Generic tobramycin elutes from bone cement faster than proprietary tobramycin.

Elution of antibiotics from antibiotic-loaded polymethylmethacrylate (AL-PMMA) increases when soluble particulate filler is added to increase the permeability of the PMMA. Antibiotic powder is in itself soluble particulate filler. For greater volume fractions of filler, greater elution occurs. The volume of generic tobramycin powder is more than 3.5 times the volume of proprietary tobramycin powder for a 1.2 g dose leading to the question: Does generic tobramycin elute from AL-PMMA faster than proprietary tobramycin? We performed elution studies on AL-PMMA beads made with 1.2 g of either generic tobramycin or proprietary tobramycin per batch of PMMA. Generic tobramycin eluted more than two times faster than proprietary tobramycin. The release mechanism started as dissolution-driven zero-order release for the generic bead set but for the proprietary bead set the released mechanism started as anomalous diffusion. The release mechanism progressed to diffusion-driven first-order release in both. The increased volume of the generic tobramycin caused more tobramycin to be available for release. The increased elution of tobramycin associated with the greater volume of generic tobramycin powder could lead to clinically higher levels of tobramycin in wound fluid and local tissues; however, the higher volume of powder could potentially cause greater mechanical compromise of the PMMA.

Particle size of fillers affects permeability of polymethylmethacrylate.

Particulate soluble filler added to polymethylmethacrylate increases its permeability, leading to increased elution. We asked whether particle size affects permeability and elution rate associated with a given volume fraction of filler. Permeability of filler-loaded PMMA was measured in 9 mm rods with a 32% volume fraction of four particle sizes (106 microm, 212 microm, 425 microm, 850 microm) and two filler materials (sucrose and xylitol) using a modified phenolphthalein-sodium hydroxide technique, which allowed quantitative serial observation on the same specimens. Fluid penetration was faster for larger particle sizes. The elution rate was greater for smaller particle sizes on qualitative visual assessment. Sucrose fillers were not different from xylitol fillers independent of particle size. For the volume fraction of 32%, larger particles lead to larger caliber porosity, less pore interconnectivity, and faster fluid penetration. Smaller size particles lead to smaller caliber porosity, greater pore interconnectivity, smaller areas between the pores with no fluid penetration and greater increase in the effective surface area causing a greater elution rate.

Salvage of infected total knee components.

Debridement and retention of components for the treatment of infected total knee replacements has not been effective, with a failure rate of more than 70%. In cases where there are solidly fixed components, particularly with long stems, a method of successfully retaining the components is desirable. A protocol of radical debridement has been developed to eradicate the biofilm related bacteria associated with these infections. Assessment of the interfaces and elimination of all spaces and unsealed interfaces that will allow penetration by bacteria is essential. Four cases of infected total knee replacements are reported without recurrence after a minimum of 18 months. Refinement of the protocol and longer followup on more cases is planned to validate the early results.

Open reduction internal fixation of supracondylar fractures above total knee arthroplasties using the intramedullary supracondylar rod.

Seven patients who had low supracondylar fractures above total knee arthroplasties were treated using the intramedullary supracondylar rod. Six of the seven patients were steroid-dependent, long-standing severe polyarticular rheumatoid arthritics with marked osteopenia. The intramedullary supracondylar rod provided stable fixation that allowed early range of motion of the knee. Union occurred in good position in all patients; return to prefracture function was achieved in three months. The surgical procedure was reliable and was associated with minimal morbidity.

Arthroscopic débridement of the knee for osteoarthrosis.

To evaluate outcome after arthroscopic débridement, the records of 171 patients with osteoarthrosis of the knee were reviewed. All patients were unresponsive to conservative management and were treated arthroscopically. Procedures included lavage, meniscectomy, chondrectomy, removal of free bodies and removal of limited osteophytes. Outcome assessment was retrospective, evaluating the need for further surgery, control of pain, improved function and patient satisfaction. Sixty-five percent of patients felt their symptoms were improved. There was excellent control of pain in 38% and improved function in 22%. Subsequent surgical procedures were required in 12% at an average follow-up of 25 months. No factors were identified that correlated with the outcome, including the extent of degenerative changes and of débridement and patient profile. Arthroscopic débridement is a temporizing procedure with good patient satisfaction. Marked, but unpredictable, improvement in symptoms is seen in one patient out of three.

Locked intramedullary fixation for metaphyseal malunion and nonunion.

Locked intramedullary rod fixation, established for metaphyseal fractures, is applicable to reconstructive procedures. Fourteen cases of complex nonunion or malunion (five infected) were reviewed retrospectively. Thirteen of the 14 fractures united. Eleven of 14 required an open procedure for removal of metal, soft-tissue release, bone grafting, osteotomy, or resection of infected bone. Infections were controlled by resection, depot antibiotics, and early stabilization. Interlocking intramedullary rods are an excellent fixation technique for posttraumatic metaphyseal reconstructive procedures.

Long-term pain and disability in relation to residual deformity after displaced pelvic ring fractures.

In a retrospective review and follow-up study of 43 patients who had had high-energy pelvic fractures 5 or more years earlier, the occurrence of late pain and the functional outcome were adversely related to residual deformity of the pelvic ring. Among patients who had no residual deformity (displacement less than 1 cm), 88% had no serious pain and 82% had normal function. Of patients who had residual deformity (displacement more than 1 cm posteriorly), only 30% had no serious pain (p less than 0.01) and only 30% had normal function (p less than 0.01). Definitive reduction and stabilization is therefore recommended early after the injury whenever possible.

Intramedullary rod fixation of femoral shaft fractures: comparison of open and closed insertion techniques.

Meta-analysis of published series of intramedullary rod fixation in fractured femurs revealed significantly higher union rates, lower deep infection rates and a better range of knee motion when closed rather than open techniques of insertion were used. A separate retrospective review of 58 femoral fractures at one hospital showed outcomes consistent with those reported in the literature; these results were obtained during a 6-year period when staff were learning closed techniques. Technical failures of the closed technique can be avoided by paying attention to well-established operative details. A system for grading outcomes was developed to compare objectively the results of treatment of fracture patients. The literature and the authors' experience support the adoption of closed techniques for intramedullary rod insertion in femoral shaft fractures.

Analysis of radionuclide arthrograms, radiographic arthrograms, and sequential plain radiographs in the assessment of painful hip arthroplasty.

An analysis of sequential plain radiographs (XR), radionuclide arthrography, (RNA), and radiographic arthrography (RGA) was performed to determine the efficacy and usefulness of each study in the diagnosis of loosening of prosthetic hip components. Over a 2-year-period, 65 hip prostheses were assessed before operation using each type of study; these results were compared to the intraoperative assessment of the status of the components. Of the three studies, sequential plain radiographs were overall the most accurate, sensitive, and specific. Radionuclide arthrography was of no use on the acetabular side but quite useful on the femoral side, especially in cases with only minimal femoral component loosening. Radiographic arthrography was overall the least accurate or sensitive of the three studies performed.

Prophylaxis with indomethacin for heterotopic bone. After open reduction of fractures of the acetabulum.

Forty-four fractures of the acetabulum that had been treated with open reduction and internal fixation necessitating dissection of the gluteal muscles were reviewed radiographically for the development of heterotopic bone. Grade-2 (Brooker classification) or more severe heterotopic ossification was seen in thirteen (50 per cent) of twenty-six patients who did not receive indomethacin but in only one (5.5 per cent) of eighteen patients who received indomethacin for six weeks postoperatively. In the patients who did not receive indomethacin, the maximum amount and extent of the heterotopic bone was evident in twelve weeks. In the patients who did receive indomethacin, the heterotopic ossification did not progress after the administration of indomethacin was discontinued. We concluded that, in patients who have a fracture of the acetabulum, indomethacin provides effective prophylaxis for heterotopic bone after operative reduction with gluteal dissection.

Anterolateral compression fracture of the thoracolumbar spine. A seat belt injury.

A thoracolumbar injury is reported in four patients who were involved in motor vehicle accidents while wearing shoulder-lap belt assemblies. These injuries consisted of anterolateral wedge compression of a thoracolumbar vertebra with lateral compression occurring on the side opposite the restrained shoulder. The posterior elements were disrupted contralateral to the anterolateral body compression. There was no translation in any of these fractures, and there were no neurological injuries. All fractures united without significant late disability. Although there was no gross clinical instability in these fractures, two of the three columns of the spine are disrupted, suggesting potential instability. The postulated mechanism of injury, referred to as the roll-out phenomenon, is flexion and rotation about the axis of the shoulder strap.

Longitudinal stress fracture of the tibia: case report.

Stress fractures usually present with vague clinical features and delayed radiographic findings. A patient with a longitudinal stress fracture of the tibia is described here. Computed tomographic images, perpendicular to the fracture, were diagnostic while plain radiographs and scintigraphy showed nondiagnostic changes due to an unexpected fracture pattern.

Biceps tendon blocks reduction of isolated radial head dislocation.

A case of an unreducible radial head dislocation found in a 7-year-old girl illustrates the frequent delay in diagnosis associated with radial head dislocation. Her initial radiographs showed the radial neck access not passing through the center of the capitulum, which is diagnostic of radial head dislocation. She had no associated injuries to the elbow joint or neurovascular structures. Closed reduction was not stable, and open reduction revealed the biceps tendon displaced posteriorly and laterally from the radial tubercle around the radial neck, which prevented stable reduction of the anteromedial dislocation of the radial head. Once it was reduced through the radial capitular joint to its normal anatomy, the reduction was stable. Following a routine postoperative course, an excellent result was obtained.

Cauda equina syndrome: a complication of lumbar discectomy.

Six cases of acute postdiscectomy cauda equina syndrome (C.E.S.) following lumbar discectomy were reviewed retrospectively in a series of 2842 lumbar discectomies over a ten-year period. Five cases had coexisting bony spinal stenosis at the level of the disc protrusion. The bony spinal stenosis was not decompressed at the time of discectomy. Inadequate decompression played a role in the neurologic deterioration postoperation. The cause of the sixth case is unknown. Bowel and bladder recovery was good when the cauda equina decompressed early; sensory recovery was universally good, and motor recovery was poor if a severe deficit had developed before decompression. Careful review of the preoperative myelogram to rule out spinal stenosis and decompression of bony stenosis at discectomy are recommended for prevention of postoperative C.E.S. Urgent decompression of postoperative C.E.S. is advisable if compression of the cauda equina is confirmed radiographically.

The pressure distribution under tourniquets.

We measured the detailed pressure distribution under pneumatic tourniquets and Esmarch bandages in canine limbs. The results showed that pressure concentration can occur in the tissue under the tourniquet. The Esmarch-bandage tourniquet was shown to be capable of producing pressures in excess of 1000 millimeters of mercury immediately beneath the tourniquet. There is a wide variation between cuff pressure and the pressures in the underlying tissues.