Tibial component alignment and risk of loosening in unicompartmental knee arthroplasty: a radiographic and radiostereometric study

Purpose

Unicompartmental knee arthroplasty (UKA) has shown a higher rate of revision compared with total knee arthroplasty. The success of UKA depends on prosthesis component alignment, fixation and soft tissue integrity. The tibial cut is the crucial surgical step. The hypothesis of the present study is that tibial component malalignment is correlated with its risk of loosening in UKA.

Methods

This study was performed in twenty-three patients undergoing primary cemented unicompartmental knee arthroplasties. Translations and rotations of the tibial component and the maximum total point motion (MTPM) were measured using radiostereometric analysis at 3, 6, 12 and 24 months. Standard radiological evaluations were also performed immediately before and after surgery. Varus/valgus and posterior slope of the tibial component and tibial–femoral axes were correlated with radiostereometric micro-motion. A survival analysis was also performed at an average of 5.9 years by contacting patients by phone.

Results

Varus alignment of the tibial component was significantly correlated with MTPM, anterior tibial sinking, varus rotation and anterior and medial translations from radiostereometry. The posterior slope of the tibial component was correlated with external rotation. The survival rate at an average of 5.9 years was 89 %. The two patients who underwent revision presented a tibial component varus angle of 10° for both.

Conclusions

There is correlation between varus orientation of the tibial component and MTPM from radiostereometry in unicompartmental knee arthroplasties. Particularly, a misalignment in varus larger than 5° could lead to risk of loosening the tibial component.

Level of evidence

Prognostic studies—retrospective study, Level II.     

Combined ACL reconstruction and closing-wedge HTO for varus angulated ACL-deficient knees

Purpose

To report the medium-term clinical and radiographic outcomes of a group of patients who underwent anterior cruciate ligament (ACL) surgery combined with high tibial osteotomy (HTO) for varus-related early medial osteoarthritis (OA) and ACL deficiency knee.

Methods

Thirty-two patients underwent single-bundle over-the-top ACL reconstruction or revision surgery and a concomitant closing-wedge lateral HTO. The mean age at surgery was 40.1 ± 8.1 years. Evaluation at a mean of 6.5 ± 2.7 years of follow-up consisted of subjective and objective IKDC, Tegner Activity Level, EQ-5D, VAS for pain and AP laxity assessment with KT-1000 arthrometer. Limb alignment and OA changes were evaluated on radiographs.

Results

All scores significantly improved from pre-operative status to final follow-up. KT-1000 evaluation showed a mean side-to-side difference of 2.2 ± 1.0 mm. Two patients were considered as failures. The mean correction of the limb alignment was 5.6° ± 2.8°. Posterior tibial slope decreased at a mean of 1.2° ± 0.9°. At final follow-up, the mechanical axes crossed the medial–lateral length of tibial plateau at a mean of 56 ± 23 %, with only 1 patient (3 %) presenting severe varus alignment. OA progression was recorded only on the medial compartment (p = 0.0230), with severe medial OA in 22 % of the patients. No patients underwent osteotomy revision, ACL revision, UKA or TKA.

Conclusions

The described technique allowed patients with medial OA, varus alignment and chronic ACL deficiency to restore knee laxity, correct alignment and resume a recreational level of activity at 6.5 years of follow-up.

Level of evidence

Case series with no comparison group, Level IV.     

Tibial component designs in primary total knee arthroplasty: should we reconsider all-polyethylene component?

Purpose

Despite the frequency with which total knee arthroplasties (TKAs) are performed, whether they are best performed using all-polyethylene or metal-backed tibial components remains a controversy. The aim of the present study was to determine the advantages and disadvantages of metal-backed compared with all-polyethylene tibial components during TKAs through an evaluation of current literature.

Methods

A meta-analysis and systematic review of randomized and non-randomized comparative studies comparing metal-backed with all-polyethylene tibial components during TKAs were performed. The focus of the analysis was on the outcomes of knee score, range of motion (ROM), quality of life, implant alignment, tibial migration, radiolucent line, complication, reoperation, and implant survivorship.

Results

A total of 10 randomized/quasi-randomized controlled trials and 13 non-randomized comparative studies assessing 19,767 TKAs were eligible. On the basis of these studies, no significant differences were found between the 2 groups with regard to knee score, ROM, quality of life, complication, and reoperation. The findings indicated that using all-polyethylene tibial components is associated with lower continuous migration rate compared with metal-backed tibial components. Only 13 studies provided adequate data on implant survivorship during intermediate or long-term follow-up. Of these, 9 found that no statistical significance existed between the 2 groups. The other 3 studies found that using all-polyethylene components yielded a higher survival rate than using metal-backed components.

Conclusions

Metal-backed tibial components had no obvious advantages over all-polyethylene tibial components in TKAs. However, this finding should be interpreted with caution due to publication bias, low methodological quality of the included studies, and different surgical interventions.

Level of evidence

Therapeutic study (systematic review and meta-analysis), Level III.     

In vivo kinematics comparison of fixed- and mobile-bearing total knee arthroplasty during deep knee bending motion

Purpose

The in vivo kinematics of fixed-bearing and mobile-bearing total knee prostheses remains unclear, particularly for knee flexion over 120°. The purpose of this study was to compare the in vivo kinematics of fixed-bearing and mobile-bearing posterior-stabilized prosthesis during deep knee bending with knee flexion exceeding 120° under weight-bearing conditions.

Methods

In vivo kinematics was analysed for 20 patients implanted with either a fixed-bearing posterior-stabilized or mobile-bearing posterior-stabilized prosthesis. Under fluoroscopic surveillance, each patient performed weight-bearing deep knee bending. Motion between each component was analysed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial positions of the femoral and tibial components from single-view fluoroscopic images.

Results

Patients who had fixed-bearing prostheses experienced posterior femoral rollback at a mean of 1.4 mm (SD 1.6) of the medial condyle, whereas patients who had mobile-bearing prostheses experienced 0.8 mm (SD 1.2). The posterior femoral rollback of the femoral lateral condyle in patients with a fixed-bearing prosthesis was a mean of 6.4 mm (SD 1.7) motion in the posterior direction, whereas patients who had a mobile-bearing prosthesis had 6.5 mm (SD 2.4) motion. The mean tibial internal rotation was 7.5° (SD 2.1) for fixed-bearing prosthesis and 9.2° (SD 3.2) for mobile-bearing prosthesis.

Conclusions

The present results demonstrated that the fixed-bearing and mobile-bearing posterior-stabilized designs had similar posterior condylar translation and tibial axial rotation during weight-bearing deep knee flexion exceeding 120°.

Level of evidence

Retrospective comparative study, Level III.     

Single-bundle transtibial posterior cruciate ligament reconstruction using a bioabsorbable cross-pin tibial back side fixation

Purpose

The purpose of this study was to examine a developed surgical technique by performing a mid-term evaluation of clinical and stability results and complications.

Methods

Thirty patients who underwent transtibial posterior cruciate ligament (PCL) reconstruction using a bioabsorbable cross-pin tibial back side fixation method were enrolled in this prospective study. Lysholm and International Knee Documentation Committee (IKDC) knee scales were used to evaluate clinical outcomes. Stability was evaluated using a Telos device with a 150 N force at 90 degrees of knee flexion. Follow-up magnetic resonance imaging (MRI) was also performed in 20 (66.7%) patients, and complications were evaluated. Those with complication by MRI were assigned to an abnormal MRI group.

Results

The follow-up period was 47 (range, 25–62) months. On comparing preoperative and final follow-up clinical results, Lysholm and IKDC knee scale scores were found to have improved significantly (P < 0.001). The mean side-to-side difference in posterior translation measured using a Telos device was 13.4 ± 3.1 mm (range 10–20 mm) preoperatively and 3.2 ± 1.5 mm (range 1–7 mm) at last follow-up, which represented a significant improvement in stability (P < 0.001). Five patients showed cyst formation in the tibial tunnel and two patients showed a significant signal increase at the anterior portion of the tibial tunnel, which was believed to indicate a pro-cystic status. The normal and abnormal MRI groups had similar Lysholm and IKDC knee scale scores and stress radiographs (P > 0.05).

Conclusions

Single-bundle transtibial PCL reconstruction using a bioabsorbable cross-pin tibial back side fixation was found to produce satisfactory clinical and stability results. However, despite these satisfactory results, a potential complication of tibial cyst formation was observed.

Level of evidence

Case series, Level IV.     

Variability of the location of the tibial tubercle affects the rotational alignment of the tibial component in kinematically aligned total knee arthroplasty

Purpose

Our experience with computer plans of kinematically aligned total knee arthroplasty showed that the anteroposterior (AP) axis of the tibial component when viewed in an axial plane did not consistently intersect either the medial border or the medial 1/3 of the tibial tubercle. The purposes were (1) to determine the variability in the mediolateral location of the tibial tubercle with respect to the medial tibia on the magnetic resonance image (MRI) of the knee and (2) to determine whether the AP axis of the kinematically aligned tibial component intersects either the medial border or the medial 1/3 of the tibial tubercle.

Methods

One hundred and fifteen knees in 111 consecutive subjects treated with total knee arthroplasty were studied. The mediolateral location of the tibial tubercle was measured from a magnetic resonance image (MRI) of the knee. The distances between the AP axis of the tibial component and the medial border of the tibial tubercle and between the AP axis and the medial 1/3 of the tibial tubercle were measured from a computer plan of the reconstructed knee.

Results

On the MRI, the medial border of the tibial tubercle varied 15 mm from the medial border of the tibia. On the computer plan, the AP axis of the tibial component in an axial view of the tibia did not intersect either the medial border (p < 0.0001) or the medial 1/3 of the tibial tubercle (p < 0.0001). In 70 and 86 % of knees, the mediolateral distance of the AP axis of the tibial component was 2 mm or greater from the medial border of the tibial tubercle and the medial 1/3 of the tibial tubercle, respectively, which causes a clinically meaningful error in rotation of 5° or more.

Conclusions

Because the mediolateral location of the tibial tubercle varies, the medial border and medial 1/3 of the tibial tubercle are not reliable landmarks when the goal is to kinematically align the rotation of the tibial component on the tibia.

Level of evidence

IV.     

Similar survival between screw cementless and cemented tibial components in young patients with osteoarthritis

Purpose

The aim of this study was to compare the outcomes of tibial fixation with either a cemented or cementless with screw augmentation component in young patients with non-inflammatory arthritis.

Methods

Ninety-three patients aged 55 or younger with non-inflammatory arthritis were randomized to compare outcomes between cemented tibial fixation (48 patients) and cementless fixation with screw augmentation (45 patients). The femoral component was cementless in both groups. Post-operative evaluation was assessed by the clinical and radiological criteria of The Knee Society and WOMAC questionnaire.

Results

The median follow-up was 6.7 (5–12) years. Significant differences were found for knee score (p = 0.02), range of motion (p = 0.04), and WOMAC score (p = 0.03). In the cemented group, there was one deep wound infection, four tibial aseptic loosening, and one polyethylene wear, all of which were revised. In the cementless group there was one tibial aseptic loosening and one polyethylene wear, both being revised. There was no difference in revision rate, and the cumulative survival at 9-year for aseptic reason was 93.7 % (95 % CI, 82–100 %) in the cementless group and 90.0 % (95 % CI, 80–100 %) in the cemented group (n.s.).

Conclusions

Cementless total knee arthroplasty was found to be a reliable option in younger patients with osteoarthritis. Although the revision rate and survival were similar in both groups, better clinical outcomes were obtained with cementless tibial components.

Level of evidence

I.     

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.     

Arthroscopic single-bundle ACL reconstruction with modified double-layer bone-patellar tendon-bone allograft

Purpose

The objective of present study was to introduce a modified double-layer bone-patellar tendon-bone (BPTB) allograft for arthroscopic single-bundle ACL reconstruction and investigate the clinical outcomes.

Methods

From 2007 to 2009, a total of 136 patients underwent arthroscopic single-bundle ACL reconstructions with BPTB allograft. Of which, 66 patients were with double-layer BPTB allograft (Group 1), and 70 patients were with conventional BPTB allograft (Group 2). Clinical outcomes including Lachman and pivot-shift tests, KT-1000 arthrometer measurements, and Lysholm and Tegner activity scores were compared between the two groups at a 2-year minimum follow-up.

Results

Forty-six patients in each group were at a two-year minimum follow-up. The mean side-to-side difference on the KT-1000 arthrometer was 1.2 ± 1.2 mm for group 1 and 2.1 ± 1.9 mm for group 2, with significant difference between the two groups (p = 0.017). The knee function was significantly better for group 1 than for group 2, because the mean Lysholm score was 94.2 ± 4.8 points versus 86.6 ± 7.1 points (p = 0.000), and the median Tegner score was 8 (range 5–10) points versus 6 (range 4–10) points (p = 0.001).

Conclusions

On the basis of the KT-1000 arthrometer evaluation and clinical measures, single-bundle ACL reconstruction with double-layer BPTB allograft achieves significantly lesser anterior laxity and better knee function than a single-layer allograft reconstruction.

Level of evidence

Therapeutic, retrospective comparative study, Level III.     

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.     

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

Purpose

Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images.

Methods

Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions.

Results

Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87–0.88; p < 0.001).

Conclusions

The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited.

Level of evidence

Development of diagnostic criteria in a consecutive series of patients and a universally applied ‘gold’ standard, Level II.     

Comparison of custom to standard TKA instrumentation with computed tomography

Purpose

There is conflicting evidence whether custom instrumentation for total knee arthroplasty (TKA) improves component position compared to standard instrumentation. Studies have relied on long-limb radiographs limited to two-dimensional (2D) analysis and subjected to rotational inaccuracy. We used postoperative computed tomography (CT) to evaluate preoperative three-dimensional templating and CI to facilitate accurate and efficient implantation of TKA femoral and tibial components.

Methods

We prospectively evaluated a single-surgeon cohort of 78 TKA patients (51 custom, 27 standard) with postoperative CT scans using 3D reconstruction and contour-matching technology to preoperative imaging. Component alignment was measured in coronal, sagittal and axial planes.

Results

Preoperative templating for custom instrumentation was 87 and 79 % accurate for femoral and tibial component size. All custom components were within 1 size except for the tibial component in one patient (2 sizes). Tourniquet time was 5 min longer for custom (30 min) than standard (25 min). In no case was custom instrumentation aborted in favour of standard instrumentation nor was original alignment of custom instrumentation required to be adjusted intraoperatively. There were more outliers greater than 2° from intended alignment with standard instrumentation than custom for both components in all three planes. Custom instrumentation was more accurate in component position for tibial coronal alignment (custom: 1.5° ± 1.2°; standard: 3° ± 1.9°; p = 0.0001) and both tibial (custom: 1.4° ± 1.1°; standard: 16.9° ± 6.8°; p < 0.0001) and femoral (custom: 1.2° ± 0.9°; standard: 3.1° ± 2.1°; p < 0.0001) rotational alignment, and was similar to standard instrumentation in other measurements.

Conclusions

When evaluated with CT, custom instrumentation performs similar or better to standard instrumentation in component alignment and accurately templates component size. Tourniquet time was mildly increased for custom compared to standard.

Level of evidence

Level I, prospective diagnostic.     

Arthroscopic inside-out repair of complete radial tears of the meniscus with a fibrin clot

Purpose

To report on the results of 12 complete radial tears of the meniscus treated using arthroscopic inside-out repair with fibrin clots, the results showed good meniscal healing and excellent clinical outcomes.

Methods

From 2007 to 2009, 12 patients with complete radial tears of the meniscus were treated by arthroscopic inside-out repair with fibrin clots. In all patients, the International Knee Documentation Committee (IKDC) subjective knee form and Lysholm score were determined pre- and post-operatively. We performed magnetic resonance imaging (MRI) and if indicated, we performed a second-look arthroscopic examination.

Results

At a mean of 30 ± 4 postoperative months, the Lysholm score and IKDC subjective knee score had improved from 65 ± 6 and 57 ± 7 to 94 ± 3 and 92 ± 3, respectively. Eleven of 12 cases showed complete healing on follow-up MRI. Six of 7 patients undergoing a second-look arthroscopic examination had healed completely.

Conclusion

This study shows successful meniscal repairs using fibrin clots in complete radial tears. This surgical procedure appears to be a good treatment method for complete radial tear of the meniscus.

Level of evidence

Case series, Level IV.     

Alignment outcomes in navigated total knee arthroplasty: a meta-analysis

Purpose

Whether navigated total knee arthroplasty can improve the limb and component alignment is a matter of debate. This systematic literature review analyzed the differences on alignment outcomes between navigated total knee arthroplasty and conventional total knee arthroplasty.

Methods

Multiple databases, online registers of randomized controlled trials were searched. Published and unpublished randomized controlled trials were included, and data on methodological quality, population, intervention, and outcomes were abstracted in duplicate. Data were pooled across studies, and odds ratios for categorical outcomes were calculated according to study sample size.

Results

Twenty-one randomized controlled trials of varying methodological quality involving 2,414 patients were included. Statistically significant differences were observed between navigated group and conventional group in mechanical axis malalignment of >3° (odds ratio, 0.26; 95% confidence interval, 0.17–0.38) and mechanical axis malalignment of >2° (odds ratio, 0.33; 95% confidence interval, 0.26–0.42). Navigated group had a lower risk of malalignment for both coronal femoral component and coronal tibial component of >3° and >2°. Both sagittal femoral component alignment and tibial slope showed statistical significance in favor of navigated arthroplasty at >2° and 3° malalignment.

Conclusion

Meta-analysis indicates significant improvement in alignment of the limb and the component position with use of computer navigation system. Its clinical benefits are unclear and remain to be defined on a larger scale randomized controlled trials with long-term follow-up.

Level of evidence

Therapeutic study (Systematic review of Level-I studies with inconsistent results), Level II.     

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.     

The treatment of acquired patella baja with proximalize the tibial tuberosity

Purpose

Acquired patella baja may result in decreased range of motion of the knee, extensor lag, and anterior knee pain. The aim of the study was to evaluate the efficacy of tibial tubercle osteotomy with proximal displacement.

Methods

Between 1998 and 2011, a proximalization of the tibial tuberosity was performed in 15 patients (15 knees) with patella baja diagnosed using the Blackburne–Peel ratio. Clinical outcomes included the Tegner Lysholm knee scoring scales, the WOMAC questionnaire, the short form-12 (SF-12), and a visual analogue score (VAS) pain scale.

Results

Fifteen proximalizations of the tibial tuberosity were performed, with a mean follow-up period of 64 months (5–160). The mean patient age was 59 years (41–86 years). The mean preoperative Blackburne–Peel ratio of 0.4 (0.1–0.6) was improved to a mean of 1.0 (0.8–1.2) post-operatively, which was associated with significant improvements in the Lysholm knee scoring scale from 13.3 ± 13.0 to 86.7 ± 10.4 points (p < 0.0001). Quality of life, as measured using the SF-12 outcome, also improved significantly (p < 0.0001), as did all WOMAC questionnaire score subscales (p < 0.0001). The VAS preoperative status for pain improved from 8.3 ± 2.0 to 1.5 ± 1.8. No patient had delayed or non-union of the osteotomy site.

Conclusions

A series of patients with patella baja, treated with proximalization of the tibial tuberosity, achieved satisfactory outcomes in terms of pain relief and improved function, without major complication.     

Extension gap needs more than 1-mm laxity after implantation to avoid post-operative flexion contracture in total knee arthroplasty

Purpose

In total knee arthroplasty (TKA), a high soft-tissue tension in extension at the time of operation would cause a post-operative flexion contracture. However, how tight the extension gap should be during surgery to avoid a post-operative flexion contracture remains unclear. The hypothesis is that some laxity in the intraoperative extension gap is necessary to avoid the post-operative flexion contracture.

Methods

A posterior-stabilized TKA was performed for 75 osteoarthritic knees with a varus deformity. The intraoperative extension gap was measured using a tensor device that provides the gap length and the angle between the femoral component and the tibial cut surface. The medial component gap was defined as the gap calculated by subtracting the selected thickness of the tibial component, including the polyethylene liner, from the extension gap at the medial side. Then, the patients were divided into three groups according to the medial component gap, and post-operative extension angle measured 1 year after the surgery was compared between each groups.

Results

One year post-operatively, a flexion contracture of more than 5° was found in 0/34 patients when the medial component gap was more than 1 mm, in 2/26 (8 %) patients when the gap was between 0 and 1 mm, and in 3/15 (20 %) patients when the gap was <0 mm. Three factors were associated significantly with the post-operative extension angle: age, preoperative extension angle, and medial component gap.

Conclusion

The intraoperative extension gap is related to the post-operative extension angle. Surgeons should leave more than 1-mm laxity after the implantation to avoid the post-operative flexion contracture. As a clinical relevance, this study clarified the optimal extension gap to avoid the post-operative flexion contracture.

Level of evidence

Prospective comparative study, Level II.     

Patellar height modification after high tibial osteotomy by either medial opening-wedge or lateral closing-wedge osteotomies

Purpose

High valgus tibial osteotomy is used to treat medial femoro-tibial osteoarthritis. Changes in patellar height due to high valgus tibial osteotomy can cause technical difficulties during subsequent knee arthroplasty. The primary objective of this study was to assess the hypothesis that patellar height decreases after opening-wedge osteotomy and increases after closing-wedge osteotomy. The secondary objective was to assess whether frontal axis correction and tibial slope modification correlated with patellar height changes.

Methods

A multicentre, prospective, comparative, observational, non-randomised study was conducted in consecutive patients undergoing isolated high valgus tibial osteotomy according to standard practice in each of the ten study centres. Patellar height was assessed based on the Caton-Deschamps index.

Results

Of 321 included patients, 224 underwent opening-wedge and 97 closing-wedge osteotomy. Patellar height did not change significantly after closing-wedge osteotomy (1.07 ± 0.2 pre-operatively and 1.0 ± 0.19 postoperatively). Patellar height decreased significantly after opening-wedge osteotomy (from 0.98 ± 0.19 to 0.88 ± 0.21, p < 0.0001, mean decrease 9 ± 22 %). Patellar height decreased by more than 20 % in 49 (28 %) patients after opening-wedge osteotomy. The patellar height decrease after opening-wedge osteotomy correlated significantly with axis correction magnitude and tibial slope change.

Conclusion

Our results support routine baseline measurement of patellar height before high valgus tibial osteotomy and posterior positioning of the opening wedge to limit the tibial slope change in patients requiring major axis correction by opening-wedge osteotomy.

Level of evidence

Prospective cohort study, Level II.     

Tibial rotational osteotomy and distal tuberosity transfer for patella subluxation secondary to excessive external tibial torsion: surgical technique and clinical outcome

Purpose

Recurrent patella subluxation may be secondary to excessive external tibial torsion. The purpose of this study is to evaluate the clinical and radiographic outcome of patients undergoing tibial derotation osteotomy and tibial tuberosity transfer for recurrent patella subluxation in association with excessive external tibial torsion.

Methods

A combined tibial derotation osteotomy and tibial tuberosity transfer was performed in 15 knees (12 patients) with recurrent patella subluxation secondary to excessive external tibial torsion. Clinical evaluation was carried out using preoperative and post-operative Knee Society Score (KSS), Kujala Patellofemoral score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire, the short form-12 (SF-12) and a visual analogue score (VAS) pain scale.

Results

The median follow-up period was 84 months (range 15–156) and median patient age was 34 years (range 19–57 years). The median preoperative external tibial torsion was 62° (range 55°–70°), with a median rotational correction of 36° (range 30°–45°) after surgery. Significant improvement (p < 0.05) was found in the KSS part I (37 ± 14 to 89 ± 11 points), KSS part II (25 ± 26 to 85 ± 14 points), Kujala score, the SF-12 outcome, WOMAC score and VAS score (8.8 ± 1.9 to 2.4 ± 1.5). Two patients had a nonunion of the tibial osteotomy site; one patient required bone grafting, while another patient required revision to total knee arthroplasty.

Conclusion

Patients presenting with recurrent patella subluxation secondary to excessive external tibial torsion >45° who underwent tibial derotation osteotomy and tibial tuberosity transfer achieved a satisfactory outcome in terms of pain relief and improved function. A significant complication was seen in 2/15 patients.

Level of evidence

Case series, Level IV.     

Partial resection of the PCL insertion site during tibial preparation in cruciate-retaining TKA

Purpose

Based on the anatomy of the tibial PCL insertion site, we hypothesized that at least part of it is damaged while performing a standard tibial cut in a PCL-retaining total knee replacement. The purpose of this study was to determine and quantify the amount of resection of the tibial PCL attachment with a 9 mm tibial cut with 3 degrees of posterior slope.

Methods

Twenty cadaver tibias were used. The borders of the PCL footprint were demarcated, and calibrated digital pictures were taken in order to determine the surface area. A standard tibial intramedullary guide was used to prepare and perform a tibial cut at a depth of 9 mm with 3 degrees posterior slope. After the tibial cut was made, a second digital picture was taken using the same methodology to measure the surface area of the remaining PCL insertion.

Results

The mean surface area of the intact tibial PCL footprint before the cut was 148.9 ± 25.8 mm² and after the tibial cut 47.1 ± 28.0 mm². On average, 68.8 ± 15.3 % of the surface area of the PCL insertion was removed.

Conclusion

The results of this study, therefore, indicate that the conventional technique for tibial preparation in cruciate-retaining total knee arthroplasty can result in damage or removal of a significant part of the tibial PCL insertion.