William M. Mihalko

Antibiotic-impregnated Cement Spacers for the Treatment of Infection Associated with Total Hip or Knee Arthroplasty

![Graphic][1] Infection at the site of a total joint arthroplasty can be classified into four basic categories: Type I (early postoperative), Type II (late chronic), Type III (acute hematogenous), and Type IV (positive intraoperative cultures with clinically unapparent infection).nn![Graphic][2] The current standard of care for late chronic infection is considered to be two-stage revision arthroplasty including removal of the prosthesis and cement, thorough debridement, placement of an antibiotic-impregnated cement spacer, a course of intravenous antibiotics, and a delayed second-stage revision arthroplasty.nn![Graphic][3] The choice of the spacer, either articulating or nonarticulating, is based on many factors, including the amount of bone loss, the condition of the soft tissues, the need for joint motion, the availability of prefabricated spacers or molding methods, and antibiotic selection.nn![Graphic][4] Current data have demonstrated that the use of antibiotic-impregnated cement spacers has improved the outcomes of the treatment of infection associated with total joint arthroplasty.nnTotal joint replacement is one of the most frequent and successful types of operations in orthopaedics. Infection is a rare yet devastating complication of the procedure, with a reported prevalence of 0.5% to 3% and with a higher reported prevalence after total knee arthroplasty than after total hip arthroplasty1-4. There is also a higher rate of infection after revision hip and knee arthroplasties than after primary hip and knee arthroplasties1-8.nnTwo-stage revision surgery was first described in 1983 by Insall et al., who demonstrated the necessity of removing the implants as well as the cement and of introducing antibiotic therapy for definitive treatment9. This procedure has emerged as the standard of care for a late chronic infection at the site of a total joint replacement4,5,10-17. Garvin and Hanssen reviewed twenty-nine studies and found that two-stage …nn [1]: /embed/inline-graphic-1.gifn [2]: /embed/inline-graphic-2.gifn [3]: /embed/inline-graphic-3.gifn [4]: /embed/inline-graphic-4.gif

A new technique for determining proper mechanical axis alignment during total knee arthroplasty: progress toward computer-assisted TKA.

Successful total knee arthroplasty (TKA) relies on proper positioning of prosthetic components to restore the mechanical axis of the lower extremity. This report presents and analyzes a new noninvasive method using the Optotrack (Northern Digital Inc, Ontario, Canada) to accurately determine the center of the femoral head. This method, together with direct digitization of the bony landmarks of the knee and ankle intraoperatively, permits placement of the lower extremity in proper alignment intraoperatively. It also permits the surgeon to follow all the angles of movement or rotation and all displacements that occur at each step of the operative procedure. knee intraoperatively via a customized Windows-based program. In addition to presenting our first case, which, importantly, represents the first computer-assisted TKA in a patient, we report on the accuracy and reproducibility of the technique for locating the center of the femoral head obtained during an extensive series of cadaver studies. Location of the femoral head, a major aspect of effecting neutral mechanical axis alignment, appears to be possible to within 2-4 mm, which corresponds to an angular accuracy of better than 1 degree. This method requires no computed tomography scans or other preliminary marker placement. The only basic requirement other than the instrumentation described is a freely mobile hip, which is generally present in TKA patients.

Flexion-extension joint gap changes after lateral structure release for valgus deformity correction in total knee arthroplasty: A cadaveric study

At the time of total knee arthroplasty, the surgeon generally corrects excessive valgus knee alignment to anatomic valgus through release of lateral supporting structures. This study used a cadaveric model to i) study the amount of correction achieved with each release step in 2 sequences of lateral release, ii) compare the amount of release in extension versus flexion, and iii) measure any associated rotational changes of the tibia. Six fresh-frozen cadaveric knees were used to test the amount of change into varus after sectioning the iliotibial band (ITB), the popliteus tendon (Pop), the lateral collateral ligament (LCL), and the tendon of the lateral head of the gastrocnemius (LG). This sequence was then compared with a second sequence in another 6 cadavers as follows: LCL, Pop, ITB, and LG. The amount of valgus correction was tested in 90 degrees, 45 degrees flexion, and full extension. At each flexion angle, the corresponding releases were assessed with the tibia oriented vertically under its own weight, under tibial distraction with equal support from the lateral and medial soft tissues, and under a maximal varus deforming stress. Results showed that complete lateral structure release provides limited correction into a varus direction with a balanced distracted soft tissue gap or extension space (8.9 degrees with the LG released), and the lateral aspect of the flexion gap opens more than the extension gap (8.9 degrees compared with 18.1 degrees in flexion). Early LCL release provided a more uniform release of the joint gap, and rotational changes were variable, tending toward external rotation of the tibia (6.0 degrees in full extension with release of the LCL). We suggest that when severe valgus deformities are present, the LCL should be considered first for release and the Pop and ITB be used to grade the release.

Anatomic and Biomechanical Aspects of Pie Crusting Posterolateral Structures for Valgus Deformity Correction in Total Knee Arthroplasty A Cadaveric Study

Correction of valgus deformity during total knee arthroplasty is usually carried out by releasing lateral supporting structures from the femoral side of the joint. A new technique has been advocated that involves multiple stabs of the scalpel blade or pie crusting of the posterolateral corner. It is the hypothesis of this study that the correction achieved by using this technique occurs when the lateral collateral ligament is effectively released and that the common peroneal nerve may be at risk. Using a cadaveric model with 6 knees tested, significant differences were determined between 2 separate pie crusting steps as well as between releasing the lateral collateral ligament and popliteus tendons. Anatomic dissection studies also showed that in full extension the peroneal nerve may be less than the depth of a number 11 blade (16 mm) from the posterolateral corner, and the nerve may be at risk during this technique. These results show that major deformity correction obtained using the pie crusting technique is probably through effective release of the lateral collateral ligament.

F-18 Fluoride Positron Emission Tomography of the Hip for Osteonecrosis

AbstractOsteonecrosis (ON) of the femoral head continues to be a devastating disorder for young patients. We evaluated the F-18 fluoride positron emission tomography (PET) imaging modality for use in detection of the bone involved in ON of the hip. We retrospectively reviewed the records of 60 consecutive patients diagnosed with ON and interviewed all by phone. Eleven patients (17 hips) of those interviewed agreed to participate in the study. We classified the ON using the University of Pennsylvania classification system and compared each patient’s plain AP bone scan, single photon emission 3-D computed tomography, and MRI. ON was associated with HIV, alcohol, steroid use, and polycythemia vera in this group. Nine of 17 hips (8 patients) had acetabular increased uptake when using the F-18 fluoride PET scans that were not seen on MRI, single photon emission computed tomography, or bone scans. These data suggest earlier acetabular changes in osteonecrosis may exist that traditional imaging modalities do not reveal.n Level of Evidence: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Does Concomitant Low Back Pain Affect Revision Total Knee Arthroplasty Outcomes

AbstractThe number of revision total knee arthroplasties (rev-TKA) is increasing every year. These cases are technically difficult and add considerable burden on the healthcare system. Many patients have concomitant low back pain that may interfere with functional outcome. We asked whether having low back pain at baseline would influence amount and rate of improvement on standardized outcomes measures after rev-TKA. We retrospectively reviewed 308 patients from prospectively collected data in a multicenter study. A minimum 24-month followup was available for 221 patients (71.8%). Patients with low back pain at baseline had worse scores on most instruments than their counterparts at baseline, 12xa0months postsurgery, and 24xa0months postsurgery. The data suggest concomitant back pain in patients undergoing rev-TKA affects their outcomes as measured by standardized instruments. Orthopaedic surgeons should counsel their patients with back pain regarding the possibility of slower or less complete recovery.n Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Passive knee kinematics before and after total knee arthroplasty: are we correcting pathologic motion?

The change in coronal plane deformity throughout a range of flexion before and after total knee arthroplasty (TKA) has not been reported. Unlike most alignment assessments traditionally reporting coronal plane alignment in a standing position under static conditions, this study reports deformity throughout the flexion arc before and after deformity correction. One hundred fifty-two TKA patients using the anteroposterior axis for femoral component rotation and computer navigation techniques were included in the study. Deformity before TKA ranged from 17.5 degrees varus (deformity apex away from the midline) to 20.5 degrees valgus (deformity apex toward the midline) in full extension. Before TKA, deformity was not constant through an arc of motion and significantly decreased with flexion of 60 degrees and more (P < .01). The deformity after performing a TKA was not different (P = .478) throughout the flexion arc. The data determined that deformity is not constant throughout flexion in osteoarthritic knees preoperatively and that deformity throughout flexion can be corrected with the use of conventional alignment techniques during TKA.

Effect of one- and two-pin reference anchoring systems on marker stability during total knee arthroplasty computer navigation

Objective: This study investigated different infrared marker reference base attachments in cadaveric bone and their effects on alignment outcome when different loads were applied. Material and Methods: Five cadaveric specimens were used to test four reference base attachments: a locking one-pin (4.0 mm and 5.0 mm pins) and a two-pin clamp (Hoffman fixator, 3.0 mm and 5.0 mm pins, Stryker Inc., NJ). Each was tested with metaphyseal and diaphyseal attachments. A navigation system (Stryker Navigation, MI) was used for testing with applied incremental loads and torques (65 N and 1.0 Nm) to the different reference base configurations. Results: With 65 N the maximum change in distance to a verification point was 4.3u2009+u20091.6 mm with the 4.0 mm locking pin in metaphyseal bone. No difference in verification point distances was found with any two-pin configuration. Alignment changes greater than 4° resulted with the 65 N loads and a 4.0 mm pin. Conclusion: The results may prove beneficial in comparing the resulting error of different manufacturers and allow surgeons to realize the variability that may occur through incidental contact in the operating room.

Transient peroneal nerve palsies from injuries placed in traction splints

Two patients thought to have distal femur fractures presented to the emergency department (ED) of a level 1 trauma center with traction splints applied to their lower extremities. Both patients had varying degrees of peroneal nerve palsies. Neither patient sustained a fracture, but both had a lateral collateral ligament injury and one an associated anterior cruciate ligament tear. One patient had a sensory and motor block, while the other had loss of sensation on the dorsum of his foot. After removal of the traction splint both regained peroneal nerve function within 6 hours. Although assessment of ligamentous knee injuries are not a priority in the trauma setting, clinicians should be aware of this possible complication in a patient with a lateral soft tissue injury to the knee who is placed in a traction splint that is not indicated for immobilization of this type of injury.

Primary total knee arthroplasty for a complex distal femur fracture in the elderly: a case report

Fractures of the distal femur in the elderly account for 4–5% of fractures in the geriatric population and are usually due to low energy ground level fall onto a flexed knee. A high incidence of postoperative complications and poor results are secondary to associated co-morbidities and osteopenia in this age group resulting in high levels of comminution and articular damage at the time of injury. Preservation of knee function and early weight bearing should be the objectives of management in the geriatric population. We present in this case report of an elderly patient with comminuted distal femoral fracture who had Primary total knee arthroplasty as an alternative to internal fixation.RésuméLes fractures du fémur distal du vieillard représentent entre 4–5% des fractures des personnes âgées et surviennent habituellement par une chute sur le sol à basse énergie et le genou étant fléchi. Une haute fréquence de complications post-opératoires et des résultats médiocres sont de règle, associés à des co-morbidités, à l’ostéoporose fréquente à cet âge et responsable de lésions articulaires au moment du traumatisme.. La préservation de la fonction du genou et la mise en charge précoce doivent être les objectifs du traitement de la population âgée. Nous présentons un cas chez une personne âgée avec une fracture comminutive du fémur distal, traitée par une arthroplastie totale de première intention du genou, comme alternative à l’ostéosynthèse interne.