Effect of meniscal loss on knee stability after single-bundle anterior cruciate ligament reconstruction

Purpose

The menisci are known to be important secondary constraints to anterior translation of the tibia in the ACL-deficient knee. The effect of meniscal loss on knee stability as measured by the magnitude of the pivot shift following ACL reconstruction is unknown. The objective of this investigation was to determine the effect of meniscectomy on knee stability following two single-bundle ACL reconstruction strategies.

Materials and Methods

A mechanized pivot shift was performed on cadaveric specimens in the ACL-intact and ACL-deficient state. Tibiofemoral translation was recorded using a surgical navigation system. The ACL was reconstructed utilizing a nonanatomic graft (n = 10) extending from the posterolateral tibial footprint to the anteromedial femoral footprint, or an anatomic anteromedial single-bundle graft extending from the anteromedial tibial footprint to the anteromedial femoral footprint (n = 10) and testing repeated. The medial or lateral meniscus was sectioned and the examination repeated. The other meniscus was sectioned and the examination subsequently repeated.

Results

Lateral compartment translation during the pivot shift was significantly reduced following anatomic ACL reconstruction. In the nonanatomic group, lateral compartment translation increased by 9.1 mm (P < 0.001) after unicomparmental meniscectomy and 11.5 mm (P < 0.001) after bicompartmental meniscectomy. In the anatomic reconstruction group, lateral compartment translation increased by 7.6 mm (P < 0.001) after bicompartmental meniscectomy.

Conclusion

With isolated ACL injury, anatomic single-bundle ACL reconstruction controlled the pivot shift during time zero testing. However, significant increases in lateral compartment translation during the pivot shift are seen following bicompartmental meniscectomy. Nonanatomic ACL reconstruction was less effective in controlling the pivot shift at time zero testing, and significant increases in lateral compartment translation during the pivot shift were seen following both unicomparmental and bicompartmental meniscectomy.

     

Deep Venous Thrombosis Prophylaxis After Unicompartmental Knee Arthroplasty: A Prospective Study on the Safety of Aspirin

Background

Although venous thromboembolism is one of the leading causes of morbidity after knee arthroplasty, little data exist on the risk of deep venous thrombosis (DVT) after unicompartmental knee arthroplasty (UKA).

Effect of digitalis on response of the ventricular pacemaker to sympathetic neural stimulation and to isoproterenol

It is established that digitalis antagonizes the chronotropic effect of adrenergic stimulation of the heart, and this finding suggests that the sympathetic nervous system does not play a significant role in ventricular arrhythmias produced by digitalis. However, this antagonism has been established by testing the response of the sinus nodal pacemaker to digitalis and adrenergic stimulation. Since clinically significant digitalis-induced arrhythmias are ventricular in origin, the response of the ventricular pacemaker seems the more critical variable. To test this hypothesis, we applied two types of adrenergic stimulation before and after ouabain administration to anesthetized dogs with complete atrio-ventricular block. Ouabain in a dose of 40 μg/kg caused no significant change in the increase in heart rate produced either by electrical stimulation of postganglionic sympathetic nerves or by isoproterenol administration. In 6 of the 12 dogs ventricular tachycardia developed after digitalis administration at levels of adrenergic stimulation that did not cause arrhythmia before the drug was given. These results indicate that digitalis does not affect the chronotropic response to adrenergic stimulation of ventricular pacemakers. Moreover, the heart exposed to digitalis appears to be sensitized to the arrhythmogenic effects of adrenergic stimuli.     

Cost comparison for laparoscopic nephrectomy and open nephrectomy: analysis of individual parameters

Objectives. To identify the cost components of laparoscopic nephrectomy (LN) that could be targeted to reduce the cost of the procedure. LN is typically more costly than open nephrectomy (ON) because of longer operative times and the use of disposable equipment.Methods. We compared the overall cost and individual cost centers for uncomplicated LN (n = 11) and ON (n = 8) at a large metropolitan county hospital. A model was created using the DATA program (TreeAge software, version 3.5) to compare the costs of treatment with either ON or LN. We conducted a series of one-way sensitivity analyses to evaluate the effect of varying individual probabilities and costs. Two-way sensitivity analyses were performed to evaluate the costs of ON and LN while varying the hospital length of stay, operative time, and cost of laparoscopic equipment.Results. LN was less costly overall than ON by $1211 (P = 0.037), despite significant differences favoring ON in overall operating room costs and operating room supply costs. The cost superiority of LN was a consequence of statistically significant differences in the cost of hospitalization, including room and board, that favored the laparoscopic group. One-way sensitivity analyses showed that LN was less costly if (a) the operative time of LN was less than 281 minutes; (b) the length of hospitalization after LN was less than 5.8 days; (c) the operating room costs for LN were less than $3439; (d) the laparoscopic equipment costs were less than $2129; (e) the ON time exceeded 78 minutes; (f) the length of hospitalization for ON was more than 3.6 days; or (g) the operating room costs for ON were greater than $1333.Conclusions. The sensitivity analyses enable individual surgeons and institutions to determine the cost impact of ON and LN, given their unique clinical scenarios. At our institution, key cost centers in determining cost effectiveness include length of operating time, hospitalization, and cost of laparoscopic instrumentation for ON and LN. LN is cost effective compared with ON if short operating times and brief length of stays are achieved.     

Laparoscopic nephrectomy for benign disease

Nearly 10 years of experience with laparoscopic nephrectomy for benign renal disease has shown that the procedure can be performed safely with a complication rate comparable with open surgery. Improvements in the skill, instrumentation, and technique of the laparoscopist have expanded the indications for the procedure to include larger (polycystic kidneys) and in some cases more complex (xanthogranulomotous pyelonephritis) specimens. Continued demonstration of reduced postoperative pain, shorter hospital stay, and more rapid recovery along with decreasing operative times have made laparoscopy the preferred approach for the surgical removal of benign kidneys.     

Renal parenchymal injury after standard and mini percutaneous nephrostolithotomy

PURPOSE: Mini percutaneous nephrostolithotomy was developed for use in children and in adults with a reduced renal reserve to minimize the morbidity and renal parenchymal damage presumed to occur with traditional percutaneous nephrostolithotomy. We compared the extent of renal injury incurred by different sized nephrostomy tracts in female farm pigs undergoing 11 or 30Fr percutaneous nephrostomy. MATERIALS AND METHODS: Bilateral percutaneous nephrostomy was attempted via a mid or lower pole calix under fluoroscopic guidance in 6 pigs. In 2 pigs the procedure was unsuccessful on 1 side, leaving 5 successfully established nephrostomy tracts on each side. In each pig the right percutaneous tract was dilated with a 28Fr dilating balloon and a 30Fr Amplatz working sheath (Cook Urological, Spencer, Indiana) was positioned in the collecting system. On the left side an 11Fr sheath (Cook Urological) was placed. The sheaths were removed after 1 hour and nephrostomy tubes (22Fr on the right and 8Fr on the left side) were left in place overnight and then removed. Six weeks later the pigs were sacrificed and the kidneys were harvested. The nephrostomy tracts were identified grossly and examined microscopically, and the fibrotic scar was measured using digital analysis. The volume of scar was estimated using the calculated volume of a cylinder. RESULTS: At kidney harvest all 10 kidneys appeared grossly normal. No intra-abdominal urine collection or perirenal hematoma was noted. Mean estimated scar volume of the 30 and 11Fr tracts was 0.29 and 0.40 cc, which translates into a mean fractional loss of parenchyma of 0.63% and 0.91%, respectively (p not significant). CONCLUSIONS: Renal parenchymal damage resulting from the creation of a nephrostomy tract is small compared to overall renal volume regardless of the size of the nephrostomy tract. Consequently there is no advantage to the use of a small access sheath based on renal scarring alone.