Effect of tibial component position on patellar strain following total knee arthroplasty.

Patellar fracture following total knee arthroplasty has been related to component alignment and tibiofemoral joint-line position. The purpose of this study was to determine the effect of anteroposterior displacement of the tibial component and inferosuperior displacement of the tibiofemoral joint line on patellar strain following total knee arthroplasty with a cruciate-substituting design. Patellar strain increased (decreased) with anterior and inferior (posterior and superior) displacement. When averaged across all flexion angles, the strain changed approximately 1.7%/mm of anteroposterior displacement and 1.0%/mm of inferosuperior displacement. For individual specimens, changes in strain as high as 3.2%/mm of inferosuperior displacement of the joint were seen. These changes in strain may be associated with changes in tibiofemoral joint-line position. These changes in strain may be a biomechanical indicator of the efficacy of retaining the preoperative position of the tibiofemoral joint line.

Triple arthrodesis for diabetic peritalar neuroarthropathy.

From 1963 to 1990, the senior authors (R.E.M. and K.G.H.) performed eight triple arthrodeses in seven patients with diabetes mellitus with sensory loss in the lower extremities. By clinical and roentgenographic examination, all patients were diagnosed with peritalar neuroarthropathy before surgery. All patients underwent a two-incision triple arthrodesis with internal fixation. Patient follow-up averaged 44 months and included repeat physical examinations and radiographs. All patients went on to clinical union and were satisfied with the procedure. One patient had prolonged wound drainage that resolved with antibiotic therapy; another had a residual rocker-bottom deformity and plantar ulceration that resolved after modification of custom shoe wear. We believe comprehensive management of diabetic peritalar neuroarthropathy can include surgical arthrodesis of the involved joints. The disease process and surgical indications are discussed.

Knee function after patellectomy and cruciform repair of the extensor mechanism.

When patellectomy is performed, the objectives should include restoration of a moment arm, centralization of the extensor mechanism, adequate range of motion, and cosmesis. The cruciate repair of the extensor mechanism described in this report has been developed to meet the aforementioned objectives. Eight patients with 12 patellectomies described herein were examined with Cybex testing of the knee at a follow-up period of 18 months to 20 years (mean, 56 months). A four-quadrant tissue dissection of the patellar soft-tissue enclosure was reconstructed in a cruciform pants-over-vest fashion, with the superomedial flap containing the vastus medialis insertion on top. This "soft-tissue" patella attempts to provide a greater moment arm than simpler repairs. This study examines whether this construct restored the torque of extension while concomitantly facilitating centralization of the extensor mechanism. Cybex testing of both knees examined both extensor and flexor function with specific regard to the ratio of extensor to flexor forces. Patients with patellectomies had few subjective complaints, with a mean knee score of 94 (median, 100). The extensor torque was not completely restored and there was a moderate decrease in the quadriceps function, both subjectively and objectively as measured by Cybex testing. The authors also found that in patients with unilateral patellectomies, the ratios of extension to flexion function, a parameter not yet reported in the literature, were significantly different between the normal and patellectomized knees. The same extension to flexion ratios were seen in patients with bilateral patellectomies. Because patients with patellar pathology requiring patellectomy frequently have chronic and bilateral disease, comparative functional evaluation may be difficult.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of hip force calculations and measurements in the same patient.

Many investigations report hip-contact-force estimates based either on mathematical models or on the output of instrumented implants. Data from instrumented implants have been consistently lower than mathematical predictions. The authors compared mathematical estimates derived from gait laboratory observations made in a patient with an instrumented hip implant. Appropriate modifications to past models resulted in force predictions that were reasonably similar to the output of the instrumented implant. Peak resultant forces were in the range of 2.5-3.5 body weight during level walking at a freely selected speed, while peak out-of-plane forces ranged from 0.6 to 0.9 body weight. Previous parametric hip-force predictions resulting from mathematically modeled surgical alterations may be high insofar as absolute peak values, but trends are likely correct.

Midshaft clavicle nonunions treated with intramedullary Steinman pin fixation and onlay bone graft.

The current literature tends to favor rigid internal fixation with plates for symptomatic midclavicular nonunions. From 1985 to 1992, 14 patients with clavicular nonunions were treated by open reduction and intramedullary Steinman pin fixation with onlay iliac crest bone grafting. The average age of patients was 36 years (range 18-62). The majority of nonunions occurred after high-energy injuries to the clavicle. Three patients had failed previous plating and one initial fracture was pathological through irradiated bone. At an average follow-up of 4 years, all nonunions healed uneventfully and all were satisfied with the result of surgery. There were no infections or pin migrations. All hardware was removed at an average of 12.7 weeks (7-24 weeks). The most significant complications were two refractures occurring through osteopenic bone. We have found this technique to be as effective as plating procedures, yet it maintains the great advantage of ease of hardware removal. It allows early motion and has been useful in those whose previous plating procedures have failed.

Telemeterized in vivo hip joint force data: a report on two patients after total hip surgery.

Two telemeterized femoral components were implanted in two patients as part of normal total hip replacement procedures. The two components were instrumented to measure the three force components directed along: (a) the neck axis, (b) transverse to the neck axis and in the plane of the prosthesis, and (c) transverse to the neck axis and perpendicular to the plane of the prosthesis. Data were collected at multiple sessions during the early postoperative period for a number of standard activities, including gait, stair climbing, rising from a chair, single leg stance, double leg stance, ipsilateral and contralateral straight leg lifts while supine, ipsilateral flexion and extension while standing, and ipsilateral abduction while standing and lying on the contralateral side. These data are summarized and compared with the published results from analytic studies and with the results from previous studies using instrumented femoral components. Peak loads for gait during the period of study were roughly 2.7 body weights (BW) when the patients walked at their normal pace. Contact forces at the hip during stationary single leg stance approximated the peak loads during gait with values ranging from 2.1 to 2.8 BW. The highest forces recorded reached values approaching 5.5 BW and occurred during periods of instability while the patient engaged in stationary single leg stance. Our in vivo data indicate that forces generated during the above activities increase in magnitude quite rapidly during the early postoperative period and that during this period the patients have the ability to perform the activities of daily living without generating the high amplitude joint contact forces suggested by the results of dynamic studies. Joint contact forces during gait were found to depend on speed, but the high absolute magnitudes predicted by model studies were not supported by the in vivo data.

Total knee arthroplasty for the treatment of chronic hemophilic arthropathy.

Total knee arthroplasty (TKA) for hemophilic (factor VIII deficiency) arthropathy is a complex and demanding procedure with a high complication rate. However, the long-term benefits have not previously been reported. This study reviews 19 TKAs performed for hemophilic arthropathy that were followed for a minimum of 5.5 years and an average of 9.5 years. At present, 13 knees have good or excellent results, and six knees rate as poor or failures. Those patients with excellent results have maintained good pain relief and function. Four of the six failures were among the first seven arthroplasties performed, when only 80% factor VIII coverage was used during the perioperative period. Since the use of 100% factor VIII coverage was instituted, the failure rate has declined. Ten of the 19 knees suffered complications, including one deep infection, six superficial skin necroses, three nerve palsies, seven postoperative bleedings, and one transfusion reaction. Six of the seven knees operated on under 80% factor VIII coverage had complications. Once 100% factor VIII coverage was instituted, the only complications included one skin necrosis and three postoperative bleedings. The roentgenographic failure rate has remained high with progressive roentgenographic lucencies in 13 of 19 tibial components, associated with component shift in three knees. While these roentgenographic findings have not necessarily correlated with clinical results, they are disturbing and may portend future failures. However, pain relief and improved function are maintained at longer follow-up times. The best results were obtained under 100% factor VIII coverage using a posterior stabilized prosthesis and patellar resurfacing.

Prevention of ligament and meniscus atrophy by active joint motion in a non-weight-bearing model.

This study describes the effect of active joint motion on the maintenance of ligament and meniscus mass in a non-weight-bearing model of disuse. Denervation and fixation models of immobilization have shown that resorption of isotope and atrophy of mass occurred for hard tissue (bone) and soft tissues (ligament, tendon, or meniscus). A unilateral ankle disarticulation model of disuse that maintains active knee motion without weight bearing was studied for 8 weeks in dogs that were chronically prelabeled with three different isotopes. The effects of non-weight-bearing without denervation or fixation were analyzed for the resorption of isotopes, and net atrophy of bone mass (femur or tibia) and soft-tissue mass (collateral or cruciate ligaments, menisci). A large and similar loss of all three isotopes, as well as collagen and calcium mass occurred for whole femur and tibia; this indicated that mass loss was equivalent to bone resorption and suggests little replacement with new bone. No loss of isotope or mass per whole tissue occurred for the collateral and cruciate ligaments or menisci. The strength of the femur-anterior cruciate ligament-tibia complex was analyzed by a tensile failure test when a fast rate of deformation was applied; the results did not differ qualitatively or quantitatively between control and experimental limbs. The absence of weight bearing for 8 weeks resulted in marked bone atrophy without resorption or atrophy of soft tissues, or decrease of the mechanical strength for the femur-ligament-tibia complex.

Use of a total condylar knee prosthesis for treatment of osteoarthritis and rheumatoid arthritis. Long-term results.

Between May 1975 and December 1979, 113 patients had 153 arthroplasties using a total condylar knee prosthesis. Thirty patients (forty-two knees) died, and one (two knees) was lost to follow-up. Thirty-eight of these forty-four knees had been followed for more than two years, and none had had a revision. The remaining eighty-two patients (109 knees) were followed for an average of nine years (range, seven to 11.5 years). At the time of the latest examination, ten had had a revision for various reasons. For the ninety-nine knees that had the original prosthesis, the findings were compared with those of an evaluation that had been done four years postoperatively. The average over-all knee score was found to have decreased between the four-year and the latest follow-up evaluation, primarily because of a 7-point decrease in the score for function. The rate of infection was 0.6 per cent. The knees that had had patellar resurfacing had better over-all scores and better scores for pain than those that had not. This was particularly true in the patients who had osteoarthritis. The results of arthroplasty using a total condylar prosthesis appeared to be consistent and durable. Although there was a decrease in the quality of the functional result with increasing age, the patients reported consistent relief of pain.

Telemetric force measurements across the hip after total arthroplasty.

A telemeterized total hip prosthesis was implanted in one patient and force-data were obtained. Thirty-one days postoperatively, the magnitude of the joint-contact force during double-limb stance was 1.0 times body weight. During ipsilateral single-limb stance the joint-contact force was 2.1 times body weight, and during the stance phase of gait the peak force typically was 2.6 to 2.8 times body weight, with the resultant force located on the anterosuperior portion of the ball. During stair-climbing, the force was 2.6 times body weight. At peak loads, the angle between the resultant force and the axis of the neck was 30 to 35 degrees and that between the resultant force and the plane of the prosthesis was 20 degrees. During stair-climbing or straight-leg raising, the out-of-plane orientation of the resultant force increased substantially. These data provide information concerning the forces that must be sustained by prosthetic hip joints during a number of common activities of daily living within the first month after implantation. The results also provide insight into the progression of early recovery and demonstrate the variety of forces that are generated during this period.

Biology of cancellous bone grafts.

Despite 30 years of experimental bone grafting research, the fresh cancellous bone graft remains the most osteogenic and reliable bone grafting material. Recent experimental data suggest that modification of the graft-host interaction by antigen matching or immune manipulation may allow increasingly successful use of allografts.

The influence of tibial-patellofemoral location on function of the knee in patients with the posterior stabilized condylar knee prosthesis.

Function of the knee and patellofemoral symptoms were correlated with the position of the implant in 101 consecutive patients with 116 posterior stabilized condylar knee prostheses. All of the patients were followed for a minimum of two and a half years with sequential physical examinations, radiographs, and functional evaluation of the knee. In sixteen knees (14 per cent), clicking or catching of the patella in terminal extension or painless crepitation throughout the arc of flexion developed without lowering the functional knee-evaluation score. Pain or mechanical problems, or both, that lowered the functional knee-evaluation score occurred in another fourteen knees (12 per cent), within the first postoperative year. Of these fourteen, eight required revision solely for patellofemoral complaints. Critical analysis of the tibial-patellofemoral mechanical axis identified three surgical variables that were found to markedly affect the functional result of the prosthesis: the distance from the center line of the tibial prosthesis to the center line of the tibial plateau, a change in the position of the joint line of the prosthesis relative to the hip and ankle, and the patellar height, measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis. Functional knee scores, range of motion, patellofemoral pain or mechanical symptoms, the need for revision, and the necessity of manipulation could all be statistically significantly correlated with the three independent variables. In addition, a range of neutral alignment was developed.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of tibial-femoral angle on the failure mechanics of the canine anterior cruciate ligament.

A series of canine femur-ACL-tibia complexes were subjected to tensile tests with axial tibial orientation and 0 degree, 45 degrees or 90 degrees femoral orientation with respect to load direction. A deflection rate of 51.0 cm min-1 was used in all tests. Marked differences occurred in ultimate loads, deflection and energy absorbed as a consequence of differences in femoral-tibial orientation. The mode of structural failure, as determined by post-test examination, also varied markedly as a function of femoral-tibial orientation. It is concluded that differences both in measured mechanical properties and observed failure details are a consequence of varying the loading pattern of the fiber bundles across the finite breadth of the ligament.

The long-term fate of fresh and frozen orthotopic bone allografts in genetically defined rats.

Fresh and frozen orthotopic iliac crest bone grafts in rats were studied histologically for determination of the long-term effects of histocompatibility matching and the freezing process on orthotopic bone graft incorporation. Grafts exchanged between groups of inbred rats, syngeneic or differing with respect to major or minor histocompatibility loci, were studied histologically at 20, 30, 40, 50, and 150 days after bone transplantation. A numerical histologic scoring system was developed and used by three observers for evaluation of coded hematoxylin and eosin sections. All frozen graft groups had the same fate regardless of histocompatibility relations between donors and recipients, and all grafts were inferior to fresh syngeneic grafts. Both fresh allograft groups received similar scores and initially at 20 and 30 days had scores similar to those of the fresh syngeneic groups. In the later intervals, however, the fresh allografts were inferior to the fresh syngeneic grafts and similar to the frozen groups. This is consistent with an older model describing two distinct phases of osteogenesis. In the long term, frozen syngeneic and fresh and frozen allografts across major and minor histocompatibility barriers were comparable, but all were significantly inferior to fresh syngeneic bone grafts.

Femoral shaft nonunion treated by a fluted intramedullary rod.

Twenty-five consecutive nonunions or delayed unions of the femoral shaft were treated by a fluted intramedullary rod. Fourteen patients were men; 11 were women. Sixteen fractures represented failures of closed management. Five patients had failures of primary open reduction and internal fixation. Four patients had had one attempt at operative treatment of nonunion. All but one fracture united. The one exception required a second procedure. Excellent bending and rotary fixation were achieved and union occurred promptly in most cases. Iliac crest bone grafting was not routinely required for good results. There were no major complications in this series. Two patients with severe knee extension contractures required quadricepsplasty at a later date to recover knee motion. One fracture healed with a 15 degree valgus malunion. The strength and rigidity make this device extremely reliable for the treatment of femoral shaft nonunion.

Effects on bone of vascular interruption. Turnover and morphology in isotope-prelabelled rats.

The effects of bone devascularization were evaluated histologically and metabolically in rats prelabelled with 45Ca, 3H-tetracycline and 3H-proline by quantifying cortical bone resorption and formation. The interruption of blood supply to bone without invading its integrity resulted in a marked increase in bone turnover (resorption and formation) during the first and second months. The stimulated increase in bone resorption and formation did not affect the resultant mass of collagen and calcium. Thus, the increase in bone resorption was compensated by an equivalent increase in bone formation.

Bone grafting: role of histocompatibility in transplantation.

The role of histocompatibility matching in bone allografting was studied in two canine bone graft models. In a cancellous ulnar segmental replacement model, frozen bone allografts exchanged between closely matched dogs were significantly better incorporated by radiographic and histologic criteria than were strongly incompatible grafts. Frozen allografts from disparate donors in recipients receiving immunosuppression appeared indistinguishable 6 months later from those in the untreated closely matched groups and from fresh autografts. Fresh vascularized orthotopically placed fibular bone grafts were evaluated by quantitative blood flow assessment, microangiography, and fluorochrome histomorphometry. Revascularized grafts exchanged between untreated closely matched dogs demonstrated preservation of blood flow and a pattern of repair that was delayed but not otherwise different than vascularized autografts. These results suggest that fresh vascularized grafts in the judiciously matched or immunosuppressed recipient offer attractive clinical possibilities.

Anisotropic yield behavior of bone under combined axial force and torque.

In this study the yield behavior of cortical bone was determined under combined loading conditions involving tension, compression and torsion. The axis of each test sample coincided with the long bone axis. To minimize viscoelastic behavior, tests were conducted using an effective strain rate in the range of 0.01-0.06 s-1. Experimental yield loci for bovine and human cortical bone were determined using a strain offset technique to determine the 'common yield point' for combined loading. Several failure criteria which have been used for composite materials were examined for applicability to the experimental results. Data were obtained for bovine and human tibial and femoral bone. The Tsai-Wu criterion was in best agreement to the test data, although Hill's criterion could describe the individual compression-torsion or tension-torsion regimes with good accuracy.