Vesicoacetabular fistula in a chronically infected total hip arthroplasty

Fistula formation between the bladder and acetabulum related to total hip arthroplasty (THA) is rare, and few cases have been documented. Common features of the reported cases include a defect in the medial wall of the acetabulum, a chronically infected THA, a history of bladder injury, vesicocutaneous fistulas, and a history of pelvis radiation exposure. We report the case of a vesicoacetabular fistula discovered during antibiotic spacer placement in a woman with a chronically infected THA. The patient received bilateral ureteral stents extending from the renal pelvis to the urethra. Three months later, the patient was free of infection and was able to undergo reimplantation arthroplasty.

Surgical treatment of developmental hip dislocation in children aged 1 to 3 years: a mean 18-year, 9-month follow-up study

Forty-six consecutive patients with 57 congenitally dislocated hips were treated with open reduction and femoral or acetabular procedures as indicated. Patient age ranged from 12 to 36 months at the time of surgery. We evaluated the outcome of 38 of the 46 patients (83%) with 47 hips (83%) at a mean follow-up of 18 years, 9 months (range, 13 years, 7 months to 24 years, 7 months) after all patients had reached skeletal maturity.Using Severin's radiographic classification, 24 hips (52%) were rated as class I, 12 (26%) as class II, 8 (17%) as class III, 2 (4%) as class IV, and 0 as class V. The mean Iowa Hip Score was 92 points. One patient had significant abductor weakness and a Trendelenburg gait. The mean leg-length discrepancy was <1 cm. Disturbance in growth of the proximal aspect of the femur occurred in 10 hips (22%).In our experience, open reduction of the congenitally dislocated hip in children aged 1 to 3 years, combined with femoral or acetabular procedures, leads to successful clinical and radiographic results in most cases. These patients have an opportunity for normal hip function during childhood and the potential for a straightforward reconstructive procedure should they develop severe degenerative hip arthrosis.

The anatomy of the acetabulum: what is normal?

Published studies of the human hip make frequent reference to the normal pelvis and acetabulum. However, other than qualitative descriptions we found no clinically applicable published references describing a normal pelvis and acetabulum; such information is important for designing certain kinds of implants (eg, reconstruction cages). We describe a method to quantify, average, and apply data gathered from normal human specimens to create a standard representation of the ilium and ischium. One hundred healthy hemipelves from 50 human skeletons were evaluated. We measured angles and distances between major anatomic landmarks in the pelvis. The data collected were analyzed for variance and averaged to create a normal topographic map. Finally, we examined several commercially available acetabular reconstruction cages to determine the fit to the anatomically determined normal pelvis. These results provide a representation of true acetabular geometry and may serve as the basis for future acetabular reconstruction cage design.

Management of posttraumatic extensive bone loss and osteomyelitis using a customized articulating knee spacer

The combination of infection and extensive bone loss presents a challenging reconstructive situation for surgeons performing total knee arthroplasty (TKA). We describe the case of a patient that suffered a grade III open fracture of the tibial plateau and developed a recurrent infection which resulted in loss of the proximal 15 cm of the tibia. Our solution was interim use of custom-made articulating, antibiotic-impregnated spacers followed by a structural tibial allograft and hinged TKA. At 2-year follow-up the patient is infection-free and is able to ambulate without the use of support.

Total hip arthroplasty with the Secur-Fit and Secur-Fit plus femoral stem design a brief follow-up report at 5 to 10 years

This report represents a 5- to 10-year follow-up of our initial 2- to 5-year data with this proximally hydroxyapatite-coated stem design (Secur-Fit, Stryker Orthopaedics, Mahwah, NJ). This is a retrospective review of a single surgeon's consecutive cases. A total of 105 cases were available for complete review. The average follow-up was 6.7 years (60-123 months). All stems achieved bony ingrowth. Harris hip score and Oxford hip score averaged to 91 and 17, respectively, with no differences seen between the 132 degrees and the 127 degrees stem designs. Leg length measurements were considered equal side-to-side differences of 7 mm or less in 87% of cases: 82% of standard- and 92% of high-offset cases (P < .05). Four cases of osteolysis were identified and occurred only in patients with an elevated rim liner, implicating neck-liner impingement. The stem design performed exceedingly well over the course of this study. Having a high-offset option aids the surgeon in proper leg length management.

Early revision for component malrotation in total knee arthroplasty

Component malrotation may result in unsuccessful total knee arthroplasty. We asked whether revision improves function in patients with malrotated total knee arthroplasty components. We retrospectively reviewed 22 revision total knee arthroplasties performed for femoral and/or tibial component malrotation. Revision surgery was performed within 2 years of the primary arthroplasty in 81% of the cases (18 of 22) with the remainder within 5 years. Although all patients had pain, 32% of patients had associated instability and 36% of patients had poor range of motion. Average Knee Society Scores improved from 42 preoperatively to 77 postoperatively. Average Oxford Knee Scores improved from 38 preoperatively to 29 postoperatively. Although clinical and functional improvement was observed, these results are inferior to those for primary knee arthroplasty, and they emphasize the need for proper component rotational positioning during primary total knee arthroplasty. Internal component malrotation leads not only to patellofemoral problems, but also to difficulty in gap balancing and femoral component sizing, which may in turn lead to either poor range of motion or symptoms of knee instability.

Kneeling kinematics after total knee arthroplasty: anterior-posterior contact position of a standard and a high-flex tibial insert design

Deep flexion activities including kneeling are desired by patients after total knee arthroplasty. This in vivo radiographic study sought to reveal the effect of tibial insert design on tibiofemoral kinematics during kneeling. One group of patients received standard posterior stabilized tibial inserts, whereas the other group received posterior stabilized tibial inserts (Flex inserts) that were designed to allow more flexion. The patients with the Flex inserts achieved greater range of motion without different tibiofemoral contact behavior.

Use of an intramedullary nail for correction of femoral deformities combined with total knee arthroplasty: a technical tip

Simultaneous femoral deformity correction combined with total knee arthroplasty can be a complex procedure, which can be simplified with this described technique. A femoral component that allows access to the intramedullary canal is necessary to be able to use this technique.

The safety and efficacy of a new adjustable plate used for proximal tibial opening wedge osteotomy in the treatment of unicompartmental knee osteoarthrosis

Twenty opening wedge tibial osteotomies were performed using the Osteotrac plate, which consists of a two-piece plate with a one-way ratcheting mechanism with two degrees of freedom. A variety of concomitant procedures were performed including osteochondral transfer, tibial tubercle medialization, and anterior cruciate ligament reconstruction. The change in tibiofemoral alignment in the coronal plane and the shift in lower extremity mechanical axis were determined. The average lateral shift in the lower extremity mechanical axis was 24% of the tibial plateau width. The average change in the mechanical tibiofemoral angle was 7 degrees of valgus. Union rate at the osteotomy site was 95%. No deep infections, clinical deep venous thrombosis, or device failures occurred. The Osteotrac plate provides safe and effective fixation and intraoperative adjustability to achieve and maintain a lateral shift of the lower extremity mechanical axis and valgus correction of the tibiofemoral alignment in patients with varus knees undergoing proximal tibial opening wedge osteotomy and associated meniscal and chondral procedures.

The use of a hydroxyapatite-coated primary stem in revision total hip arthroplasty

Proximal ingrowth of femoral components in total hip arthroplasty (THA) is desirable because it minimizes proximal stress shielding associated with distal ingrowth stems and maximizes bone stock. This is a retrospective evaluation of initial results of revision THA using a proximally hydroxyapatite-coated femoral stem nominally designed for primary use. Patients requiring femoral stem revision were included if they had sufficient femoral bone stock to support a proximally fixed prosthesis (n = 33). This represents 53% of the femoral revisions performed during the period of the study. The average follow-up was 5 years (range 48-88 months). The mean Harris hip and Oxford hip scores were 86.5 and 25.2, respectively. Radiographically, 100% of the stems demonstrated bone ingrowth fixation. These results are superior to previous reports of primary cementless stems for revision THA. The use of a cementless nonmodular implant provides a viable option in some patients undergoing revision THA.

Simultaneous bilateral total hip arthroplasty with a cementless femoral stem

Simultaneous bilateral total hip arthroplasty (THA) is an increasingly common procedure. Although use of a cementless stem can eliminate cement complications, some surgeons limit application of cementless THA because of concerns about early implant loosening. In this article, we report on 30 cementless THA cases (15 patients) followed up for a minimum of 2 years (range, 26-50 months). Despite 73% of femoral bone being type B or type C, all stems showed stable bone ingrowth fixation and no evidence of subsidence. Polyethylene wear rates (left, 0.154 mm/y; right, 0.114 mm/y) did not differ significantly. The excellent clinical results obtained with simultaneous bilateral cementless THA are comparable with those obtained with unilateral THA.

Tibiofemoral kinematic analysis of kneeling after total knee arthroplasty

Some surgeons warn against kneeling after total knee arthroplasty (TKA), because limited clinical data exist. We describe the tibiofemoral contact position of TKA components during kneeling in vivo. Ten posterior-substituting (PS) and 10 cruciate-retaining (CR) designs were examined using a radiographic image-matching technique. Movement from standing to kneeling at 90 degrees produced different responses. CR knees translated anteriorly (medial, 4 +/- 4 mm; lateral, 2 +/- 6 mm). PS knees underwent little posterior translation (medial, 0.2 +/- 3 mm; lateral, 1 +/- 4 mm). Movement from 90 degrees to maximum flexion produced femoral posterior translation (CR medial, 5 +/- 4 mm; CR lateral, 5 +/- 4 mm; PS medial, 6 +/- 4 mm; PS lateral, 6 +/- 3 mm). The relationship between tibiofemoral contact position and flexion angle was more variable for CR (r2=.38) than for PS (r2=.64). Knee kinematics was similar to other deep-flexion weight-bearing activities.

Femoral component sizing in total knee arthroplasty: size matched resection versus flexion space balancing

Generally, 2 different methods are used to select femoral size. These can be termed "size-matched resection" and "flexion-space balancing." The purpose of this paper is to compare these 2 methods during 50 sequential total knee arthroplasty surgeries. The flexion-space-balancing method led to a smaller size selection than the size-matched-resection method in 28 (56%) knees. In the remaining 22 knees, the measurement methods led to the selection of the same size femoral component. The difference in measurement methods was significant (P<.05). The preoperative varus knees were more sensitive to the differences in measurement methods than the valgus knees (P<.05). A flexion space that is too small may adversely affect the clinical outcome of knee arthroplasty.

Femoral component revision using an extensively hydroxyapatite-coated stem

Femoral component revisions with extensively coated stems have shown promising clinical results, although concerns over stress shielding still exist. We retrospectively reviewed 59 patients undergoing femoral component revision with an extensively hydroxyapatite (HA)-coated stem. The average length of follow-up was 3.3 years (range, 2-5 years). The average preoperative Harris Hip Score was 43 points, which improved to 86 points at the latest follow-up (P < .01). The overall mechanical failure rate was 2%. No evidence of stress shielding was seen in 78% of patients. The clinical results of this series using an extensively HA-coated stem are similar to those using an extensively porous-coated stem. Long-term follow-up is required to determine if an extensively HA-coated implant will be superior to an extensively porous-coated implant with regard to stress shielding.

Efforts to improve cementless femoral stems in THR: 2- to 5-year follow-up of a high-offset femoral stem with distal stem modification (Secur-Fit Plus)

A retrospective review of 81 sequential primary total hip arthroplasties using a cementless, high-offset femoral stem was performed. Follow-up was 24 to 60 months. The average age at the time of surgery was 54 years. The femoral bone types were: 36% Dorr A, 51% Dorr B, and 13% Dorr C. The mean postoperative Harris Hip Score was 95. The mean postoperative Oxford score was 17. Eighty-five percent had no clinical leg-length difference. All stems were radiographically stable. The stem features of hydroxyapatite coating on a rough circumferential titanium arc-deposit proximal surface in conjunction with distal flutes seem to provide immediate stability, making this implant clinically versatile. Potential benefits of increased offset include improved joint stability and avoidance of leg lengthening.

A stem-allograft composite for femoral revision in total hip arthroplasty

Femoral revision is difficult when the femoral canal exceeds 20 mm in diameter. For this subset of patients, we used a technique of cementing cortical allograft sleeves to a proximal ingrowth stem. The diameter of the allograft sleeves are matched to the diameter of the host femur. The stem-allograft construct provides initial stability with the opportunity for proximal bone ingrowth.

Tibial axis and patellar position relative to the femoral epicondylar axis during squatting

A laboratory-based study was performed to describe the tibial axis and patellar position relative to the femoral epicondylar (FE) axis during squatting. During the squat, the angle between the tibial and FE axes averaged 90.5 degrees, and 66% of internal rotation of the tibia occurred before 15 degrees flexion. In the mid-sagittal plane of the femur, the patella followed a circular arc, and mediolateral patellar shift averaged 4.3 mm. These findings can be used as the basis for development of new total knee arthroplasty components that recreate normal patellofemoral kinematics, and may provide important guidelines for alignment of the tibial and femoral components. The perpendicular relationship between the tibial and the FE axes may be useful in locating the FE axis intraoperatively. The reduced mediolateral shift of the patella suggests that alignment of the femoral component with the FE axis will aid patellar tracking about a circular arc with small deviations in the medial-lateral direction.

Clinical performance of a highly cross-linked polyethylene at two years in total hip arthroplasty: a randomized prospective trial

We report the 2-year results for a prospective randomized trial comparing highly cross-linked with standard polyethylene in total hip replacements. In our study, 46 hips were available for radiographic analysis at 2- and 3-year follow-up. Femoral bearings were 28-mm cobalt chrome with the polyethylene insert randomly selected at the time of implantation to be highly cross-linked polyethylene (Crossfire; Stryker Howmedica Osteonics, Allendale, NJ) or standard polyethylene (N(2)/Vac, Stryker Howmedica Osteonics). Polyethylene wear rates were measured based on anterior-posterior (AP) and lateral pelvis radiographs at 6 weeks and at yearly intervals using a validated computer-assisted edge-detection method. Wear rates between the 2 groups were compared using the nonparametric Mann-Whitney test at the 95% level. A significant reduction in 2- and 3-dimensional linear wear rates (42% and 50%) was found in the highly cross-linked group (P =.001 and P =.005).

Anatomic rotational relationships of the proximal tibia, distal femur, and patella: implications for rotational alignment in total knee arthroplasty

The orientation of the femur, tibia, and patella are important considerations in total knee arthroplasty. Our goal was to describe the relationships between the femoral epicondylar (FE) axis, posterior femoral (PF) axis, posterior tibial (PT) axis, patellar (PAT) axis, and patellar ligament (PL). A secondary goal was to determine where the short axis of the tibial tray intersects the patellar ligament as a function of tibial component rotation. Thirty normal magnetic resonance imaging (MRI) scans were analyzed. Strong relationships were found between the FE and PAT axes (2 degrees +/- 3 degrees, r(2) = 0.73), and between the FE and PF axes (6 degrees +/- 2 degrees, r(2) = 0.77). When the tibial baseplate was aligned along the PT axis, 30% of the cases were in an ideal position. When the FE axis was used, 73% were ideal.

Effects of early and late stage cement intrusion into cancellous bone

Minimizing aseptic loosening of cemented femoral stems in total hip arthroplasty remains a goal. Recent investigation suggests that improved cement intrusion may result from elevated pressures shown to occur during stem placement into higher viscosity late stage polymethylmethacrylate cement when compared with low viscosity early stage cement. The hypothesis tested is that placement of a femoral stem in late stage cement can increase cement-bone contact as compared with placement in early stage cement. The variable tested in this experiment was cement viscosity. Radiographic analysis was done on nine paired femurs from cadavers that had placement of a cemented femoral stem with either early or late stage polymethylmethacrylate. Radiographs were assessed quantitatively by measuring the extent of radiolucency observed at the cement-bone interface. Specimens that had late stage cement had significantly less radiolucency in the middle zone region, corresponding to combined Gruen Zones 2 and 6. Similar trends were observed in the proximal and distal zone regions of the stem. Elevated stem insertion pressure associated with late stage cement can minimize void space between the cement and trabecular bone. These findings suggest that the surgeon should consider femoral stem placement later in the cement cure cycle, generating higher intramedullary pressure, and leading to improved cement intrusion into the surrounding bone.

Femoral stem insertion generates high bone cement pressurization

Adequate bone cement pressurization is critical in obtaining optimal femoral cement mantles during total hip arthroplasty. Pressurization can be generated during insertion of the femoral stem into the cement-filled canal. This may be clinically useful in augmenting conventional cement gun pressurization. Two factors, which were expected to influence the amount of insertion-induced pressurization, are the cement's cure state (viscosity) at the time of insertion and the femoral stem profile. This study evaluated the effect of these factors on cement pressurization during stem insertion. Femoral stems were inserted at a controlled rate into a reusable, simulated femoral canal. Intramedullary pressures were monitored at four locations along the canal's medial midline. The intrusion factor quantity, which accounts for pressure magnitude, duration of pressurization, and cement viscosity, was developed to quantify pressurization. Stem insertion into late cure stage (high viscosity) cement resulted in significantly higher intramedullary pressures (as much as 187% higher) and intrusion factors (as much as 43% higher) as compared with early stage (low viscosity) cement. The highest pressures and intrusion factors were found in the distal canal. A tapered stem profile resulted in significantly higher pressures (as much as 65%) and higher intrusion factors (as much as 63%) than a straight stem.

The influence of femoral rollback on patellofemoral contact loads in total knee arthroplasty

Increasing femoral rollback in flexion is thought to reduce patellofemoral contact load in total knee arthroplasty (TKA). The objectives of this study were to quantify the dependence of patellar load on rollback and to assess the effectiveness of posterior cruciate ligament (PCL)-retaining, PCL-sacrificing, and PCL-substituting TKA types in generating rollback. Nine cadaver knees were tested in simulated squatting. Six TKAs that were expected to produce varying amounts of femoral rollback were evaluated: PCL-retaining TKA, PCL-sacrificing TKA, a commercially available PCL-substituting TKA, and 3 modified PCL-substituting TKAs in which the anteroposterior position of the tibial post was varied. Kinematics, quadriceps loads, and patellofemoral contact loads were recorded. Significant differences in rollback were observed in the 30 degrees to 90 degrees flexion range. PCL-sacrificing TKAs generated the least rollback. PCL-retaining TKAs produced greater rollback but had the most variability. PCL-substituting TKAs produced the greatest and most reproducible rollback. Moving the tibial post posteriorly further increased rollback. Increased rollback correlated with reduced patellar load (-2.2%/mm). Reductions in patellar load of 17.6% were observed. Quadriceps loads were reduced by increasing rollback but to a smaller degree (-0.9%/mm). Rollback primarily affects patellar load rather than quadriceps load or efficiency.

Bending stiffness, torsional stability, and insertion force of cementless femoral stems

In cementless total hip arthroplasty, increased femoral stem flexibility and decreased fracture propensity are desirable characteristics. The slotting and tapering of the stem have been introduced to achieve this. These features should not, however, be allowed to interfere with the ability of the distal stem to provide initial mechanical stability, especially under rotation. This study was done to investigate the ability of slotted and tapered stem designs to reduce stiffness and insertion force while still maintaining adequate torsional strength. The torsional strength, maximum insertion force, and insertional work of straight, slotted, and taper stems were measured by inserting each type into rigid polyurethane foam and torque testing to failure. Bending stiffness of each stem design was calculated using numerical methods. When compared to a straight stem, a unislot stem has similar torsional strength, maximum insertional force, and work of insertion. The bending stiffness is decreased by 19% to 82% depending on the bending direction. A trislot design decreased torque strength by 29%, maximal insertion force by 36%, and work by 11%. Bending stiffness was decreased by 74% and was not dependent on bending direction. A 0.5-mm taper decreased torque strength by 11% and insertional work by 14%. No difference was seen in maximum insertional force. We conclude that the design features studied (slots and taper) are effective in decreasing stem stiffness and reducing fracture propensity.

Arthrodesis of the knee: experience with intramedullary nailing

Knee arthrodesis using an intramedullary nail has gained acceptance as treatment in difficult cases such as infection after total knee arthroplasty (TKA), neuropathic joint, and obesity. A retrospective review of 22 cases treated at our institution using an intramedullary nail for knee arthrodesis was performed. Deep infection after primary (11) or revision (6) TKA was the most common indication for this procedure. A long intramedullary nail was used in 3 cases, a long nail with a proximal interlocking screw was used in 6 cases, and a customized nail with a valgus bend and a proximal interlocking screw was used in 11 cases. A modular knee fusion nail was used in 1 case. Successful fusion occurred in all cases, although 4 patients required additional surgery. Average operative blood loss was 748 mL, and average time to union was 7 months. Shortening of the extremity averaged 3.2 cm. Tibiofemoral alignment was improved by using a customized valgus nail (average, 3.1 valgus; range, 1-5) when compared with a straight nail (average, 0.2 valgus; range, 3 varus to 3 valgus). No patient developed infection in the hip or ankle region as a result of the long intramedullary nail. Intramedullary nailing is an excellent technique for knee arthrodesis in difficult cases. A customized proximal interlocking nail with 5 degrees to 7 degrees of valgus and 5 degrees of anterior angulation improves tibiofemoral alignment and is straightforward to insert or extract should it be necessary. Stability and pain relief are rapid, and the fusion rate is maximized.

The effect of patella preparation for total knee arthroplasty on patellar strain: a comparison of resurfacing versus inset implants

This study was conceived to quantify variables in surgical technique that may lead to patellar fracture after total knee arthroplasty. Anterior surface strain on load-bearing cadaveric patellae was measured before and after patellar resurfacing or inset prosthesis placement. Variables studied were i) the type of prosthesis (resurfacing vs inset), ii) the depth of reaming or osteotomy during surface preparation, and iii) the overall thickness of the polyethylene/patella composite after implantation. Comparison of measured patellar surface strain patterns for the different prosthesis styles, which were implanted at varying depths, provided statistically significant data from which the following clinically relevant conclusions can be made: i) Patellar resurfacing is superior to inset prosthesis placement when comparing postoperative patellar strain (22% vs 28% increase in strain compared with preoperative values). ii) Osteotomy for patellar resurfacing is more tolerant to error by excess cutting than is reaming for inset prosthesis placement (25% vs 42% increase in strain with a 2-mm error). iii) If the ideal depth of cut or reaming is surpassed, attempts to re-create the original patellar thickness by using a thicker prosthesis are mechanically detrimental. Key words: patella, strain, resurfacing, complications.

Hip osteotomy arthroplasty: ten-year follow-up

We previously reported the initial success of combined osteotomy and arthroplasty of the hip for arthritis with femoral deformity. This technique has gained acceptance. We now report, for the first time, the ten year clinical and radiographic results with histology of 2 specimen. The osteotomies healed and the proximal femoral segment remained viable. One of three patients is symptom free without subsequent operative treatment. One of three patients had revision for acetabular loosening at eight years and biopsy of the proximal femur showed the proximal femoral segment to be viable. One of three patients had loosening of a macrofit bipolar prosthesis which required revision to total hip replacement at five years. Histology revealed viability of the proximal femur. All three patients are doing well at ten year follow-up. Based on the results of this study and current knowledge, the technique of osteotomy and arthroplasty for hip arthritis associated with femoral deformity is effective when combined with current techniques of ingrowth femoral component of total hip arthroplasty.

The transepicondylar axis approximates the optimal flexion axis of the knee

The traditional understanding of knee kinematics holds that no single fixed axis of rotation exists in the knee. In contrast, a recent hypothesis suggests that knee kinematics are better described simply as two simultaneous rotations occurring about fixed axes. Knee flexion and extension occurs about an optimal flexion axis fixed in the femur, whereas tibial internal and external rotations occur about a longitudinal rotation axis fixed in the tibia. No other translations or rotations exist. This hypothesis has been tested. Tibiofemoral kinematics were measured for 15 cadaveric knees undergoing a realistic loadbearing activity (simulated squatting). An optimization technique was used to identify the locations of the optimal flexion and longitudinal rotation axes such that simultaneous rotations about them could best represent the measured kinematics. The optimal flexion axis was compared with the transepicondylar axis defined by bony landmarks. The longitudinal rotation axis was found to pass through the medial joint compartment. The optimal flexion axis passed through the centers of the posterior femoral condyles. No significant difference was found between the optimal flexion and transepicondylar axes. To an average accuracy of better than 3.4 mm in translation, and 2.9 degrees in orientation, knee kinematics were represented successfully by simple rotations about the optimal flexion and longitudinal rotation axes. The optimal flexion axis is fixed in the femur and can be considered the true flexion axis of the knee. The transepicondylar axis axis, which is identified easily by palpation, closely approximates the optimal flexion axis.

The effect of surface coating of femoral prostheses implanted without cement: a 2- to 4-year follow-up study

A randomized, concurrently controlled, prospective, single-blinded, multicenter study was done to evaluate the effect of proximal surface coating of a femoral prosthesis on clinical and radiographic results of cementless total hip arthroplasty (THA). The Profile femoral prosthesis (DePuy, Warsaw, IN), an anatomic titanium alloy stem, was used in one of three configurations: (1) smooth, (2) porous coated, or (3) hydroxyapatite (HA) coated. Ninety-one cases were enrolled in the study, with seven cases lost to follow-up and 79 cases available for clinical review with 24- to 48-month follow-up. The study shows that HA-coated stems performed as well, if not better than, porous-coated or smooth stems. Results show HA-costed stems with statistically superior total Harris hip scores (microHA = 96.0) than smooth stems (microS = 85.1) (Student's t-test, P = 0.004). This was primarily due to differences between the functional score of the two groups (microHA - 31.6; microS = 27.9, P = 0.003). Porous-coated stems were intermediate in performance (microPC = 89.8), with hip scores that were statistically indistinguishable from both smooth and HA-coated stems. Our data support the hypothesis that clinical differences exist and are attributable to the type of surface coating used for the cementless femoral components in THA.

Knee kinematics in genesis total knee arthroplasty. A comparison of different tibial designs with and without posterior cruciate substitution in cadaveric specimens

Knee joint kinematics after total knee arthroplasty (TKA) are not well understood. This study measured knee kinematics before and after TKA in six cadaveric specimens. Different tibial surface contours (standard, flat, and dished) and slopes (10 degrees and 15 degrees) with the posterior cruciate ligament (PCL) intact as well as a posterior-stabilized design were studied. The anteroposterior and proximal-distal displacements of the tibia relative to the femur were measured during active knee extension. For the standard design, it was possible to restore the normal position of the tibia relative to the femur at 90 degrees of flexion to within 2 mm; however, restoration of the tibiofemoral position was not achieved with the knee in the extended position. At 90 degrees of flexion, all of the TKA components resulted in a posteriorly positioned tibia compared with the normal knee. The standard, flat, and dished components shifted the tibia into a proximal position compared with the normal knee, while the 15 degrees and posterior-stabilized components shifted the tibia distally. With the knee in the extended position, the standard, flat, dished, and posterior-stabilized designs placed the tibia posteriorly and proximally compared with the normal position of the tibia relative to the femur. The 10 degrees and 15 degrees sloped components placed the tibia in a more anterior position. Of the PCL-retaining designs tested, the 10 degrees sloped tibial component produced the closest to normal knee kinematics. Overall, normal kinematic behavior of the knee was not restored after TKA.

One-stage revision of periprosthetic fractures around loose cemented total hip arthroplasty

Fourteen cases of femoral fracture occurring about a loose cemented proximal femoral prosthesis are presented. All fractures occurred with relatively minor trauma, and significant preinjury osteolysis was present in all cases. Treatment consisted of immediate surgical revision of the loose femoral component using a long-stem noncemented component in conjunction with cerclage wiring. In most instances, morselized bone graft was used. Strut grafts were used in seven cases to improve stability. Two patients with extensive bone loss were unable to support a prosthesis and were treated with whole femoral allografts. Follow-up ranged from 24 to 84 months (mean, 49 months), except for one patient lost to follow-up at 12 months; evaluations consisted of Harris hip scores and radiographic analysis for fracture healing and implant stability. All fractures healed, and patient function increased dramatically. Postoperative Harris hip scores increased to an average of 74 points. Complications consisted of one postoperative fracture and four patients with femoral component loosening. No cases of component loosening were seen in the five cases in which components were designed for distal stability (four fully porous-coated, one fluted). Of the seven cases relying on proximal stability, two cases of early loosening and two cases of late loosening occurred. We recommend revision with long-stem, cementless implants in conjunction with cerclage wiring and strut grafts for the treatment of femoral fractures about loose cemented hip prostheses. Implant stability distal to the fracture is emphasized.

Cementless hemispheric acetabular components. A 4- to 8-year follow-up report

A retrospective radiographic analysis was performed on 71 cementless acetabular components followed from 4 to 8 years after surgery. A Harris-Galante (Zimmer, Warsaw, IN) cup was used in 46 cases and an Optifix (Smith & Nephew Richards, Memphis, TN) cup was used in 25 cases. There were 66 primary and 5 revision cases. Nonprogressive radiolucencies were common in both types of cups (64% of Optifix, 70% of Harris-Galante). Radiolucencies were almost exclusively less than or equal to 1 mm in width and were most common in zones 1 and 3. Ten cups had continuous but nonprogressive radiolucencies, none greater than 1 mm in all three zones. No radiolucent lines wider than 2 mm were seen in any case. Four cups had progressive radiolucency that stabilized. Radiolucency around fixation screws was seen in one case, and demonstrated stable ingrowth at revision surgery. No cases of osteolysis, screw breakage, migration, or loss of fixation surface occurred. A single case of a broken locking mechanism of a Harris-Galante cup 2 years after liner exchange is reported.

Posterior cruciate ligament strain biomechanics in total knee arthroplasty

To evaluate the role of the posterior cruciate ligament in total knee arthroplasty, 8 normal whole-leg cadaveric legs were studied. Strain patterns of the posterior cruciate ligament were measured during active and passive knee flexion extension. Total knee arthroplasty was performed, and posterior cruciate ligament strain was measured again. The standard tibial insert was removed, and 3 additional tibial trays were used: flat, 10 degrees sloped, and 15 degrees sloped. The posterior cruciate ligament strain was recorded for each tibial insert. Total knee arthroplasty with a standard insert produced a large range of posterior cruciate ligament strain values (+/- 6%). Of the 8 specimens, 3 produced excessively taut posterior cruciate ligament strain, 3 were slack, and 2 returned strain to the baseline strain value. Changing the surface contour and slope of the tibial inserts did not produce any consistent change in the posterior cruciate ligament strain pattern. The ability of total knee arthroplasty to reproduce normal posterior cruciate ligament strain behavior has not been demonstrated.

Allograft-host mismatch in revision total hip replacement

Mismatch between a structural femoral allograft and the distal host canal is a difficult problem in femoral reconstruction for revision of total hip replacement. A technique is presented that satisfactorily solves this problem and offers additional advantages over other allograft techniques, as illustrated in two cases.

Penetration of piperacillin-tazobactam into cancellous and cortical bone tissues

The penetration characteristics of piperacillin-tazobactam into cortical and cancellous bone tissues were investigated in 10 patients undergoing total hip replacement. The concentration ratios of piperacillin/tazobactam were 9.4 +/- 1.8 in cancellous bone tissue and 8.0 +/- 2.2 in cortical bone tissue, which were close to the 8:1 ratio of drugs administered. The mean ratios of drug concentrations in bone and plasma for cancellous and cortical tissue were 23 and 18%, respectively, for piperacillin and 26 and 22%, respectively, for tazobactam. The concentrations of tazobactam achieved are sufficient to exert anti-beta-lactamase activity and supportive of clinical trials involving bone and joint infections, including those caused by beta-lactamase-producing pathogens.

Tibial plateau coverage in total knee arthroplasty

Optimizing coverage of the resected tibial plateau is an important consideration in total knee arthroplasty. The tibial coverage of eight different tibial tray designs was examined in 35 resected tibial specimens. When no component overlap was permitted, the average tibial coverage of the different designs ranged from 76.4% to 80.8%. When the component was allowed slight overlap, a "surgical fit," the average coverage ranged from 78.5% to 85.5%. As a group, the six symmetric designs provided more coverage than the two asymmetric designs (p < 0.05). Areas of poor coverage were identified, and different tray geometries were compared. Asymmetric tibial components are thought to be more anatomic in nature and therefore cover the tibial plateau surface more completely than symmetric components. The results of this study do not support this, and in fact demonstrate that symmetric components can provide more coverage when compared with two asymmetric component designs.

Cementless hemispheric acetabular components. 2-4-year results

A retrospective clinical and radiographic analysis was performed on 99 patients (106 hips) undergoing total hip arthroplasty with noncemented Harris-Galante (Zimmer, Warsaw, IN) or Optifix (Smith Nephew Richards, Memphis, TN) acetabular components. There were 94 primary and 12 revision procedures with a minimum follow-up period of 24 months (range, 24-52 months). The cups were evaluated for evidence of vertical and horizontal migration, as well as the presence of radiolucencies at the bone-implant interface. Age, sex, component inclination and medialization, cup coverage, and number of fixation screws used were examined to determine the influence of these factors on the incidence of cup migration or radiolucent line formation. A radiolucent line was present in at least one zone in 60% of the Harris-Galante and 45% of the Optifix cups. Progressive radiolucent lines were noted in two of the Optifix and three of the Harris-Galante components. Two Harris-Galante cups (1.9%) were revised. There were no Optifix cup migrations or evidence of instability in the Optifix or remaining Harris-Galante cups. Although there was a trend toward an increased incidence of radiolucencies in those cups lacking complete coverage, no statistically significant radiographic predictors for failure or impending failure could be determined from this short-term follow-up study. With the exception of the two revisions, all acetabular components performed well clinically over the study period.

Prevention of longitudinal crack propagation around a femoral prosthesis: a study of cerclage wire fixation

This study examined the effect of single versus triple-wrap cerclage fixation techniques in preventing propagation of a longitudinal fracture around a cementless femoral prosthesis. A proximal filling femoral component was implanted in 14 matched pairs of fresh-frozen bovine femora, following placement of a 45-mm longitudinal crack in the anteromedial cortical wall of the proximal femur. In one group of seven pairs, a single cerclage wire was applied to one specimen of each pair. A triple-wrap of a single cerclage wire was similarly placed in one specimen of each of the other seven pairs. All specimens were axially loaded on a materials testing system machine and the force required to propagate the fracture of the proximal femur was recorded. A triple-wrap cerclage technique required a significant increase in the force to propagate a proximal femur fracture around a non-cemented prosthesis when compared to a single cerclage wire.

Failure of the polyethylene liner leading to notching of the femoral component in bipolar prostheses

Polyethylene wear is an increasingly recognized problem in joint replacement surgery. Three cases of polyethylene wear in bipolar hip prostheses are presented. Owing to failure of the polyethylene liner, impingement of the metal shell produced notching of the femoral component.

Operative treatment of distal femoral fractures proximal to total knee replacements

Twenty fractures of the distal part of the femur proximal to a total knee replacement were treated operatively by members of the New England Trauma Study Group. Notching of the anterior aspect of the femoral cortex was associated with only two of these fractures, and none of the knee prostheses was loose at the time of the fracture. All twenty fractures were treated with open reduction and stable internal fixation, and the operation on fifteen fractures was supplemented with bone grafts. Every fracture healed, and eighteen healed after a mean of sixteen weeks (range, six to forty weeks). Union of the other two fractures was delayed, but repeat open reduction and internal fixation combined with autogenous bone-grafting resulted in union. After operative treatment, the patients returned to the level of activity that they had had before the fracture. The pre-existing tibiofemoral alignment and range of motion of the knee were also restored. At the time of follow-up, the average clinical rating of the Knee Society for all twenty knees had not decreased compared with the score before the fracture.

Longitudinal crack propagation in bone around femoral prosthesis

Intraoperative femoral fracture is a well-recognized technical complication of cementless total hip arthroplasty. This study was designed to establish an in vitro model for initiation and propagation of fractures of the proximal femur in cementless THA and to assess the effect of fracture fixation in the form of cerclage wiring and drilling a hole in the distal extent of the fracture line. Fourteen human anatomic femur specimens were studied. Longitudinal cracks were made and propagation was performed on a materials testing system machine. A drill hole at the tip of a longitudinal crack does not prevent crack propagation. However, cerclage wiring has a statistically significant effect (p less than 0.025) on the ability of the fractured femur to withstand increased load.

Strength of cerclage fixation systems: a biomechanical study

This study examined the load to failure ratio and stiffness of eight different cerclage techniques commonly used in the clinical management of fractures. For a single-loop cerclage, titanium cable was the strongest, while stainless steel wire secured with a commercial tightener was the weakest (P < 0.05). When a single-loop configuration is necessary (i.e. trochanteric attachment) a cable system is superior to cerclage wiring. A double-wrap of either cable or wire was considerably stronger than any single-wrap cerclage technique and stronger than two cerclage wires (P < 0.05).

Extension splinting of palmar plate avulsion injuries of the proximal interphalangeal joint

Hyperextension injuries of the proximal interphalangeal joint have traditionally been immobilized in flexion. This may lead to a proximal interphalangeal flexion contracture of the joint. In an effort to prevent flexion contracture and to simultaneously avoid hyperextension laxity, we have immobilized these injuries in zero degrees of extension for 7 to 10 days. Immobilization is followed by buddy taping and active range of motion until 3 weeks after injury. Protective buddy taping is used until the 6-week point. We report our results using this treatment for only palmar plate avulsion fractures. We did not include proximal interphalangeal joint injuries associated with dorsal dislocation or major collateral ligament injury. Twenty-two of 45 patients were available for follow-up evaluation. Length of follow-up averaged 30 months (range, 6 to 36 months). A high percentage of patients had good or excellent results. In no patient did hyperextension laxity develop and in only one was there a flexion contracture. On the basis of these results, we recommend this treatment protocol for hyperextension injuries of the palmar plate of the proximal interphalangeal joint associated with small avulsion fractures.

Giant synovial cyst of the hip joint

Synovial cysts are known to occur in patients with rheumatoid arthritis. Their presentation in the hip joint, however, continues to be a diagnostic challenge. A case is presented involving a patient with a large synovial cyst of the hip, emphasizing the need for the orthopaedic surgeon to include synovial cyst in the differential diagnosis of a painless groin mass, particularly in patients with rheumatoid arthritis.

Occurrence of the plantaris tendon in patients sustaining subcutaneous rupture of the Achilles tendon

Many surgeons treat closed subcutaneous rupture of the Achilles tendon with primary surgical repair. Reinforcement of the primary repair can be accomplished easily using the plantaris tendon. Unfortunately, in the population of patients who sustain this injury, the plantaris is absent in 60% of patients. This is a statistically significant difference when compared to the absence of the plantaris tendon of less than 10% in reported cadaveric studies.

Retrieval of a broken intramedullary nail

This is a report of an improvised useful instrument for retrieving the distal fragment of a fractured intramedullary nail. Using a modified Kuntscher reaming guide and closed technique, the method was successfully used in three cases.