Takuya Otani

Cutting errors in preparation of femoral components in total knee arthroplasty.

Cutting errors that occur during preparation of the femoral component can deter fixation in cementless total knee arthroplasty. This study evaluated the causes of femoral cutting errors and identified methods to minimize these errors. The cutting error caused by toggle of the saw blade in the guide-slot was measured with wood blocks, a cutting guide with 1.5 mm guide slots, and four kinds of saw blades (narrow and wide blades with thicknesses of standard 1.2 mm and thicker 1.4 mm). Another cause of cutting errors, relative motions between the cutting guide and distal femur due to vibration of the saw blade during bone cuts, was measured with preserved cadaver femurs. Various combined fixation methods with intramedullary rod, pins, and clamps were compared. The maximum cutting error caused by toggle of the saw blade in the slot was significantly reduced by using the thicker 1.4 mm saw blade, but the differences between wide and narrow blades in each thickness were not significant. Mean maximum cutting error at the cutting depth of 5 cm with 1.2 mm thick saw blades was 802 microns, and with 1.4 mm thick saw blades it was 488 microns. In the measurement of relative motion, fixation with only pins or clamps did not provide tight fixation and had deflections from 200 microns to more than 1 mm. The best fixation was obtained by combining fixation methods of intramedullary rod and pins or clamps. This resulted in total movement of less than 100 microns. The results of this study indicate that both toggle of the saw blade in the slot and motion of the cutting guide can cause major cutting errors. Cutting error can be minimized by using thicker saw blades and by fixing the cutting guide to the distal femur with combined fixation methods of a central rod and peripheral pins or clamps.

Effect of medial displacement of the tibial tubercle on patellar position after rotational malposition of the femoral component in total knee arthroplasty

A large Q angle induced by technical error such as an internally rotated femoral component causes patellar failure after total knee arthroplasty. The effect of medial displacement of the tibial tubercle to decrease the Q angle for patellar tracking was studied by evaluating the patellar position relative to the patellar groove on the femoral component in cadaver specimens. A 5 degrees internally rotated femoral component caused the patella to shift medially about 5 mm, and also caused the tibia to rotate internally about 3 degrees at full extension. With a 5 degrees externally rotated femoral component, normal patellar tracking occurred. The distance of medial displacement was determined so that the patellar tendon was parallel to the longitudinal axis of the tibia at full extension. This allowed the quadriceps tendon, the patella, and the patellar tendon to form a straight line. The average distance of medial transposition of the tibial tubercle was 9.32 mm. Medialization of the tibial tubercle caused the patella to shift about 2 mm medially from the patellar groove. The transfer also caused an external rotation of the tibia (2 degrees-5 degrees). Medial transfer of the tibial tubercle changes patellar kinematics and corrects the tendency toward lateral patellar dislocation caused by internally rotating the femoral component; however, it also creates minor patellar and tibial kinematic changes that may have a clinical effect.

A Modified S-ROM Stem in Primary Total Hip Arthroplasty for Developmental Dysplasia of the Hip

This study examined the clinical outcome of 220 hips in 196 Asian patients who underwent primary total hip arthroplasty (THA) for treatment of developmental dysplasia of the hip (DDH) using a modified S-ROM modular (S-ROM-A) stem designed for Asians, after 2-5 years (mean, 3.3 years) of follow-up. The stem was placed so that the anteversion angle of the neck was decreased against the sleeve in 56% of the hips and increased in 18% of the hips. Bone ingrown fixation was achieved in 99.5% of the hips on X-ray at final follow-up. There were 2 (0.9%) dislocations postoperatively. In primary THA for treatment of DDH accompanied by femoral rotational deformity, the freely-rotatable modular stem provided favorable short-term outcomes by affording both morphological and functional advantages.

Late mechanical stability of the proximal coated AML prosthesis.

Micromotion of a bone-ingrown anatomic medullary locking (AML) femoral component was evaluated in a specimen retrieved from a 66-year-old man who died 4 years following total hip replacement. Radiographic signs suggested bone ingrowth into the proximal porous coating, but a radiolucent line surrounded by a sclerotic line was present around the distal stem. Both torsional and axial loading to physiologic levels elicited minimal micromotion at the proximal bone-prosthesis interfaces. However, medial-lateral micromotion at the distal tip was found to be as high as 44 microns with axial load. An AML femoral component of similar design was inserted into the opposite normal femur using the cementless press-fit technique originally used for the implanted specimen. Micromotion proximally was much greater in the freshly implanted systems in response to both torsional and axial loading than in the bone ingrown specimen. However, distal medial-lateral micromotion was much greater for the bone-ingrown stem. These findings show that bone ingrowth provides rigid fixation of the implant to bone; however, flexibility of the femur causes increased micromotion of the femur around the smooth distal stem despite initial tight distal fit.

Impingement After Total Knee Arthroplasty Caused by Cement Extrusion and Proximal Tibiofibular Instability

A 57-year-old patient with rheumatoid arthritis showed posterolateral impingement after total knee arthroplasty. The radiographs showed bone cement extrusion posterolateral to the tibial tray. Arthrotomy through a posterolateral approach revealed that the impingement was caused not only by cement extrusion against the fibular head but also by proximal tibiofibular joint instability. It was speculated that rheumatoid arthritis had caused proximal tibiofibular instability, active knee motion had caused fibular head shift by tension of biceps femoris and the fibular head had been impinged on the extruded cement. In cementing the tibial tray, especially in a rheumatoid patient, it is of paramount importance to take caution against posterolateral cement extrusion in order to minimize the risk of fibular head impingement during total knee arthroplasty.

Treatment for unstable slipped capital femoral epiphysis: Current status and future challenge in Japan

BACKGROUND Treatment for unstable slipped capital femoral epiphysis (SCFE) is challenging and controversial. For many years, the debate centered around closed treatments and especially the pros and cons of manual reduction and its concrete procedure. However, recent studies reported on open treatments such as open reduction through an anterior approach and modified Dunn procedure. Being in a period of such transition, we investigated the current status and future challenge of treatment for unstable SCFE. METHODS A questionnaire survey of medical institutions specializing in pediatric hip disorders across Japan was conducted. Survey items were the accurate diagnosis of physeal stability, the pre- and intra-operative evaluation of epiphyseal hemodynamics, and current treatment strategy. RESULTS Survey responses returned from 29 out of 40 participant institutions (response rate: 73%) revealed that 55% of the institutions evaluated physeal stability based on clinical findings of ambulation capability in accordance with the Loder classification. Another 38% diagnosed physeal stability comprehensively by combining the Loder classification and imaging findings. Epiphyseal hemodynamics was assessed preoperatively in 18% of the institutions, effectively using angiography, contrast-enhanced magnetic resonance imaging (MRI), and bone scintigraphy. Intraoperative assessment was performed in 13% based on the bleeding through a drilling hole on the articular surface and observation of the cancellous bone color during open surgeries. As a treatment strategy, 52% of the institutions used in-situ fixation, while another 38% used manual reduction and internal fixation. On the other hand, open reduction was used at 3 institutions (the remaining 10%): the modified Dunn procedure at 2 institutions and arthrotomy at 1 institution. CONCLUSION Treatment for unstable SCFE remains controversial, but closed treatments without hemodynamic monitoring is no longer the center of the controversy. Today, the topic of the discussion is shifting toward how to correlate hemodynamic findings with treatment procedures and the indications for open treatments.

Indications and Midterm Results of Modified Spitzy Acetabuloplasty for Osteoarthritis of the Hip

We investigated midterm clinical and radiological outcomes of modified Spitzy shelf acetabuloplasty, one of several established modes of joint-preserving surgery for young adults. We reviewed 23 hips of 23 patients who had undergone this procedure (17 females, 6 males); mean age at the time of surgery was 32 (range, 15–43) years. Mean follow-up period was 5 years (range, 1 year 5 months to 12 years 2 months). In total, 16 hips were in the pre-osteoarthritis (OA) or the early stage, 4 hips in the advanced stage, and 3 hips in the terminal stage. All cases showed considerable clinical and radiographical improvement demonstrable by improved coverage of the femoral head. No cases showed OA progression that required conversion to total hip arthroplasty or exhibited marked bone resorption. Our results suggest that age at the time of surgery is associated with postoperative outcome, but not disease stage at the time of surgery or the height and size of the shelf. We note that the rate of performing this procedure has decreased. However, it is a less invasive procedure with several unique advantages compared with other methods. Shelf acetabuloplasty is an effective surgical option for symptomatic hip dysplasia even in patients with relatively advanced disease who are treated for DDH in childhood and who have femoral head deformity. We hope that this procedure is reconsidered and revived.

Indications for Shelf Acetabuloplasty and Rotational Acetabular Osteotomy for Developmental Dysplasia of the Hip

Developmental dysplasia of the hip (DDH) is typically the underlying disease in adult patients with hip joint disorders and a high proportion of DDH in Japanese hip osteoarthritis patients have been reported. Pathophysiology in DDH varies due to morphological/patient-related factors and, considering these variations, it is important for hip surgeons to have several available treatment options and make the appropriate selection. In this chapter we describe our technique in several joint-preserving surgeries for DDH, and discuss the indications for these treatments. The features of our shelf acetabuloplasty include that we carefully determine the level of the shelf by using fluoroscopy and that we try to construct a large shelf to cover as wide area of the femoral head as possible. In patients who require exceptionally large coverage we harvest two half-thickness bone plates and use both to create a large three-dimensional shelf. The features of our rotational acetabular osteotomy include that we use a trans-trochanteric approach to obtain wide exposure of the ilium and that we modify the osteotomy line and osteotomy technique. The aims of this technique are to preserve continuity of the whole pelvic ring and to achieve mechanical stability/broad surface contact between the two bone pieces. Favorable postoperative outcomes can be expected from either surgical procedure in patients with a spherical hip morphology and mild/early DDH. However, in patients who have DDH complicated with femoral head deformity, joint incongruity, head subluxation, and disease advancement, personalized treatment indications need to be investigated on an individual basis. Authors believe that features of shelf acetabuloplasty such as versatility for femoral head deformity and remodeling ability of the constructed shelf are particular to this procedure and attractive. It is expected that shelf acetabuloplasty will continue to attract attention, fostering further development and advancement in the future.

Diagnosis and treatment of slipped capital femoral epiphysis: Recent trends to note

Slipped capital femoral epiphysis (SCFE) is not frequently encountered during routine practice and diagnosis and treatment are often delayed. It is important to understand symptoms and imaging features to avoid delayed diagnosis. After the diagnosis is made correct classification of the disease is required. The classification should be based on the physeal stability in order to choose safe and effective treatment. However, surgeons should bear in mind that the assessment is challenging and actual physeal stability is not always consistent with the stability predicted by a clinical classification method. TREATMENT OF STABLE SCFE Closed reduction is not indicated for stable SCFE, where continuity between the epiphysis and metaphysis has not been disrupted. Treatment method(s) is (are) chosen from in-situ fixation, osteotomy and femoroacetabular impingement treatment. A single screw fixation is often used to fix the epiphysis and the dynamic method is considered especially for young patients. Traditional three-dimensional trochanteric osteotomies have been associated with procedural complexity and uncertainty. A simpler osteotomy method using an updated imaging analysis technology should be considered. Modified-Dunn procedure is indicated for a severe stable SCFE. However, caution is required because recent studies have reported a high rate of complications including postoperative femoral head avascular necrosis (AVN) and hip instability when this method is indicated for stable SCFE. TREATMENT OF UNSTABLE SCFE Treatment of unstable SCFE is difficult and complication rate is high. Most of unstable SCFE patients were previously treated with closed method and it was difficult to predict an occurrence of postoperative AVN. However, treatment of unstable SCFE has gradually changed in recent years and many studies have shown that physeal hemodynamics can be assessed during treatment. Preoperative assessments include contrast-enhanced MRI and bone scintigraphy. Intraoperative assessments include confirmation of bleeding after drilling the femoral head and monitoring the intracranial pressure by laser doppler flowmetry. It is expected that postoperative AVN can be prevented in many cases by performing the treatment while assessing the intraoperative physeal hemodynamics. Open surgeries have begun to be indicated in the treatment of unstable SCFE through either of anterior approach or (modified) Dunn procedure. The authors expect that recent improvements in assessment of physeal hemodynamics and open treatment method provide improved clinical outcomes in the treatment of SCFE.

Retrospective Evaluation of Surgical Treatments for Slipped Capital Femoral Epiphysis

The summary of our treatment strategy for SCFE is presented. Acute/unstable SCFE in which epiphyseal mobility is observed under fluoroscopy is treated by manual reduction as early as possible, followed by internal fixation with two screws. Chronic/stable SCFE with posterior tilt angle (PTA) less than 40° is treated by in situ single-screw fixation with the dynamic method. For those with PTA of 40° and more, it is important to comprehend the pathology using a CT scan for accuracy, and intertrochanteric flexion osteotomy seems to be one of the simplest and most predictable treatment modalities.