Biomedical subjects

Roger H Emerson

Publications and source records attributed to Roger H Emerson.

9 recordsLinked to original sources

PubMed2005

Metal-on-metal total hip arthroplasty with large heads may prevent early dislocation.

UNLABELLED: Postoperative dislocation is one of the major causes of morbidity and failure of total hip arthroplasty. We reviewed 327 patients (377 hips) retrospectively with varying diagnoses and indications but all of whom received large-diameter metal-on-metal prostheses. Two surgical approaches were used: the anterolateral abductor splitting (342 procedures) and a mini-incision posterior approach (35 procedures). Average age at time of surgery was 55.9 years and average followup was 4.0 months. There were 346 (91.8%) primary procedures, 15 (4.0%) conversion procedures, and 16 (4.2%) revisions or reimplantations. The most common preoperative diagnoses included osteoarthritis (250 hips; 66.3%) and avascular necrosis (46 hips; 12.2%). There were 62 (16.4%) patients with high-risk diagnoses for dislocation. The status in terms of postoperative dislocation was known for all patients. During the short followup period, there were no dislocations. Use of large-diameter femoral heads and metal-on-metal articulations decreases the risk of dislocations, making their use a viable choice for primary and revision procedures. LEVEL OF EVIDENCE: Therapeutic study, Level IV-1 (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Adult↗

PubMed2005

Unicompartmental mobile-bearing knee arthroplasty.

Two diferent mobile-bearing unicompartmental knee replacement designs have been available since the late 1970s. The primary difference between these two designs is that one has a constrained bearing in a track and the other has a freely moving bearing. Both implants are currently indicated for the treatment of patients with medial unicompartmental osteoarthritis and are available for use in the United States. The benefits of such designs are restoration of normal knee joint kinematics and protection of the polyethylene by reduction of high-contact stresses that occur with nonmobile-bearing designs. Experience has shown that careful patient selection and careful surgical technique both are factors critical to the success of mobile-bearing unicompartmental knee implants. The most important patient selection criteria have proved to be the diagnosis of anteromedial osteoarthritis with a passively correctable varus deformity and intact anterior cruciate ligament. Precise instrumentation is necessary to consistently balance and align a mobile-bearing implant. Ten-year survivorship data for freely mobile-bearing implants are available from multiple centers that show survivorship rates ranging from 85% to 98%, which are comparable to survivorship rates for total knee replacement.

Arthroplasty, Replacement, Knee↗

PubMed2004

Proximal ingrowth components.

The advantage of using a proximal ingrowth hip revision component is restoring physiologic load to the revision femur. Although first generation components had limited survivorship and diminished clinical outcomes, subsequent designs have proven much better with rates of aseptic loosening of 2% to 5%, and good clinical scores. Titanium is the favored substrate metal for these components because of its bone affinity and low modulus of elasticity. A series of 107 consecutive revisions of standard stems is presented using a calcar replacement long stem design with an overall 92.7% 11-year survivorship. Bone ingrowth was achieved in all but two components. Radiographic stress shielding was seen in 11.4% with 42.6% having some calcar healing. These implants can be used in most revision situations, but require sufficient proximal metaphysis of the femur to provide support of the component. Supplemental allograft may need to be used. These implants require a tight fit in the isthmus of the femur and fill of the proximal femur. Modularity makes achieving this easier, but monoblock designs also can be successful.

Arthroplasty, Replacement, Hip↗

PubMed2004

A comparison of highly instrumented and minimally instrumented unicompartmental knee prostheses.

In this study, two specific implants are compared: the Oxford prosthesis, which uses a highly instrumented technique and was placed through a traditional arthrotomy; and the Repicci prosthesis, which uses a minimally instrumented technique and was placed with a minimally invasive surgical approach. The study looked specifically at limb alignment, because achieving appropriate alignment is correlated with the best long-term implant function and achieving alignment is a function of the implant instrumentation. The rationale of more instrumentation for a surgical technique is to add precision and reproducibility; less instrumentation requires less surgical exposure and therefore is more minimally invasive. The senior author presents his long-term experience with the Oxford implant (55 implants; average followup 10.4 years) and short-term experience with the Repicci implant (164 implants; average followup 1.3 years for the first 30 implants.). With available followup, the clinical results using both implants have been favorable. The average alignment of the Oxford prosthesis was 5.6 degrees valgus and the average alignment of the Repicci prosthesis was 4.5 degrees valgus. Side-to-side long-term comparison is not yet available, although the literature would suggest that both implants can have satisfactory long-term results. Specific implant selection probably is not as important as precise patient selection.

Arthroplasty, Replacement, Knee↗

PubMed2003

A multimodality regimen for deep venous thrombosis prophylaxis in total knee arthroplasty.

Data indicate that deep venous thrombosis (DVT) occurs at the time of knee arthroplasty. Nevertheless, literature concerning DVT prophylaxis has only recently addressed this contention. This prospective study evaluated the efficacy of a perioperative prophylactic regimen. Between January 1996 and June 2001, 1,308 knees (964 surgeries) underwent total knee arthroplasty. Patients were treated routinely with intraoperative heparin (1000 units intravenous push before inflation of the tourniquet and 500 units at deflation), hypotensive epidural anesthesia (MAP 70-90), external pneumatic compression boots, and aspirin (325 mg, PO, BID for 6 weeks). Duplex venous ultrasonography was performed before discharge. DVT was detected in 4% of cases (1% proximal and 3% distal). Bleeding complications occurred in 1%, and perioperative medical complications occurred in 12%.

Aged↗

PubMed2003

Clinical and radiographic analysis of the Mallory-Head femoral component in revision total hip arthroplasty. A minimum 8.8-year and average eleven-year follow-up study.

BACKGROUND: Although many designs of cementless femoral stems are available for revision hip arthroplasty, there is no consensus about which design features are required to achieve an optimal clinical outcome and maximum preservation of bone. The purpose of this study was to report the clinical and radiographic results for a specific design. METHODS: A selected series of 107 revision total hip arthroplasties with use of the Mallory-Head calcar-replacement prosthesis was reviewed with clinical and radiographic evaluation. The study group consisted of sixty-six hips (sixty patients), with an average follow-up of 11.5 years (range, 8.8 to 14.5 years). All revisions in this series were performed because of failure of a cemented or cementless femoral component of standard length. All revision stems were 220 mm long. RESULTS: Three of the 107 original stems demonstrated subsidence of 3, 7, and 9 mm. Two stems had definite loosening, resulting in a 1.9% rate of mechanical failure. The rate of survival was 94% with revision for any reason as the end point and 97.1% with revision because of mechanical failure (aseptic loosening) as the end point. The Harris clinical score was 49 points preoperatively and 80 points postoperatively. Radiographic analysis demonstrated that the average percentage of the diaphysis filled by the prosthesis was 86%. Fifty-four (88.5%) of the sixty-one hips with complete radiographic follow-up showed no stress-shielding on final radiographs, whereas seven hips (11.4%) showed some stress-shielding. CONCLUSIONS: This proximal load-bearing calcar-replacement design achieves reliable fixation and stability at intermediate-term follow-up. There is no deterioration in the clinical outcome or radiographic findings at an average of eleven years of follow-up. The prevalence of disuse osteopenia from stress-shielding is very low. Proper surgical technique includes maximum fill of the diaphysis of the femur, with contact of the collar on part of the proximal aspect of the femoral shaft.

Arthroplasty, Replacement, Hip↗

PubMed2002

A comparison of cemented and cementless titanium femoral components used for primary total hip arthroplasty: a radiographic and survivorship study.

Titanium has a low modulus of elasticity that makes it an attractive metal for femoral hip components. We directly compared 2 similar titanium stems, one cemented (n = 102 hips) and the other cementless (n = 78 hips), controlling for the most important surgical variables. The average radiographic follow-up was 6.7 and 7.0 years. Osteolysis below the joint line, zones 2 through 6, was 12.7% (13 of 102) in the cemented group and 0% in the cementless group (P<.001). There were 17 acetabular revisions in each study group. The cementless group had no femoral revisions, whereas 9 acetabular revisions in the cemented group had a simultaneous femoral revision (P=.005). Survivorship, defined as revision of the femur, was 84% for the cemented group and 100% for the cementless group at 10 years. Cementless titanium stems are more resistant to osteolysis and mechanical failure compared with similar cemented titanium stems.

Acetabulum↗

PubMed2002

Comparison of a mobile with a fixed-bearing unicompartmental knee implant.

Two well-matched groups of patients with unicompartmental knee arthroplasties were compared. The first 51 knees were treated with a fixed-bearing knee implant and the second 50 knees were treated with a mobile meniscal-bearing implant. Followup was 7.7 years for the patients with fixed-bearing implants and 6.8 years for patients with mobile-bearing implants. Both groups functioned well clinically. Radiographic analysis with 3-foot standing views taken preoperatively showed both groups had an average varus alignment of -2 degrees. Postoperatively patients with fixed-bearing implants had an average +2.6 degrees alignment and the patients with mobile-bearing implants had +5.5 degrees alignment, which was significantly different. Survivorship analysis based on component loosening and revision showed a 99% survival for the meniscal-bearing implant and 93% survival for the fixed-bearing implant at 11 years. However, the fixed-bearing knee implants failed significantly more often because of tibial component failure, in six of eight knees, at an average of 6.3 years. The mobile-bearing implants showed a trend to fail because of arthritic degeneration in the lateral compartment, at an average of 10 years, although not statistically significant. The mobile-bearing implants had no tibial component failures. These differences may be attributable to implant design or surgical technique.

Adult↗

PubMed2002

Comparison of a static with a mobile spacer in total knee infection.

Patients with infections of a total knee arthroplasty were stratified by medical status. Twenty-six knees in 26 patients treated with a static antibiotic-impregnated polymethylmethacrylate block spacer before 1995 were compared with 22 knees in 22 patients treated after 1995 with a mobile articulating spacer. Both groups were treated with 6 weeks of parenteral antibiotics and had reimplantation within 6 to 12 weeks after placement of the spacer. Followup for the patients who had block spacers was an average 7.5 years (range, 2.8-12.7 years), and followup for the patients with a mobile spacer was an average of 3.8 years (range, 2.6-6.4 years). Results showed that the patients with the mobile spacers had significantly better average range of motion at followup compared with patients who had block spacers (107.8 degrees compared with 93.7 degrees ). The reinfection rate was the same between the two groups at 36 months, 7.6% (two of 26) for the patients with block spacers and 9% (two of 22) for the patients with mobile spacers. Extended followup available for the patients who had block spacers revealed a late reinfection rate of 23% (six of 26) with a new organism. There was no difference in the reinfection rate, with new or old organisms, in healthy hosts compared with patients with as many as two medical problems.

Aged↗