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.

Neurovascular structures at risk with percutaneous fixation in tarsometatarsal fusion: A cadaveric study.

INTRODUCTION: First tarsometatarsal (TMT) joint fusion is routinely used for arthritis and deformities. Common fixation methods include a locking plate construct, cross-screws, or combinations of the two. Cross screws have proven effective for union and stability; however, there is a potential for harm to nearby neurovascular structures due to the nature of percutaneous insertion technique. This study assessed risk of damage to the superficial peroneal nerve with percutaneous TMT fusion. METHODS: Nine fresh-frozen cadaver specimens were included. A medial incision in the internervous plane was made for TMT joint preparation. Two crossed percutaneous wires followed by 4.0 cc screws were placed in the dorsal aspect of the proximal aspect of first metatarsal and in the medial cuneiform. Both were 10-15 mm from the TMT joint line. The dorsal aspect of the foot was dissected and examined for neurovascular interruptions, particularly branches of the superficial peroneal nerve. RESULTS: Results showed a mean distance of 4.33 mm from the proximal pin to the medial branch of the superficial peroneal nerve. The distal pin had a mean distance of 6.44 mm from the medial branch, with one pin 9 mm from the lateral branch. One incident of direct injury to the neurovascular bundle was observed. CONCLUSION: Preparing the joint from the medial side using a percutaneous approach is less invasive, but presents a relative risk for neuritis. Care should be taken during insertion of the percutaneous screw after TMT joint preparation for fusion. LEVEL OF EVIDENCE: Level V, cadaver study.

Structures at Risk During Percutaneous Screw Fixation for Talonavicular Fusion.

BACKGROUND:: Talonavicular (TN) fusion using screws dorsomedially and dorsolaterally can cause neurovascular injury. The purpose of our cadaveric study was to evaluate the safety of percutaneous screw insertion in relation to dorsal neurovascular structures. METHODS:: Ten fresh-frozen cadaver legs were used for this study. Percutaneous cannulated screws were inserted to perform isolated TN arthrodesis. The screws were inserted at 3 consistent sites: a "medial screw" at the dorsomedial navicular where it intersected at the medial plane of the first cuneiform, a "central screw" at the edge of the dorsal navicular between the medial and intermediate cuneiforms, and a "lateral screw" at the edge of the dorsal navicular between the intermediate and lateral cuneiforms. Superficial and deep dissections were carried out to identify any injured nerves, arteries, and/or tendons. RESULTS:: The medial screw injured the anterior tibialis tendon in 2 cases (20%), the central screw injured the extensor hallucis longus tendon in 3 cases (30%), and the lateral screw injured the anterior branch of the superior peroneal nerve (SPN), the lateral branch of the SPN, and the medial branch of the distal peroneal nerve (DPN) once each in a total of 3 cases (30%). Despite no direct injury, the central screw indicated a potential risk of neurovascular injury: closest distance to the anterior SPN was 2 mm and to the medial DPN 2 mm. CONCLUSION:: Although neurovascular injury risk exists for all of these screw placements, TN fusion with a central screw introduced a potentially decreased risk of neurovascular injury at the expense of increased risk of tendon injury compared to the lateral screw. CLINICAL RELEVANCE:: Based on these results, we recommend a careful dissection be performed prior to percutaneous screw insertion.

Strain and excursion of the sciatic, tibial, and plantar nerves during a modified straight leg raising test.

A modified straight leg raising (SLR) in which ankle dorsiflexion is performed before hip flexion has been suggested to diagnose distal neuropathies such as tarsal tunnel syndrome. This study evaluates the clinical hypothesis that strain in the nerves around the ankle and foot caused by ankle dorsiflexion can be further increased with hip flexion. Linear displacement transducers were inserted into the sciatic, tibial, and plantar nerves and plantar fascia of eight embalmed cadavers to measure strain during the modified SLR. Nerve excursion was measured with a digital calliper. Ankle dorsiflexion resulted in a significant strain and distal excursion of the tibial nerve. With the ankle in dorsiflexion, the proximal excursion and tension increase in the sciatic nerve associated with hip flexion were transmitted distally along the nerve from the hip to beyond the ankle. As hip flexion had an impact on the nerves around the ankle and foot but not on the plantar fascia, the modified SLR may be a useful test to differentially diagnose plantar heel pain. Although the modified SLR caused the greatest increase in nerve strain nearest the moving joint, mechanical forces acting on peripheral nerves are transmitted well beyond the moving joint.

Calcitonin gene-related peptide, substance P, and tyrosine hydroxylase-immunoreactive innervation of rat bone marrows: an immunohistochemical and ultrastructural investigation on possible efferent and afferent mechanisms.

The presence of nerve fibers in bone marrow has been noted by various investigators, and recent developments in immunohistochemistry have enabled differential localization of the intramedullary nerve fibers. Much interest has been devoted to the efferent activities of the afferent fibers, which probably act on the target tissues by secreting a variety of neurotransmitters. The present study aimed to further characterize intramedullary substance P, calcitonin gene-related peptide, and tyrosine hydroxylase-immunoreactive nerve fibers of the rat lower limb by comparing those of the knee, ankle, and tarsal joints. The ultrastructural details of intramedullary calcitonin gene-related peptide-immunoreactive axons were also investigated to provide a morphological basis for their possible efferent actions. Intramedullary calcitonin gene-related peptide and substance P-immunoreactive fibers in the proximal tibia and the knee joint were found to be as reported earlier, but the marrow of the distal metaphysis was also noted to be richly innervated, and the tarsal joints displayed dense innervation at the subchondral regions that underlie the joint cartilage. The articular and intramedullary innervations that function for joint protection might participate in characteristic clinical features of joint damage secondary to the neuropathies. Ultrastructurally, the intramedullary calcitonin gene-related peptide-immunoreactive axons were minimally engulfed by the Schwann cell, and naked intramedullary calcitonin gene-related peptide-immunoreactive axons were noted along an extraordinarily long extension, suggesting much efferent activity.

Anterior tarsal tunnel syndrome.

We have reviewed 10 patients treated for anterior tarsal tunnel syndrome produced by compression of the deep peroneal nerve or its branches, and we have studied the anatomy of the tunnel in 25 adult feet. The causes of onset of the syndrome included contusion of the dorsum of the foot, tight shoe laces, talonavicular osteophytosis, ganglion, and pes cavus. The clinical signs were often diagnostic but electromyography was helpful. Operative decompression in nine feet of eight patients gave successful results at 1.5 to 4 years follow-up.

Arthroscopy of the subtalar joint: establishing a medial portal.

One of the recently introduced procedures for studying the posterior subtalar joint is subtalar arthroscopy. There is no reference in the literature to the possibility of a medial portal that might be used either for arthroscopic insertion, probing, or instrumental manipulation. The two portals mentioned in the literature are the anterolateral and the posterolateral portals. For evaluating the possibility of establishing a medial portal, six embalmed adult cadaver feet were used to study the anatomical relations to the proposed medial portal. The subtalar joints of another six fresh adult cadaver feet were then arthroscoped, after distraction of the joint, using the anterolateral, posterolateral, and medial portals. Findings indicated that the medial portal gives good visualization of the posterior subtalar joint. Clinical application has not yet been assessed.

Neurohistology of the sinus tarsi and sinus tarsi syndrome.

The purpose of this study was to clarify the neural anatomy of the sinus tarsi. The nerve endings of the synovium in the sinus tarsi were examined. The synovial membrane in the sinus tarsi was excised in 20 patients with sinus tarsi syndrome (20 feet) and in 2 feet from subjects without symptoms (controls). In 15 of the 20 patients and the two controls, the excised synovial membrane was studied histologically with staining by a modified Gairns gold chloride method. Numerous neural elements were observed in the sinus tarsi in all examined synovium. There were abundant free nerve endings and three types of mechanoreceptors: Pacinian corpuscles, Golgi corpuscles, and Ruffini corpuscles. Macroscopic observation and histological examination, using hematoxylin and eosin, in the other 5 patients revealed chronic synovitis in the sinus tarsi. Our findings suggest that the sinus tarsi is not only a talocalcaneal joint space but a source of nociceptive and proprioceptive information on the movement of the foot and ankle. Sinus tarsi syndrome may result from disorders of nociception and proprioception in the foot.