Warren G. Stamp

The nonsurgical management of odontoid fractures in adults.

Twenty-five odontoid fractures that were treated nonsurgically at the University of Virginia Hospital in the last 5 years were reviewed. Motor vehicle accidents were the major cause of this injury in our series. Early recognition and firm external stabilization of Type I and Type III fractures of the odontoid resulted in union in 100% of our patients. There were 12 Type II fractures with a nonunion rate of 42%. Thus, an overall rate of union of 80% was obtained. It is suggested in the literature and by this series that early recognition, reduction, and rigid external Immobilization of Types I and III fractures of the odontoid should promote bony union. Type II fractures may also be managed successfully by closed methods, although the outcome is less certain.

Cortisone-induced Intrafemoral Head Pressure Change and its Response to a Drilling Decompression Method

Intramedullary head pressure changes were studied in a group of cortisone-treated New Zealand white rabbits. In addition to femoral head pressure measurements, serum cholesterol levels were followed serially and pathologic specimens from cortisone-treated femoral heads were obtained. Surgical decompression by a drilling method was performed and pressures were remeasured at four weeks following decompression. Persistent increases in cholesterol levels and in intrafemoral head pressures were noted, particularly from six to eight weeks after initiation of steroid treatment. Cholesterol levels were elevated to four times control values and femoral head pressures averaged 2 1/2 times the control values (60 cm of water vs 24.6 +/- 5.5 cm of water). Surgical decompression by drilling effectively reduced the once elevated pressures to control values. A relationship between increased fat cell size, increased intramedullary pressure and decreased femoral head blood flow in steroid-treated rabbits is postulated. The applicability of these data to humans with steroid-induced ischemic necrosis of the femoral head has yet to be demonstrated.

Steroid-induced Femoral Head Pressure Changes and their Response to Lipid-clearing Agents

In rabbits, cortisone increases marrow fat cell size and intrafemoral head pressure, produces systemic fatty embolization, and probably is one of the causes of avascular necrosis of the femoral head. Clofibrate, a lipid-clearing agent, decreases the serum cholesterol level, reduces the marrow fat cell size changes, and decreases intrafemoral head pressure. This might be significant in improving femoral head venous outflow in long-term steroid-treated persons.

Experimental femoral fracture immobilized by rigid and flexible rods (a rabbit model).

Experimental fractures in rabbits demonstrated that flexible intramedullary rod fixation of the midshaft long bone fracture enhances the fracture healing and may promote early mobility. When compared to rigid fixation, both excess flexibility and excess rigidity inhibited optimal fracture healing. The occurrence of angulation deformities with plastic rods also demonstrate the disadvantage of a very flexible rod.

Transfibular compression arthrodesis of the ankle joint.

Eleven ankle arthrodeses were performed on ten patients using a transfibular technique. This technique employs a lateral approach in which the distal fibula is resected while preserving the peroneal tendon sheath, allowing excellent exposure and contouring of the tibiotalar joint. Compression is attained by using a T-plate placed across the tibiotalar joint with the aid of an AO compression apparatus. At 2.5 years after operation, fusion was achieved in ten ankles. Average time in immobilization was 11.8 weeks, and the fused ankle was cosmetically pleasing. Fusion occurred in nine of 11 ankles fused using other methods during this period. Pin tract infection occurred in three, the time in immobilization averaged 16.2 weeks, and the cosmetic result was inferior.

The operative treatment of Achilles tendon injuries.

Twenty cases of Achilles tendon injury treated surgically at the University of Virginia Medical Center from 1970 to 1979 were reviewed and reevaluated with up to 9 years of follow-up. Three treatment groups were identified: Group I--primary repair of a lacerated Achilles tendon; Group II--primary repair of an acutely ruptured Achilles tendon; and Group III--subacute repair of Achilles tendon rupture (performed more than 72 hours after injury). Acute repairs were performed by end-to-end suture. In subacute cases the anastomosis was reinforced with one or 2 flaps from the gastrocnemius tendon. Strenuous exercise accounted for nearly all the cases of acute tendon rupture. Surgical complications and overall functional results were determined for each treatment group. Open repair provides excellent results when applied to lacerations. A good-to-excellent overall result can be expected for patients with acute ruptures and primary repair, but an awareness of the possible postoperative complications is necessary. Achilles tendon ruptures that go unrecognized for more than 72 hours are best treated conservatively.

Femoral head blood flow in long-term steroid therapy: study of rabbit model

ABSTRACT: Using a rabbit model, previous studies showed steroid-induced hyperlipidemia with subsequent fatty embolization of the subchondral arteries and hypertrophy of the marrow fat cells, followed by elevation of femoral head pressure from the normal level of 25 cm to nearly 60 cm H2O after eight weeks of treatment. This has led us to believe that pressure changes lead to decreased blood flow in the femoral head. In our study of 22 New Zealand white adult rabbits, weighing an average of 4.0 kg, 14 received a weekly dose of 12.45 mg of methylprednisolone (Depo-Medrol), and eight served as control. Femoral head blood flow was established using the radioactive microsphere technique. Control and cortisone-treated rabbits had femoral head blood flow measured 6, 8 and 10 weeks after treatment. The average blood flow in the control femoral, heads averaged 0.2039 ± 0.076 ml/min/gm, with no difference in the left side and the right side. In the treated group, the average blood flow at ten weeks was 0.162 ± 0.039 ml/min/gm on the right and 0.164 ± 0.037 ml/min/gm on the left, which was significantly different. This is parallel to unpredictable clinical findings in human beings.

Semirigid rod fixation for long-bone fracture

Experiments on 119 New Zealand rabbits were performed to measure healing strength of femurs. Four pairs of normal rabbit femurs were also studied in vitro by use of a four-point bending test to measure bending rigidity. Rabbit-sized octagonal cross-sectioned intramedullary rods with 12%, 20%, 50%, 75%, and 100% of femoral bending rigidity were specially prepared. For each animal, one intramedullary rod was implanted in an osteotomized femur through a standard lateral approach, with the other femur serving as a control. The results from the 12% rigidity rods were widely variable. In the 20% and 50% rigidity groups, the callus diameter was increased over the 75% rigidity group through all phases of healing. The torque ratio in this group increased up to eight weeks and then converged to the ratios of the other rigidities. The 75% rigidity group had shown increase of angular displacement up to eight weeks, while the 20% and 50% rigidity groups continued to improve and reached control strength at 12 weeks of treatment. Furthermore, the 20% and 50% groups absorbed more energy to failure in the later stage of healing than the 75% and 100% rigidity groups. Rods of 20% and 50% rigidity stimulate external callus formation and improve the stability of healing bone.

The safety of cement fixation in the cervical spine. Studies of a rabbit model.

Immediate postoperative ambulation of patients with terminal neoplastic disease of the cervical spine can be permitted by vertebral stabilization with wire reinforced with polymethylmethacrylate. Precautions are necessary to avoid a temperature rise during cement polymerization and prevent vasular or nerve damage. Experiments on 20 rabbits and 2 human cadavers indicate that temperature at the cement-lamina interface can rise as high as 90 degrees while temperature under the intact lamina measures only 50 degrees. Precooling and insulation with Gelfoam may prevent heat injury to spinal cord.

Comparative strength of anterior spinal fixation with bone graft or polymethylmethacrylate. Experimental operations and observations on dogs.

In 23 dogs, polymethylmethacrylate (PMMA) was safely implanted in the region of the spinal cord. The dogs were treated by bone or cement fixation after anterior excision of a single cervical vertebral body. Fixation was compared at 0-18 weeks, with control values obtained from 11 dogs. Anterior cement fixation did not displace after 18 weeks. The anterior bone graft appeared to achieve adequate fixation strength around six weeks. The strength of the bone-graft fixation increased, while that of cement fixation decreased somewhat with time. At all time intervals, the ratio of energy absorption to structural failure was somewhat higher with bone graft than with PMMA.