Introduction & aims

Osteonecrosis may be triggered by bone temperature above 45°C during routine orthopaedic bone cuts using power-driven saws, with potentially negative impacts on bone healing. A new oscillating-tip saw blade design (Precision; Stryker, Kalamazoo, Mich) has been recently developed but the saw blade design may influence the amount of heat generated. We have therefore sought to compare the bone temperature during a standardised cutting task with two different saw blade designs.

Purpose

Patient-matched instrumentation is advocated as the latest development in arthroplasty surgery. Custom-made cutting blocks created from preoperative MRI scans have been proposed to achieve perfect alignment of the lower limb in total knee arthroplasty (TKA). The aim of this study was to determine the efficacy of patient-specific cutting blocks by comparing them to navigation, the current gold standard.

High tibial osteotomy is a well established joint preserving procedure for the treatment of unicompartmental knee osteoarthritis. Of particular interest are the alterations in knee loading compartments during dynamic activities such as locomotion. Computer modelling can indirectly assess contact and muscle forces in the patient. This study aimed to develop a valid model representative of high tibial osteotomy to assess the medial joint contact force at the knee during gait.

Software for Interactive Musculoskeletal Modelling (version 2, SIMM Inc, USA) was used to develop a model to replicate the effects of high tibial osteotomy surgery on tibial alignment. The program was then used to perform a detailed analysis on gait data collected from two high tibial osteotomy patients preoperatively and 6 months post operatively. Inverse dynamics simulations were conducted to investigate knee joint contact force on the medial compartment of the two patients during the stance phase of their operated limbs.

Significant decreases (p<0.05) in the medial joint contact force were observed during both early and late stance for both patients. Force generated in muscles crossing the knee was found to be the major contributor to the joint contact force. Total muscle force was found to increase significantly (p<0.05) following surgery, however decreased loads were calculated for the medial compartment. The pattern and magnitude of joint reaction force was found to be consistent before and after surgery and replicated the results of previous studies. The HTO-specific model was valid and sensitive to changes in joint reaction force, medial joint contact force and muscle forces crossing the knee.

High tibial osteotomy reduced the medial joint contact force at the knee as a result of the coronal realignment of the limb. Osteoarthritis symptoms were relieved in terms of knee pain and function. Finally, a difference in compensatory strategies was observed between patients. This novel technique allows non-invasive assessment of the mechanical effect of procedures such as HTO. This should allow more accurate planning and assessment of such surgical procedures.

Patient-matched instrumentation is advocated as the latest development in arthroplasty surgery. Custom-made cutting blocks created from preoperative MRI scans have been proposed to achieve perfect alignment of the lower limb in total knee arthroplasty (TKA). The aim of this study was to determine the efficacy of patient-specific cutting blocks by comparing them to navigation, the current gold standard.

25 TKA patients were recruited to undergo their surgery guided by Smith & Nephew Visionaire Patient-Matched cutting blocks. Continuous computer navigation was used during the surgery to evaluate the accuracy of the cutting blocks. The blocks were assessed for the fit to the articular surface, as well as alignment in the coronal and sagittal planes, sizing, and resection depth. Actual postoperative alignment was then assessed by detailed CT scans following the Perth protocol, comparing the results with intraoperative measurements.

All patient-matched cutting blocks were a good fit intra-operatively. Significant differences (p<0.05) in the resection depths of the distal femur and tibial plateau were observed between the cutting blocks and computer navigation for the medial compartment. Cutting block alignment of the femur and tibia in the coronal and sagittal planes also differed significantly (p<0.05) to navigation measurements. In addition, intraoperative assessment of sagittal femoral alignment differed to planned alignment by an average of 4.0 degrees (+/−2.3).

This study suggests the use of patient-matched cutting blocks is not accurate, particularly in the guidance of the sagittal alignment in total knee arthroplasty. Despite this technique creating well fitting cutting blocks, intraoperative monitoring, validated by postoperative CT scans, revealed an unacceptable degree of potential limb mal-alignment, resulting in increased outliers particularly when compared with standard computer navigation.

Computer navigation has been shown to improve the accuracy of total knee replacement (TKR) when compared to intra or extra osseous referencing. Currently the surgical transepicondylar axis (TEA) is used to help determine femoral component rotation. This relies on the surgeon identifying medial and lateral epicondyles intra-operatively. This process has been shown to have a high variability and operator dependency. The functional flexion axis (FFA) of the femur is a kinematically derived reference axis which has previously been shown in a cadaveric model to correspond well with the transepicondylar axis. This study was therefore designed to evaluate its accuracy in vivo.

50 patients undergoing total knee replacement under the care of the three senior authors were prospectively recruited. A preoperative CT scan was obtained and the TEA evaluated by 2 independent clinicians. TKR was undertaken in the standard fashion using Stryker navigation. The FFA was derived at 3 time points during the procedure: pre-incision, post osseous registration and following component implantation. The deviations of the FFA and surgical TEA (surTEA) to the CT-derived TEA (ctTEA) was calculated and comparisons drawn between the 2 methods with respect to validity, as well as within and between-patient reproducibility.

While the FFA results were highly correlated between pre and post-arthrotomy (r = 0.89), the post-incision FFA (−1.60+/−3.7) was significantly internally rotated (p<0.01) relative to the pre-incision FFA (−2.50+/−3.4). In addition the surgical TEA (−0.40+/−3.6) was significantly internally rotated (p = 0.02) relative to the post-incision FFA (1.80+/−3.7) for the combined data from all 2 surgeons. However, when examined individually, 1 of the 2 surgeons showed no significant difference between the FFA and TEA. In addition, the two methods demonstrated comparable between-patient variability in the knee axis, although surgeon-dependent patterns remained.

The FFA has been shown to be of equivalent accuracy to the surgical TEA but surprisingly does not avoid its operator-dependency. Further evaluation of the FFA method with possible adjustments to the algorithm is warranted.

Computer assisted surgical navigation has played an increasingly central role in total knee arthroplasty (TKA). Given the recognized importance of subtle component position changes in knee function, navigation has emerged as a promising tool for reducing the occurrence of significant malalignment. The ability of this technology to reliably measure multiple parameters intraoperatively allows analysis to possibly identify a correlation between intraoperative computer assisted surgical navigation data and functional outcomes of patients undergoing elective total knee arthroplasty.

Intraoperative navigation data was collected for 121 patients undergoing cemented, posterior stabilized TKA. Three forward stepwise regression analyses were performed to associate intraoperative coronal alignment correction, tibiofemoral external rotation, and alignment under varus and valgus stress with one year outcomes, including range of motion, Oxford and SF-36 scores.

The amount of alignment correction and the maximum flexion achieved intraoperatively were significantly correlated (p <0.05, R-sq = 13%) with clinically measured maximum flexion at one year. Maximum flexion achieved intraoperatively, external tibiofemoral rotation and maximum varus under stress were also significantly associated (p < 0.05, R-sq = 31%) with the physical component of the SF-36 outcome score.

Analyses of computer navigation in TKA to date have primarily focused on precision of sagittal plane correction. Alternatively we have identified four intraoperative parameters that correlate with functional outcome at one year. Correct intraoperative interpretation of navigation data may allow surgeons to make subtle changes in real time to produce superior short-term outcomes for patients.

The question of whether to reconstruct an ACL-deficient knee as early as possible following injury or to delay surgery remains unanswered. Early reconstruction potentially reduces the risk of secondary damage. However, there is also concern regarding the risk of arthrofibrosis if surgery is undertaken too soon. The aim of this study was to investigate whether injury-to-surgery delay determines ACL-reconstruction outcomes at up to 2years post-operatively.

A retrospective analysis of prospectively collected data from 211 knees with isolated primary ACL ruptures was performed. Patients were examined preoperatively, at 6months, 1 year, and 2 years post-operatively using International Knee Documentation Committee (IKDC) and Lysholm scores. Side to side differences in knee laxity were also measured with a KT1000 arthrometer. Spearman's rho correlations were used to associate injury-to-surgery delay with outcome scores.

Outcomes scores significantly increased for both IKDC (p<0.05) and Lysholm (p<0.05) questionnaires. Significant positive correlations (p<0.05) were also found between injury-to-surgery delay and IKDC and Lysholm subjective scores. Strongest correlation coefficients were noted at the 2yr follow-up for both IKDC and Lysholm scores (r = 0.79 and 0.8 respectively). Side-to-side laxity measures also showed significant positive correlations with injury-to-surgery delay at 1 year (r = 0.17) and 2 year (r = 0.41) follow ups. The positive correlation suggests that delayed surgery is positively related to subjective outcomes, as well as objective measures of knee laxity.

However, this relationship also suggests that other factors such as the patient's functional status at time of surgery may play a role in their post-operative function. For example, those who can compensate for the ruptured ligament may function well following delayed surgery. These findings highlight the need for more detailed investigation of the interaction between functional status, injury-to-surgery delay and post-operative recovery.

An ACL reconstruction is designed to restore the normal knee function and prevent the onset and progression of degenerative changes such as osteoarthritis. However, contemporary literature provides limited consensus on whether knee degeneration can be attenuated by the reconstruction procedure. The aim of this pilot study was to identify the presence of early osteoarthritis after ACL reconstruction using MRI analysis.

19 patients who had undergone an ACL reconstruction (9 isolated ACL rupture, 8 ACL rupture and meniscectomy, 2 ACL rupture and meniscal repair) volunteered for this study. MRI's were collected preoperatively and postoperatively for analysis with a mean follow up of 23 months. The Boston-Leeds Osteoarthritis Knee Score (BLOKS) was used for the analysis of the articular cartilage by a consultant orthopaedic surgeon. Scores ranged from 0–3, with 0 being total coverage and thickness of the cartilage and 3 being no coverage. Qualitative analysis was then conducted on each patient to determine if the articular cartilage improved, degenerated, or did not change between preoperative and follow-up scans.

All patients with isolated ACL rupture were found to either have no change or improved articular cartilage scores in their follow up scans compared preoperatively. In contrast, patients with a meniscal repair displayed worse cartilage scores postoperatively. Lastly, of the patients who had an associated meniscectomy, 6 had worse follow-up results, with the remaining patients showing no change or improved cartilage scores.

The present results indicate that patients with an isolated ACL rupture have a reduced risk of developing OA compared to those with associated meniscal injuries. This has implications for analysing the outcome of current ACL reconstruction techniques and in predicting the likelihood of patients developing OA after ACL reconstruction. Future work will involve confirming this pattern in a larger patient sample, as well as exploring additional factors such as time to surgery delay and rehabilitation strategy.

Femoral nerve block is a reliable and effective method of providing anaesthesia and analgesia in the peri-operative period but there remains a small but serious risk of neurological complication. We aimed to determine incidence and outcome of neurological complications following femoral nerve block in patients who had major knee surgery.

During the period January 2003 to August 2008, medical records of all patients undergoing knee surgery by Dr Myles Coolican and Dr David Parker, who had been administered femoral block for peri-operative analgesia, were evaluated.

Patients with a neurological complication were invited take part in the study. A detailed physical examination including sensory responses, motor response and reflexes in both limbs was performed by an independent orthopaedic surgeon. Subjective outcome and pain specific questionnaires as well as clinical measurements were also collected.

Out of 1393 patients administered with femoral nerve block anaesthesia during this period, 28 subjects (M:F= 5:23) were identified on the basis of persistent symptoms (more than three months) of femoral nerve dysfunction. All the patients had sensory dysfunction in the autonomous zone of femoral nerve sensory distribution. The incidence of neurological complications was 2.01%. One patient was deceased of unrelated causes and five patients declined to participate in the study. 14 patients out of the 22 have been examined so far. Nine cases had a one shot nerve block and five had continuous peripheral nerve block catheter. Areas of hypoesthesia/anaesthesia involving femoral nerve distribution occurred in 7 subjects and hyperaesthesia/paresthesia occurred in four. One subject had a combination of hypoesthesia and hyperesthesia in different areas of the femoral nerve distribution. Three subjects had bilateral symptoms following bilateral simultaneous nerve blocks. Dysesthesias in the affected dermatomes were found in seven cases and paresthesias were found in eight cases. Douleur Neuropathique en 4 questions (DN4) score of ï³ 4 was found in all the patients (average value: 5.55). The average scores for tingling, pins and needles and burning sensation (in a scale from 0 to 10) are 3.8, 3.1 and 2.9 respectively.

The incidence of persistent neurological complication after femoral nerve block in our series is much higher compared to the reported incidence in the contemporary literature (Auroy Y. et al. Major complications of regional anesthesia in France: Anesthesiology 2002; 97:1274 80). The symptoms significantly influence the quality of life in the affected cases and question the value of the femoral nerve block in knee surgery.

Osteotomies are performed in patients with lower limb malalignment, usually associated with osteoarthritis of the knee or instability. The surgery realigns the mechanical axis of the leg by either an opening or closing wedge procedure with the goal of decreasing symptoms, improving function, and delaying the progression of osteoarthritis.

The 103 patients that had undergone osteotomy surgery were studied prospectively, and data was analysed one year post surgery. We examined subjective outcomes, patient history and surgical variables using backwards stepwise multiple regression models to determine whether there were any associations between these.

Subjective outcomes from a total of 103 osteotomy patients at one year post surgery were compared to patient history and surgical variables. All categories of KOOS and WOMAC scores were improved after surgery.

The multivariate models showed that variables significantly influencing the outcomes were pre-operative flexion, pre-operative weight, the size of the HTO plate used and tourniquet time.

Greater pre-operative flexion; lower weight; larger plate used, indicating larger corrections; and lower tourniquet times were shown to result in improved scores. Not all variables influenced all categories of the scores. While flexion and pre-operative weight influenced across the categories of both scores, plate size influenced KOOS pain and symptoms and tourniquet time influenced KOOS sport and quality of life.

Knee flexion and body weight were the most influential variables when considering KOOS and WOMAC outcome scores as a measure of success. The size of the correction may have influenced the pain and symptom scores because patients with greater malalignment may have initially had worse symptoms and their perception of their current function and pain is affected by their previous levels of pain and function. Osteotomy results in improved function and pain scores and our results indicate that there are several variables which significantly influence patient outcomes and may be of greater importance than other variables.