Hip dislocation following minor trauma in a patient with neurofibromatosis type 1: a case report and review of the literature.

Neurofibromatosis type 1 (NF-1) is a common autosomal dominant disorder which is known to have associated skeletal manifestations. There are documented cases of hip dislocation in NF-1, although it is a rare occurrence. Previous cases have been associated with intra-articular neurofibromas, acetabular protrusio and femoral deformities such as coxa valga and in one case increased femoral offset.The authors review the literature on pelvic manifestations and report a case of hip dislocation in a 19-year-old woman with neurofibromatosis-one following minor trauma believed to be secondary to markedly increased femoral offset.This case illustrates the effect the NF-1 can have on the anatomy of the proximal femur and one of the complications that can present to the orthopaedic surgeon, without the presence on an intra-articular neurofibroma. In a review of the literature the authors found only two other cases of hip dislocation associated with NF-1 that occurred without the presence of an intra-articular neurofibroma.

Long term survival of an hydroxyapatite-coated threaded cup in the presence of a high polythene wear rate.

We describe the long term clinical results and polythene wear rate measurement of 144 uncemented total hip arthroplasties in 118 patients (Male: Female-65: 53, Mean age: 52.8 years (range 21-78 years) performed between 1988 and 2000 using the Furlong HAC coated threaded acetabular cup. The mean follow-up for the group was 10.2 years (range: 5-17.5, median: 9.7). One femoral stem and two acetabular shells were revised due to aseptic loosening. The mean polythene wear rate was 0.24 mm/year. Ten-year survival for the acetabular and femoral components with radiological evidence of aseptic loosening as an end point was 99.15 (CI: 98.3-99.9) and 99.28 (CI: 98.5-99.9). There was no evidence of osteolysis around the femoral or acetabular components in spite of a relatively high polythene wear rate (0.24 mm/year). Our study demonstrates excellent survival of threaded HAC coated acetabular sockets at 10 years in spite of a relatively high polythene wear rate.

Staged bilateral total hip arthroplasty using rough and smooth surface femoral stems with similar design: 10-year survivorship of 48 cases.

BACKGROUND: Various studies have reported good long-term results using femoral stems with either smooth or rough surfaces. In this retrospective cross-sectional survivorship study, we reviewed the 10-year results of 51 bilateral staged cemented total hip arthroplasties using the Harvard or the Charnley femoral stems-which have almost similar geometry but a different surface finish. METHODS: 51 patients were reviewed at median interval of 10 (Harvard group) and 11 years (Charnley group) after the primary operation. We evaluated cement mantle thickness, alignment of the components, presence of radiolucent lines, and aseptic loosening. Kaplan-Meier analysis was performed to calculate the survival rate using various endpoints. RESULTS: 8 hips in the Harvard group were revised for aseptic loosening of the femoral component at a median interval of 6.3 years after the primary procedure. 3 hips in the Charnley group were revised for aseptic loosening of the femoral and acetabular components between 10 and 11 years after the primary procedure. The 10-year survival rate for the femoral component using revision surgery for aseptic loosening as an endpoint was 80% (95% CI: 31-42) and 95% (95% CI: 44-47) in the Harvard and the Charnley group, respectively. Cox regression analysis did not reveal any statistically significant effect of various radiographical parameters on the survival rate (p < 0.05). INTERPRETATION: Our results demonstrate that in the group of patients studied, the femoral stem component with the matt surface finish had less satisfactory 10-year survival than the femoral stem of similar design which had a smooth surface finish.

Morphometric study of the thoracic vertebral pedicle in an Indian population.

STUDY DESIGN: Morphometric study of the thoracic vertebral pedicular parameters and comparison with the previous studies in the literature. OBJECTIVES: To define pedicular dimensions and screw placement in the Indian population. SUMMARY OF THE BACKGROUND DATA: Pedicular morphometric characteristics vary in different population groups. Thoracic pedicular screw fixation is being used more frequently with the advent of better imaging methods. Because of the small size and close proximity to the neurovascular structures, thoracic pedicle fixation has little margin of safety. METHODS: T1-T12 vertebral pedicles were studied in 18 cadavers by direct, roentgenographic, and computerized tomographic scan methods. The following parameters were studied: transverse diameter, transverse angle, sagittal diameter, sagittal angle, chord length, interpedicular distance, pedicle entrance point, and pedicle cortical thickness (medial and lateral). RESULTS.: Transverse diameter was more than 6 mm at both ends of the thoracic spine (T1, T2, T11, and T12). Between T3-T9 levels, it was less than 5 mm at some levels. The transverse angle was widest at T1 (30 degrees) and was less than 5 degrees from T5 to T12. Pedicles were directed cephalad in the sagittal plane at all thoracic levels. Sagittal angle was less than 12 degrees at all thoracic levels. Chord length was largest at T11 (37.3 mm) and smallest at T1 and T2 (29.9 mm). Interpedicular distance was 29 mm at T12 and 21.3 mm at T1. Medial pedicular cortex was thicker than lateral cortex at all levels. CONCLUSIONS: These results suggest that even a 4-mm screw should be used carefully at the midthoracic level; 5-mm screw seems to be safe at upper and lower thoracic spine. Because of very small sagittal and transverse angle at mid and lower thoracic levels, the pedicular screw should be inserted along almost perpendicular line in these planes; 25-mm and 30-mm screw length appears to be safe at upper thoracic and lower thoracic levels, respectively. Pedicle entrance point lies along the midtrans-verse line at upper thoracic levels and along the upper border of transverse process at lower thoracic levels.

Femoral cement pressurization in hip arthroplasty: a laboratory comparison of three techniques.

BACKGROUND: Several cementing techniques are used for the proximal femur. MATERIAL AND METHODS: We evaluated 3 femoral cement pressurization techniques (standard, pressurizer in situ, and thumb pressurization) in 12 plastic femurs, with 4 sets of observations for each technique. Intramedullary pressure readings were obtained using proximal and distal pressure monitoring transducers. The peak pressure and the length of time for which the pressure was above a particular cutoff level (5 KPa and 100 KPa) were compared for the different techniques. RESULTS: We found significant differences between the 3 cementing techniques in the peak pressure and the length of time for which the pressure was above 100 KPa. The pressurizer in situ technique gave higher peak pressure (p < 0.001), both proximally (398) and distally (597). The standard technique produced a pressure of 100 KPa for a longer duration, both proximally and distally (mean 67 sec and 45 sec, p < 0.001) compared to the other two techniques (less than 5 and 17 sec for the thumb pressurization technique and the pressurizer in situ technique, respectively, both proximally and distally). Although the pressurizer in situ technique produced the highest peak pressure, the standard technique produced an optimum pressure of longer duration. INTERPRETATION: The standard technique appears to be adequate for achievement of optimum pressurization during femoral cementing without increased risk of embolization.

Morphometric study of the lumbar pedicle in the Indian population as related to pedicular screw fixation.

STUDY DESIGN: A morphometric study of lumbar vertebral pedicular parameters in cadavers and comparison with previous studies in the literature was conducted. OBJECTIVES: To suggest dimensions for pedicular implants in the Indian population, and to improve the pedicular screw placement technique. SUMMARY OF BACKGROUND DATA: Detailed knowledge of pedicle morphometry is critical for proper placement of a transpedicular screw. The size and shape of the vertebral pedicle vary between different races. Morphometric studies have been conducted in white and nonwhite populations (e.g., Chinese, Koreans). METHODS: The vertebral pedicles at L1-L5 were studied in 20 cadavers by direct roentgenographic and computerized tomographic scan methods. The following parameters were studied: transverse diameter, transverse angle, sagittal diameter, sagittal angle, chord length, interpedicular distance, medial and lateral cortical thickness. RESULTS: Transverse diameter was largest at L5 (16.19 mm) and smallest at L1 (7.05 mm). The transverse angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). The pedicles were directed cranially in the sagittal plane at all lumber levels except L5. The sagittal angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). Chord length was largest at L2 (47.5 mm) and smallest at L1 (46.01 mm). The values of linear measurements were smaller in females at all levels. CONCLUSIONS: On the basis of this limited study in a subset of the Indian population, it appears that the transverse diameter and pedicle entrance point differ from those in the white population. The results suggest that a 5-mm screw would be safer in the upper lumbar levels (L1, L2), and 6-mm screw in the lower lumbar levels (L3-L5). The pedicle entrance point migrates laterally for lower lumbar levels, especially at L5. The medial pedicle cortex can be safely sounded while the pedicle is probed.