3. Adult Reconstruction (Hip & Knee) MCQs

As stated in the above article, the number one location for osteolysis is at the sites of screw fixation for the tibial component. Development of osteolysis on the tibial side of the implant may be influenced by threefactors. First gravity and weight bearing through the medial side of the knee tend to localize the debris particulate polyethylene on the tibial side. Second, on the femoral side if the osteolytic process is initiated along the implant-bone interface, the flanges of the femoral implant obscure a radiographic diagnosis. Finally, the addition of screws to the tibial implant provide avenues for the migration of debris into the bone. In the patients with osteolysis all had very large amounts of polythylene and metal particles less than one micrometer in size leading to intense histiolytic response.

DISCUSSIONThe tibial polyethylene insert shows anterior post wear damage from anterior CAM-post impingement in a posterior stabilized knee. It is associated with excessive femoral component flexion and excessive posterior tibial slope in a TKA construct. It is not associated with coronal plane alignment.

Cement technique, relative stem to canal size and position, stem design, surgical technique, and femoral anatomy are important factors in cemented stem survivorship. Varus stem position, a wide diaphyseal to metaphyseal ratio (stovepipe femur), thin cement mantles (1 mm or less), and nonrounded femoral stem designs are negative prognostic factors for stem survivorship. A 2 to 3 mm circumferential cement mantle is considered optimal for survivorship.

Poor reference for this question. You can arrive at the answer by strict process of elimination. A few things first. Keep in mind that ceramic/ceramic bearings have the lowest wear rates and thus produce fewer number of particles (1 and 5 out). Serum metal levels in metal-on-metal arthroplasties increase following surgery, as corrosion takes place (3 out). In the mid 90's there was a concern for malignancy in patients with metal-on-metal arthroplaties; however, studies have found gross variation in the incidence of cancer in patients with such arthroplasties, and no statistical significant difference. There is still no consensus concerning the long-term effects of metal-onmetal articulations (2 out).This leaves 4 as an attractive answer. We know that metals are subject to corrosion, which is a chemical reaction process that weakens the metal. All metals corrode; the severity of corrosion is determined by the chemical composition of the metal. There are three types of corrosion affecting implant materials: galvanic, crevice, and fatigue. Galvanic corrosion occurs when an electrical current is established between two metals that have different chemical compositions. To avoid catastrophic galvanic corrosion, stainless steel should never be used with either cobalt or titanium alloys. Crevice corrosion occurs when the fluid in contact with the metal becomes stagnant, which then becomes acidic secondary to oxygen depletion. Finally fatigue corrosion may occur if the passive oxide film on the implant surface has been scratched or cracked. Once fatigue corrosion begins, the implant weakens and may fail below the endurance limit of the material.Orthopaedic Knowledge Update: Hip & Knee Reconstruction 2. Rosemont, IL, Americal Academy of Orthopaedic Surgeons, 2000, pp 25-34. Jazrawi L, Kummer FJ, Di Cesare PE: Alternative Bearing Surfaces for Total Joint Arthroplasty. J Am Acad Orthop Surg 1998;6:198-203Which of the following findings is a predisposing factor for an acute lateral patellar dislocation?Hypoplastic medial femoral condyleDysplastic vastus lateralisPatella bajaDecreased Q angleExcessive internal rotation of the femurMost acute patellar dislocations occur during the second decade. Lateral dislocations are by far the most common direction of injury. Patients with abnormal patellofemoral mechanics sustain patellar dislocations with less trauma and soft tissue injury compared with normal subjects. Predisposing factors for dislocation include hypoplastic lateral femoral condyle, dysplastic vastus medialus obliqus (VMO), patella alta, contracted iliotibial band, tight lateral retinaculum, valgus knee deformity, increased Q angle, ligamentous laxity, lateral insertion of patellar tendon on tibia, excess internal rotation of the femur / external rotation of tibia, previous patellar dislocations and injury to medial patellofemoral ligament (MPFL). Some authors favor open exploration of the MPFL following arthroscopic examination for acute patella dislocations.Braham S, Vrahas MS, Fu FH: Knee fractures in the athlete. Orthop Clin North Am 2002;33:566-574Which of the following substances is labeled with technetium Tc 99m in a conventional bone scan?calciumphosphateAlkaline phosphataseBiphosphonateType I collagenItem deleted 04.47What is the preferred type of graft for skin loss of the palmar aspect of the hand?Unmeshed split-thicknessMeshed split-thicknessMultiple pinchFull-thicknessFull-thickness with attached subcutaneous fatIn general, soft tissue coverage in the hand should supply tissue that is thin, pliable, durable, and that allows for tendon gliding. The goal is to replace "like with like". Ideally, the reconstruction should allow for sensation, dynamic function, and restoration of form. Skin grafts are usually autografts and they are either splitthickness skin grafts (STSG) or full-thickness skin grafts (FTSG). Compared to STSG, full thickness grafts contract less, are more durable and flexible, and have better sensation. They are the preferred grafts for areas prone to shear and load such as fingertips, the palm, and areas over joints. STSG are better for dorsal hand wounds. STSG can be meshed or unmeshed. Meshed STSG have fewer problems with seromas, hematomas, and infections; therefore, they have better take. However, the appearance of unmeshed STSG is more aesthetically satisfying.Hand Surgery Update 3: Hand, Elbow, & Shoulder. Rosemont, IL, American Society for Surgery of the Hand, 2003, pp470-492.What ligament is attached to the displaced distal tibial articular fracture shown in Figures12a and 12b?Anterior talofibularAnterior tibiofibularPosterior talofibularPosterior tibiofibularCalcaneofibularAnkle (AP & lateral) x-rays show a non-displaced lateral malleolus fracture and a minimally displaced posterior malleolar fracture. Mortise is well preserved. No tibiotalar dislocation/subluxation. Medial malleolus seems intact. The injury to the posterior plafond component orposterior malleolus is a posterolateral avulsion fracture resulting from the pull of the posterior-inferior tibiofibular ligament. If this fragment constitutes >25-30% of the plafond surface, and/or is displaced more than 2 mm, the fragment needs internal fixation. The origin of the posterior tibiofibular ligament is broad, covering most of the horizontal distal surface of the tibia. As the ligament fibers sweep laterally and distally to insert on the fibula they fit over the trochlea.Orthopaedic Knowledge Update: Trauma 2. Rosemont, IL, Americal Academy of Orthopaedic Surgeons, 2000, pp 203-225Michelson JD: Ankle fractures resulting from rotational injuries. J Am Acad Orthop Surg 2003;11:403-412A 35-year-old man with ankylosing spondylitis has progressive sagittal plane imbalance, difficulty with horizontal gaze, and thigh fatigue with standing. Radiographs are shown in Figures 13a and 13b. Maximum correction of the sagittal decompensation can be accomplished at a single level by which of the following procedures?Smith-Peterson osteotomy (posterior closing wedge hinging on the posterior longitudinal ligament)Transpedicular wedge resection osteotomyCombined anterior and posterior surgeryAnterior opening wedge osteotomyVertebral column resectionIn the radiographs we have AP / lateral spinal xrays of a patient with known ankylosing spondylitis. Of note, there are bilateral total hip arthroplasties. There is marked thoracic kyphosis, and mild thoracolumbar scoliosis. No evidence of acute fx/ dislocations. Notice that the question specifically states… maximum correction of the sagittal decompensationcan be accomplished at a single levelby which of the following procedures? Surgical correction of the kyphosis deformity with osteotomy was first done in 1945. Since then, surgeons have tried several different approaches and techniques to correct the stiff kyphosis. The transpedicular wedge osteotomy was described by Thomasen (1985) for the correction of deformity secondary to ankylosing spondylitis. In this technique the spinous process of L2 and the upper part of L3 are removed; the laminae of the second and the upper part of the third lumbar vertebrae are also removed as well as the articular processes of L2-3 and the pedicles of L2. A wedge fracture is created on the posterior wall of the vertebral body of L2. Then, plates are fixed to the spinous processes of T12-L1 and L3-4. Thomasen osteotomy places the apex of correction anteriorly, serving to shorten the spine and avoid anterior column lengthening. Advantages include the prevention of neural compression by creation of a large, shared neural foramen through removal of the pedicles, limited stretch of anterior structures, and cancellous bone healing. This technique provides maximum correction of the deformity, and can be accomplished at a single level. You either know it, or you don’t.Berven SH, Deriven V, Smith JA, Emami A, Hu SS, Bradford DS: Management of fixed sagittal plane deformity: Results of the transpedicular wedge osteotomy. Spine 2001;26:2036-2043.Thomasen E: Vertebral osteotomy for correction of kyphosis in ankylosing spondylitis.Clin Orthop 1985;194:142-152

DISCUSSION: The radiographs show posterior instability caused by an absent posterior cruciate ligament. The tibia is significantly displaced posteriorly with respect to the femur. This can be demonstrated with a lateral radiograph obtained with the knee in flexion. The anterior cruciate ligament has been resected but is not responsible for the instability shown.

The incidence of osteolysis, particularly around fixation screws in the tibia, can be as high as 30%. Stable femoral component fixation is generally maintained. Infection, subluxation of the patella, and stiffness can occur with either cemented or cementless fixation.

Periprosthetic fracture is the third most common reason (after loosening and infection) for revision surgery after total hip arthroplasty (THA). Late periprosthetic fracture risk is 0.4% to 1.1% after primary THA and 2.1% to 4% after revision THA. Risk factors for periprosthetic fracture include age over 70 years, decreasing bone mass, and loosening of implants and osteolysis. The risk of concomitant infection in the presence of a periprosthetic fracture is 11%, according to Chevillotte and associates. Obtaining presurgical aspiration or intrasurgical tissue for culture is recommended if concomitant infection is suspected.

DISCUSSION: The surface hardness of titanium is low compared with that of cobalt-chromium alloys. Titanium articulations are easily scratched, resulting in a significantly increased rate of wear and debris production. The wear and resulting lysis can also result in an increased rate of loosening.

Retrieval studies have shown that the debris particles produced by metal-on-metal articulations in total hip arthroplasty are several orders of magnitude smaller and may be up to 100 times more numerous than those found with metal-on-polyethylene articulations.

External rotation of the femoral and tibial components has been shown to aid in tracking. Likewise, medialization of the patellar button aids in patellar tracking and prevention of lateral subluxations and dislocations.

Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.

A 32-mm head design results in less linear wear but more volumetric wear particles. Modular components that allow motion between the polyethylene insert and the shell can result in backside wear. The oxidative degradation of gamma-irradiated polyethylene stored in air leads to increased wear. All of these factors lead to a greater particulate load and more osteolysis. Circumferential porous coating blocks ingrowth of particle-laden fluid and decreases osteolysis.

The radiographs show substantial valgus malalignment of the femoral component, with lateral mechanical axis deviation. Clinically, by examination she displays instability and stiffness as a result. Revision knee replacement is appropriate and should consist of total revision to stemmed femoral and tibial components with a varus-valgus constrained insert, given the likely attenuation of the medial collateral ligament. Open debridement with ligament balancing and polyethylene exchange do not address the underlying cause and are inappropriate. Distal femoral osteotomy is not useful in the setting of previous total knee replacement. Nonsurgical treatment with an unloader brace would be ineffective in correcting the alignment.

The patient has grade IV heterotopic ossification with the limb in an abnormal nonfunctional position. Treatment should consist of excision of the bone to restore hip motion and prophylaxis to prevent recurrent formation. The best time to excise the bone is controversial, with no conclusive evidence supporting early or late excision.

Slight external rotation of the tibial component will cause a net medialization of the tibial tubercle when the knee is articulated. This will help centralize the extensor mechanism over the trochlear groove and minimize the tendency for lateral subluxation. Internal rotation of the femoral component increases the risk of patellar instability. Anterior translation of the tibial component moves the patellar tendon insertion posteriorly, and may increase force on the patella but should not substantially alter patellar tracking. Clinical studies have shown no patellofemoral benefits to the use of fixed- or mobile-bearing designs. Thicker patellar components will not improve tracking, and may compound the problem.

DISCUSSION: Most clinical venous thromboembolism events occur between the second and sixth weeks after surgery. It is estimated that 10% of patients are readmitted to the hospital within the first 3 months after total hip or knee arthroplasties. Most pulmonary events on the day of surgery are related to fat embolism or cardiac events.

DISCUSSION: In the absence of component malpositioning, hip pain, or other compelling reasons to reoperate, a squeaking ceramic bearing is not an indication for revision surgery. The patient can be reassured and observed. Hopefully, with a better understanding of acoustic phenomena following ceramic total hip arthroplasty, this complication can be minimized.

DISCUSSION: Controversy persists over what exactly is the best approach to managing patients with metal-on-metal (MOM) hip arthroplasties. All patients with painful MOM hip arthroplasties should be examined for fixation loosening, wear/osteolysis, and infection—no differently than patients without MOM hip arthroplasties. It is recommended to obtain serum trace element levels. If the levels are high, cross-sectional imaging should be obtained to determine whether any pseudotumor or tissue necrosis is present around the hip arthroplasty. Hip aspiration should be considered if concern for infection exists. Adverse tissue reaction has been identified to occur around MOM hip arthroplasties. The predominant histologic feature is tissue necrosis with infiltration of lymphocytes and plasma cells.

DISCUSSION: The radiograph reveals that the femoral component is grossly loose as evidenced by disruption of the cement column; therefore, retention of the original components will not yield a successful outcome. A cementless revision is the procedure of choice. A strut graft and/or plate may be added at the surgeon’s discretion. A resection arthroplasty would only be considered in a nonambulatory patient. Cemented fixation of the revision component would be problematic given the numerous fracture fragments and the inability to contain the cement.

In this scenario, the flexion gap needs to be increased. Increase in flexion gap can be accomplished by downsizing the femoral component and increasing posterior tibial slope. In posterior cruciate-retaining TKA procedures, recession or release of the posterior cruciate ligament can loosen the flexion gap, allowing for an increase in flexion. Flexing the femoral component tightens the flexion gap, and downsizing the tibial insert thickness decreases flexion and extension gaps, while resection of the distal femur only increases the extension gap.