Reconstruction of the anterior cruciate ligament with an intra-articular patellar tendon graft and an extra-articular tenodesis. Results after six years.

We describe 74 patients with disabling instability of the knee due to isolated anterior cruciate deficiency. None responded to conservative measures or correction of internal derangements. All patients were treated by replacement of the anterior cruciate ligament with the medial third of the patellar tendon as a free graft, supplemented by an extra-articular MacIntosh lateral reconstruction. A satisfactory outcome was found in 93% of knees after an average of 70 months follow-up. Cast immobilisation after operation, the interval between injury and reconstruction, the age of the patient and the severity of symptoms before reconstruction had no significant effect on the final outcome.

The accuracy of tibial intramedullary alignment devices in total knee arthroplasty.

The accuracy of a tibial medullary alignment device is assessed radiographically in 30 varus and 30 valgus knees undergoing total knee arthroplasty. The results suggest that although the device is reliable and accurate for varus knees, it may lead to malalignment of up to 5 degrees in valgus knees. Overall neutral alignment was achieved in 83% of the varus knees and 37% of the valgus knees. Tibial bowing was the main source of error and was present in 66% of the valgus knees, with mean of 3 degrees. Preoperative long films or cross-checking with external alignment devices is recommended to assure neutral alignment in genu valgus deformity.

Uncemented press-fit total knee arthroplasty.

Nineteen total knee arthroplasties in 16 patients were performed using a new prosthesis designed specifically for uncemented, press-fit fixation without any provision for tissue ingrowth. This design may be suited for use in patients with juvenile rheumatoid arthritis, postseptic knees, failed total knee arthroplasties with large bone stock deficiencies, and young, active, overweight individuals. Preservation of bone stock is possible because the fixation stems are nails rather than larger cement pegs, removal for revision is easier without cement, sequestration of microbes within cement cannot occur, and bone graft may be continually loaded with this type of prosthesis. Pain relief, discarding crutch support, operative blood loss, and corrective alignment were equivalent to results obtained with cemented arthroplasty. Seventeen of the 18 knees available for review (average follow-up period, 3 years, 7 months; range of follow-up period, 2 years, 10 months to 4 years, 11 months) were pain-free. Range of motion averaged -2 degrees of extension to 101 degrees of flexion. Ambulation was unrestricted and unsupported in the majority of patients. Radiographic evaluation showed the development of increased bone density under the tibial plateau as well as a sclerotic line at the ends of the femoral and tibial stems. This observation gives support to the theory that multiple microtrabecular fractures with healing form a new supportive "subchondral bone plate." There was one incidence of tibial subsidence. Prosthesis migration and loosening were not observed.

Bone loss in the distal anterior femur after total knee arthroplasty.

Bone loss in the distal anterior femur in asymptomatic total knee arthroplasty (TKA) patients has been noted roentgenographically and during revision surgery. A retrospective roentgenographic review of 147 TKA cases was carried out to document bone loss. The influence that the mode of fixation (porous coated and cemented) and the implant design have on bone loss was examined. The time of onset and the progression of bone loss were studied. Bone loss occurred in the distal anterior femur in the majority of cases reviewed (68%). The prevalence of bone loss was independent of the mode of fixation and the implant design. By qualitative observation, roentgenographically detectable bone loss occurred within the first postoperative year and did not progress further. Previously three-dimensional finite element analysis demonstrated that the replacement of the bearing surface of the femur with a stiff metallic implant reduces the stress in the distal anterior femur by at least one order of magnitude. It is therefore speculated that the observed bone loss results from stress shielding. The apparent lack of progression may reflect the development of a new remodeling equilibrium under the altered stress conditions. The bone loss in the distal anterior femur described has not been implicated as a source of failure. However, since the bone strength in the femoral region is compromised as it becomes osteopenic, bone failure may occur with longer periods of cyclic loading. Furthermore, as a result of bone loss, revision arthroplasty may be more difficult.