Femoral footprint of the popliteus tendon may be at the risk of damage during total knee arthroplasty

Purpose

The present study focused on the prevalence of incidental excision of the femoral footprint of the popliteus tendon during total knee arthroplasty and its associated risk factors.

Methods

A total of 275 knee arthroplasties were performed for 226 patients with varus knee osteoarthritis. The status of the femoral footprint of the popliteus tendon was intraoperatively evaluated and classified into three groups (preserved, partially excised, and completely excised), and the prevalence of the excision was identified. Femoral component size, the thickness of the resected distal femoral condyle, and preoperative patient demographic data were compared for the three groups. Ordinal logistic regression analysis was performed to reveal risk factors associated with the excision.

Results

The femoral footprint of the popliteus tendon was preserved in 132 knees (48.0 %), partially excised in 94 knees (34.2 %) and completely excised in 49 knees (17.8 %). The ordinal logistic regression analysis revealed thicker resection of the distal femoral condyle (p < 0.0001) and shorter body height (p = 0.0266) to be the independent risk factors for the excision.

Conclusions

The incidental partial or complete excision of the femoral footprint of the popliteus tendon was identified in approximately half of the evaluated knees. Thicker resection of the distal femoral condyle and shorter body height were the most significant risk factors for the excision.

Level of evidence

Case–control study, Level III.

     

The shape and orientation of the trochlea run more parallel to the posterior condylar line than generally believed

Purpose

This study was set up to identify the native trochlear geometry and define its relationship with the rotational landmarks of the distal femur.

Methods

The rotational landmarks of the distal femur were analysed on CT-scans of 281 patients with end-stage knee osteoarthritis.

Results

The anterior trochlear line (ATL) was on average 4.3° (SD 3.3°) internally rotated relative to the surgical transepicondylar axis (sTEA). The ATL was on average 2.1° (SD 3.0°) internally rotated relative to the posterior condylar line (PCL). The relationship between the ATL and the sTEA was statistically different in the different coronal alignment groups (p = 0.004): 3.9° (SD 3.0°) in varus knees, 4.0° (SD 2.9°) in neutral knees and 5.4° (SD 3.8°) in valgus knees. The lateralisation of the trochlea, represented by the distance between the perpendicular to PCL and the perpendicular to the posterior parallel line to the sTEA, was on average 2.2 mm (SD 1.8 mm).

Conclusion

The ATL was on average 4.3° (SD 3.3°) internally rotated relative to the sTEA and 2.1° (SD 3.0°) internally rotated relative to the PCL. The ATL is more externally orientated in varus knees and more internally rotated in valgus knees. The trochlear groove is lateralised by only 2.2 mm when the femoral component is externally rotated.

Level of evidence

III.

     

Anterolateral ligament abnormalities in patients with acute anterior cruciate ligament rupture are associated with lateral meniscal and osseous injuries

Objective

To determine the frequency of anterolateral ligament (ALL) injury in patients with acute anterior cruciate ligament (ACL) rupture and to analyse its associated injury patterns.

Methods

Ninety patients with acute ACL rupture for which MRI was obtained within 8 weeks after the initial trauma were retrospectively identified. Two radiologists assessed the status of the ALL on MRI by consensus. The presence or absence of an ALL abnormality was compared with the existence of medial and lateral meniscal tears diagnosed during arthroscopy. Associated collateral ligament and osseous injuries were documented with MRI.

Results

Forty-one of 90 knees (46 %) demonstrated ALL abnormalities on MRI. Of 49 knees with intact ALL, 15 (31 %) had a torn lateral meniscus as compared to 25 torn lateral menisci in 41 knees (61 %) with abnormal ALL (p?=?0.008). Collateral ligament (p?≤?0.05) and osseous injuries (p?=?0.0037) were more frequent and severe in ALL-injured as compared with ALL-intact knees.

Conclusion

ALL injuries are fairly common in patients with acute ACL rupture and are statistically significantly associated with lateral meniscal, collateral ligament and osseous injuries.

Key Points

? ALL injuries are fairly common in patients with acute ACL rupture. ? ALL injuries are highly associated with lateral meniscal and osseous injuries. ? MRI assessment of ACL-injured knees should include evaluation of the ALL.

     

Quantitative magnetic resonance imaging (MRI) morphological analysis of knee cartilage in healthy and anterior cruciate ligament-injured knees

Purpose

To analyze the morphological change in the cartilage of the knee after anterior cruciate ligament (ACL) injury by comparing with that of the intact contralateral knee.

Methods

A total of 22 participants (12 male and 10 female patients) who had unilateral ACL injury underwent MRI scan of both the injured and intact contralateral knees. Sagittal plane images were segmented using a modeling software to determine cartilage volume and cartilage thickness in each part of the knee cartilage that were compared between the ACL-injured and the intact contralateral knees. Furthermore, the male and female patients’ data were analyzed in subgroups.

Results

The ACL-injured knees had statistically significant lower total knee cartilage volume than the intact contralateral knees (P = 0.0020), but had similar mean thickness of total knee cartilage (not significant: n.s.). In the male subgroup, there was no significant difference in cartilage volume and thickness between normal and ACL-injured knees. In the female subgroup, the ACL-injured knees demonstrated statistically significant difference in total knee cartilage volume (P = 0.0004) and thickness (P = 0.0024) compared with the normal knees. The percentage change in the cartilage thickness in women was significantly greater than that in men.

Conclusion

Cartilage volume was significantly smaller in the ACL-injured knees than in the contralateral intact knees in this cohort. Women tended to display greater cartilage volume and thickness change after ACL injury than men. These findings indicated that women might be more susceptible to cartilage alteration after ACL injuries.

Level of evidence

III.

     

Evaluation of the size and position of the insertion of the anterior medial meniscus root in varus osteoarthritic knees

Purpose

Recent studies have suggested radial displacement of the medial meniscus as a cause of varus knee osteoarthritis (OA). Two anatomical studies reported that such displacement may be associated with anterior insertion of the medial meniscus anterior horn. It was aimed to evaluate the location and area of this insertion in patients with advanced knee OA.

Methods

Medial meniscus anterior horn insertions were classified into four types, as described in a previously reported classification during 225 total knee arthroplasty (TKA) in 184 patients. The incidence rates of insertion type were compared with previously reported rates in nearly normal or non-arthritic knees. The insertion surface area was also measured during 158 TKAs.

Results

Of the 225 knees, 82 (36.4 %), 93 (41.3 %), 35 (15.6 %), and 15 (6.7 %) were classified as I, II, III, and IV, respectively. An anteriorly inserted anterior horn was not more frequent in advanced varus OA knees than in previously reported nearly normal or non-arthritic knees. The insertion surface areas were 57.5 ± 18.9, 56.1 ± 16.0, and 56.4 ± 14.4 mm² for types I, II, and III, respectively; these areas did not differ significantly.

Conclusion

Since the incidence of an anteriorly inserted medial meniscus anterior horn was not higher in advanced varus OA knees than in normal or non-arthritic knees, an anteriorly inserted anterior horn may have little or no effect on the aetiology of varus OA knees. This study provides some information for clarifying the aetiology of knee OA.

Level of evidence

IV.

     

Effects of total knee arthroplasty on ankle alignment in patients with varus gonarthrosis: Do we sacrifice ankle to the knee?

Purpose

Total knee arthroplasty is one of the most commonly preferred surgical methods in the treatment of patients with varus gonarthrosis. In this study, we aimed to evaluate the radiological changes observed in the ankles after total knee arthroplasty.

Methods

Between May 2012 and June 2013, 80 knees of 78 patients with varus deformity over 10° underwent total knee arthroplasty. For each patient, full-leg standing radiographs were obtained pre- and post-operatively. Mechanical and anatomical axes (HKA and AA), lateral distal femoral angle, medial proximal tibial angle, lateral distal tibial angle (LDTA), ankle joint line orientation angle (AJOA), tibial plafond talus angle (PTA) and talar shift were measured for each patient both pre- and post-operatively.

Results

Pre-operatively, the mean HKA was 16.6° and the mean AA was 10.41°, both in favour of varus alignment. Post-operatively, the mean HKA decreased to 3.6° and the mean AA to ?2.1. The mean LDTA was 87.3°. Before the operation, the mean AJOA was ?7.6°, opening to the medial aspect of the ankle, and it was 0.04° after the operation and opening to the lateral aspect (p < 0.05).

Conclusion

Our study reveals the changes occurring in the ankle after acute correction of long-standing varus deformity of the knee using total knee arthroplasty. In cases undergoing knee arthroplasty, effect of the acute change in the alignment of the knee on the ankle should be taken into consideration and the amount of correction should be calculated carefully in order not to damage the alignment of the ankle.

Level of evidence

IV.

     

Following the correction of varus deformity of the knee through total knee arthroplasty,significant compensatory changes occur not only at the ankle and subtalar joint,but also at the foot

Purpose

This study aimed to assess radiological changes of the ankle joint, subtalar joint and foot following the correction of varus deformity of the knee with total knee arthroplasty (TKA). It was hypothesized that following the correction of varus deformity by TKA, compensatory reactions would occur at the subtalar joint in accordance with the extent of the correction.

Methods

For this prospective study, 375 knees of patients who underwent TKA between 2011 and 2012 were enrolled. The varus angle of the knee, talar tilt of the ankle joint (TT), ground-talar dome angle of the foot (GD), anterior surface angle of the distal tibia and lateral surface angle of the distal tibia, heel alignment ratio (HR), heel alignment angle (HA), and heel alignment distance (HD) were measured on radiographs obtained pre-operatively and at post-operative 6 months.

Results

The mean correction angle in varus deformity of the knee was 10.8?±?4.1°. TT and GD changed significantly from 0.4?±?1.9° and 6.5?±?3.1° pre-operatively to 0.1?±?1.8° and 0.2?±?2.1°, respectively (p?=?0.007, p?<?0.001). No correlation was found between the preop–postop variance in mechanical axis of the lower extremity (MA) and TT, but there was a strong correlation between the preop–postop variance in MA and GD (r?=?0.701). HR, HA and HD also changed significantly post-operatively, and the preop–postop variance in MA showed correlations with the preop–postop variances in HR, HA and HD (r?=?0.206, ??0.348, and ??0.418). TT and the three indicators of hindfoot alignment all shifted to varus whereas GD was oriented in valgus.

Conclusion

Following the correction of varus deformity of the knee through TKA, significant compensatory changes occurred not only at the ankle and subtalar joints, but also at the foot. The findings of this study are useful in predicting the orientation of changes in the ankle and subtalar joints and the foot following TKA, and in determining the sequence of surgery when both the ankle and knee have a problem. In other words, changes in the parts of the lower extremity below the ankle joint following the correction of varus deformity of the knee must be considered when TKA is planned and performed. Patients who have problems at the ankle, subtalar, and foot joints in addition to varus deformity of the knee are recommended to undergo knee joint correction first.

Level of evidence

II.

     

Significant influence of rotational limb alignment parameters on patellar kinematics: an in vitro study

Purpose

Component malrotation has a major impact on patellar kinematics in total knee arthroplasty. The influence of natural rotational limb alignment on patellar kinematics is unclear so far. Based on recent clinical investigations, we hypothesized that rotational limb alignment significantly influences patellar kinematics.

Methods

Patellar kinematics of ten cadaveric knees was measured using computer navigation during passive motion. Data were correlated with different rotational limb alignment parameters of preoperative CT scans.

Results

Femoral antetorsion showed a significant influence on patellar rotation, while tibial tubercle–posterior cruciate ligament distance additionally displayed a significant influence on patellar mediolateral shift (p < 0.05). Femoral posterior condylar angle was sensitive to patellar epicondylar distance, rotation and tilt (p < 0.05). Patellar rotation was influenced by five out of eight rotational limb alignment parameters (p < 0.05).

Conclusions

Rotational limb alignment should be paid more attention in terms of clinical evaluation of patellar tracking and future biomechanical and clinical investigations.

     

Predictive factors for the progression of spontaneous osteonecrosis of the knee

Purpose

To assess potentially predictive factors that were evaluated 1 year after the onset of symptoms in patients with spontaneous osteonecrosis of the knee (SONK) and to determine receiver operating characteristic (ROC) curve cut-off values.

Methods

Within 1 year of symptom onset, patients with SONK-selected treatment options, mainly based on severity of pain, chose either conservative treatment (n = 27 knees) or operative treatment (n = 27 knees). Knee and whole-leg radiographs, knee MRIs and bone mineral density scans of the lumbar spine, femoral neck and femoral condyles were obtained. The parameters measured were: (1) anatomical angle on whole-leg radiograph and (2) lesion size and medial meniscus extrusion on MRI.

Results

The anatomical angle and lesion size in the sagittal section (depth) on MRI were markedly larger in the operative treatment group than those in the conservative treatment group. The anatomical angle and depth on MRI of SONK at Stages 1–3 were significantly different between groups, with odds ratios (95 % confidence intervals) of 1.16 (1.18–2.34) and 1.11 (1.01–1.23). One year after symptom onset, ROC curve cut-off value for anatomical angle was 180° and depth on MRI was 20 mm.

Conclusion

An anatomical angle >180° and depth >20 mm on MRI were predictive factors for a poorer prognosis 1 year after symptom onset in patients with SONK. Our results on radiographs and MRI provided a predictive prognosis for patients with SONK at the initial visit to their orthopaedic surgeons.

Level of evidence

III.

     

Assessing coronal laxity in extension and flexion at a minimum of 10 years after primary total knee arthroplasty

Purpose

Favourable long-term results after total knee arthroplasty (TKA) require appropriate soft tissue balance. However, the relationships between long-term results after TKA surgery and mediolateral laxities at extension and at 90° flexion remain unknown. This study therefore quantitatively assessed ligament balance at extension and at 90° knee flexion at least 10 years after primary TKA, as well as clarifying the relationships between long-term outcomes and mediolateral laxities.

Methods

This study included 49 knees (19 CR type and 30 PS type) of 33 patients followed up for at least 10 years after TKA at our hospital. Plain radiographs were obtained with about 150 N of varus or valgus stress using a Telos arthrometer at extension. At 90° flexion, epicondylar views were obtained under a 1.5-kg load and with about 10 kg of varus or valgus stress.

Results

Lateral laxity of about 5° was observed in both extension and flexion, with total laxities of varus and valgus stress each less than 10°. Postoperative clinical outcomes were good, with significant improvements in extension angle, femorotibial angle, and KSS, and no loosening in any knee.

Conclusions

Good long-term results of TKA can be obtained with a lateral laxity of about 5°, equivalent to that of healthy knees.

Level of evidence

III.

     

Knee hyperextension does not adversely affect dynamic in vivo kinematics after anterior cruciate ligament reconstruction

Purpose

To evaluate the effect of knee hyperextension on dynamic in vivo kinematics after anterior cruciate ligament reconstruction (ACL-R).

Methods

Forty-two patients underwent unilateral ACL-R. Twenty-four months after surgery, subjects performed level walking and downhill running on a treadmill while dynamic stereo radiographs were acquired at 100 (walking) and 150 Hz (running). Tibiofemoral motion was determined using a validated model-based tracking process, and tibiofemoral translations/rotations were calculated. The range of tibiofemoral motions from 0 to 10% of the gait cycle (heel strike to early stance phase) and side-to-side difference (SSD) were calculated. Maximum knee extension angle of ACL-reconstructed knees during walking was defined as active knee extension angle in each subject. Correlations between maximum knee extension angle and tibiofemoral kinematics data were evaluated using Spearman’s rho (P < 0.05).

Results

No significant correlation was observed between maximum knee extension angle and the range of anterior tibial translation during functional activities in the ACL-R knees. Maximum knee extension angle was weakly correlated with internal tibial rotation range in ACL-R knee during running (ρ = 0.376, P = 0.014); however, maximum extension angle was not correlated with SSD of internal tibial rotation. SSD of internal tibial rotation was ?0.4° ± 1.9° (walking), ?1.6° ± 3.1° (running), indicating ACL-R restored rotatory knee range of motion during functional movements.

Conclusion

Knee hyperextension was not significantly correlated with greater SSD of anterior translation and internal rotation. The clinical relevance is that knee hyperextension does not adversely affect kinematic outcomes after ACL-R and that physiologic knee hyperextension can be restored after ACL-R when knee hyperextension is present.

Level of evidence

III.

     

Alignment in knee flexion position during navigation-assisted total knee arthroplasty

Purpose

The aim of this study was to demonstrate the lower limb alignment in knee flexion position after navigation-assisted total knee arthroplasty using the gap technique and to identify the correlative factors.

Methods

One hundred and twenty consecutive osteoarthritic knees (120 patients) were prospectively enrolled for intraoperative data collection. All TKA surgeries were performed using the navigation system (OrthoPilot?, version 4.0; B. Braun Aesculap, Tuttlingen, Germany). Before and after final prosthesis implantation, the lower limb navigation alignment in both knee extension (0°) and knee flexion (90°) position was recorded. The knee flexion alignment was divided into three groups: varus, neutral and valgus alignment. To determine the factors of the alignment in knee flexion position, preoperative demographics, radiologic and intraoperative data were obtained. Pearson’s correlation (r) analysis was performed to find the correlation. The Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index were compared between groups.

Results

Although all postoperative extension alignment was within neutral position (between ?2° and +2°), postoperative knee flexion alignment was divided into three groups: varus (≤?3°), 24 cases (20 %); neutral (between ?2° and +2°), 85 cases (70.8 %) and valgus (≥+3°) alignment, 11 cases (9.2 %). There were a good correlation of alignment in knee flexion position with the rotation of femoral component relative to posterior condylar axis (r = ?0.502, p = 0.000) and weak correlations with posterior femoral cut thickness (lateral condyle) (r = 0.207, p = 0.026), medial flexion (90°) gap after femoral component rotation adjustment (r = 0.276, p = 0.003). Other variables did not show correlations. There were no statistical clinical differences between varus, neutral and valgus knee flexion alignment groups.

Conclusion

About 30 % of the cases showed malalignment of more than 3° in knee flexion position although with neutral alignment in extension position. The knee flexion alignment had a good correlation with the rotation of femoral component relative to posterior condylar axis. Neutral alignment in knee flexion position may be adjusted by femoral component rotation especially by the use of navigation system.

Level of evidence

IV.

     

Influence of sagittal plane component alignment on kinematics after total knee arthroplasty

Purpose

Knee kinematics is pivotal to patient satisfaction and functional ability after total knee arthroplasty (TKA). The aim of this study is to examine the influence of sagittal plane component alignment as defined by femoral component angle (FCA), tibial slope (TS) and posterior condylar offset (PCO) on knee kinematics as defined by maximum extension angle (MEA), maximum flexion angle (MFA) and range of motion (ROM) after TKA.

Methods

This is a prospective, cross-sectional study of 105 osteoarthritic knees that underwent primary cruciate retaining TKA using a single implant design at a single tertiary institution. The sagittal plane component alignment was measured on weight-bearing true lateral radiographs taken day one post-operation and knee kinematics measured using a goniometer 1 year after TKA by the primary investigator.

Results

Although the MFA was influenced by gender (P = 0.04); age, gender and pre-operative kinematics did not otherwise influence post-operative knee kinematics. The prediction model for MFA was statistically significant (P = 0.03) and accounted for 8.4 % of the variance. FCA (r = 0.3, P = 0.01) and PCO (r = 0.2, P = 0.05) demonstrated a statistically significant correlation with MFA. However, the prediction models for ROM and MEA did not achieve statistical significance. FCA (r = 0.2, P = 0.02) demonstrated a statistically significant correlation with ROM.

Conclusion

The most important findings of this study are that the FCA demonstrates weak positive correlation with MFA and ROM and that PCO demonstrates weak positive correlation with MFA. However, TS does not contribute significantly to knee kinematics after TKA. This is clinically relevant as orthopaedic surgeons can increase the PCO in cruciate retaining TKA and the FCA within therapeutic limits to improve knee kinematics.

Level of evidence

II.

     

Comparison of the efficiency of an extra-articular absorber system and high tibial osteotomy for unloading the medial knee compartment: an in vitro study

Purpose

The unloading effect of an extra-articular absorber system on the knee joint medial compartment was compared with high tibial osteotomy (HTO) under physiological conditions in vitro.

Methods

Seven fresh-frozen cadaveric knees were used to test isokinetic flexion–extension motions under physiological loading using a biomechanical knee simulator. Tibiofemoral area contact and peak contact pressures were measured using pressure-sensitive film in the untreated medial compartment. Pressures were measured after KineSpring System implantation and HTO (5° and 10° correction angles) performed with an angular-stable internal fixator (Tomofix).

Results

Implantation of the unloading device resulted in significantly decreased medial compartment area contact pressure (Δ0.02 ± 0.01 MPa, p = 0.001) and peak contact pressure (Δ0.3 ± 0.1 MPa, p = 0.001) compared with the first test cycle results in the untreated knee. HTO significantly decreased the pressure (p = 0.001). Compared with the first test cycle, HTO (5° correction angle) decreased the mean contact pressure by Δ0.03 ± 0.01 MPa and peak contact pressure by Δ0.3 ± 0.01 MPa. With a 10° correction angle, HTO decreased contact pressure by Δ0.04 ± 0.02 MPa and peak contact pressure by Δ0.4 ± 0.1 MPa compared with that at the 5° correction angle.

Conclusion

Implantation of an extra-capsular unloading device resulted in a significant unloading effect on the medial compartment comparable to that achieved with HTO at 5° and 10° correction angles. Thus, implantation of an extra-articular, extra-capsular absorber could become the method of choice when treating patients with unicompartmental osteoarthritis that cannot be adequately treated by HTO because of their straight-leg axis.

     

Early patellar dislocation can lead to tibial tubercle lateralization in rabbits

Purpose

To investigate the effects of early patellar dislocation on the tibial tubercle location.

Methods

Sixty knees from 30 healthy 1-month-old New Zealand white rabbits were randomly divided into two groups of 30 knees each. Group A (control group) comprised the left knees, which underwent no surgical procedures. Group B comprised the right knees, which underwent patellar dislocation surgery. Computed tomography (flexion 0°) was performed preoperatively and 6 months post-operatively. Measurements included the tibial tuberosity–trochlear groove distance (TT–TG) and tibial tubercle lateralization.

Results

No significant difference in the TT–TG or tibial tubercle lateralization was found between the two groups preoperatively. Six months post-operatively, however, the mean TT–TG in Group A (no patellar dislocation) and Group B (patellar dislocation) was 1.0 ± 0.4 and 3.0 ± 0.7 mm, respectively (p < 0.05). The mean tibial tubercle lateralization also showed a significant difference between Groups A and B at 6 months post-operatively (0.5 ± 0.1 and 0.6 ± 0.0, respectively; p < 0.05).

Conclusions

Early patellar dislocation can lead to tibial tubercle lateralization and an increased TT–TG. Clinically, early intervention for adolescent patients with patellar dislocation will be important.

Level of evidence

Prospective comparative study, Level II.

     

Image-matching technique can detect rotational and AP instabilities in chronic ACL-deficient knees

Purpose

The purpose of this study was to quantify rotational and antero-posterior instabilities using biplanar image-matching technique.

Methods

Biplanar radiographs of both chronic ACL-deficient knees and contralateral uninjured knees were taken in the pivot shift test and in the “giving way position” and lateral radiographs in stress arthrometer at 30° and 90°. Three-dimensional knee models were constructed using computed tomography. Using biplanar image-matching technique, the external rotational angle and the translation of the center of the both condyles of the femur were analyzed.

Results

The external rotation angle of geometric center axis in the pivot shift test was 16.9° ± 5.6° and 10.9° ± 7.3° (P = 0.004), and in the “giving way position” was 16.1° ± 5.7° and 10.7° ± 6.6° (P = 0.004) in ACL-deficient knees and intact knees, respectively. In the pivot shift test, the medial and the lateral femoral condylar centers of ACL-deficient knees were translated 1.2 ± 5.1 mm anteriorly and 3.9 ± 3.4 mm posteriorly, respectively, and in the “giving way position,” 2.0 ± 3.7 mm anteriorly and 2.9 ± 2.6 mm posteriorly, respectively. In stress arthrometer at 30°, the medial and the lateral femoral condylar center translated 7.1 ± 6.0 and 6.6 ± 4.8 mm posteriorly (n.s.), respectively, and at 90° translated 2.7 ± 3.4 and 2.6 ± 3.5 mm posteriorly (n.s.), respectively.

Conclusion

Rotational instability was evaluable in the pivot shift test and in the “giving way position.” Translation of both condylar centers was similar in stress arthrometry. The image-matching technique is able to quantify dynamic rotational and antero-posterior instabilities with static parameters in ACL-deficient knees.

Level of evidence

III.

     

Surgical versus conservative management of acute patellar dislocation in children and adolescents: a systematic review

Purpose

The goal of this study was to perform a comparative review to determine whether there is a significant difference in the rate of repeat dislocation and clinical outcome between surgical and conservative management of acute patellar dislocation in children and adolescents.

Methods

A systematic review of the MEDLINE database was performed. English-language clinical outcome studies with a primary outcome/treatment specific to acute patella dislocation in a paediatric population were included. Eleven studies met inclusion criteria; Chi-square analysis, independent t tests and weighted mean pooled cohort statistics were performed where appropriate.

Results

A total of 470 conservatively managed and 157 operatively treated knees were included. Conservatively managed patients were on average 17.0 years and had a mean follow-up of 3.9 years; surgically managed patients were on average 16.1 years and had a mean follow-up of 4.7 years. Conservatively managed knees had a 31 % rate of recurrent dislocation rate compared to 22 % in surgical knees (p = 0.04). Trochlear dysplasia and skeletal immaturity confer greater risk for recurrent instability. Surgical treatment may provide clinically important quality of life and sporting benefit.

Conclusions

Surgical treatment of first time patella dislocation in children and adolescents is associated with a lower risk of recurrent dislocation and higher health-related quality of life and sporting function. There is a paucity of evidence on MPFL reconstruction for first time traumatic patella dislocation in this population.

Level of evidence

IV.

     

Tibial component rotation during the unicompartmental knee arthroplasty: is the anterior superior iliac spine an appropriate landmark?

Purpose

No “ideal” landmark for tibial component rotation in medial unicompartmental knee arthroplasty (UKA) has been suggested by a biomechanical and clinical study. The aim of this study was to investigate whether the anterior superior iliac spine (ASIS) could provide a consistent rotational landmark of the tibial component during mobile-bearing medial UKA using computed tomography (CT).

Methods

During sagittal tibial resection, we utilized the ASIS as a rotational landmark. In 47 knees that underwent postoperative CT scans after medial UKA, the tibial component position was assessed by drawing a line tangential to the lateral wall of the tibial component. Rotation of the tibial component was measured using two reference lines: a line perpendicular to the posterior cortical rim of the tibia (angle α) and Akagi’s line (angle β). Instant bearing position and posterior cruciate ligament (PCL) fossa involvement were also evaluated. External rotation of the tibial component relative to each reference line was considered positive values.

Results

The mean α and β angles were 8.0° ± 6.1° (range ?4.0 to 24.3) and 8.7° ± 4.8° (range 1.9–25.2), respectively. Fourteen knees (29.8 %) showed PCL fossa involvement of the tibial resection margin. One bearing showed complete 180° rotation at 2 weeks postoperatively.

Conclusion

Due to the wide variation and inherent difficulty of identifying the ASIS during the operation, it is not recommended for guidance of sagittal tibial resection during medial UKA. In cases of inappropriate tibia component rotation, risk of PE bearing spinning and iatrogenic PCL injury should be reminded after medial UKA.

Level of evidence

IV.

     

The remnant preservation technique reduces the amount of bone tunnel enlargement following anterior cruciate ligament reconstruction

Purpose

The aim of the present study was to investigate the correlation between postoperative tunnel enlargement after ACLR and remnant tissue preservation using the hamstring tendon.

Methods

One hundred and ninety-two subjects (male, n = 101; female, n = 91; mean age 27.1) who had undergone double-bundle ACL reconstruction were included in the present study. The patients were divided into two groups: the remnant tissue preservation group (Group R) and the non-remnant tissue preservation group (Group N). Computed tomographic scans of the operated knee were obtained at 2 weeks and 6 months after surgery. The area of the tunnel aperture for the anteromedial femoral tunnel (FAMT), posterolateral femoral tunnel (FPLT), anteromedial tibial tunnel (TAMT), and posterolateral tibial tunnel (TPLT) was measured. The area at 2 weeks after ACLR was subtracted from the area at 6 months after ACLR and then divided by the area at 2 weeks after ACLR. The differences in the outcomes and characteristics of the two groups were evaluated.

Results

Seventy-seven knees were classified into Group R, and 115 knees were classified into Group N. The age, gender, and body mass index did not differ to a statistically significant extent. The percentages of FAMT and TAMT enlargement in Group R were significantly smaller in comparison with Group N (P = 0.003 and P = 0.03, respectively). The percentage of FPLT and TPLT enlargement in the two groups did not differ to a statistically significant extent.

Conclusion

The remnant-preserving technique reduces the amount of bone tunnel enlargement. The present findings indicate the advantages of the remnant-preserving ACLR technique, and therefore the remnant-preserving technique should be recommended.

Level of evidence

II.