Medial Branch Research Articles

3D nerve proximity mapping of the medial branch of lumbar dorsal ramus: An anatomical study

ObjectiveLumbar medial branch (MB) radiofrequency ablation is a common intervention to treat facetogenic low back pain. Consensus among spine pain interventionalists is that the cannula tip should be placed adjacent to the periosteum of the lateral neck of the superior articular process (SAP) to ensure maximum contact with the MB. The spatial relationship of the nerve to the periosteum of the lateral neck of the SAP has not been quantified in 3D. The objectives of the current study were to: 1) use 3D modelling technology to quantify the location along the lateral neck of the SAP where the MB is in direct contact with the periosteum; and 2) identify target site(s) to optimize lumbar MB denervation. DesignSeventy lumbar dorsal rami in 14 formalin-embalmed specimens were dissected, digitized, and modeled in 3D. The 3D positional data of the MB were used to generate a novel nerve proximity map which provided a method to quantify and visualize the 3D course of the MB in relation to the periosteum of the lateral neck of SAP. The percent of the lateral neck of SAP in contact with the MB was quantified and consistent target site(s) identified. ResultsThere was variability in the percentage of the lateral neck of SAP in contact with the MB. The mean percentage of the lateral neck of SAP in contact with the MB for the L1-L5 levels ranged between 57.39 ± 10.72 % (for L1) to 81.54 ± 10.48 % (for L5). The nerve proximity map showed consistent course of the MB along the posterior portion of the lateral neck of SAP and at a novel target site distal to the mamillo-accessory notch (i.e. sub-mammillary landmark). ConclusionThe percent of the lateral neck that was in contact with the MB was quantified and visualized using a novel nerve proximity mapping methodology which may be used to inform cannula tip depth placement. Further, the nerve proximity maps were used to identify an alternative landmark to extend the length of the MB captured. The proposed sub-mammillary landmark may be a viable target site pending future anatomical and clinical investigations.

Application of three-dimensional ultrasound technique in repairing dorsal foot wounds with medial sural artery perforator flaps

To investigate the accuracy of positioning perforator of medial sural artery with three-dimensional ultrasound technique guided by a wide band linear matrix array volume transducer probe before operation, and the effectiveness of the flap design based on this in repairing the dorsal foot wounds. Between January 2019 and December 2022, 30 patients with skin and soft tissue defects of the dorsal foot were treated. There were 19 males and 11 females, with an average age of 43.9 years (range, 22-63 years). There were 12 cases of traffic accident injury, 15 cases of heavy crushing injury, and 3 cases of machine injury. The time from injury to hospitalization was 1-8 hours (mean, 3.5 hours). The wounds in size of 5 cm×3 cm to 17 cm×5 cm were thorough debrided and covered with vacuum sealing drainage dressing. Then the wounds were repaired with the medial sural artery perforator flaps after no obvious infection observed. To obtain the complete three-dimensional image, the number and position of the medial sural artery perforator branches and the position of the main blood vessels in the muscle were detected and recorded by wide band linear matrix array volume transducer probe before operation. Suitable perforating branches were selected to design the flap and guide the flap incision on this basis. The size of the perforating flap ranged from 6 cm×4 cm to 18 cm×6 cm. The sensitivity and positive predictive value were calculated by comparing preoperative exploration with intraoperative observation of perforating branches, so as to evaluate the positioning accuracy of three-dimensional ultrasound technique. The donor sites were sutured directly in 25 cases and repaired with free skin grafting in 5 cases. The 60 perforating branches of medial sural artery were found before operation and 58 during operation in 30 patients. Among them, pre- and intra-operative perforations were consistent with 56. The sensitivity was 93.3% and positive predictive value was 96.6%. The intramuscular position and route of the main blood vessels were basically consistent with the pre- and intra-operative observation. All flaps survived and wounds healed by first intention. All incisions at the donor sites healed by first intention, and all skin grafts survived. All patients were follow up 9-24 months (mean, 14.7 months). The appearance, color, and texture of the flaps were good, and no obvious effect on wearing shoes and walking. At last follow-up, the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hind score ranged from 80 to 92, with an average of 87.5. The patient satisfaction was excellent in 29 cases and good in 1 case. The three-dimensional ultrasound technique guided by the wide band linear matrix array volume transducer probe can accurately locate the perforating branch of the medial sural artery, and the three-dimensional imaging is more intuitive, which can be used to guide the design and incision of the medial sural artery perforator flap.

True lateral imaging during lumbar medial branch radiofrequency neurotomy: Interobserver reliability

BackgroundTrue lateral imaging (TLI), obtained by superimposing bilateral lumbar spine structures and aligning superior endplate cortical bone, requires deliberate rotational adjustments of the laterally positioned fluoroscope in both the axial and longitudinal planes. True lateral segmental imaging is necessary to depict true and accurate radiofrequency (RF) cannula positioning relative to bony anatomy during lumbar medial branch radiofrequency neurotomy (LMBRFN). ObjectiveTo determine the interobserver reliability of TLI during LMBRFN. MethodsThis was a retrospective review of a prospectively generated collection of lateral fluoroscopic images to determine the interobserver reliability of TLI during LMBRFN. Lateral fluoroscopic images were prospectively collected from 34 consecutive L4-5 and L5-S1 LMBRFN procedures during routine clinical practice. Employing International Pain and Spine Intervention Society (IPSIS) LMBRFN and TLI techniques, an RF cannula was positioned parallel to the L3 and L4 medial branches and the L5 dorsal rami. During the normal course of TLI, untrue and final true lateral segmental images were obtained and saved. An original data set of 100 pairs of true and untrue lateral images was reviewed to verify true laterality using established criteria; disagreement was resolved by consensus or discarding ambiguous cases. To measure interobserver reliability (Cohen's Kappa), two blinded expert reviewers independently reviewed the image set, identifying the true lateral image and the plane requiring correction. ResultsThe observers agreed upon 98/98 true lateral RF-segment images (Kappa score 1.0 [1.00,1.00]). The observers agreed upon 86/98 maneuvers to correct the untrue RF-segment image. The Kappa score for determining the most appropriate corrective maneuver was 0.76 (0.63,0.89), showing substantial interobserver agreement. ConclusionsThe true lateral image of the targeted RF segment during LMBRFN was reliably determined with perfect interobserver agreement. Interobserver agreement was substantial regarding the maneuver to achieve TLI.

Upper Extremity Nerve Transfers for Treatment of Nerve Injury After Cervical Spine Surgery: A Single-Center Retrospective Review.

Nerve transfers to restore or augment function after spinal cord injury is an expanding field. There is a paucity of information, however, on the use of nerve transfers for patients having undergone spine surgery. The incidence of neurologic deficit after spine surgery is rare but extremely debilitating. The purpose of this study was to describe the functional benefit after upper extremity nerve transfers in the setting of nerve injury after cervical spine surgery. A single-center retrospective review of all patients who underwent nerve transfers after cervical spine surgery was completed. Patient demographics, injury features, spine surgery procedure, nerve conduction and electromyography study results, time to referral to nerve surgeon, time to surgery, surgical technique and number of nerve transfers performed, complications, postoperative muscle testing, and subjective outcomes were reviewed. Fourteen nerve transfers were performed in 6 patients after cervical spine surgery. Nerve transfer procedures consisted of a transfer between a median nerve branch of flexor digitorum superficialis into a biceps nerve branch, an ulnar nerve branch of flexor carpi ulnaris into a brachialis nerve branch, a radial nerve branch of triceps muscle into the axillary nerve, and the anterior interosseous nerve into the ulnar motor nerve. Average patient age was 55 years; all patients were male and underwent surgery on their left upper extremity. Average referral time was 7 months, average time to nerve transfer was 9 months, and average follow-up was 21 months. Average preoperative muscle grading was 0.9 of 5, and average postoperative muscle grading was 4.1 of 5 ( P < 0.00001). Upper extremity peripheral nerve transfers can significantly help patients regain muscle function from deficits secondary to cervical spine procedures. The morbidity of the nerve transfers is minimal with measurable improvements in muscle function.

A transmuscular path of the medial branch of the high division of the median nerve: an anatomical variation of clinical and surgical importance

The median nerve (MN) is a mixed nerve formed in the brachial plexus, which innervates a large part of the upper limb. It presents several variations in its trajectory, resulting in many pathologies and iatrogenic surgical compromises. This report highlights a transmuscular route of the medial branch of the upper division of the MN, which to date does not fit into the classifications described in the literature on MN variations. Knowledge of this high division of the MN, as well as its transfixation by the flexor digitorum superficialis muscle, is of fundamental importance in neuropathy syndromes due to entrapment of the MN, as well as in surgical guidance to prevent injuries. Late diagnosis of traumatic peripheral nerve injuries results in greater functional impairment and greater socioeconomic loss, especially in young patients. Therefore, timely identification is essential to minimize long-term consequences and improve the patient's quality of life.

Cryoneurolysis versus radiofrequency ablation outcome on pain experience in chronic low back pain (COPE): a single-blinded randomised controlled trial

ObjectiveA comparison of cryoneurolysis or radio frequency (RF) with placebo in patients with facetogenic chronic low back pain (LBP) for patient global impression of change (PGIC), pain intensity, function and...

Transfer of Motor Fascicle From the Ulnar Nerve to the Axillary Nerve by Posterior Access. New Approach.

We describe a new technique of transferring the motor branch ulnar nerve (UN) to the axillary nerve (AN) by posterior approach. Three patients with C5, C6, and C7 brachial plexus injury were operated. By supraclavicular approach, the spinal accessory was transferred to the suprascapular nerve. By posterior approach in the arm, the AN was identified within the quadrilateral space, and the UN was identified medially with intrafascicular dissection of a motor fascicle, which is lifted to 4 cm in length and transferred to AN. By medial approach, a motor branch from the median nerve is transferred to the biceps nerve. At a follow-up minimum of 10 months, the maximum abduction was 160 and the minimum 90 degrees. This technique, neurotization of the AN with fascicles of the UN, spinal accessory to suprascapular nerve, and median nerve branch to biceps nerve are indicated in C5-C7 avulsion when there is no radial nerve available. Level IV.

Targeted multifidus muscle activation reduces fibrosis of multifidus muscle following intervertebral disc injury

PurposeAerobic exercise produces beneficial outcomes in patients with low back pain and partially attenuates the fibrotic changes to the multifidus in a model of intervertebral disc (IVD) degeneration. More targeted exercise might be required to fully attenuate these fibrotic alterations. This study aimed to investigate whether activation of the multifidus induced by neurostimulation could reduce fibrosis of the multifidus in a model of IVD degeneration in sheep.MethodsIVD degeneration was induced in 18 merino sheep via a partial thickness unilateral annulus fibrosus lesion to the L1/2 and L3/4 IVDs. All sheep received an implantable neurostimulation device that provides stimulation of the L2 medial branch of the dorsal ramus. Three months after surgery, the animals were assigned to Injury or Activated groups. Activated animals received neurostimulation and the Injury group received no stimulation. Six months after surgery, the multifidus was harvested at L2 and L4. Van Gieson’s, Sirius Red and immunofluorescence staining for Collagen-I and -III and quantitative PCR was used to examine fibrosis. Muscle harvested from a previous study without IVD injury was used as a control.ResultsNeurostimulation of the multifidus attenuated IVD degeneration dependent increases in the connective tissue, including Collagen-I but not Collagen-III, compared to the Injury group at L4. No measures of the multifidus muscle at L2, which received no stimulation, differed between the Injury and Activated groups.ConclusionsThese data reveal that targeted activation of the multifidus muscle attenuates IVD degeneration dependent fibrotic alterations to the multifidus.

Fluoroscopy-guided high-intensity focused ultrasound neurotomy of the lumbar zygapophyseal joints: a prospective, open-label study

ObjectiveThe objective of this study is to investigate safety and effectiveness of a fluoroscopy-guided high-intensity focused ultrasound (HIFU) system for thermal ablation of the lumbar medial branch nerves.MethodsThis dual center...

How do different agricultural managements interfere with the Phytoseiidae mite (Acari: Phytoseiidae) community in apple trees?

In this study we performed the sampling of phytoseiid mites in different apple production orchards, and we evaluated the richness and abundance of these mites, as well as their distribution in the different strata of the plants. Furthermore, we studied how the different apple tree cultivars affect the diversity and distribution of these predatory mites. Collections were carried out in apple orchards in three different production areas: 1- organic agriculture (Antônio Prado, RS); 2- conventional agriculture (Muitos Capões, RS); 3- regenerative agriculture (São Joaquim, SC). In total, seven orchards were evaluated, in Muitos Capões and São Joaquim, two orchards of the Fuji and Gala, whereas in Antônio Prado, three cultivars (Eva, Fuji and Gala) were considered. In each orchard, 40 plants were evaluated, and from each plant a median branch was randomly chosen from which a leaf was removed from the apical, median and basal thirds. The collected leaves were taken to the laboratory, they were observed and the mites found mounted in Hoyer's medium and identified. A total of 695 phytoseiid specimens were collected. Greater abundance was noted in the apical stratum of plants of the Gala cultivar, demonstrating the effect of cultivar and stratum on phytoseiid richness, abundance and distribution. Neoseiulus californicus (McGregor) (Phytoseiidae) was the main species in areas of conventional and regenerative cultivation, being present in all evaluated orchards, but with low occurrence in areas of organic management. In organic orchards, species of the genus Euseius [Euseius mesembrinus (Dean) and Euseius inouei (Ehara and Moraes)] (Phytoseiidae) were more abundant. The results suggest that producers consider less intensive use of pesticides and herbicides in orchards in order to maintain populations of predatory mites due to their potential for biological control.

Laser and radio frequency technologists in the treatment of degenerative polysegmental pathologies of the spine in elderly people

The article discusses outcomes after treating 88 elderly patients with degenerative pathologies of the spine, 42 of whom had previous decompression- stabilizing surgical interventions. Clinical manifestations of the disease were characterized by prolonged pain syndrome, lumboishialgia caused by degenerative-dystrophic changes in the arch-process joints and progressive degeneration of the intervertebral discs. Surgical intervention in 65 patients included puncture laser ablation of the medial branch of the spinal nerve in the facet joint. In 23 patients, ablation of the medial branch of the spinal nerve was performed at two (n = 8) and three (n = 15) levels using four-channel radio frequency generator COSMAN G4.Excellent and good results after surgery were found in 58 (65.9%) patients. The researchers assessed intermediate results within 3 years in 55 patients, and 37 (42.01%) of them had a stable positive state. Minimally invasive laser and radiofrequency technologies in the treatment of degenerative polysegmental pathologies of the spine in elderly and old people is justifi ed, and it is an important component of their rehabilitation

Comparison of the Efficacy of Different Radiofrequency Techniques for the Treatment of Lumbar Facet Joint Pain: Combined with Anatomy.

Lumbar facet pain is generally considered to be one of the major causes of chronic low back pain. Each lumbar facet joint is innervated by the medial branch of the posterior spinal nerve from its own level and above. Radiofrequency (RF) of the medial branch of the posterior branch of the spinal nerve is an effective method for the treatment of lumbar facet pain. RF technology is diverse, including traditional radiofrequency (TRF), pulsed radiofrequency (PRF), cooled radiofrequency (CRF), low-temperature plasma radiofrequency ablation (CA), and other treatment methods. The purpose of this paper is to compare the efficacy of different radiofrequency techniques and to analyze the reasons for this in the context of anatomy. There have been studies confirming the differences in efficacy of different RF techniques. However, most of the studies only compared two RF techniques, not four techniques, TRF, CRF, PRF, and CA, and did not analyze the reasons for the differences in efficacy. This article reviews the differences in the efficacy of the above four RF techniques, clarifies that the differences are mainly due to the inability to precisely localize the medial branch of the posterior branch of the spinal nerve, analyzes the reasons for the inability to precisely localize the posterior branch of the spinal nerve in conjunction with anatomy, and proposes that the development of RF technology for lumbar facet pain requires more in-depth anatomical, imaging, and clinical studies.

The Origin and Course of the Blood Supply to the Lower Eyelid Orbital Fat: Anatomical Study and Clinical Significance.

The aim of this study is to investigate the origin and course of the orbital fat arterial supply in the lower eyelid using traditional anatomy and three-dimensional computed tomography (CT). Twenty-seven cadaver heads were infused with mercury sulfide contrast media through the ophthalmic artery, maxillary artery, transverse facial artery, and facial artery. CT images were obtained after contrast agent injection, three-dimensional CT scans were reconstructed, and the cadaver heads were dissected. Forty-five qualified hemifaces showed that the orbital fat arterial supply in the lower eyelid originates primarily from the inferomedial muscular trunk (IMT) of the ophthalmic artery and the orbital branch of the infraorbital artery. The medial branch of the IMT terminated at the medial fat pad (35.6%) or the orbital floor (64.4%). The lateral branch terminated at the inferior oblique (IO) muscle (28.9%) or the central and lateral fat pads (17.8%). In 53.3%, the lateral branch extended to the anterior part of the lateral fat pad and terminated in the orbital wall or the zygomaticoorbital foramina. The orbital branch of the infraorbital artery coursed between the orbital floor and the orbital fat, providing supply to the IO muscle, inferior rectus (IR) muscle, nasolacrimal duct, and orbital fat. This study elucidated the origin and course of the orbital fat arterial supply in the lower eyelid, which may help to avoid reducing the blood supply of the orbital fat pedicles during surgery. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Asymmetrical atrophy of the paraspinal muscles in patients undergoing unilateral lumbar medial branch radiofrequency neurotomy.

Lumbar medial branch radiofrequency neurotomy (RFN), a common treatment for chronic low back pain due to facet joint osteoarthritis (FJOA), may amplify paraspinal muscle atrophy due to denervation. This study aimed to investigate the asymmetry of paraspinal muscle morphology change in patients undergoing unilateral lumbar medial branch RFN. Data from patients who underwent RFN between March 2016 and October 2021 were retrospectively analyzed. Lumbar foramina stenosis (LFS), FJOA, and fatty infiltration (FI) functional cross-sectional area (fCSA) of the paraspinal muscles were assessed on preinterventional and minimum 2-year postinterventional MRI. Wilcoxon signed-rank tests compared measurements between sides. A total of 51 levels of 24 patients were included in the analysis, with 102 sides compared. Baseline MRI measurements did not differ significantly between the RFN side and the contralateral side. The RFN side had a higher increase in multifidus FI (+4.2% [0.3-7.8] vs +2.0% [-2.2 to 6.2], P = 0.005) and a higher decrease in multifidus fCSA (-60.9 mm 2 [-116.0 to 10.8] vs -19.6 mm 2 [-80.3 to 44.8], P = 0.003) compared with the contralateral side. The change in erector spinae FI and fCSA did not differ between sides. The RFN side had a higher increase in multifidus muscle atrophy compared with the contralateral side. The absence of significant preinterventional degenerative asymmetry and the specificity of the effect to the multifidus muscle suggest a link to RFN. These findings highlight the importance of considering the long-term effects of lumbar medial branch RFN on paraspinal muscle health.

Mitigating Factors in L4 and L5 Medial Branch Motor Stimulation During Radiofrequency Ablation.

Radiofrequency ablation (RFA) is a minimally invasive procedure for facet joint pain. The targets for the procedure are the medial branches of the dorsal spinal nerves which innervate the facet joints. Before RFA, patients undergo diagnostic meal branch blocks to ensure appropriate pain relief and confirm the utility of proceeding to RFA. The success of RFA relies heavily on procedural technique and accurate placement near the medial branch. Motor testing is utilized in the lumbar region to assess the response of the multifidus and ensure proper placement of the RFA probe to prevent inadvertent damage to surrounding spinal anatomy. However, relying on motor responses in this area presents challenges given the frequency of lack of muscle twitching. Factors contributing to limited muscle twitch responses include muscle atrophy, excessive lordosis, facet arthropathy, local anesthetic use before ablation, and previous surgical neurotomy. These complexities highlight the challenges in ensuring precise motor stimulation during RFA. Despite these obstacles, accurate anatomical placement remains crucial. For RFA cases that prove challenging, relying on anatomical placement can be adequate to proceed with the procedure. Bridging knowledge gaps is vital for standardized practices and safer procedures. Further research is necessary to refine techniques, understand patient-specific factors, and enhance the efficacy of RFA in managing chronic lumbar facet joint pain.

Fluoroscopy-guided high-intensity focused ultrasound ablation of the lumbar medial branch nerves: dose escalation study and comparison with radiofrequency ablation in a porcine model

BackgroundRadiofrequency ablation (RFA) is a common method for alleviating chronic back pain by targeting and ablating of facet joint sensory nerves. High-intensity focused ultrasound (HIFU) is an emerging, non-invasive, image-guided...

Prospective evaluation of the safety of ultrasound-guided cervical medial branch blocks using the in-plane technique

BackgroundWhile fluoroscopic guidance is currently the imaging standard for cervical medial branch blocks (CMBBs), ultrasound guidance (USG) offers several potential safety advantages such as real-time needle visualization and the ability...

The effect of hallux valgus on the anatomy of the nerves around the first metatarsal bone.

To identify the variations in the location of the nerves that may be at risk in hallux valgus (HV) surgery, and to reveal whether these nerves are affected by the anatomical changes associated with HV. In the formalin fixed, 46 lower extremities (19 female, 27 male) (9 normal, 14 mild HV, 21 moderate/severe HV), extensor hallucis longus tendon (EHL), deep plantar artery, medial dorsal cutaneous (MDCN), deep fibular (DFN), common plantar digital (CPDN) and proper plantar digital (PPDN) nerves were examined. The branches of MDCN extending to the medial side of foot were recorded in three segments. The positional topography of nerves according to EHL were analyzed on 360° circle and clock models. Sex-related differences observed in some parameters in direct measurements were not found in the clock model comparisons. In advanced HV angles (> 20°), DFN was closer to EHL in the distal part of the metatarsal bone, while there was no difference in the proximal. The intersection of the medial branch of the MDCN with the EHL was more proximal in HV cases than in normal feet. The location of the nerves in the clock pattern did not change in HV. Of the nerve branches reaching the medial side of the foot, 65.2% were in Part I, 71.7% in Part II, and 4.3% in Part III. Sex differences in the distance of the nerves to the EHL disappeared when the size effect of the cross-section of the first metatarsal bone region was eliminated with the clock model. Only in advanced HVA (>20°) (not in mild HV), the DFN being closer to the EHL distally and the intersection of the medial branch of the MDCN with the EHL in HV being more proximal than in normal can be interpreted as specific reflections of HV progress. The variations we revealed in the number of branches reaching the inside of the foot may explain the diversity of neuromas or nerve injuries associated with HV surgery.

Cadaveric study of the ultrasound-guided erector spinae plane block over the transverse process of the twelfth thoracic vertebra in dogs: Transversal vs longitudinal approach

This study describes a transversal (TV) ultrasound-guided erector spinae plane (ESP) block technique over the transverse process of T12. And evaluates the distribution of the dye and affected nerves branches compared to a longitudinal (LNG) approach over the transverse process of T12 in canine cadavers. Secondly, it also compares de anatomy and dimensions of the transverse processes of T12 with T9 and T5. For this double-masked, cadaveric experimental study, 12 adult Beagle cadavers were injected with 0.6 mL/kg of dye/contrast. Spread was evaluated by computed tomography (CT) and dissection.Mean bodyweight was 9.76 (±0.59) kg. The TV and LNG approaches stained a median (range) of four (2–6) and three (1–6) medial branches of the dorsal rami of the spinal nerves, three (2–6) and three (2–5) lateral branches, and one (0−3) and one (0−4) ventral branches, respectively. Dye was detected in the epidural space in 55.6% and 66.7% of cases for the TV and LNG approaches, respectively (P=0.63). And in the ventral paravertebral compartment in 22.2% and lymphatics in 88.8% in both approaches. There were no statistical differences for the spread. The dorsolateral edge of the transverse process (TP) was not visible with CT at T12. The mean (±SD) length of the TP was significantly shorter at T12 [3.34 (±0.22)] mm, compared to T9 [6.08 (±0.47)] mm and T5 [5.93 (±0.62)] mm (P <0.001). This study showed similar distribution whether using a TV or LNG approach and differences in the anatomy and length of the T12 TP.

Investigation of the anatomical course of articular branches to the thoracic zygapophysial joints

BackgroundRecent studies have questioned the validity of targeting the thoracic medial branch via anesthetic blocks or radiofrequency neurotomy for the diagnosis or treatment of pain from the thoracic zygapophysial joints. PurposeTo define the origin and course of the articular branches to the thoracic zygapophysial joints at all levels. DesignCadaveric dissection. SettingThe Gross Anatomy Laboratory at the University of New England College of Osteopathic Medicine. SubjectsOne cadaveric thoracic spine. MethodsGross and stereoscopic dissection of the bilateral dorsal rami T1–T12 was performed on one embalmed cadaver. The medial and lateral branches were traced from their cutaneous distribution to the origin at the dorsal ramus. The articular branches were identified using stereoscopic dissection by tracing their origin from the dorsal ramus or medial branch to the capsule of the zygapophysial joint. The images were recorded using digital photography. ResultsTwenty-two of the twenty-four articular branches were identified in a single cadaveric specimen. Articular branches at T7 on the right side and T9 on the left side were not identified. 5 of the 22 (18%) articular branches were observed to arise from the proximal segment of the medial branch of the dorsal ramus. Of the remainder, 17 of the 22 (78%) articular branches were observed to arise from the dorsal primary ramus itself. At levels T1-9, the articular branch coursed inferiorly along the lamina to reach the joint capsule. At levels T10-T12, the articular branch traversed the intervertebral foramen to reach the facet joint. The T12 medial branch on the left was seen to travel inferior to innervate the L1/L2 zygapophysial joint. ConclusionThe source of the innervation for the thoracic zygapophysial is variable and can arise from the dorsal ramus itself or from the proximal segment of the medial branch. Unlike the cervical and lumbar medial branches, which innervate two joints each, in this case, the thoracic dorsal rami appear to innervate only the zygapophysial joint at the level of the nerve exit. It should be noted that the findings may be limited in their generalizability due to the reliance on a single cadaver study.