，恢复踝关节内外侧结构的稳定性。下胫腓联合分离仍不稳定者，给予皮质骨螺钉横向内固定。[结果]全部病例得到16个月-3a随访，平均1．5a。按齐氏疗效评定标准：优良30例，可8例，差2例，优良率75％。[结论]强调踝关节骨折切开解剖复位，坚强内固定的同时，应充分重视修复重建三角韧带。     

Anterior-inferior tibiofibular ligament anatomical repair and augmentation versus trans-syndesmosis screw fixation for the syndesmotic instability in external-rotation type ankle fracture with posterior malleolus involvement: A prospective and comparative study

PurposeSyndesmosis injury is common in external-rotation type ankle fractures (ERAF). Trans-syndesmosis screw fixation, the gold-standard treatment, is currently controversial for its complications and biomechanical disadvantages. The purpose of this study was to introduce a new method of anatomically repairing the anterior-inferior tibiofibular ligament (AITFL) and augmentation with anchor rope system to treat the syndesmotic instability in ERAF with posterior malleolus involvement and to compare its clinical outcomes with that of trans-syndesmosis screw fixation.Methods53 ERAFs with posterior malleolus involvement received surgery, and the syndesmosis was still unstable after fracture fixation. They were randomised into screw fixation group and AITFL anatomical repair with augmentation group. Reduction quality, syndesmosis diastasis recurrence, pain (VAS score), time back to work, Olerud–Molander ankle score and range of motion (ROM) of ankle were investigated.ResultsOlerud–Molander score in AITFL repair group and screw group was 90.4 and 85.8 at 12-month follow-up (P > 0.05). Plantar flexion was 31.2° and 34.3° in repair and screw groups (P = 0.04). Mal-reduction happened in 5 cases (19.2%) in screw group while 2 cases (7.4%) in repair group. Postoperative syndesmosis re-diastasis occurred in 3 cases in screw group while zero in repair group (P > 0.05). Pain score was similar between the two groups (P > 0.05). Overall complication rate and back to work time were 26.9% and 3.7% (P = 0.04), 7.15 months and 5.26 months (P = 0.02) in screw group and repair group, respectively.ConclusionsFor syndesmotic instability in ERAF with posterior malleolus involvement, the method of AITFL anatomical repair and augmentation with anchor rope system had an equivalent functional outcome and reduction, earlier rehabilitation and less complication compared with screw fixation. It can be selected as an alternative.     

An anatomical study about the arthroscopic repair of the lateral ligament of the ankle

Background

The purpose of this anatomical study to was to determine the relationship of the structures involved in the arthroscopic repair of the anterior talofibular ligament.

Deltoid ligament injuries: diagnosis and management

The medial ligaments of the ankle are injured more often than generally believed. Complete deltoid ligament tears are occasionally seen in association with lateral malleolar fractures or bimalleolar fractures. Chronic deltoid ligament insufficiency can be seen in several conditions, including posterior tibial tendon disorder, trauma- and sports-related deltoid disruptions, and valgus talar tilting in patients who have a history of triple arthrodesis or total ankle arthroplasty. This article focuses on the anatomy and function of the medial ligaments of the ankle and establishes a rationale for the diagnosis and treatment of incompetent deltoid ligament.     

Ankle fractures resulting from rotational injuries

Ankle fractures are among the most common skeletal injuries; selection of an optimal management method depends on ankle stability. Stable fractures (eg, isolated lateral malleolar) generally are managed nonsurgically; unstable fractures (eg, bimalleolar, bimalleolar equivalent) usually are managed with open reduction and internal fixation. Stress radiographs may aid in the management of incomplete deltoid injury in which there is medial swelling and tenderness without radiographic talar shift. A posterior malleolar fracture should be reduced and stabilized if it comprises >30% of the articular surface and remains displaced after fibular stabilization. Ankle fractures with syndesmotic injury have additional tibiofibular instability that can be controlled by screw fixation. However, the choice between metal and bioabsorbable screws, screw size, number of cortices fixed, and indications for screw removal remain controversial. Conditions such as diabetes or advanced age are no longer contraindications to usual management recommendations.     

Nonunion of a medial malleolar stress fracture in an adolescent athlete secondary to lateral ankle instability: A case report

IntroductionMedial malleolar stress fractures are relatively uncommon. This report describes the successful treatment of nonunion of a medial malleolar stress fracture due to chronic lateral ankle instability.Presentation of caseA 13-year-old middle school student who belonged to a football club presented to our clinic with chronic medial left ankle pain lasting over a year. He had sprained his left ankle several times 6 years earlier. A plain anteroposterior ankle radiograph showed a vertical fracture line in the medial malleolus involving the epiphyseal plate, and computed tomography demonstrated the vertical fracture seen on the plain radiographs and bone sclerosis at the fracture site. We performed internal fixation for nonunion of the medial malleolar stress fracture with arthroscopic modified Broström for lateral ankle instability. Two years after surgery, the Self-Administered Foot Evaluation Questionnaire improved in all parameters, and both the anterior drawer and varus stress tests were negative.DiscussionEarly diagnosis of medial malleolar stress fracture is important for a rapid return to sports. Magnetic resonance imaging is helpful for early diagnosis. Because lateral ankle instability can cause medial malleolar stress fracture, arthroscopic modified Broström procedure is meaningful for medial malleolar stress fracture with lateral ankle instability.ConclusionInternal fixation and the arthroscopic modified Broström procedure could achieve good clinical outcomes for medial malleolar stress fractures with lateral ankle instability.