3. Adult Reconstruction (Hip & Knee) MCQs

DISCUSSIONThis patient has symptomatic severe pelvic and femoral osteolysis occurring after a metal-on-metal bearing THA. Bearing surface wear and taper wear (corrosion) are debris sources contributing to osteolysis, and both sources should be addressed at surgery. Current recommendations are to not remove a stable cementless femoral component unless the taper is damaged so badly that a new ball will not lock on the taper. There have been reports of repeat local tissue reactions when a new cobalt chromium ball is placed on a taper with corrosion damage. The current recommendation is to minimize the amount of cobalt at the taper junction, and this can be done by avoiding a cobalt chromium ball in favor of a titanium taper sleeve on the damaged taper with a ceramic ball on the new sleeve. Use of a ceramic head on a previously used trunnion poses risk for fracture of the ceramic head.

DISCUSSION: An unconstrained prosthesis dislocation is a disconcerting problem that is not easily resolved; however, revision to a semiconstrained prosthesis would best achieve both pain relief and stability. Removal of the components and distraction arthroplasty or conversion to a resection arthroplasty are options, but the results would be unpredictable with regards to pain relief, postoperative motion, or elbow stability. Arthrodesis is poorly tolerated. With revision to another unconstrained prosthesis, there is the risk of continued redislocation because of chronic ligamentous insufficiency. REFERENCES: Linscheid RL: Resurfacing elbow replacement arthroplasty: Rationale, technique and results, in Morrey BF (ed): The Elbow and Its Disorders, ed 3. Philadelphia, PA, WB Saunders, 2000, pp 602-610. Morrey BF, King GJ: Revision of failed total elbow arthroplasty, in Morrey BF (ed): The Elbow and Its Disorders, ed 3. Philadelphia, PA, WB Saunders, 2000, pp 685-700.

DISCUSSIONManaging complications following a failed TKA requires an understanding of the mode of failure and treatment principles. Generally, TKA can fail for the following reasons: infection, instability, aseptic loosening, stiffness, and extensor mechanism dysfunction.Managing an infected TKA requires knowledge of the timing and circumstances surrounding the infected implant. Patients with acute infections (symptom duration of fewer than 3 weeks) are candidates for debridement and prosthesis retention. Chronic infections (symptoms lasting longer than 3 weeks and for more than 3 months from the time of index arthroplasty) should be treated with resection arthroplasty, parenteral antibiotics, and reimplantation surgery at a later date. Evaluation of possible acute infections should include aspiration, serology, and alpha-defensin.Instability following TKA is a common cause of early failure and revision surgery. The etiology of instability can include overresection of the posterior condyles, collateral ligament insufficiency, and late rupture of the posterior cruciate ligament. Recognizing the cause of instability is critical to eventual successful revision. Typically, isolated polyethylene exchange is not effective or reliable to address instability. In many cases, component malrotation and ligament imbalance contribute to instability. Revision surgery focuses on restoration of the joint line, proper femoral and tibial component rotation, and restoration of the femur posterior condylar.Component loosening and osteolysis are the common mechanisms of TKA failure. Prior to revision, concurrent infection must be ruled out as a source of failure. At the time of revision, proper fixation and rotation of the femoral and tibial components must be ensured. If the components are well fixed and rotated, successful isolated bearing exchange and bone grafting in the setting of osteolysis is possible. Isolated component exchanges also can be successfully performed, provided the remaining components are in an acceptable position. However, when in doubt, revision of both components generally yields more consistent results.Stiffness following TKA can affect as many as 10% of patients following surgery. Depending on the timing and extent of arthrofibrosis, treatment options include manipulation under anesthesia or revision TKA. Manipulation typically is effective early during the postsurgicalcourse (for up to 4 months) and is most effective for loss of flexion. To address chronic stiffness and arthrofibrosis, revision TKA offers modest improvements in range of motion. Isolated polyethylene exchange has proven inconsistent in this setting, so revision of both components to ensure proper component rotation and joint line restoration offers the best chance to improve range of motion.Extensor mechanism complications also can occur following TKA. Although the frequency is decreasing with improved component design and surgical techniques, periprosthetic patella fractures can occur. Treatment centers on the integrity of the extensor mechanism and fixation of the patellar component (if resurfaced). In general, if the extensor mechanism is intact, nonsurgical treatment is favored. Surgical treatment of periprosthetic patellar fractures following TKA has been associated with high complication rates and low healing rates.

DISCUSSION: Salvage of a total elbow arthroplasty is possible with early aggressive management of acute infection (symptoms for less than 30 days) with serial irrigation and debridement and antibiotic bead placement. This form of treatment is indicated when there are no radiographic or intraoperative signs of loosening. However, successful treatment is largely dependent on the organism. Staphylococcus epidermidis is associated with persistent infection because it is an encapsulating organism, and it is best treated with implant removal and IV antibiotics.

DISCUSSION: The radiographs show disruption of the posterior column of the acetabulum with radiolucencies about the component. Because the patient requires a stable construct to allow the bone to heal, the treatment of choice is an antiprotrusio cage and a graft.

DISCUSSIONThis patient has a large postsurgical hematoma. Although his ESR and CRP level are elevated, they are not considered elevated given his recent surgery. Additionally, the hip aspiration reveals a synovial cell count lower than 10000 WBC/µL along with a low percentage of polymorphonucleocytes. Treatment at this time should consist of observation. The hematoma is likely attributable to postsurgical anticoagulation, considering his history of atrial fibrillation.

DISCUSSION: Proximal tibial osteotomy is appropriate for the younger and/or athletic patient who has mild to moderate medial compartment osteoarthritis. Relative contraindications include limited range of motion (e.g., flexion contracture of 15°), anatomic varus of greater than 10°, advanced patellofemoral arthritis, and tibial subluxation. Inflammatory arthritides involve all the compartments and are a contraindication to osteotomies around the knee. REFERENCE: Kelly MA: Nonprosthetic management of the arthritic knee, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 245-249.

The radiograph and intraoperative photograph show osteonecrosis with near complete head loss/collapse. A stemmed implant is more appropriate in this patient because there is very little bone to support a resurfacing implant. In a younger patient, a glenoid implant should be delayed as long as possible because of the eventual need for revision secondary to glenoid loosening and wear, especially in a young active male. The hemiarthroplasty may be converted to a total shoulder arthroplasty in the future.

DISCUSSION: Polyethylene particles generated as mechanical wear debris can be phagocytized by macrophages and enter a metabolically active state that releases cytokines, causing periprosthetic bone resorption. Significant osteolysis can occur in the pelvis with a porous-coated cementless socket without loosening of the component. If the acetabular component is modular, well positioned, well-designed with a good survivorship record, and remains undamaged after liner removal, the polyethylene liner can be exchanged and the lytic defects can be debrided and bone grafted. This implant is well positioned, has a good survivorship record, a good locking mechanism, and is modular. The hip arthroplasty needs to be aseptic for consideration of liner exchange.

DISCUSSION: The clinical result in this patient has been good, with no dislocations, suggesting that the components are in reasonably good position. The radiograph and examination at the time of surgery suggest that the acetabular component is well fixed. The surrounding bone of the acetabulum is osteopenic and there would most likely be considerable bone loss if the acetabular component is removed. Access to the osteolytic lesions is possible. Cementing an acetabular component into the retained socket will cause the least amount of bone loss, shorten the procedure, and most likely result in a functional hip.

A factorial randomized control trial design is more easily represented in a two by two table. Practically, patients are randomized to either treatment A and B, treatment A or control, treatment B or control, or no treatment. The strength of this trial design is that two interventions can be assessed with the same study population. Also, any interaction between the treatments can be determined (for example, does treatment A work differentially when combined with treatment B). The parallel design trial is the simplest and most classic design for a randomized controlled trial. In this trial design, participants are randomized to two or more groups of different treatments and each group is exposed to a different intervention and only that intervention. In the crossover design trial, both groups receive both interventions over a randomly allocated time period. Group A can receive the treatment, and after a suitable washout period, can receive the placebo. Group B can receive the placebo and later can receive the treatment; this produces within-participant comparisons. The crossover trial design has a limited role in surgical interventions because it is difficult or impossible for patients to receive both treatment interventions, such as plate and nail fixation, or a cemented versus a cementless total hip arthroplasty. Case control and case series are not randomized trials, but observational studies.

Advanced glycation end-products (AGEs) are found in aging and osteoarthritis (OA) and result in increased articular cartilage stiffness and increased brittleness.AGEs are produced from spontaneous nonenzymatic glycation of proteins when sugars (glucose, fructose, ribose) react with lysine or arginine residues. Because of the low turnover, cartilage is susceptible to AGEs accumulation. The accumulation of AGEs has been thought to play a role in the development of OA of the knee and ankle.Li et al. reviewed age-related changes in cartilage. They state that with aging, there is excessive collagen cross-linking increases cartilage stiffness, while shortening/degradation of aggrecan leads to loss of sugar side chains and water-binding ability, while increased levels of AGEs are associated with a decline in anabolic activity. There is also increased chondrocyte death and/or apoptosis.Anderson et al. reviewed the relationship between osteoarthritis and aging. They state that knee cartilage thins with aging (especially on the femoral and patellar sides, suggesting a gradual loss of cartilage matrix. AGEs formation leads to modification of type II collagen by cross-linking of collagen molecules, increasing stiffness and brittleness and increasing susceptibility to fatigue failure.Incorrect Answers:

The radiographs reveal acetabular component failure with bone loss. The best option for survivorship is a cementless porous-coated acetabular component. This patient may or may not require structural bone graft, which may need to be determined at the time of surgery. Bipolar implants and cemented acetabular components for revision surgery have not demonstrated long-term success. The use of a protrusio ring is reserved primarily for massive bone loss such as a Paprosky type III bone loss with significant superior migration of the acetabular component.

DISCUSSION: Both cemented and cementless total knee arthroplasties depend on adequate fixation of the tibial component to promote long-term survivorship. An effective stem and adequate peripheral fixation of the tibial component to the cancellous-cortical portion of the proximal tibia are necessary for cementless fixation. Peripheral screws and pegs can serve as adjunctive fixation to decrease micromotion and shear forces and allow bone ingrowth to occur. Careful preparation of the proximal tibial surface can minimize fixation failure. Cemented fixation of the tibial stem should be performed in addition to the plateau. Osteolysis, polyethylene wear, and failure at the insert/tray locking mechanism have not occurred. Posterior cruciate ligament retention has not caused the tibial component fixation failure. REFERENCE: Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 275-279.

DISCUSSION: Peak embolization is observed during femoral stem insertion. Embolization is also observed during acetabular preparation and hip reduction. REFERENCES: Lewallen DG, Parvizi J, Ereth MH: Perioperative mortality associated with hip and knee arthroplasty, in Morrey BF (ed): Joint Replacement Arthroplasty, ed 3. Philadelphia, PA, Churchill-Livingstone, 2003, pp 119-127. Ereth MH, Weber JG, Abel MD, et al: Cemented versus noncemented total hip arthroplasty: Embolism, hemodynamics, and intrapulmonary shunting. Mayo Clin Proc 1992;67:1066-1074.

DISCUSSIONIn Question 138, pain and swelling following a metal-on-metal large-head THA represent a classic presentation for a pseudotumor from metallosis secondary to either articular metal wear or trunnionosis. For this patient, infection should be ruled out with laboratory studies (erythrocyte sedimentation rate and C-reactive protein) and joint aspiration. Metal ion levels and metal artifact reduction sequence MR imaging or ultrasound would be helpful to confirm the diagnosis of pseudotumor. In Question 139, chronic hip pain following elective THA with an antecedent postsurgical wound constitutes a typical presentation for chronic periprosthetic infection. Aseptic loosening could be considered although the timeline is short; bloodwork and joint aspiration would be appropriate investigations. In Question 140, giving way of the knee suggests quadriceps muscle dysfunction likely related to prolonged pressure on the femoral nerve from retractors during a long revision case. The pattern of weakness does not fit a sciatic nerve palsy. In Question 141, the presentation is typical of a prosthetic dislocation, most of which occur during the early postsurgical period following THA.

DISCUSSION: The patient has extensive degenerative changes in both the medial and lateral compartments within the knee; therefore, arthroscopic debridement or an osteotomy will not be helpful. A patellar arthroplasty will not address the medial and lateral compartments. Because the extensor mechanism provides a significant amount of anteroposterior stability, a posterior cruciate-substituting total knee arthroplasty is the treatment of choice for this patient. REFERENCES: Martin SD, Haas SB, Insall JN: Primary total knee arthroplasty after patellectomy. J Bone Joint Surg Am 1995;77:1323-1330. Pagnano MW, Cushner FD, Scott WN: Role of the posterior cruciate ligament in total knee arthroplasty. J Am Acad Orthop Surg 1998;6:176-187.

DISCUSSION: Trunnionosis is a recently recognized complication following total hip arthroplasty and can occur when a cobalt alloy femoral head is used on a titanium alloy or cobalt alloy femoral stem. Patients often present with pain or swelling around the hip but at times can present with instability. Certain femoral stem designs have been associated with increased reports of trunnionosis. In a patient with a cobalt alloy femoral head who presents with instability, swelling, and weakness around the hip, the potential for trunnionosis and an adverse local tissue reaction should be considered.

Again referenced article is not helpful. Here is the thought process. Porous coating allows for bony ingrowth, andcreates stress shielding. The force is seen through the femoral head into the stem and transfers to the bone at areas ofingrowth and transmitted distally. As a result the part being skipped is the greater trochanter and leads to osteolysis by Wolf’s law and can result in fracture.The osteolysis created about the acetabulum is due an inflammatory mechanism imparted on the wear debris from thebearing surfaces. This osteolysis rarely creates fractures.The fractures about the stem are most commonly caused by the difference in modulus between the stem and boneback to thisquestion next question

DISCUSSION: In patients with infected implants, treatment usually involves debridement and exchange of the infected components. In rare cases, when there is severe comorbidity and immune system compromise, as there is with this patient, a form of chronic suppression is indicated. This patient’s function is quite satisfactory and, even though there is only a 21% to 38% chance of success (Hirawaka as quoted by Mulvey and Thornhill), an attempt at suppression therapy is indicated. The patient must be followed closely to monitor the potential complications of long-term antifungal therapy and to monitor the integrity of the joint, looking for bone or soft-tissue destruction. Because the patient has satisfactory motion and quadriceps strength, no bracing or other assistive device (except for the walker he is now using) is indicated. REFERENCE: Mulvey TJ, Thornhill TS: Infected total knee arthroplasty, in Insall JN, Scott WN (eds): Surgery of the Knee, ed 3. Philadelphia, PA, Churchill Livingstone, 2001, vol 2, pp 1857-1890.