3. Adult Reconstruction (Hip & Knee) MCQs

Displaced intra-articular fractures of the glenoid fossa, as in this case, are best treated with open reduction and internal fixation through a posterior approach. ORIF through an anterior approach is very difficult and is not recommended. Significant disabilities are seen if these fractures are treated conservatively including chronic instability and DJD..............................................................

The modular femoral stem has fractured. Revision of the acetabular implant is appropriate because of the potential for damage to the existing cup from metal debris and femoral implant contact and to convert from a metal-on-metal articulation. Retention of the femoral stem is not recommended because of the concern for failure with only a neck exchange. Revision of both components is necessary.

DISCUSSION: The incidence of osteolysis is minimal in studies reporting the use of all polyethylene or monolithic metal-backed tibial components. Osteolysis has been reported in patients with total knee arthroplasties using cementless implants with modular components. Micromotion between the tibial tray and the polyethylene results in backside wear, leading to osteolysis. Osteolysis also has been reported in cemented posterior cruciate-substituting modular components. O’Rourke and associates reported a 16% incidence of osteolysis in patients with a posterior stabilized implant because of the use of modular polyethylene and the subsequent abrasive wear. Oxidation of the polyethylene that is the result of the method of sterilization and shelf life has also been implicated in the high incidence of osteolysis, along with patient factors such as activity level and weight. REFERENCE: O’Rourke M, Callaghan J, Goetz D, Sullivan P, Johnson R: Osteolysis associated with a cemented modular posterior cruciate substituting total knee design. J Bone Joint Surg Am 2002;84:1362-1371.

DISCUSSION: The patient’s symptoms at follow-up—pain, swelling, and difficulty descending stairs—suggest knee flexion instability. Considering his history, an incompetent PCL must be considered. Revision of the knee to a posterior stabilized or nonlinked constrained condylar implant (depending on the condition of the ligaments) likely is needed to address his symptoms. The difference in extension stability and flexion stability makes polyethylene exchange a poor option. A constrained rotating hinge design is not necessary. Repeat use of a PCL-retaining insert is not recommended. Tibial and femoral revision both are required. Correction of excessive slope will be attained with tibial revision, femoral component revision is required to convert to a PCL-substituting design. There is also an opportunity to increase posterior condylar offset if needed.

DISCUSSION: Advocates of resurfacing hip arthroplasty cite preservation of the proximal femoral bone stock as the main advantage of this procedure over total hip arthroplasty. Fracture of the retained femoral neck has been reported following resurfacing arthroplasty. The exact etiology of the latter is unknown. Technical errors, such as notching of the femoral neck or possibly disruption of the blood supply to the femoral head during extensive soft-tissue exposure, may result in femoral neck fracture. REFERENCES: Gabriel JL, Trousdale RT: Stem fracture after hemiresurfacing for femoral head osteonecrosis. J Arthroplasty 2003;18:96-99. Amstutz HC, Campbell PA, Le Duff MJ: Fracture of the neck of the femur after surface arthroplasty of the hip. J Bone Joint Surg Am 2004;86:1874-1877.

DISCUSSIONVideo 22 for referenceThis patient has an unstable cruciate-retaining TKA. The tibial cut appears to be substantial, necessitating a very thick polyethylene liner. In addition, the femoral component may be slightly more proximally located. Tests for flexion-extension gap balancing would indicate flexion instability. However, the possibility of infection remains, so screening blood tests are appropriate. The surgical treatment for this unstable knee is revision TKA to a more constrained implant, ensuring flexion-extension gap balancing. No evidence indicates that the knee is infected. A thicker polyethylene insert will not adequately balance the knee.

DISCUSSION: Stems are available for cemented and press-fit implantation. To be effective, press-fit stems should engage the diaphysis, as shown in Figures 3 and 4. They also assist in obtaining correct limb alignment. Short metaphyseal-engaging stems are associated with failure rates that range between 16% and 29%. Cemented stems may be shorter than press-fit stems, because they do not have to engage the diaphysis. Short, fully cemented stems offer the advantage of metaphyseal fixation. Hybrid stem fixation makes use of the metaphysis for cement fixation with metaphyseal cones or sleeves and diaphyseal-engaging press-fit stems.

The radiographs reveal both cement debonding at the lateral shoulder of the prosthesis and a cement mantle fracture. Both of these indicate a loose femoral component. The radiographs show a stress fracture with reactive bone on the lateral femoral cortex in conjunction with the cement mantle fracture. The acetabular component shows no evidence of loosening. Heterotopic bone usually is not a source of pain when it is Brooker grade I, as in this case. Parkinsonism generally is not associated with hip pain.

DISCUSSIONHip resurfacing offers several potential advantages over conventional total hip arthroplasty, particularly for patients younger than 75 years of age. This intervention can berelatively bone conserving and is appropriate in settings involving proximal femoral deformity, precluding the use of a traditional femoral component. The use of hip resurfacing in osteonecrosis has been controversial, however. Although there are several reports of successful use of these implants to address osteonecrosis, concerns remain about extensive femoral head involvement (exceeding 40%) and ability to support the femoral head cap. Consequently, hip resurfacing is not recommended for patients with large femoral head lesions.Evaluation of painful hip resurfacings requires a systematic approach. Radiographs can help surgeons assess implant position, loosening, or fractures. Serological studies including ESR, CRP, and serum cobalt and chromium levels can give clues as to whether infection, metallosis, or both are the underlying cause(s) of failure. Hip aspiration in the setting of metal-on-metal bearings necessitates a manual cell count and differential to avoid falsely elevated automated cell counts.Revision of failed hip resurfacings should involve revisions of both the femoral and acetabular components. Although successful retention of the acetabular shell has been described, concerns remain regarding cup circumference mismatch, which can lead to suboptimal clearance between the new bearing surfaces.

Patella baja is commonly encountered when converting a high tibial osteotomy (HTO) to a TKA. Patella baja most likely occurs because of scarring.

DISCUSSIONThe lateral femoral cutaneous nerve can be injured during a direct anterior approach to the hip. The superior gluteal nerve enters the gluteus medius from posterior to anterior approximately 5 cm above the greater trochanter. This nerve can be injured during the direct lateral and anterolateral approaches to the hip. Branches of the inferior gluteal nerve as well as the sciatic nerve can be injured during the posterior approach, and the obturator nerve can be damaged when performing a medial approach to the hip.

Question.16 . When comparing the results of cemented all-polyethylene tibial components to metal-backed components,the all-polyethylene tibiais more expensive.is more susceptible to fracture.is associated with an elevated risk for polyethylene wear.has an equivalent rate of aseptic loosening.has higher failure rates when used in patients younger than age 70.Question. 17 . When the liquid monomer (monomethacrylate) is added to polymer powder (polymethylmethacrylate),the activator in the liquid monomer (N,N-Dimethyl-p-toluidine) comes in contact with the initiator in the polymer powder and polymerization is initiated. What is the initiator?HylamerPolystyreneBarium sulfateBenzoyl peroxideZirconium dioxideQuestion.18 . Figure 197 is the radiograph of a 62-year-old woman who is seen in the emergency department with a dislocated left total hip arthroplasty. This is her seventh dislocation during the last 3 months and she most recently had a liner revision. What is the best next treatment step?Skeletal tractionOpen reductionClosed reductionComponent revisionHip abduction orthosis

DISCUSSION: The Thompson posterior approach is used in treatment of fractures of the proximal radius. Dissection is carried out through the interval between the extensor carpi radialis brevis (radial nerve) and the extensor digitorum communis (posterior interosseous nerve). To identify this interval, the forearm is pronated and the mobile lateral wad of muscles (the ulnar-most belly is the extensor carpi radialis brevis) is grasped with the thumb and finger and pulled from the much less mobile mass of the extensor digitorum communis. The furrow created is marked with a skin marker for subsequent skin incision. The skin incision follows a line from the lateral epicondyle of the humerus to a point corresponding to the middle of the posterior aspect of the wrist. Distally, the intermuscular plane is between the extensor carpi radialis brevis and the extensor pollicis longus. REFERENCES: Crenshaw AH Jr: Surgical techniques and approaches, in Canale ST (ed): Campbell’s Operative Orthopaedics, ed 9. St Louis, MO, Mosby-Year Book, 1998, vol 1, pp 128-129. Hoppenfeld S, deBoer P: Posterior approach to the radius, in Surgical Exposures in Orthopaedics: The Anatomic Approach, ed 2. Philadelphia, PA, Lippincott-Raven, 1992, pp 136-146. Thompson JE: Anatomical methods of approach in operations on the long bones of the extremities. Ann Surg 1918;68:309-316.

DISCUSSION: The radiographs show posterior flexion instability that is the result of a flexion-extension gap imbalance and posterior cruciate ligament incompetence after a posterior cruciate ligament-retaining TKA. The femur is anteriorly displaced on the tibia, with lift-off of the femoral component from the tibial polyethylene. Revision to a larger femoral component will address the larger flexion gap relative to the extension gap, and a posterior stabilized implant will address the posterior cruciate ligament insufficiency. Pagnano and associates, reporting on a series of painful TKAs previously diagnosed as pain of unknown etiology, showed that the pain was secondary to flexion instability. Pain relief was achieved by revision to a posterior stabilized implant. REFERENCES: Pagnano MW, Hanssen AD, Lewallen DG, et al: Flexion instability after primary posterior cruciate retaining total knee arthroplasty. Clin Orthop 1998;356:39-46. Fehring TK, Valadie AL: Knee instability after total knee arthroplasty. Clin Orthop 1994;299:157-162. Fehring TK, Odum S, Griffin WL, et al: Early failures in total knee arthroplasty. Clin Orthop 2001;392:315-318.

DISCUSSION: Nickel allergy is not an infrequent preoperative finding. Stainless steel and cobalt-chromium alloys contain relatively high concentrations of nickel. Titanium, oxidized zirconium, and polyethylene do not contain significant amounts of nickel. Titanium is not a good surface for the articulating portion of the femoral component because of its propensity for metallosis. Oxidized zirconium is the only suitable femoral component for patients allergic to nickel. A modular titanium tibial component or an all-polyethylene tibial component would be satisfactory for these patients. REFERENCES: Laskin RS: An oxidized Zr ceramic surfaced femoral component for total knee arthroplasty. Clin Orthop 2003;416:191-196.

This patient presents with HO 4 months after undergoing THA. Symptomatic HO may complicate nearly 7% of primary THA cases. Improvement in pain is expected within 6 months, and most patients will not need surgical treatment. Surgical excision may be warranted for symptomatic patients after full maturation of the HO, usually 6 to 18 months after the surgery. Patients can be followed with repeated serum alkaline phosphatase levels, which are elevated initially and should return to normal upon maturation of HO. Alternatively, a bone scan can show decreased activity once the HO has matured. Twenty-five milligrams of indomethacin 3 times daily for 6 weeks or 1 dose of irradiation at 700 to 800 Gy is effective in the prevention of HO, not for the treatment of established HO.

Extended tibial tubercle osteotomy is an extensile approach to revision total knee arthroplasty that affords excellent exposure and can facilitate removal of tibial sleeves and cones. This patient has had multiple surgeries, including a proximal tibial osteotomy, as well as poor range of motion, patella baja, and a well-fixed metaphyseal sleeve component. Classically, an extended tibial tubercle osteotomy provides outstanding exposure for component removal in the setting of prior high tibial osteotomy and patella baja. For this patient, it is important to recognize the patella baja on the radiographs, as well as the tibial sleeve. In many of these cases the osteotomy provides access to the sleeve to help with extraction, because the stem will not pull through the sleeve or detach from the tray to allow visualization of the sleeve. The extended medial parapatellar approach is just a long medial approach that typically yields good exposure but would not help with the patella baja or extraction of the tibial sleeve. The quadriceps snip would give good exposure to the knee but would not aid in tibial component removal. Lastly, the medial epicondyle osteotomy could help with exposure and tensioning of the medial complex of the knee but would not help with tibial component extraction.

DISCUSSIONThis patient likely has 1 conventional polyethylene hip (1999) and 1 hip with highly cross-linked polyethylene (HXLPE) (2002); most centers transitioned to HXLPE around 2001 to 2002. This explains the clear difference in the clinical and radiographic performance of the 2 hips during the second decade. There is clear evidence of decreased wear and osteolysis and clinical benefits (ie, decreased revision rate) during the second decade following the introduction of HXLPE for THA. Acute infection is unlikely considering the chronicity of symptoms. The radiographs show no obvious evidence of cup loosening. A pseudotumor attributable to trunnionosis, while reported, remains an infrequent clinical issue.

Pitting and delamination seen in tibial component retrievals on the bearing surface of a TKA is related to fatigue wear. Backside wear is shown in the photograph; this is where the lot numbers usually are present, but now they are not distinguishable because of backside wear. This wear mechanism is attributable to adhesive and abrasive wear. The nanometer-size particles created by this wear mechanism account for the higher prevalence of osteolysis associated with modular tibial components.

The recognized treatment for a proximal periprosthetic fracture is to first identify the extent and then optimize the correction of the fracture. Several studies indicate that proximal cerclage wiring is adequate to create "barrel hoop" stability of the proximal femur. Braided cables offer superior stability compared with twisted wires or Luque wires. Finally, the appropriate postoperative treatment is protected weight bearing for 6 weeks, with periodic radiographs taken at 2-week intervals. Other options such as cementing the femoral stem and using a revision arthroplasty device are indicated for unstable fractures.