Intraoperative assessment of resected condyle thickness in total knee arthroplasty

Purpose

The purpose of this study was to assess the use of resected condyle thickness measurement, obtained with caliper, when verifying the accuracy of distal femoral bone resection in total knee arthroplasty.

Methods

Fifty-two total knee arthroplasties were performed to treat osteoarthritis with varus knee. The difference of caliper-measured thickness of resected medial and lateral femoral condyles after removal of cartilage from the lateral condyle was compared with radiographically measured values. The preoperative planned valgus cut angles and the postoperative femoral component valgus angles were compared.

Results

The difference of radiograph-measured thickness averaged 2.4 ± 2.2 mm and the difference of caliper-measured thickness averaged 2.0 ± 2.1 mm (r = 0.735, P < 0.001). The postoperative femoral component valgus angle averaged 4.8° ± 1.6° (range, 2.0°–7.6°). The difference between the valgus cut angle and femoral component valgus angle averaged ?0.3° ± 1.5°.

Conclusions

The confirmation of correspondence between the caliper-measured and radiographically measured thickness of resected condyles could verify the accuracy of distal femoral bone resection in total knee arthroplasty.

Level of evidence

III.     

Is valgus unloader bracing effective in normally aligned individuals: implications for post-surgical protocols following cartilage restoration procedures

Purpose

Utilizing valgus unloader braces to reduce medial compartment loading in patients undergoing cartilage restoration procedures may be an alternative to non-weightbearing post-operative protocols in these patients. It was hypothesized that valgus unloader braces will reduce knee adduction moment during the stance phase in healthy subjects with normal knee alignment.

Methods

Gait analysis was performed on twelve adult subjects with normal knee alignment and no history of knee pathology. Subjects were fitted with an off-the-shelf adjustable valgus unloader brace and tested under five conditions: one with no brace and four with increasing valgus force applied by the brace. Frontal and sagittal plane knee angles and external moments were calculated during stance via inverse dynamics. Analyses of variance were used to assess the effect of the brace conditions on frontal and sagittal plane joint angles and moments.

Results

With increasing tension in the brace, peak frontal plane knee angle during stance shifted from 1.6° ± 4.2° varus without the brace to 4.1° ± 3.6° valgus with maximum brace tension (P = 0.02 compared with the no brace condition). Peak knee adduction moment and knee adduction impulse decreased with increasing brace tension (main effect of brace, P < 0.001). Gait velocity and sagittal plane knee biomechanics were minimally affected.

Conclusion

The use of these braces following a cartilage restoration procedure may provide adequate protection of the repair site without limiting the patient’s mobility.

Level of evidence

Therapeutic prospective comparative study, Level II.     

Femoral bone and cartilage wear is predictable at 0° and 90° in the osteoarthritic knee treated with total knee arthroplasty

Purpose

Kinematically aligned total knee arthroplasty (TKA) positions the femoral component at the natural angle and level of the distal (0°) and posterior (90°) joint line. This technique applies referencing guides at 0° and 90° that are adjusted to compensate for wear and kerf and perform resections equal in thickness to the femoral component. Knowing whether femoral bone and cartilage wear is predictable would assist in establishing general guidelines for adjusting the resection level of these two referencing guides. This study tests the hypothesis that femoral bone and cartilage wear is predictable at 0° and 90° in the varus and valgus osteoarthritic knee treated with TKA.

Methods

The study consists of 205 patients and 208 knees with Kellgren–Lawrence Grade 3 or 4 osteoarthritis and treated with a TKA. Each knee had a narrow slice (2 mm) preoperative 1.5 tesla magnetic resonance image in the sagittal plane. Femoral bone and cartilage wear at 0° and 90° was computed from best-fit circles superimposed on the peripheral boundary of the subchondral bone on the medial and lateral femoral condyles.

Results

Overall, 99.5 % of knees had minimal bone wear (<1 mm) at 0° and 90°. In the 74 % (154 of 208) of knees with a varus deformity, 92 % at 0° and 2 % at 90° had >1 mm cartilage wear on the medial femoral condyle. In the 26 % (54 of 208) of knees with a valgus deformity, 78 % at 0° and 55 % at 90° had ≥1 mm cartilage wear on the lateral femoral condyle.

Conclusions

As a general guideline, adjustment for femoral bone wear is rarely required when performing kinematically aligned TKA. Most osteoarthritic knees require adjustment of the distal referencing guide to compensate for cartilage wear on the medial femoral condyle in the varus knee and the lateral femoral condyle in the valgus knee. Adjustment of the posterior referencing guide is required in about half of valgus osteoarthritic knees to compensate for lateral cartilage wear at 90°. Knowing that bone wear is rare and cartilage wear is predictable in varus and valgus Kellgren–Lawrence Grade 3 or 4 osteoarthritic knees helps establish general guidelines for adjusting the distal and posterior femoral referencing guides to restore the natural angle and level of the femoral joint lines when performing kinematically aligned TKA with generic instruments.

Level of evidence

IV.     

Association between varus alignment and post-traumatic osteoarthritis after anterior cruciate ligament injury

Purpose

To investigate the association between varus alignment and post-traumatic osteoarthritis (OA) after an anterior cruciate ligament (ACL) injury.

Methods

One hundred subjects with an acute complete ACL tear were followed for 15 years. Anterior–posterior radiographs of the tibiofemoral joint were obtained with a knee flexion of 20°, and the patellofemoral joint was examined with skyline view at 50° knee flexion. Joint space narrowing and osteophytes were graded in the tibiofemoral and patellofemoral joints in the injured (ACL) and uninjured knee according to the radiographic atlas of the Osteoarthritis Research Society International. The alignment of the uninjured, contralateral knee was measured at follow-up, using full-limb radiographs of leg with the knee in full extension. Alignment was expressed as the hip-knee-ankle (HKA) angle. Alignment was defined as valgus (HKA ≤178°), neutral (179°–181°) or varus (≥182°).

Results

Data from 68 subjects were included in the analysis. Varus alignment of the uninjured knee at follow-up appeared to be associated with OA of the injured knee 15 years after an ACL injury (odds ratio (95 % confidence interval) 3.9 (1.0–15.8, p = 0.052)).

Conclusions

Varus alignment of the uninjured knee at follow-up may be associated with OA of the injured knee 15 years after an ACL injury.

Level of evidence

II.     

Hindfoot alignment at one year after total knee arthroplasty

Purpose

It has previously been found that valgus hindfoot alignment (HFA) improves 3 weeks following total knee arthroplasty (TKA) for varus knee osteoarthritis (OA). In the present study, HFA was evaluated prior to TKA, as well as 3 weeks and 1 year following TKA. Using these multiple evaluations, the chronological effects of TKA on HFA were investigated.

Methods

The study included 71 patients (73 legs) who underwent TKA for varus knee OA. Radiograph examinations of the entire limb and hindfoot were performed in the standing position prior to TKA, as well as 3 weeks and 1 year following TKA. The varus–valgus angle was used as an indicator of HFA in the coronal plane. Patients were divided into two groups according to the preoperative varus–valgus angle: a hindfoot varus group (varus–valgus angle <76°) and a hindfoot valgus group (varus–valgus angle ≥76°). The changes in the varus–valgus angle were evaluated and compared in both groups.

Results

In the hindfoot valgus group, the mean ± standard deviation varus–valgus angle significantly declined from 80.5 ± 3.1° prior to TKA to 78.6 ± 3.7° 3 weeks following TKA and 77.1 ± 2.7° 1 year following TKA. However, in the hindfoot varus group, the mean varus–valgus angle prior to TKA (72.7 ± 2.6°) did not differ significantly from the mean varus–valgus angles 3 weeks (72.3 ± 3.3°) or 1 year (73.5 ± 3.0°) following TKA.

Conclusions

HFA improved chronologically in legs with hindfoot valgus as a result of the alignment compensation ability of the hindfoot following TKA. However, no improvement was noted in legs with hindfoot varus because the alignment compensation ability of the hindfoot had been lost. The patients with hindfoot varus should be attended for ankle pain in the outpatient clinic after TKA.

Level of evidence

III.

     

A case series of lateral opening wedge high tibial osteotomy for valgus malalignment

Introduction

Lateral opening wedge high tibial osteotomy is a rarely employed surgical technique used for the treatment of lateral knee pain and degeneration in the setting of genu valgum. There exists little evidence of the suitability of this procedure for patients requiring osteotomies with a small correction.

Materials and methods

A case series of 23 patients (24 knees) undergoing lateral opening wedge high tibial osteotomy with a minimum follow-up of 2 years was performed between 2002 and 2008. A surgical technique avoiding the need for fibular osteotomy is described. Adverse events, patient-reported outcomes and radiographic measures of alignment were assessed at baseline, at 6 months postoperatively, and at time of final follow-up. A subgroup of 12 patients also underwent 3D gait analysis at the same time points.

Results

The mean follow-up was 52 months (±20.4). Statistically and clinically significant improvements were identified in the lower extremity functional scale [mean change (95 %CI) = 10 (2.4, 17.6)], and in the knee injury and osteoarthritis outcome score [mean change (95 %CI) = 10.9 (0.5, 21.4)]. Mechanical axis changed from 2.4 ± 2.4° valgus to 0 ± 2.6° varus (p<0.001), anatomical axis from 6.9 ± 2.8° to 4.7 ± 2.5° valgus (p < 0.001), with weight-bearing line offset changing from 60.2 ± 11.4 % to 49.5 ± 12.4 % (p < 0.001). Change in lateral tibial slope, from 6.5 ± 2.2° to 7.5 ± 2.3°, was very small and not statistically significant (n.s.). The peak knee adduction moment during gait significantly increased [mean change (95 %CI) = 0.72 %BW*Ht (0.42, 1.02), suggesting a medial shift in dynamic knee joint load. Two patients underwent total knee arthroplasty during the study period.

Conclusions

Lateral opening wedge high tibial osteotomy is a viable surgical option for patients with lateral knee pain and valgus malalignment requiring small degrees of correction.

Level of evidence

IV.     

No influence of coronal laxity and alignment on lift-off after well-balanced and aligned total knee arthroplasty

Purpose

In vivo fluoroscopic analyses have revealed the kinematics after total knee arthroplasty (TKA), including femoral condylar lift-off. This study asked whether differences in static varus–valgus laxity or coronal limb alignment after TKA affect lift-off under weight-bearing conditions. It was hypothesised that there is a correlation between coronal laxity or alignment and lift-off during walking.

Methods

The current study analysed nineteen subjects undergoing cruciate-retaining TKA performed by the measured resection technique. The varus–valgus laxity at knee extension was measured using a 150 N stress radiograph. The mechanical axis was measured using a full-standing radiograph. Continuous radiological images were taken while the subject walked on a treadmill, and the images during single-leg stance were analysed to determine the lift-off using a 3D-to-2D image-to-model registration technique.

Results

The average angle in varus/valgus stress was 6.8 ± 1.8°/6.6 ± 2.1°. No statistically significant differences were observed between the varus and valgus laxity. The average amount of lift-off was 0.7 ± 0.4 mm. The static varus–valgus laxity (n. s.) or the differences in the laxities (n. s.) on the stress radiograph did not influence lift-off. The weight-bearing ratio was achieved within the middle third of the knee in 90 % of subjects. Two outliers with valgus alignment (68 ± 1 %) demonstrated no significant difference in lift-off in comparison with the majority of the subjects (46 ± 9 %).

Conclusion

The static coronal laxity and alignment did not influence the lift-off under dynamic weight-bearing conditions after well-balanced and aligned cruciate-retaining TKA. Measured resection technique can produce sufficient coronal stability and alignment without significant lift-off during walking.

Level of evidence

IV.     

Comparison of stability and kinematics of the natural knee versus a PS TKA with a ‘third condyle’

Purpose

The goal of this study was to compare the kinematics of knees before and after total knee arthroplasty (TKA) that relies on an inter-condylar ‘third condyle’. The hypothesis was that the ‘third condyle’ provides sufficient flexion stability and induces a close to normal femoral rollback, thus granting natural joint kinematics.

Methods

Intra-operative navigation data were collected from 29 consecutive cases that received a cemented TKA (HLS Noetos, Tornier SA, France) designed with an inter-condylar ‘third condyle’ that engages within the tibial insert beyond 35° flexion. Operations were guided by a non-image-based system (BLU-IGS, Orthokey Italia srl, Italy) that recorded relative femoral and tibial positions in native and implanted knees during: passive range of motion, anterior drawer test at 90° flexion, and varus–valgus stress tests at full extension and at 30° flexion.

Results

The total internal tibial rotation during flexion was similar for native (8.2 ± 4.2°) and implanted knees (8.0 ± 5.4°). The lateral femoral condyle was more posterior in implanted knees (1.2 ± 9.4 mm) than in native knees (9.5 ± 3.6 mm) throughout early flexion (p < 0.01), but this difference diminished beyond 100° flexion (n.s.). The implanted knees did not exhibit paradoxical external tibial rotation. Varus–valgus laxity in full extension was lower for implanted knees than for native knees (p = 0.0221), but at 30° flexion was almost identical for both native and implanted knees. Anteroposterior laxity was similar in implanted and native knees.

Conclusions

The ‘third condyle’ TKA provides similar anteroposterior and mediolateral stability to the natural knee. This feature granted an adequate balance between laxity and constraint to reproduce natural joint kinematics, including smooth femoral rollback, without causing paradoxical external tibial rotation.

Level of evidence

Comparative study, Level III.     

Tibial internal rotation is affected by lateral laxity in cruciate-retaining total knee arthroplasty: an intraoperative kinematic study using a navigation system and offset-type tensor

Purpose

The purpose of this study was to test the hypothesis that intraoperative soft-tissue balance assessed by an offset-type tensor influences post-operative knee kinematics after cruciate-retaining (CR) total knee arthroplasty (TKA).

Methods

The influence of intraoperative soft-tissue balance on knee kinematics in CR-TKA was retrospectively analysed in 30 patients. Intraoperative soft-tissue balance parameters such as varus angle (varus ligament balance), joint component gap (centre gap), and medial and lateral compartment gaps were measured in the navigation system while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Tibial internal rotation and tibial anterior translation were measured as the differences between the values at 60° and 120° of flexion using the navigation system. Correlations between the soft-tissue parameters and post-operative knee kinematics were analysed.

Results

The varus ligament balance was positively correlated with tibial internal rotation at 60° and 90° of flexion (R = 0.54, P < 0.05; R = 0.60, P < 0.01, respectively). Furthermore, the joint component gap was positively correlated with tibial internal rotation at 90° of flexion (R = 0.44, P < 0.05), and the lateral compartment gap was positively correlated with tibial internal rotation at 60°, 90°, and 120° of knee flexion.

Conclusions

The intraoperative varus ligament balance and joint component gap values were factors that predicted post-operative knee kinematics after CR-TKA. Lateral laxity at mid-to-deep knee flexion plays a significant role in tibial internal rotation.

Level of evidence

III.     

The coronal alignment after medial unicompartmental knee arthroplasty can be predicted: usefulness of full-length valgus stress radiography for evaluating correctability

Purpose

We aimed to clarify whether the coronal alignment after medial unicompartmental knee arthroplasty (UKA) is predictable using preoperative full-length valgus stress radiography.

Methods

Thirty-seven consecutive patients with a mean age of 71.5 ± 7.0 years awaiting medial UKA were recruited. Full-length weight-bearing radiographs of the lower limbs were obtained pre- and postoperatively. Preoperative full-length valgus stress radiography in the supine position was also performed, and the transition of the hip-knee-ankle angle (HKAA) and the weight-bearing ratio were assessed. The tibia first cut technique was used, and the distal femur was cut parallel to the cutting surface of the proximal tibia during surgery.

Results

The mean postoperative HKAA was 2.0° ± 2.1° varus, and the mean weight-bearing ratio was 43.1 ± 7.7 %; each of these parameters demonstrated significantly strong correlations with the values on the preoperative valgus stress radiographs (p < 0.01), while the correlation between the postoperative alignment and the preoperative standing alignment without stress was moderate (p < 0.01). The postoperative alignment was slightly undercorrected compared to that observed on the valgus stress radiographs (p < 0.05), and no knees exhibited evident overcorrection compared to that on the valgus stress radiographs.

Conclusion

Preoperative valgus stress radiography is useful for evaluating the correctability of varus deformities and predicting the postoperative coronal alignment. For clinical relevance, performing preoperative valgus stress radiography would help to more precisely select patients and, when combined with the tibia first cut technique, aid in achieving the expected knee alignment and avoid severe undercorrection or overcorrection.

Level of evidence

Diagnostic study, Level II.     

The effect of lateral opening wedge distal femoral osteotomy on medial knee opening: clinical and biomechanical factors

Purpose

The case of a patient with knee valgus and instability due to combined ACL–MCL laxity who underwent lateral opening wedge distal femoral osteotomy (DFO) is presented. The symptoms of instability resolved following the surgery. It was unclear whether the increase in valgus stability was related only to a decrease in valgus moments during stance or also to a medial tensioning effect. We therefore performed a laboratory cadaveric study. The purpose of this study was to examine whether after MCL and ACL sectioning, lateral opening wedge DFO would result in decrease in medial opening under static conditions of valgus stress.

Methods

Medial knee opening under valgus load of 9.8 Nm was tested in 8 cadaveric specimens in scenarios of MCL and ACL sectioning and compared before and after performing lateral opening wedge DFO.

Results

When the superficial MCL was sectioned, medial knee opening in 30° flexion decreased after lateral opening wedge DFO compared to medial opening before the osteotomy (i.e. from 6.5 ± 0.5° to 5.6 ± 0.5°, p = 0.01). When the superficial MCL, deep MCL, and ACL were all sectioned, medial knee opening in extension decreased after lateral opening wedge DFO compared to medial opening before the osteotomy but this was not significant (i.e. from 6.8 ± 0.5° to 6.1 ± 0.5°, p = n.s.).

Conclusion

In superficial MCL-transected knees, medial laxity at 30° of knee flexion decreased after lateral opening wedge DFO. However, the clinical relevance of the laxity decrease observed remains uncertain since the reduction was small in magnitude.

Level of evidence

Controlled laboratory study.     

Variation in joint stressing magnitudes during knee arthroscopy

Purpose

When performing knee arthroscopy, joint stressing is essential to increase the operative joint space. Adequate training of joint stressing is important, since high stressing forces can damage knee ligaments, and low stressing might not give sufficient operative space. As forces are difficult to transfer since they cannot be seen, simulators might be suited to train joint stressing as they can visualise the amount of applied stress. This requires the joint stressing thresholds to be validated. The purpose of this study was to measure the variation in the maximum joint stressing forces applied by various surgeons in vivo in a human population and based on that derive thresholds for safe stressing.

Methods

From studies on ligament failure properties, we inferred a theoretical maximum stressing force of 78 N. Twenty-one patients were included, and knee arthroscopies were performed by five experienced surgeons. Forces solely performed in the varus and in valgus direction were measured. A load sensor was mounted on a belt, which was rotated along the hip to measure both varus and valgus stressing. The measurements started as soon as the interior of the knee joint was visualised using joint stressing.

Results

The average maximum stressing force was 60 N (SD = 28 N). The mean first frame force was 47 N (SD = 34 N). No significant differences were found between varus and valgus stressing.

Conclusion

Since variation in stressing forces is high, offering training cases on simulators where the complete range of stressing forces can be experienced is recommended. Abiding to safety levels is essential to increase patient safety.     

Intra-articular injection of hyaluronic acid for the reduction in joint adhesion formation in a rabbit model of knee injury

Purpose

Our purpose was to evaluate the effectiveness of intra-articular injections of hyaluronic acid (HA) into immobilized joints for reducing rigidity and formation of joint adhesions following surgery and prolonged joint immobilization.

Methods

Twenty-four New Zealand white rabbits were randomly divided into experimental (n = 12) and control groups (n = 12). A model of knee injury was created in the right hind leg, and external plaster fixation was performed for 8 weeks. The experimental and control groups received weekly intra-articular injections of 0.3 mL HA solution or normal saline, respectively, in the knee joint. The degree of adhesions, range of motion (ROM), and collagen content of the synovium of the knee joint were observed after 8 weeks.

Results

At the end of 8 weeks, the experimental compared with control group had significantly higher mean ROM (70.3° ± 11.1° vs. 54.6° ± 11.2°, respectively; P = 0.002) and mean adhesion score. The experimental group compared with the control group had significantly lower mean adhesion score (2.2 ± 0.9 vs. 3.1 ± 0.7, respectively; P = 0.012) and collagen content (32.4 ± 4.7 vs. 39.0 ± 4.2 μg/mg, P = 0.001).

Conclusions

In a rabbit model of knee injury, intra-articular injection of HA decreased adhesion formation and collagen content and increased ROM after prolonged immobilization. These results indicate that HA may be clinically useful to prevent adhesions and improve joint mobility in patients who require joint immobilization for up to 8 weeks.     

Accurate alignment and high function after kinematically aligned TKA performed with generic instruments

Purpose

Performing kinematically aligned total knee arthroplasty (TKA) with generic instruments is less costly than patient-specific instrumentation; however, the alignment and function with this new technique are unknown.

Methods

One hundred and one consecutive patients (101 knees) treated with kinematically aligned TKA, implanted with use of generic instruments, were prospectively followed. The medial collateral ligament was not released. The lateral collateral ligament was released in the 17 % of patients with a fixed valgus deformity. Six measures of alignment were categorized from a scanogram of the extremity, an axial scan of the knee, and an intraoperative measurement. Both the Oxford Knee and WOMAC? scores were assessed as function. High function was a mean Oxford Knee score >41.

Results

The frequency that patients were categorized as in-range was 93 % for the mechanical alignment of the limb (0° ± 3°), 94 % for the joint line (?3° ± 3°), 57 % for the anatomic axis of the knee (?2.5° ± ?7.4° valgus), 4 % for the varus–valgus rotation of the tibial component (≤0° valgus), 98 % for the rotation of the tibial component with respect to the femoral component (0° ± 10°), and 94 % for the intraoperative change in the anterior–posterior distance of the tibia with respect to the femur at 90° of flexion (0 ± 2 mm). The mean OKS score was 42, and WOMAC? score was 89. For each alignment, the function was the same for patients categorized as an outlier or in-range.

Conclusions

The authors prefer the use of generic instruments to perform kinematically aligned TKA in place of mechanically aligned TKA because five of six alignments were accurate and because high function was restored regardless of whether patients had an alignment categorized as an outlier or in-range.

Level of evidence

IV.     

Dynamic KINE-MRI in patellofemoral instability in adolescents

Purpose

The impact of kinematic MRI (KINE-MRI) in the patellofemoral instability and anterior knee pain of the adolescents is rarely reported. Our special interest was to evaluate the patellofemoral joint biomechanics with KINE-MRI in adolescents with affected and unaffected knees in a case–control study.

Methods

KINE-MRI was performed in 29 adolescents (affected knee group, n = 29 and unaffected knee group, n = 26) aged 11–16 years with unilateral patellofemoral instability. For the control group, we enrolled ten healthy age- and sex-matched volunteers (healthy knee group, n = 19). The study parameters, bisect offset, lateral patellar displacement, patellar tilt angle, sulcus angle and Insall–Salvati ratio at 0, 10, 20 and 30° of flexion–extension, were measured for the affected knee patients (n = 29), unaffected knee patients (n = 26) and the healthy knee subjects (n = 19).

Results

The affected knee and the healthy knee subjects had a significant difference in the bisect offset ratio, lateral patellar displacement test and patellar tilt angle test. In these parameters, the difference between the affected knee patients and the healthy knee subjects progressively increased towards the full extension of the knee. In the affected knee and unaffected knee patients, bisect offset ratio at 0° ranged between 0.50 and 1.20 in both groups, whereas the bisect offset ratio in the healthy knee subjects ranged between 0.33 and 0.75 (p < 0.001). At the 0°, the lateral patellar displacement test ranged between 0 and 10 mm in the affected knee patients and between 0 and 35 mm in the unaffected knee patients, whereas the lateral displacement test ranged between 0 and 5 mm in the healthy knee subjects (p = 0.003). Patellar tilt angle test ranged between ?30 and 20° in the affected knee patients and between ?30 and 24° in the unaffected knee patients, and in the healthy knee subjects, the patellar tilt angle test ranged between 10 and 24° (p < 0.001).

Conclusions

The KINE-MRI was able to detect significant differences in patellofemoral joint kinematics between the patients and the healthy subjects. A new finding with clinical relevance in our work is that the unaffected knee is very similar to the dislocated knee in adolescents and this should be taken in account in rehabilitation of patients.

Level of evidence

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.     

No difference between tibia-first and femur-first techniques in TKA using computer-assisted surgery

Purpose

The measured resection technique and the gap-balancing technique are two philosophies used in total knee surgery. It is still unknown whether one or the other technique provides superior results when computer-assisted surgery is performed. We hypothesized that the gap-balancing technique improves joint stability because the technique relies primarily on the soft tissue.

Methods

A prospective controlled study was performed in 116 patients using the tibia-first or femur-first technique. The Columbus^TM total knee system and the Orthopilot^? (Aesculap^? AG, Tuttlingen, Germany) navigation system were used in all cases. Sixty-three patients were allocated to the femur-first technique (group F) and 53 patients to the tibial first technique (group T). The mean follow-up time was 11.4?±?1.1?months. The KSS, KOOS and SF-36 were taken prior to surgery and at the time of follow-up for clinical assessment. Long-leg weight-bearing radiographs were performed to assess ligament alignment. Radiographs in varus and valgus stress were performed using the Telos^?-Instrument (Telos^? GmbH, Greisheim, Germany) under a force of 15 N at the time of follow-up for the assessment of medial–lateral stability. The nonparametric t test (Mann–Whitney U-test) was used in order to compare the ligament stability and the scores between group F and group T.

Results

The lateral joint space opening for groups F and T was 3.4°?±?1.4° and 3.9°?±?1.7°, respectively (n.s.), and the medial joint space opening for groups F and T was 4°?±?1.4° and 4.1°?±?1.7°, respectively (n.s.). The femorotibial mechanical axis for groups F and T revealed 1.4°?±?1.2° and 0.7°?±?2.0° of varus, respectively (p?=?0.138). The clinical assessment showed significant improvement according to KSS, KOOS and SF-36 in all subscales. Neither of the sores showed significant differences between the two groups.

Conclusion

The surgeon should use his/her preferred surgical technique providing the implantation is performed with computer assistance. It remains unclear whether the same findings will occur after conventional surgery.

Level of evidence

II.     

Does varus alignment increase after medial meniscectomy?

Purpose

In patients who underwent arthroscopic meniscectomy for medial meniscus tears, the authors wished to ascertain (1) whether varus alignment in the lower extremity would increase after an operation and (2) if so, what the related factors would be.

Methods

Among 181 patients from 20 to 60 years of age who underwent arthroscopic medial meniscectomy for medial meniscus tears between 2002 and 2005, 56 patients followed for a minimum period of 5 years were enroled for this study. Alignment in the lower extremity was measured preoperatively and again at the last follow-up. Change in varus alignment (the difference between preoperative alignment and alignment at the last follow-up) was analyzed in relation to sex, age, body mass index (BMI), resection amount (partial vs. total), preoperative alignment, and follow-up duration, using multiple linear regression analysis.

Results

Varus deformity increased by 1.7° ± 1.5° from a preoperative mean of 2.4° ± 2.4° to a mean of 4.1° ± 3.0° at the last follow-up, which was statistically significant (p = 0.000). From multiple linear regression analysis, only the resection amount (partial meniscectomy or total meniscectomy) was found to be significantly related to the change in varus alignment (p = 0.002). Other factors including sex, age, BMI, preoperative alignment, presence of cartilage injury and follow-up duration were not significantly related to the change in varus alignment after the operation.

Conclusions

Arthroscopic meniscectomy performed in patients with medial meniscus tears aggravated varus alignment in the lower extremity at the last follow-up. In addition, the increase in varus deformity was significantly higher among patients with total meniscectomy than among those with partial meniscectomy.

Level of evidence

Retrospective comparative study, Level III.     

The alignment of the knee joint in relationship to age and osteoarthritis

Introduction

The aim of the present study was to describe the changes in the axis of the knee joint in both radiologically osteoarthritic and non-osteoarthritic knees, on the basis of angles measurable in standardized clinical short knee radiographs, in a cross sectional study of an epidemiological cohort.

Design

From the third inclusion of the Copenhagen City Heart Study, 4,151 subjects were selected for standardized radiography of the knees. After censuring the inclusion, the resulting cohort was comprised of 3,488 individuals. Images were analyzed for radiological knee joint osteoarthritis (OA) and the anatomical femorotibial axis of the knee joint was measured.

Results

The prevalence of knee joint OA in males was 27.9 % and 27.5 %, for the left and right knees respectively. In females this was 32.8 % and 36.4 %. The mean knee joint angles were 4.11° in males; and 5.45° in females. A difference of 1.3° was found between the genders. In non-osteoarthritic knees the increase in valgus orientation in relationship to increasing age was found to be 0.03° and 0.04° per year, respectively, for males and females. Likewise, Kellgren and Lawrence found that OA was seen to influence a shift towards varus of 0.55°–0.76° per level of OA.

Conclusion

Stratification in accordance with morphological severity of OA documented a clear tendency for the axis of the diseased knees to depart from the mean, primarily in the direction of varus. In knees exhibiting no signs of radiographic osteoarthritis we found a significant relationship between increasing age and a shift in the anatomical axis in the direction of valgus.     

The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty

Purpose

The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation (PSI) surgery versus conventional total knee arthroplasty (TKA).

Methods

Sixty patients scheduled for a primary TKA were prospectively divided into PSI or conventional technique. Coronal and sagittal radiographic long limb films were taken post-operatively. The accepted values for normal alignment were 180° ± 3° for hip-knee-ankle angle; 90° ± 3° for coronal femoral component angle or coronal tibia component angle; 0° to 3° flexion for sagittal femoral component angle and 0° to 7° posterior slope for sagittal tibia component angle.

Results

For hip-knee-ankle angle, there were 21 % more outliers in the PSI group compared to the conventional group (p = 0.045). Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (p = 0.045). For implant placement, there was no difference in the proportion of outliers between the two groups. There was also no difference in the duration of surgery.

Conclusions

This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment. PSI surgery as an alternative to conventional TKA is not advisable.

Level of evidence

II.