Why two-thirds of patients accepted the second session in staged bilateral total knee arthroplasty: a prospective analysis of 111 patients

Association of the joint line orientation angle of the contralateral limb with the alignment change of the unilateral and bilateral opening-wedge high tibial osteotomy

PURPOSE

This study aimed to evaluate and compare unilateral and bilateral open-wedge high tibial osteotomy (OWHTO) using mid-term serial assessment of clinical and radiological outcomes, especially focussing on coronal lower extremity alignment.

METHODS

Serial radiological assessments were performed in 40 patients (80 knees) with bilateral OWHTO and 49 patients (49 knees) with unilateral OWHTO. Both groups were further divided into four subgroups to compare each limb (unilateral involved and non-involved limbs and bilateral primarily and secondarily treated limbs). Radiological and clinical outcomes were evaluated and compared among the four groups. For the alignment change assessment, the pelvic tilt angle (PTA), weight-bearing line ratio (WBLR), joint line orientation angle (JLOA), medial proximal tibia angle (MPTA), joint line convergence angle (JLCA), distal tibia articular angle (DTAA), and talar inclination (TI) were measured pre- and postoperatively at 3, 6, and 12 months and annually thereafter. Student's t-test, one-way repeated-measures analysis of variance, and correlation analysis were used to compare the groups.

RESULTS

Patients in the unilateral and bilateral OWHTO groups had similar postoperative radiological and clinical outcomes. Each unilaterally involved limb and primarily treated bilaterally involved limb were negatively affected by the contralateral limb with respect to increased JLOA during the postoperative period (unilateral OWHTO group: r = -0.350, p = 0.023; bilateral OWHTO group: r = -0.520, p = 0.005). The correction change of the ankle parameters in the secondarily treated limb showed greater varus alignment than the primarily treated limb after bilateral OWHTO (DTAA (0.1 ± 3.0 vs. -0.5 ± 3.8°, p = 0.014) and TI (0.9 ± 3.2° vs. -0.3 ± 2.9, p = 0.001)).

CONCLUSION

Unilateral and bilateral OWHTOs shared similar postoperative radiological and clinical outcomes. Alignment changes of the unilateral OWHTO and the primarily treated limb of the bilateral OWHTO were associated with the JLOA of the contralateral limb.

LEVEL OF EVIDENCE

Cohort study; Level III.

Does Early-Period Patient Dissatisfaction Turn Into Satisfaction Over Time After Total Knee Replacement?

BACKGROUND Total knee arthroplasty (TKA) is frequently used in the treatment of end-stage gonarthrosis, and the patient satisfaction rate varies. This study aimed to reveal the change in mid-term patient satisfaction results and functional scores of patients with low early postoperative satisfaction scores. MATERIAL AND METHODS We included 163 patients who underwent total knee prosthesis between September 2017 and February 2018. Among these patients, early (6 months) and mid-term (24 months) satisfaction and functional results of 34 patients with low satisfaction scores (Likert evaluations 1, 2, and 3) were evaluated. We assessed early-term functional results and satisfaction rates, mid-term analysis of patients who were not satisfied in the early period, and the relationship between functional scores and satisfaction. RESULTS The Likert score was 4 or 5 in 124 (80%) of 158 patients, and early dissatisfaction was detected in 34 patients (20%). In the early-period dissatisfied group, satisfaction scores 6 months after surgery were 1.9±1.1 (1-3) and 4.2±1 (3-5) 24 months after surgery. A statistically significant difference was observed between the dissatisfied group's early and mid-term KSS and KS values. A correlation was observed between satisfaction scores and KS and KSS scores (P<0.05). CONCLUSIONS Patients who do not have mechanical problems with total knee arthroplasty but are not satisfied with the surgery in the early period can be satisfied over time after regular follow-up, appropriate communication and information, and effective rehabilitation.

Should Sequential Bilateral Total Knee Arthroplasty Be Limited to Patients Younger than 80? A Two-Arm Propensity Matched Study

Despite multiple studies, there remains a debate on the safety of bilateral total knee arthroplasty (BTKA) in the average age patient, with a paucity of data on the outcome of BTKA in an elderly population. This study included 89 patients aged 80 years and older undergoing sequential BTKA over 14 years were identified in a prospectively collected database. Two matched comparison groups were created: patients under 80 undergoing sequential BTKA and patients over 80 undergoing unilateral TKA (UTKA). An analysis of complications, mortality, revision, and patient-reported outcome measures was performed. Mean age of the elderly cohorts was similar: 82.6 for BTKA and 82.9 for UTKA. The average age BTKA cohort had a mean age of 69.1. Complication rates were higher in bilateral cohorts, more so in the elderly BTKA cohort. Pulmonary embolism (PE) was observed in bilateral cohorts only. In these patients, history of PE and ischemic heart disease was a strong predictive factor for developing a major complication. There was no difference in revision rates and infection rates between the three cohorts, and no difference in patient survivorship between the two elderly cohorts. Through the combination of low revision and high survivorship rates and comparable clinical outcomes, this article demonstrates that simultaneous BTKA is an appropriate option to consider for an elderly patient, with proper patient selection and perioperative management. The demonstrated risk groups show that emphasis on patient selection should be focused on medical history rather than chronological age.

Complications Associated With Same-Day Bilateral Total Knee Arthroplasties

Same-day bilateral total knee arthroplasties (SBTKAs) are associated with shorter rehabilitation and lower cost. However, controversy surrounding the safety of SBTKAs exists. Recent studies are lacking to determine whether patient selection has brought SBTKA in line with unilateral total knee arthroplasty (UTKA). Therefore, the authors evaluated and compared patient characteristics, hospital characteristics, and inpatient course between UTKA and SBTKA from 2009 to 2016. The National Inpatient Sample was queried from 2009 to 2016 for UTKA and SBTKA patients. Of the 5,329,466 patients identified, 5,084,328 (95.4%) patients received UTKAs and 245,138 (4.6%) patients underwent SBTKAs. Incidence, rate, patient and hospital characteristics, health status, length of stay (LOS), discharge disposition, hospital charges, hospital costs, and complications were analyzed and statistically compared. The incidence (-1.4%) and rate (15.8%) of SBTKAs decreased (both P<.001). The SBTKA cohort had more patients who were younger, male, White, obese, healthier, and using private insurance (P<.001 for all). The SBTKA cohort had longer LOS, a higher proportion of discharges to skilled nursing facilities, higher cost and charges, and more complications, including deep venous thromboses/pulmonary emboli (DVT/PE) and transfusions (P<.001 for all). Conversely, SBTKA was associated with fewer myocardial infarctions (P<.001). Although improved from previous literature, SBTKA is still associated with longer LOS, higher cost and charges, and more complications, including DVT/PE and transfusions, although with a lower rate of myocardial infarction. However, studies are needed to determine whether the risk of 1 SBTKA outweighs the cumulative risk of staged UTKAs. [Orthopedics. 2021;44(3):e407-e413.].

Are patient-reported outcomes the same following second-side surgery in primary hip and knee arthroplasty?

Aims

Up to one in five patients undergoing primary total hip (THA) and knee arthroplasty (TKA) require contralateral surgery. This is frequently performed as a staged procedure. This study aimed to determine if outcomes, as determined by the Oxford Hip Score (OHS) and Knee Score (OKS) differed following second-side surgery.

Methods

Over a five-year period all patients who underwent staged bilateral primary THA or TKA utilizing the same type of implants were studied. Eligible patients had both preoperative and one year Oxford scores and had their second procedure completed within a mean (2 SDs) of the primary surgery. Patient demographics, radiographs, and OHS and OKS were analyzed.

Results

A total of 236 patients met the inclusion criteria, of which 122 were THAs and 114 TKAs. The mean age was 66.5 years (SD 9.4), with a 2:1 female:male ratio. THAs showed similar significant improvements in outcomes following first- and second-side surgery, regardless of sex. In contrast for TKAs, although male patients demonstrated the same pattern as the THAs, female TKAs displayed significantly less improvement in both OKS and its pain component following second-side surgery.

Conclusion

Female patients undergoing second-side TKA showed less improvement in Oxford and pain scores compared to the first-side. This difference in outcome following second-side surgery did not apply to male patients undergoing TKA, or to either sex undergoing THA.

Cite this article: Bone Jt Open 2021;2(4):243–254.

Contralateral knee pain reduces the rate of patient satisfaction but does not clinically impair the change in WOMAC score after total knee arthroplasty

Aims

The primary aim of this study was to assess whether pain in the contralateral knee had a clinically significant influence on the outcome of total knee arthroplasty (TKA) according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score. Secondary aims were to: describe the prevalence of contralateral knee pain; identify if it clinically improves after TKA; and assess whether contralateral knee pain independently influences patient satisfaction with their TKA.

Methods

A retrospective cohort of 3,178 primary TKA patients were identified from an arthroplasty database. Patient characteristics, comorbidities, and WOMAC scores were collected preoperatively and one year postoperatively for the index knee. In addition, WOMAC pain scores were also collected for the contralateral knee. Overall patient satisfaction was assessed at one year. Preoperative contralateral knee pain was defined according to the WOMAC score: minimal (> 78 points), mild (59 to 78), moderate (44 to 58), and severe (< 44). Multivariate regression analysis was used to adjust for confounding.

Results

According to severity there were 1,425 patients (44.8%) with minimal, 710 (22.3%) with mild, 518 (16.3%) with moderate, and 525 (16.5%) with severe pain in the contralateral knee. Patients in the severe group had a greater clinically significant improvement in their functional WOMAC score (9.8 points; p < 0.001). Only patients in the moderate (22.9 points) and severe (37.8 points) groups had a clinically significant improvement in their contralateral knee pain (p < 0.001), but they were significantly less likely to be satisfied with their TKA (moderate: odds ratio (OR) 0.64, 95% confidence interval (CI) 0.4 to 0.92, p = 0.022; severe: OR 0.57, 95% CI 0.39 to 0.82, p = 0.002).

Conclusion

Contralateral knee pain did not impair improvement in the WOMAC score after TKA, and patients with the most severe contralateral knee pain had a clinically significantly greater improvement in their functional outcome. More than half the patients presenting for TKA had mild-to-severe contralateral knee pain, most of whom had a clinically meaningful improvement but were significantly less likely to be satisfied with their TKA. Cite this article: Bone Joint J. 2020;102-B(1):125–131

Asynchronous Bilateral Total Knee Arthroplasty: Predictors of the Functional Outcome and Patient Satisfaction for the Second Knee Replacement

BACKGROUND

The primary aim of this study is to identify independent preoperative predictors of outcome and patient satisfaction for the second total knee arthroplasty (TKA).

METHODS

A retrospective cohort of 454 patients undergoing an asynchronous (6 weeks or more apart) bilateral primary TKA were identified from an arthroplasty database. Patient demographics, comorbidities, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-12 scores were collected preoperatively and 1 year postoperatively. Overall patient satisfaction was assessed at 1 year.

RESULTS

The 1 year WOMAC pain score (P = .01), and improvement in WOMAC pain (P < .001) and functional (P = .002) scores were significantly lower for the second TKA. Worse preoperative WOMAC pain, function, and stiffness scores were demonstrated to be independent predictors of improvement in the WOMAC pain, function, and stiffness scores, respectively, for both the first and second TKA. The overall rate of satisfaction with the first TKA was 94.0% and 94.7% for the second TKA (P = .67). The rate of satisfaction for the second TKA was 77.8% for patients that were dissatisfied with their first TKA, which was an independent predictor of dissatisfaction (P = .02).

CONCLUSION

Improvement in pain and function is less with the second TKA, but the satisfaction rate remains similar. There are common independent predictors for change in the WOMAC score for the first and second TKA; however, the predictors of satisfaction were different with no common factors. Patients that were dissatisfied with their first TKA were more likely to be dissatisfied with their second TKA.

LEVEL OF EVIDENCE II

Prognostic retrospective cohort study.

Delivery of bupivacaine from UHMWPE and its implications for managing pain after joint arthroplasty

Total joint replacement is a widely used and successful surgical approach. Approximately 7 million US adults are currently living with a hip or knee replacement. However, the surgical procedures for total joint replacement are associated with significant postoperative pain, and current strategies do not adequately address this pain, which leads to patient dissatisfaction, reduced mobility, and increased risk of opioid addiction. We hypothesized that the ultra-high-molecular-weight polyethylene (UHMWPE) bearing surfaces used in total joint prosthetics could provide sustained release of the local anesthetic bupivacaine to provide relief from joint pain for an extended period of time after surgery. In this paper, we describe the production of bupivacaine-loaded UHMWPE (BPE) and measure the in vitro bupivacaine release kinetics of BPE. We found that bupivacaine could be released from BPE at clinically relevant rates for up to several days and that BPE possesses antibacterial effects. Therefore, bupivacaine-loaded UHMWPE is a promising material for joint replacement prostheses, and future studies will evaluate its safety and efficacy in in vivo models. STATEMENT OF SIGNIFICANCE: Total joint replacement is associated with significant pain and risk of infection. In our paper, we introduce bupivacaine-loaded ultra-high-molecular-weight polyethylene (BPE), which releases bupivacaine, a pain-treating drug, at doses comparable to currently used doses. Additionally, BPE inhibits the growth of infection-causing bacteria. Therefore, BPE may be able to reduce both postsurgical pain and risk of infection, potentially treating two of the most prominent complications associated with total joint replacement. To our knowledge, this is the first development of a material that can address both complications, and devices incorporating BPE would represent a significant advancement in joint arthroplasty prosthetics. More generally, the incorporation of therapeutic agents into ultra-high-molecular-weight polyethylene could impact many orthopedic procedures owing to its ubiquity.

Effects of anaesthesia and analgesia on long-term outcome after total knee replacement: A prospective, observational, multicentre study

BACKGROUND

Perioperative regional anaesthesia may protect from persistent postsurgical pain (PPSP) and improve outcome after total knee arthroplasty (TKA).

OBJECTIVES

Aim of this study was to evaluate the impact of regional anaesthesia on PPSP and long-term functional outcome after TKA.

DESIGN

A web-based prospective observational registry.

SETTING

Five Italian Private and University Hospitals from 2012 to 2015.

PATIENTS

Undergoing primary unilateral TKA, aged more than 18 years, informed consent, American Society of Anesthesiologists (ASA) physical status classes 1 to 3, no previous knee surgery.

INTERVENTION(S)

Personal data (age, sex, BMI and ASA class), preoperative pain assessed by numerical rating scale (NRS) score, and risk factors for PPSP were registered preoperatively. Data on anaesthetic and analgesic techniques were collected. Postoperative pain (NRS), analgesic consumption, major complications and patient satisfaction were registered up to the time of discharge. PPSP was assessed by a blinded investigator during a phone call after 1, 3 and 6 months, together with patient satisfaction, quality of life (QOL) and walking ability.

MAIN OUTCOME MEASURES

Experience of PPSP according to the type of peri-operative analgesia.

RESULTS

Five hundred sixty-three patients completed the follow-up. At 6 months, 21.6% of patients experienced PPSP, whereas autonomy was improved only in 56.3%; QOL was worsened or unchanged in 30.7% of patients and improved in 69.3%. Patients receiving continuous regional anaesthesia (epidural or peripheral nerve block) showed a lower NRS through the whole peri-operative period up to 1 month compared with both single shot peripheral nerve block and those who did not receive any type of regional anaesthesia. No difference was found between these latter two groups. Differences in PPSP at 3 or 6 months were not significantly affected by the type of anaesthesia or postoperative analgesia. A higher NRS score at 1 month, younger age, history of anxiety or depression, pro-inflammatory status, higher BMI and a lower ASA physical status were associated with a higher incidence of PPSP and worsened QOL at 6 months.

CONCLUSION

Continuous regional anaesthesia provides analgesic benefit for up to 1 month after surgery, but did not influence PPSP at 6 months. Better pain control at 1 month was associated with reduced PPSP. Patients with higher expectations from surgery, enhanced basal inflammation and a pessimistic outlook are more prone to develop PPSP.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02147730.

Effects of anaesthesia and analgesia on long-term outcome after total knee replacement: A prospective, observational, multicentre study

BACKGROUND

Perioperative regional anaesthesia may protect from persistent postsurgical pain (PPSP) and improve outcome after total knee arthroplasty (TKA).

OBJECTIVES

Aim of this study was to evaluate the impact of regional anaesthesia on PPSP and long-term functional outcome after TKA.

DESIGN

A web-based prospective observational registry.

SETTING

Five Italian Private and University Hospitals from 2012 to 2015.

PATIENTS

Undergoing primary unilateral TKA, aged more than 18 years, informed consent, American Society of Anesthesiologists (ASA) physical status classes 1 to 3, no previous knee surgery.

INTERVENTION(S)

Personal data (age, sex, BMI and ASA class), preoperative pain assessed by numerical rating scale (NRS) score, and risk factors for PPSP were registered preoperatively. Data on anaesthetic and analgesic techniques were collected. Postoperative pain (NRS), analgesic consumption, major complications and patient satisfaction were registered up to the time of discharge. PPSP was assessed by a blinded investigator during a phone call after 1, 3 and 6 months, together with patient satisfaction, quality of life (QOL) and walking ability.

MAIN OUTCOME MEASURES

Experience of PPSP according to the type of peri-operative analgesia.

RESULTS

Five hundred sixty-three patients completed the follow-up. At 6 months, 21.6% of patients experienced PPSP, whereas autonomy was improved only in 56.3%; QOL was worsened or unchanged in 30.7% of patients and improved in 69.3%. Patients receiving continuous regional anaesthesia (epidural or peripheral nerve block) showed a lower NRS through the whole peri-operative period up to 1 month compared with both single shot peripheral nerve block and those who did not receive any type of regional anaesthesia. No difference was found between these latter two groups. Differences in PPSP at 3 or 6 months were not significantly affected by the type of anaesthesia or postoperative analgesia. A higher NRS score at 1 month, younger age, history of anxiety or depression, pro-inflammatory status, higher BMI and a lower ASA physical status were associated with a higher incidence of PPSP and worsened QOL at 6 months.

CONCLUSION

Continuous regional anaesthesia provides analgesic benefit for up to 1 month after surgery, but did not influence PPSP at 6 months. Better pain control at 1 month was associated with reduced PPSP. Patients with higher expectations from surgery, enhanced basal inflammation and a pessimistic outlook are more prone to develop PPSP.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02147730

Comparison of Functional Outcomes Between the First and Second Knee in Staged Bilateral Total Knee Arthroplasty With Diverse Intervals Between Stages

BACKGROUND

The objective of the study was to analyze if the length of interval time between stages influenced functional and quality of life outcomes in patients with staged bilateral primary total knee arthroplasty (TKA).

METHODS

This is a retrospective comparative study between 93 patients with an interval between stages of 6-8 months (6-month group), 112 of 12-14 months (1-year group), and 108 of 24-26 months (2-year group). Outcome variables were Knee Society scores, Western Ontario and McMaster Universities, Short Form, and patient satisfaction.

RESULTS

Overall, the mean follow-up for the first TKA was 8.2 (range, 7-10) years, and for the second TKA, 6.7 (range, 5-10) years. At last follow-up, functional and patient-related outcomes were similar for both knees, regardless of the interval. However, mental score and patient satisfaction were significantly better for the second than for the first TKA in the 2-year group. Age did not correlate significantly with the functional scores but was significantly correlated with the mental score.

CONCLUSION

The performing staged bilateral TKA with a wide interval between surgeries provided equivalent functional outcomes and quality of life for both knees. Postoperative outcomes were not affected by the length of the time interval between procedures or age. Our results can help the surgeon to inform the patients reliably about what they can expect in the delay of a second knee replaced. Thus, patients could make an informed decision.

Comparison of the outcome between unilateral and bilateral open wedge high tibial osteotomy in the bilateral varus knees

INTRODUCTION

Bilateral open wedge high tibial osteotomy (OWHTO) can be performed in a staged manner to enable the healing and rehabilitation of each limb separately after surgery. However, the effects of staged bilateral OWHTO on the pattern of recovery and changes over time for each limb have not been established. Additionally, there is a lack of information regarding the optimal timing for staged surgery.

METHODS

Twenty-two patients (44 knees) in the bilateral OWHTO group and 42 patients (42 knees) in the unilateral OWHTO group were analyzed. Clinical and radiological results were evaluated and compared between the two groups. For the alignment change assessment, the hip-knee-ankle (HKA) angle and weight-bearing line (WBL) ratio were measured preoperatively and at postoperative 6 weeks, 3 months, 6 months, and 1 year.

RESULTS

The correction loss of HKA angle in the bilateral OWHTO group was significantly larger than that in the unilateral OWHTO group (0.5° ± 1.4° vs 1.3° ± 2.0°, p = 0.049). The correction loss of WBL ratio was significantly greater in the patients with staged bilateral OWHTO within a 3-month interval compared to those with staged bilateral OWHTO in an interval longer than 3 months (WBL ratio; 7.5% vs 2.1%, p = 0.01). There was no significant difference in the clinical scores and range of motion at the last follow-up.

CONCLUSION

The smaller loss of correction in the unilateral OWHTO group occurred compared to the bilateral OWHTO group. Additionally, surgeons should keep in mind that the amount of correction loss may be greater if staged bilateral OWHTO is performed at intervals of 3 months or less.

Affective temperament does not influence satisfaction after total knee arthroplasty

BACKGROUND

Inherent temperament of the patient may predict the outcome of the surgical procedure. The purpose of this study was to ascertain whether negative affective temperament affects patient satisfaction and outcome measures.

METHODS

This prospective study included 143 patients who underwent total knee arthroplasty for primary arthrosis. Preoperatively, the Memphis, Pisa, Paris and San Diego-Auto questionnaire was used to define the temperament of the patient. Knee Society Score (KSS) and short form-36 (SF-36) outcome measures were used to evaluate the functional outcome.

RESULTS

No relationship was determined between temperament and satisfaction (P = .734). Overall, the satisfaction rate of the procedure in our patients was 93%. The KSS improved from a mean of 47.9 to 70.1 (F = 124.275; P < .05) and the SF-36 physical component summary, and SF-36 mental component summary scores improved to a mean of 39.5 and 43.04 points, respectively.

CONCLUSION

Temperament was not found to have any effect on patient satisfaction. However, patient satisfaction was directly related to better functional outcomes.

Outcomes of unilateral and bilateral total knee arthroplasty in 238,373 patients

Background and purpose - There is no consensus about the outcome of simultaneous vs. staged bilateral total knee arthroplasty (TKA). We examined this issue by analyzing 238,373 patients. Patients and methods - Demographic, clinical, and outcome data were evaluated for TKA patients (unilateral: 206,771; simultaneous bilateral: 6,349; staged bilateral: 25,253) from the Canadian Hospital Morbidity Database for fiscal years 2006-2007 to 2012-2013. Outcomes were adjusted for age, sex, comorbidities, and hospital TKA volume. Results - Simultaneous bilateral TKA patients were younger than staged bilateral TKA patients (median 64 years vs. 66 years), were more likely to be male (41% vs. 39%), and had a lower frequency of having ≥1 comorbid condition (2.9% vs. 4.2%). They also had a higher frequency of blood transfusions (41% vs. 19%), a shorter median length of stay (6 days vs. 8 days), a higher frequency of transfer to a rehabilitation facility (46% vs. 9%), and a lower frequency of knee infection (0.5% vs. 0.9%) than staged bilateral TKA patients, but they had higher rate of cardiac complications within 90 days (2.0% vs. 1.7%). Simultaneous patients had higher in-hospital mortality compared to the second TKA in staged patients (0.16% vs. 0.06%), but they had similar rates of in-hospital mortality compared to unilateral patients (0.16% vs. 0.14%). The cumulative 3-year revision rate was highest in the unilateral group (2.3%), but it was similar in the staged and simultaneous bilateral groups (1.4%). Interpretation - We found important differences between the outcomes of simultaneous and staged bilateral TKA. Further clarification of outcomes would be best determined in an adequately powered randomized trial, which would remove the selection bias inherent in this retrospective study design.

Using the anatomical tibial axis for total knee arthroplasty alignment may lead to an internal rotation error

INTRODUCTION

Despite intensive research, current total knee arthroplasty (TKA) designs do not always provide the correct kinematics for the native joint and thus further optimisation is necessary. Several studies support the importance of malrotation of the tibial components in the failure of TKA. We hypothesise that using the anatomical tibial axis (ATA) to align tibial component rotation on the resected tibial surface may lead to an internal rotation error due to relative anterior shift of the lateral articular surface centre compared to the medial one. The aim of this study was to compare the anatomical tibial axis of the physiological tibial joint surface to the resected one.

METHOD

Twenty formalin-fixed cadaveric knees were obtained for study. After computed tomography scanning the data of each specimen were entered into a standardised coordinate system and virtual bone cuts were performed with 6, 8 and 10 mm resection depths. The positions of the articular surface centres were determined at each resection depth.

RESULTS

The lateral articular surface centre had moved anteriorly after the resection by a mean 1.475 mm, while the medial one had not changed significantly. Resecting the tibia at a 6-mm cut and using the transverse tibial axis to align the prosthetic tibial plateau will result in a mean 4.0° (95 % confidence interval, 2.5-5.5°) of internal rotation compared to the uncut tibia.

DISCUSSION

The ATA lies in 6 degrees of external rotation compared to the perpendicular to the posterior tibial condylar axis (PTCA). Graw et al. suggest aligning the tibial component in 10 degrees of external rotation to the latter. Thus, if we accept the above suggestion, the ATA is 4 degrees internally rotated compared to the same line on the resected proximal tibia. These prior studies appear to be in accordance with our findings.

CONCLUSIONS

We conclude that using the ATA on the resected tibial surface may contribute to an internal rotation error.