Introduction

Fifty thousand knee replacements are performed annually in the UK at an estimated cost of £150 million. However, there is uncertainty as to the best surgical approach to the knee joint for knee arthroplasty. We undertook a randomised controlled trial to compare a standard medial parapatellar arthrotomy with sub-vastus arthrotomy for patients undergoing primary total knee arthroplasty in terms of short and long term knee function.

Orthopaedic surgeons vary in their surgical approaches to total knee arthroplasty. The aim of this investigation was to compare outcomes after two different surgical approaches. The study was a prospective single-centre longitudinal randomized controlled trial. A sub-vastus approach was compared with a medial para-patellar approach. Participating surgeons elected to randomize their patients to one of the two types of approach. Outcomes included the Knee Society (KS) Clinical Rating System, WOMAC Osteoarthritis Index, SF-36, and EuroQol (measured at 1, 6, 12 and 52 weeks post-operatively compared to baseline) complications, surgeon rated ease of exposure, and proportion of patients who had a lateral release.

Two hundred and thirty one patients were randomized to the two approaches. One hundred and sixteen patients were randomized to the sub-vastus approach. At one week compared to baseline, range of motion, KS global, KS knee, and KS pain scores were significantly better in the sub-vastus group. At six weeks, the medial para-patellar group tended to have better outcomes, but not statistically significantly. At fifty-two weeks compared to baseline, the WOMAC global and pain scores, the SF36 physical function and role-physical scores, and the EuroQol utility and pain score were significantly better in the sub-vastus group. Surgeons reported the ease of exposure in the sub-vastus group was significantly worse on average.

This trial is the largest of its kind to date, and the first, so far as we are aware, to compare clinical outcomes of different surgical approaches at one year post-operatively. The sub-vastus approach to total knee arthroplasty was more effective than a medial para-patellar approach at both one week and fifty-two weeks post-operatively in patients whose surgeons considered either approach would be suitable. However, surgeons reported worse ease of exposure in the sub-vastus group.

Optimal soft tissue tension maximises function following total knee arthroplasty. Excessive tension may lead to stiffness and or pain, while inadequate tension can lead to instability. Composite component thickness is a prime determinant of this soft tissue tension. The variable component thickness provided by polyethylene inserts generally allows for 2–3mm incremental change. This study analyzed the effect of 1-mm incremental changes in polyethylene thickness on soft tissue tension. Our hypothesis was that soft tissue tension would be markedly affected by increases in insert thickness.

Computer assisted TKA was performed on eight cadaveric knee specimens (four pairs). The knees were passively moved through full flexion-extension range of motion, for each tibial construct thickness. Kinematics were recorded using the computer navigation software. Soft tissue tension was analyzed by measuring compartmental loads. A validated load cell instrumented tibial insert was used to measure medial and lateral compartmental loads independently. The effect of 1-mm increments in polyethylene thickness on compartmental loads was evaluated.

An increase in compartmental loads was measured with increasing insert thickness. Loading in contralateral compartments showed differing behaviour, reflecting varying tension in the medial and lateral sides. Many generated loads showed a reduction after reaching a maximal level with further increase in insert thickness (seven of eight specimens), indicative of tissue failure, although there were no overt indications of failure during the procedure. With a 1-mm increase in insert thickness, six of eight specimens showed an increase in peak loads greater than 100N at some point in the testing procedure, although not always with the same shim thickness.

Compartmental loads varied as a function of insert thickness. Most specimens showed signs of soft tissue “micro-failure”. The high sensitivity of compartmental loads to a 1-mm incremental increase is significant and has not been previously appreciated, especially intra-operatively. Currently available inserts with 2–3mm incremental sizes may make obtaining optimal soft tissue tension difficult. In addition to the current focus of obtaining accurate leg alignment, further computer-assisted techniques are required to address soft tissue tension.

Statement of Purpose: We tested the null hypothesis of no significant difference in arthroscopy rates for patients on a waiting list for arthroscopy in patients in which surgeons had a knee magnetic resonance imaging scan report prior to surgery, compared to those who did not have a report.

Methods and Results: This is a single-centre randomised controlled trial. 252 eligible patients consented and randomised. The two groups were similar with respect to a range of baseline factors. Very few arthroscopies were not performed–4.8% in the intervention arm and 5.5% in the control arm (χ2=0.06, df=1, p> 0.05). A longitudinal analysis of the secondary outcomes showed that there were no significant differences between the intervention and the control arms of the study.

Conclusion: Magnetic resonance imaging, prior to knee arthroscopy, does not lead to a reduction in the number of arthroscopies undertaken in the intervention group nor improve patient outcome in a range of secondary measures.

Introduction: Fifty thousand knee replacements are performed annually in the UK at an estimated cost of £150 million. However, there is uncertainty as to the best surgical approach to the knee joint for knee arthroplasty. We undertook a randomised controlled trial to compare a standard medial parapatellar arthrotomy with sub-vastus arthrotomy for patients undergoing primary total knee arthroplasty in terms of short and long term knee function.

Methods: Two-hundred and thirty-one patients undergoing primary total knee arthroplasty during 2001–2003 were recruited into the study. Patients were randomised into subvastus (116) or medial parapatellar (115) approaches to knee arthroplasty. The primary outcome measures were the American Knee Society and WOMAC Scores. The secondary outcome measures were patient based measures of EuroQol and SF-36. All outcomes were measured pre-operatively, 1, 6, 12 and 52 weeks post-operatively. We also looked at a pain diary, analgesia diary, ease of surgical exposure, and complications.

Results: Pain as measured by WOMAC was significantly less in the subvastus group but only at 52 weeks. The Knee Society Score showed some early benefit at one week to the subvastus group. There was no difference between the two groups in relation to the knee function score, EuroQol, SF-36, pain diary, analgesia usage and length of hospital stay.

Conclusion: There is some benefit to patients receiving sub-vastus arthrotomy relative to medial para-patellar. Although the results show some statistical significance in using the sub-vastus approach the clinical importance of these findings and the costs of the various procedures involved remain to be ascertained.

Introduction: Fifty thousand knee replacements are performed annually in the UK at an estimated cost of £150 million. However, there is uncertainty as to the best surgical approach to the knee joint for knee arthroplasty. We undertook a randomised controlled trial to compare a standard medial parapatellar arthrotomy with sub-vastus arthrotomy for patients undergoing primary total knee arthroplasty in terms of short and long term knee function.

Methods: Two-hundred and thirty-one patients undergoing primary total knee arthroplasty during 2001–2003 were recruited into the study. Patients were randomised into subvastus (116) or medial parapatellar (115) approaches to knee arthroplasty. The primary outcome measures were the American Knee Society and WOMAC Scores. The secondary outcome measures were patient based measures of EuroQol and SF-36. All outcomes were measured pre-operatively, 1, 6, 12 and 52 weeks post-operatively. We also looked at a pain diary, analgesia diary, ease of surgical exposure, and complications.

Results: Pain as measured by WOMAC was significantly less in the subvastus group but only at 52 weeks. The Knee Society Score showed some early benefit at one week to the subvastus group. There was no difference between the two groups in relation to the knee function score, EuroQol, SF-36, pain diary, analgesia usage and length of hospital stay

Conclusion: There is some benefit to patients receiving sub-vastus arthrotomy relative to medial para-patellar. Although the results show some statistical significance in using the sub-vastus approach the clinical importance of these findings and the costs of the various procedures involved remain to be ascertained.

This in-vitro study was conducted to determine the effect of rotator cuff tears on joint kinematics. A shoulder simulator produced unconstrained active abduction of the humerus. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the tear increased. It is concluded that in order to generate the same motions achieved by the intact joint other muscle groups must be employed, inevitably resulting in altered joint loading.

This in-vitro study was conducted to determine the effect of simulated progressive tears of the rotator cuff on active glenohumeral joint kinematics.

Five cadaveric shoulders were tested using a shoulder simulator designed to produce unconstrained active motion of the humerus. Forces were applied to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, anterior, middle, and posterior deltoid muscles based upon variable ratios of electromyographic data and average physiological cross-sectional area of the muscles. Three sequential 1cm lesions were created, the first two in the supraspinatus tendon and the third in the subscapularis tendon. Simulated active glenohumeral abduction was performed following the creation of each lesion. Five successive tests were performed to quantify repeatability.

The plane of abduction moved posteriorly and became more abnormal throughout abduction as the size of the lesion increased (p=0.01) (Figure 1).

In order to generate the same motions achieved with an intact rotator cuff other muscle groups must be employed, inevitably resulting in altered joint loading.

A better understanding of the effects that rotator cuff tears have on the kinematics of the glenohumeral joint may result in the development of innovative rehabilitation strategies to compensate for this change in muscle balance and improve the clinical outcomes.

Please contact author for diagram and/or graph.

This study was conducted to determine the effect of passive and active muscle loading on humeral head translation during glenohumeral abduction. A shoulder simulator produced unconstrained active glenohumeral abduction using several sets of loading ratios. Significantly greater translations occurred in passive motion as compared to active motion between 30 and 70 degrees of elevation in three dimensions and in the anterosuperior plane. No difference was found between the active motions. Also, translations of the humeral head decreased with active simulation of abduction emphasizing the importance of the rotator cuff muscles in creating and maintaining the ball-and-socket kinematics of the shoulder.

This in-vitro study was conducted to determine the effect of passive and active loading on humeral head translation during glenohumeral abduction.

Five cadaveric shoulders were tested using a shoulder simulator designed to produce unconstrained abduction of the humerus. Forces were applied to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, anterior, middle, and posterior deltoid muscles using four different sets of loading ratios. These were based on:

equal loads to all cables (Constant-Constant);

In three dimensions, significantly greater translations occurred in passive motion as compared to active motion between 30 and 70 degrees of elevation (p< 0.001). No difference was found between the active motions. Similar results were observed in the two-dimensional resultant translations in the anterosuperior plane of the scapula, with more translation occurring during passive motion (3.6 ± 1.1mm) than active (2.1 ± 1.0mm) (p=0.002), and no significant differences between the active loading methods (Figure 1). The majority of translation tended to occur in the superior-inferior direction for all loading ratios employed.

It was clearly shown that the translations of the humeral head decreased with active simulation of abduction. These findings are in agreement with other in-vivo and in-vitro investigations.

This emphasizes the importance of the rotator cuff muscles in creating and maintaining the ball-and-socket kinematics of the shoulder.

Optimal soft tissue tension maximises function after total knee arthroplasty (TKA). Excessive tension may lead to stiffness and or pain, while inadequate tension can lead to instability. Composite component thickness is a prime determinant of this soft tissue tension. The thickness provided by polyethylene inserts currently allows for a 2–3 mm incremental change. This study analyses the effect of incremental change in polyethyl-ene thickness on soft tissue tension.

Computer assisted (Stryker Knee Nav) TKA was performed on 8 cadaveric knee specimens (4 pairs). Kinematic data was collected through the navigation software. The soft tissue tension was analysed by measuring compartmental loads. A validated load cell instrumented tibial insert was used to measure medial and lateral compartmental loads independently. The effect of 1mm increments in polyethylene thickness on compartmental loads was evaluated.

We measured an increase in compartmental loads with increasing insert thickness. The peak loads in each compartment showed different behaviour reflecting varying tension in the medial and lateral sides. The peak loads generated showed a reduction after reaching a maximal level with further increase in insert thickness. With a one mm increase in insert thickness, 75 % of specimens showed greater than 200 % increase in the peak loads in the lateral compartment. Similarly the medial loads showed a greater than 100% increase. Individual specimens showed a high variability in loading patterns.

Our study highlights high variation of knee loads present between subjects. The compartmental loads vary as a function of insert thickness. The high sensitivity of compartmental loads with a 1mm increment is significant and has not been previously appreciated, especially intraoperatively. The currently available TKA inserts with 2–3 mm increments may make obtaining optimal soft tissue tension difficult. In addition to the current focus of obtaining accurate leg alignment, further computer aided techniques are required to address soft tissue tension.

Statement of Purpose: We tested the null hypothesis of no significant difference in arthroscopy rates for patients on a waiting list for arthroscopy in patients in which surgeons had a knee magnetic resonance imaging scan report prior to surgery, compared to those who did not have a report.

Methods and Results: This is a single-centre randomised controlled trial. 252 eligible patients consented and randomised. The two groups were similar with respect to a range of baseline factors. Very few arthroscopies were not performed −4.8% in the intervention arm and 5.5% in the control arm (χ²=0.06, df=1, p> 0.05). A longitudinal analysis of the secondary outcomes showed that there were no significant differences between the intervention and the control arms of the study.

Conclusion: Magnetic resonance imaging, prior to knee arthroscopy, does not lead to a reduction in the number of arthroscopies undertaken in the intervention group nor improve patient outcome in a range of secondary measures.

The aim of this study was to assess the accuracy of pedicle screw placement using NAVITRAK, a system of Computer Assisted Orthopaedic Surgery and conventional fluoroscopic technique.

Twelve porcine lumbar spines were scanned pre-operatively by computer tomography for 3-D reconstruction ( 1 mm slice thickness, 1mm increment and 2.5 mm pitch ).

Computer randomisation divided the specimens between surgeons of different experience, and the two pedicles of each vertebral level between the two surgical techniques. Stainless steel screws (6.5 spongiosa) were inserted.

Post-operatively, fluoroscopic- and CT imaging were blindly assessed for accuracy by two independent observers, and compared to macroscopic dissection of the spinal segments.

Of 168 pedicles in 12 porcine specimens, 166 received a pedicle screw. Two pedicle screw placements were abandoned. Sixyty-one screws (73%) were placed satisfactorily with the CAOS system, 56 (67.5%) in the conventional group.

In 26 pedicles the screws were placed unsatisfactorily (12 pedicles (46.2%) with the NAVITRAK system and 14 pedicles (53.8%) with the conventional technique.

The NAVITRAK system in combination with stainless steel screws showed a difference of 5.5% in misplacement in favour for the computer assisted technique.

The aim of this study was to demonstrate a correlation between FASTRAK readings of spinal movement and established disability scores in-patients undergoing litigation.

A retrospective, blind study was conducted on patients who had been evaluated clinically between January 1994-October 1998. Statistical regression analysis between evaluated Oswestry Disability Score (ODS) and MSPQ/Zung questionnaires and the mean ROM was obtained. 49 patients with soft tissue injuries of the cervical (n = 14) and lumbar (n = 34) spine were assessed. All of them were undergoing litigation.

A standardised Fastrak trace measuring flexion, extension, right and left bending and rotation of the cervical and lumbar spine was recorded. An ODS and MSPQ/Zung questionnaire was filled in under the supervision of a senior physiotherapist.

There was no correlation between the ODS and MSPQ/Zung and mean ROM for the cervical spine. In the lumbar spine, flexion and ODS correlated statistically significantly (p< 0.01) and right rotation with the combined MSPQ/Zung score (p< 0.014).

This preliminary study is encouraging in that it demonstrates a direct correlation between FASTRAK measurements and recognised disability scores in the lumbar spine. Further analysis of non- litigation cohorts will contribute to establish these correlations.

The aim of this study was to assess the accuracy of pedicle screw placement comparing Computer Assisted Orthopaedic Surgery equipment with conventional fluoroscopic technique.

Twelve porcine cervical spines were scanned pre-operatively by computer tomography for 3D reconstruction (1 mm slice thickness, 1mm increment and 1 mm pitch).

Computerised randomisation divided the specimens between surgeons of different experience, and the two pedicles of each vertebral level between the two surgical techniques. Stainless steel screws (6.5 diameter, spongiosa) were inserted. Post-operatively, fluoroscopic imaging was used for accuracy assessment by two independent observers, and findings were compared to macroscopic dissection of the spinal segments.

Of 96 pedicles in 12 porcine specimens, 78 received a pedicle screw, 18 screw placements were abandoned, 38 (39.6%) were satisfactorily placed (19 in each, p> 0.05). 40 screws were misplaced, 18 (45%) with the NAVITRAK system vs. 22 (55%) with the conventional technique. These single factor results (all non-significant), were corroborated using a linear logistic regression model. Some heterogeneity in performance was detected between surgeons, independently of the type of technique used.

Computer assisted surgery is an aiming device and is not advantageous over conventional methods in spines with high bone density.