Functional outcome of surgically and conservatively managed dens fractures.

STUDY DESIGN: Fifty-seven patients with dens fractures were identified from 1986 to 1996 at the authors' institution. Forty-six were available for reevaluation by two independent observers with a mean follow-up period of 26 months. OBJECTIVE: To determine by age and fracture type which treatment regimen provided the best functional outcome in patients with dens fractures. SUMMARY OF BACKGROUND DATA: There were no Type I fractures, but there were 37 Type II and 20 Type III fractures. Twenty-nine patients were under 60 years of age, and 28 were 60 years and older. Six patients had been treated by immediate C1-C2 posterior fusion, and five received treatment with a Philadelphia collar only. Forty-six patients were placed in a halo thoracic immobilizer with a symptomatic nonunion rate of 19.5%. These patients ultimately required posterior cervical fusion. METHODS: Final functional outcome, level of pain, and cervical range of motion were all statistically evaluated using multivariate analysis (Wilcoxon's two-sample test). The influence of age, fracture type, and treatment method were determined. RESULTS: There were no cases of short- or long-term neurologic deterioration in any of the patients in the study group. There was a significantly higher rate of complications associated with halo use in the older population. Pain scores were higher in Type II fractures and in patients treated conservatively with halo immobilization, especially those patients over 60 years of age. No statistically significant difference in these parameters were found. Older patients treated surgically did not have a better functional outcome score than those treated nonoperatively (P < 0.8). Persons over 60 years of age treated in a halo had a significantly (P < 0.05) decreased range of motion when compared with younger patients treated similarly. CONCLUSION: Patients over 60 years of age with a dens fracture had a higher complication rate and lower cervical range of motion when treated conservatively with a halo. Final functional outcome and overall pain levels, however, did not differ significantly by age group or treatment modality.

The role of distraction in improving the space available for the cord in cervical spondylosis.

STUDY DESIGN: This study analyzed the effects of distraction via strut graft insertion on the canal dimensions in spondylotic human cadaver cervical spines. Transverse and anteroposterior diameters and cross-sectional areas were measured by transverse computed tomography imaging before and after distraction without direct decompression. OBJECTIVES: This experiment was designed to address whether distraction across the disc space without direct canal decompression can improve the space available for the cord. SUMMARY OF BACKGROUND DATA: Smith-Robinson anterior discectomy and fusion have been shown to improve clinical symptoms of radiculopathy and myelopathy even in the absence of direct decompression. This has been postulated to be the result of gradual resorption of intruding osteophytes. However, the immediate effects of indirect distraction alone have not been previously investigated. METHODS: Four cadaver spines from elderly donors were harvested intact. The transverse diameter, anteroposterior diameter, and cross-sectional area of the spinal canal were measured before and after discectomy and distraction via insertion of fibular strut graft by digitization of contiguous computed tomography scan slices. RESULTS: The spinal canal dimensions before distraction were found to vary in a sinusoidal pattern around the disc space, with the maximum measurements located at the pedicle and the minimum measurements at the spondylotic ridge above or below the disc space. Distraction via strut graft insertion significantly increased the anteroposterior diameter and cross-sectional area, but had a negligible effect on transverse diameter. CONCLUSIONS: Anterior discectomy and distraction with a strut graft can significantly improve the space available for the cord in cervical spondylosis. Osteophyte debridement, which risks iatrogenic injury to the cord, may not always be necessary for improving clinical radiculopathy and myelopathy.

Mechanics of anatomic reduction of thoracolumbar burst fractures. Comparison of distraction versus distraction plus lordosis, in the anatomic reduction of the thoracolumbar burst fracture.

The adequate reduction of vertebral burst fractures is dependent on successful application of distractive forces in combination with the restoration of normal spinal lordosis. However, the optimal sequence of distraction in comparison to distraction plus lordosis in the anatomic restoration of the fractured thoracolumbar spine has not been described. Burst fractures of the L1 vertebra were first created and the reduced in vitro using three differing reduction techniques. In six fresh human cadaver spine specimens, the mean fracture severity based on the degree of canal compromise was 31% (SD +/- 20%) after fracture. Reductions were performed using the AO Fixator Intern, the Reduction Fixation (RF) Device, and the Steffee plate systems following standard clinical techniques. The AO Fixator Intern provided independent but variable control of distraction and lordosis, the RF device provided variable distraction with independent, but preset, correction of lordosis and the Steffee system provided set distraction and stabilization. Both the AO and RF devices restored the lordosis (7.6 degrees +/- 5.2 degrees and 9.7 degrees +/- 4.5 degrees, respectively) better than the Steffee plate system (0 degrees +/- 1.6 degrees). However, the AO device provided poorest restoration of the posterior vertebral body height (92% vs 96% for the RF device and 99% for the Steffee plate). The RF device, which restored both lordosis and posterior vertebral body height to the near anatomic prefracture level, provided significantly better canal clearance (9% +/- 8%) than the other techniques, P < 0.05. The study demonstrates that instrumentation systems that provide independent correction of distraction and lordosis can best restore anatomic alignment, with indirect neurodecompression of the compromised spinal canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Vertebral burst fractures: an experimental, morphologic, and radiographic study.

Spinal burst fractures are produced by rapid compressive loading, and may result in spinal cord injury from bone fragments forced from the vertebral body into the spinal canal. This fracture is one of the most difficult injuries of the spine to successfully treat, in part because the biomechanics of reduction and the exact mechanism by which the distraction forces are transmitted to the intracanal fragments of the burst fracture have not been adequately investigated. The authors developed a reproducible technique for creating these fractures in vitro. The fractures produced were identical to those observed in clinical practice, and were used for investigating the mechanics of this fracture and its reduction. This work describes the pathologic anatomy of the burst fracture both on the gross structure and also on microtome sections of the vertebrae, and examines the biomechanics of fracture reduction. The margins of the vertebral bone fragment, which was forced posteriorly into the spinal canal during fracture, were noted to extend far laterally beyond the pedicles. The authors also found extensive damage not only to the disc above the injured level, but also to that below, explaining the clinical observation that disc degeneration frequently occurs at both levels. Examination of anatomic data provided by microtome section supported the hypothesis that the fibers that actually reduce the intracanal fragment originate in the anulus of the superior vertebra in the midportion of the endplate and insert into the lateral margins of the intracanal fragment. Investigations using magnetic resonance imaging confirmed that these obliquely directed fibers account for the indirect reduction of the fragment. The authors' studies demonstrate that the posterior longitudinal ligament provides only a minor contribution in the reduction of the fracture in comparison to the attachments of the posterior portion of the anulus fibrosus. The forces required to reduce this fragment were studied. Distraction was found to be the predominant force required for indirect posterior reduction. This was confirmed by a series of tests using devices that provided segmental fixation. The application of uniform distraction forces was most effective in the posterior reduction of the intracanal fragment.

Analysis of the forefoot on pointe in the ballet dancer.

The forefoot positions of nine ballet dancers standing on pointe were determined using a mold technique. These molds revealed three positions of the toes: (1) no crossing of the three medial toes; (2) crossing of the third toe behind the second; and (3) crossing of the hallux partially in front of the second. Almost half of all the toes seen on the molds had some deformation of the toenails. These molds also indicated a wide variability in the amount and location of contact between the shoes and toes.

Does the angle of the computed tomographic scan change spinal canal measurements?

Computed tomographic scanning at 0 degrees, 10 degrees, and 20 degrees was used on two human cadaver cervical spines to determine whether altering the scan angle affects spinal canal measurement. Maximum anteroposterior diameter, cross-sectional area, and transverse diameter were determined by digitization of the scans. Both spines exhibited a regular sinusoidal pattern of variation in anteroposterior diameter and cross-sectional area, with less of a pattern for transverse diameter. The maximum values occurred around the discs in the normal spine, moving to just below the pedicle in the spondylotic spine. Minimum values were at the pedicle in the normal spine and near the discs in the spondylotic spine. Changing the computed tomographic scan angle to 10 degrees in either a cephalad or caudad direction had a negligible effect on the pattern or absolute values for any dimension in either spine. Changing the angle to 20 degrees in either direction significantly and irregularly altered both the pattern and values of anteroposterior diameter and cross-sectional area in both spines. There was little effect on transverse diameter. It was concluded that comparison of different scans should be interpreted with caution unless the change in angulation is 10 degrees or less.

Interference screw fixation of cervical grafts: a biomechanical study of a new method of cervical fixation.

The dislodgement of anterior bone graft in the cervical spine is a frequent complication of attempted fusion following discectomy or corpectomy. It has been hypothesized that fixation augmented with interference screws may increase the pull-out strength of the construct and decrease the rate of these complications. Mechanical tests were conducted to compare interference screw fixation methods for enhancing the fixation between the bone graft and the adjacent vertebra. The anterior pull-out strengths of cervical bone grafts were compared using fixation with and without the addition of interference screws. Both discectomy and corpectomy graft models were examined in vitro. The mean pull-out force for a Smith-Robinson type bone graft alone was 58.1 N (SD +/- 11.4 N); for the graft augmented with two 3.5 mm cancellous bone screws, 153.9 N (+/- 58.9 N); for the graft with four 3.5 mm screws, 217.1 N (SD +/- 69.9 N). The pull-out strengths of the two and four 3.5 mm screw constructs were significantly greater than the strength of the graft alone (p less than 0.05). Similarly placed 2.7 mm cortical screws of the same length provided increased pull-out strength (123.7 N +/- 38.6 N and 142.5 N +/- 38.2 N for two and four screws, respectively); however, in comparison to the graft alone, these differences were not statistically significant. For both screw types, the four screw fixations were stronger than the two-screw fixations, although these differences were not statistically different.(ABSTRACT TRUNCATED AT 250 WORDS)

The Syracuse I-plate.

The Syracuse I-Plate is a versatile neutralization plate for anterior spinal fixation following decompression for burst fractures and pathologic vertebral body destruction by tumor. In this article, the history, current use, and indications are discussed. The anterior approach and application of the I-plate to the lower thoracic and lumbar spine is presented, as well as a brief summary of a current clinical series of 34 patients. Fusion rates were high and hardware failure most frequent in patients with associated osteoporosis or extensive posterior disruption, such that the device was contraindicated in cases of extensive three-column injuries or significantly osteoporotic bone.

Further observations on metal-backed patellar component failure.

The clinical data, failure pattern, symptoms, roentgenographic findings, and failure mechanism of a series of 25 metal-backed patellar component failures are summarized. Diagnosis of implant failure was unknown prior to arthrotomy in seven of 25 cases (28%). Clinical findings and history were not helpful in making the diagnosis. Roentgenographic findings led to the diagnosis in 17 of 18 and were by far the most useful data. Metal-backed patellar component failure is a new complication of total knee arthroplasty and will be seen in increasing numbers. Caution is urged in implanting metal-backed designs until further design research is done.

Failure of the metal-backed patellar component after total knee replacement.

Twenty-five patients had failure of a metal-backed patellar component after total knee replacement. Five manufacturers and seven designs were involved. There was no apparent correlation between failure of the component and the age or sex of the patient, the diagnosis, the use of cement, the femorotibial alignment, or the use of lateral release. The patients in whom the patellar implant failed were relatively heavy, and the diagnosis in most of them was osteoarthritis. The failure was due to one of two mechanisms: wear or fracture, or both, of the polyethylene over the edge of the metal backing (eighteen components), or dissociation of the polyethylene or the base-plate, or both, from the anchoring pegs (seven components). In many of the patients, failure of the component was not suspected before arthrotomy. The failure led to considerable wear of the femoral component in eleven patients and to metal-induced synovitis in twenty-three. We concluded that metal backing may predispose the patellar component to a small but important likelihood of failure, and we urge caution in choosing a metal-backed patellar implant. Additional research is necessary to improve designs for the patellar component, especially if metal backing is to be used.

Lower extremity fractures in paraplegics: pattern, treatment, and functional results.

Eighty-seven lower extremity fractures in 71 paraplegics were retrospectively evaluated to determine adequacy of treatment, functional result, and range of motion of the hip and knee. Most fractures treated closed healed without difficulty, but with a complication rate of 19%. Length of hospitalization averaged almost 3 months in the group treated closed, and residual hip and knee stiffness was the major complication. This was not a problem except in high demand patients, such as wheelchair athletes, in whom decreased range of motion was a significant limitation. Treatment with circular casts produced a high number of complications and is not recommended for patients with insensate skin. Open reduction and internal fixation is recommended for a small subgroup of paraplegics: wheelchair athletes, hip fractures, and those in whom autonomic dysreflexia and/or uncontrollable spasticity due to fracture manipulation is a significant hazard.

The weight-bearing shoulder. The impingement syndrome in paraplegics.

The cases of ninety-four patients who had complete paraplegia were studied to determine whether they had complaints about the shoulder during transfer activities. Thirty-one patients reported pain on transferring, and twenty-three of these patients were found to have a chronic impingement syndrome with subacromial bursitis. Arthrography of the shoulder was done for each of these twenty-three patients, and fifteen were found to have a tear of the rotator cuff. Five of the thirty-one patients were found to have aseptic necrosis of the head of the humerus. We also measured the intra-articular pressure in the shoulder in five patients during different activities, including transfer from wheelchair to bed, and found that this pressure exceeded the arterial pressure by two and one-half times. We believe that this high pressure, in conjunction with abnormal distribution of stress transmitted across the subacromial area during transfer or propulsion of a wheelchair, contributes to the high rate of problems about the shoulder in paraplegics.

Long-term results of total hip arthroplasty in protrusio acetabuli.

Ninety-three total hip arthroplasties were examined radiographically and clinically to investigate the best method of correction in protrusio acetabuli. Fifty-three percent were treated with cement alone, 36% with mesh or protrusio shell, and 11% with bone graft. Long-term follow-up study revealed a high percentage of immediate and late radiolucent lines. The highest rate of loosening, 50%, occurred in the cement alone group, which had not been corrected to within 10 mm of anatomic position. Sex, cause of protrusio, age at operation, and degree of osteopenia were not significantly different between the groups. The follow-up period was longer in the cement alone group, but this did not account for the excessively high rate of loosening. Correction of the anatomic position in protrusio deformity is vital, whether accomplished with cement, mesh, protrusio shell, or bone graft. Late radiolucent lines are common and do not reliably indicate loosening.