Introduction

Hind foot Charcot deformity is a disastrous complication of diabetic neuropathy and can lead to instability, ulceration and major amputation. The treatment of these patients is controversial. Internal stabilization and/or external fixation have demonstrated variable results of limb salvage and some authorities thus advise patients to undergo elective major amputation. However, we report a series of 9 diabetic patients with severe hind foot deformity complicated by ulceration in 5/9, who underwent acute corrective internal fixation with successful correction of deformity, healing of ulceration in 4/5 patients and limb salvage in all cases.

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).

Background and Literature Research: Fixed sagittal mal-rotation of pelvis is commonly encountered in patients with ankylosing spondylitis. The pelvis positioning for total hip arthroplasty in these patients can be a pitfall to an oblivious surgeon, and gives rise to mal-positioning of the acetabular component and subsequently leads to dislocation of the arthroplasty.

Objective: To quantify the effect of sagittal pelvic rotation on the positioning of acetabular component using three dimensional computer model.

Materials and Methods: Ten embalmed cadaveric pelvis with intact ligaments were scanned in 1 mm slices using computed tomogram (CT). The image reconstruction was done by the software “MIMICS” in microcomputer. The resulting three dimensional models can be rotated freely using “MIMICS.” Insertion of acetabular component was stimulated in different sagittal rotation of the pelvis. The ratio of the longitudinal to the transverse dimension of the obturator foramen was noted, and the uncovered area of the acetabular components was calculated.

Discussion: Pelvic rotation on the sagittal plane cannot be easily measured by radiographs. The shape of the obturator foramen on plane pelvic radiographs centered at pubic symphysis varies with the pelvic rotation on the sagittal plane and thereby serves as an indirect way to measure pelvic rotation. The shape of obturator foramen on plain radiographs therefore provided a guideline for patient positioning and the alignment of insertion of acetabular component during surgery.

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.

Introduction: Normal axial alignment of the lower extremity is important to surgeons who perform reconstruction surgery of the knee. The data are, however, not available for Chinese adults.

Methods: The axial alignment of the lower extremity of twenty-five adult males and twenty-five adult females of southern Chinese origin was measured by using weight-bearing radiographs of the entire lower limb. The mean age of the male and female volunteers was twenty-four years and twenty-three years respectively. The axial alignment of the lower extremity was measured and the results were compared with two similar studies conducted in the United States.

Results: The medial inclination of the tibial plateau in the Chinese volunteers was greater than the commonly cited 3 degrees (with a mean of 5.4 ± 2.5 degrees for females and 4.9 ± 2.3 degrees for males). The extremities in Chinese volunteers were found to have a mean of 2.2 ± 2.5 degrees varus (females) and 2.2 ± 2.7 degrees varus (males).

Conclusions and Discussion: The medial inclination (knee joint obliquity) of the Chinese knee joint was significantly larger than Caucasian subjects. The higher knee joint obliquity exposes the cartilage of the Chinese knee to a higher shearing force and subsequently result in osteoarthritis. This may explain the racial difference in the ratio of knee to hip osteoarthritis. When performing total knee arthroplasty, a 5-degree, instead of the commonly cited 3-degree, external rotation of the femoral component may be required to obtain a rectangular flexion gap in total knee arthroplasty in Chinese patients.

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.