Femoral head vitality after femoral neck fracture. Comparison between pre- and peroperative tetracycline labeling

Trabecular, but not cortical, bone tissue protein synthesis rates are lower in the femoral head when compared to the proximal femur following an intracapsular hip fracture

BACKGROUND

All musculoskeletal tissues are in a constant state of turnover, with a dynamic equilibrium between tissue protein synthesis and breakdown rates. The synthesis of protein allows musculoskeletal tissues to heal following injury. Yet, impaired tissue healing is observed following certain injuries, such as geriatric hip fractures. It is assumed that the regenerative properties of femoral head bone tissue are compromised following an intracapsular hip fracture and therefore hip replacement surgery is normally performed. However, the actual impact on in vivo bone protein synthesis rates has never been determined.

DESIGN

In the present study, 10 patients (age: 79 ± 10 y, BMI: 24 ± 4 kg/m2) with an acute (<24 h) intracapsular hip fracture received a primed continuous intravenous infusion of L-[ring-13C6]-phenylalanine before and throughout their hip replacement surgery. Trabecular and cortical bone tissue from both the femoral head and proximal femur were sampled during surgery to assess protein synthesis rates of affected (femoral head) and unaffected (proximal femur) bone tissue, respectively. In addition, tissue samples of gluteus maximus muscle, synovium, ligamentum teres, and femoral head cartilage were collected. Tissue-specific protein synthesis rates were assessed by measuring L-[ring-13C6]-phenylalanine incorporation in tissue protein.

RESULTS

Femoral head trabecular bone protein synthesis rates (0.056 [0.024-0.086] %/h) were lower when compared to proximal femur trabecular bone protein synthesis rates (0.081 [0.056-0.118] %/h; P = 0.043). Cortical bone protein synthesis rates did not differ between the femoral head and proximal femur (0.041 [0.021-0.078] and 0.045 [0.028-0.073] %/h, respectively; P > 0.05). Skeletal muscle, synovium, ligamentum teres, and femoral head cartilage protein synthesis rates averaged 0.080 [0.048-0.089], 0.093 [0.051-0.130], 0.121 [0.110-0.167], and 0.023 [0.015-0.039] %/h, respectively.

CONCLUSION

In contrast to the general assumption that the femoral head is avital after an intracapsular displaced hip fracture in the elderly, our data show that bone protein synthesis is still ongoing in femoral head bone tissue during the early stages following an intracapsular hip fracture in older patients. Nonetheless, trabecular bone protein synthesis rates are lower in the femoral head when compared to the proximal femur in older patients following an acute intracapsular hip fracture. Trial register no: NL9036.

Femoral neck fracture fixation with hook-pins. 2-year results and learning curve in 626 prospective cases

We performed a prospective 2-year follow-up study of 626 consecutive femoral neck fractures treated with closed reduction and hook-pin fixation in all cases. The woman:man ratio was 2.9:1, the displaced:undisplaced fracture ratio 2.6:1. Mean patient age was 78 (18-100) years. The first 476 fractures were operated on by one of six surgeons with special interest in the technique, while the remaining operations were performed by any of the 35 surgeons in the department, all specialists in orthopedic surgery. Mortality within two years was 31 percent. Healing complications (redisplacement, nonunion or segmental femoral head collapse) in the total material/survivors only were for undisplaced fractures 5/7 percent, for displaced fractures 30/41 percent and for the total material 23/32 percent. According to life-table analysis, the complication rate in the total material at two years was 24 percent. The rate of secondary arthroplasty for healing complications was 13/19 percent. For displaced fractures, as well as for the total material, the group of specially interested surgeons had better results than the department as a whole.

Femoral head vitality at reoperation for femoral neck fracture complications

In seven patients suffering redisplacement, nonunion or segmental collapse after nailing of femoral neck fractures, subsequent changes in the vitality of the femoral head were studied with tetracycline labeling and 99mTc-MDP scintimetry. At reoperation (total hip arthroplasty), the femoral heads were extracted and sawn into slices which were then analyzed. Vitality before nailing was totally lacking (tetracycline labeling) in one case (nonunion), and in the remaining cases moderate reduction was seen, most pronounced in the apical part of the head. In all cases, scintimetry 1-2 weeks after nailing showed reduced femoral head uptake of 99mTc-MDP, but scintimetry some hours before reoperation showed increased femoral head uptake. Isotope analysis of the slices from the extracted femoral heads showed marked reduction of uptake in the apical part of the head, moderate reduction in the distal and anterior parts, and satisfactory uptake in the posterior part of the head and the foveal region, though with individual variations. It was concluded that there is a genuine increase in uptake (revascularization) later in the course in postoperatively avascular heads, and that the apical part of the femoral head sustains the most pronounced vascular damage in femoral neck fracture and is probably the slowest to revascularize.

Avascular necrosis associated with nailing of femoral neck fracture. Two cases examined pre- and postoperatively by tetracycline and radionuclide tracer techniques

Two patients with femoral neck fractures, one displaced and one undisplaced, are presented. Preoperative intravital staining with tetracycline and Tc-MDP scintimetry both showed intact femoral head circulation while Tc-MDP-scintimetry 1 week after operation showed pronounced circulatory deficiency. Sr85-scintimetry performed at the same time was inconclusive. Segmental collapse was observed radiographically, 8 and 12 months postoperatively. The major vascular injury resulting in avascularity most probably occurred during the procedure of osteosynthesis, and Tc-MDP-scintimetry was found suitable for early postoperative recognition of avascular necrosis in both fractures.