Purpose:

Imageless navigation has improved the accuracy of acetabular cup placement but relies on manual identification of pelvic anatomy. Thick soft tissues in obese patients could obscure these landmarks and result in large variances of cup placement. The purpose of this study was to investigate the relationship between BMI, soft tissue thickness, navigated cup and final post-operative cup position.

Purpose:

Correct placement of the acetabular cup is a crucial step in hip replacement to achieve a satisfactory result and remains a challenge with free hand techniques. Imageless navigation may provide a viable alternative to freehand technique and improve placement significantly. The purpose of this project was to assess and validate intra-operative placement values as displayed by an imageless navigation system to postoperative measurement of cup position using high resolution CT scans.

Introduction:

Gait analysis is an important tool to measure function following total knee replacement. It is currently unknown whether there is a correlation between subjective and objective outcome. The purpose of this study was to analyse relationships between subjective outcome scores and kinematic and kinetic data.

Background:

The aim of this study was to investigate the outcome after ACL reconstruction between a group of patients receiving a standardized supervised physiotherapy guided rehabilitation program and a group of patients who followed an un-supervised, home-based rehabilitation program.

Purpose:

A higher posterior tibial slope can potentially result in kinetic and kinematic changes of the knee. These changes may influence knee functionality in ACL-deficient and ACL-reconstructed subjects. The purpose of this study was to investigate the relationship between knee functionality and posterior tibial slope in ACL-deficient and ACL-reconstructed subjects.

Purpose:

Malpositioning of the acetabular cup component in total hip arthroplasty can result in increased wear, early nonseptic loosening and is the most common cause of dislocation. Previous research has defined a safe zone with an inclination of 40±10 degrees and anteversion of 15±10 degrees. The purpose of this study was to compare cup placement using imageless navigation to a matched control group using CT based measurements.

Given their role in reducing anterior tibial translation, the recruitment patterns and viscoelastic properties of the hamstring muscles have been implicated as neuromuscular factors contributing to the ACL gender bias. Nevertheless, it is uncertain whether patterns of aberration displayed by the female neuromuscular system significantly alters the antagonist moments generated by the hamstrings during maximal effort knee extension. The purpose of the current study was to examine the effect of gender on hamstring antagonist moments in order to explain the higher ACL injury rates in females.

Eleven females (age 30.6 ± 10.1 years, mass 62.1± 6.9 kg, height 165.9 ± 4.6) and 11 males (age 29.0 ± 8.2 years, mass 78.6± 14.4 kg, height 178.5± 6.2) were recruited as subjects. Surface electrodes were placed over the semitendinosus (ST) and biceps femoris (BF) muscles of the dominant and non-dominant limbs. Each subject performed two sets of five maximal extension and flexion repetitions at 180-1. EMG, isokinetic torque and knee displacement data were sampled at 1000Hz using an AMLAB data acquisition system.

Average hamstring antagonist torque data across the range of knee flexion for female subjects was significantly higher (%Diff=24%) than for the male control subject. Statistical analyses revealed a significant main effect of gender (F = 4.802; p = 0.036).

Given that females possess a more compliant ACL and hamstring musculature, compared with their male counterparts, an augmented hamstring antagonist may represent a compensatory neuromuscular strategy to increase knee stiffness to control tibial translation and ACL strain. The results of this project suggest that it is unlikely that gender-related differences in hamstring antagonist torque is one of the predisposing factors contributing to the higher ACL injury rates in females.

Anthropometric anatomical factors may influence mechanical and functional stability of joints. An increased posterior tibial slope places the anterior cruciate ligament at a theroretical biomechanical disadvantage. An increased posterior tibial slope can potentially alter forces during landing tasks by either increasing anterior tibial translation and/or ACL loading. The purpose of this study is to investigate the relationship between posterior tibial slope and anterior cruciate ligament injuries. It is hypothesised that subjects with an ACL injury have an increased posterior tibial slope compared to a normal population.

Posterior tibial slope in 211 patients (154 male, 57 female), aged 15–49, who underwent anterior cruciate ligament reconstruction was measured using the posterior tibial cortex as reference. A matched control group was used for comparison.

The average posterior tibial slope in the ACLR population was 6.1 degrees, whilst the control group had average values of 5.4 degrees. This finding nearly reached statistical significance (p=0.057). In the male population, average values were 5.5 degrees in the ACLR group and 5.9 in the control group. This was not significant (p=0.21). However, there was a significant difference (p=0.04) in the female group. ACLR females had higher values 6.5 degrees whereas the control group had average values of 5.2 degrees.

Increased posterior tibial slope decreases the inclination of the ACL and potentially decreases vector force during dynamic tasks. We could not confirm the results of previous studies demonstrating an increased degree of posterior tibial slope in ACL injured patients. However, we demonstrated a significant difference in tibial slope in females. Based on our results, an increased posterior tibial slope is not a risk factor in males but possibly contributes to ACL injuries in females. Increased posterior tibial slope may be one of the reasons why females have a higher incidence of ACL injuries.

Previous research has shown that tunnel placement is critical in ACL reconstruction. The ultimate position of both the femoral and tibial tunnel determines knee kinematics and overall function of the knee post surgery. As with all techniques there is a definite learning curve for the arthroscopic technique. However, the effect of the learning curve on tunnel placement has been studied sparsely. The purpose of this project therefore is to investigate the effect of the learning curve on tunnel placement.

Postoperative radiographs of the first 200 anterior cruciate reconstructions with bone-tendon-bone patella tendon of a single orthopaedic surgeon performed during the first four years of independent practice were analysed for tunnel placement. Radiographs were digitalised and imported into a CAD program.

Tunnel placement both femoral and tibial antero-posterior and sagittal was assessed using Sommer's criteria. A rating scale was developed to assess overall placement. A total of 100 points indicated perfect placement. A maximum of 30 points each were allocated for sagittal femoral and tibial placement and a maximum of 20 points each were allocated for coronal placement.

Tunnel placement scores improved from 66 for the first 25 procedures to 87 for the last 25 procedures. Sagittal femoral placement (zone 1–4 with zone 1 being the preferred zone of placement) improved from an average of 1.44 to 1.08. Sagittal tibial placement (45% from anterior border of tibia) did not change significantly and remained between 42.82 t0 44.76%. Coronal femoral placement (between 10:00–11:00 o'clock for the right knee and 1:00–2:00 for the left knee) ranged from 10.45–11.15 and 12:45-1:15 o'clock respectively. This finding may be related to the transtibial tibial technique used to place the femoral tunnel. Coronal tibial placement (45% from medial tibial border) ranged from 45-46.58%.

Correct placement of the femoral and tibial bone tunnels is important for a successful reconstruction of the anterior cruciate ligament (ACL). This study demonstrated a definitive learning curve and steady improvement of tunnel placement. Whilst there was no significant improvement in sagittal placement, overall placement improved significantly.

A higher posterior tibial slope can potentially result in kinetic and kinematic changes of the knee. These changes may influence knee functionality in ACL-deficient and ACL-reconstructed subjects. The purpose of this study is to investigate the relationship between knee functionality and posterior tibial slope in ACL-deficient and ACL-reconstructed subjects.

Subjects with isolated ACL injuries and subjects who underwent ACL- reconstruction with BPTP between 18 and 24 months post surgery were included in the study. Posterior tibial slope was measured on a lateral radiograph using the posterior tibial cortex as a reference. The Cincinnati scoring system was used to assess knee functionality.

Frty-four ACL-deficient patients with a mean age of 26.6 years, and 44 ACL-reconstructed patients with a mean age of 27.2 (25–49) years were included. The posterior tibial slope in the ACL-deficient group averaged 6.10±3.57 degrees (range 0–17 degrees) and 7.20±4.49 degrees (range 0–17) in the ACL-reconstructed group. The mean Cincinnati score in the ACL-deficient subject was 62.0±14.5 and 89.3±9.5 in the ACL-reconstructed subject.

There was a moderate but non-significant correlation (r=0.47) between knee functionality and slope in the ACL-deficient subject. By dividing posterior tibial slope into intervals, a strong significant correlation (r=0.91, p=0.01) was observed between knee functionality and slope. There was a weak but non-significant correlation (r=0.24) between knee functionality and slope in the ACL-reconstructed patient. Dividing posterior tibial slope into intervals (0-4, 5-9, >10) a strong and significant correlation (r=0.96, p=0.0001) was observed between knee functionality and slope.

The results of this study suggest that subjects with a higher posterior tibial slope have higher knee functionality. This is in contrast to previous research.

Estrogen fluctuations have been implicated in the soft tissue injury gender-bias due to the hormones effect on the viscoelastic properties. The isolated effect of estrogen on the mechanical behaviour of human tendon is unknown. The purpose of this study was to elucidate the effect of circulating levels of estrogen on the strain properties of the human Achilles tendon.

Twenty females (18–35 years) who were using the pill together with 20 matched, non-pill users, participated in this study. Non-pill users were tested at the time of lowest (menstruation) and highest (ovulation) estrogen whilst pill users, who exhibited constant and attenuated estrogen levels, were tested at menstruation and two weeks later. At each test session, maximal isometric plantarflexion efforts were performed on a calf-raise apparatus whilst synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Connective tissue length (Lo) of the triceps surae complex was measured and tendon strain was calculated by dividing aponeurosis displacement during plantarflexion by Lo.

Repeated measures ANOVA revealed a significant (p < 0.05) main effect of subject group with significantly higher Achilles strain rates (16.1%) in the non-pill users compared to the pill users. Augmented Achilles tendon strain was associated with higher average estrogen levels in non-pill users.

Those results suggest that higher estrogen levels diminish the joint stabilising capacity of the triceps surae musculotendinous unit and may alter the energy storage capacity of the Achilles tendon during stretch-shorten cycle activities. This may result in a higher incidence of injuries during periods of high estrogen concentration.

A number of validated knee outcome rating scales are used to assess knee function in the ACL-deficient and ACL-reconstructed knee. These scores use a numeric system to rate findings such as pain, swelling, subjective assessment of function and level of activity.

However, it is unknown whether there is a correlation between the outcome rating scales and whether they can be used interchangeably. The aim of this study was to investigate the correlation between the four commonly used outcome rating scales (Lysholm, IKDC, Cincinnati and Tegner).

Inclusion criteria included physically active patients between the age of 18 and 35 years with isolated ACL injuries. A power calculation for sample size was performed. Selecting an alpha level of 0.05 and power value of 0.8, 24 ACL- deficient and 24 ACL-reconstructed subjects were needed to achieve adequate statistical power. Statistical analysis included the calculation of means and standard deviations for the dependant variables. Pearson's product moment correlation coefficients were used to establish the strength of the relationships.

Forty-four ACL-deficient and 24 ACL reconstructed subjects (mean age 27.0, range 16–49), with a minimum of 12 months post surgery, completed the tests. Pre-operatively, strong significant correlations (r=0.53-0.74, p=0.0001-0.001) between IKDC and the other scoring systems (Cinncinati, Lysholm and Tegner) were observed. The Lysholm score was significantly correlated to IKDC (r=0.74, p=0.0001) and Cinncinati (r=0.60, p=0.001) scores. Non-significant moderate correlations were observed between Lysholm and Tegner (r=0.38, p=0.17) and Cinncinati and Tegner (r=0.36, p=0.18) scores. Post-operatively all scores were strongly related (r=0.61- 0.93). However, only the relationships between Lysholm and IKDC score (p=0.001) and IKDC and Cinncinati score (p=0.01) reached statistical significance.

The results of this study indicate that the commonly used rating scales produce interchangeable results in the ACL-deficient patient. In the ACL-reconstructed patient, knee scoring systems seem to measure different aspects of physical activity, physical disability and subjective patient satisfaction—all of which are not interchangeable. As such, the classification of results may vary and may explain the findings.

Epidemiologic studies project an increase of hip fractures worldwide. They are an important cause of morbidity and mortality in the elderly and represent an increasing burden on a country's health service. The aim of the study was to evaluate the mortality of hip fractures admitted to a regional hospital in Australia and calculate the relative risk ratio of morbidity variables on mortality.

This retrospective review included all patients admitted from 2003 to 2008 to a regional Queensland hospital with a hip fracture. The relative risk ratio for the probability of death was calculated for the following variables: previous mobility (independent, home with help, nursing home), type of treatment (hemiarthroplasty, ORIF, DHS/Nail, total hip arthroplasty, conservative), ASA, comorbidities (dementia, hypertension, cardiac, respiratory, renal, previous hip fractures, diabetes), pre-operative haemoglobin, BUN ratio, length of stay, operative time, anaesthetic time and type (general, spinal) and, gender.

A total of 211 patients (136 female, 75 male) with an average age of 79.1 years were admitted. Seventy-six patients died during the specified interval. The average 30 day mortality was 6.2% and the average time of survival was 318 days. The relative risk of death was above one for the following variables: female gender 1,16; nursing home 1,11; more than 1 comorbidity 1,38; more than 4 comorbidities 1,78; dementia 1,12; diabetes 1,3; hypertension 1,35, previous fractures 1,43; ASA 4 1,5; operating time more than 120 minutes 7,4; length of stay more than 20 days 2,16, BUN ratio>0.1 1,38 and BUN ration<0.04 1,78.

This retrospective project identified a number of variables influencing mortality of hip fractures. These results demonstrate that the relative risk substantially increases with length of surgical time, length of hospital stay in excess of 20 days and more than four associated comorbidities.

The level of hamstring antagonist activation is thought to be related to knee functionality following anterior cruciate ligament (ACL) injury/surgery as pronounced co-activation can control anterior tibial translation (ATT). The purpose of this study was to examine relationships between knee functionality and hamstring antagonist activation during isokinetic knee extension in ACL deficient (ACLD) and ACL reconstructed (ACLR) patients. Knee functionality was rated using the Cincinnati Knee Rating System for the involved limb of 10 chronic, functional ACLD patients and 27 ACLR patients (14 using a patella tendon (PT) graft and 13 using a semitendinosus/gracilis tendon (STGT) graft). Each subject also performed maximal effort isokinetic knee extension and flexion at 180°. s^-1 for the involved limb with electromyographic (EMG) electrodes attached to the semitendinosus (ST) and biceps femoris (BF) muscles. Antagonist activity of the ST and BF muscles was calculated in 10° intervals between 80-10° knee flexion.

For the ACLD group, Pearson product moment correlations revealed significant (p<0.05) moderate, positive relationships between knee functionality and ST and BF antagonist activity across the majority of the knee flexion intervals. For both ACLR groups, several significant (p<0.05) moderate, negative associations were found between ST and BF antagonist activity and knee functionality.

Amplified hamstring antagonist activity in ACLD patients at flexion angles representative of those at footstrike and deceleration improves knee functionality as increased crossbridge formation increases hamstring stiffness and decreases ATT. Lower-level hamstring activation is sufficient to unload the ACL graft and improve knee functionality in ACLR patients.

Introduction: Anthropometric anatomical factors may influence mechanical and functional stability of joints. An increased posterior tibial slope places the anterior cruciate ligament at a theroretical biomechanical disadvantage. An increased posterior tibial slope can potentially alter forces during landing tasks by either increasing anterior tibial translation and/or ACL loading. The purpose of this study is to investigate the relationship between posterior tibial slope and anterior cruciate ligament injuries. It is hypothesized that subjects with an ACL injury have an increased posterior tibial slope compared to a normal population.

Methods: Posterior tibial slope in 211 patients (154 male, 57 female) aged 15–49 who underwent anterior cruciate ligament reconstruction was measured using the posterior tibial cortex as reference. A matched control group was used for comparison.

Results: The average posterior tibial slope in the ACLR population was 6.1 degrees while the control group had average values of 5.4 degrees. This finding nearly reached statistical significance (p=0.057). In the male population average values were 5.5 degrees in the ACLR group and 5.9 in the control group. This was not significant (p=0.21). However there was a significant difference (p=0.04) in the female group. ACLR females had higher values 6.5 degrees whereas the control group had average values of 5.2 degrees.

Discussion: Increased posterior tibial slope decreases the inclination of the ACL and potentially decreases vector force during dynamic tasks. It may further result in suboptimal length-tension relationships of agonistic muscles, increases in electromechanical delays and result in lower force development further leading to increased vector forces on the ACL. Posterior tibial slope angles were slightly smaller than with other published studies. However by using the posterior tibial cortex as reference an average of 3 degrees must be added to the measured values. We could not confirm the results of previous studies demonstrating an increased degree of posterior tibial slope in ACL injured patients. However we demonstrated a significant difference in tibial slope in females. Based on our results an increased posterior tibial slope is not a risk factor in males but possibly contributes to ACL injuries in females. Increased posterior tibial slope may be one of the reasons why females have a higher incidence of ACL injuries.

Anterior cruciate ligament reconstruction has become a standard procedure with a documented good and excellent outcome of 70–90%. Important variables of outcome after surgery consist of objective and subjective variables. It is important to examine the relationship between commonly used knee rating systems and functional tests to assess whether there is a correlation between rating systems and functional performance. The purpose of this study was to determine if a correlation exists between four commonly used knee rating systems (Lysholm, Tegner, IKDC, Noyes) and commonly performed dunctional tests: single and timed hop, vertical jump and isometric, isokinetic and eccentric muscle strength.

44 consecutive patients (31 males and 13 females) were selected (mean age 27.9 years). All subjects were tested prior and 12 month following anterior cruciate ligament reconstruction. The subjects completed the above knee rating scores. The patients were then evaluated performing the following tests: single leg hop for distance, timed hop and vertical jump. Muscle strength was assessed using a Biodex dynamometer. Isometric strength was examined at 30 and 60 degrees of flex-ion. Isokinetic testing (concentric and eccentric) was performed at 120 and 180 degrees/sec. Their results of functional testing were expressed as percentage of the contralateral non involved limb.

A positive correlation was found between single leg hop, Lysholm (r=0.53, p< 0.05). IKDC (r=0.30, p< 00002) and Noyes score (r=0.45, p< 0.01). A positive correlation was found between vertical jump, Lysholm (r=0.21, p< 0002), IKDC (r=0.31, p< 0.0001) and Noyes score (r=0.31, p< 0.0001). There was no correlation between timed hop and knee scores. A negative correlation (r=0.25–0.46) was noted between eccentric peak extension torque at 120 degrees/sec and 180 degrees/sec (r=0.230.26). However it only reached significance (p< 0.04) between IKDC and eccentric torque at 120 degrees/sec and 180 degrees/sec (p< 0.01). In addition there was a moderate negative correlation (r=0.26, p< 0.0004)) between Lysholm score and eccentric peak torque at 180 degrees/sec. No correlations were found for isokinetic and isometric torque for the knee flexors.

Knee rating systems seem to reflect functional capabilities and subjective satisfaction of patients prior and post ACL reconstruction. Isokinetic strength does not seem to be an important predictor of knee function.

Malpositioning of the acetabular cup component in total hip arthroplasty can result in increased wear, early nonseptic loosening and is the most common cause of dislocation. Previous research has defined a safe zone with an inclination of 40±10 degrees and anteversion of 15±10 degrees. The purpose of this study was to using CT based measurements.

32 patients receiving a primary hip replacement between June 2005 and December 2006 were enrolled in the study. Alignment of the implant is based on the acquisition of landmarks (ASIS and pubic tubercle) and placement of tracking pins into the ASIS. The target position for all patients was 45 degrees of inclination and 15 degrees of anteversion. The position was determined by postoperative Ct scans of the pelvis. This group was compared to a historical control group.

Descriptive statistics revealed that the demographics of both groups were comparable. Mean cup placement in the navigation group was 46.6±5.9 deg of inclination and 18.8±5.6 deg of anteversion. Mean cup placement in the control group was 45.8±9.5 deg of inclination and 27.3±15.0 deg of anteversion. With navigation 73.7% resp 89.5% of cups were placed within the safe zone for inclination resp. anteversion whereas only 60.9% resp. 39% of cups were placed with freehand technqie. Taking both inclination and anteversion into consideration 68.4% of cups were placed in the safe zone with navigation. Only 25.7% were placed for both inclination and anteversion were placed into the safe zone.

Computer navigation for total joint arthroplasty, if helpful to the surgeon, has to increase reliability of component placement and show a significant reduction in variation compared to freehand techniques. Our results demonstrate that imageless navigation is a reliable tool which significantly increases precision of acetabular cup placement. Further studies are needed to evaluate and further increase the accuracy of the system

Anterior cruciate ligament reconstruction has become a standard procedure with a documented good and excellent outcome of 70–90%. It has been demonstrated by previous research that all patients following surgery demonstrate a strength deficit of almost 20%. However it is not known whether these strength deficits have an influence on postoperative functionality.

52 consecutive patients (38 males and 14 females) were selected (mean age 27.9 years). All subjects were tested prior and 12 month following anterior cruciate ligament reconstruction. Muscle strength was assessed using a Biodex dynamometer. Isometric strength was examined at 30 and 60 degrees of flexion. Isokinetic testing was performed at 180 degrees/sec and peak torque and symmetry indices were analysed.

No correlations were found between the Cinncinnati Score and isokinetic peak torque for extension. A moderate significant (p=0.001–0.007) correlation (r=0.200.45) was found for peak flexion torque in ACL reconstructed patients. In ACL deficient patients symmetry indices (r=0.36–0.43, p=0.001–0.004) were moderately related to functionality for both flexion and extension.

Quadriceps muscle strength does not seem to be an important predictor of knee function after ACL reconstruction. Flexors seem to be important to protect the graft from overload. In ACLD knees functionality is related to high symmetry indices suggesting similar strength is necessary to perceive knee function as near normal. This is possibly a normal neuromuscular adaptation caused by contralateral quadriceps avoidance.

Gait analysis is an important tool to measure function following total knee replacement. It is currently unknown whether there is a correlation between subjective and objective outcome variables. The purpose of this study was to analyse relationships between subjective outcome scores and kinematic and kinetic data.

25 consecutive patients (15 males, 10 females) were selected (mean age 68 years, BMI 31.8). All subjects were tested a minimum of 24 months following total knee replacement. SF12, Oxford knee score, knee society and KOOS scores were collected. Muscle strength was assessed using a Biodex dynamometer and symmetry indices were analysed. A timed up and go test and KT2000 measurements were performed.

Strong correlations (r=0.52–0.74) were found between scoring systems (SF 12, Oxford knee score, knee society score, KOOS score) and the timed up and go test. Moderate correlations (r=0.27–0.35) were found between knee scores and KT2000 measurements. Only weak correlations (r=0.09–0.12) were found between knee scores and strength. None of the correlations reached statistical significance. Post hoc contrasts demonstrated adequate power (0.95) of the study.

The finding of this study suggests that outcome scores and objective and functional tests following total knee arthroplasty measure different variables of outcome. Whilst objective tests and gait analysis provide an understanding of joint mechanics after surgery and can be used to calculate resultant forces and moments, patient perceived outcomes have no Significant correlation to knee biomechanics. This may be related to factors such as pain relief, improved quality of life and the ability to perform activities of daily life. In contrast modern implants may provide a satisfactory outcome resulting in high patient satisfaction. The results of this study underline the importance of using subjective patient outcome measures to follow up total knee replacement patients.

Non-operative treatment of lateral clavicle fractures presents a difficult problem. A high incidence of non-union, residual pain and shoulder girdle instability has been reported. A variety of fixation techniques have been described but the complication rates of these procedures can be high. This retrospective review describes the use of distal radius locking plates for fixation of lateral unstable clavicle fractures.

From January 2006 until December 2007 23 patients (17 males, 5 females; mean age 31 yrs (12–70) presented to our service. 2 patients sustained type 1, 16 patients type 2, 2 patients type 4 and 3 patients type 5 fractures (Neer classification). Patients were reviewed clinically, radiographically and with Constant score assessment.

Union was acchieved at a mean follow up of 7.2 weeks. The mean Constant score at 6 months was 84, the mean DASH score 27.7. The following complications were seen during the follow-up period: 1 superficial infection settling with oral antibiotics and 1 non-union in a type 5 fracture requiring bone grafting.

Clavicle fractures of the lateral aspect are controversial. The mechanism of injury often results in ruptures of the adjacent coracoclavicular ligaments and create instability and increased motion between the proximal and distal fragment. The result of this series of cases are encouraging and we recommend the use of distal radius locking plates to treat unstable lateral clavicle fractures. However a larger study is needed to further evaluate mid- and long-term shoulder function.