Innervation of three weight-bearing areas of the foot: an anatomic study and clinical implications.

The aim of this cadaver study is to improve our knowledge on the anatomy of the sensory fibres of the three weight-bearing areas of the plantar region. Previous studies mainly focused on the innervation of the heel but the innervation of the other two weight-bearing areas over the most medial and lateral metatarses have been neglected and are not well known. The study was carried out on 10 feet of five male cadavers. The tibial nerve was dissected down to the fat pads over the heel and the first and fifth metatarsal heads under the microscope. The distances of the branching point of the tibial nerve and origins of the medial and inferior calcaneal nerves to a line drawn from the centre of the medial malleolus to the centre of the calcaneous were all measured. The tibial nerve was divided into two branches called the lateral and medial plantar nerves 23.45 mm proximal to the predefined axis. The medial plantar nerve passed underneath the abductor hallucis muscle and gave two sensory branches to the fat pad over the first metatarsal head. The lateral plantar nerve coursed beneath the abductor hallucis and flexor digitorum brevis muscles and supplied innervation of the fat pad over the fifth metatarsal head. The sensory innervation of the heel was provided by medial calcaneal and inferior calcaneal nerves. The medial calcaneal nerve originated from the tibial nerve 41.89 mm proximal to the axis. It divided into two or three branches innervating the fat pad over the heel. The inferior calcaneal nerve originated from the lateral plantar nerve (70%) or the medial calcaneal nerve (30%) 10.66 mm proximal to the axis. This study describes the sensory fibres to the heel and the previously neglected weight-bearing areas over the first and fifth metatarses. Reconstruction of defects in these areas is very difficult so every attempt should be made to protect the sensory fibres during any surgical procedure.     

跟骨内外侧经皮置针安全区解剖学研究

目的 划定国人跟骨内、外侧外固定针进针位置解剖学相对安全区.方法 解剖14具正常成年人足踝部标本.于跟骨内侧取跟骨最内下后点为A点,内踝最下点为B点,足舟骨结节为C点.解剖出跟骨内侧神经、足底外侧神经最后分支、足底外侧神经、足底内侧神经、胫后动脉、足底外侧动脉和足底内侧动脉.根据各结构行经AB、AC线的位置,确定跟骨内侧的相对安全区;于跟骨外侧取跟骨最外下后点为D点,外踝最下点为E点,解剖出跟骨外侧神经、腓肠神经、小隐静脉主干,同理确定跟骨外侧的相对安全区.结果 跟骨内侧神经、足底外侧神经最后分支、足底外侧神经、足底内侧神经、胫后动脉分别行经AB线后下22%、50%、56%、64%及58%处,跟骨内侧神经、足底外侧神经最后分支、足底外侧神经、足底内侧神经、足底外侧动脉、足底内侧动脉分别行经AC线后下14%、39%、49%、63%、41%及57%处.跟骨外侧神经、腓肠神经、小隐静脉分别行经DE线后下 19%、65%及61%处.结论 在跟骨内侧,AB线后1/2、AC线后1/3所在圆形区域为经皮置针相对安全区.在跟骨外侧,经DE线中点垂线后方的跟骨为经皮穿针相对安全区.     

Plantar Fascia Release Through a Single Lateral Incision in the Operative Management of a Cavovarus Foot: A Cadaver Model Analysis of the Operative Technique

Plantar fascia release and calcaneal slide osteotomy are often components of the surgical management for cavovarus deformities of the foot. In this setting, plantar fascia release has traditionally been performed through an incision over the medial calcaneal tuberosity, and the calcaneal osteotomy through a lateral incision. Two separate incisions can potentially increase the operative time and morbidity. The purpose of the present study was threefold: to describe the operative technique, use cadaveric dissection to analyze whether a full release of the plantar fascia was possible through the lateral incision, and examine the proximity of the medial neurovascular structures to both the plantar fascia release and calcaneal slide osteotomy when performed together. In our cadaveric dissections, we found that full release of the plantar fascia is possible through the lateral incision with no obvious damage to the medial neurovascular structures. We also found that the calcaneal branch of the tibial nerve reliably crossed the osteotomy in all specimens. We have concluded that both the plantar fascia release and the calcaneal osteotomy can be safely performed through a lateral incision, if care is taken when completing the calcaneal osteotomy to ensure that the medial neurovascular structures remain uninjured.     

Percutaneous pin placement in the medial calcaneus: is anywhere safe?

OBJECTIVE: To redefine the medial calcaneal anatomic safe zone for pin placement with respect to reproducible palpable landmarks. DESIGN: Anatomic study. SETTING: Medical school anatomy laboratory. INTERVENTIONS: Thirty-three fresh-frozen adult cadaveric feet were used. Three palpable anatomic landmarks were identified on each ankle and labeled as Point A (posteroinferior medial calcaneus), Point B (inferior medial malleolus), and Point C (navicular tuberosity). The medial neurovascular bundle was carefully dissected, and the medial calcaneal nerve, the most posterior branch of the lateral plantar nerve, the lateral plantar nerve, the medial plantar nerve, and the posterior tibial artery were identified. These structures were recorded at the point at which they transected a line from Point A to B and from Point A to C. Based on the findings of the first thirty-three feet, two pins were placed percutaneously into the medial calcaneus of ten additional feet. Pin 1 was placed one half the distance from Point A to B. Pin 2 was placed one third the distance from Point A to C. The neurovascular structures were then dissected and identified in relation to the pin position. RESULTS: The medial calcaneal, most posterior branch of the lateral plantar, and lateral plantar nerves are at significant risk for abutting the pins or being directly injured at the margins of these relative safe zones. CONCLUSION: The medial calcaneus provides a small window for safe percutaneous pin placement. Posterior to the halfway point from Point A to B and posterior to the one-third mark from Point A to C remain the relatively safest regions; a more posterior placement in the safe zone is safest. Careful blunt dissection and the use of cannulas may help to avoid neurovascular injury.     

A Case of Posterior Tibial Nerve Injury After Arthroscopic Calcaneoplasty

We report the first case of distal posterior tibial nerve injury after arthroscopic calcaneoplasty. A 59-year-old male had undergone right arthroscopic calcaneoplasty to treat retrocalcaneal bursitis secondary to a Haglund's deformity. The patient complained of numbness in his right foot immediately after the procedure. Two years later and after numerous assessments and investigations, a lateral plantar nerve and medial calcaneal nerve lesion was diagnosed. In the operating room, the presence of an iatrogenic lesion to the distal right lateral plantar nerve (neuroma incontinuity involving 20% of the nerve) and the medial calcaneal nerve (complete avulsion) was confirmed. The tarsal tunnel was decompressed, and both the medial and the lateral plantar nerve were neurolyzed under magnification. To the best of our knowledge, our case report is the first to describe iatrogenic posterior tibial nerve injury after arthroscopic calcaneoplasty. It is significant because this complication can hopefully be avoided in the future with careful planning and creation of arthroscopic ports and treated appropriately with early referral to a nerve specialist if the patient's symptoms do not improve within 3 months.     

Neuromas of the calcaneal nerves.

A neuroma of a calcaneal nerve has never been reported. A series of 15 patients with heel pain due to a neuroma of a calcaneal nerve are reviewed. These patients previously had either a plantar fasciotomy (n = 4), calcaneal spur removal (n = 2), ankle fusion (n = 2), or tarsal tunnel decompression (n = 7). Neuromas occurred on calcaneal branches that arose from either the posterior tibial nerve (n = 1), lateral plantar nerve (n = 1), the medial plantar nerve (n = 9), or more than one of these nerves (n = 4). Operative approach was through an extended tarsal tunnel incision to permit identification of all calcaneal nerves. The neuroma was resected and implanted into the flexor hallucis longus muscle. Excellent relief of pain occurred in 60%, and good relief in 33%. One patient (17%) had no improvement and required resection of the lateral plantar nerve. Awareness that the heel may be innervated by multiple calcaneal branches suggests that surgery for heel pain of neural origin employ a surgical approach that permits identification of all possible calcaneal branches.     

跗管综合征的应用解剖学研究

目的:为跗管综合征的诊治提供形态学基础。方法:对61例成人下肢标本的跗管进行观测。结果:(1)跗管可分为前室、后浅室和后深室,胫神经、胫动静脉位于浅后室内;(2)跗管内容物有3％的变异率;(3)足内外侧神经分叉部59％位于踝跟轴线上方,26％位于下方,9％平轴线;(4)跟神经2支及2支以上者占51.3％。57.8％的跟神经来源于足外侧神经,35.4％来自胫神经,6.8％来自足内侧神经。结论:任何导致后浅室内高压的因素均可引起跗管综合征,手术以松解后浅室为主,各神经支的解剖变异在诊治时应加注意。     

Endoscopic flexor hallucis longus decompression: a cadaver study

BACKGROUND: New indications for arthroscopy are being considered because arthroscopy limits incision size and potentially decreases operative morbidity. This cadaver study investigated the utility of performing an all-endoscopic flexor hallucis longus (FHL) decompression. METHODS: Eight fresh-frozen cadaver legs were used. In the simulated prone position with large joint arthroscopic equipment, posterolateral and posteromedial portals were used to perform posterolateral talar process bony excision and FHL sheath debridement and release. We noted the integrity of the sural nerve, FHL tendon, and medial tibial neurovascular bundle. After open dissection, values for sural nerve distance to the posterolateral portal, the amount of FHL sheath released and the proximity of the arthroscopic instrumentation to the medial tibial neurovascular structures were recorded. RESULTS: Three of eight FHL tendons were injured during the attempted FHL release. Furthermore, no FHL sheath was completely released down to the level of the sustentaculum. Although posterolateral portal placement was on average 12.1 mm from the sural nerve, it was only 6.1 mm from the lateral calcaneal branch of the sural nerve. Moreover, in all cases the medial calcaneal nerve and first branch of the lateral plantar nerve were closely juxtaposed and in some cases adherent to the FHL fibro-osseous sheath. CONCLUSIONS: Although os trigonum or posterolateral talar process excision was performed without difficulty, endoscopic release of the FHL tendon proved technically demanding with significant risk to the local neurovascular structures. Given the reliability and low morbidity of open techniques, this cadaver study calls into question the clinical use of complete endoscopic FHL release to the level of the sustentaculum. Moreover, hindfoot endoscopic surgery should be performed by surgeons familiar with open posterior ankle anatomy and experienced in hindfoot endoscopy.     

Neurosensory testing of the medial calcaneal and medial plantar nerves in patients with plantar heel pain

Eighty-two patients with a chief complaint of plantar heel pain were evaluated for sensory abnormalities within the cutaneous distribution of both the medial calcaneal nerve and the medial plantar nerve, using quantitative neurosensory testing with a pressure-specified sensory device. The results showed that 22.68% of the patients displayed isolated abnormal sensory function within the distribution of the medial calcaneal nerve, whereas 49.48% of the patients displayed abnormal function within the distribution of both the medial calcaneal and the medial plantar nerves. Thus, 72.17% of the patients displayed abnormal sensory function within the distribution of the medial calcaneal nerve. Statistical analysis of the results, using the Pearson chi-square statistic and odds ratio, indicated that a significant percentage of patients with plantar heel pain, even early in the clinical course of plantar heel pain, display abnormal sensibility within the branches of the posterior tibial nerve, and specifically, within the distribution of the medial calcaneal nerve (P <.0008) and the medial plantar nerve (P <.0001).     

An anatomical study of tarsal tunnel

In order to understand the pathogenesis and improve the treatment of tarsal tunnel syndrome, we investigated the tarsal region anatomically on 62 feet of 31 cadavers and five freshly amputated feet. The following results were thus obtained: 1. The bifurcation into the medial and lateral plantar nerves mostly occurred within the flexor retinaculum. 2. The medial calcaneal branch showed many anatomical variations. 3. The flexor retinaculum was not clearly demarcated at its superior and inferior borders, and it was not as thick as previously thought. 4. The neurovascular bundle was separated from other tendon sheaths, and enclosed in its own tunnel. 5. A fibrous septum found at the entrance of the abductor hallucis muscle, may represent an entrapment point of the medial plantar nerve. 6. The ganglion from the talocalcaneal joint tended to compress only the medial plantar nerve.     

A touch pressure sensory assessment of the surgical treatment of the tarsal tunnel syndrome

Background

Decompressive tarsal tunnel surgery may improve dysfunctional plantar foot sensation in, patients with tarsal tunnel syndrome and peripheral neuropathy. However, quantitative sensory, assessment is lacking.

Method

Quantitative sensory threshold evaluation of 42 feet in 37 consecutive (29 non-diabetic and 8 diabetic) patients was done before and after surgical decompression for tarsal tunnel syndrome. Insensitivity was documented quantitatively (grams force) before and after surgery using a graded series of twenty Semmes–Weinstein monofilaments applied to the anatomic nerve regions of the plantar aspect of the foot.

Results

Sensory evaluation at an average of 12 months after surgery showed significant improvement, of mean sensory threshold, compared with preoperative values, for medial calcaneal, medial plantar, and lateral plantar nerves.

Conclusion

Quantitative sensory assessment with a graded series of twenty Semmes–Weinstein, monofilaments showed significant sensory improvement in the medial calcaneal, medial plantar, and, lateral plantar nerves after posterior tibial nerve decompression.     

A Posttraumatic, Joint-connected Sural Intraneural Ganglion Cyst—With a New Mechanism of Intraneural Recurrence: A Case Report

Intraneural ganglion cysts are rare in occurrence and most commonly involve the peroneal nerve at the fibular neck. We present a case of a traumatically induced intraneural ganglion cyst of the sural nerve that developed after a nondisplaced posterior malleolus ankle fracture. The intraneural ganglion cyst was connected to the subtalar joint by its articular branch and ascended several centimeters into the distal fourth of the leg. It was resected from the sural nerve proper and the posterior branch of the lateral calcaneal nerve, and the articular trunk was ligated. The patient developed subclinical intraneural recurrence, which was detected on a postoperative magnetic resonance imaging (MRI). Retrospective reinterpretation of the preoperative and postoperative MRIs revealed that ligation of the articular trunk proximal to a major branch (ie, the anterior branch of the lateral calcaneal nerve) led to increased intraneural cyst propagation distally: within the blind stump of the articular trunk and within several anterior branches of the lateral calcaneal nerve but not within the parent sural nerve or its continuation, the lateral dorsal cutaneous nerve. This mode of intraneural, but extraparental nerve recurrence can be easily understood by considering the altered fluid dynamics, particularly the increased resistance. This case report provides further evidence not only supporting the articular theory of intraneural ganglion formation but also highlighting the importance of searching for, identifying, and treating the pathologic articular branch connection near its joint connection in all cases. LEVEL OF CLINICAL EVIDENCE: 4.     

Outcome of neurolysis for failed tarsal tunnel surgery

Revision tarsal tunnel surgery was performed on 44 patients (two bilaterally). The surgical procedure included a neurolysis of the tibial nerve in the tarsal tunnel, the medial plantar, lateral plantar, and calcaneal nerves in their respective tunnels, excision of the intertunnel septum, and neuroma resection as indicated. A painful tarsal tunnel scar or painful heel was treated, respectively, by resection of the distal saphenous nerve or a calcaneal nerve branch. Postoperative, immediate ambulation was permitted. Outcomes were assessed with a numerical grading scale that included neurosensory measurements. Outcomes were also assessed by patient satisfaction and their own estimate of residual pain and/or numbness. Mean follow-up time was 2.2 years. Outcomes in terms of patient satisfaction were 54% excellent, 24% good, 13% fair, and 9% poor results. The mean preoperative numerical score was 6.0 and the mean postoperative score was 2.7. There was a significant improvement seen, based on the median difference between scores (P<0.001). Prognostic indicators of poor results in our patient group were coexisting lumbosacral disc disease and/or neuropathy. An approach related to resecting painful cutaneous nerves and neurolysis of all tibial nerve branches at the ankle offers hope for relief of pain and recovery of sensation for the majority of patients with failed previous tarsal tunnel surgery.     

Effects of medial and lateral displacement calcaneal osteotomies on tibiotalar joint contact stresses

Translational calcaneal osteotomies are used clinically to realign the mechanical axis of the lower limb. In this study, the effects of medial and lateral displacements of the posteroinferior fragment on tibiotalar joint contact mechanics were assessed using pressure-sensitive film. Eight osteotomized fresh-frozen cadaver specimens were loaded in each of three testing positions: neutral position (no shift), 1 cm of lateral displacement of the inferior fragment with respect to the superior fragment, and 1 cm of medial displacement of the inferior fragment. For an applied load of 1.330 N, two times body weight, a 1 cm lateral displacement shifted the center of pressure an average of 1.06 mm laterally, whereas a 1 cm medial displacement shifted the center of pressure an average of 1.58 mm medially. While global contact parameters (contact area, spatial mean contact stress, and peak local contact stress) were not appreciably altered by osteotomy, regional contact parameters changed in a reproducible and statistically significant manner. Among four nominally equal-sized, parasagittally bounded cartilage zones, lateral displacements consistently unloaded the most medial zone and increased loading of the most lateral zone; medial calcaneal displacements had the converse effect. These cadaver results suggest that translational calcaneal osteotomies may be used clinically to partially offload focal areas of cartilage along the medial and lateral borders of the tibiotalar joint.     

Bypasses to plantar arteries and other tibial branches: an extended approach to limb salvage

During the past 6 years, we have encountered 24 cases in which all major infrapopliteal arteries were occluded as determined by adequate preoperative angiography. Each patient initially had critical ischemia, 14 had a previous failed ipsilateral distal bypass, and seven had an unsuccessful lumbar sympathectomy. Instead of resorting to an amputation, we attempted to perform a bypass using patent branches of distal vessels. Of the 24 bypasses, 14 were to the lateral or medial plantar branches, three were to the deep plantar branch (plantar arch), three were to the lateral tarsal branch, and four were to unnamed branches of the proximal one third of the posterior tibial arteries (two) or anterior tibial arteries (two). All bypasses were performed with reversed saphenous vein with origins at or distal to the superficial femoral artery. Eight bypasses (four plantar and four unnamed branches) became thrombosed up to 30 months postoperatively, resulting in four below-knee amputations. Fifteen bypasses (all plantar branches) have been patent from 6 to 52 months (mean 26 +/- 13 months). The remaining patient required a below-knee amputation at 2 months despite a patent graft. These results underscore the value of this extended approach to limb salvage in situations previously believed to be indications for major amputations. Although bypasses to unnamed branches of the proximal tibial arteries did not fare well, those to the plantar branches and lateral tarsal branch resulted in excellent graft patency and limb salvage.     

Tarsal tunnel syndrome. Nerve compression syndrome in the foot

Pathological changes in sensation over the sole of the foot do not always correspond to the full area of distribution of the posterior tibial nerve. Some neurologists advise separate examination of the tibial nerve, the medial and lateral plantar nerves, in order to ascertain whether either or both might be affected. 60 preparations of cadaveric feet in the Department of Anatomy were examined. Using a measuring grid, the position and size of the nerves in the tarsal tunnel were assessed and the facial band which define and divide the osteofibrous canal delineated. The corners of the measuring grid were the tip of the medial malleolus (A), the tip of the calcaneal tubercle at its greatest distance from the medial malleolus (B) and the tuberosity of the navicular bone (C). These points can also be clearly identified clinically. They define a triangle whose sides A-B and B-C are of constant equal length and whose base A-C varies little. The operative approach includes a T-shaped incision of the retinaculum. The vertical line of the T lies underneath the skin incision. The horizontal line corresponds with the upper border of the abductor hallucis muscle. The upper border of the abductor hallucis is defined and the muscle retracted medially to expose the deep fascia. This layer is removed together with the connective tissue bridge which stretches between the fascia and the calcaneus. The plantar nerves are discovered and run to the sole of the foot without further obstruction.     

Anatomic study of a new axial skin flap based on the cutaneous branch of the medial plantar artery

A new axial skin flap based on the middle cutaneous branch of the medial plantar artery was evaluated in 33 fresh cadaver legs. The vascular pedicle of the skin flap is based on the middle cutaneous artery, its venae comitantes, and segments of the great saphenous vein, if necessary. The middle cutaneous artery is the largest cutaneous branch, arising from the medial plantar artery 2.5 cm distal to its origin. The diameter of its origin is 1.2 mm, and its pedicle is 2 cm long. The midline of the flap runs from the first web space to the heel tip. The upper and lower borders of the flap are 3 to 4 cm on either side of this line. The upper border is medial to the extensor hallucis tendon, and the lower border is medial to the abductor hallucis. Distally, the border begins 2 cm proximal to the metatarsalphalangeal joint; proximally, the border is at the middle of the medial malleolus. The flap diameter can be up to 8 × 12 cm. The middle cutaneous branch of the medial plantar artery was found in all cadaver specimens, except for one with a common trunk. The new flap design leaves the major blood supply to the foot and the plantar aponeurosis intact. It is easy to harvest and may be used either as an island flap or free flap. © 1995 Wiley-Liss, Inc.     

Quantitation of and landmarks for the muscular branches of the ulnar nerve to the forearm for application in peripheral nerve neurotization procedures

OBJECT: In neurotization procedures, donor nerves--either whole or in part-with relatively pure motor function can be carefully chosen to provide the optimal nearby motor input with as little donor site morbidity as possible. In this context, the ulnar nerve branches to the forearm muscles are relatively dispensable; however, quantitation of and landmarks for these branches are lacking in the literature. METHODS: The ulnar branches to the flexor carpi ulnaris (FCU) and flexor digitorum profundus (FDP) muscles in 20 upper extremities obtained in adult cadaveric specimens were dissected and quantified. In the forearm, a mean of four nerve branches led to the FCU and FDP muscles. A mean of 3.4 branches led to the FCU muscle; of these, one to three were medial branches and zero to two were lateral. Medial branches to the FCU muscle originated a mean of 2.7 cm inferior to the medial epicondyle. Lateral branches to the FCU muscle originated at a mean of 3.3 cm inferior to the medial epicondyle. The mean length of the medial branches was 3.2 cm, whereas the mean length of the lateral branches was 3.3 cm. All nerves had a single trunk for the FDP muscle, and in all specimens this branch was located deep to the main ulnar nerve trunk, originating from the ulnar nerve a mean of 2.7 cm inferior to the medial epicondyle. These branches had a mean length of 5.6 cm. The mean diameter of all medial and lateral branches to the FCU muscle was 1 mm, and the mean diameter of the branch to the FDP muscle was 2.1 mm. All branches to both the FCU and FDP muscles arose from the ulnar nerve, over its first approximately 5 cm from the level of the medial epicondyle. Additionally, all branches could be easily lengthened by gentle proximal dissection from the main ulnar nerve. CONCLUSIONS: Ulnar branches to the forearm can be easily localized and used for neurotization procedures. The branch to the FDP muscle had the greatest diameter and longest length, easily reaching the median nerve and posterior interosseous nerve via a transinterosseous membrane tunneling procedure. Furthermore, this branch could be teased away from the main ulnar nerve trunk and made to reach the distal branches of the musculocutaneous nerve in the arm.     

Innervation of calf muscles in relation to calf reduction

Plump and muscular calves, a so-called radish-like leg, embarrass young women and cause a feeling of inferiority in Korea. Damage to motor nerves innervating a muscle makes the muscle paralyzed and dystrophic, with loss of muscle volume. The authors studied the morphometry of the motor branches of the tibial nerve innervating the gastrocnemius and soleus muscle and sensory medial sural cutaneous nerve in popliteal fossa. Dissection and exploration of the tibial nerve were performed in the popliteal fossae of 70 legs (of 18 males and 17 females) of embalmed Korean cadavers. The main branch of the tibial nerve innervating medial and lateral gastrocnemius muscle originated 3 cm above and below the popliteal crease. The medial gastrocnemius muscle had an additional nerve (49%). The medial sural cutaneous nerve came off the nerve into the medial gastrocnemius muscle (30%) and diverged 5.5 mm from the tibial nerve. The nerve into the soleus muscle originated from the nerve innervating the lateral gastrocnemius muscle (30%) and was 12.3 mm away from it. Surgeons should keep in mind that the medial sural cutaneous nerve originates from the nerve to medial gastrocnemius in 30% and the nerve to soleus muscle originates from the nerve to lateral gastrocnemius in 30%.