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Biomedical subjects

Harry E Rubash

Publications and source records attributed to Harry E Rubash.

48 records · Page 3Linked to original sources
PubMed2003

Optimizing flexion after total knee arthroplasty: advances in prosthetic design.

The clinical results with most modern total knee arthroplasty (TKA) designs are highly satisfactory regarding pain relief and improving walking ability. However, one problem that has not been addressed fully by most current designs is the ability to consistently achieve flexion greater than 120 degrees. Although the human knee is capable of flexion of more than 150 degrees, an analysis of the results of contemporary TKA reveals that on average, patients rarely flex beyond 120 degrees. Key factors influencing range of flexion after TKA include preoperative knee motion, surgical technique, prosthetic design, and rehabilitation. The success of any total knee system may in part be linked to its ability to optimally restore normal kinematic function. Some arthroplasty designs currently are available that incorporate modifications aimed at improving range of flexion, but limited data currently are available on their function and potential advantages. Currently, an in vitro experimental model incorporating robotics is being used to investigate the kinematics of the native knee and various TKA designs at flexion angles beyond 120 degrees. This robotic model in conjunction with clinical studies may provide an understanding of the limitations of contemporary knee designs regarding achieving higher degrees of knee flexion. This may lead to the refinement of existing designs and development of newer prostheses that may enhance the range of flexion that is achievable after TKA.

Arthroplasty, Replacement, Knee↗
PubMed2003

The kinematics of fixed- and mobile-bearing total knee arthroplasty.

The success of any total knee arthroplasty (TKA) is influenced by a complex interaction between component geometry and the surrounding soft tissues. The objective of this study was to investigate posterior femoral translation and tibial rotation in a single design posterior-stabilized TKA offering fixed- and mobile-bearing tibial components. Specifically, we examined whether mobile-bearing TKA restores normal knee translation and rotation better than fixed-bearing TKA design. Eleven human knee specimens retrieved postmortem were tested using a robotic system. The translation and rotation of the intact and reconstructed knees were compared. The data indicate that for all knees, posterior femoral translation occurs along the passive path and under muscle loading conditions. Furthermore, increasing flexion angle corresponded with increased internal tibial rotation. Femoral translation and tibial rotation for fixed- and mobile-bearing posterior-stabilized TKAs were similar despite component design variations. However, both arthroplasties only partially restored intact knee translation and rotation. The data presented here may serve as an aid in the development of a rationale for additional improvement in surgical techniques and prosthesis design, so that normal knee function may be restored.

Aged↗
PubMed2003

The efficacy of BMP-2 to induce bone ingrowth in a total hip replacement model.

The purpose of this canine total hip arthroplasty (THA) study was fourfold: (1) to quantify the efficacy of rhBMP-2 in a carrier (alphaBSM) versus alphaBSM alone, and versus untreated controls to induce bone formation across a defect between a porous acetabular component and host bone; (2) to quantify whether rhBMP-2/alphaBSM improves bone growth into the porous surface beneath that defect; (3) to quantify the efficacy of rhBMP-2/alphaBSM in inducing bone ingrowth into the porous layer at points of intimate bone-implant contact; and (4) to determine whether rhBMP-2/alphaBSM placed in the lateral uncovered aspect of the porous acetabular component promotes de novo bone formation. Fifteen dogs were sacrificed 12 weeks after uncemented THA. Five dogs received rhBMP-2/alphaBSM, five dogs received alphaBSM, and five dogs were controls. In contrast to the controls in which no bone filled the defect, the rhBMP-2/alphaBSM induced defect filling and full bone formation in the underlying porous coating. The alphaBSM produced an intermediary response. However, no increase in new bone formation occurred at sites of intimate bone porous surface contact. Recombinant bone morphogenetic protein-2/alphaBSM promoted defect filling and bone ingrowth into the porous coating beneath the defect region, both of potential value in future total joint replacement surgery.

Animals↗
PubMed2003

Osteolysis of the pelvis: evaluation and treatment.

Osteolysis of the pelvis is a common and well-recognized complication associated with total hip arthroplasty. The diagnosis and treatment of osteolysis of the pelvis is a challenging and controversial problem. Osteolysis of the pelvis often is asymptomatic and does not present with symptoms until considerable bone loss and loosening of the acetabular socket occur. Radiographs are the most common way to detect and monitor osteolysis around an implant. However, lesions viewed radiographically usually are underestimations of the lesions found intraoperatively. Moreover, some advocate computed tomography scanning to evaluate these lesions. The indications for treatment of osteolysis with cemented acetabular components are defined more clearly than with a cementless component. If the cemented or cementless acetabular component is loose, then revision is necessary. However, it is less clear when to intervene surgically with a well-fixed cup with osteolysis. Many early reports advocated the removal of a well-fixed socket during revision surgery for osteolysis and polyethylene wear. However, the removal of a well-fixed socket has the potential for significant damage and loss of the surrounding bone resulting in loss of integrity of a column or pelvic discontinuity, which may compromise placing another acetabular component. Recently, a new treatment strategy of retaining a well-fixed socket, exchanging the liner, and grafting lesions has proven successful. Without the removal of the acetabular shell, different techniques are needed to graft the osteolytic lesions. Osteolysis is a difficult problem; however, with radiographic surveillance to monitor patients for lesions, proper indications, and good surgical techniques, the treatment of osteolysis of the pelvis can result in a well-functioning total hip arthroplasty.

Algorithms↗
PubMed2003

Vascularized compared with nonvascularized fibular grafting for the treatment of osteonecrosis of the femoral head.

BACKGROUND: We are not aware of any clinical studies in the literature comparing the results of vascularized and nonvascularized fibular grafting for the treatment of osteonecrosis of the femoral head. The purpose of this study was to compare the clinical results of free vascularized fibular grafting with those of nonvascularized fibular grafting. METHODS: Two hundred patients (220 hips) with osteonecrosis of the femoral head were treated with free vascularized fibular grafting at the University of Pittsburgh Medical Center, and ninety-nine patients (123 hips) were treated with nonvascularized fibular grafting at the Kyungpook National University Hospital in Korea. From these populations, two groups of fifty hips each, followed for a minimum of three years (average, five years), were matched by the stage, size, and etiology of the lesion and by the mean preoperative Harris hip score. A retrospective case-control study of these groups was then performed to compare the postoperative Harris hip scores as well as the prevalences of radiographic progression and collapse of the femoral head following free vascularized fibular grafting with those measures following nonvascularized fibular grafting. RESULTS: The mean Harris hip score improved for 70% of the hips treated with free vascularized fibular grafting: seventeen hips (34%) were rated excellent, fourteen (28%) were rated good, nine (18%) were rated fair, and ten (20%) were rated poor. The mean Harris hip score improved for 36% of the hips treated with nonvascularized fibular grafting: five hips (10%) were rated excellent; nine (18%), good; sixteen (32%), fair; and twenty (40%), poor. The rate of survival at seven years for the Stage-I and II hips (precollapse) was 86% after treatment with free vascularized fibular grafting compared with 30% after nonvascularized fibular grafting. CONCLUSIONS: The results of this study strongly suggest that vascularized fibular grafting is associated with better clinical and radiographic results.

Adolescent↗
PubMed2002

Femoral head sizes larger than 32 mm against highly cross-linked polyethylene.

The advent of highly cross-linked ultrahigh molecular weight polyethylene, which shows extremely low wear independent of head size in vitro, allows for the reevaluation of the use of femoral heads larger than 32 mm. The current authors discuss information that supports this hypothesis. The supporting information includes in vitro wear testing and in vitro anatomic studies, and prior clinical studies in which large femoral heads were used.

Hip Dislocation↗
PubMed2002

Reconstruction of a ruptured patellar tendon with achilles tendon allograft following total knee arthroplasty.

BACKGROUND: Rupture of the patellar tendon after total knee arthroplasty is a rare and debilitating complication. Proper surgical management of this condition remains controversial. The purpose of this study was to review the results of reconstruction of a ruptured patellar tendon with an Achilles tendon allograft following total knee arthroplasty. METHODS: We reviewed our experience with the use of a fresh-frozen Achilles tendon allograft with an attached calcaneal bone graft to restore extensor function in nine patients with patellar tendon rupture following total knee arthroplasty (five primary and four revision). All patients were examined clinically and radiographically at an average of twenty-eight months. RESULTS: The average knee and functional scores improved from 26 and 14 points, respectively, before the surgery to 81 and 53 points after the surgery. The average extensor lag decreased from 44 degrees preoperatively to 3 degrees postoperatively, and the average range of motion of the knee increased from 88 degrees to 107 degrees. Two grafts failed in the early postoperative period. Both were repaired successfully. Radiographs showed an average proximal patellar migration of 17.8 mm, which did not appear to affect extensor function. CONCLUSIONS: This short-term follow-up study showed that once an Achilles allograft has healed, it can serve as a reliable reconstruction of a ruptured patellar tendon following total knee arthroplasty. This technique may be particularly suited for patients in whom the extensor mechanism was compromised by multiple prior operations. Continued follow-up is necessary to determine the long-term durability of these results.

Achilles Tendon↗
PubMedDate not supplied

The optimal fixation of the cementless acetabular component in primary total hip arthroplasty.

The optimal fixation of the acetabular component in primary total hip arthroplasty remains controversial. Long-term follow-up studies show that significant loosening rates occur with cemented acetabular components and that these problems persist despite attempts to improve cementing technique. Cementless acetabular components that rely on biologic fixation can have lower rates of radiographic loosening at 10 years compared with cemented acetabular components. Although revision rates for both modes of fixation are largely equivalent at 10 years, the superior radiographic performance of cementless acetabular components at 10 years suggests that biologic fixation through bone ingrowth may provide more durable long-term implant survival compared with cemented fixation. Osteolysis is the major obstacle to long-term cementless acetabular component survival. Potential future options that may inhibit osteolysis include decreasing bone resorption that results from debris-stimulated foreign body response through the use of medications; decreasing the number of particles generated by using alternative bearing surfaces; and improving bone ingrowth, particularly through the use of growth factors and improved implant materials and designs.

Acetabulum↗
PubMedDate not supplied

Dislocation after total hip arthroplasty.

Dislocation is one of the most common complications after total hip arthroplasty (THA). Risk factors include neuromuscular and cognitive disorders, patient non-compliance, and previous hip surgery. Surgical considerations that must be addressed include approach, soft-tissue tension, component positioning, impingement, head size, acetabular liner profile, and surgeon experience. Recent improvements in posterior soft-tissue repair after primary THA have shown a reduced incidence of dislocation. When dislocation occurs, a thorough history, physical examination, and radiographic assessment help in choosing the proper intervention. Closed reduction usually is possible, and nonsurgical management frequently succeeds in preventing recurrence. When these measures fail, first-line revision options should target the underlying etiology. This most often involves tensioning or augmentation of soft tissues, as in capsulorrhaphy or trochanteric advancement; correction of malpositioned components; or improving the head-to-neck ratio. If instability persists, or if a primary THA repeatedly dislocates without a clear cause, a constrained cup or bipolar femoral prosthesis may be as effective as a salvage procedure.

Arthroplasty, Replacement, Hip↗