Introduction

The anatomic abnormalities are observed in developmental dysplasia of the hip (DDH) and it is challenging to perform the total hip arthroplasty (THA) for some DDH patients. If acetabular cup was placed at the original acetabular position in patients with high hip dislocation, it may be difficult to perform reduction of hip prosthesis because of soft tissue contracture. The procedures resolving this problem were to use femoral shortening osteotomy, or to place the acetabular cup at a higher cup position than the original hip center. Femoral shortening osteotomy has some concerns about its complicated procedure, time consuming, and risk of non-union. Conversely, implantation of the acetabular cup at the higher cup position may eliminate these shortcomings and this procedure is considered to be preferred if possible. However, the criteria of cases without femoral shortening osteotomy are not clear. In this study, we retrospectively analysed the clinical outcomes of patients performed THAs for high hip dislocation, and clarified the adaptation of THA with or without femoral shortening osteotomy.

INTRODUCTION

To obtain appropriate joint gap and soft tissue balance, and to correct the lower limb alignment are important factor to achieve success of total knee arthroplasty (TKA). A variety of computer-assisted navigation systems have been developed to implant the component accurately during TKA. Although, the effects of the navigation system on the joint gap and soft tissue balance are unclear. The purpose of the present study was to investigate the influence of accelerometer-based portable navigation system on the intraoperative joint gap and soft tissue balance.

INTRODUCTION

The concept of anatomical stam is fit-and-fill in the proximity of the femur and to expect wall fixation, following to reduce thigh pain and stress shielding. Although the femoral medullary form and size are different in each races. CentPillar TMZF stem (stryker ^®) is anatomical stem designed based on computer-tomography of Japanese femurs. The purpose of this study was to evaluate clinical and radiographic outcomes of CentPillar TMZF stem at a mean of 3.6 years postoperatively.

Modulus femoral prosthesis is a modular cementless femoral system which consists of 5 degree tapered conical stem made of a titanium alloy with 8 fins of 1mm and modular neck. Modular neck enables to control any ideal stem anteversion as a surgeon prefers. This system is considered to be useful in severe hip deformity, for example developmental dysplasia of the hip (DDH). In this study, clinical and radiographic outcomes of the Modulus femoral prosthesis were evaluated at a mean of 3.6 (2–6) years postoperatively.

We assessed the results of 193 primary total hip arthroplasty using a Modulus femoral prosthesis in 169 patients (15 males, 154 females) undergoing surgery between September 2007 and December 2011. The mean age at the time of surgery was 65.6 (31–86) years old. The diagnoses were osteoarthritis (OA) in 178 hips (including 167 hips of DDH), rapidly destructive coxopathy (RDC) in 6 hips, rheumatoid arthritis (RA) in 6 hips, osteonecrosis in 2 hips, and subchondral insufficiency fracture in one hip. Clinical outcomes were assessed using Japan Orthopedic Association (JOA) hip scores and complications. Radiographic assessments were including stem alignment, bone on-growth, cortical hypertrophy, stress shielding and stem subsidence.

43.8 points of the preoperative mean JOA score was significantly improved to 93.1 points postoperatively. In one case intraoperative femoral fracture was occurred. One dislocation had occurred and thigh pain was observed in one hip. No revision surgery was required. In 192 hips of 193 hips (99.5%), stem was implanted in neutral position (within ±2 degrees). Bone on-growth was observed in all cases (94.3% in zone 3; 73.1% in zone 5; 30.6% in zone 2; 22.3% in zone 6). Cortical hypertrophy was observed in 66 hips (34.2%) at zone 3 and 5. Reduction of bone density due to stress shielding was observed (1^st degree was 58.5%; 2^nd degree was 29.5%; 3^rd degree was 11.9%; 4^th degree was 0%). In 22 cases (11.4%), more than 2mm of stem subsidence was observed, however the subsidence was stopped within 6 months in all cases.

Modulus femoral prosthesis showed good clinical results and radiographic findings up to 6 years postoperatively.

Metal on metal total hip arthroplasty (MoM THA) provides the potential improvement in articular wear. However, several adverse events including pseudotumor had been reported. Magnetic resonance imaging (MRI) was considered to be the proposal tool for detection of pseudotumor after MoM THA. In this study, we performed the screening of pseudotumor after MoM THA using the MRI.

We studied 43 patients with M2a Magnum® (Biomet) and 34 patients with M2a Taper® (Biomet) of MoM THA from December 2009 to December 2011 with follow-up of 2.5 years (2.0–4.0 years) after surgery. MRI assessments were performed at a mean of 2.1 years postoperatively. Pseudotumor findings were graded using Anderson classification (Skeletal Radiol, 2011: 40; 303). Age, sex, height, weight, Harris Hip Score, EQ5D satisfaction score, UCLA activity score, and blood metal ion levels were evaluated.

The prevalence of pseudotumor was 27.2%; 56 normal (Type A), 13 mild (C1), 8 moderate (C2) and none were graded severe (C3). Weight and BMI in the mild group was significantly higher than those in normal. There was no significant difference in age, sex and height among these groups. With regard to Harris Hip score, pain and ROM score in moderate group was significantly lower than that in normal and mild group. EQ5D satisfaction score and UCLA activity score showed not significant differences among groups. 3.01±3.32 μg/L of blood cobalt ion levels in the moderate groups was significantly higher than 0.97±0.64 μg/L in normal group. Blood cobalt ion levels of 1 mild and 2 moderate were over the threshold of 7 μg/L. These patients were implanted with M2a Taper, not M2a Magnum. 14% of the prevalence in the patients with M2a Magnum was significantly lower than 41% in the patients with M2a Taper. No revision surgeries were required.

The patients with no pseudotumor did not show the increase of blood metal ion. Contrarily, several patients showed the increase of blood metal ion in case of detecting pseudotumor. MRI assessments were useful for screening of pseudotumor after MoM THA and blood metal ion should be investigated for patients with mild and moderate pseudotumor in MoM THA.

The patellar clunk syndrome describes painful catching, grinding or jumping of the patella when the knee moves from a flexed to an extended position after total knee replacement (TKR). The posterior stabilised TKR had been noted to have a higher incidence of this problem. Mobile-bearing posteriorly stabilised TKRs have been introduced to improve patellar tracking and related problems by a mechanism of self-alignment. We evaluated the patellar clunk syndrome in 113 knees in 93 patients with such a TKR at a mean follow-up of 2.3 years (2.0 to 3.2). The syndrome was identified in 15 knees (13.3%).

Logistic regression analysis showed that the absolute value of the post-operative angle of patellar tilt was significantly associated with the occurrence of patellar clunk (p = 0.025). Patellar tracking should be carefully checked during surgery.