3. Adult Reconstruction (Hip & Knee) MCQs

The experimental data for this answer came from Anouchi et al The Effects of Axial Rotational Alignment of the Femoral Component on Knee Stability and Patellar Tracking in Total Knee Arthroplasty Demonstrated on Autopsy Specimens. This study looked at knee stability, patellar tracking, and patellofemoral contact points with the femoral component positioned in 5 degrees internal, 5 degrees external, and neutral alignment in relation to the posterior femoral condyles. Total knee arthroplasty was performed on four cadavaric specimens without lateral release.Internally rotating the femoral component produced abnormal laxity seen at 30, 60, and 90 degrees of flexion. There was no gapping noted in the neutral or externally rotated specimens.The normal pattern for patellar tracking was a gentle curve with maximal deflection at 15 and 60 degrees of flexion. The maximal medial displacement were lowest for the externally rotated specimens.Although contact areas could not be quantitatively measured accurately, the contact areas were more evenly distributed between the medial and lateral sides of the patella in the externally rotated specimens than they were in either the internally rotated or neutral specimens.You have to be careful interpreting this data at least in reference to knee stability. In this study a perpendicular tibial cut was made. The normal tibia has a 30 degree varus slope and thus more bone is resected from the lateral surface. External rotation of the femoral component compensates for this.No tests were done with lateral placement of the femoral component or medial placement of the patellar component.

DISCUSSIONThe literature has demonstrated increased risk for complications among obese patients undergoing TKA (10%-30%). An evaluation of TKA among obese patients revealed 3- to 9-fold higher incidence of wound complications and deep-seated infection. Belmont and associates demonstrated that patients with a BMI higher than 40 are at higher risk for overall complications than patients with a BMI lower than 25, with a particularly high risk for developing local wound complications and infection. An increased risk for thromboembolic complications was not shown among obese patients undergoing TKA. Patient-reported outcome scores among obese patients undergoing TKA are equivalent to those of nonobesepatients. There are conflicting data regarding the outcome and survivorship following TKA for obese patients. Although some studies show a difference in patient-reported outcomes at differing postsurgical intervals, most obese patients undergoing TKA are satisfied with the procedure.

Many studies have looked at patient outcomes following hip fracture surgery. While early surgery in these patients is recommended, medical optimization prior to surgical intervention is warranted in all cases. Anesthetic type and discharge status have not been proven to alter patient outcomes. Total hip arthroplasty has improved function at 1 year compared with hemiarthroplasty; no changes in mortality have been reported.

DISCUSSION: In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia, as seen in varus knees. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA. The anteroposterior (Whiteside's) axis is a reliable reference for femoral rotation.

DISCUSSION: The authors cited in the references examined large databases to determine the risk factors for conversion to total hip arthroplasty after arthroscopic surgery of the hip. In the study by Kester and associates, obesity had an odds ratio (OR) of 5.6 for conversion to hip arthroplasty, whereas age over 60 years had an OR of 3.8. Diagnosis of osteoarthritis is also a significant factor, but obesity is often cited as the strongest predictor in these studies.

DISCUSSION: Although dislocation can occur anytime after hip arthroplasty, the highest incidence is observed within the first few months. Dislocation occurring many years after arthroplasty has also been described. The presumed etiologic factors for late instability include long-standing problems with the prosthesis (such as malpositioning of the components) with late manifestation, trauma, deterioration in the neurologic status of the patient, and polyethylene wear. The eccentric position of the femoral head in this patient confirms polyethylene wear. The femoral stem is well-fixed, and the greater trochanter osteotomy has united well. The minor osteolysis observed around the proximal femur is also the consequence of wear and is not the cause of instability.

DISCUSSION: Multiple studies have shown that the size of an ultra-high molecular weight polyethylene particle generated by total hip implants is typically less than 1 micron. This finding is significant in that particles of that size are readily phagocytized by macrophages. REFERENCES: Campbell P, Ma S, Yeom B, McKellop H, Schmalzried TP, Amstutz HC: Isolation of predominantly submicron-sized UHMWPE wear particles from periprosthetic tissues. J Biomed Mater Res 1995;29:127-131. Shanbhag AS, Jacobs JJ, Glant TT, Gilbert JL, Black J, Galante JO: Composition and morphology of wear debris in failed uncemented total hip replacement. J Bone Joint Surg Br 1994;76:60-67. Maloney WJ, Smith RL, Schmalzried TP, Chiba J, Huene D, Rubash H: Isolation and characterization of wear particles generated in patients who have had failure of a hip arthroplasty without cement. J Bone Joint Surg Am 1995;77:1301-1310.

EXPLANATION: Wall and Stern published a report on MCP joint pyrolytic carbon arthroplasty for osteoarthritis and another on PIP joint pyrolytic carbon resurfacing arthroplasty for osteoarthritis. They found different outcomes, and MCP joint implants outperformed PIP joint implants. Of eleven MCP joint arthroplasties, two produced asymptomatic squeaking and clicking, whereas eleven of 31 PIP joint implants produced this problem. No dislocations were reported among the MCP joint implants, but five PIP joint dislocations were observed. Outcomes were measured by the Michigan Hand Outcomes Questionnaire in both studies and were satisfactory for the MCP joint implants, with an average score of 80. The PIP implants did not fare as well, showing a higher degree of pain along with an average score of 53. The authors noted that, in the 15 patients in the PIP study who had unilateral surgery, the uninvolved, nonsurgical hand motion was actually statistically significantly (P<0.01) better than the surgical hand. MCP joint motion increased from 62º before surgery to 76º after surgery, whereas PIP joint motion got worse after surgery, with the average motion decreasing from 57º to 31º.

Discussion: This is an example of a Vancouver B3 periprosthetic fracture that consists of a fracture around a loose femoral stem with poor proximal bone support. Therefore, open reduction and internal fixation is not an option. PFR is an excellent choice for elderly inactive patients with poor femoral bone stock. The surgery can be performed in an expeditious manner, which is very important in a patient with mild coagulopathy.

Treatment of an early infection demands thorough debridement of the wound and appropriate parenteral antibiotics. Systemic treatment with appropriate antimicrobial agents should continue for a minimum of 4 weeks following debridement for an early infection. An infection diagnosed later than 4 weeks following surgery is less likely to have a successful result without removal of the components. OKU V pg. 490.Arthroscopic debridement not recommended secondary to missing cutaneous tracks and soft tissue/muscle involvement.

DISCUSSION: The management of patients with proximal femoral deformity can be difficult. Appropriate implant selection and preoperative templating are critical. In this patient, it would be difficult to avoid increasing the combined offset by too much, which could contribute to the overtensioning of the soft tissues and trochanteric pain. By medializing the acetabular component (decreasing the combined offset), using a low offset femoral component or a cemented component placed more valgus (decreasing the combined offset), and making a longer neck cut (to avoid shortening of the lower extremity), restoration of the patient’s native offset and leg length can be achieved.

DISCUSSION: Several studies have shown that ultra-high molecular weight polyethylene liners used in total hip arthroplasties wear at a rate of 0.1 to 0.2 mm/yr. The orthopaedic surgeon performing total hip arthroplasties should be aware of the average wear rate so that potential problems can be identified when following patients postoperatively. REFERENCES: Callaghan JJ, Albright JC, Goetz DD, Olejniczak JP, Johnston RC: Charnley total hip arthroplasty with cement: Minimum twenty-five year follow-up. J Bone Joint Surg Am 2000;82:487-497. Isaac GH, Wroblewski BM, Atkinson JR, Dowson D: A tribological study of retrieved hip prostheses. Clin Orthop 1992;276:115-125.

After a fall 2 months ago, an 82-year-old woman presents with the inability to straighten her leg. She has had several subsequent falls. She had a successful primary total knee arthroplasty (TKA) 3 years ago. AP and lateral radiographs are shown Figures 1 and 2. On examination, she has a 45° extensor lag, no significant pain and good knee stability. She can flex to 110° without difficulty. A full allograft reconstruction versus synthetic mesh reconstruction are the two options discussed with the patient and family. What is the difference between the two surgical options?

DISCUSSION: The radiographs show a loose femoral component with an associated medial condyle distal femoral fracture. The treatment of choice is open reduction and internal fixation with revision of the femoral component because of the femoral component loosening. REFERENCES: Moran MC, Brick GW, Sledge CB, et al: Supracondylar femoral fracture following total knee arthroplasty. Clin Orthop 1996;324:196-209. McLaren AC, DuPont JA, Schroeber DC: Open reduction internal fixation of supracondylar fractures above total knee arthroplasties using the intramedullary supracondylar rod. Clin Orthop 1994;302:194-198. Figgie MP, Goldberg VM, Figgie HE III, et al: The results of treatment of supracondylar fracture above total knee arthroplasty. J Arthroplasty 1990;5:267-276.

The surgical treatment of periprosthetic fractures of total hip replacement with a loose implant and progressive bone loss is associated with a high complication rate. The recent literature would favor the use of long "Wagner-type" stems, which have a long distal taper that may optimally engage the remaining femoral shaft isthmus. Plating options are problematic, because the intramedullary stem limits the ability to use screws with the plate. Using long distally fixed stems circumvents this problem by enhancing fracture healing and creating a long-term prosthetic solution in these most difficult cases.

DISCUSSIONBalancing a total knee is important for longevity of the device and functional benefit. The surgeon should be systematic in the release of a varus knee. The deep MCL is typically released as part of the approach and osteophytes are then removed. The semimembranosus tendon can then be released from the posterior medial aspect of the tibia. A downsizing osteotomy can be considered for a large deformity if a patient has adequate tibial sizing. If a patient has the smallest implant available prior to the osteotomy, an osteotomy will lead to overhang of the implant and medial impingement on the MCL.A valgus knee can be treated with pie crusting of the iliotibial band in mild extension deformity. Surgeons should pause prior to taking down the popliteus and lateral collateralligament because this can induce posterior rotatory subluxation of a primary knee, especially in the case of a posterior collateral ligament-sacrificing total knee arthroplasty design.

DISCUSSION:This patient has pre-existing right hip osteoarthritis. The most correct option for the treatment of this active patient is a right total hip arthroplasty. Hemiarthroplasty would not address the patient's pain from osteoarthritis,  and  open  reduction  and  internal  fixation  would  not  fix  the  femoral  head  issue  or  theosteoarthritis.

DISCUSSION: In a study of 52 patients with infected total knee arthroplasties, Windsor and associates showed that the average leukocyte count was 8,300/mm3 and that aspirated knee fluid was positive in all patients except one. Knee radiographs can be unclear in showing infection, which may be present without radiographic signs of loosening. Technetium Tc 99m and gallium bone scans may not conclusively show the presence of infection, particularly in the first 3 years after knee arthroplasty.

The term “effective joint space” was initiated in the article that this question was referenced from. It is defined as all the regions that are accessible to joint fluid. The significance of the effective joint space is that patterns of joint fluid flow (preferential flow) will determine the concentration and pattern of particulate wear debris. Where there is wear debris there is the potential for lytic and linear bone loss secondary to macrophage concentrations.

DISCUSSION: The overriding factor determining treatment in this case is the appearance of the surgical wound. Based on MacPhearson’s work, this “C” wound is best managed with two-stage exchange. The functional outcome is markedly diminished following a knee arthrodesis compared to revision knee arthroplasty. REFERENCES: Harwin SF: The diagnosis and management of infected total knee replacement. Seminars Arthroplasty 2002;13:9-22. Goldmann RT, Scuderi GR, Insall JN: 2-stage reimplantation for infected total knee replacement. Clin Orthop 1996;331:118-124. Morrey BF, Westholm F, Schoifet S, Rand JA, Bryan RS: Long-term results of various treatment options for an infected total knee arthroplasty. Clin Orthop 1989;248:120-128.