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Biomedical subjects

R H Emerson

Publications and source records attributed to R H Emerson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Revision total hip arthroplasty in the deficient femur with a proximal load-bearing prosthesis.

The proximal femur is frequently structurally deficient in revision hip arthroplasty, and makes obtaining prosthesis stability more difficult. Between 1984 and 1990, 174 patients were treated with revision total hip arthroplasty, performed by a standardized surgical technique, using cortical onlay strut allografts to restore the structural integrity of the femur, and a calcar replacement proximally porous-coated femoral prosthesis, composed of titanium alloy. The grafts united 98% of the time, and showed evidence of revascularization, and in some cases, complete incorporation. To date, six have been revised for femoral failure. Successful reconstruction of the deficient femur after failed total hip arthroplasty is dependent on several factors: the revision prosthesis must be stable, the deficient femoral bone stock must be augmented, and load must be transferred to the proximal femur so that the future proximal femoral resorption is minimized. The host femur and allograft will respond physiologically to load bearing, and the graft increases bone quantity and quality. The prosthesis must be supported primarily on host bone; the graft may enhance prosthetic support, but can never be used for primary prosthetic support when using uncemented revision prostheses.

Aged↗
PubMed1994

Extensor mechanism reconstruction with an allograft after total knee arthroplasty.

The authors report on a series of 15 knees in which an extensor mechanism allograft was used to treat a rupture of the patellar tendon associated with a total knee arthroplasty. Nine of the knees have greater than two-year follow-up evaluation (average, 4.1 years; range, 2.3-7 years). Postoperatively, the average flexion was 106 degrees. All but three patients achieved full passive extension. Six of the nine knees had no extensor lag. The average post-operative clinical score for the follow-up group was 78 points. Graft complications include one early graft rupture, one early quadriceps junction failure, and one patellar component loosening. One graft fractured after revision of a metal-backed patella.

Adult↗
PubMed1993

Dealing with the deficient acetabulum in revision hip arthroplasty: the importance of implant migration and use of the jumbo cup.

The complexity of acetabular anatomy makes operative planning for revision difficult. Plain radiographs do not provide as much detail about structural damage to the acetabulum as the surgeon would like in order to decide on the need for special components and bone grafts. The authors have found that analysis of acetabular implant migration has been a reliable surgical planning technique to indirectly assess residual acetabular bone stock. Superior shift on the anterioposterior radiograph implies posterior superior acetabular roof loss, seriously compromising the major weight-bearing area of the acetabulum. Although this may require a structural allograft, the authors have found that bone stock at the level of the true acetabulum is much better than in the false acetabulum created by the migration. Therefore, rather than a small cup placed high on the ilium, a large jumbo cup can frequently restore better hip biomechanics and take advantage of all of the remaining host bone for component stability and support, without the need for structural grafts. Medial shift implies medial superior migration leaving the physiologically strong rim of the acetabulum intact and therefore, less structurally damaging than posterior superior migration. Because the acetabular rim is anatomically designed for load bearing, a rim fit cup restores physiological weight transfer across the pelvis. Bone graft behind such a cup is protected from full weight-bearing forces and has proven to be very reliable.

Acetabulum↗
PubMed1993

Cortical strut allografts for femoral reconstruction in revision hip arthroplasty.

One hundred thirty-six cortical strut allografts fixed to the femur in revision hip surgery were studied using quantitative and qualitative radiographic analysis. In addition, 58 patients were clinically evaluated. The grafts showed a consistent behavior characterized by some resorption, bony bridging between host and graft, and a high incidence of union. The grafts showed evidence of revascularization and in some cases complete incorporation. The average Harris scores in the clinical group increased from 48 to 79 and was not influenced by the quality of bone before revision. Strut allografting of the femur in revision surgery is a reliable method of augmenting bone stock.

Adult↗
PubMed1993

Proximal femoral allografts in revision total hip arthroplasty.

The senior authors have performed 141 proximal femoral whole-bone allografts in failed total hip reconstruction. The results of the first 50 have been previously reported. This study reviews 70 additional cases performed since 1987 and reflects improved technique and several different junctional constructs. Modest improvements in the rate of union (64% v 80%) and of dislocation (28% v 16%) have been achieved. The infection rate (6% v 4%) and demographics of the groups have remained constant. The frequency of complications (67% v 53%) has decreased, but unfortunately remains high. A step-out allograft junction with a long lateral sleeve has been the most reliable construct.

Adult↗
PubMed1993

Restoration of femoral bone stock in revision total hip arthroplasty.

The presence of femoral deficiencies in revision total hip arthroplasty may contribute to loosening, subsidence, and fracture. Between 1984 and 1990, 174 patients were treated with revision total hip arthroplasty, preformed by a standardized operative technique using cortical onlay strut allografts to restore the structural integrity of the femur and a calcar deficient proximally porous coated femoral prosthesis, composed of titanium alloy. The grafts united 98% of the time and showed evidence of revascularization and, in some cases, complete incorporation. Cortical onlay strut grafting in conjunction with a proximal load- bearing prosthesis is a viable method of reconstructing the structurally deficient femur in revision total hip arthroplasty.

Aged↗
PubMed1992

Disease and specific considerations in total hip replacements.

Total hip replacement arthroplasty has evolved where multiple options may be provided to the patient depending on disease, age, activity level, bone quality, and bone geometry. For elderly patients, the hybrid hip (uncemented acetabular and cemented femoral components) is widely used. In the young active population, uncemented porous bone ingrowth designs predominate. Special considerations involving the total hip patient include management of blood loss anemia, prevention of infection, and prevention of heterotopic ossification. Autologous blood donation as well as collection and infusion of shed blood in the postoperative patient greatly minimize the need for homologous transfusions. Optimizing the surgical environment, meticulous and efficient surgical technique, and antibiotic prophylaxis continue to be the cornerstones of infection prevention. Nonsteroidal anti-inflammatory medication and radiation are effective means of preventing heterotopic ossification.

Adolescent↗
PubMed1992

Soft-tissue balance and alignment in medial unicompartmental knee arthroplasty.

We reviewed two similar groups of patients with medial osteoarthritis of the knee treated by unicompartmental arthroplasty. The group receiving an Oxford meniscal-bearing implant, with no medial release, showed significantly better mechanical alignment than that receiving a fixed-bearing implant. Under-correction, with its ominous mechanical implications, was much more common with the fixed-bearing design. Over-correction was rare and was seen in both designs about equally. Degenerative stenosis of the intercondylar notch was common and appeared to put the anterior cruciate ligament at risk of rupture, especially after correction of the varus deformity. We consider that postoperative leg alignment and soft-tissue balance after unicompartmental knee replacement are determined more by the implant design and the surgical technique than by any variation in soft-tissue contracture. Release of the medial collateral ligament is not necessary for realignment, but a generous notchplasty is often needed to allow normal anterior cruciate ligament function.

Follow-Up Studies↗
PubMed1992

Cortical strut allografts in the reconstruction of the femur in revision total hip arthroplasty. A basic science and clinical study.

Repeated total hip arthroplasties cause a loss of bone stock that will produce diminished component support, and can compromise implant function. There is, therefore, a compelling argument to return bone stock to the femur at the time of revision arthroplasty. Cortical strut allografts serve this purpose. They unite consistently and reliably, by 8.4 months on average. The overall rate of strut union is 96.6%. The sequence of healing events starts with round-off, followed by partial bridging and complete bridging. The repair process includes remodeling of the host femur, as well as the graft. Although there is variable resorption of some grafts, usually where not opposed to the host bone, there is also extension of others from host callus build-up such that, on average, there is no significant measurable loss of graft length or width. Most of the allograft struts, 78%, maintained a radiodense appearance. Clinical results of femoral revision with strut allografting have shown satisfactory end results compared with historic controls, with an average Harris score of 79.6 and a 2.7% subsidence rate. Of particular note is that the subsidence rate and clinical scores did not vary with the state of the preoperative femur, as has been shown repeatedly in the past. The canine model shows that the strut allografts are biologically active. Through mobilization of mesenchymal tissue, they are transformed into vascularized calluslike structures while maintaining good strength, and then further remodel to lamellar bone.

Animals↗
PubMed1991

Prophylactic and early therapeutic use of the Greenfield filter in hip and knee joint arthroplasty.

The orthopaedic literature does not provide clear guidelines for the protection of the extremely high-risk thromboembolic patient undergoing hip and knee total joint or related reconstructive surgery. Nor is there agreement of how to protect the immediate postoperative patient with thromboembolic complications. The authors, believing that routine anticoagulation measures are ill-advised in these two circumstances, elected instead to place a Greenfield vena cava filter for prevention of life-threatening thromboembolism. Using prospective selection criteria, 47 patients could be followed over a 24-76-month period. There were no clinical embolic episodes in either group and no late complications of the filter placement. The few complications in this series were related to insertion, only one of which lead to minor long-term disability. The caval patency rate was 96%. The authors have concluded that such prophylactic use of the Greenfield vena cava filter is justified since it contributes to safer and more reliable total hip and total knee surgery with only minor morbidity.

Aged↗
PubMed1991

Comparison of the early healing course of porous titanium with hydroxyapatite-coated porous titanium hip implants: clinical considerations for the use of hydroxyapatite coating in total hip replacement.

The role of hydroxyapatite (HA) coating in the fixation of human total joint prostheses remains to be established. Results of animal studies have been favorable, showing very rapid bone formation with a corresponding increase in bone-implant bond strength. In addition, the quantity of bone may be increased. This study compared identical porous titanium primary total hip implants with and without HA in similar patient populations. All of these patients were healthy and reliable, and had optimal bone geometry and bone quality for cementless fixation. The purpose of the study was to contrast the sequence of events, in the first year after surgery, between the two implant groups to identify the contribution of HA to early patient function and early radiographic appearance of the prosthesis. No significant clinical difference could be demonstrated between the two groups at 1 year from surgery. However, the HA group progressed more rapidly when comparing clinical scores at 6 months (P = .0058), and appeared to demonstrate more rapid bone remodeling at 6 months on the femoral side, although this observation did not quite make statistical significance (P = .0618). There was no difference between the acetabular components during the course of this study.

Female↗
PubMed1991

Failure mechanisms of unicompartmental knee replacement: the impact of changes in operative technique and component design.

Reliable unicompartmental knee replacement requires knowledge of the common failure mechanisms of this type of arthroplasty. The problem in the past has been loosening of components because of design flaws and technical failure. Whereas recent reports are very encouraging in terms of clinical results and enhanced durability of unicompartmental replacements, the current study confirms the observation that nonparallel orientation of femoral and tibial components is common and may produce excessive polyethylene wear and clinical failure. Newer unicompartmental designs with meniscal bearings may be the answer to this problem.

Evaluation Studies as Topic↗
PubMed1990

Massive allografts in salvage revisions of failed total knee arthroplasties.

Ten patients with failed total knee arthroplasties and severe bone loss were treated with massive whole distal femur and proximal tibial allografts in combination with prosthetic implants. Fourteen allografts were inserted either as invaginated or segmental grafts and were rigidly fixed to the host bone. Clinically and roentgenographically, 12 of 14 grafts (86%) seemed to have united to the host bone. The average range of motion was 92 degrees. Five patients developed complications; two of these involved the allograft (nonunion and fracture) and two were caused by inadequate healing at the ligament-allograft junction. One patient had a late infection. With careful planning and improved surgical techniques, these complications can be avoided. The massive allograft-prosthesis composite techniques is a viable reconstructive alternative worthy of further clinical trials.

Aged↗
PubMed1990

Reconstruction of patellar tendon rupture after total knee arthroplasty with an extensor mechanism allograft.

Although patellar tendon rupture after total knee arthroplasty (TKA) is a rare complication, the consistently poor outcome of conventional tendon repair has convinced some to abandon such reconstruction in favor of a prospective protocol using an allograft distal extensor mechanism. The graft consists of a quadriceps tendon, a patella with a cemented prosthesis, a patellar tendon, and a tibial tubercle. Since December 1985, 13 knees in 12 patients were reconstructed using this method. Ten knees were followed for six to 51 months; five of these knees were followed for more than 24 months. Knee extension power and improved function were ultimately attained in all cases, although minimal extensor lags were present in three cases. Preoperative motion returned in all but one knee. Healing of the allograft to the host tissue was attained primarily at all of the tibial junctions. Two graft complications occurred, both in the first three months after surgery: one quadriceps junction treated by resuture failed at the one-month mark, and the other graft had to be revised for extensor weakness from rupture of the graft at the patella-patellar tendon junction, which was attributed to surgical damage to the tendon. After completion of healing to the host and rehabilitation of the knee joint, no grafts in the series failed during the course of normal daily activities. One patient fractured the allograft patella in a severe fall. The long-term durability of this construct needs to be studied further.

Aged↗
PubMed1989

Noncemented acetabular revision arthroplasty using allograft bone.

The authors retrospectively reviewed a series of 106 acetabular revisions for failed cemented total hip arthroplasties followed from 12 to 56 months. All of the sockets had extensive bone deficiency requiring bone graft surgery. The deficiencies were classified as cavitary, combined cavitary and segmental, and pelvic discontinuity. The purpose was to evaluate clinical experience with three different acetabular components. In chronological order, the three components tested were bipolar type, truncated-cone screw-in type, and porous-coated titanium press-fit type with fins. These were combined with four different bone augmentation constructs, using nonstructural morselized fresh-frozen allograft or segmental freeze-dried allograft. Follow-up evaluation of both the bipolar and screw-in designs showed frequent migration with bone graft resorption, compromising the clinical scores and leading to some revisions. The press-fit design had little migration, reliable graft healing, and better clinical scores. No revisions have been done. The nonstructural morselized bone allograft fared better under stable cups. The large segmental grafts did much better when buttress plating was combined with interfragmentary screw fixation compared to screws alone.

Acetabulum↗
PubMed1987

Extensile exposure of the hip for revision arthroplasty.

The authors describe a lateral approach to the hip without trochanteric osteotomy that allows sufficient access to the femur and acetabulum for revision total hip arthroplasty. When bone loss is extensive, this approach permits massive autograft/allograft arthroplasty of the proximal femur and acetabulum. This approach follows anatomic muscle planes, maintains abductor function, and allows wound closure with a viable muscle cuff around the acetabulum and upper femur. The exposure is adequate for anatomic placement of components and correction of leg length discrepancy.

Follow-Up Studies↗
PubMed1987

Proximal femoral allografts in revision total hip arthroplasty.

Patients with total hip arthroplasty (THA) and aseptic loosening associated with severe bone deficiency were treated with freeze-dried bone allografts of the proximal one-third of the femur. Twenty-two of the first 25 patients were available for review with an average follow-up period of 28 months. Significant functional improvement was obtained in 16 patients (73%). The following complications occurred with allograft revisions: dislocation, wound hematoma, joint instability, nonunion, implant failure, and acetabular loosening. Nine patients required additional surgical procedures. There have been no infections or rapid lysis indicative of an allograft rejection phenomenon. The 73% success at the two-year postoperative interval of incorporation of freeze-dried allografts for salvage situations has been encouraging. However, the long-term durability of these grafts is not known and will require further follow-up study.

Adult↗