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Biomedical subjects

Allan E Gross

Publications and source records attributed to Allan E Gross.

At least 19 recordsLinked to original sources
PubMed2006

Notching of the anterior femoral cortex during total knee arthroplasty characteristics that increase local stresses.

Notching of the anterior femoral cortex during primary total knee arthroplasty can occur when making an anterior femoral bone cut. To examine the increased stress caused by a notch, we used a validated 3-dimensional finite element model of the femur under gait loads. Three factors that affected the stress concentration were identified: First, larger notches associated with increased stress concentrations. Second, sharper notches led to increased local stresses. Third, the proximity of the notch to the prostheses affected the stress concentration. In summary, anterior femoral notches greater than 3 mm with sharp corners located directly at the proximal end of the prosthesis produced the highest stress concentrations and may lead to a significant risk of periprosthetic fracture.

Arthroplasty, Replacement, Knee↗
PubMed2006

Restoration of acetabular bone loss 2005.

The surgical strategy for revision of the acetabular component is determined by available host bone stock. Contained (cavitary) bone loss is the most common pattern of bone loss and can be addressed by morsellized bone graft. If contact can be made with at least 50% host bone, conventional uncemented cups can be used. If, however, contact with 50% host bone cannot be achieved, a protective cage and a cemented cup is an acceptable option but with a significant complication rate. The use of trabecular metal, which provides a more favorable environment for bone graft remodeling and host bone ingrowth, has allowed us to address larger contained defects without resorting to a cage. For massive contained defects, a combination of a trabecular metal cup protected by a cage has been used.

Acetabulum↗
PubMed2006

What would you do? Challenges in hip surgery.

The panel reviewed cases involving both revision and primary total hip arthroplasties. The panelists are Hugh Cameron and Allan Gross from Toronto, Charles Engh from Arlington, Aaron Rosenberg from Chicago, and Bernard Stulberg from Cleveland. The cases discussed brought up some controversial issues.

Adult↗
PubMed2006

Surgical options for articular defects of the knee.

Cartilage and osteochondral defects of the knee can in most cases be treated with total knee replacement in the elderly population. However, these lesions pose a difficult treatment problem in the younger patient. A number of surgical options are available today to address this increasingly common condition and each has its own indications and limitations. This article reviews debridement and microfracture, fixation, metallic spacing devices, autologous chondrocyte implantation, osteochondral autograft transplantation, fresh cadaveric allografts and osteotomies. In addition, possible future developments are discussed.

Animals↗
PubMed2006

Total knee replacement in previous recipients of fresh osteochondral allograft transplants.

BACKGROUND: Fresh osteochondral allograft transplantation is a treatment option for young patients with osteochondral lesions of the knee. The present study evaluated the surgical complexity of, and the prevalence of complications related to, total knee arthroplasty in patients who had had a previous osteochondral graft transplantation. METHODS: A retrospective analysis was performed on thirty-three consecutive patients (thirty-five knees) who underwent total knee arthroplasty from 1974 to 2000 after having had a previous transplantation of a fresh osteochondral allograft into the same knee. The mean duration of follow-up was ninety-two months. Perioperative data were analyzed with regard to etiology, preoperative impairment, intraoperative technical complications, early and late postoperative complications, and postoperative functional and subjective outcomes. The Knee Society clinical rating system was used for clinical evaluation beginning in 1990. RESULTS: Four knees required additional techniques for exposure. Three knees required stemmed components, one knee required a tibial augment, and two knees required morselized grafts. The mean Knee Society objective score (available for eighteen knees) improved from 34.7 preoperatively to 87.9 at the time of the latest follow-up, and the mean Knee Society function score improved from 45 to 82. The mean range of motion of all knees improved from 85 degrees to 105 degrees . Six of the thirty-five knees underwent revision total knee arthroplasty because of aseptic loosening, with two knees being revised within two years after the index total knee arthroplasty. CONCLUSIONS: Total knee arthroplasty after previous fresh osteochondral allograft transplantation provides improvements in knee function and range of motion, with manageable technical difficulties. Compared with routine total knee arthroplasty, an increased rate of early revision can be expected.

Adult↗
PubMed2006

Predictors of functional outcome two years following revision hip arthroplasty.

BACKGROUND: Little is known about factors that might predict functional outcome following revision hip arthroplasty. The purpose of this study was to identify predictors of pain and physical function at two years following revision total hip arthroplasty and to evaluate whether the time that the patient waited for the surgery and whether the patient had complications were significant predictors of outcome. METHODS: One hundred and twenty-six patients (126 hips) were entered prospectively into the study when their name was placed on the waiting list for surgery. Baseline measures included demographic factors, comorbidities, and the responses to the Short Form-36 (SF-36) and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaires. Follow-up was carried out at six-month intervals while the patient was waiting for the surgery; within one week prior to the surgery; and at six, twelve, and twenty-four months after the surgery. Patient age and gender, the preoperative WOMAC pain and function scores, the physical and mental component scores of the SF-36, comorbidities, the number of revisions, bilateral joint replacement, and the severity of the revision were evaluated as possible predictors of ultimate pain and function as measured with the WOMAC instrument. RESULTS: The mean age of the patients was 68.6 years. Improvement in WOMAC pain and function scores plateaued at six months. The mean pain score (and standard deviation) improved from 9.4 +/- 4.1 points preoperatively to 3.9 +/- 3.9 points at six months postoperatively, and the mean function score improved from 35.4 +/- 14.1 to 19.1 +/- 13.2 points. Preoperative pain (p = 0.002) and comorbidity (p = 0.02) were significant predictors of pain at two years. There was a trend toward preoperative function predicting function at twenty-four months (p = 0.07). There was no significant deterioration in the WOMAC pain or function score while the patients waited for surgery. Twenty-eight patients had complications. When the time that the patient waited for the surgery and complications were added to the models, only complications were found to be predictive of outcome (p = 0.04 for pain and p = 0.05 for function). Four patients required repeat revision during the follow-up period. CONCLUSIONS: Patients with better preoperative pain scores and fewer comorbidities have better outcomes following revision total hip arthroplasty. Although the time that the patient waited for the revision was not predictive of the ultimate WOMAC pain and function scores, we believe that performing revision arthroplasty before the patient has substantial functional compromise potentially improves the outcome.

Adult↗
PubMed2005

Rebuilding the skeleton: the intraoperative use of trabecular metal in revision total hip arthroplasty.

Cages provide a scaffold for restoration of bone stock in revision arthroplasty of the acetabulum. A major problem with cages is failure at 5 to 10 years due to loss of fixation. The present generation of cages are not made of a material that provides biologic fixation. Trabecular metal cups provide excellent biologic fixation and a favorable environment for bone graft remodeling. For large bone defects where there is not optimal contact with host bone at the correct anatomic level, a trabecular cup is placed against bone graft, fixed with screws, and protected by a cage into which the polyethylene cup is cemented. The initial stability is via the cage, but when graft remodeling takes place, the stress will be taken by the trabecular metal relieving the stress on the cage.

Acetabulum↗
PubMed2005

The role of polymethylmethacrylate bone cement in revision arthroplasty of the hip.

When restoration of bone stock is necessary in revision arthroplasty of the hip using morselized or structural allograft bone, cement is used. Cement strengthens allograft bone, impairs its resorption, allows anatomic positioning of components (ie, cementing the cup in a protective ring), and allows delivery of antibiotics. Allograft bone provides a perfect lattice for cementation and also allows a cementless reconstruction as far as host bone is concerned.

Arthroplasty, Replacement, Hip↗
PubMed2005

Long-term followup of the use of fresh osteochondral allografts for posttraumatic knee defects.

UNLABELLED: Posttraumatic osteochondral defects of the distal femur or proximal tibia pose a reconstructive challenge for the young active patient. Fresh osteochondral allografts have been used to reconstruct these defects and this report deals with the long-term clinical and radiographic follow-up in this patient population. This is a prospective nonrandomized study. Sixty patients with an average followup of 10 years received femoral condylar grafts. Twelve grafts failed, requiring removing of the graft in three patients and conversion to total knee replacement in nine patients. Kaplan-Meier survivorship showed 95% graft survival at 5 years and 85% at 10 years. Sixty-five patients received fresh osteochondral allografts to reconstruct the tibial plateau with an average followup of 11.8 years. In this group of patients, conversion to total knee arthroplasty was done in 21 patients at a mean interval of 9.7 years. Survival analysis revealed 95% survival at 5 years, 80% at 10 years, and 65% at 15 years. Through our long-term prospective study, we confirm the value of fresh osteochondral allografts to reconstruct articular defects of the knee in the young active patient. LEVEL OF EVIDENCE: Therapeutic study, Level II-1 (prospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗
PubMed2004

Management of periprosthetic femoral fractures after total knee arthroplasty using a distal femoral allograft.

This study is a review and discussion of 12 consecutive patients who were revised with a distal femoral allograft for periprosthetic supracondylar fractures of the femur associated with poor bone quality by the same surgeon between 1990 and 2001. Two were lost to follow-up. The average age was 65 years, and the mean follow up was 6 years. Charts were reviewed to identify complications and graft survivorship. Functional assessment consisted of the modified Hospital for Special Surgery (HSS) knee score and the MOS 36-ITEM Short Form Health Survey. Radiographs were evaluated by 3 independent observers to determine graft union, resorption, and component loosening. The average postoperative HSS score and SF-36 were 75 and 88, respectively. Mean flexion was 100 degrees. Nine patients achieved union and were able to fully bear weight. Three patients required more surgery as a result of postoperative complications. Radiographs showed no migration, no loosening, and good interface union in 9 of the 10 patients available for follow-up. We concluded that this is a viable salvage procedure for this type of injury.

Aged↗
PubMed2004

Periprosthetic fractures of the knee: puzzle pieces.

Periprosthetic fractures associated with total knee arthroplasty occur intraoperatively or postoperatively. The parameters that determine the treatment are stability of the fracture and the implant, site of the fracture, and bone quality. Intraoperative fractures, if undisplaced and stable, can be managed by protected weight bearing and motion. If displaced, they are treated by internal fixation and a stem. Postoperative fractures, if undisplaced and stable, can be managed by restricted weight bearing and motion. If the fracture is displaced, in association with a stable implant, management is by internal fixation. If the fracture is associated with an unstable implant, then a revision with a stemmed component must be performed. If there is associated loss of bone stock, then augments or structural grafts may be necessary.

Arthroplasty, Replacement, Knee↗
PubMed2004

The current role of structural grafts and cages in revision arthroplasty of the hip.

Treating large segmental acetabular defects that comprise more than 50% of the acetabulum is one of the most difficult challenges in revision arthroplasty of the hip. One of the surgical options is a structural acetabular allograft. Unless these allografts are protected by a cage that extends from ilium to ischium, there is an unacceptable incidence of graft failure. The cage allows reconstruction at the correct anatomic level. It provides a scaffold for bone grafting (structural and morsellized). The use of cement to stabilize the cup allows the surgeon to adjust the cup position independent of the cage. The current generation of cages does not provide biologic fixation and with time may loosen or fracture. Recent experience with a combination of a trabecular metal shell protected by a cage may offer a more favorable environment for bone grafting with permanent biologic fixation of the cup cage construct.

Acetabulum↗
PubMed2003

Large segment allograft survival is improved with intramedullary cement.

BACKGROUND AND OBJECTIVES: The most common cause of failure in large segment bone allografts used for oncologic reconstruction is allograft fracture. Reinforcement with pressurized intramedullary cement may improve the mechanical properties of allografts. METHODS: We reviewed the prospectively collected records of 45 patients who underwent en bloc resection of an extremity bone tumor and reconstruction using an allograft with intramedullary cement. RESULTS: Seven allografts were used for arthrodesis, 20 were intercalary, and 18 were osteochondral. Twenty eight of 45 patients were alive at a mean 5.8 years (SD 1.9; range 3-11.2) with 24 allografts in situ. In these 45 patients, there were four allograft fractures and four infections. Six of these complications resulted in allograft removal. The estimated 5-year allograft survival rate was 86% (95% confidence interval 74-98%). Seven patients required secondary autogenous bone grafting for non-unions. Function measured by the Toronto Extremity Salvage Score and the 1987 and 1993 Musculoskeletal Tumor Society Rating Scales demonstrated a consistent pattern with worse function in patients with osteochondral allografts and best function with intercalary allografts. CONCLUSIONS: These results suggest the addition of intramedullary cement to large segment bone allografts improves their survival by decreasing the fracture risk, particularly for allografts used for arthrodesis and intercalary reconstructions.

Adolescent↗
PubMed2003

Onlay cortical strut grafting in revision arthroplasty of the hip.

Cortical strut allografts are used to restore uncontained noncircumferential femoral defects, to bypass stress risers, to stabilize proximal femoral allograft host junctions, and to fix periprosthetic fractures. These struts can be made from hemicylinders of diaphyseal bone or from fibulae. They are fixed to host bone by circumferential wires. If autograft bone is available, it is placed between the strut and host, particularly at the ends of the strut. A radiographic study of 52 cortical strut allografts with an average follow-up of 4.8 years revealed 2 nonunions and 2 progressive resorptions. All other struts united with minimal resorption.

Arthroplasty, Replacement, Hip↗
PubMed2003

Cartilage resurfacing: filling defects.

Chondral defects with no significant bone involvement can be managed arthroscopically using surface treatments such as debridement and drilling, abrasion arthroplasty, and microfracture. Chondral defects can also be managed arthroscopically using osteochondral autografts (mosaicplasty) or by cartilage cell transplant or periosteal grafts, both of which are performed in open surgery. The arthroscopic surface treatments are best reserved for small defects, but cell transplantation and mosaicplasty have been used for defects up to 3 cm in diameter. Periosteal grafting can be used for large defects affecting an entire condyle, but clinical experience with this procedure is limited and it is still considered investigational. Larger osteochondral defects (uncontained defects greater than 3 cm in diameter and greater than 1 cm in depth) are managed using osteochondral allografts. Realignment osteotomy should be considered in conjunction with any of these techniques in the presence of a coexisting deformity.

Bone Transplantation↗
PubMed2003

Classifying failed hip arthroplasty: generalizability of reliability and validity.

Interrater reliability and validity of a radiographic severity classification was evaluated in 81 patients having revision hip arthroplasty. Severity was rated separately on the femoral and acetabular sides using a five-level scale ranging from no significant loss of bone stock to uncontained loss of bone stock and discontinuity. Three academic orthopaedic surgeons rated preoperative anteroposterior radiographs taken within 6 weeks of surgery. Interrater reliability was 0.54 (weighted kappa) with 57% agreement on the acetabular side and 0.56 with 52% agreement on the femoral side. Rater to intraoperative findings agreed 45% of the time and weighted kappa was 0.41 on the acetabular side and agreed 38% of the time with weighted kappa of 0.39 on the femoral side. When radiographic and intraoperative ratings disagreed, 30% of the time no bony defect was found on the acetabular side. Fifty-eight percent of femoral radiographic ratings were upgraded intraoperatively. These results differ from previously reported results of high reliability from one institution with trained raters. A reliable and valid severity classification that is generalizable to multiple raters from different institutions is required to stratify patients for intervention studies, and to aid preoperative planning. Training in the classification system may improve generalizability.

Adult↗