Charles N. Cornell

BONE CELLS AND MATRICES IN ORTHOPEDIC TISSUE ENGINEERING

The ability to harvest and manipulate osteogenic cells gives clinicians the opportunity to harness capacity of these cells for targeted regeneration and repair of skeletal tissues. Further opportunities to optimize use of cells exist in the ability to design specialized matrices that act as conductive scaffolds. Realization of the full potential of engineered matrix materials and cell-matrix composites can provide new solutions to many clinical problems in skeletal reconstruction.

Treatment of Acute Fractures with a Collagen-Calcium Phosphate Graft Material. A Randomized Clinical Trial*†

A prospective, randomized clinical trial was conducted concurrently at eighteen medical centers in order to compare the safety and efficacy of two types of graft material for the treatment of fractures of long bones: autogenous bone graft obtained from the iliac crest, and a composite material composed of purified bovine collagen, a biphasic calcium-phosphate ceramic, and autogenous marrow. Two hundred and thirteen patients (249 fractures) were followed for a minimum of twenty-four months to monitor healing and the occurrence of complications. We observed no significant differences between the two treatment groups with respect to rates of union (p = 0.94, power = 88 per cent) or functional measures (use of analgesics, pain with activities of daily living, and impairment in activities of daily living; p > 0.10). The prevalence of complications did not differ between the treatment groups except for the rate of infection, which was higher in the patients who were managed with an autogenous graft. Twelve patients who were managed with a synthetic graft had a positive antibody titer to bovine collagen; seven of them agreed to have intradermal challenge with bovine collagen. One patient had a positive skin response to the challenge but had no complications with regard to healing of the fracture. We concluded that, for traumatic defects of long bones that necessitate grafting, use of the composite graft material appears to be justified on the grounds of safety, efficacy, and elimination of the increased operative time and risk involved in obtaining an autogenous graft from the iliac crest.

Protein depletion and metabolic stress in elderly patients who have a fracture of the hip.

A prospective study was performed to determine the effect of protein depletion and postoperative nutritional status on the outcome in sixty-three elderly patients who had been admitted to the hospital because of a fracture of the hip. The parameters that were used to determine the degree of protein depletion included levels of albumin, of prealbumin, and of transferrin; total lymphocyte count; and nitrogen-balance studies. The outcomes that were examined were the development of complications, the length of the stay in the hospital, the ability to return to the pre-fracture level of function, and over-all survivorship. The hypothesis was that the acute fracture and the subsequent operation are severe stresses in these elderly, often compromised patients. The results supported the hypothesis. Thirty-seven patients (58 per cent) in the study group were in a protein-depleted state during the period of hospitalization. The patients who were protein-depleted had a higher prevalence of complications, were less likely to return to their pre-fracture environment, and tended to stay in the hospital longer, as compared with the nonprotein-depleted patients. Survivorship analysis showed that protein-depleted patients had a significantly lower probability of survival one year after the fracture of the hip (p = 0.02). Elderly patients who sustain the trauma of a fracture of the hip should be managed appropriately with regard to intake of nutrients in the postoperative period.

Cardiac arrest during hip arthroplasty with a cemented long-stem component. A report of seven cases.

Seven patients had a cardiac arrest during hip arthroplasty with a cemented long-stem femoral component. Four patients died in the operating room, and three patients were successfully resuscitated. When the three survivors were eventually discharged from the hospital, they had no known permanent cardiac, pulmonary, or neurological sequelae. Factors that were common to all of the patients were advanced age, osteoporotic bone, a previously undisturbed intramedullary canal, and use of a long-stem femoral component and several batches of methylmethacrylate. Hip arthroplasty with a long-stem femoral component is associated with substantial risk in these patients. Excessive pressurization of cement should be avoided, and invasive hemodynamic monitoring should be used when the described conditions are present.

OSTEOCONDUCTIVE MATERIALS AND THEIR ROLE AS SUBSTITUTES FOR AUTOGENOUS BONE GRAFTS

The term osteoconduction applies to a three-dimensional process that is observed when porous structures are implanted into or adjacent to bone. Capillaries, perivascular tissues, and osteoprogenitor cells migrate into porous spaces and incorporate the porous structure with newly formed bone. The observed process is characterized by an initial ingrowth of fibrovascular tissue that invades the porous structure followed by the later development of new bone applied directly within it. This article reviews observations of commonly used osteoconductive matrices to increase understanding of this process.

Management of proximal humeral fractures based on current literature

Proximal humeral fractures are the second most common upper-extremity fracture and the third most common fracture, after hip fractures and distal radial fractures, in patients who are older than sixty-five years of age1. Although the overwhelming majority of proximal humeral fractures are either nondisplaced or minimally displaced and can be treated with sling immobilization and physical therapy, approximately 20% of displaced proximal humeral fractures may benefit from operative treatment. Many surgical techniques have been described, but no single approach is considered to be the standard of care. Surgeons who treat proximal humeral fractures should be able to identify the fracture pattern and select an appropriate treatment on the basis of this pattern and the underlying quality of the bone. Orthopaedic surgeons should have experience with a broad range of techniques, including transosseous suture fixation, closed reduction and percutaneous fixation, open reduction and internal fixation with conventional and locked-plate fixation, and hemiarthroplasty. In the future, locked-plate technology and the use of osteobiologics may play an increasingly important role in the treatment of displaced proximal humeral fractures, facilitating preservation of the humeral head in appropriately selected patients. The goals of this article are to enable the reader to: (1) become familiar with the recent literature on the classification of and treatment options for proximal humeral fractures, and (2) better identify fracture characteristics and devise an appropriate treatment plan. ### Transosseous Suture Fixation #### Surgical Technique Park et al.2 described different operative approaches for each fracture pattern described by Neer 3. For two-part greater tuberosity fractures, an anterosuperior approach along the Langer lines extending from the lateral aspect of the acromion toward the lateral tip of the coracoid is used. The split occurs in the anterolateral raphe and allows exposure of the displaced greater tuberosity fracture. When a surgical neck fracture exists, Park et al.2 …

Internal Fracture Fixation in Patients With Osteoporosis

&NA; Because of the decreased holding power of plate‐and‐screw fixation in osteoporotic bone fractures, internal fixation can have a high failure rate, ranging from 10% to 25%. Screws placed into cortical bone have better resistance to pullout than do those placed into adjacent trabecular bone. Plates should not be used to bridge unstable regions of bony comminution in osteoporotic patients. Fixation stability is optimized by securing stable bone contact across the fracture site and by placing screws both as close to and as far from the fracture as possible. Intentional shortening can improve stability and load sharing of the fracture construct. Structural bone graft or other types of fillers can be used to fill voids when comminution prevents stable contact. Load‐sharing fixation devices such as the sliding hip screw, intramedullary nail, antiglide plate, and tension band constructs are better alternatives for osteoporotic metaphyseal locations. Proper planning is essential for improved fracture fixation in this high‐risk patient group.

Current understanding of osteoconduction in bone regeneration

Bone tissue is osteoconductive. In particular, cancellous bone with its porous and highly interconnected trabecular architecture allows easy ingrowth of surrounding tissues. When placed in an osseous environment, living tissue for the host bed migrates into the cancellous structure, which results in new bone formation and incorporation of that structure. This is the process of osteoconduction. The mineral and collagenous components of bone are osteoconductive. Osteoconduction also is observed in fabricated materials that have porosity similar to that of bone structure. Corallin ceramics, hydroxyapatite beads, and combinations of hydroxyapatite and collagen all have osteoconductive properties, and porous metals and biodegradable polymers. Osteoconduction appears to be optimized in devices that mimic not only bone structure, but also bone chemistry. The incorporation of calcium salts and collagen by osteoconductive matrices leads to more complete ingrowth with new bone formation.

Innovations in the Management of Displaced Proximal Humerus Fractures

Abstract The management of displaced proximal humerus fractures has evolved toward humeral head preservation, with treatment decisions based on careful assessment of vascular status, bone quality, fracture pattern, degree of displacement, and patient age and activity level. The AO/ASIF fracture classification is helpful in guiding treatment and in stratifying the risk for associated disruption of the humeral head blood supply. Nonsurgical treatment consists of sling immobilization. For patients requiring surgery, options include closed reduction and percutaneous fixation; transosseous suture fixation; open reduction and internal fixation, with either conventional or locking plate fixation; bone graft; and hemiarthroplasty. Proximal humerus fractures must be evaluated on an individual basis, with treatment tailored according to patient and fracture characteristics.

Measuring Recovery after a Hip Fracture Using the SF-36 and Cummings Scales

Abstract: The objective of this study was to assess outcomes of traditional treatment of fractures using the SF-36 and the Cummings Hip Scale. In designing randomized clinical trials, it is necessary to determine the timing of assessment either for progress or for the main outcome. We set out to document the recovery of patients after surgery for hip fracture using current standard methods of medical care. This was a prospective study of a cohort of patients. Patients who were receiving standard medical care completed the SF-36 and the Cummings Hip Scale at previously determined times postoperatively. The SF-36 has eight subscales, including assessments of physical function, physical role behaviors, bodily pain, mental health, social role, emotional role, vitality and general health. Thirty-eight patients completed the questionnaires at 1 year postoperatively as well as previous time points. On the Cummings Hip Scale and the physical function, bodily pain, mental health, social function, emotional role, vitality and general health subscales of the SF-36, recovery is near complete at 6 months. Only the physical role subscale differs, with a statistically significant difference between the values at 6 months and 1 year, (p= 0.02). Patients attained over 90% of the 1 year value by 6 months for all except the physical role subscale. The physical role subscale reached 85%. For a hip fracture patient who is on the road to recovery, the majority of the recovery has therefore taken place by 6 months.