Introduction and Aim

Quadriceps strength is crucial for physical function in patients with knee osteoarthritis (KOA). This study aimed to investigate the effect of combining blood flow restriction (BFR) with low-intensity training (LIT) on quadricep strength in patients with advanced KOA.

Aims

The surgical helmet system (SHS) was developed to reduce the risk of periprosthetic joint infection (PJI), but the evidence is contradictory, with some studies suggesting an increased risk of PJI due to potential leakage through the glove-gown interface (GGI) caused by its positive pressure. We assumed that SHS and glove exchange had an impact on the leakage via GGI.

Uncemented femoral components have been used in total hip arthroplasties (THAs) for over three decades. Data on long-term performance of hydroxyapatite-coated femoral stems is however limited. This study reports the survivorship of a collarless, straight, hydroxyapatite-coated femoral stem (Omnifit HA, Osteonic) with a minimum of 20 years of follow-up.

We reviewed the results of 165 THAs using Omnifit HA in 138 patients performed between August 1993 and December 1999. The mean age at surgery was 46 years (range 20 – 77 years). Avascular necrosis was the most common cause of THA, followed by ankylosing spondylitis and primary osteoarthritis. The mean follow-up was 22 years (range 20–31 years). At 20 and 25 years, 113 arthroplasties (91 patients) and 63 arthroplasties (55 patients) were available for follow-up respectively, while others had deceased or were lost to follow-up.

Kaplan-Meier survivorship analysis was performed to evaluate the survival of the femoral component. Radiographs were reviewed at regular intervals, and implant stability was evaluated using Engh classification.

Seven out of 165 stems were revised upon the latest follow-up; that included one case of aseptic loosening with revision done at 15 years, three peri-prosthetic fractures, two infections, and one recurrent dislocation.

At 20 years, survivorship with revision of the femoral stem for any cause and aseptic loosening as the endpoint was 96.0% (95% CI, 92.6 – 99.5%) and 98.4% (95% CI, 96.2 – 100%) respectively. At 25 years, the corresponding survivorship rates were 94.5% (95% CI, 91.9 – 97.3%) and 98.1% (95% CI, 95.7 – 99.6%) respectively.

Radiographic findings of stable bony fixation were seen in 86 stems (76.1%) and those of loosening in 4 stems (3.5%) at 20 years. All patients with radiographic signs of loosening were asymptomatic and did not require revision.

The Omnifit HA femoral stem offered promising long-term survivorship into the third decade.

Highly crosslinked polyethylene (HXLPE) has been used with great clinical success in total hip arthroplasty (THA) since its debut in the late 1990's. However, reports regarding this bearing couple in its second decade of service are still scant. The aim of this study was to 1. Determine the long term clinical and radiological results and 2. Investigate what factors affect wear rates using a metal-on-HXLPE bearing articulation.

55 THA's using a single brand of HXLPE liner, cementless cup and 28mm hip ball were performed in 44 patients. Age, sex, and Charlson Comorbidity Index (CCI) and need for revision surgery were recorded. Linear and volumetric wear was determined using the Martell method.

Mean age at operation was 51.2 (29–73 +/− 12.1) years. Mean duration of follow up was 16.9 years (range 15.0–20.1 +/− 1.1 years). Osteolysis was not present in the latest follow up radiographs.

Median linear and volumetric wear rate was 0.035mm/year (95% CI 0.031–0.047) and 7.12mm³/year (95% CI 6.92–17.25) respectively. Acetabular component position was not found to be related to both linear and volumetric wear. No significant difference was found in the linear and volumetric wear rates of thinner and thicker liners (8mm or below and > 8mm) (p=0.827 and p=0.843 respectively).

HXLPE is associated with very low linear and volumetric wear rates which has virtually obviated osteolysis and has translated to excellent survivorship even at long term follow up. In-vivo oxidation does not appear to be of clinical concern at this point in its service cycle.

Summary Statement

OA knee with subchondral cyst formation presented differential microstructure and mechanical competence of trabecular bone. This finding sheds light on the pivot role of subchondral cyst in OA bone pathophysiology.

Unicompartment knee arthroplasty (UKA) was proven to be one of the standard treatments of medial compartment osteoarthritis. The key to success was restoration of pre-operative alignment. Overcorrection of coronal (AP) alignment may predispose to early osteoarthritis in the contralateral compartment, change in post-operative tibial slope may predispose to proximal tibial bone collapse and loosening of tibial prosthesis. Minimally invasive surgery (MIS) in UKA was developed quickly in the last ten years. However, MIS has limited access to visualize the surgical field and limb alignment. Computer navigation may help the surgeon to place the component in more accurate position. We aim to study the radiological alignment of computer assisted MIS UKA.

Eighteen patients with UKA (PreservationTM, all poly tibia, DePuy Orthopaedics Inc, Warsaw, IN) implanted using MIS technique were studied prospectively. The CiTM system (DePuy International Ltd, Warsaw IN) were used for computer navigation. Five male and 13 female patients were studied. The mean age of the patients was 58.2 (range, 45 to 70). All patients had medial compartment osteoarthritis with varus deformity. The postoperative coronal (AP) alignment and tibial slope of the operated limb were compared with the pre-operative alignment for any significant difference.

The mean pre-operative and post-operative radiographic coronal (AP) alignment of the operated limb were 8.4° varus (range, 2° to 12°) and 7.2° varus (range, 1° to 15°) respectively, the difference was not significant (p = 0.537). The mean pre-operative and post-operative tibial slope were 6.8° (range, 3° to 11°) and 5.8° (range, 3° to 10°) respectively, the difference was not significant (p = 0.066). The post-operative tibial slope correlated well with the intra-operative tibial slope recorded by computer after bone cut was made (Cronbach’s Alpha = 0.771). The mean tourniquet time was 124 minutes (range, 94 to 140 minutes).

There was no significant difference in pre-operative and post-operative coronal alignment of the operated limb. Computer assisted MIS UKA could reproduce the pre-operative coronal alignment and tibial slope. Restoration of the pre-operative limb alignment in coronal plane and tibial slope was crucial to the survival of UKA. Computer navigation could help the surgeon to position the component during minimally invasive surgery. However, the learning curve of computer assisted MIS UKA was steep.

Malalignment of more than three degrees in coronal plane was associated with poor outcome. Most of the alignment occurred in the tibial coronal plane alignment. Computer assisted surgery (CAS) in total knee arthroplasty (TKA) aimed to minimize malalignment. Most of the CAS-TKA results were using infrared tracking system. Electromagnetic navigation in total knee arthroplasty was developed in recent years. It aimed at high accuracy and easy signal detection. However, there was limited result being published.

From August, 2006 to March, 2008, 50 patients had TKA performed with Medtronic electromagnetic navigation (EM CAS-TKA). The results were compared with 50 matched patients who had TKA performed with conventional technique. The post-operative limb alignments were compared. More than three degrees deviation from neutral alignment was defined as outliers.

There was no significant difference in the age, sex distribution, pre-operative range of motion and pre-operative deformity between the two groups. EM-CAS TKA group had significantly less deviation from neutral in the tibial coronal plane (p < 0.001) and femoral sagittal plane (p = 0.006) plane than conventional group. There was no significant difference in femoral coronal plane and tibial sagittal plane alignment between the two groups (p = 0.069 and 0.185 respectively). There were significantly more outliers (> 3 malalignment) in tibial coronal plane (p = 0.004) and femoral sagittal plane (p = 0.049) in conventional group than EM-CAS TKA group. There was no significant difference in the outliers in femoral coronal plane, and tibial sagittal plane (p = 1 and 0.1 respectively). The mean tourniquet time of the EM-CAS TKA group, 95.7 minutes (range, 65 to 126 minutes), was significantly higher than the conventional group, mean 72.1 minutes (range, 45 to 120 minutes), p value < 0.001. There was no pin tract complication and infection in the electromagnetic navigation group.

Electromagnetic navigation had improved the tibial coronal plane and femoral sagittal plane alignment in total knee arthroplasty with less outlier. Better alignment may improve the survival of the prosthesis. The learning curve is short and it is easy to handle. Electromagnetic navigation has the potential application in minimally invasive total knee arthroplasty.

This study investigated the intra-observer errors in obtaining visually selected anatomic landmarks that were used in registration process in a non-image based computer assisted TKR system.

The landmarks studied were centre of distal femur, medial and lateral femoral epicondyle, centre of proximal tibia, medial malleolus and lateral malleolus. Repeated registration in the above sequence was done for one hundred times by one single surgeon.

The maximum combined errors in the mechanical axis of the lower limb were only 1.32 degrees (varus/valgus) in the coronal plane and 4.17 degrees (flexion/extension) in the sagittal plane. The maximum error in transepicondylar axis was 8.2 degrees.

The errors using the visual selection of anatomic landmarks for the registration technique of bony landmarks in non-image based navigated TKR did not introduce significant error in the mechanical axis of the lower limb in the coronal plane. However, the error in the transepicondylar axis was significant in the “worst case scenario”.

Two hundred and thirty six posterior stabilized total knee arthroplasties were performed consecutively. Twenty seven patellar clunk syndromes were identified in 25 patients. Insall-Salvati ratio, position of joint line, postoperative patellar height and anterior-posterior position of tibial tray were measured. We found that post-operative low-lying patella (p< 0.001) and anterior placement of tibial tray (p=0.011) was associated with patellar clunk syndrome. Thirteen patients had bilateral total knee replacements of the same prosthesis (5 bilateral AMK and 8 bilateral IB) but unilateral patellar clunk syndrome. The non-clunk sides were used as control for comparison with the clunk sides. The congruency and tilting of the patellar button in the skyline view were documented. We observed that the congruency of the patella button was less satisfactory in the clunk side (p=0.019).

Objective: To compare the outcomes of two cementless total hip arthroplasty systems in young patients.

Methods: Between 1987 and 1995, 68 cementless total hip replacements were performed in 50 patients younger than 40 years (range 22–40). Five patients were excluded, and 61 hips in 45 patients were available for evaluation after 7.6 years (range 3.1–11.4). There were 27 Anatomic Medullary Locking (AML, Depuy, Warsaw, Indiana) and 34 Porous Coated Anatomic (PCA, Howmedica, Rutherford, New Jersey) prostheses. The two groups were comparable in gender, age, pre-operative diagnoses, activity levels, sizes of components used and the follow-up periods.

Results: Seven PCA (20.6%) and one AML acetabular components (3.7%) were radiologically loose (p = 0.02). Osteolysis was seen in five AML (18.5%) and 24 PCA hips (70.6%) (p = 0.001). Harris hip scores, revision rates, cumulative survival rates, femoral loosening rates, extent of stress shielding and the average linear penetration rates did not show significant differences between AML and PCA hips.

Discussion and conclusion: the PCA acetabular components had a higher loosening rate; the latter was comparable to the reported rates with this design. Osteolysis was more frequently seen in the PCA hips. Since the two groups were otherwise comparable, it was possible that either the polyethylene particles generated at the articulation could be different, or there could be increased backside wear in PCA acetabular components.

Introduction: We compared the early results of mobile-bearing knee prosthesis with fixed-bearing knee prosthesis in 20 patients who had one-stage, sequential, bilateral replacements.

Patients and Methods: In each patient, a Low Contact Stress (LCS, Depuy) rotating-platform prosthesis was inserted in one side, and an Anatomic Modular Knee (AMK, Depuy) posterior-stabilised prosthesis was inserted in the other side. The same surgical routines were adopted for both sides in each patient. The LCS and AMK knees were comparable in Knee Society knee scores, knee flexion and flexion contracture before surgery.

Results: There were significant improvements in the Knee Society knee and functional scores after surgery (p < 0.001) for both LCS and AMK knees. Although the LCS knees had better Knee Society knee score, better knee flexion, and less residual flexion contracture at final follow-up, all these were not statistically significant when compared with the AMK knees.

Discussion and Conclusion: The results of mobile-bearing knee replacements were as good as those that followed fixed-bearing knee replacements.

From 1992 to 1999, 713 total joint arthroplasties were performed in The Department of Orthopaedic Surgery, The University of Hong Kong. Since January 1993, a uniform prophylactic antibiotic regime was employed: one dose of first generation cephalosporin (one gram cephazonlin) on induction and every 4-hourly. In case of sequential bilateral total knee arthroplasty, one gram of cephazolin will be given on induction for the first knee and one hour before the operation on the opposite knee. Antibiotic will be discontinued post-operatively. No significant difference was identified between the infection rate before (1.4%) and after (1.2%) the adoption of the prophylactic antibiotic guidelines (p > 0.4). The study had shown that one dose of first generation cephalosporin is as effective as multiple dose of prophylactic antibiotic, either first or second generation cephalosporin, in preventing infection in total joint arthroplasty.