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Erysipelas is the most common bacterial dermal-hypodermal acute not necrotizing infection [1,2]. Its evolution is usually mild but can be complicated mainly by local abscess or necrosis [3-7]. In this context osteo-articular complications and septic acute tenosynovitis are rarely described in the literature with a rate of 1.2% [3]. We report in the light of a literature review a case of recurrent erysipelas of the leg in a young patient of 29 years complicated by septic acute tenosynovitis of the flexor hallucis longus (FHL), to remind this complication mainly observed in severe forms of erysipelas which is not the case of our patient.

Background: Length of flexor hallucis longus (FHL), localisation of master knot of Henry (MKH) and relationship between MKH and neurovascular bundle are essential for the achievement of FHL tendon transfer. The purpose of this study is to define the localisation of MKH in reference to bony landmarks of the foot, its relationship to plantar neurovascular bundle and to investigate in situ and ex vivo length of FHL tendon in single incision, double incision and minimally invasive techniques. Materials and methods: Foot length was examined in 62 feet of 31 soft cadavers (9 males, 22 females). Various parameters including the relationship between MKH and neurovascular bundle, the distances from MKH to medial malleolus (MM), navicular tuberosity (NT) and the first interphalangeal joint of great toe (IP) were measured. Surface localisation of MKH in relation to a line joining the medial end of plantar flexion crease at the base of great toes (MC) to NT (MC-NT line) was determined. Lengths of FHL tendon graft from three surgical techniques were examined. In situ length was measured in the plantar surface of foot and ex vivo length was measured after tendon was cut from its insertion. Results: The mean length of foot was 230.98 ± 15.35 mm with a statistically significant difference between genders in both sides (p < 0.05). No distance was found between medial plantar neurovascular bundle (MPNVB) and MKH. Mean distance of 17.13 ± 3.55 mm was found between lateral plantar neurovascular bundle (LPNVB) and MKH. MKH was located at a mean distance of 117.11 ± 1.00 mm proximal to IP, 26.28 ± 4.75 mm under NT and 59.58 ± 7.51 mm distal to MM with a statistically significant difference of MKH-IP distance between genders in both sides and MKH-NT in right side. MKH was located anterior to NT (66.1%), at NT (27.4%) and posterior to NT (6.5%) on the MC-NT line. Surface localisation of MKH was 94.75 ± 8.43% of MC-NT line from MC with a perpendicular distance of 25.11 ± 5.37 mm below MC-NT line. The in situ and ex vivo tendon lengths from MTJ to ST, to MKH and to IP were 39.05 ± 10.88 mm and 34.43 ± 10.23 mm, 73.45 ± 9.91 mm and 68.63 ± 9.43 mm, 197.98 ± 13.89 and 191.79 ± 14.00 mm, respectively. A statistically significant difference between genders was found in MTJ-IP of in situ and ex vivo length of both sides (p < 0.05). The mean length of tendon between in situ and ex vivo was significantly different in all techniques (p < 0.05). A moderate positive correlation between foot length and tendon length was found in MTJ-IP of both in situ and ex vivo tendon length. Conclusions: A statistically significant difference between in situ and ex vivo tendon length was shown in all harvesting techniques. Surface location of MKH was approximately at 95% of MC-NT line from MC with a perpendicular distance of 25 mm from MC-NT line.

This article offers an overview of os trigonum syndrome, complications, operative techniques, and the authors' preferred protocol. Os trigonum is an ossicle like many other ossicles in the foot and ankle. Individuals who require repetitive plantarflexion of the ankle for activity may develop symptoms of an enlarged os trigonum. Usually, symptoms will be isolated to the posteriolateral aspect of the ankle. Because of the normal anatomic route of the flexor hallucis longus tendon, its range of motion may also elicit pain to the posterolateral ankle. Conservative, as well as surgical including both endoscopic and open excision, has been described.

Long-segment disease involving the insertional region of the Achilles tendon can be a challenging problem. These patients often have significant disability and functional problems. Surgical management requires some type of tissue replacement, regional tissue rearrangement or tendon transfer. Various types of allograft tissue as well as synthetic materials have been described. Patients often have residual weakness and functional deficits following surgery. We have utilized an Achilles tendon-bone block allograft in combination with a flexor hallucis longus tendon transfer for long-segment Achilles tendon deficits involving the insertion. A retrospective review was performed on this group of patients to assess complication rates. A chart review was performed on 14 patients who underwent this procedure. The average postoperative follow-up duration was 24.7 months (range 6-48). Postoperatively, all patients exhibited grade 5 muscle strength with manual muscle testing and 12 of 14 patients were able to perform a single limb heel rise. This case series reviews the surgical technique as well as the patient demographics and complication rates. This procedure has been reliable for those patients with long-segment Achilles tendon deficits involving the insertion who desire to resume a high demand occupation or active lifestyle. The complication rate is relatively low.

The rupture of the Achilles tendon (AT) usually occurs in high-caliber athletes, but low-demand patients are also are risk, mainly if they are under corticoids or quinolones. The diagnosis of the AT rupture is usually neglected, and this could result in a worse prognosis for the patient if not treated in an appropriate time. For these patients or for those with high surgical risk, an option of minimally invasive surgery remains attractive. Classical techniques consist of direct repair or augmentation with the tendon of the flexor hallucis longus as well as nonanatomical tendon transfers which can generate issues with the donor site. We present a pioneering technique that is analogous to that used for the surgical treatment of distal rupture of the biceps tendon, which consist of a transfer technique of flexor hallucis longus by extracortical fixation interference screw associated to a direct tendon reinsertion performed through a bone tunnel on the superior and posterior aspect of the calcaneus using an extracortical drilling system and an interference screw within the calcaneal tunnel. The arthroscopic approach may be technically challenging, and a high-level of arthroscopic skills are required to complete the procedure but after a learning curve it represents a feasible a safe technique. Levels of Evidence:Therapeutic, Level IX: Evidence from opinion of authorities and/or reports of expert committee

Background It was hypnotized that presence and larger size of os trigonum (OT) can affect flexor hallucis longus tendon (FHL), so tenosynovitis, degeneration and partial tear can be developed. Methods A total of 98 (Study group: 50, Control: 48) subjects included to study and compered status of FHL lesions. Sagittal length and axial width of OT were measured on MRI to determine effect of OT on FHL lesions and correlated with arthroscopic findings. Results FHL tenosynovitis (p: 0,025), degeneration (p: 0,01) and partial tear (p: 0.008) was identified statistically high in study group. Statistical analysis revealed that as length of OT increased, frequency of degeneration (p: 0.03) and partial tear (p: 0.00) of FHL increased. Conclusion Analyzes were showed that the presence of os trigonum had an important role on the FHL pathologies. Additional finding of study was to demonstrate that possibility of FHL lesion increased as length of OT extended. Levels of Evidence Level 3

Background: Flexor hallucis longus tendon transfer (FHL) with a cortical button tension slide is an innovative addition that has not been measured against traditional methods. Methods: 12 pairs (n=24) of fresh-frozen cadaveric tibia-to-toe samples were used and randomized to receive one of the operative FHL techniques. Specimens underwent bone density analysis. Biomechanical loading was applied between 20 and 60 N at 1 Hz for 100 cycles. Post–cyclic load to failure occurred at 1.25 mm/s. Cyclic displacement, structural stiffness, and ultimate load were derived from load-displacement curves. Student t tests evaluated significant effects between both FHL techniques. Linear regression analysis assessed interactions between bone density and strength of FHL technique. Results: Average tendon diameter was 5.44±0.46 mm. Average bone density was 1.06±0.08 g/cm2. Addition of a cortical button to FHL transfer did not significantly affect cyclic displacement (0.78±0.52 mm vs 0.87±0.80 mm) or structural stiffness (162.11±43.34 N/mm vs 167.57±49.19 N/mm). Cortical button addition to FHL transfer resulted in significantly increased ultimate load (343.72±68.93 N) compared with interference screw alone (255.62±77.17 N) ( P = .0002). Linear regression analyses did not reveal any significant interactions between bone density and FHL tendon transfer technique. Conclusion: Enhanced strength can be achieved with FHL tendon transfer to calcaneus using an interference screw and cortical button tension slide technique as compared to an interference screw alone. Cortical buttons in the setting of FHL tendon transfer to the calcaneus offers an additional level of support. Clinical Relevance: Operative cases presenting with poor bone quality due to osteoporosis or osteopenia could benefit from cortical button fixation during FHL transfer. Clinical studies are needed to determine if the increased construct stability conferred from the additional use of a flip button results in fewer FHL transfer failures or better clinical outcomes. Level of Evidence: Level V, Controlled Laboratory Study.

Flexor hallucis longus transfer is routinely used as a technique to salvage a chronic or neglected Achilles tendon rupture. The single-incision (or short harvest) technique provides adequate graft suitable for fixation with interference screws. We have used a bore corer instead of a drill to establish the tendon tunnel and at the same time use the harvested autograft for interference fit and avoid the use of screws, providing what we consider to be a more biologic form of fixation.

Functional Hallux Limitus is the expression of the gliding restraint of the Flexor Hallucis Longus (Fhl) tendon, resulting in several painful syndromes. This impingement is located along the tract of the Fhl tendon at the level of its retrotalar tunnel sealed posteriorly by a fibrous pulley. This pulley, although poorly anatomically characterized, has been arthroscopically proven that its presence or resection plays a pivotal clinical role in the biomechanics of the lower leg, being the main restraint to the physiological movement of the Fhl tendon. The aim of our study was to identify and characterize this anatomical structure. Eleven cadaveric lower legs were initially assessed by computer tomography (CT) imaging, subsequently plastinated, dissected and histologically evaluated by use of Mayer's and Hematoxylin stain. We have shown that the retrotalar pulley of the Fhl shares the same histological characteristics with the retinaculum of the long fibularis muscle and the retinaculum of flexor digitorum muscle, thus it constitutes a different entity than the adjacent formations.

Background: Use of the flexor hallucis longus (FHL) tendon is well described for several tendon augmentation procedures. Harvesting the FHL through an open medial approach is commonly done, but is associated with anatomic risks. Recently, several authors have described a minimally invasive (MI) technique to harvest the FHL tendon utilizing a hamstring tendon stripper commonly used in ACL reconstruction. The purpose of this study was to evaluate the safety and effectiveness of harvesting the FHL tendon using this novel minimally invasive retrograde approach. Methods: The FHL tendon was harvested through a transverse plantar incision over the interphalangeal joint of the great toe in 10 fresh-frozen cadaver lower extremities. A lateral-based incision for peroneal tendon repair was made and the FHL was retrieved. Tendon length, complications, and interconnections between the FHL and flexor digitorum longus (FDL) were recorded and classified. The specimens were then dissected by a single surgeon in a standardized fashion, and damage to any surrounding structures was recorded. Results: The average length of the FHL tendon from the distal stump to the first intertendinous connection was 13.3 cm (range 8.8-16 cm, SD 2.3 cm). Eight cadavers demonstrated Plaass type 1 interconnections whereas 2 demonstrated type 3. There was no injury to the medial and lateral plantar arteries and nerves, plantar plate, or FDL tendons. One FHL tendon was amputated at the level of the sustentaculum during graft harvest. No injury of the medial neurovascular structures occurred with retrieval of the FHL tendon through the lateral incision. Conclusions: We found that care must be taken when approaching the sustentaculum with the tendon harvester in order to avoid amputation of the graft against a hard bony endpoint. Additionally, flexion and extension of the lesser toes could aid in successful tendon harvest when tendon interconnections were encountered. Clinical Relevance: Using this MI technique appears to be a safe and effective way to obtain a long FHL tendon graft for tissue augmentation.

A 44-year-old woman with a history of an open ganglionectomy 2 years prior presented with a recurrent ganglion cyst. The ganglion cyst, extending from the flexor hallucis longus tendon sheath, was confirmed with magnetic resonance imaging. The patient declined another surgical incision. An experimental procedure was performed: ultrasound-guided ganglionectomy using a coablation wand. She achieved full symptom resolution, with no recurrence 1 year afterwards. To our knowledge, this is the first case report in the literature describing the use of this instrument for treating a ganglion cyst.

Achilles tendon rupture is a common athletic injury that results in a painful and antalgic gait. Flexor hallucis longus tendon transfer through arthroscopic, single-incision, or double-incision techniques is used as a treatment approach to address this rupture; however, no studies have compared postoperative complications between these three techniques. A systematic search of published articles was conducted using keywords “Achilles rupture,” “flexor hallucis tendon,” “transfer,” and “recovery.” Articles were then selected based on their title, abstract, and content following full-text review. From each article's reported surgical outcomes, a comparison was made between arthroscopic and single- and double-incision postoperative complications using a χ2 test with significance set at a value of P < .05 followed by post hoc analysis. The arthroscopic approach maintained the lowest rate of postoperative complications, followed by the single- and double-incision techniques. A significant difference in the number of postoperative complications was found between all incisional approaches. The pairwise comparisons, however, could not identify which incisional approaches significantly differed between each other. A reduction in postoperative complications places arthroscopy and the single-incision techniques as the preferred approaches for flexor hallucis longus tendon transfer following an Achilles tendon rupture. Although current literature shows arthroscopy to be superior to single- and double-incision methods, this review demonstrates the need for a greater number of published cases using arthroscopy to establish significance regarding postoperative complications.

Sprains are the most common injury of the ankle joint and the most common traumatic injury of the musculoskeletal system. Ultrasound (US) examination of the posterior ankle joint is a challenge for the examiner. This paper focuses on this difficult area and provides guidance on how to effectively perform US examination of the posterior ankle.

Background Insertional Achilles tendinopathy is a common complaint among patients. Oftentimes, conservative treatment is inadequate, and surgical treatment is required. However, there is no published consensus regarding surgical intervention in reference to insertional Achilles tendinopathy. Methods The purpose of this systematic review was to evaluate the surgical management of insertional Achilles tendinopathy and report which surgical procedures provide the greatest pain reduction and improvement in functional outcome. A review of PubMed, OVID, Google Scholar, and Cochrane Controlled Trials Register was performed using a defined search strategy and inclusion criteria. Results Of 2,863 articles identified using the defined strategy, 20 met the inclusion criteria (three prospective and 17 retrospective). Operative interventions included Achilles tendon debridement, reattachment with suture anchors, reconstruction with flexor hallucis longus tendon autograft or bone-patellar tendon autograft, and gastrocnemius recession. All of the studies, regardless of intervention, showed generalized improvement after surgery. Wide variation in outcome scoring systems prevented direct comparison between studies and interventions. Conclusions This systematic review did not identify a superior treatment for insertional Achilles tendinopathy but rather found that the surgical treatment should be based on the extent of tendon injury.

CASE An otherwise healthy 13-year-old girl presented with a firm nodule on the plantar right forefoot that was tender after cheerleading. Initial workup was unremarkable, but magnetic resonance imaging revealed a multilobulated mass surrounding the flexor hallucis longus tendon. Surgical resection revealed a tenosynovial mass without tendon infiltration. Pathologic examination was consistent with tenosynovial giant cell tumor. The patient resumed cheerleading and remained asymptomatic after 1 year. CONCLUSION As far as we know, this is the first report of a tenosynovial giant cell tumor of the flexor hallucis longus in a pediatric patient; it illustrates the importance of considering this lesion when diagnosing a pediatric plantar mass.

Checkrein deformity is an uncommon disease with a well-described etiology. It is characterized by a dynamic deformity of the hallux or great toe. We report two cases of checkrein deformity due a fibular graft harvesting in two patients with a mandibular bone defect secondary to an oral cancer treatment. We report two young patients with mandibular cancers that had been treated several years before our visit and were currently free of disease. The patients had a mandibular bone defect due to the maxillofacial treatment, solved with a free fibular graft. The current complaint was a great toe deformity that caused pain and made them walk with difficulties. Diagnosis was a checkrein deformity, and after a surgical release of the flexor hallucis longus tendon, both cases returned to normal activities with no walking limitations. Our cases highlight that an accurate patient examination is warranted following these reconstructions as many of them can be misdiagnosed, and a relatively simple surgery can improve the patients’ limitations.

Background Corticosteroid injections are used in the conservative treatment of Flexor hallucis longus (FHL) tendinopathy. Studies for imaging guided injection are done, however, the accuracy of blind injection has not yet been studied. Purpose The aim of this study was to determine the accuracy of a blind injection technique into the FHL tendon sheath. Hypothesis We hypothesize that a blind injections technique into the FHL tendon sheath based on clinical examination has a high accuracy. Study design Descriptive cadaveric study. Methods Ten ankles of human cadavers were blindly injected with radiologic contrast mixed with methylene blue into the FHL tendon sheath. After injection, a CT scan of each ankle was performed to evaluate the location of contrast material. CT scans were reviewed by an experienced musculoskeletal radiologist blinded to the procedure. Anatomic dissection was undertaken to assess the location of the injection fluid. Results In nine ankles the radiological contrast was injected in the FHL tendon sheath. In one cadaver there was a technical problem and was therefore excluded. Conclusion This study shows that the FHL tendon sheath can be blindly injected based on only clinical examination with high accuracy. Level of evidence: Descriptive cadaveric study.

Background To evaluate the medium-to-long term clinical outcome of flexor hallucis longus tendon transfer through a single incision in the treatment of chronic Achilles tendon rupture with a defect greater than 5 cm. Methods Clinical data of patients treated with flexor hallucis longus tendon transfer due to chronic Achilles tendon rupture between January 2009 and December 2016 were reviewed retrospectively. All cases were presented with Achilles tendon rupture for more than 4 weeks after injury. The defect of the Achilles tendon was greater than 5 cm after debridement in all patients. Clinical outcomes were assessed with AOFAS Ankle-Hindfoot Scale (AOFAS-AH), Achilles tendon Total Rupture Score (ATRS) and AOFAS Hallux Metatarsophalangeal-lnterphalangeal Scale (AOFAS-HM). Results 18 patients were followed successfully for 24-83 months (mean follow-up time of 43.2 months) and 5 were lost. According to the complete datasets obtained from 18 patients, none of the tendons re-ruptured during the follow-up. The AOFAS-AH and ATRS at last follow-up visit was 94.4 ± 3.2 (87-100) and 89.6 ± 5.9 (72-98) respectively, which revealed statistically significant improvement from the preoperative score of 58.2 ± 6.3 (49-70) and 53.3 ± 7.3(42-68). The AOFAS-HM at last follow-up visit was 90.1 ± 5.2 (77-97). Conclusion The flexor hallucis longus tendon transfer through a single incision is a safe and simple method for chronic Achilles tendon rupture with minimal morbidity and complications.

Flexor hallucis longus tendon release for surgical treatment of functional hallux limitus–associated conditions is described. This release is obtained by arthroscopic correction of the tendon's blockage, which is located at the retrotalar pulley. The procedure restores the ability for dorsiflexion of the first toe in ankle dorsiflexion (positive stretch test result). Such movement was not possible before, causing a modified gait pattern and affecting the biomechanics of the foot and leg. This explains why the procedure creates favorable changes concerning foot dynamics by restoration not only of the normal tendon glide but also of the normal mobility of the subtalar joint.

We report a rare case of massive accumulation of fluid in the flexor hallucis longus tendon sheath with stenosing tenosynovitis and os trigonum. A 34-year-old woman presented to our hospital with pain and swelling in the posteromedial aspect of the left ankle joint after an ankle sprain approximately 8 months earlier. There was tenderness at the posteromedial aspect of the ankle, and the pain worsened on dorsiflexion of the left great toe. Magnetic resonance imaging revealed massive accumulation of fluid around the flexor hallucis longus tendon. We removed the os trigonum, performed tenosynovectomy around the flexor hallucis longus, and released the flexor hallucis longus tendon via posterior arthroscopy using standard posterolateral and posteromedial portals. At 1 week postoperatively, the patient was asymptomatic and able to resume her daily activities. There has been no recurrence of the massive accumulation of fluid around the flexor hallucis longus tendon as of 1 year after the surgery. To our knowledge, this is a rare case report of extreme massive effusion in the flexor hallucis longus tendon sheath with stenosing tenosynovitis and os trigonum treated successfully by removal of the os trigonum, tenosynovectomy around the flexor hallucis longus, and release of the flexor hallucis longus tendon via posterior ankle arthroscopy.

A 65-year-old Japanese man was admitted to our hospital with fever and inflammation of the right ankle. We initiated antibiotics on suspicion of cellulitis. After no clinical improvement, we performed magnetic resonance imaging, which showed a fluid collection in the flexor hallucis longus (FHL) tendon sheath. Synovial fluid analysis revealed monosodium uric crystals. Final diagnosis was FHL tendonitis secondary to gout proven by synovial fluid analysis. To our knowledge, this is the first case report of FHL tendonitis caused by gout. When ankle inflammation is examined in clinical situations, FHL tendonitis caused by gout should be considered.

Chronic lateral ankle pain can have many different etiologies. Peroneal tendon pathology is a major cause. Fissuring and longitudinal splitting of the peroneus brevis and longus tendons have been reported as a common etiology for chronic lateral ankle pain and functional instability. Patients with advanced pathology who have failed both primary repair and anastomosis of peroneus brevis and longus present a surgical challenge, especially in young active patients where the goal is to achieve dynamic stabilization of the ankle and to restore peroneal tendon function. Staged reconstruction using a Hunter rod and the flexor hallucis longus (FHL) tendon has been described as a salvage procedure for treatment of chronic ruptures of both peroneal tendons. The first stage involves debridement of the remaining portion of the peroneal tendons and sheath followed by implantation of a Hunter rod to the insertion of the peroneus brevis. Passive range-of-motion exercises for 3 months are allowed before removal of the Hunter rod. The second stage involves removal of the Hunter rod and transfer of the flexor hallucis longus (FHL) into the newly formed sheath, attaching it to the insertion of the peroneus brevis on the fifth metatarsal base.

Objective: To demonstrate that transfer of the flexor hallucis longus (FHL) through a single access site for Achilles tendinosis provides good results and can allow satisfactory recovery of ankle flexion strength. Methods: This is a case-control study with 28 consecutive patients who underwent surgery for Achilles tendon debridement and FHL transfer between January 2009 and July 2015. The patients’ body mass index (BMI), plantar flexion strength and ankle dorsiflexion strength were assessed using an isokinetic dynamometer (Humac Norm model, CSMi) and the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale. Results: Of the 28 patients, 53.8% were women, and the mean age was 55 years. After a median follow-up of 3.1 years, the plantar flexion strength of the operated ankles was 26.42 Nm (± 2.18), and the dorsiflexion strength was 16 Nm (± 1.99). The final AOFAS score was 85.3 points, with 82.1%of patients achieving good and excellent results. The results showed a significant difference in plantar flexion strength (p=0.0001) between the operated foot and the contralateral foot. No significant difference was found when comparing patients with different BMIs in relation to muscle strength and AOFAS score.Conclusion: FHL transfer surgery using a single posteromedial route for chronic Achilles tendinopathy presents good functional results and is a safe technique with a low complication rate. Level of Evidence III; Therapeutic Studies; Case Control Study.

Aims The traditional transosseus flexor hallucis longus (FHL) tendon transfer for patients with Achilles tendinopathy requires two incisions to harvest a long tendon graft. The use of a bio-tenodesis screw enables a short graft to be used and is less invasive, but lacks supporting evidence about its biomechanical behaviour. We aimed, in this study, to compare the strength of the traditional transosseus tendon-to-tendon fixation with tendon-to-bone fixation using a tenodesis screw, in cyclical loading and ultimate load testing. Materials and Methods Tendon grafts were undertaken in 24 paired lower-leg specimens and randomly assigned in two groups using fixation with a transosseus suture (suture group) or a tenodesis screw (screw group). The biomechanical behaviour was evaluated using cyclical and ultimate loading tests. The Student’s t-test was performed to assess statistically significant differences in bone mineral density (BMD), displacement, the slope of the load-displacement curves, and load to failure. Results The screw group showed less displacement (loosening) during cyclical loading, which was significant during 300, 500, 600, 700, 800, 900, and 1000 cycles (p Conclusion Fixation of the FHL tendon with a tenodesis screw enables a less invasive procedure to be undertaken and shows similar biomechanical behaviour and primary strength compared with fixation using a transosseus suture. Cite this article: Bone Joint J 2018;100-B:1175–81.

Background and Aims: Hallux sesamoid bones forms an integral part of the first metatarsophalangeal joint for stability during weight bearing. Hallux sesamoids are paired bones located on the plantar aspect of the first metatarsal head within the flexor hallucis longus tendon. Hallucal sesamoids vary in shape and size; can be single, double, bipartite and multipartite. Traumatic insult to the hallux sesamoids can lead to fracture & dislocation, while majority of symptomatic hallux sesamoids can be treated non-surgically; certain specific injuries require a high index of suspicion, careful management, and surgical intervention. Hence present study was taken up to know the incidence, presence/absence, number and partition of hallux sesamoid to enlighten the surgeons and radiologists in early diagnosis and treatment of cases presenting with history of trauma, pain and fractures of foot. Methods: Retrospective radiographic study on the incidence, anatomical variants & distribution ofhallux sesamoids inlOOO radiographs ofthe foot. Result: Hallux Sesamoid bones were seen plantar to first metatarsal head in 994 radiographs [99.4%], while the absence ofHallucal sesamoids were noted in 6 radiographs [0.6%], Single Hallucal sesamoid were noted in 9 radiographs [0.9%], medial bipartition was noted in 20 radiographs [2%], lateral bipartition was noted in 15 radiographs [1.5%]. Conclusion: Knowledge regarding hallux sesamoids helps us in differentiating the various conditions arising out of fractures of foot bones with overlapping signs and symptoms, from actual involvement of sesamoid bone itself, which assists in the early diagnosis and management of foot pathologies.

The calcaneus is the most commonly fractured tarsal bone. However, locked fracture-dislocation of the calcaneus is a rare condition because of the bone and ligament stability between the calcaneus, talus, and cuboid. We report the unique features of a case of bilateral fracture-dislocation of the calcaneus, including open fractures, bilateral fibular dislocation, and bilateral interposition of the flexor hallucis longus tendon at the fracture site. A literature review identified only 19 cases of locked fracture-dislocation, but none of these cases involved the combination of injuries observed in this case. Fracture of the calcaneus may be associated with a variety of injuries requiring proper diagnosis and treatment. Level of evidence V; Therapeutic Studies; Expert Opinion.

The purpose of the present study was to quantify the learning curve for arthroscopic os trigonum excision using the log-linear model. Twenty-three consecutive feet underwent arthroscopic os trigonum excision and release of the flexor hallucis longus. The required time from the beginning of shaving of the soft tissue until completion of os trigonum excision and release of the flexor hallucis longus (van Dijk time) was recorded. Regression analysis was applied to predict the required time on the basis of the cumulative case volume after logarithmic transformation of both statistics. The mean required time was 35.2 (range 9 to 90) minutes. After logarithmic transformation, a significant linear correlation was observed between the required time and the cumulative case volume ( p = .0043). The best-fit linear equation was calculated as log (y, estimated required time) = −0.41 log (x, case volume) + 1.86, resulting in an estimated learning rate of 75.3% (= 2 −0.41 ). The results showed an overall time reduction in arthroscopic os trigonum excision in support of a learning curve effect with an ~75% learning rate, indicating that the required time for arthroscopic os trigonum excision can decrease by ≤25% when the cumulative volume of cases has doubled.

Background To describe the clinical and magnetic resonance imaging findings of ganglion cysts with effusion in the flexor hallucis longus tendon sheath around the hallux to evaluate their origin. Methods Patients with recurrent or painful ganglion cysts around the hallux with effusion in the flexor hallucis longus tendon sheath who underwent surgical treatment at St. Vincent's Hospital from February 2007 to August 2016 were investigated. Surgical indication was a painful or recurrent mass caused by the cystic lesions. Those without effusion of the flexor hallucis longus tendon sheath were excluded. We assessed the clinical and magnetic resonance imaging findings. Results Magnetic resonance imaging findings in all patients showed several ganglion cysts around the hallux and large fluid accumulations within the flexor hallucis longus tendon sheath. Regarding the location, six ganglion cysts were on the dorsomedial aspect, one on the plantar medial aspect, seven on the plantar lateral aspect, and one in the toe pulp. Ten patients showed joint effusions in both the metatarsophalangeal and interphalangeal joints, two in the metatarsophalangeal joints, and three in the interphalangeal joints. There were communication stalks with a tail shape or abutment between ganglion cysts with surrounding joint effusions. Intraoperatively, connections between ganglion cysts, the synovial cyst of the flexor hallucis longus tendon sheath, and surrounding joints were seen. Conclusions Synovial fluid accumulation in the metatarsophalangeal or interphalangeal joint supplies the synovial cyst of the flexor hallucis longus tendon sheath and subsequently ganglion cysts in the hallux. In clinical practice, the surgeon should carefully check surrounding joints with tendon sheaths to prevent recurrence of the ganglion cysts around the hallux.

Coalition of the hallux sesamoids is an extremely rare condition. To our knowledge, only 1 case report has been published. We report a case of severe hallux valgus deformities with coalitions of the hallux sesamoids. The coalitions themselves were asymptomatic; however, this severe hallux valgus deformity needed to be surgically treated. The hallux sesamoids in both feet appeared to be fused and heart shaped on anteroposterior radiographs and dumbbell shaped on axial radiographs. It is known that postoperative incomplete reduction of the medial sesamoids can be a risk factor for the recurrence of hallux valgus. The computed tomography scan demonstrated a groove in the bottom of the center of the heart-shaped sesamoid. The flexor hallucis longus tendon was located in the groove. Therefore, a modified Lapidus procedure was performed considering the medial half of the heart-shaped sesamoid as the medial sesamoid. Although delayed union occurred, successful correction of the deformity was achieved. Levels of Evidence: Level IV

Rationale: Acute rupture of the flexor halluces longus (FHL) tendon due to trauma or laceration is a well-known phenomenon. Partial rupture of the FHL tendon caused by tendinitis or stenosing tenosynovitis is common in ballet dancers and athletes. However, atraumatic complete rupture of the FHL is rare: as of 2018, only 7 cases of closed atraumatic complete rupture of the FHL tendon have been reported in the literature. Here, we report on a patient who presented with a closed atraumatic complete rupture of the FHL tendon during a forward lunge exercise. Patient concerns: A 35-year-old female visited the clinic with pain in the plantar medial aspect of the left foot, along with weakness and loss of great toe flexion. The patient had a normal foot structure and no history of trauma or systemic disease. She performed a forward lunge exercise more than 50 times on 1 leg per day, more than once a week to strengthen her leg muscles. She reported that she felt a slight pain in her left, great toe while exercising for 3 weeks prior to her visit. One week prior to presentation, severe pain occurred suddenly when her left hallux dorsiflexed strongly during an anterior lunge exercise motion. Diagnosis: Magnetic resonance imaging revealed complete rupture of the FHL tendon near the level of the metatarsal head and neck junction. The lesion was prolonged, with the proximal end displaced to the metatarsal shaft region. Interventions: Complete rupture of the FHL tendon was treated with a primary suture. Outcomes: At the 1-year follow-up, active plantar flexion of the interphalangeal joint was possible but joint function had a range of 0° to 25°. Flexion strength was reduced slightly, measuring about 70% when compared to the contralateral side, but flexion strength of the metatarsophalangeal joint was normal. Lessons: We describe an extremely rare case of complete rupture of the FHL tendon at the level of metatarsal head and neck junction. It should be understood that this injury can occur not only in professional athletes but also in the general public, and we recommend educating personal trainers on how to prevent it.

Introduction: Achilles tendon ruptures cause significant functional limitations. The treatment for acute injury is controversial; conservative or surgical treatment and open or minimally invasive surgery are available options. The objective of this study is to evaluate the clinical and functional outcomes of patients with acute Achilles tendon rupture treated with minimally invasive tendon repair and augmentation with flexor hallucis longus tendon transfer assisted by posterior ankle arthroscopy. Methods: A retrospective, cross-sectional and observational study in which 5 patients with more than 24 months of postoperative follow-up were evaluated using the American Orthopedic Foot and Ankle Society (AOFAS) score, the Victorian Institute of Sport Assessment-Achilles (VISA-A), the Achilles Tendon Total Rupture Score (ATRS), the pain visual analog scale (VAS), and assessments of range of motion and strength. Results: The mean scores on the following instruments were obtained: pain VAS: 0.6; AOFAS: 98; VISA-A: 98.2 and ATRS: 100. The mean dorsiflexion range of motion was smaller (4.8º) than the contralateral range of motion (7.6º). The mean plantar flexion strength was 24.02 kgf on the operated side and 24.64 kgf on the contralateral side. The flexion strength of the hallux interphalangeal joint was weaker on the operated side (13.94 kgf) than on the contralateral side (17.6 kgf), albeit with no complaints from the patients. Conclusion: The proposed surgical treatment method had good clinical and functional outcomes among the patients evaluated in this study. The surgical technique presented herein may be a good alternative for the treatment of uncooperative patients diagnosed with acute Achilles tendon rupture due to tendinosis with important tendon degeneration.

[Introduction][1] Posterior ankle and hindfoot arthroscopy, performed with use of posteromedial and posterolateral portals with the patient in the prone position, has become an important diagnostic and therapeutic procedure for various intra-articular and extra-articular disorders. [Step 1: Position the Patient Prone][2] If you are planning to use fluoroscopy for surgery and wire distraction, position the patient prone, flex the contralateral knee, and wrap the contralateral leg to a padded holder. ![Figure][3] [Step 2: Apply Distraction If Necessary][4] Invasive distraction is used primarily to improve access to the ankle and subtalar joints. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 3: Place the Posterolateral and Posteromedial Portals Under Fluoroscopic Guidance][5] Using a mini-c-arm fluoroscopy unit to guide portal placement, place the posterolateral and posteromedial portals just lateral and medial to the Achilles tendon. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 4: Perform the Intra-Articular and/or Extra-Articular Procedure][6] Specific procedures include posterior arthroscopic arthrodesis of the subtalar joint, ankle arthrodesis, and excision of the os trigonum with tenolysis of the flexor hallucis longus tendon. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 5: Close the Arthroscopy Portals][7] Close the skin incision with nonabsorbable nylon sutures, and apply a sterile bulky dressing. [Step 6: Postoperative Care][8] Postoperatively, a plaster splint or walking boot with the foot in neutral is used for the first five to seven days. [Results][9] Posterior ankle and hindfoot arthroscopy was performed in 189 ankles (186 consecutive patients with a mean age of 37.1 years). [What to Watch For][10] [Indications][11] [Contraindications][12] [Pitfalls & Challenges][13] [Introduction][1] Posterior ankle and hindfoot arthroscopy, performed with use of posteromedial and posterolateral portals with the patient in the prone position, has become an important diagnostic and therapeutic procedure for various intra-articular and extra-articular disorders. [Step 1: Position the Patient Prone][2] If you are planning to use fluoroscopy for surgery and wire distraction, position the patient prone, flex the contralateral knee, and wrap the contralateral leg to a padded holder. ![Figure][3] [Step 2: Apply Distraction If Necessary][4] Invasive distraction is used primarily to improve access to the ankle and subtalar joints. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 3: Place the Posterolateral and Posteromedial Portals Under Fluoroscopic Guidance][5] Using a mini-c-arm fluoroscopy unit to guide portal placement, place the posterolateral and posteromedial portals just lateral and medial to the Achilles tendon. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 4: Perform the Intra-Articular and/or Extra-Articular Procedure][6] Specific procedures include posterior arthroscopic arthrodesis of the subtalar joint, ankle arthrodesis, and excision of the os trigonum with tenolysis of the flexor hallucis longus tendon. ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] ![Figure][3] [Step 5: Close the Arthroscopy Portals][7] Close the skin incision with nonabsorbable nylon sutures, and apply a sterile bulky dressing. [Step 6: Postoperative Care][8] Postoperatively, a plaster splint or walking boot with the foot in neutral is used for the first five to seven days. [Results][9] Posterior ankle and hindfoot arthroscopy was performed in 189 ankles (186 consecutive patients with a mean age of 37.1 years). [What to Watch For][10] [Indications][11] [Contraindications][12] [Pitfalls & Challenges][13] [1]: #sec-10 [2]: #sec-11 [3]: pending:yes [4]: #sec-12 [5]: #sec-13 [6]: #sec-14 [7]: #sec-19 [8]: #sec-20 [9]: #sec-21 [10]: #sec-22 [11]: #sec-23 [12]: #sec-24 [13]: #sec-25

Background The flexor hallucis longus (FHL) muscle often has a tendinous slip with a variable number of branches. We aimed at developing the FHL branch test to determine the number of FHL branches. Methods In anatomical validation study, 6 intact cadavers were used. The toe flexion angles were measured while the FHL and flexor digitorum longus (FDL) were manually pulled individually. For electrophysiological studies, 4 healthy men participated. The FHL was electrically stimulated, and electromyography (EMG) of the FHL and FDL were recorded during the FHL branch test. Results The toe flexion angles’ changes in the FHL pulling condition were equivalent with pulling FDL in toes with FHL branching. The electrical stimulation of the FHL produced similar flexion as the FHL branch test. EMG of the FHL was higher than FDL during the FHL branch test (p = 0.036). Conclusions The FHL branch test could be used to evaluate the number of FHL branches.

The neglected Achilles tendon rupture requires surgical reconstruction for the best functional outcome. According to the current literature, there are many reconstructive options available that demonstrate acceptable functional results in most cases. These procedures require large incisions, leading to potential wound-healing complications. Therefore, these procedures may not be suitable for patients who are at high risk for wound-healing problems. A minimally invasive approach is desirable in this situation to decrease the risk of this potential complication. Endoscopic transfer of the flexor hallucis longus tendon is described in this series as an alternative to reconstruct the Achilles tendon in 2 such high-risk individuals. Both patients had a successful outcome with no wound-healing problems and regained acceptable functional status.

Isolated rupture of the flexor hallucis longus tendon is an injury rarely reported in literature. In this case report, a 47-year-old female presented 3 months after traumatic injury which resulted in rupture of the flexor hallucis longus. End to end repair was not possible due to substantial gapping provided by proximal retraction of the tendon proximally into the calf and disruption of the fibrous connection of the FHL and FDL. A split flexor digitorum longus tendon transfer was performed to restore function and prevent hyperextension of the hallux and the patient was followed for one year.

An isolated open rupture of the flexor hallucis longus tendon is an uncommon injury. We present a case of a chronic flexor hallucis longus rupture distal to the sesamoid complex in an active 12-year-old male after he stepped on a piece of glass. Surgical repair involved a flexor hallucis longus adhesiotomy and tenoplasty with autogenous peroneus longus tendon graft. We present the operative repair of the flexor hallucis longus tendon to reduce pain, to regain the function and strength of the hallux, to reduce the extension of the distal phalanx and to maintain the longitudinal arch of the foot.

CASE We present 2 cases of Achilles reconstruction using flexor hallucis longus (FHL) tendon transfer for the augmentation of Achilles surgical repair during which the patients were noted to have accessory FHL tendons. Structure identification in the posterior ankle is important because the neurovascular bundle is in close proximity to the FHL; knowledge of the anatomy of variations is helpful, and 2 cases of accessory tendon variation are reported. CONCLUSIONS Achilles tears are typically primarily repaired. Some patients may require augmentation with allograft or autograft transfer of the FHL tendon. Accessory FHL tendons discovered during posterior approach to the Achilles has not been described in the literature.

The aim of this study was to assess the functional outcomes after a combined FHL transfer and a gastrocnemius recession for treatment of chronic ruptures of Achilles tendon with a gap and to investigate the patient's satisfaction about the great toe function after transfer.19 patients with chronic rupture of the Achilles tendon with a gap were treated with a flexor halluces longus tendon transfer combined with a gastrocnemius recession, Clinical diagnosis depends on the presence of gap in the tendon on examination, inability of tip toe walking on the affected side and positive calf-squeeze test, MRI was used to confirm the clinical diagnosis. American Orthopedic FootAnkle Society hind foot score was used for assessment of the results.The AOFAS score improved significantly from a mean of 65 preoperatively to 94 at the last follow up (p0.001), there was no significant difference in the final outcome between patients with FHL tendon weaved through the stump of the Achilles tendon and those with trans osseous tunnels, the mean AOFAS score at the last follow up was 94.2, 93.8 respectively, no patient complained of big toe dysfunction.Management of chronic rupture of the Achilles tendon with a gap with flexor halluces longus tendon transfer combined with a gastrocnemius recession is a safe and reliable method with a significantly improved functional outcome, muscle advancement through gastrocnemius recession decreases the length of the gap without affecting the muscle function, flexor halluces longus tendon transfer doesn't harm the big toe function.

Introduction. Flexor hallucis longus (FHL) tendon transfer to the calcaneus is commonly used in the surgical treatment of chronic Achilles tendinopathy. This study assesses the integrity of FHL tendon biotenodesis screw fixation with respect to 2 variables: incorporation of a terminal whipstitch and tunnel depth. Materials and methods. A total of 60 fresh-frozen cadaver FHL tendons and 28 calcanei were harvested for analysis in 4 sets of fixation constructs; 14 whipstitched tendons were compared against their nonwhipstitched paired tendon via pull-out strength load testing, and 16 tendon pairs were randomized for fixation in either a full-depth tunnel (bicortical) or a 25-mm partial tunnel (unicortical). All comparisons were carried out in native bone and synthetic models. Results. Whipstitched tendons demonstrated significantly stronger mean clinical load (253.68 vs 177.24 N, P = .008) and maximum load to failure (294.31N vs 194.57 N, P = .001) compared with the nonwhipstitched tendons in synthetic bone. There were no statistical differences in mean clinical load (200.96 vs 228.31 N, P = .63) and maximum load to failure (192.69 vs 217.74 N, P = .73) between full and partial tunnel groups. There were no significant differences found in trials carried out in cadaveric bone. Conclusion. Use of a terminal whipstitch achieves greater fixation strength in FHL tendon biotenodesis transfers. Complete and partial tunnel constructs are equivocal in their pull-out strength. Data produced in a homogeneous bone substitute model demonstrate the biomechanical superiority of the whipstitch as well as the noninferiority of the partial tunnel technique. Levels of Evidence: Level IIb

Background: Transfer of a flexor hallucis longus (FHL) tendon can not only reconstruct the Achilles tendon but also provide ischemic tendinous tissues with a rich blood supply to enhance wound healing. This retrospective study aims to investigate clinical outcomes in patients who underwent repair of Kuwada grade IV chronic Achilles tendon rupture with long hallucis longus tendons harvested using a minimally invasive technique. Materials and Methods: 35 patients who were treated for Kuwada grade IV Achilles tendon injuries from July 2006 to June 2011 were included in this retrospective study. The age ranged between 23 and 71 years. The duration from primary injury to surgery ranged from 29 days to 34 months (mean value, 137.6 days). All 35 patients had difficulties in lifting their calves. Thirty two were followed up for a mean 32.2 months (range 18–72 months), whereas three were lost to followup. Magnetic resonance imaging (MRI) showed that the tendon rupture gap ranged from 6.0 to 9.2 cm. During surgery, a 2.0 cm minor incision was made vertically in the medial plantar side of the midfoot, and a 1.5 cm minor transverse incision was made in the plantar side of the interphalangeal articulation of the great toe to harvest the FHL tendon, and the tendon was fixed to the calcaneus with suture anchors. Postoperative appearance and function were evaluated by physiotherapists based American Orthopedic Foot and Ankle Society-ankle and hindfoot score (AOFAS-AH), and Leppilahti Achilles tendon ratings. Results: Results were assessed in 32 patients. Except for one patient who suffered complications because of wound disruption 10 days after the operation, all other patients had primary wound healing, with 28 of 32 able to go up on their toes at last followup. The AOFAS-AH score was increased from preoperative (51.92 ± 7.08) points to (92.56 ± 6.71) points; Leppilahti Achilles tendon score was increased from preoperative (72.56 ± 7.43) to (92.58 ± 5.1). There were statistically significant differences. The result of the total excellent and good rate was 93.8% (30/32). MRI of Achilles tendon showed even signal without evidence of tear or cystic degeneration. Conclusion: Reconstruction of a chronic Achilles tendon rupture with an FHL tendon harvested using a minimally invasive technique showed good outcomes.

Fracture of the posterior process of the talus with concomitant subtalar dislocation is rare; thus, the mechanism of injury, appropriate treatment, and prognosis are unclear. We report the case of a 50-year-old male with a fracture of the posterior process of the talus with concomitant subtalar dislocation that was recognized early and successfully treated operatively.

Background There are various techniques of Achilles tendon (TA) repair and reconstruction in chronic Achilles tear. However, there is no clear consensus on the relevance of one method over the other. The short flexor hallucis longus tendon (FHL) transfer has recently gained popularity because of its same phasic action, ease of harvesting and tensile strength. Methodology Fifteen chronic Achilles tear (>6 weeks) were treated with tendon repair using gastrocnemius advancement flap augmented with FHL transfer. The patients were followed-up at 1.5, 3, 6, 12 and 24 months. The clinical outcome at latest follow-up was evaluated using the American Orthopedic Foot and Ankle Score (AOFAS) and the Achilles Tendon Rupture Score (ATRS). Results The mean age was 43.5 ± 12.4 years and the median time from injury to surgery was 17.13 ± 9.64 weeks. The mean gap between the retracted ends of the ruptured tendon was 5.67 ± 1.63 cm (range 4–10 cm). The mean follow-up was 19.07 ± 3.15 months (range, 13–24 months). The mean AOFAS and ATRS improved from 72.07 ± 8.29 (62–83) to 98.4 ± 2.03 (94–100) and 61.73 ± 8.16 (52–70) to 98 ± 1.85 (94–100) respectively (paired t-test, p-value 0.0001). All patients resumed their pre-injury daily activities, and there was no donor site morbidity. Two patients had sterile serous discharge, and one patient had a staphylococcus infection. These patients responded to debridement with prolonged antibiotic therapy. There were no nerve injuries or re-rupture. Conclusion The functional outcome of chronic Achilles tear treated with gastrocnemius advancement flap augmented with short FHL transfer is rewarding.

Rupture of the flexor hallucis longus (FHL) tendon is a rare condition that can occur with direct or indirect trauma; most of the injuries are complete ruptures resulting from laceration. Endoscopic calcaneoplasty is used for treatment of symptomatic Haglund's deformity, and complications of this procedure are rare. Iatrogenic FHL tendon rupture occurring after endoscopic calcaneoplasty has not been reported previously. This case report presents a rare complication after endoscopic calcaneoplasty and the proper method of treatment.

Background:Operative management of chronic Achilles tendon ruptures is challenging, and numerous techniques have been described. Risk of infection and wound breakdown have been described after open techniques, and minimally invasive methods have been proposed to avoid them. The aim of this study was to describe the clinical and radiological results obtained after endoscopic flexor hallucis longus (FHL) tendon transfer in patients with chronic Achilles tendon rupture.Methods:Between 2012 and 2015, a total of 22 patients were endoscopically treated for chronic Achilles tendon rupture. Mean age was 69 years (range, 59-84 years). Mean follow-up was 30.5 months (range, 18-46 months). Preoperative magnetic resonance imaging (MRI) was obtained and tendon gap measured. An MRI was obtained at 9 to 12 months following surgery to evaluate Achilles tendon changes.Results:Preoperative MRI examination showed a mean tendon gap of 6.3 cm (range, 3-10.7 cm). The MRI control was obtained only in 12 patients, and a normal or close to normal Achilles tendon was observed in all but 1 patient. The mean American Orthopaedic Foot & Ankle Society score increased from 55 preoperatively (range, 26-75) to 91 (range, 74-100) at final follow-up. All patients returned to their daily activities without difficulties. No patients reported complaints or symptomatic deficits of great toe flexion strength. No major complications were encountered.Conclusion:Chronic Achilles tendon ruptures were successfully treated by an all-endoscopic procedure. The endoscopically assisted FHL transfer provided excellent results while benefiting from the minimally invasive procedure advantages. However, it entailed some technical challenges and may not be suitable for less experienced surgeons.Level of Evidence:Level IV, retrospective case series.

Background The transfer of Flexor Hallucis Longus Tendon (FHL) is an established method for the treatment of chronic Achilles tendon ruptures. An extensive examination of power, strength, endurance and complications related to this procedure is presented. Methods 21 patients treated with open FHL transfer for chronic Achilles tendon rupture were studied retrospectively. Medical records were reviewed. The patients were examined with a test battery for triceps surae strength, functional tests and PROMs. Results The median maximal concentric strength was equal,1300 vs 1336 W, comparing affected with unaffected side. The endurance tests showed a larger difference, 219 J vs. 2398 J, respectively. The median AOFAS score was 87. 11 of 21 patients sustained one or more complications; the most common were infection, disturbed wound healing, and clawing of small toes. Conclusions Patients achieve almost normal maximal strength after open FHL transfer, but endurance is notably lower. The complication rate was high. Keywords Chronic Achilles ruptureFHL tendon transferFunctional outcomeComplications