Importance of Three-Dimensional Evaluation of Surgical Transepicondylar Axis in Total Knee Arthroplasty.

In total knee arthroplasty, the surgical transepicondylar axis (SEA) is one of the most reliable rotation axes for stabilizing of the patellofemoral joint. The SEA is identified with reference to the lateral epicondyle and the medial sulcus of the medial epicondyle. However, these two structures rarely appear on the same plane on computed tomography (CT), and it is necessary to take two points in separate images. Many surgeons measure the SEA on the same image (pseudo SEA) instead. We aimed to determine the difference between true SEAs and pseudo SEAs. A total of 31 normal knees and 24 varus knees were included in this study. Three-dimensional (3D) models of the femur were reconstructed from CT images, and a reconstructed plane was made using the International Society of Biomechanics coordinate system. Pseudo SEAs drawn in the plane passing through the lateral epicondyle and medial sulcus were defined as l-SEA and m-SEA, respectively. L-SEA, m-SEA, true SEA, and posterior condylar axis (PCA) were projected onto the International Society of Biomechanics coordinate plane and, "p l-SEA," "p m-SEA," "p true SEA," and "p PCA" were obtained. The true SEA angle was defined as the angle between p true SEA and p PCA. The l-SEA angle or m-SEA angle was defined as the angle between the p l-SEA or p m-SEA and p PCA, respectively. There were no statistically significant differences between true SEA angle (2.64 ± 2.01 degrees) and pseudo SEA angle (l-SEA angle: 2.74 ± 2.07 degrees, m-SEA: 2.54 ± 2.19 degrees). Conversely, 12 knees in the normal group and 2 knees in the varus group had differences of more than 1 degree (p = 0.01). Among them, 6 knees in the normal group and 0 knees in the varus group had a difference of 2 degrees or more (p = 0.03). In most cases, pseudo SEA can be substituted for true SEA.

The efficacy of total hip arthroplasty on locomotive syndrome and its related physical function in patients with hip osteoarthritis.

BACKGROUND: Locomotive syndrome (LS) is a predictive factor of future motor dysfunction. Our aim was to evaluate the change in the total LS grade and, its the association with the Japanese Orthopaedic Association (JOA) hip score after total hip arthroplasty (THA) among patients with hip osteoarthritis. METHODS: This was a prospective case-control study of 72 patients who underwent primary THA. The functional outcomes were measured before, and at 6 and 12 months after THA. LS was evaluated using the following tests: stand-up test, 2-step test, and 25-question Geriatric Locomotive Function Scale (GLFS-25). In addition, factors affecting the improvement of LS grade were examined. RESULTS: Prior to THA, 7% and 93% of patients were classified as LS grades 1 and 2. At 6 months after THA, an improvement in the total LS grade was observed in 57% of patients, with this percentage further increasing to 65% at 1 year. Only the preoperative GLFS-25 was correlated with the preoperative JOA hip scores. The postoperative GLFS-25 and the two-step test were correlated with the postoperative JOA hip scores. The preoperative functional reach test (FRT) was significantly correlated with the total LS grade improvement. CONCLUSIONS: THA can improve the total LS grade in 65% of patients at 1 year postoperatively. Improvement was largely achieved in the first 6 months after THA, with a change from LS grade 2 to grade 1. FRT could be used an indicator of the total LS grade improvement.

Postsurgical infection from using a computed tomography-based hip navigation system during total hip arthroplasty.

PURPOSE: A computed tomography (CT)-based hip navigation system is a useful tool for achieving precise implant alignment angle. However, it has the disadvantage of prolonged procedure duration. A prolonged procedure duration may increase the incidence of postoperative surgical site infection (SSI) or periprosthetic joint infection (PJI) following primary THA. Studies identifying whether CT-based hip navigation system increases the incidence of SSI and PJI compared to the free-hand technique for total hip arthroplasty (THA) are rare. The study aimed to assess whether the CT-based hip navigation system can cause SSI and PJI compared to the free-hand technique. METHODS: We investigated 366 patients with osteoarthritis who completed the minimum 2-year follow-up and underwent primary THAs (n = 435), including 70 hips in 62 patients of the non-navigation group and 365 hips in 304 patients of the navigation group. We compared the incidence rate of SSI and PJI between the non-navigation group and navigation group. RESULTS: Only three patients in the navigation group (0.8%) developed SSI or PJI, while no patient developed SSI or PJI in the non-navigation group. There was no significant difference in the incidence rate of SSI or PJI between the two groups (P = 1.0), although the mean operation time in the navigation group was about 20 min longer. CONCLUSIONS: CT-based hip navigation system may not be associated with SSI or PJI after primary THA, although it prolongs the operation time.

Effect of changing femoral head diameter on bony and prosthetic jumping angles.

BACKGROUND: In THA, using a larger femoral head can increase the oscillation angle and jumping distance. However, there have been no reports which indicate precisely how increasing the jumping distance leads to an increase in the angle from impingement to dislocation (jumping angle). In this study, we clarified the jumping angle of various head diameters and its relationship with pelvic morphology. METHODS: Using a three-dimensional templating system, virtual THA and ROM simulations were performed in 82 patients. We investigated the distance between bony and prosthetic impingement points and the head centre and calculated the jumping angle for various head diameters. We measured various pelvic shapes and length to clarify the relationship between pelvic morphology and impingement distance. RESULTS: Jumping angles were 7.7° ± 3.2°, 12.1° ± 1.6°, 15.4° ± 2.5° and 10.0° ± 3.0° with flexion, internal rotation with 90° flexion (IR), extension and external rotation (ER), respectively, when we used a 22-mm head diameter. Bony jumping angle increased about 0.5°, 0.8°, 1.0° and 0.7° per 2-mm increase in head diameter with flexion, IR, extension and ER. On the other hand, prosthetic jumping angle remained almost stable at about 31°. Impingement distance was related to pelvic morphology in all directions. Bony jumping angles differed with ROM; the biggest was seen with extension, followed by IR, ER and flexion. On the other hand, bony jumping angle was less than prosthetic jumping angle in all cases. CONCLUSION: Bony jumping angles differed with ROM; the biggest was seen with extension, followed by IR, ER and flexion. Prosthetic impingement angles were stable. In addition, the bony jumping angle was less than the prosthetic jumping angle in all cases.

The optimal combined anteversion pattern to achieve a favorable impingement-free angle in total hip arthroplasty.

BACKGROUND: There have been no studies on the differences in impingement-free angle that result from different combined anteversion (CA) patterns. The aim of this study was to find the optimal CA pattern for achieving a favorable impingement-free angle, including bony and prosthetic impingement, in total hip arthroplasty. METHODS: We evaluated 100 patients with no hip arthritis. We investigated the impingement-free angle (flexion, internal rotation with 90° flexion, extension, and external rotation) after changing the stem and cup anteversions to satisfy several CA patterns [cup anteversion + stem anteversion = 30°, 40°, 50°, and 60°; cup anteversion + 0.7 × stem anteversion = 37.3° (:Widmer's theory); and cup anteversion + 0.77 × stem anteversion = 43.3° (:Yoshimine's theory)] using 3-dimensional templating software. RESULTS: The impingement-free angle changed dramatically among the various CA patterns. The optimal CA was changed by various stem anteversion. Only CA: Widmer with stem anteversion of 20° satisfied daily-life range of motion (ROM) requirements (flexion ≥130°, internal rotation with 90° flexion ≥ 45°, extension ≥ 40°, external rotation ≥ 40°). CONCLUSION: Good impingement-free angle cannot be obtained with single fixed CA. Different CA patterns should be used, depending on the differences in the stem anteversion. A CA of 30° with 0° ≤ stem anteversion ≤10°; a CA:Widmer with 20° of stem anteversion; a CA of 40° or Widmer with 30° of stem anteversion. When stem anteversion is ≥40°, CA should be decided by each patient's state. Among them, a stem anteversion of 20° with cup anteversion of 23.3° was found to be the best CA pattern.

A proposed new rotating reference axis for the tibial component after proximal tibial resection in total knee arthroplasty.

PURPOSE: During total knee arthroplasty, few rotating reference axes can be reliably used after tibial resection. We speculated that a line that passes through the lateral edge of the posterior cruciate ligament (PCL) at its tibial attachment after resection and the most prominent point of the tibial tubercle [after-tibial resection (ATR) line] will provide a good reference axis. In this study, we aimed to evaluate the association between ATR and Akagi's lines. MATERIALS AND METHODS: In this case-control simulation study, we retrospectively evaluated 38 patients with varus knee and 28 patients with valgus knee. We defined the reference cutting plane as 10 mm distal from the lateral articular surface of the tibia in varus group and as 7 mm distal from the medial articular surface in the valgus group. We measured angles between Akagi's line and the ATR line (ATR line angle) as well as between Akagi's line and 1/3 Akagi's line (1/3 Akagi's line angle), which passes through the midpoint of PCL and the medial third of the patellar tendon. We used paired t-tests to determine the significance of differences between these angles, with p < 0.05 indicating statistical significance. Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi's line angle and ATR line angle were analyzed by two surgeons. RESULTS: We found that 1/3 Akagi's line angle was 10.2° ± 1.3° in the varus group and 10.9° ± 1.3° in the valgus group (p = 0.017). The ATR line was positioned externally compared with Akagi's line in all patients. Mean ATR line angles at 0°, 3° and 7° posterior slopes were 6.1° ± 1.9°, 5.8° ± 2.0° and 6.0° ± 1.7° in the varus group and 6.3° ± 2.3°, 6.2° ± 2.3° and 5.4° ± 2.1° in the valgus group, respectively. There were no significant differences in the ATR line angle between the varus and valgus groups. (p = 0.34-0.67) Intra- and interclass correlation coefficients for the reproducibility of 1/3 Akagi's line angle were 0.936 and 0.986 and those for the reproducibility of ATR line angle were 0.811 and 0.839. CONCLUSIONS: The ATR line was positioned between Akagi's line and 1/3 Akagi's line in all patients and was a valid option for evaluating rotational tibial alignment after tibial resection.

Clinical Results of Total Hip Arthroplasty in Two Patients with Charcot Hip Joints due to Congenital Insensivity to Pain with Anhydrosis.

Traditionally, Charcot arthropathy has been considered an absolute contraindication for total hip arthroplasty (THA). However, some recent reports have shown that good short- to mid-term results can be achieved by improving the durability of the implant. This paper reports the mid- to long-term results of THA in two patients with Charcot hip joints caused by congenital insensivity to pain with anhydrosis. Both patients suffered multiple posterior dislocations in the six months immediately following surgery. However, with the continuous use of a hard abduction brace, one patient was eventually able to walk with a lofstrand cane and the other with the use of one crutch. Although one patient experienced a dislocation five years after surgery, X-rays taken after nine years and five years, respectively, revealed no clinical signs of implant loosening. We conclude that, with careful planning and appropriate precautions, THA may be a viable treatment option for Charcot hip joints caused by congenital insensivity to pain with anhydrosis.

Three-dimensional limb lengthening after total knee arthroplasty in a simulation study.

OBJECTIVES: Limb lengthening after total knee arthroplasty (TKA) has been reported in some cases, all of which were evaluated using two-dimensional images. To our knowledge, no case has been evaluated using three-dimensional (3D) images. We investigated 3D limb lengthening after TKA. METHODS: We simulated 100 varus knees using 3D templating software. Virtual TKA was performed to maintain the original joint line by conducting a measured-resection technique. We examined the relationships of 3D distance between the femoral head center and ankle center before and after TKA, degree of hip-knee-ankle angle (HKA) improvement, and degree of flexion contracture angle improvement. RESULTS: All cases showed limb lengthening (average, 9.4 ± 6.0 mm). The coefficients of correlation with limb lengthening and the degree of HKA improvement and the degree of flexion contracture angle improvement were good (0.730 and 0.751, respectively). The correlation between the degree of total improvement (the degree of HKA improvement + the degree of flexion contracture angle improvement) and limb lengthening was strong (r = 0.896). CONCLUSION: The expected limb lengthening when performing measured-resection TKA is expressed as 0.58 × (the degree of HKA improvement + the degree of flexion contracture angle improvement) mm and is a useful index.

Comparison with the osteoconductivity and bone-bonding ability of the iodine supported titanium, titanium with porous oxide layer and the titanium alloy in the rabbit model.

BACKGROUND: One of the serious postoperative complications associated with joint replacement is bacterial infection. In our recent investigations, iodine supported titanium implants demonstrated antibacterial activity in both in vitro and in vivo studies. The surfaces of the implants have porous anodic oxide layer with the antiseptic properties of iodine. According to the literature the titanium with porous anodic oxide have good osteoconductivity. But it is not clear whether the properties of iodine influence bone bonding of implants. OBJECTIVES: The aim of this study is to evaluate the influence of the properties of iodine and porous anodic oxide layer in the bone bonding ability of titanium implants. STUDY DESIGN & METHODS: Titanium rods were implanted in intramedullary rabbit femur models, in regard to the cementless hip stem. The implant rods were 5 mm in diameter and 25 mm in length. Three types of titanium rods were implanted.One was untreated titanium (control group (CL)), another was titanium with oxide layer without iodine (oxide layer group (OL)), and the other was Iodine treated Titanium (iodine group (ID)). The rods were inserted into the distal femur. We assessed the bonding strength by a measuring pull-out test at 4, 8, and 12 weeks after implantation. The bone-implant interfaces were evaluated at 4 weeks after implantation. RESULTS: Pull-out test results of the ID implants were 202, 355, and 344 N, and those of the OL implants were 220, 310, 329 N at 4, 8, and 12 weeks, significantly higher than those of the CL implants (102, 216, and 227 N). But there were no significant difference in ID implants and OL implants. Histological examination revealed that new bone formed on the surface of each types of implants, but significantly more bone made direct contact with the surfaces of the ID implants and OL implants. CONCLUSIONS: This research showed that new type of coating, iodine coated titanium has low toxicity and good osteoconductivity.

Usefulness of the "grand-piano sign" for determining femoral rotational alignment in total knee arthroplasty.

BACKGROUND: The "grand-piano sign" is a well-known indicator of proper rotational femoral alignment. We investigated changes in the shape of the femoral anterior cutting plane by changing the rotational alignment, anterior portion depth, and cutting plane flexion angle. METHODS: We simulated various cutting planes after cutting the anterior portion of the femur next to the distal femoral osteotomy in 50 patients with varus knee and also a femoral anterior osteotomy with four degree (S group) and seven degree (T group) flexion angles regarding the mechanical axis. We defined the final cutting plane as the farthest position that we could reach without making a notch and the precutting plane as two millimeters anterior from the final cutting plane. The simulated resection plane was rotated to produce external and internal rotation angles of 0°, three degrees, and five degrees relative to the surgical transepicondylar axis (SEA). We investigated medial and lateral portions of the femoral anterior cutting plane length ratio (M/L). RESULTS: When we cut parallel to SEA, M/L was 0.67±0.09 and 0.62±0.12 in the T and S groups, respectively. M/L was approximately 0.8 and 0.5 with five degree internal and external rotations, respectively (P<0.01). On comparing final cutting and precutting planes, there were no significant differences in M/L without five degree external rotation in the T group and no significant difference in any case in the S group (P>0.01). CONCLUSIONS: The ideal M/L of the femoral anterior cutting plane was 0.62-0.67. M/L did not change with a precutting plane in almost all rotational patterns.

Differences in range of motion with the same combined anteversion after total hip arthroplasty.

PURPOSE: We investigated the various impingement angles (including both bony and prosthetic impingement) and impingement types that can occur after THA, even when the same combined anteversion parameter is used. We also investigated the relationship between impingement angle and acetabular morphology or femoral anteversion. METHODS: We evaluated 83 patients with no hip arthritis. We divided them into six groups according to acetabular CE angle (≤15°, >15-≤25°, and >25°) and femoral anteversion (≤20° and >20°). Using three-dimensional templating software, we changed stem and cup anteversion to satisfy a combined anteversion (CA) of 50° in each hip (stem anteversion + cup anteversion = 50°) and investigated the resulting impingement angles. RESULTS: Even with the same CA, differences in impingement angle occurred: 18.3° ± 7.2° with flexion, 30.2° ± 9.7° with internal rotation at 90° flexion, 20.2° ± 12.5° with extension, and 26.2° ± 7.8° with external rotation. As stem anteversion increased, the impingement type changed from prosthetic impingement to bony impingement in flexion and internal rotation and from bony impingement to prosthetic impingement in extension and external rotation. The flexion angle and internal rotation angle at 90° flexion increased (p < 0.016) as CE angle decreased. There were no significant differences between high and low femoral anteversion. CONCLUSIONS: Combined anteversion theory should be used with care because of large differences in impingement angles. A stem anteversion of 30° and cup anteversion of 20° appear to be ideal for obtaining a larger impingement angle under this condition.

The accuracy of the "projected surgical transepicondylar axis" relative to the "true surgical transepicondylar axis" in total knee arthroplasty.

BACKGROUND: In TKA, we have used the "projected SEA", which is obtained by projecting the "true SEA" on the distal femoral cutting plane in clinical practice to determine the femoral component rotation. There are no reports examining the accuracy of the "projected SEA". In this study, we investigated the difference between the "true SEA" and "projected SEA". METHODS: The present study was a CT-based computer-simulated case series. We evaluated 34 knees without osteoarthritis changes. These patients were selected from the operative schedule prior to THA. We defined the "true SEA" on the 3D model and the "projected SEA" on the cutting plane parallel to the distal femoral axis obtained based on the "true SEA". We changed the cutting angles from 20° flexion to 20° extension, and from five degrees varus to five degrees valgus. We measured the "true SEA angle" and "projected SEA angle" regarding the posterior condylar axis (PCA). RESULTS: The mean "true SEA angle" was 3.04°±1.34° (0.6-5.0°). The mean "projected SEA angle" was 3.43°±1.58° at 20° flexion, 3.42°±1.56° at 0° flexion, 3.43°±1.52° at 20° extension, 3.39°±1.59° at five degrees valgus, and 3.39°±1.50° at five degrees varus. At each cutting angle, the "projected SEA angle" was significantly larger than the "true SEA angle" (p<0.001). There was no significant difference between any of the "projected SEA angles" (p>0.001). CONCLUSIONS: We found that the true SEA and projected SEA do not differ significantly (0.39°±0.29° [range 0-1.0°]).

The influence of surgical approach on postoperative pelvic tilt after total hip arthroplasty.

BACKGROUND: Past reports have shown the tendency of posterior pelvic tilt to increase over time after total hip arthroplasty (THA). We have hypothesized that the volume and extent of released joint capsule may influence the change in postoperative pelvic tilt. This study was conducted to ascertain whether surgical approach during THA (posterior or anterior) has an effect on postoperative changes in pelvic tilt. METHODS: We conducted a retrospective review of 81 hips in 60 patients. Patients classified as Crowe group 2, 3, and 4, those who had multiple previous compression fractures, and those with spinal fusion due to spinal arthrosis were excluded. Also, those who had previously undergone THA or total hip resurfacing also were excluded. Patients were divided into two groups, those with preoperative anterior pelvic tilt and those with posterior tilt. Preoperative and postoperative X-rays and CT scans for each group were assessed to determine the chronological change in pelvic tilt, and the data were statistically analyzed for patients who had experienced both the posterior and anterior approaches. RESULTS: Regardless of surgical approach, there was no significant difference in the mean change in postoperative APP angle over time in either the bilateral or unilateral cases or in the groups of preoperative anterior or posterior pelvic tilt. CONCLUSIONS: Our results showed that surgical approach does not influence postoperative pelvic tilt after THA. In preoperative planning for THA, therefore, surgeons may need not to consider the difference of surgical approach with regard to postoperative changes in pelvic tilt.

Selection of a surgical approach for total hip arthroplasty according to the depth to the surgical site.

BACKGROUND: The surgical depths of approaches for total hip arthroplasty (THA) have not been reported previously. In this study, we investigate the relationships between the distances to the centre of the femoral head in different approaches and body mass index (BMI). METHODS: The study included patients with normal hip joints who presented to our hospital. We used the pelvic coordinate system relative to the anterior pelvic plane and the femur coordinate system relative to the posterior condylar plane. We assessed the anterior, anterolateral, lateral and posterior approaches, and defined each approach line. We evaluated each distance in terms of BMI and gender. RESULTS: 164 hips were assessed. The distance to the centre of the femoral head was the longest in the posterior approach, followed by the lateral, anterolateral, and anterior approaches (p<0.05). Additionally, the distance in each approach increased as patients' BMI increased. The approximated line tilts were almost the same. The correlation coefficients between BMI and the distance to the centre of the femoral head were high in all approaches. In the anterior and anterolateral approaches, men with low BMI had a short distance to the femoral head. The distance for each approach was measured according to the pelvic coordinate system and the femur coordinate system. The results showed no significant differences between them. CONCLUSIONS: The distance to the centre of the femoral head is the shortest in the anterior approach, regardless of BMI and gender. The distance in each approach might increase with an increase in BMI. BMI has similar effects in all approaches.

Increase in safe zone area of the acetabular cup using dual mobility cups in THA.

BACKGROUND: Dual mobility cup (DMC) inserts reduce the risk of dislocation after total hip arthroplasty (THA). No available research has clearly delineated stability advantages of DMC inserts in primary and revision THA. We investigated: (i) the degree of change in the safe zone of the cup when a DMC insert is used compared to a fixed insert; (ii) the method of selecting candidates for a DMC insert without changing the position of the acetabular (cup) component during revision THA in frequent dislocation cases caused by implant impingement. METHODS: A model of the pelvis and femur was developed from computed tomography images. The safe zone was defined as the area in the acetabular component, over which conditions for stable range of motion were satisfied. The safe zone was calculated for both a fixed and a DMC insert over a predetermined range of 3-D motion, and the effect of increasing the anteversion position of the femoral component from 5° to 35° was quantified. RESULTS: The lowest ratio of the area of the safe zone was about 4.9 at 20° anteverison of the femoral component. Safe zone of DMC inserts zone had increased stability of 10°-15° in both vertical and horizontal directions, compared to fixed inserts.A 5- to10-fold expansion of the safe zone can be expected with the use of DMC insert. CONCLUSIONS: DMC insert could help to set the acetabular component more accurately in primary and revision THA.