Objectives

Acetabular component orientation in total hip arthroplasty (THA) influences results. Intra-operatively, the natural arthritic acetabulum is often used as a reference to position the acetabular component. Detailed information regarding its orientation is therefore essential. The aim of this study was to identify the acetabular inclination and anteversion in arthritic hips.

Objective

This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability.

Objectives

We performed in vitro validation of a non-invasive skin-mounted system that could allow quantification of anteroposterior (AP) laxity in the outpatient setting.

The routine use of a fixed distal femoral resection angle in total knee arthroplasty (TKA) assumes little or no variation in the angle between the anatomical and mechanical femoral axes (FMA angle) in different patients. The aims of this study were threefold, firstly to investigate the distribution of FMA angle in TKA patients, secondly to identify any correlation between the FMA angle and the pre-operative coronal mechanical femoro-tibial (MFT) angle and in addition to assess post-operative MFT angle with fixed or variable distal femoral resection angles.

277 primary TKAs were performed using either fixed or variable distal femoral resection angles (174 and 103 TKAs respectively), with intramedullary femoral and extramedullary tibial jigs. The variable distal femoral resection angles were equal to the FMA angle measured on pre-operative Hip-Knee-Ankle (HKA) digital radiographs for each patient. Outcomes were assessed by measuring the FMA angle and the pre- and post-operative MFT angles on HKA radiographs.

The FMA angle ranged from 2° to 9° (mean 5.9°). Both cohorts showed a correlation between FMA and pre-operative MFT angles (fixed: r = -0.499, variable: r = -0.346) with valgus knees having lower FMA angles. Post-operative coronal alignment within ±5° increased from 86% in the fixed angle group to 96% when using a variable angle, p = 0.025. For post-operative limb alignment within ±3°, accuracy improved from 67% (fixed) to 85% (variable), p = 0.002.

These results show that the use of a fixed distal femoral resection angle is a source of error regarding post-operative coronal limb malalignment. The correlation between the FMA angle and pre-operative varus-valgus alignment supports the rational of recommending the adjustment of the resection angle according to the pre-operative deformity (3°-5° for valgus, 6°-8° for varus) in cases where HKA radiographs are not available for pre-operative planning.

The CALEDonian Technique™, promoting enhanced recovery after surgery, is a multimodal multidisciplinary technique. This has demonstrated excellent analgesic control allowing early mobilisation and discharge following TKA, whilst maintaining patient safety.

All patients follow a planned programme beginning with pre-operative out-patient education at the pre-assessment visit. An anaesthetic regimen consisting of pre-emptive analgesia is combined with a spinal/epidural with propofol sedation. Intra-articular local anaesthetic soft tissue wound infiltration by the surgeon under direct vision is supplemented by post-operative high volume intermittent boluses via an intra-articular catheter. Early active mobilisation is positively encouraged.

A prospective audit of over 1000 patients demonstrated 35% of patients mobilised on day 0 and 95% by day 1, with rescue analgesia required in only 5% of cases. 79% of patients experienced no nausea or vomiting helping reduce length of stay from six to four postoperative days. A catheterisation rate of 7%, a DVT rate of 0.6% and a PE rate of 0.5% remained within or below previously published levels.

Laboratory studies examining the performance of the epidural filter and injection technique used for the post-operative intra-articular injections demonstrated this to be robust and effective at preventing bacterial ingress. This in-vitro data is supported by clinical results demonstrating no increase in the deep infection rate of 0.7% since the implementation of the technique at our institution.

We conclude that the CALEDonian Technique™ effectively and safely improves patient post-operative recovery following TKA.

Purpose

We report our initial results of a new comprehensive patient care plan to manage peri-operative pain, enable early mobilisation and reduce length of hospital stay in TKA.

Recent studies suggest the use of computer navigation during TKA can reduce intraoperative blood loss. The purpose of this study was to assess if navigation affected blood loss after TKA in the morbidly obese patient (BMI> 40).

Total body blood loss was calculated from body weight, height and haemotocrit change, using a model which accurately assess true blood loss.

The computer navigated group comprised of 60 patients, 30 with BMI > 40 and 30 with BMI< 30. The matched conventional knee arthroplasty group consisted of 62 consecutive patients, 31 with BMI> 40 and 31 with BMI< 30 The groups were matched for age, gender, diagnosis and operative technique.

Following TKA, the mean total loss was 1014mls (521-1942, SD 312) in the computer assisted group and 1287mls (687-2356, SD 330) in the conventional group. This difference was statistically different (p< 0.001). The mean calculated loss of haemoglobin was 19 g/dl in the navigated group versus 25 g/dl in the conventional group; this was also significant at p< 0.01. The mean total loss was 1105mls in patients with a BMI> 40 in the navigated group compared to 1300mls in the conventional group (p< 0.01). A significant correlation was found between total blood loss and BMI (r=0.2, p< 0.05).

This study confirms a highly significant reduction in total body blood loss and calculated Hb loss between computer assisted and conventional TKA in obese patients. Therefore navigation-assisted TKA could present an effective and safe method for reducing blood loss and preventing blood transfusion in obese patients undergoing TKA.

Computer navigated total knee arthroplasty (TKA) has several proposed benefits including reduced post operative blood loss. We compared the total blood volume loss in a cohort of morbidly obese (BMI> 40) patients undergoing computer navigated (n=30) or standard intramedullary techniques (n=30) with a cohort of matched patients with a BMI< 30 also undergoing navigated (n=31) or standard TKA (n=31). Total body blood loss was calculated from body weight, height and haemotocrit change, using a model which accurately assesses true blood loss as was maximum allowable blood loss. The groups were matched for age, gender, diagnosis and operative technique.

The mean true blood volume loss was significantly (p< 0.001) less in the computer assisted group (1014±312mls) compared to the conventional group (1287±330mls). Patients with a BMI > 40 and a computer navigated procedure (1105 ±321mls) had a significantly lower (p< 0.001) blood volume loss compared to those who underwent a conventional TKA (1399±330mls). There was no significant difference in the transfusion rate or those reaching the maximum allowable blood loss between groups.

This study confirms a significant reduction in total body blood loss between computer assisted and conventional TKA in morbidly obese patients. However computer navigation did not affect the transfusion rate or those reaching the transfusion trigger in the morbidly obese group. Therefore computer navigation may reduce blood loss in the morbidly obese patient but this may not be clinically relevant to transfusion requirements as previously suggested.

Purpose: The aim of this study was to evaluate the rate of surgical site infection (SSI) in all patients undergoing a primary total knee arthroplasty (TKA) and to audit the outcomes for those who were obese.

Methods/Results: We retrospectively reviewed data for 839 primary TKAs done at a National Arthroplasty Centre over one year (April 2007 – March 2008). BMI data was available for 824 (98%) of the patients. SSI data had been collected prospectively by the Infection Control team for up to 30 days post-operatively and was available for all patients. Patients were grouped based on their BMI and the WHO classifications (WHO Technical Report Series 894).

31.2% of the patients were obese class I (BMI 30 – 35), 19.0% were obese class II (BMI 35 – 40) and 8.6% were obese class III (BMI > 40). There were 23 patients with SSIs, 22 having superficial SSI and only one patient with a deep SSI. The overall superficial SSI rate was 2.7%. The superficial SSI rates for each group were as follows: normal (BMI < 25) = 1.3%; overweight (BMI 25 –30) = 2.3%; obese class I = 1.6%; obese class II = 3.2%; obese class III = 8.5%. The Fisher’s Exact Test between all obese patients and those with BMI < 30 showed no significant difference in superficial SSI rates (p = 0.39) but did show a significant difference between superficial SSI rates in the obese class III patients and the rest of the cohort (p = 0.008).

Conclusions: Obese class III (BMI > 40) patients are at an increase risk of superficial SSI as compared to other patients undergoing primary TKA. However, obese class I and II patients do not appear to have an increased likelihood of superficial SSI as compared to patients who have BMI < 30.

Total knee replacement (TKR) has become the standard procedure in management of degenerative joint disease with its success depending mainly on two factors: three dimensional alignment and soft tissue balancing. The aim of this work was to develop and validate an algorithm to indicate appropriate medial soft tissue release during TKR for varus knees using initial kinematics quantified via navigation techniques.

Kinematic data was collected intra-operatively for 46 patients with primary end-stage osteoarthritis undergoing TKR surgery using a CT-free navigation system. All patients had preoperative varus knees and medial release was made using the surgeon’s experience. From this data an algorithm was developed to define the medial release based on the pre-operative mechanical femoral-tibial angle with valgus stress;

No release (tibial cut only) when valgus stress > −2/3°. Moderate release (medial aspect of tibia +/− semimembranosous tendon) when valgus stress > −5° and < −2°. Extensive release (proximal) when valgus stress < −5°. If there was a fixed flexion deformity > 5° then a posterior release was performed.

This algorithm was validated on a further set of 35 patients where it was used to determine the medial release based only on the kinematic data. The post-operative varus and valgus stress angles for the two groups were compared and showed good outcomes in terms of distribution and outliers.

The results showed that the algorithm was a suitable tool to indicate the type of release required based on intra-operatively measured pre-implant valgus stress and extension deficit angles. It reduced the percentage of releases made and the results were more appropriate than the decisions made by an experienced surgeon.