Dose response relationships for isobaric spinal mepivacaine using the combined spinal epidural technique.

UNLABELLED: Mepivacaine, a local anesthetic with similar physiochemical properties to those of lidocaine, is an adequate alternative for patients undergoing ambulatory procedures, and is associated with a lower incidence of transient neurologic symptoms (TNS) than lidocaine. We studied the dose-response characteristics of isobaric intrathecal mepivacaine using the combined spinal epidural technique for patients undergoing ambulatory arthroscopic surgery of the knee. Seventy-five patients were randomized prospectively to receive one of three doses of isobaric mepivacaine for spinal anesthesia: 30 mg (2 mL 1.5%), 45 mg (3 mL 1.5%), or 60 mg (4 mL 1.5%). An observer, blinded to the dose, recorded sensory level to pinprick and motor response until resolution of the block. In addition, the incidence of TNS was determined. An initial intrathecal dose of 30 mg of isobaric mepivacaine 1.5% produced satisfactory anesthesia in 72% of ambulatory surgical patients undergoing unilateral knee arthroscopy with a significantly shorter duration of sensory (158 +/- 32 min) and motor blockade (116 +/- 38 min) than doses of 45 and 60 mg. An intrathecal dose of 45 mg produced satisfactory anesthesia in all patients with a shorter duration of sensory (182 +/-38 min) and motor blockade (142 +/- 37 min) than 60 mg of mepivacaine 1.5% (203 +/- 36 min and 168 +/- 36 min, respectively). The incidence of TNS was 7.4% overall (1.2%-13.6% confidence intervals), less than the rates previously reported after spinal anesthesia with lidocaine in ambulatory surgical patients undergoing knee arthroscopy. We conclude that mepivacaine can be used as an adequate alternative to lidocaine for ambulatory procedures. IMPLICATIONS: This study evaluated the postoperative duration of spinal anesthesia after varying doses of isobaric mepivacaine and the incidence of transient radiating back and leg pain. We found that 45 mg of mepivacaine provided adequate anesthesia, a timely discharge, and a lower incidence of back pain than that previously reported after lidocaine spinals.

Intramedullary versus extramedullary tibial alignment systems in total knee arthroplasty.

One hundred twenty consecutive total knee arthroplasties were performed to compare the accuracy of intramedullary versus extramedullary tibial resection guides. An intramedullary guide (group 1) was used in 60 cases and an extramedullary guide (group 2) was used in another 60 cases. In group 2, the distal portion of the extramedullary guide was shifted 3 mm medial to the midpoint of the ankle in order to position it over the center of the talus. Postoperative tibial component alignment angles were similar in both groups (group 1, 0.43 degrees varus; group 2, 0.36 degrees valgus). However, 88% of tibial components in group 2 were aligned within 2 degrees of the 90 degrees goal versus only 72% of tibial components in group 1. Satisfactory alignment can be obtained with either intramedullary or extramedullary resection guides, although a wider range of error was encountered with intramedullary guide use. Distal positioning of the extramedullary guide over the center of the talus rather than the midpoint of the ankle is important to avoid varus tibial resection. Extramedullary guides avoid the potential complications of intramedullary guide use, including fat embolization and hypoxia, intraoperative fracture, loss of polymethyl methacrylate pressurization, and inability of intramedullary rod passage due to deformity, retained hardware, or pathologic bone disease.

Internal fixation compression arthrodesis of the ankle.

Sixteen patients were treated by internal compression arthrodesis of the ankle using cancellous screw fixation. Thirteen patients had a preoperative diagnosis of traumatic osteoarthritis, and three patients had rheumatoid arthritis. All patients were followed until clinical and roentgenographic evidence of union had been obtained (average, 15.1 months). Union was obtained in 15 of 16 cases (94%) by an average of 9.2 weeks. The average ankle evaluation score was 77 points, with 80% of the patients rated good or excellent. Suboptimal results were attributed to technical errors. Midtarsal motion averaged 18 degrees, and subtalar motion was present in the majority of patients after surgery. This technique provides a high union rate while permitting early mobilization of the adjacent hindfoot and midfoot joints with earlier return to satisfactory function.

Surgery of the rheumatoid foot.

The typical rheumatoid foot deformity is that of hallux valgus, bunion, hammer claw toes with contracted dorsal soft tissue, depressed metatarsal heads and associated painful callosities and corns both under metatarsal heads and on dorsal surfaces of cocked-up lesser toes. Deformity and pain will be amendable with surgery if patients are selected properly and correct surgery is performed to achieve a pain free weight-bearing foot.