MRI findings of spinal accessory neuropathy.

AIM: To characterise the magnetic resonance imaging (MRI) appearance of patients with spinal accessory nerve (SAN) denervation. MATERIAL AND METHODS: Twelve patients who had SAN denervation on electromyography (EMG) were included. The sternocleidomastoid and trapezius muscles and the SAN were assessed using MRI. RESULTS: Trapezius muscle atrophy was seen in 11 (92%), and of those patients, T2/short tau inversion recovery (STIR) signal hyperintensity was also demonstrated in seven (58%). All three patients with prior neck surgery had scarring around the SAN, and one of these patients demonstrated a neuroma, which was confirmed surgically. CONCLUSION: Features of SAN neuropathy on MRI include atrophy and T2/STIR signal hyperintensity of the trapezius, and in patients who have had posterior triangle neck surgery, scarring may be seen around the nerve.

Functional kinematics of the wrist.

The purpose of this article is to review past and present concepts concerning functional kinematics of the healthy and injured wrist. To provide a context for students of the wrist, we describe the progression of techniques for measuring carpal kinematics over the past century and discuss how this has influenced today's understanding of functional kinematics. Next, we provide an overview of recent developments and highlight the clinical relevance of these findings. We use these findings and recent evidence that supports the importance of coupled motion in early rehabilitation of radiocarpal injuries to develop the argument that coupled motion during functional activities is a clinically relevant outcome; therefore, clinicians should develop a framework for its dynamic assessment. This should enable a tailored and individualized approach to the treatment of carpal injuries.

Noninvasive technique for measuring in vivo three-dimensional carpal bone kinematics.

Our present knowledge of the three-dimensional kinematic behavior of skeletal joints has been largely acquired with cadaveric models and use of invasive monitoring. In the wrist, the small size and complex motion of the carpal bones present a difficult challenge for implanted internal or external marker systems. This paper describes a technique for quantifying the three-dimensional kinematics of the wrist and carpal bones in vivo using noninvasive computed tomographic imaging. An error analysis employing a cadaveric specimen suggests that noninvasive carpal kinematics can be measured with an accuracy within 2 degrees of rotation and 1 mm of translation along a helical axis of motion. The in vivo application of this technique is illustrated with a single normal individual. Potential applications include the quantification of normal wrist motion, analysis of pathomechanics, and evaluation of surgical intervention. The technique is also applicable to other joints and imaging modalities.

The osteo-anconeus flap. An approach for total elbow arthroplasty.

Twenty-seven consecutive primary total elbow arthroplasties were done with a technique that preserved the continuity of the attachment of the triceps brachii muscle with a wafer of bone from the reflected extra-articular portion of the olecranon and with the lateral fascia of muscles of the forearm. During closure, the wafer was reattached to the broad cancellous surface of the olecranon with sutures through the bone. The elbows were immobilized for an average of sixteen days postoperatively. The patients who were available for follow-up were re-examined at an average of 3.9 years, and the strength of the triceps muscle was checked. No extensor lag or avulsion of the triceps occurred, and mild extensor weakness was seen in only two elbows. No patient had early or late drainage of the wound or infection. The average range of motion compared favorably with that in other reported series. This osteo-anconeus posterior approach is advocated for total elbow arthroplasty because it provides rapid and wide exposure, it is associated with a low rate of complications related to the wound, and it preserves the strength of the triceps.

Management of infection about total elbow prostheses.

Deep infection was a complication after twelve (7.3 per cent) of 164 primary total elbow replacements. Two additional patients who had an infection about an elbow prosthesis were referred for treatment after total elbow replacement elsewhere. A statistical analysis of all of these primary total elbow arthroplasties, including the two in patients who were referred from outside institutions, identified preoperative factors that placed a patient at significant risk for subsequent infection. The risk factors included a previous operation on the elbow, a previous infection in the region of the elbow, psychiatric illness, class-IV rheumatoid arthritis, drainage from the wound after operation, spontaneous drainage after ten days, and reoperation for any reason. Three modes of treatment were used for patients who had an established infection: débridement and salvage of the implant, resection arthroplasty, and arthrodesis. After early operative débridement and suppression of the infection with long-term antibiotic therapy, three patients were able to retain the prosthesis, with restoration of range of motion and function of the upper extremity. One prosthesis was reimplanted after a six-week course of intravenous administration of antibiotics.

Load-displacement behavior in a distal radial fracture model. The effect of simulated healing on motion.

External fixation of fractures of the distal end of the radius neutralizes external forces and maintains axial alignment during healing. As far as we know, there have been no biomechanical studies of the effects of early removal of the fixator in a partially healed fracture model. The purpose of the present study was to observe the load-displacement behavior of a distal radial fracture model in which we had simulated partial healing by injection of butyl-rubber caulk and augmented this simulated healing with Kirschner-wire fixation. Sixteen fresh-frozen hand-wrist-forearm specimens from cadavera were mounted in mid-rotation in resin pots, and a load was applied. An osteotomy was used to simulate the fracture. Relative motion at the site of the osteotomy was compared, with use of a three-dimensional Optotrak kinematic device, during physiological loading of six constructs with Kirschner-wire transfixion or outrigger fixation. In the experimental group, partial healing was simulated by injection of butyl-rubber caulk into the site of the osteotomy and testing with simulated muscle-loading was performed through a full range of motion of the wrist. No difference could be detected between the relative motion at the osteotomy sites that had been treated with standard fully augmented external fixation and that in the experimental group (p > 0.05). T test analysis revealed that motion was equivalent regardless of whether Kirschner-wire transfixion or outrigger fixation had been used (p = 0.62) and that all of the augmented constructs had significantly less relative motion than all of the nonaugmented constructs (p < 0.001).

In vivo kinematic behavior of the radio-capitate joint during wrist flexion-extension and radio-ulnar deviation.

The capitate is often considered the "keystone" of the carpus, not simply because of its central and prominent position in the wrist, but also because of its mechanical interactions with neighboring bones. The purpose of this study was to determine in vivo three-dimensional capitate kinematics. Twenty uninjured wrists were investigated using a recently developed, non-invasive markerless bone registration (MBR) technique. Surface contours of the capitate, third metacarpal and radius were extracted from computed tomography images of seven wrist positions and the three-dimensional motions of the capitate and third metacarpal were calculated with respect to the radius in wrist flexion-extension and radio-ulnar deviation. We found that in vivo capitate motion does not simply occur about a single pivot point like a universal joint, as demonstrated by non-intersecting rotation axes for different capitate motions. The distance between flexion and ulnar deviation axes was 3.9+/-2.0 mm, and the distance between extension and ulnar deviation axes was 3.9+/-1.4 mm. Furthermore, capitate axes for males tended to be located more distally than axes for females. However, we believe that this result is related to subject size and not to gender. We also found that there is minimal relative motion between the capitate and third metacarpal during these in vivo wrist motions. These findings demonstrate the complexity of capitate kinematics, as well as the different mechanisms through which wrist flexion, extension, radial deviation and ulnar deviation occur.

Two-dimensional rigid-body kinematics using image contour registration.

A method for calculating two-dimensional rigid-body kinematic parameters using shape features is presented. Proposed applications include the noninvasive quantification of planar joint motion in vivo. By using digitized images (computed tomographs, radiographs, etc.) of a bone contour at two positions, the contour curvatures can be 'best-fit' to obtain a one-to-one mapping or registration of the bone images. This produces a dense field of displacement vectors from which planar rigid-body kinematic parameters can be estimated. Accuracy was studied using radiographic images of cadaveric femoral bone. The two motions of pure rotation with a fixed center of rotation and of pure translation were simulated. For pure rotation, error in rotation was independent of the rotation magnitude, with an average (n = 10) error of 0.3 +/- 0.8 degrees. The translation error averaged 0.9 +/- 0.5 mm. For pure translation, the error in rotation was -0.01 +/- 0.69 degrees and the error in translation was -0.62 +/- 0.98 mm (n = 10). This novel method has broad applications in the field of planar kinematics, especially in cases for which marker fixation is neither possible nor practical.

Optimal marker placement for calculating the instantaneous center of rotation.

A computer simulation with error propagation was performed to determine the optimal placement of marker points for calculating the instantaneous center of rotation (CRi). The authors assume that planar rigid body motion occurs between two positions, each defined by marker points. Noisy marker points were generated by perturbing their coordinates with random values from a normal population of errors. The effects of these errors on the range of errors in calculating CRi location were investigated. Parametric analysis determined that marker point placement had important effects on CRi error. Marker placement was optimal when the estimated CRi was located at the midpoint between the marker points. While increasing the distance between marker points increased accuracy, there is a critical distance above which no additional increase in accuracy was noted when using this placement. The farther the marker midpoint was from the CRi, the greater was the error. At these placements, increasing the distance between the marker points continually decreased CRi error. The methodologies presented here help to improve the accuracy with which the location of the CRi can be calculated. However, it is emphasized that the CRi remains sensitive to noise and investigations should apply this kinematic parameter knowingly.

Unilateral blindness as a complication of patient positioning for spinal surgery. A case report.

Extreme care must be used in positioning patients for surgery in a prone position. A padded Mayfield headrest may not be appropriate for all patients undergoing spinal surgery, as exophthalmus or a flattened nasal bridge may allow transmission of pressure to the globe. Our current approach is to use supplementary foam rubber support, with repeated, meticulous attention to keeping the eyes free from all pressure. Finally, unexplained intraoperative occurrence of a bradyarrhythmia or conduction disturbance may signal increased intraorbital pressure during general anesthesia.

Ruptures of the pectoralis major muscle. An anatomic and clinical analysis.

We evaluated 12 patients with 14 ruptures of the pectoralis major muscle to compare surgical and conservative management of this injury. Because 9 of the injuries occurred while weight lifting, we performed an anatomic study on human hemithorax specimens during a simulated bench press to determine the mechanism of this rare occurrence. Excursion of individual pectoralis muscle fibers was measured at seven points along the broad muscle origin by the use of fine wires connected to the humeral insertion and to dial gauges on the study apparatus. Excursions in the concentric and eccentric phases of the lift were expressed as a percentage of resting fiber length. The short, inferior fibers of the muscle lengthened disproportionately during the final 30 degrees of humeral extension. We concluded that the inferior fibers have a mechanical disadvantage in the final portion of the eccentric phase of the lift, and application of high loads to these maximally stretched fibers produces rupture. We repaired five acute and two chronic ruptures, and measured peak torque and work production against the contralateral side using Cybex isokinetic testing. Surgically treated patients showed comparable torque and work measurements, while conservatively treated individuals demonstrated and marked deficit in both peak torque and work/repetition. We recommend repair of complete pectoralis muscle ruptures in active patients who require maximum strength in vocational or avocational activities.

Primary semiconstrained total elbow arthroplasty. Survival analysis of 113 consecutive cases.

We used survival analysis to evaluate 113 consecutive semiconstrained total elbow arthroplasties (TEAs) in 95 patients at a maximum follow-up of 99 months. Our criteria for failure were mechanical malfunction, revision for any reason, and deep infection. The primary diagnosis was inflammatory arthritis in 86 elbows, post-traumatic arthritis in 6, supracondylar nonunion or fracture in 12, osteoarthritis in 2 and other causes in 3. Seven failures were due to deep infection, and five of these had a primary diagnosis of inflammatory arthritis. Eight failures were revised or had revision recommended for aseptic loosening, and six of these were in patients with post-traumatic arthritis or supracondylar nonunion. The cumulative survival for TEAs performed for post-traumatic arthritis, fractures or supracondylar nonunion was 73% at three years and 53% at five years, significantly worse than the cumulative three- and five-year survivals of 92% and 90%, respectively, for patients with inflammatory arthritis. TEA with a semiconstrained prosthesis appears to have a satisfactory survival in selected patients with arthritic disorders. The incidence of deep infection was reduced by improvements in surgical technique and postoperative management, and the routine use of antibiotic-impregnated cement. The incidence of aseptic loosening was low, except in patients with supracondylar nonunion or post-traumatic arthritis.

Peripheral nerve injury and repair.

Peripheral nerve injuries are common, and there is no easily available formula for successful treatment. Incomplete injuries are most frequent. Seddon classified nerve injuries into three categories: neurapraxia, axonotmesis, and neurotmesis. After complete axonal transection, the neuron undergoes a number of degenerative processes, followed by attempts at regeneration. A distal growth cone seeks out connections with the degenerated distal fiber. The current surgical standard is epineurial repair with nylon suture. To span gaps that primary repair cannot bridge without excessive tension, nerve-cable interfascicular auto-grafts are employed. Unfortunately, results of nerve repair to date have been no better than fair, with only 50% of patients regaining useful function. There is much ongoing research regarding pharmacologic agents, immune system modulators, enhancing factors, and entubulation chambers. Clinically applicable developments from these investigations will continue to improve the results of treatment of nerve injuries.

Limited incision open techniques for distal radius fracture management.

This article discusses recent innovations in the management of distal radius fractures. Clinical and biomechanical studies have shown that stable fixation can be achieved with small implants aligned in an orthogonal fashion. This technique greatly diminishes the necessary soft tissue dissection needed at surgery and allows for early mobilization of the wrist, which may lead to improved outcomes and fewer soft tissue complications.

Advances in the in vivo measurement of normal and abnormal carpal kinematics.

This article presents the development of an in vivo, three-dimensional methodology using markerless bone registration for examining the normal and abnormal kinematics of the wrist carpal bones. The resulting descriptions of three-dimensional kinematics from healthy patients and patients with documented unilateral scapholunate interosseous ligament injuries are briefly presented.

A non-invasive method for studying in vivo carpal kinematics.

Seven uninjured and three injured patients were studied using midsagittal computed tomographic (CT) images at 10 degrees increments from full extension to full flexion. Each injured patient had a confirmed scapholunate ligament tear and normal radiographs. CT bony contours were digitized, and incremental motion determined using a specifically designed automated contour-matching algorithm. We expressed wrist motion as a ratio of lunocapitate (midcarpal) motion, and radiolunate (radiocarpal) motion. In normal wrists, motion occurred equally at the midcarpal and radiocarpal joints. In wrists with scapholunate ligament disruption, lunocapitate motion increased significantly throughout the arc of motion.

Effects of scaphoid fractures on the biomechanics of the wrist.

Scaphoid fractures are the most commonly fractured carpal bone. They most often occur from a fall on dorsiflexed, radially deviated wrist. The severity of the fall and position of the wrist influence the fracture pattern and the extent of ligamentous damage. Recent studies have correlated fracture pattern stability and any associated ligamentous disruption with the degree of alternation of wrist biomechanics. It is well documented that instability and altered kinematics can lead to nonunion and abnormal joint loads, which then can accelerate the onset of arthritis. Understanding these biomechanical consequences is critical when managing scaphoid fractures.

Infection following total elbow arthroplasty.

Total elbow arthroplasty can be a safe, effective means of relieving the pain and loss of motion owing to arthritis of the elbow; however, infection is a frequent and devastating complication that occurs in 1 of every 20 total elbows. Through careful patient selection, meticulous operative technique, and vigilant postoperative care, this risk can be decreased. If infection does develop, early, aggressive operative management provides the best hope for salvage of the joint.

Radiographic progression to dorsal intercalated segment instability.

We present a case of an acute hyper-extension wrist injury that progressed from normal carpal alignment to dorsal intercalated segment instability over a short period of time. Disruption of the scapholunate interosseous and radioscapholunate ligaments was proven arthroscopically, while the intercapsular ligaments were demonstrated to be intact. We have shown that lunate malalignment can occur over time, as secondary lunate ligamentous supports attenuate under abnormal carpal kinetics.

Computed tomographic evaluation of fatty neoplasms of the extremities. A clinical, radiographic, and histologic review of cases.

Eleven lipomatous tumors of the extremities (7 liposarcomas, 4 lipomas) were evaluated radiographically by several modalities, including computed tomography (CT) in all lesions. Lipomas were seen on CT scan as well delineated, homogeneous masses with negative attenuation coefficients ranging from -95 to -160. Liposarcomas were inhomogeneous, multilobulated, poorly delineated lesions located exclusively in the subfascial or intramuscular planes, with an intermediate range of attenuation coefficients between those of fat and those of muscle. In six of seven liposarcomas, definite low density areas were identified by attenuation coefficient as fatty tissue. Magnetic resonance imaging (MRI) was obtained in two patients and was helpful in defining the extent of the tumors and their relationship to vital structures, but MRI could not differentiate benign from malignant tissue. Computed tomography is recommended as the cornerstone in the initial radiographic evaluation of growing or painful lipomatous soft tissue masses of the extremities.