Treatment of infected total knee arthroplasty using an articulating spacer.

Twenty-six patients with late infected total knee arthroplasties were treated by debridement and removal of components and all cement, preserving collateral ligaments. At time of debridement, an articulating spacer was fashioned to allow partial weightbearing and knee range of motion (ROM) during rehabilitation. This spacer was implanted using antibiotic-impregnated bone cement. For this purpose, 4.8 g of powdered tobramycin was mixed with each 40-g batch of Simplex cement. Cement was applied early to the components, but applied late to the femur, tibia, and patella to allow molding to the defects and bone without adherence to bone. Patients received tailored intravenous antibiotic therapy for 6 weeks in addition to this antibiotic-impregnated cement for treatment of a variety of gram positive and gram negative organisms. All patients had cemented revision total knee arthroplasty using antibiotic-impregnated cement with standard cementing techniques used. All patients but 1 had reimplantation; this patient died of unrelated causes before revision. Range of motion before revision was 10 degrees to 95 degrees. Followup averaged 30 months (range, 13-70 months). The average Modified Hospital for Special Surgery Knee Score after revision was 87 points (range, 53-100 points), with 92% good to excellent results. Range of motion after reimplantation was 5 degrees to 106 degrees. There have been no recurrences of infection. Use of an articulating spacer to treat infected total knee arthroplasty improves ultimate ROM and soft tissue health and significantly decreases the risk of reinfection.

Microscopic analysis of autograft bone applied at the interface of porous-coated devices in human cancellous bone.

This study describes the response of human cancellous bone when autologous bone chips are added at operation to the interface between host bone and porous-coated implants. During the first operation of a staged bilateral total knee arthroplasty, seven patients consented to have paired porous-coated devices implanted into their opposite medial femoral condyle. One device of each pair had autologous bone chips applied to the porous-coating, and the other was not grafted and was a control. The devices were removed en bloc at the second total knee arthroplasty 6 to 49 weeks later. Backscattered electron imaging showed significantly more bone (p < or = 0.05) in the porous-coating of the implant treated with autologous bone chips which significantly increased (p < or = 0.05) the amount of bone available at the interface. The grafted devices had a mineral apposition rate of 1.04 +/- 0.20 microns/day for the interface and 0.81 +/- 0.09 microns/day for the peripheral bone. This compared with corresponding figures of 1.03 +/- 0.38 microns/day and 0.79 +/- 0.19 microns/day at the ungrafted devices. The mineral apposition rate at the interface of the porous-coated implants was significantly increased (p < or = 0.05) relative to the host bone in the periphery. Our results support the view that autologous bone chips are effective in attaching cementless porous-coated total knee replacements to the human skeleton by bone ingrowth.

Premature closure of the triradiate cartilage: a potential complication of pericapsular acetabuloplasty.

A case of premature triradiate cartilage closure secondary to a Gill acetabuloplasty performed at age 14 months is reported. The deficiency in acetabular development and failure of the pelvis to grow to its anticipated height is documented. A proximal femoral redirectional osteotomy and an innominate osteotomy performed near maturity improved femoral head coverage and hip biomechanics. Acetabuloplasties performed adjacent to the triradiate cartilage typically do not have any adverse effect on its function. Despite this low risk of injury to the triradiate cartilage after a Gill or Pemberton acetabuloplasty, long-term follow-up is recommended to observe acetabular development. Premature closure is most likely to occur if the bone graft used to maintain fragment displacement crosses the triradiate cartilage.

Subvastus (Southern) approach for primary total knee arthroplasty.

The subvastus or Southern approach to the knee had been described as early as 1929 but is not found in standard modern orthopedic textbooks. This approach for primary total knee arthroplasty (TKA) preserves the integrity of the extensor mechanism and maintains the vascular supply to the patella. To appreciate the potential benefits of this approach, a complete understanding of the surgical anatomy is essential. The benefits of the subvastus approach make it a valuable technique for primary TKA.