Anatomical study of the medial plantar proper digital nerve using ultrasound.

PURPOSE: To determine whether ultrasound allows precise assessment of the course and relations of the medial plantar proper digital nerve (MPPDN). MATERIALS AND METHODS: This work was initially undertaken in six cadaveric specimens and followed by a high-resolution ultrasound study in 17 healthy adult volunteers (34 nerves) by two musculoskeletal radiologists in consensus. Location and course of the MPPDN and its relationship to adjacent anatomical structures were analysed. RESULTS: The MPPDN was consistently identified by ultrasound along its entire course. Mean cross-sectional area of the nerve was 0.8 mm2 (range 0.4-1.4). The MPPDN after it branches from the medial plantar nerve was located a mean of 22 mm (range 19-27) lateral to the medial border of the medial cuneiform. More distally, at the level of the first metatarsophalangeal joint, mean direct distances between the nerve and the first metatarsal head and the medial hallux sesamoid were respectively 3 mm (range 1-8) and 4 mm (range 2-9). CONCLUSION: The MPPDN can be depicted by ultrasonography. Useful bony landmarks for its detection could be defined. Precise mapping of its anatomical course may have important clinical applications. KEY POINTS: • The medial plantar proper digital nerve (MPPDN) rises from the medial plantar nerve to the medial side of the hallux. • Because of its particularly long course and superficial position, the MPPDN may be subject to trauma, resulting in a condition known as Joplin's neuroma. • The MPPDN can be clearly depicted by ultrasound along its entire course. Precise mapping of its anatomical course may have important clinical applications.

Minimally Invasive Dorsal Cheilectomy of the First Metatarsal: A Cadaveric Study.

BACKGROUND:: Minimally invasive dorsal cheilectomy (MIDC) for hallus rigidus is gaining in popularity. The optimal position for the stab incision for MIDC is dorsomedial to allow an ergonomic sweeping movement of the burr, potentially putting the dorsomedial cutaneous nerve (DMCN) to the hallux at risk. We aimed to quantify the risk of using this minimally invasive technique with a cadaveric study. METHODS:: A total of 13 fresh-frozen cadaveric specimens amputated below the knee were obtained for this study. After the procedure, the specimens were dissected, and structures were inspected for damage. RESULTS:: The DMCN to the hallux was cut completely in 2 specimens (15%). All the extensor hallucis longus tendons were intact, although in 1 specimen, the tendon showed some fraying on the underside of the tendon. The average distance of the stab incision from the first metatarsophalangeal (MTP) joint was 17.7 (range, 10-23) mm. The relationship of the DMCN to the stab incision was variable. The average distance of the DMCN to the incision was 3.8 (range, 0-7) mm. The danger zone for damaging the DMCN was at one-third the length of the first metatarsal proximal to the first MTP joint. CONCLUSION:: The DMCN has been well studied by several authors and has a variable course. This nerve was damaged in 15% of our specimens following MIDC. CLINICAL RELEVANCE:: We believe patients should be made aware of this risk when considering surgery. A carefully made working capsular pocket for the burr and marking this nerve before making the incision if palpable could mitigate this risk.

Increasing the safety of minimally invasive hallux surgery-An anatomical study introducing the clock method.

BACKGROUND: The purpose of this study is to describe a simple and reproducible method to localize the neurological structures at risk and to describe a safe zone for hallux minimally invasive surgery (MIS) procedures. METHODS: Ten fresh-frozen cadaveric feet were dissected to identify the dorsomedial digital nerve (DMDN) and the dorsolateral digital nerve (DLDN) of the first toe. Axial sections were performed at the sites of metatarsal osteotomies. We documented the position of the nerves with respect to the extensor hallucis longus (EHL) tendon using a clock method superimposed on the axial section RESULTS: The DMDN was found at an average of 26.2° medial to the medial border of the EHL tendon. (SD 11.26, range 14.5-45.5), whereas the average distance of the DLDN was 32.3° lateral to the medial border of the EHL tendon. (SD 6.29, range 13.5-40). CONCLUSIONS: Using the clock method the DMDN and DLDN were found consistently between 10 o'clock and 2 o'clock in either right and left feet. The clock method may facilitate avoiding the area where these nerves are located serving as a valuable tool in minimally invasive foot surgery.

The Use of Ultrasonography to Identify the Intersection of the Dorsomedial Cutaneous Nerve of the Hallux and the Extensor Hallucis Longus Tendon: A Cadaveric Study.

Terminal branches of the superficial fibular nerve are at risk of iatrogenic damage during foot surgery, including hallux valgus rigidus correction, bunionectomy, cheilectomy, and extensor hallucis longus tendon transfer. One terminal branch, the dorsomedial cutaneous nerve of the hallux, is particularly at risk of injury at its intersection with the extensor hallucis longus tendon. Iatrogenic injuries of the dorsomedial cutaneous nerve of the hallux can result in sensory loss, neuroma formation, and/or debilitating causalgia. Therefore, preoperative identification of the nerve is of great clinical importance. The present study used ultrasonography to identify the intersection between the dorsomedial cutaneous nerve of the hallux and the extensor hallucis longus tendon in cadavers. On ultrasound identification of the intersection, dissection was performed to assess the accuracy of the ultrasound screening. The method successfully pinpointed the nerve in 21 of 28 feet (75%). The sensitivity, positive likelihood ratio, and positive and negative predictive values of ultrasound identification of the junction of the dorsomedial cutaneous nerve and the extensor hallucis longus tendon were 75%, 75%, 100%, and 0%, respectively. We have described an ultrasound protocol that allows for the preoperative identification of the dorsomedial cutaneous nerve of the hallux as it crosses the extensor hallucis longus tendon. The technique could potentially be used to prevent the debilitating iatrogenic injuries known to occur in association with many common foot surgeries.

Anatomic basis and clinical application of the distally based medialis pedis flaps.

BACKGROUND: Soft-tissue defects of the forefoot are difficult to cover adequately, particularly, although multiple options for reconstruction are available. This study especially focused on the vascularization of the medial side of the foot and the determination of the contribution of the nutrient vessels to medialis pedis flap viability. METHODS: Thirty cadavers were available for this anatomical study. Microdissection was conducted under a microscope, and details of the course and distribution and the communication of the first plantar metatarsal artery with the fascial vascular network of the medial side of the foot were recorded. Clinically, six cases of soft-tissue defects at the forefoot region were reconstructed with distally based medialis pedis flap. RESULTS: The perforator of the first plantar metatarsal artery pierces in the superficial fascia of the medial aspect of the foot 2.2 ± 0.7 cm proximal to the first metatarsophalangeal joint, vascularize the skin of the medial plantar region. The anatomical study showed that the vasculature pattern could roughly be classified into two types. In terms of clinical application, all flaps completely survived, and one patient had partial loss of skin graft. CONCLUSION: The perforators of the medialis pedis flap are presented constant. The forefoot region can be repaired by the distally based medialis pedis flap on the perforator of the medial plantar artery of the hallux or the first plantar metatarsal artery perforator with medial plantar vein, medial plantar cutaneous nerve and nutrient vessels.

The Diagnosis and Treatment of Joplin's Neuroma.

Joplin's neuroma is a rare perineurial fibrosis of the medial plantar digital proper nerve arising from various etiologies but most commonly after bunion surgery. Treatment for this painful great toe problem remains controversial. It is our purpose to describe our experience with this chronic pain problem, considering it to be a neuroma requiring resection. A retrospective medical record review of 8 patients with medial hallux pain related to the digital nerve was performed. Each patient had failed to respond to >6 months of nonoperative therapy. At surgery, the medial digital nerve to the hallux was identified distally, the neuroma was resected distally, and the proximal end of the nerve was implanted into the arch of the foot in 7 (87.5%) of the 8 patients. At a mean follow-up of 25 (range 13 to 43) months, 6 results (75%) were excellent, 1 (12.5%) was good, and 1 (12.5%) was fair. The 1 fair result was in the only patient in whom the distal end of the divided nerve was not implanted proximally, according to the patient's request. In conclusion, surgical resection of the medial plantar nerve to the hallux with implantation of the proximal end of the nerve into the arch of the foot, can be expected to result in good to excellent relief of pain in 80% of the patients.

Proposal of a new method for the use of the Rydel-Seiffer tuning fork in the screening of diabetic polyneuropathy. A pilot study.

We investigated the usefulness of a new examiner-independent method based on the duration of vibration sensation following the placement of the Rydel-Seiffer tuning fork over the dorsum of the interphalangeal hallux joint. This method demonstrated the same diagnostic efficacy as the Rydel-Seiffer method coupled with greater ease of use.

The sentinel vein: an anatomical guide to localisation of the dorsomedial cutaneous nerve in hallux surgery.

Damage to the dorsomedial branch of the medial dorsal cutaneous nerve is not uncommon in surgery of the hallux. The resultant morbidity can be disabling. In the light of the senior author's operative observation of a sentinel vein, we undertook a cadaver study to investigate the anatomical relationships of the dorsomedial branch of the medial dorsal cutaneous nerve. This established that in 14 of 16 cadaver great toes exposed via a modified medial incision, there is an easily identified vein which runs transversely superficial and proximal to the nerve. In a prospective clinical study of 171 operations on the great toe using this approach, we confirmed this anatomical relationship in 142 procedures (83%), with no complaint of numbness or pain in the scar at follow-up. We attribute this to careful identification of the 'sentinel' vein and the subjacent sensory nerve, which had been successfully protected from damage. We recommend this technique when operating on the great toe.

Arthroscopic debridement for first metatarsophalangeal joint arthrodesis with a 2- versus 3-portal technique: a cadaveric study.

PURPOSE: To evaluate the safety and efficacy of arthroscopic debridement for arthrodesis of the first metatarsophalangeal (MTP) joint using a 2-portal technique versus a 3-portal technique. METHODS: Twelve cadavers, with a mean age of 60 years, were subjected to arthroscopic debridement of the first MTP joint. Dorsolateral and dorsomedial portals were used in 6 specimens, whereas a medial portal was added in the other 6 specimens. The articular cartilage was debrided on both the proximal and distal surfaces and stabilized with a K-wire. The surrounding neurovascular structures were evaluated for injuries and measured for the distance from the portals. The fusion contact areas were estimated and denuded surfaces were measured on both sides. Results between the 2- and 3-portal techniques were compared. Statistical significance was taken as P < .05. RESULTS: The mean estimated fusion contact area was 180.19 mm(2) on the proximal phalanx and 180.21 mm(2) on the distal metatarsal articular surfaces. On the proximal phalanx, the percentage of denuded area was 94.71% with the 2-portal technique and 97.60% with the 3-portal technique. On the distal metatarsal, the percentage of denuded area was 93.31% with the 2-portal technique and 95.22% with the 3-portal technique. The 3-portal technique statistically increased the area of debridement on the plantar-medial surface of the distal metatarsal. The mean distance from the dorsolateral portal to the dorsolateral hallucal nerve was 3.4 mm. The mean distance from the dorsomedial portal to the dorsomedial hallucal nerve was 4 mm. The medial portal was, on average, 10.5 mm from the dorsomedial hallucal nerve and 13 mm from the plantar-medial hallucal nerve. There was no visible nerve injury detected. CONCLUSIONS: The 3-portal technique for arthroscopic-assisted arthrodesis of the first MTP joint allowed more complete cartilage debridement when compared with the 2-portal technique. The additional medial portal was found to be safe from the surrounding neurovascular structures. CLINICAL RELEVANCE: Joint preparation for arthroscopic assisted arthrodesis of the first MTP joint can be safely and effectively performed using 3-portal technique, which may reduce the risk of non-union.

A randomized controlled trial to compare two techniques for partial digital local anesthetic blocks.

The administration of local anesthetic before surgery to the great toe is often associated with significant difficulties, delaying surgery and increasing risk. Anxious patients can faint, refuse injection, or withdraw the foot while an anesthetic is being delivered. Such events led us to consider whether delivering a small amount of anesthetic throughout the injection site, before the main injection, may reduce pain intensity and duration. This study was designed to test this possibility. A randomized controlled, single-blinded, parallel-grouped clinical trial was carried out with a sample of 50 patients. All study participants received each injection method (1 or 2 stage) to either the medial or lateral side of the great toe. The primary end points were pain intensity, measured by scores on a visual analogue scale and duration, recorded by the patient with a stopwatch. The 2-stage method was associated with less intense pain (reduced from moderate to mild visual analogue scale level) of a shorter duration. The differences were highly statistically significant. In the 2-stage method, it is believed that they were due to the initial infiltration of a small quantity of the anesthetic solution throughout the injection site, with the remainder being administered, after a 2-minute interval, into tissue that was predominantly anesthetized. This differs from raising a traditional bleb where a small amount of anesthetic is infiltrated into superficial tissue. The 2-stage technique is therefore recommended as the method of choice for adults.

Anatomy of the plantarmedial hallucal nerve in relation to the medial approach of the first metatarsophalangeal joint.

BACKGROUND: The medial approach has been widely utilized for various pathologies of the first metatarsophalangeal joint. Injury to the plantarmedial hallucal nerve has been cautioned but never been reported. This study evaluated the proximity of the plantarmedial hallucal nerve to the midline and the vertical capsulotomy through the medial approach. MATERIALS AND METHODS: Nine fresh cadaver legs were dissected under loupe magnification after AP radiographs were obtained. The distances from the plantarmedial hallucal nerve to the midline and to the plantar extent of the vertical capsulotomy were measured. The nerves were documented for their course, branching, and integrity. RESULTS: The average hallux valgus angle was 10.3 +/- 3.8 degrees (Mean +/- SD). The distances from the nerve to the midline and to the plantar extent of the vertical capsulotomy averaged 10.6 +/- 3.2 mm and 2.4 +/- 1.6 mm. One specimen demonstrated a partial nerve transection. All the nerves were found underneath the crural fascia and covered by vertical fibers investing the plantar fat pad at the level of the metatarsophalangeal joint. They gave off an average of seven terminal branches toward the pulp and tip of the hallux. CONCLUSION: The plantarmedial hallucal nerve is at risk for injury with the vertical capsulotomy during a medial approach to the first metatarsophalangeal joint due to its proximity to the plantar extent of the vertical capsulotomy. CLINICAL RELEVANCE: Surgeons should be vigilant in doing the vertical capsulotomy of the first metatarsophalangeal joint especially if the plantarmedial hallucal nerve is not identified.

Nerve disorders of the hallux.

Nerve disorders about the hallux can generate remarkable pain and dysfunction. Whether caused by soft tissue entrapment, trauma, iatrogenic injury, or from an idiopathic basis; nerve disorders are approached by careful history and examination followed by nonoperative treatment. In cases that do not respond, meticulous surgical management can be helpful in many cases.

Anatomical study of the communicating branches between the medial and lateral plantar nerves.

The plantar areas of the foot have specific biomechanical characteristics and play a distinct role in balance and standing. For the forefoot surgeon, knowledge of the variations in the anatomy of communicating branches is important for plantar reconstruction, local injection therapy and an excision of interdigital neuroma. The anatomy of the communicating branches of the plantar nerves between the fourth and third common plantar digital nerves in the foot were studied in 50 adult men cadaveric feet. A communicating branch was present between the third and fourth intermetatarsal spaces nerves in all eight left feet and in six right feet (overall, 28%), and absent in 36 (72%). A communicating branch was found in 14 ft. Ten of the 14 communications were from the lateral to the medial plantar nerve. The length of the communicating branch ranged from 8 to 56 mm (average 16.4 mm) and its diameter was 0.2-0.6 times of the fourth common plantar digital nerve. The angle of the communicating branch with the common plantar digital nerve from which it originated was less than 30 degrees in 11 ft, 30-59 degrees in 27 ft, 60-80 degrees in 8 ft, and more than 80 degrees in 4 ft. Classification of the branch is based on the branching pattern of the communicating branch and explains variations in plantar sensory innervations. We think that the perpendicular coursing communicating branch is at higher risk to be severed during surgery.

Finger reconstruction with a free neurovascular wrap-around flap from the big toe.

From 1983 to 1998, 16 cases of finger reconstruction with a free neurovascular wrap-around flap from the big toe were treated. Fourteen cases were successful, and two cases failed. The authors reviewed these cases on the average of about 38 months after surgery. Pinch power was 51 percent of the unaffected normal hand, and two-point discrimination was 7.6 mm. The mean resorption of the grafted bone was 13 percent in width and 9 percent in length. There were no complications such as fracture of the grafted bone, nonunion, and pulp dislodgement. This procedure provided length, stability, and adequate sensibility for a functional pinch and grasp. Sensory return to the wrap-around flap on the thumb was often greater than for the same area on the opposite foot. The donor site of the wrap-around flap was acceptable, both aesthetically and functionally, and allowed the wearing of open-toed shoes by young women. Finger reconstruction with a wrap-around flap from the big toe yielded excellent cosmetic and functional results in cases involving amputation at the level of the metacarpophalangealjoints or distal to it. In addition, this procedure was an excellent choice for treatment in cases involving avulsion injuries of the fingers and reconstruction of soft-tissue defects after tumor excision.

The surgical anatomy of the dorsomedial cutaneous nerve of the hallux.

Most techniques described for the correction of hallux valgus require exposure of the distal aspect of the first metatarsal. A dorsomedial incision is often recommended. Texts counsel against damaging the dorsal digital nerve, as a painful neuroma is an unwelcome surgical complication. Our study on cadavers aimed to investigate the anatomy of the dorsomedial cutaneous nerve in the metatarsophalangeal region, with special reference to surgical incisions. A constant, previously unrecognised branch of the nerve was identified. This branch is likely to be damaged if a dorsomedial approach is used. It is recommended that a mid-medial incision be used instead, i.e. at the junction of the plantar and dorsal skin.

Somatotopic organization of human secondary somatosensory cortex.

This fMRI study investigated the human somatosensory system, especially the secondary somatosensory cortex (SII), with respect to its potential somatotopic organization. Eight subjects received electrical stimulation on their right second finger, fifth finger and hallux. Within SII, the typical finding for both fingers was a representation site within the contralateral parietal operculum roughly halfway between the lip of the lateral sulcus and its fundus, whereas the representation site of the hallux was found more medially to this position at the fundus of the lateral sulcus, near the posterior pole of the insula. Somatotopy in SII seems to be less fine-grained than in primary somatosensory cortex (SI), as, in contrast to SI, no separate representations of the two fingers in SII were observed. A similar somatotopic representation pattern between fingers and the hallux was also observed within ipsilateral SII, indicating somatotopy of contra- as well as ipsilateral SII using unilateral stimulation. Further areas exhibiting activation were found in the superior and inferior parietal lobule, in the supplementary and cingulate motor area, and in the insula.

Tibial nerve F-waves recorded from the abductor hallucis.

The purpose of this study was to develop a large database of normal values for the tibial nerve F-wave. A total of 159 asymptomatic subjects without risk factors for neuropathy were recruited and had ten tibial F-waves performed on each leg. Data were collected for the shortest F-wave (Fmin), the mean F-wave (Fmean), and the range of F-waves (Frange). Age, gender, and height were associated with differences in the results. The mean Fmin was 50.8 +/- 5.3 ms. Mean Fmean was 53.0 +/- 5.6 ms and mean Frange was 4.5 +/- 2.4 ms. The mean side-to-side difference for Fmin was 0.6 +/- 2.3 ms and the mean side-to-side difference for Fmean was 0.4 +/- 2.5 ms.

Tibial nerve motor conduction to the abductor hallucis.

Tibial motor studies to the abductor hallucis are commonly performed in electrodiagnosis. Numerous authors have investigated this nerve to derive the normal ranges for latency, amplitude, and nerve conduction velocity (NCV). Many of the studies were performed without regard to temperature control, fixed distance measurement, and demographic characteristics such as age, gender, and height, which are known to affect nerve conduction studies. They often used small sample sizes, and some did not use true normal controls. This study was performed to create an expanded database of normative values for the tibial nerve. In this study, 250 asymptomatic subjects without risk factors for neuropathy were recruited and tested for their tibial motor response. Latency, amplitude, area, duration, and NCV were recorded. A repeated measures analysis of variance was performed with the waveform measures as the dependent variables and age, gender, and height as independent variables. Factors that were significant at the P < or = 0.01 level were used to create separate normative databases. Age was found to be associated with different results for amplitude, area, and NCV. Height was found to be associated with different results for NCV. Once these statistically significant factors were determined, Tukey-adjusted pair-wise comparisons of least squares means were used to collapse categories (by decade for age) that were not significantly different from each other at the P < or = 0.05 level. Side-to-side and proximal-to-distal differences were analyzed. The normal range was derived as mean +/- 2 standard deviations (SD) and at the 97th (third) percentiles of observed values. Mean onset latency was 4.5 ms (SD, 0.8). Mean amplitude was 15.3 mV (SD, 4.5), 12.9 mV (SD, 4.5), and 9.8 mV (SD, 4.2) for the respective age groups of 19-29, 30-59, and 60-79 yr. Nerve conduction velocity ranged from a mean of 44 to 51 m/s depending on the demographic groups of various ages and heights. The upper limit of side-to-side latency variation was 1.4 ms (at the 97th percentile), and the upper limit of normal amplitude difference from side to side was 50% (at the 97th percentile). The other measures are presented in the article.

A comparison of train-of-four monitoring: mechanomyography at the thumb vs acceleromyography at the big toe.

BACKGROUND: It is not known if the information on neuromuscular function obtained from the hand is interchangeable with that of the foot. In the present study the agreement of thumb mechanomyography with acceleromyography of the big toe was studied. METHODS: Ten healthy patients scheduled for oral surgery were studied. Anaesthesia was induced with fentanyl 2 micrograms kg-1 and propofol 2 mg kg-1, and maintained with propofol 100-175 micrograms kg-1 min-1, nitrous oxide 60-70%, and fentanyl 1-2 micrograms kg-1 h-1. Vecuronium 0.1 mg kg-1 was used for muscle relaxation. Mechanomyography (MMG) of the thumb (Myograph 2000) and acceleromyography (AMG) of the big toe (TOF-Guard) were recorded simultaneously in all patients, and onset, period of no-twitch response, duration of action, and spontaneous recovery time obtained from both muscle groups. The agreement between methods was tested by calculation of bias and limits of agreement. RESULTS: The onset time and duration of action were significantly shorter (87 s vs 154 s, and 35 min vs 38 min, respectively), and the spontaneous recovery time significantly longer in the thumb than in the big toe (32 min vs 19 min). Period of no-twitch response was not significantly different in the two muscle groups. Limits of agreement (thumb big toe) were -21 to -113 s, -7 to 1 min, and -9 to 35 min, for onset time, duration of action, and spontaneous recovery time, respectively. CONCLUSIONS: We conclude that clinically acceptable agreement between thumb mechanomyography and big toe acceleromyography was found for the period of no-twitch response, suggesting that the timing of supplemental doses of vecuronium can be guided by AMG at the big toe. However, the spontaneous recovery time agreement (to TOF ratio = 0.75) between the thumb and the big toe was poor.

Dropped hallux after the intramedullary nailing of tibial fractures.

We made a prospective study of 208 patients with tibial fractures treated by reamed intramedullary nailing. Of these, 11 (5.3%) developed dysfunction of the peroneal nerve with no evidence of a compartment syndrome. The patients with this complication were significantly younger (mean age 25.6 years) and most had closed fractures of the forced-varus type with relatively minor soft-tissue damage. The fibula was intact in three, fractured in the distal or middle third in seven, with only one fracture in the proximal third. Eight of the 11 patients showed a 'dropped hallux' syndrome, with weakness of extensor hallucis longus and numbness in the first web space, but no clinical involvement of extensor digitorum longus or tibialis anterior. This was confirmed by nerve-conduction studies in three of the eight patients. There was good recovery of muscle function within three to four months in all cases, but after one year three patients still had some residual tightness of extensor hallucis longus, and two some numbness in the first web space. No patient required further treatment.