Safety of the neurovascular bundles when performing minimally invasive calcaneal osteotomy: A cadaveric study.

BACKGROUND: Calcaneal osteotomies correct hindfoot deformities and are often performed using a minimally invasive technique. The aim was to compare the safety of three calcaneal osteotomy techniques (oblique, chevron with apex anterior and chevron with apex posterior). METHODS: Each osteotomy technique was performed on five cadavers (n = 15). These were then dissected to identify any injury to the neurovascular bundles. The distance between the burr and these structures was measured. RESULTS: Using the apex posterior technique, the burr was closer to the medial and lateral neurovascular structures, and in one case the sural nerve was injured. There were no neurovascular injuries using the other techniques. CONCLUSIONS: Minimally invasive surgery using a burr is generally a safe, reliable method for performing calcaneal osteotomies. The chevron with apex posterior osteotomy should be performed with caution given the closer relationship between the burr and neurovascular bundles. The other two techniques provide safer alternatives.

A calcaneal tunnel for CFL reconstruction should be directed to the posterior inferior medial edge of the calcaneal tuberosity.

PURPOSE: Anatomical reconstruction of the calcaneofibular ligament (CFL) is a common technique to treat chronic lateral ankle instability. A bone tunnel is used to fix the graft in the calcaneus. The purpose of this study is to provide some recommendations about tunnel entrance and tunnel direction based on anatomical landmarks. METHODS: The study consisted of two parts. The first part assessed the lateral tunnel entrance for location and safety. The second part addressed the tunnel direction and safety upon exiting the calcaneum on the medial side. In the first part, 29 specimens were used to locate the anatomical insertion of the CFL based on the intersection of two lines related to the fibular axis and specific landmarks on the lateral malleolus. In the second part, 22 specimens were dissected to determine the position of the neurovascular structures at risk during tunnel drilling. Therefore, a method based on four imaginary squares using external anatomical landmarks was developed. RESULTS: For the tunnel entrance on the lateral side, the mean distance to the centre of the CFL footprint was 2.8 ± 3.0 mm (0-10.4 mm). The mean distance between both observers was 4.2 ± 3.2 mm (0-10.3 mm). The mean distance to the sural nerve was 1.4 ± 2 mm (0-5.8 mm). The mean distance to the peroneal tendons was 7.3 ± 3.1 mm (1.2-12.4 mm). For the tunnel exit on the medial side, the two anterior squares always contained the neurovascular bundle. A safe zone without important neurovascular structures was found and corresponded to the two posterior squares. CONCLUSION: Lateral landmarks enabled to locate the CFL footprint. Precautions should be taken to protect the nearby sural nerve. A safe zone on the medial side could be determined to guide safe tunnel direction. A calcaneal tunnel should be directed to the posterior inferior medial edge of the calcaneal tuberosity.

Interfascicular septum of the calcaneal tunnel and its relationship with the plantar nerves: A cadaveric study.

The relationship between the plantar nerves and internal fascial structure of the calcaneal tunnel is clinically important to alleviate pain of the sole. The study aimed to investigate the three-dimensional (3D) anatomy of the calcaneal tunnel and its internal fascial septal structure by using microcomputed tomography (mCT) with a phosphotungstic acid preparation, histologic examination, and ultrasound-guided simulation. Twenty-one fixed cadavers and three fresh-frozen cadavers (13 men and 11 women, mean age 82.1 years at death) were used in this study. The 3D images of the calcaneal tunnel harvested by mCT were analyzed in detail. Modified Masson trichrome staining and serial sectional dissection after ultrasound-guided injection were conducted to verify the 3D anatomy. Within the calcaneal tunnel, the interfascicular septum (IFS) commenced proximal to the malleolar-calcaneal line and distal to the bifurcation of the tibial nerve into the plantar nerves. The medial and lateral plantar nerves were separated by the IFS, which divided the calcaneal tunnel into two compartments. The plantar nerves were ramified into two or three branches within each compartment. The IFS terminated around the talocalcaneonavicular joint, and the plantar nerves traveled into the sole. Clinical manipulation of the plantar nerves should be performed in consideration of the fact that they are clearly separated by the IFS. Clin. Anat. 32:877-882, 2019. © 2019 Wiley Periodicals, Inc.

Surgical approaches to the calcaneus and the sural nerve: There is no safe zone.

BACKGROUND: Sural nerve related symptoms following the extensile lateral approach to the calcaneus (ELA) and the sinus tarsi approach (STA) are a known postoperative complication despite awareness of the course the sural nerve. While the main trunk of the sural nerve and its location relative to the approaches have been previously described, the nerve gives rise to lateral calcaneal branches (LCBs) and an anastomotic branch (AB) that may be at risk of injury. The purpose of this study was to describe the course of the sural nerve, its LCBs and the AB in relation to the ELA and STA. METHODS: 17 cadaveric foot specimens were dissected, exposing the sural nerve, the LCBs and the AB. A line representing the ELA and STA incision was then created. It was noted if the line crossed the sural nerve trunk, any of the LCBs, and the AB, and at what distance they were crossed using the distal tip of the fibula as a reference. RESULTS: The sural nerve was identified in all specimens, and the main trunk was noted to cross the path of the ELA in no specimens and the path of the STA in 2 (12%) specimens. At least one LCB of the sural nerve was identified in all specimens. The ELA crossed the path of at least one LCB in 15 specimens (88%). An AB was present in 9 specimens (53%). If an AB was present, this was crossed by the STA in every instance. CONCLUSIONS: The ELA and the STA traverses the path of either the main trunk of the sural nerve, the LCBs, or the AB in the majority of specimens, potentially accounting for the presence of sural nerve postoperative symptoms regardless of the approach used.

Time-Dependent Changes in the Structure of Calcified Fibrocartilage in the Rat Achilles Tendon-Bone Interface With Sciatic Denervation.

The enthesis transmits a physiological load from soft to hard tissue via fibrocartilage. The histological alterations induced by this physiological loading remain unclear. This study was performed to examine the histomorphological alterations in the collagen fiber bundle alignment and depth of collagen interdigitation between the calcified fibrocartilage and the bone. We examined the Achilles enthesis of rats with sciatic denervation to explore the mechanical effects of structural changes in the enthesis. The parallelism of the collagen fiber bundles was significantly reduced 8 weeks after denervation. However, the depth of collagen interdigitation significantly increased at 2 and 4 weeks after denervation and then significantly decreased 8 weeks after denervation. In conclusion, a lack of muscle loading induced structural alterations in the distal calcified fibrocartilage. These findings suggest that while structural changes in the enthesis are necessary for the development of physiological loading, structural deformities are required in the long term. Anat Rec, 300:2166-2174, 2017. © 2017 Wiley Periodicals, Inc.

Medial calcaneal neuropathy: A rare cause of prolonged heel pain.

Pain heel constitutes 15% of foot pain. Pain may be caused by plantar fasciitis, calcaneal fractures, calcaneal apophysitis, heel pad atrophy, inflammatory diseases or related with nerve involvement. Tibial, plantar and/or medial nerve entrapment are the neural causes of pain. Most of the heel soft tissue sensation is provided by medial calcaneal nerve. Diagnosis of heel pain due to neural causes depends on history and a careful examination. Surgery should not be undertaken before excluding other causes of heel pain. Diagnosis should be reconsidered following conservative therapy.

Nerve distributions in insertional Achilles tendinopathy - a comparison of bone, bursae and tendon.

BACKGROUND/AIM: In a condition of pain in the Achilles tendon insertion there are multiple structures involved, such as the Achilles tendon itself, the retrocalcaneal bursa and a bony protrusion at the calcaneal tuberosity called Haglund's deformity. The innervation patterns of these structures are scarcely described, and the subcutaneous calcaneal bursa is traditionally not considered to be involved in the pathology. This study aimed at describing the innervation patterns of the four structures described above to provide a better understanding of possible origins of pain at the Achilles tendon insertion. METHODS: Biopsies were taken from 10 patients with insertional Achilles tendinopathy, which had pathological changes in the subcutaneous and retrocalcaneal bursae, a Haglund deformity and Achilles tendon tendinopathy as verified by ultrasound. The biopsies were stained using immunohistochemistry in order to delineate the innervation patterns in the structures involved in insertional Achilles tendinopathy. RESULTS: Immunohistochemical examinations found that the subcutaneous bursa scored the highest using a semi-quantitative evaluation of the degree of innervation when compared to the retrocalcaneal bursa, the Achilles tendon, and the calcaneal bone. CONCLUSIONS: These findings suggest that the subcutaneous bursa, which is traditionally not included in surgical treatment, may be a clinically important factor in insertional Achilles tendinopathy.

An Anatomic Study of the Percutaneous Endoscopically Assisted Calcaneal Osteotomy Technique to Correct Hindfoot Malalignment.

BACKGROUND: Open calcaneal osteotomy using traditional methods is associated with complications such as sural nerve injury and potential wound healing problems. We hypothesized that by using novel minimally invasive techniques, these potential risks could be mitigated. This anatomic cadaveric study serves to assess the safety of percutaneous endoscopically assisted calcaneal osteotomy (PECO) compared to a traditional open osteotomy technique. METHODS: Anatomic safety of PECO was assessed using 8 fresh-frozen cadaver below-knee specimens. Lateral calcaneal nerve (LCN) damage was primarily noted and then secondly compared to a potential open surgical incision approach. RESULTS: Only 1 of 11 LCN branches (n = 8 limbs) was transected using PECO, compared to up to 8 of 10 LCN branches (n = 6 limbs) that potentially would have been injured during open surgery. CONCLUSIONS: Percutaneous endoscopically assisted calcaneal osteotomy is a minimally invasive technique that had fewer nerve injuries in this cadaveric model than traditional open surgery. CLINICAL RELEVANCE: Percutaneous endoscopically assisted calcaneal osteotomy due to its less invasive nature may result in fewer neurovascular injuries relative to an open procedure.

Safe Zone for Neural Structures in Medial Displacement Calcaneal Osteotomy: A Cadaveric and Radiographic Investigation.

BACKGROUND: We aimed to define reference lines on standard lateral ankle radiographs that could be used intraoperatively to minimize iatrogenic nerve injury risk in medial displacement calcaneal osteotomy. METHODS: Forty cadaveric specimens were used. In 20 specimens, the sural, medial plantar (MP), and lateral plantar (LP) nerves were sutured to radiopaque wire, and a lateral ankle radiograph was obtained. On the radiograph, a line was drawn from the posterior superior apex of the calcaneal tuberosity to the origin of the plantar fascia and labeled as the "landmark line." A parallel line was drawn 2 mm posterior to the most posterior nerve, and the area between these lines was defined as the safe zone. In 20 additional specimens, an osteotomy was performed 1 cm anterior to the landmark line using a percutaneous or open technique. Dissection was performed to assess for laceration of the sural, MP, LP, medial calcaneal (MC), or lateral calcaneal (LC) nerves. RESULTS: The safe zone was determined to be within the area 11.2 ± 2.7 mm anterior to the landmark line. After open osteotomy, lacerations were found in 3 of 10 MC nerves and 3 of 10 LC nerves. After percutaneous osteotomy, lacerations were found in 2 of 10 MC nerves and 1 of 10 LC nerves. No lacerations of the sural, MP, or LP nerves were found with either osteotomy. CONCLUSIONS: The safe zone extended 11.2 ± 2.7 mm anterior to the described landmark line. The MC and LC nerves were always at risk during medial displacement calcaneal osteotomy. CLINICAL RELEVANCE: Nerve injury to both major and minor sensory nerves is likely underrecognized as a source of morbidity after calcaneal osteotomy. The current study provides a ready intraoperative guideline for minimizing this risk.

Anatomic structures at risk: curved hindfoot arthrodesis nail--a cadaveric approach.

Retrograde intramedullary nailing of the hindfoot and ankle is an established procedure for salvage of severe foot and ankle deformity, arthritis, tumor, and instability. In the present study, retrograde hindfoot (tibiotalocalcaneal) arthrodesis nailing was performed using a standardized technique on 7 cadaver specimens by trained senior surgeons. The specimens were then dissected to determine the distance of the subcalcaneal structures at risk from the insertion point of the nail. The findings showed that the distance of the lateral neurovascular bundle from the edge of the nail was 6.5 (range 3.5 to 8, 95% confidence interval 5.9 to 7.1) mm. No neurovascular bundle was compromised, and all were within a previously described "safe window."

Fibrolipomatous hamartoma of the inferior calcaneal nerve (Baxter nerve).

Fibrolipomatous hamartoma (FLH) is a rare, benign lesion of the peripheral nerves most frequently involving the median nerve and its digital branches (80 %). Pathognomonic MR features of FLH such as coaxial-cable-like appearance on axial planes and a spaghetti-like appearance on coronal planes have been described by Marom and Helms, obviating the need for diagnostic biopsy. We present a case of fibrolipomatous hamartoma of the inferior calcaneal nerve (Baxter nerve) with associated subcutaneous fat proliferation.

Entrapment involving the lateral calcaneal branch of the sural nerve: a case study.

Sural nerve impingement is frequently reported and often arises from localized trauma but much less understood are its mechanical etiologies. This case report describes the effects of local traction on the lateral calcaneal branch of the sural nerve. The association is confirmed anatomically and symptoms are alleviated with a heel lift.

Assessment of medial and lateral neurovascular structures after percutaneous posterior calcaneal displacement osteotomy: a cadaver study.

A prospective investigation of the effects on the medial and lateral neurovascular structures of the rearfoot after percutaneous posterior calcaneal displacement osteotomy was performed using 20 below the knee fresh frozen cadaver specimens. This anatomic study aimed to examine the medial and lateral neurovascular structures to determine whether they were jeopardized during execution of the osteotomy. After completion of the osteotomy, the medial plantar, lateral plantar, medial calcaneal, sural, and posterior tibial neurovascular structures, along with their respective branches, were inspected for iatrogenic injury. Our findings demonstrated that the percutaneous, subperiosteal osteotomy minimized trauma to the local soft tissue envelope and protected the adjacent neurovascular structures. Because no iatrogenic injury was observed in the cadaveric specimens, we postulated that percutaneous calcaneal displacement osteotomy is a safe, predictable, and advantageous alternative compared with open techniques for osteotomy and could result in reduced postoperative complications. The results of this investigation remain to be confirmed in the clinical setting.

Calcaneal traction pin placement simplified: a cadaveric study.

BACKGROUND: The tibial neurovascular bundle and sural nerve are at risk with errant pin placement during transcalcaneal pin placement. The purpose of this study was to determine a relative safe zone using a single osseous landmark to establish a technique applicable in the presence of trauma. We describe the neural anatomy anatomically and radiographically, giving surgeons a reliable and relatively safe technique for transcalcaneal pin placement. MATERIALS AND METHODS: Twenty-four cadavers were dissected for the major medial neurovascular structures and the sural nerve. The closest distance from the neurovascular structures to the posterior inferior calcaneus was measured. RESULTS: The mean distance from the posterior inferior calcaneus to the closest major medial neurovascular structure was 3.4 cm (SD ± 0.36; range, 2.6 to 4.1 cm). The mean distance to the sural nerve was 3.4 cm (SD ± 0.54; range, 2.3 to 4.6 cm). According to the 95% confidence intervals, a relative safe zone of 3.1 cm as a radius from the posterior inferior calcaneus was determined. CONCLUSION: A relatively safe zone of 3.1 cm based on 95% confidence intervals as described as a radius from the posterior inferior calcaneus can be used for transcalcaneal pin placement in most cases without injury to the medial neurovascular bundle or sural nerve. However anatomic variation may result in the neurovascular bundle being within this zone. CLINICAL RELEVANCE: We describe a surgical technique for reliable placement of a transcalcaneal pin within this relative safe zone and a safe distance from the closest neurovascular structure.

Relationship of the Scarf valgus-inducing osteotomy of the calcaneus to the medial neurovascular structures.

BACKGROUND: The Scarf valgus inducing osteotomy of the calcaneus is an operative technique to correct varus deformity of the hindfoot. It is versatile with significant corrective power; however, the neurovascular structures are in close proximity on the medial side and thus may be harmed during the osteotomy. Moreover, because this type of osteotomy can cause a great lateral translation, traction of the medial neurovascular structures is possible. We performed an anatomic study to evaluate the medial soft tissues after a lateralizing Scarf-type calcaneal osteotomy. MATERIALS AND METHODS: The osteotomies were carried out on ten fresh-frozen cadaver specimens. We performed the osteotomy and induced valgus. Then we performed a medial dissection to identify the important medial structures: the medial and lateral plantar nerve (MPN , LPN) and the posterior tibial artery (PTA). We noted their relation to the osteotomy and their integrity. RESULTS: In several cases, one or more of the structures were sectioned. In five cases, all the structures crossed the osteotomy, four of which even a transection of one or both of the plantar nerves occurred. Although the PTA crossed the osteotomy in eight specimens, there was no transection of this structure. CONCLUSION: Scarf osteotomy of the calcaneus is a highly corrective osteotomy. However, caution must be exercised when performing as the medial neurovascular structures cross the osteotomy lines and transection can occur. CLINICAL RELEVANCE: When performing the osteotomy one should keep in mind that vigorous sawing and large displacement can cause damage to the medial neurovascular structures.

Tarsal tunnel syndrome.

Tarsal tunnel syndrome, unlike its similar sounding counterpart in the hand, is a significantly misunderstood clinical entity. Confusion concerning the anatomy involved, the presenting symptomatology, the appropriateness and significance of various diagnostic tests, conservative and surgical management, and, finally, the variability of reported results of surgical intervention attests to the lack of consensus surrounding this condition. The terminology involved in various diagnoses for chronic heel pain is also a hodgepodge of poorly understood entities.

The painful neuroma and the use of conduits.

Treatment of neuromas in the foot and ankle is evolving. A paucity of studies deals with neuromas in this region; most knowledge comes from hand surgery. A trend toward reconstructive surgery using nerve grafts and conduits for nerves with critical function is being seen. For noncritical nerves, generally accepted treatment is neuroma resection and burial into a tissue bed. A clear knowledge of neural anatomy is paramount, together with correct identification of all the nerves involved in the pain-generation process. More studies dealing with neuromas in this area are needed for evidence-based information.

[Anatomic characteristics and clinic significance of the medial calcaneal nerve].

OBJECTIVE: To provide anatomic evidence for choosing medial calcaneal nerve(MCN ) as recipient cutaneous nerve to rebuild heel sensation. METHODS: We chose 20 adult cadavers' lower limbs, dissected the MCNs, observed their original sites, shapes, courses and distribution, and measured the perpendicular distance from original sites of MCNs from tibial nerve, original sites of their branches to the tip of medial malleolus, and the external diameters of their main trunks and branches. RESULTS: The frequency of the MCN was 95% in this array. All the MCNs arose from the tibial nerve at 3.3 cm up the horizontal plane of the tip of medial malleolus. They sent out anterior branches and posterior branches from 0.3 cm below the horizontal plane of the tip of medial malleolus on average. The anterior branch dominated the cutaneous sensation of the anterior part of the medial calcaneal and heel weight loading field, while the posterior branch dominated the sensation of the posterior and median part. The shape of MCNs, main trunks, anterior branches and posterior branches was like circular cylinder. At the origination, the external diameter of the MCN, the anterior branch and the posterior branch was 1.58, 1.13 and 0.90 mm on average, respectively. CONCLUSION: The anatomical position of MCN is relatively constant, and its external diameter is suitable. The initiation is not close to the heel weight loading area. Its anatomic characteristics meet the requirements of sensation recovery of the heel, especially the heel weight loading field.

Bilateral Baxter's neuropathy secondary to plantar fasciitis.

BACKGROUND: Baxter's neuropathy is a nerve entrapment syndrome that results from the compression of the inferior calcaneal nerve. The causes of Baxter's neuropathy include altered foot biomechanics such as flatfoot, plantar calcaneal enthesophytes, and plantar fasciitis. Baxter's neuropathy and causative pathologies such as plantar fasciitis can be identified with the help of typical MRI findings. CASE REPORT: In this report, bilateral Baxter's neuropathy developed in a 42-year-old woman secondarily to bilateral plantar fasciitis. On MR images, fatty atrophy of the abductor digiti minimi muscles was found in both feet, revealing high-signal areas in the T1-weighted images and low-signal areas in the T2-weighted images. Additionally, findings of plantar fasciitis were observed in both feet. CONCLUSIONS: To the authors' knowledge, no case of bilateral Baxter's neuropathy secondarily to plantar fasciitis has been reported. Baxter's neuropathy and causative disorders are easily recognized with help of typical MRI findings. Selective fatty atrophy of the abductor digiti minimi muscle is the unique sign of this neuropathy. Recognition of unique MRI findings of this rare condition that can cause heel pain are important since they provide an effective treatment plan.