Prediction of range of motion 2?years after mobile-bearing total knee arthroplasty: PCL-retaining versus PCL-sacrificing

Purpose  

This study evaluated the changes in the range of motion (ROM) with time postoperatively.     

Navigated total knee arthroplasty: is it error-free?

Purpose

The aim of this study was to determine whether errors do occur in navigated total knee arthroplasty (TKAs) and to study whether errors in bone resection or implantation contribute to these errors.

Methods

A series of 20 TKAs was studied using computer navigation. The coronal and sagittal alignments of the femoral and tibial cutting guides, the coronal and sagittal alignments of the final tibial implant and the coronal alignment of the final femoral implant were compared with that of the respective bone resections. To determine the post-implantation mechanical alignment of the limb, the coronal alignment of the femoral and tibial implants was combined.

Results

The median deviation between the femoral cutting guide and bone resection was 0° (range ?0.5° to +0.5°) in the coronal plane and 1.0° (range ?2.0° to +1.0°) in the sagittal plane. The median deviation between the tibial cutting guide and bone resection was 0.5° (range ?1.0° to +1.5°) in the coronal plane and 1.0° (range ?1.0° to +3.5°) in the sagittal plane. The median deviation between the femoral bone resection and the final implant was 0.25° (range ?2.0° to 3.0°) in the coronal plane. The median deviation between the tibial bone resection and the final implant was 0.75° (range ?3.0° to +1.5°) in the coronal plane and 1.75° (range ?4.0° to +2.0°) in the sagittal plane. The median post-implantation mechanical alignment of the limb was 0.25° (range ?3.0° to +2.0°).

Conclusions

When navigation is used only to guide the positioning of the cutting jig, errors may arise in the manual, non-navigated steps of the procedure. Our study showed increased cutting errors in the sagittal plane for both the femur and the tibia, and following implantation, the greatest error was seen in the sagittal alignment of the tibial component. Computer navigation should be used not only to guide the positioning of the cutting jig, but also to check the bone resection and implant position during TKA.

Level of evidence

IV.     

What have we learned from LCS mobile-bearing knee system?

Three hundred and sixty-four low contact stress (LCS) total knee arthroplasties that could be followed up for more than 5 years were clinically and radiographically analyzed. The median postoperative Hospital for Special Surgery score improved from 56 (range 32–77) to 91 (range 64–100) points, but median range of motion did not change from 120° (range 50°–135°) to 120° (range 85°–135°). Complications occurred in 16 cases (4%), and included postoperative polyethylene dislocation and intraoperative tibial condylar fracture, while five knees (1%) required revision surgery due to mechanical reasons. The overall prosthesis survival rate was 91% at 12 years. Although the LCS mobile-bearing knee system has theoretical advantages in terms of wear and loosening, the problem of polyethylene dislocation, intraoperative tibial fracture, and radiolucent lines should be solved for long survival. The clinical relevance of this study is that the LCS system provided good clinical and survival results.     

Computer-assisted total knee arthroplasty versus the conventional technique: how precise is navigation in clinical routine?

Restoration of the mechanical leg axis and component positioning are crucial factors affecting long-term results in total knee arthroplasty (TKA). In a prospective study, 1,000 patients were operated on either using a CT-free navigation system or the conventional jig-based technique. Leg alignment and component orientation were determined on postoperative X-rays. The mechanical leg axis was significantly better in the computer-assisted group (95%, within ±3° varus/valgus) compared to the conventional group (74%, within ±3° varus/valgus) (P < 0.001). On average, the operating time was increased by 8 min in the computer-assisted group. No significant differences were seen between senior and younger surgeons regarding postoperative leg alignment and operating time. Computer-assisted TKA leads to a more accurate restoration of leg alignment and component orientation compared to the conventional jig-based technique. Potential benefits in long-term outcome and functional improvement require further investigation.     

Is bicompartmental knee arthroplasty more favourable to knee muscle strength and physical performance compared to total knee arthroplasty?

Purpose

Bicompartmental knee arthroplasty features bone and ligament sparing as unicompartmental knee arthroplasty and is presumably better in the recovery of muscle strength and function compared to total knee arthroplasty (TKA) though not previously reported in the literature. The aim of the study was to compare isokinetic knee muscle strength and physical performance in patients who underwent either bicompartmental knee arthroplasty or TKA.

Methods

Each of 24 patients (31 knees) was prospectively examined preoperatively, at 6 and 12 months after each surgery. Isokinetic knee extensor and flexor strength as well as position sense were measured using the Biodex system. Timed up and go test, stair climbing test, and the 6-min walk test were used to assess physical performance. The results of each group were also compared with those from the corresponding healthy control, respectively.

Results

Demography showed significant difference in the mean age between bicompartment (54.8 ± 5.6 years) and TKA groups (65.7 ± 6.7 years). Comparing between the two groups, knee extensor and flexor torque, hamstring/Quadriceps ratio, position sense, and physical performance were not significantly different preoperatively, at 6 and 12 months after surgery. In intra-group analysis, muscle strength and position sense at each time point were not different in both groups. In physical performance, both groups resulted in improvement in the 6-min walk test, and only TKA group showed enhancement in stair climbing test.

Conclusions

Although theoretically plausible, bicompartmental knee arthroplasty was not superior in knee muscle strength and physical performance at 1 year compared with total knee arthroplasty.

Level of evidence

II.     

Does total knee arthroplasty modify flexion axis of the knee?

Purpose

To prospectively investigate whether preoperative functional flexion axis in patients with osteoarthritis- and varus-alignment changes after total knee arthroplasty and whether a correlation exists both between preoperative functional flexion axis and native limb deformity.

Methods

A navigated total knee arthroplasty was performed in 108 patients using a specific software to acquire passive joint kinematics before and after implant positioning. The knee was cycled through three passive range of motions, from 0° to 120°. Functional flexion axis was computed using the mean helical axis algorithm. The angle between the functional flexion axis and the surgical transepicondylar axis was determined on frontal (α ^F) and axial (α ^A) plane. The pre- and postoperative hip-knee-ankle angle, related to femur mechanical axis, was determined.

Results

Postoperative functional flexion axis was different from preoperative only on frontal plane, while no differences were found on axial plane. No correlation was found between preoperative α ^A and native limb deformity, while a poor correlation was found in frontal plane, between α ^F and preoperative hip-knee-ankle angle.

Conclusions

Total knee arthroplasty affects functional flexion axis only on frontal plane while has no effect on axial plane. Preoperative functional flexion axis is in a more varus position respect to the transepicondylar axis both in pre- and postoperative conditions. Moreover, the position of the functional axis on frontal plane in preoperative conditions is dependent on native limb alignment, while on axial plane is not dependent on the amount of preoperative varus deformity.

Level of evidence

IV.     

Symptomatic versus asymptomatic knees after bilateral total knee arthroplasty: what is the difference in SPECT/CT?

Purpose

The primary purpose of this retrospective study was to evaluate the differences of bone tracer uptake (BTU) in symptomatic and asymptomatic knees after bilateral total knee arthroplasty (TKA) and identify typical BTU patterns with regards to TKA component position and alignment.

Methods

A consecutive number of 37 patients after bilateral TKA were retrospectively included. The knees were grouped into symptomatic (group A) and asymptomatic (group B) knees. All patients underwent 99m-Tc-HDP-SPECT/CT. Coronal, rotational, and sagittal TKA component position was analysed in 3D reconstructed CT. BTU was anatomically localised and quantified using a validated standardized localization scheme. Maximum BTU values for each area were recorded and normalized values calculated. Signed log-rank test, chi-square test, paired t-tests, and Pearson correlations were used (

Results

Symptomatic TKAs were significantly more flexed and had a tendency to be more internally rotated when compared to asymptomatic ones (p?=?0.061) and at the tip of the tibial stem (symptomatic 5.49; asymptomatic 4.74, p?=?0.048). The lowest BTU was found in the posterior femoral regions (flatsp, flatip, fmedsp, fmedip) (Table 3). Tibial and patellar areas showed twice as high mean BTUs than femoral areas (Fig. 3). A significant correlation of TKA component position and BTU was demonstrated.

Conclusions

Distribution and intensity of BTU in SPECT/CT depends on TKA component position and alignment. In addition, typical BTU patterns in symptomatic and asymptomatic knees were identified. A profound knowledge of BTU pattern, TKA component position, and alignment helps to identify pathologies in patients after TKA.

Clinical evidence

Diagnostic study, level II

     

Anterior knee pain after total knee arthroplasty: does it correlate with patellar blood flow?

Purpose  

Total knee arthroplasty (TKA) disturbs patellar blood flow, an unintended accompaniment to TKA that may be a cause of postoperative anterior knee pain. We examine whether disrupted patellar blood flow correlates with anterior knee pain following TKA.     

Do tibiofemoral contact point and posterior condylar offset influence outcome and range of motion in a mobile-bearing total knee arthroplasty?

Purpose

The posterior condylar offset (PCO) and the tibiofemoral contact point (CP) have been reported as important factors that can influence range of motion and clinical outcome after total knee arthroplasty. A mobile-bearing knee implant with an anterior posterior gliding insert would in theory be more sensitive for changes in PCO and CP. For this reason, we analysed the PCO and CP and the relation with outcome and range of motion in 132 patients from a prospectively documented cohort in this type of implant.

Methods

The prosthesis used was a posterior cruciate retaining AP gliding mobile-bearing total knee replacement (SAL II Sulzer Medica, Switzerland). In 132 knees, the pre- and postoperative PCO and postoperative CP were evaluated. Measurements were made on X-rays of the knee taken in approximately 90° of flexion and with less than 3-mm rotation of the femur condyles. The outcome parameters, range of motion (ROM) and the knee society score (KSS), for each knee were determined preoperatively and at 5-year follow-up.

Results

The mean KSS improved from 91 to 161 at 5-year follow-up (p < 0.001) and the mean ROM from 102 to 108 (p < 0.05). The mean PCO difference (postoperative PCO–preoperative PCO) was—0.05 mm (SD 2.15). The CP was on average 53.9 % (SD 5.5 %). ROM was different between the 3 PCO groups (p = 0.05): patients with 3 or more mm decrease in PCO had the best postoperative ROM (p = 0.047). There was no statistical difference between the postoperative ROM between patients with a stable PCO and those with an increased PCO. There was no correlation between the difference in PCO and the difference in ROM; R _Pearson = ?0.056. There was no difference in postoperative ROM or postoperative total KSS between CP <60 % and CP >60 %: p = 0.22, p = 0.99, for ROM and KSS, respectively. Scatter plots showed uniform clouds of values: increase or decrease in PCO and CP had no significant influence on ROM or KSS.

Conclusion

The hypotheses that a stable PCO and a more natural CP increase postoperative ROM and improve clinical outcome could not be confirmed. On the contrary, a decreased PCO seemed to improve knee flexion. Furthermore, a relationship between PCO and CP could not be found.

Level of evidence

Prospective cohort study, Level II.     

Revision total knee arthroplasty with varus–valgus constrained prosthesis versus posterior stabilized prosthesis

Purpose

The aims of this retrospective study were to provide the basis for the choice of prosthesis in revision total knee arthroplasty (TKA) and to evaluate the outcome with varus–valgus constrained prosthesis compared with posterior stabilized (PS) prosthesis.

Methods

One hundred and five patients (121 knees) received revision TKA; of which thirty-seven patients (42 knees) received PS prosthesis and sixty-eight patients (79 knees) received varus–valgus constrained prosthesis. The mean follow-up duration was 64.8 ± 31.5 months and 63.2 ± 28.1 months in the PS and varus–valgus constrained groups, respectively. The criterion of prosthesis choice was a subjective laxity assessed by the surgeon intraoperatively. A multivariate analysis was performed to evaluate the preoperative factors in the choice of the prosthesis.

Results

The grade of femoral bone defect was the only factor that affected the choice of prosthesis. Clinical results improved significantly in both groups after surgery. There were no significant differences in clinical results between the two groups. Complication rates were 9.5 % in the PS group and 10.1 % in the varus–valgus constrained group, and the Kaplan–Meier survivorship analysis revealed 8-year component survival rates of 83.1 and 93.0 % in the PS and varus–valgus constrained groups, respectively.

Conclusions

Femoral bone defect is an important factor to be considered in the choice of prosthesis for revision TKA. The varus–valgus constrained prosthesis showed an outcome similar to that of the PS prosthesis. For clinical relevance, varus–valgus constrained prosthesis is recommended in revision TKA when the PS prosthesis seems unsuitable for the management of instability.

Level of evidence

III.     

Is previous knee arthroscopy related to worse results in primary total knee arthroplasty?

According to literature, knee arthroscopy is a minimal invasive surgery performed for minor surgical trauma, reduced morbidity and shortens the hospitalization period. Therefore, this type of surgery before total knee arthroplasty (TKA) could be considered a minor procedure with minimum postoperative complication. A retrospective and cohort series of 1,474 primary TKA was performed with re-assessment after a minimum follow-up period of 2 years: 1,119 primary TKA had no previous surgery (group A) and 60 primary TKA had arthroscopic debridement (group B). All the patients underwent a clinical and radiological evaluation as well as IKS scores. Statistical analysis of postoperative complications revealed that group B had a higher postoperative complication rate (P < 0.01). In this group, 30% of local complications were re-operated and 8.3% of these cases underwent revision TKA (P < 0.01). The mean interval between arthroscopy and primary TKA was 53 months. However, statistical analysis did not reveal a direct correlation between arthroscopy/primary TKA interval and postoperative complications/failures (P = 0.55). The Kaplan–Meier survival curves showed a survival rate of 98.1 and 86.8% at 10 years follow-up for groups A and B, respectively. Our data allow us to conclude that previous knee arthroscopy should be considered a factor related to postoperative primary TKA outcomes as demonstrated by the higher rate of postoperative complications and failures (P < 0.001) as well as a worse survival curve than group A.     

Patellofemoral arthroplasty, where are we today?

Purpose

Patellofemoral arthroplasty remains controversial, primarily due to the high failure rates reported with early implants. Numerous case series have been published over the years detailing results of various first- and second-generation implants. The purpose of this work is to summarize results published to date and identify common themes regarding implants, surgical techniques, and indications in order to maximize results of future procedures.

Methods

A comprehensive review of the MEDLINE database was carried out to identify all clinical studies related to patellofemoral arthroplasty.

Results

First-generation resurfacing implants were associated with relatively high failure rates in the medium term. Second-generation implants, with femoral cuts based on TKA designs have yielded more promising medium-term results. Surgical indications are specific and must be carefully followed to minimize poor results. Short-term complications are generally related to patellar maltracking, while long-term complications are generally related to progression of osteoarthritis in the tibiofemoral joint. Implant loosening and polyethylene wear are rarely reported. Short-term results are favourable for new technology including custom implants and computer navigated surgery.

Conclusions

Overall, recent improvements in implant design and surgical techniques have resulted in improvements in short- and medium-term results. More work is required to assess the long-term outcomes of modern implant designs.

Level of evidence

IV.     

Three- to six-year follow-up results after high-flexion total knee arthroplasty: can we allow passive deep knee bending?

Purpose  

We evaluated 3- to 6-year clinical and radiological follow-up results after NexGen^? LPS-flex total knee arthroplasty (TKA).     

Can we define envelope of laxity during navigated knee arthroplasty?

Purpose

Functional outcomes after knee arthroplasty (TKA) remain poor. The ability to restore the soft tissue envelope intraoperatively may improve such outcomes. The aim of this study was to extend the scope of computer navigation as a tool to quantifying the envelope of laxity during subjective stress testing preoperatively and to quantify the effects of knee replacement and how it changes as a result of ligamentous failure.

Methods

Loaded cadaveric legs were mounted on a purpose-built rig. Envelope of laxity was measured in 3 degrees of freedom using computer navigation. Knees were subjectively stressed in varus/valgus, internal/external rotation and anterior draw. This was performed preoperatively, during TKA and after sequential sectioning of ligaments. Real-time data were recorded at 0°, 30°, 60° and 90° of flexion. Mixed effect modelling was used to quantify the effects of intervention on degree of laxity.

Results

In all cases, there was an increase in laxity with increasing flexion or ligament sectioning. Operator and movement cycle had no effect. Insertion of a TKA showed increased stability within the joint, especially in internal/external rotation and anterior drawer. Once the PCL and popliteus were cut, the implant only maintained some rotatory stability; thereafter, the soft tissue envelope failed.

Conclusions

This work has shown a novel way by which computer navigation can be used to analyse soft tissue behaviour during TKA beyond the coronal plane and throughout range of motion. Despite subjective stress testing, our results show reproducible patterns of soft tissue behaviour—in particular a wide range of mid-flexion excursion. It also quantifies the limits within which a cruciate-retaining TKR can maintain knee stability. This functionality may guide the surgeon in identifying and/or preventing soft tissue imbalances intra-operatively, improving functional results.