W. Thomas Jackson

Tibial Nerve Branching in the Tarsal Tunnel

Tarsal tunnel syndrome is an infrequent and probably underdiagnosed clinical condition. Diagnosis and treatment depend on understanding the tibial branching pattern within the tarsal tunnel. A total of 68 foot dissections were performed. Bifurcation into the medial and lateral plantar nerves occurred within the tunnel in 93% and proximal in 7%. Proximal bifurcation may predispose to tarsal tunnel syndrome, and its infrequent occurrence correlates with the infrequent clinical diagnosis. Nine different calcaneal branching patterns were noted; they provide an anatomical explanation for heel sparing. An understanding of anatomic variations should aid in providing complete surgical release and in avoiding accidental heel denervations.

Incidence of anatomic variants in Guyon's canal☆

This study was undertaken to determine the frequency of variations involving the anatomy of Guyons canal. A series of 58 wrist dissections revealed a 22.4% incidence of anomalous muscles and a 1.7% incidence of anomalous nerve paths. The relationship of the deep branch of the ulnar artery to the superficial and deep branches of the ulnar nerve was found to vary. Accessory muscles passing through Guyons canal are common, and are often found bilaterally. Aberrant branching of the ulnar nerve in this area is rare.

Carpal tunnel changes and median nerve compression during wrist flexion and extension seen by magnetic resonance imaging

Magnetic resonance imaging was done on the wrists of 14 volunteer subjects with the wrists in the neutral position, then flexed and extended at 45 degrees. Computer enhanced cross-sectional areas were measured on each subject at the level of the hook of the hamate. In the neutral position the distance between confining structures around the median nerve is 2.0 +/- 0.2 mm in the anteroposterior direction, and the mean cross-sectional area of the carpal tunnel is 1.52 cm2. With the wrist in the extended position the distance available for the median nerve measures 2.2 +/- 0.4 mm and the cross-sectional area increases to 1.75 cm2. When the wrist is flexed, the distance available for the median nerve between the flexor tendons and transverse carpal ligament decreases to 1.1 +/- 0.4 mm, and the cross-sectional tunnel area decreases to 1.36 cm2. Flexion of the wrist and/or fingers both produces a palmar rearrangement of the flexor tendons creating potential compression of the median nerve. The nerve responds to these forces by becoming interposed in various positions between the superficial flexor tendons.

Cigarette smoking and Dupuytren's contracture of the hand

Microvascular occlusion has been implicated as a possible causative factor of Dupuytrens contracture. Cigarette smoking is one of the most significant factors in the development of peripheral vasculopathy. The relationship between smoking and Dupuytrens contracture of the hand is explored in this article. One hundred thirty-two consecutive patients who had a partial fasciectomy for treatment of Dupuytrens contracture from 1980 to 1985, were analyzed retrospectively. There were 111 males and 21 females. Ninety (68.2%) of 132 patients smoked cigarettes compared with 110 (37.2%) of 296 randomized hospitalized control patients (p less than 0.00001). Eighty (72.1%) of 111 men smoked cigarettes compared with 65 (44.2%) of 147 male control patients (p = 0.000015). Cigarette smoking is linked statistically to Dupuytrens disease and may be involved in its pathogenesis by producing microvascular occlusion and subsequent fibrosis and contracture or by some other mechanism.

Scapulothoracic dissociation (closed avulsion of the scapula, subclavian artery, and brachial plexus): a newly recognized variant, a new classification, and a review of the literature and treatment options.

Scapulothoracic (ST) dissociation is a closed complete traumatic forequarter amputation manifested by a flail pulseless arm and well-defined roentgenographic findings. These roentgenographic findings were previously reported to be lateral displacement of the scapula and either acromioclavic-ular separation (17) or displaced clavicular fracture (20). In this paper we present four patients with ST dissociation who had a previously unreported combination of roentgenographic findings: lateral displacement of the scapula and sternoclavicular separation. Polytrauma was present in all previously reported cases of patients with ST dissociation. We present one patient, however, in whom ST dissociation is an isolated finding. A review of the literature, and a review of treatment options that includes some combination of amputation, shoulder arthrodesis, prosthetic fitting, and reconstructive tendon transfers, are presented.

Reflex sympathetic dystrophy and cigarette smoking

Although the cause of reflex sympathetic dystrophy (RSD) remains unknown, hyperactivity of the sympathetic nerves and secondary vasospasm may be pathogenic in this syndrome. A retrospective epidemiologic study of RSD was done on 53 in-patients from 1978-1985. Cigarette smoking was strikingly increased in patient frequency in RSD (68% versus 37% of hospitalized controls, p less than 0.0001). Eighty-seven percent of the patients had a history of trauma or surgery, and 38% had other associated diseases. Cigarette smoking is statistically linked to RSD and may be involved in its pathogenesis by enhancing sympathetic activity, vasoconstriction, or by some other unknown mechanism.

Anatomical Considerations of Posterior Tibialis Tendon Entrapment in Irreducible Lateral Subtalar Dislocation

Irreducible lateral subtalar dislocation is associated with posterior tibialis tendon entrapment. Mulroy 7 and Leitner 6 have proposed conflicting theories regarding the exact mechanism of tendon entrapment. Cadaveric analysis of lateral subtalar dislocation supported Leitners 5 contention that tearing of the flexor retinaculum promotes posterior tibialis tendon entrapment. Retinacular disruption allowed tendon subluxation over the medial malleolus and talar head to the entrapped position. Entrapment of the flexor digitorum longus only occurred in the Leitner model. When the flexor retinaculum and deep posterior compartment fascia were preserved, the muscle failed at the musculotendinous junction. Flexor hallucis longus entrapment could not be produced in either experimental model. Plantarflexion of the great and lesser toes, noted on clinical presentation, is caused by functional lengthening of the route coursed by the flexor digitorum longus and flexor hallucis longus.

Danger zone of the acetabulum

Summary The danger zone of the acetabulum is defined by Marvin Tile as that part of the posterior wall and column at the mid-acetabulum lying above the ischial spine. Screws inserted in the danger zone are at risk of violating the hip joint. Unfortunately, this zone is frequently used in the fixation of posterior wall and column fractures. Cadaveric studies were performed analyzing 1-cm cross-sections through the acetabulum for the purpose of studying the anatomical configuration of the danger zone. The plane of the cross-section was perpendicular to the posterior column. Each cross-section had the medial boundary of the acetabulum projected onto the posterior column. The cross-sections were then assembled to form the original acetabulum. By analyzing the projections on the posterior column, the exact configuration of the danger zone was determined. Screws placed at the margin of the danger zone and directed perpendicular to the posterior column violated the hip joint. Through analysis of the cross-sections, safe anatomic pathways were developed for screw placement. Cortical screws (4.5 mm), placed at entry points of 2 cm and 3 cm medial to the lateral acetabular margin and angled medially 45 and 15, respectively, did not violate the hip joint. The angulation was respective to the perpendicular to the posterior column. In this study, the average width of the posterior column at the mid-acetabular level was 4.8 cm. Computed tomography scan of the acetabulum yielded valuable information regarding screw placement in the posterior column. Software analysis of the inclination of the acetabulum, with respect to the perpendicular to the posterior column, provided safe anatomic pathways for screw placement. This method of analysis could prove valuable in preoperative planning for internal fixation of posterior wall fractures.

Comminuted Fracture of the Calcaneus Associated with Subluxation of the Talus

Two cases of complex fracture dislocation of the calcaneus having an unusual pattern of injury are described. The cases exhibit the following special characteristics: (1) fracture dislocation of the calcaneus where the primary fracture line separates the calcaneus into an anteromedial fragment that maintains its normal relationship to the talus and a posterolateral fragment that is dislocated from the subtalar joint. This posterolateral fragment moves laterally and lies adjacent to the fibula; (2) a secondary fracture line separating the lateral portion of the posterior facet from the tuberosity of the calcaneus. Both fragments are dislocated from their normal anatomical position; (3) talar tilt as shown on AP view of the ankle caused by inversion of the talus due to rupture of the lateral collateral ligament. Also, the posterolateral fragments impinging on the fibula pushes the heel downward and contributes to the talar tilt; (4) involvement of the calcaneocuboid joint; (5) dislocation of the peroneal tendons. This fracture pattern is unusual and has not been described before. Recognition of this unusual injury with subsequent and proper management may prevent major disability to the patient. Conservative treatment by casting or early range of motion is contraindicated. Closed reduction should be attempted immediately, and if not successful, a lateral approach with open reduction and internal fixation is the treatment of choice for this complex injury.

Radiological diagnosis of screw penetration of the hip joint in acetabular fracture reconstruction.

Screw penetration of the hip joint following acetabular fracture reconstruction is a relatively uncommon complication but, if not corrected, may have a catastrophic effect on the postoperative function of the hip joint. Intraoperative radiographs and postoperative standard anteroposterior (AP) radiographs frequently show super-imposition of the screws and acetabulum. Computed tomographic (CT) scanning has been the only diagnostic technique available allowing documentation of screw penetration into the hip joint. CT scan, however, can be performed only after termination of surgery. In search for a radiological view that will help in diagnosing screw penetration into the hip joint both intra- and postoperatively, we undertook a controlled study of 25 patients having either a posterior or extensile lateral surgical approach and six cadaveric specimens. A combination of a cross-table lateral view of the hip and a Judet iliac view proved more informative than AP or Judet obturator views in demonstrating absence or presence of the screw in the hip joint (if the screws were placed along the posterior wall or column). Intraoperative AP radiographs projected as a Judet obturator view were the least helpful in making this determination. When screw penetration is suspected, we recommend the use of intraoperative fluoroscopy in multiple projections or intraoperative arthrogram in the lateral projection of the pelvis. Also, Judet iliac and cross-table lateral radiographs in the operating room while the patient is still under anesthesia might exclude any screw penetration into the hip joint.