Acetabular reconstruction with impacted morselized cancellous allografts in cemented hip arthroplasty: a histological and biomechanical study on the goat.

Bone defects in total hip arthroplasty revision surgery can be restored with different types of bone graft. The use of impacted morselized allograft chips in combination with cement is the treatment of our choice. To establish the incorporation capacity of the grafts and mechanical stability of the implant, an animal model in the goat was developed. An acetabular defect was created and restored with morselized grafts and a cemented cup. Postoperative performance of the reconstruction was followed both histologically and biomechanically. Histology showed that consolidation of the graft with the host bone bed had occurred within 3 weeks. In the following period a front of vascular sprouts infiltrated the graft. Graft resorption, woven bone deposition, and subsequent remodeling resulted in a new trabecular structure. This structure contained only scarce remnants of the original dead graft material. At the graft-cement interface, graft resorption and new bone formation had resulted in areas of direct vital bone-cement contact. Locally, a soft tissue interface was present. After longer follow-up periods, progressive interface formation and loosening of the cups were found in most animals. Mechanical testing showed that the stability of the reconstruction increased during the first 12 postoperative weeks. Thereafter, the stability decreased, probably by soft-tissue interface formation at the graft cement interface. We conclude that cemented morselized allografts have a high capacity to incorporate. Initial cup stability is adequate to provoke graft incorporation with decreasing stability after the incorporation process has been completed.

Acetabular and femoral reconstruction with impacted graft and cement.

Loosening of primary cemented and noncemented components of total hip arthroplasties always is accompanied by a loss of bone stock. There are several options for reconstruction of the acetabular and femoral defects. The authors' treatment of choice is a standardized cemented revision procedure with tight impaction of morsellized cancellous autograft or allograft chips in acetabular and femoral reconstructions. In this study, the clinical and radiographic evaluation of acetabular defects reconstructed with impacted morsellized allograft femoral heads was described. A cemented cup supplemented with morsellized cancellous grafts and wire meshes in cases of segmental defects was sufficiently stable to allow for complete graft consolidation. After a mean followup of 70 months of 88 hips, 4 cases of clinical failures (including 1 infection) and 6 cases of radiologic failure of the reconstructions were observed, resulting in a failure percentage of 11.4% after 5 years. Autografts and allografts were equally effective. Because the clinical success of the technique also was supported by the results of histologic and biomechanic studies in animals, the authors were encouraged to continue this technique, not only in the acetabulum, but also in the femur.

Kotz modular femur and tibia replacement. 28 tumor cases followed for 3 (1-8) years.

In the period 1984-1991, 33 lower limb reconstructions were performed with an uncemented Kotz modular femur tibia reconstruction (KMFTR) prosthesis after resection of 32 malignant bone tumors and 1 benign giant cell tumors. Tumor localization was proximal femur in 12, distal femur in 17, and proximal tibia in 4. The mean age of the patients was 38 years. 28 patients with a minimum follow-up of 1 year were studied after 3 (1-8) years. 7 patients were reoperated because of complications. Good or excellent results were obtained in 6 of the 10 proximal and 13 of the 14 distal femur reconstructions. In 2 of the 4 patients undergoing combined distal femur and proximal tibia resection, a deep infection developed, and above-knee amputation was performed. One local recurrence occurred after proximal femur resection.

Cemented fixation with bone grafts.

Loosening of the acetabular cup in cemented total hip arthroplasty is always accompanied by a loss of bone stock. Acetabular lesions can be reconstructed in several ways. Preoperative planning must be through, and specifically if graft procedures are considered, infection must be ruled out. The treatment of choice is a standardized cemented acetabular revision procedure with tight impaction of morsellized cancellous grafts. The clinical success of the technique is supported by the results of an animal experiment.

Primary fit of the Lord cementless total hip. A geometric study in cadavers.

Two Lord prostheses, bilaterally implanted in cadavers, were sectioned. The contact areas between bone and prosthesis were studied and measured using a specially developed reproducible method. Primary fixation of the femoral components appeared to be based principally on wedging of the prosthetic stem in the femoral shaft with a rather small contact surface. In both acetabuli the screw threads of the rings were only marginally in contact with the acetabular bone.