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Biomedical subjects

Robert L Barrack

Publications and source records attributed to Robert L Barrack.

At least 37 records · Page 2Linked to original sources
PubMed2003

Effect of cementless bowed stem distal surface contour and coronal slot on femoral bone strains and torsional stability.

Six pairs of unembalmed cadaver femurs were instrumented with strain gauges and prepared with flexible reamers for insertion of long bowed cementless femoral stems. A fully porous-coated cobalt chrome stem was inserted into each left femur, and a distally fluted, slotted, stem of the same implant geometry and implant material was inserted into each right femur. Bone strains were measured during stem insertion and torsional stability tested after the stems were fully seated. Distal strains were significantly higher (p < 0.05) for the fully porous compared to the distally fluted, slotted stem. Three fractures occurred in femurs with fully porous-coated stems. There was no difference in torsional stability between the two stem geometries. Our data demonstrate that a long bowed cementless stem with a distal coronal slot and flutes is associated with decreased bone strains and fracture risk during stem insertion compared to a fully porous-coated stem.

Biomechanical Phenomena↗
PubMed2003

Orthopaedic crossfire--Stem modularity is unnecessary in revision total hip arthroplasty: in the affirmative.

Numerous options are available for femoral stem fixation in revision total hip arthroplasty, including cemented stems, proximally-coated cementless stems, extensively coated cementless stems, impaction grafting cemented stems, and modular cementless stems. In terms of versatility, ease of insertion, use with an extended trochanteric osteotomy, and clinical results, extensively coated cementless stems remain the gold standard. Modular cementless stems have not matched the clinical results of extensively coated cementless stems. In addition, modular stems introduce increased complexity, cost, and potential complications and are therefore, rarely, if ever, necessary in revision total hip arthroplasty.

Arthroplasty, Replacement, Hip↗
PubMed2003

Orthopaedic crossfire--All patellae should be resurfaced during primary total knee arthroplasty: in opposition.

After more than 20 years of debate, the decision on whether to resurface the patella in primary total knee arthroplasty (TKA) remains controversial. Laboratory testing suggests that performing a TKA alters knee kinematics. Every study to date has suggested that kinematics are more abnormal when the patella is resurfaced than when it is retained. In addition, patellofemoral contact areas are higher and contact stresses are lower with the native patella compared with the resurfaced patella after TKA. Virtually every clinical study of bilateral knee arthroplasty in which one patella has been resurfaced and the other has not has shown either equivalent results or a preference for the unresurfaced side. Laboratory and clinical data indicate that not resurfacing the patellar is a viable if not preferable option in most TKA patients.

Arthroplasty, Replacement, Knee↗
PubMed2003

Patellar options in revision total knee arthroplasty.

There are numerous options that need to be considered by the surgeon at the time of revision total knee arthroplasty (TKA). One needs to consider the reason for the revision, the type of patella in place, and the length of time the patella has been in place. The surgeon also needs to consider the status of the patellar bone stock, the stability of the patellar component (well-fixed or loose), and the component type (cemented or metal-backed). Assuming that the existing prosthesis is not metal-backed and has minimal PE wear, then it is preferable to retain a well-fixed all-PE cemented patellar button. However, if the button is metal-backed, then it probably is best to remove the button and replace it with an all-PE domed patellar component. Assuming more than 8 mm of patellar bone stock is remaining, it usually is best to cement an all-PE dome-shaped patella. However, if less than 8 mm is remaining, then that patient can be left with a patelloplasty, recognizing that this individual is going to continue with a high likelihood of anterior knee pain, subluxation, and poor functional results. In that situation, it may be preferable to consider a bone stock augmentation.

Arthroplasty, Replacement, Knee↗
PubMed2003

Treating extensor mechanism disruption after total knee arthroplasty.

A consecutive series of 14 patients with chronic extensor mechanism disruption after total knee arthroplasty (TKA) were treated with allograft reconstruction. Preoperatively all patients had full passive extension but a complete extensor lag. The average time from extensor mechanism disruption to surgery was 7 months (range, 3-24 months). Two methods of reconstruction were used depending on specific indications: an Achilles tendon with calcaneal bone block (eight patients) or a quadriceps tendon-patella-patellar tendon-tibial tubercle composite graft (six patients). At followup averaging 42 months (range, 24-60 months) all patients were community ambulators, five patients used a cane, two patients used a walker, and seven patients used no assistive devices. One patient had a partial rerupture and a 45 degrees extensor lag, one patient had a 30 degrees extensor lag, two patients had a 15 degrees extensor lag, and 10 patients had a lag of less than 10 degrees. All patients thought that their functional status had been improved and were satisfied with the results of the allograft reconstruction.

Achilles Tendon↗
PubMed2003

Induction of bone ingrowth from acetabular defects to a porous surface with OP-1.

Reliable ingrowth of bone into porous-coated cementless total hip components can be expected in primary surgery. In the revision scenario, however, bone deficiency frequently is encountered and the remaining bone may have less ingrowth potential. Allograft bone and bone graft substitutes may be successful in healing bone defects, but have virtually no capacity to induce bone growth from the defect into the porous surface. To evaluate the role osteoinductive bone proteins may play in enhancing bone ingrowth, six canines had bilateral total hip arthroplasties with a cementless press-fit porous-coated acetabular component. A defect 8 mm in diameter and 5 mm in depth was created in the superior weightbearing area of each acetabulum. One defect in each animal was filled with recombinant human osteogenic protein-1. Each contralateral defect was filled with allograft bone, left empty (defect healing control), or no defect was created (intact) to serve as a control for ideal conditions for bone ingrowth. The osteogenic protein-treated defects healed more completely than allograft bone-treated or empty defects and achieved a bone density equivalent to the intact acetabulum. Bone ingrowth also occurred to a significantly higher degree in the osteogenic protein group compared with the allograft or empty defects achieving a degree of ingrowth equivalent to the intact acetabulum controls. The osteogenic bone protein was successful in achieving complete defect healing and inducing extensive ingrowth from the defect into the adjacent porous coating.

Acetabulum↗
PubMed2003

Osteoinductive agents in reconstructive hip surgery: a look forward.

The use of autograft and allograft material to restore bone stock and promote healing and implant stabilization is a crucial part of total hip arthroplasty, especially in the revision situation. Recent research has centered on the use of osteoinductive materials such as osteogenic proteins or bone morphogenetic proteins to promote bone formation. These proteins are members of the transforming growth factor-beta superfamily of proteins that either alone or in combination with other regulatory molecules induce new bone formation. The cloning and genetic expression of recombinant human bone proteins has led to production of quantities sufficient for their clinical development. Preclinical studies have shown that the osteoinductive capacity of autograft and allograft bone can be improved with the addition of osteogenic proteins. Although these proteins are effective alone, their use with cancellous and cortical allograft and autograft consistently improved the amount and rate of new bone formation compared with graft alone resulting in earlier graft incorporation and consolidation. When placed in defects adjacent to porous acetabular components, the use of an osteogenic protein resulted in earlier defect healing and improved component fixation by the enhancement of bone ongrowth and ingrowth. Although no detailed clinical studies have been reported to date, an anecdotal report of their use with and without bone graft indicate results consistent with those obtained in preclinical studies.

Arthroplasty, Replacement, Hip↗
PubMed2003

Avoidance and management of neurovascular injuries in total hip arthroplasty.

Neural injuries that occur after total hip arthroplasty (THA) can be classified as involving either the central nervous system or peripheral nerves. Central nervous system changes after THA may be attributed to increased appreciation of fat embolism syndrome associated with THA. Certain maneuvers such as impacting the acetabulum, femoral reaming, and cement pressurization can force marrow fat into the venous system. When there is an associated right to left shunt, paradoxical embolization can occur, which may account for previously unexplained cases of confusion and mental status changes after surgery. Peripheral nerve injuries are rare and can involve either distant sites or nerves in the immediate vicinity of the hip joint. Upper extremity nerve injuries are usually associated with patient positioning. Sciatic nerve injury is the most common nerve injury following THA. In comparison, femoral nerve injury is much less common and is associated with an anterior approach. Diagnosis is often delayed, and the prognosis is generally better than with sciatic nerve injury. The superior gluteal nerve is at risk during the direct lateral approach. Obturator nerve injury is the least common type of injury and has the least functional consequence. It can present as groin or inguinal pain. Vascular injuries are less common but more immediately life threatening. The mechanisms of vascular injury include occlusion associated with preexisting peripheral vascular disease and vascular injury during removal of cement during screw fixation of acetabular components, cages, or structural grafts. Perioperative assessment should include vascular evaluation of patients with absent pulses, previous vascular bypass surgery, or dysvascular limbs. A CT scan should be considered when cement or components extend medially into the pelvis.

Arthroplasty, Replacement, Hip↗
PubMed2002

Stress fracture of the medial wall of the acetabulum adjacent to a cementless acetabular component.

There are numerous potential causes of hip pain after total hip arthroplasty other than loosening or infection. A case is described that is consistent with stress fracture of the medial wall of the acetabulum after cementless acetabular revision. The clinical presentation, diagnosis, and treatment are described. This is an uncommon cause for localized groin pain after total hip arthroplasty, which should be considered particularly in an elderly woman with a relatively acute onset of symptoms after an increase in activity level.

Acetabulum↗
PubMed2002

The effect of demineralized bone matrix gel on bone ingrowth and fixation of porous implants.

The presence of demineralized bone matrix (DBM) gel did not enhance or accelerate attachment strength or bone ingrowth and resulted in a significant decrease in implant interface attachment strength at 3 weeks. Hydroxyapatite (HA) coating resulted in significant increases in interface shear strength and bone ingrowth compared with non-HA-coated porous implants at all time periods. The HA-coated implants achieved greater attachment strength and bone ingrowth at earlier time periods and maintained greater attachment strength at long-term periods. The results of this study indicate that in the presence of a good bone-implant interference fit, there is no beneficial effect in applying DBM gel to a porous-coated or HA-coated porous implant surface. The small amount that can be applied and the degree of osteoinductivity of DBM seem to preclude it from having a significant biologic effect.

Animals↗
PubMed2002

Rush pin technique for temporary antibiotic-impregnated cement prosthesis for infected total hip arthroplasty.

A technique is described for intraoperative fabrication of an antibiotic-impregnated temporary prosthesis using a rod pin as an endoskeleton. The technique has the advantage of the availability of numerous rod lengths and diameters, which allows the surgeon to produce a custom component with a wide range of lengths and offsets. The technique has been used successfully in many cases over a 5-year period.

Anti-Bacterial Agents↗
PubMed2002

Heterotopic ossification after revision total knee arthroplasty.

A consecutive series of revision total knee arthroplasties done at two centers was evaluated for the presence of heterotopic ossification on radiographs taken before and after revision using the classification system of Harwin et al. Knee Society scores were obtained preoperatively and at annual intervals postoperatively. The patients' demographics and clinical scores were correlated with the incidence and grade of heterotopic ossification. Minimum 2-year followup was obtained in 135 of 151 patients who had revision total knee arthroplasty during this period (89%). The incidence of heterotopic ossification before revision surgery was 23%, which increased to 56% at most recent followup (mean, 30 months; range, 24-48 months). The only risk factor identified for the development of heterotopic ossification was the presence of infection (76%), which was significantly higher than the 47% incidence of heterotopic ossification in patients who did not have an infection. The average postoperative Knee Society score was lower in patients with heterotopic ossification compared with patients without heterotopic ossification (129 points versus 148 points). Patients with heterotopic ossification had significantly lower functional scores particularly on stair climbing but did not have a significantly decreased range of motion. Parameters not associated with subsequent development of heterotopic ossification included gender (males), patient size (body mass index), surgical time, operative approach, or number of prior knee procedures.

Arthroplasty, Replacement, Knee↗
PubMed2002

Magnetic resonance imaging of the knee after ipsilateral femur fracture.

OBJECTIVE: The purpose of this study is to identify and characterize the nature of internal knee derangement associated with ipsilateral femur fractures. DESIGN: A prospective consecutive investigation with the musculoskeletal radiologist being blinded to the clinical examination. SETTING: A certified Level I trauma center. PATIENTS: All adult (skeletally mature) patients with femur fractures resulting from blunt traumatic injury were included. Patients with penetrating, periprosthetic, pathologic, or previous femur fractures were excluded. In addition, all patients with previous knee injuries or previous knee surgery were excluded. Of the fifty-one patients with diaphyseal femur fractures originally enrolled in this investigation, fifteen were excluded by protocol and eleven were unable to obtain timely MRI studies. INTERVENTIONS: All patients were evaluated initially according to Advanced Trauma Life Support protocol. When appropriate, skeletal traction was used as provisional fracture stabilization. In most cases, however, operative fixation was performed immediately. In one case open reduction internal fixation was performed. In the remainder, fracture fixation with an anterograde ( = nineteen) or retrograde ( = seven) intramedullary nail was used. OUTCOME MEASURE: After surgical fixation, twenty-five patients with twenty-seven knees were examined clinically and with an MRI. RESULTS: Five anterior cruciate ligament and two posterior cruciate ligament injuries were discovered (19 percent and 7 percent, respectively). Four complete (Grade 3) medial meniscus tears (15 percent) and seven complete lateral meniscus tears (26 percent) were identified by postoperative MRI studies. The medial collateral ligament was injured in eleven knees (41 percent), with five (19 percent) identified as complete (Grade 3) injuries. The lateral collateral ligament was also injured in eight knees (30 percent); in half (15 percent) the injury was complete. Bone contusions (periarticular infractions of cortical and medullary trabecular bone) were noted in eight (30 percent) tibia (equally divided between medial and lateral compartments) and in 17 (63 percent) femurs (also equally divided between medial and lateral condyles). CONCLUSION: Given the large number of soft tissue injuries about the knee, it would be prudent to emphasize the importance of a thorough intraoperative examination once the femur fracture has been stabilized. Additionally, there should be a low threshold to obtain an MRI if the postoperative clinical examination suggests an associated knee injury. Bone bruises, which can only be identified by MRI studies, are increasingly being acknowledged as a source of persistent symptoms.

Adult↗